Preoperative Preparation Every patient must be treated on an individual basis with age, activity level, and medical comorbidities and risk factors taken into consideration. Deep groin pain is the most common presenting symptom. Appropriate diagnostic imaging including plain radiographs, magnetic resonance imaging, and on rare occasion CT scans (to assess for collapse) should be available both preoperatively and intraoperatively for accurate location of the lesion. Because osteonecrosis of the femoral head is often first diagnosed by the orthopedic surgeon, the possibility of an occult contralateral femoral head lesion must be evaluated as there is a 50% to 80% chance of involvement (1,16,17). If the patient is also complaining of other arthralgias, namely, at the knee, the surgeon should have a high index of suspicion for further osteonecrotic lesions. This is especially true for those with risk factors for the development of femoral head osteonecrosis (e.g., corticosteroid use, alcohol abuse). If other areas are found to be affected, the possibility of performing preservation procedures (e.g., core decompression) of multiple sites under the same anesthetic setting may be considered and discussed with the patient.

Technique The rationale behind the use of core decompression is to reduce excessive intraosseous pressure within the femoral head. Traditional core decompressions use 8- to 10-mm trephines and/or cannulas (Fig. 8-1) and are often combined with nonvascularized cortical strut grafting (Phemister technique) or vascularized grafts with encouraging results. Grafts are either cortical or cancellous bone and can be from an autogenous or allogeneic source. This technique not only relieves the intraosseous pressure from the core decompression but can remove necrotic bone (Fig. 8-2), provide additional structural support to prevent collapse, as well as provide both osteoconductive and osteoinductive media depending on what type of graft is used (Video 8-1). At our institution, we use a variation of a core decompression using a percutaneous technique with a 1/8-inch Steinmann pin with either a single pass or multiple passes depending on the size of the lesion as determined by plain radiographs and/or magnetic resonance imaging. Small-sized lesions are treated with 1 to 2 passes, while large-sized lesions are treated with 2 to 3 passes (Video 8-2). We do not routinely incorporate cortical or cancellous strut grafting during the core compression.

In the operating room, the patient is placed in a supine position on a radiolucent table or a fracture table. Preoperative prophylactic antibiotics are routinely given. We have found that this procedure can be done under sedation without the need for general anesthesia. Once the patient is adequately sedated, the fluoroscopy unit is brought into the field prior to prepping and draping the extremity to ensure adequate imaging of the involved hip in both the anteroposterior (AP) and frog-leg orthogonal views.

Once adequate images free of metal artifact can be obtained, the hip is prepped and draped in the usual aseptic manner. The extremity is slightly internally rotated by an assistant to neutralize the natural anteversion of the femoral neck while performing the procedure. The proper starting point is immediately inferior to the lateral cortical flare at the metaphyseal-diaphyseal junction in the center of the proximal femur. The 1/8-inch Steinman pin is then inserted percutaneously at the predetermined level. Care must be taken not to create a starting point below the level of the lesser trochanter in order to minimize the risk of creating a stress riser and potential future subtrochanteric femur fracture. The pin is then advanced to the level of the proximal femoral neck under fluoroscopic guidance towards the lesion as previously determined from imaging studies. There is a risk of thermal skin necrosis from the Steinman pin, and as such, we prefer to use saline-soaked 4 × 4
gauze around the skin-pin junction during all drilling maneuvers. The position and trajectory of the pin is now assessed in the AP and frog-leg lateral planes by removing the drill from the pin and having an assistant maneuver the leg into the appropriate position. If the trajectory is acceptable, the leg is brought back into the starting position and the pin advanced through the femoral neck towards the lesion. If unacceptable, the pin is backed out and redirected ensuring that the same starting hole is used to avoid creating another stress riser. The pin is then advanced to the appropriate depth in the subchondral bone taking care not to penetrate through the articular surface into the joint. While drilling through the lesion, it is common for areas of sclerosis to be encountered. The surgeon must avoid the urge to use larger amounts of force when attempting to drill through these lesions as the risk of plunging through the femoral head into the hip joint is increased. Larger-sized lesions may be treated with 2 to 3 passes of the Steinman pin using the same technique and starting hole (Fig. 8-3). Once adequate decompression is obtained, the pin is backed out while holding a saline-soaked 4 × 4 gauze around the pin-skin junction. Direct pressure is held at the skin entry site until adequate
hemostasis is achieved. A simple suture using absorbable monofilament may be required although a Band-Aid is usually sufficient.