Biomechanical evaluation of three adjunctive methods of orthopedic tension band-wire fixation to augment simulated patella tendon repairs in dogs.

OBJECTIVE: To evaluate the effects of three adjunctive methods of tension band wire fixation (TBWF) on the biomechanical properties, gap formation, and failure mode in simulated canine patella tendon rupture (RPT). STUDY DESIGN: Randomized, ex vivo. SAMPLE POPULATION: Paired hindlimbs from 32 dog cadavers. METHODS: Patellar tendons (PTs) and associated bone-muscle-tendon units were harvested. Each PT was transected then sutured using a core locking loop and simple continuous epitendinous pattern. Each hindlimb was randomly assigned to one of three groups (n = 18 hindlimbs/group) using 18 gauge 316 L wire, anchored to the tibial crest distally, to perform transpatellar, suprapatellar, or combined tension band-wire (TBW) augmentation. Ten hindlimbs were utilized as control specimens. Yield, peak, and failure loads, stiffness, loads to 1 and 3 mm gap formation, and failure mode were evaluated. RESULTS: Combined transpatellar and suprapatellar TBW augmentation was superior to transpatellar or suprapatellar groups alone. Yield (p = .0008), peak (p = .004), and failure loads (p = .005) were greater for the combined group than for the transpatellar (p = .048) and suprapatellar groups (p = .01) respectively. There was no difference regarding the occurrence of 1 or 3 mm gap formation (1 mm, p = .05; 3 mm, p = .06); however, loads required to cause gap formation were greater in the combined group (p = .036). Mode of failure differed between techniques used for PT augmentation (p < .001). CONCLUSION: Combined transpatellar and suprapatellar adjunctive TBW augmentation for simulated PT repairs was biomechanically superior to either transpatellar or suprapatellar TBWF alone. CLINICAL SIGNIFICANCE: Combined suprapatellar and transpatellar TBWF may offer a viable surgical option for increased repair-site strength and greater loads to gap formation. Further studies investigating alternative techniques and materials for RPT repair augmentation are warranted.

Influence of crotch suture augmentation on leakage pressure and leakage location during functional end-to-end stapled anastomoses in dogs.

OBJECTIVE: To determine the influence of anastomotic crotch suture augmentation on leakage pressures and leakage location following intestinal functional end-to-end stapled anastomosis (FEESA) in dogs. STUDY DESIGN: Ex vivo, randomized, experimental. SAMPLE POPULATION: Chilled jejunal segments from 3 adult dogs. METHODS: Jejunal specimens were tested within 24 hours of collection. A FEESA was performed and randomly assigned to 1 of 4 treatment groups (n = 12/group): (1) no crotch suture (NCS); (2) simple interrupted crotch suture (SICS); (3) two simple interrupted crotch sutures (TCS) placed laterally on opposing jejunal limbs; (4) simple continuous crotch suture (SCCS) augmentation. Crotch sutures were performed using 3-0 USP polydioxanone. Initial (ILP) and maximal (MLP) leakage pressures (Mean ± SD mm Hg) and leakage location were recorded and compared between groups. RESULTS: Initial leakage pressure was greater after placement of TCS (37.8 ± 6.4, P < .039) and SCCS (47.6 ± 11.0, P < .002) than NCS (27.1 ± 2.5) and SICS (33.0 ± 6.0). Maximal leakage pressure was greater in specimens including SICS, TCS, and SCCS than those without crotch suture augmentation (P < .043). Leakage occurred at the anastomotic crotch in 8/12 NCS, 6/12 SICS, 11/12 TCS, and 12/12 SCCS constructs (P < .001). CONCLUSION: Augmentation of FEESA with TCS and SCCS increased ILP and decreased the occurrence of leakage from the anastomotic crotch, while all methods of anastomotic crotch augmentation increased MLP. CLINICAL SIGNIFICANCE: Augmenting the FEESA with crotch suture(s) improved the resistance of the jejunal anastomosis to leakage in normal cadaveric segments. Placing 2 crotch sutures or use of a simple continuous pattern for anastomotic augmentation appeared to be superior to the placement of a single suture.

Influence of barbed suture oversew of the transverse staple line during functional end-to-end stapled anastomosis in a canine jejunal enterectomy model.

