Association of lateral humeral offset with functional outcome and geometric restoration in stemless total shoulder arthroplasty

Shoulder Physiological Offset Parameters in Asian Populations-A Magnetic Resonance Imaging Study

Background/Objectives: Physical shoulder offset parameters (SOPs) play important roles in the diagnosis and treatment of shoulder diseases. However, there is little research analyzing SOPs in healthy shoulders using cross-sectional MRI images, especially in Asians. Therefore, this study aimed to establish physiological reference values of shoulder parameters for Asian populations. Methods: This was a retrospective imaging study using MRI images of the shoulder joints of 500 patients (mean age: 55.9 ± 14.0 years). We measured the following SOPs of the normal joint: HO, GO, lateral glenoidal humeral offset (LGHO), humeral shaft axis offset (HAO), and cortical offset (CO). In addition, the offset parameters were examined for associations with age, gender, side, and osteoarthritis. Results: The mean HO was 22.9 (±2.4) mm, the mean GO was 62.3 (±6.6) mm, the mean LGHO was 48.9 (±4.2) mm, the mean HAO was 25.2 (±2.8) mm, and the mean CO was 15.7 (±2.7) mm. Male patients exhibited significantly higher values across all SOPs compared to female patients. In addition, there was a significantly lower mean value for HAO in left shoulders (HAO: 24.7± 2.8 mm vs. 25.5 ± 2.8 mm, p = 0.011). There was a negatively significant correlation between age and all SOPs. No significant difference in mean values was noted between shoulders with osteoarthritis and non-osteoarthritis in any SOPs. Conclusions: Significant gender- and age-specific differences were noted for all measured SOPs. In addition, right shoulders did not show higher mean SOP values than left shoulders, except for HAO, suggesting that the contralateral joint is a reliable reference for surgical planning. These findings should be considered in shoulder surgery planning.

A comparative analysis of a central metaphyseal humeral fixation stemless shoulder arthroplasty to an anatomic shoulder arthroplasty in a national registry cohort

Background

This study aimed to determine the revision outcome between a centrally fixed stemless anatomic design and other total anatomic shoulder replacements using data from a large national arthroplasty registry.

Methods

The study period was from December 2011 to December 2022 and included three cohorts; primary Affinis stemless anatomic (AFS), all other primary total stemless anatomic (sTSA) and primary total stemmed anatomic shoulder arthroplasty (aTSA). The endpoint was all-cause revision using cumulative percent revision (CPR). Hazard ratio (HR) models were adjusted for age and gender.

Results

There were 2489 primary AFS, 1593 primary sTSA and 11,023 primary aTSA. There was no difference in revision rates between the AFS and the sTSA group. The aTSA group had a significantly higher rate of revision compared to both AFS (HR = 1.63, 95% confidence interval (CI) 1.30-2.05, p < 0.001) and sTSA (HR = 1.61, 95% CI 1.21-2.15, p = 0.001). However, sub-analyses stratifying for highly crosslinked polyethylene (XLPE) showed no differences between the groups.

Discussion

The rates of revision between the AFS design and other stemless prostheses were similar. Stemless had lower revision rates to aTSA. When only considering XLPE cemented glenoids, there was no significant difference in revision rates.

Influence of humeral position of the Affinis Short stemless shoulder arthroplasty system on long-term survival and clinical outcome

BACKGROUND

The purpose of this study was to evaluate the influence of humeral position of the Affinis Short implant in stemless anatomic total shoulder arthroplasties (STSAs) on clinical and radiologic results and mid- to long-term survival in the treatment of primary osteoarthritis (OA) of the shoulder.

METHODS

Eighty patients treated with a stemless shoulder arthroplasty for OA of the shoulder were evaluated with a mean follow-up of 92 ± 14 months (range 69-116 months) by the Constant Score (CS), Disabilities of the Arm, Shoulder, and Hand questionnaire (DASH), and active range of motion (ROM). Radiographic assessment for bone adaptations and humeral implant position was performed by plain radiographs. Comparison of the pre- and postoperative centers of rotation (CORs) was used to assess the restoration of the geometry of the humeral head. The appraisal of proper humeral component positioning was correlated with the functional outcomes. A Kaplan-Meier analysis was performed to investigate the influence of humeral implant position compared to survival time. Complications were noted.

