Case Report

Bilateral peroneal compartment syndrome after horse riding

Abstract

A healthy 20-year-old woman developed acute ischemia of the lateral compartment of both calves shortly after a 30-minute horse ride. On one side, she developed compartment syndrome with resultant complete myonecro- sis of the compartment, whereas on the other side, there was spontaneous resolution. To our knowledge, this is the first report of bilateral lateral compartment ischemia after horse riding. Atraumatic compartment syndrome is a rare entity and is often missed at initial presentation. We discuss aspects of her management together with a review of the literature. Late fasciotomy and exploration may be beneficial in decompressing the deep peroneal nerve in peroneal compartment syndrome. Awareness of atraumatic compartment syndrome is important in any case of limb pain and swelling.

Compartment syndrome is a condition in which raised pressure in an enclosed fascial space decreases tissue perfusion leading to ischemia [1]. Muscle and nerve are the most sensitive tissues to ischemia, and so, early signs relate to these. Pain is often out of proportion to the setting and is worsened by passive muscle stretching. Paraesthe- sia, which can progress to numbness, is another early sign. The compartments are tender and firm to palpation. Other signs of established compartment syndrome include neurologic changes (numbness, paraesthesia, weakness) and vascular changes (delayed capillary refill and absent pulses) [2].

Unresolved pressure ischemia results in tissue necrosis. Necrotic muscle is then replaced by contracted fibrous tissue, and loss of function is permanent (Volkmann’s Ischemic contracture). Additional complications of compartment syndrome include the effects of rhabdo- myolysis, namely, acute Renal impairment and cardiac arrhythmias [2,3].

Atraumatic compartment syndrome is a rare entity [4,5] but has been described after prolonged walking or marching [6], athletic activity [7-10], and horse riding [11,12]. It may

manifest insidiously and can be missed on initial presentation with severe consequences.

Bilateral acute atraumatic isolated peroneal compart- ment syndrome after horse riding has not been reported in the literature.

A 20-year-old healthy woman on a working holiday presented to the emergency department (ED) with a 12- hour history of left anterolateral Calf pain with associated numbness of the dorsum of the foot and inability of ankle dorsiflexion. Her symptom began 20 minutes after a 30-minute horse ride. She had been riding horses frequently over the preceding weeks, though had shortened her stirrups somewhat for this ride. She did not have any significant discomfort during the ride. She was discharged from the ED with a presumptive diagnosis of peroneal muscle tear, with instructions for rest and analgesics.

Her symptoms persisted, and she re-presented to the ED more than 3 days after the onset of symptoms. She was referred to the orthopedic unit with the possible diagnosis of an established compartment syndrome. At that stage, she had pain and swelling over her left peroneal compartment, which was moderately firm. She had a foot drop with 0/5 power of all the muscles of her anterior and lateral compartments. She had pain on inversion of her ankle. There was numbness over the dorsum of the foot in the distribution of the superficial and deep peroneal nerves. Her right leg was completely asymptomatic.

She was admitted to the ward, and magnetic resonance imaging (MRI) (Fig. 1) and magnetic resonance angiogram were performed, which suggested bilateral peroneal compartment syndrome. On the left side, the scan confirmed an established compartment syndrome with loss of muscle architecture, indicating myonecrosis, and complete occlusion of the peroneal artery. On the right side, the peroneal compartment was edematous and expanded, but with normal muscle architecture and intact vascular supply. Her serum creatine kinase was significantly elevated at 8076 IU/L (Ref 20-160 IU/L serum Creatinine kinase), but she had normal renal biochemistry and a good urine output.

She underwent decompression and exploration of her left peroneal and anterior compartments in theater at just more

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than 4 days after the onset of symptoms. Her compartment pressures were recorded as follows (diastolic blood pressure was 40 mm Hg):

Left leg compartment Peroneal

Anterior Posterior–superficial Posterior–deep

Pressure (mm Hg) 66

18

16

16

The muscles in the peroneal compartment were found to be completely necrotic and were excised. The superficial peroneal nerve was identified, protected, and traced proximally to its origin from the common peroneal nerve. The deep peroneal nerve, which appeared to have been compressed as it crossed the peroneal compartment, was decompressed to the neck of the fibular. The muscles of the anterior compartment were healthy. Her wound was packed. She returned to theater 2 days later for definitive closure. Histology showed muscle necrosis consistent with compart- ment syndrome.

