Containment and Stabilization of Bone Graft in Anterior Lumbar Interbody Fusion: The Role of the Hartshill Horseshoe Cage

The Hartshill Horseshoe cage is a titanium implant that is inserted after removal of the disc in anterior lumbar interbody fusion. The authors use corticocancellous iliac crest graft, which is contained within the confines of the implant. The cage and the motion segment are stabilized by inserting screws into the adjacent vertebral bodies through holes in the implant. Between 1995 and 1997, 27 patients had this implant inserted. Minimum follow-up was 2.1 years (mean: 2.9 years). Patients were assessed using the Oswestry disability index, a core set of six questions, a pain drawing, and psychometrically using the Zung Depression Scale and the Modified Somatic Perception Questionnaire. The patients' subjective assessment was also obtained. Twenty-one patients (77.8%) improved significantly on the Oswestry disability index and 22 patients (81.5%) improved by subjective assessment using the "core set" of six questions. There was no evidence of pseudarthrosis, loosening, or osteolysis around the implant or the screws. The cage prevents graft extrusion, collapse, or sinkage through the endplates. The normal lumbar lordosis is restored and, by restoring normal intervertebral disc space height, the Horseshoe opens up the neural foraminae. This cage stabilizes the motion segments and secures the graft, preventing micromotion at the graft vertebral body interface and providing a conducive environment for fusion.