RESULTS

The ROM (P < .001), CS (P < .001), and DASH scores (P < .001) showed significant improvements after surgery for the entire series. The COR restoration was anatomic in 75% (n = 60) of all implants and in 25% (n = 20) nonanatomic implants (pre- and postoperative COR deviation of 2.7 ± 1.8 mm vs. 5.1 ± 3.2 mm, P = .0380). The humeral component position did not affect the functional outcome whereas the 10-year unadjusted cumulative survival rate for the anatomic group was significantly higher in comparison with the nonanatomic group (96.7% vs. 75%, P = .002). The radiologic evaluation revealed minor periprosthetic bone adaptions in various forms without clinical significance or further intervention. No revision was necessary because of a failed fixation of the stemless humeral component.

CONCLUSIONS

Regarding the treatment of primary OA of the shoulder, STSA shows excellent long-term survival and clinical outcomes. In particular, STSA implants are able to restore the geometry of the humeral head. Nonanatomic reconstruction may influence the survival over the long term in different pathways. Further studies are necessary to elucidate the effect of humeral component position in STSA on function, pain, and implant survival rates.

Glenohumeral Cartilage Thickness: Implications in Prosthetic Design and Osteochondral Allograft Transplantation

OBJECTIVE

A complete understanding of the glenohumeral joint anatomy is crucial for osteochondral allograft (OCA) transplantation and prosthetic design. However, existing data on the cartilage thickness distribution are not consistent. This study aims to describe the cartilage thickness distribution at both the glenoid cavity and humeral head in males and females.

DESIGN

Sixteen fresh cadaveric shoulder specimens were dissected and separated to expose the glenoid and humeral head articular surfaces. The glenoid and humeral head were cut into 5-mm coronal sections. Sections were imaged and cartilage thickness was measured at 5 standardized points on each section. Measurements were analyzed based on age, sex, and regional location.

RESULTS

For the humeral head, cartilage was thickest centrally (M = 1.77 ± 0.35 mm) and thinnest superiorly and inferiorly (M = 1.42 ± 0.37 mm, 1.42 ± 0.29 mm). At the glenoid cavity, cartilage was thickest in the superior and inferior areas (M = 2.61 ± 0.47 mm, 2.53 ± 0.58 mm) and thinnest centrally (M = 1.69 ± 0.22 mm). Males were found to have thicker cartilage at both the humeral head and glenoid (P = 0.0014, P = 0.0133).

CONCLUSIONS

Articular cartilage thickness distribution of the glenoid and humeral head is nonuniform and reciprocal in nature. These results can be used to further inform prosthetic design and OCA transplantation. We noted a significant difference in cartilage thickness between males and females. This suggests that the sex of the patient should be taken into consideration when matching donors for OCA transplantation.

Restoration of the joint geometry after stemless shoulder arthroplasty

Aim

This study aims to evaluate restoration of anatomy following Total Shoulder Arthroplasty (TSA) with the Mathys Affinis Short prosthesis.

Background

Over the last decade stemless shoulder arthroplasty has increased in popularity. One of the reported advantages of the stemless designs is the ability to restore anatomy following surgery. However, very few studies have evaluated restoration of anatomy following stemless shoulder arthroplasty.

Methods

The study included all patients who had undergone TSA using the Affinis Short (Mathys Ltd, Bettlach, Switzerland) prosthesis for primary osteoarthritis between 2010 and 2016. The mean follow up was 42.8 months (range 9.4 to 83.4 months). Pre and post-operative radiographs were assessed for Centre of Rotation (COR), Humeral Head Height (HHH), Humeral Head Diameter (HHD), Humeral Height (HH) and, Neck Shaft Angle (NSA) using the best fit circle method on PACS software. Measurements were scored and compared to assess the accuracy of the implant in restoring the native geometry, including the intraobserver variability. The same data was collected by another experienced observer to measure the interobserver variability.

