Effect of sagittal plane deformity of the lumbar spine on epidural fibrosis formation after laminectomy: an experimental study in the rat

Screw migration and oesophageal perforation after surgery for osteosarcoma of the cervical spine

Background

Even though internal fixation has expanded the indications for cervical spine surgery, it carries the risks of fracture or migration, with associated potential life threatening complications. Removal of metal work from the cervical spine is required in case of failure of internal fixation, but it can become challenging, especially when a great amount of scar tissue is present because of previous surgery and radiotherapy.

Case presentation

We report a 16 year old competitive basketball athlete who underwent a combined anterior and posterior approach for resection of an osteosarcoma of the sixth cervical vertebra. Fourteen years after the index procedure, the patient eliminated spontaneously one screw through the intestinal tract via an oesophageal perforation and developed a severe dysphagia. Three revision surgeries were performed to remove the anterior plate because of the great amount of post-surgery and post-irradiation fibrosis.

Conclusions

Screw migration and oesophageal perforation after cervical spine surgery are uncommon potentially life-threatening occurrences. Revision surgery may be challenging and it requires special skills.

Chronic Paraspinal Muscle Injury Model in Rat

Objective

The objective of this study is to establish an animal model of chronic paraspinal muscle injury in rat.

Methods

Fifty four Sprague-Dawley male rats were divided into experimental group (n=30), sham (n=15), and normal group (n=9). Incision was done from T7 to L2 and paraspinal muscles were detached from spine and tied at each level. The paraspinal muscles were exposed and untied at 2 weeks after surgery. Sham operation was done by paraspinal muscles dissection at the same levels and wound closure was done without tying. Kyphotic index and thoracolumbar Cobb's angle were measured at preoperative, 2, 4, 8, and 12 weeks after the first surgery for all groups. The rats were sacrificed at 4, 8, and 12 weeks after the first surgery, and performed histological examinations.

Results

At 4 weeks after surgery, the kyphotic index decreased, but, Cobb's angle increased significantly in the experimental group (p<0.05), and then that were maintained until the end of the experiment. However, there were no significant differences of the kyphotic index and Cobb's angle between sham and normal groups. In histological examinations, necrosis and fibrosis were observed definitely and persisted until 12 weeks after surgery. There were also presences of regenerated muscle cells which nucleus is at the center of cytoplasm, centronucleated myofibers.

Conclusion

Our chronic injury model of paraspinal muscles in rats shows necrosis and fibrosis in the muscles for 12 weeks after surgery, which might be useful to study the pathophysiology of the degenerative thoracolumbar kyphosis or degeneration of paraspinal muscles.

A musculatura epaxial e a fibrose epidural na compressão medular em cães submetidos à laminectomia dorsal modificada

O objetivo deste experimento foi isolar a musculatura epaxial da medula espinhal de cães submetidos à laminectomia dorsal modificada (LDM) e averiguar se os músculos influenciaram na formação da fibrose epidural, na compressão medular e no aparecimento dos sinais neurológicos. Para isso, dez cães hígidos foram submetidos à LDM entre as vértebras T13 e L1 e distribuídos aleatoriamente em dois grupos denominados controle (I) onde a medula espinhal permaneceu exposta sem a presença de implante, e tratado (II)onde foi colocado um im-plante a base de alumínio entre a musculatura epaxial adjacente e a medula espinhal exposta pela LDM. As avaliações constaram de exames neurológicos diários até 180 dias de pós-operatório (PO); mielografia, decorridos 15, 30 e 60 dias de PO; e avaliação macroscópica mediante a reintervenção cirúrgica. Não houve diferença durante as avaliações neurológicas. Aos 15 dias de PO, foi verificado na mielografia, que o grau de compressão da linha de contraste foi maior no grupo tratado (P<0,05) quando comparado ao grupo controle, não havendo diferença dos demais tempos estudados. Na avaliação macroscópica, pode-se observar que no Grupo II, a musculatura epaxial adjacente à medula espinhal não estava em contato com a fibrose epidural, diferentemente do grupo controle. O implante pôde ser removido facilmente e apresentava discreto grau de deformidade crânio-dorsal. Pode-se concluir que a musculatura epaxial adjacente é isolada da medula espinhal pelo implante à base de alumínio em cães submetidos à LDM, e esta não influencia na formação da fibrose epidural, compressão medular e no aparecimento dos sinais neurológicos.

