Long-Term Survivorship and Clinical Outcomes Following Total Knee Arthroplasty

Skin Temperature Following Total Knee Arthroplasty: A Longitudinal Observational Study

BACKGROUND

Total knee arthroplasty (TKA) is the most effective method of pain relief and increased functional status for end-stage knee arthritis. We aimed to assess in patients undergoing unilateral, primary TKA whether the temperature of the operated limb, compared to the nonoperative limb, remains elevated up to 1 year postoperatively.

METHODS

Using a prospective, longitudinal, observational study design, 1,094 patients were enrolled, and 889 patients completed a minimum of 4 out of 5 follow-up appointments. There were 864 patients who had a normal postoperative course, while 25 patients were deemed to have a superficial or deep infection. Skin temperatures were measured using an infrared thermometer on the operated and nonoperated knees preoperatively, at 2, 6, 12 weeks, and 1 year postoperatively. A subgroup analysis was performed on the 25 patients deemed to have a superficial or deep infection.

RESULTS

There was a statistically significant increase in skin temperature in the operated versus nonoperated knee at every follow-up, with a P < .001. However, the effect size was small at the 1-year follow-up, with a mean difference in skin temperature of 0.3 °C. In the infected subgroup, there was a statistically significant difference in skin temperature at 2, 6, and 12 weeks, with a greater difference in skin temperature between the operated and nonoperated knees (4.05 versus 3.78 °C in the noninfected). However, there was little clinical difference (0.27 °C) at 2 weeks between infected and noninfected patients.

CONCLUSIONS

This study could improve postoperative interactions between patients and surgeons. It is normal for skin temperature post-TKA to increase initially and improve over time, but it can take up to 1 year before there is little clinical difference. Because of the small difference in the rise of skin temperature between infected and noninfected patients, there is little indication that skin temperature is a reliable indicator of infection.

Prior Patellectomy: A Systematic Review and Meta-Analysis Comparing Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty Survivorship and Reported Outcomes

BACKGROUND

In the setting of total knee arthroplasty (TKA), prior patellectomy historically prompted the use of increased constraint implants, specifically posterior-stabilized (PS) designs. However, modern case series have reported similar outcomes utilizing cruciate-retaining (CR) implants. The primary outcome of this study was to compare implant retention rates between these 2 implant designs in prior patellectomy patients. Secondary outcomes included a comparison of patient-reported outcome scores and cause for revision.

METHODS

A comprehensive systematic review was performed using Web of Science, PubMed, and Scopus databases per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Boolean operator search terms included "patellectomy AND (arthroplasty) OR (replacement)." Case reports, review articles, < 2 years of follow-up, and studies in which the implant design could not be ascertained were excluded. An initial screening of titles and abstracts for inclusion was performed, followed by a full manuscript review of eligible articles. Single-data extraction was performed, followed by subsequent statistical analysis.

RESULTS

A total of 9 studies (209 knees) met the inclusion criteria. The average time from patellectomy to TKA was 16.1 years. While all patients had significant improvement in functional outcomes, CR implants displayed proportionally greater improvement in Knee Society Scores compared to PS implants (+108 versus +98%, P ≤ .001). However, there was a significantly greater rate of revision in the CR cohort compared to PS (18.6 versus 2.6%, P = .002).

CONCLUSIONS

Prior patellectomy patients undergoing TKA have significant improvements in patient-reported functional outcomes and high midterm retention rates. While CR implant designs portend a potentially greater improvement in functional outcomes, they also have a greater risk for revision than their PS implant counterparts. However, contemporary implant designs and operative techniques likely render revision rates equivocal between CR and PS implants in postpatellectomy patients.

Long-term results of a rotationally unconstrained fixed-bearing total knee prosthesis

PURPOSE

Introduced in the market in 1990 by Ceraver (France), the posterior-stabilised (PS) Hermes prosthesis has limited literature regarding long-term survivability. The purpose of the study is to evaluate the survival and functional outcomes of the prosthesis.

METHODS

A retrospective case series was performed including 164 patients (176 knees) having undergone total knee arthroplasty with the Hermes prosthesis between 1997 and 2000 with a follow-up period of 18 years.

RESULTS

Kaplan-Meier analysis showed a survival rate of 99.4% (95% CI. 96.0-100.0%) at 18.4 years with one revision. At final follow-up, the International Knee Society (IKS) functional score was 93.2 ± 15.6 and IKS knee score was 99.1 ± 2.5.

CONCLUSION

The Hermes PS model is a low conformity prosthesis that offers reliable durability that is comparable to other popular designs while minimizing rotational constraints and having an approachable learning curve for new users.

Total knee arthroplasty survivorship and outcomes in young patients: a review of the literature and 40-year update to a longitudinal study

INTRODUCTION

Growing numbers of younger patients are electing to undergo total knee arthroplasty (TKA) for end-stage osteoarthritis. The purpose of this study was to compare established literature regarding TKA outcomes in patients under age 55, to data from an ongoing longitudinal young patient cohort curated by our study group. Further, we aimed to provide a novel update on survivorship at 40 years post-TKA from our longitudinal cohort.

METHODS

A literature search was conducted using the electronic databases PubMed, Embase, and Cochrane Library, using terms related to TKA, patients under age 55, and osteoarthritis. Demographic and outcome data were extracted from all studies that met the inclusion criteria. Data were divided into the "longitudinal study (LS) group," and the "literature review (LR) group" based on the patient population of the study from which it came.

RESULTS

After screening, 10 studies met the inclusion criteria; 6 studies comprised the LR group, and 4 studies comprised the LS group. 2613 TKAs were performed among the LR group, and 114 TKAs were longitudinally followed in the LS group. The mean patient ages of the LR and LS groups were 46.1 and 51, respectively. Mean follow-up was 10.1 years for the LR group. Mean postoperative range of motion was 113.6° and 114.5° for the LR and LS groups, respectively. All-cause survivorship reported at 10 years or less ranged from 90.6% to 99.0%. The LS cohort studies reported survivorship ranges of 70.1-70.6% and 52.1-65.3% at 30 and 40 years, respectively.

CONCLUSIONS

Young TKA patients demonstrated improved functionality at each follow-up time point assessed. Survivorship decreased with increasing lengths of follow-up, ultimately ranging from 52.1-65.3% at 40 years post-TKA. The paucity of literature on long-term TKA outcomes in this patient population reinforces the necessity of further research on this topic.

Long-term clinical and radiological outcome of a cementless titanium-coated total knee arthroplasty system

INTRODUCTION

To ensure a high-quality standard, it is important to frequently evaluate different prostheses models to avoid prostheses with high failure rates. Thus, the aim of the study was to evaluate the long-term outcome of the uncemented titanium-coated total knee arthroplasty (TKA) system (Advanced Coated System (ACS) III, Implantcast, GERMANY). We hypothesized that the ACS III would have a similar performance as other cemented TKA systems.

MATERIALS AND METHODS

A total of 540 ACS III mobile-bearing knee joint prostheses were implanted in 495 patients. The visual analogue scale (VAS) score, Tegner activity score (TAS), knee society score (KSS), Western Ontario and McMaster (WOMAC) score, and the Short Form 12 (SF-12) score for the evaluation of quality of life (QoL) were taken after at least 9 years of follow-up. In addition, we measured range of motion (ROM) and assessed potential sex differences. In addition, the survival analysis was calculated at a median follow-up of 16.7 years.

RESULTS

At the final follow-up, 142 patients had died, and 38 had been lost to follow-up. The rate of revision-free implant survival at 16.7 years was 90.0% (95% CI 87.1-92.2%) and the rate of infection-free survival was 97.0% (IQR 95.2-98.2%). The reasons for revision surgery were aseptic loosening (32.9%), followed by infection (27.1%), inlay exchange (15.9%), and periprosthetic fractures (5.7%). At the clinical follow-up visit, the mean VAS score was 1.9 ± 1.9, the median TAS was 3 (IQR 2-4), and the mean KSS for pain and function were 83.5 ± 15.3 and 67.5 ± 25.2, respectively. The mean WOMAC score was 81.1 ± 14.9, and the median SF-12 scores for physical and mental health were 36.9 (IQR 29.8-45.1) and 55.8 (IQR 46.2-61.0), respectively. The mean knee flexion was 102.0° ± 15.4°. Male patients had better clinical outcome scores than female patients [SF-12 mental health score, p = 0.037; SF-12 physical health score, p = 0.032; KSS pain score (p < 0.001), and KSS functional score (p < 0.001)].

CONCLUSION

The ACS III TKA system is a suitable option for the treatment of end-stage osteoarthritis of the knee joint because of its adequate long-term survival. Our findings are in line with published data on similar TKA systems that have shown favourable clinical scores in males.

LEVEL OF EVIDENCE

Level III-Retrospective cohort study.

