Development of an instrumented couch to measure forces during manual physiotherapy treatment

Devices Used to Measure Force-Time Characteristics of Spinal Manipulations and Mobilizations: A Mixed-Methods Scoping Review on Metrologic Properties and Factors Influencing Use

Background: Spinal manipulations (SMT) and mobilizations (MOB) are interventions commonly performed by many health care providers to manage musculoskeletal conditions. The clinical effects of these interventions are believed to be, at least in part, associated with their force-time characteristics. Numerous devices have been developed to measure the force-time characteristics of these modalities. The use of a device may be facilitated or limited by different factors such as its metrologic properties.

Objectives: This mixed-method scoping review aimed to characterize the metrologic properties of devices used to measure SMT/MOB force-time characteristics and to determine which factors may facilitate or limit the use of such devices within the context of research, education and clinical practice.

Methods: This study followed the Joanna Briggs Institute's framework. The literature search strategy included four concepts: (1) devices, (2) measurement of SMT or MOB force-time characteristics on humans, (3) factors facilitating or limiting the use of devices, and (4) metrologic properties. Two reviewers independently reviewed titles, abstracts and full articles to determine inclusion. To be included, studies had to report on a device metrologic property (e.g., reliability, accuracy) and/or discuss factors that may facilitate or limit the use of the device within the context of research, education or clinical practice. Metrologic properties were extracted per device. Limiting and facilitating factors were extracted and themes were identified.

Results: From the 8,998 studies initially retrieved, 46 studies were finally included. Ten devices measuring SMT/MOB force-time characteristics at the clinician-patient interface and six measuring them at patient-table interfaces were identified. Between zero and eight metrologic properties were reported per device: measurement error (defined as validity, accuracy, fidelity, or calibration), reliability/repeatability, coupling/crosstalk effect, linearity/correlation, sensitivity, variability, drift, and calibration. From the results, five themes related to the facilitating and limiting factors were developed: user-friendliness and versatility, metrologic/intrinsic properties, cost and durability, technique application, and feedback.

Conclusion: Various devices are available to measure SMT/MOB force-time characteristics. Metrologic properties were reported for most devices, but terminology standardization is lacking. The usefulness of a device in a particular context should be determined considering the metrologic properties as well as other potential facilitating and limiting factors.

The development and evaluation of a novel repurposing of a peripheral gaming device for the acquisition of forces applied to a hydraulic treatment plinth

This technical note details the stages taken to create an instrumented hydraulic treatment plinth for the measurement of applied forces in the vertical axis. The modification used a widely available low-cost peripheral gaming device and required only basic construction and computer skills. The instrumented treatment plinth was validated against a laboratory grade force platform across a range of applied masses from 0.5-15 kg, mock Gr I-IV vertebral mobilisations and a dynamic response test. Intraclass correlation coefficients demonstrated poor reliability (0.46) for low masses of 0.5 kg improving to excellent for larger masses up to15 kg respectively; excellent to good reliability (0.97-0.86) for the mock mobilisations and moderate reliability (0.51) for the dynamic response test. The study demonstrates how a cheap peripheral gaming device can be repurposed so that forces applied to a hydraulic treatment plinth can be collected reliably when applied in a clinically reasoned manner.

Design and construction of a novel low-cost device to provide feedback on manually applied forces

STUDY DESIGN

Design and evaluation, technical note.

OBJECTIVES

To describe the design of a simple, low-cost device for providing feedback of manually applied forces to the cervical spine, and to assess the device against specific design criteria.

BACKGROUND

The forces applied during manual therapy may vary by as much as 500% between practitioners. But consistency can be improved in students when they are provided with contemporaneous feedback. The current methods of providing feedback, however, are expensive, complex, and/or preclude their performance in a clinically relevant manner.

METHODS

The design of the device was assessed in accordance of the following criteria: (1) ease of use, (2) low cost, (3) minimal interference with technique, (4) ability to provide feedback with suitable accuracy at forces up to 50 N, and (5) no requirement of specialized skills to construct.

RESULTS

A device is described that interfaces with standard computers through the sound card and measures force, using thin, low-cost, force-sensing resistors. Evaluated against the design criteria, the device (1) is easy to set-up and use, (2) can be produced for under $30 US dollars, (3) creates minimal interference with performance of a variety of techniques, (4) has limits of agreement from -3.8 to 4.2 N for forces of 5 to 45 N and repeatability coefficients of ± 2.0 N or 12%, and (5) can be constructed without specialized skills or knowledge.

