Laminectomy Defect Research Articles

Experimental Rabbit Hemilaminotomy Model in the Evaluation of Peridural Fibrosis: A Minimally Invasive Peridural Fibrosis Model

The neuronal adhesions of newly synthesized scar tissue to dura mater after spinal peridural operations represent an unsolved problem in neurosurgical practice. This experimental study was planned to compare the success of a rabbit hemilaminotomy procedure with the total laminectomy model in the evaluation of peridural fibrosis in terms of proposing a lesser invasive peridural adhesion model. Fourteen New Zealand white rabbits were used in this experiment. Laminectomy was performed in one level, and hemilaminotomy was done in another level. Four weeks after operation the rabbits were sacrificed by perfusion with 10 % neutral buffered formalin solution. The lumbar spines were removed and immersed in 10 % neutral buffered formalin for approximately 24 hours. Then each specimen was decalcified in 5 % formic acid for approximately 3 weeks. Specimens were cut coronally for gross inspection. Two blocks of tissue were taken from each laminectomy site to be processed and embedded in paraffin. In seven (50 %) of the laminectomy sites of the rabbits, fibrous tissue penetrated the spinal canal through the laminectomy defect and produced neural compression (Grade III). Eight (57 %) hemilaminotomy sites were in Grade III fibrosis. There was no difference between laminectomy and hemilaminotomy in regard to the dural adhesions. In this experimental study, we modified the rabbit total laminectomy model by using a hemilaminotomy procedure in the study of peridural scar formation. The authors conclude that this procedure is more simple, reliable, and lesser invasive than the total laminectomy model.

5:49 69. Transincisionally placed epidural catheters for postoperative analgesia in instrumented lumbar spinal fusion surgery

BACKGROUND CONTEXT: The use of epidural catheters for postoperative analgesia in spine surgery has been previously reported. The technique described herein varies from previously described intraoperative epidural catheterization techniques with epidural catheter placement through a nonoperated interspace rather than though an open laminectomy defect thereby giving the same control of catheter insertion as percutaneously placed catheters. Furthermore leakage of the infusion solution into the wound via the laminectomy defect is minimized and analgesic efficacy is maximized.

Topical high-molecular-weight hyaluronan and a roofing barrier sheet equally inhibit postlaminectomy fibrosis

Topical high-molecular-weight hyaluronan and a roofing barrier sheet equally inhibit postlaminectomy fibrosis

The effects of free fat graft or cellulose membrane implants on laminectomy membrane formation in dogs

The purpose of this study was to determine the effect of cellulose membrane or free fat grafts (FFG) on laminectomy membrane (LM) formation. Eighteen dogs were randomly divided into three groups of six dogs. All dogs underwent a modified dorsal laminectomy on T 13–L 1. The laminectomy defect was left uncovered in the control group but either a FFG or a cellulose membrane implant was provided in the other two groups. The dogs were evaluated through neurological examination, myelography, macroscopic roundness index of spinal cord and histological evaluations of epidural fibrosis and spinal cord. The results showed a significant difference between the control and the FFG group, with the FFG causing neurological deficits and spinal cord compression as assessed by the roundness index of the spinal cord. Both FFG and cellulose membrane were partially effective in preventing LM formation. The use of FFG was associated with a high rate of significant neurological complications and spinal cord lesions.

The Efficacy of Convex Hemiepiphysiodesis in Patients With Iatrogenic Posterior Element Deficiency Resulting from Diastematomyelia Excision

