Degassing of early-formed planetesimals restricted water delivery to Earth.

The timing of delivery and the types of body that contributed volatiles to the terrestrial planets remain highly debated1,2. For example, it is unknown if differentiated bodies, such as that responsible for the Moon-forming giant impact, could have delivered substantial volatiles3,4 or if smaller, undifferentiated objects were more probable vehicles of water delivery5-7. Here we show that the water contents of minerals in achondrite meteorites (mantles or crusts of differentiated planetesimals) from both the inner and outer portions of the early Solar System are ≤2 µg g-1 H2O. These are among the lowest values ever reported for extraterrestrial minerals. Our results demonstrate that differentiated planetesimals efficiently degassed before or during melting. This finding implies that substantial amounts of water could only have been delivered to Earth by means of unmelted material.

Can a Blade-Stopping Mechanism on Circular Table Saws Reduce the Severity of Hand Injuries in Contact Scenarios? A Cadaveric Study.

PURPOSE: Table saws are commonly used woodworking tools that carry a substantial risk of injury. Blade-stopping technology has been developed and has the potential to reduce the frequency and severity of injury. This study aimed to evaluate this technology on human tissue and characterize the resulting injuries. METHODS: Twenty-seven fresh, frozen cadaveric specimen hands were used. Three scenarios were tested, with the specimen (1) moving forward ("forward"); (2) moving backward, such as in a kickback scenario ("reverse"); and (3) dropped from above the saw blade ("top"). Each scenario was tested at both slow (0.001 m/sec) and fast (forward: 0.6 m/sec; reverse: 0.5 m/sec; top: 2.4 m/sec) approach speeds. The severity of the injuries was characterized by anatomic evaluation and confirmed with radiographic evaluation. Injuries were classified as no laceration, superficial soft tissue injury, deep soft tissue injury, and bony injury. RESULTS: For the slow approach speed, the brake cartridge engaged in 100% of the trials for all 3 scenarios, and 100% of the specimens sustained no injuries. Forward testing at a fast approach speed revealed the brake cartridge engaged in 89% of the trials (injuries: 4 superficial, 2 deep, 3 bony). Reverse testing at a fast approach speed revealed the brake cartridge engaged in 11% of trials (injuries: 1 superficial, 8 bony). Top testing at a fast approach speed revealed the brake cartridge engaged in 89% of the trials (injuries: 9 bony). CONCLUSIONS: Modern blade-stopping technology did not prevent all traumatic hand injuries in fast approach speed scenarios, but it reduced the incidence and severity of injuries. The technology was more effective at low approach speed scenarios. CLINICAL RELEVANCE: The findings of this study provide information to help understand the factors that can prevent or reduce the severity of contact injuries (hand, finger, or thumb) for operators of table saws.

Use of electrocautery devices for suture passage through the greater tuberosity: a biomechanical study.

BACKGROUND: The use of electrocautery to facilitate passage of a suture needle through bone without the aid of a drill or burr is a novel technique that has potential utility in orthopedic procedures, but there is a scarcity of research to support its utility. The specific aims of this cadaveric biomechanical study were to evaluate (1) the axial force reduction during suture passage using electrocautery when applied to rotator cuff repair, (2) the temperature change caused while using electrocautery, and (3) the failure loads and failure modes of this technique. METHODS: Five matched pairs of fresh frozen humeri were used, classified into 2 groups: with electrocautery on needle (study group) and without electrocautery on needle (control group). Four individual osseous tunnels were made on the greater tuberosity around the insertion of the supraspinatus tendon. Each specimen was sequentially tested in 2 parts: a needle penetration test (part I) to measure the peak axial force and temperature change and a single load-to-failure test (part II) to measure the maximum load to failure as well as the mechanism of failure. A No. 2 FiberWire suture with a straight needle was used. RESULTS: In part I, the mean peak axial force was lower in the study group compared with the control group for all osseous tunnels but was not statistically significant for individual tunnels. However, there was a significant decrease in peak axial force in the study group of 36% compared with the control group overall (P = .033). There was no significant change in temperature of the tunnel site with the use of electrocautery (mean: 0.2 ± 0.3°C, P = .435). In part II, 100% of the samples from each study group experienced bone tunnel failure. Forty percent of the trials in the study group found lower ultimate failure loads compared with the control group (reduction range: 7%-38%). There was no statistically significant difference in the ultimate failure load between either the loop tested or between the 2 study groups (loop 1: P = .352; loop 2: P = .270). CONCLUSION: Suture passage using electrocautery does significantly decrease the peak force needed to pass a needle directly through the greater tuberosity. This technique does not appear to burn the bone or weaken the bone tunnels. This technique may be useful during open rotator cuff repair or shoulder arthroplasty, although clinicians should be cautious when using this technique as its utility depends on bone quality and cortical thickness, and in vivo results may differ.

