Biomedical subjects

M M Panjabi

Publications and source records attributed to M M Panjabi.

At least 55 records · Page 3Linked to original sources

PubMed1998

Simulation of whiplash trauma using whole cervical spine specimens.

STUDY DESIGN: Whiplash injuries were studied in an experiment using whole cervical spine specimen. OBJECTIVES: To develop a whiplash trauma model that uses a whole cervical spine specimen, and to show the feasibility and unique features of such a model. SUMMARY OF BACKGROUND DATA: Whiplash trauma has been simulated in biomechanical experiments using volunteers, whole body cadavers, animals, anthropometric dummies, and mathematic models. These experiments require large facilities, are expensive, and provide limited information about cervical spine injuries. METHODS: An alternate approach, in which a bench-top sled accelerating apparatus is used to produce whiplash trauma, has been developed to study such trauma in whole cervical spine specimens. Several transducers were developed to monitor soft tissue injuries during the trauma. The model also provides quantification of injuries to the cervical spine. RESULTS: To assess the feasibility and usefulness of the model, a specimen was traumatized, and the following parameters were monitored during the trauma: linear acceleration of the sled, linear and angular acceleration of the head surrogate, displacements of the head surrogate, loads at T1 and C1 vertebrae, and linear deformations of capsular ligaments and vertebral artery. CONCLUSIONS: This model, which incorporates a fresh cadaveric whole human cervical spine specimen, can simulate whiplash trauma effectively and is useful in providing a comprehensive set of clinically relevant information during the trauma. This model gives insight into the complex events and interactions that cause the injuries that occur during whiplash trauma.

Cadaver↗

PubMed1998

[Biomechanics of whiplash injury].

The article reports a new hypothesis of whiplash injury based on a series of experimental studies using isolated human cadaveric specimens. Although the clinical symptoms of whiplash are widely known, the understanding of the underlying injury mechanism is poor. The prevailing view of neck-hyper-extension as the essential injury mechanisms was not supported by recent experiments. In a series of experiments using eight human cadaveric specimens which underwent experimental stepwise whiplash acceleration from 2.5 to 10.5 g functional radiographs and flexibility tests were performed at the end of each acceleration step. Ligament strains, vertebral alignment and elongation of the vertebral artery were monitored during the whiplash trauma by highspeed cinematography and specially designed transducers. After the trauma CT- and MRI-scans were taken and specimens were sectioned using Cryomicrotomy. We found a distinct biphasic kinematic response of the cervical spine to whiplash trauma. In the first phase the spine formed an S-shaped curve with flexion at the upper levels and hyper-extension at the lower levels. This phase was found to be the vulnerable phase of whiplash trauma. The largest dynamic elongation of the capsular ligaments was observed at the C6-C7 level during this initial S-shaped phase of whiplash. The maximum elongation of the vertebral artery could be observed synchronously in the first S-shaped curve of the cervical spine. In the second phase of whiplash all levels of the cervical spine were extended, so that the head reached is maximum extension. No injuries were observed in the second phase. We propose, based on our experimental findings, that with low accelerations the anterior structures of the lower cervical spine are injured during the first phase of whiplash, when the cervical spine forms an S-shaped curve and before the neck is fully extended. At higher trauma accelerations there is also a tendency for the injuries to occur at upper levels of the cervical spine. Based on our findings the traditional view of whiplash as hyper-extension injury can be modified by a differentiated, time dependent, biphasic biomechanical model of the injury, thus allowing better and more effective injury prevention, diagnosis and therapy.

Biomechanical Phenomena↗

PubMed1998

Intervertebral disc distraction with a laparoscopic anterior spinal fusion system.