CONCLUSION

A device is described that fulfills most of the design criteria for providing feedback on forces for physical therapy students and may have applications in other fields.

Investigation of the frequency and force of chest vibration performed by physiotherapists

PURPOSE

To investigate the frequency and force of chest vibration as applied by 18 physiotherapists working in a teaching hospital.

METHOD

CHEST VIBRATION WAS APPLIED TO A HEALTHY ADULT MALE LYING SUPINE ON A PLINTH WITH SEVEN MOUNTED SENSORS MEASURING FREQUENCY AND FORCE, DURING THREE TEST CONDITIONS: (1) directly on the chest, (2) on the chest through a layer of sheet, and (3) on the chest through a layer of towelling. The influence of gender and current practice area (physiotherapists working in cardiopulmonary areas [cardiopulmonary physiotherapists] and physiotherapists who presently did not work in the cardiopulmonary area, but had treated cardiopulmonary patients within the last year [general practice physiotherapists]) on the frequency and force of chest vibrations was examined.

RESULTS

Physiotherapists demonstrated a mean frequency of 5.7, 5.3, and 5 Hz and a mean maximum force of 272.78, 273.47, and 271.13 N for conditions 1, 2, and 3 respectively. There were no significant differences in the frequency or forces generated by vibration between cardiopulmonary and general practice physiotherapists, between genders, or among the three test conditions.

CONCLUSIONS

Vibration frequency was lower and force higher than previously recorded. Force may vary depending on the patient. The addition of a sheet or towel did not affect the force or frequency of vibration compared to vibration performed directly on the chest.

Calibration of an instrumented treatment table for measuring manual therapy forces applied to the cervical spine

Manual therapy techniques are commonly used to treat musculoskeletal neck disorders, but little is known about the manual forces applied during cervical spine treatment. Forces may vary between practitioners, and this may affect patient outcomes. This study reports the development of an instrumented treatment table and its calibration for measuring posteroanterior-directed forces applied during cervical spine mobilisation. A treatment table surface was instrumented with seven biaxial load cells to measure manually applied forces in three planes. Accuracy of the system was evaluated using known weights (unloaded and loaded to represent a patient's body weight), selected to be consistent with the level of forces expected to be applied during cervical mobilisation. Recorded force values strongly correlated with known weights (Pearson's r=0.999 to 1.000 for forces applied in different directions and locations, unloaded and loaded). The accuracy of forces in the unloaded condition was very good for vertical forces (mean absolute error 1.1N, SD 1.5), and reasonably good for horizontal forces (2.8N, SD 2.4 for mediolateral, 3.4N, SD 1.5 for caudad-cephalad). In the loaded condition absolute error increased slightly for horizontal forces. The accuracy of measured forces indicates the instrumented table is acceptable for measuring cervical mobilisation forces. Using it allows practitioners to perform manual techniques using their usual clinical technique, however interpretation of force data is limited because it represents force applied to the table rather than at a specific joint.

Manual Forces Applied During Posterior-to-Anterior Spinal Mobilization: A Review of the Evidence

OBJECTIVE

The objective of this review was to evaluate the evidence for the consistency of force application by manual therapists when carrying out posterior-to-anterior (PA) mobilization techniques, including the factors that influence the application and measurement of mobilization forces.

METHODS

Studies were identified by searching 6 electronic databases up to April 2005, screening the reference lists of retrieved articles, and contacting experts by e-mail. Relevant articles were defined as those that described the measurement of forces applied during spinal mobilization or discussed the reliability of measurement of manual forces.

RESULTS

Twenty studies described the quantitative measurement of applied force during a PA mobilization technique, with most focusing on the lumbar spine. When defined by magnitude, frequency, amplitude, and displacement, PA mobilization forces are extremely variable among clinicians applying the same manual technique. Variability may be attributed to differences in techniques, measurement or reporting procedures, or variations between therapists or between patients.

CONCLUSIONS

The inconsistency in manual force application during PA spinal mobilization in existing studies suggests that further studies are needed to improve the clinical standardization of manual force application. Future research on mobilization should include forces applied to the cervical and thoracic spines in addition to the lumbar spine while thoroughly describing force parameters and measurement methods to facilitate comparison between studies.

