A Curricular Model for Simulation Within Orthopaedic Residency Training

Introduction

American Board of Orthopaedic Surgery/American Council on GraduateMedical Education Residency Review Committee training requirements have necessitated the need for the adoption of simulation education into existing programmatic requirements. Current guidelines focus only on interns at a potentially significant cost to programs; both in total dollar amount and time.

Methods

The authors aim to provide a model that can maximize utility for all resident levels, manage cost by maximizing the use of cadaveric material, and allow integration of varied industry support.

Results

The Oregon Health & Science University Orthopaedic education program has developed a high-fidelity training curriculum that (1) is applicable to both junior and senior residents (2) has minimized the cost per resident with the reuse of cadaveric specimens and (3) has nurtured partnerships with industry stakeholders to reduce bias in training by collaborating with most major industry representatives.

Conclusion

The simulation curriculum outlined in this manuscript may serve as a reference for other programs and institutions to develop their own residency educational curriculum models.

Resident Performance on the Fundamentals of Arthroscopic Surgery Training (FAST) Workstation Does Not Predictably Improve With Postgraduate Year

Purpose

To identify differences in performance on the Fundamentals of Arthroscopic Surgery Training (FAST) workstation between residents across different postgraduate years and training sites.

Methods

During the 2018-2019 academic year, 102 orthopaedic surgery residents from 4 training sites completed 6 FAST modules. Failure was defined as either completion time exceeding benchmark time or commission of task-specific errors. With the exception of knot tying, each module was completed by participants twice-once with each hand serving as the camera hand. Time to completion (except for knot tying) and errors were recorded for each of the modules. Completion times and failure rates were compared between postgraduate years, seniority groups, and training sites.

Results

In all modules for which time was recorded, except for the suture-passage module, there was no significant difference in time to completion based on seniority (P < .01 for suture passage and P > .05 for all others). Significant differences in completion time were observed between sites for all modules except for the suture-passage module (P = .957 for suture passage and P < .05 for all others). Site predicted failure by at least 1 measure (time or technical error) for all modules (P < .05) except for number probing and suture passage. Failure rate across training years varied for each module.

Conclusions

Time to completion and rate of failure did not predictably decrease with level of training. Training site proved to be a significant predictor of performance. Factors such as hand dominance and familiarity with the equipment proved to be important considerations for some modules.

Clinical Relevance

Objective assessment of arthroscopic skills among orthopaedic trainees is difficult. Using reproducible methodology to assess trainees on specific skills at all postgraduate years and at multiple training sites may provide important information about orthopaedic training.

Antibody-mediated prevention of vaginal HIV transmission is dictated by IgG subclass in humanized mice

HIV broadly neutralizing antibodies (bNAbs) are capable of both blocking viral entry and driving innate immune responses against HIV-infected cells through their Fc region. Vaccination or productive infection results in a polyclonal mixture of class-switched immunoglobulin G (IgG) antibodies composed of four subclasses, each encoding distinct Fc regions that differentially engage innate immune functions. Despite evidence that innate immunity contributes to protection, the relative contribution of individual IgG subclasses is unknown. Here, we used vectored immunoprophylaxis in humanized mice to interrogate the efficacy of individual IgG subclasses during prevention of vaginal HIV transmission by VRC07, a potent CD4-binding site-directed bNAb. We find that VRC07 IgG2, which lacks Fc-mediated functionality, exhibited substantially reduced protection in vivo relative to other subclasses. Low concentrations of highly functional VRC07 IgG1 yielded substantial protection against vaginal challenge, suggesting that interventions capable of eliciting modest titers of functional IgG subclasses may provide meaningful benefit against infection.

Female Residents Give Themselves Lower Scores Than Male Colleagues and Faculty Evaluators on ACGME Milestones

OBJECTIVE

Orthopedic surgery is one of the specialties with the lowest number of women residents and practicing surgeons. The gender discrepancy in orthopedic residency training may drive a competency bias. We asked whether female orthopedic surgery residents score themselves lower on the Accreditation Council for Graduate Medical Education (ACGME) Milestones than their male counterparts, and lower than their faculty evaluators.

DESIGN

We conducted a retrospective review of ACGME Milestone data from faculty and residents over a 4-year period. The data were analyzed using a snapshot of PGY2 (n = 20 residents) and PGY4 (n = 19 residents) scores, and using a Generalized Estimation Equation (GEE) to account for additional data points from the same residents over the 4-year data collection period.

SETTING

Assessment scores were compiled from a single orthopedic surgery residency at Oregon Health & Science University from 2014 to 2017.

PARTICIPANTS

The residency program has 5 residents in each program year (PGY1 through PGY5); a total of 25 residents during each year of the study were included.

RESULTS

On average, female residents scored themselves lower than both their male counterparts and their faculty mentors. Female PGY2 self-evaluation scores were lower than males in both patient care (p = 0.005) and medical knowledge (p < 0.001). When the GEE model was applied to 99 responses from 41 residents over a 4-year period, there were no gender-related differences in resident self-evaluation scores and in faculty scores of male and female residents, with the exception of meniscal tear. For this milestone, faculty rated female residents lower than males. Furthermore, the differences between faculty evaluation scores and resident self-evaluation scores were significantly lower for males than for females for 4 of the clinical domains, as well as the systems-based practice domains of cost and communication.

CONCLUSIONS

Our results indicate female residents are at risk for a competency bias during training, as reflected by evaluations using the ACGME Milestones.

Reliability of Radiologic Assessments of Clinically Relevant Growth Remaining in Knee MRI of Children and Adolescents With Patellofemoral Instability: Data From the JUPITER Cohort

Background

Surgical decision making and preoperative planning for children and adolescents with patellofemoral instability rely heavily on a patient's skeletal maturity. To be clinically useful, radiologic assessments of skeletal maturity must demonstrate acceptable interrater reliability and accuracy.

Purpose

The purpose of this study was to examine the interrater reliability among surgeons of varying experience levels and specialty training backgrounds when evaluating the skeletal maturity of the distal femur and proximal tibia of children and adolescents with patellofemoral instability.

Study Design

Cohort study (diagnosis); Level of evidence, 3.

Methods

Six fellowship-trained orthopaedic surgeons (3 pediatric orthopaedic, 2 sports medicine, and 1 with both) who perform a high volume of patellofemoral instability surgery examined 20 blinded knee radiographs and magnetic resonance images in random order. They assessed these images for clinically relevant growth (open physis) or clinically insignificant growth (closing/closed physis) remaining in the distal femoral and proximal tibial physes. Fleiss' kappa was calculated for each measurement. After initial ratings, raters discussed consensus methods to improve reliability and assessed the images again to determine if training and new criteria improved interrater reliability.

Results

Reliability for initial assessments of distal femoral and proximal tibial physeal patency was poor (kappa range, 0.01-0.58). After consensus building, all assessments demonstrated almost-perfect interrater reliability (kappa, 0.99 for all measurements).

