Bone remodelling of the humerus after a resurfacing and a stemless shoulder arthroplasty

Age-dependent change and intraskeletal variability in secondary osteons of elderly Australians

There is a need to fully understand intra-skeletal variability within different populations to develop and improve age-at-death estimation methods. This study evaluates age-related histomorphometric changes in three different bones intra-individually in a modern Australian sample. Four female and 13 male elderly Australian adult donors (67-93 years) were examined for osteon population density (OPD), osteon area (On.Ar), and Haversian canal area (H.Ar) of secondary osteons to compare between femora, ribs, and humeri and assess against age. In the pooled sex sample, no statistically significant correlations were observed between age and each histological variable. In the males, OPD of the femur increased significantly with age, as did porosity in the rib. In the male humeri, OPD increased moderately with age, while H.Ar was decreased moderately with age. Intra-bone comparisons showed that males had significantly higher osteon counts in their ribs compared to their femora, while their ribs showed statistically significantly less porosity than their humeri. When bone size was accounted for, by adjusting the femur and humerus histology data by robusticity indices, histology values were found to be similar between bones within the same individual. This is despite the upper and lower limbs receiving different ranges and types of biomechanical load. Our findings demonstrate that bone size influences histomorphometry, and this could confound age-at-death estimations that have not been adjusted for robusticity. Future studies would benefit from examining bone histomorphometry within a larger sample size and incorporating bone robusticity measures into histology analyses.

Radiologic, clinical, and patient-reported outcomes in stemless reverse shoulder arthroplasty at a mean of 46 months

BACKGROUND

The humeral stem can be a cause of problems in shoulder arthroplasty, for example, loss of bone stock, intraoperative and postoperative periprosthetic fractures, or postoperative infections involving the medullary canal. Therefore, stemless reverse shoulder arthroplasty (slRSA) has gained popularity, particularly in terms of preserving bone stock. However, there are limited data available on the midterm outcomes of slRSA. The objective of this study was to evaluate the clinical, radiologic, and patient-reported outcomes of slRSA at a minimum follow-up period of 2 years.

METHODS

Data on all stemless reverse shoulder prostheses implanted between January 2016 and October 2020 were collected. Patients were followed up at 6 weeks and 6, 12, and 24 months postoperatively. Clinical and radiologic data as well as patient-reported outcome measures were assessed with validated questionnaires (University of California at Los Angeles Shoulder Score [UCLA], American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form [ASES], Quick Disabilities of the Arm, Shoulder, and Hand questionnaire [Quick-DASH], visual analog scale [VAS] for pain, Subjective Shoulder Value [SSV], and Constant-Murley score [CS]). All patients had a minimum follow-up of 2 years.

RESULTS

During the observation period, 26 shoulders in 25 patients fulfilled the inclusion criteria. The mean follow-up was 46.8 months (range 25-66). The mean age was 70.1 years (range 59.9-86.4). At the most recent follow-up, a significant improvement was noted in the ASES score (55.9 ± 19.9 vs. 85.6 ± 10.7, P < .001), SSV (44.3 ± 18.7 vs. 85.3 ± 10.4, P < .001), Quick-DASH score (40.6 ± 22.0 vs. 17.8 ± 13.9, P < .001), VAS pain score (4.6 ± 3.2 vs. 0.9 ± 1.2, P < .001), and range of motion in flexion (66 ± 53 vs. 154 ± 22, P < .001) as well as in the absolute (44.1 ± 18.7 vs. 83.1 ± 10.1, P < .001) and relative CS (62.1 ± 27.8 vs. 111.9 ± 13.3, P < .001). Scapular notching was observed in 16% of cases, and radiolucent lines were detected in 28% of cases without symptoms of implant loosening. No revision was necessitated by any causes related to the stemless humeral component. Hence, implant survivorship was 100%.

CONCLUSIONS

With an ASES score showing a 30-point improvement and thus exceeding the minimal clinically important difference of 21 points and no revisions due to the stemless component, these results indicate that slRSA is a viable option, providing good to excellent midterm outcomes that are comparable to those of stemmed reverse shoulder prostheses, with the added advantage of bone stock preservation.

