Muscular variations in the lower limb are very common. They have been described by many authors when performing cadaveric dissections and when using the different imaging techniques. The presence of these muscle is frequently asymptomatic, but some times it can cause symptoms due to  overcrowding and mechanical compression of adjacent structures. The lateral compartment of the leg contains the peroneus longus and peroneus brevis muscles. The peroneus quartus muscle is one of the accessory muscles present in the lateral compartment of the leg. It said to have been first depth in 1923 by Hecker(1) who estimated its incidence to be 13% in the general population. There are only few studies concerning this muscle.surgeons should be aware of the possible presence of peroneus quartus muscle, not only because of possible associated pathology, but also for use in surgical reconstruction. Various anatomists have described it and given it different names according to its various origins and insertions. Sobel, W Levy and Bohne(2) described the anatomical variations of the muscle in a cadaver study on 124 legs with particular reference to the origins and insertions of the defferent anomalous muscles in the lateral compartment and suggested that these should all be referred to as variants of the same muscle, the peroneus quartus. They showed that it was present in 21.7% of cadavers.

The peroneous quartus muscle, arises from the lower third of the fibula, peroneus brevis muscle,and/or peroneus longus muscle. However, its distal insertion has shown great variability, most often inserting onto the lateral surface of the calcaneus on the retrotrochlear eminence(3). Believed to be an evolutionary acquisition for bipedal gait, the peroneus quartus muscle is unique to humans, assisting with eversion of the lateral border of the foot, pronation of the foot against the walking surface, and lateral stabilization of the ankle(1-6). The peroneus quartus muscle was first described by Otto in 1861(3) and has since bbeen termed the peroneus sextus,peroneus calcaneus externus,peroneocuboidian,peroneus accessorius,peroneus medius(7), and paroneus muscle of the tarsus(1). Anatomist, surgeons, and radiologists have discovered slight variations in the distal insertion of the peroneus quartus, resulting in both increased and ambiguous nomenclature(8-11).

The reported points of insertion include (from proximally to distally):retrotrochlear eminence of the calcaneus, the fibular (peroneal) trochlea of the calcaneus,tendons of the fibularis longus and brevis muscle, the cuboid, and the fifth metatarsal (10,12-14). In 1923, Hecker(1) classified the peroneus quartus variants into 3 catagories according to the inserteion onto the calcaneus(peroneocalcaneus externum)cuboid(peroneocuboideus), or tendon of peroneus longus (peroneaoperoneolongus).However, the peroneoperoneolongus muscle is now referred to as the peroneus accessories(10,15,16).Other peroneus quarts variants include the peroneua digiti minimi, which inserts onto the fifth metatarsal(10)and the peroneotalocalcaneus muscle(17). With so many variations of the peroneus quartus muscle, 2 studies attempted to resolve the nomenclature issues by suggesting that the peroneus quartus muscle inserts onto the lateral aspect of the calcaneus and variants of the muscle have other distal attachments(10,14,12,18).

This study aims at investigating the incidence, anatomical variations and possible pathology relating to the peroneus quarus muscle

MATERIALS AND METHODS

This study was conducted at the faculty of Department of anatomy, Zydus Medical College And Hospital, DAHOD, GUJARAT, JAN-2026.Twenty lower limbs of adult cadavers, were dissected to perform this study. Their ages range between 45 to 80 years old. Each limb was dissected by an incision which was start about 10cm proximal to the lateral malleolus and end 5 cm distal to it.The compartment was examined for the presence of an accessory muscle. If this ispresent, the dissection was extended and the site of its origin and insertion and passage in the retromalleolar groove was noted. All anatomical variations was registered, recorded and photographed.

Ethical Consideretions:

All cadavers were source from pre-existing from Zydus Medical College and Hospital, Dahod, Gujarat, India, with institutional ethical approval ensuring respectful of human remains and adherence to ethical standards for anatomical reaserch.

RESULTS

A peroneus quartus was present in 1(5%) of the 20 legs which were dissected (fig.1). The muscles which were indentified  different area of origins and insertions. This muscle was origin from the posterior intermuscular septum and inserted into the retrotrochlear eminence of the calcaneus bone (fig. 1),

DISCUSSION

Knowledge of the anatomy of the peroneal muscles and its variations is important to surgeons dealing with pathologies in this region. There are no precise data on the incidence of the peroneus quardrus muscle in the literature, and the stufies are mainly based on the findings of many years ago(19).

In this study we found the incidence of peroneus qurtus was 5%. In our specimens.Bhargava et al (20) gave the incidene of peroneus quadrus as 15.5%.Reimen(21) reported the presence of peroneus quardrus as 79.5%. Based on these data, Yammine(22) stated that there were differences regarding incidence of the muscle and declared that ethnicity was important in considering the incidence of peroneus quadrus in each community.

In our specimen muscle was origin from the posterior intermuscular septum and inserted into the retrotrochlear eminence of the calcaneus bone, As previous reports, The most frequent origin was from the muscle fibres of peroneus brevis and its most frequent insertion was into the retrotrochlear eminence of the calcaneum.

CONCLUSION

Surgeon should be aware of the existence of this muscle, not only because of possible associated pathology, but also because of its potential use in reconstructive surgery.peroneal muscle which would be important for reconstructive foot surgeons attempting to repair this area.This study will supplement our knowledge on the possible variations of the muscles in this region, which would be useful for lower limbs surgeons.

REFERENCES

1. Hecker P. Study of the peroneous of the tarsus. Anat Rec 1923;26:79-82.
2. Sobel M, Levy Me, Bohne WH. Congenital variations of the peroneus quartus muscle: an anatomical study. Foot Ankle 1990;11:81.
3. Sarrafian SK. In: Sarrafian’s Anatomy of the foot and Ankle: Descriptive, Topographic, Functional, ed 3, pp. 240-245, edited by AS Kelikian, Lippincott, Williams & Wilkins, Philadelphia, 2011.
4. Trono M, Tueche S, Quintart C, Libotte M, Baillin JM. Peroneus quartus muscle: a case report and review of the literature.Foot Ankle Int. 1990;20:659-662.
5. Wachter S, Beekman S. Peroneus quartus: a case report. J Am Podiatr Med Assoc 1983;73:523-524.
6. Athavale SA, Gupta V, Kotgiwar S, Singh V.The peroneus quartus muscle:clinical correlation with evolutionary importance. Anat Sci Int. 2012;87:106-110.
7. Bejjani FJ, Jahss MH. Le Double’s study of muscle variations of the human body part I: muscle variations of the leg. Foot Ankle 1985;6:111-134.
8. Wood J. Variations in human mycology observed during the winter session of 1867-1868 at King’s college, London. Proc R Soc London 1868;16:483-525.
9. Macalister A. On muscular anomalies in human anatomy, and their bearing upon homotypical mycology. Proc R Irish Acad. 1866-1869;10:121-164.
10. Sobel M, Levy ME, Bohne WH. Congenital variations of the peroneus quartus muscle: an anatomic study. Foot Ankle 1990;11:81-89.
11. Saupe N, Mengiardi B, Pfirmann CW, Vienne P, Seifert B, Zanetti M. Anatomic Variants associated with peroneal tendon disorders: MR imaging findings in volunteers with asymptomatic ankles. Radiology 2007;242:509-517