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PURPOSE: Robotic adoption in knee surgery has yielded several benefits, but its application in patellofemoral arthroplasty (PFA) remains barely reported. The purpose of this study was to determine implant survival, patient satisfaction, and functional outcomes after robotic-assisted PFA at an intermediate follow-up. METHODS: This prospective analysis targeted 18 knees of 16 consecutive patients who underwent robot-aided PFA with three-year minimum follow-up (range, 3 to 6 years). Each patient was evaluated collecting pre-operative and post-operative medical record data, including range of motion, radiographic images, and multiple scores, such as VAS, APKS, and OKS. RESULTS: At surgery, the mean age was 55.4 years ± 14.4 (range, 32 to 78 years), and the mean BMI was 26.8 kg/m² ±5.2 (range, 20 to 36). Etiologies of patellofemoral osteoarthritis included idiopathic degeneration (28%), post-traumatic (33%), and dysplasia (39%). Pre-implantation scores were VAS 7.9 ± 1.4, AKPS 34.6 ± 23.3, and OKS 17.3 ± 10.3. One implant was revised with primary total knee arthroplasty for osteoarthritis progression. Clinical and radiographic follow-up showed no signs of loosening or infection. The maximum flexion reached an average of 131.1°±10.5° (range, 110° to 145°), accompanied by significantly improved score results (P-value < 0.01): VAS 1.1 ± 1.4, AKPS 90.2 ± 8.6, and OKS 46.3 ± 1.8. CONCLUSIONS: At 3 years after robotic assisted patellofemoral arthroplasty, excellent implant survival and patient satisfaction rates can be expected along with significantly improved functional and pain control outcomes. Although the limitations imposed by the restricted cohort, these findings indicate that robotic assistance in PFA is both safe and effective at intermediate follow-up.

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BACKGROUND: Limited data are available on return to sports and patient psychometric ratings of success after patellofemoral arthroplasty (PFA) in younger patients with high expectations to return to an active lifestyle. PURPOSE/HYPOTHESIS: The purpose of this article was to determine the role of PFA and its success in meeting patient expectations regarding the return to low-impact recreational sports and an active lifestyle in younger, active patients. It was hypothesized that PFA would allow younger patients to return to low-impact sports and an active lifestyle and achieve high patient psychometric ratings. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: In this 10-year prospective study (2009-2018), robotic-assisted PFA was performed on 44 patients (32 women and 12 men; n = 51 consecutive knees), with a mean age of 37.2 years (range, 21-50 years). The follow-up rate was 98%, with a mean of 5.3 years (range, 2-9.3 years). Primary clinical outcomes were as follows: the validated Cincinnati Knee Rating System sports activity and symptom rating scales, patient psychometric ratings of the substantial clinical benefit (SCB), and the Patient Acceptable Symptom State (PASS). Secondary outcomes were the Cincinnati Knee Rating System occupational rating, visual analog pain scale, and the 12-Item Short Form Health Survey. Survivorship was defined by conversion to total knee replacement (TKR). RESULTS: Before PFA, 78% of patients (35/45 knees) were symptomatic and unable to perform recreational sports, with only 20% of patients (9/45 knees) performing some low-impact sports. After PFA, 80% of patients (36/45 knees) were able to perform low-impact sports, and 7% (3/45 knees) performed jumping-pivoting sports (P < .001). The SCB scored by the patient showed 87% of knees as good, very good, or normal. On the PASS analysis, 89% of patients (95% CI, 76%-96%) were "pleased," and 93% (95% CI, 82%-99%) would undergo surgery again. There were clinically relevant improvements in symptoms of pain, swelling, and giving way (P = .0001). Preoperatively, 91% of knees had moderate to severe pain with activities of daily living, and only 11% of knees had pain at the follow-up. Five of the 50 knees (10%) underwent TKR conversion with one patient lost to follow-up. CONCLUSION: PFA resulted in a high return of patients to low-impact sports with high SCB and PASS psychometric ratings. The robotic-assisted 3-dimensional preoperative planning allowed precise intraoperative trochlear implant alignment in knees with severe trochlear dysplasia. PFA is recommended as an alternative treatment in younger patients with end-stage symptomatic patellofemoral arthritis. REGISTRATION: NCT02738476 (ClinicalTrials.gov identifier).

