A 22 year old international shot-putter initially presented to the sports medicine clinic in December, 2009 complaining of 1-2 year history of steadily increasing right hand first and second proximal metacarpal pain with no history of trauma. The pain appeared to be particularly provoked on right first and second metacarpal extension and abduction. On examination there was no obvious swelling or deformity and no anatomical snuffbox tenderness. There was however bony tenderness on deep palpation of the proximal first and second metacarpals. Hand and wrist x-rays and bed-side ultrasound imaging were initially negative. The hand x-rays are included in Figure 1.

As no bony or ligament injury was identified, treatment initially included local massage, local anaesthetic injection into the area of tenderness, extracorpeal shock wave therapy and subsequently an injection of platelet-rich plasma (PRP) into the area of maximal tenderness. Due to the failure to respond to treatment, subsequent investigations included a technetium bone scan, which showed increased uptake in the region of the trapezium, trapezoid and first and second metatarsal. A CT scan then showed the lesion more clearly, a stress fracture of the right trapezoid with no ligament disruption (Figure 2).

The patient was initially treated with a thumb spica splint for approximately 8 weeks and magnetic therapy which provided significant symptomatic improvement. He also undertook hand therapy with the physiotherapists, involving stretching and strengthening exercises of the wrist and hand. If the athlete had failed to respond to conservative management, then the next stage would have involved surgical management as discussed by previous authors (Sadowski and Montilla, 2008). He is currently asymptomatic and continues to compete as an international standard shot-putter.

The trapezoid is the least commonly fractured carpal bone, with Sadowski and Montilla, 2008 reporting trapezoid fractures to account for 0.4% of all carpal injuries. The trapezoid is infrequently injured due its position within the wrist, situated within strong intercarpal ligaments and between the base of the second metacarpal and carpal bones (Afifi and Lu, 2011). Single-bone traumatic fractures of the trapezoid have been previously reported in the medical press by several authors (Afifi and Lu, 2011; Ekstrand and Torstveit, 2012; Kain and Heras-Palou, 2012; Kam et al., 2011, Miyawaki et al., 2000, Nagumo et al., 2002, Sadowski and Montilla, 2008) but this is the first time a stress fracture of the trapezoid has been described.

Stress fractures have classically been divided into fatigue and insufficiency fractures, with our case being categorised under a fatigue fracture (Anderson, 2006). Positive xrays for stress fractures have been reported to be as low as 15% initially (Anderson, 2006). Indeed Afifi and Lu, 2011 have previously commented that the overlapping of the carpal bones makes plain radiographs difficult to interpret and this has been supported by previous authors (Sadowski and Montilla, 2008). Trapezoid fractures often give poor localising signs and symptoms as reported in our athlete and in previous cases (Kain and Heras-Palou, 2012). Thus a high degree of suspicion for trapezoid stress fractures merits further investigation with a bone scan, MRI and/or CT scanning and this statement is supported by Gruson et al., 2008 who advise MRI or CT for imaging of trapezoid fractures after plain x-ray. Indeed Kain and Heras-Palou, 2012 reported on 11 traumatic trapezoid fractures and found CT scanning to be the primary mode of diagnosis, accounting for 8 of the diagnoses.

Sadowski and Montilla, 2008 previously described a case of a traumatic trapezoid fracture following a punch which was successfully treated with cast immobilisation for 6 weeks and then a thumb splint for the following 2 weeks. Similarly, our athlete’s pain was successfully treated with thumb spica splinting for approximately 8 weeks. Conservative management of trapezoid fractures have also been supported by Gruson et al., 2008 in those fractures that are nondisplaced, with surgical management limited to those with displaced trapezoid fractures or associated carpal injuries.

Sadowski and Montilla, 2008 also reported in their traumatic trapezoid fracture that the patient presented with wrist swelling, snuffbox tenderness, reduced range of motion of the wrist and pain at the base of the second metacarpal. Clinical features reported to occur in trapezoid fractures are base of second metacarpal tenderness, anatomical "snuffbox" tenderness or pain on axial loading of the second finger (Afifi and Lu, 2011) although these signs are not universal. Our patient had pain at the base of the 2^nd metacarpal as well as the 1^st metacarpal with pain on extension and abduction of these two fingers although no wrist swelling, snuffbox tenderness or reduced range of motion. Thus stress trapezoid fractures seem to present slightly differently from traumatic trapezoid fractures although it is difficult to comment further on this with no other case reports in the literature.

The mechanism of traumatic trapezoid injury has been previously reported by Miyawaki et al., 2000 as excessive wrist dorsiflexion, which the authors suggest occurs, "in the same manner that a walnut is broken with nutcrackers." Gruson et al., 2008 also report the mechanism of injury to the trapezoid as an axial load or bending stress. Indeed international shot putts weight 7.26 kg, with the technique requiring significant wrist movement, particularly dorsiflexion, and thus the wrist and carpal bones are placed under considerable forces during this sport. This requires further exploration through, for example biomechanical assessments, to enable sport physicians to gain further knowledge regarding trapezoid fractures.

When a stress fracture is diagnosed, it is important to consider the potential underlying mechanisms for this injury and previous authors have classified these as intrinsic and extrinsic (Pegrum et al., 2012). These risk factors must be considered when taking the history, performing the examination of the athlete with relevant investigations and then corrected as appropriate. Ekstrand and Torstveit, 2012 have recently reported on the underlying mechanisms for stress fractures in elite footballers. They report that athletes who sustain a stress fracture tend to be younger. They also report repetitive loading, rapid increases in load and low calorific intake as risk factors. The relevant risk factors for this athlete are his relatively young age and the repetitive loading nature of his sport to the dominant wrist. Thus methods to help reduce the subsequent risk of stress fractures in athletes are ensuring an appropriate diet with no negative energy balance, monitoring training loads with appropriate rest periods, especially in young athletes who are at risk of stress fractures, and introducing diversity into the training regime to avoid overload, particularly of a specific joint like the wrist.

It is also imperative to consider the female athletic triad (Otis et al., 1997) (disordered eating, menstrual dysfunction, and osteoporosis) when dealing with this athletic population, which has been proposed to be due to an energy deficit following on from a relatively low energy intake in combination with high energy demands (Ekstrand and Torstveit, 2012).

This is one case report study and further evidence is therefore required into this unique injury and underlying mechanisms for this injury.

We presented the first case report of a trapezoid stress fracture in the dominant hand of an international-standard shot-putter. The mechanism for traumatic trapezoid fracture has been previously reported to occur with excessive wrist dorsiflexion by Miyawaki et al., 2000 and Gruson et al., 2008. The investigation of choice for trapezoid fractures would appear to be MRI or CT after initial plain x-rays. Non-displaced isolated trapezoid stress fractures appear to respond well to simple immobilisation. Trapezoid stress fractures should be considered in the differential diagnosis of persistent pain in the proximal first and second metacarpals which is not responding to treatment, particularly in the dominant arm of throwing athletes. It is also important to consider the underlying intrinsic and extrinsic risk factors when treating any stress fracture.