The lumbar spines of twenty-one dogs were used as an experimental model. The animals were divided into three groups. In the first group, selective damage to the perimeningeal blood vessels was induced and the resultant hematoma was left untouched in the spinal canal. In the second group, the posterior longitudinal ligament was incised, and in the third group, the posterior longitudinal ligament was incised and damage induced to the perimeningeal blood vessels. The pathology examination revealed: (1) the hematoma itself did not lead to the formation of perineural fibrosis, (2) the incision of the posterior longitudinal ligament led to the formation of a limited amount of fibrosis, and (3) the coexistence of hematoma and incision of the posterior longitudinal ligament led to the formation of extensive perineural fibrosis. When discs are removed using microsurgical techniques, it is possible to avoid the formation of the postoperative hematoma and consequently to eliminate the perineural fibrosis. 8 1992 wiley-Liss, Inc. MICROSURGERY 13:192-194
1992
POST-DISCECTOMY PERINEURAL FIBROSIS: COMPARISON OF CONVENTIONAL VERSUS MICROSURGICAL TECHNIQUES ALEXANDROS S. TOULIATOS, M.D., PANAYOTIS N. SOUCACOS, M.D., and ALEXANDROS E. BERIS, M.D.
T h e prolapse of the nucleus pulposus of the lumbar intervertebral disc was described as a syndrome for the first time in 1934 by Mixter and Barr.’ The same investigators developed the surgical treatment for this syndrome and soon the discectomy was accepted worldwide. However, initial enthusiasm over the results of the discectomy was followed by skepticism. A considerable number of patients who obtained immediate postoperative improvement in their symptoms developed recurrence of symptoms a few months or years later which sometimes were so severe that they required a second ~peration.’.~ The constant feature in all the reoperated cases was the presence of adhesions around the dura mater and the nerve roots. These adhesions gradually lead to perineural fibrosis, local ischaemia, and subsequent i n t r a n e d fibrosis, added to the intraneural fibrosis which was present prior to the first operation due to the prolapsed intervertebral disc .4-6 This results in further sensitization of the nerve, and pain even under mild changes of the intraneural tension, such as during usual daily activities. The mechanisms by which this pain is transmitted is either through the nerva nervorum of the nerve root or through the “artificial synapses”.’ The severity of the pain depends upon the amount of the
From the Orthopaedic Department, The University of loannina Medical School, loannina. Greece. Address reprint requests to Alexandros S.Touliatos, M.D., Assistant Professor, Orthopaedic Department, The University of loannina, Medical School, 451 10 loannina, Greece. 0 1992 Wiley-Liss, Inc.
intraneural fibrosis which was present prior to the operation and upon that which was added after the operation. The postoperative fibrosis was attributed to the surgical trauma of the posterior longitudinal ligament by Key and Fordin in 194K8 Three decades later, La Rocca and McNab suggested that the fibrosis was due to the “laminectomy membrane” which is formed by the surgical trauma of the sacrolumbar muscles during the operation.’ In order to prevent the invasion of the laminectomy membrane into the spinal canal, the laminectomy gap has been successfully covered with free autografts of fat or sacrolumbar fascia.’07” Besides the laminectomy membrane and the injury to the posterior longitudinal ligament, the postoperative hematoma is also considered to be a causative factor for the formation of postoperative adhesions and fibrosis. MATERIALS AND METHODS
The lumbar spines of adult mongrel dogs were used as an experimental model. A total of twenty-one dogs were used and divided into three groups, seven dogs in each group. Surgical Technique. Under general anesthesia, a midline incision was made along the spinous processes of the lumbosacral area. After the dissection of the subcutaneous tissue and the fascia, total laminectomy of the L4 vertebra was performed and the underlying dura was exposed. This stage of the operation was done by conventional techniques. The following stage was different in each group and was done
Microsurgery, Microsurgical vs. Conventional Discectomy
Figure 1. Microscopic findings of a representative specimen from the animals of the first group (postoperative hematoma in the spinal canal), six months postoperatively, which show that the dura mater is free of adhesions. L: posterior longitudinal ligament; D: dura mater; N: nerve root.
