Microinstability of the hip: a previously unrecognized pathology

Abstract

Background: Hip microinstability is an established diagnosis; however, its occurrence is still debated by many physicians. Diagnosis of hip microinstability is often challenging, due to a lack of specific signs or symptoms, and patients may remain undiagnosed for long periods. This may lead to early manifestation of degenerative joint disease. Consequently, careful patient and family history must be obtained and diagnostic imaging should follow. After a thorough clinical evaluation of the patient with suspected hip microinstability, the physician should focus on how to improve symptoms and functionality in daily and sports activities.

Purpose: The purpose of this review article was to give a current update regarding this diagnosis and to provide a complete diagnostic approach in order to effectively treat hip microinstability.

Methods: We reviewed the literature on the diagnosis, the non-operative and operative indications for the treatment of this complex and often misdiagnosed pathology.

Conclusion: Conservative treatment is considered the best initial approach, though, surgical intervention should be considered if symptoms persist or other hip pathology exists. Successful surgical intervention, such as hip arthroscopy, should focus on restoring the normal anatomy of the hip joint in order to regain its functionality. The role of the hip joint capsule has gained particular research interest during the last years, and its repair or reconstruction during hip arthroscopy is considered necessary in order to avoid iatrogenic hip microinstability. Various capsular closure/plication techniques have been developed towards this direction with encouraging results.

Level of evidence: V.

Keywords: hip arthroscopy; hip dysplasia; hip microinstability.

Figure 1

Anteroposterior radiographic image of a left hip demonstrating the coxa profunda sign, in which the floor of the fossa acetabuli (white dotted line) exceeds the ilioischial line medially (green dotted line).

Figure 2

Anteroposterior left hip radiography showing a crossover sign. Note that the anterior rim line (yellow dotted line) lies lateral to the posterior rim (green dotted line) in the cranial aspect of the acetabulum and crossing the latter in the distal aspect of the acetabulum.

Figure 3

Anteroposterior radiographic image of both hips demonstrating the most important radiographic measurements. The lateral CEA angle is formed by a vertical line through the center of the femoral head and a line connecting the femoral head center with the most lateral edge of the acetabulum. A normal lateral center edge angle ranges between 25 to 40°. The Sharp angle can be measured by drawing a line that connects both tear drop signs on the right and left side of the ischial bones and measuring from this line to the most lateral aspect (most sclerotic portion) of the lateral acetabulum or the pincer deformity. Finally, the Tönnis angle that can be calculated by drawing a horizontal line connecting the base of the acetabular teardrops; next a parallel horizontal line running through the most distal point of the sclerotic acetabular sourcil; the angle is measured between this line and the lateral margin of the acetabular sourcil.