Manohar M Panjabi

• PhD
• Professor Emeritus at Yale University

Unlike complete ligament ruptures, there is limited information on the injury and healing mechanisms of mild and moderate ligament sprains. These sprains comprise 85% or more of all ligament injuries. Previously we studied the effects of sprain (subfailure) injury on the in vitro mechanical properties of the rabbit anterior cruciate ligament (Panja...

A surgical implant is provided that includes first and second abutment surfaces between which are positioned a force imparting mechanism. A sheath is positioned between the first and second abutment surfaces, and surrounds the force imparting mechanism. The sheath is fabricated from a material that accommodates relative movement of the abutment mem...

The field of biomechanics combines the disciplines of biology and engineering, attempting to quantitatively describe the complicated properties of biological materials. These properties depend not only upon the inherent attributes of its constituents but also upon how the constituents are arranged relative to each other. Its importance in understan...

Previous epidemiological studies have observed that an initial head restraint backset greater than 10 cm is associated with a higher risk of neck injury and persistent symptoms. The objective of this study was to investigate the relation between the active head restraint position and peak neck motion using a new human model of the neck. The model c...

The goal of this study was to compute the dynamic neck loads during simulated high-speed bilateral facet dislocation and investigate the injury mechanism. Ten osteoligamentous functional spinal units (C3/4, n = 4; C5/6, n = 3; C7/T1, n = 3) were prepared with muscle force replication, motion tracking flags, and a 3.3-kg mass rigidly attached to the...

Nackenverletzungen, welche während Autounfällen auftreten, können zu chronischen Symptomen, inklusive Nacken- und Schulterschmerzen, Muskelkater, Kopfschmerzen, Schwindel, verschwommenem Sehen und Gedächtnisverlust führen [11,31]. Die geschätzten jährlichen Sozialausgaben belaufen sich auf 10 Milliarden Dollar in den USA und 10 Milliarden Euro in E...

Thoracolumbar burst fracture is one of the most common and most studied injuries of the spine. Radiography and quantitative discomanometry have previously demonstrated that intervertebral discs adjacent to a burst fracture were disrupted; however, there have been conflicting data on the properties of the next-adjacent discs. Also, no data exists on...

Data on the role of platelet concentrate (PC) in spinal fusion are limited. Using the New Zealand white rabbit model, we compared fusion rates at L5-L6 using 2 different volumes (1.5 cm(3), 3.0 cm(3)) of iliac crest autograft with and without PC (4 groups total, 10 animals in each). PC was collected from donor rabbits and adjusted to a concentratio...

Previous clinical studies have identified the cervical facet joint, including the capsular ligaments, as sources of pain in whiplash patients. The goal of this study was to determine whether whiplash caused increased capsular ligament laxity by applying quasi-static loading to whiplash-exposed and control capsular ligaments. A total of 66 capsular...

Side impact may cause neck and upper extremity pain, paresthesias, and impaired neck motion. No studies have quantified the cervical spine mechanical instability and injury threshold acceleration due to side impact. The goals of the present study were to identify and quantify cervical spine soft tissue injury and the injury threshold acceleration f...

Rationale behind motion preservation devices is to eliminate the accelerated adjacent-level effects (ALE) associated with spinal fusion. We evaluated multidirectional flexibilities and ALEs of StabilimaxNZ and simulated fusion applied to a decompressed spine. StabilimaxNZ was applied at L4-L5 after creating a decompression (laminectomy of L4 plus b...

Most previous studies have investigated ligament mechanical properties at slow elongation rates of less than 25 mm/s. To determine the tensile mechanical properties, at a fast elongation rate, of intact human cervical anterior and posterior longitudinal, capsular, and interspinous and supraspinous ligaments, middle-third disc, and ligamentum flavum...

An in vitro biomechanical study. The objectives were to: quantify dynamic canal pinch diameter (CPD) narrowing during simulated bilateral facet dislocation of a cervical functional spinal unit model with muscle force replication, determine if peak dynamic CPD narrowing exceeded that observed post-trauma, and evaluate dynamic cord compression. Previ...

