Mechanical factors in the initiation and propagation of tears of the rotator cuff. Quantification of strains of the supraspinatus tendon in vitro.

Differential strain has been proposed to be a causative factor in failure of the supraspinatus tendon. We quantified the strains on the joint and bursal sides of the supraspinatus tendon with increasing load (20 to 200 N) and during 120 degrees of glenohumeral abduction with a constant tensile load (20 to 100 N). We tested ten fresh frozen cadaver shoulders on a purpose-built rig.

An anatomical study of meniscal allograft sizing.

Meniscus-to-femoral condyle congruity is essential for the development of circumferential hoop stresses and thus function of the meniscus. When meniscal allograft transplantation is performed using bony anchorage of the insertional ligaments, accurate graft-to-host size matching is therefore essential. The standard method currently employed for size matching of meniscal allografts is to rely on plain radiographs of the host's knee, from which expected meniscal dimensions are measured.

Supraspinatus tears: propagation and strain alteration.

It was hypothesized that there would be an alteration in strain when macroscopically normal supraspinatus tendons were subjected to three patterns of surgically created tear. The propagation of joint-side partial-thickness tears was also examined. Cadaveric shoulders were tested on a purpose-built rig with static loading from 20 to 200 N and during glenohumeral abduction from 0 degrees to 120 degrees with a 100-N tensile load.

Scoliosis in an Orangutan.

Study Design: The first case of scoliosis in an Orangutan spine is reported.

Objectives: To study the nature of scoliosis in the spinal specimen, and to determine the etiologic significance to human idiopathic scoliosis.

Summary Of Background Data: Idiopathic scoliosis has not been observed in primates other than man.

The effect of screw length and position on fixation of four-stranded hamstring grafts for anterior cruciate ligament reconstruction.

The aim of this study was to examine interference screw fixation of four strand hamstring grafts for anterior cruciate ligament reconstruction in vitro. Bovine tibiae and cannon tendons were used. Screws were introduced from 'outside-in'.

The magnitude of cutting forces at high speed.

Statement Of The Problem: Previous research has used a range of cutting forces for preparing teeth, but there are no data available on the forces actually imposed while cutting teeth with high-speed handpieces.

Purpose: The purpose of this study was to measure the forces imposed while cutting teeth with tungsten carbide burs used in high-speed handpieces.

Material And Methods: Thirty-one dentists each cut 8 conventional class II MO and DO preparations in intact extracted third molars, by use of 2 different air turbine handpieces with different torque-speed characteristics.

A review of the function and biomechanics of the meniscofemoral ligaments.

Purpose: The goal of this study was to review current knowledge on the anatomy, biomechanics, and functions of the meniscofemoral ligaments.

Type Of Study: Literature review.

Methods: A systematic search of the literature spanning the past 2 centuries was performed.

Arthroscopically insertable force probes in the rotator cuff in vivo.

In vivo loading data for the rotator cuff would be of value to scientists and clinicians interested in the shoulder. The Arthroscopically Insertable Force Probe (AIFP; Microstrain, Burlington, VT) offers a potential method for collecting this information. A technique for insertion and retrieval of the AIFP from the subscapularis is described.

A biomechanical study of four different meniscal repair systems, comparing pull-out strengths and gapping under cyclic loading.

Most studies comparing the biomechanical properties of different meniscal repair systems have simply investigated load to failure. Meniscal tissue is highly anisotropic, and far weaker under tension in the radial direction. Radially oriented loading to failure may not therefore be the most physiologically relevant in vitro test for repair of circumferential tears, and determining gapping across repair sites under cyclical loading at lower loads may be of greater importance.

Meniscofemoral ligaments--structural and material properties.

The meniscofemoral ligaments (MFLs) of 28 human cadaveric knees were studied to determine their incidence, structural and material properties. Using the Race-Amis casting method for measurement, the mean cross-sectional area for the anterior MFL (aMFL) was 14.7 mm(2) (+/-14.

Patellofemoral malalignment: looking beyond the viewbox.

A clear understanding of the pathophysiology of anterior knee pain is inhibited by the use of imprecise, poorly defined, and often interchanged words, such as malalignment, patellar alignment, maltracking, subluxation, dislocation, and congruence. The literature is filled with articles regarding the diagnosis, "malalignment of the patella," most of which give no precise diagnosis. This article presents a definition of malalignment and a plea for rational descriptive and scientific analysis.

Intraoperative measurement of knee kinematics in reconstruction of the anterior cruciate ligament.

Our objectives were to establish the envelope of passive movement and to demonstrate the kinematic behaviour of the knee during standard clinical tests before and after reconstruction of the anterior cruciate ligament (ACL). An electromagnetic device was used to measure movement of the joint during surgery. Reconstruction of the ACL significantly reduced the overall envelope of tibial rotation (10 degrees to 90 degrees flexion), moved this envelope into external rotation from 0 degrees to 20 degrees flexion, and reduced the anterior position of the tibial plateau (5 degrees to 30 degrees flexion) (p < 0.

