Relationship Between the Thickness of the Coracoid Process and Latarjet Graft Positioning—An Anatomical Study on 70 Embalmed Scapulae

Journal of Clinical Medicine

Article Relationship between the Thickness of the Coracoid Process and Latarjet Graft Positioning—An Anatomical Study on 70 Embalmed Scapulae

Markus Gregori 1,* , Lukas Eichelberger 2, Claudia Gahleitner 1, Stefan Hajdu 1 and Michael Pretterklieber 3 1 Department of Orthopedics and Trauma-Surgery, Vienna General Hospital, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria; [email protected] (C.G.); [email protected] (S.H.) 2 Department of Orthopedics and Trauma-Surgery, Krankenhaus der Barmherzigen Brüder Eisenstadt, Johannes von Gott-Platz 1, 7000 Eisenstadt, Austria; [email protected] 3 Center for Anatomy and Cell Biology, Division of Anatomy, Medical University of Vienna, Währinger Straße 13, 1090 Vienna, Austria; [email protected] * Correspondence: [email protected]; Tel.: +43-1-40400-59010

Received: 10 December 2019; Accepted: 9 January 2020; Published: 12 January 2020

Abstract: Background: The Latarjet procedure is a popular technique with the aim of the reconstruction of glenoid cavity bone defects in patients with chronic anterior shoulder instability. Studies have shown that the Congruent arc Latarjet procedure is better able to reconstruct larger defects than the Classic Latarjet, but there is a lack of information on the limitations of both methods. Methods: The dimensions of the glenoid width and the native coracoid process of two groups with 35 Formol-Carbol embalmed scapulae each were measured using a digital caliper. The relationship between the coracoid graft and the anterior-posterior diameter of the glenoid cavity was calculated to determine the maximum defect size of the glenoid cavity width, which can be treated by both Latarjet techniques. Results: The average restorable defect size of the anterior segment of the glenoid cavity was 28.4% 4.6% (range 19.2%–38.8%) in the Classic Latarjet group, and 45.6% 5.2% (range ± ± 35.7%–57.1%) in the Congruent arc Latarjet group. Based on our results, the feasibility of the Classic Latarjet procedure to reconstitute the anatomical width of the glenoid cavity was 86% in a 25% bone loss scenario, and only 40% in a 30% bone loss scenario. Conclusion: Based on our results we are unable to deﬁne a clear threshold for the optimal Latarjet graft position. In glenoid cavity defects <20%, the Classic Latarjet technique usually provides enough bone stock for anatomical reconstruction. Defects 35% of the glenoid cavity width should only be treated with a coracoid graft ≥ in the Congruent arc position. In the critical area between 20% and 35% of bone loss, we suggest the preoperative assessment of coracoid dimensions, based on which the graft position can be planned to restore the anatomical anterior-posterior diameter of the glenoid cavity.

Keywords: shoulder; instability; Latarjet; glenoid; bone defect; graft position

1. Introduction In patients with recurrent shoulder instability, the incidence of bone lesions of the anterior and anterior-inferior parts of the glenoid cavity is high—in some studies up to 70%–90% of the cases [1–3]. Studies have revealed that the rate of recurrent shoulder dislocations remains high, if patients with quantitative bone loss of at least 20%–25% are treated with soft-tissue repair alone [4,5]. More recently, unacceptable outcomes following arthroscopic Bankart reconstruction have led to a new deﬁnition of subcritical bone loss, if the glenoid cavity defect size exceeds 13.5% of its original width [6].

J. Clin. Med. 2020, 9, 207; doi:10.3390/jcm9010207 www.mdpi.com/journal/jcm J. Clin. Med. 2020, 9, 207 2 of 9

The threshold which indicates the necessity for glenoid bone augmentation is not clearly defined. Most authors recommend reconstruction of the glenoid bone stock if the amount of the anterior glenoid defect exceeds 20%–25% [4,7–9]. Current concepts of anterior glenoid bone augmentation involve the transfer of the coracoid process, the use of tricortical iliac crest grafts and allografts [10–13]. In contrast to other bone block techniques, the Latarjet procedure shows stabilizing capsular and muscular effects additionally to the bone effect, which was best described by Patte as the so-called “triple effect” [4,14–17]. Large studies show excellent clinical results and low recurrence rates of instability between 0% and 8%. [4,18–23] However there are also studies reporting redislocations and subluxations following the Bristow–Latarjet procedure in up to 25.8% of the cases [24]. Most clinical trials describe a flush position of the coracoid bone block, lying with its under-surface attached to the scapular neck, so that it can be deemed as the current “Classic Latarjet position” [18,19,22,25–27]. De Beer modified the graft fixation technique to the “Congruent arc-Latarjet” [28,29], where the graft is rotated 90◦ externally to the scapular plane, so that the under-surface lies in line with the glenoid cavity and becomes the articular side of the graft. Studies have shown that the shape of the under-surface more accurately correlates with the articular shape of the glenoid cavity and that the trimming of the graft in a Congruent arc fashion is not necessary [11,30]. On the other hand, the Classic Latarjet position is associated with a greater bone-to-bone attachment area, which may enhance fusion rates and counteract bending forces [30,31]. Radiographic studies have proved, that the Congruent arc Latarjet is able to restore greater defects of the glenoid cavity compared with the Classic Latarjet transfer [11]. However, the influence of preparation and decortication on graft sizes is underestimated. There is only a paucity of studies investigating the two modifications of graft positions while considering bone loss during graft preparation [31,32], but it remains unclear if a graft in lying position can, in general, restore the anatomical width of the glenoid cavity in a patient with large defects (i.e., >25%). Some authors believe that surgeons do not have to consider coracoid graft dimensions in the preoperative setting in defects between 25% and 30% [32]. It has been noted that 30% of bone loss would probably be the amount where most surgeons would decide between either a Classic or a Congruent arc position [30]. Therefore, the purpose of our study was to detect a cut-off value for maximal glenoid bone loss, which should help surgeons to decide if a transfer of the coracoid process for anatomical reconstruction of the glenoid width is possible in the Classic or Congruent arc manner, or if other bone augmentation techniques should be considered. Our hypothesis was that glenoid cavity defects up to 25% can usually be treated with Classic Latarjet procedures.

