Reduction and ring fixation of instable C1 fractures with monoaxial pedicle screws.

INTRODUCTION: Ring fixation of C1 can be performed using pedicle screws and a rod in case of unstable Jefferson or lateral mass fractures of C1. MATERIALS AND METHODS: In a case series of three patients, we stabilized C1 fractures surgically using a modified technique of C1 ring fixation by using monoaxial instead of polyaxial screws. Functional outcome and pain was recorded postoperatively. RESULTS: In this very small case series, we observed good results concerning pain and functional outcome. All fractures were bony healed within 13 weeks. In one case, a screw penetrated the spinal canal and had to be repositioned. A mild irritation of C2 nerve root occurred in two cases postoperatively. CONCLUSION: C1 Ring fusion with monoaxial screws provides a good ability to reduce the fracture indirectly by the screws and the rod itself.

Demineralization after balloon kyphoplasty with calcium phosphate cement: a histological evaluation in ten patients.

PURPOSE: Balloon kyphoplasty (BKP) with calcium phosphate cement (CPC) is increasingly being used for spinal surgery in younger patients. In routinely performed follow-up CT scans we observed considerable areas of demineralization in CPC processed vertebrae in several patients. To rule out infections or inflammations histological examinations were planned for these patients. METHODS: Ten patients (23-54 years; six men) with significant demineralization areas in CT scans after CPC balloon kyphoplasty were selected. Punch biopsies from these areas were taken in local anesthesia using a biopsy needle. One half of the specimen was decalcified and embedded in paraffin, and sections were examined histologically using hematoxylin and eosin, Van Gieson, and trichrome staining. The second half of the specimen was cast directly in methyl methacrylate and sections were examined by Paragon and von Kossa/Safranin staining. Stained slides were viewed under light microscopy. RESULTS: Bone-punch specimens were taken at 17.5 months (mean) after BKP with CPC. In most cases, the cement was well surrounded by newly formed lamellar bone with very tight connections between the cement and new bone. Unmineralized areas were observed sporadically at the cement surface and adjacent to the implant. There were no pronounced signs of inflammation or osteolysis of adjacent bone. No complications were observed during or following patients' biopsy procedures. CONCLUSIONS: CPC demonstrated good biocompatibility and osseointegration in clinical use, with no evidence of inflammation or osteonecrosis. Demineralized areas in CT scans could be a result of remodeling of the cancellous bone in vertebral bodies.