A Dynamic Ankle Orthosis Reduces Tibial Compressive Force and Increases Ankle Motion Compared With a Walking Boot.

PURPOSE: Tibial bone stress injuries are a common overuse injury among runners and military cadets. Current treatment involves wearing an orthopedic walking boot for 3 to 12 wk, which limits ankle motion and leads to lower limb muscle atrophy. A dynamic ankle orthosis (DAO) was designed to provide a distractive force that offloads in-shoe vertical force and retains sagittal ankle motion during walking. It remains unclear how tibial compressive force is altered by the DAO. This study compared tibial compressive force and ankle motion during walking between the DAO and an orthopedic walking boot. METHODS: Twenty young adults walked on an instrumented treadmill at 1.0 m·s -1 in two brace conditions: DAO and walking boot. Three-dimensional kinematic, ground reaction forces, and in-shoe vertical force data were collected to calculate peak tibial compressive force. Paired t -tests and Cohen's d effect sizes were used to assess mean differences between conditions. RESULTS: Peak tibial compressive force ( P = 0.023; d = 0.5) and Achilles tendon force ( P = 0.017; d = 0.5) were moderately lower in the DAO compared with the walking boot. Sagittal ankle excursion was 54.9% greater in the DAO compared with the walking boot ( P = 0.05; d = 3.1). CONCLUSIONS: The findings from this study indicated that the DAO moderately reduced tibial compressive force and Achilles tendon force and allowed more sagittal ankle excursion during treadmill walking compared with an orthopedic walking boot.

Impact of a dynamic ankle orthosis on acute pain and function in patients with mechanical foot and ankle pain.

BACKGROUND: Over two million Americans visit the doctor each year for foot and ankle pain stemming from a degenerative condition or injury. Ankle-foot orthoses can effectively manage symptoms, but traditional designs have limitations. This study investigates the acute impact of a novel "dynamic ankle-foot orthosis" ("orthosis") in populations with mechanical pain (from motion or weight-bearing). METHODS: With and without the brace, participants (n = 25) performed standing, over-ground level walking, treadmill level walking, stair ascent, stair descent, single leg hold, squat, and sitting. Instrumented insoles captured in-shoe vertical forces and a visual analog scale was used to assess pain levels during each activity. Subsequently, the self-perceived impact of the orthosis on the patient's symptoms and function was ranked on a scale from -10 (most worsened) to +10 (most improved). FINDINGS: Peak in-shoe force was reduced during level and stair walking (P < 0.05). Average perceived pain was 1.2 to 1.6 points lower in the orthosis than the unbraced control for the active tasks. The majority of participants reported that the brace improved their symptoms (n = 19), while a smaller group reported that the brace did not affect their symptoms (n = 5), although average function scores were improved for both groups (+2.4 to +4.5). The group of individuals with improved symptoms included cases of osteoarthritis, tendon dysfunction, chronic pain, sprains, and nerve disorders. INTERPRETATION: The orthosis effectively improved pain symptoms and improved the ability of impaired individuals to complete functional activities of daily living such as level walking and stair walking.

Biomechanical Comparison of a New Dynamic Ankle Orthosis to a Standard Ankle-Foot Orthosis During Walking.