Previous biomechanical models of cervical bilateral facet dislocation (BFD) are limited to quasi-static loading or manual ligament transection. The goal of the present study was to determine the facet joint kinematics during high-speed BFD. Dislocation was simulated using ten cervical functional spinal units with muscle force replication by frontal...

The goal of the present study was to determine the dynamic sagittal flexibility coefficients, including coupling coefficients, throughout the human cervical spine using rear impacts. A biofidelic whole cervical spine model (n=6) with muscle force replication and surrogate head was rear impacted at 5 g peak horizontal accelerations of the T1 vertebr...

An in vitro human cadaveric biomechanical study. To evaluate intervertebral rotation changes due to lumbar ProDisc-L compared with simulated fusion, using follower load and multidirectional testing. Artificial discs, as opposed to the fusions, are thought to decrease the long-term accelerated degeneration at adjacent levels. A biomechanical assessm...

An in vitro human cadaveric biomechanical study. To quantify effects on operated and other levels, including adjacent levels, due to CHARITE disc implantations versus simulated fusions, using follower load and the new hybrid test method in flexion-extension and bilateral torsion. Spinal fusion has been associated with long-term accelerated degenera...

Several clinical studies have documented long-term adjacent-level effects of spinal fusion, due to stress concentration and motion loss at the fused segment. Non-fusion motion preservation devices are designed to eliminate or slow down such adverse effects. Therefore, appropriate biomechanical evaluation of the adjacent-level effects in spine is im...

Traditionally, spinal degeneration and injury have been associated with abnormal intervertebral motion; thus, treatment for lowback pain has centered on prevention of motion through spinal fusion. Although the rate of successful spinal fusions is improving, complications such as adjacent-level syndrome emphasize the need to develop alternatives for...

Elongation-induced vertebral artery (VA) injury has been hypothesized to occur during nonphysiological coupled head motions during automobile impacts. Although previous work has investigated VA elongation during head-turned and head-forward rear impacts, no studies have performed similar investigations for frontal or side impacts. The present study...

The neutral zone (NZ) is a region of intervertebral motion around the neutral posture where little resistance is offered by the passive spinal column. The NZ appears to be a clinically important measure of spinal stability function. Its size may increase with injury to the spinal column, which in turn may result in spinal instability or low-back pa...

Previous clinical studies have documented successful neck pain relief in whiplash patients using nerve block and radiofrequency ablation of facet joint afferents, including capsular ligament nerves. No previous study has documented injuries to the neck ligaments as determined by altered dynamic mechanical properties due to whiplash. The goal of the...

To quantify the dynamic loads and intervertebral motions throughout the cervical spine during simulated rear impacts. Using a biofidelic whole cervical spine model with muscle force replication and surrogate head and bench-top mini-sled, impacts were simulated at 3.5, 5, 6.5, and 8 g horizontal accelerations of the T1 vertebra. Inverse dynamics was...

Intervertebral Neck Injury Criterion (IV-NIC) hypothesizes that dynamic three-dimensional intervertebral motion beyond physiological limit may cause multiplanar soft-tissue injury. Present goals, using biofidelic whole human cervical spine model with muscle force replication and surrogate head in head-turned rear impacts, were to: (1) correlate IV-...

A rotated head posture at the time of vehicular rear impact has been correlated with a higher incidence and greater severity of chronic radicular symptoms than accidents occurring with the occupant facing forward. No studies have been conducted to quantify the dynamic changes in foramen dimensions during head-turned rear-impact collisions. The obje...

Between 23 and 70% of occupants involved in frontal impacts sustain cervical spine injuries, many with neurological involvement. It has been hypothesized that cervical spinal cord compression and injury may explain the variable neurological profile described by frontal impact victims. The goals of the present study, using a biofidelic whole cervica...