OBJECTIVE: To evaluate the influence of barbed suture oversew of the transverse staple line during functional end-to-end stapled anastomosis (FEESA) in dogs. STUDY DESIGN: Randomized, experimental, ex vivo. ANIMALS OR SAMPLE POPULATION: Grossly normal jejunal segments from 14 adult canine cadavers. METHODS: Ninety-eight jejunal segments (n = 14/FEESA group, n = 14 controls) were harvested and randomly assigned to a control group, FEESA + monofilament suture oversew, FEESA + unidirectional barbed suture oversew or FEESA + bidirectional barbed suture oversew. Oversew techniques were performed using a Cushing suture pattern. Initial (ILP) and maximum leakage pressure (MLP), repair time (s), and location of observed leakage were recorded. RESULTS: No differences were detected in ILP (p = .439) or MLP (p = .644) respectively between experimental groups. Repairs times using barbed suture were ~ 18% faster (~25 s faster; p < .001) compared to monofilament suture. There was no difference between barbed suture types (p = .697). Mean ILP (p < .001) and MLP (p < .0001) were 6.6x and 5.1x greater respectively in the control group. Leakage location occurred predominately at the crotch of the FEESA in all groups. CONCLUSION: FEESAs closed with a transverse staple line oversew using barbed suture, regardless of barb orientation, were completed faster and resulted in similar resistance to anastomotic leakage compared to monofilament suture. CLINICAL SIGNIFICANCE: Oversewing the transverse staple line following FEESA using barbed suture offers similar resistance to anastomotic leakage, and may be associated with decreased surgical times in dogs compared to monofilament suture. Further studies are necessary to determine the benefits of barbed suture use in both open and laparoscopic gastrointestinal surgical applications following FEESA in dogs.

Effect of calcanean bone-tunnel orientation for teno-osseous repair in a canine common calcanean tendon avulsion model.

OBJECTIVE: To determine the influence of bone-tunnel anchoring technique on teno-osseous repair of the common calcanean tendon (CCT) in dogs. STUDY DESIGN: Randomized, ex vivo, biomechanical. POPULATION: Forty-two skeletally mature canine hindlimbs. METHODS: Canine hindlimbs were dissected to produce a model simulating avulsion of the CCT and accessory tendons from the calcaneus. Hindlimbs were randomized to 1 of 3 anchoring techniques (n = 14/group): a single transverse tunnel (TT), vertical tunnels (VT), or modified bone tunnels (MT) for teno-osseous repair in a 3-loop-pulley (3LP) pattern using 0 USP polypropylene. Yield, peak and failure loads, construct stiffness, loads to produce a 3 mm teno-osseous gap, and failure modes were compared between groups. RESULTS: The only difference detected consisted of TT constructs yielding at loads 25% higher than MT constructs (P = .027). CONCLUSION: Although yield loads were lower in MT constructs than other groups, the bone-tunnel anchoring techniques tested here did not appear to influence the biomechanical properties or gapping characteristics of teno-osseous repairs in this canine CCT avulsion model. CLINICAL SIGNIFICANCE: All drilling techniques and bone-tunnel orientations tested in the study reported here offer viable options to reattach the CCT to the calcaneus. Surgeons should evaluate how bone-tunnel orientation may affect placement of adjunctive fixation methods to stabilize the talocrural joint after primary CCT repair in dogs.

Biomechanical analysis of accessory tendon graft augmentation for primary gastrocnemius tendon reconstruction in dogs.

OBJECTIVE: To evaluate the effect of accessory tendon graft (ATG) augmentation as an adjunct to a core locking-loop (LL) and epitendinous suture (ES) repair in a gastrocnemius tendon (GT) model. STUDY DESIGN: Randomized, ex vivo, biomechanical. POPULATION: Twenty-two canine GT musculotendinous constructs. METHODS: GT repair constructs were randomly divided into two groups (n = 10/group). After transection, paired GT were repaired with LL + ES alone or with concurrent ATG augmentation. Yield, peak and failure loads, tensile loads required to create 1 and 3 mm gapping, and failure modes were evaluated. Four GT were used as intact controls for validation of testing methodology. ATG constructs were compared to LL + ES and control specimens. RESULTS: Yield (p < .0001), peak (p = .0001) and failure loads (p = .0003) were greater when ATG was used for repair. Greater force was required to cause 1 mm (p = .0001) and 3 mm (p = .0002) gap formation in the ATG group, however, the frequency of gap formation did not differ between groups. All repaired constructs failed exclusively by suture pull-through. CONCLUSION: Autologous ATG augmentation as an adjunct to primary GT repair increased yield, peak and failure forces by approximately 1.6×, 1.9×, 1.8× respectively and required 2.1× greater force to cause 1 and 3 mm formation respectively compared to LL + ES repairs alone. CLINICAL SIGNIFICANCE: ATG augmentation should be considered as an autologous method to support and strengthen the primary GT repair. These results justify studies to determine the effect of ATG on clinical function following graft harvest in dogs.

