The evolution and role of patellofemoral joint arthroplasty: The road less travelled, but not forgotten

Outcomes After Patellofemoral Arthroplasty With the Arthrex iBalance-A Third Generation Implant

Background

Patellofemoral arthroplasty (PFA) is an attractive option for patients who have isolated patellofemoral disease. This study aimed to assess the functional outcomes and revision rates of primary PFA with a third-generation implant with short- to medium-term follow-up.

Methods

We retrospectively reviewed the records of 49 patients (70 knees) undergoing PFA with the iBalance system by a single surgeon at a quaternary center between January 2015 and September 2022 for demographic and surgical data, as well as complications and revision rates. Patient-reported outcome scores were then collected.

Results

The population was majority female (81.6%) with a median age of 50 years. Four knees were revised to a total knee arthroplasty (5.7%) at an average time point of 2.3 years postoperatively (range: 1.3-3.5 years). The median Single Assessment Numeric Evaluation score at the time of follow-up was 82.5, while the median Kujala score was 72. Lower preoperative Kellgren-Lawrence grade was significantly associated with lower Knee Injury and Osteoarthritis Outcome Scores in all 5 domains (P < .05 for all). Additional procedures were required in 17 knees (24.3%), in most cases to improve patella tracking.

Conclusions

This study is, to our knowledge, the first to examine outcomes of the iBalance PFA system. The results show favorable patient-reported outcomes in this cohort consistent with other 2nd and 3rd generation PFA implants, along with a revision rate similar to its prosthetic peers.

Outcomes of patellofemoral joint arthroplasty: a systematic review of revision timelines and complication rates

INTRODUCTION

This systematic review attempts to address survivorship of patellofemoral joint replacements, with conversion to a total knee arthroplasty (TKA) as an endpoint.

METHODS

Survival estimates from multiple case series and national registries were pooled to calculate survival at 5, 10, 15 and 20 years, respectively. As a secondary outcome, the type and number of complications were recorded. A complication was defined as any any adverse event or unintended outcome that occurs as a result of the joint replacement, either during the immediate postoperative period or over the longer term. As arthroplasty registries do not report this information, this data was only included from publicly available series.

RESULTS

1015 eligible articles were identified, with 21 reporting survival and reasons for revision or complications. Data from registries were extracted. Using publicly available results from international joint registries, survival at 5 and 10 years were 90.30% (95% CI 88.32 to 92.27) and 82.23% (95% CI 78.90 to 85.56), respectively. However, long-term survivorship decreased to 73.74% (95% CI 69.12 to 78.37) and 72.68% (95% CI 69.58 to 75.53) at 15 and 20 years.

CONCLUSION

Our pooled data, survival data from case series show similar results to international joint registries up to 10 years with a survival rate of 82.33%. These findings will be of use to patients and arthroplasty surgeons who require further information in order to predict how long patellofemoral joint replacements will last.

Outcomes of isolated patellofemoral arthroplasty

Osteoarthritis of the patellofemoral compartment can cause significant functional impairment. Isolated patellofemoral osteoarthritis affects greater than 10% of males and females over the age of 60. Patellofemoral arthroplasty (PFA) was developed as a joint-preserving procedure that maintains natural knee kinematics in those with isolated patellofemoral disease. First-generation implants were fraught with complications, a high rate of revision, and early conversion to total knee arthroplasty (TKA). Second-generation implants have demonstrated significant improvements in patient-reported outcome measures, complication rates and implant survivorship. Factors that can affect outcomes include surgical indications, patient selection, and PFA prosthesis design. Modern PFA for isolated patellofemoral osteoarthritis has comparable outcomes to TKA for isolated patellofemoral osteoarthritis. In this article, we discuss the use of PFA, implant design, the indications and factors affecting outcomes, and comparison to TKA.

Should we recommend patellofemoral arthroplasties to patients?

Aims

With up to 40% of patients having patellofemoral joint osteoarthritis (PFJ OA), the two arthroplasty options are to replace solely the patellofemoral joint via patellofemoral arthroplasty (PFA), or the entire knee via total knee arthroplasty (TKA). The aim of this study was to assess postoperative success of second-generation PFAs compared to TKAs for patients treated for PFJ OA using patient-reported outcome measures (PROMs) and domains deemed important by patients following a patient and public involvement meeting.

Methods

MEDLINE, EMBASE via OVID, CINAHL, and EBSCO were searched from inception to January 2022. Any study addressing surgical treatment of primary patellofemoral joint OA using second generation PFA and TKA in patients aged above 18 years with follow-up data of 30 days were included. Studies relating to OA secondary to trauma were excluded. ROB-2 and ROBINS-I bias tools were used.

Results

A total of nine studies were included, made up of four randomized controlled trials (domain 1) and five cohort studies (domain 2). PROMs and knee function specific scores developed for reporting TKA were unable to detect any difference between PFA and TKA. There was no significant difference in complications between PFA and TKA. PFAs were found to have a better postoperative range of motion.

