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Anatomic Study of the Coracoid Process: Safety Marginand Practical Implications

Bernardo Barcellos Terra, M.D., Benno Ejnisman, M.D., PhD.,Eduardo Antônio de Figueiredo, M.D., Carina Cohen, M.D., Gustavo Cará Monteiro, M.D.,

Alberto de Castro Pochini, M.D., Ph.D., Carlos Vicente Andreoli, M.D., Ph.D., andMoises Cohen, M.D., Ph.D.

Purpose: The aim of this study was to define a safety margin for coracoid process osteotomy that does not compromise thecoracoclavicular ligaments and that can be used in the coracoid transfer procedures. Methods: Thirty shoulders from 15cadavers were dissected, exposing the coracoid process and attached anatomic structures. The distance of the insertion ofthese structures to the coracoid process apexwasmeasured.Results: The average length of the coracoid process was 4.26�0.26 cm. The averagewidth andheight at the tipwere 2.11� 0.2 and 1.49� 0.12 cm, respectively. The average distance fromthe tip to the anterior and posterior margin of the pectoralis minor was 0.1 � 1.17 and 1.59 � 0.27 cm, respectively. Theaverage distance from the tip to the posterior margin of the coracoacromial ligament was 2.79 � 0.33 cm. The averagedistance from the apex to the most anterior part of the trapezoid ligament was 3.33 � 0.38 cm. We obtained a constantvalue of 0.85 cm for this measure, and the value increased with each 1.0-cm increase in the distance from the tip to theposterior margin of the pectoralis minor. The safety margin for osteotomy (i.e., available bone distance for the coracoidprocess transfer) was 2.64 cm. Conclusions: This study established a safety margin of 2.64 cm for the osteotomy of thecoracoid process and its relationwith the posteriormargin of the pectoralisminor. The anatomic descriptions of bone and softtissue, as well as a measure of correlation for the safety margin of the coracoid, provide tools for surgeons performinganatomic surgical procedures to correct glenohumeral instability with significant bone loss. Clinical Relevance: Knowingthe safety margin allows the surgeon to perform a safe osteotomy without direct visualization of the coracoclavicularligaments attachments, thereby making procedures more anatomic.

he peculiar anatomy of the shoulder joint makes it

Tsusceptible to various diseases, including insta-bility. In the therapeutic management of significant gle-nohumeral bone loss, bone block procedures withmodifications play an important role as treatment optionsin these cases.The incidence of glenoid bone defects following

traumatic anterior glenohumeral instability is high,occurring in up to 22% of acute shoulder dislocationcases and 86% of recurrent cases. Furthermore, largeareas of humeral and glenoid bone loss, such as the

From the Department of Orthopaedic Surgery and Sports Medicine, Federalniversity of São Paulo, São Paulo, Brazil.The authors report that they have no conflicts of interest in the authorship

nd publication of this article.Received December 19, 2011; accepted June 26, 2012.Address correspondence to Bernardo Barcellos Terra, M.D., Federalniversity of São Paulo, Rua Capitão Macedo, 171, CEP 04021-020, Sãoaulo, Brazil. E-mail: bernardomed@hotmail.com� 2013 by the Arthroscopy Association of North America0749-8063/11854/$36.00http://dx.doi.org/10.1016/j.arthro.2012.06.022

Arthroscopy: The Journal of Arthroscopic and Related S

inverted pear glenoid, increase the likelihood of recur-rent instability and the likelihood of failure afterarthroscopic soft-tissue stabilization surgery.1-3 In casesof glenoid bone loss or an engaging Hill-Sachs lesion,glenoid bone augmentation using a coracoid processtransfer may be helpful in reducing the incidence ofrecurrent instability. However, the associated bonyanatomy, including the safety margin that does notaffect the coracoclavicular ligaments and its relation tothe transfer procedures, is not well defined.There is no consensus in the literature on the

appropriate level of coracoid process osteotomy thatdoes not compromise the coracoclavicular ligaments.Such a standardized osteotomy level could be consid-ered as a safety margin.4-12 The purpose of this studywas to define the area that is free of coracoclavicularinjury (safety margin) or other structural injury in thetransfer procedures of the coracoid process. Thehypothesis was that this safety margin may be appli-cable in coracoid transfer procedures (i.e., if the amountof coracoid available supports one or two 3.5-mmscrews that are used in Bristow-Latarjet procedures).

urgery, Vol 29, No 1 (January), 2013: pp 25-30 25

Fig 2. Anatomic structures of the coracoid process of the leftshoulder with emphasis on the measurement of the distanceA with a nondigital caliper. (A) T-CAL, distance from the tipof the coracoid process to the coracoacromial ligament. (CL,conoid ligament; TL, trapezoid ligament; CP, coracoid process;PMi, pectoralis minor; *, anterior and posterior margins ofpectoralis minor.)

