Educational Exhibit Authors: S. A. FARUQUI, Y. J. Lee, S. Sciacca, B. Annan, P. Brooks ; 1

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1 Multi-detector CT (MDCT) of the gleno-humeral joint for pre-operative assesssment of reverse total shoulder arthroplasty (RTSA) : what a surgeon needs to know? Poster No.: C-1706 Congress: ECR 2016 Type: Educational Exhibit Authors: S. A. FARUQUI, Y. J. Lee, S. Sciacca, B. Annan, P. Brooks ; STEVENAGE, HERTFORDSHIRE/UK, London/UK, 8RT/UK, 3 4 Stevenage/UK Keywords: Prostheses, Structured reporting, Computer Applications-3D, Image manipulation / Reconstruction, CT, Musculoskeletal joint DOI: /ecr2016/C-1706 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 27

2 Learning objectives Illustrate the anatomical details offered by a multidetector computerised tomography (MDCT) study of the glenohumeral joint and the advantages of its multiplanar and 3D reconstruction capability. Familiarise the reader with the indications and mechanics of reverse total shoulder arthroplasty (RTSA). Highlight through illustration the role of MDCT in pre-operative assessment of the shoulder joint and planning of RTSA thus contributing in good postoperative outcome. Page 2 of 27

3 Background MDCT: Multidetector CT (MDCT) uses multiple row of detectors (currently up to 128) to acquire multiple thin contiguous slices which provides multiplanar reformatting. Fig. 1: MDCT - Multiplanar reformats and 3D reconstruction. References: RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK The acquired slices can also be rendered into 3D images which can be rotated and viewed in desired positions (Fig.1) The Shoulder Joint: Page 3 of 27

4 The gleno-humeral joint is the most mobile joint in the body. This wide range of motion also makes the shoulder joint unstable, an instability compensated for by rotator cuff muscles, tendons, ligaments and the glenoid labrum. Shoulder Replacement: Shoulder arthroplasty is the replacement of one (hemi-arthroplasty) (Fig.2) or both (total arthroplasty) (Fig. 3,4,5) of the articular surfaces that comprise the gleno-humeral joint. Total shoulder arthroplasty (TSA), is a successful and popular procedure for treating severe pain and stiffness which are often an end stage result of degenerative or inflammatory arthritis. Shoulder arthroplasty primarily aims at pain relief but has secondary benefit of restoring joint function. Reverse shoulder arthroplasty (RTSA): A conventional shoulder replacement surgery mimics the normal anatomy of the shoulder i.e. a plastic "cup/socket " is fitted into the glenoid, and a metal "ball" is attached to the top of the decapitated humerus. In RTSA this ball and socket arrangement is reversed (Fig. 4,5) and the prosthetic components used are: Convex glenoid (hemispheric ball) Concave humerus (articulating cup). Biomechanics of RTSA : Contrary to the normal shoulder and conventional total shoulder arthroplasty where the joint movements are dependent on preserved rotator-cuff muscle function (Fig. 6), RTSA is used in rotator-cuff deficient shoulders and the deltoid is used to its best mechanical advantage. The arrangement provides (Fig.7 ): (1) medialized centre of rotation at the glenosphere (stable fulcrum)- this reduces torque and shearing forces on the glenoid component, thus reducing the risk of loosening. (2) medialized and lowered humerus - lengthens the deltoid and keeps it in tension - which in turn pushes the humerus socket against the glenosphere thereby not only keeping it stable but also improving elevation and abduction. Page 4 of 27

