Anatomical and functional segments of the deltoid muscle

Transcription

1 Journl of Antomy J. Ant. (2011) 218, pp doi: /j x Antomicl nd functionl segments of the deltoid Yoshims Skom, 1,2 Hirotk Sno, 1 Nouhis Shinozki, 1 Yoshiki Itoigw, 1 Nouyuki Ymmoto, 1 Toshifumi Ozki 2 nd Eiji Itoi 1 1 Deprtment of Orthopedic Surgery, Tohoku University School of Medicine, Sendi, Jpn 2 Science of Functionl Recovery nd Reconstruction, Deprtment of Orthopedic Surgery, Okym University Grdute School of Medicine, Dentistry nd Phrmceuticl Sciences, Okym, Jpn Astrct Previous studies showed tht the insertion of the intrmusculr tendons of the deltoid formed three discrete lines. The purpose of the present study ws to estlish new dividing method of the deltoid into vrious ntomicl segments sed on the distriution of the intrmusculr tendons with their insertions (ntomicl study). We further hoped to clrify the reltionship etween the ntomicl segments nd their ctivity pttern ssessed y positron emission tomogrphy with [ 18 F]-2-fluoro-deoxyglucose (FDG PET; PET study). Sixty cdveric shoulders were investigted in the ntomicl study. Three tendinous insertions of the deltoid to the humerus were identified. Then, the intrmusculr tendons were trced from their humerl insertions to the proximl musculr origins. The extent of ech ntomicl segment of the including its origin nd insertion ws determined through creful dissection. Six helthy volunteers were exmined using FDG PET for the PET study. PET imges were otined fter exercise of elevtion in the scpulr plne. On the PET imges, mrgins of ech ntomicl segment of the deltoid were determined using mgnetic resonnce imges. Then, the stndrdized uptke vlue in ech segment ws clculted to quntify its ctivity. The ntomicl study demonstrted tht the deltoid ws divided into seven segments sed on the distriution of its intrmusculr tendons. The PET study reveled tht the intke of FDG ws not uniform in the deltoid. The re with high FDG intke corresponded well to the individul musculr segments seprted y the intrmusculr tendons. We conclude tht the deltoid hs seven ntomicl segments, which seem to represent the functionl units of this. Key words ntomy; deltoid; function; intrmusculr tendon; positron emission tomogrphy. Introduction The deltoid hs een clssiclly divided into three ntomicl portions: the nterior; the middle; nd the posterior portions. The nterior deltoid tkes its origin from the lterl one-third of the clvicle s well s the nterior cromion; the middle deltoid origintes from the lterl mrgin of the cromion; nd the posterior deltoid from the scpulr spine (Willims & Wrwick, 1980). It hs een elieved tht the ctivtion pttern of this during shoulder motion is different mong these three portions (Reinold Correspondence Hirotk Sno, Deprtment of Orthopedic Surgery, Tohoku University School of Medicine, 1-1 Seiryo-mchi, Ao-ku, Sendi, Miygi , Jpn. T: ; F: ; E: snohirotk@med.tohoku.c.jp Accepted for puliction 28 Octoer 2010 Article pulished online 30 Novemer 2010 et l. 2007). Even in the sme ntomicl portion, its function my vry s the direction of fiers chnges grdully with chnging the sites of their origins nd insertions. It hs een reported tht the intrmusculr tendons ply importnt roles for the force trnsmission to one (Lieer & Fridén, 2001; Huijing, 2003; Finni, 2006). In the deltoid, the insertion of the intrmusculr tendons forms three discrete lines (Klepps et l. 2004). Klepps et l. lso descried tht the clssicl three prts of the deltoid sed on its origin did not correspond to the three insertions t the humerl shft. More recently, Leijnse et l. (2008) proposed generic model of deltoid consisting of multiple segments through their detiled ntomicl oservtions. All these reports suggest tht the deltoid hs more complex ntomicl rchitecture thn hs een elieved. Thus, the distriution of these intrmusculr tendons should e tken into considertion when we ssess the function of this. Recent studies reveled tht the function of skeletl s could e evluted successfully using positron emission Journl of Antomy ª 2010 Antomicl Society of Gret Britin nd Irelnd