26 B. B. TERRA ET AL.

MethodsThis anatomic study did not require laboratory

investigational review board or ethics committeeapproval. We dissected 30 shoulders from 15 freshcadavers (9 male and 6 female) with a mean age of 54years (age range, 24 to 68). Specimens with scars aboutthe shoulder or limitations in passive shoulder rangeof motion were excluded because these would disturbthe determination of proper measurements. The skin,subcutaneous tissue, deltoid, and overlying soft tissuewere removed, exposing the coracoid, lateral clavicle,and acromion. The footprints of each ligament andtendon attached to the coracoid were preserved (Fig 1).Measurements were performed using a nondigitalcaliper accurate to 0.1 mm (Digimess, São Paulo, SP,Brazil; Fig 2). Each measurement was carried out twiceby 2 of the authors, blinded to each other. The reportedvalue is the average of the 4 measurements. If anymeasurements were significantly different, a thirdmeasurement by another author was be taken.The dimensions, width and height at the tip and length

(from tip to base) in the long axis of the coracoid process,were recorded. The distance from the coracoid tip tothe tendon and ligament structure insertionsdanteriormargin of the pectoralis minor (T-aPMi), posterior mar-gin of the pectoralis minor (T-pPMi), conjoint tendon(T-CT), posterior margin of the coracoacromial ligament(T-CAL), coracohumeral ligament (T-CHL), the moredistal point of the trapezoid ligament (T-TL), and conoidligamentdalso were measured (Fig 2). We defined thetip as the distal point and the base as a specific pointat which the coracoidal superior surface propagationchanges from a horizontal to a vertical direction.Because of the large interindividual variability of the

values of anatomic measurements, we correlatedthe safety margin with the posterior margin of the

Fig 1. Anatomic structures isolated in coracoid process of theleft shoulder. (CAL, coracoacromial ligament; CP, coracoidprocess; CT, conjoint tendon; CUL, coracohumeral ligament;PMi, pectoralis minor; TL, trapezoid ligament.)

pectoralis minor (which is easily accessible duringsurgery) to reduce this variability. Statistical analysis wasperformed with linear regression to predict the valueof the T-TL distance (coracoid tip to trapezoid ligament)as a function of the T-pPMi distance (Figs 3 and 4).Based on the results of the linear regression, a safetylimit was estimated at 99% of the T-pPmi normality.Values were expressed as means, standard deviations,and 99th percentile normal ranges. A level of statisticalsignificance was established at P <.05%. Statisticalanalysis was performed using SPSS version 15 (SPSS,Chicago, IL).

Fig 3. Top view of the coracoid process showing the distancesfor (A) T-pPMi, distance from the tip of the coracoid process tothe posterior margin of pectoralis minor and (B) T-TL,distance from the tip of the coracoid process to the trapezoidligament (safety margin).

Fig 4. Superior view of the coracoid process showing therelationship of the distances T-pPMi and T-TL. (CL, conoidligament; TL, trapezoid ligament; CAL, coracoacromial liga-ment; PMi, pectoralis minor; T-pPMi, distance from the tip ofthe coracoid process to the posterior margin of pectoralisminor; T-TL, distance from the tip of the coracoid process tothe trapezoid ligament [safety margin].)

Fig 5. Measurements of the distance T-pMi of the cora-coid process of the left shoulder. (A) T-pPMi, distance fromthe tip of the coracoid process to the posterior margin ofpectoralis minor. (CAL, coracoacromial ligament; CT, conjointtendon.)

Table 2. Dimensions of and Relationships Between the Soft-Tissue Footprints on the Coracoid

VariableMean(cm)

SD(mm)

Minimum(cm)

Maximum(cm)

IN (99%)*

Minimum Maximum

T-pCAL 2.79 0.33 2.00 4.00 2.03 3.55T-CT 0.53 0.27 0.20 1.20 �0.11 1.17T-aPMi 1.17 0.10 1.00 1.40 0.93 1.42

ANATOMIC STUDY OF THE CORACOID PROCESS 27

ResultsBone anatomy measurement values are shown in

Table 1 and represented in Fig 2. The average length ofthe coracoid process was 4.26� 0.26 cm. The width andheight at the tip were 2.11 � 0.2 cm and 1.49 � 0.12cm, respectively (Table 1).The average T-aPMi and T-pPMi were 0.1 � 1.17 cm

and 1.60 � 0.27 cm, respectively (Fig 5). The averageT-CAL was 2.79 � 0.33 cm. The average T-CT was0.53 � 0.27 cm, the average T-CHL was 1.73 � 0.32 cm,the average T-LT was 3.33 � 0.38 cm, and the averagedistance from the apex to the most anterior part ofconoid ligament was 3.66 � 0.35 cm (Table 2).We correlated the T-TL (safety margin) distance to the

