High-throughput micro-CT analysis identifies sex-dependent biomarkers of erosive arthritis in TNF-Tg mice and differential response to anti-TNF therapy.

BACKGROUND: Development of reliable disease activity biomarkers is critical for diagnostics, prognostics, and novel drug development. Although computed tomography (CT) is the gold-standard for quantification of bone erosions, there are no consensus approaches or rationales for utilization of specific outcome measures of erosive arthritis in complex joints. In the case of preclinical models, such as sexually dimorphic tumor necrosis factor transgenic (TNF-Tg) mice, disease severity is routinely quantified in the ankle through manual segmentation of the talus or small regions of adjacent bones primarily due to the ease in measurement. Herein, we sought to determine the particular hindpaw bones that represent reliable biomarkers of sex-dependent disease progression to guide future investigation and analysis. METHODS: Hindpaw micro-CT was performed on wild-type (n = 4 male, n = 4 female) and TNF-Tg (n = 4 male, n = 7 female) mice at monthly intervals from 2-5 (females) and 2-8-months (males) of age, since female TNF-Tg mice exhibit early mortality from cardiopulmonary disease at approximately 5-6-months. Further, 8-month-old WT (n = 4) and TNF-Tg males treated with anti-TNF monoclonal antibodies (n = 5) or IgG placebo isotype controls (n = 6) for 6-weeks were imaged with micro-CT every 3-weeks. For image analysis, we utilized our recently developed high-throughput and semi-automated segmentation strategy in Amira software. Synovial and osteoclast histology of ankle joints was quantified using Visiopharm. RESULTS: First, we demonstrated that the accuracy of automated segmentation, determined through analysis of ~9000 individual bones by a single user, was comparable in wild-type and TNF-Tg hindpaws before correction (79.2±8.9% vs 80.1±5.1%, p = 0.52). Compared to other bone compartments, the tarsal region demonstrated a sudden, specific, and significant bone volume reduction in female TNF-Tg mice, but not in males, by 5-months (4-months 4.3± 0.22 vs 5-months 3.4± 0.62 mm3, p<0.05). Specifically, the cuboid showed significantly reduced bone volumes at early timepoints compared to other tarsals (i.e., 4-months: Cuboid -24.1±7.2% vs Talus -9.0±5.9% of 2-month baseline). Additional bones localized to the anterolateral region of the ankle also exhibited dramatic erosions in the tarsal region of females, coinciding with increased synovitis and osteoclasts. In TNF-Tg male mice with severe arthritis, the talus and calcaneus exhibited the most sensitive response to anti-TNF therapy measured by effect size of bone volume change over treatment period. CONCLUSIONS: We demonstrated that sexually dimorphic changes in arthritic hindpaws of TNF-Tg mice are bone-specific, where the cuboid serves as a reliable early biomarker of erosive arthritis in female mice. Adoption of automated segmentation approaches in pre-clinical or clinical models has potential to translate quantitative biomarkers to monitor bone erosions in disease and evaluate therapeutic efficacy.

A high-throughput semi-automated bone segmentation workflow for murine hindpaw micro-CT datasets.

INTRODUCTION: Micro-computed tomography (µCT) is a valuable imaging modality for longitudinal quantification of bone volumes to identify disease or treatment effects for a broad range of conditions that affect bone health. Complex structures, such as the hindpaw with up to 31 distinct bones in mice, have considerable analytic potential, but quantification is often limited to a single bone volume metric due to the intensive effort of manual segmentation. Herein, we introduce a high-throughput, user-friendly, and semi-automated method for segmentation of murine hindpaw µCT datasets. METHODS: In vivo µCT was performed on male (n = 4; 2-8-months) and female (n = 4; 2-5-months) C57BL/6 mice longitudinally each month. Additional 9.5-month-old male C57BL/6 hindpaws (n = 6 hindpaws) were imaged by ex vivo µCT to investigate the effects of resolution and integration time on analysis outcomes. The DICOMs were exported to Amira software for the watershed-based segmentation, and watershed markers were generated automatically at approximately 80% accuracy before user correction. The semi-automated segmentation method utilizes the original data, binary mask, and bone-specific markers that expand to the full volume of the bone using watershed algorithms. RESULTS: Compared to the conventional manual segmentation using Scanco software, the semi-automated approach produced similar raw bone volumes. The semi-automated segmentation also demonstrated a significant reduction in segmentation time for both experienced and novice users compared to standard manual segmentation. ICCs between experienced and novice users were >0.9 (excellent reliability) for all but 4 bones. DISCUSSION: The described semi-automated segmentation approach provides remarkable reliability and throughput advantages. Adoption of the semi-automated segmentation approach will provide standardization and reliability of bone volume measures across experienced and novice users and between institutions. The application of this model provides a considerable strategic advantage to accelerate various research opportunities in pre-clinical bone and joint analysis towards clinical translation.