Biomechanical evaluation of a novel barbed suture pattern with epitendinous suture augmentation in a canine flexor tendon model.

OBJECTIVE: To determine the effect of a novel barbed suture pattern (NBSP) compared to a three-loop-pulley (3LP) with and without epitendinous suture (ES) augmentation on the biomechanical strength and gap formation of repaired canine tendons. STUDY DESIGN: Ex vivo, cadaveric, randomized, experimental study. SAMPLE POPULATION: Forty, adult superficial digital flexor tendons (SDFT). METHODS: SDFT were randomly assigned to one of four groups (n = 10/group). Sharp tenotomy was performed and repaired with 3LP, NBSP, 3LP + ES, and NBSP + ES. Constructs were tested to failure while evaluating yield, peak, and failure loads, loads at 1 and 3 mm gap formation, and failure mode. RESULTS: Constructs augmented with ES sustained 80% greater yield (p < .001), peak (p < .001), and failure (p < .001) loads, with no difference between 3LP + ES and NBSP + ES constructs regarding peak (p = .614), and failure forces (p = .865). Loads resulting in 1 and 3 mm gap formation were greater when constructs were augmented with an ES (p ≤ .003). Failure mode differed between groups (p < .001), occurring predominantly due to suture pull-through in 3LP and NBSP groups compared to tissue failure distant to the repair site in ES augmented constructs. CONCLUSION: Tendons repaired with the NBSP used in this study resisted similar forces as those repaired with 3LP. Augmentation with an ES improved the biomechanical properties of repaired constructs, including resistance to gap formation. CLINICAL RELEVANCE: The NBSP repair tested here may be advantageous over monofilament suture repair as it uses a similar-sized barbed core suture but eliminates the requirement for knot tying.

Influence of preconstructed effector loop location using a barbed unidirectional suture on leakage pressures following canine enterotomy closure.

OBJECTIVE: To evaluate the influence of preconstructed effector loop location using a barbed unidirectional suture on leakage pressures following canine enterotomy closure. STUDY DESIGN: Randomized, experimental, cadaveric. ANIMALS OR SAMPLE POPULATION: Grossly normal jejunal segments from three canine cadavers. METHODS: Jejunal segments were harvested and randomly assigned based upon effector loop location from the beginning of the incisional line. Groups (n = 12/group) included 0 mm, 5 mm, 10 mm, 15 mm, and intact controls (n = 6/group), repaired using a 3-0 unidirectional barbed suture in a simple continuous pattern. Initial leakage pressure (ILP), maximum intraluminal pressure (MIP), repair time, and leakage location were recorded. RESULTS: Mean ILP for 0 mm group (24.42 ± 8.43 mmHg) was lower (p ≤ .001) compared to all experimental groups with ILP ~40% lower. There was no difference in MIP among experimental groups (p = .239). Repair time increased (p < .0001) as the distance of the effector loop increased ≥5 mm from the beginning of the incisional line. Leakage location differed among groups (p < .001) with leakage in the 0 mm group from the incisional line (75%), compared to leakage from predominantly from the suture holes in other groups, respectively. CONCLUSION: Effector loop location influenced ILP and leakage location. Effector loops placed at the beginning of the incisional line (0 mm) decreased ILP compared to loops placed at 5, 10, and 15 mm. CLINICAL SIGNIFICANCE: Effector loop location using a unidirectional barbed suture should be placed ≥5 mm from beginning of the incisional line for enterotomy closure. Further in vivo studies are necessary to determine the clinical significance of these findings.

Evaluation of staple line reinforcement after partial gastrectomy closure in an ex vivo canine model.

