Chondral defects of the acetabulum and femoral head as well as tears of the ligamentum teres can be a significant source of hip joint pain. Although often encountered during hip arthroscopy, chondral injuries and ligamentum teres pathologies are commonly difficult to diagnose clinically and radiographically. Articular cartilage defects can be acute or chronic, full thickness or partial thickness, and traumatic or atraumatic in origin. Chondral lesions can arise from many causes including loose bodies, Perthes deformities, slipped capital femoral epiphysis, femoroacetabular impingement, osteonecrosis, osteochondritis dissecans, hip dysplasia, hip instability, and degenerative joint disease (1). Regardless of cause, articular cartilage injuries have been shown to have a limited healing capacity (2,3).

The ligamentum teres develops from mesenchymal cells in the acetabular fossa during the second month of gestation with its composition changing to mature fibrous tissue during the third trimester (4). The ligamentum teres is attached to the ischial and pubic margins of the acetabular notch by two fascicles. With a typical length of 30 to 35 mm, the ligamentum transitions in shape from a flat, pyramidal shape at its acetabular attachment to an ovoid shape near the femoral attachment into a tightly wound round ligament attaching to the fovea capitis (4,5,6). The composition of the ligamentum teres includes a deep, thick, well-organized collagen layer with bundles composed of Type I, III, and V collagens. The acetabular attachment is at the inferior and posterior aspect of the cotyloid fossa. The fovea capitis is an ovoid depression bare of hyaline cartilage located posterior and inferior to the center of the femoral head. Although some still consider it a vestigial structure, the contribution of the ligamentum teres in patients with hip pain has been defined (4,5,7). Free type IVa nerve endings have been found within the ligamentum supporting its role as a cause of hip pain (8). The incidence of ligamentum teres ruptures in patients undergoing hip arthroscopy has been reported to vary between 4% and 15% (4,5,9). Ligamentum teres tears can occur with or without degenerative joint disease and may be partial or complete.

The prevalence of articular cartilage injuries encountered during hip arthroscopy has been well documented (10,11). Beck et al. (10,12) demonstrated that femoroacetabular im-pingement can be a cause of labral tears in a nondysplastic hip. Wenger et al. (13) showed that labral tears rarely occur in isolation and are usually associated with bony abnormalities. Treatment of labral pathology alone without addressing the osseous abnormality predisposes the hip for failure (10,12,14). McCarthy and Lee (15) demonstrated that chondral injuries have been shown to be highly associated with labral tears. Of 457 hips, 59% had anterior acetabular articular cartilage injuries, 24% had superior acetabular injuries, and 25% had posterior chondral lesions. Surgical treatment of chondral injuries is commonly performed using hip arthroscopy or open surgical dislocation. The treatment of chondral injuries of the acetabulum and femoral head has evolved from the technique and results of surgical treatment of chondral injuries in the knee. Treatment options described for chondral defects include chondroplasty, abrasion chondroplasty, microfracture, osteoarticular autograft or allograft, autologous chondrocyte implantation, and hemiCAP resurfacing (16,17,18,19). This chapter will focus on the more commonly performed and accepted techniques of chondroplasty and microfracture. Surgical treatment of ligamentum teres ruptures is more limited and nearly exclusively treated arthroscopically. Treatments include debridement, thermal shrinkage, or rarely reconstruction utilizing autograft of fascia lata or synthetic graft (7,9,20,21). This chapter will focus on the more commonly performed techniques of debridement and thermal shrinkage.

Recognition of hip disorders is most effectively performed using plain radiographs initially. A complete young adult hip radiographic series should include an anteroposterior (AP) pelvis, modified Dunn view, cross-table lateral, frog-leg lateral, and a false profile radiograph. This combination of radiographs should allow the clinician to clearly visualize hip dysplasia, femoroacetabular impingement, slipped capital femoral epiphysis, Perthes-like deformities, osteonecrosis, loose bodies, and degenerative disease. As discussed in previous chapters, standardized radiographs with neutral pelvic tilt and rotation are essential for an accurate radiographic evaluation.

Articular cartilage defects, labral pathology, and ligamentum teres tears are not reliably identified on routine MRI (24), but are more accurately diagnosed using MRI arthrogram (25,26). Chondral injuries can be visualized by evaluating asymmetry (lookup) in the outline of the gadolinium contrast. The ligamentum teres is best seen on coronal, axial, and axial oblique images. Partial and complete ligamentum teres tears can be evaluated using T1 and T2 imaging; a normal ligamentum teres is visualized as a homogeneous structure with low signal intensity on all pulse sequences. Since ligamentum teres tears are more common near the fovea capitis, tears near this location will demonstrate increased signal intensity on T2-weighted MR images or T2-weighted fat suppressed proton density images (6). Other MR findings may include abnormal intrasubstance signal intensity, edema in the acetabular fossa, or a joint effusion.

While the effectiveness of MRI arthrogram has substantially improved the recognition of labral tears, it is not as reliable when evaluating for chondral pathology and ligamentum teres tears. When compared to arthroscopic findings, Keeney et al. (24) demonstrated that MRI arthrogram detected only 76% of labral tears and 62% of articular cartilage defects. Furthermore, the effective diagnosis of ligamentum teres ruptures remains even more elusive. In a series of more than 1,000 hip arthroscopies, a preoperative diagnosis of a ligamentum teres rupture was accurate in only 5% (4). In another prospective study of 328 subjects, there were no ligamentum teres ruptures diagnosed preoperatively, but they encountered 13 ruptures during arthroscopy (27). In a retrospective review of 23 hips with arthroscopically visualized ligamentum teres ruptures, the authors were only able to detect two tears from preop MR arthrograms (9). Today, the most reliable method of detecting ligamentum teres tears is hip arthroscopy (24).

Recently delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) has been established as a useful modality of articular cartilage imaging at the microscopic level (28,29,30,31). dGEMRIC is a gadolinium-based biochemical MRI sensitive to glycosaminoglycan (GAG) content. After administration, the uptake of negatively charged gadolinium contrast is inversely proportional to the GAG content in hyaline cartilage (28). Thus healthy articular cartilage will have a high GAG content and decreased uptake with dGEMRIC T1 imaging. However, degenerative articular cartilage with decreased GAG content will have increased uptake. Although not in widespread use yet, dGEMRIC is a useful preoperative diagnostic tool to evaluate hip articular cartilage.

The classification of articular cartilage defects and ligamentum teres ruptures is most reliably performed during hip arthroscopy (24

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