Twenty-year survivorship cohort study of total knee arthroplasty in Asian patient using a single posterior-stabilized implant performed by a single surgeon

INTRODUCTION

As life expectancy has improved, the potential number of revision candidates is also expected to increase among patients who have undergone a total knee arthroplasty (TKA). The longevity of modern posterior stabilized knee prostheses after 20 years of use has not been well documented, especially in Asian populations that require a deeper flexion range due to a floor-based lifestyle.

HYPOTHESIS

Firstly, the implant longevity regarding mechanical failures such as aseptic loosening and polyethylene (PE) wear would vary over a longer follow-up depending on the age groups; and secondly there would be unique risk factors for revision surgery in an Asian TKA cohort.

MATERIAL AND METHODS

We conducted this age-stratified survival analysis in a consecutive series of 368 NexGen Legacy Posterior Stabilized (LPS) TKAs performed by a single surgeon. These cases were divided into four age groups (< 60 years, early 60s, late 60s, and ≥ 70 years). The implant longevity against aseptic mechanical failures was calculated using the Kaplan-Meier method. The revision surgery risk was evaluated using postoperative factors including a deep flexion capability (> 135̊), and postoperative mechanical alignments.

RESULTS

Overall survivorship was significantly lower in the youngest groups than other groups (Log-rank test, p=0.001). The cumulative 20-year implant longevity was more than 95% in the two oldest groups, but less than 60% in the youngest group. It was notable that the post-TKA implant longevity was not apparent up to 10 years between the age groups (p=0.073∼0.458). Aseptic loosening was observed with an earlier onset (3.1 to 18.9 years) trend than PE wear (9.8∼17.9 years), with most cases arising in the youngest groups. Flexion limitation and varus alignment were significant risks to aseptic loosening and PE wear (Cox proportional hazard regression: p=0.001 and 0.045, respectively).

DISCUSSION

A younger age (< 60 years), inability of postoperative deep flexion, and varus alignment were significant risk factors for aseptic loosening and PE wear after modern PS design in this Asian cohort. The difference in postoperative longevity affected by these factors was not obvious during the first 10 years but emerged over a second decade.

LEVEL OF PROOF

III; retrospective cohort study.

The landscape of surgical robotics in orthopedics surgery

Orthopedic surgery is one of the first surgical specialties to apply surgical robotics in clinical practice, which has become an interesting field over the years with promising results. Surgical robotics can facilitate total joint arthroplasty by providing robotic support to accurately prepare the bone, improving the ability to reproduce alignment, and restoring normal kinematics. Various robotic systems are available on the market, each tailored to specific types of surgeries and characterized by a series of features with different requirements and/or modus operandi. Here, a narrative review of the current state of surgical robotic systems for total joint knee arthroplasty is presented, covering the different categories of robots, which are classified based on the operation, requirements, and level of interaction with the surgeon. The different robotic systems include closed/open platform, image-based/imageless, and passive/active/semi-active systems. The main goal of a robotic system is to increase the accuracy and precision of the operation regardless of the type of system. Despite the short history of surgical robots, they have shown clinical effectiveness compared to conventional techniques in orthopedic surgery. When considering which robotic system to use, surgeons should carefully evaluate the different benefits and drawbacks to select the surgical robot that fits their needs the best.

Insertion of a spacer block translates the tibia anteriorly during evaluation of soft tissue balance in cruciate-retaining total knee arthroplasty

BACKGROUND

Soft tissue balance is an important determinant of the outcome of total knee arthroplasty (TKA). However, there are differences in the joint gap and ligament balance between the osteotomized femoral and tibial surfaces and those after TKA. The aim of this study was to compare the relationship between the femur and tibia at insertion of a spacer block with that after cruciate-retaining (CR) TKA.

METHODS

Thirty knees in 30 patients (26 women, 4 men) who underwent primary CR TKA with a navigation system were enrolled. Mean age at surgery was 76.3 (range, 63-87) years. After osteotomy of the femur and tibia, the flexion-extension gap and ligament balance were evaluated using a spacer block. The location of the tibial center in relation to the femoral center in the sagittal plane calculated from navigation data at insertion of an appropriately sized spacer block in knee flexion was compared with that after CR TKA using the paired t-test.

RESULTS

The mean sagittal location of the tibial center relative to the femoral center in knee flexion was 5.16 (range, -2.4, 16.3) mm at insertion of the spacer block and 6.60 (range, -1.4, 15.1) mm after CR TKA, and this difference was significant (p = 0.016).

CONCLUSION

Assessment of soft tissue balance using a spacer block in CR TKA during knee flexion changes the location of the tibia. Surgeons should be aware of the potential for overestimating the postoperative flexion gap in CR TKA when using a spacer block to assess the flexion gap.

Trends in Computer-Assisted Surgery for Total Knee Arthroplasty in Germany: An Analysis Based on the Operative Procedure Classification System between 2010 to 2021

Alignment strategies for primary total knee arthroplasty (TKA) have changed significantly over time with a shift towards a more individualized alignment goal. At the same time, computer-assisted surgery (CAS) has gained interest for intraoperative control and accuracy in implant positioning and limb alignment. Despite the often discussed benefits and drawbacks of robotics and navigation for TKA, the routine use of these new devices on a day-to-day basis remains obscure. Therefore, nationwide hospital billing data based on the Operation Procedure Classification System (OPS) were retrieved from the Federal Statistical Office of Germany for the period from 2010 to 2021. OPS codes for primary total knee arthroplasty (OPS code: 5-822*) were further analyzed regarding the usage of computer navigation (additional OPS code: 5-988) or robotic devices (additional OPS code: 5-987). Gender and age at the time of surgery were also assessed. The results show a total of 2,226,559 primary TKAs were implanted between 2010 and 2021, of which 2,044,914 were performed conventionally (91.84% of all TKAs). A total of 170,276 TKAs were performed using navigation technique (7.65% of all TKAs) and another 11,369 TKAs were performed using robotics (0.51% of all TKAs). For the period from 2018 to 2021, a substantial increase in robot-assisted TKA (R-TKA) was observed, with an average increase rate of 84.74% per year, while the number of navigated TKAs declined (-3.67% per year). Computer-assisted surgery, and particularly robotics for TKA, are seeing growing popularity and stepwise translation into routine clinical use in Germany, with a steep increase rate of more than 80% per year since 2018. Nevertheless, the majority of TKAs are still performed using manual instrumentation, rendering conventional TKA the currently unchanged gold standard.

Optimización preoperatoria del paciente antes de una artroplastia de cadera o rodilla: parte 1

Las artroplastias de cadera y rodilla son estrategias que han demostrado ser efectivas en el tratamiento de la patología degenerativa articular. El reemplazo articular mejora la calidad de vida de la mayoría de los pacientes cuando el tratamiento conservador falla. Sin embargo, estas son cirugías mayores que conllevan un riesgo significativo de complicaciones, incluyendo la necesidad de una revisión. El propósito de este artículo es analizar los factores de riesgo modificables del paciente antes de la cirugía, a finde disminuir el riesgo de complicaciones posoperatorias. Estudios recientes han descripto ciertos factores de riesgo modificables, inherentes al paciente y que incrementan la posibilidad de complicaciones posoperatorias luego de un reemplazo articular de cadera o rodilla. Estos incluyen obesidad, malnutrición, tabaquismo, diabetes, anemia, deficiencia de vitamina D, consumo de opioides, artropatías inflamatorias, insuficiencia renal crónica y colonización por estafilococco meticilino-resistente. Si conseguimos optimizar estas condiciones durante el preoperatorio, reduciremos el riesgo de complicaciones posoperatorias.

Where are We Now and What are We Hoping to Achieve with Robotic Total Knee Arthroplasty? A Critical Analysis of the Current Knowledge and Future Perspectives

Robotic-assisted total knee arthroplasty (rTKA) has been developed to improve knee kinematics and functional outcomes, expedite recovery, and improve implants long-term survivorship. Robotic devices are classified into active, semi-active, and passive, based on their degree of freedom. Their capacity to provide increased accuracy in implants positioning with reduced radiographic outliers has been widely proved. However, these early advantages are yet to be associated with long-term survivorship. Moreover, multiple drawbacks are still encountered including a variable learning curve, increased setup and maintenance costs, and potential complications related to the surgical technique. Despite recent technologies applied to TKA have failed to prove substantial improvements, robotic-assisted surgery seems to be here to stay and revolutionize the field of TKA. To support its consistent usage on a daily basis, long-term results are still awaited, and further improvements are necessary to reduce the expenses related to it.

High Survivorship of a Modular Titanium Baseplate Independent of Body Mass Index and Malalignment

BACKGROUND

Tibial component aseptic loosening remains problematic in primary total knee arthroplasty (TKA). Influential factors include component design, metallurgy, and cement technique. Additionally, reports advocate for longer tibial stem fixation in high body mass index (BMI) patients. We have utilized a single stem length modular titanium baseplate in patients regardless of BMI, bone quality, or malalignment. We report the survivorship of this implant with focus on the impact of elevated BMI and postoperative malalignment.

