In vivo testing of an injectable matrix gel for the treatment of shoulder cuff muscle fatty degeneration.

INTRODUCTION: Extracellular matrix (ECM) gels have shown efficacy for the treatment of damaged tissues, most notably cardiac muscle. We hypothesized that the ECM gel prepared from skeletal muscle could be used as a treatment strategy for fatty shoulder cuff muscle degeneration. METHODS: We conducted experiments to (1) evaluate host biocompatibility to ECM gel injection using a rat model and (2) examine the effect of ECM gel injection on muscle recovery after delayed repair of a released supraspinatus (SSP) tendon using a rabbit model. RESULTS: The host biocompatibility to the ECM gel was characterized by a transient rise (first 2 weeks only) in several genes associated with macrophage infiltration, matrix deposition, and inflammatory cytokine production. By 8 weeks all genes had returned to baseline levels and no evidence of fibrosis or chronic inflammation was observed from histology. When gel injection was combined with SSP tendon repair, we observed a significant reduction (7%) in SSP muscle atrophy (24 + 3% reduction from uninjured) when compared with treatment with tendon repair only (31 + 7% reduction). Although fatty degeneration was elevated in both treatment groups, fat content trended lower (2%) in response to combined tendon repair and intramuscular ECM injection (4.1 + 2.1%) when compared with tendon repair only (6.1 + 2.9%). Transcriptome analysis revealed adipogenesis and osteoarthritis pathway activation in the repair only group. These key pathways were abrogated in response to treatment using combined repair plus gel. DISCUSSION: The findings suggest that ECM injection had a modest but positive effect on muscle mass, fatty degeneration, and key cellular signaling pathways.

Partition-based optimization model for generative anatomy modeling language (POM-GAML).

BACKGROUND: This paper presents a novel approach for Generative Anatomy Modeling Language (GAML). This approach automatically detects the geometric partitions in 3D anatomy that in turn speeds up integrated non-linear optimization model in GAML for 3D anatomy modeling with constraints (e.g. joints). This integrated non-linear optimization model requires the exponential execution time. However, our approach effectively computes the solution for non-linear optimization model and reduces computation time from exponential to linear time. This is achieved by grouping the 3D geometric constraints into communities. METHODS: Various community detection algorithms (k-means clustering, Clauset Newman Moore, and Density-Based Spatial Clustering of Applications with Noise) were used to find communities and partition the non-linear optimization problem into sub-problems. GAML was used to create a case study for 3D shoulder model to benchmark our approach with up to 5000 constraints. RESULTS: Our results show that the computation time was reduced from exponential time to linear time and the error rate between the partitioned and non-partitioned approach decreases with the increasing number of constraints. For the largest constraint set (5000 constraints), speed up was over 2689-fold whereas error was computed as low as 2.2%. CONCLUSION: This study presents a novel approach to group anatomical constraints in 3D human shoulder model using community detection algorithms. A case study for 3D modeling for shoulder models developed for arthroscopic rotator cuff simulation was presented. Our results significantly reduced the computation time in conjunction with a decrease in error using constrained optimization by linear approximation, non-linear optimization solver.

A Cadaveric Study of Cutaneous Vascular Anatomy about the Elbow Using Computed Tomography Angiography.

The posterior approach is a commonly employed exposure of the elbow that provides excellent visualization and efficacy for various orthopedic procedures, including total elbow arthroplasty (TEA) and fracture care. The posterior approach to the elbow has been associated with an increased rate of wound complications, including infection, skin necrosis, and wound dehiscence. Despite an association between these complications and decreased elbow perfusion, data regarding the intrinsic anatomic etiology for preferential complications in this area has been scarcely reported in the literature. This study characterizes the subdermal and cutaneous vascular perfusion about the elbow by describing the predominant direction of circulation, subdermal anastomoses, and volume of perfusion through cadaveric modeling using computed tomography angiography (CTA). Fifteen upper extremity cadaver specimens were prepared with injection of radiographic contrast directly into the axillary artery immediately preceding CTA imaging of each specimen. Sectra IDS7 software for Windows was used for analysis of all images to produce superimposed axial and 3-D reconstructions of each CTA series. From these images it was discerned that the predominant direction of flow in the posterior elbow integument is anterior medial to posterior lateral. Both the posterior medial and posterior lateral subdermal vascular networks emanate from proximally derived medial arterial sources with few anastomoses and minimal collateral perfusion from the anterolateral location. Consequently, it is important to preserve medial subdermal vascular structures to prevent ischemic wound complications. This is especially true in previously incised elbow integuments. Clin. Anat. 32:509-514, 2019. © 2019 Wiley Periodicals, Inc.

