The simulated early learning of cervical spine manipulation technique utilising mannequins

Neck stiffness and range of motion for young males and females

Well characterised mechanical response of the normal head-neck complex during passive motion is important to inform and verify physical surrogate and computational models of the human neck, and to inform normal baseline for clinical assessments. For 10 male and 10 female participants aged 20 to 29, the range of motion (ROM) of the neck about three anatomical axes was evaluated in active-seated, passive-lying and active-lying configurations, and the neck stiffness was evaluated in passive-lying. Electromyographic signals from the agonist muscles, normalised to maximum voluntary contractions, were used to provide feedback during passive motions. The effect of sex and configuration on ROM, and the effect of sex on linear estimates of stiffness in three regions of the moment-angle curve, were assessed with linear mixed models and generalised linear models. There were no differences in male and female ROM across all motion directions and configurations. Flexion and axial rotation ROM were configuration dependent. The passive-lying moment-angle relationship was typically non-linear, with higher stiffness (slope) closer to end of ROM. When normalising the passive moment-angle curve to active lying ROM, passive stiffness was sex dependent only for lateral bending region 1 and 2. Aggregate moment-angle corridors were similar for males and females in flexion and extension, but exhibited a higher degree of variation in applied moment for males in lateral bending and axial rotation. These data provide the passive response of the neck to low rate bending and axial rotation angular displacement, which may be useful for computational and surrogate modelling of the human neck.

Mechanical properties of a thoracic spine mannequin with variable stiffness control

OBJECTIVE

To test the posterior-to-anterior stiffness (PAS) of a new thoracic spine training simulator under different conditions of "fixation."

METHODS

We constructed a thoracic spine model using plastic bones and ribs mounted in a wooden box, with skin and soft tissue simulated by layers of silicone and foam. The spine segment could be stiffened with tension applied to cords running through the vertebrae and ribs. We tested PAS at 2 tension levels using a custom-built device to apply repetitive loads at the T6 spinous process (SP) and over adjacent soft tissue (TP) while measuring load and displacement. Stiffness was the slope of the force-displacement curve from 55 to 75 N.

RESULTS

Stiffness in the unconstrained (zero tension) condition over the SP averaged 11.98 N/mm and 6.72 N/mm over the TP. With tension applied, SP stiffness increased to 14.56 N/mm, and TP decreased to 6.15 N/mm.

CONCLUSION

Thoracic model compliance was similar to that reported for humans. The tension control system increased stiffness by 21.3% only over the SP. Stiffness over the TP was dominated by the lower stiffness of the thicker foam layer and did not change. The mannequin with these properties may be suitable for use in manual training of adjusting or PAS testing skills.

A pilot study to determine the consistency of peak forces during cervical spine manipulation utilizing mannequins

OBJECTIVE

Cervical spine manipulation is a complex motor skill used to treat musculoskeletal ailments such as neck pain. There is evidence demonstrating the effectiveness of objective feedback and mannequins for the teaching of spinal manipulation (SM) in the thoracic and lumbar spine. This paper examines the effectiveness of an educational intervention combining both mannequins and force-sensing technology for teaching cervical SM.

METHODS

Fourth-year chiropractic interns were separated into 2 groups: an intervention group and a group trained with the standard curriculum. The intervention included a 60-minute educational session focused on targeting 100 N total peak force cervical manipulations on mannequins, with objective feedback through force-sensing table technology. Pre- and post-CMs were recorded on both a mannequin and a paired student partner, with an attempt to have a target total peak force of 100 N.

RESULTS

Ninety students were recruited. The invention group (n = 46) scored significantly better at the outcome compared to the control group (n = 44) when manipulating the mannequin (p = .003). These improvements did not carry over when manipulating a paired human partner (p = .067).

CONCLUSION

Following a 1-hour cervical SM educational intervention utilizing thrusting on mannequins and force-sensing table technology, students demonstrated improved peak force control for SM delivered on the mannequin. However, this improvement was not carried over to SM delivered on human subjects.

Changes in adjustment force, speed, and direction factors in chiropractic students after 10 weeks undergoing standard technique training

OBJECTIVE

To assess the force profiles of high-velocity low-amplitude thrusts delivered to a mannequin on a force platform by novice students given only verbal instructions.

METHODS

Student volunteers untrained in adjusting delivered a series of adjustments to a mannequin on a force platform. Participants performed 3 light, 3 normal, and 3 heavy thrusts on 5 listings specifying contact point, hand, and direction. Force profiles were analyzed for speed and amplitude, consistency, and force discrimination. Two recording sessions occurred 10 weeks apart.

RESULTS

Sixteen participants (11 females, 5 male) completed the study. Peak forces ranged from 880 to 202 N for heavy thrusts and 322- to 66 N for light thrusts. Thrust rate was from 8.1 to 1.8 Newtons per millisecond. Average coefficients of variability (CV = STD/mean) at each load level (initial/final) were heavy: 17%/15%; normal: 16%/15%; and light: 20%/20%, with 0 as ideal. A force ratio measured students' abilities to distinguish thrust magnitude. The heavy/normal ratio (initial/final) was 1.35/1.39, and the light/normal ratio was 0.70/0.67.

CONCLUSIONS

At this point, without force feedback being used in the classroom, novice students can produce thrusts that look like those of their teachers and of experienced practitioners, but they may not produce similar speed and force values. They are consistent within and between sessions and can discriminate between light and heavy loads. A natural next step in our educational research will be to measure adjustment factors on more experienced cohorts of students with and without the presence of force-feedback training apparatus.

Risks in teaching manipulation techniques in master programmes

High Velocity Techniques (HVT) in the (high) cervical spine are part of the standard curricula of manual therapy educational programmes. Little is known about the risk or the presence of adverse events during skills training sessions. This article describes two cases of students with both being at risk for an adverse event; one with a congenital artery aberration and one with cancer in the high cervical region. Teachers and educational programme developers should take risk management into account when teaching HVT.