2. Material and Methods The study protocol was approved by the local Ethics Committee. We included 70 unpaired Formol-Carbol embalmed scapulae, of which 48 were male and 22 female. We examined 39 left and 31 right scapulae. The shapes of the glenoid cavities were pear-like throughout and the maximum width was usually located near the 3 o’clock position or slightly lower. The scapulae were allocated into two groups of 35 bones each for Classic Latarjet and Congruent arc Latarjet procedures. Prior to graft harvesting, we assessed the maximum glenoid width (GCW), the maximum length (CPL), the maximum width (CPW) and the maximum thickness (CPT) of the coracoid process along the vertical axis. Osteotomy of the coracoid process was performed directly distal its knee with an oscillating saw (Johnson & Johnson, DePuy Synthes, Vienna, Austria) using a 10 0.5 mm sagittal saw blade. The bone × blocks were then fixed in the bench vice in a lying position for a Classic Latarjet procedure to prepare the under-surface of the graft, and in a 90 degrees rotated position to prepare the medial border of the graft for Congruent arc Latarjet grafts. Decortication and ablation of extremely thin layers (1 mm) was performed to gain a flat cancellous bone bed, and to an amount to ensure secure and correct screw placement for potential graft fixation. (Figure1) In Congruent Latarjet grafts, a minimal distance of J. Clin. Med. 2020, 9, 207 3 of 9 J. Clin. Med. 2020, 9, x FOR PEER REVIEW 3 of 9 J. Clin. Med. 2020, 9, x FOR PEER REVIEW 3 of 9 2–3screws mm between(Ø 3.5 mm, the drillJohnson holes & and Johnson, the graft DePuy cortex Synt washes, considered Vienna, as Austria) secure. Afterwere the placed preparation to ensure of thescrewsenough requested (Ø distance 3.5 cancellous mm, from Johnson the area, graft two& Johnson,cortex. cannulated After DePuy short-threadedosteotomy Synthes, we Vienna, cancellousassessed Austria) the screws maximum were (Ø 3.5 placed mm,length Johnsonto (CPL-O), ensure & Johnson,enoughmaximum distance DePuy width Synthes, from (CPW-O) the Vienna, graft maximum cortex. Austria) thicknessAfter were os placedteotomy (CPT-O) to ensurewe of assessedthe enough grafts. the All distance maximum measurements from length the graft were (CPL-O), cortex. taken Aftermaximumusing osteotomy a digital width caliper we(CPW-O) assessed which maximum thedisplays maximum thickness measurements length (CPT-O) (CPL-O), with of the an maximum grafts.accuracy All widthof measurements 0.01 (CPW-O) mm. Measurements were maximum taken thicknessusingwere performeda digital (CPT-O) caliper by of one the which trauma grafts. displays Allsurgeon, measurements measurements who specia werelizes with taken in an shoulder usingaccuracy a surgery digital of 0.01 caliper (MG), mm. whichandMeasurements one displays trauma measurementsweresurgeon performed who withhas by one anworked accuracy trauma extensively surgeon, of 0.01 mm. whoin Measurementsthe specia fiellizesd of in human wereshoulder performed bone surgery and by (MG),joint one traumaanddissection one surgeon, trauma (LE). whosurgeonDocumentation specializes who has in and shoulder worked measurements surgery extensively (MG), were andinperformed the one fiel trauma dblind of surgeon humanby each who investigator.bone has and worked joint The extensively graftdissection dimensions in(LE). the fieldDocumentationwere of set human in relation bone and measurementsto and the joint maximum dissection were width performed (LE). of Documentationthe glenoid blind by cavity each and toinvestigator. measurementsassess the maximumThe graft were dimensions performeddefect size, blindweresimilar set by to eachin arelation method investigator. to alreadythe maximum The published graft width dimensions [1]. of Figurethe wereglenoid 2 setdemonstrates cavity in relation to assess tothe the thearea maximum maximum of decortication width defect of size, theand glenoidsimilarmeasurement cavityto a method topoints. assess already the maximum published defect [1]. size, Figure similar 2 demonstrates to a method alreadythe area published of decortication [1]. Figure and2 demonstratesmeasurement thepoints. area of decortication and measurement points.

Figure 1. (a) Classic Latarjet graft after decortication and preparation. View on the under-surface of the graft showing the attachment side to the scapular neck. (b) Congruent arc Latarjet graft after FigureFigure 1.1. ((a)) Classic Classic Latarjet Latarjet graft graft after after decortication decortication an andd preparation. preparation. View View on on the the under-surface under-surface of decortication and preparation. View on the medial side of the graft showing the attachment side to ofthe the graft graft showing showing the the attachment attachment side side to to the the scapular scapular neck. neck. ( (bb)) Congruent Congruent arc arc Latarjet graftgraft afterafter the scapular neck. Maximum length (CPL-O), maximum width (CPW-O) maximum thickness (CPT- decorticationdecortication andand preparation. preparation. View View on on the the medial medial side side of of the the graft graft showing showing the the attachment attachment side side to the to O). scapularthe scapular neck. neck. Maximum Maximum length length (CPL-O), (CPL-O), maximum maximum width width (CPW-O) (CPW-O) maximum maximum thickness thickness (CPT-O). (CPT- O).

