The medial coracoclavicular ligament (MCCL), up to now rarely reported in the literature, was studied in a formol-fixed cadaver by means of dissection, morphometry, and light microscopy. This entity represents a true ligament within the coracoclavicular fascia. Although longer and narrower than its lateral counterpart, the medial coracoclavicular ligament follows the same morphological pattern, including the cartilage at the level of the coracoidal attachment. Its clinical significance and implications together with a review of the literature is presente

Fasel, Jean

Lädermann, Alexandre

Stimec, Bojan

Wohlwend, Annelise

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ORTHOPAEDIC SURGERYMedial coracoclavicular ligament revisited: an anatomic studyand review of the literatureBojan V. Stimec • Alexandre La¨dermann •Annelise Wohlwend • Jean H. D. FaselReceived: 23 November 2011 / Published online: 24 April 2012 Springer-Verlag 2012Abstract The medial coracoclavicular ligament (MCCL),up to now rarely reported in the literature, was studied in aformol-fixed cadaver by means of dissection, morphometry,and light microscopy. This entity represents a true ligamentwithin the coracoclavicular fascia. Although longer andnarrower than its lateral counterpart, the medial coracocla-vicular ligament follows the same morphological pattern,including the cartilage at the level of the coracoidal attach-ment. Its clinical significance and implications together witha review of the literature is presented.Keywords Medial coracoclavicular ligament  Anatomy Histology  ShoulderIntroductionThe coracoclavicular ligament (CCL) complex tradition-ally implies two components, the conoid and the trapezoidligaments [8, 15, 17, 21]. Rare references mention besidethem a medial coracoclavicular ligament (MCCL) [6, 14].To our knowledge, data on morphometric and microscopicproperties of this anatomical entity are lacking, in contrastto numerous studies of the lateral CCL [2, 7, 15, 18, 20].This study was undertaken to define the anatomicalcharacteristics of the medial CCL as well as its histologicalproperties, in particular as compared to the lateral CCL.Materials and methodsThe study was conducted on a 92-year-old formol-fixedfemale cadaver, without previous medical history on inju-ries, deformities, or functional disabilities of the pectoralgirdle. The body was bequeathed under the terms of locallegal framework and under the directives of Swiss Acad-emy of Medical Sciences. A dissection of the MCCL wasperformed and its relations to other anatomic structuresnoted. The dimensions (width and length) were determinedwith a Vernier caliper (Etalon, Roch, Switzerland).After morphometry, the ligament was excised and under-went histological workup. It was divided into thirds (medial,middle, and lateral), embedded in paraffin, sectioned in theplane of its longitudinal axis and stained with hematoxylin-eosin, Masson’s trichrome, and aldehyde fuchsin-modifiedGoldner’s trichrome. The conoid ligament (CL) was used forcontrol and underwent the same embedding and staining.Particular attention was drawn to preserve the ligaments in theirnatural position and avoid iatrogenic torque and deformities.ResultsThe routine anatomical dissection of the shoulder andpectoral region revealed bilaterally in the infraclavicularB. V. Stimec  J. H. D. FaselAnatomy Sector, Department of Cellular Physiologyand Metabolism, Faculty of Medicine, University of Geneva,Rue Michel-Servet 1, 1211 Geneva 4, SwitzerlandA. La¨dermann (&)Division of Orthopaedics and Trauma Surgery,Department of Surgery, Geneva University Hospitals,Rue Gabrielle-Perret-Gentil 4, 1211 Geneva 14, Switzerlande-mail: Alexandre.laedermann@hcuge.chA. La¨dermannDivision of Orthopaedics and Trauma Surgery, Latour Hospital,Av. J.