Introduction. In 1976 the senior author presented to the Associations the results of patellectomy with satisfactory results in less than 50% of cases. In 1989 with the increasing success of TKR we started a prospective study of the Lubinus prosthesis for patellofemoral arthritis. After 4 years results were not satisfactory. The main causes of failure were mal-tracking and instability leading to polythene button wear, and arthritic disease progression. A new prosthesis was designed in 1996 to correct these problems. Methods. We have prospectively recorded the results of a consecutive cohort of 537 Avon arthroplasties. The outcomes have been assessed with survivorship, pain, Oxford and WOMAC scores. We have identified 24 patients from our own series and from tertiary referrals who have persistent pain, due to technical error rather than arthritic disease progression. Results. Survivorship for revision at 5 Years was 96% and overall there were 63 revisions. Results over 10 years show excellent and consistent improvement in both pain and function as judged by the median WOMAC score and are similar to patients with a TKR. The pain score improved from 45% (16) to 87% (7.5), the function score improved from 50% (21) to 80% (12.5). The Oxford score improved from 39.5% (19) to 69% (33). Symptomatic arthritic disease progression occurred in 12% of cases causing recurrent pain. Persistent non-arthritic pain was due to three main causes: minor misplacement of the femoral or patella components or over sizing, leading to retinacular impingement and over stuffing of the patellofemoral joint. Conclusion. This prosthesis has shown consistently good results with few problems over 14 years. New instruments will increase the accuracy of insertion and attention to detail in the performance of the operation will prevent problems. Disease progression remains the main cause of failure and strict pre-operative criteria are essential

Background

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

Introduction

The optimal treatment for isolated patello-femoral arthritis is unclear. Patello-femoral arthroplasty (PFA) may offer superior knee function in isolated patello-femoral osteoarthritis compare to TKA. The literature is controversial for patient outcomes in PFA. Some reports showed improved outcomes while others were disappointing. We assessed our outcomes to try to identify causes for poor outcomes.

Total knee arthroplasty (TKA) has produced excellent results, but many surgeons are hesitant to perform TKA in younger patients with isolated patellofemoral arthritis. In properly selected patients, patellofemoral arthroplasty (PFA) is an effective procedure with good long-term results. Contemporary PFA prostheses have eliminated many of the patellar maltracking problems associated with older designs, and short-term results, as described here, are encouraging. Long-term outcome and prospective trials comparing TKA to PFA are needed. Incidence. Isolated patellofemoral arthritis occurs in as many as 11% of men and 24% of women older than age 55 years with symptomatic osteoarthritis (OA) of the knee; Isolated patellofemoral arthritis found in 9.2% of patients older than age 40 years; 7% to 19% of patients experience residual anterior knee pain when TKA is done for isolated patellofemoral arthritis. Imaging. Weight bearing AP radiographs as supine radiographs can underestimate the extent of tibiofemoral arthritis; Midflexion posteroanterior radiographs to rule out posterior condylar wear; Lateral radiographs to identify the presence or absence of patella alta or baja; Axial radiographs identify the presence of trochlear dysplasia, patellar tilt or subluxation, and extent of patellofemoral arthritis; Magnetic resonance imaging and arthroscopic photographs should be reviewed if available. Indications. Osteoarthritis limited to the patellofemoral joint; Symptoms affecting daily activity referable to patellofemoral joint degeneration unresponsive to lengthy nonoperative treatment; Posttraumatic osteoarthritis; Extensive Grade-III chondrosis; Failed extensor unloading surgical procedure; Patellofemoral malalignment/dysplasia-induced degeneration. Contraindications. No attempt at nonoperative care or to rule out other sources of pain; Arthritis of greater than Grade 1 involving tibiofemoral articulation; Systemic inflammatory arthropathy; Osteoarthritis/chondrosis of the patellofemoral joint of Grade 3 or less; Patella baja; Uncorrected patellofemoral instability or malalignment; Uncorrected tibiofemoral mechanical malalignment; Active infection; Evidence of chronic regional pain syndrome or evidence of psychogenic pain; Fixed loss of knee range of motion, minimum 10–110 degrees ROM. Results. Majority of failures related to patellar instability from uncorrected patellar malalignment, soft-tissue imbalance, or component malposition; With improved implant designs tibiofemoral arthritis has become the primary source of failure; Failure from component subsidence or loosening occurring in <1% of knees. Our Series. Retrospective review 34 patients, 40 knees average 30 month follow-up using Natural Knee II Patello-femoral Joint System (Zimmer, Warsaw, IN); Average age 61, ranging from 34–84 years of age; Average subset KOOS scores were 93 for pain, 94 for symptoms, 94 for ADL's, 70 for sports and recreation, 82 for quality of life; Average pre-operative Tegner score 2.6, increasing to 4.7 post-operatively; 38/40 survival over 30 months with the two failures undergoing revision for traumatic injuries; No revisions to TKA; At most recent follow-up no progression of OA to involve tibiofemoral compartments; No evidence of component loosening

