Patellofemoral arthroplasty

Patello-femoral arthroplasty- indications and contraindications

Patellofemoral arthroplasty (PFA) is emerging as an attractive alternative to total knee arthroplasty (TKA) for isolated patellofemoral-osteoarthritis (PF-OA) for selected patients. The success of PFA is highly dependent on patient selection. This intervention is still burdened with a higher rate of revisions and a lower survival rate than TKA when the indications or the surgical technique are not optimal. We highlight the indications and contraindications of PFA to obtain satisfying functional outcomes and survivorship. Preoperative clinical and radiological assessment is critical to determine the presence of PFA indications, the absence of contraindications and the necessity of any associated procedures, particularly for the tibial tubercle. The typical indications are patients with isolated symptomatic PF-OA, with trochlear dysplasia, when bone-on-bone Iwano 4 osteoarthritis is observed, without significant malalignment and with the absence of risk factors for developing progressive tibiofemoral-OA. The three main causes of isolated PF-OA are primary OA, trochlear dysplasia and posttraumatic OA following patellar fracture. Trochlear dysplasia is the preferred indication for PFA. Lack of experience with arthroplasty or realignment of the extensor mechanism is a relative contraindication to performing PFA.

Isolated patellofemoral arthroplasty-surgical technique and tips: current concepts

Successful patellofemoral arthroplasty (PFA) requires appropriate patient selection, correct implant positioning and attention to surgical technique. Whilst the original concept and rationale offered an attractive surgical option for patients with isolated patellofemoral arthritis, early results were disappointing and consequently many surgeons became reluctant to offer it. With newer-generation designs, outcomes have been more promising. However, attention to surgical technique remains an integral component to a successful outcome, with results being unforgiving when surgical errors are made. This paper explores the key components of the surgical technique in PFA, including implant design, patient selection and tips to avoid common mistakes.

Unicompartmental knee replacement: controversies and technical considerations

BACKGROUND

Unicompartmental knee replacement (UKR) is one of the effective interventions for the treatment of symptomatic knee osteoarthritis. Moreover, it has multiple advantages over total knee arthroplasty (TKA), including reduced intraoperative blood loss, decreased risk of transfusion, and faster recovery. This study aimed to discuss critical technical considerations regarding UKR and some of the controversies and updates.

METHODS

We conducted a review to provide an overview of the controversies and technical considerations about UKR in several aspects. Only peer-reviewed articles were included, up to December 2023 using PubMed, Google Scholar, ERIC, and Cochrane database for systematic reviews databases.

RESULT

UKR is associated with superior patient-reported clinical and functional outcomes, as well as shorter hospital stays, fewer postoperative complications, and revealed favorable outcomes in patients' return to sport. The choice between mobile- and fixed-bearing prostheses depends, in part, on the surgeon's preference. The mobile-bearing UKR is a less constrained prosthesis and can potentially result in less wear, but it is more technically demanding. While no significant difference between mobile-bearing versus fixed-bearing prostheses, cementless is superior to cemented design. Furthermore, UKR can be a good alternative for high tibial osteotomy (HTO) and still can be considered after a failed HTO. Lastly, recent reviews have shown a revision rate comparable to that of TKA. This is probably influenced by Improved comprehension of the best indications, patient selection criteria, as well as of the design, materials, and technological advances.

CONCLUSION

UKR treatment for unicompartmental knee osteoarthritis is secure and effective. Based on clinical and functional outcomes, decreased morbidity and mortality, and cost-effectiveness, long-term studies suggest that UKR is superior to TKA. Further investigation in this area is warranted.

Patellar resurfacing might not be mandatory in contralateral second total knee replacement even if performed during replacement of the first knee

INTRODUCTION

The appropriateness or necessity of patellar resurfacing in total knee arthroplasty (TKA) is not clearly established. The objective of the present study was to compare the clinical and functional results of patients with bilateral involvement, operated on in one knee by TKA with patellar resurfacing and in the other knee by TKA without resurfacing. The hypothesis was that there was no difference in results between the two sides.

METHOD

This was a retrospective cohort of patients operated on by TKA without patellar resurfacing in a second osteoarthritic knee after contralateral TKA with patellar resurfacing. Twenty consecutive patients who underwent second primary TKA constituted their own control group (40 knees). Iwano scores were comparable. Mean age was 75.9±6.2years. Mean time between the two procedures was 20.6±11.9months.

RESULTS

There were no differences in SF-36, KOOS or Lille patellofemoral scores between the right and left knees. Sixty-five percent of patients were unable to differentiate the performance of their knees in activities of daily living.

CONCLUSION

The present study did not differentiate results according to patellar resurfacing, showing the limitations of resurfacing for early functional gain after primary TKA. Resurfacing might thus not be essential, even if it was performed in replacement of the first knee.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

Modern Patellofemoral Arthroplasty

INTRODUCTION

The ideal procedure for isolated patellofemoral arthritis is a controversial topic. Patellofemoral arthroplasty (PFA) is an option that aims to restore normal kinematics to the knee while preserving bone. PFA has been shown to have benefits compared with total knee arthroplasty (TKA) in this patient population but has historically had a high failure rate. Revision rates are improving with modern implants and tight indications but still remain higher than TKA. This review summarizes current thinking around PFA using modern implants and techniques in 2023, provides an implant-specific analysis, and assesses how we can improve outcomes after PFA based on the current literature. The aim was to provide an outline of the evidence around PFA on which surgeons can make decisions to optimize patient outcome in this young and active population.

