Three-dimensional kinematic stress magnetic resonance image analysis shows promise for detecting altered anatomical relationships of tissues in the cervical spine associated with painful radiculopathy.

For some patients with radiculopathy a source of nerve root compression cannot be identified despite positive electromyography (EMG) evidence. This discrepancy hampers the effective clinical management for these individuals. Although it has been well-established that tissues in the cervical spine move in a three-dimensional (3D) manner, the 3D motions of the neural elements and their relationship to the bones surrounding them are largely unknown even for asymptomatic normal subjects. We hypothesize that abnormal mechanical loading of cervical nerve roots during pain-provoking head positioning may be responsible for radicular pain in those cases in which there is no evidence of nerve root compression on conventional cervical magnetic resonance imaging (MRI) with the neck in the neutral position. This biomechanical imaging proof-of-concept study focused on quantitatively defining the architectural relationships between the neural and bony structures in the cervical spine using measurements derived from 3D MR images acquired in neutral and pain-provoking neck positions for subjects: (1) with radicular symptoms and evidence of root compression by conventional MRI and positive EMG, (2) with radicular symptoms and no evidence of root compression by MRI but positive EMG, and (3) asymptomatic age-matched controls. Function and pain scores were measured, along with neck range of motion, for all subjects. MR imaging was performed in both a neutral position and a pain-provoking position. Anatomical architectural data derived from analysis of the 3D MR images were compared between symptomatic and asymptomatic groups, and the symptomatic groups with and without imaging evidence of root compression. Several differences in the architectural relationships between the bone and neural tissues were identified between the asymptomatic and symptomatic groups. In addition, changes in architectural relationships were also detected between the symptomatic groups with and without imaging evidence of nerve root compression. As demonstrated in the data and a case study the 3D stress MR imaging approach provides utility to identify biomechanical relationships between hard and soft tissues that are otherwise undetected by standard clinical imaging methods. This technique offers a promising approach to detect the source of radiculopathy to inform clinical management for this pathology.

Changes in mechanics and composition of human talar cartilage anlagen during fetal development.

OBJECTIVE: Fetal cartilage anlage provides a framework for endochondral ossification and organization into articular cartilage. We previously reported differences between mechanical properties of talar cartilage anlagen and adult articular cartilage. However, the underlying development-associated changes remain to be established. Delineation of the normal evolvement of mechanical properties and its associated compositional basis provides insight into the natural mechanisms of cartilage maturation. Our goal was to address this issue. MATERIALS AND METHODS: Human fetal cartilage anlagen were harvested from the tali of normal stillborn fetuses from 20 to 36 weeks of gestational age. Data obtained from stress relaxation experiments conducted under confined and unconfined compression configurations were processed to derive the compressive mechanical properties. The compressive mechanical properties were extracted from a linear fit to the equilibrium response in unconfined compression, and by using the nonlinear biphasic theory to fit to the experimental data from the confined compression experiment, both in stress-relaxation. The molecular composition was obtained using Fourier transform infrared (FTIR), and spatial maps of tissue contents per dry weight were created using FTIR imaging. Correlative and regression analyses were performed to identify relationships between the mechanical properties and age, compositional properties and age, and mechanical vs compositional parameters. RESULTS: All of the compositional quantities and the mechanical properties excluding the Poisson's ratio changed with maturation. Stiffness increased by a factor of ∼2.5 and permeability decreased by 20% over the period studied. Collagen content and degree of collagen integrity increased with age by ∼3-fold, while the proteoglycan content decreased by 18%. Significant relations were found between the mechanical and compositional properties. CONCLUSION: The mechanics of fetal talar cartilage is related to its composition, where the collagen and proteoglycan network play a prominent role. An understanding of the mechanisms of early cartilage maturation could provide a framework to guide tissue-engineering strategies.

Cartilage anlagen adapt in response to static deformation.

