Patellar Resurfacing in Total Knee Arthroplasty: Systematic Review and Meta-Analysis

Over a decade of experience in total knee arthroplasty with a multiradius design and fixed bearing at a single centre: Data from the Catalan Arthroplasty Registry

Purpose

Arthroplasty registers can provide feedback information on the results of arthroplasties performed by a certain institution or surgeon. The use of real-world data to achieve real-world evidence can help evaluate the performance of the implants used and help counsel our patients. The main objective of our study was to determine the survivorship of the total knee implant we are currently using.

Methods

A retrospective cohort study of patients who received a total knee arthroplasty from January 2009 to December 2020 in our hospital was conducted, using data from the Catalan arthroplasty registry and the Catalan health service database. Demographic and surgical data were analysed using the Kaplan-Meier method, log-rank test and Cox proportional hazards models with the R Project software (p < 0.05).

Results

A total of 1336 total knee arthroplasties were included in the study, of which 992 were women. The causes for revision included aseptic loosening (17), infection (29), instability (13), patellar implantation (13), arthrofibrosis (5) and quadriceps tendon rupture (1).The cumulative risk for revision at 5 years using the Kaplan-Meier method was 6.0% and at 10 years 6.5%. Considering gender, this risk was 7.0% and 7.5% at 5 and 10 years, respectively, in women and 3.3% in men, both at 5 and 10 years (p = 0.009). A higher risk for revision in women was seen, which is considered statistically significant (p = 0.012).

Conclusion

Our survivorship results are comparable to those published in the literature, but with a higher revision risk in women that is only statistically significant for the whole group of reoperations and for patellar implantation, but not for the rest of the diagnoses.

Level of Evidence

Level IV.

The clinical and cost-effectiveness of elective primary total knee replacement with PAtellar Resurfacing compared to selective patellar resurfacing: a pragmatic multicentre randomized controlled Trial (PART)

Aims

During total knee replacement (TKR), surgeons can choose whether or not to resurface the patella, with advantages and disadvantages of each approach. Recently, the National Institute for Health and Care Excellence (NICE) recommended always resurfacing the patella, rather than never doing so. NICE found insufficient evidence on selective resurfacing (surgeon's decision based on intraoperative findings and symptoms) to make recommendations. If effective, selective resurfacing could result in optimal individualized patient care. This protocol describes a randomized controlled trial to evaluate the clinical and cost-effectiveness of primary TKR with always patellar resurfacing compared to selective patellar resurfacing.

Methods

The PAtellar Resurfacing Trial (PART) is a patient- and assessor-blinded multicentre, pragmatic parallel two-arm randomized superiority trial of adults undergoing elective primary TKR for primary osteoarthritis at NHS hospitals in England, with an embedded internal pilot phase (ISRCTN 33276681). Participants will be randomly allocated intraoperatively on a 1:1 basis (stratified by centre and implant type (cruciate-retaining vs cruciate-sacrificing)) to always resurface or selectively resurface the patella, once the surgeon has confirmed sufficient patellar thickness for resurfacing and that constrained implants are not required. The primary analysis will compare the Oxford Knee Score (OKS) one year after surgery. Secondary outcomes include patient-reported outcome measures at three months, six months, and one year (Knee injury and Osteoarthritis Outcome Score, OKS, EuroQol five-dimension five-level questionnaire, patient satisfaction, postoperative complications, need for further surgery, resource use, and costs). Cost-effectiveness will be measured for the lifetime of the patient. Overall, 530 patients will be recruited to obtain 90% power to detect a four-point difference in OKS between the groups one year after surgery, assuming up to 40% resurfacing in the selective group.

Conclusion

The trial findings will provide evidence about the clinical and cost-effectiveness of always patellar resurfacing compared to selective patellar resurfacing. This will inform future NICE guidelines on primary TKR and the role of selective patellar resurfacing.

What are the Outcomes of Secondary Patella Resurfacing for Dissatisfaction Following Primary Knee Arthroplasty? A Systematic Review and Meta-Analysis of 604 Knees

BACKGROUND

Secondary patella resurfacing is often performed for dissatisfaction following primary knee arthroplasty where the native patella was retained. The purpose of this meta-analysis was to evaluate outcomes of secondary patella resurfacing.

METHODS

The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies reporting on patients who underwent secondary patella resurfacing after previous primary knee arthroplasty with retention of the native patella were considered eligible. The risk of bias was assessed using the Methodological Index for Non-Randomized studies tool. A random-effects model and the inverse-variance weighting method was used for meta-analysis. There were sixteen retrospective studies including 604 knees (594 patients) with a mean follow up of 42 months (range, 2 to 197).

RESULTS

An overall improvement in patient-reported outcomes (PROMs) was achieved in 53% of cases from pooled data available for 293 knees [95% Confidence Interval (CI) (0.44, 0.62), I2=68% - moderate heterogeneity]. The pooled proportion of patients satisfied with the procedure was 59% [95% CI (48, 68), I2 = 70% - moderate heterogeneity] in a sample size of 415. There was a minimal rate (2%) of complication incidence when performing secondary patella resurfacing and a pooled rate of revision surgery of 10%.

CONCLUSIONS

An improvement in pain, satisfaction, and PROMs was achieved in slightly more than half of the patients following secondary patella resurfacing. However, studies lacked standardized objective selection criteria for the procedure and the available data was predominantly retrospective, with high heterogeneity and variation in outcome reporting.

Meta-analysis of factors influencing anterior knee pain after total knee arthroplasty

BACKGROUND

Total knee arthroplasty (TKA) is a mature procedure recommended for correcting knee osteoarthritis deformity, relieving pain, and restoring normal biomechanics. Although TKA is a successful and cost-effective procedure, patient dissatisfaction is as high as 50%. Knee pain after TKA is a significant cause of patient dissatisfaction; the most common location for residual pain is the anterior region. Between 4% and 40% of patients have anterior knee pain (AKP).

AIM

To investigate the effect of various TKA procedures on postoperative AKP.

METHODS

We searched PubMed, EMBASE, and Cochrane from January 2000 to September 2022. Randomized controlled trials with one intervention in the experimental group and no corresponding intervention (or other interventions) in the control group were collected. Two researchers independently read the title and abstract of the studies, preliminarily screened the articles, and read the full text in detail according to the selection criteria. Conflicts were resolved by consultation with a third researcher. And relevant data from the included studies were extracted and analyzed using Review Manager 5.4 software.

RESULTS

There were 25 randomized controlled trials; 13 were comparative studies with or without patellar resurfacing. The meta-analysis showed no significant difference between the experimental and control groups (P = 0.61). Six studies were comparative studies of circumpatellar denervation vs non-denervation, divided into three subgroups for meta-analysis. The two-subgroup meta-analysis showed no significant difference between the experimental and the control groups (P = 0.31, P = 0.50). One subgroup meta-analysis showed a significant difference between the experimental and control groups (P = 0.001). Two studies compared fixed-bearing TKA and mobile-bearing TKA; the results meta-analysis showed no significant difference between the experimental and control groups (P = 0.630). Two studies compared lateral retinacular release vs non-release; the meta-analysis showed a significant difference between the experimental and control groups (P = 0.002); two other studies compared other factors.

CONCLUSION

Patellar resurfacing, mobile-bearing TKA, and fixed-bearing TKA do not reduce the incidence of AKP. Lateral retinacular release can reduce AKP; however, whether circumpatellar denervation can reduce AKP is controversial.

Debridement, antibiotics, and implant retention (DAIR) for the early prosthetic joint infection of total knee and hip arthroplasties: a systematic review

PURPOSE

Early periprosthetic joint infection (PJI) represents one of the most fearsome complications of joint replacement. No international consensus has been reached regarding the best approach for early prosthetic knee and hip infections. The aim of this updated systematic review is to assess whether debridement, antibiotics, and implant retention (DAIR) is an effective choice of treatment in early postoperative and acute hematogenous PJI.

METHODS

This systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The diagnostic criteria defining a PJI, the most present pathogen, and the days between the index procedure and the onset of the PJI were extracted from the selected articles. Additionally, the mean follow-up, antibiotic regimen, and success rate of the treatment were also reported.

RESULTS

The articles included provided a cohort of 970 patients. Ten studies specified the joint of their cohort in PJIs regarding either hip prostheses or knee prostheses, resulting in 454 total knees and 460 total hips. The age of the patients ranged from 18 to 92 years old. Success rates for the DAIR treatments in the following cohort ranged from 55.5% up to a maximum of 90% (mean value of 71%).

CONCLUSION

Even though the DAIR procedure is quite limited, it is still considered an effective option for patients developing an early post-operative or acute hematogenous PJI. However, there is a lack of studies, in particular randomized control trials (RCTs), comparing DAIR with one-stage and two-stage revision protocols in the setting of early PJIs, reflecting the necessity to conduct further high-quality studies to face the burden of early PJI.

Different modalities of patellar management in primary total knee arthroplasty: a Bayesian network meta-analysis of randomized controlled trials

BACKGROUND

The primary management modalities for the patella in TKA include patellar resurfacing, patellar non-resurfacing, patellar resurfacing with denervation, and patellar non-resurfacing with denervation. Traditionally, meta-analyses have predominantly focused on examining comparisons between two management modalities. However, this study performed a network meta-analysis to compare all four patellar management interventions to identify the most optimal approach for patellar management in TKA.

