Learning curve of basic hip arthroscopy technique: CUSUM analysis

Abstract

Purpose: Hip arthroscopy is known to have a steep learning curve by measuring operation times or complication rates. However, these measures are arbitrary and are based on the number of procedures performed rather than clinical outcomes. Recently, Cumulative sum (CUSUM) analysis has been used to monitor the performance of a single surgeon by evaluating clinical outcomes. Our purpose was to determine the learning curve for basic hip arthroscopy technique using CUSUM technique.

Methods: Forty consecutive patients who underwent hip arthroscopy were evaluated. Modified Harris Hip Score less than 80 at 6 months postoperatively was considered as treatment failure. Patients were chronologically stratified in two groups (the early group--cases 1-20, and the late group--cases 21-40), and age, gender, body mass index, and operation time were compared in both group. CUSUM analysis was then used to plot the learning curve.

Results: Eight patients (20 %) experienced treatment failure. Although there was no significant difference of treatment failure rate between the early and late groups (30 vs. 10 %, n.s.), the operation time was shorter in the late group (p = 0.014). In addition, CUSUM analysis showed that failure rates diminished rapidly after 21 cases and reached an acceptable rate after 30 cases.

Conclusions: Surgeon's experience is an important predictor of failure after hip arthroscopy, and CUSUM analysis revealed that a learning period is required to become proficient at this procedure, and that experience of approximately 20 cases is required to achieve satisfactory outcomes in terms of clinical outcomes. Surgeon can use the present learning curve for self-monitoring and continuous quality improvement in hip arthroscopy.

Level of evidence: Retrospective case series, Level IV.