Conclusion

Surgical decision making and preoperative planning for children and adolescents with patellofemoral instability rely heavily on radiologic assessment of skeletal maturity. This study found that initial interrater reliability of physeal patency and clinical decision making was unacceptably low. However, with the addition of new criteria, a consensus-building process, and training, these variables became highly reliable.

Orthopaedic Resident Arthroscopic Knot-Tying Skills Are Improved Using a Training Program and Knot-Tying Workstation

Purpose

To quantify an orthopaedic trainee’s ability to tie arthroscopic knots before and after a short cadaveric-based arthroscopy training period using a commercially available knot-tying workstation.

Methods

During a weeklong cadaveric arthroscopic training camp, 15 third- and fourth-year orthopaedic residents were evaluated using a commercially available benchtop knot-tying workstation. At the beginning of the week (baseline), each participant was asked to tie 3 knots of his or her choice backed up by 3 half-hitches using nonabsorbable suture. Successful knots fit the sizer and elongated less than 3 mm after application of a 15-lb load. Afterward, residents watched a video demonstrating a sample knot and were encouraged to practice over the ensuing days. At the end of the week (post-training), residents were asked to tie 3 knots. The time to completion and success of each knot were recorded. To compare baseline and post-training knot success, t tests and χ² analysis were performed.

Results

During baseline testing, residents successfully tied 26.7% of their knots (12 of 45 knots) in 352 ± 116 seconds (mean ± standard deviation). During post-training testing, residents successfully tied 66.7% of knots (30 of 45 knots, P = .00014) in 294 ± 63 seconds (P = .023), showing significant improvement in the time and ability to tie arthroscopic knots.

Conclusions

With a short cadaveric-based training period, orthopaedic trainees showed a significant improvement in their ability to tie arthroscopic knots on a commercially available benchtop knot-tying workstation. Given the initial low percentage of successfully tied knots and the limited opportunities for trainees to improve, trainees should be encouraged to practice and improve their skills.

Clinical Relevance

With training, residents can improve arthroscopic knot-tying abilities, which may allow them to successfully perform this critical task in the operating room.

Development of a Multivariable Model Based on Individual Risk Factors for Recurrent Lateral Patellar Dislocation

BACKGROUND

Nonoperative treatment after first-time patellar dislocation is the standard of care. There is evidence that certain patients may be at high risk for recurrent instability. The aim of this study was to develop a multivariable model to guide management of patients based on their individual risk of recurrent dislocation.

METHODS

A multivariable model was developed using 291 patients from 4 institutions to identify which patients were at higher risk for recurrent patellar dislocation within 2 years. This model was informed by a univariable logistic regression model developed to test factors based on the patient's history, physical examination, and imaging. The discriminatory ability of the model to classify who will or will not have a recurrent dislocation was measured using the area under the receiver operating characteristic curve (AUC).

RESULTS

Age, a history of a contralateral patellar dislocation, skeletal immaturity, lateral patellar tilt, tibial tubercle-trochlear groove (TT-TG) distance, Insall-Salvati ratio, and trochlear dysplasia were the most important factors for recurrent patellar dislocation. Sex, mechanism of injury, Caton-Deschamps ratio, sulcus angle, inclination angle, and facet ratio were not factors for recurrent dislocation. The overall AUC for the multivariable model was 71% (95% confidence interval [CI]: 64.7% to 76.6%).

CONCLUSIONS

Optimizing the management of lateral patellar dislocation will improve short-term disability from the dislocation and reduce the long-term risk of patellofemoral arthritis from repeated chondral injury. This multivariable model can identify patients who are at high risk for recurrent dislocation and would be good candidates for early operative treatment. Further validation of this model in a prospective cohort of patients will inform whether it can be used to determine the optimal treatment plan for patients presenting with an initial patellar dislocation. Until validation of the model is done with new patients, it should not be used in clinical practice.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

When Is an Orthopedic Intern Ready to Take Call?

OBJECTIVE

While orthopedic residency training varies among programs, an inevitable phenomenon is a transition for interns from consistent oversight to independent call with indirect supervision. It is therefore crucial to reliably assess trainees' ability to perform basic procedures. The objective of the study was to evaluate the utility of a novel Orthopaedic Intern Skills Assessment (OISA) to assess skill level.

DESIGN

In a cohort study, participants were evaluated on their ability to complete eleven skills in a simulated environment. Using a standardized patient and/or cadaveric specimen, we assessed skeletal traction, joint aspiration, joint injection, laceration repair, ankle brachial index measurement, compartment pressure monitoring, upper and lower extremity splinting, informed consent, spine trauma exam, and cervical spine clearance abilities.

SETTING

The assessment took place in a medical simulation lab at the Oregon Health & Science University in Portland, Oregon.

PARTICIPANTS

Third- or fourth-year medical students interested in orthopedics, incoming interns (preinterns), and residents within 1 month of completing their intern year (postinterns) were invited to participate in the study. All interested individuals were included. Of the 20 individuals contacted, 14 (70%) consented: 4 medical students (40%), 5 preinterns (100%), and 5 postinterns (100%). All consenting individuals finished their participation in the research.

RESULTS

Postintern skill completion rate was significantly higher than preinterns (p = 0.006) and medical students (p < 0.001). Completion rates for preinterns were also significantly higher rate than medical students (p = 0.035).

CONCLUSIONS

Our OISA found that postinterns had reached a basic orthopedic skill level expected of a junior resident without in-house supervision. Our OISA also highlighted areas of training that needed further attention, which will help orthopedic training programs verify an appropriate level of skill as trainees' progress from a supervised intern year to taking indirectly supervised junior resident call, and help identify areas where increased training is needed.

Comparison of Ligament Isometry and Patellofemoral Contact Pressures for Medial Patellofemoral Ligament Reconstruction Techniques in Skeletally Immature Patients

BACKGROUND

Adult medial patellofemoral ligament (MPFL) reconstruction techniques are not appropriate for the skeletally immature patient given the proximity of the distal femoral physis. Biomechanical consequences of reconstructions aimed at avoiding the physis have not been adequately studied.

PURPOSE

To quantify the biomechanical effects of MPFL reconstruction techniques intended for skeletally immature patients.

STUDY DESIGN

Controlled laboratory study.

METHODS

Four MPFL reconstruction techniques were evaluated using a computationally augmented cadaveric model: (1) Schoettle point: adult-type reconstruction; (2) epiphyseal: socket distal to the femoral physis; (3) adductor sling: graft wrapped around the adductor tendon; (4) adductor transfer: adductor tendon transferred to patella. A custom testing frame was used to cycle 8 knees for each technique from 10° to 110° of flexion. Patellofemoral kinematics were recorded using a motion camera system, contact stresses were recorded using Tekscan pressure sensors, and MPFL length was computed using an inverse kinematics computational model. Change in MPFL length, patellar facet forces, and patellar kinematics were compared using generalized estimating equation modeling.

