Sorin Siegler

ISB recommendation on definitions of joint coordinate system of various joints for the reporting of human joint motion-part I: ankle, hip, and spine

The Standardization and Terminology Committee (STC) of the International Society of Biomechanics (ISB) proposes a general reporting standard for joint kinematics based on the Joint Coordinate System (JCS), first proposed by Grood and Suntay for the knee joint in 1983 (J. Biomech. Eng. 105 (1983) 136). There is currently a lack of standard for reporting joint motion in the field of biomechanics for human movement, and the JCS as proposed by Grood and Suntay has the advantage of reporting joint motions in clinically relevant terms. In this communication, the STC proposes definitions of JCS for the ankle, hip, and spine. Definitions for other joints (such as shoulder, elbow, hand and wrist, temporomandibular joint (TMJ), and whole body) will be reported in later parts of the series. The STC is publishing these recommendations so as to encourage their use, to stimulate feedback and discussion, and to facilitate further revisions. For each joint, a standard for the local axis system in each articulating bone is generated. These axes then standardize the JCS. Adopting these standards will lead to better communication among researchers and clinicians.

Analysis of Lumbar Spine and Hip Motion During Forward Bending in Subjects With and Without a History of Low Back Pain

Study Design. This study analyzed two groups of subjects during forward bending. Group 1 (n = 20) contained subjects with a history of low back pain and Group 2 (n = 21) included subjects without a history of low back pain. Objective. The purposes of this study were to establish the amount and pattern of lumbar spine and hip motion during forward bending, and determine differences in motion in subjects with and without a history of low back pain. Summary of Background Data. Reported values for lumbar spine motion during forward bending vary from 23.9° to 60° and hip motion during forward bending ranges from 26° to 66°. There has been no direct study of both lumbar spine and hip motion during forward bending in subjects with and without a history of low back pain to establish differences in total amounts or pattern of lumbar spine and hip motion during forward bending. Methods. A three‐dimensional optoelectric motion analysis system was used to measure the amount and velocity of lumbar spine and hip motion during forward bending. Each subject performed three trials of forward bending that were averaged and used for statistical analysis. Hamstring flexibility was also assessed by two clinical tests, the passive straight leg raising and active knee extension tests. Results. Mean total forward bending for all subjects was 111°: 41.6° from the lumbar spine and 69.4° from the hips. There were no group differences for total amounts of lumbar spine and hip motion or velocity during forward bending. The pattern of motion was described by calculating lumbar‐to‐hip flexion ratios for early (0‐30°), middle (30‐60°), and late (60‐90°) forward bending. For all subjects, mean lumbar‐to‐hip ratios for early, middle, and late forward bending were 1.9, 0.9, and 0.4, respectively. Therefore, the lumbar spine had a greater contribution to early forward bending, the lumbar spine and hips contributed almost equally to middle forward bending, and the hips had a greater contribution to late forward bending. A t test revealed a difference between groups for the pattern of motion. Group 1 tended to move more at their lumbar spine during early forward bending and had a significantly lower lumbar‐to‐hip flexion ratio during middle forward bending (P < 0.01). Hamstring flexibility was strongly correlated to motion in subjects with a history of low back pain, but not in healthy subjects. Conclusions. The results provide quantitative data to guide clinical assessment of forward bending motion. Results also suggest that although people with a history of low back pain have amounts of lumbar spine and hip motion during forward bending similar to those of healthy subjects, the pattern of motion is different. It may be desirable to teach patients with a history of low back pain to use more hip motion during early forward bending, and hamstring stretching may be helpful for encouraging earlier hip motion.

The Three-Dimensional Kinematics and Flexibility Characteristics of the Human Ankle and Subtalar Joints—Part I: Kinematics

The in-vitro, three dimensional kinematic characteristics of the human ankle and subtalar joint were investigated in this study. The main goals of this investigation were: 1) To determine the range of motion of the foot-shank complex and the associated range of motion of the ankle and subtalar joints; 2) To determine the kinematic coupling characteristics of the foot-shank complex, and 3) To identify the relationship between movements at the ankle and subtalar joints and the resulting motion produced between the foot and the shank. The tests were conducted on fifteen fresh amputated lower limbs and consisted of incrementally displacing the foot with respect to the shank while the motion of the articulating bones was measured through a three dimensional position data acquisition system. The kinematic analysis was based on the helical axis parameters describing the incremental displacements between any two of the three articulating bones and on a joint coordinate system used to describe the relative position between the bones. From the results of this investigation it was concluded that: 1) The range of motion of the foot-shank complex in any direction (dorsiflexion/plantarflexion, inversion/eversion and internal rotation/external rotation) is larger than that of either the ankle joint or the subtalar joint.; 2) Large kinematic coupling values are present at the foot-shank complex in inversion/eversion and in internal rotation/external rotation. However, only a slight amount of coupling was observed to occur in dorsiflexion/plantarflexion.; 3) Neither the ankle joint nor the subtalar joint are acting as ideal hinge joints with a fixed axis of rotation.; 4) Motion of the foot-shank complex in any direction is the result of rotations at both the ankle and the subtalar joints. However, the contribution of the ankle joint to dorsiflexion/plantarflexion of the foot-shank complex is larger than that of the subtalar joint and the contribution of the subtalar joint to inversion/eversion is larger than that of the ankle joint.; 5) The ankle and the subtalar joints have an approximately equal contribution to internal rotation/external rotation movements of the foot-shank complex.

