Development and validation of a computational model of the knee joint for the evaluation of surgical treatments for osteoarthritis.

A three-dimensional (3D) knee joint computational model was developed and validated to predict knee joint contact forces and pressures for different degrees of malalignment. A 3D computational knee model was created from high-resolution radiological images to emulate passive sagittal rotation (full-extension to 65°-flexion) and weight acceptance. A cadaveric knee mounted on a six-degree-of-freedom robot was subjected to matching boundary and loading conditions.

Precision of the PRECICE internal bone lengthening nail.

Background: Previous designs of internal bone lengthening devices have been fraught with imprecise distraction, resulting in nerve injuries, joint contractures, nonunions, and other complications. Recently, a magnet-operated PRECICE nail (Ellipse Technologies, Inc, Irvine, CA, USA) was approved by the FDA; however, its clinical efficacy is unknown.

Questions/purposes: We evaluated this nail in terms of (1) accuracy and precision of distraction, (2) effects on bone alignment, (3) effects on adjacent-joint ROM, and (4) frequency of implant-related and non-implant-related complications.

Are joint structure and function related to medial knee OA pain? A pilot study.

Background: Although the severity of knee osteoarthritis (OA) usually is assessed using different measures of joint structure, function, and pain, the relationships between these measures are unclear.

Purpose: Therefore, we: (1) examined the relationships between the measures of knee structure (flexion-extension range of motion, radiographic tibiofemoral angle, and medial joint space), function (Knee Osteoarthritis Outcome Scores [KOOS], peak adduction angle, and moment), and pain (visual analog scale [VAS]); and (2) identified variables that best predicted knee pain.

Methods: We assessed 15 patients with medial knee OA using VAS pain, KOOS questionnaire, 3-D gait analysis, and radiographic examination.

Mechanical characteristics of a novel posterior-step prosthesis for biconcave glenoid defects.

Background: Posterior glenoid defects increase the risk of glenoid component loosening after total shoulder arthroplasty (TSA). The goal of this work was to evaluate the mechanical performance of a novel posterior-step glenoid prosthesis, designed to compensate for biconcave (type B2) glenoid defects. Two prototypes ("Poly-step" and "Ti-step") were constructed by attaching polyethylene or titanium step-blocks onto standard (STD) glenoid prostheses.

Evidence of isometric function of the flexor hallucis longus muscle in normal gait.

Studying mechanics of the muscles spanning multiple joints provides insights into intersegmental dynamics and movement coordination. Multiarticular muscles are thought to function at "near-isometric" lengths to transfer mechanical energy between the adjacent body segments. Flexor hallucis longus (FHL) is a multiarticular flexor of the great toe; however, its potential isometric function has received little attention.

Contribution of the flexor hallucis longus to loading of the first metatarsal and first metatarsophalangeal joint.

Background: A recent clinical study suggested that restrictive tenosynovitis of the flexor hallucis longus (FHL) may play an important causative role in hallux rigidus. The goals of this research were to assess normal function of the FHL and the effect of restricted FHL gliding on the loading of the hallux metatarsophalangeal joint (MTPJ). We hypothesized that proximal displacement of the FHL would increase the forces carried by the FHL tendon, causing increased loading of the first metatarsal and MTPJ.