Defining Clinically Important Outcomes for the Modified Harris Hip Score and Nonarthritic Hip Scope for Hip Arthroscopy to Treat Femoroacetabular Impingement at a Minimum 10-Year Follow-up

Abstract

Background: The minimal clinically important difference (MCID), Patient Acceptable Symptom State (PASS), and substantial clinical benefit (SCB) are valuable clinical thresholds used to provide clinical relevance to patient outcome scores. In hip arthroscopy (HA) for femoroacetabular impingement (FAI) syndrome, these values have been defined for the short- and midterm postoperative period, but meaningful long-term thresholds have not been established.

Purpose: To define the MCID, PASS, and SCB for the modified Harris Hip Score (mHHS) and Nonarthritic Hip Score (NAHS) at a minimum follow-up of 10 years for patients who underwent HA for FAI syndrome.

Study design: Case series; Level of evidence, 4.

Methods: A retrospective cohort study including all patients who underwent primary HA for FAI with a single surgeon from February 2010 to December 2013 was performed. Patient outcomes were assessed with an anchor question, mHHS, and NAHS at baseline and at 1, 5, and 10 years of follow-up. MCID was calculated using the distribution-based method at all time points, using 0.5 standard deviations as the threshold. The anchor-based MCID, PASS, and SCB were calculated at 10 years using thresholds representing the optimal cutoff on a receiver operating characteristic curve. Correlations between baseline characteristics and achievement of the MCID, PASS, and SCB were assessed with binomial logistic regressions.

Results: The 154 patients included in the study had a mean age of 38.8 ± 13.0 years, a mean body mass index of 24.6 ± 3.9 kg/m², and 63.6% were female. The distribution-based MCID values for 1-year, 5-year, and 10-year scores were 7.8, 8.3, and 9.5 for mHHS and 9.5, 10.4, and 10.2 for NAHS, respectively. The anchor-based MCID was 20.3 for mHHS and 24.4 for NAHS. The PASS was 81.9 for mHHS and 83.1 for NAHS. The SCB values were 34.0 and 41.9 for mHHS and NAHS, respectively. Increased body mass index was associated with decreased achievement of SCB for mHHS (P = .03) and NAHS (P = .04), as well as NAHS PASS (P = .01) and anchor-based MCID (P = .01).

Conclusion: The establishment of the MCID, SCB, and PASS for the NAHS and mHHS provides a valuable clinical context for improvements in outcome scores after HA. Anchor-based calculations were consistently higher than distribution-based calculations.

Keywords: FAIS; MCID; NAHS; PASS; SCB; arthroscopy; hip; mHHS.