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

Objective The mechanical properties of three materials (No. 2 polypropylene, No. 5 polybutilate-coated multifilament polyester and 18, 27 and 36 kg test monofilament nylon leader material) commonly used for extra-capsular stabilisation of the stifle in dogs with cranial cruciate ligament insufficiency were determined. The ability of No. 5 polybutilate-coated multifilament polyester and 36 kg test monofilament nylon leader material, when placed as extra-capsular sutures, to mitigate cranial drawer was evaluated in hindlimbs of cadavers. Design An in vitro mechanical study. Animals Seven pairs of hindlimbs harvested from adult greyhound dogs recently euthanased for other reasons. Procedure Samples of each material, including samples of 27 kg test leader material that had been sterilised by one of three methods (ethylene oxide, one or five cycles in an autoclave), were loaded to determine tensile and stress relaxation properties. The effect of cyclic loading on a No. 5 polybutilate-coated multifilament polyester and 36 kg test leader material was also determined. Using the harvested hindlimbs, cranial drawer was measured before and after transection of the cranial cruciate ligament and on the first and twelfth cycle following extra-capsular stabilisation with either No. 5 polybu-tilate-coated multifilament suture or 36 kg test leader material. Results Leader material was found to have the most suitable mechanical characteristics for use as extracapsular stabilisation of the cranial cruciate ligament deficient stifle. Of the sterilisation methods, ethylene oxide was found to have the least detrimental effects on the handling and material characteristics of the leader material. Stifles stabilised with 36 kg test leader material had significantly less drawer than those stabilised with No. 5 polybutilate-coated multifilament polyester suture. Clinical implications Monofilament nylon leader material would appear to have suitable mechanical properties for extra-capsular stabilisation of the cranial cruciate ligament deficient stifle. If possible the material should be sterilised using ethylene oxide.     

Response of Canine Synovial Membrane to Three Different Types of Suture Material

The synovial tissue response to three different suture materials was assessed in nine dogs. Stifle joint arthrotomies were sutured with either chromic gut, teflon coated polyester suture, or polypropylene suture; all joint capsule layers were penetrated, exposing the suture material to the joint cavity. The synoviocytic and subsynviocytic layers at the arthrotomy site were examined histologically one, two, and three weeks following surgery. Chromic gut caused the greatest cellular inflammatory response and polypropylene the least. Teflon coated polyester and chromic gut were associated with nearly the same degree of tissue fibrosis. Polypropylene was associated with much less fibrosis than the other suture materials.     

Correlative biomechanical and histologic study of the cranial cruciate ligament in dogs

The mechanical properties of the cranial cruciate ligament were determined, using unilateral bone-ligament-bone preparations from 65 dogs of various ages and body sizes. Tensile loading of the cranial cruciate ligament from 1 of each pair of stifle joints demonstrated a decrease in material properties (modulus, maximum stress, strain energy) with aging. The decreases in maximum stress and strain energy with age were significantly less (P less than 0.05 and P less than 0.05, respectively) in the cranial cruciate ligament from dogs weighing less than 15 kg, compared with those weighing 15 kg or more. The cranial cruciate ligament and remaining femorotibial ligaments were collected from the opposite stifle joints and examined microscopically. By 5 years of age, the cranial cruciate ligaments of dogs weighing greater than 15 kg consistently had microscopic evidence of degenerative disease (loss of ligamentocytes, metaplasia of surviving ligamentocytes to chondrocytes, and failure to maintain collagen fibers and primary collagen bundles) which progressed in severity with age. The caudal cruciate ligaments were similarly affected, although the degenerative changes were rarely as severe as in the cranial cruciate ligament. The collateral ligaments underwent minimal degeneration. Sex differences had no bearing on degeneration. The cranial cruciate ligaments in dogs weighing less than 15 kg generally had less severe alterations than those in heavier dogs, and the onset of the degenerative process was delayed by several years. Cranial cruciate ligaments removed from dogs after ligament failure not only had degenerative disease, but also had undergone unsuccessful attempts at repair. In contrast, fibrous repair was rarely present in intact ligaments of asymptomatic dogs with degenerative disease of the cranial cruciate ligament.     

