A Comparison of Repair Methods for Gap Healing in Equine Flexor Tendon

In nine horses (18 forelimbs), a 3 cm section of superficial digital flexor tendon was removed and the tendons were repaired with immobilization for 6 weeks and (1) no suture (n = 6); (2) a double locking loop tenorrhaphy with carbon fiber (n = 6); or (3) a double locking loop tenorrhaphy with size 2 nylon suture (n = 6). Clinical assessment, gross evaluation, morphometry, histology, and mechanical testing were performed on two limbs from each treatment group at weeks 6, 12, and 24. At weeks 6 and 12, the unsutured tissue was less mature than the tissue sutured with nylon. By week 24, the carbon fiber repair had breaking stress (mean, 12.5 M Pa) similar to the unsutured repair (mean, 10.6 M Pa). There was necrosis and a granulomatous foreign body reaction around the carbon fiber. The nylon suture repair had significantly greater strength per unit area (mean breaking stress, 20.4 M Pa) because of a smaller area of repair tissue in the gap (mean, 3.6 cm2). At week 24, the nylon suture repair tissue was the most mature with the least inflammation of the three repair methods. A nylon double locking loop suture was the preferred method for equine flexor tenorrhaphy of a tendon gap because of greater breaking stress, histologic maturity, biocompatibility, and the adequate functional and cosmetic outcome.     

The effects of polyester (terylene) fibre implants on normal equine superficial digital flexor tendon

AIM: To determine the effect of polyester (terylene) fibre implants on normal equine superficial digital flexor (SDF) tendon structure. METHODS: Normal forelimb SDF tendons (n=24) of 12 horses were divided into unoperated, sham-operated, and implanted (terylene fibre implant) groups. Horses were assessed for lameness and ultrasonographic changes to SDF tendons at intervals up to 48 weeks post-operatively. After euthanasia, SDF tendons were collected for histological and ultrastructural examination. Histological sections were examined for alcian blue staining intensity, cellularity, fibril bundle alignment, fascicle separation and crimp morphology. Mass-average diameters (MADs) of collagen fibrils were calculated from electron micrographs and compared between treatment groups. RESULTS: Insertion of terylene fibre implants resulted in short-term (8 weeks) lameness in implanted limbs. Ultrasonographically, the implants could be detected in 50% of implanted tendons, but were associated with tendon swelling and the presence of hypoechoic core lesions in 7/8 implanted limbs. There were significant alterations in alcian blue staining, cellularity and crimp morphology in the central fascicles of sham-operated and implanted tendons, and alteration in fibril alignment in the central fascicles of implanted tendons. Unoperated tendons remained histologically normal. MADs of collagen fibrils did not differ between sham-operated, implanted and unoperated limbs. CONCLUSIONS: Both the sham procedure and the insertion of terylene fibre implants led to alterations in tendon structure that persisted for up to 48 weeks. Persistence of disorganised connective tissue at the proximal and distal ends of the terylene fibre implants may predispose implanted tendons to continued risk of injury. CLINICAL RELEVANCE: It is unlikely that terylene fibre implants offer any advantage over standard non-surgical treatments for mild to moderate cases of SDF tendonitis in the horse.     

Histopathological findings in the medial palmar and dorsomedial intercarpal ligaments of the equine midcarpal joint

Medial palmar intercarpal ligaments (MPICL) and dorsomedial intercarpal ligaments (DMICL) from the midcarpal joints of 11 adult horses in training were examined histopathologically. These were compared with ligaments from seven horses less than 12 months of age, and 10 grossly enlarged DMICLs of adult horses. Tearing of the MPICL was observed in 15 of 22 joints from adult horses. Collagen fibre bundles of the MPICLs generally were disorganized and poorly aligned, and there were large areas of loose connective tissue. In young horses there was more parallel alignment of collagen bundles and less loose connective tissue. Collagen bundles of adult DMICLs were well organized and showed parallel alignment, whereas in foals the structure appeared more like that of fibrous joint capsule. Grossly enlarged DMICLs in adults consistently had discrete areas of fibrovascular infiltration. Degeneration of the MPICL was associated with increasing age and could explain the high incidence of tearing of the ligament. Enlargement of the DMICL was associated with low-grade tearing and repair.     