METHODS

We retrospectively reviewed patients who underwent TKA with a single modular titanium baseplate with a cruciate-shaped keel between 2004 and 2018. In total, 2,949 TKAs with a minimum of 1-year follow-up were included. The mean follow-up was 7 years. The primary outcome was component failure stratified by BMI and postoperative malalignment. High viscosity cement was utilized in all cases. Chi-squared and t-tests were used to compare outcome variables across groups.

RESULTS

Eighty-five implants (2.8%) were revised with 46 (1.6%) for aseptic loosening. Failure was not associated with BMI, gender, American Society of Anesthesiologists class, or Charlson Comorbidity Index. There was no difference in failure rate by BMI (P = .26) or by malalignment (outside of 3° from neutral mechanical axis) (P = .67). Age was associated with failure as patients with failed TKAs were younger (61 vs 65, P < .01).

CONCLUSION

This design of a specific modular titanium base plate with a cruciate-shaped keel and grit blast surface demonstrated 99% survivorship regardless of patient BMI or malalignment over 7-year follow-up period. Consistent cement technique with high viscosity cement indicates that component design remains an important variable impacting survivorship in TKA.

Patella Strength Characteristics in Cemented vs Press-fit Implants: A Biomechanical Analysis of Initial Stability

Background

Patellar resurfacing is routinely performed during total knee arthroplasty to reduce pain associated with patellofemoral osteoarthritis. With 3-dimensional ingrowth materials readily available, the present study aimed to evaluate if cemented polyethylene (CP) patellar buttons conferred higher ultimate load to failure than press-fit metal-backed (PF) buttons in axial compression.

Material and methods

Ten matched cadaveric and 20 composite patellae were resurfaced and implanted with either a PF or CP button. Biomechanical testing using an MTS machine was performed to measure the force required to generate a periprosthetic patella fracture. Mean load to failure and load to failure per 1-mm patellar thickness were compared with a paired and independent samples Students’ t-test for the cadaveric and composite patellae, respectively.

Results

The average load to failure for the matched cadaveric patellae with PF implants was significantly lower than that for patellae with CP buttons (4082.05 N vs 5898.37 N, P = .045). The average load to failure for composite patella with PF implants was significantly higher than that for composite patellae with CP implants (6004.09 N vs 4551.40 N, P = .001). The mean load to failure per 1-mm patellar thickness was also significantly higher for composite patellae with PF implants (263.80 N/mm vs 200.37 N/mm, P = .001).

Conclusion

Cadaveric patellae with cemented implants had a significantly higher ultimate load to failure in axial compression than press-fit patella. However, this result was reversed in the composite model. Exploration of biological and composite model properties could provide further insight into patellar implant selection during total knee arthroplasty.

Effect of two types of shoulder prosthesis on the muscle forces using a generic multibody model for different arm motions

Background

This study aims to analyze the effects of a novel dual-bearing shoulder prosthesis and a conventional reverse shoulder prosthesis on the deltoid and rotator cuff muscle forces for four different arm motions. The dual-bearing prosthesis is a glenoid-sparing joint replacement with a moving center of rotation. It has been developed to treat rotator cuff arthropathy, providing an increased post-operative functionality.

Methods

A three-dimensional musculoskeletal OpenSim® model of an upper body, incorporating a natural gleno-humeral joint and a scapula-thoracic joint developed by Blana et al. (J Biomech 41: 1714-1721, 2008), was used as a reference for the natural shoulder. It was modified by integrating first a novel dual-bearing prosthesis, and second, a reverse shoulder prosthesis into the shoulder joint complex. Four different arm motions, namely abduction, scaption, internal and external rotation, were simulated using an inverse kinematics approach. For each of the three models, shoulder muscle forces and joint reaction forces were calculated with a 2 kg weight in the hand.

Results

In general, the maximal shoulder muscle force and joint reaction force values were in a similar range for both prosthesis models during all four motions. The maximal deltoid muscle forces in the model with the dual-bearing prosthesis were 18% lower for abduction and 3% higher for scaption compared to the natural shoulder. The maximal rotator cuff muscle forces in the model with the dual-bearing prosthesis were 36% lower for abduction and 1% higher for scaption compared to the natural shoulder. Although the maximal deltoid muscle forces in the model with the dual-bearing prosthesis in internal and external rotation were 52% and 64% higher, respectively, compared to the natural shoulder, the maximal rotator cuff muscle forces were 27% lower in both motions.

Conclusion

The study shows that the dual-bearing shoulder prosthesis is a feasible option for patients with rotator cuff tear and has a strong potential to be used as secondary as well as primary joint replacement. The study also demonstrates that computer simulations can help to guide the continued optimization of this particular design concept for successful clinical outcomes.

SMOC approach for total knee arthroplasty in valgus knees

Objective

This study was performed to compare clinical outcomes among patients with valgus knees undergoing total knee arthroplasty via the medial parapatellar approach and the subvastus with minimal oblique cut approach.

Methods

A total of 232 patients (246 knees) undergoing total knee arthroplasty between December 2014 and December 2016 were retrospectively included in the investigation. The study population consisted of 120 patients (128 knees; 32 men and 88 women) with a mean age of 62.43 ± 8.12 years treated via the medial parapatellar approach, and 112 patients (118 knees; 30 men and 82 women with a mean age of 63.15 ± 7.83 years) treated via the subvastus with minimal oblique cut approach. Nine preoperative parameters (number of patients, sex, age, body mass index, number of knees, valgus angle, visual analogue scale score, range of motion, Hospital for Special Surgery score), five perioperative parameters (operative time, amount of drainage, Visual analogue scale score at 24 h after the operation, time to straight leg raising, radiological alignment), and two postoperative parameters (range of motion, Hospital for Special Surgery score) were assessed at 1 day, 1 week, 6 weeks, 8 weeks and 1 year after the operation, along with postoperative complications.

Results

There were no significant differences in the nine preoperative parameters between the two groups. The subvastus with minimal oblique cut group had a longer operative time, while the parapatellar approach group showed more drainage and a higher mean Visual analogue scale score. Compared to the medial parapatellar group, the subvastus with minimal oblique cut group had a shorter time to straight leg raising. There were no differences in radiological alignment between the two groups. The groups showed similar range of motion and Hospital for Special Surgery scores at 8 weeks and 1 year, but both were higher in the subvastus with minimal oblique cut group at 1 day, 1 week and 6 weeks. During postoperative follow-up, postoperative subluxation of the patella occurred in five cases in the medial parapatellar group. Neither group showed any instability, recurrent valgus deformity or radiographic loosening.

Conclusion

The subvastus with minimal oblique cut approach provides excellent early recovery for total knee arthroplasty of valgus knees with no increase in complications.

A Comparison of Clinical Outcomes and Implant Preference of Patients with Bilateral TKA: One Knee with a Patient-Specific and One Knee with an Off-the-Shelf Implant

BACKGROUND

The purpose of this retrospective study was to compare clinical outcome results, perceived function, and overall preference among patients who had undergone staged bilateral total knee arthroplasty (TKA) with a cruciate-retaining, customized implant (customized TKA, or C-TKA) in 1 knee and an off-the-shelf (OTS) implant in the contralateral knee.

METHODS

Forty-seven patients (94 knees) from a single study center who underwent C-TKA in 1 knee and had previously undergone TKA with an OTS implant in the contralateral knee were included in this study. As the primary outcome measures, the Knee injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR) and the Forgotten Joint Score (FJS) were self-administered by the study subjects at a single follow-up time point. Additionally, a follow-up questionnaire to compare patients' perceived joint stability, knee mobility, perceived feeling of the replaced joint, pain levels, and overall preference between their knees was administered.

RESULTS

The average follow-up was 2.3 years (range, 0.7 to 3.8 years) for C-TKA and 6.7 years (range, 1.6 to 11.1 years) for the OTS TKA. Significantly higher KOOS, JR (82 versus 77; p = 0.03) and FJS (68 versus 58; p = 0.04) results were found with C-TKA. The evaluation of the follow-up questionnaire showed that more patients reported having "a little" or "a lot" less pain (49% versus 15%), better perceived mobility (45% versus 12%) and stability (36% versus 13%), and a more "normal" feeling of their knee (60% versus 10%) with the C-TKA implant compared with their OTS counterpart. When patients were asked to directly compare their knees, we found that 72.3% of the patients preferred the knee that received C-TKA over the contralateral OTS knee replacement, with 21.3% seeing no difference and 6.4% preferring the OTS knee replacement.

CONCLUSIONS

We believe that this is the first study to examine patient-reported outcomes of customized and OTS TKA implant designs in the same patient. We conclude that patients in this study cohort who underwent staged bilateral TKA with a C-TKA implant in 1 knee and an OTS prosthesis in the other knee reported better for their patient-specific knee replacement, with higher FJS and KOOS, JR values, and overall, preferred the C-TKA knee more often compared with the OTS knee replacement.

