Photobiomodulation and Vascularization in Conduit-Based Peripheral Nerve Repair: A Narrative Review.

Background: Peripheral nerve injuries pose a significant clinical issue for patients, especially in the most severe cases wherein complete transection (neurotmesis) results in total loss of sensory/motor function. Nerve guidance conduits (NGCs) are a common treatment option that protects and guides regenerating axons during recovery. However, treatment outcomes remain limited and often fail to achieve full reinnervation, especially in critically sized defects (>3 cm) where a lack of vascularization leads to neural necrosis. Conclusions: A multitreatment approach is, therefore, necessary to improve the efficacy of NGCs. Stimulating angiogenesis within NGCs can help alleviate oxygen deficiency through rapid inosculation with the host vasculature, whereas photobiomodulation therapy (PBMT) has demonstrated beneficial therapeutic effects on regenerating nerve cells and neovascularization. In this review, we discuss the current trends of NGCs, vascularization, and PBMT as treatments for peripheral nerve neurotmesis and highlight the need for a combinatorial approach to improve functional and clinical outcomes.

Interactions of Cells and Biomaterials for Nerve Tissue Engineering: Polymers and Fabrication.

Neural injuries affect millions globally, significantly impacting their quality of life. The inability of these injuries to heal, limited ability to regenerate, and the lack of available treatments make regenerative medicine and tissue engineering a promising field of research for developing methods for nerve repair. This review evaluates the use of natural and synthetic polymers, and the fabrication methods applied that influence a cell's behavior. Methods include cross-linking hydrogels, incorporation of nanoparticles, and 3D printing with and without live cells. The endogenous cells within the injured area and any exogenous cells seeded on the polymer construct play a vital role in regulating healthy neural activity. This review evaluates the body's local and systemic reactions to the implanted materials. Although numerous variables are involved, many of these materials and methods have exhibited the potential to provide a biomaterial environment that promotes biocompatibility and the regeneration of a physical and functional nerve. Future studies may evaluate advanced methods for modifying material properties and characterizing the tissue-biomaterial interface for clinical applications.

Do Preoperative Supine Radiographs Predict Postoperative Residual Lumbar Curvatures in Adolescent Idiopathic Scoliosis? A Retrospective Cohort Study.

STUDY DESIGN: Retrospective comparative study. OBJECTIVES: This study compares supine vs bending flexibility radiographs and evaluates their ability to predict residual postoperative lumbar curvature after selective thoracic fusion for Lenke 1 and 2 curves across different lumbar modifiers (A, B, and C) in adolescent idiopathic scoliosis (AIS). METHODS: This was a retrospective review of AIS Lenke 1 and 2 patients who underwent posterior fusion. All patients had preoperative flexibility radiographs including side-bending and supine posteroanterior (PA) films, in addition to pre- and post-operative standing PA and lateral radiographs. We used SurgiMap 2.0 software for all radiographic measurements. Pearson correlations and linear regression models were developed in SAS. RESULTS: A total of 86 patients were included mean age 14.9 years and follow-up 72.3 months. Preoperative supine lumbar Cobb angle and preoperative side-bending Cobb angles had similar, positive correlations with postoperative lumbar Cobb angle, r = .55 (P < .001) and r = .54 (P < .001), respectively. Three regression models were built to predict postoperative lumbar Cobb angles from preoperative information: Model S (R2 = .39) uses preoperative supine lumbar curve; Model B (R2 = .44) uses preoperative side-bending lumbar curve; Model SB (R2 = .49) uses both preoperative supine and side-bending lumbar curves. Model S and B performed just as well as Model SB. CONCLUSION: Either supine or side-bending radiographs alone may be used to estimate mean residual postoperative lumbar curvature after selective posterior thoracic fusion, but little is to be gained by taking both supine and side-bending radiographs.

Temporal Changes in Reverse Torque of Locking-Head Screws Used in the Locking Plate in Segmental Tibial Defect in Goat Model.

