Risk factors for positive urine cultures in cats with subcutaneous ureteral bypass and ureteral stents (2010-2016).

BACKGROUND: Ureteral stent and subcutaneous ureteral bypass (SUB) placement are commonly used for managing ureteral obstructions. Urinary tract infection (UTI) is a recognized complication. OBJECTIVES: To determine postoperative incidence of positive urine cultures in cats undergoing ureteral stent and SUB placement and to identify risk factors associated with positive urine cultures. DESIGN: Retrospective study. ANIMALS: Forty-three cats that underwent 48 surgical events. PROCEDURES: Medical records were reviewed. Cats were included if urine cultures were performed before and after surgery. Variables were compared to identify risk factors. RESULTS: Urine cultures were positive postoperatively pre-discharge in 5/20 (25%) cats. Median duration of follow-up post-discharge was 209 days (range, 11-2184 days), with a total of 143 urine cultures performed in cats post-discharge. Of these, 16 (11%) were positive in 12/48 (25%) cats. Nine different bacteria were identified; Enterococcus spp. (n = 8) predominated as monomicrobic or mixed infections. In 14/16 instances of positive urine cultures, affected cats had lower urinary tract signs, signs of pyelonephritis or both. Cats that received antibiotics postoperatively were significantly less likely to have a positive urine culture compared to those that did not (odds ratio, 0.2, 95% confidence interval, 0.05, 0.8, P = 0.02). Chronic kidney disease, renal implant type and postoperative urinary catheterization were not associated with positive urine cultures. CONCLUSIONS AND CLINICAL RELEVANCE: Postoperatively, occurrence of positive urine cultures was similar to previous reports. Subclinical bacteriuria was less common than UTI. Postoperative urinary catheterization has been speculated to increase risk of bacteriuria, but this was not the case in this cohort.

Protocol changes to reduce implant-associated infection rate after tibial plateau leveling osteotomy: 703 dogs, 811 TPLO (2006-2014).

OBJECTIVE: To determine the influence of a stricter aseptic protocol on implant-associated infection (IAI) rates after tibial plateau leveling osteotomy (TPLO). STUDY DESIGN: Retrospective cohort study. SAMPLE POPULATION: Seven hundred three dogs (811 TPLO). METHODS: Medical records (2006-2014) of dogs with TPLO with a ≥18-month follow-up were reviewed. An established TPLO protocol was altered to include an iodophore-impregnated adhesive drape, cefazolin administration every 90 minutes intraoperatively and then every 4 hours until hospital discharge, orthopedic surgical gloves, triclosan-coated intradermal sutures (instead of staples), soft-padded bandage with mupirocin ointment, use of single-use gloves while handling treated dogs, and placement of an Elizabethan collar. Signalment, affected limb, protocol changes, IAI, time to explant, and culture and susceptibility results were recorded. Data were analyzed by using Fisher's exact test, Wilcoxon rank-sum test, and a multivariable logistic regression model. RESULTS: TPLO plates were removed from 31 dogs (8.5% prechange, 1.3% postchange) because of a suspected IAI. Bacterial culture results from an explanted screw were positive in 26 dogs (7.4% prechange, 0.94% postchange). The odds ratio (OR) of IAI in the postchange cohort was decreased by 88% (OR 0.12, 95% CI 0.05-0.33) compared with the prechange cohort, after controlling for variables. Staphylococcus spp. were isolated from all implants removed from IAI-positive postchange dogs, 4/5 of which were methicillin resistant. No methicillin-resistant isolates were grown from the prechange cohort implants. CONCLUSION: The protocol tested here decreased IAI rates after TPLO, but most infections diagnosed after its implementation involved methicillin-resistant isolates. CLINICAL SIGNIFICANCE: The protocol reported here may be used as a guide in clinics seeking to reduce their IAI rates after TPLO. Postoperative infections after implementation of this protocol should be monitored to evaluate its potential impact on the emergence of antibiotic resistance.

Postoperative complications associated with external skeletal fixators in cats.

