Prestalk-like positioning of de-differentiated cells in the social amoeba Dictyostelium discoideum.

The social amoeba Dictyostelium discoideum switches between solitary growth and social fruitification depending on nutrient availability. Under starvation, cells aggregate and form fruiting bodies consisting of spores and altruistic stalk cells. Once cells socially committed, they complete fruitification, even if a new source of nutrients becomes available. This social commitment is puzzling because it hinders individual cells from resuming solitary growth quickly. One idea posits that traits that facilitate premature de-commitment are hindered from being selected. We studied outcomes of the premature de-commitment through forced refeeding. Our results show that when refed cells interacted with non-refed cells, some of them became solitary, whereas a fraction was redirected to the altruistic stalk, regardless of their original fate. The refed cells exhibited reduced cohesiveness and were sorted out during morphogenesis. Our findings provide an insight into a division of labor of the social amoeba, in which less cohesive individuals become altruists.

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.

Biomechanical effects of cranial closing wedge osteotomy on joint stability in normal canine stifles: an ex vivo study.

BACKGROUND: Cranial closing wedge osteotomy (CCWO) is a functional stabilisation technique for cranial cruciate ligament (CrCL) ruptures. This biomechanical study aimed to evaluate the influence of CCWO on the stability of the stifle joint. Eighteen Beagle stifle joints were divided into two groups: control and CCWO. The stifle joints were analyzed using a six-degree-of-freedom robotic joint biomechanical testing system. The joints were subjected to 30 N in the craniocaudal (CrCd) drawer and proximal compression tests and 1 Nm in the internal-external (IE) rotation test. Each test was performed with an extension position, 135°, and 120° of joint angle. RESULTS: The stifle joints were tested while the CrCLs were intact and then transected. In the drawer test, the CCWO procedure, CrCL transection, and stifle joint flexion increased CrCd displacement. The CCWO procedure and CrCL transection showed an interaction effect. In the compression test, the CCWO procedure decreased and CrCL transection and stifle joint flexion increased displacement. In the IE rotation test, CCWO, CrCL transection, and stifle joint flexion increased the range of motion. CONCLUSIONS: CCWO was expected to provide stability against compressive force but does not contribute to stability in the drawer or rotational tests. In the CCWO-treated stifle joint, instability during the drawer test worsened with CrCL transection. In other words, performing the CCWO procedure when the CrCL function is present is desirable for stabilizing the stifle joint.

Partial tarsal arthrodesis with closing wedge ostectomy for treatment of bilateral twisted leg deformity in a cat.

A 5-month-old male domestic shorthair cat was presented with severe bilateral hind-limb deformities that caused the cat to walk on the dorsal aspect of the metatarsals. Computed tomography (CT) images revealed that the calcaneus was externally rotated, and the distal end of the calcaneus was turned medially to the talus in both hind limbs. The cat was diagnosed with twisted leg deformity, a congenital tarsal hyperextension deformity (clubfoot). Based on CT images, closing wedge ostectomy was done at the level of the tarsometatarsal joint with the wider part facing laterally. Partial transection of the common calcaneal tendon was not performed. Nine weeks after surgery, the cat was able to walk and jump, with its paws correctly placed on the ground, despite the limited range of motion in the tarsal joints. Based on radiographs with maximum tarsal flexion, the angle of the partial tarsal arthrodesis limited the range of motion. This is apparently the first case report describing CT images and closing wedge ostectomy in a cat with twisted leg deformity. Key clinical message: This article reports the findings obtained from CT imaging of a cat with twisted leg deformity. The current case was successfully managed by closing wedge ostectomy without partial transection of the common calcaneal tendon.

