Computed tomographic imaging of subchondral fatigue cracks in the distal end of the third metacarpal bone in the thoroughbred racehorse can predict crack micromotion in an ex-vivo model.

Articular stress fracture arising from the distal end of the third metacarpal bone (MC3) is a common serious injury in Thoroughbred racehorses. Currently, there is no method for predicting fracture risk clinically. We describe an ex-vivo biomechanical model in which we measured subchondral crack micromotion under compressive loading that modeled high speed running.

Arthroscopic assessment of stifle synovitis in dogs with cranial cruciate ligament rupture.

Cranial cruciate ligament rupture (CR) is a degenerative condition in dogs that typically has a non-contact mechanism. Subsequent contralateral rupture often develops in dogs with unilateral CR. Synovitis severity is an important factor that promotes ligament degradation.

Percutaneous lovastatin accelerates bone healing but is associated with periosseous soft tissue inflammation in a canine tibial osteotomy model.

Experimental studies have shown the ability of statins to stimulate bone formation when delivered locally or in large oral doses, however most have been studied in rodents. This anabolic effect is through the selective activation of BMP-2. Our purpose was to determine the effects of local treatment with lovastatin on bone healing in mammals as a preclinical animal model.

Systemic effects of ulna loading in male rats during functional adaptation.

Functional skeletal adaptation is thought to be a local phenomenon controlled by osteoctyes. However, the nervous system also may have regulatory effects on adaptation. The aim of this study was to determine the effects of loading of a single bone on adaptation of other appendicular long bones and whether these responses were neuronally regulated.

Exercise-induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse.

Repetitive bone injury and development of stress fracture is a common problem in humans and animals. The Thoroughbred racehorse is a model in which adaptive failure and associated development of stress fracture is common. We performed a histologic study of the distal end of the third metacarpal bone in two groups of horses: young Thoroughbreds that were actively racing (n = 10) and a group of non-athletic horses (n = 8).

Functional adaptation to loading of a single bone is neuronally regulated and involves multiple bones.

Regulation of load-induced bone formation is considered a local phenomenon controlled by osteocytes, although it has also been hypothesized that functional adaptation may be neuronally regulated. The aim of this study was to examine bone formation in multiple bones, in response to loading of a single bone, and to determine whether adaptation may be neuronally regulated. Load-induced responses in the left and right ulnas and humeri were determined after loading of the right ulna in male Sprague-Dawley rats (69 +/- 16 days of age).

Histologic evaluation of thermal capsulorrhaphy of human shoulder joint capsule with monopolar radiofrequency energy during short- to long-term follow-up.

Purpose: The purpose of this study was to evaluate the histologic morphology of human shoulder joint capsule after thermal capsulorrhaphy with monopolar radiofrequency energy (mRFE) during short- to long-term follow-up.

Methods: This study comprised 27 patients who received an arthroscopic mRFE thermal capsulorrhaphy and 10 patients without mRFE treatment serving as the control group. Biopsy samples from 3 locations (anterior-superior, anterior-inferior, and posterior-medial) of the shoulder joint capsule were harvested from both the mRFE-treated patients and the control patients.

Morphologic changes associated with functional adaptation of the navicular bone of horses.

Failure of functional adaptation to protect the skeleton from damage is common and is often associated with targeted remodeling of bone microdamage. Horses provide a suitable model for studying loading-related skeletal disease because horses are physically active, their exercise is usually regulated, and adaptive failure of various skeletal sites is common. We performed a histologic study of the navicular bone of three groups of horses: (1) young racing Thoroughbreds (n = 10); (2) young unshod ponies (n = 10); and (3) older horses with navicular syndrome (n = 6).

Effect of short-term treatment with alendronate on ulnar bone adaptation to cyclic fatigue loading in rats.

Targeted remodeling of fatigue-injured bone involves activation of osteoclastic resorption followed by local bone formation by osteoblasts. We studied the effect of parenteral alendronate (ALN) on bone adaptation to cyclic fatigue. The ulnae of 140 rats were cyclically loaded unilaterally until 40% loss of stiffness developed.

