The kinematics of motion palpation and its effect on the reliability for cervical spine rotation☆

Article Outline

• Abstract
• Introduction
• Method
  • Participants
  • Technical training
  • Equipment and procedure
  • Directive to the examiner
  • Clinical profile
  • Directive to the subject
  • Study variables
• Results
  • The compilation of data
  • The study of reliability
• Discussion
• Conclusion
• Acknowledgements
• References
• Copyright

Abstract 

Background: The reliability of a test depends on its standardization. Instrumental measurement of the reproducibility of the test is an effective way to evaluate the level of standardization obtained. Improved standardization is believed to yield greater reliability. Objective: The objectives of this study were to measure the technical ability of an examiner to reproduce the kinematics of motion palpation for cervical spine rotation and to evaluate the effect of standardization on the reliability of the test. Design: A study of reproducibility of the kinematics of the test for cervical spine rotation was conducted by means of a computerized system of analysis of movement. The reliability when reproducibility was achieved was compared with reliability when it failed. Results: The data collected enable us to establish a standardized protocol for the execution of the test. The standardized palpation is executed within 6° of inclination from the pure plane of rotation. The successful reproduction of the kinematics of the test raises its reliability to detect the presence of fixations (kappa raising from 0.337 and 0.352 to 0.682). Conclusions: A greater reliability, arising from a high level of reproducibility, enables us to document the advantages of the standardization of motion palpation in chiropractic. (J Manipulative Physiol Ther 2002;25:e7)

Keywords:  Cervical Vertebrae, Spine, Motion, Chiropractic

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Introduction 

Reviews published in the chiropractic literature¹, ², ³, ⁴ identified the poor reliability that often accompanies motion palpation. They note that the lack of standardization and the use of young patients without symptoms are prejudicial to the reliable detection of minimal or nominally existent lesions. It is a troublesome fact that the nature of intervertebral dysfunction evaluated by palpation is subtle and engages the subjectivity of examiners.⁵ In spite of this state of affairs, DeBoer et al⁶ and Dishman¹ postulated that optimal standardization of motion palpation testing could produce a higher reliability than that revealed until now.

Johnston et al,⁷, ⁸, ⁹, ¹⁰, ¹¹, ¹² on behalf of the osteopaths, chose with a certain degree of success the strategy of standardization to check the reliability of palpation to detect the intervertebral dysfunction related to the osteopathic lesion (supposedly equivalent to the chiropractic subluxation). Certain chiropractic studies such as those by Herzog et al¹³ and Mior et al¹⁴ for sacroiliac function and Love and Brodeur¹⁵ for thoraco-lumbar spine function also attempted to control certain parameters of standardization to improve reliability. Mior et al,¹⁶ after their study on the high cervical spine, estimated that it would be necessary to secure strong to very strong reproducibility (k = 0.8) during standardized technical training of the test in the hope of undertaking a successful reliability study.

The level of interexaminer reliability that manual testing achieves in motion palpation is believed to be directly dependent on the degree of reproducibility with which the examiners perform such a test. The more a test is reproduced under the same experimental conditions, the better is the likelihood of obtaining the same result. Hence, standardization of the execution of a test increases its reliability.¹⁷

In the case of motion palpation of a vertebral functional unit, maximum reproducibility is achieved when the maneuver is conducted with the same kinetics (force and pressure) and the same kinematics (position and movement).

The standardization of motion palpation implies 2 technical variables. One, the kinetics, comprises the force or pressure of palpation used by the examiner during the conduct of the test. The second variable is the subject of our current research: the kinematics of palpation. We propose that the spatial orientation of the palpation is important for the faithful reproduction of the test. When the maneuver is conducted in an optimal way, the course of palpation will be parallel to the plane of pure movement as accepted by the international system of coordinates, that is, the horizontal (transverse), frontal (coronal), and sagittal planes.

