Effects of A2 Pulley Venting on Bowstringing and Tendon Slack: A Biomechanical Investigation.

BACKGROUND: A2 pulley release is often needed for exposure of the lacerated tendon, retrieval of retracted tendons, placement of core sutures, or to permit full motion and gliding of the repaired and edematous tendon. However, there is no agreement in the literature on the specific quantity of pulley venting that can be performed and recommendations are limited to an undefined "judicious release" of the pulleys when necessary. METHODS: Following a previously developed testing protocols, finger kinematics, tendon excursion, and bowstringing were evaluated on cadaveric hands for venting in increments of 20% of the pulley length. RESULTS: In our study, we found a statistically significant influence of venting on bowstringing, although no difference was found between fingers, and a significant difference in tendon slack, which was variable depending on the finger. Bowstringing started increasing at 20% of A2 venting and peaked at full release. Tendon slack did not start until 40% of A2 venting on the index finger, but started at 20% on the middle, ring, and small fingers. CONCLUSIONS: Venting of the A2 pulley leads to an incremental increase in tendon bowstringing and tendon slack. However, differences in metacarpophalangeal flexion angle were not observed until full A2 pulley release, and only observed in the index finger, and no differences were observed in proximal interphalangeal flexion angles. Therefore, the benefit of releasing the A2 pulley when clinically necessary will likely outweigh the risks of loss of motion or strength.

Impact of bone density and integrated screw configuration on standalone anterior lumbar interbody construct strength.

Background: In anterior lumbar interbody fusion (ALIF), the use of integrated screws is attractive to surgeons because of the ease of implantation and no additional profile. However, the number and length of screws necessary for safe and stable implantation in various bone densities is not yet fully understood. The current study aims to determine how important both length and number of screws are for stability of ALIFs. Methods: Three bone models with densities of 10, 15, and 20 pounds per cubic foot (PCF) were chosen as surrogates. These were instrumented using the Z-Link lumbar interbody system with either 2, 3, or 4 integrated 4.5 × 20 mm screws or 4.5 × 25 mm screws (Zavation, LLC, Flowood, MS). The bone surrogates were tested with loading conditions resulting in spine extension to measure construct stiffness and peak force. Results: The failure load of the construct was influenced by the length of screws (p=.01) and density of the bone surrogate (p<.01). There was no difference in failure load between using 2 screws and 3 screws (p=.32) or when using four 20 mm screws versus three 25 mm screws (p=.295). Conclusion: In our study, both bone density and length of screws significantly affected the construct's load to failure. In certain cases where a greater number of screws are unable to be implanted, the same stability can potentially be conferred with use of longer screws. Future clinical studies should be performed to test these biomechanical results.

The Joystick Method: A Mini Open Technique for Repairing Patellar Osteochondral Fractures With Concomitant Medial Patellofemoral Ligament Reconstruction.

Fixation of osteochondral fractures after patellar dislocation is typically done using an open approach due to the location of the defect. This is traditionally performed through a medial parapatellar arthrotomy to allow adequate visualization. By using the joystick method, adequate visualization is achieved with a smaller arthrotomy. Careful placement of the joystick in the planned anchor site of the medial patellofemoral ligament reconstruction reduces the number of drill sites in the patella.

Biomechanical Comparison of All-Suture, All-Inside Meniscus Repair Devices in a Human Cadaveric Meniscus Model.

