This study proposes a novel titanium 3D printing patient-specific implant: a lightweight structure with enough biomechanical strength for a distal femur fracture with segmental large defect using nonlinear finite element (FE) analysis. CT scanning images were processed to identify the size and shape of a large bone defect in the right distal femur of a young patient. A novel titanium implant was designed with a proximal cylinder tube for increasing mechanical stability, proximal/distal shells for increasing bone ingrowth contact areas, and lattice mesh at the outer surface to provide space for morselized cancellous bone grafting. The implant was fixed by transverse screws at the proximal/distal host bone. A pre-contoured locking plate was applied at the lateral site to secure the whole construct. A FE model with nonlinear contact element implant-bone interfaces was constructed to perform simulations for three clinical stages under single leg standing load conditions. The three stages were the initial postoperative period, fracture healing, and post fracture healing and locking plate removal. The results showed that the maximum implant von Mises stress reached 1318 MPa at the sharp angles of the outer mesh structure, exceeding the titanium destruction value (1000 MPa) and requiring round mesh angles to decrease the stress in the initial postoperative period. Bone stress values were found decreasing all the way from the postoperative period to fracture healing and locking plate removal. The overall construct deformation value reached 4.8 mm in the postoperative period, 2.5 mm with fracture healing assisted by the locking plate, and 2.1 mm after locking plate removal. The strain value at the proximal/distal implant-bone interfaces were valuable in inducing bone grafting in the initial postoperative period. The proposed patient-specific 3D printed implant is biomechanically stable for treating distal femoral fractures with large defect. It provides excellent lightweight structure, proximal/distal bone ingrowth contact areas, and implant rounded outer lattice mesh for morselized cancellous bone grafting.
Chronic ulnar collateral ligament humeral origin avulsion fracture in young baseball players is a rare condition and a difficult problem to treat. Eight high school or college student baseball players with onset of symptoms in their adolescent ages were collected in this series. Their mean age at surgical intervention was 17.8 ± 1.99 years. The fracture was operated on with muscle splitting, ulnar nerve-sparing technique. Suture anchors were employed to fix the avulsed fragment. Visual analog scale, Mayo elbow performance score, and Conway scale were used for objective patient evaluation. The patients were followed up for 30.8 ± 10.2 months. Six patients have achieved solid bony union, and 2 had partial union. All patients showed no medial space widening on followed-up stress films. Visual Analogue Scale score improved from 9 to 0. The Mayo elbow performance score improved from 60 ± 10 to 85 ± 15 points pre- and post-operatively. The Conway scale had 3 excellent, 3 good, and 2 fair results. The average return to pitching occurred 7 months post-operatively at a rate of 75%. The present results indicate that open reduction and fixation with suture anchors is an effective treatment method for chronic ulnar collateral ligament humeral origin avulsion fracture in young baseball players.
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