Hierarchical process using Brier Score Metrics for lower leg injury risk curves in vertical impact.

INTRODUCTION: Parametric survival models are used to develop injury risk curves (IRCs) from impact tests using postmortem human surrogates (PMHS). Through the consideration of different output variables, input parameters and censoring, different IRCs could be created. The purpose of this study was to demonstrate the feasibility of the Brier Score Metric (BSM) to determine the optimal IRCs and derive them from lower leg impact tests. METHODS: Two series of tests of axial impacts to PMHS foot-ankle complex were used in the study. The first series used the metrics of force, time and rate, and covariates of age, posture, stature, device and presence of a boot. Also demonstrated were different censoring schemes: right and exact/uncensored (RC-UC) or right and uncensored/left (RC-UC-LC). The second series involved only one metric, force, and covariates age, sex and weight. It contained interval censored (IC) data demonstrating different censoring schemes: RC-IC-UC, RC-IC-LC and RC-IC-UC-LC. RESULTS: For each test set combination, optimal IRCs were chosen based on metric-covariate combination that had the lowest BSM value. These optimal IRCs are shown along with 95% CIs and other measures of interval quality. Forces were greater for UC than LC data sets, at the same risk levels (10% used in North Atlantic Treaty Organisation (NATO)). All data and IRCs are presented. CONCLUSIONS: This study demonstrates a novel approach to examining which metrics and covariates create the best parametric survival analysis-based IRCs to describe human tolerance, the first step in describing lower leg injury criteria under axial loading to the plantar surface of the foot.

Lightweight low-profile nine-accelerometer package to obtain head angular accelerations in short-duration impacts.

Despite recognizing the importance of angular acceleration in brain injury, computations using data from experimental studies with biological models such as human cadavers have met with varying degrees of success. In this study, a lightweight and a low-profile version of the nine-accelerometer system was developed for applications in head injury evaluations and impact biomechanics tests. The triangular pyramidal nine-accelerometer package (PNAP) is precision-machined out of standard aluminum, is lightweight (65 g), and has a low profile (82 mm base width, 35 mm vertex height). The PNAP assures accurate orthogonal characteristics because all nine accelerometers are pre-aligned and attached before mounting on a human cadaver preparation. The feasibility of using the PNAP in human cadaver head studies is demonstrated by subjecting a specimen to an impact velocity of 8.1 m/s and the resultant angular acceleration peaked at 17 krad/s2. The accuracy and the high fidelity of the PNAP device at high and low angular acceleration levels were demonstrated by comparing the PNAP-derived angular acceleration data with separate tests using the internal nine-accelerometer head of the Hybrid III anthropomorphic test device. Mounting of the PNAP on a biological specimen such as a human cadaver head should yield very accurate angular acceleration data.

Sensitivity of head and cervical spine injury measures to impact factors relevant to rollover crashes.

OBJECTIVE: Serious head and cervical spine injuries have been shown to occur mostly independent of one another in pure rollover crashes. In an attempt to define a dynamic rollover crash test protocol that can replicate serious injuries to the head and cervical spine, it is important to understand the conditions that are likely to produce serious injuries to these 2 body regions. The objective of this research is to analyze the effect that impact factors relevant to a rollover crash have on the injury metrics of the head and cervical spine, with a specific interest in the differentiation between independent injuries and those that are predicted to occur concomitantly. METHODS: A series of head impacts was simulated using a detailed finite element model of the human body, the Total HUman Model for Safety (THUMS), in which the impactor velocity, displacement, and direction were varied. The performance of the model was assessed against available experimental tests performed under comparable conditions. Indirect, kinematic-based, and direct, tissue-level, injury metrics were used to assess the likelihood of serious injuries to the head and cervical spine. RESULTS: The performance of the THUMS head and spine in reconstructed experimental impacts compared well to reported values. All impact factors were significantly associated with injury measures for both the head and cervical spine. Increases in impact velocity and displacement resulted in increases in nearly all injury measures, whereas impactor orientation had opposite effects on brain and cervical spine injury metrics. The greatest cervical spine injury measures were recorded in an impact with a 15° anterior orientation. The greatest brain injury measures occurred when the impactor was at its maximum (45°) angle. CONCLUSIONS: The overall kinetic and kinematic response of the THUMS head and cervical spine in reconstructed experiment conditions compare well with reported values, although the occurrence of fractures was overpredicted. The trends in predicted head and cervical spine injury measures were analyzed for 90 simulated impact conditions. Impactor orientation was the only factor that could potentially explain the isolated nature of serious head and spine injuries under rollover crash conditions. The opposing trends of injury measures for the brain and cervical spine indicate that it is unlikely to reproduce the injuries simultaneously in a dynamic rollover test.

