Investigation of the association between oxygen reserve index and arterial partial oxygen pressure in anesthetized dogs.

OBJECTIVE: To evaluate the relationship between oxygen reserve index (ORI) and arterial partial pressure of oxygen (PaO2) in anesthetized dogs. STUDY DESIGN: Prospective experimental study. ANIMALS: A total of eight healthy adult Beagle dogs with a median age of 38 (range 20-87) months and a median body mass of 8.6 (range 7.0-13.8) kg. METHODS: After induction of general anesthesia with propofol, dogs were mechanically ventilated and anesthesia maintained with isoflurane carried in oxygen. Arterial blood samples were collected from a catheter placed in the femoral artery. ORI was measured by placing a CO-oximeter sensor on the tongue. Inspired oxygen fraction (FiO2) was increased from 21% to > 95% in increments of 5%. PaO2 and ORI were recorded and compared at different times. The relationship between ORI and PaO2 was investigated using a nonlinear function, the Hill equation, and a linear regression analysis was performed, as appropriate. RESULTS: A total of 128 pairs of values were compared for all dogs. Applying the Hill equation to the relationship between ORI and PaO2 resulted in R2 = 0.80 (p < 0.001) with a Hill coefficient of 3.7. It was predicted that ORI ranged 0.1-0.9 as PaO2 ranged 127.0-417.9 mmHg and that in the more linear portion of the range, PaO2 of 127.0-289.9 mmHg ORI ranged 0.1-0.7. Linear regression analysis in the more linear portion showed a weak correlation (R2 = 0.29, p = 0.006). CONCLUSIONS AND CLINICAL RELEVANCE: In the present study, the Hill equation predicted the relationship between PaO2 and ORI for PaO2 ranging 127.0-417.9 mmHg in anesthetized dogs. However, in the linear portion of the PaO2, the coefficient of determination was low, indicating that ORI is not a surrogate for PaO2.

Evaluation of the quadriceps muscle length to femoral length ratio in small breed dogs with medial patellar luxation.

OBJECTIVE: To determine the quadriceps muscle length (QML) to femoral length (FL) ratio (QML/FL) and its associated factors in small breed dogs with medial patellar luxation (MPL) and to compare the differences in the QML/FL between MPL grades. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Small breed dogs (<10 kg) with MPL: 78 dogs (134 limbs). METHODS: Medical records and computed tomography (CT) images from 2008-2020 were reviewed. Furthermore, age, bodyweight, sex, laterality, MPL grade, femoral inclination angle (FIA), femoral torsion angle (FTA), anatomical lateral distal femoral angle (aLDFA), and patellar ligament length to patellar length ratio were included in the regression analysis to determine the factors associated with QML/FL. Each measurement parameter was compared among the four MPL grade groups. RESULTS: The final model demonstrated that the QML/FL increased with increasing age (p = .004) and decreased with increasing FTA and aLDFA (p = .015 and p < .001, respectively). The MPL grade IV group had a lower QML/FL than the grade I, II, and III groups (p = .002, p < .001, and p < .001, respectively). CONCLUSION: Among small breed dogs, those with MPL grade IV had a shortened QML associated with femoral deformities. CLINICAL SIGNIFICANCE: Noninvasive evaluation of the QML/FL improves our understanding of the length mismatch between the quadriceps muscle and the femur.

Escherichia coli-derived recombinant human bone morphogenetic protein-2 combined with bone marrow-derived mesenchymal stromal cells improves bone regeneration in canine segmental ulnar defects.