None of the studies of Boline et al,¹⁸ Keating et al,¹⁹ and Tuchin et al,²⁰ nor those already cited, mention any attempt to ensure or measure the reproducibility of the dynamics (kinetics and kinematics) of the test. In our study we made every effort to ensure the test was reproduced in the same manner at each repetition. Through multiple sessions of supervised standardization training, the control of the parameters of the test was optimized to ensure reproducibility. Moreover, our study measured the degree of reproducibility obtained by means of a computerized system of analysis of movement.

The objective of this study is to analyze the degree of reproducibility of the kinematics of motion palpation in cervical rotation after standardization. Our study simultaneously analyzed the reliability of the test to detect fixations when reproducibility was successful versus when it failed.

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Method 

Participants 

The participants in this study were selected from among the students and professors in the Doctor of Chiropractic program at the Université du Québec à Trois-Rivières. Twenty-four trained students and an experienced chiropractor served as examiners. Twelve patients between 22 and 42 years of age were selected on the basis of previous episodes of mechanical cervical spine pain and on the presence of fixation as detected by the experienced chiropractor. Nine of the patients served for technical training, and 3 were kept for the experiment. Informed consent was obtained from all the participants.

Technical training 

Before the experiment was performed, the examiners submitted to sessions of practical and theoretical technical training. In addition to their academic technical education, the examiners participated in a total of 12 hours of supervised training. At the start of the experiment, the examiners were believed to reproduce accurately the kinematics of motion palpation in cervical rotation as described in our experimental protocol.

Equipment and procedure 

Motion palpation of cervical spine rotation proceeded with the use of the “Peak-5,” a computerized system of movement analysis. Two S-VHS cameras, a system of luminescent markers, a microphone, a stool, and a chiropractic table were also used. The markers, cameras, and microphone were installed according to the following pattern (Figs 1 and 2).

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• Fig. 1. 

  The experiment (side view).

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• Fig. 2. 

  The experiment (top view).

Directive to the examiner 

The examiner was stationed at the head of the subject and conducted a rotatory motion palpation of the cervical spine. The latero-palmar surface of the distal interphalangeal joint of the index finger contacted the articular pillar of the palpated vertebra. Two series of palpation (1 left and 1 right) consisting of 8 trials (from C0 to C7 or C7 to C0) were performed by each examiner on 1 of 3 patients who were kept exclusively for the actual experiment. At the end of the course of each trial, the examiner mentioned the vertebra palpated while evaluating the corresponding end-feel. After the palpation, the examiner noted (blinded to the others) the intervertebral levels presenting fixation. The minimal or dubious fixations were considered normal and were not retained.

As a result of cutaneous movement relative to the underlying osseous tissue, the identification of vertebrae by skin marking²¹ proved to be an unrewarding practice in motion palpation. We believe that the examiners would actually palpate the same segment but could identify either of 2 contiguous segments. For this reason we accepted a margin of error in identification of 2 contiguous vertebrae. For example, identification at C3 in left rotation could correlate with identification at either C3 or C4 in left rotation.

Clinical profile 

The selected patients had histories of cervical spine mechanical disorders. Moreover, the experienced chiropractor had already performed a palpation according to our protocol of standardization. The subjects presented with cervical rotatory fixation, sufficiently significant to allow identification by the other examiners. We believe this to be representative of normal chiropractic clientele. To avoid inhibition reflexes or muscle spasms caused by pain, the subjects also had no symptoms at the time of the experiment.

Directive to the subject 

The subject was required to remain supine on the chiropractic table and to slacken and not aid or resist the movement of his or her head and neck by the examiner. The subject who contracted during palpation was recalled to passivity, a necessary state for passive motion palpation.

Study variables 

The examiner was asked to conduct the motion palpation in the 2 directions of cervical rotation (+θY and −θY). We measured the inclination of the palpation in relation to the plane of pure rotation (transverse plane). This inclination, measured in degrees, corresponded to the components of palpation in the directions of flexion and extension (±θX) and of lateral flexion (±θZ) by the examiner during the administration of the test. The precision of our instrument allowed us measurement to ±0.5°.