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INTRODUCTION: Patellofemoral arthroplasty (PFA) has been shown to provide symptomatic improvement for isolated patellofemoral osteoarthritis (PFOA). The efficacy of robotic-assisted PFA and the most suitable PFA implant design, however, remain ongoing matters of debate. This study sought to compare clinical outcomes between patients who underwent robotic-assisted versus conventional PFAs with inlay and onlay prosthetic designs. METHODS: A single-center retrospective review found 237 knees (211 patients) which underwent PFA between 2011 and 2021. One hundred eighty-four knees were included in the final analysis after cases were excluded for having indications other than osteoarthritis or having less than one year of follow-up. There were 90 conventional PFAs and 94 robotic-assisted PFAs performed. Inlay components were implanted in 89 knees and onlay components were implanted in 95 knees. Propensity score matching was utilized to address demographic differences between groups. RESULTS: Overall, there was a revision-free survivorship rate of 89.7% with an average time to follow-up of 4.6 years (range 1.2 to 11.1). Twenty-nine knees (15.8%) required various non-conversion procedures. The conventional matched cohort exhibited a higher all-cause revision rate, accounting for revision PFAs and conversions to TKA, (18.8 vs. 6.4%, p = 0.014) and a shorter mean time to revision than the robotic-assisted cohort (3.1 vs. 5.8 years, p = 0.026). A Kaplan-Meier survivorship curve showed differences between the conventional and robotics cohorts (p = 0.041). All revisions following robotic-assisted PFA were caused by progression of osteoarthritis, whereas conventional PFAs also required revision due to aseptic loosening and patellar maltracking. The rate of infection resulting in irrigation and debridement was higher for conventional cases (4.3 vs. 0%, p = 0.041). No significant differences in clinical outcomes between the inlay and onlay prosthetic design matched cohorts were identified. CONCLUSION: PFA is an effective treatment for addressing advanced patellofemoral arthritis. Robotic-assisted surgery may lead to improved clinical outcomes. LEVEL OF EVIDENCE: III.

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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.

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BACKGROUND: As the popularity of unicondylar knee arthroplasty (UKA) and patellofemoral arthroplasty (PFA) have expanded, more patients who have limited arthritis are undergoing partial knee arthroplasty. No studies have evaluated if any regional differences in the United States (U.S.) exist between partial versus total knee arthroplasty (TKA). The purpose of this study was to utilize the American Joint Replacement Registry to evaluate regional differences in UKA, PFA, and TKA. METHODS: The American Joint Replacement Registry was queried for all TKA, PFA, and UKA procedures between 2012 and 2021. Surgical volume was compared between the Midwest (MW), Northeast (NE), South, and West (W) regions. Trends were compared using multivariate logistic regression analyses and least squared mean logistic regression models. RESULTS: Since 2012, there has been a steady increase in the amount of UKAs performed across the U.S., except during the COVID-19 pandemic when numbers decreased. Logistic regression analyses demonstrated a higher likelihood of receiving a UKA compared to TKA in the NE compared to other regions, and higher likelihood of receiving a PFA in the NE and W compared to other regions over the study period. Other factors that increased the likelihood of having a UKA nationally were men, the procedure being performed at a teaching hospital, and having surgery in urban areas. Patients were more likely to have a PFA in the NE compared to the S and MW, and higher odds in the South and W compared to the MW, with rates of PFA consistently lower in the MW compared to other regions. CONCLUSIONS: Patients were more likely to have a UKA in the NE compared to other regions of the country. Patients had higher odds of having a PFA in the NE and W regions relative to the MW. Men had higher odds of having either UKA or PFA than women across the nation.

