Instrumented Posterolateral Lumbar Fusion Research Articles

773 A Prospective Randomized Study of Mineralized Collagen and Bone Marrow Aspirate versus Iliac Crest Autograft for Instrumented Posterolateral Lumbar Fusion

773 A Prospective Randomized Study of Mineralized Collagen and Bone Marrow Aspirate versus Iliac Crest Autograft for Instrumented Posterolateral Lumbar Fusion

773 A Prospective Randomized Study of Mineralized Collagen and Bone Marrow Aspirate versus Iliac Crest Autograft for Instrumented Posterolateral Lumbar Fusion

773 A Prospective Randomized Study of Mineralized Collagen and Bone Marrow Aspirate versus Iliac Crest Autograft for Instrumented Posterolateral Lumbar Fusion

Endoscopic instrumented posterolateral lumbar fusion with Healos and recombinant human growth/differentiation factor-5.

The goal of this study was to use a minimally invasive endoscopic surgical technique in a sheep model to evaluate the efficacy of an osteoinductive growth factor, recombinant human growth/differentiation factor-5 (also designated MP52), and an osteoconductive matrix formulation (Healos; DePuy AcroMed, Inc., Mountain View, CA) for inducing and facilitating bone formation. Twelve mature sheep underwent bilateral posterolateral lumbar fusion and pedicle screw fixation via a posterior endoscopic approach. Each sheep received two different types of graft material, autogenous iliac crest bone, or a bone graft substitute (MP52 with Healos), inserted into the right and left sides of the spine in an alternating fashion. Groups of four sheep were killed at 2, 4, and 6 months postoperatively for manual, radiographic, and histological evaluation. No neurological impairments, infections, or other complications were observed. After 2 months, partial fusion on both sides was observed, but radiographic evaluation showed greater bone growth on the side that received the bone graft substitute. Solid posterolateral fusion was observed in both autograft and bone graft substitute sites at 4 and 6 months, and autograft and Healos MP52 fusion sites were essentially the same at histological examination. There was no abnormal overgrowth of new bone from either of these two materials. Endoscopic posterolateral lumbar arthrodesis and instrumentation is feasible, safe, and effective in a sheep model. Healos is a useful bonding agent that mimics natural bone in posterolateral intertransverse fusion sites. Combined with MP52, it produced fusion comparable to that of autogenous bone graft. Minimally invasive techniques and bone graft substitutes could eliminate morbidity and increase the likelihood of successful fusion.

107. A biomechanical, histological and radiographic comparison of instrumented versus non-instrumented posterolateral lumbar fusion with osteogenic protein-1 in an ovine model

107. A biomechanical, histological and radiographic comparison of instrumented versus non-instrumented posterolateral lumbar fusion with osteogenic protein-1 in an ovine model

Bilateral Pedicle Stress Fracture after Instrumented Posterolateral Lumbar Fusion

A case of bilateral pedicle stress fracture is reported, and the literature is reviewed. To report the rare case of bilateral pedicle stress fracture after instrumented posterolateral fusion, and to investigate the contributing factors. A 62-year-old man underwent revision spinal surgery for adjacent-segment degeneration. Decompression and instrumented posterolateral fusion from L1 to L3 were performed after removal of the previously inserted pedicular screws. In the patient's history, he had undergone L3-L5 instrumented posterolateral fusion for spinal stenosis 6 years previously. At 1 year after the revision surgery, he presented with severe progressive low back pain. Computer-assisted tomogram and bone scan demonstrated bilateral L4 pedicle stress fracture. To the best of the authors' knowledge, only two cases of pedicle stress fracture after lumbar posterolateral fusion have been reported. This study reviewed the reported patient's medical record, his imaging studies, and related literature. The possible factors contributing to bilateral pedicle stress fractures were investigated. In the reported case, the features of radiographic studies confirmed bilateral pedicle stress fracture. The involved vertebra was L4. In all three cases reported so far, including the current case, the site of the pedicle stress fracture was at the junction of the pedicle and vertebral bodies. Bilateral pedicle stress fracture occurs as a complication of posterolateral lumbar fusion. Pedicle weakening by prior inserted screws and persistent anterior motion after posterolateral fusion are the contributing factors.