We determined ahead of time that the reference point for the standardized execution of the test would be the degree of inclination up to which 80% of the examiners would perform. Reliability results from both the standardized and nonstandardized examiners were obtained from compilation of the fixations detected by both study groups and by the experienced chiropractor.

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Results 

The compilation of data 

The mobile markers allowed us to note that palpation was conducted on a regular curvilinear course with a more or less pronounced inclination in relation to the transverse plane. The marker on the head allowed measurement of the inclination angle of palpation compared with the transverse plane. Some trials of palpation were not included in the data because of markers obstruction by the examiner during the course of palpation. The examiners achieved reproducibility when inclination (deviation) was consistently less then 6°.

Of the results compiled in Table 1 and Fig 3 for the group “Success of reproducibility,” one extracts the values of:

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• Fig. 3. 

  Group: success of reproducibility. Degree in inclination of the course of palpation.

Table 1. Group: success of reproducibility

Certain examiners, although having participated in the training sessions, did not exhibit standardization (inclination consistently over 6°) and were included in the group “Failure for reproducibility.” The data on the 2 experimental groups will be used as criteria for comparison between the successful standardized group and the failed nonstandardized group. Moreover, the identification of fixations by the 2 groups can be compared with that of the experienced chiropractor to evaluate reliability when standardization is achieved and when it is failed.

From Table 2 and Fig 4 for the group “Failure for reproducibility,” one extracts:

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• Fig. 4. 

  Group: failure of reproducibility. Inclination of the course of palpation (°).

Table 2. Group: failure for reproducibility

The study of reliability 

Reliability to detect the presence of fixations was evaluated for the 2 groups.

Reliability was analyzed with the index of concordance, kappa, and the matrix of compilation of Kramer and Feinstein,²² Feinstein,²³ and Rosner,²⁴ the benchmark for this form of clinical testing. Calculation of the percent agreement (%), the coefficient of concordance (k), and the P value (P) between the examiners who succeeded in the reproducibility test were compared with those of the examiners who failed reproducibility (Figs 5-7).

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• Fig. 5. 

  Reliability for group “success of reproducibility” versus experienced chiropractor.

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• Fig. 6. 

  Reliability for group “failure for reproducibility” versus experienced chiropractor.

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• Fig. 7. 

  Interexaminer reliability within the group “failure for reproducibility.”

The strength of the agreement between the examiners, that is, the reliability of the test, is provided by the value kappa (k) following Landis and Koch.²⁵ The statistical power of kappa is determined by the following z-score: k < 0.0 Null; 0.0 < k < 0.2 Weak, slight; 0.2 < k < 0.4 Poor; 0.4 < k < 0.6 Moderate; 0.6 < k < 0.8 Strong; 0.8 < k < 1.0 Very strong; k is significant at .05 (P < .05) for z > 1.96; k is significant at .01 (P < .01) for z > 2.58.

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Discussion 

Note the strong reliability of the examiners of the group “Success of reproducibility” with that of the experienced chiropractor (Fig 5: k = 0.682). This also indicated strong interexaminer reliability within the group. For example, 2 examiners who would agree with the experienced chiropractor for a right rotatory fixation at C5 would obviously agree between themselves.

Note also the reliability of the group having failed the reproducibility test versus the experienced chiropractor (Fig 6: k = 0.352) and the interexaminer reliability within the group having failed the reproducibility test (Fig 7: k = 0.337). A typical example would be that for a fixation at C5 by the experienced chiropractor, a nonstandardized examiner would identify C2, whereas another nonstandardized examiner would identify the fixation at C7. They would not agree with the experienced chiropractor, nor would they agree between themselves.

The reliability of the group having successful reproducibility is strong (kappa between 0.6 and 0.8). Comparing this result with the lower reliability of the group “Failure for reproducibility” confirmed the assumption of an increased reliability associated with standardization of the test.

