3D kinematics of tibiotalar motion in patients with mobile bearing and fixed bearing total ankle arthroplasty: In vivo videofluoroscopic feasibility study.

BACKGROUND: As total ankle arthroplasty (TAA) is an increasingly common surgical intervention for patients with end-stage ankle arthritis, there is a need to better understand the dynamic performance of prosthetic implants during activities of daily living. Our purpose was to quantify and compare relative tibiotalar motion during gait in persons with a fixed-bearing (FB) and mobile-bearing (MB) total ankle arthroplasty. We hypothesized a FB prosthesis would have lower tibiotalar range of motion (ROM). METHODS: Patients at least 12 months postoperative with either a FB (n=5) or MB (n=3) total ankle arthroplasty were tested. We used high-speed biplanar videoradiography to quantify tibiotalar kinematics during self-selected gait. Angular and linear ROM in three axes were compared between the groups. RESULTS: ROM for dorsiflexion-plantarflexion, internal-external rotation, and inversion-eversion angles in FB subjects averaged 7.47±4.05°, 7.39±3.63°, and 4.51±2.13°, respectively. ROM in MB subjects averaged 6.74±2.04°, 6.28±4.51°, and 5.68±2.81°, respectively. Linear ROM along anteroposterior, mediolateral, and superior-inferior axes in FB subjects averaged 1.47±2.07 mm, 1.13±1.49 mm, and 0.28±0.30 mm, respectively. Linear ROM in MB subjects averaged 0.68±1.44 mm, 0.60±1.41 mm, and 0.20±0.13 mm, respectively. We found no significant difference between the two groups for any of these ROM parameters (p>0.05). CONCLUSION: Total ankle arthroplasty using either FB or MB design appears to confer similar ankle motion during the gait cycle in this biplanar fluoroscopic model. LEVEL OF EVIDENCE: Level IV, case series.

Attenuation of muscle spindle firing with artificially increased series compliance during stretch of relaxed muscle.

Muscle spindles relay vital mechanosensory information for movement and posture, but muscle spindle feedback is coupled to skeletal motion by a compliant tendon. Little is known about the effects of tendon compliance on muscle spindle feedback during movement, and the complex firing of muscle spindles makes these effects difficult to predict. Our goal was to investigate changes in muscle spindle firing using added series elastic elements (SEEs) to mimic a more compliant tendon, and to characterize the accompanying changes in firing with respect to muscle-tendon unit (MTU) and muscle fascicle displacements (recorded via sonomicrometry). Sinusoidal, ramp-and-hold and triangular stretches were analysed to examine potential changes in muscle spindle instantaneous firing rates (IFRs) in locomotor- and perturbation-like stretches as well as serial history dependence. Added SEEs effectively reduced overall MTU stiffness and generally reduced muscle spindle firing rates, but the effect differed across stretch types. During sinusoidal stretches, peak and mean firing rates were not reduced and IFR was best-correlated with fascicle velocity. During ramp stretches, SEEs reduced the initial burst, dynamic and static responses of the spindle. Notably, IFR was negatively related to fascicle displacement during the hold phase. During triangular stretches, SEEs reduced the mean IFR during the first and second stretches, affecting the serial history dependence of mean IFR. Overall, these results demonstrate that tendon compliance may attenuate muscle spindle feedback during movement, but these changes cannot be fully explained by reduced muscle fascicle length or velocity, or MTU force.

Attenuation of muscle spindle firing with artificially increased series compliance during stretch of relaxed muscle.

Muscle spindles relay vital mechanosensory information for movement and posture, but muscle spindle feedback is coupled to skeletal motion by a compliant tendon. Little is known about the effects of tendon compliance on muscle spindle feedback during movement, and the complex firing of muscle spindles make these effects difficult to predict. Our goal was to investigate changes in muscle spindle firing using added series elastic elements (SEEs) to mimic a more compliant tendon, and to characterize the accompanying changes in firing with respect to muscle-tendon unit (MTU) and muscle fascicle displacements (recorded via sonomicrometry). Sinusoidal, ramp-hold-release, and triangular stretches were analyzed to examine potential changes in muscle spindle instantaneous firing rates (IFRs) in locomotor- and perturbation-like stretches as well as history dependence. Added SEEs effectively reduced overall MTU stiffness and generally reduced muscle spindle firing rates, but the effect differed across stretch types. During sinusoidal stretches, peak firing rates were reduced and IFR was strongly correlated with fascicle velocity. During ramp stretches, SEEs reduced the dynamic and static responses of the spindle during lengthening but had no effect on initial bursts at the onset of stretch. Notably, IFR was negatively related to fascicle displacement during the hold phase. During triangular stretches, SEEs reduced the mean IFR during the first and second stretches, affecting the history dependence of mean IFR. Overall, these results demonstrate that tendon compliance may attenuate muscle spindle feedback during movement, but these changes cannot be fully explained by reduced muscle fascicle length and velocity.