Influence of Graft Positioning during the Latarjet Procedure on Shoulder Stability and Articular Contact Pressure: Computational Analysis of the Bone Block Effect

The Latarjet procedure is the most popular surgical procedure to treat anterior glenohumeral (GH) instability in the presence of large anterior glenoid bone defects. Even though the placement of the bone graft has a considerable influence on its efficacy, no clear indications exist for the best graft position. The aim of this study was to investigate the influence of the medial-lateral positioning of the bone graft on the contact mechanics and GH stability due to the bone block effect. Four finite element (FE) models of a GH joint, with a 20% glenoid bone defect, treated by the Latarjet procedure were developed. The FE models differed in the medial-lateral positioning of the bone graft, ranging from a flush position to a 4.5 mm lateral position with respect to the flush position. All graft placement options were evaluated for two separate shoulder positions. Anterior GH instability was simulated by translating the humeral head in the anterior direction, under a permanent compressive force, until the peak translation force was reached. Joint stability was computed as the ratio between the shear and the compressive components of the force. The lateralization of the bone graft increased GH stability due to the bone block effect after a 3 mm lateralization with respect to the flush position. The increase in GH stability was associated with a concerning increase in peak contact pressure due to the incongruous contact between the articulating surfaces. The sensitivity of the contact pressures to the medial-lateral positioning of the bone graft suggests a trade-off between GH stability due to the bone block effect and the risk of osteoarthritis, especially considering that an accurate and consistent placement of the bone graft is difficult in vivo.

Metaphyseal sleeves in revision total knee arthroplasties: Computational analysis of bone remodeling

BACKGROUND

Metaphyseal sleeves help maintain long term stability and reduce revision rate for aseptic loosening in total knee arthroplasty (TKA) revision. However, their performance regarding bone remodeling is still poorly known for the long term. This study aimed to investigate the impact of metaphyseal sleeves on the bone remodeling of the tibia.

METHODS

Five finite element models of a female tibia with different implant configurations (regarding stem length and metaphyseal sleeve application) were developed. Loading conditions included joint reaction force, muscle, and tibia-fibula loads from 6 instances of the gait cycle. The bone remodeling model applied was adapted to the subject under analysis by selecting the bone remodeling parameters that best replicated the bone density distribution of the tibia estimated from the CT data. Changes in bone density after TKA were evaluated in 8 regions of interest.

RESULTS

Global bone loss ranged from -31.16%, in 115 mm stemmed configurations, to -20.93%, in 75 mm stemmed configurations. Apart from the lateral and posterior regions in the proximal tibia, whose bone loss reduced and increased, respectively, due to the incorporation of a metaphyseal sleeve, changes in bone density were similar with and without a metaphyseal sleeve for each stem length.

CONCLUSION

The results suggest that bone remodeling of the tibia is not critically affected by the incorporation of metaphyseal sleeves. Considering that sleeves are believed to present a favorable clinical outcome in stability and osseointegration, reducing the revision rate for aseptic loosening, their advantages seem to outweigh their disadvantages regarding bone remodeling.

Proximal humeral bone loss in stemless shoulder arthroplasty: potential factors influencing bone loss and a new classification system

INTRODUCTION

Proximal humeral bone loss in total shoulder arthroplasty (TSA) is more frequent than in hemiarthroplasty. Factors such as age, gender, inclination angle, and radiolucent lines may also contribute. Additionally, current bone loss grading systems are often not sensitive enough to detect slight bone changes, especially at the medial calcar where bone loss is commonly observed. This study uses a new, more detailed bone loss grading system to evaluate factors that could influence bone loss at the proximal humerus.

MATERIALS AND METHODS

In this single-center prospective study, patients underwent hemiarthroplasty or TSA with an anatomic stemless prosthesis. Bone loss was measured at the proximal humerus using the new grading system. The effect of treatment type, age, gender, radiolucent lines, and inclination angle on bone loss was evaluated. The Constant-Murley score of patients was assessed and complications recorded.

RESULTS

Ninety-one shoulders were available for the final follow-up examination at a median of 85.0 months (range 82.6-121.1 months). Bone loss was found at the proximal humerus in approximately one-third of shoulders, and significantly more shoulders had bone loss in TSA than in hemiarthroplasty (P = 0.03). However, this difference was no longer significant after stratifying by gender and age (P > 0.05). Bone loss significantly correlated with gender (P = 0.03) but not with treatment type, radiolucent lines, and the postoperative inclination angle (P > 0.05). Most Constant-Murley score components did not differ significantly between shoulders with and without bone loss (P > 0.05). Lastly, six complications and four revisions were reported.

