Not all hand injuries are created equal
Assessment of hand injuries can be complex and the AMA Guide provides a reliable structure around how this can be done in a reproducible manner. The Guide does however have some quirks which main that on summer occasions injuries which might initially appear equivalent are attributed markedly different impairment percentages.
The following are a couple of talking points and interesting examples of this phenomenon.
1. NEUROLOGICAL INJURY DIFFERENCES
Median nerve dysfunction rates higher in terms of sensory loss while the ulnar nerve losses are weighted towards motor deficit.
Table 16.15 of the Guide describes the upper extremity impairment for various deficits of major peripheral nerves in the upper limb. The maximum deficit for sensory dysfunction of the median nerve is 39%UEI (below the mid forearm) while sensory losses of the ulnar nerve rate to only a maximum of 7%UEI. The reverse is true of motor deficit – maximum median nerve motor impairment 10%UEI versus maximum ulnar nerve motor impairment of 35%UEI.
The reasoning behind this is nature of the contribution of these nerves to hand function and the relative utility of that function. It is, for the most part, a reasonable delineation but can cause significant variations in assessable impairment between the nerves. This goes some way to explaining why permanent sensory loss after a condition such as carpal tunnel syndrome can be assigned a seemingly large impairment when compared to sensory loss of the ulnar nerve or range of motion losses following trauma.
2. RANGE OF MOTION VARIATION
Range of motion losses in the ulna (little finger) side of the hand are considered less impairing than the radial (thumb) side.
Table 16.1 of the Guide converts the impairments of the digits to impairment of the hand. Digital impairments of the little and ring finger have considerably lower conversions with a 100% impairment ultimately being considered 50% less impairing (10%HI vs 20%HI).
This is not widely accepted by hand surgeons to be a true representation of hand function as the little and ring finger are vitally important to power grip. Many hand surgeons would argue that the conversions are the wrong way around or should at least be equal. Nonetheless, the Guide is as it is for now and the significance of the little finger in particular is underrated.
Those with functional losses of the little and or ring finger will have a higher level of functional disability than their rateable impairment would imply. This should be considered carefully in the medical report with respect to functional and vocational capability.
There are many other quirks and points of intrigue in the Guide and the procedure around assessing hand injury. If you have any interesting matters where these types of issues are apparent I would be happy to discuss them with you.