Patients who sustain irreversible cartilage damage or joint instability from ankle injuries are likely to develop ankle osteoarthritis (OA). A dynamic ankle orthosis (DAO) was recently designed with the intent to offload the foot and ankle using a distractive force, allowing more natural sagittal and frontal plane ankle motion during gait. To evaluate its efficacy, this study compared ankle joint kinematics and plantar pressures among the DAO, standard double upright ankle-foot orthosis (DUAFO), and a nonorthosis control (CON) condition in healthy adults during walking. Ten healthy subjects (26 ± 3.8 yr; 69.6 ± 12.7 kg; and 1.69 ± 0.07 m) walked on a treadmill at 1.4 m/s in three orthosis conditions: CON, DAO, and DUAFO. Ankle kinematics were assessed using a three-dimensional (3D) motion capture system and in-shoe plantar pressures were measured for seven areas of the foot. DAO reduced hallux peak plantar pressures (PPs) compared to CON and DUAFO. PPs under toes 2-5 were smaller in DAO than DUAFO, but greater in DUAFO compared to CON. Early stance peak plantarflexion (PF) angular velocity was smaller in DAO compared to CON and DUAFO. Eversion (EV) ROM was much smaller in DUAFO compared to CON and DAO. Early stance peak eversion angular velocity was smaller in DAO and much smaller in DUAFO compared to CON. This study demonstrates the capacity of the DAO to provide offloading during ambulation without greatly affecting kinematic parameters including frontal plane ankle motion compared to CON. Future work will assess the effectiveness of the DAO in a clinical osteoarthritic population.

Mechanical Testing of a Novel Fastening Device to Improve Scoliosis Bracing Biomechanics for Treating Adolescent Idiopathic Scoliosis.

Velcro fastening straps are commonly used to secure a scoliosis brace around the upper body and apply corrective forces to the spine. However, strap loosening and tension loss have been reported that reduce spinal correction and treatment efficacy. A novel fastening device, or controlled tension unit (CTU), was designed to overcome these limitations. A scoliosis analog model (SAM) was used to biomechanically compare the CTU fasteners and posterior Velcro straps on a conventional brace (CB) as well as on a modified brace (MB) that included a dynamic cantilever apical pad section. Brace configurations tested were (1) CB with posterior Velcro straps, (2) CB with posterior CTU fasteners, (3) MB with posterior Velcro straps, and (4) MB with posterior CTU fasteners. MB configurations were tested with 0 N, 35.6 N, and 71.2 N CTU fasteners applied across the apical pad flap. Three-dimensional forces and moments were measured at both ends of the SAM. The CTU fasteners provided the same corrective spinal loads as Velcro straps when tensioned to the same level on the CB configuration and can be used as an alternative fastening system. Dynamically loading the apical flap increased the distractive forces applied to the spine without affecting tension in the fastening straps.

A mechanical analog thoracolumbar spine model for the evaluation of scoliosis bracing technology.

INTRODUCTION: Thoracolumbar braces are used to treat Adolescent Idiopathic Scoliosis. The objective of this study was to design and validate a mechanical analog model of the spine to simulate a thoracolumbar, single-curve, scoliotic deformity in order to quantify brace structural properties and corrective force response on the spine. METHODS: The Scoliosis Analog Model used a linkage-based system to replicate 3D kinematics of spinal correction observed in the clinic. The Scoliosis Analog Model is used with a robotic testing platform and programmed to simulate Cobb angle and axial rotation correction while equipped with a brace. The 3D force and moment responses generated by the brace in reaction to the simulated deformity were measured by six-axis load cells. RESULTS: Validation of the model's force transmission showed less than 6% loss in the force analysis due to assembly friction. During simulation of 10° Cobb angle and 5° axial rotation correction, the brace applied 101 N upwards and 67 N inwards to the apical connector of the model. Brace stiffness properties were 0.5-0.6 N/° (anteroposterior), 0.5-2.3 N/° (mediolateral), 23.3-26.5 N/° (superoinferior), and 0.6 Nm/° (axial rotational). CONCLUSIONS: The Scoliosis Analog Model was developed to provide first time measures of the multidirectional forces applied to the spine by a thoracolumbar brace. This test assembly could be used as a future design and testing tool for scoliosis brace technology.

Development of a Robotic Assembly for Analyzing the Instantaneous Axis of Rotation of the Foot Ankle Complex.