LEVEL OF EVIDENCE

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

Outcomes of total knee replacement with the use of a NexGen MIS Tibial Component (Mini-keel) : a systematic review

NexGen MIS Tibial Component (Mini-keel) is a tibial component specially developed for minimally invasive surgery in total knee replacement (TKR), and the size limitations of its design and the modular system could affect tibial fixation strength, however, this has not been precisely evaluated thus far. This study aimed to systematically review the literature describing the outcome following TKR with the use of a Mini-keel. Electronic searches of databases were undertaken in July 2019 by two experienced orthopaedic surgeons according to the PRISMA guidelines for literature describing the outcomes of TKR with the use of a Mini-keel. Quality of studies was assessed using the Joanna Briggs Institute Critical Appraisal Checklist. The initial search found a total of 623 studies from all the databases. Seven studies met all the inclusion criteria and were eligible for critical appraisal and quality assessment. In total, 2,198 cases were included in the systematic review. Thirty-five revision cases due to aseptic loosening were found from the systematic review. Two studies were negative about using a Mini-keel and three studies were positive about it, while the other two studies did not judge the quality of a Mini-keel. There have been conflicting conclusions among studies for the use of a Mini-keel. There remains a paucity of prospective cohort studies between TKRs with the use of a Mini-keel and those with the use of a conventional implant, which makes it difficult to determine the usefulness and reliability of this implant.

Effects of the Medial Plateau Bearing Insert Conformity on Mid-Flexion Paradoxical Motion in a Posterior-Stabilized Total Knee Arthroplasty Design

BACKGROUND

One of the most common kinematic abnormalities reported for posterior-stabilized (PS) total knee arthroplasty (TKA) design is paradoxical anterior sliding during early and mid-flexion. PS TKAs have been designed such that the cam-post mechanism does not engage until later in flexion, making these implants vulnerable to anterior sliding during early and mid-flexion. The objective of this study is to investigate the biomechanical effect of increasing bearing conformity on a PS TKA.

METHODS

Using a validated computational model of the knee joint, the sagittal conformity of the medial plateau of a PS TKA design was altered. Three scenarios were created and evaluated for mechanics: (1) baseline conformity, (2) increased conformity, and (3) decreased conformity.

RESULTS

From full extension to approximately 70° of knee flexion, the medial condyle demonstrated minimal anterior sliding for the increased medial conformity design but revealed anterior sliding of 2 and 4 mm for the baseline and decreased conformity designs, respectively. After cam-post engagement, the medial condyle consistently rolled back for all 3 designs. The lateral condyle experienced consistent rollback throughout the entire flexion range for all 3 designs. However, femorotibial contact force was higher for the increased conformity design, peaking at 3.13 times body weight (×BW) compared to 3.0 × BW contact force for other 2 designs.

CONCLUSION

Increasing medial conformity of the bearing insert appears to reduce mid-flexion sliding for PS TKA designs, although this comes at the expense of increased femorotibial forces. This could be due to kinematic conflicts that may be introduced with highly constraining designs.

The Association Between Cement Viscosity and Revision Risk After Primary Total Knee Arthroplasty

BACKGROUND

Recent case series have reported early failure with the use of high-viscosity cement (HVC) in total knee arthroplasty (TKA). We evaluated revision risk after TKA with HVC compared with medium-viscosity cement (MVC) in a large cohort.

METHODS

We conducted a cohort study using data from Kaiser Permanente's Total Joint Replacement Registry. Patients who underwent fully cemented primary TKA for osteoarthritis were identified (2001-2018). Only posterior-stabilized, fixed-mobility designs of the 3 highest-volume implant systems (DePuy PFC, Zimmer NexGen, and Zimmer Persona) were included to mitigate confounding from implant characteristics. Palacos (Zimmer/Heraeus) and Simplex (Stryker) cements comprised the HVC and MVC exposure groups, respectively. Propensity score-weighted Cox proportional hazards regression was used to evaluate risk for any revision during follow-up and risk for revision from aseptic loosening specifically.

RESULTS

The final cohort comprised 76,052 TKAs, 41.1% using MVC. The crude 14-year cumulative revision probability was 4.55% and 5.12% for TKA with MVC and HVC, respectively. In propensity score-weighted Cox models, MVC compared with HVC had a lower risk of any revision (hazard ratio = 0.82, 95% confidence interval = 0.70-0.95) while no difference was observed for revision from aseptic loosening (hazard ratio = 0.80, 95% confidence interval = 0.56-1.13).

CONCLUSION

While we observed a lower risk for any revision with the use of Simplex MVC compared with Palacos HVC, we did not observe a difference in revision for aseptic loosening specifically. Given the widespread use of HVC, additional research to investigate other HVC and potential mechanisms for failure outside of loosening is warranted.

LEVEL OF EVIDENCE

Level III.

Increased rate of complications in myasthenia gravis patients following hip and knee arthroplasty: a nationwide database study in the PearlDiver Database on 257,707 patients

Background and purpose - The increasing prevalence of total hip arthroplasty (THA) and total knee arthroplasty (TKA) within the growing elderly population is translating into a larger number of patients with neuromuscular conditions such as myasthenia gravis (MG) receiving arthroplasty. We compared systemic and joint complications following a THA or TKA between patients with MG and patients without MG.Patients and methods - Patient records were queried from PearlDiver (Pearl Diver Inc, Fort Wayne, IN, USA), an administrative claims database, using ICD-9/ICD-10 and Current Procedural Terminology codes. In-hospital and 90-day post-discharge rates of systemic and joint complications were compared between the 2 cohorts.Results - 372 patients with MG and 249,428 patients without MG who received a THA or TKA were included in the study. At 90 days post-discharge, MG patients exhibited exhibited between 1.6 and 15% higher rates of systemic complications, including cerebrovascular event, pneumonia, respiratory failure, sepsis, myocardial infarction, acute renal failure, anemia, and deep vein thrombosis (all p < 0.001). The same results were also found during the in-hospital time period. 90-day incidence of aseptic loosening was the only joint complication with significantly increased odds risk for the MG cohort (OR 5; 95% CI 2-12).Interpretation - Patients with MG exhibited significantly higher risk for multiple systemic complications during the index hospital stay and in the acute post-discharge setting.

Efficacy and safety of duloxetine for postoperative pain after total knee arthroplasty in centrally sensitized patients: study protocol for a randomized controlled trial

Background

Postoperative residual knee pain after total knee arthroplasty (TKA) is a significant factor that contributes to patient dissatisfaction. Patients with preoperative central sensitization (CS) may be more susceptible to unexplained chronic pain after TKA, and duloxetine has been reported to be effective in post-TKA pain control in patients with CS. However, there remains limited evidence to support this off-label use in routine clinical practice. Hence, we designed this randomized, placebo-controlled, triple-blind clinical trial to evaluate the effects of preoperative screening and targeted duloxetine treatment of CS on postoperative residual pain compared with the care-as-usual control group.

Methods

This randomized controlled trial includes patients with knee osteoarthritis on a waiting list for primary unilateral TKA. Patients with preoperative CS will be randomly allocated to the perioperative duloxetine treatment group (duloxetine group) or the care-as-usual control group (placebo group). Patients in the duloxetine group will receive a half-dose of preemptive duloxetine (30 mg/day) for a week before surgery and a full-dose of duloxetine (60 mg/day) for six weeks after surgery. The primary outcome is the intensity of residual pain at six months after TKA, including the visual analogue scale, 11-point numeric rating scale, the sensory dimension of the brief pain inventory, and the pain subscale of the Knee injury and Osteoarthritis Outcome Score. The secondary outcome measures will include the pain and function related outcomes. All of the patients will be followed up at one, three, and six months after surgery. All adverse events will be recorded and immediately reported to the primary investigator and ethics committee to decide if the patient needs to drop out from the trial.

Discussion

This clinical trial will convey the latest evidence of the efficacy and safety of the application of duloxetine in postoperative pain control in CS patients who are scheduled for TKA. The study results will be disseminated at national and international conferences and published in peer-reviewed journals.

Trial registration

Chinese Clinical Trial Registry (http://www.chictr.org.cn) registration number: ChiCTR2000031674. Registered 07 April 2020.

Knee Flexion Angle Following Total Knee Arthroplasty Relates to a Preoperative Range of Motion of the Hip

BACKGROUND

Many factors have been reported to affect postoperative range of knee flexion after total knee arthroplasty (TKA); however, no study has reported the impact of preoperative range of motion of the hip to the postoperative flexion angle of the knee thus far.