A Biomechanical Evaluation of Casting Technique and Cast Core Size Effect.

BACKGROUNDS: The goals of this study were to (1) compare the effect of casting technique on biomechanical function with different casting materials and different cast core diameters, and (2) compare the strength of a cast based on the number of layers in relation to the core diameter. METHODS: Two standardized cylindrical cast model sizes were used to simulate forearm and short leg casts (core diameter: 60 mm, 100 mm) with 2 different casting techniques (non-smoothing vs. smoothing with lamination), utilizing 2 casting materials [fiberglass and Plaster of Paris (POP)]. Each cast was created using 3 different layers (Fiberglass: 2 to 4 layers; POP: 3 to 5 layers). Ultimate load-to-failure and flexural rigidity were analyzed through cyclic 4-point bend testing. RESULTS: The biomechanical comparison between forearm and short leg casts were significantly different regardless of the same number of layers for both casting materials and between 2 casting techniques. Increased cast thickness significantly increased the ultimate load-to-failure and bending strength. An increased core diameter size significantly decreased the cast's ultimate load-to-failure (fiberglass: 50% to 108%; POP: 10% to 93%) and bending strength (fiberglass: 17% to 35%; POP: 37% to 49%). Casting technique with smoothing with lamination technique had a negative biomechanical effect on POP and a minimal effect on fiberglass. CONCLUSION: The number of layers to apply for a cast should be based on the size of the extremity. Smoothing and lamination technique did not significantly improve the cast mechanical behavior. CLINICAL RELEVANCE: The findings of this study provide valuable evidence, analysis, and supplementary knowledge that helps guide physicians in proper casting technique.

Computed Tomography Derived Patient-specific Instrumentation Total Ankle Arthroplasty Survivorship Outcomes.

Computed tomography (CT) derived patient-specific total ankle arthroplasty (TAA) systems have been utilized for improved accuracy and reproducible implant alignment. The purpose of the present study was to report the overall implant survivorship as well as radiographic analysis of patients who underwent primary TAA utilizing CT-derived patient-specific instrumentation. A retrospective review of medical charts and radiographs were performed on patients who had undergone primary TAA at a single institution in the Midwest region from March 2013 to October 2020. Radiographic analysis included preoperative, initial postoperative, and final follow-up coronal and sagittal tibiotalar alignment as well as periprosthetic radiolucency. A total of 96 patients with a mean follow-up of 3 years (range, 0.3-7.3 years) were included. Implant survivorship was found to be 92% at median follow-up of 3 years. A total of 8 cases (8.3%) required revision/reoperation, with 6 (6.3%) of these reoperations directly related for failure of one of the metallic implant components. There was significant improvement in both coronal and sagittal tibiotalar alignment from preoperative to initial postoperative follow-up (p < .001). At latest postoperative follow-up, there were 88% of TAAs that remained in a neutral alignment following surgery. A total of 10 cases were found to have radiolucency at latest follow-up. In conclusion, the use of CT derived patient-specific TAA showed high implant survivorship with significant improvement of sagittal and coronal tibiotalar alignment. With better implant alignment and position, it potentially reduces the risk of early implant failure or implant loosening in long-term follow-up.

Biomechanical Comparison of Knotless Suture Anchor Versus Percutaneous End-to-End Technique for Mid-Substance Achilles Tendon Rupture Repair.

