MORPHOMETRY AND VARIATIONS OF MALLEUS WITH CLINICAL CORRELATIONS

Int J Anat Res 2014, 2(1):191-94. ISSN 2321-4287 191

Original Article

M ORPHOM ETRY AND VARIATIONS OF M ALLEUS W ITH CLINICAL

CORRELATIONS

V inaya cha n dra P H

_{, V ive ka S}

_{, Sud ha M J}

_{, Ba la kr ish na She t t y}

_,

Santhosh Kuriakose

_{, Srinivasa Sagar}

_.

ABSTRACT

Address for Correspondence: Dr. Viveka S. M D (Anat omy), DNB (Anat omy), Assist ant Professor, Dep ar t m en t o f An at o m y, Azeezi a In st i t ut e of M ed i cal Sci en ces, Ko l lam , In d ia. E-M ail: vivekabharat hi@gm ail.com

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1 _{Associat e Professor, Dept . of Anat omy, Kannur M edical College, Anjarakandy, India.} * 2

Assist ant Professor, Dept . of Anat omy, Azeezia Inst it ut e of M edical Sciences, Kollam , India. 3 _{Assist ant Professor, Dept . of Pharm acology, Azeezia Inst it ut e of M edical Sciences, Kollam , India.} 4

Assist ant Professor, Dept . of Anat omy, Azeezia Inst it ut e of M edical Sciences, Kollam , India. 5 _{Assist ant Professor, Dept . of Anat omy, Am ala Inst it ut e of M edical Sciences, Thrissur, India.} 6 _{Post Graduat e, Dept . of Anat omy, A J Inst it ut e of M edical Sciences, M angalore, India.}

Background: Ossicular m or p hology an d m or phom et r ic considerat ion s play co r nerst one im por t an ce in reconst ruct ive surgeries. An at t em pt is m ade t o have an insight int o such m orphological variat ions and evaluat e t he m orphom et ric values of m alleus in sout h Indian populat ion t hrough cadaveric dissect ion.

M aterials and methods: 25 hum an head specim ens taken f rom t he dissect ion hall, aft er rem oval of brain and duram at er, subarcuat e fossa and arcuat e em inance of t he pet rous part of t he t em poral bone w ere chipped off w it h help of fine edged chissel and ham m er. Wit h help of bone cutt er t he tegm en t ym pani form ing t he rem aining roof w as rem oved, t ill t he m idd le ear cavit y and t hree ossicles are proper ly exposed and ident ified.

Results:M alleus height ranged from 6.94 m m t o 7.78 m m on bot h sides w it h average of 7.37m m on r ight and 7.51 m m on left . Weight ranged from 16.85 m g t o 19.25 m g w it h average of 18 m g on r ight side and 18.52 m g on left bot h side. Lengt h and w eight of left m alleus bones w ere stat ist ically m ore t han t heir right count erpar t s.

Conclusions:M or phologically m alleus show ed lesser var iat ions in com parison t o stapes. The left sided m alleus dom inat ed t he right sided ones in bot h lengt h and w eight .

KEYW ORDS:M alleus; M or phom et ry; M orphological variat ions; Cadaveric dissect ion; M anubrium .

INTRODUCTION

Int ernat ional Journal of Ana tomy and Research,

Int J Anat Res 2014, Vol 2(1):191-94. ISSN 2321- 4287

Received: 24 Dec 2013

Peer Review : 24 Dec 2013 Published (O):31 Jan 2014 Accept ed: 09 Jan 2014 Published (P):30 M ar 2014

Int ernat ional Journal of Anat omy and Research ISSN 2321-4287

w w w.ijm hr.org/ ijar.ht m

The m iddle ear bones in m am m als are derived from bones in t he dent ary bone (m andible) of Therapsids. The t ym panic, m alleus, and incus are ho m olo gou s t o t h e angu lar, ar t icular, and q uad r at e bo n es. In ear l y Th er ap si ds, t h e quadrat e, angular and art icular w ere direct ly connect ed t o t he dent ary bone in t he jaw hinge. These bones w ere essent ial for jaw m ovem ent [1]. The m alleus is t he largest of t he ossicles. The w ord m alleus is derived from lat in w ord, m alleus m eaning ham m er. It s shape resem bles a m allet .

