Clinical Anatomy 6~106-110 (1993)

A Cadaveric Study of the Peroneus Tertius Muscle KATHRYN STEVENS, ALASTAIR PLATT, AND HAROLD ELLIS

Department of Anatomy, University of Cambridge, Cambridge, United Kingdom

Most anatomy textbooks state that peroneus tertius arises from the distal third of the fibula and is inserted into the fifth metatarsal. In a study of one limb from each of 40 cadavers, peroneus tertius was absent in 2 limbs, and in 35 it arose from the lower middle quarter of the fibula. The origin was continuous with that of extensor digitorum longus in 33 limbs, and the length of the origin was correlated with the width of the tendon (r = 0.67). The tendon was single in 37 limbs and double in 1. Intertendinous connections between peroneus tertius and extensor digitorum longus were found in 6 limbs. The trapezoidal insertion of peroneus tertius into the fifth metatarsal was bifurcate in two cases and trifurcate in one. Our study suggested that the standard textbook descriptions of peroneus tertius need to be revised.

Key words: muscle, peroneus tertius, intertendinous connections

o 1993 wiley-Liss, Inc.

INTRODUCTION Peroneus tertius (PT) is a small muscle, situated in

the anterior compartment of the leg, which assists in dorsiflexion and eversion of the foot. Anatomy text- books describe the muscle as arising from the distal third of the fibula (Lumley et al., 1980; Gosling et al., 1991; Moore, 1985; Snell, 1986; Woodburne and Burke], 1988; Williams et al., 1989; McMinn, 1990), or the distal quarter of the fibula (Romanes, 1976; Bas- majian and Slonecker, 1989) and adjacent interosseous membrane. T h e origin is usually described as being continuous with that of extensor digitorum longus (EDL) and the tendons of these two muscles share a common synovial sheath. Peroneus tertius is inserted into the dorsum of the base of the fifth metatarsal bone, and by a thin falciform extension into the superior surface of the shaft of the bone (Frazer, 1933).

We carried out a survey on embalmed cadavers in the Anatomy Department at the University of Cambridge to map out the origin and insertion of PT more pre- cisely.

MATERIALS AND METHODS One leg from each of 40 cadavers was dissected to

show the origin and insertion of PT. There were 35

right legs and 5 left legs. T h e cadavers were all Cauca- sians from the East Anglia region and varied in age from 62 to 100 years. Twenty were female and twenty male. We noted whether the muscle bellies of P T and E D L were separate or came from a common origin, and whether there was any other connection between the two muscles. T h e location and length of the origin, and the site and nature of the insertion of P T , were care- fully documented. T h e length of the fibula and the minimum width of the tendon were measured with a tape measure. T h e connections of the tendon with the other extensor tendons, and the nature of its insertion into the fifth metatarsal, were noted.

RESULTS In our study no differences were observed between

male and female cadavers, or between right and left limbs. Peroneus tertius was absent in two limbs. Unfor- tunately, we only had one limb from each cadaver, and so we were unable to tell whether this absence was bilateral.

Received for publication March 1, 1992; revised July 12, 1992.

Address reprint requests to Professor H. Ellis, Department of Anat- omy, University of Cambridge, Downing Street, Cambridge CB4 3DY, United Kingdom.

0 1993 Wiley-Liss, Inc.

ao-

70 -

60 -

4 50- P

A

A

Y L

40- f m c -I x 30-

A

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i 2 3 4 5 6

Minimum Tendon width Imml

Fig. 1. The relationship between the percentage of the fibula from which PT originated and the minimum width of the PT tendon.

Peroneus Tertius Muscle 107

In 33 limbs the origin of PT was continuous with that of E D L (82.5%). T h e length of origin was correlated with the width of the tendon ( r = 0.67) (Fig. 1) and varied in length from 6 to 26 em. We found that on average, PT took origin from 30.2 2 11.8% of the length of the fibula. We divided the fibula into quarters and found that in 35 limbs the origin was centered around the lower middle quarter, not the distal quarter. T h e tendon of PT was single in 37 limbs (92.5%) (Fig. 2) and double in one (2.5%). T h e tendons of PT and E D L were fused in four legs (10.0%). In one, the tendon of E D L to the fifth metatarsal arose from the belly of the PT muscle.

Examples of intertendinous connections were found in six limbs (15.0%). In one, a fibrous band passed from the tendon of PT to EDL, and in five, one or more bands passed from E D L to PT. In three limbs these were single (Fig. 3). In one there were three bands (Fig. 4), and in one there were four.

T h e insertion of PT into the fifth metatarsal was trapezoid in shape and varied between 0.5 to 6.0 cm in

EDL

Fig. 2. a,b: The usual arrangement of tendons at the ankle (EDL gives off a slip to the shaft of the fifth metatarsal).

108 Stevens et al.

b

PT EDL

Fig. 3. a,b An intertendinous connection passing from EDL to PT.

length. T h e length of insertion was not related to the length of origin of the muscle. T h e insertion was bifur- cate in two cases (5.0%) and trifurcate in one (2.5%). In two limbs, E D L gave off a slip to the fifth metatarsal. In another both E D L and P T gave off slips which fused before being inserted into the fifth metatarsal (Fig. 5).

