Biomechanical overload syndrome: defining a new diagnosis

To cite: Franklyn-Miller A, Roberts A, Hulse D, et al. Br J Sports Med 2014;48: 415–416. Chronic exertional compartment syndrome (CECS) was first described in 1956, but little research has been performed since then to confirm the pathological physiology. An assumption is made that elevated subfascial or intramuscular pressure during exercise causes tissue hypoxia and subsequent ischaemic pain due to decreased blood flow. To date, no conclusive evidence exists to demonstrate cellular hypoxic damage or decreased capillary perfusion. Further supposition is made regarding muscle hypertrophy, reduced compartment volume due to a decreased fascial compliance, and shorter periods of muscle relaxation as the underlying pathophysiology of CECS. There are many questions over whether the technique of intracompartmental pressure measurement is reliable. Examination of the widely accepted diagnostic criteria published in the seminal paper by Pedowitz et al reveals significant flaws, as the CECS and non-CECS groups were preselected by their differences in intramuscular pressure. We have also demonstrated significant overlap of the published diagnostic criteria for CECS with the published normative data. Furthermore, intramuscular pressure measurement varies considerably with the depth of the catheter tip, the means of measurement and the mode of exercise. It is also important that the criteria presented are only applicable to the anterior compartment. CECS is also reported as being diagnosed in the deep posterior and peroneal compartments of the leg, the foot and the forearm, despite diagnostic pressure criteria never having been established in these other myofascial compartments. What is undeniable however is that exertional lower-limb symptoms localised to the myofacial compartments are commonly reported in elite and recreational athletes, military personnel, 12 and non-athletes alike, and that CECS is included in the differential diagnosis. As a tertiary referral centre for exertional leg pain, we have conducted large numbers (c.100/ year) of intracompartmental pressure measurements, often with subsequent referral for fasciotomy. While short-term outcome following fasciotomy reflected published data 15 we have found long-term outcome (>12 months) to be disappointing, using objective measures. Both the previously reported groups used athletes or adolescents as subjects and may differ in that the ‘return to play’ criteria were less objective, which may explain the differences in outcome. Biomechanical factors have been shown to improve running economy. In particular stride length, ground contact time, vertical oscillation and lower extremity angles all have an effect on running efficiency. Despite this, recreational athletes and military recruits rarely receive training in running technique, either with verbal cues, video analysis or feedback as running is assumed to be a natural skill that man has acquired over several millennia. During walking gait, tibialis anterior dorsiflexes the ankle concentrically to provide foot clearance during swing phase, and isometrically (with lengthening of the tendon) to control the lowering of the forefoot during the first part of stance; this is assisted by the long-toe extensors (extensor hallucis longus, extensor digitorum longus) and peroneus tertius. During running gait, both the tibialis anterior and gastrocnemius have a high degree of preactivation prior to foot strike. Tibialis anterior activity decreases more rapidly during running-induced metabolic fatigue, compared with the gastrocnemius. We have consistently observed, in military personnel referred with anterior compartment pain, prolonged ankle dorsiflexion and reduced heel lift during swing phase with excessive dorsiflexion at heel strike, reduced ankle plantarflexion at toe-off and persistent ankle dorsiflexion and toe extension at mid-stance. Within minutes of initiating running, the patient develops an audible ‘slapping’ of the foot at heel strike. These observations are consistent with repeated and prolonged inner range tibialis anterior contraction, which may therefore result in early onset of fatigue and the development of cramp-like symptoms. Perhaps this is why many patients express the desire to passively stretch the anterior compartment as pain develops. It follows that fatigue combined with poor running biomechanics may cause the dorsiflexors to become rapidly overloaded. If the load on the dorsiflexors is further increased by extrinsic factors such as load-carrying, heavy footwear, gradient and increased training load, a gradual onset of exertional symptoms may result. Tightness, cramping pain and engorged muscles are all commonly described symptoms of those referred with anterior CECS. Eccentric contractions of the anterior leg compartment have, in the short term, been associated with an increase in intracompartmental pressure; however, there is currently no evidence of a direct association between this rise in compartment pressure and the pain and reduced muscle function described in chronic anterior compartment syndrome. However, Kirby and McDermott have confirmed reduction in anterior compartment pressures with forefoot running and Diebal showed improvements in pain and function with changing from a heel strike to forefoot strike in patients with CECS. The same principles can be applied to other compartments of the leg in which CECS has been Open Access Scan to access more free content