Compartment Pressure Measurements Have Poor Specificity for Compartment Syndrome in the Traumatized Limb

The Journal of Emergency Medicine, Vol. 44, No. 5, pp. 1039–1044, 2013 Copyright Ó 2013 Elsevier Inc. Printed in the USA. All rights reserved 0736-4679/$ - see front matter

http://dx.doi.org/10.1016/j.jemermed.2012.09.040

Clinical Reviews COMPARTMENT PRESSURE MEASUREMENTS HAVE POOR SPECIFICITY FOR COMPARTMENT SYNDROME IN THE TRAUMATIZED LIMB James A. Nelson, MD Emergency Department, Pioneers Memorial Hospital, Brawley, California and Department of Emergency Medicine, University of California at San Diego Medical Center, San Diego, California Reprint Address: James A. Nelson, MD, Department of Emergency Medicine, University of California at San Diego Medical Center, Mailcode 8676, 200 W. Arbor Dr., San Diego, CA 92103

, Abstract—Background: Osseofascial compartment syndrome is defined by ischemic necrosis of muscle caused by elevated pressure within fascial compartments. The diagnosis can be made either clinically or through compartment pressure measurements. Compartment pressure above 30 mm Hg was traditionally used as the threshold for diagnosis of compartment syndrome, but was challenged due to a high number of false-positive results. Perfusion pressure (diastolic blood pressure compartment pressure) <30 mm Hg came to be promoted as a confirmatory diagnostic test. Objective: The objective of this article is to review the specificity of perfusion pressure for compartment syndrome in the acutely traumatized limb. Discussion: Perfusion pressure has been shown to generate false-positive results in 18–84% of patients with tibial fractures. Two studies showed that not a single patient with measurements qualifying for fasciotomy actually needed the procedure. Conclusion: Both absolute compartment pressure and tissue perfusion pressure generate a high rate of false-positive results in the acutely traumatized limb. An alternative diagnostic test or process is needed to prevent overtreatment. In the meantime, emergency medicine and orthopedic surgery textbooks and guidelines should promote awareness of the limitations of the test. Ó 2013 Elsevier Inc.

INTRODUCTION The osseofascial compartment, designed for strength, is inelastic and does not deform to accommodate severe swelling. The two most common conditions that cause such swelling are fractures (69%) and soft-tissue injury (23%) (1). Beyond a certain pressure, microvascular blood flow is compromised, defining the onset of acute limb compartment syndrome, or osseofascial compartment syndrome. The process is consummated in ischemic necrosis of the enclosed muscles. Necrotic muscle heals with scar tissue, forming myotendinous adhesions and contractures (2). The process can be averted before full infarction occurs by cutting through the fascia and releasing the swollen and ischemic muscles, allowing blood flow to resume. This procedure, called fasciotomy, is not benign. Complications of fasciotomy include 77% altered sensation at the wound margins, 25% swollen limbs, 26% tethered scars, 13% recurrent ulceration, 13% muscle herniation, and 7% tethered tendons. It causes 23% of patients to keep their limb covered, 28% to change hobbies, and 12% to change jobs (3). Both underdiagnosis and overdiagnosis will cause significant patient harm. Therefore, the diagnostic process needs to have excellent sensitivity and specificity. Although the ischemic contractures of compartment

, Keywords—compartment syndrome; physical examination; manometry; fasciotomy; diagnosis; unnecessary surgery

RECEIVED: 20 January 2012; FINAL SUBMISSION RECEIVED: 3 September 2012; ACCEPTED: 18 September 2012 1039

