The effects of glenoid component alignment variations on cement mantle stresses in total shoulder arthroplasty

doi:10.1016/j.jse.2004.04.008

Journal of Shoulder and Elbow Surgery

Volume 13, Issue 6, November–December 2004, Pages 668-675

https://doi.org/10.1016/j.jse.2004.04.008 Get rights and content

Loosening of the glenoid component has been cited as the most frequent cause of patient dissatisfaction with total shoulder arthroplasty, and it has been demonstrated in clinical studies that misalignment of the prostheses can be a causative factor. Finite element analyses of five different glenoid component alignments (central, anteverted, retroverted, inferiorly inclined, and superiorly inclined) were conducted in order to predict changes in the survivability of the cement mantle surrounding the glenoid component. The potential for mechanical failure of the mantle in the centrally aligned implant, during unloaded abduction, was seen to be lower than for any other alignment. Normal bone outperformed simulated rheumatoid models in all cases. Retroversion was worse than anteversion, and superoinferior misalignment was worse than anteroposterior. The quality of the supporting bone stock was found to be particularly significant to cement survivability, more so than the occurrence of eccentric loading of the joint. Shear forces acting on the glenoid component were found to be more detrimental than axial forces, resulting in a greater likelihood of failure toward the extremes of motion. The study suggests that significant efforts should be made to align the glenoid component correctly and also to ensure suitably consistent support of the prosthesis within the bone.

Section snippets

Materials and methods

By using the computed tomography data of the Visible Human Project male data set,¹⁸ 2-dimensional contours of the right scapula were generated with the software AMIRA (TGS Software, Bordeaux, France), which were compiled into a preoperative surface mesh of the bone. Finite element models of the five different preoperative cases of glenoid erosion were generated through subtraction of a sphere of radius equal to that of the natural geometry of the glenoid from the preoperative surface, as shown

Results

Table I shows the resulting eccentricity ratios of the joint loading in response to the translation of the humeral head. The percentage by volume of the cement mantle with a greater than 95% probability of failure under cyclic loading is presented in Figure 5, Figure 6, Figure 7, Figure 8, Figure 9 for the normal and simulated rheumatoid bones, throughout the range of unloaded abduction.

Discussion

Misalignment has been linked clinically to loosening of the glenoid component,1, 11 although to our knowledge, no investigations before this study have quantified the effects of this misalignment on the integrity of the implant fixation. Over the entire range of unloaded glenohumeral abduction, finite element analyses conducted in this study have predicted that central alignment of the prosthesis is the most desirable when considering cement mantle fixation survivability. Overall, and for both

