Traumatic fragmented medial coronoid process in a Chihuahua.

Fragmented medial coronoid process (FMCP) is a disease process that has not previously been reported in toy-breed dogs. This report describes a presumptive case of FMCP in a 14-month-old Chihuahua that was presented for evaluation approximately four weeks following acute onset of moderate lameness in the left forelimb. Definitive diagnosis of a fragmented medial coronoid process was based upon computed tomography (CT) scan. A CT scan also demonstrated moderate joint incongruity in the affected elbow. Surgical removal of the fragment and subtotal coronoidectomy were performed via a medial arthrotomy. An ulnar ostectomy was also performed to address joint incongruity. Histology of specimens removed at surgery did not demonstrate evidence of microdamage as characteristic of FMCP in large breed dogs, and instead, suggested that the fracture was acute and traumatic in nature. Rapid return to function was observed following surgery.

Comparison of the effects of caudal pole hemi-meniscectomy and complete medial meniscectomy in the canine stifle joint.

OBJECTIVE: To compare the effects of caudal pole hemi-meniscectomy (CPHM) and complete medial meniscectomy (MM), specifically with respect to development of secondary osteoarthritis, in the stifle joints of clinically normal dogs. ANIMALS: 14 large-breed dogs. PROCEDURE: Unilateral CPHM (7 dogs) or MM (7) was performed, and the left stifle joints served as untreated control joints. Gait was assessed in all dogs before surgery and at 4, 8, 12, and 16 weeks postoperatively. After euthanasia, joints were evaluated grossly; Mankin cartilage scores, subchondral bone density assessment, and articular cartilage proteoglycan extraction and western blot analyses of 3B3(-) and 7D4 epitopes were performed. RESULTS: Weight distribution on control limbs exceeded that of treated limbs at 4 and 16 weeks after surgery in the CPHM group and at 4 and 8 weeks after surgery in the MM group; weight distribution was not significantly different between the 2 groups. After 16 weeks, incomplete meniscal regeneration and cartilage fibrillation on the medial aspect of the tibial plateau and medial femoral condyle were detected in treated joints in both groups. Mankin cartilage scores, subchondral bone density, and immunoexpression of 3B3(-) or 7D4 in articular cartilage in CPHM- or MM-treated joints were similar; 7D4 epitope concentration in synovial fluid was significantly greater in the MM-treated joints than in CPHM-treated joints. CONCLUSIONS AND CLINICAL RELEVANCE: Overall severity of secondary osteoarthritis induced by CPHM and MM was similar. Investigation of 7D4 epitope concentration in synovial fluid suggested that CPHM was associated with less disruption of chondrocyte metabolism.

Evaluation of 5 types of fishing material, 2 sterilization methods, and a crimp-clamp system for extra-articular stabilization of the canine stifle joint.

OBJECTIVE: To evaluate the mechanical properties of 5 types of fishing material, 2 sterilization methods, and a commercially designed crimp-clamp system for the extra-articular repair of the canine stifle joint. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Animals were not used in this study. METHODS: Two brands of monofilament nylon fishing line and 3 brands of monofilament nylon leader line were used to determine the effect of steam and ethylene oxide sterilization on strength and elongation of the material. A strand of 36-kg test monofilament nylon fishing material was wrapped around 2 rods or knotted to form a loop around 2 rods on a materials-testing machine. Ten trials of each brand of unsterilized, steam-sterilized, and ethylene oxide-sterilized fishing material were tested. A strand of each material was elongated to failure at a constant displacement of 1,000 mm/min to determine strength. A strand of each material was cycled 10 times to a load of 50 N to determine percent elongation. The brand of fishing material with the greatest strength and least elongation was crimped to form a loop around 2 rods on a materials-testing machine and tested as described above. ANOVA was used to determine the effect of sterilization method, brand of material, knot, wrap, and crimp on strength and elongation of the material, and a post-hoc t test was used when significant differences were found. A Student t test was used to compare fixation techniques (wrap, knot, and crimp). RESULTS: Sterilization by steam or ethylene oxide had no significant effect on the strength of the nylon fishing material. Steam sterilization resulted in significant increases (2- to 4-fold) in elongation of most nylon fishing material when compared with unsterilized material. Ethylene oxide sterilization had minimal effect on elongation of the fishing material. Mason leader line showed no significant change in strength or elongation regardless of sterilization method. Significantly less strength and significantly less elongation were demonstrated in Mason leader line that was crimped as compared with Mason leader line that was knotted. CONCLUSION: Ethlylene oxide was the preferred method of sterilization to preserve strength and minimize elongation of the fishing material. Of the materials tested, Mason leader line had the least elongation and the greatest preservation of strength when ethylene oxide was used as the sterilization method. Mason leader line and Sufix fishing line were comparable choices when steam was used as the sterilization method. Significantly less elongation was demonstrated in crimped Mason leader line as compared with knotted Mason leader line. CLINICAL RELEVANCE: Of the materials tested, Mason leader line and Sufix fishing line had the best mechanical properties for extracapsular stabilization of the canine stifle joint. Crimping is an attractive alternative to knotting and results in a reduction in elongation of the nylon fishing material.

