Mechanical comparison of materials used for extra-capsular stabilisation of the stifle joint in dogs

Crimped monofilament nylon leader for median sternotomy closure in 10 dogs

OBJECTIVE

To describe and report the outcomes after closure of median sternotomies with crimped monofilament nylon leader (MNL) in dogs.

STUDY DESIGN

Retrospective observational study.

ANIMALS

Dogs (n = 10) that underwent intrathoracic surgery through a median sternotomy approach.

METHODS

The median sternotomy was closed in a peristernal figure eight pattern with crimped MNL. Medical records were reviewed for clinical and histopathological findings and complications. Owners or veterinarians were contacted to collect long-term follow-up information.

RESULTS

The technique was simple, with no intraoperative complications. Postoperative infection was documented in one dog, requiring removal of a single MNL and associated crimp clamp. Delayed healing of the surgical incision in one dog was managed conservatively. No other complications were documented throughout long-term follow-up at a median of 488 days (range, 199-608).

CONCLUSION

Median sternotomies were successfully closed with crimped MNL and were associated with a low complication rate.

CLINICAL SIGNIFICANCE

Crimped MNL represents an alternative method to close median sternotomies in dogs.

Treatment of cranial cruciate ligament rupture in the feline stifle

Objective: To determine whether a lateral suture placed with bone anchors between quasi-isometric points in a cat is superior to a standard fabella-tibial suture for the stabilization of cranial cruciate ligament (CrCL) rupture compared to an intact stifle joint.

Study design: Biomechanical cadaveric study.

Methods: Six stifle joints with intact cruciate ligaments from three skeletally mature cats were placed in a loading mounting set and tested with axial loads of 20N and 60N at three different joint angles (75°,130° and 160°). The procedure was repeated with a transected CrCL; a stabilized stifle joint after a combination of three lateral suture techniques (fabella-tibial suture technique [SFT]; femoro-tibial suture technique 1 [FTS-1] and femoro-tibial suture technique 2 [FTS-2]). Radiographic examination of the relative position of the tibia to the fixed femur was compared.

Results: Stabilization of the stifle joint with lateral sutures had comparable stability to the intact specimens in the cranio-caudal direction (p = 0.2) but not in the proximo- distal direction for the SFT (p = 0.04) and FTS-2 technique (p = 0.03). There was no significant difference between the three stabilization techniques (p >0.05).

Clinical significance: Lateral sutures placed with bone anchors at quasi-isometric points performed better than SFT and FTS-2 in stabilizing the feline stifle after CrCL rupture in the proximo-distal plane. Biomechanical stability in the cranio-caudal plane after placement of a lateral suture across the feline stifle was similar to the intact CrCL.

Inter- and intra-operator variability associated with extracapsular suture tensioning

Objectives: To determine inter- and intra- operator variability associated with extracapsular suture tensioning as performed during lateral fabello-tibial suture placement.

Study design: Ex vivo study.

Methods: Fifteen Greyhound cadaveric pelvic limbs were prepared by cutting the cranial cruciate ligament and placing an extracapsular fabello-tibial suture. On two occasions, three surgeons tensioned the extracapsular suture of each stifle. Stifles were returned to 135 degrees of flexion and the suture tension was measured using a commercially available suture tensioner with inbuilt tensiometer.

Statistical analysis: Intra-operator and inter-operator agreement were assessed using the limits of agreement method. A linear mixed effects model was specified to assess the effect of operator, repeated estimates and stifle order on tension applied.

Results: The mean difference within the three operators ranged from 0 to 14.7N. With 95% limits of agreement, on most occasions for all three operators, the difference was between –31.7 and 41.0 N. The mean difference between the three operators ranged from 6.0 to 30.7 N. With 95% limits of agreement, on most occasions the difference between operators was between –25.6 and 62.5 N.

Clinical significance: Marked variation exists in the tension applied during fabello- tibial suture application, both within and between surgeons. This variation may lead to inconsistent clinical outcomes. Further studies are required to determine the clinical consequences of this marked variation in extracapsular suture tensioning.

