Leon L. Wiltse

Analysis of the morphometric characteristics of the thoracic and lumbar pedicles

A total of 2,905 pedicle measurements were made from T1–L5. Measurements were made from spinal computerized tomography (CT) scan examinations and individual vertebral specimen roentgenograms. Parameters considered were the pedicle isthmus width in the transverse and sagittal planes, pedicle angles in the transverse and sagittal planes, and the depth to the anterior cortex in a line parallel to the midline of the vertebral body and along the pedicle axis. There was no significant difference between data obtained from CT scans and specimen roentgenograms. Pedicles were widest at L5 and narrowest at T5 in the transverse plane. The widest pedicles in the sagittal plane were seen at T11, the narrowest at T1. Due to the oval shape of the pedicle, the sagittal plane width was generally larger than the transverse plane width. The largest pedicle angle in the transverse plane was at L5. The posterolateral to anterolateral pedicle axis orientation in the transverse plane, seen at other levels throughout the thoracolumbar spine, reversed at T12. In the sagittal plane, the pedicles angled caudally at L5 and cephaladly from L3–T1. The depth to the anterior cortex was significantly longer along the pedicle axis than along a line parallel to the midline of the vertebral body at all levels with the exception of T12 and T11.

Anatomic analysis of pedicle cortical and cancellous diameter as related to screw size.

The effective thoracic and lumbar pedicle diameter as related to screw size for that pedicle was studied in six fresh-frozen human cadaver spines. Measurements of the pedicle were obtained before screw insertion using axial and coronal reformatted computed tomographic (CT) Images, as well as graduated sounding of the pedicle. After sequentially loading each pedicle with increasingly larger screws, measurements were taken of the outer cortical diameters. Plastic deformation of the pedicle preceded pedicle fracture or cutout when the screw thread diameter became larger than the endosteal diameter or within 80% of the outer cortical diameter as measured from the CT scan. Pedicle screws did not obtain cortical purchase within the pedicle.

The transition zone above a lumbosacral fusion

Study Design. The clinical and radiographic effect of a lumbar or lumbosacral fusion was studied in 42 patients who had undergone a posterolateral fusion with an average follow‐up of 22.6 years. Objective. To examine the long‐term effects of posterolateral lumbar or lumbosacral fusion on the cephalad two motion segments (transition zone). Summary of Background Data. It is commonly held that accelerated degeneration occurs in the motion segments adjacent to a fusion. Most studies are of shortterm, anecdotal, uncontrolled reports that pay particular attention only to the first motion segment immediately cephalad to the fusion. Methods. Forty‐two patients who had previously undergone a posterolateral lumbar or lumbosacral fusion underwent radiographic and clinical evaluation. Rate of fusion, range of motion, osteophytes, degenerative spondylolisthesis, retrolisthesis, facet arthrosis, disc ossification, dynamic instability, and disc space height were all studied and statistically compared with an age‐ and gender‐matched control group. The patients selfreported clinical outcome was also recorded. Results. Degenerative changes occurred at the second level above the fused levels with a frequency equal to those occurring in the first level. There was no statistical difference between the study group and the cohort group in the presence of radiographic changes within the transition zone. In those patients undergoing fusion for degenerative processes, 75% reported a good to excellent outcome, whereas 84% of those undergoing fusion for spondylolysis or spondylolisthesis reported a good to excellent outcome. Conclusion. Radiographic changes occur within the transition zone cephalad to a lumbar or lumbosacral fusion. However, these changes are also seen in control subjects who have had no surgery.

Treatment of degenerative spondylolisthesis.

The purpose of this article is to evaluate three surgical approaches to the treatment of degenerative spondylolisthesis. A review of 107 surgically treated cases were used to select a group of patients who met the following criteria: (1) No previous spine surgery, no involvement in litigation, and no significant lesions at other levels of the spine. (2) Adequate follow-up. The selected group of 47 surgically treated cases of degenerative spondylolisthesis had follow-up of 2–7 years. Three surgical approaches to the treatment of degnerative spondylolisthesis were analyzed. A relatively small patient group with a wide posterior decompression, at the level of the slip, sacrificing the articular processes had good to excellent results in only 33% of the cases. A second group with a midline posterior decompression with preservation of the articular processes had 80% good to excellent results after 2 years. The third group with a midline decompression and preservation of the articular processes had an added intertransverse process fusion between the olisthetic levels. This group had 90% good to excellent results. The conclusion is that a posterior decompression with preservation of the articular processes plus a transverse process fusion at the involved level is the preferred method of treatment for degenerative spondylolisthesis without regard to age.

Relationship of the dura, Hofmann's ligaments, Batson's plexus, and a fibrovascular membrane lying on the posterior surface of the vertebral bodies and attaching to the deep layer of the posterior longitudinal ligament. An anatomical, radiologic, and clinical study.

