Influence of Canal Preparation Depth on the Incidence of Femoral Medullary Infarction with Zurich Cementless Canine Total Hip Arthroplasty

Objective— To determine the incidence of femoral medullary infarction after modifying the depth of femoral reaming and filing when performing total hip replacement (THR) using the Zurich Cementless Total Hip Replacement system (ZCTHR).
Study Design— Case series.
Animals— Dogs (n=31) that had ZCTHR (34).
Methods— Thirty-one dogs (34 THR) had ZCTHR (May 2003–September 2006) and with >1 year radiographic (craniocaudal, mediolateral views) follow-up after THR were evaluated for the presence of femoral medullary infarcts. Incidence was compared with a previous study performed before the technique modification.
Results— Femoral medullary infarction occurred in 1 femur (2.9%; dog <18 months at THR) compared with 19.5% before the technique change, a significant decrease ( P <.001).
Conclusion— Limiting the depth of reaming and filing of the medullary canal resulted in a significant decrease in the incidence of femoral medullary infarction.
Clinical Relevance— Depth of reaming and filing the medullary canal should be limited when performing THR using the ZCTHR.     

Biomechanical Comparison of Four Soft Tissue Replacement Materials: An In Vitro Evaluation of Single and Multilaminate Porcine Small Intestinal Submucosa, Canine Fascia Lata, and Polypropylene Mesh

Objective— To compare mechanical performance of 4 soft tissue replacement materials.
Study Design— Experimental.
Sample Population— Polypropylene mesh (PM), single-layer porcine small intestinal submucosa (SIS), multilaminate (4-layer) porcine small intestinal submucosa (MLSIS), and canine fascia lata (FL).
Methods— The mechanical properties of each material were determined by testing to failure on a materials testing machine. Samples of each material (n=10) were tested in 3 different modes: resistance to suture pullout, tensile testing, and push-through testing. PM was tested both parallel (PMa) to and perpendicular (PMb) to its longitudinal cord orientation. SIS and FL were similarly tested in 2 orthogonal directions.
Results— With some exceptions, the following generalizations can be made regarding the mechanical performance of the materials tested:
Suture pullout— FL>PMa=PMb>MLSIS>SIS ( P ≤.04).
Tensile testing —FL>PMa>PMb>MLSIS>SIS ( P ≤.02).
Push-through testing— FL>PM>MLSIS>SIS ( P ≤.003).
Conclusions— PM accommodated a significantly higher load and energy to yield when its longitudinal cords were oriented parallel with the tension axis (PMa). FL performed similarly to the PM, with the exception of limited elongation in tension. MLSIS had biomechanical characteristics that were inferior to FL and PM but superior to SIS.
Clinical Relevance— PM's orientation may need to be considered when used clinically. FL is a biomechanically suitable soft tissue replacement material but its use may be limited by currently available sizes. SIS cannot be recommended in high-strain environments.     

Laparoscopic Ovariectomy in Dogs: Comparison Between Single Portal and Two-Portal Access

Objective: To compare surgical times and perioperative complication rates of single portal access and 2-portal laparoscopic ovariectomy (LapOVE) in dogs using a bipolar vessel sealer/divider device, and to evaluate the performance of novice laparoscopists for right ovariectomy.
Study Design: Controlled clinical trial.
Animals: Female dogs (n=42).
Methods: Dogs were divided into groups: 1=single portal and 2=2 portal. LapOVE was performed using a 5 mm vessel sealer/divider device and a 10 mm operating laparoscope (Group 1) or a 5 mm laparoscope (Group 2). Dog characteristics (weight, body condition score, ovarian ligament fat score), operative time, and perioperative complication rate were compared between groups. Right ovariectomy duration was evaluated for 2 novice laparoscopists.
Results: No significant difference was found in mean total surgical time between group 1 (21.07 min/s) and group 2 (19.06 min/s). Factors significantly affecting times included body condition scores, ovarian ligament fat score, ovarian bleeding, and surgeon expertize. Minor complications (bleeding from ovaries or after splenic trauma) occurred and were similar in both groups. Bleeding was correlated to body condition score and ovarian ligament fat score. Interindividual differences were found among surgeons for right ovariectomy time.
Conclusions: Single portal access LapOVE using vessel sealer/divider device is feasible, safe, and does not significantly increase total surgical time in comparison with 2-portal approach. Laparoscopic skills may play a role in ability to perform single portal LapOVE.
Clinical Relevance: LapOVE can be performed using single portal access.     

