Safe bearing region for avoiding meniscal bearing impingement and overhang in mobile-bearing unicompartmental knee arthroplasty

The purposes of this study were to propose a quantitative method of bearing overhang to minimize the effect of bearing spinning on mobile-bearing unicompartmental knee arthroplasty (MB UKA), suggest and apply safe bearing regions in daily activities. The overhang distance and area were calculated for neutral and spinning positions. The safe bearing regions were based on the relationship between bearing overhang and linear wear rate. Eleven patients were included in an in-vivo experiment under dual fluoroscopic imaging following medial MB UKA. The bearing position was tracked by minimal joint space width, and the bearing overhang was calculated accordingly. Due to an equal contribution of 1 mm increase in medial overhang and 30 mm2 overhang areato wear rate, the maximum effect of potential bearing spinning on medial overhang distance was approximately three times as large as the overhang area. The safe bearing distance and area regions were rectangles and arches with different scales for different size combinations of bearing, femoral and tibial components. The maximum bearing overhang area during lunge (R = 0.76, p = 0.006) and open-chain exercise (R = 0.68, p = 0.02) significantly correlated with the overhang area in standing. The overhang area can be an appropriate parameter for evaluating dislocation degree less affected by potential bearing spinning than the overhang distance in clinical practice. The corresponding safe overhang area regions were proposed for surgical planning and postoperative dislocation degree evaluation. The bearing overhang area in static standing posture can be a valuable reference to estimate the dynamic overhang area and dislocation degree during motion.

Knee kinematics are not different between asymmetrical and symmetrical tibial baseplates in total knee arthroplasty: A fluoroscopic analysis of step-up and lunge motions

PURPOSE

This clinical fluoroscopy study investigated knee kinematics of two different cemented fixed-bearing, posterior-stabilised (PS) total knee arthroplasty (TKA) designs: an asymmetric tibial component including an asymmetric insert designed to optimise personalised balance and fit and its precursor symmetrical design with symmetric insert.

METHODS

A consecutive series of patients (16 TKAs from each treatment group) participating in a randomised controlled trial comparing TKA migration was included. The exclusion criterion was the use of walking aids. Flat-panel fluoroscopic recordings of step-up and lunge motions were acquired 1-year postoperatively. Medial and lateral contact points (CPs) were determined to calculate CP displacement, femoral axial rotation and pivot position. Using linear mixed-effects modelling techniques, kinematics between TKA designs were compared.

RESULTS

During knee extension between 20° flexion and full extension, the CPs moved anteriorly combined with a small internal femoral rotation (a screw-home mechanism). Whereas CP movement was reversed: femoral rollback, external femoral rotation while flexing the knee between full extension and 20° knee flexion, At larger flexion angles, femoral axial rotation (FAR) occurred around a lateral pivot point both during step-up and lunge. The symmetric design had a 2.3° larger range of FAR compared to the asymmetric design during lunge (p = 0.02). All other kinematics were comparable.

CONCLUSION

Despite the differences in design, this study showed that the asymmetric and symmetric PS TKA designs had mostly comparable knee kinematics during step-up and lunge motions. It is therefore expected that the functionality of the successor TKA design is similar to that of its precursor design.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Comparison of Alignment Accuracy and Clinical Outcomes between a CT-Based, Saw Cutting Robotic System and a CT-Free, Jig-guided Robotic System for Total Knee Arthroplasty

OBJECTIVE

The different cutting mode of robot-assisted TKAs may influence the accuracy of alignment. The purpose of this study was to compare alignment accuracy and early clinical outcomes between a CT-based, saw cutting robotic system (MAKO) and a CT-free, jig-guided robotic system (ROSA) for total knee arthroplasty (TKA).

METHODS

A total of 20 MAKO TKAs and 20 ROSA TKAs from June 2021 to June 2022 were retrospectively analyzed. Differences in the postoperative hip-knee-ankle (HKA) angle, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), posterior tibial slope (PTS) and 3° outlier frequency of the HKA, LDFA, MPTA and PTS were studied at 3 months and 1 year of follow-up. The operative time and total blood loss (TBL) were compared between these two groups. Clinical outcomes at 1 year after surgery, including range of motion (ROM), Western Ontario McMaster University Osteoarthritis Index (WOMAC) score, and Knee Society Score-2011 (KSS-2011), were also compared between these two groups.

RESULTS

The baseline characteristics of the two groups were comparable. There were no significant differences in the mean deviations of postoperative HKA, LDFA, MPTA or PTS between the two groups at 3 months or 1 year (all ps > 0.05). Moreover, there was no significant difference in the percentage of 3° outliers for HKA, LDFA, MPTA, or PTS between the two groups at 3-month or 1-year follow-up (all ps > 0.05). The mean operation time of MAKO was longer than that of ROSA (112.7 ± 12.8 min vs 94.8 ± 23.0 min, p = 0.001), but the mean TBL (1356.7 ± 648.5 mL vs 1384.5 ± 676.3 mL) and transfusion rate (15.0% vs 5.0%) were not significantly different between the two groups (all ps > 0.05). No significant differences were found in postoperative ROM, WOMAC score or KSS score at 1 year (all ps > 0.05).

CONCLUSION

The MAKO and ROSA had similar accuracy and precision in TKA alignment. The clinical outcomes at 1 year after surgery were also comparable.

Mobile medial pivot (lateral slide)-type total knee arthroplasty exhibited different motion patterns between under anaesthesia and weight-bearing condition

PURPOSE

Total knee arthroplasty (TKA), which has medial pivot and mobile-bearing mechanisms, has been developed and clinically used. However, the in vivo dynamic kinematics of the mobile medial pivot-type TKA (MMPTKA) is unclear. This study analysed the in vivo kinematics of MMPTKA in weight-bearing and nonweight-bearing conditions.

METHODS

The study included 10 knees that underwent primary TKA using MMPTKA. After TKA, lateral view radiographs of the knee in full extension, 90° of flexion and passive full flexion were taken under general anaesthesia in the nonweight-bearing condition. At least 6 months postoperatively, knee motion during squatting from a weight-bearing standing position was observed using a flat-panel detector and analysed using the three-dimensional-to-two-dimensional image registration technique.

RESULTS

Under anaesthesia: in passive full flexion, the anteroposterior (AP) locations of the femoral component's medial and lateral distal points were 10.2 and 16.0 mm posterior, and the rotational angles of the femoral component's X-axis (FCX) and insert were 8.1° external rotation and 18.5° internal rotation to full extension, respectively. Squatting: the AP translations of the femoral component's medial and lateral most distal points were 2.2 and 6.4 mm, and the rotational angles of the FCX and insert were 5.7° and 1.6° external rotation, respectively. Significant differences were observed in the AP translation of the femoral component's medial and lateral most distal points and changes in the insert's rotational angle when comparing under anaesthesia and squatting.

CONCLUSIONS

The kinematics of the insert in MMPTKA was significantly influenced by loading and muscle contraction. The femoral component exhibited substantial external rotation and posterior translation under anaesthesia, which may contribute to achieving an optimal range of motion. The insert remained relatively stable during squatting and minimal rotation was observed, indicating good stability. MMPTKA was expected to demonstrate rational kinematics by incorporating mobile and medial pivot mechanisms.

LEVEL OF EVIDENCE

Level IV, prospective biomechanical case series study.

Long-term results (after a mean 11.3years, and up to 22years, of follow-up) of the Legacy Constrained Condylar Knee (LCCK™) in primary total knee arthroplasty

INTRODUCTION

The use of a sliding prosthesis in total knee arthroplasty (TKA) with increased stress is an intermediate solution in primary surgery, between posteriorly stabilized prostheses and hinged prostheses, in cases of ligamentous laxity and/or loss of bone substance. Favorable results have been reported in the medium term but to our knowledge, this type of prosthesis has not been evaluated in Europe beyond 10 years of follow-up. We therefore conducted a retrospective study in order to carry out: 1) the study of the survival of the Legacy Constrained Condylar Knee (LCCK™) prosthesis in primary surgery, 2) the analysis of complications, functional scores and radiographic data, 3) the analysis of the link between the diaphyseal filling rate and prosthetic loosening.

HYPOTHESIS

The LCCK™ sliding prosthesis with increased constraint has equivalent long-term survival and clinical results to standard posteriorly stabilized TKA and superior to hinged TKA.

MATERIAL AND METHOD

A retrospective series of 141 LCCK™ implanted in 134 patients between 1997 and 2010 was analyzed. Survival was assessed with censoring through an evaluation of partial or total revision of the implants. The functional results were evaluated using the IKS and Oxford 12 scores. Data regarding the Canal Fill Ratio (CFR) and the presence of pathological periprosthetic lines were also collected.

RESULTS

The average follow-up was 11.3±5.3years with a maximum follow-up of 22.7years. Survival at 20years was 90.8% [95% CI: 83.7-95.7]. The rate of early complications was 13.5% (19/141), predominantly comprised of venous thrombosis (6/141), hematomas (3/141 including two requiring surgical drainage), stiffness (3/141) and early infections (3/141). The rate of late complications was 17% (24/141), led by stiffness (4.4%; 6/141), infections (2.9%; 4/141) and hardware failure (2. 2%; 3/141). Ten of the 141 patients (7.1%) had LCCK failure, including 3 (2.1%) for stiffness, 3 (2.1%) for hardware failure, 2 (1.4%) for infection, 1 (0.7%) for laxity and 1 (0.7%) for a periprosthetic fracture. No aseptic loosening was found. The total IKS score went from 65 [0-116] to 143 [79-200] at follow-up, the IKS knee score went from 30 [0-66] to 85 [44-100], and the IKS function score went from 35 [0-70] to 57 [0-100]. The Oxford score went from 14 [2-25] to 34 [15-48] at follow-up. Only two patients (1.4%) presented with a partial periprosthetic line. The tibial CFR was 0.81 and the femoral CFR was 0.76. The influence of the CFR could not be analyzed due to the absence of loosening.

DISCUSSION

The LCCK™ prosthesis in primary surgery has good medium-term survival, a significant improvement in functional scores and a complication rate comparable to posteriorly stabilized prostheses. The complication rate is lower than that of hinged prostheses.

LEVEL OF EVIDENCE

IV; single-center retrospective study.

Comparison of the coverage and rotation of asymmetrical and symmetrical tibial components: a systematic review and meta-analysis

BACKGROUND

An optimized fit of the tibial component to the resection platform and correct rotational alignment are critical for successful total knee arthroplasty (TKA). However, there remains controversy regarding the superiority of symmetric tibial component versus asymmetric tibial component. The objective of this systematic review and meta-analysis was to evaluate the current evidence for comparing the coverage and rotation of asymmetrical and symmetrical tibial component.

METHODS

We searched potentially relevant studies form PubMed, Web of science, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and China National Knowledge Infrastructure (CNKI), up to 1 March 2023. Data extraction and quality assessment were performed by two independent reviewers. Meta-analysis was conducted using Review Manager 5.4.

RESULTS

Sixteen articles were identified. Compared to symmetric tibial component, asymmetric tibial component increased the coverage of the proximal tibial cut surface (MD, -2.87; 95%CI, -3.45 to -2.28; P < 0.00001), improved the prevalence of tibial baseplate underhang (OR, 0.16; 95%CI, 0.07 to 0.33; P < 0.00001) and malrotation (OR, 0.13; 95%CI, 0.02 to 0.90; P = 0.04), and reduced the degree of tibial component rotation (MD, -3.11; 95%CI, -5.76 to -0.47; P = 0.02). But there was no statistical significance for improving tibial baseplate overhang (OR, 0.58; 95%CI, 0.08 to 3.97; P = 0.58). Additionally, no revision had occurred for the two tibial components in the included studies.

