A Biomechanical Study And Clinical Application Of K-wire Tension Band For Distal Humerus Fractures

Object:Fractures of distal humerus is a severe injury in the elbow, treatment can be done by traditional conservatives to open reduction and internal fixation, but the outcome is unacceptable. With the evaluation of biomechanical study and clinical experience, open reduction and internal fixation is optimal for this injury, but how to get stable fixation is controversial, however it is a challenge for the orthopedic surgeons. This study, biomechanical study and clinical experience of k-wire tension band to distal humerus fractures, intend to investigate the characteristic of fixation and provide clinical guide for distal humerus fractures.Method:1. Biomechanical study:6 fresh cadaver humerus species, excluded pathology by x-ray, were removed soft tissue and apply osteoectomy proximal 2 cm to articular surface. Every two species were fixed with single k-wire tension band, double k-wire and tension band, double plates and then change another style. CSS—44000 electronic multipurpose biomechanical apparatus were used to determine the stable features. Distal part were fixed with a multiple screw set clamp and four direction loading were given on humerus shaft 7 cm to articular surface to imitate the elbow extension, flexion, adduction and abduction. We set up velocity for 3mm/min and maximum loading for 40N to prevent the species damage. Measure the loading and deformity relationship then the maximum loading, all the data input computer and output loading deformity line, the slop rigidity represent stability.2. Clinical application:There were 30 case distal humerus in this study, male 11 case, female 19case, age from 16 to 67, average 41, left 13 and right 17. open fracture 9 case, with GustiloⅠ5 case,Ⅱ4case, close fracture 21 case, cause of fracture falling 21 case, motor vehicle accident 7 case, according to AO/ASIF classification:C14 case, C2 14 case, C3 12 case. All the patients undergone operation 0 to 17day after injury, brachial plexus block anesthesia, with a posterior midline incision exposure the fracture, double plate 17 case, double tension band 13 case.Result Double plate group with highest rigidity for 9.71±3.53 N/mm (p<0.05) in posterior direction, while double tension band group with highest rigidity 5.36±2.17 N/mm (p<0.05) in anterior direction. There is no difference between medial and lateral direction. Clinical study show double tension band group with less time and less blood lose, but with the same elbow function.Conclusion Stability for distal humerus fracture was determined by character of bone and style of internal fixation, double tension band conform to biomechanical character but double k-wire is better to strengthen the rigidity. Double tension band has more indication, easy and can achieve the same result with double plate.