OBJECTIVE: Newer all-suture, all-inside meniscus repair devices utilize soft suture anchors. The purpose of this study was to compare the biomechanical performance of 4 meniscus repair devices in human cadaver menisci: the JuggerStitch (all-suture, all-inside), the FiberStitch (all-suture, all-inside), a polyether ether ketone (PEEK) all-inside, and an inside-out device. DESIGN: Forty human cadaver menisci were tested after creating 20 mm longitudinal tears in the posterior meniscus. Each knee was randomized to 1 of 4 meniscus repair groups: JuggerStitch (all-suture, all-inside), FiberStitch (all-suture, all-inside), FAST-FIX 360 (PEEK-based anchor all-inside), and inside-out (with BroadbandTM tape meniscus needles). For each meniscus, 2 devices were used to prepare vertical mattress repair construct. The specimens were tested by pre-conditioning 20 cycles between 5 N and 30 N and then the tear diastasis was measured, followed by distraction to failure phase after imposing a displacement at a rate of 0.5 mm/s. RESULTS: Ten menisci were tested in each of the 4 groups. After pre-conditioning, there was no significant difference in the gap formation among groups (P = 0.212). The average failure load for the JuggerStitch, FiberStitch, PEEK all-inside, and inside-out was 384 N, 311 N, 207 N, and 261 N, respectively, with a significant difference between groups (P = 0.034). Post hoc analysis showed the JuggerStitch failure load was higher than the PEEK all-inside and inside-out (P = 0.005, and P = 0.045, respectively). There was no significant difference between the failure load of the JuggerStitch and FiberStitch (P = 0.225). CONCLUSION: The JuggerStitch all-suture device, FiberStitch all-suture device, PEEK all-inside, and inside-out devices have similar biomechanical properties for gapping and stiffness. The JuggerStitch all-suture, all-inside device has superior failure load compared with the PEEK all-inside and inside-out repair for longitudinal meniscus tear repair.

In Vitro Evaluation of Lateral Femur Condyle Free Chondral Fragment Swelling after Soaking in Normal Saline.

OBJECTIVE: After traumatic knee injuries, chondral fragments can avulse off bone with the progeny fragment becoming a loose body. The loose fragment may be larger than expected when trying to surgically repair the fragment back to its original site. The purpose of this study was to determine whether a loose chondral fragment from the lateral femur condyle would increase in size and weight after soaking in normal saline (NS) for 14 days. DESIGN: Twelve 6-mm OAT (osteoarticular transfer) plugs were harvested from 6 cadaver knees on the lateral femoral condyle to simulate a chondral fragment. The chondral fragments were then placed inside an airtight specimen container with NS (0.9% sodium chloride) and were measured over 14 days. RESULTS: After 14 days, the chondral fragments showed no increase in diameter as they measured an average of 5.567 ± 0.448 mm on Day 1 and 5.702 ± 0.253 mm on Day 14 (P = 0.183). The chondral fragments showed an increase in mass from an average of 0.058 ± 0.012 g on Day 1 to 0.073 ± 0.012 g on Day 14 (P < 0.001) and an increase in thickness from an average of 2.038 ± 0.346 mm on Day 1 to 2.229 ± 0.297 mm on Day 14 (P = 0.033). CONCLUSIONS: Chondral fragments in NS increase in mass and thickness over time, but do not change in diameter. When surgeons are evaluating loose chondral fragments for fixation, they should consider that these fragments may appear thicker than the recipient location.

Acetabular Wall Weakening in Total Hip Arthroplasty: A Pilot Study.

Total hip arthroplasty is a widely performed operation allowing disabled patients to improve their quality of life to a degree greater than any other elective procedure. Planning for a THA requires adequate patient assessment and preoperative characterizations of acetabular bone loss via radiographs and specific classification schemes. Some surgeons may be inclined to ream at a larger diameter thinking it would lead to a more stable press-fit, but this could be detrimental to the acetabular wall, leading to intraoperative fracture. In the attempt to reduce the incidence of intraoperative fractures, the current study aims to identify how increased reaming diameter degrades and weakens the acetabular rim strength. We hypothesized that there is proportionality between the reaming diameter and the reduction in acetabular strength. To test this hypothesis, this study used bone surrogates, templated from CT scans, and reamed at different diameters. The obtained bone surrogate models were then tested using an Intron 8874 mechanical testing machine (Instron, Norwood, MA) equipped with a custom-made fixture. Analysis of variance (ANOVA) was used to identify differences among reamed diameters while linear regression was used to identify the relationship between reamed diameters and acetabular strength. We found a moderate correlation between increasing reaming diameter that induced thinning of the acetabular wall and radial load damage. For the simplified acetabular model used in this study, it supported our hypothesis and is a promising first attempt in providing quantitative data for acetabular weakening induced by reaming.

Compressibility of Osteochondral Autograft Transfer Donor Grafts: A Comparison of Different Donor Regions and How Much Shortening Occurs of Plugs After Impaction.

