Os lunatum cannot resist this pressure which is considered to be one of the reasons for the development of Kienbock s disease. This resistance to the considerable pressure depends on some morphological features of the wrist bones and ofOs lunatum in particular. The variations of the anatomical features were studied on 12 cadaver wrists. The results showed that Os lunatum could contact the bones of the distal wrist row and those of the forearm in different ways: i) with Os capitatum and with two separated articular surfaces for radius and discus articularis - in 33,33 % and ii) Os capitatum, Os hamatum and with two separated articular surfaces for radius and discus articularis - in 66,67 %

Dyankova, S.

Kamburov, D.

Marinov, G.

English

Varna Medical University Press: Journals

Scripta Scientifica Medica, vol. 30 (1998), pp. 49-55 Copyright © Medical University, Varna ANATOMICAL FEATURES OF OS LUNATUM: SIGNIFICANCE IN T H E WRIST JOINT STATICS AND MECHANICS D. Kamburov , G. Marinov*, S. Dyankova* partment of Orthopaedics and Traumatology and ^Department of Anatomy, Histology and Embryology, Medical University of Varna, Varna Os lunatum cannot resist this pressure which is considered to be one of the reasons for the development of Kienbock s disease. This resistance to the considerable pressure depends on some morphological features of the wrist bones and ofOs lunatum in particular. The variations of the anatomical features were studied on 12 cadaver wrists. The results showed that Os lunatum could contact the bones of the distal wrist row and those of the forearm in different ways: i) with Os capitatum and with two separated articular surfaces for radius and discus articularis - in 33,33 % and ii) Os capitatum, Os hamatum and with two separated articular surfaces for radius and discus articularis - in 66,67 %. Key-words: Os lunatum, wrist bones, articular interrelations, morphology, biomechanics Wrist represents the most com­plex joint in the human organism that performs numerous movements, pos­sesses an enormous adaptation capac­ity and considerable stability as well (7). The adequate diagnosis and com­plete restoration of the wrist after in­jury or disease depends on the level of knowledge and understanding of the morphology and biomechanics of this joint complex. One needs a more de­tailed research of the anatomy and k i ­nematics of the wrist as well as of the Address for correspondence: kamburov, Dept. of Orthopaedics and Traumatology, Medical University, 55 Marin Drinov St, BG-9002 Varna, BULGARIA E-mail: kamburov@asclep.muvar.acad.bg forces acting on it and defining its load­ing, the compensatory mechanisms and the factors leading under certain condi­tions to decompensation of these mechanisms. There is no united opin­ion about the role and significance of the single wr i s t bones for carpal stabilility in the literature available (4-6,9-11,14). It is due, in our opinion, to the insufficient knowlege of the varia­tions in the contacts of single carpal bones with each other and with fore­arm bones as well . The considerable differences of carpal joint contacts detected by dissec­tion and x-ray methos of investigation suggest that radiography does not pro-'1РШ Scientifica Medica 4 D. Kamburov , G. Marinov, S. Dyankova vide sufficiently reliable information about the degree of development of these contacts. That is why it should be supplemented by a more objective method such as direct visual examina-tion of macerated and non-macerated osseous and bone-articular preparations (1,12,13). The aim of the present work was to enlarge the existing knowledge about macerated osseous material through investigation of non-macerated articu-lar preparations and to reveal the fol-lowing carpal interactions with a view to further discussion devoted to their possible role in the etiopathogenesis of Kienbock's disease: i ) of Os lunatum wi th Os capitatum and Os hamatum; i i ) of Os lunatum with Os scaphoideum and Os triquetrum; i i i ) of Os lunatum with ra-dius and cartilage triangularis-ulna complex of the distal radioulnar joint, and iv) between distal ends of radius and ulna. MATERIAL AND METHODS Twelve cadaver wrist prepara-tions from the collection of the Depart-ment of Anatomy, Histology, and E m -bryology, Medical University of Varna, were examined. As a rule, the articular preparations in the collection were from individuals older than 60 years although single preparations from younger indi-viduals could also be involved. The scopical examination was performed through a magnifying glass (3x) and in-cluded description of joint surfaces, number of joint facettes and cartilage patterns. The examination of the single bones consisted in the following: a) Os lunatum - proximal joint surface to ra-dius and Discus articularis along with joint surfaces to Os capitatum and Os hamatum; b) Os capitatum - joint sur-faces to Os scaphoideum and Os luna-tum; c) Os scaphoideum - joint surfaces to radius, Os lunatum, and Os capitatum; d) Os