Chondral Damage After Arthroscopic Repair Techniques for Acute Bony Bankart Lesions: A Biomechanical Study.

BACKGROUND: Bony Bankart lesions can be encountered during treatment of shoulder instability. Current arthroscopic bony Bankart repair techniques involve intra-articular suture placement, but the effect of these repair techniques on the integrity of the humeral head articular surface warrants further investigation. PURPOSE: To quantify the degree of humeral head articular cartilage damage secondary to current arthroscopic bony Bankart repair techniques in a cadaveric model. STUDY DESIGN: Controlled laboratory study. METHODS: Testing was performed in 13 matched pairs of cadaveric glenoids with simulated bony Bankart fractures, with a defect width of 25% of the glenoid diameter. Half of the fractures were repaired with a double-row technique, while the contralateral glenoids were repaired with a single-row technique. Samples were subjected to 20,000 cycles of internal-external rotation across a 90° arc at 2 Hz after a compressive load of 750 N, or 90% body weight (whichever was less) was applied to simulate wear. Cartilage defects on the humeral head were quantified through a custom MATLAB script. Mean cartilage cutout differences were analyzed by the Wilcoxon rank-sum test. RESULTS: Both single- and double-row repairs showed macroscopic damage. The histomorphometric analysis demonstrated that the double-row technique resulted in a significantly (P = .036) more chondral damage (mean, 57,489.1 µm2; SD, 61,262.2 µm2) than the single-row repair (mean, 28,763.5 µm2; SD, 24,4990.2 µm2). CONCLUSION: Both single-row and double-row arthroscopic bony Bankart fixation techniques resulted in damage to the humeral head articular cartilage in the concavity-compression model utilized in this study. The double-row fixation technique resulted in a significantly increased cutout to the humeral head cartilage after simulated wear in this cadaveric model. CLINICAL RELEVANCE: This study provides data demonstrating that placement of intra-articular suture during arthroscopic bony Bankart repair techniques may harm the humeral head cartilage. While the double-row repair of bony Bankart lesions is more stable, it results in increased cartilage damage. These findings suggest that alternative, cartilage-sparing arthroscopic techniques for bony Bankart repair should be investigated.

A Biomechanical, Cadaveric Evaluation of Single- Versus Double-Row Repair Techniques on Stability of Bony Bankart Lesions.

BACKGROUND: Previous studies comparing stability between single- and double-row arthroscopic bony Bankart repair techniques focused only on the measurements of tensile forces on the bony fragment without re-creating a more physiologic testing environment. PURPOSE: To compare dynamic stability and displacement between single- and double-row arthroscopic repair techniques for acute bony Bankart lesions in a concavity-compression cadaveric model simulating physiologic conditions. STUDY DESIGN: Controlled laboratory study. METHODS: Testing was performed on 13 matched pairs of cadaveric glenoids with simulated bony Bankart fractures with a defect width of 25% of the inferior glenoid diameter. Half of the fractures were repaired with a double-row technique, and the contralateral glenoids were repaired with a single-row technique. To determine dynamic biomechanical stability and ultimate step-off of the repairs, a 150-N load and 2000 cycles of internal-external rotation at 1 Hz were applied to specimens to simulate early rehabilitation. Toggle was quantified throughout cycling with a coordinate measuring machine. Three-dimensional spatial measurements were calculated. After cyclic loading, the fracture displacement was measured. RESULTS: The bony Bankart fragment-glenoid initial step-off was found to be significantly greater (P < .001) for the single-row technique (mean, 896 µm; SD, 282 µm) compared with the double-row technique (mean, 436 µm; SD, 313 µm). The motion toggle was found to be significantly greater (P = .017) for the single-row technique (mean, 994 µm; SD, 711 µm) compared with the double-row technique (mean, 408 µm; SD, 384 µm). The ultimate interface displacement was found to be significantly greater (P = .029) for the single-row technique (mean, 1265 µm; SD, 606 µm) compared with the double-row technique (mean, 795 µm; SD, 398 µm). CONCLUSION: Using a concavity-compression glenohumeral cadaveric model, we found that the double-row arthroscopic fixation technique for bony Bankart repair resulted in superior stability and decreased displacement during simulated rehabilitation when compared with the single-row repair technique. CLINICAL RELEVANCE: The findings from this study may help guide surgical decision-making by demonstrating superior biomechanical properties (improved initial step-off, motion toggle, and interface displacement) of the double-row bony Bankart repair technique when compared with single-row fixation. The double-row repair construct demonstrated increased stability of the bony Bankart fragment, which may improve bony Bankart healing.

