Testing of a Novel Method for Securing Ligaments Against Bone During Simultaneous Medial and Lateral Elbow Ligament Reconstruction.

PURPOSE: A ligament reconstruction method that simultaneously tensions the medial and lateral sides of the elbow and maintains tension with compression plates on the proximal ulna is proposed for the treatment of bidirectional elbow ligament instability. Graft slippage, catastrophic failure, and excessive displacement were evaluated. Biomechanical stability without graft slippage was hypothesized. METHODS: Eight cadaveric ligament reconstruction simulations were created through the dissection of three cadaver arms. Each reconstruction was statically tested with 160 N in a manner where it was first augmented with an absorbable suture and then without. Then, 3 more ligament reconstruction simulations were created for dynamic testing with each undergoing testing at 80 N for 2,000 cycles at 2 Hz. Construct displacement and graft slippage were recorded for each load application. RESULTS: No grafts failed catastrophically and no graft slippage was observed with either static or dynamic loading. Under static loading, the mean change in displacement between augmented and nonaugmented ligament reconstruction simulations was 28.7% ± 21% (augmented 3.95 ± 1.81 mm vs nonaugmented 4.89 ± 2.22 mm). The mean stiffness was 66.6 ± 26.6 N/mm for augmented and 64.6 ± 23.2 N/mm for nonaugmented simulations. With dynamic loading, the mean displacement for augmented graft ligament reconstruction simulations was 1.55 ± 0.16 mm compared with 2.18 ± 0.77 mm for nonaugmented reconstruction simulations. CONCLUSIONS: This method of fixation to the proximal ulna for the simultaneous reconstruction of medial and lateral elbow ligaments successfully prevented graft slippage without excessive construct displacement during static and dynamic testing. Ligament augmentation with absorbable sutures decreased the construct displacement. CLINICAL RELEVANCE: This ligament fixation method may be a viable alternative for the treatment of concomitant medial and lateral elbow instability.

Testing of Novel Total Elbow Prostheses Using Active Motion Experimental Setup.

PURPOSE: The goal of this study was to test a novel uncemented and unconstrained total elbow arthroplasty (Kaufmann total elbow) design that is stabilized through a ligament reconstruction. METHODS: We quantified the implant stability after 25,000 cycles, which represents the time between implantation and when ligament and bone healing has occurred. We used an active motion experimental setup that applies tendon loads via pneumatic cylinders and reproduces the forearm-originating dynamic stabilizers of the elbow. The novel total elbow arthroplasty was actuated for 5,000 full flexion-extension cycles at 5 different shoulder positions. Four Sawbones and 4 cadaver elbows were employed. Angular laxity and implant stability were recorded prior to testing and after each 5,000-loading cycle. RESULTS: Four Sawbones and 4 cadaver elbows were implanted with the uncemented total elbow arthroplasty and did not demonstrate fixation failure or substantial laxity after 25,000 cycles of loading imparted at different shoulder positions. CONCLUSIONS: Our findings demonstrate that the Kaufmann total elbow replacement implanted into cadaver and Sawbones specimens did not exhibit fixation failure or excessive laxity after 25,000 cycles. CLINICAL RELEVANCE: An uncemented, nonmechanically linked total elbow arthroplasty that gains component fixation using intramedullary screws and employs a ligament reconstruction to stabilize the elbow has the potential to be a valuable management option, particularly in younger patients.

Strength of Humeral and Ulnar Intramedullary Screw Fixation.

PURPOSE: The goal of this study was to test the pullout strength of intramedullary (IM) screws from within the humerus to establish their ability to seat an uncemented elbow arthroplasty. METHODS: Six humerus and 6 ulna Sawbones specimens were drilled with a drill bit diameter of 5/16 inches, and the inner cortex was hand tapped for a ⅜-16 thread. A ⅜-16 custom-made titanium screw with an outer bolt diameter of 3/8 inches and 16 threads per inch was inserted by hand into the tapped holes. The specimens were then axially tensile loaded at a rate of 5 mm per minute until either the screw began to pull out from the bone or a fracture was noted. RESULTS: Intramedullary screw fixation in the humerus achieved an average pullout strength of 1,439 pound-force (6,401 N), and IM screw fixation in the ulna achieved an average pullout strength of 882 pound-force (3,923 N). A fracture was noted in 3 humeral specimens, with 3 screws pulling out. In the ulna, the IM axial load caused a fracture in 5 specimens, and in 1 specimen, the screw pulled out. CONCLUSIONS: Our findings demonstrate that IM screw fixation can create a tensile force within the screw that is greater than that required to generate the calculated level of compression between the implant and bone. CLINICAL RELEVANCE: This may be beneficial in ensuring fixation between arthroplasty components and bone.

