Introduction

Articular cartilage defects are one of the pathologies that are most commonly encountered during hip arthroscopy. Limited information is available regarding the best treatment of these lesions; however, microfracture has been demonstrated to be effective for the treatment of articular cartilage defects of the knee and other weight-bearing joints, and several small series and case reports have been published that have described the use of microfracture for the treatment of articular cartilage defects in the hip. Several investigators are conducting ongoing outcome studies with regard to this treatment.

There are many conditions that can cause chondral defects that necessitate microfracture and chondroplasty, and these conditions can be acute, chronic, traumatic, or atraumatic. Defects can be full or partial thickness. Acute causes include hip dislocation, hip subluxation, and direct blows to the hip. Chronic causes include labral pathology, femoral acetabular impingement, loose bodies, dysplasia of the hip, a history of slipped capital femoral epiphysis, avascular necrosis, and degenerative joint disease.

It is critical to note that the diagnosis of these lesions is often only established intraoperatively, and patients should be aware that labral pathology is often associated with articular cartilage damage. The postoperative rehabilitation process and the patient’s prognosis can be significantly different if such a lesion is discovered, and the patient and surgeon should be prepared for this possibility. A working knowledge of chondroplasty and microfracture will be helpful for any orthopedic surgeon who attempts to treat these diseases.

Basic science

Microfracture is a type of a marrow-stimulating technique. After the removal of the avascular calcified cartilage layer, perforations are made through the subchondral plate to allow blood and marrow elements to enter the area of the articular cartilage defect. These marrow elements include stem cells as well as clotting and growth factors. The factors are crucial to the formation of a fibrin clot, which ultimately serves as an environment for nourishing pluripotent and mesenchymal stem cells. Initially, the regenerated tissue is fibrous tissue; however, with the use of appropriate biomechanical stimuli, a durable fibrocartilage repair tissue can be formed that will fill the defect.

Indications

Indications for microfracture of the hip are largely derived from the knee literature and the author’s experience. Factors that have been associated with good outcomes are listed here, although the particular indications for any procedure should be based on the physician’s best judgment.

Brief history and physical examination

As with other musculoskeletal conditions, a careful history and physical examination are warranted. An understanding of the acuity and cause of the injury has important prognostic indications. Acute injuries (e.g., hip dislocations, subluxation events) are often associated with significant articular cartilage lesions that are sometimes asymptomatic. A direct lateral blow to the greater trochanter (e.g., a fall) can cause a medial impaction injury to the femoral head. A more gradual onset of pain or discomfort suggests a degenerative or impingement cause of the articular cartilage injury.

The location, frequency, and radiation of pain should be determined. Furthermore, alleviating or worsening symptoms or activities should be noted. Attention should be paid to any presence of mechanical symptoms (e.g., clicking, snapping, popping), because chondral defects can be associated with labral injuries. Defects associated with impingement may result in a history of pain with daily activities that involve hip flexion (e.g., prolonged sitting).

Physical examination features will be similar to those of other intra-articular pathologies, with pain usually experienced deep in the groin rather than posteriorly or laterally. The passive and active range of motion should be assessed. Specific testing for impingement symptoms should be performed, which includes the assessment of pain with combined hip flexion, internal rotation, and adduction. A loss of internal rotation with the hip flexed suggests a potential cam- or pincer-type deformity. Limited range of motion during the logrolling of the supine patient’s leg suggests either synovitis or another, more diffuse pathology (e.g., arthritis, synovial chondromatosis). Unfortunately, there is no single clinical examination that reveals the presence or absence of a chondral defect. If a specific area of the joint is suspected of being damaged, weight-bearing activity that loads the area of the defect may elicit symptoms.

Imaging and diagnostic studies

Plain radiographs may initially provide the most information. Degenerative joint disease, dysplasia, loose bodies, avascular necrosis (AVN), cam- or pincer-type impingement, and a history of slipped capital femoral epiphysis (SCFE) may be apparent on plain films. We recommend the use of a weight-bearing anteroposterior pelvic film and a frog-leg lateral view to evaluate bony morphology around the hip joint, with attention paid to the femoral head–neck offset and crossover lesions of the acetabulum in addition to the standard evaluation of loose bodies. A joint space narrowing of more than 2 mm to 3 mm is indicative of arthritis, and we would not recommend microfracture for this patient population. A pure cross-table lateral view has also been advocated by some authors to obtain additional information about the femoral head–neck offset.

Magnetic resonance imaging may be helpful to obtain a cause of the pain; however, many authors have noted that articular cartilage defects are frequently not clearly identified by the imaging sequences and resolutions that are often used (Keeney CORR 2004). Secondary signs of articular cartilage damage may be identified, such as subchondral bony cysts, bone edema (Figure 22-1), and joint effusions. High-resolution images may demonstrate distinct defects (Figure 22-2), articular cartilage thinning, or heterogeneity of the articular cartilage signal (Figure 22-3). The use of a surface coil with high-resolution, cartilage-sensitive images in the axial, coronal, and sagittal planes may provide a higher spatial resolution that could be helpful for diagnosis. Magnetic resonance arthrography improves the ability to evaluate the articular surface, but current techniques lack reliable sensitivity. In the future, the use of delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) may provide additional information about the proteoglycan content of the articular cartilage.

Figure 22–1 Magnetic resonance image of the hip of a 41-year-old woman with associated subchondral cysts and irregular heterogeneous articular cartilage.

Figure 22–2 Magnetic resonance image of a 16-year-old football player with a focal chondral defect in the acetabulum.

Figure 22–3 Magnetic resonance image that demonstrates irregular articular cartilage with thinning subchondral edema.

Surgical technique

The patient should be positioned on a fracture table or with a hip distraction system and in either a supine or lateral position, depending on surgeon preference. In most cases, the author prefers to have the patient in the supine position, with a commercially available hip distraction system placed on the leg that allows for the free movement of the limb. The hip is generally slightly internally rotated, flexed, and in neutral coronal alignment. The affected extremity is placed in 25 lb to 50 lb of longitudinal traction to distract the joint. A well-padded perineal post should be used to decrease the risk of pudendal nerve injury. The joint can then be distracted 7 mm to 15 mm under fluoroscopic guidance. The patient should be prepared and draped in the usual sterile fashion. Typically, after the surgical preparation solution has been applied and has dried, a large, clear drape with an adhesive central section (i.e., a “shower curtain” drape) is applied to the lateral aspect of the hip, and the top of the drape is allowed to cover the contralateral limb.

A spinal needle is then placed into the hip joint, and the stylet is removed; this breaks the vacuum seal and decreases the force needed to distract the joint. If necessary, the needle should be repositioned to avoid the labrum. This initial portal should be placed so that the tip of the needle enters the fovea of the acetabulum; this helps to ensure the good visualization of the joint. After the appropriate placement of the initial spinal needle and the guidewire, portal placement with the use of cannulated trocars can be performed to allow for access to the joint for visualization and instrumentation. A thorough diagnostic examination of the hip should occur, and this should involve the use of multiple portals. In some cases, defects on the femoral head are relatively medial (Figure 22-4), and careful instrument placement (Figure 22-5) is necessary to identify and treat defects (Figure 22-6, A and B).

Figure 22–4 Magnetic resonance image of the pelvis that demonstrates irregular articular cartilage at the medial femoral head lesion.