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PURPOSE: Patellofemoral arthroplasty (PFA) was shown to be a potentially effective surgical technique for isolated patellofemoral osteoarthritis but varying reports on PFA-related implant failure and complications have rendered the procedure controversial. This study aimed to identify impactful publications, research interests/efforts, and collaborative networks in the field of PFA research. METHODS: The study used the Web of Science Core Collection (WOSCC) database, Medline, Springer, BIOSIS Citation Index, and PubMed to retrieve relevant publications on PFA research published between 1950-2022. Statistical tests in R software were used for analysis while VOSviewer, Bibliometrix, and CiteSpace were employed for data visualization. RESULTS: Two hundred forty-one articles were analyzed with the number of published papers increasing over time. Knee was the most frequent journal and Clinical Orthopaedics and Related Research was the most cited journal. Clinical outcomes, such as prosthesis survival, revision, and complications, were researched most frequently as demonstrated by keyword analysis. The United States was the top contributor to cooperative networks, followed by the United Kingdom while Technical University Munich formed close ties among authors. CONCLUSION: Publications on PFA research have witnessed a notable surge. They primarily came from a limited number of centers and were characterized by low-level evidence. The majority of studies primarily focused on the clinical outcomes of PFA, while revision of PFA and patient satisfaction have emerged as new research areas.

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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.

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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.

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Background: The purpose of this study is the evaluation of the patellofemoral arthroplasty (PFA) survival and clinical and radiological outcomes in our institution. Methods: A retrospective evaluation of our institution patellofemoral arthroplasty cases from 2006 to 2018 was performed; the n sample after applying exclusion and inclusion criteria was 21. All patients excepting one were female with a median age of 63 (20–78). A Kaplan–Meier survival analysis at ten years was calculated. Informed consent was obtained from all patients prior being included in the study. Results: The total revision rate was 6 out of 21 patients (28.57%). The progression of the osteoarthritis in the tibiofemoral compartment was the main cause (50% of revision surgeries). The degree of satisfaction with the PFA was high, with a mean Kujala score of 70.09 and a mean OKS of 35.45 points. The VAS score improved significantly (p<0.001) from a preoperative mean of 8.07 to a postoperative mean of 3.45, with an average improvement of 5 (2–8). Survival at 10 years, with revision for any reason as the endpoint, was 73.5%. A significant positive correlation between BMI and the WOMAC pain (r=0.72, p<0.01) and between BMI and the post-operative VAS (r=0.67, p<0.01) was observed. Conclusions: The results of the case series under consideration suggest that PFA could be a possibility in the joint preservation surgery on the isolated patellofemoral osteoarthritis. BMI >30 seems to be a negative predictor factor in relationship with the postoperative satisfaction, increasing the pain proportionally to this index and requiring more replacement surgery than patients with BMI <30. Meanwhile the radiologic parameters of the implant are not correlated with the clinical or functional outcomes.(AU)

Antecedentes: El propósito de este estudio es la evaluación de la supervivencia de la prótesis femoropatelar y los resultados clínicos y radiológicos en nuestro centro. Métodos: En el presente estudio se realiza una evaluación retrospectiva de los casos de prótesis femoropatelar en nuestro centro entre los años 2006 y 2018. El tamaño muestral, tras aplicar los criterios de inclusión y de exclusión, fue de 21 pacientes. Todos los pacientes excepto uno fueron mujeres, con una media de edad de 63 años (rango 20-78). Se calculó una gráfica de Kaplan-Meier de supervivencia en los primeros 10 años. El consentimiento informado de todos los pacientes fue obtenido previamente a la inclusión en este estudio. Resultados: La tasa de recambio a prótesis total fue 6 de 21 pacientes (28,57%). La progresión de la osteoartrosis en el compartimento tibiofemoral fue la causa principal (50% de las cirugías de revisión). El grado de satisfacción con la PFA fue alto, con una media en la escala de Kujala de 70,09 y una media de OKS de 35,45 puntos. La EVA mejoró significativamente (p<0,001), de una media preoperatoria de 8,07 a una media postoperatoria de 3,45, siendo la media de mejoría de 5 puntos (2 a 8 puntos). La supervivencia a los 10 años, con rescate de la prótesis debido a cualquier causa, fue del 73,5%. Se observó una correlación positiva ente el IMC y la escala WOMAC (r=0,72, p>0,01) y entre el IMC y la EVA postoperatoria (r=0,67 y p<0,01). Conclusiones: Los resultados de esta serie de casos mostraron que la prótesis femoropatelar puede ser una alternativa de tratamiento como cirugía de preservación de la osteoartritis femoropatelar aislada. El IMC>30 parece ser un factor predictor negativo en relación con la satisfacción postoperatoria, incrementando el dolor con una correlación positiva con este índice y requiriendo mayor cirugía de reemplazo que los pacientes con IMC<30. Por otra parte, los parámetros radiológicos relacionados con el implante no están...(AU)