Clinical reports and research studies have documented the behavior of chronic low back and neck pain patients. A few hypotheses have attempted to explain these varied clinical and research findings. A new hypothesis, based upon the concept that subfailure injuries of ligaments (spinal ligaments, disc annulus and facet capsules) may cause chronic ba...

Carpal bones show hysteresis that is dependent on the direction of wrist motion during a continuous active loading protocol. We describe an accurate methodology for analyzing the hysteresis effect and we apply this model to analyze the effect of sequential ligament sectioning on scapholunate instability. In 8 fresh cadaver forearms scaphoid, lunate...

Prior to implantation, medical devices are subjected to rigorous testing to ensure safety and efficacy. A full battery of testing protocols for implantable spinal devices may include many steps. Testing for biocompatibility is a necessary first step. On selection of the material, evaluation protocols should address both the biomechanical and clinic...

Prior to implantation, medical devices are subjected to rigorous testing to ensure safety and efficacy. A full battery of testing protocols for implantable spinal devices may include many steps. Testing for biocompatibility is a necessary first step. On selection of the material, evaluation protocols should address both the biomechanical and clinic...

Determination of alar, transverse, and apical ligament strains during simulated head-turned rear impact. To quantify the alar, transverse, and apical ligament strains during head-turned rear impacts of increasing severity, to compare peak strains with baseline values, and to investigate injury mechanisms. Clinical and epidemiologic studies have doc...

To assess the biomechanical stability relative to screw length and K-wire augmentation in scaphoid fracture fixation using a flexibility testing protocol and cadaver scaphoids whose soft tissue attachments remained undisturbed. Our hypothesis was 2-fold: increasing screw length and augmenting fixation with a K-wire would improve fracture fragment s...

A biomechanical study of intervertebral foraminal narrowing during simulated automotive rear impacts. To quantify foraminal width, height, and area narrowing during simulated rear impact, and evaluate the potential for nerve root and ganglion impingement in individuals with and without foraminal spondylosis. Muscle weakness and paresthesias, docume...

Previous methods to determine spinal ligament deformation have included either custom-designed transducers or computational methods using rigid body transformation of kinematic data. Goals of the present study were to describe a computational methodology to determine dynamic deformations of an arbitrarily oriented ligament in a spine specimen and i...

Elongation-induced vertebral artery injury has been hypothesized to occur during non-physiological coupled axial rotation and extension of head. No studies have quantified dynamic vertebral artery elongation during head-turned rear impacts. Therefore, we evaluated effect of rotated head posture vs. forward head posture at the time of impact on dyna...

Head-turned whole cervical spine model was stabilized with muscle force replication and subjected to simulated rear impacts of increasing severity. Multiplanar flexibility testing evaluated any resulting injury. To identify and quantify cervical spine soft tissue injury and injury threshold acceleration for head-turned rear impact, and to compare t...

Finite element model of L3-S1 segment and confirmatory cadaveric testing were used to investigate the biomechanical effects of a mobile core type artificial disc (Charité artificial disc; DePuy Spine, Raynham, MA) on the lumbar spine. To determine the effects of the Charité artificial disc across the implanted and adjacent segments. Biomechanical s...

Radiofrequency treatment is increasingly used to treat shoulder instability. Patients are asked to restrain their physical activities after this treatment but there is no precise information concerning the necessity for the restrain. There were two groups of ten specimens each. Treatment group specimens were stretched to subfailure injury, treated...

Intervertebral Neck Injury Criterion (IV-NIC) is based on the hypothesis that dynamic three-dimensional intervertebral motion beyond physiological limits may cause multiplanar injury of cervical spine soft tissues. Goals of this study, using a biofidelic whole human cervical spine model with muscle force replication and surrogate head in simulated...

Whole cervical spine model with muscle force replication was subjected to simulated frontal impacts of increasing severity, and resulting injuries were evaluated via flexibility testing. To identify and quantify cervical spine soft tissue injury and the injury threshold acceleration due to frontal impact. Cervical spine instability may result from...