Background: Osteochondral autograft transfer (OAT) is a useful technique for full-thickness cartilage lesions of the distal femur. Various techniques recommend harvesting a plug 2 mm longer than the recipient hole to allow for graft impaction. Grafts with limited compressibility may not sit flush when impacted. Purpose: To compare the compressibility/shortening of OAT donor plug regions from the distal femur of human cadaveric knees after impaction. Study Design: Controlled laboratory study. Methods: A total of 20 cadaveric knees (mean age, 70.3 ± 8.4 years) were divided into 4 donor regions: medial intercondylar (IC) notch, lateral IC notch, medial trochlea, and lateral trochlea. Each region was subdivided into 4 zones: far superior (FSZ), middle superior (MSZ), middle inferior (MIZ), and far inferior (FIZ). A total of 320 grafts (6-mm diameter, 15-mm depth) were extracted, and a custom-built machine was used to strike the graft 5 times using a predetermined energy of 0.11 J. The graft length was measured initially and after each impact. Statistical analysis of the compressibility for each of the 4 regions and all 16 zones was performed utilizing analysis of variance, with post hoc testing using the Fisher's least significant difference. Results: Compression in the lateral IC notch, medial IC notch, medial trochlea, and lateral trochlea was 2.4 ± 1.5, 2.1 ± 0.7, 3.1 ± 2.2, and 2.1 ± 0.6 mm, respectively, with significant differences between the 4 regions (P < .01) and the most compression in the medial trochlea (P < .01). Subgroup analysis showed that the lateral trochlea had higher compressibility for FIZ versus MIZ (P = .02) and the lateral IC notch had higher compressibility for FSZ versus FIZ and MIZ (P < .05 for both). Conclusion: Compressibility varied between OAT donor sites in the distal femur. OAT donor grafts showed the highest compressibility in the medial trochlea (3.1 mm) and lateral IC notch FSZ (3.0 mm). Clinical Relevance: The lateral trochlea, medial IC notch, and the lower zones of the lateral IC notch grafts should not be oversized more than 2 mm in length, as these grafts may not compress adequately.

Experimental validation of a portable tidal volume indicator for bag valve mask ventilation.

INTRODUCTION: Short-term emergency ventilation is most typically accomplished through bag valve mask (BVM) techniques. BVMs like the AMBU® bag are cost-effective and highly portable but are also highly prone to user error, especially in high-stress emergent situations. Inaccurate and inappropriate ventilation has the potential to inflict great injury to patients through hyper- and hypoventilation. Here, we present the BVM Emergency Narration-Guided Instrument (BENGI) - a tidal volume feedback monitoring device that provides instantaneous visual and audio feedback on delivered tidal volumes, respiratory rates, and inspiratory/expiratory times. Providing feedback on the depth and regularity of respirations enables providers to deliver more consistent and accurate tidal volumes and rates. We describe the design, assembly, and validation of the BENGI as a practical tool to reduce manual ventilation-induced lung injury. METHODS: The prototype BENGI was assembled with custom 3D-printed housing and commercially available electronic components. A mass flow sensor in the central channel of the device measures air flow, which is used to calculate tidal volume. Tidal volumes are displayed via an LED ring affixed to the top of the BENGI. Additional feedback is provided through a speaker in the device. Central processing is accomplished through an Arduino microcontroller. Validation of the BENGI was accomplished using benchtop simulation with a clinical ventilator, BVM, and manikin test lung. Known respiratory quantities were delivered by the ventilator which were then compared to measurements from the BENGI to validate the accuracy of flow measurements, tidal volume calculations, and audio cue triggers. RESULTS: BENGI tidal volume measurements were found to lie within 4% of true delivered tidal volume values (95% CI of 0.53 to 3.7%) when breaths were delivered with 1-s inspiratory times, with similar performance for breaths delivered with 0.5-s inspiratory times (95% CI of 1.1 to 6.7%) and 2-s inspiratory times (95% CI of -1.1 to 2.3%). Audio cues "Bag faster" (1.84 to 2.03 s), "Bag slower" (0.35 to 0.41 s), and "Leak detected" (43 to 50%) were triggered close to target trigger values (2.00 s, 0.50 s, and 50%, respectively) across varying tidal volumes. CONCLUSIONS: The BENGI achieved its proposed goals of accurately measuring and reporting tidal volumes delivered through BVM systems, providing immediate feedback on the quality of respiratory performance through audio and visual cues. The BENGI has the potential to reduce manual ventilation-induced lung injury and improve patient outcomes by providing accurate feedback on ventilatory parameters.