Saturday, November 2, 2001 9:31–10:01 am Focused Review: Lumbar Fusion Techniques and Outcomes: 9:31 Radiologic assessment of all the unfused lumbar segments after an instrumented posterolateral lumbar fusion

Purpose of study: It is commonly held that accelerated degeneration occurs in the motion segment adjacent to a fusion. Most studies pay particular attention only to the motion segments immediately adjacent to the fusion.Objective: To examine the long-term effects of posterolateral instrumented lumbar fusion (LF) on all the unfused lumbar segments.Methods used: A total of 212 unfused lumbar segments were evaluated in 62 patients, 32 men and 30 women with a mean age of 45.92 years (range, 23 to 67) in whom LF had been performed. The mean number of fused segments per patient was 1.53 (range, 1 to 4). The fused levels were LA–L5 (19), L5–S1 (15), L4–S1 (11), L3–L5 (9), L3–S1 (4), L2–L3 (1), L2–L5 (1) and L2–S1 (1). Two independent observers, using the AutoCad 2000 and the distortion-compensated method [1], measured lordosis, disc height (DAXc) and dorso-ventral displacement (Dc) of all the noninstrumental lumbar segments in digitized standing lateral radiographs taken immediately before and after surgery, and at a mean follow-up of 7.5 years (range, 4 to 11.5). The collected data were analyzed along with spinopelvic balance and sagittal angular parameters.of findings: DAXc and Dc of the 31 segments below the LF did not show significant differences between before surgery and follow-up. At the first (62 patients), second (59) and third (45) segments above the LF, the same significant (p<.05) loss of DAXc was observed between before surgery and follow-up. Dc of the first, third and fourth (15) cephalad segments did not change between before surgery and follow-up. At the second cephalad segment retrolysthesis increased significantly (p<.01) between before surgery and follow-up. Loss of DAXc did not correlate with changes in lordosis at the LF, spinopelvic balance parameters, number of fused segments and length of follow-up. Age correlated weakly with DAXc decrease (p<.05, r=0.38). Loss of DAXc at the second cephalad segment correlated significantly with loss of DAXc at the first (p<.01, r=0.53) and third (p<.01, r=0.55) cephalad segments.Relationship between findings and existing knowledge: Biochemical studies in human cadaver support the view that fusion in the lumbar spine is likely to be associated with an increased incidence of degeneration at adjacent levels, but there is little reliable information on the incidence of juxtafusion degeneration from the few long-term studies of lumbar spine fusion reported in the literature.Overall significance of findings: After an instrumented lumbar fusion, radiographic changes suggesting disc degeneration appear homogeneously at several levels cephalad to the fusion area and seem to be determined more by individual characteristics than by fusion itself.Disclosures: Device or drug: pedicle screws. Status: approved.Conflict of interest: No conflicts.

9:37 Circumferential lumbar spinal fusion with anterior lumbar interbody fusion Brantigan cage versus posterolateral fusion with titanium CD-Horizon: a prospective, randomized, clinical study of 146 patients

Purpose of study: Circumferential fusion has become a common procedure in lumbar spine fusion both as a primary and as a salvage procedure. The present study documented that ALIF with Brantigan cage improves fusion rate and spinal sagittal alignment and removes pain originating from the disc. We have analyzed the effects of circumferential fusion using ALIF brantigan cages and titanium posterior instrumentation on functional outcome, fusion rate, complications and lumbar lordosis.Methods used: From April 1996 through November 1999, a total of 148 patients with severe chronic low back pain were randomly selected for either posterolateral lumbar fusion (PLF) with titanium CD-Horizon (posterolateral group) or circumferential fusion with ALIF Brantigan cage plus posterior instrumentation (ALF plus group). Dallas Pain Questionnaire (DPQ), Low Back Pain Rating Scale (LBPR) and a questionnaire concerning work status assessed their outcomes. Responses were registered preoperatively and at 1-and 2-year follow-ups.of findings: In both groups, 95% follow-ups at 1 and 2 years showed highly significant improvement in all four categories of life quality (DPQ) as well as in the back pain and leg pain index (LBPR) compared with preoperative status. There was a clear tendency toward better overall functional outcome for patients with the circumferential procedure (p<.08), and this patient group also experienced significantly less leg pain at 1-year follow-up (p<.03) and less peak back pain at 2 years (p<.04). There was no difference in admission days or blood loss, although operation time was significantly longer in the circumferential group. Sagittal lordosis was restored and maintained in the circumferential group (p<.01). Circumferential fusion patients showed a higher posterolateral fusion rate (92%) compared with the posterolateral group (80%; p<.04). The reoperation rate, including implant removal, was significantly lower in the circumferential group (7%; p<.002) versus that in the posterolateral group (22%) in the study period up to 5.5 years postoperatively. The overall study showed a significant correlation between fusion and good functional outcome.Relationship between findings and existing knowledge: To our knowledge, this is the first randomized prospective study to analyze a standardized spinal circumferential fusion procedure with a PLF procedure. Previous randomized controlled studies of supplemental pedicle screw instrumentation in PLF have not been able to show significant difference in clinical outcome between surgical methods. Our results have showed the patients with a circumferential fusion had a 92% union of the PLF mass and improved clinical outcome, significantly different from instrumented posterolateral fusion alone.Overall significance of findings: Circumferential lumbar fusion restored lordosis, provided a higher union rate with significantly fewer reoperations, showed a tendency toward better functional outcome and resulted in less peak back pain compared with instrumented PLF. However, circumferential fusion is a more extensive surgical procedure. The clinical perspective of our study implies a recommendation to favor circumferential fusion as a definitive surgical procedure in complex lumbar pathology involving major instability, flatback and previous disc surgery in younger patients compared with posterolateral fusion with pedicle screws alone.Disclosures: Device or drug: ALIF Brantigan cage. Status: investigational. Device or drug: titanium CDI. Status: approvedConflict of interest: Cody Bünger, grant research support.