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3-dimensional printing and custom implants in shoulder arthroplasty
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Preoperative planning to preserve glenoid subchondral bone in anatomical total shoulder replacement
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Glenoid loosening remains a concern in anatomical total shoulder replacement. Preoperative planning software allows optimization of the component positioning, but the target orientation remains unclear due to conflicting optimization priorities. Commonly, the component is aligned to the prescribed version and inclination that reflect the population’s average anatomy. The freehand technique attempts to secure strong fixation by aiming to preserve the subchondral bone. This study compared the state of the subchondral plate after reaming and compared the results of these two techniques.
Two groups of shoulder computed tomography scans were assessed, 34 normal and 34 osteoarthritic. Preoperative planning software was used to place the glenoid component in prescribed adjusted angles, with neutral (0^o,0^o), retroverted (−10^o,0^o) and inclined alignment (0^o,10^o). The computed tomography Hounsfield values at the virtually reamed surface were assessed to determine the percentage of the intended component-bone interface consisting of cortical bone, here termed “cortical bone seating”. This was then compared to positioning the component using a freehand technique.
The freehand technique improved cortical bone seating in the osteoarthritic group with a mean (standard deviation) of 53.3% (14.3), while neutral alignment resulted in 36.7% (10.8), retroversion 40.4% (13.1), and inclination 39.3% (13.5), P < .001. A similar trend was observed in the normal group.
The freehand method resulted in significantly improved cortical bone seating compared to the prescribed adjusted angles. These findings question the use of a one-size-fits-all-orientation and suggest that applying a technique that aims for maximum cortical fixation (freehand) may reduce the risk of aseptic loosening.
Scapular coronal inclination in total shoulder arthroplasty
2023, Seminars in Arthroplasty JSES
Implant position is critical in the outcomes of reverse and anatomic total shoulder arthroplasties (RTSA and ATSA). Studies to date focused on glenoid orientation but the literature on scapular position is lacking. This study aims to assess scapular coronal inclination (SCI) on erect shoulder X-rays compared with that on shoulder planning software. In addition, we compare SCI on erect shoulder X-rays before and after RTSA and ATSA.
This is a single-center retrospective review of erect X-rays of patients who had ATSA and RTSA performed by a single surgeon (J.T.) between January 2013 and May 2021. SCI was measured using the Scapular Coronal Axis (SCA) and the Scapular Spine Line–Medial Border (SSL-MB) relative to the horizontal axis. To achieve our primary aim, the SCA was measured on preoperative X-rays and compared to those in shoulder planning software. The difference in SSL-MB angles preoperatively and postoperatively was our secondary outcome. X-rays were screened to ensure acceptable rotation in the sagittal and axial planes, using coracoclavicular distance and coracoacromial angle, respectively, to enable reliable comparison. A repeat measurement was performed 1 month apart to determine intraobserver reliability. Three investigators performed measurements separately to determine interobserver reliability.
There were 177 total shoulder arthroplasties (TSAs) identified during the study period but only 24 ATSA and 29 RTSA fulfilled the selection criteria. The SCA had an inferior tilt of mean −16.3° (95% confidence interval [CI] −18.38 to −14.13) compared to horizontal (0°) in planning software. Using the SSL-MB, the mean difference for ATSA was 0.5° (95% CI −1.59° to 2.56°) and the mean difference for RTSA was −0.2° (95% CI −2.73° to 2.37°). The SSL-MB differences were not statistically significant. All interobserver and intraobserver Intraclass Correlation Coefficients measurements were ≥ 0.85 except 0.73 for intraobserver coracoclavicular distance.
In conclusion, the native SCA was tilted inferiorly at a mean of −16.3° and not perfectly horizontal like portrayed in shoulder planning software. Surgeons need to be aware of this to accurately place the glenoid component in TSA. There was no change in SCI after TSA. Correlation with clinical outcomes is needed.
Computed tomography revealed the correlation between radiolucency and alignment of all-polyethylene pegged glenoid component more than 10 years after total shoulder arthroplasty in the Japanese population
2023, Journal of Orthopaedic Science
Anatomical total shoulder arthroplasty (TSA) provides successful long-term outcomes but complications can occur after 10 years that require revision. Computed tomography (CT) is a useful tool for assessing radiolucent lines around the glenoid component of TSA; however, the merits of long-term post-TSA follow up with CT are unclear. The purpose of this study was to evaluate the long-term outcomes after TSA of Japanese population and to identify factors related to radiolucency around the glenoid component using CT.
A retrospective review was conducted of TSA patients who had completed at least 10 years of clinical follow up. Radiographs and CT images of the affected shoulder obtained at the last follow up were evaluated for radiolucent lines around the stem and each peg, superior inclination and retroversion of the glenoid component, subluxation index, and critical shoulder angle (CSA). Shoulder ROM, Constant–Murley score and UCLA score were compared between the preoperative and last follow up period.