RESULTS

Schoettle point reconstruction was the most isometric, demonstrating isometry from 10° to 100°. The epiphyseal technique was isometric until 60°, after which the graft loosened with increasing flexion. The adductor sling and adductor transfer techniques were significantly more anisometric from 40° to 110°. Both grafts tightened with knee flexion and resulted in significantly more lateral patellar tilt versus the intact state in early flexion and significantly higher contact forces on the medial facet versus the epiphyseal technique in late flexion.

CONCLUSION

In this cadaveric simulation, the epiphyseal technique allowed for a more isometric ligament until midflexion, when the patella engaged within the trochlear groove. The adductor sling and adductor transfer grafts became tighter in flexion, resulting in potential loss of motion, pain, graft stretching, and failure. Marginal between-condition differences in patellofemoral contact mechanics and patellar kinematics were observed in late flexion.

CLINICAL RELEVANCE

In the skeletally immature patient, using an epiphyseal type MPFL reconstruction with the femoral attachment site distal to the physis results in a more isometric graft compared with techniques with attachment sites proximal to the physis.

COVID-19 in Australia: Impacts on Separated Families, Family Law Professionals, and Family Courts

Around the globe, many families are experiencing significant anxieties linked to COVID-19. These include health concerns and economic pressures, both of which are frequently taking place against a backdrop of various levels of social isolation. In addition, many parents have been juggling home schooling requirements in the face of radically different work arrangements including the loss of employment altogether. Unsurprisingly, additional challenges and stresses are emerging for separated families, family law professionals, and family courts. In this article - written at a point-in-time in a rapidly evolving COVID-19 context - we reflect on key challenges for separated families in Australia, and some of the emerging professional responses.

Surgical Simulation Maximizing the Use of Fresh-Frozen Cadaveric Specimens: Examination of Tissue Integrity Using Ultrasound

BACKGROUND

Arthroscopic surgical simulation, including the use of cadaveric tissue, is valuable for training orthopedic surgery residents. However, it is unclear how often fresh-frozen cadaveric tissue can be reused to provide a reproducible model for developing arthroscopic skills.

OBJECTIVE

We determined the usefulness of ultrasound in evaluating tissue degradation in fresh-frozen shoulder and knee joints used for surgical simulation.

METHODS

Between February 7 and April 11, 2017, orthopedic residents participated in 6 wet lab sessions during 1 rotation. Knee and shoulder specimens were subjected to ultrasound using a SonoSite Edge machine and a linear probe after each freeze-and-thaw cycle. Degradation of each structure was determined based on standards created for living tissue and comparisons to previous images of the same tissue before initial use.

RESULTS

Ultrasonographic assessment of the 2 knee and 2 shoulder specimens revealed lost integrity in subcutaneous fat and muscle with evidence of increased hypoechoicity and loss of normal fiber orientation and density in all specimens examined. Tendons, ligaments, cartilage, iliotibial band, and bone did not lose integrity during freezing and thawing. Ultrasonographic assessment revealed no loss of joint structure integrity. However, the intra-articular work assigned for the simulation curriculum had been carried out to a degree that by the third use, little opportunity remained for further arthroscopic practice on that specimen.

CONCLUSIONS

In this study, ultrasound findings showed that fresh-frozen shoulder and knee specimens maintained structural integrity useful for simulation training after 3 cycles of freezing.

A biomechanical comparison of all-inside cruciate ligament graft preparation techniques

Background

The all-inside cruciate ligament graft preparation technique has become popular due to its utility in sparing a growing physis, preserving a tendon in ACL surgery, and/or reduction of pain. However, few studies have compared graft preparation techniques to determine the ideal construct for cruciate ligament reconstruction. We sought to compare biomechanical properties of two quadrupled all-inside cruciate ligament graft preparation techniques and three alternative all-inside graft preparation techniques that may be used when the available tendon is too short to be quadrupled.

Methods

Fifty porcine extensor tendons were evenly divided into five groups (n = 10) representing all-inside graft preparation techniques, including two quadrupled (Quad-A, Quad-B) and three alternative methods (Tripled, Folded, Two-Doubled). Each graft construct underwent preconditioning (10 loading cycles from 20 to 50 N at 0.1 Hz), cyclic loading (500 loading cycles from 50 to 250 N at 1.0 Hz) and load-to-failure (tension applied at 20 mm/min).

Results

Quad-A and Quad-B demonstrated no significant differences in cyclic displacement (10.5 ± 0.3 vs 11.7 ± 0.4 mm; p = 0.915), cyclic stiffness (1086.2 ± 487.3 vs 460.4 ± 71.4 N/mm; p = 0.290), pullout stiffness (15.9 ± 4.3 vs 7.4 ± 4.4 N/mm; p = 0.443), ultimate failure load (641.2 ± 84.7 vs 405.9 ± 237.4 N; p = 0.672), or ultimate failure displacement (47.3 ± 6.7 vs 55.5 ± 0.7 mm; p = 0.778). The mean cyclic displacement of the Two-Doubled group was significantly greater than the Quad-A (29.7 ± 2.2 vs 10.5 ± 0.3 mm; p < 0.001), Quad-B (29.7 ± 2.2 vs 11.7 ± 0.4 mm; p < 0.001), Tripled (29.7 ± 2.2 vs 11.3 ± 0.2 mm; p < 0.001), and Folded group (29.7 ± 2.2 vs 13.3 ± 0.2 mm; p < 0.001). There were no other statistically significant differences between the three alternative all-inside graft preparation techniques.

Conclusion

The current study demonstrates the biomechanical properties of two quadrupled all-inside graft constructs, Quad-A and Quad-B, are not significantly different. When the available tendon is of insufficient length, the Two-Doubled group demonstrated more than twice the cyclic displacement of all other graft preparation techniques, and is therefore not recommended for use in all-inside cruciate ligament reconstruction.

Firefighters Have a Higher Incidence of Trochlear Chondral Lesions than the Normal Population

BACKGROUND

Firefighters' knees are subjected to significant dynamic and static forces, resulting in increased knee complaints and a higher relative risk of osteoarthrosis, compared with aged-matched office workers. Firefighters wear or carry a total of 80 to 100 lbs. of gear while performing intensive physical activity.

PURPOSE/QUESTION

The purpose of this study was to determine whether a central femoral trochlear lesion was observed in firefighters undergoing knee arthroscopy for other diagnoses.

METHODS

A retrospective chart review of 159 knees in 146 firefighters undergoing arthroscopy for treatment of acute meniscal injury or anterior cruciate ligament reconstruction over a 14-year period was undertaken. Patient demographics, physical examination results, trochlear lesion size and grade, and firehouse type (engine vs. ladder company) and firefighter position (seniority) were recorded. Comparisons of characteristics in those with and without trochlear lesions were performed.

