Long-Term Outcomes at Skeletal Maturity of Combined Pelvic and Femoral Osteotomy for the Treatment of Legg-Calve-Perthes Disease.

Surgical treatment for Legg-Calve-Perthes disease (LCPD) is recommended for older children with moderate to severe disease. We sought to determine whether double osteotomies lead to improved radiologic outcomes compared to reported non-operative outcomes. Patients older than 6 years of age diagnosed with LCPD lateral pillar B or C who were treated with pelvic and femoral osteotomies were included. Radiologic outcomes and leg-length discrepancies were assessed using the Stulberg classification and were compared with the current literature. Fifteen hips in fourteen patients were treated with double osteotomy for LCPD, and seven had lateral pillar C disease (47%). The mean age at surgery was 8.6 years (range, 7.2-10.4) and the mean age at follow-up was 20.2 years (range, 14.2-35.6). At a mean 11.6-year follow-up (range: 6.3-25.2), double osteotomy resulted in 40% of patients having Stulberg I/II scores, 27% having Stulberg III scores, and 33% having Stulberg IV/V scores. The mean leg-length discrepancy was 1.4 cm in lateral pillar C patients compared to 0.8 cm in lateral pillar B patients. Four patients underwent additional surgeries, including two who required total hip arthroplasty. Double osteotomy as an alternative surgical procedure for the treatment of LCPD did not show improved outcomes when compared to historic non-operative cohorts.

Toxoplasma ERK7 protects the apical complex from premature degradation.

Accurate cellular replication balances the biogenesis and turnover of complex structures. In the apicomplexan parasite Toxoplasma gondii, daughter cells form within an intact mother cell, creating additional challenges to ensuring fidelity of division. The apical complex is critical to parasite infectivity and consists of apical secretory organelles and specialized cytoskeletal structures. We previously identified the kinase ERK7 as required for maturation of the apical complex in Toxoplasma. Here, we define the Toxoplasma ERK7 interactome, including a putative E3 ligase, CSAR1. Genetic disruption of CSAR1 fully suppresses loss of the apical complex upon ERK7 knockdown. Furthermore, we show that CSAR1 is normally responsible for turnover of maternal cytoskeleton during cytokinesis, and that its aberrant function is driven by mislocalization from the parasite residual body to the apical complex. These data identify a protein homeostasis pathway critical for Toxoplasma replication and fitness and suggest an unappreciated role for the parasite residual body in compartmentalizing processes that threaten the fidelity of parasite development.

Comparison of Fixation Techniques for Lower Extremity Rotationplasty.

BACKGROUND: Rotationplasty is a reconstructive, limb-sparing surgery indicated for patients with lower extremity musculoskeletal tumors. The procedure involves rotation of the distal lower extremity to allow the ankle to function as the new knee joint and provide an optimum weight-bearing surface for prosthetic use. Historically there is limited data comparing fixation techniques. The purpose of this study is to compare clinical outcomes between intramedullary nailing (IMN) and compression plating (CP) in young patients undergoing rotationplasty. METHODS: A retrospective review of 28 patients with a mean age of 10±4 years undergoing a rotationplasty for either a femoral (n=19), tibial (n=7), or popliteal fossa (n=2) tumor was performed. The most common diagnosis was osteosarcoma (n=24). Fixation was obtained with either an IMN (n=6) or CP (n=22). Clinical outcomes of patients undergoing rotationplasty were compared between the IMN and CP groups. RESULTS: Surgical margins were negative in all patients. The mean time to union was 24 months (range 6 to 93). There was no difference in the meantime to the union between patients treated with an IMN versus those with a CP (14±16 vs. 27±26 mo, P =0.26). Patients undergoing fixation with an IMN were less likely to have a nonunion (odds ratio: 0.35, 95% confidence interval: 0.03-3.54, P =0.62). Postoperative fracture of the residual limb only occurred in patients undergoing CP fixation (n=7, 33% vs. n=0, 0%, P =0.28). Postoperative fixation complications occurred in 13 (48%) patients, most commonly a nonunion (n=9, 33%). Patients undergoing fixation with a CP were more likely to have a postoperative fixation complication (odds ratio: 20, 95% CI: 2.14-186.88, P <0.01). CONCLUSIONS: Rotationplasty is an option for limb salvage for young patients with lower extremity tumors. The results of this study reveal fewer fixation complications when an IMN can be used. As such, IMN fixation should be considered for patients undergoing a rotationplasty, though equipoise should be shown by surgeons when determining technique.