Connective tissue adaptation, including the development of cartilaginous anlagen into bones, is widely believed to be related to dynamic, intermittent load and stress histories. Static stresses, on the other hand, are generally believed deleterious in tissue adaptation. Using serial MRI in a natural human experiment (manipulation and corrective casting of infant clubfoot), we have observed casting produces two effects: (1) the well recognized change in relative positions of the hindfoot anlagen; (2) a newly recognized immediate shape change in the anlagen. These changes seemingly enhance the rate of growth of the anlagen and of the ossific nucleus. The shape change or deformation in the anlagen would occur as a result of alterations in the magnitudes and directions of loading from soft tissue attachments and muscle activity and would necessarily be associated with changes in the stress states within the anlagen and, when present, the ossific nuclei. Given the known role of load and stress history in tissue adaptation, we presume the reduced stress histories influence the enhanced growth rates. These observations contradict some current theories of tissue adaptation since static, rather than dynamic stresses play a crucial role in accelerating the growth and development of anlagen in the infant clubfoot.

The effect of ankle ligament damage and surgical reconstructions on the mechanics of the ankle and subtalar joints revealed by three-dimensional stress MRI.

Common image-based diagnostic techniques used to detect ankle ligament injuries or the effects of those injuries (e.g., mechanical instability) include magnetic resonance imaging (MRI) and stress radiography. Each of these techniques has limitations. The interpretation of the results obtained through stress radiography, a two-dimensional technique, is highly controversial. MRI can facilitate visualization of soft tissue, but three-dimensional visualization of the full length of the ligaments or detecting partial ligament damage is difficult. This work is part of a long-term study aimed at improving the diagnostic ability of MRI by utilizing it not only to visualize the ligaments but also to detect the mechanical instability produced at the ankle and subtalar joints due to ligament damage. The goal of the present study was to evaluate the ability of a previously developed technique called 3D stress MRI (sMRI) to detect in vitro the effect of damage to the lateral collateral ligaments and the stabilizing effect produced by two common surgical reconstruction techniques. MRI data were collected from eight cadaver limbs in a MR compatible ankle-loading device in neutral, inversion, and anterior drawer. Each specimen was tested intact, after cutting the anterior talo-fibular ligament followed by the calcaneo-fibular ligament and after applying two reconstructions. Ligament injuries produced significant changes in the response of the ankle and subtalar joints to load as detected by the 3D stress MRI technique. Both surgical procedures restored mechanical stability to the joints but they differed in the amount and type of stabilization achieved. We concluded that 3D sMRI can extend the diagnostic power of MRI from the current practice of slice-by-slice visualization to the assessment of mechanical function, the compromise in this function due to injury, and the effects of surgery.

Mechanics of the ankle and subtalar joints revealed through a 3D quasi-static stress MRI technique.

A technique to study the three-dimensional (3D) mechanical characteristics of the ankle and of the subtalar joints in vivo and in vitro is described. The technique uses an MR scanner compatible 3D positioning and loading linkage to load the hindfoot with precise loads while the foot is being scanned. 3D image processing algorithms are used to derive from the acquired MR images bone morphology, hindfoot architecture, and joint kinematics. The technique was employed to study these properties both in vitro and in vivo. The ankle and subtler joint motion and the changes in architecture produced in response to an inversion load and an anterior drawer load were evaluated. The technique was shown to provide reliable measures of bone morphology. The left-to-right variations in bone morphology were less than 5%. The left-to-right variations in unloaded hindfoot architecture parameters were less than 10%, and these properties were only slightly affected by inversion and anterior drawer loads. Inversion and anterior drawer loads produced motion both at the ankle and at the subtalar joint. In addition, high degree of coupling, primarily of internal rotation with inversion, was observed both at the ankle and at the subtalar joint. The in vitro motion produced in response to inversion and anterior drawer load was greater than the in vivo motion. Finally, external motion, measured directly across the ankle complex, produced in response to load was much greater than the bone movements measured through the 3D stress MRI technique indicating the significant effect of soft tissue and skin interference.

A comparison of three screw types for unicortical fixation in the lateral mass of the cervical spine.