CONCLUSION

The current evidence shows asymmetric tibial component offer advantages in terms of coverage and rotation compared with symmetric tibial component in TKA.

Aseptic loosening of the option stemmed tibial tray in the Zimmer NexGen LPS total knee arthroplasty system

BACKGROUND

We investigated the relationship between the backside deformation of polyethylene (PE) tibial inserts and aseptic loosening of the Option stemmed tibial tray used with Zimmer NexGen posterior-stabilised (PS) devices. We hypothesized that explanted inserts used in PS designs would exhibit greater extents of PE backside deformation than those used in equivalent cruciate retaining (CR) designs and that PE inserts retrieved from total knee arthroplasties (TKAs) revised for aseptic tibial tray loosening would exhibit greater extents of backside deformation than TKAs revised for other reasons.

METHODS

A total of 73 explanted fixed-bearing TKAs (42 CR and 31 PS) were examined. PE components underwent geometric examination with a coordinate measuring machine using validated techniques. Multiple regression modelling was used to identify variables associated with revision secondary to aseptic loosing and to determine factors associated with increased PE backside deformation.

RESULTS

PE inserts retrieved from TKAs with aseptic loosening had significantly greater backside deformation than those retrieved from TKAs revised for other reasons (p < 0.001). Greater PE backside deformation was significantly associated with larger tray/insert clearance heights (p < 0.001), thinner inserts (p < 0.001) and PS TKAs (p = 0.001).

CONCLUSION

PE backside deformation was significantly greater in the PS TKAs. This may provide one explanation for the increased rate of aseptic loosening reported with the Option tibial tray used with the Legacy Posterior Stabilised (LPS) system.

Longer term follow up of outcomes following implantation of a modular rotating hinge knee prosthesis: 53 implants at mean 7.6 year follow up

BACKGROUND

Rotating hinge knee replacements are becoming more common but have historically had high complication and failure rates. This study is one of the largest to assess the implant survival and patient outcomes of a third-generation rotating hinge knee replacement at a single tertiary orthopaedic centre.

METHODS

Data for consecutive operations at our tertiary unit between 2006 to 2020 were assessed with review of electronic patient and radiology records. The Oxford Knee Score was used to assess outcomes and the Kaplan Meier method used to estimate survivorship.

RESULTS

53 rotating hinge knees were implanted in 46 patients (13 male, 33 female) at a mean age of 67.8 years. 21 were primary and 32 were revision procedures. Indications for use of this implant included instability, loosening, fracture and infection. Survivorship was 77.8% at the mean follow up of 7.6 years. A total of 29 complications were noted with ongoing pain, stiffness, infection and patellofemoral symptoms being the most common. 8% of unresurfaced patellas required a subsequent secondary resurfacing. The Oxford Knee Score demonstrated a significant improvement from 14.6 preoperatively to 27.5 at one year postoperatively, which was maintained in the longer term.

CONCLUSION

The third-generation rotating hinge knee implant in use at our unit has improved outcomes for patients. The survivorship of the implant is comparable to the published literature, although there is a paucity of data. The complication rates remain relatively high and patients should be counselled appropriately. We advise resurfacing the patella to avoid the need for secondary procedures.

A morphometric medial compartment-specific unicompartmental knee system: 5 years follow up results from a pilot center

BACKGROUND

Unicompartmental Knee Arthroplasty (UKA) is a valuable solution for the treatment of medial osteoarthritis of the knee. New implants feature designs for the elective substitution of a specific compartment. Aim of this study was to assess the survivorship and functional outcomes at minimum 4 years of the first 60 implanted patients in a pilot center of a new medial UKA as the evolution of a well performing long lasting fixed bearing implant.

METHODS

Between June 2017 and the end of 2018, 60 medial UKA were implanted in 58 patients. All patients were available for the last follow up and were analyzed prospectively. 37 were females and 21 were males with a mean age of 67 years (SD 10,71) and a mean of BMI 27.16 (SD 3.94) for the male population and of 26.73 (SD 4.05) for the female population.

RESULTS

At final follow up the mean Oxford Knee Score (OKS) was 44,02 (SD 3,1) and the mean Forgotten Joint Score (FJS) 78,6 (SD 7,9). The Knee Society Score (KSS) score was 95,2 for the "knee" score and 89.8 for the "function" score. No patients were revised. Kaplan-Meyer survival estimate showed a 100% survivorship at final follow up. No progressive radiolucent lines were found and no direct or indirect signs of polyethylene wear were registered on the final radiographs.

CONCLUSIONS

This new implant demonstrated promising clinical results with an excellent survival rate at short to midterm follow- up. Further follow up is needed to confirm this trend at longer term.

First long-term analysis of survival and clinical outcome in patient-specific instrumentation for total knee arthroplasty: follow-up of a prospective cohort study

Patient-specific instrumentation (PSI) was introduced to improve post-operative alignment, and consequently the revision rate and clinical results after total knee arthroplasty (TKA). Short- to mid-term data are conflicting regarding these theoretical advantages of PSI. The purpose of this retrospective analysis was to evaluate the survival rate and clinical outcome in PSI TKA 8.4 years after initial surgery. To our knowledge, no other study investigated long-term follow-up of TKA procedures using PSI. From a total cohort of 184 consecutive patients (200 TKA) 136 patients (144 TKA, 72%) were prospectively analysed at a mean follow-up of 8.4 years (±0.4). A survival analysis with all-cause revision of TKA as endpoint was performed. Patient-reported outcome measures (PROMs) were obtained preoperatively and after 1-, 2-, 5-, and 8.4-years of follow-up. Differences between these moments of follow-up were analysed. At final follow-up, 4 TKAs (2%) had undergone revision, all between 2-4 years after primary surgery. Reasons for revision were late infection, aseptic loosening, instability and polyethylene insert breakage. The median score of certain PROMs (WOMAC, VAS, EQ-index, EQ-VAS) decreased compared to previous follow-up scores but were significantly higher than preoperative scores. After 8.4 years of follow-up, no additional revision surgery was performed compared to 5-years postoperatively. Certain PROMs at 8.4-year follow-up decreased compared to earlier moments of follow-up, but all PROMs improved compared to preoperative PROMs.

The wear and kinematics of two medially stabilised total knee replacement systems

BACKGROUND

Medially stabilised total knee replacement systems aim to provide a more natural feeling knee replacement by providing increased stability through flexion. The aim of this study was to compare the kinematics and wear of two different medially stabilised total knee replacement systems in an experimental simulation study. The Medial Rotation Knee™ system (MRK) is an early medially stabilised knee (>20 years clinical success); the SAIPH® knee system being a more modern and refined, bone conserving evolution of the original design with a larger size range.

METHODS

Three SAIPH and three MRK total knee replacements (MatOrtho Ltd, UK) were investigated. The study was performed on a knee simulator with load controlled input kinematic conditions (ISO 14243-1). 6 million cycles of simulation were carried out with the wear of the UHMWPE tibial components assessed gravimetrically. The resulting anterior-posterior translation and tibial rotation position was measured throughout the study.

RESULTS

The mean UHMWPE wear rate was 0.57 ± 0.71 and 1.24 ± 2.0 mm3/million cycles for SAIPH and MRK total knee replacement systems respectively with no significant difference in wear (p = 0.24). Analysis of simulator output kinematics showed a larger range of anterior-posterior motion for SAIPH total knee replacements compared to MRK. The magnitude of tibial rotation was low for both knee replacement systems.

CONCLUSION

The small magnitude of anterior-posterior displacement and tibial rotation motion demonstrates the inherent stability of this knee system design offered by the constrained medial compartment. This study shows the potential for medially stabilised knee systems as a low polyethylene surface wear solution.

Analysis of alternate material Onyx™ for total knee arthroplasty instrumentation sets

CONTEXT

A 25-pound weight limit is currently set on containerized instrumentation sets by the Association of periOperative Registered Nurses (AORN) and the Association for the Advancement of Medical Instrumentation (AAMI), in order to reduce strain on the staff and ensure that the sets are not too crowded in order to preserve sterilization and drying of the instruments. This is pushing companies to reduce the weight and number of instrumentation sets for the operating room. One solution has been to explore the viability of new, lighter materials such as Onyx.

OBJECTIVES

The goal of this study is to evaluate the novel material Onyx as a viable material utilized in reusable total knee arthroplasty (TKA) instrumentation sets utilizing traditional steam sterilization as the sterilization method.

METHODS

Mechanical and biocompatibility tests according to the American Society for Testing Materials (ASTM) and International Organization for Standardization (ISO) 10,993 were run to evaluate the Onyx Material to see if it would be a viable alternative to the stainless and martensitic steel that is currently being utilized.

RESULTS

Gross warping and cracking after 10 rounds of sterilization was observed. This was qualitatively worse in the Onyx without a carbon fiber component. The Onyx material did not meet biocompatibility standards for its application.

CONCLUSIONS

Onyx was determined to not be a viable material for TKA instruments regarding multiple high-pressure and -temperature sterilizations and cytotoxic cell testing.

3D-printed, patient-specific cutting guides improve femoral and tibial cut alignment in canine total knee replacement

OBJECTIVES

The purpose of this cadaveric study was to determine whether patient-specific guides (PSGs) improve the accuracy of tibial and femoral cut alignment in canine total knee replacement (TKR), as compared with generic cutting guides.

STUDY DESIGN

Original research.

ANIMALS

Sixteen pelvic limbs from skeletally mature medium- to large-breed canine cadavers.

METHODS

Specimens were randomly allocated to one of two groups (PSG or Generic; N = 8/group). In the Generic group, femoral and tibial ostectomies were made using the standard canine TKR femoral cutting blocks and tibial alignment guide. In the PSG group, the cuts were made using a series of custom 3D-printed cutting guides. "Planned" and "actual" tibial and femoral cut alignments were compared in the frontal and sagittal planes, and errors were calculated by subtracting actual from planned values.

RESULTS

Use of 3D-printed PSGs improved tibial cut alignment in the frontal plane but not the sagittal plane. PSGs also improved the alignment of the cranial and distal femoral ostectomies but did not impact varus-valgus alignment.

CONCLUSIONS

These findings support the use of PSGs for TKR in dogs. Clinical trials are now needed to determine whether the benefits of PSGs translate into measurable improvements in joint function and implant longevity.

CLINICAL SIGNIFICANCE

PSGs have the potential to improve femoral and tibial component alignment in canine TKR.

Do Fixed or Mobile Bearing Implants Have Better Survivorship in Medial Unicompartmental Knee Arthroplasty? A Study From the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

During the last 5 years, there has been an increase in the use of unicompartmental knee arthroplasty (UKA) to treat knee osteoarthritis in Australia, and these account for almost 6% of annual knee replacement procedures. However, there is debate as to whether a fixed bearing or a mobile bearing design is best for decreasing revision for loosening and disease progression as well as improving survivorship. Small sample sizes and possible confounding in the studies on the topic may have masked differences between fixed and mobile bearing designs.

