Weightbearing after combined medial and lateral plate fixation of AO/OTA 41-C2 bicondylar tibial plateau fractures: a biomechanical study.

BACKGROUND: Combined medial and lateral plate fixation is recommended for complex tibial plateau fractures with medial fragments or no cortical bone contact. Although such fixation is adequate to resist forces during range of motion, it may be insufficient to support immediate postoperative weightbearing. Here, we analyzed displacement, stiffness, and fixation failure during simulated full weightbearing of bicondylar tibial plateau fractures treated with combined medial and lateral locking plate fixation. METHODS: We used 10 fresh-frozen adult human cadaveric tibias and mated femurs. Osteotomies were performed with an oscillating saw and cutting template to simulate an AO Foundation and Orthopaedic Trauma Association (AO/OTA) 41-C2 fracture (simple articular, multifragmentary metaphyseal fracture). Specimens were anatomically reduced and stabilized with combined medial and lateral locking plates (AxSOS, Stryker, Mahwah, NJ). Specimens were loaded axially to simulate 4 weeks of walking in a person weighing 70 kg. The specimens were cyclically loaded from 200 N to a maximum of 2800 N. Then, if no failure, loading continued for 200,000 cycles. We measured displacement of each bone fragment and defined fixation failure as ≥5 mm of displacement. Construct stiffness and load at failure were calculated. Categorical and continuous data were analyzed using Chi-squared and unpaired t-tests, respectively. RESULTS: Mean total displacement values after 10,000 loading cycles were as follows: lateral, 0.4 ± 0.8 mm; proximal medial, 0.3 ± 0.7 mm; distal medial, 0.3 ± 0.6 mm; and central 0.4 ± 0.5 mm. Mean stiffness of the construct was 562 ± 164 N/mm. Fixation failure occurred in 6 of 10 specimens that reached 5 mm of plastic deformation before test completion. In the failure group, the mean load at failure was 2467 ± 532 N, and the mean number of cycles before failure was 53,155. After test completion, the greatest displacement was found at the distal medial fracture site (2.3 ± 1.4 mm) and lateral fracture site (2.2 ± 1.7 mm). CONCLUSIONS: Although combined medial and lateral plate fixation of complex tibial plateau fractures provides adequate stability to allow early range of motion, immediate full weightbearing is not recommended.

Comparison of Lag Versus Nonlag Screw Fixation for Long Oblique Proximal Phalanx Fractures: A Biomechanical Study.

PURPOSE: To compare lag versus nonlag screw fixation for long oblique proximal phalanx (P1) fractures in a cadaveric model of finger motion via the flexor and extensor tendons. METHODS: We simulated long oblique P1 fractures with a 45° oblique cut in the index, middle, and ring fingers of 4 matched pairs of cadaveric hands for a total of 24 simulated fractures. Fractures were stabilized using 1 of 3 techniques: two 1.5-mm fully threaded bicortical screws using a lag technique, two 1.5-mm fully threaded bicortical nonlag screws, or 2 crossed 1.14-mm K-wires as a separate control. The fixation method was randomized for each of the 3 fractures per matched-pair hand, with each fixation being used in each hand and 8 total P1 fractures per fixation group. Hands were mounted to a custom frame where a computer-controlled, motor-driven, linear actuator powered movement of the flexor and extensor tendons. All fingers underwent 2,000 full flexion and extension cycles. Maximum interfragmentary displacement was continuously measured using a differential variable reluctance transducer. Our primary outcome was the difference in the mean P1 fragment displacement between lag and nonlag screw fixation at 2,000 cycles. RESULTS: The observed differences in mean displacement between lag and nonlag screw fixation were not statistically significant throughout all time points. A two one-sided test procedure for paired samples confirmed statistical equivalence in the fragment displacement between these fixation methods at all time points, including the primary end point of 2,000 cycles. CONCLUSIONS: Nonlag screws provided equivalent biomechanical stability to lag screws for simulated long oblique P1 fractures during cyclic testing in this cadaveric model. CLINICAL RELEVANCE: Fixation of long oblique P1 fractures with nonlag screws has the potential to simplify treatment without sacrificing fracture stability during immediate postoperative range of motion.

An Ecological Accounting System for Integrated Aquatic Planning and Habitat Banking with Case Study on the Toronto Waterfront, Ontario, Canada.

