Biomechanical effects of laminectomy on thoracic spine stability

Classification of thoracic spine fractures: the four-column theory

PURPOSE

The purpose of this study is to present a classification of thoracic spine fractures based on anatomical and biomechanical characteristics.

METHODS

This is a narrative review of the literature.

RESULTS

The classification is based on the relationship between movement and common forces acting on the spine. A mechanistic concept is incorporated into the classification, which considers both movements and the application of forces, leading to pathomorphological characteristics. A hierarchical ranking determines the severity of fractures within the thoracic spine, and treatment recommendations are presented in each category. The fourth column of the spine is incorporated into the classification through direct and indirect mechanisms.

CONCLUSIONS

The proposed classification accommodates several advantages, such as simplicity and practicality, that make this classification helpful in daily practice. The dynamic relationship between movement and force provides a better understanding of the fracture mechanism. Finally, incorporating the fourth column will strengthen the indication for surgical management. To the best of our knowledge, this classification is the first classification developed uniquely for the thoracic spine fractures and will help to address a critical gap in the literature.

Influence of occupant collision state parameters on the lumbar spinal injury during frontal crash

Introduction

Developed a detailed finite element model of spine and validated with the experimental or cadaveric tests to gain insight on occupant safety.

Objectives

This study evaluates the influence of occupant collision state parameters such as height of the drop, occupant seating posture (occupant posture angle) and mass of the upper body on the risk of lumbar spinal injury during a frontal crash.

Methods

This parametric evaluation utilizing response surface methodology (RSM) performed. ANOVA was used to test the significance of parameters.

Results

Higher axial force of 3547 N is observed with higher dropping distance of 1500 mm. Similarly, higher strain and energy absorption were observed for the same dropping condition respectively.

Conclusion

The result shows that all the factors considered in the experiment contribute to the risk of spinal lumbar injury during the frontal crash. Among all, height of the drop and the occupant posture angle are the most significant parameters in determining the lumbar spinal injury of occupant. It is observed that the injury criteria are directly proportional to the posture angle of the seat and height of drop.

Intermediate screws or kyphoplasty: Which method of posterior short-segment fixation is better for treating single-level thoracolumbar burst fractures?

PURPOSE

To compare intermediate screws (IS) with kyphoplasty (KP) in posterior short-segment fixation (PSSF) for patients with single-level thoracolumbar burst fractures.

METHODS

Between 2010 and 2016, 1465 patients were retrospectively reviewed; 48 patients were enrolled with a minimal follow-up of 2 years. Perioperative and functional outcomes were compared. The regional Cobb angle (CA) was included in radiographic analysis. Implant failures or CA correction loss over 10° were regarded as surgical failures. Multiple linear regression was performed to investigate the risk factors of kyphosis recurrence.

RESULTS

Fluoroscopic time (23.7 ± 3.6 vs. 79.3 ± 12.1 s, p < 0.001), operative time (109.6 ± 13.1 vs. 123.8 ± 19.0 min, p = 0.006) and blood loss (104.6 ± 34.9 vs. 129.1 ± 21.7 ml, p = 0.005) were all lower in the IS group. The KP group had lower Visual Analogue Scale scores (3.3 ± 0.9 vs. 2.7 ± 0.8, p = 0.028) and greater anterior body height (ABH) (30.3 ± 9.0 vs. 36.3 ± 11.0%, p = 0.044) after surgery, and less correction loss (5.6 ± 2.7 vs. 0.4 ± 1.2%, p < 0.001). Both groups had a CA correction loss of 4° with a 10% failure rate. The A3 Magerl subclassification, smaller preoperative ABH and smaller postoperative CA had positive correlations with CA correction loss.

CONCLUSION

PSSF with KP provides better back pain relief, greater ABH reduction and less correction loss, while IS has the advantages of less operative time, fluoroscopic time and blood loss. Magerl subclassification of burst fracture is a potential predictor for recurrent kyphosis. Reducing fractured vertebral body height rather than segmental curvature may be more important in PSSF.