Vibration and its effect on the respiratory system

Vibration is a manual technique used widely to assist with the removal of pulmonary secretions. Little is known about how vibration is applied or its effect on the respiratory system. The purpose of this study was to describe mechanical consequences of vibration on the chest wall of a normal subject and the effects of vibration on expiratory flow rates and volumes. The effects of vibration were compared to other interventions of chest wall compression, chest wall oscillation, cough, huff from high lung volume, inspiration to total lung capacity with relaxed expiration, tidal breathing, and sham. Sixteen physiotherapists applied vibration and other interventions in a randomised order to the chest wall of a healthy adult female subject. The magnitude and direction of the force and the frequency of vibration were measured by an instrumented bed with seven load cells. Inductive plethsysmography measured the change in chest wall circumference with vibration. A heated pneumotachometer measured inspiratory and expiratory flow rates, which were integrated to provide volumes. Vibration was applied with a mean resultant force of 74.4 N (SD 47.1). The mean (SD) change in chest wall circumference and frequency of vibration were 0.8 cm (SD 0.4) and 5.5 Hz (SD 0.8) respectively. The mean peak expiratory flow rate was 0.97 l/s (SD 0.27). Peak expiratory flow rates with vibration were less than 20% of those achieved with cough or huff from high lung volume but greater than with chest wall compression, chest wall oscillation, relaxed expiration from total lung capacity, sham treatment or tidal breathing.

Manual vibration increases expiratory flow rate via increased intrapleural pressure in healthy adults: an experimental study

QUESTION

What is the relationship between vibration of the chest wall and the resulting chest wall force, chest wall circumference,intrapleural pressure, and expiratory flow rate? Is the change in intrapleural pressure during vibration the sum of the intrapleural pressure due to recoil of the lung, chest wall compression, and chest wall oscillation?

DESIGN

Randomised, within-subject,experimental study.

PARTICIPANTS

Seven experienced cardiopulmonary physiotherapists and three healthy adults.

INTERVENTION

Vibration (compression + oscillation), compression alone, and oscillation alone were applied manually to the chest walls of healthy participants during passive exertion and compared with passive expiration alone.

OUTCOME MEASURES

Chest wall force, chest wall circumference, intrapleural pressure, and expiratory flow rate.

RESULTS

During vibration, coherence was high(r2 > 0.97) between external chest wall force, chest wall circumference, intrapleural pressure, and expiratory flow. The mean change in intrapleural pressure during vibration was 9.55 cmH2O (SD 1.66), during chest compression alone was 8.06 cmH2O(SD 1.65), during oscillation alone was 7.93 cmH2O (SD 1.57), and during passive expiration alone was 6.82 cmH2O (SD 1.51). During vibration, compression contributed 13% of the change in intrapleural pressure, oscillation contributed 12%, and lung recoil contributed the remaining 75%.

CONCLUSIONS

During vibration the chest behaves as a highly linear system. Changes in intrapleural pressure occurring during vibration appear to be the sum of changes in pressure due to lung recoil and the compressive and oscillatory components of the technique, which suggests that all three components are required to optimise expiratory flow.

Forces applied during manual therapy to patients with low back pain

BACKGROUND

To date, there is little information available regarding the forces used during mobilization treatment of patients with low back pain (LBP).

OBJECTIVE

This study measured such forces and investigated whether the force characteristics could be predicted on the basis of physical therapist and patient characteristics.

SUBJECTS

Ten physical therapists applied a central posteroanterior (PA) mobilization treatment to 80 patients with LBP, providing data on treatment of 123 lumbar levels.

METHODS

Physical therapists were required to treat their patients while the patients lay on an instrumented couch. This couch has been shown to be highly accurate in its measurement of force in 3 directions (error <2%) and has demonstrated high test-retest reliability (ICC [2, 1], 99% CI = 0.99-1.00). The forces applied by the physical therapists were recorded over a 10-second period. Data on the characteristics of the physical therapists and patients were collected by means of questionnaires.

RESULTS

The force used by physical therapists related not only to patient characteristics but also to physical therapist characteristics. Interestingly, current pain intensity and nature of symptoms did not affect the forces used. The overall patterns of the force characteristics were generally consistent with previous studies performed in asymptomatic subjects. However, the magnitude of the force applied and the frequency of each grade used in the present study are relatively higher than in earlier studies.

CONCLUSION

These preliminary data provide some useful quantitative information about the forces used during mobilization treatment of patients with LBP. Also, the force characteristics described here may provide useful data for both teaching and research in manual therapy.