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.

To resurface or not to resurface? Investigating the impact of patellar resurfacing on anterior knee pain in rheumatoid arthritis patients undergoing total knee replacement

BACKGROUND

Routine patellar resurfacing is a controversial issue in total knee replacement (TKR), especially for rheumatoid arthritis (RA). Anterior knee pain (AKP) is a common complaint after TKR that may be related to patellofemoral joint condition. The aim of this study was to investigate the prevalence and factors associated with AKP after TKR for RA compared between non-resurfaced patella (NRP) and resurfaced patella (RP).

METHODS

This retrospective study included RA patients who underwent TKR at our institute from 2002 to 2019. All included patients had at least 1 year of follow up. Patients were divided into the NRP and RP groups. At the last follow up visit, the prevalence of AKP, and the severity of AKP, including visual analogue pain score (VAPS) and Kujala score, were compared between groups. Univariate and multivariate logistic regression analysis was performed to identify independent predictors of AKP.

RESULTS

A total of 141 RA patients (median age: 60 years, 90% female, 219 knees) were included. There was no significant difference in AKP between the NRP and RP groups (12.7% vs. 7.3%, P = 0.185). Regarding AKP severity, there was no significant difference in VAPS or Kujala score between groups (P = 0.147 and P = 0.067, respectively). No independent predictors of AKP were identified.

CONCLUSION

Although patellar resurfacing is recommended in TKR for RA, this study found no significant difference in prevalence of AKP, VAPS and Kujala score between those with and without patellar resurfacing during TKR.

Do we need to restore patellar thickness after total knee arthroplasty with patellar resurfacing?

PURPOSE

The aim of this study was to investigate whether increased patellar thickness after resurfacing decreased knee flexion angle and had any effect on functional outcomes comparing with patellar thickness restoration (patelloplasty) in patients undergoing primary total knee arthroplasty (TKA) or not.

METHODS

We retrospectively reviewed 220 patients undergoing primary TKA: 110 patients undergoing patelloplasty and 110 patients received overstuffed patellar resurfacing using subchondral bone cut at lateral facet technique were recruited. The mean increase in patellar thickness after resurfacing equal to 2 ± 1.2 mm. The outcomes were postoperative knee flexion angle and modified Western Ontario and McMaster University Osteoarthritis Index (WOMAC) score at minimum 2 year after surgery.

RESULTS

The mean postoperative knee flexion angles were similar between overstuffed resurfacing group and patelloplasty group (132 ± 7° vs. 134 ± 8°, 95% confidence interval [CI] - 6.9-1.8°, p = 0.1). The mean increase in postoperative knee flexion was 13° in both groups (p = 0.94). The mean change of overall modified WOMAC score was also similar between the two groups (42 ± 12 vs. 39 ± 9 points, 95% CI - 1.7-9.4 points, p = 0.17).

CONCLUSION

This study demonstrated that increased patellar thickness has no effect on postoperative knee flexion angle and functional outcomes in TKA. The finding clarified the misunderstanding principle of native patellar thickness restoration after resurfacing which had made many surgeons to refrain from resurfacing especially in patient who had thin patella.

Systematic lateral retinacular release does not reduce anterior knee pain after total knee arthroplasty with patellar resurfacing

PURPOSE

The aim of this study was to assess the effect of systematic lateral retinacular release (LRR) on anterior knee pain (AKP), as well as its impact on the functional and radiological outcomes after total knee arthroplasty (TKA) with patellar resurfacing.

METHODS

A prospective randomized study was designed. It included patients scheduled for a TKA procedure with patellar resurfacing, who were recruited and randomized into either the LRR group or the non-release group. 198 patients were included in the final analysis. The pressure pain threshold (PPT) assessed by pressure algometry (PA), the visual analogue scale (VAS), Feller's patellar score, the Knee Society Score (KSS), patellar height, and patellar tilt were recorded both preoperatively and at the 1-year follow-up. The Mann-Whitney U test was performed to determine comparisons between both groups as well as to determine differences' intragroup.

RESULTS

Relative to the clinical variables and scores, no difference was detected between the two groups at the 1-year follow-up (p = n.s.). However, there was a slight difference in patellar tilt (0.1º vs. 1.4º, p = 0.044), with higher tilt values in the non-release group. There was no difference in terms of improvement in the clinical and radiological scores and variables recorded between the two groups (p = n.s.).

CONCLUSION

LRR in primary TKA with patellar resurfacing does not show an improvement in AKP and functional outcomes over patellar resurfacing without release.

LEVEL OF EVIDENCE

I.

Higher failure rate of secondary patellar resurfacing following bicompartmental knee arthroplasty

INTRODUCTION

The role of secondary patellar resurfacing (SPR) in anterior knee pain (AKP) is still debated in literature. A regional arthroplasty registry was investigated, aiming to: (1) assess the survival rate of SPR; and (2) compare SPR to tricompartmental TKA.

MATERIALS AND METHODS

The regional arthroplasty registry RIPO was investigated about all SPRs performed after bicompartmental arthroplasty. The survival rates and the reasons for revision were assessed as any other factor that could have influenced implants failure. SPR survivorship was compared to tricompartmental TKAs.

RESULTS

406 SPRs performed after bicompartmental arthroplasty were analyzed. The survival rates were 80.6% (CI 95% 75.9-84.5) at 5 years and 77.6% (CI 95% 72.4-82) at 7 years. Half of the SPRs was performed 0.9-2.4 years after the index bicompartmental arthroplasty. SPR achieved lower survival than tricompartmental TKA (80.6% vs 96.7%, p < 0.001), with an adjusted hazard ratio for failure of 5.5 (CI 95% 4.2-7.1, p < 0.001). SPRs performed within 2 years after primary implant had a significantly higher rates of failure when compared to tricompartmental TKA (HR: 6.4, CI 95% 4.8-8.4, p < 0.001).

CONCLUSION

SPR after bicompartmental knee arthroplasty showed modest 5- and 7-year survival rates, worse than primary tricompartmental TKA. When SPRs are performed within 2 years after primary arthroplasty, a significant higher risk of failure should be expected, highlighting than appropriate pre-operative work-up and patient selection is crucial for SPR successful outcome.

LEVEL OF EVIDENCE

III, therapeutic study.

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).

Patellar resurfacing and kneeling ability after total knee arthroplasty: a systematic review

BACKGROUND

Difficulty kneeling following total knee arthroplasty (TKA) remains highly prevalent, and has cultural, social, and occupational implications. With no clear evidence of superiority, whether or not to resurface the patella remains debatable. This systematic review examined whether resurfacing the patella (PR) or not (NPR) influences kneeling ability following TKA.

METHODS

This systematic review was conducted by following PRISMA guidelines. Three electronic databases were searched utilizing a search strategy developed with the aid of a department librarian. Study quality was assessed using MINROS criteria. Article screening, methodological quality assessment and data extraction were performed by two independent authors, and a third senior author was consulted if consensus was not reached.