Improved prediction of femoral fracture toughness in mice by combining standard medical imaging with Raman spectroscopy.

Bone fragility and fracture risk are assessed by measuring the areal bone mineral density (aBMD) using dual-energy X-ray absorptiometry (DXA). While aBMD correlates with bone strength, it is a poor predictor of fragility fracture risk. Alternatively, fracture toughness assesses the bone's resistance to crack propagation and fracture, making it a suitable bone quality metric. Here, we explored how femoral midshaft measurements from DXA, micro-computed tomography (µCT), and Raman spectroscopy could predict fracture toughness. We hypothesized that ovariectomy (OVX) decreases aBMD and fracture toughness compared to controls and we can optimize a multivariate assessment of bone quality by combining results from X-ray and Raman spectroscopy. Female mice underwent an OVX (n = 5) or sham (n = 5) surgery at 3 months of age. Femurs were excised 3 months after ovariectomy and assessed with Raman spectroscopy, µCT, and DXA. Subsequently, a notch was created on the anterior side of the mid-diaphysis of the femurs. Three-point bending induced a controlled fracture that initiated at the notch. The OVX mice had a significantly lower aBMD, cortical thickness, and fracture toughness when compared to controls (p < 0.05). A leave one out cross-validated (LOOCV) partial least squares regression (PLSR) model based only on the combination of aBMD and cortical thickness showed no significant predictive correlations with fracture toughness, whereas a PLSR model based on principal components derived from the full Raman spectra yielded significant prediction (r2 = 0.71, p < 0.05). Further, the PLSR model was improved by incorporating aBMD, cortical thickness, and principal components from Raman spectra (r2 = 0.92, p < 0.001). This exploratory study demonstrates combining X-ray with Raman spectroscopy leads to a more accurate assessment of bone fracture toughness and could be a useful diagnostic tool for the assessment of fragility fracture risk.

Effects of tamoxifen on tendon homeostasis and healing: Considerations for the use of tamoxifen-inducible mouse models.

The use of tamoxifen-inducible models of Cre recombinase in the tendon field is rapidly expanding, resulting in an enhanced understanding of tendon homeostasis and healing. However, the effects of tamoxifen on the tendon are not well-defined, which is particularly problematic given that tamoxifen can have both profibrotic and antifibrotic effects in a tissue-specific manner. Therefore, in the present study, we examined the effects of tamoxifen on tendon homeostasis and healing in male and female C57Bl/6J mice. Tamoxifen-treated mice were compared to corn oil (vehicle)-treated mice. In the "washout" treatment regimen, mice were treated with tamoxifen or corn oil for 3 days beginning 1 week prior to undergoing complete transection and surgical repair of the flexor digitorum longus tendon. In the second regimen, mice were treated with tamoxifen or corn oil beginning on the day of surgery, daily through day 2 postsurgery, and every 48 hours thereafter (D0-2q48) until harvest. All repaired tendons and uninjured contralateral control tendons were harvested at day 14 postsurgery. Tamoxifen treatment had no effect on tendon healing in male mice, regardless of the treatment regimen, while Max load was significantly decreased in female repairs in the Tamoxifen washout group, relative to corn oil. In contrast, D0-2q48 corn oil treatment in female mice led to substantial disruptions in tendon homeostasis, relative to washout corn oil treatment. Collectively, these data clearly define the functional effects of tamoxifen and corn oil treatment in the tendon and inform future use of tamoxifen-inducible genetic models.

Lactate Dehydrogenase Inhibition With Oxamate Exerts Bone Anabolic Effect.

