Mandi J. Lopez

The effect of radiofrequency energy on the ultrastructure of joint capsular collagen.

This study evaluated the effect of radiofrequency energy on the histological and ultrastructural appearance of joint capsular collagen. Femoropatellar joint capsular specimens from adult sheep were treated with one of three treatment temperatures (45 degrees C, 65 degrees C, and 85 degrees C) with a radiofrequency generator or served as control in a randomized block design. Twenty-four specimens (n = 6) were processed for histological examination as well as ultrastructural analysis using transmission electron microscopy. A computer-based area determination program was used to calculate the area affected in histological samples. Histological changes consisted of thermal tissue damage characterized by collagen fiber fusion and fibroblastic nuclear pyknosis at all application temperatures with clear demarcations between treated and untreated tissue. Mean tissue affected ranged from 50.4% for 85 degrees C to 22.5% for 45 degrees C. There was a strong correlation between treatment temperature and percent area affected (P < .001, R2 = .65). Ultrastructural alterations included a general increase in cross-sectional fibril diameter and loss of fibril size variation with increasing treatment temperature. Longitudinal sections of collagen fibrils showed increased fibril diameter and the loss of cross-striations in the treated groups. Thermally induced ultrastructural collagen fibril alteration is likely the predominant mechanism of tissue shrinkage caused by application of radiofrequency energy.

A comparison of joint stability between anterior cruciate intact and deficient knees: a new canine model of anterior cruciate ligament disruption

Transection of the canine anterior cruciate ligament (ACL) is a well‐established osteoarthritis (OA) model. This study evaluated a new method of canine ACL disruption as well as canine knee joint laxity and joint capsule (JC) contribution to joint stability at two time points (16 and 26 weeks) after ACL disruption (n = 5/time interval). Ten crossbreed hounds were evaluated with force plate gait analysis and radiographs at intervals up to 34 weeks after monopolar radiofrequency energy (MRFE) treatment of one randomly selected ACL. Each contralateral ACL was sham treated. The MRFE treated ACLs ruptured approximately eight weeks (mean 52.5 days, SEM ± 1.0, range 48–56 days) after treatment. Gait analysis and radiographic changes were consistent with established canine ACL transection models of OA. Anterior‐posterior (AP) translation and medial‐lateral (ML) rotation were measured in each knee at 30°, 60°, and 90° of flexion with and then without JC with loads of 40 N in AP translation and 4 N m in ML rotation. A statistically significant interaction in AP translation included JC by cruciate (P = 0.02), and there was a trend for a cruciate by time (P = 0.07) interaction. Significant interactions in ML rotational testing included the presence of joint capsule (P = 0.0001) and angle by cruciate (P = 0.0012). This study describes a model in which canine ACLs predictably rupture approximately eight weeks after arthroscopic surgery and details the contribution of JC to canine knee stability in both ACL intact and deficient knees. The model presented here avoids the introduction of potential surgical variables at the time of ACL rupture and may contribute to studies of OA pathogenesis and inhibition. This model may also be useful for insight into the pathologic changes that occur in the knee as the ACL undergoes degeneration prior to rupture.

Effect of rhBMP-2 on tibial plateau fractures in a canine model.

This study was to determine the efficacy of recombinant human bone morphogenetic protien‐2 (rhBMP‐2)/calcium phosphate matrix (CPX) paste to accelerate healing in a canine articular fracture model with associated subchondral defect. rhBMP‐2/CPX (BMP), CPX alone (CPX) or autogenous bone graft (ABG) was administered to a canine articular tibial plateau osteotomy with a subchondral defect in each of 21 female dogs. The unoperated contralateral limbs served as controls. Ground reaction forces, synovial fluid, radiographic changes, mechanical testing, bone density, and histology of bone and synovium were analyzed at 6 weeks after surgery. Radiographic analysis demonstrated that the BMP and CPX groups showed improved bony healing compared to the ABG group at week 6. Histomorphometric analysis demonstrated that the BMP group had significantly increased trabecular bone volume compared to the CPX and ABG groups. Mechanical testing revealed that the BMP group had significantly greater maximum failure loads than the ABG group. Histological analysis demonstrated that the BMP group had significantly less sub‐synovial inflammation than CPX group. This study demonstrated that rhBMP‐2/CPX accelerated healing of articular fractures with subchondral defect compared to ABG in most of the parameters evaluated, and had less subsynovial inflammation than the CPX alone in a canine model.

Histologic Analysis of Bone Healing

The histologic analysis of fracture healing can be accomplished through a combination of techniques, including determination of callus area, grading of fracture union, fracture-gap tissue type, new bone formation, cell kinetics, immunohistochemistry, and tissue vascularity. Previous chapters have presented details on techniques related to bone labeling, tissue collection and fixation, embedding, sectioning, staining, and basic histomorphometry. This chapter focuses on measurements that determine the stage and quality of fracture healing.

Effects of monopolar radio frequency on soft and fibrocartilagenous tissue

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