METHODS

A computer-based search of PubMed, China National Knowledge Infrastructure (CNKI), The Cochrane Library, Web of science, Embase, and MEDLINE databases was performed to identify randomized controlled trials focusing on the four management interventions for the patella in TKA. Comparisons included two-by-two comparisons as well as those involving more than two concurrent comparisons. The search timeframe spanned from inception to June 30, 2023. Two independent authors extracted the data and evaluated the quality of the literature. The Cochrane Collaboration Risk of Bias (ROB) tool was used to evaluate the overall quality of the literature. Subsequently, a network meta-analysis was conducted using the "gemtc" package of the R-4.2.3 software. Outcome measures such as anterior knee pain (AKP), reoperation rate, and patient satisfaction rate were evaluated using odd ratio (OR) and 95% confidence intervals (CI). Additionally, the knee society score (KSS), function score (FS), and range of motion (ROM) were evaluated using mean differences (MD) with associated 95% CI. The different treatment measures were ranked using the surfaces under the cumulative ranking curves (SUCRA).

RESULTS

A total of 50 randomized controlled trials involving 9,283 patients were included in the analysis. The findings from this network meta-analysis revealed that patellar resurfacing exhibited significantly lower postoperative reoperation rate (OR 0.44, 95% CI 0.24-0.63) and AKP (OR 0.58, 95% CI 0.32-1) compared to non-resurfacing. Additionally, patellar resurfacing exhibited higher postoperative KSS clinical scores in comparison with non-resurfacing (MD: 1.13, 95% CI 0.18-2.11). However, for postoperative FS, ROM, and patient satisfaction, no significant differences were observed among the four management interventions.

CONCLUSION

Patellar resurfacing emerges as the optimal management modality in primary TKA. However, future studies should aim to reduce sources of heterogeneity and minimize the influence of confounding factors on outcomes.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023434418 identifier: CRD42023434418.

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).

Outcomes and Survivorships of Total Knee Arthroplasty Comparing Resurfaced and Unresurfaced Patellae

BACKGROUND

The decision to resurface the patella in total knee arthroplasty (TKA) is controversial. While there is some consensus that leaving the patella unresurfaced increases risk of reoperation, there is conflicting evidence about patient reported outcomes or indications for resurfacing. This study sought to determine recent rates of patellar resurfacing, examine factors affecting rates of resurfacing, and analyze the associations between patellar resurfacing and both revision rates and patient-reported outcome measures (PROMs).

METHODS

The American Joint Replacement Registry was used to identify primary TKAs performed for osteoarthritis between 2012 and 2021. Cases were classified as resurfaced patella and unresurfaced patella (URP). Outcomes analyzed included trends in patellar resurfacing, factors influencing rate of resurfacing, revision rates, operative time, and 2 PROMs.

RESULTS

Rates of patellar resurfacing decreased and rates of URP increased significantly faster in ambulatory surgery centers and among high volume surgeons. Operative time was significantly lower in URP versus resurfaced patella (88.15 versus 89.90 minutes). The URP were significantly more likely to require revision surgery (odds ratio = 1.206 (1.078, 1.35), P = .0011). There was no significant difference in the likelihood of achieving the minimal clinically important difference in PROMs between resurfaced and nonresurfaced TKAs at 1 year (odds ratio = 1.060 (0.710, 1.581), P = .7755).

CONCLUSION

There was no difference in minimal clinically important difference between resurfaced and URPs and no clinically relevant difference in operative time. However, URPs were more likely to require revision surgery. Therefore, the decision not to resurface should be made carefully considering the known risk of revision and the uncertain benefit.

Harnessing Biofabrication Strategies to Re-Surface Osteochondral Defects: Repair, Enhance, and Regenerate

Osteochondral tissue (OC) is a complex and multiphasic system comprising cartilage and subchondral bone. The discrete OC architecture is layered with specific zones characterized by different compositions, morphology, collagen orientation, and chondrocyte phenotypes. To date, the treatment of osteochondral defects (OCD) remains a major clinical challenge due to the low self-regenerative capacity of damaged skeletal tissue, as well as the critical lack of functional tissue substitutes. Current clinical approaches fail to fully regenerate damaged OC recapitulating the zonal structure while granting long-term stability. Thus, the development of new biomimetic treatment strategies for the functional repair of OCDs is urgently needed. Here, we review recent developments in the preclinical investigation of novel functional approaches for the resurfacing of skeletal defects. The most recent studies on preclinical augmentation of OCDs and highlights on novel studies for the in vivo replacement of diseased cartilage are presented.

A Narrative Review of Patellar Resurfacing Versus Non-resurfacing in Total Knee Arthroplasty

The number of individuals who experience the symptoms of gonarthrosis rises proportionally as life expectancy rises and the population becomes more active. The purpose of total knee arthroplasty (TKA) is to lessen pain and restore knee function, and it has a high success rate. The restoration of patellar tracking in addition to the proper alignment of the femoral and tibial components contributes to the success of the arthroplasty and the patient's happiness. Replacement of the knee is not an easy process. One of the major objectives of total knee replacement is to achieve the proper rotation of the femoral components. A critical step that affects postoperative outcomes in total knee arthroplasty is the correct alignment of the femoral component. The axial plane of the femoral component is to blame for flexion stability, knee joint kinematics, flexion alignment, and patellar tracking. The patella is the largest sesamoid bone in the human body, and its major role is to enhance the quadriceps' moment arm, which allows the knee to expand. The distribution of patellofemoral compressive pressures during knee flexion and the centralization of the quadriceps muscles' multidirectional pull during extension are both critical functions of the patella. After primary knee arthroplasty, there are 8% more cases of anterior knee discomfort than there were before. Whether or not the patella was resurfaced, patients with primary TKA experience anterior knee discomfort. Patella baja is caused by excessive joint line elevation, which causes persistent overload and discomfort. The design of the TKR might have an impact on postoperative patellofemoral problems. After TKR, patellofemoral maltracking and patellar dislocation are often caused by surgical mistakes.

Selective Patella Resurfacing in Contemporary Cruciate Retaining and Substituting Total Knee Arthroplasty: A Matched Cohort Analysis

BACKGROUND

Leaving the patella unresurfaced in total knee arthroplasty (TKA) is increasing due to modern patella-friendly implants, awareness that complications are not uncommon with resurfacing, and knowledge that historical studies were scientifically confounded. This study examined the effect of selective patellar resurfacing on patient-reported outcome measures (PROMs) using modern implants and techniques in cohorts rigorously matched for demographics and osteoarthritis severity.

METHODS

A total of 166 TKAs performed without patellar resurfacing were case-control matched to 166 TKAs with patella resurfacing. Case-control matching was based on demographics, American Society of Anesthesiology Physical Status, comorbidities, and osteoarthritis severity. No significant differences were observed between cohorts for demographics (P ≥ .347), comorbidities (P ≥ .443), or radiographic osteoarthritis severity (P ≥ .078). Radiographic alignment and prospectively collected PROMs were evaluated preoperatively and at latest clinical follow-up.

RESULTS

Preoperatively, patellar tilt was less for the unresurfaced patella group (3 versus 4°, P = .003); however, postoperative patellar tilt was not different (3 versus 3°, P = .225). At a mean of 2.1 years follow-up (range, 1 to 7), University of California Los Angeles Activity Level was significantly higher for the unresurfaced patella group (6.3 versus 5.5, P = .002), but the mean group difference did not reach a minimal clinically important difference. There were no other significant differences in PROMs or reoperation rates between cohorts (P ≥ .135).

CONCLUSION

In contemporary cruciate retaining and substituting TKA designs, not resurfacing the patella in select patients may achieve comparable PROMs and re-operation rates; and potentially greater activity level compared to patella resurfacing at early follow-up.

LEVEL OF EVIDENCE

III.

Patellar Component Design Does Not Impact Clinical Outcomes in Primary Total Knee Arthroplasty

BACKGROUND

Round or oval implants are used in patellar resurfacing during total knee arthroplasty (TKA). However, whether component geometry affects clinical outcomes is unclear. This study aimed to determine if one implant shape conferred superior outcomes to the other.

METHODS

A retrospective review of primary TKA cases performed from 2016 to 2020 was conducted at an urban, tertiary academic center. Four hundred consecutive, primary TKAs were included in these analyses. Cases were included if a surgeon used the round design then oval design for fifty consecutive cases. Baseline demographic data and radiographic measurements were assessed. Surgical data, reasons for revision, and patient-reported outcome measures were analyzed. Independent samples t-test and chi-square tests were used to compare means and proportions. There were no demographic differences between the cohorts.

RESULTS

Postoperative patellar tilt was statistically different between the cohorts. Sixteen patients required revision surgery; however, revision rates did not differ between the cohorts. Of the 9 rounds, 1 button was revised for infection. Of the 7 ovals, 1 button was revised for infection and 1 for loosening. Veterans RAND 12 Physical Component Score at 3 months postoperatively was higher for the round cohort, but no differences were observed at 1 year.

CONCLUSION

While radiographic patellar tilt was significantly different between the cohorts, there was no clinical correlation in outcomes at 3 months or 1 year postoperatively. Longer-term follow-up studies are needed to evaluate the implications of patellar component design on outcomes and function. Nevertheless, the current study affirms that both designs are clinically equivalent which should be used to guide clinical decision-making.

LEVEL III EVIDENCE

Retrospective Cohort.