Cellular bioenergetics is a promising new therapeutic target in aging, cancer, and diabetes because these pathologies are characterized by a shift from oxidative to glycolytic metabolism. We have previously reported such glycolytic shift in aged bone as a major contributor to bone loss in mice. We and others also showed the importance of oxidative phosphorylation (OxPhos) for osteoblast differentiation. It is therefore reasonable to propose that stimulation of OxPhos will have bone anabolic effect. One strategy widely used in cancer research to stimulate OxPhos is inhibition of glycolysis. In this work, we aimed to evaluate the safety and efficacy of pharmacological inhibition of glycolysis to stimulate OxPhos and promote osteoblast bone-forming function and bone anabolism. We tested a range of glycolytic inhibitors including 2-deoxyglucose, dichloroacetate, 3-bromopyruvate, and oxamate. Of all the studied inhibitors, only a lactate dehydrogenase (LDH) inhibitor, oxamate, did not show any toxicity in either undifferentiated osteoprogenitors or osteoinduced cells in vitro. Oxamate stimulated both OxPhos and osteoblast differentiation in osteoprogenitors. In vivo, oxamate improved bone mineral density, cortical bone architecture, and bone biomechanical strength in both young and aged C57BL/6J male mice. Oxamate also increased bone formation by osteoblasts without affecting bone resorption. In sum, our work provided a proof of concept for the use of anti-glycolytic strategies in bone and identified a small molecule LDH inhibitor, oxamate, as a safe and efficient bone anabolic agent. © 2020 American Society for Bone and Mineral Research (ASBMR).

Peritalar Kinematics With Combined Deltoid-Spring Ligament Reconstruction in Simulated Advanced Adult Acquired Flatfoot Deformity.

BACKGROUND: Adult acquired flatfoot deformity (AAFD) is a complex and progressive deformity involving the ligamentous structures of the medial peritalar joints. Recent anatomic studies demonstrated that the spring and deltoid ligaments form a greater medial ligament complex, the tibiocalcaneonavicular ligament (TCNL), which provides medial stability to the talonavicular, subtalar, and tibiotalar joints. The aim of this study was to assess the biomechanical effect of a spring ligament tear on the peritalar stability. The secondary aim was to assess the effect of TCNL reconstruction in restoration of peritalar stability in comparison with other medial stabilization procedures, anatomic spring or deltoid ligament reconstructions, in a cadaveric flatfoot model. METHODS: Ten fresh-frozen cadaveric foot specimens were used. Reflective markers were mounted on the tibia, talus, navicular, calcaneus, and first metatarsal. Peritalar joint kinematics were captured by a multiple-camera motion capture system. Mild, moderate, and severe flatfoot models were created by sequential sectioning of medial capsuloligament complex followed by cyclic axial loading. Spring only, deltoid only, and combined deltoid-spring ligament (TCNL) reconstructions were performed. The relative kinematic changes were compared using 2-way analysis of variance (ANOVA). RESULTS: Compared with the initial condition, we noted significantly increased valgus alignment of the subtalar joint of 5.1 ± 2.3 degrees (P = .031) and 5.8 ± 2.7 degrees (P < .01) with increased size of the spring ligament tear to create moderate to severe flatfoot, respectively. We noted an increased tibiotalar valgus angle of 5.1 ± 2.0 degrees (P = .03) in the severe model. Although all medial ligament reconstruction methods were able to correct forefoot abduction, the TCNL reconstruction was able to correct both the subtalar and tibiotalar valgus deformity (P = .04 and P = .02, respectively). CONCLUSION: The TCNL complex provided stability to the talonavicular, subtalar, and tibiotalar joints. The combined deltoid-spring ligament (TCNL) reconstructions restored peritalar kinematics better than isolated spring or deltoid ligament reconstruction in the severe AAFD model. CLINICAL RELEVANCE: The combined deltoid-spring ligament (TCNL) reconstruction maybe considered in advanced AAFD with medial peritalar instability: stage IIB with a large spring ligament tear or stage IV.

Teriparatide (recombinant parathyroid hormone 1-34) enhances bone allograft integration in a clinically relevant pig model of segmental mandibulectomy.