2 186 Antomicl nd functionl segments of deltoid, Y. Skom et l. tomogrphy with [ 18 F]-2-fluoro-deoxyglucose (FDG PET; Fujimoto et l. 1996; Ohnum et l. 2006; Tshiro et l. 1999). FDG PET is nucler medicine tool for non-invsive quntifiction of oth regionl lood flow nd tissue glucose metolism in vivo. There re two mjor dvntges to pplying FDG PET on skeletl s. First, the ctivity of the whole cn e quntified non-invsively. Second, FDG PET cn visulize the working pttern of ech smll segment in lrge during ny type of exercise y synchronizing with computed tomogrphy or mgnetic resonnce imging (MRI). These dvntges enle us to ssess the function of ech segment in lrge, such s the deltoid. Bsed on these fcts, the im of the present study ws to estlish new dividing method of the deltoid sed on the distriution of the intrmusculr tendons s well s their insertions. We further hoped to clrify the reltionship etween these ntomicl segments nd their ctivity ptterns ssessed y FDG PET. Mterils nd methods Antomicl study Sixty shoulder girdles were otined from 30 emlmed cdvers. There were 15 mles nd 15 femles, with n verge ge of 82 yers (rnge, yers). No specimens hd prior history of shoulder surgery. After removing skin, we first investigted the surfce ntomy of the deltoid nd oserved their fiers superficilly (Fig. 1). Then, the origin s well s insertion of this ws crefully dissected to clrify their detiled ntomy. As Rispoli et l. (2009) reported, the tendinous insertion of the deltoid consists of three distinct lines, which form n M-shpe (Fig. 2). These tendinous insertions were nmed s nterior, middle nd posterior insertions, respectively. At this level, the elly of the deltoid ws first divided into three prts. Then, the intrmusculr end tendons were identified, which were trced proximlly to their origins. The fiers were divided into segments y their ttching intrmusculr tendons. At the origin of the fiers, the ntomicl lndmrks tht indicted the proximl ttchment of ech segment were identified. The ony fcets where ech segment originted were determined nd their width ws mesured y digitl cliper. Finlly, the extent of ech segment of the deltoid ws compred with tht of the conventionl three portions. PET study Six helthy volunteers without ny histories of shoulder pin or trum were exmined using FDG PET. There were four mles nd two femles, with n verge ge of 74 yers (rnge; yers). These sujects underwent FDG PET with the protocol, Acromion Clvicle Proximl Deltoid Pectorlis mjor IMTs Humerl shft Trpezius Biceps Clvicle Acromion Humerl shft Distl Proximl Insertions Scpul Deltoid Humerl shft Triceps Humerl shft Fig. 1 Surfce ntomy of the deltoid. () The nterolterl view of the deltoid. The fiers run in the nteroinferior direction (red rrows), which converge the nterior side of the deltoid tuercul. () The posterior view of the deltoid. Distl Fig. 2 Antomy of the insertion of the deltoid into the humerl shft. () Three intrmusculr tendons insert individully into the humerl shft (IMTs, intrmusculr tendons). () The insertions of the intrmusculr tendons form three discrete lines (TMj, teres mjor ). Journl of Antomy ª 2010 Antomicl Society of Gret Britin nd Irelnd

