Secondary Patellar Resurfacing in TKA: A Combined Analysis of Registry Data and Biomechanical Testing

Conceptual foundations of a REFRAME-based approach to discriminate across total knee implant designs based on the positions of functional centres of rotation

In modern knee arthroplasty, surgeons increasingly aim for individualised implant selection based on data-driven decisions to improve patient satisfaction rates. The identification of an implant design that optimally fits to a patient's native kinematic patterns and functional requirements could provide a basis towards subject-specific phenotyping. The goal of this study was to achieve a first step towards identifying easily accessible and intuitive features that allow for discrimination between implant designs based on kinematic data. A squat-cycle was simulated on eight fresh frozen specimens mounted in a weight-bearing knee rig, each initially tested under native conditions, and then after implantation with four different implant types (CR/CS, MS, LS, and PS). The kinematic signals of these five configurations were compared to determine whether key differences between implants could be detected leveraging two methodological approaches: (1) statistical parametric mapping to directly compare waveforms and (2) simple paired t-tests to compare the three-dimensional coordinates of the functional centres of rotation determined using a previously published REference FRame Alignment Method (REFRAME). While statistical parametric mapping of the kinematic data revealed only small differences in certain comparisons (e.g. LS vs. PS, and MS vs. LS) under lenient statistical testing conditions, the application of REFRAME showed clear differences between implants (for all implant combinations except for CR/CS vs. LS), even under conservative statistical testing. Since for most implant combinations, significant differences in the centres of rotation were found using REFRAME, this approach could present a suitable tool for discriminating between the kinematics of different implant types. Preoperative assessment of joint kinematics, combined with this REFRAME application, could therefore provide a key approach for improved clinical selection of implant type.

No Increased Risk of Patella-Related Revisions When Comparing Ultra-Congruent versus Cruciate-Retaining Polyethylene Liners in Primary Total Knee Arthroplasties With an Unresurfaced Patella: An Australian Registry Study of 42,105 Knee Arthroplasties

BACKGROUND

Ultra-congruent (UC) polyethylene liners are designed to add additional anterior-posterior stability in primary total knee arthroplasties (TKAs), compensating for actual or potential posterior cruciate ligament incompetence, somewhat like a posterior-stabilized knee. The literature supports patella resurfacing in primary posterior-stabilized compared to cruciate-retaining (CR) TKA due to higher revision rates with nonresurfaced patella. However, it is unclear if UC liners alter patella-related revisions. The aim of the study was to compare patella revision rates and survivorship of UC versus CR liners in primary TKA without patella resurfacing using two common prostheses in patients who had osteoarthritis.

METHODS

This was a retrospective cohort analysis of data from the Australian Orthopedic Association National Joint Replacement Registry. Patients who underwent primary TKA utilizing one of two common knee systems with cemented tibial fixation for osteoarthritis and did not have their patella resurfaced between January 1, 2007, and December 31, 2022, were included for analysis. A total of 42,105 primary TKA procedures were included (UC, n = 18,989 and CR, n = 23,116). The risk of patella-related revision and survivorship for primary TKA procedures with UC compared to CR liners were analyzed.

RESULTS

The cumulative revision at 14 years was 5.7% (95% confidence interval [CI] 4.7 to 6.9) and 5.4% (95% CI 4.8 to 6.1) for the CR and UC group, respectively, with no difference between groups (entire period: HR [hazard ratio] = 1.07 (95% CI 0.95 to 1.20), P = 0.256). When revision TKA for patella-related diagnoses was analyzed, there was no difference between the CR and UC groups (entire period: HR = 1.10 (95% CI 0.88 to 1.38), P = 0.406). The prosthesis-specific analyses did not produce any differences between the groups for all-cause or patella-related revisions.

CONCLUSIONS

The use of UC compared to CR liners in primary TKA without patella resurfacing was not associated with an increased rate of all-cause or patella-related revisions. Surgeons should make clinical decisions on the need for patella resurfacing based on other patient, surgical, and implant factors.

