The feasibility of vibration as a tool to assess spinal integrity

Women with Chronic Pelvic Pain Demonstrate Increased Lumbopelvic Muscle Stiffness Compared to Asymptomatic Controls

Background: Although lumbopelvic muscle stiffness is commonly clinically assessed in women with chronic pelvic pain (CPP), it has not been objectively quantified in this population, and its association with other pain-related impairments has not yet been established. Objective: To compare superficial lumbopelvic muscle stiffness in women with and without CPP. In addition, pressure pain threshold (PPT) was compared between groups and the associations between muscle stiffness and PPT were assessed in women with CPP. Study Design: Case-control. Methods: Muscle stiffness and PPT of 11 lumbopelvic muscles were assessed in 149 women with CPP and 48 asymptomatic women. Subjective outcome measures, including pelvic floor function, health history, and psychosocial outcomes, were collected before muscle stiffness and PPT measurements. Analysis of covariance was used to compare muscle stiffness differences between groups, and independent t-tests were used to compare PPT between groups. Associations between measurements of PPT and muscle stiffness were calculated using correlation analysis. Results: Five of the 11 muscles measured were significantly stiffer in women with CPP than those without CPP (p < 0.05). PPT was significantly decreased in all muscles measured in women with CPP; however, there was not a significant association between muscle stiffness and PPT in women with CPP. Conclusion: The study identified the abdominal lumbopelvic muscles that have increased stiffness in women with CPP compared to asymptomatic women. In addition, muscle stiffness and PPT are two distinct impairments within this population. The results suggest that women with CPP have peripheral muscle impairments, which may be addressed without intravaginal or intrarectal intervention. Clinical Trial Registration: NCT04851730.

Non-invasive spinal vibration testing using ultrafast ultrasound imaging: A new way to measure spine function

Ultrafast ultrasound imaging is used to capture driven spinal vibrations as a new method for non-invasive spinal testing in living subjects. Previously, it has been shown that accelerometer-based vibration testing in cadaveric models can reveal the presence, location and magnitude of spinal pathology. However, this process remains an invasive procedure as current non-invasive sensors are inadequate. In this paper, the ability of non-invasive ultrafast ultrasound to quantify in vivo vertebral vibration response across a broad range of frequencies (10–100Hz) in anesthetized pig models is investigated. Close agreement with invasive accelerometer measurements is achieved using the non-invasive ultrasound method, opening up unique opportunities to investigate spinal pathologies.

Structural health monitoring (vibration) as a tool for identifying structural alterations of the lumbar spine: a twin control study

Structural health monitoring (SHM) is an engineering technique used to identify mechanical abnormalities not readily apparent through other means. Recently, SHM has been adapted for use in biological systems, but its invasive nature limits its clinical application. As such, the purpose of this project was to determine if a non-invasive form of SHM could identify structural alterations in the spines of living human subjects. Lumbar spines of 10 twin pairs were visualized by magnetic resonance imaging then assessed by a blinded radiologist to determine whether twin pairs were structurally concordant or discordant. Vibration was then applied to each subject’s spine and the resulting response recorded from sensors overlying lumbar spinous processes. The peak frequency, area under the curve and the root mean square were computed from the frequency response function of each sensor. Statistical analysis demonstrated that in twins whose structural appearance was discordant, peak frequency was significantly different between twin pairs while in concordant twins, no outcomes were significantly different. From these results, we conclude that structural changes within the spine can alter its vibration response. As such, further investigation of SHM to identify spinal abnormalities in larger human populations is warranted.

Use of wavelet energy for spinal cord vibration analysis during spinal surgery

BACKGROUND

An online non-contact measurement system using a laser displacement sensor was developed for obtaining the vibration amplitude of spinal cord and hard tissue.

METHODS

The discrete wavelet transform was used to extract the distinctive features of tissue vibration signals. The spinal cord and spinal cancellous bone can be discriminated by the comparison of wavelet energy over a characteristic scale. We also derived the integro-differential equation of motion to describe the spinal cord vibration excited by the motion of bone.

RESULTS

Experimental results show that the method works well in identifying spinal cord and bone. However, available viscoelastic constants cannot describe the high-frequency features of spinal cord.

CONCLUSIONS

The examined issue of tissue vibration due to the operation power device is a significant problem. The proposed method can be used by a surgery robot, and then spinal surgery may greatly benefit from the enhanced safety of robotics.

The reproducibility of signals from skin-mounted accelerometers following removal and replacement

Signals from skin-mounted accelerometers may contain measurement error when compared to those obtained from bone-mounted sensors. While this error may be minimized through various techniques, additional error may arise as a result of accelerometer removal from the skin and subsequent replacement. The purpose of this experiment was to determine if skin-mounted accelerometer signals remain similar before and after sensor replacement when sensors are stimulated within a consistent vibration environment. The spines of five porcine and five human cadavers were vibrated non-invasively and the resulting response measured using accelerometers glued to the skin overlying the vertebrae of interest (T-9 in porcine cadavers, L2-L4 in human cadavers). Accelerometers were removed, then replaced, to their perceived original positions. Accelerometer signals showed high repeatability within an original placement, however, once replaced, pre- and post-replacement signals were statistically dissimilar in all cadavers tested. Specifically, the similarity of pre- and post-replacement signals was poor for different skin types (porcine and human) and did not improve with accelerometer proximity to the vibration source. From these data, we conclude that accelerometers adhered to the skin overtop spinous processes are able to obtain highly repeatable signals for a given placement, however, signals change significantly after sensor replacement. When skin-mounted accelerometers are used in gait and other studies, investigators should consider performing test/re-test analyses to ensure that sensor data are not affected if sensor replacement is required by design or by accident.

Dynamic response of the idiopathic scoliotic spine to axial cyclic loads

STUDY DESIGN

Numerical techniques were used to study the vibration response of idiopathic scoliosis patients with single thoracic curve.

OBJECTIVE

To analyze the dynamic characteristics of the idiopathic scoliotic spine under the whole-body vibration condition. The influence of the upper body mass was also studied.

SUMMARY OF BACKGROUND DATA

The relationship between the whole-body vibration and the spinal disorders has been investigated using finite element method. However, the dynamic response features of the scoliotic spine to the vibration were poorly understood.

METHODS

The resonant frequencies of the scoliotic spine and the effects of the body weight were studied using a finite element model described previously. Modal and harmonic analysis was conducted. The amplitudes of 6 fundamental vertebral movements around the long, coronal and sagittal axis were quantified in the frequency range of 1 to 35 Hz.

RESULTS

The vibration-induced rotation amplitudes of the apex of the thoracic deformity were higher than that of the lumbar segments. The apical vertebrae had the greatest rotation amplitudes at 2 and 8 Hz, and the largest lateral translation amplitudes at 16 Hz. Vibration could cause large lateral flexion amplitudes in the apex of the thoracic deformity. The apical vertebrae had the largest side flexion amplitudes at 6 Hz. Increasing upper body mass could not change resonant frequency of vibration-induced lateral translation and rotation around the long axis of the apical vertebrae.

CONCLUSION

The scoliotic spine is more sensitive to vibration than the normal spine. For a patient with single thoracic curve, long-term whole-body vibration may do more harm to the thoracic deformity than to the lower lumbar segments. Axial cyclic loads applied to an already deformed spine may cause further rotational and scoliotic deformity. The patients with idiopathic scoliosis are more likely to suffer from vibration-induced spinal disorders than those by normal persons.