5 Clinical conditions for RTSA/Indications: Rotator cuff tear. Pseudoparalysis inability to actively elevate the arm in the presence of free passive ROM and in the absence of a neurological cause. Typically occurs secondary to irreparable rotator cuff tear in setting of glenohumeral arthritis. Acute 3 or 4-part proximal humerus fractures in the elderly. Rotator cuff insufficiency/'equivalent' - non-union or mal-union of the greater tuberosity following trauma or prior arthroplasty. Failed arthroplasty. Rheumatoid arthritis -only if glenoid bone stock is sufficient and axillary nerve is intact. Patient characteristics for RTSA selection: Low functional demand patients. Physiological age >70 years. Rotator -cuff arthropathy. Sufficient glenoid bone stock. Working deltoid muscle - intact axillary nerve. Contraindications : Deltoid deficiency (axillary nerve palsy) Page 5 of 27

6 Glenoid osteoporosis Active infection Page 6 of 27

7 Images for this section: Fig. 2: Hemiarthroplasty, resurfacing of the humeral component (blue arrow). RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 7 of 27

8 Fig. 3: Conventional total shoulder arthroplasty (TSA)using both humeral(blue arrow)and glenoid (red arrow)components. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 8 of 27

9 Fig. 4: Reverse total shoulder arthroplasty (RTSA).Humeral component (blue arrow)is a socket and glenoid component (red arrow)is a ball, thus reversing the normal anatomical configuration. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 9 of 27

10 Fig. 5: RTSA prostheses components- G-Glenoid component(glenosphere)'ball'. HHumeral component 'socket'. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 10 of 27

11 Fig. 6: Normal Shoulder Biomechanics- The lever arm (blue line) of the deltoid muscle (red line)is small. But normal rotator cuff muscles help in abduction. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 11 of 27

12 Fig. 7: Biomechanics in RTSA: In a rotator cuff deficient shoulder after the implantation of the RTSA prosthesis. The centre of rotation is shifted medially(green dot)which increases the lever arm (blue line) of the deltoid(red line),secondly there is also distal positioning of the humeral prosthesis, these two features help the deltoid in facilitating the elevation of the arm. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 12 of 27

13 Findings and procedure details The added value of MDCT in pre-operative assessment of RTSA Positioning of the glenosphere on the glenoid is crucial to the success and longevity of RTSA. Hence, pre-operative assessment of glenoid morphology (version) and glenoid bone stock is paramount in planning intra-operative glenoid reaming, correction of retroversion and sizing of the glenoid component (glenosphere). MDCT also provides information about : Humeral shaft diameter for humeral stem. Status of the rotator cuff tendons, deltoid and teres minor muscles. Presence of intra-articular loose bodies. 1. Glenoid Version: The relationship of the glenoid cavity with the humeral head is termed 'Glenoid version', this angle is an important two-dimensional representation of the complex threedimensional shape of the scapula. Prior to MDCT, glenoid version was measured on axillary radiographs although this has been shown to be ineffective in assessing the glenoid. Why is version important? Glenoid version is of interest in understanding normal shoulder biomechanics and pathological conditions inclusive of instability, arthritis, and developmental dysplasia. [2] Variance from normal version alters gleno-humeral mechanics and may predispose to instability and arthropathy. In the prosthetic shoulder, deviation from the native version has been shown to increase stress and wear of the glenoid component. [1], [3]. Studies have shown that failure to correct glenoid retroversion predisposes to joint instability, posterior subluxation, and glenoid component loosening due to abnormal forces across the implant and cement-bone interfaces [4]. It is recommended that surgeons either graft the erosions or ream the glenoid in an attempt to align the glenoid prosthesis perpendicular to the scapular axis. Page 13 of 27

