Kai-nan An - Profile on Academia.edu (original) (raw)

Papers by Kai-nan An

Journal of Biomechanics, Aug 1, 2017

Surgical repair for large rotator cuff tear remains challenging due to tear size, altered muscle ... more Surgical repair for large rotator cuff tear remains challenging due to tear size, altered muscle mechanical properties, and poor musculotendinous extensibility. Insufficient extensibility might lead to an incomplete reconstruction; moreover, excessive stresses after repair may result in repair failure without healing. Therefore, estimates of extensibility of cuff muscles can help in presurgical planning to prevent unexpected scenarios during surgery. The purpose of this study was to determine if quantified mechanical properties of the supraspinatus muscle using shear wave elastography (SWE) could be used to predict the extensibility of the musculotendionous unit on cadaveric specimens. Forty-five fresh-frozen cadaveric shoulders (25 intact and 20 with rotator cuff tear) were used for the study. Passive stiffness of 4 anatomical regions in the supraspinatus muscle was first measured using SWE. After detaching the distal edge of supraspinatus muscle from other cuff muscles, the detached muscle was axially pulled with the scapula fixed. The correlation between the SWE modulus and the extensibility of the muscle under 30 and 60 N loads was assessed. There was a significant negative correlation between SWE measurements and the experimental extensibility. SWE modulus for the anterior-deep region in the supraspinatus muscle showed the strongest correlation with extensibility under 30 N (r = 0.70, P < 0.001) and 60 N (r = 0.68, P < 0.001). Quantitative SWE assessment for the supraspinatus muscle was highly correlated with extensibility of musculotendinous unit on cadaveric shoulders. This technique may be used to predict the extensibility for rotator cuff tears for pre-surgical planning.

Journal of wrist surgery, Apr 23, 2015

Although the newest-generation designs have some notable differences, they share features of peg/... more Although the newest-generation designs have some notable differences, they share features of peg/screw fixation distally into the carpus and a press-fitted proximal radial component. They also have a metal-plastic articulation. Early and secondgeneration designs have had difficulty with long-term

European Spine Journal, Apr 29, 2009

The technology used in surgery for spinal deformity has progressed rapidly in recent years. Commo... more The technology used in surgery for spinal deformity has progressed rapidly in recent years. Commonly used fixation techniques may include monofilament wires, sublaminar wires and cables, and pedicle screws. Unfortunately, neurological complications can occur with all of these, compromising the patients' health and quality of life. Recently, an alternative fixation technique using a metal clamp and polyester belt was developed to replace hooks and sublaminar wiring in scoliosis surgery. The goal of this study was to compare the pull-out strength of this new construct with sublaminar wiring, laminar hooks and pedicle screws. Forty thoracic vertebrae from five fresh frozen human thoracic spines (T5-12) were divided into five groups (8 per group), such that BMD values, pedicle diameter, and vertebral levels were equally distributed. They were then potted in polymethylmethacrylate and anchored with metal screws and polyethylene bands. One of five fixation methods was applied to the right side of the vertebra in each group: Pedicle screw, sublaminar belt with clamp, figure-8 belt with clamp, sublaminar wire, or laminar hook. Pull-out strength was then assessed using a custom jig in a servohydraulic tester. The mean failure load of the pedicle screw group was significantly larger than that of the figure-8 clamp (P = 0.001), sublaminar belt (0.0172), and sublaminar wire groups (P = 0.04) with no significant difference in pull-out strength between the latter three constructs. The most common mode of failure was the fracture of the pedicle. BMD was significantly correlated with failure load only in the figure-8 clamp and pedicle screw constructs. Only the pedicle screw had a statistically significant higher failure load than the sublaminar clamp. The sublaminar method of applying the belt and clamp device was superior to the figure-8 method. The sublaminar belt and clamp construct compared favorably to the traditional methods of sublaminar wires and laminar hooks, and should be considered as an alternative fixation device in the thoracic spine.