Percutaneous Achilles tendon repairs can be performed with 2 distal fixation techniques: knotless suture anchor repair (KL) or percutaneous end-to-end repair (ETE). There is a paucity of literature comparing the biomechanical strength of these 2 distal fixation techniques. The aim of this study was to compare the strength of KL and ETE repairs using flat-braided suture for mid-substance Achilles tendon rupture during simulated progressive rehabilitation. Nine matched pairs of fresh-frozen below-knee cadaveric extremities were randomly assigned into these 2 repair groups. Each specimen was tested in 2 parts sequentially; Part I simulating passive ankle range of motion (cyclic: 20N-100N), and Part II simulating ambulation in a walking boot (cyclic: 20N-190N). The number of cycles, gap displacement, and the mode of failure were recorded for each repair. Achilles tendon repairs using the percutaneous methods of ETE and KL techniques showed no significant difference in the number of cycles to clinical failure, mean gap displacement, or overall failure rate. During Part I, the survival rate in terms of clinical failure for KL and ETE groups was 8 of 9 repairs and 7 of 9 repairs, respectively. During Part II, all repairs experienced clinical failure in both groups. Five repairs in the KL group experienced suture anchor pull out from the calcaneus, and 3 repairs failed at suture-tendon interface. Four repairs in the ETE group failed due to knot slippage and 5 repairs failed at suture-tendon interface. Both techniques are viable options in treating acute mid-substance Achilles tendon ruptures.

Symptomatic Hammertoes Treatment Comparison: Peg-in-Hole Arthrodesis Versus End-to-End Screw Fixation.

Proximal interphalangeal (PIP) arthrodesis technique utilizing the peg-in-hole arthrodesis was founded to avoid the use of retained internal fixation implants and thereby potentially decrease the concern of hardware complication. The specific aim of this study was to report the complication rates of the modified peg-in-hole arthrodesis technique and the end-to-end arthrodesis with single screw fixation technique for correcting symptomatic hammertoe deformities in lesser digits. This retrospective chart review included patients who underwent surgical hammertoe correction of lesser digits between the dates of January 2012 and December 2019. Patient demographic data and charts were reviewed to evaluate need for revision including screw/pin removal and complications related to corrective surgery. Five hundred ninety-three symptomatic hammertoe deformity cases (443 female, 150 male) were identified, with 113 cases (88 female, 25 male) treated with peg-in-hole arthrodesis technique and 480 cases (355 female, 125 male) treated with end-to-end arthrodesis with a single screw technique. The deformity recurrence rate was not significantly different between the two techniques (peg-in-hole: 10%, end-to-end: 13%, p = .428). There were 97 cases with postoperative complications that required re-operation (peg-in-hole: 7 cases, end-to-end: 90 cases) with the majority detected at <6 months. There was no statistically significant difference in reoperation rate between the peg-in-hole technique and the end-to-end arthrodesis technique reoperated with reasons excluding simple screw removal (p = .068). This study tended to show these two arthrodesis techniques have equivalent risks and similar success in bone healing; however, the peg-in-hole arthrodesis technique offers an advantage that does not result in retained hardware.

Contrasting recruitment of skin-associated adipose depots during cold challenge of mouse and human.

