Review Question - QID 219924

The patient has femoroacetabular impingement (FAI) with a very large residual bone spur extending from the anterior inferior iliac spine, resulting in persistent post-operative subspinous impingement.

Femoroacetabular impingement (FAI) occurs due to abnormal contact between the femur and acetabulum that leads to varying degrees of labral pathology, chondral injury, and progressive hip pain. The diagnosis is often made with radiographs showing an aspherical femoral head with an alpha angle exceeding 50-55° (CAM type) and/or anterosuperior acetabular overhang (Pincer type) below the level of the anterior inferior iliac spine (AIIS). Treatment may be operative or non-operative depending on the chronicity of symptoms, pathology involved, and presence or absence of significant joint arthritis. When operative treatment is indicated, it has been shown that simple labral debridement without acetabular rim trimming (osteoplasty) will not provide long-term symptom relief. As such, it is important to address both femoral and acetabular-sided bony defects, including those in the subspinous region in order to fully treat the pathology and prevent persistent or recurrent symptoms.

Bloom et al. reviewed the radiographic factors associated with failure of revision hip arthroscopy. The authors reviewed 26 patients with a minimum 2-year follow-up who underwent revision hip arthroscopy for FAI and found that the failure group showed a significantly smaller decrease in the alpha angle with surgery, measured
on the Dunn view, compared with the success group. They concluded that complete resection of cam lesions as determined by changes in the alpha angle, anterior offset, and head-neck ratio when measured on the Dunn 45° view correlates with positive clinical outcomes after revision hip arthroscopy.

Cvetanovich et al. performed a systematic review of the diagnoses, operative findings, and outcomes of revision hip arthroscopy. The authors reviewed five studies including 348 revision hip arthroscopies and found that residual femoroacetabular impingement was the most common indication for and operative finding of revision hip arthroscopy (81% of cases). They concluded that statistically significant and clinically relevant improvements have been shown in multiple patient-reported clinical outcome scores at short-term follow-up after revision hip arthroscopy, with the reoperation rate after revision hip arthroscopy being 5% within 2 years, including further arthroscopy or conversion to hip arthroplasty.

Figures A and B are AP and frog leg lateral radiographs showing a large bone spur originating from the AIIS that impinges on the proximal femur in the frog leg position. Figures C and D are T1 and T2-weighted coronal MRI images showing the large bony spur as a dark-tendon-like structure and the edema within the femoral head-neck region caused by the impingement, respectively. Illustration A demonstrates how to measure the alpha angle for assessing CAM pathology.

Incorrect Answers:
Answer 1: There is no radiographic evidence of arthritic progression beyond Tönnis grade 2 (i.e., grade 3) that would include large cysts and joint space obliteration, and her dictated operative report indicates overall low-grade cartilage changes with focal areas of partial-thickness involvement (Grade 2).
Answers 2: The surgeon used a peri-portal capsulotomy technique which involves making multiple small portals that do not connect to one another to make a large capsulotomy that requires repair. Thus, no plication would have been performed and would not be a reason for this patient's persistent pain.
Answer 3: An alpha angle of > 50-55° is associated with symptomatic CAM deformity. The patient's post-operative alpha angle is 47°.
Answer 4: Given that an inter-portal capsulotomy was not performed, lack of capsular repair in this instance would be unlikely to contribute to hip micro-instability in this patient.