Characterization of regional variation of bone mineral density in the geriatric human cervical spine by quantitative computed tomography.

BACKGROUND: Odontoid process fractures are among the most common in elderly cervical spines. Their treatment often requires fixation, which may include use of implants anteriorly or posteriorly. Bone density can significantly affect the outcomes of these procedures. Currently, little is known about bone mineral density (BMD) distributions within cervical spine in elderly. This study documented BMD distribution across various anatomical regions of elderly cervical vertebrae. METHODS AND FINDINGS: Twenty-three human cadaveric C1-C5 spine segments (14 males and 9 female, 74±9.3 y.o.) were imaged via quantitative CT-scan. Using an established experimental protocol, the three-dimensional shapes of the vertebrae were reconstructed from CT images and partitioned in bone regions (4 regions for C1, 14 regions for C2 and 12 regions for C3-5). The BMD was calculated from the Hounsfield units via calibration phantom. For each vertebral level, effects of gender and anatomical bone region on BMD distribution were investigated via pertinent statistical tools. Data trends suggested that BMD was higher in female vertebrae when compared to male ones. In C1, the highest BMD was found in the posterior portion of the bone. In C2, BMD at the dens was the highest, followed by lamina and spinous process, and the posterior aspect of the vertebral body. In C3-5, lateral masses, lamina, and spinous processes were characterized by the largest values of BMD, followed by the posterior vertebral body. CONCLUSIONS: The higher BMD values characterizing the posterior aspects of vertebrae suggest that, in the elderly, posterior surgical approaches may offer a better fixation quality.

Variability in rod to bone distance needed in pelvic subcutaneous internal fixation to avoid nerve compression: A tridimensional population-based study.

INTRODUCTION: Pelvic internal fixation has become a popular method for treatment of unstable pelvic ring injuries. Although successful, one complication is femoral nerve palsy from compression of the connecting rod. In light of this complication, this study was designed to evaluate sagittal inclinations of the rod and the feasibility of using a rod with a constant curvature. HYPOTHESIS: It is hypothesized that that there is a connection between the sagittal inclination of the rod and the rod to bone distance, as well as single rod can be contoured with a constant curvature to be used in the majority of all patients. METHODS: Three dimensional models of pelvis CTs from a single level 1 trauma center were created and imported into a program where software superimposed a pre-contoured rod in the sagittal planes upon the pelvic slices. The sagittal inclination was deemed acceptable is no interference occurred between the area of compression risk and the rod. For each pelvis and considered sagittal rod inclination, the rod radius of curvature (ROC), minimal rod to bone distance (RTB) and transverse inclinations (φL and φR) were measured at which the pedicle screws should be inserted to follow the direction of the smallest RTB. RESULTS: The sagittal inclinations feasible for all subjects were between 15° to 30°. In this sagittal range, the average RTB varied in values ranging from 4.0±0.9mm to 25.4±11.4mm (p<0.01). Only 46% of subjects allowed a rod with constant curvature. DISCUSSION AND CONCLUSION: Our study found that a rod to bone distance of 15mm was not safe for all models. As well, many subject models did not allow placement of pre-contoured rod. Patient specific templating of pelvic subcutaneous internal fixation is strictly needed to limit complications. LEVEL OF EVIDENCE: VII; Basic Science.

Efficacy and safety testing of a COVID-19 era emergency ventilator in a healthy rabbit lung model.

