Description
We sought to determine what anatomic findings are associated with a persistent J-sign after MPFL-R with tibial tubercle distalization (d-TTO) in patients with recurrent lateral patellar dislocation (RLPD).
Retrospective chart review of 168 consecutive subjects operated for RLPD and patella alta, with an MPFL-R and d-TTO. 93 subjects had preoperative J sign and were included for analysis. Caton-Deschamps Index (CDI), patello-trochlear index, TT-TG, Patellar Tendon - Lateral Trochlear Ridge (PT-LTR) distance, lateral patellar tilt (LPT), tibiofemoral joint rotation (TFJR), lateral trochlear inclination angle (LTIA), trochlear depth (TD), sulcus angle and sagittal bump height were measured. Amount of TTO distalization and medialization was registered
Mean follow-up was 42.5 mo. Mean age 20.1 yrs (±6.8 yrs), 84% females. Persistent J-sign was present in 36 subjects (39%). 86% of subjects with and 60% of subjects without a post op J-sign also had a lateral retinaculum lengthening. Distalization did not differ between groups (p=0.66). Based on ROC analysis and Youden’s index PTLTR, TFJR, and LTIA had the highest predictability for persistent J-sign with optimal threshold value of >13mm (OR: 7.2, 95%CI: 2.1 - 24.9), >6.0º external rotation (OR: 9.5, 95%CI: 2.8-31.8), or <10º (OR: 3.95, 95%IC: 1.1 - 13.9) respectively.
