Pathological conditions with refractory skeletal pain are often characterized by regional osteoporotic changes such as transient osteoporosis of the hip, regional migratory osteoporosis, or complex regional pain syndrome (CRPS). Our previous study demonstrated that the acidic microenvironment created by osteoclast activation under high bone turnover conditions induced pain-like behaviors in ovariectomized mice through the stimulation of acid-sensing nociceptors. The aim of the present study was to examine whether regional transient osteoporotic changes are related to pain-like behaviors in the hind limb using tail-suspended model mice. The hind limbs of tail-suspended mice were unloaded for 2 weeks, during which time the mice revealed significant regional osteoporotic changes in their hind limbs accompanied by osteoclast activation. In addition, these changes were significantly recovered by the resumption of weight bearing on the hind limbs for 4 weeks. Consistent with the pathological changes in the hind limbs, pain-like behaviors in the mice were induced by tail suspension and recovered by the resumption of weight bearing. Moreover, treatment with bisphosphonate significantly prevented the triggering of the regional osteoporosis and pain-like behaviors, and antagonists of the acid-sensing nociceptors, such as transient receptor potential channel vanilloid subfamily member 1 and acid-sensing ion channels, significantly improved the pain-like behaviors in the tail-suspended mice. We, therefore, believe that regional transient osteoporosis due to osteoclast activation might be a trigger for the pain-like behaviors in tail-suspended model mice. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1226-1236, 2017.

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Background: The phalanx bones in several cases of lateral polydactyly of foot revealed complicated alignment with radiographic findings revealing medial-protrusion and lateral deviation of the middle phalanx. We previously defined such cases as showing “mosaic-like alignment” and demonstrated favorable postoperative outcomes using our surgical procedure. The aim of this study was to evaluate the midterm and long-term postoperative outcomes in such cases. Methods: The study included 17 feet from 16 patients; 5 male and 11 female, with one bilateral case. The radiographic findings in all cases revealed a mosaic-like alignment of phalanges. Average age of the patients at the initial surgery was 12 months and average duration of post-operative follow-up was 89 months (60 to 132 mo). The surgical procedures were focused on the alignment between the distal and proximal phalanges independent of the middle phalanx alignment. Ligamentous joint stability was restored using collateral ligament reconstruction. We retrospectively evaluated post-operative outcomes, and subjective evaluation by the patients and parents was carried out. Results: No cases revealed either varus or valgus deformities, pigmentation of the grafted skin, or functional disturbance. As for postoperative complications, we observed visible thickening in 7 toes, 3 of which further underwent partial resection of the middle phalanx. Subjective evaluation of the postoperative results by the patients and parents was “very satisfied” or “satisfied” in 15 of 16 cases. Conclusion: On the basis of our midterm to long-term postoperative outcomes, we believe that our method of surgical reconstruction provides a new option for the treatment of lateral polydactyly of the foot with mosaic-like alignment of the phalanx bones. Level of Evidence: Level IV—therapeutic studies.

Radial head dislocation in multiple osteochondroma leads to functional impairment and cosmetic problems, and surgical intervention has not been successful to date, with high rates of redislocation. Simple correction of the longitudinal axis and distraction oste8ogenesis of the ulna without corrective osteotomy of the radius were performed within 1 year of radial head dislocation. The mean age of the patients was 7.2 years and the postoperative follow-up duration was 63.6 months. In all cases, the dislocated radial head was repositioned without surgical invention involving the radius. All patients were pain free, with no impairment of daily activity, and all were satisfied with the cosmetic appearance, indicating successful medium-term postoperative outcomes for our surgical procedure.

Recent studies have indicated that teriparatide, an anti-osteoporosis agent, significantly improves back pain regardless of the presence of vertebral fracture in osteoporosis patients. The aims of this study were to examine whether teriparatide improves pain-like behavior in an ovariectomized (OVX) mouse model, and to evaluate changes in osteoclast marker levels and inflammatory cytokine expression levels induced by teriparatide treatment in bone tissue in association with improvements in pain-like behavior. OVX and sham operations were performed in 8-week-old mice, followed by teriparatide treatment for 2 weeks. Pain-like behavior tests (von Frey, paw flick and spontaneous pain test), and the measurement of serum tartrate-resistant acid phosphatase 5b (TRAP5b) level and inflammatory cytokine (interleukin [IL]-1β, IL-6 and tumor necrosis factor [TNF]-α) expression levels in the bone tissue were conducted after teriparatide treatment in OVX mice. Pain-like behavior in the von Frey test was significantly improved by teriparatide treatment in OVX mice. With regard to the early phase (within the first 7 days of treatment), teriparatide significantly improved pain-like behavior in the von Frey test, the paw flick test and the spontaneous pain test. Teriparatide significantly inhibited the expression of IL-1β, IL-6 and TNF-α in OVX mice in the early phase of the treatment, while the TRAP5b level in OVX mice was not significantly affected. We demonstrated that the teriparatide-induced rapid improvement effect on pain-like behavior in OVX mice was associated with the downregulation of inflammatory cytokine expression, including IL-1β, IL-6 and TNF-α.

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