The Mechanical Characteristics of the Collateral Ligaments of the Human Ankle Joint

In the present study, the tensile mechanical properties of all of the collateral ligaments of the human ankle joint were determined, in vitro, from tensile tests conducted on 120 ligaments obtained from 20 fresh lower limbs. The ultimate load of the lateral collateral ligaments increased in an anteroposterior sequence, with the anterior fibulotalar ligament less than the fibulocalcaneal ligament and less than the posterior fibulotalar ligament. For the medial collateral ligaments, the increasing order of ultimate load was found to be tibiocalcaneal ligament, tibionavicular ligament, tibiospring ligament, posterior tibiotalar ligament. The posterior tibiotalar ligament and tibiospring ligament, so frequently neglected in the anatomical and orthopaedic literature, demonstrated the highest yield force and ultimate load of all of the collateral ligaments of the ankle. Additionally, the tibiospring ligament showed high yield and ultimate elongation properties probably related to its distal attachment to the spring ligament. The fibulocalcaneal ligament was found to have high linear elastic modulus suggesting some type of unique material properties or internal fiber organization. Knowledge of the mechanical characteristics of the ligaments of the ankle joint contributes to an understanding of their normal function, pathomechanics of injury, and their optimal surgical reparative procedure and reconstructive material. A knowledge of the normal mechanical properties of the ankle ligaments provides a data base to evaluate which of the multiplicity of present tendon graft materials has mechanical properties similar to those of the ligaments to be replaced. Those tendon grafts will be the most suitable for replacement of specific ligaments. Finally, data on the mechanical properties of these ligaments offer the possibility for evaluating any future biological or prosthetic grafts.

Kinematic Analysis of Lumbar and Hip Motion While Rising From a Forward, Flexed Position in Patients With and Without a History of Low Back Pain

Study Design. This study analyzed two groups of individuals during return to an upright position (extension) from a forward, bent position. Group 1 (n = 12) included individuals with a history of low back pain who were currently asymptomatic, and group 2 (n = 12) included individuals with no history of low back pain. Objectives. To determine the amount and pattern of lumbar spine and hip motion that occur as an individual rises from a forward, flexed position, to determine if differences exist in this measurement between individuals with and without a history of low back pain, and to determine if hamstring length is related to the pattern of motion. Summary of Background Data. Reports of interaction between lumbar spine and hip movement vary for forward bending and extension. Differences may be a result of variations in measurement methods, loading conditions, or the pathology present, such as low back pain. Methods. A three‐dimensional optoelectric motion analysis system was used to measure the amount and velocity of lumbar spine and hip motion during extension. Each participant in the study performed three trials of a complete flexion‐extension cycle at a self‐selected speed. The data for the extension portion of the cycle were averaged and used for statistical analysis. Hamstring length also was determined using two clinical tests, the passive straight‐leg raise and the active knee‐extension tests. Results. The pattern of movement was described by calculating lumbar to hip extension ratios for each 25% interval of total extension. Individuals with a history of low back pain tended to move from the lumbar spine earlier than those with no history of low back pain, especially in the initial 25% of the extension motion. For all participants, mean lumbar to hip extension ratios were 0.26 for 0–25% of extension, 0.61 for 25–50%, 0.81 for 50–75%, and 2.3 for 75–100%. The lumbar to hip ratios were different in each 25% interval, demonstrating that the hips had a greater contribution to early extension, with the lumbar spine contribution increasing in the middle intervals and becoming the primary source of motion in the final interval. When lumbar to hip extension ratios were compared with corresponding intervals of flexion, three of four were positively correlated to flexion ratios, demonstrating a reversible lumbopelvic rhythm. Although participants with a history of low back pain had significantly tighter hamstrings than participants with no history of low back pain, hamstring length was not correlated with any of the kinematic characteristics during extension. Conclusions. Participants who were currently asymptomatic but had a history of low back pain moved in a manner similar to that of participants with no history of low back pain except that they demonstrated greater lumbar motion and velocity during the initial phase of extension. This may have been the result of low back pain or a contributing factor in recurrent low back pain.