A review of extra-articular prosthetic stabilization of the cranial cruciate ligament-deficient stifle

Extra-articular prosthetic stabilization techniques have been used as a method of stabilization of the cranial cruciate ligament (CrCL)-deficient stifle for decades. During extra-articular prosthetic stabilization, the prosthesis is anchored to the femur and tibia, and tensioned in the attempt to resolve femorotibial instability. The position of the anchor points of the prosthesis is crucial for restoring a normal range of joint motion and mitigating alterations in prosthesis tension during motion. Recently developed techniques offer several innovations with potential advantages such as bone-to-bone fixation, prosthetic materials with better mechanical properties, and improved isometry of the anchor points. Whether these innovations provide clinically superior results to the traditional techniques such as lateral circumfabellar-tibial suture techniques has yet to be determined.

Use of a novel extracapsular bone anchor system for stabilisation of cranial cruciate ligament insufficiency

OBJECTIVES

To evaluate early clinical experiences using the novel extracapsular bone anchor Ruby system for stabilisation of the cranial cruciate ligament deficient stifle in the dog and report short-term outcome and complications for 17 clinical cases.

MATERIALS AND METHODS

Seventeen dogs with cranial cruciate ligament insufficiency were treated using the Ruby system. Dogs were eligible if diagnosed via orthopaedic examination with unilateral or bilateral cranial cruciate ligament instability without any comorbidities. Subjective lameness assessments on a 0 to 4 scale were made pre-operatively and at six to eight weeks post-operatively; complications were also recorded. Lameness was also assessed on a visual analogue scale at six to eight months post-operatively.

RESULTS

All cases had substantial improvement in lameness following surgery. Mean post-operative lameness grade was 1·18 (±0·53) out of 4, compared to a grade of 3·06 (±0·9) before surgery, and owner assessment at six to eight months after surgery was also positive. There were major complications that required surgical intervention in one dog.

CLINICAL SIGNIFICANCE

The Ruby system is a feasible method of extracapsular stabilisation with comparable outcomes and complication rates to previously reported methods of addressing cranial cruciate ligament insufficiency. Further work is required to acquire more data on objective outcome measurement and mechanisms of failure.

Surgical management of dorsal scapular luxation in three dogs

Scapular luxation is an uncommon cause of forelimb lameness in dogs and cats. Traumatic rupture of the serratus ventralis muscle allows the scapula to displace dorsally during weight-bearing. Specific documentation regarding clinical presentation and surgical techniques is limited, with no medium- to long-term results of surgical intervention in dogs described. Presented here are three cases of scapular luxation in dogs, treated with a modified surgical technique. Clinical outcome was considered good to excellent, with resolution of lameness and abnormal scapular motion in all three dogs. Medium- and long-term outcomes were assessed in two of the dogs, with an excellent outcome in both cases.

Ability of the Tightrope® and percutaneous lateral fabellar suture techniques to control cranial tibial translation

OBJECTIVE

To compare the ability of the Tightrope® (TR) cranial cruciate ligament (CCL) technique, percutaneous lateral fabella suture (pLFS) technique, and normal CCL to control cranial tibial translation (CTT).

STUDY DESIGN

In vitro biomechanical study.

SAMPLE POPULATION

Cadaveric canine pelvic limbs (n = 18 pairs).

METHODS

Six small animal surgical residents (1 pair each) and a Diplomate of the American College of Veterinary Surgeons (10 pairs) performed TR and pLFS techniques on paired limbs. Two intact limb pairs served as controls. Limbs were assessed by palpation, radiographs, and dissection before mechanical testing of resistance to CTT. Forces resisted during displacement were compared between groups with a mixed ANOVA and post hoc tests.

RESULTS

With 5 mm of displacement, the pLFS resisted 72 ± 45 N and the TR resisted 66 ± 48 N of load. The intact CCL resisted 400 ± 35 N. The intact CCL resisted displacement significantly more than either surgical technique.

CONCLUSIONS

TR and pLFS had similar ability to resist CTT but neither restored the biomechanical properties of an intact CCL.