Abstract. Background. The primary objective of the study is to determine the function outcome and survivorship of patellofemoral replacement. The secondary aim is to find the determinants of successful/poor outcome. Methods. This retrospective study involved 45 patients who underwent AVON patellofemoral replacement between January 2015 to December 2020 with the minimal follow-up off for 12 months. The functional outcome was measured using Oxford Knee score (OKS), EuroQol five dimension (EQ-5D). IWANO and Kellgren-Lawrence classification was used to analyse radiographs. To identify determinants of outcome, the following subgroups the presence or absence of normal alignment, tibiofemoral arthritis, trochlear dysplasia and previous surgery. Complications and revision rates were also recorded. Results. The mean follow-up period was 41.7 +/− 8.3 months with no patients lost in follow-up. Patellofemoral replacement significantly improved the Oxford Knee score (OKS), EuroQol five dimension (EQ-5D) (p<0.001). Four out of 45(8.9%) patients underwent revision surgery. Patients with normal alignment preoperatively did worse than those with abnormal alignment with patellar instability. Patients with grade two tibiofemoral arthritis, history of previous surgery did significantly worse with poorer functional outcome. Conclusion. Patellofemoral arthroplasty is reliable treatment option which improves patient function and quality of life with good survivorship in isolated patellofemoral arthritis in mid-term follow-up

Isolated patellofemoral arthritis is not an uncommon problem, with no clear consensus on treatment. Nonoperative and many forms of operative treatments have failed to demonstrate long-term effectiveness in the setting of advanced arthritis. Total knee arthroplasty (TKA) has produced excellent results, but many surgeons are hesitant to perform TKA in younger patients with isolated patellofemoral arthritis. In properly selected patients, patellofemoral arthroplasty (PFA) is an effective procedure with good long-term results. Contemporary PFA prostheses have eliminated many of the patellar maltracking problems associated with older designs, and short-term results, as described here, are encouraging. Long-term outcome and prospective trials comparing TKA to PFA are needed

Isolated patellofemoral arthritis is not an uncommon problem, with no clear consensus on treatment. Nonoperative and many forms of operative treatments have failed to demonstrate long-term effectiveness in the setting of advanced arthritis. Total knee arthroplasty (TKA) has produced excellent results, but many surgeons are hesitant to perform TKA in younger patients with isolated patellofemoral arthritis. In properly selected patients, patellofemoral arthroplasty (PFA) is an effective procedure with good long-term results. Contemporary PFA prostheses have eliminated many of the patellar maltracking problems associated with older designs, and short-term results, as described here, are encouraging. Long-term outcome and prospective trials comparing TKA to PFA are needed

Isolated patellofemoral arthritis is not an uncommon problem, with no clear consensus on treatment. Nonoperative and many forms of operative treatments have failed to demonstrate long-term effectiveness in the setting of advanced arthritis. Total knee arthroplasty (TKA) has produced excellent results, but many surgeons are hesitant to perform TKA in younger patients with isolated patellofemoral arthritis. In properly selected patients, patellofemoral arthroplasty (PFA) is an effective procedure with good long-term results. Contemporary PFA prostheses have eliminated many of the patellar maltracking problems associated with older designs, and short-term results, as described here, are encouraging. Long-term outcome and prospective trials comparing TKA to PFA are needed

