Shin-splints: Common exercise-related syndromes affecting the lower leg

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1 272 Shin-splints: Common exercise-related syndromes affecting the lower leg Surg Sub Lt BL Williamson, Surg Lt Cdr CHC Arthur Abstract Lower leg pain is a common complaint of athletically active individuals, often limiting physical activities. As such, the group of lower leg conditions related to athletic pursuits and physical exercise confer considerable operational implications for the military. Whilst acute injuries to the lower limb are commonly encountered and are clearly of significance, this article focuses instead on chronic conditions related to physical activity. These include insults to bone such as stress fractures and medial tibial stress syndrome, and those related to the soft tissues such as chronic exertional compartment syndrome. In this article we will examine the presentation and management of these conditions. Introduction Despite the common label shin-splints, there are in fact many causes of exercise-induced lower leg pain, overwhelmingly linked to weight-bearing activity. Physical activities involving repeated large load transmission through the lower limb, such as long-distance running and extended marches with heavy equipment, are thought to contribute to the high rates of lower leg pain seen in military populations (1, 2). It is important to note that a whole range of physical activities has been implicated in this group of conditions; one should not exclude these diagnoses in non-runners (2). Differential Diagnoses Chronic lower leg pain usually presents following an insidious onset, with symptoms of varying duration and severity (3). There are three main differential diagnoses to consider in a patient presenting with chronic exerciseinduced lower limb pain: medial tibial stress syndrome, stress fracture, and chronic exertional compartment syndrome (4). In addition, one should consider other serious causes of lower limb pain, such as peripheral nerve compression, vascular insufficiency, osteomyelitis and malignancy (Box 1). Exercise-induced Lower Limb Pain Main Differential Diagnoses Medial Tibial Stress Syndrome (MTSS) Stress Fractures Chronic Exertional Compartment Syndrome (CECS) Peripheral Nerve Entrapment Popliteal Artery Entrapment Syndrome (PAES) Box 1. Main differential diagnoses of exercise-induced lower limb pain. Medial Tibial Stress Syndrome (MTSS) MTSS is one of the most common leg injuries in highly active individuals, including military personnel (5). One study demonstrated an incidence of 35% in a cohort of naval cadets (6). Whilst universally recognised, the finer detail of the definition is widely debated, with various terms used synonymously (5). MTSS is characterised by exercise-related pain affecting the posteromedial aspect of the middle or distal tibia, generally affecting a length of at least 5cm (5). Pain from ischaemia, stress fractures and exertional compartment syndrome should first be excluded in order for MTSS to be confidently diagnosed (5). MTSS was previously thought to be due to traction-induced periostitis, though recent consensus is that the aetiology is related to bone overload (5). There is continuing debate as to whether microfractures are a component part of MTSS, possibly placing MTSS on a continuum with tibial stress fractures (5). There is a plethora of risk factors associated with developing MTSS (7). The most relevant in a military setting are: female gender (RR 1.71; 95% CI ), orthotic use (RR 2.31; 95% CI ), and increased body mass index (BMI) (standard mean difference 0.24; 95% CI ) (7). The traditional treatment for MTSS was entirely conservative, though various innovative therapeutic approaches have recently been evaluated, including iontophoresis, extracorporeal shock wave therapy, periosteal pecking (percutaneous needling of the tibia), and ice massage. Whilst this range of treatments has brought benefit in individual cases, all high quality reviews have to

