Introduction

Advances in technology have allowed for the arthroscopic treatment of an evolving series of conditions in and around the hip joint. Labral tears are the most common pathologies that are treated with hip arthroscopy, and they may contribute to the progression of degenerative arthritis. Patients who are at increased risk for developing arthritis in the presence of labral tears are those with developmental dysplasia, those with full-thickness chondral lesions, and those who have had tears present for more than 5 years. The key point to be emphasized is that surgical outcomes are significantly correlated with the extent of articular surface involvement and the degree of damage.

The labrum is innervated with all types of nerve fibers, including pain fibers, and thus tears of the labrum can result in hip pain in addition to mechanical symptoms of locking, catching, and buckling. The limited capacity of the labrum to heal in combination with the relative ease of the partial labrectomy procedure (as compared with labral repair) explains why partial labrectomy is currently the most commonly performed hip arthroscopy procedure.

Basic science and rationale for treatment

Microvascular studies have confirmed that the vascular supply of the acetabular labrum comes via the obturator artery, the superior gluteal artery, and the inferior gluteal artery, which are the same vessels that supply the bony structure of the acetabulum. These studies also showed no evidence of the penetration of vessels from the underlying acetabular bone into the labral substance. Labral tears most frequently occur on the articular nonvascular white zone, and they will not heal with conservative treatment. These tears are often delaminating tears that are not amenable to suture repair (Figure 13-1).

Figure 13–1 Intraoperative photo of a delaminating tear (arrow) of the anterior acetabular labrum. Articular cartilage, AC; labrum, L; femoral head, FH.

Labral tears are most frequently seen in the anterior acetabular quadrant (more than 90% in most series), and they are common in patients with degenerative hip disease or acetabular dysplasia. A common finding even with mild acetabular dysplasia is hypertrophy of the anterior labrum, which makes this area more susceptible to tearing. Because of the avascularity and degenerative nature of these lesions, they too are usually not amenable to suture repair (Figure 13-2). Posterior labral tears are most frequently seen after a posterior hip dislocation. Lateral tears are usually associated with additional labral and acetabular lesions.

Figure 13–2 Intraoperative photo of a hypertrophied (arrow), degenerative, torn anteromedial labrum. Articular cartilage, AC; labrum, L; femoral head, FH.

When a labral tear occurs at the watershed zone, over time, it destabilizes the adjacent acetabular cartilage. When the destabilized cartilage is subjected to repetitive loading, joint fluid is pumped beneath the delaminating acetabular cartilage, thus accelerating the wear. Eventually, the fluid burrows beneath the subchondral bone to form a subchondral cyst. Thus, most labral tears have a limited capacity to heal, and the resultant treatment is a partial labrectomy.

History and physical examination

Labral tears most often present with mechanical symptoms such as buckling, clicking, or catching and a painful and restricted range of joint motion. Mechanical symptoms (i.e., catching, locking, or buckling) usually persist despite normal radiographic findings and failed conservative therapy. Positive examination findings include a positive McCarthy sign. (The hip is flexed, externally rotated, and then brought into extension. This may be repeated with internal rotation.) Most often, the painful click will accompany extension. The patient may also experience pain or a sensation of blocked range of motion with abduction or external rotation. Often patients will experience inguinal pain with resisted straight leg raising. Labral tears can also be associated with other intra-articular disorders. Degenerative labral tears, as mentioned previously, are seen with erosive changes in the acetabulum, the femoral head, or both. Anterior acetabular chondral injuries are frequently seen with anterior labral tears.

Imaging and diagnostic studies

Radiologic studies including plain radiographs, arthrography, bone scintigraphy, computed tomography, and magnetic resonance imaging often have a poor diagnostic yield for intra-articular lesions. Although the addition of contrast agents in conjunction with computed tomography and magnetic resonance imaging may increase their sensitivity for evaluating intra-articular lesions of the acetabular labrum, these studies still have a limited ability to accurately evaluate chondral lesions of the acetabulum and the femoral head.

Occasionally an intra-articular joint injection with a steroid and Marcaine that is performed under fluoroscopic control may help to clarify whether the source of pain is intra-articular.