Cryo-tomography reveals rigid-body motion and organization of apicomplexan invasion machinery.

The apical complex is a specialized collection of cytoskeletal and secretory machinery in apicomplexan parasites, which include the pathogens that cause malaria and toxoplasmosis. Its structure and mechanism of motion are poorly understood. We used cryo-FIB-milling and cryo-electron tomography to visualize the 3D-structure of the apical complex in its protruded and retracted states. Averages of conoid-fibers revealed their polarity and unusual nine-protofilament arrangement with associated proteins connecting and likely stabilizing the fibers. Neither the structure of the conoid-fibers nor the architecture of the spiral-shaped conoid complex change during protrusion or retraction. Thus, the conoid moves as a rigid body, and is not spring-like and compressible, as previously suggested. Instead, the apical-polar-rings (APR), previously considered rigid, dilate during conoid protrusion. We identified actin-like filaments connecting the conoid and APR during protrusion, suggesting a role during conoid movements. Furthermore, our data capture the parasites in the act of secretion during conoid protrusion.

Does Shorter Time to Treatment of Pediatric Supracondylar Humerus Fractures Impact Clinical Outcomes?

BACKGROUND: Treatment of supracondylar humerus (SCH) fractures within 18 hours of presentation is a tracked quality metric for ranking of pediatric hospitals. This is in contrast with literature that shows time to treatment does not impact outcomes in SCH fractures. We aim to determine whether an 18-hour cutoff for pediatric supracondylar humerus fracture treatment is clinically significant by comparing the complication risks ofpatients on either side of this timepoint. Our hypothesis is that there will be no statistically significant differences based on time to treatment. METHODS: A retrospective review of clinical outcomes was performed for 472 pediatric patients who underwent surgical management of isolated supracondylar humerus fractures between 1997 and 2022 at a single level I pediatric trauma hospital. The cohort was split based on time to surgery (within or ≥18 h from Emergency Department admission). RESULTS: Surgical treatment occurred within 18 hours of arrival in 435 (92.2%) patients and after 18 hours in 37 (7.8%) patients. Mean age was 5.6±2.2 years and 51.5% of patients were female. Gartland fracture classification was type II [n=152 (32.3%)], type III [n=284 (60.3%)], type IV [n=13 (2.8%)], or flexion-type [n=18 (3.8%)]. There were no differences in demographic characteristics or fracture classification between cohorts. Fractures in the ≥18-hour cohort were treated more commonly with 2 pins (62.2% vs. 38.5%, P =0.04). There were no statistically significant differences in open versus closed reduction, utilization of medial pins, or postoperative immobilization between cohorts. We were unable to detect any differences in postoperative complications, including non-union, delayed union, stiffness, malunion, loss of reduction, iatrogenic nerve injury, or infection. This remained true when type II fractures were excluded. CONCLUSIONS: Using an arbitrary time cutoff of <18 hours does not influence clinical outcomes in the surgical treatment of SCH fractures. This held true when type II fractures were excluded. For this reason, we recommend modification to the USNWR guidelines to decrease emphasis on time-to-treatment of SCH fractures. LEVEL OF EVIDENCE: Level III.

Normative Femoral and Tibial Lengths in a Modern Population of Twenty-First-Century U.S. Children.

