Adolescent Femoroacetabular Impingement from Malunion of the Anteroinferior Iliac Spine Apophysis Treated with Arthroscopic Spinoplasty

This article describes a case of an acute anterior inferior iliac spine apophyseal avulsion fracture in an adolescent athlete progressing to secondary symptomatic femoroacetabular impingement from an inferiorly displaced malunion and its arthroscopic management. A 13-year-old boy with an acute minimally displaced avulsion fracture of the anterior inferior iliac spine apophysis had initial symptomatic improvement with conservative treatment and a 3-month symptom-free period but then developed flexion-induced deep anterior groin pain and mechanical symptoms. Radiographs confirmed an inferiorly displaced malunion of the ipsilateral anterior inferior iliac spine apophysis in addition to acetabular retroversion and cam deformity. Surgical treatment, including arthroscopic spinoplasty, was performed. Despite some nonrestrictive heterotopic ossification, the patient had a successful clinical outcome at 18 months, with return to football, and a nonarthritic hip score of 98. Although anterior inferior iliac spine avulsion fractures have historically been considered relatively self-limiting injuries, their malunion may be a previously missed cause of unrelenting or bimodal pain from secondary femoroacetabular impingement with possible degenerative consequences in young athletic patients. Anterior inferior iliac spine avulsion fractures may merit a lower degree of tolerance for displacement in the acute setting and a higher degree of clinical and radiographic scrutiny with surgical intervention, possibly in the form of arthroscopic spinoplasty in the more chronic one.