BACKGROUND: The COVID-19 pandemic revealed a substantial and unmet need for low-cost, easily accessible mechanical ventilation strategies for use in medical resource-challenged areas. Internationally, several groups developed non-conventional COVID-19 era emergency ventilator strategies as a stopgap measure when conventional ventilators were unavailable. Here, we compared our FALCON emergency ventilator in a rabbit model and compared its safety and functionality to conventional mechanical ventilation. METHODS: New Zealand white rabbits (n = 5) received mechanical ventilation from both the FALCON and a conventional mechanical ventilator (Engström Carestation™) for 1 h each. Airflow and pressure, blood O2 saturation, end tidal CO2, and arterial blood gas measurements were measured. Additionally, gross and histological lung samples were compared to spontaneously breathing rabbits (n = 3) to assess signs of ventilator induced lung injury. RESULTS: All rabbits were successfully ventilated with the FALCON. At identical ventilator settings, tidal volumes, pressures, and respiratory rates were similar between both ventilators, but the inspiratory to expiratory ratio was lower using the FALCON. End tidal CO2 was significantly higher on the FALCON, and arterial blood gas measurements demonstrated lower arterial partial pressure of O2 at 30 min and higher arterial partial pressure of CO2 at 30 and 60 min using the FALCON. However, when ventilated at higher respiratory rates, we observed a stepwise decrease in end tidal CO2. Poincaré plot analysis demonstrated small but significant increases in short-term and long-term variation of peak inspiratory pressure generation from the FALCON. Wet to dry lung weight and lung injury scoring between the mechanically ventilated and spontaneously breathing rabbits were similar. CONCLUSIONS: Although conventional ventilators are always preferable outside of emergency use, the FALCON ventilator safely and effectively ventilated healthy rabbits without lung injury. Emergency ventilation using accessible and inexpensive strategies like the FALCON may be useful for communities with low access to medical resources and as a backup form of emergency ventilation.

Medial Transmalleolar Portal Technique for Ankle Arthroscopic Headless Screw Fixation of Talar Osteochondritis Dissecans Lesions.

This article describes a technique for arthroscopic fixation of an osteochondritis dissecans (OCD) lesion of the medial talar dome with headless compression screws. This technique involves creation of a medial transmalleolar portal using a guide and drill. The medial transmalleolar portal grants perpendicular access for screw fixation of OCD lesions in addition to the potential for osteochondral autograft transplantation (OAT). Advantages include access to the medial talar dome without performing a medial malleolar osteotomy. After completion of OCD fixation, an inverted osteochondral plug can be used to backfill the portal.

The Ideal Cortical Button Location on the Lateral Femur for Anterior Cruciate Ligament Suspensory Fixation is 30 mm Proximal to the Lateral Epicondyle.

PURPOSE: To determine the ideal location for anterior cruciate ligament (ACL) suspensory cortical button placement on the lateral femur with the highest failure load and to establish the relationship of tunnel diameter and cortical thickness on load to failure. METHODS: Computed tomography (CT) data were obtained from 45 cadaveric distal femurs. A Cartesian coordinate system was established along the lateral femur with the lateral epicondyle (LE) as a reference point. Locations 0, 20 and 30 mm from the LE along lines 0°, 25°, 50°, and 75° posterioproximal from the axial plane were created. Tunnels connecting from each location to the center of the ACL footprint were simulated. Cortical thickness and long axis diameter of the oval cortical holes were determined for each location. Based on the CT data, custom drill guides were created and used to drill 4.5 mm tunnels at each lateral femur location to the ACL footprint on the cadaver femurs. Cortical buttons were placed at each location and pulled using a servohydraulic testing system. The correlation of tunnel diameter and cortical thickness to button failure load were analyzed using a regression analysis. RESULTS: Significant differences were found for failure load (P<.0001) and cortical thickness between the locations tested (P<.0001). The location 30 mm proximal from the LE and 75° from the axial plane had the highest failure load of 573 N. A regression analysis (R2 = .15) indicated that the cortical thickness was significantly correlated with load to failure (P <.0001), whereas the long-axis diameter was not (P = .33). CONCLUSION: The ideal cortical button location on the lateral femur for ACL suspensory fixation was located 30 mm proximal from the lateral epicondyle, based on this area's high failure load. Oblique tunnel drilling of this proximal location may cause a larger long-axis diameter cortical hole, but the cortex is also thicker, which is more closely correlated with failure load. CLINICAL RELEVANCE: Different ACL suspensory cortical button locations on the lateral femur have different failure loads based on the cortical thickness of the bone supporting the button. It is important for surgeons to understand which drilling techniques place the button in a proximal and posterior location, especially if the bone quality of the patient is of concern.

Salvaging Pull-Out Strength in a Previously Stripped Screw Site: A Comparison of Three Rescue Techniques.