Journal of shoulder and elbow arthroplasty, 2018

Background: The purpose of this study is to assess the incidence of acromial stress fractures in ... more Background: The purpose of this study is to assess the incidence of acromial stress fractures in a population of reverse shoulder arthroplasties (RSA) and determine potential risk factors for fracture. Patients and Methods: Between August 2004 and December 2013, 1082 primary RSA were performed at a single institution. Twelve (1.11%) patients were diagnosed with a postoperative acromial stress fracture. This group was casematched to a control group of 48 shoulders. Clinical and radiographic risk factors for fracture were assessed. Results: Compared to controls, fractures were less satisfied with their outcome despite equivalent American Shoulder and Elbow Surgeons scores, pain scores, and range of motion. Osteoporosis was significantly associated with acromial fractures (P ¼.027). A smaller lateral offset of the greater tuberosity, greater arm lengthening, and a thinner acromion were more common in the fracture group (P ¼.026, P ¼.004, and P ¼.008, respectively). Conclusions: In summary, postoperative acromial stress fractures appear to be incidental lesions with little influence on the outcome after RSA. The combination of a thin acromion and superior migration of the humeral head increase the risk of acromial fracture. Lateralized designs that do not excessively verticalize the deltoid line of pull on the acromion may decrease the risk of postoperative acromial fractures.

Journal of biomechanical engineering, Jul 1, 2015

Accurate quantification of subtle wrist motion changes resulting from ligament injuries is crucia... more Accurate quantification of subtle wrist motion changes resulting from ligament injuries is crucial for diagnosis and prescription of the most effective interventions for preventing progression to osteoarthritis. Current imaging techniques are unable to detect injuries reliably and are static in nature, thereby capturing bone position information rather than motion which is indicative of ligament injury. A recently developed technique, 4D (three dimensions þ time) computed tomography (CT) enables threedimensional volume sequences to be obtained during wrist motion. The next step in successful clinical implementation of the tool is quantification and validation of imaging biomarkers obtained from the four-dimensional computed tomography (4DCT) image sequences. Measures of bone motion and joint proximities are obtained by: segmenting bone volumes in each frame of the dynamic sequence, registering their positions relative to a known static posture, and generating surface polygonal meshes from which minimum distance (proximity) measures can be quantified. Method accuracy was assessed during in vitro simulated wrist movement by comparing a fiducial bead-based determination of bone orientation to a bone-based approach. The reported errors for the 4DCT technique were: 0.00-0.68 deg in rotation; 0.02-0.30 mm in translation. Results are on the order of the reported accuracy of other image-based kinematic techniques.

Journal of Orthopaedic Research, Dec 22, 2008

The ideal scaffold for tendon engineering would possess the basic structure of the tendon, native... more The ideal scaffold for tendon engineering would possess the basic structure of the tendon, native extracellular matrix, and capability of cell seeding. The purpose of this study was to assess the tissue engineering potential of a novel composite consisting of a decellularized multilayer sliced tendon (MST) scaffold seeded with bone marrow stromal cells (BMSC). BMSC and infraspinatus tendons were harvested from 20 dogs. The tendons were sectioned in longitudinal slices with a thickness of 50 µm. The slices were decellularized, seeded with BMSC, and then bundled into one composite. The composite was incubated in culture media for 14 days. The resulting BMSCseeded MST was evaluated by qRT-PCR and histology. The BMSC viability was assessed by a fluorescent tracking marker. Histology showed that the seeded cells aligned between the collagen fibers of the tendon slices. Analysis by qRT-PCR showed higher tenomodulin and MMP13 expression and lower collagen type I expression in the composite than in the BMSC before seeding. BMSC labeled with fluorescent tracking marker were observed in the composite after culture. Mechanical testing showed no differences between scaffolds with or without BMSC. BMSC can survive in a MST scaffold. The increased tenomodulin expression suggests that BMSC might express a tendon phenotype in this environment. This new composite might be useful as a model of tendon tissue engineering.

PLOS ONE, Aug 11, 2016

The flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) are critical for fi... more The flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) are critical for finger flexion. Although research has recently focused on these tendons' coactivity, their contributions in different tasks remain unclear. This study created a novel simultaneous approach to investigate the coactivity between the tendons and to clarify their contributions in different tasks. Ten human cadaveric hands were mounted on our custom frame with the FDS and FDP of the third finger looped through a mechanical pulley connected to a force transducer. Joint range of motion, tendon excursion and loading force were recorded during individual joint motion and free joint movement from rest to maximal flexion. Each flexor tendon's moment arm was then calculated. In individual motions, we found that the FDP contributed more than the FDS in proximal interphalangeal (PIP) joint motion, with an overall slope of 1.34 and all FDP-to-FDS excursion (P/S) ratios greater than 1.0 with force increase. However, the FDP contributed less than the FDS in metacarpophalangeal (MCP) joint motion, with an overall slope of 0.95 and P/S ratios smaller than 1.0 throughout the whole motion except between 1.9% and 13.1% force. In free joint movement, the FDP played a greater role than the FDS, with an overall ratio of 1.37 and all P/S ratios greater than 1.0.

