ABSTRACT
BACKGROUND: Compared with the metal screws, absorbable screws have more obvious advantages, such as does not have to conduct internal fixation removal, non-metal ic components, no influence on the magnetic resonance imaging of patients after implantation, relatively simple operations, namely dril ing-tapping-screws fixation, more in line with the principles of minimal y invasive in orthopedics. OBJECTIVE: To investigate the biomechanical characteristics of absorbable screw fixation in repair of simple lateral mal eolus fractures by means of finite element technology. METHODS: The three-dimensional model of simple lateral mal eolus fractures and absorbable screw model were established, and then fixed according to standard orthopedic surgical techniques. The reference load when the load bearing of fibulotalar joint reaching the peak value in a normal adult gait cycle was loaded. The stress distribution and displacement of fibula and absorbable screws were analyzed. RESULTS AND CONCLUSION: There were total y 38 542 units, 8 790 nodes in the single screw fixation model. When the articular facet of lateral mal eolus loading 300 N, the maximum stress of screws was 89.35 MPa, the maximum displacement was 0.5 mm, the maximum displacement of the distal fracture was 0.5 mm. When the articular facet of lateral mal eolus loading 450 N, the maximum stress of screws was 152.58 MPa, the maximum displacement was 0.59 mm, the maximum displacement of the distal fracture was 0.77 mm. There were total y 43 115 units, 9 496 nodes in the double screws fixation model. When the articular facet of lateral mal eolus loading 300 N, the maximum stress of screws was 38 MPa, the maximum displacement was 0.44 mm, the maximum displacement of the distal fracture was 0.44 mm. When the articular facet of lateral mal eolus loading 450 N, the maximum stress of screws was 66.68 MPa, the maximum displacement was 0.48 mm, the maximum displacement of the distal fracture was 0.49 mm. The experiment verified the biomechanical feasibility of absorbable screw fixation in repair of simple lateral mal eolus fractures. For simple involving only the lower lateral fibular fracture, absorbable screw fixation is entirely feasible, and usual y requires at least two screws to maintain the stability of the articular surface of the reset.
ABSTRACT
BACKGROUND:For unstable intertrochanteric fracture repair, there are two views:extramedul ary fixation or intramedul ary fixation. Theoretical y, intramedul ary fixation is in line with the principles of minimal y invasive, more mechanical and biological advantages. However, evidence-based medicine and related studies have shown that compared with the extramedul ary fixation, intramedul ary fixation did not reflect the proper theoretical advantage. OBJECTIVE:To compare the biomechanical performance of two kinds of internal fixation systems:dynamic hip screw and Gamma nail which commonly used in repair of intertrochanteric fractures by finite element method, and to evaluate the advantages and disadvantages of dynamic hip screw and Gamma nail in treatment of unstable intertrochanteric fracture. METHODS:Three-dimensional finite element model of human femur unstable intertrochanteric fractures (31-A2;AO fracture classification), and the three-dimensional finite element models of dynamic hip screw and Gamma nail were established respectively, and were fixed according to the requirement of orthopedic surgery. The reference load which the joint bearing was at the peak time in adult step state period with the body mass of 700 N was stimulated. The stress distribution of bone, bone-internal fixation model, nail or screw, the strain and deformation of fracture location on the surface of the bone and bone-internal fixation model, the stress distribution along the femur and the loading transfer condition along the internal fixator and the like were analyzed. RESULTS AND CONCLUSION:Dynamic hip screw and Gamma nail have good sliding compression features which could make the continuous and dynamical y axial compression of the fractured section. Under the load conditions, the displacement value of dynamic hip screw was larger. In the treatment of unstable intertrochanteric fracture, Gamma nail was stronger than dynamic hip screw. Two kinds of internal fixations al make the bearing load of the proximal femur reduce. In the treatment of 31-A2 type unstable intertrochanteric fractures, we should choose dynamic hip screw for fixation if the femoral calcar was not seriously crushed, little defect or no defects and can immediately rebuild the stability of femoral calcar during operation, otherwise, stronger internal fixation, namely Gamma nail fixation should be chosen.
ABSTRACT
Objective To evaluate the medium and long term follow-up results of vascularized bone grafts dorsal distal radius in treatment of chronic scaphoid nonunion. Methods A retrospective study was carried out in 13 patients with chronic scaphoid nonunion treated with vascularized bone grafts dorsal distal radius in our hospital from 1995 to 2006. Nine patients were accompanied by avascular necrosis of the proximal pole. The vascular pedicle was 1,2 intercompartmental supraretinacular artery. The nonunion was stabilized by screws or external fixators. Radiographic finding and Mayo scoring system on wrist mobilization were used to evaluate the clinical outcomes. Results The interval between injury and treatment was average 22.2 months. All patients were followed up for average 76.6 months, which showed that 12 patients obtained fracture union, with average union time of 11.2 weeks. Functional evaluation results were defined as excellent in three patients, good in eight and fair in two. The last follow-up revealed significant improvement of the range of motion of the wrist, Mayo scores, grip strength, intrascaphoid angles and scapholunate angles. Conclusions Vascularized bone grafts from dorsal distal radius has relatively surgical procedure and can achieve satisfactory results in management of scaphoid nonunion. The perioperative arthrolysis and early postoperative mobilization of the wrist under exernal fixation play critical role in restoration of wrist function.
ABSTRACT
Objective To evaluate the medium-term follow-up outcomes of treatment of chronic scaphoid nonunion with vascularized bone graft based on 1, 2 intercompartmental supraretinacular artery.Methods From February, 1995 to November, 2006, 13 cases of chronic scaphoid nonunion were treated with vascularized bone graft based on 1, 2 intercompartmental supraretinacular artery in our hospital. Nine cases were complicated with avascular necrosis of the proximal pole. The interval between injury and treatment averaged 22. 2 months. The nonunions were stabilized by screw or external fixator. Procedures of arthrolysis were applied and early wrist mobilization was initiated under the protection of external fixator. Radiographic finding and Mayo scoring system were used to evaluate the clinical outcomes. Results The mean time of follow-up was 82.9 months. The union time for the 13 cases averaged 11.2 weeks. At the final follow-up,there were 3 excellent, 8 good and 2 fair evaluations;the range of motion of the wrist, Mayo score, grip strength, intrascaphoid angle and scapholunate angle were significantly improved. Conclusions Chronic scaphoid nonunion can be well treated with vascularized bone graft based on 1, 2 intercompartmental supraretinacular artery. A simple arthrolysis during the procedure can produce satisfactory results. External fixation plays a critical role in early mobilization and functional restoration of the wrist.