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1. Anterior Cruciate Ligament Graft Tunnel Placement and Graft Angle Are Primary Determinants of Internal Knee Mechanics After Reconstructive Surgery

   https://doi.org/10.1177/0363546520966721  

   Vignos, Michael F. ; Smith, Colin R. ; Roth, Joshua D. ; Kaiser, Jarred M. ; Baer, Geoffrey S. ; Kijowski, Richard ; Thelen, Darryl G. ( November 2020 , The American Journal of Sports Medicine)

   Graft placement is a modifiable and often discussed surgical factor in anterior cruciate ligament (ACL) reconstruction (ACLR). However, the sensitivity of functional knee mechanics to variability in graft placement is not well understood.

   To (1) investigate the relationship of ACL graft tunnel location and graft angle with tibiofemoral kinematics in patients with ACLR, (2) compare experimentally measured relationships with those observed with a computational model to assess the predictive capabilities of the model, and (3) use the computational model to determine the effect of varying ACL graft tunnel placement on tibiofemoral joint mechanics during walking.

   Controlled laboratory study.

   Eighteen participants who had undergone ACLR were tested. Bilateral ACL footprint location and graft angle were assessed using magnetic resonance imaging (MRI). Bilateral knee laxity was assessed at the completion of rehabilitation. Dynamic MRI was used to measure tibiofemoral kinematics and cartilage contact during active knee flexion-extension. Additionally, a total of 500 virtual ACLR models were created from a nominal computational knee model by varying ACL footprint locations, graft stiffness, and initial tension. Laxity tests, active knee extension, and walking were simulated with each virtual ACLR model. Linear regressions were performed between internal knee mechanics and ACL graft tunnel locations and angles for the patients with ACLR and the virtual ACLR models.

   Static and dynamic MRI revealed that a more vertical graft in the sagittal plane was significantly related ( P < .05) to a greater laxity compliance index ( R²= 0.40) and greater anterior tibial translation and internal tibial rotation during active knee extension ( R²= 0.22 and 0.23, respectively). Similarly, knee extension simulations with the virtual ACLR models revealed that a more vertical graft led to greater laxity compliance index, anterior translation, and internal rotation ( R²= 0.56, 0.26, and 0.13). These effects extended to simulations of walking, with a more vertical ACL graft inducing greater anterior tibial translation, ACL loading, and posterior migration of contact on the tibial plateaus.

   This study provides clinical evidence from patients who underwent ACLR and from complementary modeling that functional postoperative knee mechanics are sensitive to graft tunnel locations and graft angle. Of the factors studied, the sagittal angle of the ACL was particularly influential on knee mechanics.

   Early-onset osteoarthritis from altered cartilage loading after ACLR is common. This study shows that postoperative cartilage loading is sensitive to graft angle. Therefore, variability in graft tunnel placement resulting in small deviations from the anatomic ACL angle might contribute to the elevated risk of osteoarthritis after ACLR.

    

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2. Functional Resistance Training Differentially Alters Gait Kinetics After Anterior Cruciate Ligament Reconstruction: A Pilot Study

   https://doi.org/10.1177/19417381221104042  

   Washabaugh, Edward P. ; Brown, Scott R. ; Palmieri-Smith, Riann M. ; Krishnan, Chandramouli ( June 2022 , Sports Health: A Multidisciplinary Approach)

   Quadriceps weakness is common after anterior cruciate ligament (ACL) reconstruction and can alter gait mechanics. Functional resistance training (FRT) is a novel approach to retraining strength after injury, but it is unclear how it alters gait mechanics. Therefore, we tested how 3 different types of FRT devices: a knee brace resisting extension (unidirectional brace), a knee brace resisting extension and flexion (bidirectional brace), and an elastic band pulling backwards on the ankle (elastic band)–acutely alter gait kinetics in this population.

   The type of FRT device will affect ground-reaction forces (GRFs) during and after the training. Specifically, the uni- and bidirectional braces will increase GRFs when compared with the elastic band.

   Crossover study.

   Level 2.

   A total of 15 individuals with ACL reconstruction received FRT with each device over 3 separate randomized sessions. During training, participants walked on a treadmill while performing a tracking task with visual feedback. Sessions contained 5 training trials (180 seconds each) with rest between. Vertical and anterior-posterior GRFs were assessed on the ACL-reconstructed leg before, during, and after training. Changes in GRFs were compared across devices using 1-dimensional statistical parametric mapping.