Patella is rarely resurfaced during primary total knee arthroplasty in clinical trials conducted in Greece: a systematic review

PURPOSE

The aim of the present study was to report the approach of Greek surgeons regarding patellar management and provide the outcomes and the rate of the need for secondary patella resurfacing.

METHODS

Following the PRISMA guidelines, PubMed, Scopus, and The Cochrane Central Register of Controlled Trials (CENTRAL) databases were accessed in January 2024. Clinical studies evaluating the outcomes of patients undergoing primary TKA were considered eligible for this systematic review if the following predefined criteria were fulfilled: (1) published in English, (2) were conducted in Greece, and had a minimum of 2-year follow-up. The methodological quality and publication bias were assessed using the Modified Coleman Methodology Score (mCMS) and ROBIS tool, respectively. Data was presented in tables using absolute values from individual studies. Pooled data were presented as means, ranges, and percentages.

RESULTS

Six clinical studies with a total of 1084 TKAs were included. Four studies were retrospectives, and two studies were prospective. Patella was only resurfaced in 0.6% of total TKAs. TKA without patellar resurfaced, which resulted in an improvement in functional outcome. Among studies, the overall need for revision incidence was 7.6% (68 out of 892 TKAs). Additionally, Aseptic loosening (2.4%) was the most common reason for revision due to patellofemoral joint complications, followed by secondary patellar resurfacing (2.1%) and deep infection (1.3%). The mean mCMS demonstrated a fair methodological quality level, and the ROBIS toll a low risk of bias in all four domains.

CONCLUSION

The available evidence supports that Greek surgeons mainly do not resurface the patella. However, patellar non-resurfacing yields good functional outcomes and presents relatively low revision rates for secondary patellar resurfacing.

LEVEL OF EVIDENCE

IV.

Validation of Inertial-Measurement-Unit-Based Ex Vivo Knee Kinematics during a Loaded Squat before and after Reference-Frame-Orientation Optimisation

Recently, inertial measurement units have been gaining popularity as a potential alternative to optical motion capture systems in the analysis of joint kinematics. In a previous study, the accuracy of knee joint angles calculated from inertial data and an extended Kalman filter and smoother algorithm was tested using ground truth data originating from a joint simulator guided by fluoroscopy-based signals. Although high levels of accuracy were achieved, the experimental setup leveraged multiple iterations of the same movement pattern and an absence of soft tissue artefacts. Here, the algorithm is tested against an optical marker-based system in a more challenging setting, with single iterations of a loaded squat cycle simulated on seven cadaveric specimens on a force-controlled knee rig. Prior to the optimisation of local coordinate systems using the REference FRame Alignment MEthod (REFRAME) to account for the effect of differences in local reference frame orientation, root-mean-square errors between the kinematic signals of the inertial and optical systems were as high as 3.8° ± 3.5° for flexion/extension, 20.4° ± 10.0° for abduction/adduction and 8.6° ± 5.7° for external/internal rotation. After REFRAME implementation, however, average root-mean-square errors decreased to 0.9° ± 0.4° and to 1.5° ± 0.7° for abduction/adduction and for external/internal rotation, respectively, with a slight increase to 4.2° ± 3.6° for flexion/extension. While these results demonstrate promising potential in the approach's ability to estimate knee joint angles during a single loaded squat cycle, they highlight the limiting effects that a reduced number of iterations and the lack of a reliable consistent reference pose inflicts on the sensor fusion algorithm's performance. They similarly stress the importance of adapting underlying assumptions and correctly tuning filter parameters to ensure satisfactory performance. More importantly, our findings emphasise the notable impact that properly aligning reference-frame orientations before comparing joint kinematics can have on results and the conclusions derived from them.

