The Key Pinch Stress Radiograph to Evaluate Dorsal Subluxation in the Basilar Thumb Joint.

The basilar thumb joint is the joint second most commonly affected by osteoarthritis (OA) in the hand. Evaluation of dorsal subluxation of the thumb during a functional task such as key pinch could help assess OA risk. The objectives of this study were to determine the best imaging angle for measuring thumb dorsal subluxation during key pinch and to compare subluxation to corresponding OA grades on the Eaton-Glickel, Outerbridge, and International Cartilage Repair Society scales.

Elution of rifampin and vancomycin from a weight-bearing silorane-based bone cement.

Aims: Poly(methyl methacrylate) (PMMA)-based bone cements are the industry standard in orthopaedics. PMMA cement has inherent disadvantages, which has led to the development and evaluation of a novel silorane-based biomaterial (SBB) for use as an orthopaedic cement. In this study we test both elution and mechanical properties of both PMMA and SBB, with and without antibiotic loading.

Biomechanics of prophylactic tethering for proximal junctional kyphosis: effects of cyclic loading on tether strength and failure properties.

Study Design: Biomechanical evaluation of woven polyester tethers.

Objectives: To quantify changes in tether elongation, stiffness, and failure characteristics after cyclic loading. Ligamentous augmentation is gaining interest as a technique to prevent proximal junctional kyphosis (PJK) in adult spinal fusions.

Mechanical and degradation properties of poly(methyl methacrylate) cement/borate bioactive glass composites.

Bone cement is used extensively in orthopedics to anchor prostheses to bone and fill voids. Incorporating bioactive glass into poly(methyl methacrylate) (PMMA)-based bone cement could potentially improve its effectiveness for these tasks. This study characterizes the mechanical and degradation properties of composites containing PMMA-based bone cement and particles of borate bioactive glass designated as 13-93B3.

The Effect of the Joint Capsule and Anterior Oblique Ligament on Dorsal Subluxation of the First Metacarpal During Key Pinch.

Laxity of the anterior oblique ligament (AOL) and/or the dorsoradial ligament (DRL) are believed to contribute to the progression of osteoarthritis in the trapeziometacarpal joint through increased dorsal subluxation. Stress radiographs during functional tasks, such as key pinch, can be used to evaluate such joint instability. Cadaveric experiments can explore joint contact pressures as well as subluxation under varying conditions, to gain knowledge about joint mechanics.

Initial Response of Mature, Experienced Runners to Barefoot Running: Transition to Forefoot Strike.

Introduction: Forefoot strike has been advocated for many runners because of the relatively lower impact and push-off forces compared to a heel strike. The purpose of this study was to explore the ability of mature (> 30 years old), experienced runners to transition from a heel foot strike to a forefoot strike when first introduced to barefoot running on a treadmill. We hypothesized: 1) mature runners who heel strike while wearing traditional training shoes would persist in heel striking immediately following a switch to barefoot, 2) mean shoe heel-to-toe drop would be significantly greater in runners who persist in heel striking when running barefoot compared to those who transition to a forefoot strike pattern, and 3) there would be a significant decrease in heel striking in the barefoot condition as running speeds increased.

Characterization of the conversion of bone cement and borate bioactive glass composites.

Borate bioactive glass 13-93B3 converts into an osteoconductive hydroxyapatite-like material in a liquid medium. In this study, 13-93B3 was incorporated into a commercial PMMA (poly(methyl methacrylate)) bone cement, and the conversion of the glass into a precipitate in solution was investigated with scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared (spectroscopy)-attenuated total reflection, and micro-Raman spectroscopy. Glass particles of 5, 33, and 100 μm diameter were each mixed with the PMMA cement to create 20, 30, and 40% glass-loaded composites.

Effect of Ultrasound Frequency and Treatment Duration on Antibiotic Elution from Polymethylmethacrylate Bone Cement.

