Hip III: Adolescent Hip

Ernest L. Sink, MD

Ira Zaltz, MD¹

¹Guru:

Since the description of femoroacetabular impingement (FAI) by Professor Ganz in 2000 as a cause of hip pain and eventual arthritis, the field, now known as hip preservation, has grown exponentially. With the introduction of surgical dislocation as an approach to manage intra-articular hip pathology, there has been tremendous growth of surgery for the prearthritic hip. The surgical dislocation approach enabled elucidation of the pathology of certain hip disorders. With the expanding knowledge of FAI and improved techniques of hip arthroscopy, arthroscopic procedures have increased exponentially. Also, with increased adolescent sports participation, many more adolescents are being evaluated for hip pain. A labral tear diagnosed by hip MRI is now an epidemic in adolescent athletes. Because there is a “tear” of the labrum, patients have been referred for arthroscopic labral repair often without a complete understanding of the underlying pathology or an effort to promote nonoperative care. A labral tear is not always a true tear like a knee ligament, but the word creates significant angst in patients and parents. The labral tear can be seen in many asymptomatic hips and in most cases does not need an isolated repair. A better description would be labral irritation present in deformities such as FAI or hip dysplasia. Surgeons should be aware that hip pain and labral findings may be instability or dysplasia that is not recognized or inappropriately diagnosed as FAI. NEWSFLASH! It’s not always about the labrum but the true cause of hip pain, which may be abductor weakness, hip flexor overuse in adolescents associated with growth, version abnormalities of the femur or acetabulum, FAI, or instability and dysplasia. Focusing of the labrum and arthroscopic repair has resulted in many patients improperly diagnosed and treated. Therefore, a careful history, examination, and three-dimensional imaging are often necessary.

Three Important Components of Evaluation and Treatment of the Prearthritic Hip

Finding the Correct Diagnosis

This is sometimes a challenge as many patients can have significant discomfort with subtle deformities.
The correct diagnosis is still evolving as FAI is not always the diagnosis, and the true pathomechanics of hip discomfort can be debated among experts.
The pain may be associated with spinal pathology or muscular injury to the pelvis such as athletic pubalgia.

Determining the Best Treatment

When it comes to operative treatment there are only a few treatments and approaches that surgeons utilize: hip arthroscopy, surgical dislocation, periacetabular osteotomy (PAO), femoral osteotomy, or a combination of any of the above.
While the surgical treatment option may be straightforward in a patient with significant dysplasia (PAO) or a male with a large cam lesion (hip arthroscopy), the best option is not always clear (for example, a female with a mild dysplasia and radiographic criteria of impingement or patients with version abnormalities of the acetabulum and/or femur).

Technical Implementation

Hip arthroscopy is a technically challenging procedure. Not only are the indications for its use still evolving, but how to manage the labrum, rim, and capsule is still debated. Hip arthroscopy has a very steep learning curve where training and volume is necessary. Unfortunately hip arthroscopy is not a large portion of residency training. A majority of those performing hip arthroscopy receive some training during a 1-year sports medicine fellowship, and a majority of those performing hip arthroscopy are doing only a handful a year.
The same applies for the PAO, for which volume, training, and mentorship are essential.
The surgical dislocation has the fastest technical learning curve. Management of the acetabulum and femur present many options and making the appropriate decision, e.g., repair the labrum, rim resection, trochanteric resection, proximal femoral osteotomy, is challenging and often a point of controversy. Furthermore, we are now recognizing that extra-articular deformities are a cause of hip pain that may need to be addressed by trochanteric osteoplasty and even femoral osteotomy.

Causes of Adolescent Hip Pain

MUSCULAR

After a period of rapid growth, the pelvis and hip muscles have to accommodate the forces to move and support a longer leg. This creates problems, particularly in teens who are high-intensity, year-round athletes or dancers. The gluteal and core muscles (abdominal rectus, obliques, proximal hamstrings) are underdeveloped and not coordinated. This can also be a cause of anterior knee pain. It can be accentuated with anteversion of the femur giving the abductor mechanics a disadvantage.

OVERUSE SYNDROMES AND APOPHYSITIS

Apophysitis of the anterior inferior iliac spine is common from rectus femoris overuse in sprinters and soccer players. Iliac apophysitis is common in runners and will often take months to become asymptomatic. Iliac apophysitis is common in abductor overuse and occasionally is an early symptom of hip dysplasia.

Impingement disorders: The most common is FAI from a decreased offset between the femoral head and neck (cam lesion) that appears to develop during the final growth of the proximal femur in response to overload. With hip motion this “bump” can damage the anterior labral cartilage junction. NEWSFLASH! FAI is much more common in males than females. It is more subtle in females, and surgeons should be aware of dysplasia or instability as the main reason for pain in females. Impingement can result from an overly deep hip socket, but this diagnosis of pincer impingement was overdiagnosed previously in adolescents. Extra-articular impingement can also occur where aspects of the greater and lesser trochanter impinge on the pelvis. This is not an easy diagnosis but needs to be considered prior to jumping in to treat intra-articular FAI.

DYSPLASIA

This is more common in females. A wise mentor has a saying that “all female hips are unstable until proven otherwise.” Our center has a complex case conference each week that composed mostly of female patients who had prior hip arthroscopy that failed due to missed acetabular dysplasia. Historically, the lateral center edge was the primary measurement used to diagnose hip dysplasia. We now know that acetabular deficiency is highly variable and anatomically complex and a normal lateral center edge angle is not sufficient to exclude dysplasia. Undercoverage can also be posterior-superior, anterior only, global, or nearly normal associated with ligamentous laxity or iatrogenic instability from prior hip arthroscopy.

Physical Examination and Imaging