KEY POINTS: Several distinct strategies produce and conserve heat to maintain the body temperature of mammals, each associated with unique physiologies, with consequences for wellness and disease susceptibility Highly regulated properties of skin offset the total requirement for heat production  We hypothesize that the adipose component of skin is primarily responsible for modulating heat flux; here we evaluate the relative regulation of adipose depots in mouse and human, to test their recruitment to heat production and conservation We found that insulating mouse dermal white adipose tissue accumulates in response to environmentally and genetically induced cool stress; this layer is one of two adipose depots closely apposed to mouse skin, where the subcutaneous mammary gland fat pads are actively recruited to heat production In contrast, the body-wide adipose depot associated with human skin produces heat directly, potentially creating an alternative to the centrally regulated brown adipose tissue ABSTRACT: Mammalian skin impacts metabolic efficiency system-wide, controlling the rate of heat loss and consequent heat production. Here we compare the unique fat depots associated with mouse and human skin, to determine whether they have corresponding functions and regulation. For humans, we assay a skin-associated fat (SAF) body-wide depot to distinguish it from the subcutaneous fat pads characteristic of the abdomen and upper limbs. We show that the thickness of SAF is not related to general adiposity; it is much thicker (1.6-fold) in women than men, and highly subject-specific. We used molecular and cellular assays of ß-adrenergic-induced lipolysis and found that dermal white adipose tissue (dWAT) in mice is resistant to lipolysis; in contrast, the body-wide human SAF depot becomes lipolytic, generating heat in response to ß-adrenergic stimulation. In mice challenged to make more heat to maintain body temperature (either environmentally or genetically), there is a compensatory increase in thickness of dWAT: a corresponding ß-adrenergic stimulation of human skin adipose (in vivo or in explant) depletes adipocyte lipid content. We summarize the regulation of skin-associated adipocytes by age, sex and adiposity, for both species. We conclude that the body-wide dWAT depot of mice shows unique regulation that enables it to be deployed for heat preservation; combined with the actively lipolytic subcutaneous mammary fat pads they enable thermal defence. The adipose tissue that covers human subjects produces heat directly, providing an alternative to the brown adipose tissues.

Prior Anterior Cruciate Ligament Reconstruction Effects on Future Total Knee Arthroplasty.

BACKGROUND: The impact of prior anterior cruciate ligament (ACL) reconstruction on total knee arthroplasty (TKA) has rarely been studied. The objective of this study was to compare intraoperative characteristics in patients who underwent TKA with pre-existing hardware from prior ACL reconstruction with a matched cohort control group. METHODS: A retrospective study of patients who had undergone primary TKA with pre-existing hardware from prior ACL reconstruction was performed from June 2012 through June 2017. These patients were 2-to-1 matched to the ACL group based on similar patient demographic and provider variables. Outcomes investigated included operative time, estimated blood loss (EBL), and postoperative complications. RESULTS: One hundred one patients met the inclusion/exclusion criteria. The mean age was 54 ± 9 years, and the mean body mass index was 32.6 ± 6.5 kg/m2. The ACL group was divided into 4 subgroups: group 1, no pre-existing hardware removed (22 TKAs); group 2, pre-existing hardware removed from the femur only (8 TKAs); group 3, pre-existing hardware removed from the tibia only (45 TKAs); and group 4, pre-existing hardware removed from both the femur and tibia (26 TKAs). There was no statistical difference in EBL and postoperative complication between the ACL group and controls. Statistical differences were detected between 2 subgroups regarding mean operative time variables: ACL group 3 (74 ± 23 minutes; control: 64 ± 21 minutes, P = .020) and group 4 (79 ± 24 minutes; control: 65 ± 19 minutes, P = .010). CONCLUSION: Hardware retained, especially on the tibia, from prior ACL reconstruction has a major impact on TKA surgical procedure operative time but not on EBL and/or complications.

The nature, origin and modification of insoluble organic matter in chondrites, the possibly interstellar source of Earth's C and N.

All chondrites accreted ~3.5 wt.% C in their matrices, the bulk of which was in a macromolecular solvent and acid insoluble organic material (IOM). Similar material to IOM is found in interplanetary dust particles (IDPs) and comets. The IOM accounts for almost all of the C and N in chondrites, and a significant fraction of the H. Chondrites and, to a lesser extent, comets were probably the major sources of volatiles for the Earth and the other terrestrial planets. Hence, IOM was both the major source of Earth's volatiles and a potential source of complex prebiotic molecules. Large enrichments in D and 15N, relative to the bulk solar isotopic compositions, suggest that IOM or its precursors formed in very cold, radiation-rich environments. Whether these environments were in the interstellar medium (ISM) or the outer Solar System is unresolved. Nevertheless, the elemental and isotopic compositions and functional group chemistry of IOM provide important clues to the origin(s) of organic matter in protoplanetary disks. IOM is modified relatively easily by thermal and aqueous processes, so that it can also be used to constrain the conditions in the solar nebula prior to chondrite accretion and the conditions in the chondrite parent bodies after accretion. Here we review what is known about the abundances, compositions and physical nature of IOM in the most primitive chondrites. We also discuss how the IOM has been modified by thermal metamorphism and aqueous alteration in the chondrite parent bodies, and how these changes may be used both as petrologic indicators of the intensity of parent body processing and as tools for classification. Finally, we critically assess the various proposed mechanisms for the formation of IOM in the ISM or Solar System.

