DIFFERENTIAL DIAGNOSIS

DIFFERENTIAL DIAGNOSIS - CURRENT CONCEPTS UNDERLYING MEDIAL TIBIAL STRESS SYNDROME

By Thomas Bennett, MSc (Sports Med) GSR

INTRODUCTION Chronic lower leg pain is common amongst the active population with lower limb injuries accounting for a high proportion of total sports injuries. In a study of injury prevalence in a large cohort of runners (n=2002) lower leg injuries accounted for 29.8% of all injuries sampled (1). A number of pathologies are responsible for injuries to the lower leg including compartment syndromes both chronic and acute, stress fracture, nerve entrapment and medial tibial stress syndrome (MTSS). Clinically, differential diagnosis is made increasingly difficult due to the common characteristics shared by a number of these pathologies.

Due to its complex histopathology, MTSS is a condition that epitomises the difficulties faced by allied health professionals when forming a clinical impression. Research findings by Clement et al (2) highlighted that MTSS accounted for 10.7% of injuries in men and 16.8% of injuries in women which would suggest it is a common pathology. However, relatively little is known about its causes.

A number of aetiological factors including altered biomechanics, gender and muscle dysfunction have been implicated as possible causes. The aim of this literature review is to present the current research findings surrounding MTSS and provide allied health practitioners with information which can be factored into the clinical reasoning process.

NOMENCLATURE An area of much contention when dealing with exercise induced leg pain is the variety of terms often used interchangeably, to describe the condition, these include shin splints, medial tibial stress syndrome and periostitis. As a clinician it is imperative that we understand the nature of the condition in order to provide treatment interventions based on sound clinical reasoning. This process is not helped by the variety of nomenclature surrounding the condition.

The lay term ‘shin splints’ which has been used over the past forty years can be defined as the ‘pain and discomfort in the leg resulting from repetitive running on hard surfaces and a forcible use of the foot flexors’ (3). This term however bares no resemblance to pathophysiological findings. In light of this,

Slocum (4) commented that shin splints cannot be considered a diagnosis for any lower leg condition and can only be used as an all encompassing descriptive definition.

The term medial tibial stress syndrome was first introduced by Mubarak et al (5). Clinically it has been defined as 'dull aching to intense pain that is alleviated by rest and tenderness over the posteromedial border of the tibia with the absence of any neurovascular abnormalities' (6). MTSS, as with shin splints, is descriptive and does not represent one specific pathophysiology, consequently it should be considered a generic term for symptoms associated with the posteromedial tibia.

Problems identifying the histopathology of acute posteromedial tibial shin pain have lead researchers to propose a number of sub- terms relative to clinical findings (Box 1).

BOX 1:PROPOSED ACUTE CONDITIONS AFFECTING THE POSTEROMEDIAL TIBIA

■ periostitis (tibial and tractional) ■ tibial bone stress reaction ■ tibialis posterior tendonitis ■ soleus tendonitis ■ flexor hallucis longus tendonitis ■ flexor digitorium longus tendonitis

Periostitis has been defined as 'an overuse injury with associated tearing of Sharpeys fibres between muscle and bone' (8), in this instance the tibia. Tractional periostitis involves tractional force to the periostium with associated muscle contraction.

If periostitis were the cause of MTSS one would expect to see an active inflammatory process of the periosteum at the site of injury. Yet an increasing body of evidence extrapolated from biop- sy and scintography studies refute this assumption (5,8-13). A review of the literature concerning biopsy samples taken from the periosteum, fascia and bone during surgical intervention showed, that of the 75 samples taken, only four documented evidence of periostitis (14). This would suggest that periostitis is not the sole cause of MTSS. However it cannot be ruled out as one of a num- ber of possible pathologies causing MTSS. Thus periostitis must be vectored into any clinical reasoning when making a diagnosis.

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