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We reviewed the medical records of 115 patients with 130 hips with developmental dysplasia with complete dislocation in the absence of a neuromuscular disorder, spontaneous reduction with a Pavlik harness, and a minimum of 14 years' follow-up. The mean age at the time of harness application was 4.8 months (1 to 12) and the mean time spent in the harness was 6.1 months (3 to 12). A total of 108 hips (83.1%) were treated with the harness alone and supplementary surgery for residual acetabular dysplasia, as defined by an acetabular index > 30 degrees , was performed in 22 hips (16.9%). An overall satisfactory outcome (Severin grade I or II) was achieved in 119 hips (91.5%) at a mean follow-up of 16 years (14 to 32) with a follow-up rate of 75%. Avascular necrosis of the femoral head was noted in 16 hips (12.3%), seven of which (44%) underwent supplementary surgery and nine (56%) of which were classified as satisfactory. The acetabular index was the most reliable predictor of residual acetabular dysplasia.

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Some physicians recommend treating tendinopathies with multiple sessions of shock waves. Some evidence, however, suggests shock wave application can induce nerve fiber degeneration. We questioned whether repeated shock wave application provides a cumulative effect on nerve fibers compared with the effect of one application. One thousand shock wave impulses of an energy flux density of 0.08 mJ/mm were applied to the foot pad of 32 rats. After 14 days, 16 rats received a second application. The foot pads were resected on Days 7, 14, 28, and 42. Sections were processed immunohistochemically using antibodies for sensory nerve. We compared the number of epidermal nerve fibers in rats that received one application of shock waves with the fibers in rats that received two applications. During the first 4 weeks, there was nearly complete degeneration of epidermal nerve fibers in both groups. By the end of 6 weeks, reinnervation of the epidermis began in the single-treatment group. Reinnervation occurred slower in the repeated-treatment group. These data show that a second application has a cumulative effect on nerve fibers. Our data suggest multiple applications of low-energy shock waves might a provide longer-lasting antinociceptive effect.

It is known that free nerve endings are degenerated after application of shock waves. We therefore hypothesized that the application of shock waves to muscle induces dysfunction of neuromuscular transmission at neuromuscular junctions. We investigated changes in neuromuscular transmission in response to shock wave application. Sprague-Dawley rats were used in this study. Two thousand shock waves at an energy flux density of 0.18 mJ/mm 2 were applied to their right calf muscles. Neuromuscular junctions of gastrocnemius muscles were evaluated using rhodamine-a-bungarotoxin on the day of treatment (n ¼ 5). Amplitude and latency of compound muscle action potentials were measured on the day of treatment and 1, 2, 4, 6, and 8 weeks after treatment (n ¼ 10, each group). Degenerated acetylcholine receptors existed in all treated muscles. Although the action potential amplitude on the treated side was significantly less than on the control side from the day of treatment (25.1 AE 7.8 vs. 34.5 AE 9.1, p ¼ 0.012) to 6 weeks (27.9 AE 7.2 vs. 34.5 AE 7.2, p ¼ 0.037), there was no significant difference at 8 weeks. There was no significant difference in transmission latency between the groups. Keywords: neuromuscular junction; extracorporeal shock wave therapy; compound muscle action potential; neuromuscular transmission; acetylcholine receptor Impaired muscle coordination of limbs afflicted with central nervous system dysfunctions such as cerebral infarction, cerebral palsy, and dystonia is very common. This impairment causes severe limitations of daily living 1,2 and affects patients for their lifetime. Injection of botulinum toxin to focal muscles decreases muscle tone and is effective in improving motor function for impaired muscle coordination of limbs.3,4 For the past 20 years, treatment using botulinum toxin has gained acceptance as a popular treatment. However, the treatment using botulinum toxin has several difficulties with complications including severe allergic reaction and asthenia.3 Moreover, economic considerations inhibit many patients from undergoing this treatment because of its high cost. Recently, it has been reported that extra corporal shock wave treatment (ESWT) is able to improve function without inducing weakness in patients who suffer from spasticity and dystonia. 5,6 However, the mechanism of its clinical effect in the treatment of spasticity and dystonia has not been clarified. It is known that free nerve endings and sensory nerve fibers are degenerated after the application of shock waves.7,8 Therefore, we hypothesized that the application of shock waves to muscles induces dysfunction of neuromuscular transmission at neuromuscular junctions (NMJs). The purpose of this study was to investigate the changes in NMJs in response to ESWT to clarify its mechanism in the treatment of spasticity and dystonia. MATERIALS AND METHODSSeventy, 8-week-old male Sprague-Dawley rats (Japan SLC, Shizuoka, Japan) were used in this study. Animals were housed in an animal resources facility. Their room was mai...