Development And Biomechanical Studying Of A Internal Fixation Of Olecranon Fractures

Objective: Olecranon fracture is one of the commondiseases of orthopedic trauma, because of its superficial anatomicalposition,and is vulnerable to external injury, the fracture often occur inthe middle of the olecranon and the base.As belonging to intra-articularfracture, it is difficulty to reduce and fixation, and is prone todeformity.Surgical treatment is needed, its emphasis is the earlypostoperative functional exercise to restore elbow activities, and to avoidthe occurrence of complications such as osteoarthritis. Therefore, toselect suitable internal fixation and early postoperative functionalexercise is very importent. This study designed a new type of interlockingintramedullary nail and compared with tension band wire and AOanatomical plate by biomechanical testing. Methods:15pairs of theantiseptic human ulna specimens (all preserved the triceps tendon),excluded the pathological deformity and severe osteoporosis by the X-raytest, then randomly divided into three groups (A, B, C), each consisting of5pairs. With standardized osteotomy, the olecranon oblique fracturemodel were established.The fractures were fixed by:grup A--tension bandwire,grup B--AO anatomical plates and grup C--new design olecranon intramedullary nail. Each specimen have a continuous dynamic loadingtest, the test program cycle was: elbow flexion vary from0°to100°, thetriceps tendon tension vary from30N to200N. After10,100,200,400cycles loading,measured the distance of fracture displacement, the datawere recorded and laid in SPSS19.0.Statistically analyzed were donewith Paired-Samples T-test. Results:(1) after10cycles loading: group A(tension band wire group) distance of fracture displacement was0.33±0.02mm; group B (anatomical plate group) distance0.32±0.02mm; Cgroup (experimental developed by interlocking intramedullary nail)distance0.32±0.01mm, Group C compared group A or group B, therewas not statistically significant (p>0.05).(2) after100cycles loading:group A of fractures displacement distance was1.12±0.05mm; group B1.05±0.03mm; group C1.00±0.04mm, Group C compared group A orgroup B, there was statistically difference(p <0.05).(3) after200cyclesloading: group A of fractures displacement distance was1.64±0.04mm;group B1.60±0.07mm; group C1.51±0.05mm, Group C comparedgroup A or group B, there was statistically difference(p <0.05).(4) after400cycles loading: group A of fractures displacement distance was2.02±0.07mm; group B1.75±0.06mm; group C1.65±0.06mm, Group Ccompared group A or group B, there was statistically difference(p <0.05).Conclusion: The biomechanical test data indicate that the new designintramedullary nail system have a superior anti-compression and anti-rotation ability than the tension band wire and AO anatomy plate,itcan provide adequate excellent stability to fix olecranon fracture.