Scientific Reports, Jan 31, 2023

Kinesio taping (KT) is widely used in sports for performance improvement and injury prevention. H... more Kinesio taping (KT) is widely used in sports for performance improvement and injury prevention. However, little is known of the behavior of the muscle region beneath the KT with movement, particularly when the muscle is fatigued. Accordingly, this study investigated the changes in the medial gastrocnemius muscle architecture and fascia thickness when using KT during maximum isometric plantar flexion (MVIC) and badminton lunges following heel rise exercises performed to exhaustion. Eleven healthy collegiate badminton players (4 males and 7 females) were recruited. All of the participants performed two tasks (MVIC and badminton lunge) with a randomized sequence of no taping, KT and sham taping and repeated following exhaustive repetitive heel rise exercise. In the MVIC task, the fascia thickness with the medial gastrocnemius muscle at rest significantly decreased following fatigue induction both without taping and with KT and sham taping (p = 0.036, p = 0.028 and p = 0.025, respectively). In the lunge task, the fascia thickness reduced after fatigue induction in the no taping and sham taping trials; however, no significant change in the fascia thickness occurred in the KT trials. Overall, the results indicate that KT provides a better effect during dynamic movement than in isometric contraction. As one of the world's fastest racket sports 1 , badminton requires players to reach the shuttlecock as fast as possible and with the minimal effort within the physical constraints of the court 2 . In order to meet this requirement, badminton players must master a range of specific footwork strategies. Among these strategies, one of the most important is the forward lunge, which accounts for up to 17.86 ± 4.83% of the movements performed during a singles match 3 . Due to the rapid, repetitive, and stop-and-go nature of the lunge movement, the leg muscles may easily become fatigued and painful, particularly in long rallies. Fatigued muscles not only harm athletic performance, but also increase the risk of injury 4 . Thus, athletes (including badminton players) commonly apply kinesio tape (KT) to the muscle region after suffering muscle fatigue during training or competition . According to the inventor of KT, Dr. Kenzo Kase's report, KT exerts five main physiological effects: skin, circulatory/lymphatic, fascia, muscle, and joint 7 , where these effects are induced through a recoil action produced by the wave-pattern elastic nature of the tape, which leads to skin convolutions of the involved region. For example, by lifting the skin, the tape creates space in the muscle fascia-a soft connective tissue wrapping the muscle fibers, which contains nerves, blood and lymphatic vessels . The study in rabbit hind leg by Shim et al. resulted that the tape induces lymphatic drainage during passive exercise and hastened blood flow to the taped area 10 , thereby helping reduce swelling and speeding up the self-healing process. Thus, as described above, athletes often make use of adjuncts such as braces and taping techniques to speed the muscle recovery process following intensive training or tournament play 11 . Many studies have examined the effects of KT on ability enhancement in vertical jumping 12 , or in improving the medial gastrocnemius muscle strength and push-off force in healthy inactive individuals . It has been shown that KT provides an effective means of enhancing the recovery from

PLOS ONE, Oct 26, 2015

Short-segment pedicle screw instrumentation (SSPI) is used for unstable burst fractures to correc... more Short-segment pedicle screw instrumentation (SSPI) is used for unstable burst fractures to correct deformity and stabilize the spine for fusion. However, pedicle screw loosening, pullout, or breakage often occurs due to the large moment applied during spine motion, leading to poor outcomes. The purpose of this study was to test the ability of a newly designed device, the Trans-Endplate Pedicle Pillar System (TEPPS), to enhance SSPI rigidity and decrease the screw bending moment with a simple posterior approach. Six human cadaveric spines (T11-L3) were harvested. A burst fracture was created at L1, and the SSPI (Moss Miami System) was used for SSPI fixation. Strain gauge sensors were mounted on upper pedicle screws to measure screw load bearing. Segmental motion (T12-L2) was measured under pure moment of 7.5 Nm. The spine was tested sequentially under 4 conditions: intact; first SSPI alone (SSPI-1); SSPI+TEPPS; and second SSPI alone (SSPI-2). SSPI+TEPPS increased fixation rigidity by 41% in flexion/extension, 28% in lateral bending, and 37% in axial rotation compared with SSPI-1 (P<0.001), and it performed even better compared to SSPI-2 (P<0.001 for all). Importantly, the bending moment on the pedicle screws for SSPI+TEPPS was significantly decreased 63% during spine flexion and 47% in lateral bending (p<0.001). TEPPS provided strong anterior support, enhanced SSPI fixation rigidity, and dramatically decreased the load on the pedicle screws. Its biomechanical benefits could potentially improve fusion rates and decrease SSPI instrumentation failure.

