Evaluation of stress-related anterior lower leg pain with magnetic resonance imaging and intracompartmental pressure measurement

Military Medicine, Jan 2003 by Kiuru, Martti J

The purpose of this work was to evaluate stress-related anterior lower leg pain with clinical examination, magnetic resonance imaging, and measurement of anterior tibial compartment pressure findings. All medical data were gathered from 24 conscripts with stress-related anterior lower leg pain. Twenty exhibited bilateral symptoms. In 22 of the 44 cases, the intracompartmental pressure was pathological. Symptoms were exhibited for longer periods by patients with chronic exertional compartment syndrome (CECS) than by other patients (p 0.05). Stress-related anterior lower leg pain can be related to CECS, bone stress injury, and traction periostitis. Clinical diagnosis is unreliable. CECS and bone stress injury or traction periostitis can occur separately or together.

Introduction

Stress-related anterior lower leg pain is common in conscripts and endurance athletes.1 It is often known as the shin splints or medial tibial stress syndrome. The term is not well defined, because spectrum of conditions covered is extensive, ranging from chronic exertional compartment syndrome (CECS) to fatigue bone stress injuries and traction periostitis.2-6 Some authors suggest that shin splints are related to the compartment syndrome.1,3.7,8

In CECS, extensive repetitive loading of muscles leads to increased intracompartmental pressure, which probably follows from tissue edema, causing a decreased arteriovenous pressure gradient and decreased muscular perfusion.9 A diagnosis of CECS can be confirmed by means of intracompartmental pressure measurement.10

Magnetic resonance imaging (MRI) is sensitive in detecting early changes related to bone stress injuries.9 Associated soft tissue involvement can also be visualized in detail because of high contrast and spatial resolution.11,12 MRI findings relating to muscle but not to bone involvement have been also published in connection with CECS.13-16

Clinically differentiating the various findings of the anterior stress-related anterior lower leg pain may be difficult because they occur at the same site with similar symptoms. Measurement of compartment pressure and different imaging studies can help the diagnosis. The purpose of the study was to evaluate with MRI and measurement of anterior tibial compartment pressure the findings of stress-related anterior lower leg pain in military conscripts.

Materials and Methods

The retrospective study was performed in the Central Military Hospital in Helsinki, Finland. Over a 1-year period, we reviewed 24 consecutive conscripts (1 woman, 23 men; age range, 18-23 years; mean, 20 years) who had undergone both MRI and intracompartmental pressure measurement attributable to anterior lower leg pain related to physical activity during military training. On the basis of clinical examination, the symptoms exhibited by these patients were considered to be those of anterior CECS or bone stress injury. Clinical examination included careful history taking, palpation, and passive stretch of the compartment. Movements of the distal joints were studied. Distal pulses and sensation in the lower extremity were tested. Skin changes were recorded. The mean duration of symptoms was 14.7 weeks (range, 5-60 weeks). Patients were subjected to MRI and measurement of intracompartmental pressure within 5 days of each other on average (range, 0-21 days). Twenty patients exhibited bilateral symptoms. Forty-four legs were therefore examined. The study was approved by the Medical Ethics Committee of the Central Military Hospital.

MRI of both the legs was performed at rest using a 1.0 T. scanner (Signa Horizon, GE Medical Systems, Milwaukee, Wisconsin) and a body coil. Routine coronal T1-weighted spin echo sequence images (repetition time/echo time = 600 milliseconds per 19 milliseconds with two signals averaged and a 256 x 224 matrix) were obtained, followed by coronal and axial 72weighted fast spin echo (FSE) sequences with fat suppression (3,000-6,200/75-80 with two signals averaged and a 512-- 256 x 224 matrix). A coronal short tau inversion recovery (STIR) sequence was also used (5,400/17, inversion time = 140 milliseconds with two signal averaged and a 256 x 224 matrix). The field of view was 32 to 48 cm x 24 to 48 cm, and section thickness was 4.0 or 5.0 mm with a 0.5- or 1.0-mm intersection gap. Two radiologists (M.J.K. and J.A.A.) interpreted the MRI findings. A consensus was recorded in each case. The radiologists were unaware of intracompartmental pressure measurements. MRI findings recorded related edema of the bone marrow, periosteum, and muscles surrounding the bones and any fracture line and callus in cortical bone. Edema was represented as an intermediate signal intensity on Tl-weighted images and as high signal intensity on T2-weighted and STIR images. A fracture line was a low signal intensity line on all MRIs.

From the axial T2-weighted images, three region of interest (ROI) were chosen in both anterior and superficial posterior compartment for signal intensity analysis. The ROIs were in identical locations outside vascular structures. The total surface area of each ROI was approximately 2 cm^sup 2^. The average signal intensity of each ROI was calculated. The average value of the signal intensities was the compartment's signal intensity. A ratio of signal intensities for the anterior and superficial posterior compartment was calculated for each patient.