OBJECTIVES: The objective of this study was to quantify complications associated with external skeletal fixators (ESFs) in cats and to identify potential risk factors. METHODS: A retrospective review of medical records and radiographs following ESF placement was performed. RESULTS: Case records of 140 cats were reviewed; fixator-associated complications (FACs) occurred in 19% of cats. The region of ESF placement was significantly associated with complication development. Complications developed most frequently in the femur (50%), tarsus (35%) and radius/ulna (33%). Superficial pin tract infection (SPTI) and implant failure accounted for 45% and 41% of all FACs, respectively. SPTI occurred more frequently in the femur, humerus and tibia, with implant failure more frequent in the tarsus. No association between breed, age, sex, weight, fracture type (open vs closed), ESF classification, number of pins per bone segment, degree of fracture load sharing, and the incidence or type of FAC was identified. No association between region of placement, breed, age, sex, weight, fracture type (open vs closed), ESF classification, number of pins per bone segment, fracture load sharing and the time to complication development was identified. CONCLUSIONS AND RELEVANCE: Complication development is not uncommon in cats following ESF placement. The higher complication rate in the femur, tarsus and radius/ulna should be considered when reviewing options for fracture management. However, cats appear to have a lower rate of pin tract infections than dogs.

Perioperative administration of antimicrobials during tibial plateau leveling osteotomy.

OBJECTIVE: To evaluate perioperative antimicrobial administration during tibial plateau leveling osteotomy (TPLO) in dogs at the Ontario Veterinary College Health Sciences Centre. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs (n = 184) that had TPLO (n = 226). METHODS: Medical records were reviewed and data collected included timing and dosage of pre, intra, and postoperative antimicrobial administration, method of stifle inspection, duration of surgery, duration of anesthesia, development of surgical site infection (SSI), microbiological investigation, implant removal, and possible comorbidities. Univariable analysis was conducted, followed by stepwise forward logistic regression to determine factors associated with SSI. RESULTS: Of the 225 cases administered perioperative antimicrobials, 96 (42.5%) received appropriate perioperative antimicrobial prophylaxis based on target times for preoperative and intraoperative dosing. Postoperative antimicrobials were administered to 54 (23.9%) of cases. Surgical site infection was documented in 30 (13.3%) cases. Staphylococcus pseudintermedius was isolated from 15/17 (88.2%) SSI from which a bacterium was isolated, with 6/15 (40%) being methicillin-resistant Staphylococcus pseudintermedius (MRSP). Postoperative administration of antimicrobials was protective for SSI (OR 0.1367; P = .0001; 95% CI = 0.021, 0.50). Duration of anesthesia time was associated with the likelihood of development of SSI (OR = 1.0094; P = .001; 95% CI = 1.00, 1.02). CONCLUSION: Current practices for administration of antimicrobial prophylaxis during TPLO can be improved. There was no association between timing of antibiotic administration that was inconsistent with the target and development of SSI. Further study into risk factors of TPLO SSI is required.

Management of an infected cementless cup with prosthetic retention and antibiotic therapy in a dog.

A two-year-old Rottweiler presented for acute onset of a right hindlimb lameness 20 weeks after a cementless total hip replacement (THR) and 16 weeks after open reduction to address luxation of the THR. Radiographs revealed periosteal proliferation of the medial acetabulum and a stable implant. Synovial fluid cytology was consistent with inflammatory joint fluid. Treatment consisted of surgical debridement and intravenous and oral antibiotics. THR implants were not removed. Culture of tissue removed from the THR site yielded growth of Pseudomonas and Staphylococcus species. Lameness resolved 2 months after surgery. Twenty months after surgery, the dog was exercising normally with no clinical lameness and pelvic radiographs revealed no evidence of implant loosening and markedly decreased periosteal reaction. To the authors' knowledge, this is the first report of an infected THR site successfully treated without prosthesis explantation in the dog.

Implant removal rate from infection after tibial plateau leveling osteotomy in dogs.

OBJECTIVE: To determine implant removal rate associated with infection after tibial plateau leveling osteotomy (TPLO) in dogs and to report antimicrobial susceptibility patterns for isolates. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs (n = 255; 282 TPLO). METHODS: Medical records (April 2006-April 2008) for dogs that had TPLO with ≥ 18 month follow-up were reviewed. Dogs that had implant removal with confirmed bacterial isolation from the implant were studied. Cefazolin (22 mg/kg intravenously) was administered before anesthesia induction for TPLO, every 2 hours intraoperatively, and every 6 or 8 hours until the next morning. Antimicrobial susceptibility testing was performed on isolates. RESULTS: Twenty-one (7.4%) of 282 TPLO required implant removal because of infection. Bacterial species isolated were Actinomyces spp. (1), Corynebacterium spp. (1), Enterococcus spp. (3), hemolytic Staphylococcus coagulase negative (2), nonhemolytic Staphylococcus coagulase negative (3), Staphylococcus spp. coagulase positive (7), methicillin-oxacillin-resistant Staphylococcus coagulase positive (2), and Serratia marcesens (2). Of the antibiotics that had ≥10 isolates tested against them, gentamicin had the highest susceptibility rate (94%), followed by tribrissen (71%), and amoxicillin/clavulanic acid (67%). CONCLUSION: Staphylococcus spp. was reported in 14 of the 21 infections cultured in this study. Based on antimicrobial susceptibility testing, amoxicillin/clavulanic acid would be the best empirical treatment.