14 a) Measurement of glenoid version (2D CT): Friedman et al. [5] calculated the glenoid version angle on an axial 2D CT slice selected just below the level of the tip of the coracoid level. (Fig, 8,9 ) Glenoid version angle is defined as the angle between the glenoid line and the line perpendicular to the scapular axis. (Fig.8) A]Glenoid line- (Blue) line connecting the anterior and posterior rim of the glenoid. B]Scapular axis-(green) line joining the medial most border of the scapular spine and the centre of the glenoid. C]Line perpendicular to the scapular axis (Dotted red) Therefore glenoid version angle = angle formed by line A and line C. Normal glenoid version in most studies [4] has been reported close to 0, sometimes with slight anteversion but more often slight retroversion with values typically less than 10 in either direction. Role of 3D CT in glenoid version- (2D CT vs 3D CT): Friedman's method of calculation of glenoid version has been widely used by surgeons, however, with the advent of 3D CT there have been efforts to improvise the angle calculation by using the multidimensional reformation capability of the new CT scanners thus ignoring the errors due to the position of the shoulder in the CT scanner. The axial 2D CT version measurements depend on the relation of the plane of the scapula to the axis of the CT scanner. It has been shown that every 1 of abduction of the scapula increases the value of glenoid anteversion by a mean of 0.42 [6]. Hoenecke et al showed 3D CT to be more accurate in detecting posterior glenoid erosion[7]. Another study showed greater than 5 difference in measurements of version between 2D CT and 3D CT images in nearly 50% of patients [8]. Version Measurement on 3D CT: Page 14 of 27

15 On 3D CT, a vertical line can be drawn on the 3D surface of the glenoid face, centered in the anteroposterior direction.(fig.10) A transverse 2D plane is then generated perpendicular to the midpoint of the vertical line passing through the scapular axis (center of glenoid and tip of scapular spine) to obtain an image for glenoid version angle measurement similar to the measurement by Friedman.[8]. (Fig.11) These findings have led to the prevailing recommendation to strive for normalization or neutralization of glenoid version during shoulder arthroplasty [9]. Glenoid Version - summary: These findings have led to the prevailing recommendation to strive for normalization or neutralization of glenoid version during shoulder arthroplasty [10] Error in measuring version and depth of maximum wear can substantially affect the determination of the degree of correction necessary in arthritic glenoids. Accurately measuring glenoid version and locating the direction of maximum wear requires a full 3DCT reconstruction and analysis [7]. Thus, 3D CT is suggested as the most accurate preoperative means of assessing glenoid version and morphology. b) Glenoid morphology in OA and dysplasia: In moderate to severe gleno-humeral osteoarthritis (GHOA), erosive changes and wear are usually greater in the posterior half of the glenoid articular surface, thus increasing glenoid retroversion [9] The Walch classification of glenoid morphology is best assessed on CT (Fig.8 ). Type A morphology is a centered humeral head (No subluxation) with (A1)- minor erosions or Page 15 of 27

16 (A2)- major erosions. Type B describes a posteriorly subluxed humeral head with (B1)-posterior joint space narrowing and osteophytes or (B2)-posterior rim erosions and glenoid retroversion (> 2 ). Type C is the most severe, with glenoid retroversion of more than 25. (regardless of erosion)- retroversion is primarily dysplastic in origin. Fig. 12: Walch Classification References: RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK In primary GHOA, classification of the glenoid can discriminate retroversion, posterior erosion and dysplasia [6] 2. Glenoid Bone Stock Page 16 of 27

17 Fixation of the glenoid component needs good amount of bone (bone stock) to provide a solid attachment for the anchoring screws. In severe OA changes, bone loss due to erosions and replacement of the bone by cysts may significantly reduce the glenoid bone mass. Pre-operative CT becomes of value in such conditions as bone graft may be required. The glenoid bone stock is measured by taking the maximum and minimum widths in a 3D axial image. (Fig. 14) or by calculating the maximum bone depth from the centre of the glenoid, these should not be less than 2cms.(Fig.15) Page 17 of 27

18 Images for this section: Fig. 8: Calculating glenoid version. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 18 of 27

19 Fig. 9: 2D calculation of glenoid version. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 19 of 27

20 Fig. 10: Glenoid angle using 3D: First marking the 3D plane and then selecting the plane of the horizontal line(red), then measuring at the corresponding site on 2D image (see the next image). RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 20 of 27