Eighteen shoulders in 16 patients met the inclusion criteria. Mean patient age was 61 years, mean follow up period was 137 months, and mean Yian CT score was 19%. CT score was significantly highest in pegs located inferiorly (p < 0.05). Mean glenoid superior inclination was 12.6°, retroversion was −0.3°, subluxation index was 46%, and CSA was 33.7°. Glenoid superior inclination was significantly lower (p = 0.007) in shoulders with possible loosening than in cases with no loosening (5.0° vs 15.6°). Mean Constant score and UCLA score improved significantly after TSA, from 25.8 to 10.7 points preoperatively to 70.1 and 28.9 points postoperatively, respectively. Mean shoulder flexion, internal rotation, and external rotation also showed improvement postoperatively.
TSA provides good long-term outcomes. Radiolucency was present most frequently around the inferior pegs of the glenoid component. Glenoid superior inclination may affect the formation of radiolucent lines around glenoid pegs.
Level IV; Case Series; Treatment study.
Statistical shape modeling-based reconstruction eliminates the need for full scapular computed tomography scan data in preoperative total shoulder arthroplasty planning
2022, Seminars in Arthroplasty JSES
Preoperative total shoulder arthroplasty (TSA) planning tools use a three-dimensional (3D) model of the full scapula based on computed tomography (CT) images with a scan length covering the complete scapula with a given radiation exposure for patients. The aim of this study is to investigate whether full scapular models can be reconstructed from partial CT data.
In this retrospective cohort study, bone models representing 5 scan lengths with decreasing levels of scapular coverage (level 1-5) were created. All the models were reconstructed with a validated statistical shape model (SSM) allowing automatic 3D measurements of glenoid version, inclination, scapular offset, and center point position. Radiation exposure between 2 patient groups (group 1 = corresponding to L1, group 2 = complete scapula) was compared.
In terms of inclination and version, we found a mean absolute difference between the complete model and the different partial scan models of 0.5° (SD 0.4°). The maximum difference was 3° for inclination and 2° for version. For scapular offset and center point position, the mean difference was 0 mm (max 1 mm). The mean radiation exposure was 4 mSv (SD 2 mSv) for group 1 and 13 mSv (SD 6 mSv) for group 2 (P = .009).
An SSM-based reconstruction technique can accurately reconstruct complete scapular bone models based on partial CT scan data. Incorporation of an SSM-based reconstruction technique in software tools for preoperative TSA planning would lead to decreased radiation exposure (9 mSv) for patients without influencing its accuracy.
Commercial 3-dimensional imaging programs are not created equal: version and inclination measurement positions vary among preoperative planning software
2022, JSES International
Variability exists between total shoulder arthroplasty preoperative planning software (PPS) systems for glenoid angular measurements. The purpose of this study is to locate the region on the glenoid at which inclination and version are measured on the PPS modalities of Blueprint and VIP.
Preoperative computed tomography scans of 30 consecutive patients undergoing primary arthroplasty were analyzed using two PPS systems (VIP and Blueprint) to independently obtain glenoid version and inclination measurements through their respective protocols. Three-dimensional equivalent images were independently analyzed utilizing open-source OsiriX DICOM software by two board-certified orthopedic sports medicine surgeons measuring glenoid version and inclination along ten equal intervals of the glenoid from superior to inferior and anterior to posterior. Manual version and inclination measurements were compared to both the VIP and the Blueprint measurements, and variances were analyzed by calculating root mean square error (RMSE). The closest interval (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) to the VIP and Blueprint measurement was identified for both version and inclination to determine the region of the glenoid both software programs obtained their measurements.
Mean glenoid retroversion manually measured using OsiriX was 13.5° compared with 15.1° recorded by Blueprint (P = .516) and 12.2° by VIP (P = .621). Mean inclination using OsiriX was 5.5°, compared with 7.1° (P = .314) and 9.0° (P = .024) recorded by Blueprint and VIP, respectively. RMSE for version between Osirix and VIP was 4.65°, for Osirix and Blueprint was 4.44°, and for VIP and Blueprint was 4.45°. RMSE for inclination between Osirix and VIP was 6.43°, for Osirix and Blueprint was 5.25°, and for VIP and Blueprint was 5.13°. For version, VIP measurements most frequently aligned with the inferior quadrant of the glenoid (n = 13) with a median interval of 7, while Blueprint aligned with the superior quadrant of the glenoid (n = 13) with a median interval of 4. Inclination measurements aligned with the posterior quadrant of the glenoid for both VIP (n = 19) and Blueprint (n = 15) with a median interval of 8.
PPS systems for shoulder arthroplasty vary in the region of the glenoid for which version and inclination are measured, which may affect the absolute values generated. Location of version measurement was different among the two commercial software programs, with VIP corresponding closest to the most inferior region of the glenoid, while Blueprint to the most superior one. Further research should assist in determining the version and inclination variations among commercial planning software.

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: This project was funded by a research grant from the Engineering and Physical Sciences Research Council (EPSRC).

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Original articlesThe effects of glenoid component alignment variations on cement mantle stresses in total shoulder arthroplasty

Section snippets

Materials and methods

Results

Discussion

J Shoulder Elbow Surg

J Shoulder Elbow Surg

J Arthroplasty

J Shoulder Elbow Surg

J Shoulder Elbow Surg

J Shoulder Elbow Surg

Int J Fatigue

J Shoulder Elbow Surg

J Biomech

J Biomech

J Shoulder Elbow Surg

J Photogramm Remote Sens

J Biomech

Original articles
The effects of glenoid component alignment variations on cement mantle stresses in total shoulder arthroplasty