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Evaluation of glenoid bone loss.

In recent years, we have witnessed increased interest in bony lesion of the glenoid rim as acute factor (bony Bankart) and as a chronic bone defect in instability. This interest derives from three main clinical and statistical finding: a significant incidence of bony Bankart lesion after a first dislocation, a high percentage of glenoid bone defects in chronic instability, and, finally, a close relationship between bone defect and incidence of recurrence after arthroscopic stabilization.

We are in fact agree on determining glenoid bone defect that exeeds 15 - 20% as the main contraindication to arthroscopic stabilization.

Despite the importance of determining, localizing and measuring the glenoid bone lesion, at present, the literature does not report simple and accurate methods capable of providing such important data when it comes to choosing between arthroscopy or open surgery with bone graft.

It is the purpose of our study to describe a simple and accurate CT method in determining and calculating glenoid bone defect in term of an area (expressed in mm 2) or in term of surface percentage.

Material and Method

A Philips MX 800 Spiral Double Slice CT available at the Radiology Service at the Mirandola Hospital in Modena was used. In order to test the method the right and left shoulders of 20 patients who had undergone lun CT for others reason were analyzed. The patients were submitted to CT of the glenoid using the "Pico" method (named for the philosopher Pico della Mirandola). In the study were included:

- patients who were on a waiting list for antero-inferior post traumatic instability, true multidirectional instability, posterior instability.

- patients who had come to our emergency service to treat acute dislocation (first episode and recurrent).

It is the purpose of this study to simply describe the CT method capable of providing and calculation of the amount of bone defect in terms of surface area and surface percentage.( 17)

A future publication will report in detail the results relative to these five groups of patients and when the number of patients submitted to surgery is sufficient from a statistical point of view, we will able to correlate our findings with arthroscopic result.

Pico method includes a comparative study of shoulders by spiral double slice CT based on 3 indispensable parameters:

  1. filter for bone

  2. 1.3 slice thickness

  3. Advancement of sliced every 0.6 mm.

Images thus obtained are then processed in MPR (Multi Planar Reconstruction) shifting the axes with which we work parallel to the glenoid on three planes:

In this way we obtain a frontal image of the entire glena as photographed anatomical specimen.

Neither 3D reconstructions for subtractions of images were required.

On the frontal images of the healthy glenoid (en face view) we draw a circumferential area centered on the lower half from 3 to 9 o'clock, using a common system of dawing and measuring (linear and area) present in the machine software and thus obtaining the area for the glenoid.

The same circumferential area is drawn on the glenoid with deficit, and we then trace the outline of any bony Bankart bone fragment or of the bone defect, thus obtaining the area of the glenoid defect.

Finally, we use a simple equation to calculate the percentage of the glenoid defect (normal glenoid area:100=area of glenoid defect:X).

This method was used to study 16 patients post-trauma:

4 dislocations and 12 recurrences of glenohumeral dislocation and 4 bony Bankart (1 in first dislocation and 3 in recurrences) with a mean size of 60 mm 2 and mean incidence of 11%. In the group of patients awaiting stabilization (24 post trauma, 3 MDI and 3 posterior) the following was observed:

1) bony defect exceeding 20% in 3 patients, requiring a switch of treatment from arthroscopic to a open coracoid transfert (Latarjet procedure)

2) a glenoid defect between 10% and 20% in 12 patients in whom arthroscopic indications had been maintained

3) a glenoid defect that did not exeed 10% in 6 patients

4) no bone deficit in 9 patients.

Of the 21 glenoids present in 30 patients in the waiting list, 4 were bony Bankart.

Discussion

Glenoid bone defect and recurrence after stabilization surgery has been reported by several authors. In 1961, Rowe reported an incidence of recurrent dislocation that rose from 6 to 62% if glena bone defect was present.

In 2000, Burkhart and De Beer analyzed 194 patients operated by the two authors using the same method ( suture anchor technique), and selected 21 recurrences, of which 11 with significant glenoid defect.