STUDY DESIGN

Retrospective, non-randomized controlled study. These slides can be retrieved under Electronic Supplementary Material.

Risk factors and outcomes in thoracic stenosis with myelopathy: A single center experience

OBJECTIVE

Identify risk factors predisposing to thoracic spinal stenosis and myelopathy (TS) and address treatment options and outcomes.

METHODS

A retrospective review of our center's experience with TS over 10 years. Clinical and magnetic resonance imaging (MRI) data, surgical intervention and outcomes using Frankel and Japanese Orthopedic Association (JOA) scales were collected.

RESULTS

A total of 44 patients with TS were identified. There were 30 men and 14 women with a mean age±SD of 66±15years. Neurological performance was evaluated using the Frankel scale (A-E or 1-5), and JOA scale for myelopathy (0-11). Frankel scores (1-5) and JOA scores (0-11) on admission were 3.5±0.9 and 6.8±2.6 respectively. At follow-up, Frankel scores had improved to 4.1±0.8 (p=0.041) and JOA scores had improved to 8.3±2.4 (p=0.021). The presence on admission of increased signal from the cord on T2-weighted MRI was associated with lower Frankel and JOA scores (3.3±0.9, and 6.2±2.5 respectively) than in those with absent increased signal (4.0±0.4 and 8.6±2.1, p=0.02 and p=0.008 respectively). There were 4 complications, requiring exploration and debridement for dehiscence in 3 and an epidural hematoma in the fourth that necessitated evacuation, with a good outcome. A fifth patient underwent reoperation at the same level 18 months later for persistent stenosis.

CONCLUSION

Thoracic stenosis with myelopathy should be entertained in patients with myelopathy. Over half of our patients with TS were over the age of 70, and men outnumbered women by a ratio of 2:1. Nearly half the patients with TS had concomitant cervical and/or lumbar degenerative disease warranting surgery also. Increased signal intensity on T2-weighted MRI images correlated with lower Frankel and JOA scores compared to those without. Decompression for thoracic stenosis is associated with neurological improvement.

Biomechanics of the lower thoracic spine after decompression and fusion: a cadaveric analysis

BACKGROUND CONTEXT

Few studies have evaluated the extent of biomechanical destabilization of thoracic decompression on the upper and lower thoracic spine. The present study evaluates lower thoracic spinal stability after laminectomy, unilateral facetectomy, and unilateral costotransversectomy in thoracic spines with intact sternocostovertebral articulations.

PURPOSE

To assess the biomechanical impact of decompression and fixation procedures on lower thoracic spine stability.

STUDY DESIGN

Biomechanical cadaveric study.

METHODS

Sequential surgical decompression (laminectomy, unilateral facetectomy, unilateral costotransversectomy) and dorsal fixation were performed on the lower thoracic spine (T8-T9) of human cadaveric spine specimens with intact rib cages (n=10). An industrial robot was used to apply pure moments to simulate flexion-extension (FE), lateral bending (LB), and axial rotation (AR) in the intact specimens and after decompression and fixation. Global range of motion (ROM) between T1-T12 and intrinsic ROM between T7-T11 were measured for each specimen.

RESULTS

The decompression procedures caused no statistically significant change in either global or intrinsic ROM compared with the intact state. Instrumentation, however, reduced global motion for AR (45° vs. 30°, p=.0001), FE (24° vs. 19°, p=.02), and LB (47° vs. 36°, p=.0001) and for intrinsic motion for AR (17° vs. 4°, p=.0001), FE (8° vs. 1°, p=.0001), and LB (12° vs. 1°, p=.0001). No significant differences were identified between decompression of the upper versus lower thoracic spine, with trends toward significantly greater ROM for AR and lower ROM for LB in the lower thoracic spine.