A key aspect of contemporary fish habitat management is the need to account for losses and gains associated with development and offsetting measures while protecting high quality features. We propose an ecological accounting framework for aquatic ecosystems using habitat equivalents scaled to aquatic productivity, and using fish-to-habitat associations by life stage, based on local fish community needs. The framework uses both landscape-scale and site-level evaluations of pre- and post-project habitat changes to assign and track habitat parcels, using ecological baselines and fish-habitat target setting. Concepts of natural capital reserves and productivity-based ecotypes are used for trading losses and gains between impacts from development projects and offsets, including restoration actions, while maintaining ecologically important areas intact. Traditional accounting terms such as deposits, withdrawals, and transfers are defined using scaled habitat-equivalents as the currency. Other key features of the framework include setting a service area that is ecologically meaningful, and conducting habitat transactions guided by habitat conservation, protection, and restoration (habitat CPR) principles. The nearshore area of the Toronto and Region is used as a case study to illustrate the eco-accounting framework and how habitat banking could be incorporated along with planned restoration to remediate this degraded but continually developed area. The framework represents significant advances in managing cumulative habitat effects in an integrated way, moving away from a focus on only project- or site-level assessments. We feel this approach could be adapted to other ecosystem types in addition to the lake, nearshore area example provided here.

High-efficiency, fifth-harmonic generation of a joule-level neodymium laser in a large-aperture ammonium dihydrogen phosphate crystal.

High-energy deep ultraviolet (UV) sources are required for high-density plasma diagnostics. The fifth-harmonic generation of large-aperture neodymium lasers in ammonium dihydrogen phosphate (ADP) can significantly increase UV energies due to the availability of large ADP crystals. Noncritical phase matching in ADP for (ω + 4ω) was achieved by cooling a 65 × 65-mm crystal in a two-chamber cryostat to 200 K. The crystal chamber used helium as the thermally conductive medium between the crystal and the crystal chamber, which was surrounded by a high-vacuum chamber with a liquid nitrogen reservoir. A temperature variation of 0.2 K across the crystal aperture was obtained. The total conversion efficiency from the fundamental to the fifth harmonic at 211 nm was 26%.

Advanced laser development and plasma-physics studies on the multiterawatt laser.

The multiterawatt (MTW) laser, built initially as the prototype front end for a petawatt laser system, is a 1053 nm hybrid system with gain from optical parametric chirped-pulse amplification (OPCPA) and Nd:glass. Compressors and target chambers were added, making MTW a complete laser facility (output energy up to 120 J, pulse duration from 20 fs to 2.8 ns) for studying high-energy-density physics and developing short-pulse laser technologies and target diagnostics. Further extensions of the laser support ultrahigh-intensity laser development of an all-OPCPA system and a Raman plasma amplifier. A short summary of the variety of scientific experiments conducted on MTW is also presented.

Dermal allograft superior capsule reconstruction biomechanics and kinematics.

PURPOSE: To investigate the effect of a dermal allograft superior capsule reconstruction (SCR) on kinematics and joint pressure biomechanics immediately after simulated superior irreparable rotator cuff tear. METHODS: This controlled laboratory study tested 8 fresh-frozen cadaveric shoulders using a custom test frame. Balanced loading configuration centered the humeral head on the glenoid, and unbalanced load created a force pulling the head toward the acromion. Experimental conditions included the intact rotator cuff, irreparable supraspinatus tear (ISST), and dermal allograft SCR. A digital sensor measured glenohumeral and subacromial contact pressure maps, and a microscribe measured the acromion-humeral distance. RESULTS: Glenohumeral contact pressure of ISST was 175% (295 ± 44 kPa; P = .018) of the intact rotator cuff value (169 ± 10 kPa) at 0° in the balanced condition and 176% (P = .048) of intact at 30°. SCR decreased glenohumeral contact pressure to 110% (185 ± 27 kPa; P = .044) of intact at 0° and to 95% (P = .034) at 30°. Unbalanced ISST contact pressure was 146% (365 ± 23 kPa; P = .009) of intact (250 ± 24 kPa) at 0° and 122% (P = .045) at 60°. SCR decreased contact pressures to 110% (274 ± 21 kPa; P = .039) of intact at 0° and to 89% (P = .003) at 60°. ISST increased superior migration of the humeral head, decreasing the acromion-humeral distance by 3.0 ± 0.6 mm (P = .006) in the unbalanced condition at 0°. SCR increased the acromion-humeral distance to a value similar to that of the intact cuff (P = .003). SCR significantly lowered subacromial pressures in the unbalanced condition. CONCLUSIONS: In an irreparable supraspinatus tear model, the dermal allograft SCR showed competency in stabilizing the glenohumeral joint, decreasing glenohumeral and subacromial contact pressures, and increasing the acromion-humeral distance.