Biomechanical analysis of suture anchors and suture materials used for toggle pin stabilization of hip joint luxation in dogs

OBJECTIVE: To compare in vitro mechanical properties of toggle pins and toggle rods used as suture anchors and of 3 suture materials (50-lb monofilament polybutester, No. 5 braided polyester, and 5-mm woven polyester) commonly used as prosthetic ligaments in the repair of hip joint luxation in dogs. SAMPLE POPULATION: Femoropelvic specimens from the cadavers of 18 dogs. PROCEDURE: Suture anchors were compared by use of pullout tests. Suture materials were compared by use of monotonic and cyclic tensile tests; cyclic tensile tests were performed with the suture placed over the edge of an aluminum bar to simulate the edge of the femoral bone tunnel. In vitro mechanical properties of the ligament of the femoral head were determined by use of monotonic tensile tests, using bone-ligament-bone cadaveric specimens. The in vitro mechanical properties of the acetabulum-ligament-femur complex and of this complex following rupture of the ligament and stabilization with a toggle rod and 5-mm woven polyester were determined by use of compression tests that simulated weight-bearing. RESULTS: Mechanical properties of the toggle rod were not significantly different from those of the toggle pin. Woven polyester had the longest fatigue life in cyclic testing. Hip joints stabilized with a toggle rod and woven polyester had less than half the strength in vitro of intact joints. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a toggle rod or toggle pin can be used for stabilization of hip joint luxations in dogs. Of the materials tested, braided polyester had the best in vitro mechanical properties.     

Partial Maxillectomy in the Dog Comparison of Suture Materials and Closure Techniques

This study compares the healing of oronasal defects created by partial maxillectomy when closed using two different suture materials and two different suture patterns. In experiment 1, 24 dogs were divided into four equal groups. Partial maxillectomy was performed on each dog and was closed using either a two-layer simple interrupted suture pattern (12 dogs) or a modified Mayo mattress pattern (12 dogs) with either polyglactin 910 (12 dogs) or polypropylene (12 dogs) sutures. On the seventh postoperative day, the dogs were euthanized, suture line bursting pressures were measured, and wound healing was evaluated grossly and histopathologically. Suture line dehiscence occurred in one dog from each of the four groups. These were the only dogs in which electrocoagulation had been used. The healing of suture lines closed with the two-layer simple interrupted pattern was superior to that of those closed with the modified Mayo mattress pattern based on the degree of gross oral ulceration, suppurative inflammation, fibrosis and oral epithelial covering at the suture line, and the number of necrotic sites in the adjacent tissue. The healing of suture lines closed with polypropylene was superior to that of those closed with polyglactin 910 based on suture line bursting pressures and the degree of suppurative inflammation and tissue necrosis at the suture sites. In Experiment 2, partial maxillectomies were performed on four dogs, and closure was achieved using a two-layer simple interrupted suture pattern with either polyglactin 910 (two dogs) or polypropylene (two dogs). On the 30th postoperative day, the dogs were euthanized, and wound healing was evaluated grossly and histopathologically. All suture lines were well healed. All polyglactin 910 oral sutures were absent, while all polypropylene oral sutures were still present.     

Prosthetic Replacement of the Cranial Cruciate Ligament Under Arthroscopic Guidance: A Pilot Project

A prosthetic replacement for the cranial cruciate ligament was successfully implanted under arthroscopic guidance in four canine cadavers and seven normal dogs. Several strands of size 2 braided polyester were implanted in the cadavers and one normal dog, and a copolymer coated tow of 10,000 carbon fibers was implanted in six normal dogs. The average time required to surgically implant the carbon fiber prosthetic ligaments was 60 minutes. All of the dogs had slight to no drawer sign postoperatively. Five of the dogs were bearing more weight 3 weeks postoperatively than after transection of the cranial cruciate ligament. The surgical technique for implantation was successful for elimination of the cranial drawer sign, but carbon fibers were broken prematurely and instability reoccurred.     

Anatomy of the collateral ligaments of the feline elbow joint: functional implications

Cats show a higher capability to supinate their forearms than dogs. This suggests a special arrangement of the collateral ligaments of the feline elbow joint. Therefore, the course of the ligaments was examined in 13 adult cats. The size of the ligaments was measured, and effects of passive joint movements were studied. Ligaments of five additional cats were examined histologically. The lateral collateral ligament (LCL) had a superficial and deep part, both originating from the humerus. The free humeral portion of the LCL was short and contained fibrous cartilage. Fibre bundles of the deep part inserted into the annular ligament, while the remaining deep fibres and the superficial part inserted with a long antebrachial portion on the radius. The medial collateral ligament (MCL) originated from the humeral epicondyle and divided into cranial and caudal parts. The caudal part inserted medioproximally on the ulna, while the cranial part attached primarily with a long thin part to the caudal aspect of the radius. During supination, the MCL loosened thus allowing medial widening of the joint space, up to 2 mm. A specific feature of the feline elbow is the long thin part of the MCL. Its course through a special furrow distal to the medial coronoid causes the tightening of the feline MCL during pronation. Apart from that, the feline collateral ligaments combine the features of both human and canine cubital anatomy. This explains the range of supination in cats, which is intermediate between humans and dogs.     

