Biomedical subjects

S P Arnoczky

Publications and source records attributed to S P Arnoczky.

At least 19 recordsLinked to original sources

PubMed2001

Anatomic placement of the Herbert-Whipple screw in scaphoid fractures: a cadaver study.

An anthropometric cadaver study was performed to determine the optimal placement of a Herbert-Whipple screw in the scaphoid. Twenty pairs of cadaver wrists were examined and anthropometric analysis of the scaphoids using plain radiography, computed tomography, and en bloc resection was performed. Scaphoid vascularity was evaluated using India ink injection. Radiographic and actual measurements of height and width confirmed symmetry in paired scaphoids. Anatomic evaluation defined a safe zone for screw placement. K-wire placement defined the extent of this zone. The entry point of this zone was found by moving dorsally and distally 15% of the lateral radiographic length of the contralateral scaphoid from the volar aspect of the scaphoid tuberosity. Moving 10% of this same length from the membranous central portion of the scapholunate ligament defined the target site. Computed tomography confirmed proper position of the screw to maximize bony purchase and avoid articular penetration while maintaining dorsal vascular integrity.

Anthropometry↗

PubMed2001

Kinetic study of the replacement of porcine small intestinal submucosa grafts and the regeneration of meniscal-like tissue in large avascular meniscal defects in dogs.

Porcine small intestinal submucosa (SIS) was used to replace large, avascular defects in the medial menisci of dogs. Twelve dogs received SIS grafts and 3 dogs were left untreated as controls. Dogs were evaluated at 4, 8, and 12 weeks by means of lameness scoring and ultrasonography. Dogs were sacrificed at 1, 6, or 12 weeks after implantation, and the tissue at the site of meniscal resection was evaluated for gross and histologic appearance, cross-sectional and surface area, and collagen types I and II. The femoral and tibial condyles were assessed for articular cartilage damage. Control dogs were significantly more lame than grafted dogs 8 and 12 weeks after instrumentation. Grafted dogs' replacement tissue appeared meniscal-like when evaluated grossly and ultrasonographically 12 weeks after instrumentation. The amount of replacement tissue was significantly greater in both cross-sectional and surface area for grafted dogs than for controls at all time points. Histologically, the SIS biomaterial could be identified in all grafted dogs at 1 week post-implantation, but in none at 6 weeks post-implantation. Subjectively, grafted dogs' replacement tissue was histologically superior to that of controls with respect to tissue type, organization, and architecture. Collagen types I and II immunoreactivity in grafted menisci were similar to that of normal menisci. Control dogs had significantly more articular cartilage damage than grafted dogs. SIS appears to induce regeneration of meniscal-like tissue in large, avascular meniscal defects in dogs, resulting in superior clinical function and articular cartilage protection compared to ungrafted controls.

Analysis of Variance↗

PubMed2001

Photoelastic stress analysis of strain patterns in equine hooves after four-point trimming.

OBJECTIVE: To evaluate changes in strain patterns in normal equine hooves following 4-point trimming, using photoelastic stress analysis. SAMPLE POPULATION: 15 equine front limbs with normal hoof configuration. PROCEDURE: Limbs were disarticulated at the carpometacarpal joint. Weight-bearing surfaces of each hoof were trimmed level to ensure 100% ground contact. Hoof walls were coated with a custom-made strain-sensitive plastic, and limbs were loaded to a third of body weight. Using a polariscope, strain distribution, magnitudes, and directions were evaluated in level hooves as well as before and after standardized 4-point trimming. Repeated-measures ANOVA was used to compare strain magnitudes and directions before and after trimming. RESULTS: In leveled specimens, strain fields were symmetrically distributed above the heels and at quarter-toe junctions along a line between the middle and distal thirds of the hoof wall. After 4-point trimming, strain epicenters localized above the contact points, whereas strain magnitudes significantly increased by approximately 50%. Decreasing contact area by 50% resulted in an additional significant increase (32%) in strain magnitude. Trimming did not have a significant effect on strain orientations. CONCLUSION AND CLINICAL RELEVANCE: This study documents that 4-point trimming results in strain concentration above the hoof contact points and that strain magnitude is dependent on contact area.

Animals↗

PubMed2001

Myofibroblasts in the accessory ligament (distal check ligament) and the deep digital flexor tendon of foals.

