Clinical reports and research studies have documented the behavior of chronic low back and neck pain patients. A few hypotheses have attempted to explain these varied clinical and research findings. A new hypothesis, based upon the concept that subfailure injuries of ligaments (spinal ligaments, disc annulus and facet capsules) may cause chronic back pain due to muscle control dysfunction, is presented. The hypothesis has the following sequential steps. Single trauma or cumulative microtrauma causes subfailure injuries of the ligaments and embedded mechanoreceptors. The injured mechanoreceptors generate corrupted transducer signals, which lead to corrupted muscle response pattern produced by the neuromuscular control unit. Muscle coordination and individual muscle force characteristics, i.e. onset, magnitude, and shut-off, are disrupted. This results in abnormal stresses and strains in the ligaments, mechanoreceptors and muscles, and excessive loading of the facet joints. Due to inherently poor healing of spinal ligaments, accelerated degeneration of disc and facet joints may occur. The abnormal conditions may persist, and, over time, may lead to chronic back pain via inflammation of neural tissues. The hypothesis explains many of the clinical observations and research findings about the back pain patients. The hypothesis may help in a better understanding of chronic low back and neck pain patients, and in improved clinical management.

A hypothesis of chronic back pain: ligament subfailure injuries lead to muscle control dysfunction

https://www.archives-pmr.org/article/S0003-9993(01)85923-2/pdf

Back and abdominal muscle function during stabilization exercises

Cervical muscle response during whiplash: evidence of a lengthening muscle contraction.

The validity of whiplash syndrome has been a source of debate in the medical literature for many years. Some authors have published articles suggesting that whiplash injuries are impossible at certain collision speeds; others have stated that the problem is psychological, or is feigned as a means to obtain secondary financial gain. These articles contradict the majority of the literature, which shows that whiplash injuries and their sequelae are a highly prevalent problem that affects a significant proportion of the population. The authors of the current literature critique reviewed the biomedical and engineering literature relating to whiplash syndrome, searching for articles that refuted the validity of whiplash injuries. Twenty articles containing nine distinct statements refuting the validity of whiplash syndrome were found that fit the inclusion criteria. The methodology described in these articles was evaluated critically to determine if the authors' observations regarding the validity of whiplash syndrome were scientifically sound. The authors of the current critique found that all of the articles contained significant methodologic flaws with regard to their respective authors' statements refuting the validity of whiplash syndrome. The most frequently found flaws were inadequate study size, nonrepresentative study sample, nonrepresentative crash conditions (for crash tests), and inappropriate study design. As a result of the current literature review, it was determined that there is no epidemiologic or scientific basis in the literature for the following statements: whiplash injuries do not lead to chronic pain, rear impact collisions that do not result in vehicle damage are unlikely to cause injury, and whiplash trauma is biomechanically comparable with common movements of daily living. Language: en

A review and methodologic critique of the literature refuting whiplash syndrome.

Study Design. Cross-sectional design. Objective. To compare lumbar multifidus electromyographic activity (EMG) during predictable and unpredictable trunk loading between people with and without recurrent unilateral low back pain (LBP) during symptom remission. Summary of Background Data. Unpredictable loading is a common injury mechanism for LBP. Paraspinal muscle responses to trunk loading differ between people with and without a history of LBP, but whether the response differs between specific regions within the paraspinal muscles is unclear. Differences between deep (DM) and superficial fibers (SM) of multifidus have been implicated in other tasks. It is unknown whether DM and SM EMG differ between people in remission from recurrent LBP and healthy people during trunk loading. Methods. DM and SM EMG was recorded bilaterally at L5 with intramuscular electrodes during predictable and unpredictable trunk loading and compared during 10 milliseconds epochs (250 milliseconds before to 150 milliseconds after loading) between sides, loading conditions, and groups. Results. DM EMG increased above baseline before and after predictable load onset, but returned to baseline at the time of impact. Both DM EMG bursts were less in the remission group and less on the non-painful side. Peak SM EMG amplitude on the previously painful side was earlier in the remission group than healthy participants. DM and SM EMG were less after unpredictable load onset in the remission group than healthy participants. Conclusion. Despite symptom remission, DM EMG during predictable loading and DM and SM EMG during unpredictable loading were less in people with recurrent LBP than healthy participants.

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People with recurrent low back pain respond differently to trunk loading despite remission from symptoms.

A study was conducted to find out whether in a rear-impact motor vehicle accident, velocity changes in the impact vehicle of between 10 and 15 km/h can cause so-called “whiplash injuries”. An assessment of the actual injury mechanism of such whiplash injuries and comparison of vehicle rear-end collisions with amusement park bumper car collisions was also carried out. The study was based on experimental biochemical, kinematic, and clinical analysis with volunteers. In Europe between DM 10 and 20 billion each year is paid out by insurance companies alone for whiplash injuries, although various studies show that the biodynamic stresses arising in the case of slight to moderate vehicle damage may not be high enough to cause such injuries. Most of these experimental studies with cadavers, dummies, and some with volunteers were performed with velocity changes below 10 km/h. About 65% of the insurance claims, however, take place in cases with velocity changes of up to 15 km/h. Fourteen male volunteers (aged 28–47 years; average 33.2 years) and five female volunteers (aged 26–37 years; average 32.8 years) participated in 17 vehicle rear-end collisions and 3 bumper car collisions. All cars were fitted with normal European bumper systems. Before, 1 day after and 4–5 weeks after each vehicle crash test and in two of the three bumper car crash tests a clinical examination, a computerized motion analysis, and an MRI examination with Gd-DTPA of the cervical spine of the test persons were performed. During each crash test, in which the test persons were completely screened-off visually and acoustically, the muscle tension of various neck muscles was recorded by surface eletromyography (EMG). The kinematic responses of the test persons and the forces occurring were measured by accelerometers. The kinematic analyses were performed with movement markers and a screening frequency of 700 Hz. To record the acceleration effects of the target vehicle and the bullet vehicle, vehicle accident data recorders were installed in both. The contact phase of the vehicle structures and the kinematics of the test persons were also recorded using high-speed cameras. The results showed that the range of velocity change (vehicle collisions) was 8.7–14.2 km/h (average 11.4 km/h) and the range of mean acceleration of the target vehicle was 2.1–3.6 g (average 2.7 g). The range of velocity change (bumper car collisions) was 8.3–10.6 km/h (average 9.9 km/h) and the range of mean acceleration of the target bumper car was 1.8–2.6 g (average 2.2 g). No injury signs were found at the physical examinations, computerized motion analyses, or at the MRI examinations. Only one of the male volunteers suffered a reduction of rotation of the cervical spine to the left of 10° for 10 weeks. The kinematic analysis very clearly showed that the whiplash mechanism consists of translation/extension (high energy) of the cervical spine with consecutive flexion (low energy) of the cervical spine: hyperextension of the cervical spine during the vehicle crashes was not observed. All the tests showed that the EMG signal of the neck muscles starts before the head movement takes place. The stresses recorded in the vehicle collisions were in the same range as those recorded in the bumper car crashes. From the extent of the damage to the vehicles after a collision it is possible to determine the level of the velocity change. The study concluded that, the “limit of harmlessness” for stresses arising from rear-end impacts with regard to the velocity changes lies between 10 and 15 km/h. For everyday practice, photographs of the damage to cars involved in a rear-end impact are essential to determine this velocity change. The stress occurring in vehicle rear-end collisions can be compared to the stress in bumper car collisions.

K. Wortler

Papers

Do "whiplash injuries" occur in low-speed rear impacts?