Int J Anat Res 2014, 2(1):191-94. ISSN 2321-4287 192 M ATERIALS AND M ETHODS

of handle of m alleus, t he t endon of t ensor t ym pani is at t ached. Just below t he neck, t here is an ant erior project ion, referred as ant erior process, connected t o t he pet rot ympanic fissure. From t he root of handle of m alleus, conical lat eral process arise and is at t ached t hrough ant erior and post erior m alleolar folds t o upper part of t ym panic m em brane.

The cart i laginous precursor of t he m alleus originat es as part of t he dorsal end of M eckel’s cart ilage. W it h t he except ion of it s ant erior process, t he m alleus ossifies from a single endochondral cent er w hich appears near t he fut ure neck of t he bone in t he fourt h m ont h in ut ero. The ant erior process ossifies separat ely in dense connect ive t issue and joins t he rest of t he bone at about t he sixt h m ont h of fet al life [2].

St udies concent rat ing on t he m orphom et ry of ossicles are sparse from Indian subcont inent . Know ledge of ossicular m orphology dat es back t o fift eent h cent ury [3]. M orphological variat ions have been report ed in t he past in all t he t hree ossicles [4,5]. Schafer and Sym ingt on have st udied all t hree ossicles and t hey report t he lengt h of m alleus t o be 8 t o 9 m m [6]. Anson and Bast st u d ied 22 set s of o ssi cles an d concludes t hat t he m orphological variat ions in m alleus and incus are less frequent t han st apes [7]. They report t hat t he lengt h of malleus varies bet w een 7.61 – 9.11 m m .

In t he present st udy aim w as t o st udy t he m orphom et ry and m orphom et ric variat ion, if any, in t he m alleus of sm all sam ple of cadavers of sout h Indians.

Tw ent y five hum an head specim ens t aken from t he dissect ion hall of A J Inst it ut e of M edical Sciences, M angalore w ere used for t he st udy. The cranial cavit y and it s m iddle cranial fossa w ere properly exposed aft er rem oval of brain and duram at er. Port ion above t he int ernal acoust ic m eat us, Sub arcuat e fossa and arcuat e em inance of t he pet rous part of t he t em poral bone w ere chipped off w it h help of fine edged chissel and ham m er. Care w as t aken so t hat chipped off port ion from exceeding 1 cm from t he surface of t he m iddle cranial fossa. W it h help of bone cut t er t he t egm en t ym pani form ing t he

rem aining roof was rem oved, t ill t he m iddle ear cavit y and t hree ossicles are properly exposed and ident ified.

W it h help of m agnifying lens - observat ions w ere m ade in exposed part . M alleus ident ified easily by it s globular head and incus by it s body. Follow ing t he body and long process of t he lower end of incus t he head of t he st apes was reached and gent ly pulled w it h help of a point ed forceps. St apes foot plat e was separat ed from t he oval w indow and st apes in t ot o delivered out of t he m iddle ear cavit y.

By using ECG recording paper, having a scale of 1m m , t he lengt h and w idt h of t he m alleus was not ed. Using elect ronic w eighing m achine – t he w eight s of t he st apes bone t hus ext ract ed not ed after it was completely dried. The measurem ent s w ere t abulat ed for evaluat ion, com parison and int erpret at ion. M orphological variat ions – if any w ere not ed. Variat ions of t he individual m alleus bones not ed.

RESULTS

M etric Considerations:

M alleus height ranged from 6.94 mm t o 7.78 m m on bot h sides w it h average of 7.37m m on right and 7.51 m m on left (graph 1). Weight ranged from 16.85 m g t o 19.25 m g w it h average of 18 m g on right side and 18.52 m g on left bot h side (graph 2). Table 1 show s com pilat ion of values of bot h right and left malleus. Lengt h and weight of left m alleus bones were stat ist ically more t han t heir right count erpart s.

Table 1: Tabulat ion of param et ers of m alleus of bot h sides. n = num ber of m alleus, st udent s t t est value and pearsons value derived from com parison of right and lef t m alleus.

