FP5.3 Tönnis 1 Hips Demonstrate Significant Clinical Improvement with Low Conversion to Total Hip Arthroplasty at Mid-Term Following Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Multicentered Propensity Matched Analysis

Background: Mild osteoarthritis, considered as Tönnis grade 1, may be associated with inferior outcomes following hip arthroscopy (HA). Existing studies assessing the relationship between Tönnis grade and outcomes have demonstrated a wide range of clinical improvement and survivorship.

Purpose: To compare mid-term functional outcomes and survivorship following HA for femoroacetabular impingement syndrome between Tönnis grade 0 and 1 hips.

Methods: Within a multicenter surgical database, hips undergoing primary HA, including labral repair, femoroplasty, and capsular repair with minimum 5-year follow-up available were identified. Hips with Tönnis grade 1 were propensity matched to Tönnis grade 0 hips by age, sex, and body mass index (BMI). Patient reported outcome (PROs) measures were collected at baseline, 2-year, and 5-year time-points. Achievement of minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) were determined using previously described thresholds and compared across groups. Incidence of conversion to total hip arthroplasty (THA) was compared.

Results: Ninety-one hips with Tönnis grade 1 were matched at a 1:1 ratio to Tönnis grade 0 hips, with similar age (44.0±10.1 vs. 44.0±10.1, p=0.926), sex (65.9% female vs 61.5%, p=0.644), BMI (27.0±5.3 vs. 27.2±5.9, p=0.883), and follow-up time (5.3±0.46 vs. 5.3 ± 0.52, p=0.969). There were no observed differences in PROs at baseline (p≤0.258, for all) or at minimum 5-year follow-up (p=0.193, for all). Hips from both groups demonstrated significant improvement from pre- to post-operative time-points for all PROs measured (p<0.001, for all). Both groups achieved MCID for measured PROs at similar rates (p≥0.457, for all). Tönnis grade 1 hips had lower PASS achievement rates for modified Harris Hip Score (39.6% vs. 62.7%, p=0.023) with otherwise similar PASS achievement (p≥0.187, for all). THA conversion was 6.3% for Tönnis grade 1 hips and 4.5% for Tönnis grade 0 hips at final follow-up, which was statistically similar (p=0.718).

Conclusions: Although Tönnis grade 1 is associated with inferior outcome measures than their Tönnis grade 0 counterparts, patients can see clinical improvement regardless of Tönnis grade. With evolving surgical technique and indications, rates of THA conversion at mid-term follow-up may be lower than previously reported.