JNK inactivation suppresses osteogenic differentiation, but robustly induces osteopontin expression in osteoblasts through the induction of inhibitor of DNA binding 4 (Id4).

Osteoblasts are versatile cells involved in multiple whole-body processes, including bone formation and immune response. Secretory amounts and patterns of osteoblast-derived proteins such as osteopontin (OPN) and osteocalcin (OCN) modulate osteoblast function. However, the regulatory mechanism of OPN and OCN expression remains unknown. Here, we demonstrate that p54/p46 c-jun N-terminal kinase (JNK) inhibition suppresses matrix mineralization and OCN expression but increases OPN expression in MC3T3-E1 cells and primary osteoblasts treated with differentiation inducers, including ascorbic acid, bone morphogenic protein-2, or fibroblast growth factor 2. Preinhibition of JNK before the onset of differentiation increased the number of osteoblasts that highly express OPN but not OCN (OPN-OBs), indicating that JNK affects OPN secretory phenotype at the early stage of osteogenic differentiation. Additionally, we identified JNK2 isoform as being critically involved in OPN-OB differentiation. Microarray analysis revealed that OPN-OBs express characteristic transcription factors, cell surface markers, and cytokines, including glycoprotein hormone α2 and endothelial cell-specific molecule 1. Moreover, we found that inhibitor of DNA binding 4 is an important regulator of OPN-OB differentiation and that dual-specificity phosphatase 16, a JNK-specific phosphatase, functions as an endogenous regulator of OPN-OB induction. OPN-OB phenotype was also observed following LPS from Porphyromonas gingivalis stimulation during osteogenic differentiation. Collectively, these results suggest that the JNK-Id4 signaling axis is crucial in the control of OPN and OCN expression during osteoblastic differentiation.-Kusuyama, J., Amir, M. S., Albertson, B. G., Bandow, K., Ohnishi, T., Nakamura, T., Noguchi, K., Shima, K., Semba, I., Matsuguchi, T. JNK inactivation suppresses osteogenic differentiation, but robustly induces osteopontin expression in osteoblasts through the induction of inhibitor of DNA binding 4 (Id4).

Advancing patient age is associated with worse outcomes in low- and intermediate-grade primary chondrosarcoma of the pelvis.

BACKGROUND: Conventional primary pelvic chondrosarcoma often presents as a low- or intermediate-grade tumor in older patients. Although this is the most common variant of pelvic chondrosarcoma, studies examining treatment outcomes are lacking. The purpose of this study was to evaluate patients with these tumors to determine their outcomes of treatment. METHODS: Seventy-three patients (grade I [n = 19, 26%] and grade II [n = 54, 74%]) were reviewed including 55 (75%) males and 18 (25%) females, with a mean age of 51 (range, 17-81) years and follow-up of 9 ± 5 years. RESULTS: The 10-year disease-specific survival was 71%. Grade II disease (hazard ratio [HR], 6.74; P = .04) and age ≥50 years (HR, 3.97; P = .02) was associated with death due to disease. The 10-year local recurrence- and metastatic-free survival were 79% and 72%. Of the patients with a local recurrence (n = 11), 7 (64%) recurred at a higher histological grade. Patient age ≥50 years was associated with local recurrence (HR, 10.03; P = .02) and metastatic disease (HR, 4.20; P = .02). CONCLUSION: Advancing patient age was an independent risk factor for worse survival and disease recurrence. Tumors often recurred locally at a higher grade and as such wide local excision remains the treatment of choice for these tumors.

Contrasting Temporal Patterns of Mercury, Niche Dynamics, and Body Fat Indices of Polar Bears and Ringed Seals in a Melting Icescape.