Retrospective analysis was performed. To investigate the safety and efficacy of anterior and posterior hemiepiphysiodesis in patients with iatrogenic posterior element deficiency. Anterior and posterior convex hemiepiphysiodesis is a well-accepted treatment method for severe and progressive congenital scoliosis in young children. Many patients with congenital spinal deformities have intraspinal pathologies that require neurosurgical intervention with laminectomy. The efficacy of this method has not been studied in these patient populations. Between 1990 and 2001, among 82 patients with congenital spinal deformity, 38 were treated with convex epiphysiodesis. This study included 18 of these patients (2 males and 16 females) who underwent diastematomyelia excision and had at least 2 years of follow-up evaluation. Diastematomyelia excision was performed before the orthopedic procedure in 8 patients and at the same anesthetic setting sequentially in 10 patients. The mean age at the time of the fusion was 20 months (range, 6-60 months), and the average follow-up period was 39 months (range, 24-120 months). The mean Cobb angle was 54 degrees (range, 31-90 degrees) before surgery and 48 degrees (range, 30-84 degrees) at the final follow-up assessment. Any increase of more than 6 degrees was accepted as progression. Eight patients (44%) had a true epiphysiodesis effect: 58 degrees (range, 40-90 degrees ) before surgery and 39 degrees (range, 30-70 degrees) at follow-up evaluation. Eight patients (44%) had a fusion effect: 49 degrees (range, 31-68 degrees) before surgery and 50 degrees (range, 37-74 degrees) at follow-up assessment. Two patients (12%) had a postoperative progression of deformity: 63 degrees (range, 54-72 degrees) before surgery and 75 degrees (range, 65-84 degrees) at follow-up evaluation. Convex epiphysiodesis is an effective method for patients with midline laminectomy defect as those with intact posterior elements. Because the facet joints and transverse processes usually are unaffected, the presence of midline defect does not diminish the efficacy of the technique.

Usefulness of color doppler ultrasound in the management of a spinal arteriovenous fistula

BACKGROUND While color Doppler ultrasonography and microvascular Doppler recordings have been used intraoperatively for spinal cord vascular malformations, they have not been employed for similar spinal cord lesions preoperatively. CASE DESCRIPTION We report the usefulness of color Doppler ultrasonography through a lumbar laminectomy defect in the management of a spinal arteriovenous fistula. CONCLUSION Color Doppler ultrasonography should be considered for spinal lesions in which a laminectomy defect is present.

Inhibition of epidural scar tissue formation after spinal surgery: external irradiation vs. spinal membrane application

Purpose: The scar tissue that forms after lumbar dissection is a severe complication and a cause of lumbar and radicular pain. It was recently shown that radiotherapy could inhibit peridural fibrosis after laminectomy. In this study, the efficiency of external irradiation was compared with spinal membrane application.Method and Materials: Thirty male New Zealand rabbits underwent L5 laminectomy. Ten rabbits each received a single fraction of 900-cGy external irradiation administered by 9-MeV electron beam 24 h after the surgery. Ten other rabbits each had spinal membrane applied during laminectomy. The remaining 10 rabbits constituted the control group. All of the rabbits were killed 30 days after the laminectomy. Axial histologic sections through the laminectomy defect were evaluated. Each specimen was scored for the extent and density of fibrosis and arachnoidal adherence.Results: The extent and density of fibrosis and arachnoidal adherence differed significantly between the control group and the treatment groups (p < 0.05). However, the extent and density of fibrosis and arachnoidal adherence did not differ significantly between the spinal membrane and irradiation groups (p > 0.05).Conclusion: This preliminary study showed that high-single-fraction/low-total-dose administered postoperatively can successfully inhibit postsurgical epidural fibrosis as effectively as applied spinal membrane.

Inhibition of peridural fibrosis after laminectomy using low-dose external beam radiation in a dog model.

Clinical studies have demonstrated a significant association between the presence of extensive postlumbar discectomy peridural scar formation and the recurrence of low back and radicular pain. Low-dose perioperative radiation therapy has previously been demonstrated to inhibit peridural fibrosis after laminectomy in a rat model. The current study was designed to measure the effect of low-dose radiation on postlaminectomy peridural fibrosis development in a larger animal model. Three dogs underwent a total of 12 lumbar hemilaminectomies. For each animal, two levels received 1) external beam radiation 24 hours before surgery, 2) surgery alone, or 3) radiation alone. Radiation was administered in a single fraction of 700 cGy using computed tomographic guidance for dosimetry planning. The isodose distribution was such that the dose conformed to the posterior epidural space with minimal exit dose to normal tissue. Port films were used to confirm the correct levels. Gadolinium-enhanced magnetic resonance imaging (MRI) of the lumbar spines was obtained before the animals were killed 12 weeks after surgery. The spines were harvested, and axial sections through the laminectomy defect were stained with hematoxylin and eosin and Masson's trichrome. All specimens were evaluated for extent of fibrosis along the dura, density of fibrosis, nerve root entrapment, and sublaminar fibrosis. There were no complications from the surgery, and no new neurological deficits were noted. There was a statistically significant difference between the irradiated and nonirradiated groups regarding the extent of fibrosis (P = 0.001) and the density of fibroblasts (P = 0.001). There was also a marked difference in nerve root entrapment (P = 0.182) and the presence of sublaminar fibrosis (P = 0.061) between the treatment and control groups. MRI revealed less gadolinium enhancement at the irradiated levels compared with the nonirradiated levels, confirming the usefulness of MRI in predicting the degree of epidural fibrosis. Low-dose external beam radiation therapy administered 24 hours before laminectomy in a dog model significantly decreased the extent and density of peridural fibrosis as well as nerve root entrapment and sublaminar fibrosis. This treatment strategy may be efficacious in patients with recurrent radicular pain after lumbar discectomy that is thought to be secondary to peridural fibrosis on the basis of gadolinium-enhanced MRI studies, and who might benefit from reoperation for nerve root decompression.