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 to leakage. In vivo investigation is warranted to evaluate influence of closure technique on gastric healing, postoperative stasis, ischemic injury, and postoperative dehiscence.

Ex vivo evaluation of novel core tenorrhaphy patterns in dogs.

OBJECTIVE: To compare the biomechanical properties and gapping characteristics of four novel tenorrhaphy patterns in a canine flexor tendon model. STUDY DESIGN: Ex vivo, randomized, biomechanical study. SAMPLE POPULATION: Superficial digital flexor tendons of 60 forelimbs (30 dogs). METHODS: Each tendon was transected 25 mm distal to its musculotendinous junction prior to tenorrhaphy with 2-0 polypropylene. Repair patterns included the three-loop pulley (3LP, control), exposed double-cross-lock (ExDCrL), embedded double-cross-lock (EmDCrL), triple-circle-lock (TCiL), and Modified-Tang patterns (MTang) were randomly assigned to each experimental group (n = 12/group). Yield, peak, and failure loads, gap formation and failure modes were compared. RESULTS: Tendons repaired with ExDCrL (p < .0001), EmDCrL (p < .0001), and MTang (p < .0001) sustained yield, peak, and failure loads ~2.2x, ~2.0x, and ~1.9x, respectively, greater than those repaired with 3LP. Loads to 1 and 3 mm gapping were also higher for ExDCrL (p < .0001), EmDCrL (p < .0004), and MTang constructs (p < .0017) compared to 3LP. Although TCiL constructs sustained higher loads, their resistance to gap formation did not differ from that of 3LP repairs. Failure mode differed between groups (p < .0001), EmDCrL, ExDCrL, MTang, and TCiL constructs failing predominantly by suture breakage compared to 3LP repairs that failed by suture pull-through. CONCLUSION: Use of novel patterns ExDCrL, EmDCrL, and MTang improved resistance to loads and gap formation and were biomechanically superior compared to 3LP in healthy canine tendon repairs. CLINICAL SIGNIFICANCE: These results justify in vivo evaluation of ExDCrL, EmDCrL, or MTang pattern for tenorrhaphy in dogs.

Influence of closure technique on leakage pressures in an ex vivo canine typhlectomy model.

OBJECTIVE: To determine the influence of three closure techniques on leakage pressures of canine typhlectomies. STUDY DESIGN: Experimental, ex vivo. SAMPLE POPULATION: Grossly normal cecal segments from 24 adult canine cadavers. METHODS: Typhlectomies 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. RESULTS: Typhlectomies 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. CONCLUSION: Placement 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 SIGNIFICANCE: These 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.

Ex vivo comparison of the effect of storage temperature on canine intestinal leakage pressures.

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.

Effect of partial vs complete circumferential epitendinous suture placement on the biomechanical properties and gap formation of canine cadaveric tendons.

OBJECTIVE: To determine the effect of partial vs complete circumferential epitendinous suture (ES) placement in addition to a core suture on the biomechanical strength and gapping characteristics of repaired canine tendinous constructs. STUDY DESIGN: Ex vivo, biomechanical study. SAMPLE POPULATION: Thirty-six canine superficial digital flexor tendons. METHODS: Superficial digital flexor tendons were randomly assigned to three groups (n = 12), sharply transected and repaired with a core locking-loop suture with Group 1 a partial circumferential ES, 180° on the palmar side; Group 2 a complete circumferential ES, 360° and double knotting technique; or Group 3 a complete circumferential ES, 360° and single knotting technique. After preloading, constructs were distracted to monotonic failure. Failure mode, gap formation, yield, peak, and failure forces were analyzed. RESULTS: Mean yield (group 1 = 68.6 N, group 2 = 106.5 N, group 3 = 114 N, P < .013), peak (group 1 = 92.8 N, group 2 = 134.6 N, group 3 = 147.3 N; P < .001), and failure (group 1 = 88.7 N, group 2 = 133.0 N, group 3 = 145.5 N, P < .001) loads differed between groups. No difference in yield (P = .874), peak (P = .434), or failure load (P = .434) was detected between complete circumferential ES groups. Force to create 1-mm (P < .001) and 3-mm (P < .038) gap formation was greater in specimens with complete vs partial circumferential ES placement. Complete circumferential ES repairs failed primarily by suture pull-through compared with suture breakage in most partial circumferential ES constructs. CONCLUSION: Addition of a complete circumferential ES with a single or double knotting technique increased the biomechanical strength of normal tendon repairs while reducing gap formation compared with partial ES placement alone. CLINICAL SIGNIFICANCE: Complete circumferential ES is recommended over partial ES placement.