The objective of this study was to evaluate changes in peak reverse torque (PRT) of the locking head screws that occur over time. A locking plate construct, consisting of an 8-hole locking plate and 8 locking screws, was used to stabilize a tibia segmental bone defect in a goat model. PRT was measured after periods of 3, 6, 9, and 12 months of ambulation. PRT for each screw was determined during plate removal. Statistical analysis revealed that after 6 months of loading, locking screws placed in position no. 4 had significantly less PRT as compared with screws placed in position no. 5 (p < 0.05). There were no statistically significant differences in PRT between groups as a factor of time (p > 0.05). Intracortical fractures occurred during the placement of 151 out of 664 screws (22.7%) and were significantly more common in the screw positions closest to the osteotomy (positions 4 and 5, p < 0.05). Periosteal and endosteal bone reactions and locking screw backout occurred significantly more often in the proximal bone segments (p < 0.05). Screw backout significantly, negatively influenced the PRT of the screws placed in positions no. 3, 4, and 5 (p < 0.05). The locking plate-screw constructs provided stable fixation of 2.5-cm segmental tibia defects in a goat animal model for up to 12 months.

An evaluation of Indigenous Tobacco Program smoking prevention workshops with First Nations youth in Ontario, Canada.

SETTING: The Indigenous Tobacco Program (ITP) operated by the Indigenous Cancer Care Unit at Cancer Care Ontario provides customized tobacco prevention workshops to First Nations youth across Ontario, in partnership with First Nations communities and partner organizations. INTERVENTION: First Nations youth in Canada are more likely than non-Indigenous youth to be smokers. The ITP aims to address the negative health impacts of commercial tobacco, using culturally relevant approaches, tools and resources while remaining respectful to the significance of sacred tobacco. This paper aims to determine whether a culturally tailored tobacco prevention workshop increases tobacco-related knowledge among First Nations youth in Ontario. OUTCOMES: The workshops exhibited promise in impacting First Nations youth knowledge on the harms of commercial tobacco, as after the workshop intervention, all indicators showed improved knowledge. Building strong and ongoing relationships with communities and partner organizations is vital to the success of the program. IMPLICATIONS: Culturally tailored workshops grounded in traditional knowledge and values provide an opportunity to increase the knowledge of the harms of commercial tobacco among First Nations youth in Ontario. With commercial tobacco use and exposure having tremendous health consequences, such interventions are essential.

RéSUMé: CADRE: Le Programme pour la lutte contre le tabagisme chez les peuples autochtones (PLTPA) administré par l'Unité des soins de cancérologie chez les peuples autochtones à Cancer Care Ontario dispense des ateliers personnalisés de prévention du tabagisme aux jeunes Autochtones dans tout l'Ontario, en partenariat avec les communautés et organismes partenaires des Premières Nations. INTERVENTION: Les jeunes des Premières Nations canadiennes sont plus susceptibles de fumer que les jeunes non autochtones. Le PLTPA vise à remédier aux effets négatifs sur la santé du tabac commercial à l'aide d'approches, d'outils et de ressources pertinents sur le plan culturel, tout en demeurant respectueux de l'importance du tabac sacré. Cet article vise à déterminer si un atelier de prévention adapté sur le plan culturel permet d'accroître les connaissances relatives au tabac parmi les jeunes des Premières Nations de l'Ontario. RéSULTATS: Les ateliers ont eu des répercussions prometteuses sur les connaissances des jeunes des Premières Nations ayant trait aux effets néfastes du tabac commercial, puisqu'à la suite de l'atelier d'intervention, tous les indicateurs dénotaient une amélioration des connaissances à ce sujet. L'entretien de relations solides et continues avec les communautés et organismes partenaires est essentiel à la réussite du programme. IMPLICATIONS: Les ateliers culturellement adaptés et fondés sur des connaissances et des valeurs traditionnelles permettent d'accroître les connaissances des jeunes des Premières Nations ontariennes ayant trait aux effets néfastes du tabac commercial. Au vu des impacts énormes sur la santé, liés à la consommation de tabac commercial et à l'exposition à celui-ci, de telles interventions sont essentielles.

Induced hypothyroidism alters articular cartilage in skeletally immature miniature swine.

