Assessment of Intraosseous Femoral Head Pressures During Cement Augmentation of the Perforated Proximal Femur Nail Antirotation Blade

Abstract

The benefits of cement augmentation with fixation of osteoporotic pertrochanteric fractures have been previously demonstrated. The objective of this study was 3-fold: (1) To quantify the intraosseous pressure produced during cement augmentation of the perforated proximal femoral nail antirotation (PFNA) blades; (2) To assess whether the pressure generated is influenced by the injection rate; and (3) To assess the amount of force applied during the injection. Six pairs of human cadaveric femurs were used in the study. A basicervical osteotomy was performed, and the heads were instrumented with the PFNA blade. Each pair was randomly assigned into 1 of 2 groups: slow versus rapid injection with polymethylmethacrylate (PMMA) cement. In the slow group, the augmentation was performed using 6 consecutive 1 mL injections, each over 10 seconds. In the rapid group, each 1 mL injection was performed over 5 seconds. For intraosseous pressure measurements, transmitters were inserted to a depth of 5 mm at both the superior and inferior apices of the head. The reaction forces on the syringe were measured as well. There were no significant differences between the slow and rapid injection rates with respect to the peak pressures measured at the 6 time points immediately after cement injection. In both groups, elevations in pressure were transient and returned to baseline values within 30 seconds. The highest pressure recorded in the slow group was 37.3 and 30.7 mm Hg in the rapid group. The force required after each sequential injection increased in both groups; however, significantly higher forces were required to inject cement over 5 than 10 seconds (P = 0.036). This in vitro model is the first one to demonstrate that femoral head cement augmentation is associated with a small transient increase in intraosseous pressure with sequential fast and slow 1 mL injections of up to 6 mL PMMA. We conclude that cement augmentation of the perforated PFNA blade carries a low risk of pressure-induced avascular necrosis.