A point-wise normalization method for development of biofidelity response corridors.

An updated technique to develop biofidelity response corridors (BRCs) is presented. BRCs provide a representative range of time-dependent responses from multiple experimental tests of a parameter from multiple biological surrogates (often cadaveric). The study describes an approach for BRC development based on previous research, but that includes two key modifications for application to impact and accelerative loading. First, signal alignment conducted prior to calculation of the BRC considers only the loading portion of the signal, as opposed to the full time history. Second, a point-wise normalization (PWN) technique is introduced to calculate correlation coefficients between signals. The PWN equally weighs all time points within the loading portion of the signals and as such, bypasses aspects of the response that are not controlled by the experimentalist such as internal dynamics of the specimen, and interaction with surrounding structures. An application of the method is presented using previously-published thoracic loading data from 8 lateral sled PMHS tests conducted at 8.9m/s. Using this method, the mean signals showed a peak lateral load of 8.48kN and peak chest acceleration of 86.0g which were similar to previously-published research (8.93kN and 100.0g respectively). The peaks occurred at similar times in the current and previous studies, but were delayed an average of 2.1ms in the updated method. The mean time shifts calculated with the method ranged from 7.5% to 9.5% of the event. The method may be of use in traditional injury biomechanics studies and emerging work on non-horizontal accelerative loading.

Biomechanics of skull fracture.

This study was conducted to determine the biomechanics of the human head under quasistatic and dynamic loads. Twelve unembalmed intact human cadaver heads were tested to failure using an electrohydraulic testing device. Quasistatic loading was done at a rate of 2.5 mm/s. Impact loading tests were conducted at a rate of 7.1 to 8.0 m/s. Vertex, parietal, temporal, frontal, and occipital regions were selected as the loading sites. Pathological alterations were determined by pretest and posttest radiography, close-up computed tomography (CT) images, macroscopic evaluation, and defleshing techniques. Biomechanical force-deflection response, stiffness, and energy-absorbing characteristics were obtained. Results indicated the skull to have nonlinear structural response. The failure loads, deflections, stiffness, and energies ranged from 4.5 to 14.1 kN, 3.4 to 16.6 mm, 467 to 5867 N/mm, and 14.1 to 68.5 J, respectively. The overall mean values of these parameters for quasistatic and dynamic loads were 6.4 kN (+/- 1.1), 12.0 mm (+/- 1.6), 812 N/mm (+/- 139), 33.5 J (+/- 8.5), and 11.9 kN (+/-0.9), 5.8 mm (+/- 1.0), 4023 N/mm (+/- 541), 28.0 J (+/- 5.1), respectively. It should be emphasized that these values do not account for the individual variations in the anatomical locations on the cranium of the specimens. While the X-rays and CT scans identified the fracture, the precise direction and location of the impact on the skull were not apparent in these images. Fracture widths were consistently wider at sites remote from the loading region. Consequently, based on retrospective images, it may not be appropriate to extrapolate the anatomical region that sustained the impact forces. The quantified biomechanical response parameters will assist in the development and validation of finite element models of head injury.

Contribution of disc degeneration to osteophyte formation in the cervical spine: a biomechanical investigation.

Cervical spine disorders such as spondylotic radiculopathy and myelopathy are often related to osteophyte formation. Bone remodeling experimental-analytical studies have correlated biomechanical responses such as stress and strain energy density to the formation of bony outgrowth. Using these responses of the spinal components, the present study was conducted to investigate the basis for the occurrence of disc-related pathological conditions. An anatomically accurate and validated intact finite element model of the C4-C5-C6 cervical spine was used to simulate progressive disc degeneration at the C5-C6 level. Slight degeneration included an alteration of material properties of the nucleus pulposus representing the dehydration process. Moderate degeneration included an alteration of fiber content and material properties of the anulus fibrosus representing the disintegrated nature of the anulus in addition to dehydrated nucleus. Severe degeneration included decrease in the intervertebral disc height with dehydrated nucleus and disintegrated anulus. The intact and three degenerated models were exercised under compression, and the overall force-displacement response, local segmental stiffness, anulus fiber strain, disc bulge, anulus stress, load shared by the disc and facet joints, pressure in the disc, facet and uncovertebral joints, and strain energy density and stress in the vertebral cortex were determined. The overall stiffness (C4-C6) increased with the severity of degeneration. The segmental stiffness at the degenerated level (C5-C6) increased with the severity of degeneration. Intervertebral disc bulge and anulus stress and strain decreased at the degenerated level. The strain energy density and stress in vertebral cortex increased adjacent to the degenerated disc. Specifically, the anterior region of the cortex responded with a higher increase in these responses. The increased strain energy density and stress in the vertebral cortex over time may induce the remodeling process according to Wolff's law, leading to the formation of osteophytes.

