Int J. MorphoL, 25(2):381-383, 2007.

CASE REPORT

Cyamella in Man - Its Morphology and Review of Literature

Cyamella en el Hombre - Su Morfología y Revisión de la Literatura

*Sreenivasulu Reddy; **Venkata Ramana Vollala & **Rajashekar Rao

* Department of Anatomy, Melaka Manipal Medical College (Manipal Campus), ICHS, Manipal, Karnataka-576 104, India.
**Department of Biochemistry, Melaka Manipal Medical College (Manipal Campus), ICHS, Manipal, Karnataka-576 104, India.

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SUMMARY: A sesamoid bone is a little bone embedded in a joint capsule or tendon. We observed a very rare sesamoid bone (cyamella) in the popliteus muscle of a 48 - year - old male cadaver. Further, the related literature is reviewed and the probable functions, morphology and clinical significance of the variation are discussed.

KEY WORDS: Cadaver; Cyamella; Popliteus muscle; Sesamoid bone.

RESUMEN: Un hueso sesamoideo es un pequeño hueso incrustado en una cápsula articular o tendón. Observamos un raro hueso sesamoideo (cyamella) en el músculo poplíteo de un cadáver de un hombre de 48 años de edad. Además, revisamos la literatura relacionada y las funciones probables y se discute su morfología y significación clínica.

PALABRAS CLAVE: Cadáver; Cyamella; Músculo poplíteo; Hueso sesamoideo.

INTRODUCTION

Normally, popliteus muscle is attached to the lateral condyle of the femur at the anterior end of popliteal groove and to the back of the lateral meniscus both within the capsule of the knee joint. It emerges from the capsule of the joint and the tendon then expands into a triangular fleshy belly which is attached to the posterior surface of the tibia above the soleal line. In the present paper we discussed the presence of a rare sesamoid bone in the tendon of popliteus muscle.

MATERIAL AND METHOD

The study involved the lower limb dissection of a 48-year-old male cadaver of South Indian origin in the department of anatomy, Melaka Manipal Medical College, Manipal, India. The dissections of lower limbs were carried out according to the instructions by Cunningham's manual of practical anatomy (Romanes, 2003). Both lower extremities (right and left) of the body were dissected. The dissections took place during 2005-2006. The bodies were preserved by the injection of a formalin - based preservative (10% formalin) and stored at - 4°C. Before taking photographs, the dissected region was rinsed with water.

RESULTS OF CASE

The present variation was found in the right lower extremity. However the left lower extremity was normal. During routine dissection classes to undergraduate medical students a cadaver showed a very rare sesamoid bone (cyamella) in the popliteus muscle of right leg (Fig 1). It was observed at the tendomuscular junction, articulating with posterior aspect of the lateral condyle of the tibia and lying close to the head of the fibula.

DISCUSSION

Popliteus is a flat muscle that forms the floor of the lower part of the popliteal fossa. It arises within the capsule of the knee joint by a strong tendon, which is attached to a depression at the anterior end of the groove on the lateral aspect of the lateral condyle of the femur. Fleshy fibres expand from the inferior limit of the tendon to form a somewhat triangular muscle that descends medially to be inserted into the medial two thirds of the triangular area above the soleal line on the posterior surface of the tibia, and into the tendinous expansion that covers its surface (Standring et al, 2005).

The popliteus muscle has a similar arrangement in all primates and most other mammals. A sesamoid bone may exist in the tendon of the popliteal muscle and it has been called cyamella (Pearson & Davin, 1921), or popliteal fabella (Taylor & Bonney, 1905), or fabella distalis (Slanina), or os sesamoideum genu inferius laterale (Pfitzner, 1892). The popliteal sesamoid bone has been described in numerous mammal orders-Edentata, Fissipeda, Rodentia, Chiroptera, Insectívora (Pearson & Davin; Taylor & Bonney).

The cyamella is absent or very rare in humans. When it does occur, it can articulate with the lateral condyle of the tibia and lies very close to the head of fibula. It is within the popliteus muscle and is therefore a sesamoid bone (Le Minor, 1992). It is mostly confused with the fabella, which lies within the lateral head of gastrocnemius muscle (Murray et al, 1990).