Figure 2. Schematic illustration of a right coracoid process for Classic Latarjet preparation (a) and a rightFigure coracoid 2. Schematic process illustration for Congruent of a arc right Latarjet coracoid preparation process (forb). TheClassic uncolored Latarjet area preparation shows the (a area) and of a decorticationFigureright coracoid 2. Schematic at process the under-surface illustration for Congru of in enta Classicright arc Latarjetcoracoid Latarjet preparation process grafts (a for) and ( bClassic). at The the uncoloredLatarjet medial sidepreparation area of Congruentshows (a the) and area arc a Latarjetrightof decortication coracoid grafts( bprocess). at All the measurements forunder-surf Congruaceent prior arcin Classic Latarjet to osteotomy Latarjet preparation weregrafts taken ((ba).) andThe at intact atuncolored the scapulae medial area side (native shows of Congruent thickness the area (CPT)ofarc decortication Latarjet and maximum grafts at the (b width ).under-surf All (CPW)measurementsace in in Figure Classic prior2a,b). Latarjet to osteotomy grafts (a )were and attaken the medialat intact side scapulae of Congruent (native arcthickness Latarjet (CPT) grafts and (b ).maximum All measurements width (CPW) prior in toFigure osteotomy 2a,b). were taken at intact scapulae (native Statisticalthickness (CPT) analysis: and maximum Interobserver width agreement(CPW) in Figure of individual 2a,b). measurements of both investigators was calculatedStatistical for analysis: each parameter Interobserver using agreement the intraclass-correlation-coe of individual measurementsﬃcient (ICC) of as both shown investigators in Table1. Thewas Pearson Statisticalcalculated correlation analysis: for each parameterInterobserver coeﬃcient using (Pearson’s agreement the intracla r) wasof ss-correlation-coefficientindividual used to describe measurements the correlation (ICC) of both as shown investigators between in Table the maximumwas1. The calculated Pearson width for correlation of each the parameter glenoid coefficient cavity using (GCW)(Pearson’s the intracla and r) the ss-correlation-coefficientwas native used thicknessto describe (CPT) the (ICC)correlation or width as shown (CPW) between in ofTable the the coracoid1.maximum The Pearson process. width correlation Data of the are glenoid represented coefficient cavity (Pearson’s as (GCW) mean and standardr) wasthe nativeused deviation to thickness describe in mm. (CPT) the The correlation or equality width (CPW)between of variances of the the ± formaximumcoracoid variables process. width of both of Data the groups areglenoid represented was cavity calculated (GCW) as mean with and ± standard the the Levene native deviation thickness test. To in ensure mm.(CPT) The normalor equalitywidth distribution (CPW) of variances of the of coracoidfor variables process. of both Data groups are represented was calculated as mean with ± standardthe Levene deviation test. To ensurein mm. normalThe equality distribution of variances of the forrelative variables defect of sizeboth data, groups we wasused calculated the Shapiro–Wilk with the test. Levene As the test. assumptions To ensure normal were fulfilled, distribution a student's of the relativet-test was defect used size to data, compare we used the themaximum Shapiro–Wilk relative test. defect As the size assumptions between the were Congruent fulfilled, arc a student's and the t -test was used to compare the maximum relative defect size between the Congruent arc and the

J. Clin. Med. 2020, 9, 207 4 of 9

J.the Clin. relative Med. 2020 defect, 9, x FOR size PEER data, REVIEW we used the Shapiro–Wilk test. As the assumptions were fulﬁlled,4 of a9 student’s t-test was used to compare the maximum relative defect size between the Congruent arc and Classic Latarjet group. p-values less than 0.05 were considered significant. All statistical analyses the Classic Latarjet group. p-values less than 0.05 were considered signiﬁcant. All statistical analyses were performed using SPSS, version 24, IBM Corp., 2016. were performed using SPSS, version 24, IBM Corp., 2016.

Table 1. Analysis of interobserver reliability. Table 1. Analysis of interobserver reliability. Measure ICC * p-Value Measure ICC * p-Value GCW 0.907 <0.001 GCW 0.907 <0.001 CPL 0.866 <0.001 CPL 0.866 <0.001 CPWCPW 0.659 <0.001<0.001 CPTCPT 0.910 <0.001<0.001 CPL-OCPL-O 0.953 <0.001<0.001 CPW-OCPW-O 0.927 <0.001<0.001 CPT-O 0.943 <0.001 CPT-O 0.943 <0.001 * ICC, intraclass coeﬃcient. For all other abbreviations refer to Figures1 and2 and to the main text above. * ICC, intraclass coefficient. For all other abbreviations refer to Figures 1,2 and to the main text above. 3. Results 3. Results At intact scapulae of both groups (n = 70), the mean width of the glenoid cavity was 30.1 3.1 mm At intact scapulae of both groups (n = 70), the mean width of the glenoid cavity was 30.1± ± 3.1 (median 29.6; range 25.1–38.3). The mean length, width and thickness of the coracoid process were mm (median 29.6; range 25.1–38.3). The mean length, width and thickness of the coracoid process 45.8 4.4 mm (median 45.5; range 35.5–55.5), 16.8 2.1 mm (median 16.3; range 13.1–22.3) and were ±45.8 ± 4.4 mm (median 45.5; range 35.5–55.5), 16.8± ± 2.1 mm (median 16.3; range 13.1–22.3) and 11.7 1.8 mm (median 11.3; range 8.6–15.9), respectively. 11.7 ± 1.8 mm (median 11.3; range 8.6–15.9), respectively. There was a strong correlation between the maximum width of the glenoid cavity and the width There was a strong correlation between the maximum width of the glenoid cavity and the width of the coracoid process (Pearson’s r = +0.628, p < 0.001) on the one hand, and between the width of the of the coracoid process (Pearson’s r = +0.628, p < 0.001) on the one hand, and between the width of the glenoid cavity and the thickness of the coracoid process (Pearson’s r = +0.616, p < 0.001) on the other glenoid cavity and the thickness of the coracoid process (Pearson’s r = +0.616, p < 0.001) on the other (Figure3). (Figure 3).

(a) (b)

Figure 3. Correlation between the glenoid cavity width (GCW) and the width of the coracoid process Figure 3. Correlation between the glenoid cavity width (GCW) and the width of the coracoid process (CPW) (a). Correlation between the glenoid cavity width (GCW) and the native thickness of the (CPW) (a). Correlation between the glenoid cavity width (GCW) and the native thickness of the coracoid coracoid process (CPT) (b). process (CPT) (b).