European Spine Journal, Dec 4, 2010

Treatment of chronic low back pain due to degenerative lumbar spine conditions often involves fus... more Treatment of chronic low back pain due to degenerative lumbar spine conditions often involves fusion of the symptomatic level. A known risk of this procedure is accelerated adjacent level degeneration. Motion preservation devices have been designed to provide stabilization to the symptomatic motion segment while preserving some physiologic motion. The aim of this study was to compare the changes in relative range of motion caused as a result of application of two non-fusion, dynamic stabilization devices: the Universal Clamp (UC) and the Wallis device. Nine fresh, frozen human lumbar spines (L1-Sacrum) were tested in flexion-extension, lateral bending, and axial rotation with a custom spine simulator. Specimens were tested in four conditions: (1) intact, (2) the Universal Clamp implanted at L3-4 (UC), (3) the UC with a transverse rod added (UCTR), and (4) the Wallis device implanted at L3-4. Total range of motion at 7.5 N-m was determined for each device and compared to intact condition. The UC device (with or without a transverse rod) restricted motion in all planes more than the Wallis. The greatest restriction was observed in flexion. The neutral position of the L3-4 motion segment shifted toward extension with the UC and UCTR. Motion at the adjacent levels remained similar to that observed in the intact spine for all three constructs. These results suggest that the UC device may be an appropriate dynamic stabilization device for degenerative lumbar disorders.

Archives of Physical Medicine and Rehabilitation, 2016

Objective-To assess the correlation of clinician identified myofascial taut bands with their pres... more Objective-To assess the correlation of clinician identified myofascial taut bands with their presence and characteristics on Magnetic Resonance Elastography (MRE) imaging. Design-Cross-sectional study. Participants-A convenience sample of 65 adults (45 women, 20 men) identified by skilled musculoskeletal physicians as having upper trapezius myofascial pain associated taut bands. Interventions-Subjects had their taut bands outlined and were positioned within a 1.5T MRI machine. Shear waves were induced with a pneumatic transducer located over the belly of the involved muscle. Wave propagation was visualized with MRE images across a vibration-cycle. Imaging data was assessed independently by two skilled MRE interpreters. Main Outcome Measures-The primary outcome measure was the determination of the intraand inter-rater reliabilities of MRE taut band identification and their correlation with clinician identification of band presence. Secondary outcomes consisted of the elucidation of the physical characteristics of taut bands and their surrounding muscle tissue. Results-MRE intra-and inter-rater reliability was excellent with Kappa's and 95% Confidence intervals (CI) of 0.86, [0.68, 1.00]; and 0.93, [0.79, 1.00], respectively. Stiffness in MRE identified taut bands was elevated at a mean of 11.5 KPa (±2.4 KPa) and fell to a mean of 5.8 KPa (± 0.9 KPa) in surrounding muscle tissue (p<0.001); muscular tone in trapezius muscles without a taut band was relatively uniform at a mean of 6.6 KPa (±2.1 KPa). Agreement between the physicians and the MRE raters, however, was relatively poor (63.1%, 95% CI [50.2%, 74.7%]).

