The equine forelimb suspensory ligament exhibits a heterogeneous strain pattern under tensile load.

OBJECTIVES: To determine if regional variations in strain patterns occur within the suspensory ligament under tensile load. Local increases in strain may put certain regions of the suspensory ligament at risk and may explain the poor healing and high recurrence rates associated with suspensory branch injuries. METHODS: The suspensory ligament and its bone attachments were isolated from each of 10 adult equine cadaveric forelimbs and radiodense reference beads were inserted throughout the length of the ligament. Specimens were attached to a custom fixture secured to a materials testing system. Radiographs were acquired at 50, 445, 1112, and 2224 N of applied tensile load. Changes in distances between the beads in each region of the suspensory ligament were measured and the regional strain was calculated. Significant differences were determined using a repeated-measures analysis of variance. RESULTS: The suspensory ligament exhibited significant differences in regional strain (p <0.001). The distal branches of the suspensory ligament had significantly greater strains than the proximal (p = 0.025) and mid-body (p = 0.002) regions. The mid-body of the suspensory ligament also exhibited local strain variation, with the distal mid-body having significantly higher strains than the proximal mid-body (p = 0.038). CLINICAL SIGNIFICANCE: The equine suspensory ligament demonstrates a heterogeneous strain pattern during tensile loading, with the distal regions exhibiting significantly more strain than the proximal region. The non-homogenous strain pattern could explain the regional difference in injury and re-injury rates.

The microvasculature in the equine distal phalanx: implications for fracture healing.

OBJECTIVES: To describe the intra-osseous microvasculature of the distal phalanx of the equine forelimb with regard to its potential clinical relevance. METHODS: Eleven clinically normal equine forelimbs were used from six adult horses (range: 4 to 18 years old) euthanatized for reasons unrelated to lameness. In each limb the median artery was catheterized at the level of the carpus and India ink was injected under constant manual pressure. The limbs were frozen and 5 mm thick sections of the foot were cut in the sagittal, coronal, or transverse planes on a band saw. The sections were fixed in 10% formalin and cleared using a modified Spalteholz technique. Once cleared, the sections were photographed and the microvascular anatomy identified. RESULTS: The vascular injections revealed a rich intra-osseous microvascular supply of the distal phalanx originating from the medial and lateral palmar digital arteries. In addition, numerous smaller vessels from the terminal arch, formed by anastomosis of the medial and lateral palmar digital arteries, could be seen branching into the distal aspects of the distal phalanx. This distal portion of the distal phalanx appeared more densely vascularized than the proximal part in all specimens examined. CLINICAL SIGNIFICANCE: The increased vascularity demonstrated in the distal portion of the distal phalanx appears to correlate with improved fracture healing reported in this area. This may also explain why healing fractures which involve both the distal and proximal portions of the distal phalanx have been described as progressing from distal-to-proximal.

Three dimensional, radiosteriometric analysis (RSA) of equine stifle kinematics and articular surface contact: a cadaveric study.

REASONS FOR PERFORMING STUDY: Studies examining the effect of stifle joint angle on tibial rotation, adduction-abduction angle and articular contact area are lacking. OBJECTIVES: To test the hypothesis that tibial rotation, adduction-abduction angle and articular contact area change with stifle joint angle. STUDY DESIGN: Descriptive study of normal kinematics and articular contact patterns of the equine stifle through the functional range of motion using 3 dimensional (3D) radiosteriometric analysis (RSA) and equine cadaver stifles. METHODS: Multiple, radiopaque markers were embedded in the distal femur and proximal tibia and sequential, biplanar x-rays captured as the stifle was passively extended from 110° to full extension. Computer-programmed RSA was used to determine changes in abduction-adduction and internal-external rotation angles of the tibia during stifle extension as well as articular contact patterns (total area and areas of high contact) through the range of motion. RESULTS: The tibia rotated externally (P < 0.001) as the stifle was extended. Tibial abduction occurred from 110-135° of extension (P < 0.001) and tibial adduction occurred from 135° through full extension (P = 0.009). The centre of joint contact moved cranially on both tibial condyles during extension with the lateral moving a greater distance than the medial (P = 0.003). Articular contact area decreased (P = 0.001) in the medial compartment but not in the lateral compartment (P = 0.285) as the stifle was extended. The area of highest joint contact increased on the lateral tibial condyle (P < 0.001) with extension but decreased (P = 0.001) on the medial tibial condyle. CONCLUSIONS: Significant changes occur in tibial rotation, adduction-abduction angle and articular contact area of the equine stifle through the functional range of motion. Understanding the normal kinematics of the equine stifle and the relationship between joint positions and articular contact areas may provide important insight into the aetiology and location of common stifle joint pathologies (articular cartilage and meniscal lesions).