Polar bears (Ursus maritimus) and ringed seals (Pusa hispida) have a strong predator-prey relationship and are facing climate-associated Arctic habitat loss and harmful dietary exposure to total mercury (THg) and other pollutants. However, little is known about whether both species inhabiting the same area exhibit similar temporal patterns in Hg concentration, niche dynamics, and body fat indices. We used THg, δ13C, and δ15N values of western Hudson Bay polar bear hair (2004-2016) and ringed seal muscle samples (2003-2015) to investigate temporal trends of these variables and multidimensional niche metrics, as well as body fat indices for both species. We found a decline in THg concentration (by 3.8% per year) and δ13C (by 1.5‰) in ringed seals suggesting a change in feeding habits and carbon source use over time, whereas no significant changes occurred in polar bears. In contrast, the polar bear 3-dimensional niche size decreased by nearly half with no change in ringed seal niche size. The δ13C spacing between both species increased by approximately 1.5× suggesting different responses to annual changes in sympagic-pelagic carbon source production. Ringed seal body fat index was higher in years of earlier sea ice breakup with no change occurring in polar bears. These findings indicate that both species are responding differently to a changing environment suggesting a possible weakening of their predator-prey relationship in western Hudson Bay.

Biomechanical Analysis of Zone 2 Flexor Tendon Repair With a Coupler Device Versus Locking Cruciate Core Suture.

PURPOSE: To compare flexor tendon repair strength and speed between a tendon coupler and a standard-core suture in a cadaver model. METHODS: In 5 matched-pair fresh cadaver hands, we cut the flexor digitorum profundus tendon of each finger in zone 2 and assigned 20 tendons to both the coupler and the suture groups. Coupler repair was with low-profile stainless steel staple plates in each tendon stump, bridged by polyethylene thread. Suture repair was performed using an 8-strand locking-cruciate technique with 4-0 looped, multifilament, polyamide suture. One surgeon with the Subspecialty Certificate in Surgery of the Hand performed all repairs. Via a load generator, each flexor digitorum profundus was loaded at 5 to 10 N and cycled through flexion just short of tip-to-palm and full extension at 0.2 Hz for 2,000 cycles to simulate 6 weeks of rehabilitation. We recorded repair gapping at predetermined cycle intervals. Our primary outcome was repair gapping at 2,000 cycles. Tendons that had not catastrophically failed by 2,000 cycles were loaded to failure on a servohydraulic frame at 1 mm/s. RESULTS: Tendon repair gapping was similar between coupled and sutured tendons at 2,000 cycles. Tendons repaired with the coupler had higher residual load to failure than sutured tendons. Mean coupler repair time was 4 times faster than suture repair. CONCLUSIONS: Zone 2 flexor repair with a coupler withstood simulated early active motion in fresh cadavers. Residual load to failure and repair speed were better with the coupler. CLINICAL RELEVANCE: This tendon coupler may eventually be an option for strong, reproducible, rapid flexor tendon repair.

Synthetic coracoclavicular ligament vs. coracoclavicular suspensory construct for treatment of acromioclavicular dislocation: a biomechanical study.

BACKGROUND: A synthetic ligament (LockDown, Worcestershire, England) has become available to treat complete acromioclavicular dislocation with promising clinical results and potential benefit to avoid postoperative loss of reduction. We investigated the biomechanics of this synthetic ligament in a simulated immediate postoperative rehabilitation setting, hypothesizing that the synthetic ligament would demonstrate less superior coracoclavicular displacement to cyclic loading and higher ultimate load-to-failure values than a coracoclavicular suspensory construct. METHODS: Seven matched-pair cadaveric shoulders (mean age at time of death, 79 years) were loaded cyclically and to failure. One specimen in each pair was randomly assigned to the synthetic ligament or coracoclavicular suspensory construct. Superiorly directed 70-N cyclic loading for 3000 cycles at 1.0 Hz was applied through the clavicle in a fixed scapula simulating physiologic states during immediate postoperative rehabilitation, followed by a load-to-failure test at 120 mm/min. RESULTS: After 3000 cycles, the superior displacement of the clavicle in the synthetic ligament (9.2 ± 1.1 mm) was 225% greater than in the coracoclavicular suspensory construct (2.8 ± 0.4 mm, 95% confidence interval [CI] 3.4, 8.3; P < .001). Average stiffness of the synthetic ligament (32.8 N/mm) was 60% lower than that of the coracoclavicular suspensory construct (81.9 N/mm, 95% CI 43.3, 54.9; P < .001). Ultimate load-to-failure of the synthetic ligament was 23% (95% CI 37.9, 301.5; P = .016) lower than the coracoclavicular suspensory construct (580.5 ± 85.1 N and 750.2 ± 135.5 N, respectively). CONCLUSION: In a simulated immediate postoperative cadaveric model, the synthetic ligament demonstrated poorer biomechanics than the coracoclavicular suspensory construct. These findings suggest that a coracoclavicular suspensory construct may be preferable to a synthetic ligament if early rehabilitation is intended.