The incidence of recurrence in the group without deficit was 4%, while in the group with bone defect it rose to 67%, particularly if patients did contact sport. The glenoid with bone defect was defined as an inverted pear because of it resemblance to a pear rotated 180°.

Tauber and Resh reviewed 41 patients who had had recurrence of instability and identified a bone deficit of the glenoid rim in 56% of cases, capsular injury in 27%, and recurrence of Bankart in 17.

In 2003 , Lim presented a study conducted on 20 patients with glenoid defect and 20 patients without bone deficit who had undergone open surgery involving Bankart capsule-ligament reinsertion, and observed a significant deficit in rotation and a 5% incidence of recurrence (vs 0%) in patients with bone defect. Once the relationship between recurrence and bone defect has been established, it is necessary from an anatomopathologic and radiologic point of view to classify the lesion of the glena.

In 1998, Bigliani was the first to coin the term bony Bankart indicating the presence in cases of instability of an anteroinferior bone fragment with preserved insertion of the inferior glenohumeral ligament (Bigliani type 1).

He also determined a type 2 in which the fragment had poorly consolidated and the relationship with the pad -ligament complex was no longer recognizable; finally, he introduce the concept of glenoid bone defect classifying an erosion that was less than 25% ( type 3 ) and one that was greater than 25% ( type 3B ) of the total glenoid surface . In such cases he believed vthat it was necessary to proceed with bone graft .

Walch classified glenoid bone loss in 3 forms after radiologic examination ( x ray in AP and Bernangeau ) : bony bankart ,that is , fracture with fragment that is still visible , bone loss with loss of antero-inferior angle without visible fragment ( cliff sign ) , bone loss with rounding -compression of glenoid rima ( blunted angle )

It is important to establish the frequency of bone defect in acute glenohumeral dislocation ( first episode ) and in chronic instability

In 1999 , Ssaragaglia demostrated a 20% incidence of glenoid bony lesion on simple x - RAY examination in AP in acute dislocations ( first episode ) wich had been observed in emergency room .

Walch (6) reports a 90% of glenoid bone lesion in 160 chronic unstable shoulder diagnosed by radiologic examination alone ( AP and Bernangeau profile ) . Griffith (7) demostrates the presence of anteroinferior bone defects of the glena in 90% of shoulders affected with instability as compared to 4% in healthy controlateral shoulders .

Sugaya (8) studied 100 instable shoulders by CT in 3D and monitored arthroscopically , to determine only 10% normal shoulders , 40% erosion - compression of the glenoid rima and 50% bony-bankarts .

Thus, over the years , we have come to observe the considerable frequency of glenoid bone defect in the form of bony-bankart and in erosion of the antero-inferior glenoid border , as the need to diagnose it , measure it and express the critical entity of the bone defect in addition to planning bone graft surgery .

In his experimental study , Itoi ( 9,10 ) stated that 21% was the statistically significant threshold beyond which stability was critical and loss of external rotation was excessive , and showed how this amount of bone defect corresponded to a deficit of 18% in the West Point X-ray examination and to a loss of 50% of glenoid depth on CT slice through the lower ¼ .

Burkhart ( 11) in 2002 and in 2004 (12) attempted to determine the entity of glenoid bone loss than can create an inverted pear and illustrated an arthroscopic method used to identify bone defect in 6 anatomical specimens and 53 patients operated on . The author believes that in normal glenoids the glenoid bare spot , that is the central area of the glenoid partially deprived of cartilage and nearly equidistant from the anterior ,posterior and inferior glenoid margin ( 11,7 +/- 0,9 ) . In 11 patients with the inverted pear image anterior defect was 8,6 mm +/- 2,2 mm corresponding to a mean loss of 36% of depth of the inferior glena and concluded that by using the bare spot and a graduated posterior palpator the bone defect can accurately be observed during surgery .

But none of radiologic methods proposed by Itoi and Walch is accurate , sensitive ,specific and easily reproducible . On the other hand , it is not logical to determine and calculated this bone defect only at the time of arthroscopic examination , so that problem to solve is that of determining an accurate preoperative method of measuring the glenoid bone lesion which is as sensitive , specific and simple as possible .