Mean values for the maximum glenoid width (GCW), the the native coracoid process process on on an intact scapulascapula (CPL, (CPL, CPW, CPW, CPT) and the coracoid process following osteotomy and preparation for graft placement (CPL-O, CPW-O, CPT-O) of both groups areare shown in Table 2 2.. InIn thethe Classic Latarjet group (n = 35),35), the the mean coracoid thickness (8.4 ± 1.61.6 mm) mm) was was smaller smaller compared compared with with the Congruent arc ± Latarjet group (11.3 ± 1.81.8 mm). mm). In In contrast, contrast, the the width width of of the the Congruent Congruent arc Latarjet grafts (n = 35)35) were were ± smallersmaller (13.9 ± 2.22.2 mm) mm) compared compared with with those those of of the the Classic Classic Latarjet Latarjet grafts grafts (16.0 (16.0 ± 2.02.0 mm). mm). ± ± Evaluation of the maximal glenoid defect size for Classic Latarjet procedure: After decortication of Table 2. Dimensions of glenoid cavity and coracoid process prior and post graft preparation in mm (n = the coracoid grafts for Classic Latarjet positioning, the coracoid graft thickness declined by 3.1 1.3 mm. 70). ± The average relative glenoid defects size was 28.4% 4.6% and was calculated with the formula ± CPT-O*100/GCW. If weClassic assume Latarjet a 30% (n bone = 35) loss scenario, reconstruction Congruent arc of theLatarjet anatomical (n = 35) glenoid cavityMeasure would have been possible in onlyMin 14 cases (40%), whereas 30 grafts were largeMin enough to restore Mean Med⸷ SD * Max ° Mean Med⸷ SD * Max ° + + GCW 29.8 29.6 3.1 25.1 36.4 30.5 29.6 3.2 25.9 38.3 CPL 44.5 44.4 4.0 35.5 52.3 47.1 46.4 4.4 38.8 55.5 CPW 16.4 16.1 2.3 13.1 22.3 17.1 16.5 2.0 14.1 21.7

J. Clin. Med. 2020, 9, 207 5 of 9 a 25% bone loss scenario (86%). The amount of maximum glenoid defect size, which could be restored J. Clin. Med. 2020, 9, x FOR PEER REVIEW 5 of 9 by a Classic LatarjetJ. Clin. graftMed. 20 ranged20, 9, x FOR between PEER REVIEW 19.2% and 38.8%. 5 of 9 CPT 11.5 11.1 1.8 8.6 15.4 11.8 11.3 1.8 8.8 15.9 Table 2. DimensionsCPT of glenoid11.5 cavity11.1 and coracoid1.8 8.6 process 15.4 prior and11.8 post graft11.3 preparation 1.8 in8.8 mm 15.9 CPL-O(n = 70). 22.0CPL -O22.1 22.0 2.6 22.1 15.8 2.6 26.315.8 23.026.3 23.623.0 2.523.6 16.62.5 16.627.4 27.4 CPW-O 16.0CPW -O15.4 16.0 2.0 15.4 12.9 2.0 21.312.9 13.921.3 13.613.9 2.213.6 10.42.2 10.418.2 18.2 CPT-O 8.4 CPT-O 8.3 Classic 8.4 Latarjet 1.6 8.3 ( n5.8= 35) 1.6 12.75.8 11.312.7 Congruent10.911.3 arc1.810.9 Latarjet (1.8n8.3= 35) 8.317.0 17.0 Measure ⸷ + + + ⸷ Med,Mean Median;Med * Med, SD,SD standardMedian; * Min * deviation;SD, standardMax + ◦ Min,deviation;Mean minimum; Min,Med minimum; ° Max, SDmaximum. ° *Max, Minmaximum Max. ◦ GCW 29.8 29.6 3.1 25.1 36.4 30.5 29.6 3.2 25.9 38.3 Evaluation of theEvaluation maximal of glenoi the maximald defect glenoid size fordefect Classic size for Latarjet Classic procedure: Latarjet procedure: After decortication After decortication CPLof 44.5the coracoid 44.4 grafts 4.0for Classic 35.5 Latarjet 52.3 positioning 47.1, the 46.4 coracoid 4.4graft thickness 38.8 declined 55.5 by 3.1 ± of the coracoidCPW grafts 16.4 for Classic 16.1 Latarjet 2.3 position 13.1ing, 22.3 the coracoid 17.1 16.5graft thickness 2.0 declined 14.1 21.7by 3.1 ± 1.3 mm. The average relative glenoid defects size was 28.4% ± 4.6% and was calculated with the 1.3 mm.CPT The average 11.5 relative 11.1 glenoid 1.8 defects 8.6 size 15.4 was 28.4% 11.8 ± 4.6% 11.3 and 1.8was calculated 8.8 15.9with the CPL-Oformula 22.0 CPT 22.1-O*100/GCW. 2.6 If we 15.8 assume 26.3 a 30% bone 23.0 loss 23.6scenario, 2.5reconstruction 16.6 of 27.4the anatomical formulaCPW-O CPT-O*100/GCW.glenoid 16.0 cavity 15.4 If would we assume 2.0have been a12.9 30% possible bone 21.3 in loss only scenario, 13.914 cases (40%), 13.6reconstruction whereas 2.2 30 of grafts 10.4 the wereanatomical 18.2 large enough glenoidCPT-O cavity wouldto restore 8.4 have a 25% 8.3been bone possible 1.6loss scenario in 5.8only (86%). 1412.7 cases The (40%),amount 11.3 whereas of maximum 10.9 30 grafts 1.8 glenoid were 8.3defect large size, 17.0 enough which could + to restore a 25%be bone restoredMed, loss Median; byscenario a Classic * SD, (86%). standard Latarjet The deviation; graft amount rangedMin, of between maximum minimum; 19.2◦ Max, %glenoid and maximum. 38.8%. defect size, which could be restored by a ClassicEvaluation Latarjet of graft the maximumranged between glenoid 19.2% defect and size 38.8%. for the Congruent arc Latarjet procedure: EvaluationFollowing ofof the the maximum maximum the preparation glenoid glenoid for defect graft defect size fixation forsize the in for Congruenta Co thengruent Congruent arc arc Latarjet manner arc procedure:, theLatarjet coracoid procedure: Following width declined theFollowing preparation the preparation forby 3.2 graft ± 1.6 ﬁxation mm. for graftThe in a average Congruentfixation relative in arca Congruent manner,defect size the arcof coracoid the manner, glenoid width the cavity coracoid declined was 45.6 bywidth% 3.2 ± 5.2%, declined1.6 which mm. was ± Theby 3.2 average ± 1.6 mm. relativecalculated The defect average with size therelative of formula the glenoid defect CPW size cavity-O * 100/GCW.of wasthe glenoid 45.6% The amount cavity5.2%, whichofwas maximum 45.6% was calculated± glenoid 5.2%, which defect with sizewas the which could be restored by a Congruent arc Latarjet graft ranged± between 35.7% and 57.1%. formulacalculated CPW-O with the *100 formula/GCW. The CPW-O amount *100/GCW. of maximum The amount glenoid defectof maximum size which glenoid could defect be restored size which by a Congruent arc Latarjet grafts were able to restore a larger defect size compared with Classic Congruent arc Latarjet graft ranged between 35.7% and 57.1%. could be restoredLatarjet by a graftsCongruent (p < 0.001) arc Latarjet(Figure 4) graft. ranged between 35.7% and 57.1%. Congruent arc Latarjet grafts were able to restorerestore a largerlarger defectdefect sizesize comparedcompared with Classic Latarjet grafts (p < 0.001) (Figure 44).).

