Advances in operative techniques
9 Springer-Verlag 1992 Child's Nerv Syst (1992) 8:226-228
Laminotomy: a technical note D. Douglas Cochrane and Paul Steinbok Division of Neurosurgery, Department of Surgery, University of British Columbia and Department of Pediatric Neurosurgery, British Columbia's Children's Hospital, Vancouver, British Columbia, Canada Received July 27, 1991
Abstract. In order to restore spinal integrity following posterior exposures o f the spinal canal in children, we describe modifications o f R a i m o n d i ' s l a m i n o t o m y technique. The use o f a p n e u m a t i c dissecting tool with footplate to create a hinged osteoplastic l a m i n o t o m y is described, as are techniques for securing the l a m i n o t o m y flap in place at the end o f the procedure. Key words: L a m i n o t o m y - L a m i n e c t o m y - Posterior decompression - Spinal canal
Spinal d e f o r m i t y is a well-recognized complication o f laminectomies in children, certainly in the cervical and thoracic regions . It has been suggested that replacem e n t o f the posterior elements m a y help to prevent spinal deformity f r o m occurring . Stimulated by R a i m o n d i , the authors have u n d e r t a k e n laminotomies with replacement o f the posterior elements in preference to laminectomies for posterior spinal canal access in children. W i t h the institution o f selective functional posterior r h i z o t o m y for the treatment o f spasticity in children with cerebral palsy, the n u m b e r o f cases requiring a posterior a p p r o a c h to the spinal canal, especially the l u m b a r canal, has increased in our institution, as it has in m a n y other centers. In the absence o f contraindications such as spinal stenosis, we have replaced posterior elements as a routine p a r t o f our operative procedure. This technical note describes the i n s t r u m e n t a t i o n and m e t h o d s we use to effect a l a m i n o t o m y , with emphasis on the reconstitution o f spinal integrity and the protection o f the intradural elements.
Operative procedure Lumbar laminotomy Following the midline exposure of the supraspinous ligament and the lumbodorsal fascia, paramedian incisions are made in the lum-
Correspondence to."D.D. Cochrane, Department of Pediatric Neurosurgery, British Columbia's Children's Hospital, 4480 Oak Street, Vancouver, BC V6H 3V4, Canada
bodorsal fascia, preserving the attachment of the supraspinous ligament to the spinous processes. The multifidus and interspinalis muscles are reflected from the spinous processes and laminae to expose the medial half of the inferior articular processes. This provides a sufficient width of exposure so that the pneumatic drill with B5 dissecting tool and B5 attachinent (Midas Rex Pneumatic Tools, Fort Worth, Texas) can be used easily. For older children and teenagers who have thicker laminae, a B1 dissecting tool and attachment may be required. With self-retaining retractors in place, a Howarth, Cloward periosteal osteophyte or Adson elevator is used to strip the ligamenrum flavum from the undersurface of the lowest lamina to be removed. The supraspinous ligament is left intact as it stabilizes the laminae while the laminotomies are cut. The footplate of the B5 attachment provides protection to the epidural fat and dura while the B5 dissecting toolcuts the laminotomy. The instrument is inserted into the spinal canal and drawn up against the undersurface of the lamina, away from the dural sac. The degree of overlap of lamina and infolding of the ligamentum flavum affects how the instrument is handled during the cutting process. As the instrument is moved from caudal to cranial over the extent of the exposure, tilting the handpiece cranially while applying dorsal pressure on the footplate allows the dissecting tool to cut through the lamina. Gentle caudal movement of the handpiece once the lamina is cut aUows safe advancement of the footplate under the superior ligamentum flavum. This rocking movement is repeated at each level. With completion of the laminotomies on both sides, the caudal attachment of the supraspinous ligament is incised with a scalpel. Residual ligamentum flavum is incised, and the laminotomy flap is elevated and reflected cranially and hinged on the intact supraspinous and interspinous ligaments and the ligamentum flavum at the cranial end of the exposure. The laminotomy flap is not removed but wrapped in a saline-soaked gauze and secured out of the field using a suture or Kocker or towel clip (Fig. 1). In the lumbar area, drill holes are not required to return the flap to its anatomical position, so that at this stage all bone edges are waxed and the intraspinal procedure is carried out. To reposition the laminar flap at the end of the procedure, 2-0 polygalactin sutures (Vicryl, Ethicon, Peterborough, Ontario) are placed at each interlaminar level through the ligamentum flavum on the flap and through the residual ligamentum flavum or facet joint capsule laterally (Fig. 2). A final suture is placed through the supraspinous and interspinous ligament at the caudal end of the flap, joining it with the lowest intact spinous process. The stabilizing sutures on both sides are tied simultaneously, starting cranially and working caudally. The last suture tied is that between the lowest lamina of the flap and its caudal neighbor. The paraspinal musculature can be approximated using 2-0 sutures placed through the interspinous ligament at each level, or they
227 spinous processes facilitate the approximation of the paraspinal musculature. This elevates the laminar flap out of the spinal canal. The ligamentum nuchae is then closed.
Fig. 1. Laminotomy flap retracted cranially out of the operative field. Supraspinous, interspinous and ligamentum flavum are left intact
In the thoracic area, obstruction caused by the vertical orientation of the spinous processes precludes the reflection of the laminotomy flap. Excision of part of all of the spinous process of the intact vertebra at the cranial end of the exposure, while leaving the ligamentum flavum intact, removes this impediment and allows the flap to be hinged superiorly as described. A similar technique is used to deal with bulky spinous processes in the lumbar spine in older children. Drill holes are required for fixation in the thoracic area as described for the cervical laminotomy. Paraspinal musculature and fascia are sutured to the spinous process or supraspinous ligament. Transverse drill holes through the spinous processes many be required.