Anterior knee pain and sit-up tests predicts patients' satisfaction and improvement in quality of life after anterior stabilized total knee replacement without patellar resurfacing

PURPOSE

The purpose of this study was to assess patient satisfaction and identify risk factors for dissatisfaction after anterior stabilised conventional total knee arthroplasty (TKA) without patellar resurfacing, using the Goodman score.

METHODS

We conducted a cross-sectional study using data from our institutional database from 1 January 2018 to 1 March 2021. Patients who underwent TKA with the Vanguard® Cruciate Retaining Anterior Stabilized Knee System (Zimmer Biomet, Warsaw, Indiana, USA) without patellar replacement were included. Patients with other bearing surfaces (posterior stabilised or medial congruent) or diagnosed with infection or instability were excluded. Patients' reported outcomes, body mass index (BMI), passive range of motion, the timed up-and-go test, sit-up test, and algometry were assessed. Patients were also asked if they had anterior knee pain. Satisfaction was assessed using the Goodman scale, and logistic multivariate regression was used to identify variables associated with dissatisfaction and perceived improvement in quality of life.

RESULTS

A total of 131 TKA patients were included in the study. The median satisfaction score was 100 (interquartile range [IQR], 87.5 to 100), with the 75-point threshold at the 90th percentile according to Section A of Goodman. Section B of Goodman showed that 113 TKA patients (86.26%) reported "great improvement" or "more than I ever dreamed." Multivariate logistic regression revealed that anterior knee pain (OR 5.16, 95% CI 1.24 to 21.39), the sit-up test (OR 0.63, 95% CI 0.49 to 0.81), and BMI (OR 0.84, 95% CI 0.70 to 0.99) were significantly associated with patient dissatisfaction and a worse perceived improvement in quality of life. The receiver operating characteristics curve for the models had areas under the curve of 0.83 (95% CI 0.69 to 0.97) and 0.82 (95% CI 0.70 to 0.94), respectively.

CONCLUSION

Anterior stabilised TKA without patellar resurfacing can achieve 90% satisfaction and 86% improvement in quality of life. To improve these results, it is essential to prevent and treat anterior knee pain and enhance quadriceps strength.

LEVEL OF EVIDENCE

Level III (retrospective cohort study).

Influence of kinematic alignment on femorotibial kinematics in medial stabilized TKA design compared to mechanical alignment

INTRODUCTION

Worldwide more and more primary knee replacements are being performed. Kinematic alignment (KA) as one of many methods of surgical alignment has been shown to have a significant impact on kinematics and function. The aim of the present study was to compare KA and mechanical alignment (MA) with regard to femorotibial kinematics.

MATERIALS AND METHODS

Eight fresh frozen human specimens were tested on a knee rig during active knee flexion from 30 to 130°. Within the same specimen a medial stabilized (MS) implant design was used first with KA and then with MA.

RESULTS

The femorotibial kinematics showed more internal rotation of the tibia in KA compared to MA. At the same time, there was a larger medial rotation point in KA. Both alignment methods showed femoral rollback over the knee bend.

CONCLUSION

Relating to an increased internal rotation and a more precise medial pivot point, it can be concluded that KA combined with a MS implant design may partially support the reproduction of physiological knee joint mechanics.

Strain evaluation of axially loaded collateral ligaments: a comparison of digital image correlation and strain gauges

The response of soft tissue to loading can be obtained by strain assessment. Typically, strain can be measured using electrical resistance with strain gauges (SG), or optical sensors based on the digital image correlation (DIC), among others. These sensor systems are already established in other areas of technology. However, sensors have a limited range of applications in medical technology due to various challenges in handling human soft materials. The aim of this study was to compare directly attached foil-type SG and 3D-DIC to determine the strain of axially loaded human ligament structures. Therefore, the medial (MCL) and lateral (LCL) collateral ligaments of 18 human knee joints underwent cyclic displacement-controlled loading at a rate of 20 mm/min in two test trials. In the first trial, strain was recorded with the 3D-DIC system and the reference strain of the testing machine. In the second trial, strain was additionally measured with a directly attached SG. The results of the strain measurement with the 3D-DIC system did not differ significantly from the reference strain in the first trial. The strains assessed in the second trial between reference and SG, as well as between reference and 3D-DIC showed significant differences. This suggests that using an optical system based on the DIC with a given unrestricted view is an effective method to measure the superficial strain of human ligaments. In contrast, directly attached SGs provide only qualitative comparable results. Therefore, their scope on human ligaments is limited to the evaluation of changes under different conditions.