-D. Maillard 3, 1217 Meyrin, SwitzerlandA. WohlwendFaculty of Medicine, Histology Core Facility,University of Geneva, Rue Michel-Servet 1,1211 Geneva 4, Switzerland123Arch Orthop Trauma Surg (2012) 132:1071–1075DOI 10.1007/s00402-012-1512-9area a slender ligamentous structure of pearly yellowappearance This ligament stretched from the medial kneeof the coracoid, where the coracoidal undersurface changesdirection from vertical to horizontal, to the anterior lip ofthe impression for costoclavicular ligament (Fig. 1). Itscoracoid insertion was distal to the attachment sites of theconoid and trapezoid ligaments, and medial to the origin ofthe pectoralis minor muscle. According to the origin/insertion sites of this entity, we adopted the denominationmedial coracoclavicular ligament (MCCL) [14]. In thereclined supine position, the ligament was tight; however,on protraction of the shoulder it became relaxed. TheMCCL was completely enclosed within the clavipectoralfascia, ventral and caudal in relation to the subclaviusmuscle. As for vascular syntopy, the MCCL stretched outof the course of the cephalic vein and the thoracoacromialartery. The morphometry of MCCL revealed symmetrici-ty—the length was 91 mm on the right and 86 mm on theleft, and the width (for both sides) 2 mm, expanding into3.5 mm at the level of the coracoid attachment.On low-power light microscopy (Fig. 2), the MCCLdisplayed a dense core of tightly packed collagen bundlesrunning parallel to each other, surrounded by a thin layer ofirregular, often looser, well-vascularized connective tissue.At the lateral—coracoid—attachment site (Fig. 2a) thesurrounding connective tissue was significantly enlarged,with abundant collagen fibers, adipose tissue, blood vesselsand nerves. Although of significantly reduced size, themedial—clavicular—attachment site displayed the sametype of structures. Near this medial attachment site, theMCCL’s collagen fibers start to twist with fibers crossing inmultiple directions (Fig. 2c). Although bone and cartilagewere macroscopically dissected out to allow direct histo-logical processing without any prerequisite demineraliza-tion, some smaller zones of partially calcified cartilagewere still present in the close vicinity of both attachmentsites; some focal, possibly ageing-related microcalcifica-tions were occasionally observed within the connectivetissues.At higher magnification (Fig. 3), hematoxylin-eosinstaining of the MCCL (Fig. 3b) confirmed typical featuresof ligaments, i.e., dense, closely apposed collagen fibersforming aligned bundles of thick diameter, with more orless evenly distributed fibrocytes in between; this micro-scopic organization was closely similar to that of thecontrol CL (Fig. 3a). MCCL’s collagen bundles werespecifically stained in blue (Masson’s trichrome, Fig. 3c)or green (aldehyde fuchsin-modified Goldner’s trichrome(AF), Fig. 3d). This collagen staining was homogenous atthe periphery and at the ligament endings but, surprisingly,the central core of both the MCCL and the CL (not shown)displayed more irregular staining. These modified stainingproperties of collagen could possibly result from some ofthe ageing-related changes. Finally, the AF staining—which allows the concomitant staining of thick collagenbundles (in green) and thin elastic fibers (in violet)—showed similar content and distribution of these fibers inboth MCCL (Fig. 3d) and CL, elastic fibers distribution inthese ligaments being sparse and less abundant than in thesurrounding fascia.Taken together, the microscopic observation of theMCCL confirms its ligamentary nature. The histologicalstructure and overall composition of the MCCL is also veryclose to those of the CL.Fig. 1 Medial coracoclavicular ligament (MCCL—asterisk) in aright shoulder region. View from in front. C clavicle, CP coracoidprocess (horizontal portion), DM deltoid muscle (resected), PMpectoralis minor, SM subclavius muscleFig. 2 Low-power, microscopic reconstruction of the MCCL thirds(a, lateral; b, middle; c, medial) from paraffin sections stained withhematoxylin-eosin. Note abundant surrounding connective tissue atthe lateral attachment site and torque of the MCCL’s collagen fibersstart to twist at the medial attachment site1072 Arch Orthop Trauma Surg (2012) 132:1071–1075123DiscussionThe herewith-described MCCL can be interpreted as acordlike thickening of the clavipectoral fascia [14]. Itsgross appearance and microscopic structure resemble a trueligament. In the latest edition of Gray’s Anatomy, however,the only ligamental entity related to the clavipectoral fasciais the costocoracoid ligament, a dense whitish bandextending