Anatomical Evaluation of the Proximity of Neurovascular Structures During Arthroscopically Assisted Acromioclavicular Joint Reconstruction: A Cadaveric Pilot Study.

PURPOSE: The purpose of this study was to examine the safety of an arthroscopic technique for acromioclavicular joint (ACJ) reconstruction by investigating its proximity to important neurovascular structures. METHODS: Six shoulders from 4 cadaveric specimens were used for ACJ reconstruction in this study. The procedure consists of performing an arthroscopic acromioclavicular (AC) reduction with a double button construct, followed by coracoclavicular ligament reconstruction without drilling clavicular tunnels. Shoulders were subsequently dissected in order to identify and measure distances to adjacent neurovascular structures. RESULTS: The suprascapular artery and nerve were the closest neurovascular structures to implanted materials. The mean distances were 8.2 (standard deviation [SD] = 3.6) mm to the suprascapular nerve and 5.6 (SD = 4.2) mm to the suprascapular artery. The mean distance of the suprascapular nerve from implants was found to be greater than 5 mm (P = .040), while the distance to the suprascapular artery was not (P > .5). Neither difference was statistically significant (P = .80 for artery; P = .08 for nerve). CONCLUSIONS: Mini-open, arthroscopically assisted ACJ reconstruction safely avoids the surrounding nerves, with no observed damage to any neurovascular structures including the suprascapular nerve and artery, and may be a viable alternative to open techniques. However, surgeons must remain cognizant of possible close proximity to the suprascapular artery. CLINICAL RELEVANCE: This study represents an evaluation of the safety and feasibility of a minimally invasive ACJ reconstruction as it relates to the proximity of neurovascular structures.

Current Concepts in Sternoclavicular Joint Injuries.

LEVEL OF EVIDENCE: Therapeutic Level V. See Instructions for Authors for a complete description of levels of evidence.

Borna disease virus infection alters synaptic input of neurons in rat dentate gyrus.

Granule cells are major targets of entorhinal afferents terminating in a laminar fashion in the outer molecular layer of the dentate gyrus. Since Borna disease virus (BDV) infection of newborn rats causes a progressive loss of granule cells in the dentate gyrus, entorhinal fibres become disjoined from their main targets. We have investigated the extent to which entorhinal axons react to this loss of granule cells. Unexpectedly, anterograde DiI tracing has shown a prominent layered termination of the entorhinal projection, despite an almost complete loss of granule cells at 9 weeks after infection. Combined light- and electron-microscopic analysis of dendrites at the outer molecular layer of the dentate gyrus at 6 and 9 weeks post-infection has revealed a transient increase in the synaptic density of calbindin-positive granule cells and parvalbuminergic neurons after 6 weeks. In contrast, synaptic density reaches values similar to those of uninfected controls 9 weeks post-infection. These findings indicate that, after BDV infection, synaptic reorganization processes occur at peripheral dendrites of the remaining granule cells and parvalbuminergic neurons, including the unexpected persistence of entorhinal axons in the absence of their main targets.

A single probe spatial averaging technique for guided waves and its application to surface wave rail inspection.

The nondestructive testing of structures using guided waves requires systems with high mode selectivity. Usually this is achieved with relatively complex probes comprising multiple transducer rings or arrays. For the rapid inspection of very long structures with only partial access to the waveguide, this may not be a viable solution. In this paper we present a very flexible alternative whereby a simple robust probe is scanned along the wave guide, and the acquired scan data is used for customizing the mode selectivity at the postprocessing stage. The characteristics of this spatial averaging method are discussed using a simple analytical model and compared to an existing linear array technique. The mode selectivity is found to be mainly limited by the uncertainty of the phase velocity assumed for the mode of interest. The method was successfully applied to surface wave rail inspection and was found to suppress unwanted modes very efficiently.

Open Reduction and Internal Fixation of a Middle-Third Clavicle Fracture with a Superior Plate.

Open reduction and internal fixation has become a reliable technique to treat complex middle-third clavicle fractures (AO/OTA B-15). Nonoperative treatment of these fractures may result in higher rates of symptomatic malunion, nonunion, dissatisfaction with cosmetic appearance, and even dysfunction and muscular weakness. Risk factors such as substantial displacement or comminution, far lateral fractures, fractures in the elderly, open fractures, or those occurring in polytrauma scenarios are appropriate indications for surgery. The aim of the procedure is to reconstitute the initial curvature and length of the clavicle, restore a normal connection from the arm to the axial skeleton, and provide stable fixation of the proximal and distal fragments, to allow an immediate full range of motion during rehabilitation. The procedure includes the following steps. Step 1: Place the patient in a beach-chair, semi-sitting position.Step 2: Make a transverse skin incision along the anteroinferior aspect of the clavicle.Step 3: Expose the fracture site, identify and prepare the fragments unless they are comminuted, and preserve soft-tissue attachments to the extent possible.Step 4: Reduce the fragments by direct or indirect manipulation, and maintain the reduction with clamps, Kirschner wires, or mini-fragment plates. Consider bridging comminuted zones to allow secondary fracture-healing.Step 5: Apply a contoured plate to the superior or anterior surface of the clavicle, and obtain at least 6 cortices of fixation on each side with strategic nonlocking and locking screws. The working length of the plate is more important than the number of screws or cortices.Step 6: Obtain a single intraoperative anteroposterior radiograph of the clavicle.Step 7: Separately close the wound in layers (deltotrapezial fascia, platysma, and skin). Apply sterile dressings and a sling. The patient is discharged home on the same day if the injury is isolated, and a full range of motion of the affected shoulder is allowed immediately. The patient is expected to regain full function and strength of the arm once healing occurs.