Validation of Improvement of Basic Competency in Arthroscopic Knot Tying Using a Bench Top Simulator in Orthopaedic Residency Education.

PURPOSE: To validate basic competency in arthroscopic knot tying using a unique simulator device to compare the level of training needed for learning and tying the arthroscopic knot by evaluating the tensile properties of the arthroscopic knots. METHODS: Three groups of surgeons of various experience levels (postgraduate year [PGY] 1, PGY 3, and experienced surgeons) tied 2 different arthroscopic knots (Tennessee Slider, considered easier, and Weston, considered more difficult) over a 10-week period. Each group went through 3 separate stages of knot tying: stage 1, tying 8 knots without cannula or knot pusher; stage 2, tying 12 knots with knot pusher; and stage 3, tying 20 knots with knot pusher through a cannula that simulates knot tying during surgery. A single load-to-failure test was performed and ultimate clinical failure loads were recorded. Time needed to tie each knot was also recorded. RESULTS: At stages 1 and 2, the PGY 1 group had a significantly weak knot tensile strength (Tennessee Slider stage 1: 60 v 129 N, P = .001; Tennessee Slider stage 2: 69 v 132 N, P = .0029; Weston stage 1: 73 v 184 N, P = .0000; Weston stage 2: 125 v 173 N, P = .0045) and were slower (Weston: 56 v 30 seconds, P = .0010) than the experienced surgeon group for both knots. At stage 3, only the initial 2 weeks of Tennessee Slider showed a significant difference between groups 1 and 3 (week 6: 87 v 118 N, P = .0492; week 7: 89 v 126, P = .01485). Even though the Tennessee Slider knot is one of the easier arthroscopic knots to learn to tie, the results showed a slow trend of improvement in this knot-tying skill for group 1 after each stage. CONCLUSIONS: The data validated an important learning effect in all trainees in arthroscopic knot tying over a 10-week period and showed that inexperienced trainees will be able to improve their knot-tying skill with training in 3 stages with a simulator environment. CLINICAL RELEVANCE: The findings of this study indicated the importance of hands-on experience in performing arthroscopic knot tying, as determined by both knot performance and ultimate suture loop strength. In addition, each orthopaedic resident learned and developed his or her arthroscopic knot-tying skills and provided a foundation for his or her future practice in orthopaedic medicine.

Intrusion Characteristics of Three Bone Cements for Tibial Component of Total Knee Arthroplasty in a Cadaveric Bone Model.

The purpose of this study was to evaluate and compare the intrusion characteristics of Simplex-HV to Simplex-P and Palacos-R in cadaveric proximal tibial bone. Eighteen fresh-frozen cadaver proximal tibiae were examined with standard arthroplasty tibial cuts. Each tibia was randomly assigned to receive one of the three bone cements for use with finger packing technique. Sagittal sections were prepared and analyzed using digital photography and stereoscopic micrographs to evaluate cement intrusion characteristics. The cement penetration depth was measured from the tibial bone cut surface, which did not include the cement thickness under the tibial base plate. Significant differences were detected in the bone cement penetration between the three cements. Penetration was increased using the Simplex-HV (average, 2.7 mm; range, 2.0-3.0 mm) compared with Simplex-P (average, 2.2 mm) and Palacos-R (average, 1.8 mm). These depths approximate to 3.7, 3.2, and 2.8 mm of total cement penetration, respectively. The data suggest that high-viscosity bone cement may provide good fixation of the tibial component of a total knee arthroplasty when using the finger packing technique.

A new quantitative rating scale for dyskinesia in nonhuman primates.