Histopathological Findings in the Medial Palmar and Dorsomedial Intercarpal Ligaments of the Equine Midcarpal Joint; Book Review

Medial palmar intercarpal ligaments (MPICL) and dorsomedial intercarpal ligaments (DMICL) from the midcarpal joints of 11 adult horses in training were examined histopathologically. These were compared with ligaments from seven horses less than 12 months of age, and 10 grossly enlarged DMICLs of adult horses. Tearing of the MPICL was observed in 15 of 22 joints from adult horses. Collagen fibre bundles of the MPICLs generally were disorganized and poorly aligned, and there were large areas of loose connective tissue. In young horses there was more parallel alignment of collagen bundles and less loose connective tissue. Collagen bundles of adult DMICLs were well organized and showed parallel alignment, whereas in foals the structure appeared more like that of fibrous joint capsule. Grossly enlarged DMICLs in adults consistently had discrete areas of fibrovascular infiltration. Degeneration of the MPICL was associated with increasing age and could explain the high incidence of tearing of the ligament. Enlargement of the DMICL was associated with low-grade tearing and repair.     

Morphologic study of repair of induced osteochondral defects of the distal portion of the radial carpal bone in horses by use of glued periosteal autografts [corrected

The use of periosteal autografts to resurface osteochondral defects was investigated in 10 horses (2 to 3 years old), and the repair tissue was characterized morphologically. Middle carpal joint arthrotomies were made, and osteochondral defects were induced bilaterally on the distal articular surface of each radial carpal bone. Each defect measured approximately 1 cm2 and extended 3 mm into the subchondral bone plate. Residual subchondral bone plate of control and principal defects was perforated by drilling. A sterile fibrin adhesive was made by mixing a fibrinogen component and a thrombin component. A periosteal autograft was harvested from the proximal portion of the tibia and was glued onto the recipient osseous surface, with its cambium facing the joint cavity. Control defects were glued, but not grafted. Horses were walked 1 hour daily on a walker, starting at postoperative week 7 and continuing for 9 weeks. Sixteen weeks after the grafting procedure was done, carpal radiography was performed, after which horses were euthanatized. Quality of repair tissue of control and grafted defects was evaluated and compared grossly, histologically, and histochemically. Using a reticule, the proportions of various repair tissue types filling each defect were quantitated. Seven weeks after the grafting procedure was done, bilateral arthroscopy revealed synovial adhesions and marginal pannus formation in control and grafted defects. None of the autografts was found floating unattached within the respective middle carpal joints. At 16 weeks, the gross appearance of most grafted and nongrafted defects was similar, and repair was dominated by a fibrous pannus. In 4 grafted defects, bone had formed either concentrically within the defect or eccentrically in the fibrous adhesions between the defect and the joint margin. Histologically, all grafted and nongrafted defects were repaired similarly by infiltration of a mixture of fibrous tissue, fibrocartilage, and bone. Fibrous tissue was the predominant tissue in most defects and its mean proportion was 56 and 59% in the grafted and nongrafted defects, respectively. Fibrocartilaginous tissue in the deeper layers approximated 20%, and woven bone at the base of the defect was 20% in all defects. Histochemically, difference in staining for proteoglycans was not observed between grafted and nongrafted defects. Little remaining original periosteal graft tissue was evident at the defect sites. The only distinguishing feature of grafted defects was the presence of islands of bone formation either at the defect site (n = 2 horses), or in somewhat dorsally displaced tissue that was incorporated in fibrous adhesions (n = 2 horses).(ABSTRACT TRUNCATED AT 400 WORDS)     

Experimental and clinical investigations of the use of carbon fiber sutures in equine tendon repair

Braided carbon fiber sutures were used to repair surgically transected or lacerated digital flexor tendons of 20 mature horses (10 experimental and 10 clinical cases). In addition, 4 experimental horses had tenectomies that were not surgically repaired; these served as controls for the horses with carbon-implanted tendons. Six of the 10 clinically affected horses were returned to their intended use; 2 were euthanatized because of complications and 2 were still recuperating. The experimental horses were euthanatized at 12 days and 1, 2, 4, 8, and 12 months. Tendon scars were structurally and functionally similar in all of these horses. The main histologic difference between the controls and principals was the more extensive remodeling in the latter group at 8 months.     