Transforaminal Lumbar Interbody Fusion: The Effect of Various Instrumentation Techniques on the Flexibility of the Lumbar Spine

Study Design. In vitro comparison of four reconstruction techniques following transforaminal lumbar interbody fusion in a human cadaveric model. Introduction. Transforaminal lumbar interbody fusion (TLIF) is a relatively new technique that avoids the morbidity of an anterior approach and the nerve root manipulation of a posterior interbody fusion. This study measured the effects of a TLIF on the overall and segmental flexibility of the lumbar spine using four different spinal implant configurations. Summary of Background Data. Anterior lumbar interbody fusion, posterior lumbar interbody fusion, and combined anterior–posterior spinal procedures are gaining wide acceptance for the treatment of selected patients with segmental spinal instability and spondylolisthesis with associated degenerative changes. Each fusion technique may have different effects on the overall flexibility of the lumbar spine. The unilateral TLIF procedure with adjunctive pedicular fixation is one variation of an interbody fusion technique that requires less bony and soft tissue dissection and minimizes nerve root manipulation compared with other interbody fusion methods. Methods. Five fresh-frozen, human lumbar spines were nondestructively subjected to flexion, extension, lateral bending, and axial rotation moments using a previously validated spine flexibility tester, and displacements were measured. Testing the intact lumbar spine was followed by testing of a unilateral L4–L5 TLIF using a single ramp carbon fiber cage without adjunctive internal fixation. The single carbon fiber (Brantigan) cage was inserted obliquely in a posterolateral to anteromedial position in the L4–L5 disc space. Following testing of the cage alone, three different adjunctive stabilization techniques were tested. Posterior stabilization involved one of the following: a contralateral translaminar facet screw, single side/ipsilateral nonsegmental pedicle screw fixation, and bilateral nonsegmental pedicle screw fixation. The overall flexibility of each lumbar spine was calculated from load-displacement curves for each axis of rotation. The flexibility of the L4–L5 segment of each spine was computed from kinematic motion data acquired via attached LED sensors to the L4 and L5 vertebral bodies. Statistical testing was performed with paired t tests. Results. The flexibility of the entire (T12–S1) destabilized spine after TLIF with interbody cage alone and with all three reconstructive techniques was comparable with the intact spine. However, the motion at the L4–L5 segment was significantly increased for the TLIF with interbody cage alone in axial rotation (299% of intact, P < 0.01), with no significant change in flexion–extension (79% of intact, P = 0.22) or lateral bending (87% of intact, P = 0.39). With the addition of a contralateral translaminar facet screw, the motion at the L4–L5 segment remained significantly more flexible in axial rotation (250% of intact, P = 0.06) although less than with the cage alone. With the unilateral pedicle screw construct, the L4–L5 segment remained more flexible in axial rotation (182% of intact, P = 0.07) although significantly less than with the facet screw construct (P < 0.05). The addition of bilateral pedicle screws most closely reapproximated the flexibility of the intact spine with no significant difference in axial rotation (91% of intact, P = 0.30), flexion–extension (93% of intact, P = 0.19), or lateral bending (99% of intact, P = 0.47). The motion at the L4–L5 segment with bilateral pedicle screws was not significantly different than for the intact specimen in axial rotation (144% of intact, P = 0.17), flexion–extension (81% of intact, P = 0.21), or lateral bending (86% of intact, P = 0.27). Conclusions. TLIF reconstruction with a solitary cage did not increase overall spine flexibility from the intact condition but significantly increased segmental flexibility at L4–L5 in axial rotation. A unilateral translaminar facet screw had minimal stabilizing effect at L4–L5. Unilateral pedicle screws further increased stiffness at the L4–L5 segment. However, TLIF with bilateral pedicle screws most closely approximated the L4–L5 segmental flexibility of the intact spine.

PASSIVE AND ACTIVE COMPONENTS OF THE INTERNAL MOMENT DEVELOPED ABOUT THE ANKLE JOINT DURING HUMAN AMBULATION

The internal moment developed about a joint during a functional activity is the result of contraction of muscles and the visco-elastic properties of the joint and its surrounding soft tissues. In this study, the contribution of each one of these mechanisms to the total internal moment developed about the ankle joint during human level walking was assessed. The results indicate that during normal level walking the internal moment about the ankle is mainly due to contraction of muscles surrounding the joint. The contribution of the passive component was found to be negligible. These results, however, were found to be different for the pathological case tested. The results indicated that in a subject with a mild equinus ankle deformity, a substantial portion (21%) of the total internal moment was contributed by the passive resistance of the joint and its surrounding structures.