The aim of this study was to develop a quantitative scale to assess levodopa-induced dyskinesias (LIDs) in nonhuman primates using a video-based scoring system [Quantitative Dyskinesia Scale (QDS)]. Six macaques with stable Parkinsonism and LID were used for tests of the new QDS, in comparison with our current standardized scale (Drug-Related Side effects), which provides a classic subjective measurement of dyskinesia. QDS scoring is based on systematic movement counts in time frames, using videotape recordings. For both scales, body segments scored included each extremity, the trunk, the neck, and the face, and raters were blinded to L-dopa treatments. Comparison of the two scales revealed that their scores are highly correlated with and are parallel to the L-dopa pharmacokinetic profile, although the QDS provided significantly more quantifiable measurements. This remained the case after separating animals into groups of mild and severe dyskinesias. Inter-rater reliability for application of the QDS was confirmed from scores obtained by three examiners. We conclude that the QDS is a quantitative tool for reliably scoring LID in parkinsonian monkeys at all levels of severity of dyskinesia. The application of this new standard for scoring LID in primates will allow for more precise measurements of the effects of experimental treatments and will improve the quality of results obtained in translational studies.

Novel flexible suture fixation for the distal tibiofibular syndesmotic joint injury: a cadaveric biomechanical model.

Syndesmotic injuries of the ankle commonly occur by an external rotation force applied to the ankle joint. Ten fresh-frozen lower extremities from cadavers were used. A specially designed apparatus was used to stabilize the specimen and rotate the ankle joint from internally rotated 25° to externally rotated 35° at a rate of 6°/s for 10 cycles. Two stages were tested (stage I, specimens intact; and stage II, simulated pronation external rotation type injury with fixation). Group 1 was fixed with a novel suture construct across the syndesmotic joint, and group 2 was fixed with a single metallic screw. The torque, rotational angle, and 3-dimensional syndesmotic diastasis readings were recorded. Three-dimensional tibiofibular diastasis was identified. The fibula of the intact specimens displaced an average of 8.6 ± 1.7, 2.4 ± 1.0, and 1.4 ± 1.0 mm in the anterior, lateral, and superior direction, respectively, when the foot was externally rotated 35°. The sectioning of the syndesmostic ligaments and deltoid ligament resulted in a significant decrease in syndesmotic diastasis and foot torsional force (p < .05). The ligament-sectioned specimen lost 57% (externally rotated) and 17% (internally rotated) torsional strength compared with the intact specimen. Groups 1 and 2 provided similar biomechanical stability in this cadaveric model of a syndesmosis deficiency.

Biomechanical Comparison of Impaction Techniques and Cross-Sectional Femoral Stem Shapes for Cementless Total Hip Arthroplasty.

Introduction: Traditional mallet broaching and stem seating in cementless total hip arthroplasty (THA) can result in femoral stem misalignment, potentially reducing implant longevity. This study aimed to compare the pullout strength of cementless THA femoral stems with different cross-sectional designs achieved through the powered impactor method versus the traditional mallet method. Methods: The authors utilized 24 polyurethane foam femurs and two femoral bone preservation stems with different proximal cross-sectional shapes (double taper: ACTIS®, size 5; flat taper: TRI-LOCK®, size 5). A single orthopedic surgeon broached each femur from size 0 to size 5 using either the powered impactor or mallet impaction methods. Broaching time and component implantation times were recorded. A load-to-failure pullout strength test was conducted, and the ultimate pullout load was recorded. Results: The broaching time for the TRI-LOCK® stem showed a statistically significant difference between the two impaction methods (powered: 37±7 seconds, mallet: 75±29 seconds, F[3, 20] = 4.56, p = 0.002), but no statistically significant difference was detected for the ACTIS® stem between the two impaction methods (powered: 47±22 seconds, mallet: 59±9 seconds, F[3, 20] = 4.56, p = 0.304). There was a statistically significant difference in pullout strength between the two impaction groups, and this strength was influenced by the implant cross-sectional shape (ACTIS®: 774±75N versus 679±22N, F(3,20) = 16.38, p = 0.018; TRI-LOCK®: 616±57N versus 859±85N, F(3, 20) = 16.38, p <0.001). Conclusions: The technique used for femoral bone preparation (powered impactor versus mallet) and the cross-sectional design of the cementless femoral stem are crucial factors that affect initial stem stability and operation time.

