Osteonecrosis of the Hip
Kevin L. Garvin
• The acetabular bone in patients with osteonecrosis is often of poor quality, and the surgeon must be careful in reaming the acetabulum. Aggressive reaming of the acetabulum can lead to loss of bone stock and proximal placement of the acetabular component.
Total hip arthroplasty (THA) for osteonecrosis of the hip poses several unique challenges when compared with hip replacement for osteoarthritis1–10; these include abnormal bone quality of osteonecrosis, the young age of the patient who typically develops osteonecrosis, and underlying diseases associated with osteonecrosis.2,3,7,11-13 Surgical challenges may also be present because of previous hip surgery performed to help prevent femoral head collapse. Surgery to preserve the femoral head via core decompression with or without adjunct bone graft or an osteotomy to rotate the osteonecrotic segment from the weight-bearing area of the femoral head is commonly performed. The purpose of this chapter is to provide essential information to assist in the management of patients with osteonecrosis. Defining features and teaching points relevant to THA for patients with osteonecrosis are discussed as well.14–16
The quality of acetabular and proximal femoral bone in patients with osteonecrosis is far from normal. Arlot and associates evaluated bone histomorphometry in 77 patients with osteonecrosis of the femoral head.2 All patients were ambulatory, and none was confined to a bed or wheelchair. Among these patients, factors associated with osteonecrosis included steroids (15 patients) and alcoholism (33 patients) and were unknown in the remaining patients (29). Bone biopsy and histomorphometric analysis were performed on horizontal transiliac crest bone. Trabecular bone volume, trabecular osteoid volume, trabecular osteoid surface, thickness index of osteoid seams, total resorption surfaces, calcification rate, tetracycline-labeled surfaces, and bone formation rates at the basic multicellular unit level and at the tissue level were determined. Results suggested a marked decrease in osteoblastic appositional rate and in bone formation rate at cell and tissue levels. The extent of disease has also been studied. Calder3 examined 16 patients with advanced osteonecrosis of the hip (Ficat III and IV)11 and compared them with 19 patients with osteoarthritis who had undergone THA. Histologic specimens from the hip and the proximal femur were examined. Extensive osteonecrosis extending to 4 cm below the lesser trochanter was identified. Overall, a statistically significant difference in extent of disease was noted between the two groups (P < .001). This report may explain why patients with osteonecrosis are more likely to develop early aseptic loosening of the femoral prosthesis.3,17-19
The second challenging factor that affects the results of surgery for this patient population is age. In general, patients with osteonecrosis are younger than those undergoing total hip replacement for osteoarthritis. Results of THA in younger patients have not been as good as in an older population.19–21 By definition, this group is more active than their elderly counterparts; this may account for the difference in results.9,18,19,22-27
Systemic diseases associated with osteonecrosis are a third factor contributing to the poor results of THA. Steroids, alcoholism, connective tissue disease, sickle cell disease, end-stage renal failure, human immunodeficiency virus (HIV), and trauma all possess characteristics that may compromise early and long-term results of total hip arthroplasty.7,12,13,26 Furthermore, the complications associated with total hip arthroplasty in these patients are unique and occur more frequently than complications of THA in patients with osteoarthritis.
Surgery to correct the problem of osteonecrosis is not always successful, thereby leading to total hip arthroplasty. Alterations to the surgical site caused by previous surgery may pose a substantial challenge to the surgeon at the time of joint replacement and therefore are another factor contributing to the poor results of total hip replacement in this population. Core decompression with placement of a fibular strut graft, tantalum construct, or dowel poses unique challenges. Intertrochanteric osteotomy may result in abnormal and scarred anatomy.28–32 Finally, because of abnormalities related to age, bone quality, and previous surgery, thorough preoperative planning, meticulous surgery, and selection of the correct implant are imperative for achieving a good result in this patient population.
Indications and Contraindications
Indications for total hip arthroplasty in patients with osteonecrosis include disabling pain and loss of function and are present in this population of patients at an average age that is younger than patients with osteoarthritis. The heavy demand over a longer time requires that the prosthesis is durable, thus minimizing the risk of early revision. Modest expectations and a lower level of activity may increase implant durability and longevity. Unfortunately, it is unlikely that this population will become less active after surgery because one of their main goals is to obtain relief from pain so they can be more active.