The Pelvic Bridge: A Subcutaneous Approach for Anterior Pelvic Fixation.

INTRODUCTION: An alternative method to external fixation for the treatment of unstable anterior pelvic ring injuries, termed the pelvic bridge technique, provides equivalent results with fewer complications and is performed using occipital cervical rods subcutaneously, with fixation into the iliac wings and parasymphyseal bone. STEP 1 PREOPERATIVE PLANNING: For preoperative planning, review the appropriate imaging, including radiographs and computed tomography (CT) scans, to mesh the findings on imaging to the clinical picture of the patient and ensure that the patient meets operative criteria and that none of the contraindications are present. STEP 2 PATIENT POSITIONING: Position the patient to facilitate anterior and posterior fixation. STEP 3 APPROACH: Make the incisions necessary to expose the osseous contour where fixation will be utilized. STEP 4 CONTOURING THE PLATE-ROD CONSTRUCT: Carefully contour the plate-rod construct, which is necessary to minimize postoperative complications. STEP 5 PASSING THE PLATE-ROD CONSTRUCT: Use care when inserting the rod as doing so will help to avoid neurovascular complications. STEP 6 ACHIEVING ADEQUATE REDUCTION: To recreate pelvic stability, the pelvic ring needs to heal in as close to anatomic position as possible and there are multiple methods that help to obtain an adequate reduction. STEP 7 FRACTURE FIXATION: Multiple constructs may be used to stabilize the anterior pelvic ring, but the fundamental principle is to attach the 2 hemipelves to achieve stability, and the location where fixation can be achieved depends on the fracture pattern. STEP 8 WOUND CLOSURE: Ensure meticulous closure to reduce the chance of infection and achieve appropriate soft-tissue coverage over hardware. STEP 9 REHABILITATION: Early mobilization is a fundamental goal of this procedure, but the time to full weight-bearing is dependent on fracture characteristics and healing. RESULTS: Anterior pelvic internal fixation (APIF) using the pelvic bridge technique has been demonstrated to have significantly fewer complications than APEF2.

Virtual Reality Compared with Bench-Top Simulation in the Acquisition of Arthroscopic Skill: A Randomized Controlled Trial.

BACKGROUND: Work-hour restrictions as set forth by the Accreditation Council for Graduate Medical Education (ACGME) and other governing bodies have forced training programs to seek out new learning tools to accelerate acquisition of both medical skills and knowledge. As a result, competency-based training has become an important part of residency training. The purpose of this study was to directly compare arthroscopic skill acquisition in both high-fidelity and low-fidelity simulator models and to assess skill transfer from either modality to a cadaveric specimen, simulating intraoperative conditions. METHODS: Forty surgical novices (pre-clerkship-level medical students) voluntarily participated in this trial. Baseline demographic data, as well as data on arthroscopic knowledge and skill, were collected prior to training. Subjects were randomized to 5-week independent training sessions on a high-fidelity virtual reality arthroscopic simulator or on a bench-top arthroscopic setup, or to an untrained control group. Post-training, subjects were asked to perform a diagnostic arthroscopy on both simulators and in a simulated intraoperative environment on a cadaveric knee. A more difficult surprise task was also incorporated to evaluate skill transfer. Subjects were evaluated using the Global Rating Scale (GRS), the 14-point arthroscopic checklist, and a timer to determine procedural efficiency (time per task). Secondary outcomes focused on objective measures of virtual reality simulator motion analysis. RESULTS: Trainees on both simulators demonstrated a significant improvement (p < 0.05) in arthroscopic skills compared with baseline scores and untrained controls, both in and ex vivo. The virtual reality simulation group consistently outperformed the bench-top model group in the diagnostic arthroscopy crossover tests and in the simulated cadaveric setup. Furthermore, the virtual reality group demonstrated superior skill transfer in the surprise skill transfer task. CONCLUSIONS: Both high-fidelity and low-fidelity simulation trainings were effective in arthroscopic skill acquisition. High-fidelity virtual reality simulation was superior to bench-top simulation in the acquisition of arthroscopic skills, both in the laboratory and in vivo. Further clinical investigation is needed to interpret the importance of these results.

Femoral nerve palsy after pelvic fracture treated with INFIX: a case series.

OBJECTIVE: The treatment of some pelvic injuries has evolved recently to include the use of a subcutaneous anterior pelvic fixator (INFIX). We present 8 cases of femoral nerve palsy in 6 patients after application of an INFIX to highlight this potentially devastating complication to pelvic surgeons using this technique and discuss how it might be avoided in the future. DESIGN: Retrospective chart review. Case series. SETTING: Five level 1 and 2 trauma centers, tertiary referral hospitals. PATIENTS/PARTICIPANTS: Six patients with anterior pelvic ring injury treated with an INFIX who experienced 8 femoral nerve palsies (2 bilateral). INTERVENTION: Removal of internal fixator, treatment for femoral nerve palsy. MAIN OUTCOME MEASUREMENTS: Clinical and electromyographic evaluation of patients. RESULTS: All 6 patients with a total of 8 femoral nerve palsies had their INFIX removed. Variable resolution of the nerve injuries was observed. CONCLUSIONS: Application of an INFIX for the treatment of pelvic ring injury carries a potentially devastating risk to the femoral nerve(s). Despite early implant removal after detection of nerve injury, some patients had residual quadriceps weakness, disturbance of the thigh's skin sensation, and/or gait disturbance attributable to femoral nerve palsy at the time of early final follow-up. LEVEL OF EVIDENCE: Therapeutic level IV. See Instructions for Authors for a complete description of levels of evidence.