Low-intensity pulsed ultrasound promotes bone morphogenic protein 9-induced osteogenesis and suppresses inhibitory effects of inflammatory cytokines on cellular responses via Rho-associated kinase 1 in human periodontal ligament fibroblasts.

Periodontal ligament fibroblasts (PDLFs) have osteogenic capacity, producing bone matrix proteins. Application of bone morphogenic proteins (BMPs) to PDLFs is a promising approach for periodontal regeneration. However, in chronic bone metabolic disorders, such as periodontitis, proper control of accompanying inflammation is essential for optimizing the effects of BMPs on PDLFs. We have previously shown that low-intensity pulsed ultrasound (LIPUS), a medical technology that induces mechanical stress using sound waves, significantly promotes osteogenesis in mesenchymal stem cells. Here, we demonstrate that LIPUS promotes the BMP9-induced osteogenic differentiation of PDLFs. In contrast, BMP2-induced osteogenic differentiation was not altered by LIPUS, probably due to the LIPUS-induced secretion of Noggin, a BMP2 antagonist, from PDLFs. To examine if LIPUS affects inflammatory responses of PDLFs to lipopolysaccharide (LPS) derived from Porphyromonas gingivalis (LPS-PG), we also simultaneously treated PDLFs with LIPUS and LPS-PG. Treatment with LIPUS significantly inhibited the phosphorylation of ERKs, TANK-binding kinase 1, and interferon regulatory factor 3 in LPS-PG-stimulated PDLFs, in addition to inhibiting the degradation of IκB. Furthermore, LIPUS treatment reduced messenger RNA (mRNA) expression of interleukin-1alpha (IL-1alpha), IL-1beta, IL-6, IL-8, C-C motif chemokine ligand 2, C-X-C motif chemokine ligand 1 (CXCL1), CXCL10 and receptor activator of nuclear factor kappa-B ligand, and also diminished IL-1ß and tumor necrosis factor a (TNFa)-induced inflammatory reactions. Phosphorylation of Rho-associated kinase 1 (ROCK1) was induced by LIPUS, while ROCK1-specific inhibitor prevented the promotive effects of LIPUS on p38 phosphorylation, mRNA expression of CXCL1 and Noggin, and osteogenesis. The suppressive effects of LIPUS on LPS-PG-stimulated inflammatory reactions were also prevented by ROCK1 inhibition. Moreover, LIPUS treatment blocked inhibitory effects of LPS-PG and IL-1ß on osteogenesis. These results indicate that LIPUS suppresses inflammatory effects of LPS-PG, IL-1ß, and TNFa and also promotes BMP9-induced osteogenesis through ROCK1 in PDLFs.

Posterior reversible encephalopathy syndrome with lumbar drainage and surgery: coincidence or correlation? A case report.

BACKGROUND: Posterior reversible encephalopathy syndrome (PRES) is a rare neurological disorder usually associated with specific medical conditions that cause a disturbance of the CNS homeostasis. It has seldom been reported to be a consequence of an iatrogenic intervention causing intracranial hypotension. CASE PRESENTATION: We report the case of an individual 69-year-old male presenting with headache and blurred vision following cerebrospinal fluid (CSF) leak from resection of a sellar mass. The patient developed the condition following removal of the lumbar drain post-operatively. Magnetic Resonance Imaging showed bilateral occipital, parieto-occipital, and cerebellar T2 FLAIR hyper-intensities, suggesting a radiological diagnosis of posterior reversible encephalopathy syndrome (PRES). The patient's symptoms started to improve shortly afterwards and had completely resolved at 3 months follow-up. CONCLUSIONS: The absence of severe hypertension and presence of an intraoperative CSF leak requiring placement of the lumbar drain suggests that decreased CSF volume and associated reactive hyperemia could have a role in the pathophysiology of the disease.