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.

Comparison of three methods of gluteal muscle attachment to an allograft/endoprosthetic composite in a canine model.

This study used radiography, gait analysis, gluteal muscle mass, mechanical testing, and qualitative histology to compare three methods of gluteal muscle attachment to an allograft/endoprosthetic composite of the proximal 25% of the femur in an in vivo canine model. The three methods of gluteal muscle attachment were identical to those used clinically in human patients for hip revision and proximal femoral limb salvage: the host gluteal tendon sutured to the allograft tendon (tendon group), the host greater trochanter with intact gluteal tendons secured to the allograft with a cable-grip system (grip group), and periosteally vascularized proximal femoral bone onlay with intact tendons wrapped around the allograft (wrap group). On the basis of radiographs taken every 2 months, the tendon group had more graft fractures than did the grip or wrap group. Radiographic union of the graft-host bone junction occurred more rapidly and there was less graft resorption in the wrap group than in the other two groups. In all dogs, peak vertical ground-reaction forces in the treated limb decreased immediately after surgery and then slowly increased over the length of the study. The dogs in the wrap group regained normal weight-bearing on the treated limb more quickly than did those in the other groups. The constructs in the tendon group were weaker and less stiff immediately after surgery than were those in the other groups or in intact controls. Histologic analysis confirmed that the wrap technique resulted in complete union of the host bone-allograft junction more often than did the other techniques. The wrap method had the best functional outcome after 9 months when an allograft/endoprosthetic composite was used during total hip arthroplasty in this canine model.

Alterations in bone remodeling in the femur after medullary reaming and cemented hip arthroplasty in dogs.

OBJECTIVE: To determine whether medullary reaming alone, or followed by cemented hemiarthroplasty, influenced porosity, vascularity, and new bone formation in the proximal portion of the femur in dogs. ANIMALS: 12 adult mixed-breed dogs. PROCEDURE: Unilateral femoral head and neck excisions were performed, followed by femoral medullary reaming in 6 dogs and femoral medullary reaming and cemented hemiarthroplasty in 6 dogs; the contralateral femur was used as a control. All dogs were euthanatized 28 days after surgery, and femurs were harvested. Vascularity, porosity, and new bone formation were quantified for all femurs of dogs from both groups at 3 proximal-to-distal levels, 3 regions (periosteal, midcortical, and endosteal), and 4 quadrants (cranial, caudal, medial, and lateral) of the femur. RESULTS: Medullary reamed and cemented hemiarthroplasty femurs had significant increases in vascularity and porosity at all levels and in new bone formation at levels 2 and 3. Porosity was increased significantly in the periosteal region of the cemented hemiarthroplasty (9.7+/-0.7%), compared with control (2.3+/-0.2%) and medullary reamed (8.4+/-0.7%) femurs. Porosity was increased in the caudal and medial quadrants in the medullary reamed and cemented hemiarthroplasty femurs; vascularity results were similar. CONCLUSION: Increased porosity, vascularity, and new bone formation in reamed and cemented hemiarthroplasty-treated femurs supports the theory that surgical trauma associated with medullary reaming is an important factor in early cortical bone loss after hip arthroplasty. CLINICAL RELEVANCE: Femoral remodeling associated with reaming and broaching is appreciable but may be only a temporary response, whereas other factors may be responsible for chronic cortical bone loss.

Arthrodesis of the shoulder for synovial osteochondromatosis.

A case of synovial osteochondromatosis (SOC) in a young deerhound's shoulder is reviewed. The age of onset and initially unaffected articular surfaces suggested primary SOC. Histological criteria for primary versus secondary osteochondromatosis are contradictory and unclear. Initial loose body removal and partial synovectomy resulted in several months of improvement but loose bodies returned. Severe degenerative changes were found one year after the initial exploratory surgery. Arthrodesis resulted in a functional, non-painful joint.

Force-plate analysis of gait before and after surgical excision of calcified lesions of the supraspinatus tendon in two dogs.

Two dogs with supraspinatus calcifying tendinopathy were lame in their forelimbs and were treated by the surgical excision of the calcified lesion. The lameness in both dogs improved after surgery without additional medical treatment, as evidenced by force-plate analysis of their gait.

Comparison of hemilaminectomy and dorsal laminectomy for thoracolumbar intervertebral disc extrusion in dachshunds.