Figure 4. Relation between the anatomical reconstruction and defect size of the glenoid cavity for Classic Latarjet grafts and Congruent arc Latarjet grafts.

Figure 4.4. Relation4. Discussion between the anatomical reconstruction and defect size of the glenoid cavity for Classic Latarjet graftsWith andthis CongruentstudyCongruent, we wanted arcarc LatarjetLatarjet to detect grafts.grafts a cut. -off level regarding the maximum glenoid defect size, which can be restored by both the Congruent arc and Classic Latarjet technique, considering changes 4. Discussion in graft dimension following the preparation and decortication of harvested bone blocks. But the main scientific value of this trial is the evidence that graft dimensions influence the Latarjet graft With this study, study, we we wanted wanted to to detect detect a cut-off a cut-o levelff level regarding regarding the themaximum maximum glenoid glenoid defect defect size, size, which canpositioning be restored in by different both the bone Congruent loss scenarios. arc and Although Classic there Latarjet was technique, a strong correlation considering between which can be restoreddimensions by both of the the native Congruent coracoid arc process and Classicand the Latarjetglenoid cavitytechnique, width considering(Figure 3a,b), changes the maximum changes in graft dimension following the preparation and decortication of harvested bone blocks. in graft dimensionrestorable following defect thesize preparationfor the anatomical and reconstrdecorticationuction ofof the harvested glenoid cavity bone widelyblocks. ranged But the between But the main scientific value of this trial is the evidence that graft dimensions influence the Latarjet main scientific 19.2value% andof this38.8% trial if a isgraft the was evidence used in that a Classic graft Latarjet dimensions configuration. influence In athe 25% Latarjet bone loss graft scenario , graftpositioning positioning in anatomicaldifferent in different bonereconstruction bone loss loss scenarios. could scenarios. be performedAlthough Although inthere only there 86%was was of a the astrong strong cases. Butcorrelation already 50% betweenbetween of the grafts dimensions of thewe re native improperly coracoid sized process for defects and measuring thethe glenoid 28% cavity of the widtharticular (Figure width.3 3a,b),Thea,b), larger thethemaximum themaximum amount of the restorable defectglenoid size for defect, the anatomicalthe lesser the reconstructionreconstr chance uctionthat anatomical of the glenoid reconstruction cavity widelycan be achieved. ranged betweenTherefore, this 19.2%19.2% and 38.8%study if a graftdisprovedgraft waswas our usedused hypothesis inin aa ClassicClassic that LatarjetLatarjetthe critical configuration.configuration. threshold value In for a 25%the Classic bone loss Latarjet scenario, technique is anatomical reconstruction25% of the original couldcould bebeglenoid performedperformed cavity width. inin onlyonly 86%86% ofof thethe cases.cases. But already 50% of the grafts Current publications do not provide enough information on the maximal amount of defects in were improperly sized for for defects defects measuring measuring 28% 28% of of the the articular articular width. width. The The larger larger the theamount amount of the of the glenoid defect,the anterior the lesser segment the chance of the glenoid that anatomical cavity which reconstruction can adequately can be berestored achieved. by either Therefore, the Classic or glenoid defect, Congruentthe lesser arcthe Latarjetchance procedure. that anatomical The amount reconstruction of bone harvest can hasbe achieved.already been Therefore, published thisin several this study disproved our hypothesis that the critical threshold value for the Classic Latarjet technique study disprovedstudies our hypothesis [33,34]. Of coursethat the, measurements critical threshold frequently value differ for the by Classica few mm. Latarjet However, technique our results is for is 25% of the original glenoid cavity width. 25% of the originalnative glenoid coracoid cavity process width. dimensions do not significantly differ from those published by several Current publicationsauthors [11,34,35 do not]. Bueno provide et enoughal. [34] proved information a strong on correlation the maximal between amount coracoid of defects thickness in and the anterior segment segment of of the the glenoid glenoid cavity cavity which which ca cann adequately adequately be be restored restored by by either either the the Classic Classic or Congruent arc Latarjet procedure. The amount of bone harvest has already been published in several studies [33,34]. Of course, measurements frequently differ by a few mm. However, our results for native coracoid process dimensions do not significantly differ from those published by several authors [11,34,35]. Bueno et al. [34] proved a strong correlation between coracoid thickness and

