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Bilateral Core Decompression for Osteonecrosis of the Femoral Head

Israelite, Craig; Nelson, Charles, L; Ziarani, Cezar, F; Abboud, Joseph, A; Landa, Joshua; Steinberg, Marvin, E

Section Editor(s): Hanssen, Arlen D MD, Guest Editor

Clinical Orthopaedics and Related Research: December 2005 - Volume 441 - Issue - p 285-290
doi: 10.1097/01.blo.0000192365.58958.84
SECTION I: SYMPOSIUM: Papers Presented at the Hip Society Meeting 2005

Early treatment of osteonecrosis of the femoral head yields better results than late treatment. Because osteonecrosis frequently is bilateral, it often is advisable to treat both hips simultaneously. Core decompression is one of the more common methods of treatment; however the safety of doing simultaneous bilateral core decompression has been questioned. We sought to evaluate the safety and effectiveness of simultaneous bilateral core decompression compared with unilateral core decompression. One hundred ninety-three patients (276 hips) who had core decompression with bone grafting were followed up for 24 to 145 months. One hundred twenty-four procedures were unilateral and 152 were bilateral. Patients were evaluated by change in Harris hip score, radiographic progression, postoperative complications, and conversion to total hip arthroplasty. Total hip arthroplasty was required in 56 of 124 (45%) of hips in the unilateral, and 48 of 152 (32%) of hips in the bilateral group. Postoperative complications were similar. In the unilateral group there were two major and nine minor complications; in the bilateral group there were three major and 10 minor complications. When bilateral core decompression is indicated, it can be done simultaneously on both hips, allowing earlier treatment of the contralateral hip without risk of increased complications and possibly with a better outcome. It requires only one hospitalization and decreases recovery time compared with two separate procedures. Therefore, it provides advantages over procedures that cannot be done simultaneously on both hips.

Level of Evidence: Therapeutic study, Level IV (case series-no common or historical control group). See the Guidelines for Authors for a complete description of levels of evidence.

From the Department of Orthopaedic Surgery, University of Pennsylvania School of Medicine, Philadelphia, PA.

Each author certifies that his or her institution has approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent was not required for this study as it was a retrospective study without identification of patients.

Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.

Correspondence to: Marvin E. Steinberg, MD, University of Pennsylvania School of Medicine, 3400 Spruce Street/2 Silverstein, Philadelphia, PA 19104. Phone: 215-349-8695; Fax: 215-349-5928; E-mail:

Several methods of treating osteonecrosis of the femoral head have been described. Core decompression with or without bone grafting is one of the more commonly done procedures. Early treatment, before the head has begun to collapse, yields the best result.6,7,9,10,13 Because the condition is bilateral in more than 60% of patients, it often is advisable to treat both hips simultaneously rather than delaying the second procedure by weeks or months. This is not possible with procedures like osteotomies and free vascularized fibular grafting. The safety of doing simultaneous bilateral core decompression has been questioned; however, little has been published on this subject.

Most studies have indicated the outcome after core decompression is better than in patients treated nonoperatively.4,6-9,12-15 However, some authors have reported little difference.5,6,13 Camp and Cowell2 found a high prevalence of complications after unilateral core decompression, including fractures in four of 40 hips treated using this technique.

We sought to determine the safety and effectiveness of simultaneous bilateral core decompression in our own series of patients. Patients having unilateral core decompression were compared with patients having simultaneous bilateral core decompression under a single anesthetic. The safety of the procedure was determined by comparing the prevalence of major and minor postoperative complications in these two groups. The effectiveness was determined by comparing the postoperative outcome regarding radiographic progression, change in Harris hip scores, and the need for total hip arthroplasty (THA).

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We retrospectively reviewed 215 patients (316 hips) with osteonecrosis treated by a single surgeon (MES) with core decompression and bone grafting between 1980 and 1994. The surgical technique has been described previously.12,13 The results of surgery were evaluated by the change in Harris hip score to the last followup visit, the radiographic resolution or progression, and the need for subsequent THA. The safety of the procedure was determined by the prevalence of major and minor complications. The results of core decompression were considered successful if the operated hip appeared clinically and radiographically stable, and the patient had not had THA or was not considered a candidate for further surgery in the near future. Patients were divided into two groups: those who had unilateral core decompression and those who had simultaneous bilateral core decompression. All patients had grafting The results in these two groups were compared.