Healing characteristics of deep digital flexor tenorrhaphy within the digital sheath of horses

OBJECTIVE: To describe the healing characteristics of deep digital flexor tenorrhaphy within the digital sheath. STUDY DESIGN: Experimental study. ANIMALS: Five mature horses. METHODS: Right thoracic limb, deep digital flexor tenorrhaphy was performed within the digital sheath. Limbs were cast in partial flexion using a short limb cast for 6 weeks. Next, extended heel shoes were used for limb support for 14 weeks. Healing was evaluated by sequential ultrasonographic examinations, and limb use was evaluated by force plate analysis. At 26 weeks, mechanical strength and morphologic characteristics of the repair site were evaluated. RESULTS: Gap (mean, 0.93 cm.) formation was evident in unloaded limbs at 3 weeks. This increased markedly by 6 weeks and was 5 cm at 26 weeks. Demarcation between the deep and superficial flexor tendons decreased as the transected ends adhered to the dorsal surface of the superficial flexor tendon. The intrathecal space was reduced by fibrous tissue. Mean maximum load to failure of the repair tissue was 4,616 +/- 3,556 N, with a mean stress of 12.99 +/- 2.78 MPa. The repair consistently failed at the adhesion between the transected tendon and the superficial flexor tendon. CONCLUSIONS: Intrathecal tenorrhaphy with external coaptation (in partial limb flexion) for 6 weeks resulted in gap healing, fibrous adhesion between the deep and superficial flexor tendons, fibrous tissue reduction of the intrathecal space, and a pasture-sound horse at 26 weeks. CLINICAL RELEVANCE: Without improved methods for immobilizing the deep digital flexor tendon, intrathecal tenorrhaphy is unlikely to result in first intention tendon healing.     

Healing of Transected Equine Superficial Digital Flexor Tendons With and Without Tenorrhaphy

Healing of transected superficial digital flexor tendons was evaluated mechanically and histologically in eight horses. Tendons sutured with polyglyconate had higher loads at failure than nonsutured tendons at weeks 5 and 9. The tendon stress at failure (force per unit area) was higher in the sutured tendons at week 5 but not at week 9, reflecting the increased size of the scar at week 9. Histologically, scars after tenorrhaphy were consistently more mature than nonsutured tenotomy scars. The mean maturity score for sutured tendons was higher than for nonsutured tendons at weeks 5 and 9. Overall, these data support tenorrhaphy with absorbable suture.     

Use of a bioabsorbable implant for the repair of severed digital flexor tendons in four horses

A new bioabsorbable implant composed of poly-L-lactic acid was used to repair the severed digital flexor tendons of four horses. The limbs were immobilised with distal casts which were changed after six to eight weeks and removed after 12 to 16 weeks. The horses were followed clinically and ultrasonographically for from seven to 19 months after the surgery. The ultrasonographic examination after the cast had been removed showed that the implants had been well incorporated into scar tissue. Two of the horses were mildly lame at the trot seven months after the surgery, but had returned to work after 12 months. The other two horses are still lame. No complications were observed with the implant.     

Healing of surgically created defects in the equine superficial digital flexor tendon: collagen-type transformation and tissue morphologic reorganization

Full-thickness defects were surgically created in the superficial digital flexor tendons of the front limbs of 20 horses. Tissues formed within the defect were evaluated histologically, and the collagen composition of the tissue was determined by immunofluorescence. Transformation occurred from loose fibrillar areas of types I and III collagen and pericellular types IV and V collagen to dense bundles of type I collagen fibers. Loose fibrillar areas of types I and III collagen were present after 24 weeks. Histologically, in horses killed after 2 weeks, the tissue within the defect was a randomly oriented mass of fibrovascular tissue. In horses killed after 24 weeks the tissue within the defect resembled normal tendon tissue.     

The Effect of Exercise on the Healing of Articular Cartilage Defects in the Equine Carpus

Arthroscopic surgery was performed on 12 horses (2-4 years of age) to create a 7 x 14 mm full-thickness cartilage defect in one radial carpal bone and in the contralateral third carpal bone. Six horses remained confined to a small paddock and six horses underwent a program of increasing exercise consisting of walking, trotting, and cantering for 13 weeks. All lesions showed evidence of healing at week 6 that progressed to more complete healing at week 13. There was no difference in the amount of repair tissue covering the defect. Histologically, the lesions healed with a combination of fibrous tissue and fibrocartilage. The repair tissue was significantly thicker in the exercised horses but there was no difference in repair quality. It was concluded that radial carpal and third carpal lesions have an equal ability to heal and that early postoperative exercise is not detrimental to the repair tissue within these carpal cartilage defects.     