Relative and absolute contraindications to hip replacement also exist for patients with osteonecrosis of the hip. Many of these patients are at increased risk for complications after hip replacement, but the operation itself is not contraindicated. However, because many of these patients at baseline are at increased risk for infection, the presence of active infection before elective hip replacement must be ruled out and is an absolute contraindication to surgery. One example of this problem is the patient on dialysis who is especially prone to infection. It is incumbent on the treating surgeon to make certain that infection is not present before elective hip replacement is performed. The same is true for patients on steroids and for those who are immunocompromised because of medications used to treat their underlying disease process.
Peripheral vascular disease is also common in patients with end-stage renal disease. Evaluation of peripheral arterial blood flow should be performed preoperatively to assess the presence of peripheral vascular disease. In addition to systemic and diffuse disease processes that require preoperative evaluation, local problems challenge the surgical reconstruction or may be a contraindication to hip replacement.
Retained hardware after osteotomy or fracture fixation increases the risk for infection. Low-grade or active infection may be present in these patients as well. If an infection is suspected, staged surgical removal of the retained hardware, débridement, and antibiotics are necessary before total hip replacement is performed.
Preoperative planning for total hip arthroplasty focuses on optimization of underlying medical conditions in these patients and on their orthopedic evaluation. In addition, it is important that appropriate preoperative planning for the hip surgery is performed. This process of preoperative planning and templating helps to identify technical factors that may require special attention.
Description of Technique
Surgical reconstruction and total hip replacement for patients with avascular necrosis can pose unique challenges. Overall, the quality of bone in this patient population is less robust than that in their osteoarthritis counterparts. Fracture of the bone at the time of surgical implantation of the total hip components caused by osteoporotic bone is possible, and the surgeon must take caution while reaming and broaching the bone. Because of the osteoporotic bone, it may be prudent to place a prophylactic wire around the femur to prevent a fracture.
A unique group of patients with avascular necrosis is the sickle cell patient population, whose repeated sickle cell crises may result in deformity of the femur and a narrow sclerotic femoral canal. Preparation of the femur for femoral component placement requires careful surgical technique and possible use of high-speed reaming tools with radiographic assistance to avoid fracture or component malposition.
Finally, techniques like hip resurfacing arthroplasty are not indicated for this population of patients with femoral head osteotomy and osteoporosis.
Technical Variations/Unusual Situations
Specifically, total hip arthroplasty after osteotomy or after core decompression with a fibular bone graft or tantalum placement requires careful planning for surgery. Total hip arthroplasty after previous osteotomy is a technically difficult operation. Kawasaki and associates15 studied 15 hips converted to total hip arthroplasty after a failed transtrochanteric rotational osteotomy. The authors compared these hips with those of a control group of 16 with avascular necrosis who had not had prior osteotomy and were treated with total hip arthroplasty. In the study group of osteotomy patients, surgery was significantly longer than in the primary total hip arthroplasty group (P = .003), and perioperative blood loss was greater (P = .036). The authors attributed these difficulties to rotational changes in the geometry of the proximal femur after anterior or posterior rotational osteotomy. The authors did not report more frequent complications during surgery for the osteotomy group, but this is not the experience of other surgeons. At least two previous studies28 reported a greater risk of complications in a group of patients with osteotomy before total hip arthroplasty. In only one patient in the two studies did the complication result in revision surgery.15
Core decompression followed by the use of a fibula bone graft or a tantalum implant is not always a successful treatment for patients with avascular necrosis of the hip. If the hip is converted to a total hip arthroplasty, the retained fibular bone or the tantalum implant must be adequately removed to allow for proper placement of the femoral component. Tanzer and colleagues33 performed a total hip replacement for 17 hips in which a porous tantalum implant had been used for the treatment of Steinberg stage II osteonecrosis of the hip. During the hip replacement surgery in 13 of the 15 hips, large quantities of metallic debris from the implant were present at the femoral neck base after the implant had been transected. The long-term effect of the tantalum particles is unknown, but they could potentially accelerate wear of the prosthetic bearing. The authors reported that less debris could possibly be generated if the implant was cored out or transected with an osteotome rather than with a high-speed oscillating saw. Shuler and coworkers34 reported on 24 patients treated with a tantalum implant for avascular necrosis; 3 of these patients had their hip converted to a total hip arthroplasty. None had complications, but the authors reported concern about third-particle wear.