Summary

This study on a large, national sample of patients reports the rate and factors influencing conversion from hip arthroscopy to total hip arthroplasty within a 2 year follow up period.

Abstract

Introduction

Despite the growing popularity of hip arthroscopy (HA) amongst surgeons and patients, the conversion rate of HA to total hip arthroplasty (THA) has been found to range from 4% to as high as 10%. HA to THA conversion is associated with higher risks of prosthetic dislocation and THA revision. Existing literature is lacking in its investigation of risk factors increasing the risk of HA to THA conversion while having limited sample size. Thus, the purpose of this study is to utilize a large, national database to analyze rate and predictors of conversion to THA within 2 years after HA.

Methods

This retrospective cohort study utilized the 2013-2017 U.S. IBM MarketScan Commercial Claims Encounter database to identify patients who converted to THA within 2 years post-HA at inpatient and outpatient facilities. Current Procedural Terminology (CPT) codes were used to place HA patients into three cohorts: 1) Femoroacetabular impingement (FAI) surgery, 2) isolated debridement, and 3) isolated labral repair. Multivariable logistic regression estimated odds ratios (OR), with their corresponding 95% confidence intervals (CI), for the outcome of conversion to THA adjusted for patient age, gender, Deyo-Charlson Comorbidity Index (DCCI) score, HA procedure performed, and comorbidities such as obesity, smoking, and osteoarthritis. Kaplan-Meier tests estimated median time to conversion from HA to THA for each HA procedure. Univariable comparisons were made with log-rank tests. Chi-square tests compared rates of conversion between the three HA cohorts within each age group. Statistical significance was set at p<0.05.

Results

5194 patients were identified (3640 FAI, 1047 isolated debridement, 507 isolated labral repair). The debridement group had both the highest rate of HA to THA conversion (debridement: 12.51%, repair: 8.68%, FAI: 6.87%, p<0.001) and the shortest median time to conversion (debridement: 10.13 months, repair: 10.50 months, FAI: 11.82 months, log-rank p=0.018). Osteoarthritis diagnosis, isolated debridement procedure, and older age increased risk for conversion (p<0.05). Gender, geographic location, insurance type, and year of surgery were not risk factors for HA to THA conversion (p>0.05).
Within the 41-50 age group, there was a significant difference in conversion rates between the FAI, debridement, and labral repair groups (p=0.043), but no significant differences between the 3 cohorts were found for =40 or >50 age groups.

Conclusion

HA debridement procedures have significantly higher rates of conversion to THA compared to labral repair or FAI surgery. The rate of 2-year conversion to THA following HA is very low (2.7%) for patients <40 years old, particularly for those undergoing labral repair and/or FAI surgery. Patients over age 50, especially those with a diagnosis of osteoarthritis, are much more likely to convert to THA within 2 years (14.7%). While there may be value in HA in the over 50 age group, patients should be counseled that HA may be a staging procedure for eventual THA.