The Three-Dimensional Kinematics and Flexibility Characteristics of the Human Ankle and Subtalar Joint—Part II: Flexibility Characteristics

The objective of the present study was to investigate the in-vitro, coupled, three-dimensional load-displacement and flexibility characteristics of the human ankle joint complex consisting of the talocrural and the talocalcaneal joints and to determine the effects that sectioning of the anterior talofibular ligament has on these characteristics. Similar to other anatomical joints such as the knee and the intervertebral joint, the ankle joint complex was found to exhibit highly nonlinear load-displacement characteristics with the angular displacement approaching asymptotic values as the external load was increased. Therefore, a procedure of incremental linearization was used to derive the flexibility characteristics of this structure. According to this procedure, external loads were applied to the calcaneus in small increments and its resulting three dimensional displacements were recorded. The incremental flexibility coefficients were then derived by assuming linear load-displacement relationship for each increment. From the results obtained from fifteen human ankle specimens, it was evident that the ankle joint complex exhibit highly coupled flexibility and load-displacement characteristics. It was further concluded that the ankle joint complex is the most flexible in the neighborhood of the unloaded, neutral position and that all the flexibility coefficients of the structure decrease rapidly toward the extremes of the range of motion. Rupture of the anterior talofibular ligament was found to have a significant effect on the load-displacement and flexibility characteristics of the ankle joint complex. This effect was manifested as a change in the load-displacement characteristics and a large increase in the flexibility coefficients primarily in those corresponding to rotations in the transverse and the coronal plane. The results of the present study can provide the necessary data base for the development of quantitative diagnostic technique for identifying the site and the extent of injury to the collateral ligaments of the ankle.

Three-dimensional flexibility characteristics of the human cervical spine in vivo.

Study Design. A test‐retest design to establish the reliability of a new system capable of quantifying the load‐displacement characteristics of the cervical spine. The study was primarily descriptive, but the design allowed comparisons between men and women as well as within‐group comparisons among different cervical motions. Objectives. To determine the flexibility of the entire cervical spine in vivo and to establish the reliability of a new system developed for this purpose. Summary of Background Data. The flexibility of the cervical spine has been studied primarily in vitro by applying loads to isolated osteoligamentous segments. Quantification of the mechanical characteristics of the cervical spine in vivo may provide insights to the effects of pathology and treatment interventions. In vivo flexibility measurements differ from those in vitro in that they involve the entire cervical spine composite, including the muscles, rather than isolated segments. Methods. Our method uses a 6° of freedom mechanical linkage system aligned anatomically according to Grood and Suntay parameters and allows manual application of torque around each axis. We determined the range of motion and flexibility of the cervical spine in a sample of young, healthy subjects (n = 20) for flexion, right lateral bending, and bilateral axial rotation. Results. Acceptable test‐retest reliability were found for range of motion and flexibility measurements performed several days apart. The general shape of the torque‐angle curves was nonlinear and biphasic. An early, very flexible portion of the curve was defined as the neutral zone, and the less flexible, end portion of the curve was defined as the elastic zone. We found that men were less flexible than women and that men could tolerate greater amounts of passively applied torques. All subjects showed significantly greater flexibility and less torque tolerance in axial rotation compared with those values in flexion and lateral bending. Possible anatomic explanations for these differences include the effect of muscle alignment and flexibility differences between synovial and fibrocartilaginous articulations. Conclusions. This study provides data regarding the in vivo flexibility of the human neck in young, healthy subjects and forms the basis for comparison in future studies that assess the effects of pathology and treatment. Men have lower flexibility than women, and axial rotation flexibility is significantly greater than that in lateral bending and flexion.

Three-dimensional, six-degrees-of-freedom kinematics of the human hindfoot during the stance phase of level walking

Abstract The goal of this study was to develop a technique to measure the unconstrained, six-degrees-of-freedom motion of the hindfoot during level walking and to apply this technique to characterize this motion in a young healthy population. The motion was described using a joint coordinate system which provided a description of motion in terms of three angular displacements and three linear displacements. The accuracy of the technique was first determined using a six-degrees-of-freedom linkage. The motion of the hindfoot was then measured during level walking on ten young healthy volunteers. For this purpose, a motion analysis system was used to record the motion of eight reflective skin markers attached over bony landmarks on the tibia-fibula and calcaneus. The results indicate that the baseline accuracy of the technique (not including skin motion) was 1 degree for rotations and 1.4 mm for translations. From the gait data it was concluded that the patterns of hindfoot motion are similar amongst individuals in some joint parameters but not in others. Specifically, dorsiflexion/plantarflexion had a very consistent pattern, followed by inversion/eversion and to a lesser extent by compression/distraction. The other parameters (axial rotation, anterior/posterior displacement and medial/lateral displacement) demonstrated a highly variable pattern amongst the individuals tested. In terms of the range of motion of the six joint parameters it was found that angular excursions were smaller than 20 ° and that linear displacements in both anterior/posterior direction and medial/lateral direction was smaller than 3.5 mm.