ASME eBooks, Jun 25, 2010

Information on the elasticity of skeletal muscle (often called muscle stiffness) in vivo has clin... more Information on the elasticity of skeletal muscle (often called muscle stiffness) in vivo has clinical applications in several fields, including orthopaedics, sports medicine, physical medicine and rehabilitation, endocrinology, and rheumatology. Muscle stiffness can be evaluated in either the relaxed (passive) state or the contracted state; the mechanisms involved in each state are different. Muscle resistance to passive stretching comes primarily from two sources: titin and the extracellular matrix (ECM). 1-3 In contrast, when muscle is actively contracted, muscle stiffness reflects the elasticity of the actin-myosin cross-bridges within the muscle fibers. The ECM of skeletal muscle occupies the intercellular space and is indirectly connected to the contractile proteins of the muscle cell through the subsarcolemmal cytoskeleton. 4 In addition to providing mechanical support for the tissue and passive resistance to stretching, the ECM has a number of important roles. 5-7 Two are particularly important: the transmission of force from muscle fibers to the tendon and the transfer of mechanical signaling to the muscle cells (mechanotransduction). Pathological skeletal muscle tissues often exhibit a noticeable difference in stiffness compared with normal healthy tissue. This change in muscle stiffness is thought to likely result from structural or compositional changes in either the ECM or muscle fiber. Examples of these two situations are idiopathic inflammatory myopathy (IIM) and Graves' disease, respectively, both of which are briefly described below. IIM is a heterogeneous group of disorders characterized by symmetrical proximal muscle weakness and elevated serum levels of enzymes derived from skeletal muscle. Types of myositis include dermatomyositis, polymyositis, and inclusion body myositis. All have in common lymphocytic infiltration of muscles, edema within the muscle, altered muscle composition, and impaired muscle function. Associated with these changes is a decrease in

Journal of Biomechanical Science and Engineering, 2014

Although trigger finger is a relatively common hand disorder, its exact cause remains unknown. Wh... more Although trigger finger is a relatively common hand disorder, its exact cause remains unknown. Whether the etiology of the abnormality resides in the tendon or in the pulley continues debate. The purpose of this review is to summarize what is known about the clinical and biomechanical presentation of trigger finger. While the A1 pulleys are more accessible for examination than the flexor tendons during surgery and have been more extensively studied, it should not yet be assumed that the tendons are any less responsible for the entrapment symptom. Previous assessments of these tissues include testing of their compliance, friction coefficient, and changes in gene expression have also been identified in trigger finger tendons. Further investigation into the role of flexor tendons in trigger finger should be performed to facilitate the understanding of the etiology and mechanism of trigger finger development. Future studies could incorporate non-invasive medical imaging in order to understand the appearance and material properties of the involved pulley and tendons, and to combine these characteristics with finger kinematics. Furthermore, understanding the mechanism of biologic adaptations of the A1 pulley and the flexor tendons in response to the mechanical loading might be helpful in providing clues and evidence for effective, novel treatment for trigger finger.

IN VIVO LOCATION OF JOINT CENTERS OF THE SHOULDER SYSTEM: GLENO-HUMERAL AND SCAPULO-THORACIC JOINTS BETWEEN TWO POSTURES DESCRIBING THE ARM ELEVATION IN THE PLANE OF SCAPULA USING TECHNIQUES BASED UPON BIPLANAR RADIOGRAPHY

Journal of Mechanics in Medicine and Biology, Dec 1, 2006

In biomechanics, the knowledge of accurate location of a joint center is essential because equili... more In biomechanics, the knowledge of accurate location of a joint center is essential because equilibration of the external loads and muscular forces about the joint is performed about this specific point. This paper focuses on the location of centers of gleno-humeral joint and scapulo-thoracic joint in a subject moving their arm in the scapular plane with a magnitude of 120°. Biplanar radiography with successive exposures has been used locating anatomical axes of bones. Geometric models of bones were defined allowing access to bone morphology by superposing model projections onto X-ray imaged bone contours. Functional models were used so as to represent the behavior in motion of shoulder joints. These techniques allowed us to access to results describing the linear and angular relative displacements of the shoulder bones between two different postures. The gleno-humeral and scapulo-thoracic finite joint centers (F H and F S ) are first defined through the location of the corresponding helical axis of motion (HAM) moving the joint from positions occupied in initial and final postures. The gleno-humeral and scapulo-thoracic mean joint centers (M H and M S ) are then calculated using a new technique, which defines that each joint center has the point having the smallest migrations while moving continuously from initial to final postures. This allows for the analysis of the linear and angular clearances, which affect joint center migration. The whole continuous movement has been parsed into several steps to test the stability of the mean joint center throughout the motion.