RESULTS

A total of 459 records were identified, with eight studies included in the final analysis, and all deemed to be level III evidence. The average MINORS score was 16.5 for comparative studies and 10.5 for non-comparative studies. The total number of patients was 24,342, with a mean age of 67.6 years. Kneeling ability was predominantly measured as a patient-reported outcome measure (PROM), with two studies also including an objective assessment. Two studies demonstrated a statistically significant link between PR and kneeling, with one demonstrating improved kneeling ability with PR and the other reporting the opposite. Other potential factors associated with kneeling included gender, postoperative flexion, and body mass index (BMI). Re-operation rates were significantly higher in the NPR cohort whereas PR cohorts had higher Feller scores, patient-reported limp and patellar apprehension.

CONCLUSION

Despite its importance to patients, kneeling remains not only under-reported but also ill-defined in the literature, with no clear consensus regarding the optimum outcome assessment tool. Conflicting evidence remains as to whether PR influences kneeling ability, and to clarify the situation, large prospective randomized studies are required.

Patellar resurfacing was not associated with a clinically significant advantage when a modern patellar friendly total knee arthroplasty is employed: A systematic review and meta-analysis

BACKGROUND

Modern total knee arthroplasty (TKA) femoral components are designed to provide a more optimal articular surface for the patella whether or not it has been resurfaced. Previous systematic reviews comparing outcomes of patellar resurfacing and no resurfacing combine both historic and modern designs.

AIMS

The aim of this study was to investigate the effect of patellar resurfacing in modern "patellar friendly" implants on (1) incidence of anterior knee pain, (2) patient reported outcomes (3) complication rates, and (4) reoperation rates compared with unresurfaced patellae in primary TKA.

METHODS

MEDline, PubMed and google scholar studies were evaluated using SIGN assessment tool and data analysis was conducted using Review Manager 5.2 on only randomised controlled trials. The search terms were: arthroplasty, replacement, knee (Mesh), TKA, prosthesis, patella, patellar resurfacing, patellar retaining.

RESULTS

Thirty-two randomised controlled studies were identified that reported the type of TKA implant used: 11 used modern "patellar friendly" implants; and 21 older "patellar non-friendly" implants. Among "patellar friendly" TKAs there were no significant differences in anterior knee pain rates between resurfaced and unresurfaced groups. Patellar resurfacing with "patellar friendly" implants had significantly higher clinical (mean difference (MD) -0.77, p = 0.007) and functional (MD -1.87, p < 0.0001) knee society scores (KSS) than unresurfaced counterparts but these did not exceed the minimal clinically important difference (MCID). Resurfacing with "patellar friendly" implants was not associated with a significant (p = 0.59) difference in the Oxford knee score (OKS), in contrast when a "patellar non-friendly" implant was used there was a significant difference (MD 3.3, p = 0.005) in favour of resurfacing. There was an increased risk of reoperation for unresurfaced TKAs with "non-patellar friendly" implants (Odds ratio (OR) 1.68, 95% CI 1.03-2.74, p = 0.04), but not for unresurfaced patellae with "patellar friendly" implants (OR 1.17, CI 0.59-2.30).

CONCLUSIONS

Patellar resurfacing in combination with a modern patellar friendly implant was not associated with a lower rate of anterior knee pain, complications, or reoperations compared to not resurfacing, nor did it give a clinically significant improvement in knee specific function. In contrast patellar resurfacing in combination with a "non-friendly" TKA implant was associated with a significantly better OKS and lower reoperation rate. Implant design should be acknowledged when patellar resurfacing is being considered.

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.

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.

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.

Patellar resurfacing has minimal impact on in vitro tibiofemoral kinematics during deep knee flexion in total knee arthroplasty

BACKGROUND

While patellar resurfacing can affect patellofemoral kinematics, the effect on tibiofemoral kinematics is unknown. We hypothesized that patellar resurfacing would affect tibiofemoral kinematics during deep knee flexion due to biomechanical alteration of the extensor mechanism.

METHODS

We performed cruciate-retaining TKA in fresh-frozen human cadaveric knees (N = 5) and recorded fluoroscopic kinematics during deep knee flexion before and after the patellar resurfacing. To simulate deep knee flexion, cadaver knees were tested on a dynamic, quadriceps-driven, closed-kinetic chain simulator based on the Oxford knee rig design under loads equivalent to stair climbing. To measure knee kinematics, a 2-dimensional to 3-dimensional fluoroscopic registration technique was used. Component rotation, varus-valgus angle, and anteroposterior translation of medial and lateral contact points of the femoral component relative to the tibial component were calculated over the range of flexion.

RESULTS

There were no significant differences in femoral component external rotation (before patellar resurfacing: 6.6 ± 2.3°, after patellar resurfacing: 7.2 ± 1.8°, p = 0.36), and less than 1° difference in femorotibial varus-valgus angle between patellar resurfacing and non-resurfacing (p = 0.01). For both conditions, the medial and lateral femorotibial contact points moved posteriorly from 0° to 30° of flexion, but not beyond 30° of flexion. At 10° of flexion, after patellar resurfacing, the medial contact point was more anteriorly located than before patellar resurfacing.

CONCLUSION

Despite the potential for alteration of the knee extensor biomechanics, patellar resurfacing had minimal effect on tibiofemoral kinematics. Patellar resurfacing, if performed adequately, is unlikely to affect postoperative knee function.

Tibial Osteolysis After Long-Term Isolated Polyethylene Patellar Resurfacing

Isolated patellar resurfacing served as an early treatment for patellofemoral arthritis but was abandoned because of erosion of the native femoral trochlear groove over time. We present the case of a large native tibial osteolytic lesion 20 years after isolated patellar resurfacing with a cemented polyethylene component. The patient had severe tricompartmental arthritic changes. The patellar component was very worn, and the resultant particle debris produced a large cavitary lesion in the proximal tibia. Osteolysis is a rare complication in patellofemoral arthroplasty, and, to our knowledge, this is the first reported case of native tibial osteolysis after isolated patellar resurfacing. The patient was treated with initial curettage and bone grafting of the lesion followed by total knee arthroplasty with a tibial cone and stemmed tibial fixation.

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.

Is obesity associated with short-term revision after total knee arthroplasty? An analysis of 121,819 primary procedures from the Dutch Arthroplasty Register

BACKGROUND

The prevalence of obesity is increasing. The association with knee osteoarthritis is well documented, resulting in the population requesting total knee arthroplasty (TKA) for invalidating symptoms to be heavier in nature. The purpose of the current analysis was to assess the association between preoperative body mass index (BMI) and short-term revision rate after TKA. The secondary aim was to investigate the influence of implant fixation method on the association between BMI and survivorship.

