Pre-existing osteoarthritis remains a key feature of arthroscopy patients who convert to total hip arthroplasty.

Objectives: To determine the rate of conversion to total hip arthroplasty following ipsilateral hip arthroscopy by a single surgeon in New Zealand and to describe patient-related and surgical characteristics of patients who converted.

Methods: A retrospective cohort analysis of hip arthroscopy patients with 2 years of minimum follow-up identified the total hip arthroplasty conversion rate using the New Zealand National Joint Registry. Prospective data collected from patients who subsequently converted to hip arthroplasty included: sex, age at arthroscopy, body mass index, side of hip arthroscopy and arthroplasty, duration of symptoms and patient-reported outcome measures. Imaging (Tönnis grade and lateral centre-edge angle) and surgical findings (labral, ligamentum teres and osteochondral pathology) along with the arthroscopic procedures performed were also documented.

Results: Sixty-six out of 1856 (3.56%) primary hip arthroscopies were followed by an ipsilateral hip arthroplasty during the follow-up period (mean 87 ± 29 months). Most patients had pre-existing osteoarthritis and/or chondral lesions (n=51). Dysplasia and over-resection of the acetabulum were also identified as contributing factors.

Conclusion: Conversion rate by a high-volume surgeon in New Zealand was relatively low. Most patients had pre-existing osteoarthritis and/or chondral lesions that became apparent at arthroscopy. Dysplasia is also a factor to be cautious of when selecting patients for arthroscopy. Acetabular resection must be approached cautiously.

Level Of Evidence: Level IV.