Abstract: Anatomical morphometric studies of the coracoid process and coraco-glenoid space were carried out on 204 dry scapulae. No statistically significant correlations were found between length, or thickness of the coracoid process, prominence of the coracoid tip, coracoid slope, coraco-glenoid distance, or position of the coracoid tip with respect to the uppermost point of the glenoid. These anatomical characteristics were independent. of the dimensions of the scapulae. Three configurations of the coraco-glenoid space were identified. Type I configuration was found in 45% of scapulae and Type II and Type III, in 34% and 21% of specimens, respectively. The lowest value of the coraco-glenoid distance were seen in Type I scapulae. Morphometric characteristics which might predispose to subcoracoid impingement were found in 4% of Type I scapulae. A total of 27 scapulae, nine with each type of configuration were submitted to CT scanning. Scapulae with a Type I configuration were found to have low values for the coraco-glenoid angle and coracoid overlap, which are known to be associated with a short coraco-humeral distance. Subjects with a Type I configuration, and severe narrowing of the coraco-glenoid space, appear to be predisposed to coraco-humeral impingement. These morphometric characteristics may be easily evaluated on CT scans

CINOTTI, Gianluca

GUMINA, STEFANO

ORSINA L

POSTACCHINI, Franco

English

PubMed

Archivio della ricerca- Università di Roma La Sapienza

Abstract Anatomical morphometric studies of the cora-coid process and coraco-glenoid space were carried outon 204 dry scapulae. No statistically significant correla-tions were found between length, or thickness of the co-racoid process, prominence of the coracoid tip, coracoidslope, coraco-glenoid distance, or position of the cora-coid tip with respect to the uppermost point of the gle-noid. These anatomical characteristics were independentof the dimensions of the scapulae. Three configurationsof the coraco-glenoid space were identified. Type I con-figuration was found in 45% of scapulae and Type II andType III, in 34% and 21% of specimens, respectively.The lowest value of the coraco-glenoid distance wereseen in Type I scapulae. Morphometric characteristicswhich might predispose to subcoracoid impingementwere found in 4% of Type I scapulae. A total of 27scapulae, nine with each type of configuration were sub-mitted to CT scanning. Scapulae with a Type I configu-ration were found to have low values for the coraco-gle-noid angle and coracoid overlap, which are known to beassociated with a short coraco-humeral distance. Sub-jects with a Type I configuration, and severe narrowingof the coraco-glenoid space, appear to be predisposed tocoraco-humeral impingement. These morphometric char-acteristics may be easily evaluated on CT scans.Résumé Des études d’anatomie morphométrique duprocessus coraco ont été menées sur 204 omoplates sè-ches. Aucune corrélation statistiquement significativen’a été trouvée entre la longueur, ou l’épaisseur, du pro-cessus coraco, la proéminence du point coraco, la pentecoraco, la distance coracogléno et la position du pointcoraco par rapport au sommet de la gléno. Ces caracté-ristiques sont indépendantes des dimensions de l’omo-plate. Trois configurations de l’espace coracogléno ontété identifiées: Type I, Type II et Type III. Les caractéris-tiques morphometriques qui peuvent prédisposer à unefriction subcoraco ont été trouvées sur 4% des omoplatesavec une configuration de Type I. Un total de 27 omo-plates, 9 de chaque type de configuration, a été soumis àune tomographie osseuse. Les omoplates du premier typede configuration présentent un angle coracogleno de fai-ble valeur, ce qui est connu pour être associé avec unedistance coracohumerale faible. Les sujets présentantune configuration de premier type et un sévère rétrécis-sement de l’espace coracogleno, apparaissent être prédis-posés à une friction coracohumérale. Ces caractéristiquesmorphométriques peuvent aisément être évaluées partomographie osseuse.IntroductionGerber et al. [4] described the aetiology of sub-coracoidimpingement. Few patients had idiopathic impingement,which appeared to be caused by a long coracoid processprojecting more laterally than normal. Coracoid