An experimental simulation model to assess wear of the porcine patellofemoral joint.

Eileen Ingham,Louise M Jennings,Divya Baji,Jj Cray,Raelene M Cowie,Hazel L Fermor,Philippa Bowland,John Fisher

doi:10.1371/journal.pone.0250077

Abstract

A range of surgical techniques and osteochondral interventions have been developed for early stage chondral/osteochondral repair interventions in the knee however, methods for functional, pre-clinical assessment of these therapies are limited. In this study, a method for simulating physiological loading and motion in the porcine patellofemoral joint was developed using a 6-axis simulator. As an example of how the method can be used, the influence of surgical positioning of osteochondral allografts in the patella on cartilage wear, deformation and damage and graft stability was investigated in this porcine patellofemoral joint model. The functional performance of allografts implanted either optimally (flush with the cartilage surface) or 1 mm proud of the cartilage surface was compared to a positive control (stainless steel pin implanted 1 mm proud of the cartilage surface), a negative control (no intervention) and a defect model. Allografts implanted flush with the surrounding cartilage could restore the articulating surface of the patella resulting in low wear, damage and deformation of the opposing cartilage surface, similar to that of the negative control group. Implanting the graft proud of the patella surface resulted in cartilage lesions on the femoral trochlea (ICRS grade 2) and a cartilage volume difference of 2.0 ± 3.9 mm3; the positive controls resulted in more severe lesions, a higher volume difference (14.2 ± 7.4 mm3) which in some cases exposed subchondral bone (ICRS grade 4). Defects in the patella caused deformation of the opposing cartilage surface. All grafts implanted in the patella subsided over the duration of the study. This study demonstrated a method that can be used to evaluate osteochondral repair strategies in the patellofemoral joint applying physiological loading and motions.

Highlights

Chondral and osteochondral lesions in the patellofemoral joint (PFJ) are common, reporting of the prevalence of these lesions is highly variable
Following setup of the joint, Microset 121FF was applied to the trochlea and the simulation run to determine the contact between the trochlear groove and patella
Six samples were tested for 3 hours without an intervention, dislocation did not occur in any samples some isolated scratches were visible on both the patella and femoral trochlea

Summary

Introduction

Chondral and osteochondral lesions in the patellofemoral joint (PFJ) are common, reporting of the prevalence of these lesions is highly variable. Widuchowski et al showed 36% of all lesions in the knee occurred in the PFJ, more common than the medial femoral condyle [1, 2], with 40% of these lesions graded 3 or 4 on the Outerbridge classification [3]. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. The funders had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript

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