With the advent of computed tomography (CT) and magnetic resonance imaging (MRI), visualization of soft tissue structures in the spinal canal, which were previously undetectable, is possible. This study was undertaken to more accurately identify these soft tissue layers and to determine factors such as when is a disc contained and when is it not; in discography, when the disc leaks, into what layer is the contrast going; or when a nuclear fragment creeps upward or downward, just where is it. The works of Fick, Dommisse, Kikuchi, Schellinger, Hofmann, Batson, and Parke were studied. The professors of anatomy of four major medical schools were consulted along with several neuroradiologists and embryologists. Forty lumbar spines were dissected (20 fresh, 20 preserved). Magnetic resonance imaging scans were taken. Photographs and photomicrographs were made. A fibrous membrane, first mentioned by Fick, can be identified lying anterior to the posterior longitudinal ligament and attaching to the deep layer of the posterior longitudinal ligament. It has been given relatively little attention in the past. This membrane has about one fourth the toughness of the dura and is made up largely of fibrous tissue. The veins of Batson lie on its dorsal surface and pierce it to go ventral to this membrane and enter the vertebral body. Batsons plexus crosses the disc space. The peridural membrane extends from one side to the other, spanning the width of the vertebral body and encircling the bony canal around the outside of the dura. There is a potential space between it and the dura. It does not cross the disc space. A probe can easily be passed posterior or anterior to it, between it and the posterior longitudinal ligament or between it and the vertebral body. We also identified Hofmanns ligament anterior to the dura, attaching the dura to the posterior longitudinal ligament. Laterally, tiny attachments between this fibrovascular membrane and the circumneural sheaths of the spinal nerves can be observed as the nerves enter the foramina. The posterior longitudinal ligament (PLL) is very tough and strong and seldom ruptures. The annulus frequently ruptures. Fragments of nucleus pulposus can creep out at the vertebral rim and get under the PLL and the peridural membrane. Hematoma can form by the same route and have the exact appearance as a sequestrated disc. There is no periosteum inside the vertebral canal. With MRI, hematomas can be differentiated from an extruded fragment. They may cause symptoms similar to an extruded disc but will probably heal with time.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparative study of the incidence and severity of degenerative change in the transition zones after instrumented versus noninstrumented fusions of the lumbar spine

The purpose of this study was to determine whether the addition of pedicle screws and rods to a fusion of two or more vertebrae of the lowest three motion segments of the lumbar spine increases the incidence or severity of transition zone change (TZC) above or below the fused area. A study group of 52 patients who had a fusion with fixation and a control group of 31 who had a nearly identical operation but without fixation were obtained. Radiographs and computed tomography scans of the area of study were taken preoperatively and were repeated approximately 7 years after the operation. Results showed that the addition of pedicle screw fixation does not increase the incidence or severity of TZC in the first 7 years after surgery.

The long-range prognosis of arachnoiditis

Fifty patients with arachnoiditis were studied, and longterm follow-up ranging from 10 to 21 years was obtained on 36 (72%). Prior to developing arachnoiditis, 90% originally had intervertebral disc disease, Pantopaque (Alcon Surgical, Ft. Worth, Texas) myelography, and subsequent lumbar spine surgery. Pain and functional disability tended to remain the same as at the time of diagnosis, although severity of symptoms fluctuated. Increased neurologic deficits were more frequently due to surgical intervention than to the natural course of the disease. Urinary symptoms characterized by urgency, frequency, and occasional incontinence, with no other apparent cause, developed late in 23%. Although the majority were able to walk and drive a car without jimitation, ability to return to previous full-time occupations was markedly limited. The majority depended on daily narcotic analgesics; a few admitted to alcohol abuse. There were two deaths by suicide. Although other deaths were not directly related to arachnoiditis, the average lifespan was shortened by 12 years. Treatment results were disappointing. Arachnoiditis may be disabling; however, longterm follow-up indicates that progression of symptoms and functional impairment are not the natural course of the disease.

The wiltse pedicle screw fixation system: early clinical results

Ninety-nine patients were studied prospectively after spine fusion augmented with the Wiltse pedicle screw fixation system. Follow-up ranged from 12 to 34 months, averaging 20 months. There were 33 men and 66 women. Their ages ranged from 20 to 86, with the average age of 52. This was the first spine surgery in 23 patients. Seventy-six patients had had prior spine surgery. Spine fusion was attempted at one to four levels of the lumbosacral spine. Major perioperatlve complications were seen in seven patients (7%). Hardware failure was seen in seven cases (7%). Union was assessed by radiographs at 1 year or more after surgery in 82 patients (85%). In those 82 patients, union was seen in 56 (68%) and nonunion in 26 (32%). Change in lordosis was measured in 54 patients. The average change was a loss of 1.7° lordosis per level fused. A questionnaire was answered by 79 patients (81%). Overall, 55 (70%) stated that they had some benefit from surgery, ten (13%) had no change, and 13 (17%) were worse.

A Modification of the Scott Wiring Technique

The authors describe a modification of Scotts technique using both a paraspinous approach and a two-wire double knot tension band

History of Spinal Fusion

This chapter is intended, not to cover every aspect of the early history of spinal fusion, but to touch on the early landmark advances and interpret the importance of these in light of subsequent developments.