1040

syndrome were described as early as the 1880s, and its prevention with fasciotomy was shown to be effective in 1926, it wasn’t until the mid-1970s that an objective confirmatory test for compartment syndrome came to be proposed and widely adopted (4–7). Compartment pressure measurement quickly became the accepted confirmatory test for this disease. Early studies that led to its widespread use were uncontrolled (8). Therefore, its specificity was unknown. In the late 1980s and early 1990s, absolute compartment pressure measurements were challenged as leading to an unacceptably high rate of false positives (9,10). In the mid-1990s, the decades-old Whiteside technique of measuring compartment perfusion pressure (diastolic blood pressure compartment pressure) started to be more widely advocated as a more accurate technique (7,11). Thought to reflect the ability of diastolic blood flow to overcome tissue resistance and supply perfusion to the limb, it is referred to as delta P, differential pressure, or critical pressure (7,12–14). In a 1996 study on a postoperative population, it was shown that the use of absolute pressure elevations would qualify 43% of patients with tibial fractures for fasciotomy, but that using mean perfusion pressure for the first and second 12 h after surgery brought the actual fasciotomy rate down to 2.6% (13). Despite excellent outcomes, this study was criticized for having a 12-h mean time of observation in a condition where traditional teaching calls this a time-dependent diagnosis (15). Current emergency medicine practices are largely extrapolated from the orthopedic literature (largely on postoperative patients with tibial fractures) and applied to the larger heterogeneous pool of Emergency Department (ED) patients with suspected compartment syndrome. Although emergency medicine textbooks acknowledge controversy over thresholds for surgery, they promote traditional thresholds: [the] ‘‘mainstay of treatment is fasciotomy, particularly for compartment pressures >30–40 mm Hg’’ (16). A similar rule is stated in another text: ‘‘Pressures exceeding 30 mm Hg or within 30 mm Hg of the patient’s mean arterial pressure are an indication for fasciotomy’’ (17). Neither of these texts comment on the potential for false positives and non-therapeutic fasciotomy. One text states ‘‘equivocal measurements still require clinical judgment,’’ but fails to state that all measurements require such judgment (18). Practitioners are urged to ‘‘have a very low threshold for measuring pressures within a muscle compartment,’’ and that ‘‘the key to early detection of compartment syndrome is a high index of clinical suspicion’’ (19,20). The reader comes away with a sense of the need to check pressures in low- to moderate-risk patients and to have the orthopedic surgeon perform fasciotomy for absolute pressure readings above 30 mm Hg and perfusion pressure measurements below 30 mm Hg.

J. A. Nelson

The body of this article presents the accumulating evidence that not only absolute compartment pressure, but now even the use of perfusion pressure in the acutely traumatized limb is known to have poor specificity. It generates an unacceptably high rate of false-positive results in low- to moderate-risk patients. The article urges emergency medicine textbooks to reveal the critical limitations of this diagnostic test, and calls for practicing Emergency Physicians to exercise restraint in the use of this test. DISCUSSION Compartment Pressure Measurement As alluded to earlier, using an absolute compartment pressure of >30 mm Hg as the indication for fasciotomy was challenged in the 1980s and 1990s for poor specificity, and using perfusion pressure of <30 was advised (9,10,13). In the past decade, several studies have emerged challenging perfusion pressure as well. A 2001 article, a portion of whose title was ‘‘Beware of overtreatment!’’, reported on 95 patients with tibial fractures and warned ‘‘if we had decompressed all legs with a [perfusion pressure] under 30 mm Hg . 45.4% of them would have been fasciotomized’’ (15). Instead, they used surgical judgment as the confirmatory test. Switching the gold standard from perfusion pressure to the surgeon’s clinical judgment avoided 28 fasciotomies in 97 limbs (95 patients). All patients had 1-year follow-up and none developed sequelae of compartment syndrome. The authors estimated the specificity of perfusion pressure <30 as 65% for compartment syndrome. This poor specificity occurred despite the unblinded use of perfusion pressure to help decide surgery, which biases toward defining the test as accurate and inflates the apparent specificity. The actual specificity may have been even lower. The only randomized controlled trial of compartment pressure monitoring compared to clinical examination found that pressure monitoring would have qualified 18% of patients for a fasciotomy (using perfusion pressure <30) (21). The study population was post-operative patients with tibial fracture. Because none of the 18% of patients with low perfusion pressure had clinical signs of compartment syndrome, none received fasciotomy, and none of these patients experienced sequelae of compartment syndrome. Not a single patient whose perfusion pressure indicated fasciotomy actually needed the procedure. A study of surgeon behavior showed that although some surgeons have low fasciotomy rates of 2%, others have rates of 24%, with the difference correlating with how frequently they checked compartment pressure

