ABSTRACT
Objective To study the biomechanical performance of proximal femoral nailing antirotation (PFNA) in the treatment of femoral intertrochanteric fracture involving the lateral wall using finite element analysis and the significance of the lateral wall.Methods A healthy senior volunteer,male,80 years of age,was recruited for this study.The CT data of his proximal femur were used to establish a three-dimensional finite element model of proximal femur by software Mimics17.0 and Geomagic Stusio.After the intertrochanteric fracture of AO-type 31-A1.2 was simulated together with coronal displacement of the lateral wall fracture,it was assembled with PFNA into the three-dimensional finite element model.Finite element analysis was performed on the femoral head,neck,fracture ends,lateral wall,and internal components of the model to observe the stress values of various parts of the model under the same load,with different degrees of fracture reduction (no displacement,anterior displacement of 5％,10％,15％ and 20％,posterior displacement of 5％,10％,15％ and 20％) and with or without the lateral wall.Results The stress values for internal components at the femoral head,neck,fracture ends,main nail with anatomical reduction of fracture ends and integrity of the lateral wall were 0.40 MPa,30.05 MPa,74.35 MPa and 121.68 MPa,respectively.The respective stress values of the above with lateral wall fracture were 0.82 MPa,47.32 MPa,151.92 MPa and 266.88 MPa,increased by about 100％.With every horizontal reduction loss increased by 5％ forward or backward,the stress exerting on the corresponding spots would see a 10％ progressive growth,plus 20％ lateral wall fracture and reduction loss.The stress of the main nail (468.43 MPa) was thrice that (121.68 MPa) of the stress posing on the complete lateral wall with the fracture ends 100％ reduced.Conclusions When PFNA is used in the treatment of femoral intertrochanteric fractures involving the lateral wall,stresses on the internal components may be doubled.Loss of coronal reduction may lead to the most significant increase in stress on the bonding site between the main nail and screw blade.
ABSTRACT
Objective To investigate the surgical strategies for management of unstable fractures of intertrochanteric lateral wall.Methods From July 2012 to June 2014,50 patients with unstable fractures of intertrochanteric lateral wall received osteosynthesis with proximal femoral nail anti-rotation.They were 37 men and 13 women,with an average age of 65.6 years (range,from 42 to 87 years).According to our morphology classification,25 patients belonged to type Ⅰ (comminuted fracture of lateral wall),4 to type Ⅱ (split fracture of lateral wall with loss of medial support),21 to type Ⅲ (comminuted fracture of lateral wall and subtrochanteric part with loss of medial support).The fractures were managed differently according to our classification.Type Ⅰ were treated by intramedullary fixation with compression screws to reconstruct the lateral wall,type Ⅱ by intramedullary fixation after reconstruction of the lateral wall lby cables,and type Ⅲ by intramedullary fixation after optimal reduction of the coronal plane and neck-shaft angle because the lateral wall could not be reconstructed.Results The 50 patients obtained an average follow-up of 17 months (range,from 5 to 24 months).No deep infection or wound dehiscence happened.Deep vein thrombosis occurred in 2 patients.No nonunion,cutout of the sliding screw,or coxa vara occurred.The operation time,blood loss,time of weight loading after operation and time of union increased with our increased classification.One patient died from a heart disease 5 months after operation.Functional outcome of the other 49 patient was assessed by Harris hip score one year after operation.Forty patients were excellent,6 good and 3 fair,giving an excellent to good rate of 93.9％.Conclusion Unstable fractures of intertrochanteric lateral wall should be treated using different surgical strategies based on the morphology classification system.