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Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_8 | Pages 27 - 27
1 Aug 2020
Abdic S Athwal G Wittman T Walch G Raiss P
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The use of shorter humeral stems in reverse shoulder arthroplasty has been reported as safe and effective. Shorter stems are purported to be bone preserving, easy to revise, and have reduced surgical time. However, a frequent radiographic finding with the use of uncemented short stems is stress shielding. Smaller stem diameters reduce stress shielding, however, carry the risk of varus or valgus malalignment in the metadiaphyseal region of the proximal humerus. The aim of this retrospective radiographic study was to measure the true post-operative neck-shaft (N-S) angle of a curved short stem with a recommended implantation angle of 145°.

True anteroposterior radiographs of patients who received RTSA using an Ascend Flex short stem at three specialized shoulder centres (London, ON, Canada, Lyon, France, Munich, Germany) were reviewed. Radiographs that showed the uncemented stem and humeral tray in orthogonal view without rotation were included. Sixteen patients with proximal humeral fractures or revision surgeries were excluded. This yielded a cohort of 124 implant cases for analysis (122 patients, 42 male, 80 female) at a mean age of 74 years (range, 48 – 91 years). The indications for RTSA were rotator cuff deficient shoulders (cuff tear arthropathy, massive cuff tears, osteoarthritis with cuff insufficiency) in 78 patients (63%), primary osteoarthritis in 41 (33%), and rheumatoid arthritis in 5 (4%).

The humeral component longitudinal axis was measured in degrees and defined as neutral if the value fell within ±5° of the humeral axis. Angle values >5° and < 5 ° were defined as valgus and varus, respectively. The filling-ratio of the implant within the humeral shaft was measured at the level of the metaphysis (FRmet) and diaphysis (FRdia). Measurements were conducted by two independent examiners (SA and TW). To test for conformity of observers, the intraclass correlation coefficient (ICC) was calculated.

The inter- and intra-observer reliability was excellent (ICC = 0.965, 95% confidence interval [CI], 0.911– 0.986). The average difference between the humeral shaft axis and the humeral component longitudinal axis was 3.8° ± 2.8° (range, 0.2° – 13.2°) corresponding to a true mean N-S angle of 149° ± 3° in valgus. Stem axis was neutral in 70% (n=90) of implants. Of the 34 malaligned implants, 82% (n=28) were in valgus (mean N-S angle 153° ± 2°) and 18% (n=6) in varus position (mean N-S angle 139° ± 1°). The average FRmet and FRdiawere 0.68 ± 0.11 and 0.72 ± 0.11, respectively. No association was found between stem diameter and filling ratios (FRmet, FRdia) or cortical contact with the stem (r = 0.39).

Operative technique and implant design affect the ultimate positioning of the implant in the proximal humerus. This study has shown, that in uncemented short stem implants, neutral axial alignment was achieved in 70% of cases, while the majority of malaligned humeral components (86%) were implanted in valgus, corresponding to a greater than 145° neck shaft angle of the implant. It is important for surgeons to understand that axial malalignment of a short stem implant does influence the true neck shaft angle.


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_6 | Pages 71 - 71
1 Jul 2020
Mahaffy M Athwal G Johnson J Knowles N Berkmortel C Abdic S Walch G
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This study examined the regional variations of cortical and cancellous bone density present in superiorly eroded glenoids. It is hypothesized that eroded regions will contain denser bone in response to localized stress. The shift in natural joint articulation may also cause bone resorption in areas opposite the erosion site.

Clinical CT scans were obtained for 32 shoulders (10m/22f, mean age 72.9yrs, 56–88yrs) classified as having E2-type glenoid erosion. The glenoid was divided into four measurement regions - anterior, inferior, posterior, and superior - as well as five depth regions. Depth regions were segmented in two-millimeter increments from zero to 10 millimeters, beginning at the center of the glenoid surface. A repeated-measures multiple analysis of variance (RM-MANOVA) was performed using SPSS statistical software to look for differences and interactions between mean densities in each depth, quadrant, and between genders. A second RM-MANOVA was performed to examine effects of gender and quadrant on cortical to cancellous bone volume ratios. Significance was set at p < 0 .05.

