Development of a Cadaveric Shoulder Motion Simulator with Open-Loop Iterative Learning for Dynamic, Multiplanar Motion: A Preliminary Study.

Ex vivo shoulder motion simulators are commonly used to study shoulder biomechanics but are often limited to performing simple planar motions at quasi-static speeds using control architectures that do not allow muscles to be deactivated. The purpose of this study was to develop an open-loop tendon excursion controller with iterative learning and independent muscle control to simulate complex multiplanar motion at functional speeds and allow for muscle deactivation. The simulator performed abduction/adduction, faceted circumduction, and abduction/adduction (subscapularis deactivation) using a cadaveric shoulder with an implanted reverse total shoulder prosthesis. Kinematic tracking accuracy and repeatability were assessed using maximum absolute error (MAE), root mean square error (RMSE), and average standard deviation (ASD). During abduction/adduction and faceted circumduction, the RMSE did not exceed 0.3, 0.7, and 0.8 degrees for elevation, plane of elevation, and axial rotation, respectively. During abduction/adduction, the ASD did not exceed 0.2 degrees. Abduction/adduction (subscapularis deactivation) resulted in a loss of internal rotation, which could not be restored at low elevation angles. This study presents a novel control architecture, which can accurately simulate complex glenohumeral motion. This simulator will be used as a testing platform to examine the effect of shoulder pathology, treatment, and rehabilitation on joint biomechanics during functional shoulder movements.

Pullout force of minimally invasive surgical and open pedicle screws-a biomechanical cadaveric study.

BACKGROUND: To assess whether lumbar pedicle screw placement with a minimally invasive surgical (MIS) vs. open technique imparts different biomechanical parameters and thus may affect failure rates. METHODS: Human cadaveric disarticulated lumbar vertebrae 1-5 were stabilised in cement. Pedicle screws were inserted either via the 'MIS' or 'open' technique, based on previously described anatomical landmarks. Each vertebra had one 'MIS' and one 'open' technique screw. Specimens were tested with an Instron mechanical testing machine, positioned to allow for testing of direct coaxial force. Load was applied until failure occurred, and load-displacement curves generated for each screw. RESULTS: Average failure load was found to be 685±399 N for MIS, versus 661±323 N for open technique (P=0.75). The average ultimate failure load was 748±421 N for MIS, versus 772±326 N for open (P=0.74). Average displacement until failure was 0.95±0.49 mm for MIS as compared to 0.95±0.62 mm for open (P=0.996). Axial stiffness was 936±217 N/mm for MIS and 1,016±263 N/mm for open (P=0.19). Average work required to result in failure was 0.84±1.09 J for MIS and 0.82±1.05 J for open (P=0.94). CONCLUSIONS: There was no significant difference in the biomechanical properties of the MIS as compared with open lumbar pedicle screws, when tested until failure under direct coaxial force. The clinical implication may be that there is no significant advantage in the biomechanical properties of MIS versus open lumbar pedicle screw insertion techniques.

Ultrasound-Guided Microinvasive Carpal Tunnel Release Using a Novel Retractable Needle-Mounted Blade: A Cadaveric Study.

Ultrasound (US)-guided microinvasive procedures are defined as those performed via needles without notable scarring. Ten cadaver hands underwent US-guided microinvasive carpal tunnel release using a novel needle-based tool, the micro i-Blade (Summit Medical Products, Inc, Sandy, UT). A US-imaged landmark, the inflexion point of the ligaments distal to the hook of the hamate, was used to position the distal extent of the cut. The transverse carpal ligament was successfully released in all hands without damage to nerves or arteries. In 3 specimens, the fascia between the thenar and hypothenar muscles was partly preserved, whereas the palmar aponeurosis was partly cut in 1 specimen. The micro i-Blade with the cutting knife retracted was also useful as a probe palpated through the palm of the cadaver hand, to test the release of the transverse carpal ligament and to guide the procedure.

The new injury severity score is a better predictor of extended hospitalization and intensive care unit admission than the injury severity score in patients with multiple orthopaedic injuries.

OBJECTIVE: To compare the scoring efficacy of the injury severity score (ISS) and the new injury severity score (NISS) in predicting extended hospital length of stay (LOS) and intensive care unit (ICU) admission and to determine the effect of multiple orthopaedic injuries (MOI) on the discrepancies between the ISS and NISS and their impact on extended LOS and ICU admission. DESIGN: Prospective cohort study. SETTING: Level 1 university trauma center. PATIENTS: All consecutive trauma admissions during the 2-year period ending on December 31, 2000, with age older than 14 years and survival greater than 24 hours were entered into the study. MAIN OUTCOMES: Extended (>or=10 days) hospital LOS and ICU admission. RESULTS: Of 3,100 patients, 7.5% had a higher NISS than ISS, spent more days in the hospital (22 versus 8; P < 0.001) and in the ICU (3.4 versus 0.1; P < 0.001), and had a higher mortality rate (8% versus 1.2%; P < 0.001) than patients with identical NISS and ISS. The NISS was found to be more predictive of longer (>or=10 days) LOS (receiver operating characteristic [ROC] NISS = 0.794, ISS = 0.782; P < 0.0001) and ICU admission (ROC NISS = 0.944, ISS = 0.918; P < 0.0001). The multivariate predictive model including NISS showed a better goodness of fit compared with the same model that included ISS. Patients with discrepant scores (NISS > ISS) spent a longer time in the hospital and in the ICU in addition to having an increased frequency of ICU admission. In 61% of the cases, MOI were responsible for the discrepant (NISS > ISS) scores. CONCLUSIONS: MOI have a significant effect on trauma outcomes such as LOS and ICU admission. The recognition of this high-risk group is not possible using the traditional ISS alone from retrospective or prospective databases. Considering its easier calculation and better predictive power, it is suggested that the NISS should replace the traditional ISS in trauma outcome research.