   Resistance applied via bidirectional brace acutely increased gait kinetics during terminal stance/pre-swing (ie, push-off), while resistance applied via elastic band acutely increased gait kinetics during initial contact/loading (ie, braking). Both braces behaved similarly, but the unidirectional brace was less effective for increasing push-off GRFs.

   FRT after ACL reconstruction can acutely alter gait kinetics during training. Devices can be applied to selectively alter gait kinetics. However, the long-term effects of FRT after ACL reconstruction with these devices are still unknown.

   FRT may be applied to alter gait kinetics of the involved limb after ACL reconstruction, depending on the device used.

    

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3. Biomechanical Properties of Various Surgical Suture Needles in a Cadaveric Quadriceps Tendon Model

   Diaz, Miguel A. ; Branch, Eric A. ; Dunn, Jake ; Brothers, Anthony ; Jordan, Steve ( February 2023 , Transactions of the annual meeting of the Orthopaedic Research Society)

   INTRODUCTION: Quadriceps tendon autografts have experienced a rapid rise in popularity for anterior cruciate ligament (ACL) reconstruction due to advantages in graft sizing and potential improvement in biomechanics. While there is a growing body of literature on use of quadriceps tendon grafts, deeper investigation into the biomechanical properties of stitch techniques in this construct has been limited. The purpose of this study was to evaluate the performance of a novel suture needle against different conventional suture needles by comparing the biomechanical properties of two commonly used stitch methods, a whip stitch, and a locking stitch in quadriceps tendon. It was hypothesized that the new device would be capable of creating both whip stitches and locking stitches that are biomechanically equivalent to similar stitch techniques performed with conventional needle products. METHODS: This was a controlled biomechanical study. A total of 24 matched pair cadaveric knees were dissected and a total of 48 quadriceps tendons were harvested and tested. All tendon grafts were standardized to the same size. Samples were then randomized into the following groups, keeping the matched pairs together: (Group 1, n=16) consisted of Company W’s novel two-part suture needle design, (Group 2, n=16) consisted of Company A suture, and (Group 3, n=16) consisted of Company B suture. For each group, the matched pairs were categorized into subgroups to be instrumented with either a whip stitch or a locking stitch. Two fellowship-trained surgeons performed all stitching, where they each instrumented 8 tendon grafts per group. For instrumentation, the grafts were clamped to a preparation stand in accordance with the manufacturer’s recommendations for passing each suture needle. A skin marker was used to identify and mark five evenly spaced points, 0.5 cm apart, as a guide to create a 5-stitch series. For Group 1, the whip stitch as well as the locking whip stitch were performed with a novel 2-part needle. For Group 2, the whip stitch was performed with loop suture needle and the locking stitch was krackow with a curved needle. Similarly, for Group 3, the whip stitch was performed with loop suture needle and the locking stitch was krackow with a curved needle (Figure 1). Cyclical testing was performed using a servohydraulic testing machine (MTS Bionix) equipped with a 5kN load cell. A standardized length of tendon, 7 cm, was coupled to the MTS actuator by passing it through a cryoclamp cooled by dry ice to a temperature of -5°C (Figure 2). All testing samples were then pre-conditioned to normalize viscoelastic effects and testing variability through application of cyclical loading to 25-100 N for three cycles. The samples were then held at 89 N for 15 minutes. Thereafter, the samples were loaded to 50-200 N for 500 cycles at 1 Hz. If samples survived, they were ramped to failure at 20 mm/min. Displacement and force data was collected throughout testing. Metrics of interest were total elongation (mm), stiffness (N/mm), ultimate failure load (N) and failure mode. Data are presented as averages plus/minus standard deviation. A one-way analysis of variance (ANOVA) with a Tukey pairwise comparison post hoc analysis was used to evaluate differences between the various stitching methods. Statistical significance was set at P = .05. RESULTS SECTION: For the whip stitch methods, the total elongation was found to be equivalent across all methods (W: 36 ± 10 mm; A: 32 ± 18 mm; B: 33 ± 8 mm). The stiffness of Company A (103 ± 11 N/mm) method was significantly larger than Company W (64 ± 8 N/mm; p=.001), whereas stiffness of whip stitch by Company W was equivalent to Company B (80 ± 32 N/mm). The ultimate failure load was equivalent across all whip stitch methods (W: 379 ± 31 mm; A: 412 ± 103 mm; B: 438 ± 63 mm). For the locking stitch method, the total elongation (W: 26 ± 10 mm; A: 14 ± 2 mm; B: 29 ± 5 mm), stiffness (W: 75 ± 11 N/mm; A: 104 ± 23 N/mm; B: 79 ± 10 N/mm) and ultimate load (W: 343 ± 22 N; A: 369 ± 30 N; B: 438 ± 63 N) were found to be equivalent across all methods. The failure mode for all groups is in Table 1. The common mode of failure across study groups and stitch configuration was suture breakage. However, the whip stitch from Company A and Company B had varied failure modes. DISCUSSION: Products from the three manufacturers were found to produce biomechanically equivalent whip stitches and locking stitches with respect to elongation and ultimate failure load. The only significant difference observed was that the whip stitch created with Company A’s product had a higher stiffness than Company W’s product, which could have been due to differences in the suture material. In this cadaveric quadriceps tendon model, it was shown that when using Company W’s novel two-part suture needle, users were capable of creating whip stitches and locking stitches that achieved equivalent biomechanical performance compared to similar stitch techniques performed with conventional needle products. A failure mode limited solely to suture breakage for methods completed with Company W’s needle product suggest a reliable suture construct with limited tissue damage. SIGNIFICANCE/CLINICAL RELEVANCE: Having a suture needle device with the versatility to easily perform different stitching constructs may provide surgeons an advantage needed to improve clinical outcomes. The data presented illustrates a strong new suture technique that has equivalent performance when compared to conventional needle devices and has promising applications in graft preparation for ligament and tendon reconstruction. 

