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Biomedical subjects

T A Zdeblick

Publications and source records attributed to T A Zdeblick.

At least 55 records · Page 3Linked to original sources

Anterior spinal fixators. A biomechanical in vitro study.

In vitro calf spine testing was performed in flexion, rotation, and axial load, using a vertebral body corpectomy and anterior iliac crest bone grafting model. Anterior spinal fixation devices then were sequentially tested, and axial stiffness, torsional stiffness, and flexural strain determined. The constructs tested were the Contoured Anterior Spinal Plate (CASP), the Kaneda device, the Kostuik-Harrington device (KH), and the Texas Scottish Rite Hospital (TSRH) vertebral body screw construct. In torsion, the Kaneda device returned spinal stability to that of the intact spine. The Kostuik-Harrington device was unstable in torsion. In axial loading and flexion, the Kaneda device and the TSRH construct proved the most stiff, with the KH and CASP systems significantly lower in stiffness. The authors believe that the Kaneda device and the TSRH vertebral body screw construct are effective in restoring acute stability to the lumbar spine after corpectomy.

Animals↗

Spinal instrumentation for metastatic disease: in vitro biomechanical analysis.

A calf spine corpectomy model was employed to compare the ability of various spinal instrumentation techniques to restore stability after destruction of the anterior and middle columns. The constructs tested were an intact specimen, a Harms titanium cage, a cross-linked rectangular anterior Texas Scottish Rite Hospital construct, posterior segmental Luque rods combined with a cross-linked rectangular anterior TSRH construct, posterior Luque rods alone, cross-linked posterior Luque rods, and posterior Luque rods embedded in polymethyl-methacrylate (PMMA). When compared to the intact state, only the combined anterior/posterior construct and the anterior TSRH construct were able to restore axial, sagittal, and torsional stiffnesses to levels equal to or higher than control levels. Embedding Luque rods in PMMA provided greater stiffness than either Luque rods alone or cross-linked Luque rods. If the anterior and middle columns of the spine are incompetent, as frequently occurs with metastatic disease, the goal of surgical treatment is to restore spinal stability while decompressing the neural elements. Either anterior or posterior techniques may be used. The findings of this study imply that commonly used spinal instrumentation constructs differ in their ability to restore axial, sagittal, and torsional stiffnesses to normal levels.

Animals↗

Quantitative histologic study of the influence of anterior spinal instrumentation and biodegradable polymer on lumbar interbody fusion after corpectomy. A canine model.

Histomorphometric and microradiographic studies were performed to investigate whether there are different rates of bone remodeling based on the intrinsic stability with anterior spinal instrumentation and to evaluate if biodegradable polymer could be used clinically as the material of choice for anterior spinal instrumentation. Twenty-one coon hounds underwent anterior and posterior spinal destabilizing procedures to produce a reproducible amount of spinal instability: corpectomy of L5, discectomies and partial facetectomies of L4-5 and L5-6, resections of L5 lamina, spinous process, supra- and interspinous ligament, and ligamentum flavum. Group 1 (N = 7) underwent anterior autogenous ulna strut graft alone at L4-6; group 2 (N = 7) underwent anterior biodegradable polymer strut alone at the same level; group 3 (N = 7) underwent same bone graft as in group 1, augmented by anterior Kaneda device. Six months after surgery quantitative histologic study showed that device-related osteopenia occurred in spines treated with Kaneda device. Within the L5 vertebral body the volumetric density of bone (mm3/cm3) was less for the group with Kaneda device (group 3) compared with that without instrumentation (group 1, P less than 0.05). In the spine treated with biodegradable polymer, no adverse host tissue responses were observed histologically. In addition, osteoconductive abilities of the polymer were suggested microscopically. Its mechanical property, however, was not rigid enough to stabilize the corpectomized spine.

Animals↗

Anterior cervical discectomy and fusion. A comparison of techniques in an animal model.

