Abstract
Growing awareness of chronic exertional compartment syndrome of the foot has led to the need for site-specific analysis of normative resting and postexertional intracompartment pressures. Thirty-four asymptomatic athletes underwent pressure testing of the medial foot compartment with an intracompartmental pressure measurement apparatus. Pressure measurements were recorded before exercise and after 20 minutes of running. Mean resting intracompartment pressure was 7.7 mm Hg, whereas mean pressures 1 and 5 minutes after exercise were 19.1 mm Hg and 10.7 mm Hg, respectively. These data were then compared with data from compartment pressure studies performed in nine symptomatic subjects, each with a clinical history suggestive of chronic exertional compartment syndrome of the medial foot compartment. The results demonstrated normative compartment pressures of the medial foot compartment are comparable with previously measured pressures of the leg. This study shows that previously defined criteria for diagnosis of chronic exertional compartment syndrome of the leg may also be used for diagnosis of chronic exertional compartment syndrome of the foot.
Chronic exertional compartment syndrome is a well-recognized entity, typically affecting the lower leg 2,5,17,28,29 and various other sites.3,6,7,13,21,32 Recent case reports indicate that the condition may affect the foot.15,19,20,30 The medial compartment has been the site of involvement in all published reports of chronic exertional compartment syndrome affecting the foot, although Lokiec et al. 15 described concurrent involvement of the medial and central compartments.
There have been many recent proposals of new diagnostic techniques for chronic exertional compartment syndrome.1,4,10,11,22 However, the accepted view is that pre-and postexercise intracompartment pressure testing is integral to diagnosis.5,8,18,23–26,28–31 Despite the importance of intracompartment pressure measurements in the diagnosis of chronic exertional compartment syndrome, there has been no previous study investigating normative pre- and postexercise compartment pressures in the foot.
In one study of 25 subjects of unspecified athletic status in whom the resting intracompartment pressure in the central foot compartment was measured, 9 the medial compartment was not considered, despite the apparent propensity for this anatomic area to be affected by compartment syndrome. Subjects were tested while under the effects of either general or spinal anesthesia, immediately before elective foot surgery. The effects of preexisting foot injuries or abnormalities and anesthesia on compartment pressure readings were not addressed.
Objective criteria for diagnosis of chronic exertional compartment syndrome of the leg were defined by Pedowitz et al. 24 after review of 131 pressure studies in patients with chronic exertional leg pain. These criteria may be applied to other anatomic sites if one assumes there is pressure uniformity throughout the body. Although pressure equivalence is a reasonable supposition, confirmation with site-specific data is appropriate.
The primary aim of this study was to assess pre- and postexercise compartment pressures in the medial foot compartment among a cohort of asymptomatic athletes. The second objective was to review pressure studies performed in nine athletes suspected of having chronic exertional compartment syndrome in the medial foot compartment. From the two groups of data, normative medial foot compartment pressures were determined. Furthermore, the validity of applying the criteria defined by Pedowitz et al. 24 in the diagnosis of chronic exertional compartment syndrome in the medial compartment of the foot was assessed.
Materials and Methods
Asymptomatic Athletes
Thirty-four subjects (18 women and 16 men) underwent testing. The mean age of the subjects was 26.5 years (range, 18.5 to 32.5). Before inclusion in the study, each subject read and signed an informed consent form outlining the research procedure. No subject had undergone foot or ankle surgery. Subjects had been free from any foot and ankle pain for a minimum of 2 years before the study. All subjects were training several times per week for competitive sports (either track and field, triathlon, Australian Rules football, netball, or basketball) at the time of testing.
Each subject underwent testing in one randomly chosen foot. Data from 17 left and 17 right feet were assessed. The Stryker Solid-State Transducer IntraCompartment (S.T.I.C.) Pressure Monitor System (Stryker Corporation, Kalamazoo, Michigan) was used for all pressure tests. This apparatus is widely used in the analysis of compartment pressures.9,11,17–20,28,29 The pressure-testing unit was calibrated before the study began and was readied for use according to the manufacturer's instructions. In all tests, an 18-gauge (1.2-mm diameter) side-ported needle was inserted into the medial foot compartment, inferior to the medial surface of the medial cuneiform bone. No anesthetic agent was administered, so as to closely simulate clinical intracompartment pressure testing conditions.
The influence of body positioning on compartment pressure measurements has been documented previously.9,12 All pressure measurement injections were performed with subjects positioned according to previously described guidelines. 9 Each subject was placed supine, with feet and heart on the same horizontal plane, during all test conditions. The ankle and foot were maintained at an angle 90° to the leg. During injection, the pressure-testing unit was maintained at 45° in relation to the horizontal plane, as stipulated in the manufacturer's instructions.
Once the subject was correctly positioned, the process of injection with the Stryker unit was begun. After the needle was inserted into the medial foot compartment, a small quantity of saline (not more than 0.3 ml) was slowly injected into the compartment, to equilibrate with interstitial fluids, in accordance with the manufacturer's instructions. Within several seconds, a restingpressure measurement was acquired. Subjects then undertook the exercise test. Each subject ran at a self-chosen, typical training intensity, in their own socks and shoes, for 20 minutes.
There is no universally recognized exercise protocol for testing patients suspected of having chronic exertional compartment syndrome. Exertion until the onset of pain is desired, whatever activity is adopted.4,23,28,32 Given the asymptomatic status of the subjects in this study, exertion until onset of pain was not possible. It has been suggested that the nature of an exercise test should be specific to the sport of the athlete undergoing clinical assessment. 23 The exercise test used for this study (20 minutes of running) closely resembled training conditions experienced by all participants in the study. It was thought that 20 minutes of running was also sufficient in duration and intensity to precipitate typical compartment pressure changes commensurate with aerobic exercise. Additionally, patients suspected of having chronic exertional compartment syndrome may describe histories in which pain arises with such activity and within such a time period.