PURPOSE/AIM: Thyroid hormone has been implicated in the normal growth and development of articular cartilage; however, its effect on a disease state, such as hypothyroidism, is unknown. The purpose of this investigation was to compare normal articular cartilage from proximal femurs of immature miniature swine to proximal femurs from hypothyroid-induced immature miniature swine. MATERIALS AND METHODS: Two 11-week-old male Sinclair miniature swine were made hypothyroid by administration of 6-propyl-2-thiouracil (PTU) in their drinking water; two control animals did not receive PTU. At 25 weeks of age, the animals were euthanized and their proximal femurs were fixed and decalcified. Samples were sectioned and analyzed by histology to define extracellular matrix (ECM) structure, immunohistochemistry (IHC) to identify types II and X collagen, and histomorphometry to assess articular cartilage mean total and localized height and cell density. Statistics included nested mixed-effects ANOVA with p ≤ 0.05 considered statistically significant. RESULTS: Compared to controls, hypothyroid articular cartilage demonstrated statistically significant quantitative differences in mean tissue height, mean cell density and type II collagen localized zone height. Qualitative differences in ECM proteoglycans and overall collagen types were also found. Type X collagen was not detected in either hypothyroid or control articular cartilage specimens. CONCLUSIONS: Significant changes in articular cartilage structure in hypothyroid compared to control immature miniature swine suggest that thyroid hormone is critical in the growth and development of articular cartilage. CLINICAL SIGNIFICANCE: Understanding articular cartilage development in immature animal models may provide insight into healing or repair of degenerative human articular cartilage.

Ex-vivo Mechanical Testing of Novel Laryngeal Clamps Used for Laryngeal Advancement Constructs.

Rostral laryngeal advancement, also known as laryngeal tie-forward, is used to treat horses for intermittent dorsal displacement of the soft palate and has a morbidity rate of about 6%. We hypothesized that a novel laryngeal clamp would prevent morbidity associated with the sutures tearing through the thyroid cartilage. Larynges (n = 35 horses) were used for ex vivo testing. For uniaxial testing, 15 equine larynges were tested in one of three laryngeal tie-forward constructs [standard laryngeal tie-forward; modified laryngeal tie-forward using a suture-button; and modified laryngeal tie-forward using a laryngeal clamp]. For biaxial testing, 20 larynges were tested in one of two treatment groups: laryngeal tie-forward and laryngeal tie-forward using a laryngeal clamp. Constructs were tested in single cycle-to-failure. Statistical analyses were performed using ANOVA for uniaxial testing and t-tests for biaxial testing. The laryngeal tie-forward using a laryngeal clamp construct was superior to laryngeal tie-forward and laryngeal tie-forward using a suture-button constructs in resistance to pullout in uniaxial testing. The laryngeal tie-forward using a laryngeal clamp presented a significantly different method of failure than the standard laryngeal tie-forward in the biaxial testing. Failure modes for each construct were primarily by suture failure at the clamp (laryngeal tie-forward using a laryngeal clamp), suture pullout through the thyroid cartilage, or, less commonly, tearing of the cricothyroid ligament (laryngeal tie-forward). In uniaxial testing, the laryngeal tie-forward using a laryngeal clamp failed most commonly due to tearing of the cricothyroid ligament, whereas the standard laryngeal tie-forward and the laryngeal tie-forward using a suture-button failed due to the tearing of the cartilage. The laryngeal clamps provided greater stiffness, load at yield, and tensile stress at yield than did the standard construct. Laryngeal clamps may offer an alternative to standard methods of anchoring the thyroid cartilage when performing the laryngeal tie-forward procedure. Further testing and clinical trials are needed to elucidate the utility of the laryngeal tie-forward using a laryngeal clamp.

Plasmonic Nanofactors as Switchable Devices to Promote or Inhibit Neuronal Activity and Function.

Gold nanosystems have been investigated extensively for a variety of applications, from specific cancer cell targeting to tissue regeneration. Specifically, a recent and exciting focus has been the gold nanosystems' interface with neuronal biology. Researchers are investigating the ability to use these systems neuronal applications ranging from the enhancement of stem cell differentiation and therapy to stimulation or inhibition of neuronal activity. Most of these new areas of research are based on the integration of the plasmonic properties of such nanosystems into complex synthetic extracellular matrices (ECM) that can interact and affect positively the activity of neuronal cells. Therefore, the ability to integrate the plasmonic properties of these nanoparticles into multidimensional and morphological structures to support cellular proliferation and activity is potentially of great interest, particularly to address medical conditions that are currently not fully treatable. This review discusses some of the promising developments and unique capabilities offered by the integration of plasmonic nanosystems into morphologically complex ECM devices, designed to control and study the activity of neuronal cells.

