Validation of a biomechanical testing protocol of craniodorsal hip luxation in feline cadavers and comparison of two ultra-high molecular weight polyethylene materials used for extra-articular hip stabilisation

OBJECTIVES

The aim of our study was to describe a biomechanical testing protocol to reproduce ex vivo craniodorsal hip luxation specific to the feline model, and evaluate the biomechanical properties of an intact hip joint compared with the fixation strength of two different techniques of extra-articular hip stabilisation.

METHODS

Eighteen hip joints (femur and hemipelvis) were harvested from nine mature feline cadavers. CT was performed for each hip joint so that a biomechanical base specific to each joint morphotype could be created using computer-aided design. The biomechanical bases were then produced using a three-dimensional printer to secure the hip joints during testing. A total of 34 biomechanical compression tests were performed. Eighteen compression tests were performed in the control group, of which two fractured. The remaining 16 hip joints were then randomly assigned either to group A (hip joints stabilised with an extra-articular ultra-high molecular weight polyethylene (UHMWPE) implant secured by an interference screw [n = 8]) or to group B (hip joints stabilised with a UHMWPE iliofemoral suture [n = 8]).

RESULTS

Mean ± SD yield, failure load and linear stiffness in the control group were 616 ± 168 N, 666 ± 158 N and 231 ± 50 N/mm, respectively. The relative fixation strength (% of intact joint) before hip luxation in groups A and B was 43.8% and 34.7%, respectively. No statistical difference was found between groups A and B for yield and failure load. However, the reoccurrence of craniodorsal hip luxation was higher in group B than in group A, in 5/8 and 0/8 tests, respectively. Moreover, in group A, the extra-articular UHMWPE implant induced caudodorsal hip luxation, reported as failure mode in 7/8 cases.

CONCLUSIONS AND RELEVANCE

This modified biomechanical protocol for testing craniodorsal hip luxation in a feline model was validated as repeatable and with acceptable variance. The extra-articular UHMWPE implant stabilisation technique proved to be more efficient in avoiding reoccurrence of craniodorsal hip luxation than UHMWPE iliofemoral suture.

Risk factors for reluxation after toggle rod stabilization for treatment of coxofemoral luxation in 128 dogs

OBJECTIVE

Evaluate the risk factors for reluxation and outcomes for dogs with a toggle rod construct.

STUDY DESIGN

Retrospective case series.

ANIMALS

One hundred twenty-eight client-owned dogs.

METHODS

Medical records from 2007 to 2018 were reviewed for signalment, history, surgery, and outcome for dogs with a coxofemoral luxation repaired with a commercial toggle rod and nylon monofilament suture construct. Univariate and multiple logistics regression analysis were performed to assess risk factors associated with postoperative luxation. Primary veterinarians and owners were contacted for follow-up via telephone or electronic communication.

RESULTS

The overall complication rate was 24.2%, and the reluxation rate was 14.8%. There was a decreased risk of reluxation when the cause was traumatic in origin (odds ratio [OR] 0.10) or when the lameness was severe at presentation (OR 0.42). Fifteen of 58 (25.9%) owners contacted completed a follow-up survey.

CONCLUSION

Dogs with nontraumatic, low impact luxations were at a higher risk for reluxation.

CLINICAL SIGNIFICANCE

Dogs of any body condition with a traumatic coxofemoral luxation are at lowest risk for reluxation.

Coxofemoral Joint Luxation in Dogs Treated with Toggle Rod Stabilization: A Multi-Institutional Retrospective Review with Client Survey

Coxofemoral luxation is the most common type of joint luxation observed clinically in dogs. This retrospective study determines the complications and outcomes of open reduction and internal fixation of coxofemoral luxations using a toggle rod stabilization in 58 dogs. The purpose of the study was to compare the results with previous studies to ascertain commonalities and differences. A majority of the canine luxations were stabilized using a 4.0 or 3.2 mm commercial toggle rod and either one or two strands of OrthoFiber, FiberWire, or monofilament nylon suture. Postoperative complications developed in 25 of the 58 (43%) dogs, with major complications in 9 cases (15.5%). The most common major complication was reluxation, which occurred in 6 dogs (10%). Five of the 6 cases of reluxation received monofilament suture, although there was not a statistically significant relationship between suture type and reluxation. Owner responses to a questionnaire reported good to excellent results for satisfaction with the procedure in 90% of cases. Results of the present study suggest that toggle rod stabilization remains an effective method for the treatment of coxofemoral joint luxation in dogs.

Minimally invasive technique for coxofemoral luxation stabilisation using transarticular toggle system: a cadaveric study

OBJECTIVE

To present a novel, semi-closed, surgical technique for coxofemoral luxation stabilisation using a transarticular toggle rod.

STUDY DESIGN

Cadaveric study.

MATERIALS AND METHODS

Craniodorsal luxation was generated by transecting the ligamentum teres in 12 coxofemoral joints and was then reduced using a closed technique. Anteversion and inclination angles were measured using fluoroscopic projections. An arthroscope was inserted through a bone tunnel drilled from the third trochanter through the femoral neck. Following retraction of the arthroscope, a hole was drilled through the acetabular fossa via the femoral bone tunnel. A standard Arthrex® TightRope toggle button was pushed through the femoral bone tunnel into the acetabular fossa hole and tied over the oval metallic button above the third trochanter site. The exit point of the drill hole over the femoral head and that in the acetabular fossa were evaluated by surgical exposure of the coxofemoral articular surfaces.

RESULTS

The TightRope entrance point into the acetabular fossa was accurate in all joints, with a mean distance from the acetabular fossa centre of 0·06 ±0·1 mm. The measured distance of the TightRope exit point from the femoral head to the fovea capitis was 2·04 ±1·7 mm. Femoral head cartilage damage was detected in nine of 12 joints.

CONCLUSION AND CLINICAL RELEVANCE

Closed reduction and stabilisation of coxofemoral luxations can be achieved using this minimally invasive technique. Refinements to the technique may be needed for its application in clinical cases due to relative high incidence of femoral head cartilage damage.