2 273 Clinical date failed to demonstrate that any of these treatments are superior to the rest (5, 8). Therefore these treatments are not currently recommended in military patients. Stress fractures Fatigue stress fractures occur following a period of repeated increased loading of normal bone. The loading involved is below the single cycle failure threshold, but creates an imbalance in the rate of resorption and formation of bone, leading to acute painful failure of the bone. The most common bones affected are the tibia, metatarsals and fibula, due to the large axial loading associated with high impact weight-bearing activities (9, 10). Whilst running is most strongly linked to development of stress fractures, countless other athletic activities are also implicated, including rowing, volleyball and ballet (2). of plain films, a normal radiograph by no means excludes the diagnosis when clinical suspicion is high. Magnetic resonance imaging (MRI) remains the best modality for stress fracture assessment, being more sensitive and specific than plain radiographs (1). Treatment requires unloading of the affected limb followed by a gradual increase in weight-bearing activity, titrated according to pain (1). Fredericson et al. recommend increased limb rest according to MRI grading of injury (Table 1) (10). Some debate exists around whether stress fractures should be considered part of the tibial stress syndrome spectrum that also encompasses MTSS, with failure of the bone being a manifestation of repeated heavy loading in excess of that which causes MTSS (9). Grade MRI (T1) MRI (T2 and STIR*) *short-tau inversion study Time without loading 0 Normal Normal 1 Normal Mild periosteal swelling 2-3 weeks 2 Normal Evident periosteal and bone marrow swelling 4-6 weeks 3 Bone marrow swelling Severe periosteal and bone marrow swelling 6-9 weeks 4 low-signal fracture Severe periosteal and bone marrow swelling 12 weeks, 6 with cast Table 1. Stress fracture grading, MRI appearance and recommended conservative treatment. Stress fractures generally present with gradual onset pain, progressing to pain at rest. There is generally localised tenderness due to soft tissue inflammation around the fracture site. Virtually any bone in the body may be affected. The history typically reveals a recent increase in exercise intensity, with symptoms commonly occurring within two weeks of such an increase in training, or commencement of a new activity (1, 9). Tibial stress fractures are usually related to just such an increase in weight-bearing activity. The international military literature has often studied stress fractures, with medical opinion used to formulate physical training regimes that reduce stress fracture incidence. A review of Royal Marine training highlighted the importance of such efforts, finding stress fractures to be the single most important cause of lost training days at Commando Training Centre Royal Marines (CTCRM) (11). Whilst conventional radiography is commonly used in diagnosis, changes only become visible on plain films two to twelve weeks after symptoms appear, and the sensitivity in both early (15-35%) and follow-up (30-70%) radiographs is low (1). When visible, stress fractures appear as radiolucent lines in cortical bone and as sclerotic lines in trabecular bone (1). More commonly however, only a periosteal reaction is visible. In light of the poor sensitivity Chronic Exertional Compartment Syndrome (CECS) CECS usually occurs in the lower leg or forearm. It has a characteristic presentation, with poorly localised pain commencing during activity and ceasing with rest. During exercise, muscular contraction and increased blood flow result in an increase in compartment pressure. The tight fascia of the lower leg makes its compartments particularly susceptible to CECS. Increasing compartment pressure causes a subsequent reduction in tissue perfusion as capillary pressure is exceeded, causing ischaemic pain. Pain may persist for some time after cessation of exercise and, though pain is usually localised to the involved compartment, symptomatic nerve compression may occur simultaneously, causing additional pain not necessarily confined to the affected compartment (12). Complete diagnostic workup involves radiological exclusion of other causes and intra-compartment pressure recordings in the presence of appropriate clinical findings any one of Mubarak s three pressure criteria are considered diagnostic (Box 2) (12). It is important to confirm the diagnosis objectively in this way, as conservative treatment for CECS is often ineffective; therefore surgical intervention is likely to be considered. Whilst fasciotomy is usually successful in relieving symptoms, there may be associated post-operative strength deficit or iatrogenic neurovascular