An investigation to validate the equivalence of physes obtained from different anatomic regions in a single animal species: Implications for choosing experimental controls in clinical studies.

Control tissue in studies of various orthopedic pathologies is difficult to obtain and presumably equivalent biopsies from other anatomic sites have been utilized in its place. However, for growth plates, different anatomic regions are subject to dissimilar mechanical forces and produce disproportionate longitudinal growth. The purpose of this study was to compare gene expression and structure in normal physes from different anatomic regions within a single animal species to determine whether such physes were equivalent. Thirteen female New Zealand white rabbits (five 15-week-old and eight 19-week-old animals) were euthanized and physes harvested from their proximal and distal femurs and proximal tibiae. Harvested physes were divided into groups for histological, immunohistochemical (IHC), and reverse transcription-quantitative polymerase chain reaction analyses. All physes analyzed demonstrated no apparent differences in morphology or proteoglycan staining intensity on histological examination or in type II collagen presence determined by IHC study. Histomorphometric measures of physeal height as well as gene expression of type II collagen and aggrecan were found to be statistically significantly equivalent (p < 0.05) among the three different bones from the total number of rabbits. Summary data suggest that the structural similarities and statistical equivalence determined among the various physes investigated in the rabbit validate these tissues in this species for use as surrogate controls by which physeal abnormalities may be compared and characterized in the absence of otherwise normal control tissues. Other species may exhibit the same similarities and equivalence among different physes so that such tissues may serve in like manner as controls for assessing a variety of orthopedic conditions, including those occurring in humans.

Orthopaedic Resident Use of an Electronic Medical Record Template Does Not Improve Documentation for Pediatric Supracondylar Humerus Fractures.

INTRODUCTION: Pediatric supracondylar humerus fractures are associated with a high incidence of nerve injury. Therefore, it is imperative that documentation be complete and accurate. This investigation compares orthopaedic resident history and physical (H&P) documentation of pediatric supracondylar fractures for completeness and accuracy with and without the use of an electronic medical record template. METHODS: The electronic medical record H&P documentation of 119 supracondylar humerus fractures surgically treated at a single pediatric institution was retrospectively reviewed. Templated and nontemplated groups were compared for documentation completeness and accuracy. Definitive diagnosis of a nerve palsy was made by a supervising orthopaedic attending surgeon. RESULTS: Forty-two cases had a templated H&P and 77 did not. The H&P documentation in the templated group was markedly more complete than that in the nontemplated group. However, the accuracy of the H&P documentation to identify nerve palsy was not statistically different between the two groups. Overall, the voluntary use of the orthopaedic template declined over time. CONCLUSION: Resident use of an orthopaedic template for documenting the H&P of pediatric supracondylar humerus fractures compared with nontemplated notes resulted in more complete documentation but only comparable accuracy. LEVEL OF EVIDENCE: III.

Biometric Data Comparison Between Lewis and Sprague Dawley Rats.

Introduction: Pressure mapping systems are often used for indirect assessment of kinematic gait parameter differences after repair of critical peripheral nerve defects in small animal models. However, there does not appear to be any literature that studies the differences in normal gait pattern of Sprague Dawley rats compared to Lewis rats using a Tekscan VH4 pressure mat system. The purpose of this study is to assess the gait profile of Lewis and Sprague Dawley rats generated by Tekscan's VH4 system to detect similarities and/or differences in gait parameters involving both force and temporal variables. Materials and Methods: The gait profile of 14 Lewis and 14 Sprague Dawley rats was recorded using a Tekscan VH4 pressure map system with two successful walks per animal and gait parameter data was normalized for mean variance between the two rodent strains. Results: The results showed that temporal and normalized force parameters were not significantly different between the two types of rats. Maximum force, contact area, stride length, and adjusted pressure variables were significantly different between the two strains, likely attributed to the body size and weight differential between the strains. Variation in some of these parameters were considered due to differences in overall body size between the two strains, variations in gait kinematics between individual rodent subjects, and the limitations of the current experimental design. Conclusion: For future in vivo models, either Sprague Dawley or Lewis rat strains would be acceptable animal models when comparing base-line gait profiles using the Tekscan VH4 pressure map system when assessing critical defect repairs of peripheral nerves.

Interprofessional education model for geriatric falls risk assessment and prevention.

