Anterior Approach to the Thoracolumbar
Spine
Technical Considerations John D.
Burrington, MD; Courtney Brown, MD;
Eli R.
Wayne, MD; John Odom,
\s=b\ Forty-five patients, of whom most were children, underwent extensive exposure of the thoracolumbar spine to correct serious orthopedic abnormalities. The spine was exposed through a combined thoracotomy and retroperitoneal approach that gave excellent access with minimal morbidity. The diaphragm was opened circumferentially after the peritoneum had been dissected from its muscular portion. This permitted repair of the diaphragm with no detectable loss of function. Although this approach was developed for exposure of the spine, it can also be utilized to expose the entire aorta, both kidneys and their blood supply, and the retroperitoneal area for possible excision of large tumors.
(Arch Surg 111:456-463, 1976) and Yau'
the anterior
Hodgson repopularized correcting orthopedic spine Sinceapproach Dwyer'7 perfected techniques to the
for his
of internal anomalies and deformities children have can severe spinal fixation, corrected or stabilized. As experience with this direct exposure of the vertebral bodies has accumulated, indica¬ tions for exposing long segments of the spine have expanded. Whereas Hodgson and Yau1 originally reported wedge resection of a single hemivertebra and fusion of a publication Dec 29, 1975. departments of surgery (Drs Burrington and Wayne) and orthopedics (Drs Brown and Odom), the Children's Hospital, Denver. Dr Burrington is now with the Department of Surgery at the University of Chicago. Read before the 83rd annual meeting of the Western Surgical Association, Colorado Springs, Colo, Nov 22, 1975. Reprint requests to Department of Surgery, Box 163, University of Chicago, 950 E 59th St, Chicago, IL 60637 (Dr Burrington).
Accepted
From the
for
MD
single disk space, it is possible to expose and fuse up to 14 disk spaces in a single operation. The anterior approach has also made it possible to stabilize the spine in children with congenital spinal deformities and prevent the progressive neurologic and pulmonary deterioration that would other¬ wise develop. With the anterior portion of the vertebral bodies exposed, strut grafts of rib or fibula can be mortised into position to prevent progression of a kyphos when the vertebrae are so deficient that posterior fusion is not possible. The Dwyer internal fixation apparatus will also hold the spine in correction during a healing phase of a spinal fusion in complex abnormalities that are not suitable for correc¬ tion with Harrington compression and distraction rods. These conditions include the following: (1) rigid congenital scoliosis; (2) severe acquired or congenital kyphosis; and (3) lumbar scoliosis with lordosis and hyperlordosis. Mechani¬ cally, the Dwyer apparatus is able to distribute more evenly the stress produced by correction of the spinal curve. Long screws in each vertebral body braced by a large staple absorb the stress that results from pulling adjacent vertebral bodies into alignment.7 Application of the staples directly to the vertebral bodies also aids in correcting the
rotational deformities that become marked in advanced scoliosis. Although the cables do occasionally break, failure is much less common than it is with Harrington rods, and pseudarthrosis occurs in less than 10% of the patients. Earlier reports noted frequent worsening of neurologic status7'1 following anterior exposure of the lower thoracic spine, but this disastrous complication has been reduced to acceptable levels by a better understanding of the circula-
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
tion of the spinal cord, performance of preoperative myelograms to detect diplomyelia, and preoperative halofemoral traction when necessary. This article reviews our experience with anterior expo¬ sure of the vertebral bodies in 45 patients who underwent operation at the Children's Hospital, Denver, for correction of spinal anomalies. We emphasize the details of patient management and surgical technique as well as the implica¬ tions for broadening the use of this exposure to include large retroperitoneal tumors and for exposure in extensive reconstructive procedures involving the aorta and its branches. SUBJECTS AND METHODS Selection of Patients
Initially, all patients had severe decompensated spinal curves that were judged unsuitable for posterior fusion and Harrington instrumentation because of the nature of the curve or absence of the posterior structures resulting from trauma, congenital defects, or destruction by neurofibromatosis. As experience accumulated, the indications for anterior fusion and fixation with bone struts or the Dwyer apparatus widened to include all patients with a decompensated or progressive curve who were believed unsuitable for posterior fusion. Evaluation of Patients Each patient was carefully evaluated for overall general health. Full-length spinal roentgenograms were obtained with the patient lying supine, standing, and in maximal lateral flexion for detailed analysis of the curves and identification of transitional vertebral bodies above and below the deformity. Most patients had recent intravenous pyelograms to rule out unsuspected urinary tract deterioration; myelograms were taken of all children with congenital anomalies involving the spine so as to rule out unsus¬ pected diplomyelia or any other bony abnormality that might produce neurologic symptoms when the spine was straightened. All children old enough to cooperate underwent evaluation of their pulmonary function by measurement of functional residual capac¬ ity, forced vital capacity, peak flow rate, and maximum ventila¬
tory volume.
Preparation
of Patients
Patients were prepared by being put in a plaster jacket, Milwaukee brace, or halofemoral traction for four to six weeks to reduce the deformity. Slow, progressive spinal extension allows accommodation for nerve roots that may be partially entrapped in scar or foreshortened because of the marked curve. Preoperative traction has also been shown to improve pulmonary ventilationperfusion ratios.' In no patient was it necessary to interrupt traction because of neurologic symptoms. All children with urinary tract infection were treated with appropriate antibiotics during this preparation phase. Those with severe neurologic deficit or a history of constipation had their colons cleansed with enemas and began a low-residue diet, receiving laxatives as required.
Operative
Procedure
All patients underwent intubation with a cuffed nasotracheal tube that was taped securely in place after applying benzoin to the tube and skin. A plastic cannula introduced percutaneously into the radial artery at the wrist aided in monitoring blood gases throughout the procedure. A central venous line introduced into either the subclavian or jugular vein aided in monitoring blood and
fluid administration throughout the procedure and recovery period. These lines were inserted using meticulous aseptic tech¬ nique and were held securely in place by sterile dressings. Patients with scoliosis were placed in the lateral position with the convex portion of the major curve uppermost. In some in¬ stances, it was helpful to raise the kidney rest to accentuate the curve and facilitate removal of intervertebral disks prior to fusion. In patients whose primary problem is kyphosis or lordosis, the spine can be approached from either side. Since many of the children had an ileal bladder or some other form of urinary tract diversion, we tried whenever possible to place the new incision on the side of the abdomen opposite the stoma. If no previous surgery had been performed, we approached the spine from the right, so that the artery of Adamkiewicz supplying the spinal cord was less likely to be disturbed. A Foley catheter with a 30-cu cm balloon introduced into an ileal conduit and partially inflated just below the level of the fascia provided a satisfactory means of keeping the urine from the operative field. It also permitted urine collection so that output and specific gravity could be monitored throughout the procedure. The iliac crest and occasionally the ipsilateral fibula may be propped and draped so that bone can be taken from these areas if it is required for grafting. Large thoracoabdominal incisions cause the patient to lose heat rapidly throughout the procedure and administration of large amounts of refrigerated blood cools the patient even more. To prevent this, we preferred to maintain the operating room at 26.6 C with 50% or more relative humidity. Each patient was positioned on a fluid-filled mattress that could be used for heating or cooling as necessary to maintain normal body temperature. Blood was passed through a warming unit prior to infusion and core temperature was monitored continuously with a rectal or esophageal probe. Cardiac monitoring was also essen¬ tial. The skin incision was placed over the rib originating at or one vertebra above the highest vertebral body to be fused (Fig 1, upper left). Marked rib cage deformity present in some children may make it necessary to also excise the next higher rib to facilitate placement of the highest staple. The initial incision followed the course of the rib to be excised from the costal margin to approximately the level of the trans¬ verse process. The rib was removed subperiosteally throughout its entire length and kept in sterile saline solution for use as bone grafts in the fusion (Fig 1, upper right). The pleura was then entered and the cartilagenous portion of the costal margin was divided. The abdominal portion of the skin incision was then extended from the costal margin toward the pubic tubercle. The abdominal muscles were divided down through the transversus abdominus, but the peritoneum was left intact. The peritoneum was dissected bluntly from the diaphragm near its lateral attachment and the diaphragm was divided with cautery about one inch from its costal attachment (Fig 1, lower left). This peripheral detachment preserved the diaphragmatic innervation so that its postoperative function was normal and cautery reduced blood loss. The peri¬ toneum and its contents including kidneys and ureters were then dissected bluntly from the flank muscles to expose the lumbar spine (Fig 1, lower right). Gravity helps hold the viscera forward. A rib spreader introduced into the thoracic portion of the incision opened it widely. The pleura overlying the spine was opened in a Convenient spot and individual intercostal vessels were ligated close to their origin from the aorta. If only the intercostal and lumbar vessels on the convex side of the curve are divided, collateral flow from the contralateral vessels will maintain perfu¬ sion of the spinal cord.7' Division of all aortic branches on the
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
Fig 1.—Steps
in approach to spine from left side. Upper left, Incision follows course of rib attached to highest vertebral body to be exposed. Abdominal portion extends from costal margin to pubic tubercle. Upper right, Rib is removed for bone graft and abdominal musculature is divided down to peritoneum, which is left intact. Diaphragm remains attached except where costal
has been divided. Lower left, Peritoneum is dissected off under surface of diaphragm and diaphragm is divided circumferentially about 2 cm from its attachment. Lower right, Diaphragm has been divided and attachments to spine removed. Spine lies in base of incision with segmental branches from aorta clearly visible.