METHODS

Four databases (MEDLINE, Embase, Scopus, and SPORTDiscus) were searched for concepts of patellofemoral joint arthroplasty. After abstract and text review, a screening software was used to assess articles based on inclusion criteria for studies describing indications, outcomes, and techniques for isolated PFA using modern implants, with or without concomitant procedures.

RESULTS

A total of 191 articles were included for further examination, with 62 articles being instructional course lectures, systematic reviews, technique articles, narrative reviews, expert opinions, or meta-analyses. The remaining articles were case reports, trials, or cohort studies. Articles were used to create a thorough outline of multiple recurrent topics in the literature.

CONCLUSIONS

PFA is an appealing option that has the potential to provide a more natural feeling and functioning knee for those with isolated PF arthritis. The high rate of revision is a cause for concern and there are several technical details that should be stressed to optimize results. The uncertain outcome after revision to TKA also requires more investigation. In addition, the importance of strict selection criteria and firm indications cannot be stressed enough to optimize longevity and attempt to predict those who are likely to have progression of tibiofemoral osteoarthritis. The development of new third-generation implants is promising with excellent functional outcomes and a much lower rate of maltracking and implant complications compared with earlier generations. The impact of these implants and improvement in surgical techniques on the revision rate of PFA will be determined from longer-term outcomes.

Patellofemoral Arthroplasty Is an Efficient Strategy for Isolated Patellofemoral Osteoarthritis with or without Robotic-Assisted System

There is relative paucity in the literature concerning outcomes after robotic-assisted Patellofemoral Arthroplasty (PFA). The aims were (1) to evaluate outcomes in patients undergoing PFA with inlay or onlay components, with or without robotic arm assistance and (2) to identify risk factors of poor outcomes after PFA. This retrospective study included 77 PFA for isolated patellofemoral joint osteoarthritis, assigned to three groups (18 conventional technique, 17 image-free robotic-assisted system and 42 image-based robotic-assisted system). The demographic data were comparable between the three groups. The clinical outcomes assessed were: Visual Analogue Scale, Knee Society Score, Kujala score and satisfaction rate. The radiological measures were: Caton Deschamps index, patellar tilt and frontal alignment of the trochlea. Functional outcomes, satisfaction rate and residual pain were comparable between the three groups. Patellar tilt improvement was superior when a robotic device was used (either image-based or image-free) compared to the conventional technique. There were three revisions (3.9%) at the last follow-up related to femorotibial osteoarthritis progression. Multivariate analysis found no significant risk factors for poor outcomes, with respect to the surgical technique or implant design. Functional outcomes and revisions rate after PFA were comparable between the surgical techniques and implants. Robotic-assisted systems were associated with a superior improvement of the patellar tilt compared to the conventional technique.

Unicompartmental knee arthroplasty: A French multicenteric retrospective descriptive study from 2009 to 2019 with projections to 2050

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) is a reliable and reproducible procedure. While some surgeons have incorporated it into their therapeutic armamentarium, others do not use it routinely, leading to a large disparity in practice. The objective of this study was to investigate in France the epidemiology of UKA from 2009 to 2019 to identify: (1) the evolution of growth trends by sex and age, (2) the evolution of the state of comorbidity of patients during the operation, (3) the evolution of trends according to the regions, (4) the projection best suited to the observations at 2050.

HYPOTHESIS

Our hypothesis was that in France, an increase would be observed over the period studied, differing according to the characteristics of the population.

MATERIALS AND METHOD

The study was conducted in France over the 2009-2019 period for each gender and age group. The data was taken from the NHDS (National Health Data System) database, which includes all the procedures carried out in France. Based on the collection of procedures performed, the incidence rates (per 100,000 inhabitants) and their evolution were deduced, as well as the indirect assessment of the patient's comorbidity status. Using linear, Poisson, and logistic projection models, incidence rates were projected to the years 2030, 2040, and 2050.

RESULTS

Between 2009 and 2019, the incidence rate of UKA increased sharply (from 12.76 to 19.57; +53%), the growth was different in men (from 10.78 to 20.34; +89%) and women (from 14.61 to 18.85; +29%). The male/female sex ratio increased from 0.69 in 2009 to 1.0 in 2019. The increase was greatest among men under 65 (from 4.9 to 9.9; +100%) and lowest among women over 75 (from 41.2 to 40.5; -2%). Over the period studied, the proportion of patients with mild comorbidities (HPG1) increased (from 71.7% to 81.1%) at the expense of the other classes with more severe comorbidities. This dynamic was observed for all age groups: 0-64 years (from 83.3% to 90%), 65-74 years (from 81.4% to 88.4%), 75 years and over (38 .2% to 52.6%) regardless of sex. There was a strong disparity between the regions with a change in the incidence rate ranging from -22% (from 29.8 to 23.1) for Corsica to +251% (from 13.9 to 48.7) for Brittany. The proposed projection models suggested an increase in the incidence rate of +18% in logistic regression, +103% in linear regression by 2050.