BACKGROUND: Large bone defects in canines usually require assistance to achieve healing. Implantation of osteoinductive factors can promote bone healing, while transplantation of osteoprogenitor cells can enhance bone regeneration. We hypothesized that implantation of an osteoinductive factor, recombinant human bone morphogenetic protein-2 (rhBMP-2), combined with osteoprogenitor cells, bone marrow-derived mesenchymal stromal cells (BMSCs), would synergistically promote bone healing. In this study, we examined the combined effects of Escherichia coli-derived rhBMP-2 and BMSCs on bone healing after implantation into canine ulnar defects. RESULTS: Critical-sized osteoperiosteal segmental defects (2.5 cm) were created in the ulnae of healthy female beagle dogs, and implanted with combinations of E. coli-derived rhBMP-2 (560 or 140 µg) and autologous BMSCs (10(7), 10(5), or 0 cells). In the present study,18 forelimbs of nine healthy purpose-bred female beagles were used. All six treatment groups contained three forelimbs, and the animals were euthanized after 12 weeks. The control groups (560 and 140 µg/0 cells) were cited from our previous study to reduce the number of experimental animals. Radiographically, the regenerated bone width was significantly increased in the 560 or 140 µg with 10(7) and 10(5) cells groups compared with the 0 cells groups. By quantitative CT, the bone mineral density was higher in the 560 µg with 10(7) and 10(5) cells groups, while non-uniformity of the bone mineral density was improved in the 560 µg with 10(7) and 10(5) cells groups and 140 µg/10(7) cells group. Mechanically, the maximum loads at failure were significantly higher in the 560 µg with 10(7) and 10(5) cells groups. Histologically, the regenerated bone was well-developed and contained osteocyte-like cells marrow cavities, and vessels. However, the osteoclasts and osteoblasts were hardly observed. The osteocyte-like cell numbers were significantly higher in the 560 µg with 10(7) and 10(5) cells and 140 µg with 10(7) and 10(5) cells groups. CONCLUSIONS: Implantation of E. coli-derived rhBMP-2 and BMSCs led to significantly enhanced bone formation, with improved bone mineral density and reduced non-uniformity of the regenerated bone. Combined implantation of rhBMP-2 and BMSCs may be useful for promotion of bone healing in critical-sized defects in canines.

A Retrospective Study of Risk Factors Associated with Refracture after Repair of Radial-Ulnar Fractures in Small-Breed Dogs.

OBJECTIVE: The aim of this study was to identify risk factors for refracture after radial union in small-breed dogs. STUDY DESIGN: In our retrospective study, medical records of radial-ulnar fracture cases in small dogs treated with plates and screws were reviewed. General information and postoperative course (days until confirmed radial fracture healing, with or without ulnar union, time to final follow-up, with or without plate removal and refracture) were recorded. The fracture line location, screw positions, radial thickness and width, and pixel values throughout the postoperative periods were obtained from the radiographs. The affected limbs were classified into non-plate removal (P) and plate removal (R) groups. RESULTS: Refracture occurred in 5 of the 141 limbs at the most distal screw in the P group and 5 of the 40 limbs at the same site as the initial fracture in the R group. Multivariate analysis indicated that refracture was linked to the amount of relative change with growth in the position of the most distal screw in the P group, with pixel value and radial thickness ratios at the same site as the initial fracture in the R group. CONCLUSION: Reducing the screw diameter relative to the radial width to the appropriate extent may be considered in cases where the screw positioned at the most distal end of the radius is expected to be relatively proximal as the distal radius grows; not removing the plate may be considered in cases with a decreased radial thickness or bone mineral density beneath the plate during plate removal.

Stress Changes in the Canine Radius after Locking Plate Fixation Using Finite Element Analysis.

OBJECTIVE: The aim of this study was to evaluate the stress changes in the radii beneath the locking plates (LP) of dogs implanted with LP using finite element analysis (FEA). STUDY DESIGN: The study included radii harvested from eight dogs. After computed tomography (CT) scans of the forelimb, the articular surface of the radius was fixed using resin. Material tests were conducted to identify the yield and fracture points and for verification with FEA. The CT data of the radius were imported into FEA software. The radii were classified into three groups based on the placement of the LP (nonplate placement, intact group; 1 mm above the radial surface, LP + 1 mm group; 3 mm above the radial surface, LP + 3 mm group). Equivalent, maximum, and minimum principal stresses and minimum principal strain were measured after FEA at the radial diaphysis beneath the plate. RESULTS: In shell elements, the LP + 1 mm and LP + 3 mm groups showed a significantly lower maximum principal stress compared with the intact group. In solid elements, the LP + 1 mm and LP + 3 mm groups showed a significantly higher equivalent stress and a significantly lower maximum principal stress compared with the intact group. CONCLUSION: When an axial load is applied to the radius, LP placement reduces the tension stress on the cortical bone of the radius beneath the plate, possibly related to implant-induced osteoporosis and bone formation in the cortical bone beneath the plate.