STUDY DESIGN: In vitro comparison of three different screws for unicortical fixation in lateral masses of the cervical spine. OBJECTIVES: To compare the axial load-to-failure of cervical lateral mass screws and their revision screws in a cadaveric model. SUMMARY OF BACKGROUND DATA: Lateral mass screws are used for posterior fixation of the cervical spine. Risks to neurovascular structures have led many surgeons to advocate unicortical application of these screws, although fixation strength may vary with screw design. METHODS: Screws from three posterior cervical fixation systems were used: Axis, Starlock/Cervifix, and Summit. Tested were 3.5-mm cancellous screws, along with revision screws for each system. The C3-C6 vertebrae from three cadaveric specimens were fixed with screws inserted into the lateral masses at a depth of 10 mm with 30 degrees cephalad and 20 degrees lateral angulation. Coaxial pullout force was recorded for each primary and revision screw. RESULTS: Axial load-to-failure (mean +/- SD) of the screws was 459 +/- 60 N for Axis screws, 423 +/- 78 N for Starlock screws, and 319 +/- 97 N for Summit screws. The Axis and Starlock screws were significantly stronger than Summit screws (P = 0.017 and P = 0.067, respectively). The load-to-failure of revision screws was much lower than that of primary screws (Axis 54%, Starlock 56%, Summit 63% of the primary screw), without significant difference between screw types. CONCLUSIONS: The Axis and Starlock screws resisted significantly greater axial load-to-failure than did the Summit screws. For all three systems, the revision screws could not restore the load-to-failure of the primary screw in this model. The tested unicortical screws had a consistently higher load-to-failure than those previously tested under similar conditions, suggesting that currently available screws may be superior to those previously tested.

Fixation strength of swellable bone anchors in low-density polyurethane foam.

This study represents a natural extension of our previous efforts in the design and development of a new class of swellable bone anchors, which absorb body fluids and achieve fixation by an expansion-fit mechanism. Specifically, this study investigates (i) correlations between the optimal swelling strain for highest fixation strength and the foam (or bone) density, and (ii) the influence of a threaded surface on the fixation strength of the swellable implant. For this purpose, the immediate and the final (after swelling) fixation strengths of two variations of the swellable bone anchor designs (a smooth anchor and a screw anchor) were measured in two different foams (used to simulate bone) with different densities. The amount of swelling was varied systematically for each foam and anchor design combinations. This study indicates that the screw swellable anchors have higher initial fixation strength than smooth swellable anchors, but the final fixation strengths of both anchors are quite similar. Further, it is observed that the optimal swelling strain decreased with increasing foam density. Both the smooth and screw swellable anchors were also found to exhibit higher fixation strengths than the metallic screws of similar geometry.

Quantitative measurement of ankle passive flexibility using an arthrometer on sprained ankles.

OBJECTIVE: The purpose of this study was to quantitatively examine the flexibility of sprained ankles using an arthrometer device and compare the differences in flexibility between ankles following the first sprains and ankles with repeated severe sprains and chronic symptoms. DESIGN: A retrospective in vivo study was used. BACKGROUND: Many in vitro studies have demonstrated a significant role of joint flexibility in determining mechanical laxity of human cadaveric ankles after sectioning of the lateral ligaments, but few in vivo studies have used the technique to provide objective measurement on the sprained ankles. Furthermore, there is a lack of extensive studies that compared the difference in the ankle flexibility between ankles following the first sprain and ankles with multiple repeated severe sprains and chronic symptoms. METHODS: A total of 27 subjects with unilateral ankle sprains participated in this study. The subjects were divided into a first injury group (group A, n=12) and a chronic symptom group (group B, n=15) based on the history of their ankle injuries. The ankle flexibility in anterior drawer and inversion/eversion tests was measured in both ankles of the subjects using an arthrometer device, the ankle flexibility tester -- a six-degree-of-freedom instrumented linkage used for measurements of applied forces/moments and resultant rotations and/or translations of the ankle joint complex. The difference in ankle flexibility between the injured ankle and the contralateral intact side was analyzed. RESULTS: The flexibility in anterior drawer test of the injured ankles significantly increased compared to the intact ankles of the same individual in group B, but the same difference was not significant in group A. There were more subjects in group B (46.6%) than in group A (33.3%) who showed a sign of mechanical laxity in their injured ankles. CONCLUSIONS: The results indicated that the approach with measurement of ankle flexibility may be a potential tool used to detect the mechanical laxity in the sprained ankles. A tendency was found that patients with multiple ankle sprains and chronic symptoms had a higher occurrence rate of mechanical laxity. The result of the present study may also be interpreted that the ankles with mechanical laxity had higher risk of re-injury and leading to chronic symptoms.