T-pPMi. According to the performed linear regression,a constant value of 0.85 cm was obtained for the T-TLfor every 1.0-cm increase in the distance of the T-pPMi(i.e., for each increase in distance of 1.0 cmof the T-pPMi,there is an increase of 0.85 cm in the T-TL [safetymargin]; Table 3 and Fig 6). There was no difference inmeasurements between male and female specimens.As shown in Fig 6, the safety margin for an average

T-pPMi distance of 1.6 cm (which was the averagedistance of this measure in this study) is 2.64 cm. If we

Table 1. Bony Anatomy Dimensions of the Coracoid

Variable Mean (cm) SD (cm) Minimum (cm) Maximum (cm)

Coracoidlength

4.26 0.26 3.8 4.6

Tip width 2.11 0.2 1.82 2.42Tip height 1.49 0.12 1.2 1.7

consider that the T-pPMi distance is 2.2 cm, we thus havea safety margin with 3.15 cm with a safety limit of 99%.

DiscussionIn 1954, Latarjet11 described an osteotomy where the

reference was the base of the coracoid process. In 1958,Helfet6 described the Bristow procedure where the cutwas made 1 cm from the tip with the insertion of theconjoint tendon. May7 modified the technique, advo-cating a cut just proximal to the insertion of the cor-acobrachialis tendon. Mead13 in 1964 modified theBristow procedure adding 1 to 3 cm of the coracoidprocess to the conjunct tendon during the bony trans-fers. Didier-Patte established the concept of tripleanterior-inferior stability through which a bone frag-ment of 2.5 cm is inserted into the glenoid witha portion of the coracoacromial ligament and tendontogether, thereby providing bone static stabilization andcapsuloligamentous and tendinomuscular dynamicstabilization.5 Burkhart et al.9 described the osteotomy

T-pPMi 1.59 0.27 1.10 2.30 0.96 2.22T-CL 3.66 0.35 3.00 4.20 2.84 4.48T-TL 3.33 0.38 2.80 4.40 2.46 4.20T-CUL 1.73 0.32 1.20 2.40 0.99 2.47

aPMi, anterior pectoralis minor; CAL, coracoacromial ligament; CL,conoid ligament; CUL, coracohumeral ligament; CT, conjoint tendon;IN, interval normality; pPMi, posterior pectoralis minor; T, tip; TL,trapezoid ligament.*Descriptive measurements with 99% of normality interval.

Table 3. Variables Used to Plot the Linear Regression Graph

Factor Coefficient SE t P R2

Constant 1.981 0.334 5.923 <.001 .374T-pPMi 0.85 0.208 4.092 <.001

NOTE. The coefficient of the T-pPMi measure is 0.85; that is, foreach increase of 1.0 cm in the T-pPMi measure, there should be anincrease of 0.85 cm in the safety margin (T-TL) for the osteotomy ofthe coracoid process.

28 B. B. TERRA ET AL.

distal to the angle (elbow) of the coracoid process;however, it was unclear where it would be the angle orelbow of the coracoid process.There appears to be no consensus in the literature on

the cutoff level for osteotomy of the coracoid process intransfer procedures, with surgical descriptions rangingfrom osteotomies of 1, 2.5, and 3 cm to osteotomies thattake as reference regions such as the base of the elbowof the coracoid. In our study, we established thata coracoid process osteotomy 2.64 cm from the tip ofthe coracoid process for shoulder with a T-pPMi of1.6 cm does not compromise the insertion of the cor-acoclavicular ligaments and therefore does not causeany instability of the acromioclavicular joint. This iswhat has been defined as the safety margin.Arthroscopic techniques for coracoid process transfer

have recently been described.4,14 Lafosse et al.4 describedone such technique in which the coracoid processosteotomy is made posterior to the 2 supporting guidesthat are positioned at the superior part of the coracoidprocess. This creates a coracoid bone graft approximately2 to 2.5 cm long and thus a measure that is in accordancewith the safety margin.Previous studies have reported on the anatomic

measurements of the coracoid process and the footprintof the coracoclavicular ligaments.15,16 Salzmann et al.17

reported a length of approximately 4.31 � 0.22 cm anda width and height at the tip of 1.36 � 0.21 and 0.82 �0.1 cm, respectively. Mazzocca et al.18 reported a length

Fig 6. The linear regression graph according to T-TL andT-pPMi with 99% of safety limit. (T-TL, distance from the tipof the coracoid process to the trapezoid ligament, T-pPMi,distance from the tip of the coracoid process to the posteriormargin of pectoralis minor.)