Posterolateral Lumbar Intertransverse Process Spine Arthrodesis With Recombinant Human Bone Morphogenetic Protein 2/Hydroxyapatite-Tricalcium Phosphate After Laminectomy in the Nonhuman Primate

Study Design. A nonhuman primate lumbar intertransverse process arthrodesis model was used to evaluate recombinant human bone morphogenetic protein 2 (rhBMP-2) in a hydroxyapatite-tricalcium phosphate (HA- TCP) carrier as a complete bone graft substitute. Objectives. To assess the ability of a ceramic material to serve as a carrier for various doses of rhBMP-2 as a bone graft substitute in a primate model of posterolateral intertransverse process spinal fusion after laminectomy. Summary of Background Data. The reported nonunion rates for posterolateral lumbar spine fusion with autogenous iliac crest bone range from 5-35%. Recombi nant human bone morphogenetic protein 2 has shown potential to serve as a bone graft substitute for postero lateral intertransverse process spine fusion. Although a resorbable collagen sponge was a suitable carrier in rabbits and dogs, it was too compressible for the paraspinal muscles in rhesus monkeys. This failure of the collagen carrier has prompted evaluation of the feasibility of an alternative carrier material and the required dose of rhBMP-2. Methods. Twenty-one adult rhesus monkeys underwent a laminectomy at L4-L5 followed by bilateral intertransverse process arthrodesis via the same midline incision (n = 16) or a minimally invasive video-assisted posterolateral approach (n = 5). Bone graft implants on each side consisted of either 5 cm3 of autogenous iliac crest bone or 60:40 HA-TCP blocks (1.2 × 0.5 × 3.7 cm) loaded with a solution containing 0, 6, 9, or 12 mg of rhBMP-2 per side. The monkeys were killed 24 weeks after surgery. Inspection, manual palpation, radiography, and histology were used to assess fusion and to detect any bony growth into the laminectomy defect. Results. Fusion was not achieved in any of the monkeys treated with autogenous iliac crest bone graft. Both of the monkeys treated with the HA-TCP blocks with 0 mg rhBMP-2 achieved fusion. All 15 monkeys treated with the HA-TCP blocks and either of the three doses of rhBMP-2 achieved solid fusion. Two animals had extension of the fusion on one side because of malpositioned ceramic block. The results in animals fused via the minimally invasive video-assisted technique were the same as inthose fused with the open technique. Histologic analysis showed some ingrowth of bone into the ends but not-through the ceramic block in the absence of rhBMP-2. When the ceramic blocks were loaded with rhBMP-2 there was a dose-dependent increase in the amount and quality of bone throughout the ceramic carrier based on qualitative assessment. No significant bone encroachment on the exposed thecal sac through the laminectomy defect was observed in any of the monkeys. Conclusion. Hydroxyapatite-tricalcium phosphate proved to be a suitable carrier for rhBMP-2 in the posterolateral spine fusion model in rhesus monkeys. Even in the presence of a laminectomy defect, there was no evidence of bone induction outside the confines of the ceramic carrier.

Posterolateral lumbar intertransverse process spine arthrodesis with recombinant human bone morphogenetic protein 2/hydroxyapatite-tricalcium phosphate after laminectomy in the nonhuman primate.