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Background: The purpose of this study is the evaluation of the patellofemoral arthroplasty (PFA) survival and clinical and radiological outcomes in our institution. Methods: A retrospective evaluation of our institution patellofemoral arthroplasty cases from 2006 to 2018 was performed; the n sample after applying exclusion and inclusion criteria was 21. All patients excepting one were female with a median age of 63 (20–78). A Kaplan–Meier survival analysis at ten years was calculated. Informed consent was obtained from all patients prior being included in the study. Results: The total revision rate was 6 out of 21 patients (28.57%). The progression of the osteoarthritis in the tibiofemoral compartment was the main cause (50% of revision surgeries). The degree of satisfaction with the PFA was high, with a mean Kujala score of 70.09 and a mean OKS of 35.45 points. The VAS score improved significantly (p<0.001) from a preoperative mean of 8.07 to a postoperative mean of 3.45, with an average improvement of 5 (2–8). Survival at 10 years, with revision for any reason as the endpoint, was 73.5%. A significant positive correlation between BMI and the WOMAC pain (r=0.72, p<0.01) and between BMI and the post-operative VAS (r=0.67, p<0.01) was observed. Conclusions: The results of the case series under consideration suggest that PFA could be a possibility in the joint preservation surgery on the isolated patellofemoral osteoarthritis. BMI >30 seems to be a negative predictor factor in relationship with the postoperative satisfaction, increasing the pain proportionally to this index and requiring more replacement surgery than patients with BMI <30. Meanwhile the radiologic parameters of the implant are not correlated with the clinical or functional outcomes.(AU)

Antecedentes: El propósito de este estudio es la evaluación de la supervivencia de la prótesis femoropatelar y los resultados clínicos y radiológicos en nuestro centro. Métodos: En el presente estudio se realiza una evaluación retrospectiva de los casos de prótesis femoropatelar en nuestro centro entre los años 2006 y 2018. El tamaño muestral, tras aplicar los criterios de inclusión y de exclusión, fue de 21 pacientes. Todos los pacientes excepto uno fueron mujeres, con una media de edad de 63 años (rango 20-78). Se calculó una gráfica de Kaplan-Meier de supervivencia en los primeros 10 años. El consentimiento informado de todos los pacientes fue obtenido previamente a la inclusión en este estudio. Resultados: La tasa de recambio a prótesis total fue 6 de 21 pacientes (28,57%). La progresión de la osteoartrosis en el compartimento tibiofemoral fue la causa principal (50% de las cirugías de revisión). El grado de satisfacción con la PFA fue alto, con una media en la escala de Kujala de 70,09 y una media de OKS de 35,45 puntos. La EVA mejoró significativamente (p<0,001), de una media preoperatoria de 8,07 a una media postoperatoria de 3,45, siendo la media de mejoría de 5 puntos (2 a 8 puntos). La supervivencia a los 10 años, con rescate de la prótesis debido a cualquier causa, fue del 73,5%. Se observó una correlación positiva ente el IMC y la escala WOMAC (r=0,72, p>0,01) y entre el IMC y la EVA postoperatoria (r=0,67 y p<0,01). Conclusiones: Los resultados de esta serie de casos mostraron que la prótesis femoropatelar puede ser una alternativa de tratamiento como cirugía de preservación de la osteoartritis femoropatelar aislada. El IMC>30 parece ser un factor predictor negativo en relación con la satisfacción postoperatoria, incrementando el dolor con una correlación positiva con este índice y requiriendo mayor cirugía de reemplazo que los pacientes con IMC<30. Por otra parte, los parámetros radiológicos relacionados con el implante no están...(AU)

