Biomechanical Evaluation of Different Designs of Glenospheres in the SMR Reverse Shoulder Prosthesis: Micromotion of the Baseplate and Risk of Loosening

Background Early outcomes of reverse shoulder arthroplasty have been encouraging. Scapular notching remains a major concern. In an attempt to reduce this problem, newer glenospheres are available. This biomechanical study performed in vitro, assessed the micromotions of baseplate in different designs of glenospheres and the relative risk of loosening. Methods A dynamic shear force was applied to each type of glenosphere in various angles of abduction. The micromotion of the glenoid baseplate after 1000 cycles of dynamic loading was measured and compared. Results Eccentric glenospheres were shown to have increased micromotion compared to the concentric designs of the same size. The greatest baseplate micromotion (26.83 μm) was well within the accepted limit for osseous in growth into uncemented prosthesis. Discussion We therefore conclude that the magnitude of the increased micromotion is small and is not expected to adversely affect osseous in growth onto the glenoid baseplate.

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Assessment of glenoid baseplate initial micromotion and fixation strength in reverse total shoulder arthroplasty designs using a direct shear force methodology

Shoulder & Elbow ◽

10.1177/17585732211032945 ◽

2021 ◽

pp. 175857322110329

Author(s):

Therese E Parr ◽

Jennifer K Anderson ◽

Alan M. Marionneaux ◽

John M Tokish ◽

Stefan J Tolan ◽

...

Keyword(s):

Shoulder Arthroplasty ◽

Shear Force ◽

Total Shoulder Arthroplasty ◽

Reverse Total Shoulder Arthroplasty ◽

Fixation Strength ◽

Shoulder Prosthesis ◽

Direct Shear ◽

Device Failure ◽

Glenoid Baseplate ◽

Reverse Total Shoulder

Background In a reverse total shoulder arthroplasty, the altered glenohumeral joint center of rotation subjects the glenoid baseplate to increased shear forces and potential loosening. Methods This study examined glenoid baseplate micromotion and initial fixation strength with the application of direct shear force in a Sawbone model. The reverse total shoulder arthroplasty systems examined were the DJO Reverse® Shoulder Prosthesis, the Exactech Equinoxe® Reverse System, and the Tornier AequalisTM Reverse Shoulder Prosthesis. Specimens were cyclically tested with increasing shear loads until 150 µm of displacement between the implant and glenoid was achieved, and subsequently until failure, classified as either 1 cm of implant/glenoid displacement or fracture. Results The average load withstood for the 150 µm threshold for DJO, Tornier, and Exactech was 460 ± 88 N, 525 ± 100 N, and 585 ± 160 N, respectively. The average total load at device failure for DJO, Tornier, and Exactech was 980 ± 260 N, 1260 ± 120 N, and 1350 ± 230 N, respectively. Discussion The Exactech implant design trended toward requiring more load to induce micromotion at each threshold and to induce device failure, most commonly seen as inferior screw pull out. This study proposes design features that may enhance fixation and suggests little risk of initial micromotion or failure during initial post-operative recovery.

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Biomechanical evaluation of a non-locking pre-manufactured loop suture technique compared to a three-loop pulley suture in a canine calcaneus tendon avulsion model

Veterinary and Comparative Orthopaedics and Traumatology ◽

10.3415/vcot-15-04-0061 ◽

2016 ◽

Vol 29 (02) ◽

pp. 131-135 ◽

Cited By ~ 4

Author(s):

Anna Dunlap ◽

Thomas McNicholas ◽

Stanley Kim

Keyword(s):