Aim. Patellofemoral Arthroplasty (PFA) prosthesis with asymmetric trochlear component was introduced as an improvement from existing designs for surgical treatment of symptomatic isolated patellofemoral arthritis. The purpose of this study was to evaluate midterm results in patients who underwent PFA procedure using such prosthesis. Methods. Our study involved a continuous retrospective cohort of patients who underwent PFA using Journey PFJ with asymmetric trochlear component, performed between June 2007 and October 2018 at a non-designer centre. The Patient Reported Outcome Measures and patient satisfaction questionnaires were collected for final evaluation. Results. A total of 128 PFA performed on 96 patients were evaluated. All patients were under regular follow up, and no patient was lost to follow up. Eighteen patients underwent simultaneous bilateral procedures, and 14 patients underwent PFA of the contralateral knee later. Median age at the time of surgery was 59 years (interquartile range 53 – 66 years); the median follow up period was 6 years (interquartile range 2.5 – 7 years). The Oxford Knee Score showed improvement from a median of 18 to 37. There were statistically significant improvements in functional outcome scores. Beverland satisfaction questionnaire revealed that 22.1 % (19/86) were ‘Very happy’ and 39.5% (34/86) were ‘Happy’ following the procedure. Four knees were revised to Total Knee Arthroplasty for reasons not related to the implant. The cumulative survival estimated by the Kaplan-Meier method was 95.2% (95% confidence interval: 90.4%– 99.9%). Conclusion. This series of patients who underwent PFA with the asymmetric trochlear component has shown promising mid-term results with no implant related complications

Objective. Open-wedge high tibial osteotomy (OWHTO) involves performing a corrective osteotomy of the proximal tibia and removing a wedge of bone to correct varus alignment. Although previous studies have investigated changes in leg length before and after OWHTO using X-rays, none has evaluated three-dimensional (3D) leg length changes after OWHTO. We therefore used 3D preoperative planning software to evaluate changes in leg length after OWHTO in three dimensions. Methods. The study subjects were 55 knees of 46 patients (10 men and 36 women of mean age 69.9 years) with medial osteoarthritis of the knee or osteonecrosis of the medial femoral condyle with a femorotibial angle of >185º and restricted range of motion (extension <–10º, flexion <130º), excluding those also suffering from patellofemoral arthritis or lateral osteoarthritis of the knee. OWHTO was simulated from computed tomography scans of the whole leg using ZedHTO 3D preoperative planning software. We analyzed the hip-knee-ankle angle (HKA), flexion contracture angle (FCA), mechanical medial proximal tibial angle (mMPTA), angle of correction, wedge length, 3D tibial length, 3D leg length, and 3D increase in leg length before and after OWHTO. We also performed univariate and multivariate analysis of factors affecting the change in leg length (preoperative and postoperative H-K-A angle, wedge length, and correction angle). Results. Mean HKA increased significantly from −4.7º ± 2.7º to 3.5º ± 1.3º, as did mean mMPTA from 83.7º ± 3.3º to 92.5º ± 3.0º (p <0.01). Mean FCA was 4.7º ± 3.6° preoperatively and 4.8º ± 3.3º postoperatively, a difference that was not significant (p = 0.725). The mean correction angle was 9.1º ± 2.8º and the mean wedge length was 9.4º ± 3.2º mm. Mean tibial length increased significantly by 4.7 ± 2.3 mm (p <0.01), and mean leg length by 5.6 ± 2.8 mm (p <0.01). The change in leg length was strongly correlated with wedge length (R = 0.846, adjusted R. 2. = 0.711, p <0.01). Discussion and Conclusion. Mean 3D leg length after OWHTO increased significantly by 5.4 ± 3.1 mm. A difference in leg length of >5 mm is believed to affect back pain and gait abnormalities, and changes in leg length must therefore be taken into consideration. The 3D dimensional change in leg length was strongly correlated with wedge length, and could be predicted by the formula (change in leg length in mm) = [(wedge length in mm) ×0.75) − 1.5]. For any figures or tables, please contact authors directly

