Minimally invasive desmotomy of the accessory ligament of the deep digital flexor tendon in horses

This retrospective study describes ultrasound guided desmotomy of the accessory ligament of the deep digital flexor tendon in 35 cases, and a modification of this procedure using an adapted surgical instrument. The procedure was successful in 97% of cases. Wound healing was excellent in all except 4 cases. Corrective shoeing prior to surgery contributes to success. The procedure can be performed on the standing horse and offers the advantages of minimally invasive surgery which include: reduced incision length, reduced morbidity and improved cosmetic outcome. The adapted surgical instrument can be an alternative to isolate the ligament under ultrasound guidance.     

Desmotomy of the accessory ligament of the deep digital flexor tendon for treatment of chronic deep digital flexor tendinopathy in three Quarter Horses

Effective treatments for horses diagnosed with severe deep digital flexor (DDF) tendinopathy are limited. In this study, three Quarter Horses diagnosed with severe bilateral DDF tendinopathy underwent bilateral desmotomy of the accessory ligament of the DDF tendon after failing to respond to conservative therapy. Lameness markedly improved in all three horses. Given that severe DDF tendinopathy is typically associated with persistent or recurrent lameness, desmotomy of the accessory ligament of the DDF tendon might be a treatment option to alleviate lameness in horses with DDF tendinopathy. This treatment option appears promising; however, a larger number of cases is necessary to support the results in these three horses.     

Desmotomy for treatment of chronic desmitis of the accessory ligament of the deep digital flexor tendon in a horse.

Chronic lameness was determined to be caused by desmitis of the accessory ligament of the deep digital flexor tendon and adhesions associated with these 2 structures. Desmotomy of the accessory ligament, resection of adhesions, and controlled exercise during convalescence resulted in return to normal use without apparent lameness.     

Influence of the position of the foot on MRI signal in the deep digital flexor tendon and collateral ligaments of the distal interphalangeal joint in the standing horse

Reasons for performing study: Hyperintense signal is sometimes observed in ligaments and tendons of the equine foot on standing magnetic resonance examination without associated changes in size and shape. In such cases, the presence of a true lesion or an artifact should be considered. A change in position of a ligament or tendon relative to the magnetic field can induce increased signal intensity due to the magic angle effect. Objectives: To assess if positional rotation of the foot in the solar plane could be responsible for artifactual changes in signal intensity in the collateral ligaments of the distal interphalangeal joint and in the deep digital flexor tendon. Methods: Six isolated equine feet were imaged with a standing equine magnetic resonance system in 9 different positions with different degrees of rotation in the solar plane. Results: Rotation of the limb induced a linear hyperintense signal on all feet at the palmar aspect of one of the lobes of the deep digital flexor tendon and at the dorsal aspect of the other lobe. Changes in signal intensity in the collateral ligaments of the distal interphalangeal joint occurred with rotation of the limb only in those feet where mediolateral hoof imbalance was present. Conclusions: The position and conformation of the foot influence the signal intensity in the deep digital flexor tendon and in the collateral ligaments of the distal interphalangeal joint. Potential relevance: The significance of increased signal intensity in the deep digital flexor tendon and in the collateral ligaments of the distal interphalangeal joint should be interpreted with regard to the position and the conformation of the foot.     

Two clinical manifestations of desmopathy of the accessory ligament of the deep digital flexor tendon in the hindlimb of 23 horses

REASONS FOR PERFORMING STUDY: Desmopathy of the accessory ligament of the deep digital flexor tendon (ALDDFT) in the hindlimb is an unusual cause of lameness in horses, and reports of the condition are sparse. OBJECTIVES: To describe the clinical and ultrasonographic findings, therapy and outcome of 23 horses treated for desmopathy of the ALDDFT in the hindlimb. METHODS: Records of 23 horses with ultrasonographic evidence of desmopathy of the ALDDFT in one or both hindlimbs from 3 referral centres were reviewed retrospectively. Age, breed, sex, duration and nature of clinical signs, results of clinical and lameness examinations, treatment and outcome were recorded. RESULTS: In 13 horses (Group A), there was an acute onset of unilateral lameness. Ten horses (Group B) had an insidious or sudden onset of postural abnormality. There were 10 cobs, 5 British native-breed ponies and 8 horses of various larger breeds. Twenty horses were used for general purposes, and mean age was 12 years. Enlargement of the ALDDFT in the affected hindlimb(s) was identified in all horses. In 44% of horses, ultrasonographic abnormalities were localised to part of the ALDDFT. Treatment included box-rest and controlled exercise, and 10 horses were subjected to desmotomy or desmectomy of the ALDDFT. Seventy-three percent of horses in Group A returned to full function, while 90% of those in Group B remained lame. CONCLUSIONS: Two distinct clinical conditions are associated with the ALDDFT of the hindlimb. Traumatically induced injury resulting in acute onset lameness appears to have a favourable prognosis, with most horses returning to previous work. However, postural changes, once present, are irreversible and indicate a poor prognosis. POTENTIAL RELEVANCE: Desmopathy of the ALDDFT should be recognised as a potential cause of hindlimb lameness and this study provides clinical and prognostic information. Knuckling and/or semiflexion of the metatarsophalangeal joint may accompany the condition; therefore, if a horse is presented with a flexural deformity of this joint, desmopathy of the ALDDFT should be considered as a primary differential diagnosis.     

Effects of extracorporeal shock wave therapy on desmitis of the accessory ligament of the deep digital flexor tendon in the horse

Objective: To evaluate the effects of extracorporeal shock wave therapy (ESWT) on collagenase‐induced lesions in the accessory ligament of the deep digital flexor tendon (ALDDFT) of horses. Study Design: Paired, blinded controlled study. Animals: Eight Thoroughbred horses (3 mares, 5 geldings; mean±SD weight, 464±26 kg, mean age, 8±1.7 years). Methods: Lesions were created in both ALDDFTs of all horses by injection of 2 × 10³ IU of collagenase type I. Percent lesion and structure (fiber alignment and echogenicity) were quantified with ultrasonographic imaging 3, 6, and 9 weeks after collagenase injection. After ultrasound examinations, ESWT (1000 shocks at 0.15 mJ/mm²) was applied to 1 ALDDFT in each horse. ALDDFT were harvested 15 weeks after collagenase injection and the microstructure, mRNA levels of collagen types I and III, and collagen and glycosaminoglycan content were evaluated. Results: There were no differences in percent lesion, echogenicity, or fiber alignment between control‐ and ESWT‐treated ligaments at each evaluation time; however, compared with 3‐week values, there was a significant increase in percent lesion and echogenicity for EWST treated ligaments at 6 weeks and significant decrease in both variables for treated and control ligaments at 12 weeks. Fiber alignment improved significantly at 9 weeks in controls and at 12 weeks in treated and control ligaments. Collagen type I mRNA levels were significantly higher in the ESWT treatment group compared with the control group 15 weeks after collagenase injection though differences in other mRNA levels, microstructure, and composition were not significant. Conclusions: Our results do not support an effect of ESWT on collagenase‐induced lesions in the equine ALDDFT.     

Anatomical, magnetic resonance imaging and histological findings in the accessory ligament of the deep digital flexor tendon of forelimbs in nonlame horses

Reasons for performing the study: Detailed magnetic resonance imaging (MRI) and histological appearances of the accessory ligament of the deep digital flexor tendon (AL‐DDFT) have not been documented previously in detail. Objectives: To: 1) describe anatomical connections between the AL‐DDFT and adjacent structures; 2) describe high‐field and low‐field MRI and histological appearances of the AL‐DDFT in the forelimb of horses with no carpal or proximal metacarpal pain; and 3) assess the relationship between age, breed, gender, height, weight and MRI findings. Methods: Ten forelimbs were dissected to determine anatomical relationships among the AL‐DDFT and adjacent structures. High‐ and low‐field MR images of the AL‐DDFT and related structures from 29 cadaver limbs of nonlame horses were analysed subjectively and objectively. The relationship between age, breed, gender, height, weight and MRI findings was assessed using a Chi‐squared test. Twelve ALs‐DDFT were examined histologically. Histological and MRI findings were compared subjectively. Results: Fibrous bundles were seen between the AL‐DDFT and the lateral aspect of the superficial digital flexor tendon (n = 9) and the DDFT (n = 2). The AL‐DDFT had low to intermediate signal intensity in most limbs in most high‐field and low‐field MRI sequences. In 69% of limbs, oblique bands of higher signal intensity than the rest of the ligament were identified in high‐field images of the AL‐DDFT. The cross‐sectional area of the AL‐DDFT in the proximal 7 cm of the metacarpal region ranged from 68.1–299 mm². There was no significant relationship between age, gender, weight or height and either the cross‐sectional area of the AL‐DDFT or the presence of oblique higher signal intensity bands. Histological examination revealed that the AL‐DDFT had thick collagen bundles arranged in large crimps and sometimes crossing in oblique directions. The cellularity was greater than in the deep digital flexor tendon in all limbs. Conclusion and potential relevance: The large variability in the MRI appearance and size of the AL‐DDFT in nonlame horses should be borne in mind when interpreting MR images of lame horses.     

Septic tendonitis of the deep digital flexor tendon in a Thoroughbred horse referred for weight loss and intermittent fever

This case report describes the history, clinical and diagnostic findings, treatment and outcome of a 3‐year‐old Thoroughbred gelding. The horse was examined for chronic weight loss, intermittent fever of 4 months' duration and acute lameness of 2 weeks' duration, and was finally diagnosed with septic tendonitis of the deep digital flexor tendon and digital flexor tendon sheath caused by Streptococcus equi ssp. zooepidemicus. Investigation of the lower respiratory tract also allowed isolation of S. equi ssp. zooepidemicus. Although surgical treatment was recommended, because of the severity of the lesion and the guarded prognosis for a return to full athletic function, the owner declined surgery. The horse was therefore treated aggressively with antimicrobials using systemic, local and regional approaches, and with anti‐inflammatory drugs. At 20 months after discharge, the horse was able to race, and he is now in full work with 20 races finished successfully.     

Myofibroblasts in the accessory ligament (distal check ligament) and the deep digital flexor tendon of foals

OBJECTIVE: To demonstrate myofibroblasts in the accessory ligament of the deep digital flexor tendon (ie, distal check ligament) and deep digital flexor tendon of clinically normal foals. SAMPLE POPULATION: Tissue specimens from 25 foals that were necropsied for reasons unrelated to this study and unrelated to musculoskeletal disease. PROCEDURE: The distal check ligament and deep digital flexor tendon of both forelimbs were examined histologically. Myofibroblasts were identified by immunohistochemical staining specific for alpha-smooth muscle actin (alpha-SMA). RESULTS: Most of the cells in the distal check ligament and deep digital flexor tendon of all foals stained positive for alpha-SMA. CONCLUSION AND CLINICAL RELEVANCE: Myofibroblasts made up most of the cells in the distal check ligament and deep digital flexor tendon of clinically normal foals. These cells have contractile ability and therefore, may play a role in flexure contracture of these tendons. The ability of tetracycline to chelate calcium or decrease the expression of the contractile protein alpha-smooth muscle actin could inhibit the myofibroblasts' ability to contract, thus providing a rationale for tetracycline administration as a treatment of distal interphalangeal joint flexor deformity in foals.     

Evaluation of a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon in horses

Objective: To develop a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon (AL‐DDFT) in horses. Study Design: Experimental. Animals: Cadaveric forelimbs (n=10) and 4 forelimbs from 2 horses anesthetized for terminal teaching procedures, and 12 forelimbs of 6 experimental horses. Methods: Saline distention of the carpal flexor sheath facilitated insertion of an arthroscope into the distal medial aspect of the sheath between the AL‐DDFT and deep digital flexor tendon (DDFT). Location of an instrument portal on the lateral aspect of the metacarpus was identified with a needle. The lateral aspect of the AL‐DDFT was transected and the arthroscope and instrument were switched to transect the remaining fibers on the medial aspect. Cadaveric specimens were dissected for evaluation. Experimental horses were monitored for 30 days postoperatively. Results: Minor complications including incomplete division of the AL‐DDFT and shallow incision into the suspensory ligament were observed in some cadaver specimens. The AL‐DDFT was completely transected in all experimental horses with no suspensory ligament damage. Mean±SD surgical time (incision to skin closure) was 28.3±11.8 minutes. On ultrasonographic examination, transection of the AL‐DDFT was complete in all experimental horses. Minor DDFT fiber disruption was noted in 1 limb during ultrasound examination at day 30. Conclusions: A tenoscopic approach through the carpal flexor sheath provided adequate access for desmotomy of the AL‐DDFT.     

Concurrent proximal suspensory desmopathy and injury of the proximal aspect of the accessory ligament of the deep digital flexor tendon in forelimbs or hindlimbs in 19 horses

Clinical features of proximal suspensory desmopathy (PSD) and concurrent injury of the proximal aspect of the accessory ligament of the deep digital flexor tendon (ALDDFT) have not been documented. The objectives were to describe clinical signs and diagnosis. This was a retrospective study. Patient details, lame limb(s), response to diagnostic analgesia, and radiographic and ultrasonographic findings were recorded. PSD and injury of the proximal aspect of the ALDDFT were identified in 19 horses, 14 with forelimb lameness (unilateral 5, bilateral 9) and 5 with hindlimb lameness (unilateral 2, bilateral 3). Localising clinical signs were seen in 7/31 lame limbs (subtle thickening in the region of the ALDDFT [n = 3], pain on palpation of the body of the suspensory ligament (SL) [n = 6], heat in the proximal metacarpal or metatarsal region [n = 2]). Forelimb lameness was abolished by perineural analgesia of the palmar metacarpal (subcarpal) nerves in 17/23 limbs. In the remaining limbs intra‐articular analgesia of the middle carpal joint (n = 2) or an ulnar nerve block (n = 4) were required to eliminate the lameness. Hindlimb lameness was abolished by perineural analgesia of the deep branch of the lateral plantar nerve (n = 2) or local infiltration of the proximal plantar aspect of the metatarsus (n = 3); a tibial nerve block resolved lameness in the remaining 3 limbs. Lesions of the SL and of the ALDDFT were characterised ultrasonographically by enlargement, heterogeneous echogenicity and loss of long linear echoes in longitudinal images. In 3 horses adhesions between the ALDDFT and the SL were identified post mortem. Close apposition of these structures seen ultrasonographically may indicate adhesion formation. It was concluded that the clinical features of PSD and concurrent injury of the ALDDFT are similar to those for PSD alone, highlighting the need for comprehensive and systematic ultrasonographic assessment.     

Aseptic tenosynovitis of the carpal flexor sheath caused by rupture of the accessory ligament of the deep digital flexor tendon

A mare was evaluated for acute left forelimb lameness with effusion of the carpal flexor sheath. No osseous abnormalities were noted during radiographic examination. Significant disruption of the accessory ligament of the deep digital flexor tendon was seen during ultrasonographic examination. Carpal sheath effusion and lameness resolved after medical treatment.     

Computed tomographic contrast tenography of the digital flexor tendon sheath of the equine hindlimb

Pre‐surgical investigation of digital flexor tendon sheath pathology remains challenging with current standard imaging techniques. The aim of this prospective, anatomical, pilot study was to describe the anatomy of the equine hind limb digital flexor tendon sheath using a combination of computed tomography (CT) and computed tomographic contrast tenography in clinically normal cadaver limbs. Ten pairs of hind limbs with no external abnormalities were examined from the level of the tarsometatarsal joint distally. Limbs initially underwent non‐contrast CT examination using 120 kVp, 300 mAs, and 1.5 mm slice thickness. Sixty millilitres of ioversol iodinated contrast media and saline (final concentration 100 mg/ml) were injected using a basilar sesamoidean approach. The computed tomographic contrast tenography examination was then repeated, before dissection of the specimens to compare gross and imaging findings. The combined CT and computed tomographic contrast tenography examinations provided excellent anatomical detail of intra‐thecal structures. The borders of the superficial and deep digital flexor tendons, and the manica flexoria were consistently identifiable in all limbs. Detailed anatomy including that of the mesotenons, two of which are previously undescribed, and the plantar annular ligament were also consistently identifiable. Dissection of all 10 pairs of limbs revealed there to be no pathology, in accordance with the imaging findings. In conclusion, the combination of CT and computed tomographic contrast tenography may be useful adjunctive diagnostic techniques to define digital flexor tendon sheath pathology prior to surgical exploration in horses.     

Retrospective analysis of distal limb conformation and lameness in mature horses after desmotomy of the accessory ligament of the deep digital flexor tendon for management of a flexural deformity

Mature horses that present with flexural deformity of the distal interphalangeal joint and lameness isolated to the foot may obtain long‐term benefits from desmotomy of the accessory ligament of the deep digital flexor tendon (ALDDFT). This retrospective analysis of medical records and radiographs included 13 horses, aged ≥2 years, presented for lameness isolated to the hoof region and diagnosed with flexural deformity of the distal interphalangeal joint. Radiographic angles of the hoof and distal interphalangeal joint and lameness scores were compared before and after desmotomy of the ALDDFT. Follow‐up data including the ability to perform the intended use were obtained at least one year after surgery. There was improvement in the angle between the dorsal aspect of the third phalanx and the weightbearing surface of the hoof, improved alignment between the dorsal hoof wall and dorsal aspect of the third phalanx, and improved alignment of the distal interphalangeal joint. Lameness was decreased in 9/13 horses and 10/13 horses were performing at their level of intended use. Evidence of improved hoof conformation and lameness following desmotomy of the ALDDFT in lame horses with flexural deformity of the distal interphalangeal joint would indicate this procedure should be considered in mature horses.