CHANGES IN BONE DURING BSI RECOVERY
Typical BSI recovery involves relative rest and gradual re-loading over a period of 6-12 weeks, depending on the grade and site of the injury.
Though this is the typical timeline for return to sport, stress fracture recurrence rates are high - which begs the question, are we failing to properly rehabilitate athletes after BSI? Are we rushing them back into running before their body is ready for those demands? Or is something else occurring while recovering that increases one’s risk for subsequent BSI?
A study by Popp et al. in 2021 attempted to answer that final question by looking at volumetric bone mineral density (vBMD) over the 12 months following a diagnosis of tibial BSI.
Their study included 30 female athletes with a tibial BSI, grade 2 or higher. They collected information on vBMD at baseline and 6, 12, 24 and 52 weeks after BSI diagnosis.
They found that vBMD declined in BOTH the injured and uninjured limbs after a BSI diagnosis, and did not return to baseline for 3-6 months following.
vBMD in the injured leg decreased by 0.58-0.94% while it decreased by 0.61-0.67% in the uninjured leg. The drop on both sides can be attributed to the necessary decrease in weight-bearing activity that occurred to allow healing, and it appears the changes in bone lagged behind the change in activity - the study found that weight-bearing activity was lowest during the first several weeks post-diagnosis, while vBMD was lowest at 12 weeks.
Off-loading (minimizing or avoiding weight-bearing activity) is often a necessity in bone stress injury rehab - so although some of this decline in BMD may be unavoidable, it makes me think about how we can mitigate that bone density loss during recovery to set athletes up for a successful return to running.
First, to reduce complete off-loading and the negative impacts on bone, we may be able to allow partial or full weight-bearing early on in the rehab process (particularly with lower-grade BSIs in low-risk sites e.g. posteromedial tibia, fibula, metatarsal shafts 2-4, calcaneus). If an athlete is not having pain with activities of daily life, we can consider just removing running & other pain-inducing activities versus having them go non weight-bearing.
Second, we can re-evaluate our timelines for their return to typical levels of activity and communicate these new timelines to the athlete. Emphasizing a more gradual return to running with strategic deload and rest weeks as well as being particularly conservative during those first 12 weeks of recovery may reduce the risk of recurrence or bone injury on the opposite limb.
Finally, there may be a way to mitigate bone loss on the unaffected limb with potential crossover effects to the affected limb through aggressive loading & strength training early on in rehab. Yes, it’s important to unload the affected side, but that doesn’t mean rehab just has to be swimming or biking - incorporating single leg plyometrics and strength on the unaffected side may maintain or mitigate both bone loss & muscular atrophy on both limbs, setting the athlete up for an easier return to running.
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Popp, K. L., Ackerman, K. E., Rudolph, S. E., Johannesdottir, F., Hughes, J. M., Tenforde, A. S., ... & Bouxsein, M. L. (2021). Changes in volumetric bone mineral density over 12 months after a tibial bone stress injury diagnosis: implications for return to sports and military duty. The American Journal of Sports Medicine, 49(1), 226-235.