Ankle instantaneous axis of rotation (IAR) measurements represent a more complete parameter for characterizing joint motion. However, few studies have implemented this measurement to study normal, injured, or pathological foot ankle biomechanics. A novel testing protocol was developed to simulate aspects of in vivo foot ankle mechanics during mid-stance gait in a human cadaveric specimen. A lower leg was mounted in a robotic testing platform with the tibia upright and foot flat on the baseplate. Axial tibia loads (ATLs) were controlled as a function of a vertical ground reaction force (vGRF) set at half body weight (356 N) and a 50% vGRF (178 N) Achilles tendon load. Two specimens were repetitively loaded over 10 degrees of dorsiflexion and 20 degrees of plantar flexion. Platform axes were controlled within 2 microns and 0.008 degrees resulting in ATL measurements within ±2 N of target conditions. Mean ATLs and IAR values were not significantly different between cycles of motion, but IAR values were significantly different between dorsiflexion and plantar flexion. A linear regression analysis showed no significant differences between slopes of plantar flexion paths. The customized robotic platform and advanced testing protocol produced repeatable and accurate measurements of the IAR, useful for assessing foot ankle biomechanics under different loading scenarios and foot conditions.

A novel distractive and mobility-enabling lumbar spinal orthosis.

PURPOSE: Lumbar spinal orthoses are often used as non-surgical treatment and serve to support the spine and alleviate low back pain. More recently, dynamic orthoses claiming to decompress the spine have been introduced. A previously developed prototype of dynamic mobility orthosis (DMO1) was designed that provided a distractive load across the lumbar spine but required higher sagittal bending moments and was unable to maintain spinal off-loading throughout extended ranges of movement. The objective was to design a new orthosis (DMO2) that reduced bending moment buildup and sustained spinal off-loading throughout daily living ranges of flexion and extension movement. METHODS: A mechanical analog upper torso model and programmable robotic testing platform were used to design features of DMO2: a mobility-enabling component and a distractive force component. Test conditions for DMO2 were 300 N of applied vertical torso load over a range of 25° flexion to 10° extension. Loads carried by the brace were determined throughout flexion and extension ranges. Applied moments to the upper torso model and transferred moments to the spine were measured. The difference in applied and transferred moments represented brace moment effects. RESULTS: The DMO2 prototype improved spinal off-loading capacity from 172 N to 290 N at end-range flexion and from 247 N to 293 N at end range extension compared to the original DMO1 prototype. End-range applied moments (flexion-DMO1: 32.4 Nm/DMO2: 21.7 Nm; extension-DMO1: 15.0 Nm/DMO2: 10.9 Nm) and brace moments (flexion-DMO1: 18.6 Nm/DMO2: 6.6 Nm; extension-DMO1: 15.0 Nm/DMO2: 4.4 Nm) were also reduced. CONCLUSIONS: A novel dynamic spinal orthosis was designed that maintained spinal off-loading throughout extended ranges of flexion and extension movement without buildup of adverse bending moments.

Biomechanical Comparison of Robotically Applied Pure Moment, Ideal Follower Load, and Novel Trunk Weight Loading Protocols on L4-L5 Cadaveric Segments during Flexion-Extension.

BACKGROUND: Extremely few in-vitro biomechanical studies have incorporated shear loads leaving a gap for investigation, especially when applied in combination with compression and bending under dynamic conditions. The objective of this study was to biomechanically compare sagittal plane application of two standard protocols, pure moment (PM) and follower load (FL), with a novel trunk weight (TW) loading protocol designed to induce shear in combination with compression and dynamic bending in a neutrally potted human cadaveric L4-L5 motion segment unit (MSU) model. A secondary objective and novelty of the current study was the application of all three protocols within the same testing system serving to reduce artifacts due to testing system variability. METHODS: Six L4-L5 segments were tested in a Cartesian load controlled system in flexion-extension to 8Nm under PM, simulated ideal 400N FL, and vertically oriented 400N TW loading protocols. Comparison metrics used were rotational range of motion (RROM), flexibility, neutral zone (NZ) range of motion, and L4 vertebral body displacements. RESULTS: Significant differences in vertebral body translations were observed with different initial force applications but not with subsequent bending moment application. Significant reductions were observed in combined flexion-extension RROM, in flexibility during extension, and in NZ region flexibility with the TW loading protocol as compared to PM loading. Neutral zone ranges of motion were not different between all protocols. CONCLUSIONS: The combined compression and shear forces applied across the spinal joint in the trunk weight protocol may have a small but significantly increased stabilizing effect on segment flexibility and kinematics during sagittal plane flexion and extension.

