The spine: assessment of dysmetria
This material is issued by the State Insurance Regulatory Authority (SIRA) under s.65 (2) of the Motor Accidents Compensation Act 1999 (the Act) in the interests of promoting accurate and consistent medical assessments under the Act. The interpretation provided here is not legally binding but represents the clinically recommended interpretation in an area where more than one interpretation of existing provisions may be possible. This recommended interpretation is publically available. Any medical assessment which does not adopt this interpretation should be accompanied by clinical justification for the interpretation adopted, supported by full, robust reasons.
- The Permanent Impairment Guidelines - Guidelines for the assessment of permanent impairment of a person injured as a result of a motor vehicle accident 1 October 2007 (PI Guidelines): Chapter 4 Spinal Impairment pages 21-29.
- The American Medical Association Guides to the Evaluation of Permanent Impairment, Fourth Edition (AMA 4 Guides): section 3.3 The Spine pages 94-111.
The PI Guidelines direct that only the diagnosis-related estimate (DRE) method is to be used for evaluation of impairment of the spine (clause 4.1 of the PI Guidelines). This method relies especially upon evidence of neurological deficits and uncommon, adverse structural changes, such as fractures and dislocations. DREs are differentiated according to clinical findings that are verifiable using standard medical procedures (clause 4.2 of the PI Guidelines). The AMA 4 Guides (page 109, Table 71) and the PI Guidelines provide that non-uniform loss of range of motion, or dysmetria, is one of the differentiators in the assessment of cervical, thoracic and lumbar spine assessments.
Issue requiring clarification
Whilst the PI Guidelines provide a definition of nonuniform loss of spinal motion (page 24 of the PI Guidelines), neither the AMA 4 Guides nor the PI Guidelines describe how non-uniform loss of range of motion is to be assessed. Medical assessors tend to record the motion that is present rather than the lack of motion. Some medical assessors record degrees of motion and some record the motion in fractional or percentage terms.
This can be problematic for the parties, particularly for motion in the sagittal plane (flexion/extension) where normal range of motion is not symmetric in absolute terms.
Additionally, muscle spasm or guarding can cause a tilt/deviation to one side during movement, even when there is no demonstrable loss of motion in absolute terms. This could be seen as dysmetria by some medical assessors, but not by those who rely upon absolute terms.
Clause 4.5 of the PI Guidelines precludes use of the Range of Motion Model for spinal impairment evaluation. There is therefore no mandated method for assessing nonuniform loss of motion or any mandated equipment to be used.
Recording degrees of motion, whilst easily understood by the parties for the motions spinal rotation and lateral flexion, causes confusion in flexion and extension as it is normal for full flexion and extension to be different. For example, if flexion and extension of the lumbar spine are both 25°, this looks symmetric on face value, but represents a normal range of extension but a significant loss of flexion.
Accordingly, this Guidance Note recommends that:
- Nonuniform loss of range of motion should be allowed as described for the three planes of motion for the cervicothoracic spine (flexion/extension, lateral flexion and rotation) or two planes of motion for the thoracolumbar spine (flexion/extension and rotation) and lumbosacral spine (flexion/extension and lateral flexion). This reflects the movement that occurs at each spinal level.
- Medical assessors should record the range of spinal motion as a fraction or percent of range. For example, if cervical flexion is 3/4 of the normal range (75%) and cervical extension is 1/2 the normal range (50%), dysmetria or non-uniform range of motion is present. Similarly, 25% (1/4) loss of lumbar flexion compared with 25% (1/4) loss of extension is symmetric, even though in absolute terms the degrees of movement are actually different.
- Medical assessors should not refer to body landmarks to describe the available motion. For example if lumbar flexion is described as ‘able to touch knees’, this does not quantify the loss of range of motion in such a way as, to allow for objective comparison with extension.
Justification for preferred interpretation
In order to promote consistency specific planes of movement must be considered when observing spinal motion and the loss of spinal motion must be recorded in fractional or percentage terms.
Injury Prevention and Rehabilitation
Updated December 2016