The effect of the beach-chair position angle on cerebral oxygenation during shoulder surgery.

BACKGROUND: Although the safety of the beach-chair position (BCP) is widely accepted, rare devastating neurologic complications have been reported and attributed to cerebral hypoperfusion. Cerebral oxygenation (regional oxygen saturation [rSO2]) can be monitored noninvasively using near-infrared spectroscopy. The purpose of this study was to determine the effect of BCP angle on cerebral oxygenation in patients undergoing shoulder surgery in the BCP. METHODS: Fifty patients undergoing shoulder arthroscopy were prospectively enrolled to participate. Following induction of general anesthesia, each patient's rSO2 was recorded at 0° of elevation and again at 30°, 45°, 60°, and 80° of elevation. Mean rSO2 values and mean differences in rSO2 were reported. RESULTS: An average total decrease of 5% in rSO2 was seen when comparing 0° with 80° (P < .001). There were statistically significant differences in rSO2 values at beach-chair angles of 0° versus 30° (P <.001), 30° versus 45° (P = .007), and 45° versus 60° (P <.001) but not between 60° and 80° (P = .12). The decrease in rSO2 was similar between each progressive increase in the beach-chair angle, leading to a linear decline in rSO2 as the BCP increased (regression slope of -0.060%/°, P <.001). No patient's cerebral oxygenation dropped greater than 20% from baseline. Neither body mass index nor American Society of Anesthesiologists score had a significant impact on the relation of rSO2 to BCP angle. CONCLUSIONS: The average drop in rSO2 is significantly less than the threshold of 20% used as an identifier for a cerebral deoxygenation event. This study illustrates the direct effect the BCP angle has on cerebral oxygenation.

Wound complications after distal humerus fracture fixation: incidence, risk factors, and outcome.

BACKGROUND: This study set out to accurately determine the incidence of wound complications after distal humerus fracture fixation, to assess risk factors, and to determine their implications on outcome. METHODS: Eighty-nine distal humerus fractures (mean patient age, 58 years) were treated with internal fixation at an average of 4 days after injury. Mean follow-up time was 15 months (range, 6-72 months). Twenty-nine (33%) fractures were open. Medical records and radiographs were reviewed to determine wound complications. Logistic regression analysis was carried out to determine associated risk factors. RESULTS: Fourteen patients (15.7%) developed a major wound complication requiring on average 2.5 (range, 1-6) additional surgical procedures. Six patients required plastic surgical soft tissue coverage. All 14 fractures complicated by wound problems united. The final mean range of motion in the major wound complication group was 100° (range, 65°-130°), compared with 100° (range, 10°-140°) in those with no or minor wound problems. Grade III open fractures and the use of a plate to stabilize the olecranon osteotomy were identified as significant risk factors for development of major wound complications. CONCLUSIONS: The incidence of major wound complications after fixation of distal humerus fractures is substantial. The presence of a grade III open fracture and the use of an olecranon osteotomy stabilized with a plate are significant risk factors for major wound complications. Fracture healing rates and functional elbow range of motion do not appear to be affected by major wound complications when they are handled with proper soft tissue coverage techniques.

The incidence and risk factors for blood transfusion in revision shoulder arthroplasty: our institution's experience and review of the literature.

