Hip Microinstability: Understanding a Newly Defined Hip Pathology in Young Athletes

Abstract

Microinstability is an increasingly recognized diagnosis in young athletes presenting with hip pain. Causes of microinstability may include abnormality of the hip bony anatomy, acetabular labral tears, joint capsule laxity or injury, and muscle dysfunction. Borderline hip dysplasia is an increasingly recognized factor predisposing to microinstability. The capsuloligamentous structures of the hip, particularly the iliofemoral ligament, provide important restraints to femoral head motion, and iatrogenic defects can predispose patients to instability after surgery. Injury to the acetabular labrum may disrupt its important hip-stabilizing properties including the suction seal and improved acetabular depth. Hip muscle weakness or imbalance may result in increased femoral head motion within the acetabulum. The diagnosis of hip microinstability can be challenging, and the history is often nonspecific. Physical examination maneuvers include the anterior apprehension, prone instability, axial distraction, and abduction-hyperextension-external rotation tests. Radiographic features may include borderline hip dysplasia, femoral head-neck junction cliff sign, and an elevated femoralepiphyseal acetabular roof index. Magnetic resonance arthrography may demonstrate a capsular defect, capsular thinning, or labral pathology. Diagnostic intra-articular injection of anesthetic can confirm the intra-articular nature of the pathology. Management of hip microinstability focuses on strengthening the dynamic stabilizers of the hip through focused physical therapy. Surgery may be considered in recalcitrant cases where symptoms persist despite optimization of hip stabilizer strength. In such cases, addressing the primary source of instability through labral repair or reconstruction and capsular repair or plication can be considered. In highly selected cases, surgery can result in excellent outcomes.

Female gender, decreased lateral center edge angle and a positive hyperextension–external rotation test are associated with ease of hip distractability at time of hip arthroscopy

“…Hip microinstability, or atraumatic hip instability, is increasingly recognized as a contributing factor in non‐arthritic hip pain and disability in young patients and athletes [3, 7, 14, 26]. Microinstability can be defined as extraphysiologic motion or pathological laxity that leads to symptomatic abnormal mechanics of the hip [14, 26].…”

Association of Cam Deformity on Anteroposterior Pelvic Radiographs and More Severe Chondral Damage in Femoroacetabular Impingement Syndrome

“…Second, this study did not evaluate demographic or physical examination variables that have been correlated with microinstability. 14-16,40 However, previous data have demonstrated that atraumatic microinstability is associated with less articular cartilage damage compared with cam deformity FAIS. 1 Therefore, it is unlikely that this limitation would confound the study results.…”

Can Hip Passive Range of Motion Predict Hip Microinstability? A Comparative Study

“…We identified 69 patients with isolated hip microinstability (without bony FAI morphology) based on previously published intraoperative criteria (ease of hip distraction, residual hip subluxation after release of traction, straight anterior or lateral chondral and labral pathology). 4,6,7,14,15,22,26 The force required for hip distraction was measured based on a consistent and standardized method, recorded as the number of turns of traction (1 turn ¼ 4 mm of axial traction) to obtain 10 mm of hip distraction, as has been previously reported. 6 The initial state was obtained by placing the patient firmly against a perineal post with body weight traction applied by the senior surgeon as previously described.…”