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Updated: Jun 6, 2026
In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy
Published on: July 2, 2021
Risk factors for conversion to total hip arthroplasty after hip arthroscopy for femoroacetabular impingement: a
Roberto Seijas1, Miguel Vázquez-Gómez2,3, Patricia Laiz2
1Instituto Cugat, Barcelona, Spain. roberto6jas@gmail.com.
Purpose:
To identify independent risk factors for conversion to total hip arthroplasty (THA) after hip arthroscopy for femoroacetabular impingement syndrome (FAIS) in a large European single-centre cohort with minimum five-year follow-up, and to further evaluate the Hip Arthroscopy Risk (HAR) Index. We hypothesised that HAR Index ≥ 3, Tönnis grade 2, and Outerbridge grade 4 would be independently associated with THA conversion at five years.
Methods:
This retrospective cohort study included 827 consecutive hips undergoing primary hip arthroscopy for FAIS between January 2007 and April 2021, with minimum five-year follow-up. The primary endpoint was THA conversion within 60 months. Kaplan-Meier analysis and multivariable Cox regression were performed. Predictors included Tönnis grade, Outerbridge grade, ALAD grade, HAR Index, age, sex, and body mass index.
Results:
A total of 86 hips (10.4%) were converted to THA within five years (overall survivorship 89.6%). Conversion rates increased with Tönnis grade: 1.0% (grade 0), 7.7% (grade 1), and 36.2% (grade 2) (P < 0.001). Outerbridge grade 4 was associated with a 33.3% conversion rate versus 2.3% for grades 0-1 (P < 0.001). The HAR Index showed a dose-response from 0.3% (HAR 0) to 66.7% (HAR 4). Two pre-specified multivariable Cox models were constructed to address multicollinearity between the HAR Index and its component variables. Model 1 (composite model): HAR Index ≥ 3 (HR 8.30; 95% CI, 4.84-14.26), Outerbridge grade 4 (HR 6.32; 95% CI, 3.29-12.14), and Outerbridge grade 2-3 (HR 3.16; 95% CI, 1.48-6.73) were independent predictors (C-index 0.853; all P ≤ .003). Model 2 (component model): Tönnis grade 2-3 (HR 19.41; 95% CI, 6.03-62.53), Tönnis grade 1 (HR 7.09; 95% CI, 2.18-23.06), Outerbridge grade 4 (HR 2.16; 95% CI, 1.06-4.37), and age 50-60 years (HR 5.49; 95% CI, 2.47-12.17) were independent predictors (C-index 0.885; all P ≤ .033).
Conclusions:
Tönnis grade, Outerbridge grade, age, and the HAR Index were independently associated with THA conversion within five years. A HAR Index ≥ 3 may help guide patient selection and preoperative counselling. External validation is required.