Endoscopic instrumented posterolateral lumbar fusion with Healos and recombinant human growth/differentiation factor-5

Daniel Kim, MD, Stanford, CA, USA; Tsai-Sheng Fu, Taoyuan, Republic of China; Tae-Ahn Jahng, MD, Chonbuk, South KoreaBackground context: Autogenous bone is considered the most effective bone graft material for posterolateral lumbar fusion, yet nonunions occur in up to 35% of patients. The donor site complications may occur in 25% to 30% of patients. In addition, many surgeries are lengthy procedures, which involve a relative large surgical field, and are associated with a great deal of morbidity and a long hospital stay.Purpose: The primary goal of this study is to use the minimal invasive surgical technique and to evaluate the efficacy of a novel osteoinductive growth factor and osteoconductive matrix formulation (recombinant human growth/differentiation factor [rhGDF-5] and Healos) at inducing and facilitating bone formation in a lumbar spinal posterolateral fusion sheep model.Materials and methods: Twelve skeletally mature sheep underwent bilateral posterolateral spinal fusion at the L4–L5 level. All surgeries were performed using a posterolateral endoscopic approach and transpedicle screw fixation. The animals were randomized in two groups based on the side and material applied. Autogenous iliac crest bone graft or bone graft substitute (rhGDF-5 and Healos) was used either on the right or the left side alternatively. Every animal had both the materials. Three groups were formed on the basis of the survival time: 60 days, 120 days and 180 days. All animals were euthanized after survival time for manual, radiographic, histologic and dual-energy X-ray absorptiometry (DEXA) evaluation.Results: There were no neurologic impairments, infections nor other complications. All four sheep had partial fusion on both sides at 60 days, but greater bone growth was found in the side of rhGDF-5 and Healos by radiograph and DEXA. In the eight animals that survived after 120 days, the manual palpation, radiograph and computed tomography scans determined that fusion rate for rhGDF-5 and Healos was 100% (eight of eight fusion sites), compared with 88% (seven of eight fusion sites) using autogenous iliac bone graft. There was no abnormal overgrowth of new bone by these two materials.Conclusion: These results show that endoscopic posterolateral spinal arthrodesis and instrumentation is a feasible, effective and safe method in the sheep model. Minimal invasive endoscopic surgery will minimize the morbidity of paraspinal muscle denervation and devascularization seen with open techniques. Healos (osteoconductive matrix) can be a useful carrier in the biologic and mechanical environment of a posterolateral intertransverse fusion site. In combination with rhGDF-5 (osteoinductive material), it produces fusion rates that are compatible with those of autologous bone graft. Use of the minimal invasive technique and the bone graft substitutes will eliminate the problem of graft donor site morbidity and possibly increase the chances for successful fusion.

Instrumented posterolateral lumbar fusion using coralline hydroxyapatite with or without demineralized bone matrix, as an adjunct to autologous bone

Background context: Autogenous posterolateral fusion with and without instrumentation has been reported with good results. However, difficult-to-fuse patients, such as smokers, elderly patients with poor bone quality and/or quantity, or patients with prior posterior surgeries, may have somewhat lower fusion rates. Purpose: To determine the efficacy of coralline hydroxyapatite with or without demineralized bone matrix as a bone graft extender in a human clinical model with long-term follow-up. Study design/setting: A retrospective series of 40 patients undergoing instrumented autogenous posterolateral lumbar fusion augmented with coralline hydroxyapatite with or without demineralized bone matrix. Patient sample: Long-term clinical and radiographic follow-up were examined for 40 patients who underwent an instrumented posterolateral fusion only. Patients undergoing anterior lumbar interbody fusion (ALIF) procedures were not considered part of the sample. Methods: All patients underwent successful transpedicular fixation with autogenous posterolateral lumbar fusion. Fifteen cc of Pro Osteon™ 500 coralline hydroxyapatite (Interpore Cross International, Irvine, CA) was used at each level. An additional 10 cc of Grafton demineralized bone matrix gel (Osteotech, Eatontown, NJ) was used in 70% of these patients. Results: An overall fusion rate of 92.5% was achieved. Pain and function improvement were good but somewhat age dependent and correlated with the number of comorbidities. Patients with Grafton DBM gel had a lower fusion rate of 89.3%. Conclusions: Based on this small retrospective review, coralline hydroxyapatite is an effective bone graft extender in difficult-to-fuse patients as an adjunct to autologous bone for posterolateral fusion of the lumbar spine when combined with rigid instrumentation.