Patella resurfacing is not associated with a difference in the Oxford knee score after total knee arthroplasty but stair descent is enhanced

BACKGROUND

The primary aim was to assess the Oxford knee scores (OKS) on patients who underwent a total knee arthroplasty (TKA) with patellar resurfacing compared to those who did not. Secondary aims were to identify: (1) factors associated with resurfacing, (2) the effect of resurfacing on specific components of the OKS related to patellofemoral function, (3) the influence on patient satisfaction, and (4) whether a subgroup of patients had an improved outcome when resurfacing was undertaken.

METHODS

A retrospective cohort study was undertaken using outcome data from the arthroplasty database held at the study centre. Patient demographics and OKS were collected preoperatively and at 1 and 2 years postoperatively. Patient satisfaction was assessed at 1 and 2 years postoperatively.

RESULTS

Three thousand one hundred and twenty-two patients met the inclusion criteria of which 46.5% (n = 1453) underwent resurfacing. There were no differences in the OKS change at 1 or 2 years between those undergoing and not undergoing resurfacing (difference 0.2, p ≥ 0.469). Patients undergoing resurfacing were more likely to be female (odds ratio (OR) 1.53, 95% CI 1.30-1.79, p < 0.001), undergo a posterior stabilised knee (OR 6.87, 95% CI 5.71-8.27, p < 0.001) or had a worse response to question 5-standing from a chair, (p = 0.011) or 12-stair descent, (p = 0.017) of the OKS preoperatively. There was no difference in postoperative patient satisfaction (p ≥ 0.180). There was a significantly greater improvement in question 12 of the OKS at 1 year (p = 0.019) in the resurfaced group. There were no patient-related factors or symptoms that were associated with a clinically significant (≥ 5 points) greater postoperative OKS.

CONCLUSION

Patella resurfacing was not associated with a clinically important improvement in OKS. No specific indications for patella resurfacing were identified that offered an improved outcome, but when it was undertaken there was a greater improvement in the ability to descend stairs. Level of evidence Retrospective diagnostic study, Level III.

Patellar Resurfacing in Total Knee Arthroplasty, a Never-Ending Controversy; Case Report and Literature Review

Total knee arthroplasty (TKA) remains a lifesaving procedure for advanced gonarthrosis. However, patella resurfacing (PR) in TKA remains a controversial procedure, leading to extensive discussions amongst orthopedic surgeons, regarding its indications and results. Based on these premises, we present a clinical case of a 70-year-old Caucasian woman admitted for pain, swelling and limitation of left knee joint mobility. Her medical history records an Ahlback stage IV gonarthrosis with simultaneous bilateral TKA surgery performed in different hospital, when two NexGen cemented total prostheses were implanted with patellar resurfacing being performed only on the right side. Our clinical (American Knee Society Score, Lonner and Feller scales) and radiological evaluations (CT scan and Xray) revealed left patellar arthrosis and a slight lateral subluxation of the patella. The chosen treatment plan was revision surgery for PR and patellar prosthesis with a cemented patellar component, cross-linked polyethylene, no 32 NexGen model with 8.5 mm thickness. The immediate and distant postoperative evolution was favorable. Extensive literature review shows that, at present, PR remains at surgeon's discretion mainly based on his previous results. Therefore, we believe there is an imperative need to develop high quality studies based on accurate scientific evidence to universally establish valid guidelines for PR in TKA.

Supervised versus unsupervised rehabilitation following total knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

Outcomes after total knee arthroplasty (TKA) are strongly influenced by the adequacy of rehabilitation and the consequent functional recovery. The economic impact of rehabilitation it is not negligible. Inpatient rehabilitation can be 5 to 26 times more expensive than the home-based rehabilitation. This topic is extremely relevant as the COVID-19 pandemic has highlighted the importance of unsupervised rehabilitation in orthopedic surgery. The aim of this review and meta-analysis is to investigate the scientific evidence regarding the comparison between supervised and unsupervised rehabilitation following TKA.

MATERIALS AND METHODS

Following PRISMA guideline, a comprehensive search of PubMed, Cochrane and Scopus databases using combinations of keywords and MeSH descriptors: "total "Knee replacement," "Arthroplasty", "Rehabilitation" was performed from inception to December 2021. All relevant articles were retrieved, and their bibliographies were searched for further relevant references. Only English written randomized controlled trials comparing supervised and unsupervised rehabilitation following TKA were included in this systematic review. The outcomes considered were long-term pain, physical function, knee flexion and extension ROM, 6 minute walking test (6MWT) and timed up and go test (TUG).

RESULTS

11 studies (2.181 patients in total) were included in this systematic review. The long-term pain outcome showed no significant differences (Std. Mean Difference [SMD] = 0.00, 95 % confidence interval [CI] -0.16, 0.017) between the supervised (n = 397) and unsupervised (n = 255). Physical function showed no significant differences among the two groups (mean difference [MD] = 0.84, 95 % CI = -1.82, 3.50). Non-significant differences were also found for knee ROM flexion (mean difference [MD] = -0.46, 95 % CI = -2.95, 2.04) and for knee extension (mean difference [MD] = 0.54, 95 % CI = -0.89, 1.97). At the 52-week follow-up, the unsupervised group showed significant better results in 6MWT (mean difference [MD] = -26.10, 95 % CI = -47.62, -4.59) and in Timed up and go test (mean difference [MD] = 1.33, 95 % CI = 0.50, 2.15).

CONCLUSION

This systematic review did not show a significant clinical difference in improving pain, function, and mobility outcomes after TKA between supervised PT and unsupervised PT. Therefore, it would appear that supervised rehabilitation did not had additional benefits compared to unsupervised rehabilitation.

Patellar Resurfacing in Primary Total Knee Arthroplasty: A Meta-analysis and Trial Sequential Analysis of 50 Randomized Controlled Trials

OBJECTIVE

During total knee arthroplasty, femur and tibia parts are regularly replaced, while resurfacing the patellar or not is an ongoing discussion. To compare revision rate, anterior knee pain rate, patient-reported outcome measures, complication, radiographic, and clinical outcomes after patellar resurfacing versus non-resurfacing in total knee arthroplasty.

METHODS

PubMed, Medline, EMBASE, CENTRAL, and CINAHL databases were searched on 25 April 2021 to enroll randomized controlled trials that compared patellar resurfacing versus non-resurfacing. We used the grading of recommendations assessment, development and evaluation (GRADE) framework to assess the certainty of evidence. Our primary outcome was revision rate and secondary outcomes was anterior knee pain rate. Outcomes were pooled using the random-effect model and presented as risk ratio (RR), or mean difference (MD), with 95% confidence interval (CI).

RESULTS

Fifty studies (5586 knees) were included. Significant reductions in patellar revision rate (RR 0.41, 95% CI [0.19, 0.88]; P = 0.02; I²  = 24.20%) and non-patellar revision rate (RR 0.64, 95% CI [0.55, 0.75]; P < 0.001; I²  = 0%) were seen after patellar resurfacing. Patellar resurfacing significantly reduced the anterior knee pain rate than nonresurfacing (RR 0.72, 95% CI [0.57, 0.91]; P = 0.006; I²  = 69.5%). Significant differences in patient-reported outcome measures were found. However, these differences were inconsistent and lacked clinical importance. Patellar resurfacing resulted in a significant lower rate of patellar clunk (RR 0.58, 95% CI [0.38, 0.88]; P = 0.01; I²  = 0%), a higher patellar score (MD 1.24, 95% CI [0.67, 0.81]; P < 0.001; I²  = 73.8%), but prolonged surgical time (MD 8.59, 95% CI [5.27, 11.91]; P < 0.001; I²  = 88.8%).

CONCLUSIONS

The clear relationship is that patellar resurfacing reduces revisions, anterior knee pain, and patellar clunk. It will be interesting to compare the initial cost with the revision cost when required and cost-utility analysis with long-term results in future studies.

Does the degree of intraoperatively identified cartilage loss affect the outcomes of primary total knee arthroplasty without patella resurfacing? A prospective comparative cohort study

Purpose

The aim of this study was to investigate whether the degree of patellar cartilage loss confirmed during index surgery affects the clinical and radiologic outcomes of total knee arthroplasty (TKA) performed without patellar resurfacing.

Methods

We prospectively divided 2012 patients with a minimum follow-up of 12 months into two groups according to intraoperatively graded cartilage lesions graded using the International Cartilage Repair Society (ICRS) system: group 1, grades 0‒2 (n = 110); group 2, grades 3‒4 (n = 102). Relevant locations, such as medial, lateral, or both facets of the patella, were also assessed. Clinical outcomes were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index, Feller’s patella score, and Kujala anterior knee pain score. Radiographic outcomes included patellar tilt angle and lateral patellar shift on Merchant’s view.

Results

Clinical and radiographic outcomes were not significantly different between the two groups. No patient underwent secondary patellar resurfacing. Although the lateral facet was significantly more involved, there were no significant differences in outcomes.

Conclusions

The degree of intraoperatively identified patellar cartilage loss did not affect the short-term outcomes following primary TKA without patellar resurfacing.

Level of evidence II: Prospective comparative 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.

Clinical effectiveness of patellar resurfacing, no resurfacing and selective resurfacing in primary total knee replacement: systematic review and meta-analysis of interventional and observational evidence

Background

Patellar resurfacing is optional during total knee replacement (TKR). Some surgeons always resurface the patella, some never resurface, and others selectively resurface. Which resurfacing strategy provides optimal outcomes is unclear. We assessed the effectiveness of patellar resurfacing, no resurfacing, and selective resurfacing in primary TKR.