The Relationship Between Hemihamate Graft Size and Proximal Interphalangeal Joint Flexion for Reconstruction of Fracture-Dislocations: A Biomechanical Study.

PURPOSE: The purpose of this study was to determine the relationship between hemihamate graft size and proximal interphalangeal (PIP) joint flexion in a biomechanical fracture-dislocation model. METHODS: We simulated middle finger PIP fracture-dislocations in 5 cadaver hands by resecting 50% of the palmar articular surface of the middle phalanx (P2) base. Fluoroscopy was used to confirm dorsal subluxation of the middle phalanx base after resection. A 10-mm osteochondral hamate graft was contoured to reconstruct the volar lip of the middle phalanx and was progressively downsized by 2-mm increments for each trial. A computer-controlled articulator and jig simulated active flexion and extension of the fingers. Maximum PIP flexion was measured at each graft size using fluoroscopy and digital imaging software. Clinically significant flexion block was defined as PIP flexion less than 90°. RESULTS: The actual mean size of the volar defect created was 52% (3.5 mm) of the middle phalanx articular surface, which created instability and dorsal subluxation in all tested fingers. After hemihamate reconstruction, all specimens were stable throughout flexion and extension for all graft sizes. A flexion block of 90° occurred at a mean graft size of 191% of the defect (6.5 mm). With regard to the volar lip of the P2, grafts that projected an average 0.8 mm past the native volar lip position had 98° (range, 84°-107°) maximum PIP flexion. Grafts that projected an average of 3.1 mm past the native volar lip position had 90° (range, 69°-100°) maximum PIP flexion. Linear regression modeling incorporating all of the results predicted flexion block to occur at a graft size as small as 166% of the 50% volar P2 defect. In this model, for every 50% (1.7-mm) increase in graft size relative to the defect, PIP flexion decreased by approximately 6°. CONCLUSIONS: Nonanatomical hemihamate grafts produce a PIP flexion block at extreme sizes, predicted to occur at greater than 166% of a 50% P2 base articular defect in our model. This suggests that relatively large grafts can be used for reconstruction of PIP fracture-dislocations without substantial biomechanical block to PIP flexion. We suggest sizing no larger than 3 mm past the native P2 volar lip position to avoid an important mechanical block to PIP flexion. CLINICAL RELEVANCE: The information from this study helps surgeons understand how large a hemihamate graft can be used for P2 volar base reconstruction before having a negative impact on PIP flexion.

Generating Differential Ligamentotaxis Across the Radiocarpal Joint.

This study sought to determine if traction through the index or long finger metacarpal provided a selective distraction force through either the distal radius' radial or ulnar column. In eight specimens, the radius was cut transversely 1 cm proximal to the Lister tubercle. Index and long finger metacarpals were cut and two-hole plates were fixed to metacarpals. Traction forces were alternately applied to index, then long finger metacarpals, sequentially through each metacarpal from 4.5N to 89N. Traction loading through the index finger metacarpal resulted in significantly more distraction force transmitted through the distal radius fragment's radial column at all force intervals. Traction loading through long finger metacarpal resulted in significantly higher force transmission through distal radius' ulnar column. In both cohorts, force transmission increased linearly in response to higher loads. Selective traction force of either the index or long finger metacarpal resulted in differential tensioning of the distal radius' ulnar and radial columns. (Journal of Surgical Orthopaedic Advances 28(2):104-107, 2019).

The role of the miR-200 family in epithelial-mesenchymal transition in colorectal cancer: a systematic review.

