ABSTRACT
BACKGROUND: Lag screw cut-out failure following fixation of unstable intertrochanteric fractures in osteoporotic bone remains an unsolved challenge. This study tested if resistance to cut-out failure can be improved by using a dual lag screw implant in place of a single lag screw implant. Migration behavior and cut-out resistance of a single and a dual lag screw implant were comparatively evaluated in surrogate specimens using an established laboratory model of hip screw cut-out failure. METHODS: Five dual lag screw implants (Endovis, Citieffe) and five single lag screw implants (DHS, Synthes) were tested in the Hip Implant Performance Simulator (HIPS) of the Legacy Biomechanics Laboratory. This model simulated osteoporotic bone, an unstable fracture, and biaxial rocking motion representative of hip loading during normal gait. All constructs were loaded up to 20,000 cycles of 1.45 kN peak magnitude under biaxial rocking motion. The migration kinematics was continuously monitored with 6-degrees of freedom motion tracking system and the number of cycles to implant cut-out was recorded. RESULTS: The dual lag screw implant exhibited significantly less migration and sustained more loading cycles in comparison to the DHS single lag screw. All DHS constructs failed before 20,000 cycles, on average at 6,638 +/- 2,837 cycles either by cut-out or permanent screw bending. At failure, DHS constructs exhibited 10.8 +/- 2.3 degrees varus collapse and 15.5 +/- 9.5 degrees rotation around the lag screw axis. Four out of five dual screws constructs sustained 20,000 loading cycles. One dual screw specimens sustained cut-out by medial migration of the distal screw after 10,054 cycles. At test end, varus collapse and neck rotation in dual screws implants advanced to 3.7 +/- 1.7 degrees and 1.6 +/- 1.0 degrees , respectively. CONCLUSION: The single and double lag screw implants demonstrated a significantly different migration resistance in surrogate specimens under gait loading simulation with the HIPS model. In this model, the double screw construct provided significantly greater resistance against varus collapse and neck rotation in comparison to a standard DHS lag screw implant.
ABSTRACT
OBJECTIVE: Open intra-articular fractures of the distal humerus can be associated with considerable bone loss and extensive soft tissue damage. The management of these injuries is quite challenging, and the restoration of elbow anatomy may require multiple bone and soft tissue surgical procedures. The purpose of this case report is to present the option of addressing at the same time a complex skin, muscular, and bone distal humerus defect by using a composite vascularized graft. METHODS: We present a case of a high-energy open fracture of the distal humerus in a polytrauma young patient. Apart from the significant damage of all skin layers and underlying muscle units at the posterolateral side of the elbow, the medial column of the distal humerus (6 cm in length) was completely absent. After patient resuscitation and wound debridement, a free vascularized osteocutaneous fibular graft was used for the reconstruction of the bone defect and the restoration of elbow anatomy. RESULTS: No complications were encountered during the postoperative period, and both bone and soft tissues progressed to sound healing. At 26 months follow-up, the patient had a functional and stable elbow and the Mayo Elbow Performance Score was 85 points, which is equivalent to a good result. CONCLUSIONS: Vascularized osteocutaneous fibular graft could effectively address complex traumatic defects of the elbow joint and enhance the potential for bone healing and early functional recovery.