CONCLUSIONS

The lower thoracic spine was not destabilized by sequential unilateral decompression procedures. Addition of dorsal fixation increased segment rigidity at intrinsic levels and also reduced overall ROM of the lower thoracic spine to a greater extent than did fusing the upper thoracic spine (level of the true ribs). Despite the lack of true ribs, the lower thoracic spine was not significantly different compared with the upper thoracic spine in FE and LB after decompression, although there were trends toward significance for greater AR after decompression. In certain patients, instrumentation may not be needed after unilateral decompression of the lower thoracic spine; further validation and additional clinical studies are warranted.

Quantification of Increase in Three-dimensional Spine Flexibility Following Sequential Ponte Osteotomies in a Cadaveric Model

BACKGROUND

Posterior-only procedures are becoming more popular for treatment of rigid adolescent idiopathic scoliosis, but little is known about the quantitative correction potential for Ponte osteotomies. The objective of this study was to quantify and compare the range of motion of intact multilevel thoracic spine segments with the same segments after each of 3 sequential Ponte osteotomies.

METHODS

We tested 5 human cadaveric thoracic spine segments, spanning T-T6, or T7-T12, in an 8-degree-of-freedom servo-hydraulic load frame, monitoring motion of each vertebra with an optical motion tracker. We measured range of motion while we applied cyclic, pure moment loading to produce flexion-extension, lateral bending, and axial rotation at a rate of 0.5°/second, to a maximum of ± 6 Nm. Each specimen was tested intact and after each of 3 sequential Ponte osteotomies.

RESULTS

Total range of motion for the segments (either T2-T5 or T8-T11) increased by as much as 1.6° in flexion, 1.5° in extension, 0.5° in lateral bending, and 2.8° in axial rotation with each osteotomy. Because of the variation in initial specimen stiffness, we normalized motions to the intact values. In flexion, average range of motion increased after each osteotomy compared with intact, by 33%, 56%, and 69%. In extension, slightly smaller increases were seen, increasing by as much as 56% after the third osteotomy. In lateral bending, Ponte osteotomies had little effect on range of motion. In axial rotation, range of motion increased by 16%, 29%, and 65% after 3 osteotomies.

CONCLUSIONS

Sequential Ponte osteotomies increased range of motion in flexion, extension, and axial rotation, but not in lateral bending. These results suggest that the Ponte osteotomy may be appropriate when using derotational correction maneuvers, or to improve apical lordosis at the apex of curvature during posterior spinal fusion procedures. Although these techniques are effective in gaining correction for kyphotic deformities and rigid curvatures, they add time and blood loss to the procedure.

Dorsal paddle leads implant for spinal cord stimulation through laminotomy with midline structures preservation

Background:

Pain relief obtained with spinal cord stimulation (SCS) in failed back surgery syndrome (FBSS) has been shown to be more effective with paddle leads than with percutaneous catheters. A laminectomy is generally required to implant the paddles, but the surgical approach may lead to iatrogenic spinal instability in flexion. In contrast, clinical and experimental data showed that a laminotomy performed through flavectomy and minimal resection of inferior and superior lamina with preservation of the midline ligamentous structures allowed to prevent iatrogenic instability. Aim of the study was to assess degree of instability and pain level in patients operated for SCS through laminectomy or laminotomy with midline structures integrity. The surgical technique is described and our preliminary results are discussed.

Methods:

Nineteen patients with FBSS underwent SCS, 12 through laminectomy and 7 through uni- or bilateral interlaminotomy with supraspinous ligament preservation. Postoperative local pain was evaluated at 15, 30, and 60 days. Static and dynamic X-rays were performed after 2 months.

Results:

The techniques allowed implanting the paddle leads in all cases. No intraoperative complications occurred. Local pain was higher and recovery time was longer in patients with laminectomy. We did not observe radiological signs of postoperative iatrogenic vertebral instability. Nevertheless, two patients who underwent laminectomy showed persistence of local pain after 2 months probably due to pathologic compensatory stability provided by the paraspinal musculature.

Conclusions:

The laminotomy is a minimally invasive approach that ensures rapid recovery after surgery, spinal functional integrity, and complete reversibility. Further studies are needed to confirm our preliminary results.