An animal model for three-level anterior cervical discectomy and fusion was established in the goat. Twenty-one goats underwent surgery, with seven goats in each of three experimental groups. In Group I, all seven goats underwent three-level anterior cervical discectomy without fusion. In Group II, each of the seven goats had a three-level discectomy with autogenous bone performed according to the Smith-Robinson technique. In Group III, fresh-frozen allograft bone was used for each of the three-level discectomy and fusion. Each goat was then killed after 12 weeks. Analysis consisted of radiographic review, fluorochrome labeling, biomechanical rigidity and flexion and extension, axial compressive load, and torsion. Histologic analysis was also performed for evidence of fusion and vertebral body histomorphometric analysis. The analysis of results showed that radiographic union was judged to have occurred in 0 of 21 Group I disc spaces, 10 of 21 Group II disc spaces, and 8 of 21 Group III disc spaces. Histologic fusion was judged to have occurred in 0 of 21 Group I goats, 10 of 21 Group II goats, and 0 of 21 Group III goats. The histologic fusion rate was significantly higher in Group II than either Group I or Group III. Biomechanically, the spines that had autogenous bone grafting (Group II) were significantly stiffer in compressive axial load and in extension. Both Group II and Group III were stiffer in flexion than Group I. An evaluation of the peri-endplate vascularity showed that the vascularity measured 10.4% in Group I, 16.7% in Group II, and 8.5% in Group III.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Modified Smith-Robinson procedure for anterior cervical discectomy and fusion.

Fifty-one consecutive patients with cervical radiculopathy or spondylosis were treated with single or multilevel anterior discectomy and fusion using a modified Smith-Robinson procedure. There were 33 single-level fusions, 16 two-level fusions, and 2 three-level fusions. The three modifications included: 1) the endplates at the fusion level were completely removed with a high-speed bur to exposed bleeding cancellous bone in parallel planes; 2) the Caspar distractor (Aesculap, Burlingame, CA) was used to increase distraction and improve visualization; 3) the tricortical autologous iliac crest bone graft was placed in reverse position, that is, with the cortical cross-section facing posteriorly, creating a stabilizing strut in the middle column. With an average follow-up of 1 year, the fusion rate was 94% (67 of 71 levels). The single-level fusion rate was 97%, the two-level fusion rate was 94%, and the three-level fusion rate was 83%. Of the four nonunions, only two were symptomatic. Results by clinical examination revealed 36 (71%) excellent, 11 (21%) good, 3 (6%) satisfactory, and 1 (2%) poor outcomes. There were no significant disc collapses or extrusions. One patient had an increase in kyphotic deformity of > 5 degrees, none with > 10 degrees kyphosis. There were no wound infections or neurologic complications. The modified Smith-Robinson procedure for anterior cervical discectomy and fusion has led to the successful treatment of cervical radiculopathy and spondylosis with improved results and few complications.

Bone Transplantation↗

Cervical stability after foraminotomy. A biomechanical in vitro analysis.

Laminectomy or facetectomy of the cervical spine, or both, may be needed for decompression of the spinal cord or of the nerve-roots. Acute stability of the cervical spine was tested after laminectomy and progressive staged foraminotomies in an in vitro model. Twelve cervical spines from human cadavera were used in the experiment. Biomechanical testing included the application of an axial load, the application of a flexion and extension moment, and the application of a torsional moment. Each specimen was tested intact, after laminectomy of the fifth cervical vertebra, and after progressive foraminotomy of the sixth cervical root. Foraminotomy was performed by resection of 25, 50, 75, and 100 per cent of the facet joint and capsule. Torsional stiffness decreased dramatically when more than 50 per cent of the facet had been resected. Statistically equivalent subsets were the intact specimen, laminectomy, 25 per cent facetectomy, and 50 per cent facetectomy in one subset, and 75 and 100 per cent facetectomy in the least-stiff subset. Flexion-moment testing showed that the posterior strain did not differ among three groups: the intact specimens, those that had been treated with laminectomy, and those that had been treated with a 25 per cent facetectomy. The 50 per cent facetectomy resulted in a 2.5 per cent increase in posterior strain, and the 75 or 100 per cent facetectomy, in a 25 per cent increase in posterior strain compared with the intact specimen. Segmental hypermobility of the cervical spine results if a foraminotomy involves resection of more than 50 per cent of the facet.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Neuropathologic changes with experimental spinal instrumentation: transpedicular versus sublaminar fixation.

Fifty-six mature beagles underwent lumbar spine destabilization, followed by fusion using four techniques. Spinal cord neuropathologic analysis was carried out to determine the number of abnormalities within each group. Group I (n = 14) had posterolateral bone grafting without instrumentation. Group IIa (n = 14) had Cotrel-Dubousset (CD) pedicle screws and rods. Group IIb (n = 14) had Steffee pedicle screws and plates. Group III (n = 14) had sublaminar wires and rods. All of the animals remained clinically neurologically normal throughout the 6 months of the study. The incidence of moderate to severe neuropathologic changes was 21% in Group I, 18% in Group II, and 64% in Group III. Thus, a significantly higher percentage of neuropathologic abnormalities occurred with sublaminar instrumentation than with no instrumentation (p = 0.027), or with transpedicular instrumentation (p = 0.027). In this controlled animal study, the theoretical advantage of pedicle screws, which should not violate the spinal canal, over sublaminar devices, which must enter the canal, was confirmed.