A nonhuman primate lumbar intertransverse process arthrodesis model was used to evaluate recombinant human bone morphogenetic protein 2 (rhBMP-2) in a hydroxyapatite-tricalcium phosphate (HA-TCP) carrier as a complete bone graft substitute. To assess the ability of a ceramic material to serve as a carrier for various doses of rhBMP-2 as a bone graft substitute in a primate model of posterolateral intertransverse process spinal fusion after laminectomy. The reported non-union rates for posterolateral lumbar spine fusion with autogenous iliac crest bone range from 5-35%. Recombinant human bone morphogenetic protein 2 has shown potential to serve as a bone graft substitute for posterolateral intertransverse process spine fusion. Although a resorbable collagen sponge was a suitable carrier in rabbits and dogs, it was too compressible for the paraspinal muscles in rhesus monkeys. This failure of the collagen carrier has prompted evaluation of the feasibility of an alternative carrier material and the required dose of rhBMP-2. Twenty-one adult rhesus monkeys underwent a laminectomy at L4-L5 followed by bilateral intertransverse process arthrodesis via the same midline incision (n = 16) or a minimally invasive video-assisted posterolateral approach (n = 5). Bone graft implants on each side consisted of either 5 cm3 of autogenous iliac crest bone or 60:40 HA-TCP blocks (1.2 x 0.5 x 3.7 cm) loaded with a solution containing 0, 6, 9, or 12 mg of rhBMP-2 per side. The monkeys were killed 24 weeks after surgery. Inspection, manual palpation, radiography, and histology were used to assess fusion and to detect any bony growth into the laminectomy defect. Fusion was not achieved in any of the monkeys treated with autogenous iliac crest bone graft. Both of the monkeys treated with the HA-TCP blocks with 0 mg rhBMP-2 achieved fusion. All 15 monkeys treated with the HA-TCP blocks and either of the three doses of rhBMP-2 achieved solid fusion. Two animals had extension of the fusion on one side because of malpositioned ceramic block. The results in animals fused via the minimally invasive video-assisted technique were the same as inthose fused with the open technique. Histologic analysis showed some ingrowth of bone into the ends but not-through the ceramic block in the absence of rhBMP-2. When the ceramic blocks were loaded with rhBMP-2 there was a dose-dependent increase in the amount and quality of bone throughout the ceramic carrier based on qualitative assessment. No significant bone encroachment on the exposed thecal sac through the laminectomy defect was observed in any of the monkeys. Hydroxyapatite-tricalcium phosphate proved to be a suitable carrier for rhBMP-2 in the posterolateral spine fusion model in rhesus monkeys. Even in the presence of a laminectomy defect, there was no evidence of bone induction outside the confines of the ceramic carrier.

Posterolateral Intertransverse Process Spinal Arthrodesis with rhBMP-2 in a Nonhuman Primate

Recombinant osteoinductive proteins have been used successfully in canine and rabbit models of posterolateral intertransverse process arthrodesis, but little is known about the ability of these compounds to achieve fusion in nonhuman primates. The goals of this investigation were to compare different combinations of recombinant human bone morphogenetic protein-2 (rhBMP-2) dosages and carriers in a nonhuman primate model of posterolateral intertransverse process spinal fusion and to determine the feasibility of using rhBMP-2 in the presence of exposed dura in a laminectomy model. Posterolateral intertransverse process arthrodeses were performed at L4-5 in 29 rhesus monkeys. The most striking findings were as follows: rhBMP-2 could induce bone in a nonhuman primate spine; the presence of a laminectomy defect with exposed dura did not preclude the safe use of rhBMP-2 for posterolateral fusion; soft tissue compression of the collagen sponge carrier prevented bone induction at standard BMP doses, presumably due to squeezing of the protein out of the sponge; and longer rhBMP-2 loading time into the collagen carrier and mechanical protection from the soft tissue compression both allowed more bone induction at a lower dose of rhBMP-2.

Expanded polytetrafluoroethylene membrane for the prevention of peridural fibrosis after spinal surgery: an experimental study.