Surgical technique

The lateral approach requires that the patient be positioned in the lateral decubitus position with the affected hip up. Most intra-articular lesions are found anteriorly, and these can easily be treated via the two primary portals of the lateral approach. A modified fracture table or a dedicated hip distractor can be used for lateral positioning. Adequate distraction is required to lift the femoral head away from the acetabulum to allow for the passage of instruments without scuffing the chondral surfaces. Fluoroscopic images determine the relative distraction of the femoral head from the acetabulum. General anesthesia with adequate skeletal muscle relaxation also reduces the force that is required to distract the hip. Meticulous attention to detail can help to prevent an inadvertent loss of traction while instruments are in the joint, which may result in harm to the articular cartilage or instrument breakage within the joint.

The intra-articular structures in the hip joint can most often be visualized with a standard 30-degree arthroscope; however, there are times when a 70-degree lens may be needed. The arthroscope can be exchanged among the portals to facilitate the visualization of the existing pathology. Instruments should always be passed through long, tapered cannulas to protect the surrounding tissues and to provide safe entry into the joint. A variety of probes and hooks are first used to evaluate the intra-articular structures. Labral tears can be resected with a variety of long suction punches that have been designed specifically for hip arthroscopy. Extra-long mechanical shavers can also be useful for the debridement of labral tears. Flexible thermal devices that provide precise control of temperature and coagulation are extremely useful for debriding the torn labral rim. Although these tools are beneficial, they must be used judiciously to avoid the over-resection of tissue or the thermal injury of bone. Inflamed, redundant synovial tissue can also be resected and coagulated.

The arthroscopic treatment of these tears involves careful and conservative debridement back to a stable base and to tissue that appears to be healthy. The resection should never approach the rim, because this could result in an unstable hip. This procedure will eliminate the source of the mechanical symptoms that result from labral lesions.

Bony resection should not accompany the labral resection unless it has been dynamically proven at the time of surgery that bony collision is the source of the labral injury, which is done at the time of surgery by releasing the traction. The hip is then flexed and rotated under the arthroscopic vision of the peripheral compartment. Most bony impingement labral lesions occur superolaterally, whereas isolated labral lesions occur anteromedially. If the labral lesion is congruous with bony collision, then microresection of the labrum and judicious bone resection are appropriate. For noncongruous labral lesions, microresection is sufficient.

Contraindications

Moderate dysplasia is a contraindication for labral debridement or resection, because it may result in accelerated wear and instability. Pain in the absence of mechanical symptoms (e.g., catching, locking, buckling) is also a contraindication for labral surgery, especially for patients who are more than 30 years old. Advanced degenerative joint disease, protrusion, and a marked and limited range of motion are also contraindications.

Postoperative rehabilitation

Hip arthroscopy is outpatient surgery, and most patients require crutches for 2 to 7 days postoperatively. Patients may progress to full weight bearing as soon as comfort allows. Most patients are able to drive within 24 to 48 hours after the surgery. Aspirin is prescribed as an anticoagulant for the first 4 weeks after surgery.

Activity is gradually increased as comfort permits. This includes walking (not on a treadmill), using a stationary bike, or swimming after the stitches are removed. High-impact activity and twisting and pivoting motions should be avoided for the first 6 weeks, because they may produce sharp pain until postoperative swelling has subsided. Other activities to be avoided include the NordicTrack, StairMaster leg-press machines, and deep squats. Depending on the job and the type of physical labor required, most patients return to work after 4 to 7 days.

Formal physical therapy is not encouraged for the first 6 weeks after surgery while joint effusion persists. Therapy protocols for patients with high demand (e.g., competitive athletes) also begin after the first 6 weeks. These patients begin with general conditioning and lower-body resistance training and then progress to more sport-specific activities.

Outcomes

Surgical outcomes are directly dependent on the extent of articular surface involvement. More than 90% of patients will have an excellent result if the labral tear is addressed and if the femoral and acetabular chondral surfaces are intact. If there is a grade I or II chondral lesion of either the adjacent acetabular chondral surface or the femoral head, 70% to 80% will have a good to excellent result. Conversely, if the articular cartilage involvement is full thickness and diffuse on the femoral head and the acetabulum, 70% to 80% of cases are associated with a poor result during follow up, and 40% to 50% will require total joint arthroplasty within 2 years of arthroscopy. Table 13-1 shows arthroscopic results at 2 to 5 years of follow up for 170 patients with hips with mild to moderate dysplasia.