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.
• The 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.

5. • 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 reason.

6. 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.

8. • 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.

9. 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 compressive trabeculae are visible,
and they are reduced) based on the ordered
reduction in trochanteric, tensile, and
ultimately primary compressive trabeculae.

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

12. 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.

14. • Within the capsule these are referred to as
retinacular vessels. There are four main
groups (anterior, medial, lateral, 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.

16. The portion of the femoral neck within the
hip joint capsule has no cambial layer in its
fibrous covering to participate in callus
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.

17. 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.

27. • 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.

34. Thank you