CHAPTER OUTLINE
Labral Tears 39
Chondral Lesions 40
Loose Bodies 41
Synovial Conditions 41
After Total Hip Arthroplasty 42
After Trauma 42
Contraindications 42
Surgical Technique 42
Complications 43
Outcomes 43
Summary 43
Early diagnosis and minimally invasive treatment of hip disorders are playing an increasingly important role in current orthopedic practice. Although described in 1931 by Burman, clinical application of hip arthroscopy did not evolve until the 1980s, when Eriksson and colleagues described hip capsule distention and distraction forces necessary to allow adequate visualization of the femoral head and the acetabulum. Glick and associates later described lateral positioning, cannula placement, and anatomic landmarks.
Hip arthroplasty allows thorough inspection of the hip despite the anatomical challenges presented by the bony acetabulum fibrocapsular and muscle envelope. In addition, the relative proximity of the sciatic nerve, lateral femoral cutaneous nerve, and femoral neurovascular structures gives this technically challenging procedure its own risks and potential complications. Despite these anatomic challenges, evolving techniques and instrumentation in hip arthroscopy have improved the ability to treat various intra-articular and extra-articular problems around the hip.
Patients who are candidates for hip arthroscopy typically present with mechanical symptoms. These often painful symptoms include clicking, catching, locking, or buckling; these symptoms also can compromise function. Hip pain caused by an intra-articular lesion in an adult can manifest as pain in the anterior groin, anterior thigh, buttocks, greater trochanter, or medial knee. Anterior labral lesions most typically produce anterior inguinal pain. The pain is generally exacerbated with activity and fails to respond to conservative treatment of ice, rest, nonsteroidal anti-inflammatory drugs, and physical therapy.
In a study correlating radiographic findings with hip arthroscopy findings, McCarthy and Busconi showed that the most commonly overlooked cause of pain was acetabular labral lesions. Acetabular labral tears detected arthroscopically also correlated significantly with symptoms of anterior inguinal pain.
Intra-articular hip lesions are often missed by radiologic studies commonly performed to evaluate intractable hip pain, including plain radiographs, arthrography, bone scintigraphy, CT, and MRI. Plain radiographs may show calcified loose bodies or joint space narrowing in degenerative joint disease (DJD), but do not detect labral tears or more focal cartilage changes associated with the early stages of DJD. The addition of contrast agents such as gadolinium in conjunction with CT and MRI has been shown to increase the diagnostic yield principally in the detection of labral lesions.
LABRAL TEARS
Labral tears represent the most common cause for mechanical hip symptoms. Acetabular labral lesions occur anteriorly in most reported series. Labral tears can be classified according to location, morphology, and associated articular changes. With respect to location, tears can be anterior, posterior, or superior (lateral). The etiology of labral tears is currently undergoing dynamic debate. A widely accepted theory is that torque and hyperextension forces applied to the weight-bearing portion of the acetabulum subject the anterior labrum to higher mechanical demands, making it more vulnerable to injury and wear.
These lesions occur in the anteromedial portion of the labrum ( Fig. 5-1 ). Symptoms may be preceded by a traumatic event, such as a fall or twisting injury, or may have an insidious onset in patients who have sustained occult trauma or have intractable hip pain related to athletic participation. Often the inciting event is a pivoting maneuver during an athletic activity (e.g., tennis, karate, hockey, football, or soccer). Patients with minor trauma without dislocation almost invariably have anterior tears, which are accompanied by mechanical symptoms and intractable pain. Labral tears secondary to trauma are generally isolated to one particular region depending on the direction and extent of trauma. Physical examination findings can include any or all of the following: a positive McCarthy sign (with both hips fully flexed, the patient’s pain is reproduced by extending the affected hip, first in external rotation, then in internal rotation), inguinal pain with flexion, adduction and internal rotation of the hip, and anterior inguinal pain with ipsilateral resisted straight leg raising.
A current theory that has gained much attention focuses on congenital abnormalities of the acetabulum and proximal femur, which sometimes result in decreased anterior offset of the femoral head causing “cam”- or “pincer”-type impingement (or both). In these cases not only the etiology is different, but also the location of lesions. Labral lesions caused by bony impingement, although still found in the anterior quadrant, tend to occur anterolaterally ( Fig. 5-2 ).
Clinical examination also can be helpful in determining the mechanism of injury by the way in which symptoms are reproduced. Typically, if the mechanism of injury is from hyperextension or pivoting, a painful click is reproduced going from flexion to extension while the hip is externally rotated as described earlier with the McCarthy test. If the mechanism of injury is caused by impingement, the pain is reproduced with flexion and internal rotation. More research is needed to determine the benefit of performing osteochondroplasty of the femoral head or acetabular rim to correct impingement that may damage the labrum and adjacent acetabular cartilage. Despite the cause of injury, these intra-articular lesions are problematic because they occur primarily at the labral-chondral junction, which is essentially avascular and lacks healing capacity.
CHONDRAL LESIONS
Acetabular chondral lesions may occur in association with loose bodies, posterior dislocation, osteonecrosis, slipped capital femoral epiphysis, dysplasia, and degenerative arthritis; they are also frequently seen in association with labral tears. Chondral injuries are most frequently associated with a labral tear, they also are most often located in the anterior acetabulum. The severity of the chondral lesion is highly correlated with the surgical outcome; this severity can be graded according to Outerbridge’s criteria. Patients with fraying or a tear of the labrum often have chondral lesions, most of which are located in the same region of the acetabulum adjacent to the labral tear. The severity of the chondral lesions (Outerbridge grade III or IV) ( Fig. 5-3 ) is greater in patients with labral tears or fraying than in patients with a normal labrum.
The most frequently observed chondral lesion is the watershed lesion ( Fig. 5-4 ). This lesion consists of a labral tear with separation of the acetabular cartilage from the articular surface at the labral-cartilage junction. The watershed lesion, which occurs at the labral-chondral junction, may destabilize adjacent acetabular cartilage. When the damaged labral cartilage is subjected to repetitive loading conditions, joint fluid is pumped beneath acetabular chondral cartilage causing delamination of the articular cartilage. By this same mechanism, the fluid eventually burrows beneath subchondral bone to form a subchondral cyst. It is important to note that this cyst is the result and not the cause of the patient’s symptoms ( Fig. 5-5 ). These cysts sometimes may be visualized on a plain radiograph in the absence of joint space narrowing or other degenerative changes, but are more frequently detected on MRI.