Biodegradable sleeves for metal implants to prevent implant-associated infection: an experimental in vivo study in sheep.

OBJECTIVE: To evaluate biocompatibility of biodegradable sleeves containing antimicrobial agents, designed for local drug delivery to prevent implant-related infection. STUDY DESIGN: Synthetic polyester sleeves (a copolymer of glycolide, caprolactone, trimethylene carbonate, lactide) were cast as thin films. The antimicrobial agents incorporated in the sleeves included gentamicin sulfate, triclosan, or a combination of these drugs. ANIMALS: Adult sheep (n = 15). METHODS: Two limited contact dynamic compression plates (LC-DCP) with or without sleeves were implanted on tibiae (bilateral) of 15 sheep. Sleeves were placed over the plates before implantation. Beneath half of the plates, 5-mm drill hole defects were made in the near cortex. Samples were harvested 4 weeks later for histology and microradiography. RESULTS: Macroscopically, no irritation of bone or adjacent tissue was seen. Small remnants of sleeves were visible on histology, and positively correlated with the presence of macrophages and foreign body cells. Thick sections showed no difference between the test samples and controls in terms of fibrous capsule formation, periosteal remodeling, and defect remodeling. Inflammatory cells, macrophages, and foreign body cells were more prominent in sections with sleeves, but were not statistically significantly different from controls. Cell numbers were within normal physiologic limits normally seen as cellular response to foreign bodies consisting of polymers. CONCLUSION: The normal healing response indicated that the biodegradable sleeves demonstrate tissue biocompatibility.

Risk factors and clinical relevance of positive intraoperative bacterial cultures in dogs with total hip replacement.

OBJECTIVE: To report incidence and relevance of positive intraoperative total hip replacement (THR) bacterial cultures taken at the time of surgical closure in dogs having unilateral THR. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs (n = 100) with cemented (CFX), cementless (BFX), or hybrid THR. METHODS: Medical records (January 2007-March 2010) of dogs that had THR were reviewed. Signalment, type and side of THR, concurrent surgery, operative and anesthetic times, intraoperative coxofemoral closing (CC) bacterial culture results, organism cultured, duration of postoperative antibiotic administration, physical examination findings at 3 weeks, 3 months, and at 6 months to 1 year after surgery, radiographic findings at 3 months and between 6 months and 1 year after surgery, and incidence of complications were retrieved. RESULTS: There was a significant difference in duration of surgery between CC culture negative and CC culture positive groups (103.27 minutes versus 122.50 minutes, respectively, P < .038) and in total anesthetic time between CC culture negative and culture positive groups (165.20 minutes versus 189.50 minutes, respectively, P < .038). There was no significant difference between CC culture negative and culture positive groups for median age (30 months versus 39 months, respectively, P < .75), median weight (36.91 kg versus 35.68 kg, respectively, P < .61), median clinical signs (4 months versus 3.5 months, respectively, P < .65), sex (males 44.32% versus females 25.00%, respectively, P < .20), laterality (left 55.68% versus right 50.00%, respectively, P < .71), concurrent surgery (extracapsular lateral imbrication/medial patella luxation/lateral patella luxation [ECLI/MPL/LPL] 22.73% versus none 25.00%, respectively, P < 1.00), and THR type (hybrid 17.05% versus 25.00% respectively; CFX 60.23% versus 75.0%; BFX 22.73% versus 0.0%; Fisher's exact test P < .17). CONCLUSIONS: Surgical and anesthetic duration were significantly associated with positive CC culture results. Positive CC culture results were not associated with adverse results at 3 months and at 6-month to 1-year follow-up evaluation.

Revision of cemented total hip arthroplasty with cementless components in three dogs.

OBJECTIVE: To report revision of cemented total hip arthroplasty failure with cementless components in 3 dogs. STUDY DESIGN: Clinical case reports. ANIMALS: Dogs with total hip arthroplasty failure (n=3). METHODS: Cementless total hip arthroplasty revision was performed in 3 dogs with previously cemented femoral and acetabular components. All dogs required revision of the femoral component and 1 dog also required revision of the acetabular component. RESULTS: Revisions resulted in a stable functional prosthesis with successful bone integration. CONCLUSIONS: Use of cementless components may be a viable option for revision of loosened cemented prosthesis after explantation of failed cemented canine total hip replacements. CLINICAL RELEVANCE: Failed canine-cemented total hip arthroplasties can be successfully revised with cementless components.