Perturbing the muscle work loop paradigm to unravel the neuromechanics of unsteady locomotion.

Muscle function during movement is more than a simple, linear transformation of neural activity into force. The classic work loop technique has pioneered our understanding of muscle, but typically only characterizes function during unperturbed movement cycles, such as those experienced during steady walking, running, swimming and flying. Yet perturbations away from steady movement often place greater demands on muscle structure and function and offer a unique window into muscle's broader capacity. Recently, studies in diverse organisms from cockroaches to humans have started to grapple with muscle function in unsteady (perturbed, transient and fluctuating) conditions, but the vast range of possible parameters and the challenge of connecting in vitro to in vivo experiments are daunting. Here, we review and organize these studies into two broad approaches that extend the classic work loop paradigm. First, in the top-down approach, researchers record length and activation patterns of natural locomotion under perturbed conditions, replay these conditions in isolated muscle work loop experiments to reveal the mechanism by which muscle mediates a change in body dynamics and, finally, generalize across conditions and scale. Second, in the bottom-up approach, researchers start with an isolated muscle work loop and then add structural complexity, simulated loads and neural feedback to ultimately emulate the muscle's neuromechanical context during perturbed movement. In isolation, each of these approaches has several limitations, but new models and experimental methods coupled with the formal language of control theory give several avenues for synthesizing an understanding of muscle function under unsteady conditions.

Physiotherapists could detect changes of 12 degrees or more in single-plane movement when observing forward bending, squat or hand-over-head: A cross-sectional experiment.

BACKGROUND: The visual accuracy of physiotherapists to detect changes in dynamic joint angles is currently unknown. OBJECTIVE: To investigate (i) the smallest detectable change in movement that physiotherapists could visually observe, and (ii) whether visual accuracy was associated with the functional activity observed or characteristics of the physiotherapist. METHODS: Thirty-four physiotherapists viewed and rated videos of squat, hand-over-head, forward bend functional activities and an artificial test condition (a reference movement followed by subsequent movements showing random differences in peak angle from 0° to 15°, so 18 sets of paired videos per functional activity). They rated each range of movement (same/more/less) relative to the reference movement, while their visual tracking was continuously monitored. Accuracy was calculated (multilevel regression) using two thresholds - two correct out of three viewings (2/3) and three correct out of three viewings (3/3). RESULTS: More than 80% of physiotherapists were able to detect 9° difference using the 2/3 threshold and 12° using the 3/3 threshold. There was no association (p > 0.05) between visual accuracy and experience, sex, or movement type, except when viewing shoulder abduction compared with knee flexion using the 3/3 threshold. The only association between accuracy and visual tracking characteristics was for assessing lumbar flexion, where use of more visual fixation areas and a shorter fixation time per area were more accurate. CONCLUSION: Physiotherapists were consistently accurate at detecting changes of ≥12° in single-plane, low-speed functional activities. Visual accuracy was not explained by experience or sex, and rarely associated with functional activity type or visual fixation.

Elbow Fracture-Dislocations: Determining Treatment Strategies.

Elbow dislocations represent common injuries. A quarter of these injuries involve at least 1 fracture. The sequel of elbow fracture-dislocations can be fraught with complications, including recurrent instability, posttraumatic arthritis, elbow contracture, and poor functional results. The 3 main patterns of injury are valgus posterolateral rotatory instability, varus posteromedial rotatory instability, and transolecranon fracture-dislocation. This article discusses each pattern individually, including the anatomy, the typical injury pattern, and treatment strategies. It also discusses common complications that can occur.

Cost-Effective Approach to the Laparoscopic Appendectomy : Balancing Disposable Instrument Cost With Operative Time.

