Cervical Spine Muscle-Tendon Unit Length Differences Between Neutral and Forward Head Postures: Biomechanical Study Using Human Cadaveric Specimens.

BACKGROUND: Forward head posture (FHP) may be associated with neck pain and poor health-related quality of life. Literature describes only qualitative muscle length changes associated with FHP. OBJECTIVE: The purpose of this study was to quantify how muscle-tendon unit lengths are altered when human cadaveric specimens are placed in alignments representing different severities of FHP. DESIGN: This biomechanical study used 13 fresh-frozen cadaveric cervical spine specimens (Occiput-T1, 54±15 y). METHODS: Specimens' postural changes simulating increasing FHP severity while maintaining horizontal gaze were assessed. Specimen-specific anatomic models derived from computed tomography-based anatomic data were combined with postural data and specimen-specific anatomy of muscle attachment points to estimate the muscle length changes associated with FHP. RESULTS: Forward head posture was associated with flexion of the mid-lower cervical spine and extension of the upper cervical (sub-occipital) spine. Muscles that insert on the cervical spine and function as flexors (termed "cervical flexors") as well as muscles that insert on the cranium and function as extensors ("occipital extensors") shortened in FHP when compared to neutral posture. In contrast, muscles that insert on the cervical spine and function as extensors ("cervical extensors") as well as muscles that insert on the cranium and function as flexors ("occipital flexors") lengthened. The greatest shortening was seen in the major and minor rectus capitis posterior muscles. These muscles cross the Occiput-C2 segments, which exhibited extension to maintain horizontal gaze. The greatest lengthening was seen in posterior muscles crossing the C4-C6 segments, which exhibited the most flexion. LIMITATIONS: This cadaver study did not incorporate the biomechanical influence of active musculature. CONCLUSIONS: This study offers a novel way to quantify postural alignment and muscle length changes associated with FHP. Model predictions are consistent with qualitative descriptions in the literature.

Postural Consequences of Cervical Sagittal Imbalance: A Novel Laboratory Model.

STUDY DESIGN: A biomechanical study using human spine specimens. OBJECTIVE: To study postural compensations in lordosis angles that are necessary to maintain horizontal gaze in the presence of forward head posture and increasing T1 sagittal tilt. SUMMARY OF BACKGROUND DATA: Forward head posture relative to the shoulders, assessed radiographically using the horizontal offset distance between the C2 and C7 vertebral bodies (C2-C7 [sagittal vertical alignment] SVA), is a measure of global cervical imbalance. This may result from kyphotic alignment of cervical segments, muscle imbalance, as well as malalignment of thoracolumbar spine. METHODS: Ten cadaveric cervical spines (occiput-T1) were tested. The T1 vertebra was anchored to a tilting and translating base. The occiput was free to move vertically but its angular orientation was constrained to ensure horizontal gaze regardless of sagittal imbalance. A 5-kg mass was attached to the occiput to mimic head weight. Forward head posture magnitude and T1 tilt were varied and motions of individual vertebrae were measured to calculate C2-C7 SVA and lordosis across C0-C2 and C2-C7. RESULTS: Increasing C2-C7 SVA caused flexion of lower cervical (C2-C7) segments and hyperextension of suboccipital (C0-C1-C2) segments to maintain horizontal gaze. Increasing kyphotic T1 tilt primarily increased lordosis across the C2-C7 segments. Regression models were developed to predict the compensatory C0-C2 and C2-C7 angulation needed to maintain horizontal gaze given values of C2-C7 SVA and T1 tilt. CONCLUSION: This study established predictive relationships between radiographical measures of forward head posture, T1 tilt, and postural compensations in the cervical lordosis angles needed to maintain horizontal gaze. The laboratory model predicted that normalization of C2-C7 SVA will reduce suboccipital (C0-C2) hyperextension, whereas T1 tilt reduction will reduce the hyperextension in the C2-C7 segments. The predictive relationships may help in planning corrective strategy in patients experiencing neck pain, which may be attributed to sagittal malalignment. LEVEL OF EVIDENCE: N/A.

Interdisciplinary group learning in a kinesiology course: a novel approach.

This paper describes an active, collaborative learning project that occurred during a kinesiology course for first-year graduate students in physical (PT) and occupational therapy (OT) that was taught by faculty from both disciplines and designed to promote teamwork and integration of kinesiology concepts. The project required the students to describe and illustrate an assigned functional task, including the involved bony structure, joint mechanics, and muscle actions for joints of the lower extremities. Students from the PT and OT cohorts were intentionally mixed into groups of five students. They were provided with a topic for the assignment and a clear grading rubric. Each group gathered information from a variety of sources to address the topic. The final project was a poster that was presented to the class through an elaborate schedule that required all members of an individual group to present their poster to the group when they arrive at their poster. The presentations were well done and received high marks overall. Student scores were much less critical than faculty scores and included very few comments. The high scores awarded by course faculty indicated the thoroughness of the detail in the posters, as well as the preparedness of the students. An informally determined majority of students commented that being required to present the entire poster required them to comprehend material from the entire course, which we viewed as a positive learning experience.

Agreement of measures obtained radiographically and by the OSI CA-6000 Spine Motion Analyzer for cervical spinal motion.

The purpose of this study was to determine the agreement between angular measures of cervical spinal motion obtained from radiographs and from measures recorded by the OSI CA 6000 Spine Motion Analyzer (OSI SMA) in asymptomatic subjects. Fourteen subjects performed each of the following motions two times while wearing the OSI SMA: cervical flexion, extension, side bending to the right and left. Each motion was performed once for the cervical radiograph. The difference between the values obtained by the two methods was plotted against the average of those values for each subject to illustrate the level of agreement of the two methods. The plotted points were widely scattered, with a large range between the limits of agreement. Range of motion values taken from the OSI SMA were not similar to those obtained from radiographs for the motions of the cervical spine.

Reliability of lumbar spinal palpation, range of motion, and determination of position.

BACKGROUND: The study purposes were to investigate the level of agreement of palpation of lumbar spinous processes between examiners, test-retest repeatability of lumbar spine range of motion, and the reliability of upright position measures in asymptomatic subjects. METHODS: The modified CA 6000 spinal motion apparatus with a new skin fixation system was used by three operators for the test-retest spine measurements (3 days apart), and to obtain measures at one session of spinal position. Mean ranges of motion in all planes for 22 asymptomatic subjects were reported using the Intra-class Correlation Coefficient. RESULTS: Overall, differences in palpation agreement for lumbar segments occurred in three subjects and did not affect range of motion values. For upright spinal position, ICC (2,3) values for sagittal, coronal, and horizontal plane positions were 0.96, 0.80, and 0.98 respectively. There were statistically significant differences between examiners for position values, determined by the Bonferroni t-test (p < 0.05), but the magnitude of the differences were 2 degrees or less, and not considered clinically important. CONCLUSION: Results suggest that lumbar spinal motion measurements and position determination between different operators can be consistent particularly if utilizing the modified instrument. Static lumbar position also appears to be recorded reliably between different operators. Results justify progression to multi-center lumbar research using the modified CA 6000 and the work is considered relevant to medical clinicians working with spinal dysfunction, surgical interventions, or occupational health.