Abstract
Aggressive bone neoplasms, such as giant cell tumors, often affect the proximal tibia warranting bony resection via curettage leaving behind massive defects that require extensive reconstruction. Reconstruction is usually accomplished with poly(methyl methacrylate) (PMMA) packing supplemented with an internal fixation construct. The purpose of this study is to compare Steinmann pin augmentation to locking plate constructs to determine which offers the stiffer reconstruction option.
Large defects were created below the lateral condyle of fresh frozen tibias. The defects extended for an average of 35 mm beneath the lateral plateau in the frontal plane, and from the anterior to posterior cortex in the sagittal plane. Distally the defect extended for an average of 35 mm to the metadiaphyseal junction. In the Pin group, the tibias were reconstructed with three 4-mm diameter Steinmann pins placed in the medullary canal and PMMA packing. In the Plate group, the tibias were reconstructed with a 6-hole 3.5-mm LCP Proximal locking plate fixed to the proximal-lateral tibia utilizing seven 3.5-mm screws and PMMA packing. The tibias were tested for stiffness on a MTS machine by applying up to 400 N to the tibial plateau in force control at 5 N/s. Fatigue properties were tested by applying a haversine loading waveform between 200 N and 1,200 N at 3 Hz simulating walking upstairs/downstairs.
Locking plate constructs (801.8 ± 78 N/mm) had greater (p = 0.041) stiffness than tibial constructs fixed with Steinmann pins (646.5 ± 206.3 N/mm).
Permanent deformation was similar between the Pin and Plate group; however, two tibia from the Pin group exhibited displacements >5 mm which we considered failure.
n/a.