Contact Mechanics of Simulated Meniscal Tears in Cadaveric Canine Stifles

Objective— To evaluate the biomechanical effects of 5 types of meniscal lesions on contact mechanics in the canine stifle.
Study Design— Experimental study.
Animals— Cadaveric canine stifles (n=12 pair).
Methods— Medial meniscal lesions (radial, vertical longitudinal, nonreducible bucket handle, flap, and complex tears) were simulated in cadaveric stifles. A contact map was recorded from each tear type and contact area (CA) and peak contact pressure (PCP) from each tear type were compared.
Results— A significant difference in PCP was detected between control and nonreducible bucket handle, flap, and complex tears. PCP increased by >45% in nonreducible bucket handle, flap, and complex meniscal tears when compared with control. No significant difference was found in PCP between control and radial and vertical longitudinal tears. No significant difference was found in CA between any of the meniscal conditions.
Conclusions— Nonreducible bucket handle, flap, and complex tears cause a significant increase in PCP. Radial and vertical longitudinal tears had a minimal impact on the contact pressures of the medial compartment of the stifle.
Clinical Relevance— Based on this ex vivo model, we support the clinical recommendation of debriding nonreducible bucket handle, flap, and complex tears because the injured portion of the meniscus no longer contributes significantly to the function of the meniscus. Radial and vertical longitudinal tears do not cause a change in contact mechanics allowing consideration of nonsurgical treatment and meniscal repair, respectively. Future experimental and clinical studies should aim to refine the treatment of specific meniscal injuries.     

Potential Iatrogenic Medial Meniscal Damage During Tibial Plateau Leveling Osteotomy

Objective— To evaluate potential iatrogenic medial meniscal (MM) damage during tibial plateau leveling osteotomy (TPLO) and to establish a safe zone (SZ) for hypodermic needle (HN) identification of the medial aspect of the stifle joint.
Study Design— Prospective cohort.
Animals— Cadaveric canine stifles (n=40).
Methods— HN (20 or 25 G) were inserted through the medial collateral ligament (MCL) of the femorotibial joint and through the SZ insertion points. The medial meniscus was inspected for iatrogenic damage. Statistical comparison of MM damage caused by different needle sizes and insertion sites was performed using Fisher's exact test with significance at P <.05.
Results— Twenty-gauge group: 65% of stifles had minor MM damage with MCL insertion compared with 35% of stifles with SZ insertion ( P =.0049). Severe MM damage occurred in 25% of stifles with MCL insertion compared with 0% of stifles with SZ insertion ( P =.0014). Twenty-five-gauge group: 85% of stifles had minor MM damage with MCL insertion compared with 30% after SZ insertion ( P =.0011); however, no severe MM injury was noted.
Conclusions— HN insertion though the MCL can produce iatrogenic damage to the MM. Use of a 25 G HN and SZ site for insertion reduced the frequency and severity of MM damage.
Clinical Relevance— HN insertion into the medial aspect of the femorotibial joint during TPLO can cause gross iatrogenic MM damage, which may contribute to the incidence and misdiagnosis of latent MM injuries after TPLO.     

Evaluation of a Transcondylar Toggle System for Stabilization of the Cranial Cruciate Deficient Stifle in Small Dogs and Cats

Objective— To evaluate use of a transcondylar toggle system (TCTS) for stabilization of the cranial cruciate ligament (CrCL) deficient stifle in small dogs and cats. Study Design— Prospective clinical study. Animals— Small dogs (<7 kg; n=14) and cats (2) with CrCL‐associated lameness of <3 months duration and a tibial plateau angle <32°. Methods— Affected animals had an extracapsular CrCL repair using the TCTS. Lameness score, muscle atrophy, osteoarthritis (OA) score, and range of motion (ROM) were evaluated preoperatively, and at 6 weeks and 7–10 months postoperatively. Results— Operative time was 75 ± 16 minutes. Fifty‐six percent required >1 bone tunnel attempts. One dog required revision at 2 weeks because of suture loosening. All stifles were stable at 6 weeks postoperatively. Fifteen animals were available for follow‐up (7–10 months). Lameness improved significantly at 6 weeks (P<.0001), whereas muscle atrophy was worse at 6 weeks (P=.008) but improved at 7–10 months (P<.0001). OA scores were unchanged at 6 weeks (P=.08) but were significantly worse at 7–10 months (P<.0001). ROM remained unchanged at 6 weeks (P=1) and 7–10 months (P=.6). Conclusions— The medially placed toggle provides a reliable short‐term proximal anchor for the extracapsular suture with outcomes similar to other extracapsular techniques. The aiming device and drill bit are not recommended in their current form. Clinical Relevance— The TCTS appears to be a well‐tolerated technique for proximal suture anchoring in extracapsular CrCL repair in small dogs and cats where instrumentation and anatomic constraints preclude other techniques.     