The role of fusion in the management of burst fractures of the thoracolumbar spine treated by short segment pedicle screw fixation: a prospective randomised trial

The purpose of this study was to determine whether patients with a burst fracture of the thoracolumbar spine treated by short segment pedicle screw fixation fared better clinically and radiologically if the affected segment was fused at the same time. A total of 50 patients were enrolled in a prospective study and assigned to one of two groups. After the exclusion of three patients, there were 23 patients in the fusion group and 24 in the non-fusion group. Follow-up was at a mean of 23.9 months (18 to 30). Functional outcome was evaluated using the Greenough Low Back Outcome Score. Neurological function was graded using the American Spinal Injury Association Impairment Scale. Radiological outcome was assessed on the basis of the angle of kyphosis. Peri-operative blood transfusion requirements and duration of surgery were significantly higher in the fusion group (p = 0.029 and p < 0.001, respectively). There were no clinical or radiological differences in outcome between the groups (all outcomes p > 0.05). The results of this study suggest that adjunctive fusion is unnecessary when managing patients with a burst fracture of the thoracolumbar spine with short segment pedicle screw fixation.

Biomechanical properties of human thoracic spine disc segments

BACKGROUND

The objective was to determine the age-dependent compressive and tensile properties of female and male thoracic spine segments using postmortem human subjects (PMHS).

MATERIALS AND METHODS

Forty-eight thoracic disc segments at T4-5, T6-7, T8-9, and T10-11 levels from 12 PMHS T3-T11 spinal columns were divided into groups A and B based on specimen age and loaded in compression and tension. Stiffness and elastic modulus were computed. Stiffness was defined as the slope in the linear region of the force-displacement response. Elastic modulus was defined as the slope of the stress strain curve. Analysis of Variance (ANOVA) was used to determine significant differences (P<0.05) in the disc cross-sectional area, stiffness, and elastic modulus based on gender, spinal level, and group.

RESULTS

Specimen ages in group A (28 ± 8 years) were significantly lower than in group B (70 ± 7 years). Male discs had significantly greater area (7.2 ± 2.0 sq cm) than female discs (5.9 ± 1.8 sq cm). Tensile and compressive stiffness values were significantly different between the two age groups, but not between gender and level. Specimens in group A had greater tensile (486 ± 108 N/mm) and compressive (3300 ± 642 N/mm) stiffness values compared to group B specimens (tension: 397 ± 124 N/mm, compression: 2527 ± 734 N/mm). Tensile and compressive elastic modulus values depended upon age group and gender, but not on level. Group A specimens had significantly greater tensile and compressive moduli (2.9 ± 0.8 MPa, 19.5 ± 4.1 MPa) than group B specimens (1.7 ± 0.6 MPa, 10.6 ± 3.4 MPa). Female specimens showed significantly greater tensile and compressive moduli (2.6 ± 1.0 MPa, 16.6 ± 6.4 MPa) than male specimens (2.0 ± 0.7 MPa, 13.7 ± 5.0 MPa).

DISCUSSION

Using the two groups to represent "young" and "old" specimens, this study showed that the mechanical response decreases in older specimens, and the decrease is greater in compressive than distractive properties. While the decrease is expected, the relative change between the two modes of loading has not been reported. Another conclusion from the study is that the mechanical properties depend on gender, although not as decisive due to sample size.

Outcome of thoracolumbar burst fractures treated with indirect reduction and fixation without fusion

