The Metatarsus Stress Fracture Prevention.

The stress fracture is often experienced as a fatality for the athlete and his entourage. And for good reason, it requires a total hold on physical activity over a period of 6 to 12 weeks (8.5 on average), not counting the period of rehabilitation. Unlike tendinopathy (which can become chronic) there is very rarely recurrence at a fracture site because the bone after consolidation is more resistant. The impact is short and medium-term rather than long-term.

In France, a care protocol is rarely put in order despite some scientific evidences about calcitonin reducing the time it takes to consolidate. 

The athlete, his coaches and his medical team often find themselves unarmed in the face of this pathology, hence the interest of having a preventive approach. 

In the guide you will find some exercises specific to running and related to strengthening the intrinsic muscles of the foot.

Here we will expose the various factors of the onset of this injury.

I – GENERALITIES

This injury is characterized by pain that appears abruptly and intensifies to the point of causing a complete cessation of activity. It is not really a fracture, but a failure to adapt the bone to the stress, however, if the athlete maintains a high training load, a blunt fracture can form by adding minimal injuries.

The clinical examination reveals “exquisite” pain at the fracture point and the percussion of the bone in question.

This type of bone pathology has been described for the first time on metatarsals. Since then, it has been noted that its appearance takes place on areas heavily stressed by the physical activity of the subject. It is therefore characteristic of the discipline in which the athlete fits. In the middle this concerns the long bones of the lower limbs and the bones of the pelvic girdle.

II – ETIOLOGIES

Below in italics, you will find details provided by the analysis of a questionnaire concerning 67 high-level athletes in the middle distance (2017).

Mechanical stresses:
Bones adapt to muscle strength, however muscles reshape faster and in greater proportions than bone tissue, increasing the risk of fracture. Note that any sudden variations can be a factor : 

  1. Increased training load (volume and/or intensity) 
  2. Shoe change (materials, drop, lacing, physiognomy)
  3. Changing a sporting and/or postural gesture (strides, supports, terrain)

In 89% of cases this injury occurs in training and follows an increase in load for 58% of athletes.

In podiatry we will monitor areas of hyper support and certain risk factors (hollow feet, supination or pronation too large)

Psychological fatigue: (related to private, professional or sporting life).
These stressors have an inflammatory effect on the body and promote the development of injuries. Many coaches turn to cardiac variability methods to prevent these acute phases of physical and mental fatigue (by heart rythme analysis upon awakening) and bypass the risk of injury. In addition, certain behaviors can inform the athlete’s entourage about physical or mental wear (reciprocal) of the athlete: lack of desire, anxiety, decreased appetite, irritability, poor quality sleep, difficulty memory, nervousness, decreased self-confidence …

In 52% of cases a fracture occurs in a period of stress or change in the pace of life, illustrated by the transition to higher education, a period of examination, a disease, a decrease in the quality of sleep. 
It is interesting to note that they are all part of the pivotal periods of winter or summer preparation, where physiological and physical stress is important, as is fatigue.

Food intake:
When the energy balance is negative, the body draws on its reserves and ultimately decreases its metabolic activity. As a result, certain physiological mechanisms are impaired, including reproductive functions in women and bone remodeling.

The too large gap between the shape weight and the off-season weight is a factor. In addition, a change in diet coincides with the occurrence of this pathology in 32% of cases.

Deficiencies :
The link between vitamin D deficiency and the onset of fatigue fracture has already been demonstrated. This organic substance ensures bone remodeling and mineralization by maintaining a physiological level of calcium and phosphorus within the tissues. Vitamin D deficiency results in a 10-15% reduction in calcium absorption and 50-60% of phosphorus.

Iron deficiency is also implicated in the case of stress fractures, it is an integral part of a mathematical model that can predict 76.5% of the occurrences of this pathology. It includes the following parameters: Size, Body Mass Index (BMI), serum iron, ferritin and subjective fatigue score (SSF):

-13.98 – 0.079 x Size – 0.014x Iron – 0.464 x SSF – 0.105 x IMC – 0.035 x Ferritine

This refers to the major role of Iron in the oxygenation of tissues, muscles (this is the first observation of the deficient sportsman), but also bone.

Age :
In some studies, there is a lower prevalence among juniors and increased prevalence among older athletes.

According to our analysis, the onset of injuries of any type is more related to years of practice than to age.

Sex and hormones:
The disparity in cases of fatigue fracture by sex is edifying. An incidence of 1 man for 10 women was found (after puberty).

Menstrual cycle disorders called dysmenorrhea affect 64% of women who practice more than 10 hours of exercise per week. Below 5 cycles per year we speak of amenorrhea. The hypoestrogeny they cause is a contributing factor to fatigue fractures. Indeed, this hormonal disorder seems to lower the threshold of mechanical stress beyond which osteolastic activity (which destroys the ocessor cells) takes over the osteoblastic genesis (construction of new bone cells). This ovarian problem is caused by insufficient food intake in relation to energy expenditure and not by intense muscle activity.

Of the middle-distance athletes affected by this injury, 87% are women. 70% of them have disorders of menstrual cycles (54.5% amenorrhea and 15.5% dysmenorrhea).

Genetics:
If 20-50% of the factors predisposing to a decrease in DMO are controllable by hormonal status, diet and physical activity, the response to these stimuli remains genetically determined (these cases are characteristic of a bone deficiency fracture).

Another genetic parameter is found: black populations remain less affected by this pathology.

III – CONCLUSION

The role of muscles in the protection of the skeleton, mentioned above, corroborates the importance of a specific physical preparation. An increase in maximum strength and an improvement in technique, would allow a better economy of stroke decreasing muscle fatigue but also physiological and would spare musculo-tendino-skeletal structures. 

Beyond physical preparation, nutritional, biological and psychological follow-ups are relevant. Other prevention options are to be explored, including HRV (Heart Rate Variavility) follow-up.

Physical stress is directly related to the training load and recovery, psychological stress is dependent on the emotional and mental state. These two concepts rank among the main etiologies of stress fractures. The entourage can play an important role in preventing injuries by paying attention to the athlete’s behaviour. The latter should avoid any sudden changes in these conditions of practice and take into account certain warning factors, such as sudden amenorrhea for women. In the event of recurrence, a posturological and densitometric study of bone tissue may be relevant.

Sport Chiropodist, Johanna Geyer-Carles.

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