BACKGROUND: Surgeons can help reduce health care spending by selecting affordable and efficient instruments. The laparoscopic appendectomy (LA) is commonly performed and can serve as a model for improving health care cost. METHODS: We retrospectively reviewed all adult patients who underwent LA for non-perforated appendicitis from March 2015 to November 2017. Our objective was to determine which combination of disposable instruments afforded the lowest total operative cost without compromising postoperative outcomes. RESULTS: In total, 1857 consecutive patients were reviewed from 2 hospitals. After determining the 8 most commonly utilized combinations of disposable instruments, 846 patients were ultimately analyzed. The combination of a LigaSure, Endoloop, and an EndoBag (LEB) had the shortest median operative time (25 minutes, P < .001) and lowest median total operative cost ($1893, P < .001). CONCLUSIONS: The LEB instrument combination rendered the shortest operative time, lowest total operative cost, and can be used to maximize surgical value during LA.

Hurry Up and Get Out of the Way! Exploring the Limits of Muscle-Based Latch Systems for Power Amplification.

Animals can amplify the mechanical power output of their muscles as they jump to escape predators or strike to capture prey. One mechanism for amplification involves muscle-tendon unit (MT) systems in which a spring element (series elastic element [SEE]) is pre-stretched while held in place by a "latch" that prevents immediate transmission of muscle (or contractile element, CE) power to the load. In principle, this storage phase is followed by a triggered release of the latch, and elastic energy released from the SEE enables power amplification (PRATIO=PLOAD/PCE,max >1.0), whereby the peak power delivered from MT to the load exceeds the maximum power limit of the CE in isolation. Latches enable power amplification by increasing the muscle work generated during storage and reducing the duration over which that stored energy is released to power a movement. Previously described biological "latches" include: skeletal levers, anatomical triggers, accessory appendages, and even antagonist muscles. In fact, many species that rely on high-powered movements also have a large number of muscles arranged in antagonist pairs. Here, we examine whether a decaying antagonist force (e.g., from a muscle) could be useful as an active latch to achieve controlled energy transmission and modulate peak output power. We developed a computer model of a frog hindlimb driven by a compliant MT. We simulated MT power generated against an inertial load in the presence of an antagonist force "latch" (AFL) with relaxation time varying from very fast (10 ms) to very slow (1000 ms) to mirror physiological ranges of antagonist muscle. The fastest AFL produced power amplification (PRATIO=5.0) while the slowest AFL produced power attenuation (PRATIO=0.43). Notably, AFLs with relaxation times shorter than ∼300 ms also yielded greater power amplification (PRATIO>1.20) than the system driving the same inertial load using only an agonist MT without any AFL. Thus, animals that utilize a sufficiently fast relaxing AFL ought to be capable of achieving greater power output than systems confined to a single agonist MT tuned for maximum PRATIO against the same load.

In Pursuit of the Most Cost-Effective Pediatric Laparoscopic Appendectomy: The Effect of Disposable Instrument Choice on Operative Time and Surgeon-Controllable Cost.

BACKGROUND: There is a movement toward cost savings in healthcare worldwide. Surgeons can affect two main cost variables in an operation (controllable cost): disposables and time. Our hypothesis is that increasing disposable costs do not change outcome or operative time, but simply increases controllable cost. METHODS: We retrospectively reviewed patients younger than the age of 18 years undergoing laparoscopic appendectomies for nonperforated appendicitis from January 2013 to November 2016. Data obtained included demographic information in addition to intraoperative details, including disposables used and associated cost, resident participation, operative time, and final pathology. Patients were excluded if perforation was present as confirmed by operative findings or pathology (Kansas City definition). Patients were also excluded if concurrent procedures were performed during the appendectomy. RESULTS: We reviewed 918 patients and excluded 288 for a total of 690. Disposable cost, operative time, and complications were compared between cases with a resident present and those without. Residents did not increase the use of disposables, but did increase operative time and therefore the total controllable cost. Transumbilical laparoscopic-assisted technique was significantly faster with lower controllable cost when compared with all other methods. Using disposable trocars with an endostapler was the second fastest and second lowest controllable cost and retained a significant difference when compared with most other methods. Endoloop methods did not show overall controllable cost savings versus the vast majority of methods. CONCLUSIONS: To maximize controllable cost savings, we recommend a transumbilical laparoscopic-assisted appendectomy or a standard three-port laparoscopic appendectomy, with disposable trocars and the endostapler.