To resurface or not to resurface the patella… that is the question. It all comes down to where you practice. It is controversial in that there is a risk of possible complications from resurfacing versus the potential for simply having complaints of pain which may supposedly arise from the anterior knee stemming from the unresurfaced patella. The evolution of more favorable anatomic femoral component designs which are very friendly to the patellofemoral articulation have resulted in lower patella resurfacing complications. The insertion of appropriately externally rotated tibial and femoral components, if not reducing anterior knee pain, have certainly minimised the risk of resurfaced patella complications. Also, with current surgical techniques of component insertion, the lateral release rate is extremely low, thus avoiding the possibility of avascularity developing in the resurfaced patella. This complication will almost completely be eliminated if the patella thickness is kept greater than 13 mm after patella resection. In my experience, patella complications from the resurfaced patella are extremely rare. Many unicompartmental knees require re-operation because of the development of progressive patellofemoral arthritis. Re-operation from anterior knee pain from progressive arthritis from the unresurfaced patella has given inferior results. Overall, meta-analysis data demonstrates decreased satisfaction, increased anterior knee pain and higher early revision rates in the unresurfaced group. National joint registries, especially the Australian registry support routine resurfacing; complications are low and outcomes are improved. Even though there exists controversy as to whether the patella should be resurfaced or not, there is an overwhelming consensus in the U.S. that there is little downfall nowadays with respect to resurfacing the patella

This talk reviews the topic of patellofemoral arthroplasty from a historical, technical, and clinical perspective. Emphasis is placed on the design rationale, surgical technique, and 11 year clinical results of so-called “patient-matched” or “patient-specific” patellofemoral arthroplasty in which the trochlear implant is matched to the anatomy of the individual patient through the use of pre-operative computerized imaging scans. The implants are inlayed into the articular cartilage without any intra-operative femoral bone resection. Clinical results involving patient-matched patellofemoral arthroplasty are presented with an average follow-up of 11 years. Case studies reviewing our experience with patient-matched trochlear implants in the setting of femoral trochlear dysplasia are also presented. Patient-specific patellofemoral arthroplasty is a safe and effective treatment for patients with isolated patellofemoral arthritis. The results compare favorably with off-the-shelf patellofemoral arthroplasties that have been reported on over the past thirty years and can be carried out more efficiently. We believe the key elements that contribute to the success of patient-matched patellofemoral arthroplasty are as follows: (a) a strict inclusion criteria based on pre-operative radiographic evaluation; (b) a meticulous attention to soft-tissue balance and patellofemoral tracking at the time of arthroplasty; and (c) a patient-specific design and manufacturing methodology that ensures accurate and precise anatomic fit while simultaneously providing proper patellofemoral alignment and medial-lateral constraint

This study aims to show that our series of Avon Patellofemoral Joint Replacements (APFJR) with over 5 year follow up, have comparable functional, radiological and revision rate results to other published reports. Retrospective analysis occurred for all consecutive cases of APFJR from October 1999 and January 2010; all operations were performed by the senior author (AL). Each patient had both clinical and radiological follow up. Patient demographics, pre and post op Oxford Knee scores and complications were all recorded. An independent post-operative radiological review took place to check for loosening and progression of disease. Revision to Total Knee Replacement was taken as the endpoint. 83 consecutive APFJR's were implanted in 56 patients for established isolated patellofemoral arthritis. The average age was 68.2(34-95) with 18 males and 38 females. The mean follow-up was 5.4 years (1.25 to 11). There were 5 revisions with the five-year survival rate being 95.2% (95% confidence interval 88.12% - 99.88%). The median Pre Op Oxford knee score was 17 of 48 points (interquartile range 11 to 21) showed significant improvement when compared to the median Post Op Oxford knee score of 35 (interquartile range 26 to 41). There was one superficial infection, no deep infections and one transient sciatic nerve palsy. These results compare very closely to those in the designing surgeon's series (Ackroyd et al JBJS Br 2007). These results reveal satisfactory survivorship and functional outcome results in the medium term leading to increased confidence in the use of this patellofemoral arthroplasty