Tendon injuries in horses treated with carbon fibre implants

Implants of carbon fibre, made by plaiting a tow of 10,000 filaments of Grafil type HT-S, were used to treat strains and ruptures of digital flexor tendons in 46 horses. The relevant clinical data, the techniques employed and an analysis of the results are described. Apart from two horses in which the implant was extruded and had to be removed, there were minimal untoward consequences of the surgery. Of the 34 horses with acute or chronic tendinitis, 14 returned to racing, seven were used as hunters and seven as hacks. Among the former group, seven suffered a further strain while racing but the others performed well for some time. Twelve horses with severed tendons recovered well and only in one did infection occur. Overall the results in the latter were better than had previously been achieved using other repair materials.     

Evaluation of the repair process of cartilage defects of the equine third carpal bone with and without subchondral bone perforation

To determine the effect of subchondral bone drilling (forage) on the cartilage repair process after injury has occurred, a cartilage defect (1 cm in diameter) was created on the radial facet of the proximal surface of each third carpal bone in 6 adult horses. In one of the third carpal bones (right or left thoracic limb) of each horse, a 1-cm cartilage defect was created, and 5 holes (1 mm in diameter and 10 mm deep) were drilled through the subchondral bone into the cancellous bone. In the other thoracic limb, an identical defect was created, but not drilled. Analyses of cell numbers and types in the synovia and the mucin precipitate quality were done before, at 1 week after, and 3 weeks after surgical manipulation was done and showed no significant difference between the joint environment of drilled carpi and those of nondrilled carpi. At 21 weeks after surgical manipulation was done, each joint was examined radiographically, macroscopically, and microscopically to compare the condition of the joints and the state of repair of the cartilage in each defect. The amount of surface of the defect covered by the dense fibrous and fibrocartilagenous repair tissue and the thickness of the repair tissue were significantly greater (P less than 0.05 and P less than 0.01, respectively) in the drilled carpal bones. In addition, the attachment of the repair tissue to underlying chondro-osseous tissue was better in the drilled carpal bones. Fibrocartilage was resurfacing the drilled defects, whereas only fibrous tissue was present in the nondrilled defects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tissue strength and wound morphology of the equine linea alba after ventral median celiotomy

OBJECTIVE: To evaluate the tensile strength and wound morphology of the equine linea alba at intervals over 6 months after ventral median celiotomy. STUDY DESIGN: Linea alba tensile strength and wound morphology were determined at 2, 4, 8, 16, and 24 weeks postoperatively. Linea alba samples from 3 unoperated horses were used as controls. ANIMALS: Eighteen adult horses, weighing 400 to 500 kg, 4 to 15 years old. METHODS: Tensile strength and thickness of incised linea alba samples collected at 2, 4, 8, 16, and 24 weeks after ventral median celiotomy were compared with control linea alba samples. Additional samples were subjectively evaluated for wound morphology, notably collagen morphology. RESULTS: Control linea alba had a mean (+/-SEM) tensile strength of 484.9 +/- 58.3 N and was significantly (P < or = .05) stronger than at 2 weeks (87.7 +/- 61.4 N) after surgery. The tensile strength of 4-week (305.8 +/- 61.7 N), 8-week (465.4 +/- 56.5 N), and 16-week (477.8 +/- 57.2 N) samples were not significantly different from control linea alba. At 24 weeks, the tensile strength (721.0 +/- 57.9 N) was significantly stronger than control. The 2-, 4-, and 8-week samples were significantly thicker than controls, whereas the 16- and 24-week samples were not different from controls. On microscopy, control samples were characterized by dense mature collagen bundles. At 2 weeks, samples consisted primarily of granulation tissue, whereas at 4 weeks, samples had immature collagen fibers that were not formed into bundles, and at 8, 16, and 24 weeks, all samples had abundant mature collagen fibers formed into bundles. CONCLUSIONS: At 8 weeks, incised and sutured equine linea alba had a tensile strength comparable with non-incised linea alba and was characterized by mature collagen. CLINICAL RELEVANCE: Based on tensile strength and wound morphology, horses that have had an uncomplicated recovery after ventral median celiotomy should be able to return to controlled exercise as early as 60 days after surgery.     