Results

The deviation of COR of the prosthesis from the anatomical centre was less than 3 mm in 58 cases (85%). Humeral head height and humeral head diameter showed a variation of less than 3 mm in 66 cases (97%) and 43 cases (63%) respectively. Humeral height followed a similar trend, with 62 cases (91.2%) showing a difference of less than 5 mm. The neck shaft angle showed a variation of more than 8 degrees in 38 cases (55%), and 29 cases (42.6%) had a postoperative angle of less than 130 degrees.

Conclusion

Overall, stemless total shoulder arthroplasty with the Affinis Short prosthesis allows excellent restoration of anatomy confirmed by most of the measured radiographic parameters. The variability in neck shaft angle might be due to differing surgical techniques, with some surgeons preferring a slightly vertical neck cut to protect the rotator cuff insertion.

Midterm results of stemless impaction shoulder arthroplasty for primary osteoarthritis: a prospective, multicenter study

Background

Stemless shoulder arthroplasty using 4 open-fin press-fit anchors has been showing promising short-term clinical and radiographic results for patients' primary osteoarthritis. This prospective, multicenter study presents 5-year postoperative clinical and radiological outcomes of a stemless shoulder arthroplasty for primary osteoarthritis.

Methods

Between November 2012 and December 2015, 100 patients were treated for primary osteoarthritis with the Sidus stem-free shoulder system at 7 European centers. Clinical assessment included the Constant-Murley Score, American Shoulder and Elbow Standardized Shoulder Assessment Form score, Subjective Shoulder Value, and range of motion. True anteroposterior, axial and lateral radiographs were reviewed for osteolysis, glenoid and humerus loosening, heterotopic ossification, radiolucent lines, component migration and humeral bone resorption. In addition to a Kaplan-Meier survival analysis, a comparative analysis between total shoulder arthroplasty and hemiarthroplasty was performed.

Results

Seventy-one patients (36 females) with a mean age of 63.8 years (range: 47-79 years) were available for the 5-year clinical and radiographic follow-up (range: 52-79 months). There was a significant increase (P < .0001) in all outcome scores compared to baseline values. Patients with total shoulder arthroplasty (n = 48) achieved significantly better functional outcome than patients with shoulder hemiarthroplasty (n = 23) with regard to the absolute and relative Constant-Murley Score, American Shoulder and Elbow Standardized Shoulder Assessment Form score, and Subjective Shoulder Value as well as greater abduction strength and range of motion in forward elevation and external rotation (P ≤ .004). There were no cases of osteolysis or humeral loosening. There were some cases of heterotopic ossification (1.4%), radiolucency around the humerus (1.4%) or glenoid (25%), glenoid migration (2.1%), inferior osteophytes (1.4%) or humerus bone resorption (9.9%). The 5-year survival was 94%.

Conclusion

Patients treated with the Sidus stem-free shoulder system for primary osteoarthritis continue to achieve good clinical and radiographic results without any signs of aseptic humeral implant loosening at 5 years postsurgery.

Patient-specific instrumentation reduces deviations between planned and postosteotomy humeral retrotorsion and height in shoulder arthroplasty

BACKGROUND

Patient-specific instrumentation (PSI) may potentially improve humeral osteotomy in shoulder arthroplasty. The purpose of this study was to compare the deviation between planned and postosteotomy humeral inclination, retrotorsion, and height in shoulder arthroplasty, using PSI vs. standard cutting guides (SCG).