BACKGROUND: The Green-Anderson (GA) leg-length data remain the gold standard for the age-based assessment of leg lengths in children despite their methodologic weaknesses. We aimed to summarize current growth trends among a cross-sectional cohort of modern U.S. children using quantile regression methods and to compare the median femoral and tibial lengths of the modern U.S. children with those of the GA cohort. METHODS: A retrospective review of scanograms and upright slot-scanning radiographs obtained in otherwise healthy children between 2008 and 2020 was completed. A search of a radiology registry revealed 3,508 unique patients between the ages of 2 and 18 years for whom a standard-of-care scanogram or slot-scanning radiograph had been made. All patients with systemic illness, genetic conditions, or generalized diseases that may affect height were excluded. Measurements from a single leg at a single time point per subject were included, and the latest available time point was used for children who had multiple scanograms made. Quantile regression analysis was used to fit the lengths of the tibia and femur and overall leg length separately for male patients and female patients. RESULTS: Seven hundred patients (328 female and 372 male) met the inclusion criteria. On average, the reported 50th percentile tibial lengths from the GA study at each time point were shorter than the lengths in this study by 2.2 cm (range, 1.4 to 3.3 cm) for boys and 2 cm (range, 1.1 to 3.1 cm) for girls. The reported 50th percentile femoral lengths from the GA study at each time point were shorter than the lengths in this study by 1.8 cm (range, 1.1 to 2.5 cm) for boys and 1.7 cm (range, 0.8 to 2.3 cm) shorter for girls. CONCLUSIONS: This study developed new growth charts for femoral and tibial lengths in a modern U.S. population of children. The new femoral and tibial lengths at nearly all time points are 1 to 3 cm longer than traditional GA data. The use of GA data for epiphysiodesis could result in underestimation of expected childhood growth. LEVEL OF EVIDENCE: Prognostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Bedside hip aspiration results in decrease in total general anesthesia time in pediatric patients: A multicenter study.

Purpose: The purpose of this study is to compare pediatric hip aspiration in the operating room under general anesthesia or via bedside aspiration under moderate sedation and delineate the anesthetic time required. Methods: A database query conducted at two academic institutions identified all patients under the age of 17 who underwent hip aspiration between 2000 and 2017. At one institution, aspiration was performed in the operating room under general anesthesia. Patients were kept anesthetized until cell count was complete. At the second institution, aspiration was performed in the emergency room at bedside under sedation. The medical record was reviewed for demographic data, hip aspiration results, diagnoses, treatment, and anesthesia time. Results: A total of 233 patients (233 hips) with a mean age of 7.2 years were identified. Seventy-five patients underwent aspiration in the operating room, and 158 patients underwent bedside aspiration. Patients with a negative aspiration averaged 87 min under anesthesia when performed in the operating room and 29 min under sedation when performed at bedside. Patients with a negative aspiration performed in the operating room after 5 pm averaged 99 min under anesthesia, and 73 min under anesthesia when performed between 7 am and 5 pm (p < 0.01). Seventy-eight (49%) patients who underwent bedside aspiration did not require operative intervention and therefore avoided general anesthesia. Conclusion: Pediatric hip aspiration performed in the operating room results in prolonged anesthesia times while synovial fluid is transported and processed. Anesthesia times are significantly longer after 5 pm. Bedside aspiration resulted in significantly less anesthesia exposure, with half of patients undergoing bedside aspiration avoiding general anesthesia altogether. Level of evidence: Level III.

Predictors of Total Hip Arthroplasty Following Pediatric Surgical Treatment of Developmental Hip Dysplasia at 20-Year Follow-Up.

Long-term outcomes of surgical treatment for pediatric developmental dysplasia of the hip (DDH) are not well defined. The purpose of this study was to report long-term radiographic and clinical outcomes, survivorship free of total hip arthroplasty (THA), and predictors of subsequent THA following childhood treatment of DDH. This study was a single-institution retrospective review of hips treated for DDH with closed or open reduction at a minimum 10-year follow-up. 107 patients (119 hips) were included with a mean patient age of 3.3 years at childhood treatment. At mean 30.5 years follow-up, 24 hips had undergone THA (20%). Mean patient age at time of THA was 33.5 years. None of the hips treated with closed reduction alone required THA, whereas 8 hips treated with open reduction (25%) underwent THA. Hips with patient age > 4 years at the time of treatment had lower survivorship at 35 years follow-up (50% vs. 85%; p < 0.001). Additionally, femoral osteotomy (OR 2.0, p < 0.001), and previous treatment elsewhere (27% vs. 16%; p < 0.01) were associated with subsequent THA. Early referral and appropriate intervention may prove important, as age and prior treatment were predictive of subsequent THA.

Not your Mother's MAPKs: Apicomplexan MAPK function in daughter cell budding.

Reversible phosphorylation by protein kinases is one of the core mechanisms by which biological signals are propagated and processed. Mitogen-activated protein kinases, or MAPKs, are conserved throughout eukaryotes where they regulate cell cycle, development, and stress response. Here, we review advances in our understanding of the function and biochemistry of MAPK signaling in apicomplexan parasites. As expected for well-conserved signaling modules, MAPKs have been found to have multiple essential roles regulating both Toxoplasma tachyzoite replication and sexual differentiation in Plasmodium. However, apicomplexan MAPK signaling is notable for the lack of the canonical kinase cascade that normally regulates the networks, and therefore must be regulated by a distinct mechanism. We highlight what few regulatory relationships have been established to date, and discuss the challenges to the field in elucidating the complete MAPK signaling networks in these parasites.

