BY PHYSIOTHERAPISTS PAUL NEW AND WAYNE GILL

OVERVIEW Epidemiology

It has been estimated that stress fractures make up 10% of all significant sports-related injuries (4) and in sports that involve running such as football, prevalence ranges from 10% to 31% (5). According to Matheson et al (6) in the athletic population the areas most commonly affected are the tibia (49.9%), tarsals (25.3%) and metatarsals (8.8%). Less commonly they are seen in the femur (7.2%), fibula (6.6%), pelvis (1.6%), sesamoids (0.9%) and spine (0.6%) (5). A stress fracture can strike virtually any bone in the body but in football they are more frequently seen in the lower extremities.

Pathophysiology Physical activity plays a crucial role in the maintenance of bone density as exercise promotes beneficial changes in bone mass and structural strength (7). However, ball sports such as football have been shown to produce a higher peak strain in bone than running alone and may confer a high risk of stress fracture (8). Bone is a dynamic tissue

constantly remodelling in response to the physiological demands placed upon it (9) and abrupt increases in training intensity without adequate rest days predispose players to stress fractures for the following reasons (10); micro damage from repeated tensile loading occurs at an area of stress concentration which, when exposed to further stress produces microscopic cracks in the bone, ‘crack Initiation’. This can be seen on MRI scanning as bone oedema or ‘stress response’ (Fig 1). If the player does not rest

sufficiently to allow these microscopic cracks to be repaired then further

Figure 1: MRI showing a) bone marrow oedema and b) crack initiation

ACADEMY FOOTBALL

STRESSED TO THE BONE

Professional football is a very demanding sport in which stress fractures are a commonly seen overuse injury. First described in 1855 by Breithaupt in military recruits, they are common to certain populations under significant physical demands, principally soldiers and athletes (1). They have a high prevalence in all codes of professional football (2) and are regarded as either fatigue or insufficiency fractures caused by the repeated sub-threshold loading of bone (3). Academy players at professional football clubs are a specific ‘at risk’ group of athletes who like new military recruits are often unaccustomed to their new role. This article aims to outline some of the demanding sportpertinent issues in diagnosis, treatment and prevention to ensure that a healthy environment exists within the sport to develop future talent.

damage accumulates and the crack extends, ‘crack propagation’. An area of weakness forms in the bone and the remodelling process is accelerated with increased osteoclastic reabsorption of bone tissue and a lag in osteoblastic bone synthesis resulting in resorption

cavities and decreased bone strength (11). Thus a dynamic balance exists between the host repair processes and the accumulation of micro damage. When micro damage occurs in excess of the healing process bone strain develops and progresses along a continuum of which a stress fracture is the final outcome (Fig 2).

Any factor which increases the stress placed on a bone such as poor anatomical alignment, will cause an increase in the accumulation of micro damage with each loading episode and an increased risk. New academy players are particularly at risk after six weeks of pre-season training as the new season and competitive fixtures begin (12).

22 sportEX medicine 2010;43(Jan):22-27