Diagnosis and treatment of the navicular syndrome in horses

Navicular syndrome can be treated in a variety of ways. This is related to the fact that it has a variety of causes. Prognostically, most horses will improve with treatment. One can expect about 50 per cent of the horses to become useably sound for 1 year, no matter what treatment is used. The disease is progressive, and affected horses eventually will need to be retired because of lameness. The author's therapeutic approach is to utilize shoeing as the primary therapy. Shoeing is performed to correct structural problems and to ensure that shoeing is physiologically sound. Nonsteroidal anti-inflammatory drugs are not used unless radical changes have been made in the shoeing. In cases of confirmed distal interphalangeal joint synovitis, either sodium hyaluronate or polysulfated glycosaminoglycans will be used in conjunction with shoeing. In cases where decreased circulation is documented, isoxsuprine hydrochloride will be administered if shoeing alone has not improved the horse within 6 weeks. If therapy does not improve the horse within 6 to 12 weeks, palmar digital neurectomy is recommended.     

Management of acquired flexural deformity of the metacarpophalangeal joint in Equidae

Fifteen horses with flexural deformity of the metacarpophalangeal joint were evaluated and their conditions were designated as mild, moderate, or severe. Evaluations were made on the basis of clinical signs and lesions seen on radiography. Horses with mild deformities were treated with corrective trimming and shoeing; those with moderate deformities were treated with desmotomy of the accessory ligament of the deep digital flexor tendon and corrective shoeing. Desmotomies of the accessory ligaments of both deep and superficial digital flexor tendons were performed on horses severely affected, followed by corrective shoeing. In this long-term study, 4 horses with mild lesions and 4 horses with moderate lesions returned to useful work. None of the horses with severe disease responded enough to withstand strenuous athletic training.     

Injection of corticosteroids, hyaluronate, and amikacin into the navicular bursa in horses with signs of navicular area pain unresponsive to other treatments: 25 cases (1999-2002)

OBJECTIVE: To determine history, clinical and radiographic abnormalities, and outcome in horses with signs of navicular area pain unresponsive to corrective shoeing and systemic nonsteroidal anti-inflammatory drug administration that were treated with an injection of corticosteroids, sodium hyaluronate, and amikacin into the navicular bursa. DESIGN: Retrospective study. ANIMALS: 25 horses. PROCEDURE: Data collected from the medical records included signalment, history, horse use, severity and duration of lameness, shoeing regimen, results of diagnostic anesthesia, radiographic abnormalities, and outcome. RESULTS: 17 horses had bilateral forelimb lameness, 7 had unilateral forelimb lameness, and 1 had unilateral hind limb lameness. Mean duration of lameness was 9.2 months. All horses had been treated with corrective shoeing and nonsteroidal anti-inflammatory drugs for at least 6 months; 18 had previously been treated by injection of corticosteroids and sodium hyaluronate into the distal interphalangeal joint. Fourteen horses had mismatched front feet, and 21 horses had signs of pain in response to application of pressure over the central aspect of the frog. Palmar digital nerve anesthesia resulted in substantial improvement in or resolution of the lameness in all horses. Twenty horses (80%) were sound and returned to intended activities 2 weeks after navicular bursa treatment; mean duration of soundness was 4.6 months. Two horses that received numerous navicular bursa injections had a rupture of the deep digital flexor tendon at the level of the pastern region. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that navicular bursa treatment may provide temporary improvement in horses with signs of chronic navicular area pain that fail to respond to other treatments.     

Thoracic limb digital extensor denervation in young horses

Low radial neurectomy in the left thoracic limb was performed in 4 mixed-breed weanling horses, with subsequent paralysis of the lateral and common digital extensor muscles. Weight bearing of the denervated and control limbs was discouraged by the use of special shoeing. Clinical signs of flexural deformity were not induced in the horses.     

