A novel treatment of grade III acromioclavicular joint dislocations with a C-hook implant.

INTRODUCTION: This study evaluates the results of the new surgical treatment of complete acromioclavicular (ac) dislocations using coracoclavicular (cc) fixation with a shape memory metal C-hook implant. MATERIALS AND METHODS: Fifteen patients were prospectively analyzed. They all had a Tossy III ac dislocation due to trauma. The ac ligament was reinserted using a surgical bone anchor, and the position of the joint was restored by fixing it with a C-hook. After 3 months the C-hook was removed. Functional status, symptom severity, X-rays and patient satisfaction were analyzed during clinical control visits. The follow-up time was 1 year. RESULTS: At 12 weeks, full shoulder function had been achieved by 93% of the patients. The final control visit showed full recovery of active ROM in all patients. Two patients had mild pain during certain movements. X-rays showed the precise anatomical position of ac joint with no statistically significant differences compared to the healthy side. Patient contentment was excellent in 14 cases and satisfactory in one case. The average sick-leave was 58 days, including the removal operation. Minor osteolysis of the clavicle was noticed in two patients. CONCLUSION: The new C-hook implant provides accurate anatomical reduction, conserves the articular surfaces and enables fast functional recovery with excellent patient contentment. Technically, the implant is easy to use. Based on this study, the C-hook presents a reliable novel treatment option in surgical ac repair.

Biocompatibility and strength properties of nitinol shape memory alloy suture in rabbit tendon.

Nitinol (NiTi) is a promising new tendon suture material with good strength, easy handling and good super-elastic properties. NiTi sutures were implanted for biocompatibility testing into the right medial gastrocnemius tendon in 15 rabbits for 2, 6 and 12 weeks. Additional sutures were implanted in subcutaneous tissue for strength measurements in order to determine the effect of implantation on strength properties of NiTi suture material. Braided polyester sutures (Ethibond) of approximately the same diameter were used as control. Encapsulating membrane formation around the sutures was minimal in the case of both materials. The breaking load of NiTi was significantly greater compared to braided polyester. Implantation did not affect the strength properties of either material.

Bone modeling controlled by a nickel-titanium shape memory alloy intramedullary nail.

Nitinol (NiTi) shape memory metal alloy makes it possible to prepare functional implants that apply a continuous bending force to the bone. The purpose of this study was to find out if bone modeling can be controlled with a functional intramedullary NiTi nail. Pre-shaped intramedullary NiTi nails (length 26 mm, thickness 1.0-1.4 mm) with a curvature radius of 25-37 mm were implanted in the cooled martensite form in the medullary cavity of the right femur in eight rats, where they restored their austenite form, causing a bending force. After 12 weeks, the operated femurs were compared with their non-operated contralateral counterpairs. Anteroposterior radiographs demonstrated significant bowing, as indicated by the angle between the distal articular surface and the long axis of the femur (p = 0.003). Significant retardation of longitudinal growth and thickening of operated femurs were also seen. Quantitative densitometry showed a significant increase in the average cross-sectional cortical area (p = 0.001) and cortical thickness (p = 0.002), which were most obvious in the mid-diaphyseal area. Cortical bone mineral density increased in the proximal part of the bone and decreased in the distal part. Polarized light microscopy of the histological samples revealed that the new bone induced by the functional intramedullary nail was mainly woven bone. In conclusion, this study showed that bone modeling can be controlled with a functional intramedullary nail made of nickel-titanium shape memory alloy.