Biological and mechanical characteristics of the interface between a new swelling anchor and bone.

We recently evaluated the peak pullout loads for anchors made from our new copolymeric swelling-type material compared with anchors made of a nonswelling material. In vitro and in vivo peak pullout loads of these anchors were evaluated after different intervals of implantation in the lateral femoral condyles of New Zealand White rabbits. Scanning electron microscopy and energy dispersive x-ray analyses were additionally performed on selected retrieved samples after pullout to examine the characteristics of bone attachment to the implant. The mean peak pullout load was greater for the swelling anchors than for the nonswelling anchors after 48 hours in vitro (46.0 +/- 15.8 compared with 10.8 +/- 9.1 N, p = 0.0541). After 2 weeks in vivo, it was significantly greater for the swelling anchors than for the nonswelling controls (177.7 +/- 41.3 compared with 53.7 +/- 17.5 N, p = 0.0024). The peak pullout load was also greater for the swelling anchors after 8 weeks in vivo; however, this difference was less pronounced than at 2 weeks (101.8 +/- 35.0 compared with 58.9 +/- 9.7 N, p = 0.0508). Furthermore, the swelling implants tended to induce bone deposition at the bone-implant interface. Results from this investigation reveal that the new family of dynamic implants has potential for applications requiring fixation to cancellous or osteoporotic bone.

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 degrees 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.

The three-dimensional passive support characteristics of ankle braces.

Studies of the passive support provided by ankle braces have focused primarily on inversion support. The goal of this study was to develop a technique to measure the support provided by ankle braces in all rotational directions and to use this technique to compare four common braces (Ascend, Swede-O, Aircast, and Active Ankle). For this purpose, a 6 degrees-of-freedom linkage was used to measure the flexibility of the ankle complex in 10 healthy subjects. Each subject was tested without brace support and with each of the four braces. Testing was repeated on each subject on two different occasions. The angular displacement at specified moment values and the four segmental flexibility values obtained from the loading portion of the moment-angular displacement data were used in the data analysis. Repeated measure analysis of variance followed by a Student Neuman-Keuls test at p < 0.05 was performed. This statistical analysis was used to identify significant differences among the braces and differences between each brace and the no brace condition. Each of the four braces provided significant support in inversion, eversion, and internal rotation, but the amount of support varied significantly among the braces. In external rotation, only the stirrup braces provided significant support. The braces also varied significantly in the amount of interference with dorsiflexion and plantar flexion. Clinicians may be assisted by objective data on the amount and nature of passive support when prescribing braces to their patients.

Changes in the flexibility characteristics of the ankle complex due to damage to the lateral collateral ligaments: an in vitro and in vivo study.