The BAK spinal fusion system has been applied to laparoscopic anterior lumbar interbody fusion. The system, consisting of a pair of cylindrical implants with threads, placed symmetrically about the sagittal plane, functions by tensioning the annulus fibrosis. Cylindrical plugs of increasing size are inserted prior to the implant placement. As the procedure may affect spinal posture and disc height, we measured changes due to incremental plug insertion using human cadaveric spine specimens (L5-S1, n = 4). Multi-directional flexibility of the construct was also measured as a function of plug size. The disc height change was found to increase initially and then to level off at 13-mm diameter plugs. In the sagittal plane, the intervertebral posture first shifted towards kyphotic then came back to the initial lordotic posture with plugs of bigger size. However, changes in disc height and spine posture were not statistically significant. Comparing the neutral zone (NZ) flexibility after inserting the plugs to the intact values, neither the flexion/extension nor the axial rotation NZ showed any significant change. In lateral bending, the NZ decreased after the insertion of 13-mm plugs (p < 0.05). Insertion of plugs of increasing size from 9 mm to 12 mm decreased the range of motion (ROM) in all directions (p < 0.05). Insertion of 13-mm and 14-mm plugs decreased the flexion/extension and lateral bending ROM, but not the axial rotation ROM, probably indicating some injury to the annulus fibers.

Adult↗

PubMed1998

Graded thoracolumbar spinal injuries: development of multidirectional instability.

Injuries of the thoracolumbar spine are serious, disabling, and costly to society. These injuries vary from mild ligament tears to severe bony fractures. Increased range of motion (ROM) and neutral zone (NZ) have been suggested as indicators of the resulting clinical instability. The purpose of the present study was to investigate the relative sensitivities and merits of the ROM and NZ in relation to spinal injuries of the thoracolumbar junction. A graded spinal trauma experiment was designed, in which the threshold of injury and injury progression were examined. Ten thoracolumbar human spine specimens (T11-L1) were traumatized using a high-speed incremental trauma model. The ROM and NZ, which indicate altered mechanical properties, were determined for three physiological motions: flexion/extension (FE), lateral bending (LB), and axial rotation (AR). The injury threshold was found to be 84 J (or 84 Nm) by examining both ROM and NZ for all motion types (P < 0.05), but the NZ was more sensitive. At the injury threshold, the NZ showed an overall average increase of 566% above that of the intact, while the equivalent increase in the ROM was only 94%. The NZ was also a more sensitive parameter documenting the progression of the injury beyond the injury threshold. After the maximum trauma of 137 J, the NZs for the three motions (FE, LB, and AR) increased by 700%, 1700%, and 3000% above their respective intact values. Corresponding increases in the ROM were much smaller: 115%, 184%, and 425% respectively. Direct extrapolation of the in vitro experimental findings to the clinical situation, as always, should be done with care. Our findings, however, suggest that the ROM, as measured from functional radiographs of a traumatized patient, may underestimate the true injury to the spinal column.

Adult↗

PubMed1998

Whiplash injuries and the potential for mechanical instability.

Whiplash injury to the cervical spine is poorly understood. Symptoms often do not correlate to the clinical findings. It has been hypothesized that the long-term clinical symptoms associated with whiplash have their basis in mechanical derangement of the cervical spine caused at the time of trauma. Before such a hypothesis can be proven, one needs to document and quantify the soft tissue injuries of the cervical spine in whiplash. The purpose of the study was to quantify the mechanical changes that occur in the cervical spine specimen as a result of experimental whiplash trauma. Utilizing a whiplash trauma model, injuries to human cadaveric cervical spine specimens (C0-T1 or C0-C7) were produced by increasingly severe traumas. The flexibility tests determined the motion changes at each intervertebral level in response to 1.0 Nm pure flexion-extension moment. Parameters of range of motion (ROM) and neutral zone (NZ) were determined before and after each trauma. Significant flexibility increases first occurred in the lower cervical spine after 4.5-g rear-end (anteriorly directed) acceleration of the T1 vertebra. At this acceleration magnitude, extension ROM and NZ at C5-C6 increased (P < 0.05) by 98% and 160% respectively. There was also a tendency (P < 0. 1) for the extension NZ at C0-C1 and C6-C7 levels to increase after the 6.5-g acceleration by 52% and 241% respectively. There were no such tendencies for the ROM parameter. We have identified the threshold and sites of whiplash injury to the cervical spine. This information should help the clinician make more precise diagnoses in the case of whiplash trauma patients.