Massive craniofacial bone loss poses a clinical challenge to maxillofacial surgeons. Structural bone allografts are readily available at tissue banks but are rarely used due to a high failure rate. Previous studies showed that intermittent administration of recombinant parathyroid hormone (rPTH) enhanced integration of allografts in a murine model of calvarial bone defect. To evaluate its translational potential, the hypothesis that rPTH would enhance healing of a mandibular allograft in a clinically relevant large animal model of mandibulectomy was tested. Porcine bone allografts were implanted into a 5-cm-long continuous mandible bone defect in six adult Yucatan minipigs, which were randomized to daily intramuscular injections of rPTH (1.75 µg/kg) and placebo (n = 3). Blood tests were performed on Day 56 preoperation, Day 0 and on Day 56 postoperation. Eight weeks after the surgery, bone healing was analyzed using high-resolution X-ray imaging (Faxitron and micro computed tomography [CT]) and three-point bending biomechanical testing. The results showed a significant 2.6-fold rPTH-induced increase in bone formation (p = 0.02). Biomechanically, the yield failure properties of the healed mandibles were significantly higher in the rPTH group (yield load: p < 0.05; energy to yield: p < 0.01), and the post-yield displacement and energy were higher in the placebo group (p < 0.05), suggesting increased mineralized integration of the allograft in the rPTH group. In contrast to similar rPTH therapy studies in dogs, no signs of hypercalcemia, hyperphosphatemia, or inflammation were detected. Taken together, we provide initial evidence that rPTH treatment enhances mandibular allograft healing in a clinically relevant large animal model.

Inhibition of the Prostaglandin EP-1 Receptor in Periosteum Progenitor Cells Enhances Osteoblast Differentiation and Fracture Repair.

Fracture healing is a complex and integrated process that involves mesenchymal progenitor cell (MPC) recruitment, proliferation and differentiation that eventually results in bone regeneration. Prostaglandin E2 (PGE2) is an important regulator of bone metabolism and has an anabolic effect on fracture healing. Prior work from our laboratory showed EP1-/- mice have enhanced fracture healing, stronger cortical bones, higher trabecular bone volume and increased in vivo bone formation. We also showed that bone marrow MSCs from EP1-/- mice exhibit increased osteoblastic differentiation in vitro. In this study we investigate the changes in the periosteal derived MPCs (PDMPCs), which are crucial for fracture repair, upon EP1 deletion. EP1-/- PDMPCs exhibit increased numbers of total (CFU-F) and osteoblastic colonies (CFU-O) as well as enhanced osteoblastic and chondrogenic differentiation. Moreover, we tested the possible therapeutic application of a specific EP1 receptor antagonist to accelerate fracture repair. Our findings showed that EP1 antagonist administration to wild type mice in the early stages of repair similarly resulted in enhanced CFU-F, CFU-O, and osteoblast differentiation in PDMPCs and resulted in enhanced fracture callus formation at 10 days post fracture and increased bone volume and improved biomechanical healing of femur fractures at 21 days post fracture.

Transcriptomic Analysis of Cellular Pathways in Healing Flexor Tendons of Plasminogen Activator Inhibitor 1 (PAI-1/Serpine1) Null Mice.

Injuries to flexor tendons can be complicated by fibrotic adhesions, which severely impair the function of the hand. Plasminogen activator inhibitor 1 (PAI-1/SERPINE1), a master suppressor of fibrinolysis and protease activity, is associated with adhesions. Here, we used next-generation RNA sequencing (RNA-Seq) to assess genome-wide differences in messenger RNA expression due to PAI-1 deficiency after zone II flexor tendon injury. We used the ingenuity pathway analysis to characterize molecular pathways and biological drivers associated with differentially expressed genes (DEG). Analysis of hundreds of overlapping and DEG in PAI-1 knockout (KO) and wild-type mice (C57Bl/6J) during tendon healing revealed common and distinct biological processes. Pathway analysis identified cell proliferation, survival, and senescence, as well as chronic inflammation as potential drivers of fibrotic healing and adhesions in injured tendons. Importantly, we identified the activation of PTEN signaling and the inhibition of FOXO1-associated biological processes as unique transcriptional signatures of the healing tendon in the PAI-1/Serpine1 KO mice. Further, transcriptomic differences due to the genetic deletion of PAI-1 were mechanistically linked to PI3K/Akt/mTOR, PKC, and MAPK signaling cascades. These transcriptional observations provide novel insights into the biological roles of PAI-1 in tendon healing and could identify therapeutic targets to achieve scar-free regenerative healing of tendons. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:43-58, 2020.

Evolving concepts in bone infection: redefining "biofilm", "acute vs. chronic osteomyelitis", "the immune proteome" and "local antibiotic therapy".