Indirect reduction and fixation is not a new method in the treatment of thoracolumbar burst fractures but the indications and efficacy are controversial. The current study was designed to evaluate the efficacy of indirect reduction without fusion. Sixty-four patients with single-level thoracolumbar burst fractures were identified and treated by this method. The outcome was analyzed by the Frankel method, radiographic measurements, and at the latest follow-up the Denis Pain Scale and Oswestry disability index (ODI) were used to assess back pain and functional outcome. The average follow-up period was 40.1 months. The anterior vertebral height (AVH) was corrected from 55.2 to 97.2% post-operatively and decreased to 88.9% after hardware removal. The posterior vertebral height (PVH) increased from 88.9 to 99.1% post-operatively and decreased slightly after implant removal to 93.7%. The average pre-operative canal compromise was 41.4%, which decreased to 13.7% at last follow-up. Except for three paraplegic patients, neurological status significantly improved or stayed normal in the study's remaining 61 patients. Fifty-two of sixty-four patients had excellent or good function. At latest follow-up the average ODI score was 16.7 and the Denis pain score improved in all patients but one. Indirect reduction and fixation can not only restore vertebral column structure but also, more importantly, patients' functional outcome.

The change of adjacent segment and sagittal balance after thoracolumbar spine surgery

OBJECTIVE

To characterize perioperative biomechanical changes after thoracic spine surgery.

METHODS

Fifty-eight patients underwent spinal instrumented fusions and simple laminectomies on the thoracolumbar spine from April 2003 to October 2008. Patients were allocated to three groups; namely, the laminectomy without fusion group (group I, n = 17), the thoracolumbar fusion group (group II, n = 27), and the thoracic spine fusion group (group III, n = 14). Sagittal (ADS) and coronal (ADC) angles for adjacent segments were measured from two disc spaces above lesions at the upper margins, to two disc spaces below lesions at the lower margins. Sagittal (TLS) and coronal (TLC) angles of the thoracolumbar junction were measured from the lower margin of the 11th thoracic vertebra body to the upper margin of the 2nd lumbar vertebra body on plane radiographs. Adjacent segment disc heights and disc signal changes were determined using simple spinal examinations and by magnetic resonance imaging. Clinical outcome indices were determined using a visual analog scale.

RESULTS

The three groups demonstrated statistically significant differences in terms of angle changes by ANOVA (p < 0.05). All angles in group I showed significantly smaller angles changes than in groups II and III by Turkey's multiple comparison analysis. Coronal Cobb's angles of the thoracolumbar spine (TLC) were not significantly different in the three groups.

CONCLUSION

Postoperative sagittal balance is expected to change in the adjacent and thoracolumbar areas after thoracic spine fusion. However, its prevalence seems to be higher when the thoracolumbar spine is included in instrumented fusion.

The effect of posterior thoracic spine anatomical structures on motion segment flexion stiffness

STUDY DESIGN

This in vitro human cadaveric study tested the loss of thoracic motion segment flexion stiffness after sequential posterior upper instrumented vertebra anchor placement techniques and posterior column destabilization.

OBJECTIVE

This study was designed to determine the possible destabilizing effects of upper thoracic instrumentation anchor site preparation.

SUMMARY OF BACKGROUND DATA

Proximal junctional kyphosis after instrumentation and arthrodesis for scoliosis and related spine deformities has recently been reported to range from 10% to 46%. The effect of posterior skeletal dissection associated with upper instrumented vertebra anchor placement on adjacent motion segment flexion stiffness has not been previously studied. METHODS.: Twenty-three intact thoracic motion segments were obtained from 6 human cadavers. Biomechanical testing was performed with each motion segment flexed to approximately 3.2 degrees at a rate of 0.1 Hz, with corresponding torques recorded. Data were collected after a series of 6 posterior procedures. Differences with P value <0.01 were considered significant and those with P value <0.05 marginally significant.

RESULTS

Supratransverse process hook, supralaminar hook, pedicle screw placement, or pedicle screw removal done, bilaterally, produced similar, small (range, 2.09%-6.03%), nonsignificant reductions in motion segment flexion stiffness. But when totaled, these 4 procedures resulted in a significant 16.31% loss of flexion stiffness. The fifth procedure of supraspinous and interspinous process ligament transection added a marginally significant 6.59% incremental loss of flexion stiffness. Supralaminar hook site preparation combined with supraspinous and interspinous process ligament transection resulted in a marginally significant 12.62% incremental loss of flexion stiffness. Transection of the remaining posterior structures (facet joints and all other posterior soft tissue structures) produced a significant additional flexion stiffness loss of 44.72%. The anterior column alone provided only 32.39% of the total motion segment flexion stiffness. Transection of all posterior stabilizing structures, similar to a Smith-Peterson/chevron/Ponte resection, decreased motion segment flexion stiffness significantly, 67.61%.