QUESTIONS/PURPOSES

Using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), we selected the four contemporary designs of medial compartment UKA: mobile bearing, fixed modular, all-polyethylene, and fixed molded metal-backed used for the treatment of osteoarthritis to ask: (1) How do the different designs of unicompartmental knees compare with survivorship as measured by cumulative percentage revision (CPR)? (2) Is there a difference in the revision rate between designs as a function of patient sex or age? (3) Do the reasons for revision differ, and what types of revision procedures are performed when these UKA are revised?

METHODS

The AOANJRR longitudinally maintains data on all primary and revision joint arthroplasties, with nearly 100% capture. The study population included all UKA procedures undertaken for osteoarthritis between September 1999 and December 2018. Of 56,628 unicompartmental knees recorded during the study period, 50,380 medial UKA procedures undertaken for osteoarthritis were included in the analysis after exclusion of procedures with unknown bearing types (31 of 56,628), lateral or patellofemoral compartment UKA procedures (5657 of 56,628), and those performed for a primary diagnosis other than osteoarthritis (560 of 56,628). There were 50,380 UKA procedures available for analysis. The study group consisted of 40% (20,208 of 50,380) mobile bearing UKA, 35% (17,822 of 50,380) fixed modular UKA, 23% (11,461 of 50,380) all-polyethylene UKA, and 2% (889 of 50,380) fixed molded metal-backed UKA. There were similar sex proportions and age distributions for each bearing group. The overall mean age of patients was 65 ± 9.4 years, and 55% (27,496 of 50,380) of patients were males. The outcome measure was the CPR, which was defined using Kaplan-Meier estimates of survivorship to describe the time to the first revision. Hazard ratios from Cox proportional hazards models, adjusted for sex and age, were performed to compare the revision rates among groups. The cohort was stratified into age groups of younger than 65 years and 65 years and older to compare revision rates as a function of age. Differences among bearing groups for the major causes and modes of revision were assessed using hazard ratios.

RESULTS

At 15 years, fixed modular UKA had a CPR of 16% (95% CI 15% to 17%). In comparison, the CPR was 23% (95% CI 22% to 24%) for mobile bearing UKA, 26% (95% CI 24% to 27%) for all-polyethylene UKA, and 20% (95% CI 16% to 24%) for fixed molded metal-backed UKA. The lower revision rate for fixed modular UKA was seen through the entire period compared with mobile bearing UKA (hazard ratio 1.5 [95% CI 1.4 to 1.6]; p < 0.001) and fixed molded metal-backed UKA (HR 1.3 [95% CI 1.1 to 1.6]; p = 0.003), but it varied with time compared with all-polyethylene UKA. The findings were consistent when stratified by sex or age. Although all-polyethylene UKA had the highest revision rate overall and for patients younger than 65 years, for patients aged 65 years and older, there was no difference between all-polyethylene and mobile bearing UKA. When compared with fixed modular UKA, a higher revision risk for loosening was shown in both mobile bearing UKA (HR 1.7 [95% CI 1.5 to 1.9]; p < 0.001) and all-polyethylene UKA (HR 2.4 [95% CI 2.1 to 2.7]; p < 0.001). The revision risk for disease progression was higher for all-polyethylene UKA at all time points (HR 1.4 [95% CI 1.3 to 1.6]; p < 0.001) and for mobile bearing UKA after 8 years when each were compared with fixed modular UKA (8 to 12 years: HR 1.4 [95% CI 1.2 to 1.7]; p < 0.001; 12 or more years: HR 1.9 [95% CI 1.5 to 2.3]; p < 0.001). The risk of revision to TKA was higher for mobile bearing UKA compared with fixed modular UKA (HR 1.4 [95% CI 1.3 to 1.5]; p < 0.001).

CONCLUSION

If UKA is to be considered for the treatment of isolated medial compartment osteoarthritis, the fixed modular UKA bearing has the best survivorship of the current UKA designs.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Custom Implants in TKA Provide No Substantial Benefit in Terms of Outcome Scores, Reoperation Risk, or Mean Alignment: A Systematic Review

BACKGROUND

Failure to accurately replicate the native anatomy and biomechanics of the knee has been suggested to contribute to dissatisfaction after TKA. Custom implants promise a personalized surgical approach, with the aim of improving patient satisfaction and pain as well as lowering revision rates. However, some published research on custom TKA implants has found no clinically important improvements in postoperative validated outcomes scores, risks of revision or reoperation, and implant alignment. In the interest of helping to settle this controversy, a systematic review seems warranted.

QUESTION/PURPOSE

In this systematic review, we asked whether custom implants result in clinically important improvements over conventional off-the-shelf implants for anatomically uncomplicated primary TKA in terms of (1) validated outcomes scores, (2) the risk of revision or reoperation, and (3) implant alignment.

METHODS

The US National Library of Medicine (PubMed/Medline), Embase, Web of Science, and Cochrane Database of Systematic Reviews were systematically searched to identify publications from the past 10 years relevant to this review. Publications that compared the clinical outcome measures, number of revisions and reoperations, and radiological assessment of implant alignment of custom and standard implants with validated endpoints were eligible for inclusion. In the interest of capturing as much potentially relevant information as possible, we applied no requirement for minimum follow-up duration. Clinical outcomes were assessed using patient-reported outcome (PROM) scores including the Knee Society Score (KSS), Forgotten Joint Score, and Knee Injury and Osteoarthritis Outcome Score. The risk for revision or reoperation were evaluated by the number of early and late manipulations, debridement procedures, and replacement of one or more components. Implant alignment was compared using postoperative deviation from the neutral (0°) mechanical axis of the limb and each component and the posterior tibial slope. All qualified studies were retrospective, and all compared custom implants with standard implants. Data on 1510 patients were reviewed (749 with custom implants and 761 with off-the-shelf implants). The mean follow-up time ranged from 12 to 33 months.

RESULTS

There was no apparent advantage to custom implants in terms of PROM scores. Of the five studies evaluating clinical outcomes, only one reported better KSS-Function scores at 3 months; two reported no difference, and two found inferior KSS scores. In several studies, custom implants were associated with more frequent reoperations than standard implants. Although in general there were no differences between custom and standard implants in terms of mean coronal plane limb alignment, one of seven studies found that the proportion of patients whose alignment was outside ± 3° from the neutral axis in the coronal plane was lower in the custom group than in the standard group.

CONCLUSION

With generally poorer outcomes scores for pain and function, generally higher risks of reoperation and reintervention, and no overall benefit to alignment, custom implants for primary TKA for the general population currently appear to be inferior to standard implants. Whether the slight reduction in the proportion of patients with alignment outliers observed in a minority of studies will result in a substantial reduction in revision risk over time must be addressed by future studies. However, until or unless such a reduction is proven, we recommend against the routine use of custom implants in practice because of increased costs and the risks associated with their novelty.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Long-term survivorship of total knee arthroplasty with a single-radius, high-flexion posterior stabilized prosthesis

BACKGROUND

The purpose of this study was to determine functional outcomes, implant survival rate, and complications of a single-radius, high-flexion posterior stabilized (PS) total knee prosthesis at a minimum follow up of 10 years for a consecutive series.

METHODS

This retrospective observational study included 395 consecutive patients who underwent 585 single-radius, PS total knee arthroplasties (TKAs) between January 2009 and December 2009. Their functional outcomes, implant survival rates, radiological findings, and complications were evaluated.

RESULTS

At a mean follow up of 11.2 years (range, 10.6-11.8 years), 395 (80.8%) patients were available for review. At final follow up, preoperative Knee Society knee scores were improved from 37.3 to 80.1 (P < 0.05) and function scores were improved from 35.7 to 80.5 points (P < 0.05). Sixteen knees (2.7%) in 15 patients required revision surgery due to 11 septic loosening (1.9%) and five aseptic loosening events (0.8%). Cumulative survival for the prosthesis was 97.3% for any cause at 10 years. A total of 34 radiolucent lines (5.8%) were detected an average of 2.4 years following surgery and radiological assessment did not reveal any evidence of component migration at final follow up.

CONCLUSIONS

Single-radius, high-flexion PS TKA showed good long-term survival rates and clinical outcomes. Further study is required to determine whether limited radiolucency findings at the tibial component-tibial plateau could progress to or result in the loosening of components.

How Can We Differentiate Local Recurrence From Heterotopic Ossification After Resection and Implantation of an Oncologic Knee Prosthesis in Patients with a Bone Sarcoma?

BACKGROUND

Heterotopic ossification (HO) is common after total joint arthroplasty and usually does not cause diagnostic problems. However, the occurrence of HO after oncologic prostheses implantation can be troublesome as it may mimic a locally recurrent tumor. Because this distinction could have a profound impact on the surgeon and patient, it is important to distinguish the two entities; to our knowledge, no study has evaluated this after oncologic endoprosthetic reconstruction around the knee after tumor resection.

QUESTIONS/PURPOSES

(1) How common is the occurrence of HO compared with local recurrence (LR) after resection of bone sarcoma and the use of an oncologic knee prosthesis? (2) Are there any factors associated with the development of HO after limb salvage procedures with an endoprosthesis? (3) What features allow the surgeon to differentiate HO from a locally recurrent tumor in this setting?

METHODS

Between 2002 and 2018, we performed 409 resections of primary bone tumors followed by reconstructions with oncologic endoprostheses. Of these, 17% (71 of 409) died before 2 years and did not have HO at that time, 2% (8 of 409) were lost to follow-up before 2 years, and another 2% (10 of 409) did not have radiographs available at a minimum of 2 years after surgery (and had not developed HO before then), and so could not be analyzed, leaving 320 patients for analysis in this retrospective study. Forty-two patients were excluded; 2% (5 of 320) for a history of failed allograft reconstruction, 3% (8 of 320) for pathologic fracture at presentation, 2% (6 of 320) for inadequate or complicated biopsy, 1% (2 of 320) for stem fractures, 2% (7 of 320) for stem loosening, and 4% (14 of 320) for extracortical bone bridging, leaving 278 patients for final evaluation. Two observers analyzed AP and lateral radiographs for signs of HO at a mean follow-up of 63 ± 33 months after surgery. We defined HO as extraskeletal bone formation in soft tissues. The primary study endpoint was survivorship free from HO, as ascertained by a competing-risks estimator. To identify factors associated with HO appearance, the demographic, radiographic, clinical, pathologic, and surgical characteristics were compared between patients with HO and those who had no lesion. Characteristic features were also compared between patients with HO and those with LR to help their differentiation. Univariate analysis was used for all statistical evaluations.

RESULTS

HO developed in 8% (21 of 278) of patients in whom oncologic knee prosthesis was implanted. LR developed in 10% (28 of 278) of the patients. According to survivorship estimates, the HO-free survival rate was not different from the LR-free survival rate at 2 years after oncologic knee reconstruction (76 ± 5% [95% CI 63 to 87] versus 74 ± 5% [95% CI 62 to 88]; p = 0.19). History of infection was more common in patients with HO than in patients with no lesion (19% [4 of 21] versus 5% [12 of 229], Odds ratio [OR] 6 [95% CI 2 to 17]; p < 0.001). The male sex was more common in the HO group as well (76% [16 of 21] versus 55% [128 of 229], OR 2 [95% CI 1 to 5]; p = 0.03). The Modular Universal Tumor and Revision System prosthesis was more frequently used in patients with HO (67% [14 of 21]) compared to those with no lesions (40% [92 of 229]; OR 2 [95% CI 1 to 5]; p = 0.02). The lesion border in radiographs was ill-defined in 19% (4 of 21) of patients with HO and 100% (28 of 28) of patients with LR (OR 8 [95% CI 3 to 20]; p < 0.001). The median time to the appearance of HO was shorter than the time to LR (8 months [3 to 13] versus 16 months [11 to 21], [95% CI 10 to 13]; p < 0.001). Pain at presentation was more frequent in patients with LR than in those with HO (86% [24 of 28] versus 14% [3 of 21], OR 36 [95% CI 7 to 181]; p < 0.001).

