Paul A. Manley

Cranial Cruciate Ligament Pathophysiology in Dogs With Cruciate Disease: A Review

Cruciate disease is a common cause of chronic lameness in dogs. Midsubstance rupture of the cranial cruciate ligament (CCL) arises from progressive pathological failure, often under conditions of normal loading in adult dogs with CCL instability. A high risk of rupture is associated with inflammation of the synovium and adaptive or degenerative changes in the cells and matrix of the CCL. In contrast, CCL rupture in puppies is usually associated with traumatic injury and avulsion of the CCL from its sites of attachment.

Histomorphometric description of allograft bone remodeling and union in a canine segmental femoral defect model: A comparison of rhBMP-2, cancellous bone graft, and absorbable collagen sponge

The purpose of this study was to determine the effect of recombinant human bone morphogenetic protein type 2 (rhBMP‐2) on the histomorphometry of femoral allograft‐host bone union and allograft remodeling. A 6 cm mid‐diaphyseal femoral defect was created and filled with an allograft stabilized with an interlocking nail in 21 dogs. Dogs were randomly divided into three equal groups and the allograft‐host bone junctions and the mid‐diaphyses of the allografts were treated with either an absorbable collagen sponge (ACS) loaded with rhBMP‐2 (BMP group), an autogenous cancellous bone graft (CBG group), or ACS loaded with buffer solution (ACS group). All dogs received daily tetracycline until sacrifice at 24 weeks to label new bone formation. Histomorphometric analyses on sections of proximal and distal allograft‐host bone junctions and the mid‐diaphyseal portion of allografts were performed using fluorescent and regular light microscopy. Analyses of the host bone and junctions between allograft and host bone revealed significantly greater new bone formation and larger osteon radii in the BMP group compared to CBG and ACS groups and contralateral intact bone. Porosity in CBG and ACS groups was significantly higher than in the BMP group, which had similar values to intact bone. In transverse sections of allografts, the largest pore diameters were present in the CBG group. Based on all parameters measured, significantly higher bone turnover occurred in the outer cortical area of the allograft in all groups as compared to the inner cortical and mid‐cortical areas. New bone formation and osteon radius/osteon width in allografts were similar for all three groups. Higher porosity and larger pore diameters in the CBG and ACS groups suggested higher bone resorption versus formation in these groups compared to the BMP group. The results of this study reveal more balanced allograft bone resorption and bone formation in the BMP group, with greater resorptive activity in the CBG and ACS groups. However, neither rhBMP‐2 nor autogenous bone graft increased allograft incorporation when compared to the negative control (ACS group).

The effect of recombinant human bone morphogenetic protein-2 on femoral reconstruction with an intercalary allograft in a dog model

This study compared the effect of augmentation of allograft–host bone junctions with recombinant human bone morphogenetic protein‐2 (rhBMP‐2) on an absorbable collagen sponge (ACS), autogenous cancellous bone graft (CBG), and a collagen sponge alone in a canine intercalary femoral defect model repaired with a frozen allograft. Outcome assessment included serial radiographs, dual energy X‐ray absorptiometry scans, and gait analyses, and mechanical testing and histology of post‐mortem specimens. The distal junction healed more quickly and completely with rhBMP‐2 than ACS alone based on qualitative radiography and histologic evaluations. The primary tissue in the unhealed gaps in the ACS group was fibrous connective tissue. The proximal allograft–host bone junction had complete bone union in the three treatment groups. There was significantly greater new bone callus formation at both junctions with rhBMP‐2 than with CBG or ACS alone that resulted in increased bone density around the allograft–host bone junctions. All dogs shifted their weight from the treated leg to the contralateral pelvic limb immediately after surgery. Weight bearing forces were redistributed equally between the pelvic limbs at 12 weeks after surgery with rhBMP‐2, at 16 weeks after surgery with CBG, and at 24 weeks after surgery with ACS alone. Bending and compressive stiffnesses of the whole treated femora were equal to the contralateral control femora in all treatment groups, whereas torsional rigidities of the whole treated femora for the CBG and ACS groups were significantly less than the control. Both the proximal and distal junctions the treated with rhBMP‐2 had torsional stiffnesses and strengths equal to intact control bones. Ultimate failure torques of the proximal junctions of the CBG group and of both junctions of the ACS group were significantly less than the BMP‐treated bones. Augmentation of the allograft–host bone junctions with rhBMP‐2 on an ACS gave results for all parameters measured that equaled or exceeded autogenous graft in this canine intercalary femoral defect model.