Biomechanics of penetrating trauma.

It is well known that injuries and deaths due to penetrating projectiles have become a national and an international epidemic in Western society. The application of biomedical engineering to solve day-to-day problems has produced considerable advances in safety and mitigation/prevention of trauma. The study of penetrating trauma has been largely in the military domain where war-time specific applications were advanced with the use of high-velocity weapons. With the velocity and weapon caliber in the civilian population at half or less compared with the military counterpart, wound ballistics is a largely different problem in today's trauma centers. The principal goal of the study of penetrating injuries in the civilian population is secondary prevention and optimized emergency care after occurrence. A thorough understanding of the dynamic biomechanics of penetrating injuries quantifies missile type, caliber, and velocity to hard and soft tissue damage. Such information leads to a comprehensive assessment of the acute and long-term treatment of patients with penetrating injuries. A review of the relevant military research applied to the civilian domain and presentation of new technology in the biomechanical study of these injuries offer foundation to this field. Relevant issues addressed in this review article include introduction of the military literature, the need for secondary prevention, environmental factors including projectile velocity and design, experimental studies with biological tissues and physical models, and mathematical simulations and analyses. Areas of advancement are identified that enables the pursuit of biomechanics research in order to arrive at better secondary prevention strategies.

Biomechanics of abdominal injuries.

Although considerable efforts have been advanced to investigate the biomechanical aspects of abdominal injuries, reviews have been very limited. The purpose of this article is to present a comprehensive review of the topic. Traumatic abdominal injuries occur due to penetrating or blunt loading. However, the present review is focused on blunt trauma. Because of the complexity of the abdomen, biomechanically relevant anatomical characteristics of the various abdominal organs are presented. The proposed mechanism of injury for these organs and methods for abdominal injury quantification are described. This is followed by a detailed analysis of the biomechanical literature with particular emphasis on experiments aimed to duplicate real world injuries and attempt to quantify trauma in terms of parameters such as force, deflection, viscous criteria, pressure criteria, and correlation of these variables with the severity of abdominal injury. Experimental studies include tests using primates, pigs, rats, beagles, and human cadavers. The effects of velocity, compression, padding, and impactor characteristics on tolerance; effects of pressurization and postmortem characteristics on abdominal injury; deduction of abdominal response corridors; and force-deflection responses (of the different abdominal regions and organs) are discussed. Output of initial research is presented on the development of a device to record the biomechanical parameters in an anthropomorphic test dummy during impact. Based on these studies and the current need for abdominal protection, recommendations are given for further research.

Mathematical and finite element analysis of spine injuries.

A critical review of the anatomical, physiological, epidemiological, and biomechanical aspects of spine injuries are presented. These are discussed in light of the mechanical load that produces the trauma. Emphasis is given to the mathematical and finite element modeling aspects of spinal injury that focuses on the tolerance criteria. In the area of spinal mechanics, static and dynamic models are reviewed. Included are the continuum and discrete parameter models of the intact spine and finite element models of its components. A section on the role of constituent law in the assessment of trauma to the spine is given. Finally, a discussion follows on the future research in this domain.

Biomechanical evaluation of Caspar cervical screws: comparative stability under cyclical loading.