Cadaver↗

PubMed1998

Head kinematics during in vitro whiplash simulation.

Knowledge of precise head kinematics during whiplash trauma is important for identifying possible injury mechanisms and their prevention. This study reports a comprehensive data set describing head kinematic response to horizontal accelerations simulating whiplash. Seven isolated fresh human cervical spine specimens (C0 to T1 or C7), each carrying a surrogate head designed to represent a 50th percentile human head, were mounted on the sled and subjected to incremental trauma by horizontal sled accelerations of 2.5, 4.5, 6.5, 8.5, and 10.5 g. Sled and head kinematics were measured with potentiometers and accelerometers. The incremental sled accelerations resulted in average (standard deviations) sled velocity changes (delta V) ranging from 5.8 (0.2) to 15.8 (0.2) km/h. Generally, all the peak head kinematic parameters increased with increasing sled acceleration, except for the peak head angular displacement, which decreased. In the initial phase of a whiplash trauma, the head translated posteriorly with respect to T1, without rotation. In the later phase, the head rotated backwards, but much less than its physiological limit. Maximum head rotation of 31.5 (23.9) degrees occurred in a 2.5 g trauma class, and this was less than the maximum physiological head extension of 55.1 (13.3) degrees. Head kinematics expressed in the T1 or shoulder coordinate system is better suited to study potential neck injury in whiplash.

Accidents, Traffic↗

PubMed1998

Augmented external fixation of distal radius fractures: a biomechanical analysis.

An in vitro model of an unstable extra-articular distal radius fracture was created in 8 fresh-frozen cadaveric specimens and stabilized with an external fixator. Rotation and translation kinematics of the distal radial fracture fragment were measured in relation to the proximal radius during physiologic loading, using infrared light-emitting diodes and a 3-dimensional motion-sensing device. The effect of supplemental single and combination Kirschner wire (K-wire) fixation on fracture fragment stability was assessed. Fixation of supplemental K-wires to the fixator frame via a custom-developed outrigger assembly was also analyzed. Significant reductions in sagittal plane (flexion/extension) rotation and neutral zone were recorded when the fracture fragment was stabilized with a single styloid or dorsal transfixion K-wire. Equivalent stability was afforded by attachment of a nontransfixion K-wire to the fixator frame via the outrigger assembly. The dorsal constructs compared favorably to the styloid constructs in reduction of the sagittal plane neutral zone and coronal (radioulnar) rotation. These data lend biomechanical support to the concept of augmentation of distal radius external fixation and provide a physiologic model to test fixation methods for other fracture patterns.

Bone Wires↗

PubMed1998

Biomechanical study of lumbar spinal stability after osteoplastic laminectomy.

The biomechanical stability of the lumbar spine after two surgical procedures of total facetectomy and osteoplastic laminectomy was investigated using fresh-frozen human cadaveric lumbar spine specimens. Six pure moments in flexion-extension, right-left bending, and right-left twisting were applied and intervertebral motions were recorded using an optoelectronic motion measurement system. Neutral zone (NZ) and range of motion (ROM) under three conditions of intact, total facetectomy, and osteoplastic laminectomy were analyzed statistically to determine comparative biomechanical potential for instability. Results of NZ showed no changes in any direction with respect to the intact behavior after the two procedures. Also, in lateral bending, there were no significant increases in ROM after the two procedures. However, flexion-extension ROM increased significantly (+33%, p < 0.05) after the total facetectomy, but not after osteoplastic laminectomy. Axial rotation ROM increased remarkably after the total facetectomy (+113%, p < 0.05), but only moderately (+57%, p < 0.05) after the osteoplastic laminectomy. The osteoplastic laminectomy, which preserves the spinous process as well as the facet joints, maintains greater spinal stability than the total facetectomy.