DISCUSSION

Our study showed strong growth in the number of UKAs in France over the period studied, being highest in young men. The proportion of patients with fewer comorbidities increased for all age groups. A disparity in inter-regional practice was identified, with indications that remain ambiguous and differ according to the practitioner. We can expect continued growth in the years to come, adding to the care burden.

LEVEL OF EVIDENCE

IV; Descriptive epidemiological study.

Patellar button compatibility in the conversion of Patellofemoral Arthroplasty to a Total Knee Arthroplasty: A review of the contemporary literature

BACKGROUND

Compared to total knee arthroplasty (TKA), patellofemoral arthroplasty (PFA) is a far less commonly performed operation. However, in carefully selected cohorts, PFA continues to be an appropriate treatment option for end-stage isolated patellofemoral joint osteoarthritis. In the later situation whereby a PFA is considered for conversion to a TKA - often due to disease progression - uncertainty remains regarding optimal management of the in situ patellar button. This review of the contemporary literature aimed to provide a summary of the current evidence to support surgeon decision-making, by evaluating the compatibility, efficacy, and survivorship of retained versus revised patellar buttons in PFA-to-TKA conversion. Specific focus was paid to implant design and technical considerations during revision, plus post-operative patient-reported outcomes and modes of secondary patellar component failure.

METHODS

A review of the Embase, Cochrane and PubMed databases was performed following PRISMA search principles.

RESULTS

This investigation highlights that the fate of patellar buttons in PFA-to-TKA conversion has previously been poorly studied, with scant publication data available. Most reports have been of singular cases or small cohort series. Larger formal RCTs and level 1 evidence are lacking.

CONCLUSION

The findings herein suggest that surgeons can confidently retain well-fixed, undamaged, dome-shaped all-polyethylene patellar buttons in the conversion of a PFA to TKA with the expectation of acceptable mid-term performance and survivorship, as long as congruent tracking with the new tibiofemoral components is achieved. This result is likely translatable to the majority of contemporary, all-polyethylene, dome-shaped patellar buttons, even with manufacturer mismatch.

Rotational alignment of the femoral trochlea in Asians: Implication on implant choice and position for managing isolated patellofemoral osteoarthritis

Introduction

Maltracking of the patella is a key contributor to early failure of patellofemoral arthroplasty (PFA). Native femoral trochlear morphology dictates implant rotation and patella tracking of in-lay PFA implants. This is the first study amongst Asians designed to assess the normal rotational alignment of the trochlear groove and evaluate its implication on PFA implant choice and position.

Methods

Trochlear inclination angle (TIA) was measured from 211 magnetic resonance images of Asian knees retrieved from a single centre in Hong Kong. TIA assesses rotation of the femoral trochlear groove relative to the axis perpendicular to Whiteside’s line (anteroposterior axis of the femur).

Results

The mean trochlear inclination in normal Asian knees was 11.5°  ±  2.5° (mean  ±  standard deviation) internal rotation. High-grade dysplastic knees, according to Dejour classification, were significantly more internally rotated with a mean of 12.8°  ±  3.6° (p = 0.025).

Conclusion

Trochlear inclination in Asians is comparable to Caucasians. In-lay PFA implants do not alter native pathological bony trochlear anatomy, and may result in patella maltracking in patients with high grade trochlear dysplasia or excessive trochlear inclination. These patients may benefit from on-lay implants, which allows restoration of normal trochlear inclination, as well as lateralisation and deepening of the trochlear groove. Patella tracking is however, dynamic and multi-factorial. Further clinical studies are therefore warranted to reconcile our anatomical findings with clinical outcomes.

A Newly Identified Complication of Patellofemoral Arthroplasty: Case Report and Literature Review

Background

Patellofemoral arthroplasty (PFA) is a surgical option for patients older than 40 years old who are affected by patellofemoral osteoarthritis. Regarding the complications of PFAs, few studies have investigated periprosthetic fractures. The purpose of this literature review was to highlight a previously overlooked complication of primary prosthetic surgery of the patellofemoral joint.

Methods

Three literature databases were searched for studies published between 2000 to 2020 using relevant keywords. A total of 4,942 articles were originally identified. After excluding duplicates and analysing the titles and abstracts, 20 studies were considered. From these, data regarding the number of cases, clinical outcomes and complications were extracted.

Results

Among the 20 selected articles, only one described periprosthetic fractures as a complication of PFAs. Herein, we also report an illustrative case of an unknown fracture complication. No cases in the literature were found that described the type of complications experienced by our patient during the postoperative period.

Conclusions

This review confirms the lack of data about clinical outcomes and fracture complications of PFAs. In primary prosthetic surgery of the patellofemoral joint, patient selection and close consideration of demographic factors (such as BMI and age) and intraoperative factors (such as patellar thickness and size of the trochlear component) play a key role in optimising pre-operative planning to avoid intraoperative periprosthetic fractures.

Onlay Patellofemoral Arthroplasty in Patients With Isolated Patellofemoral Arthritis: A Systematic Review

BACKGROUND

Patellofemoral arthroplasty (PFA) for isolated patellofemoral osteoarthritis (OA) remains controversial due to variable postoperative outcomes and high failure rates. Second-generation (2G) onlay prostheses have been associated with improved postoperative outcomes. This systematic review was performed to assess the current overall survivorship and functional outcomes of 2G PFA.