surface of the curve was necessary to permit access to disk spaces and allow safe application of the staples. In severe scoliosis, the aorta frequently comes to rest in the concavity of the curve at some distance from the spine so that this dissection is not
fibers that cross the midline. Figures 2, 3, and 4 illustrate the thoracoabdominal incision. In children who have had previous surgical exposure of either anterior or posterior portions of the spine or those who have undergone extensive urologie diversion or reconstruction, the normal retroperitoneal space may have been obliterated. This added to the difficulty of the dissection, but in all cases it was possible to dissect the peritoneum and its contents free of the spine and trunk musculature. If a rent was inadvertently produced in the peritoneum, it was closed immediately with running catgut sutures to prevent undue exposure and possible damage to the bowel. The position of the iliac vessels in relationship to the lumbosacral spine is variable in children with congenital spinal anoma¬ lies. In all cases where the L-5 disk space had to be fused it was possible to expose the S-l vertebral body sufficiently to allow placement of a staple and screw without damage to the vessels or ureter; however, this may require extensive mobilization of the aortic bifurcation and iliac artery and vein. Each vertebral body must be'exposed sufficiently to permit measurement of its exact diameter for selection of the proper length of fixation screw. The surgeon must also be able to feel the screw tip when it is positioned to be sure that it does not protrude inordinately from the vertebral body and endanger adjacent structures. When this dissection was
convex
difficult. The diaphragmatic crura were divided after marking points of attachment with large silk sutures to aid alignment at the time of closure. The origin of the psoas muscle was then dissected off the vertebral bodies in the subperiosteal plane and displaced poste¬ riorly. This plane was developed over the body of L-l or L-2 and extended throughout the entire length of spine to be fused, since it permitted more rapid dissection of the muscles off the vertebral bodies and exposed the disk spaces widely. In muscular teenagers, this dissection is considerably more difficult than it is in children who have been incapacitated by underlying neurologic disorders. Subperiosteal dissection also decreases blood loss and protects the intervertebral foramina from damage to either the nerve root or radicular artery. The dissection must be continued across the anterior surface of the vertebral body, which may in severe scoliosis be rotated 90° or more toward the convex surface. By staying in the subperiosteal plane, the contralateral intercostal and lumbar vessels are protected from injury even when the vertebral body is severely deformed and rotated. The sympathetic chain can usually be retracted posteriorly by dividing the small
margin
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
complete, the intervertebral disk spaces were cleaned out thor¬ oughly with special care in the posterior portion to protect the dura. The uppermost Dwyer staple and screw were then placed and the cable was inserted. After each staple and screw was in place, the interspace was packed with cancellous bone removed from the excised rib. The cable could then be tightened as necessary to produce the desired correction of the curve and also correction of the vertebral rotation. The screw head was then crimped about the cable to hold this correction. Tension can be measured and is limited to 100 pounds per square inch (psi) or less to prevent breaking the cable. Once the fusion and cable placement were complete, the periosteum and spinal ligaments were returned to their normal position as completely as possible. The repositioned periosteum and the overlying psoas musculature protect the viscera and great vessels from the metallic components protruding from the vertebral bodies. The crura of the diaphragm also help cover the metallic implants. In the thorax it was usually possible to approximate pleura over the spine and thus protect the lung completely from the metallic implants. When this was completed, the entire diaphragm was reattached using interrupted sutures of 2/0 silk. Since the marked straightening and derotation of the spine may change shape of the thorax considerably, care was taken to approximate the edges of the diaphragm to avoid redundancy in the anterior portion, since this can cause "pseudoparalysis" of the diaphragm." There was often considerable overlapping of the cartilagenous portion of the costal margin so that excess cartilage had to be excised before approximating the ends with interrupted silk sutures. Two large chest drains were placed, one anterior and one posterior to the root of the lung. The chest wall was then closed in layers and the abdominal portion of the incision was closed anatomically.
Postoperative Care The patient was then returned to the intensive care area with a nasogastric tube on suction and the nasotracheal tube still in place. We preferred to have the patient breathe spontaneously through a T-piece delivering humidified 40% oxygen. The awake patient objected much less to a nasotracheal tube than he did to an orotracheal tube and the nasal tubes were easier to secure, so that accidental extubation was unlikely. If the postoperative chest x-ray film showed any substantial atelectasis, the nasotracheal tube was connected to deliver constant positive airway pressure (CPAP) between 5 and 7 cm of water. Kanamycin sulfate and ampicillin sodium were administered preoperatively and contin¬ ued throughout the first postoperative week. Chest drainage was replaced with equal volumes of whole blood and the anterior chest tube was removed within 24 hours when the drainage became serous. The posterior chest tube was removed the following day. The nasotracheal tube was removed the morning after surgery if the patient maintained normal blood gases while breathing room air. Central venous pressure was measured hourly and infusions were adjusted to maintain a pressure between 5 and 7 cm ILO. Arterial gases, hematocrit, urine flow, and urine specific gravitywere monitored as necessary. Electrolytes were measured several hours postoperatively and if normal, the patient received 5% dextrose in 0.2N saline solution for intravenous maintenance. We also infused 10 ml/kg of plasma to replace serum lost into the large, raw area of dissection. A nasogastric tube was left on gentle suction, since most children had extensive ileus after the retroper¬ itoneal dissection. Motion and sensation in both lower extremities were checked hourly. The catheter was removed from the ileal stoma or bladder on the day after surgery and the central venous pressure line and radial artery cannula were removed as soon as the patient was
Fig 2.—Entrance into retroperitoneal space beneath diaphragm after a thoracoabdominal incision on right (patient's feet to the right). 1, Thoracic portion of incision; 2, lung; 3, diaphragm as it appears after costal margin has been divided; 4, properitoneal fat; 5, abdominal musculature. Plane between peritoneum and dia¬ phragm is then fully developed.
Fig 3.—Same incision as in Fig 2 now viewed from behind patient at a later stage in procedure. 1, Edge of diaphragm; 2, diaphrag¬ matic insertion on spine being detached; 3, intact peritoneal sac.