Infectious feline herpesvirus detected in distant bone and tendon following mucosal inoculation of specific pathogen-free cats.

Emerging evidence suggests that cats infected with feline herpesvirus-1 (FHV-1) may experience a brief viremic phase. The objective of this study was to determine whether natural routes of FHV-1 inoculation could result in viremic transmission of infectious virus to connective tissues (cortical bone, tendon). Three specific pathogen-free cats were experimentally inoculated with FHV-1 via a combined mucosal (oronasal, ocular) route. Cats were euthanized at the peak of clinical signs to aseptically harvest tissues (cortical bone, tendon, trachea/tongue) for co-culture with a susceptible cell line to promote spread of infectious virus. Viral infection of Crandall-Rees feline kidney cells was microscopically visualized by cytopathic effect (CPE). Additionally, co-culture DNA was extracted either at the point of CPE or 16 days of culture without evidence of CPE, to amplify FHV-1 glycoprotein B gene using real-time PCR. Infectious virus was detected in distant cortical bone (two cats, moderate to severe clinical signs) and tendon (one cat, severe clinical signs). Direct infection of mucosal (trachea, tongue) tissues also was confirmed in these two cats. In contrast, all co-cultured tissues from the third cat (mild clinical signs) were negative for FHV-1 by CPE and PCR. Results of this study demonstrated that early primary FHV-1 viremia may be distributed to distant connective tissues.

Stifle extension results in differential tensile forces developing between abaxial and axial components of the cranial meniscotibial ligament of the equine medial meniscus: a mechanistic explanation for meniscal tear patterns.

REASON FOR PERFORMING THE STUDY: To identify potential functional-anatomical characteristics of the cranial horn attachment of the medial meniscus (MM) that may help explain the pathogenesis of the common tear patterns that have been reported. HYPOTHESIS: Full extension of the stifle generates a significant increase in tensile forces within the cranial meniscotibial ligament (CrMTL) of the MM, which may predispose this structure to injury. METHODS: The effect of femorotibial angle (160°, 150°, 140° and 130°) on tensile forces in the axial and abaxial components of the CrMTL was examined in 6 mature cadaver stifles using an implantable force probe. Three additional specimens were used to examine the histological structure of the CrMTL and its connection to the cranial horn of the MM. RESULTS: Full extension of the stifle (160°) resulted in a significantly greater tensile force in the abaxial component of the CrMTL when compared with the axial component (P = 0.001). The tensile force in the abaxial component of the CrMTL increased significantly between 150° and 160° of stifle extension (P = 0.011). The CrMTL appears to be comprised of 2 functional components, which become more visually distinct as the stifle is extended. Histologically, these components are separated by a cleft of highly vascularised, less organised connective tissue, which becomes less prominent at the junction of the ligament and the cranial horn of the MM. CONCLUSION: A 4-fold difference in the tensile forces in the 2 functional components of the CrMTL of the MM was observed with full extension of the stifle. POTENTIAL RELEVANCE: The functional anatomy of the CrMTL may place this region at greater risk of injury during hyperextension of the stifle and, therefore, may provide a mechanistic rationale for the commonly reported meniscal tear patterns in the horse.

Meniscal translocation and deformation throughout the range of motion of the equine stifle joint: an in vitro cadaveric study.