193
Figure 2. Microscopic findings of a representative specimen from the animals of the second group (incisionof the posterior longitudinal ligament), six months postoperatively, which show the presence of fibrous connective tissue in the area of the damaged posterior longitudinal ligament. The dura mater itself is free of adhesions. G: granulation connective tissue; D: dura mater; N: nerve root.
with the aid of an operating microscope and microsurgical The operative elements, including posterior longitudinal instruments. ligaments, adjacent dura mater, and nerve roots underwent First Group. After exposure of the dura mater in each microscopic examination revealing the following: animal of this group, selective damage to the perimeningeal blood vessels was induced, while attention was paid to First Group. The dura mater was free of adhesions in its avoid damaging the dura mater itself. The resultant he- entirety. Fibrous connective tissue around the dura mater matoma was left untouched in the spinal canal. The opera- was not found. No evidence of necrosis or infection was tion was completed by covering the laminectomy gap with present (Fig. 1). free fascia grafts and then suturing the soft tissues in layers. Second Group. At the damaged area of the posterior lonSecond Group. After exposure of the dura mater, the gitudinal ligament, granulation tissue was present, spreadposterior longitudinal ligament was incised, simulating the ing into the adjacent dura mater, although fibrosis had not trauma induced when discectomy is performed. Provided developed in the dura mater itself (Fig. 2). that no damage was done to the vessels and bleeding was not present, the operation was completed, as in the first Third Group. The dura mater was stuck to the adjacent spinal walls by adhesions and a considerable amount of group. granulated connective tissue had developed between the Third Group. After exposure of the dura mater, the pos- nerve roots (Fig. 3). terior longitudinal ligament was incised, cross-like, and damage to the perimeningeal blood vessels was induced. DISCUSSION The resultant hematoma was abandoned in the spinal canal. From this experimental study, it is obvious that the exThe operation was completed as in the previous groups. istence of the hematoma in the spinal canal does not lead to Each animal was sacrificed six months postoperatively. the formation of adhesions. The hematoma itself, provided
194
Touliatos et al.
both hematoma and fibroblasts, derived from the injured posterior longitudinal ligament, lead to the formation of extensive fibrous connective tissue, perimeningeal adhesions, and perineural fibrosis. When a disc is removed using conventional surgical technique, it is known that creation of a postoperative hematoma is inevitable. It is also known that disc removal is a procedure where injury to the posterior longitudinal ligament cannot be avoided. Using microsurgical techniques, it is possible to avoid injury to the perimeningeal blood vessels as well as to the venous network which lies between the posterior longitudinal ligament and the vertebrae. The resultant absence of hematoma in the spinal canal greatly reduces the growth of fibrous connective tissue and perimeningeal fibrosis.
REFERENCES
Figure 3. Microscopic findings of a representative specimen from the animals of the third group (hematoma in the spinal canal and incision of the posterior longitudinal ligament) which show considerable amount of granulation connective tissue between the nerve roots. G: granulation connective tissue; N: nerve roots.
that no other factors are present, is absorbed gradually by the rich network of the perimeningeal blood vessels and is not responsible for the formation of any infectious reaction or for perimeningeal fibrosis. The damage to the posterior longitudinal ligament alone leads to the formation of a limited amount of granulation connective tissue at the damaged area. This granulation connective tissue may lead to the formation of perimeningeal adhesions, but the dura mater, more or less, remains free of adhesions. The coexistence of
1. Mixter WJ, Barr JS: Rupture of the intervertebral disc with involvement of the spinal canal. N Engl J Med 211:210, 1934. 2. Aitken AP, Bradford CH:End results of ruptured intervertebral discs in industry. Am J Surg 73:365, 1975. 3. Hirsch C, Nachemson A: The reliability of lumbar disc surgery. Clin Orthop 29:198, 1963. 4. Eames RE, Lang IS: Clinical and pathological study of ischaemic neuropathy. J Neurol Neurosurg Psychiatr 30:215, 1967. 5. Gill GG,Sakovich L, Thompson E Pedicle fat grafts for the prevention of scar formation after laminectomy. An experimental study on dogs. Spine 4:176-186, 1979. 6. Gertzbein SD, Tile M, Gross A, Falk R: Autoimmunity in degenerative disc disease of the lumbar spine. Orthop Clirt North Am 6:67, 1975. 7. Roberts JT: The effect of occlusive arterial extremities on the blood supply of nerves: Experimental and clinical studies on the vasa nervorum. Am Heart J 35:369, 1948. 8. Key JA, Ford LT: Experimental intervertebral disc lesions. J Bone Joint Surg 30A:621-630, 1948. 9. La Rocca H, MacNab I: The laminectomy membrane: Studies in its evolution, characteristics, effects and prophylaxis in dogs. J Bone Joint Surg 56B:545-550, 1974. 10. Keller JT, Dunsker SB, McWhorter JM, Ongkiko CM, Saunders MC, Mayfield FH: The fate of autogenous grafts to the spinal dura: An experimental study. J Neurosurg 49:412-418, 1978. 11. Yong-Hing K, Reilly J, De Korompay V, Kirkaldy-Willis WH: Prevention of nerve root adhesions after laminectomy. Spine 559-64, 1980.