Meniscofemoral ligaments revisited. Anatomical study, age correlation and clinical implications.

The meniscofemoral ligaments were studied in 84 fresh-frozen knees from 49 cadavers. Combined anterior and posterior approaches were used to identify the ligaments. In total, 78 specimens (93%) contained at least one meniscofemoral ligament.

Patellar tendon fiber strains: their differential responses to quadriceps tension.

This study tested the hypothesis that the posterior fibers of the patellar tendon are subjected to higher tensile strains than the anterior fibers in response to quadriceps tension. The quadriceps tendon was loaded to 1 kN in 10 human cadaver knees and the tensile strain was measured in the anterior and posterior fibers of the patellar tendon. The central third patellar tendon was divided into anterior and posterior halves which were tensile tested to failure.

Standardisation of the description of patellofemoral motion and comparison between different techniques.

Patellofemoral motion is significant clinically, yet in the literature many different methods and terminologies are used, thus making comparison between studies difficult. We review and explain the different methods used for the description of patellofemoral joint motion, compare these methods by experimentation, and propose a standardised method. We found three main methods for describing patellar motion: motion of the patella about femoral body fixed axes, about patellar body fixed axes, and a combination of these.

Preliminary study of potential for rapid prototype and surface scanned radiotherapy facemask production technique.

Preliminary investigations into the potential of an elegant technique to create a rudimentary facemask for patient immobilization during radiotherapy treatment are presented. This method combines modern technology to cause the patientfar less discomfort compared with current plaster of Paris (POP) face mould procedures. Near instantaneous patient face scanning is accomplished with charge-coupled devices for imaging in an optical surface scanning system.

Anatomic and biomechanical study of the lateral collateral and popliteofibular ligaments.

The position of the fibula around the proximal tibia varies in different people; it was therefore hypothesized that this variation would affect the orientation of the lateral collateral ligament and the popliteofibular ligament complex. This hypothesis was studied in 10 cadaveric knees by measuring the orientation and length changes in these structures as the knee was flexed. The data were correlated with tibiofibular joint position.

Periprosthetic bone mineral density changes with femoral components of differing design philosophy.

We measured the bone mineral density in 22 patients with the cylindrical stemmed cobalt-chrome AML prosthesis (collared) and in 22 patients with the tapered stem titanium CLS prosthesis (collarless). DEXA scanning was undertaken at a mean of 40 months in the AML and 52 months in the CLS group from the time of implant insertion. In both groups the greatest mean loss of BMD was found in Gruen zone 7 and the least change in Gruen zone 5.

A comparative study of 'isometric' points for anterior cruciate ligament graft attachment.

Anterior cruciate ligament (ACL) reconstruction depends critically on isometric graft placement. Unfortunately, different supposedly isometric points have been published, and no prior work has compared them to find out which are really isometric. The purpose of this study was to compare the isometry of previously published 'isometric' points for ACL reconstruction.

The anatomy of the patellar tendon.

The morphology of the attachment of the patellar tendon, its bundle orientation, the differential fascicles length and the position of the apex of the patella were assessed in 22 cadaveric human knees. The patellar apex was 39+/-6% of the width of the tendon from its medial edge. The bulk of tendon was attached to the distal two-thirds of the anterior aspect of the patella.

Comparison of the biomechanical properties of rottweiler and racing greyhound cranial cruciate ligaments.

An in vitro study of rottweiler and racing greyhound cranial cruciate ligaments revealed that the rottweiler ligaments had a significantly greater cross-sectional area at their distal attachments. Mechanical testing showed that the ultimate load related to body mass was significantly higher in the extended racing greyhound stifle during cranial tibial loading to failure, as were linear stiffness, tensile strength and tangent modulus. During ligament axis loading to failure, the only significant difference in structural and mechanical properties recorded between the two breeds was a greater ultimate strain for the greyhound ligament with the stifle joint flexed.

Cranial cruciate stability in the rottweiler and racing greyhound: an in vitro study.

An in vitro biomechanical study of cadaver stifles from rottweilers and racing greyhounds was undertaken to evaluate the contribution of the cranial cruciate ligament to stifle joint stability. This was performed at differing stifle joint angles, first with the joint capsules and ligaments intact and then with all structures removed except for the cranial cruciate ligament. Craniocaudal laxity increased in both breeds as stifle flexion increased.

Bone adaptation to a polyester fiber anterior cruciate ligament replacement.

A series of polyester fiber ACL implants was studied in ovine stifle joints up to 2 years postimplantation. The implants were linked to the bone-tunnel wall by oriented fibrous tissue. Cross-sections of the tunnels showed bone ingrowth among the implant fibers at 2 years.