Seven patients (10 hips) were lost to followup, and 15 patients (30 hips) who had bilateral procedures fewer than 10 weeks apart were excluded from the study. One hundred seventeen patients (124 hips) had unilateral surgery; in seven of these patients the second hip was operated on more than 10 weeks after the first and they therefore were included in the unilateral group. Seventy-six patients (152 hips) had simultaneous bilateral core decompression under the same anesthetic. Therefore, 193 patients (276 hips) were included in this study. The minimum followup was 2 years.

Patients were included if they were adults with established nontraumatic avascular necrosis of one or both femoral heads, if their hips were classified as Stages I to IV according to the University of Pennsylvania staging system,11 if they had satisfactory hip function with minimal pain, and if it was thought that they would benefit from a procedure designed to retard or reverse the progression of the disease process. Patients with moderate to advanced degrees of femoral head collapse or acetabular involvement as seen on radiographs, or those with substantial pain and poor hip function were not included. The indications for doing surgery in cases of unilateral or bilateral disease generally were similar, but patients and physicians might be more willing to include patients with earlier and later stages of involvement in the bilateral cohort than in the unilateral cohort.

All patients were placed on partial weightbearing with two crutches for 3 months after the surgery. They were followed up every 3 months for the first year, every 6 months for the second year, and yearly thereafter. Before surgery and on each followup visit patients were evaluated clinically by use of Harris hip scores3 and by anteroposterior (AP) and lateral radiographs. Magnetic resonance imaging (MRI) was used to evaluate preradiographic lesions preoperatively. Postoperative complications were noted and patients who required subsequent THA were recorded. The stage and extent of necrosis were determined preoperatively and postoperatively by two examiners (MES, KMH), using the University of Pennsylvania staging system.11 Small lesions (A) occupied less than 15% of the femoral head; intermediate lesions (B) occupied 15% to 30%; and large lesions (C) occupied more than 30%.

The demographics for the unilateral and bilateral core decompression groups were similar regarding age, sex, weight, and etiology of the osteonecrosis. The mean followup for patients having unilateral surgery was 68 months (range, 25-145 months) if THA was not required, and 27 months (1 to 156 months) if THA was required. Mean followup in the bilateral group was 56 months (24-136 months) and 31 months (1-102 months), respectively.

The patients in this study who had core decompression were compared with 39 patients (55 hips) treated by the authors before 1980 with partial weightbearing alone and with published reports of other series.4-10,13-15

An analysis of variance (ANOVA) was used to evaluate the prevalence of THA as related to the size of the necrotic lesion. Fisher’s exact test was used to evaluate the prevalence of THA after bilateral and unilateral core decompression. Results were considered significant at p < 0.05.

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The results in the two groups as measured by radiographic progression, change in Harris hip score, and need for THA were similar. The Harris hip score was worse in patients treated initially after femoral head collapse than in those treated before femoral head collapse in both groups. However, there was no difference between patients in Stages I, II, and III. For each stage, the results after decompression and grafting were better than those seen in control hips that had been treated symptomatically12 (Fig 1). For the entire series of patients that had core decompression, 104 of 276 (38%) of hips in 193 patients required THA at a mean of 29 months from surgery (range, 1-155 months). The Harris hip score for these patients decreased from a mean 69 points preoperatively to 45 points postoperatively. The Harris hip score for those patients who did not require replacement increased from a mean 74 points preoperatively to 85 points postoperatively. In the control group, which did not have core decompression, 42 of 55 (77%) of hips required THA (Fig 1).

Fig 1.

Fig 1.

In patients treated before femoral head collapse (Stages I and II), patients with small lesions had a better (p < 0.05) outcome than patients with intermediate or large lesions (Fig 2).

Fig 2.

Fig 2.

There was no significant difference in the preoperative radiographic stage of the patients having unilateral surgery compared with those who had bilateral surgery (Table 1). The distribution of lesion size between these two groups was similar, but it was noted that in the bilateral group 50% of lesions were small, whereas in the unilateral group only 42% of lesions were small (Table 2).

Table 1

Table 1

Table 2

Table 2

There were no differences in the Harris hip scores between the unilateral and bilateral groups. The preoperative Harris hip scores for patients who did not require THA were 71 in the unilateral group and 77 in the bilateral group. The postoperative scores were 90 and 82, respectively. In patients who eventually did require THA, the scores at the time of core decompression were 68 in the unilateral group, and 71 in the bilateral group. At the time of THA, the scores were 44 and 45, respectively.

More (p < 0.05) patients in the unilateral group required THA (56 of 124 hips; 45%; in 117 patients) than in the bilateral group (48 of 152 hips; 32%; in 76 patients).