CONCLUSION

Posterior thoracic skeletal structures involved in upper instrumented vertebra exposure andanchor placement were found to contribute to adjacent segment flexion stiffness. Although stiffness loss was small after individual procedures, the effects were additive for routinely used combinations.

Do alterations in vertebral and disc dimensions affect an elliptical model of thoracic kyphosis?

STUDY DESIGN

Mathematical modeling, using least squares method, of thoracic kyphosis was constructed as digitized points from radiographs of 50 healthy patients.

OBJECTIVE

To determine a simple geometric model of the thoracic kyphosis.

SUMMARY OF BACKGROUND DATA

Thoracic kyphosis is an important parameter of health, but geometric models of kyphosis are rare. Few papers report vertebral body and disc height data.

METHODS

Thoracic vertebral bodies were digitized on lateral radiographs of 50 healthy patients. The average path of the posterior vertebral body corners of T1 through T12 was modeled, in the least squares sense, with a portion of an ellipse. The best-fit ellipse was sectioned with different model partitions using four sets of vertebral body heights and disc heights. Segmental and global angles derived from these four models were compared with reported values in the literature.

RESULTS

A 72 degrees portion of an ellipse, with a minor-to-major axis ratio of 0.69, can closely approximate the path of the posterior body corners from the inferior of T1 to the superior of T12. The posterior vertebral body heights and disc heights have an average ratio of approximately 5:1. Segmental angles from T3-T4 through T11-T12 for all four models are close to other reported values. The thoracic spine has a height-to-length ratio of approximately 0.96.

CONCLUSIONS

Thoracic kyphosis from inferior-posterior T1 to superior-posterior T12 can be closely modeled (least squares error per point < 1 mm) with a 72 degrees piece of an ellipse with a minor-to-major axis ratio of 0.69. The major axis is parallel to the posterior body margin of T12, whereas the minor axis passes through the superior endplate of T12. Segmental angles derived from this elliptical modeling are in the range of values from healthy patients.

An in vitro human cadaveric study investigating the biomechanical properties of the thoracic spine

STUDY DESIGN

An in vitro human cadaveric study comparing the effects of anterior and posterior sequential destabilization conditions on thoracic functional unit mechanics was studied.

OBJECTIVES

To investigate the biomechanical properties of the human thoracic spine.

SUMMARY OF BACKGROUND DATA

Few studies have addressed the mechanical role of the costovertebral joints under torsion in the stability of the human thoracic spine.

METHODS

Sixteen functional spinal units with intact costovertebral joints were obtained from six human cadavers and randomized into two groups based on destabilization procedures: Group 1, anterior to posterior sequential resection; and Group 2, posterior to anterior sequential destabilization. Biomechanical testing was performed after each destabilization procedure, and the range of motion under maximum load was calculated.

RESULTS

Group 1: Under flexion-extension, lateral bending, and axial rotation loading, discectomy increased the range of motion by 193%, 74%, and 111%, respectively. Moreover, subsequent right rib head resection further increased the range of motion by 81%, 84%, and 72%, respectively. Group 2: Under all loading conditions laminectomy + medial facetectomy resulted in a 22-30% increase in range of motion. Subsequent total facetectomy led to an additional 15-28% increase in range of motion.

CONCLUSION

The rib head joints serve as stabilizing structures to the human thoracic spine in the sagittal, coronal, and transverse planes. In anterior scoliosis surgery additional rib head resection after discectomy may achieve greater curve and rib hump correction. The lateral portion of the facet joints plays an important role in providing spinal stability and should be preserved to minimize postoperative kyphotic deformity and segmental instability when performing decompressive wide laminectomy.