HYPOTHESIS: The purposes of this study were to determine the incidence of blood transfusion after revision shoulder arthroplasty and to assess risk factors associated with an increased risk of transfusion. MATERIALS AND METHODS: Between 1994 and 2008, 566 consecutive revision shoulder procedures were performed at our institution, which formed the basis of this study. The patient's age, sex, body mass index, comorbidities, preoperative and postoperative hemoglobin level, details of the surgery, operative time, and transfusion details were documented retrospectively from medical records. RESULTS: Overall, 11.3% of patients (64 of 566) required a transfusion. An increased transfusion rate was associated with age (odds ratio [OR] per 10 years, 1.5 [95% confidence interval (CI), 1.2 to 2.0]; P = .002), operative time (≤ 5 hours vs >5 hours) (OR, 3.3 [95% CI, 1.9 to 5.8]; P < .001), diabetes (OR, 2.3 [95% CI, 1.2 to 4.4]; P = .01), and cardiac disease (OR, 2.7 [95% CI, 1.5 to 5.0]; P < .001). There were significant associations between preoperative hemoglobin level (OR, 0.4 per 1 point [95% CI, 0.3 to 0.5]; P < .001) and a decreased odds of transfusion. The type of surgery (surgery on humeral component) also had an impact on the need for transfusion (P < .001). CONCLUSIONS: Older age, low preoperative hemoglobin level, increased operative time, diabetes, presence of cardiac disease, and type of revision surgery are associated with higher postoperative transfusion rates. These factors should be taken into consideration to more accurately predict the need for transfusion and modify preoperative blood-ordering protocols.

The biomechanics of three different fracture fixation implants for distal femur repair in the presence of a tumor-like defect.

The femur is the most common long bone involved in metastatic disease. There is consensus about treating diaphyseal and epiphyseal metastatic lesions. However, the choice of device for optimal fixation for distal femur metaphyseal metastatic lesion remains unclear. This study compared the mechanical stiffness and strength of three different fixation methods. In 15 synthetic femurs, a spherical tumor-like defect was created in the lateral metaphyseal region, occupying 50% of the circumference of the bone. The defect was filled with bone cement and fixed with one of three methods: Group 1 (retrograde nail), Group 2 (lateral locking plate), and Group 3 (lateral nonlocking periarticular plate). Constructs were tested for mechanical stiffness and strength. There were no differences between groups for axial stiffness (Group 1, 1280 +/- 112 N/mm; Group 2, 1422 +/- 117 N/mm; and Group 3, 1403 +/- 122N/mm; p = 0.157) and offset torsional strength (Group 1, 1696 +/- 628N; Group 2, 1771 +/- 290N; and Group 3, 1599 +/- 253 N; p = 0.816). In the coronal plane, Group 2 (296 +/- 17 N/mm) had a higher stiffness than Group 1 (263 +/- 17N/mm; p = 0.018). In the sagittal plane, Group 1 (315 +/- 9 N/mm) had a higher stiffness than Group 3 (285 +/- 19 N/mm; p = 0.028). For offset torsional stiffness, Group 1 (256 +/- 23 N/mm) had a higher value than Group 3 (218 +/- 16 N/mm; p = 0.038). Group 1 had equivalent performance to both plating groups in two test modes, and it was superior to Group 3 in two other test modes. Since a retrograde nail (i.e. Group 1) would require less soft-tissue stripping in a clinical context, it may be the optimal choice for tumor-like defects in the distal femur.

Evaluation of WebRTC in the Cloud for Surgical Simulations: A case study on Virtual Rotator Cuff Arthroscopic Skill Trainer (ViRCAST).

Web Real-Time Communication (WebRTC) is an open-source technology which enables remote peer-to-peer video and audio connection. It has quickly become the new standard for real-time communications over the web and is commonly used as a video conferencing platform. In this study, we present a different application domain which may greatly benefit from WebRTC technology, that is virtual reality (VR) based surgical simulations. Virtual Rotator Cuff Arthroscopic Skill Trainer (ViRCAST) is our testing platform that we completed preliminary feasibility studies for WebRTC. Since the elasticity of cloud computing provides the ability to meet possible future hardware/software requirements and demand growth, ViRCAST is deployed in a cloud environment. Additionally, in order to have plausible simulations and interactions, any VR-based surgery simulator must have haptic feedback. Therefore, we implemented an interface to WebRTC for integrating haptic devices. We tested ViRCAST on Google cloud through haptic-integrated WebRTC at various client configurations. Our experiments showed that WebRTC with cloud and haptic integrations is a feasible solution for VR-based surgery simulators. From our experiments, the WebRTC integrated simulation produced an average frame rate of 33 fps, and the hardware integration produced an average lag of 0.7 milliseconds in real-time.

