CD47 is Required for Mesenchymal Progenitor Proliferation and Fracture Repair.

CD47 is a ubiquitous and pleiotropic cell-surface receptor. Disrupting CD47 enhances injury repair in various tissues but the role of CD47 has not been studied in bone injuries. In a murine closed-fracture model, CD47-null mice showed decreased callus bone volume, bone mineral content, and tissue mineral content as assessed by microcomputed tomography 10 days post-fracture, and increased fibrous volume as determined by histology. To understand the cellular basis for this phenotype, mesenchymal progenitors (MSC) were harvested from bone marrow. CD47-null MSC showed decreased large fibroblast colony formation (CFU-F), significantly less proliferation, and fewer cells in S-phase, although osteoblast differentiation was unaffected. However, consistent with prior research, CD47-null endothelial cells showed increased proliferation relative to WT cells. Similarly, in a murine ischemic fracture model, CD47-null mice showed reduced fracture callus bone volume and bone mineral content relative to WT. Consistent with our in vitro results, in vivo EdU labeling showed decreased cell proliferation in the callus of CD47-null mice, while staining for CD31 and endomucin demonstrated increased endothelial cell mass. Finally, WT mice administered a CD47 morpholino, which blocks CD47 protein production, showed a callus phenotype similar to that of non-ischemic and ischemic fractures in CD47-null mice, suggesting the phenotype was not due to developmental changes in the knockout mice. Thus, inhibition of CD47 during bone healing reduces both non-ischemic and ischemic fracture healing, in part, by decreasing MSC proliferation. Furthermore, the increase in endothelial cell proliferation and early blood vessel density caused by CD47 disruption is not sufficient to overcome MSC dysfunction.

Scaphoid Nonunions Treated with Nonvascularized Bone Grafting and Screw Fixation.

Background Vascularized bone grafting with screw fixation is currently considered the treatment of choice for scaphoid nonunions with avascular necrosis (AVN) of the proximal pole. A viable alternative to using vascularized bone grafts for scaphoid nonunions with AVN is nonvascularized bone grafting with screw fixation. Question What are the functional outcomes of patients with scaphoid nonunions and associated proximal pole AVN who are treated with nonvascularized distal radius bone grafting and screw fixation? Patients and Methods Eight scaphoid nonunions with AVN, which received nonvascularized distal radius bone graft and screw fixation, underwent a retrospective review. Range of motion, strength, and Disabilities of the Arm, Shoulder, and Hand (DASH) scores were obtained. Follow-up X-rays were compared with immediate postoperative X-rays. Results At a mean follow-up of 88.9 months, thumb palmar abduction and radial abduction were significantly higher on the operative side ( p = 0.28 and 0.49, respectively). Extension/flexion arc was significantly lower in the operative wrist ( p = 0.148). There was no significant difference between the operative and nonoperative sides with regard to strength. The median postoperative DASH score was 2.9 (interquartile range [IQR]: 8.3). There was no progression of osteoarthritis when immediate postoperative and follow-up X-rays were compared. Radiographic union was observed in six of the seven (85.7%) patients who were able to return to the office for follow-up radiographs. The mean scapholunate and radioscaphoid angles measured on X-rays were within normal anatomic range postoperatively. Conclusions Using nonvascularized distal radius bone graft and screw fixation in the treatment of scaphoid nonunions with associated AVN has favorable radiologic and functional outcomes and should be considered a viable treatment option for this difficult problem.

Failure of Screw/Shell Interface in the Trident II Acetabular System in Total Hip Arthroplasty.

We report a case series of 2 patients with screw/shell interface failure in the Stryker Trident II Acetabular System. Both failures consisted of screw penetration through the Trident II acetabular shell. One failure was observed postoperatively after a revision from a cephalomedullary nail to a total hip arthroplasty while the other was observed intraoperatively during a primary total hip arthroplasty. Both component failures were managed conservatively with weight-bearing as tolerated and radiographic monitoring. These are the first reported cup/screw failures of the Stryker Trident II system and should raise awareness of the potential complication and implant design flaw. When placing acetabular screws, we recommend obtaining intraoperative orthogonal screw radiographs that are tangential to the shell surface to assess for screw/shell failure.