Methods

A systematic review and meta-analysis was performed. MEDLINE, Embase, Web of Science, The Cochrane Library, and bibliographies were searched to November 2021 for randomised-control trials (RCTs) comparing outcomes for two or more resurfacing strategies (resurfacing, no resurfacing, or selective resurfacing) in primary TKR. Observational studies were included if limited or no RCTs existed for resurfacing comparisons. Outcomes assessed were patient reported outcome measures (PROMs), complications, and further surgery. Study-specific relative risks [RR] were aggregated using random-effects models. Quality of the evidence was assessed using GRADE.

Results

We identified 33 RCTs involving 5,540 TKRs (2,727 = resurfacing, 2,772 = no resurfacing, 41 = selective resurfacing). One trial reported on selective resurfacing. Patellar resurfacing reduced anterior knee pain compared with no resurfacing (RR = 0.65 (95% CI = 0.44–0.96)); there were no significant differences in PROMs. Resurfacing reduced the risk of revision surgery (RR = 0.63, CI = 0.42–0.94) and other complications (RR = 0.54, CI = 0.39–0.74) compared with no resurfacing. Quality of evidence ranged from high to very low. Limited observational evidence (5 studies, TKRs = 215,419) suggested selective resurfacing increased the revision risk (RR = 1.14, CI = 1.05–1.22) compared with resurfacing. Compared with no resurfacing, selective resurfacing had a higher risk of pain (RR = 1.25, CI = 1.04–1.50) and lower risk of revision (RR = 0.92, CI = 0.85–0.99).

Conclusions

Level 1 evidence supports TKR with patellar resurfacing over no resurfacing. Resurfacing has a reduced risk of anterior knee pain, revision surgery, and complications, despite PROMs being comparable. High-quality RCTs involving selective resurfacing, the most common strategy in the UK and other countries, are needed given the limited observational data suggests selective resurfacing may not be effective over other strategies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05877-7.

Higher risk of knee arthroplasty during ten-year follow-up if baseline radiographic osteoarthritis involves the patellofemoral joint: a CHECK Cohort Study

Background

Patellofemoral OA is a strong risk factor for progression to generalized whole knee OA, but it is unknown whether involvement of the patellofemoral joint in early radiographic OA (ROA) is associated with risk of undergoing future knee arthroplasty. This is clinically relevant because patellofemoral OA likely requires a different treatment approach than tibiofemoral OA, and identifying prognostic factors for future arthroplasty might assist clinicians with prioritizing and guiding early interventions that could improve long-term outcomes. Therefore, we evaluated association of baseline patellofemoral or tibiofemoral ROA with undergoing knee arthroplasty over 10 years.

Methods

Using the multicenter Cohort Hip and Cohort Knee (CHECK) study, we acquired three views of radiographs in both knees of individuals aged 45–65 years with complaints of knee symptoms in at least one knee. From baseline radiographs, we categorized each knee as having one of four patterns of ROA: no ROA, isolated patellofemoral ROA, isolated tibiofemoral ROA, or combined ROA. We evaluated the 10-year relative hazard for undergoing going arthroplasty, based on baseline ROA pattern, using Cox proportional hazard models, adjusting for age, sex body mass index, and pain severity.

Result

Our sample (n = 842) included 671 (80%) women and had mean (SD) age 56 (5) years, and BMI 26.3 (4.0) kg/m². Arthroplasties were undertaken in 44/1678 knees. In comparison to having no ROA at baseline, adjusted hazard ratios (aHR) for arthroplasty were highest for combined ROA (aHR 14.2 [95% CI 5.8, 34.6]) and isolated patellofemoral ROA (aHR 12.7 [5.6, 29.0]). Isolated tibiofemoral ROA was not significantly associated with arthroplasty (aHR 2.9 [0.6, 13.6]).

Conclusions

In a sample of middle-aged individuals with complaints in one or both knees, the 10-year relative hazard for undergoing arthroplasty, compared to no ROA, was increased when OA involved the patellofemoral joint, regardless of whether it was isolated to the patellofemoral joint or occurred in combination with tibiofemoral OA. Further research is needed to confirm this association and to clarify the causal mechanism of this relationship. However, our results provide preliminary evidence that identifying patellofemoral ROA may be a clinically useful prognostic indicator in early knee OA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05549-6.

Comparison of clinical outcomes between patellar resurfacing and patellar non-resurfacing in cruciate retaining total knee arthroplasty

BACKGROUND

It is not established whether patellar resurfacing is better than patellar non-resurfacing during total knee arthroplasty (TKA). This study was to compare the clinical outcomes between groups with patellar resurfacing and non-resurfacing during cruciate retaining (CR) TKA.

METHODS

In this retrospective cohort study, subjects undergoing primary CR TKA for osteoarthritis between 2012 and 2019 were included. Of 500 subjects, 250 had patellar resurfacing (group 1) and 250 had patellar non-resurfacing (group 2) CR TKA. Knee society knee score (KSKS), knee society function score (KSFS), Western Ontario and McMaster Universities Osteoarthritis (WOMAC) scale, Kujala score, anterior knee pain, patellar compression test and range of motion (ROM) of the replaced knee were assessed and compared between the two groups.

RESULTS

There were no significant differences in KSKS, KSFS, WOMAC scale, Kujala score, prevalence of anterior knee pain and ROM of the replaced knee between the two groups at the last follow-up (p > .05). Group 2 had more subjects with positive patellar compression test than group 1 at the last follow-up (p = .010).

CONCLUSIONS

Clinical and functional outcomes of the replaced knee were not different between patellar resurfacing and non-resurfacing groups. Anterior knee pain was significantly reduced after total knee arthroplasty regardless of patellar resurfacing.

LEVEL OF EVIDENCE

Retrospective cohort study, Level III.

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.

Factors Affecting the Risk of Aseptic Patellar Complications in Primary TKA Performed with Cemented All-Polyethylene Patellar Resurfacing

BACKGROUND

Patellar complications are a consequential cause of failure of primary total knee arthroplasty (TKA). The purpose of this study was to evaluate the association of demographic and patient factors with the long-term risk of patellar complications as a function of time in a very large cohort of primary TKAs performed with patellar resurfacing.

METHODS

We identified 27,192 primary TKAs utilizing cemented all-polyethylene patellar components that were performed at a single institution from 1977 through 2015. We evaluated the risk of any aseptic patellar complication and any aseptic patellar reoperation or revision, subanalyzed risks of reoperation or revision for loosening, maltracking/instability, and wear, and evaluated the risk of clinical diagnosis of patellar fracture and clunk/crepitus. The mean age at TKA was 68 years (range, 18 to 99 years); 57% of the patients were female. The mean body mass index (BMI) was 32 kg/m2. The primary diagnosis was osteoarthritis in 83%, and 70% of the TKAs were posterior-stabilized. Median follow-up was 7 years (range, 2 to 40 years). Risk factors for each outcome were evaluated with Cox regression models.

RESULTS

Nine hundred and seventy-seven knees with all-polyethylene patellae developed patellar complications. Survivorship free from any aseptic patellar complication was 93.3% at 20 years. Twenty-year survivorship free from any aseptic patellar reoperation was 97.3% and free from any aseptic patellar revision was 97.4%. Fifteen-year survivorship for the same end points for procedures performed from 2000 to 2015 was 95.7%, 99.2% and 99.3% respectively, representing substantial improvements compared with implants placed before 2000. Univariate analysis demonstrated that male sex (hazard ratio [HR], 1.4), an age of <65 years (HR, 1.3), and a BMI of ≥30 kg/m2 (HR, 1.2) were associated with increased risk of patellar complications (all p ≤0.01). Posterior-stabilized designs were associated with fewer patellar reoperations and revisions overall (HR, 0.4 and 0.4; p < 0.001) but higher risk of patellar clunk/crepitus (HR, 14.1; p < 0.001).

CONCLUSIONS

The 20-year survivorship free from any aseptic patellar complication in this series of cemented all-polyethylene patellae was 93%. Important risk factors for any aseptic patellar complication were male sex, an age of <65 years, a BMI of ≥30 kg/m2, and a patella implanted before 2000.

LEVEL OF EVIDENCE

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

No difference between resurfaced and non-resurfaced patellae with a modern prosthesis design: a prospective randomized study of 250 total knee arthroplasties

PURPOSE

Despite numerous well-conducted studies and meta-analyses, the management of the patella during total knee arthroplasty (TKA) remains controversial. The aim of our study was to compare the clinical and radiological outcomes between patients with and without patellar resurfacing and to determine the influence of resurfacing on patellar tracking with a "patella-friendly" prosthesis.

METHODS

A single-centered prospective randomized controlled study was performed between April 2017 and November 2018. Two hundred and forty-five consecutive patients (250 knees) scheduled for TKA were randomized for patellar resurfacing or patella non-resurfacing. All patients received the same total knee prosthesis and were evaluated clinically and radiologically, including the International Knee Society Score (KSS knee and function), Forgotten Joint Score (FJS), anterior knee pain (AKP), pain when climbing stairs, patellar tilt, and patellar translation.