Recent trends in the characteristics of patients prescribed sitagliptin and other oral antihyperglycaemic agents in a large U.S. claims database.

AIM: This study was designed to determine if differences in baseline characteristics of patients with type 2 diabetes mellitus (T2DM) being treated with sitagliptin vs. other oral antihyperglycaemic agents (OAHA) during the initial 2 years following sitagliptin's introduction in the U.S. continued during the second 2 years of sitagliptin availability. METHODS: Patients with T2DM and at least one new prescription for sitagliptin or another OAHA from Oct 2006 to April 2010 were identified in an insurance claims database. Multivariate logistic regression adjusting for age, gender, treatment type (monotherapy, dual or triple therapy), new or existing T2DM diagnosis, and comorbidities and diabetes complications in the prior 12 months was used to estimate odds ratios for sitagliptin vs. other OAHAs. RESULTS: During 2006-2007 or 2008-2010, new sitagliptin users were older and more likely to be male, have prior diagnosis of T2DM, or initiating combination therapy compared with new users of other OAHAs. Prevalence of comorbidities and complications was consistently higher for new sitagliptin users across most of the conditions assessed during both time periods. CONCLUSIONS: New sitagliptin users consistently tended to be older and have greater comorbidity/complication burden compared with new users of other OAHAs. These differences in baseline characteristics persisted up to 4 years postapproval. This observation has significant implications for observational studies using electronic medical record or insurance claims databases. Appropriate adjustment is needed to try to control for potential confounding and channelling bias resulting from this non-random prescribing pattern, and the limitations of such analyses acknowledged.

Syndecan-1 is required for Wnt-1-induced mammary tumorigenesis in mice.

Syndecan-1 is a cell-surface, heparan-sulphate proteoglycan (HSPG) predominantly expressed by epithelial cells. It binds specifically to many proteins, including oncoproteins. For example, it induces the assembly of a signalling complex between FGF ligands and their cognate receptors. But so far there has been no direct evidence that this proteoglycan contributes to tumorigenesis. Here we have examined the role of syndecan-1 (encoded by Sdc1) during mammary tumour formation in response to the ectopic expression of the proto-oncogene Wnt1. We crossed syndecan-1-deficient mice with transgenic mice that express Wnt1 in mammary gland (TgN(Wnt-1)1Hev; ref. 2). Ectopic Wnt-1 expression induces generalized mammary hyperplasia, followed by the development of solitary tumours (median time 22 weeks). We show that in Sdc1-/- mice, Wnt-1-induced hyperplasia in virgin mammary gland was reduced by 70%, indicating that the Wnt-1 signalling pathway was inhibited. Of the 39 tumours that developed in a test cohort of mice, only 1 evolved in the Sdc1-/- background. In addition, we show that soluble syndecan-1 ectodomain purified from mouse mammary epithelial cells stimulates the activity of a Wnt-1 homologue in a tissue culture assay. Our results provide both genetic and biochemical evidence that syndecan-1 can modulate Wnt signalling, and is critical for Wnt-1-induced tumorigenesis of the mouse mammary gland.

The Effect of Bone Quality on Treatment of Intertrochanteric Fractures with Helical Blade Versus Lag Screw Fixation in Cephalomedulary Nails.

Introduction: The specific aim of this retrospective study was to determine whether bone quality has any effect on the complication rates or overall survivorship between helical blades and lag screws in cephalomedullary nails used for intertrochanteric hip fractures. Methods: The authors reviewed clinical charts and radiographic studies of patients between January 2012 and August 2019. We reviewed radiographic images (pre-, intra-, and post-operative) to evaluate fracture fixation type, fracture reduction grade, and post-operative complications. We collected dual energy x-ray absorptiometry scan results (T-score) and serum alkaline phosphatase (ALP) isoenzyme activity values to evaluate patient bone quality. Results: We included 303 cases (helical: 197, screw: 106) in the study. Complications were found in 31 (16%) helical blade cases and 23 (22%) lag screw cases. No statistically significant difference was detected when comparing complication rates with patient bone quality between the two groups. These two groups had similar one-year implant survivorship with respect to T-score, the low ALP level group, and normal ALP level group. The helical blade had higher implant survivorship compared to lag screw in five-year survival rate with respect to osteoporotic group, high ALP level group, and normal ALP level group (osteoporotic: 77% vs 69%, high ALP: 73% vs 67%, normal ALP: 70% vs 64%). Conclusions: Similar complication rates were observed between helical blade and lag screw constructs in cephalomedullary femoral nails when accounting for patient bone quality. However, the helical blade design had a higher five-year survival rate.