BACKGROUND: One in three people over the age of 65 fall every year, with 1/3 sustaining at least moderate injury. Falls risk reduction requires an interprofessional health team approach. The literature is lacking in effective models to teach students how to work collaboratively in interprofessional teams for geriatric falls prevention. The purpose of this paper is to describe the development, administration and outcome measures of an education programme to teach principles of interprofessional care for older adults in the context of falls prevention. METHODS: Students from three academic institutions representing 12 health disciplines took part in the education programme over 18 months (n=237). A mixed method one-group pretest and post-test experimental design was implemented to measure the impact of a multistep education model on progression in interprofessional collaboration competencies and satisfaction. RESULTS: Paired t-tests of pre-education to posteducation measures of Interprofessional Socialization and Valuing Scale scores (n=136) demonstrated statistically significant increase in subscales and total scores (p<0.001). Qualitative satisfaction results were strongly positive. DISCUSSION: Results of this study indicate that active interprofessional education can result in positive student attitude regarding interprofessional team-based care, and satisfaction with learning. Lessons learnt in a rapid cycle plan-do-study-act approach are shared to guide replication efforts for other educators. CONCLUSION: Effective models to teach falls prevention interventions and interprofessional practice are not yet established. This education model is easily replicable and can be used to teach interprofessional teamwork competency skills in falls and other geriatric syndromes.

Tailoring and field-testing the use of a knowledge translation peer support shared decision making strategy with First Nations, Inuit and Métis people making decisions about their cancer care: a study protocol.

PLAIN ENGLISH SUMMARY: Tailoring and testing a peer support decision making strategy with First Nations, Inuit and Métis people making decisions about their cancer care: A study protocol.First Nations, Inuit and Métis (FNIM) people face higher risks for cancer compared to non-FNIM populations. They also face cultural barriers to health service use. Within non-FNIM populations an approach to health decision making, called shared decision making (SDM), has been found to improve the participation of people in their healthcare. Peer support with SDM further improves these benefits. The purpose of this study is to tailor and test a peer support SDM strategy with community support workers to increase FNIM people's participation in their cancer care.This project has two phases that will be designed and conducted with a Steering Committee that includes members of the FNIM and cancer care communities. First, a peer support SDM strategy will be tailored to meet the needs of cancer system users who are receiving care in urban settings, and training in the SDM strategy developed for community support workers. Three communities will be supported for participation in the study and community support workers who are peers from each community will be trained to use the SDM strategy.Next, each community support worker will work with a community member who has a diagnosis of cancer or who has supported a family member with cancer. Each community support worker and community member pair will use the SDM strategy. The participation and experience of the community support worker and community member will be evaluated.The research will be used to develop strategies to support people who are making decisions about their health. ABSTRACT: Tailoring and field-testing the use of a knowledge translation peer support shared decision making strategy with First Nations, Inuit and Métis people making decisions about their cancer care: A study protocol Background First Nations, Inuit and Métis ("FNIM") people face increased cancer risks in relation to general populations and experience barriers to health service use. Shared decision making (SDM) has been found to improve peoples' participation and outcomes in healthcare and peer support with SDM further improves these benefits. The purpose of this study is to tailor and then field test, by and with FNIM communities, a peer support SDM strategy for use in cancer care. Methods This project has 2 theory-driven phases and 5 stages (a-e). A core research team that includes members of the Aboriginal Cancer Control Unit of Cancer Care Ontario communities and academic researchers, will work with a Steering Committee. In phase 1, (stage a) a peer support SDM strategy will be tailored to meet the needs of cancer system users who are receiving care in urban settings and (stage b), training developed that will i) introduce participant communities to SDM, and ii) train community support workers (CSWs) within these communities. Next (stage c), three communities will be approached for voluntary participation in the study. These communities will be introduced to SDM in community meetings, and if in agreement then CSWs from each community will be recruited to participate in the study. One volunteer CSW from each community will be trained to use the peer support SDM strategy to enable phase 2 (field test of the peer support SDM strategy).During phase 2 (stage d), each CSW will be matched to a volunteer community member who has had a diagnosis of cancer or has supported a family member with cancer and is familiar with Ontario cancer systems. Each CSW-community member pair (3 to 4 pairs/community) will use the tailored peer support SDM strategy; their interaction will be audio-recorded and their participation and experience evaluated (total of 9 to 12 interviews). As well (stage e), data will be collected on health systems' factors related to the use of the peer support SDM strategy. Discussion Findings will develop peer support SDM strategies to enhance participation of FNIM people in cancer care decisions, advance knowledge translation science, and support a proposal to conduct a multi-site implementation trial.