RESULTS

The average patient age was 42.2 years (range, 27 to 64 years). Ninety-eight knees (62%) had trochlear lesions and 33 knees (51%) had matching patellar lesions. Patients with lesions were older (43.2 vs. 40.5 years). Mean trochlear lesion size was 19.5 ± 13.7 mm by 18.9 ± 12.4 mm. Lesion grade distribution was grade 1 or 2 in 24 knees (24%) and grade 3 or 4 in 67 knees (44%). Trochlear lesion presence was associated with a body mass index of over 30. Current engine company members had more advanced lesions.

CONCLUSIONS

A "firefighter's trochlea" was present in the majority of firefighters undergoing knee arthroscopy. Higher age and longer tenure as a firefighter prior to surgery were associated with more advanced lesions. Firefighters working in engine companies at the time of arthroscopy were at a greater risk of developing low-grade lesions but not high-grade lesions. Firefighters move between ladder and engine companies, thus a definitive association with company type cannot be reached in this retrospective study. This lesion may reflect the increase in patellofemoral biomechanical stresses secondary to the physical demands of the occupation.

Use of TT-PCL versus TT-TG

PURPOSE OF REVIEW

The tibial tubercle-to-trochlear groove (TT-TG) distance and tibial tubercle-to-posterior cruciate ligament (TT-PCL) distance have both been proposed for use in the evaluation of patients with patellofemoral instability.

RECENT FINDINGS

While the TT-TG value may be confounded by several factors, including age, gender, body mass index, and varying degrees of knee flexion on cross-sectional imaging, recent literature supports its utility for differentiation of patients with and without patellofemoral instability, and stratification of patients with and without coronal malalignment. The TT-PCL describes pure lateralization of the tibial tubercle, and may be used in conjunction with the TT-TG to better understand the path taken by the extensor mechanism of the knee joint. The TT-TG measurement is superior to the TT-PCL measurement for differentiating patients with patellofemoral instability from their stable counterparts, though TT-PCL may be useful in conjunction with TT-TG for better understanding the path of the extensor mechanism across the knee joint.

Comparison of fluoroscopic techniques for assessment of femoral rotational alignment

Objectives:

Anatomic rotational reduction of diaphyseal femur fractures is essential in restoring limb mechanics. Errors in reproducing anteroposterior (AP) or lateral knee reference radiographs of the contralateral limb could result in inaccuracies during rotational reduction. The objective of this study was to examine whether fluoroscopic rotational variation can be observed with the same degree of precision with AP and lateral distal femur projections.

Methods:

AP and lateral radiographs were obtained from intact knees of 7 cadaveric specimens using fluoroscopy. The lateral condylar width and coronal femoral width from the AP images and the posterior condylar offset and sagittal femoral width from the lateral images were measured by 3 reviewers. Interclass correlation coefficients (ICCs) among the 3 reviewers were calculated. The mean data from all reviewers were plotted against angle of rotation, and the slope (M) and regression of the line were then determined.

Results:

ICCs were 0.997 (lateral) and 0.994 (AP), demonstrating excellent interobserver agreement. The mean (±SD) M value for lateral images was 0.016 ± 0.001 and for AP images was 0.009 ± 0.001 (P < .0001). The higher lateral M value represents a more appreciable difference in size of the measured segment for the same rotational change.

Conclusions:

The observed rotational change was 1.76 times greater on lateral images compared to AP images; thus, the lateral images may be more precise as a reference for rotation. The routine use of lateral knee radiographs to guide intraoperative rotational alignment of the femur may therefore be justified.

Clinical Outcomes After Isolated Medial Patellofemoral Ligament Reconstruction for Patellar Instability Among Patients With Trochlear Dysplasia

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction has become one of the most common and widely used procedures to regain stability among patients with recurrent lateral patellar dislocation. While recent studies demonstrated low recurrence rates, improved patient-reported outcome measures, and a high rate of return to sports, limited literature explored its effectiveness as an isolated intervention in the context of trochlear dysplasia.

PURPOSE

To determine the efficacy of isolated MPFL reconstruction in treating patellar instability in the setting of trochlear dysplasia.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This was a retrospective review of consecutive patients who underwent uni- or bilateral medial patellofemoral ligament reconstruction for patellofemoral instability with a minimum 2-year follow-up. No osteotomies were included. Pre- and postoperative assessment included ligamentous laxity, patellar crepitus, tilt, translation, apprehension, and radiographic features, including tibial tubercle-trochlear groove (TT-TG) distance, Dejour classification, and Caton-Deschamps index.

RESULTS

A total of 121 MPFL reconstructions were included. Mean age at surgery was 23.8 years, and 4.4 dislocation events occurred before surgery. Mean follow-up was 44 months; 76% of patients were female. Mean preoperative TT-TG ratio was 13.5, and mean Caton-Deschamps ratio was 1.2; 92% of patients had Dejour B, C, or D trochlear dysplasia. Kujala score improved from 55.0 preoperatively to 90.0 ( P < .001). Almost all patients (94.5%) were able to return to sports at 1 year, with 74% returning to the same or higher level of play. Only 3 patients reported a postoperative dislocation or subluxation event.

DISCUSSION

For patients without significantly elevated TT-TG distances or significant patella alta, isolated MPFL reconstruction provides a safe and effective treatment for patellofemoral instability, despite the presence of trochlear dysplasia. Most patients are able to return to sports by 1 year postoperatively at the same or higher level of play.

Anisometry of Medial Patellofemoral Ligament Reconstruction in the Setting of Increased Tibial Tubercle-Trochlear Groove Distance and Patella Alta

PURPOSE

To assess the impact elevated tibial tubercle-trochlear groove (TT-TG) distance and patella height, as measured by the Caton-Deschamps Index (CDI), have on the isometry of a reconstructed medial patellofemoral ligament (MPFL).

METHODS

Nine fresh-frozen cadaveric knees were placed on a custom testing fixture, with a fixed femur and a mobile tibia. A suture fixed to the MPFL origin on the patella and free to move at the Schöttle point on the femur represented a reconstructed MPFL. A local coordinate system was established, and retroreflective markers attached to the suture quantified MPFL length changes by use of a 3-dimensional motion capture system. The tubercle was transferred to create TT-TG distances of 20 mm and 25 mm and CDIs of 1.2 and 1.4 (patella alta). Recordings of the MPFL suture length change as the knee was brought through a range of motion were made using all combinations of tubercle anatomy in a randomized order for each specimen. A generalized estimating equation modeling technique was used to analyze and control for the clustered nature of the data.

RESULTS

Knees with native tibial tubercle anatomy showed MPFL isometry through 20° to 70° range of motion. Tibial tubercle lateralization (increased TT-TG distance) significantly altered MPFL isometry with a TT-TG distance of 20 mm (P < .0001). Patella alta significantly altered MPFL isometry with a CDI of 1.2 (P = .0182). The interaction of tibial tubercle lateralization combined with patella alta significantly increased the amount of anisometry seen in the reconstructed MPFL (P < .001).

