Alendronate can prevent femoral head collapse from osteonecrosis

During follow-up, only one alendronate-treated hip needed total hip replacement, compared to 16 control hips requiring THR.

Treatment with alendronate can prevent femoral head collapse in patients with femoral head osteonecrosis, reducing the need for total hip replacement, researchers in Taiwan show.

Many surgical and nonsurgical treatments have been developed to try to preserve the joints of osteonecrosis patients, but pharmacologic options have remained limited. Without treatment, over 70% of patients require joint replacement within four years of diagnosis, according to the study.

“Although osteonecrosis is the result of various conditions, the common final pathway leading to collapse of the femoral head is an uncoupling of the rates of osteoclastic bone resorption and osteoblastic bone regeneration,” the authors said in the study.

“We reasoned that by inhibiting the activity of the osteoclasts, collapse of the femoral head might be delayed or even prevented,” they said.

Prospective study

To test their concept, Kuo-An Lai, MD, and colleagues at the National Cheng Kung University Medical Center in Tainan, and at the Po-Cheng Orthopedic Institute in Kaohsiung, randomly assigned 40 patients with Steinberg stage II or stage III femoral head osteonecrosis to either weekly treatment with 70 mg of alendronate (Fosamax, Merck) or no treatment.

Alendronate is a bisphosphonate that reduces osteoclast activity. The researchers used 70 mg because it is the recommended dose for treating osteoporosis patients.

The alendronate-treated group included 29 hips of 15 men and five women with a mean age of 42.6 years. The control group included 25 hips of 15 men and five women with a mean age of 42.4 years.

Patients received NSAIDs to use as needed and were followed radiographically at 10-week intervals over two years. An experienced surgeon not involved in caring for the study patients read all radiographs in a blinded fashion. THR was indicated when femoral head collapse (Steinberg stage IV or V) and intractable pain developed, according to the study.

Significantly reduced progression

At the start of the study, control patients had a mean Harris hip score of 67.6 points and alendronate-treated patients had a mean score of 65.7 points. At final follow-up, the mean Harris hip score decreased to 49.2 ± 9.2 points for control patients, but increased to 74.4 ± 7.8 points for alendronate-treated patients, according to the study.

Significantly more control hips increased in Steinberg stage, with 19 hips having collapsed by final follow-up. Of 13 control hips initially at stage II, three remained at stage II, one progressed to stage III and nine collapsed. Of 12 control hips initially at stage III, two remained at stage III and 10 collapsed.

In contrast, only four of 29 alendronate-treated hips progressed; two hips progressed from stage II to stage III and two progressed from stage III to stage IV (P<.001). Only the two hips that progressed to stage IV had collapsed, according to the study.

The control group also required significantly more surgeries throughout the study, the authors noted. Seventeen control hips underwent a total of 21 operations — five core decompressions and 16 THRs — while only three of the 29 alendronate-treated hips underwent four operations — three core decompressions and one THR (P<.001).

The researchers continue to follow patients to determine whether the benefits of alendronate therapy are maintained. They have also initiated a prospective, double-blind, multicenter study evaluating different alendronate treatment regimens and alendronate combined with shock wave treatment.

For more information:
Lai K, Shen W, Yang C, et al. The use of alendronate to prevent early collapse of the femoral head in patients with nontraumatic osteonecrosis. J Bone Joint Surg Am. 2005;87-A:2155-2159.