METHODS

This is a retrospective analysis of prospectively collected registry data (Dutch Arthroplasty Register; LROI). All primary TKA procedures in patients >18 years of age with registered BMI were selected (n = 121,819). Non-obese patients (BMI 18-25) were compared with overweight (BMI 25-30) and class I-III obese (BMI >30, >35, >40) patients. Crude all-cause revision rates were calculated using competing risk analysis. Adjusted hazard ratios (HRs) were determined with Cox multivariable regression analyses for all-cause, septic and aseptic revision and secondary patellar resurfacing.

RESULTS

Revision rates were 3.3% for non-obese patients, 3.5% for overweight patients, 3.7% for class I obese patients, 3.6% for class II obese patients and 3.7% for class III obese patients. Class III obese patients had a significant higher risk for septic revision compared with non-obese patients (HR 1.53, 95% confidence interval (CI) 1.06-2.22). Class I obese patients had a higher risk for secondary patellar resurfacing (HR 1.52, 95% CI 1.12-2.08). All-cause and aseptic revision rates were similar between BMI groups.

CONCLUSIONS

Obesity appeared to be associated with some short-term revision risks after TKA, but was not associated with an overall increase in revision rate.

Long-Term Comparison Study of Patella Resurfacing Versus Non-resurfacing in Total Knee Arthroplasty with Minimum 10-Year Follow-Up

BACKGROUND

Management of the patella during total knee arthroplasty is a matter of constant debate. Numerous studies have assessed and compared the mechanical and clinical results of total knee arthroplasty with native as well as resurfaced patellae. However, the consensus has not been reached yet on this subject. This study aims to compare the outcome between patella resurfaced (PR) and non-resurfaced patellae (NPR) after a follow-up of minimum 10 years following total knee arthroplasty.

MATERIALS AND METHODS

This is a retrospective study including 63 subjects (103 knees) who had undergone total knee arthroplasty with a follow-up of 10-14 years. In this study, we evaluated the knees implanted with either press fit condylar (PFC) sigma (Depuy, Johnson & Johnson) or Nexgen (CR flex/LPS flex) (Zimmer, Warsaw, Indiana, USA) implants. Whether to perform patella resurfacing or not and choice of implants as well as implant design (posterior stabilized/cruciate retaining) was surgeons' preference. At final follow-up, clinical and functional outcome was assessed using Knee Society Scores (KSS), and comparison of difference between pre-op scores and scores at final follow-up among resurfaced versus non-resurfaced patellae groups was carried out. Patello-femoral function was assessed at final follow-up using Feller's score and the results were compared between resurfaced and non-resurfaced patellae.

RESULTS

The mean follow-up was 140 months (range 124-168 months). There were 62 knees with their patella resurfaced and 41 knees with non-resurfaced patellae There was no significant difference in the mean pre-op Knee Society Scores between PR (46.29 ± 5.17) and NPR (47.34 ± 5.95), p value 0.34. Similarly there was no significant difference in their pre-op functional score as well PR (38.53 ± 5.14) and NPR (39.22 ± 6.79), p value 0.56. Both groups had significantly improved post-operative Knee Society Scores PR (85.95 ± 5.23) and NPR (84.65 ± 5.30). However, there is no difference between these groups, p value 0.22. Functional scores also maintained significant improvement at final follow-up. Between the two groups, the resurfaced group showed a significantly higher functional score at final follow-up: PR (70.90 ± 7.73) and NPR (66.44 ± 7.12), p value 0.02. Feller's score at final follow-up for PR group was (23.36) and NPR group was (21.98), p value 0.001, which showed clear superiority of PR over NPR.

CONCLUSION

After a minimum follow-up of 10 years, there were no differences in clinical results; however, the knee function score and patello-femoral function scoring was found to be significantly higher with patella resurfacing and it was persistent across all the subgroups we had included in the study-posterior stabilized/cruciate retaining or between implants made by two different manufacturers.

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.

The effect of patellar thickness on gait biomechanics following total knee arthroplasty

BACKGROUND

Patella resurfacing is commonly performed during total knee arthroplasty; however, determining the appropriate patellar thickness remains a challenge. The purpose of this study was to evaluate the role of post-TKA patellar thickness on knee extensor strength and biomechanical joint loading forces during walking and stair negotiation.

METHODS

Fifteen patients (21 knees) underwent gait analysis prior to TKA and post-TKA at six weeks, three months, six months, and one year. Knee extensor strength and biomechanics were collected during level walking and stair negotiation and analyzed using Pearson correlation coefficients.

RESULTS

Knee extensor strength was positively correlated to patellar thickness at three months and one year post-TKA (p ≤ .05). During walking, no significant correlations were present. During stair ascent, there was a positive correlation between patellar thickness and peak knee flexion angle one year post-TKA (p ≤ .05). During stair descent, there was a positive correlation between patellar thickness and maximum vertical ground reaction forces at one year post-TKA (p ≤ .01).

CONCLUSIONS

The loss of patellar thickness when compared to measured pre-resurfacing thickness was correlated with a decrease in knee extensor strength; however, changes in patellar thickness were not significantly correlated to biomechanical loading forces during walking. Increases in demand of activity increase the torque to the knee joint, which elicit increases in compensatory motions, likely reducing the extent to which differences in joint loading during stair negotiation may be attributable to changes in patellar thickness. Therefore, the effect of post-patellar thickness on patient function in primary TKA is limited.

Prevalence of anterior knee pain after patellar retention total knee arthroplasty: Comparison of patients with rheumatoid arthritis versus primary osteoarthritis

Objective

The aim of this study was to investigate whether there is an increased risk of anterior knee pain (AKP) after total knee arthroplasty (TKA) without patellar resurfacing in patients with rheumatoid arthritis (RA) versus primary osteoarthritis (OA).

Methods

This study was a retrospective review of 388 patients (577 knees) who underwent TKA without patellar resurfacing between 2003 and 2011, with a minimum of 5 years of follow-up. Patients were divided into two groups: Group OA (273 knees of 206 patients; 83 males, 123 females; mean age: 64.4 (47–87) years) and Group RA (304 knees of 182 patients; 92 males, 90 females; mean age: 50.7 (21–72) years). In the clinical evaluation, the knee range of motion (ROM) and several outcome measures such as The Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and International Knee Documentation Committee (IKDC) scores were used preoperatively and at the final follow-up visit. The quality of life was measured using Short Form (SF)-36 MCS and PCS scores. The primary outcome was the frequency and severity of patient-reported AKP. The AKP Scale was used to determine the severity of AKP.

