FP4.3 Proms and Survivorship Are Not Impacted By The Size Of Cam Deformity Observed At Time Of Arthroscopic Correction Of Femoroacetabular Impingement (Fai). A 10-Year Follow-Up Study

Background: Larger cam deformities are thought to be a poor prognostic factor in FAI.

Aim: To investigate the association between the size of cam deformity on measurable hip range of motion (ROM) pre-operatively, and patient-reported outcome measures and survivorship at 10-years post-operatively.

Method: Retrospective review of data prospectively collected and stored in an institutional hip arthroscopy registry. Patients undergoing arthroscopic FAI correction and labral repair as the index procedure between Jan 2013-March 2014 were included. Exclusion criteria consisted of Tonnis >1 (n=41), dysplasia (n=39), protrusio (n=1). Intra-operative assessment of cam deformity size (small, moderate, large) defined the study groups. PROMs were evaluated pre-operatively and 10-years post-op, and included the mHHS, UCLA, SF36 and WOMAC. ROM was measured using a hand-held goniometer. Kaplan-Meier survival analysis evaluated survivorship (avoidance of THA) between groups. Analysis of variance and non-parametric analysis was performed to compare ROM and PROMs respectively between groups. Statistical analysis was performed using SPSS software.

Results: 254 cases met the inclusion criteria, of which 180 (71%) (140 patients) had 10-year follow-up and were included in the final analysis. Cam size was defined as small (n=101, 56%), moderate (n=54, 30%), large (n=19, 11%), and not reported (n=6, 3%). Alpha angles measured on Dunn view were as follows: 54.5°±10.5° (small), 64.1°±7.7° (moderate), 70.1°±8.1° (large), with subsequent correction reducing the measured AA by mean 7°, 9° and 11° respectively (p=0.166). Of the measured ROMs, Internal Rotation was the only movement significantly different between groups pre-operatively - a reduced ROM was associated with increasing cam deformity: (31.8° vs 26.4° vs 21.6° for small, moderate and large cam respectively, p<0.001). No significant difference in any PROMs between groups pre-operatively or post-operatively (p>0.05 following Bonferroni correction for multiple tests). 34 (18.9%) cases underwent a repeat HA; 6 (3.3%) underwent THA conversion at 10-years. No significant difference in the rates of THA conversion between groups – 95%, 100%, 100% survivorship for small, moderate and large groups respectively (x=3.7, p=0.155).

Conclusion: The magnitude of cam deformity at time of surgery was not associated with PROMs or survivorship at 10 years post-op. Baseline internal rotation is reduced with increasing cam size and can be considered a useful examination in the diagnostic work-up of FAI.