Cement interdigitation and bone-cement interface after augmenting fractured vertebrae: A cadaveric study

Abstract

BackgroundThe treatment of painful osteoporotic vertebral compression fractures with transpedicular cement augmentation has grown significantly over the last 20 years. There is still uncertainty about long-term and midterm effects of polymethyl methacrylate in trabecular bone. Preservation of the trabecular structures, as well as interdigitation of the cement with the surrounding bone, therefore has been gaining increasing attention. Interdigitation of cement is likely relevant for biological healing and the biomechanical augmentation process. In this study a cutting and grinding technique was used to evaluate the interdigitation for 4 augmentation techniques.MethodsBy use of a standardized protocol, wedge fractures were created in vertebrae taken from a fresh-frozen spine. Thereafter the vertebrae were assigned to 1 of 4 similar groups with regard to the vertebral size and force required to produce the fracture. The 4 groups were randomized to the following augmentation techniques: balloon kyphoplasty, radiofrequency (RF) kyphoplasty, shield kyphoplasty, and vertebral stenting. Histologic analysis was designed to examine the bone structure and interdigitation after the augmentation.ResultsFor the void-creating procedures, the distance between bone and cement was 341.4 ± 173.7 µm and 413.6 ± 167.6 µm for vertebral stenting and balloon kyphoplasty, respectively. Specifically, the trabecular bone was condensed around the cement, forming a shield of condensed bone. The procedures without a balloon resulted in shorter distances of 151.2 ± 111.4 µm and 228.1 ± 183.6 µm for RF and shield kyphoplasty, respectively. The difference among the groups was highly significant (P < .0001). The percentage of interdigitation was higher for the procedures that did not use a balloon: 16.7% ± 9.7% for balloon kyphoplasty, 20.5% ± 12.9% for vertebral stenting, 66.45% ± 12.35% for RF kyphoplasty, and 48.61% ± 20.56% for shield kyphoplasty. The difference among the groups was highly significant (P < .00001).ConclusionsCavity-creating procedures reduce the cement interdigitation significantly and may accordingly reduce the effectiveness of the augmentation procedures.

Stress Distribution at the Bone-cement Interface Changes during Kyphoplasty Rehabilitation

“…Applying these findings in the context of Kyphoplasty, where poor cement interdigitation is prevalent [6], indicates an increased likelihood of sliding at the contact points between the bone and cement. It has been shown [15] that localized deformation at bone-cement contact sites constitute a significant proportion of the deformation seen in the interface region.…”

“…The authors statistically correlated this radiological feature with a 78% re-collapse rate and attributed the phenomenon to a lack of cement interdigitation into the trabecular structure. A recent in-vitro study [6] confirmed cement infiltration and mechanical interlock was restricted following Kyphoplasty due to the presence of compacted bone. Two studies [7,8] involving cyclical loading of Kyphoplasty treated vertebrae showed statistically significant height losses over the course of 100,000 loading cycles to replicate the rehabilitation period.…”

Height and Volume Restoration In Osteoporotic Vertebral Compression Fractures: A Biomechanical Comparison Of Standard Balloon Kyphoplasty Versus Tektona In A Cadaveric Fracture Model

“…Often the balloons have to touch the lateral walls of the vertebral bodies before craniocaudal expansion occurs. Interdigitation of cement with trabecular bone is limited (11). The ideal tool for height restoration and endplate reconstruction would allow the surgeon to direct the power of the device directly to where it is needed inside the vertebral body.…”

Radiofrequency kyphoplasty for the treatment of osteoporotic vertebral fractures: A review of the literature

“…Krüger et al conducted a cadaveric study to assess cement interdigitation and bone-cement interface after vertebral fracture augmentation 8 . This study was the first to evaluate cement interditation on a histological basis.…”