Biomechanical Evaluation of a Toggle Pin Technique for Management of Coxofemoral Luxation

Toggle pin stabilization is an accepted technique for the management of coxofemoral (CF) luxation in dogs. The purpose of this study was to determine, in vitro, the respective contributions of several aspects of toggle pin repair to the overall stability of fixation. Factors evaluated were the manner and frequency with which toggle pins oriented on insertion, effect of orientation on toggle pin strength, effect of suture type on ligament prosthesis strength and load sustained by the fixation, and comparison of repair using a modified toggle design to that of capsulorrhaphy. When placed in cadavers using standard technique, conventional toggle pins were found to orient significantly more frequently in one of two possible positions. Mechanical testing of fixations performed in experimentally luxated cadaver hips demonstrated a high (12/20) incidence of toggle pin failure using the conventional implant in the most common orientation. When tested alone, toggle pins were weakest mechanically in this orientation. Rotating the implant 180° increased mean load to failure by 249%. There was no significant difference in load sustained by conventional toggle fixations using No. 2 braided polyester versus 50 lb test monofilament nylon as the suture ligament prosthesis. However, the higher stiffness of the polyester suture may be more favorable for use in this application. Fixation using a toggle rod designed to allow evaluation of construct stability when failure of the toggle is eliminated resulted in an increase in maximum load sustained before luxation (47% of the intact control hips). This load was not significantly different than the resistance to luxation afforded by capsulorrhaphy. This study suggests that when implanting conventional toggle pins, consideration should be given to ensuring placement in the strongest orientation.     

Tibial plateau leveling osteotomy in a llama with a ruptured cranial cruciate ligament

A 3-year-old 155-kg (342-lb) castrated male llama was examined because of left hind limb lameness of acute onset. A diagnosis of cranial cruciate ligament and medial collateral ligament rupture was made, and tibial plateau leveling osteotomy was recommended. The tibial plateau leveling osteotomy procedure was performed as described for dogs, except that 2 orthopedic plates were used to stabilize the osteotomy because of the size of the llama. The medial collateral ligament was sutured and reinforced with 2 strands of size-2 polypropylene placed in a figure-8 fashion between cancellous bone screws in the femur and tibia. Four days after surgery, failure of the medial collateral ligament repair was evident. Approximately 3.5 years after surgery, the llama was reexamined. The owners reported that the llama had full use of its left hind limb, and only mild lameness (grade 1 of 5) was evident. Results suggest that tibial plateau leveling osteotomy may be applicable in camelids with rupture of the cranial cruciate ligament. However, additional study is needed before tibial plateau leveling osteotomy can be routinely recommended. In particular, additional information is needed on the tibial plateau slope in healthy camelids, the role of the fibula in tibial plateau leveling osteotomy procedures, and the prevalence of cranial cruciate ligament rupture in camelids.     

Replacement of the Collateral Ligaments of the Canine Tarsocrural Joint: A Proposed Technique

A technique for replacement of the medial and lateral collateral ligaments of the tarsocrural joint in dogs was developed based on studies of normal anatomy and function. The medial or lateral tarsocrural joint was made unstable by removal of the respective malleolus, ligaments, and joint capsule; the component parts of the collateral ligaments were replaced using suture material to function as ligament prostheses. The technique was found to be effective in maintaining near normal joint motion and adequate joint stability in cadavers immediately following surgery, and in dogs observed for up to 39 months postoperatively. No degenerative joint disease was noted upon gross or radiographic examination.     

Biomechanical Comparison of Six Suture Configurations Using a Large Diameter Polyester Prosthesis in the Muscular Process of the Equine Arytenoid Cartilage