Fixation and durability of a bone-ingrowth component for glenoid bone loss.

BACKGROUND: Deficient glenoid bone is a reconstructive challenge in shoulder arthroplasty. One solution is an ingrowth anatomic glenoid with column and screw fixation, with or without supplemental bone graft. This study examines the outcome of patients managed in this manner. MATERIALS AND METHODS: This type of glenoid component was used in 21 shoulder arthroplasties with central or peripheral glenoid bone deficiencies: 13 for bone loss due to arthritic wear and 8 for revision arthroplasty. Patients were monitored clinically for a mean of 11.1 years (range, 7.6-15.1 years) and by x-ray imaging for a mean of 9.1 years (range, 2.2-14.2 years). RESULTS: Revision procedures were needed for 7 shoulders at a mean of 10.4 years (range 5.5-14.3 years), 6 for polyethylene or metal wear leading to glenoid loosening in 4. In the 14 nonrevised shoulders, pain ratings (1 to 5 scale) decreased from a mean of 4.5 to 1.9 (P < .001). Mean active elevation increased from 100° to 125° (P = .02). Mean external rotation increased from 28° to 43° (P = .06). Results assessed by the Neer rating were excellent in 3, satisfactory in 10, and unsatisfactory in 1. In radiographic assessment of the unrevised shoulders, 4 were at risk for glenoid loosening, and 1 was at risk for humeral loosening. CONCLUSIONS: This method of reconstruction can offer pain relief and improved motion. However, the large number of revision procedures and additional adverse changes on x-ray imaging suggest other reconstructive options may be more successful and durable.

Patient reported activities after reverse shoulder arthroplasty: part II.

BACKGROUND: Reverse shoulder arthroplasty (RSA) is becoming a commonly performed procedure. Surgeons are advised to select older patients with lower demands. This study defines patient reported activities following RSA. MATERIALS AND METHODS: Seventy-eight patients with 81 treated shoulders (average age 73 years; 49 women, 32 men) completed a survey asking about clinical parameters: pain, motion, strength, and 72 different activities. Diagnoses were rotator cuff tear arthropathy in 70 shoulders, massive rotator cuff tears with psuedoparalysis in 6, and failed treatment for proximal humeral fractures in 5. Average time from surgery to survey was 3.6 years (range, 3-5). RESULTS: All clinical parameters were favorable. The 3 most commonly reported activities were low demand (cooking, baking, and driving), medium demand (gardening, leaf raking, and lawn mowing), and high demand (snow shoveling, wheelbarrow use, and dirt shoveling). These were comparable to the activities reported for total shoulder arthroplasty and hemiarthroplasty. There was no clinical or activity difference between those components with a lateral or a medial center of rotation. CONCLUSION: A significant proportion of patients continue medium or high demand activities following RSA. These are similar to other types of shoulder arthroplasties. Future studies to determine the safety level of different activities would be helpful to counsel patients accordingly.

Towards Real-time Bone Drilling Simulation for Anchor Placement in VR Based Arthroscopic Rotator Cuff Surgery Simulation.

Arthroscopic Rotator Cuff (ARC) is a minimally invasive surgery of the shoulder. ARC training for surgeons is challenging due to confined space, anatomical complexity, requirement of complex hands-eye coordination skills, subjectivity, and low fidelity in existing training mediums. We therefore offer a virtual reality based photorealistic medical simulation, Virtual Rotator Cuff Arthroscopic Skill Trainer (ViRCAST) for objective training. In this study, as a part of ViRCAST, we introduce a virtual reality-based bone drilling simulation. Bone drilling task is one of the most important tasks that surgeons need to perform before anchor placement in ARC. Realistic simulation of bone drilling with force feedback is complex due to real-time mesh modification and simulation constraints. We introduce a GPU based realtime bone drilling simulation for ViRCAST using an adaptive mesh refinement technique. Our GPU based solution improves the drilling simulation realism by enhancing mesh resolution without sacrificing the simulation performance.