RESULTS

Two hundred and twenty-nine knees were available for clinical evaluation and 221 knees for radiographic analysis. The revision rate for patellofemoral cause was 3.1% (7 cases) with no difference between the groups (p = 0.217). There was no difference in survival rate between patellar resurfacing (88.3%) and non-resurfacing (85.3%) after 24 months (p = 0.599). There were no differences in KSS functional component (p = 0.599), KSS knee component (p = 0.396), FJS (p = 0.798), and AKP (p = 0.688) at a mean follow-up of 18 months. There was twice as much stair pain for the non-resurfacing group (17.1% versus 8.5%) (p = 0.043). There was patellar tilt in 43% of resurfaced knees (n = 50/116) versus 29% in non-resurfaced knees (n = 30/105) (p = 0.025); however, there was more patellar translation in the non-resurfaced group (21.0% versus 7.8%) (p < 0.001). There were no specific complications attributed to the patellar resurfacing procedure. There were four secondary patellar resurfacing procedures (3.6%) in the non-resurfaced group after a mean of 10 ± 7 months (1-17) postoperatively.

CONCLUSION

There is no superiority of patellar resurfacing or non-resurfacing in terms of clinical or radiological outcomes at mid-term. Secondary patellar resurfacing is rare. There is not enough evidence to recommend systematic patellar resurfacing with a "patella-friendly" prosthesis.

To Resurface or Not to Resurface the Patella in Total Knee Arthroplasty, That Is the Question: A Meta-Analysis of Randomized Controlled Trials

Background and Objetives: Currently, total knee arthroplasty is one of the most common surgeries, increasing with the increase in life expectancy. Whether or not to replace the patella has been a subject of debate over the years, remaining in controversy and without reaching a consensus. Over the years, different meta-analyses have been carried out in order to provide evidence on the subject, although, in recent times, there have not been many new studies in this regard. Therefore, it is considered necessary that the latest works form part of a new meta-analysis. Materials and Method: We searched the literature using PUBMED, SCOPUS, the Cochrane database and VHL from 2010 to 2020. The search terms used were “patellar” AND “resurfacing” OR “Replacement” and “no resurfacing” OR “no replacement”. A meta-analysis was performed with Stata software (Stata version 15.1). Forest plots were generated to illustrate the overall effect of knee arthroplasty interventions. Results: As a result, it was obtained that there is a significantly higher risk of suffering AKP in the non-resurfacing group, in addition to a significant increase in the risk of undergoing a reoperation in the non-resurfacing group. On the other hand, significant differences were obtained in favor of the resurfacing group in both the clinical and Feller KSS, with functional KSS being inconclusive. After analyzing different variables throughout the literature, it does seem clear that the non-resurfacing group may present a higher risk of reoperation than the resurfacing group. Conclusion: For all these reasons, we think that, although it does seem that not replacing the patella can precipitate a reoperation, it is not clear whether this reoperation is a direct consequence of not having replaced the patella. Therefore, in our opinion, the treatment must be individualized for each patient.

Patella related problems as common reason for revision of NexGen PS® total knee arthroplasty without patella resurfacing: An analysis of 5911 primary total knee arthroplasties registered in the Dutch Arthroplasty Register

BACKGROUND

Patella resurfacing remains controversial in primary total knee arthroplasty (TKA).The aim of this study was to investigate if there was a difference in revision rate and reason for revision within 8 years after single brand primary cemented TKA with or without patella resurfacing, using data from the Dutch Arthroplasty Register.

METHODS

All primary TKA surgeries with a posterior stabilized cemented primary NexGen®, between 2010 and 2013 with diagnosis osteoarthritis were analyzed (n = 5911). Multivariate cox regression analyses were performed to analyze differences in revision rate between TKA with or without patella component, and was adjusted for age and previous surgery.

RESULTS

Of 5911 TKA surgeries, 4795 were performed without patella resurfacing (81.1%) and 1116 with patella resurfacing (18.9%). There was a significant difference in patellar problems as reason for revision between patients after primary TKA with patella resurfacing (9.3%) and without patella resurfacing (29.9%) (p = 0.01). This was mostly caused by patellar pain (28.0%). There was no significant difference in cumulative revision rate within between TKA with patella resurfacing and without patella resurfacing.

CONCLUSION

In conclusion, 30% of patients who need revision surgery after TKA using NexGen® PS without patella resurfacing the reason for revision is patella related problems, compared to 9% after TKA NexGen® PS with patella resurfacing. There was no difference in cumulative incidence of revision after primary surgery of all TKA's using NexGen® PS with or without patella. To reduce the probability of reoperation for patella related problems, our data suggest the patella should be resurface during primary TKA.

Chondrocalcinosis does not affect functional outcome and prosthesis survival in patients after total or unicompartmental knee arthroplasty: a systematic review

PURPOSE

There are contentious data about the role calcium pyrophosphate (CPP) crystals and chondrocalcinosis (CC) play in the progression of osteoarthritis (OA), as well as in the outcomes after knee arthroplasty. Hence, the purpose of this systematic review was to analyse the clinical and functional outcome, progression of OA and prosthesis survivorship after unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) in patients with CC compared to patients without CC.

METHODS

A systematic review of the literature in PubMed, Medline, Embase and Web of Science was performed using the "Preferred Reporting Items for Systematic Reviews and Meta-Analysis" (PRISMA) guidelines. Articles which reported the outcome and survival rates of prosthesis after TKA or UKA in patients with CC were included.

RESULTS

A total of 3718 patient knees were included in eight selected publications, with a median sample sizes of 234 knees (range 78-1000) and 954 knees (range 408-1500) for publications including UKA and TKA, respectively. At time of surgery, the mean age was 69 years and the prevalence for CC ranged from 12.6 to 36%. Chondrocalcinosis did not significantly influence the functional and clinical outcome, the implant survival as well as the radiologic progression of OA disease after UKA and TKA.

CONCLUSION

The presence of CPP crystals in tissue samples, synovial fluid or evidence of calcifications on preoperative radiographs did not significantly influence the postoperative functional and activity scores. It also had no significant influence on prosthesis survival rate, whether it was a UKA or a TKA. This study shows that the impact of a subclinical form of chondrocalcinosis may not be of clinical relevance in the context of arthroplasty.

LEVEL OF EVIDENCE

IV.

To Retain or Resurface the Patella in Primary Total Knee Arthroplasty: A Comparative Study

Objective  To evaluate and compare clinically and functionally patients undergoing primary total knee arthroplasty (TKA) with preservation or replacement of the patella.

Methods  In a cross-sectional study, the functional results were evaluated and compared, using the Western Ontario and McMaster Universities (WOMAC) and Lequesne scores, of 158 patients undergoing primary TKA (162 knees); in 81 knees the patella was submitted to arthroplasty and in 81 the joint surface of the patella was preserved.

Results  No significant differences were identified in terms of the Lequesne score (p = 0.585), global WOMAC score (p = 0.169), nor in terms of its subdivisions regarding stiffness (p = 0.796) and functional capacity (p = 0.190). There was a significant difference only in terms of the subdivision that evaluates pain in the WOMAC score, being lower in the group undergoing patellar arthroplasty (p = 0.036).

Conclusion  In the present study, there was no difference in functional assessment in patients who underwent or not patellar replacement during primary knee arthroplasty surgery. However, individuals in whom the patella was preserved reported more pain.

Patellar management during total knee arthroplasty: a review

The optimal management of the patella during total knee arthroplasty (TKA) remains controversial and surgeons tend to approach the patella with one of three general mindsets: always resurface the patella, never resurface the patella, or selectively resurface the patella based on specific patient or patellar criteria.

Studies comparing resurfacing and non-resurfacing of the patella during TKA have reported inconsistent and contradictory findings.

When resurfacing the patella is chosen, there are a number of available patellar component designs, materials, and techniques for cutting and fixation.

When patellar non-resurfacing is chosen, several alternatives are available, including patellar denervation, lateral retinacular release, and patelloplasty. Surgeons may choose to perform any of these alone, or together in some combination.

Prospective randomized studies are needed to better understand which patellar management techniques contribute to superior postoperative outcomes. Until then, this remains a controversial topic, and options for patellar management will need to be weighed on an individual basis per patient.

Cite this article: EFORT Open Rev 2021;6:861-871. DOI: 10.1302/2058-5241.6.200156

Patellar denervation does not reduce post-operative anterior knee pain after primary total knee arthroplasty with patellar resurfacing

PURPOSE

Anterior knee pain (AKP) is a frequent symptom after a total knee arthroplasty (TKA). Patellar denervation (PD) has been put forth as a technique to reduce this pain; however, its effects have not been assessed in combination with patellar resurfacing. The aim of this study is to evaluate the effect of PD on AKP and functional outcomes after TKA with patellar resurfacing.

METHODS

A prospective study was designed that included patients scheduled for TKA with patellar resurfacing. The 202 recruited patients were randomized into either the PD group or the non-denervation group [mean age 72.7 years (SD 8.2); 119 (70.4%) women and 50 (29.6%) men; average body mass index 31.4 kg/m² (SD 4.9)]. Pressure pain threshold (PPT) assessed by pressure algometry (PA), visual analogue scale(VAS), patellofemoral Feller score and the Knee Society Scores (KSS) were recorded preoperatively and at the 1-year follow-up.

RESULTS

169 patients were included in data analysis. At the 1-year follow-up, there were mild differences between denervation and non-denervation group in PPT value (494.4 kPa vs. 552.3 kPa, p = 0.047) and in VAS at stairs (2.9 vs. 1.5, p = 0.003) in favour of the non-denervation group. There was no difference in the improvement between groups in patellofemoral Feller score and KSS, but slightly higher improvement in non-denervation group in PPT (94.1 kPa vs. 160 kPa, p = 0.047), VAS walking (5.3 vs. 6.2, p = 0.041) and VAS at stairs (4.6 vs. 5.7, p = 0.022).