METHODS

Of 38 consecutive patients who underwent posterior-stabilized TKA, we assessed 21 patients after excluding 17 patients who met exclusion criteria. The range of motion of the knee and the hip, age, body-mass index, serum albumin level, HbA1c, Kellgren-Lawrence grade, knee extension strength and radiological femorotibial angle as well as postoperative knee flexion angle at three months were evaluated. The preoperative data and the knee flexion angle at three months after TKA were compared using Spearman's rank correlation coefficient.

RESULTS

Knee flexion angle at three months after TKA was positively correlated with preoperative flexion (ρ = 0.616, p = 0.007) and external rotation angle (ρ = 0.576, p = 0.012) of the hip as well as preoperative knee flexion angle (ρ = 0.797, p = 0.001). There were no correlations between postoperative knee flexion angle and other preoperative data.

CONCLUSIONS

Patients with restricted flexion and/or external rotation of the hip may have contractures of Gluteus maximus, Gluteus medius and Tensor fasciae latae, which can cause hypertension of iliotibial tract. It may cause decreased internal rotation of the tibia when the knee is flexed, which affects postoperative knee flexion angle, thus limited flexion and/or external rotation of the hip might restrict knee flexion angle following TKA.

Minimally invasive surgery total knee arthroplasty is less popular, but the prosthesis designed specifically for MIS provides good survival and PROMs with a minimum follow-up of 10 years

BACKGROUND

The concept of minimally invasive surgery (MIS) was introduced in total knee arthroplasty (TKA) in the late 1990s. The number of MIS TKAs has clearly decreased in recent years. An implant designed specifically for MIS TKA has been used all over the world, but there are no reports of long-term postoperative results. The purpose of this study was to characterize long-term clinical results with a minimum follow-up of 10 years.

METHODS

This retrospective study included 109 consecutive patients with 143 NexGen CR-Flex prostheses, which are MIS tibial component prostheses designed specifically for MIS TKA. Twelve-year survival analysis was performed using Kaplan-Meier method. Revision surgery for any reason was the endpoint. Long-term clinical and radiographic results of 74 knees (55%) in 60 patients with more than 10 years of follow-up were analyzed.

RESULTS

The cumulative survival rate of the single-radius posterior-stabilized TKA of 74 knees was 94.7% (95% confidence interval, 90-99%) at 12 years after surgery. Seven knees (9%) required additional surgery during the 10-year follow-up because of periprosthetic infections. Mean postoperative Knee Society knee score and functional score were 91 and 74 points, respectively. There were no cases of prosthesis breakage, polyethylene wear, or aseptic loosening of the prosthesis.

CONCLUSION

The prosthesis designed specifically for MIS TKA is associated with good survival and clinical results with a minimum follow-up of 10 years, even though MIS TKA has become less popular.

LEVEL OF EVIDENCE

III.

Use of Simple Geometry to Predict Changes in Coronal and Sagittal Alignments Using an Extramedullary Tibial Cutting Guide During Total Knee Arthroplasty

During total knee arthroplasty, balancing is necessary for long-term stability and longevity of implants as improper balancing leads to abnormal surface strain. A routine practice among surgeons is to add more posterior slope to the proximal tibia to provide an increase in the flexion gap to balance the knee throughout the entire range of motion, particularly when doing cruciate-retaining knees. The aim of this technique guide is to provide a simple estimate of the posterior slope added or subtracted when cutting the proximal tibia using a standard extramedullary guide.  It can also be applied to predict the amount of coronal change instituted using a standard extramedullary drop guide. Using a few basic calculations with a sine equation, a surgeon can accurately predict the amount of change in the slope applied when cutting the proximal tibia. This can be done to control the degree of slope added to the anterior-posterior direction and can be used to predict coronal alignment changes as well. This technique can be applied to any length extramedullary guide and applied across all companies to provide surgeons with an exact degree change in the tibial slope and coronal alignment with simple calculations.

Not All Robotic-assisted Total Knee Arthroplasty Are the Same

Because value in healthcare has shifted to a measurement of quality relative to the cost, a greater emphasis exists on improving clinical and functional outcomes and patient satisfaction. Despite advances in implant design, surgical technique, and postoperative rehabilitation, multiple studies demonstrate that nearly 20% of patients remain dissatisfied with their overall outcomes after primary total knee arthroplasty (TKA). Because implant positioning, alignment, and equal soft-tissue balance are critical for a successful TKA, malalignment in the coronal, sagittal, and rotational planes continue to increase failure rates and cause poor clinical outcomes. Robotic-assisted TKA has gained momentum within the past 10 years to better control surgical variables by mitigating technical errors caused by insecure cutting guides and imprecise bone cuts. Contemporary robotic platforms have evolved along with our ability to collect high-quality patient-reported outcome measures data, and this combination is proving the clinical effectiveness. This comprehensive review investigates the advent of robotic-assisted TKA including advantages, disadvantages, historical, and commercially available newer generation systems, clinical outcomes, and cost analysis to better understand the potential added value of this technology.

Robotic Total Knee Arthroplasty vs Conventional Total Knee Arthroplasty: A Nationwide Database Study

Background

As robot-assisted equipment is continuously being used in orthopaedic surgery, the past few decades have seen an increase in the usage of robotics for total knee arthroplasty (TKA). Thus, the purpose of the present study is to investigate the differences between robotic TKA and nonrobotic TKA on perioperative and postoperative complications and opioid consumption.

Methods

An administrative database was queried from 2010 to Q2 of 2017 for primary TKAs performed via robot-assisted surgery vs non-robot-assisted surgery. Systemic and joint complications and average morphine milligram equivalents were collected and compared with statistical analysis.

Results

Patients in the nonrobotic TKA cohort had higher levels of prosthetic revision at 1-year after discharge (P < .05) and higher levels of manipulation under anesthesia at 90 days and 1-year after discharge (P < .05). Furthermore, those in the nonrobotic TKA cohort had increased occurrences of deep vein thrombosis, altered mental status, pulmonary embolism, anemia, acute renal failure, cerebrovascular event, pneumonia, respiratory failure, and urinary tract infection during the inpatient hospital stay (all P < .05) and at 90 days after discharge (all P < .05). All of these categories remained statistically increased at the 90-days postdischarge date, except pneumonia and stroke. Patients in the nonrobotic TKA cohort had higher levels of average morphine milligram equivalents consumption at all time periods measured (P < .001).

Conclusions

In the present study, the use of robotics for TKA found lower revision rates, lower incidences of manipulation under anesthesia, decreased occurrence of systemic complications, and lower opiate consumption for postoperative pain management. Future studies should look to further examine the long-term outcomes for patients undergoing robot-assisted TKA.

Level of Evidence

Level III.

Robotic-assisted total knee arthroplasty is comparable to conventional total knee arthroplasty: a meta-analysis and systematic review

BACKGROUND

Total knee arthroplasty (TKA) is a successful procedure in managing end-stage arthritis when non-operative treatments fail. New technologies such as robotic TKA (rTKA) have been developed to improve the accuracy of prosthesis implantation. While short-term cohort studies on rTKA have shown excellent results, the evidence comparing between rTKA and conventional TKA (cTKA) is not yet well established. This meta-analysis aims to compare the efficacy and safety of rTKA versus cTKA in terms of clinical outcomes, radiographic results, complications, peri-operative parameters and costs.

METHODS

A multi-database search was performed according to PRISMA guidelines. Data from studies comparing between rTKA and cTKA were extracted and analyzed.

RESULTS

Eighteen studies were included in this review, consisting of 2234 rTKA and 4300 cTKA. Robotic TKA led to a more precise prosthesis implantation with significantly fewer outliers in the mechanical axis (p < 0.001), femoral coronal (p = 0.002) and tibial sagittal (p = 0.01) alignments. Only the Hospital for Special Surgery (HSS) (p < 0.001) score at final follow-up was significantly better in rTKA than cTKA. rTKA also had a lower mean blood loss (p < 0.001) despite a longer mean operation time (p = 0.006). There were no statistically significant difference in terms of other clinical outcome measures, range of motion and complications.

CONCLUSION

Both rTKA and cTKA are reliable and safe to perform. However, rTKA is capable of achieving superior alignment in several axes, lower mean blood loss and this may lead to marginally better clinical outcomes than cTKA.

EVIDENCE LEVEL

Level II, Meta-analysis of non-homogeneous studies.

Revision total knee arthroplasty for patellar dislocation in patients with malrotated TKA components

PURPOSE

Patellar dislocation is a serious complication leading to patient morbidity following total knee arthroplasty (TKA). The cause can be multifactorial. Extensor mechanism imbalance may be present and result from technical errors such as malrotation of the implants. We sought to understand the reasons for post-arthroplasty patellar dislocation and the clinical outcomes of patients in whom it occurs.

METHODS

This is a retrospective cohort study assessing the outcomes of revision surgery for patellar dislocation in patients with component malrotation in both primary and revision TKAs. Patient demographics, dislocation etiology, presurgical deformity, intraoperation component position, complications, reoperation, and Knee Society Scores (KSS) were collected.

