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Femoral head asymmetry and coxa magna: anatomic study
Ernest Y Young1, Jeremy J Gebhart, Navkirat Bajwa
1*Department of Orthopaedics, Case Western Reserve University School of Medicine †University Hospitals Case Medical Center, Cleveland Heights, OH.
Insights
This study found high symmetry between left and right femurs in adults, establishing a baseline for defining coxa magna (femoral head enlargement). African Americans showed more symmetry and left-sided enlargement compared to whites.
Area of Science:
- Orthopedics
- Radiology
- Human Anatomy
Background:
- Coxa magna, characterized by femoral head enlargement, is a sequela of pediatric hip disorders.
- Existing definitions of coxa magna lack standardization due to limited research on normal femoral head asymmetry distribution.
- Understanding normal asymmetry is crucial for diagnosing conditions like coxa magna.
Purpose of the Study:
- To define the normal distribution of femoral head and neck asymmetry in a population.
- To investigate the influence of demographics on femoral asymmetry.
- To determine side dominance patterns (left vs. right) in femoral dimensions.
Main Methods:
- Measurement of 230 paired femurs from adults aged 20-40 years.
- Recording of individual height and weight, along with sex and ethnicity data.
- Determination of femoral head and minimal femoral neck diameters, calculating absolute and percent differences to quantify asymmetry.
Main Results:
- The majority of the population exhibited femoral head asymmetry within 3% and femoral neck asymmetry within 4%.
- Maximum observed femoral head asymmetry was 7.4%.
- African Americans demonstrated greater femoral head symmetry and a tendency towards left-sided enlargement compared to white individuals.
Conclusions:
- A high degree of symmetry exists between left and right femoral heads and necks in the general population.
- Findings support existing definitions of coxa magna exceeding 10% asymmetry.
- This study provides a quantitative definition of femoral head asymmetry in healthy individuals, aiding in coxa magna diagnosis.
Background:
Coxa magna, the asymmetrical circumferential enlargement of the femoral head, is an important sequela of pediatric disorders such as Legg-Calvé-Perthes disease. Definitions vary because of lack of controls and a scarcity of research on the distribution of the femoral head asymmetry. This study aims at defining the normal distribution of asymmetry between the left and the right femoral head and neck in the population and how demographics affect these properties. The study also looked at the distribution of side dominance (left or right).
Methods:
This study measured 230 paired femurs from individuals (20 to 40 y old) distributed for sex and ethnicity. The height and weight of the individuals were also recorded. The femoral head diameter and minimal femoral neck diameter in the anteroposterior view were measured on each paired femurs. The absolute and percent differences were determined to define asymmetry.
Results:
Most of the population fell within 3% of asymmetry for the femoral head and 4% for the femoral neck. The maximum head percent asymmetry was 7.4%. Absolute difference in millimeters to percent asymmetry showed a ratio of 2:1 for the femoral head and 3:1 for the femoral neck. African Americans showed greater femoral head symmetry and a bias toward left-sided femoral head and neck enlargement when compared with their white counterparts.
Conclusions:
There was a high degree of symmetry between the left and right femoral heads and necks, which supports definitions found in the literature that define coxa magna above 10%. This study defines asymmetry in the femoral head in the normal population, which will help to define a quantitative definition of coxa magna.
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