Biomechanical effects of transthoracic microdiscectomy

STUDY DESIGN

Nondestructive flexibility testing was performed to quantify biomechanical parameters of human cadaveric thoracic spines before and after microdiscectomy.

OBJECTIVES

To assess the biomechanical differences between the normal thoracic spine and the thoracic spine after microdiscectomy and to determine whether microdiscectomy results in spinal instability.

SUMMARY OF BACKGROUND DATA

Previous studies have investigated thoracic disc properties and the biomechanical effects of thoracic ligament or bone trauma. No studies were found assessing the effects of thoracic discectomy.

METHODS

Eight motion segments (T4-T5 to T11-T12) from five human cadaveric thoracic spines were studied before and after microdiscectomy. Three-dimensional motion was recorded in response to nondestructive, nonconstraining pure moments. Parameters measured included the neutral zone, elastic zone, range of motion, rotational flexibility, and instantaneous axis of rotation.

RESULTS

The neutral zone, elastic zone, and range of motion increased a small but significant (average P = 0.02 for range-of-motion increase) amount in all directions after thoracic microdiscectomy (mean bilateral range of motion increase, 2.1 degrees; range, 0.5-4.2 degrees). Flexibility increased slightly during lateral bending and flexion. The instantaneous axis of rotation location usually did not change, but sometimes shifted slightly away from the discectomy site after microdiscectomy.

CONCLUSIONS

Thoracic microdiscectomy had small effects on the immediate mechanics and kinematics of the thoracic spine and did not overtly destabilize the motion segments.

Biomechanical role of the posterior elements, costovertebral joints, and rib cage in the stability of the thoracic spine

STUDY DESIGN

This is a biomechanical study of the thoracic spine. Various ligaments and joints were resected sequentially and nondestructive cyclic loading tests were performed. Effects of each resection were analyzed biomechanically.

OBJECTIVES

To investigate the role of the posterior elements, costovertebral joints, and rib cage in the stability of the thoracic spine.

SUMMARY OF BACKGROUND DATA

There have been no experimental studies concerning the mechanical interaction between the thoracic spine and rib cage.

METHODS

Eight canine rib cage-thoracic spine complexes, consisting of the sixth to eighth ribs, sternum, and T5-T9 vertebrae, were used. Six pure moments along three axes were applied to the specimens, and angular deformation of T6-T7 was recorded. After testing the intact specimen, resection of the stabilizers was conducted incrementally in the following manner: 1) removal of the posterior elements at T6-T7, 2) resection of the bilateral seventh costovertebral joints, and finally, 3) destruction of the rib cage. The same loading tests were repeated at each stage. The ranges of motion and neutral zones were calculated by digitization.

RESULTS

A large increase in the range of motion in flexion-extension was observed after resection of the posterior elements and in lateral bending and axial rotation after resection of the costovertebral joints. A significant increase in the neutral zone in lateral bending and axial rotation was observed after bilateral resection of the costovertebral joints and destruction of the rib cage.

CONCLUSIONS

The costovertebral joints and rib cage play an important role in providing stability to the thoracic spine. The state of the costovertebral joints and rib cage should be assessed to evaluate the stability of the thoracic spine.

General management of vertebral fractures

Vertebral fractures cause pain and disability. Four concepts should guide their comprehensive management: treat the patient, not the skeleton; use a multidisciplinary approach; engage the patient and his or her family in the treatment; and provide appropriate goals, education, encouragement, and support. The goals include procuring bone mass and preventing injury: back support, physical therapy, occupational therapy, psychosocial support, and prevention of falls. Initial treatment includes bed rest, pain management with local and systemic analgesia, bracing to improve comfort, and patient reassurance. Long-term management includes spinal stretching exercises and continuing ordinary activities within limits permitted by pain. A back school program is an effective addition to conventional concepts using physiotherapy exclusively. In certain selected patients, the indication for operative treatment of vertebral fracture depends on the additional injury, and extent and characteristics of cord compression; stability of the fracture; and the amount of deformity. Vertebroplasty can be effective in the control of pain and in obtaining stability of the spine.