Osteomyelitis is a devastating disease caused by microbial infection of bone. While the frequency of infection following elective orthopedic surgery is low, rates of reinfection are disturbingly high. Staphylococcus aureus is responsible for the majority of chronic osteomyelitis cases and is often considered to be incurable due to bacterial persistence deep within bone. Unfortunately, there is no consensus on clinical classifications of osteomyelitis and the ensuing treatment algorithm. Given the high patient morbidity, mortality, and economic burden caused by osteomyelitis, it is important to elucidate mechanisms of bone infection to inform novel strategies for prevention and curative treatment. Recent discoveries in this field have identified three distinct reservoirs of bacterial biofilm including: Staphylococcal abscess communities in the local soft tissue and bone marrow, glycocalyx formation on implant hardware and necrotic tissue, and colonization of the osteocyte-lacuno canalicular network (OLCN) of cortical bone. In contrast, S. aureus intracellular persistence in bone cells has not been substantiated in vivo, which challenges this mode of chronic osteomyelitis. There have also been major advances in our understanding of the immune proteome against S. aureus, from clinical studies of serum antibodies and media enriched for newly synthesized antibodies (MENSA), which may provide new opportunities for osteomyelitis diagnosis, prognosis, and vaccine development. Finally, novel therapies such as antimicrobial implant coatings and antibiotic impregnated 3D-printed scaffolds represent promising strategies for preventing and managing this devastating disease. Here, we review these recent advances and highlight translational opportunities towards a cure.

Deletion of NFKB1 enhances canonical NF-κB signaling and increases macrophage and myofibroblast content during tendon healing.

Flexor tendon injuries heal with excessive scar tissue that limits range of motion and increases incidence of re-rupture. The molecular mechanisms that govern tendon healing are not well defined. Both the canonical nuclear factor kappa B (NF-κB) and mitogen activated protein kinase (MAPK) pathways have been implicated in tendon healing. The gene NFKB1 (proteins p105/p50) is involved in both NF-κB and MAPK signaling cascades. In the present study, we tested the hypothesis that global NFKB1 deletion would increase activation of both NF-κB and MAPK through loss of signaling repressors, resulting in increased matrix deposition and altered biomechanical properties. As hypothesized, NFKB1 deletion increased activation of both NF-κB and MAPK signaling. While gliding function was not affected, NFKB1 deletion resulted in tendons that were significantly stiffer and trending towards increased strength by four weeks post-repair. NFKB1 deletion resulted in increased collagen deposition, increase macrophage recruitment, and increased presence of myofibroblasts. Furthermore, NFKB1 deletion increased expression of matrix-related genes (Col1a1, Col3a1), macrophage-associated genes (Adgre1, Ccl2), myofibroblast markers (Acta2), and general inflammation (Tnf). Taken together, these data suggest that increased activation of NF-κB and MAPK via NFKB1 deletion enhance macrophage and myofibroblast content at the repair, driving increased collagen deposition and biomechanical properties.

Reconstruction of the Superior Glenoid Labrum With Biceps Tendon Autograft: A Cadaveric Biomechanical Study.

PURPOSE: To describe 2 superior labral reconstruction techniques using long head of the biceps (LHB) autograft and to investigate the ability of the 2 reconstruction techniques to restore superior restraint to the glenohumeral joint compared with superior labrum-deficient models. METHODS: In this biomechanical study, 10 cadaveric shoulders were cycled on a servohydraulic machine while the force required to cause superior subluxation was recorded. Each specimen was cycled under 4 conditions: intact labrum, SLAP tear, posterior (9- to 12-o'clock position) labral reconstruction using LHB autograft (superior labral reconstruction 1 [SLR1]), and 180° (9- to 3-o'clock position) labral reconstruction using LHB autograft (superior labral reconstruction 2 [SLR2]). RESULTS: The mean peak force required to cause superior subluxation in the intact labrum was 32.75 N versus 19.75 N in the SLAP tear (P = .0120). SLR1 required a mean peak force of 31.23 N versus 44.09 N for SLR2 (P = .0175). SLR1 required 94.96% of the force needed in the intact labrum to cause subluxation, whereas SLR2 required 140.6%. SLR1 and SLR2 required 34.21% higher (P = .0074) and 79.84% higher (P = .0033) forces, respectively, to generate subluxation compared with the SLAP tear state. CONCLUSIONS: Both proposed superior labral reconstruction techniques increased the force needed for humeral head superior migration in the setting of a labral tear. SLR1 (posterior labral reconstruction) closely matched the constraint of an intact labrum, whereas SLR2 (180° labral reconstruction) provided greater superior constraint than an intact labrum. CLINICAL RELEVANCE: The natural history of irreparable rotator cuff tears results in superior glenohumeral escape and eventual arthrosis. The superior glenoid labrum is an important contributor to superior glenohumeral constraint and is often degenerated in this setting. Clinical application of the 2 described superior labral reconstruction techniques may improve glenohumeral superior stability in patients with rotator cuff disease and superior labral deficiency.