OBJECTIVE: To demonstrate myofibroblasts in the accessory ligament of the deep digital flexor tendon (ie, distal check ligament) and deep digital flexor tendon of clinically normal foals. SAMPLE POPULATION: Tissue specimens from 25 foals that were necropsied for reasons unrelated to this study and unrelated to musculoskeletal disease. PROCEDURE: The distal check ligament and deep digital flexor tendon of both forelimbs were examined histologically. Myofibroblasts were identified by immunohistochemical staining specific for alpha-smooth muscle actin (alpha-SMA). RESULTS: Most of the cells in the distal check ligament and deep digital flexor tendon of all foals stained positive for alpha-SMA. CONCLUSION AND CLINICAL RELEVANCE: Myofibroblasts made up most of the cells in the distal check ligament and deep digital flexor tendon of clinically normal foals. These cells have contractile ability and therefore, may play a role in flexure contracture of these tendons. The ability of tetracycline to chelate calcium or decrease the expression of the contractile protein alpha-smooth muscle actin could inhibit the myofibroblasts' ability to contract, thus providing a rationale for tetracycline administration as a treatment of distal interphalangeal joint flexor deformity in foals.

Actins↗

PubMed2001

Thermal modification of connective tissues: basic science considerations and clinical implications.

Wound healing is a natural and well-orchestrated biologic event. Indeed, the ability of wounds to heal is the foundation on which the practice of surgery is predicated. The successful surgeon maintains a delicate alliance with nature, balancing the magnitude of the surgical insult against the capacity of the tissue for repair. Thermal injury is one of the most traumatic insults a tissue can sustain and the high degree of cell death and matrix alteration associated with thermal burns have been shown to result in a protracted healing time. Thus, the use of thermal energy as a stimulant for tissue shrinkage must be tempered with an appreciation of the biologic events that accompany this phenomenon. Furthermore, it must be realized that the initial degree of capsular shrinkage observed following the application of thermal energy may have little bearing on the long-term biologic and biomechanical status of the joint capsule. Therefore, the desire to see a redundant capsule shrink and become taut at surgery should be weighed very carefully against the level of damage imparted to the tissue to achieve this result. The simple initiation of the healing response may be sufficient to rehabilitate an incompetent structure via the creation of new cellular tissue. While the ultimate application(s) of thermal modification of connective tissues has yet to be completely defined, its ultimate role may be best suited to that of a low level stimulant for inducing a biologic repair response rather than a highly aggressive mechanism for primary tissue shrinkage.

Connective Tissue↗

PubMed2000

The effect of an exogenous fibrin clot on the regeneration of the triangular fibrocartilage complex: an in vivo experimental study in dogs.

The effect of an exogenous fibrin clot on the regeneration of the triangular fibrocartilage complex (TFCC) was examined in a dog model. In 12 mature dogs, bilateral TFCC resection was performed. The resulting defect was packed with an exogenous fibrin clot (experimental) while the contralateral side was left empty (control). Tissue regeneration was evaluated grossly and histologically at 6, 12, and 26 weeks. At each time period, the regenerated tissue in the fibrin clot-filled defect appeared more mature and more congruent with the adjacent cartilaginous surfaces than did the control (empty) defect. At 26 weeks, the clot regenerated tissue had the histological appearance of a normal TFCC with a homogeneous fibrocartilaginous matrix, regularly oriented collagen fibers, and normal integration with the adjacent support structures of the joint. The results of this study indicate that an exogenous fibrin clot could be used to promote a fibrocartilaginous repair tissue for a resected TFCC. Such therapy could be used in the arthroscopic treatment of TFCC injury and resection in an effort to improve postoperative outcome.

Animals↗

PubMed2000

Basal joint arthroplasty using an allograft tendon interposition versus no interposition: a radiographic, vascular, and histologic study.

To assess the role of a tendon spacer that fills the trapezial void, the trapeziums were excised and anterior oblique ligaments were reconstructed in 25 monkeys. In addition to the ligament reconstruction, 20 of the monkeys had the trapezial void filled with a tendon allograft. The trapezial space was investigated at 0, 3, 6, 15, and 40 weeks using routine histologic staining, arterial perfusion (Spalteholz), and standardized radiographs. There was a statistically greater decline in trapezial height in the animals without tendon interposition allografts. The tendon grafts became progressively neovascularized and populated with fibroblasts. By 40 weeks, the allograft was no longer a folded tendon but a homogeneous mass of collagen, fibroblasts, and capillaries. The specimens without an interpositional tendon graft had loose fibroadipose tissue filling the carpal void. Polarized light microscopy showed fibers crossing the subchondral bone and moving into the adjacent fibrous spacer in the specimens implanted with a tendon graft. The results indicate that filling the trapezial void with an interposition tendon spacer may aid in maintaining normal wrist anatomy.