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
Fig 4.—Same orientation as in Fig 2 and 3. Final exposure of spine preparatory to exposing individual vertebral bodies. 1, Convex surface of scoliotic spine rises into incision (note rotational deformity of vertebral bodies); 2, bowel within intact peritoneum; 3, edge of diaphragm that lies flaccid after it has been detached.
stable (usually within 24 hours after the conclusion of surgery). For the first several days, the patient was turned every two hours on a frame or electric bed. None of the patients in this series received anticoagulants. We believed that the risk of bleeding from the rather extensive retroperitoneal dissection and raw bony surfaces outweighed the risk of pulmonary emboli.
Fig 5.—Segmental blood supply to spinal cord. Aorta (3) supplies segmental arteries (5) that give off nutrient arteries (4) to vertebral body. These are paired and anastomosed freely through vertebral body with contralateral nutrient artery. Each segmental artery sends a branch (6) through neural foramen that anastomoses with anterior spinal artery (2), which in turn is connected through meningeal collaterals with paired posterior spinal arteries. Segmental artery continues (7) as intercostal vessel that receives flow from internal mammary artery. Division of segmental artery close to aorta on side of surgical exposure gives adequate access to vertebral bodies and preserves collateral flow (after Lazorthes et al·). 1 indicates one of the paired dorsal spinal arteries; 8 indicates transverse process of vertebra.
Complications No patient developed a deep wound infection or permanent worsening of neurologic function. There was one late death occurring three weeks after surgery from right ventricular failure secondary to multiple pulmonary emboli. As noted by McMaster and co-workers,' most patients having anterior fusion of the low thoracic or lumbar spine showed evidence of partial sympathectomy of the lower extremity on the same side as the exploration. Their usual complaint was that the contralateral normal leg felt cold in contrast to the warmth produced in the sympathectomized leg. The sympathectomy produced temperature differences in the legs for five to seven days; no patients experienced urinary or other symptoms. In most cases, the sympathetic trunk was preserved in its entirety, but the mobilization and retraction necessary to clear it from the vertebral bodies probably produced extensive damage in the trunk and in the segmental contribution to each ganglion. Additional complica¬ tions are shown in Tables 1 and 2.
COMMENT
As experience accumulates with the anterior approach to the spine, it is apparent that the morbidity, mortality, and blood loss are no greater than for posterior fusions. Advan¬ tages of the anterior approach include avoidance of previously scarred and ulcerated skin associated with myelomeningoceles, strong internal fixation, more reliable fusion, and correction of the rotational deformity of verte¬ bral bodies. The major risks involved are those of direct injury to the spinal cord inflicted at the time of disk removal and interruption of blood supply to the spinal cord. The first complication can be avoided by thorough dissec¬ tion of the vertebral bodies and disk spaces prior to disk removal. The posterior longitudinal ligament and dura separate the disk space from the cord so that direct injury should rarely if ever occur. By cleaning off the vertebral bodies and disk in the subperiosteal plane, the radicular arteries are protected where they enter the intervertebral foramina. By ligating the segmental arteries close to the aorta only on the side of exposure and carefully protecting the segmental arteries on both sides, there should be no ischemie injury to the cord, since as Lazorthes et al5 have shown, there is rich collateral communication between the
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
Table
Patient/Age, yr/Sex
1.—Summary of Patients Undergoing Anterior Exposure of Spine Side of Incision
Segments
1/10/M
Birth
Type of Fusion Dwyer
2/11/M
Myelodysplasia
Dwyer
T-5-T-10
3/11/M
Myelodysplasia*
Resection vertebral bodies
T-10-S-1
4/14/M 5/24/M 6/10/F 7/8/F
Myelodysplasia Myelodysplasia Myelodysplasia*
Dwyer Dwyer Dwyer Dwyer
T-10-L-4 L-1-L-5 T-10-L-4 T-4-T-11
Dwyer
T-5-L-4 T-9-L-4 T-8-L-2 T-10-L-4
Diagnosis injury, quadriplegia
Fused
T-4-L-4
No. of Transfusions 6
13
paraplegia
8/18/F 9/12/M 10/14/M 11/19/M
Traumatic
12/10/M 13/13/M 14/14/M 15/15/F 16/12/F
Myelodysplasia Myelodysplasia* Cerebral palsy Myelodysplasia Hemivertebra,
Dwyer Dwyer
Meningitis Idiopathic Idiopathic
Anterior strut
L-1
Anterior strut Anterior strut
Dwyer Anterior strut Resection of
Complications Pseudarthrosis, upper gastrointestinal bleeding, pneumonia, pneumothorax Congestive heart failure,
superficial urinal infection Multiple pulmonary emboli, death on day 13
(Dwyer)
Neurofibromatosis
Respiratory Support, Days
None None None
Dislodgement of endo¬ tracheal tube, pleural effusion None
None, pseudarthrosis? None
Urinary tract infection, superficial wound infec¬ tion, atelectasis None None Pleural effusion None None
T-10-S-1 T-12-L-5 T-10-L-4 T-10-S-1 T-11-L-2
hemivertebra,
anterior fusion
17/12/M
18/15/F 19/12/F 20/15/F 21/4/F 22/17/F 23/9/F 24/14/M 25/20/M 26/5/F 27/15/M 28/20/M
29/9/F 30/11/M 31/6/M 32/14/F
33/II/2/F 34/20/F 35/6/M 36/5/M
37/21/M 38/20/F 39/4/F
T-9-L-4
myelitis Idiopathic
Dwyer
Dwyer
Neurofibromatosis
Anterior strut
Quadriplegia, (measles encephalitis) Myelodysplasiaf Idiopathic
Dwyer
T-11-L-4 T-6-L-1 T-9-L-4
Anterior strut Anterior strut Anterior
T-11-L-4 T-8-L-2 T-11-L-4
None None
Dwyer
T-11-S-1 T-7-T-12 L-1-L-5 T-10-L-4 T-10-L-3
None None
T-9-L-3 T-11-L-3 T-4-L-1 T-5-T-10
None None None None
Anterior Anterior
T-10-S-1 T-9-L-4 T-10-L-2 T-10-L-2
None None None None
Hemivertebra,
Dwyer Dwyer Excision, L-2
T-11-L-4 T-10-L-5 T-12-L-3
None None RML collapse
Lower motor
Anterior
T-10-L-4
Wound infection, methicillin
T-10-S-3 T-9-L-3
failure None Burn from cautery
Transverse
Radiation for neuroblastoma Polio
Idiopathic Myelodysplasia Myelodysplasia Compression fracture, T-12
Anterior Anterior Anterior Anterior strut
Myelodysplasiaf
Dwyer Dwyer Dwyer
Neurofibromatosis Neurofibromatosis
Congenital kyphoscoliosis Myelodysplasia Cerebral palsy Achondroplasla Hemivertebra,
T-12 Cerebral palsy
Idiopathic L-2
40/11/M
neuron
41/3/F 42/16/F
Anterior strut Anterior strut
Dwyer
10
disorder
Myelodysplasia Myelodysplasia*
Insulin reaction (diabetic) urinary tract infection None None Inclsional bleeding, trans¬ fusion reaction
Intraoperative cardiac arrest, granuloma of larynx
Urinary tract infection None None
on
day 1
nephritis, congestive
Anterior strut
Dwyer
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
plate (Continued
on
462)
Table
Patient/Age, yr/Sex
1.—Summary of Patients Undergoing Anterior Exposure of Spine (Cont.)