CONCLUSIONS

Results showed gender had the greatest influence on bone loss after stemless shoulder arthroplasty. Furthermore, both patients with or without bone loss can expect similar clinical outcomes with the stemless prosthesis used in this study. Lastly, the new grading system is simple and straightforward to use.

Stemless Total Shoulder: A Review of Biomechanical Fixation and Recent Results

Introduction: Anatomic total shoulder arthroplasty is the replacement of the humeral head and glenoid surfaces with the goal of replicating normal anatomy. It is commonly utilized for patients with osteoarthritis, rheumatoid arthritis, and osteonecrosis, who have decreased range of motion (ROM), persistent pain, and loss of strength. Total shoulder Arthroplasty (TSA) is the third most common joint replacement in the United States. The incidence of TSA has been increasing, some data suggest that by the year 2025, TSA incidence may rise to 439,206 operations per year. In recent years, stemless total shoulder implants have become available. Results: These implants preserve bone stock while decreasing complications such as osteolysis, stress shielding and periprosthetic fracture. Stemless implants improve anatomic reconstruction and biomechanical function of the shoulder joint. Conclusion: Increasing amounts of data suggest stemless TSA to be a safe and effective technology that will become more common in the coming year.

Experimental characterization and micromechanical modeling of the elastic response of the human humerus under bending impact

This paper investigates the characterization and numerical modeling of the elastic behavior of the human humerus bone using a recently developed micromechanical approach coupled to nanoindentation measurements. At first, standard three-point bending experiments were conducted under low static loading, using several humerus diaphysis in order to identify the apparent elastic modulus of the bone in static regime. Then, a drop tower impact experiment was used on the same set of humerus diaphysis specimens, in order to assess the elastic modulus in dynamic regime. These measurements will be used as reference bases for comparison purpose. The originality of this work, lies in the coupling between a two-phase micromechanical approach based on Mori-Tanaka homogenization scheme for cylindrical voids and nanoindentation measurements of the elastic modulus of the bone matrix phase. This model has been implemented using a user defined material subroutine VMAT in ABAQUS© Explicit code. The bone mechanical response prediction using the proposed methodology was validated against previous standard experimental data. Finally, it was shown that the numerical predictions are consistent with the physical measurements obtained on human humerus via the good estimation of the ultimate impact load.

Primary stability analysis of stemless shoulder implants

Although the primary stability of joint implants is fundamental for successful osseointegration, little is know about this issue in the context of stemless shoulder implants. Considering 3D finite element models, the purpose of this study was to evaluate the primary stability of five stemless designs, based on the Sidus, SMR, Simpliciti, Eclipse, and Global Icon stemless systems. Three alternative bone quality conditions were considered for cancellous bone. For the Sidus, SMR, and Simpliciti designs, which do not possess a collar that sits on the cortical rim of the humeral resected surface, contact and no contact conditions were considered between the bone surface and the humeral head components. Micromotions at bone-implant interfaces promoting osseointegration were computed as a measure of primary stability for eight load cases consisting of peak in vivo joint loads measured during selected upper limb activities. Under good bone quality conditions, all stemless designs presented micromotions below 150 μm. The Eclipse-based and Global-Icon based designs were the least sensitive to bone quality. Stemless designs presenting a solid collar or contact between the humeral head component and bone provided more stability. Overall, the Eclipse-based and Global Icon-based designs presented the best performance from the primary stability point of view. However, if bone adaptation data available in the literature are considered along with the primary stability data computed here, the Global Icon-based design, as well as other designs, might be considered superior long-term options due to their better compromise between primary stability and impact on bone adaptation.

A multicenter, prospective 2-year analysis of the Sidus stem-free shoulder arthroplasty system

Background

The purpose of this multicenter, prospective study was to evaluate the efficacy and safety of a stemless total shoulder arthroplasty compared with a traditional stemmed control.

Methods

Ninety-five shoulders were selected for participation in this Food and Drug Administration investigational device exemption clinical trial and underwent stemless total shoulder arthroplasty. Subjects returned for follow-up at 6 weeks, 6 months, 12 months, and 2 years postoperatively. Outcome measures included pain; range of motion; American Shoulder and Elbow Surgeons, Western Ontario Osteoarthritis of the Shoulder, and Short Form 12 scores; and radiographic review. Baseline data were compared with 2-year follow-up data to determine the rate of composite clinical success compared with the stemmed control.

