PATIENT SAMPLE: NA.

OUTCOME MEASURES: NA.

METHODS: The C2 vertebrae of 420 adult specimens were studied. Lam-

inar thickness, spinolaminar angle, and the length from the spinolaminar

junction to the contralateral lamina/lateral mass junction were measured.

Statistical analysis was performed using unpaired Student t tests and

regression analysis (p!.05).

RESULTS: Mean laminar thickness was 5.7761.31 mm. 70.6% of speci-

mens had a laminar thickness !5 mm. 92.6% had a thickness !4.0 mm.

The spinolaminar angle was 48.59 degrees 65.42 degrees. The mean screw

length that could be used was 2.4660.23 cm. O99% of specimens had an

estimated screw length of at least 20 mm. Gender had a significant effect

on all of the measurements studied, but race, height, and weight did not.

CONCLUSIONS: The majority of specimens can safely accept placement

of a laminar screw. This study establishes anatomic guidelines to allow for

accurate screw selection and insertion. Preoperative planning is essential

for safe screw placement via this technique.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2006.06.252

P57. Total Vertebrectomy and Replacement for Thoracic Spine

Tumors by a Single-Stage Costotransversectomy Approach

Jefferson Leal, MD1, Resende Rogerio, MD2, Mariana Leal, PhD2;1Department of Orthopedic Surgery, Group of Spinal Surgery, Federal

University of State of Minas Gera, Belo Horizonte, Minas Gerais, Brazil;2Federal University of State of Minas Gerais, Belo Horizonte, Minas

Gerais, Brazil

BACKGROUND CONTEXT: Because of the limitations imposed by the

upper thoracic segments where a thoracotomy is difficult for application of

anterior fixation devices and carries a high morbidity, especially for pa-

tients with pulmonary disease who cannot tolerate a standard thoracotomy,

the procedure presented can provide adequate descompression and stabili-

zation for tumors in this region throgh a single, extrapleural and postero-

lateral approach.

PURPOSE: To demonstrate the feasibility, benefits, and complications us-

ing a costotransversectomy approach.

STUDY DESIGN/SETTING: We retrospectively reviewed 11 consecu-

tive patients who underwent extrapleural vertebrectomy with vertebral

body reconstruction and posterior stabilization using pedicle screw fixation

for tumor of the thoracic spine between October 1999 and January 2005.

PATIENT SAMPLE: Eleven consecutive patients who underwent single-

stage complete spondylectomy with reconstruction using cage, methylme-

thacrylate, and posterior pedicle screw fixation for thoracic spine tumors.

The technique was performed in patients with or without neurological def-

icit, intractable pain, or because they were poor candidates for a transcavi-

tary approach.

OUTCOME MEASURES: Our review includes surgical outcomes and

complications. The following variables were evaluated: postoperative pain,

survival, maintenance of alignment, and associated complications.

METHODS: All patients were subjected to the technique described:

vertebrectomy, vertebral body reconstruction with cage and methylmetha-

crylate, and posterior stabilization with pedicle screw fixation for thoracic

spine tumors throgh a single, extrapleural approach. Surgical indications

and technique are provided and initial clinical results are described.

RESULTS: Acceptable complications happened in two patients: one tran-

sient respiratory distress and one excessive bleeding. There were no cases

of worsening of neurological status postoperatively, and five patients had

improved their neurological deficit. There was no immediate postoperative

mortality. All patients were functionally improved and with stable spinal

alignment until the day of reevaluation or until the days before the death.

CONCLUSIONS: The authors conclude that this surgical approach is safe

and feasible for resection of vertebral tumors located in thoracic spine

when combined with reconstruction and stabilization. This technique

represents a useful alternative to other surgical approaches for the treat-

ment of thoracic spine tumors, especially in its upper segments, and it

could aid surgeons in selecting a better approach for individual patients.

FDA DEVICE/DRUG STATUS: Pedicle screw fixation: Not approved for

this indication; Cage: Not approved for this indication.

CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2006.06.253

P58. Abnormal Spread of Junctional Acetylcholine Receptor of

Paravertebral Muscles in Scoliosis Associated With Syringomyelia

Yong Qiu, MD; Spine Surgery, the Affiliated Drum Tower Hospital

of Nanjing University Medical School, Nanjing, Jiangsu, China

BACKGROUND CONTEXT: The mechanism by which scoliosis de-

velops secondary to syringomyelia is yet to be determined. Some authors

hypothesize the scoliosis may be caused by an alteration in the innervation

of the trunk musculature, attributable to the syrinx causing injury either on

the lower motor neurons or on the dorsomedial and ventromedial nuclei of

the anterior horn of the spinal cord. Denervation is a typical condition in

which acetylcholine receptor (AChR) is found outside the neuromuscular

junctions (NMJs).

PURPOSE: To examine the denervation of paraspinal muscles and further

investigate the pathogenesis of scoliosis associated with syringomyelia via

detecting the spread of AChR beyond the confines of the functional NMJs.

STUDY DESIGN/SETTING: All the patients were divided into three

groups, and the results of AChR staining were compared.

PATIENT SAMPLE: 25 patients with scoliosis associated with syringo-

myelia, 16 adolescents with idiopathic scoliosis, and 10 cases without sco-

liosis were enrolled.

OUTCOME MEASURES: Acetylcholinesterase staining defined the

limits of the NMJs, and AChR staining that appeared outside of these

limits indicated an abnormal distribution of AChR, which meant the pa-

tient was judged positive.

METHODS: All the enrolled patients were divided into three groups: the

SS (scoliosis associated with syringomyelia) group consisted of 25 patients

with scoliosis associated with syringomyelia, the AIS (adolescent idio-

pathic scoliosis) group included 16 adolescents with idiopathic scoliosis,

and the NS (nonscoliosis) group included 10 cases without scoliosis. His-

tological evaluation of paraspinal muscles used a double-stain immunoflu-

orescence technique for AChR and acetylcholinesterase, wherein

acetylcholinesterase staining defined the limits of the NMJs, and AChR

staining that appeared outside of these limits indicated an abnormal distri-

bution of AchR, which meant the patient was judged positive.

RESULTS: Histological analysis showed that none of the patients in the

AIS group or NS group was judged positive, but 14 of 25 patients in the

SS group scored positive for the presence of AChR outside of the NMJs.

The positive rate was 44% on the convex side of the curve, and 28% on

the convex side.

CONCLUSIONS: The denervation of paraspinal muscles is present in

some patients with scoliosis associated with syringomyelia, suggesting that

scoliosis may be caused by the strength imbalance of paraspinal muscles in

these patients.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2006.06.254

P59. Lumbar Vertebral End Plate Biomechanics Are Affected

by Disc Replacement Size

Joshua D. Auerbach, MD1, Carrie M. Ballester, MS2, Ehren T. Carine,

MS3, Frank Hammond, MS3, Richard A. Balderston, MD4, Dawn Elliott,

PhD5; 1University of Pennsylvania, Philadelphia, PA, USA; 2University of

Pennsylvania, PA, USA; 3McKay Orthopaedic Laboratory, PA, USA;4Booth, Bartolozzi, Balderston Orthopaedics, Philadelphia, PA, USA;

111SProceedings of the NASS 21st Annual Meetings / The Spine Journal 6 (2006) 1S–161S