Papagelopoulos Panayiotis J, Currier Bradford L, Neale Patricia G, Hokari Yukitaka, Berglund Lawrence J, Larson Dirk R, Fisher Dean R, An Kai-Nan
Department of Orthopedic Surgery, Mayo Clinic and Mayo Foundation, Rochester, MN, USA.
Clin Orthop Relat Res. 2003 Jun(411):13-24. doi: 10.1097/01.blo.0000068359.47147.bd.
Sixteen fresh-frozen spines from cadavers (C4-T1) were randomized on the basis of dual energy xray absorptiometry analysis of bone mineral density. The specimens were subjected to physiologic loads (<or= 1.5 N-m) in a device that applied pure unconstrained, flexion and extension, lateral bending, and torsional moments. After a major injury, including a wide C6 laminectomy, bilateral capsulectomies, and 65% facetectomy at C6-C7, four constructs were applied to each specimen in a balanced sequence, and the stability tests were repeated. All the constructs were identical posterior cervical rods secured to the spine with lateral mass screws in C5 and pedicle screws in C7. The constructs differed only in the presence or absence of a transverse connector between the rods, presence or absence of lateral mass screws in C6, and unicortical or bicortical lateral mass screws. Insertional screw torque was higher in specimens with greater bone mineral density. Pedicle screws had greater torque than lateral mass screws. Posterior cervical spine rod fixation provided an equivalent stability by use of either unicortical or bicortical lateral mass screws. A transverse stabilizer between the rods reduces the number of lateral mass screws needed in posterior cervical spinal rod systems. Repeated stability tests, even when done with physiologic loads, may compromise the screw-bone interface. This effect is most pronounced in specimens that have low bone mineral density.
对16具尸体（C4 - T1）的新鲜冷冻脊柱进行双能X线吸收法骨密度分析，并据此进行随机分组。将标本置于一个能施加纯无约束、屈伸、侧弯和扭转力矩的装置中，使其承受生理负荷（≤1.5 N - m）。在造成包括广泛的C6椎板切除术、双侧关节囊切除术以及C6 - C7节段65%的小关节切除术等严重损伤后，以平衡的顺序对每个标本应用四种固定结构，并重复稳定性测试。所有固定结构均为相同的后路颈椎棒，通过C5的侧块螺钉和C7的椎弓根螺钉固定于脊柱。这些固定结构的区别仅在于棒之间是否存在横向连接体、C6是否存在侧块螺钉以及侧块螺钉是单皮质还是双皮质。骨密度较高的标本中，螺钉的插入扭矩更高。椎弓根螺钉的扭矩大于侧块螺钉。后路颈椎棒固定采用单皮质或双皮质侧块螺钉时提供的稳定性相当。棒之间的横向稳定器可减少后路颈椎棒系统所需的侧块螺钉数量。即使在生理负荷下进行重复稳定性测试，也可能损害螺钉 - 骨界面。这种影响在骨密度低的标本中最为明显。