METHODS

Twenty fresh-frozen cadaveric specimens were allocated to undergo humeral osteotomy using either PSI or SCG, such that the 2 groups have similar age, gender, and side. Preosteotomy computed tomography (CT) scan was performed and used for the 3-dimensional (3D) planning. The osteotomy procedure was performed using a PSI designed for each specimen or an SCG depending on the group. A postosteotomy CT scan was performed. The preosteotomy and postosteotomy 3D CT scan reconstructions were superimposed to calculate the deviation between planned and postosteotomy inclination, retrotorsion, and height. Outliers were defined as cases with 1 or more of the following deviations: >5° inclination, >10° retrotorsion, and >3 mm height. The deviation and outliers in inclination, retrotorsion, and height were compared between the 2 groups.

RESULTS

The deviations between planned and postosteotomy parameters were similar among the PSI and SCG groups for inclination (P = .260), whereas they were significantly greater in the SCG group for retrotorsion (P < .001) and height (P = .003). There were 8 outliers in the SCG group, compared with only 1 outlier in the PSI group (P = .005). Most outliers in the SCG group were due to deviation >10° in retrotorsion.

CONCLUSION

After 3D planning, PSI had less deviation between planned and postosteotomy humeral retrotorsion and height, relative to SCG.

The Evolution of Reverse Total Shoulder Arthroplasty-From the First Steps to Novel Implant Designs and Surgical Techniques

PURPOSE OF REVIEW

The purpose of this review is to summarize recent literature regarding the latest design modifications and biomechanical evolutions of reverse total shoulder arthroplasty and their impact on postoperative outcomes.

RECENT FINDINGS

Over the past decade, worldwide implantation rates of reverse total shoulder arthroplasty have drastically increased for various shoulder pathologies. While Paul Grammont's design principles first published in 1985 for reverse total shoulder arthroplasty remained unchanged, several adjustments were made to address postoperative clinical and biomechanical challenges such as implant glenoid loosening, scapular notching, or limited range of motion in order to maximize functional outcomes and increase the longevity of reverse total shoulder arthroplasty. However, the adequate and stable fixation of prosthetic components can be challenging, especially in massive osteoarthritis with concomitant bone loss. To overcome such issues, surgical navigation and patient-specific instruments may be a viable tool to improve accurate prosthetic component positioning. Nevertheless, larger clinical series on the accuracy and possible complications of this novel technique are still missing.

Determining the ideal osteotomy for stemless total shoulder replacement: a cadaveric study

HYPOTHESIS

We sought to determine the angle of osteotomy that produces a circular humeral cut surface.

METHODS

A total of 49 cadaveric shoulders, from 25 cadavers, underwent sequential humeral head osteotomy from 180° (vertical, in line with the humeral diaphyseal shaft), in 10° increments, until the rotator cuff insertion was encountered. At each stage, the anteroposterior (AP) and superoinferior (SI) distances were recorded. The data were analyzed for normality and then assessed to determine the optimum cut angle.

RESULTS

The AP/SI ratio is an indication of roundness. Plotting values of 1 - AP/SI (ie, error) vs. cut angle allowed us to plot the likelihood of producing a circular cut surface using a third-order curve that created the best fit to the data set (R² = 0.99). The results from this study suggest that the optimum osteotomy angle that produces a circular cut surface is 23° from the vertical. The cohort data illustrated that at this angle, the average roundness error was 1% with a 95% confidence limit of <1%. There was no significant difference (P > .05) between sexes.

CONCLUSION

The humeral head shape changes from oval to circular and then to an oval cut surface as the osteotomy angle increases from the vertical toward the horizontal. The range of angles within which the cut surface is circular, within a 10% error margin, is 18°-27° from the vertical, which is much less than the traditional osteotomy angle of 45°.

Lateralized versus nonlateralized reverse total shoulder arthroplasty

Throughout the history of reverse total shoulder arthroplasty, the extent of lateral offset has changed considerably from "too lateral" to "too medial" and has been lately swinging back towards a point somewhere in between. Nonlateralized designs minimize shear forces on the glenoid and decrease force required by the deltoid. Glenoid lateralization decreases impingement and scapular notching and improves range of motion. Humeral lateralization achieves a more anatomic position of the tuberosities while maintaining a nonlateralized center of rotation. Several factors play a role in choosing the extent of lateral offset and method of lateralization.