hamatum - joint sur-face to Os lunatum; e) radius - degree of distinguishing of the parts of carpal joint surface of radius articulating with Os scaphoideum and Os lunatum. A descriptive scale was used indicating: 1) not distinguished (completely fused); 2) distinguished through an incomplete demarcating crista, and 3) distinguished through a complete demarcating crista. The degree of the development of the crista was defined as low, middle, and high, and f) ulna - assessment of the different length of distal ends of radius and ulna using the following descrip-tive scale: equal length, ulna (+) vari-ance, and ulna (-) variance. Metric examination of joint car-tilage surfaces was done by means of calliper-gauge with an allowance of 0,1 mm: a) Os lunatum - joint surface width to Os capitatum and to Os hamatum] b) Os capitatum - to Os lunatum, and c) Os hamatum - to Os lunatum. 50 Anatomical features of Os lunatum RESULTS AND DISCUSSION 1. Interactions of Os lunatum with Os capitatum and Os hamatum Os lunatum contacts distally with Os capitatum only in 4 of 12 joints under study (33,33 % ) - Os lunatum, type 1 after Viegas et al. (13). In the rest preparations the bone possesses a single medial facette on its distal surface to Os hamatum, too - Os lunatum, type 2 after Viegas et al. (13). The width of the facette to Os capitatum varies be-tween 6,0 and 11,6 mm, at an average of 9,33 mm. When present, the medial facette to Os hamatum varies between 1,0 and 6,5 mm, at an average of 3,41 mm (Table 1, Fig. 1 and Fig . 2). Table 1 Metric characteristics of distal joint surface of Os lunatum in 12 preparations Parameters Whole surface Facette to Facette to Os hamatum in mm Os capitatum in all bones in bones with such facette only n - % bones 12/100%/ 12/100%/ 12/100%/ 8 /66.67%/ maximal 15.1 11.6 6.5 6.5 minimal 8.4 6.0 0 1.0 averape 11.61 9.33 2.28 3.41 F*8* 1. Articulating faccete to Os capitatum only on the distal joint surface of Os lunatum The surface width to Os capitatum only compared to the total distal one (for both Os capitatum and °* hamatum) varies between 55,56 % a n d 100 %, at an average of 82,66 % (Table 2). 2. Interactions of Os lunatum with Os scaphoideum and Os tri-quetrum In two cases the proximal sur-faces of Os lunatum and Os scaphoideum form a common oval and 51 D. Kamburov , G. Marinov, S. Dyankova are not displaced one to another. The bones are displaced in anterior-poste-rior direction in 9 cases: slightly in 3, moderately in 4, and considerably in 2 cases. Because of severe lesion of the joint surfaces the precise estimation of the interarticular interaction is impos-sible in one case. The proximal surfaces of Os lunatum and Os triquetrum form a common oval in 6 cases without any Table 2 Joint surface width ofOs capitatum to-wards the whole distal joint surface in number in percentage 4 100% 1 90 -99,99% 1 80 -89,99% 4 70 -79,99% 0 60 -69,99% 2 50 -59,99% Table 3 Degree of distinguishing of the parts of radius carpal joint surface articulating with Os lunatum and Os scaphoideum Indistinguishable (completely fused) Distinguished by demarcating crista n / % incomplete crista complete crista n / % 0 /0% low middle 0 /0% 12/16,67% 6/50,00% high 4 / 33,33% displacements in distal-proximal direc-tion. Os triquetrum expands distally in three cases but Os lunatum does in two. 3. Interaction of Os lunatum with radius and the cartilage triangu-laris-ulna complex of the distal radioul-nar joint The degree of distinguishing be-tween the parts of carpal surface of the radius ar t icula t ing wi th wi th Os scaphoideum and Os lunatum is illus-trated on Table 3. 52 Anatomical features of Os lunatum . Hk These surfaces are differenti-ated through a demarcating crista in all the cases. ••gjj 4. Interactions between distal ends of radius and ulna • I K T h e s e ends are equally long in 4 cases. A different degree of ulna (+) variance are observed in 5 cases but of ulna (-) one - in 3 cases. Fischer et al (3) point out that Os lunatum is located in a osseous-liga-mentary bed and fixed under conditions of very labile balance resulting in per-manent change of its position accord-ing to the position of the hand. Meta-phorically speaking (2), Os lunatum lies like in a nut-cracker. The first shoulder consists of the distal carpal row and par-ticularly of the head of Os capitatum transferring the pressure of the metac-arpal bones. The second shoulder con-sists of the forearm bones and particu-larly of the radius contacting with the proximal carpal row. As previously shown by us on macerated bones (1) both Os hamatum containing a joint surface to Os luna-tum and the cartilage triangularis-ulna complex of the distal radioulnar joint are related to this balance. It is due to the possible contacts of Os lunatum in 4 different ways with distal carpal row and forearm bones. The relation of the radius wi th Os lunatum and Os scaphoideum is similar. The existing complete demarcating crista on the car-riage surface although