3 274 damage. It is therefore essential to have objective evidence to support a CECS diagnosis (12, 13). Mubarak s CECS Diagnostic Criteria 1. Resting pressure > 15mmHg OR 2. 1 minute post-exercise pressure > 30mmHg OR 3. 5 minute post-exercise pressure > 20mmHg Box 2. Mubarak s compartment pressure criteria for confirming diagnosis of chronic exertional compartment syndrome (CECS). months (1, 3, 15). Clinical features give a strong indication of the diagnosis (Table 2). Investigations History and examination alone do not effectively differentiate between the different causes of exerciserelated lower limb pain (4). Plain radiographs are of low sensitivity for suspected stress fractures, especially in the early stages of the condition, and MRI remains the gold standard for stress fracture diagnosis (3). Radiographs are normal in cases of MTSS, reinforcing the role of MRI as the most sensitive and specific investigation in early tibial stress injuries (3). In cases of suspected CECS, invasive monitoring of compartment pressures may be indicated, but Typical Pain Features Nature On Palpation Onset Location Laterality Progression of Pain (at rest) MTSS Variable Generalised Starts Posteromedial Unilateral Pain no longer severity tenderness gradually tibia with continued Diffuse Begins on Middle/distal exercise Pain activity initiation third becomes present at rest Tibial Focal Focal Insidious Proximal tibia Unilateral Pain becomes Stress tenderness Soft (military recruits) present during Fracture tissue swelling Junction of middle minor stress (occasional callus) and distal tibial Pain at rest (1) thirds (runners)(2) CECS Cramping/ Asymptomatic Pain begins Anterior Bilateral Pain begins to burning/aching after a certain compartment (85-95%)(3) persist for Tightness of distance/intensity (45%)(3) (3) longer the leg (11) following activity cessation Table 2. Typical pain features of medial tibial stress syndrome (MTSS), tibial stress fractures and chronic exertional compartment syndrome (CECS) can assist in differentiating these conditions. The mainstay of surgical treatment is fasciotomy of the affected compartment. This surgical release of the tight fascia prevents an exercise related increase in compartment pressure. The best outcomes are achieved when surgery is performed within twelve months of the onset of the symptoms (14). Reported success rates are relatively high in the short term, with good to excellent results achieved in 80-90% of cases (13, 14). Diagnosis History-taking and a thorough physical examination are of utmost importance in correctly diagnosing exerciseinduced lower limb pain. A careful and detailed history will narrow down the differential diagnosis and will often reveal a change in training habit (intensity, distance, load) or footwear that predates the onset of symptoms, often by less than two weeks, though sometimes up to several Pathology Conservative Management Surgical Treatments MTSS Rest Not applicable Gradual resumption of activity Low impact exercise (e.g. cross training) Tibial Rest (2-12 weeks) Fracture fixation Stress Gradual resumption Fracture of activity Low impact exercise CECS Rest Fasciotomy Table 3. Conservative management of medial tibial stress syndrome (MTSS), tibial stress fractures and chronic exertional compartment syndrome (CECS) is largely similar, whilst surgical management is markedly different.

4 275 Clinical this investigation should be only be considered by specialist clinicians, given the many different ways of assessing compartmental pressures and the subsequent complexity of accurately interpreting results (12). Management The essential first line management for all exercise-induced chronic leg pain is a trial of activity cessation and rest (Table 3). The duration of rest required is unclear, although provided symptom relief is achieved, a gradual return to training can be attempted. The majority of cases of MTSS and stress fractures should resolve with conservative measures, and referral to physiotherapy services may be helpful in supervising a return to training program. In patients with suspected CECS, refractory cases, and in patients where there is diagnostic uncertainty, referral should be made for specialist assessment by either a Sports and Exercise Medicine (SEM) trained physician or an orthopaedic surgeon with a special interest in this area. Prevention There is a notable paucity of data on prevention of most conditions which cause exercise-induced chronic leg pain. However, given the probable shared aetiology of this group of conditions it is reasonable to extrapolate some of the research on MTSS preventative measures, assuming commonality in the absence of any other evidence. Moen et