1992
POST-DISCECTOMY PERINEURAL FIBROSIS: COMPARISON OF CONVENTIONAL VERSUS MICROSURGICAL TECHNIQUES ALEXANDROS S. TOULIATOS, M.D., PANAYOTIS N. SOUCACOS, M.D., and ALEXANDROS E. BERIS, M.D.
T h e prolapse of the nucleus pulposus of the lumbar intervertebral disc was described as a syndrome for the first time in 1934 by Mixter and Barr.’ The same investigators developed the surgical treatment for this syndrome and soon the discectomy was accepted worldwide. However, initial enthusiasm over the results of the discectomy was followed by skepticism. A considerable number of patients who obtained immediate postoperative improvement in their symptoms developed recurrence of symptoms a few months or years later which sometimes were so severe that they required a second ~peration.’.~ The constant feature in all the reoperated cases was the presence of adhesions around the dura mater and the nerve roots. These adhesions gradually lead to perineural fibrosis, local ischaemia, and subsequent i n t r a n e d fibrosis, added to the intraneural fibrosis which was present prior to the first operation due to the prolapsed intervertebral disc .4-6 This results in further sensitization of the nerve, and pain even under mild changes of the intraneural tension, such as during usual daily activities. The mechanisms by which this pain is transmitted is either through the nerva nervorum of the nerve root or through the “artificial synapses”.’ The severity of the pain depends upon the amount of the
From the Orthopaedic Department, The University of loannina Medical School, loannina. Greece. Address reprint requests to Alexandros S.Touliatos, M.D., Assistant Professor, Orthopaedic Department, The University of loannina, Medical School, 451 10 loannina, Greece. 0 1992 Wiley-Liss, Inc.
intraneural fibrosis which was present prior to the operation and upon that which was added after the operation. The postoperative fibrosis was attributed to the surgical trauma of the posterior longitudinal ligament by Key and Fordin in 194K8 Three decades later, La Rocca and McNab suggested that the fibrosis was due to the “laminectomy membrane” which is formed by the surgical trauma of the sacrolumbar muscles during the operation.’ In order to prevent the invasion of the laminectomy membrane into the spinal canal, the laminectomy gap has been successfully covered with free autografts of fat or sacrolumbar fascia.’07” Besides the laminectomy membrane and the injury to the posterior longitudinal ligament, the postoperative hematoma is also considered to be a causative factor for the formation of postoperative adhesions and fibrosis. MATERIALS AND METHODS
The lumbar spines of adult mongrel dogs were used as an experimental model. A total of twenty-one dogs were used and divided into three groups, seven dogs in each group. Surgical Technique. Under general anesthesia, a midline incision was made along the spinous processes of the lumbosacral area. After the dissection of the subcutaneous tissue and the fascia, total laminectomy of the L4 vertebra was performed and the underlying dura was exposed. This stage of the operation was done by conventional techniques. The following stage was different in each group and was done
Microsurgery, Microsurgical vs. Conventional Discectomy
Figure 1. Microscopic findings of a representative specimen from the animals of the first group (postoperative hematoma in the spinal canal), six months postoperatively, which show that the dura mater is free of adhesions. L: posterior longitudinal ligament; D: dura mater; N: nerve root.
193
Figure 2. Microscopic findings of a representative specimen from the animals of the second group (incisionof the posterior longitudinal ligament), six months postoperatively, which show the presence of fibrous connective tissue in the area of the damaged posterior longitudinal ligament. The dura mater itself is free of adhesions. G: granulation connective tissue; D: dura mater; N: nerve root.
