Koji Kaneoka

Motion analysis of cervical vertebrae during whiplash loading

STUDY DESIGN The motion of each cervical vertebra during simulated rear-end car collisions was analyzed. OBJECTIVES To clarify the mechanism of zygapophysial joint injury during whiplash loading. SUMMARY OF BACKGROUND DATA The zygapophysial joint is the suspected origin of neck pain after rear-end car collision. However, no studies have been conducted on the mechanisms of zygapophysial joint injuries. METHODS Ten healthy male volunteers participated in this study. Subjects sat on a sled that glided backward on inclined rails and crashed into a damper at 4 km/kr. The motion of the cervical spine was recorded using cineradiography. Each vertebras rotational angle and the instantaneous axes of rotation of the C5-C6 motion segments were quantified. These measurements implemented the template method. RESULTS There were three distinct patterns of cervical spine motion after impact. In the flexion-extension group, C6 rotated backward before the upper vertebrae in the early phase; thus, the cervical spine showed a flexion position (initial flexion). After C6 reached its maximum rotational angle, C5 was induced to extend. As upper motion segments went into flexion, and the lower segments into extension, the cervical spine took an S-shaped position. In this position, the C5-C6 motion segments showed an open-book motion with an upward-shifted instantaneous axis of rotation. CONCLUSIONS The cervical spine is forced to move from the lower vertebrae during rear-end collisions. This motion completely differs from normal extension motion and is probably related to the injury mechanism.

CERVICAL INJURY MECHANISM BASED ON THE ANALYSIS OF HUMAN CERVICAL VERTEBRAL MOTION AND HEAD-NECK-TORSO KINEMATICS DURING LOW SPEED REAR IMPACTS

Twelve male volunteers participated in this study. They sat on a seat mounted on a newly developed sled that simulated actual car impact acceleration. Impact speeds (4, 6 and 8 km/h), seat stiffness, neck muscle tension, and cervical spine alignment were selected for the parameter study of the head-neck-torso kinematics and cervical spine responses. The motion patterns of cervical vertebrae in the crash motion and in the normal motion were compared. Subjects muscles in the relaxed state did not affect the head-neck-torso kinematics upon rear-end impact. The ramping-up motion of the subjects torso was observed due to the seatback inclination. An axial compression force occurred when this motion was applied to the cervical spine, which in turn developed the initial flexion, with the lower cervical vertebral segments extended and rotated prior to the motions of the upper segments. Those motions were beyond the normal physiological cervical motion, which should be attributed to the facet joint injury mechanism. The difference in alignment of the cervical spine affected the impact responses of head and neck markedly. Based on the differences in the alignment of the cervical spine between male and female occupants, it is pointed out that the neck injury incidence tends to become higher for women than for men.(A) For the covering abstract of the conference see IRRD E201172.

Trunk Muscle Activity During Lumbar Stabilization Exercises on Both a Stable and Unstable Surface

STUDY DESIGN Controlled laboratory study. OBJECTIVES To clarify whether differences in surface stability influence trunk muscle activity. BACKGROUND Lumbar stabilization exercises on unstable surfaces are performed widely. One perceived advantage in performing stabilization exercises on unstable surfaces is the potential for increased muscular demand. However, there is little evidence in the literature to help establish whether this assumption is correct. METHODS Nine healthy male subjects performed lumbar stabilization exercises. Pairs of intramuscular fine-wire or surface electrodes were used to record the electromyographic signal amplitude of the rectus abdominis, the external obliques, the transversus abdominis, the erector spinae, and lumbar multifidus. Five exercises were performed on the floor and on an unstable surface: elbow-toe, hand-knee, curl-up, side bridge, and back bridge. The EMG data were normalized as the percentage of the maximum voluntary contraction, and data between doing each exercise on the stable versus unstable surface were compared using a Wilcoxon signed-rank test. RESULTS With the elbow-toe exercise, the activity level for all muscles was enhanced when performed on the unstable surface. When performing the hand-knee and side bridge exercises, activity level of the more global muscles was enhanced when performed on an unstable surface. Performing the curl-up exercise on an unstable surface, increased the activity of the external obliques but reduced transversus abdominis activation. CONCLUSION This study indicates that lumbar stabilization exercises on an unstable surface enhanced the activities of trunk muscles, except for the back bridge exercise.

