Review Question - QID 219852

The patient's history, physical exam findings, and radiograph of the right hip showing a "cliff sign" are indicative of hip microinstability. The most appropriate initial treatment for hip microinstability is physical therapy focused on strengthening the hip stabilizers with 70% of patients experiencing resolution of their symptoms.

Hip microinstability is the result of pathologic laxity of the hip joint resulting in pain and impairment, and can occur with or without symptoms of joint instability. Multiple factors are associated with microinstability and can be broadly categorized as bony abnormality or developmental dysplasia of the hip, connective tissue disorder, post-traumatic, microtrauma, iatrogenic, and idiopathic. Abnormal translation of the femoral head leads to increased femoral head translation resulting in microtrauma to the hip joint, capsular stretching, and increased sheer stress. Diagnosis can be made utilizing physical examination maneuvers with abduction-hyperextension-external rotation (sensitivity 80.6% specificity 89.4%), prone instability test (sensitivity 33.9% specificity 97.9%), and hyperextension-external rotation (sensitivity 71% specificity 85.1%). Radiographs and hip MRI arthrogram are also utilized, and can show loss of femoral head sphericity (cliff sign), anterior hip joint recess widening, thinning of the anterior hip capsule, defects in the hip capsule, or torn hip labrum. The management of these patients is initially conservative with physical therapy focusing on core and hip stabilizer strengthening resulting in symptom resolution in more than 70% of patients. Surgical intervention is typically reserved for patients without symptom resolution after a course of physical therapy and can include hip arthroscopy (capsular repair, capsular pliccation, etc) or open bony procedures.

Ejnisman et al. published a case series of 64 patients with hip microinstability undergoing initial nonoperative management to determine the effectiveness of physical therapy. They found that after an average follow-up of 46 months, 70.2% of patients had resolution of their symptoms with 29.8% requiring capsular plication. The authors concluded that physical therapy is an effective modality in the treatment of hip microinstabilty.

Mortensen et al. reviewed the role of hip capsular deficiency as a potential cause of hip microinstability following hip arthroscopy. They found rates of post-surgical hip instability as high as 35% following hip arthroscopy and identified failure to repair the capsule as a potential cause of subsequent hip instability. They concluded that capsular closure restores the native stability of the hip, and capsular repair improves pain and functional outcomes following hip arthroscopy.

Safran et al. wrote a review article on microinstability of the hip in 2022 reviewing the pathophysiology, diagnosis, and management of this pathology. Positive results of all three of these exam maneuvers have a positive predictive value of 95%. He highlighted the sensitivity and specificity of the anterior apprehension test (71% and 85%), abduction-extension-external rotation test (81% and 89%), and prone external rotation test (33% and 98%) as well as the role of MRI imaging. He summarized that the best initial treatment for these patients is a course of physical therapy with surgical intervention in those with refractory symptoms focused on addressing the underlying cause of the pathology including periacetabular osteotomies in patients without hip dysplasia.

Figure A shows an AP plain film of the right hip showing a "cliff sign" or the loss of femoral head sphericity found in more than 89% of patients with hip microinstability. Illustration A shows a series of AP right hip radiographs. There are two sets of AP right hip x-rays, one with and one without the "cliff sign".

Incorrect Answers:
Answer 1: Intra-articular cortisone may alleviate the sensation of pain associated with the instability but will not address the underlying cause of instability or improve hip stabilization.
Answer 3: Periacetabular osteotomy can be an intervention for hip microinstability but is reserved for patients failing non-operative management and is typically used to correct significant bony abnormalities or dysplasia.
Answers 4 and 5: Capsular repair and capsular plication are both surgical interventions used to address hip microinstability, but are reserved for patients who do not improve with physical therapy.