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4. Florida mangrove saltmarsh reference surface soils

   https://doi.org/10.6073/pasta/0e08cbe07c84488cb7b9dd16669946d0  

   Lewis, David Bruce ( January 2021 , Environmental Data Initiative)

   Site description. This data package consists of data obtained from sampling surface soil (the 0-7.6 cm depth profile) in black mangrove (Avicennia germinans) dominated forest and black needlerush (Juncus roemerianus) saltmarsh along the Gulf of Mexico coastline in peninsular west-central Florida, USA. This location has a subtropical climate with mean daily temperatures ranging from 15.4 °C in January to 27.8 °C in August, and annual precipitation of 1336 mm. Precipitation falls as rain primarily between June and September. Tides are semi-diurnal, with 0.57 m median amplitudes during the year preceding sampling (U.S. NOAA National Ocean Service, Clearwater Beach, Florida, station 8726724). Sea-level rise is 4.0 ± 0.6 mm per year (1973-2020 trend, mean ± 95 % confidence interval, NOAA NOS Clearwater Beach station). The A. germinans mangrove zone is either adjacent to water or fringed on the seaward side by a narrow band of red mangrove (Rhizophora mangle). A near-monoculture of J. roemerianus is often adjacent to and immediately landward of the A. germinans zone. The transition from the mangrove to the J. roemerianus zone is variable in our study area. An abrupt edge between closed-canopy mangrove and J. roemerianus monoculture may extend for up to several hundred meters in some locations, while other stretches of ecotone present a gradual transition where smaller, widely spaced trees are interspersed into the herbaceous marsh. Juncus roemerianus then extends landward to a high marsh patchwork of succulent halophytes (including Salicornia bigellovi, Sesuvium sp., and Batis maritima), scattered dwarf mangrove, and salt pans, followed in turn by upland vegetation that includes Pinus sp. and Serenoa repens. Field design and sample collection. We established three study sites spaced at approximately 5 km intervals along the western coastline of the central Florida peninsula. The sites consisted of the Salt Springs (28.3298°, -82.7274°), Energy Marine Center (28.2903°, -82.7278°), and Green Key (28.2530°, -82.7496°) sites on the Gulf of Mexico coastline in Pasco County, Florida, USA. At each site, we established three plot pairs, each consisting of one saltmarsh plot and one mangrove plot. Plots were 50 m^2 in size. Plots pairs within a site were separated by 230-1070 m, and the mangrove and saltmarsh plots composing a pair were 70-170 m apart. All plot pairs consisted of directly adjacent patches of mangrove forest and J. roemerianus saltmarsh, with the mangrove forests exhibiting a closed canopy and a tree architecture (height 4-6 m, crown width 1.5-3 m). Mangrove plots were located at approximately the midpoint between the seaward edge (water-mangrove interface) and landward edge (mangrove-marsh interface) of the mangrove zone. Saltmarsh plots were located 20-25 m away from any mangrove trees and into the J. roemerianus zone (i.e., landward from the mangrove-marsh interface). Plot pairs were coarsely similar in geomorphic setting, as all were located on the Gulf of Mexico coastline, rather than within major sheltering formations like Tampa Bay, and all plot pairs fit the tide-dominated domain of the Woodroffe classification (Woodroffe, 2002, "Coasts: Form, Process and Evolution", Cambridge University Press), given their conspicuous semi-diurnal tides. There was nevertheless some geomorphic variation, as some plot pairs were directly open to the Gulf of Mexico while others sat behind keys and spits or along small tidal creeks. Our use of a plot-pair approach is intended to control for this geomorphic variation. Plot center elevations (cm above mean sea level, NAVD 88) were estimated by overlaying the plot locations determined with a global positioning system (Garmin GPS 60, Olathe, KS, USA) on a LiDAR-derived bare-earth digital elevation model (Dewberry, Inc., 2019). The digital elevation model had a vertical accuracy of ± 10 cm (95 % CI) and a horizontal accuracy of ± 116 cm (95 % CI). Soil samples were collected via coring at low tide in June 2011. From each plot, we collected a composite soil sample consisting of three discrete 5.1 cm diameter soil cores taken at equidistant points to 7.6 cm depth. Cores were taken by tapping a sleeve into the soil until its top was flush with the soil surface, sliding a hand under the core, and lifting it up. Cores were then capped and transferred on ice to our laboratory at the University of South Florida (Tampa, Florida, USA), where they were combined in plastic zipper bags, and homogenized by hand into plot-level composite samples on the day they were collected. A damp soil subsample was immediately taken from each composite sample to initiate 1 y incubations for determination of active C and N (see below). The remainder of each composite sample was then placed in a drying oven (60 °C) for 1 week with frequent mixing of the soil to prevent aggregation and liberate water. Organic wetland soils are sometimes dried at 70 °C, however high drying temperatures can volatilize non-water liquids and oxidize and decompose organic matter, so 50 °C is also a common drying temperature for organic soils (Gardner 1986, "Methods of Soil Analysis: Part 1", Soil Science Society of America); we accordingly chose 60 °C as a compromise between sufficient water removal and avoidance of non-water mass loss. Bulk density was determined as soil dry mass per core volume (adding back the