CONCLUSION

Patellar denervation does not improve AKP and clinical outcomes in primary TKA with patellar resurfacing compared to patellar replacement without denervation. PD cannot be recommended when patellar replacement is performed in TKA.

LEVEL OF EVIDENCE

II.

Management of the Patella During Total Knee Arthroplasty

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The optimal management of the patella during total knee arthroplasty (TKA) remains a controversial topic with no consensus.

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Patellar management techniques during TKA include patellar retention or resurfacing with or without patellaplasty, as well as circumferential denervation and partial lateral facetectomy (PLF).

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Special considerations such as patient age, etiology of disease, implant design, and surgeon preference should be accounted for when determining optimal management.

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We recommend that most patellae be circumferentially denervated, regardless of whether they are resurfaced, as the potential benefits outweigh the small associated risks.

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Evidence demonstrates improved functional outcomes with the addition of PLF to nonresurfaced patellae. There is currently a paucity of evidence of this technique with respect to resurfaced patellae.

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Patellar resurfacing adds additional costs and health-care resources that should be considered in the decision-making process.

Functional Outcomes Following Total Knee Arthroplasty Without Patellar Resurfacing: A Minimum Two-Year Follow-Up Retrospective Cohort Study

This paper seeks to address the effectiveness of total knee arthroplasty (TKA) when performed without patellar resurfacing. The objective of this article is to investigate the effect of total knee arthroplasty without patellofemoral resurfacing on postoperative outcome.

All patients with degenerative knee osteoarthritis (OA) that underwent TKA without patellar resurfacing were included in the study. The clinical data of 163 patients, including 98 females and 65 males with a mean age of 63 years (range 54-78 years) were retrospectively analyzed from April 2008 to April 2011. Intraoperative cartilage degeneration according to Outerbridge classification criteria was as follows: 22 cases of grade I, 38 cases of grade II, 64 cases of grade III, 39 cases of grade IV. There were no significant differences in gender, age, and side differences between the patients at all levels (P > 0.05). The duration of tourniquet use and related complications were recorded. Knee function was assessed using the American Knee Society Scoring System (KSS) and the patellar score (PS). Patient satisfaction and knee pain were assessed by the pain visual analog scale (VAS). The evaluation was conducted using routine X-ray film to observe the position of the prosthesis and the patella. Statistical analysis used included a comparison between groups by analysis of variance (ANOVA) using the Student-Newman-Keuls (SNK) test and comparison of grade data using the rank-sum test.

The average tourniquet time was 125 minutes, with a range of 90-150 minutes. All the incisions healed with primary intention without early complications. All patients were followed for two to five years with an average of 3.6 years. At six months and at the last follow-up, the KSS and PS scores were significantly higher than those before surgery (P < 0.05). There was no significant difference between the sixth month and the last follow-up (P > 0.05). There were significant differences in preoperative KSS and PS scores between patients with different grades of cartilage degeneration (P < 0.05), but there was no significant difference at the last follow-up (P > 0.05). At the last follow-up, seven patients had persistent anterior knee pain, five patients had mild pain, and two patients had moderate pain according to the VAS assessment criteria. Patient satisfaction evaluation was as follows: 90 patients were very satisfied, 66 patients were satisfied, five patients were uncertain, and two patients were unsatisfied. There were no significant differences in satisfaction and knee pain between patients with different grades of patellofemoral degeneration (P > 0.05).

In conclusion, at six months and at the last follow-up, outcome measures for patients were significantly higher than before surgery for TKA without the use of patellar resurfacing and the majority of patients were satisfied with the outcome of the procedure. TKA continues to be a successful procedure without the use of patellar resurfacing.

Patellar resurfacing during primary total knee replacement is associated with a lower risk of revision surgery

AIMS

Debate remains whether the patella should be resurfaced during total knee replacement (TKR). For non-resurfaced TKRs, we estimated what the revision rate would have been if the patella had been resurfaced, and examined the risk of re-revision following secondary patellar resurfacing.

METHODS

A retrospective observational study of the National Joint Registry (NJR) was performed. All primary TKRs for osteoarthritis alone performed between 1 April 2003 and 31 December 2016 were eligible (n = 842,072). Patellar resurfacing during TKR was performed in 36% (n = 305,844). The primary outcome was all-cause revision surgery. Secondary outcomes were the number of excess all-cause revisions associated with using TKRs without (versus with) patellar resurfacing, and the risk of re-revision after secondary patellar resurfacing.

RESULTS

The cumulative risk of all-cause revision at ten years was higher (p < 0.001) in primary TKRs without patellar resurfacing (3.54% (95% confidence interval (CI) 3.47 to 3.62)) compared to those with resurfacing (3.00% (95% CI 2.91 to 3.11)). Using flexible parametric survival modelling, we estimated one 'excess' revision per 189 cases performed where the patella was not resurfaced by ten years (equivalent to 2,842 excess revisions in our cohort). The risk of all-cause re-revision following secondary patellar resurfacing was 4.6 times higher than the risk of revision after primary TKR with patellar resurfacing (at five years from secondary patellar resurfacing, 8.8% vs 1.9%).

CONCLUSION

Performing TKR without patellar resurfacing was associated with an increased risk of revision. Secondary patellar resurfacing led to a high risk of re-revision. This represents a potential substantial healthcare burden that should be considered when forming treatment guidelines and commissioning services. Cite this article: Bone Joint J 2021;103-B(5):864-871.

Patellar Denervation Reduces Postoperative Anterior Knee Pain After Patellar Resurfacing Total Knee Arthroplasty: A Randomized Controlled Trial

BACKGROUND

The benefit of patellar denervation (PD) in patellar resurfacing total knee arthroplasty (TKA) is still debatable. This prospective, randomized controlled trial investigated whether circumferential PD should be performed in patellar resurfacing TKA.

METHODS

A total of 241 patients who underwent unilateral TKA were randomized into PD or non-PD groups. Incidence, intensity, and presentation time of anterior knee pain (AKP) and clinical outcomes were evaluated at 3, 6, 9, 12, 18, and 24 months postoperatively.

RESULTS

The incidence of AKP was significantly lower in the PD group (6.4% vs 16.2%, P = .032). The intensity of AKP and patient satisfaction scores were significantly better in the PD group at 3 months but not after 3 months. The presentation time of AKP mostly occurs at 3 months after surgery. The Knee Society score, range of motion, Oxford score, patellar score, activity of daily living score, and visual analog scale of overall knee pain were not significantly different between the two groups during the follow-up period.

CONCLUSION

Given that PD can improve AKP and patient satisfaction at an early period postoperatively without jeopardizing clinical outcomes at no additional cost, this inexpensive procedure readily available in nearly every operation room is strongly recommended during primary TKA with patellar resurfacing.

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

The German Arthroplasty registry (EPRD) has shown that different prosthesis systems have different rates of secondary patellar resurfacing: four years after implantation, the posterior-stabilized (PS) Vega prosthesis has a 3.2% risk of secondary patellar resurfacing compared to the cruciate-retaining (CR) Columbus prosthesis at 1.0% (both Aesculap AG, Tuttlingen, Germany). We hypothesized that PS implants have increased retropatellar pressure and a decreased retropatellar contact area compared to a CR design, which may lead to an increased likelihood of secondary patellar resurfacing. Eight fresh frozen specimens (cohort 1) were tested with an established knee rig. In addition, a possible influence of the registry-based patient collective (cohort 2) was investigated. No significant differences were found in patient data–cohort 2-(sex, age). A generally lower number of PS system cases is noteworthy. No significant increased patella pressure could be detected with the PS design, but a lower contact area was observed (cohort 1). Lower quadriceps force (100°–130° flexion), increased anterior movement of the tibia (rollback), greater external tilt of the patella, and increasing facet pressure in the Vega PS design indicate a multifactorial cause for a higher rate of secondary resurfacing which was found in the EPRD patient cohort and might be related to the PS’ principle function.

The Patellar Resurfacing in Total Knee Prosthesis: Indications for Bone Stock and Patellar Morphology

The patellar resurfacing is still a controversial and unresolved problem. The choice to use the patellar resurfacing in the total knee prosthesis (TKP) is decided by the surgeon's experience; he analyzes the thickness, the shape, consumption of the surface and he chooses the use of patellar resurfacing or to limit itself to cheiloplasty, denervation, or often to the release of the lateral wing ligament. He also assesses the metabolic state of the bone linked to Osteoporosis and the potential fragility of the joint and kneecap in particular. Bone loss after total knee arthroplasty (TKP) may lead to periprosthetic fractures that are associated with significant costs (morbidity, economic, etc.) and pose a challenge to operative fixation. The literature doesn't express a definitive judgment on the two options, since the results can be overlapped on average. Each option has advantages and disadvantages to be considered in the overall balance of the patellar operation. In reality, however, this technical choice requires more consolidated decision-making criteria so as to minimize the incidence of post-surgical femoral-patellar pain syndrome, the second cause of failure, which frequently leads to revision of the implant. The balance between experience and evidence can be a compromise in the choice of surgery. The experience documented in the literature must identify the parameters capable of constructing an algorithm aimed not only at the secondary resurfacing rate, but at the overall clinical evaluation. This has implications also for the rehabilitation of these patients after surgery.

Patellar component size effects patellar tilt in total knee arthroplasty with patellar resurfacing

PURPOSE

Patellar component positioning and patellofemoral kinematics are of great importance in total knee arthroplasty (TKA). The factors influencing patellar tilt are femoral rotation and lateral patellar release. However, the effect of patellar component size remains unknown. The aim of this study was to evaluate the intra-operative risk factors for patellar tilt, particularly the effect of the patellar component size. The hypothesis was that increasing the patellar component size would reduce the risk of patellar tilt.