3 Antomicl nd functionl segments of deltoid, Y. Skom et l. 187 which we previously estlished (Omi et l. 2010). All sujects refrined from eting nd drinking for t lest 3 h efore the exmintion. The FDG ws dissolved in pproximtely 2 ml sline, which ws then injected intrvenously vi the cuitl vein. The men dose nd stndrd devition of injected FDG were 86.5 nd 8.0 MBq, respectively. Exercise of scption (elevtion in the scpulr plne) for 10 min ws performed efore nd fter injection of FDG. The exercise consisted of 200 repetitions of scption etween 0 nd 90 of elevtion with 250-g weights round the wrists. PET imges were collected 40 min fter the injection with whole-ody positron cmer (SET- 2400W; Shimzu, Kyoto, Jpn). To quntify the ctivities in ech segment, it ws necessry to determine its exct loction on the PET imges. For this purpose, n MRI scn ws performed for imge fusion (Sign Horizon LX 1.5T Ver.9.1; GE Helthcre, Milwukee, WI, USA). The mesurement conditions were s follows: repetition time echo time ws ms; numer of excittions ws 1; the field of view ws 46 cm; numer of mtrix ws ; slice thickness ws 3 mm; nd slice gp ws 1.5 mm. A T2-weighted trnsverse MR imge with ft suppression ws used to determine the outer mrgin of ech segment in the deltoid on the PET imge t the sme level. The volumes of interest (VOI) in ech portion of the defined on MR imges were superimposed onto the registered PET imges using softwre, Dr View LINUX (AJS, Tokyo, Jpn) for evlution of rdioctivity in ech. After fusion of PET nd MR imges, the stndrdized uptke vlues (SUVs) in ech segment of the deltoid were clculted to quntify their ctivity with the following eqution: SUV ¼ men VOI ctivity (g/mbq)= FDGinentireodytequldistriutionðMBq=gÞ Bsed on the definition of SUV, this eqution cn e modified s follows: injected dose (MBq) SUV ¼ men VOI ctivity ðg=mbqþ= ody weight (g) men VOI count (cps/g) ody weight (g) ¼ injected dose (MBq) clirtion fctor (cps/mbq) posterior end tendons). The direction of these two tendons ws superoposterior ginst the humerl shft. At the level of the proximl deltoid, the nterior nd posterior end tendons rnched into three intrmusculr tendons, respectively (Fig. 3). A totl of seven intrmusculr tendons were identified t this level (nterior tendon: 3; middle tendon: 1; posterior tendon: 3). These intrmusculr tendons were nmed, nd tendons (nterior intrmusculr tendons); M1 tendon (middle intrmusculr tendon); nd P1, P2 nd P3 tendons (posterior intrmusculr tendons), respectively. Consequently, the deltoid ws divided into seven segments, including,,, M1, P1, P2 nd P3 segments sed on the ttchment to these seven intrmusculr tendons (Fig. 3c). Proximl origins nd their lndmrks The nterior prt of the deltoid widely spred over the clvicle, nd the nterior surfce nd the nterior-third of the lterl cromion. The middle prt ws reltively nrrow,whichttchedtothemid-thirdofthelterlspect of the cromion. The posterior prt ttched to the posterior-third of the lterl cromion s well s the scpulr spine. There were severl ntomicl lndmrks for dividing ech segment t the proximl origin of the deltoid. The order etween nd segments locted pproximtely 5 mm medil from the cromioclviculr joint in ll specimens (Fig. 4). The ony lndmrk etween nd segments ws the nterolterl corner of the cromion. From the lterl spect of the cromion, three segments (, M1 nd P1) originted (Fig. 4). There were two smll ony tuercul on the lterl order of the cromion, which seprted these segments (, M1 nd P1) (Fig. 4). Sttisticl nlysis ws performed using STATMATE III sttisticl softwre (version 3.16; Atms, Tokyo, Jpn). Sttisticl significnce of difference in ctivity level (SUV) etween six segments ws exmined for SUVs using one-wy ANOVA. A P-vlue < 0.05 ws considered s sttisticlly significnt. Results Antomicl study Segments of the deltoid The presence of three insertions (nterior, middle nd posterior) ws confirmed in ll shoulders. Among them, thick intrmusculr tendon (nterior end tendon), which ttched to the nterior insertion, ws identified (Fig. 2A). The direction of this tendon ws lmost prllel to the humerl shft. Intrmusculr tendons lso inserted to the middle nd posterior insertions, respectively (middle nd Fig. 3 () Directions of the intrmusculr tendons. Arrows indicte the direction of ech intrmusculr tendon (,,, M1, P1, P2 nd P3, intrmusculr tendons; c, cromion; cl, clvicle; PM, pectorlis mjor ). () Seven segments t the proximl prt of the deltoid on the trnsverse plne. Journl of Antomy ª 2010 Antomicl Society of Gret Britin nd Irelnd

