Background Carpal tunnel release and conservative interventions are widely used in clinical therapies of carpal tunnel syndrome. The efficacy of these treatment and interventions mainly lies in the exploitation of the mechanical properties of carpal tunnel. This study investigated the structural mechanics of the transverse carpal arch using cadaveric hands. Methods Paired force was applied to the insertion sites of the transverse carpal ligament at both the distal (hamate -trapezium) and proximal (pisiform - scaphoid) level of the carpal tunnel. The two pairs of forces were simultaneously applied in an inward or outward direction when the transverse carpal ligament was intact and transected. Transverse carpal arch and carpal tunnel compliance in response to the forces were analyzed. Three-way repeated measures ANOVA were used to examine the effect of the transverse carpal ligament status (intact/transected), the level of the carpal tunnel (distal/proximal) and the force application direction (inward/outward) on the biomechanics of the transverse carpal arch. Findings Transverse carpal ligament plays a stabilizing role in resisting outward deformation of the carpal tunnel. The carpal tunnel at the proximal level is more flexible than the carpal tunnel at the distal level. The carpal tunnel is more compliant under the inward force application than under the outward force application. Interpretation The understanding of carpal tunnel mechanics potentially helps to improve the existing strategies and to develop alternatives for the treatment of carpal tunnel syndrome.

Osseointegration of implant provides a stable support for the prosthesis under functional loads. The timing of loading is a critical parameter that can govern the success of the osseointegration of implant. However, it is not clear whether the early loading can affect the success of osseointegration, or whether the no-loading healing period can be shortened. This paper presents an animal study conducted to investigate how external loads influence the osseointegration at the initial stage of healing. Titanium implants were inserted into the goat tibia laterally, and different axial loadings were applied to the implants in 4 weeks after surgery. After the 2 weeks period of early loading, animals were sacrificed and the tibia bones with the implants were cut off from the bodies. Then mechanical test was employed to find out the differences in the pull-out force, and shear strength at the bone-implant interface between the non-loaded and the loaded implants. The implant-bone interfaces were analyzed by histomorphometric method, SEM (scanning electron micrograph) and EDS (energy density spectrum). The results indicated that the bone-implant interface did not well integrate 4 weeks after surgery, and the fibrous tissue could be found at the interfaces of the specimens without loadings. While the results of loaded specimens with 10 N axial force showed that that parts of the interface were well integrated, indicating that the early mild loading may play a positive role in the process of the osseointegration. The results support that a certain range of external loading would influence the process of osseointegration, and appropriate mechanical loading can be applied to shorten the osseointegration period after surgery.