Comparison of the mechanical characteristics of polymerized caprolactam and monofilament nylon loops constructed in parallel strands or as braided ropes versus cranial cruciate ligaments of cattle

OBJECTIVE

To compare the mechanical characteristics of polymerized caprolactam and monofilament nylon loops with those of the cranial cruciate ligament (CCL) in cattle.

SAMPLE

6 femorotibial joints harvested from 3 cows and suture constructs made from No. 8 polymerized caprolactam, 80-lb test monofilament nylon fishing line, and 450-lb test monofilament nylon fishing line.

PROCEDURES

Joints were cleared of soft tissue structures except the CCL, connected to a load frame, and loaded to failure while measuring force and elongation. Synthetic constructs tested in a similar manner included single-stranded and 3-stranded No. 8 polymerized caprolactam, 3- and 6-stranded 80-lb test monofilament nylon fishing line, and 3- and 6-stranded 450-lb test monofilament nylon fishing line.

RESULTS

The CCL ruptured at a mean ± SD force of 4,541 ± 1,417 N with an elongation of 2.0 ± 0.3 cm. The tensile strength of 3-stranded 450-lb test monofilament nylon fishing line was similar to that of the CCL, rupturing at loads of 5,310 ± 369 N (braided strands) and 6,260 ± 239 N (parallel strands). Elongation was greater for braided constructs.

CONCLUSIONS AND CLINICAL RELEVANCE

The 3-stranded cords of 450-lb test monofilament nylon fishing line most closely approximated the strength of the CCL. Marked increases in elongation occur when large-sized materials are constructed in braided configurations, and this elongation would likely not provide stability in CCL-deficient stifle joints. Additional studies are needed to determine whether any of these materials are suitable CCL replacements in cattle.

Assessment of the craniocaudal stability of four extracapsular stabilization techniques during two cyclic loading protocols: a cadaver study

OBJECTIVE

To (1) compare the effect of cyclic loading on craniocaudal tibial translation in cranial cruciate ligament (CrCL)-deficient stifles after extracapsular stabilization, and (2) evaluate the effect of peak force during cyclic loading on the rate of development of craniocaudal laxity.

STUDY DESIGN

Biomechanical cadaveric study.

SAMPLE POPULATION

Cadaveric pelvic limbs (n = 24 pairs) from skeletally mature dogs.

METHODS

Twenty-four pairs of stifles were randomly assigned to 4 stabilization groups: nylon leader lateral circumfabellar-tibial suture (NLS); FiberTape lateral circumfabellar-tibial suture (FTLS); TightRope (TR); or bone anchor (BA). Contralateral limbs were cyclically loaded to produce cranial tibial translation at peak forces of either 80 or 160 N. Craniocaudal displacement of the tibia was measured with a mechanical testing machine during cyclic loading with the CrCL intact, after CrCL transection, and after extracapsular stabilization. The number of cycles each construct underwent before reaching 200% and 300% of the mean craniocaudal displacement present during cyclic loading of the CrCL-intact stifles was calculated. Number of cycles among treatment groups was compared with a Kruskal-Wallis test. P < .05 was considered significant.

RESULTS

Mean ± SD translation before and after CrCL transection were 3.9 ± 0.6 and 14.6 ± 1.7 mm, respectively. TR constructs resisted significantly more cycles than NLS constructs before reaching 7.8 mm (200%) and 11.7 mm (300%) of translation when loaded to 80 N. No other differences between constructs were significant at a peak load of 80 N. All constructs reached 7.8 and 11.7 mm of translation in fewer cycles when loaded to 160 N than at 80 N.

CONCLUSIONS

TR constructs were most resistant to elongation during cyclic loading. Doubling the peak force during cyclic loading significantly decreased the number of cycles constructs withstood, supporting recommendations for restricting postoperative activity after extracapsular stabilization of the CrCL-deficient stifle.