An update on reverse total shoulder arthroplasty: current indications, new designs, same old problems

Reverse total shoulder arthroplasty (RTSA) was originally developed because of unsatisfactory results with anatomic shoulder arthroplasty options for the majority of degenerative shoulder conditions and fractures.

After initial concerns about RTSA longevity, indications were extended to primary osteoarthritis with glenoid deficiency, massive cuff tears in younger patients, fracture, tumour and failed anatomic total shoulder replacement.

Traditional RTSA by Grammont has undergone a number of iterations such as glenoid lateralization, reduced neck-shaft angle, modular, stemless components and onlay systems.

The incidence of complications such as dislocation, notching and acromial fractures has also evolved.

Computer navigation, 3D planning and patient-specific implantation have been in use for several years and mixed-reality guided implantation is currently being trialled.

Controversies in RTSA include lateralization, stemless humeral components, subscapularis repair and treatment of acromial fractures.

Cite this article: EFORT Open Rev 2021;6:189-201. DOI: 10.1302/2058-5241.6.200085

Stemless Total Shoulder Arthroplasty With Orthobiologic Augmentation

Total shoulder arthroplasty (TSA) has evolved over the years and is used for a variety of indications, with arthritis being the most common. Stemless TSA is a unique bone-preserving design that can eliminate rotational malalignment. Additionally, recent literature has found utility in the use of biological mesh and a platelet-rich plasma injection to improve healing. The purpose of this article is to outline the process of TSA using a stemless system and how to incorporate the use of amnion matrix and platelet-rich plasma into the surgical technique.

Radiographic humeral head restoration after total shoulder arthroplasty: does the stem make a difference?

BACKGROUND

Humeral stem designs for total shoulder arthroplasty have varied over the years, with a recent trend toward shorter stems. The purpose of this study was to examine the impact of humeral component stem length on the ability to restore the native humeral head anatomy.

METHODS

We performed a retrospective review including patients who underwent total shoulder arthroplasty for primary osteoarthritis between 2007 and 2017 with complete operative reports and adequate radiographs. Surgical data including stem design were collected. Preoperative and postoperative radiographic measurements of the center of rotation (COR), humeral head height (HH), and neck-shaft angle were performed. Restoration of the native humeral anatomy was deemed "acceptable" based on postoperative differences in the COR ≤ 3 mm, HH ≤ 5 mm, and neck-shaft angle > 130°. Deviations between preoperative and postoperative measurements were compared across stem types. All available 2-year stemless implant radiographs were also analyzed.

RESULTS

In total, 261 patients were included, with 31 stemless, 43 short-stem, and 187 standard-stem implants. There was no significant difference in COR restoration in the x-axis direction (P = .060) or y-axis direction (P = .579). There was no significant difference in restoration of acceptable HH by stem type (P = .339). Stemless arthroplasty implants were more likely to be placed in varus (22.6%) compared with short-stem (7.0%) and standard-stem (3.7%) designs (P < .001).

CONCLUSION

Restoration of humeral anatomic parameters occurred significantly less with stemless implants than with short- and standard-stem implants. The stem of a shoulder arthroplasty implant aids surgeons in accurately restoring patient-specific anatomy.

An interpopulation comparison of 3-dimensional morphometric measurements of the proximal humerus

Background

Precise anatomic reconstruction of the proximal humerus is essential to a favorable outcome of total shoulder arthroplasty. Because of the wide variation in the geometric features of the proximal humerus, prosthetic designs incorporating these disparities are being developed.

Methods

The aim of this study is to use data obtained from cadavers and computed tomographic scans to investigate the 3-dimensional morphometric parameters of the proximal humerus of South African and Swiss samples and make an interpopulation comparison. In addition, the study combines the interarticular variations between populations with the differences in sex and shoulder sides. With the aid of medical imaging techniques and engineering design tools, various geometric features were measured.