Screw stripping during bone fixation is a common occurrence during operations that results in decreased holding capacity and bone healing. We aimed to evaluate the rescue of the stripped screw site using screws of different dimensions. Five screw configurations were tested on cadaveric specimens for pull-out strength (POS). The configurations included a control screw tightened without stripping, a configuration voluntarily stripped and left in place, and three more configurations in which the stripped screws were replaced by a different screw with either increased overall length, diameter, or thread length. Each configuration was tested five times, with each screw tested once. The POS of the control screw, measured to be 153.6 ± 27 N, was higher than the POS measured after stripping and leaving the screw in place (57.1 ± 18 N, p = 0.001). The replacement of the stripped screw resulted in a POS of 158.4 ± 64 N for the screw of larger diameter, while the screws of the same diameter but increased length or those with extended thread length yielded POS values of 138.4 ± 42 and 185.7 ± 48 N, respectively. Screw stripping is a frequent intraoperative complication that, according to our findings, cannot be addressed by leaving the screw in place. The holding capacity of a stripped screw implanted in cancellous bone can successfully be restored with a different screw of either larger diameter, longer length, or extended thread length.

Role of the transverse ligament of the ulnar collateral ligament of the elbow: a biomechanical study.

BACKGROUND: The ulnar collateral ligament (UCL) complex of the elbow plays a primary role in valgus and posteromedial stability of the elbow. The anterior oblique ligament (AOL) of the UCL is believed to provide the majority of resistance to external forces on the medial elbow. The transverse ligament (TL) of the UCL is generally thought to have minimal contribution to the elbow's overall stability. However, recent studies have suggested a more significant role for the TL. The primary aim of this study was to identify the TL's contribution to the stability of the elbow joint in determining the joint stiffness and neutral zone variation in internal rotation. METHODS: Twelve cadaveric elbows, set at a 90° flexion angle, were tested by applying an internal rotational force on the humerus to generate a medial opening torque at the level of the elbow. The specimens were preconditioned with 10 cycles of humeral internal rotation with sinusoidal torque ranging from 0 to 5 Nm. Elbow stiffness measures and joint neutral zone were first evaluated in its integrity during a final ramp loading. The test was subsequently repeated after cutting the TL at 33%, 66%, and 100% followed by the AOL in the same fashion. RESULTS: The native UCL complex joint stiffness to internal rotation measured 1.52 ± 0.51 Nm/°. The first observable change occurred with 33% sectioning of the AOL, with further sectioning of the AOL minimizing the joint stiffness to 1.26 ± 0.32 Nm/° (P = .004). A 33% resection of the TL found an initial neutral zone variation of 0.376 ± 0.23° that increased to 0.771 ± 0.41° (P < .01) at full resection. These values were marginal when compared with the full resection of the AOL for which we have found 3.69 ± 1.65° (P < .01). CONCLUSION: The TL had no contribution to internal rotation elbow joint stiffness at a flexion angle of 90°. However, sequential sectioning of the TL was found to significantly increase the joint neutral zone when compared with the native cadaveric elbow at a flexion angle of 90°. This provides evidence toward the TL having some form of contribution to the elbow's overall stability.

Construction and Performance Testing of a Fast-Assembly COVID-19 (FALCON) Emergency Ventilator in a Model of Normal and Low-Pulmonary Compliance Conditions.