CONCLUSION

HO may occur after the use of oncologic knee prostheses for reconstruction after tumor resection. In most patients, HO could be differentiated from local recurrence through identifying a well-defined border on radiographs. Otherwise, factors such as an earlier time of presentation and absence of pain could suggest an HO, rather than an LR.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Finn/Orthopaedic Salvage System Distal Femoral Rotating-Hinge Megaprostheses in Oncologic Patients: Long-Term Complications, Reoperations, and Amputations

BACKGROUND

There is a lack of evidence regarding long-term outcomes of rotating-hinge knee prostheses with distal femoral replacement in a large oncologic patient series. In this study, we investigated the proportion of patients experiencing complications requiring surgery in the long term, as well as the cumulative incidence of implant removal/revision and amputation at 5, 10, 15, and 20 years through competing risk analyses.

METHODS

We retrospectively studied 214 patients treated with a Finn/Orthopaedic Salvage System (OSS) knee prosthesis (Zimmer Biomet) after distal femoral resection from 1991 to 2017. The study end points were postoperative complications requiring surgery. Reoperations were classified as major when there was (1) removal of the metal-body femoral component, the tibial component, or the bone-implant fixation; (2) major revision (exchange of the metal-body femoral component, the tibial component, or the bone-implant fixation); or (3) amputation. Minor reoperations were defined as all other reoperations. Competing risk analysis was used to estimate the cumulative incidence of implant removal/revision or amputation.

RESULTS

There were 312 reoperations in 113 patients (98 major reoperations in 68 patients and 214 minor reoperations). Seventeen patients (8%) required ≥5 additional operations, and 21 patients (10%) required >1 major reoperation. Although the number of reoperations decreased over time, major and minor reoperations continuously accrued after 10 years. The cumulative incidences of implant removal or revision for any reason at 5, 10, 15, and 20 years were 22.6%, 30.1%, 34.3%, and 42.5%, respectively. Although most implant removals/revisions occurred in the first 10 years, the risk persisted after 10 years, at a mean of 1.24%/year, mainly due to deep infection (1.06%/year).

CONCLUSIONS

The long-term outcomes of treatment with a Finn/OSS distal femoral rotating-hinge knee prosthesis showed it to be a durable reconstruction technique. The rate of implant removal/revisions after 10 years was gradual (1.24%/year). Deep infection remains a major late-failure mechanism, and lifetime surveillance for prosthetic problems is needed.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Better clinical outcomes and overall higher survival with hybrid versus cemented primary total knee arthroplasty: a minimum 15 years follow-up

PURPOSE

To compare the clinical outcomes and survival at long-term between hybrid and cemented primary total knee arthroplasty (TKA). A better clinical outcome and survival following a follow-up as long as 15 years with the use of hybrid fixation as compared with cemented fixation was hypothesized.

METHODS

Case-control study of 126 patients with a mean age of 62.4 years who underwent hybrid TKA matched with 126 patients underwent cemented TKA. Clinical outcome was assessed by the Knee Society scores (KSS) and reduced Western Ontario and MacMaster Universities questionnaire (WOMAC). Radiological assessment was made by the Knee Society method.

RESULTS

The mean follow-up was 15.7 (range 15-17) years. At the final follow-up, clinical scores were significantly better in the hybrid group, although the differences were not clinically relevant. Revisions for all reasons were performed in five knees in the hybrid group and 15 knees in the cemented group (p = 0.033). In the hybrid group, there was one aseptic femoral loosening and no aseptic tibial loosening. In the cemented group, the main reasons for aseptic revisions were polyethylene wear (six knees) and tibial loosening (four knees). Cemented fixation was a significant risk factor for aseptic revision (hazard ratio 2.3; 95% CI 1.3-3.7%; p = 0.004). Survival at 15 years for aseptic reasons was 96.5% (95% CI 93.4-98.7%) in hybrid groups and 90.3% (95% CI 88.7-93.9%) in cemented group (p = 0.020).

CONCLUSION

After a minimum follow-up of 15 years, hybrid fixation of primary TKA for osteoarthritis provide significantly higher clinical benefits compared with cemented fixation, but the differences were not clinically relevant. Hybrid fixation provides longer overall survival, although the femoral component survival was similar between groups.

LEVEL OF EVIDENCE

III.

Comparison of clinical and radiographic results between total knee arthroplasties using medial pivot and posterior-stabilized prosthesis: A meta-analysis

OBJECTIVE

To evaluate the clinical and radiographic outcomes of total knee arthroplasties (TKA) between using medial-pivot (MP) and posterior-stabilized (PS) prosthesis. Does MP prosthesis and PS prosthesis influence the clinical results of a TKA?

METHODS

An electronic literature search of PubMed Medline and the Cochrane Library was performed from inception to October 1, 2019. A meta-analysis to compare postoperative outcomes of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, Knee Society Score (KSS), range of motion (ROM), complications, and radiographic results between MP and PS prosthesis were conducted.

RESULTS

Seven eligible studies involving 934 adult patients (MP group, n = 461; PS group, n = 473) were identified for analysis. This study showed no significant difference between the 2 groups in the WOMAC scores, KSS, ROM, and complications (P > .05). The differences of the femorotibial angle, position of implant, and patellar tilt were also not significant between the 2 groups (P > .05).

CONCLUSION

The present meta-analysis has shown that patients with the MP prosthesis have similar clinical results as patients with PS prosthesis. Furthermore, the radiographic results, especially patella tilt angle, were also similar between the 2 groups. Therefore, surgeons should be aware that the types of prostheses are not a decisive factor to ensure successful operation.

Systematic review and meta-analysis of bearing dislocation in lateral meniscal bearing unicompartmental knee replacement: Domed versus flat tibial surface

BACKGROUND

Bearing dislocation is a problem following mobile bearing Oxford lateral Unicompartmental Knee Replacement (UKR). Therefore, the design of the tibial component was changed from a flat tibial surface to a domed tibial surface with a biconcave bearing to increase bearing entrapment. This systematic review compared the dislocation and revision rates of the two designs.

METHODS

Two authors independently searched MEDLINE, EMBASE and ISI Web of Science, reference lists of retrieved articles, and the internet. Randomised, cohort, case-control and case studies of adult patients with lateral knee osteoarthritis treated with flat or domed Oxford lateral UKR and their outcomes were included. The overall dislocation rate and the annual revision rate (per 100 component years) were determined.

RESULTS

Nine studies (937 knees) met the inclusion criteria (3 flat, 6 domed). Four studies (all domed) had a low risk of bias and five had a high risk (3 flat, 2 domed), so data should be interpreted with caution. The bearing dislocation rate decreased from 17% (flat) to 3.7% (domed). Dislocations occurred on average at 16 months and medial dislocations were most common. The revision rate excluding dislocation decreased from 1.1%pa to 0.7%pa. PROSPERO registration: CRD42019139250.

CONCLUSION

Modifying the tibial component from a flat to a domed shape decreased the bearing dislocation rate to 3.7% and increased the 10 year survival rate excluding dislocation to 93%. The dislocation rate is still relatively high so bearing stability should be assessed intra-operatively and if unacceptable, a fixed bearing version of the Oxford lateral tibial component can be inserted.

Use of Navigation-Enhanced Instrumentation to Mitigate Surgical Outliers During Total Knee Arthroplasty

Computer-assisted orthopedic surgery improves mechanical alignment and the accuracy of surgical cuts in the context of total knee arthroplasty (TKA). A simplified, navigation-enhanced instrumentation system was assessed to determine whether the same effects could be achieved with a less intrusive system. Two cohorts of surgeons (experienced and trainees) performed a series of TKA cuts using models with and without navigation-enhanced instrumentation. The accuracy of each system was determined via the rate of outliers, measured as any cut that deviated from the planned cut by more than 2° or 2 mm. The effect of experience level was limited, with only the outlier rate for tibial varus or valgus measurement showing a significant difference between user groups with conventional instrumentation (P=.004). The use of navigation-enhanced instrumentation significantly reduced the total outlier rate compared with conventional instrumentation from 35% to 4% for experienced users (P<.001) and from 34% to 10% for trainees (P<.001). These results suggest that navigation-enhanced instrumentation is a viable alternative to conventional instrumentation to reduce outlier rates and improve cut accuracy. This trial also showed that additional experience may not correlate with improved surgical accuracy. Outliers may not reflect individual surgical ability as much as limitations of the instrumentation or other unidentified factors. [Orthopedics. 2021;44(1):54-57.].

Impact of tourniquet during knee arthroplasty: a bayesian network meta-analysis of peri-operative outcomes

INTRODUCTION

The role of tourniquet during knee arthroplasty is controversial. The present study compares various tourniquet protocols using a Bayesian network meta-analysis of peri-operative data.

MATERIAL AND METHODS

The present study was conducted in accordance with the PRISMA extension statement for reporting systematic reviews incorporating network meta-analyses of health interventions. The literature search was conducted in September 2020. All clinical trials investigating the role of tourniquet in knee arthroplasty were considered for inclusion. Methodological quality was assessed using Review Manager 5.3. A Bayesian hierarchical random-effects model analysis was used in all comparisons.

RESULTS

Ultimately, pooled data from 68 studies (7413 procedures) were analysed. Significant inconsistency was found in the data relating to total estimated blood lost; no assumption could be made on this outcome. Full-time tourniquet resulted in the shortest surgical duration and lowest intra-operative blood lost, in both cases followed by incision-to-suture. The incision-to-suture protocol achieved the smallest drop in haemoglobin during the first 72 h post-operatively and the lowest rate of blood transfusion, both followed by full-time tourniquet. Hospitalisation was shortest in the absence (no-tourniquet) group, followed by the cementation-to-end group.

CONCLUSION

For knee arthroplasty, longer tourniquet use is associated with the shorter duration of surgery, lower intra-operative blood lost, lower drops in haemoglobin and fewer transfusion units. The shortest average hospitalisation was associated with no tourniquet use.

Molded, Gamma-radiated, Argon-processed Polyethylene Components of Rotating Hinge Knee Megaprostheses Have a Lower Failure Hazard and Revision Rates Than Air-sterilized, Machined, Ram-extruded Bar Stock Components

BACKGROUND

Megaprostheses are commonly used for reconstruction after distal femoral resection in orthopaedic oncology. The polyethylene bearings in these reconstructions experience wear and wear-related complications that may result in revision surgery. Improved manufacturing and processing of polyethylene has increased the durability of components commonly used for routine arthroplasty. Alterations in the manufacture of polyethylene is expected to reduce the revision risk of oncologic megaprostheses, resulting in fewer revision procedures, but this has not been proven.

QUESTIONS/PURPOSES

Is there a difference in the hazard of polyethylene wear or breakage leading to prosthetic revision between differences in polyethylene manufacture and processing based on a competing risk analysis?