RESULTS

Twenty patients (21 knees) were identified. The average time from primary arthroplasty to onset of dislocation was 33.6 months (SD 44.4), and the average time from dislocation to revision was 3.38 months (SD 2.81). Seventeen knees (80.9%) had internal rotation of the tibial component and seven knees (33.3%) had combined internal rotation of both the femoral and tibial components. Fifteen knees (71.4%) were treated with a condylar constrained implant at the time of revision, and five knees were converted to a hinged prosthesis. The average follow-up time was 56 months. During this time, one patient (4.54%) had a recurrent dislocation episode, requiring further surgery. At final follow up, the mean KSS was 86.2.

CONCLUSION

Revision TKA following patellar dislocation for patients with malrotated components was associated with high success rates. After revision surgery, patients had a low recurrence of patellar dislocation, low complication rates, and excellent functional outcomes.

Using Cluster Analysis to Identify Patient Factors Linked to Differential Functional Gains After Total Knee Arthroplasty

BACKGROUND

The basis of poor outcomes following total knee arthroplasty (TKA) is multifactorial. Previous research aimed at predicting outcome following TKA focuses largely on outcomes measured between two specific time points (pre-to post-TKA). Analysis of outcomes measured over multiple time points (trajectory) may expose relationships between patients' characteristics and longitudinal outcome patterns that may otherwise remain obscured.

METHODS

The current study analyzed Short Form 36 Physical Component Score (PCS) trajectories of 656 patients composed of 3 time points over a 1-year period. Clusters were constructed utilizing MultiExperiment Viewer hierarchical clustering algorithm. Statistical significance of these clusters was assessed using MeV's built-in bootstrapping method. Patient characteristics of the resulting statistically conserved clusters were summarized and compared using Wilcoxon rank-sum test or chi-squared test as appropriate.

RESULTS

Two distinct clusters of outcome trajectory were identified. Cluster 1 included 550 patients (84%) who demonstrated persistent PCS improvement at 6 and 12 months. Cluster 2 included 106 patients (16%) who demonstrated decline in PCS at 6 months followed by improvement at 12 months. Cluster 1 achieved earlier success, greater absolute mental and physical health scores as compared to Cluster 2 (P < .05), and demonstrated higher baseline mental health scores, lower baseline PCS, and a significantly higher proportion of non-Hispanic Whites (P ≤ .05).

CONCLUSION

Cluster analysis identified distinct functional outcome trajectories following TKA. Specific differentiating patient factors were associated with differing trajectories. Future studies should focus on this method's ability to inform predictive models regarding patient outcomes.

Long-Term Implant Survivorship and Modes of Failure in Simultaneous Concurrent Bilateral Total Knee Arthroplasty

BACKGROUND

There is limited evidence describing long-term implant survivorship and modes of failure in simultaneous concurrent bilateral total knee arthroplasty (TKA).

METHODS

We performed a retrospective review of 266 consecutive patients (532 knees) who underwent simultaneous concurrent bilateral TKA. We reviewed medical records for preoperative characteristics, perioperative complications, and revision surgeries. The primary outcome was TKA survivorship. Secondary outcomes included indication and type of revision surgery. We used the Kaplan-Meier method to estimate survivorship and characterize risk of revision up to 20 years post-TKA.

RESULTS

Our cohort had median follow-up of 9.8 years (interquartile range, 3.9-15.9). Forty-four patients (17%) underwent revision. Revision was more common among younger and male patients. The cumulative incidence of first-time revision per knee (n = 532) was 1.27 per 100 component-years. Implant survival was 99% (confidence interval, 97%-99%) at 5 years, 92% (89%-95%) at 10 years, 83% (77%-87%) at 15 years, and 62% (50%-73%) at 20 years. Five and 10-year survivorship compared favorably to estimates of TKA survivorship in the literature. The cumulative incidence of revision surgery per patient was 1.91 per 100 component-years. Implant survival at 5-, 10-, 15-, and 20-year time points was 96% (CI, 92%-98%), 84% (77%-89%), 71% (62%-79%), and 59% (46%-70%), respectively. Aseptic loosening (40%), polyethylene wear (34%), and infection (11%) were the most common indications for revision.

CONCLUSION

Simultaneous concurrent bilateral TKA is associated with a higher risk of reoperation for the patient when both knees are evaluated but similar implant survivorship to the literature when each knee was evaluated in isolation.

Outcomes and component-positioning in total knee arthroplasty may be comparable between supervised trained surgeons and their supervisor

PURPOSE

There are concerns that malalignment in total knee arthroplasty (TKA) occurs with less experienced surgeons. This study investigates the influence of surgical experience on TKA outcomes.

MATERIALS AND METHODS

Nineteen patients (38 knees) who underwent bilateral TKA between 2011 and 2015 were included. A supervisor performed knee replacements associated with lower Knee Society Scores (KSS); trainee surgeons operated on the other knee. Knees were categorized into two groups: operations by the supervisor (group S) versus operations by trainee surgeons (group T). Range of motion (ROM), KSS, operative time, hip-knee-ankle angle, and femoral and tibial component angle were evaluated.

RESULTS

The mean operative time was 92.5 min in group S and 124.2 min in group T (p < 0.01). The mean postoperative maximal flexion was 113.2° in group S and 114.2° in group T (not significant). The mean postoperative KSS was 92.9 in group S and 93.9 in group T (not significant). No significant differences between groups in terms of proportion of inliers for the hip-knee-ankle angle, femoral component angle, or tibial component angle were observed.

CONCLUSIONS

Although operative time was significantly longer for trainee surgeons versus the supervisor, no significant differences in ROM, KSS, or component positioning between supervisor and trainee surgeons were observed.

LEVEL OF EVIDENCE

IV (retrospective case series design).

Intraoperative analysis of the kinematics of the native knee including two-dimensional translation of the femur using a navigation system : a cadaveric study

The aim of this cadaveric study was to evaluate the intraoperative kinematics of the native knee including two-dimensional translation of the femur using a navigation system. Eight native knees of 4 fresh-frozen whole-body cadavers were used for the study. The kinematics of each knee were analyzed intraoperatively using the navigation system. Although anterior-posterior translation could not be assessed directly, it could be calculated using a formula derived from the parameters in the navigation system. The native knee showed external rotation of the femur in early knee flexion, transient internal rotation in mid flexion, and gradual external rotation in late flexion. There was no marked change in the coronal rotation angle of the mechanical axis during knee flexion. The femoral center moved anteriorly in early knee flexion and posteriorly in late flexion. The distance moved in the medial-lateral direction was relatively smaller than that in the anterior-posterior direction. Two-dimensional translation of the surgical epicondylar axis showed a medial pivot-like motion. In this cadaveric study, the kinematics of the native knee, including two-dimensional translation of the femur, could be satisfactorily assessed intraoperatively using a navigation system. The intraoperative kinematics of the knee can be analyzed in more detail using this methodology. J. Med. Invest. 66 : 367-371, August, 2019.

When can I go home after my knee replacement? Factors affecting the duration of in-hospital stay after knee replacement

BACKGROUND

Despite a sevenfold decline in the number of postoperative nights (21-3) after a total knee arthroplasty (TKA) over the last four decades, predictors of length of stay (LOS) are not fully understood. We attempted to ascertain these factors by analyzing a large cohort of patients.

METHODS

Prospectively collected data between January 2016 and March 2017 were retrospectively analyzed at our institute. Charts of 1663 consecutive, simple primary unilateral and bilateral TKAs were reviewed for the LOS excluding staggered bilateral, complex primary and revision knees.

STATISTICAL ANALYSIS

Preoperative variables [demographics, cash/credit status, historical, clinical, laboratory findings, Knee Society Function Scores and Oxford Knee Scores (OKSs)] were scrutinized by multivariate regression to identify significant factors affecting LOS and formulate model equations for patients and health caregivers. Results were incorporated into an iOS application, which was tested for accuracy.

RESULTS

Among 1524 unilateral and 139 bilateral TKAs, mean LOS was 4.4 and 5.2 days, respectively. Five factors, namely insurance, flexion/hyperextension deformity, preoperative OKS and a rheumatoid etiology, were significantly associated with prolonged LOS in unilateral knees. The impact of these independent variables on LOS could be calculated by: [Formula: see text]For bilateral cases, the only significant variable extending LOS was a low preoperative OKS and the equation is given as follows: [Formula: see text]The iOS-app-predicted LOS and actual LOS were similar (p > 0.05) for 115 prospectively operated knees.

CONCLUSION

Poor preoperative OKS, rheumatoid etiology, flexion and hyperextension deformity and delays in insurance affected unilateral TKR LOS, while poor preoperative OKS alone affected LOS in bilateral cases.

