Cross, William

AbstractPeriprosthetic fractures around a total knee arthroplasty (TKA), comminuted and intra-articular femur fractures, or fracture nonunions in osteoporotic bone represent technically challenging problems. This is particularly true when the fracture involves a loose femoral component or the pattern results in suboptimal fixation potential. These clinical indications often arise in an older and comorbid patient population in whom a principal goal of treatment includes allowing for early mobilization. Limited data indicate that arthroplasty via distal femoral replacement (DFR) is a reasonable alternative to open reduction and internal fixation, allowing for early ambulation with low complication rates. We performed a retrospective review of trauma and arthroplasty surgeries at three tertiary referral institutions. Adult patients treated for the above with a DFR were included. Patients with active infection, open and/or high-energy injuries and revisions unrelated to fracture were excluded. Patient demographics, treatment details, and outcomes were assessed. Between 2002 and 2017, 90 DFR's were performed for the above indications with a mean follow-up of 24 months. Postoperatively, 80 patients (88%) were allowed to weight bear as tolerated, and at final follow-up, 9 patients (10%) remained dependent on a wheelchair. The average arc of motion at final follow-up was 95 degrees. There were seven (8%) implant-related complications requiring secondary surgeries: two infections, one with associated component loosening; one fracture of the hinge mechanism and one femoral component failure in conjunction with a patellofemoral dislocation (both requiring revision); one case of patellofemoral arthrosis in a patient with an unresurfaced patella; one periprosthetic fracture with associated wound dehiscence; and one case of arthrofibrosis. In each of these cases, only modular components of the DFR were exchanged. All nonmodular components cemented into the femur or tibia were retained. DFR provides a viable reconstruction option in the treatment of acute distal femur fractures, periprosthetic femur fractures, and fracture nonunions. We noted that in an elderly patient population with high comorbidities, the complication and secondary surgery rates remained relatively low, while allowing for immediate weight bearing.

Objectives: To validate a neck-shaft angle (NSA) correction formula using the known angle between the medullary nail and lag screw of an indwelling cephalomedullary nail (CMN). Methods: Pertrochanteric femur fractures were created in 7 synthetic femurs and reconstructed with a CMN. Anteroposterior x-rays were taken with the proximal femur in 0, 15, 30, and 45 degrees of internal/external rotation and 10 and 20 degrees of flexion with neutral rotation. The femoral NSA and the nail angle were measured on anteroposterior x-rays. The corrected NSA was obtained by multiplying the known nail angle by the quotient of the measured NSA over the measured nail angle. Results: With increasing degrees of internal or external rotation, the difference between the actual and the measured NSA increased. After correction using the known angle of the nail, the measured NSA was reduced to within 3 degrees of the actual NSA over all degrees of rotation. At neutral rotation, 15 degrees of external rotation, and 10 and 20 degrees of hip flexion, there was minimal difference between the actual NSA and the measured NSA, negating the effect of the correction formula. Conclusions: The measured NSA after CMN of intertrochanteric fractures is altered by hip rotation. This study validates the correction formula, which determines this difference by using the known angle between the lag screw and the nail.

Objectives: To determine whether fixation of pertrochanteric hip fractures with cephalomedullary nails (CMNs) with a neck-shaft angle (NSA) less than the native NSA affects reduction and lag screw cutout. Design: Retrospective comparative study. Setting: Level I trauma center. Patients/Participants: Patients treated with a CMN for unstable pertrochanteric femur fractures (OTA/AO 31-A2.2 and 31-A2.3) between 2005 and 2014. Intervention: CMN fixation. Main Outcome Measurement: NSA reduction and lag screw cutout. Results: Patients fixed with a nail angle less than their native NSA were less likely to have good reductions [17% vs. 60%, 95% confidence interval (CI), −63% to −18%; P = 0.0005], secondary to more varus reductions (41% vs. 10%, 95% CI, 9%–46%; P = 0.01) and more fractures with ≥4 mm of displacement (63% vs. 35%, 95% CI, 3%–49%; P = 0.03). The cutout was not associated with the use of a nail angle less than the native NSA (60% vs. 76%, 95% CI, −56% to 18%; P = 0.5), varus reductions (60% vs. 32%, 95% CI, −13% to 62%; P = 0.3), or poor reductions (20% vs. 17%, 95% CI, −24% to 44%; P = 1.0). Conclusions: The fixation of unstable pertrochanteric hip fractures with a nail angle less than the native NSA was associated with more varus reductions and fracture displacement but did not affect the lag screw cutout. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.