43/36/F
Polio
Type of Fusion Anterior
44/3/F
Myelodysplasia
Anterior strut
Myelodysplasia
Anterior
45/13/F
Diagnosis
Side of Incision
Fused T-10-L-4
No. of Transfusions 12
T-10-S-1
1
Segments
Respiratory Support, Days
Complications Psychosis, urinary tract infection, respiratory insufficiency Prolonged ileus
graft L-1-S-1
None
Patient with ¡leal diversion. t Patient with colostomy. *
Table
2.—Postoperative Complications
Complication Respiratory (N = 24) Required ventilatory support
No. of Patients
15
Pneumonia Atelectasis Pleural effusion Pulmonary embolus Pneumothorax Granuloma of larynx from endotracheal tube Incision (N = 4) Minor Skin separation Deep infection Bleeding from wound edge Urinary tract (N = 4) Infection Methicillin nephritis Transfusion reaction (N : Hives
Hemolysis Other (N
=
6)
Congestive heart failure Burn from cautery Upper gastrointestinal bleeding Insulin reaction
Prolonged ileus Total No. of patients
39
vessels within the vertebral body and neural canal. The nutrient artery entering the verte¬ bral body on the exposed surface must be interrupted in order to allow safe application of the staple and screw. It may also be necessary to interrupt the contralateral nutrient artery of a severely rotated vertebral body, but this can be done without injuring the remainder of the segmental artery that supplies the spinal cord (Fig 5). The artery of Adamkiewicz is a major feeding vessel of the anterior and posterior spinal artery that supplies much of the lumbar and lower thoracic cord. This major vessel is a branch of the intercostal vessel at the T-10 level in most individuals, and. it arises on the left in 80%. While most idiopathic scoliosis develops with a primary thoracic curve convex to the right and the spine is approached from the right in this series, 31 patients had their spine approached from the left and none had evidence of cord ischemia. The rich collateral plexus connecting the intercostal circulation
paired intersegmental
with that about the spine, meninges, and paraspinous muscles undoubtedly gives the cord considerable protection against ischemia, since the collateral flow from above, below, and across the midline supplies the cord even when several contiguous intercostal vessels are divided close to the aorta. Patients having extensive thoracoabdominal exposure of the spine for correction of scoliosis or other reasons should be watched carefully during and after the procedure for pulmonary insufficiency. Lin and colleagues8 showed that all patients having posterior spine fusions for scoliosis had worsening of elastic compliance, flow resistance, and vital capacity during and immediately following the procedure. Right-to-left shunting through the lung increases so that arterial oxygen pressure (Po2) decreases as the patient breathes room air. Our practice of monitoring blood gases from the radial artery cannula and nasotracheal intubation for 12 to 24 hours after surgery enabled us to detect and correct these impairments of pulmonary function with the least risk to the patient. Dwyer and Shafer," and in two separate works, Dwyer,1"" emphasized the frequency of pulmonary complications and preferred a tracheostomy to aid in airway management. No patients in this series have had any diaphragmatic paralysis or "pseudoparalysis"6 following operation, so this is not an important factor in postoperative respiratory
insufficiency.
Prediction of normal vital capacity correlates poorly with both height and weight in patients with severe spinal deformities, especially when the curve is greater than 60° or if there is agenesis of the lumbosacral spine. Arm span can be helpful in predicting "normal" height of the individ¬ ual, since arm span/1.03 ± .02 nondeformed height. This height can then be used to predict vital capacity.12 None of the patients in this series have had postopera¬ tive pulmonary function studies, since this aspect of scol¬ iosis surgery has been explored extensively.81315 Experience with extensive exposure of the thoraco¬ lumbar spine has demonstrated its wide applicability for any procedure that requires extensive retroperitoneal and thoracic exposure. From the left, the aorta is exposed throughout its length. The origin of celiac axis, superior mesenterie artery, and both renal arteries can be widely exposed for endarterectomy, embolectomy, reconstruction, or bypass. Both kidneys, their blood supply, and the entire length of the ipsilateral ureter are exposed sufficiently to permit extensive en bloc dissection without opening the
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
=
Removal of a midline herniation of an intervertebral disk fragment, biopsy and fusion of diseased vertebral bodies, and wide excision of retroperi¬ toneal sarcomas are also facilitated by this approach. Our experience indicates that this extensive exposure of the spine gives superior exposure to the retroperitoneal struc-
peritoneal cavity.
tures with
mortality.
surprisingly
little blood loss,
morbidity,
or
Nonproprietary Name and Trademarks of Drug Ampicillin sodium—Alpen-N, Amcill-S, Omnipen-N, Penbritin-S, Polycillin-N, Principen/N, Totacillin-N.
References 1. Hodgson AR, Yau ACMC: Anterior surgical approaches to the spinal column, in Apley AG (ed): Recent Advances in Orthopedics. Baltimore, Williams & Wilkins Co, 1969, pp 289-323. 2. Riseborough EJ: The anterior approach to the spine for the correction of deformities of the axial skeleton, in Urist MR (ed): Clinical Orthopaedics and Related Research. Philadelphia, JB Lippincott Co, 1973, vol 93, pp
207-214. 3. Dommisse GF: The blood supply of the spinal cord: A critical vascular zone in spinal surgery. J Bone Joint Surg 56B:225-235, 1974. 4. Westgate HD, Johnson BE: Effects of scoliosis therapy on pulmonary function. J Bone Joint Surg 52A:400, 1970. 5. Lazorthes G, Gouaze A, Zadeh JO, et al: Arterial vascularization of the spinal cord: Recent studies of the anastomotic substitution pathways. J Neurosurg 35:253-262, 1971. 6. Dommisse GF, Enslin TB: Hodgson's circumferential osteotomy in correction of spinal deformity. J Bone Joint Surg 52B:778, 1970. 7. McMaster W, Marrero R, Bonnett C: Sympathectomy effect following the anterior approach for Dwyer instrumentation. J Bone Joint Surg 56A:441, 1974. 8. Lin HY, Nash CL, Herndon CH, et al: The effect of corrective surgery on pulmonary function in scoliosis. J Bone Joint Surg 56A:1173-1179,
1974. 9. Dwyer AF, Schafer MF: Anterior approach to scoliosis: Results of treatment in fifty-one cases. J Bone Joint Surg 56B:218-224, 1974. 10. Dwyer AF: Experience of anterior correction of scoliosis, in Urist MR (ed): Clinical Orthopaedics and Related Research. Philadelphia, JB Lippincott Co, 1973, vol 93, pp 191-206. 11. Dwyer AF: Experience of anterior correction of scoliosis. Clin Orthop 93:191-206, 1973. 12. Johnson BE, Westgate HD: Methods of predicting normal lung volumes in scoliotic and other deformed patients. J Bone Joint Surg 52A:399, 1970. 13. Davies G, Reid L: Effect of scoliosis on growth of alveoli and pulmonary arteries and on the right ventricle. Arch Dis Child 46:623-632, 1971. 14. Nachemson A, Bake B, Bjure J, et al: Clinical follow-up and regional lung function studies in patients with non-treated idiopathic scoliosis. J Bone Joint Surg 52A:401, 1970. 15. Riseborough EJ, Shannon D: The effects of scoliosis on pulmonary function as determined by studies with Xenon-133. J Bone Joint Surg 52A:400, 1970.
Discussion Robert Hickey, MD, Houston: I have one question and a By way of comment, I think this is a magnificent presentation, but have you used this procedure or had occasion to use this procedure for those patients who have had injury and deformity as a consequence of radiation therapy for such as Wilms tumor? Dr Burrington: I suspect what Dr Hickey is getting at is the fact that these planes are often obliterated by obviously previous surgery. About one third of our patients had undergone previous spinal surgery and almost one third had had some sort of urinary tract diversion. Whenever possible, we tried to attack the spine
comment.
from the side opposite the ileal bladder, but we have found that even in patients who have had as many as five previous exposures to the spine these planes can still be developed. Dissection is obviously somewhat more difficult in patients with previous surgery, and the only time that I can recall when we had any substantial venous bleeding, I injured the iliac vein in a woman who had five previous exposures of that area. Two patients in this series had scoliosis secondary to radiation of childhood tumors and both had excellent results. The technical aspects of exposure and correction of the curve were in no way different from the idiopathic curves.
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
Spine
Technical Considerations John D.
