Secondary Displacement was Common in Healing Distal Femur Fractures in a Cohort of Elderly Patients.

Introduction: Surgical treatment of distal femoral fractures (DFFs) in osteoporotic bone is challenging despite improvements in hardware and surgical techniques. The occurrence and degree of secondary displacement during healing after bridging plate fixation are still unknown. This study aimed to assess the occurrence and degree of secondary displacement in healing DFFs in elderly patients and correlate the secondary displacement to body mass index, bone density, and weight-bearing regimen.

Patients and methods: The study involved 32 patients, 65 years or older, with a DFF of AO/OTA types 33 A2-3, B1-2, C1-2, and 32(c) A-C,1-3, including peri-prosthetic fractures with stable implants. Twenty-seven patients had at least 8 weeks of follow-up, and 21 patients had a complete 1-year follow-up. Minimally invasive surgery was performed using a distal anatomical femoral plate as a long bridge-plating construct. Secondary displacement was assessed with computed tomography of the entire femur postoperatively and at 8, 16, and 52 weeks. Femoral length, coronal angulation (varus/valgus), and subsidence as the change in distance between the distal joint surface and a specified locking screw were measured.

Results: There was a statistically significant mean femoral shortening at 52 weeks of 4.7 mm (SD 3.9, (95% CI 2.9-6.5), P < 0.001) mainly by subsidence of the distal fragment. Most patients experienced limited coronal angulation. There was no correlation between body mass index or bone density and secondary displacement. At the 1-year follow-up, no patient needed revision surgery for non-union or plate breakage. Restricted weight-bearing for 8 weeks did not prevent secondary displacements or adverse events such as cut-outs.

Conclusion: Modern dynamic plate osteosynthesis could not prevent commonly occurring fracture subsidence in DFF in an elderly cohort. Restricted weight-bearing for 8 weeks did not prevent secondary displacements or mechanical adverse events.