Results

The IKDC raised from 21.62 (range, 13–29.9) preoperatively to 85.1 (range, 80–88) for group OA and from 21.8 (range, 13–29.9) to 85.2 (range, 81–88) for group RA (p < 0.001). The mean KSS improved from 28.35 (range, 22–38) preoperatively to 90.04 (range, 88–95) for group OA and from 21.9 (range, 18–35) preoperatively to 89.7 (range, 86–95) for group RA. The mean WOMAC increased from 20.61 (range, 17.4–24.2) preoperatively to 95.7 (range, 90.9–97.7) for group OA (p < 0.001) and from 20.2 (range, 16.7–24.2) preoperatively to 95.8 (range, 90.9–98.5) for group RA (p < 0.001). The mean ROM improved from 80.14° (range, 55°–130°) preoperatively to 113.17° (range, 95°–140°) in group OA (P = 0.003) and from 73.4° (range, 10°–130°) to 112.8° (range 90°–140°) in group RA (P = 0.003) postoperatively. The frequency of AKP was 8% in Group OA and 7% in Group RA (p = 0.27). For patients with AKP, the mean AKP Scale was 92.74 (range, 84–98) in Group OA and 93.39 (range, 82–98) in Group RA (p = 0.3).

Conclusion

After TKA without resurfacing the patella, patients with RA were determined to have a similar risk for AKP as those with OA.

Level of evidence

Level III, Therapeutic Study.

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.

Does navigated patellar resurfacing in total knee arthroplasty result in proper bone cut, motion and clinical outcomes?

BACKGROUND

In total knee arthroplasty with patellar resurfacing, patellar bone preparation, component positioning and motion assessments are still not navigated. Only femoral/tibial component positioning is supported by computer-assistance. The aim of this study was to verify, in-vivo, whether knee surgical navigation extended to patellar resurfacing, by original instrumentation and procedures for patellar-based tracking, could achieve accurate patella preparation in terms of original thickness restoration, bone cut orientation, and normal knee motion.

METHODS

An additional navigation system for patellar data acquisition was used together with a standard navigation system for total knee arthroplasty in 20 patients. This supported the surgeon for patellar resurfacing via measurement of removed bone thickness, three-dimensional patellar cut orientations, and patello-femoral motion. Radiological and clinical examinations at 6 and 24-month follow-up were also performed.

FINDINGS

The medio-lateral patellar-bone cut orientation was respectively 0.5° (standard deviation: 3.0°) and 1.4° (1.7°) lateral tilt, as measured via navigation and post-operatively on the Merchant x-ray view. The cranio-caudal orientation was 3.8° (7.2°) of flexion. The thickness variation between patellar pre- and post-implantation was 0.2 (1.3) mm. Immediately after implantation, patello-femoral as well as tibio-femoral kinematics was within the normality. Good radiological and clinical examinations at 6 and 24-month follow-up were also observed.

INTERPRETATION

For the first time, the effect of patellar navigation for its resurfacing was assessed in-vivo during surgery, with very good results for thickness restoration, proper cut orientation, and normal knee motion. These results support the introduction of patella-related navigation-based surgical procedures for computer-assisted total knee arthroplasty.

Better outcomes with patellar resurfacing during primary total knee arthroplasty: a meta-analysis study

BACKGROUND

Total knee arthroplasty (TKA) is a feasible and cost-effective procedure. However, resurfacing of the patella sparks a heated debate. Anterior knee pain after TKA was supposed to be correlated to the patellofemoral joint, and the resurface of the patella was believed to be effective to avoid this complication.

AIM

A meta-analysis was performed to update current evidence concerning the outcomes of patellar resurfacing versus retaining for total knee arthroplasty. The first outcomes of interest were to compare the rate of anterior knee pain and revision surgeries.

MATERIAL AND METHODS

This study was conducted according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA). A comprehensive review of the literature was conducted accessing the main databases: Embase, Google Scholar, PubMed, Scopus. All the prospective clinical trials comparing the outcomes between patellar resurfacing versus retaining were included in this study. Only articles classified as level of evidence I to II were considered for inclusion. Only studies reporting a minimum 24 months follow-up were included. The following data were extracted: demographic baseline, anterior knee pain, reoperations, clinical scores (HSS, KSS and related subscales) and range of motion (ROM). Studies solely reporting quantitative data under the outcomes of interest were included.

RESULTS

In favor of the resurfacing group, we observed a statistically significant reduced rate of anterior knee pain (odd ratio 1.73) and reoperation (odd ratio 3.24). In the resurfacing group, a prevalence of anterior knee pain of 11.15% was detected, whereas in the retaining group it amounted to 17.39%. Furthermore, a greater KSS pain (+ 0.97%), KSS clinical (+ 0.23%), KSS functional (+ 2.44%), KSS overall (+ 2.47%) and HSS (+ 5.64%) were reported. In the retaining group, we found a better range of motion (+ 3.09°).

CONCLUSION

Based on the main findings of this meta-analysis, patellar resurfaced TKA was demonstrated to have performed superior overall. Patellar resurfacing detected a lower rate of postoperative anterior knee pain and reoperation. Moreover, the resurfacing group showed greater value of the HSS, KSS and related subscales. In favor of the retaining group, a slightly better ROM was evidenced.

LEVEL OF EVIDENCE

Level II, meta-analysis of prospective clinical trials.

Comparison between Patellar Resurfacing and Retention in Total Knee Arthroplasty Regarding the Postoperative Satisfaction of Patients and Patellar Crepitus

BACKGROUND

Patellar crepitus after total knee arthroplasty (TKA) is not uncommon. The choice between patellar resurfacing or retention in TKA has remained controversial. Therefore, this randomized controlled trial aimed to evaluate the impact of patellar resurfacing on the incidence of patellar crepitus. In addition, we compared the clinical outcomes and satisfaction between the patients who underwent patellar retention or resurfacing.

METHODS

A total of 63 patients randomly received patellar resurfacing or non-resurfacing TKA by one surgeon at Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Iran during May 2014-February 2017. Finally, 29 patients in the resurfaced group and 44 subjects with retained patella were evaluated pre-op and in an average follow-up period of 8.68 months using the clinical Knee Society Score (KSS), functional KSS, and Knee injury and Osteoarthritis Outcome Score (KOOS).

RESULTS

Our findings demonstrated no significant difference between the two groups regarding the satisfaction of patients, KSS, and KOOS. It was shown that the latter scores improved in both groups in the follow-up period. Nonetheless, patellar crepitus was not statistically different between the two groups.

CONCLUSION

According to the results of the present study, patellar resurfacing did not lead to decreased patellar crepitus or enhanced clinical outcomes of TKA.

Resurfacing versus not-resurfacing the patella in one-stage bilateral total knee arthroplasty: a prospective randomized clinical trial

Purpose

Resurfacing the patella in one-stage bilateral total knee arthroplasty (TKA) remains debatable. This study aimed to assess the mid-term outcomes of patients after one-stage bilateral TKA performed with and without patellar resurfacing, respectively, with at least five years of follow-up.