Animals↗

Two-point fixation of the lumbar spine. Differential stability in rotation.

Single vertebral motion segments were tested in torsion. The adjacent vertebrae were transfixed by two 3-mm Steinman pins placed vertically. These were applied in five different positions: between the anterior vertebral bodies, posterior vertebral bodies, pedicles, transverse processes, and lamina. Rotational displacement was limited the most by transfixation between the vertebral bodies (position one or two). Disrupting the anulus fibrosus significantly increased rotation in all positions except those in the vertebral body. These findings may imply that spinal fixation devices that engage the vertebral bodies may offer inherent advantages over purely posterior devices in stabilizing a vertebral motion segment. In addition, an interbody arthrodesis may prevent intervertebral motion better than a posterior or posterolateral fusion.

Adult↗

The use of freeze-dried allograft bone for anterior cervical fusions.

A consecutive series of 87 patients undergoing Smith-Robinson anterior cervical fusion were analyzed. Either freeze-dried tricortical iliac crest bone or tricortical autograft bone was used. Surgical technique was otherwise identical. Radiography showed delayed union at 3 months in 13% of patients with autograft and in 37% of patients with freeze-dried allograft. At 1 year, radiography showed nonunion in 8% of patients with autograft and in 22% of patients with allograft. One-level procedures had a delayed union rate of 7% for autograft and 21% for allograft. Nonunion in one-level procedures was 5% for both autograft and allograft. For two-level procedures, the nonunion rate was 17% for autograft and 63% for allograft. Graft collapse was more commonly seen with freeze-dried allograft (30%) than with autograft (5%). Relief of neck and arm pain, however, was similar in both groups.

Adult↗

Biomechanical evaluation of methods of posterior stabilization of the spine and posterior lumbar interbody arthrodesis for lumbosacral isthmic spondylolisthesis. A calf-spine model.

In order to evaluate biomechanically the efficacy of four types of posterior instrumentation for the stabilization of isthmic spondylolisthesis of the lumbosacral spine, mechanical non-destructive cyclic testing in axial compression, flexion, extension, and rotation was performed on six fresh lumbosacral spines from calves. Each segment contained four motion segments, including the lumbosacral junction. Isthmic spondylolisthesis was created by sectioning the pars interarticularis of the sixth lumbar vertebra and all posterior ligaments between the fifth and sixth lumbar levels. Eight constructs were tested sequentially: (1) the intact spine, (2) the destabilized spine, (3) the spine fixed with Harrington double-distraction rods, (4) the spine treated with transpedicular Cotrel-Dubousset instrumentation with a transverse approximating device, (5) the spine treated with Steffee transpedicular screws and plates, (6) the spine treated with posterior lumbar interbody arthrodesis, (7) the spine treated with Cotrel-Dubousset instrumentation and posterior lumbar interbody arthrodesis, and (8) the spine treated with Steffee instrumentation and posterior lumbar interbody arthrodesis. One motion segment was involved in each construct, except for the spine that was fixed with Harrington instrumentation, which involved three segments. Strain across the supraspinous and anterior longitudinal ligaments was measured with two extensometers that were attached at the spondylolisthetic level and at the intact motion segments adjacent to the fixed level. Harrington instrumentation was the least rigid construct under any type of loading except axial compression (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Anterior spinal fixation after lumbar corpectomy. A study in dogs.

An animal model was developed to simulate an unstable lumbar burst fracture that had been treated with corpectomy. A fifth lumbar laminectomy, partial facetectomy, and corpectomy was performed in twenty-one dogs. In seven dogs (the control group), a biodegradable polymer spacer was used to create a definite failure of fusion (Group I). Seven dogs were treated with a traditional anterior arthrodesis with an autogenous ulnar strut and without instrumentation (Group II). The remaining seven dogs were treated with an ulnar strut and anterior Kaneda instrumentation that was of an appropriate size for the dog (Group III). At twenty-four weeks, the results were analyzed in terms of the rate of fusion, biomechanical rigidity, neuropathological findings, and histomorphometric data on the vertebral response. The rate of fusion was significantly higher in Group III, in which the Kaneda device had been used, than it was in either Group I or Group II, in which instrumentation had not been used. Biomechanically, the spines in Group III were stiffer in torsion than those in Group I or II. There was no difference between groups in terms of the number of neuropathological changes in the spinal cord. Histomorphometric analysis showed that no meaningful device-related osteopenia occurred in the vertebrae that were spanned by the fixation device. Trabecular density was increased in the vertebrae in which the instrumentation was anchored.

