Biomechanical Analysis of Humeral Diaphyseal Segmental Defect Fixation

Does the Second-generation Intercalary Humeral Spacer Improve on the First?

“…Single-cycle torque to failure showed the spacer devices to have a greater peak torque (mean, 41.4 N-m) and stiffness (mean, 2.1 N-m/degrees) than intramedullary nail specimens with cemented stems and cement in the defect (mean peak torque, 23.1 N-m; mean stiffness, 1.6 N-m/degrees). Both the intercalary spacers and the cement/intramedullary nail constructs were stronger and stiffer than an intercalary allograft nail composite specimen without supplemental cement (mean peak torque, 12.4 N-m; mean stiffness, 0.6 N-m/degrees) [8].…”

“…The second-generation lap joint intercalary spacer devices have also been studied in the biomechanics laboratory using a 5-cm middle third segmental defect model in allograft bone [8]. Single-cycle torque to failure showed the spacer devices to have a greater peak torque (mean, 41.4 N-m) and stiffness (mean, 2.1 N-m/degrees) than intramedullary nail specimens with cemented stems and cement in the defect (mean peak torque, 23.1 N-m; mean stiffness, 1.6 N-m/degrees).…”

“…However, in exceptional situations with extensive cortical destruction or segmental diaphyseal bone loss, conventional treatment may not yield stable fixation even with supplemental cement. In these situations, standard means of fixation may have a higher risk of device failure or at least a lower likelihood of providing immediate stability to most completely restore function [1,3,8,12].…”

“…One option in this situation is the use of a cemented intramedullary spacer device [1,3,8,12]. This device has previously been reported in a smaller series of patients in whom an early version of the device was implanted [3].…”

Outcome of the intramedullary diaphyseal segmental defect fixation system for bone tumors

“…Despite the potential complications including mechanical failure and infection [30], megaprostheses including segmental diaphyseal implants [22,31,32] or interposition metallic spacers [33][34][35][36] remain the main option for reconstruction after limb salvage surgery for bone tumors with up to 68% 10-year survival [19,[37][38][39]. Their advantages include preservation of the physes in children, preservation of joint function, immediate postoperative stability, early weight-bearing and rapid rehabilitation, off-the-shelf availability, and low infection rate [13,14,16,19,30,37,38,[40][41][42][43].…”