INTRODUCTION: The COVID-19 pandemic has revealed an immense, unmet and international need for available ventilators. Both clinical and engineering groups around the globe have responded through the development of "homemade" or do-it-yourself (DIY) ventilators. Several designs have been prototyped, tested, and shared over the internet. However, many open source DIY ventilators require extensive familiarity with microcontroller programming and electronics assembly, which many healthcare providers may lack. In light of this, we designed and bench tested a low-cost, pressure-controlled mechanical ventilator that is "plug and play" by design, where no end-user microcontroller programming is required. This Fast-AssembLy COVID-Nineteen (FALCON) emergency prototype ventilator can be rapidly assembled and could be readily modified and improved upon to potentially provide a ventilatory option when no other is present, especially in low- and middle-income countries. HYPOTHESIS: We anticipated that a minimal component prototype ventilator could be easily assembled that could reproduce pressure/flow waveforms and tidal volumes similar to a hospital grade ventilator (Engström CarestationTM). MATERIALS AND METHODS: We benched-tested our prototype ventilator using an artificial test lung under 36 test conditions with varying respiratory rates, peak inspiratory pressures (PIP), positive end expiratory pressures (PEEP), and artificial lung compliances. Pressure and flow waveforms were recorded, and tidal volumes calculated with prototype ventilator performance compared to a hospital-grade ventilator (Engström CarestationTM) under identical test conditions. RESULTS: Pressure and flow waveforms produced by the prototype ventilator were highly similar to the CarestationTM. The ventilator generated consistent PIP/PEEP, with tidal volume ranges similar to the CarestationTM. The FALCON prototype was tested continuously for a 5-day period without failure or significant changes in delivered PIP/PEEP. CONCLUSION: The FALCON prototype ventilator is an inexpensive and easily-assembled "plug and play" emergency ventilator design. The FALCON ventilator is currently a non-certified prototype that, following further appropriate validation and testing, might eventually be used as a life-saving emergency device in extraordinary circumstances when more sophisticated forms of ventilation are unavailable.

Ideal Donor Site for Osteochondral Autografting of the Distal Femur Using Radius of Curvature: A 3-Dimensional High-Resolution Scanner Comparison.

OBJECTIVE: To compare radius of curvature (RoC) of distal femur osteochondral autograft transfer (OAT) donor sites from the intercondylar notch and trochlear ridge with recipient sites on the distal and posterior condyles and evaluate differences between recipient sites. DESIGN: Nineteen cadaveric femurs were scanned with a 3-dimensional high-resolution sensor. Donor regions included the lateral (LTR) and medial trochlear ridges (MTR), and the lateral (LICN) and medial intercondylar notch (MICN). Recipient regions analyzed were the distal medial (DMFC), posterior medial (PMFC), distal lateral (DLFC), and posterior lateral femur condyle (PLFC). Six-millimeter OAT grafts were simulated, and average RoC of all regions was compared using an analysis of variance. Post hoc testing was performed using Fisher's least significant difference. RESULTS: We found no significant differences in RoC of the LICN compared with all 4 recipient sites (P = 0.19, 0.97, 0.11, and 0.75 for DLFC, PLFC, DMFC, and PMFC, respectively) or the LTR and MTR to the posterior condyles (LTR vs. PLFC and PMFC; P = 0.72, 0.47, MTR vs. PLFC and PMFC P = 0.39, 0.22, respectively). Significant differences were found for RoC of the MICN compared with each recipient site (P < 0.001) and between distal and posterior femoral condyles (DLFC vs. PLFC, P = 0.016; DMFC vs. PMFC, P = 0.023). CONCLUSION: The LICN is the ideal donor option for all recipient sites on the femoral condyles with respect to RoC of 6-mm OAT plugs. The MTR and LTR were acceptable donor sources for the posterior condyles, while the MICN was a poor match for all recipient sites. Additionally, the distal femur condyle and posterior femur condyle have different RoCs.

Experimental Evaluation of the Elson Test Efficiency Following Central Slip Injury.

Purpose: The purpose of this article is to explore the amount of work, quantitated by flexion and extension cycles, that is needed to obtain a positive Elson test following a central slip injury. Methods: Thirteen frozen cadaveric fingers from individuals with an average age of 79.6 years were used. Testing was performed by imposing sinusoidal displacement of the 2 tendons, with loads ranging from 30 N to 2 N at 1 Hz. Following transection to the central slip, each finger was cycled 1,000 times using the same protocol adopted for the control. Following 100, 200, 300, and 1,000 cycles, we measured the extension angles of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints from the flexed position and the distance between landmarks of the extensor apparatus and simulated an Elson test. Results: In both the fingers, the range of motion of the metacarpophalangeal and distal interphalangeal joints measured in the controls remained unchanged, whereas the range of motion of the proximal interphalangeal joint was significantly reduced immediately after central slip transection. Combining both ring and middle fingers, for a displacement of 5 mm, the force measured in the control (1.05 ± 0.69 N) increased to the value of 2.36 ± 0.97 N at the 1,000th cycle. Although the middle finger has shown a significant difference in force at 100 cycles following central slip transection, 200 cycles were needed to observe a difference on the ring finger. Conclusions: In controlled conditions, there is a variation in resistance to flexion of the distal interphalangeal joint. However, the amplitude of the forces is so small that they are likely imperceptible clinically. Delayed testing should be considered to increase the sensitivity of the test or in patients experiencing pain. Type of study/level of evidence: Diagnostic V.