Colorectal cancer (CRC) is associated with significant morbidity and mortality as many patients are diagnosed with advanced stage disease. MicroRNAs are small, noncoding RNA molecules that have a major role in gene expression regulation and are dysregulated in CRC. The miR-200 family is involved in epithelial-mesenchymal transition (EMT). This systematic review describes the roles of the miR-200 family in EMT in CRC. A search of electronic databases (PubMed and Embase) was conducted between January 2000 and July 2017. Both in vitro and human studies reporting on the miR-200 family and CRC were included. Studies describing molecular pathways and the role of the miR-200 family in the diagnostic and therapeutic management of CRC were analyzed. Thirty-four studies (22 in vitro and 18 human studies) were included. miR-200 family expression is regulated epigenetically and via transcriptional factor regulation. In vitro studies show that transfection of miR-200 family members into chemo-resistant colon cancer cell lines results in improved chemo-sensitivity and epithelial phenotype restoration. There is intra-tumoral variability in the tissue expression of miR-200 family members with decreased expression at the invasive front. Clinical studies in CRC patients have shown decreased primary tumor tissue expression of miR-429, miR-200a and miR-200c may be associated with worse survival. Conversely, increased blood levels of miR-141, miR-200a and miR-200c may be associated with worse outcomes. The miR-200 family has a central role in EMT. The miR200 family has potential for both prognostic and therapeutic management of CRC.

Distal triceps transosseous cruciate versus suture anchor repair using equal constructs: a biomechanical comparison.

BACKGROUND/HYPOTHESIS: Suture anchor-based repair has been advocated for repair of distal triceps avulsion, but previous models have used an unequal number of sutures across the repair site. We hypothesized that there would be no difference in triceps tendon displacement between gold standard repair with transosseous cruciate bone tunnels and suture anchor repair with an equal number of sutures in the constructs. METHODS: The triceps tendon footprint was measured in 20 cadaveric elbows (10 matched pairs), and a distal triceps tendon rupture was created. The specimens in each pair were randomly assigned to transosseous cruciate repair or knotless, double-row, anatomic footprint, suture anchor repair. Specimens underwent cyclic loading to 1500 cycles and then load to failure. Footprint uncoverage was measured at 1500 cycles. Data for medial and lateral triceps tendon displacement, footprint uncoverage, and failure load were obtained. RESULTS: Triceps displacement did not differ significantly between the transosseous cruciate and the suture anchor repair group at 1500 cycles on the medial (3.6 ± 0.9 mm vs. 4.3 ± 1.6 mm [mean ± standard deviation], respectively; P = .27) and lateral side (3.1 ± 1.2 mm vs. 2.0 ± 1.2 mm, respectively; P = .06). No other differences were found between the constructs. DISCUSSION/CONCLUSION: Transosseous cruciate distal triceps repair and knotless double-row suture anchor repair using constructs with an equal number of sutures showed no significant difference in tendon displacement at 1500 loading cycles. These findings suggest that the biomechanical strength of an all-suture construct is not different from that of suture anchors for repair of distal triceps avulsions.

Is Dual Semitendinosus Allograft Stronger Than Turndown for Achilles Tendon Reconstruction? An In Vitro Analysis.

BACKGROUND: Large Achilles tendon defects pose a treatment challenge. The standard treatment with a turndown flap requires a large extensile incision, puts the sural nerve at risk, and demands slow, careful rehabilitation. Dual allograft semitendinosus reconstruction is a new clinical alternative that has the theoretical advantages of a smaller incision, less dissection, and a stronger construct that may allow for faster rehabilitation. QUESTIONS/PURPOSES: In a cadaver biomechanical model, we compared the dual allograft semitendinosus reconstruction with the myofascial turndown in terms of (1) mechanical strength and resistance to deformation and (2) failure mechanisms in reconstruction of large segmental Achilles defects. METHODS: An 8-cm segmental Achilles defect was created in 18 cadaveric lower extremities, nine matched pairs without defect or previous surgery (mean age, 78.4 years; range, 60-97 years; three female and six male pairs). Femoral neck densitometry to determine bone mineral density found that all specimens except two were osteopenic or osteoporotic. Specimens in each pair were assigned to allograft or turndown reconstruction. The constructs were mounted on a load frame and differential variable reluctance transducers were applied to measure deformation. Specimens were preconditioned and then loaded axially. Tensile force and proximal and distal construct deformation were measured at clinical failure, defined as 10 mm of displacement, and at ultimate failure, defined as failure of the reconstruction. Failure mechanism was recorded. RESULTS: Tensile strength at time zero was higher in the allograft versus the turndown construct at clinical failure (156.9 ± 29.7 N versus 107.2 ± 20.0 N, respectively; mean difference, -49.7 N; 95% CI, -66.3 to -33.0 N; p < 0.001) and at ultimate failure (290.9 ± 83.2 N versus 140.7 ± 43.5 N, respectively; mean difference, -150.2 N; 95% CI, -202.9 to -97.6 N; p < 0.001). Distal construct deformation was lower in the turndown versus the allograft construct at clinical failure (1.6 ± 1.0 mm versus 4.7 ± 0.7 mm medially and 2.2 ± 1.0 mm versus 4.8 ± 1.1 mm laterally; p < 0.001). Semitendinosus allograft failure occurred via calcaneal bone bridge fracture in eight of nine specimens. All myofascial turndowns failed via suture pullout through the fascial tissue at its insertion. CONCLUSION: In this comparative biomechanical study, dual semitendinosus allograft reconstruction showed greater tensile strength and construct deformation compared with myofascial turndown in a cadaveric model of large Achilles tendon defects. CLINICAL RELEVANCE: Further study of dual semitendinosus allograft for treatment of severe Achilles tendon defects with cyclic loading and investigation of clinical results will better elucidate the clinical utility and indications for this technique.