Compartment Pressure Measurement Nonspecific

(22). Given that the low fasciotomy surgeons did not suffer from missed diagnosis, the implicit hypothesis is that high compartment pressure, and even diminished perfusion pressure, is probably common in tibial fractures and does not in itself signify that the patient will suffer the sequelae of a true compartment syndrome. The more a practitioner relies on a test prone to false positives, the higher the rate of fasciotomy. One article addressed this possibility by studying the population of patients with tibial fracture not suspected of having compartment syndrome; 84% had at least one measurement of perfusion pressure <30 that would have qualified them for fasciotomy (23). None received fasciotomy, and none suffered from any sequelae of compartment syndrome. Perfusion pressure has been shown in multiple studies to generate high rates of false-positive results. Due to its poor specificity in the acutely traumatized limb, it has the potential to over-diagnose compartment syndrome, leading to non-therapeutic fasciotomy. The current alternative confirmatory test of compartment syndrome is clinical judgment. Clinical Diagnosis There is one evidence-based systematic review on the physical diagnosis of compartment syndrome. It asserts that neurological deficits are only 13% sensitive and pain is only 19% sensitive (24). These figures are sometimes cited by textbooks and even clinical practice guidelines without critical discussion of its methods (25,26). The author retroactively changed the definition of compartment syndrome supplied in the original articles. There were a total of only three fasciotomies among the four articles, but the author instead used the much larger group of patients with elevated pressure measurements as the population with ‘‘compartment syndrome.’’ A more accurate conclusion from the article would be that clinical signs have poor sensitivity for abnormal pressure results. The article therefore has no utility in assessing the sensitivity and specificity of physical signs for true compartment syndrome. The physical signs will be briefly reviewed below. Disproportionate pain. Disproportionate pain, although not necessarily objectively definable, is considered an excellent sign of tissue ischemia. However, painless presentations do occur (27). Despite this limitation, it may be one of the most sensitive signs we have. A recent systematic review of 28 articles on the effect of analgesia on diagnosis indicates that disproportionate pain remains the most common sign of compartment syndrome and that most patients have typical presentations (28).

1041

Pain on passive stretch. Assessing for pain on passive stretch is an attempt to make this finding more specific, by isolating the pain to the suspected compartment. For example, if the anterior compartment of the tibia is suspected, pain on passive toe flexion is understood to indicate the pain was arising from the anterior compartment. However, this approach to our knowledge has not been scientifically validated. Motor weakness. Motor weakness of the affected muscles is a classic sign of compartment syndrome, but in practice is limited by pain and injuries (2). This sign is widely used but does not seem to have been extensively studied. Sensory deficits. Signs of neurological dysfunction have been considered classic for compartment syndrome. However, some patients with neurologic deficits have normal pressure, and when these particular patients are treated without fasciotomy they seem not to develop sequelae of compartment syndrome (15). Therefore, sensory deficits have limitations in specificity, though the exact value has not yet been adequately studied. Vibration sensation to 256 Hz tuning fork has been proposed as most sensitive for compartment syndrome, though it is not clear whether this is detecting early compression neuropathy rather than true ischemia (29). Palpation.Palpation is useful for directing our attention to one particular area, but is not sensitive for degree of pressure elevation (30). Articles that report on using clinical examination for the diagnosis of compartment syndrome report some of the lowest rates of morbidity from fasciotomy or untreated compartment syndrome. The only randomized controlled trial of clinical examination vs. pressure monitoring for compartment syndrome was alluded to earlier (21). It showed that in 200 patients with tibial fractures, only 5 needed fasciotomy, and the rates of non-union, sensory loss, muscle weakness, contracture, and clawing of toes were the same in both groups. Eighteen percent of monitored patients would have qualified for fasciotomy, and none of them received this surgery. None of these particular patients suffered complications. Because this was an inpatient post-operative orthopedic population, the study would not necessarily apply to the ED. Other studies mentioned earlier also show that by relying on clinical diagnosis to overrule pressure measurements, they greatly reduced the number of fasciotomies that would otherwise have been performed (15,23). In summary, due to lack of an independent criterion standard, the clinical diagnosis of compartment syndrome has not yet been adequately studied. Articles tend to show that institutions relying on clinical judgment