The right side was asymptomatic throughout with normal compartment pressures, so no treatment was required on this side.

She was discharged from hospital in a plaster backslab for 2 weeks followed by a removable splint and physiotherapy. Her wound healed uneventfully. At the 5-week follow-up, she had recovered 4/5 power of tibialis anterior and 2/5 power of extensor hallucis longus. Her sensory loss persisted, and she returned to her homeland thereafter.

Acute atraumatic compartment syndrome is a rare entity, and isolated bilateral peroneal compartment syndrome is even rarer. Awareness of the condition, particularly among primary care physicians, is essential in being able to diagnose the condition and appropriately refer the patient for specialist management. Delayed or missed diagnoses result in significant morbidity and can be potentially fatal [3].

The position of the lower limbs in horse riding is one with the hips abducted and flexed, the knee flexed, and the ankle dorsiflexed. Dorsiflexion of the ankle leads to increased peroneal compartment pressure [13]. Flexion of the hips and knees has an obstructing effect on the vascular system [14]. Leg position thus has an intrinsic effect of increasing lower limb compartment pressure.

Fig. 1 Axial and coronal MRI showing lateral peroneal compartment Ischemic changes.

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The presence of a foot drop in acute peroneal compart- ment syndrome is explained by the course of the deep peroneal nerve, which, as one of the terminal branches of the common peroneal nerve, passes proximally through the peroneal compartment before piercing the lateral intermus- cular septum to enter the anterior compartment and there supply the muscles of dorsiflexion of the ankle and toes (tibialis anterior, extensor digitorum, extensor hallucis longus, and peroneus tertius) [15].

In all of the published reports of acute atraumatic peroneal compartment syndrome, the diagnosis has been significantly delayed. In this case, the delay was more than 3 days, and the MRI showed convincing evidence of myonecrosis and Arterial occlusion. After some discussion and review of the literature, it was decided that exploration was indicated to decompress the deep peroneal nerve and confirm the viability of the anterior compartment while accepting that this would involve removal of the necrotic peroneal muscles. In view of the early improvement in power of ankle dorsiflexion seen in this patient, we believe that this approach may be indicated in cases of late diagnosis of acute peroneal compartment syndrome with persisting elevation of the compartment pressures.

The MRI scan revealed edema and swelling in the peroneal compartment on the asymptomatic side. This may represent simple postexercise muscle edema; however, the large amount of fluid in the muscle and the significant expansion of the compartment suggested to us that she may have had an episode of swelling followed by transient increase in pressure, which did not reach the threshold required to produce the congestion and vascular occlusion, which would progress to Acute compartment syndrome. An alternative theory is that the initiating event was a temporary arterial occlusion caused by the extreme positioning during horse riding. On the right, the flow was reestablished after the ride, leaving asymptomatic MRI changes consistent with temporary vascular occlusion, whereas on the left, the blood flow was not restored causing muscle necrosis followed by raised compartment pressure.

Atraumatic unilateral peroneal compartment syndrome after horse riding has been reported in the literature [5,11,12]. Our case was unique in that MRI findings revealed bilateral changes, with complete muscle necrosis on one side and asymptomatic edema on the other. Delayed diagnosis is common; however, we recommend exploration to decom- press the deep peroneal nerve in cases with persisting elevated pressure to maximize the chance of recovery of the anterior compartment muscle function.

Krishant S. Naidu MBBS

Orthopaedic Unit Department of Surgery Sunshine Hospital

Western Health, Victoria 3021, Australia E-mail address: [email protected]

Terence Chin MBBS Orthopaedic Unit Department of Surgery Sunshine Hospital

Western Health, Victoria 3021, Australia

Christain Harris MBBS Orthopaedic Unit Department of Surgery Sunshine Hospital

Western Health, Victoria 3021, Australia

Simon Talbot MBBS Orthopaedic Unit Department of Surgery Sunshine Hospital

Western Health, Victoria 3021, Australia

doi:10.1016/j.ajem.2008.11.009

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