Published online May 31, 2009.
https://doi.org/10.3346/jkms.2009.24.S2.S299
Development of Korean Academy of Medical Sciences Guideline Rating the Physical Impairment: Lower Extremities
Abstract
Lower Extremities Committee of Korean Academy of Medical Sciences Guideline for Impairment Rating develops new guidelines which are based on McBride method, American Medical Association Guides, Disability evaluation by The Korean Orthopaedic Association, The Korean Neurosurgery Society, and Korean Academy of Rehabilitation Medicine. The committee analyzed and discussed to create an ideal method practical in Korea. Our committee endeavors to develop new methods which are easy to use, but are suitable for professional use and also independent from the examinee's intentions. The lower extremities are evaluated on the basis of anatomic change, functional change, and diagnosis based evaluation. Nine methods are used to assess the lower extremities. Anatomic assessment includes leg length discrepancy, ankylosis, amputation, skin loss, peripheral nerve injury, and vascular disease. In functional assessment, range of motion and muscle strength are included. Diagnosis-based assessments are used to evaluate impairment caused by specific fractures, deformities, ligament instability, meniscectomies, post-traumatic arthritis, fusion of the foot, and lower extremity joint replacements.
INTRODUCTION
Ten methods can be used to assess the lower extremities. These methods are classified by assessment methods: anatomic, functional, diagnosis-based.
The evaluator decides the diagnosis at first, then checks whether or not the individual has reached maximal medical improvement (MMI). The next step is to identify each part of the lower extremities (pelvis, hip, thigh, knee, foot, and toe). The evaluator estimates the disability using the ten items: amputation, leg length discrepancy, ankylosis, partial ankylosis (range of motion), nerve injury, muscle weakness, diagnosis-based estimation, joint replacement, vascular disease, skin loss, and then calculate the impairment rating. Assessment by muscle weakness is chosen when the other estimations are inappropriate. If lower extremity impairment is due to an underlying spine disorder, the evaluation of the impairment would be conducted with the spine impairment rating.
There are some methods to calculate the impairment rating scales that can be combined, but other methods can not be combined. If the evaluator cannot determine which methods are correct, then the evaluator uses all methods that are related to the condition, and chooses the highest impairment rating.
MATERIALS AND METHODS
The Korean Academy of Medical Sciences comprises the Lower Extremities Committee of Korean Guideline for Impairment Rating in which orthopedic surgeons, neurosurgeons, physiatrists, and occupational and environmental medicine doctors participated. This committee analyzed the American Medical Association (AMA) Guides (1), McBride method (2), the guide of Korean Orthopaedic Association (3), the guide of Korean Neurosurgical Society (4), the Korean Academy of Rehabilitation Medicine (5) and created a new guide based on the AMA Guides.
RESULTS
Methods of assessment
There are three methods to assess the disability of the lower extremities. These methods are based on anatomical, functional, and diagnosis-based estimations (Table 1).
Table 1
Methods used in evaluating impairments of the lower extremities
Combination of evaluation methods
The amputation cannot be combined with leg length discrepancy, ankylosis, nerve injury, partial ankylosis, or muscle weakness. The leg length discrepancy cannot be combined with amputation. Ankylosis and partial ankylosis cannot be combined muscle weakness and diagnosis-based estimates. Nerve injury and muscle weakness cannot be combined each other. If there is arthritis without ankylosis, it can be estimated by muscle weakness. When we use the muscle weakness, it should be Grade III or IV by the manual muscle test. If the muscle power is less than Grade III, it should be assessed by the nerve injury. Diagnosis-based estimates cannot be combined with ankylosis, partial ankylosis, or muscle weakness.
Amputation
The impairment rate depends on the site of amputation and length of the stump. The impairment rate of lower extremity is presented in Table 2. The maximal impairment rate is less than 100% of the leg except hemipelvictomy. The hemipelvictomy is 110% of lower extremity function. In case of metatarsal amputation, if the remnant of the metatarsal bone is less than 25%, it is categorized as a Lisfran amputation. Tarsometatarsal amputation includes the proximal one-fourth transmetatarsal amputation. The length of stump is estimated by the radiography.
Table 2
Impairment estimates for amputations
Leg length discrepancy
The minimum disability is more than 1.5 cm difference. The measurement for leg length is done in supine position. Measurement is done for the distance between the anterior superior iliac spine and the medial malleollus on the involved side, and compare it with the opposite side. This method has at least 0.5 to 1.0 cm variance (6). In case of pelvic angulation, knee contracture, and severe leg edema, scanogram is recommended (Table 3).
Table 3
Impairment due to leg length discrepancy
Total ankylosis
Hip joint
Impairment due to ankylosis of hip estimate flexion, adduction, abduction, internal rotation, and external rotation. The optimal position of ankylosis is 25° to 40° flexion and neutral rotation, adduction, and abduction. This position represents a 50% lower extremity impairment. Impairment estimates for rotation, abduction and adduction deformities are added (Table 4).
Table 4
Impairment due to hip ankylosis
Knee joint
Impairment for flexion, valgus, varus, internal rotation, and external rotation. The optimal ankylosis position is 10° to 15° of flexion with neutral alignment. Ankylosis in the optimal position is a 67% lower extremity impairment (Table 5).