Aged↗

PubMed1998

Capsular ligament stretches during in vitro whiplash simulations.

Clinical symptoms of whiplash are presently not well understood. Injuries to capsular and other spinal ligaments of the cervical spine during trauma are a possible pathomechanism that could explain some aspects of the whiplash symptom complex. This study quantified the elongations of capsular ligaments (CLs) at all cervical spinal levels during whiplash simulation using an in vitro model. Seven fresh human cadaveric specimens (occiput-C7 or T1) were carefully dissected, preserving the osteoligamentous structures. Spinal ligament transducers were attached across the CLs from C2-C3 to C6-C7 in each specimen, alternating the two sides. Physiological elongations of the CLs were measured with a standard flexibility test using 1 Nm of pure moments. Next, the specimen was fitted with a surrogate head representing 50th percentile human head. The specimen was mounted on a sled designed to simulate whiplash and subjected to 2.5, 4.5, 6.5, 8.5, and 10.5 g (1 g = 9.81 m/s2) horizontal accelerations sequentially. The dynamic elongations of the CLs were continuously recorded during the entire trauma and were later converted to strains. There were modest increases in capsular ligament strains during the trauma over the maximum physiological values. The two largest peak strains of 29.5 and 35.4% were seen at C6-C7 during the 6.5- and 10.5-g accelerations. We did not find strong correlation between the strain during the trauma and the trauma sled acceleration.

Acceleration↗

PubMed1998

Quantitative discomanometry: technique and reproducibility in vitro.

Quantitative discomanometry is a study of intradiscal pressure and volume measurements during the injection of fluid into an endplate-disc-endplate complex. The purpose of this article was to describe the technique of quantitative discomanometry, determine the reproducibility of the injection technique in a cadaveric thoracolumbar spine, and standardize the technique for future clinical investigations. Nineteen fresh human cadaveric thoracolumbar discs were injected using quantitative discomanometry to determine: (a) the time necessary for a disc to return to a baseline pressure-volume curve, (b) the reproducibility of the technique in vitro, (c) effects of the injection approach and position of the needle in the disc, and (d) effects of the type and length of tubing as well as gauge of spinal needle. A pressure-volume curve was obtained for each disc injection. Reproducibility was measured by nine parameters obtained from each pressure-volume curve: intrinsic pressure, leakage pressure, initial slope, slope between 0-0.1 ml, slope between 1-4 ml, pressure at 2 ml, pressure at 4 ml, maximum pressure, and volume at maximum pressure. The results demonstrated that (a) the injector apparatus was reproducible, (b) the time necessary for a disc to return to a baseline pressure-volume curve was 24 h, (c) the technique using fresh human cadaveric thoracolumbar discs was reproducible, (d) the anterior and posterolateral approaches had similar results if the needle was placed into the center of the nucleus pulposus using radiographic control, and (e) the type and length of tubing, and gauge of needle did not affect the results.

Aged↗

PubMed1997

Whiplash produces an S-shaped curvature of the neck with hyperextension at lower levels.

STUDY DESIGN: A bench-top trauma sled was used to apply four intensities of whiplash trauma to human cadaveric cervical spine specimens and to measure resulting intervertebral rotations using high-speed cinematography. OBJECTIVES: To determine the cervical spine levels most prone to injury from whiplash trauma and to hypothesize a mechanism for such injury. SUMMARY OF BACKGROUND DATA: Whiplash injuries traditionally have been ascribed to hyperextension of the head, but other mechanisms such as hypertranslation also have been suggested. METHODS: Six occiput to T1 (or C7) fresh cadaveric human spines were studied. Physiologic flexion and extension motions were recorded with an Optotrak motion analysis system by loading up to 1.0 Nm. Specimens then were secured in a trauma sled, and a surrogate head was attached. Flags fixed to the head and individual vertebrae were monitored with high-speed cinematography (500 frames/sec). Data were collected for 12 traumas in four classes defined by the maximum sled acceleration. The trauma classes were 2.5 g, 4.5 g, 6.5 g, and 8.5 g. Significance was defined at P < 0.01. RESULTS: In the whiplash traumas, the peak intervertebral rotations of C6-C7 and C7-T1 significantly exceeded the maximum physiologic extension for all trauma classes studied. The maximum extension of these lower levels occurred significantly before full neck extension. In fact, the upper cervical levels were consistently in flexion at the time of maximum lower level extension. CONCLUSIONS: In whiplash, the neck forms an S-shaped curvature, with lower level hyperextension and upper level flexion. This was identified as the injury stage for the lower cervical levels. A subsequent C-shaped curvature with extension of the entire cervical spine produced less lower level extension.

