Stress fractures

Bone is a dynamic structure and, unlike the scaffolding of a building, it adapts to the stresses placed upon it according to Wolff’s law. Plain radiographs will chart the activity of a limb, the osteopenia of a nonweight-bearing foot or the thickened metatarsal shafts of an army recruit. Fractures of bone may be due to a single high load or cyclical low loads leading to a stress fracture.

  Any repetitious activity, particularly endurance training, is a risk factor for the development of stress fractures. Diagnosis should be suspected from the patient’s history, particularly if there has been a recent change in the training pattern, different footwear, a new playing surface or a sudden increase in intensity. Pain and tenderness are often poorly localised and radiographs may be normal in the early phase. Bone scintigraphy, or MRI if it is available, is the investigation of choice to demonstrate the earliest changes of marrow hypervascularity and trabecular microfracture (Fig. 29.5).

A common theme for treating these conditions is the necessity for a reduction in weight-bearing, particularly high-impact activity, for healing to occur. This disruption to the athlete’s training regime requires counselling but, more importantly, a satisfactory replacement activity must be found to keep up the athlete’s supply of endorphins! Cycling, with the pedal held under the heel, is the ideal substitute for runners, whilst swimming is less well tolerated.

Two patient subgroups should be identified: children and women. Children often present late with vague symptoms and the radiological changes to the growth plate may be difficult to interpret. The contralateral limb should be X-rayed to provide a control. Female athletes appear to be at increased risk of developing stress fractures. There appears to be a complex interplay between dysmenorrhea, exercise and decreased bone density, particularly if an eating disorder is superimposed.

  The distribution of stress fractures amongst runners is: tibia 49 per cent, tarsals 25 per cent, metatarsals 9 per cent, femur 7 per cent and fibula 7 per cent.

  The majority of fractures can be treated nonoperatively without great risk, but femoral neck stress fractures must be carefully assessed. There are two types: a tension fracture, which begins as a cortical defect on the superior aspect of the femoral neck, and the compression type, which appears as a haze of callus around the inferior cortex. Failure to recognise these fractures may result in displacement of the fragments with the subsequent risk of osteonecrosis, malunion and nonunion. Internal fixation with multiple screws should be considered in cases where symptoms are not controlled by reduction in weight-bearing.

Stress fractures of the pelvis occur about the ischium, but the ilium and sacrum may be involved. The tarsal navicular and metatarsal stress fractures are the bane of the armed forces owing to marching, but particular care must be taken of the base elf fifth metatarsal fracture as it has a high rate of delayed union or nonunion. Stress fractures are not confined to the lower limb and may occur in the ribs, clavicle, acromion, olecranon and metacarpals (Fig. 29.6).