There was little difference in hospital stay or blood loss between the two groups. The hospital stay ranged from 2 to 4 days, with the stay being approximately 1 day longer for patients having bilateral core decompression than those having unilateral surgery. There was a minimal increase in blood loss in the bilateral group, but no patient in either group required a transfusion. Simultaneous bilateral surgery required 30 to 45 minutes of increased operative time compared with unilateral surgery.

There were no differences in major or minor complications between the two groups. Major complications were present in two of 124 unilateral hips (1.6%) in 117 patients. These included one high transverse femoral neck fracture and one massive but nonfatal pulmonary embolism. In the bilateral group, there were three of 152 (2.0%) hips in 76 patients with major complications. These included one intertrochanteric fracture through the core decompression site, one femoral thrombophlebitis, and one case of pneumonia. Both of the fractures occurred because of falls in the first month after surgery.

Minor complications were noted in nine of 124 hips (7.3%) in 117 patients in the unilateral group. These included a superficial wound infection, transitory hypotension, prolonged wound drainage, a flare of systemic lupus erythematosis, and a reaction to adhesive tape. Minor complications occurred in 10 of 152 hips (6.6%) in 76 patients in the bilateral group. These included pharyngeal edema, povidone-iodine allergy, a systematic lupus erythematous flare, a minor gastrointestinal bleed, and an acute attack of gout.

One woman in our series had steroid-related osteonecrosis of the femoral head. Her left hip before core decompression and bone grafting was graded as a Stage II-C (Fig 3A). Six years after surgery the osteonecrotic region shows a considerable amount of healing, and the articular surface of the femoral head remains intact without evidence of collapse (Fig 3B). She was doing well clinically at the time of this examination.

Fig 3.

Fig 3.

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Our goal was to determine the safety and effectiveness of simultaneous bilateral core decompression compared with unilateral core decompression for the treatment of osteonecrosis of the femoral head. This was done by retrospectively comparing the outcome in 117 patients (124 hips) who had unilateral surgery, with 76 patients (152 hips) who had bilateral surgery done by a single surgeon (MES). The rationale for this investigation was the concern expressed by some surgeons regarding the safety of doing core decompression simultaneously on both hips, and our inability to find any reports in the literature specifically addressing this question.

The primary limitation of this study was that it was retrospective, going back as far as 25 years. Accordingly, certain types of data analysis that we would like to have done were not possible. The study showed that there was no significant difference between unilateral and bilateral core decompression regarding safety, as determined by the prevalence of postoperative complications. It also indicated that the outcome in the bilateral group was better than in the unilateral group. This observation was not anticipated and should be viewed with some caution. We do not have a complete explanation for this finding, but it may be related to the fact that the mean size of the lesions in the bilateral group was somewhat smaller than in the unilateral group.

It was not possible to compare our results regarding bilateral core decompression with other reports in the literature as usually is done because we were unable to locate publications specifically dealing with this approach. However, our results with core decompression itself (unilateral and bilateral) were similar to other reports in the literature.4,6-9,12-15

Although there is no completely satisfactory treatment for the earlier stages of osteonecrosis of the femoral head, a number of procedures are available, including core decompression with or without bone grafting. Most reports indicate that this approach has results that are superior to symptomatic treatment.4,6-9,12-15 In a comprehensive review of the literature, Mont et al7 reviewed 42 reports involving 2205 hips. Core decompression was used to treat 1206 hips, and 819 hips were treated nonoperatively. Satisfactory results were noted in 64% of the hips treated by core decompression but in only 23% of hips treated nonoperatively. In hips treated before femoral head collapse occurred, good results were obtained in 71% compared with only 35% of hips treated nonoperatively. These results are similar to the results observed in our study. However, Camp and Colwell,2 in a retrospective series, reported a 10% prevalence of fracture after unilateral core decompression.

One of the advantages of core decompression is that it is a relatively simple surgical procedure. If attention is paid to technical details, the prevalence of complications is low and there is minimal morbidity associated with this. It can be done as an inpatient procedure with a short hospitalization, but there is a recent trend toward doing this procedure on an outpatient basis. Patients are usually maintained on partial weightbearing with crutches for 6 weeks to 3 months. In contrast, some procedures, such as angulation or rotation osteotomies, free vascularized fibular grafting, and other grafting procedures are of greater magnitude, are more demanding technically, require a longer hospital stay, have a higher prevalence of morbidity and postoperative complications, and require more vigorous protection from weightbearing, usually for a minimum of 3 months.