im-pingement was reported in seven patients, all of whomunderwent surgical excision of the coracoid tip [2]. Inspite of these reports, many shoulder surgeons, includingCodman [1], have expressed doubt about the existence ofthis idiopathic syndrome.We performed an anatomical morphometric study ona large number of coracoid processes in dry scapulae anda CT morphometric study on some of the specimens. Theaim was to determine if anatomical variations of the co-racoid process might predispose to the idiopathic im-pingement syndrome.S. Gumina (✉) · F. Postacchini · G. CinottiDepartment of Orthopaedics, University “La Sapienza”,I-00185 Rome, ItalyL. OrsinaDepartment of Mathematics, University “La Sapienza”,I-00185 Rome, ItalyMailing address:S. Gumina, Via Tacito 74 B/10, I-00193 Rome, Italy,e-mail: orsina@mat.uniroma1.it,Tel.: +39-6-3207073, Fax: +39-6-44701007International Orthopaedics (SICOT) (1999) 23:198–201 © Springer-Verlag 1999O R I G I N A L  PA P E RS. Gumina · F. Postacchini · L. Orsina · G. CinottiThe morphometry of the coracoid process – its aetiologic rolein subcoracoid impingement syndromeAccepted: 6 May 1999199Material and method204 scapulae (76 right and 128 left) were entered into the study;most (82%) were from cadavers with a presumed age between 30and 60 years. Sixty-eight pairs of scapulae were from the sameskeletons. None of the scapulae showed degenerative changes ofthe coracoid process.The measurements shown in Figs. 1a,b were performed. Statis-tical analysis was performed to investigate the relationship be-tween variables; the R2-coefficient was also calculated.A total of 27 randomly selected scapulae among those whoseglenoid retroversion ranged from 11° to 14°, nine for each of thethree types of configuration of coraco-glenoid space, were studiedby computerized tomography. Since for every 1° of change in gle-noid retroversion there is a change of 0.37 mm in coraco-humeraldistance [5], a 3° range yields minimal variations in the measure-ments. Each scapula was placed in the same position as it is in vi-vo at CT examination of the shoulder; ie, as if the humerus were atthe side and the forearm under the lumbar spine. The coraco-gle-noid angle and the coracoid overlap were measured according tothe method of Gerber et al. [5]. The coraco-glenoid angle isformed by: the line originating from the anterior glenoid rim andrunning tangentially to the most prominent part of the tip of thecoracoid; and the line passing through the anterior and posteriorglenoid rims. The coracoid overlap represents the distance bywhich the coracoid process overlaps the plane of the glenoid fossa.ResultsThree groups of scapulae were arbitrarily identified,based on the height to width ratio: Group I (ratio1.18–1.34), Group II (ratio 1.35–1.50) and Group III (ra-tio 1.51–1.75). Group I included 52% of scapulae, GroupII, 44% and Group III, 4%.The mean, extreme values and standard deviations ofL, T, cp, cs and d are reported in Table 1. The differentpositions of the coracoid tip with respect to the uppermostpoint of the glenoid fossa are shown in Fig. 2a, b.Three types of configurations of the coraco-glenoidspace were identified. In Type I this space had a “roundbracket” configuration (Fig. 3a), whereas in Type II andIII it had the shape of a “square bracket” (Fig. 3b) and a“fish hook” (Fig. 3c), respectively. Type I configurationwas observed in 45% of scapulae, and Type II and IIIconfiguration in 34% and 21% of specimens, respective-ly. The three types of configuration were equally distrib-uted in the scapulae of Group I, II and III. The shortestcoraco-glenoid distance was found in Type I configura-tion (mean value 15.7 mm) compared with Type II andType III (whose mean values are 16.9 mm and 16.0 mmrespectively). Only 4% of the specimens with Type I con-figuration were found to have the following characteris-tics, which affect the width of the coraco-humeral space:T>8.2 mm; cp>16.6 mm; cgd<14.5 mm; cs>30°. Each ofthese values was obtained by taking the mean value plusor minus the standard deviation of each variable.Table 1 Extreme values, average and standard deviations of cora-coid length and thickness; coracoid prominence; coraco-glenoiddistance; coracoid slope; distance between the coracoid tip and theuppermost point of the