Thrombospondin-2 spatiotemporal expression in skeletal fractures.

Fracture healing is a complex process that relies heavily on the carefully orchestrated expansion and differentiation of periosteal mesenchymal progenitor cells (MSC). Identification of new markers for periosteal MSCs is essential for the development of fracture therapeutics. Expression of the matricellular protein thrombospondin-2 (TSP2) increases during early fracture healing; however, it is currently unknown what cell population expresses TSP2. Using a TSP2 GFP reporter mouse and a stabilized murine fracture model, we characterized the expression of TSP2 during the inflammatory, soft callus formation, and hard callus formation phases of fracture healing. In addition, using TSP2 GFP positive cells harvested from reporter mouse cells, we characterized the cell population using flow cytometry and colony formation assays. In uninjured diaphyseal bone, we observed TSP2 expression in the cells located along the inner periosteum. We also observed a population of TSP2 expressing cells in undifferentiated regions of early fracture callus and along the periphery of the callus. Later in callus development, TSP2 cells were broadly distributed in the undifferentiated callus, but GFP was not expressed by chondrocytes. Flow cytometry confirmed that the majority of TSP2 expressing cells were positive for traditional murine MSC markers. Our in vitro assays further supported these findings by demonstrating all adherent and colony-forming cells expressed TSP2. Taken together, our results suggest that TSP2 is expressed by undifferentiated MSCs, but downregulated in chondrocytes. Clinical significance: expression of the matricellular protein TSP2 is a promising new marker to identify MSCs in early fracture healing.

CTRP3 Regulates Endochondral Ossification and Bone Remodeling During Fracture Healing.

C1q/TNF-related protein 3 (CTRP3) is a cytokine known to regulate a variety of metabolic processes. Though previously undescribed in the context of bone regeneration, high throughput gene expression experiments in mice identified CTRP3 as one of the most highly upregulated genes in fracture callus tissue. Hypothesizing a positive regulatory role for CTRP3 in bone regeneration, we phenotyped skeletal development and fracture healing in CTRP3 knockout (KO) and CTRP3 overexpressing transgenic (TG) mice relative to wild-type (WT) control animals. CTRP3 KO mice experienced delayed endochondral fracture healing, resulting in abnormal mineral distribution, the presence of periosteal marrow compartments, and a nonunion-like state. Decreased osteoclast number was also observed in CTRP3 KO mice, whereas CTRP3 TG mice underwent accelerated callus remodeling. Gene expression profiling revealed a broad impact on osteoblast/osteoclast lineage commitment and metabolism, including arrested progression toward mature skeletal lineages in the KO group. A single systemic injection of CTRP3 protein at the time of fracture was insufficient to phenocopy the chronic TG healing response in WT mice. By associating CTRP3 levels with fracture healing progression, these data identify a novel protein family with potential therapeutic and diagnostic value. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:00-19966, 2020.

Improved outcomes in patients with positive metal sensitivity following revision total knee arthroplasty.

BACKGROUND: Metal sensitivity as a cause for painful joint replacement has become increasingly prevalent; however, there is a lack of reported clinical outcome data from total knee arthroplasty patients with metal allergies. The purpose of this study was to determine whether patients presenting with a painful total knee arthroplasty with a positive metal sensitivity have improved outcomes following revision to a hypoallergenic implant. METHODS: A retrospective review was conducted for patients that underwent a revision total knee arthroplasty after metal sensitivity testing over a 3-year period from January 1, 2015, to December 31, 2017. Based on the results of sensitivity testing, patients underwent revision total knee arthroplasty to a hypoallergenic component or a standard component. Following revision, patients returned to the clinic at an interval of 6 weeks, 5 months, and 12 months for functional, pain, and satisfaction assessment. Outcomes were compared within and between sensitivity groups. RESULTS: Of the included patients, 78.3% (39/46) were positive for metal sensitivity. The most common metal sensitivity was to nickel (79.5%, 32/39). Both non-reactive and reactive patients significantly improved in range of motion after revision arthroplasty. The reactive group saw a 37.8% decrease in pain at 6 weeks post-revision (p < 0.001) Whereas, the non-reactive group only saw a moderate, non-significant improvement in pain reduction at 6 weeks post-revision (27.0%; p = 0.29). Frequency of pain experienced did not vary significantly between groups. Maximum metal lymphocyte transformation test (LTT) sensitivity score did not correlate with pain level at the time of revision (R2 = 0.02, p = 0.38) or percent improvement after revision (R2 = 0.001, p = 0.81). Overall, all patients reported being very satisfied after revision total knee arthroplasty; there was no difference between positive and negative sensitivity groups (W = 62, p = 0.89). CONCLUSIONS: Patients presenting with a painful knee arthroplasty and positive metal LTT have improved pain scores, walking function, and range of motion following revision to a hypoallergenic component. This study also provides a treatment algorithm for patients presenting with a painful knee replacement, in order to provide effective and timely diagnosis and management.