The influence of fixed sagittal plane centers of rotation on motion segment mechanics and range of motion in the cervical spine.

The center of rotation (CoR) has become an increasingly used metric for biomechanical evaluation of spinal joints however traditional methods of determination remain prone to high degrees of uncertainty. The objective was to use a novel robotic testing protocol to investigate the effects of placement of fixed CoRs in the cervical spine. Human cadaveric C4-C5 (n=3) and C6-C7 (n=5) motion segment units (MSU) were rotated in flexion-extension to limits of 2.5 N m bending or 225 N resultant force about three points in a disc plane (A1, C1, P1) located at 25%, 50% and 75% along the length of the midline of the intervertebral disc respectively in the sagittal view, and three points (A2, C2, P2) in a sub-adjacent plane 5mm below the disc plane. Significant differences in range of rotation occurred between CoRs within the same plane but not between the same points in different planes (e.g. A1-A2). In flexion and extension axial forces at posterior points of rotation (P1, P2) were significantly different from those at anterior and central points. Shear forces were significantly different between points within the same plane except for the disc plane in extension, and between the same points in different planes in flexion and extension. The results indicate that the native cervical MSU is highly sensitive to the CoR location in terms of mechanics and range of motion, and that the CoR location likely varies between flexion and extension. The methodology developed has potential for application towards investigation of optimal CoR locations and in-vitro evaluations of the effects of implantable instrumentation.

Biomechanical comparison of a novel C1 posterior locking plate with the harms technique in a C1-C2 fixation model.

STUDY DESIGN: A biomechanical testing protocol was used to study atlantoaxial fixation techniques in a human cadaveric model. OBJECTIVE: To compare the in vitro biomechanics of locking plate fixation of the posterior arch of C1 to C2 laminar screw fixation, with that of conventional C1 lateral mass to C2 pars screw fixation. SUMMARY OF BACKGROUND DATA: Current methods of atlantoaxial fixation pose a risk to neurologic and vascular structures. A novel posterior locking plate for C1 was designed, that when rigidly linked to C2 translaminar screws may offer alternative C1-C2 fixation with greatly decreased surgical risk. No comparative in vitro biomechanical testing has been previously done to evaluate the feasibility of this method. METHODS: Cadaveric and CT assessments of the thickness of the C1 ring were performed. Seven spines (C0-C4) were evaluated in flexion-extension, left-right bending, and left-right axial rotation in a cadaveric C1-C2 fixation model. Three conditions were evaluated: (1) intact spine, and after odontoidectomy, (2) C1 plate to C2 laminar screw fixation, (3) C1 lateral mass to C2 pars screw fixation. Flexibility and motion data were compared using a 1-way RM analysis of variance and Student-Newman-Kuels tests. RESULTS: Anatomic data indicated that 6 mm of screw purchase was viable for C1 plate fixation. Both the Harms and C1-plated conditions significantly reduced global flexibility in flexion-extension and left-right axial rotation. Motion at the C1-C2 level was significantly reduced for all loading modes for both instrumented conditions with the exception of the C1 plate in right bending. No significant differences occurred between the 2 fixation methods. CONCLUSION: A novel C1 posterior locking plate was designed and tested in a C1-C2 fixation model. The C1 locking plate technique functioned in an equivalent manner to the existing Harms technique. The C1 plate may be a viable alternative that is technically less demanding with decreased surgical risk.

Biomechanical testing of a novel four-rod technique for lumbo-pelvic reconstruction.