Aim. We aim to show that our series of Avon Patellofemoral Joint Replacements (APFJR) with over 5 year follow up, have comparable functional, radiological and revision rate results to other published reports. Methods. Retrospective analysis occurred of all consecutive cases of APFJR from October 1999 and January 2010. All operations were performed by the senior author (AL). Each patient had both clinical and radiological follow up. Patient demographics, pre and post op Oxford Knee scores and complications were all recorded. An independent post operative radiological review took place to check for loosening and progression of disease. Revision to Total Knee Replacement (TKR) was taken as the endpoint. Results. 83 consecutive APFJR's were implanted in 56 patients for established isolated patellofemoral arthritis. The average age was 68.2(34–95) with 18 males and 38 females. The mean follow-up was 5.4 years (1.25 to 11). There were 5 revisions with the five-year survival rate being 95.2% (95% confidence interval 88.12%-99.88%). The median Pre Op Oxford knee score was 17 of 48 points (interquartile range 11 to 21) showed significant improvement when compared to the median Post Op Oxford knee score of 35 (interquartile range 26 to 41))(p=< 0.001). There was no loosening with the main complication being radiological progression of arthritis. There was one superficial infection and no deep infections. There was also one transient sciatic nerve palsy. These results compare very closely to those in the designing surgeon's series (Ackroyd et al JBJS Br 2007). Conclusions. These results reveal satisfactory survivorship and functional outcome results in the medium term leading to increased confidence in the use of patellofemoral arthroplasty

Patellofemoral unicompartmental joint replacement is a controversial subject with a relatively small evidence base. Of the 50,000 total knee arthroplasties performed each year in the UK, approximately 10% are performed for predominantly patellofemoral arthritis. There are several patellofemoral unicompartmental prostheses on the market with the National Joint Registry recording 745 such prostheses used in 2007. Most evidence in favour of this procedure comes from experience with the Avon prosthesis (Stryker) predominantly from designer-surgeons. The FPV patellofemoral joint replacement (Wright Medical) has been in use in Europe for several years. The instruments have recently been redesigned and the device marketed in the UK. In 2007 the FPV had 5.9% market share (n=44). We present our early experience with the FPV patellofemoral joint replacement, which to our knowledge, is the first clinical outcome series for this prosthesis. 33 consecutive FPV joint replacements in 29 patients were performed between April 2007 and September 2009 for unicompartmental patellofemoral OA. All cases were performed or directly supervised by the senior author. Results are presented with a minimum follow-up of six months. Oxford and American Knee Society scores (AKSS) were obtained on all patients preoperatively and at subsequent outpatient visits. Mean preoperative AKSS knee score was 49.7 points and postoperative scores at 6 months and 1 year were 82.5 and 86.4 respectively. Mean Oxford score preoperatively was 30.4 (37%) and at 6 months and 1 year were 21.3 (56%) and 11.2 (77%) respectively. There were no complications related to the implant. One knee required a secondary open lateral release due to inadequate balancing at the index procedure. Further medium to long-term follow up data are required, but our initial experience with this device is encouraging