Introduction: The objective of this study was to evaluate the effect of ultrasound frequency and treatment duration on antibiotic-impregnated polymethylmethacrylate (PMMA) antibiotic elution rates and mechanical strength.

Methods: Two batches of PMMA were prepared: one with five grams of vancomycin powder and one without. Each batch was divided into two frequency groups: kHz and MHz.

Biomechanics of Prophylactic Tethering for Proximal Junctional Kyphosis: Comparison of Posterior Tether Looping Techniques.

Study Design: Biomechanical study.

Objectives: Compare effects of four spinous process (SP) tether looping methods on segmental flexion range of motion (ROM), intervertebral disc (IVD) pressures, and peak tether forces.

Summary Of Background Data: SP tethering has been gaining interest as a prophylactic technique to prevent PJK caused by ligamentous laxity in ASD corrective surgery.

Biomechanics of Prophylactic Tethering for Proximal Junctional Kyphosis: Characterization of Spinous Process Tether Pretensioning and Pull-Out Force.

Study Design: Biomechanical evaluation of cadaver functional spinal units (FSUs).

Objectives: Demonstrate the effect of increasing spinous process (SP) tether pretension on FSU flexion range of motion (ROM), intervertebral disc (IVD) pressure, and SP force. Quantify SP tether pull-out forces and relate them to SP forces generated at maximum flexion.

Antibiotic Elution and Mechanical Strength of PMMA Bone Cement Loaded With Borate Bioactive Glass.

Local delivery of antibiotics using bone cement as the delivery vehicle is an established method of managing implant-associated orthopedic infections. Various fillers have been added to cement to increase antibiotic elution, but they often do so at the expense of strength. This study evaluated the effect of adding a borate bioactive glass, previously shown to promote bone formation, on vancomycin elution from PMMA bone cement.

Evaluation of midcarpal capitate contact mechanics in normal, injured and post-operative wrists.

Background: Scapholunate ligament injury is a commonly occurring carpal ligament injury. Pathology associated with scapholunate ligament injury depends on several factors such as the time after injury, type of injury (instability) and the development of osteoarthritis. The aim of this study was to investigate and compare contact mechanics in the lunocapitate and scaphocapitate joints in the normal, injured (scapholunate dissociation) and repaired (postoperative) wrist.

Neuroanatomical distribution of mechanoreceptors in the human cadaveric shoulder capsule and labrum.

The distribution, location, and spatial arrangement of mechanoreceptors are important for neural signal conciseness and accuracy in proprioceptive information required to maintain functional joint stability. The glenohumeral joint capsule and labrum are mechanoreceptor-containing tissues for which the distribution of mechanoreceptors has not been determined despite the importance of these tissues in stabilizing the shoulder. More recently, it has been shown that damage to articular mechanoreceptors can result in proprioceptive deficits that may lead to recurrent instability.

Computationally efficient magnetic resonance imaging based surface contact modeling as a tool to evaluate joint injuries and outcomes of surgical interventions compared to finite element modeling.

Joint injuries and the resulting posttraumatic osteoarthritis (OA) are a significant problem. There is still a need for tools to evaluate joint injuries, their effect on joint mechanics, and the relationship between altered mechanics and OA. Better understanding of injuries and their relationship to OA may aid in the development or refinement of treatment methods.

Intrawound Vancomycin Powder Decreases Staphylococcal Surgical Site Infections After Posterior Instrumented Spinal Arthrodesis.

Study Design: A retrospective historical cohort design.

Objective: To determine what effect the addition of intrawound vancomycin powder to the prophylactic regimen of posterior instrumented spinal arthrodesis procedures has had on acute surgical site infections (SSIs).

Summary Of Background Data: SSIs are known complications in instrumented spinal arthrodesis procedures, and are predominately caused by Staphylococcus aureus.

Effectiveness of surgical reconstruction to restore radiocarpal joint mechanics after scapholunate ligament injury: an in vivo modeling study.