Objective— To compare biomechanical properties of 6 suture configurations using a large diameter polyester prosthesis in the muscular process (MP) of the arytenoid cartilage and to determine failure mode.
Study Design— Experimental study.
Sample Population— Cadaveric equine larynges (n=121).
Methods— Suture configurations (4 single, 2 double) were inserted, and then constructs were tested in a single-cycle to failure at a 100 mm/min distraction. Load deformation curves were generated to assess the biomechanical properties of each construct. A 1-way ANOVA was used to compare the mean differences in construct failure force, cricoarytenoid joint (CAJ) disarticulation force, and energy stored at failure. A 2-sample t-test was used to compare single versus double suture patterns and a Fisher's exact test was used to compare failure mode.
Results— Both construct and CAJ failure force were significantly greater ( P <.05) for double suture patterns compared with single suture patterns; however, there were no significant differences in energy stored at construct failure. Failure at the MP accounted for ≥50% of construct failures for 3 of the single suture patterns and 1 of the double suture patterns tested. The remaining 2 patterns had an increased frequency of clamp failures as well as failure of the cricoid cartilage.
Conclusions— Sutures that sufficiently engage the spine of the MP alone or in conjunction with a second suture were found to be biomechanically superior.
Clinical Relevance— Engaging the spine of the MP appears to result in the most biomechanically sound laryngeal construct.     

Closure of median sternotomy in dogs: suture versus wire

Twenty normal, large-breed dogs underwent median sternotomy. Median sternotomies were closed with 20-gauge orthopedic wire in 10 dogs and no. 2 polybutester in 10 dogs. Closure with suture was faster than with wire (6.7 +/- 1.8 minutes versus 9.1 +/- 1.9 minutes, respectively). Significant differences were not observed in degree of postoperative pain or wound complication rates. Sternotomies closed with wire showed a trend to be more stable and had significantly less displacement on radiographic evaluation at 28 days. All sterna closed with wire examined histopathologically showed evidence of chondral or osteochondral bridging, while sterna closed with suture only showed fibrous union.     

In Vitro Comparison of the Three Loop Pulley and Locking Loop Suture Patterns for Repair of Canine Weightbearing Tendons and Collateral Ligaments

Both triceps tendons and the medial collateral ligaments of both stifles of 10 freshly euthanized dogs were sharply transected. One tendon and one ligament of each dog were sutured with a three loop pulley pattern, and the opposite tendons and ligaments were sutured with a locking loop pattern. The tendons and ligaments were harvested with their muscular and bony attachments. The anastomoses were slowly tested in tension until failure occurred. The amount of tensile load required to produce failure of the anastomosis, the amount of distraction of the sutured ends prior to failure, and the modes of failure were recorded. In both tendons and ligaments, the three loop pulley pattern provided significantly greater tensile strength (p < 0.01) and allowed significantly less distraction between the sutured ends (p < 0.01) than the locking loop pattern. In tendons, disruption of the suture material was the most common mode of failure with both patterns. In ligaments, both patterns failed most commonly by pulling free from the tissue.     

Surgical reconstruction of a ruptured medial collateral ligament in a foal

An avulsed carpal medial collateral ligament was diagnosed by clinical and radiographic examination in a 1-day-old foal that was unable to bear weight on the affected limb. The foal had a valgus deviation originating at the carpus and medial to lateral instability of the affected carpus. The ligament was reconstructed with screws and suture tape. Surgical reconstruction is a viable alternative to long-term casting or splinting for treatment of a ruptured carpal medial collateral ligament in a foal.     

Comparison of Stainless Steel Fascial Staples and Polypropylene Suture Material for Closure of the Linea Alba in Dogs

Five centimeter segments of the linea alba in mature, female, mixed breed dogs were incised and then approximated with either stainless steel fascial staples or size 0 polypropylene suture material. Breaking strength of the linea alba closures was determined at 0 (Phase I, 18 dogs) and at 7,14, and 31 days (Phase II, 18 dogs). Histology and videointeractive planar morphometry were used to evaluate healing of the linea alba. Breaking strength and histologic and morphometric variables were analyzed statistically using analysis of variance in a split plot design. In a clinical trial, 20 cm linea alba incisions were approximated with stainless steel fascial staples after elective ovariohysterectomy in mature, female, mixed breed dogs (Phase III, eight dogs). The dogs were evaluated at 1, 2, 7,14, 31, 90, and 180 days. Linea alba incisions approximated with polypropylene suture material were significantly stronger than linea alba incisions approximated with stainless steel fascial staples on day 0. There was no significant difference between breaking strength values, histologic, and morphometric appearance of linea alba incisions closed with stainless steel fascial staples or polypropylene suture material when compared 7,14, and 31 days after surgery. All of the dogs in the clinical trial appeared to be normal at all evaluation times. Approximation of linea alba incisions with stainless steel fascial staples compares favorably to closure with a simple continuous pattern of polypropylene suture material with regard to breaking strength, clinical, histologic, and morphometric appearance.     

