STUDY DESIGN: Retrospective comparative study and technical note. PURPOSE: To determine if there is a difference in clinical and radiographic parameters between unilateral and bilateral kyphoplasty in a uniform cancer population and to stress the importance of preoperative planning. OVERVIEW OF LITERATURE: While unipedicular kyphoplasty is gaining popularity, a few comparative studies have reported on superior kyphotic reduction with the bipedicular approach. METHODS: We reviewed 69 myeloma patients with 105 operated levels (51 levels were done bilaterally vs. 54 unilaterally). Pain reduction, height restoration, cement volume and complications were recorded up to three months postoperatively. A technical note to identify the skin entry point on the basis of the magnetic resonance imaging and fluoroscopy (lateral view) is being described. RESULTS: Both procedures resulted in significant pain reduction (5.4-5.6/10 points, p=0.8). There was significant height restoration after the operation (p<0.001), while there was no sustained difference between the procedures (p=0.5) up to three months postoperatively. More cement was injected in the bilateral group (4.1 mL vs. 4.9 mL, p=0.002); no difference in cement extravasation in the spinal canal was observed (p=0.5). CONCLUSIONS: There was no difference in the clinical or radiological outcomes between the unilateral and bilateral approaches. Therefore, unilateral kyphoplasty may be performed whenever it is technically feasible and this may be determined preoperatively.
Fluoroscopy ; Fractures, Compression ; Humans ; Kyphoplasty* ; Magnetic Resonance Imaging ; Multiple Myeloma* ; Retrospective Studies ; Skin ; Spinal Canal

Methods: Model 1 (M1) was an intact C2C6 model with a 0.5 mm endplate. In model 2 (M2), a cage was implanted after removal of the C4–C5 and C5–C6 discs with preservation of the osseous endplate. In model 3 (M3), 1 mm of the osseous endplate was removed at the upper endplate. Model 4 (M4) resembles M3, except that 3 mm of the osseous endplate was removed. Results: The range of motion (ROM) at C2C6 in the M2–M4 models was reduced by at least 9º compared to the M1 model. The von Mises stress results in the C2C3 and C3C4 interbody discs were significantly smaller in the M1 model and slightly increased in the M2–M3 and M3–M4 models. Migration and subsidence decreased from the M2–M3 model, whereas further endplate removal increased the migration and subsidence as shown in the transition from M3 to M4. Conclusions The M3 model had the least subsidence and migration. The ROM was higher in the M3 model than the M2 and M4 models. Endplate preparation created small stress differences in the healthy intervertebral discs above the ACDF site. A 1 mm embedding depth created the best balance of mechanical strength and contact area, resulting in the most favorable stability of the construct.

The cervical spine poses many complex challenges that require complex solutions. Anterior cervical discectomy and fusion (ACDF) has been one such technique often employed to address such issues. In order to address the problems with ACDF and assess the modifications that have been made to the technique over time, finite element analyses (FEA) have proven to be an effective tool. The variations of cervical spine FEA models that have been produced over the past couple of decades, particularly more recent representations of more complex geometries, have not yet been identified and characterized in any literature. Our objective was to present material property models and cervical spine models for various simulation purposes. The outlining and refinement of the FEA process will yield more reliable outcomes and provide a stable basis for the modeling protocols of the cervical spine.