Anterior displacement of the TMJ disk: repositioning of the disk using a Mitek system. A 3D finite element study

In this paper the behaviors of the temporomandibular joint (TMJ) with an anteriorly displaced disk without reduction and with a surgically repositioned one were compared with the response of a healthy disk during jaw opening. The movement of each joint was obtained imposing the same opening path between incisors and assuming that the movement of the condyle is determined by the passive action of the masticatory muscles and the restrictions imposed by the articulating surfaces and the ligaments. A fiber-reinforced porohyperelastic model was used to simulate the behavior of the articular disk. The influence of the friction coefficient in the diseased joint was also analyzed, finding that the final displacement of the complex condyle-disk was smaller as the friction coefficient increased. On the other hand, its displacement in the repositioned joint was different than in the healthy case because the artificial sutures used in the surgery do not fully stabilize the disk posteriorly as the retrodiscal tissue does. The stress response of the disk changed in both pathologic cases: in the displaced joint the highest stresses moved from the intermediate zone (healthy case) to the posterior band, and in the reconstructed one the most loaded zone moved posteriorly at total opening. Besides, local stress concentrations appeared in the neighborhood of the artificial sutures and therefore damage of the disk and releasing of the sutures might be possible postoperatively.

In Vitro Evaluation of the 18 and 36 kg Securos Cranial Cruciate Ligament Repair Systemtm

OBJECTIVE

To evaluate the mechanical properties of the 18 and 36 kg Securos Cranial Cruciate Ligament Repair System.

STUDY DESIGN

In vitro mechanical evaluation.

SAMPLE POPULATION

Loop constructs of 18, 27, and 36 kilogram test (kgt) nylon leader line (NLL) secured with Securos crimp-clamps (SCC, n=40 per NLL test weight) or by a clamped square knot (CSK; n=40/NLL test weight).

METHODS

The 36 kg SCC were used for the 27 and 36 kgt NLL, and 18 kg SCC were used for the 18 kgt NLL. Loop constructs were mounted on a material testing machine, and distracted at 500 mm/min for static tests, and for cyclic tests at 500 mm/min to a distraction limit of 6 mm (18 kgt) or 7.5 mm (27 and 36 kgt) for 49 cycles, until failure. Constructs were tested at 20 degrees C except for 1 group of 27 kgt CSK loops tested at 40 degrees C. Load at failure, elongation, and stiffness was recorded and compared between groups under static or cyclic testing conditions.

RESULTS

All 27 and 36 kgt loops failed by disruption of NLL contained within the knot or crimp-clamp, whereas 18 kgt SCC loops failed by the NLL pulling through the crimp-clamp. The 18 kg SCC loops had considerable variability in ultimate load and elongation (coefficient of variation 29.6% and 18.3%, respectively). There was no significant difference in elongation between 27.3 kgt CSK loops tested at 20 degrees C and 40 degrees C. Generally, in both static and cyclic testing, SCC constructs formed with 27.3 or 36.4 kgt NLL performed as well or better than CSK constructs, resulting in loops that were strong, underwent minimal elongation, and had high stiffness.

CONCLUSION

The results support use of the 36 kg Securos system but not the 18 kg Securos system (with the clamp and crimping device used). The significantly lower load required for failure, slippage through the clamp, and substantial variability suggested that the crimp tube diameter or the crimping device tested may be inappropriate for use with 18 kgt NLL.

CLINICAL RELEVANCE

Surgeons should be aware that crimp-clamp design is important in controlling suture slippage or breakage within the clamp, and that novel systems should undergo mechanical testing with the size suture material they are intended to secure before clinical use.

An In Vitro Study to Determine the Effectiveness of a Patellar Ligament/Fascia Lata Graft and New Tibial Suture Anchor Points for Extracapsular Stabilization of the Cranial Cruciate Ligament-Deficient Stifle in the Dog

OBJECTIVE

(1) To determine whether an extracapsular patellar ligament/fascia lata graft would provide stability in the cranial cruciate ligament (CrCL)-deficient stifle comparable with that of the intact stifle. (2) To determine if different tibial anchor points would enhance stability of the CrCLdeficient stifle when compared with the standard fabellar-tibial suture (FTS) placement.

STUDY DESIGN

Experimental.

ANIMALS

Twenty-eight canine cadaver hind limbs.

