Objective: To evaluate the effect of an autologous flexor digitorum lateralis (FDL) graft to augment a three-loop pulley (3LP) core repair in a canine cadaveric gastrocnemius tendon (GT) laceration model. Study design: Ex vivo, biomechanical study. Sample population: Twenty-six canine cadaveric hind limbs. Methods: Tendons were divided into two groups (n = 13). After sharp transection, paired GT were repaired with 3LP or 3LP + FDL tendon augmentation. Yield, peak and failure loads, tensile loads required to create 1 and 3-mm gapping, and failure modes were analyzed. Significance was set at P < .05. Results: Yield and failure force (mean ± SD) for 3LP + FDL were 134.9 ± 44.1 N and 205.4 ± 46.4 N, respectively, which were greater than for 3LP alone (67.9 ± 12.2 N and 91.8 ± 9.9 N, respectively, P < .0001). No constructs (0%) formed 1 or 3-mm gaps in the 3LP + FDL graft group compared with 84% and 39% for 3LP, respectively (P < .0001). Failure modes were different between groups (P < .001), with 85% of 3LP + FDL constructs failing by tissue rupture at the myotendinous junction, distant to the repair site. Conclusion: Addition of an autologous FDL graft to a core 3LP tendon repair increased yield, peak, and failure forces by twofold, 2.3-fold, and 2.2-fold, respectively, compared with core 3LP alone while preventing the occurrence of gap formation. Clinical significance: Use of FDL tendon augmentation for GT laceration may increase repair site strength and resist gap formation better than 3LP core suture use alone. Additional studies are required in vivo to determine the effect of FDL graft augmentation on clinical function.

OBJECTIVE To determine effects of bite depth for placement of an epitendinous suture on the biomechanical strength and gap formation of repaired canine tendons. SAMPLE 48 superficial digital flexor tendons (SDFTs) obtained from 24 canine cadavers. PROCEDURES Tendons were assigned to 3 groups (16 tendons/group). Each SDFT was transected and then repaired with a continuous epitendinous suture placed with a bite depth of 1, 2, or 3 mm for groups 1, 2, and 3, respectively. Specimens were loaded to failure. Failure mode, gap formation, yield force, peak force, and failure force were analyzed. RESULTS Yield, peak, and failure forces differed significantly between groups 1 and 3 and groups 2 and 3 but not between groups 1 and 2. Comparison of the force resisted at 1 and 3 mm of gapping revealed a significant difference between groups 1 and 3 and groups 2 and 3 but not between groups 1 and 2. Failure mode did not differ among groups; suture pull-through occurred in 43 of 48 (89.6%) specimens. CONCLUSIONS AND CLINICAL RELEVANCE Increasing bite depth of an epitendinous suture toward the center of the tendon substance increased repair site strength and decreased the incidence of gap formation. Repair of tendon injuries in dogs by use of an epitendinous suture with bites made deep into the tendon should result in a stronger repair, which potentially would allow loading and rehabilitation to begin sooner after surgery. Suture techniques should be investigated in vivo to determine effects on tendinous healing and blood supply before clinical implementation.

Highlights d Microglia respond to Schaffer collateral stimulation in the neonatal hippocampus d Responses depend on microglial GABA B Rs and astrocytic glutamate and GABA transporters d Lack of responses in adults may be due to developmental changes in astrocyte physiology Authors

Objective To determine the effect of storage temperature on cadaveric small intestinal leakage pressures after enterotomy. Study design Experimental ex vivo study. Animals Grossly normal jejunal segments from four canine cadavers. Methods Thirty‐six jejunal segments (n = 12 segments/group) were harvested immediately after euthanasia and assigned to a fresh group (tested within 4 hours), chilled group (stored for 24 hours at 4°C before testing), or freeze–thaw group (frozen at −20°C for 7 days and thawed at 21°C for 6 hours before testing). A 2‐cm antimesenteric enterotomy was performed and repaired with 4‐0 monofilament suture in a simple‐continuous pattern. Initial leakage pressure (ILP), maximal intraluminal pressure (MIP), and leakage location were recorded, with testing performed at room temperature. Results Mean ± SD ILP for fresh, chilled, and frozen–thawed specimens was 52.9 ± 8.4, 51.8 ± 11.9 and 29.8 ± 4.4 mm Hg, respectively. There was a difference in ILP among groups (P < .003), with freeze–thaw samples demonstrating lower ILP compared with other groups. There was no difference in MIP between groups (P = .186) There was a difference in leakage location among groups (P = .004), with the majority of chilled and freeze–thaw samples leaking at the suture holes compared with the incisional line in fresh samples. Conclusion Freezing and subsequent thawing prior to specimen testing reduced ILP compared with use of fresh and chilled specimens but did not affect MIP among experimental groups. Clinical significance Cadaveric canine intestinal specimens tested immediately after collection or after chilling for 24 hours should be recommended for ex vivo burst pressure assessment in dogs. Additional studies to evaluate loss in testing viability of chilled intestinal specimens are warranted to help govern experimental methodologies.