Scoring metrics for assessing skills in arthroscopic rotator cuff repair: performance comparison study of novice and expert surgeons.

PURPOSE: We aim to develop quantitative performance metrics and a deep learning model to objectively assess surgery skills between the novice and the expert surgeons for arthroscopic rotator cuff surgery. These proposed metrics can be used to give the surgeon an objective and a quantitative self-assessment platform. METHODS: Ten shoulder arthroscopic rotator cuff surgeries were performed by two novices, and fourteen were performed by two expert surgeons. These surgeries were statistically analyzed. Two existing evaluation systems: Basic Arthroscopic Knee Skill Scoring System (BAKSSS) and the Arthroscopic Surgical Skill Evaluation Tool (ASSET), were used to validate our proposed metrics. In addition, a deep learning-based model called Automated Arthroscopic Video Evaluation Tool (AAVET) was developed toward automating quantitative assessments. RESULTS: The results revealed that novice surgeons used surgical tools approximately 10% less effectively and identified and stopped bleeding less swiftly. Our results showed a notable difference in the performance score between the experts and novices, and our metrics successfully identified these at the task level. Moreover, the F1-scores of each class are found as 78%, 87%, and 77% for classifying cases with no-tool, electrocautery, and shaver tool, respectively. CONCLUSION: We have constructed quantitative metrics that identified differences in the performances of expert and novice surgeons. Our ultimate goal is to validate metrics further and incorporate these into our virtual rotator cuff surgery simulator (ViRCAST), which has been under development. The initial results from AAVET show that the capability of the toolbox can be extended to create a fully automated performance evaluation platform.

Biomechanics of axial load transmission across the native human elbow.

BACKGROUND: Elbow and forearm motion are thought to affect elbow load transmission, yet little empirical evidence exists to quantify the biomechanics. METHODS: Eight fresh-frozen human cadaver upper extremities were utilized. A 100 N axial force was applied across the elbow joint at elbow flexion angles of (0°, 30°, 60°, and 90°) and forearm rotation angles (0°, 45° supination, and 45° pronation). Pressure mapping sensors were placed in both the radiocapitellar and ulnotrochlear joints. Force distributions and contact areas were measured, and paired t-tests were used for comparison (p < 0.05). RESULTS: The average maximum loading percentage of the radiocapitellar and ulnotrochlear joint pressures were 57.8 ± 4.6% and 42.2 ± 4.6%, respectively. Elbow flexion angle and forearm rotation did not significantly affect the joint loading. There was no significant difference between the contact areas of each joint, although ulnotrochlear and radiocapitellar joints demonstrated an inverse relationship. CONCLUSION: Our study is the only one to date to comprehensively evaluate loading mechanics throughout both functional elbow flexion and forearm rotation across both articulations. The load sharing ratio across the radiocapitellar and ulnotrochlear joints was 58%:42%, agreeing with previously reported ratios with limited parameters. A relationship may be present between increasing radiocapitellar and decreasing ulnotrochlear contact areas as elbow flexion increases.

High-Energy Proximal Humerus Fractures in Geriatric Patients: A Review.

High-energy proximal humerus fractures in elderly patients can occur through a variety of mechanisms, with falls and MVCs being common mechanisms of injury in this age group. Even classically low-energy mechanisms can result in elevated ISS scores, which are associated with higher mortality in both falls and MVCs. These injuries result in proximal humerus fractures which are commonly communicated via Neer's classification scheme. There are many treatment options in the armamentarium of the treating surgeon. Nonoperative management is widely supported by systematic review as compared to almost all other treatment methods. ORIF is particularly useful for complex patterns and fracture dislocations in healthy patients. Hemiarthroplasty can be of utility in patients with fracture patterns with high risk of AVN and poor bone quality risking screw cut-out. Reverse total shoulder arthroplasty is a popular method of treatment for geriatric patients also, with literature now showing that even late conversion from nonoperative management or ORIF to rTSA can lead to good clinical outcomes. Prevention is possible and important for geriatric patients. Optimizing medical care including hearing, vision, strength, and bone quality, in coordination with primary care and geriatricians, is of great importance in preventing fractures and decreasing injury when falls do occur. Involving geriatricians on dedicated trauma teams will also likely be of benefit.