Arthrodèse partielle du tarse avec ostectomie de fermeture pour le traitement d'une déformation bilatérale des pattes tordues chez un chat. Un chat domestique à poil court mâle âgé de 5 mois a été présenté avec de graves déformations bilatérales des membres postérieurs qui ont amené le chat à marcher sur la face dorsale des métatarsiens. Les images de tomodensitométrie (CT) ont révélé que le calcanéus était en rotation externe et que l'extrémité distale du calcanéum était tournée médialement vers le talus dans les deux membres postérieurs. Le chat a été diagnostiqué avec une déformation de la jambe tordue, une déformation congénitale du tarse en hyperextension (pied bot). Sur la base d'images par CT, une ostectomie de fermeture a été réalisée au niveau de l'articulation tarsométatarsienne avec la partie la plus large tournée latéralement. Aucune section partielle du tendon calcanéen commun n'a été réalisée. Neuf semaines après l'opération, le chat était capable de marcher et de sauter, les pattes correctement posées au sol, malgré l'amplitude de mouvement limitée des articulations du tarse. Sur la base de radiographies avec une flexion tarsienne maximale, l'angle de l'arthrodèse partielle du tarse limitait l'amplitude de mouvement. Il s'agit apparemment du premier rapport de cas décrivant des images CT et une ostectomie de fermeture chez un chat présentant une déformation de la jambe tordue.Message clinique clé:Cet article rapporte les résultats obtenus à partir de l'imagerie CT d'un chat avec une déformation des pattes tordues. Le cas actuel a été géré avec succès par une ostectomie de fermeture sans section partielle du tendon calcanéen commun.(Traduit par Dr Serge Messier).

Finite element analysis predictions in the canine lumbar spine are useful and correlate with ex vivo biomechanical studies.

OBJECTIVE: To verify the validity of finite element analysis (FEA) predictions obtained from a canine lumbar segment model in comparison with experimental biomechanical testing results from the same subjects. ANIMALS: 6 healthy beagle dogs were euthanized for other purposes. METHODS: The L1-2 and L5-6 segments were harvested from euthanized animals and subjected to rotation tests and compression tests, respectively, using both ex vivo mechanical testing and FEA. For each method, we recorded the maximum torque value and angle of vertebral body rotation at rupture observed in rotation tests, as well as the maximum stress value and displacement of the vertebral body endplate at rupture measured from compression tests. We then calculated Pearson's correlation coefficient to determine correlations between the angle of gyration and displacement at rupture determined by mechanical testing and FEA. The study started on March 26, 2021, and ended on March 18, 2023. RESULTS: For the rotation test, correlation coefficients for the maximum torque and rotation angle of the vertebral body at rupture were r = 0.92 and 0.96, respectively. For the compression test, correlation coefficients for the maximum stress and displacement of the vertebral body endplate at rupture were r = 0.73 and 0.94, respectively. All results showed strong correlations between the FEA predictions and ex vivo mechanical test results. CLINICAL RELEVANCE: These findings suggest that FEA predictions are sufficiently reliable for ex vivo mechanical test results for biomechanical studies of canine lumbar segment models.

Vertebral fixation does not affect recovery or recurrence of cervical intervertebral disc herniation in small dogs (< 15 kg).

OBJECTIVE: To compare the prognosis of small dogs with cervical intervertebral disc herniation (C-IVDH) when treated with ventral slot decompression (VSD) alone or with concomitant vertebral fixation (VF). ANIMALS: Small dogs (n = 303) weighing < 15 kg diagnosed with C-IVDH and treated with VSD. PROCEDURES: We recorded signalment, cervical myelopathy grade, surgical site, use of VF, degree of adjacent disc degeneration, recovery, recurrence, recurrence site, and postoperative course, including the time elapsed from recovery to recurrence. We examined factors associated with recovery and recurrence during the 30-month postoperative period using multivariate logistic regression analysis. RESULTS: VF did not affect recovery (P = .79). However, nonchondrodystrophic breeds had poorer recovery (OR, 5.89; P = .023) than chondrodystrophic breeds, and a higher preoperative cervical myelopathy grade (grade 3 or 4) was associated with poorer recovery (OR, 7.09 or 3.46, respectively; P = .019 or .042, respectively), compared with grade 1. VF did not affect recurrence (P = .79); however, increasing age was associated with recurrence (OR, 1.79; P = .001). CLINICAL RELEVANCE: In small dogs weighing < 15 kg, there was no difference in postoperative recovery and recurrence rates after VSD with or without concomitant VF. Therefore, in small dogs with C-IVDH, even if the slot volume is increased to remove sufficient disc material during VSD, a good prognosis can be achieved with or without VF.