J. Clin. Med. 2020, 9, 207 6 of 9 or Congruent arc Latarjet procedure. The amount of bone harvest has already been published in several studies [33,34]. Of course, measurements frequently differ by a few mm. However, our results for native coracoid process dimensions do not significantly differ from those published by several authors [11,34,35]. Bueno et al. [34] proved a strong correlation between coracoid thickness and glenoid width. Our results do not significantly differ from their study, but we would have expected a more accurate correlation. However, the authors supposed that the Classic Latarjet may be limited to smaller glenoid defects less than 30% of the glenoid width. Armitage et al. [11] measured coracoid dimensions at 3D-CT-reconstructions. They have shown that a Congruent arc Latarjet is able to reconstitute greater defects than the Classic Latarjet, but they did not take into consideration bone loss during graft preparation. Although several authors have demonstrated that bone defects of 25%–30% can be successfully treated with Latarjet grafts in lying position [20,32], it is not clear if an anatomic reconstruction of the original glenoid cavity width can be achieved in every patient as a rule. Changes of the glenoid shape correlate with the amount of bone loss [36]. If the native pear shape of the glenoid cavity becomes inverted, it usually indicates anterior bone loss of 25% [36]. In larger anterior defects, Burkart described a more banana-like shape of the glenoid [4]. It still remains unclear if a Classic Latarjet position is adequate in cases with such large defects, or if a defect between 25%–30% would necessitate a Congruent arc Latarjet or other bone augmentation techniques instead. Beyond contention, abrasion of the attachment site of the coracoid graft is necessary to enhance bone healing [22,25,37]. Hantes et al. [32] demonstrated that the Latarjet procedure with the graft in lying position sufficiently restores the anatomy of the glenoid cavity in a model based on anatomic specimens with a 25% anterior-inferior bone defect. The mean defect area was 28.7% 6% of the intact ± glenoid. Most anatomic studies create anterior-inferior bone defects, but clinical findings revealed that bone loss of the glenoid cavity is usually located more anteriorly [38,39]. However, our results do not confirm those of Hantes et al., as we proved, that only 86% of the Classic Latarjet grafts are able to reconstruct bone defects of 25%. In our study, the average defect size in the Classic Latarjet group was 28.4% 4.6%, which is equivalent to the mean defect area of this study group treated with ± Classic Latarjet. Nonetheless, based on our results, we cannot agree that there is no need to calculate the surface area of the coracoid, because almost full reconstruction can be expected in 25%–30% scenarios [32]. According to our results, only 40% of the Classic grafts were able to reconstruct 30% of the glenoid width. Bathia et al. [12] noted that not all their coracoid grafts were thick enough to fill up a 30% bone defect. In their study, 30% bone loss was represented by a defect width of 9.2 mm 0.75 mm, ± which correlates closely to our results, where 30% bone loss was equivalent to a defect width of 9.0 mm 0.9 mm. Provencher et al. noted that a 5% increment of the glenoid width comprises 1–2 mm ± of bone. [10] This corresponds to our findings, where 5% of the glenoid width is equal to 1.5 mm of bone. Ghodagra et al. [40] found that in a 30% bone loss model, Latarjet grafts in a Congruent arc fashion fully restored the anatomical width, whereas grafts placed flush with their undersurface lying on the scapular neck left an average defect of 5%. Based on our results we are unable to define a clear threshold for the optimal Latarjet graft position. Our study shows that the probability of a Classic Latarjet procedure to reconstitute the anatomical glenoid cavity width ranges between 19.2% and 38.8%. Therefore, we would consider preoperative measurements of the coracoid process in addition to the glenoid cavity defect size in the preoperative setting. The determination of both dimensions should help surgeons to assess if reconstruction of a defect larger than 20%–25% can be achieved with the graft in lying position, or if a 90◦ rotated position would be more suitable. Some studies show that postoperative recurrence of instability occurred in patients where the graft healed in anatomic position without any signs of bone resorption [20]. We think that more precise planning in the preoperative setting can help surgeons to decide on the best fitting graft position and prevent recurrent instability. In the Congruent arc Latarjet group, the J. Clin. Med. 2020, 9, 207 7 of 9 range of anatomical reconstruction of a defect glenoid was between 35.7% and 57.1%, suggesting that large defects exceeding 30% of the articular width—which are, of course, not very common—can be successfully treated with a Congruent arc Latarjet. Despite these anatomical findings, we want to point out the important biomechanical results of Montgomery et al. [31], who showed that Classic graft fixation is stiffer than a Congruent arc graft. Additionally, they found that the attachment area is larger than in Congruent arc grafts, which may influence postoperative healing rates. Therefore, we agree with other study groups [30,31] and conclude that the graft position should be decided on a case-to-case-basis, after consideration of all the pros and cons, with the important ancillary suggestion to determine both the amount of glenoid bone loss and coracoid dimensions in the preoperative planning stage to ensure the full anatomical reconstruction of the glenoid cavity width. This seems to become important in defects involving more than 20% of the glenoid width, as our results show that the feasibility of anatomical reconstruction of the glenoid width using Classic Latarjet grafts declines from 86% in a 25% bone loss scenario, to 40% in a 30% bone loss scenario. Of course, large defects are rarely seen. Anyway, a study has shown that patients with an inverted pear shape of the glenoid cavity had a mean loss of width of 36% (25%–45%) [3]. There are several limitations in our study. Firstly, it is an anatomical investigation, which can never exactly replicate intraoperative realities. Secondly, we randomly assigned the scapulae into the two groups. At the end we had slightly more female scapulae in the Classic group (13/22) compared with the Congruent arc group (9/26). However, the dimensions of the coracoid process and the glenoid cavity width were similar in both groups. Thirdly, the sling effect provides additional stability, which has not been incorporated in this anatomic study. However, our emphasis was to find a threshold for a more accurate anatomic bony reconstruction of the glenoid width, which may influence residual instability in terms of subluxations or recurrent dislocations following Latarjet procedures. The strength of this study is that there was a strong positive correlation of the interrater measurements concerning all relevant data. Furthermore, we included a larger number of scapulae, and considered changes of graft dimensions after preparation.

5. Conclusions We conclude that defects within the anterior segment of the glenoid cavity of at least 35% should be generally treated with Congruent arc Latarjet or other bone augmentation techniques. Defects lower than 20% of the glenoid width could be treated with the Classic Latarjet procedure without considering the potential amount of coracoid harvest in the preoperative setting. If bone loss of the glenoid cavity makes up between 20% and 35% of the original width, we would decide on the coracoid graft position based upon the dimensions of the coracoid process or, generally, use the Congruent arc Latarjet.

Author Contributions: Conceptualization, M.G.; Methodology, M.G., C.G., M.P.; Software, M.G., C.G.; Validation, M.G., L.E., C.G.; Formal analysis, M.G., L.E., C.G., M.P.; Investigation, M.G., L.E.; Resources, S.H., M.P.; data curation, M.G., L.E.; Writing—Original draft preparation, M.G.; Writing—Review and editing, S.H., M.P.; Visualization, M.G., C.G., M.P.; Supervision, M.P.; Project administration, M.G. All authors have read and agreed to the published version of the manuscript. Acknowledgments: Screws, which were used for graft preparation, were provided by DePuy Synthes, Vienna, Austria GmbH. The authors did not receive payments. Special thanks to Theresia Steinkellner, who performed the schematic illustrations of the Latarjet procedure. Conﬂicts of Interest: The authors declare no conﬂict of interest.

