Background: Osteonecrosis of the femoral head is the end point of a disease process that results in bone necrosis, joint edema, and cartilage damage. It leads to joint arthritis that necessitates total hip arthroplasty in many patients. Because of its positive effects on osteogenesis and its chondroprotective effect of articular cartilage, pulsed electromagnetic field stimulation has been proposed as a method to prevent or delay the progression of osteonecrosis.
Methods: A retrospective analysis of the results of treatment with pulsed electromagnetic field stimulation of seventy-six hips in sixty-six patients with osteonecrosis of the femoral head was performed. Patients with Ficat stage I, II, or III osteonecrosis of the femoral head were treated with pulsed electromagnetic field stimulation for eight hours per day for an average of five months. Clinical and diagnostic imaging information was collected at the start of the treatment and at the time of follow-up. The primary end point analyzed was the avoidance of hip surgery, and the secondary end point was limiting the radiographic progression (according to Ficat stage) of osteonecrosis of the femoral head.
Results: Fifteen hips required a total hip arthroplasty; twelve of these hips were in patients with Ficat stage-III disease. The need for total hip arthroplasty was significantly higher in patients with Ficat stage-III disease than in patients with Ficat stage-I (p < 0.0001) or II (p < 0.01) disease at the beginning of treatment. Pulsed electromagnetic fields preserved 94% of Ficat stage-I or II hips. Furthermore, radiographic progression (according to Ficat stage) occurred in twenty hips (26%). Pain, present in all patients at the start of the treatment, disappeared after sixty days of stimulation in thirty-five patients (53%) and was of moderate intensity in seventeen patients (26%).
Conclusions: The results of this study confirm that pulsed electromagnetic field treatment may be indicated in the early stages of osteonecrosis of the femoral head (Ficat stages I and II). Pulsed electromagnetic field stimulation may be able to either preserve the hip or delay the time until surgery. The authors hypothesize that the short-term effect of pulsed electromagnetic field stimulation may be to protect the articular cartilage from the catabolic effect of inflammation and subchondral bone-marrow edema. The long-term effect of pulsed electromagnetic field stimulation may be to promote osteogenic activity at the necrotic area and prevent trabecular fracture and subchondral bone collapse.
Level of evidence: Therapeutic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.