Quadrant and depth variables showed significant multivariate main effects (p 0.147 respectively). Quadrant, depth, and their interaction showed significant univariate main effects for cortical bone (p≤0.001) and cancellous bone (p < 0 .001). The lowest bone density was found to be in the inferior quadrant for cancellous bone (307±50 HU, p < 0 .001). The superior quadrant contained the highest mean density for cortical bone (895±97 HU), however it was only significantly different than in the posterior quadrant (865±97 HU, p=0.022). As for depth, it was found that cortical bone is most dense at the glenoid surface (zero to two millimeters, 892±91 HU) when compared to bone at two to eight millimeters in depth (p < 0 .02). Cancellous bone was also most dense at the surface (352±51 HU), but only compared to the eight to 10 millimeters depth (p=0.005). Cancellous bone density was found to decrease with increasing depth. For cortical-to-cancellous bone volume ratios, the inferior quadrant (0.37±0.28) had a significantly lower ratio than all other quadrants (p < 0 .001)

The superoposterior region of the glenoid was found to have denser cancellous bone and a high ratio of cortical to cancellous bone, likely due to decreased formation of cancellous bone and increased formation of cortical bone, in response to localized stresses. The inferior quadrant was found to have the least dense cortical and cancellous bone, and the lowest volume of cortical bone relative to cancellous bone. Once again, this is likely due to reduction in microstrain responsible for bone adaptation via Wolff's law. The density values found in this study generally agree with the range of values found in previous studies of normal and arthritic glenoids. An important limitation of this study is the sizing of measurement regions. For a patient with a smaller glenoid, a depth measurement of two millimeters may represent a larger portion of the overall glenoid vault. Segments could be scaled for each patient based on a percentage of each individual's glenoid size.


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_7 | Pages 52 - 52
1 Jul 2020
Abdic S Knowles N Johnson J Walch G Athwal G
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Superiorly eroded glenoids in cuff tear arthropathy represent a surgical challenge for reconstruction. The bone loss orientation and severity may influence glenoid component fixation. This computed-tomography study quantifies both the degree of erosion and orientation in superiorly eroded Favard E2 glenoids. We hypothesized that the erosion in E2 glenoids does not occur purely superiorly, rather, it is oriented in a predictable posterosuperior orientation with a largely semicircular line of erosion.

Three-dimensional reconstructions of 40 shoulders with E2 glenoids (28 female, 12 male patients) at a mean age of 74 years (range, 56–88 years) were created from computed-tomography images. Point coordinates were extracted from each construct to analyze the morphologic structure. The anatomical location of the supra- and infraglenoid tubercle guided the creation of a superoinferior axis, against which the orientation angle of the erosion was measured. The direction and, thus, orientation of erosion was calculated as a vector. By placing ten point coordinates along the line of erosion and creating a circle of best fit, the radius of the circle was placed orthogonally against a chord that resulted by connecting the two outermost points along the line of erosion. To quantify the extent of curvature of the line of erosion between the paleo- and neoglenoid, the length of the radius of the circle of best fit was calculated. Individual values were compared against the mean of circle radii. The area of bony erosion (neoglenoid), was calculated as a percentage of the total glenoid area (neoglenoid + paleoglenoid). The severity of the erosion was categorized as mild (0% to 33%), moderate (34% to 66%), and severe erosion (>66%).

The mean orientation angle between the vector of bony erosion and the superoinferior axis of the glenoid was 47° ± 17° (range, 14° – 74°) located in the posterosuperior quadrant of the glenoid, resulting in the average erosion being directed between the 10 and 11 o'clock position (right shoulder).

In 63% of E2 cases, the line of erosion separating the paleo- and neoglenoids was more curved than the average of all bony erosions in the cohort. The mean surface area of the neoglenoid was 636 ± 247 mm2(range, 233 – 1,333 mm2) and of the paleoglenoid 311 ± 165 mm2(range, 123 – 820 mm2), revealing that, on average, the neoglenoids consume 67% of the total glenoid surface. The extent of erosion of the total cohort was subdivided into one mild (2%), 14 moderate (35%) and 25 severe (62%) cases.