ObjectiveTo determine the influence of three closure techniques on leakage pressures of canine typhlectomies.Study designExperimental, ex vivo.Sample populationGrossly normal cecal segments from 24 adult canine cadavers.MethodsTyphlectomies were assigned to one of three closure techniques: simple continuous closure with a Parker‐Kerr pattern with 4‐0 polydioxanone (group 1), closure with a 60‐mm gastrointestinal stapler loaded with a 3.8‐mm staple cartridge (group 2), and placement of a Cushing suture to augment the stapled closure (group 3). The median (range) of initial leakage pressure (ILP) and maximum leakage pressure (MLP) was compared between groups along with leakage location.ResultsTyphlectomies in group 3 leaked at higher ILP (310 mm Hg; 188‐310) than those in groups 1 (43 mm Hg; 31‐80) and 2 (109.5 mm Hg; 68‐173; P < .0001). Maximum leakage pressure were greater in group 3 than in other groups (P < .0001). Leakage was detected in 20 of 24 (83%) typhlectomies, located at the incisional line in 13 of 24 (54%) specimens and from suture holes in seven of 24 (29%) specimens.ConclusionPlacement of a Cushing suture pattern to augment stapled incisions improved the ability of typhlectomies to sustain pressure compared with sutured or stapled cadaveric specimens alone.Clinical significanceThese results provide evidence to support placement of a Cushing suture pattern to augment the staple line for typhlectomies in dogs, although in vivo studies are required to determine the clinical significance of these findings.

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Objective: To determine the influence of stapling on leakage pressures after canine partial gastrectomy. Study design: Ex vivo study. Sample population: Gastric specimens from 24 adult canine cadavers. Methods: Partial gastrectomy constructs were assigned to one of three closure techniques (n = 8 per group): group 1, stapled closure with a 90-mm thoracoabdominal stapling device and a 4.8-mm staple cartridge; group 2, hand-sewn double-layer inverting suture closure with 3-0 glycomer 631; and group 3, staple line reinforcement with an inverting Cushing suture pattern. Leakage and pressure testing were performed. Initial leakage pressure (ILP), maximal leakage pressure (MLP), and leakage location were recorded. Significance was set at P < .05. Results: Placement of a Cushing suture (group 3) increased ILP and MLP by 3.2-fold and 2.8-fold, respectively, compared with stapled closures alone (P < .001). Constructs closed with double-layer suture closure reached ILP and MLP 4.5-fold and threefold greater, respectively, compared with those with stapled closures alone (P < .001). Maximal leakage pressure did not differ between groups 2 and 3 (P = .14). Leakage occurred from the inverting suture line in all constructs of groups 2 and 3 and from staple holes in six of eight group 1 constructs. Conclusion: Double-layer suture closure of canine partial gastrectomies achieved superior biomechanical properties compared with stapled closure techniques. Reinforcing staple closures with an inverting suture line improved resistance to leakage. Clinical significance: Reinforcing single-layer closure of partial gastrectomies with an inverting Cushing pattern is recommended to improve resistance

OBJECTIVE To evaluate the effect of suture caliber on the tensile strength of tenorrhaphies performed with a locking-loop technique in cadaveric canine tendons SAMPLE 60 superficial digital flexor tendons (SDFTs) from 30 cadaveric adult dogs. PROCEDURES Transverse tenotomy was performed, and SDFTs were repaired with a locking-loop technique and polypropylene suture of 5 randomly assigned calibers: size-0, 2-0, 3-0, 4-0, or 5-0 (n = 12 SDFTs/suture caliber). Tendon constructs were tested to failure. Yield, peak, and failure forces and causes of failure were compared between groups. RESULTS Mean ± SD failure force for the constructs was significantly greater with large-caliber suture (size-0: 73.5 ± 3.1 N; size 2-0: 54.4 ± 7.1 N; size 3-0: 28.7 ± 4.9 N; size 4-0: 18.7 ± 3.4 N; and size 5-0: 8.8 ± 2.8 N). The likelihood of construct failure by suture pullout through the tendon substance increased with large-caliber suture (size-0: 12/12), whereas the likelihood of construct failure by suture breakage increased with small-caliber suture (2-0: 10/12; 3-0, 4-0, and 5-0: 12/12 each). CONCLUSIONS AND CLINICAL RELEVANCE Large-caliber suture had greater tensile strength for tenorrhaphies performed with a locking-loop technique in cadaveric canine tendons. Prior to the use of large-caliber suture in patients requiring tenorrhaphy, however, in vivo studies are required to confirm the results obtained here.