glenoid fossa (L coracoid length; T cora-coid thickness; cp coracoid prominence; cgd coraco-glenoid dis-tance; cs coracoid slope (measured according to Edelson and Taitz[3]); d distance between the coracoid tip and the uppermost pointof the glenoid fossa; S.d. standard deviation)L (mm) T (mm) cp (mm) cgd (mm) cs (degrees) d (mm)Max 50 10.2 22 22.1 42 12Min 31 5 11 11.8 19 0.5Average 38.15 7.19 14.62 16.23 25.57 7.11S.d. 3.97 1.04 1.96 1.7 4.71 1.23Fig. 1a, b Drawings showing the measurements performed. a L,coracoid length; T, coracoid thickness; cp, prominence of the cora-coid tip beyond the plane of the glenoid; cs, coracoid slope (ac-cording to Edelson and Taitz [3]). b cgd, distance between the lat-eral border of the coracoid tip and the nearest point of the antero-superior margin of the glenoid; d, distance between the horizontalplane tangent to the lowermost point of the coracoid tip and thehorizontal plane tangent to the uppermost point of the glenoid200Fig. 2 Photographs showing the different position of the coracoidtip with respect to the uppermost point of the glenoid fossa in twoscapulae. In the scapula of the Fig. 2a the horizontal line tangentto the caudal margin of the coracoid tip (X) is situated cranially(maximum 3 mm), and in the scapula of the Fig. 2b caudally(maximum 12 mm), compared with the horizontal line tangent tothe cranial end of the glenoid (Y)Fig. 3a–c Configurations of the arch-like space delimited by theanterosuperior border of the glenoid and the posterolateral marginof the coracoid process. a Type I configuration; b Type II configu-ration; c Type III configurationThe values for L, T, cp, cgd, cs and d of the coracoidprocess were found to be independent of the dimensionsof the scapulae.No correlations emerged between the anatomicalcharacteristics of the coracoid process and the presenceof degenerative changes of the acromion. Statisticalanalysis showed no correlations among the variables.The supplementary CT study showed that the meanvalue of the coraco-glenoid angle was 146.4° in Type Iscapulae and 151.1° and 151.3° in the specimens withType II or Type III configuration (Table 2). The meancoracoid overlap in the three types of scapulae was, re-spectively, 8.7 mm, 11.2 mm and 10.7 mm (Table 2).DiscussionThe subcoracoid space is occupied in vivo by severalsoft tissue structures, such as the articular capsule of thegleno-humeral joint, the subscapularis tendon and thesubacromial bursa. The thickness of these tissues mayvary, but variations are small and do not affect the widthof the subcoracoid space, unless there is local pathology.The shape and size of this space depend on its limitingskeletal structures [6,8]. Therefore, anatomical morpho-metric studies of these structures may provide informa-tion as to the aetiology of the subcoracoid impingementsyndrome. To elucidate the possible aetiological role ofscapular morphometry in idiopathic coraco-humeral im-pingement, we examined dry scapulae with an age rangesimilar to that of patients presenting with the clinicalsyndrome [2]. Gender, and side of the scapulae were notrior migration of the humeral head) [4,7] should also bepresent for the clinical syndrome to develop.Severe degenerative changes of the coracoid pillarwere not observed in our skeletons, even when the acro-mion showed anterior spurs or a pseudoarticular surfacefor the humeral head. This suggests that the coracoidprocess is not involved in, or affected by, subacromialimpingement. Furthermore, degenerative changes havenot been observed in patients with subcoracoid impinge-ment [2].In conclusion, our study suggests that subjects whoare at risk of developing an idiopathic subcoracoid im-pingement syndrome are those showing a Type I config-uration, associated with severe narrowing of the coraco-glenoid space. The morphometric characteristics of thisspace may be easily evaluated on standard CT scans ofthe shoulder.References1. Codman EA (1984) The shoulder: rupture of the supraspinatusand other lesions in or about the subacromial bursa. Krieger,Malabar, Florida2. Dines DM, Warren RF, Inglis AE, Pavlov H (1990) The cora-coid impingement syndrome. J Bone Joint Surg [Br] 72:314–3163. Edelson JG, Taitz C (1992) Anatomy of the coraco-acromialarch. Relation to degeneration of the