Partial or non-union after triple arthrodesis in children: does it really matter?

PURPOSE: Triple arthrodesis is a commonly performed salvage procedure to correct hindfoot deformity. Non-union is considered an undesirable radiographic outcome; however, the clinical ramifications of this are not as well defined. The purpose of this study was to determine the incidence of partial or complete radiographic non-union after triple arthrodesis in children and characterize the clinical consequences. METHODS: An IRB-approved retrospective review of triple arthrodesis surgeries in patients less than 16 years of age performed by a single surgeon (DSW) identified 159 cases meeting the inclusion criteria. Plain radiographs were reviewed for bony fusion (defined as over 80 % radiographic bony union of the subtalar, calcaneocuboid, and talonavicular bones) and charts for clinical outcomes (pain, return to activity, and subsequent hindfoot surgeries). Statistics were used to compare the fused and unfused cases, with p < 0.05 considered to be significant. RESULTS: Of the 159 cases included in the study, 9 % did not achieve at least 80 % plain film radiographic union. The fused and unfused groups had similar clinical outcomes. Only one patient required surgery for sequelae of symptoms arising from a pseudoarthrosis related to the triple arthrodesis. The fused and unfused groups were similar in terms of gender and pin removal time, but differed significantly in surgical age and underlying diagnosis. CONCLUSIONS: This is one of the largest case series of pediatric triple arthrodesis surgery presented in the literature. This study demonstrated that good clinical outcomes can be achieved despite the lack of radiographic union after triple arthrodesis surgery in children. LEVEL OF EVIDENCE: IV.

Improving health equity for First Nations, Inuit and Métis people: Ontario's Aboriginal Cancer Strategy II.

Cancer incidence is increasing more rapidly and cancer survival is worse among Ontario's First Nations, Inuit and Métis (FNIM) populations than among other Ontarians. Cancer Care Ontario's Aboriginal Cancer Strategy II aims to reduce this health inequity and to improve the cancer journey and experience for FNIM people in Ontario. This comprehensive, multi-faceted strategy was developed and is being implemented with and for Aboriginal Peoples in Ontario in a way that honours the Aboriginal Path of Well-being.

The effects of hypothyroidism on the proximal femoral physis in miniature swine.

As a potential means of comparing hypothyroidism in humans, this work intended to establish a defined hypothyroid state in immature miniature swine and evaluate specific molecular, cellular, and extracellular responses of their growth plates. Two male, 11-week-old Sinclair miniature swine were given 6-propyl-2-thiouracil (PTU) in their water and two other like animals (controls) were provided water without PTU. Blood levels of thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxin (T4) were monitored weekly. At 25 weeks of age, the hind limb proximal femoral physes were harvested and divided into portions for histology and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. Compared to controls, swine administered PTU exhibited increased TSH and decreased T3 and T4 serum levels during the study period, features consistent with a hypothyroid state. Compared to controls, hypothyroid swine exhibited structurally altered physes and demonstrated significantly decreased gene expression of aggrecan (p < 0.05) and type X collagen (p ≤ 0.1). This is the first hypothyroid model established in miniature swine and represents a potentially important advance for understanding the condition in humans, in which, like this swine model, there are changes critical to growth plate molecular biology, biochemistry and structure.

A prospective comparison of computer-navigated and fluoroscopic-guided in situ fixation of slipped capital femoral epiphysis.