1042

J. A. Nelson

have good outcomes, but this is subject to publication bias. Limitations Acute limb compartment syndrome is a heterogenous disease, but the studies available largely represent tibial fractures, usually post-operative. Therefore, the population assessed is more narrow than the populations we might see in clinical practice. The diagnostic gold standard by default is the decision for operation, which itself is subjective. An objective gold standard is needed. This review does not address non-traumatic causes of compartment syndrome, which need to be studied separately. The conclusions in this article would also not necessarily apply to patients who do not have a reliable examination. Finally, this review addresses perfusion pressure as a diagnostic test, but cannot evaluate the use of the test to decide surgery. That would require estimates of the number-needed-to-treat to prevent one case of ischemic contracture, and balancing the probability of benefit vs. the probability of harm. This article challenges the uncritical use of pressure measurements to decide fasciotomy and calls for further research to be done. But from a current practice perspective, no alternative, including clinical judgment, has been adequately studied. At this time, the decision for fasciotomy remains the burden of the orthopedic surgeon and patient during the informed consent process. CONCLUSION Compartment Pressure Measurement is Not a Confirmatory Test It is time to acknowledge that perfusion pressure, like absolute compartment pressure, has poor specificity. Specificity has been estimated as 65%, and in two of the populations described in this article, every single positive result was a false positive (21,23). A test with such poor specificity is probably not the best candidate for use as a confirmatory test. It generates an unacceptable rate of false positives and will tend to promote over-utilization of fasciotomy. Tests with poor specificity can sometimes have a role for screening if the sensitivity is good. For the case of compartment pressure though, medicolegal considerations may lead to patient harm. If the emergency physician screens the patient and discovers low perfusion pressure, should the patient go to the operating room? For a surgeon to forgo fasciotomy risks a later accusation of missing compartment syndrome. The non-therapeutic fasciotomy is currently undetectable. Both extremes can cause harm, but only one poses demonstrable medicole-

