Outcomes following structural allograft-chain impaction kyphoplasty

Kyphoplasty (KP) commonly uses bone cement to augment vertebral bodies and to reduce pain after a compression fracture or vertebral collapse. However, cement may pose risk of extravasation and potentially compromise future operations on the injured vertebral body. Impaction grafting with allografts is a commonly used orthopedic technique to support weak bones, fill bone voids, and restore normal bone within a region. The goal of this study is to evaluate height restoration, pain relief, and extravasation in a 1-year follow-up of patients who underwent impaction grafting kyphoplasty with allograft.

Patients underwent impaction grafting kyphoplasty procedures either with or without an initial cavity. Preoperative and 1-year postoperative MRI and CT images were used to determine vertebral height (corrected for adjacent vertebrae) and incidence of adjacent vertebral fractures. In addition, pain relief using the NRS was measured over the 6-month postoperative period. Incidence of extravasation and presence of a radiolucent halo were measured for each vertebra 1-year postoperatively. The unit of analysis for clinical outcomes was the patient and for radiological outcomes was the vertebra. Paired t-tests were used to compare pre- and postoperative vertebral heights and NRS pain scores.

Vertebral body height was maintained (>0 mm change) in 41 (51%) of 80 vertebrae, and 28 (35%) increased more than 1 mm. The average increase for 80 vertebral bodies was 0.35 mm (±3.94). The average pre-op pain score was 8.08, the average post-op pain was 3.23 (±2.16) at 1 to 3 months and 3.48 (±2.47) at 4 to 6 months. All post-op timepoints showed a significant reduction (p = .00) from pre-op pain levels. There was regional graft extravasation in 22 (27.5%) vertebrae, with the most frequent sites being the intervertebral disc (18 vertebrae, 22.5%) followed by perivertebral soft tissue (3, 3.75%) and spinal canal (1, 1.25%). No patients presented with venous extravasation. Bony irregularities were remodeled after 1 year, and extravasated bone diminished in size or disappeared.

Impaction grafting KP appears to be a viable and safe alternative to traditional cement KP for vertebral compression fractures. Impact grafting appears to produce height maintenance and improve pain scores postoperatively. When compared to cementation published data, allograft impaction has comparable pain reduction, may avoid venous extravasation, and allows future bony restoration.