METHODS

A search was performed using PubMed, Cochrane Library, EMBASE, and Google Scholar. Thirty-three studies published in the last 15 years (2005-2020) were included; of these 22 studies reported patient-reported outcome measures. Operative and nonoperative complications were analyzed. Pooled statistical analysis was performed for survivorship and functional scores using Excel 2016 and Stata 13.

RESULTS

The mean age of the patients was 59.7. When analyzing all studies, weighted survival at mean follow-up of 5.52 was 87.72%. Subanalysis of studies with minimum 5 years of follow up showed a survival of 94.24%. Fifteen studies reported Oxford Knee Score with a weighted mean postoperative Oxford Knee Score of 33.59. Mean American Knee Society Score pain was 79.7 while mean American Knee Society Score function was 79.3. The most common operative complication was OA progression for all implants. The percentage of revisions and conversions reported after analyzing all studies was 1.37% and 7.82% respectively.

CONCLUSION

Safe and acceptable results of functional outcomes and PFA survivorship can result from 2G PFAs at both short and mid-term follow-up for patients with isolated patellofemoral OA. However, long-term follow-up outcomes are still pending for the newer implants. More extensive studies using standardized functional outcomes and long-term cost benefits should be evaluated.

Reliable improvements in participation in low-impact sports following implantation of a patellofemoral inlay arthroplasty at mid-term follow-up

PURPOSE

The aim of this study was, to investigate the rate of return to sports (RTS) and physical activity after implantation of PFIA and to identify factors predictive of improved postoperative sporting ability.

METHODS

Sixty-two patients with a mean age of 46 ± 11 years, who underwent implantation of PFIA at the senior authors' institution, were enrolled. They were prospectively evaluated preoperatively and at a minimum of 2 years postoperatively with a mean follow-up of 60 ± 25 months. Clinical outcomes, return to sports and activity, type of sport or activity, subjective satisfaction, and frequency were evaluated by questionnaire.

RESULTS

The transformed overall Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score improved from 67 ± 16 to 77 ± 19 (p = 0.003), Tegner activity scale results improved from 3 ± 2 points to 4 ± 1 points (p < 0.001), and scores on the visual analog scale (VAS) pain scale decreased from 6 ± 2 points to 3 ± 2 points (p < 0.001). The sports frequency increased from 1 ± 2 sessions to 2 ± 1 sessions per week (p = 0.001). Ninety-four percent of the patients who did not fail could return to the same or higher level of sports, with 74% of the patients reporting an improved ability to perform sports. No preoperative factors could be detected to significantly influence RTS after surgery.

CONCLUSIONS

PFIA is a valid treatment option for the active patient with end-stage isolated patellofemoral OA. Reliable improvements in knee function, pain, and participation in low-impact sports were found.

LEVEL OF EVIDENCE

IV.

Patellofemoral Arthroplasty: Short-Term Complications and Risk Factors

There is a paucity of literature regarding the short-term readmission, reoperation, and complication rates of patellofemoral arthroplasty (PFA). The purpose of this study is to determine the incidence and risk factors of 30-day postoperative complications in patients undergoing PFA. A retrospective cohort study of subjects who underwent PFA from 2010 to 2015 was performed using the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database. Perioperative outcomes and 30-day postoperative complications were ascertained, and patient demographics and comorbidities were analyzed using linear and binomial logistic regression analyses to determine risk factors for postoperative complications. Among the 1,069 patients identified in the NSQIP database, there was a 30-day readmission rate of 4.3% and a 30-day reoperation rate of 1.5%. The leading complications identified were bleeding requiring transfusion (11.7%), urinary tract infection (0.8%), and deep vein thrombosis (DVT) (0.8%). Younger age was a risk factor for superficial wound infection (p = 0.012). Older age was a significant risk factor for longer hospital stays, readmission, bleeding requiring transfusion, urinary tract infection, and pneumonia (p < 0.05 for all). Male sex was a risk factor for longer operation time and DVT (p = 0.001 and p = 0.017, respectively), while female sex was associated with greater incidence of bleeding requiring transfusion (p = 0.049). Elevated body mass index (BMI) was a risk factor for longer hospital stays, greater total operation time, and bleeding requiring transfusion (p < 0.001, p < 0.001, and p = 0.001, respectively). Nonwhite race was a significant risk factor for readmission (p = 0.008). This represents the largest study on early readmissions and the associated risk factors after PFA. PFA 30-day readmission and reoperation rates were <5%. Older age and elevated BMI were both identified as risk factors for adverse perioperative outcomes, including longer operation times, longer hospital stays, and bleeding requiring transfusion.

Minimally Invasive Robotic-Assisted Patellofemoral Arthroplasty

Isolated patellofemoral arthritis is a common debilitating condition in adults older than 40 years of age. Surgical options such as patellofemoral arthroplasty exist for those who failed to respond to nonoperative treatment. However, early patellofemoral arthroplasty techniques often resulted in poor outcomes due to mal-tracking and malalignment of components. Robotic-assisted surgery recently has been introduced as an alternative to classic patellofemoral arthroplasty, with the potential to improve the anatomical fit and reproducibility of implant positioning. We present the technique for minimally invasive robotic-assisted patellofemoral arthroplasty system.