STUDY DESIGN: A biomechanical testing protocol was used to study different lumbo-pelvic fixation techniques in a human cadaveric lumbar spine model. OBJECTIVE: To compare the in vitro biomechanics of a novel four-rod lumbo-pelvic reconstruction technique with and with out cross-links, to that of a conventional cross-linked two-rod technique. SUMMARY OF BACKGROUND DATA: Numerous lumbo-pelvic reconstruction methods based on the Galveston two-rod technique have been proposed for cases involving total sacrectomy. Recently a technique that proposes novel use of 4 supporting longitudinal rods across the lumbo-pelvic junction has been reported. No comparative in vitro biomechanical testing has been previously done to evaluate these different reconstruction methods. METHODS: Five spines were evaluated in flexion, extension, left-right lateral bending and left-right axial rotation in a human total sacrectomy model. The model was comprised of cadaveric lumbar spines (L1-L5) with custom fabricated polyethylene blocks used to simulate pelvic fixation. Three conditions were evaluated: Linked Four-Rod, Linked Two-Rod, and Four-Rod (no cross-links). Flexibility and motion data were compared using a one-way repeated measures analysis of variance and SNK tests. RESULTS: The Linked Four-Rod and Four-Rod conditions significantly decreased flexibility and reduced L5-Pelvic motion over the Linked Two-Rod construct in flexion and extension. The Linked Four-Rod condition significantly decreased flexibility in left-right axial rotation compared with the Four-Rod and Linked Two-Rod conditions. No significant differences occurred in relative lateral movement between left and right pelvic polyethylene blocks. CONCLUSION: The four-rod technique improved fixation stability over the conventional linked two-rod technique in flexion and extension, and when cross-linked, in left-right axial rotation. The four-rod technique also significantly reduced L5-Pelvic junction movement in flexionand extension, which may have implications for bony fusion. The use of cross-links is recommended.

A biomechanical study of artificial cervical discs using computer simulation.

STUDY DESIGN: A virtual simulation model of the subaxial cervical spine was used to study the biomechanical effects of various disc prosthesis designs. OBJECTIVE: To study the biomechanics of different design features of cervical disc arthroplasty devices. SUMMARY OF BACKGROUND DATA: Disc arthroplasty is an alternative approach to cervical fusion surgery for restoring and maintaining motion at a diseased spinal segment. Different types of cervical disc arthroplasty devices exist and vary based on their placement and degrees of motion offered. METHODS: A virtual dynamic model of the subaxial cervical spine was used to study 3 different prosthetic disc designs (PDD): (1) PDD-I: The center of rotation of a spherical joint located at the mid C5-C6 disc, (2) PDD-II: The center of rotation of a spherical joint located 6.5 mm below the mid C5-C6 disc, and (3) PDD-III: The center of rotation of a spherical joint in a plane located at the C5-C6 disc level. RESULTS: A constrained spherical joint placed at the disc level (PDD-I) significantly increased facet loads during extension. Lowering the rotational axis of the spherical joint towards the subjacent body (PDD-II) caused a marginal increase in facet loading during flexion, extension, and lateral bending. Lastly, unconstraining the spherical joint to move freely in a plane (PDD-III) minimized facet load build up during all loading modes. CONCLUSION: The simulation model showed the impact simple design changes may have on cervical disc dynamics. The predicted facet loads calculated from computer model have to be validated in the experimental study.

Biomechanical testing simulation of a cadaver spine specimen: development and evaluation study.