CONCLUSIONS

Increased tibial tubercle lateralization and patella alta produce anisometry in an MPFL reconstruction using currently recommended landmarks, leading to potentially increased graft tension and potential failure.

CLINICAL RELEVANCE

Tibial tubercle transfer should be considered when performing an MPFL reconstruction for recurrent patellofemoral instability in the setting of significant patella alta and an elevated TT-TG distance-especially when both are present-because an isolated MPFL reconstruction will be prone to failure given the anisometry shown in this study.

Cerebral organoids derived from Sandhoff disease-induced pluripotent stem cells exhibit impaired neurodifferentiation

Sandhoff disease, one of the GM2 gangliosidoses, is a lysosomal storage disorder characterized by the absence of β-hexosaminidase A and B activity and the concomitant lysosomal accumulation of its substrate, GM2 ganglioside. It features catastrophic neurodegeneration and death in early childhood. How the lysosomal accumulation of ganglioside might affect the early development of the nervous system is not understood. Recently, cerebral organoids derived from induced pluripotent stem (iPS) cells have illuminated early developmental events altered by disease processes. To develop an early neurodevelopmental model of Sandhoff disease, we first generated iPS cells from the fibroblasts of an infantile Sandhoff disease patient, then corrected one of the mutant HEXB alleles in those iPS cells using CRISPR/Cas9 genome-editing technology, thereby creating isogenic controls. Next, we used the parental Sandhoff disease iPS cells and isogenic HEXB-corrected iPS cell clones to generate cerebral organoids that modeled the first trimester of neurodevelopment. The Sandhoff disease organoids, but not the HEXB-corrected organoids, accumulated GM2 ganglioside and exhibited increased size and cellular proliferation compared with the HEXB-corrected organoids. Whole-transcriptome analysis demonstrated that development was impaired in the Sandhoff disease organoids, suggesting that alterations in neuronal differentiation may occur during early development in the GM2 gangliosidoses.

Magnetic Resonance Imaging Validation of Tibial Tubercle Transfer Distance in the Fulkerson Osteotomy: A Clinical and Cadaveric Study

PURPOSE

To validate the medialization and anteriorization distances, and the osteotomy angle of anteromedialization tibial tubercle osteotomies using postoperative axial imaging.

METHODS

From March 2004 to August 2015, 117 consecutive patients who underwent anteromedialization osteotomies of the tibial tubercle by a single surgeon were identified. Only patients with pre- and postoperative magnetic resonance imaging (MRI) studies were included. Using MRI multiplanar reformats, distances that the tibial tubercle was translated medially (medialization) and anteriorly (anteriorization) were measured. In addition, the osteotomy angle was measured on the postoperative MRI. The measured values were compared with intraoperative estimates. Tibial tubercle osteotomies were then performed on 3 cadaveric knee specimens and imaged with pre- and postprocedure MRIs to correlate intraoperative measurements with MRI findings.

RESULTS

A total of 40 patients (41 knees) (34.2%) had both pre- and postoperative MRIs and were included. Compared with intraoperative assessment, MRI measured medialization values average 94.7% (standard deviation [SD] 37.7) of dictated values (P = .1). MRI measured anteriorization averaged less than half of dictated values (48.9%, SD 18.2%, P < .0001). MRI measured osteotomy angles averaged 67.2% of dictated values (SD 50.3%, P < .0001). The steepest osteotomy angle that could be performed without violating the posterior cortex and/or endangering the posterior neurovascular structures was 46.3°.

CONCLUSIONS

Surgeons often overestimate both the anteriorization distance and the osteotomy angle in anteromedialization tibial tubercle osteotomies. The steepest osteotomy angle is less than the 60° described in the literature. Modifications should be considered when more anteriorization is desired with tubercle transfers.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Wearable Inertial Sensors Allow for Quantitative Assessment of Shoulder and Elbow Kinematics in a Cadaveric Knee Arthroscopy Model

PURPOSE

To develop a model using wearable inertial sensors to assess the performance of orthopaedic residents while performing a diagnostic knee arthroscopy.

METHODS

Fourteen subjects performed a diagnostic arthroscopy on a cadaveric right knee. Participants were divided into novices (5 postgraduate year 3 residents), intermediates (5 postgraduate year 4 residents), and experts (4 faculty) based on experience. Arm movement data were collected by inertial measurement units (Opal sensors) by securing 2 sensors to each upper extremity (dorsal forearm and lateral arm) and 2 sensors to the trunk (sternum and lumbar spine). Kinematics of the elbow and shoulder joints were calculated from the inertial data by biomechanical modeling based on a sequence of links connected by joints. Range of motion required to complete the procedure was calculated for each group. Histograms were used to compare the distribution of joint positions for an expert, intermediate, and novice.

RESULTS

For both the right and left upper extremities, skill level corresponded well with shoulder abduction-adduction and elbow prono-supination. Novices required on average 17.2° more motion in the right shoulder abduction-adduction plane than experts to complete the diagnostic arthroscopy (P = .03). For right elbow prono-supination (probe hand), novices required on average 23.7° more motion than experts to complete the procedure (P = .03). Histogram data showed novices had markedly more variability in shoulder abduction-adduction and elbow prono-supination compared with the other groups.

CONCLUSIONS

Our data show wearable inertial sensors can measure joint kinematics during diagnostic knee arthroscopy. Range-of-motion data in the shoulder and elbow correlated inversely with arthroscopic experience. Motion pattern-based analysis shows promise as a metric of resident skill acquisition and development in arthroscopy.

CLINICAL RELEVANCE

Wearable inertial sensors show promise as metrics of arthroscopic skill acquisition among residents.

The Tibial Tubercle-to-Trochlear Groove Distance Is Reliable in the Setting of Trochlear Dysplasia, and Superior to the Tibial Tubercle-to-Posterior Cruciate Ligament Distance When Evaluating Coronal Malalignment in Patellofemoral Instability

PURPOSE

To determine best practices for consistent and accurate evaluation of coronal alignment in patients with patellofemoral (PF) instability.

METHODS

Six reviewers examined 239 knee magnetic resonance images (MRIs) in patients with PF instability and anterior cruciate ligament (ACL) rupture. Measurements included tibial tubercle-to-trochlear groove (TT-TG) distance measured at the most proximal and distal portions of the trochlea, tibial tubercle-to-PCL (TT-PCL) distance, and Dejour classification of trochlear dysplasia.

RESULTS

Interrater reliability was low for Dejour classification (k = 0.289), but improved to moderate (k = 0.448) when patients were separated into normal/Dejour A and Dejour B/C/D. Interrater reliability was high for proximal and distal TT-TG measurements (interclass correlation coefficients [ICCs] = 0.807 and 0.936, respectively). TT-PCL was moderately reliable (ICC = 0.625), and correlated with TT-TG (r = 0.457, P < .001 proximal and r = 0.451, P < .001 distal). No significant difference was found between the proximal and distal measurements of TT-TG in each patient, though the PF group exhibited higher values than the ACL group (P < .001 for both). TT-PCL was significantly higher for the PF group than the ACL group (P = .015), but this difference lost significance when the group was divided by the TT-PCL cutoff of 24 mm (P = .371).