The relationship between lower extremity swelling, quadriceps strength, and functional performance following total knee arthroplasty

BACKGROUND

The relationships between swelling after total knee arthroplasty (TKA) and quadriceps strength and functional performance are poorly understood. Therefore, the aim of this study was to examine the relationships between lower extremity swelling, measured using bioelectrical impedance assessment (SF-BIA), and quadriceps strength and timed up and go (TUG) times following TKA.

METHODS

53 participants (64 ± 9.5 y/o, 43% male) undergoing primary unilateral TKA were recruited for the longitudinal observational study with repeated measures. Quantities of swelling were examined for contribution to two and six-week outcomes of strength and TUG time using hierarchical regression controlling for age, sex, and the baseline value of the dependent variable. Swelling was assessed using bioelectrical impedance assessment and quantified as the peak level of swelling and cumulative swelling (integral) over the post-TKA time window. Maximum isometric quadriceps strength (MVIC) was measured using a electromechanical dynamometer and participant functional performance measured using the TUG.

RESULTS

Neither peak swelling nor cumulative swelling significantly contributed to the variance of two-week quadriceps strength. At six weeks, peak swelling significantly improved the variance in maximal quadriceps strength by an additional four percent (p = 0.05), while cumulative swelling did not significantly contribute. Peak swelling significantly contributed to the variance in two-week (16%) and six-week (five percent) TUG times (p < 0.05), but the cumulative swelling did not.

CONCLUSIONS

Peak swelling represents a value of post-TKA swelling that is associated with strength and function. Reducing the peak level of swelling, occurring early after surgery, may improve patient functional recovery.

LEVEL OF EVIDENCE

Level II - Prospective observational study.

Risk factors for ileus after hip and knee arthroplasty

PURPOSE

Postoperative ileus (POI) is one of the complications that can occur after every surgical procedure including arthroplasty. It can have detrimental consequences for the patient and portrays an economic burden on health care systems. The risk factors for POI after arthroplasty described in the literature are scarce and include hip arthroplasty, male gender and previous abdominal surgery. The purpose of the study was to determine the risk factors for POI after hip and knee arthroplasty.

METHODS

A retrospective review of 2760 patients undergoing primary hip and knee arthroplasty was performed. An in-depth analysis of patient history and physical operative and postoperative course was reviewed and statistically analyzed in a univariate and multivariate setting.

RESULTS

Overall incidence of POI was 0.54%. History of myocardial infarction and chronic kidney disease were statistically significant risk factors for developing POI after arthroplasty with values of p = 0.023 and p = 0.004, respectively. Other risk factors included previous abdominal surgery (p < 0.001) and hip arthroplasty (p = 0.026). Age or gender correlations were not observed.

CONCLUSIONS

Although postoperative ileus is an uncommon complication after joint arthroplasty, in addition to the known risk factors of male age, hip arthroplasty, and previous abdominal surgery, this study describes two previously unknown risk factors: chronic kidney disease and history of myocardial infarction. Patients with these risk factors should be monitored closely for developing postoperative ileus.

Uncemented Tantalum Monoblock Tibial Fixation for Total Knee Arthroplasty in Patients Less Than 60 Years of Age: Mean 10-Year Follow-up

BACKGROUND

Although tibial component loosening has been considered a concern after total knee arthroplasty without cement, such implants have been used in younger patients because of the potential for ingrowth and preservation of bone stock. However, mid-term and long-term studies of modern uncemented implants are lacking. We previously reported promising prospective 5-year outcomes after using an uncemented porous tantalum tibial component in patients who underwent surgery before the age of 60 years. The purpose of this study was to determine clinical and radiographic implant survivorship at 10 years in this large series of young patients.

METHODS

The original cohort included 79 patients (96 knees) who were <60 years old at the time of surgery. All procedures were performed with an uncemented, posterior-stabilized femoral component and a porous tantalum monoblock tibial component by 1 high-volume arthroplasty surgeon at a single institution. Patients were followed prospectively. The Knee Society Score (KSS), radiographic findings, and any complications or revisions were recorded.

RESULTS

At the latest follow-up, 76% (60) of the 79 patients (74% [71] of the 96 knees) were available for evaluation or had undergone revision (n = 6); 7 patients had died with the implants in place, and 12 patients were lost to follow-up. The average follow-up for the available implants was 10 years (range, 8 to 12 years). There were no progressive radiolucencies on radiographic review. The mean functional KSS was 68 points (range, 0 to 100 points). All revisions were for reasons unrelated to tibial fixation: femoral component loosening (1), stiffness (1), pain and swelling (2), and instability (2). The all-cause revision rate was 6% (6 of 96 knees).

CONCLUSIONS

Uncemented porous tantalum monoblock tibial components provided reliable fixation, excellent radiographic findings, and satisfactory functional outcomes at a mean of 10 years postoperatively. We identified no cases of tibial component loosening. These promising clinical and radiographic results support the use of uncemented tibial components. Such implants may produce well-integrated, durable long-term constructs in young patients.

LEVEL OF EVIDENCE

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

Radiolucent lines are decreased at 3 years following total knee arthroplasty using trabecular metal tibial components

Objective To analyse location and frequency, and change over time, of radiolucent lines (RLLs) around trabecular metal tibial components in total knee arthroplasty (TKA). Methods Osteoarthritic knees in patients who had undergone TKA were retrospectively evaluated via analysis of RLLs on anteroposterior and lateral X-rays obtained at 2 and 6 months, and 1, 2 and 3 years following TKA. Results In 125 osteoarthritic knees from 90 patients (mean age, 75.0 ± 6.2; 21 male/69 female), frequency of RLLs around trabecular metal tibial components was generally highest at 2 and 6 months, and 1 year following TKA, then gradually decreased over the 3-year follow-up. Frequency of RLLs around trabecular metal tibial components was greater at the tip of the two pegs, particularly the medial peg, and around the pegs, versus other zones. No postoperative revisions were performed for loosening. Conclusions Over 3 years following TKA, RLLs were most frequently observed up to 1 year, then gradually decreased. RLLs were significantly more frequent in the medial peg zone and zones close to the medial peg than in other zones.

Influence of conformity on the wear of total knee replacement: An experimental study

Wear of total knee replacement continues to be a significant factor influencing the clinical longevity of implants. Historically, failure due to delamination and fatigue directed design towards more conforming inserts to reduce contact stress. As new generations of more oxidatively stable polyethylene have been developed, more flexibility in bearing design has been introduced. The aim of this study was to investigate the effect of insert conformity on the wear performance of a fixed bearing total knee replacement through experimental simulation. Two geometries of insert were studied under standard gait conditions. There was a significant reduction in wear with reducing implant conformity. This study has demonstrated that bearing conformity has a significant impact on the wear performance of a fixed bearing total knee replacement, providing opportunities to improve clinical performance through enhanced material and design selection.

Good outcome scores and high satisfaction rate after primary total ankle replacement

Background and purpose - Total ankle replacement (TAR) is gaining popularity for treatment of end-stage ankle arthritis. Large patient-centered outcome studies are, however, few. Here, we report data from the Swedish Ankle Registry. Patients and methods - We examined outcomes after primary TAR in patients from the Swedish Ankle Registry using PROMs (Patient Reported Outcome Measures; generic: EQ-5D and SF-36, region specific: SEFAS (Self-Reported Foot and Ankle Score), and a question on satisfaction). We included 241 patients registered with primary TAR between 2008 and 2016 and who completed PROMs preoperatively and postoperatively up to 24 months. We evaluated changes in PROMs following surgery and estimated effects of age, diagnosis, prosthetic design, and preoperative functional score on the outcomes. Results - All absolute scores improved from preoperative to 24 months after surgery (p ≤ 0.001). 71% of the patients were satisfied or very satisfied at the latest follow-up and 12% dissatisfied or very dissatisfied. Postoperative SEFAS correlated with age (r = 0.2, p = 0.01) and preoperative SEFAS (r = 0.3, p < 0.001), as did patient satisfaction (r = -0.2; p ≤ 0.03). Postoperative SEFAS and EQ-5D were similar between different diagnoses or prosthetic designs. Preoperative SF-36 was associated with diagnosis (p ≤ 0.03), postoperative SF-36 with age (r = 0.2, p = 0.01) and diagnosis (p < 0.03). Interpretation - We found statistically and clinically significant improvements in patient-reported outcomes following TAR surgery. The postoperative region-specific SEFAS was positively associated with older age. Prosthetic design seemed not to influence patient-reported outcome, whereas diagnosis partly did. Studies with longer follow-up are necessary to establish the long-term outcome of TAR and to elucidate whether short- and mid-term outcomes may predict implant failure.

