Summary

The clinical outcomes of an autologous chondrocyte implantation (ACI) for the patellofemoral joint (PFJ) are comparable for patients with and without trochlear dysplasia.

Abstract

Background

Autologous chondrocyte implantation (ACI) is a viable treatment option for cartilage lesions in the patellofemoral joint (PFJ). Several studies have demonstrated the deleterious effects of uncorrected abnormal biomechanics on cartilage repair in the PFJ. It remains unknown, however, the influence of trochlear dysplasia on the postoperative outcomes. The purpose of this study was therefore to evaluate the influence of trochlear dysplasia on the outcomes of ACI for the treatment of large cartilage lesions in the PFJ with a minimum of 2 years follow-up.

Methods

Data of all patients submitted to cartilage repair with ACI for focal cartilage defects in the PFJ were retrospectively assessed. Patient’s age at the time of surgery, body mass index (BMI), sex, diagnosis (i.e. traumatic lesion, instability, etc.) and whether the patient had multiple previous surgeries on the index knee were reviewed. Cartilage defect morphology, including the size, number, and location was collected from surgical notes. Pre- and postoperative patient-reported outcomes measures (PROMs) were collected. Patients with previous or concomitant procedures to the index knee - with exception of TTO - were excluded from the study. Patients without at least 2 years of follow-up or incomplete preoperative self-assessments, demographic data, missing preoperative radiographic or magnetic resonance imaging (MRI) or unreported defect morphology were also excluded. Two independent observers evaluated preoperative radiographic and MRI to determine the presence and grade of trochlear dysplasia using the Dejour classification. Patients were stratified into two groups based on the presence or absence of trochlear dysplasia with patients without trochlear dysplasia serving as controls in this study. Patients were matched 1:1 for sex, age, BMI, lesion size and location. After assessing all data for normality, patient-reported outcomes were compared utilizing the independent t-test and Mann-Whitney U test for normally and non-normally distributed outcomes, respectively. Finally, a sub-analysis was performed comparing patients with high-grade dysplasia to those without dysplasia, excluding patients with Dejour type A dysplasia.

Results

Forty-six patients that underwent ACI in the PFJ with a mean follow-up of 3.7 ? 1.9 years (range, 2 to 9 years) were enrolled in this study. Patient’s mean age at the time of surgery was 30.1 ? 8.8 years with a male predominance (54.3%) in both groups. Interobserver reliability (k) was 76.1% for the Dejour classification and 91.9% when stratified into low-grade (Dejour type A) and high-grade (Dejour types B, C and D) dysplasia according to Lippacher (p < 0,001). PROMs at final follow-up did not differ between both groups (p > 0.05). No difference was seen regarding failure rates between both groups (n=1 [4.3%] for dysplasia group, n=1 [4.3%] for control group, p > 0.999). In the sub-analysis, no significant difference was observed between patients with high-grade dysplasia and patients without dysplasia.

Conclusion

This is the first report to specifically analyze the effects of trochlear dysplasia on the clinical outcomes of ACI for the treatment of chondral lesions in the PFJ. The current study suggests that ACI in the PFJ can provide favorable results even in patients with trochlea dysplasia, which are comparable to those of patients with normal trochlear anatomy. Therefore, the presence of trochlear dysplasia should not be considered as a contra-indication to PF cartilage repair with ACI.