METHODS

This was a single-center, observational, retrospective comparative study of 224 patients who had distal femur megaprostheses with identical rotating hinge articulations and knee kinematics after oncologic surgery from 1993 to 2015. No differences in surgical indications, joint articular components and kinematics, age, sex, diagnosis, BMI, use of chemotherapy, or tumor stage were seen with the patient numbers available. Prosthetic survivorship free from prosthetic revision surgery because of polyethylene wear-related revisions, defined as breakage, increased excursion on varus-valgus stress, or new locking or giving way was compared between two groups of patients: group 1 polyethylene (P1) (66 patients) who had air-sterilized machined ram-extruded bar stock or group 2 polyethylene (P2) (158 patients) molded gamma-radiated argon-processed polyethylene components. The mean follow-up duration for the P1 group (89 ± 55 months) was not different from that of patients with P2 polyethylene (79 ± 63 months; p = 0.24) including 27% (18 of 66) of patients in the P1 group and 25% (40 of 158) of patients in the P2 group followed for more than 10 years. More patients in the P2 group were lost to follow-up (9.2%, 16 of 174) than in the P1 group (5.7%, 4 of 70) but this was not statistically different (chi square; p = 0.37). The hazard of revision because of polyethylene wear or breakage was calculated with a competing risk analysis using the Fine-Gray subdistribution hazard model.

RESULTS

The P1 implants had a higher hazard ratio for revision caused by polyethylene damage at 120 months than did the P2 polyethylene implants (P1 HR 0.24 [95% CI 0.13 to 0.36] versus HR 0.07 [95% CI 0.03 to 0.12]), which represents an estimated absolute risk reduction of 17% (95% CI 6.15 to 27.9).

CONCLUSION

Polyethylene damage can result in megaprosthetic revisions in patients undergoing oncologic procedures. The hazard of polyethylene failure resulting in revision surgery was lower in patients who received recent polyethylene than in patients with polyethylene produced by previous methods, enhancing the durability of distal femoral megaprosthetic reconstructions. Despite improvements in polyethylene manufacture and clinical results, revision solely because of polyethylene damage still occurs in 7% of patients by the 10-year timepoint; thus, more improvement is needed. Patients who receive these implants should be monitored for signs and symptoms of polyethylene damage.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Short-term Outcomes of 3D-Printed Titanium Metaphyseal Cones in Revision Total Knee Arthroplasty

Recently, 3-dimensional (3D) printing technology has been used in the development of titanium metaphyseal cones to manage severe bone loss in revision total knee arthroplasty (rTKA). This study assessed (1) radiographs; (2) functional outcomes; (3) complications; and (4) 2-year implant survivorship in patients receiving 3D-printed titanium metaphyseal cones for moderate-to-severe tibial and femoral bone loss in rTKA. A single institution, retrospective chart review was performed for patients with large bone defects treated with a 3D-printed femoral or tibial titanium metaphyseal cone between 2015 and 2017 during rTKA (N=54). Paired sample t tests analyzed Knee Society Scores (KSS). Kaplan-Meier analyses determined implant survivorship when the endpoint was cone revision for aseptic loosening, cone revision for any reason, and reoperation for any reason. The authors found that 51 (98.1%) of 52 available radiographs demonstrated well-fixed components without any evidence of loosening or migration. Mean postoperative KSS scores were significantly higher when compared with preoperative scores (80.4 vs 52.0; P>.001). One patient experienced aseptic loosening of their cone. Seven additional cones were explanted as a consequence of reinfection, 1 of which was removed prior to arthrodesis. Cone survivorship was 98.5% when the endpoint was cone revision due to aseptic loosening, 88.2% when cone revision was due to any reason, and 77.9% for any reoperation. Metaphyseal cones appear to be well-suited for large bone defects during rTKA and the authors' findings suggest that cones may be a viable option for metaphyseal fixation during rTKA. Future studies should focus on their durability during a longer time period. [Orthopedics. 2021;44(1):43-47.].

Medium term clinical outcomes of tibial cones in revision knee arthroplasty

INTRODUCTION

Trabecular metal cones are a relatively new option for reconstruction of major bone defects during revision total knee arthroplasty (TKA). The purpose of the present study was to retrospectively assess medium-term results for tibial cones in revision TKA with a severe proximal tibial bone defect. We hypothesized that revision TKA patients with bone defects treated with trabecular metal cones have excellent medium-term clinical and radiological results.

PATIENTS AND METHODS

A single-center retrospective review included all consecutive cases of tibial revision using trabecular metal cones. All patients with a minimum 2-year follow-up were included in the study. There were no exclusion criteria. The primary endpoint was tibial cone survivorship. The secondary endpoints were revision TKA all-cause survivorship, patient-reported outcome measures with a Knee injury and Osteoarthritis Outcome Score (KOOS), SF 12, and radiographic analysis.

RESULTS

Five of the 57 patients alive at last follow-up (8.77%) had undergone revision (4 for infection and 1 for instability). Complications comprised four cases (7.02%) of infection, 2 cases (3.51%) of tibial and femoral implant aseptic loosening that did not require revision surgery, 1 of which (1.75%) with associated patellar loosening, and 1 case (1.75%) of instability. Kaplan-Meier estimates showed 100% 5-year survivorship with tibial cone revision for aseptic loosening and 93.44% (95% CI 83.47-97.49%) for all-cause revision.

DISCUSSION

The present study of cones used for tibial revision supports shows excellent results; however, longer and larger follow-up is needed to better assess results in revision TKA.

LEVEL OF EVIDENCE

4, retrospective study.

Successful Two-Stage Exchange Arthroplasty for Periprosthetic Infection Following Total Knee Arthroplasty: The Impact of Timing on Eradication of Infection

Background: Periprosthetic joint infection (PJI) represents a serious complication following total knee arthroplasty. In the setting of chronic infections, the two-staged approach has traditionally been the preferred treatment method. The aim of this study was to determine the optimal period of rest between the first and second stage. Furthermore, we analyzed potentially outcome-relevant parameters, such as general and local conditions and the presence of difficult-to-treat or unidentified microorganisms, with regard to their impact on successful treatment of PJI. Patients and Methods: We performed a retrospective analysis of prospectively collected data for all patients treated for PJI at our institution. Seventy-seven patients who had undergone two-stage revision arthroplasty for PJI of the knee were included into the study. Antibiotic-loaded cement spacers were used for all patients. Results: After a median follow-up time of 24.5 months, infection had reoccurred in 14 (18.7%) patients. A prolonged spacer-retention period of more than 83 days was related to a significantly higher proportion of reinfections. Furthermore, significant compromising local conditions of the prosthetic tissue and surrounding skin, as well as repeated spacer-exchanges between first- and second-stage surgery, negatively influenced the outcome. Neither the patients' age nor gender exerted a significant influence on the outcome regarding reinfection rates for patients' age or gender. Conclusions: We observed the best outcome regarding infection control in patients who had undergone second-stage surgery within 12 weeks after first-stage surgery. Nearly 90% of these patients stayed free from infection until the final follow-up. An increased number of performed spacer-exchanges and a bad local extremity grade also had a negative impact on the outcome.

The Biomechanical Performance of the Latest All-Inside Meniscal Repair Devices

PURPOSE

To evaluate the biomechanical characteristics of recently introduced meniscal repair devices with a hand-tied, inside-out meniscal suture in a human meniscus model.

METHODS

In detached adult human menisci, vertical longitudinal cuts were created 3 mm from the synovial-meniscal junction, simulating a bucket-handle meniscal tear. Each cut was repaired using a single device. Group 1 received a vertical mattress suture of No. 2-0 OrthoCord; group 2, TrueSpan device with PEEK (polyether ether ketone) anchors containing No. 2-0 OrthoCord suture; group 3, TrueSpan device with biodegradable poly-lactide-co-glycolide (PLGA) anchors containing No. 2-0 OrthoCord suture; group 4, Meniscal Cinch II device; group 5, AIR meniscal repair device; and group 6, FasT-Fix 360 device. All samples were preloaded at 5 N and cycled 200 times between 5 and 20 N. The specimens that survived cyclic loading were destructively tested at 12.5 mm/s. Endpoints included maximum load, displacement, stiffness, and failure mode.

RESULTS

The mean failure loads were as follows: 95.8 N for OrthoCord suture, 87.1 N for TrueSpan with PEEK, 84.6 N for TrueSpan with PLGA, 48.6 N for Meniscal Cinch II, 72.3 N for AIR, and 68.1 N for FasT-Fix 360. Repairs performed with OrthoCord suture (P = .002) and both TrueSpan devices (P < .03) but not the FasT-Fix 360 device or AIR device were statistically significantly stronger than Meniscal Cinch II repairs. Mean cyclic displacement measured 1.1 mm for OrthoCord, 1.5 mm for TrueSpan with PEEK, 1.5 mm for TrueSpan with PLGA, 2.1 mm for Meniscal Cinch II, 1.1 mm for AIR, and 1.4 mm for FasT-Fix 360. The Meniscal Cinch II device showed more displacement than all other devices (P < .05). The FasT-Fix 360, AIR, and Meniscal Cinch II devices failed by anchor pullout from the peripheral meniscus. OrthoCord and both TrueSpan devices failed by suture pulling through the bucket-handle tissue.

CONCLUSIONS

OrthoCord suture is stronger than the AIR, FasT-Fix 360, and Meniscal Cinch II devices. The TrueSpan device with PEEK and TrueSpan device with PLGA are stronger than the Meniscal Cinch II device. The Meniscal Cinch II device failed during cyclic loading with greater cyclic displacement than the AIR device, FasT-Fix 360 device, OrthoCord, and TrueSpan device with PEEK. The Meniscal Cinch II, AIR, and FasT-Fix 360 devices failed by anchor pullout, whereas OrthoCord and both TrueSpan devices failed by suture pull-through.

CLINICAL RELEVANCE

Some newly introduced all-inside meniscal repair devices show inferior failure strength compared with earlier versions that might adversely impact clinical outcomes.

Lifetime revision risk for medial unicompartmental knee replacement is lower than expected

PURPOSE

Unicompartmental knee replacement (UKR) is widely considered to be a pre-total knee replacement (TKR) particularly in the young. The implication of this is that it is sensible to do a UKR, even though it will be revised at some stage, as it will delay the need for a TKR. The chance of a UKR being revised during a patient's life time has not previously been calculated. The aim of this study was to estimate this lifetime revision risks for patients of different ages undergoing UKR.

METHODS

Calculations were based on data from a designer series of 1000 medial Oxford UKR with mean 10-year follow up. These UKR were implanted for the recommended indications using the recommended surgical technique. Parametric survival models were developed for patients of different ages based on observed data, and were extrapolated using a Markov model to estimate lifetime revision risk.

RESULTS

The estimated lifetime revision risk reduced with increasing age at surgery. Lifetime revision risk at age 55 was 15% (95% CI 12-19), at 65 it was 11% (8-13), at 75 it was 7% (5-9), and at 85 it was 4% (3-5).

CONCLUSION

Provided UKR is used appropriately, the lifetime revision risk is markedly lower than expected. UKR should be considered to be a definitive knee replacement rather than a Pre-TKR even in the young. These lifetime estimates, alongside established benefits for UKR in speed of recovery, morbidity, mortality and function, can be discussed with appropriate patients when considering whether to implant a UKR or TKR.

LEVEL OF EVIDENCE

III.

Metallosis after knee replacement: a review

INTRODUCTION

Although metallosis is a well-known complication after total hip arthroplasty, little is known about this phenomenon after total (TKA) or unicompartmental knee arthroplasty (UKA). The aim of the present work was to review the current knowledge about the reasons and the diagnostic as well as therapeutic management of metallosis after knee arthroplasty.