On completion of the exercise test, the subject's shoe and sock were immediately removed from the test foot. Subjects were quickly repositioned, the needle was reinserted at the original test site, and pressure readings were obtained 1 and 5 minutes after exercise. An antiseptic dressing then was applied over the test site.
Symptomatic Athletes
Between 1997 and 2000, 27 patients were referred to the primary author of this study (MBM) for evaluation of exertional medial midfoot pain. The clinical history in nine athletes included chronic exertional pain of a tight, cramping nature at the plantar-medial midfoot. These nine patients were included in this study. They consisted of five women and four men with a mean age of 26.7 years (range, 19 to 35). One of the patients was the subject of a previously published case report. 19 Seven of the nine patients described unilateral symptom distribution, whereas two described pain of equal intensity in both feet. All nine experienced pain in direct proportion to duration or intensity (or both) of activity. Pain was relieved by rest. During physical examination of all nine athletes, tense swelling was consistently seen in the medial foot compartment after activity in which the pain was reproduced. Passive maximal first metatarsophalangeal joint dorsiflexion performed immediately at that time was also painful.
All nine patients underwent pre- and postexercise intracompartment pressure testing on one symptomatic foot. The measurement procedure was the same as that adopted for asymptomatic athletes in this study. All nine athletes reported reproduction of pain during the exercise test.
Results
Mean pre- and postexercise intracompartment pressures obtained from the 34 asymptomatic athletes and the 9 symptomatic athletes are provided in Table 1. Data pertaining to asymptomatic male and female subjects are compared in Table 2. No significant differences were found between the sexes.
Results of Pressure Testing in the Medial Foot Compartment of 34 Asymptomatic Athletes and 9 Symptomatic Athletes a
Results give in millimeters of mercury (mm Hg) as means ± standard deviations and ranges in parentheses.
Comparison of Mean Pressure Measurements of 34 Asymptomatic Male and Female Subjects a
Pressure measurements provided in millimeters of mercury (mm Hg).
Fisher's least significant difference.
Discussion
Foot compartment anatomy has been described by several authors.14,16,27 Description of the medial compartment is consistent in these works. Of all of the foot compartments, the medial foot compartment appears to be most susceptible to the development of chronic exertional compartment syndrome. This compartment has been involved in all documented cases of the condition in the foot.15,19,20,30 Among these reported cases, pressures and compartment pressure testing techniques have varied considerably (Table 3).
Compartment Pressures and Testing Techniques Reported in Published Cases of Chronic Exertional Compartment Syndrome in the Foot a
L, Left foot; R, right foot; M, medial compartment; C, central compartment.
Bilateral onset described in case report, yet only one foot assessed. Pressures after exercise were not given.
Lokiec et al. 15 describe concurrent involvement in the medial and central compartments of both feet.
It is not possible to retrospectively review these cases and accurately propose normative compartment pressure values or diagnostic guidelines from the available data. Indeed, in only one article were pressure data presented for 1- and 5-minute intervals after exercise in which symptoms were reproduced. 19 Furthermore, in one report the diagnosis of chronic exertional compartment syndrome was made with pressures within a range that may be considered normal immediately after activity. 15
Objective criteria for the diagnosis of chronic exertional compartment syndrome of the leg have been established by Pedowitz et al. 24 Positive diagnosis in the leg is achieved when appropriate clinical observations are accompanied by one or more of the following pressure measurements: resting pressure, 15 mm Hg or more; 1-minute postexercise pressure, 30 mm Hg or more; and 5-minute postexercise pressure, 20 mm Hg or more. Although it is reasonable to assume that compartment pressures are equivalent throughout the body, confirmation with site-specific data is appropriate.
A group of asymptomatic athletes was assessed in this study. Mean resting compartment pressure was 7.7 ± 2.2 mm Hg. Mean pressures 1 and 5 minutes after exercise were 19.1 ± 3.3 mm Hg and 10.7 ± 2.5 mm Hg, respectively. The pressures of all 34 asymptomatic athletes conformed to the Pedowitz criteria 24 (Fig. 1). This was also true of pressure studies from the nine symptomatic patients assessed in this study, with high pressures recorded at 1 and 5 minutes after exercise.
Data recorded in this study compared with the diagnostic criteria for chronic exertional compartment syndrome of the leg proposed by Pedowitz et al. 24
Interestingly, the resting pressures of all but one symptomatic athlete were below 15 mm Hg. All postexercise measures were high. This suggests that resting pressures considered in isolation are insufficient for diagnosis of chronic exertional compartment syndrome.
The results of this study show that normative pressures of the foot and leg are consistent. Additionally, pressure measurement criteria for the diagnosis of chronic exertional compartment syndrome of the leg may be confidently applied for diagnosis involving the medial foot compartment.
Conclusion
We have presented and discussed pre- and postexercise compartment pressure measurements at the medial compartment of the foot obtained from 34 asymptomatic athletes. Pressures from a group of symptomatic patients were also presented. Normative pre- and postexercise compartment pressures were seen to be in accordance with previously reported values for the leg. The results of this work suggest that previously defined diagnostic criteria for chronic exertional compartment syndrome of the leg may be adopted when the condition is suspected in the medial compartment of the foot.