There is great contemporary interest to provide treatments for knees with medial or medial plus patellofemoral arthritis that allow retention of the cruciate ligaments and the natural lateral compartment. Options for bicompartmental arthroplasty include custom implants, discrete compartmental implants and monoblock off-the-shelf implants. Each approach has potential benefits. The monoblock approach has the potential to provide a cost-efficient off-the-shelf solution with relatively simple surgical instrumentation and procedure. The purpose of this study was to determine if monoblock bicompartmental knee arthroplasty shows evidence of retained cruciate ligament function and clinical performance more similar to unicompartmental arthroplasty than total knee arthroplasty. Nine females and one male patient were enrolled in this IRB approved study. Each subject received unilateral bicompartmental knee arthroplasty an average of 2.6 years (2.0 to 3.6 years) prior to this study. Subjects averaged 65 years (58–72 years) and 28 BMI (25–31) at the time of surgery. Mean outcome scores at the time of study were 97/95 for the Knee Society knee/function score, 16.4 Oxford score, 6.5 UCLA Activity score and 137 degrees range of motion. Subjects were observed using dynamic fluoroscopy during lunge, kneeling and step-up/down activities. Subjects also received CT scans of the knee in order to create bone/implant composite shape models. Model-image registration techniques were used to determine 3D knee kinematics (Figure 1). Knee angles were quantified using a flexion-abduction-rotation Cardan sequence and condylar translations were determined from the lowest point on the condyle with respect to the transverse plane of the tibial segment. Maximum knee flexion during lunge and kneeling activities averaged 112°±8° and 125°±7°, respectively. Tibial internal rotation averaged 10°±6° and 12°±10° for the lunge and kneeling activities. For both deeply flexed postures, the medial condyle was 1 mm anterior to the AP center of the tibia while the lateral condyle was 11 mm and 13 mm posterior to the tibial center. For the step-up/down activity, tibial internal rotation increased an average of 2° from 5° to 75° flexion, but was quite variable (Figure 2). Medial condylar translations averaged 4 mm posterior from 5° to 25° flexion, followed by 6 mm anterior translation from 25° to 80° flexion (Figure 3). All knees showed posterior condylar translation from extension to early flexion. An important potential benefit to any bicompartmental arthroplasty treatments is retention of the cruciate ligaments and maintenance of more natural knee function. The knees in this study showed excellent or good clinical outcomes and functional scores, and relatively activity high levels. There was no evidence of so-called paradoxical anterior femoral translation during early flexion, indicating retained integrity of the natural AP stabilizing structures. Weight-bearing deep flexion during lunge and kneeling activities was comparable to previously reported unicompartmental and well-performing total knee arthroplasty subjects. Kinematics were quite variable between subjects. Monoblock bicompartmental arthroplasty appears to permit functional retention of the cruciate ligaments, consistent with functionally stable knees. Further efforts should focus on the specific surgical placement of off-the-shelf bicompartmental implants to optimize knee function and provide consistent knee mechanics

Introduction. Epidemiologic studies indicate that isolated patellofemoral (PF) arthritis affects nearly 10% of the population over 40 years of age, with a predilection for females. A small percentage of patients with PF arthritis may require surgical intervention. Surgical options include non-arthroplasty procedures (arthroscopic debridement, tibial tubercle unloading procedures, cartilage restoration, and patellectomy), and patellofemoral or total knee arthroplasty (PFA or TKA). Historically, non-arthroplasty surgical treatment has provided inconsistent results, with short-term success rates of 60–70%, especially in patients with advanced arthritis. Although TKA provides reproducible results in patients with isolated PF arthritis, it may be undesirable for those interested in a more conservative, kinematic-preserving approach, particularly in younger patients, who may account for nearly 50% of patients undergoing surgery for PF arthritis. Due to these limitations, patellofemoral arthroplasty (PFA) has become utilised more frequently over the past two decades. Indications for PFA. The ideal candidate for PFA has isolated, non-inflammatory PF arthritis resulting in “anterior” pain and functional limitations. Pain should be retro- and/or peri-patellar and exacerbated by descending stairs/hills, sitting with the knee flexed, kneeling and standing from a seated position. There should be less pain when walking on level ground. Symptoms should be reproducible during physical examination with squatting and patellar inhibition testing. An abnormal Q-angle or J-sign indicate significant maltracking and/or dysplasia, particularly with a previous history of patellar dislocations. The presence of these findings may necessitate concomitant realignment surgery with PFA. Often, patients with PF arthritis will have significant quadriceps weakness, which should be treated with preoperative physical therapy to prevent prolonged postoperative pain and functional limitations. Tibiofemoral joint pain suggests additional pathology, which may not be amenable to PFA alone. Conclusion. PFA is effective for the treatment of arthritis localised to the PF compartment. Outcomes can be optimised with proper patient selection, meticulous surgical technique, and selection of an onlay-style implant that can be positioned perpendicular to the AP axis of the femur. Minimizing the risk of patellar instability by using onlay-design PFAs has enhanced mid- and long-term results, and leaves progressive tibiofemoral arthritis as the primary failure mechanism beyond 10–15 years