Flexor tendon-pulley interaction after annular pulley reconstruction: A biomechanical study in a dog model In vivo

The Journal of Hand Surgery, Mar 1, 1998

The excursion resistance between the canine flexor digitorum profundus tendon and A2 pulley was c... more The excursion resistance between the canine flexor digitorum profundus tendon and A2 pulley was compared after pulley reconstruction using tendon grafts of either intrasynovial or extrasynovial origin at 10 days, 3 weeks, and 6 weeks after surgery. The changes over time in the underlying flexor digitorum profundus tendon after pulley reconstruction were also evaluated. The excursion resistance for both types of pulley reconstruction was significantly greater than that of the control group at all time periods. The excursion resistance of the extrasynovial tendon graft reconstruction was greater than that of intrasynovial pulley reconstruction at all time periods. In conclusion, pulley reconstruction with intrasynovial tendon grafts may facilitate tendon gliding after surgery.

IN VITRO SIMULATION OF THE STANCE PHASE IN HUMAN GAIT

Journal of Musculoskeletal Research, Jun 1, 2001

The purpose of this study is to develop an electromechanical system for dynamic simulation of the... more The purpose of this study is to develop an electromechanical system for dynamic simulation of the stance phase of a human gait using cadaveric foot specimens. The system can be used for quantification of foot and ankle pathomechanics and design of foot and ankle reconstructive surgeries. Servo-pneumatic systems were used for application of the tibial weight loading and muscle loadings. A four-bar mechanism was constructed to provide the progressive motion of a tibia during the simulation while the external loadings were simultaneously applied. Muscle loadings were estimated based on the physiological cross-sectional area and normal electromyography (EMG) data with the assumption of the linear EMG–force relationship. Ad hoc tuning of the unknown muscle gains was conducted until a reasonable match with the normal vertical ground reaction force profile, center of pressure advancement, and characteristic foot motion events (heel strike, foot flat, heel rise and toe-off) could be made. Three cadaver feet and an artificial foot were tested with five repeated trials. The simulator reproduced the stance phase of a human gait in the sagittal plane with reasonable accuracy and consistency without compromising either kinematics or kinetics of the foot and ankle complex.

A normal data base of posteroanterior roentgenographic measurements of the wrist

Journal of Bone and Joint Surgery, American Volume, Oct 1, 1992

In 120 adults, we measured the dominant wrist on posteroanterior roentgenograms in order to deter... more In 120 adults, we measured the dominant wrist on posteroanterior roentgenograms in order to determine the normal dimensions and variations according to age and sex. Men and women were equally represented as were two age-groups (twenty-five to forty years and forty-one to sixty years). The roentgenograms were made, with standard exposure and development techniques, with the wrist and forearm in a neutral position and the x-ray tube aligned vertical to the radial styloid. The roentgenogram that was made with the wrist in the mid-coronal plane was digitized and was used to measure distances between specified landmarks. The mean ulnar variance was -0.9 millimeter (normal range, -4.2 to 2.3 millimeters). The average carpal height ratio was 53 per cent (normal range, 46 to 61 per cent). The mean radial inclination was 24 degrees (range, 19 to 29 degrees). The carpal-radial and carpal-ulnar ratios were smaller in women. The width of the distal radio-ulnar joint was reduced in the older subjects. There was a significant positive relationship (p < 0.0001) between the maximum force reached and the length of the third metacarpal. We believe that information concerning the normal roentgenographic measurements and relationship between the bones of the wrist can be used (1) to follow the progression of carpal instabilities, osteonecrosis, osteoarthrosis, or rheumatoid arthritis; (2) in clinical research; and (3) in the design of wrist implants.

Prediction of Effects of Mechanical Stress and Estrogen on Bony Structure Using Fuzzy Logic Control

Advances in Bioengineering, 1998

A theoretical model has been developed based on fuzzy logic control to predict bony response to m... more A theoretical model has been developed based on fuzzy logic control to predict bony response to mechanical load and estrogen. The results show good agreement with the experimental findings, which suggests that bone may be regulated by simple remodeling rules, similar to those used in the fuzzy logic control.

Custom-Made Spine Testing Apparatus

PLOS ONE, 2015

<p>A 7.5-Nm moment was applied to the spine during flexion/extension, lateral bending, and ... more <p>A 7.5-Nm moment was applied to the spine during flexion/extension, lateral bending, and axial rotation. Segmental motion was measured using the Optotrak Certus video-based data acquisition system (Northern Digital Inc, Waterloo, Ontario, Canada).</p