DISCUSSION Our study has confirmed that P T is a variable muscle

which may be completely absent. Although many text- books describe P T as arising from the distal third of the fibula, we found that more often it arose from the lower middle quarter. In some legs the tendons of E D L and PT were fused, and in six they were linked by interten- dinous connections. Peroneus tertius was inserted into the base of the fifth metatarsal, but the aponeurotic insertion was trapezoidal and often extended along the whole length of the dorsal surface of the shaft of the fifth metatarsal, blending with the dorsal fascia. These

results agree closely with some of the older literature on the detailed anatomy of the muscle (Wood Jones, 1944; Schaefer and Thane, 1892; Testut, 1884; Werneck, 1957). Werneck studied the inferior limbs of 90 ca- davers between the ages of 5 months of intrauterine life and 62 years. T h e cadavers came from three different racial groups, but no racial or sexual differences in peroneus tertius were demonstrated. Although our study was small we found that there were no differ- ences between the lower limbs of males and female cadavers.

Peroneus tertius is not considered to be an impor- tant muscle, and its precise function is not well un- derstood. I t is thought to be a simultaneous dor- siflexor and evertor of the foot. However, functionally the combined actions of peroneus longus, peroneus brevis and EDL would suffice in this movement. Peroneus tertius is thought to play a role in the plan- tigrade use of the foot. In human gait there are two features which are involved in the transmission of

Peroneus Tertius Muscle 109

PT EDL

Fig. 4. a,b: Intertendinous connections passing from EDL to PT.

force to the ground (Morton, 1935). In modern hu- man feet the hallux is no longer divergent but proj- ects beyond the other toes. The re is also a longitudi- nal arch of the foot in addition to a transverse arch. Peroneus tertius assists in the support of the longi- tudinal arch, holding the sole in a plane transversely parallel with the ground.

Gorillas and chimpanzees are generally regarded as the apes most closely related to Man. However, detailed anatomical studies of the lower limbs of go- rillas and chimpanzees are sparse. Straus (1930) re- viewed the publications on PT in gorillas and found that it was present in 6 of 18 specimens. Hecker (1922) also reported a case of a P T in a chimpanzee. The re are however no reported examples of a PT in the lesser apes such as baboons. I t would therefore seem reasonable to suggest that PT is yet another character that developed in association with bipedalism.

REFERENCES Basmajian, J.V., and C.E. Slonecker 1989 Grant’s Method

of Anatomy (1 1 th edition). Baltimore: Williams & Wilkins.

Frazer, J.E. 1933 T h e Anatomy of the Human Skeleton (3rd edition). London: J & A Churchill.

Gosling, J.A., P.F. Harris, J.R. Humpherson, I. Whitmore, and P.L.T. Willan 1991 Human Anatomy; Textbook and Colour Atlas. London: Gower Medical Publishing.

Hecker, P. 1922 Formation du Peronier anterieur chez un chim- panze. Arch. Anac., I : 147-155.

Lumley, J.S.P., J .L. Craven, and J .T . Aitken 1980 Essen- tial Anatomy (3rd edition). Edinburgh: Churchill Liv- ingstone.

McMinn, R.M.H. 1990 Last’s Anatomy: Regional and Applied (8th edition). Edinburgh: Churchill Livingstone.

Moore, K.L. 1985 Clinically Oriented Anatomy (2nd edition). Baltimore: Williams & Wilkins.

Morton, D. J. 1935 T h e Human Foot: Its Evolution, Physiology and Functional Disorders. New York: Columbia University Press.

110 Stevens et al.

PT EDL

Fig. 5. a,b: Fibrous slips from the tendons of PT and EDL passing to the fifth metatarsal.

Romanes, G.J. 1976 Cunningham’s Manual of Practical Anat- omy (14th edition). Oxford: Oxford University Press.

Schaefer, E.A., and G.D. Thane. 1892 Quain’s Anatomy (10th edition): Arthrology, Myology, Angiology. London: Long- mans, Green & Co.

Snell, R.S. 1986 Clinical Anatomy for Medical Students (3rd edition). Boston: Little & Brown.

Straus, W.L. 1930 T h e foot musculature of the Highland Gorilla (Gorilla Beringei). Quart. Rev. Biol. 5:261-317.

Testut, L. 1884 Les anomalies musculaires chez I’homme, Paris: J. Masson.

Werneck, H.J.L. 1957 Contribuicao para o estudo de alguns aspectos morfologicos do M. fibularis tertius em brancos, negros e mulatos, com pesquisa in vivo da presenca de seu tendao. Anais Fac. Med. Univ. Minas Gerais, 17:417-520.

Williams, P.L., R. Wanvick, M. Dyson, and L.H. Bannister 1989 Gray’s Anatomy (37th edition). Edinburgh: Churchill Livingstone.

Woodburne, R.T., and W.E. Burke1 1988 Essentials of Human Anatomy (8th edition). Oxford: Oxford University Press.

Wood Jones, F. 1944 Structure and Function as Seen in the Foot. London: Bailliere, Tindall and Cox.