STUDY DESIGN: This article describes a computer model of the cadaver cervical spine specimen and virtual biomechanical testing. OBJECTIVES: To develop a graphics-oriented, multibody model of a cadaver cervical spine and to build a virtual laboratory simulator for the biomechanical testing using physics-based dynamic simulation techniques. SUMMARY OF BACKGROUND DATA: Physics-based computer simulations apply the laws of physics to solid bodies with defined material properties. This technique can be used to create a virtual simulator for the biomechanical testing of a human cadaver spine. An accurate virtual model and simulation would complement tissue-based in vitro studies by providing a consistent test bed with minimal variability and by reducing cost. METHOD: The geometry of cervical vertebrae was created from computed tomography images. Joints linking adjacent vertebrae were modeled as a triple-joint complex, comprised of intervertebral disc joints in the anterior region, 2 facet joints in the posterior region, and the surrounding ligament structure. A virtual laboratory simulation of an in vitro testing protocol was performed to evaluate the model responses during flexion, extension, and lateral bending. RESULTS: For kinematic evaluation, the rotation of motion segment unit, coupling behaviors, and 3-dimensional helical axes of motion were analyzed. The simulation results were in correlation with the findings of in vitro tests and published data. For kinetic evaluation, the forces of the intervertebral discs and facet joints of each segment were determined and visually animated. CONCLUSIONS: This methodology produced a realistic visualization of in vitro experiment, and allowed for the analyses of the kinematics and kinetics of the cadaver cervical spine. With graphical illustrations and animation features, this modeling technique has provided vivid and intuitive information.

Motion compensation associated with single-level cervical fusion: where does the lost motion go?

STUDY DESIGN: Seven adult human cadaveric cervical spines (C2-T1) were biomechanically tested in a programmable testing device. OBJECTIVE: Compare the effects of incremental single-level fusion at different levels of the cervical spine. SUMMARY OF BACKGROUND DATA: Clinical studies have reported degenerative symptomatic disc disease at disc levels adjacent to fusion. No known study has attempted to delineate the effects of single-level fusion at different levels of the cervical spine. METHODS: The spines were tested in flexion, extension, right and left lateral bending, and right and left axial rotation for 7 different conditions: harvested and 6 independent single-level fused conditions (i.e., C2-C3, C3-C4, C4-C5, C5-C6, C6-C7, and C7-T1). Segmental motion and global stiffness data were normalized to the harvested condition and compared using a 1-way analysis of variance followed by a SNK test (P < 0.01). RESULTS: Motion compensation was distributed among the unfused segments with significant compensation at the segments adjacent to fusion. Significant increases occurred at the level above C3-C4 and C4-C5 fusions, and below for C5-C6 and C6-C7 fusions in both flexion and extension. CONCLUSIONS: Increase motion compensation occurred at segments immediately adjacent to a single-level fusion. Significant differences occurred at the level above the fusion site for the C3-C4 and C4-C5 fusion in both flexion and extension. When the lower levels (C5-C6, C6-C7) were fused, a significant amount of increased motion was observed at the levels immediately above and below the fusion. However, greater compensation occurred at the inferior segments than the superior segments for the lower level fusions (C5-C6, C6-C7).

Cervical spine arthroplasty biomechanics.

The advent of cervical intervertebral disc replacement represents an exciting and new frontier in the treatment of myelopathy and discogenic pain. The goal of most disc arthroplasty designs is to attempt to approximate the normal spinal motion as much as possible. This survey article provides a general overview as to the goals of cervical disc replacement, the current state of knowledge concerning how these devices have been evaluated, and a commentary on future work that should be performed to characterize these devices fully.

An improved biomechanical testing protocol for evaluating spinal arthroplasty and motion preservation devices in a multilevel human cadaveric cervical model.

OBJECT: An experimental study was performed to determine the biomechanical end-mounting configurations that replicate in vivo physiological motion of the cervical spine in a multiple-level human cadaveric model. The vertebral motion response for the modified testing protocol was compared to in vivo motion data and traditional pure-moment testing methods. METHODS: Biomechanical tests were performed on fresh human cadaveric cervical spines (C2-T1) mounted in a programmable testing apparatus. Three different end-mounting conditions were studied: pinned-pinned, pinned-fixed, and translational/pinned-fixed. The motion response of the individual segmental vertebral rotations was statistically compared using one-way analysis of variance and Student-Newman-Keuls tests (p < 0.05 unless otherwise stated) to determine differences in the motion responses for different testing methods. CONCLUSIONS: A translational/pinned-fixed mounting configuration induced a bending-moment distribution across the cervical spine, resulting in a motion response that closely matched the in vivo case. In contrast, application of pure-moment loading did not reproduce the physiological response and is less suitable for studying disc arthroplasty and nonfusion devices.