Biomechanical Analysis of Patellar Tendon Repair With Knotless Suture Anchor Tape Versus Transosseous Suture.

BACKGROUND: Patellar tendon ruptures have routinely been repaired with transosseous suture tunnels. The use of knotless suture anchors for repair has been suggested as an alternative. PURPOSE: To compare the load to failure and gap formation of patellar tendon repair at the inferior pole of the patella with knotless suture anchor tape versus transosseous sutures. A secondary objective was to investigate whether either technique shows an association between bone density and load to failure. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 20 human tibias with attached patellar and quadriceps tendons were sharply incised at the bone-tendon junction at the inferior pole of the patella. A total of 10 tendons were repaired using 2 knotless suture anchors in the inferior pole of the patella and a single suture tape with 2 core sutures. The other 10 tendons were repaired using No. 2 suture passed through 3 transosseous tunnels. A distracting force was then applied through the suture in the quadriceps tendon. Gap distance through load cycling at the repair site and maximum load at repair failure were then measured. Bone density was measured using computed tomography scanning. RESULTS: No difference was found in the mean load to failure of knotless patellar tendon repair versus transosseous suture repair (367.6 ± 112.2 vs 433.9 ± 99 N, respectively; P = .12). After 250 cycles, the mean repair site gap distance was 0.85 ± 0.45 mm for the knotless patellar tendon repair versus 2.94 ± 2.03 mm for the transosseous suture repair (P = .03). A small correlation, although not statistically significant, was found between bone density and load to failure for the knotless tape repair (R 2 = 0.228; P = .66). No correlation was found between bone density and load to failure for the transosseous repair (R 2 = 0.086; P = .83). CONCLUSION: Suture tape repair with knotless anchors for repair of patellar tendon rupture has comparable load to failure with less gap formation than transosseous suture repair. There is a small correlation between bone density and failure load for knotless anchor repair, which may benefit from further investigation. CLINICAL RELEVANCE: Using knotless suture anchors for patellar tendon rupture repair would allow for a smaller incision, less dissection, and likely shorter operating time.

Biomechanical comparison of anterior cruciate ligament repair with internal brace augmentation versus anterior cruciate ligament repair without augmentation.

BACKGROUND: Newer repair techniques of anterior cruciate ligament tears, including augmentation with internal brace, have shown promising clinical results. Few biomechanical studies exist comparing anterior cruciate ligament repair only versus repair with internal brace. The purpose of this study was to compare the load to failure and stiffness of anterior cruciate ligament repair with internal brace augmentation versus repair-only. METHODS: Proximal femoral avulsion type anterior cruciate ligament injuries were created in 20 cadaver knees. Anterior cruciate ligament repair-only or repair with internal brace was performed using arthroscopic tools. Load to failure and failure modes were collected, with calculations of stiffness and energy to failure performed. FINDINGS: The average load to failure for the internal brace group was higher than the repair-only group: 693 N (SD 248) versus 279 N (SD 91), P = .002. The stiffness and energy to failure values were higher for the internal brace group than the repair-only group: 83 N/mm versus 58 N/mm, P = .02 and 16.88 J (SD 12.44) versus 6.91 J (SD 2.49), P = .04, respectively. Failure modes differed between groups (P = .00097) with 80% failure in the repair-only due to suture pull through the anterior cruciate ligament and 90% failure in the internal brace group due to suture button pull through the femur. INTERPRETATION: There was higher load to failure, stiffness, and energy to failure for the internal brace group compared to the repair-only group, and a high positive correlation between bone density and load to failure for the internal brace group. CLINICAL SIGNIFICANCE: Anterior cruciate ligament repair with internal brace augmentation demonstrates significantly higher load to failure. It may be a useful adjunct to protect the anterior cruciate ligament repair from failure during the early stages of healing.