REASON FOR PERFORMING STUDY: By study of the translocation and deformation of equine menisci throughout the range of motion, it may be possible to identify potential mechanical factors in the pathogenesis of injury to the cranial horn of the medial meniscus. OBJECTIVE: To quantitatively document meniscal translocation and deformation using radiographic and MR imaging, and to evaluate for potential variation between the medial and lateral menisci. METHODS: Radiographic markers were embedded in the periphery of the menisci in 6 cadaver stifles. Proximal-distal radiographs were taken at 15° intervals ranging from full flexion (30°) to full extension (160°). Magnetic resonance imaging sequences of 3 additional cadaver stifles were obtained in axial and sagittal planes at the predetermined stifle angles. RESULTS: A significantly greater overall mean cranial-caudal translocation (1.6 times) of the lateral meniscus relative to the medial was seen from full extension to full flexion (P = 0.002). The cranial horn of the medial meniscus was the least mobile of the 4 horns, yet a significant cranial displacement relative to the cranial horn of the lateral meniscus was seen in the terminal 10° of extension. MRI images revealed a significantly greater axial compressive strain in the cranial horn of the medial meniscus relative to the cranial horn of the lateral meniscus in the terminal 10° of extension (P = 0.017). CONCLUSION: The equine menisci exhibit a cranial-caudal translocation over the tibia throughout the range of motion. While the cranial horn of the medial meniscus is the least mobile of the 4 horns, it undergoes significant cranial translocation and axial compression in the terminal 10° of extension. POTENTIAL RELEVANCE: Hyperextension of the stifle may place the cranial horn of the medial meniscus at risk of injury and thus explain the higher prevalence of meniscal tears at this location.

Histological evaluation of the equine larynx after unilateral laser-assisted ventriculocordectomy.

REASONS FOR PERFORMING STUDY: Trans-endoscopic laser surgery, such as unilateral laser-assisted ventriculocordectomy (LVC), has gained popularity in the treatment of RLN because a laryngotomy incision or general anaesthesia are not required. However, removal of the vocal fold and ventricle takes considerable laser energy and could cause collateral tissue damage, including injury to the adjacent laryngeal cartilages. OBJECTIVES: To document the histological effects of laser surgery on laryngeal tissues in horses that have undergone LVC for the treatment of laryngeal hemiplegia (LH). METHODS: Six horses were used: 4 with experimentally induced LH that had subsequently undergone LVC 6 months prior to euthanasia; and, 2 horses were used as controls. One of the control horses with naturally occurring LH was used to study the effect of neuropathy alone, whereas the other was subjected to euthanasia immediately following LVC to evaluate the acute effect of laser surgery. Using a band saw, each larynx was sectioned transversely at 5 mm intervals and evaluated histologically. RESULTS: Acutely, LVC caused thermal damage to adjacent soft tissues but did not affect the histology of the laryngeal cartilages. Six months after LVC, laryngeal cartilages were histologically normal and there was squamous metaplasia of the repaired laryngeal mucosa, resulting in restitution of the mucosal integrity. CONCLUSIONS: Using a diode laser in contact fashion at 20 W, LVC can be used to remove the laryngeal vocal fold and ventricle without causing laryngeal cartilage damage. POTENTIAL RELEVANCE: Laryngeal chondritis is an unlikely consequence of LVC.

Collagen fibril diameter distribution does not reflect changes in the mechanical properties of in vitro stress-deprived tendons.

The purpose of this study was to determine if an association exists between the tensile properties and the collagen fibril diameter distribution in in vitro stress-deprived rat tail tendons. Rat tail tendons were paired into two groups of 21 day stress-deprived and 0 time controls and compared using transmission electron microscopy (n = 6) to measure collagen fibril diameter distribution and density, and mechanical testing (n =6) to determine ultimate stress and tensile modulus. There was a statistically significant decrease in both ultimate tensile strength (control: 17.95+/-3.99 MPa, stress-deprived: 6.79+/-3.91 MPa) and tensile modulus (control: 312.8+/-89.5 MPa, stress-deprived: 176.0+/-52.7 MPa) in the in vitro stress-deprived tendons compared to controls. However, there was no significant difference between control and stress-deprived tendons in the number of fibrils per tendon counted, mean fibril diameter, mean fibril density, or fibril size distribution. The results of this study demonstrate that the decrease in mechanical properties observed in in vitro stress-deprived rat tail tendons is not correlated with the collagen fibril diameter distribution and, therefore, the collagen fibril diameter distribution does not, by itself, dictate the decrease in mechanical properties observed in in vitro stress-deprived rat tail tendons.