Biomechanical Phenomena↗

PubMed1997

Stabilizing function of trunk flexor-extensor muscles around a neutral spine posture.

STUDY DESIGN: This study examined the coactivation of trunk flexor and extensor muscles in healthy individuals. The experimental electromyographic data and the theoretical calculations were analyzed in the context of mechanical stability of the lumbar spine. OBJECTIVES: To test a set of hypotheses pertaining to healthy individuals: 1) that the trunk flexor-extensor muscle coactivation is present around a neutral spine posture, 2) that the coactivation is increased when the subject carries a load; and 3) that the coactivation provides the needed mechanical stability to the lumbar spine. SUMMARY OF BACKGROUND DATA: Theoretically, antagonistic trunk muscle coactivation is necessary to provide mechanical stability to the human lumbar spine around its neutral posture. No experimental evidence exists, however, to support this hypothesis. METHODS: Ten individuals executed slow trunk flexion-extension tasks, while six muscles on the right side were monitored with surface electromyography: external oblique, internal oblique, rectus abdominis, multifidus, lumbar erector spinae, and thoracic erector spinae. Simple, but realistic, calculations of spine stability also were performed and compared with experimental results. RESULTS: Average antagonistic flexor-extensor muscle coactivation levels around the neutral spine posture as detected with electromyography were 1.7 +/- 0.8% of maximum voluntary contraction for no external load trials and 2.9 +/- 1.4% of maximum voluntary contraction for the trials with added 32-kg mass to the torso. The inverted pendulum model based on static moment equilibrium criteria predicted no antagonistic coactivation. The same model based on the mechanical stability criteria predicted 1.0% of maximum voluntary contraction coactivation of flexors and extensors with zero load and 3.1% of maximum voluntary contraction with a 32-kg mass. The stability model also was run with zero passive spine stiffness to simulate an injury. Under such conditions, the model predicted 3.4% and 5.5% of maximum voluntary contraction of antagonistic muscle coactivation for no extra load and the added 32 kg, respectively. CONCLUSIONS: This study demonstrated that antagonistic trunk flexor-extensor muscle coactivation was present around the neutral spine posture in healthy individuals. This coactivation increased with added mass to the torso. Using a biomechanical model, the coactivation was explained entirely on the basis of the need for the neuromuscular system to provide the mechanical stability to the lumbar spine.

Adult↗

PubMed1997

Multidirectional instability of the thoracic spine due to iatrogenic pedicle injuries during transpedicular fixation. A biomechanical investigation.