Burrington, MD; Courtney Brown, MD;
Eli R.
Wayne, MD; John Odom,
\s=b\ Forty-five patients, of whom most were children, underwent extensive exposure of the thoracolumbar spine to correct serious orthopedic abnormalities. The spine was exposed through a combined thoracotomy and retroperitoneal approach that gave excellent access with minimal morbidity. The diaphragm was opened circumferentially after the peritoneum had been dissected from its muscular portion. This permitted repair of the diaphragm with no detectable loss of function. Although this approach was developed for exposure of the spine, it can also be utilized to expose the entire aorta, both kidneys and their blood supply, and the retroperitoneal area for possible excision of large tumors.
(Arch Surg 111:456-463, 1976) and Yau'
the anterior
Hodgson repopularized correcting orthopedic spine Sinceapproach Dwyer'7 perfected techniques to the
for his
of internal anomalies and deformities children have can severe spinal fixation, corrected or stabilized. As experience with this direct exposure of the vertebral bodies has accumulated, indica¬ tions for exposing long segments of the spine have expanded. Whereas Hodgson and Yau1 originally reported wedge resection of a single hemivertebra and fusion of a publication Dec 29, 1975. departments of surgery (Drs Burrington and Wayne) and orthopedics (Drs Brown and Odom), the Children's Hospital, Denver. Dr Burrington is now with the Department of Surgery at the University of Chicago. Read before the 83rd annual meeting of the Western Surgical Association, Colorado Springs, Colo, Nov 22, 1975. Reprint requests to Department of Surgery, Box 163, University of Chicago, 950 E 59th St, Chicago, IL 60637 (Dr Burrington).
Accepted
From the
for
MD
single disk space, it is possible to expose and fuse up to 14 disk spaces in a single operation. The anterior approach has also made it possible to stabilize the spine in children with congenital spinal deformities and prevent the progressive neurologic and pulmonary deterioration that would other¬ wise develop. With the anterior portion of the vertebral bodies exposed, strut grafts of rib or fibula can be mortised into position to prevent progression of a kyphos when the vertebrae are so deficient that posterior fusion is not possible. The Dwyer internal fixation apparatus will also hold the spine in correction during a healing phase of a spinal fusion in complex abnormalities that are not suitable for correc¬ tion with Harrington compression and distraction rods. These conditions include the following: (1) rigid congenital scoliosis; (2) severe acquired or congenital kyphosis; and (3) lumbar scoliosis with lordosis and hyperlordosis. Mechani¬ cally, the Dwyer apparatus is able to distribute more evenly the stress produced by correction of the spinal curve. Long screws in each vertebral body braced by a large staple absorb the stress that results from pulling adjacent vertebral bodies into alignment.7 Application of the staples directly to the vertebral bodies also aids in correcting the
rotational deformities that become marked in advanced scoliosis. Although the cables do occasionally break, failure is much less common than it is with Harrington rods, and pseudarthrosis occurs in less than 10% of the patients. Earlier reports noted frequent worsening of neurologic status7'1 following anterior exposure of the lower thoracic spine, but this disastrous complication has been reduced to acceptable levels by a better understanding of the circula-
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
tion of the spinal cord, performance of preoperative myelograms to detect diplomyelia, and preoperative halofemoral traction when necessary. This article reviews our experience with anterior expo¬ sure of the vertebral bodies in 45 patients who underwent operation at the Children's Hospital, Denver, for correction of spinal anomalies. We emphasize the details of patient management and surgical technique as well as the implica¬ tions for broadening the use of this exposure to include large retroperitoneal tumors and for exposure in extensive reconstructive procedures involving the aorta and its branches. SUBJECTS AND METHODS Selection of Patients
Initially, all patients had severe decompensated spinal curves that were judged unsuitable for posterior fusion and Harrington instrumentation because of the nature of the curve or absence of the posterior structures resulting from trauma, congenital defects, or destruction by neurofibromatosis. As experience accumulated, the indications for anterior fusion and fixation with bone struts or the Dwyer apparatus widened to include all patients with a decompensated or progressive curve who were believed unsuitable for posterior fusion. Evaluation of Patients Each patient was carefully evaluated for overall general health. Full-length spinal roentgenograms were obtained with the patient lying supine, standing, and in maximal lateral flexion for detailed analysis of the curves and identification of transitional vertebral bodies above and below the deformity. Most patients had recent intravenous pyelograms to rule out unsuspected urinary tract deterioration; myelograms were taken of all children with congenital anomalies involving the spine so as to rule out unsus¬ pected diplomyelia or any other bony abnormality that might produce neurologic symptoms when the spine was straightened. All children old enough to cooperate underwent evaluation of their pulmonary function by measurement of functional residual capac¬ ity, forced vital capacity, peak flow rate, and maximum ventila¬
tory volume.
Preparation
of Patients
Patients were prepared by being put in a plaster jacket, Milwaukee brace, or halofemoral traction for four to six weeks to reduce the deformity. Slow, progressive spinal extension allows accommodation for nerve roots that may be partially entrapped in scar or foreshortened because of the marked curve. Preoperative traction has also been shown to improve pulmonary ventilationperfusion ratios.' In no patient was it necessary to interrupt traction because of neurologic symptoms. All children with urinary tract infection were treated with appropriate antibiotics during this preparation phase. Those with severe neurologic deficit or a history of constipation had their colons cleansed with enemas and began a low-residue diet, receiving laxatives as required.
Operative
Procedure
All patients underwent intubation with a cuffed nasotracheal tube that was taped securely in place after applying benzoin to the tube and skin. A plastic cannula introduced percutaneously into the radial artery at the wrist aided in monitoring blood gases throughout the procedure. A central venous line introduced into either the subclavian or jugular vein aided in monitoring blood and
fluid administration throughout the procedure and recovery period. These lines were inserted using meticulous aseptic tech¬ nique and were held securely in place by sterile dressings. Patients with scoliosis were placed in the lateral position with the convex portion of the major curve uppermost. In some in¬ stances, it was helpful to raise the kidney rest to accentuate the curve and facilitate removal of intervertebral disks prior to fusion. In patients whose primary problem is kyphosis or lordosis, the spine can be approached from either side. Since many of the children had an ileal bladder or some other form of urinary tract diversion, we tried whenever possible to place the new incision on the side of the abdomen opposite the stoma. If no previous surgery had been performed, we approached the spine from the right, so that the artery of Adamkiewicz supplying the spinal cord was less likely to be disturbed. A Foley catheter with a 30-cu cm balloon introduced into an ileal conduit and partially inflated just below the level of the fascia provided a satisfactory means of keeping the urine from the operative field. It also permitted urine collection so that output and specific gravity could be monitored throughout the procedure. The iliac crest and occasionally the ipsilateral fibula may be propped and draped so that bone can be taken from these areas if it is required for grafting. Large thoracoabdominal incisions cause the patient to lose heat rapidly throughout the procedure and administration of large amounts of refrigerated blood cools the patient even more. To prevent this, we preferred to maintain the operating room at 26.6 C with 50% or more relative humidity. Each patient was positioned on a fluid-filled mattress that could be used for heating or cooling as necessary to maintain normal body temperature. Blood was passed through a warming unit prior to infusion and core temperature was monitored continuously with a rectal or esophageal probe. Cardiac monitoring was also essen¬ tial. The skin incision was placed over the rib originating at or one vertebra above the highest vertebral body to be fused (Fig 1, upper left). Marked rib cage deformity present in some children may make it necessary to also excise the next higher rib to facilitate placement of the highest staple. The initial incision followed the course of the rib to be excised from the costal margin to approximately the level of the trans¬ verse process. The rib was removed subperiosteally throughout its entire length and kept in sterile saline solution for use as bone grafts in the fusion (Fig 1, upper right). The pleura was then entered and the cartilagenous portion of the costal margin was divided. The abdominal portion of the skin incision was then extended from the costal margin toward the pubic tubercle. The abdominal muscles were divided down through the transversus abdominus, but the peritoneum was left intact. The peritoneum was dissected bluntly from the diaphragm near its lateral attachment and the diaphragm was divided with cautery about one inch from its costal attachment (Fig 1, lower left). This peripheral detachment preserved the diaphragmatic innervation so that its postoperative function was normal and cautery reduced blood loss. The peri¬ toneum and its contents including kidneys and ureters were then dissected bluntly from the flank muscles to expose the lumbar spine (Fig 1, lower right). Gravity helps hold the viscera forward. A rib spreader introduced into the thoracic portion of the incision opened it widely. The pleura overlying the spine was opened in a Convenient spot and individual intercostal vessels were ligated close to their origin from the aorta. If only the intercostal and lumbar vessels on the convex side of the curve are divided, collateral flow from the contralateral vessels will maintain perfu¬ sion of the spinal cord.7' Division of all aortic branches on the
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
Fig 1.—Steps
in approach to spine from left side. Upper left, Incision follows course of rib attached to highest vertebral body to be exposed. Abdominal portion extends from costal margin to pubic tubercle. Upper right, Rib is removed for bone graft and abdominal musculature is divided down to peritoneum, which is left intact. Diaphragm remains attached except where costal
has been divided. Lower left, Peritoneum is dissected off under surface of diaphragm and diaphragm is divided circumferentially about 2 cm from its attachment. Lower right, Diaphragm has been divided and attachments to spine removed. Spine lies in base of incision with segmental branches from aorta clearly visible.