MATERIALS AND METHODS

A literature search was performed through PubMed until April 2019. Search terms were "metallosis" in combination with "knee", "knee prosthesis", "knee arthroplasty" and "knee replacement", respectively. All publications were analyzed regarding publication year, level of evidence, number of knees/patients treated, type of prosthesis, metallosis cause, time period between primary implantation and metallosis emergence, laboratory examination, treatment, complications and follow up.

RESULTS

A total of 38 studies reporting on a total of 97 knees were identified. 29 studies reported on metallosis after TKA, 8 after UKA, and one study after both procedures. The time period between the primary implantation and metallosis emergence ranged between 6 weeks and 26 years. The most common reason was the failure of a metal-backed patellar component in 40%, followed by implant/structural- and PE failure (wear/dislocation) in 27% and 18% of the cases, respectively. Complete blood cell count, serum chemistry, erythrocyte sedimentation rate or C-reactive protein serum values were not indicative to diagnose metallosis. The diagnosis was confirmed by histopathological analyses and macroscopic evaluation during surgery. Depending on the particular cause various surgical procedures have been performed. Complete prosthesis exchange was the most common one showing no complications in 89.4% of the cases.

CONCLUSIONS

Metallosis after knee arthroplasty is a rare and perhaps underestimated or under published complication. A systematic diagnostic approach is necessary for the timely and correct diagnosis. A thorough debridement as well as a (sub)total synovectomy should be always performed. In cases with a damaged component, a partial/complete prosthesis exchange leads to the best results. Should a malalignment be the cause of the metallosis, then it should be corrected within the revision surgery.

Use of a Modified Rep Model in Primary Joint Arthroplasty: Lessons Learned

Orthopedic implant device sales representatives ("reps") can provide intraoperative guidance based on their product knowledge, as part of their many responsibilities. However, for experienced high-volume arthroplasty surgeons, a representative may not be required in the room for most primary total knee arthroplasty (TKA) procedures. The goal of this study was to describe the authors' experience with a modified rep model for primary TKA. Between January and December 2017, a total of 100 unilateral primary TKAs were performed with a modified rep model and compared with 100 primary TKAs that were performed before this protocol. The authors adopted 2 additional initiatives to institute this protocol safely: (1) improved education of operating room staff and allocation of responsibilities; and (2) reengineering of the existing surgical trays. No perioperative complications, including readmission, periprosthetic fracture, or infection, occurred in either group. In addition, no difference was found in mean length of stay between the modified rep and conventional cohorts (2.2 and 2.4 days, respectively; P=.49). Mean operating room time was less with the modified rep cohort (102.1 vs 117.8 minutes; P<.001), as was total instrument turnover time in the operating room (13.9 vs 29.7 minutes; P<.0001) and in central sterilization (59.4 vs 126.8 minutes; P<.001). No errors occurred with implant accuracy or trays, and there was no need to change the type of implant with the modified rep model, compared with 6% of trays requiring additional sterilization with the conventional model. The negotiated implant cost with the modified rep model was approximately $2000 less than that for the conventional group. This study found that the modified rep model for primary TKA is safe and has the potential for substantial cost savings. [Orthopedics. 2020;43(6):e538-e542.].

Comparison Between the Attune and PFC Sigma in Total Knee Arthroplasty: No Difference in Patellar Clunk and Crepitus or Anterior Knee Pain

Patellar crepitus and clunk (PCC) is a known complication in total knee arthroplasty (TKA) and the cause of dissatisfaction. Patellofemoral articulations have reportedly been optimized in newer TKAs. This study compared the incidence of PCC between a historical and modern TKA design. A single-surgeon retrospective review of primary PFC Sigma (DePuy Synthes, Warsaw, Indiana) or Attune TKA (DePuy Synthes) was performed. A total of 114 PFC Sigma and 103 Attune implants were analyzed at a mean 3.2 years follow-up for overall PCC, painful PCC, anterior knee pain (regardless of crepitus), and PCC necessitating revision. Similar rates of overall PCC (14.6% vs 20.2%, P=.803), painful PCC (8.7% vs 6.1%, P=.605), and anterior knee pain (15.5% vs 9.7%, P=.219) were observed in the Attune and PFC Sigma groups, respectively. No clinically significant differences in range of motion, pain, or Knee Society Scores were found between groups. Subgroup analyses of mobile vs fixed bearing PFC Sigma implants demonstrated higher rates of overall PCC (32.4% vs 15.0%, P=.043), painful PCC (20.6% vs 5.0%, P=.016), anterior knee pain (17.6% vs 1.3%, P=.003), and crepitus requiring revision surgery (17.6% vs 1.3%, P=.003) for mobile bearing PFC Sigma implants. No difference was found in the rates of anterior knee pain or PCC between the PFC Sigma and Attune implants. Subgroup analysis suggests that a mobile bearing PFC Sigma implant results in higher PCC. The authors believe the true incidence of anterior knee pain and PCC is underreported in the literature because many outcome measures do not capture these complications. [Orthopedics. 2020;43(6):e508-e514.].

Association of Laminar Airflow During Primary Total Joint Arthroplasty With Periprosthetic Joint Infection

IMPORTANCE

Whether laminar airflow (LAF) in the operating room is effective for decreasing periprosthetic joint infection (PJI) after total joint arthroplasty remains a clinically important yet controversial issue.

OBJECTIVE

To investigate the association between operating room LAF ventilation systems and the risk of PJI in patients undergoing total joint arthroplasty.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective cohort study was conducted of 6972 consecutive patients undergoing primary total knee arthroplasty or total hip arthroplasty at 2 surgical facilities within a single institution from January 1, 2013, to September 15, 2017, with a minimum of 1 year of follow-up. All procedures were performed by 5 board-certified arthroplasty surgeons. Statistical analysis was performed from January 1, 2014, to September 15, 2018.

EXPOSURE

Patients underwent total joint arthroplasty in operating rooms equipped with either LAF or turbulent airflow.

MAIN OUTCOMES AND MEASURES

Patient characteristics were extracted from clinical records. Periprosthetic joint infection was defined according to Musculoskeletal Infection Society criteria within 1 year of the index arthroplasty. A multivariable logistic regression model was performed to explore the potential association between LAF and risk of PJI at 1 year, and then a sensitivity analysis using propensity score matching was performed to further validate the findings.

RESULTS

A total of 6972 patients (2797 who underwent total knee arthroplasty and 4175 who underwent total hip arthroplasty; 3690 women [52.9%]; mean [SD] age, 63.9 [10.7] years) were included. The incidence of PJI within 1 year for patients from the facility without LAF was similar to that of patients from the facility with LAF (0.4% [12 of 3027] vs 0.5% [21 of 3945]). In the multivariable logistic regression analysis, after all confounding factors were taken into account, the use of LAF was not associated with a reduction of the risk of PJI (adjusted odds ratio, 0.94; 95% CI, 0.40-2.19; P = .89). After propensity score matching, there was no significant difference in the incidence of PJI within 1 year for patients who underwent total joint arthroplasty at these 2 sites.

CONCLUSIONS AND RELEVANCE

This study suggests that the use of LAF in the operating room was not associated with a reduced incidence of PJI after primary total joint arthroplasty. With an appropriate perioperative protocol for infection prevention, LAF does not seem to play a protective role in PJI prevention.

Use of the No Tourniquet Technique in Jehovah's Witness Patients Undergoing Total Knee Arthroplasty

BACKGROUND

Many orthopedic surgeons decline to perform total knee arthroplasty on patients for whom the use of blood components are not an option due to the perceived risk of acute blood loss-related anemia and subsequent mortality. While tourniquets were previously believed to reduce blood loss during total knee arthroplasty, recent studies suggest similar volumes of blood loss and increased risk of other complications when performed with using a tourniquet. Antifibrinolytics are a safe alternative to tourniquets in reducing blood loss in total knee arthroplasty.

MATERIALS AND METHODS

The current study analyzed the use of antifibrinolytics in Jehovah's Witness patients for total knee arthroplasty performed without a tourniquet. Hemoglobin values were measured on 64 patients preoperatively, 1 hour postoperative, and 72 hours postoperatively. Relative change in hemoglobin was analyzed by the t-test.

RESULTS

The average drop in hemoglobin from preoperatively to postoperatively was 1.61 g/dl (p < 0.001). At a mean follow-up of 20 months (range: 1 to 73 months) there was one incidence of a deep vein thrombosis, one deep infection requiring a two-stage revision, and three patients requiring manipulation for stiffness. There were no pulmonary embolisms (PEs) and a 0% mortality rate.

CONCLUSIONS

Total knee arthroplasty in Jehovah's Witness patients can be done safely and efficiently using antifibrinolytic therapy without a tourniquet.

Non-invasive navigation in total knee arthroplasty : a validation study

The purpose of this study was to evaluate intraope- rative alignment during total knee arthroplasty using a handheld navigation system, iAssist, in comparison with conventional optical surgical navigation. Sixty-two consecutive patients were enrolled in this prospective study. iAssist was used to determine implant component positioning. Orientation of the cuts were verified using a conventional optical sur- gical navigation system. We compared the iAssist system with the conventional system in terms of accuracy, percentage of outliers, bias, and precision. The occurrence of component malalignment was low. Taking standard radiography as the reference, there were no relevant differences between the handheld device and optical navigation in terms of measure- ment of accuracy or in outlier occurrence. Bias was small for both technologies, and precision was comparable. The study provides preliminary evidence that the use of iAssist leads to satisfactory implant alignment. The results from this study imply that iAssist could be a viable alternative to conventional optical navigation.

Periprosthetic knee infection reconstruction with a hinged prosthesis: Implant survival and risk factors for treatment failure

BACKGROUND

Severe bone and soft tissue defects are common after failed two-stage exchange arthroplasty for periprosthetic joint infection (PJI). There is a paucity of evidence on the outcomes of using a hinged prosthesis for knee PJI reconstruction during second-stage re-implantation, especially regarding implant survivorship, reinfection risk factors, and functionality after successful reconstruction.

METHODS

A total of 58 knee PJI patients with Anderson Orthopaedic Research Institute (AORI) type II/III defect and soft tissue insufficiency underwent reconstruction with hinged prosthesis. Enrolled patients adhered to a two-stage exchange arthroplasty protocol and were evaluated for a mean follow up of 65.1 months. Kaplan-Meier analysis was conducted for implant survivorship and infection-free survival. Multivariate analysis was used to determine independent risk factors for recurrent infections. Knee Society Score (KSS) was used to evaluate functional outcomes.

RESULTS

The survivorship of hinged prosthesis was 86.2% at 2 years and 70.2% at 5 years. Infection-free analysis revealed an estimation of 68.9% at 2 years and 60.6% at 5 years. Of the 58 patients, 13 (22.4%) developed recurrent PJI, three (5.2%) aseptic loosening, and one (1.7%) periprosthetic fracture. Multivariate analysis revealed that obesity (hazard ratio (HR), 3.11), high-virulent pathogen (HR, 3.44), and polymicrobial infection (HR, 3.59) were independent risk factors for reinfection. Patients showed a mean improvement of 32.8 ± 7.7 in Knee Society Clinical Score (KSCS) and 30.8 ± 11.0 in Knee Society Function Score (KSFS) after successful reconstruction (P<0.001).

CONCLUSIONS

Using hinged knee prosthesis for PJI reconstruction provided an overall implant survival of 70.2% and an infection-free survival of 60.6% at mid-term follow up. Obesity, virulent pathogens, and polymicrobial infections were independent risk factors for infection recurrence.

