Biomechanical comparison of one pin versus two pin fixation in a canine tibial tuberosity avulsion fracture model.

OBJECTIVE: To determine whether one larger or two smaller diameter pins used for tibial tuberosity avulsion fracture (TTAF) stabilization provides greater axial tensile strength and stiffness when subjected to monotonic mechanical load to failure in normal skeletally mature canine cadavers. STUDY DESIGN: Paired ex vivo biomechanical study. SAMPLE POPULATION: Eleven pairs of adult cadaveric dog tibias. METHODS: Twenty-two tibias from 11 dogs were collected to model a TTAF. Each limb of a pair was randomly assigned a one or two-pin fixation. Tibias were subjected to monotonic, axial load to failure. Fixation stiffness, strength, and pin insertion angles were analyzed with parametric testing. Significance was set at p < .05. RESULTS: The mean strength of the single-pin fixation was 426.2 ± 50.5 N compared to two-pin fixation at 639.2 ± 173.5 N (p = .003). The mean stiffness of the single-pin fixation was 57.3 ± 18.7 N/mm and the two-pin fixation was 71.7 ± 20.5 N/mm (p = .029). The normalized ratio between one and two-pin fixation had a mean stiffness of 68% ± 25.8% and strength of 82.8% ± 24.6%. CONCLUSIONS: In an ex vivo cadaveric TTAF model, vertically aligned two-pin fixation offers greater strength and stiffness when compared to a single-pin fixation. CLINICAL SIGNIFICANCE: When repairing TTAF, surgeons should aim to apply two vertically aligned pins rather than a single pin for greater strength and stiffness.

Good clinical outcomes achieved in young dogs with tibial tuberosity avulsion fracture repairs when implants were left in situ past skeletal maturity.

OBJECTIVE: To evaluate outcomes of tibial tuberosity avulsion fractures (TTAF) in dogs with implants left in situ past skeletal maturity and to compare clinical outcomes with published outcomes in dogs whose implants were removed 4 to 6 weeks postoperatively. ANIMALS: 47 client-owned dogs. PROCEDURES: In this retrospective study, 47 dogs had surgery to correct a TTAF before 10 months of age and had the implants left in situ past skeletal maturity. Of these, 42 were followed for a median of 36 months postoperatively. Short- and long-term complications were recorded and compared with historically published data in which the implants were removed within 6 weeks of surgery. RESULTS: 14% (6/42) of our population experienced minor long-term complications (stiffness and lameness), 6% (3/47) experienced major short-term complications (repair failure), and 14% (6/24) experienced major long-term complications (implant removal). There was no difference in long-term outcomes when compared with results of historical reports in which implants were removed 4 to 6 weeks postoperatively. Client satisfaction was high, with 93% (38/41) grading outcomes as excellent and 95% (39/41) stating they would have surgery performed again in retrospect. CLINICAL RELEVANCE: Immature dogs with surgically repaired TTAFs have favorable long-term outcomes when the implants were left in situ past skeletal maturity. Dogs with TTAF repairs may not need implant removal unless it becomes clinically necessary. Avoiding a second procedure will decrease patient morbidity, recovery time, and cost.

Factors Contributing to the Need for Non-Elective Explant following Surgical Repair of Tibial Tuberosity Avulsion Fracture.

OBJECTIVE: The aim of this study was to evaluate factors contributing to the need for non-elective explant following surgical repair of tibial tuberosity avulsion fractures. STUDY DESIGN: Retrospective multicentre case-control study. Over a 5-year period, dogs (n = 63) that underwent surgical repair of tibial tuberosity avulsion fractures (n = 64) were considered. Dogs that underwent a non-elective explant were compared with those that did not. Continuous variables were compared with the Mann-Whitney U test. Categorical variables were compared with the Fisher's exact test. Variables which were significant on univariate analysis were entered into a multiple logistic regression model. Significance was set at p < 0.05. RESULTS: Non-elective explant was performed in 20/64 fractures and elective explant was performed in 2/64 fractures. Neutered dogs were found to be 19 times (95% confidence interval: 2.1-172) more likely to require explant compared with intact dogs (p = 0.009). Every 0.25 mm increase in average pin size was found to make it 2.5 times (95% confidence interval: 1.3-4.9) more likely to require explant (p = 0.006). CONCLUSION: The findings suggest that use of the smallest appropriate pin should be considered for standard surgical repair of tibial tuberosity avulsion fractures to minimize the risk of requiring non-elective explant.

Use of a hybrid external skeletal fixator construct for managing tibial tuberosity avulsion fractures in three dogs.

CASE DESCRIPTION: 3 juvenile (4 to 5 months of age) medium- to large-breed or crossbred dogs were evaluated for sudden unilateral non-weight-bearing lameness in a pelvic limb after a fall during strenuous activity. CLINICAL FINDINGS: All dogs had non-weight-bearing lameness (n = 2) or bore minimal weight (1) on the affected pelvic limb, had soft tissue swelling over the cranial aspect of the stifle joint in the affected limb, seemed to resist manipulation of the affected joint, and had tibial tuberosity avulsion fracture confirmed with radiography. TREATMENT AND OUTCOME: Each dog underwent surgical fracture reduction and stabilization with a hybrid circular-linear external skeletal fixator construct with interfragmentary Kirschner wires used to stabilize the avulsed tibial tuberosity. Successful fracture reduction and stabilization were achieved, and only minor postoperative complications occurred. Construct removal 2 weeks postoperatively resulted in no displacement of the tibial tuberosity in 2 dogs and only minor proximal displacement in the remaining dog, allowed for continued unencumbered growth through the apophysis and proximal tibial epiphysis in all dogs, and did not result in tibial conformational anomalies. Clinical outcome was considered excellent in 2 dogs with complete resolution of lameness and good in 1 dog with subsequent occasional mild lameness. CLINICAL RELEVANCE: Our findings suggested that the described hybrid external skeletal fixator construct could be used as a minimally invasive strategy to successfully manage tibial tuberosity avulsion fractures in dogs and may be advantageous in very young medium- to large-breed dogs in which premature closure of the tibial tuberosity apophysis could result in distal translocation of the tibial tuberosity and deformity of the tibial plateau.

Biomechanical evaluation of a non-locking pre-manufactured loop suture technique compared to a three-loop pulley suture in a canine calcaneus tendon avulsion model.

OBJECTIVE: The purpose of this cadaveric study was to compare the strength of a non-locking pre-manufactured loop (SpeedWhip™ [SW]) suture pattern using Fiberwire® with the three-loop pulley (TLP) suture pattern using polypropylene for the surgical repair of canine calcaneal tendon avulsion injuries. METHODS: In vitro biomechanical study using 22 paired tendons collected from 11 canine cadavers. Paired tendons were repaired with either a SW suture pattern using Fiberloop® suture or a TLP suture pattern using polypropylene suture. Tensile loads required to create a 1 mm gap, 3 mm gap, and construct failure were measured. RESULTS: The mean loads to achieve a 1 mm gap in the TLP and SW constructs were not significantly different. Gap formation at 3 mm occurred at significantly lower loads for the SW (106.4 ± 21.5N) than for the TLP (127.2 ± 27.5N) (p = 0.05). The mean loads to construct failure for the TLP (172.8 ± 39.4N) and SW (131.3 ± 34.3N) were significantly different (p = 0.001). CLINICAL SIGNIFICANCE: The TLP with polypropylene suture is superior to the SW using Fiberloop® at resistance to 3 mm gap formation.