Canine intersegmental hip joint forces and moments before and after cemented total hip replacement

Intersegmental forces and moments (i.e. resultant free body forces and moments computed at the joint centers) were studied in canine hindlimbs before and after cemented total hip replacement (THR). Five large, adult, mixed-breed dogs were selected. Their gait was recorded (while leash-walked) before surgery using high-speed cinematography and a force plate. Cemented total hip replacement was unilaterally performed on each dog. Gait was again recorded at one and four months after surgery. Segmental properties (mass, center of mass, and mass moment of inertia) of the hindlimbs were experimentally determined, and an inverse dynamics approach was used to compute intersegmental forces and moments in the sagittal plane. Significant reductions in intersegmental joint forces and moments were observed in the operated hindlimb one month after surgery, although kinematic gait parameters were unaltered. Decreases of 77.0% for vertical forces, 61.9% for craniocaudal forces, and 66.2% for extension moments were determined. Four months after surgery, the joint forces and moments had returned to their preoperative values. This experiment demonstrates that the dynamics of normal walking can be restored in a canine model by four months after THR. It also shows that kinetic (rather than kinematic) parameters are more descriptive of antalgic gait in the canine.

Synovitis in Dogs with Stable Stifle Joints and Incipient Cranial Cruciate Ligament Rupture: A Cross‐Sectional Study

OBJECTIVE To evaluate stifle joints of dogs for synovitis, before development of joint instability and cranial cruciate ligament rupture (CrCLR). STUDY DESIGN Cross-sectional study. ANIMALS Dogs (n = 16) with CrCLR and stable contralateral stifles; 10 control dogs with intact CrCL. METHODS Arthritis and tibial translation were graded radiographically. Synovitis severity and cruciate pathology were assessed arthroscopically. Presence of inflammatory cells in synovial membrane biopsies was scored histologically. CrCLR stifle pairs and control stifles were compared. RESULTS Radiographic evidence of arthritis, cranial tibial translation, and arthroscopic synovitis were increased in unstable stifles, when compared with stable contralateral stifles in CrCLR dogs (P < .05). Arthroscopic synovitis in both joints of CrCLR dogs was increased compared with controls, was correlated with radiographic arthritis (S(R) = 0.71, P < .05), and was present in all stable contralateral stifles. Arthroscopically, 75% of stable stifle joints had CrCL fiber disruption, which correlated with severity of synovitis (S(R) = 0.56, P < .05). Histologic evidence of synovitis was identified in all CrCLR dogs, but was only significantly correlated with arthroscopic observations in stable stifles (r(2) = 0.57, P < .005). CONCLUSION Synovitis is an early feature of the CrCLR arthropathy in dogs before development of joint instability clinically. Severity of synovitis is correlated with radiographic arthritis in joints with minimal to no clinically detectable CrCL damage.

Risk Factors Associated with Fibular Fracture After Tibial Plateau Leveling Osteotomy

OBJECTIVE To determine the incidence of, and risk factors for, fibular fracture after tibial plateau leveling osteotomy (TPLO) in dogs. STUDY DESIGN Case series. SAMPLE POPULATION TPLO (n=168) on 142 dogs. METHODS Medical records (January 2006-September 2007) and radiographs of all dogs that had TPLO were reviewed. Data retrieved were breed, sex, age, weight, type of plate, use of a jig, time to recheck, preoperative tibial plateau angle (TPA), immediate postoperative TPA, and presence or absence of fibular fracture. RESULTS Fibular fractures occurred in 5.4% TPLOs. Body weight, change in TPA, and preoperative TPA were significantly higher in dogs with fibular fracture. TPLO without use of a jig was significantly associated with fibular fracture. Age, postoperative TPA, and plate type were not significantly associated with fibular fracture. CONCLUSIONS Fibular fracture is uncommon after TPLO. Risk factors are increased body weight, greater preoperative TPA, greater change in TPA, and TPLO performed without a jig. All fractures occurred during convalescence. CLINICAL RELEVANCE Owners should be warned of potential complications and risk factors associated for fibular fracture after TPLO.

Alterations in femoral strain, micromotion, cortical geometry, cortical porosity, and bony ingrowth in uncemented collared and collarless prostheses in the dog

The effects of a collared femoral endoprosthesis in uncemented total hip arthroplasty were evaluated in 12 dogs. This experimental study compared the biomechanic and histologic responses between collared and collarless femoral prostheses 4 months after implantation. Implant stability (micromotion) and cortical surface strain were evaluated immediately and 4 months after implantation in a simulated postoperative condition, whereas bone ingrowth, cortical porosity, and cortical remodeling were assessed after 4 months only. There were no significant differences in implant stability or cortical surface strains when the collared and collarless groups were compared acutely or after 4 months (P > .05). There were also no significant differences in percent fill, bony ingrowth, or cortical geometry after 4 months (P > .05). There was a significant increase in cortical porosity measured from the proximal femur after 4 months for both the collared (P = .0002) and collarless groups (P = .009) and when both groups were compared (collarless, 8.2% and collared, 5.8%; P = .03). The results suggest that a collar may be beneficial in decreasing the cortical remodeling that occurs in the proximal femoral cortex after implantation of an uncemented total hip arthroplasty.

