Osmolality Selectively Offsets the Impact of Hyperthermia on Mouse Skeletal Muscle in vitro

Hyperthermia and dehydration can occur during exercise in hot environments. Nevertheless, whether elevations in extracellular osmolality contributes to the increased skeletal muscle tension, sarcolemmal injury, and oxidative stress reported in warm climates remains unknown. We simulated osmotic and heat stress, in vitro, in mouse limb muscles with different fiber compositions. Extensor digitorum longus (EDL) and soleus (SOL) were dissected from 36 male C57BL6J and mounted at optimal length in tissue baths containing oxygenated buffer. Muscles were stimulated with non-fatiguing twitches for 30 min. Four experimental conditions were tested: isotonic-normothermia (285 mOsm•kg-1 and 35°C), hypertonic-normothermia (300 mOsm•kg-1 and 35°C), isotonic-hyperthermia (285 mOsm•kg-1 and 41°C), and hypertonic-hyperthermia (300 mOsm•kg-1 and 41°C). Passive tension was recorded continuously. The integrity of the sarcolemma was determined using a cell-impermeable fluorescent dye and immunoblots were used for detection of protein carbonyls. In EDL muscles, isotonic and hypertonic-hyperthermia increased resting tension (P < 0.001). Whereas isotonic-hyperthermia increased sarcolemmal injury in EDL (P < 0.001), this effect was absent in hypertonic-hyperthermia. Similarly, isotonic-hyperthermia elevated protein carbonyls (P = 0.018), a response not observed with hypertonic-hyperthermia. In SOL muscles, isotonic-hyperthermia also increases resting tension (P < 0.001); however, these effects were eliminated in hypertonic-hyperthermia. Unlike EDL, there were no effects of hyperthermia and/or hyperosmolality on sarcolemmal injury or protein carbonyls. Osmolality selectively modifies skeletal muscle response to hyperthermia in this model. Fast-glycolytic muscle appears particularly vulnerable to isotonic-hyperthermia, resulting in elevated muscle tension, sarcolemmal injury and protein oxidation; whereas slow-oxidative muscle exhibits increased tension but no injury or protein oxidation under the conditions and duration tested

Flap-enabled next-generation capture (FENGC): precision targeted single-molecule profiling of epigenetic heterogeneity, chromatin dynamics, and genetic variation

Targeted sequencing is an increasingly sought technology. Available methods, however, are often costly and yield high proportions of off-target reads. Here, we present FENGC, a scalable, multiplexed method in which target sequences are assembled into 5′ flaps for precise excision by flap endonuclease. Recovery of length-matched sequences, amplification with universal primers, and exonucleolytic removal of non-targeted genomic regions mitigate amplification biases and consistently yield ≥80% on-target sequencing. Furthermore, optimized sequential reagent addition and purifications minimize sample loss and facilitate rapid processing of sub-microgram quantities of DNA for detection of genetic variants and DNA methylation. Treatment of cultured human glioblastoma cells and primary murine monocytes with GC methyltransferase followed by FENGC and high-coverage enzymatic methyl sequencing provides single-molecule, long-read detection of differential endogenous CG methylation, dynamic nucleosome repositioning, and transcription factor binding. FENGC provides a versatile and cost-effective platform for targeted sequence enrichment for analysis of genetic and/or epigenetic heterogeneity.This work was supported by grants HDTRA1-16-1-0048 awarded by the Defense Threat Reduction Agency to P.C. and R01 CA155390 awarded by The National Institutes of Health to M.P.K.N

Comparable Outcomes of Cartiva Implant, Cheilectomy, and Fusion for Hallux Rigidus of the 1st Metatarsophalangeal Joint: A Matched Cohort Study