of 4.52 � 0.41 cm and a width and height of 2.49 �0.24 and 1.19 � 0.18 cm, respectively. In our study, theaverage length of the coracoid process was 4.26 cm andits height and width at the tip were 1.49 and 2.11 cm,respectively. Our opinion is that the safety margin ismore important than the raw anatomic measurements.Armitage et al.19 conducted an anatomic study and

computed tomography assessment of the coracoidprocess to determine the dimensions of the coracoid andto compare the radius of curvature of the intact glenoidwith the radius of curvature of the coracoid undersur-face, as oriented in the congruent-arc Latarjet procedure.They reported a mean length, width, and thickness of

the coracoid of 16.8 mm, 15.0 mm, and 10.5 mm,respectively.19 Dolan et al.20 reported a value for thedistance from the tip to the trapezoid ligament of 2.85cm and a mean coracoid length, tip width, and tipheight of 4.56, 1.83, and 1.15 cm, respectively. In ourstudy, the mean distance from the tip to the trapezoidligament was 3.33 cm; however, we believe that indi-vidual measures can vary greatly from person toperson, so we correlated the T-TL (safety margin)distance to the T-pPMi (posterior border of the pector-alis minor). We did not correlate with the height of thespecies, which is also interesting and perhaps statisti-cally significant data. We chose to correlate with theposterior margin of the pectoralis minor tendon,because it is an easily accessible measure during thesurgery and found that for each increase of 1.0 cm inthe T-pPMi measure, there should be an increase of0.85 cm in the safety margin (T-TL) for the osteotomyof the coracoid process (Figs 4 and 7), confirmed by theanalyze of the linear regression graph. The averageT-pPMi distance was 1.60 cm. When analyzing thenormality limit according to the parameters of thelinear regression graph, we obtained for the average of1.60 cm a safety margin of 2.64 cm for osteotomy of thecoracoid process, increasing the safety margin in directrelation to the T-pPMi distance.The safety margin of 2.64 cm for the osteotomy of the

coracoid process found in our study is applicable to

Fig 7. The coracoid process with two 3.5-mm screws.

ANATOMIC STUDY OF THE CORACOID PROCESS 29

procedures for transfer of the coracoid process as in theLatarjet-Patte surgery, where we use 2 screws (3.5 or4.0 mm), confirming the hypothesis of the study. In thiscase, it is recommended that a distance of 1.0 cm is leftbetween the screws to avoid breaking the graft (Fig 7).However, if the T-pPMi distance has a small value, thesafety margin will also be small, leaving a little externalbone bridge when 2 screws are used for coracoid fixa-tion. In these cases, the Bristow procedure with 1 screwmust be taken into consideration.Others have studied the anatomic measurements of

several of the distances that we also studied in this workand a relationship with reconstruction procedures ofcoracoclavicular ligaments for acromioclavicular jointinjuries. However, we did not find any studies thatprovided a safety margin for osteotomy and thatcorrelated this measure (with statistical analysis) withthe posterior border of the pectoralis minor.A limitation of this investigation involves the meth-

odology of studying a curved 3-dimensional anatomicstructure. It is challenging to establish consistently thelongest axis and the most anterior portion or tip of thecoracoid process because of its curved and tortuousmorphology. Thus, to reduce observer bias, 2 observersperformed all measurements (if was necessary, a thirdperson also performed the measurements), and theobservers performed measurements on cadaveric spec-imens with ligaments and tendons intact to enhancereproducibility. Another limitation was that, as ananatomic study in cadavers with no history, it is possiblethat in patients with subcoracoid impingement, themorphology of the coracoid process was altered.We know the consequences of injury to the cor-

acoclavicular ligaments,16,18,21,22 but future researchmay provide the consequences and clinical and biome-chanical implications of manipulating other structures(e.g., the pectoralis minor, coracohumeral ligament, andcoracoacromial) in the transfer procedures of the cora-coid process.

ConclusionThis study established a safety margin of 2.64 cm for

the osteotomy of the coracoid process and its relationwith the posterior margin of the pectoralis minor. Theanatomic descriptions of bone and soft tissue, as wellas a measure of correlation for the safety margin ofthe coracoid, provide tools for surgeons performinganatomic surgical procedures to correction of gleno-humeral instability with significant bone loss.

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30 B. B. TERRA ET AL.

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double-button fixation for chronic acromioclavicular jointdislocation. Arthroscopy 2010;26:149-160.

22. Harris RI, Wallace AL, Harper GD, Goldberg JA,Sonnabend DH, Walsh WR. Structural properties of theintact and the reconstructed coracoclavicular ligamentcomplex. Am J Sports Med 2000;28:103-108.

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