Animals↗

PubMed2000

Effects of a 98% solution of glycerol or sterilization with ethylene oxide on FeLV in bone allografts and effects on bone incorporation of allografts in cats.

OBJECTIVES: To compare virucidal effects and bone incorporation properties of cortical bone allografts transplanted into specific-pathogen-free (SPF) cats. Allografts consisted of untreated bone from a SPF cat (negative-control group) and bone from 5 FeLV-infected cats that was subjected to sterilization with ethylene oxide (ETO), preservation with glycerol, or no treatment (positive-control group). SAMPLE POPULATION: Bones from the aforementioned groups and twenty 8-week-old SPF cats (5 cats/group) implanted with an allograft from 1 of the aforementioned groups. PROCEDURE: After implantation, blood samples were collected weekly to monitor FeLV p27 antigen and antibody titers. Quantification of FeLV provirus was performed on blood samples at weeks 0, 4, and 8 and donor bone samples at time of implantation. Cats were euthanatized 8 weeks after transplantation, and graft sites were evaluated. RESULTS: All results for negative-control cats were negative. All ETO group cats had negative results for antigen and provirus in blood, whereas 1 cat had a low antibody titer. Although 3 ETO-treated allografts were positive for provirus, the DNA appeared denatured. One cat in the glycerol group had positive results for all tests in blood samples. All glycerol-preserved allografts were positive when tested for provirus. All results for positive-control group cats were positive. Differences in incorporation of bone grafts were not observed. CONCLUSIONS AND CLINICAL RELEVANCE: Glycerol preservation of FeLV-infected bone allografts did not eliminate transmission of retrovirus to recipients. In contrast, ETO sterilization appeared to denature DNA and prevent infection. Treatments did not affect incorporation of bone grafts in young cats.

Animals↗

PubMed1999

Use of small intestinal submucosal implants for regeneration of large fascial defects: an experimental study in dogs.

A single layer of porcine small intestinal submucosa (SIS) was sutured into a 5 x 5 cm window created in the fascia lata of ten adult mongrel dogs in order to determine the efficacy of this material in promoting tissue regeneration of large fascial defects. A similar defect in the contralateral limb was left empty and served as a negative control. Tissue regeneration was examined grossly and histologically at 6 and 12 weeks. By 6 weeks, marked fibroplasia and angiogenesis had occurred throughout the SIS scaffold. The regenerated tissue was well organized and showed good integration with the adjacent fascia while the control specimens were filled with loose areolar connective tissue. At 12 weeks the experimental defects were filled with a regenerated tissue that grossly and histologically resembled normal fascia. There was no evidence of adhesions to the underlying musculature. Conversely, the tissue that filled the control defects remained disorganized and was markedly thinner than the adjacent fascia. The results of this study suggest that SIS is capable of supporting tissue regeneration in large fascial defects. The ability of this material to induce regeneration of a substantial area of tissue grossly and histologically similar to normal fascia and without adhesions to the underlying musculature makes its application in reconstructive surgery appear promising.

Animals↗

PubMed1999

The effect of bone compaction on early fixation of porous-coated implants.

The effect of a bone compaction technique versus conventional drilling on the early fixation of porous-coated implants was examined in a canine model. Compaction dilation resulted in a significant increase in implant fixation stiffness (P < .01) and ultimate fixation strength (P < .01) at 0 and 3 weeks. Fixation stiffness remained significantly increased at 6 weeks (P < .01); however, the ultimate fixation strength was not statistically significant between the 2 techniques (P > .05). There was no significant difference in either fixation value at 9 weeks (P > .05). Histological examination of the bone-implant interface demonstrated an increase in the density of cancellous bone immediately adjacent to the implants placed in the compaction dilated holes. The results of this study suggest that the compaction method of host bone preparation may optimize the initial stability of the implant interface of porous-coated prostheses.

Animals↗

PubMed1999

A method for determination of equine hoof strain patterns using photoelasticity: an in vitro study.

During impact, equine hooves undergo viscoelastic deformations which may result in potentially harmful strains. Previous hoof strain studies using strain gauges have been inconclusive due to arbitrary gauge placement. Photoelastic stress analysis (PSA) is a full-field technique which visually displays strains over entire loaded surfaces. This in vitro study identifies normal hoof strain patterns using PSA. Custom-made photoelastic plastic sheets were applied to the hoof surface. The hooves were axially loaded (225 kg) under level and varus/valgus conditions. Strain patterns were video-recorded through a polariscope. Strains were concentrated between middle and distal thirds of the hoof wall regardless of the loading conditions. This strain distribution appears to result from the differential expansion of the hoof wall under load. Increasing load resulted in higher strains and asymmetric loading resulted in an ipsilateral increase in strain magnitudes without altering strain locations. This study shows that PSA is a reliable method with which to evaluate hoof strains in vitro and is sensitive enough to reflect subtle load-related strain alterations.