Biomechanical evaluation of an autologous flexor digitorum lateralis graft to augment the surgical repair of gastrocnemius tendon laceration in a canine ex vivo model.

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.

Influence of barbed epitendinous sutures combined with a core locking-loop suture to repair experimental flexor tendon lacerations.

OBJECTIVE: To determine the influence of barbed epitendinous sutures (ES) on the biomechanical properties and gap formation of repaired canine tendons. STUDY DESIGN: Ex vivo, experimental study. SAMPLE POPULATION: Eighty (n = 16/group) canine superficial digital flexor tendons (SDFT). METHODS: After transection, SDFT were repaired with a locking-loop (LL) pattern alone (group 1), an LL + smooth ES with monofilament suture (group 2), an LL + V-loc-ES (group 3), an LL + Quill-ES (group 4), or an LL + Stratafix-ES (group 5). All core LL repairs were performed with 0 USP polypropylene, and all ES were placed with 2-0 USP equivalent. Constructs were preloaded and tested to failure. Yield, peak, and failure loads; occurrence of gap formation; and failure modes were compared. RESULTS: Yield loads were greater for groups 2 and 5 (P < .0001). Peak and failure loads were greater when an ES was used (P < .005), especially for groups 2 and 5 (P < .0001). Groups with an ES required higher loads to generate 1- and 3-mm gaps compared with specimens without an ES (P < .002). Force to create 1- and 3-mm gaps was greater for group 5 (P < .0001) and groups 2 and 5 (P < .0001), respectively. Failure mechanism did not differ (P = .092) between ES groups, consisting of suture breakage in 51 of 64 constructs compared with pull-through in seven of 16 group 1 constructs. CONCLUSION: Epitendinous suture placement improved the biomechanical properties of repaired tendons. Stratafix barbed suture performed better as an ES compared with other barbed sutures and similarly to monofilament suture. CLINICAL SIGNIFICANCE: Stratafix barbed suture eliminates the requirement for knot tying and seems to be equivalent to smooth monofilament suture when used as an ES in this pattern.

Influence of Kirschner-Wire Insertion Angle on Construct Biomechanics following Tibial Tuberosity Osteotomy Fixation in Dogs.

OBJECTIVES: The aim of this study was to evaluate the effect of Kirschner wire insertion angle on the biomechanical characteristics following tibial tuberosity osteotomy fixation in dogs. STUDY DESIGN: Twelve pairs of cadaveric tibia were harvested and randomly assigned to two treatment groups. Kirschner wires were placed either transversely (0 degrees) or placed caudodistally (30 degrees) with respect to the tibial tuberosity osteotomy. Each limb acted as its own respective control. Radiographic analysis allowed for the calculation of Kirschner wire insertion angle variance. Constructs were tested to monotonic failure while evaluating yield, peak, and failure forces, construct stiffness, and failure mode. RESULTS: Kirschner wire insertion angles were 1.1 ± 2.2 degrees and 30.5 ± 2.3 degrees, respectively, for 0-degree and 30-degree groups (p <0.0001). Yield (p = 0.0095), peak (p <0.024) and failure loads (p <0.030) were all significantly greater for Kirschner wires inserted at an angle of 0 degrees compared with 30 degrees. Construct stiffness did not differ regardless of insertion angle (p = 0.068). Failure mode did not differ (p = 0.87) with tibial tuberosity avulsion and Kirschner wire pull-out seen in the majority of constructs (67%). CONCLUSION: Kirschner wires placed transversely (0 degrees) for tibial tuberosity osteotomy fixation were biomechanically superior, increasing yield, peak, and failure forces by 1.6 times, 1.3 times, and 1.4 times, respectively, to those placed in a caudodistal (30 degrees) orientation. Kirschner wire insertion angle is an important consideration following tibial tuberosity osteotomy in dogs, with Kirschner wires placed at 0 degrees conferring increased resistance of the repair to construct deformation.

Influence of three different closure techniques on leakage pressures and leakage location following partial cystectomies in normal dogs.