METHODS

Stifles were mounted in a jig and tested between loads of -65 and 80 N. After testing the intact CrCL, 4 stabilization techniques were tested after CrCL transection: lateral graft technique (LGT) and 3 FTS with different tibial anchor points.

RESULTS

There were no significant differences in displacement between the LGT and standard FTS, between the LGT and the intact CrCL, or between the FTS and the intact CrCL, in either the Securos or the Screw-washer experiments. Stiffness of the intact CrCL was significantly greater than that of any stabilization technique and the cut CrCL. The standard FTS showed the least displacement of all suture stabilization techniques. Differences in stiffness were not significant between the suture stabilization techniques.

CONCLUSIONS

Securely anchored, the LGT results in a reduction in drawer motion similar to that of the intact CrCL and the standard FTS. Altering the tibial anchor point for the FTS does not improve stiffness or enhance stabilization of the CrCL-deficient stifle.

CLINICAL RELEVANCE

The LGT could be used for the treatment of CrCL ruptures in the dog. A clinical study is recommended.

Evaluation of 5 types of fishing material, 2 sterilization methods, and a crimp-clamp system for extra-articular stabilization of the canine stifle joint

OBJECTIVE

To evaluate the mechanical properties of 5 types of fishing material, 2 sterilization methods, and a commercially designed crimp-clamp system for the extra-articular repair of the canine stifle joint.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Animals were not used in this study.

METHODS

Two brands of monofilament nylon fishing line and 3 brands of monofilament nylon leader line were used to determine the effect of steam and ethylene oxide sterilization on strength and elongation of the material. A strand of 36-kg test monofilament nylon fishing material was wrapped around 2 rods or knotted to form a loop around 2 rods on a materials-testing machine. Ten trials of each brand of unsterilized, steam-sterilized, and ethylene oxide-sterilized fishing material were tested. A strand of each material was elongated to failure at a constant displacement of 1,000 mm/min to determine strength. A strand of each material was cycled 10 times to a load of 50 N to determine percent elongation. The brand of fishing material with the greatest strength and least elongation was crimped to form a loop around 2 rods on a materials-testing machine and tested as described above. ANOVA was used to determine the effect of sterilization method, brand of material, knot, wrap, and crimp on strength and elongation of the material, and a post-hoc t test was used when significant differences were found. A Student t test was used to compare fixation techniques (wrap, knot, and crimp).

RESULTS

Sterilization by steam or ethylene oxide had no significant effect on the strength of the nylon fishing material. Steam sterilization resulted in significant increases (2- to 4-fold) in elongation of most nylon fishing material when compared with unsterilized material. Ethylene oxide sterilization had minimal effect on elongation of the fishing material. Mason leader line showed no significant change in strength or elongation regardless of sterilization method. Significantly less strength and significantly less elongation were demonstrated in Mason leader line that was crimped as compared with Mason leader line that was knotted.

CONCLUSION

Ethlylene oxide was the preferred method of sterilization to preserve strength and minimize elongation of the fishing material. Of the materials tested, Mason leader line had the least elongation and the greatest preservation of strength when ethylene oxide was used as the sterilization method. Mason leader line and Sufix fishing line were comparable choices when steam was used as the sterilization method. Significantly less elongation was demonstrated in crimped Mason leader line as compared with knotted Mason leader line.

CLINICAL RELEVANCE

Of the materials tested, Mason leader line and Sufix fishing line had the best mechanical properties for extracapsular stabilization of the canine stifle joint. Crimping is an attractive alternative to knotting and results in a reduction in elongation of the nylon fishing material.

Biomechanical properties of braided polyester tapes intended for use as intra-articular cranial cruciate ligament prostheses in dogs

OBJECTIVE

To determine the in vitro structural and material properties of braided, multifilament, nonabsorbable polyester tapes, used for intra-articular stabilization of cranial cruciate ligament- (CCL-) deficient stifle joints in dogs, and compare those with properties of multifilament polyamide tapes.

SAMPLE POPULATION

30 polyester tapes (width, 4 mm), 10 polyester tapes (width, 7 mm), and 30 polyamide tapes (width, 4 mm) were tested to failure. Cyclic loading experiments were also performed, using 3 polyester tapes of each width.