A partition-based optimization model and its performance benchmark for Generative Anatomy Modeling Language.

BACKGROUND: This paper presents a novel iterative approach and rigorous accuracy testing for geometry modeling language - a Partition-based Optimization Model for Generative Anatomy Modeling Language (POM-GAML). POM-GAML is designed to model and create anatomical structures and their variations by satisfying any imposed geometric constraints using a non-linear optimization model. Model partitioning of POM-GAML creates smaller sub-problems of the original model to reduce the exponential execution time required to solve the constraints in linear time with a manageable error. METHOD: We analyzed our model concerning the iterative approach and graph parameters for different constraint hierarchies. The iteration was used to reduce the error for partitions and solve smaller sub-problems generated by various clustering/community detection algorithms. We empirically tested our model with eleven graph parameters. Graphs for each parameter with increasing constraint sets were generated to evaluate the accuracy of our method. RESULTS: The average decrease in normalized error with respect to the original problem using cluster/community detection algorithms for constraint sets was above 63.97%. The highest decrease in normalized error after five iterations for the constraint set of 3900 was 70.31%, while the lowest decrease for the constraint set of 3000 was with 63.97%. Pearson correlation analysis between graph parameters and normalized error was carried out. We identified that graph parameters such as diameter, average eccentricity, global efficiency, and average local efficiency showed strong correlations to the normalized error. CONCLUSIONS: We observed that iteration monotonically decreases the error in all experiments. Our iteration results showed decreased normalized error using the partitioned constrained optimization by linear approximation to the non-linear optimization model.

Systematic approach for content and construct validation: Case studies for arthroscopy and laparoscopy.

BACKGROUND: In minimally invasive surgery, there are several challenges for training novice surgeons, such as limited field-of-view and unintuitive hand-eye coordination due to performing the operation according to video feedback. Virtual reality (VR) surgical simulators are a novel, risk-free, and cost-effective way to train and assess surgeons. METHODS: We developed VR-based simulations to accurately assess and quantify performance of two VR simulations: gentleness simulation for laparoscopy and rotator cuff repair for arthroscopy. We performed content and construct validity studies for the simulators. In our analysis, we systematically rank surgeons using data mining classification techniques. RESULTS: Using classification algorithms such as K-Nearest Neighbors, Support Vector Machines, and Logistic Regression we have achieved near 100% accuracy rate in identifying novices, and up to an 83% accuracy rate identifying experts. Sensitivity and specificity were up to 1.0 and 0.9, respectively. CONCLUSION: Developed methodology to measure and differentiate the highly ranked surgeons and less-skilled surgeons.

Radial-to-Axillary Nerve Transfer Resolves Symptoms of Axillary Nerve Injury Due to Proximal Humerus Fracture-Dislocation in an Elderly Patient Treated With Hemiarthroplasty.

Proximal humerus fractures in elderly patients are a common injury that can often be treated nonoperatively. However, surgery is indicated with some fracture patterns. Arthroplasty is an attractive option with poor bone quality, when there is a low likelihood of success with open reduction and internal fixation, and due to a timely return to function and weight bearing of the extremity in this patient population. A prerequisite for shoulder function for both native and replacement joints is a functional deltoid. Unfortunately, elderly patients with complex fracture patterns can sustain axillary nerve palsies that make management more difficult. The authors present a case of an elderly patient with a complex fracture-dislocation of the proximal humerus with traumatic axillary nerve palsy treated with hemiarthroplasty, followed by radial-to-axillary nerve transfer after the deltoid failed to improve. Congruency of the joint was restored and significant improvement in objective scoring metrics was achieved, making nerve transfer in this clinical scenario a viable option. [Orthopedics. 2019; 42(4):e395-e398.].