Fresh Osteochondral Resurfacing of the Patellofemoral Joint

Large osteochondral lesions of the knee in young patients continue to be a challenge for orthopaedic surgeons and the focus of continual research. This is particularly true if the injury is a consequence of a dysplastic trochlea and involves both articular surfaces of the biomechanically complex patellofemoral joint. To obtain a healthy and congruent patellofemoral joint, the use of a bipolar fresh osteochondral allograft transplantation of the patella and trochlea is one of the few options to biologically treat these injuries. This would achieve a replacement of the entire articular surface of the patellofemoral joint with a high number of viable chondrocytes and respect the unique structural characteristics of the cartilage. The aim of this study was to obtain symptomatic and functional improvements while delaying the timing of prosthetic surgery. We present a reproducible although demanding surgical technique to perform a bipolar fresh osteochondral allograft transplantation of the patella and trochlea.

Similar postoperative patient-reported outcome in both second generation patellofemoral arthroplasty and total knee arthroplasty for treatment of isolated patellofemoral osteoarthritis: a systematic review

INTRODUCTION

Due to inconsistent results and high failure rates, total knee arthroplasty (TKA) is more often used to treat isolated patellofemoral osteoarthritis (PFOA) despite the theoretical advantage of patellofemoral arthroplasty (PFA). It is perceived that second-generation PFA may have improved the outcomes of surgery. In this systematic review, the primary aim was to compare outcomes of second-generation PFA and TKA by assessment of patient-reported outcome measures (PROMs).

METHODS

A systematic search was made in PubMed, Medline, Embase, Cinahl, Web of Science, Cochrane Library and MeSH to identify studies using second-generation PFA implants or TKA for treatment of PFOA. Only studies using The American Knee Society (AKSS), The Oxford Knee Score (OKS) or The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) to report on PROMs were included.

RESULTS

The postoperative weighted mean AKSS knee scores were 88.6 in the second-generation PFA group and 91.8 in the TKA group. The postoperative weighted mean AKSS function score was 79.5 in the second-generation PFA group and 86.4 in the TKA group. There was no significant difference in the mean AKSS knee or function scores between the second-generation PFA group and the TKA group. The postoperative weighted mean OKS score was 36.7 and the postoperative weighted mean WOMAC score was 24.4. The revision rate was higher in the second-generation PFA group (113 revisions [8.4%]) than in the TKA group (3 revisions [1.3%]). Progression of OA was most commonly noted as the reason for revision of PFA, and it was noted in 60 cases [53.1%]; this was followed by pain in 33 cases [29.2%].

CONCLUSION

Excellent postoperative weighted mean AKSS knee scores were found in both the second-generation PFA group and in the TKA group, suggesting that both surgical options can result in a satisfying patient-reported outcome. Higher revision rates in the second-generation PFA studies may in part be due to challenges related to patient selection. Based on evaluation of PROMs, the use of second-generation PFA seems to be an equal option to TKA for treatment of isolated PFOA in appropriately selected patients. Hopefully, this can be considered by physicians in their daily clinical work.

LEVEL OF EVIDENCE

IV.

What Is the Risk of Repeat Revision When Patellofemoral Replacement Is Revised to TKA? An Analysis of 482 Cases From a Large National Arthroplasty Registry

BACKGROUND

Patellofemoral replacements (PFRs) have a higher rate of revision than unicompartmental knee arthroplasty or TKA. However, there is little information regarding why PFRs are revised, the components used for these revisions, or the outcome of the revision procedure. Some contend that PFR is a bridging procedure that can easily be revised to a TKA with similar results as a primary TKA; however, others dispute this suggestion.

QUESTIONS/PURPOSES

(1) In the setting of a large national registry, what were the reasons for revision of PFR to TKA and was the level of TKA constraint used in the revision associated with a subsequent risk of rerevision? (2) Is the risk of revision of the TKA used to revise a PFR greater than the risk of revision after a primary TKA and greater than the risk of rerevision after revision TKA?

METHODS

Data were obtained from the Australian Orthopaedic Association Joint Replacement Registry through December 31, 2016, for TKA revision procedures after PFR. Because revisions for infection may be staged procedures resulting in further planned operations, for the revision analyses, these were excluded. There were 3251 PFRs, 482 of which were revised to TKA during the 17-year study period. The risk of second revision was calculated using Kaplan-Meier estimates of survivorship for PFRs revised to TKAs, and that risk was compared with the risk of first revision after TKA and also with the risk of a second revision after revision TKA. Hazard ratios (HRs) from Cox proportional hazards models were used to compare second revision rates among the different levels of prosthesis constraint used in the index revision after PFR (specifically, cruciate-retaining versus cruciate-substituting).

RESULTS

The main reasons for revising a PFR to TKA were progression of disease (56%), loosening (17%), and pain (12%). With the numbers available for analysis, there was no difference in the risk of a second revision when a PFR was revised to a cruciate-retaining TKA than when it was revised to a cruciate-substituting TKA (HR, 1.24 [0.65-2.36]; p = 0.512). A total of 204 (42%) of the PFR revisions had the patella component revised when the PFR was converted to a TKA. There difference in rates of second revision when the patella component was revised or not revised (HR, 1.01 [0.55-1.85]; p = 0.964). When we eliminated the devices that ceased to be used before 2005 (older devices), we found no change in the overall risk of repeat revision. The risk of a PFR that was revised to a TKA undergoing a second revision was greater than the risk of TKA undergoing a first revision (HR, 2.39 [1.77-3.24]; p < 0.001), but it was less than the risk of a revision TKA undergoing a second revision (HR, 0.60 [0.43-0.81]; p = 0.001).

