Postoperative alpha angle not associated with patient-centered midterm outcomes following hip arthroscopy for FAI
The most commonly used parameter for defining cam-type femoroacetabular impingement(FAI) has been the alpha angle. The purpose of this study was to determine if patient-reported outcomes 5 years following hip arthroscopy for FAI were associated with postoperative alpha angle. We hypothesized that patient-reported outcomes would not be influenced by postoperative alpha angle in patients with FAI.
230 patients had primary hip arthroscopy for FAI and chondrolabral dysfunction. The median age was 40 years (range 18–69). All patients had preoperative and 1 day postoperative alpha angles recorded. At minimum 5 years following arthroscopy, all patients completed an online questionnaire that included the modified Harris Hip score(MHHS), WOMAC, HOS ADL, HOS Sport, SF12 and patient satisfaction. This study was IRB approved. Patients were grouped into two, based on their postoperative alpha angle: <55° (n = 158) and ≥ 55° (n = 56).
The median preoperative alpha angle was 72° (range 50°–105°) and the median postoperative alpha angle was 45° (range 30°–100°). The postoperative alpha angle did not correlate with any outcome measure. The median preoperative alpha angle in the < 55° group was 71° and in ≥ 55° group the median was 74° (p = 0.044). The median follow-up was 5.1 years (range 5–7). The median mHHS was 85 (range 47–100) in the < 55° and 85 (range 54–100) in the ≥ 55° group (n.s); WOMAC was 5 (range 0–73) in the < 55° and 4.5 (range 1–57) in the ≥ 55° group(n.s); HOS ADL was 95 (range 31–100) in the < 55° and 96 (range 50–100) in the ≥ 55° group (n.s); HOS Sport was 88 (range 0–100) in the < 55° and 88 (range 13–100) in the ≥ 55° group (n.s) Median patient satisfaction was 9 (range 1–10) in both groups.
This study shows no statistically significant differences between the investigated patient-reported outcome scores at a 5 years postoperatively in relation to a correction of the alpha angle to 55°. While alpha angle has been shown to be an excellent preoperative diagnostic tool, the postoperative angle does not correlate with midterm outcomes or the development of osteoarthritis based on patient symptoms. The amount of osteoplasty should be based on dynamic examination at arthroscopy, and not by alpha angle.
Level of evidence
III Case–control, retrospective comparative study.
KeywordsFemoroacetabular impingement Diagnosis Alpha angle Hip arthroscopy Outcomes
Flexion abduction external rotation
Hip outcome score
Activities of daily living
Modified Harris hip score
KKB participated in study conception and design, carried out acquisition of data and analysis and interpretation of data, and carried out drafting and revising of the manuscript. ES participated in study conception and design, interpretation of data and participated in drafting and revising the manuscript. SB participated in study conception and design, interpretation of data and participated in drafting and revising the manuscript. MJP participated in study conception and design, collected data, participated in interpretation of data and participated in drafting and revising of the manuscript. All authors have given final approval of the manuscript submitted and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Compliance with ethical standards
Conflict of interest
No financial or non-financial competing interest exists for this manuscript. The manuscript was not influenced by personal or financial relationship with other people or organizations.
This study was approved by the Internal Review Board/Ethics Committee at the Vail Valley Hospital.
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