These population-based nationwide analyses may be reassuring for patients who receive bisphosphonates. Although there was a high prevalence of current bisphosphonate use among patients with atypical fractures, the absolute risk was small. (Funded by the Swedish Research Council.).

The WNT16 locus is a major determinant of cortical bone thickness and nonvertebral fracture risk in humans. The disability, mortality and costs caused by osteoporosis-induced nonvertebral fractures are enormous. We demonstrate here that Wnt16-deficient mice develop spontaneous fractures as a result of low cortical thickness and high cortical porosity. In contrast, trabecular bone volume is not altered in these mice. Mechanistic studies revealed that WNT16 is osteoblast derived and inhibits human and mouse osteoclastogenesis both directly by acting on osteoclast progenitors and indirectly by increasing expression of osteoprotegerin (Opg) in osteoblasts. The signaling pathway activated by WNT16 in osteoclast progenitors is noncanonical, whereas the pathway activated in osteoblasts is both canonical and noncanonical. Conditional Wnt16 inactivation revealed that osteoblast-lineage cells are the principal source of WNT16, and its targeted deletion in osteoblasts increases fracture susceptibility. Thus, osteoblast-derived WNT16 is a previously unreported key regulator of osteoclastogenesis and fracture susceptibility. These findings open new avenues for the specific prevention or treatment of nonvertebral fractures, a substantial unmet medical need.

Animal experiments show a dramatic improvement in skeletal repair by teriparatide. We tested the hypothesis that recombinant teriparatide, at the 20 mg dose normally used for osteoporosis treatment or higher, would accelerate fracture repair in humans. Postmenopausal women (45 to 85 years of age) who had sustained a dorsally angulated distal radial fracture in need of closed reduction but no surgery were randomly assigned to 8 weeks of once-daily injections of placebo (n ¼ 34) or teriparatide 20 mg (n ¼ 34) or teriparatide 40 mg (n ¼ 34) within 10 days of fracture. Hypotheses were tested sequentially, beginning with the teriparatide 40 mg versus placebo comparison, using a gatekeeping strategy. The estimated median time from fracture to first radiographic evidence of complete cortical bridging in three of four cortices was 9.1, 7.4, and 8.8 weeks for placebo and teriparatide 20 mg and 40 mg, respectively (overall p ¼ .015). There was no significant difference between the teriparatide 40 mg versus placebo groups ( p ¼ .523). In post hoc analyses, there was no significant difference between teriparatide 40 mg versus 20 mg (p ¼ .053); however, the time to healing was shorter in teriparatide 20 mg than placebo ( p ¼ .006). The primary hypothesis that teriparatide 40 mg would shorten the time to cortical bridging was not supported. The shortened time to healing for teriparatide 20 mg compared with placebo still may suggest that fracture repair can be accelerated by teriparatide, but this result should be interpreted with caution and warrants further study. ß

Background Blood platelets release a cocktail of growth factors when activated, some of which are thought to initiate and stimulate repair.Experiment and findings We studied whether a platelet concentrate injection would improve Achilles tendon repair in an established rat model. The Achilles tendon was transected and a 3 mm segment removed. After 6h, a platelet concentrate was injected percutaneously into the hematoma. This increased tendon callus strength and stiffness by about 30% after 1 week, which persisted for as long as 3 weeks after the injection. At this time, the mechanical testing indicated an improvement in material characteristics-i.e., greater maturation of the tendon callus. This was confirmed by blinded histological scoring.Interpretation Platelet concentrate may prove useful for the treatment of Achilles tendon ruptures.

Background