Collateral ligament reconstruction in two horses following traumatic avulsion fracture using a knotless suture anchor construct

This case report describes a technique for repair of medial collateral ligament avulsions in two horses. Both horses sustained traumatic injuries resulting in avulsion fractures at the origin of their medial tarsal and carpal collateral ligaments. This report describes the use of a knotless suture anchor to mechanically reconstruct medial collateral ligament avulsion injuries in two horses. The first horse, a 9‐year‐old Hannovarian Warmblood gelding presented for an acute nonweightbearing lameness in the right hindlimb. The injury was localised to the medial malleolus of the tibia and an avulsion fracture of the origin of the short medial collateral ligament of the tibiotarsal joint with disruption of the ligament was found on radiographs and ultrasound. The horse was taken to surgery and a reconstruction of the short medial collateral ligament was performed with a modified single row construct using a biocompatible, multistrand, long chain ultra‐high molecular weight polyethylene braided composite suture tape (2 mm Fibertape) and a single knotless suture anchor (5.5 × 19.1 mm PEEK SwivelLock C). The second horse, a 5‐year‐old Thoroughbred gelding presented for an acute nonweightbearing lameness in the left forelimb. The injury was localised to the medial styloid process of the radius and an avulsion fracture of the origin of the medial collateral ligament of the antebrachial carpal joint was found on radiographs and ultrasound. The horse was taken to surgery and a similar reconstruction procedure was performed to the collateral ligament. Both horses were recovered in a Robert Jones bandage without the use of casts or splints and recovered without incident. Both horses are sound and returned to previous level of athletic performance at 18 months and 8 months, respectively.     

Knot Security of Suture Materials

The knot security of chromic gut, polyglycolic acid, polyglactin 910, polydioxanone, polypropylene, and monofilament nylon size 2-0 suture materials were tested biomechanically in vitro. Twenty reproducible knots were tied and incubated in canine serum at 37 degrees for 24 hours before testing. A "secure knot" was defined as a knot that, when tested to failure, broke rather than untied by slippage. The minimum number of throws necessary to make a secure, snug (1500 g tension) square knot was three for gut, polyglycolic acid, polyglactin 910, and polypropylene and four for polydioxanone and nylon. All throws including the first were counted. With all suture materials tested, surgeon's knots were as secure as square knots. Only gut, polyglycolic acid, and polydioxanone granny knots were as secure as square knots; no loosely tied (500 g tension) asymmetric square knots were as secure as snug square knots, and only polydioxanone and polypropylene loose square knots were as secure as snug square knots. Square knots used to start a continuous pattern required one additional throw with gut, polydioxanone, and nylon. Square knots used to end a continuous pattern required two to three additional throws with all materials tested.     

COLLATERAL PULMONARY CIRCULATION IN DOGS EXPERIMENTALLY INFECTED WITH DIROFILARIA IMMITIS: ITS ANGIOGRAPHIC EVALUATION*

Collateral pulmonary circulation was evaluated angiographically 11 months after experimental infection of dogs with either 25 or 100 infective larvae of Dirofilaria immitis. In both groups, collateral pulmonary circulation developed from bronchial arteries and esophageal branches of the left gastric artery. Of the four dogs receiving 25 larvae, one had no detectable collateral circulation, one developed collateral pulmonary circulation from the bronchial arteries only, and two had collateral pulmonary circulation from the bronchial arteries and esophageal branches of the left gastric artery. Of the three dogs receiving 100 larvae, all had collateral pulmonary circulation from the bronchial arteries and the esophageal branches of the left gastric artery. Bronchial artery collateral pulmonary circulation was more extensive in the 100-larvae dogs than in the 25-larvae dogs. Collateral pulmonary circulation from the left gastric artery esophageal branches was similar in both dog groups. Angiographically detectable collateral pulmonary circulation developed within the first year of heaertworm infection. In some respects, the extent of collateral pulmonary circulation development was related to the severity of heartworm infection.     

Foreign body attachment to polypropylene suture material extruded into the small intestinal lumen after enteric closure in three dogs

Three dogs in which polypropylene suture material was used to close an enteric surgery site in a continuous pattern were evaluated at a later date because of recurrence of signs of intestinal disease. Surgery in each dog revealed that the suture material had been extruded into the lumen of the intestine and acted as a site for attachment of a foreign body. The nonabsorbable nature of polypropylene and its use in a continuous pattern are possible explanations for this complication. Polydioxanone or poliglecaprone 25 may be suitable alternatives to polypropylene for use in a continuous pattern for closure of small intestinal surgery sites.