Biceps Femoris
The two parts of biceps femoris probably represent two separate muscles that are united in humans. In rare cases, the parts remain separate either partially or entirely or the short head may be absent. The two parts are innervated by two different nerves. The normal attachment of the muscle to the crural fascia represents an extension to the leg that is found in some mammals. The crural extension may be seen as muscular slips (tensor fasciae suralis) attached to the fascia, gastrocnemius, or tendo achillis. Accessory slips have been noted, which arise from various sources including the sacrum, coccyx, sarcotuberous ligament, ischial tuberosity, gluteus maximus, gluteal ridge of the femur, the linea aspera at its upper extremity, fascia lata, gastrocnemius and lateral condyle of the femur, adductor magnus, or vastus lateralis.
In 41% of 62 limbs, the long head took origin from the sacrotuberous ligament.
Macalister reported the variations of biceps flexor cruris (biceps femoris) as follows:
1. Its short head may be absent (Otto, Meckel, Budge, Henle);
2. It may have a second long head from the tuber ischii (Sömmerring);
3. A third head may arise from the upper part of the linea aspera (Meckel);
4. Or from the medial condylar ridge of the femur (Gruber);
5. Or from the fascia under gluteus maximus, as a rounded fusiform slip, which joins the long head (Wood);
6. From the fascia lata, near the upper end of the linea aspera (Henle);
7. A slip continued over the great sciatic (sacrotuberous) ligament to the side of the sacrum;
8. The short head may receive an accessory fascicle from vastus externus (lateralis);
9. Or from adductor magnus;
10. Macalister saw the short head split into several fascicles;
11. A third head arising in common with a middle head of gastrocnemius. In this case it lay behind the vessels and nerves of the popliteal fossa. The most common head arises from the tuber ischii as described by Sömmerring, by Gantzer, and by Blandin;
12. The two heads have been found separated until near their insertion;
13. The insertion may be by two tendons separated by the external lateral ligament;
14; One slip may be attached to the lateral tuberosity of the tibia;
15. One slip may join the fascia of the leg;
16. A slip may join the posterior aspect of the lateral condyle of the tibia;
17. A slip from the long head to the tendo Achillis has been described by Otto and by Kelch. Macalister said this reminded him of the insertion of the rectus in many animals, as for example, in the lion.
Syn.: m. biceps cruris, flexor cruris fibularis, flexor cruris lateralis, Wadenbeinbeuger, aeusserer Beuger, zweikopfiger Beuger.
References
Bajaj, I.D. and S. Sood. (1962) Anomalous insertion of the biceps femoris muscle. J. Anat. Soc. India 11:92.
Barry,D. and J.S. Bothroyd. (1924) Tensor fasciae suralis. J. Anat. 58:382-383.
Gladykowska-Rzeczyczka, J. (1964) Accessory bundle of the short head of biceps femoris muscle. Folia Morphol. (Warsaw) 23:75-78.
Gruber, W. (1872) Sur un muscle tenseur de l'aponeurose surale partant du demitendineaux. Bull. Acad. Imp. Sci. St. Petersbourg 17:289-291.
Gruber, W. (1873) Sur une variante du muscle tenseur de l'aponeurose surale, partant du muscle demi-tendineux. Bull. Acad. Imp. Sci. St. Petersbourg 18:157-158.
Gruber, W. (1886) Tensor fascia femoris posterior digastricus. Arch. Path. Anat. Physiol. Klin. Med. 103:475-477.
Hepburn, D. (1893) Complete separation of the two heads of biceps flexor cruris muscle. J. Anat. Physiol. 27: 282-284.
Hildebrand, R. (1978) Discovery of a variant in the region of the adductor magnus and the short head of the biceps femoris. Anat. Anz. 144:48-50.
Holmgren, H. Ein Fall von bilateraler Doppelbildung des caput longum Musculi bicipitis femoris. Anat. Anz. 86:269-271.
Klaatsch, H. (1911) Über eine dem Tenissimus ahnliche Variation am biceps femoris des Menschen. Anat. Anz. 38:305-310.
Macalister, A. (1875) Additional observations on muscular anomalies in human anatomy (third series), with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-134.
Miyauchi, R. (1985c) A case of tensor fasciae suralis muscle. Acta Medica Nagasakiensia. 30:285-292.
Moore, A.T. (1922) An anomalous connection of the pyriformis and biceps femoris muscles. Anat. Rec. 23:307-309.
Niizima, M.. (1938) Ein Fall von überzähligem Kopf des M. biceps femoris beim Menschen. Okajimas Folia Anat. Jpn. 16:187-192.
Nonaka, T. and T. Ishii. (1953) One case of tensor fasciae suralis. Chiba Igakkai Zasshi 29:261. In Japanese.
Wood, J. (1867) On human muscular variations in relation to comparative anatomy. J. Anat. Physiol. 1:44-59.