Fixation of Regan-Morrey Type II Coronoid Fractures: A Comparison of Screws and Suture Lasso Technique for Resistance to Displacement.

PURPOSE: The aim of this study was to compare the load to failure and stiffness achieved in coronoid fractures treated with a posterior-to-anterior screw versus a suture lasso technique. METHODS: We performed a biomechanical study using 10 pairs of fresh-frozen cadaveric elbows. A transverse osteotomy at the midpoint of the coronoid height was created to simulate a Regan-Morrey type II coronoid fracture. The specimens were randomized to screw fixation or suture lasso fixation. The load to failure and stiffness were then measured using a materials testing machine. RESULTS: Screw fixation provided greater strength and stiffness than suture lasso fixation. Mean load to failure was 405 N in the screw fixation group compared with a load to failure of 207 N for suture fixation. Screw fixation resulted in a mean stiffness of 284 kPa/mm compared with 119 kPa/mm after suture fixation. CONCLUSIONS: Screw fixation was biomechanically superior to fixation using a suture lasso technique. For coronoid fractures in which screw or suture fixation is feasible, screw fixation may provide greater resistance to displacement of the coronoid compared with a suture lasso technique. CLINICAL RELEVANCE: Clinical studies have reported a higher rate of failure after screw fixation compared with suture lasso fixation; however, this study demonstrated a greater stiffness and load to failure after screw fixation of type II coronoid fractures. Screw fixation may provide a stronger fixation construct for fractures of adequate size to support a screw. Further studies may be warranted to assess the importance of securing the anterior capsule to the coronoid tip when using a suture lasso construct because this may affect the stability of the elbow after fixation.

Comparison of Suture-Based Anchors and Traditional Bioabsorbable Anchors in Foot and Ankle Surgery.

We compared the pullout strength of a suture-based anchor versus a bioabsorbable anchor in the distal fibula and calcaneus and evaluated the relationship between bone mineral density and peak load to failure. Eight paired cadaveric specimens underwent a modified Broström procedure and Achilles tendon reattachment. The fibula and calcaneus in the paired specimens received either a suture-based anchor or a bioabsorbable suture anchor. The fibular and calcaneal specimens were loaded to failure, defined as a substantial decrease in the applied load or pullout from the bone. In the fibula, the peak load to failure was significantly greater with the suture-based versus the bioabsorbable anchors (133.3 ± 41.8 N versus 76.8 ± 35.3 N; p = .002). No significant difference in load with 5 mm of displacement was found between the 2 groups. In the calcaneus, no difference in the peak load to failure was found between the 2 groups, and the peak load to failure with 5 mm of displacement was significantly lower with the suture-based than with the bioabsorbable anchors (52.2 ± 9.8 N versus 75.9 ± 12.4 N; p = .003). Bone mineral density and peak load to failure were significantly correlated in the fibula with the suture-based anchor. An innovative suture-based anchor had a greater peak load to failure compared with a bioabsorbable anchor in the fibula. In the calcaneus, the load at 5 mm of displacement was significantly lower in the suture-based than in the bioabsorbable group. The correlation findings might indicate the need for a cortical bone shelf with the suture-based anchor. Suture-based anchors could be a viable alternative to bioabsorbable anchors for certain foot and ankle procedures.