21 Fig. 11: Glenoid angle using 3D: First marking the 3D plane (see previous image) and then measuring at the corresponding site on 2D image. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 21 of 27

22 Fig. 13: Walch (A1) - Minor glenoid erosion at the posterior aspect. No subluxation. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 22 of 27

23 Fig. 14: Glenoid bone stock measurement. RADIOLOGY, EAST & NORTH NHS TRUST, LISTER - STEVENAGE/UK Page 23 of 27

24 Conclusion MDCT with 3D reconstruction is the most accurate pre-operative means of assessing glenoid morphology, version, osseous stock, subchondral changes and chronic rotator cuff abnormalities. The versatility of the RTSA has led to its increasing popularity, knowledge of pre-operative MDCT assessment of the glenohumeral joint prior to RTSA has hence become of prime importance to ensure positive surgical outcome. Page 24 of 27

25 Personal information Shakeel Ahmad Faruqui,MSK Fellow, Department of Radiology, Lister Hospital,East and North NHS trust,stevenage,hertfordshire,england. Sara Sciacca,Registrar,Department of Radiology, Lister Hospital,East and North NHS trust,stevenage,hertfordshire,england. Yu Jin Lee, Registrar, Department of Radiology, Lister Hospital,East and North NHS trust,stevenage,hertfordshire,england. Bertrand Annan,MSK Consultant,Department of Radiology, Lister Hospital,East and North NHS trust,stevenage,hertfordshire,england. Peter Brooks, MSK Consultant, Department of Radiology, Lister Hospital,East and North NHS trust,stevenage,hertfordshire,england. Page 25 of 27

26 References [1]Shapiro TA, McGarry MH, Gupta R, Lee YS, Lee TQ. Biomechanical effects of glenoid retroversion in total shoulder arthroplasty. J Shoulder Elb Surg. 2007; [2]Nyffeler RW, SheikhR,AtkinsonTS, Jacob HAC, Favre P, Gerber C. Effects of glenoid component version on humeral head displacement and joint reaction forces: an experimental study. J Shoulder Elb Surg. 2006;15: [3]Farron A, Terrier A, Büchler P. Risks of loosening of a prosthetic glenoid implanted in retroversion. J Shoulder Elb Surg. 2006;15: ]. [4]Farron A, Terrier A, Buchler P. Risks of loosening of a prosthetic glenoid implanted in retroversion. J Shoulder Elbow Surg 2006; 15: ]. [5]Friedman RJ, Hawthorne KB, Genez BM. The use of computerized tomography in the measurement of glenoid version. J Bone Joint Surg Am 1992; 74: [6] Bryce CD, Davison AC, Lewis GS, Wang L, Flemming DJ, Armstrong AD. Twodimensional glenoid version measurements vary with coronal and sagittal scapular rotation. J Bone Joint Surg Am 2010; 92: [7]Hoenecke HR Jr, Hermida JC, Flores-Hernandez C, D'Lima DD. Accuracy of CT-based measurements of glenoid version for total shoulder arthroplasty. J Shoulder Elbow Surg 2010; 19: [8]Budge MD, Lewis GS, Schaefer E, Coquia S, Flemming DJ, Armstrong AD. Comparison of standard two-dimensional and three-dimensional corrected glenoid version measurements. J Shoulder Elbow Surg 2011; 20: Page 26 of 27

27 [9] Nowak DD, Bahu MJ, Gardner TR, Dyrszka MD, Levine WN, Bigliani LU, et al. Simulation of surgical glenoid resurfacing using three-dimensional computed tomography of the arthritic glenohumeral joint: the amount of glenoid retroversion that can be corrected. J Shoulder Elb Surg ; 18 : ] [10] Walch G, Badet R, Boulahia A, Khoury A. Morphologic study of the glenoid in primary glenohumeral osteoarthritis. J Arthroplasty 1999; 14: ]. Page 27 of 27