References

1. Sugaya, H.; Moriishi, J.; Dohi, M.; Kon, Y.; Tsuchiya, A. Glenoid rim morphology in recurrent anterior glenohumeral instability. J. Bone Jt. Surg. Am. 2003, 85, 878–884. [CrossRef][PubMed] 2. Edwards, T.B.; Boulahia, A.; Walch, G. Radiographic analysis of bone defects in chronic anterior shoulder instability. Arthroscopy 2003, 19, 732–739. [CrossRef] J. Clin. Med. 2020, 9, 207 8 of 9

3. Lo, I.K.; Parten, P.M.; Burkhart, S.S. The inverted pear glenoid: An indicator of significant glenoid bone loss. Arthroscopy 2004, 20, 169–174. [CrossRef][PubMed] 4. Burkhart, S.S.; De Beer, J.F.; Barth, J.R.; Cresswell, T.; Roberts, C.; Richards, D.P. Results of modified Latarjet reconstruction in patients with anteroinferior instability and significant bone loss. Arthroscopy 2007, 23, 1033–1041. [CrossRef][PubMed] 5. Boileau, P.; Villalba, M.; Héry, J.Y.; Balg, F.; Ahrens, P.; Neyton, L. Risk factors for recurrence of shoulder instability after arthroscopic Bankart repair. J. Bone Jt. Surg. Am. 2006, 88, 1755–1763. [CrossRef] 6. Shaha, S.; Cook, J.B.; Song, D.J.; Rowles, D.J.; Bottoni, C.R.; Shaha, S.H.; Tokish, J.M. Redefining “Critical” Bone Loss in Shoulder Instability: Functional Outcomes Worsen With “Subcritical” Bone Loss. Am. J. Sports Med. 2015, 43, 1719–1725. [CrossRef][PubMed] 7. Beran, M.C.; Donaldson, C.T.; Bishop, J.Y. Treatment of chronic glenoid defects in the setting of recurrent anterior shoulder instability: A systematic review. J. Shoulder Elbow Surg. 2010, 19, 769–780. [CrossRef] 8. Bigliani, L.U.; Newton, P.M.; Steinmann, S.P.; Connor, P.M.; Mcllveen, S.J. Glenoid rim lesions associated with recurrent anterior dislocation of the shoulder. Am. J. Sports Med. 1998, 26, 41–45. [CrossRef] 9. Yamamoto, N.; Itoi, E.; Abe, H.; Kikuchi, K.; Seki, N.; Minagawa, H.; Tuoheti, Y. Effect of an anterior glenoid defect on anterior shoulder stability: A cadaveric study. Am. J. Sports Med. 2009, 37, 949–954. [CrossRef] 10. Provencher, M.T.; Bhatia, S.; Ghodadra, N.S.; Grumet, R.C.; Bach, B.R., Jr.; Dewing, C.B.; LeClere, L.; Romeo, A.A. Recurrent shoulder instability: Current concepts for evaluation and management of glenoid bone loss. J. Bone Jt. Surg. Am. 2010, 92 (Suppl. 2), 133–151. [CrossRef] 11. Armitage, M.S.; Elkinson, I.; Giles, J.W.; Athwal, G.S. An anatomic, computed tomographic assessment of the coracoid process with special reference to the congruent-arc latarjet procedure. Arthroscopy 2011, 27, 1485–1489. [CrossRef][PubMed] 12. Bhatia, S.; Van Thiel, G.S.; Gupta, D.; Ghodadra, N.; Cole, B.J.; Bach, B.R., Jr.; Shewman, E.; Wang, V.M.; Romeo, A.A.; Verma, N.N.; et al. Comparison of glenohumeral contact pressures and contact areas after glenoid reconstruction with latarjet or distal tibial osteochondral allografts. Am. J. Sports Med. 2013, 41, 1900–1908. [CrossRef][PubMed] 13. Warner, J.J.; Gill, T.J.; O’Hollerhan, J.D.; Pathare, N.; Millett, P.J. Anatomical glenoid reconstruction for recurrent anterior glenohumeral instability with glenoid deficiency using an autogenous tricortical iliac crest bone graft. Am. J. Sports Med. 2006, 34, 205–212. [CrossRef][PubMed] 14. Patte, D.; Bernageau, J.; Bancel, P. The anteroinferior vulnerable point of the glenoid rim. In Surgery of the Shoulder; Bateman, J.E., Welsh, R.P., Eds.; Marcel Dekker: New York, NY, USA, 1985; pp. 94–99. 15. Giles, J.W.; Boons, H.W.; Elkinson, I.; Faber, K.J.; Ferreira, L.M.; Johnson, J.A.; Athwal, G.S. Does the dynamic sling effect of the Latarjet procedure improve shoulder stability? A biomechanical evaluation. J. Shoulder Elbow Surg. 2013, 22, 821–827. [CrossRef] 16. Wellmann, M.; Petersen, W.; Zantop, T.; Herbort, M.; Kobbe, P.; Raschke, M.J.; Hurschler, C. Open shoulder repair of osseous glenoid defects: Biomechanical effectiveness of the Latarjet procedure versus a contoured structural bone graft. Am. J. Sports Med. 2009, 37, 87–94. [CrossRef] 17. Latarjet, M. Treatment of recurrent dislocation of the shoulder. Lyon Chir. 1954, 49, 994–999. 18. Allain, J.; Goutallier, D.; Glorion, C. Long-term results of the Latarjet procedure for the treatment of anterior instability of the shoulder. J. Bone Jt. Surg. Am. 1998, 80, 841–852. [CrossRef] 19. Shah, A.A.; Butler, R.B.; Romanowski, J.; Goel, D.; Karadagli, D.; Warner, J.J. Short-term complications of the Latarjet procedure. J. Bone Jt. Surg. Am. 2012, 94, 495–501. [CrossRef] 20. Moon, S.C.; Cho, N.S.; Rhee, Y.G. Quantitative assessment of the latarjet procedure for large glenoid defects by computed tomography: A coracoid graft can sufficiently restore the glenoid arc. Am. J. Sports Med. 2015, 43, 1099–1107. [CrossRef] 21. Schmid, S.L.; Farshad, M.; Catanzaro, S.; Gerber, C. The Latarjet procedure for the treatment of recurrence of anterior instability of the shoulder after operative repair: A retrospective case series of forty-nine consecutive patients. J. Bone Jt. Surg. Am. 2012, 94, e75. [CrossRef] 22. Young, A.A.; Maia, R.; Berhouet, J.; Walch, G. Open Latarjet procedure for management of bone loss in anterior instability of the glenohumeral joint. J. Shoulder Elbow Surg. 2011, 20 (Suppl. 2), S61–S69. [CrossRef] [PubMed] J. Clin. Med. 2020, 9, 207 9 of 9

