Vertebral body stenting: a new method for vertebral augmentation versus kyphoplasty

Vertebroplasty and kyphoplasty are well-established minimally invasive treatment options for compression fractures of osteoporotic vertebral bodies. Possible procedural disadvantages, however, include incomplete fracture reduction or a significant loss of reduction after balloon tamp deflation, prior to cement injection. A new procedure called “vertebral body stenting” (VBS) was tested in vitro and compared to kyphoplasty. VBS uses a specially designed catheter-mounted stent which can be implanted and expanded inside the vertebral body. As much as 24 fresh frozen human cadaveric vertebral bodies (T11-L5) were utilized. After creating typical compression fractures, the vertebral bodies were reduced by kyphoplasty (n = 12) or by VBS (n = 12) and then stabilized with PMMA bone cement. Each step of the procedure was performed under fluoroscopic control and analysed quantitatively. Finally, static and dynamic biomechanical tests were performed. A complete initial reduction of the fractured vertebral body height was achieved by both systems. There was a significant loss of reduction after balloon deflation in kyphoplasty compared to VBS, and a significant total height gain by VBS (mean ± SD in %, p < 0.05, demonstrated by: anterior height loss after deflation in relation to preoperative height [kyphoplasty: 11.7 ± 6.2; VBS: 3.7 ± 3.8], and total anterior height gain [kyphoplasty: 8.0 ± 9.4; VBS: 13.3 ± 7.6]). Biomechanical tests showed no significant stiffness and failure load differences between systems. VBS is an innovative technique which allows for the possibly complete reduction of vertebral compression fractures and helps maintain the restored height by means of a stent. The height loss after balloon deflation is significantly decreased by using VBS compared to kyphoplasty, thus offering a new promising option for vertebral augmentation

Anatomy of Knee Arthritis - Consequences for the Planning of TKAs

Background: Principles in total knee arthroplasty include a reconstructed mechanical axis and minimal bone loss. So far no study has analysed the anatomy of knee arthritis and its consequences for the implant planning. Therefore it has been the aim of our study to analyse typical deformities of arthritic knees and their consequences for the implant planning. Material and Methods: The data of 712 navigated total knee arthroplasties have been analysed. The deformities of the tibia and femur were measured. Algorithms have been developed to calculate the optimal tibial and femoral resection depths. Results: The deformity in varus arthritis must be corrected on the tibial side, in valgus arthritis on the femoral side. The optimal tibial resection depth in varus arthritis corresponds to the thinnest insert; in valgus arthritis 3 mm less is adequate. The femoral resection depth in varus arthritis corresponds to the implant thickness; in valgus arthritis a 1 mm deeper resection is mostly required. Conclusions: Varus and valgus deformities significantly differ in location of the deformity and required resection depth. A knowledge of these typical deformities enables an intraoperative control of the axis correction. A reduced tibial resection depth in valgus deformities saves bone stock for revision surgery and avoids larger insert sizes