M ean 7.45 18.26

St andard deviat ion 0.39 0.78

M aximum 7.78 19.25

M inimum 6.94 16.85

N 50 50

T 0.291 0.957

Pearsons 0 0.37

Paramet ers M alleus Lengt h (in mm)

W eight (in mg)

Int J Anat Res 2014, 2(1):191-94. ISSN 2321-4287 193 M orphological Considerations:

M al l eus sho w ed m i ni m u m var i at io n s i n com parison t o ot her ossicles. Variat ions ranged from large globular head t o sm all head. Nodular bony project ion from t he head was not ed in one of t he right sided m alleus. One left sided malleus show ed t hin and short handle. Rudim ent ary ant erior and lat eral process was encount ered in anot her left sided m alleus.

Graph 1: M ean lengt h of right and left m alleus in m m .

Graph 2: M ean w eight of right and left m alleus in m g.

DISCUSSION

Anat omy of t he ossicles of t ym panic cavit y has unfort unat ely rem ained as an area of peripheral int erest . Scant dat a exist s on individual feat ures and variat ions in each bone. The m ult iplicit y of t he cont ribut ing developm ent al sources only serves t o add t o t he range and frequency of t he variat ions in t he st apes. This is w ell evidenced by t he am ount of variat ions not ed in t his st udy of 25 set s of t he st apes. Not surprisingly, t he b on es an d t h eir ano m ali es ar e d ef in i t iv e com ponent s of m any congenit al head and neck defect s such as Treacher- Collins syndrom e and Pierre Robin syndrom e. In many such syndromes of first and second arch involvem ent , obvious aud i t or y def ect s hav e b een i d en t i f i ed i n new borns.

Our st udy result s cor relat es w it h previous st udies. Bouchet has report ed t he lengt h of

m alleus t o be 7.9 m m [ 8] . M asali et al [9], Arrensburg et al [4], Harada et al [10] and Aycan et al [ 11] have report ed t he m orphological feat ures of m alleus and report ed lengt hs of m alleus are 7.6 m m , 7.3 m m , 8 m m and 8.1 m m respect ively. In t he present st udy t he lengt h of m alleus was found t o be 7.45 m m . Ram irez has st udied 23 set s of m alleus and report ed 8.18 m m lengt h [12].

The st udy from Indian subcont inent t hough had done on m alleus m orphom et ry; west erners have done t he st udy using m or e m or phom et r ic param et ers. The param et ers of t he m alleus st udied include t ot al lengt h (m axim al dist ance bet w een t he t op of t he head and t he end of t he handle), lengt h of handle (dist ance from t he end of t he lat eral process t o t he end of handle) and lengt h of head and neck (m axim al dist ance bet w een t he t op of t he head and t he end of t he lat eral process). Vincent iis & Cim ino st udied m alleus from infant s, juvenile, adult m ale & fem ales. They h av e repo r t ed a di f f er en ce bet w een right and left m alleus. In our st udy t h er e w as n o si gn if icant d if fer en ce n ot ed bet w een m ale and fem ale m alleus. This is in accordance w it h m any previous st udies [13,14]. Our st udy goes in cont rast w it h anot her st udy from Indian subcont inent in w hich 60 m alleus show ed skew ed m or ph ology of m al es and females m alleus [15]. The m orphomet ric analysis of m alleus m ay help in underst anding various m i dd l e ear p at ho l o gi es. It m ay ai d t h e ot orhinolaryngologist s in ossicular replacem ent surgeries.

CONCLUSION

M orphologically m alleus show ed lesser varia-t ions in com parison varia-t o svaria-t apes. The lefvaria-t sided m alleus dom inat ed t he right sided ones in bot h lengt h and w eight .

Conflicts of Interests: None

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Int J Anat Res 2014, 2(1):191-94. ISSN 2321-4287 194 Vi nayachandra P H et al ., M ORPHOM ETRY AND VARIATIONS OF M ALLEUS W ITH CLINICAL CORRELATIONS.

How to cite this article

:

Vinayachandra P H, Viveka S, Sudha M J, Balakrishna Shet t y, Sant hosh Kuriakose, Srinivasa Sagar. M ORPHOM ETRY AND VARIA-TIONS OF M ALLEUS WITH CLINICAL CORRELAVARIA-TIONS. Int J Anat Res 2014;2(1):191-94.

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