23. Bhatia, S.; Frank, R.M.; Ghodadra, N.S.; Hsu, A.R.; Romeo, A.A.; Bach, B.R., Jr.; Boileau, P.; Provencher, M.T. The outcomes and surgical techniques of the Latarjet procedure. Arthroscopy 2014, 30, 227–235. [CrossRef] [PubMed] 24. Gordins, V.; Hovelius, L.; Sandström, B.; Rahme, H.; Bergström, U. Risk of arthropathy after the Bristow-Latarjet repair: A radiologic and clinical thirty-three to thirty-five years of follow-up of thirty-one shoulders. J. Shoulder Elbow Surg. 2015, 24, 691–699. [CrossRef][PubMed] 25. Lafosse, L.; Boyle, S.; Gutierrez-Aramberri, M.; Shah, A.; Meller, R. Arthroscopic latarjet procedure. Orthop. Clin. N. Am. 2010, 41, 393–405. [CrossRef] 26. Young, A.A.; Baba, M.; Neyton, L.; Godeneche, A.; Walch, G. Coracoid graft dimensions after harvesting for the open Latarjet procedure. J. Shoulder Elbow Surg. 2013, 22, 485–488. [CrossRef] 27. Bachy, M.; Lapner, P.L.; Goutallier, D.; Allain, J.; Hernigou, P.; Bénichou, J.; Zilber, S. Coracoid process x-ray investigation before Latarjet procedure: A radioanatomic study. J. Shoulder Elbow Surg. 2013, 22, e10–e14. [CrossRef] 28. De Beer, J.; Burkhart, S.S.; Roberts, C.P.; van Rooyen, K.; Cresswell, T.; du Toit, D.F. The Congruent-Arc Latarjet. Tech. Shoulder Elbow Surg. 2009, 10, 62–67. [CrossRef] 29. De Beer, J.F.; Roberts, C. Glenoid bone defects: Open Latarjet with congruent arc modification. Orthop. Clin. N. Am. 2010, 41, 407–415. [CrossRef] 30. Boons, H.W.; Giles, J.W.; Elkinson, I.; Johnson, J.A.; Athwal, G.S. Classic versus congruent coracoid positioning during the Latarjet procedure: An in vitro biomechanical comparison. Arthroscopy 2013, 29, 309–316. [CrossRef] 31. Montgomery, S.R.; Katthagen, J.C.; Mikula, J.D.; Marchetti, D.C.; Tahal, D.S.; Dornan, G.J.; Dahl, K.D.; Brady, A.W.; Turnbull, T.L.; Millett, P.J. Anatomic and Biomechanical Comparison of the Classic and Congruent-Arc Techniques of the Latarjet Procedure. Am. J. Sports Med. 2017, 45, 1252–1260. [CrossRef] 32. Hantes, M.E.; Venouziou, A.; Bargiotas, K.A.; Metafratzi, Z.; Karantanas, A.; Malizos, K.N. Repair of an anteroinferior glenoid defect by the latarjet procedure: Quantitative assessment of the repair by computed tomography. Arthroscopy 2010, 26, 1021–1026. [CrossRef] 33. Dolan, C.M.; Hariri, S.; Hart, N.D.; McAdams, T.R. An anatomic study of the coracoid process as it relates to bone transfer procedures. J. Shoulder Elbow Surg. 2011, 20, 497–501. [CrossRef] 34. Bueno, R.S.; Ikemoto, R.Y.; Nascimento, L.G.; Almeida, L.H.; Strose, E.; Murachovsky, J. Correlation of coracoid thickness and glenoid width: An anatomic morphometric analysis. Am. J. Sports Med. 2012, 40, 1664–1667. [CrossRef][PubMed] 35. Salzmann, G.M.; Paul, J.; Sandmann, G.H.; Imhoff, A.B.; Schöttle, P.B. The coracoidal insertion of the coracoclavicular ligaments: An anatomic study. Am. J. Sports Med. 2008, 36, 2392–2397. [CrossRef][PubMed] 36. Burkhart, S.S.; De Beer, J.F. Traumatic glenohumeral bone defects and their relationship to failure of arthroscopic Bankart repairs: Significance of the inverted-pear glenoid and the humeral engaging Hill-Sachs lesion. Arthroscopy 2000, 16, 677–694. [CrossRef] 37. Kraus, T.M.; Martetschläger, F.; Graveleau, N.; Klouche, S.; Freude, T.; Stöckle, U.; Hardy, P. CT-based quantitative assessment of the surface size and en-face position of the coracoid block post-Latarjet procedure. Arch. Orthop. Trauma Surg. 2013, 133, 1543–1548. [CrossRef] 38. Ji, J.H.; Kwak, D.S.; Yang, P.S.; Kwon, M.J.; Han, S.H.; Jeong, J.J. Comparisons of glenoid bony defects between normal cadaveric specimens and patients with recurrent shoulder dislocation: An anatomic study. J. Shoulder Elbow Surg. 2012, 21, 822–827. [CrossRef] 39. Saito, H.; Itoi, E.; Sugaya, H.; Minagawa, H.; Yamamoto, N.; Tuoheti, Y. Location of the glenoid defect in shoulders with recurrent anterior dislocation. Am. J. Sports Med. 2005, 33, 889–893. [CrossRef] 40. Ghodadra, N.; Gupta, A.; Romeo, A.A.; Bach, B.R., Jr.; Verma, N.; Shewman, E.; Goldstein, J.; Provencher, M.T. Normalization of glenohumeral articular contact pressures after Latarjet or iliac crest bone-grafting. J. Bone Jt. Surg. Am. 2010, 92, 1478–1489. [CrossRef]

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