Results

The results obtained from these analyses revealed several differences in sex and shoulder sides. On average, the Swiss were larger in most of the measured parameters than the South Africans. The male shoulders of Swiss and South Africans were observed to significantly vary in 4 of the parameters measured. The South African male and female right shoulders varied considerably in one-fourth of the measured shoulder variables. Generally, for both populations, the left and right shoulders of the same individuals were not different in all the measured variables irrespective of sex.

Conclusion

The knowledge acquired in this study is expected to assist in the development of a population-specific shoulder prosthetic design and surgical planning procedures.

Stemless anatomic total shoulder arthroplasty: a systematic review and meta-analysis

BACKGROUND

Stemless anatomic total shoulder arthroplasty (TSA) is used in the treatment of osteoarthritis of the shoulder joint and other degenerative shoulder diseases. It has several proposed advantages over stemmed TSA including increased bone preservation, decreased operative time, and easier removal at revision.

METHODS

A systematic search was conducted using MEDLINE, Embase, PubMed, and CENTRAL (Cochrane Central Register of Controlled Trials) to retrieve all relevant studies.

RESULTS

The literature search yielded 1417 studies, of which 22 were included in this review, with 962 patients undergoing stemless TSA. Stemless TSA led to significant improvements in range of motion and functional scores in all included studies. Meta-analysis of comparative studies between stemless and stemmed TSA identified no significant differences in postoperative Constant scores (mean difference [MD], 1.26; 95% confidence interval [CI], -3.29 to 5.81 points; P = .59) or complication rates (odds ratio, 1.79; 95% CI, 0.71-4.54; P = .22). Stemless TSA resulted in a significantly shorter operative time compared with stemmed TSA (MD, -15.03 minutes; 95% CI, -23.79 to -6.26 minutes; P = .0008). Stemless TSA also resulted in significantly decreased intraoperative blood loss compared with stemmed TSA (MD, -96.95 mL; 95% CI, -148.53 to -45.36 mL; P = .0002).

CONCLUSION

Stemless anatomic TSA resulted in similar functional outcomes and complication rates to stemmed TSA with decreased operative time and lower blood loss. Further research is required to investigate the long-term durability of the stemless implant.

Stemless Humeral Implants in Total Shoulder Arthroplasty

Through an iteration of various advancements, both short stem and stemless options for humeral fixation have been proposed and have shown clinical promise. The proposed benefits of a stemless humeral implant include greater bone preservation, less stress shielding, less risk of a diaphyseal stress riser, decreased surgical time, and less intraoperative blood loss. Potential downsides include the dependence on proximal bone quality for fixation, increased cost, the dependence on the strength of subscapularis fixation, and pending FDA approval for multiple implants. The purpose of this article is to review the evidence behind stemless implants including the biomechanical advantages and disadvantages, surgical technique, and clinical outcomes.

A reliable method of determining glenohumeral offset in anatomic total shoulder arthroplasty

BACKGROUND

Glenohumeral offset (GHO) may change from the preoperative state after anatomic total shoulder arthroplasty (TSA), and has been identified as a factor that may affect shoulder mechanics, strength, and function. The primary objective was (1) to establish a reliable method of measuring GHO with standardized computed tomography (CT) imaging planes and (2) to determine whether an association exists between GHO and functional outcomes in TSA.

METHODS

Thirty-seven patients underwent TSA for glenohumeral osteoarthritis. Preoperative and postoperative CT scans were reformatted along standardized measurement planes for the glenoid and humerus separately. Inter-rater and intrarater reliability was determined for 3 methods to measure humeral offset and 2 methods to measure glenoid offset. Univariate regression analysis was used to determine the association between GHO and functional outcomes including the Constant score and strength.

RESULTS

Of all methods tested, the highest preoperative and postoperative inter-rater reliability was r = 0.84 and r = 0.8, and r = 0.7 and r = 0.8 for humeral and glenoid offset, respectively. Intrarater reliability was >0.94. There was a mean increase of 4.3 mm (standard deviation, 4.6; range, -10.6 to 10.8) in combined GHO from preoperative to postoperative time points. No associations were observed between change in offset and functional or strength scores.

