Development and Validation of Finite Element Analysis Model (FEM) of Craniovertebral Junction: Experimental Biomechanical Cadaveric Study.

STUDY DESIGN: Experimental Cadaveric Biomechanical Study. OBJECTIVE: To establish an experimental procedure in cadavers to estimate joint stiffness/stability at craniovertebral junction (CVJ) region with various implant systems and to develop/validate an indigenous cost effective 3D-FEM (three-dimensional finite element model) of CVJ region. SUMMARY OF BACKGROUND DATA: Finite element analysis (FEM) tools can provide estimates of internal stress and strain in response to external loading of various implant systems used in CVJ fixations. METHODS: Experimental setup for conducting biomechanical movements on CVJ region of cadaver was developed using cost effective innovative tools. A manually actuated seven- degrees of freedom parallel manipulator motion testing system (MA7DPM) was designed and developed to impart designed trajectories and to conduct various biomechanical motion studies at CVJ region for the present study. RESULTS: FEM model of CVJ region was developed and subsequently validated with CVJ morphometry data of 15 human subjects of Asian origin. Validated FEM was subjected to force motion studies at the CVJ region. The force-motion maps obtained from the FEM studies were subsequently validated against biomechanical experiment results from cadaveric experiment results obtained with three different implant fixations. CONCLUSIONS: A cost effective biomechanical tool (which did not require decapitation of cadaveric head) and a customised chair (to place cadaver in sitting position during conduct of biomechanical movements simulating real-life scenario) was indigenously designed and developed. Developed biomechanical tool (MA7DPM) for this study is likely to be useful for stress-testing analysis of various implant systems for individual patients undergoing surgery at CVJ region in near future. LEVEL OF EVIDENCE: 5.

Is PFNA-II a better implant for stable intertrochanteric fractures in elderly population ? A prospective randomized study.

INTRODUCTION: Intertrochanteric fracture is one of the most common and severe fractures occurring in the elderly population. We conducted a randomized prospective study to compare the functional and radiological outcome of Proximal Femoral Nail anti-rotation-Asia(PFNA-II) and Dynamic Hip screw (DHS) used in fixation of stable (AO type 31 A1-A2.1) intertrochanteric fractures in elderly. METHODS: 60 elderly patients with stable intertrochanteric fractures treated with DHS and PFNA-II between August 2014 to Dec 2016 were enrolled in the study. Intraoperative variables-surgical time, blood loss, fluoroscopy time and post-operative variables-union rate, change in neck shaft angle(NSA), functional outcome in terms of Modified Harris Hip Score(HHS) & SF-12, complication rate and mortality at one year were studied and compared between both the groups. RESULTS: The mean age of patients in our study was 70.96 years. We found patients treated with DHS required significantly longer surgical time and had more blood loss compared to PFNA-II group. However, there was no significant difference in both the groups in terms of intra-operative fluoroscopy time, change in neck shaft angle, union rate, complication rate and Modified Harris Hip Score & SF-12 at three months; six months and one year follow-up. CONCLUSIONS: Both DHS and PFNA-II can be used effectively in the treatment of elderly patients with stable intertrochanteric fracture with comparable outcome. However, in high-risk elderly patients requiring shorter surgical time and less blood loss, PFNA-II can be used.