BACKGROUND: Slipped capital femoral epiphysis (SCFE) is usually treated with percutaneous in situ screw fixation to prevent further progression of deformity. The purpose of this investigation is to compare computer navigation (CN) techniques with traditional fluoroscopic (fluoro) techniques for in situ fixation of SCFE. METHODS: This study was an IRB-approved prospective study of 39 hip pinnings in 33 children. CN techniques were used in 22 cases and fluoro in 17. The CN and fluoro groups were statistically similar in terms of grade and acuity of the slip. Children were assigned to the groups based on the intraoperative imaging technique used by the attending on call, with 3 surgeons in each group taking equal amounts of call. The "approach-withdraw" technique was used in all cases. Postoperative limited-cut, reduced-dose computed tomography (CT) scans were obtained to evaluate screw placement. This included blinded analysis for screw penetration of the joint, screw tip-to-apex distance, the distance the screw passed to the center of the physis, and attainment of center-center position. The number of pin passes, intraoperative radiation exposure, and operating room (OR) time were also analyzed. Statistics used included ANOVA, the χ and median tests. RESULTS: Compared with the fluoro group, CN resulted in more accurate screw placement. There was 1 case of joint penetration in the fluoro group not appreciated intraoperatively but detected on postoperative CT. CN also resulted in statistically significant (P < 0.05) reduced screw tip-to-apex distance and distance to the center of the physis. There was no statistically significant difference between the 2 groups in attainment of the center-center position, number of pin passes, or intraoperative radiation exposure. OR time averaged 19 minutes longer in the CN group. There was no case of avascular necrosis or chondrolysis in either of the groups. CONCLUSIONS: Compared with traditional fluoro techniques, CN in situ fixation of SCFE results in more accurate screw placement, comparable number of pin passes and intraoperative radiation exposure, and increased OR time. The cost-benefit ratio of this technology requires careful consideration at each individual institution. LEVEL OF EVIDENCE: II.

History and progress on accurate measurements of the Planck constant.

The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10(-34) J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, N(A). As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 10(8) from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the improved techniques and discoveries in quantum mechanics steadily reduced the uncertainty of h. The central part of this review describes the technical details of the watt balance technique, which is a combination of the mechanical and electronic measurements that now determine h as a direct result, i.e. not requiring measured values of additional fundamental constants. The first technical section describes the basics and some of the common details of many watt balance designs. Next is a review of the ongoing advances at the (currently) seven national metrology institutions where these experiments are pursued. A final summary of the recent h determinations of the last two decades shows how history keeps repeating itself; there is again a question of whether there is a shift in the newest results, albeit at uncertainties that are many orders of magnitude less than the original experiments. The conclusion is that there is room for further development to resolve these differences and find new ideas for a watt balance system with a more universal application. Since the next generation of watt balance experiments are expected to become kilogram realization standards, the historical record suggests that there is yet a need for proof that Planck constant results are finally reproducible at an acceptable uncertainty.

A study in vivo of the effects of a static compressive load on the proximal tibial physis in rabbits.

BACKGROUND: The effect of compression on the physis is generally defined by the Hueter-Volkmann principle, in which decreased linear growth of the physis results from increased compression. This investigation examined whether mechanically induced compression of rabbit physes causes changes in gene expression, cells, and extracellular components that promote physeal resilience and strength (type-II collagen and aggrecan) and cartilage hypertrophy (type-X collagen and matrix metalloprotease-13). METHODS: Static compressive loads (10 N or 30 N) were applied for two or six weeks across one hind limb proximal tibial physis of thirteen-week-old female New Zealand White rabbits (n = 18). The contralateral hind limb in all rabbits underwent sham surgery with no load to serve as an internal control. Harvested physes were divided into portions for histological, immunohistochemical, and quantitative reverse transcription-polymerase chain reaction analysis. Gene expression was statistically analyzed by means of comparisons between loaded samples and unloaded shams with use of analysis of variance and a Tukey post hoc test. RESULTS: Compared with unloaded shams, physes loaded at 10 N or 30 N for two weeks and at 10 N for six weeks showed histological changes in cells and matrices. Physes loaded at 30 N for six weeks were decreased in thickness and had structurally disorganized chondrocyte columns, a decreased extracellular matrix, and less intense type-II and X collagen immunohistochemical staining. Quantitative reverse transcription-polymerase chain reaction analysis of loaded samples compared with unloaded shams yielded a significantly (p ≤ 0.05) decreased gene expression of aggrecan and type-II and X collagen and no significant (p > 0.05) changes in the matrix metalloprotease-13 gene expression with increasing load. CONCLUSIONS: Compressed rabbit physes generate biochemical changes in collagens, proteoglycan, and cellular and tissue matrix architecture. Changes potentially weaken overall physeal strength, consistent with the Hueter-Volkmann principle, and lend understanding of the causes of pathological conditions of the physis.