Anterior cervical instrumentation is used as an adjunct to bone fusion; however, definitive biomechanical data to support some applications and techniques are lacking. In the absence of supportive experimental data, posterior cortical penetration has been recommended with the Caspar system. Previously, we compared the axial pull-out strength of Caspar screws with and without posterior cortical penetration. This study compares the stability of unicortical versus bicortical screw penetration groups under cyclical loading simulating physiological flexion-extension. Caspar screws were placed in human cadaveric vertebrae with or without posterior cortical purchase. Each screw was separately tested, simulating flexion-extension to 200 cycles. Deformation time data allowed a direct comparison of screw "wobble" with and without posterior cortical purchase. The mean deformation differences between subcortical and bicortical groups were statistically significant and increased over time within both groups. Enhanced stability was noted with bicortical purchase throughout most of the examined range, becoming more pronounced over longer periods of cyclical loading. Significant (P < 0.05) increases in deformation over time were noted for both groups, suggesting potentially significant deterioration at the screw-bone interface, despite bicortical purchase. Such deterioration with repeated flexion-extension loading may be of concern in the use of Caspar plates in the presence of multicolumn instability.

Biomechanics of lumbar pedicle screw/plate fixation in trauma.

This investigation was conducted to determine alterations in the biomechanical strength and stiffness characteristics of the lumbar spine fixated with Steffee instrumentation. Comparative studies of these parameters were conducted using seven lumbar columns from fresh human cadavers. Three runs were conducted on each T12-L5 column: control, injured, and fixated. The specimens were loaded under the compression-flexion mode until failure (control run) and then reloaded (injury run) to the failure deformation determined in the control run. Screw/plates were then inserted one level proximal and distal to injury, and the specimens were reloaded (fixation run). Radiographs were taken before and after each trial. Data on deformation and force histories were gathered. The load-deflection response of the injured and fixated specimens were bimodal with two representative stiffnesses. Control failure loads and stiffnesses were higher than those for the injured (P less than 0.001) or fixated (P less than 0.01) spine. Initial stiffness was significantly higher for the fixated than for injured columns (P less than 0.001), but the final stiffnesses were similar. The increase in the initial stiffness in the fixated specimen compared to the injured specimen indicates the strength added to the posterior region of the spine. The relatively smaller alteration in the final stiffness between the fixated and the injured columns, corresponding to the load shared by the anterior column, may suggest that, above a critical strain level, the anterior column absorbs a higher portion of the external load and posterior fixation may be inadequate as sole treatment in trauma.

Pull-out strength of Caspar cervical screws.

Anterior cervical instrumentation as an adjunct to bone fusion has an important role in cervical spine surgery. Posterior vertebral body cortex purchase is strongly recommended in the use of the Caspar system, although few biomechanical data exist to validate this requirement. In this study, Caspar screws were placed in 43 human cadaveric cervical vertebral bodies, either putting them into the posterior vertebral cortex as identified radiographically or penetrating it by 2 mm as recommended in the literature. Pull-out tests were conducted with tension applied to a connected plate at 0.25 mm/s, and force-deformation data were obtained. Failure typically occurred with clean pull-out; in most instances, cancellous bone remained attached to screw threads. Mean load without posterior cortical purchase was 375 +/- 53 N; with penetration it was 411 +/- 70 N. These differences were nonsignificant. Average deformation to failure was 1.41 +/- 0.10 mm in the group without posterior cortical penetration. In the posterior penetration group, mean deformation was 1.56 +/- 0.16 mm. Again, differences were not significant. Posterior cortical penetration does not improve the pull-out strength of Caspar screws in an isolated vertebral body model, but other biomechanical studies need to be done before insertion methods are altered.

Biomechanical effects of laminectomy on thoracic spine stability.

Thoracic columns (T1-L1 levels) from 15 fresh human cadavers were used to quantify alterations in the biomechanical response after laminectomy. Eight specimens were tested intact (Group I); the remaining seven preparations were tested after two-level laminectomy (Group II) at the midheight of the column. All specimens were fixed at the proximal and distal ends and loaded until failure. Force and deformation were collected by use of a data acquisition system. Failure of the Group I specimens included compressive fractures with or without posterior element distractions, generally at the midheight of the column. Group II preparations failed at the superior aspect of laminectomy or at a level above laminectomy, suggesting an increased load sharing. Biomechanical responses of the Group II preparations were significantly different (P < 0.05) from those of the Group I specimens at deformations from the physiological to the failure range. In addition, failure forces for Group II preparations were significantly lower (P < 0.001) than for Group I specimens. The stiffness and energy-absorbing capacities of the laminectomized specimens were also significantly different (P < 0.05) from those of the intact columns. In contrast, the deflections at failure for the two groups were not statistically different, suggesting that the human thoracic spine is deformation sensitive. Our data demonstrate that a two-level laminectomy decreases the strength and stability of the thoracic spine throughout the loading range. Although this is not a practical concern with an otherwise intact vertebral column, laminectomy, when other abnormalities such as vertebral fracture, tumor, or infection exist, may require stabilization by fusion and instrumentation.