Methods

Sixty-six patients (132 knees) scheduled for first-ever one-stage bilateral TKA due to osteoarthritis received patellar resurfacing and retention, respectively, on one knee and the other, randomly selected. All patients received Scorpio NRG knee prostheses and were evaluated by radiology (anteroposterior, lateral, and axial views) pre-operatively and yearly post-operatively, for at least five years. Knee Society Score and Feller Score values were measured. Anterior knee pain, patellar clunk, and patient satisfaction were assessed.

Results

One patient died within five years of operation and four were lost to follow-up. One patient developed severe dementia and could not be constructively questioned. Therefore, 60 patients (120 knees) were finally analyzed. There were significantly improved Knee Society and Feller scores (P < 0.001) in the resurfacing group compared with the non-resurfacing group post-operatively. Anterior knee pain and patellar clunk rates were lower on the resurfaced side compared with the non-resurfaced side (P < 0.001). Meanwhile, 47% and only 7% patients preferred the resurfaced and non-resurfaced sides, respectively, at final follow-up. No revision was performed for patellofemoral complications, and no significant differences were found between the two groups in radiographic outcomes.

Conclusions

Using the Scorpio NRG knee prosthesis, patellar resurfacing is superior to non-resurfacing in patients with osteoarthritis observed for ≥ five years.

Registration trials number

NCT03600922

Key Points

• Findings Patellar resurfacing is superior to non-resurfacing in osteoarthritis (OA) patients undergoing total knee arthroplasty (TKA) with the Scorpio NRG knee prosthesis.

• Implications Patellar resurfacing should be performed in OA patients during TKA.

• Caution Several prosthesis types should be assessed in the same study setting, and multicenter studies are required before generalizability of the present findings.

Electronic supplementary material

The online version of this article (10.1007/s00264-019-04361-7) contains supplementary material, which is available to authorized users.

Patients undergoing total knee arthroplasty using a contemporary patella-friendly implant are unaware of any differences due to patellar resurfacing

PURPOSE

Anterior knee pain after total knee arthroplasty (TKA) is often unexplained, spurring ongoing debates on the need for patellar resurfacing. It was hypothesized that a contemporary patella-friendly implant would restore patellofemoral kinematics more physiologically than outdated implants and that there would be no perceived or clinically demonstrable differences due to resurfacing of patella (RP).

METHODS

This prospective bilateral randomized study was undertaken in 49 patients scheduled for the same-day bilateral TKAs. One knee was subjected at random to RP while withholding RP on the opposing side (non-RP). A recently approved single-radius femoral prosthesis featuring a deep, elongate trochlear groove with lateral tilt and a high lateral flange was implanted bilaterally in all patients. Mean follow-up duration was 5 years. Group comparisons were based on patient-reported outcomes [anterior knee pain, Forgotten Joint Score (FJS), and side preference], physician-rated results [Feller patellofemoral (PF) score], radiographic patellar position, patella-related complications, and need for reoperation.

RESULTS

There were no differences in midterm rates of anterior knee pain (RP 8%; non-RP 4%; n.s.), FJS (all n.s.), or side preference (RP 47%; non-RP 45%; n.s.), nor did the groups differ by Feller PF score (all n.s.) or radiographic patellar position (all n.s.). No secondary resurfacings of non-RP or RP revisions were required.

CONCLUSIONS

Patients were incapable of distinguishing whether RP was done, casting doubt on its benefits. Surgeons may thus forego RP during TKA when using contemporary patella-friendly TKA implants.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Patellar resurfacing versus patellar retention in primary total knee arthroplasty: a systematic review of overlapping meta-analyses

PURPOSE

The need of patellar resurfacing in total knee arthroplasty (TKA) is a subject of debate. This systematic review of overlapping meta-analyses aimed to assess and analyze current evidence regarding patellar resurfacing and non-resurfacing in TKA.

METHODS

A systematic literature search was performed in March 2017 in PubMed, CINAHL and Cochrane Library. Inclusion criteria were meta-analysis of randomized controlled trials that compared TKA with and without patellar resurfacing considering as outcomes re-operations rate, complications, anterior knee pain, functional scores. The quality of meta-analyses was evaluated with AMSTAR score and the most relevant meta-analysis was determined by applying the Jadad algorithm.

RESULTS

Ten meta-analyses, published between 2005 and 2015, were included in the systematic review. Two studies found a significantly increased Knee Society Score in the resurfacing group. According to four meta-analyses, anterior knee pain incidence was lower in resurfacing group. Six of the included studies described a greater risk of re-intervention in the non-resurfacing groups. The overall quality of included studies was moderate. The most relevant meta-analysis reported no differences in functional scores and incidence of anterior knee pain between the groups.

CONCLUSIONS

Comparable outcomes were found when comparing patellar resurfacing and non-resurfacing in TKA. The higher risk of re-operations after non-resurfacing should be interpreted with caution due to the methodological limitations of the meta-analyses regarding search criteria, heterogeneity and the inherent bias of easier indication to reoperation when the patella is not resurfaced. There is no clear superiority of patellar resurfacing compared to patellar retention.

LEVEL OF EVIDENCE

Level II, systematic review of meta-analyses.

Increased in vivo patellofemoral loading after total knee arthroplasty in resurfaced patellae

PURPOSE

The primary purpose of the study was to investigate if and how patellar bone tracer uptake (BTU) distribution in SPECT/CT is influenced by patellar resurfacing and the position of femoral and tibial TKA component position.

METHODS

A total of 104 knees of 103 consecutive patients who underwent primary TKA were prospectively investigated. Primary patellar resurfacing was done in 40 knees while 64 had a TKA without patellar resurfacing. All patients underwent clinical assessment using the knee society score (KSS) and standardized radiographs and Tc-99m-HDP-SPECT/CT before and 12 and 24 months after TKA. Measurements of BTU including intensity and anatomical distribution pattern in eight different patellar regions were performed. Tibial and femoral TKA component position was assessed from 3D reconstructed CT data. Patellar height, thickness and tilt were measured and the distance between the tibial tuberosity and the trochlear groove (TT-TG) was measured. Univariate analysis was performed to identify differences between the two groups (p < 0.05).

RESULTS

Significantly higher BTU was found in the anterior, non-articular, areas of the patella in patients who underwent patellar resurfacing (p < 0.05). The BTU pattern was similar between the groups, as the maximal uptake in both groups was seen in the superior posterior parts and the minimal uptake was seen in the inferior anterior parts. The mean postoperative KSS was significantly higher in the unresurfaced group after 12 months (p < 0.05), but with no significant difference after 24 months.

CONCLUSIONS

Based on the findings of the present study, patellar resurfacing is related to significantly higher BTU in the anterior parts of the patella and lower clinical outcomes. In light of these results, routine patellar resurfacing as part of a primary TKA might be reevaluated. SPECT/CT enables a precise localization of the BTU and might be considered as the ideal imaging modality for evaluation and investigate of patellofemoral disorders after TKA.