One of the most common complications of lumbar spine surgery is peridural fibrosis, a fibroblastic invasion of the nerve roots and the peridural sac exposed at operation. Peridural fibrosis may produce symptoms similar to those the patient experienced preoperatively and, if another spinal operation is necessary, may increase the risk of injury at reexposure. In a controlled study in dogs, we assessed the use of expanded polytetrafluoroethylene (ePTFE) as a barrier to postoperative invasion of fibrous tissue into the laminectomy defect. In 14 dogs, a two-level laminectomy was done, at L4-L5 and L6-L7. In 12 dogs, an ePTFE membrane was placed directly over the dorsal surface of the laminectomy defect at L4-L5 and within the defect (over the surface of the dura) at L6-L7. No material was implanted in two dogs (controls). Tissue for histologic studies was obtained from the controls and from ten dogs with the membrane 12 weeks postoperatively. Two dogs with the membrane underwent reoperation. The study found that there was no peridural fibrosis in seven of the ten specimens in which the ePTFE membrane had been placed directly on the dorsal surface of the laminectomy defect, some peridural fibrosis in all specimens in which the membrane had been placed within the defect, and extensive fibrosis in controls. The ePTFE membrane created an excellent plane of dissection for reoperation. No foreign-body reactions to the membrane or membrane-related infections occurred. We conclude that the ePTFE spinal membrane, when properly implanted, is an effective barrier to postsurgical fibrous invasion of the vertebral canal. Clinical studies of use of this material in spinal surgery are warranted.

Expanded polytetrafluoroethylene membrane for the prevention of peridural fibrosis after spinal surgery: a clinical study

Peridural fibrosis developing after laminectomy may cause pain that can necessitate reoperation. Many materials have been used as a barrier to invasion of fibrous tissue into the vertebral canal, but the ideal material has not been found. Various studies in animals have achieved favourable results with an expanded polytetrafluoroethylene (ePTFE) membrane. In a prospective, randomized study, we compared postoperative results in 33 patients who had an ePTFE membrane implanted to cover the defect caused by laminectomy during lumbar spine decompression with the results in 33 patients in whom no material was implanted. At operation, an ePTFE membrane was placed after the decompression procedure to cover the laminectomy defect completely. Systematic clinical and MRI follow-up evaluations of patients with and without the membrane were conducted 3, 6, 12, and 24 months postoperatively. The effect of ePTFE membrane implantation over laminectomy sites on postoperative peridural fibrosis, pain and neurological claudication was assessed. The ePTFE-membrane group had a significantly lower rate of epidural fibrosis on MRI (P<0.0001) and of clinical manifestations of radiculalgia (P = 0.002) compared with the no-material group. Epidural fibrosis that occurred in the ePTFE group was generally less extensive than that in the no-material group. There was no significant difference in the rate of postoperative claudication in the two groups. Significantly more seromas occurred in the ePTFE group (P = 0.0002). There were no infections or other complications in either group. The results showed that placement of an ePTFE spinal membrane over the laminectomy defect produced by lumbar spine surgery provided a physical barrier to invasion of fibrous tissue into the vertebral canal, and patients with the membrane had less postoperative radicular pain.

Marsupialisation of an arachnoid cyst in a dog

ABSTRACTA seven‐month‐old West Highland white terrier was presented with hindlimb ataxia and paraparesis. Radiographic studies revealed an arachnoid cyst at thoracic vertebrae 12 and 13. A dorsal laminectomy and durotomy were performed to decompress the spinal cord. The cyst was marsupialised by suturing the dura mater to the edge of the laminectomy defect. There were no postoperative complications and the dog improved to normality.

An experimental study on prevention of postlaminectomy scar formation

In repeat lumbar surgery for failed back syndrome, well organized fibrous scar tissue is often noted, binding together the dura, nerve roots, and paraspinal muscles. An animal experimental study was done to investigate the prevention of scar formation after lumbar laminectomy by using dacron and sodium hyaluronate. The experimental animals consisted of three groups: 1) control group, 2) D group (covering the laminectomy defect with dacron sheet), and 3) H group (covering the laminectomy defect with sodium hyaluronate gel). Animals were sacrificed at varying intervals (3-12 weeks) and the lumbar spines were evaluated with histologic preparations. Scar adhesion to the dura was most significantly suppressed in the D group, followed by the H group and the control group.