DISCUSSION

A reliable approach to measure prearthroplasty and postarthroplasty GHO with CT plane standardization has been described. A net increase in GHO was observed after TSA. No associations were found between change in offset after TSA and functional scores or strength up to 2 years postoperatively.

The short-term survival of total stemless shoulder arthroplasty for osteoarthritis is comparable to that of total stemmed shoulder arthroplasty: a Nordic Arthroplasty Register Association study

BACKGROUND

The purpose of this study was to compare the short-term survival rate of total stemless, metaphyseal fixated, shoulder arthroplasty with that of total stemmed shoulder arthroplasty in the treatment of osteoarthritis.

METHODS

Data were collected by the national arthroplasty registries in Denmark, Finland, Norway, and Sweden and merged into 1 dataset under the umbrella of the Nordic Arthroplasty Register Association. For the present study, we included all patients with osteoarthritis treated with either stemless (n = 761) or stemmed (n = 4398) shoulder arthroplasty from 2011 to 2016.

RESULTS

A total of 21 (2.8%) stemless and 116 (2.6%) stemmed shoulder arthroplasties were revised. The 6-year unadjusted cumulative survival rates were 0.953 for stemless shoulder arthroplasty and 0.958 for stemmed shoulder arthroplasty, P = .77. The most common indication for revision of both arthroplasty types was infection. Five (0.7%) stemless and 16 (0.4%) stemmed shoulder arthroplasties were revised because of loosening of either the glenoid or the humeral component. In the multivariate cox regression model, which included age, category, gender, year of surgery, previous surgery, and arthroplasty type, the hazard ratio (HR) for revision of the stemless shoulder arthroplasty was 1.00 (95% confidence interval [CI], 0.63-1.61), P = .99, with the stemmed shoulder arthroplasty as reference. Male gender (HR = 1.50 [95% CI, 1.06-2.13], P = .02) and previous surgery (HR = 2.70 [95% CI, 1.82-4.01], P < .001) were associated with increased risk of revision.

CONCLUSION

The short-term survival of total stemless shoulder arthroplasty appears comparable with total stemmed shoulder arthroplasty, but longer observation time is needed to confirm whether they continue to perform equally.

Radiographic restoration of native anatomy: a comparison between stemmed and stemless shoulder arthroplasty

BACKGROUND

Shoulder arthroplasty is a reliable procedure for patients with degenerative glenohumeral disease, and reproduction of native shoulder anatomy leads to superior outcomes. The aim of this study was to compare the ability of stemmed and stemless implants to radiographically restore native glenohumeral anatomy.

METHODS

Shoulder arthroplasties were performed in 79 patients, with 58 receiving a stemless implant and 21 receiving a stemmed implant. Preoperative and postoperative radiographs were assessed for humeral head height, humeral head centering, humeral head medial offset, humeral head diameter, humeral neck angle, and lateral humeral offset by 2 independent viewers. Measurements were scored and summed to identify the anatomic reconstruction index (ARI). Radiographic measurements were compared using the Student t test, and significance was set at P < .05 for all statistical analyses. Interobserver agreement of radiographic analyses was assessed using the intraclass correlation coefficient, finding excellent reliability (intraclass correlation coefficient, 0.92).

RESULTS

Five of six radiographic measurements along with the calculated ARI demonstrated no differences between stemmed and stemless shoulder implants (humeral head diameter, P = .651; humeral head height, P = .813; humeral head medial offset, P = .592; lateral humeral offset, P = .311; humeral head centering, P = .414; and ARI, P = .862). Stemless implants showed improved restoration of the native humeral neck angle (0° for stemless vs. -3° for stemmed, P = .017).

CONCLUSION

Radiographic restoration of anatomy is similar for stemmed and stemless shoulder arthroplasty implants.