Intravertebral pressure changes caused by spinal microtrauma.

Clinical studies indicate variations in intravertebral pressures in patients with and without low back pain. It is known that not all patients with back pain have abnormal lumbar radiographs and, furthermore, microfractures of the endplate may be one of the causes in the origin of low back pain. Consequently, this study was conducted to determine the interrelationship between microtrauma and intraosseous pressures in the lumbar spine. Miniature pressure transducers were inserted into the vertebral bodies and spinous processes of human cadaver spinal units. Radio-opaque medium was injected into the nucleus to fluoroscopically monitor the movement of the fluid from the disc as the preparation was loaded up to the initiation of microtrauma (before reaching the ultimate load-carrying capacity). The onset of injury was evidenced by the microfracture of one of the two endplates and impregnation of the contrast medium into the spongiosa. After relaxation, another cycle of loading was applied by limiting the deflections to the maximum compression sustained under the intact configuration. The load, stiffness, and energy-absorbing capacities were lower (P < 0.05) for the injured specimen compared with the intact configuration. The intraosseous pressures were higher (P < 0.05) in the vertebral body and the spinous process of the vertebra where the endplate exhibited microtrauma in the injured cycle compared with the intact cycle. In contrast, the intraosseous pressures in the vertebral body and the spinous process at the level where the endplate remained intact were not significantly different between the two cycles of loading.(ABSTRACT TRUNCATED AT 250 WORDS)

An experimental technique to induce and quantify complex cyclic forces to the lumbar spine.

The human spine is a complex, heterogeneous nonlinear and viscoelastic structure. In addition, in vivo loading is not uniaxial. Although many studies on the mechanical behavior of the spine under "pure" forces and single cycle load applications exist, little research is conducted with complex cyclic loads. In this study, we developed a technique to induce and quantify controlled complex physiological loads to the lumbar spinal column under cyclic (chronic) conditions. The methods described include specimen preparation and mounting to induce controlled complex loading (cyclic compression-flexion vector was chosen as an example), instrumentation, and biomechanical data to achieve the objectives. The results indicated that the specimen sustained the external load in a combined compression-flexion mechanism without considerable off-axis forces (lateral shears) and moments (lateral bending and torsion). By mounting the anchoring bolt in appropriate places (such as an anterolateral placement to induce compression-flexion-lateral bending), this technique can be used to apply and continuously quantify complex physiological acute or cyclic loads to describe the biomechanics of the spine. This procedure of inducing complex loads eliminates the difficulty in applying the principles of superposition, using the response from individual "pure" forces to account for the nonlinearity and viscoelasticity of the human lumbar spinal column.

Microtrauma in the lumbar spine: a cause of low back pain.

Excessive mechanical stress on the intervertebral disc may be one of the causes of low back pain. Most studies testing this thesis, however, have been based on quantification of the mechanical response of functional units at failure. Typically, radiography is used to demonstrate trauma to the vertebral body at the failure load. The description of failure and radiographic demonstration of damage are meaningful in specifying the tolerance limits of the structure. It is important, however, to understand the sequence underlying the initiation of injury, which may occur at subfailure physiological loads. In this study, we identified the initiation of injury to the lumbar spine by subjecting functional units to axial compressive loads using the mechanical response as a basis. Because conventional radiography failed to detect trauma at this level, advanced sectioning techniques were used. The initiation of injury (microtrauma) is defined as the point on the load-deflection curve where the structure exhibits a decreasing level of resistance for the first time before reaching its ultimate load-carrying capacity. The load deflection curve on this basis was classified into the ambient or preload phase, physiological loading phase, traumatic phase, and post-traumatic phase. Structures loaded to the end of the physiological loading phase did not exhibit any yielding or microtrauma. Injury in the form of microfractures of the endplate not detected on radiography, however, was observed under cryomicrotomy for structures loaded into the traumatic loading phase.

Biomechanics of sequential posterior lumbar surgical alterations.

