Background
Hip arthroscopy (HA) is most commonly utilised in the treatment of femoroacetabular impingement (FAI). Conversely, the arthroscopic management of dysplasia (classically quantified by a lateral centre-edge angle, <25o) remains controversial with peri-acetabular osteotomy (PAO) still considered by many surgeons as the ‘gold-standard’.
As a consequence of bony under-coverage with anterior instability, symptoms may develop from labral tearing/detachment and a reactive bony prominence on the anterior rim. Arthroscopic resection of the anterior rim deformity and stabilisation of the labrum may resolve symptoms without the need for a more invasive PAO procedure.
The aim of this study was to investigate 2-year clinical outcomes following resection of anterior rim deformity in a cohort of cases with dysplasia.
Methods
Prospectively collected data from an institutional hip preservation registry was reviewed for patients with radiographic dysplasia and who underwent primary arthroscopy as the index procedure between 2014-2022. Dysplasia was defined by measurement of lateral centre-edge angle (LCEA) of Wieberg <25o on standing anteroposterior x-ray or anterior centre-edge angle (ACEA) <25o to the edge of the anterior sourcil on modified false profile (FP) x-ray. ACEA to the most anterior aspect of the acetabulum on FP was used to define the extent of additional acetabular coverage beyond the true weight-bearing aspect of the joint. Surgery aimed to restore the ACEA to that of the sourcil (i.e. remove bony prominence anteriorly). Exclusion criteria consisted of Tonnis >1, AVN, previous hip surgery, where comparative, standardised pre- and post-op x-rays were unavailable. PROMs included mHHS, UCLA, SF36 and WOMAC. Clinical relevance was measured through calculated distribution-based (0.5 SD) minimal clinically important difference (MCID). Repeat hip arthroscopy and conversion to THA was recorded. Statistical analysis was performed using SPSS with an alpha value of <0.05 considered significant.
Results
246 cases were included. Dysplasia was defined by LCEA <25o (12.6%, n=31), ACEA sourcil <25o (72%, n=177), and both LCEA and ACEA <25o (15.4%, n=38). Majority male cohort (69%), mean age 34.1±11.6 years, mean BMI 25.7±5.4, 83% Tonnis 0. There was a significant decrease in the measurable LCEA (29.9±7.3 to 25.2±5.5, <0.001, Cohen’s d=0.885) and ACEA to the most anterior aspect (34.3±5.8 to 27.3±7.1, p<0.001, d=0.857) from pre-op to post-op. The sourcil ACEA did not change (21.8±3.8 to 21.4±6.8, p=0.179). 81% follow-up at 2 years for survivorship: 6.1% (n=15) repeat HA, 2.4% (n=6) conversion to THA, 0.4% (n=1) PAO convert. Significant improvement in all PROMs at 2-years post-op: mHHS 71.5 (64.9-84.7) to 95.7 (84.7-100), p<0.001, r=0.712; UCLA 6 (4-9) to 7 (6-10), p<0.001, r=0.326; SF36 Overall 72.6 (54.3-82.5) to 87.0 (71.8-93.4), p<0.001, r=0.589; WOMAC 24 (12-38) to 5 (2-18), p<0.001, r=0.664. Rates of MCID achievement: mHHS (73.5%), UCLA (56%), SF36 (58.4%), WOMAC (73.8%).
Conclusion
In this cohort of cases with dysplasia, arthroscopic resection of the anterior rim deformity and stabilisation of the labrum resulted in significant improvement in PROMs and low rates of secondary surgery, at 2-years post-op. Resection of the anterior deformity is a safe and effective procedure which does not increase instability or progression toward joint failure.