The use of carbon fibre implants for the repair of Achilles tendon rupture in dogs

Implants of plaited carbon fibre have been used in the repair of ruptured Achilles tendons in ten dogs. Additionally the hock was held in extension by inserting a screw through the fibular tarsal bone and the tibia. When the screw was removed in the sixth week the repaired tendon was thick and taut, and leg use was thereafter virtually normal.     

Laparoscopic surgical technique for repair of rectal and colonic tears in horses: an experimental study

OBJECTIVE: To determine the efficacy of laparoscopic surgical techniques for repair of rectal lacerations in horses. STUDY DESIGN: Experimental study. ANIMAL OR SAMPLE POPULATION: Thirty-two segments of equine bowel placed in an equine pelvitrainer, 8 equine cadavers, and 3 normal horses. METHODS: In experiment 1, 3 laparoscopic intestinal-repair techniques were evaluated in an equine pelvitrainer: suturing with needle holders, with an automatic suture device, and stapling with a hernia stapler. In experiment 2, descending colon lacerations were sutured laparoscopically using needle holders in a pelvitrainer and in equine cadavers. In experiment 3, iatrogenic rectal lacerations were sutured laparoscopically with needle holders in horses under general anesthesia. These horses were evaluated for 7 days' postoperatively by clinical examination and blood and peritoneal fluid analysis. The horses were euthanatized 7 days' postoperatively and necropsied. The repaired colonic segments were collected for determination of bursting pressures, degree of luminal narrowing, and microscopic examination of the suture line. RESULTS: For the 3 techniques, there was no significant difference in repair time or degree of luminal narrowing, but bursting pressure was higher in segments repaired by use of needle holders or with the suture device. Colonic and rectal lacerations were sutured successfully with laparoscopic needle holders. No major complications were recorded. At necropsy, adequate healing was confirmed by a high bursting strength (>140 mm Hg) and by histologic examination. CLINICAL RELEVANCE: A novel laparoscopic method can be used to repair iatrogenic rectal lacerations in horses. Whether this method may be used for clinical cases of rectal tears must be investigated.     

Partial Arytenoidectomy in the Horse with and without Mucosal Closure

Left-sided partial arytenoidectomy was performed in eight horses to evaluate healing. Four horses underwent conventional partial arytenoidectomy with suture apposition of the mucosa. In four horses, most of the arytenoid cartilage, including overlying mucosa, vocal fold, and laryngeal saccule, were excised en bloc without mucosal closure. The horses were monitored clinically by endoscopic examination. One horse from each group was euthanatized at weeks 2, 4, 8, and 16. Complete necropsies with gross and histologic examination of the arytenoidectomy sites were performed. Postoperative complications such as coughing, dysphagia, and aspiration pneumonia were not encountered and problems with wound healing were minimal in both groups. The defect created by partial arytenoidectomy without mucosal closure initially filled to the level of the luminal surface with granulation tissue, with a gradual transition to mature fibrous connective tissue. Grossly, the defect appeared to be healed and was completely epithelialized by week 16 without apparent narrowing of the laryngeal lumen. Partial arytenoidectomy sites with mucosal closure healed in a similar pattern by week 8. Partial dehiscence of the dorsal portion of the sutured mucosa occurred in three horses.     

Ex vivo strength comparison of bioabsorbable tendon plates and bioabsorbable suture in a 3-loop pulley pattern for repair of transected flexor tendons from horse cadavers