METHODS

878 primary TKAs with patellar resurfacing were included between January 2015 and October 2018. Analysis was performed at 1-year postoperatively on patients categorized into two groups: patellar tilt (PT) and no patellar tilt (NPT). A multivariate analysis was performed for the effect of patellar component size, femoral rotation, femoral overbuilding, patellar thickness and lateral release on patellar tilt risk. Secondary analysis was performed for any difference in clinical outcomes and revision rates between groups.

RESULTS

Multivariate analysis showed that increasing the patellar component size decreased the risk of patellar tilt by 37% (p < 0.001). Placing the femoral component at 3° of external rotation decreased the risk of patellar tilt by 67% (p < 0.001). Secondary analysis showed better clinical outcomes in the NPT group, especially regarding global satisfaction, and KSS objective and subjective scores. The revision for any cause was less in the NPT group (p = 0.019). The cause for TKA revision was related to the patellar in 11% of cases in the NPT group and 65% in the PT group (p < 0.001).

CONCLUSION

Increased patellar component size and positioning the femoral component in external rotation decreases the risk of patellar tilt, improves clinical outcomes and decreases the rate of surgical revision.

LEVEL OF EVIDENCE

III.

Patellar resurfacing versus nonresurfacing in total knee arthroplasty: an updated meta-analysis of randomized controlled trials

BACKGROUND

Whether resurface the patella or not in total knee arthroplasty (TKA) was controversial. In 2013, we conducted a meta-analysis of randomized controlled trials (RTCs). After that, plenty of studies have been carried out, but there still existed a great deal of controversy. In order to update our previous study, we conducted this update meta-analysis to evaluate the efficacy of patellar resurfacing in TKA.

METHODS

Databases were searched for RCTs comparing the outcomes of patellar resurfacing and nonresurfacing in TKA. Outcomes of knee relevant indicators were analysed. To see the short- and long-term effects, we calculated the data in total and divided the patients who were followed up for ≤ 3 years and ≥ 5 years into two subgroups as well.

RESULTS

Thirty-two trials assessing 6887 knees were eligible. There was a significant difference in terms of reoperation (in total and ≥ 5 years), Knee Society Score (KSS), function score (in total and ≥ 5 years) and noise. While no significant difference was found in the following items: reoperation (≤ 3 years), anterior knee pain (AKP), function score (≤ 3 years), range of motion (ROM), Oxford score, the Knee Injury and Osteoarthritis Outcome Score (KOOS), visual analogue score (VAS), Feller score, patellar tilt and the patients' satisfaction.

CONCLUSIONS

We found that patellar resurfacing could reduce the occurrence of reoperation and noise after surgery, as well as increase the KSS and function score, while it might not influence the outcomes such as AKP, ROM, Oxford score, KOOS, VAS, Feller score, patellar tilt and the patients' satisfaction. The results are different from our previous finding in the meta-analysis. In conclusion, we prefer patellar resurfacing in TKA.

Patellar cartilage loss does not affect early outcomes of total knee arthroplasty performed without patella resurfacing

BACKGROUND

The aim of this study was to compare the outcomes and cost economics of TKA without patella resurfacing in patients with and without patellar cartilage loss.

METHODS

Prospective case control study of 209 consecutive patients undergoing TKA without patella resurfacing. Patella cartilage status was documented intra-operatively: 108 patients had patella cartilage loss (mean age 70 ± 9.7, mean BMI 31 ± 6.2, 72 (67%) female) and 101 control patients did not (age 68 ± 9.2, BMI 31 ± 5.6, 52 (51%) female). The primary outcome measure was Oxford Knee Score (OKS) improvement at one year. Secondary outcomes included OKS, EQ-5D, anterior knee pain (AKP), Kujala scores and reoperation at 2-4 years. The cost to prevent secondary patella resurfacing was calculated.

RESULTS

There were more women in the patella cartilage loss group (67% Vs 51%, p = 0.037), but no other preoperative characteristics differed. There was no difference in OKS improvement between those with and without patella cartilage loss at 1 year (mean difference -1.03, -3.68 to 1.62 95%CI, p = 0.446) or 2-4 years (mean difference 1.52, -1.43 to 4.45 95%CI, p = 0.310). At 2-4 years there was no difference in AKP (14/87 with vs 17/80 without, p = 0.430) nor Kujala score (mean difference 2.66, -3.82 to 9.13 95%CI, p = 0.418). Routine patella resurfacing would have cost £58,311 to prevent one secondary resurfacing.

CONCLUSION

There was no difference in OKS, anterior knee pain, reoperation or Kujala scores up to 2-4 years between patients with and without patellar cartilage loss following TKA without patella resurfacing. Resurfacing for this indication would not have been a cost effective intervention.

Patellar facet ratio affects knee pain, stair climbing and stair descent after TKA without patellar resurfacing

PURPOSE

To determine whether knee pain or functional impairment after total knee arthroplasty (TKA) without patellar resurfacing are correlated with preoperative patellar morphology or postoperative patellar orientation. The hypotheses were that patellar shape, increased tilt and lateral displacement would be associated with pain and functional impairment.

METHODS

From a consecutive series of 152 knees that received a cemented postero-stabilized TKA, the Oxford Knee Score (OKS) and the Knee injury and Osteoarthritis Outcome Score (KOOS) were collected at a minimum follow-up of 12 months. Uni- and multi-variable linear regression analyses were performed to determine associations between the collected clinical scores and patient demographics and patellar morphology, measured from pre- and post-operative frontal, lateral and skyline view radiographs.

RESULTS

The OKS was 75 ± 23, whereas the KOOS pain, stair climbing, and descent were respectively 77 ± 24, 3.9 ± 1.1 and 3.8 ± 1.2. OKS was not associated with any radiographic outcomes, whereas KOOS pain was better for knees with larger medial patellar facets. The KOOS stair climbing and descent were also better for knees with larger medial patellar facets.

CONCLUSION

The findings of this study partly confirm the hypotheses that pain and functional impairments after TKA without patellar resurfacing are associated with patellar shape. No association was revealed between postoperative patellar orientation and function nor pain. Quantitative consideration of patellar congruency could therefore prevent pain and improve function after TKA without patellar resurfacing.

LEVEL OF EVIDENCE

Retrospective study, Level III.

Does Patellar Resurfacing Matter? Midterm Follow-Up of MRK Total Knee Replacement

BACKGROUND

Many designs of TKR have been developed to optimize the kinematics and improve satisfaction, including the 'medial rotating' philosophy. The purpose of this study is to report the mid-term clinical outcome of MRK knees and evaluate whether resurfacing the patella makes any difference in outcome.

METHODS

A retrospective analysis was done of 104 MRK total knee replacement done between 2008 and 2017. Patients were called for a review for evaluation of OKS, Baldini and Feller scores. Demographics of the patients, clinical outcome, complications were assessed.

RESULTS

62 had patellar resurfacing. Mean follow-up was 74.45 months in non- resurfaced and 54.93 months in resurfaced group. Mean flexion range in both groups at final follow-up was 101.45. Median OKS at follow-up was 36 (12-47) in non-resurfaced and 37 (9-48) in resurfaced group. Patella scores were better in resurfaced group-Baldini score median (range) was 90 (25-100) in non-resurfaced v/s 100 (30-100) in resurfaced, Feller score median (range) was 25 (12-30) in non-resurfaced v/s 28 (10-30) (p 0.042) in resurfaced. The patellofemoral component of the OKS (Q5 + Q7 + Q12) median showed an improvement from 3 (1-11) to 6.5 (3-11) in non-resurfaced and from 3 (0-12) to 8 (2-12) (p 0.039) in resurfaced group. There were five complications overall (4.8%).

CONCLUSION

These results show a satisfactory outcome at mid-term follow-up. We found a statistically significant difference in Feller score and in the patellofemoral component of OKS between the groups of MRK knee suggesting specific benefits of patellar resurfacing with this implant.

The effect of patellar facet angle on patellofemoral alignment and arthritis progression in posterior-stabilized total knee arthroplasty without patellar resurfacing

Background

The purpose of this study was to evaluate the effect of patellar facet angle on pre- and postoperative patellofemoral alignment and the progress of arthritis of the patellofemoral joint in posterior-stabilized total knee arthroplasty (PS TKA) without patellar resurfacing.

Methods

Patients who had a PS TKA for a varus osteoarthritic knee who were followed up for more than 2 years were included in this study. The radiologic and clinical outcomes were compared between 72 knees (group A) whose patellar facet angle was greater than 126° (> 126°) and 32 knees (group B) whose patellar facet angle was smaller than or equal to 126° (≤ 126°). For the radiologic assessment, the Kellgren-Lawrence grade, mechanical femorotibial angle, Insall-Salvati ratio, patellar tilt angle, patellar displacement and the osteosclerosis of the patellar ridge were evaluated. The range of motion (ROM) and patient-reported outcomes (the Knee Society knee score, the Knee Society function score, the Feller patellar score, and the Kujala patellofemoral score) were used for the clinical assessment.