expressed to a different extent argues for an anticipat-ing modelling of the cartilage joint sur-faces as compared to that of the osseous ones. Our data convincingly confirm the preliminary conclusions from the study of the macerated bone materials that the presence of Os lunatum, type 1 is much more seldom than that reported in x-ray studies (only in one third of the cases) while Os lunatum, type 2 occurs much more commonly (in 66,67 % of the cases) (8,13). In one third of the cases the whole distal surface of Os lu-natum is exposed to distal pressure of the third metacarpal bone mediated by Os capitatum. In the rest cases, how-ever, this pressure is exerted on some part of the distal surface of Os lunatum only while the rest part is exposed to the pressure of the fourth metacarpal bone mediated by Os hamatum. This is of clinical interest by two main reasons. It has been reported that the considerable cartilage erosions of the proximal pole of Os lunatum, type 2 cannot roentgenological^ be visual-ized but are arthroscopically detectable (13). In the present study we establish such erosions as well as lesions on the medial facette of Os lunatum. They could cause some unclear pains in the ulnar aspect of the wrist (8,13). That is why such an origin of this pain should be more often considered because of the higher incidence of Os lunatum, type 2 with medial facette to Os hamatum (1). The significance of this exist-ing medial facette for the etiopathogen-53 D. Kamburov , G. Marinov, S. Dyankova esis of Kienbock's disease is a second substantial issue in this aspect. The presence of Os lunatuyn, type 2 could be related with peculiarities of blood supply and wrist kinematics as well (13). Other authors deny the causal role of the medial facette (12). In our opin­ion, under equal other conditions, in the presence of a medial facette of Os lu-natum the pressure exerted by the third metacarpal bone mediated by Os capitation on a surface unit of Os luna-tum is stronger than in the absence of a medial facette Referring the present re­sults to this model enhances the reli­ability of the conclusions about the fre­quency and importance of this facette. These different interrelation types of Os lunatum with the other wrist and fore­arm bones enable the analysis of the complex process of pressure transmis­sion from the precarpal to the forearm bones taking into consideration the variations of the mediating bones. R E F E R E N C E S К К а м б у р о в , Д . , Г. М а р и н о в , С. Д я н к о в а . Год. сб.Науч. тр. ИМАБ, 4, 1998, № 1, 26-32.- 2. C h u i n a r d , R . С . Атек Soc. Surg. Hand. Orthop. Trans., 4, 1980, p. 18.-3. F i s c h e r , M . , G . S e g m u l l e r , G . S e n n w a l d . Orthopade, 22, 1993, 52-56.- 4. H o r i i , Е . , M . G a r c i a - E l i a s , K . A n , A . B i s h o p , W. Cooney , R . L i n s c h e i d , E . C h a o . J. Hand Surg., 16A, 1991, No 2, 355-362.- 5. K a p a n d j i , A . Orthopade, 15,1986,№2, 60-73.-6. L i e h t m a n , D . , J . Schne ide r , A . S w a f f o r d , G . M a c k . J. Hand. Surg., 6,1981, №5,515-523.- 7. L i n s c h e i d , R . L . Clin. Orthop. Rel. Res., 202, 1986, 27-39.- 8. N a k a m u r a , R , S . T s u g e , K . Watanabe , K . T s u n o d a . J. Bone Joint Surg., 73A, 1991, No 9, 1391-1396.- 9. N a v a r o , A . An. Fac. Med. (Montevideo), 6, 1921, 113-141.- 10. R u b y , L . , W. Cooney , K . A n , R . L i n s c h e i d , E . C h a o . J. Hand Surg., 13A, 1988, No 1,1-1 0 . - l l . T a l e i s n i k , J . J. Hand Surg., 1A, 1976, No 1, 110-118.- 12. T s u g e , S . , R . N a k a m u r a . J. Hand Surg., ISB, 1993, 70-75.- 13. V i e g a s , S . F . , K . Wagner , R . Pa t t e r son , P. Pe te r son . У. Hand Surg., 15 A, 1990,564-571.-14. Weber, E . Orthop. Clin. North Атек, 2, 1984, 193-207. 54 Anatomical features of Os lunatum Анатомични особености на Os lunatum: значение за статиката и механиката на ставата на китката Д. Камбуров, Г. Маринов*, С. Дянкова* Катедра по ортопедия и травматология и *Катедра по анатомия, хистология и ембриология, Медицински университет-Варна Резюме: Os lunatum не може да устоява на налягането на метакарпалните и дисталните кости на китката към костите на предмишницата, което се счита за една от причините за болеста на Кинбьок. Изследвани са вариациите на анатомичните особености при 12 китки от труп. Резултатите показват, че Os lunatum може да контактува с костите на дисталната редица на китката и на предмишницата по следните начини: а) с Os capitatum и с две отделни ставни повърхности за радиуса и ставния диск (при 33,33 % от случайте) и б) с Os capitatum, Os hamatum и с две отделни ставни повърхности за радиуса и ставния диск (при 66,67 % от случайте). 55 

ANATOMICAL FEATURES OF OS LUNATUM: SIGNIFICANCE IN THE WRIST JOINT STATICS AND MECHANICS

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ANATOMICAL FEATURES OF OS LUNATUM: SIGNIFICANCE IN THE WRIST JOINT STATICS AND MECHANICS

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