Knee arthroplasty system with medialized keel: Seven-year follow-up of a pioneer cohort

BACKGROUND

In this clinical investigation, a new design with a progressive increased keel medialization according to the size was implanted. The cohort of patients was followed up for seven years.

METHODS

From May 2012 to November 2012, we implanted 70 total knee arthroplasties in 69 patients. The mean age of the patients was 76.2 years. We followed up 56 patients for seven years; we evaluated the patients at six and 60 months after surgery by Patient Reported Outcome Measures score. During the seven-year follow-up, all patients were clinically re-evaluated using the Knee Society Score and the Forgotten Joint Score. All patients underwent a preoperative and postoperative radiographic investigation. At the last follow-up the presence of any radiolucency lines was checked using the Knee Society Total Knee Arthroplasty Radiographic Evaluation and Scoring System.

RESULTS

The patients defined the surgical results as excellent in 66% of the cases, very good in 23%, good in five percent. The analysis of the functional data at seven years, performed by administering the Forgotten Joint Score, showed average values of 70.4. The clinical analysis, performed through the Knee Society Score at the same follow-up, showed average values of 90.4. The seven-year radiological analysis revealed the presence of radiolucency lines in 20 implants. The sum of the line widths never exceeded the critical value of nine millimeters, always remaining below four millimeters. Only one patient was revised.

CONCLUSIONS

The results showed an excellent outcome of this design. The medialization of the tibial keel showed good bone fixation and component alignment at seven-year follow-up.

Posterior tibial slope of the knee measured on X-rays in a Turkish population

PURPOSE

Posterior tibial inclination of the knee joint should be considered during anterior cruciate ligament reconstruction and total knee replacement surgery. This inclination is called the posterior tibial slope (PTS) angle. The PTS differs among populations and the aim of this study was to determine the mean PTS in a Turkish population.

METHODS

PTS was measured retrospectively on lateral knee X-rays (n = 1024). The angle between the line connecting the anterior and posterior points of the lateral tibial plateau and the tibial longitudinal axis was taken as the PTS angle. Intra- and inter-observer agreement regarding the measurements on 20 X-rays were checked.

RESULTS

The mean PTS angle for the entire cohort was 8.36 ± 3.3° (range: 2.1-18.7°); it was 8.57 ± 3.4° (range: 2.3-17.4°) in men and 8.16 ± 3.2° (range: 2.1-18.7°) in women. Although no significant correlation was detected between PTS and age, PTS was higher in men than in women.

CONCLUSION

The increasing number of total knee replacement surgeries has increased the need for studies on implant mismatch. In this study, reference PTS values were determined for a Turkish population. It may be beneficial to use patient-specific implants in some cases.

Dislocation of modern design rotating hinge total knee arthroplasty : case series and narrative review

Knee dislocation is an infrequent complication after rotating hinge total knee arthroplasty (RHTKA). The aim of the present study was to describe our experience with dislocating RHTKA in a consecutive prospective large series, its occurrence rate, causative mechanisms and to perform a review of available literature. In total, six dislocations were observed in 303 RHTKA procedures (NexGen RHK, ZimmerBiomet, Warsaw, Indiana, US) at a mean of 10 (range, 2 - 24) months after surgery. This results in a 2% dislocation rate, which is lower than the 3.1% cumulative rate reported earlier in literature. Men and women were distributed equally, with a mean age of 56 years old. The indication for RHTKA among the six dislocations was revision in 4 cases and primary arthroplasty for the other 2 cases. Analysis revealed that the main mechanism of hinge dislocation was forced knee flexion with concomitant extensor mechanism insufficiency (4/6 cases). The second cause was unscrewing of the locking pin (2/6 cases). This is probably caused by the screw home mechanism that results in a counterclockwise torque -and therefore a loosening- effect on locking bolts, specifically in right-sided RHTKA. Obesity probably predisposes to hinge dislocation since 83% of patients in this series were obese (BMI, range 34 to 52). The findings of this study suggest that dislocation of RHTKA is a rare complication that could happen to obsese patients without an adequate extensor mechanism. Level of evidence : IV.

Barbed suture versus traditional suture in primary total knee arthroplasty: A systematic review and meta-analysis of randomized controlled studies

BACKGROUND

Barbed suture has been widely used in some surgical fields, and it has achieved good results, but the application in total knee arthroplasty is still controversial.

OBJECTIVE

Literature is collected for statistical analysis so as to provide evidence for the use of barbed suture in Total knee arthroplasty.

METHODS

We searched PubMed, the Cochrane library and EMBASE database for randomized controlled trials (RCTs) using barbed suture and conventional suture to close incisions after primary total knee arthroplasty, and the retrieval time was from July 2019 to the establishment of the database. Literature was screened according to inclusion and exclusion criteria, quality evaluation and data extraction were conducted for the final included literature, and statistical analysis was conducted using RevMan 5.3 software.

RESULTS

A total of six RCTs (826 knees) were included in our meta-analysis. The results showed that the re-negative conversion could shorten the wound closure time (MD -4.41, 95% CI -5.11 to -3.72, P < .00001) and reduce the wound closure total cost (MD -282.61, 95% CI -445.36 to -119.85, P = .0007) and acupuncture injury (RR 0.14, 95% CI 0.03-0.78, P = .02), and did not significantly increasing the incidence of complications (RR 0.80, 95% CI 0.05-0.96, P = .38) or suture breakages (RR 4.58, 95% CI 0.16-128.29, P = .37). There were no significant differences in ROM at postoperative 6 weeks and 3 months (MD -0.74, 95% CI -4.19 to 2.71, P = .67; MD -0.30, 95% CI -2.62 to 2.02, P = .80) and no significant differences in KSS at postoperative 6 weeks (MD -0.22, 95% CI -3.10 to 2.66, P = .88).

CONCLUSIONS

Our study shows that barbed suture is a fast, low-cost, safe and effective suture method in total knee arthroplasty compared with traditional suture, we also need more literature and longer follow-up to confirm this conclusion.

Gap balancing versus measured resection in primary total knee arthroplasty: A retrospective cohort study protocol

BACKGROUND

Recently, controversy still exists regarding the clinical effects of measured resection or gap-balancing technique in total knee arthroplasty (TKA). The objective of this retrospective study was to compare the clinical outcomes of conventional measured resection technique and computer-assisted gap-balancing technique in TKA.

METHODS

Strengthening the Reporting of Observational studies in Epidemiology checklist. Patients underwent primary TKA by a single surgeon between 2014 and 2016 were reviewed. This study was approved by the institutional review board in our hospital and was registered in the Research Registry. Outcome measures included surgical time, intraoperative complications, patient satisfaction, Oxford Knee Score, range of motion, postoperative complications, and revision.

RESULTS

This study had limited inclusion and exclusion criteria and a well-controlled intervention.

CONCLUSION

We were able to directly compare the outcomes of measured resection versus gap-balancing techniques and might reveal a better technique in TKA.

TRIAL REGISTRATION

This study protocol was registered in Research Registry (researchregistry5441).

Malpositioning of patient-specific instruments within the possible degrees of freedom in high-tibial osteotomy has no considerable influence on mechanical leg axis correction

PURPOSE

Patient-specific instruments (PSIs) are helpful tools in high tibial osteotomy (HTO) in patients with symptomatic varus malalignment of the mechanical leg axis. However, the precision of HTO can decrease with malpositioned PSI. This study investigates the influence of malpositioned PSI on axis correction, osteotomy, and implant placement.

METHODS

With a mean three-dimensional (3D) model (0.8° varus), PSI-navigated HTOs were computer simulated. Two different guide designs, one with stabilising hooks and one without, were used. By adding rotational and translational offsets of different degrees, wrong placements of PSI were simulated. After 5° valgisation of the postoperative mechanical axis, the distance between joint-plane and osteotomy screws, respectively, were measured. The same simulations were performed in a patient with varus deformity (7.4° varus).

RESULTS

In the mean 3D model, the postoperative mechanical axis was within 3.9°-4.5° valgus with mean value of 4.1° ± 0.1° (correct axis 4.2° valgus). Surgical failure concerning osteotomy occurred in 17 of 76 HTOs. Significantly safer screw placement was observed using PSI with stabilising hooks (p = 0.012). In the case of the 3D model with 7.4° varus deformity, the postoperative mechanical axis was within 3.2°-3.9° valgus with mean value of 3.8° ± 0.2° (correct axis 3.9° valgus). Surgical failure concerning osteotomy occurred in 3 of 38 HTOs. Screws were always within the safety distance.

CONCLUSION

The clinical relevance of the presented study is that malpositioning of a PSI within the possible degrees of freedom does not have a relevant influence on the axis correction. The most vulnerable plane for surgical failure is the sagittal plane, wherefore the treating surgeon should verify correct guide placement to prevent surgical failure, particularly in this plane.

LEVEL OF EVIDENCE

III.

Anatomy-mimetic design preserves natural kinematics of knee joint in patient-specific mobile-bearing unicompartmental knee arthroplasty

PURPOSE

This study aims to evaluate whether different tibial-femoral conformities for patient-specific mobile-bearing unicompartmental knee arthroplasties (UKAs) preserve natural knee kinematics, using computational simulations.

METHODS

Different designs for patient-specific mobile-bearing UKAs were evaluated using finite element analysis. Three designs for the identical femoral component were considered: flat (non-conforming design), anatomy-mimetic, and conforming for the tibial insert.

RESULTS

The conforming design for the patient-specific mobile-bearing UKAs exhibited a 1.2 mm and 0.7° decrease in the translation and rotation, respectively, in the swing phase compared with those of the natural knee. In addition, the femoral rollback and internal rotation were 2.6 mm and 1.2° lower, respectively, than those of the natural knee, for the conforming design under the deep-knee-bend condition. The flat design for the patient-specific mobile-bearing UKAs exhibited a 2.2 mm and 1.4° increase in the femoral rollback and rotation compared with the natural knee under the deep-knee-bend condition. The anatomy-mimetic patient-specific mobile-bearing UKAs best preserved the natural knee kinematics under the gait and deep-knee-bend loading conditions.

CONCLUSIONS

The kinematics of the loading conditions in patient-specific mobile-bearing UKAs was determined to closely resemble those of a native knee. In additional, by replacing the anatomy-mimetic design with a mobile-bearing, natural knee kinematics during gait and deep-knee-bend motions is preserved. These results confirm the importance of tibiofemoral conformity in preserving native knee kinematics in patient-specific mobile-bearing UKA.

Total knee arthroplasty with simultaneous tibial shaft osteotomy in patient with multiple hereditary osteochondromas and multiaxial limb deformity - a case report

BACKGROUND

Hereditary multiple osteochondromas (hereditary multiple exostoses, HME) is a rare genetic disease characterized by the development of benign osteocartilaginous tumors that may cause severe limb deformities and early onset osteoarthritis. Total knee arthroplasty (TKA) is the method of choice for the treatment of advanced gonarthrosis, however the surgical management with coexisting severe axial limb deformity remains unclear.

CASE PRESENTATION

65-year-old man with HME and extra-articular multi-axial limb deformity was admitted to the orthopedic department due to chronic knee pain and limited range of motion caused by secondary osteoarthritis. Regarding to the clinical and radiological examinations, after preoperative planning he was qualified to a one-stage TKA combined with tibial shaft osteotomy (TSO). In a one year follow-up full bone union was confirmed with no signs of implant loosening or prosthesis displacement. Patient was very satisfied, did not report any joint pain and has sufficient range of motion without knee instability.