surface of the curve was necessary to permit access to disk spaces and allow safe application of the staples. In severe scoliosis, the aorta frequently comes to rest in the concavity of the curve at some distance from the spine so that this dissection is not
fibers that cross the midline. Figures 2, 3, and 4 illustrate the thoracoabdominal incision. In children who have had previous surgical exposure of either anterior or posterior portions of the spine or those who have undergone extensive urologie diversion or reconstruction, the normal retroperitoneal space may have been obliterated. This added to the difficulty of the dissection, but in all cases it was possible to dissect the peritoneum and its contents free of the spine and trunk musculature. If a rent was inadvertently produced in the peritoneum, it was closed immediately with running catgut sutures to prevent undue exposure and possible damage to the bowel. The position of the iliac vessels in relationship to the lumbosacral spine is variable in children with congenital spinal anoma¬ lies. In all cases where the L-5 disk space had to be fused it was possible to expose the S-l vertebral body sufficiently to allow placement of a staple and screw without damage to the vessels or ureter; however, this may require extensive mobilization of the aortic bifurcation and iliac artery and vein. Each vertebral body must be'exposed sufficiently to permit measurement of its exact diameter for selection of the proper length of fixation screw. The surgeon must also be able to feel the screw tip when it is positioned to be sure that it does not protrude inordinately from the vertebral body and endanger adjacent structures. When this dissection was
convex
difficult. The diaphragmatic crura were divided after marking points of attachment with large silk sutures to aid alignment at the time of closure. The origin of the psoas muscle was then dissected off the vertebral bodies in the subperiosteal plane and displaced poste¬ riorly. This plane was developed over the body of L-l or L-2 and extended throughout the entire length of spine to be fused, since it permitted more rapid dissection of the muscles off the vertebral bodies and exposed the disk spaces widely. In muscular teenagers, this dissection is considerably more difficult than it is in children who have been incapacitated by underlying neurologic disorders. Subperiosteal dissection also decreases blood loss and protects the intervertebral foramina from damage to either the nerve root or radicular artery. The dissection must be continued across the anterior surface of the vertebral body, which may in severe scoliosis be rotated 90° or more toward the convex surface. By staying in the subperiosteal plane, the contralateral intercostal and lumbar vessels are protected from injury even when the vertebral body is severely deformed and rotated. The sympathetic chain can usually be retracted posteriorly by dividing the small
margin
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
complete, the intervertebral disk spaces were cleaned out thor¬ oughly with special care in the posterior portion to protect the dura. The uppermost Dwyer staple and screw were then placed and the cable was inserted. After each staple and screw was in place, the interspace was packed with cancellous bone removed from the excised rib. The cable could then be tightened as necessary to produce the desired correction of the curve and also correction of the vertebral rotation. The screw head was then crimped about the cable to hold this correction. Tension can be measured and is limited to 100 pounds per square inch (psi) or less to prevent breaking the cable. Once the fusion and cable placement were complete, the periosteum and spinal ligaments were returned to their normal position as completely as possible. The repositioned periosteum and the overlying psoas musculature protect the viscera and great vessels from the metallic components protruding from the vertebral bodies. The crura of the diaphragm also help cover the metallic implants. In the thorax it was usually possible to approximate pleura over the spine and thus protect the lung completely from the metallic implants. When this was completed, the entire diaphragm was reattached using interrupted sutures of 2/0 silk. Since the marked straightening and derotation of the spine may change shape of the thorax considerably, care was taken to approximate the edges of the diaphragm to avoid redundancy in the anterior portion, since this can cause "pseudoparalysis" of the diaphragm." There was often considerable overlapping of the cartilagenous portion of the costal margin so that excess cartilage had to be excised before approximating the ends with interrupted silk sutures. Two large chest drains were placed, one anterior and one posterior to the root of the lung. The chest wall was then closed in layers and the abdominal portion of the incision was closed anatomically.
Postoperative Care The patient was then returned to the intensive care area with a nasogastric tube on suction and the nasotracheal tube still in place. We preferred to have the patient breathe spontaneously through a T-piece delivering humidified 40% oxygen. The awake patient objected much less to a nasotracheal tube than he did to an orotracheal tube and the nasal tubes were easier to secure, so that accidental extubation was unlikely. If the postoperative chest x-ray film showed any substantial atelectasis, the nasotracheal tube was connected to deliver constant positive airway pressure (CPAP) between 5 and 7 cm of water. Kanamycin sulfate and ampicillin sodium were administered preoperatively and contin¬ ued throughout the first postoperative week. Chest drainage was replaced with equal volumes of whole blood and the anterior chest tube was removed within 24 hours when the drainage became serous. The posterior chest tube was removed the following day. The nasotracheal tube was removed the morning after surgery if the patient maintained normal blood gases while breathing room air. Central venous pressure was measured hourly and infusions were adjusted to maintain a pressure between 5 and 7 cm ILO. Arterial gases, hematocrit, urine flow, and urine specific gravitywere monitored as necessary. Electrolytes were measured several hours postoperatively and if normal, the patient received 5% dextrose in 0.2N saline solution for intravenous maintenance. We also infused 10 ml/kg of plasma to replace serum lost into the large, raw area of dissection. A nasogastric tube was left on gentle suction, since most children had extensive ileus after the retroper¬ itoneal dissection. Motion and sensation in both lower extremities were checked hourly. The catheter was removed from the ileal stoma or bladder on the day after surgery and the central venous pressure line and radial artery cannula were removed as soon as the patient was
Fig 2.—Entrance into retroperitoneal space beneath diaphragm after a thoracoabdominal incision on right (patient's feet to the right). 1, Thoracic portion of incision; 2, lung; 3, diaphragm as it appears after costal margin has been divided; 4, properitoneal fat; 5, abdominal musculature. Plane between peritoneum and dia¬ phragm is then fully developed.
Fig 3.—Same incision as in Fig 2 now viewed from behind patient at a later stage in procedure. 1, Edge of diaphragm; 2, diaphrag¬ matic insertion on spine being detached; 3, intact peritoneal sac.