High rate of return to sport in adolescent athletes following anterior shoulder stabilisation: a systematic review.

IMPORTANCE: Traumatic anterior shoulder instability remains common for the adolescent athletes. AIM OR OBJECTIVE: To perform a systematic review on the outcomes and return to sport (RTS) following Bankart repair in adolescent athletes. EVIDENCE REVIEW: A systematic review using the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines was conducted of studies reporting outcomes following open and/or arthroscopic Bankart repair using modern suture anchors following traumatic anterior shoulder dislocations in adolescent patients (ages 10-19 years). Quality assessment was evaluated with ROBINS-I and MINORS instruments. The outcomes analysed included RTS, timetable to unrestricted activity, recurrent instability and revision surgery. FINDINGS: This systematic review identified 11 studies comprising 461 adolescent athletes with a mean age of 15.7 years (range, 11-19 years) and an average follow-up of 48.8 months (range, 22-85.2 months). A total of 392 patients (400 shoulders) underwent arthroscopic Bankart repair, while the remaining 69 patients (69 shoulders) underwent an open procedure. The average MINORS score was 9.6 for non-comparative studies and 17 for comparative studies. ROBINS-I revealed six studies to have a moderate risk of bias, while the remaining five studies presented serious risk of bias. There was an overall 81.5% rate of RTS to preinjury levels of athletic competition at an average of 5.3 months following Bankart repair for traumatic anterior shoulder instability. The overall total mean incidence of recurrent instability was 18.5%, while the mean incidence of revision surgery was 12.1%. Contact athletes had a 31.1% and 13% rate of recurrence and revision surgery, respectively. In comparison, collision athletes were shown to have a 10.4% and 1.4% incidence of recurrent instability and revision surgery, respectively. CONCLUSIONS AND RELEVANCE: Adolescent athletes who undergo Bankart repair for traumatic anterior shoulder instability have an 81.5% rate of RTS to preinjury levels of play at an average of 5 months following surgery. The overall total mean incidence of recurrent instability in the adolescent population is 18.5%, while the mean incidence of revision surgery is 12.1%. The results of anterior shoulder stabilisation in contact athletes is much less predictable, with higher reported rates of recurrent instability and revision surgery. LEVEL OF EVIDENCE: Level IV.

Cellular biology of fracture healing.

The biology of bone healing is a rapidly developing science. Advances in transgenic and gene-targeted mice have enabled tissue and cell-specific investigations of skeletal regeneration. As an example, only recently has it been recognized that chondrocytes convert to osteoblasts during healing bone, and only several years prior, seminal publications reported definitively that the primary tissues contributing bone forming cells during regeneration were the periosteum and endosteum. While genetically modified animals offer incredible insights into the temporal and spatial importance of various gene products, the complexity and rapidity of healing-coupled with the heterogeneity of animal models-renders studies of regenerative biology challenging. Herein, cells that play a key role in bone healing will be reviewed and extracellular mediators regulating their behavior discussed. We will focus on recent studies that explore novel roles of inflammation in bone healing, and the origins and fates of various cells in the fracture environment. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Fracture Apparatus Design and Protocol Optimization for Closed-stabilized Fractures in Rodents.