Table 5
Impairment due to knee ankylosis
Ankle joint
Impairment due to ankylosis of ankle estimate dorsiflexion, plantar flexion, valgus, varus, internal rotation, and external rotation. The optimal position of ankylosis is neutral position. Ankylosis in the optimal position is a 25% lower extremity impairment. Impairment of foot deformities are added (Table 6).
Table 6
Impairment due to ankle ankylosis
Partial ankylosis (range of motion)
Lower extremity impairment can be evaluated by assessing the range of motion of its joints. If the restricted range of motion is based on organic abnormality, measurement is done for the range three times and use the greatest range as an evaluation (7).
Hip
Flexion, extension, internal rotation, external rotation, abduction, and adduction are estimated. The impairment rate due to partial ankylosis of the hip is presented in Table 8.
Table 8
Hip motion impairment
Knee
Flexion, flexion contracture, varus, and valgus position are estimated. The impairment rate due to partial ankylosis of the knee is presented in Table 9.
Table 9
Knee impairment
Ankle and foot
In ankle motion, platar flexion, flexion contracture and dorsiflexion are estimated. In foot motion, inversion, eversion, valgus, and varus position are estimated. The impairment rate due to partial ankylosis of the ankle and foot is presented in Table 10, 11, 12, 13.
Table 10
Ankle motion impairment
Table 11
Hindfoot impairment
Table 12
Forefoot impairment
Table 13
Toe impairment
Muscle weakness
Muscle weakness is measured by manual muscle testing. When we use muscle weakness method, it should be Grade III or IV by manual muscle test. If the muscle power is less than Grade III, it should be assessed according to peripheral nerve injury (Table 14).
Table 14
Impairment due to lower extremity muscle weakness
Diagnosis-based estimation
Sometimes the diagnosis-based estimation is more precise than other methods. This method includes fractures, ligament injury, meniscal injury, fractures with deformity. In fracture category, malunion, nonunion, angulation and malrotation are estimated. Joint instability due to ligament injury in the knee and ankle is evaluated by stress radiography (8).
Hip
The impairment rate of hip based on diagnosis-based estimation method is presented in Table 15.
Table 15
Impairment estimate for the hip lesion
Knee
The impairment rate of knee based on diagnosis-based estimation method is presented in Table 16.
Table 16
Impairment estimate for the knee lesion
Joint replacement
The evaluation of joint replacement is based on the functional score in the hip (9) and knee joint (10) and the range of motion in the ankle joint (Table 18).
Table 18
Impairment estimate for the hip and knee joint replacement
Hip joint replacement
Pain, function, activities, deformity, range of motion are evaluated. Each category has points and add the points to determine the total scores. Rating hip replacement results are presented in Table 19.
Table 19
Rating hip replacement results*
Knee joint replacement
Pain, range of motion, stability, flexion contracture, extension lag, and alignment are evaluated. Rating knee replacement results are presented in Table 20.
Table 20
Rating knee replacement results*
Peripheral vascular disease
Impairment due to peripheral vascular disease is based on clinical symptoms. Table 22 shows the lower extremity impairment rate due to peripheral vascular disease. This table provide impairment due to arterial disease, vascular disease, and lymphedema of lower extremity. These diseases should be confirmed by radiologic study, sonography or lymphoscintigraphy.
Table 22
Lower extremity impairment due to peripheral vascular disease
In the lymphedema patient, lymphatic flow decrease is detected by lymphoscintigraphy. For stage II lymphedema and more than 3 cm circumference difference which needs elastic support is class 2. For stage III lymphedema and more than 5 cm circumference difference which needs elastic support is class 3.
DISCUSSION
Korean Guideline for Impairment Rating of lower extremities were developed mainly based on the criteria in the 5th edition of AMA Guides. It is different from AMA Guides in that Korean Guideline omits some classification which is not realistic in Korea. In the muscle weakness category, if muscle power is less than Grade III it would be evaluated in the peripheral nervous system. It may reduce inaccuracy. In this guideline, the method which can be modified by examinee such as gait derangement is excluded. Through this process we can make it simpler and more objective guideline than AMA Guides. When we use this new guideline for the evaluation of disability, the examiner should know about comprehensive medical history and review the all records. After understanding the patient's symptoms and signs, evaluator should do physical examination thoroughly. The physician should record lower extremity-related physical findings, such as range of motion, limb length discrepancy, deformity, reflexes, muscle strength, muscle atrophy, ligament laxity, motor and sensory deficits, and specific diagnoses such as fractures.
In summary, a stepwise approach of evaluating a lower extremity impairment is as follows;
Establish the diagnosis.
Determine whether maximal medical improvement has been reached.
Identify each lower extremity anatomic region with abnormalities that are related to injury in question.
Calculate impairment according to the text and tables for each applicable method.
Identify and calculate injury which is related to peripheral nervous system impairment.
Identify and calculate all injuries which is related to the peripheral vascular system.
The lower extremity impairment rating for each limb is then converted to whole person impairment.
References
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MeSH Terms
Tables
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