Medical assessor guidance note 3

Musculoskeletal System: Lower Extremity Impairment

Assessment of tibial shaft fracture, rotational deformity

This material is issued by the Motor Accidents Authority 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 Motor Accidents Authority 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 (MAA Guidelines): Chapter 1 Clause 1.26, page 5.
  • The American Medical Association Guides to the Evaluation of Permanent Impairment, 4th Edition (AMA 4 Guides): Chapter 3 3.2i Diagnosis-based Estimates page 84, Table 64 page 85.

"1.26 A condition may present which is not covered in the MAA Guidelines or the AMA 4 Guides.

If objective clinical findings of such a condition are present, indicating the presence of an impairment, then assessment by analogy to a similar condition is appropriate. Include the rationale for the methodology chosen in the impairment evaluation report."


Rotational deformity of tibial shaft fractures is not dealt with in Table 64 AMA 4 Guides.

Issue requiring clarification

In the absence of any impairment rating for rotational deformity following tibial shaft fractures it is possible that some Medical Assessors may not focus attention on this deformity and may not provide an impairment rating.

Preferred interpretation

Medical Assessors should assign the values for Tibial shaft fracture, malalignment of (Table 64 page 85 AMA 4 Guides) for rotational deformity.

Recommended method for measurement of rotational malalignment (tibial torsion) following tibial shaft fracture

Tibial torsion is the degree of rotation of the tibia along its long axis from the knee to the ankle. The recommended method of assessment is by measuring the thigh-foot axis (TFA) with the person prone with knees flexed to 90°.

The examiner looks at the foot from above. The relevant measurement is the angle between the line of axis of the thigh and the line along the axis of the foot.

By convention, external rotation values are positive, and internal rotation values are negative.

A normal TFA is 10-15° of external rotation. The value of the normal side should be used as a baseline. Both legs are measured and the discrepancy between the injured and the uninjured leg constitutes the amount of malrotation.

Suggested method of assessment of impairment

The level of impairment for tibial rotational malalignment following tibial shaft fracture is derived from Table 64 page 85 AMA 4 Guides.

It is recommended that the same Table should be used for longitudinal and rotational malalignment. (This is then analogous with the methodology used for femoral shaft fractures).

Justification for preferred interpretation

In the absence of an impairment rating for rotational deformity of tibial shaft fracture, the preferred interpretation and methodology is suggested to promote consistency of assessment.

Issued by:

Injury Strategy Branch

February 2012