A comparison of face-to-face and fully online problem-based learning: Student results and staff experiences, 2014-2020.

ISSUE ADDRESSED: Problem-based learning (PBL) is a student-directed pedagogy that promotes critical thinking, self-directed learning and communication skills essential for health promotion students and practitioners. This paper reports on student results, student evaluation and staff experience of PBL in the face-to-face and fully online environment in an undergraduate health sciences unit in an Australian university. METHODS: A single time-point study using quantitative and qualitative administrative student data (2014-2020) and narrative reflection from teaching academics (n = 5) was undertaken. Descriptive, independent t test and bivariate analyses for student results data were conducted; an inductive approach was used to analyse qualitative data and create codes. RESULTS: Student sample (n = 472) consisted face-to-face (n = 358, 75.8%) and online (n = 114, 24.2%) enrolments. Final Unit Mark was significantly higher for fully online students compared with face-to-face students in 2018 (P = .007) and 2019 (P = .001). Final Unit Achievement was significantly higher for fully online students compared with face-to-face students in 2018 (P = .017) and 2019 (P = .043). Three themes emerged: The PBL approach; Evolution of PBLs; Student skills and competencies. DISCUSSION: PBL allows students to learn through facilitated problem solving and strong collaborative skills. The face-to-face and fully online PBLs improved the student and academic staff experience, while supporting the development of critical thinking and self-directed research. Further, it supported students to develop their core health promotion competencies; and enhanced the online student learning experience. SO WHAT?: Vital for contemporary, global graduates, the fully online PBL approach allows students to build critical academic and professional skills utilising current information technology relevant for collaborative professional practice.

Active Motion Laboratory Test Apparatus for Evaluation of Total Elbow Prostheses.

Purpose: The goal of this study was to develop a dynamic elbow testing apparatus that reproduces active joint motion at different shoulder positions to quantify the capabilities of total elbow arthroplasty designs. Methods: We designed a testing apparatus to create active cyclic elbow joint motion in human cadaveric and sawbones composite upper extremities. Two pneumatic actuators recreated humerus-originating muscles while rubber bands simulated forearm muscle action. Arthroplasty durability was quantified through laxity assessment at predetermined cyclic loading intervals. Results: Humeral forces were recorded in three specimens to generate active elbow motion at different degrees of shoulder abduction. The laxity in varus and valgus was measured as deflection between two fixed markers. Conclusions: In vitro simulation of elbow biomechanics through active cyclic elbow motion at different degrees of shoulder abduction may characterize in vivo performance of total elbow arthroplasty. Clinical relevance: Quantifying total elbow arthroplasty stability after cyclic loading in different shoulder positions may assist preclinical evaluation of arthroplasty designs.

Posterior Flange Cyclic Loading in a Novel Total Elbow Arthroplasty.

Purpose: The goal of this study was to test the static and dynamic strength and loosening resistance of the posterior flange of a novel total elbow arthroplasty. We also examined the forces experienced by the ulnohumeral joint and the posterior olecranon during expected elbow use. Methods: Static stress analysis was performed for 3 flange sizes. Failure testing was conducted on 5 flanges (1 medium size and 4 small sizes). Loading occurred to reach 10,000 cycles. If this was accomplished, the cyclic load was increased until failure occurred. If failure occurred before 10,000 cycles, a lower force was employed. The safety factor for each implant size was calculated, and implant failure or loosening was observed. Results: Static testing revealed a safety factor of 6.6, 5.74, and 4.53 for the small, medium, and large flanges, respectively. The medium-sized flange completed 10,000 cycles with 1,000 N at 1 Hz, and then the force was increased until it failed at 23,000 cycles. Two small-sized flanges failed at 2,345 and 2,453 cycles, respectively, when loaded with 1,000 N. Two more small flanges were loaded with 729 N for 10,000 cycles, and then the cyclic load was continued until they failed at 17,000 and 17,340 cycles, respectively. No screw loosening was noted in any specimens. Conclusions: This study demonstrates that the posterior flange withstood static and dynamic forces greater than what is expected during in vivo use of a novel total elbow arthroplasty design. Static strength calculation and cyclic loading demonstrate that the medium-sized posterior flange is stronger than the small-sized posterior flange. Clinical Relevance: Ensuring that the ulnar body component and the posterior flange maintain secure connectivity with the polyethylene wear component may be beneficial to the proper function of a novel nonmechanically linked total elbow arthroplasty.