Glenoid implant orientation and cement failure in total shoulder arthroplasty: a finite element analysis.

To minimize glenoid implant loosening in total shoulder arthroplasty (TSA), the ideal surgical procedure achieves correction to neutral version, complete implant-bone contact, and bone stock preservation. These goals, however, are not always achievable, and guidelines to prioritize their impact are not well established. The purpose of this study was to investigate how the degree of glenoid correction affects potential cement failure. Eight patient-specific computer models were created for 4 TSA scenarios with different permutations of retroversion correction and implant-bone contact. Two bone models were used: a homogeneous cortical bone model and a heterogeneous cortical-trabecular bone model. A 750-N load was simulated, and cement stress was calculated. The risk of cement mantle fracture was reported as the percentage of cement stress exceeding the material endurance limit. Orienting the glenoid implant in retroversion resulted in the highest risk of cement fracture in a homogeneous bone model (P < .05). In the heterogeneous bone model, complete correction resulted in the highest risk of failure (P = .0028). A positive correlation (ρ = 0.901) was found between the risk of cement failure and amount of exposed trabecular bone. Incorporating trabecular bone into the model changed the effect of implant orientation on cement failure. As exposed trabecular bone increased, the risk of cement fracture increased. This may be due to shifting the load-bearing support underneath the cement from cortical bone to trabecular bone.

Yongpravat C ，Kim HM ，Gardner TR ，Bigliani LU ，Levine WN ，Ahmad CS ... -  《-》

Risks of loosening of a prosthetic glenoid implanted in retroversion.

Farron A ，Terrier A ，Büchler P 《JOURNAL OF SHOULDER AND ELBOW SURGERY》

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

Hopkins AR ，Hansen UN ，Amis AA ，Emery R ... -  《JOURNAL OF SHOULDER AND ELBOW SURGERY》

Effects of osteoarthritis on load transfer after cemented total shoulder arthroplasty.

Total shoulder arthroplasty is commonly performed to treat glenohumeral osteoarthritis (OA); however, little is understood of the mechanics of the reconstructed OA shoulder. We sought to establish the effects of OA-induced changes in bone density and retroversion angle on load transfer and stress distribution in the bone-implant system of the scapula. We developed finite element models of reconstructed healthy and OA scapulas with a virtually implanted glenoid prosthesis design. For the OA scapula, models with uncorrected and corrected retroversion were created. Loads were applied at the center or posteriorly on the glenoid surface. Our results suggest that with reconstruction of the corrected glenoid with a contemporary implant, cement stresses increase and the load transfer pattern changes with eccentric loads. The load transfer and local stresses in the bone-implant system in the retroverted glenoid are less sensitive to changes in loading location. Furthermore, the load transfer in the OA glenoid is less sensitive to the effect of peg proximity to the cortical shell than in the healthy glenoid. We provided evidence of how load sharing is altered among healthy, corrected OA, and retroverted OA glenoids. We demonstrated that correction of retroversion in OA glenoids may actually increase the risk for stress shielding and cement failure compared with retroverted glenoids, and OA patients can accommodate shorter pegs because of the higher glenoid bone stiffness in the OA glenoid.

Patel RJ ，Gulotta L ，Wright TM ，Gao Y ... -  《-》

Three-dimensional finite element analysis of glenoid replacement prostheses: a comparison of keeled and pegged anchorage systems.

Lacroix D ，Murphy LA ，Prendergast PJ 《JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME》