Forelimb Superficial Digital Flexor Tendon Research Articles

Biomechanical Testing of a Novel Suture Pattern for Repair of Equine Tendon Lacerations

To compare in vitro biomechanical properties of a novel suture pattern to a current standard for primary repair of equine superficial digital flexor tendon (SDFT) laceration. In vitro randomized, paired design. Cadaveric equine forelimb SDFT (n = 24). The 3-loop pulley (3LP) and 6-strand Savage (SSS) suture patterns were applied to transected equine SDFT. Ultimate failure load, stiffness, mode of failure, and load required to form a 3-mm gap were obtained using a materials testing system and synchronized high-speed video analysis. Statistical comparisons were made using Student's t-test, with significance set at P < .05. The SSS repair failed at a higher ultimate load (421.1 N ± 47.6) than the 3LP repair (193.7 N ± 43.0; P < .001). There was no significant difference in stiffness (P = .99). Failure mode was suture breakage for all SSS repair and suture pull through for all 3LP repair. The maximum load to create a 3-mm gap in the SSS repair (102.0 N ± 22.4) was not significantly different from the 3LP repair (109.9 N ± 16.0; P = .27). SSS tenorrhaphy has improved strength and resistance to pull through compared with 3LP for equine SDFT in a single load-to-failure test. Load required to form a 3-mm gap was not significantly different between SSS and 3LP.

The cross-sectional area of the superficial digital flexor tendon of trained and untrained Thoroughbred racehorses

Twenty Thoroughbred racehorses were ultrasonographically evaluated to determine the relation between normal values of the cross-sectional area (CSA) of the right and left forelimbs superficial digital flexor tendons (SDFT) in the metacarpal region for trained and untrained Thoroughbreds racehorses. Ultrasonography revealed that CSA at 26cm distal to the accessory carpal bone is larger than other proximal levels, for either left or right forelimbs. In addition, the CSA at 2, 4, 6, 8, 10, 12 and 14cm distal to the accessory carpal bone of the left forelimb are larger (P&lt;0.05) for trained horses when compared with untrained horses. On the other hand, there was no significant difference (P&gt;0.05) between left and right forelimb for CSA of the SDFT, at any level, for either trained or untrained horses, and there was no significant difference between untrained or trained horses for the CSA of right forelimb. In conclusion, the CSA of the left forelimb SDFT for horses that had been in continuous race training remains larger when they were trained anticlockwise, contrary to horses that had not been training for more than one year.

Evaluation of Tensile Strength of the Superficial Digital Flexor Tendon in Horses Subjected to Transcutaneous Electrical Neural Stimulation Therapeutic Regimen

We would like to sincerely express our gratitude to the university of Tehran and faculty of veterinary medicine research council for approval and financial support for this extensive evaluation of tensile strength of the superficial digital flexor tendon in horses subjected to Transcutaneous Electrical Neural Stimulation (TENS) therapeutic regimen Problems statement: The purpose of this study was to determine the effect of TENS on the tensile strength of experimentally traumatized SDFT in horses. Approach: Eight adult castrated horses between 4-9 years-old and 310-395 Kg body-weight were considered. The left fore-limb superficial digital flexor tendon of each horse was splitted longitudinally in the middle portion in full thickness of 10 cm in length using B.P. blade (15 Times strike), then the connective tissue and skin were approximated using No 2 Nylon. Horses were divided into two groups of control and treated with 4 horses each. No treatment was given to control one, whereas treated group was subjected to the transcutaneous electrical neural stimulation (Newtens 900c) therapeutic regimens10 min daily with intensity of 80 µs, 100 Hz frequency for 14 days. After 60 days, the full length of SDFT (20 cm) was removed from the right normal countralaleral and left traumatized tendon of control and treated limbs of all horses to be subjected to test of tensile strength using Zwick/Roell MDTL Machine with speed of 0.07 mM sec−1 having Proportional Integral Deferential (PID) controller. In assessing the variation obtained data was analyzed using paired-t-test. Results: Data of the tensile strength was revealed an average 0.6625 KN for normal SDFT, 0.6375 KN for treated tendon and 0.6175 KN for control tendon .There was significant improvement in regaining tensile strength in treated tendons comparison to control ones in Conclusion: TENS significantly accelerated healing and remodeling of traumatized tendon to regain its tensile strength.

Ultrasonographic Evaluation of Transcutaneous Electrical Neural Stimulation on the Repair of Severed Superficial Digital Flexor Tendon in Horses

Problem statement: The main aim was to clinical assessment of the ultrasonographic changes of transcutaneous electrical neural stimulation after inducing injury in the SDFT in horses. Approach: Using 8 adults’ castrated horses having 350-550 Kgbw with 4-6 years of age. The left hind limb and right fore-limb Superficial Digital Flexor Tendon (SDFT) were splitted longitudinally at mid metatarsal and metacarpal regions in full thickness of 10 cm in length using B.P.blade 15 time strikes, then the connective tissue and skin was approximated using No 2 Nylon. Horses were divided into two groups of control and treated with 4 horses each. No treatment was given to control one, whereas treated group was subjected to transcutaneous neural electrical stimulation for 10 min daily with intensity of 80 I¼s and 100 Hz frequency over 14 days using TENS apparatus newtens 900c. Ultrasonograhic examination was done using Pie Medical 200 Vet Apparatus in 0, 7, 14, 21, 28, 45 and 60 days measuring Cross-Sectional Area (CSA) of SDFT in operated limbs in each horse. For assessing the variation in this finding the Repeated Measure Analysis of Variance was used. Results: After comparing the healing process between two groups, it was significantly accelerated in treated with therapeutic ultrasound. Pain relief, swelling, tenderness, heat and functional recovery in treated with therapeutic ultrasound significantly improved comparing to control group. There was significant effect on reducing lameness in treated group by 28 days after splitting, whereas lameness persisted till 60 days in control group. Ultrasonography findings showed significant decrease in SDFT diameters and Cross Sectional Area (CSA) in the treated limbs comparing with control. Conclusion: Clinically speeding wound healing beside complete reduction of swelling, pain and lameness, its application significantly accelerated functional recovery affected limb.

Monitoring the fate of autologous and allogeneic mesenchymal progenitor cells injected into the superficial digital flexor tendon of horses: Preliminary study

Autologous mesenchymal progenitor cells (MPCs) purified from bone marrow aspirates are being used in the treatment of superficial digital flexor tendon (SDFT) injuries in the horse with promising results. In this study the fate of autologous and allogeneic MPCs following injection into the SDFT was monitored by stable transfection of MPCs with green fluorescent protein (GFP). Small lesions were created manually in one forelimb SDFT of 2 horses and injected with autologous MPCs, allogeneic MPCs or bone marrow supernatant alone. Post mortem examinations performed after 10 or 34 days revealed GFP labelled cells located mainly within injected lesions, but with a small proportion integrated into the crimp pattern of adjacent healthy areas of tendon. Furthermore, there was no visible cell mediated immune response to allogeneic MPCs in either of the host horses.

Superficial digital flexor tendon lesions in racehorses as a sequela to muscle fatigue: A preliminary study

Racing and training related lesions of the forelimb superficial digital flexor tendon are a common career ending injury to racehorses but aetiology and/or predisposing causes of the injury are not completely understood. Although the injury takes place within the tendon, the lesion must be considered within the context of the function of the complete suspensory system of the distal limb, including the associated muscles. Both muscle and tendon function were investigated in vivo using implanted strain gauges in 3 Thoroughbred horses walking, trotting and cantering on a motorised treadmill. These data were combined with assessments of muscle architecture and fibre composition to arrive at an overview of the contribution of each muscle-tendon unit during locomotion. The superficial digital flexor muscle has fatigue-resistant and high force production properties that allow its tendon to store and return elastic energy, predominantly at the trot. As running speed increases, deep digital flexor tendon force increases and it stabilises hyperextension of the fetlock, thus reinforcing the superficial digital flexor in limb load support. The deep digital flexor muscle has fast contracting properties that render it susceptible to fatigue. Based on these measurements and supporting evidence from the literature, it is proposed that overloading of the superficial digital flexor tendon results from fatigue of the synergistic, faster contracting deep digital flexor muscle. Future research investigating distal limb system function as a whole should help refine clinical diagnostic procedures and exercise training approaches that will lead to more effective prevention and treatment of digital flexor tendon injuries in equine athletes.

Effects of platelet-derived growth factor-BB on the metabolic function and morphologic features of equine tendon in explant culture

To evaluate the effects of recombinant human platelet-derived growth factor-BB (rhPDGF-BB) on the metabolic function and morphologic features of equine superficial digital flexor tendon (SDFT) in explant culture. Animals-6 euthanized horses (2 to 5 years old). Forelimb SDFT explants were cultured for 6 days as untreated control specimens or treated with rhPDGF-BB (1, 10, 50, or 100 ng/mL of medium). Treatment effects on explant gene expression were evaluated via real-time PCR analysis of collagen type I, collagen type III, PDGF-A, and PDGF-B mRNA. Explants were assayed for total collagen, glycosaminoglycan, and DNA content; histologic changes were assessed via H and E staining and immunohistochemical localization of collagen types I and III. No morphologic or proliferative changes were detected in tendon explant sections. After high-dose rhPDGF-BB treatment, gene expression of collagen types I and III was increased and decreased, respectively. Expression of PDGF-A and PDGF-B mRNA was significantly increased at 24 hours, but later decreased to have few or negative autoinductive effects. Although PDGF gene expression waned after 48 hours of culture, collagen type I gene expression was significantly increased at 48 hours and reached peak value on day 6. Glycosaminoglycan and DNA content of explants were unchanged with rhPDGF-BB treatment. Results suggest that rhPDGF-BB use may be of benefit in the repair of equine tendon, particularly through induction of collagen type I mRNA. Positive autoinductive effects of PDGF-BB in equine SDFT explants were detected early following culture medium supplementation, but these diminished with time.

Association of type of sport and performance level with anatomical site of orthopaedic injury diagnosis

Although anecdotal reports of increased orthopaedic injury risk in equine sports exist, there is little scientific evidence to support this. To test whether horses undertaking a single competitive sport have increased risk of specific injuries compared to those used for general purpose riding (GP); and whether injury type varies with sport category and performance level. Data from 1069 records of horses undergoing orthopaedic evaluation (1998-2003) and meeting inclusion criteria were reviewed. Sport category (GP, showjumping, dressage, eventing, racing), level (nonelite or elite) and diagnosis were recorded. Effects of sport category and level on probability of a specific diagnosis were assessed using chi-squared tests. Logistic regression was used to determine which competitive sports and levels increased risk of injury compared with GP. Overall there was a significant effect of sport category and level on diagnosis (P<0.0001). There was significant difference between anatomical site injured and sport category (P<0.0001); a high risk of forelimb superficial digital flexor tendon injury in elite eventing (P<0.0001) and elite showjumping (P = 0.02); distal deep digital flexor tendon (DDFT) injury in elite showjumping (P = 0.002); and hindlimb suspensory ligament injury in elite (P<0.0001) and nonelite (P = 0.001) dressage. There was a low risk of tarsal injury in elite eventing (P = 0.01) and proximal DDFT injury in dressage (P = 0.01). Horses competing in different sports are predisposed to specific injuries; particular sports may increase the risk of injury at certain anatomical sites; and the type and site of injury may reflect the type and level of performance. These findings could guide clinicians in the diagnosis of sport related injuries.

The evaluation of extracorporeal shock wave therapy on collagenase induced superficial digital flexor tendonitis

Extracorporeal shock wave therapy (ESWT) is being used to treat desmitis and tendonitis in horses. This paper compares the clinical, ultrasonographic and histological characteristics of ESWT treated collagenase induced superficial digital flexor tendon (SDFT) lesions, versus untreated controls. This blinded study utilizes six mature, healthy horses where bilateral forelimb SDFT lesions were induced. One forelimb was treated while the other served as an untreated control. Three shock wave treatments were administered at three week intervals. At weekly intervals, ultrasonograms were used to measure: 1) percentage lesion at the maximum injury zone (MIZ), 2) the grey scale of the SDFT at the MIZ, 3) the percentage disruption of the longitudinal fibres at the MIZ. The data were also summed from 8-20 cm distal to the accessory carpal bone. Measurements of the external width of the SDFT were obtained through the study period. Examinations were performed on four occasions to evaluate heat, response to palpation, presence/character of swelling over the SDFT, and lameness. At the completion of the study all tendons were evaluated histologicalally. The lesion size, grey scale, and longitudinal fibre disruption at the MIZ, and sum of each variable changed significantly over time, however, there was no difference between treated and control groups. Histopathology showed increased neovascularization in treated tendons (p = 0.001). When compared to untreated controls, ESWT did not change the ultrasonographic appearance of the tendons. However, it did increase neovascularization.

Effects of Recombinant Equine Growth Hormone on In Vitro Biomechanical Properties of the Superficial Digital Flexor Tendon of Standardbred Yearlings in Training

To determine whether recombinant equine growth hormone (rEGH) would alter the in vitro biomechanical properties of the forelimb superficial digital flexor tendon (SDFT) in exercising young Standardbred horses. Randomized complete block design. Twelve Standardbred yearlings. Horses were trained for 12 weeks on a high-speed treadmill (10% positive incline). rEGH was administered intramuscularly (IM) daily (10 microg/kg during week 4; 20 microg/kg for weeks 5-9) to 6 horses (treated group), whereas 6 horses (control group) were administered an equivalent daily volume of sterile water IM. At 12 weeks, horses were euthanatized and left forelimb SDFTs were collected and stored (-70 degrees C). A section from the mid-region of the SDFT was held in cryoclamps with a 4 cm interspace distance and distracted at 10 mm/s until failure. The variables evaluated were maximal load at yield and failure, ultimate and yield tensile stress and strain, tendon stiffness, and mode of failure. Data were analyzed using unpaired, two-tailed, Student's t-test. Statistical significance was set at P < or =.05. Yield and ultimate tensile stress were significantly lower in the rEGH-treated horses compared with controls. There was a trend toward increased maximal displacement, increased ultimate tensile strain, and decreased tendon stiffness in rEGH-treated horses compared with controls. Tensile stress and cross-sectional area, and tensile stress and stiffness were significantly correlated at yield and failure points. rEGH, administered at the manufacturer's recommended dose rates to maturing Standardbred horses in training, does not significantly augment the in vitro biomechanical properties of the forelimb SDFT. Administration of rEGH to young horses in training is unlikely to enhance the physiologic adaptation of the SDFT to exercise stress.

Prevalence of superficial digital flexor tendonitis and suspensory desmitis in Japanese Thoroughbred flat racehorses in 1999.

Overstrain injuries to the superficial digital flexor tendon (SDFT) and suspensory ligament (SI) are among the most common musculoskeletal injuries which contribute to the considerable wastage of racing Thoroughbreds. Many epidemiological studies have demonstrated the prevalence of and risk factors for tendon injury when racing but have not included those injuries sustained during training. However, since tendon injury during training is seen commonly in clinical practice, it is appropriate to determine the overall prevalence of tendon injury sustained during both training and racing. To determine the prevalence of overstrain injury to the SDFT and SL during training and racing among Thoroughbred flat racehorses in Japan in 1999. A retrospective study was performed using a sample population of 10,262 Thoroughbred racehorses. The medical information database of Thoroughbred racehorses registered by the Japan Racing Association (JRA) in 1999 was analysed for SDFT and SL overstrain injury diagnosed by a veterinarian employed by JRA during training and racing. Jump racehorses were excluded from this study. The prevalence of forelimb SDFT tendonitis and SL desmitis was 11.1% (1130 cases) and 3.61% (370 cases) of the population, respectively. In the hindlimb, there were 0.06% (6 cases) and 0.14% (14 cases), respectively. Risks of SDF tendonitis in the forelimb in 3-year-olds or older horses were significantly higher than in 2-year-olds. In contrast, the risk of SL desmitis in the forelimb at age 3 and 4 years was 2.23 and 2.11 times higher, respectively, than in 2-year-olds, but this increased to 5.07 times in those age > or = 5 years. Entire males were at greater risk in comparison to females and geldings. The results suggest that the prevalence of SDF tendonitis and SL desmitis in the forelimb was associated with the horse's age and sex. The prevalence of SL desmitis increased further with age compared with SDF tendonitis, possibly reflecting a more rapid accumulation of degeneration in this structure. The age-related risk demonstrated in this study provides further support that overstrain injuries are associated with accumulated degeneration. These data provide a valuable resource for further research into the aetiology of tendon injury in the racehorse.

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.