Anterior Lumbar Interbody Fusion with a Novel Polycaprolactone-based Resorbable Cage

INTRODUCTION Anterior lumbar interbody fusion (ALIF) is an increasingly common surgical procedure performed in the clinical management of several spinal conditions including debilitating low back pain, spinal instability and scoliosis. In classical ALIF, metallic cages packed with autograft bone are implanted into a bone bed prepared at the target intervertebral disc space. Implanted cages function to stabilize the anterior element of the spinal column and provide suitable environment for bone ingrowth that will initiate bone healing and fusion. The architectural design of the implanted fusion cage has been recognized as a key factor modulating the mechanical dynamics and biological functions of the bone–scaffold system in ALIF. With metallic cages, stress shielding effects from mechanical incompatibilities with host bone and donor site morbidities are some of the serious drawbacks reported. Bone tissue engineering with biodegradable scaffolds that are mechanically and biologically compatible with host bone could offer a more efficient method of spinal arthrodesis in ALIF. Our group recently developed a new osteoconductive and resorbable scaffold (PCL-TCP biocage) fabricated from polycaprolactone -20% tricalcium phosphate and with a distinctive design for bone tissue engineering at weight bearing sites (Fig. 1) [1]. PCL-TCP biocage designed with a honeycomb-architecture has a wholly interconnected network of fenestrations and several pore orientations or lay down patterns were produced. In vitro studies showed that PCL-TCP biocage with 65-70% porosity, pore size distribution between 350-500 μm and a 0/90 lay down pattern exhibits excellent biomechanical properties including torsional stiffness comparable to cancellous bone. The main objective of this present study was to evaluate the fusion performance of PCL-TCP biocage in a large animal model of ALIF.