Working Diagnosis:
Exertional compartment syndrome of the right volar forearm secondary to an anomalous reverse palmaris longus.

Treatment:
Minimally invasive superficial fasciotomy was performed. The patient tolerated the surgery well and was without complications.
Case Photo #5 , Case Photo #6

Outcome:
The patients symptoms were significantly improved following surgery. Resumption of full activities, including Jiu Jitsu, occurred within one week of surgery. He was given grip strength exercises to be performed daily with a stress ball. After 10 months, patient has remained significantly improved, maintaining full function, and without limitations on his activity.

Author's Comments:
In this case, ECS of the forearm was likely caused by a reversed palmaris longus (rPML) variant. There are three more common anomalous forearm muscles documented in the literature. In rPML, ECS is likely precipitated by hypertrophy of the muscle belly within the unyielding ante-brachial fascia, leading to ECS symptoms.

Editor's Comments:
Exertional compartment syndrome (ECS) of the forearm is an uncommon, yet increasingly recognized condition. It is seen with repetitive isometric loading of the wrist while gripping. It causes classic symptoms of pain, swelling, loss of grip strength, and altered sensation in the hands. The timing of symptoms can be helpful to distinguish ECS from tendinopathies or sprains. Confirmation of ECS is made using intra-compartmental pressure monitoring.

References:
Duckworth AD, Mitchell SE, Molyneux SG, White TO, Court-brown CM, Mcqueen MM. Acute compartment syndrome of the forearm. J Bone Joint Surg Am. 2012;94(10):e63.

Duckworth AD, Mcqueen MM. The Diagnosis of Acute Compartment Syndrome: A Critical Analysis Review. JBJS Rev. 2017;5(12):e1.

Georgiev GP, Iliev AA, Dimitrova IN, Kotov GN, Malinova LG, Landzhov BV. Palmaris Longus Muscle Variations: Clinical Significance and Proposal of New Classifications. Folia Med (Plovdiv). 2017;59(3):289-297.

Harrison JW, Thomas P, Aster A, Wilkes G, Hayton MJ. Chronic exertional compartment syndrome of the forearm in elite rowers: a technique for mini-open fasciotomy and a report of six cases. Hand (N Y). 2013;8(4):450-3.

Marpalli S, Bhat AL, Gadahad MR. A Case of Reverse Palmaris Longus Muscle- An Additional Muscle in the Anterior Compartment of the Forearm. J Clin Diagn Res. 2016;10(3):AD03-4.

Osborn CPM, Schmidt AH. Management of Acute Compartment Syndrome. J Am Acad Orthop Surg. 2019.

Twoon M, Jones CD, Foley J, Davidson D. Reversed palmaris longus muscle: a report of two cases. Case Reports Plast Surg Hand Surg. 2017;4(1):73-76.

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