AMA Guides® Newsletter

Articles

Lower Extremity Impairments—Knee and Hip

William S. Shaw, Charles N. Brooks

Pages 1–3

DOI: 10.1001/amaguidesnewsletters.1999.JanFeb01

Abstract
The process of assessing lower extremity impairment described in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fourth Edition, differs from that in previous editions. This article addresses common questions that arise in knee and hip impairment rating according to the new edition. Anatomic, diagnostic, or functional methods can be used to estimate lower extremity impairments. Functional methods include ratings based on diminished range of motion, weakness, or gait derangement. In general, only one method should be used to rate impairment associated with an injury or illness. Section 3.2i, Diagnosis-related Estimates, in the AMA Guides lists impairment ratings for many knee conditions and operative procedures. Decreased range of motion, ankylosis, diminished muscle function, and joint space narrowing are some rating methods for the knee. Similar anatomic, diagnostic, and functional methods may be used to rate impairment due to hip pathology, but most hip impairments are estimated by range-of-motion deficits. Assessing lower extremity impairments requires a thorough medical evaluation, careful analysis, experience, and clear judgment; evaluators must determine the applicable rating methods, use the methods to rate the impairment, and then decide which method or combination best describes the impairment, without overlooking or duplicating ratings. [A related Lower Extremity Impairment Checklist and Worksheet appears on page 4 of this issue of The Guides Newsletter. A related Quick Reference, Motion at the Wrist, Elbow, and Shoulder, appears on page 5.]
Tools and Resources: Lower Extremity Impairment Checklist and Worksheet

Pages 4–4

DOI: 10.1001/amaguidesnewsletters.1999.JanFeb02

Abstract
The North Dakota Supreme Court has ruled that the “most current” and “most recent” edition of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) is the Third Edition (McCabe v North Dakota Workers’ Compensation Bureau). This counterintuitive holding involved a claimant who injured his back and neck at work and who reached maximum medical improvement in 1994. At issue was which edition of the AMA Guides to use to measure the claimant's permanent partial impairment (PPI). Specifically, the question was whether to evaluate the impairment according to the Range of Motion (ROM) Model from the Third Edition or the Diagnosis-related estimates (DRE) of the Fourth Edition. The relevant statutory language required use of the “most current” or “most recent” edition of the AMA Guides. The court held that the language must be construed to mean the most recent edition at the time of the statute's enactment. At the time of enactment, the AMA Guides, Fourth Edition, (with the DRE Model) had not been published. The court held that the claimant's impairment must be evaluated using the ROM Model. The interpretation of the North Dakota Supreme Court is not consistent with the philosophy of the AMA Guides, and legal interpretations regarding use of the AMA Guides are not always consistent with specific directions therein.
Quick Reference: Motion at the Wrist, Elbow, and Shoulder

Pages 5–5

DOI: 10.1001/amaguidesnewsletters.1999.JanFeb03

Abstract
Apportionment estimates the degree to which each of various occupational or nonoccupational factors may have caused or contributed to a particular impairment. Apportioning spinal impairment among different injuries often is challenging. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Third Edition, relied on the Range of Motion (ROM) Model, which is included in the Fourth Edition for use only in 2 circumstances: first, if the spine has a disease and no injury has occurred (eg, ankylosing spondylitis) and, second, as a tie breaker. The AMA Guides, Fourth Edition, introduced a new approach, the Injury Model or Diagnosis-related estimates (DRE) Model. The Injury Model is different from other approaches in the AMA Guides because when the individual reaches Maximal Medical Improvement (MMI), the degree of persisting anatomic or physiologic loss is rated. In contrast, the Injury Model rates the severity of the original injury, not the degree of recovery. Recurrence is common after significant back injury, so even if the individual seems to be doing well when rated, years later the functional result may be different; these concerns explain the instructions to rate soft-tissue back injury using objective findings and true radiculopathy using the Injury Model.
Legal Update: North Dakota Supreme Court: Third Edition of Guides is “Most Current”

James J. Mangraviti

Pages 6–7

DOI: 10.1001/amaguidesnewsletters.1999.JanFeb04

Abstract
The accurate measurement of hip motion is critical when one rates impairments of this joint, makes an initial diagnosis, assesses progression over time, and evaluates treatment outcome. The hip permits all motions typical of a ball-and-socket joint. The hip sacrifices some motion but gains stability and strength. Figures 52 to 54 in AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fourth Edition, illustrate techniques for measuring hip flexion, loss of extension, abduction, adduction, and external and internal rotation. Figure 53 in the AMA Guides, Fourth Edition, illustrates neutral, abducted, and adducted positions of the hip and proper alignment of the goniometer arms, and Figure 52 illustrates use of a goniometer to measure flexion of the right hip. In terms of impairment rating, hip extension (at least any beyond neutral) is irrelevant, and the AMA Guides contains no figures describing its measurement. Figure 54, Measuring Internal and External Hip Rotation, demonstrates proper positioning and measurement techniques for rotary movements of this joint. The difference between measured and actual hip rotation probably is minimal and is irrelevant for impairment rating. The normal internal rotation varies from 30° to 40°, and the external rotation ranges from 40° to 60°.
Impairment Tutorial: Spinal Impairment Apportionment

James B. Talmage, Mohammed Ranavaya

Pages 7–8

DOI: 10.1001/amaguidesnewsletters.1999.JanFeb05
Literature Review

James B. Talmage

Pages 9–9

DOI: 10.1001/amaguidesnewsletters.1999.JanFeb06
Common Tips for IMEs: Measuring Hip Range of Motion

Charles N. Brooks

Pages 10–11

DOI: 10.1001/amaguidesnewsletters.1999.JanFeb07
Questions and Answers

Christopher R. Brigham

Pages 11–11

DOI: 10.1001/amaguidesnewsletters.1999.JanFeb08