al. (5) reviewed eight MTSS prevention randomised controlled trials, all conducted in military populations. Parameters tested included graduated training programmes, boot type, insole use, calcium supplementation and preexercise stretching (5). Of these, only the use of shockabsorbing insoles demonstrated a reduction in MTSS incidence (5). Whilst not included as a testing parameter, body weight reduction is hypothesised to reduce the risk of exercise related lower leg syndromes, given the observed reduced incidence in populations with lower BMIs (5). Ross s theory of stress fractures is that fracture occurs at the point in time of maximal training load, superseding previous studies contending that stress fracture incidence is highest around six weeks after an increase in training; the notion is that load is more important than the nadir of bone density due to remodelling (11). Of course both load and bone density are likely to have an impact on incidence, as described by several methods of reducing stress fracture risk in the literature (encouraging gradual increases in loading and participating in sport prior to beginning high intensity training). Further suggestions for reducing stress fracture incidence are less intuitive, being based on the finding that muscle fatigue increases stress on the axial skeleton. There is, therefore, a need to consider adequate recovery times, general fitness and diet carefully - essentially designing physiologically progressive training syllabi (11). Conclusion Most military personnel are at increased risk of exerciserelated injuries of the lower limb due to the inherently physical nature of their profession. Personnel in training establishments are particularly susceptible to these conditions due to a combination of exercise intensity, frequency and the often marked changes in athletic demands required of the individual. These injuries carry a significant operational burden for military units, requiring military medical staff to be aware of the diagnosis, management and prevention of these conditions. A high index of suspicion is required in order to shorten recovery time, reduce recurrence and minimise the operational impact most effectively. References 1. Lassus J, Tulikoura I, Konttinen YT et al. Bone stress injuries of the lower extremity: a review. Acta Orthop Scand 2002;73(3): Caesar BC, McCollum GA, Elliot R et al. Stress fractures of the tibia and medial malleolus. Foot Ankle Clin 2013;18(2): Brewer RB, Gregory AJ. Chronic lower leg pain in athletes: a guide for the differential diagnosis, evaluation, and treatment. Sports Health 2012;4(2): Gaeta M, Minutoli F, Mazziotti S et al. Diagnostic imaging in athletes with chronic lower leg pain. AJR Am J Roentgenol 2008;191(5): Moen MH, Tol JL, Weir A et al. Medial tibial stress syndrome: a critical review. Sports Med 2009;39(7): Yates B, White S. The incidence and risk factors in the development of medial tibial stress syndrome among naval recruits. Am J Sports Med 2004;32(3): Newman P, Witchalls J, Waddington G et al. Risk factors associated with medial tibial stress syndrome in runners: a systematic review and meta-analysis. Open Access J Sports Med 2013;4: Winters M, Eskes M, Weir A et al. Treatment of medial tibial stress syndrome: a systematic review. Sports Med 2013;43(12): Swischuk LE, Jadhav SP. Tibial stress phenomena and fractures: imaging evaluation. Emerg Radiol 2014;21(2): Fredericson M, Bergman AG, Hoffman KL et al. Tibial stress reaction in runners. Correlation of clinical symptoms and scintigraphy with a new magnetic resonance imaging grading system. Am J Sports Med 1995;23(4): Ross RA, Allsopp A. Stress fractures in Royal Marines recruits. Mil Med 2002;167(7): Clanton TO, Solcher BW. Chronic leg pain in the athlete. Clin Sports Med 1994;13(4): Paik RS, Pepple DA, Pepples D et al. Chronic exertional compartment syndrome. BMJ 2013;346:f33.

5 Slimmon D, Bennell K, Brukner P et al. Long-term outcome of fasciotomy with partial fasciectomy for chronic exertional compartment syndrome of the lower leg. Am J Sports Med 2002;30(4): Hreljac A. Etiology, prevention, and early intervention of overuse injuries in runners: a biomechanical perspective. Phys Med Rehabil Clin N Am 2005;16(3): Authors Surgeon Sub Lieutenant BL Williamson RN Medical Student King s College London School of Medicine London SE1 1UL Ben.Williamson@kcl.ac.uk Surgeon Lieutenant Commander CHC Arthur RN Specialty Trainee in Trauma and Orthopaedics Edinburgh Royal Infirmary Edinburgh EH16 4SA