Three cases of dogs with osteosarcoma of the forelimb treated with liquid nitrogen for limb-sparing surgery using autologous bone.

Osteosarcoma treatment with limb-sparing surgery using liquid nitrogen can be applied to canine patients experiencing diminished quality of life after leg amputation. In particular, forelimb amputation may affect gait more than hindlimb amputation. In this study, limb-sparing surgery using liquid nitrogen was applied to primary osteosarcomas arising in the proximal scapula of a Welsh Corgi, the proximal humerus of a Golden Retriever, and the distal radius of a Great Pyrenees, according to the protocol of Tsuchiya et al. In all cases, postoperative radiographic examination revealed bone union between the treated and matrix bones. All patients recovered their gait postoperatively. These results suggest that limb-sparing surgery using liquid nitrogen-treated autologous bone is an effective option for patients with osteosarcoma.

Comparison of patellar position and moment arm between tibial plateau leveling osteotomy and cranial closing wedge ostectomy: An ex vivo study.

Background: Tibial plateau leveling osteotomy (TPLO) and cranial closing wedge ostectomy (CCWO) are common treatments for cranial cruciate ligament disease. These two techniques mainly differ in whether the proximal tibial fragment contains the attachment site of the patellar ligament. Currently, no reports compare how these techniques affect the patellofemoral joint. Aim: This ex vivo study aimed to compare the effects of TPLO and CCWO on the patellar position and moment arm in healthy Beagles. Methods: TPLO and CCWO were performed on each stifle in six cadavers of Beagles. Pre- and postoperative mediolateral radiographs with the stifle angle at approximately 90° were obtained. The modified Blumensaat index (MBI), patellar ligament length to patella length ratio (PLL:PL), and patellar moment arm (PMA) were measured in each radiograph. Mixed-model multiple regression analyses for the MBI, PLL:PL, and PMA, with the surgical procedure as the independent variable, were then performed. The joint angle was included as an independent variable for MBI and PMA. Results: The PLL:PL was decreased after TPLO. Additionally, the PLL:PL after TPLO was significantly lower than that after CCWO. The MBI decreased with flexion. Postoperative MBI values were reduced for both procedures, with lower values after CCWO than after TPLO. The PMA values decreased with flexion. Postoperative values for both methods were reduced in the PMA, with the values being lower after CCWO than after TPLO. Conclusion: Both TPLO and CCWO affect the patellofemoral joint. Compared with TPLO, CCWO produced more excellent downward traction on the patella. Therefore, CCWO may be used to correct the patellar alta and treat cranial cruciate ligament disease.

Medial patellar luxation grade IV according to the Singleton system can be classified into skeletally immature and skeletally matured types.

OBJECTIVE: To determine the signalment and musculoskeletal morphology of small-breed dogs affected by medial patellar luxation (MPL) grade IV based on the age of the CT scan. ANIMALS: 40 small-breed dogs (54 limbs) with MPL grade IV. PROCEDURES: Dogs that had undergone corrective surgery for MPL grade IV and had performed CT of the hind limb before surgery were included. Signalment (age, body weight, sex, laterality, and breed) and concomitant cranial cruciate ligament rupture (CrCLR) were recorded. Femoral inclination angle, anatomical lateral distal femoral angle (aLDFA), femoral torsion angle, quadriceps muscle length to femoral length ratio (QML/FL), and patellar ligament length to patellar length were obtained by CT images. The dogs were categorized into 2 groups based on their age at the time of the CT scan, the skeletally immature group and the skeletally matured group. Signalment and group were included in the multiple regression analysis to determine the factors associated with each measurement parameter. A logistic regression analysis was conducted to determine the risk of CrCL concomitant with age. RESULTS: The multiple regression model demonstrated that the group was associated with the value of aLDFA and QML/FL. aLDFA was higher, and QML/FL was lower in group SI than in group SM. CrCLR was present in 5/54 limbs (9.2%), with a mean age of 70.8 months and it was associated with increasing age. CLINICAL RELEVANCE: In Singleton's classification, dogs classified as grade IV can be categorized into 2 groups based on musculoskeletal morphology and pathophysiology: the skeletally immature and skeletally matured types.