The meritof having found the correct path in this difficult job goes to Sugaya ( 8) who , in 2003 , proposed and applied in 100 shoulders a method of study of the glenoid morphology using CT scan in 3D with subtraction of the humerus , capable of identifying and calculating any bony Bankart fragment and any bone defect expressed by percentage of surface .

This method tested on normal ,unstable and cadaver shoulders showed how the lower half of the glena is always half of a circumference whose diameter is a line that goes from 3 to 9 o'clock . Tridimensional CT is performed on both shoulders and the humeral head is subtracted so that we can visualize a sagittal image ( en face view ) . At this point we trace on the normal contralateral glena a circumference with a diametewr that goes from 3 to 9 o'clock following the inferior profile of the glena ,and the software immediately calculates the surface area for the normal glena .

The same procedure is repeated on the unstable shoulder tracing on the glenoid profile the normal glenoid circumference (that is equal, to the controlateral one); thus, the detached bone fragment or area of bone defect is outlined.

This method of using a CT has been commented on by Willems who monitored 40 cadaver scapulas all submitted to digital photography, CT and MRI in 3D and showed how all af the glenas could be inserted in a circumference with an equator passingthrough the bare spot from 3 to 9 o'clock. Furthermore, this produced a defect equal to 5 to 39% in 14 glena, and made it possible to measure it accurately by CT scan.

Further confirmation of the glenoid morphology comes from De Wilde who photographed and used CT to study96 cadaverscapulas demonstrating that is possible to observe 11 points on the inferior profile of the glena sufficient from a statistical point of view and to define a circumference with a mean diameter 25.8 mm.

Finally, both De Wilde and Aigner recently showed how the glenoid bare spot was always eccentric (mean 3.2 mm) as compared to real glenoid center, thus disproving the arthroscopic method of evaluation proposed by Burkhart.

The originality of our "Pico" method as compared to that proposed by Sugaya resides in its simplicity and rapidity of execution (3D reconstruction is not required nor is subsequent humeral subtraction) and in the possibility of elaborating in MPR images in CT (as long as they are obtained with 3 parameters illustrated in materials and methods) carried out elsewhere. Which consequences on our decision could the application of this method have on the preoperative study of glenoid morphology?.

If, for example, we identify a Bony Bankart after dislocation and we measure it accurately, we can decide between arthroscopic stabilization or open surgery.

If the size of the fragment is less than 25% arthroscopic stabilization with fixation of the Bony Bankart by mini screws placed on residual glenoid border and non-resorbable wires encompassing the bone fragment and the inferior glenohumeral ligament inserted thereim.

If the value is higher we can perform open stabilization. Porcellini et all reports 25 cases of Bony Bankart measuring not more than 25%, no longer than 3 to 6 months after first trauma treated by arthroscopic synthesis with a 90% incidence of excellent results at follow-up obtained after 2 years.

If glenoid bone loss is present and this is defined preoperatively, open or arthroscopic bone graft or coracoid transposition surgery may be indicated.

Prospective and retrospective studies reveal the value beyond which there is excessive loss of extrarotation due to medialization of capsuloligamentous apparatus and the value of bone defect beyond which the risk of recurrence increase sensitively.

In case of recurrence after stabilization it will be possible to know whether or not it is due to bone defect (and not to errors in technique or tissue collapse).

Thus, we believe that the determination and exact calculation of glenoid bone defect preoperatively is an essential stage for the correct surgical approach to glenohumeral instability and in order to define the limits of arthroscopic treatment. We believe that the "Pico" method in CT is a simple, accurate, sensitive and specific one to determine and measure glenoid bone defect and with integration of contrast medium (arthro-CT) it could become a complete examination for instability.

