**Core Concept:** The McKern and Stewa maturation score is a method used to assess the skeletal age of a patient based on the degree of epiphyseal ossification. It involves evaluating the degree of ossification in certain epiphyseal centers.

**Why the Correct Answer is Right:** The McKern and Stewa maturation score considers the degree of ossification in several epiphyseal centers. The correct answer is **D** because it does not include the ossification of the atlas and axis (C2-C3) in the scoring system. This score focuses on larger epiphyseal centers, such as the humerus and femur, which are more relevant for assessing skeletal maturation in most cases.

**Why Each Wrong Option is Incorrect:**

A. **Option A**: Ossification of the epiphysis of the humerus is included in the maturation score, making this incorrect.

B. **Option B**: Ossification of the epiphysis of the femur is included in the maturation score, making this incorrect.

C. **Option C**: Ossification of the epiphysis of the fibula is included in the maturation score, making this incorrect.

**Why Option D is Right:** The ossification of the atlas and axis (C2-C3) is not considered in the McKern and Stewa maturation score, making this the correct answer.

**Clinical Pearl:** The McKern and Stewa maturation score is a widely used method for estimating the skeletal age in pediatric patients, but it has its limitations. When assessing skeletal maturation in certain cases, considering factors outside of the score, such as the patient's age, pubertal status, and growth hormone levels, can provide a more accurate estimation of skeletal maturity.