Intracapsular femoral neck fractures anatomy and biomechanics

Intracapsular femoral neck fractures anatomy and biomechanics

1. Intracapsular Femoral Neck Fractures Anatomy and Biomechanics By Dr Kota Gandhi I yr PG Orthopaedics Kamineni Institute Of Medical Sciences

2. Hip fractures are common and comprise 20% of the opera- tive workload of an orthopedic trauma unit. Intracapsular femoral neck fractures account for 50% of all hip fractures. The lifetime risk of sustaining a hip fracture is high and lies within the range of 40% to 50% in women and 13% to 22% in men.

3. The hip is a large synovial ball and socket joint . T he relationship to the femur and hip joint is characterized by anteversion of the femoral neck in the transverse plane and the femoral neck shaft angle in the coronal plane. The femoral neck subtends an angle with the femoral shaft of between 130 and 135 degrees in the normal hip.

4. Hip axis length and neck shaft angle ( α). A longer hip axis length is associated with a greater lever arm and greater force being applied to the femoral neck during a fall. A lower neck shaft angle is seen in coxa vara and will also increase the risk of femoral neck fractures for the same reas on.

5. The calcar femorale is a dense vertical plate of bone extending from the portion of the femoral shaft under the lesser trochanter, radiating to the greater trochanter and reinforcing the postero inferior portion of the femoral neck .

6. The presence or absence of trabecular lines forms the basis of the classification of osteoporosis described by Singh. The grade is determined from a true AP projection of an intact proximal femur.

7. Singh’s index grades osteopenia from normal (grade 6; all trabecular groups are visible) to definite (grade 3; thinned trabeculae with a break in the principal tensile group) to severe (grade 1; only the primary compres sive trabeculae are visible, and they are reduced) based on the ordered reduction in trochanteric , tensile, and ultimately primary compressive trabeculae .

8. Ward triangle refers to a radiolucent area between principle compressive, secondary compressive and primary tensile trabeculae in the neck of femur.

9. In the adult the most important source of femoral head blood supply is derived from the capsular vessels. These vessels arise from the medial and lateral circumflex femoral arteries, which are in turn branches of the profunda femoris The medial and lateral femoral circumflex arteries form an extracapsular circular anastomosis at the base of the femoral neck, and the ascending cervical capsular vessels arise from this.

10. Within the capsule these are referred to as retinacu lar vessels. There are four main groups (anterior, medial, lat eral , and posterior) of which the lateral group is the largest contributor to femoral head blood supply. The most important retinacular vessels arise from the deep branch of the medial femoral circumflex artery.

11. The portion of the femoral neck within the hip joint capsule has no cambial layer in its fibrous covering to participate in cal lus formation during fracture healing. Fracture union depends on endosteal healing alone, which is one of the reasons why prolonged union times are common with these fractures.

12. Ligaments The hip joint capsule extends down to the intertrochanteric line over the anterior aspect of the femoral neck, but posteriorly the lateral half of the femoral neck is extracapsular . Three important condensations of the hip joint capsule are considered ligamentous stabilizers of the hip.

13. The hip is a stable ball and socket joint, formed by the femoral head and pelvic acetabulum. The abductor muscles are the main stabilisers of the pelvis in the coronal plane. The total compressive force acting on the hip joint is the resultant of forces due to body weight, tension in the abductor muscles and any impact loads transmitted upwards through the body from the foot during everyday activities. A static analysis can be used to estimate the magnitude of hip joint reaction force under different circumstances.

14. Thank you