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
Fig 4.—Same orientation as in Fig 2 and 3. Final exposure of spine preparatory to exposing individual vertebral bodies. 1, Convex surface of scoliotic spine rises into incision (note rotational deformity of vertebral bodies); 2, bowel within intact peritoneum; 3, edge of diaphragm that lies flaccid after it has been detached.
stable (usually within 24 hours after the conclusion of surgery). For the first several days, the patient was turned every two hours on a frame or electric bed. None of the patients in this series received anticoagulants. We believed that the risk of bleeding from the rather extensive retroperitoneal dissection and raw bony surfaces outweighed the risk of pulmonary emboli.
Fig 5.—Segmental blood supply to spinal cord. Aorta (3) supplies segmental arteries (5) that give off nutrient arteries (4) to vertebral body. These are paired and anastomosed freely through vertebral body with contralateral nutrient artery. Each segmental artery sends a branch (6) through neural foramen that anastomoses with anterior spinal artery (2), which in turn is connected through meningeal collaterals with paired posterior spinal arteries. Segmental artery continues (7) as intercostal vessel that receives flow from internal mammary artery. Division of segmental artery close to aorta on side of surgical exposure gives adequate access to vertebral bodies and preserves collateral flow (after Lazorthes et al·). 1 indicates one of the paired dorsal spinal arteries; 8 indicates transverse process of vertebra.
Complications No patient developed a deep wound infection or permanent worsening of neurologic function. There was one late death occurring three weeks after surgery from right ventricular failure secondary to multiple pulmonary emboli. As noted by McMaster and co-workers,' most patients having anterior fusion of the low thoracic or lumbar spine showed evidence of partial sympathectomy of the lower extremity on the same side as the exploration. Their usual complaint was that the contralateral normal leg felt cold in contrast to the warmth produced in the sympathectomized leg. The sympathectomy produced temperature differences in the legs for five to seven days; no patients experienced urinary or other symptoms. In most cases, the sympathetic trunk was preserved in its entirety, but the mobilization and retraction necessary to clear it from the vertebral bodies probably produced extensive damage in the trunk and in the segmental contribution to each ganglion. Additional complica¬ tions are shown in Tables 1 and 2.
COMMENT
As experience accumulates with the anterior approach to the spine, it is apparent that the morbidity, mortality, and blood loss are no greater than for posterior fusions. Advan¬ tages of the anterior approach include avoidance of previously scarred and ulcerated skin associated with myelomeningoceles, strong internal fixation, more reliable fusion, and correction of the rotational deformity of verte¬ bral bodies. The major risks involved are those of direct injury to the spinal cord inflicted at the time of disk removal and interruption of blood supply to the spinal cord. The first complication can be avoided by thorough dissec¬ tion of the vertebral bodies and disk spaces prior to disk removal. The posterior longitudinal ligament and dura separate the disk space from the cord so that direct injury should rarely if ever occur. By cleaning off the vertebral bodies and disk in the subperiosteal plane, the radicular arteries are protected where they enter the intervertebral foramina. By ligating the segmental arteries close to the aorta only on the side of exposure and carefully protecting the segmental arteries on both sides, there should be no ischemie injury to the cord, since as Lazorthes et al5 have shown, there is rich collateral communication between the
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
Table
Patient/Age, yr/Sex
1.—Summary of Patients Undergoing Anterior Exposure of Spine Side of Incision
Segments
1/10/M
Birth
Type of Fusion Dwyer
2/11/M
Myelodysplasia
Dwyer
T-5-T-10
3/11/M
Myelodysplasia*
Resection vertebral bodies
T-10-S-1
4/14/M 5/24/M 6/10/F 7/8/F
Myelodysplasia Myelodysplasia Myelodysplasia*
Dwyer Dwyer Dwyer Dwyer
T-10-L-4 L-1-L-5 T-10-L-4 T-4-T-11
Dwyer
T-5-L-4 T-9-L-4 T-8-L-2 T-10-L-4
Diagnosis injury, quadriplegia
Fused
T-4-L-4
No. of Transfusions 6
13
paraplegia
8/18/F 9/12/M 10/14/M 11/19/M
Traumatic
12/10/M 13/13/M 14/14/M 15/15/F 16/12/F
Myelodysplasia Myelodysplasia* Cerebral palsy Myelodysplasia Hemivertebra,
Dwyer Dwyer
Meningitis Idiopathic Idiopathic
Anterior strut
L-1
Anterior strut Anterior strut
Dwyer Anterior strut Resection of
Complications Pseudarthrosis, upper gastrointestinal bleeding, pneumonia, pneumothorax Congestive heart failure,
superficial urinal infection Multiple pulmonary emboli, death on day 13
(Dwyer)
Neurofibromatosis
Respiratory Support, Days
None None None
Dislodgement of endo¬ tracheal tube, pleural effusion None
None, pseudarthrosis? None
Urinary tract infection, superficial wound infec¬ tion, atelectasis None None Pleural effusion None None
T-10-S-1 T-12-L-5 T-10-L-4 T-10-S-1 T-11-L-2
hemivertebra,
anterior fusion
17/12/M
18/15/F 19/12/F 20/15/F 21/4/F 22/17/F 23/9/F 24/14/M 25/20/M 26/5/F 27/15/M 28/20/M
29/9/F 30/11/M 31/6/M 32/14/F
33/II/2/F 34/20/F 35/6/M 36/5/M
37/21/M 38/20/F 39/4/F
T-9-L-4
myelitis Idiopathic
Dwyer
Dwyer
Neurofibromatosis
Anterior strut
Quadriplegia, (measles encephalitis) Myelodysplasiaf Idiopathic
Dwyer
T-11-L-4 T-6-L-1 T-9-L-4
Anterior strut Anterior strut Anterior
T-11-L-4 T-8-L-2 T-11-L-4
None None
Dwyer
T-11-S-1 T-7-T-12 L-1-L-5 T-10-L-4 T-10-L-3
None None
T-9-L-3 T-11-L-3 T-4-L-1 T-5-T-10
None None None None
Anterior Anterior
T-10-S-1 T-9-L-4 T-10-L-2 T-10-L-2
None None None None
Hemivertebra,
Dwyer Dwyer Excision, L-2
T-11-L-4 T-10-L-5 T-12-L-3
None None RML collapse
Lower motor
Anterior
T-10-L-4
Wound infection, methicillin
T-10-S-3 T-9-L-3
failure None Burn from cautery
Transverse
Radiation for neuroblastoma Polio
Idiopathic Myelodysplasia Myelodysplasia Compression fracture, T-12
Anterior Anterior Anterior Anterior strut
Myelodysplasiaf
Dwyer Dwyer Dwyer
Neurofibromatosis Neurofibromatosis
Congenital kyphoscoliosis Myelodysplasia Cerebral palsy Achondroplasla Hemivertebra,
T-12 Cerebral palsy
Idiopathic L-2
40/11/M
neuron
41/3/F 42/16/F
Anterior strut Anterior strut
Dwyer
10
disorder
Myelodysplasia Myelodysplasia*
Insulin reaction (diabetic) urinary tract infection None None Inclsional bleeding, trans¬ fusion reaction
Intraoperative cardiac arrest, granuloma of larynx
Urinary tract infection None None
on
day 1
nephritis, congestive
Anterior strut
Dwyer
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
plate (Continued
on
462)
Table
Patient/Age, yr/Sex
1.—Summary of Patients Undergoing Anterior Exposure of Spine (Cont.)
