Does severity of femoral trochlear dysplasia affect outcome in patellofemoral instability treated by medial patellofemoral ligament reconstruction and anterior tibial tuberosity transfer?

Introduction: Medial patellofemoral ligament (MPFL) reconstruction associated to anterior tibial tuberosity transfer (ATTT) is recommended in objective patellofemoral instability (PFI). Efficacy, however, has not been precisely determined in trochlear dysplasia with spur. A case-control study was performed in a PFI population, comparing groups with trochlear dysplasia with and without spur (S+ vs. S-) to assess the impact of trochlear dysplasia on (1) patellofemoral stability, (2) functional results and complications, and (3) patellofemoral cartilage status on MRI. Hypothesis: Trochlear spur does not affect outcome in PFI managed by MPFL reconstruction and ATTT. Material and methods: Twenty-eight knees (26 patients) with PFI were analyzed retrospectively and divided into 2 groups of 14 knees each according to presence of trochlear spur (S+ vs. S-). All 28 knees had undergone ATTT and MPFL reconstruction by semitendinosus autograft. Results were assessed on Lille and IKDC functional scores, and cartilage status was determined on MRI at last follow-up. Results: At a mean 24 months' follow-up (range, 12-52 months), there was no recurrence of dislocation. IKDC and Lille scores tended to improve in both groups, although the only significant improvement was in IKDC score (S- gain, 21.3 +/- 16; S+ gain, 18.1 +/- 14) (P = 0.01). IKDC scores at last follow-up were better in the S+ than S- group (79 +/- 19 [range, 21-92] vs. 68 +/- 13 [range, 35-84], respectively; P = 0.012). Lille scores showed no significant inter-group differences in mean gain (P = 0.492) or mean value (P = 0.381). The S+ group showed more cartilage lesions (n = 14/14 knees, including 12/14 with grade >= 2 lesions) than the S-group (n = 9/14 knees, all grade <= 2). Conclusion: MPFL reconstruction with ATTT provided good short-term patellofemoral stability independently of the severity of trochlear dysplasia. Functional results and gain on IKDC, however, were poorer incase of dysplasia with trochlear spur. This is probably due to cartilage lesions, observed more frequently pre- and post-operatively in the spur group, especially as there was no significant difference in Lille Score, which highlights stability. (C) 2015 Published by Elsevier Masson SAS.