Comparison of a suture anchor and a toggle rod for use in toggle pin fixation of coxofemoral luxations

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.

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.

Correction of craniodorsal coxofemoral luxation in cats and small breed dogs using a modified Knowles technique with the braided polyblend TightRope™ systems

Objectives: To report the surgical technique and short-term radiographic and functional outcome data for a series of client owned, small breed dogs and cats treated for traumatic craniodorsal coxofemoral luxation using open reduction and internal fixation with the Arthrex Mini TightRope (mTR) and TightRope (TR) systems.

Methods: Data were collected retrospectively from the clinical case records, including the initial clinical and radiographic findings, surgical technique, and postoperative short-term clinical and radiographic data. Functional data collected after the six weeks reassessment were obtained via owner questionnaire.

Results: Four cats (mTR = 4) and five small breed dogs (mean weight 15 kg; TR = 4, mTR = 1) were included. Median time to postoperative weight bearing was one day. Median lameness score at six weeks postoperatively was 0 out of 5. Coxofemoral joint congruity was radiographically confirmed at the six weeks postoperative visit. Telephone follow-up (at a median of 16 weeks) revealed all animals had returned to their previous level of activity. Complications were minor, and limited to postoperative swelling (n = 1).

Clinical significance: Clinical use of the Arthrex Mini TightRope™ and TightRope™ systems can be recommended for traumatic craniodorsal coxofemoral luxation in this novel application as short-term results are at least comparable to existing surgical techniques. Long-term follow-up studies are needed.

Analysis of suture anchor eyelet position on suture failure load

OBJECTIVE

To compare mechanical performance of 2 orientations of the 5 mm Corkscrew® suture anchor with #5 Fiberwire® .

STUDY DESIGN

In vitro biomechanical study.

SAMPLE POPULATION

Suture anchor-suture constructs (n=40).

METHODS

Acute and cyclic tensile loads were applied to suture threaded through eyelets of 40 anchors perpendicular to the long axis of the anchor. Eyelets were positioned so that the suture pull was in line with (anchor rotation angle of 0° [ARA 0]) or 90° (ARA 90) to the eyelet plane. Load at failure, stiffness, and cycles to failure were determined.

RESULTS

All constructs failed by suture breakage at the eyelet. Mean load at failure was significantly higher in the ARA 90 group (634 ± 93 N) compared with the ARA 0 group (495 ± 52 N; P=.0015). No significant difference was found between groups for mean number of cycles to failure (270 ± 177 versus 178 ± 109; P=.2166) and stiffness (50 ± 4 versus 48 ± 5 N/mm; P=.3141).

CONCLUSIONS

The Corkscrew® 5 mm suture anchor with Fiberwire® suture fails via suture breakage at the eyelet under higher acute loads if the suture is loaded at an angle of 90° compared with 0° with respect to the plane of the eyelet.