Noninvasive Hemoglobin Monitoring for Postoperative Pediatric Orthopaedic Patients: A Preliminary Study.

BACKGROUND: Hemoglobin (Hgb) levels are frequently checked through venipuncture [invasive hemoglobin (iHgb)] in pediatric orthopaedic patients after high blood loss procedures. This needlestick may causes further anxiety and fear in hospitalized children. Noninvasive hemoglobin (nHgb) monitoring has been effectively utilized in the adult intensive care and postoperative total joint arthroplasty setting. nHgb monitoring has not yet been validated in children for routine postoperative Hgb assessment in pediatric orthopaedics. METHODS: In this prospective study, 46 pediatric orthopaedic patients were enrolled who were undergoing surgery and postoperative standard of care iHgb testing. On postoperative day 1, Hgb levels were obtained through venipuncture and nHgb monitor (Pronto-7; Masimo) within a 2-hour period. Patient preferences, iHgb and nHgb values, time to result, and provider preferences were recorded. Cost data were estimated based on the standard Medicare payment rates for lab services versus the cost of nHgb probe. RESULTS: nHgb results were obtained after 1 attempt in 38 patients (83%), after multiple attempts in 7 patients (15%), and could not be obtained in 1 patient. The mean time to obtain nHgb value was significantly shorter than that to obtain iHgb results (1.3±1.5 vs. 40±18.1 min; P <0.0001). The mean nHgb value was significantly higher than the mean iHgb value (11.7±1.5 vs. 10.6±1.1 g/dL, P <0.0001). nHgb exceeded iHgb by 2 g/dL or more in 12 (26%) patients (2.64±0.9 vs. 0.54±0.84 g/dL; P <0.0001). The concordance correlation coefficient between the 2 Hgb methods was 0.59, indicating moderate agreement. Forty-three (93%) of our patients and 34 (74%) of the care providers preferred nHgb over iHgb if results were equivalent. At our institution, the cost per iHgb monitoring is approximately $28 per blood draw as compared with $5 for nHgb monitoring. Interestingly, no patients required postoperative transfusion during the study period, as asymptomatic patients with no cardiac disease are typically observed unless the Hgb is <6. CONCLUSIONS: nHgb monitoring in postoperative pediatric patients overestimated Hgb levels compared with the standard of care methods; however, nHgb had high patient and provider satisfaction and had moderate agreement with iHgb. As no patients required transfusion, postoperative Hgb checks could likely be discontinued in some portion of our population. LEVEL OF EVIDENCE: Level Ib-Diagnostic study.

Vertebral body tethering compared to posterior spinal fusion for skeletally immature adolescent idiopathic scoliosis patients: preliminary results from a matched case-control study.

PURPOSE: Direct comparisons between vertebral body tethering (VBT) and posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) are limited. We aimed to evaluate 2-year results of VBT and PSF to report comparative outcomes. METHODS: 26 prospectively enrolled VBT patients were matched 1:1 by age, gender, Risser sign and major curve magnitude with PSF patients. At a minimum 2-year follow-up, surgical results and radiographic outcomes were reviewed. RESULTS: Operative time, anesthesia time, blood loss, and length of stay were significantly lower in the VBT group (< 0.001, p = 0.003, p < 0.001, p < 0.001, respectively). The major curve at 2 years was corrected by 46% in the VBT group vs. 66% in the PSF (p = 0.0004). Success following VBT, defined as no fusion surgery and Cobb angle < 35° at the 2-year follow-up, was seen in 20 VBT patients (77%) (p = 0.0003) and correlated with mean Cobb angle of < 35° on 3-month imaging. 12 VBT patients (46%) showed curve improvement over time, and those patients had significantly lower mean Cobb angle on the 3-month radiograph than non-modulators (23° vs 31°, p = 0.014). At 2 years, cord breakage occurred in five patients (19%). By 2 years, three VBT patients developed complications (2 pleural effusion and 1 overcorrection needing return to OR). In contrast to PSF, growth continued at T1-T12 (mean 13 mm) and over the instrumented levels (mean 10 mm) following VBT, compared to no growth over instrumented segments in the fusion cohort (p = 0.011, p = 0.0001). CONCLUSION: In Sanders stages 3 and 4 patients treated in the USA, Cobb angle < 35° on 3-month imaging was associated with success at the 2-year follow-up. Curve correction was superior in the PSF group with 96% achieving curve correction to < 35° vs. 77% of the VBT patients. Cord breakage was noted in 19% of VBT patients at the 2-year follow-up. Three patients developed complications in both the VBT and PSF cohorts. LEVEL OF EVIDENCE: Level II (prospective study with matched retrospective comparison group).

