Tönnis Grade 1 Is Associated With Higher Total Hip Arthroplasty Conversion Than Tönnis Grade 0 at 10-Year Follow-Up After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Cohort Analysis.

PURPOSE: To compare 10-year outcomes of hip arthroscopy in patients with Tönnis grade 1 versus grade 0 osteoarthritis, with specific focus on patient-reported outcomes, rates of minimal clinically important difference, Patient Acceptable Symptom State, Substantial Clinical Benefit, and arthroscopic revision and total hip arthroplasty (THA) conversion rates.

METHODS

Patients undergoing hip arthroscopy for femoroacetabular impingement syndrome (FAIS) were prospectively enrolled. A 1:1 propensity score match based on age, sex, body mass index, smoking status, labral treatment, capsular management, lateral center edge angle, and preoperative alpha angle matched Tönnis grade 1 patients to Tönnis grade 0 patients. Inclusion criteria were symptomatic FAIS with radiographic deformity, failure of nonoperative treatment, and ≥10-year follow-up. Patients were excluded for prior ipsilateral hip arthroscopy, Tönnis grade >1, incomplete data, dysplasia (lateral center edge angle < 18°), developmental hip disorders, or concomitant procedures. Modified Harris hip score (mHHS), Non-Arthritic Hip Score (NAHS), minimal clinically important difference, Patient Acceptable Symptom State, Substantial Clinical Benefit, and failure (revision arthroscopy or THA conversion) rates at 10 years were assessed.

RESULTS

Out of a total database of 152 patients, the study matched 32 Tönnis grade 1 patients (mean age 40.79 ± 10.1 years; body mass index 25.13 ± 3.73; follow-up 12.16 ± .96 years [range, 10.08-13.59]) to 32 Tönnis grade 0 patients (mean age 41.82 ± 11.66; body mass index 25.63 ± 3.53; follow-up 11.42 ± 1.23 years [range: 10.02-13.58]) for a total of 64 included patients within this study. Baseline characteristics were well matched with the only significantly different variable being follow-up time (P = .009), though all patients reached a minimum follow-up of 10-years. Both cohorts showed significant improvements in mHHS and NAHS at 10 years (P < .0001), with no significant differences between groups at 10-years (mHHS P = .509; NAHS P = .339) or any other time point. MCID achievement rates were high for both mHHS (Tönnis 0: 87.5%; Tönnis 1: 90.6%; P = .689) and NAHS (Tönnis 0: 87.5%; Tönnis 1: 93.8%; P = .391). Tönnis grade 1 patients showed higher failure (THA/revision) rates compared to Tönnis grade 0 patients (31.25% vs 3.13%; P = .006). Analyzed separately, Tönnis grade 1 patients had 5 cases (15.63%) of THA conversion compared to 0 cases in the Tönnis grade 0 cohort (P = .05), while revision rates were similarly elevated in the Tönnis grade 1 group (5/32; 15.63%) compared to Tönnis grade 0 patients (1/32; 3.13%) (P = .196).

CONCLUSIONS

Hip arthroscopy yields significant long-term improvements for FAIS patients with Tönnis grade 1 and 0 osteoarthritis. However, increased failure rates in Tönnis grade 1 patients suggests that preoperative osteoarthritis may predispose patients to greater rates of subsequent THA conversion or revision.

LEVEL OF EVIDENCE: Level III, retrospective comparative matched case series.