gal risk to the surgeon. Thus, the emergency physician who checks pressure in a low-risk patient may unwittingly be biasing the surgeon toward unnecessary fasciotomy. A New Confirmatory Test or Process is Needed A new confirmatory test is needed to diagnose this condition that essentially is not an abnormal pressure state but is an ischemic disease of muscle that may arise from it. Case reports demonstrate that serial creatine kinase and myoglobin measurements can make the diagnosis in equivocal cases (31). Some articles express support for using laboratory tests in an adjunctive role (32,33). Although muscle enzymes are non-specific in acute trauma, their serial measurement may have the potential to signify ongoing muscle ischemia in patients who lack alternative means of diagnosis. Certainly for equivocal presentations, this possibility deserves further study. Other possibilities might include tests of muscle viability and function, such as electromyography, which has been used for chronic compartment syndrome (34). SUMMARY In the acutely traumatized limb, both absolute compartment pressure measurement and perfusion pressure <30 mm Hg have poor specificity for compartment syndrome. Emergency physicians should not employ this test in these populations, and instead should consult the orthopedic surgeon when compartment syndrome is suspected. REFERENCES 1. McQueen MM, Gaston P, Court-Brown CM. Acute compartment syndrome. Who is at risk? J Bone Joint Surg Br 2000;82:200–3. 2. Frink M, Hildebrand F, Krettek C, Brand J, Hankemeier S. Compartment syndrome of the lower leg and foot. Clin Orthop Relat Res 2010;468:940–50. 3. Fitzgerald AM, Gaston P, Wilson Y, Quaba A, McQueen MM. Long-term sequelae of fasciotomy wounds. Br J Plast Surg 2000; 53:690–3. 4. Volkmann R. Ischaemic muscle paralyses and contractures. J Hand Surg Br 2005;30:233–4. 5. Jepson PN. Ischaemic contracture: experimental study. Ann Surg 1926;84:785–95. 6. Mubarak SJ, Hargens AR, Owen CA, Garetto LP, Akeson WH. The wick catheter technique for measurement of intramuscular pressure. A new research and clinical tool. J Bone Joint Surg Am 1976;58: 1016–20. 7. Whitesides TE Jr, Haney TC, Harada H, Holmes HE, Morimoto K. A simple method for tissue pressure determination. Arch Surg 1975; 110:1311–3. 8. Mubarak SJ, Owen CA, Hargens AR, Garetto LP, Akeson WH. Acute compartment syndromes: diagnosis and treatment with the aid of the wick catheter. J Bone Joint Surg Am 1978;60: 1091–5. 9. Van Zyl AA, Van den berg JL. Is compartment pressure measurement really necessary? J Bone Joint Surg Br 1989;71:713.

Compartment Pressure Measurement Nonspecific 10. Triffitt PD, Ko¨nig D, Harper WM, Barnes MR, Allen MJ, Gregg PJ. Compartment pressures after closed tibial shaft fracture. Their relation to functional outcome. J Bone Joint Surg Br 1992;74:195–8. 11. Heckman MM, Whitesides TE Jr, Grewe SR, Rooks MD. Compartment pressure in association with closed tibial fractures. The relationship between tissue pressure, compartment, and the distance from the site of the fracture. J Bone Joint Surg Am 1994;76:1285–92. 12. Garner AJ, Handa A. Screening tools in the diagnosis of acute compartment syndrome. Angiology 2010;61:475–81. 13. McQueen MM, Court-Brown CM. Compartment monitoring in tibial fractures. The pressure threshold for decompression. J Bone Joint Surg Br 1996;78:99–104. 14. Gourgiotis S, Villias C, Germanos S, Foukas A, Ridolfini MP. Acute limb compartment syndrome: a review. J Surg Educ 2007; 64:178–86. 15. Janzing HM, Broos PL. Routine monitoring of compartment pressure in patients with tibial fractures: beware of overtreatment!. Injury 2001;32:415–21. 16. Shermer C. Compartment syndrome. In: Schaider J, Hayden SR, Wolfe R, Barkin RM, Rosen P, eds. Rosen and Barkin’s 5-minute emergency medicine consult. 4th edn. Philadelphia, PA: Lippincott Williams & Wilkins; 2011:248–9. 17. Geiderman JM, Katz D. General principles of orthopedic injuries. In: Marx JA, Hockberger RS, Walls RM, eds. Rosen’s emergency medicine: concepts and clinical practice. 7th edn. Philadelphia, PA: Mosby Elsevier; 2010:467–88. 18. Carter MA. Compartment syndrome evaluation. In: Roberts JR, Hedges JR, eds. Clinical procedures in emergency medicine. 5th edn. Philadelphia, PA: Saunders Elsevier; 2010:986–99. 19. Hutson AM, Rovisnky D. Compartment pressure measurement. In: Reichman EF, Simon RR, eds. Emergency medicine procedures. New York, NY: McGraw Hill; 2004:541–50. 20. Haller PR. Compartment syndrome. In: Tintinalli JE, ed. Tintinalli’s emergency medicine: a comprehensive study guide. 7th edn. New York, NY: McGraw Hill Medical; 2011:1880–4. 21. Harris IA, Kadir A, Donald G. Continuous compartment pressure monitoring for tibia fractures: does it influence outcome? J Trauma 2006;60:1330–5. 22. O’Toole RV, Whitney A, Merchant N, et al. Variation in diagnosis of compartment syndrome by surgeons treating tibial shaft fractures. J Trauma 2009;67:735–41.