between the first rib and the coracoid process [8].The clavipectoral fascia, also called costocoracoid mem-brane or coracoclavicular fascia, is assumed to protect theaxillary neurovascular bundle, stretched between the pec-toralis minor and subclavius muscles. In the concept ofsupporting soft tissue planes of the glenohumeral joint, theclavipectoral fascia occupies the second layer, togetherwith the conjoined biceps/coracobrachial tendon, coracoa-cromial ligament, posterior scapular fascia, and superficialbursae tissue [3]. The clavipectoral fascia, being in conti-nuity with the suspensory fascia of the axilla below thepectoralis minor, provides dynamic anchoring of postero-medial arm subcutaneous tissue. Age, weight fluctuations,and loosening of the complex fascial system may lead toarm skin laxity [10]. It thus stands to reason that MCCLcontributes to the supportive action of clavipectoral fascia.It has been noted that the variability of soft tissue aroundthe shoulder joints mainly concerns the coracohumeralligament and capsular defects [3, 16]. According to Harriset al. [7], the variations of the CCL complex include con-fluence of conoid ligament and superior transverse scapularligament, and additional superolateral fascicles, but theMCCL has not been mentioned. If analogy is made withthe congenitally short costocoracoid ligament [1], we canassume that the MCCL could also imply an autosomaldominant mode of inheritance with variable expression, butwith the very limited number of reports available onMCCL up to now, it is difficult to predict its exact inci-dence in the general population.The biomechanical role of MCCL is also uncertain. Asfor the lateral counterparts, they are considered as con-straints: for superior and anterior translation of the clavicle(conoid ligament), and for the axial compressive loading ofthe acromioclavicular joint (trapezoid ligament) [2, 18, 20].Taking into account its origin, anatomical position andinsertion, one can argue that the MCCL restrains theretraction of the scapula in the horizontal plane. However,its true significance in stabilization of shoulder girdle isdebatable in view of its width, particularly if compared tolateral CCL. Several studies have addressed the dimensionsof conoid and trapezoid with different methodologicalapproaches. A detailed study presented the following meanlength/width of 1.61/1.58 and 1.22/0.74 cm for the trape-zoid and conoid ligaments, respectively [17]. With oneexception, the values did not significantly differ betweenmen and women. The trapezoid ligament expanded to2.15 cm at the clavicular level, a similar feature that wefound at the level of MCCL attachment to coracoid pro-cess. The CCL geometry in another study gave somewhatsmaller dimensions and, interestingly, no significant dif-ferences could be demonstrated between conoid and trap-ezoid ligament [4]. On the other hand, Ockert et al. foundthe ligaments to be larger than in the previous two studies,precisely distinguishing the 3D components—length,width, and depth [15].Despite the smaller diameter, the tensile properties ofthe MCCL should be regarded in the light of its fiberstwisting in its medial third, what should result in a sig-nificant increase in the ultimate tensile strength and resil-ience to strain.Therefore, histological processing of this ligament hasbeen performed to compare it to the conoid portion of thesame-sided lateral CCL. This comparative morphologicalanalysis confirmed the ligamentary nature and structure ofthe MCCL. It is peculiar that the microscopic anatomy ofthe coracoclavicular ligament has not attracted muchattention. In the report of Satler et al. [17] the histologicalsections included the plenitude of the acromioclavicularjoint with the surrounding ligaments, in order to studybetter the anatomical relationships of the structures inquestion. Based on tensile testing and not on histology, nostatistically significant differences could be demonstratedFig. 