STUDY DESIGN: Pedicle fracture was simulated in an in vitro model, and its effect on multidirectional stability provided by pedicle instrumentation was quantified. OBJECTIVES: To quantify the multidirectional flexibility of padicle instrumentation due to different iatrogenic pedicle injuries. SUMMARY OF BACKGROUND DATA: Misplacement of the screw and iatrogenic pedicle fracture are the main complications of pedicle instrumentation. Despite the increasing number of clinical studies dealing with this issue, there is little reliable information concerning the biomechanical effects of an intraoperative pedicle fracture. METHODS: A burst fracture was created in 10 human cadaveric five-vertebrae spine specimens, from the middle and lower thoracic spine regions. The fracture was stabilized with a semirigid pedicle screw fixation device. To simulate an intraoperative pedicle fracture, the pedicles of the instrumented segments were resected in four steps. After each pedicle injury, three-dimensional flexibility in the form of range of motion and neutral zone of the construct was determined and compared with the intact values. RESULTS: Resection of the pedicles had little effect on the multidirectional flexion-extension stability provided by the instrumentation. There were significant increases of axial rotation in the middle thoracic spine when the lateral wall was resected (range of motion, 8.2 degrees vs. 3.6 degrees; neutral zone, 4.2 degrees vs. 1.7 degrees), whereas in the lower thoracic spine, significant increases occurred only when all the pedicles were resected (range of motion, 3.8 degrees vs. 1.4 degrees; neutral zone, 1.1 degrees vs. 0.4 degree). Lateral resection of the pedicle resulted in significant increases of range of motion and neutral zone for lateral bending in both the middle thoracic spine (range of motion, 19.0 degrees vs. 10.0 degrees; neutral zone, 2.4 degrees vs. 1.1 degrees) and the lower thoracic spine (range of motion, 4.3 degrees vs. 2.5 degrees; neutral zone, 0.9 degree vs. 0.3 degree). CONCLUSIONS: Resection of the pedicles results in a significant decrease in axial rotation and lateral bending stability provided by the instrumentation. This effect was higher in the middle than in the lower thoracic spine and may be relevant to pedicle fractures produced by pedicle screws used in these regions.

Adolescent↗

PubMed1997

Transforaminal and posterior decompressions of the lumbar spine. A comparative study of stability and intervertebral foramen area.

STUDY DESIGN: Ten fresh, cadaveric, two-vertebrae, functional spinal units were used to study the pathoanatomy, intervertebral foraminal area, and flexibility changes after posterior and transforaminal decompression. OBJECTIVES: To determine the feasibility of an endoscopic transforaminal approach as an alternative to conventional approaches, to establish the adequacy of transforaminal decompression without destabilizing the spine, and to study the structural changes in the spine after decompressions. SUMMARY OF THE BACKGROUND DATA: Posterior decompression entails major dissection and excision of bone and ligaments to access the spinal canal. Posterior decompression may be complicated by acute or chronic spinal instability, and the adequacy of lateral decompression is highly subjective. METHODS: The functional spinal units were mounted in quick-setting epoxy blocks. Pre- and postoperative computed tomography scans were taken to study changes in the foraminal area. Pre- and postoperative flexibility and anatomic studies were performed to compare the results. RESULTS: A 45.5% increase in the intervertebral foraminal area was possible, there was no flexibility change, and minimal anatomic damage to the spine was noted after transforaminal decompression. A 34.2% increase in the intervertebral foraminal area and a significant increase in extension and axial rotation flexibility were noted after the posterior decompression. CONCLUSION: Transforaminal decompression produced a significantly larger increase in the intervertebral foraminal area than posterior decompression, without increasing the range of motion or neutral zone in any direction. Because there was no violation of the anatomic integrity of the spine in the transforaminal approach, the risk of surgically induced instability was minimized. Endoscopic transforaminal decompression is a feasible alternative to current approaches.

Adult↗

PubMed1997

Dynamic elongation of the vertebral artery during an in vitro whiplash simulation.

Clinical signs of whiplash are presently not well understood. Vertebral artery (VA) stretch during trauma is a possible pathomechanism that could explain some aspects of the whiplash symptom complex. This study quantified the VA elongation during whiplash simulation using an in vitro model. Seven fresh human cadaveric specimens (occiput to C7 or T1) were carefully dissected, preserving the osteoligamentous structures. The right VA was replaced with a thin nylon-coated flexible cable. This cable was fixed at one end to the occipital bone and at the other end to a specially designed VA transducer. Physiological motion of the occiput and physiological elongation of the VA were measured with a standard flexibility test. Next the specimen was mounted on a specially designed sled and subjected to 2.5, 4.5, 6.5, and 8.5 g (1 g = 9.81 m/s2) horizontal accelerations. Elongation of the VA was continuously recorded from the start of the trauma. The average (standard deviation) physiological VA elongation was 5.8 (1.6) mm in left lateral bending and 4.7 (1.8) mm in left axial rotation. Flexion and extension did not result in any appreciable elongation of the VA. The maximum VA elongation during the whiplash trauma significantly correlated with the horizontal acceleration of the sled (R2 = 0.7, P < 0.05). The VA exceeded its physiological range by 1.0 (2.1), 3.1 (2.6), 8.9 (1.6), and 9.0 (5.9) mm in the 2.5-, 4.5-, 6.5-, and 8.5-g trauma classes respectively.