Nontraumatic osteonecrosis affects the femoral heads in both hips in more than 60%13 of cases. Often the diagnosis is made when both hips still are in earlier stages. Therefore, some form of surgical intervention may be indicated bilaterally in an attempt to retard or reverse progression of the condition and preserve the femoral head. If an extensive surgical procedure is elected, it generally is not advisable to operate on both hips simultaneously, and accordingly, the second procedure often is delayed by 3 to 6 months. During this time, substantial progression may occur, and a femoral head that was previously intact may collapse. If this does occur, the hip may no longer be amenable to prophylactic surgery, and if surgery is done, the results are usually inferior to those anticipated if the surgery were done before collapse. In addition, patients treated by certain complicated procedures that must be staged if done bilaterally, such as rotational osteotomies or free vascularized fibular grafting, are subjected to a second hospitalization and anesthesia and a second period of rehabilitation.

In contrast, simultaneous bilateral core decompressions can be done on both hips safely and effectively, as the data indicate. This has been done at our institution in a large number of cases for more than 20 years. However, we are unable to find a specific description of this approach published previously by other investigators.

Our indications for doing the procedure bilaterally essentially are the same as for doing it unilaterally. These include a relatively younger healthy adult with established nontraumatic osteonecrosis. Ideally, the femoral head should be radiographically intact or have only minimal evidence of flattening. Symptoms should be minimal and motion and function should be good. Throughout the course of treating patients with this condition, we and others have found that the outcome of nonoperative treatment and core decompression in hips with small asymptomatic lesions before collapse is good enough so that these patients are given the option of having core decompression or being treated symptomatically with close followup if only one hip is involved.9,13 If there is evidence of progression either radiographically or clinically, then core decompression is advised. If a patient has a unilateral lesion that already has begun to collapse and has some degree of pain and functional impairment, the patient is given the option of symptomatic treatment until such time as arthroplasty is indicated or of having core decompression with the knowledge that the outcome will not be as good as if the hip had been treated earlier.

However, in the patient with bilateral involvement, our approach is slightly modified. If it is thought that the patient is a good candidate for core decompression on one side, then we often will extend our indications regarding the contralateral hip and recommend core decompression on hips with lesser and greater degrees of involvement than in unilateral cases. The rationale for this is based on the fact that because the patient is already planning hospitalization, surgery, and a period of recovery, doing surgery on the contralateral hip does not materially increase the morbidity or recovery period. At the same time, we think it will improve the chance of a satisfactory outcome for the operated hip compared with symptomatic treatment alone.

We found that there was no difference in the mean preoperative stage of necrosis in patients having unilateral or bilateral core decompression (Table 1). However, there was a difference in lesion size, with a greater number of small lesions in the bilateral group compared with the unilateral group (Table 2). These differences presumably are related to the fact that some lesions were diagnosed and operated on earlier in patients with bilateral involvement than in patients with unilateral involvement. The mean postoperative Harris hip score was slightly higher in patients who had only one procedure compared with those having two, as might be anticipated. We found only a small number of complications in this series with no difference between patients having unilateral versus bilateral core decompression. This confirms the safety of this procedure whether done on one hip or on both hips simultaneously. We also noted that the prevalence of failure as indicated by the need for THA was lower in the bilateral group than in the unilateral group. In the unilateral group 56 of 124 hips (45%) required THA, as compared with 48 of 152 hips (32%) in the bilateral group. (p < 0.05) However, this observation should be viewed with caution.

Core decompression with bone grafting, as described here, seems to be an effective procedure for the treatment of earlier stages of nontraumatic avascular necrosis of the femoral head compared with nonoperative management. The results are related to the stage of radiographic involvement and the extent of the necrosis. When both hips are involved, the procedure can be done simultaneously when indicated without an increase in the prevalence of either minor or major complications compared with unilateral core decompression. The results after bilateral surgery appear to be at least as good as, and perhaps better, than with unilateral surgery. We noted a lower rate of THA in patients having simultaneous bilateral core decompression. The reasons for this are not entirely clear. However, it was noted that the extent of necrosis in patients having bilateral surgery was somewhat less than in patients having unilateral surgery. This might, at least in part, explain this difference. Doing simultaneous bilateral core decompression allows earlier treatment of the contralateral hip than if the procedures had been done at separate stages. This requires only a single hospitalization and anesthetic. It cuts the recovery time in half when compared with two separate staged procedures. It is more cost effective and less disruptive for patients. It also allows us to extend the indications for decompression to include earlier and later stages once it has been determined that the indications for core decompression on the opposite side are well established. For these reasons, this approach provides certain advantages over other procedures that cannot be done simultaneously on both hips.

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The authors thank Karen M. Hartman-Sloan, BSN for the valuable technical assistance she provided, including the measurement and evaluation of radiographic changes.

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