Clinical update on Bone Stress.
Loading a bone leads to bone strain which are a normal physiologically process. However, bone strain may lead to some grad of micro bone damage of the bone structure depending on the magnitude and rate of strain.
Following tabel 1 (in the upper right corner), saying that no damage occurs, there will still be some kind of strain related remodelling which leads (positively influence from skeletal factors) to a stronger bone with a larger crosssectional area which provide the bone better options to tackle strain.
In contrast, if we think the bone strain leads to some kind of micro damage, a process of damage-related remodelling begins.
Normally this proces repairs efficient and remodelling keeps up with the range of damage so the repairs occurs without any signs of symptoms.
However, sometimes this micro fractures cause an imbalance between damage and remodelling.
A pathology continuum begins which goes from a stress reaction to a stress fracture and continues to a complete bone fracture.
The stress reactions is when there is an increased bone turnover, and there are periosteal (± marrow) oedema. This will become a stress fracture when there is a visuel and clear fracture line. When this line gets structural instabil we call it a complete bone fracture (you often dont see this in private care, however you will see the stress fracture in different stages).
Risk factors in for injuries in sport
Bahr R, Krosshaug T. Understanding injury mechanisms: a key component of preventing injuries in sport. Br J Sports Med. 6. januar 2005;39(6):324–9.
In 2005 R. Bahr and Krosshaug suggested a model for risk factors in order to prevent an injurie.
Turning this model to a bone stress case we have to identify factors which affecting bone loading and tolerance.
Loading are determined by magnitude, repetition and frequency in which can be changed with anatomical biomechanics load, choice of different training surface or footwear or technique factors influence the forces goes through the bone.
Tolerance in contrast are affected by genetic (family history), physical activity history and nutrition balance (According to a double blind randomized placebo control trail, when Calcium and Vitamin D supplementation was given as prevention strategy a decrease in stress fractors occured). Another risk factors for BSI can be found in female athletes, were it seems like there is an interrelated conditions related to energy availability, menstrual function, and bone mineral density (BMD) also refer as the female athlete triad
(further reading on this Update on stress fractures in female athletes: epidemiology, treatment, and prevention, Yin-Ting Chen & Adam S. Tenforde & Michael Fredericson, Curr Rev Musculoskelet Med (2013) 6:173–181 DOI 10.1007/s12178-013-9167-x)
Classifications for bone stress injuries.
The most common classification system for bone stress injuries are the low-risk and high risk site or MRI grade.
Return to sport prognosis.
When we combine this to classication system it provides us with an idea for the prognostic prediction for return to sport / play / run. This is explain in a study from 2012 (tabel 2 & 4) showing that low grade MRI has an quicker return-to-sport-time (RTPT) outcome.
Estimation of return-to-sports-time for athletes with stress fracture – an approach combining risk level of fracture site with severity based on imaging, Dobrindt et al. BMC Musculoskeletal Disorders 2012, 13:139 http://www.biomedcentral.com/1471-2474/13/139
However, it is important to interpret with the number before trust the mean-number because the variation are so high and it can take up to year for some people to get back to sport.
Althrough Walden, 2014 (the first article in this blogpost I refer to), does provide a graduated running program to turn to run up to 30 minutes of pain free running.
Key principles for Return To Sport
- Firstly, begin to unload the bone and then start to re-introduce a control loading strategy again (eventually, get help with load-management from a physiotherapist or a coach).
- Address all potential causes from affecting loading and tolerence (which have been mentioned previously).
- Avoid NSAID that can affect bone healing (we have not discuss this, we are saving it to another blogpost).
- Unfortunately, we don’t know enough, but a practical solution could be use pain as an guide.
- Finally, when is a bone stress injurie healed. Brukner & Khan 2012 in sports medicine (4edition) illustrates that we can’t rely on the scans but we have to judge our clinically picture
Exercise programme: stress_fracture