These results reveal that reliability in the event of failure of reproducibility is poor (kappa between 0.2 and 0.4). The examiners of the group “Failure for reproducibility” did not agree between themselves, nor did they agree with the results of the experienced chiropractor. This result indicates that in the case of an absence of standardization, the results become random and declare a reliability inferior to standardized test achievement.

A review of the chiropractic literature demonstrates the difficulty in standardizing the test of motion palpation; thus it often produces poor to fair reliability. Our study attempts to highlight the advantageous effect of supervised training and standardization of the test. Our results indicate that a high level of standardization allows a better reproducibility of the test and, as a consequence, an increased reliability.

The reliability of a palpation test has a direct relationship with the capacity of the examiners to accurately reproduce the test, hence the need for standardization. We believe that the kinematics with which the test of motion palpation is conducted is the element most likely to influence the results of the test. By limiting the test to only 1 plane of motion and by ensuring that the movement of palpation strictly corresponds to it, we satisfy this important condition. In the future all other parameters (position of the patient and the examiner, point of contact, forces, pressure of palpation, etc) must also become the subject of standardization. Moreover, the examined subject-patient must present a strong probability of intervertebral dysfunction (fixation) to be detected at the time of palpation. Only patients with a history of mechanical disorders of the area tested should be selected.

Standardized examiners can conduct a test of motion palpation in cervical rotation with a high degree of accuracy: 95% of the data ranging between 0° to 6° of inclination of the course of palpation. The average of the group having achieved successful reproducibility is approximately 2.5° of inclination. Examiners not demonstrating standardization will carry out the test with an average slope of more than 8°. These results suggest that a test not standardized is performed with important components of flexion, extension, or lateral bending, thus introducing a technical skew, a bias likely to negatively influence the ability to detect intervertebral fixations.

We note that the effect of optimal standardization of a clinical maneuver is to increase its reliability. Suppose that the maneuver is identical from 1 examiner to the next, and that the annotation of identical perceptions is equivalent; it then suggests a maximum reliability. This is what we observe in our study, which reveals a stronger reliability (k = 0.682) for the group having achieved successful reproducibility of kinematics for the test. If, however, the test is not conducted in the same manner by examiners, the reliability is reduced (k = 0.337 and 0.352). This lower reliability accounts for the difference seen in the unstandardized execution. For example, raising the head of the patient out of the vertebral axis (component in flexion) or introducing a component of lateral flexion or extension during the movement of rotation contributes to a failure of standardization.

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Conclusion 

Motion palpation is certainly a test in which emphasis is placed during the years of undergraduate training of the doctor of chiropractic. A test being used to discriminate between normal intervertebral biomechanics and dysfunction, as minimal or subtle as they may be, must in and of itself satisfy strict kinematic and kinetic parameters. The maneuver should be precise, reproducible, and highly standardized. It is important to accurately measure the parameters of the test to appreciate its limits. This should be performed in a normal clinical environment and on subjects representative of the typical chiropractic patient population.

Additional research should be conducted to further measure the parameters of motion palpation. Our research must be regarded as preliminary. Research methods and results should be subjected to a rigorous protocol of standardization before being accepted for the undergraduate training curriculum.

Instrumental measurement of manual clinical performance can be used to establish a priceless research protocol and a valuable teaching technique for exploring spinal kinematics and kinetics, which may later be incorporated into private chiropractic practice.

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Acknowledgements 

We acknowledge the notable contribution of Dr. C. Dugas, PhD, Département des Sciences de l'activité Physique, Université du Québec à Trois-Rivières (UQTR), and Dr. P. B. Boucher, DC, PhD, Département de Chiropratique, UQTR, for reviewing the original article written in French. We also acknowledge Dr. P. Kogon, DC, DACRB, Département de Chiropratique, UQTR, for the English version of the text.

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