acromion. J Bone JointSurg [Br] 74: 589–5944. Gerber C, Terrier F, Ganz R (1985) The role of the coracoidprocess in the chronic impingement syndrome. J Bone JointSurg [Br] 67: 703–7085. Gerber C, Terrier F, Zehnder R, Ganz R (1987) The subcora-coid space. An anatomic study. Clin Orthop 215: 132–1386. Goldthwait JE (1909) An anatomic and mechanical study of theshoulder-joint, explaining many of the cases of painful shoul-der, many of the recurrent dislocations and many of the cases ofbrachial neuralgias or neuritis. Am J Orthop Surg 6: 579–6067. Ko JY, Shih CH, Chen WJ, Yamamoto R (1994) Coracoid im-pingement caused by a ganglion from the subscapularis tendon.J Bone Joint Surg [Am] 76: 1709–17118. Meyer AW (1937) Chronic functional lesions of shoulder. ArchSurg 35:646–674201taken into account, since these factors do not appear toinfluence the anatomical features of the coracoid process[5].We found no significant correlations among length orthickness of the coracoid process, coraco-glenoid dis-tance, coracoid slope and prominence of the coracoid tipbeyond the anterior edge of the glenoid. Furthermore, nocorrelations were found between these anatomical fea-tures and the dimensions of the whole scapula as re-vealed by the length-width ratio. Since the anatomicalcharacteristics, which were found to be extremely vari-able, cannot be precisely evaluated on radiographs of theshoulder, no information on the dimensions of the coraco-humeral space can be obtained by radiographic studies.The anterosuperior border of the glenoid and the pos-terolateral margin of the coracoid process enclose anarch-like space of varying shape. We found that thisspace may have three configurations and presents theshortest dimensions in the Type I scapulae. Furthermore,the scapulae with this configuration were found to have,on CT, the lowest mean values of the coraco-glenoid an-gle and coracoid overlap. It has been shown that valuesof these parameters are related to the width of the cora-co-humeral space, since the latter are found to be smallin the presence of small coraco-glenoid angles and smallcoracoid overlap [5]. Therefore, Type I configuration im-plies a short coraco-humeral distance. Measurements ofthe coraco-glenoid space on standard CT scans, whichare much easier than measurements of the coraco-gle-noid angle and coracoid overlap, may identify subjectswith a narrow coraco-humeral space. This information,however, is not sufficient to diagnose idiopathic subcora-coid impingement. In fact, in 4% of Type I scapulae, oth-er anatomical characteristics were present predisposingto narrowing of the coraco-humeral space, and this is ahigher figure than the incidence of the clinical syndrome.It is thus conceivable that constitutional anomalies (e.g.prominence of the lesser tuberosity) or pathological con-ditions of the local soft tissues or bony structures (gan-glia or calcification of the subscapularis tendon, or supe-Table 2 Mean values of coraco-glenoid angle, coracoid overlap, and retroversion angle (cga coraco-glenoid angle (degrees); co cora-coid overlap (mm); ra retroversion angle (degrees); var variance; avg average)Type I Type II Type IIIcga (var) co (var) ra cga (var) co (var) ra cga (var) co (var) ra146.2 (0.2) 6.8 (0.2) 12 151.8 (0.2) 10.2 (0.2) 11 153.6 (0.3) 10 (0.0) 12142.8 (0.2) 9.2 (0.2) 12 147.6 (0.3) 12 (0.0) 12 150.2 (0.2) 10 (0.0) 13145 (0.0) 8 (0.0) 12 154.2 (0.2) 10.8 (0.2) 12 154.4 (0.3) 11.8 (0.2) 13145.2 (0.2) 10 (0.0) 11 151 (0.0) 9 (0.0) 14 152.2 (0.2) 12 (0.0) 13146.4 (0.8) 11.1 (0.1) 14 155.2 (0.2) 11.2 (0.2) 12 150 (0.0) 10 (0.0) 13147.2 (0.2) 8.2 (0.2) 12 152 (0.0) 13.9 (0.1) 13 153.6 (0.8) 9.2 (0.2) 12150.2 (0.2) 10 (0.0) 12 150.8 (0.7) 11 (0.0) 12 149.6 (0.3) 10 (0.0) 11145.2 (0.2) 7.2 (0.2) 13 149.4 (0.8) 13.4 (0.8) 12 150 (0.0) 12.8 (0.2) 12149.4 (0.3) 8 (0.0) 13 147.6 (0.8) 9.2 (0.2) 14 148.4 (0.8) 10.8 (0.2) 14avg: 146.4 avg: 8.7 avg: 12.3 avg: 151.1 avg: 11.2 avg: 12.4 avg: 151.3 avg: 10.7 avg: 12.6

THE MORPHOMETRY OF THE CORACOID PROCESS - ITS AETHIOLOGIC ROLE IN THE SUBCORACOID IMPINGEMENT SYNDROME

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THE MORPHOMETRY OF THE CORACOID PROCESS - ITS AETHIOLOGIC ROLE IN THE SUBCORACOID IMPINGEMENT SYNDROME

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