OBJECTIVE: To test the failure strength and energy of 2 bioabsorbable implants applied to transected deep digital flexor tendons (DDFT) from adult horses. STUDY DESIGN: Ex vivo biomechanical experiment. SAMPLE POPULATION: Twelve pairs of deep digital flexor tendons harvested from the forelimbs of fresh equine cadavers. METHODS: Poly-L-lactic acid tendon plates were custom manufactured for application to the cylindrical surface of an adult equine deep digital flexor tendon. Twelve pairs of DDFTs were transected 2 cm distal to the insertion of the distal check ligament of the deep digital flexor tendon. One tendon of each pair was randomly selected for repair with a biodegradable plate or a 3-loop pulley method. Size 2 polydioxanone suture was used in both repairs. Repairs were tested in tension to failure, with peak force (PF) and total energy (TE) at repair failure recorded in Newtons (N) and Joules (J), respectively. A paired t-test was used for statistical evaluation with a significant level set at P< or = .05. RESULTS: Mean+/-SD PF for failure of plated tendons (1507.08+/-184.34 N) was significantly greater than for sutured tendons (460.86+/-60.93 N). TE was also significantly greater for failure of plated tendons versus sutured tendons. CONCLUSIONS: Plate fixation of transected cadaver DDFTs appear to have superior immediate failure strength than 3-loop pulley repairs. CLINICAL RELEVANCE: Whereas in vivo testing is required, a bioabsorbable tendon plate may provide initial increased strength to support tendon healing and decrease external coaptation requirements.     

Morphologic and biochemical study of sternal cartilage autografts for resurfacing induced osteochondral defects in horses.

Using biodegradable pins, sternal cartilage autografts were fixed into osteochondral defects of the distal radial carpal bone in ten 2 to 3-year-old horses. The defects measured 1 cm2 at the surface and were 4 mm deep. Control osteochondral defects of contralateral carpi were not grafted. After confinement for 7 weeks, horses were walked 1 hour daily on a walker for an additional 9 weeks. Horses were euthanatized at 16 weeks. Half of the repair tissue was processed for histologic and histochemical (H&E and safranin-O fast green) examinations. The other half was used for the following biochemical analyses: type-I and type-II collagen contents, total glycosaminoglycan content, and galactosamine-to-glucosamine ratio. On histologic examination, the repair tissue in the grafted defects consisted of hyaline-like cartilage. Repair tissue in the nongrafted defects consisted of fibrocartilaginous tissue, with fibrous tissue in surface layers. On biochemical analysis, repair tissue of grafted defects was composed predominantly of type-II collagen; repair tissue of non-grafted defects was composed of type-I collagen. Total glycosaminoglycan content of repair tissue of grafted defects was similar to that of normal articular cartilage. Total glycosaminoglycan content of nongrafted defects was 62% of that of normal articular cartilage (P less than 0.05). Repair tissue of all defects was characterized by galactosamine-to-glucosamine ratio significantly (P less than 0.05) higher than that of normal articular cartilage. These results at 16 weeks after grafting indicate that sternal cartilage may potentially constitute a suitable substitute for articular cartilage in large osteochondral defects of horses.     

Computerized ultrasonographic tissue characterization of equine superficial digital flexor tendons by means of stability quantification of echo patterns in contiguous transverse ultrasonographic images

OBJECTIVE: To describe a method of computerized ultrasonographic tissue characterization that includes structures below the size limits of resolution in equine superficial digital flexor tendons. SAMPLE POPULATION: 2 damaged and 2 structurally normal superficial digital flexor tendons. PROCEDURE: Transverse ultrasonographic images were collected along the tendon long axis. Stability of echo pattern was quantified by means of variation in gray levels of each pixel in contiguous images and expressed as correlation, entropy, and waviness ratios. RESULTS: Normal young and normal old tissues were characterized by high correlation and low entropy and waviness ratios. In necrotic tissue, collapsed intratendinous septa resulted in high correlation, moderate entropy, and high waviness ratios. In early granulation tissue, complete lack of bundle formation resulted in values of zero for correlation and waviness ratios; loose connective tissue matrix resulted in a high entropy ratio. In late granulation tissue, formation of new bundles resulted in a high correlation ratio; swollen intratendinous septa and incomplete organization of connective tissue matrix were reflected in high entropy and waviness ratios. In early fibrotic tissue, rearrangement of tendon bundles resulted in a correlation ratio within reference range and a slight increase in the waviness ratio; an increase in cellularity and lack of fibrillar arrangement led to an increase in the entropy ratio. In late fibrotic and scar tissues, inferior quality of repair with almost complete lack of organization was reflected in low to moderate correlation, low waviness, and high entropy ratios. CONCLUSIONS AND CLINICAL RELEVANCE: Stability of echo patterns accurately reflects homogeneity of tendons in horses.