CONCLUSIONS

The proximal and distal techniques for measuring the TT-TG distance are similar to each other, and reliable despite level of reviewer training or presence of dysplasia. The TT-TG distance was predictive of patellofemoral instability. The TT-PCL distance was found to be less reliable than either method of measuring the TT-TG distance. Thus, this study demonstrated TT-TG to be superior to TT-PCL as a measurement of coronal malalignment. Given the variability in Dejour classification in this and other studies, a more reliable classification system for trochlear dysplasia as defined on cross-sectional imaging is warranted.

LEVEL OF EVIDENCE

Level III, retrospective clinical trial.

Antibody gene transfer with adeno-associated viral vectors as a method for HIV prevention

Broadly neutralizing antibodies (bNAbs) against human immunodeficiency virus (HIV) show great promise in HIV prevention as they are capable of potently neutralizing a considerable breadth of genetically diverse strains. Passive transfer of monoclonal bNAb proteins can confer protection in animal models of HIV infection at modest concentrations, inspiring efforts to develop an HIV vaccine capable of eliciting bNAb responses. However, these antibodies demonstrate high degrees of somatic mutation and other unique characteristics that may hinder the ability of conventional approaches to consistently and effectively produce bNAb analogs. As an alternative strategy, we and others have proposed vector-mediated gene transfer to generate long-term, systemic production of bNAbs in the absence of immunization. Herein, we review the use of adeno-associated virus (AAV) vectors for delivery of HIV bNAbs and antibody-like proteins and summarize both the advantages and disadvantages of this strategy as a method for HIV prevention.

Return to Activities After Patellofemoral Arthroplasty

Patellofemoral arthroplasty (PFA) is used to treat isolated patellofemoral arthritis, but little is known about post-PFA activity levels and functional outcome scores. We reviewed 48 consecutive cases (39 patients) of PFAs performed between 2009 and 2014. Three validated patient-reported outcome measures (Kujala score, Lysholm score, International Knee Documentation Committee score) were used to evaluate knee function before and after surgery. Patient-reported outcome measures were significantly improved after surgery. Return to previous preferred activity was reported by 72.2% of patients, and 52.8% of patients reported returning to the same activity level or to a higher level. Historically, the literature evaluating knee arthroplasty outcomes has focused on implant survivorship, pain relief, and patient satisfaction. Our findings show that patients who undergo PFA have a high rate of return to their preferred activities. These findings can be used to inform patients who want to remain active after PFA.

MED23-associated intellectual disability in a non-consanguineous family

Intellectual disability (ID) is a heterogeneous condition arising from a variety of environmental and genetic factors. Among these causes are defects in transcriptional regulators. Herein, we report on two brothers in a nonconsanguineous family with novel compound heterozygous, disease-segregating mutations (NM_015979.3: [3656A > G];[4006C > T], NP_057063.2: [H1219R];[R1336X]) in MED23. This gene encodes a subunit of the Mediator complex that modulates the expression of RNA polymerase II-dependent genes. These brothers, who had profound ID, spasticity, congenital heart disease, brain abnormalities, and atypical electroencephalography, represent the first case of MED23-associated ID in a non-consanguineous family. They also expand upon the clinical features previously reported for mutations in this gene.

Removal of FMRI environment artifacts from EEG data using optimal basis sets

The combination of functional magnetic resonance imaging (FMRI) and electroencephalography (EEG) has received much recent attention, since it potentially offers a new tool for neuroscientists that makes simultaneous use of the strengths of the two modalities. However, EEG data collected in such experiments suffer from two kinds of artifact. First, gradient artifacts are caused by the switching of magnetic gradients during FMRI. Second, ballistocardiographic (BCG) artifacts related to cardiac activities further contaminate the EEG data. Here we present new methods to remove both kinds of artifact. The methods are based primarily on the idea that temporal variations in the artifacts can be captured by performing temporal principal component analysis (PCA), which leads to the identification of a set of basis functions which describe the temporal variations in the artifacts. These basis functions are then fitted to, and subtracted from, EEG data to produce artifact-free results. In addition, we also describe a robust algorithm for the accurate detection of heart beat peaks from poor quality electrocardiographic (ECG) data that are collected for the purpose of BCG artifact removal. The methods are tested and are shown to give superior results to existing methods. The methods also demonstrate the feasibility of simultaneous EEG/FMRI experiments using the relatively low EEG sampling frequency of 2048 Hz.

Digital mammography: a world without film?

OBJECTIVES

eDiaMoND is a next generation Internet ("Grid") multidisciplinary research project funded by the UK e-Science Programme with the following objectives; the development of a next generation Internet enabled prototype to demonstrate the potential benefits of a national infrastructure to support digital mammography; the exploration of potential benefits for digital mammography systems, with particular emphasis being placed on selected applications, namely, screening, training, computer-aided detection and appropriate support for epidemiological studies.

METHODS

EDiaMoND has worked in conjunction with selected clinical partners to enable the collection of valuable mammography information and the design of applications based upon extensive requirements gathering exercises. The clinical partners validated both the immediate needs and assisted with defining future needs of such an architecture to support the UK Health Service.

RESULTS

The project has succeeded in invoking the interest of clinical partners and representatives of the UK NHS Breast Screening Programme in our vision of a world without film, albeit a long way off. The project has also succeeded in identifying the barriers to adopting this approach with the current limitations within the NHS, and has developed a blueprint for working towards this strategy.

CONCLUSIONS

A UK national digital mammography archive has the potential to provide major benefits for the UK. For example, such an archive could: ensure that previous mammograms are always available, and could link up seamlessly the screening, assessment and symptomatic clinics; it could provide a huge teaching and training resource; it could be a huge resource for epidemiological studies.

Fusion of contrast-enhanced breast MR and mammographic imaging data

Increasing use is being made of Gd-DTPA contrast-enhanced MRI (CE-MRI) for breast cancer assessment since it provides three-dimensional (3D) functional information via pharmacokinetic interaction between contrast agent and tumour vascularity, and because it is applicable to women of all ages as well as patients with post-operative scarring. CE-MRI is complementary to conventional X-ray mammography, since it is a relatively low-resolution functional counterpart of a comparatively high-resolution 2D structural representation. However, despite the additional information provided by MRI, mammography is still an extremely important diagnostic imaging modality, particularly for several common conditions such as ductal carcinoma in situ (DCIS) where it has been shown that there is a strong correlation between microcalcification clusters and malignancy. Pathological indicators such as calcifications and fine spiculations are not visible in CE-MRI and therefore there is clinical and diagnostic value in fusing the high-resolution structural information available from mammography with the functional data acquired from MRI. This article is a clinical overview of the results of a technique to transform the coordinates of regions of interest (ROIs) from the 2D mammograms to the spatial reference frame of the contrast-enhanced MRI volume. An evaluation of the fusion framework is demonstrated with a series of clinical cases and a total of 14 patient examples.