CONCLUSIONS

The risk of second revision when a PFR is revised is not altered if cruciate-retaining or posterior-stabilized TKA is used for the revision nor if the patella component is revised or not revised. The risk of repeat revision after revision of a PFR to a TKA was much higher than the risk of revision after a primary TKA, and these findings did not change when we analyzed only devices in use since 2005. When PFR is used for the management of isolated patellofemoral osteoarthritis, patients should be counselled not only about the high revision rate of the primary procedure, but also the revision rate after TKA. Further studies regarding the functional outcomes of these procedures may help clarify the value of PFRs and subsequent revisions.

LEVEL OF EVIDENCE

Level III, therapeutic study.

No bias for developer publications and no difference between first-generation trochlear-resurfacing versus trochlear-cutting implants in 15,306 cases of patellofemoral joint arthroplasty

PURPOSE AND HYPOTHESIS

The study aim was to assess the outcome of patellofemoral arthroplasty (PFA), paying particular interest to 'revisions for any reason'. The hypothesis was that there is a superior outcome of PFA reported in dependent clinical studies in contrast to independent clinical literature and that there is a superior outcome of 'trochlear-cutting' PFA in comparison with 'first-generation trochlear-resurfacing' implants.

METHODS

Studies on PFA from its market introduction in 1955 onwards were systematically reviewed. The revision rate, which was calculated as 'revisions per 100 component years (CY)', was evaluated in 45 studies published in indexed, peer-reviewed international scientific journals. In addition, 'first-generation trochlear-resurfacing' and 'trochlear-cutting' implants as well as dependent and independent clinical literature were analysed. Furthermore, the data of three arthroplasty registers were analysed.

RESULTS

A total of 15,306 PFA were included consisting of 2266 cases in worldwide literature data and of 13,040 cases in register data. 2.22 revisions per 100 CY were observed in worldwide literature data, which corresponds to a revision rate of 22.2% after 10 years. Revision rates between 18.9 and 27% after 10 years were shown by the included three national joint registers. In the group analyses no significant differences were detected.

CONCLUSIONS

This meta-analysis did not reveal significant differences in the comparison between developer over independent publications and between 'first-generation-resurfacing' over 'trochlear-cutting' implants. In conclusion the data of developer publications do not seem to be biased. 'Trochlear-cutting' devices of PFA had slightly superior outcomes, but that benefit was not statistically significant. Nevertheless, we would recommend 'trochlear-cutting' devices for further use in PFA.

LEVEL OF EVIDENCE

Meta-analysis of Level IV case series.

Advances in Patellofemoral Arthroplasty

PURPOSE OF REVIEW

To describe current indications, implants, economic benefits, comparison to TKA, and functional and patient-reported outcomes of patellofemoral arthroplasty.

RECENT FINDINGS

Modern onlay implants and improved patient selection have allowed for recent improvements in short- and long-term outcomes after patellofemoral joint replacement surgery. Patellofemoral arthroplasty has become an increasingly utilized technique for the successful treatment of isolated patellofemoral arthritis. Advances in patient selection, implant design, and surgical technique have resulted in improved performance and longevity of these implants. Although short- and mid-term data for modern patellofemoral arthroplasties appear promising, further long-term clinical studies are needed to evaluate how new designs and technologies will affect patient outcomes and long-term implant performance.

Fresh Osteochondral Patellar Allograft Resurfacing

The treatment of articular cartilage lesions in young patients is certainly a complex matter and subject of continuous research, particularly for those located at the patellofemoral joint, given its peculiar biomechanical characteristics. Osteochondral grafts can be of relatively small size when the defect is focal and in an area that allows good stability and consequently the graft's integration. In case of large or multifocal lesions, it is possible to consider an osteochondral transplantation of the entire articular surface of the patella. We present a simple and reproducible technique to perform a patellar fresh osteochondral allograft resurfacing attempting to reduce the symptoms and delay a prosthetic implant in young patients with advanced patellar chondral injuries.

Inadequacy of computed tomography for pre-operative planning of patellofemoral arthroplasty

PURPOSE

To evaluate the accuracy of preoperative planning for patellofemoral arthroplasty (PFA) by comparing: (1) virtual implant positioning simulated on pre-operative images versus (2) real implant positioning from post-operative images.

METHODS

The authors prospectively studied 15 patients that received a PFJ implant (Tornier, Montbonnot France). A pre-operative planning software was established to determine the size and position of the trochlear component. Pre-operative scans were used to perform virtual implantations by two different operators, which were then compared to the post-operative scans to calculate errors (ε) in implant positioning and intra-class correlation coefficients (ICC) for intra- and inter-observer repeatability.

RESULTS

Analysis was performed for 13 patients, for whom agreement between virtual and real surgery was excellent for anteroposterior (AP) position (ICC = 0.84; ε _max = 3.5 mm), fair for proximodistal (PD) position (ICC = 0.50; ε _max  = 9.5 mm), and poor for mediolateral (ML) position (ICC = 0.07; ε _max = 9.0 mm). It was fair for flexum-recurvatum (FR) alignment (ICC = 0.53; ε _max = 8.2°), poor for varus-valgus (VV) alignment (ICC = 0.34; ε _max = 10.0°), and internal-external (IE) rotation (ICC = 0.34; ε _max = 10.6°).