3 Histological characteristics of the conoid ligament (a) ascompared to the medial coracoclavicular ligament (b, c, d). a,b Hematoxylin-eosin, c Masson’s trichrome (collagen: blue),d aldehyde fuchsin-modified Goldner’s trichrome (collagen: green,elastic fibers: violet). The MCCL exhibits microscopic organization,content, and distribution of fibers typical for ligamentsArch Orthop Trauma Surg (2012) 132:1071–1075 1073123for all structural properties between the conoid and trape-zoid ligament [4]. A comprehensive immunochemistrystudy, carried out on CCL complex, revealed fibrocartilageat the level of both clavicular and coracoid entheses, con-sidering it a consequence of adaptation to compression andshear forces [15]. A similar finding was seen in our case ofMCCL. Being of relatively small quantity and surroundedby abundant fat tissue with blood vessels, it could hardlypose as a weak point in cases of injury.The presence of calcifications in our case of MCCL wasalso intriguing, despite its modest extent. The interpretationof such calcifications on plain X-rays was attributed todisplaced ossification centers, clavicular cleft, or ossifica-tion in the trapezoid ligament, due to repair or damage aftertrauma [19]. The ossifications of the costocoracoid liga-ment may be seen in cleidocranial dysostosis or, rarely,they are spontaneous [1]. In the absence of congenitaldefects or history on shoulder trauma, the calcifications inthe present case of MCCL can be related to the person’sadvanced age.The medial coracoclavicular ligament could have impacton placing pacemaker leads and central venous cathetersthrough the subclavian vein. Entrapment by intervening softtissue (subclavius muscle, costocoracoid ligament) canimpose stress on leads and catheters, particularly duringmovements of ipsilateral arm [12]. Therefore, one wouldappreciate knowledge of the presence and position ofMCCL in order to avoid such a complication.Being in the junctional region between the hypobran-chial and the pectoral regions of the body trunk, the MCCLcould contribute to the thoracic outlet syndrome, analogousto the congenital anatomical anomaly of subclavius posti-cus muscle [13]. Indeed, one of the variations of super-numerary muscles (scapuloclavicular) fits well to theattachment sites and the position of MCCL, but our his-tology revealed no muscle fibers in this entity. However,the MCCL could be formed by metaplasia of the scapu-loclavicular muscle as a response to stress during devel-opment, as it has already been described in other bodystructures [11].Knowledge of MCCL is also relevant for several oper-ations. The subcoracoid transfer of sutures or graft duringcoracoclavicular cerclage for acromioclavicular jointreconstruction [9] could be more challenging in presence ofMCCL. Soft tissue insertions on the coracoid processallows surgeons to correlate the location of the coracoidosteotomy during Latarjet procedure [5]. Confusion of theMCCL with posterior band of the pectoralis minor inser-tion could lead to a too posterior coracoid osteotomy, lat-eral CCL desinsertion and possibly acromioclavicularinstability. Moreover, medial soft tissue release for cora-coid transfer during Latarjet procedure could be moretedious.This study is limited by inherent limitation of a single(although bilateral) case in an older subject. However, it isthe first one, to our knowledge, that presents detailedmacro- and micromorphology of the MCCL.We hope that this case presentation will ignite surgeons’and anatomist’s awareness and interest in searching for thisvery rare form of connective tissue variation, enablingdetermination of its incidence rate and comparison of dif-ferent individuals.Conflict of interest None.References1. Bamforth JS, Bell MH, Hall JG et al (1989) Congenital shortnessof the costocoracoid ligament. Am J Med Genet 33:444–446. doi:10.1002/ajmg.13203304042. Boehm TD, Kirschner S, Fischer A et al (2003) The relation ofthe coracoclavicular ligament insertion to the acromioclavicularjoint: a cadaver study of relevance to lateral clavicle resection.Acta Orthop Scand 74:718–721 (no DOI found)3. 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Medial coracoclavicular ligament revisited: an anatomic study and review of the literature

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Medial coracoclavicular ligament revisited: an anatomic study and review of the literature

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