Compromise of the functional integrity of the posterior lumbar ligaments and facet joints is a common occurrence after repeated lumbar operative procedures. To evaluate the biomechanical effects of sequential surgical alterations, this investigation analyzed bilateral facetectomies (medial, total, and total with posterior ligament section) in three segments of human cadaveric lumbar spines under increasing compression-flexion. These iatrogenic alterations, designed to replicate common methods of surgical exposure, were created at the lower intervertebral joint (L4-5) while the upper joint (L3-4) remained intact. Overall strength characteristics in the physiological range of 400 N and 600 N demonstrated significant differences (p less than 0.05) in applied compressions for all preparations compared to the intact specimen. Comparison of sequential surgeries, however, did not demonstrate this tendency. Significant changes in the movement of the spinous processes at the upper (unaltered) level occurred only after posterior ligament section, whereas the lower (altered) level showed markedly increasing distraction of both the facets and the spinous processes with sequential operations. Sectioning of the supraspinous/interspinous ligament and associated fascial attachments resulted in a marked transfer of motion to the altered level. This was manifested by the increased anterior displacement of the centrode at the lower level associated with probable posterior migration of the centrode at the upper level. These data suggest that the effects of progressive surgical alterations of the lumbar facet joints are controllable in a preparation undergoing acute compression-flexion loads until the supraspinous/interspinous ligaments, with associated residual tendinous, midline muscle, and fascial attachments, are violated.

Finite element modeling approaches of human cervical spine facet joint capsule.

The human cervical spine facet joint capsule was modeled using four nonlinear finite element approaches: slideline, contact surface, hyperelastic, and fluid models. Slideline elements and contact surface definitions were used in the first two models to simulate the synovial fluid between the articulating cartilages. Incompressible solid elements approximated the synovial fluid in the hyperelastic model. Hydrostatic fluid elements idealized the synovial fluid in the fluid model. The finite element analysis incorporated geometric, material and contact nonlinearities. All models were subjected to compression, flexion, extension, and lateral bending. The fluid model idealization better approximates the actual facet joint anatomy and its behavior than the gap assumption in the slideline and contact surface models, and the solid element simulation in the hyperelastic model.

Experimental production of extra- and intra-articular fractures of the os calcis.

Although studies have been conducted in the past to duplicate traumatic fractures of the os calcis, biomechanical force data as a function of extra- and intra-articular fractures are not available. Consequently, in this study, a dynamic single impact model was used to provide such information. Using intact human cadaver lower extremities, impact loading was applied to the plantar surface of the foot using a mini-sled pendulum equipment. The proximal tibia was fixed in polymethylmethacrylate. Following impact, pathology to the os calcis was classified into intact (no injury; 14 cases), and extra-articular (6 cases) and intra-articular (6 cases) fractures. Peak dynamic forces were used to conduct statistical analysis. Mean forces for the intact and (both) fracture groups were 4144 N (standard error, SE: 689) and 7802 N (SE: 597). Mean forces for the extra- and intra-articular fracture groups were 7445 N (SE: 711) and 8159 N (SE: 1006). The peak force influenced injury outcome (ANOVA, p<0.005). Differences in the forces were found between intact and injured specimens (p<0.01); intact specimens and specimens with extra-articular pathology (p<0.001); intact specimens and specimens with intra-articular pathology (p<0.005). The present experimental protocol, which successfully reproduced clinically relevant os calcis pathology, can be extended to accommodate other variables such as the simulation of Achilles tendon force, the inclusion of other angles of force application, and the application of the impact force to limited regions of the plantar force of the foot in order to study other injury mechanisms.

Biomechanical properties of human lumbar spine ligaments.

Biomechanical properties of the six major lumbar spine ligaments were determined from 38 fresh human cadaveric subjects for direct incorporation into mathematical and finite element models. Anterior and posterior longitudinal ligaments, joint capsules, ligamentum flavum, interspinous, and supraspinous ligaments were evaluated. Using the results from in situ isolation tests, individual force-deflection responses from 132 samples were transformed with a normalization procedure into mean force-deflection properties to describe the nonlinear characteristics. Ligament responses based on the mechanical characteristics as well as anatomical considerations, were grouped into T12-L2, L2-L4, and L4-S1 levels maintaining individuality and nonlinearity. A total of 18 data curves are presented. Geometrical measurements of original length and cross-sectional area for these six major ligaments were determined using cryomicrotomy techniques. Derived parameters including failure stress and strain were computed using the strength and geometry information. These properties for the lumbar spinal ligaments which are based on identical definitions used in mechanical testing and geometrical assay will permit more realistic and consistent inputs for analytical models.