PROCEDURE

Tapes were mounted in a tensile tester as single loops, simulating intra-operative conditions, and elongated to failure at 1,000 mm/min. Additionally, the behavior of polyester tapes was tested at different elongation rates. In a second series of experiments, biomechanical variables of the polyester tapes were measured after 25 sets of 2,000 cycles between physiologic force limits.

RESULTS

Mean (+/- SD) ultimate loads of the 4-mm wide polyamide tapes, 4-mm wide polyester tapes, and 7-mm wide polyester tapes were 266.48 +/- 13.19 301.78 +/- 16.92, and 726.40 +/- 37.74 N, respectively. Corresponding stiffnesses were 15.57 +/- 0.49, 21.63 +/- 2.19, and 34.85 +/- 2.66 N/mm, respectively. Failure properties of polyester tapes were affected by previous cyclic loading.

CONCLUSIONS AND CLINICAL RELEVANCE

Polyester tapes of 4- or 7-mm widths should be able to resist forces resulting from weight bearing in dogs, suggesting that these tapes will be effective for stabilization of the stifle joint in dogs with a ruptured CCL.

Lateral glenohumeral ligament rupture in three dogs

Three adult large breed dogs were evaluated for chronic forelimb lameness. Clinical examination localised pain to the area of the shoulder joint. Traditional imaging methods, including radiography, arthrography and ultrasonography, were unrewarding. Arthroscopy performed via a lateral portal demonstrated complete tears of the proximal part of the lateral glenohumeral ligament in all cases. Two of the three cases responded to treatment with intra-articular methylprednisolone and rest with a resolution of the lameness, while the third failed to improve. Surgical intervention in this third case involved lateral capsulorraphy, and re-examination at five weeks postoperatively showed the dog to be without lameness. Tearing of the lateral glenohumeral ligament should be considered in the differential diagnosis of shoulder lameness. Surgical stabilisation should be considered in cases refractory to conservative treatment.

Repair of cranial cruciate ligament rupture in an alpaca

A mature male alpaca with acute lameness of the left handlimb was diagnosed as having a rupture of the cranial cruciate ligament. Repair was achieved using a combination of surgical techniques. A patellar ligament autograft was passed under the cranial meniscal ligament, through the joint and over the femoral condyle, and anchored using a screw and washer. Two nylon sutures were passed through a hole made in the tibial crest, and secured under the screw. The alpaca was confined in a stall for 3 months. Exercise was then increased progressively for 3 months. One year after surgery the alpaca is sound and has resumed breeding activity.

The effect of knotting method on the structural properties of large diameter nonabsorbable monofilament sutures

OBJECTIVE

To evaluate the effect of knotting method on the mechanical properties of large diameter nonabsorbable monofilament suture materials.

STUDY DESIGN

In vitro mechanical evaluation.

METHODS

A conventional square knot was compared with the surgeon's knot, sliding half-hitch, and clamped square knot. Knotted suture loops were created in a uniform manner and acutely tensioned to failure (20 mm/min loading rate; n = 20 per knot type for each material). Stiffness, yield, and failure characteristics of USP #2 nylon, #2 polybutester, #2 polypropylene, 27 kg test monofilament nylon fishing line, and 27 kg nylon leader material were evaluated.

RESULTS

Compared with a conventional square knot, a surgeon's knot decreased stiffness for #2 polypropylene, 27 kg fishing line, and 27 kg leader (P < .05). A sliding half-hitch weakened all materials except 27 kg leader (P < .05). Clamping the first throw of a square knot increased the stiffness of 27 kg leader loops (P < .05).

CONCLUSIONS

Based on clinically relevant parameters (stiffness and yield), knotting method had no effect on #2 nylon and #2 polybutester. The surgeon's knot is not recommended for #2 polypropylene and 27 kg fishing line and leader material. A sliding half-hitch decreased the yield of leader material. Clamping the first throw of a square knot had no adverse effects on acute properties of tested materials; it increased the stiffness for leader material.

CLINICAL RELEVANCE

Knotting method does influence the structural properties of suture materials and should be considered when tying knots under tension.