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.

Case report: Limb-sparing surgery of tibial chondrosarcoma with frozen autologous bone graft using liquid nitrogen in a dog.

Chondrosarcoma is the second most common primary bone tumor after osteosarcoma in dogs. Chondrosarcoma has a good prognosis owing to its low metastatic rate and long survival time, even with amputation alone. However, amputation risks reducing the quality of life in patients with other orthopedic diseases of the non-affected limb, neurological diseases, or large body size. Limb-sparing surgery with frozen autologous bone grafting using liquid nitrogen allows bone quality to be maintained in the normal bone area while killing tumor cells, thereby preserving the affected limb. Thus, it is expected to maintain the quality of life. We describe herein limb-sparing surgery for tibial chondrosarcoma with frozen autologous bone graft using liquid nitrogen in an 8-year and 8-month-old castrated male bulldog weighing 29.2 kg. The patient had chondrosarcoma of the left tibia, suspected cranial cruciate ligament rupture of the right stifle, and degenerative lumbosacral stenosis. In such a case, amputation would increase the burden on the non-affected limb or spine, which could cause difficulty in walking; therefore, we performed limb-sparing surgery. Postoperatively, although a circumduction gait associated with stifle arthrodesis remained, the patient maintained the quality of life for 20 months, and the owner was satisfied with the results.

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.

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.

Examination of Proximodistal Patellar Position in Dogs with the Stifle at Full Extension.

OBJECTIVE: The aim of this study was to determine the factors related to functional patella alta, with which the proximodistal patellar position exceeds the reference range of healthy small dogs proximally when the stifle is at full extension. STUDY DESIGN: Mediolateral-view radiographs of dogs weighing less than 15 kg were obtained and classified into the medial patellar luxation (MPL) and control groups. The reference range of the proximodistal patellar position was determined from the control group. In both groups, a patellar position exceeding this reference range proximally was considered functional patella alta. Multiple logistic regression analysis was performed to examine the factors related to functional patella alta. A receiver operating characteristic (ROC) curve was made for each factor. RESULTS: Overall, radiographs of 127 stifles of 75 dogs were obtained. Eleven stifles in the MPL group and one stifle in the control group were determined to be functional patella alta. The factors associated with functional patella alta included a greater full extension angle of the stifle joint, longer patellar ligament, and shorter femoral trochlear length. The full extension angle of the stifle joint had the biggest area under the ROC curve. CONCLUSION: Mediolateral radiographs of the stifle joint in full extension are clinically important in dogs with MPL because some dogs might have a proximally positioned patella that is recognizable only when the stifles are extended.

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 tibial plateau levelling osteotomy on the tensile forces sustained by ligaments in cranial cruciate ligament-intact canine stifles: An ex vivo pilot study.