Reduce torques and stick the landing: limb posture during landing in toads.

A controlled landing, where an animal does not crash or topple, requires enough stability to allow muscles to effectively dissipate mechanical energy. Toads (Rhinella marina) are exemplary models for understanding the mechanics and motor control of landing given their ability to land consistently during bouts of continuous hopping. Previous studies in anurans have shown that ground reaction forces (GRFs) during landing are significantly higher compared with takeoff and can potentially impart large torques about the center of mass (COM), destabilizing the body at impact. We predict that in order to minimize such torques, toads will align their COM with the GRF vector during the aerial phase in anticipation of impact. We combined high-speed videography and force-plate ergometry to quantify torques at the COM and relate the magnitude of torques to limb posture at impact. We show that modulation of hindlimb posture can shift the position of the COM by about 20% of snout-vent length. Rapid hindlimb flexion during the aerial phase of a hop moved the COM anteriorly and reduced torque by aligning the COM with the GRF vector. We found that the addition of extrinsic loads did not significantly alter landing behavior but did change the torques experienced at impact. We conclude that anticipatory hindlimb flexion during the aerial phase of a hop is a critical feature of a mechanically stable landing that allows toads to quickly string together multiple, continuous hops.

Does a kaolin-impregnated hemostatic dressing reduce intraoperative blood loss and blood transfusions in pediatric spinal deformity surgery?

STUDY DESIGN: Retrospective case-control study. OBJECTIVE: To evaluate the hemostatic benefits of using a kaolin-impregnated dressing during pediatric spinal deformity correction surgery. SUMMARY OF BACKGROUND DATA: Minimizing blood loss and transfusions are clear benefits for patient safety. A technique common in both severe trauma and combat medicine that has not been reported in the spine literature is wound packing with a kaolin-impregnated hemostatic dressing. METHODS: Estimated blood loss and transfusion amounts were analyzed in a total of 117 retrospectively identified cases. The control group included 65 patients (46 females, 19 males, 12.7±4.5 yr, 10.2±4.8 levels fused) who received standard operative care with gauze packing between June 2007 and March 2010. The treatment group included 52 patients (33 females, 19 males, 13.9±3.2 yr, 10.4±4.3 levels fused) who underwent intraoperative packing with QuikClot Trauma Pads (QCTP, Z-Medica Corporation) for all surgical procedures from July 2010 to August 2011. No other major changes in the use of antifibrinolytics or perioperative, surgical, or anesthesia technique were noted. Statistical differences were analyzed using analysis of covariance in R with P value of less than 0.05. The statistical model included sex, age, weight, scoliosis type, the number of vertebral levels fused, and surgery duration as covariates. RESULTS: The treatment group had 40% less intraoperative estimated blood loss than the control group (974 mL vs. 1620 mL) (P<0.001). Patients who received the QCTP treatment also had 42% less total perioperative transfusion volume (499 mL vs. 862 mL) (P<0.01). CONCLUSION: The use of a kaolin-impregnated intraoperative trauma pad seems to be an effective and inexpensive method to reduce intraoperative blood loss and transfusion volume in pediatric spinal deformity surgery. LEVEL OF EVIDENCE: 3.

Anticipatory motor patterns limit muscle stretch during landing in toads.

To safely land after a jump or hop, muscles must be actively stretched to dissipate mechanical energy. Muscles that dissipate energy can be damaged if stretched to long lengths. The likelihood of damage may be mitigated by the nervous system, if anticipatory activation of muscles prior to impact alters the muscle's operating length. Anticipatory motor recruitment is well established in landing studies and motor patterns have been shown to be modulated based on the perceived magnitude of the impact. In this study, we examine whether motor recruitment in anticipation of landing can serve a protective function by limiting maximum muscle length during a landing event. We use the anconeus muscle of toads, a landing muscle whose recruitment is modulated in anticipation of landing. We combine in vivo measurements of muscle length during landing with in vitro characterization of the force-length curve to determine the muscle's operating length. We show that muscle shortening prior to impact increases with increasing hop distance. This initial increase in muscle shortening functions to accommodate the larger stretches required when landing after long hops. These predictive motor strategies may function to reduce stretch-induced muscle damage by constraining maximum muscle length, despite variation in the magnitude of impact.

