Mechanical comparison of loop and crimp configurations for extracapsular stabilization of the cranial cruciate ligament-deficient stifle.

OBJECTIVE: To biomechanically compare different loop and crimp configurations used for extracapsular suture stabilization of the CCL-deficient stifle. STUDY DESIGN: In vitro study. SAMPLE POPULATION: Crimped loop constructs of 100 lb Ande type nylon leader line in 7 different configurations comprising single and double loops, single and double crimps, and the interlocking loop configuration. METHODS: Constructs premade on external skeletal fixator bars 60 mm apart and tested in tension with a custom-made split circular arm mounted on a table-top materials testing machine. Data were derived from force/displacement plots. In "load to failure" test (10/group) constructs were loaded to failure with distraction rates of 10 mm/min; ultimate load, tension at 2 mm elongation and failure were recorded. In "staircase" test (5/group) constructs cycled at 100 N/s from 75 N with incremental increases of 50 N/cycle; ultimate load, maximum tension before elongation at rest over 2 mm and failure were recorded. In "cycling and jumping" test (10/group) 3 of 7 constructs cycled at 100 N/s 100 times from 50 to 100 N, then 5 times from 50 to 600 N; failure and elongation at cycles 1, 50 and 100 and at jumps 1 to 5 recorded. RESULTS: Double-loop double-crimp configurations were statistically superior to all other configurations in ultimate load, and to single-loop and interlocking loop configurations in elongation in "load to failure" and "staircase" tests. In "cycling and jumping" test the interlocking loop configuration specimens elongated significantly more than the others and only in the double-loop double-crimp group did all constructs complete the test. CONCLUSIONS: Double-loop double-crimp configurations are mechanically superior to other previously described configurations.

Mechanical properties of isolated loops of nylon leader material, polyethylene cord, and polyethylene tape and mechanical properties of those materials secured to cadaveric canine femurs via lateral femoral fabellae, toggles placed through bone tunnels, or bone anchors.

OBJECTIVE: To determine mechanical properties of various prosthetic materials secured to cadaveric canine femurs via various methods and to compare results with those for isolated loops of prosthetic material. SAMPLE: 80 femurs obtained from cadavers of skeletally mature large-breed dogs. PROCEDURES: 10 femoral constructs in each of 8 groups (single circumfabellar loop of polyethylene cord, double loop of polyethylene tape secured via a bone anchor [BAPT], single or double circumfabellar loops of nylon leader material [CNL] or polyethylene tape [CPT], or single or double loops of polyethylene tape secured via a toggle placed through a bone tunnel [BTPT]) and 10 isolated loops of prosthetic material in each corresponding configuration were tested. Stress relaxation, creep, elongation, load at 3 mm of displacement, stiffness, and peak load at failure were determined. RESULTS: 5 single CNL constructs failed before completion of testing. Double CNL and single circumfabellar polyethylene cord constructs had the lowest loads at 3 mm of displacement. Single and double CPT constructs had the highest stiffness. Double BTPT and CPT constructs had the highest peak loads at failure. Double BTPT, double CPT, and BAPT constructs were mechanically superior on the basis of lower creep and stress relaxation and higher stiffness and load at 3 mm of displacement versus other constructs. Stiffness of femoral constructs was 28% to 69% that of corresponding isolated prosthetic loops. CONCLUSIONS AND CLINICAL RELEVANCE: Double BTPT, double CPT, and BAPT constructs were mechanically superior to other constucts. Mechanical properties and methods of anchorage and securing of free ends of prostheses contributed to mechanical properties of constructs.

In vitro mechanical evaluation and comparison of two crimping devices for securing monofilament nylon and multifilament polyethylene for use in extracapsular stabilization of the canine stifle.

OBJECTIVE: To compare the tensile strength and stiffness of non-absorbable suture loops created with two types of crimping devices. METHODS: Loops of monofilament nylon leader line (MN) of 18 kg, 36 kg, and 45 kg multifilament polyethylene (MP) with a crimp and MP with a crimp and knot were mechanically tested to failure in quasistatic tensile loading after being created with either a wave pattern crimp device or three applications of a single crimp device. Each testing group consisted of five samples. Tensile loading to failure at a rate of 9.5 mm/s was used. Failure was defined as a sudden drop in the recorded force. RESULTS: All suture materials failed by breaking near the crimp tube with both crimp devices, with exception of the MP without knot, which slipped through the crimp tube using both devices. Sutures secured with the wave pattern crimping device were significantly stronger with a higher load yield, maximum load, displacement yield, failure displacement, and maximum displacement than the single crimp device. Loops of MP suture crimped by either device plus the addition of a surgeon's knot resulted in a significantly stronger construct than unknotted crimped MP constructs. Crimped MP combined with knot were significantly stiffer, but not stronger, than crimped 45 kg MN. CLINICAL SIGNIFICANCE: Performing extra- capsular repair for ruptured cranial cruciate ligaments with the wave pattern crimp system may result in lower failure rates due to the construct being significantly stronger than the single crimp system.