Development of Korean Academy of Medical Sciences Guideline Rating the Physical Impairment: Lower Extremities



# 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 [bib_ref] Disability evaluation and principles of treatment of compensable injuries, Mcbride [/bib_ref] , the guide of Korean Orthopaedic Association, the guide of Korean Neurosurgical Society (4), the Korean Academy of Rehabilitation Medicineand 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 .

## 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 [fig_ref] Table 2: Impairment estimates for amputations [/fig_ref]. 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 onefourth transmetatarsal amputation. The length of stump is estimated by the radiography.

## 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 [bib_ref] Computed radiographic measurement of limb-length discrepancy. Full-length standing anteroposterior radiograph compared with..., Sabharwal [/bib_ref]. In case of pelvic angulation, knee contracture, and severe leg edema, scanogram is recommended [fig_ref] Table 3: Impairment due to leg length discrepancy [/fig_ref].

## 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 25to 40flexion and neutral rotation, adduction, and abduction. This position represents a 50% lower extremity impairment. Impairment estimates for rotation, abduction and adduction deformities are added ( Impairment for flexion, valgus, varus, internal rotation, and external rotation. The optimal ankylosis position is 10to 15o f flexion with neutral alignment. Ankylosis in the optimal position is a 67% lower extremity impairment [fig_ref] Table 5: Impairment due to knee ankylosis [/fig_ref].

## 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 [fig_ref] Table 6: Impairment due to ankle ankylosis S302 H [/fig_ref].
Toes Impairment due to ankylosis of toe estimate dorsiflexion and plantar flexion in the great toe [fig_ref] Table 7: Impairment due to toe ankylosis [/fig_ref].

## Ankylosis ()
Lower extremity (foot) impairment (%)

## 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 [fig_ref] Table 8: Hip motion impairment [/fig_ref]. estimated. The impairment rate due to partial ankylosis of the knee is presented in [fig_ref] Table 9: Knee impairment [/fig_ref].

## 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 [fig_ref] Table 10: Ankle motion impairment [/fig_ref] -13.

## 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.

## 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 [bib_ref] Knee ligament injuries: a standardized evaluation method, Marshall [/bib_ref].

## Hip
The impairment rate of hip based on diagnosis-based estimation method is presented in [fig_ref] Table 5: Impairment due to knee ankylosis [/fig_ref].

## Knee
The impairment rate of knee based on diagnosis-based estimation method is presented in [fig_ref] Table 6: Impairment due to ankle ankylosis S302 H [/fig_ref].

## Ankle and foot
The impairment rate of ankle and foot based on diagnosisbased estimation method is presented in [fig_ref] Table 7: Impairment due to toe ankylosis [/fig_ref]. The evaluation of joint replacement is based on the functional score in the hip [bib_ref] The use of allograft bone in revision of total hip arthroplasty, Gross [/bib_ref] and knee joint [bib_ref] Rationale of the Knee Society clinical rating system, Insall [/bib_ref] and the range of motion in the ankle joint [fig_ref] Table 8: Hip motion impairment [/fig_ref].

## 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 [fig_ref] Table 9: Knee impairment [/fig_ref].

## Knee joint replacement
Pain, range of motion, stability, flexion contracture, extension lag, and alignment are evaluated. Rating knee replacement results are presented in [fig_ref] Table 2: Impairment estimates for amputations [/fig_ref].

## Ankle joint replacement
Only range of motion is evaluated. The impairment rate due to ankle joint replacement is presented in [fig_ref] Table 2: Impairment estimates for amputations [/fig_ref].
Peripheral vascular disease Impairment due to peripheral vascular disease is based on clinical symptoms. [fig_ref] Table 2: Impairment estimates for amputations [/fig_ref] 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.
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.

## Skin loss
Full-thickness skin loss in the weight bearing area makes a disability. Impairment due to skin loss of the foot is presented in [fig_ref] Table 3: Impairment due to leg length discrepancy [/fig_ref].

# 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

## Range of motion ()
Lower extremity (foot) impairment (%) 20 20 (28) <20 25 (35) 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; 1) Establish the diagnosis.
2) Determine whether maximal medical improvement has been reached.
3) Identify each lower extremity anatomic region with abnormalities that are related to injury in question. 4) Calculate impairment according to the text and tables for each applicable method. 5) Identify and calculate injury which is related to peripheral nervous system impairment.
6) Identify and calculate all injuries which is related to the peripheral vascular system.
7) The lower extremity impairment rating for each limb is then converted to whole person impairment.
[table] Table 3: Impairment due to leg length discrepancy [/table]
[table] Table 2: Impairment estimates for amputations [/table]
[table] Table 4: Impairment due to hip ankylosis [/table]
[table] Table 5: Impairment due to knee ankylosis [/table]
[table] Table 7: Impairment due to toe ankylosis [/table]
[table] Table 6: Impairment due to ankle ankylosis S302 H.-C. Kim, J.-S. Kim, K.-H. Lee, et al. [/table]
[table] Table 8: Hip motion impairment [/table]
[table] Table 9: Knee impairment [/table]
[table] Table 10: Ankle motion impairment [/table]
[table] Table 11: Hindfoot impairment [/table]
[table] Table 12: Forefoot impairment [/table]
[table] Table 13: Toe impairment [/table]
[table] Table 15: Impairment estimate for the hip lesion [/table]
[table] Table 16: Impairment estimate for the knee lesion [/table]
[table] Table 17: Impairment estimate for the ankle and foot lesion [/table]
[table] Table 14: Impairment due to lower extremity muscle weakness [/table]
[table] Table 18: Impairment estimate for the hip and knee joint replacement [/table]
[table] Table 19: Rating hip replacement results* [/table]