DIFFERENTIAL DIAGNOSIS

tibial pain in females when trained at the same intensities as male recruits (29). It has been well documented that when women are expected to train alongside males and achieve similar fitness tar- gets, injury prevalence increases (30,31). Authors have speculated that due to women being of smaller stature than their male coun- terparts they may make changes to a number of gait parameters such as increasing stride length or increased cadence in an attempt to keep pace during exercise, increasing the possible risk of devel- oping MTSS (20). Support for this proposal can be found in research that shorter women are at greater risk of injury compared to their taller peers (32).

DIAGNOSTIC IMAGING OF MEDIAL TIBIAL STRESS SYNDROME Plain radiography (x-ray) appears to have little role in the diagno- sis of MTSS. Studies have shown the sensitivity of x-ray to be as low as 14% in symptomatic patients (33-34). A review of the available literature in which plain radiography was performed on patients with postero tibial pathologies (13,35-39) highlighted 38 positive findings consisting of bony changes in 179 patients, a sensitivity level of 21%. This level of sensitivity is low and suggests plain radi- ography is unlikely to assist the clinician in confirming a diagnosis of MTSS.

Evidence concerning magnetic resonance imaging (MRI) has proven inconclusive in studies of MTSS symptomatic populations. Positive diagnoses of signs and symptoms have ranged extensively between studies (43-90%) (10,40). Anderson et al (10) suggested method- ological difference in subject symptom duration between studies may be a possible explanation for this disparity. Within their study population subjects had signs and symptoms for a mean duration of 24 months compared to the mean of 10 months in research by Fredricson et al (40). Anderson et al (10) also identified a signifi- cant relationship between subjects with long term signs and symp- toms (average 48 weeks) and negative MRI findings leading them to propose that MTSS may consist of both chronic and acute disor- ders with two distinct histopathologies. If Anderson et al’s findings are true, MRI is not a viable diagnostic tool in the diagnosis of MTSS in patients with long term signs and symptoms especially consider- ing the cost implications of performing a scan.

Both Anderson's (10) and Fredricson's (40) studies are not without limitations. Both had small sample groups of between 18-19 symp- tomatic limbs making it difficult to relate the findings to the clini- cal population and neither studies contained asymptomatic control subjects to confirm whether findings were confined to the sympto- matic population.

Conversely Bergman et al (41) noted that MRI

images of 43% of the asymptomatic population in their study showed signs of a tibial stress reaction which suggests findings noted in symptomatic patients may not be indicative of MTSS.

It is the general consensus of the literature that triple phase bone scintography (bone scan) is the gold standard in diagnosis of MTSS (7) especially when differentiating between a stress fracture and MTSS. A positive finding occurring during either the blood flow or

Figure 2: (A) A triple phase bone scan showing a classic linear uptake visible only on delayed phase images virtually assures MTSS (B) A lateral view of a tib- ial stress fracture appears as a focally intense, fusiform area of uptake (Coulture and Karlson (28)

pooling phases suggest an acute stress fracture is the diagnosis (8).

What constitutes a positive finding for MTSS differs according to the various literature. Many authors suggest MTSS can be virtually assured when a classic diffuse longitudinal region of uptake is noted along the posteromedial portion of the tibia only visible on the delayed phase of the scan (Figure 2) (6,14,28,40).

Contrastingly Zwas et al (42) found bone lesions at up to five loci in subjects recruited with diffuse posteromedial tibial pain leading to a scintographic definition of shin splints as 'pain along the posteromedial tibia presented clinically in the absence of bone scan findings'. Further research to standardise what findings constitute a positive bone scan seem to be indicated.

A number of limitations have been suggested when using bone scanning to diagnose MTSS including concern for radiation in the young athlete and difficulty differentiating between posterior and anterior uptake (especially when the tibia is external rotated) potentially leading to poor anatomical localisation (7).

While triple phase bone scanning is the technique of choice for diagnosis, controversy still exists over what constitutes a positive finding of MTSS. This issue requires further clarification. Plain radi- ography has a poor sensitivity for detecting MTSS and thus is not a viable diagnostic option. Whilst the fact that MRI findings occur in both the asymptomatic and symptomatic populations raises the question of what MRI findings constitute a positive diagnosis. Until this question is answered via case controlled longitudinal studies, one cannot conclude that MRI is a suitable diagnostic tool, especially when the cost of performing a scan is taken into account. None of the available further diagnostic tools give a definitive diagnosis of MTSS, placing greater emphasis on the clinician to ensure a thorough physical assessment of the patient in order to provide an accurate clinical impression.

SUMMARY The condition MTSS is one of a multi-factorial nature with a num-

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