Fractures of the Femoral Neck

Femoral neck fractures are a common feature of particular populations of people with specific problems. Fractures of the neck of the femur are common in post-menopausal women and are secondary to a decrease in bone density. They are less common as stress fractures in people who put significantly increased forces on their hips such as runners and military personnel who are much younger and fitter. These fractures can also occur at almost any age by a direct fall on the hip with great force or if there are pathological changes in the bone such as tumours.

The circulatory anatomy of the femoral head and neck have long convinced specialists in orthopaedics that it is vital to restore the bony alignment of the fragments to avoid the risk of avascular necrosis (AVN) in the head of the femur. A fracture can cause loss of the blood supply in the femoral head, allowing it to die and collapse which causes significant problems and requires operation. Keeping patients immobilised in a hip plaster spica was used initially until Smith-Petersen developed a more predictable internal fixation in the 1930s. The Richards Screw Plate uses compression applied to the fracture site by a sliding fixation technique.

Walking puts both shearing and compression forces across the neck of femur in normal life but these forces are greatly magnified by activities such as sports involving jumping, sprinting or running. A typical increase in force of five to six times the body weight occurs across the femoral neck in normal activities such as climbing stairs. Hip pain refers commonly to the front of the thigh, side of the hip and the groin in a number of hip syndromes including a stress fracture, which can develop into a complete fracture plus displacement with the attendant risks.

In younger healthy people who exert abnormally high demands on normal bone the bone structures can fail mechanically due to the excessive stresses imposed on them. In older people, especially post menopausal women, normal stresses are imposed on bone which is not able to cope with them, bone with pathological changes due to insufficiency of the bone from osteoporosis or other metabolic abnormality. Oestrogen maintains the turnover and health of bone strength and without it bones become more brittle, either in older women or female athletes in high intensity training.

A femoral stress fracture should at least be suspected in an athlete who presents with hip pain after a significant increase in level of activity, with the typical picture worsened with activity and relieved by rest. As x-rays may not show anything in stress fractures bone scanning is used as a more sensitive measure. Much more common is an older person who jars themselves, twists on the hip or falls, resulting in a fracture of the femoral neck. Diagnostic indications are pain in the hip, groin or thigh, a shortened leg, lateral rotation of the leg and an inability to weight bear.

Displacement of transverse femoral neck fractures occurs in ten to fifteen percent of cases and avascular necrosis is a risk in these injuries. Operative management is the necessary option and the choice of the technique depends on the fracture. Fractures occur in many positions anatomically and are grouped into categories, with fractures just below the head carrying the highest risk of circulatory disturbance. These are managed either by Thompson hemi-arthroplasty or by total hip replacement. Fractures in the neck can be internally fixed.

In many cases the fall fractures the bone and compacts the fracture fragments together, forming a compression system which resists displacement and can bear weight. This type of fracture may not need operation as it is stable and can be managed conservatively. If the fracture is in a different area then it may be unstable as tension forces are acting on it, so must be managed by insertion of one of a large choice of fixation devices. Sub-trochanteric, trochanteric and lower neck fractures may fall into this category.

Once the fracture is replaced or fixed the patient is allowed 24 hours to recover medically then the physiotherapist and an assistant will check the operative instructions, review the patient’s observations and get the patient up weight bearing with a frame or crutches.