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.

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.

Unstable Middle Phalanx Base Fractures Treated With an Internal Joint Stabilizer: Preliminary Results.

BACKGROUND: Unstable fractures of the base of the middle phalanx are notorious for causing chronic loss of proximal interphalangeal (PIP) joint function, and they remain a challenge for the hand surgeon. We report on a temporary intraoperatively constructed internal joint stabilizer for unstable PIP joint injuries. METHODS: Across 2 institutions, a retrospective chart review was performed for cases with acute presentation of pilon fracture or fracture-dislocation of the base of the middle phalanx which were surgically treated with an internal joint stabilizer. Information collected included time from injury to surgical intervention, time from implantation to device removal, complications, and preoperative and postoperative range of motion. RESULTS: Seven patients met the inclusion criteria with a mean age of 51 (range: 24-72) years and a mean follow-up of 29 (range: 11-72) months. After removal of the fixator, the mean arc of PIP joint motion was 8° to 88° (range: 0°-100°). There were no infections, no hardware loosening or failures, and no revision procedures. CONCLUSION: The current findings are comparable to the results for dynamic external fixators. An internal joint stabilizer for unstable injuries to the base of the middle phalanx provides satisfactory functional outcomes, allows early postoperative motion, and mitigates the routine complications which may arise with external fixation.

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.

SAVIOR ICU: sonification and vibrotactile interface for the operating room and intensive care unit.

Alarm fatigue is an issue for healthcare providers in the intensive care unit, and may result from desensitization of overbearing and under-informing alarms. To directly increase the overall identification of medical alarms and potentially contribute to a downstream decrease in the prevalence of alarm fatigue, we propose advancing alarm sonification by combining auditory and tactile stimuli to create a multisensory alarm. Participants completed four trials-two multisensory (auditory and tactile) and two unisensory (auditory). Analysis compared the unisensory trials to the multisensory trials based on the percentage of correctly identified point of change, direction of change and identity of three physiological parameters (indicated by different instruments): heart rate (drums), blood pressure (piano), blood oxygenation (guitar). A repeated-measures of ANOVA yielded a significant improvement in performance for the multisensory group compared to the unisensory group (p < 0.05). Specifically, the multisensory group had better performance in correctly identifying parameter (p < 0.05) and point of change (p < 0.05) compared to the unisensory group. Participants demonstrated a higher accuracy of identification with the use of multisensory alarms. Therefore, multisensory alarms may relieve the auditory burden of the medical environment and increase the overall quality of care and patient safety.