The reliable generation of consistent stabilized fractures in animal models is essential for understanding the biology of bone regeneration and developing therapeutics and devices. However, available injury models are plagued by inconsistency resulting in wasted animals and resources and imperfect data. To address this problem of fracture heterogeneity, the purpose of the method described herein is to optimize fracture generation parameters specific to each animal and yield a consistent fracture location and pattern. This protocol accounts for variations in bone size and morphology that may exist between mouse strains and can be adapted to generate consistent fractures in other species, such as rat. Additionally, a cost-effective, adjustable fracture apparatus is described. Compared to current stabilized fracture techniques, the optimization protocol and new fracture apparatus demonstrate increased consistency in stabilized fracture patterns and locations. Using optimized parameters specific to the sample type, the described protocol increases the precision of induced traumas, minimizing the fracture heterogeneity typically observed in closed-fracture generation procedures.

R-spondin-2 is a Wnt agonist that regulates osteoblast activity and bone mass.

The R-spondin family of proteins are Wnt agonists, and the complete embryonic disruption of Rspo2 results in skeletal developmental defects that recapitulate the phenotype observed with Lrp5/6 deficiency. Previous work has shown that R-spondin-2 (Rspo2, RSPO2) is both highly expressed in Wnt-stimulated pre-osteoblasts and its overexpression induces osteoblast differentiation in the same cells, supporting its putative role as a positive autocrine regulator of osteoblastogenesis. However, the role of Rspo2 in regulating osteoblastogenesis and bone formation in postnatal bone has not been explored. Here we show that limb-bud progenitor cells from Rspo2 knockout mice undergo reduced mineralization during osteoblastogenesis in vitro and have a corresponding alteration in their osteogenic gene expression profile. We also generated the first Rspo2 conditional knockout (Rspo2floxed) mouse and disrupted Rspo2 expression in osteoblast-lineage cells by crossing to the Osteocalcin-Cre mouse line (Ocn-Cre + Rspo2f/f). Ocn-Cre + Rspo2f/f male and female mice at 1, 3, and 6 months were examined. Ocn-Cre + Rspo2f/f mice are decreased in overall body size compared to their control littermates and have decreased bone mass. Histomorphometric analysis of 1-month-old mice revealed a similar number of osteoblasts and mineralizing surface per bone surface with a simultaneous decrease in mineral apposition and bone formation rates. Consistent with this observation, serum osteocalcin in 3-month-old Ocn-Cre + Rspo2f/f was reduced, and bone marrow-mesenchymal stem cells from Ocn-Cre + Rspo2f/f mice undergo less mineralization in vitro. Finally, gene expression analysis and immunohistochemistry of mature bone shows reduced beta-catenin signaling in Ocn-Cre + Rspo2f/f. Overall, RSPO2 reduces osteoblastogenesis and mineralization, leading to reduced bone mass.

Outcomes After Arthroscopic Bankart Repair in Adolescent Athletes Participating in Collision and Contact Sports.

BACKGROUND: Literature on arthroscopic stabilization in adolescent patients participating in collision and contact sports is limited, as most studies include adolescents within a larger sample group comprised primarily of adults. PURPOSE: To review the outcomes of arthroscopic Bankart repair for anterior shoulder instability in an adolescent population participating in collision and contact sports. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: This retrospective review included 39 shoulders in 37 adolescent (≤19 years) athletes who underwent primary arthroscopic Bankart repair using suture anchors with at least 2-year follow-up. All patients had a history of trauma to their shoulder resulting in an anterior dislocation. Outcome measures included patient satisfaction, the visual analog scale (VAS) for pain, American Shoulder and Elbow Surgeons (ASES) score, and Rowe score. Recurrence of dislocation and return to sporting activity were also assessed. RESULTS: The mean age at the time of surgery was 16.9 years (range, 15-19 years), and the mean follow-up was 6.3 years (range, 4.3-10.0 years); 58.6% of patients participated in collision sports. Time to surgery after the initial dislocation episode was 9.2 months (range, 0.5-36.2 months). Four shoulders (10.3%) had dislocation events postoperatively. The majority (78.1%) of patients returned to sports at the same level of competition. Mean VAS was 0.49 ± 1.0, and the mean ASES and Rowe scores were 92.8 ± 12.6 and 85.0 ± 24.2, respectively. Univariate analyses demonstrated that subjective functional outcomes were negatively correlated with recurrence (ASES, P = .005; Rowe, P = .001) and failure to return to sport (ASES, P = .016; Rowe, P = .004). Independent variables shown to have no significant relationship to functional outcomes included age, follow-up, number of preoperative dislocations, time to surgery, sport classification, competition level, tear extent, number of anchors, concurrent Hill-Sachs lesion, and repair of a superior labral anterior-posterior (SLAP) lesion. CONCLUSION: Arthroscopic Bankart repair is an effective surgical option for traumatic shoulder instability in adolescents participating in collision and contact sports. At a minimum 4-year follow-up, arthroscopic Bankart repair effectively restored stability in 90% of cases; 80% returned to their preinjury level of sport.