Neurological improvement after decompressive surgery, without routine therapeutic or prophylactic disc fenestration, was evaluated retrospectively in a consecutive series of 93 dachshunds with thoracolumbar disc extrusion. In 24 per cent of procedures, deep pain sensation was not elicited in at least one hind paw before surgery. Median neurological status one to seven days after surgery, at the time of discharge, was significantly improved after hemilaminectomy compared with dorsal laminectomy (P < 0.05). After hemilaminectomy, deep pain sensation was not elicited in one or both hind paws of 8 per cent of dogs in which pain sensation was elicited before surgery, compared with 21 per cent after dorsal laminectomy (P > 0.05). Improvement in neurological grade at follow-up examination two to 12 weeks after hemilaminectomy was not significantly different compared with dorsal laminectomy (P > 0.05). Of dogs which were unable to walk before surgery, 83 per cent regained the ability to walk after hemilaminectomy, compared with 74 per cent after dorsal laminectomy (P > 0.05). In both groups, 50 per cent of dogs in which deep pain sensation was abnormal before surgery eventually regained the ability to walk after surgery (P = 1). One to two years after the first operation, a second laminectomy was performed in only 5 per cent of dogs because of extrusion of a different intervertebral disc which had not been fenestrated.

Stabilisation of fractures of the proximal radius and ulna in a dog by application of a single plate to the ulna.

If a plating technique is used, fractures of the radius and ulna are usually stabilised by the application of a plate to the radius, or by the placement of plates on both the radius and ulna. This report describes the treatment of comminuted fractures of the proximal radius and ulna in a young dog by the application of a single plate to the caudal surface of the ulna. Satisfactory healing of both fractures occurred by five weeks after surgery. This approach avoided the difficult surgical approach to the proximal radius, and simplified the management of a dog with multiple fractures in one limb.

Vascular and morphologic changes in canine femora after uncemented hip arthroplasty.

The effects on femoral remodeling of medullary reaming and insertion of a porous endoprosthesis in uncemented hip arthroplasty (UHA) were measured. A unilateral hip hemiarthroplasty (HA) was performed in 12 dogs, with six dogs receiving full-sized and six dogs receiving undersized femoral endoprostheses. A prosthetic head and neck, or acetabular cup, was not implanted. A control group of six dogs underwent femoral head and neck excision (FHNE) only. All dogs were killed 4 weeks after the surgical procedure. Porosity, vascularity, and bone formation were quantified in each femur of the dogs that had been operated on and in each femur of two unoperated dogs. Full-sized did not differ from undersized HA bones in vascularity, porosity, or bone formation. Femurs in which hemiarthroplasties had been performed (full-sized and undersized) had a three-fold increase in porosity, vascularity, and bone formation compared to the contralateral and the FHNE femurs. Changes in porosity and vascularity were greatest (p < .05) at the metaphyseal level and in the medial and caudal quadrants. There was a strong correlation (R2 0.77 to 0.93, and p = .0001) between the increase in porosity and vascularity. These results support the hypothesis that medullary reaming followed by uncemented prosthetic stem implantation contribute to remodeling of the proximal portion of the femur after UHA.

Chemonucleolysis with collagenase. A radiographic and pathologic study in dogs.

Collagenase, a proteolytic enzyme, was injected intradiscally in nine clinically normal, middle-aged beagles. Calcium chloride diluent solution (control), 100 ABC units of collagenase, and 250 ABC units of collagenase, were injected in randomly selected intervertebral discs (T13-L1 to L5-L6). On day 11, the discs injected with collagenase were narrowed radiographically, but there was no significant change in myelograms. Grossly and histologically, there was dissolution of the intervertebral discs, mainly nucleus pulposus, and protrusion of nucleus material in the vertebral body through bony end-plates in discs injected with collagenase. Collagenase chemonucleolysis may be an alternative to spinal surgery for intervertebral disc protrusion in dogs.

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.

Femoral strain adaptation after total hip replacement: a comparison of cemented and porous ingrowth components in canines.

The purpose of this study was to investigate if experimental strain analysis is predictive of femoral adaptation after total hip replacement (THR). Ten large adult dogs underwent unilateral THR with identical implants. Five implants were press fit for porous ingrowth fixation, and five were cemented. Four months after surgery femora were harvested. Strain gauge rosettes were applied to the femora at eight proximal locations. Femora were compressively loaded on the head of the femur or femoral component. Strain data represented three conditions: preoperative, acutely postoperative, and four-month postoperative. The unoperated femur of each dog was used to simulate preoperative and acutely postoperative behavior of the contralateral implanted femur. Strains from each condition were compared. Transverse femoral sections were obtained through the levels of the strain gauges. Fine detailed radiographs were used to quantify morphological changes. Results showed cemented and uncemented implantations produce similar trends but different amounts of bone adaptation. Adaptations were generally consistent in direction with strain perturbations caused by implantation, but the extent of adaptation did not strongly correlate with the magnitude of perturbations. Also, there was no consistent trend towards normalization of altered strains. Results suggest that strain perturbations after THR may be mechanical triggers for morphological changes, but caution is required when predicting the extent of these changes or the autoregulatory role of strain.

