ACL transection results in a posterior shift and increased velocity of contact on the medial tibial plateau.

Our objective was to quantify the effect of ACL transection on dynamic knee joint contact force distributions during simulated gait. Given the prevalence of medial compartment osteoarthritis in un-reconstructed ACL ruptured knees, we hypothesized that changes in contact mechanics after ACL transection would be most prevalent in the medial compartment. Twelve human cadaveric knees were tested using a dynamic knee gait simulator which was programmed to mimic a clinical Lachman exam and gait.

The Biomechanical Consequences of Arthroscopic Hip Capsulotomy and Repair in Positions at Risk for Dislocation.

Background: The effect of interportal (IP) capsulotomy, short T-capsulotomy, and long T-capsulotomy, and their repairs, on resistance to anterior and posterior "at risk for dislocation" positions has not been quantified.

Hypotheses: Our primary hypothesis was that an IP capsulotomy would have a minimal effect on hip resistive torque compared with both short and long T-capsulotomies in the at-risk dislocation positions. Our secondary hypothesis was that capsule repair would significantly increase hip resistive torque for all capsulotomies.

Effect of Vancomycin Soaking on Anterior Cruciate Ligament Graft Biomechanics.

Purpose: To evaluate the effect of soaking of anterior cruciate ligament (ACL) grafts in vancomycin solution on graft biomechanical properties at the time of implantation.

Methods: The central third of patellar tendons was harvested from mature bovine knees and prepared as a tendon-only graft or a bone-tendon-bone (BTB) graft. Tendons were wrapped in gauze soaked in vancomycin solution (VS) (5 mg/mL) or normal saline (NS) and left to stand for 30 minutes at room temperature, simulating graft exposure times in the operating room during ACL reconstruction.

2020 Otto Aufranc Award: Malseating of modular dual mobility liners.

Aims: This combined clinical and in vitro study aimed to determine the incidence of liner malseating in modular dual mobility (MDM) constructs in primary total hip arthroplasties (THAs) from a large volume arthroplasty centre, and determine whether malseating increases the potential for fretting and corrosion at the modular metal interface in malseated MDM constructs using a simulated corrosion chamber.

Methods: For the clinical arm of the study, observers independently reviewed postoperative radiographs of 551 primary THAs using MDM constructs from a single manufacturer over a three-year period, to identify the incidence of MDM liner-shell malseating. Multivariable logistic regression analysis was performed to identify risk factors including age, sex, body mass index (BMI), cup design, cup size, and the MDM case volume of the surgeon.

Taper Design, Head Material, and Manufacturer Affect the Onset of Fretting Under Simulated Corrosion Conditions.

Background: We investigated the effect of taper design, head material, and manufacturer on simulated mechanically assisted crevice corrosion (MACC).

Methods: Six pristine C-taper stems coupled with alumina-zirconia or cobalt-chromium (CoCr) heads were tested in a mechanical/electrochemical setup to measure average fretting currents and fretting current onset loads. Outcomes were compared with previous data from V40 tapers from the same manufacturer and 12/14 tapers from another manufacturer.

Do Well-functioning THAs Retrieved at Autopsy Exhibit Evidence of Fretting and Corrosion?

Background: Our understanding of fretting and corrosion at head-neck junctions in modular THAs in vivo is based largely on the analysis of retrieved implants removed for various diagnoses. Little is known about the condition of head-neck tapers in well-functioning THAs.

Questions/purposes: Regarding a cohort of well-functioning autopsy-retrieved modular THAs, we asked: (1) Does trunnion geometry or femoral head material affect the pull-off force of the femoral head? (2) Is there a relationship between trunnion damage and length of implantation time, head diameter, and neck length? (3) Does visual damage scoring accurately determine the presence or absence of corrosion on cobalt-chrome trunnions?

Methods: Sixty-six femoral stems and engaged femoral heads were retrieved at autopsy from 53 patients at Anderson Orthopaedic Research Institute from 1998 to 2014.

Targeting skeletal endothelium to ameliorate bone loss.

Recent studies have identified a specialized subset of CD31endomucin (CD31EMCN) vascular endothelium that positively regulates bone formation. However, it remains unclear how CD31EMCN endothelium levels are coupled to anabolic bone formation. Mice with an osteoblast-specific deletion of Shn3, which have markedly elevated bone formation, demonstrated an increase in CD31EMCN endothelium.

Assessment of Mechanical Characteristics of Ankle-Foot Orthoses.

Recent designs of ankle-foot orthoses (AFOs) have been influenced by the increasing demand for higher function from active individuals. The biomechanical function of the individual and device is dependent upon the underlying mechanical characteristics of the AFO. Prior mechanical testing of AFOs has primarily focused on rotational stiffness to provide insight into expected functional outcomes; mechanical characteristics pertaining to energy storage and release have not yet been investigated.

The onset of fretting at the head-stem connection in hip arthroplasty is affected by head material and trunnion design under simulated corrosion conditions.

Mechanically assisted crevice corrosion (MACC) is a mechanism for trunnion damage in total hip arthroplasties (THAs). Retrieval studies have shown reduced MACC-related damage for ceramic heads compared with cobalt-chromium (CoCr) heads. We propose that ceramic heads demonstrate fretting at higher cyclic compressive loads than CoCr heads on titanium alloy trunnions in a simulated corrosion model.

Determination of the structures of molecularly imprinted polymers and xerogels using an automated stochastic approach.

An automated stochastic docking program with a graphical user interface, RANDOMDOCK (RD), has been developed to aid the development of molecularly imprinted polymers and xerogels. RD supports computations with ab initio and semiempirical quantum chemistry programs. The RD algorithms have been tested by searching for the most stable geometries of a varying number of methacrylic acid molecules interacting with nicotinamide.