Lumbar Intervertebral Disk Degeneration in Athletes

Background Several studies have reported that physical loading related to competitive sports activities is associated with lumbar intervertebral disk degeneration. However, the association between types of sports activities and disk degeneration has not been clarified. Hypothesis The frequencies of disk degeneration may vary with the competitive sport because of the different postures and actions specific to each sport. Study Design Cross-sectional study (prevalence); Level of evidence, 3. Methods Study participants were 308 well-trained university athletes (baseball players, basketball players, kendo competitors, runners, soccer players, swimmers) and 71 nonathlete university students (reference group). Disk degeneration was evaluated using T2-weighted magnetic resonance imaging. A self-reported questionnaire concerning low back pain was also conducted. Results The proportions of the participants who had disk degeneration among the baseball players (odds ratio, 3.23) and the swimmers (odds ratio, 2.95) were significantly higher than among the nonathletes using logistic regression analysis. When all patients were grouped together, the association between lifetime experience of low back pain and participants with disk degeneration was significant, and a linear association between the degree of severest low back pain experienced and participants with disk degeneration, analyzed by a Cochran-Mantel-Haenszel test, was also significant. Conclusion Continuous competitive baseball and swimming activities during youth may be associated with disk degeneration. Furthermore, the study indicates that the experience of severe low back pain might be a predictor of disk degeneration in youth. The authors hope that preventive measures and management to protect against disk degeneration and low back pain in athletes will be established by further studies based on these results.

Motion analysis of human cervical vertebrae during low-speed rear impacts by the simulated sled

In an attempt to better understand the mechanism of motion of human cervical vertebrae during low speed impacts, the motion of the cervical vertebrae was analyzed using conditions such as the sitting position and the seat performance characteristics. A new impact sled was developed which simulated actual car impact acceleration. Ten volunteers participated in the experiment. Test speeds of 2, 4, and 6 km/h (.8, 1.6 and 3.2 mi/h) were selected. Two types of seat performance were used; a conventional car seat and a rigid wooden seat. Cineradiography recorded the motion of the cervical vertebrae at impact. The test results showed that a downward and rearward extension motion of C3 compared to C6 occurred and the cervical spine was compressed in an early stage of impact. Moreover, it was found that when the seat was rigid and speeds were increased, the ramping up motion of the body of the subject and neck compression were more typical. The vertebrae motion was analyzed and then compared with the differences between crash motion and normal motion. Based on this study, it is concluded that compressive vertical motion plays an important role in minor neck injuries.

Relationship Between Low Back Pain and Competitive Sports Activities During Youth

Background Low back pain is a significant problem not only for the adult, but also during youth. However, the relationship between low back pain during youth and the duration or types of competitive sports has not been clarified. Hypothesis Low back pain during youth is associated with the duration and types of competitive sports. Study Design Cross-sectional study; Level of evidence, 4. Methods Study participants were 4667 new university students who, from 2004 to 2006, answered a questionnaire concerning low back pain and their participation in competitive sports. The participants were divided into a “no” group (NO), a middle group (MID), and a high group (HI) based on the duration of participation in competitive sports. The answers to the questionnaire were analyzed using the Cochran-Mantel-Haenszel test. Furthermore, we selected students who had participated in the same sport for 5 or more years and categorized the students according to the type of sport. Differences in low back pain among the groups were analyzed using logistic regression with the NO group as the reference group. Results There were statistically significant linear associations in the NO, MID, and HI groups, with 50.0%, 61.8%, and 71.7%, respectively, of the students experiencing low back pain. Among the NO, MID, and HI groups, 4.4%, 5.7%, 9.6%, respectively, had experienced school absence due to low back pain; and 4.0%, 8.5%, and 14.6%, respectively had low back pain with associated lower extremity pain and numbness. All 8 sports groups that were analyzed had experienced low back pain significantly higher than the NO group, and the odds ratios differed by sport with the highest (3.8) for the volleyball group. Conclusion Excessive exposure to competitive sports activities during youth was associated with low back pain and symptoms in the lower extremities, with the severity varying with the sport. To reduce low back pain in youth, factors that may be causing low back pain, such as sport-specific postures and motions, need to be investigated.