Surgical Repair ◽

Suture Technique ◽

Biomechanical Study ◽

Gap Formation ◽

Calcaneal Tendon ◽

Polypropylene Suture ◽

Biomechanical Evaluation ◽

The Mean ◽

Tendon Avulsion

Summary Objective: The purpose of this cadaveric study was to compare the strength of a non-locking pre-manufactured loop (Speed -Whip™ [SW]) suture pattern using Fiber-wire® with the three-loop pulley (TLP) suture pattern using polypropylene for the surgical repair of canine calcaneal tendon avulsion injuries. Methods: In vitro biomechanical study using 22 paired tendons collected from 11 canine cadavers. Paired tendons were repaired with either a SW suture pattern using Fiberloop® suture or a TLP suture pattern using polypropylene suture. Tensile loads required to create a 1 mm gap, 3 mm gap, and construct failure were measured. Results: The mean loads to achieve a 1 mm gap in the TLP and SW constructs were not significantly different. Gap formation at 3 mm occurred at significantly lower loads for the SW (106.4 ± 21.5N) than for the TLP (127.2 ± 27.5N) (p = 0.05). The mean loads to construct failure for the TLP (172.8 ± 39.4N) and SW (131.3 ± 34.3N) were significantly different (p = 0.001). Clinical significance: The TLP with polypropylene suture is superior to the SW using Fiberloop® at resistance to 3 mm gap formation.

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A preliminary biomechanical evaluation in a simulated spinal fusion model

Journal of Neurosurgery Spine ◽

10.3171/spi-07/11/542 ◽

2007 ◽

Vol 7 (5) ◽

pp. 542-548 ◽

Cited By ~ 7

Author(s):

Lisa A. Ferrara ◽

Illya Gordon ◽

Madeline Coquillette ◽

Ryan Milks ◽

Aaron J. Fleischman ◽

...

Keyword(s):

Bone Graft ◽

Intermediate Phase ◽

Biomechanical Study ◽

Interface Pressure ◽

Fusion Model ◽

Ventral Plate ◽

Bone Fusion ◽

Biomechanical Evaluation ◽

Cervical Plate

Object A preliminary in vitro biomechanical study was conducted to determine if the pressure at a bone graft–mortise interface and the load transmitted along a ventral cervical plate could be used as parameters to assess fusion status. Methods An interbody bone graft and a ventral plate were placed at the C3–4 motion segment in six fresh cadaveric goat spines. Polymethylmethacrylate (PMMA) was used to simulate early bone fusion at the bone graft site. The loads along the plate and the simultaneous pressures induced at the graft–endplate interfaces were monitored during simulated stages of bone healing. Each specimen was nondestructively tested in compression loading while the pressures and loads at the graft site were recorded continuously. Each specimen was tested under five conditions (Disc, Graft, Plate, PMMA, and Removal). Results The pressure at the interface of the bone graft and vertebral endplate did not change significantly with the addition of the ventral plate. The interface pressure and segmental stiffness did increase following PMMA augmentation of the bone graft (simulating an intermediate phase of bone fusion). The load transmitted along the ventral plate in compression increased after the addition of the bone graft, but decreased after PMMA augmentation. Thus, there was an increase in pressure at the graft–endplate interface and a decrease in load transferred along the ventral plate after the simulation of bone fusion. Upon removal of the ventral plate, the simulated fusion bore most of the axial load, thus explaining a further increase in graft site pressure. Conclusions These observations support the notions of load sharing and the redistribution of loads occurring during and after bone graft incorporation. In the clinical setting, these parameters may be useful in the assessment of fusion after spine surgery. Although feasibility has been demonstrated in this preliminary study, further research is needed.

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Periprosthetic humeral fractures after reverse shoulder arthroplasty. Case report

Einstein (São Paulo) ◽

10.1590/s1679-45082017rc4037 ◽

2017 ◽

Vol 16 (1) ◽

Author(s):

Andre Wajnsztejn ◽

Noel Oizerovici Foni ◽

Dan Oizerovici ◽

Robinson Esteves Santos Pires ◽

Benno Ejnisman

Keyword(s):

Shoulder Arthroplasty ◽

Reverse Shoulder Arthroplasty ◽

Humeral Fracture ◽

Humeral Fractures ◽

Shoulder Prosthesis ◽

Shoulder Replacement ◽

Brazilian Literature ◽

Reverse Shoulder Prosthesis ◽

Near Future ◽

Injury Classification

ABSTRACT Periprosthetic fractures is a severe complication after joint replacement. The rapidly increase of reverse shoulder arthroplasty surgeries, periprosthetic humeral fractures, which are described as rare, may increase in the near future. We report the case of displaced humeral fracture bellow the stem of reverse shoulder prosthesis. The patient was an 85-year-old woman who had a total shoulder replacement 6 years previously. The surgical solution consisted of plate osteossynthesis and cerclage. This report describes an unprecedented case in Brazilian literature; and gives an overview of the existing literature including this injury classification.

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