Topical vancomycin powder does not affect patella cartilage degeneration in primary total knee arthroplasty and conversion rate for secondary patella resurfacing

INTRODUCTION

Vancomycin powder (VP) is an antibiotic first introduced in pediatric spinal surgery to prevent surgical site infections (SSI). Recently its topical application was expanded to total hip and knee arthroplasty (THA, TKA) and anterior cruciate ligament reconstruction (ACLR). Toxicity to cartilage is the subject of current research. The aim of this study was to prove the hypothesis that topical application of VP in TKA does not result in a degeneration of patella cartilage. We propagate that the conversion rate for secondary patella resurfacing is not influenced by its use.

MATERIALS AND METHODS

Between 2014 and 2021, 4292 joints were included in this monocentric retrospective cohort study. All patients underwent TKA without primary patella resurfacing. After a change of the procedure in the hospital, one group (VPG) was administered VP intraoperatively. The other group (nVPG) received no VP during surgery (nVPG). The remaining perioperative procedure was constant over the investigation period. Conversion rates for secondary patella resurfacing for both groups were determined without making distinctions in the indication. A second cohort was composed of patients presenting for follow-up examination 12 months after TKA and included 210 joints. Retrospective radiographic evaluations were performed preoperatively, before discharge and at follow-up examination. Patella axial radiographs were analyzed for patella tracking (lateral patellar tilt, patellar displacement) and patella degeneration (Sperner classification, patellofemoral joint space).

RESULTS

There was no significant difference in the conversion rate for secondary patella resurfacing (4.24% VPG, 4.97% nVPG). Patella tracking and patella degeneration did not differ significantly between both groups.

CONCLUSIONS

The topical application of VP does not influence the conversion rate for secondary patella resurfacing. Moreover, it does not result in a degeneration of patella cartilage in TK.

LEVEL OF EVIDENCE

Retrospective case series, Level III.

Does Posterior Tibial Slope Influence Knee Kinematics in Medial Stabilized TKA?

BACKGROUND

During total knee arthroplasty (TKA), one of the key alignment factors to pay attention to is the posterior tibial slope (PTS). The PTS clearly influences the kinematics of the knee joint but must be adapted to the coupling degree of the specific TKA design. So far, there is hardly any literature including clear recommendations for how surgeons should choose the PTS in a medial stabilized (MS) TKA. The aim of the present study is to investigate the effects of different degrees of PTS on femorotibial kinematics in MS TKA.

MATERIALS AND METHODS

An MS TKA was performed in seven fresh-frozen human specimens successively with 0°, 3°, and 6° of PTS. After each modification, weight-bearing deep knee flexion (30-130°) was performed, and femorotibial kinematics were analyzed.

RESULTS

A lateral femoral rollback was observed for all three PTS modifications. With an increasing PTS, the tibia was shifted more anteriorly on the lateral side (0° PTS anterior tibial translation -9.09 (±9.19) mm, 3° PTS anterior tibial translation -11.03 (±6.72) mm, 6° PTS anterior tibial translation 11.86 (±9.35) mm). No difference in the tibial rotation was found for the different PTS variants. All PTS variants resulted in internal rotation of the tibia during flexion. With a 3° PTS, the design-specific medial rotation point was achieved more accurately.

CONCLUSIONS

According to our findings, we recommend a PTS of 3° when implanting the MS prosthesis used in this study.