43/36/F
Polio
Type of Fusion Anterior
44/3/F
Myelodysplasia
Anterior strut
Myelodysplasia
Anterior
45/13/F
Diagnosis
Side of Incision
Fused T-10-L-4
No. of Transfusions 12
T-10-S-1
1
Segments
Respiratory Support, Days
Complications Psychosis, urinary tract infection, respiratory insufficiency Prolonged ileus
graft L-1-S-1
None
Patient with ¡leal diversion. t Patient with colostomy. *
Table
2.—Postoperative Complications
Complication Respiratory (N = 24) Required ventilatory support
No. of Patients
15
Pneumonia Atelectasis Pleural effusion Pulmonary embolus Pneumothorax Granuloma of larynx from endotracheal tube Incision (N = 4) Minor Skin separation Deep infection Bleeding from wound edge Urinary tract (N = 4) Infection Methicillin nephritis Transfusion reaction (N : Hives
Hemolysis Other (N
=
6)
Congestive heart failure Burn from cautery Upper gastrointestinal bleeding Insulin reaction
Prolonged ileus Total No. of patients
39
vessels within the vertebral body and neural canal. The nutrient artery entering the verte¬ bral body on the exposed surface must be interrupted in order to allow safe application of the staple and screw. It may also be necessary to interrupt the contralateral nutrient artery of a severely rotated vertebral body, but this can be done without injuring the remainder of the segmental artery that supplies the spinal cord (Fig 5). The artery of Adamkiewicz is a major feeding vessel of the anterior and posterior spinal artery that supplies much of the lumbar and lower thoracic cord. This major vessel is a branch of the intercostal vessel at the T-10 level in most individuals, and. it arises on the left in 80%. While most idiopathic scoliosis develops with a primary thoracic curve convex to the right and the spine is approached from the right in this series, 31 patients had their spine approached from the left and none had evidence of cord ischemia. The rich collateral plexus connecting the intercostal circulation
paired intersegmental
with that about the spine, meninges, and paraspinous muscles undoubtedly gives the cord considerable protection against ischemia, since the collateral flow from above, below, and across the midline supplies the cord even when several contiguous intercostal vessels are divided close to the aorta. Patients having extensive thoracoabdominal exposure of the spine for correction of scoliosis or other reasons should be watched carefully during and after the procedure for pulmonary insufficiency. Lin and colleagues8 showed that all patients having posterior spine fusions for scoliosis had worsening of elastic compliance, flow resistance, and vital capacity during and immediately following the procedure. Right-to-left shunting through the lung increases so that arterial oxygen pressure (Po2) decreases as the patient breathes room air. Our practice of monitoring blood gases from the radial artery cannula and nasotracheal intubation for 12 to 24 hours after surgery enabled us to detect and correct these impairments of pulmonary function with the least risk to the patient. Dwyer and Shafer," and in two separate works, Dwyer,1"" emphasized the frequency of pulmonary complications and preferred a tracheostomy to aid in airway management. No patients in this series have had any diaphragmatic paralysis or "pseudoparalysis"6 following operation, so this is not an important factor in postoperative respiratory
insufficiency.
Prediction of normal vital capacity correlates poorly with both height and weight in patients with severe spinal deformities, especially when the curve is greater than 60° or if there is agenesis of the lumbosacral spine. Arm span can be helpful in predicting "normal" height of the individ¬ ual, since arm span/1.03 ± .02 nondeformed height. This height can then be used to predict vital capacity.12 None of the patients in this series have had postopera¬ tive pulmonary function studies, since this aspect of scol¬ iosis surgery has been explored extensively.81315 Experience with extensive exposure of the thoraco¬ lumbar spine has demonstrated its wide applicability for any procedure that requires extensive retroperitoneal and thoracic exposure. From the left, the aorta is exposed throughout its length. The origin of celiac axis, superior mesenterie artery, and both renal arteries can be widely exposed for endarterectomy, embolectomy, reconstruction, or bypass. Both kidneys, their blood supply, and the entire length of the ipsilateral ureter are exposed sufficiently to permit extensive en bloc dissection without opening the
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
=
Removal of a midline herniation of an intervertebral disk fragment, biopsy and fusion of diseased vertebral bodies, and wide excision of retroperi¬ toneal sarcomas are also facilitated by this approach. Our experience indicates that this extensive exposure of the spine gives superior exposure to the retroperitoneal struc-
peritoneal cavity.
tures with
mortality.
surprisingly
little blood loss,
morbidity,
or
Nonproprietary Name and Trademarks of Drug Ampicillin sodium—Alpen-N, Amcill-S, Omnipen-N, Penbritin-S, Polycillin-N, Principen/N, Totacillin-N.
References 1. Hodgson AR, Yau ACMC: Anterior surgical approaches to the spinal column, in Apley AG (ed): Recent Advances in Orthopedics. Baltimore, Williams & Wilkins Co, 1969, pp 289-323. 2. Riseborough EJ: The anterior approach to the spine for the correction of deformities of the axial skeleton, in Urist MR (ed): Clinical Orthopaedics and Related Research. Philadelphia, JB Lippincott Co, 1973, vol 93, pp
207-214. 3. Dommisse GF: The blood supply of the spinal cord: A critical vascular zone in spinal surgery. J Bone Joint Surg 56B:225-235, 1974. 4. Westgate HD, Johnson BE: Effects of scoliosis therapy on pulmonary function. J Bone Joint Surg 52A:400, 1970. 5. Lazorthes G, Gouaze A, Zadeh JO, et al: Arterial vascularization of the spinal cord: Recent studies of the anastomotic substitution pathways. J Neurosurg 35:253-262, 1971. 6. Dommisse GF, Enslin TB: Hodgson's circumferential osteotomy in correction of spinal deformity. J Bone Joint Surg 52B:778, 1970. 7. McMaster W, Marrero R, Bonnett C: Sympathectomy effect following the anterior approach for Dwyer instrumentation. J Bone Joint Surg 56A:441, 1974. 8. Lin HY, Nash CL, Herndon CH, et al: The effect of corrective surgery on pulmonary function in scoliosis. J Bone Joint Surg 56A:1173-1179,
1974. 9. Dwyer AF, Schafer MF: Anterior approach to scoliosis: Results of treatment in fifty-one cases. J Bone Joint Surg 56B:218-224, 1974. 10. Dwyer AF: Experience of anterior correction of scoliosis, in Urist MR (ed): Clinical Orthopaedics and Related Research. Philadelphia, JB Lippincott Co, 1973, vol 93, pp 191-206. 11. Dwyer AF: Experience of anterior correction of scoliosis. Clin Orthop 93:191-206, 1973. 12. Johnson BE, Westgate HD: Methods of predicting normal lung volumes in scoliotic and other deformed patients. J Bone Joint Surg 52A:399, 1970. 13. Davies G, Reid L: Effect of scoliosis on growth of alveoli and pulmonary arteries and on the right ventricle. Arch Dis Child 46:623-632, 1971. 14. Nachemson A, Bake B, Bjure J, et al: Clinical follow-up and regional lung function studies in patients with non-treated idiopathic scoliosis. J Bone Joint Surg 52A:401, 1970. 15. Riseborough EJ, Shannon D: The effects of scoliosis on pulmonary function as determined by studies with Xenon-133. J Bone Joint Surg 52A:400, 1970.
Discussion Robert Hickey, MD, Houston: I have one question and a By way of comment, I think this is a magnificent presentation, but have you used this procedure or had occasion to use this procedure for those patients who have had injury and deformity as a consequence of radiation therapy for such as Wilms tumor? Dr Burrington: I suspect what Dr Hickey is getting at is the fact that these planes are often obliterated by obviously previous surgery. About one third of our patients had undergone previous spinal surgery and almost one third had had some sort of urinary tract diversion. Whenever possible, we tried to attack the spine
comment.
from the side opposite the ileal bladder, but we have found that even in patients who have had as many as five previous exposures to the spine these planes can still be developed. Dissection is obviously somewhat more difficult in patients with previous surgery, and the only time that I can recall when we had any substantial venous bleeding, I injured the iliac vein in a woman who had five previous exposures of that area. Two patients in this series had scoliosis secondary to radiation of childhood tumors and both had excellent results. The technical aspects of exposure and correction of the curve were in no way different from the idiopathic curves.
Downloaded From: http://archsurg.jamanetwork.com/ by a University of Manitoba User on 06/12/2015