Conclusion

TKA and PFA are both viable options for patients with primary PFJ OA. Over time, we have seen an emphasis on patient satisfaction and better quality of life. Recommending sacrificing healthy medial and lateral compartments to treat patellofemoral joint arthritis should be given further thought.

Current outcomes of patellofemoral arthroplasty for isolated patellofemoral arthritis - A narrative review

Patellofemoral (PFJ) arthritis can be primary, or secondary to underlying trochlea dysplasia and patellofemoral malalignment. Although primary PFJ osteoarthritis affects an older patient population, just like tibiofemoral arthritis, it is common for younger patients to present with isolated PFJ arthritis secondary to an abnormal PFJ. PFJ arthroplasty (PFJA) has many benefits including being less invasive, associated with lower blood loss, is more cost-effective, and leaves the kinematics of the tibiofemoral joint undisturbed. As a result, there are arguably better functional outcomes associated with PFJA, however the historical revision rate of this procedure is high. Although registry outcome data associated with the first generation of PFJ implants shows a higher revision rate compared to TKA, the comparison of PFJ outcomes with TKA is not always age-matched and there is limited comparison on functional and patient-reported outcomes, something which is more important and relevant in a younger patient cohort. Improvements in implant design, instrumentation, surgical technique, and better patient selection has now resulted in outcomes which are comparable to that of TKA, and in some cases even better. This narrative review outlines the current outcomes of PFJA including highlighting factors which need to be considered in optimising outcomes, as well as discussing advanced techniques of robotic assisted PFJA.

Patellofemoral Arthroplasty

Patellofemoral arthroplasty (PFA) as a treatment option for isolated patellofemoral disease continues to evolve. Enhancement in patient selection, surgical technique, implant design, and technology has led to improved short-term and midterm outcomes. Furthermore, in the setting of a younger patient with isolated patellofemoral arthritis, PFA represents an option for improved function with faster recovery times, bone preservation, maintenance of ligamentous proprioception, and the ability to delay total knee arthroplasty (TKA). The most common reason for revising PFA to a TKA is progression of tibiofemoral arthritis. In general, conversion of PFA to TKA leads to successful outcomes with minimal bone loss and the ability to use primary TKA implants and instrumentation. PFA seems to be a cost-effective alternative to TKA in appropriately selected patients with 5-, 10-PFA survivorships of 91.7% and 83.3%, respectively, and an annual revision rate of 2.18%; however, more long-term clinical studies are needed to determine how new designs and technologies affect patient outcomes and implant performance.

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.

Long-Term clinical results of patellofemoral arthroplasty for isolated patellofemoral osteoarthritis

OBJECTIVES

The aim of this study was to explore the clinical outcomes and long-term survival of patellofemoral arthroplasty in treatment of isolated patellofemoral osteoarthritis.

METHODS

We retrospectively studied a total of 46 type Y-L-Q PFAs that were designed at our institution in 38 patients. Implant survivorship was analyzed with a follow-up of 18.9-29.6 years. Knee Society Score (KSS), Oxford Knee Score (OKS), and University of California Los Angeles activity scale (UCLA) were used to assess functional outcomes.

RESULTS

The implant survivorship was 83.6% at 15 years, 76.8% at 20 years, and 59.4% at 25 years 14 PFAs in 12 patients were revised into total knee arthroplasty at 16.0 ± 6.7 years; 13 for progression of tibiofemoral osteoarthritis and one for polyethylene wear. The mean Knee Society Score objective scores and functional scores were 73.0 ± 17.5 (range, 49-95) and 56.4 ± 28.9 (range, 5-90), respectively. The mean Oxford Knee Score was 25.8 ± 11.5 (range, 8-44).

CONCLUSION

Type Y-L-Q patellofemoral arthroplasty can be an effective method for treating isolated patellofemoral osteoarthritis with satisfactory survival.

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.

The extensor efficiency of unicompartmental, bicompartmental, and total knee arthroplasty

Aims

Unicompartmental knee arthroplasty (UKA) and bicompartmental knee arthroplasty (BCA) have been associated with improved functional outcomes compared to total knee arthroplasty (TKA) in suitable patients, although the reason is poorly understood. The aim of this study was to measure how the different arthroplasties affect knee extensor function.

Methods

Extensor function was measured for 16 cadaveric knees and then retested following the different arthroplasties. Eight knees underwent medial UKA then BCA, then posterior-cruciate retaining TKA, and eight underwent the lateral equivalents then TKA. Extensor efficiency was calculated for ranges of knee flexion associated with common activities of daily living. Data were analyzed with repeated measures analysis of variance (α = 0.05).

Results

Compared to native, there were no reductions in either extension moment or efficiency following UKA. Conversion to BCA resulted in a small decrease in extension moment between 70° and 90° flexion (p < 0.05), but when examined in the context of daily activity ranges of flexion, extensor efficiency was largely unaffected. Following TKA, large decreases in extension moment were measured at low knee flexion angles (p < 0.05), resulting in 12% to 43% reductions in extensor efficiency for the daily activity ranges.