The weak link: do muscle properties determine locomotor performance in frogs?

Muscles power movement, yet the conceptual link between muscle performance and locomotor performance is poorly developed. Frog jumping provides an ideal system to probe the relationship between muscle capacity and locomotor performance, because a jump is a single discrete event and mechanical power output is a critical determinant of jump distance. We tested the hypothesis that interspecific variation in jump performance could be explained by variability in available muscle power. We used force plate ergometry to measure power produced during jumping in Cuban tree frogs (Osteopilus septentrionalis), leopard frogs (Rana pipiens) and cane toads (Bufo marinus). We also measured peak isotonic power output in isolated plantaris muscles for each species. As expected, jump performance varied widely. Osteopilus septentrionalis developed peak power outputs of 1047.0 ± 119.7 W kg(-1) hindlimb muscle mass, about five times that of B. marinus (198.5 ± 54.5 W kg(-1)). Values for R. pipiens were intermediate (543.9 ± 96.2 W kg(-1)). These differences in jump power were not matched by differences in available muscle power, which were 312.7 ± 28.9, 321.8 ± 48.5 and 262.8 ± 23.2 W kg(-1) muscle mass for O. septentrionalis, R. pipiens and B. marinus, respectively. The lack of correlation between available muscle power and jump power suggests that non-muscular mechanisms (e.g. elastic energy storage) can obscure the link between muscle mechanical performance and locomotor performance.

Visual loss and visual hallucinations in patients with age-related macular degeneration (Charles Bonnet syndrome).

PURPOSE: The condition in which visual hallucinations (VHs) are solely associated with a visual impairment is termed Charles Bonnet Syndrome (CBS). The study was undertaken to investigate whether the extent of visual acuity (VA) loss and central visual field loss predisposes a patient with age-related macular degeneration (AMD) to develop a CBS VH and, in addition, whether the progression in loss is mirrored in the complexity of the VHs reported. VH phenomenology and CBS prevalence were also examined. METHODS: Sixty-six patients (age range, 63-96 years, mean +/- SD 81.2 +/- 7.1 years) with bilateral AMD were questioned as to whether they had experienced any hallucinatory episodes exclusive to vision. The four-point primary inclusion criterion ensured that all patients had bilateral AMD, a bilateral central scotoma, best monocular VA poorer than or equal to 0.6 logMAR (logarithm of the minimum angle of resolution) and intact cognition (using the Mini Mental State Examination for the Blind and the Telephone Interview for Cognitive Status). The patients who did not report VH were classified into the non-VH group, with the remainder in the VH group. An extended Institute of Psychiatry Structural Interview characterized the phenomenology of the VH. A secondary inclusion criterion subdivided the VH group into the apparent CBS group, in which personal medical history may have contributed to VH generation, and the manifest CBS group, where VHs were solely as a result of the visual loss. RESULTS: Fifty-three patients met the primary inclusion criterion: 32 were classified into the non-VH group and 21 into the VH group. The VH group were slightly younger (median difference, 4 years, P = 0.03) and appeared to have a lower VA (median difference, 0.20 logMAR, P = 0.08) and a more extensive visual field loss (P = 0.06) than did the non-VH group. However, when these variables were evaluated simultaneously by logistic regression, only age emerged as a statistically significant predictor of VH (odds ratio 0.88, 95% confidence interval [CI] 0.8-0.99, P = 0.03). The prevalence of apparent CBS and manifest CBS in the AMD population was found to be 25% and 15%, respectively. With no clinical and phenomenological differences between the two CBS groups, the secondary inclusion criterion was withdrawn, the VH group was renamed the CBS group, and a prevalence of 40% was recalculated. Of the 82 visual phenomena experienced by the CBS group, 21 were classified as simple VHs and 39 as complex VHs, with the remainder classified as either entopic phenomena or visual inference. Patients who experienced both simple and complex VHs appeared to have a greater visual field loss (P = 0.06) compared with those patients who reported either solely simple or solely complex VHs. CONCLUSIONS: The extent of visual loss did not appear to be a predictor for the likelihood of a patient with AMD experiencing a CBS VH, nor was the progression of loss reflected in the complexity of the VHs reported.