Navicular disease in the horse

Navicular disease results in a chronic, progressiveforelimb lameness that is usually bilateral. Although many different horse breeds can be affected, Quarter Horses and Warmbloods appear particularly susceptible. The peak age incidence appears to be in horses aged 6–10 years. The condition has been recognized for many years and has been the source of debate and conflict for at least the last 50 years. Much of the confusion has been caused by different criteria used to establish a diagnosis. In a large series of cases examined at the University of Sydney, only 30 percent of horses that were eventually diagnosed as having navicular disease showed a positive response to hoof testers applied across the middle third of the frog. In contrast, more than 80 percent of horses with navicular disease showed a marked increase in lameness following pastern and fetlock flexion. All horses diagnosed became sound following a palmar digital nerve block and all had positive findings on radiography. However, radiography could not be utilized as a sole diagnostic technique because some horses with radiographic abnormalities of the navicular bone did not show clinical signs of navicular disease.To establish a diagnosis of navicular disease, the following criteria should be met: 1) A chronic progressive unilateral or bilateral forelimb lameness, 2) Pain in areas proximal to the foot has been excluded as a possible cause of the lameness, 3) Other conditions that could cause pain in the palmar heel region are excluded, 4) The lameness is eliminated or substantially improved following a palmar digital nerve block, and 5) There are radiographic abnormalities on upright pedal and/or skyline views of the navicular bone.Treatment of navicular disease has usually fallen into categories of a) pain alleviation, b) drugs with vascular or hemodynamic effects, or c) changing biomechanics either by corrective trimming or corrective shoeing. None of these treatments have been universally accepted and debate about their efficacy is allied to theories about the etiology.     

Surgical treatment of navicular syndrome in the horse using navicular suspensory desmotomy

Seventeen horses diagnosed as having navicular syndrome on the basis of history, clinical findings, regional local anaesthesia and radiography were subjected to bilateral navicular suspensory desmotomy. Before surgery, the duration of navicular lameness ranged from 6 weeks to 4 years. Previous unsuccessful treatments prior to surgery included nonsteroidal anti-inflammatories, corrective shoeing, rest and isoxsuprine. For the seventeen horses subject to surgery, twelve horses were sound, one horse was improved and four horses were lame at a minimum of 6 months after surgery.     

The Incidence of Australian Stringhalt in Horses in New Zealand

Seventeen horses diagnosed as having navicular syndrome on the basis of history, clinical findings, regional local anaesthesia and radiography were subjected to bilateral navicular suspensory desmotomy. Before surgery, the duration of navicular lameness ranged from 6 weeks to 4 years. Previous unsuccessful treatments prior to surgery included nonsteroidal anti-inflammatories, corrective shoeing, rest and isoxsuprine. For the seventeen horses subject to surgery, twelve horses were sound, one horse was improved and four horses were lame at a minimum of 6 months after surgery.     

Quantitative comparison of three commonly used treatments for navicular syndrome in horses

OBJECTIVE: To quantitatively compare 3 commonly used treatments for navicular syndrome (NS) in horses: heel-elevation shoeing alone, heel-elevation shoeing and phenylbutazone administration, heel-elevation shoeing and injection of the distal interphalangeal joint (DIPJ) with triamcinolone acetonide (TA), and all 3 treatments in combination. ANIMALS: 12 horses with NS. PROCEDURE: A force plate was used to measure baseline peak vertical ground reaction force (PVGRF) of the forelimbs. Each horse's forelimbs were shod with 3 degrees heel-elevation horseshoes; PVGRF was measured 24 hours and 14 days after shoeing. Fourteen days after shoeing (following data collection), phenylbutazone (4.4 mg/kg, i.v., q 12 h) was administered (5 treatments). Two hours after the fifth treatment, PVGRF was measured; TA (6 mg) was injected into the DIPJ of the forelimb that generated the lower baseline PVGRF Fourteen days later, PVGRF was measured. Phenylbutazone was administered as before, and PVGRF was measured. Percentage body weight of force (%BWF) was calculated from PVGRF measurements and used for comparisons. RESULTS: 14 days after shoeing, mean %BWF in both forelimbs significantly increased from baseline; additional administration of phenylbutazone significantly increased %BWF applied from the more lame forelimb. Compared with shoeing alone, there was no significant change in %BWF after injection of the DIPJ with TA in shod horses. CONCLUSIONS AND CLINICAL RELEVANCE: Heel-elevation shoeing alone and in combination with phenylbutazone administration quantitatively decreased lameness in horses with NS. Although not significant, additional DIPJ injection with TA resulted in further quantitative decrease in lameness, compared with that achieved via shoeing alone.     