Patient-Specific 3-Dimensional Modeling and Its Use for Preoperative Counseling of Patients Undergoing Hip Arthroscopy.

BACKGROUND: Femoroacetabular impingement (FAI) represents complex alterations in the bony morphology of the proximal femur and acetabulum. Imaging studies have become crucial in diagnosis and treatment planning for symptomatic FAI but also have limited patient understanding and satisfaction. Exploration of alternative patient counseling modalities holds promise for improved patient understanding, satisfaction, and ultimately for outcomes. PURPOSE: To compare perceived understanding of functional anatomy and FAI pathomorphology among patients counseled with routine computed tomography (CT), generic hip models, and a 3-dimensional (3D) model printed in accordance with a patient's specific anatomy. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A prospective randomized analysis of patients presenting with radiographically confirmed FAI was conducted between November 2015 and April 2017. Patients were randomized into groups that received preoperative counseling with CT imaging alone, a generic human hip model, or a haptic 3D model of their hip. All groups were subjected to a novel questionnaire examining patient satisfaction and understanding on a variety of topics related to FAI. Data were compared with bivariate and multivariate analyses. Statistical significance was determined as P < .05. RESULTS: Thirty-one patients were included in this study (25 men, 6 women). Ten patients were randomized to the CT-only group, 11 to the generic hip model group, and 10 to receive custom 3D-printed models of their hips. Patients preoperatively counseled with isolated CT imaging or a generic hip model reported greater understanding of their pathophysiology and the role of surgical intervention when compared with those counseled with haptic 3D models (P = .03). At final follow-up, patients counseled with the use of isolated CT imaging or haptic 3D models reported greater increases and retention of understanding as compared with those counseled with generic hip models alone (P = .03). CONCLUSION: Preoperative counseling with haptic 3D hip models does not appear to favorably affect patient-reported understanding or satisfaction with regard to FAI when compared with the use of CT imaging alone. Continued research into alternative counseling means may serve to further improve patient understanding and satisfaction on this complex anatomic phenomenon.

Targeting the gut microbiome to treat the osteoarthritis of obesity.

Obesity is a risk factor for osteoarthritis (OA), the greatest cause of disability in the US. The impact of obesity on OA is driven by systemic inflammation, and increased systemic inflammation is now understood to be caused by gut microbiome dysbiosis. Oligofructose, a nondigestible prebiotic fiber, can restore a lean gut microbial community profile in the context of obesity, suggesting a potentially novel approach to treat the OA of obesity. Here, we report that - compared with the lean murine gut - obesity is associated with loss of beneficial Bifidobacteria, while key proinflammatory species gain in abundance. A downstream systemic inflammatory signature culminates with macrophage migration to the synovium and accelerated knee OA. Oligofructose supplementation restores the lean gut microbiome in obese mice, in part, by supporting key commensal microflora, particularly Bifidobacterium pseudolongum. This is associated with reduced inflammation in the colon, circulation, and knee and protection from OA. This observation of a gut microbiome-OA connection sets the stage for discovery of potentially new OA therapeutics involving strategic manipulation of specific microbial species inhabiting the intestinal space.

Diblock Copolymer Hydrophobicity Facilitates Efficient Gene Silencing and Cytocompatible Nanoparticle-Mediated siRNA Delivery to Musculoskeletal Cell Types.

pH-responsive diblock copolymers provide tailorable nanoparticle (NP) architecture and chemistry critical for siRNA delivery. Here, diblock polymers varying in first (corona) and second (core) block molecular weight (Mn), corona/core ratio, and core hydrophobicity (%BMA) were synthesized to determine their effect on siRNA delivery in murine tenocytes (mTenocyte) and murine and human mesenchymal stem cells (mMSC and hMSCs, respectively). NP-mediated siRNA uptake, gene silencing, and cytocompatibility were quantified. Uptake is positively correlated with first block Mn in mTenocytes and hMSCs (p ≤ 0.0005). All NP resulted in significant gene silencing that was positively correlated with %BMA (p < 0.05) in all cell types. Cytocompatibility was reduced in mTenocytes compared to MSCs (p < 0.0001). %BMA was positively correlated with cytocompatibility in MSCs (p < 0.05), suggesting stable NP are more cytocompatible. Overall, this study shows that NP-siRNA cytocompatibility is cell type dependent, and hydrophobicity (%BMA) is the critical diblock copolymer property for efficient gene silencing in musculoskeletal cell types.