BACKGROUND: Tibial plateau levelling osteotomy (TPLO) changes the anatomical tibial conformation and might alter the positional relationship of the ligaments comprising the stifle joint. As a result, it is expected to affect the tensile force of the ligaments. However, studies analyzing the details of the effect of osteotomy are limited. OBJECTIVES: To evaluate the influence of TPLO on the tensile force on the stifle ligaments in the intact canine stifle using a six-degree-of-freedom (6-DOF) robotic testing system. METHODS: Eight stifles were categorised into the reference group and nine stifles into the TPLO group. The stifles were then analysed using a 6-DOF robotic joint biomechanical testing system. The stifles were applied 30 N at cranial, caudal, and compression loads and 1 Nm at the internal and external torque loads (the load applied to the tibia relative to the femur) on extension, at 135° and 120°, respectively. The tensile force placed on the cranial cruciate ligament (CrCL), the caudal cruciate ligament, the medial collateral ligament, lateral collateral ligament and the total tensile force placed on the four ligaments was calculated under each load. RESULTS: For the caudal load applied to the tibia relative to the femur, the CrCL tensile force in the TPLO group was lower than that in the reference group at 120° (p = 0.02). The CrCL tensile force in the TPLO group was lower than that in the reference group at 120° (p < 0.01) for the compression load. Regarding the cranial, internal, and external load, the CrCL tensile force remains unchanged between both groups at each angle. CONCLUSIONS: TPLO reduces CrCL tensile force during compression and caudal force application. TPLO may reduce tensile forces contributing to CrCL rupture.

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.

Effects of long-term and high-dose administration of glucocorticoids on the cranial cruciate ligament in healthy beagle dogs.

This study aimed to determine the effects of long-term and high-dose administration of glucocorticoids (GCs) on the histological and mechanical properties of the cranial cruciate ligament (CrCL) in healthy beagle dogs. A synthetic corticosteroid at 2 mg/kg every 12 h was administered for 84 days in nine dogs (18 CrCLs) (GC group). Twenty CrCLs from 12 healthy male beagles were used as the normal control (control group). CrCLs were histologically examined (n = 12 in the GC group and n = 14 in the control group) using hematoxylin-eosin, Alcian-Blue, Elastica-Eosin stains, and immunohistological staining of type 1 collagen and elastin. An additional 12 CrCLs were mechanically tested (n = 6 in the GC and n = 6 in the control groups) to determine failure pattern, maximum tensile strength, maximum stress, elastic modulus, and stress and strain at the transition point. The histological examination revealed a significant increase in interfascicular area and fibrillar disorientation at the tibial attachment in both groups. The ratios of mucopolysaccharide-positive area and positive areas of elastic fibers were significantly higher in the control group than in the GC group. The biomechanical examination demonstrated significantly lower stress at the transition point in the GC group than in the control group. The present study results indicate that high-dose corticosteroids may affect metabolism, such as mucopolysaccharides and elastic fibers production, although the effect on type 1 collagen production is small. These changes of the extracellular matrix had a small effect on the strength of the ligament. This study suggested that the ligamentous changes associated with GC are different from the degeneration observed in spontaneous canine CrCL disease.

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.

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.

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.

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.

Effects of long-term plate fixation with different fixation modes on the radial cortical bone in dogs.

The aim of this study was to examine the effect of long-term locking plate fixation on the cortical bone of the canine radius. Locking compression plates were fixed to the left and right radius in dogs (n = 3). The left radius was fixed with a locking head screw (Locking Plate group, LP). The locking compression plate was compressed periosteally in the right radius using a cortex screw (Compression Plate group, CP). Radial bones from dogs that were euthanized for other purposes were collected as an untreated control group (Control group). After euthanasia at 36 weeks following plate fixation, radial bones were evaluated for bone mineral density and underwent histological analysis. Bone metabolic markers were analyzed by quantitative polymerase chain reaction (qPCR). Statistical analyses were performed for comparisons between groups. The LP group showed no significant difference in bone mineral density after plate fixation, whereas the CP group showed significantly lower bone mineral density. Histological analysis indicated that the number of osteoclasts and rate of empty lacunae increased significantly in the CP group relative to the Control and LP groups. qPCR analysis indicated increased expression of inflammatory cytokines, such as tumor necrosis factor-alpha, interleukin-6, and tumor necrosis factor ligand superfamily member 11 in the CP group, whereas Runt-related transcription factor 2, an osteoblast marker, was similar in all groups. The expression of hypoxia-inducible factor-1α in the CP group was also increased relative to that in the Control and LP groups. Thus, locking plate fixation is a biologically superior fixation method that does not cause implant-induced osteoporosis in the bone in the long term.