dry mass equivalent of the damp subsample removed prior to drying). Dried subsamples were obtained for determination of soil organic matter (SOM), mineral texture composition, and extractable and total carbon (C) and nitrogen (N) within the following week. Sample analyses. A dried subsample was apportioned from each composite sample to determine SOM as mass loss on ignition at 550 °C for 4 h. After organic matter was removed from soil via ignition, mineral particle size composition was determined using a combination of wet sieving and density separation in 49 mM (3 %) sodium hexametaphosphate ((NaPO_3)_6) following procedures in Kettler et al. (2001, Soil Science Society of America Journal 65, 849-852). The percentage of dry soil mass composed of silt and clay particles (hereafter, fines) was calculated as the mass lost from dispersed mineral soil after sieving (0.053 mm mesh sieve). Fines could have been slightly underestimated if any clay particles were burned off during the preceding ignition of soil. An additional subsample was taken from each composite sample to determine extractable N and organic C concentrations via 0.5 M potassium sulfate (K_2SO_4) extractions. We combined soil and extractant (ratio of 1 g dry soil:5 mL extractant) in plastic bottles, reciprocally shook the slurry for 1 h at 120 rpm, and then gravity filtered it through Fisher G6 (1.6 μm pore size) glass fiber filters, followed by colorimetric detection of nitrite (NO_2^-) + nitrate (NO_3^-) and ammonium (NH_4^+) in the filtrate (Hood Nowotny et al., 2010,Soil Science Society of America Journal 74, 1018-1027) using a microplate spectrophotometer (Biotek Epoch, Winooski, VT, USA). Filtrate was also analyzed for dissolved organic C (referred to hereafter as extractable organic C) and total dissolved N via combustion and oxidation followed by detection of the evolved CO_2 and N oxide gases on a Formacs HT TOC/TN analyzer (Skalar, Breda, The Netherlands). Extractable organic N was then computed as total dissolved N in filtrate minus extractable mineral N (itself the sum of extractable NH_4-N and NO_2-N + NO_3-N). We determined soil total C and N from dried, milled subsamples subjected to elemental analysis (ECS 4010, Costech, Inc., Valencia, CA, USA) at the University of South Florida Stable Isotope Laboratory. Median concentration of inorganic C in unvegetated surface soil at our sites is 0.5 % of soil mass (Anderson, 2019, Univ. of South Florida M.S. thesis via methods in Wang et al., 2011, Environmental Monitoring and Assessment 174, 241-257). Inorganic C concentrations are likely even lower in our samples from under vegetation, where organic matter would dilute the contribution of inorganic C to soil mass. Nevertheless, the presence of a small inorganic C pool in our soils may be counted in the total C values we report. Extractable organic C is necessarily of organic C origin given the method (sparging with HCl) used in detection. Active C and N represent the fractions of organic C and N that are mineralizable by soil microorganisms under aerobic conditions in long-term soil incubations. To quantify active C and N, 60 g of field-moist soil were apportioned from each composite sample, placed in a filtration apparatus, and incubated in the dark at 25 °C and field capacity moisture for 365 d (as in Lewis et al., 2014, Ecosphere 5, art59). Moisture levels were maintained by frequently weighing incubated soil and wetting them up to target mass. Daily CO_2 flux was quantified on 29 occasions at 0.5-3 week intervals during the incubation period (with shorter intervals earlier in the incubation), and these per day flux rates were integrated over the 365 d period to compute an estimate of active C. Observations of per day flux were made by sealing samples overnight in airtight chambers fitted with septa and quantifying headspace CO_2 accumulation by injecting headspace samples (obtained through the septa via needle and syringe) into an infrared gas analyzer (PP Systems EGM 4, Amesbury, MA, USA). To estimate active N, each incubated sample was leached with a C and N free, 35 psu solution containing micronutrients (Nadelhoffer, 1990, Soil Science Society of America Journal 54, 411-415) on 19 occasions at increasing 1-6 week intervals during the 365 d incubation, and then extracted in 0.5 M K_2SO_4 at the end of the incubation in order to remove any residual mineral N. Active N was then quantified as the total mass of mineral N leached and extracted. Mineral N in leached and extracted solutions was detected as NH_4-N and NO_2-N + NO_3-N via colorimetry as above. This incubation technique precludes new C and N inputs and persistently leaches mineral N, forcing microorganisms to meet demand by mineralizing existing pools, and thereby directly assays the potential activity of soil organic C and N pools present at the time of soil sampling. Because this analysis commences with disrupting soil physical structure, it is biased toward higher estimates of active fractions. Calculations. Non-mobile C and N fractions were computed as total C and N concentrations minus the extractable and active fractions of each element. This data package reports surface-soil constituents (moisture, fines, SOM, and C and N pools and fractions) in both gravimetric units (mass constituent / mass soil) and areal units (mass constituent / soil surface area integrated through 7.6 cm soil depth, the depth of sampling). Areal concentrations were computed as X × D × 7.6, where X is the gravimetric concentration of a soil constituent, D is soil bulk density (g dry soil / cm^3), and 7.6 is the sampling depth in cm. 