Clinical Outcome of Total Knee Arthroplasty After Prior Microfracture: A Matched Cohort Study

Microfracture (MFX) is a common operation for articular cartilage lesions. Data for patients who underwent total knee arthroplasty (TKA) after previous MFX are limited. The purpose of this study was to determine the outcomes, complications, and factors that influence outcomes in patients with previous MFX compared with those without previous MFX. Between 2005 and 2014, twenty-one TKAs were performed at a single tertiary care academic institution in patients with prior history of MFX surgery. These patients were retrospectively reviewed and matched 2:1 to patients who did not undergo previous MFX (n=42). Knee Society Score (KSS) (Subjective [KSS-S] and Function [KSS-F]) and complications were documented. Mean KSS-S in the MFX group increased significantly less (52.9 to 77.6) (P<.01) compared with the control group (51.3 to 83.8) (P<.01). The MFX group also demonstrated significantly less improvement in KSS-F from 63.0 to 88.9 (P=.02), whereas the control group demonstrated improvement from 52.4 to 87.1 (P=.02). At 5 years, the failure rate was 4.8% in the MFX group and 2.4% in the control group. Multivariate analysis found that older age at TKA resulted in smaller improvement in KSS-S. Paired relationships between increased age and decreased preoperative range of motion and women with an increased body mass index negatively affected KSS-S. Survivorship was similar between groups, but patients with MFX had slightly less clinical improvement compared with a matched control group. This study suggests that underlying patient factors may limit clinical improvement compared with primary TKA. [Orthopedics. 2017; 40(3):e473-e478.].

Patient-Reported Outcomes, Quality of Life, and Satisfaction Rates in Young Patients Aged 50 Years or Younger After Total Knee Arthroplasty

BACKGROUND

Recent studies have shown a discrepancy between traditional functional outcomes and patient satisfaction, with some reporting less than 85% satisfaction in older patients undergoing total knee arthroplasty (TKA). As native knee biomechanics are not completely replicated, the resulting functional limitations may cause dissatisfaction in higher-demand individuals. Few studies have recorded patient-reported outcomes, health-related quality of life scores, and patient satisfaction in a young population undergoing TKA.

METHODS

One hundred thirty-six primary TKAs were performed in 114 patients aged 50 years or younger (mean age, 47.0 years; range, 30-50 years) at a single institution. The main diagnoses were osteoarthritis (85%) and rheumatoid arthritis (10%).

RESULTS

The range of motion, Knee Society Score, Oxford Knee Score, and Physical and Mental Component Scores of Short Form-36 increased significantly (P < .001). At 2 years, 85.3% of patients had good/excellent knee scores, 71.3% had good/excellent function scores, 94.9% met the minimal clinically important difference for the Oxford Knee Score, and 84.6% met the minimal clinically important difference for the Physical Component Score. We found that 88.8% of patients were satisfied with their surgeries, whereas 86.8% had their expectations fulfilled. Survivorship using revision as an end point was 97.8% at a mean of 7 years (range, 3-16 years).

CONCLUSION

Patients aged 50 years or younger undergoing TKA can experience significant improvements in their quality of life, have their expectations met, and be satisfied with their surgeries, at rates similar to those of non-age-restricted populations. Surgeons should inform them of these benefits and the potential risk of revision surgery in the future, albeit increasingly shown to be low.

Differential knee skin temperature following total knee arthroplasty and its relationship with serum indices and outcome: A prospective study

Objectives To monitor knee skin temperature changes for 12 months following total knee arthroplasty (TKA) and identify potential reasons for any differences in skin temperature and to investigate if there is a relationship between the differential temperature and clinical outcome. Methods Patients who attended for a unilateral TKA due to primary osteoarthritis between August 2012 and August 2014 were eligible for this prospective study. The skin temperature of both knees was monitored preoperatively and postoperatively using an infrared thermometer. Serum indices and Hospital for Special Surgery (HSS) knee scores were assessed. Results Thirty-nine patients were involved in the study. The skin temperature of both knees as well as the differential temperature increased following TKA. Serum haemoglobin, haematocrit and days from surgery showed inverse correlations with the differential temperature, while body mass index and American Society of Anesthesiologists scores showed positive correlations. There was a strong inverse correlation between the differential temperature and HSS. score. Conclusions Differential knee skin temperature elevation 12 months post-TKA may be a normal surgical response.

Mid-term survivorship of Mini-keel™ versus Standard keel in total knee replacements: Differences in the rate of revision for aseptic loosening

INTRODUCTION

To reduce the size of the surgical incision, modular mini-keel tibial components have been developed with or without extensions for the Nexgen™ MIS Tibial Component. Although a smaller component could theoretically result in defective fixation, this has never been evaluated in a large comparative series. Thus, we performed the following case control study to: (1) evaluate intermediate-term survival of a modular "mini-keel" tibial component compared to a reference standard keel component from the same line of products (Nexgen LPS-Flex Tibial Component, Zimmer); (2) to identify any eventual associated factors if the frequency of loosening was increased.

HYPOTHESIS

The rate of revision for aseptic tibial loosening is comparable for both components.

MATERIALS AND METHODS

This comparative, retrospective, single center series of 459 consecutive total knee arthroplasties (TKA) was performed between 2007 and 2010: with 212 modular "mini-keel" (MK) tibial components and 247 "standard" (S) components. Survival, rate of revision for aseptic tibial loosening and identification of a radiolucent line were analyzed at the final follow-up.

RESULTS

After a median follow-up of 5years, the rate of revision for tibial aseptic loosing was significantly higher in the MK group with 12 cases (5.7%) and 4 cases in the S group (1.6%) (P=0.036). The use of the MK component appears to be a prognostic factor for surgical revision (hazard ratio=3.86 (1.23-11.88), P=0.02) but not for the development of a radiolucent line (HR=1.75 (0.9-3.4), P=0.097). The mean delay before revision was 38months (8-64) in the MK group and 15.2months (8-22) in the S group (P=0.006). Individual factors, such as gender, body mass index (BMI) and pre- or postoperative alignment were not prognostic factors for revision or radiolucent lines.

CONCLUSION

The modular "mini-keel" tibial component was associated with a greater risk of revision for tibial component loosening.

LEVEL OF EVIDENCE

Case control study, III.

Is unicondylar osteoarticular allograft still a viable option for reconstructions around the knee?

BACKGROUND

Unicondylar osteoarticular allografts (UOAs) represent a possible technique for reconstructing massive bone defects around the knee when only one condyle is affected. The aim of this retrospective study is to evaluate the outcome of UOAs and describe the possible salvage procedures in case of graft failure.

METHODS

Twenty-five deep-frozen UOAs were implanted at Rizzoli Orthopedic Institute (Bologna, Italy). Twenty-two followed bone tumor resection, two cases were post-traumatic defects and one case followed UOA failure. Mean age at surgery was 33years (range: 15 to 63). Eighteen UOAs were in distal femur, seven in proximal tibia.

RESULTS

Three patients died (only one because of the tumor). One UOA was removed for chondrosarcoma relapse and one for allograft fracture. Mean overall survival with UOA failure as a primary endpoint was 129months (range 12 to 302), with differences in the femur (85%) and in the tibia (40%) at 150months. Six UOAs had to be converted into knee prostheses due to osteoarthritis after a mean follow-up of 146months. No complications were recorded in UOAs converted into knee prostheses after a mean three year follow-up. Fourteen patients with UOAs still in place at the last follow-up (mean 123months) were radiologically and functionally evaluated: no correlation was found between function and the degree of osteoarthritis.

CONCLUSIONS

In selected cases, UOAs offer good clinical results and postpone the need for knee prosthesis. Despite short-term encouraging results, longer-term follow-up is needed in order to evaluate the outcome of knee prosthesis after UOA.

Midterm Outcomes Following Total Knee Arthroplasty in Lupus Patients

BACKGROUND

An increasing number of patients with systemic lupus erythematosus (SLE) are undergoing total knee arthroplasty (TKA), but there are few studies detailing their outcomes. The purpose of this study was to evaluate TKA cohort of patients who had SLE compared with a matched cohort who did not have this disease by analyzing (1) implant survivorship, (2) functional outcomes, (3) complication rates, (4) health-related quality of life, and (5) patient-perceived activity level.

METHODS

A retrospective review of all patients who underwent TKA and had an International Classification of Diseases, Ninth Revision, code diagnosis for SLE was performed at 3 high-volume institutions. A total of 31 patients (34 arthroplasties) were identified, and they were compared with a matched cohort (1:3) who did not have SLE and had undergone a primary TKA during this same time period.

RESULTS

After a mean 6-year follow-up (range, 2-10 years), both cohorts had similar implant survivorship (91% vs 99%). In addition, each cohort had similar complication rates (odds ratio = 1.9, 0.99-13). Functional outcomes were similar as measured by Knee Society Scores objective (90 vs 91 points) and functional (89 vs 90 points). There were no differences in Short Form-36 physical (47 vs 49 points) or mental components (51 vs 53 points). University of California Los Angeles activity scores were similar as well (5.1 vs 5.9 points).

CONCLUSIONS

Our study demonstrated comparable excellent clinical and patient-reported outcomes of TKA in patients with or without SLE. Prospective studies are necessary to evaluate these outcomes at longer follow-up.