The Intervertebral Neck Injury Criterion (IV-NIC) is based on the hypothesis that intervertebral motion beyond the physiological limit may injure spinal soft tissues during whiplash, while the Neck Injury Criterion (NIC) hypothesizes that sudden changes in spinal fluid pressure may cause neural injury. Goals of the present study, using a biofidelic...

Although spine fusion is a versatile and effective technique in the treatment of spinal disorders, increased stresses on adjacent unfused levels lead to symptomatic adjacent level degeneration in many patients. The goal of nonfusion devices in spine surgery is to ablate or unload painful structures while preserving segmental motion. The intended pe...

The Intervertebral Neck Injury Criterion (IV-NIC) is based on the hypothesis that dynamic intervertebral motion beyond physiological limits may injure soft tissues. In contrast, the Neck Injury Criterion (NIC) hypothesizes that sudden change in spinal fluid pressure may cause neural injuries. The goals of this study, using the biofidelic whole huma...

Cervical disc injury due to frontal impact has been observed in both clinical and biomechanical investigations; however, there is a lack of data that elucidate the mechanisms of disc injury during these collisions. The goals of the current study were to determine the peak dynamic disc annular tissue strain and disc shear strain during simulated fro...

Whiplash has been simulated using volunteers, whole cadavers, mathematical models, anthropometric test dummies, and whole cervical spines. Many previous in vitro whiplash models lack dynamic biofidelity. The goals of this study were to (1) develop a new dynamic whole cervical spine whiplash model that will incorporate anterior, lateral and posterio...

The supraspinous and interspinous ligaments, ligamentum flavum, and capsular and posterior longitudinal ligament strains were monitored during simulated frontal impact of whole cervical spine specimens with muscle force replication and compared with corresponding physiologic strain limits. To quantify the strains in the cervical spine ligaments dur...

Automotive collision simulations have been performed using either incremental or single trauma. In single trauma, a single impact is performed, while in incremental trauma, a series of impacts of increasing severity are executed. Equivalency of incremental and single trauma for soft tissue injury severity due to the final impact has not been establ...

A biofidelic whole cervical spine model with muscle force replication was used to evaluate spinal canal pinch diameter (CPD) narrowing during simulated whiplash. To quantify CPD narrowing during simulated whiplash and to determine if whiplash resulted in a narrower post-whiplash CPD. Spinal cord injuries are uncommon in whiplash patients, although...

A kinematic analysis of cervical intervertebral disc deformation during simulated whiplash using the whole cervical spine with muscle force replication model was performed. To quantify anulus fibrosus fiber strain, disc shear strain, and axial disc deformation in the cervical spine during simulated whiplash. Clinical studies have documented acute i...

A newly developed biofidelic whole cervical spine (WCS) model with muscle force replication (MFR) was subjected to whiplash simulations of varying intensity, and the resulting injuries were evaluated through changes in the intervertebral flexibility. To identify the soft tissue injury threshold based on the peak T1 horizontal acceleration and the a...

Utilizing a rabbit anterior cruciate ligament model of ligamentous subfailure injury, biomechanical properties of injured ligament treated with radiofrequency energy were evaluated. It was hypothesized that an injured ligament treated with radiofrequency probe would demonstrate restoration of biomechanical properties lost through injury. Radiofrequ...

Facet joint kinematics and capsular ligament strains were evaluated during simulated whiplash of whole cervical spine specimens with muscle force replication. To describe facet joint kinematics, including facet joint compression and facet joint sliding, and quantify peak capsular ligament strain during simulated whiplash. Clinical studies have impl...

To develop a new method to describe cervical spine curvature and evaluate the potential for injury in the upper and lower cervical spine during simulated whiplash. A method was developed to integrate the upper and lower cervical spine rotations and describe the spine curvature. In vivo and in vitro whiplash simulations have documented the developme...