Intraoperative delivery of the Notch ligand Jagged-1 regenerates appendicular and craniofacial bone defects.

Each year, 33% of US citizens suffer from a musculoskeletal condition that requires medical intervention, with direct medical costs approaching $1 trillion USD per year. Despite the ubiquity of skeletal dysfunction, there are currently limited safe and efficacious bone growth factors in clinical use. Notch is a cell-cell communication pathway that regulates self-renewal and differentiation within the mesenchymal/osteoblast lineage. The principal Notch ligand in bone, Jagged-1, is a potent osteoinductive protein that positively regulates post-traumatic bone healing in animals. This report describes the temporal regulation of Notch during intramembranous bone formation using marrow ablation as a model system and demonstrates decreased bone formation following disruption of Jagged-1 in mesenchymal progenitor cells. Notch gain-of-function using recombinant Jagged-1 protein on collagen scaffolds promotes healing of craniofacial (calvarial) and appendicular (femoral) surgical defects in both mice and rats. Localized delivery of Jagged-1 promotes bone apposition and defect healing, while avoiding the diffuse bone hypertrophy characteristic of the clinically problematic bone morphogenetic proteins. It is concluded that Jagged-1 is a bone-anabolic agent with therapeutic potential for regenerating traumatic or congenital bone defects.

Sagittal rotational stiffness and damping increase in a porcine lumbar spine with increased or prolonged loading.

While the impact of load magnitude on spine dynamic parameters (stiffness and damping) has been reported, it is unclear how load history (exposure to prolonged loading) affects spine dynamic parameters in sagittal rotation. Furthermore, it is unknown if both spine stiffness and damping are equally affected to prolonged loading. Using a pendulum testing apparatus, the effect of load magnitude and load history on spine sagittal rotational stiffness and damping was assessed. Nine porcine lumbar functional spine units (FSUs) were tested in an increasing compressive load phase (ICP: 44.85, 68.55, 91.75, 114.6kg) and then a decreasing compressive load phase (DCP: 91.75, 68.55, and 44.85kg). Each trial consisted of flexing the FSU 5° and allowing it to oscillate unconstrained. During the ICP, both stiffness and damping linearly increased with load. However, in the DCP, stiffness and damping values were significantly higher than the identical load collected during the ICP, suggesting load history affects sagittal rotational dynamic parameters. In addition, spine damping was more affected by load history than spine stiffness. These results highlight the importance of controlling load magnitude and history when assessing spine dynamic parameters.

Wilderness First Aid Training as a Tool for Improving Basic Medical Knowledge in South Sudan.

INTRODUCTION: The challenges presented by traumatic injuries in low-resource communities are especially relevant in South Sudan. This study was conducted to assess whether a 3-day wilderness first aid (WFA) training course taught in South Sudan improved first aid knowledge. Stonehearth Open Learning Opportunities (SOLO) Schools designed the course to teach people with limited medical knowledge to use materials from their environment to provide life-saving care in the event of an emergency. METHODS: A pre-test/post-test study design was used to assess first aid knowledge of 46 community members in Kit, South Sudan, according to a protocol approved by the University of New England Institutional Review Board. The course and assessments were administered in English and translated in real-time to Acholi and Arabic, the two primary languages spoken in the Kit region. Descriptive statistics, t-test, ANOVA, and correlation analyses were conducted. RESULTS: Results included a statistically significant improvement in first aid knowledge after the 3-day training course: t(38)=3.94; P<.001. Although men started with more health care knowledge: (t(37)=2.79; P=.008), men and women demonstrated equal levels of knowledge upon course completion: t(37)=1.56; P=.88. CONCLUSIONS: This research, which may be the first of its kind in South Sudan, provides evidence that a WFA training course in South Sudan is efficacious. These findings suggest that similar training opportunities could be used in other parts of the world to improve basic medical knowledge in communities with limited access to medical resources and varying levels of education and professional experiences.