CONCLUSION

The improvement of mechanical axis during TKA is a crucial factor for achieve operative success and long implant survival. Despite the higher risk of complication rate in comparison to two-stage treatment, one-stage TKA with simultaneous TSO should be a considerable method for patients with osteoarthritis and multiaxial limb deformities. This method can give a good clinical and functional outcomes, however should be performed subsequently to careful preoperative planning and proper patient qualification.

Kinematically Aligned Total Knee Arthroplasty with Patient-Specific Instrument

Kinematically aligned total knee arthroplasty (TKA) is a new alignment technique. Kinematic alignment corrects arthritic deformity to the patient's constitutional alignment in order to position the femoral and tibial components, as well as to restore the knee's natural tibial-femoral articular surface, alignment, and natural laxity. Kinematic knee motion moves around a single flexion-extension axis of the distal femur, passing through the center of cylindrically shaped posterior femoral condyles. Since it can be difficult to locate cylindrical axis with conventional instrument, patient-specific instrument (PSI) is used to align the kinematic axes. PSI was recently introduced as a new technology with the goal of improving the accuracy of operative technique, avoiding practical issues related to the complexity of navigation and robotic system, such as the costs and higher number of personnel required. There are several limitations to implement the kinematically aligned TKA with the implant for mechanical alignment. Therefore, it is important to design an implant with the optimal shape for restoring natural knee kinematics that might improve patient-reported satisfaction and function.

Does Robotic-assisted TKA Result in Better Outcome Scores or Long-Term Survivorship Than Conventional TKA? A Randomized, Controlled Trial

BACKGROUND

Robotic-assisted TKA was introduced to enhance the precision of bone preparation and component alignment with the goal of improving the clinical results and survivorship of TKA. Although numerous reports suggest that bone preparation and knee component alignment may be improved using robotic assistance, no long-term randomized trials of robotic-assisted TKA have shown whether this results in improved clinical function or survivorship of the TKA.

QUESTIONS/PURPOSES

In this randomized trial, we compared robotic-assisted TKA to manual-alignment techniques at long-term follow-up in terms of (1) functional results based on Knee Society, WOMAC, and UCLA Activity scores; (2) numerous radiographic parameters, including component and limb alignment; (3) Kaplan-Meier survivorship; and (4) complications specific to robotic-assistance, including pin-tract infection, peroneal nerve palsy, pin-site fracture, or patellar complications.

METHODS

This study was a registered prospective, randomized, controlled trial. From January 2002 to February 2008, one surgeon performed 975 robotic-assisted TKAs in 850 patients and 990 conventional TKAs in 849 patients. Among these patients 1406 patients were eligible for participation in this study based on prespecified inclusion criteria. Of those, 100% (1406) patients agreed to participate and were randomized, with 700 patients (750 knees) receiving robotic-assisted TKA and 706 patients (766 knees) receiving conventional TKA. Of those, 96% (674 patients) in the robotic-assisted TKA group and 95% (674 patients) in the conventional TKA group were available for follow-up at a mean of 13 (± 5) years. In both groups, no patient older than 65 years was randomized because we anticipated long-term follow-up. We evaluated 674 patients (724 knees) in each group for clinical and radiographic outcomes, and we examined Kaplan-Meier survivorship for the endpoint of aseptic loosening or revision. Clinical evaluation was performed using the original Knee Society knee score, the WOMAC score, and the UCLA activity score preoperatively and at latest follow-up visit. We also assessed loosening (defined as change in the position of the components) using plain radiographs, osteolysis using CT scans at the latest follow-up visit, and component, and limb alignment on mechanical axis radiographs. To minimize the chance of type-2 error and increase the power of our study, we assumed the difference in the Knee Society score to be 25 points to match the MCID of the Knee Society score with a SD of 5; to be able to detect a difference of this size, we calculated that a total of 628 patients would be needed in each group in order to achieve 80% power at the α = 0.05 level.

RESULTS

Clinical parameters at the latest follow-up including the Knee Society knee scores (93 ± 5 points in the robotic-assisted TKA group versus 92 ± 6 points in the conventional TKA group [95% confidence interval 90 to 98]; p = 0.321) and Knee Society knee function scores (83 ± 7 points in the robotic-assisted TKA group versus 85 ± 6 points in the conventional TKA group [95% CI 75 to 88]; p = 0.992), WOMAC scores (18 ± 14 points in the robotic-assisted TKA group versus 19 ± 15 points in the conventional TKA group [95% CI 16 to 22]; p = 0.981), range of knee motion (125 ± 6° in the robotic-assisted TKA group versus 128 ± 7° in the conventional TKA group [95% CI 121 to 135]; p = 0.321), and UCLA patient activity scores (7 points versus 7 points in each group [95% CI 5 to 10]; p = 1.000) were not different between the two groups at a mean of 13 years' follow-up. Radiographic parameters such as the femorotibial angle (mean 2° ± 2° valgus in the robotic-assisted TKA group versus 3° ± 3° valgus in the conventional TKA group [95% CI 1 to 5]; p = 0.897), femoral component position (coronal plane: mean 98° in the robotic-assisted TKA group versus 97° in the conventional TKA group [95% CI 96 to 99]; p = 0.953; sagittal plane: mean 3° in the robotic-assisted TKA group versus 2° in the conventional TKA group [95% CI 1 to 4]; p = 0.612) and tibial component position (coronal plane: mean 90° in the robotic-assisted TKA group versus 89° in the conventional TKA group [95% CI 87 to 92]; p = 0.721; sagittal plane: 87° in the robotic-assisted TKA group versus 86° in the conventional TKA group [95% CI 84 to 89]; p = 0.792), joint line (16 mm in the robotic-assisted TKA group versus 16 mm in the conventional TKA group [95% CI 14 to 18]; p = 0.512), and posterior femoral condylar offset (24 mm in the robotic-assisted TKA group versus 24 mm in the conventional TKA group [95% CI 21 to 27 ]; p = 0.817) also were not different between the two groups (p > 0.05). The aseptic loosening rate was 2% in each group, and this was not different between the two groups. With the endpoint of revision or aseptic loosening of the components, Kaplan-Meier survivorship of the TKA components was 98% in both groups (95% CI 94 to 100) at 15 years (p = 0.972). There were no between-group differences in terms of the frequency with which complications occurred. In all, 0.6% of knees (four) in each group had a superficial infection, and they were treated with intravenous antibiotics for 2 weeks [corrected]. No deep infection occurred in these knees. In the conventional TKA group, 0.6% of knees (four) had motion limitation (< 60°) [corrected].

CONCLUSIONS

At a minimum follow-up of 10 years, we found no differences between robotic-assisted TKA and conventional TKA in terms of functional outcome scores, aseptic loosening, overall survivorship, and complications. Considering the additional time and expense associated with robotic-assisted TKA, we cannot recommend its widespread use.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Prediction of wear performance in femoral and tibial conformity in patient-specific cruciate-retaining total knee arthroplasty

BACKGROUND

Articular surface curvature design is important in tibiofemoral kinematics and the contact mechanics of total knee arthroplasty (TKA). Thus far, the effects of articular surface curvature have not been adequately discussed with respect to conforming, nonconforming, and medial pivot designs in patient-specific TKA. Therefore, this study evaluates the underlying relationship between the articular surface curvature geometry and the wear performance in patient-specific TKA.

METHODS

We compare the wear performances between conventional and patient-specific TKA under gait loading conditions using a computational simulation. Patient-specific TKAs investigated in the study are categorized into patient-specific TKA with conforming articular surfaces, medial pivot patient-specific TKA, and bio-mimetic patient-specific TKA with a patient's own tibial and femoral anatomy. The geometries of the femoral components in patient-specific TKAs are identical.

RESULTS

The anterior-posterior and internal-external kinematics change with respect to different TKA designs. Moreover, the contact pressure and area did not directly affect the wear performance. In particular, conforming patient-specific TKAs exhibit the highest volumetric wear and wear rate. The volumetric wear in a conforming patient-specific TKA is 29% greater than that in a medial pivot patient-specific TKA.

CONCLUSION

The findings in this study highlight that conformity changes in the femoral and tibial inserts influence the wear performance in patient-specific TKA. Kinematics and contact parameters should be considered to improve wear performance in patient-specific TKA. The conformity modification in the tibiofemoral joint changes the kinematics and contact parameters, and this affects wear performance.

Evaluation and validation of 2D biomechanical models of the knee for radiograph-based preoperative planning in total knee arthroplasty

Thorough preoperative planning in total knee arthroplasty is essential to reduce implant failure by proper implant sizing and alignment. The “gold standard” in conventional preoperative planning is based on anterior-posterior long-leg radiographs. However, the coronal component alignment is still an open discussion in literature, since studies have reported contradictory outcomes on survivorship, indicating that optimal individual alignment goals still need to be defined. Two-dimensional biomechanical models of the knee have the potential to predict joint forces and, therefore, objectify therapy planning. Previously published two-dimensional biomechanical models were evaluated and validated for the first time in this study by comparison of model predictions to corresponding in vivo measurements obtained from telemetric implants for a one- and two-leg stance. Model input parameters were acquired from weight-bearing anterior-posterior long-leg radiographs and statistical assumptions for patient-specific model adaptation. The overall time from initialization to load prediction was in the range of 7–8 minutes per patient for all models. However, no model could accurately predict the correct trend of knee joint forces over patients. Two dimensional biomechanical models of the knee have the potential to improve preoperative planning in total knee arthroplasty by providing additional individual biomechanical information to the surgeon. Although integration into the clinical workflow might be performed with acceptable costs, the models’ accuracy is insufficient for the moment. Future work is needed for model optimization and more sophisticated modelling approaches.

Utilization and Short-Term Outcomes of Computer Navigation in Unicompartmental Knee Arthroplasty

BACKGROUND

The use of navigation remains a controversial topic in knee arthroplasty. The purpose of this study is to evaluate current rates of utilization of navigation in unicompartmental knee arthroplasty (UKA) in the United States, as well as the incidence of short-term complications and operative times between navigated and non-navigated UKA.

METHODS

A query of the National Surgical Quality Improvement Project (NSQIP) database was used to identify cases of primary UKA during years 2006-2017. Additional common procedural terminology (CPT) codes were used to identify cases in which navigation was utilized. Operative time, length of stay, and short-term outcomes were compared. Propensity score matching was used to minimize differences in demographics and comorbidities between the navigation and non-navigation cohorts.

RESULTS

A total of 10,586 cases of UKA were identified; 343 of these cases (3.2%) utilized navigation. The unadjusted rate of any complication for the entire cohort was 3.6%. Navigated UKA had mean operative times 8 minutes longer than non-navigated UKA (92.1 min vs. 84.3 min; p<0.001). There was no difference in overall complication rates between the matched navigated (3.5%) and non-navigated (3.2%) cohorts (p=0.65). There was no difference in rates of readmission (0.31% vs. 0.58%; p=0.31), reoperation (0.29% vs. 0.29%; p=1.00), and mean length of stay (1.3 ± 1.6 days vs. 1.2 ± 1.9 days; p=0.15).

CONCLUSION

UKA utilizing navigation had a mean operative time 8 minutes longer than non-navigated UKA. We found no difference in rates of short-term complications, readmission, reoperation, or mean length of stay between navigated and non-navigated UKA.Level of Evidence: III.