Strength of side-to-side and step-cut repairs in tendon transfers: biomechanical testing of porcine flexor tendons.

The aim of the study was to compare side-to-side with step-cut repairs to determine how much of the width it is possible to remove and still keep the repair strong enough to start active mobilization. Porcine flexor tendons were used to create side-to-side, one-third step-cut and half step-cut repairs. There were 15 repairs in each group. The tensile properties of the constructs were measured in a biomechanical testing machine. All repairs failed by the sutures splitting the tendon longitudinally. The maximum load and stiffness were highest in the side-to-side group. Our findings suggest that the half step-cut repair can withstand the forces exerted during active unrestricted movement of the digits in tendons of this size. The advantage of the step-cut repair is reduced bulkiness and less friction, which might compensate for the difference in strength.

Strength of Pulvertaft modifications: tensile testing of porcine flexor tendons.

The aim of the study was to present two new modifications of the Pulvertaft weave, allowing a higher number of weaves without the need for a longer overlap. The mechanical properties were measured and compared with the traditional technique. Forty-five pairs of porcine flexor tendons were randomized to a Pulvertaft repair with three weaves, a Double Pulvertaft and Locking Pulvertaft repairs. In the last two repairs one of the tendons in each repair was split in two before weaving. A difference in the maximum stiffness was observed between the three groups (p = 0.024). All repairs failed by the sutures being sheared through the tendons splitting the tendon fibres longitudinally. The two modifications were both stronger than the Pulvertaft weave and provide an alternative when a strong connection is needed and a longer overlap is impossible.

Osteogenically-induced human dermal fibroblasts as a tool to regenerate bone.

Engineering of bone tissue could help to overcome the need for extensive reconstruction and associated donor site morbidity, and it has been proposed that osteogenic biomaterials, which are scaffolds that contain osteocompetent cells, could be used to fill large bone defects. This study investigated the potential of osteogenically-induced human dermal fibroblasts cultured on gelatin microcarriers combined with platelet-rich plasma in a model of a femoral defect in athymic rats. Defects were transplanted with one of the following six combinations: 1 = sodium chloride, 2 = platelet-rich plasma, 3 = microcarriers + platelet-rich plasma, 4 = human dermal fibroblasts on microcarriers + platelet-rich plasma, 5 = human osteoblasts on microcarriers + platelet-rich plasma, and 6 = osteogenically induced human dermal fibroblasts on microcarriers + platelet-rich plasma. The femoral defects were assessed 4 weeks postoperatively with computed tomography (CT), routine histological staining, fluorescence in situ hybridisation, and polyclonal antibodies directed towards osteocalcin and osteonectin. Radiographs of all groups taken 4 weeks postoperatively showed unhealed defects. Femoral defects transplanted with osteogenically-induced human dermal fibroblasts on microcarriers (group 6) contained dense clusters of cells with large quantities of extracellular matrix. These clusters were exclusive to this group and stained strongly for osteocalcin and osteonectin. Fluorescence in situ hybridisation showed viable human cells in femoral defects that had been transplanted with microcarriers seeded with cells, which confirmed the survival of implanted cells. In conclusion, osteogenically-induced human dermal fibroblasts survived in this new niche, and bone-like structures were apparent in the defects.