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Introduction: Non-classical Celiac disease is a previously undescribed cause of debilitating post-operative cutaneous complications following an orthopedic procedure. Non-specific symptoms and rarity of the disease pose a diagnostic challenge; however, given underdiagnosis and significant morbidity, after ruling out of acute pathology, Celiac disease should be included in differential diagnosis for refractory cutaneous complications following an operative procedure. Case Report: A 34-year-old woman who underwent patellofemoral arthroplasty and medial patellofemoral ligament reconstruction experienced over 5 months of post-operative knee swelling, erythema, and pain unresponsive to antihistamines and negative infectious, vascular, and implant allergy testing workups. After careful dietary monitoring by an allergy specialist, she was tested and confirmed to have Celiac disease. Following cessation of her oral contraceptive pill and dietary gluten, her knee swelling, erythema, and debilitating pain resolved. Conclusion: Skin erythema, swelling, and pain are known complications after any operative treatment, but after ruling out of acute infectious and thromboembolic processes, diagnosis and management of refractory complications pose a challenging scenario. In this rare phenomenon, previously undescribed, a patient presented with months of post-operative knee erythema, swelling, stiffness, and extreme pain on activity along with non-specific symptoms of headache and fatigue before diagnosis with Celiac disease. On cessation of her birth control and dietary gluten, her symptoms and knee function improved dramatically.

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Introduction: Indications for patellofemoral arthroplasty (PFA) remain under debate, with many surgeons favoring total knee arthroplasty (TKA) even in patients with limited degeneration in the tibiofemoral compartments. Case Report: A 30-year-old man with a history of bilateral patellar instability treated in youth with multiple surgeries presented with 8+ months of recurrent bilateral knee pain. Evaluation showed bilateral severe patellofemoral arthritis with preserved medial and lateral compartments. Bilateral sequential robotic-assisted PFAs (RA-PFA) were offered as a precise approach to reconstructing patellofemoral biomechanics while minimizing bone resection to avoid compromising potential future TKA. Four months after his latest surgery, he returned to a physically demanding job, and he remains active and pain free at 1 year postoperatively. Conclusion: RA-PFA can provide less invasive, accurate, and individualized treatment for younger patients with severe disease without compromising future conversion to TKA.

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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.

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PURPOSE: The aim of this study was to report the clinical and functional outcomes, complication rates, implant survivorship and the progression of tibiofemoral osteoarthritis (OA), after new inlay or onlay patellofemoral arthroplasty (PFA), for isolated patellofemoral OA. Comparison of different implant types and models, where it was possible, also represented one of the objectives. METHODS: A systematic literature search following PRISMA guidelines was conducted on PubMed, Scopus, Embase and Cochrane databases, to identify possible relevant studies, published from the inception of these databases until 11.11.2022. Randomized control trials (RCTs), case series, case control studies and cohort studies, written in English or German, and published in peer-reviewed journals after 2010, were included. Not original studies, case reports, simulation studies, systematic reviews, or studies that included patients who underwent TKA or unicompartmental arthroplasty (UKA) of the medial or lateral compartment of the knee, were excluded. Additionally, only articles that assessed functional and/or clinical outcomes, patient-reported outcomes (PROMs), radiographic progression of OA, complication rates, implant survival rates, pain, as well as conversion to TKA rates in patients treated with PFA, using inlay or onlay trochlea designs, were included. For quality assessment, the Methodological Index for Non-Randomized Studies (MINORS) for non-comparative and comparative clinical intervention studies was used. RESULTS: The literature search identified 404 articles. 29 of them met all the inclusion criteria following the selection process. Median MINORS for non-comparative studies value was 12.5 (range 11-14), and for comparative studies 20.1 (range 17-24). In terms of clinical and functional outcomes, no difference between onlay and inlay PFA has been described. Both designs yielded satisfactory results at short, medium and long-term follow-ups. Both designs improved pain postoperatively and no difference between them in terms of postoperative VAS has been noted, although the onlay groups presented a higher preoperative VAS. When comparing the inlay to onlay trochlea designs, the inlay group displayed a lower progression of OA rate. CONCLUSION: There is no difference in functional or clinical outcomes after PFA between the new inlay and the onlay designs, with both presenting an improvement in most of the scores that were used. A higher rate of OA progression was observed in the onlay design group. LEVEL OF EVIDENCE: III.