BACKGROUND: Transitional cell carcinoma (TCC) is the most common neoplasia affecting the canine urinary bladder. Partial cystectomy, when used adjuctively with medical management, has been shown to meaningfully extend medial survival time. Surgical stapling devices have a wide variety of uses and advantages over traditional closure methods and, to date, investigation into their use in canine partial cystectomies has not been documented. OBJECTIVE: To determine the influence of three closure techniques on ex vivo leakage pressures and leakage location following canine partial cystectomy. METHODS: Specimens were assigned to one of three closure techniques: simple continuous appositional closure with 3-0 suture, closure with a 60 mm gastrointestinal stapler with a 3.5 mm cartridge, and placement of a Cushing suture to augment the stapled closure, with each group containing 12 specimens. Mean initial leakage pressure (ILP), maximum leakage pressure (MLP), and leakage location at the time that ILP was recorded were compared between groups. RESULTS: Oversewn stapled constructs leaked at significantly higher ILP (28.5 mmHg) than those in the sutured (17 mmHg) or stapled (22.8 mmHg) group, respectively. MLP was greater in the oversewn stapled construct group compared to other groups. Leakage was detected in 97% partial cystectomies, with leakage occurring from the needle holes in 100% of the sutured closure group, from the staple holes in 100% of the stapled only group, and from the incisional line in 83% and from bladder wall rupture in 8% of the augmented staple closure group. All closure methods withstood normal physiologic cystic pressures. CONCLUSIONS: Placement of a Cushing suture to augment stapled closures improved the ability of partial cystectomies to sustain higher intravesicular pressures compared with sutured or stapled bladder closures alone. Further in vivo studies are required to determine the clinical significance of these findings and the role of stapling equipment for partial cystectomy, as well as the clinical significance of suture penetration through the urinary bladder mucosa during closure.

Loop diameter of a modified Kessler locking-loop suture affects in vitro tensile strength and gapping characteristics of canine flexor tendon repairs.

OBJECTIVE: To evaluate effects of loop diameter of a modified Kessler locking-loop (LL) suture on in vitro tensile strength and gapping characteristics of canine flexor tendon repairs. SAMPLE: 48 cadaveric superficial digital flexor tendons from 24 adult medium- to large-breed dogs. PROCEDURES: Flexor tendons were randomly assigned to 4 groups (n = 12/group) and repaired with 2-0 polypropylene in a LL pattern with loops measuring 1, 2, 3, or 4 mm in diameter. Biomechanical loads, gap formation between tendon ends, and failure modes were evaluated and compared between groups. RESULTS: Increasing loop diameter from 1 to 4 mm significantly increased yield (P = .048), peak (P < .001), and failure (P < .001) loads. There were no significant differences in yield, peak, and failure loads between 1- and 2-mm loops. Load to 3-mm gap formation was significantly (P < .001) greater for 4-mm loops, compared with 1-, 2-, and 3-mm loops. Failure mode did not differ significantly among experimental groups, with 46 of 48 (96%) of constructs failing because of suture breakage. CLINICAL RELEVANCE: Loop diameter of a LL suture pattern is an important biomechanical variable that influences construct biomechanics of canine tendon suture repairs. Loop diameters > 3 mm are recommended when the size of the tendon allows. Further studies are necessary to determine the in vivo effect of these findings, particularly the effects on tendon blood supply.

Ex vivo biomechanical characteristics and effects on gap formation of using an internal fixation plate to augment primary three-loop pulley repair of canine gastrocnemius tendons.

OBJECTIVE: To evaluate the effects of using an internal fixation plate to augment primary 3-loop pulley (3LP) repair of canine gastrocnemius tendons (GTs). SAMPLE: 48 cadaveric GTs from 24 adult dogs. PROCEDURES: GTs were dissected free from other tissues, transected, and randomly assigned to 4 groups (n = 12/group). GTs were repaired with 2-0 polypropylene with a 3LP repair alone or a 3LP repair augmented with a 3-hole veterinary cuttable plate (3VCP), a 5-hole veterinary cuttable plate (5VCP), or a 7-hole veterinary cuttable plate (7VC P). Biomechanical loads, construct stiffness, gap formation, and failure modes were compared between groups. RESULTS: Yield, peak, and failure loads were all significantly increased for the 5VCP and 7VCP groups, compared with the 3LP alone group. Increasing plate length from 3VCP to 5VCP and from 3VCP to 7VCP increased yield, peak, and failure loads. No differences were found between the 3LP and 3VCP groups with regard to yield and peak loads, but failure load was increased in the 3VCP group. Loads to create 1-mm and 3-mm gaps were significantly greater for the 5VCP and 7VCP groups, compared with the 3LP alone and 3VCP groups. Mode of plate attachment failure differed among groups. CLINICAL RELEVANCE: Tendon plate augmentation may be a viable surgical option to increase the strength of the tenorrhaphy in dogs. However, in vivo studies evaluating the effects of plate augmentation on the tendon blood supply and progression of healing are needed prior to clinical application.