Changes in connectivity profiles define functionally distinct regions in human medial frontal cortex

A fundamental issue in neuroscience is the relation between structure and function. However, gross landmarks do not correspond well to microstructural borders and cytoarchitecture cannot be visualized in a living brain used for functional studies. Here, we used diffusion-weighted and functional MRI to test structure-function relations directly. Distinct neocortical regions were defined as volumes having similar connectivity profiles and borders identified where connectivity changed. Without using prior information, we found an abrupt profile change where the border between supplementary motor area (SMA) and pre-SMA is expected. Consistent with this anatomical assignment, putative SMA and pre-SMA connected to motor and prefrontal regions, respectively. Excellent spatial correlations were found between volumes defined by using connectivity alone and volumes activated during tasks designed to involve SMA or pre-SMA selectively. This finding demonstrates a strong relationship between structure and function in medial frontal cortex and offers a strategy for testing such correspondences elsewhere in the brain.

Characterization and propagation of uncertainty in diffusion-weighted MR imaging

A fully probabilistic framework is presented for estimating local probability density functions on parameters of interest in a model of diffusion. This technique is applied to the estimation of parameters in the diffusion tensor model, and also to a simple partial volume model of diffusion. In both cases the parameters of interest include parameters defining local fiber direction. A technique is then presented for using these density functions to estimate global connectivity (i.e., the probability of the existence of a connection through the data field, between any two distant points), allowing for the quantification of belief in tractography results. This technique is then applied to the estimation of the cortical connectivity of the human thalamus. The resulting connectivity distributions correspond well with predictions from invasive tracer methods in nonhuman primate.

Non-invasive mapping of connections between human thalamus and cortex using diffusion imaging

Evidence concerning anatomical connectivities in the human brain is sparse and based largely on limited post-mortem observations. Diffusion tensor imaging has previously been used to define large white-matter tracts in the living human brain, but this technique has had limited success in tracing pathways into gray matter. Here we identified specific connections between human thalamus and cortex using a novel probabilistic tractography algorithm with diffusion imaging data. Classification of thalamic gray matter based on cortical connectivity patterns revealed distinct subregions whose locations correspond to nuclei described previously in histological studies. The connections that we found between thalamus and cortex were similar to those reported for non-human primates and were reproducible between individuals. Our results provide the first quantitative demonstration of reliable inference of anatomical connectivity between human gray matter structures using diffusion data and the first connectivity-based segmentation of gray matter.

Detecting the brain surface in sparse MRI using boundary models

We introduce a framework for the detection of the brain boundary (arachnoid) within sparse MRI. We use the term sparse to describe volumetric images in which the sampling resolution within the imaging plane is far higher than that of the perpendicular direction. Generic boundary detection schemes do not provide good results for such data. In the scheme we propose, the boundary is extracted using a constrained mesh surface which iteratively approximates a 3D point set consisting of detected boundary points. Boundary detection is based on a database of piecewise constant models, which represent the idealised MR intensity profile of the underlying boundary anatomy. A non-linear matching scheme is introduced to estimate the location of the boundary points using only the intensity data within each image plane. Results are shown for a number of images and are discussed in detail.

Estimation of compressed breast thickness during mammography

To estimate radiation dose during mammography the breast thickness must be known. We present a new method for estimating the thickness of a compressed breast using only the breast image as projected onto a mammogram, calibration data such as the mAs value and image processing techniques. The method proves to be of high accuracy (+/- 0.2 cm for craniocaudal mammograms) and has the advantage over other methods of allowing retrospective estimation of thickness.

Mammographic image analysis

We describe our recent progress aimed at computer analysis of mammograms. The overall aim is to provide the clinician with reliable quantitative information. We summarise a representation we have developed of the 'interesting' (non-adipose) tissue in a breast, then put the representation to work in three ways: (i) to propose a new quantitative measure to aid in diagnosing masses; (ii) to explore the possibility of reducing by half the radiation dose required for a mammogram; and (iii) recalling some of the results that can be provided by differential compression mammography, in which mammograms are taken at two slightly different compressions.

Detecting approximal dental caries with transillumination: a clinical evaluation

Independent examinations of 300 patients were conducted to evaluate fiber optic transillumination's performance in caries detection. FOTI was used as an adjunct to clinical and radiographic examinations for caries, restoration or secondary caries of approximal surfaces in maxillary anterior permanent teeth. Clinical and radiographic examinations were significantly more effective.

Computing the scatter component of mammographic images

The authors build upon a technical report (Tech. Report OUEL 2009/93, Engng. Sci., Oxford Uni., Oxford, UK, 1993) in which they proposed a model of the mammographic imaging process for which scattered radiation is a key degrading factor. Here, the authors propose a way of estimating the scatter component of the signal at any pixel within a mammographic image, and they use this estimate for model-based image enhancement. The first step is to extend the authors' previous model to divide breast tissue into "interesting" (fibrous/glandular/cancerous) tissue and fat. The scatter model is then based on the idea that the amount of scattered radiation reaching a point is related to the energy imparted to the surrounding neighbourhood. This complex relationship is approximated using published empirical data, and it varies with the size of the breast being imaged. The approximation is further complicated by needing to take account of extra-focal radiation and breast edge effects. The approximation takes the form of a weighting mask which is convolved with the total signal (primary and scatter) to give a value which is input to a "scatter function", approximated using three reference cases, and which returns a scatter estimate. Given a scatter estimate, the more important primary component can be calculated and used to create an image recognizable by a radiologist. The images resulting from this process are clearly enhanced, and model verification tests based on an estimate of the thickness of interesting tissue present proved to be very successful. A good scatter model opens the was for further processing to remove the effects of other degrading factors, such as beam hardening.

Evolution of the rat kallikrein gene family: gene conversion leads to functional diversity

Kallikrein-like simple serine proteases are encoded by closely related members of a gene family in several mammalian species. Molecular cloning and genomic Southern blot analysis after conventional and pulsed-field gel electrophoresis indicate that the rat kallikrein gene family comprises 15-20 members, probably closely linked at a single locus. Determination of the nucleotide sequences of the rGK-3, -4, and -6 genes here completes sequence data for a total of nine rat kallikrein family members. Comparison of the rat gene sequences to each other and to those of human and mouse kallikrein family genes reveals patterns of relatedness indicative of concerted evolution. Analysis of nucleotide sequence variants in kallikrein family members shows that most sequence variants are shared by multiple family members; the patterns of shared variants are complex and indicate multiple short gene conversions between family members. Sequence exchanges between family members generate novel assortments of variants in amino acid coding regions that may affect substrate specificity and thereby contribute to the diversity of enzyme activity. Furthermore, small sequence exchanges also may play a role in generating the diverse patterns of tissue-specific expression of rat family members. These analyses indicate an important role for gene conversion in the evolution of the functional diversity of these duplicated genes.