Animals↗

Tumors of the thoracic and lumbar spine: surgical treatment via the anterior approach.

We are reporting our experience in 23 patients with tumors of the thoracic or lumbar vertebrae treated via surgical anterior decompression and stabilization. Seventeen patients had metastatic disease and were treated with vertebral body resection followed by stabilization with anterior polymethylmethacrylate and threaded Harrington rods with sacral distraction hooks. Six patients had primary tumors and, following tumor resection and partial vertebral body resection, had autogenous bone graft struts placed anteriorly as well as posterior instrumentation. Posterior instrumentation was transpedicular one level above and below in the lumbar spine, and segmental hooks and rods three levels above and below in the thoracic spine. Nineteen patients presented with severe unremitting pain, and 16 had neurologic deficits, including 7 who were unable to ambulate. Radiation therapy was used as an additional treatment and routinely begun 2 weeks postoperatively. All patients survived the surgery, and none had neurologic deterioration immediately postoperatively. Eight patients had died at the time of review. The mean survival was 14 months and ranged from 6 to 38 months. Of the surviving patients, follow-up ranged from 24 to 40 months with an average follow-up of 30 months. Pain relief was excellent in all but two patients (93%). Motor recovery occurred to some extent in all patients, and only one remained nonambulatory. Complications were minor in three patients (13%) and major in one (4%). Tumor recurrence with neurologic deterioration occurred in two patients. We are very encouraged by these results, and we recommend that patients with tumors of the vertebral body with neurologic deficit or severe unremitting pain be studied with MRI and/or myelography and CT. The patients with gross vertebral destruction and greater than 50% collapse of the vertebral body, those in need of a tissue diagnosis, or those with major neurologic deficit can be effectively treated by anterior decompression and stabilization.

Adult↗

Cervical kyphosis and myelopathy. Treatment by anterior corpectomy and strut-grafting.

Between 1976 and 1984, fourteen patients who had severe cervical kyphosis and myelopathy were treated with anterior decompression and arthrodesis. Eight had had spondylosis; five, a traumatic injury; and one, a benign intradural tumor. In eight of the fourteen patients, the severe kyphosis and myelopathy had developed after a laminectomy of three, four, or five cervical vertebrae. The laminectomy had been done for the treatment of spondylosis in five patients, of a traumatic lesion in two, and of a tumor in one. Considering all fourteen patients, an average of 2.25 vertebral bodies was removed from each, and the average extent of the subsequent fusion was 3.25 levels. Eight patients (six of whom had spondylosis; one, a traumatic lesion; and one, a tumor) were treated with a fibular graft that spanned an average of 4.10 levels, and six patients (four of whom had a traumatic lesion and two, spondylosis) were treated with an iliac graft that spanned an average of 2.70 levels. Of the five patients who had a traumatic lesion, four were treated with anterior decompression and arthrodesis, combined with posterior arthrodesis that was performed during the same period of anesthesia. In three patients, the anterior graft dislodged during the immediate postoperative period. Two of the three patients had posterior instability due to a prior laminectomy, and in the third the graft dislodged because of technical difficulties. Two of these grafts were revised to restore stability. At the latest follow-up, twelve of the fourteen fusions were solid. In the other two patients, who died six and ten months postoperatively, the fusion had been solid, as shown by radiographs, before the time of death. The average amount of correction of the kyphotic deformities was 32 degrees, a reduction from an average of 45 degrees to an average of 13 degrees. All but one patient had some recovery of neural function; nine had complete and four, partial recovery. The remaining patient had relief of pain, but he continued to be completely quadriplegic although he had some sensory sparing. Of the four patients who had been unable to walk preoperatively, three were able to walk postoperatively. No patient lost neural function after the anterior decompression and arthrodesis. We concluded that, in the presence of severe cervical kyphosis and myelopathy, adequate anterior decompression of the spinal cord, correction of the kyphosis, and anterior arthrodesis using a strut graft can yield excellent results without undue risk.

Adult↗

Treatment of experimental frostbite with urokinase.

An experimental model of frostbite using a standard cold injury in rats was used to test the therapeutic usefulness of the fibrinolytic agent urokinase. Control groups included rapid rewarming, slow rewarming, and slow rewarming followed by saline infusion. Urokinase was administered through an intra-arterial catheter 30 minutes after cold injury and slow rewarming. Optimum results were obtained with rapid rewarming of the extremity at 43 degrees C. However, with rewarming at room temperature eventual tissue loss was significantly decreased with the infusion of urokinase compared with either no treatment or saline infusion. In the clinical situation where the patient with frostbite is seen after slow rewarming, we believe that clinical trials of the use of a fibrinolytic agent are warranted.