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.

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.

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.

Effect of tibial plateau leveling on cranial and caudal tibial thrusts in canine cranial cruciate-deficient stifles: an in vitro experimental study.

OBJECTIVES: To investigate the effect of tibial plateau leveling (TPL) on tibial subluxation and tibial axial rotation; to determine the minimal tibial plateau rotation (MinTPR) angle that provides stifle stability; and to evaluate caudal cruciate ligament (CaCL) strain following tibial plateau rotation in cranial cruciate ligament (CrCL)-deficient stifles. ANIMALS: Fifteen canine cadaver hind limbs. METHODS: Tibial subluxation was measured from lateral radiographs in intact, loaded stifles and after sequential CrCL transection, MinTPR, TPL, and CaCL transection. The MinTPR angle was determined using a custom-made hinge plate and compared with the TPL angle. Tibial axial rotation was evaluated in CrCL-deficient stifles before and after TPL. Finally, CaCL strain was recorded in intact, loaded stifles, and following MinTPR, TPL, and tibial plateau over-rotation (MaxTPR) using a force probe. RESULTS: Cranial tibial subluxation in CrCL-deficient stifles was eliminated with TPL. Tibial plateau rotation, however, induced caudal tibial subluxation, which significantly increased from MinTPR to TPL before and after CaCL transection. The MinTPR angle was 6.5 degrees +/- 0.9 degrees less than the TPL angle (P <.05). Tibial internal rotation decreased significantly after TPL in CrCL-deficient stifles. Finally, CaCL strain increased with increasing tibial plateau rotation. CONCLUSIONS: This study suggests that, during stance phase, TPL transforms cranial tibial thrust into caudal tibial thrust, thereby stabilizing the stifle in the cranio-caudal plane via the constraint of the CaCL. The increase in CaCL stress, which results from tibial plateau rotation, could predispose the CaCL to fatigue failure and therefore would caution against tibial plateau over-rotation.

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.

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.

Tensile fixation strengths of absorbable meniscal repair devices as a function of hydrolysis time. An in vitro experimental study.

To determine the effect of hydrolysis time on the fixation strength of absorbable meniscal repair devices, adult bovine menisci were repaired with five devices and a suture. The ultimate tensile strength of the repair was then tested in six specimens immediately or after 6, 12, or 24 weeks of incubation at 37 degrees C in a saline solution containing antibiotics, antimycotics, and protease inhibitors. Immediately after implantation the Bionx Meniscus Arrow had a significantly higher failure strength (57.7 +/- 13.8 N) than the Linvatec BioStinger (35.1 +/- 6.7 N), the Innovasive Clearfix screw (34.9 +/- 13 N), the Surgical Dynamics S-D-sorb staple (9.4 +/- 4.6 N), and the Mitek Meniscal Repair System (polydioxanone) (27.2 +/- 6.0 N). However, there was no significant difference between the Bionx Meniscus Arrow and a 2-0 polydioxanone vertical suture (51.6 +/- 2.7 N). The polydioxanone-based implants demonstrated a significant decrease in failure strength at 12 and 24 weeks. Similarly, the Surgical Dynamics S-D-sorb staple lost all fixation strength by 24 weeks. The remaining devices showed no significant loss of failure strength over the 24-week period, suggesting that 24 weeks of hydrolysis does not adversely affect the ultimate holding power of poly L-lactide-based meniscal fixation devices.