Effect of Escherichia coli-produced recombinant human bone morphogenetic protein 2 on the regeneration of canine segmental ulnar defects.

Because bone morphogenetic protein 2 gene transfected Escherichia coli (E-BMP-2) produce recombinant human BMP-2 (rhBMP-2) more efficiently than mammalian cells (Chinese hamster ovary [CHO]-BMP-2), they may be a more cost-effective source of rhBMP-2 for clinical use. However, use of E-BMP-2 for regenerating long bones in large animals has not been reported. In the current study, we evaluated the healing efficacy of E-BMP-2 in a canine model. We created 2.5-cm critical-size segmental ulnar defects in test animals, then implanted E-BMP-2 and 700 mg of artificial bone (beta-tricalcium phosphate; ß-TCP) into the wounds. We examined the differential effects of 5 E-BMP-2 treatments (0, 35, 140, 560, and 2240 µg) across 5 experimental groups (control, BMP35, BMP140, BMP560, and BMP2240). Radiography and computed tomography were used to observe the regeneration process. The groups in which higher doses of E-BMP-2 were administered (BMP560 and BMP2240) displayed more pronounced bone regeneration; the regenerated tissues connected to the host bone, and the cross-sectional areas of the regenerated bone were larger than those of the originals. The groups in which lower doses of E-BMP-2 were administered (BMP35 and BMP140) experienced relatively less bone regeneration; furthermore, the regenerated tissues failed to connect to the host bone. In these groups, the cross-sectional areas of the regenerated bone were equal to or smaller than those of the originals. No regeneration was observed in the control group. These findings suggest that, like CHO-BMP-2, E-BMP-2 can be used for the regeneration of large defects in long bones and that its clinical use might decrease the cost of bone regeneration treatments.

Comparison of bone marrow and adipose tissue-derived canine mesenchymal stem cells.

BACKGROUND: Bone marrow-derived mesenchymal stem cells (BM-MSCs) and adipose tissue-derived mesenchymal stem cells (AT-MSCs) are potential cellular sources of therapeutic stem cells. MSCs are a multipotent population of cells capable of differentiating into a number of mesodermal lineages. Treatment using MSCs appears to be a helpful approach for structural restoration in regenerative medicine. Correct identification of these cells is necessary, but there is inadequate information on the MSC profile of cell surface markers and mRNA expression in dogs. In this study, we performed molecular characterization of canine BM-MSCs and AT-MSCs using immunological and mRNA expression analysis. RESULTS: Samples were confirmed to be multipotent based on their osteogenic and adipogenic differentiation. And these cells were checked as stem cell, hematopoietic and embryonic stem cell (ESC) markers by flow cytometry. BM- and AT-MSCs showed high expression of CD29 and CD44, moderate expression of CD90, and were negative for CD34, CD45, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81. SSEA-1 was expressed at very low levels in AT-MSCs. Quantitative real-time PCR (qRT-PCR) revealed expression of Oct3/4, Sox2, and Nanog in BM- and AT-MSCs. There was no significant difference in expression of Oct3/4 and Sox2 between BM-MSCs and AT-MSCs. However, Nanog expression was 2.5-fold higher in AT-MSCs than in BM-MSCs. Using immunocytochemical analysis, Oct3/4 and Sox2 proteins were observed in BM- and AT-MSCs. CONCLUSION: Our results provide fundamental information to enable for more reproducible and reliable quality control in the identification of canine BM-MSCs and AT-MSCs by protein and mRNA expression analysis.

Safety of autologous bone marrow stromal cell transplantation in dogs with acute spinal cord injury.