Effect of epitendinous suture augmentation to a double Krackow suture pattern for canine gastrocnemius tendon repair.

OBJECTIVE: To evaluate the effect of a double Krackow suture pattern (DK), with and without epitendinous suture augmentation (ES), in a canine gastrocnemius tendon (GT) model. SAMPLE: Paired GTs from 12 adult dog cadavers and 4 control GT. PROCEDURES: GTs were assigned to 2 groups (n = 12/group). Transverse tenotomy was performed and repaired with a DK or DK + ES. Yield, peak, and failure force, stiffness, occurrence of 1-and 3-mm gapping, and failure mode were examined. RESULTS: Yield, peak, and failure loads were greater for DK + ES. Yield force was 48% greater for DK + ES (mean ± SD, 149.56 ± 53.26 N) versus DK (101.27 ± 37.17 N; P = 0.017). Peak force was 45% greater for DK + ES P < 0.001). Failure force was 47% greater for DK + ES (193.752 ± 31.43 N) versus DK (131.54 ± 22.28 N; P < 0.001). Construct stiffness was 36% greater for DK + ES (P = 0.04). All 12 DK and 10 of 12 DK + ES repairs produced a 1-mm gap, with all DK and 4 DK + ES repairs producing a 3-mm gap (P < 0.001). Loads required to create a 3-mm gap were significantly greater for DK + ES (P < 0.013). Suture breakage occurred in all DK repairs, which differed from DK + ES, where suture breakage (7/12) and tissue failure (5/12; P = 0.037) predominated. CLINICAL RELEVANCE: Augmentation of a primary DK repair with an ES significantly improved construct strength in canine GT constructs while increasing loads required to cause 1- and 3-mm gap formation, respectively. ES augmentation is a simple technique modification that can be used to significantly increase construct strength, compared with DK alone.

Superficial digital flexor tendon graft augmentation improves the tensile strength and resistance to gap formation following primary gastrocnemius tendon repair in dogs.

OBJECTIVE: To evaluate the influence of superficial digital flexor tendon (SDFT) graft augmentation on the biomechanical properties and resistance to gap formation in a canine gastrocnemius tendon repair model. SAMPLE POPULATION: 28 canine cadaveric hind limbs. PROCEDURES: Respective hindlimbs from each dog were randomized to one of two groups (n = 14/group) using a 3-loop-pulley (3LP) pattern alone or 3LP + SDFT graft augmentation. Biomechanical parameters evaluated included yield, peak, and failure loads; tensile loads required to create 1- and 3-mm gap formations; and mode of construct failure. RESULTS: Mean yield and failure loads for the 3LP + SDFT graft group were 483.6 ± 148.0 N and 478.3 ± 147.9 N, respectively, and were greater compared to the 3LP group (34.2 ± 6.7 N and 34.0 ± 8.0 N, P < .0001). Loads to both 1- and 3-mm gap formations for the 3LP + SDFT graft group were greater compared to 3LP alone (P < .001). Failure modes did not differ between groups (P = .120), with constructs failing most commonly by suture pulling through opposed tendinous tissues whereas SDFT grafts remained intact. CLINICAL RELEVANCE: SDFT graft augmentation increased yield, peak, and failure forces 14-fold across all examined biomechanical variables compared to the 3LP group. The 3LP + SDFT graft group required 3.6X and 6.5X greater loads to cause a 1- and 3-mm gap, respectively, between tendon ends. These data support the biomechanical advantages of SDFT graft augmentation to increase repair-site strength and to promote resistance to gap formation of the tenorrhaphy. Additional in vivo studies are required to determine the effect of SDFT augmentation on clinical function and active limb use after graft harvest in dogs.