A 16-year-old female football player presented with a one month history of right lateral lower leg pain. This came on with no clear traumatic precipitant, but was associated with an increased training load as she joined a new team. The pain had become progressively worse and was present with all weight-bearing activity.
On examination she was able to walk without distress but was very reluctant to hop on her right leg. She had localised tenderness over the distal fibula, at the junction of the middle and distal thirds. She was 172.5cm tall and weighed 59.5Kg (BMI of 20).
An x-ray of the lower leg taken two weeks after the onset of pain was completely normal. An MRI taken at the time of her presentation (four weeks after the onset of pain) shows abnormal T2 hyper-intensity involving the distal fibula over a length of approximately 12 cm. There is diffuse high signal within the marrow cavity as well as through the lateral cortex in keeping with a sub-acute fracture. There is no abnormality involving the distal tibia. The findings are in keeping with a stress fracture involving the distal fibula. A repeat x-ray taken at the same time as the MRI shows that there is now a subtle lucency through the lateral cortex of the fibula in the region of her MRI findings.
This player was initially managed with a two week period of unloading. During this time she did some water jogging and continued to train in the gym. At this point she was able to walk pain-free and started a progressive walking-jog programme. She worked on her single leg stability with a club physiotherapist, had a footwear review with a podiatrist and also had a visit with a dietician. She was back playing football without restriction at six weeks. It was felt that the primary cause of this stress injury was the sudden increase in training load. There was no clinical evidence of RED-S. At the time of her return to football she had a good understanding of the concept of energy availability and was given some nutritional strategies to try and ensure optimal energy balance. A training plan to transition her back into a high-performance environment was discussed with her team’s coaching staff.
As this case illustrates x-rays have a limited sensitivity for detecting stress fractures. It is estimated that in the first few weeks after the onset of pain that x-rays are positive in only 15 to 30% of cases. When the symptoms have persisted for longer than this (weeks to months) the sensitivity increases, with reports of up to 70% sensitivity being reported. It is important to understand that there are other imaging options. X-ray findings include periosteal reaction, increased sclerosis or cortical thickening or the “grey cortex” sign (where there is a loss of cortical density). When the problem has been present for a longer period a fracture line may be evident. When the x-ray is positive other imaging studies may not be needed. MR imaging is the most sensitive modality for diagnosing stress injuries and should be considered when there is uncertainty about the diagnosis. Typical MRI findings of a stress fracture include periosteal oedema, bone marrow oedema and a hypo-intense fracture line on T1 imaging. It is worth noting that there are several MRI grading systems that have been reported and that MR findings may correlate with recovery time.
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