Comparison of Clinical Results between Patellar Resurfacing and Non-resurfacing in Total Knee Arthroplasty: A Short Term Evaluation

BACKGROUND

There is no difference in the functional outcomes 6 months after total knee arthroplasty (TKA) for knee osteoarthritis between patellar resurfacing and non-resurfacing. Thus, we have performed this study to compare the short-term clinical outcomes of TKA performed with and without the patella resurfacing.

METHODS

A total of 50 patients with osteoarthritis of the knee (OAK) were randomized to receive patellar resurfacing (n=24; resurfaced group) or to retain their native patella (n=26; non-resurfaced group) based on envelope selection and provided informed consent. Disease specific outcomes including Knee Society Score (KSS), Knee Society Function Score (KSKS-F), Kujala Anterior Knee Pain Scale (AKPS), Western Ontario and McMaster Universities Arthritis Index (WOMAC), Short Form 36 (SF-36), and functional patella-related activities were measured within six months of follow-up.

RESULTS

There was no significant difference between the resurfaced and non-resurfaced groups in pre and post-operative improvement of range of motion (ROM) (P=0.421), KSS (P=0.782, P=0.553), KSKS-F (P=0.241, P=0.293), AKPS (P=0.128, P=0.443), WOMAC (P=0.700, P=0.282), and pain scores (P=0.120, P=0.508). There was no difference in ROM between resurfaced and non-resurfaced group pre (15.24^° and 15.45^°) and post-operative (18.48^° and 18.74). No side effects related to patella was observed in any of the groups. Revision was required in none of the participants.

CONCLUSION

The results showed no significant difference between patellar resurfacing and non-resurfacing in TKA for all outcome measures in a short term.Level of evidence: I.

Three-dimensional patellar tendon fibre kinematics in navigated TKA with and without patellar resurfacing

PURPOSE

Physiological elongation and orientation of patellar tendon fibres are among the scopes of total knee arthroplasty, but little is known in the three dimensions. The study aims to assess in vitro these variations at the intact and replaced knee, with and without patellar resurfacing. It was hypothesised that fibre patterns differ before and after prosthesis implantation, and between specific prosthesis designs. It was also expected that patellar resurfacing would affect relevant results.

METHODS

Measurements from 16 intact cadaver knees free from anatomical defects are here reported using a surgical navigation system. Data were collected at the intact joint and after implantation with cruciate-retaining or posterior-stabilised prosthesis designs, with and without patellar resurfacing. Relevant anatomical landmarks and patellar tendon attachments were digitised. Anatomical reference frames in the femur, tibia and patella were defined to measure component implantation parameters. Representative tendon fibres were defined as the straight line segments joining the two extremities. Changes in length and orientation of these fibres were calculated and reported versus flexion at the intact knee and after prosthesis implantation, both with and without patellar resurfacing.

RESULTS

A good intra- and inter-specimen repeatability was found at the intact and replaced knees. In both prosthesis designs, the patterns of fibre lengthening were similar to those in the intact knee, though significant differences were observed before and after patellar resurfacing. Corresponding fibre orientations in the frontal and sagittal planes showed significantly smaller ranges than those in the corresponding intact joints. More natural patterns were observed in the knees implanted with the posterior-stabilised design. Significant correlations were identified between patellar component implantation parameters and both patellar tendon fibre elongation and orientation.

CONCLUSIONS

Differences, however small, in patellar tendon fibre elongation and orientation were observed after total knee arthroplasty. The posterior-stabilised design provided better results, whereas patellar resurfacing affected significantly normal patellar function. In the clinical practice, the present findings can contribute to the understanding of current prosthesis designs and patellar resurfacing, recommending also enhanced care during this surgery.

The need for secondary resurfacing is affected by trochlear height in total knee arthroplasty

PURPOSE

The purpose of the study was to compare the rate of secondary resurfacing in a consecutive series of five different total knee arthroplasty (TKA) systems. It was our hypothesis that different TKA design features such as sulcus angle or trochlear height influence the rate of secondary resurfacing.

METHODS

A retrospective study was performed on data from patients who underwent TKA without primary patellar resurfacing from 2004 to 2012 in an university-affiliated hospital. The study cohort included 784 TKA patients (m:f = 302:482, mean age at surgery ± SD 71 ± 10). Five different cruciate-retaining TKA systems were used consecutively (Group A, Triathlon, Stryker, Switzerland (n = 296), Group B, PFC Sigma, DepuySynthes, Switzerland (n = 215), Group C, LCS, DepuySynthes, Switzerland (n = 81), Group D, Balansys, Mathys, Switzerland (n = 128), Group E, Duracon, Stryker, Switzerland (n = 64)). Data were retrospectively obtained from hospital archives. Patients demographics, age at surgery, type of TKA were noted. In addition, TKA component position was assessed on radiographs with respect to "The knee society total knee arthroplasty roentgenographic evaluation and scoring system" (TKA-RESS). Pearson Chi-square test was used to compare differences between groups (p < 0.05). There were no significant differences between the groups in terms of age, gender, and radiological outcomes.

RESULTS

Twenty-six of 784 patients (3.3 %) underwent secondary resurfacing due to patellofemoral pain. In group A 4/296 patients (1.4 %), in group B 15/215 patients (7 %), in group C 5/81 patients (6.2 %), in group D 1/128 patients (0.8 %), in group E 1/64 patients (1.6 %) underwent secondary patellar resurfacing during follow-up. Significantly higher rates of secondary patellar resurfacing were seen in groups B and C when compared to the others (p < 0.001). It was found that the trochlear height in these TKA was higher than in the others.

CONCLUSIONS

Based on the findings of this study, trochlear height influences the need for secondary patellar resurfacing. The resurfacing rate ranged from 1 to 7 %, with the highest rate in the PFC Sigma TKA.

LEVEL OF EVIDENCE

Therapeutic study, Level III.

Clinical and radiological results of cruciate-retaining total knee arthroplasty with the NexGen®-CR system: comparison of patellar resurfacing versus retention with more than 14 years of follow-up

BACKGROUND

The purpose of this study is to analyze clinical and radiological outcomes of patients (with a minimum of 14 years of follow-up) who underwent cruciate-retaining (CR) total knee arthroplasty (TKA) using a NexGen®-CR, comparing a patellar resurfacing group with a patellar retention group.

METHODS

From June 1996 to April 2002, 116 cases of TKA using a NexGen®-CR who had at least 14 years of follow-up were enrolled in this study. Among them, 68 cases had patellar resurfacing and 48 had patellar retention. The average follow-up period was 14.8 years (14.1-18.7). Clinical scores and range of motion (ROM) were evaluated preoperatively and at the last follow-up in all patients. The Hospital for Special Surgery (HSS) score, Knee Society Score (KSS), Western Ontario and MacMaster Universities Osteoarthritis (WOMAC) score, and a new patellar score were assessed. Radiological evaluations are done by analyzing the tibiofemoral angle, loosening, and a radiolucent line on the radiograph by American Knee Society Roentgen Graphic Evaluation.

