Biomechanical comparison of knotted and knotless stabilization techniques of the tarsal medial collateral ligament in cats: A cadaveric study.

OBJECTIVE: To compare mechanical properties of intact feline medial collateral ligaments and three techniques for treatment of feline medial tarsal instability. STUDY DESIGN: Controlled laboratory study. SAMPLE POPULATION: Forty-eight normal, adult feline tarsi. METHODS: Three repairs were tested: a bone tunnel with polypropylene (PP) suture, a bone tunnel with polyethylene (PE) cord, and a knotless anchor technique with PE cord. A cyclic (6-N preload; 5-N amplitude; 2-Hz frequency) tensile test (600 cycles) was performed on feline tarsi with either the long or the short medial tarsal ligament intact, with each reconstruction technique followed by a single-cycle load-to-failure test (0.5 mm/s) with a failure point at 2 mm of displacement. Total elongation, peak-to-peak elongation, stiffness, and maximum load to failure point were compared with the intact condition. RESULTS: No differences in stiffness, total elongation, or peak-to-peak elongation were found between specimens repaired with the knotless technique and intact controls (P > .04), whereas tarsi repaired with the tunnel technique and PP were weaker (P < .008). Total and conditioning elongation were greater after tunnel reconstruction with PP than after knotless reconstruction (P = .005). Mean load to 2 mm of displacement tended (P = .03) to be higher after knotless than after knotted PP repairs and did not differ (P = .47) between tarsi repaired with the tunnel or anchor repairs with PE. CONCLUSION: The mechanical properties of intact tarsi were superior to those of tarsi repaired with tunnel techniques and PP but were similar to those of tarsi repaired with knotless techniques with PE. CLINICAL SIGNIFICANCE: Feline tarsal stabilization with the knotless technique for tarsal medial collateral ligament insufficiency may reduce the requirement for or duration of postoperative coaptation.

Predictors of comorbidities and mortality in cats with pelvic fractures.

OBJECTIVE: To characterize and evaluate risk factors for comorbidities and death of cats with pelvic fractures. STUDY DESIGN: Retrospective case study. ANIMALS: Cats (n = 280). METHODS: Medical records were reviewed for cats in which pelvic fractures had been diagnosed (January 2003 to November 2016). Retrieved data included signalment, mechanism of injury, clinical findings, diagnostic imaging investigations, type and number of concurrent injuries based on anatomical location, type of therapy, and survival. Pelvic fractures were classified according to location and severity. Descriptive statistics were performed, and logistic regression models were constructed to examine associations between risk factors and outcome. RESULTS: Cases consisted of 280 cats with no (9%), unilateral (43%), and bilateral (48%) involvement of the weight-bearing axis. Sacral fractures were found in 12% of cats. Surgical treatment and mortality rates increased progressively with the severity of the pelvic fractures (P < .001). Mean number of concurrent body regions injured was 2.4 ± 1.2 and was associated with mortality (P < .01). Twenty percent of cats did not survive to discharge. Cats with neurologic injuries were more likely not to survive (P = .02). CONCLUSION: Concurrent injuries to at least one body region, especially the abdomen and thorax, were observed in cats sustaining pelvic fractures. Mortality was associated with increased severity of the fractures, neurologic injuries, and increased number of concurrent injuries. CLINICAL SIGNIFICANCE: Concurrent injuries are common in cats with pelvic fractures, and comorbidities may be associated with mortality.

Feasibility and safety of arthroscopic medial glenohumeral ligament and subscapularis tendon repair with knotless anchors: A cadaveric study in dogs.

OBJECTIVE: To test the feasibility and safety of an arthroscopic imbrication of the medial glenohumeral ligament (MGHL) and the subscapularis tendon with knotless anchors in dogs. STUDY DESIGN: Cadaveric study. SAMPLE POPULATION: Ten limbs. METHODS: Cranial and caudal arms of the MGHL were imbricated with a 2.9- or a 2.4-mm knotless anchor. A horizontal mattress suture secured with a 3.5-mm knotless anchor was used to imbricate the subscapularis tendon. Computed tomography measurements included (1) the bone stock around the anchors, (2) the angle between the anchor and the joint surface (insertion angle), and (3) the angle formed by lines tangent to the cortices of the bones (safety angle). Limbs were dissected to assess the position of anchors. Safety and insertion angles and bone stock were compared among anchors with a Kruskal-Wallis test (P < .05). RESULTS: Surgical repairs were achieved in all limbs, with only 2 of 30 anchors incorrectly placed, both in the glenoid. The safety angle of the humeral anchor (HA; median, 89°) was greater than that of the cranial glenoid anchor (CrGA; P = .0017) and the caudal glenoid anchor (CdGA; P < .001). The insertion angle of the HA (median, 68°) was also greater than that of the other anchors (P < .001 and P = .001). The insertion angle of the CrGA (median, 26°) was greater (P = .0191) than that of the CdGA (median, 7°). All anchors were inserted at the MGHL and subscapularis footprint. CONCLUSION: Arthroscopic imbrication of MGHL and subscapularis tendon was feasible. HA were safer to place than glenoid anchors. CLINICAL SIGNIFICANCE: The results of this feasibility study justify further evaluation of the indications and outcomes of this technique in dogs with shoulder instability.