There are some reports about presence of popliteal sesamoid bone in humans (Pearson & Davin; Slanina; Keats, 1988). This rare anomaly usually has no pathological implications; however, one case revealed by a painful symptomatology has been described (Hillion, 1982). From a phylogenetic point of view, the popliteal sesamoid bone might be reasonably regarded as a shared homologous feature in primates. In the current case the popliteal sesamoid bone was located in the angulated part of the tendon around the tibia. In this area, unusual mechanical stress occurs, and a part of the tensile stress in the muscle will be transformed into pressure on the tendon. The sesamoid bone presumably functions to resist this pressure. However, specializations of the tendon itself serve this function in the human species (Sick, 1964; Meyer et al, 1964) and other primates that lack the popliteal sesamoid bone. The presence or absence of the bone maybe connected to particular postural or locomotor behavior, but no such connection is evident from its distribution among primates. The functional significance of sesamoids in general is not well understood (Broek van den & Barents, 1947; Mottershead, 1988). The widespread loss of many other sesamoid bones in primates (Wikander et al, 1986; Le Minor, 1987, 1988) and of accessory bones such as intrameniscal ossicles (Le Minor, 1990) suggests that variably expressed tendencies toward the disappearance of these primitive structures may reflect genetic affinities more accurately than functional similarities.

REFERENCES

Broek van den, A. J. P & Barents, J. W. Absence des rotules et signification des os sesamoides. Acta Anal, 4:54-9, 1947.

Hillion, L. Le syndrome de la cyamella douloureuse. Apropos d'un cas rarissime chez un sportif presentant une gonalgie. Med. Doct. Thesis. Lyon (France), 1982.

Keats, T. E. Atlas of Normal Roentgen Variants That May Simulate Disease. Chicago, Year Book Medical Pub, 1988.

Le Minor, J. M. Comparative anatomy and significance of the sesamoid bone of the peroneus longus muscle (os peroneum). J. Anat, 151:85-99, 1987.

Le Minor, J. M. The ventral metacarpo- and metatarso-phalangeal sesamoid bones: comparative anatomy and evolutionary aspects. Gegenbaurs Morphol Jahrb., 134: 693-731, 1988.

Le Minor, J. M. Comparative morphology of the lateral meniscus of the knee in primates. J. Anat, 170:161-71, 1990.

Le Minor, J. M. Brief communication: The popliteal sesamoid bone (cyamella) in primates. Am. J Phys. Anthropol, 87:107-10, 1992.

Meyer, P.; Sick, H. & Grosshans, E. Adaptation fonctionnelle au glissement et a la reflexion des tendons, des poulies de reflexion des tendons et des ligaments articulaires. Arch.Biol, 75:745-70, 1964.

Mottershead, S. Sesamoid bones and cartilages: An inquiry into their function. Clin. Anat., 7:59-62, 1988.

Murray, R. O.; Jackson, H. O. & Stoker, D. J. Self -assessment in fundamentals. In: The radiology of skeletal disorders. New York, Churchil Livingstone, 1990. V. 2. pp. 1098.

Pearson, K & Davin, A. G. On the sesamoids of the knee joint. Biometrika, 13:133-75, 350-400, 1921.

Pfitzner, W. Die Sesambeine des menschlichen Korpers. Morphol. Arb., 7:517-762, 1892.

Romanes, G. J. Cunningham's Manual of Practical Anatomy. 15^th ed. Upper and lower limbs. Oxford University Press, 2003. V.1. pp. 160-2.

Sick, H. L'adaptation des tendons a la reflexion. Arch. Anat. Histol. Embryol, 47:369-446, 1964.

Slanina, J. Fabella distalis: A new sesamoid bone. Radiol. Clin., 25:274-7,1956.

Standring, S.; Ellis, H.; Healy, J. C; Johnson, D. & Williams, A. Gray's Anatomy. 39^th ed. Churchill & Livingstone, Baltimore, 2005, pp. 1484 -5.

Taylor, G. & Bonney, V. On the homology and morphology of the popliteus muscle: A contribution to comparative myology. J. Anat, 40:34-50, 1905.

Wikander, R.; Covert, H. H. & DeBlieux, D. D. Ontogenetic, intraspecific, and interspecific variation of the prehallux in primates: Implications for its utility in the assessment ofphylogeny.Am. J. Phys. Anthropol, 70:513-23,1986.

Received: 06-01-2007 Accepted: 12-03-2007

Corresponce to:

Venkata Ramana Vollala,
Lecturer, Department of Anatomy,
Melaka Manipal Medical College (Manipal Campus),
International Centre for Health Sciences,
Manipal-576104,
Karnataka State,
INDIA

Email: ramana.anat@gmail.com

Phone: 91-820-2922642 Fax:91-820-2571905