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Background: Patellofemoral arthroplasty (PFA) is reported to provide nearly normal PF joint kinematics but only with adequate surgical techniques. This study evaluated the effects of various femoral component settings on patellar component biomechanics. Methods: A dynamic musculoskeletal computer simulation analyzed normal knee and standard PFA models, as well as 8 femoral component malposition models: 5° internal or external rotation, 5° valgus or varus, 5° extension or flexion, and 3-mm or 5-mm anterior positioning. Mediolateral patellar translation, lateral patellar tilt, and contact force and stress at the PF joint were measured in each model during gait. Results: The patella in the standard PFA model was shifted up to 5.0 mm laterally near heel off and was tilted up to 3.0° laterally at heel strike compared to the normal knee model. The patella in the external rotation model translated more laterally in the direction of the femoral component setting than in the standard model. However, in the internal rotation and varus alignment models, the patellar lateral shift occurred largely in the opposite direction of the femoral component setting. The patella in most models was tilted in the same direction as the femoral component setting. The PF contact force was increased, especially in the anterior femoral position models, by up to 30 MPa compared with 20 MPa in the standard model. Conclusions: Internal rotation, varus, and anterior femoral component settings during PFA should be avoided to reduce postoperative complications, whereas external rotation might be appropriate only for cases with lateral patellar instability.

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BACKGROUND: The purpose of this study is the evaluation of the patellofemoral arthroplasty (PFA) survival and clinical and radiological outcomes in our institution. METHODS: A retrospective evaluation of our institution patellofemoral arthroplasty cases from 2006 to 2018 was performed; the n sample after applying exclusion and inclusion criteria was 21. All patients excepting one were female with a median age of 63 (20-78). A Kaplan-Meier survival analysis at ten years was calculated. Informed consent was obtained from all patients prior being included in the study. RESULTS: The total revision rate was 6 out of 21 patients (28.57%). The progression of the osteoarthritis in the tibiofemoral compartment was the main cause (50% of revision surgeries). The degree of satisfaction with the PFA was high, with a mean Kujala score of 70.09 and a mean OKS of 35.45 points. The VAS score improved significantly (P<.001) from a preoperative mean of 8.07 to a postoperative mean of 3.45, with an average improvement of 5 (2-8). Survival at 10 years, with revision for any reason as the endpoint, was 73.5%. A significant positive correlation between BMI and the WOMAC pain (r=.72, P<.01) and between BMI and the post-operative VAS (r=.67, P<.01) was observed. CONCLUSIONS: The results of the case series under consideration suggest that PFA could be a possibility in the joint preservation surgery on the isolated patellofemoral osteoarthritis. BMI >30 seems to be a negative predictor factor in relationship with the postoperative satisfaction, increasing the pain proportionally to this index and requiring more replacement surgery than patients with BMI <30. Meanwhile the radiologic parameters of the implant are not correlated with the clinical or functional outcomes.

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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.