OBJECTIVE: To assess the feasibility and safety of transplantation of autologous bone marrow stromal cell (BMSC) in dogs with acute spinal cord injury (SCI). STUDY DESIGN: An open-label single-arm trial. ANIMALS: Dogs (n = 7) with severe SCI from T6 to L5, caused by vertebral fracture and luxation. METHODS: Decompressive and stabilization surgery was performed on dogs with severe SCI caused by vertebral fracture and luxation. Autologous BMSCs were obtained from each dog's femur, cultured, and then injected into the lesion in the acute stage. Adverse events and motor and sensory function were observed for >1 year after SCI. RESULTS: Follow-up was 29-62 months after SCI. No complications (eg, infection, neuropathic pain, worsening of neurologic function) were observed. Two dogs walked without support, but none of the 7 dogs had any change in sensory function. CONCLUSIONS: Autologous BMSC transplantation is feasible and safe in dogs with acute SCI. Further studies are needed to determine the efficacy of this therapy.

Prophylactic Efficacy of Tibial Plateau Levelling Osteotomy for a Canine Model with Experimentally Induced Degeneration of the Cranial Cruciate Ligament.

OBJECTIVE: The aim of this study was to clarify the histological effects of tibial plateau levelling osteotomy on cranial cruciate ligament degeneration induced by excessive tibial plateau angle. STUDY DESIGN: Five female Beagles were used to bilaterally create excessive tibial plateau angle models surgically. A second tibial plateau levelling osteotomy was performed 11 months after the first surgery on the right stifle (tibial plateau levelling osteotomy group), and a sham operation that did not change the tibial plateau angle was performed on the left stifle (excessive tibial plateau angle group). At 6 months after the second surgery, the dogs were euthanatized. The cranial cruciate ligament was stained with haematoxylin-eosin to assess the cell density, Alcian-Blue to assess proteoglycans and Elastica-Eosin to assess elastic fibres, and immunohistochemically stained to assess type I (COL1) and type II collagen and SRY-type HMG box 9 (SOX9) expression. RESULTS: In each group, the cranial cruciate ligament degeneration, especially on the tibial side, including the presence of Alcian-Blue- and Elastica-Eosin-positive regions, decreased in COL1-positive regions, and enhancement of SOX9 expression was observed. Besides, compared with the tibial plateau levelling osteotomy group, the excessive tibial plateau angle group showed increases in Alcian-Blue- and Elastica-Eosin-positive regions and a decrease in the COL1-positive regions. CONCLUSION: The results suggested that excessive tibial plateau angle-induced cranial cruciate ligament degeneration can be suppressed by reducing the biomechanical load on the cranial cruciate ligament by performing tibial plateau levelling osteotomy.

Use of 3-D Models for Surgical Planning of a Malunion in a Dog.

Background: An 8-year-old, 18.9 kg, male, intact Kai Ken with a femoral shaft fracture experienced recurrent implant breakage after two fracture reductions using an internal fixator. Objectives: This case report is aimed at using a three-dimensional (3-D) printer to diagnose residual femoral rotational deviation. Implant failures and malunion occurred after two attempts at synthesis. Thus, a 3-D model was designed for preoperative planning of a third surgery. Methods: To evaluate the alignment in the postoperative state after the second surgery, we removed a broken plate from the affected limb. Subsequently, a computed tomography image produced a bone replica using 3-D printing. The distal fragment was fixed and rotated externally by 42°. In addition to correcting the rotational deformity of the femur, we used an intramedullary pin and two locking plates to stabilize the proximal and distal femoral fracture segments. Results: The bone union was confirmed four months after surgery, and no postoperative complications were observed 11 months after surgery. Conclusion: 3-D printing is a valuable tool that increases the accuracy of presurgical planning.

Postoperative outcomes of combined surgery comprising dorsal laminectomy, transarticular screws, pedicle screws and polymethylmethacrylate for dorsal fixation in 21 dogs with degenerative lumbosacral stenosis.

OBJECTIVE: To retrospectively review the efficacy of combined surgery comprising dorsal laminectomy and dorsal fixation using screws and polymethylmethacrylate as treatment for dogs with degenerative lumbosacral stenosis (DLSS). ANIMALS: 21 client owned dogs diagnosed with DLSS and treated surgically. PROCEDURES: Based on clinical records, signalments, clinical signs, findings from orthopedic and neurological examinations, imaging findings, and postoperative complications were evaluated at the following time points: preoperatively, postoperatively, and 3, 6, 12, 24, and 36 months after surgery. RESULTS: In all 21 cases, clinical signs were alleviated, proprioceptive deficits were improved from 3 months after surgery, and no recurrence of clinical signs was observed during the observation period. Minor complications were observed in 6 cases (28.6%), including implant failure in 2 (9.5%), delayed healing of surgical wounds in 2 (9.5%), seroma in 1 (4.8%), and swelling of the affected area in 1 (4.8%). There was no case with major complications. CLINICAL RELEVANCE: Combined surgery comprising dorsal laminectomy and dorsal fixation using screws and polymethylmethacrylate is a useful treatment that can improve long-term clinical signs in dogs with DLSS.