Identification of Radial Nerve in Relationship to Deltoid Tuberosity and Brachioradialis.

BACKGROUND: Several studies have identified the radial nerve in arm using different anatomic landmarks, however, a controversy remains. Deltoid tuberosity (DT) and brachioradialis (BR) are reproducible landmarks that can be used to identify the radial nerve (RN) during fracture surgery. METHODS: Dissection of RN was carried out in 17 fresh frozen adult cadavers. Using a calibrated caliper, we measured the distance between DT and the origin of BR. The distance between DT and where RN becomes lateral in its relationship with the humerus (DT-RN) and the distance between RN and BR (RN-BR) were subsequently measured. The ratio of DT-RN to DT-BR was calculated to see where the nerve lies in relationship to DT-BR. RESULTS: Average DT-BR was 81.8 (±14.86) mm, average DT-RN was 48.9 (± 7.83) mm, and average RN-BR was 33.0 (± 10.16) mm. RN was always found posterior to DT and was never found in the proximal third of DT-BR. The nerve was found in the middle third of DT-BR in 14 of 17 cadavers (82.4 %) and in the distal third in 3 out of 17 cadavers (17.6%). 16 of 17 cadavers (94%) had radial nerve in the distal half of DT-BR. CONCLUSION: Using the anatomic relationships between RN, DT, and the origin of BR, identification of RN is easily reproducible. These two structures can serve as the stationary landmarks during fracture surgery to find the radial nerve, which can be found in the distal 2/3 of the distance between the deltoid tuberosity and the origin of brachioradialis. LEVEL OF EVIDENCE: V.

Significance of Perioperative Tests to Diagnose the Infection in Revision Total Shoulder Arthroplasty.

BACKGROUND: The purpose of this study was to evaluate the value of perioperative tests for the diagnosis of infection in revision shoulder arthroplasty. METHODS: A retrospective analysis was performed on 537 shoulder arthroplasties (429 patients) that underwent revision shoulder arthroplasty at our institution. Periprosthetic tissue cultures were positive in 169/537 surgeries. RESULTS: White-blood cell count (WBC) was elevated in 3.8% revision arthroplasties. Erythrocyte sedimentation rate (ESR) was elevated in 23.1% revision arthroplasties. The C-reactive protein (CRP) was elevated in 20.8% revision arthroplasties. Bone scans (technetium, indium) were performed on 9.9% patients and it was positive for osteomyelitis in just one revision arthroplasty. Intra-operative pathology was read as consistent with acute inflammation in 11.9% revision arthroplasties. The positive and negative predictive values for intra-operative pathology were 56.7% and 71.6% respectively. CONCLUSION: All of the perioperative tests had a high specificity and negative predictive value, but low sensitivity and positive predictive value.

The effect of radial head prosthesis diameter on posterolateral rotatory instability of the elbow.

BACKGROUND: The purpose of this study is to investigate how different diameters of radial head replacement affect posterolateral translation with a valgus and supination force. We hypothesized that there would be less posterolateral rotatory translation with larger implant diameter. METHODS: Eleven cadaveric arms were stressed at 30 and 60° of flexion with a consistent supination and valgus stress force under five conditions: native radial head, radial head excision, and with 3 sizes of radial head prosthesis. Displacement of the radial head posteriorly in relation to the capitellum on radiographs was measured. Displacement was expressed as a percentage relative to the average of the maximum and minimum native radial head diameters. FINDINGS: The native radial heads had average minimum and maximum diameters of 23.3 mm and 25.2 mm, respectively. The angle of testing did not significantly change translation of the radial head. There was increased posterior translation relative to native head as the radial head sizes decreased from 24 mm to 20 mm and with excision of the radial head. Compared to the native head, the differences in displacement were statistically significant for the 20 mm radial head, but not for the 22 mm or 24 mm replacements. Radial head translation significantly increased after radial head excision. INTERPRETATIONS: This cadaveric study illustrates that patients treated with radial head excision and radial head prosthesis with undersized diameters have increased posterior translation with a valgus and supination stress. The larger the radial head prosthesis (closer to native radial head), the more closely it approximated the amount of translation of the native radial head.