RESULTS

The average HSS score of both the patellar resurfacing group and retention group increased from 42.3 and 41.2 preoperatively to 90.2 and 90.8 at the last follow-up, respectively. The KSS, WOMAC score, patellar score, and knee joint ROM also improved significantly in both groups. However, there were no significant differences in clinical results between the two groups. On the radiological evaluation, the tibiofemoral angle in both groups had improved from varus 7.8° and 7.2° preoperative to valgus 4.9° and 4.8°, respectively. The average angles of α, β, γ, and δ were 94.1°, 90.4°, 3.2°, and 87.8° in the patellar resurfacing group and 94.4°, 89.8°, 3.3°, and 88.1° in the patellar retention group, respectively. A radiolucent line shown on radiograph was noted in a total of seven cases, three in the patellar resurfacing group and four in the patellar retention group. In the patellar resurfacing group, among the seven zones on the tibia radiograph, all cases were located at the medial side of tibia and two cases were in zone 1 and one case in zone 2, and in the patellar retention group, three cases were in zone 1 and 1 case was in zone 2, also located on the same side.

CONCLUSIONS

We achieved satisfactory clinical and radiological outcomes on long-term follow-up when performing TKAs with a NexGen®-CR. There was no significant difference in clinical or radiological results between the patellar resurfacing and retention groups in our study.

Stress distribution of the patellofemoral joint in the anatomic V-shape and curved dome-shape femoral component: a comparison of resurfaced and unresurfaced patellae

PURPOSE

Whether to resurface the patella in knee replacement remains a controversial issue. The geometrical design of the trochlear groove in the femoral component could play an important role in determining the stress distribution on the patellofemoral joint, but this has not been sufficiently reported on. This study attempted to determine the effect of implant design on contact mechanics by means of a finite element method.

METHODS

Two designs, an anatomical V-shape design (VSD) and a dome-shape design (DSD), for the anterior trochlear surface in a contemporary femoral component were chosen for examining the contact characteristics. The use and absence of patella resurfacing was simulated. The stress and strain distribution on the patellar bone and the polyethylene component were calculated for comparison.

RESULTS

Without patellar resurfacing, the maximal compressive strain in the patellar bone in the VSD model was about 20 % lower than the DSD model. On the other hand, with resurfacing, the maximal strain for the VSD model was 13.3 % greater than for DSD. Uneven stress distribution at the bone-implant interface was also noted for the two designs.

CONCLUSION

The femoral component with a V-shape trochlear groove reduced the compressive strain on the unresurfaced patella. If resurfacing the patella, the femoral component with a curved domed-shape design might reduce the strain in the remaining patellar bone. Uneven stress could occur at the bone-implant interface, so design modifications for improving fixation strength and medialization of the patellar button would be helpful in reducing the risk of peg fracture or loosening.

LEVEL OF EVIDENCE

III.

Isolated patellofemoral arthroplasty reproduces natural patellofemoral joint kinematics when the patella is resurfaced

PURPOSE

The objectives of this in vitro project were to compare the dynamic three-dimensional patellofemoral kinematics, contact forces, contact areas and contact pressures of a contemporary patellofemoral prosthetic implant with those of the native knee and to measure the influence of patellar resurfacing and patellar thickness. The hypothesis was that these designs are capable to reproduce the natural kinematics but result in higher contact pressures.

METHODS

Six fresh-frozen specimens were tested on a custom-made mechanical knee rig before and after prosthetic trochlear resurfacing, without and with patellar resurfacing in three different patellar thicknesses. Full three-dimensional kinematics were analysed during three different motor tasks, using infrared motion capture cameras and retroflective markers. Patellar contact characteristics were registered using a pressure measuring device.

RESULTS

The patellofemoral kinematic behaviour of the patellofemoral arthroplasty was similar to that of the normal knee when the patella was resurfaced, showing only significant (p < 0.0001) changes in patellar flexion. Without patellar resurfacing, significant more patellar flexion, lateral tilt and lateral rotation was noticed. Compared to the normal knee, contact pressures were significantly elevated after isolated trochlear resurfacing. However, the values were more than doubled after patellar resurfacing. Changes in patellar thickness only influenced the antero-posterior patellar position. There was no other influence on the kinematics, and only a limited influence on the contact pressures in the low flexion angles.

CONCLUSION

The investigated design reproduced the normal patellofemoral kinematics acceptable well when the patella was resurfaced. From a kinematic point of view, patellar resurfacing may be advisable. However, the substantially elevated patellar contact pressures remain a point of concern in the decision whether or not to resurface the patella. This study therefore not only adds a new point in the discussion whether or not to resurface the patella, but also supports the claimed advantage that a patellofemoral arthroplasty is capable to reproduce the natural knee kinematics.

Is resurfacing the patella cheaper? An economic analysis of evidence based medicine on patellar resurfacing

BACKGROUND

Primary total knee arthroplasty is a high volume procedure which is expected to grow dramatically in the near future. The decision to resurface the patella has been discussed extensively in the literature yet the financial implications of resurfacing versus not resurfacing have not been demonstrated.

METHODS

We identified all randomized controlled trials comparing patellar resurfacing to nonresurfacing in the past ten years and identified the total number of patellofemoral revision surgeries for both resurfaced and nonresurfaced patellas in each study. An expected-value decision tree analysis was created using only data from the randomized controlled trials. Actual costs collected from Medicare reimbursement rates were then applied to the model and a sensitivity analysis was performed.

RESULTS

The expected value of primary total knee arthroplasty with patellar resurfacing was $13,788.48 while a primary total knee arthroplasty without patellar resurfacing was $14,016.41 after five years. The difference represents an additional $227.92 of Medicare dollars for every primary total knee arthroplasty performed without patellar resurfacing at five years. The model remains valid as long as patellofemoral revision rates after patellar resurfacing remain below 3.54% and patellofemoral revision rates after nonresurfaced patellas remain above 0.77%.

CONCLUSIONS

While initially counterintuitive, resurfacing the patella during a primary total knee arthroplasty is the optimal financial strategy from a Medicare perspective over a mid term period.

Does malrotation of components correlate with patient dissatisfaction following secondary patellar resurfacing?

BACKGROUND

The aim of our study was to identify whether there was any correlation between the outcome of secondary patellar resurfacing and malrotation of either the femoral or tibial component.

METHODS

We identified patients that underwent secondary patellar resurfacing following previous primary total knee arthroplasty (TKA) at a single, large orthopaedic department. Patients were reviewed for range of movement, satisfaction, health status and knee function. CT scanning was performed, assessing rotational alignment of the components.