Removal of infected canine cemented total hip prostheses using a femoral window technique.

OBJECTIVE: To evaluate a femoral window technique for retrieval of cemented total hip prostheses. STUDY DESIGN: Retrospective clinical study. ANIMALS: Twelve dogs with infection of a cemented modular total hip prosthesis. METHODS: Implant removal was performed by an extended craniolateral approach to the hip and proximal femur without trochanteric osteotomy. The femoral cement mantle was fragmented and removed with simple orthopedic instrumentation by a lateral femoral window that was repaired using cerclage wires. Surgical technique, intraoperative and postoperative complications, bacterial culture results, histopathologic findings, and completeness of cement removal were recorded. Follow-up radiographs were taken 5 to 9 weeks postoperatively. Long-term follow-up information was obtained by client questionnaire. Functional outcome was assessed by scoring ability to stand, sit, walk, run, play, climb stairs, and get into a car. RESULTS: Prosthesis retrieval was performed 2 to 41 months after implantation (median, 14 months). Complete removal of femoral cement was achieved in 10 dogs. A nondisplaced femoral fissure, extending proximally from the window, was an intraoperative complication in 2 dogs. Staphylococcus spp was most commonly isolated (6 dogs) from interfacial membrane samples. Systemic antibiotic therapy, dependent on susceptibility testing, was administered for 3 to 10 weeks postoperatively. There was radiographic evidence of osteotomy healing at 5- to 9-week reassessment. Recurrence of osteomyelitis was not observed. Long-term functional outcome was considered mildly abnormal. CONCLUSIONS: The lateral window was an effective technique for retrieval of retained femoral cement. CLINICAL RELEVANCE: Removal of an infected prosthesis using this technique generally resulted in a clinical outcome comparable to that with ab initio femoral head and neck excision.

Avaliaçäo histológica do tecido conjuntivo ao redor de placas ortopédicas confeccionadas a partir de policloreto de vinila comercial (PVC) em cäes / Histologic study of conjuntive tissue's reaction aroun bone plates made from polyvynil chloride (PVC) in dogs

A reaçäo do tecido conjuntivo ao redor de placas ortopédicas confeccionadas a partir de policloreto de vinila foi avaliada histologicamente em 30 cäes adultos, com peso médio de 13kg, distribuídos em três grupos de 10 cäes cada. Nos grupos 1 e 2 foram realizadas osteotomias transversais completas no corpo mandibular direito entre o último pré-molar e primeiro molar e as fraturas foram fixadas com placa de aço e de PVC, respectivamente. No grupo 3, os corpos mandibulares íntegros direito e esquerdo receberam placas, sendo uma de aço e outra de PVC. Histologicamente, na 18ª semana, as placas de PVC desencadearam no tecido circundante uma resposta inflamatória crônica, qualitativamente diferente das placas de aço, afetando maior número de animais e em maior intensidade, sugestiva de toxicidade e antigenicidade do material.

Pharmacokinetic model for cefazolin distribution during total hip arthroplasty in dogs.

OBJECTIVES: To compare cefazolin pharmacokinetics in serum and concentrations in tissues during total hip arthroplasty in dogs with and without hip dysplasia, and to calculate the optimal dosage of cefazolin for prophylactic use during total hip arthroplasty. ANIMALS: 10 dogs with hip dysplasia and 3 clinically normal dogs. PROCEDURE: Blood samples and tissue specimens from the coxofemoral joint capsule, acetabulum, and femur were obtained during unilateral total hip arthroplasty. Cefazolin concentrations in serum and tissue specimen supernatant were determined, using high-performance liquid chromatography, for use in pharmacokinetic analysis. Mathematical simulation of serum cefazolin concentration was used to to predict the optimal dose. RESULTS: Mean pharmacokinetic constants (SEM) were 0.146 (0.013) min-1 for alpha, 4.47 min for t1/2 alpha 0.015 (0.004) min-1 for beta, 46.83 min for t1/2 beta. Significant different was not detected for cefazolin distribution and elimination between dogs with and without hip dysplasia. Additional, significant difference was not observed in pharmacokinetic parameters describing distribution and elimination between the first and second doses of cefazolin. The predicted optimal dosage regimen was 8 mg/kg of body weight, i.v. every hour or mg/kg, i.v. every 2 hours. CLINICAL RELEVANCE: For prophylactic i.v. treatment during total hip arthroplasty, use of cefazolin at a dosage of 8 mg/kg every hour or 22 mg/kg every 2 hours should maintain serum cefazolin concentrations at least 10x the minimum inhibitory concentration for 3 to 4 hours.