Conclusion

This cadaveric study found that TKA resulted in inferior extensor function compared to UKA and BCA. This may, in part, help explain the reported differences in function and satisfaction differences between partial and total knee arthroplasty.

Cite this article: Bone Joint Res 2021;10(1):1–9.

Biomechanical effect of tibial slope on the stability of medial unicompartmental knee arthroplasty in posterior cruciate ligament-deficient knees

Aims

Unicompartmental knee arthroplasty (UKA) has become a popular method of treating knee localized osteoarthritis (OA). Additionally, the posterior cruciate ligament (PCL) is essential to maintaining the physiological kinematics and functions of the knee joint. Considering these factors, the purpose of this study was to investigate the biomechanical effects on PCL-deficient knees in medial UKA.

Methods

Computational simulations of five subject-specific models were performed for intact and PCL-deficient UKA with tibial slopes. Anteroposterior (AP) kinematics and contact stresses of the patellofemoral (PF) joint and the articular cartilage were evaluated under the deep-knee-bend condition.

Results

As compared to intact UKA, there was no significant difference in AP translation in PCL-deficient UKA with a low flexion angle, but AP translation significantly increased in the PCL-deficient UKA with high flexion angles. Additionally, the increased AP translation became decreased as the posterior tibial slope increased. The contact stress in the PF joint and the articular cartilage significantly increased in the PCL-deficient UKA, as compared to the intact UKA. Additionally, the increased posterior tibial slope resulted in a significant decrease in the contact stress on PF joint but significantly increased the contact stresses on the articular cartilage.

Conclusion

Our results showed that the posterior stability for low flexion activities in PCL-deficient UKA remained unaffected; however, the posterior stability for high flexion activities was affected. This indicates that a functional PCL is required to ensure normal stability in UKA. Additionally, posterior stability and PF joint may reduce the overall risk of progressive OA by increasing the posterior tibial slope. However, the excessive posterior tibial slope must be avoided.

Cite this article: Bone Joint Res 2020;9(9):593–600.

Short-term Revision Risk of Patellofemoral Arthroplasty Is High: An Analysis from Eight Large Arthroplasty Registries

BACKGROUND

Patellofemoral arthroplasty (PFA) is one option for the treatment of isolated patellofemoral osteoarthritis, but there are limited data regarding the procedure and results. Because isolated patellofemoral arthritis is relatively uncommon, available case series generally are small, and even within national registries, sample sizes are limited. Combining data from multiple registries may aid in assessing worldwide PFA usage and survivorship.

QUESTIONS/PURPOSES

We combined and compared data from multiple large arthroplasty registries worldwide to ask: (1) What proportion of patients undergoing primary knee arthroplasty have PFA? (2) What are the patient and prosthesis characteristics associated with PFA in common practice, as reflected in registries? (3) What is the survivorship free from revision of PFA and what are the reasons for and types of revisions?

METHODS

Data were provided by eight registries that are members of the International Society of Arthroplasty Registries (ISAR) who agreed to share aggregate data: Australia, New Zealand, Canada, Sweden, Finland, Norway, the Netherlands, and the United States. De-identified data were obtained for PFA performed from either the beginning of year 2000, or the earliest recorded implantation date after that in each individual registry when PFA data collection commenced, up to December 31, 2016. This included patient demographics, implant use, all-cause revision rate (determined by cumulative percent revision [CPR]), and reasons for and type of revision.

RESULTS

During the data collection period, 6784 PFAs were performed in the eight countries. PFAs comprised less than 1% of primary knee replacements in all registries. Patient demographics were comparable in all countries. Patients were generally more likely to be women than men, and the mean age ranged from 50 years to 60 years. All registries showed a high rate of revision for PFA. The 5-year CPR for any reason ranged from 8.0% (95% CI 4.5 to 11.5) in Norway to 18.1% (95% CI 15.5 to 20.7) in the Netherlands. The most common reason for revision across all countries was disease progression (42%, 434 of 1034). Most PFAs (83%, 810 of 980) were revised to a TKA.

CONCLUSIONS

The revision risk of PFA in all registries surveyed was more than three times higher than the reported revision risk of TKA at the same times. The survivorship of PFA is similar to that of the no-longer-used procedure of metal-on-metal conventional hip replacement. Although there may be potential functional benefits from PFA, these findings of consistent and alarmingly high rates of revision should create concern, particularly as this procedure is often used in younger patients.

LEVEL OF EVIDENCE

Level III, therapeutic study.

The evolution of patellofemoral prosthetic design in total knee arthroplasty: how far have we come?

Total knee arthroplasty (TKA) has evolved into a successful, cost-effective treatment for end-stage knee arthrosis.The patellofemoral articulation in TKA has largely been ignored during its development despite being an important determinant of outcome.New technologies still need further development to incorporate the patella in TKA surgical planning and operative technique.Alternative approaches to alignment in TKA will have a secondary impact on patellofemoral mechanics and possibly future implant designs.Technologies that assist with precise implant positioning may alter our understanding and overall practice of TKA. Cite this article: EFORT Open Rev 2019;4:503-512. DOI: 10.1302/2058-5241.4.180094.