Effect of fatigue loading and associated matrix microdamage on bone blood flow and interstitial fluid flow.

Functional adaptation of bone to cyclic fatigue involves a complex physiological response that is targeted to sites of microdamage. The mechanisms that regulate this process are not understood, although lacunocanalicular interstitial fluid flow is likely important. We investigated the effect of a single period of cyclic fatigue on bone blood flow and interstitial fluid flow.

Role of endochondral ossification of articular cartilage and functional adaptation of the subchondral plate in the development of fatigue microcracking of joints.

The mechanisms that regulate functional adaptation of the articular ends of long bones are poorly understood. However, endochondral ossification of articular cartilage and modeling/remodeling of the subchondral plate and epiphyseal trabeculae are important components of the adaptive response. We performed a histologic study of the distal end of the third metacarpal/metatarsal bone of Thoroughbreds after bones were bulk-stained in basic fuchsin and calcified sections were prepared.

Up-regulation of site-specific remodeling without accumulation of microcracking and loss of osteocytes.

Functional adaptation of bone normally protects the skeleton from fracture during daily activity. Accumulation of microcracking and loss of osteocytes have been implicated in the regulation and initiation of targeted (reparative) remodeling of bone and, in certain situations, the development of fatigue or stress fracture. We performed a histologic study of the dorsal cortex of the mid-diaphysis of the third metacarpal (Mc-III) bone of Thoroughbred racehorses after bones were bulk-stained in basic fuchsin and transverse calcified sections were prepared.

In vivo transplantation of neonatal ovine neocartilage allografts: determining the effectiveness of tissue transglutaminase.

Following transplantation of ovine neocartilage allografts, 26 sheep were divided into groups according to the following weight-bearing schedule: 8-week nonweight bearing (8NWB, n=14), and 8-week nonweight bearing+4-week weight bearing (8NWB+4WB, n=12). In addition, 7 and 6 sheep, respectively, in the 8NWB and 8NWB+4WB groups received tTG treatment after allograft transplantation, whereas the remaining 13 sheep in these groups did not receive tTG. Finally, 8 sheep served as sham-operated controls without allograft transplantation.

Progressive arthropathy in mice with a targeted disruption of the Mop3/Bmal-1 locus.

Disruption of the murine Mop3 (also known as Bmal1 or Arntl) locus results in a loss of behavioral and molecular circadian rhythms. Although Mop3 null mice do not display anomalies in early development, they do display reduced activity as they age. In an effort to explain this decreased activity, we characterized the physiological and anatomical changes that occurred with age.

Response of the osteocyte syncytium adjacent to and distant from linear microcracks during adaptation to cyclic fatigue loading.

Cyclic loading induces fatigue in bone and initiates a complex, functionally adaptive response. We investigated the effect of a single period of fatigue on the histologic structure and biomechanical properties of bone. The ulnae of 40 rats were subjected to cyclic fatigue (-6000 microepsilon) unilaterally until 40% loss of stiffness developed, followed by 14 days of adaptation.

Comparison of surgical techniques for synovectomy in New Zealand White rabbits with induced inflammatory arthritis.

Objective: To compare effects of synovectomy performed by use of monopolar radiofrequency energy (MRFE) versus mechanical debridement in rabbits with induced inflammatory arthritis.

Animals: 25 mature female New Zealand White rabbits.

Procedure: Inflammatory arthritis was induced in both femoropatellar joints of each rabbit.

Effect of focused and radial extracorporeal shock wave therapy on equine bone microdamage.

Objectives: To determine whether bone microcracks are altered after application of focused and radial extracorporeal shock wave therapy (ESWT) to the equine distal limb.

Study Design: An ex vivo experimental model.

Sample Population: A contralateral limb specimen was obtained from 11 Thoroughbred racehorses with a unilateral catastrophic injury.

Degradation of bone structural properties by accumulation and coalescence of microcracks.