This study was part of a long-term effort to develop a reliable diagnostic procedure for ankle ligament injuries. Earlier efforts led to the development and validation of a six-degrees-of-freedom instrumented linkage capable of measuring the flexibility characteristics of the ankle complex in vitro and in vivo. The major goal of the present study was to determine if these flexibility measurements are sufficiently sensitive to detect the presence of damage to the lateral collateral ligaments of the ankle joint both in vitro and in vivo. The in vitro testing was conducted on the legs from six fresh cadavers before and after serial sectioning of the anterior talofibular ligament and the calcaneofibular ligament. The flexibility in inversion-eversion, anterior drawer, and internal-external rotation was measured before and after resection of the ligaments. The in vivo testing was conducted on five patients with unilateral injuries to the ankle ligament. The flexibility evaluation used for in vitro specimens was also performed on both the injured and the intact ankles. For the in vitro testing, the data analysis was based on comparison of flexibility values before and after resection of the ligaments, whereas the data analysis for the in vivo testing was based on comparison of the flexibility of the injured joint with that of the intact contralateral joint. The results of the in vitro study indicated that both an isolated rupture of the anterior talofibular ligament and combined damage of the anterior talofibular and calcaneofibular ligaments produce statistically significant changes in flexibility. Furthermore, the most sensitive parameters to the presence of ligament injuries were found to be early flexibility in anterior drawer, early flexibility in inversion, and the amount of coupling between internal rotation and inversion. These parameters provided a basis for differentiating between an isolated injury to the anterior talofibular ligament and a combined anterior talofibular and calcaneofibular ligament injury. For an isolated anterior talofibular ligament injury, a significant increase in flexibility in anterior drawer was present, whereas the increase in inversion flexibility or in the amount of coupling was insignificant. However, the increases in inversion flexibility and the amount of coupling became significant when both ligaments were involved. The results of the in vivo study indicated that significant changes in flexibility can be detected in patients with lateral ankle injuries. Finally, both the in vitro and in vivo results suggest that development of a reliable diagnostic test for ankle ligament injury based on changes in passive flexibility may be possible.

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 no 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.

Development of self-anchoring bone implants. I. Processing and material characterization.

We recently designed and produced a family of new swelling-type materials that are potentially capable of self-fixation in bone. These materials are designed to absorb body fluids and swell by small amounts, which will allow the implants made from these materials to achieve self-fixation by an expansion-fit mechanism. The developed material system is essentially a crosslinked random copolymer based on poly (methyl methacrylate-acrylic acid). For potential structural (load-bearing) bioimplant applications, we reinforced this copolymer with AS-4 carbon and Kevlar 49 fibers. The details of processing these materials and the steps involved in optimizing their microstructures are presented in this article. A set of mechanical tests were performed on these materials in both dry and swollen conditions to measure their moduli and yield strengths. In the dry state, the copolymers were found to exhibit Young's moduli in the range of 3 to 4 GPa and yield strengths in the range of 70 to 85 MPa. The reinforced composites exhibited moduli in the range of 15 to 65 GPa and yield strengths in the range of 125 to 500 MPa. Upon controlling the volumetric swelling in these materials to be less than about 10%, the loss in mechanical properties was found to be less than about 30%. These hygromechanical properties are well suited for self-anchoring bone implant applications.

Development of self-anchoring bone implants. II. Bone-implant interface characteristics in vitro.

A new swelling copolymeric material suitable for self-anchoring bone implants was introduced in part I of this two-part article. The main goal in the second part of the study was to investigate the in vitro fixation characteristics of these novel implants in bone using push-out mechanical testing. Specifically, we examined the various factors that influence the in vitro fixation levels achieved by these anchors and identified a range of copolymer compositions that provide good fixation characteristics for these implants. The factors studied included the copolymer composition, presence of AS-4 carbon fiber reinforcement, and the time of implantation (in an environment of saline solution). The push-out tests were conducted on smooth cylindrical plugs of the swelling materials that were implanted in bovine cortical bone. The bone-implant system was then immersed in saline solution for various periods of time ranging from 1 to 28 days prior to push-out testing. The refixation characteristics of the implants were also investigated in this study by performing repeated push-out tests on a single implant without completely dislodging the implant from the bone. Holding strengths comparable and often exceeding many current orthopedic fixation techniques were obtained (push-out load exceeding 1000 N and shear strength exceeding 7 MPa) with the implant having 80/20 to 70/30 methyl methacrylate/acrylic acid ratios. Furthermore, more than 80% of the ultimate holding strength could be achieved within 7 days of implantation at ambient temperature for the 80/20 composite implants. Excellent refixation properties were demonstrated in which the implant regained its full holding strength in the bone immediately after an initial failure. These results indicate great potential for the possible use of these implants for orthopedic applications such as suture anchoring and internal fracture fixations.

