Stress fractures represent the failure of the bony skeleton to absorb repetitive loads. This results in structural fatigue of the bone, causing pain, performance impairment and potentially a complete fracture. Stress fractures result from recurrent and repetitive loading of bone, where micro-damage occurs at a rate faster than can be remodelled.
Bone tissue is continuously remodelled through the concerted actions of bone cells, which include bone resorption by osteoclasts and bone formation by osteoblasts, whereas osteocytes act as mechanosensors and orchestrators of the bone remodelling process (1)
Bone is a mineralised connective tissue that exhibits four types of cells: osteoblasts, bone lining cells, osteocytes, and osteoclasts
Bone remodelling is a highly complex process by which old bone is replaced by new bone, in a cycle comprised of three phases:
1. initiation of bone resorption by osteoclasts.
2. the transition from resorption to new bone formation.
3. bone formation by osteoblasts.
Training factors, such as volume, intensity, and surface are thought to be important. Other risk factors may include inadequate calcium or caloric intake; hormonal factors such as menstrual disturbance in females or reduced testosterone in males; osteoporosis, decreased bone density or bone geometry; muscle weakness, and leg-length differences. (2)
Risk factors:
It is important to ask about factors that may have caused the injury. These risk factors can be divided into two categories, intrinsic and extrinsic
1. Intrinsic risk factors: include, but are not limited to
· Low bone density due to poor vitamin D production & absorption (3)
· High foot arches or flat feet (3)
· Gender: Females are more likely to suffer stress fracture than males
· Age; with athletes over 40 and under 18 most at risk (3)
2. Extrinsic risk factors:
· Sudden increase in activity level and/or changes in footwear
· Hard surfaces or surfaces which are less compliant cause an increase in bone load.
· A history of a stress fracture places the athlete at significant risk for future occurrences.
Treatment:
1. Conservative treatment:
· Some fractures may require complete immobilisation, but the first step to take in any stress fracture is to stop the activity, depending on the type and severity of the fracture, modified rest of 6-8weeks is advised (4), and may switch to lower impact sport like changing from running to cycling or swimming.
· A pneumatic leg brace is often used in tibial stress fractures. This type of brace can shift a portion of the weight-bearing load from the tibia to the surrounding soft tissues, which results in less impact load being placed through the fracture site (5)
· Pulsed ultrasound can be effective to encourage bone healing (6).
· Physical therapy is recommended to help strengthen the affected bones like hydrotherapy, isometric, strengthening exercises, weight training and stretching.
2. Surgery:
Surgery to treat stress fractures often involves internal fixation, or the placement of metal pins, screws, and/or plates to help stabilise the affected bone(s) during and after the healing process. These methods are most commonly used in stress fractures of the feet if conservative treatments have failed to produce results.
It might be considered the first treatment in professional athletes.
Prevention:
Stress fractures may be prevented by understanding and reducing extrinsic risk factors. To wear appropriate footwear and replace them often. To increase exercise intensity gradually over a period of weeks or months and to allow the same period of adjustment whenever changing sport(s) or surface. Maintain proper nutrition, including dietary calcium and Vitamin D levels appropriate for the athlete's gender and age and female hormonal issues. Taking daily calcium and Vitamin D supplements in addition to eating a well-balanced diet rich in protein is recommended, especially for female athletes
References:
(1) Florencio-Silva R., Sasso GR, Sasso-Cerri E., Simoes MJ, Cerri P.S. Biology of bone tissue: Structure, function, and factors that influence bone cells. Biomed Res Int. 2015;2015:421746
(2) Bennell K., Matheson G., Meeuwisse W., Brukner P. Risk factors for stress fractures. Sports Med. 1999;28(2):91-122.
(3) http://emedicine.medscape.com/article/309106-overview accessed 16th March 2021
(4) Sanderlin, B.W. and Raspa, R.F., 2003. Common stress fractures. American family physician, 68(8), pp.1527-1532.
(5) Batt, M.E., Kemp, S. and Kerslake, R., 2001. Delayed union stress fractures of the anterior tibia: conservative management. British journal of sports medicine, 35(1), pp.74-77.
(6) Bashardoust Tajali S., Houghton P., MacDermid J.C., Grewal R. Effects of low-intensity pulsed ultrasound therapy on fracture healing: A systematic review and meta-analysis. Am J Phys Med Rehabil. 2012;91(4):349-367