Tissue-engineered rotator cuff tendon using porcine small intestine submucosa. Histologic and mechanical evaluation in dogs.

To determine its efficacy in stimulating the regeneration of a rotator cuff tendon, an implant of 10-ply porcine small intestinal submucosa was used to replace a completely resected infraspinatus tendon in 21 adult mongrel dogs. The contralateral infraspinatus tendon was elevated and then reattached to the greater tubercle with sutures to mimic conventional repair (sham operation). Mechanical evaluations were performed at 0, 3, and 6 months (five specimens at each time period). Histologic comparisons were made at 3 and 6 months (three specimens). At both times, the gross appearance, histologic continuity, and failure mode of the constructs mimicked those of sham-operated and native infraspinatus tendons, thus suggesting host tissue ingrowth and implant remodeling with solid integration of the regenerated tissue to muscular and bony interfaces. Tissue ingrowth occurred without histologic evidence of foreign body or immune-mediated reactions or adhesions to peripheral tissues. Sham operations simulated tendon mobilization and reimplantation procedures routinely performed to treat chronic rotator cuff tendon injuries. Although the ultimate strength of small intestinal submucosa-regenerated tendons was significantly less than that of native infraspinatus tendons (P < 0.001), it was similar to that of reimplanted tendons at 3 (P > 0.05) and 6 months (P > 0.05).

The effect of varied electrical current densities on lumbar spinal fusions in dogs.

BACKGROUND CONTEXT: The use of electrical stimulation has been shown to increase the rate of successful spinal fusions. It is possible that increasing the current density of these stimulators may increase the speed and success rate of these fusions. PURPOSE: This study evaluated the effects of varied current densities on the speed and success rate of spinal fusion in dogs. STUDY DESIGN/SETTING: Three different current densities (0.83 microA/cm, 4 microA/cm and 10 microA/cm) were used to stimulate spinal fusions in a canine model over a 12-week period. OUTCOME MEASURES: Radiographic and histologic assessments were used to determine the degree of facet fusions at each time period. METHODS: Fifteen dogs underwent spinal facet fusion bilaterally at the level of L1-2 and L4-5. Each fusion site was electrically stimulated using one of three current densities. At 6, 9 and 12 weeks, the specimens were evaluated using high-resolution radiography and routine histology. The fusion masses were graded and then statistically evaluated. RESULTS: The results demonstrate a dose response of fusion mass scores to increasing current density. The highest current density (10 microA/cm) demonstrated a statistically higher fusion scores than the lowest currently density (0.83 microA/cm) at 6 weeks and statistically greater than both the middle (4 microA/cm) and lowest (0.83 microA/cm) current densities at 9 weeks. No differences were noted at 12 weeks, because all groups showed complete fusion. CONCLUSIONS: This controlled study suggests that speed of fusion may be further improved by increasing the current density of the electrical stimulation.

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

Thermal modification (shrinkage) of capsular connective tissue has gained increasing popularity as an adjunctive or even a primary procedure in the arthroscopic treatment of shoulder instability. Although the physical effects of heat on collagenous tissues are well known, the long-term biologic fate of these shrunken tissues is still a matter of debate. The temperatures required to alter the molecular bonding of collagen and thus cause tissue shrinkage (65 degrees C to 70 degrees C) are also known to destroy cellular viability. Therefore, thermally modified tissues are devitalized and must undergo a biologic remodeling process. During this remodeling, the mechanical properties of the treated tissues are altered (decreased stiffness) and can be at risk for elongation if the postoperative rehabilitation regimen is too aggressive. Although anecdotal reports suggest that thermal capsular shrinkage does have a beneficial effect, the exact mechanism responsible for this clinical improvement has yet to be fully defined. The reported improvement could be due to the maintenance of initial capsular shrinkage, secondary fibroplasia and resultant thickening of the joint capsule, a loss of afferent sensory stimulation due to the destruction of sensory receptors, or a combination of all three. The clinical role for thermal modification of connective tissues has not yet been defined, but it appears that it may prove most useful as a stimulant for inducing a biologic repair response.

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.

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.