Anterior longitudinal ligament (ALL) injuries following whiplash have been documented both in vivo and in vitro; however, ALL strains during the whiplash trauma remain unknown. A new in vitro whiplash model and a bench-top trauma sled were used in an incremental trauma protocol to simulate whiplash at 3.5, 5, 6.5 and 8 g accelerations, and peak ALL...

Clinical instability is an important cause of low back pain. Although there is some controversy concerning its definition, it is most widely believed that the loss of normal pattern of spinal motion causes pain and/or neurologic dysfunction. The stabilizing system of the spine may be divided into three subsystems: (1) the spinal column; (2) the spi...

Biomechanical analysis of spinal injury in the laboratory requires the development of trauma models that simulate spinal instability. Current experimental trauma protocols consist of two types: single or incremental impacts. The incremental protocol has several advantages. However, the equivalence of the spinal instabilities produced by the two tra...

To evaluate the radiofrequency treatment applied to an intact anterior cruciate ligament, and to quantify the mechanical effects of controlled cyclic loading (simulating activities of daily living) post-treatment. An in vitro radiofrequency energy application to the rabbit anterior cruciate ligament and cyclic loading of the treated ligament. Effec...

This study biomechanically evaluated three fixation devices for stability with posterior two- and three-column injuries. To find an effective means of posteriorly stabilizing injuries at the cervicothoracic junction. The cervicothoracic spine is complex anatomically and has been a difficult challenge in approach and stabilization of traumatic and d...

Study Design. This study biomechanically evaluated three fixation devices for stability with posterior two- and three-column injuries. Objectives. To find an effective means of posteriorly stabilizing injuries at the cervicothoracic junction. Summary of Background Data. The cervicothoracic spine is complex anatomically and has been a difficult chal...

An accepted classification of thoracic and lumbar spine injuries allows clinicians to work from a common ground when managing the traumatized patient. Several perplexing questions plague the treating physician when evaluating a patient with a thoracolumbar fracture, such as: Which injuries can be managed conservatively? Which patient will require s...

The purpose of this study was to evaluate the biomechanical characteristics of short-segment anterior, posterior, and combined instrumentations in lumbar spine vertebral body replacement surgery. Eight fresh frozen human cadaveric thoracolumbar spine specimens (T12-L4) were prepared for biomechanical testing. Pure moments (2.5, 5, and 7.5 Nm) of fl...

Am menschlichen Wirbelsäulenmodell wurde die multidirektionale Stabilität kurzstreckiger ventraler, dorsaler und kombinierter Spondylodesen (L1 bis L3) nach Korpektomie L2 und Wirbelkörperersatz mit einem Karbonfaserimplantat untersucht. 8 menschliche Wirbelsäulenpräparate (T12 bis L4) wurden für die biomechanische Testung aufgearbeitet. Reine Mome...

Femurs of Sprague-Dawley rats were subjected to in vitro 3-Mrad irradiation and/or freeze-drying to investigate whether these processes have an order-dependent effect on the biomechanical properties of bone. Four experimental groups were designated-irradiated (RAD); freeze-dried (FD); irradiated, then freeze-dried (RAD/FD); and freeze-dried, then i...

An in vitro biomechanical study. To examine disc integrity at levels adjacent and next adjacent to the fractured vertebra and to determine if the disc injury can be revealed by radiographs. Thoracolumbar burst fracture is one of the most common spinal injuries. A fractured vertebra is easy to recognize, but the associated disc injuries are less wel...

An in vitro flexibility study of C2-T1 specimens under compressive preload. To determine three-dimensional flexibility test moments needed to obtain spinal kinematics representative of the in vivo spine studies. Most previous three-dimensional in vitro cervical spine studies have used equal moments in all three planes to evaluate spinal flexibiliti...

Study Design. An in vitro biomechanical study. Objective. To examine disc integrity at levels adjacent and next adjacent to the fractured vertebra and to determine if the disc injury can be revealed by radiographs. Summary of Background Data. Thoracolumbar burst fracture is one of the most common spinal injuries. A fractured vertebra is easy to rec...