4 188 Antomicl nd functionl segments of deltoid, Y. Skom et l. Anterior cl Anterior tp P3 cl Posterior c P2 These two ony tuercul were seen in 56 specimens (93.3%). The lterl order of the cromion ws divided into three fcets y these ony tuercul, which were nmed s the nterior, middle nd posterior fcets (Fig. 3)., M1 nd P1 segments originted from the nterior, middle nd posterior fcets, respectively. The width of ech fcet ws 19.5 ± 4.1 mm (men ± stndrd devition), 14.2 ± 4.0 mm nd 17.9 ± 5.0 mm, respectively. P1 nd P2 segments were divided y the posterior ngle of the cromion, where the posterior tendon originted. On the other hnd, no ony lndmrk ws identified etween P2 nd P3 segments t their origin. The reltionship etween the clssicl three portions nd the segments The clssicl clviculr portion corresponded well to the segment in the new dividing method (Fig. 4). The cromil portion consisted of,, M1 nd P1 segments, nd the spinl portion ws comptile to P2 nd P3 segments. In other words, clssicl clviculr, cromil nd spinl portions consisted of one, four nd two segments, respectively. Antomicl vritions In the present series, some ntomicl vritions were oserved. In four shoulders (6.7%), the M1 segment hd two distinct intrmusculr tendons. The middle insertion formed single line or doule lines in these shoulders. As result, these shoulders hd four cromil fcets nd five proximl tendons t the lterl spect of the cromion. M1 Posterior cl c Anterior c Posterior c Fig. 4 The lndmrks t the origin of the deltoid. () Origin of ech segment. The order etween nd loctes pproximtely 5 mm medil from the cromioclviculr joint. There re no prticulr structures etween P2 nd P3 t the proximl prt of the deltoid (c, cromion; cl, clvicle; tp, trpezius). () There re two ony tuercul t the lterl order of the cromion. These ony tuercul seprte the lterl order of the cromion into three fcets:, nterior fcet;, middle fcet; c, posterior fcet. (c) Four intrmusculr tendons originte from the nterior ngle, two ony tuercul nd posterior ngle of the cromion, respectively. P1 c PET study Becuse there ws no prticulr lndmrk etween P2 nd P3 segments on MR imges, we could not differentite these two segments on PET imges (Fig. 5). Thus, PET nlysis ws done mong the six segments, for exmple,,, M1, P1 nd P2 + P3. The PET imges reveled tht the intke of FDG ws not uniform in the deltoid. The re with high intke represented dotted pttern in the upper level of the deltoid, which corresponded well to the ntomiclly defined musculr segments (Fig. 6). At the middle nd lower level of the deltoid, the re with high intke ws not seprted. The SUV of ech segment ws shown in Fig. 6. nd M1 showed reltively higher vlues of SUV thn those of other segments, including,, P1 nd P2 + P3 (Fig. 6). Sttisticlly, the SUVs in oth nd M1 segments were significntly higher thn tht in P2 + P3 (P <0.05). Discussion P2+P3 In the clinicl prctice, the clssicl distinction of the deltoid into three portions sed on the origin of these portions is widely used. Although this method P2+P3 M1 P1 M1 P1 Fig. 5 Dividing method of the deltoid on MR imges. The intrmusculr tendons re clerly depicted in T2-weighted trnsverse MR imge with ft suppression. The deltoid is divided sed on the distriution of intrmusculr tendons. The stright lines show the order etween ech segment. The proximl intrmusculr tendons locte t the orders of ech segment. For the distl insertions,, M1 nd P1 intrmusculr tendons exist t their center. On the other hnd,, nd P3 hve their distl intrmusculr tendons t the mrgin of the segments. () At proximl deltoid level, () At distl deltoid level. Journl of Antomy ª 2010 Antomicl Society of Gret Britin nd Irelnd