Effectiveness of a mucolythic agent as a local adjuvant in revision lumbar spine surgery

Aim of this prospective randomized trial was to analyze the effectiveness of MESNA in chemical dissection of peridural fibrosis in patients who underwent revision lumbar spine surgery. Between January 2003 and October 2006, 30 patients who underwent revision lumbar spine surgery were enrolled in the study. Patients were randomly assigned to one of two groups: a study group (A) and a control group (B). Once peridural fibrosis was exposed, MESNA (Uromixetan MESNA, 50 mg/ml) was intraoperatively applied on the fibrous tissue (Group A) to ease tissue dissection and enter the canal. In patients of Group B, saline solution was used. Surgical time, preoperative and 1 week postoperative hemoglobin (Hb), length of hospitalization (days), and incidence of perioperative complications were evaluated. The blinded surgeon assigned the surgeries to one of four categories as none, minimal, moderate, and severe basing on intraoperative difficulty in dissecting the fibrous tissue and intraoperative bleeding. Statistical analysis used chi-square analysis to evaluate the difference in surgery difficulty and the incidence of intraoperative complications between the two groups. The analysis of surgical time and hemoglobin levels was performed using a one-sample Wilcoxon test and Mann-Whitney U test. Patients in whom MESNA was used intraoperatively (Group A) presented better intraoperative and perioperative parameters with respect to the control group. Average surgical time and decrease in Hb postoperatively were more in the saline group (B) respect to MESNA (A) (P = 0.004 and P = 0.001, respectively), while no difference in average hospital stay was reported between the two groups. Surgeon-blinded intraoperative report on surgical difficulty showed a significant difference between the two groups (P < 0.05). Postoperatively, no complications directly attributable to the use of MESNA were experienced. The incidence of dural tears and intraoperative bleeding from epidural veins were significantly less in Group A with respect to the control group. MESNA contributed significantly to reduce the operative complications, with a diminution of the surgical time and the grade of difficult for the surgeon, confirming its ability as chemical dissector also for epidural fibrosis in revision lumbar spine surgery.

The extent of laminectomy affects pain-related behavior in a rat model of neuropathic pain

One of the unresolved questions in neuropathic pain research is whether we can prevent or reverse mechanical hyperalgesia by rhizotomy or ganglionectomy. However, one of the obstacles in answering that question is lack of a standardized surgical procedure used in experimental ganglionectomy. We tested the hypothesis that laminectomy performed during ganglionectomy induces lumbar column deformity. We further examined whether spinal deformity is a source of pain-related behavior. Five conditions were studied. Fifth and sixth lumbar (L5 and L6) ganglionectomy were performed in rats using either minimal or extensive laminectomy technique. Two other groups had minimal and extensive laminectomy without ganglionectomies. A final control group had no surgery. Sensory responsiveness of the plantar aspect of the hind paw was repeatedly tested, and a plain radiograph in anteroposterior projection was made to assess the extent of deformity by measurement of deformity angles. Hyperalgesia resulted in groups with extensive laminectomy regardless of performance or absence of ganglionectomy, while in groups with minimal laminectomy there was no increase in pain-related behavior. Lateral deformity of the spine was observed in rats with or without ganglionectomy, confirming that laminectomy can produce deformity. The extent of deformity was more pronounced in rats exposed to the extensive laminectomy. Our results indicate that laminectomy can produce spine deformity and that there is a direct relationship between the extent of laminectomy and the development of mechanical hypersensitivity. The data presented suggest that there is a need for standardization of laminectomy procedure in rat experimental pain models.

A comparison of the effectiveness of mitomycin C and 5-fluorouracil in the prevention of peridural adhesion after laminectomy

Object

The effectiveness of the topical application of mitomycin C (MMC) or 5-fluorouracil (5FU) in preventing peridural adhesion after laminectomy was compared in this study.

Methods

Laminectomies were performed at L-1 in 30 rats. Cotton pads soaked with 0.1 mg/ml MMC, 25 mg/ml 5FU, or 9 mg/ml saline (control) were applied to the operative sites. To evaluate neurological deficits pre- and postoperatively, somatosensory evoked potentials were monitored and the Basso-Beattie-Bresnahan locomotion test was performed. Four weeks postlaminectomy the rats were killed, and peridural scar adhesion was evaluated histologically. The level of hydroxyproline, the area of peridural scar tissue, and the number of fibroblasts were determined. The degree of peridural adhesion was classified according to the Rydell standard.