Category: Midfoot/Forefoot; Other Introduction/Purpose: The primary goal of treating hallux rigidus of the 1st metatarsophalangeal (MTP) joint of the foot is to reduce pain. Treatment options include cheilectomy, interposition arthroplasty, and arthrodesis for more severe disease. Recently, the use of a synthetic cartilage implant (Cartiva, Stryker Inc., MI, USA) has been introduced with the advantage of motion preservation. While a Level 1 study has demonstrated similar outcomes of fusion and Cartiva, other comparative studies have shown less favorable results for the Cartiva implant. The purpose of this study was to evaluate minimum 2-year patient reported outcomes (PROs) of the Cartiva implant for the treatment of hallux rigidus in the 1st MTP joint in comparison to a matched cohort of patients treated with fusion or cheilectomy. Methods: Patients >18 years old who underwent surgery for treatment of 1st MTP joint hallux rigidus with Cartiva implant, cheilectomy, or fusion performed by two surgeons (T.O.C. or C.T.H.) between January 2009 and January 2020 were identified. A 2:1 matched control cohort of patients who underwent cheilectomy or fusion was constructed using a nearest neighbor, greedy algorithm based on age, sex, prior surgery, and Coughlin osteoarthritis grade. Minimum 2-year follow-up was obtained with patients completing subjective questionnaires including Foot and Ankle Ability Measure (FAAM) with Activities of Daily Living (ADL) and Sport subscales, Short Form-12 (SF-12), Tegner activity scale, and patient satisfaction with surgical outcome. Demographics and patient-reported outcomes were compared between groups. Results: Follow-up was obtained for 22/27 (82%) Cartiva patients (mean age 54±19) at median 4.3 years and 41/49 (84%) control patients (mean age 58±11) at median 3.5 years. Prevalence of Coughlin grade was similar between Cartiva and control groups (6 vs 10 grade 1, 8 vs 15 grade 2, 2 vs 6 grade 4, 6 vs 10 grade 5; p=.93), respectively. There was no significant difference in median post-operative FAAM-ADL (96 vs 95, p=.53), FAAM-Sport (92 vs 89, p=.89), SF-12 PCS (56 vs 51, p=.054), SF-12 MCS (56.3 vs 57.5, p=.50), Tegner score (4 vs 3, p=.30), or patient satisfaction (9 vs 9, p=.91) between Cartiva and control cohorts, respectively. Revision surgery was required for 3 (14%) Cartiva patients and 4 (10%) control patients (p=.70). Conclusion: Patients treated with a Cartiva synthetic cartilage implant for 1st MTP joint hallux rigidus had similar patient-reported outcomes and revision rate compared to patients treated with cheilectomy or fusion for Coughlin grade 2-5 osteoarthritis

A Percutaneous Knotless Technique for Acute Achilles Tendon Ruptures

Achilles tendon ruptures are a common tendon injury, usually occurring in middle-aged men during recreational sporting activities. Both nonoperative and operative management are employed to treat these injuries. Several operative treatments are described in the literature, including percutaneous Achilles repair, mini-open repair, and open repair. Open Achilles repair is associated with higher rates of impaired wound healing and infection, whereas minimally invasive techniques have been reported to have an increased risk of iatrogenic sural nerve injury. More recently, low complication rates, improved cosmetic appearance, reduced operating times, and improved clinical outcomes have been reported for the percutaneous Achilles repair technique. In this Technical Note, we present our preferred technique using the Percutaneous Achilles Repair System (Arthrex, Naples, FL), which has been reported to have minimal wound and nerve complications, and early return to activity

The Effect of Suture Caliber and Number of Core Strands on Repair of Acute Achilles Ruptures

Category: Sports Introduction/Purpose: Controversy exists in Achilles rupture management with options ranging from nonoperative care to open surgical repair. Current literature suggests re-rupture rates are lower with operative repair; therefore, surgery is recommended for active populations. The effect of suture caliber or number of core stands has not been studied in Achilles repair. Varying these factors may allow for a construct capable of earlier weight-bearing and rehabilitation. We hypothesized the number of core strands and suture caliber used in Achilles repair would significantly affect strength and gapping during a simulated early rehabilitation protocol. Methods: Sixteen cadaveric human foot and ankle specimens with no prior injuries or surgeries were utilized. Simulated midsubstance Achilles ruptures were created 6 cm proximal to the calcaneal insertion in 13 ankles. Specimens were randomly allocated to 1 of 4 groups: (1) intact Achilles tendon, (2) open repair using No. 2 suture with four core sutures and two 2mm suture-tape core sutures, (3) open repair using No. 2 suture with two core sutures and four 2mm suture-tape core sutures, and (4) open repair using No. 2-0 suture with 12 core sutures. Repairs consisted of three modified Kessler sutures and an epitenon stitch with a 3-0 monofilament suture. Specimens were subjected to a cyclic loading protocol simulating early, progressive postoperative rehabilitation: 250 cycles at 1 Hz for each loading range: 20-100, 20-200, 20-300, and 20-400 N. A 1-way ANOVA was used to test significance among repair groups. Results: During biomechanical testing, all repairs survived the first two loading stages. However, elongation trends during stage 1 (Figure 1) were consistent among subsequent cyclic loading stages. No significant elongation differences were observed between any of the repair groups (Groups 2-4), with mean displacements of 4.94 ± 0.90 mm, 3.93 ± 0.92 mm, and 5.35 ± 0.34 mm, respectively, at the end of the first loading stage. In Group 2, one repair failed during the fourth stage and 4 survived all four stages. In Group 3, one repair failed during the third stage and two repairs during the fourth stage. In Group 4, two repairs failed during the fourth stage and two survived all four stages. The average number of cycles to failure for Groups 2-4 was 967, 783, and 940 cycles, respectively. Conclusion: In this study, all but one repair survived 750 cycles. This was superior to a 6 core strand repair with No. 2 suture similarly evaluated in a previous study (427 cycles). When 4 of 6 strands were substituted with suture-tape, repair gapping decreased initially; yet, these repairs failed earlier. Gapping in Groups 2 and 4 was similar to the previously evaluated repair; however, the number of cycles to failure was higher. Therefore, substituting suture-tape for 2 core strands or doubling the core strands with a smaller caliber suture may be biomechanically superior and allow for earlier return to function