Animals↗

PubMed1999

Building a meniscus. Biologic considerations.

Creating a tissue engineered meniscus requires that specific biologic considerations such as cell type, matrix scaffold, bioreactor design (in vitro, in vivo, or both), and environmental conditions (media, cytokines, physical stimuli) be addressed. Meniscal cells, fibroblasts, and mesenchymal stem cells have been proposed as potential cell sources and have been grown (either in vivo or in vitro) on various cell matrices including collagen based scaffolds, biodegradable polymers, and small intestine submucosa. In addition, various environmental factors (nutrients, growth factors) have been used to optimize cell proliferation in vitro. Although these tissue engineering paradigms have produced a meniscuslike construct, the long term functional capabilities of this engineered tissue have yet to be proven. The concept of tissue engineering holds great promise for the generation of tissues or organs unable to repair or regenerate themselves. In terms of the meniscal tissue, however, the principles of tissue engineering may be best used to enhance and optimize the natural regeneration of the meniscus.

Animals↗

PubMed1998

Effects of age and location on the biomechanical and biochemical properties of canine tracheal ring cartilage in dogs.

OBJECTIVE: To evaluate effects of age (immature vs adult) and location along the trachea on the biomechanical properties (via a tensile stress relaxation test) and biochemical properties (Water content and total proteoglycan content) of canine tracheal ring cartilage. SAMPLE POPULATION: Entire trachea from 8 immature and 8 adult dogs. PROCEDURE: A section of each tracheal ring from 8 immature dogs (6 months old) and 8 adult dogs (2 to 3 years old) was tested biomechanically (maximal stress, equilibrium stress, equilibrium modulus, and percentage of relaxation) and processed for biochemical analysis (water content and total proteoglycan content). Two rings from each trachea were prepared for histologic analysis (H&E or safranin-O staining). RESULTS: Biomechanical and biochemical parameters were not different between cervical and thoracic rings of either age group. Mean maximal stress, equilibrium stress, and equilibrium modulus were significantly higher for adult, compared with immature, dogs. However, percentage of relaxation for adult dogs was significantly lower. Tracheal rings of adult dogs had a significantly higher proteoglycan content and a significantly lower water content than did those of immature dogs. Water content and biomechanical parameters were significantly correlated, and proteoglycan content and biomechanical properties were significantly but weakly correlated. On histologic sectioning, a qualitative decrease in safranin-O staining in the rings of immature dogs also was observed. CONCLUSIONS AND CLINICAL RELEVANCE: Biomechanical and biochemical properties of the canine tracheal ring cartilage are altered with age. However, location of the ring along the trachea did not affect these properties for either age group. Results lend support to the theory that proteoglycan content has some effect on tensile properties of tracheal rings and may explain increased compliance observed in rings from dogs with collapsed trachea.

Aging↗

PubMed1998

Influence of exogenous hyaluronan on synthesis of hyaluronan and collagenase by equine synoviocytes.

OBJECTIVE: To evaluate the influence of exogenous hyaluronan (HA) on in vitro synthesis of HA and collagenase by equine synoviocytes from normal and inflamed joints. ANIMALS: 9 adult horses. PROCEDURE: Synoviocytes for culture were taken from the middle carpal joint of 3 horses with normal joints (control) and 6 horses with osteochondral fractures (principal). Synoviocytes were propagated in monolayer cultures and were incubated with 3 commercial HA products at concentrations of 0, 200, 400, and 1,500 micrograms/ml. Newly synthesized HA was radiolabeled with [3H]glucosamine and quantified by cetylpyridinium chloride precipitation and liquid scintillation counting. The hydrodynamic size of radioactive HA was determined by high-performance liquid chromatography, and collagenase activity was evaluated by use of a quantitative radioactive collagen film assay. RESULTS: Exogenous HA influenced neither the rate of synthesis nor the hydrodynamic size of the newly produced HA by control or principal cell cultures. Culture supernatants from abnormal synovium, exposed to 400 and 1,500 micrograms of exogenous HA/ml, contained significantly more collagenase activity than did those exposed to lower concentrations. CONCLUSION: Although HA is thought to have beneficial effects in equine arthropathies, the principal mechanisms of action of HA do not appear to be stimulation of synthesis of HA of augmented molecular weight or marked inhibition of collagenase synthesis.

Animals↗

PubMed1997

Use of full cortical allograft to repair a metatarsal fracture in a foal.