with the aid of an operating microscope and microsurgical The operative elements, including posterior longitudinal instruments. ligaments, adjacent dura mater, and nerve roots underwent First Group. After exposure of the dura mater in each microscopic examination revealing the following: animal of this group, selective damage to the perimeningeal blood vessels was induced, while attention was paid to First Group. The dura mater was free of adhesions in its avoid damaging the dura mater itself. The resultant he- entirety. Fibrous connective tissue around the dura mater matoma was left untouched in the spinal canal. The opera- was not found. No evidence of necrosis or infection was tion was completed by covering the laminectomy gap with present (Fig. 1). free fascia grafts and then suturing the soft tissues in layers. Second Group. At the damaged area of the posterior lonSecond Group. After exposure of the dura mater, the gitudinal ligament, granulation tissue was present, spreadposterior longitudinal ligament was incised, simulating the ing into the adjacent dura mater, although fibrosis had not trauma induced when discectomy is performed. Provided developed in the dura mater itself (Fig. 2). that no damage was done to the vessels and bleeding was not present, the operation was completed, as in the first Third Group. The dura mater was stuck to the adjacent spinal walls by adhesions and a considerable amount of group. granulated connective tissue had developed between the Third Group. After exposure of the dura mater, the pos- nerve roots (Fig. 3). terior longitudinal ligament was incised, cross-like, and damage to the perimeningeal blood vessels was induced. DISCUSSION The resultant hematoma was abandoned in the spinal canal. From this experimental study, it is obvious that the exThe operation was completed as in the previous groups. istence of the hematoma in the spinal canal does not lead to Each animal was sacrificed six months postoperatively. the formation of adhesions. The hematoma itself, provided
194
Touliatos et al.
both hematoma and fibroblasts, derived from the injured posterior longitudinal ligament, lead to the formation of extensive fibrous connective tissue, perimeningeal adhesions, and perineural fibrosis. When a disc is removed using conventional surgical technique, it is known that creation of a postoperative hematoma is inevitable. It is also known that disc removal is a procedure where injury to the posterior longitudinal ligament cannot be avoided. Using microsurgical techniques, it is possible to avoid injury to the perimeningeal blood vessels as well as to the venous network which lies between the posterior longitudinal ligament and the vertebrae. The resultant absence of hematoma in the spinal canal greatly reduces the growth of fibrous connective tissue and perimeningeal fibrosis.
REFERENCES
Figure 3. Microscopic findings of a representative specimen from the animals of the third group (hematoma in the spinal canal and incision of the posterior longitudinal ligament) which show considerable amount of granulation connective tissue between the nerve roots. G: granulation connective tissue; N: nerve roots.
that no other factors are present, is absorbed gradually by the rich network of the perimeningeal blood vessels and is not responsible for the formation of any infectious reaction or for perimeningeal fibrosis. The damage to the posterior longitudinal ligament alone leads to the formation of a limited amount of granulation connective tissue at the damaged area. This granulation connective tissue may lead to the formation of perimeningeal adhesions, but the dura mater, more or less, remains free of adhesions. The coexistence of
1. Mixter WJ, Barr JS: Rupture of the intervertebral disc with involvement of the spinal canal. N Engl J Med 211:210, 1934. 2. Aitken AP, Bradford CH:End results of ruptured intervertebral discs in industry. Am J Surg 73:365, 1975. 3. Hirsch C, Nachemson A: The reliability of lumbar disc surgery. Clin Orthop 29:198, 1963. 4. Eames RE, Lang IS: Clinical and pathological study of ischaemic neuropathy. J Neurol Neurosurg Psychiatr 30:215, 1967. 5. Gill GG,Sakovich L, Thompson E Pedicle fat grafts for the prevention of scar formation after laminectomy. An experimental study on dogs. Spine 4:176-186, 1979. 6. Gertzbein SD, Tile M, Gross A, Falk R: Autoimmunity in degenerative disc disease of the lumbar spine. Orthop Clirt North Am 6:67, 1975. 7. Roberts JT: The effect of occlusive arterial extremities on the blood supply of nerves: Experimental and clinical studies on the vasa nervorum. Am Heart J 35:369, 1948. 8. Key JA, Ford LT: Experimental intervertebral disc lesions. J Bone Joint Surg 30A:621-630, 1948. 9. La Rocca H, MacNab I: The laminectomy membrane: Studies in its evolution, characteristics, effects and prophylaxis in dogs. J Bone Joint Surg 56B:545-550, 1974. 10. Keller JT, Dunsker SB, McWhorter JM, Ongkiko CM, Saunders MC, Mayfield FH: The fate of autogenous grafts to the spinal dura: An experimental study. J Neurosurg 49:412-418, 1978. 11. Yong-Hing K, Reilly J, De Korompay V, Kirkaldy-Willis WH: Prevention of nerve root adhesions after laminectomy. Spine 559-64, 1980.