The short segmental pedicle screw device is widely used for the decompression of neural elements and reduction of normal anatomy. Many biomechanical studies concerning proper decompression are available. However, no study has determined the optimal device adjustment for reduction of the burst fracture to the normal anatomy. In this study, cadaveric...

The mechanical properties of multilevel human cervical spines were investigated by applying pure rotational moments to each specimen and measuring multidirectional intervertebral motions. To document intervertebral main and coupled motions of the cervical spine in the form of load-displacement curves. Although a number of in vivo and in vitro studi...

An anatomic study of cervical vertebral bodies. To provide quantitative information on the cortical shell architecture of the middle and lower cervical vertebral bodies. Some external dimensions have been measured, but little quantitative data exists for the cortical shell architecture of the vertebral bodies of the cervical spine. Twenty-one human...

An in vitro biomechanical study of the stabilizing effect of pedicle screw instrumentation on experimental thoracolumbar burst fractures. To evaluate the effects of different adjustments applied by the pedicle screw fixation device on the stability of the spine-device construct. Pedicle screw devices are widely used to accomplish spinal reduction a...

An in vitro biomechanical study. To develop and evaluate a new in vitro whole cervical spine model that provides to the specimen, in vivo-like mechanical characteristics. In vitro studies of kinematics, kinetics, and trauma using isolated spine specimens (head-T1 vertebra) have usually applied upward force to the head, resulting in tensile spine fo...

An established rabbit posterolateral lumbar fusion model was used to evaluate the ability of osteogenic protein-1 to overcome the inhibitory effect of nicotine. To determine whether osteogenic protein-1 should be considered as a bone graft alternative for the patient who smokes. Smoking interferes with the success of posterolateral lumbar fusion. T...

The neural spaces of thoracolumbar burst fractures were investigated in an in vitro biomechanical study. To evaluate encroachments of spinal canal diameter and intervertebral foramen area as functions of where the center of rotation is located during flexion and extension. Decompression of the neural spaces is important for the recovery of neural f...

To study alterations in the ligament mechanical characteristics due to a subfailure stretch delivered at high speed. An in vitro study of rabbit anterior cruciate ligaments. Although ligamentous sprains occur more frequently than the complete failures, only a few biomechanical studies have investigated the effects of such injuries. Purpose of the s...

Biomechanics of posterolateral spinal fusion were studied in an in vivo rabbit model. To determine the extent of stabilization produced by posterolateral lumbar fusion and to test the hypothesis that motions are not completely eliminated after successful fusion. Previous human cadaveric studies, clinical studies, and animal studies have attempted t...

Instability of the cervical spine following whiplash trauma has been demonstrated in a number of studies. We hypothesized that, in patients with whiplash-associated disorder, rotation of the head would be accompanied by an earlier onset of neck muscle activity to compensate for intrinsic instability. The aim of the study was to examine the range of...

An established rabbit intertransverse process lumbar fusion model was used to evaluate osteogenic protein (OP)-1 as a potential graft substitute. To determine whether OP-1 is effective in producing intertransverse process lumbar fusion in a rabbit model. Autogenous iliac crest bone is the gold standard in grafting material for inducing intertransve...

Study Design. An established rabbit intertransverse process lumbar fusion model was used to evaluate osteogenic protein (OP)-1 as a potential graft substitute. Objectives. To determine whether OP-1 is effective in producing intertransverse process lumbar fusion in a rabbit model. Summary of Background Data. Autogenous iliac crest bone is the gold s...

An in vitro biomechanical study of lumbar spine segments. To study the characteristics of the stiffness test protocol. In an in vitro study using a flexibility protocol, forces are applied and motions are measured; no center of rotation needs to be specified. In a study using a stiffness protocol, the forces are measured and the motions are applied...

It is important to know the condition of neural spaces during the nonoperative treatment of thoracolumbar burst fractures. The goals of the current study were to identify the correlation between the degree of deformity of a fractured vertebra and the encroachment of neural spaces, and to determine how the encroachment and the deformity can be impro...