Is global humeral head offset related to intramedullary canal width? A computer tomography morphometric study

Background

While most anatomic TSA stems allow some intra-operative adjustments, the default configuration assumes that head offset is directly proportional to stem diameter. Some authors reported that humeral head diameter is proportional to intra-medullary canal width and humeral head offset, but none investigated the direct relationship between head offset and endosteal measurements. The purpose of the study was to determine whether global humeral head offset is proportional to intramedullary canal width at the distal metaphysis and proximal diaphysis.

Methods

We analyzed 100 Computed Tomography shoulder scans of patients aged 59.1 ± 20.5 with no signs of gleno-humeral arthritis nor humeral dysplasia. The width of the intramedullary diaphyseal canal was determined at four transverse sections 65, 70, 100 and 105 mm below the head center. The inter-observer agreement was excellent for intramedullary canal width (ICC = 0.96), head diameter (ICC = 0.97) and global head offset (ICC = 0.85). Correlations were analysed using Pearson’s coefficients and multivariable regressions were performed to determine associations between head offset and five independent variables (gender, age, intramedullary canal width, head diameter).

Results

Global head offset was negatively correlated with head diameter (r = − 0.31, p = 0.002), but not correlated with intramedullary canal width (r = − 0.11, p = 0.282). Multivariable regression confirmed that global head offset was independently associated with head diameter (beta = − 0.15, p = 0.005), but not with intramedullary canal width (beta = 0.06, p = 0.431).

Conclusions

The present study revealed that humeral offset is not correlated with intramedullary canal width. Implant manufacturers and shoulder surgeons should be aware of the subtle morphologic features, to enhance humeral stem design and restore native anatomy.

Fatty infiltration and muscle atrophy of the rotator cuff in stemless total shoulder arthroplasty: a prospective cohort study

BACKGROUND

The influence of preoperative rotator cuff fatty infiltration (FI) and muscle atrophy (MA) on the postoperative outcome of total shoulder arthroplasty (TSA) has only rarely been investigated and reported in the literature. We hypothesized that more FI and MA would be associated with a worse postoperative functional outcome.

METHODS

This prospective cohort study included 63 patients (31 female and 32 male patients; mean age, 71 years [range, 53-89 years; standard deviation, 7 years]) with primary osteoarthritis of the shoulder operated on with anatomic stemless TSA. Preoperatively and at 3 months and 1 year after the operation, the functional outcome (QuickDASH [short version of Disabilities of the Arm, Shoulder and Hand questionnaire] score) and range of motion (ROM) (goniometer) and strength (dynamometer) for abduction at the scapular plane and for external rotation were measured. The degree of preoperative FI and MA was evaluated using computed tomography scans according to the Goutallier classification and Warner classification, respectively, for the supraspinatus and infraspinatus.

RESULTS

We found clinically and statistically significant improvements in functional outcome, strength, and ROM at both 3 months and 1 year of follow-up compared with those preoperatively. The Pearson correlation coefficient (r) showed significant correlations between preoperative supraspinatus and infraspinatus FI and MA and preoperative and 1-year postoperative shoulder abduction and external rotation strength but not ROM. However, we found no influence of the rotator cuff FI and MA on the functional outcome after TSA.

CONCLUSION

We demonstrated a significant correlation between rotator cuff FI and MA and strength but not ROM of the shoulder joint.

Stemless Prosthesis for Total Shoulder Arthroplasty

The fourth generation of humeral components currently are being used in anatomic shoulder arthroplasty. Anatomic shoulder arthroplasty implants have evolved to better re-create anatomy, improve fixation, preserve bone, and facilitate revision surgery. Most of the design changes for shoulder arthroplasty implants have centered on the humeral stem, with a transition to shorter, metaphyseal humeral stems. Many of these humeral component design changes may be beneficial; however, long-term studies are necessary to determine if the results of anatomic shoulder arthroplasty with the use of newer humeral components can match those of anatomic shoulder arthroplasty with the use of older humeral components.