CONCLUSIONS

Pre-operative planning was insufficiently accurate to follow intra-operatively, the greatest errors being angular alignment (VV and FR). The clinical relevance of these findings is that PFA is difficult to plan pre/operatively due to non-visibility of cartilage on CT scans and to trochlear dysplasia in most cases.

LEVEL OF EVIDENCE

Prospective evaluation of operative tools on consecutive patients, Level III.

Correction of Patellofemoral Malalignment With Patellofemoral Arthroplasty

BACKGROUND

The goal of patellofemoral arthroplasty (PFA) is to replace damaged cartilage and correct underlying deformities to reduce pain and prevent maltracking. We aimed to determine how PFA modifies patellar height, tilt, and tibial tuberosity-trochlear groove (TT-TG) distance. The hypothesis was that PFA would correct trochlear dysplasia or extensor mechanism malalignment.

METHODS

The authors prospectively studied a series of 16 patients (13 women and 3 men) aged 64.9 ± 16.3 years (range 41-86 years) who received PFA. All knees were assessed preoperatively and 6 months postoperatively using frontal, lateral, and "skyline" x-rays, and computed tomography scans to calculate patellar tilt, patellar height, and TT-TG distance.

RESULTS

The interobserver agreement was excellent for all parameters (intraclass correlation coefficient >0.95). Preoperatively, the median patellar tilt without quadriceps contraction (QC) was 17.5° (range 5.3°-33.4°) and with QC was 19.8° (range 0°-52.0°). The median Caton-Deschamps index was 0.91 (range 0.80-1.22) and TT-TG distance was 14.5 mm (range 4.0-22.0 mm). Postoperatively, the median patellar tilt without QC was 0.3° (range -15.3° to 9.5°) and with QC was 6.1° (range -11.5° to 13.3°). The median Caton-Deschamps index was 1.11 (range 0.81-1.20) and TT-TG distance was 10.1 mm (range 1.8-13.8 mm).

CONCLUSION

The present study demonstrates that beyond replacing arthritic cartilage, trochlear-cutting PFA improves patellofemoral congruence by correcting trochlear dysplasia and standardizing radiological measurements as patellar tilt and TT-TG. The association of lateral patellar facetectomy improves patellar tracking by reducing the patellar tilt.

Patellofemoral Arthroplasty: Current Concepts and Review of the Literature

Patellofemoral osteoarthritis (PFOA) can be associated with anterior knee pain, stiffness, and functional impairment. Some authors report that PFOA affects approximately 9% of patients older than 40 years with a greater prevalence in females. Etiology of PFOA is multifactorial and is related to the presence of abnormal stresses at the PF joint due to knee- and patient-related factors. The need for a joint preserving treatment by isolated replacement of the injured compartment of the knee led to the development of PF arthroplasty (PFA). When a correct PF replacement is performed, PFA preserves physiologic tibiofemoral joint, thus allowing patients for a rapid recovery with a high satisfaction. The outcomes for PFA are quite variable with a trend toward good to excellent results, mainly owing to the improvement in surgical techniques, patient selection, and implant design. The development of the second generation of PFA improved the outcomes, which is attributed to the different trochlear designs. Recently, encouraging results have been provided by the association of PFA and unicompartmental knee arthroplasty (UKA). In many studies, the main cause of PFA failure is progression of tibiofemoral OA. The aim of this brief review of literature is to summarize the clinical features, indications and contraindications, surgical techniques, complications, and outcomes of PFA.

Cost effectiveness of patellofemoral versus total knee arthroplasty in younger patients

AIMS

Patellofemoral arthroplasty (PFA) has experienced significant improvements in implant survivorship with second generation designs. This has renewed interest in PFA as an alternative to total knee arthroplasty (TKA) for younger active patients with isolated patellofemoral osteoarthritis (PF OA). We analysed the cost-effectiveness of PFA versus TKA for the management of isolated PF OA in the United States-based population.

PATIENTS AND METHODS

We used a Markov transition state model to compare cost-effectiveness between PFA and TKA. Simulated patients were aged 60 (base case) and 50 years. Lifetime costs (2015 United States dollars), quality-adjusted life year (QALY) gains and incremental cost-effectiveness ratio (ICER) were calculated from a healthcare payer perspective. Annual rates of revision were derived from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man. Deterministic and probabilistic sensitivity analysis was performed for all parameters against a $50 000/QALY willingness to pay.

RESULTS

PFA was more expensive ($49 811 versus $46 632) but more effective (14.3 QALYs versus 13.3 QALYs) over a lifetime horizon. The ICER associated with the additional effectiveness of PFA was $3097. The model was mainly sensitive to utility values, with PFA remaining cost-effective when its utility exceeded that of TKA by at least 1.0%. PFA provided incremental benefits at no increased cost when annual rates of revision decreased by 24.5%.

CONCLUSIONS

Recent improvements in rates of implant of survival have made PFA an economically beneficial joint-preserving procedure in younger patients, delaying TKA until implant failure or tibiofemoral OA progression. The present study quantified the minimum required marginal benefit for PFA to be cost-effective compared with TKA and identified survivorship targets for PFA to become both less expensive and more effective. These benchmarks might be used to assess clinical outcomes of PFA from an economic standpoint within the United States healthcare system. Cite this article: Bone Joint J 2017;99-B:1028-36.

