Biomechanical analysis of anterior poly-methyl-methacrylate reconstruction following total spondylectomy for metastatic disease.

STUDY DESIGN: Three reconstruction options were evaluated biomechanically following total spondylectomy using human cadaveric spine specimens. OBJECTIVES.: To evaluate and compare the stability of combined anterior and posterior fixation incorporating poly-methyl-methacrylate with alternative accepted reconstruction techniques. SUMMARY OF BACKGROUND DATA: Total spondylectomy represents the most radical option for decompression in metastatic spinal cord compression. Poly-methyl-methacrylate is considered a useful adjunct in spinal column stabilization and arthrodesis; however, there is little published biomechanical data to support its use in this setting. METHODS: Ten fresh-frozen human cadaveric spines (T9-L3) were used. After intact analysis, a total spondylectomy was performed at T12. Three potential reconstruction techniques were tested for their ability to restore stiffness to the specimen: 1) multilevel posterior pedicle screw instrumentation from T10-L2; 2) anterior instrumentation (ATL Z plate II) and rib graft at T11-L1 with multilevel posterior pedicle screw instrumentation from T10-L2; and 3) anterior cement (Simplex P) and pins construct (T12) with multilevel posterior pedicle screw instrumentation from T10-L2. Each of the three potential reconstruction techniques was tested on each specimen in random order using nondestructive testing under load control. RESULTS: Only combined stabilization techniques (e.g., anterior instrumentation and rib graft with multilevel posterior pedicle screw instrumentation and anterior cement-and-pins construct with multilevel posterior pedicle screw instrumentation) restored stiffness to a level equivalent to or higher than that of the intact spine in all loading modes (P < 0.05). Anterior cement-and-pins construct with multilevel posterior pedicle screw instrumentation provided more stability to the specimen than anterior instrumentation and rib graft with multilevel posterior pedicle screw instrumentation in compression and flexion testing (P < 0.05). Posterior instrumentation alone did not restore stiffness to the intact level in compression and flexion testing (P < 0.005). CONCLUSIONS: Combined anterior and posterior reconstruction using a cement construct provides equal to or more stability than the intact spine in all testing modes. Posterior stabilization alone is an inferior method of reconstruction following total spondylectomy. Poly-methyl-methacrylate has the advantage over traditional anterior reconstruction techniques in that it can be inserted using a posterior approach.

[Preliminary evaluation of the efficacy of transpedicular refilling of spongiosa loss with autologous grafts in thoraco-lumbar vertebral bodies using the Daniaux method]. / Wczesna ocena skutecznosci transpedikularnego wypelniania przeszczepami ubytków kosci gabczastej zlamanych trzonów kregów piersiowo-ledzwiowej czesci kregoslupa wg Daniaux.

In Orthopaedic University Clinic in Lublin there were 35 patients with thoraco-lumbar spine fractures since 1993 to 1997. In 18 operated patients fractures of vertebral bodies were reduced and bone loss refilled by autogenous morselised grafts implanted through arc's basis using Daniaux method. There were 9 L1 fractures, 6 Th12 and single one on levels of Th11, L2 and L3. Complete spinal cord injury had 5 patients and partial 13. The degree of vertebral body compression was counted using Taillard's formula preoperatively, 4 weeks, 6 and 12 months after surgery. The anterior wall of vertebral body was decline ranged from 20% to 77%, average 51.9%. There were evaluations of 7 patients 6 months from fixator removal. Presented results support the opinion that operative reconstruction of vertebral body's fracture with autologous spongiosa grafts implantation in place of bone loss gives better chance for anterior wall height reconstitution. Small loss of correction after metal fixator removal, average 7.7%, testify good graft's remodeling and sufficient durability of Daniaux's method of treatment.

Vertebral column allografts for the treatment of segmental spine defects. An experimental investigation in dogs.

Vertebral column allografts, with their intervertebral discs, were implanted into thoracic spine defects (T7-T9) in 11 dogs in an attempt to re-establish spinal stability and preserve spinal biomechanics. Before implantation, the allografts were harvested under sterile conditions from similar-sized dogs and deep frozen at -80 C. The animals were followed for 18 months postoperatively. Radiographs demonstrated gradual loss of intervertebral disc height. Biomechanical analysis showed that the dogs with allografts had no significant difference in spine stiffness compared with normal spines in compression, flexion, and extension testing. Control spines that had been fused were significantly stiffer than the allograft spines in all modes tested (P less than 0.05). Histologic analysis showed incorporation of the allograft but with incomplete revascularization of the allograft's eighth thoracic body. This investigation found that vertebral body allografts with intervertebral discs can function successfully for 18 months in a canine model. This research may assist in the development of physiologic treatment for spinal deficiencies in humans.