Fig. 2. Replacement of the laminotomy flap. Sutures are placed through the ligamentum flavum medially and laterally at each laminotomized level (arrow). Caudal interspinous suture is tied last
can be allowed to fall in against the lamina. 2-0 Sutures are placed through the lumbodorsal fascia and supraspinous ligament (attached to the flap) drawing the flap away from the spinal canal.
Cervical laminotomy In the cervical area, the laminotomies can be made as described above; however, the overlapping of the laminae an the thin ligamenturn flavum require that drill holes be placed so that the laminotomy flap may be secured at the end of the procedure. In the flap, these holes are drilled through the full thickness of the lamina. On the anchoring side of the osteotomy, vertical holes are drilled at each level and then joined to horizontal holes placed through the diplo~. The operator is in the best position to drill the vertical holes on his or her side and the horizontal holes on the opposite. The assistant or the operator, after changing sides, then completes the holes. A shallow lateral extension made to the vertical hole allows sutures to be passed easily through the anchoring hole and then through the hole on the laminar flap. Drill holes placed transversely through the
It has yet to be shown whether laminotomy prevents or reduces the risk of kyphoscoliosis in children undergoing intraspinal procedures. Theoretically, it allows the reconstruction of normal a n a t o m y following posterior approaches to the spine at all levels. It also prevents the development of myodural cicatrix, which can compromise the spinal canal . In our experience the osteotomies heal, as demonstrated on subsequent CT imaging (Fig. 3). Our experience using this technique for posterior spinal access over two or more levels is summarized in Table 1. Exposure of the intraspinal contents has been ample for lumbar and cervical rhizotomy as well as for removal of intra- and extradural tumors, extradural abscesses, and syringostomy. Lateral undercutting of facets or facetectomy, required for patients with spinal stenosis or laterally situated dumbell tumors, was easily performed. Adequate longitudinal exposure with a hinged laminotomy flap is obtained by extending the laminotomy one level above that which would be necessary if the laminotomy flap were to be removed. The laminotomy flap has not been replaced in patients with a small spinal canal or if infection was present. Complications to date have been few. One dural tear, without arachnoid tear, occurred early in the series. This was within the operative field and easily repaired. N o thermal or abrasive injury to the dura has been noted. One patient undergoing a lumbar rhizotomy developed an anteriorly placed subdural h e m a t o m a during the opening which required evacuation. N o cause for this was found on intradural exploration. Other injury to the spinal contents has not occurred. Spinal deformity has not developed to date and in no patient have the replaced posterior elements fused. There are several technical points that recommend this approach. The Midas Rex footplate is smaller than than most rongeurs. This allows the laminotomy to be cut with minimal intrusion into the spinal canal. The lateral placement of the laminotomy and the protection afforded the
Fig. 3. Lumbar computed tomograms, 6 months following laminotomy. Left: at L4 the laminotomies have not ossified (open arrows); right: at L2 there has been complete healing on the left (arrow) and partial healing on the right
Table 1. Laminotomy for spinal canal access (1986-1990)
Cervical, cervicothoracic Thoracic Thoracolumbar Lumbar
No. of cases 3 2 8 69
Chiari malformation, tumor, spasticity Extradural abcess, tumor Spinal stenosis, tumor, syringomyelia Spastic diplegia, tethered cord, diastematomyelia, tumor
Laminar flap replaced 2 0 5 65
dura and its contents by the footplate, coupled with the fact that spinal canal is not compromised by the instrument, in our opinion justifies the use of this technique rather than an unprotected drill . The B5 or B1 dissecting tool minimizes bone loss during the osteotomy and thereby allows better bone contact when the flap is repositioned. The limited depth of the tool's cutting surface prevents the operator from inadvertently cutting into the facet joint. Hinging the flap superiorly, rather than removing it, allows the restoration of the integrity of the supraspinous ligament. Bleeding from the laminar edge on the flap is seen, suggesting that this technique preserves some vascular supply to the flap. Revascularization of the flap is critical in the child if peridural scar and deformity are to be minimized [1, 2]. The techniques described have evolved over the past 4 years. Initially, we drilled holes in the flap and lateral lamina to securely reposition lumbar laminotomy flaps.
The laminotomy was made as far lateral as possible to provide adequate intraspinal exposure and the drill holes on the anchoring side often went into the facet joints. As yet we have not seen adverse effects from facet injury, and drill holes are not necessary if the sutures are placed through the ligamentum flavum medially and laterally. In order to minimize the risk of migration of the laminar flap into the canal, the interspinous suture placed at the caudal extent of the flap and those placed through the supraspinous ligament into lumbodorsal fascia are critical. These sutures take advantage of the paravertebral muscle spasm in the early postoperative period and resultant loss of lordosis to support the flap away from the dura. The time required for laminotomy using this technique is considerably shorter than that for traditional laminectomy. When the bone is replaced, the operative time approximates that of traditional laminectomy.
1. Ishida Y, Suzuki K, Ohmori K, Kikata Y, Hattori Y (1989) Critical analysis of extensive cervical laminectomy. Neurosurgery 24:215-222 2. Ohmori K, Ishida Y, Suzuki K (1987) Suspension laminotomy: a new surgical technique for compression myelopathy. Neurosurgery 21:950-957 3. Raimondi AJ (1978) Reflection of a laminar flap for exposure of the spinal canal in children. Clin Neurosurg 25:504-511 4. Raimondi AJ (1987) Pediatric neurosurgery. Theoretical principles, art of surgical techniques. Springer, New York Berlin Heidelberg, pp 98-105, 107-109 5. Yasuoka S, Peterson HA, MacCarty CS (1982) Incidence of spinal column deformity after multilevel laminectomy in children and adults. J Neurosurg 57:441-445