Date Published: July 9, 2012
Publisher: Hindawi Publishing Corporation
Author(s): Sérgio Ricardo Rios Nascimento, Renata Watanabe Costa, Cristiane Regina Ruiz, Nader Wafae.
Objective. Quantify the presence of the fibularis quartus muscle and correlate it with the individual’s sex and concomitant presence of the fibularis tertius muscle. Materials and Methods. We evaluated 211 magnetic resonance examinations (43.13% men and 56.87% women) on the ankle and hindfoot, produced between 2009 and 2011. Results. The fourth fibularis muscle was found to be present in 7.62% of the examinations and 75% of these also contained the fibularis tertius muscle. Conclusion. The incidence of the fourth fibularis muscle is variable; moreover, its incidence does not depend on the individual’s gender or the presence of the fibularis tertius muscle.
The fibularis quartus muscle was first described by Otto in 1816  and was subsequently studied in detail by Hecker in 1923 . It forms part of one of the three groups of muscle variations that occur in the ankle: the group of muscle-tendon variants of the fibular muscles . In most cases, the presence of this muscle is asymptomatic, and it is detected by chance during the examination or surgical procedure [4–6]. However, in some cases, its presence is associated with certain symptoms: pain in the ankle, with or without anterior trauma; displacement, spraining, or tearing of the fibularis brevis tendon; tendon calcification; or painful hypertrophy of the retrotrochlear eminence [4, 5, 7]. The presence of the fibularis quartus muscle may simulate a longitudinal tear in the fibularis brevis tendon, but is differentiated by the presence of the muscle, when a muscle belly separated from the muscle belly of the fibularis brevis is present .
We evaluated 211 MRI examinations on the ankle or hindfoot between 2009 and 2011. All the examinations were performed using the Signa Horizon Lx machine (General Electric Medical Systems), with a 1.5 T magnetic field and a quadrature coil for knees. The images analyzed were acquired using the spin echo technique with T1 weighting, without administering contrast medium. The images were acquired in three planes: axial—programmed parallel to the plantar fascia, from the calcaneus; sagittal—programmed parallel to the plane of the tibia, perpendicular to the sole of the foot; coronal—programmed perpendicular to the tibial-calcaneal joint. The examinations used came from the database of the imaging diagnostics center of Hospital Santa Catarina (stored on CD-R) and were used in accordance with the authorization from the institution’s ethics committee. The data were analyzed using the ONIS 2.3 Free Edition software (Digitalcore), which is available from http://www.onis-viewer.com/, with the aid of the hospital’s radiologists. The patient’s identities were kept absolutely confidential, and only the patient’s gender and the side of the ankle examined were recorded.
Of the 211 tests evaluated, 91 (43.13%) were men, 44 (48.35%) on the right side and 47 (51.65%) on the left side, and 120 (56.87%) were women, 56 (46.67%) on the right side 64 (53.33%) on the left. Ankles rights total 100 (47.39%) and 111 left ankle (52.61%).
Since its discovery in 1826, the fibularis quartus muscle has been objective of researches with different results, but complementaries (Tables 3 and 4).
The fibularis quartus muscle was found in 7.62% of the population. In regarding to the side, its incidence was higher in left ankle (68.79%) than in rights (31.25%). In regarding to the fibularis tertius muscle, 75% of the ankles containing the fibularis quartus muscle also had this muscle. The incidence of fibularis quartus muscle, together with the fibularis tertius muscle remains inconstant, variable, and independent of the individual’s gender as well as the presence of the fibularis tertius muscle. However, the chance of a person who has fibularis tertius muscle is three times bigger when the fibularis quartus muscle is present. The presence of fibularis quartus muscle is asymptomatic in most cases, but its presence is an important source of tissue for reconstruction procedures of fibular retinaculum, must be evaluated carefully, and be considered as a differential diagnosis in cases of suspect of longitudinal rupture of fibular brevis tendon.