Bibliography

( 1 ) Rowe CR Factors related to recurrences of anterior dislocation of the shoulder Clin Orthop 1961 ; 20: 40-48

( 2) Burkhart SS De Beer JF 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 Oct; 16(7) : 677-694

( 3 ) Tauber M Resch H Reason for failure after surgical repair of anterior shoulder instability JSES 2004 Vol13 (4)

( 4 ) Lim CT Rhee YG SECEC 2003 Abstract Book Oral 7 : shoulder instability pp119

(5) Bigliani LU Glenoid rim associated with recurrent anterior dislocation of shoulder Am.J.Sports Med. 1998 ;

26 : 41-45

(6) Walch G Edwards TB Boulahia A Radiographic analysis of bone defects in chronic anterior shoulder instability

Arthroscopy 2003 Sep; 19(7):723-9

(7) Griffith JF Anterior shoulder dislocation : quantification of glenoid bone with CT Am J Roentgenol 2003 May;

180(5):1423-30

(8 ) Sugaya H Tsuchiya A Glenoid rim Morphology in recurrent anterior glenoumeral instability J BJS Am 2003

May; 85-A(5) :878-84

( 9 ) Itoi E The effect of a glenoid defect on anteroinferior stability of the shoulder after Bankart repair : a cadaveric

study JBJS Am 2000 Jan ; 82 (1) 35-46

( 10 ) Itoi E Quantitative asssessment of classic bony Bankart lesion by radiography and tomography Am J Sports Med

2003 Jan-Feb;31(1) 112-8

(11) Burkhart SS De Beer Jf Quantifying glenoid bone loss arthroscopically in shoulder instability Arthroscopy 2002

May-jun ;18(5):488-91

(12) Burkhart ss Lo IK The inverted pear glenoid: an indicator of significant glenoid bone loss Arthroscopy 2004 Feb;

20(2) : 169-174

(13) Willems WJ Huysmans PE Quantification of a glenoid defect with 3D TC 3D RMN : a cadaveric study SECEC

2003 Abstract book Oral 7 : shoulder instability pp 118

(14)De Wilde LF et Al About the variability of the shape of the glenoid cavity Surg Rad Anat 2004 26 : 54-59

( 15 ) Aigner F et Al Anatomical consideration regarding the bare spot of glenoid cavity Surg Rad Anat 2004 26:308-

311

( 16 )Porcellini G Campi F Paladini P Arthroscpic approach to acute bony Bankart lesion Arthroscopy 2002 ;18: 746-9

  1. Baudi P., Righi, D.Bolognesi ,S.Rivetta ,E.Rossi Urtoler , N.Guicciardi * ; M Carrara * How to Identify and calculate Glenoid Bone defect Chir.Organi Mov XC 145-152 ,2005

PICTURES

CT with layers of 1,3 mm thickness and  0,6 mm of space advanced with CT Spirale Double Slice

FIG 1 CT with layers of 1,3 mm thickness and 0,6 mm of space advanced with CT Spirale Doule Slice

Elaboration in MPR with parallel axis at the glena

Fig. 2 Elaboration in MPR with parallel axis at the glena

 NORMAL Circumferential glenoid area in mm2 . The " PICO " method

Fig. 3 NORMAL Circumferential glenoid area in mm2 . The "PICO" method

Circumference  “pathological glena “ and evidence of glenoid bone defect (in mm2).Definition and linear evaluation of glenoid radius.

Fig. 4 Circumference "pathological glena " and evidence of glenoid bone defect (in 2 mm.)

Definition and linear evaluation of glenoid radius.

Identification and evaluation of Bony Bankart Bony-Bankart (" PICO" method)

Fig. 5 Identification and evaluation of Bony Bankart Bony-Bankart ("PICO" method)

" PICO" evaluation of recurrence after arthroscopic stabilization

Fig. 6 "PICO" evaluation of recurrence after arthroscopic stabilization

Case 1.

In Standard X-Ray no bone deficit

1) In Standard X-Ray no bone deficit ;

in MRI little bone deficit antero-inferior in glena;

2) in MRI little bone deficit antero-inferior in glena;

Arthroscopic evaluation is unable to identified a really % of defect ( in minimal sense);

3) Arthroscopic evaluation is unable to identified a really % of defect ( in minimal sense);

Pico method is able to predict a really and exactly % of pre op defect.( 17 %)

4) Pico method is able to predict a really and exactly % of pre op defect. (17 %)

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