Disruption of the scapholunate ligament can cause a loss of normal scapholunate mechanics and eventually lead to osteoarthritis. Surgical reconstruction attempts to restore scapholunate relationship show improvement in functional outcomes, but postoperative effectiveness in restoring normal radiocarpal mechanics still remains a question. The objective of this study was to investigate the benefits of surgical repair by observing changes in contact mechanics on the cartilage surface before and after surgical treatment.

Scapholunate ligament injury adversely alters in vivo wrist joint mechanics: an MRI-based modeling study.

We investigated the effects of scapholunate ligament injury on in vivo radiocarpal joint mechanics using image-based surface contact modeling. Magnetic resonance images of 10 injured and contralateral normal wrists were acquired at high resolution (hand relaxed) and during functional grasp. Three-dimensional surface models of the radioscaphoid and radiolunate articulations were constructed from the relaxed images, and image registration between the relaxed and grasp images provided kinematics.

Increasing the elution of vancomycin from high-dose antibiotic-loaded bone cement: a novel preparation technique.

Background: Antibiotic bone cement is commonly used in staged revision arthroplasty as well as the treatment of open fractures. Multiple factors affect antibiotic elution from bone cement. This study was performed to investigate the effect of two variables, the quantity of liquid monomer and the timing of antibiotic addition, on the ultimate elution of antibiotic from bone cement.

Validation of radiocarpal joint contact models based on images from a clinical MRI scanner.

This study was undertaken to assess magnetic resonance imaging (MRI)-based radiocarpal surface contact models of functional loading in a clinical MRI scanner for future in vivo studies, by comparison with experimental measures from three cadaver forearm specimens. Experimental data were acquired using a Tekscan sensor during simulated light grasp. Magnetic resonance (MR) images were used to obtain model geometry and kinematics (image registration).

Persistent and progressive pulmonary fibrotic changes in a model of fat embolism.

Background: Fat embolism (FE) after trauma and some orthopedic procedures is known to cause acute lung injury, including acute respiratory distress syndrome. However, its potential long-term effects on the lung are unknown. A previous study using a rat model of FE found significant histopathologic changes in the lungs after intravenous injection of triolein for up to 11 days.

MRI-based modeling for radiocarpal joint mechanics: validation criteria and results for four specimen-specific models.

The objective of this study was to validate the MRI-based joint contact modeling methodology in the radiocarpal joints by comparison of model results with invasive specimen-specific radiocarpal contact measurements from four cadaver experiments. We used a single validation criterion for multiple outcome measures to characterize the utility and overall validity of the modeling approach. For each experiment, a Pressurex film and a Tekscan sensor were sequentially placed into the radiocarpal joints during simulated grasp.

Residual deformity after treatment of pediatric femur fractures with flexible titanium nails.

Introduction: Procurvatum or anterior bow deformity is a potential complication after treatment of femur fractures with flexible titanium nails (FTNs). This article reports on a clinical evaluation of angulation after treating pediatric femur fractures with FTNs. The article also reports on a complementary investigation of potential causes of these deformities using a biomechanical model.

Mitigating effects of captopril and losartan on lung histopathology in a rat model of fat embolism.

Background: Fat embolization (FE) is an often overlooked and poorly understood complication of skeletal trauma and some orthopedic procedures. Fat embolism can lead to major pulmonary damage associated with fat embolism syndrome (FES).

Methods: A model of FE in unanesthetized rats, using intravenous injection of the neutral fat triolein, was used to study the potential therapeutic effect on lung histopathology of altering the production of, or response to, endogenous angiotensin (Ang) II.

The effect of starting point placement technique on thoracic transverse process strength: an ex vivo biomechanical study.

Background: The use of thoracic pedicle screws in spinal deformity, trauma, and tumor reconstruction is becoming more common. Unsuccessful screw placement may require salvage techniques utilizing transverse process hooks. The effect of different starting point placement techniques on the strength of the transverse process has not previously been reported.