In situ bone tissue engineering via ultrasound-mediated gene delivery to endogenous progenitor cells in mini-pigs.

More than 2 million bone-grafting procedures are performed each year using autografts or allografts. However, both options carry disadvantages, and there remains a clear medical need for the development of new therapies for massive bone loss and fracture nonunions. We hypothesized that localized ultrasound-mediated, microbubble-enhanced therapeutic gene delivery to endogenous stem cells would induce efficient bone regeneration and fracture repair. To test this hypothesis, we surgically created a critical-sized bone fracture in the tibiae of Yucatán mini-pigs, a clinically relevant large animal model. A collagen scaffold was implanted in the fracture to facilitate recruitment of endogenous mesenchymal stem/progenitor cells (MSCs) into the fracture site. Two weeks later, transcutaneous ultrasound-mediated reporter gene delivery successfully transfected 40% of cells at the fracture site, and flow cytometry showed that 80% of the transfected cells expressed MSC markers. Human bone morphogenetic protein-6 (BMP-6) plasmid DNA was delivered using ultrasound in the same animal model, leading to transient expression and secretion of BMP-6 localized to the fracture area. Micro-computed tomography and biomechanical analyses showed that ultrasound-mediated BMP-6 gene delivery led to complete radiographic and functional fracture healing in all animals 6 weeks after treatment, whereas nonunion was evident in control animals. Collectively, these findings demonstrate that ultrasound-mediated gene delivery to endogenous mesenchymal progenitor cells can effectively treat nonhealing bone fractures in large animals, thereby addressing a major orthopedic unmet need and offering new possibilities for clinical translation.

NOTCH signaling in skeletal progenitors is critical for fracture repair.

Fracture nonunions develop in 10%-20% of patients with fractures, resulting in prolonged disability. Current data suggest that bone union during fracture repair is achieved via proliferation and differentiation of skeletal progenitors within periosteal and soft tissues surrounding bone, while bone marrow stromal/stem cells (BMSCs) and other skeletal progenitors may also contribute. The NOTCH signaling pathway is a critical maintenance factor for BMSCs during skeletal development, although the precise role for NOTCH and the requisite nature of BMSCs following fracture is unknown. Here, we evaluated whether NOTCH and/or BMSCs are required for fracture repair by performing nonstabilized and stabilized fractures on NOTCH-deficient mice with targeted deletion of RBPjk in skeletal progenitors, maturing osteoblasts, and committed chondrocytes. We determined that removal of NOTCH signaling in BMSCs and subsequent depletion of this population result in fracture nonunion, as the fracture repair process was normal in animals harboring either osteoblast- or chondrocyte-specific deletion of RBPjk. Together, this work provides a genetic model of a fracture nonunion and demonstrates the requirement for NOTCH and BMSCs in fracture repair, irrespective of fracture stability and vascularity.

The Effect of the Epitendinous Suture on Gliding in a Cadaveric Model of Zone II Flexor Tendon Repair.

PURPOSE: We hypothesized that increasing core sutures (4-6) may be preferable in terms of gliding coefficient (GC) measurements when compared with adding an epitendinous suture to zone II flexor tendon repairs. We hypothesized that the inclusion of epitendinous suture in 2 standard repairs would contribute negatively to the GC of the repaired tendon. METHODS: Nineteen fresh-frozen cadaveric fingers were used for testing. We compared a control group (dissected digits without repair) and 4-strand or 6-strand core tendon repairs with and without epitendinous suture. Arc of motion was driven by direct loading, and digital images were acquired and analyzed. Outcomes were defined as the difference in GC between the native uninjured and the repaired state at each load. A linear mixed-model analysis was performed with comparisons between repairs to evaluate the statistically relevant differences between groups. RESULTS: The test of fixed effects in the linear model revealed that repair type and the use of epitendinous suture significantly affected the change in GC. The addition of an epitendinous suture produced a significant decrement in gliding regardless of repair type. CONCLUSIONS: There was significant improvement in GC with the omission of the epitendinous suture in both repair types (4- or 6-strand). CLINICAL RELEVANCE: The epitendinous suture used in this model resulted in poorer gliding of the repair, which may correspond with an expected increase in catching or triggering.