Commentary & Perspective

Commentary & Perspective on
"Spontaneous Resolution of Osteonecrosis of the Femoral Head"
by Edward Y. Cheng, MD, et al.
and on
"Fate of Very Small Asymptomatic Stage-I Osteonecrotic Lesions of the Hip"
by P. Hernigou, MD, et al.

Commentary & Perspective by
Marvin E. Steinberg, MD*,
Department of Orthopaedic Surgery, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

In this issue of The Journal, two articles address a similar topic but approach it from different perspectives. Both deal with the prognosis for untreated hips with early, asymptomatic osteonecrosis of the femoral head. This is a topic of clinical importance about which little has been written and about which continuing confusion exists. Both of these articles add to our knowledge in this area.

In the article entitled "Spontaneous Resolution of Osteonecrosis of the Femoral Head," by Cheng et al., the authors followed thirty hips in patients with asymptomatic osteonecrosis (thirteen hips in patients who underwent organ transplant, and seventeen hips in patients who underwent surgical treatment of the contralateral hip for the treatment of established osteonecrosis). They found that three hips, all of which were in the organ transplant group, underwent partial or complete spontaneous resolution of the osteonecrotic lesion as determined by magnetic resonance imaging over a period of nineteen to forty-four months. These three hips all had pre-radiographic osteonecrosis (stage I) and had involvement of 30% or less of the femoral heads. The authors concluded that spontaneous resolution of osteonecrosis of the femoral head can occur; spontaneous resolution was seen in patients with early, asymptomatic disease and small lesion size and without multiple areas of involvement. However, they noted that the small size of the series precluded definite conclusions regarding the factors which might influence resolution or progression, and they did not make definitive recommendations regarding treatment.

This study was specifically focused on the three hips that exhibited spontaneous resolution on magnetic resonance imaging, and very little data were presented regarding the twenty-seven hips that did not (although additional information is provided in a previous publication by these authors, which they cited.) Thus, much useful information, such as length of follow-up, demographic factors, stage of involvement, lesion size, or specific outcome, is unfortunately not included in this manuscript for most of the hips in their series. This makes it difficult for the reader to compare these two groups. The authors did state that eleven of thirty asymptomatic hips apparently did become painful during the course of the study. Although they concluded that the spontaneous resolution may not be a rarity, they relied solely on serial magnetic resonance imaging to make this determination and found that spontaneous resolution occurred in only three of the thirty hips in their series (10%). The other twenty-seven hips (90%), apparently showed either progression or no evidence of resolution. Nevertheless, the authors stated that these observations persuaded them to defer operative treatment for patients with small, asymptomatic lesions.

Yet, on the basis of the data presented in this article, it is possible to reach an entirely different conclusion than that reached by the authors: if 90% of these originally asymptomatic hips either progressed or showed no evidence of spontaneous resolution, it might be advisable to undertake some form of early prophylactic surgery to retard or reverse this progression and preserve the femoral head rather than let it remain untreated and risk a high prevalence of progression and collapse. In addition, it is of concern that the authors apparently relied solely on the magnetic resonance images to determine if resolution had taken place, and not on the radiographic or clinical status of the involved hip. Although magnetic resonance imaging at present is the best single method for diagnosing early osteonecrosis, it may not be the most valuable method for following the resolution or the progression of the disorder^1,2. As the authors correctly stated, their series is too small to provide definitive conclusions regarding factors that might determine outcome.

In the paper entitled, "Fate of Very Small Asymptomatic Stage-I Osteonecrotic Lesions of the Hip," by Hernigou et al., the authors reported on a minimum ten-year follow-up of forty untreated hips with small, asymptomatic, stage-I lesions. They found that thirty-five (88%) of forty hips became symptomatic, and that twenty-nine (73%) went on to femoral head collapse. In a number of hips, pain developed five or more years following the diagnosis. Progression occurred very slowly, and symptoms always preceded collapse by six months. The authors concluded that because these hips did collapse in a large percentage of patients, such patients should be followed closely over a long period of time. Patients with osteonecrosis in the contralateral hip or elsewhere in the body should undergo magnetic resonance imaging of the asymptomatic hip to determine if osteonecrosis is present. Because most asymptomatic hips will eventually collapse, the authors advise that we should consider performing an early, prophylactic, conservative surgical procedure on the asymptomatic hip to improve the prognosis for preserving the femoral head, usually at the same time that the patient is undergoing surgical intervention on the symptomatic, contralateral hip. Alternatively, such intervention could be done if and when the hip first became symptomatic, as collapse does not appear to occur until six or more months following diagnosis. These conclusions and recommendations are well supported by the authors' data and are in general agreement with the opinions of many other investigators.

It was of interest to note that the authors found that collapse could take place five or more years after diagnosis, whereas in other series it has been concluded that if the hip appeared to remain stable for two years, it was unlikely to progress. The authors also reported that the average dose of prednisone-equivalent corticosteroids taken by the patients in their study was 600 mg, whereas, in most series, the dosage required to produce avascular necrosis was 2,000 mg or more.