An anatomical study of plate-rod fixation in feline tibiae.

OBJECTIVE: To investigate the feasibility of placing bi-cortical cortex (B-cort) or mono-cortical locking screws (M-lock) in a plate-rod construct applied to the feline tibia in combination with different intramedullary (IM) pins. METHODS: Twenty-four feline tibiae of cats were divided into 4 groups, corresponding to IM pin sizes filling approximately 30% (1.0 mm), 40% (1.4 mm), 45% (1.6 mm), and 50% (1.8 mm) of the medullary canal. Computed tomography (CT) was performed to trace potential screw trajectories in each group. A 12-hole, 2.4 mm locking compression plate was then applied on the medial aspect of the tibia. M-lock and B-cort screws were inserted subsequently in each plate hole. Success rates of screw insertion based on CT analysis and cadaveric simulation were compared with screw type, IM pin diameter, and anatomic location as variables. RESULTS: Screw insertion rates were underestimated on CT compared to cadaveric specimens. During cadaveric simulation, B-cort screws could be inserted in all specimens in the 3 most proximal plate holes and in at least 1 of the 3 distal plate holes. The smallest pin size (30%) allowed placement of a greater number of B-cort screws (P < .05) compared to other pins. Fewer B-cort screws could be inserted in the distal diaphyseal region (P < .05) compared to other regions. A total of 99.3% of M-lock screws could be inserted regardless of IMP size. CLINICAL SIGNIFICANCE: Plate rod constructs can include bicortical screws in the proximal and distal metaphysis, and monocortical screws in the diaphysis, combined with an IM pin filling up to 50% of the medullary canal.

Evaluation of Two Miniplate Systems and Figure-of-eight Bandages for Stabilization of Experimentally Induced Ulnar and Radial Fractures in Pigeons ( Columba livia ).

Although plate fixation has advantages over other fixation methods for certain indications, it is rarely used in avian surgery, especially in birds that weigh less than 1000 g. Exceptionally small plating systems for these birds are required, which are relatively expensive and difficult to insert. To study avian fracture healing after repair using miniplates, we evaluated 2 steel miniplate systems in 27 pigeons ( Columba livia ) divided into 4 groups. In each pigeon, the left ulna and radius were transected and the ulna was repaired with a bone plate. In groups A and B, a 1.3-mm adaption plate was applied without and with a figure-of-eight bandage; in groups C and D, a 1.0-mm compression plate was applied without and with a bandage, respectively. Healing was evaluated with radiographs after 3, 14, and 28 days; flight tests were conducted after 14, 21, and 28 days; and the wing was macroscopically examined after euthanasia of birds on day 28. Fractures healed without bending or distortion of the plate in all 27 birds, and no significant differences in healing were found between treatment groups. At the end of the study, 23 pigeons (85.2%) showed good or very good flight ability. Results show the 1.3-mm adaption plate and the 1.0-mm compression plate meet the requirements for avian osteosynthesis and can be recommended for fracture repair of the ulna or other long bones in birds weighing less than 500 g. The application of a figure-of-eight bandage might be beneficial in fracture healing.

Effect of external rotational humeral osteotomy on the contact mechanics of the canine elbow joint.

OBJECTIVE: To evaluate the effect of 15° external rotational humeral osteotomy (ERHO) on canine elbow joint contact mechanics. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: Unpaired cadaveric canine thoracic limbs (n = 8) METHODS: Digital pressure sensors placed in a subchondral osteotomy distal to the elbow joint were used to measure contact area, peak and mean contact pressure, peak pressure location, center of pressure, and total force in the subchondral bone of the radius and the ulna. Measurements were taken in the following sequence: (i) neutral and (ii) after 15° external rotation. The distal aspect of the humerus was externally rotated by a middiaphyseal osteotomy and stabilized with an internal fixator. Data were normalized and analyzed using paired t-tests; P ≤ .05 was considered significant. RESULTS: Peak pressure location and center of pressure shifted 37.5 ± 15.9% and 21.5 ± 6.8% laterally after ERHO (P < .001 for both). Both were situated over the subchondral bone of the ulna in neutral position and over the radius after rotation in all 8 specimens (P < .001). Pressure measured in the ulnar part of the osteotomy was reduced from 58.7 ± 9.1% to 27.1% after ERHO (P < .001). Contact area, peak and mean contact pressure, and total force did not vary significantly between conditions. CONCLUSION: ERHO shifts the peak pressure location and the center of pressure laterally, toward the radial head and reduced the pressure acting on the ulna. The lateral shift of peak pressure may be beneficial in dogs with medial compartment disease.