A 4-month-old Quarter Horse colt was admitted for repair of an open, comminuted fracture of the proximal portions of the diaphyses of the left second, third, and fourth metatarsal bones. Initial repair included internal fixation and cancellous bone graft. However, the third metatarsal bone became infected and failed to heal. After removal of infected portions of the bone, a 5-cm, fullthickness cortical allograft was placed in the defect. Rigid internal fixation provided stability for the allograft and remaining fracture fragments so that the horse was able to bear weight on the second and fourth metatarsal bones. The allograft was ultimately resorbed; however, appositional bone growth permitted a massive, functional metatarsal bone to form that incorporated the second, third, and fourth metatarsal bones. The colt went on to compete successfully, long term, as a show horse.

Animals↗

PubMed1996

Depressed osteoblast activity and increased osteocyte necrosis after closed bone fracture and hemorrhagic shock.

BACKGROUND: Although bone fracture and hemorrhagic shock are frequent complications in trauma patients, it remains unknown whether hemorrhagic shock after bone fracture produces any deleterious effects on osteoblast function and osteocyte necrosis. METHODS: Sham-operation, closed bone fracture (right tibia) with and without hemorrhagic shock (mean arterial blood pressure 35 +/- 5 mm Hg for 90 minutes followed by fluid resuscitation) were induced in 18 male C3H/HeN mice (25 g body weight) At 72 hours after the experiment, all animals were killed, whole blood was obtained by cardiac puncture, and plasma assayed for circulating levels of osteocalcin. RESULTS: Plasma osteocalcin levels were found to be significantly depressed after closed bone fracture in conjunction with hemorrhagic shock. Closed bone fracture alone increased plasma osteocalcin. Histologic analysis of the fracture sites revealed that hemorrhagic shock after closed bone fracture significantly increased osteocyte necrosis adjacent to the fracture site, when compared to animals with closed bone fracture alone. CONCLUSIONS: These findings suggest that severe hemorrhage after closed bone fracture depresses osteoblast activity and increases osteocyte necrosis, which should compromise fracture healing under those conditions.

Animals↗

PubMed1996

Retroviral transmission in bone allotransplantation. The effects of tissue processing.

The transmission of a retrovirus through transplantation of processed bone allografts was studied using the feline leukemia virus. The long bones of 4 previously infected donor cats were harvested and assigned to 1 of 3 treatment groups: single freeze/thaw cycle, double freeze/thaw cycle, or double freeze/thaw cycle with water flush to remove bone marrow. Cortical bone grafts and corticocancellous bone grafts from each treatment group were transplanted into individual specific-pathogen-free recipients. Samples of plasma were obtained weekly from all recipients and were tested with an enzyme-linked immunosorbent assay to detect viral antigen. For animals that tested consistently negative for viral antigen, plasma samples also were tested for antiviral antibody to feline leukemia virus measured by live cell immunofluorescence. The results of the antigen and antibody testing revealed that all of the cortical and corticocancellous bone allografts in each of the 3 treatment groups transmitted virus. The ability of the treated bone allografts to transmit a feline retrovirus suggests that routine processing and removal of bone marrow may not inhibit their ability to transmit other retroviruses, such as the human immunodeficiency virus.

Animals↗

PubMed1996

Apparent viscosity of the synovial fluid from mid-carpal, tibiotarsal, and distal interphalangeal joints of horses.

OBJECTIVE: To compare the apparent viscosity of normal synovial fluid of the mid-carpal, tibiotarsal, and interphalangeal joints of horses. DESIGN: Viscosity evaluation over a range of shear rates was used to characterize the apparent viscosity of synovial fluids from the 3 joints. ANIMALS: 60 clinically normal adult horses. PROCEDURE: Viscosity data for synovial fluid samples were obtained over a shear rate range of 10 to 250/s and apparent viscosity was calculated at 50, 100, 150, 200, and 250/s. Effect of shear rate on apparent viscosity was determined, using a two-way ANOVA, with significant differences tested, using a Tukey's test at a significance level of P < 0.05. RESULTS: Synovial fluid from all these joints indicated shear thinning behavior: decreased apparent viscosity with increased shear rate. Apparent viscosity of synovial fluid from the 3 joints was not significantly different over the shear rate range of 50 to 250/s. CONCLUSION: Results of this study indicate that the apparent viscosity of the distal interphalangeal joint is not less than that of other joints, as has been reported. CLINICAL RELEVANCE: The observation of decreased synovial fluid viscosity of distal interphalangeal joint fluid should be considered as suggestive of joint disease.

Analysis of Variance↗