Letter from JAMA Internal Medicine — Incidence of Physician-Diagnosed Carpal Tunnel Syndrome in the General Population

The macro- and micro-features of bone can be assessed by using imaging methods. However, nano- and molecular features require more detailed characterization, such as use of e.g., vibrational spectroscopy and X-ray scattering. Nano- and molecular features also affect the mechanical competence of bone tissue. The aim of the present study was to reveal the effects of mineralization and its alterations on the mineral crystal scale, by investigating the spatial variation of molecular composition and mineral crystal structure across the cross-section of femur diaphyses in young rats, and healthy and osteoporotic mature rats (N=5). Fourier transform infrared spectroscopy and scanning small- and wide-angle X-ray scattering (SAXS/WAXS) techniques with high spatial resolution were used at identical locations over the whole cross-section. This allowed quantification of point-by-point information about the spatial distribution of mineral crystal volume. All measured parameters (crystal dimensions, degree of orientation and predominant orientation) varied across the cortex. Specifically, the crystal dimensions were lower in the central cortex than in the endosteal and periosteal regions. Mineral crystal orientation followed the cortical circumference in the periosteal and endosteal regions, but was less well-oriented in the central regions. Central cortex is formed rapidly during development through endochondral ossification. Since rats possess no osteonal remodeling, this bone remains (until old age). Significant linear correlations were observed between the dimensional and organizational parameters, e.g., between crystal length and degree of orientation (R(2)=0.83, p<0.001). Application of SAXS/WAXS provides valuable information on bone nanostructure and its constituents, effects of diseases and, prospectively, mechanical competence.

Bone morphogenic proteins (BMPs) can be used in non-unions to replace autograft. BMPs induce osteoblasts and (less well known) also osteoclasts, which can in turn be controlled by a bisphosphonate. In the present study, our aim was to improve the biological effect of autologous bone graft by adding an anabolic BMP, with or without bisphosphonates, in an open-fracture model prone to non-union. Rat femurs were osteotomized and fixed with an intramedullary K-wire. Autograft was placed at the osteotomy, mixed with either saline or BMP-7. After 2 weeks, the rats had a single injection of saline or of a bisphosphonate (zoledronate). The rats were killed after 6 weeks and the femurs were evaluated by radiography, micro-CT, histology, and 3-point bending test. All fractures healed. The callus volume was doubled in the BMP-treated femurs (p < 0.01) and increased almost 4-fold in the femurs treated with both BMP and systemic zoledronate (p < 0.01) compared to autograft. In mechanical testing, the autograft group reached approximately half the strength of the contralateral, non-osteotomized femur (p < 0.001). By adding BMP to the autograft, the strength was doubled (p < 0.001) and with both BMP and systemic zoledronate, the strength was increased 4-fold (p < 0.001) compared to autograft alone. The combination of BMP and bisphosphonate as an adjunct to autograft is superior to autograft alone or combined with BMP. The combination may prove valuable in the treatment of non-unions.

Fracture dislocations of the PIP joint are challenging to treat. In hemi-hamate arthroplasty, the palmar lip joint surface is reconstructed using an osteochondral graft from the hamate and the immediate stability permits early movement. In the long term, collapse of non-vascularized osteochondral grafts might lead to degenerative arthritis. We examined the radiographic result after a minimum of 4 years with special reference to the development of osteoarthritis and its relation to clinical symptoms in eight patients, mean age 49 (25–66) years. After a mean of 60 (48–69) months, the arc of motion was 67° (45°–95°) at the PIP joint and grip strength was 91% of the uninjured side. The visual analogue score for pain (0–100) was 10 (0–70) mm. Severe arthritis (grade IV) was found in two and mild arthritis (grade II) in another two patients, but only one of these four cases had troublesome pain. The hemi-hamate technique is an attractive alternative to other treatment options, but some cases develop osteoarthritis in the medium term.