Posterior Transpedicular Zielke Instrumentation of the Lumbar Spine

Thirty-three patients treated by posterior transpedicular Zielke instrumentation of the lumbar spine were followed 1.1-2.7 years postoperatively. The average age of the patients was 64 years. The transpedicular technique allowed excellent fixation in patients with poor bone stock secondary to osteoporosis and extensive laminectomy defects. In particular, it allowed distraction and realignment of asymmetrically collapsed foramina with relief of pedicular kinking, correction of lateral deformity, and correction of reduced and fixed listhetic segments. Complications included one broken rod in the immediate postoperative interval while in the hospital. There was no late breakage of rods. The technique of transpedicular fixation with the ability to selectively distract or compress individual segments prevented any further collapse or displacement and allowed correction of areas of scoliotic collapse with relief of root entrapment. A normal lordosis was maintained as indicated by preoperative and postoperative measurements.

An experimental study on prevention of postlaminectomy scar formation by the use of new materials.

An experimental study was performed to investigate the prevention of scar formation after lumbar laminectomy, using Elastase and the new polylactic acid (PLA) membrane containing Elastase. The experimental animals consisted of four groups: control group, E group (using intravenous administration of Elastase), P group (covering the laminectomy defect with PLA membrane), and P-E group (covering the laminectomy defect with "PLA" + Elastase" membrane). The animals were killed at varying intervals (2-12 weeks) and changes in the lumbar spines were evaluated histologically. Scar formation was suppressed most significantly in the P-E group, followed in order by the E group, the P group, and the controls.

Real-time ultrasonography of the spinal cord: intraoperative and postoperative imaging.

Fourteen subjects with spinal cord pathology were studied with 10 MHz linear array or 5 MHz mechanical sector ultrasound scanners. Twelve patients were studied intraoperatively. The examinations were rapid, aiding the surgeon at the time of exploration. Sonography defined cysts, outlined the extent of neoplasia and aided in the localization of bone fragments. Guidance for placement of syringo -subarachnoid shunts reduced the amount of surgical manipulation. Four patients were examined postoperatively through laminectomy defects, three confirming adequate position and function of shunts and in one case demonstrating tumor recurrence.

Prevention of postlaminectomy scar formation.

An animal experimental study was performed to investigate prevention of scar formation under lumbar laminectomy by using new biodegradable interposing materials-- polylactic acid (PLA) foam and membrane. The experimental animals consisted of 32 dogs, 16 control and 16 experimental. The experimental surgery consisted of L5 or L6 complete laminectomy and covering of the laminectomy defect with the experimental materials. The same procedure but without the covering of the laminectomy defect was performed on the control group animals. Animals were sacrificed at varying intervals (2-52 weeks) and the lumbar spines were evaluated with histologic preparations. The PLA membrane is found to be a promising material for prevention of scar tissue extension and adhesion after laminectomy but has a problem of marginal fitting. PLA foam is found to behave as a scaffold for scar tissue extension and adhesion onto the nerve. Other foamy materials such as gelatin foam or avitane are probably behaving similarly, causing scar tissue extension and adhesion. The new materials were found to be completely biocompatible and slowly biodegradable. A combined use of posteriorly convexed stiff PLA membrane and marginal gap filler with PLA foam may provide solutions for both prevention of scar tissue extension and adhesion and prevention of postlaminectomy spinal stenosis.

Spinal cord imaging using real-time high-resolution ultrasound.

The myelographic evaluation of patients presenting with persistent or recurrent symptoms following surgery for an intrinsic spinal cord mass is difficult. Possible symptom-causing processes include tumor recurrence, intramedullary cyst formation, postirradiation effects, arachnoiditis, and spinal cord atrophy. Since tumor recurrence and syrinx formation may require further surgery, while the other entities generally do not, the distinction between these processes is clinically important. The authors have successfully employed commercially available high-resolution real-time ultrasound imaging systems to investigate a group of patients with these persistent or recurrent symptoms after surgery. The bony laminectomy defect provides an acoustic window for viewing intraspinal contents. Ultrasound can accurately differentiate between cystic and solid lesions and can clearly demonstrate whether a spinal cord is enlarged or atrophic.