Tiered Guidelines in a Pediatric Orthopaedic Practice Reduce Opioids Prescribed at Discharge.

BACKGROUND: Data regarding opioid prescribing patterns following pediatric orthopaedic procedures is limited. The aim of this work was to evaluate the effects of tiered guidelines for discharge opioid prescriptions following common pediatric orthopaedic procedures. METHODS: Quality improvement project conducted at a single academic institution. Guidelines for discharge opioid prescriptions were implemented January 2018 and established 4 tiers of increasing invasiveness for 28 common pediatric orthopaedic procedures. Patients who underwent these procedures in 2017 comprised the preguideline cohort (N=258), while patients treated in 2019 comprised the postguideline cohort (N=212). Opioid prescriptions were reported as oral morphine equivalents (OMEs). Univariate tests were performed to assess statistically significant differences before and after implementation of the guidelines. RESULTS: There was a significant decrease in OME prescribed between preguideline and postguideline cohorts (median OME 97.5 vs. 37.5). When analyzed according to procedure tiers, tiers 1, 2, and 4 showed significant decreases in OME prescribed between 2017 and 2019. The rate of no opioids prescribed at discharge increased from 13% to 23% between preguideline and postguideline cohorts. The 30-day refill rate did not significantly change. After implementation of guidelines, 91% of all prescriptions were within the guideline parameters, and there was a significant reduction in prescription variability. In tier 4 procedures, median OME prescribed decreased from 375 preguideline to 188 postguideline, but was associated with greater opioid refills within 30 days of discharge (10.2% preguideline vs. 28.8% postguideline). CONCLUSIONS: Tiered guidelines for discharge opioid prescriptions following pediatric orthopaedic procedures can significantly decrease the quantity of opioids prescribed. Furthermore, we noted excellent adherence and no overall increase in the rates of narcotic refills. Such guidelines may improve pediatric orthopaedists' ability to responsibly treat postoperative pain while limiting the distribution of unneeded opioids. LEVEL OF EVIDENCE: Level IV-quality improvement project.

The Open Triradiate Cartilage: How Young Is Too Young for Total Hip Arthroplasty?

BACKGROUND: There is, to our knowledge, no published literature regarding primary total hip arthroplasty (THA) in pediatric patients with an open triradiate cartilage. The purpose of this study was to report the outcomes following primary THA in pediatric patients with open triradiate cartilage at a single intuition. METHODS: Using a single institution's Total Joint Registry, 12 patients (13 hips) were identified as having undergone primary THA with open triradiate cartilage between the years of 2000 and 2019. The mean age and body mass index of this group were 13.1 years and 25.5 kg/m2, respectively. The cohort was composed of 10 males, and the mean follow up was 5.5 years. Indications for surgery, functional outcomes, and radiographic signs of stable fixation were analyzed. RESULTS: The most common indication for surgery was avascular necrosis secondary to corticosteroid use (31%), followed by avascular necrosis after operative management of slipped capital femoral epiphysis (23%). The proportion of patients able to achieve independent, gait-aid free, ambulation improved from 23% to 100%. Mean postoperative Harris Hip Score was 92.3. All constructs were cementless, and bearing surfaces included ceramic-on-ceramic in 62% and ceramic on highly crosslinked polyethylene bearings in the remainder. Radiographic review at final follow up demonstrated osseointegration in 12 of 13 (92%) acetabular components. Although 1 patient experienced both acetabular component loosening and instability, on separate occasions, there were no incidences of infection, wound dehiscence, thromboembolic events, or failure secondary to wear. CONCLUSIONS: In this study, THA in patients with an open triradiate cartilage yielded significant clinical improvement, low complication rates and good initial implant survivorship at early follow up. Awaiting closure of the triradiate cartilage for concerns of decreased fixation and implant survivorship may be unnecessary. LEVEL OF EVIDENCE: Level IV-case series.