Hypophosphatemia in Cats After Renal Transplantation

Objective— To report the prevalence of hypophosphatemia after renal transplantation in a historical cohort of cats. Design— Case series. Animals— Cats (n=86) that received a renal allograft. Methods— Medical records (January 200–June 2006) were reviewed. Signalment, clinical signs, pre‐ and postoperative diet, pre‐ and postoperative clinicopathologic variables, renal histopathology, and outcome were retrieved. Prevalence, onset, duration, treatment and associated clinical signs of hypophosphatemia were recorded. A χ² test was used to compare hemolysis frequency between cats with normal serum phosphorus concentration or a single spurious low serum phosphorus concentration for <24 hours duration (group 1) and confirmed hypophosphatemia for >24 hours (group 2). A Cox proportional hazards model was used to evaluate the effects of hypophosphatemia on survival while controlling for other potentially confounding variables (age, sex, weight, body condition score, and pre‐ and 24 hours postoperative clinicopathologic variables). Results— Eighty‐six cats (mean age, 7.7 years) were identified. Hypophosphatemia occurred in 32 cats (37%), with a median onset of 2 days and median duration of 4 days. Treatment was initiated in 48 (56%) of hypophosphatemic cats. Survival and hemolysis frequency was not significantly different between groups, and no risk factors were identified. Conclusion— Hypophosphatemia occurs in cats after renal transplantation and does not affect survival. Clinical Relevance— The clinical importance of hypophosphatemia in renal transplant recipients remains unknown.     

Carpometacarpal Osteoarthritis in Thirty‐Three Horses

Objective— To describe signalment, clinical, and radiographic changes associated with carpometacarpal osteoarthritis (CMC‐OA) and to report long‐term outcome. Study Design— Case series. Animals— Horses (n=33) with CMC‐OA. Methods— Medical records (1992–2007) of horses diagnosed with CMC‐OA were reviewed and signalment, clinical, and radiographic findings retrieved. Owners were contacted for information on the impact of lameness on intended use, response to treatment, progression of lameness, outcome, and owner satisfaction with response to treatment. Results— CMC‐OA identified in 39 limbs, occurred predominantly in middle‐aged and older Quarter Horses and Arabians, and caused severe lameness that prevented normal use. Characteristic swelling was centered over the 2nd metacarpal bone/2nd carpal bone articulation. Radiographic changes consisted of proliferative new bone, narrowed joint space, and subchondral lysis. Of 20 horses with follow‐up, 7 of 14 treated horses were euthanatized within 4 years and 4 of 5 nontreated horses within 3 years. Response to treatment was short lived and considered very poor by most owners. Conclusion— CMC‐OA seemingly occurs primarily in Quarter Horses and Arabians in our region. Response to conservative treatment is very poor and short‐lived with most horses being euthanatized. Clinical Relevance— Conventional treatment methods are unsuccessful for treating CMC‐OA.     

Treatment of a Periarticular Tibial Fracture in a Foal with a Hybrid External Fixator

Objective— To report repair of a right proximal tibial Salter-Harris type II fracture in a foal with a hybrid external fixator (HEF).
Study Design— Case report.
Animals— A 5-month-old male foal.
Methods— After open surgical reduction, an HEF built with wires, 2 half-rings, 3 half-threaded connecting rods, and Schanz pins was used to stabilize the fracture.
Results— Immediately after surgery, the foal had relatively good weight bearing. The HEF was removed at 60 days after radiographic confirmation of healing.
Conclusions— HEF can be used to stabilize a proximal tibial Salter-Harris type II fracture in a 5-month-old foal.
Clinical Relevance— HEF should be considered as another option for repair of proximal tibial Salter-Harris type II fractures in foals.     

Minimum Inhibitory Concentration and Postantibiotic Effect of Amikacin for Equine Isolates of Methicillin-Resistant Staphylococcus aureus In Vitro

Objective— To report the minimum inhibitory concentration (MIC) of amikacin sulfate for equine clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and characterize the initial kill and duration of the postantibiotic effect (PAE) for selected strains.
Study Design— Experimental study.
Methods— Isolates of MRSA (n=35) had their amikacin MIC determined using the E-test agar diffusion method. Two isolates with MICs>256 μg/mL limit were further characterized using broth macrodilution. Six distinct isolates with amikacin MICs of 32, 48, 128 (2 isolates) and 500 (2 isolates) μg/mL had PAE determinations made over a range of amikacin concentrations from 31.25–1000 μg/mL using standard culture-based techniques.
Results— Median MIC of the 35 isolates was 32 μg/mL (range 2 to >256 μg/mL). Mean PAE of selected MRSA strains had an overall mean (all amikacin doses) of 3.43 hours (range 0.10–9.57 hours). PAE for MRSA exposed to amikacin at 1000 μg/mL was 6.18 hours (range 3.30–9.57 hours), significantly longer than that for all other concentrations ( P <.0001). There was no statistically significant effect of isolate MIC on PAE.
Conclusions— Isolates had a wide range of MIC; however, growth of all 6 selected strains were inhibited within the range of concentrations tested, including 2 strains with MICs of 500 μg/mL. PAE duration was not influenced by the MIC of amikacin but was significantly longer with treatment at 1000 μg/mL than at lower concentrations.
Clinical Relevance— Clinical isolates of MRSA are susceptible to amikacin at concentrations achieved by regional perfusion: however, the modest duration of PAE observed suggest that further laboratory and in vivo evaluation be conducted before recommending the technique for clinical use.