Using a clock-face for orientation, the average orientation of type E2 glenoid defects was directed between the 10 and 11 o'clock position in a right shoulder, corresponding to the posterosuperior glenoid quadrant. Surgeons managing patients with E2 type glenoids should be aware that a superiorly described glenoid erosion is oriented in the posterosuperior quadrant on the glenoid clock-face when viewed intra-operatively. Additionally, the line of erosion in 63% of E2 glenoids is substantially curved, having a significant effect on bone removal techniques when using commercially available augments for defect reconstruction.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_20 | Pages 33 - 33
1 Dec 2017
Letissier H Walch G Boileau P Le Nen D Stindel E Chaoui J
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Introduction

Reverse Total Shoulder Arthroplasty (rTSA) is an efficient treatment, to relieve from pain and to increase function. However, scapular notching remains a serious issue and post-operative range of motion (ROM) presents many variations. No study compared implant positioning, different implant combinations, different implant sizes on different types of patient representative to undergo for rTSA, on glenohumeral ROM in every degree of freedom.

Material and Methods

From a CT-scan database classified by a senior surgeon, CT-exams were analysed by a custom software Glenosys® (Imascap®, Brest, France). Different glenoid implants types and positioning were combined to different humerus implant types. Range of motion was automatically computed. Patients with an impingement in initialisation position were excluded from the statistical analysis. To validate those measures, a validation bench was printed in 3D to analyse different configurations.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_28 | Pages 40 - 40
1 Aug 2013
Chaoui J Walch G Boileau P
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INTRODUCTION

The glenoid version assessment is crucial step for any Total Shoulder Arthroplasty (TSA) procedure. New methods to compute 3D version angle of the glenoid have been proposed. These methods proposed different definitions of the glenoid plane and only used 3 points to define each plane on the 3D model of the scapula. In practice, patients often come to consultation with their CT-scans. In order to reduce the x-ray dose, the scapulae are often truncated on the inferior part. In these cases, the traditional scapula plane cannot be calculated. We hypothesised that a new plane definition, of the scapula and the glenoid, that takes into account all the 3D points, would have the least variation and provide more reliable measures whatever the scapula is truncated or not. The purpose of the study is to introduce new fully automatic method to compute 3D glenoid version for TSA preoperating planning and test its results on artificially truncated scapulae.

MATERIAL AND METHODS

Volumetric preoperative CT datasets have been used to derive a surface model shape of the shoulder. The glenoid surface is detected and a 3D version and inclination angle of the glenoid surface are computed. We propose a new reference plane of the scapula without picking points on the 3D model. The method is based on the mathematical skeleton of the scapula and the least squares plane fitting. Specific software has been developed to apply the plane fitting in addition the automatic segmentation process. An orthopedic surgeon defined the traditional scapular plane based on 3 points and applied the measures on 12 patients. The manual process has been repeated 3 times and the intra-class correlation coefficient (ICC) was calculated to compare the results with our automatic method. To validate the reliability of the new plane relating to truncated scapulae, we have measured the 3D orientation variation on 37 scapulae. Nine iterations have been applied on each scapula by cutting 5mm of the scapular inferior part.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXV | Pages 70 - 70
1 Jun 2012
Gazielly D Walch G Boileau P
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Introduction

the aim of this study was to analyse the long-term radiological changes following tsa in order to better understand the mechanisms responsible for loosening.

Material and methods

between 1991 and 2003, in 10 European centers, 611 shoulder arthroplasties were performed for primary osteoarthritis using a third generation anatomic prosthesis with a cemented all-polyethylene keeled glenoid component. Full radiographic and clinical follow-up greater than 5 years was available for 518 shoulders. Kaplan-meier survivorship analysis was performed with glenoid revision for loosening and radiological loosening as end points; clinical outcome was assessed with the constant score, patient satisfaction score, subjective shoulder value and range of movement