Trends in Incidence of Adolescent Idiopathic Scoliosis: A Modern US Population-based Study.

BACKGROUND: A successful disease screening strategy requires a high incidence of the condition, efficacy of early treatment, and efficient detection. There is limited population-based data describing trends in incidence of adolescent idiopathic scoliosis (AIS) in the United States and potential role of school screening programs on the incidence of AIS. Thus, we sought to evaluate the incidence of AIS over a 20-year period between 1994 and 2013 using a population-based cohort. METHODS: The study population comprised 1782 adolescents (aged 10 to 18 y) with AIS first diagnosed between January 1, 1994 and December 31, 2013. The complete medical records and radiographs were reviewed to confirm diagnosis and coronal Cobb angles at first diagnosis. Age-specific and sex-specific incidence rates were calculated and adjusted to the 2010 United States population. Poisson regression analyses were performed to examine incidence trends by age, sex, and calendar period. RESULTS: The overall age-adjusted and sex-adjusted annual incidence of AIS was 522.5 [95% confidence interval (CI): 498.2, 546.8] per 100,000 person-years. Incidence was about 2-fold higher in females than in males (732.3 vs. 338.8/100,000, P<0.05). The incidence of newly diagnosed AIS cases with radiographs showing a Cobb angle >10 degrees was 181.7 (95% CI: 167.5, 196.0) per 100,000 person-years. The overall incidence of AIS decreased significantly after discontinuation of school screening in 2004 (P<0.001). The incidence of bracing and surgery at initial diagnosis was 16.6 (95% CI: 12.3, 20.9) and 2.0 (95% CI: 0.5, 3.4) per 100,000 person-years, respectively. CONCLUSIONS: Overall population-based incidence of AIS decreased after school screening was discontinued. However, incidence of patients with a Cobb angle >10 degrees, initiation of bracing and surgery did not change significantly over time. This provides further data to help determine the role of scoliosis screening. LEVEL OF EVIDENCE: Level III.

Brachial Plexus Birth Injuries: A Critical Analysis Review.

¼: The incidence of brachial plexus birth injury (BPBI) in the United States is declining and now occurs in <1 per 1,000 births. ¼: The gold standard for predicting the need for early intervention remains serial examination. ¼: Early treatment of BPBI with reconstructive surgery requires the ability to perform both interposition nerve grafting and nerve transfers. ¼: Given the heterogeneity of lesions, the evidence is largely limited to retrospective comparative studies and case series.

Multivalent Interactions Drive the Toxoplasma AC9:AC10:ERK7 Complex To Concentrate ERK7 in the Apical Cap.

The Toxoplasma inner membrane complex (IMC) is a specialized organelle that is crucial for the parasite to establish an intracellular lifestyle and ultimately cause disease. The IMC is composed of both membrane and cytoskeletal components, further delineated into the apical cap, body, and basal subcompartments. The apical cap cytoskeleton was recently demonstrated to govern the stability of the apical complex, which controls parasite motility, invasion, and egress. While this role was determined by individually assessing the apical cap proteins AC9, AC10, and the mitogen-activated protein kinase ERK7, how the three proteins collaborate to stabilize the apical complex is unknown. In this study, we use a combination of deletion analyses and yeast two-hybrid experiments to establish that these proteins form an essential complex in the apical cap. We show that AC10 is a foundational component of the AC9:AC10:ERK7 complex and demonstrate that the interactions among them are critical to maintaining the apical complex. Importantly, we identify multiple independent regions of pairwise interaction between each of the three proteins, suggesting that the AC9:AC10:ERK7 complex is organized by multivalent interactions. Together, these data support a model in which multiple interacting domains enable the oligomerization of the AC9:AC10:ERK7 complex and its assembly into the cytoskeletal IMC, which serves as a structural scaffold that concentrates ERK7 kinase activity in the apical cap. IMPORTANCE The phylum Apicomplexa consists of obligate, intracellular parasites, including the causative agents of toxoplasmosis, malaria, and cryptosporidiosis. Hallmarks of these parasites are the IMC and the apical complex, both of which are unique structures that are conserved throughout the phylum and required for parasite survival. The apical cap portion of the IMC has previously been shown to stabilize the apical complex. Here, we expand on those studies to determine the precise protein-protein interactions of the apical cap complex that confer this essential function. We describe the multivalent nature of these interactions and show that the resulting protein oligomers likely tether ERK7 in the apical cap. This study represents the first description of the architecture of the apical cap at a molecular level, expanding our understanding of the unique cell biology that drives Toxoplasma infections.