Failure of bone adaptation to protect the skeleton from fatigue fracture is common, and site-specific accumulation and coalescence of microcracking in regions of high strain during cyclic loading is considered a key factor that decreases the resistance of whole bones to fracture. We investigated the effect of cyclic fatigue loading on the monotonic structural properties of the rat ulna during accumulation and coalescence of microcracks. Cyclic end-loading of the ulna was performed at 4 Hz ex vivo at an initial peak strain of -6000 muepsilon to 20% loss of stiffness (n = 7) or 40% loss of stiffness (n = 7) bilaterally.

Hamstring graft technique for stabilization of canine cranial cruciate ligament deficient stifles.

Objective: To investigate the harvest and application of hamstring grafts for canine cranial cruciate ligament (CrCL) reconstruction.

Study Design: Experimental study.

Animals: Four adult female hounds, weighing 26.

Fatigue microdamage in the radial predilection site for osteosarcoma in dogs.

Objective: To evaluate whether body size and anatomic site influence the quantity of bone microdamage in dogs without osteosarcoma (OS).

Sample Population: Pairs of radii were collected from 10 small dogs (< 15 kg) and 10 large dogs (> 25 kg).

Procedure: Specimens were stained in basic fuchsin for bone microdamage.

Aging and accumulation of microdamage in canine bone.

Fractures associated with minimal trauma are common in aged human beings. However, bone safety margins are better preserved in aged dogs, which are rarely affected with minimal trauma fractures. Although the hierarchical architecture of canine and human compact bone is similar, the precise reasons for this species difference are unclear.

Histomorphometric description of allograft bone remodeling and union in a canine segmental femoral defect model: a comparison of rhBMP-2, cancellous bone graft, and absorbable collagen sponge.

The purpose of this study was to determine the effect of recombinant human bone morphogenetic protein type 2 (rhBMP-2) on the histomorphometry of femoral allograft-host bone union and allograft remodeling. A 6 cm mid-diaphyseal femoral defect was created and filled with an allograft stabilized with an interlocking nail in 21 dogs. Dogs were randomly divided into three equal groups and the allograft-host bone junctions and the mid-diaphyses of the allografts were treated with either an absorbable collagen sponge (ACS) loaded with rhBMP-2 (BMP group), an autogenous cancellous bone graft (CBG group), or ACS loaded with buffer solution (ACS group).

Effect of bipolar radiofrequency energy on human articular cartilage. Comparison of confocal laser microscopy and light microscopy.

Purpose: To evaluate chondrocyte viability using confocal laser microscopy (CLM) following exposure to bipolar radiofrequency energy (bRFE) and to contrast CLM with standard light microscopy (LM) techniques.

Type Of Study: In vitro analysis using chondromalacic human cartilage.

Methods: Twelve fresh chondral specimens were treated with the ArthroCare 2000 bRFE system (ArthroCare, Sunnyvale, CA) coupled with 1 of 2 types of probes and at 3 energy delivery settings (S2, S4, S6).

Effect of intramedullary polymethylmethacrylate and autogenous cancellous bone on healing of frozen segmental allografts.

This study was designed to compare bone mineral density, periosteal callus production, new bone formation, bone porosity, histologic appearance, and union of mid-diaphyseal segmental allografts of the femur stabilized with an interlocking nail technique in a canine model 6 months after the procedure. An in vivo study was performed to compare the effects of augmenting interlocking nail fixation with an interlocking nail alone, intramedullary polymethylmethacrylate, intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface of the host-allograft junction, autogenous cancellous bone applied to the endosteal surface of the allograft, autogenous cancellous bone applied to the periosteal surface of the host-allograft junction, and autogenous cancellous bone applied to the periosteal surface of the host-allograft junction and to the endosteal surface of the allograft. There were no differences among treatments for bone mineral density at any time interval.

Comparison of allograft/endoprosthetic composites with a step-cut or transverse osteotomy configuration.

This study was designed to compare the biomechanical and functional characteristics of allograft/endoprosthetic composites of the proximal 25% of the femur repaired with either a transverse or a step-cut osteotomy, using a canine model (10 dogs, five with each type of osteotomy). Serial radiography and weight-bearing studies were performed monthly, and mechanical testing was done 6 months after surgery. The femora were tested in torsion and compared with the contralateral control (insertion of a femoral component but no osteotomy).