Results

All outcome assessments demonstrated significant improvements (P ≤ .007). The mean American Shoulder and Elbow Surgeons score improved from 20 to 89 (P < .0001), and the mean shoulder pain score decreased from 8.3 ± 1.6 to 0.7 ± 1.5 (P < .0001). The mean Western Ontario Osteoarthritis of the Shoulder score decreased from 1443 ± 256 to 203 ± 267 (P < .0001). On the Short Form 12, the mean physical health score increased from 33 ± 7 to 48 ± 9 (P < .0001) and the mean mental health score increased from 50 ± 13 to 54 ± 8 (P = .007). Mean active forward elevation increased from 97° ± 27° to 143° ± 25° (P < .0001), and mean active external rotation increased from 21° ± 16° to 53° ± 18° (P < .0001). Kaplan-Meier analysis showed an implant survivorship rate of 98% at 2 years. The composite clinical success rate was 87% compared with 85% for the stemmed control.

Conclusions

This study showed that a stemless rough-blasted humeral implant with metaphyseal bone fixation provides good clinical and radiographic outcomes and survivorship at 2 years, with outcomes comparable to a traditional stemmed implant.

Stress analysis in a bone fracture fixed with topology-optimised plates

The design of commercially available fixation plates and the materials used for their fabrication lead to the plates being stiffer than bone. Consequently, commercial plates are prone to induce bone stress shielding. In this study, three-dimensional fixation plates are designed using topology optimisation aiming to reduce the risk of bone stress shielding. Fixation plate designs were optimised by minimising the strain energy for three levels of volume reduction (i.e. 25%, 45% and 75%). To evaluate stress shielding, changes in bone stress due to the different fixation plate designs were determined on the fracture plane of an idealised shaft of a long bone under a four-point bending load considering the effect of a patient walking with crutches of a transverse fractured tibia. Topology optimisation is a viable approach to design less stiff plates with adequate mechanical strength considering high volume reductions, which consequently increased the stress transferred to the bone fracture plane minimising bone stress shielding.

Bone adaptation impact of stemless shoulder implants: a computational analysis

BACKGROUND

Despite stemless implants showing promising functional and radiologic clinical outcomes, concerning signs of complications, such as bone resorption, have been reported. The aim of this study was to investigate the influence of 5 stemless designs on the bone adaptation process of the humerus.

METHODS

Three-dimensional finite element models of shoulder arthroplasties were developed considering stemless designs based on the Eclipse, Global Icon, SMR, Simpliciti, and Sidus stemless systems. For the designs not possessing a collar that covers the entire resected surface of the humerus, conditions of contact and no contact were simulated between the humeral head components and the bone surface. By use of a bone remodeling model, computational simulations were performed considering 6 load cases of standard shoulder movements. The bone adaptation process was evaluated by comparing differences in bone density between the implanted models and the intact model of the humerus.

RESULTS

Overall, the design of the stemless implants had a relevant impact on the bone adaptation process of the humerus. The Eclipse-based design caused the largest bone mass loss, whereas the SMR-based design caused the least. When contact was simulated between the humeral head components of the SMR-, Simpliciti-, and Sidus-based designs and the resected bone surface, bone resorption increased.

DISCUSSION

Considering only the bone adaptation process, the results suggest that the SMR-based implant presents the best performance and that contact between the humeral head component and the resected bone surface should be avoided. However, because other factors must be considered, further investigation is necessary to allow definite recommendations.

Cementless metaphyseal reverse shoulder arthroplasty: our preliminary experience

Reverse shoulder arthroplasty (rTSA) is a largely used procedure with a wide variety of indications. The incidence of this surgery is increased in recent years and the literature expects similar trend for the future. Metaphyseal stem rTSA seems to be a promising solution considering major objectives the preservation of humeral bone stock and ease of revision. In our study we analyzed 19 patients treated with cementless metaphyseal stem rTSA for osteoarthritis (group A) and acute fractures (group B). In group A (7 patients) the average Constant score improved from 21,57 (16-29) to 56,85 (38-72), the average SST improved from 2,29 (1-4) to 9,43 (8-12) and the mean VAS score improved from 14,29 to 4,86. In group B (12 patients) the mean Constant-Murlay score at last follow up was 42,17; the average SST was 7 and average pain score was 8,92. Overall active range-of-motion (ROM) improved significantly. Surgical considerations, clinical (analyzing Constant score and Simple Shoulder Test) and radiological short-term outcomes are encouraging, with low rate of complications. Long term follow-up studies are necessary to confirm our findings and the potential benefits related to these implants. (www.actabiomedica.it)