Using the RSS¹

The RSS progresses in half-point increments from 0 (no rickets) to 10 (most severe rickets), and allows for individual radiographs to be scored without referencing any prior images for comparison. To determine the overall score for a patient at a point in time, four radiographs are required—one image of each wrist and knee. Left and right images are compared to determine the side that exhibits the most severe signs of rickets, and the most severe side is then used for scoring. The indicators used to determine rachitic severity include lucency, metaphyseal fraying, metaphyseal cupping, and widening of the growth plate. These characteristics are evident at the metaphyseal margins of rachitic bones.

The radius and ulna of the most severe wrist are each scored in half-point increments and summed to give a total wrist score. The femur and tibia of the most severe knee are each scored in one-point increments and are summed together to give a total knee score. At the knee, a multiplier factor of 0.5 is assigned to the bone if ≤1 condyle or plateau is affected. If both condyles or plateaus are affected, a multiplier of 1.0 is assigned. The maximum score for the wrist is 4 and the maximum score for the knee is 6. Once both wrist and knee are scored, these values are summed to give the total RSS for a patient.

Metaphyseal margin

The edge or border of the metaphysis

Metaphyseal cupping

Concavity of the metaphysis, giving the metaphysis a cup-like appearance³

Metaphyseal fraying

Irregularity of the normally smooth distal metaphysis⁴

Lucency

Darker areas on the bone radiograph that occur as a result of decreased bone density, allowing more xrays to pass through⁵

Widening of the growth plate

An increase in the distance between the metaphysis and the epiphysis

Wrist Scoring

Rachitic abnormalities present differently at the radius and ulna. The figures below provide images that best represent the abnormality features that contribute to the RSS for each bone.

Abnormalities at the Radius

For radiographic examples of scores 0-1.5 for the radius, refer to Figure 1 below. A score of 2.0 at the radius is not typically observed in patients with XLH.*

Radius

0

Normal growth plate without changes of rickets

0.5

lucency of metaphyseal margin without fraying or irregularity

1

Widened growth plate, irregularity of metaphyseal margin, but without concave cupping

1.5

Partial metaphyseal concavity or incomplete fraying of metaphyseal margin

2

Metaphyseal concavity with fraying margin

Abnormalities at the Ulna

For radiographic examples of scores 0-2 for the ulna, refer to Figure 2 below.

Ulna

0

Normal growth plate without changes of rickets

0.5

lucency of metaphyseal margin without fraying or irregularity

1

Widened growth plate, irregularity of metaphyseal margin, but without concave cupping

1.5

Partial metaphyseal concavity or incomplete fraying of metaphyseal margin

2

Metaphyseal concavity with fraying margin

Knee Scoring

Rachitic abnormalities present differently at the femur and tibia. The figures below provide images that best represent the abnormal features that contribute to the RSS for each bone. Note that for the femur and tibia, the scores associated with each image are not representative of the entire bone score. These scores are only representative of the abnormality indicated by the arrow on each image. To determine the entire bone score, both condyles must be considered and the appropriate multiplier chosen.

Abnormalities at the Femur

For radiographic examples of scores 0-3 for the femur, refer to Figure 3 below.

Femur

0

Normal growth plate without changes of rickets

1

Partial lucency, smooth margin of metaphysis visible

Lucency Partial, smooth margin of metaphysis visible

2

Partial lucency, smooth margin of the metaphysis NOT visible

Lucency Partial, smooth margin of the metaphysis NOT visible

3

Complete lucency, epiphysis appears widely separated from distal metaphysis

Lucency Complete, epiphysis appears widely separated from distal metaphysis

Abnormalities at the Tibia

For radiographic examples of scores 0-2 for the tibia, refer to Figure 4 below. Tibia scores of 3 are not typically observed in patients with XLH.*

Tibia

0

Normal growth plate without changes of rickets

1

Partial lucency, smooth margin of metaphysis visible

Lucency Partial, smooth margin of metaphysis visible

2

Partial lucency, smooth margin of the metaphysis NOT visible

Lucency Partial, smooth margin of the metaphysis NOT visible

3

Complete lucency, epiphysis appears widely separated from distal metaphysis

Lucency Complete, epiphysis appears widely separated from distal metaphysis