Kopecky et al.³ identified twenty-five hips that had asymptomatic osteonecrosis, diagnosed with the use of magnetic resonance imaging, in 104 renal transplant recipients. Pain and radiographic changes developed in seven hips, and one hip became symptomatic despite appearing normal on radiographs. In seven of twenty-five hips (28%), the magnetic resonance image showed a decrease in lesion size, and in six of these, the magnetic resonance image showed normal findings. Mulliken et al.⁴ diagnosed osteonecrosis in fifteen hips in ten patients of a group of 132 renal transplant recipients who were evaluated with the use of magnetic resonance imaging. Eleven hips were pre-radiographic and asymptomatic. Only one of these hips eventually progressed. Ito et al.² followed ninety hips in seventy-seven patients with early osteonecrosis. At the last follow-up, fifty-six hips (62%) were symptomatic, and fifty-two of these had undergone major surgery. It is of interest that the authors were able to identify fifteen hips, diagnosed initially on magnetic resonance imaging, that remained asymptomatic and radiographically normal during the course of their study.

Other authors have reported a worse prognosis for osteonecrotic hips that were initially asymptomatic. Bradway and Morrey⁵ found that, of fifteen asymptomatic and radiographically normal hips in patients with osteonecrosis of the contralateral hip, all eventually collapsed at a mean of twenty-three months. Takatori et al.⁶ followed thirty-two radiographically normal, asymptomatic hips. They found that no collapse occurred in fifteen hips with small lesions, whereas in fourteen (82%) of seventeen hips with moderate to large lesions, collapse occurred in a mean of fifteen months. Koo et al.⁷ observed fifteen patients with asymptomatic osteonecrosis that was treated nonoperatively. Eleven (73%) went on to femoral head collapse. Jergesen and Khan⁸ found that fourteen (74%) of nineteen untreated hips that were initially asymptomatic eventually became painful. Davidson et al.⁹ found that forty-one (73%) of fifty-six initially asymptomatic hips progressed and became symptomatic at 24 months, as diagnosed with the use of magnetic resonance imaging or radiography. They concluded that because of this high prevalence of progression, even asymptomatic hips might benefit from early surgical intervention. Belmar et al.¹⁰ found that in hips treated by core decompression and grafting before femoral head collapse had occurred, the outcome was correlated with the size of the necrotic lesion, but that there was no correlation with the preoperative pain level.

Both of these articles have provided useful information that should help us evaluate the treatment of patients with osteonecrosis. Hips with small, asymptomatic lesions in stages I or II usually have a better prognosis for spontaneous healing than do hips with larger lesions or lesions in more advanced stages. Although the exact prevalence of progression and collapse is not certain, it would appear to be high. Therefore these patients should be followed closely. Several factors must be considered in determining the outcome and treatment for these hips, but early prophylactic surgical procedures that are designed to retard or reverse progression and preserve the femoral head should not be withheld specifically because of the absence or paucity of pain, especially in patients about to undergo a more definitive procedure on the contralateral, symptomatic hip. If surgery is not performed early, patients should be followed closely because a small but definite number of hips may become radiographically and clinically stable. Progression can occur even quite some time from the initial diagnosis; therefore, a long period of follow-up is needed. At the first signs of radiographic or clinical progression, prophylactic surgery should be considered for such patients.

*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Chan TW, Dalinka MK, Steinberg ME, Kressel HY. MRI appearance of femoral head osteonecrosis following core decompression and bone grafting. Skeletal Radiol. 1991;20:103-7.
2. Ito H, Matsuno T, Omizu N, Aoki Y, Minami A. Mid-term prognosis of non-traumatic osteonecrosis of the femoral head. J Bone Joint Surg Br. 2003; 85:796-801.
3. Kopecky KK, Braunstein EM, Brandt KD, Filo RS, Leapman SB, Capello WN, Klatte EC. Apparent avascular necrosis of the hip: appearance and spontaneous resolution of MR findings in renal allograft recipients. Radiology. 1991;179:523-7.
4. Mulliken BD, Renfrew DL, Brand RA, Whitten CG. Prevalence of previously undetected osteonecrosis of the femoral head in renal transplant recipients. Radiology. 1994;192:831-4.
5. Bradway JK, Morrey BF. The natural history of the silent hip in bilateral atraumatic osteonecrosis. J Arthroplasty. 1993;8:383-7.
6. Takatori Y, Kokubo T, Ninomiya S, Nakamura S, Morimoto S, Kusaba I. Avascular necrosis of the femoral head. Natural history and magnetic resonance imaging. J Bone Joint Surg Br. 1993;75:217-21.
7. Koo KH, Kim R, Ko GH, Song HR, Jeong ST, Cho SH. Preventing collapse in early osteonecrosis of the femoral head. A randomised clinical trial of core decompression. J Bone Joint Surg Br. 1995;77:870-4.
8. Jergesen HE, Khan AS. The natural history of untreated asymptomatic hips in patients who have non-traumatic osteonecrosis. J Bone Joint Surg Am.1997;79:359-63.
9. Davidson JL, Coogan PG, Gunneson EE, Urbaniak JR. The asymptomatic contralateral hip in osteonecrosis of the femoral head. In: Urbaniak JR, Jones JP Jr, editors. Osteonecrosis: Etiology, diagnosis, and treatment. Rosemont, Illinois: American Academy of Orthopaedic Surgeons; 1997. p 231-40.
10. Belmar CJ, Steinberg ME, Hartman-Sloan KM. Does pain predict outcome in hips with osteonecrosis? Clin Orthop. 2004;425:158-62.

Copyright © 2004 by the The Journal of Bone and Joint Surgery, Inc.