Use of Electrocautery to Facilitate Suture Passage Through the Greater Trochanter of the Femur: A Biomechanical Study.

Introduction: The specific aims of this study were to evaluate (1) the axial force reduction of suture passage utilizing electrocautery when applied to the greater trochanter of the femur, (2) the temperature change caused while using electrocautery for suture passage, and (3) the failure loads and failure modes utilizing this technique. Methods: Five matched pairs of fresh-frozen femurs were used and classified into two groups: with electrocautery on needle (study group) and without electrocautery on needle (control group). Two bicortical, osseous tunnels were made around the insertion of the gluteus medius tendon. Each specimen was sequentially tested in a needle penetration test and a single load-to-failure test. A #5 Ethibond suture with a straight needle was used. Results: Electrocautery reduced the peak axial force for bone penetration in 40% (near cortex) and 70% (far cortex) of the trials, and no significant difference was detected between groups or between two osseous tunnels. The average peak force was significantly higher for the far cortex for both groups and for both osseous tunnels compared to the near cortex. There was no significant change in temperature of the tunnel site with electrocautery. Ninety percent of the samples experienced bone tunnel failure for the study group compared to 70% in the control group. The average ultimate failure load for the study group was lower compared with the control group, but this finding was not statistically significant (range: 6%-15%). Conclusions: Suture passage using electrocautery may not significantly decrease the peak force needed to pass a needle directly through the greater trochanter.

Complication rate of overlapping versus nonoverlapping functional and stereotactic surgery: a retrospective cohort study.

OBJECTIVE: Overlapping surgery, in which one attending surgeon manages two overlapping operating rooms (ORs) and is present for all the critical portions of each procedure, is an important policy that improves healthcare access for patients and case volumes for surgeons and surgical trainees. Despite several studies demonstrating the safety and efficacy of overlapping neurosurgical operations, the practice of overlapping surgery remains controversial. To date, there are no studies that have investigated long-term complication rates of overlapping functional and stereotactic neurosurgical procedures. The primary objective of this study was to investigate the 1-year complication rates and OR times for nonoverlapping versus overlapping functional procedures. The secondary objective was to gain insight into what types of complications are the most prevalent and test for differences between groups. METHODS: Seven hundred eighty-three functional neurosurgical cases were divided into two cohorts, nonoverlapping (n = 342) and overlapping (n = 441). The American Society of Anesthesiologists (ASA) scale score was used to compare the preoperative risk for both cohorts. A complication was defined as any surgically related reason that required readmission, reoperation, or an unplanned emergency department or clinic visit that required intervention. Complications were subdivided into infectious and noninfectious. Chi-square tests, independent-samples t-tests, and uni- and multivariable logistic regressions were used to determine significance. RESULTS: There were no significant differences in mean ASA scale score (2.7 ± 0.6 for both groups, p = 0.997) or overall complication rates (8.8% nonoverlapping vs 9.8% overlapping, p = 0.641) between the two cohorts. Infections accounted for the highest percentage of complications in both cohorts (46.6% vs 41.8%, p = 0.686). There were no statistically significant differences between mean in-room OR time (187.5 ± 141.7 minutes vs 197.1 ± 153.0 minutes, p = 0.373) or mean open-to-close time (112.2 ± 107.9 minutes vs 121.0 ± 123.1 minutes, p = 0.300) between nonoverlapping and overlapping cases. CONCLUSIONS: There was no increased risk of 1-year complications or increased OR time for overlapping functional and stereotactic neurosurgical procedures compared with nonoverlapping procedures.