The expression of two kallikrein gene family members in the rat kidney

The mRNAs for two kallikrein gene family members expressed in the rat kidney have been characterized. One mRNA (PS) has previously been found in the pancreas and submaxillary gland and encodes true kallikrein. The second mRNA (K1) encodes a novel kallikrein-like enzyme expressed in the kidney and submaxillary gland that retains many of the key amino acid residues for the characteristic enzymatic cleavage specificity of kallikrein. Two oligonucleotide hybridization probes specific for the K1 mRNA demonstrate that the K1 mRNA is expressed in the kidney and submaxillary gland, but in none of the other eight tissues known to express one or more members of the rat kallikrein gene family. The K1 mRNA is the dominant kallikrein-related mRNA of the kidney, expressed at roughly 10 times the level of the true kallikrein (PS) mRNA. In the submaxillary gland the K1 mRNA is expressed at roughly one-fourth the level of true kallikrein mRNA.

Expression of two kallikrein gene family members in the rat prostate

We have characterized two kallikrein gene family members expressed in the prostate and submaxillary glands of rats. One mRNA (S3) is identical with the previously characterized submaxillary gland S3 mRNA that encodes an enzyme closely related to tonin. The second mRNA (P1) encodes a novel kallikrein-like enzyme that retains key amino acid residues responsible for the characteristic enzymatic cleavage specificity of kallikrein. Two P1-specific oligonucleotide probes derived from the P1 mRNA sequence were used to demonstrate the presence of P1 mRNA in the prostate and submaxillary glands and its absence in eight other rat tissues known to express one or more members of the kallikrein family. The P1-coding gene (rGK-8) was identified among genomic clones containing kallikrein family members by hybridization with a P1-specific oligonucleotide probe. The identification of the P1 gene was verified by nucleotide sequencing; the exon sequences of rGK-8 match the P1 mRNA sequence. The upstream region of rGK-8, where transcriptional regulatory elements likely reside, is very similar to that of other rat kallikrein family genes which are expressed in distinct tissue-specific patterns.

Organization and expression of the rat kallikrein gene family

We have cloned and characterized eight members of the kallikrein gene family from rat genomic DNA. Three of the cloned genes correspond to the previously characterized kallikrein family mRNAs PS, S2, and P1, which encode true kallikrein, tonin, and a novel kallikrein-like enzyme, respectively. In two cases, two kallikrein family genes are located on single genomic clones, suggesting close linkage of this family in the rat genome. Based on the total number of cloned genes and mRNAs, the minimum size of the rat family is 11 genes. Comparisons between the rat genes demonstrate a high degree of nucleotide sequence identity (greater than 80%) in exonic, intronic, and nearby flanking regions. This extensive sequence conservation not limited to clearly functional domains suggests that concerted evolution of this gene family has occurred. Despite the high overall sequence conservation among the rat family members, several discrete regions of high variability exist in the coding regions. We have defined the tissue-specific expression of the PS (true kallikrein), S2 (tonin), and S3 mRNAs with gene-specific oligonucleotide probes derived from these variant regions. PS is expressed in a wide range of tissues, while S2 mRNA is restricted to the submaxillary gland and S3 mRNA to the submaxillary and prostate glands. The high sequence conservation within the upstream flanking regions of these genes suggests that a small number of nucleotide differences determines the disparate transcriptional specificity of individual family members.

Scanning microscopy of resin infiltration patterns in acid-etched incisor enamel

Previous studies have described the surface morphologic characteristics of acid-etched enamel. The purpose of this investigation was to examine the patterns of resin infiltration into the etched enamel. Fourteen, human, incisor teeth, extracted because of advanced periodontal disease, were etched on the labial surfaces for 60 seconds with 37% phosphoric acid, washed in tap water, and then air-dried. A self-cured enamel resin was applied to the etched labial surface and supported with epoxy. The teeth were dissolved in formic acid. The resin remnants were cleaned in water, dried, mounted on specimen stubs, coated with sputtered gold, and examined in a Scanning electron microscope (SEM). Resin infiltration patterns were photographed in the SEM at a magnification of 400 in 0.125-mm2 areas of the incisal, middle, and gingival thirds of each labial surface. Resin infiltration patterns were scored according to the correspondence with the rod-core, rod-periphery, and irregular acid-etch patterns seen in enamel. The distribution of resin infiltration patterns was as follows: rod-core, 9.7%; rod-periphery, 40.5%; and irregular, 49.7%. The values were averaged over all the surface areas. Infiltration patterns into the etched enamel exhibited deep interperikymata resin penetration. Subsurface channeling of resin was responsible for the pattern seen in irregular etch and was the most common form of infiltration in the gingival region. Subsurface channeling may be related to the development of micropores observed in incipient carious lesions. Deep monomer penetration and channeling may be important factors in mechanical attachment.

Scanning electron microscopy of submandibular sialoliths: a preliminary report

This report compares the scanning electron microscopic appearances of the structures in two sialoliths, one surgically removed, the other naturally exfoliated. The first exhibited the typical structure of a lamellated outer layer with an amorphous core. The core contained a large number of structures resembling calcified filamentous organisms. The second consisted of a similar outer lamella but the core contained crystal-lined spaces, amorphous matrix and an heterogeneous array of crystal shapes: there were no structures resembling organisms.

Androgen dependence of specific kallikrein gene family members expressed in rat prostate

We have used oligonucleotide probes specific for members of the rat kallikrein/tonin gene family (PS, S1, S2, S3, K1, and P1) to establish which arginyl esteropeptidase (kallikrein-like) genes are expressed in the prostate. We have also compared the expression and androgen dependence of these genes in prostate, submaxillary gland (SMG) and kidney. Only S3 (tonin-like) and P1 (kallikrein-like) are expressed in the prostate, with S3 very much more abundant. Prostatic S3 mRNA disappears after 8 days castration and is restored to intact levels by dihydrotestosterone (DHT) but not estradiol benzoate (EB) for 8 days. Prostate P1 mRNA levels were similarly but not identically affected. All six genes are expressed in the SMG, with PS (true kallikrein) the most abundant. Levels of PS mRNA in SMG are unaffected by castration, DHT, or EB treatment, although mRNA levels of other kallikrein-like (S1, K1, and P1), tonin (S2), and tonin-like (S3) genes fall 40-60% after castration, and are unaffected or partially restored by DHT and/or EB administration. Only PS and K1 are expressed in the kidney, at much lower levels than in the SMG and unaffected by castration or steroids. These studies thus confirm and extend the concept of tissue specificity of arginyl esteropeptidase gene expression, and further demonstrate that the same gene(s) is differentially regulated by androgens in the rat prostate, SMG, and kidney.