Purpose
Sparse objective data documenting changes of the trochlea shape after trochleoplasty exists. The aim of the present study was to investigate if standardized MRI measurements that characterize TD changed significantly after arthroscopic deepening trochleoplasty (ADT). We hypothesized that MRI measurements would approximate normal values.
Methods
This was a retrospective cohort study with prospectively gathered follow up data of patients undergoing ADT in the period from October 2014 to December 2017. Inclusion criteria for ADT were patellar instability, a dynamic patella apprehension sign in 45 degrees of flexion, and a lateral trochlear inclination angle (LTI) according to Carrillon et al. below 11 degrees and failed physiotherapy. MRI was performed pre- and postoperatively and standardized MRI measurements were performed: the LTI, the trochlear depth, the trochlear asymmetry, the cartilage thickness, and the trochlea height. The Banff Patella Instability Instrument 2.0 (BPII), the Knee Osteoarthritis Outcome Score (KOOS) and the Kujala score were obtained pre- and postoperatively.
Results
15 patients (16 knees) (12 females and 3 males) were enrolled. Median (range) age at the time of surgery was 20.9 (14.1 – 51.3) years. Average follow-up 63.6 (23-97) month. The median (range) LTI improved from 1.25° (-25.1°-10.6°) preoperatively to 10.7°(-17.7°-25.8°) post operatively (P<0.001), trochlear depth increased from 0.00 (-4.2-1.8)mm to 3.23 (0.25-5.3)mm (P<0.001) and facet asymmetry improved from 4.55% (0.0-28.6) to 17.8% (0.0-55.6) (P<0.001). Cartilage thickness was unchanged 4.48 mm (1.85-7.35) to 4.85 mm (0.6-8.25) P=0.796. BPII, KOOS and Kujala score all improved statistically significant. BPII improved from 37.2 (16.5-68.3) to 74.3 (52.2-92.6) P<0.001.
Conclusion
Combined ADT and MPFL reconstruction led to statistically significantly and clinically relevant improvements of standardized MRI measurement that characterize TD and in patient reported outcome. The improvements correspond to those obtained by open trochleoplasty. No significant reduction in cartilage thickness was seen.
Clinical relevance
The findings from this study, indicate that ADT in combination with MPFL-R is a feasible procedure to improve the abnormal configuration of a dysplastic trochlea and clinical improvements can be achieved.