Is the axial spinal cord classification predictive of intraoperative neurologic alert for pediatric scoliosis patients? An independent retrospective validation study.

PURPOSE: We sought to determine whether the axial spinal cord classification by Sielatycki et al. would be associated with increased intraoperative neuromonitoring (IONM) alerts for pediatric scoliosis patients undergoing posterior spinal fusion (PSF) surgery. METHODS: Children less than age 19 with scoliosis undergoing PSF were retrospectively reviewed. Axial-T2 MRI of the thoracic apex was reviewed for spinal cord/CSF architecture as described by Sielatycki et al.: Type 1-circular cord with visible CSF, Type 2-circular cord but no visible CSF at apical concavity, and Type 3-cord deformed with no intervening CSF. Intraoperative neuromonitoring reports, operative records and preoperative radiographs were reviewed. RESULTS: 90 patients met the inclusion criteria. Rate of neurologic events was Type 1: 2% (1/41 patients), Type 2: 14.3% (4/28), Type 3: 57.1% (12/21) (Type 1 vs 2 p = 0.06; Type 1 vs 3 p < 0.0001; Type 2 vs 3 p = 0.0017). Three patients with a Type 3 cord awoke with significant deficits. In comparison to Type 1 cords, Type 3 and Type 2 spinal cords were associated with increased coronal and total deformity angular ratios (Type 1 vs 3 p = 0.035 and 0.0054 respectively; Type 1 vs 2 p = 0.042 and 0.03 respectively). There was no difference in gender, diagnosis category, age at surgery, Cobb angle or kyphosis between the three groups. CONCLUSION: The axial spinal cord classification correlated with IONM alerts and greater severity of spinal deformity in pediatric scoliosis patients. LEVEL OF EVIDENCE: IV, retrospective cohort study.

Loss of the Conserved Alveolate Kinase MAPK2 Decouples Toxoplasma Cell Growth from Cell Division.

Mitogen-activated protein kinases (MAPKs) are a conserved family of protein kinases that regulate signal transduction, proliferation, and development throughout eukaryotes. The apicomplexan parasite Toxoplasma gondii expresses three MAPKs. Two of these, extracellular signal-regulated kinase 7 (ERK7) and MAPKL1, have been implicated in the regulation of conoid biogenesis and centrosome duplication, respectively. The third kinase, MAPK2, is specific to and conserved throughout the Alveolata, although its function is unknown. We used the auxin-inducible degron system to determine phenotypes associated with MAPK2 loss of function in Toxoplasma We observed that parasites lacking MAPK2 failed to duplicate their centrosomes and therefore did not initiate daughter cell budding, which ultimately led to parasite death. MAPK2-deficient parasites initiated but did not complete DNA replication and arrested prior to mitosis. Surprisingly, the parasites continued to grow and replicate their Golgi apparatus, mitochondria, and apicoplasts. We found that the failure in centrosome duplication is distinct from the phenotype caused by the depletion of MAPKL1. As we did not observe MAPK2 localization at the centrosome at any point in the cell cycle, our data suggest that MAPK2 regulates a process at a distal site that is required for the completion of centrosome duplication and the initiation of parasite mitosis.IMPORTANCEToxoplasma gondii is a ubiquitous intracellular protozoan parasite that can cause severe and fatal disease in immunocompromised patients and the developing fetus. Rapid parasite replication is critical for establishing a productive infection. Here, we demonstrate that a Toxoplasma protein kinase called MAPK2 is conserved throughout the Alveolata and essential for parasite replication. We found that parasites lacking MAPK2 protein were defective in the initiation of daughter cell budding and were rendered inviable. Specifically, T. gondii MAPK2 (TgMAPK2) appears to be required for centrosome replication at the basal end of the nucleus, and its loss causes arrest early in parasite division. MAPK2 is unique to the Alveolata and not found in metazoa and likely is a critical component of an essential parasite-specific signaling network.