Q&A: Rating Calcaneal Fractures Using the AMA Guides, Sixth Edition

Abstract

QUESTION: In assessing impairment using the AMA Guides, Sixth Edition, what are the criteria for using Table 16-2 for calcaneal fractures—is it intra-articular displacement or is it both intra- and extra-articular displacement? What criteria are used to designate mild, moderate, and severe displacement?In the case of an extra-articular displacement, a fracture of the tuber calcanei can cause a negative angle of Bohler, and therefore, a Class 3 would apply. Is that fair compared to a Class 2 for an intra-articular fracture, which has great clinical consequences?ANSWER: You are asking about definitions for the words “mild,” “moderate,” and “very severe” found under calca-neal fractures in Table 16-2, Foot and Ankle Regional Grid: Lower Extremity Impairments (6th ed, 501-508). These terms are not defined in the table.For angulation, there is some guidance, in that Table 16-21, Ankle or Hindfoot Deformity Impairments (6th ed, 549), has criteria in degrees of angulation (measured by goniometer during physical examination) that can be used to define three levels of severity—“mild,” “moderate” (as in perhaps moderate to severe), and “severe” (as in perhaps very severe). Because there is little soft tissue over the heel, the angulation on examination does correlate fairly well with the angular deformity on X ray. However, the amount of displacement (translation) in mm that would be represented by the words in Table 16-2 is still undefined.For intra-articular fractures, 1-2 mm of displacement is generally “acceptable” to many surgeons, and >2 mm linear distances are felt to be justification for open reduction and internal fixation. If an intra-articular fracture healed with >2mm of displacement, it would be “moderately severe” to most surgeons. In developed countries, it is unlikely that anyone would heal with “very severe” displacement, unless he or she had major trauma and was not expected to survive, but did survive, and thus open reduction was never performed.For entirely extra-articular fractures, and for the “chip avulsion” fracture with very little joint surface on the “chip,” criteria for the words “mild” or “moderately severe” should logically be looser, and surgeons may disagree. Most surgeons would probably rate most of these fractures as “mild” (Class 1) per Table 16-2.An anchor to help with the decision on which class to choose might be to measure active ankle and subtalar motion, calculate a rating based on loss of motion (Table 16-20, Hindfoot Motion Impairments [6th ed, 549] and Table 16-22, Ankle Motion Impairments [6th ed, 549]), and then compare the motion loss–based impairment to the range of integers in Table 16-2 for mild malalignment of a calcaneal fracture and to the range of integers for moderate malalignment. If the motion loss impairment falls into one of these ranges, that would reinforce the wisdom of choosing that class for the diagnosis-based rating.