ULTRASONICALLY DETERMINED ELASTICITY AND CORTICAL DENSITY IN CANINE FEMORA AFTER HIP ARTHROPLASTY

Effects of canine hip replacement (with a porous-coated femoral component) on the material properties of surrounding cortical bone were evaluated. The hypotheses were: (1) after four months of implantation, mechanical properties of the cortex would change, and (2) a collared implant would be associated with smaller changes than a collarless design. Unilateral total hip arthroplasty was performed in 15 mixed-breed dogs. Nine received a collared and six received a collarless femoral component. Four months after implantation, longitudinal ultrasonic wave propagation velocities and bone mineral densities (from dual energy X-ray absorptiometry) were measured in harvested femora and used to calculate the axial elastic constitutive coefficients for the cortex surrounding the implants. Results showed no difference in bone elasticity or bone density between collared and collarless designs. Significant velocity decreases from control values (p < 0.0001) were noted in all implanted femora at four months. Bone mineral densities also displayed decreased values after four months of implantation (p < 0.0145). Elastic coefficients were consistently less after four months of implantation when compared to control values (p < 0.0001). This alteration in material properties would affect load transfer into the implanted femur via the increased disparity between implant and bone stiffnesses regardless of the component design. Significant differences in the elastic coefficients between implanted and control femora support hypothesis 1. However, no group differences were found between collared and collarless implantations; thus, the study does not support hypothesis 2.

Lymphocyte Populations in Joint Tissues from Dogs with Inflammatory Stifle Arthritis and Associated Degenerative Cranial Cruciate Ligament Rupture

OBJECTIVE To evaluate lymphocyte populations in stifle synovium and synovial fluid of dogs with degenerative cranial cruciate ligament rupture (CCLR). STUDY DESIGN Prospective clinical study. ANIMALS Dogs (n=25) with stifle arthritis and CCLR, 7 dogs with arthritis associated with cartilage degeneration (osteoarthritis [OA]), and 12 healthy Beagle dogs with intact CCL. METHODS Arthritis was graded radiographically in CCLR dogs. After collection of joint tissues, mononuclear cells were isolated and subsequently analyzed using flow cytometry for expression of CD3, CD4, CD8, and CD21. RESULTS The proportions of CD4(+) T helper lymphocytes, CD8(+) cytotoxic T lymphocytes, and CD3(+) CD4(-) CD8(-) T lymphocytes were increased in synovium from dogs with CCLR compared with synovium from healthy Beagle dogs (P<.05). The proportion of CD3(+) CD4(-) CD8(-) T lymphocytes in synovial fluid was increased in dogs with CCLR compared with dogs with OA (P<.05). In dogs with CCLR, the proportion of CD3(+) CD4(-) CD8(-) T lymphocytes in synovial fluid was inversely correlated with radiographic arthritis (S(R) =-0.68, P<.005). CONCLUSION Lymphocytic inflammation of stifle synovium and synovial fluid is an important feature of the CCLR arthropathy. Lymphocyte populations include T lymphocytes expressing CD4 and CD8, and CD3(+) CD4(-) CD8(-) T lymphocytes. Presence of CD3(+) CD4(-) CD8(-) T lymphocytes was associated with development of stifle synovitis. Further work is needed to fully identify the phenotype of these cells.

Histomorphometric analysis of the proximal portion of the femur in dogs with moderate osteoarthritis

OBJECTIVE To describe the histomorphometric properties of epiphyseal and metaphyseal trabecular bone of the proximal portion of the femur of dogs with moderate osteoarthritis. SAMPLE POPULATION Proximal portions of a femour from 24 dogs. PROCEDURE The proximal portion of a femur was obtained from each dog. Eleven and thirteen specimens were sectioned in the transverse and coronal planes, respectively. Three evenly spaced sections from each specimen were chosen, surface stained, and digitized, and the stained areas were preferentially selected. Custom software was used for histomorphometric analysis of each section. A mixed-model analysis was used to evaluate the effect of slice location and region on 6 parameters, and a Fisher protected t test was used when differences were detected. RESULTS There was a significant difference between the femoral head and femoral neck for all parameters tested. In coronal sections, the femoral neck was significantly more anisotropic than the femoral head. In transverse sections, the craniolateral region of the femoral neck was significantly more anisotropic than the caudomedial and craniomedial regions. CONCLUSIONS AND CLINICAL RELEVANCE There is a predictable cancellous microarchitecture in the proximal portion of femurs from dogs with moderate osteoarthritis. Trabeculae are more numerous, thicker, and closer together but more randomly arranged in the femoral head than in the femoral neck. Dogs with moderate osteoarthritis had an increase in trabecular anisotropy in the craniolateral region of the femoral neck. However, there was no corresponding increase in trabecular alignment of the proximomedial region of the femoral head. Results support an association between trabecular alignment and the progression of osteoarthritis.