5 Antomicl nd functionl segments of deltoid, Y. Skom et l. 189 Proximl level Middle level Distl level S UV * P < 0.05 seemed to e very convenient to understnd the ntomy of this, one should keep in mind tht these portions my not reflect the function of this. In 1911, Fick descried in his textook tht the deltoid hd seven functionl segments (Fick, 1911). Since then, severl studies hve een crried out concerning the intrmusculr rchitectures of the deltoid. Brown nd Wickhm divided the deltoid into seven segments sed on its superficil ntomy s well s the ctivtion levels ssessed y electromyogrm (EMG; Wickhm & Brown, 1998; Brown & Wickhm, 2006; Brown et l. 2007). Unfortuntely, however, it seemed tht neither of them took the morphology of the intrmusculr tendons into considertion. Recently, Leijnse suggested the dissection model of the deltoid should e sed on the morphology of the deltoid origin nd end tendons (Leijnse et l. 2008). In the present study, we confirmed tht the deltoid could e divided into seven segments with their intrmusculr tendons. It ws lso interesting to note tht the clssicl cromil portion hd four segments (,, M1 nd P1), which ttched individully to the different ony fcets. The presence of ony tuercules on the * * M1 P1 P2+P3 Fig. 6 () Axil MRI nd PET imges of the proximl, middle nd distl levels of the deltoid. At proximl level, the segments divided on MRI well correspond to the dotted FDG intke pttern in the PET imges. () SUVs of ech segment. The stndrdized uptke vlues (SUVs) of nd M1 re reltively higher thn tht of other segments. Especilly, oth nd M1 ctivities were significntly greter thn tht of P2 + P3 (P < 0.05). cromion could e useful lndmrks for surgeons to identify ech segment. To ssess the ctivity, EMG hs een widely used s stndrd technique (Kronerg et l. 1990; McMhon et l. 1995; Reddy et l. 2000; Kelly et l. 2005; Reinold et l. 2007; Ysojim et l. 2008; Cordsco et l. 2009). However, there ws mjor disdvntge to pplying this method to the deltoid. A fine needle electrode used for EMG could only reflect the ctivities of its smll portion. Bsed on these fcts, we ssessed the function of the deltoid using FDG PET in the present study. In the PET imges, the FDG intke represented dotted pttern consistent with the seprted segments t the upper level of the deltoid. These results indicted tht the deltoid worked s segments during the rm elevtion, which corresponded well to the ntomiclly defined seven musculr segments with the intrmusculr tendons. Therefore, we ssumed tht these ntomicl seven segments reflect the functionl units of the deltoid. Becuse the SUV vlues fter exercise in ll segments were greter thn the SUV vlues t rest, we ssumed tht they worked synergisticlly during the rm elevtion in the scpulr plne. The SUV vlue of deltoid t rest ws pproximtely 0.7 in our previous study (Omi et l. 2010). On the other hnd, nd M1 represented higher SUVs thn other segments. Moreover, the difference in SUV etween these two segments nd P2 + P3 ws sttisticlly significnt. These results might suggest tht the mid-prt of the cromil portion including nd M1 plyed gret role in elevting the rm in the scpulr plne. There were severl limittions in the present study. First, we did not investigte the reltionship etween the nerve endings nd the segments in the present study. Second, we filed to differentite P2 nd P3 segments on MR imges ecuse there were no prticulr structures etween these segments. Consequently, the ctivities in these two segments could not e precisely differentited. Third, only the scption exercise ws performed in the present study. Future studies using FDG PET with exercise in vrious directions would e necessry to clrify the detiled function of the deltoid. Conclusion The deltoid could e divided into seven segments seprted y their intrmusculr tendons. The ctive musculr regions in the deltoid were seprted on the PET imges y their intrmusculr tendons. Bsed on these results, we ssumed tht the ntomicl seven segments corresponded well to the functionl units of the deltoid. Acknowledgements The uthors would like to thnk Professor Mri Dezw, MD, PhD, nd Dr Jin-lin Zuo, MD, for their support. Journl of Antomy ª 2010 Antomicl Society of Gret Britin nd Irelnd