In vitro biomechanics of cervical disc arthroplasty with the ProDisc-C total disc implant.

An in vitro biomechanical study was conducted to compare the effects of disc arthroplasty and anterior cervical fusion on cervical spine biomechanics in a multilevel human cadaveric model. Three spine conditions were studied: harvested, single-level cervical disc arthroplasty, and single-level fusion. A programmable testing apparatus was used that replicated physiological flexion/extension, lateral bending, and axial rotation. Measurements included vertebral motion, applied load, and bending moments. Relative rotations at the superior, treated, and inferior motion segment units (MSUs) were normalized with respect to the overall rotation of those three MSUs and compared using a one-way analysis of variance with Student-Newman-Keuls test (p < 0.05). Simulated fusion decreased motion across the treated site relative to the harvested and disc arthroplasty conditions. The reduced motion at the treated site was compensated at the adjacent segments by an increase in motion. For all modes of testing, use of an artificial disc prosthesis did not alter the motion patterns at either the instrumented level or adjacent segments compared with the harvested condition, except in extension.

Biomechanical testing of an artificial cervical joint and an anterior cervical plate.

An in vitro biomechanical study was conducted to determine the effects of fusion and nonfusion anterior cervical instrumentation on cervical spine biomechanics in a multilevel human cadaveric model. Three spine conditions were studied: harvested, single-level artificial cervical joint, and single-level graft with anterior cervical plate. A programmable testing apparatus was used that replicated physiologic flexion/extension and lateral bending. Measurements included vertebral motion, applied load, and bending moments. Relative rotations at the superior, implanted, and inferior motion segment units (MSUs) were normalized with respect to the overall rotation of those three MSUs and compared using a one-way analysis of variance (P < 0.05). Application of an anterior cervical plate decreased motion across the fusion site relative to the harvested and artificial joint spine conditions. The reduced motion was compensated for by an increase in motion at the adjacent segments. Use of an artificial cervical joint did not alter the motion patterns at either the instrumented level or the adjacent segments compared with the harvested condition for all modes of testing.

Bioabsorbable anterior lumbar plate fixation in conjunction with cage-assisted anterior interbody fusion.

OBJECT: An in vitro biomechanical study was conducted to determine the effects of anterior stabilization on cage-assisted lumbar interbody fusion biomechanics in a multilevel human cadaveric lumbar spine model. METHODS: Three spine conditions were compared: harvested, bilateral multilevel cages (CAGES), and CAGES with bioabsorbable anterior plates (CBAP), tested under flexion-extension, lateral bending, and axial rotation. Measurements included vertebral motion, applied load, and bending/rotational moments. Application of anterior fixation decreased local motion and increased stiffness of the instrumented levels. Clinically, this spinal stability may serve to promote fusion. CONCLUSIONS: Coupled with the bioabsorbability of the plating material, the bioabsorbable anterior lumbar plating system is considered biomechanically advantageous.

Bioabsorbable anterior lumbar plate fixation in conjunction with anterior interbody fusion cages.

An in vitro biomechanical study was conducted to determine the effects of anterior stabilization on lumbar interbody cage fusion biomechanics in a multilevel human cadaveric lumbar model. Three spine conditions were compared: harvested, bilateral multilevel cages (CAGES), and CAGES with bioabsorbable anterior plates (CBAP), tested under flexion/extension, lateral bending, and axial rotation. Measurements included vertebral motion, applied load, and bending/rotational moments. Application of anterior fixation decreased local motion and increased stiffness of the instrumented levels. Clinically, this spinal stability may serve to promote fusion. Coupled with the bioabsorbability of the plating material, the bioabsorbable anterior lumbar plating system is considered biomechanically advantageous.