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Evaluation of permanent impairment arising from chronic pain

(exclude AMA5 Chapter 18)

17.1 The International Association for the Study of Pain (IASP) has defined pain as:

‘An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage’.

17.2 For chronic pain assessment using AMA5 and the Guidelines, exclude AMA5 Chapter 18, on pain (p 565–91).

17.3 The reasons for excluding chronic pain, as a separate condition from the Guidelines are:

  • It is a subjective experience and is, therefore, open to exaggeration or fabrication in the compensation setting. Assessment depends on the credibility of the subject being assessed. In order to provide reliability,  applicants undergoing pain assessments require more than one examiner at different times, concordance with the established conditions, consistency over time, anatomical and physiological consistency, agreement between the examiners and exclusion of inappropriate illness behaviour.
  • Pain cannot be measured and no objective assessment can be made.
  • Tools to measure pain are based on self-reports and may be inherently unreliable.
  • Some impairment ratings take symptoms into account and some of the ranges of impairment – eg whole person impairment (WPI) of the spine, may reflect the effect of the injury and pain on activities of daily living (ADL). This is not so for impairment assessment of the upper and lower limb, which is based on range of movement and diagnosis-based estimates, other than for peripheral nerve injury.

17.4 Where there is a peripheral nerve injury and there is sensory loss, some of the sensory nerve impairment categories permit pain to be included (AMA5 Table 16-10, categories 1-5, p 482).

17.5 AMA5 Section 17.2m, ‘Causalgia and complex regional pain syndrome (reflex sympathetic dystrophy)’ (p 553), should not be used. AMA5 Table 16-16 (p 496) has been replaced by Table 17.1 (below) in the Guidelines. Table 17.1 is used to determine if complex regional pain syndrome (CRPS) is a rateable diagnosis. It is important to exclude diagnoses that may mimic CRPS, such as disuse atrophy, unrecognised general medical problems, somatoform disorders and factitious disorder. Once the diagnosis is established, assess impairment as in AMA5.

Complex Regional Pain Syndrome Type 1

For Complex Regional Pain Syndrome Type 1 (CRPS1) to be present for the purposes of assessment:

  • the diagnosis is to be confirmed by criteria in Table 17.1 (below)
  • the diagnosis has been present for at least one year (to ensure accuracy of the diagnosis and to permit adequate time to achieve maximum medical improvement)
  • the diagnosis has been verified by more than one examining physician
  • other possible diagnoses have been excluded.
  • CRPS1 is to be assessed as follows:
    • Apply the diagnostic criteria for complex regional pain syndrome type 1 (Table 17.1).
Table 17.1: Diagnostic criteria for Complex Regional Pain Syndrome types 1 and 2

1. Continuing pain, which is disproportionate to any casual event.

2. Must report at least one symptom in each of the following four categories:

  • Sensory: Reports of hyperaesthesiae and/or allodynia.
  • Vasomotor: Reports of temperature assymetry and/or skin colour changes and/or skin colour assymetry.
  • Sudomotor/oedema: Reports of oedema and/or sweating increase or decrease and/or sweating asymmetry.
  • Motor/trophic: Reports of decreased range of joint motion and/or motor dysfunction (tremor, dystonia) and/or trophic changes (hair,nail, skin).

3. Must display at least one sign* at time of evaluation in all of the following four categories:

  • Sensory: Evidence of hyperalgesia (to pin prick) and/or allodynia (to light touch and/or deep somatic pressure and/or joint movement).
  • Vasomotor: Evidence of temperature asymmetry and/or asymmetric skin colour changes.
  • Sudomotor/oedema: Evidence of oedema and/or sweating asymmetry.
  • Motor/trophic: Evidence of decreased active joint range of motion and/or motor dysfunction (tremor,dystonia) and/or trophic changes (hair, nail, skin).

4. There i no other diagnosis that better explains the signs and symptoms.

*A sign is included only if it is observed and documented at time of the impairment evaluation.

Then consider the following in assessing CRPS1:

  • If the criteria in each of the sections 1, 2, 3 and 4 in Table 17.1, above, are satisfied, the diagnosis of CRPS1 may be made.
  • Rate the extremity impairment resulting from loss of motion of each individual joint involved.
  • Rate the extremity impairment resulting from sensory deficits and pain, according to the grade that best fits the degree or amount of interference with ADL, as described in AMA5 Table 16.10a (p 482). Use clinical judgement to select the appropriate severity grade and the appropriate percentage from within the range shown in each grade. The maximum value is not automatically applied. The value selected represents the extremity impairment. A nerve value multiplier is not used.
  • Combine the extremity impairment for loss of joint motion with the impairment for pain or sensory deficit using the Combined Values Chart (AMA5, p 604) to obtain the final extremity impairment.
  • Convert the final extremity impairment to WPI using AMA5 Table 16.3, (p 439) for the upper extremity and AMA5 Table 17.3 (p 527) for the lower extremity.

Complex Regional Pain Syndrome Type 2, causalgia

For Complex Regional Pain Syndrome Type 2 (CRPS2), the mechanism is an injury to a specific nerve. The methodology in AMA5 (pp 496–97) is to be followed:

  • If the criteria in each of sections 1, 2, 3 and 4 in Table 17.1, above, are satisfied and there is objective evidence of an injury to a specific nerve, the diagnosis of CRPS2 may be made.
  • Rate the extremity impairment due to loss of motion of each individual joint involved.
  • Rate the extremity impairment resulting from sensory deficits and pain of the injured nerves according to the determination methods described in AMA5 Chapter 16, Section 16.5b and Table 16-10a. Use clinical judgement to select the appropriate severity grade and the appropriate percentage from within each range shown in the grade.
  • Rate the extremity impairment resulting from motor deficits and the loss of power of the injured nerve according to the determination method in AMA5 Chapter 16, Section 16.5b and Table 16-11a.
  • Combine the extremity impairment percentages for loss of range of motion of the joints involved, pain or sensory deficits, and motor deficits, if present, to determine the final extremity impairment, using the Combined Values Chart in AMA5 (p 604).
  • Convert the final extremity impairment to WPI using AMA5 Table 16.3 (p 439) for the upper extremity and AMA5 Table 17.3 (p 527) for the lower extremity.