6 190 Antomicl nd functionl segments of deltoid, Y. Skom et l. Author contriutions Yoshims Skom ws principl investigtor who investigted ll of the cdver specimens with Yoshiki Itoigw. Nouhis Shinozki exmined the PET nd MRI. Nouyuki Ymmoto nd Hirotk Sno (corresponding uthor) nlyzed the dt of PET experiments s well s the ntomicl mesurements. Eiji Itoi nd Toshifumi Ozki were senior investigtors, nd supervised this project. References Brown JM, Wickhm J (2006) Neuromotor coordintion of multisegmentl during chnge in movement direction. J Musculoskelet Res 10, Brown JM, Wickhm J, McAndrew DJ, et l. (2007) Muscles within s: coordintion of 19 segments within three shoulder s during isometric motor tsks. J Electromyogr Kinesiol 17, Cordsco FA, Chen NC, Bckus SI, et l. (2010) Sucromil injection improves deltoid firing in sujects with lrge rottor cuff ters. HSS J 6, Fick R (1911) Hnduch der Antomie und Meknik der Gelenke. Jen: Gustv Fischer. Finni T (2006) Structurl nd functionl fetures of humn -tendon unit. Scnd J Med Sci Sports 16, Fujimoto T, Itoh M, Kumno H, et l. (1996) Whole-ody metolic mp with positron emission tomogrphy of mn fter running. Lncet 348, 266. Huijing PA (2003) Musculr force trnsmission necessittes multilevel integrtive pproch to the nlysis of function of skeletl. Exerc Sport Sci Rev 31, Kelly BT, Willims RJ, Cordsco FA, et l. (2005) Differentil ptterns of ctivtion in ptients with symptomtic nd symptomtic rottor cuff ters. J Shoulder Elow Surg 14, Klepps S, Auerch J, Clhon O, et l. (2004) A cdveric study on the ntomy of the deltoid insertion nd its reltionship to the deltopectorl pproch to the proximl humerus. J Shoulder Elow Surg 13, Kronerg M, Nemeth G, Brostrom LA (1990) Muscle ctivity nd coordintion in the norml shoulder. An electromyogrphic study. Clin Orthop Relt Res 257, Leijnse JN, Hn SH, Kwon YH (2008) Morphology of deltoid origin nd end tendons generic model. J Ant 213, Lieer RL, FridénJ(2001) Clinicl significnce of skeletl rchitecture. Clin Orthop Relt Res 383, McMhon PJ, Deski RE, Thompson WO, et l. (1995) Shoulder s forces nd tendon excursions during glenohumerl duction in the scpulr plne. J Shoulder Elow Surg 4, Ohnum M, Sugit T, Kokuun S, et l. (2006) Muscle ctivity during dsh shown y 18F-fluorodeoxyglucose positron emission tomogrphy. J Orthop Sci 11, Omi R, Sno H, Ohnum M, et l. (2010) Function of the shoulder s during shoulder elevtion: n ssessment using positron emission tomogrphy. J Ant 216, Reddy AS, Mohr KJ, Pink MM, et l. (2000) Electromyogrphic nlysis of the deltoid nd rottor cuff s in persons with sucromil impingement. J Shoulder Elow Surg 9, Reinold MM, Mcrin LC, Wilk KE, et l. (2007) Electromyogrphic nlysis of the suprspintus nd deltoid s during 3 common rehilittion exercises.j Athl Trin 42, Rispoli DM, Athwl GS, Sperling JW, et l. (2009) The ntomy of the deltoid insertion. J Shoulder Elow Surg 18, Tshiro M, Fujimoto T, Itoh M, et l. (1999) 18 F-FDG PET imging of ctivity in runners. J Nucl Med 40, Wickhm J, Brown JM (1998) Muscles within s: the neuromotor control of intr-musculr segments. Eur J Appl Physiol 78, Willims P, Wrwick L (1980) Gry s Antomy. Edinurgh: Churchill Livingstone. Ysojim T, Kizuk T, Noguchi H, et l. (2008) Differences in EMG ctivity in scpulr plne duction under vrile rm positions nd loding conditions. Med Sci Sports Exerc 40, Journl of Antomy ª 2010 Antomicl Society of Gret Britin nd Irelnd