Results

The preoperative patellar tilt angle was 9.8° (standard deviation [SD] 5.5) and 14.6° (SD 4.1) in group A and group B, respectively, a significant difference (p < 0.001). Other preoperative radiologic parameters and preoperative patient-reported outcomes and ROM showed no significant difference between the two groups (all parameters (p > 0.05). At the last-follow-up, 22 knees (30.6%) showed progression of osteosclerosis of the patellar ridge in group A and 13 knees (40.6%) showed progression of osteosclerosis in group B (p = 0.371). The postoperative radiologic and clinical outcomes showed no significant difference between the two groups (all parameters, p > 0.05).

Conclusions

Although a narrow patellar facet angle was related to an increase of lateral tilting of the patella, it showed no impact on the preoperative clinical assessment. The radiologic and clinical outcomes evaluated after the PS TKA showed no statistical difference according to the patellar shape. Although the patellar shape evaluated by the patellar facet angle can partially affect the preoperative patellofemoral alignment, this study result indicated insignificant clinical relevance of the patellar shape in the PS TKA.

Does Knee Prosthesis Survivorship Improve When Implant Designs Change? Findings from the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

TKA generally has excellent long-term survivorship. When a new knee system supersedes a previous model, increased survivorship, improved functional performance, or both may be expected, because key areas of design modification are often targeted to address wear, stability, and the patellofemoral articulation. However, not all design changes are beneficial, and to our knowledge, knee arthroplasty has not been systematically evaluated in the context of design changes that occur during the development of new knee arthroplasty systems.

QUESTIONS/PURPOSES

Using the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) we performed multiple old-to-new comparisons of frequently used contemporary knee implants to ask: (1) does overall prosthesis survivorship free from revision increase when a new knee prosthesis system is introduced to replace a prior prosthesis system? (2) Has survivorship free from revision improved for the revision indications of wear, instability, and patellofemoral articulation issues, where development efforts have been concentrated?

METHODS

Data from the AOANJRR from September 1999 to December 2017 were used to compare the survivorship of prostheses free from revision at a maximum of 17 years in procedures where a new design model was introduced to replace a prior knee system from the same manufacturer. Only prosthesis systems used in a minimum of 2000 primary TKA procedures for osteoarthritis that had a minimum of 5 years of follow-up were included. Varus-valgus constrained and hinge TKA designs were excluded. Cruciate-retaining, posterior-stabilized, and medial pivot-design knees were considered separately. The new and old prosthesis systems were paired for analysis. Survivorship was calculated with Kaplan Meier estimates and comparisons were performed using the Cox proportional hazards method. Subanalyses according to the three main revision indications were performed, and where possible, analyses were performed based on polyethylene types (highly cross-linked polyethylene and ultra-high-molecular-weight polyethylene), combined and separated. Revision was defined as a reoperation of a previous knee arthroplasty in which one or more of the components was removed, replaced, or added. There were 323,955 TKA procedures and 11 new prosthesis system designs that were introduced to replace an earlier knee system from the same manufacturer. Of these prosthesis system pairs, six were cruciate-retaining prostheses, four were posterior-stabilized designs, and one was a medial pivot design.

RESULTS

Six of the 11 knee system pairs showed improved survivorship with the new design, three were no different, and in two, the newer prosthesis systems had a higher rate of revision than the old one did. When revision for wear was analyzed, five prosthesis systems showed improvement, five were no different, and one had a higher rate of revision than the previous system did. There was no improvement in the rate of revision for instability; seven new prosthesis systems showed no difference from the previous system and four new prosthesis systems had a higher rate of revision than the previous system did. A subanalysis of revision for patellofemoral complications showed improvement in two comparisons, no difference in six, and a higher revision rate in two; one could not be calculated because of an insufficient number of revisions for this reason.

CONCLUSIONS

It is difficult to predict whether a new system will demonstrate better survival than a previous one, and widespread uptake of a new design before a benefit is shown in robust clinical studies is unwise. Similarly, adoption of a new system for which there is no difference in survivorship from a previous model may be premature because a new device may have associated unknown and unintended consequences. Healthcare policy makers and therapeutic device regulators should similarly be guided by results and seek out peer-reviewed evidence before accepting change to established practice. Surgeons must be aware that implant changes may not translate into better survivorship and must seek compelling evidence of improvement in survival and/or function before changing systems.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Wiberg Type III patellae and J-sign during extension compromise outcomes of total knee arthroplasty without patellar resurfacing

BACKGROUND

Understanding the risk factors associated with postoperative pain and worse outcome can guide surgeons on whether primary patellar resurfacing is warranted during total knee arthroplasty (TKA). The purpose of this study was to determine whether clinical scores and pain after TKA without patellar resurfacing are correlated with patellar shape and postoperative patellar position and kinematics.

METHODS

Radiographs as well as anterior knee pain according to the Visual Analogue Scale (pVAS) were collected pre- and postoperatively for 100 knees aged 68 ± 7.7 years that received uncemented TKA without patellar resurfacing. At a minimum follow-up of 12 months the Forgotten Joint Score (FJS), the Oxford Knee Score (OKS) as well as the flexion range of motion and the presence of J-sign during active extension were recorded. Uni- and multivariable linear regression analyses were performed to determine associations between the collected clinical scores and patient demographic and radiographic data.

RESULTS

Postoperative OKS (79 ± 14.4) was worse for Wiberg Type III patellae (β = -11.4, P = .020, compared with Type II). Anterior pVAS (2 ± 2) was greater in knees with J-sign during extension (β = 2.8, P < .001). None of the other radiographic measurements (patellar tilt, congruence angle and lateral patellar displacement) were correlated with postoperative OKS or anterior pVAS.

CONCLUSION

Incongruent patellar shape (Wiberg Type III) is associated with worse clinical scores, and abnormal kinematics (J-sign) with increased pain after TKA without patellar resurfacing. The authors therefore recommend routine resurfacing for Wiberg Type III patellae, though further studies are required to confirm whether resurfacing truly improves clinical scores and pain in this subgroup.

Age and Prosthetic Design as Risk Factors for Secondary Patella Resurfacing

BACKGROUND

Selectively resurfacing the patella based on a patient's risk of secondary patella resurfacing (SPR) may be the optimal strategy for primary total knee arthroplasty (TKA). However, exactly which factors increase the risk of SPR is unknown. Utilizing New Zealand Joint Registry data, we investigated the following: (1) What patient and surgical factors are more prevalent among TKA patients who received SPR compared to those who did not? and (2) What is the difference in Oxford Knee Scores (OKS) between those who receive SPR and those who do not?

METHODS

Prevalence of various patient and surgical factors was compared between 197 non-resurfaced TKAs that proceeded to SPR and 31,399 that did not. Multivariate analysis was used to determine the odds ratio for each factor that differed between groups. Six-month postoperative OKS for each group was utilized for comparison.

RESULTS

Posterior-stabilized designs had an odds ratio of 1.86 (95% confidence interval [CI] 1.31-2.66; P = .001) when compared to cruciate-retaining designs. When compared to age less than 55, age >75 and age 65-74 had odds ratios of 0.27 (95% CI 0.16-0.46; P < .001) and 0.44 (95% CI 0.28-0.69; P < .001) respectively. Six-month OKS was lower among those who received SPR (37.27 vs 27.26; P < .001).

CONCLUSION

Younger age, posterior-stabilized design, and a low 6-month OKS were associated with SPR.

Characteristics of three different patellar implant designs in total knee arthroplasty

BACKGROUND

Despite debate over the role of patellar resurfacing in total knee arthroplasty, many surgeons feel it decreases re-operation rates and anterior pain, and an increasing number are adopting resurfacing. This study compares intra-operative characteristics of different patellar implants to assist surgeons in gaining better understanding of these implants.

METHODS

The three most commonly used patellar implants (inset, onlay round and onlay oval) were allocated randomly to 120 patients undergoing total knee arthroplasty. We compared the groups in terms of implant size, bone coverage, lateral underhang (uncovered lateral facet) and need for partial lateral facetectomy. We also compared the patient-reported outcome measures between the groups at 6 months post-operatively.

RESULTS

The inset, onlay round and onlay oval designs had bone coverage of 48.5%, 65.9% and 85.9%, respectively (P < 0.01). Similarly, the onlay-oval implant was found to have the smallest lateral underhang of all three designs (inset 11.6 mm; onlay round 6.9 mm, onlay oval 1.6 mm, P < 0.01). The onlay-oval design was the largest implant with a median size of 35 mm, compared to 23 mm for the inset and 32 mm for the onlay round (P < 0.01). In addition, patellae using onlay-oval implants required significantly fewer lateral facetectomies due to improved bone coverage (inset 95%; onlay round 87%; onlay oval 3%; P < 0.01). Finally, comparison of patient-reported outcome measures between the groups showed no difference at an early assessment of 6 months.

CONCLUSION

Onlay-oval design allows for the use of a larger implant, improving bone coverage and reducing the need for partial lateral facetectomy; however, early assessment of outcomes shows no difference between the three designs.

Patellar osteolysis after total knee arthroplasty with patellar resurfacing: a potentially underappreciated problem

Osteolysis of the patella following total knee arthroplasty is both uncommon and poorly described in the literature. We describe 3 cases of total knee arthroplasty with patella resurfacing that later presented with anterior knee pain with patellar osteolysis without evidence of patellar implant failure: 2 males and 1 female patient, all with bilateral knee osteoarthritis. Osteolysis of the patella was identified radiographically between 2 and 16 years from the index procedure. We theorize that high pressures across the patella-femoral joint, in obese or muscular patients, may play a role in the formation of these patellar osteolytic lesions. We suspect that the prevalence of this phenomenon is under-recognized in the literature and may increase with longer term follow-up and awareness.