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 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).