A matched-pair comparison of inlay and onlay trochlear designs for patellofemoral arthroplasty: no differences in clinical outcome but less progression of osteoarthritis with inlay designs

PURPOSE

To compare clinical and radiographic results after isolated patellofemoral arthroplasty (PFA) using either a second-generation inlay or onlay trochlear design. The hypothesis was that an inlay design will produce better clinical results and less progression of tibiofemoral osteoarthritis (OA) compared to an onlay design.

METHODS

Fifteen consecutive patients undergoing isolated PFA with an onlay design trochlear component (Journey™ PFJ, Smith & Nephew) were matched with 15 patients after isolated PFA with an inlay design trochlear component (HemiCAP^® Wave, Arthrosurface). Matching criteria were age, gender, body mass index, and follow-up period. An independent observer evaluated patients prospectively, whereas data were compared retrospectively. Clinical outcome was assessed using WOMAC, Lysholm score, and pain VAS. Kellgren-Lawrence grading was used to assess progression of tibiofemoral OA.

RESULTS

Conversion to total knee arthroplasty was necessary in one patient within each group, leaving 14 patients per group for final evaluation. The mean follow-up was 26 months in the inlay group and 25 months in the onlay group (n.s.). Both groups displayed significant improvements of all clinical scores (p < 0.05). No significant differences were found between the two groups with regard to the clinical outcome and reoperation rate. No significant progression of tibiofemoral OA was observed in the inlay group, whereas 53 % of the onlay group showed progression of medial and/or lateral tibiofemoral OA (p = 0.009).

CONCLUSION

Isolated PFA using either a second-generation inlay or onlay trochlear component significantly improves functional outcome scores and pain. The theoretical advantages of an inlay design did not result in better clinical outcome scores; however, progression of tibiofemoral OA was significantly less common in patients with an inlay trochlear component. This implant design may therefore improve long-term results and survival rates after isolated PFA.

LEVEL OF EVIDENCE

III.

Annual revision rates of partial versus total knee arthroplasty: A comparative meta-analysis

BACKGROUND

Utilization of unicompartmental knee arthroplasty (UKA) and patellofemoral arthroplasty (PFA) as alternatives to total knee arthroplasty (TKA) for unicompartmental knee osteoarthritis (OA) has increased. However, no single resource consolidates survivorship data between TKA and partial resurfacing options for each variant of unicompartmental OA. This meta-analysis compared survivorship between TKA and medial UKA (MUKA), lateral UKA (LUKA) and PFA using annual revision rate as a standardized metric.

METHODS

A systematic literature search was performed for studies quantifying TKA, MUKA, LUKA and/or PFA implant survivorship. Studies were classified by evidence level and assessed for bias using the MINORS and PEDro instruments. Annual revision rates were calculated for each arthroplasty procedure as percentages/observed component-year, based on a Poisson-normal model with random effects using the R-statistical software package.

RESULTS

One hundred and twenty-four studies (113 cohort and 11 registry-based studies) met inclusion/exclusion criteria, providing data for 374,934 arthroplasties and 14,991 revisions. The overall evidence level was low, with 96.7% of studies classified as level III-IV. Annual revision rates were lowest for TKA (0.49%, CI 0.41 to 0.58), followed by MUKA (1.07%, CI 0.87 to 1.31), LUKA (1.13%, CI 0.69 to 1.83) and PFA (1.75%, CI 1.19 to 2.57). No difference was detected between revision rates for MUKA and LUKA (p=0.222).

CONCLUSIONS

Revisions of MUKA, LUKA and PFA occur at an annual rate of 2.18, 2.31 and 3.57-fold that of TKA, respectively. These estimates may be used to inform clinical decision-making, guide patient expectations and evaluate the cost-effectiveness of total versus partial knee replacement in the setting of unicompartmental OA.

Why do patellofemoral arthroplasties fail today? A systematic review

BACKGROUND

Historically poor results of patellofemoral arthroplasty (PFA) were reported in the setting of isolated patellofemoral osteoarthritis (OA). In order to lower PFA failure rates, it is important to identify failure modes using a standardized method. In this systematic review, PFA failure modes were assessed and compared in early vs. late failures and older vs. recent studies.

METHODS

Databases of PubMed, Embase and Cochrane and annual registries were searched for studies reporting PFA failures. Failure modes in studies with mean follow-up <5years were classified as early failures while >5years were classified late failures. Cohorts started before 2000 were classified as older studies and started after 2000 as recent studies.

RESULTS

Thirty-nine cohort studies (10 level II and 29 level III or IV studies) and three registries were included with overall low quality of studies (GRADE criteria). A total of 938 PFA failures were included and were caused by OA progression (38%), pain (16%), aseptic loosening (14%) and patellar maltracking (10%). Pain was responsible for most early failures (31%), while OA progression was most common in late failures (46%). In older studies, OA progression was more commonly reported as failure mode than in more recent studies (53% vs. 39%, p=0.005).

CONCLUSION

This level IV systematic review with low quality of studies identified OA progression and pain as major failure modes. Reviewing these studies, appropriate patient selection could prevent PFA failures in select cases. Future studies assessing the role of PFA in isolated patellofemoral OA are necessary.