1043 23. Prayson MJ, Chen JL, Hampers D, Vogt M, Fenwick J, Meredick R. Baseline compartment pressure measurements in isolated lower extremity fractures without clinical compartment syndrome. J Trauma 2006;60:1037–40. 24. Ulmer T. The clinical diagnosis of compartment syndrome of the lower leg: are clinical findings predictive of the disorder? J Orthop Trauma 2002;16:572–7. 25. McQueen MM. Acute compartment syndrome. In: Buchholz RW, Heckman JD, Court-Brown CM, eds. Rockwood and Green’s fractures in adults. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:688–705. 26. Wall CJ, Lynch J, Harris IA, et al., Liverpool (Sydney) and Royal Melbourne Hospitals. Clinical practice guidelines for the management of acute limb compartment syndrome following trauma. ANZ J Surg 2010;80:151–6. 27. Badhe S, Baiju D, Elliot R, Rowles J, Calthorpe D. The ‘silent’ compartment syndrome. Injury 2009;40:220–2. 28. Mar GJ, Barrington MJ, McGuirk BR. Acute compartment syndrome of the lower limb and the effect of postoperative analgesia on diagnosis. Br J Anaesth 2009;102:3–11. 29. Phillips JH, Mackinnon SE, Beatty SE, Dellon AL, O’Brien JP. Vibratory sensory testing in acute compartment syndromes: a clinical and experimental study. Plast Reconstr Surg 1987;79: 796–801. 30. Shuler FD, Dietz MJ. Physicians’ ability to manually detect isolated elevations in leg intracompartmental pressure. J Bone Joint Surg Am 2010;92:361–7. 31. Minnema BJ, Neligan PC, Quraishi NA, Fehlings MG, Prakash S. A case of occult compartment syndrome and nonresolving rhabdomyolysis. J Gen Intern Med 2008;23:871–4. 32. Liu Y, Shen HQ, Xia YX, Jiang CZ, Gui JC, Song HR. Application of monitoring phosphocreatine kinase continuously and dynamically in early diagnosis of compartment syndrome [Chinese]. Zhongguo Gu Shang 2009;22:602–4. 33. Ihedioha U, Sinha S, Campbell AC. Do creatine kinase (CK) levels influence the diagnosis or outcome in patients with compartment syndrome? Scott Med J 2005;50:158–9. 34. Zhang Q, Jonasson C, Styf J. Simultaneous intramuscular pressure and surface electromyography measurement in diagnosing the chronic compartment syndrome. Scand J Med Sci Sports 2011;21: 190–5.

1044

J. A. Nelson

ARTICLE SUMMARY 1. Why is this topic important? Compartment syndrome can cause permanent functional harm to the patient. However, fasciotomy also can cause permanent harm. To prevent overdiagnosis, one must know the specificity of the diagnostic test used. 2. What does this review attempt to show? Most of the studies during the latter 20th century that established compartment pressure measurement as the gold standard for compartment syndrome were methodologically unequipped to establish its specificity. Absolute pressure measurements were shown to be non-specific in the 1980s and 1990s. Perfusion pressure (diastolic blood pressure-absolute compartment pressure) was promoted as an alternative, but this review shows that it too has poor specificity. 3. What are the key findings? Using perfusion pressure <30 mm Hg as the threshold for surgery yields a high rate of false positives, and would promote over-utilization of fasciotomy. 4. How is patient care impacted? Patients with suspected acute limb compartment syndrome are currently subjected to unnecessary surgery by the use of a test prone to false positives. Emergency physicians should probably not check pressure at all, and instead, should consult the orthopedic surgeon when this condition is suspected. This may limit unnecessary fasciotomy.