Clinical Signs vs Pressure in Compartment Syndrome
A missed compartment syndrome can leave a young patient with dead muscle and a weak, contracted leg, while an unneeded fasciotomy leaves large open wounds that need a second operation to close.
Key terminology
- Anterior compartment
- This compartment sits in front of the tibia and fibula and holds tibialis anterior and the toe extensors. It also carries the deep peroneal nerve.
- Acute compartment syndrome (ACS)
- Pressure rises inside a closed fascial compartment until it cuts off blood flow to muscle and nerve. Left untreated, the muscle dies and the leg is left weak and contracted.
- Pain with passive stretch
- This exam moves the toes or ankle to stretch the muscles of a compartment. Severe pain on this maneuver is an early sign of rising pressure.
- Deep peroneal nerve
- This nerve runs in the anterior compartment and gives sensation to the first web space of the foot. Numbness there can be an early clue to anterior compartment pressure.
- Delta pressure (ΔP)
- This number is diastolic blood pressure minus compartment pressure. A low ΔP means compartment pressure is close to the pressure driving blood into the muscle.
- Continuous pressure monitoring
- A catheter left in the compartment records pressure for hours instead of giving one reading. It shows the trend over time, which a single needle stick cannot.
- Fasciotomy
- Long skin and fascial incisions open every tight compartment to release the pressure. The wounds are usually left open and closed or grafted days later.
Takeaways
- Tibial shaft fracture in a young man is the classic setup. In 164 patients with acute compartment syndrome, 69% had a fracture and about half of those were tibial shaft fractures. Most patients were men under 35, and 1 in 10 had a bleeding disorder or took anticoagulants (McQueen et al, J Bone Joint Surg Br 2000;82:200-203, PMID 10755426).
- Clinical findings rule compartment syndrome out better than they rule it in. A systematic review of 4 prospective studies found sensitivity of only 13-19% and positive predictive value of 11-15%, with specificity and negative predictive value of 97-98%. The probability of compartment syndrome was about 25% with 1 clinical finding and 93% with 3 (Ulmer, J Orthop Trauma 2002;16:572-577, PMID 12352566).
- Delta pressure (ΔP) under 30 mmHg outperformed an absolute pressure cutoff. ΔP is diastolic BP minus compartment pressure. In 116 tibial shaft fractures with 24 h of continuous anterior compartment monitoring, an absolute threshold of 30 mmHg would have sent 43% of patients to fasciotomy. A ΔP under 30 mmHg flagged only 3 patients and missed no case (McQueen and Court-Brown, J Bone Joint Surg Br 1996;78:99-104, PMID 8898137).
- Continuous pressure monitoring performed well in the Edinburgh unit that developed it. In 850 monitored tibial shaft fractures, estimated sensitivity was 94%, specificity 98%, PPV 93% and NPV 99%. An earlier series from the same unit found monitored patients reached fasciotomy in 16 h vs 32 h, with sequelae in 0 of 12 vs 10 of 11 (McQueen et al, J Bone Joint Surg Am 2013;95:673-677, PMID 23595064; McQueen et al, J Bone Joint Surg Br 1996;78:95-98, PMID 8898136).
- A single pressure reading over-estimates the likelihood of compartment syndrome. In 48 tibial shaft fractures with no clinical suspicion, one reading after induction met the ΔP 30 criterion in 35%, and none developed compartment syndrome over 6 months. In 19 leg fractures without clinical signs, 84% had a reading within 30 mmHg of diastolic BP. Both used one-time readings, unlike Edinburgh's continuous protocol (Whitney et al, J Trauma Acute Care Surg 2014;76:479-483, PMID 24458053; Prayson et al, J Trauma 2006;60:1037-1040, PMID 16688067).
- General anesthesia lowers diastolic BP by a mean of 18 mmHg. In 242 tibia fractures nailed under general anesthesia, intraop diastolic BP ran 18 ± 13 mmHg below the preop value, while preop and postop values differed by only 2 mmHg. An intraop ΔP can look falsely low, and the preop diastolic predicts the postop value (Kakar et al, J Orthop Trauma 2007;21:99-103, PMID 17304064).
- Signs and pressures work best together. A 2023 meta-analysis of 7 studies put the predictive value at 21% for clinical signs alone, 29% for pressure alone and 68% for both combined. AAOS rates the evidence as moderate for repeated or continuous monitoring with a ΔP threshold of 30 mmHg to help rule out compartment syndrome (Lorange et al, J Orthop Trauma 2023;37:e319-e325, PMID 37053115; Coe et al, J Am Acad Orthop Surg 2021;29:e1-e4, PMID 33201042).
- Fasciotomy within 12 h of onset gives the best chance of a normal leg. In 46 limbs treated by fasciotomy, 68% of those decompressed within 12 h regained normal function vs 8% after 12 h. Complications ran 4.5% vs 54%, and open vs closed fasciotomy made no difference (Sheridan and Matsen, J Bone Joint Surg Am 1976;58:112-115, PMID 1249096).