RESULTS

Twenty-one patients (23 knees) were reviewed. Nine out of 21 (39%) were satisfied while 14 (61%) remained dissatisfied after the secondary patellar resurfacing. There were no complications after the secondary procedure. All knees were internally rotated. The mean femoral internal rotation in the satisfied group was 0.92°, and in the dissatisfied group was 2.88° of internal rotation. In the dissatisfied group eight out of 14 TKAs were in >3° femoral internal rotation compared with only one in nine TKAs in the satisfied group (p<0.05).

CONCLUSIONS

Investigation for malrotation should be considered in patients with post-operative pain, especially anteriorly, causing significant dissatisfaction amongst patients following TKA. This is especially true if the patella has not been primarily resurfaced and secondary resurfacing is being considered. Patients with more than 3(°) of femoral internal rotation undergoing secondary patella resurfacing should be warned of the possibility of a poor outcome. It may well be that if the underlying problem is component malrotation, revision knee replacement may lead to a more satisfactory outcome than secondary resurfacing alone.

LEVEL OF EVIDENCE

Level of Evidence III.

Patellar resurfacing versus no resurfacing in two-stage revision of infected total knee arthroplasty

BACKGROUND

Cartilage debridement and staged reimplantation are the most common treatments for infected total knee arthroplasty (TKA). Very few studies have focused on the management of primarily non-resurfaced patellae in infected TKA. The purpose of this study was to compare the outcomes of patellar resurfacing and non-resurfacing in two-stage revision of infected TKA.

METHODS

This study involved a retrospective comparison of the reinfection rate and clinical outcomes of revision TKA patients managed with patellar resurfacing (22 patients, 23 knees) and patients managed without patellar resurfacing (26 patients) at a minimum two-year follow-up. The mean age in the resurfacing group was 69.4years old, and the mean age in the non-resurfacing group was 67.3years old. Three scales were used in the assessment: the Knee Society Score, Western Ontario and McMaster Universities Osteoarthritis Index, and the Anterior Knee Pain Scale.

RESULTS

Three knees had recurrent infections. All infections occurred in patients who had received patellar resurfacing. There were no significant differences between groups in clinical results and on the Anterior Knee Pain Scale. A lack of patellar resurfacing did not increase recurrence of infection and did not result in significant clinical differences compared to patellar resurfacing.

CONCLUSIONS

This study indicates that preservation of the original patellar bone is a feasible option for patellar management in revision of septic TKA.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Mobile- versus fixed-bearing modern total knee replacements- which is the more patella-friendly design?: The 11-year New Zealand Joint Registry study

OBJECTIVES

Our study aimed to examine if a mobile-bearing total knee replacement (TKR) offered an advantage over fixed-bearing designs with respect to rates of secondary resurfacing of the patella in knees in which it was initially left unresurfaced.

METHODS

We examined the 11-year report of the New Zealand Joint Registry and identified all primary TKR designs that had been implanted in > 500 knees without primary resurfacing of the patella. We examined how many of these were mobile-bearing, fixed-bearing cruciate-retaining and fixed-bearing posterior-stabilised designs. We assessed the rates of secondary resurfacing of the patella for each group and constructed Kaplan-Meier survival curves.

RESULTS

Our study showed a significantly higher rate of revision for secondary resurfacing of the patella in the fixed-bearing posterior-stabilised TKR designs compared with either fixed-bearing cruciate-retaining or mobile-bearing designs (p = 0.001 and p = 0.036, respectively).

CONCLUSIONS

This New Zealand Registry study shows that during the last 11 years, revision procedures to resurface an unresurfaced patella in primary TKR occurred at a higher rate in fixed-bearing posterior-stabilised designs.

Three dimensional CT-based virtual patellar resection in female patients undergoing total knee replacement: a comparison between tendon and subchondral method

Background

Due to its small size, variable shape, and lack of distinct anatomical landmarks, osteoarthritic knees make a precise patellar resection extremely difficult.

Methods

We performed virtual patellar resection with digital software using three dimensional computed tomography scans of knees from 49 patients who underwent primary total knee replacement at our hospital. We compared 2 commonly used resection methods, the tendon method (TM) and the subchondral method, to determine an ideal resection plane with respect to the symmetry and thickness of the patellar remnant.

Results

The TM gave a thicker resected patella, and a less oval cut surface shape, which gives better coverage for a domed prosthesis. Both methods, however, gave a symmetric resection both superior-inferiorly, as well as mediolaterally.

Conclusions

Although TM appears statistically better with respect to the thickness and cut surface shape, only further intraoperative studies with long-term clinical follow-up may provide us with the most appropriate patellar resection method.

A Comparison of Patella Retention versus Resurfacing for Moderate or Severe Patellar Articular Defects in Total Knee Arthroplasty: Minimum 5-year Follow-up Results

Purpose

The purpose of this study is to assess the clinical and radiological results of patients who underwent patellar retention or resurfacing for moderate or severe patellar articular defects during total knee arthroplasty and evaluate the clinical efficacy of patellar resurfacing according to the articular defect of the patella.

Materials and Methods

From May 2003 to March 2006, 252 patients (277 cases) underwent total knee arthroplasty by one surgeon. Intraoperatively, we divided these patients into a moderate articular defect group (50-75%: group I) and a severe articular defect group (75-100%: group II) and randomly performed patellar resurfacing. The average age was 67.2 years. There were 234 female and 17 male patients. The average follow-up period was 74.6 months. Clinical outcomes were analyzed using the Knee Society (KS) knee score. Functional score, Hospital for Special Surgery (HSS) score, Feller patellar score and range of motion (ROM). Radiological outcomes were analyzed using the congruence angle, Insall-Salvati ratio and patella tilt angle.

Results

The KS knee score and functional score at the last follow-up were 84.4/73.1 in the retention group and 85.2/71.8 in the resurfacing group (p=0.80, p=0.63) in group I. In group II, the values were 82.1/75.1 and 87.0/71.2, respectively (p=0.51, p=0.26). The HSS score and Feller patella score were 86.7/20.3 in the retention group and 84.3/21.7 in the resurfacing group (p=0.31, p=0.29) in group I. In group II, the values were 91.6/21.2 and 85.5/22.1, respectively (p=0.37/p=0.30). The knee ROM (p=0.36/p=0.41), congruence angle (p=0.22/p=0.16), Insall-Salvati ratio (p=0.16/p=0.21) and patella tilt angle (p=0.12/p=0.19) were not statistically different between the two groups.

Conclusions

In this study, we could not find any correlations between the degree of patellar articular defect and patellar resurfacing in terms of the clinical and radiological results. Therefore, patellar articular defects is thought to be less meaningful in determining patellar resurfacing.