Peripheral patellar denervation has a better effect in reducing postoperative anterior knee pain than patellar resurfacing in TKA

Patellar resurfacing (PR) and peripheral patellar denervation (PD) are common surgical treatments for knee osteoarthritis (KOA) in total knee arthroplasty (TKA). The aim of study was to compare preventive effect on postoperative anterior knee pain (AKP) between PR and peripheral PD in TKA. A total of 202 patients who underwent unilateral TKA were randomized into 3 groups: T, TPD, and TPR. Patients in T group received simple TKA, patients in TPD group received TKA combined PD while patients in TPR group received TKA combined PR. Incidence, intensity, and presentation time of AKP and clinical outcomes were evaluated at 3, 6, 9, 12, 18, and 24 months postoperatively. The incidence of AKP was significantly lower and the intensity of AKP and patients' satisfaction score were significantly better at 3 months after surgery in group TPD and TPR compared with group T. Compared with group TPR, the intensity of AKP was significantly better at 3 months after surgery in group TPD. There were no significant difference in Oxford knee score, range of motion (ROM), patellar score, knee society score (KSS) and activities of daily living (ADL) score among 3 groups in the follow-up period. Both PD and PR can effectively reduce the intensity and incidence of AKP after TKA and improve patients' satisfaction at 3 months after TKA. Additionally, PD is more effective on alleviating AKP than PR.

Isolated effects of patellar resurfacing in total knee arthroplasty and their relation to native patellar geometry

The isolated effects of patellar resurfacing on patellar kinematics are rarely investigated. Nonetheless, knowing more about these effects could help to enhance present understanding of the emergence of kinematic improvements or deteriorations associated with patellar resurfacing. The aim of this study was to isolate the effects of patellar resurfacing from a multi-stage in vitro study, where kinematics after total knee arthroplasty before and after patellar resurfacing were recorded. Additionally, the influence of the native patellar geometry on these effects was analysed. Eight fresh frozen specimens were tested successively with different implant configurations on an already established weight bearing knee rig. The patello-femoral kinematics were thereby measured using an ultrasonic measurement system and its relation to the native patellar geometries was analysed. After patellar resurfacing, the specimen showed a significantly medialized patellar shift. This medialization of the patellar tracking was significantly correlated to the lateral facet angle of the native patella. The patellar shift after patellar resurfacing is highly influenced by the position of the patellar button and the native lateral patellar facet angle. As a result, the ideal medio-lateral position of the patellar component is affected by the geometry of the native patella.

Tibial sagittal and rotational alignment reduce patellofemoral stresses in posterior stabilized total knee arthroplasty

Patellofemoral joint complications remain an important issue in total knee arthroplasty. We compared the patellofemoral contact status between cruciate-retaining and posterior-stabilized designs with varying degrees of tibial sagittal and rotational alignment using a computer simulation to ensure proper alignments in total knee arthroplasty. Knee kinematics, patellofemoral contact force and quadriceps force were computed using a musculoskeletal modeling program (LifeMOD/KneeSIM 2010; LifeModeler, Inc., San Clemente, California) during a weight-bearing deep knee bend. Two different posterior tibial slope (PTS)s (3° and 7°) and five different tibial tray rotational alignments (neutral, internal 5° and 10°, and external 5° and 10°) were simulated. Patellofemoral contact area and stresses were next computed using finite element analysis. The patellofemoral contact force for the posterior-stabilized design was substantially lower than the cruciate-retaining design after post-cam contact because of increasing femoral roll-back. Neutral rotational alignment of the tibial component resulted in smaller differences in patellofemoral contact stresses between cruciate-retaining and posterior-stabilized designs for PTSs of 3° or 7°. However, the patellar contact stresses in the cruciate-retaining design were greater than those in posterior-stabilized design at 120° of knee flexion with PTS of 3° combined with internal rotation of the tibial component. Our study provides biomechanical evidence implicating lower PTSs combined with internal malrotation of the tibial component and the resultant increase in patellofemoral stresses as a potential source of anterior knee pain in cruciate-retaining design.