Results

No obvious adhesion formed in the rats in the MMC group, but severe peridural adhesions were found in those in the 5FU and control groups. The content of hydroxyproline, the area of peridural scar tissue, and the number of fibroblasts in the MMC group were significantly lower than those in the 5FU and control groups.

Conclusions

The topical application of MMC rather than 5FU may be a successful method of preventing post-laminectomy peridural adhesions.

Spinal somatosensory evoked potential to evaluate neurophysiologic changes associated with postlaminotomy fibrosis: an experimental study

STUDY DESIGN

We evaluated electrophysiologic changes of the cauda equina after lumbar laminotomy in rats.

OBJECTIVE

To clarify immediate and long-term electrophysiologic and neurologic responses in an experimental postlaminotomy animal fibrosis model.

SUMMARY OF BACKGROUND DATA

Postspinal surgery-induced epidural fibrosis is assessed using either Gadolinium- enhanced magnetic resonance imaging (MRI) or intraoperative observations. In experimental animal models mimicking this complication, many approaches are used: advanced imaging (computed tomography, CT; and MRI), functional observations, biomechanical techniques, and histologic examinations. However, no study has reported the substantial neurophysiologic changes of the cauda equina in such a model.

METHODS

Rats were given a sham operation (laminar exposure only), a left L5 hemilaminotomy alone, or a left L5 hemilaminotomy with extradural topical collagen. Mixed-nerve-elicited somatosensory-evoked potentials (M-SSEPs) and dermatomal (D)-SSEPs were recorded at the thoracolumbar junction after percutaneous stimulation of the posterior tibial nerve at the bilateral medial ankles and the L5 dermatomal field, respectively. Potentials recorded on the operated and nonoperated sides before surgery and then 30 minutes, 2 weeks, and 1, 2, and 3 months after surgery were compared. Walking track and thermal hyperalgesia test results and a final histologic analysis of perineural fibrosis were correlated.

RESULTS

Electrical stimulation yielded reproducible responses in all rats on all tests. Preoperative and postoperative measurements showed no statistically significant differences in M-SSEP or D-SSEP. Postoperative D-SSEPs in both experimental groups showed significant reductions in relative amplitude, but the M-SSEPs of all groups and D-SSEPs of the control groups remained constant.

CONCLUSION

SSEP is valuable for detecting electrophysiologic changes after laminotomy fibrosis, but acceptable accuracy requires proper stimulation and recording settings. D-SSEP monitoring provided reliable, useful information about the functional integrity of the cauda equina in this animal model. We recommend D-SSEP monitoring as a supplemental tool for quantifying the effect of postlaminotomy fibrosis on neuropathy.

The role of mitomycin C in reducing recurrence of epidural fibrosis after repeated operation in a laminectomy model in rats

Object

Extensive peridural fibrosis after lumbar spine surgery may contribute to poor outcome and recurrent symptoms leading to repeated operation. Secondary procedures are considerably hampered by the presence of scar tissue. Moreover, after excision of the peridural scar, the fibrous tissue may recur, leading to unsuccessful surgical outcome. Mitomycin C (MMC), an alkylating antibiotic substance isolated from Streptomyces caespitosus, potentially suppresses fibroblast proliferation after surgical intervention. The authors investigated the effect of MMC on the reformation of epidural fibrosis in a laminectomy model in rats.

Methods

Twenty-four Wistar rats underwent a repeated lumbar laminectomy 3 months after the first operation. In 12 rats, MMC in a concentration of 1 mg/ml was locally applied to the laminectomy site. No treatment was performed in the control group of the other 12 rats. All rats underwent clinical evaluation. Mobility ratings and any evidence of neurological deficit were recorded. Twelve weeks after the second operation, the animals were killed for histological examination. The extent of epidural fibrosis and dural adherence was evaluated.

All MMC-treated animals showed reduced epidural scarring, compared with the control group. In nine MMC-treated rats (75%), dural adhesions were moderate. In contrast, all control sites showed dense epidural fibrosis with marked dural adherence. No side effects of the treatment were observed.

Conclusions

In this experimental study, MMC in a concentration of 1 mg/ml locally applied significantly reduced recurrence of epidural fibrosis and dural adhesions without any side effects after repeated spinal surgery in a laminectomy model in rats.