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5. Using an Arthrometer to Quantify Ankle Laxity: An Infographic Summary

   https://doi.org/10.1177/19417381221147511  

   Gulick, Dawn T. ( January 2023 , Sports Health: A Multidisciplinary Approach)

   Lateral ankle sprains are a common musculoskeletal injury. The anterior talofibular ligament (ATFL) is the primary ligament involved and is assessed via an anterior drawer test. Clinically assessing joint laxity has been a subjective task. Evaluating both magnitude of translation and quality of the endfeel has presented challenges. Until recently, a reliable and valid arthrometer to test joints other than the knee has not been available. The Mobil-Aider arthrometer has undergone bench testing for validity, reliability testing in healthy persons, and most recently the testing of participants for pathology. A summary of these studies is available in the Online Supplement . The goal of this study was to determine the ability of the arthrometer to objectively identify the anterior translation of the ankle and the relationship to the clinical diagnosis. The participant was evaluated by a physician and magnitude of ankle sprain was determined. An arthrometer was used to perform an anterior drawer test (uninjured before injured, 3 measures each) in the prone position. Both clinicians were blinded to the data of the other. There were 30 participants, 10 per group (uninjured, 1° sprain, 2° sprain). Mann-Whitney U testing found significant differences between the control and grade 1 ankle sprain groups ( P < .001), the control and grade 2 ankle sprain groups ( P < .001), and the grade 1 and grade 2 ankle sprain groups ( P = .004). There was ± 0.31 mm difference in anterior translation between healthy ankles, whereas there was 1.11 mm and 2.16 mm difference between ankles in grade 1 and grade 2 sprains, respectively. The anterior drawer test is the gold standard for clinical ATFL testing, but the subjective nature of this test poses challenges. Technology is available to assess ankle joint laxity and enhance the objectivity of patient assessment and throughout the recovery process. An arthrometer is a valuable tool in quantifying orthopaedic examination.

    

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