Animals↗

The healing of canine vascularized segmental tibial osteotomies. The effect of retained endosteal circulation.

Forty-eight pairs of canine tibial segmental osteotomies, 4 cm in length, were investigated to determine the progress of regeneration. The tibial segment was stripped of all soft tissue in one limb and the vascular pedicle was preserved in the contralateral limb. This allowed the healing of the tibial segments, vascular versus nonvascular, to be compared using sequential blood flow and roentgenographic and angiographic data. The blood flow to the vascular bone segment quadrupled at three weeks and then gradually decreased to 1.5 times baseline at one year. The nonvascular tibial segment showed a linear increase in flow for three months, achieving a level comparable to the contralateral vascular tibia segment. Peak flow in the vascular tibia at three weeks was four times that of the nonvascular tibia. Blood-vessel ingrowth from each osteotomy site progressed at a linear rate but was three times faster in the vascular bone. The deposition of callus and the rate of osteotomy healing were accelerated significantly in the vascular group. At three months 87% of the vascular tibial osteotomies healed versus 43% of the nonvascular osteotomies; these results represent significant advantages in the rate of healing in vascular versus nonvascular segmental tibial osteotomies. Segmental vascular bone grafts that are internally fixed with plate and screws can preserve the vascular structure and its advantages in bone regeneration.

Angiography↗

Anterior excision of herniated thoracic discs.

Twenty-two herniations of a thoracic disc in nineteen patients were surgically excised between 1972 and 1984. An anterior transthoracic decompression or a costotransversectomy was used for all discectomies. Pain and paraparesis were the most common symptoms preoperatively. The average length of follow-up was forty-eight months. Sixteen patients had an excellent or a good result, one had a fair result, and two had a poor result. Twelve of the fourteen patients who had had motor weakness preoperatively had varying degrees of improvement in motor function postoperatively. Pain was relieved in ten patients, reduced in eight, and unchanged in one. Anterior decompression of herniated thoracic discs yielded gratifying results, but the procedure is associated with some risk of damage to the spinal cord. It therefore requires meticulous preoperative planning and careful surgical technique.

Adult↗

The use of urokinase in ischemic replanted extremities in rats.

UNLABELLED: We compared the efficacy of intra-arterial infusion of urokinase, a fibrinolytic agent, with that of intra-arterial infusion of nitrendipine, a peripheral calcium-channel blocking agent, in preventing the no-reflow phenomenon in rats after prolonged ischemia at room temperature. Urokinase increased the survival of the limbs after both four and five hours of ischemia at room temperature to 100 per cent compared with 50 and 20 per cent, respectively, in untreated controls. Nitrendipine significantly increased the blood flow but failed to significantly increase the survival of the limb. Scanning electron microscopy was used to assist in the evaluation of the endothelium of the vessels. The etiological mechanism of the no-reflow phenomenon appears to be that ischemia damages the endothelial cells, causing impairment of the fibrinolytic system, retraction of the endothelial membrane, exposure of the subintimal collagen, and fibrin-platelet deposition. Thrombosis of the vessels ensues, resulting in the no-reflow phenomenon. CLINICAL RELEVANCE: Experimentally, intra-arterial infusion of urokinase increased the survival of the limb in replanted extremities that were subjected to ischemia. This effectively lengthened the safe limit of ischemia at room temperature before microsurgical replantation or elective free-tissue transfer. Clinical trials of the use of intra-arterial fibrinolytic agents for the treatment of revascularized tissue are indicated.

Animals↗

Preoperative use of povidone-iodine. A prospective, randomized study.

One hundred one adult orthopedic surgical patients were studied in a randomized, prospective clinical trial to compare the effectiveness of the standard povidone-iodine scrub and paint with povidone-iodine painting alone for presurgical skin preparation. No infections occurred in either group. The scrub-plus-paint group showed a 0.601 logarithmic reduction in bacteria counts, compared with 0.622 with painting alone. Further, 36.8% of the patients in the scrub-plus-paint group had skin counts that actually increased after preparation, compared with 13.8% of patients in the paint-only group. The preparation bacterial counts among inpatients, who received preoperative hexachlorophene showers, were significantly lower than that of outpatients, who did not receive preoperative showers. The data support the use of the preoperative hexachlorophene shower and the omission of scrubbing from the surgical skin preparation technique.

Ambulatory Care↗