A six-degrees-of-freedom instrumented linkage for measuring the flexibility characteristics of the ankle joint complex.

Diagnosis of ligament injuries to the ankle joint complex is a difficult clinical problem which relies primarily on manual physical examination and on radiographic evaluations. In an attempt to develop a reliable, quantitative diagnostic tool for such injuries we developed a six-degrees-of-freedom instrumented linkage (Ankle Flexibility Tester-AFT) capable of measuring the flexibility characteristics of the ankle joint complex in vivo. The unique non-serial structure of this linkage was such that these characteristics were recorded directly in an ]anatomical coordinate system which enhanced clinical interpretation. The goal of the present study was to develop this linkage and to test its accuracy and its test-retest reliability. The positional accuracy of the AFT was measured and was found to be better than 0.5 mm for translation and 1.2 degrees for rotations. The results obtained from a study conducted on two cadaveric specimens indicate negligible effect of loading rate on the flexibility characteristics within the range of possible manually applied loads. Finally, the reliability of the AFT was examined from test-retest studies conducted on a total of thirteen young healthy volunteers. The intraclass correlation coefficient (ICC), calculated from the test-retest data, indicated a reliability higher than 0.85. It was concluded that the high reliability and accuracy of the AFT, its simplicity of operation, the easy alignment procedure, the on-line load-displacement results, and the elimination of complex data processing render this device suitable for use in the clinic as well as in the research laboratory.

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 degrees to 60 degrees and hip motion during forward bending ranges from 26 degrees to 66 degrees. 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 degrees: 41.6 degrees from the lumbar spine and 69.4 degrees 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 degrees), middle (30-60 degrees), and late (60-90 degrees) 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.

Technique for in vivo measurement of the three-dimensional kinematics and laxity characteristics of the ankle joint complex.

We introduce here a technique to measure the three-dimensional kinematics and laxity characteristics of the ankle joint complex in vivo. The system consists of an optoelectric, kinematic data acquisition system that is used to measure the motion of the ankle joint complex in response to controlled moments applied through a system of pneumatic actuators. As a first step toward development of the method into a quantitative diagnostic tool for injuries of ankle ligaments, we addressed the following questions: (a) What is the reliability for measurement of range of motion and laxity of the ankle joint complex? (b) Are there significant differences in laxity between the left and right joints of a healthy individual? and (c) Are there significant differences in laxity of the ankle joint complex between men and women? To answer these questions, we performed repeated measures of range of motion and laxity of paired ankles in a population of 18 healthy young individuals. The high intraclass correlation coefficients obtained from the statistical analysis indicate that the new experimental system is highly reliable in measurement of total range of motion and total laxity of the ankle joint complex. We further concluded that, within the statistical power available in our experimental design, there are no significant differences in either range of motion or laxity between left and right ankles of healthy individuals or between men and women.

Objective diagnosis of equinus during gait prior to and following a tibial nerve block.

A quantitative evaluation technique has been developed to assist the clinician in the diagnosis and treatment of ankle equinus deformity. Specifically, the work focuses on accomplishing two major goals: 1) to develop a reliable set of quantitative criteria to assess the degree of dysfunction of the ankle joint during locomotion in patients with equinus deformity; and 2) to determine the effect of various treatment modalities on the ambulatory performance of patients with equinus deformity. A statistically significant difference in two key gait parameters has been demonstrated between healthy subjects and those with equinus deformity.

Objective identification of ankle equinus deformity and resulting contracture.

A quantitative diagnostic technique is described for identifying contracture at the ankle joint in patients with equinus deformity, hence addressing the shortcoming of the conventional clinical diagnostic procedure. To gain a better understanding of how contracture contributes to equinus deformity, a study was designed that compared the torque about the ankle joint before and after administering a tibial nerve block to equinus patients and to a control group. Functional equinus, manifested by walking and early heel rise, is defined as inadequate dorsiflexion for normal gait. The ability to accurately identify an equinus condition, and contracture as the contributing factor in equinus deformity, has important implications for the type of treatment prescribed and the evaluation of treatment effectiveness.