Influence of ventral fixation techniques on atlantoaxial joint fusion in canine models with dens partial resection.

We evaluated the completeness of bony fusion of the atlantoaxial joint (AAJ) through polymethylmethacrylate fixation (PMF) and atlantoaxial plate fixation (APF) using six canine models with dens partial resection. In both groups, the hydroxyapatite content at the AAJ was measured up to 7 months postoperatively using quantitative computed tomography. Histological assessment revealed fibrous fusion in the PMF group. Meanwhile, in the APF group, only one dog achieved fibrous fusion, whereas the remaining three showed bony fusion. To our knowledge, this study was the first to evaluate AAJ fusion histologically after PMF and APF. The present study demonstrates that PMF and APF may stabilize the AAJ without clinical complications. Therefore, PMF and APF are clinically useful fixation methods for atlantoaxial instability.

Examination of the proximodistal patellar position in small dogs in relation to anatomical features of the distal femur and medial patellar luxation.

OBJECTIVE: To determine the influence of anatomical features of the distal femur on the proximodistal patellar position and compare the proximodistal patellar position between dogs with and without medial patellar luxation (MPL). STUDY DESIGN: Retrospective case series (n = 71). METHODS: Mediolateral-view radiographs of clinical cases of dogs weighing less than 15 kg were obtained. The stifle joint angle, patellar ligament length, patellar length, size of the femoral condyle, trochlear length, and trochlear angle were measured and included in multiple linear regression analyses to ascertain their effects on the proximodistal patellar position. Radiographs were divided into MPL and control groups. The effects of MPL on the proximodistal patellar position and morphological factors were also examined. RESULTS: The final model for the proximodistal patellar position revealed that the patella became distal as the ratio of the patellar ligament length to patellar length decreased, the trochlear angle relative to the femur increased, the trochlear length relative to the patellar length increased, or the trochlear length relative to the femoral condyle width decreased. The proximodistal patellar position in the MPL group was not significantly different from that in the control group despite the trend towards a distally positioned patella (p = 0.073). The MPL group showed a significantly shorter trochlea (p<0.001) and greater trochlear angle relative to the femur (p = 0.029) than the control group. CONCLUSION: The proximodistal patellar position depends on multiple factors, and its determination based on PLL/PL alone may not be appropriate. Dogs with MPL did not have a proximally positioned patella compared with dogs without MPL. Although hindlimbs with MPL had a shorter trochlea than those without patellar luxation, this difference did not appear to be sufficient to displace the patellar position proximally in small dogs, possibly compensated by increased trochlear angle relative to the femur.

Alterations in the ground reaction force of dogs during trot after immobilization of the stifle joint: An experimental study.

This study aimed to evaluate changes in the vertical and fore-aft force generation of the hindlimbs in dogs with stifle orthoses. Custom-made orthoses were used on the right stifle joint. Force plate and marker data from four beagle dogs in trials without orthoses, with fixed orthoses, and with unfixed orthoses were collected. The vertical ground reaction force of the right side was increased with fixed orthoses and decreased with unfixed orthoses compared to that of gait without orthoses. When compared to that of gait without orthoses, the fore-aft ground reaction force changed with fixed orthoses but not with unfixed orthoses. It is suggested that the level of constraint of the orthosis affected the ground reaction force pattern.

A Retrospective Study of Postoperative Development of Implant-Induced Osteoporosis in Radial-Ulnar Fractures in Toy Breed Dogs Treated with Plate Fixation.