Ground reaction force comparison of canine cemented and cementless total hip replacement.

Ground reaction forces were studied in the hindlimbs of ten dogs after cemented and cementless total hip replacement. The femoral components in five dogs were surgically press fitted into the medullary canal for porous ingrowth fixation (cementless) while the remaining five dogs had their femoral component cemented in place. Gait analysis was performed monthly for four postoperative months. Reductions in vertical ground reaction forces were observed in both cemented and cementless implanted hindlimbs one and two months after surgery. By three months postoperative, both groups had effectively returned to their preoperative vertical ground reaction force levels on the implanted hindlimb. At three and four months post implantation, the cemented group demonstrated equal load distribution between the operated and unoperated hindlimbs, whereas the cementless group showed a disparity in load distribution between the operated and unoperated hindlimbs which persisted for the four-month test period. We believe that the paired comparisons between operated and unoperated limbs are more descriptive of antalgic gait than comparisons with preoperative control values.

Effects of immobilization on cartilage formation after periosteal grafting in the rabbit stifle.

Autogenous periosteal grafts were harvested and placed in the trochlear grooves of the stifles of 32 rabbits. Postoperative immobilization periods of 0, 7, and 14 days were compared. Grafted areas were evaluated for gross appearance, histologic morphology, attachment of cartilage to subchondral bone, cartilage depth, chondrocyte density, proteoglycan presence, collagen fiber orientation, and mitotic activity. Nonimmobilized stifles had increased gross coverage of subchondral bone, better histologic quality, increased safranin O stain uptake, and more normal collagen fiber orientation at 60 days than stifles immobilized for 7 ir 14 days. Postoperative immobilization did not affect attachment of the graft to the subchondral bone.

Therapy for osteosarcoma in dogs with intravenous injection of liposome-encapsulated muramyl tripeptide.

Canine osteosarcoma is a spontaneous malignancy in dogs, characterized by micrometastasis to pulmonary and extrapulmonary tissues at the time of diagnosis. Standard treatment involves amputation of the affected leg, but median survival time is 3-4 months with death due to metastasis. A randomized double-blind trial was conducted to evaluate liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (liposome/MTP-PE) as a treatment for metastasis in dogs undergoing amputation for osteosarcoma. Fourteen dogs were treated with liposome/MTP-PE, and 13 were treated with empty liposomes. Median survival time was 222 days for dogs treated with liposome/MTP-PE, compared to 77 days for dogs treated with empty liposomes (P less than .002). In the liposome/MTP-PE-treated group there were still four dogs alive and free of metastasis at greater than 1 year post surgery. Treatment was well tolerated; no significant toxic effects were noted except for mild elevations in body temperature (1-2 degrees C) for 2-6 hours post injection.

Calcinosis circumscripta associated with polydioxanone suture in two young dogs.

Calcinosis circumscripta associated with polydioxanone suture material was diagnosed in two young dogs. In each case, the owner noticed a firm mass at the site of a previous surgical incision. Mineralization of soft tissues was visible radiographically. At excision, multiple chalky white nodular masses within the subcutis extended in a linear pattern the length of the sutured incision, but not beyond it. Polydioxanone suture was identified within the center of the nodules, which were identified histologically as calcinosis circumscripta.

Evaluation of tension and compression forces in the canine femur in vivo.

In order to verify the existence of tension and compression forces from the cortical surface of canine femora, rosette strain gauges and a radio telemetry system were used to observe the animals during normal locomotion. Surface strain measured from the lateral cortical surface was consistently in tension whereas surface strain measured from the medial cortical surface was in compression. This data supported in vitro work which showed that eccentric loading of bone results in the convex side of bone being in tension and the concave side of bone being in compression.

Effect of internal fixation on the strain environment of the canine femur.

Strain gauge technology and telemetric transmission were utilized to investigate the dynamic strain patterns along the cortical surface of bone and the response to internal fixation, in vivo. Application of a tension band plate resulted in conversion of normal tensile strain into compressive strain which verified the tension band principle of internal fixation. Creation of a transverse osteotomy did not alter this response, provided that the fragments were rigidly fixed. The plate caused an appreciable decrease in normal surface strain measured from the lateral and medial cortices, illustrating the concept of stress protection.