Impairment Questions and Answers

Abstract

Question:How should I rate the impairment of a knee that has had an anterior cruciate ligament reconstruction with good stability on post-operative examination? Table 64 (4th ed., 85) does not discuss cruciate ligament reconstruction.Answer:In general, rate knee ligaments based on the amount of instability present after the individual reaches maximal medical improvement. Table 64 lists cruciate or collateral ligament laxity (mild, moderate, or severe). The terms mild, moderate, and severe are not defined. Many collateral ligament injuries result in a stable knee with no laxity after operative or nonoperative treatment. If there is neither laxity nor meniscal injury, then there is no impairment (0%).The cruciate ligaments have a poor blood supply and when injured heal poorly. For this reason, if a cruciate ligament is ruptured, anatomic repair is not possible and the ligament must be reconstructed (replaced) either by using one of the individual's tendons or ligaments or by using an allograft. If, post-operatively, anterior instability is still present, the degree of instability determines the impairment rating.What if the knee seems stable after the reconstruction? Is the rating no instability, therefore no impairment appropriate? A truly normal stability exam after the cruciate ligament reconstruction is unusual. Most results are mild laxity, which according, to Table 64 is 7% lower extremity impairment or 3% whole-person impairment.Question:How should I rate a patient who sustained an open displaced comminuted mid-shaft right tibial fibular fracture? On the day of injury he had an open reduction and internal fixation. Post-operative rehabilitation was performed. A one-half-inch lift was placed on his right shoe for a leg-length discrepancy and he uses orthotics. I saw him six months post-operatively for an impairment rating. He had some generalized aching, particularly in the cold, and decreased endurance for prolonged walking and climbing. I felt he was at maximal medical improvement. My exam revealed normal gait, right leg 2.0 cm shorter than the left, right calf circumference 1.6 cm smaller than the left, and normal motor strength. Ranges of motion of the knee, ankle, and subtalar joints were normal. X-ray revealed a healed fracture with normal callus and five degrees of varus angulation.Answer:First, identify the rating options and the corresponding estimates of impairment. These include leg length, 2% whole-person (Table 75, p. 75); atrophy, 1% to 2% whole-person (Table 37, p. 77); and angulation, 0% (Table 64, p. 85).Though your manual muscle testing was grossly normal, there is evidence of atrophy with a history of decreased endurance consistent with the objective findings. If other indicators of diminished muscle function were present, you would select the most appropriate and greatest impairment. Atrophy should be included in the final calculation. The 2% level is selected because the measurement is closer to the next level of impairment (moderate).Angulation is not sufficient to justify impairment, although it probably contributes to the leg-length discrepancy, which does warrant impairment. If angulation is sufficient to warrant rating, the final calculation should probably omit leg length unless true bone loss is a major contributor to the discrepancy. The final calculation of impairment is based on combining 2% and 2%, yielding 4% whole-person impairment.—William Shaw, MDQuestion:What is the relationship between impairment and the ability to perform a specific job? My patient is a nurse with a large cervical herniated disc (C5-C6) with a radiculopathy. She has an impairment of 15% whole-person. Can she resume her nursing job with this impairment?Answer:There is limited correlation among impairment, function, and disability. An impairment value does not translate directly into functional capacity, nor does it provide a basis for establishing functional restrictions. It is probable that she could be considered an individual with a disability and therefore protected by the Americans with Disabilities Act, Title I. The issue of employability is the responsibility of her employer, who must determine whether she can perform the essential functions of her job with or without reasonable accommodation. Any restrictions must be based on a direct threat analysis. A functional capacity evaluation can be useful in determining her physical abilities.