Vertebral body osteopenia associated with posterolateral spine fusion in humans.

Lateral dual-energy x-ray absorptiometry was used to examine isolated changes in vertebral body mineral density in humans after instrumented posterolateral lumbar fusion. To determine if device-related osteopenia will occur in humans who undergo spinal fusion. Device-related osteopenia is known to occur as a result of local stress shielding after instrumentation in the appendicular skeleton. This effect has not been observed, however, in humans after spine fusion. To evaluate such changes, the vertebral body mineral density was measured in eight patients who had instrumented lumbar fusion and in eight matched control patients who had lumbar surgery with no fusion. In previous studies of dogs, vertebral body osteopenia occurred as a result of instrumented spine fusions. Previous studies in humans, however, have been limited by the relative insensitivity of conventional photon absorptiometry to isolated changes in the vertebral body because of overlying posterior elements. Absorptiometry was performed an average of 31.9 months after posterolateral fusion that bridged at least one level in the region of L2-L4. To reduce the effects of individual variations in mineral metabolism, the vertebral values were standardized by using the ratio of vertebral body to femoral neck density for each patient. The mean density ratio for the group of patients who underwent spine fusion was 0.733. This value was significantly lower than the control ratio of 0.879 (P = 0.048). Patients who have undergone instrumented posterolateral lumbar fusions have decreased vertebral body bone mineral density at the level of fusion compared with that of matched controls.

The fatigue strength of the lumbar neural arch in spondylolysis.

Spondylolysis is a fracture of the bone in one or both sides of the narrow regions of the neural arch, the partes interarticulares. The fifth lumbar vertebra is the most commonly affected. Although spondylolysis is not considered to be of congenital origin (Rowe and Roche 1953; Newman and Stone 1 963), genetic factors may predispose the individual to it (Baker and McHollick 1956; Saha et al. 1970; Wiltse, Widell and Jackson 1975). There are also racial differences, the Eskimos having an unusually high incidence of the defect (Stewart 1953; Lester and Shapiro 1968; Kettelkamp and Wright 1971). The most generally favoured theory, however, is that spondylolysis is a fracture caused by mechanical stress and that the mode of failure is fatigue (Pfeil 1 97 1 ; Wiltse et al. 1975). This theory was enhanced by experiments to determine the bending strength of the lumbar neural arch (Cyron, Hutton and Troup 1976). In order to achieve a fracture, an increasing force was applied to the inferior articular facets of a lumbar vertebra and the neural arch was bent away from the vertebral body by about 0.5 centimetre. This relative movement would be difficult to accomplish in vivo, except possibly itt hyperexte nsion. When a static force acts on a material, stress is generated within the material. As the applied force increases the material will eventually fail when the stress reaches a certain value, the “ ultimate stress” . However, the material will also fail when it is subjected to cyclic repetitive stresses which never reach the ultimate stress. This mode of failure is known as fatigue failure. The fatigue life, defined as the number of cycles to failure, is dependent on the amplitude of the cyclic stresses and the method by which they are imposed. It is relatively easy to determine the fatigue life of inert materials such as metal. In bone, however, a fatigue fracture will only develop in vivo when the cellular mechanism of repair fails to keep pace with the microscopic damage caused by the repetitive force. It has been suggested that this occurs in “shin soreness” (Devas 1958). It is thought to be caused by prolonged periods of unac.customed or strenuous activities such as running. Walking with a heavy pack on the back and working in the fully flexed posture are activities that produce cyclic stresses within the partes articulares of lumbar vertebrae. If the stress generated during these activities reaches a critical value and a sufficient number of cycles is accumulated, the neural arch may fracture. This has already been considered as a likely explanation of the occurrence of spondylolysis (Stewart 1 953 ; Newman and Stone 1963). There is little published information on the fatigue properties of the lumbar neural arch. Pfeil (1971) reported on fractures resembling spondylolysis. He subjected lumbar spines from children to repetitive impact loads, but he did not measure the applied force or the number of cycles to failure. This paper describes experimental work carried out on cadaveric lumbar vertebrae to determine the fatigue life of the lumbar neural arch when subjected to forces comparable with those encountered in vivo.