OBJECTIVE: This study aimed to evaluate implant-induced osteoporosis (IIO) development in toy breed dogs treated using internal fixation with digital radiographs as the index of pixel values. STUDY DESIGN: There were 226 cases (236 limbs) of toy breed dogs with radial-ulnar fractures. Pixel values were measured on radiographs immediately, 2 weeks and 1 to 12 months after surgery. The ratio of pixel values (PVR) represented the bone mineral areal density based on the humeral condyle in the same image. The dogs were grouped based on the fixation methods, age and status of destabilization. RESULTS: There was a significant decrease in the PVR at 1 to 12 months postoperatively for all cases. There were not any significant differences in PVR of antebrachial fractures between those repaired with plates using locking head screws, cortex screws or a combination of locking and cortex screws. Implant-induced osteoporosis persisted at 1 to 12 months postoperatively in dogs aged ≧6 months, while the PVR increased after 3 months in dogs aged <6 months. Based on the destabilization method, there was a significant increase in the PVR at 3 months in the plate removal group. CONCLUSION: This study suggests that IIO occurs in small dogs treated with plates and screws. Moreover, patients aged < 6 months showed an early postoperative recovery of bone mineral areal density. Further, screw and plate removal could contribute to the recovery of bone mineral areal density.

Investigation of the effects of excessive tibial plateau angle and changes in load on ligament tensile forces in the stifle joints of dogs.

OBJECTIVE: To investigate the effect of an excessive tibial plateau angle (TPA) and change in compressive load on tensile forces experienced by the cranial cruciate, medial collateral, and lateral collateral ligaments (CCL, MCL, and LCL, respectively) of canine stifle joints. SAMPLE: 16 cadaveric stifle joints from 16 orthopedically normal Beagles. PROCEDURES: Stifle joints were categorized into unchanged (mean TPA, 30.4°) and excessive (mean TPA before and after modification, 31.2° and 41.1°, respectively) TPA groups. The excessive TPA group underwent a TPA-increasing procedure (curvilinear osteotomy of the proximal aspect of the tibia) to achieve the desired TPA. A robotic system was used to apply a 30- and 60-N compressive load to specimens. The craniomedial band of the CCL, caudolateral band of the CCL, MCL, and LCL were sequentially transected; load application was repeated after each transection. Orthogonal force components were measured in situ. Forces on ligaments were calculated after repeated output force measurements as the contribution of each component was eliminated. RESULTS: Increasing the compressive load increased tensile forces on the craniomedial and caudolateral bands of the CCL, but not on the MCL or LCL, in specimens of both groups. At the 60-N load, tensile force on the craniomedial band, but not other ligaments, was greater for the excessive TPA group than for the unchanged TPA group. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that stress on the CCL may increase when the compressive load increases. The TPA-increasing procedure resulted in increased tensile force on the CCL at a 60-N compressive load without affecting forces on the MCL or LCL.

Long-term administration of prednisolone: Effects on the myocardial tissue of healthy beagle dogs.

This study aimed to assess the structural and functional effects of long-term hyperglucocorticoidemia on canine myocardium and compare these parameters with histopathological changes. Twelve healthy male beagle dogs were enrolled and assigned to the high-dose prednisolone (P; n=6) and control (C; n=6) groups. The P group was treated with 2 mg/kg of prednisolone BID for 84 days. Clinical parameters were measured using echocardiography and non-invasive systolic blood pressure (SBP) measured before the initiation of synthetic corticosteroids and at 7, 28, 56, and 84 days after the start of medication. For histological evaluation, cardiovascular tissue was harvested from dogs in groups P (at the end of the medication period) and C (scheduled to be euthanized for unrelated reasons). In the P group, clinical changes including thickening of the left ventricular free wall (LVFW) and interventricular septum (IVS), decreased left ventricular (LV) diastolic function, and increased SBP were observed after the start of medication. During histological evaluation, fibrosis was observed in the LVFW and IVS in the P group. Furthermore, decreased glucocorticoid receptor (GCR) levels were observed in the LVFW, right ventricular free wall (RVFW), and IVS and increased mineralocorticoid receptor (MCR) levels were observed in the LVFW and RVFW in the P group compared with those in the C group. In conclusion, fibrosis may cause LV structural and functional abnormalities in dogs with hyperadrenocorticism. Furthermore, GCR downregulation and upregulated MCR might influence the myocardial fibrosis.