Introduction

The etiology of isolated patellar and trochlear cartilage defects without patellar instability is currently poorly understood. While correlations with coronal plane malalignment have been made, the effect on patellofemoral pathology of an increased posterior vector in the sagittal plane has not been fully elucidated. The purpose of this study was to evaluate the variation in knee sagittal alignment in patients with and without patellofemoral cartilage wear.

Methods

This was a single-center, retrospective review of patients that underwent a cartilage restoration procedure for isolated patellofemoral cartilage wear from 2014-2020. Patients were matched in 1:2:2 ratio for age, sex, and BMI to an anterior knee pain diagnosis cohort and a meniscectomy procedure cohort as controls. Inclusion criteria included an available MRI in the electronic medical record. Exclusion criteria included knee flexion angle >10°, Caton-Deschamps <0.6, >1.3, tibial tubercle-trochlear groove (TT-TG) distance > 20 mm, sulcus angle >145°, or ICRS patellofemoral cartilage defects of = 3 in either control group. The sagittal TT-TG (sTT-TG) distance was measured on preoperative axial T2 magnetic resonance imaging (MRI). The first point was the nadir of the anterior trochlear cartilage, and the second point was the most anterior point on the tibial tubercle. The distance between these points, perpendicular to the posterior condylar axis, was measured. Measurements were made by a sports medicine fellowship-trained attending and a senior orthopaedic surgery resident. Comparisons between the 3 groups were made using ANOVA testing with Bonferroni corrections. Reliability was assessed with the interclass correlation coefficient (ICC).

Results

Two hundred and thirty-five patients (47 cartilage restoration, 94 anterior knee pain, 94 meniscectomy) were included. Mean age, BMI, and height were 33.8 +/- 8.7 and 26.7 +/- 5.7, 170.6 +/- 24.3 respectively, with 130 males (55%) and 105 females (45%). There were no significant differences between groups for age, BMI or sex (p>0.05).
Mean sTT-TG was significantly more posterior in the cartilage restoration group compared to the meniscectomy group (-2.5 mm +/- 5.9 vs 1.72 mm +/- 5.3, p<0.001). The anterior knee pain group sTT-TG was between the meniscectomy and cartilage restoration groups, but was not significantly different from either (p=0.067, p=0.13). Interrater reliability was excellent (ICC=0.927, p<0.001).

Conclusion

Patients that underwent isolated cartilage restoration procedures had a significantly more posterior tibial tubercle than partial meniscectomy patients. Anterior knee pain patients’s sagittal TT-TG was between both groups, but was not significantly different from either.