Image Quiz

Progressive Shoulder Pain in a Forty-nine-Year-Old Woman Following Extracorporeal Shock-Wave Treatment for Rotator Cuff Tendinopathy (continued)

Answer: Humeral head osteonecrosis.

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Fig. 1-A	Fig. 1-B	Fig. 1-C
Fig. 1-D	Fig. 1-E	Fig. 1-F
Figs. 1-A through 1-F A forty-nine-year-old woman had a painful left shoulder for ten months. Serial magnetic resonance examinations show the development of osteonecrosis after extracorporeal shock-wave treatment for the painful shoulder. Coronal T1-weighted images (Figs. 1-A, 1-B, and 1-C) and axial T2-weighted images with fat saturation (Figs. 1-D, 1-E, and 1-F) were acquired before (Figs. 1-A and 1-D), at three months after (Figs. 1-B and 1-E), and at seven months after (Figs. 1-C and 1-F) extracorporeal shock-wave treatment. Figures 1-A and 1-D reveal no definite abnormality in the humeral head. Figures 1-B and 1-E reveal a geographic lesion in the humeral head with abnormal signal intensity and abnormal contrast enhancement consistent with the diagnosis of osteonecrosis. Figures 1-C and 1-F reveal progression of the disease with a "crescent sign" in the humeral head.

The shoulder pain became intolerable, and the patient also noted progressive limitation of the range of motion of the shoulder. She therefore underwent surgical core decompression of the humeral head two months later. During this hospital stay, an investigation for known predisposing factors for osteonecrosis, including a coagulation profile and blood tests for autoimmune disease, revealed negative findings. Most importantly, the clinical history included no known predisposing factors such as injury, use of steroid medication, blood disorders such as sickle cell disease, excessive alcohol use, Gaucher disease, pancreatitis, radiation treatment, chemotherapy, decompression disease, connective tissue diseases, or dyslipoproteinemia.

Discussion

Our review of the English-language literature revealed only one case, reported by Durst et al., of osteonecrosis of the humeral head after extracorporeal shock-wave treatment. In that patient, osteonecrosis was seen incidentally three years and four months after treatment, and the authors could not be sure when the disease process had started. In our patient, the osteonecrosis was diagnosed with magnetic resonance imaging three months after extracorporeal shock-wave treatment. While we cannot completely exclude the possibility of idiopathic osteonecrosis in our patient, the timing of the finding on magnetic resonance imaging in relation to the extracorporeal shock-wave treatment strongly supports our assumption that the shock-wave therapy was the cause.

Extracorporeal shock-wave treatment is not yet a standard therapeutic technique in orthopaedics. The mechanism for the treatment effect on soft-tissue lesions is still unknown. Animal studies have indicated that stimulation of the expression of angiogenesis-related growth factor, which induces in-growth of neovascularization and increases cell proliferation, is a possible mechanism. The effect of extracorporeal shock-wave treatment on tendinitis of the rotator cuff is controversial, despite some recently reported large series. Compared with a placebo, high-energy extracorporeal shock-wave treatment was found to improve shoulder function and decrease the size of calcifications in the soft tissue. However, reduction in pain was not consistent in the previous studies. Extracorporeal shock-wave treatment is supposed to be a safe procedure, but adverse effects have occasionally been reported.

The side effects of extracorporeal shock-wave treatment are dose-dependent. Chung and Wiley characterized extracorporeal shock-wave treatment according to energy categories: low (<0.08 mJ/mm²), medium (0.08 to 0.28 mJ/mm²), and high (>0.6 mJ/mm²). We are aware of only one report on the effect of high-energy extracorporeal shock-wave treatment on tendons, and no standard protocol for extracorporeal shock-wave treatment has been established to date. An animal study revealed that a local energy density of 0.3 mJ/mm² is the lower threshold for the occurrence of severe vascular damage. Rompe et al. recommended against high-energy extracorporeal shock-wave treatment (>0.6 mJ/mm²) of tendon tissue after they investigated the effects of shock waves on the rabbit Achilles tendon. Peters et al. reported hematoma formation in six patients after high-energy treatment and in two patients after low-energy treatment. In a report on 272 patients with tennis elbow, Haake et al. found more side effects in the group treated with extracorporeal shock-wave treatment than in the placebo group. The most common side effects were transitory reddening of the skin, pain, and the development of small hematomas. Our patient was treated with a high energy level, but the dose remained within the range recommended by the manufacturer. We suggest that whenever high-energy extracorporeal shock-wave treatment is used for a shoulder disorder, the possibility of osteonecrosis developing should be considered.

Extracorporeal shock-wave treatment is currently considered the standard therapy for most renal and upper ureteral stones, and low, acceptable complication rates have been reported. However, as the technique has become more widely available, serious complications as a result of injury to the kidney and the surrounding organs have been recognized. These complications have included direct injury to the organ itself and various vascular insults.

These complications are thought to be the result of cell damage caused by cavitation produced by the shock waves, rupture of small blood vessels (with an inner diameter of <300 µm) complete detachment of endothelial cells in defined regions, cell damage after ischemic-reperfusion injury, vasoconstriction, and free-radical production. We theorized that the development of osteonecrosis of the humeral head after extracorporeal shock-wave treatment may share a common mechanism with the vascular damage seen after extracorporeal shock-wave treatment of renal stones. The arterial supply of the humeral head is known to derive mainly from the anterior humeral circumflex artery. According to a cadaver study by Duparc et al., the diameter of the anterior humeral circumflex artery ranges between 0.3 and 2 mm in adults. Some patients with a small artery may be more susceptible to the development of osteonecrosis after extracorporeal shock-wave treatment.

We documented a case of osteonecrosis of the humeral head that was detected three months after high-dose extracorporeal shock-wave treatment of rotator cuff tendinopathy. Extracorporeal shock-wave treatment is widely used in orthopaedics, and the possibility of such a severe complication should be considered.

Reference

1. Liu H-M, Chao C-M, Hsieh J-Y, Jiang C-C. Humeral head osteonecrosis after extracorporeal shock-wave treatment for rotator cuff tendinopathy. A Case Report. J Bone Joint Surg Am. 2006;88:1353-6.