Biomechanical Phenomena↗

PubMed1997

Complexity of the thoracic spine pedicle anatomy.

Transpedicular screw fixation provides rigid stabilization of the thoracolumbar spine. For accurate insertion of screws into the pedicles and to avoid pedicle cortex perforations, more precise knowledge of the anatomy of the pedicles is necessary. This study was designed to visualize graphically the surface anatomy and internal architecture of the pedicles of the thoracic spine. Fifteen vertebrae distributed equally among the upper, middle, and lower thoracic regions were used. For the purpose of mapping surface anatomy, each pedicle was cleaned, spray-painted white, and marked with more than 100 fine points. Using an optoelectronic digitizer, three-dimensional coordinates of the marked points and three additional points, representing a coordinate system, were digitized. A solid modeling computer program was used to create three-dimensional surface images of the pedicle. To obtain cross-sectional information, each pedicle was sectioned with a thin diamond-blade saw to obtain four slices, 1 mm in thickness and 0.5 mm apart. The pedicle slices were X-rayed and projected onto a digitizer. The internal and external contours were digitized and converted into graphs by a computer. The pedicles exhibited significant variability in their shape and orientation, not only from region to region within the thoracic spine, but also within the same region and even within the same pedicle. These variations are extremely significant in light of current techniques utilized in transpedicular screw fixation in the thoracic spine. Information documenting the three-dimensional complexity of pedicle anatomy should be valuable for surgeons and investigators interested in spinal instrumentation.

Adult↗

PubMed1997

Significant roentgenographic parameters for evaluating the flexibility of acute thoracolumbar burst fractures. An in vitro study.

Plain lateral radiographs in a neutral position were studied in ten acute thoracolumbar burst fractures produced by high speed impact on three vertebrae human cadaveric spine segments. Six linear geometric parameters were measured on each film. The ratio of each value in the neutral injured to the intact condition was correlated linearly with the motion parameters obtained from post-traumatic three-dimensional flexibility data (neutral zone NZ; range of motion ROM). Anterior unit height (vertebra+adjacent discs) had the highest correlation with the neutral zone and flexibility in all directions, especially flexion-extension (NZ, R2 = 0.93; flexion ROM, R2 = 0.86; extension ROM, R2 = 0.79) lateral bending (NZ, R2 = 0.83; ROM, R2 = 0.90) and right axial rotation (NZ, R2 = 0.53; ROM, R2 = 0.86). The deformation ratio (average height to depth) correlated most with the neutral zone in left axial rotation (R2 = 0.91) and right lateral bending (R2 = 0.92). Due to the high correlations obtained, these parameters should be evaluated in clinical situations to assess their effectiveness in predicting the instability of burst fractures. Ultimately, prospective clinical studies are required to verify their clinical utility.

Acceleration↗

PubMed1997

Spinal ligament transducer based on a hall effect sensor.

A spinal ligament transducer (SLT) was developed to measure in situ spinal ligament elongation during the simulation of whiplash trauma with a cadaveric spine specimen. The SLT was designed to be affixed to two K-wires drilled into the bone at the approximate points of ligament origin and insertion. The transducer is low cost and is capable of measuring the linear distance between the K-wires in the range 4-12 mm with the root mean square (RMS) accuracy of 0.025 mm.

Bone Wires↗