Body CT scanning in young adults: examination indications, patient outcomes, and risk of radiation-induced cancer.

PURPOSE: To quantify patient outcome and predicted cancer risk from body computed tomography (CT) in young adults and identify common indications for the imaging examination. MATERIALS AND METHODS: This retrospective multicenter study was HIPAA compliant and approved by the institutional review boards of three institutions, with waiver of informed consent. The Research Patient Data Registry containing patient medical and billing records of three university-affiliated hospitals in a single metropolitan area was queried for patients 18-35 years old with a social security record who underwent chest or abdominopelvic CT from 2003 to 2007. Patients were analyzed according to body part imaged and scanning frequency. Mortality status and follow-up interval were recorded. The Biologic Effects of Ionizing Radiation VII method was used to calculate expected cancer incidence and death. Examination indication was determined with associated ICD-9 diagnostic code; 95% confidence intervals for percentages were calculated, and the binomial test was used to compare the difference between percentages. RESULTS: In 21 945 patients, 16 851 chest and 24 112 abdominopelvic CT scans were obtained. During the average 5.5-year (± 0.1 [standard deviation]) follow-up, 7.1% (575 of 8057) of chest CT patients and 3.9% (546 of 13 888) of abdominal CT patients had died. In comparison, the predicted risk of dying from CT-induced cancer was 0.1% (five of 8057, P < .01) and 0.1% (eight of 12 472, P < .01), respectively. The most common examination indications were cancer and trauma for chest CT and abdominal pain, trauma, and cancer for abdominopelvic CT. Among patients without a cancer diagnosis in whom only one or two scans were obtained, mortality and predicted risk of radiation-induced cancer death were 3.6% (215 of 5914) and 0.05% (three of 5914, P < .01) for chest CT and 1.9% (219 of 11 291) and 0.1% (six of 11 291, P < .01) for abdominopelvic CT. CONCLUSION: Among young adults undergoing body CT, risk of death from underlying morbidity is more than an order of magnitude greater than death from long-term radiation-induced cancer.

Frequent body CT scanning of young adults: indications, outcomes, and risk for radiation-induced cancer.

PURPOSE: The aims of this study were to define the magnitude of frequent body CT scanning of young adults and to determine associated patient diagnoses, examination indications, short-term outcomes, and estimated radiation-induced cancer risk. METHODS: Patients aged 18 to 35 years who underwent chest or abdominopelvic CT between 2003 and 2007 at any of 3 hospitals were identified and categorized by total number of scans per body part as rarely (<5), intermediately (>5 and <15), or frequently (>15) scanned. Medical records of the frequently scanned were reviewed. Cumulative radiation exposure, calculated from typical effective doses, was used to estimate cancer risk. Cancer incidence and mortality were estimated using the Biological Effects of Ionizing Radiation method. RESULTS: A total of 25,104 patients underwent 45,632 scans, of whom 23,851 (95%) and 70 (0.3%) were rarely and frequently scanned, respectively. Among frequently scanned patients, the most common diagnoses were cancer (19 of 36 [52.8%]) and cystic fibrosis with lung transplantation (11 of 36 [30.5%]) for chest CT and cancer (25 of 34 [73.5%]) for abdominopelvic CT. During the mean 5.4 years (range, 0.9-7.6 years) of follow-up, 46% of frequently scanned patients (32 of 70) died. Of the 47 cancers predicted in the entire cohort, 36 (77%) and 2 (3%) were expected in the rarely and frequently scanned. CONCLUSIONS: The majority of CT-induced cancers are predicted to result from sporadic rather than frequent scanning. Frequent scanning confers a significant cancer risk but occurs in severely ill patients, a large proportion of who die before any radiation-induced cancer would be a factor in their health.