Lumbar Intervertebral Disk Degeneration in Elite Competitive Swimmers A Case Control Study

Background The majority of orthopaedic problems experienced by competitive swimmers are related to pain in the shoulder, low back, and knee. Three of 39 national swim team members were hampered in their performance due to lumbar disk herniation at an international competition in 2001. There has been no previous research into lumbar disk degeneration in elite competitive swimmers. Hypothesis Excessive competitive swimming activities accelerate lumbar disk degeneration. Study Design Case control study; Level of evidence, 3. Methods Fifty-six elite swimmers (high-load group, 35 men and 21 women; mean age, 19.6 years) and a control group of 38 university recreational level swimmers (low-load group, 24 men and 14 women; mean age, 21.1 years) were evaluated for lumbar disk degeneration using magnetic resonance imaging. We compared the prevalence of disk degeneration and the disk level between the 2 groups and further investigated the relationship among their symptoms, swimming styles, and disk degeneration. Results Thirty-eight (68%) elite swimmers and 11 (29%) controls had degenerated disks at various disk levels, and the prevalence was significantly greater in the elite swimmers (P = .0002). Comparison between the 2 groups of the prevalence of disk degeneration at each level revealed that the disk level of L5-S1 was significantly more frequently degenerated in the high-load group (P = .026). There was no significant relationship observed among the variables of low back pain symptoms, swimming strokes, and disk degeneration. Conclusion Excessive competitive swimming activities might exaggerate lumbar intervertebral disk degeneration, especially in the L5-S1 intervertebral segment. Keywords lumbar intervertebral disk; disk degeneration; swimming; sports

Influence of seat characteristics on occupant motion in low-speed rear impacts

To analyze the effect of the seat characteristics on dummy motions and human volunteer motions, sled tests simulating low-speed rear impacts were conducted with some seats which had different characteristics. Volunteers cervical vertebral motions were photographed with an X-ray cineradiographic system at a speed of 90 frames/s as well as the visible motions of dummys and volunteers were recorded. Although the tests were conducted under limited conditions, the results indicated the relationship between the occupants visible motions, which are assumed to be closely related to the whiplash injury mechanism, and seat characteristics. It should be noted that the volunteer sled tests were discussed and approved by the Tsukuba University Ethics Committee and the volunteer submitted his informed consent in writing in line with the Helsinki Declaration.

Electromyographic Analysis of Transversus Abdominis and Lumbar Multifidus Using Wire Electrodes During Lumbar Stabilization Exercises

STUDY DESIGN Experimental laboratory study. OBJECTIVES To measure trunk muscle activity using wire electrodes during lumbar stabilization exercises and to examine if more effective exercises to activate the deep trunk muscles (local muscles) exist. BACKGROUND Lumbar stabilization exercises are performed to improve motor control of trunk muscles. However, the magnitude of activation of local muscles during lumbar stabilization exercises is not clear. METHODS Nine healthy men with no history of lumbar spine disorders participated in the study. Fine-wire electrodes were inserted into the transversus abdominis (TrA) and lumbar multifidus, bilaterally. In addition, surface electrodes were attached to the rectus abdominis, external obliques, and erector spinae, bilaterally. Electromyographic signal amplitude was measured during the following exercises: elbow-toe, hand-knee, back bridge, side bridge, and curl-up. Two-way analyses of variance were used to compare muscle activity level among exercises and between sides for each muscle. RESULTS The exercise showing the greatest activity level for the TrA was elbow-toe exercise with contralateral arm and leg lift. In addition, for the TrA, a significant side-to-side difference in activation level was demonstrated for 7 of the 11 exercises that were performed. The activity level of the multifidus was greatest during the back bridge exercises. The curl-up exercise generated the highest activity level for the rectus abdominis and the back bridge, with single-leg lift exercises generating the highest erector spinae activity. CONCLUSIONS The exercises investigated in this study resulted in a wide range of effort level for all 5 muscles monitored. Many of the exercises also resulted in an asymmetrical (right versus left side) activation level for a muscle, including the TrA.

Age-related changes in the thickness of the deep and superficial abdominal muscles in women

The study investigated age-related changes in the thickness of the deep and superficial abdominal muscles of 103 healthy women who could walk independently The participants were classified into five age groups: young (n=26; 20-24 years), young adult (n=26; 25-44 years), middle-aged (n=16; 45-64 years), young-old (n=16; 65-74 years), and old-old (n=19; 75-85 years). The muscle thicknesses of the right rectus abdominis, external oblique, internal oblique, and transversus abdominis were measured using ultrasound imaging. The rectus abdominis was significantly thicker in the young group compared with the young adult, middle-aged, young-old, and old-old groups (p<0.05). The external oblique and internal oblique muscles were significantly thicker in the young group compared with the middle-aged, young-old, and old-old groups (p<0.05). However, there were no significant differences in the thickness of the transversus abdominis between groups. The results suggest that age-related muscle atrophy occurs from an early age in superficial abdominal muscles, such as rectus abdominis, and that age-related atrophy is less in deep abdominal muscles such as the transversus abdominis.