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BACKGROUND: Outcomes of patellofemoral arthroplasty (PFA) to total knee arthroplasty (TKA) conversion are reported to be similar to primary cases. The purpose of this study was to determine whether the cause for conversion from PFA to TKA correlated to outcomes when compared to a matched cohort. METHODS: A retrospective chart review was performed to identify aseptic PFA to TKA conversions between 2000 and 2021. A cohort of primary TKAs was matched by patient sex, body mass index, and American Society of Anesthesiology score. Clinical outcomes, including range of motion, complication rates, and patient reported outcomes measurement information systems scores, were compared. Chi-squared, Fisher's Exact, and t-tests were performed. There were 20 PFA to TKA conversions that met inclusion criteria and were matched to 60 primary cases. RESULTS: There were 7 cases revised for arthritis progression, 5 for femoral component failure, 5 for patellar component failure, and 3 for patellar maltracking. PFA to TKA conversions for patellar failure (fracture, component loosening) had worse postoperative flexion (115 versus 127°, P = .023) and more complications of stiffness (40 versus 0%, P = .046) than primary TKAs. Conversions for failed patellar components had worse patient reported outcomes measurement information systems physical function (32 versus 45, P = .0046), physical health (42 versus 49, P = .0258), and pain scores (45 versus 24, P = .0465). No differences were found in rates of infection, manipulations under anesthesia, or reoperations. CONCLUSION: PFA to TKA conversion outcomes were similar to primary TKA, except in patients who had failed patellar components and demonstrated worse postoperative range of motion and patient-reported outcomes. Surgeons should avoid thin patellar resections and extensive lateral releases to minimize patellar failures.

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BACKGROUND: Patellofemoral arthroplasty (PFA) is an alternative to total knee arthroplasty (TKA) for the treatment of patellofemoral arthritis. Although PFA may preserve native kinematics and accelerate recovery, it has been associated with higher revision rates. The purpose of this study is to compare complication rates and costs between PFA and TKA. METHODS: Using the PearlDiver database, 6,179 patients with isolated patellofemoral arthritis treated with PFA or TKA from 2010-2015 were retrospectively reviewed with 5-year follow up. PFA and TKA patients were matched by age, sex, and Elixhauser Comorbidity Index via a 1:1 stepwise algorithm. Five-year costs and complications were compared between matched cohorts. The lifetime costs of PFA and TKA were evaluated with Markov decision modeling. RESULTS: Compared to TKA, PFA was associated with fewer Emergency Department (ED) visits (6.1% vs 3.9%, p = 0.004) but a higher 5-year revision rate (9.9% vs 4.2%, p < 0.001). After multivariate regression, PFA was independently more likely to require revision (odds ratio 2.60, 95% confidence interval 1.32-4.71, p = 0.003). PFA was associated with lower total healthcare costs at every time point between 3 months ($18,014 vs $26,473, p < 0.001) and 5 years ($20,837 vs $27,942, p < 0.001). On average, the lifetime cost of PFA per patient was $5,235 less than for TKA ($26,343 vs $31,578). CONCLUSIONS: PFA is a less expensive alternative to TKA with a similar risk of medical complications but is associated with a significantly higher 5-year revision rate. Future studies should examine the reasons for PFA failure and methods to mitigate this risk.

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PURPOSE: The purpose of this systematic review was to evaluate outcomes and complications rates between inlay and onlay patellofemoral arthroplasty (PFA). METHODS: According to the PRISMA statement, 42 studies with 2552 patients were included. Data considered for quantitative analysis consisted of the Knee Society Score (KSS), the range of motion (ROM), the visual analogue score (VAS), and the Western Ontario and McMaster Universities questionnaire (WOMAC). Complications and revision surgery were considered. RESULTS: Data on postoperative KSS showed no differences between the groups. The ROM was evaluated in 8 studies for 70 and 331 inlay and onlay PFA, respectively. Onlay group was favorable in terms of postoperative ROM. Postoperative VAS was available for 64 inlay and 110 onlay and no differences were found. Data on postoperative WOMAC were available for 49 inlay and 527 onlay PFA and inlay group showed better scores. A statistically significant higher rate of instability, persistent pain, malposition, stiffness, deep infection, disease progression, and wear of the patellar component were noted in the inlay group. A higher rate of lateral release was noted in the onlay group. A higher number of manipulations under anesthesia was noted in the inlay group. The revision to total knee arthroplasty was reported more frequently in the inlay group. CONCLUSION: A higher rate of conversion to total knee arthroplasty and complication rates after inlay technique was found. The potential of achieving better WOMAC scores with the inlay technique should be weighed against the higher complication and revision rates compared to the onlay technique. LEVEL OF EVIDENCE: IV.

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