Palmar digital neurectomy in 24 horses using the guillotine technique

OBJECTIVE: To determine the effectiveness and incidence of complications of palmar digital neurectomy using the guillotine technique in horses presented for lameness originating from sites innervated by these nerves. DESIGN: Retrospective study of 24 clinical cases. ANIMALS: Twenty-four horses undergoing a palmar digital nerve neurectomy between June 1997 and June 2001. METHODS: The records of all horses undergoing a uniaxial or biaxial, unilateral or bilateral neurectomy during the defined time period were retrieved. Information retrieved from the record included breed, age, gender, discipline for which the horse was used, history, results of lameness examination, results of perineural anaesthesia, radiographic findings, surgery report, postoperative care, complications and outcome. RESULTS: Seventeen geldings and seven female horses of mixed breeds, ranging in age from 1 to 16 years, that were used for a variety of non-racing, but competitive, athletic disciplines, underwent neurectomy using the guillotine technique during the specified time period. In 23 horses perineural anaesthesia was performed at the University Veterinary Centre to isolate the lameness. Anaesthesia resolved lameness in 18 horses. In five horses there was some residual lameness isolated to sites remote from the distal extremity. The most common radiographic finding was an increase in the number and or size of the synovial fossae of the navicular bone. Twenty-two horses underwent bilateral biaxial neurectomies and two horses with painful trauma-induced neuromas underwent unilateral, uniaxial neurectomy. There were no postoperative complications. All horses were rested for 3 months before returning to work. At least 1 year after surgery, 22 horses were in full work and two horses were not in work because of unrelated problems. Of the horses in work, 17 were considered free of lameness. The other five were competing, but receiving medication for residual lameness associated with sites remote from the distal extremity. CONCLUSION: Results of this study suggested that palmar digital neurectomy using the guillotine technique provided reliable and consistent resolution of lameness originating from sites innervated by these nerves. There were no significant complications.     

The effect of CO2 laser neurectomy on neuroma formation and axonal regeneration.

In an attempt to prevent neuroma formation and digital reinnervation after sharp palmar digital neurectomy in 10 adult horses with navicular disease, 18,426 W/cm2 of CO2 laser energy was applied to the proximal nerve stump. Clinical follow-up was 4 to 23 months. In two horses, palmar digital nerve biopsies were taken at month 4 (four nerves) and month 7 (two nerves). Nine horses were sound immediately and at all follow-up examinations. None had clinical evidence of painful neuroma or digital reinnervation. Histologically, there was minimal scar tissue at the surgical site; axonal sprouts were comingled with fibrous tissue.     

Lameness due to pain associated with the distal interphalangeal joint: 45 cases

This paper describes the clinical and radiographic features, and response to treatment, of 45 horses which showed lameness that was improved by intra-articular anaesthesia of the distal interphalangeal (DIP) joint. Although many horses had poor conformation of the foot of the lame limb, the majority showed no localising clinical signs suggestive of involvement of the DIP joint. Lameness was usually unilateral. No horse with bilateral lameness responded to treatment. Palmar digital nerve blocks frequently improved or alleviated lameness, although in some horses palmar (abaxial sesamoid) nerve blocks were required to eliminate lameness. This difference in response did not affect response to treatment. Intra-articular anaesthesia of the DIP joint usually resulted in resolution of lameness within 5 mins; a partial improvement in lameness or a slow response were poor prognostic indicators. None of the horses had radiographic abnormalities compatible with navicular disease. Radiographic changes of the distal interphalangeal joint per se were generally detectable only in lateromedial views and were identified in less than one third of the horses. Success rates were low following treatment of cases with radiographic abnormalities. In those with no radiographic abnormalities the response to corrective trimming and shoeing and intra-articular administration of sodium hyaluronate, once or repeatedly, was variable and no parameters could be used to predict the likely outcome. Treatment was successful in approximately 30 per cent of cases. Subsequent treatment of horses which remained lame, by intra-articular administration of polysulphated glycosaminoglycans, was not helpful; only a small proportion became sound following prolonged (nine months) rest.(ABSTRACT TRUNCATED AT 250 WORDS)     

Equine Behavior Problems—Around Farriery: Foot Pain in 11 Horses

Although foot pain may clearly be the cause when a horse with foot pathology does not tolerate farriery, it may be overlooked or underappreciated as the cause of this behavioral problem when the pathology is mild and/or chronic. In this study, the records of 11 adult horses whose behavior for farriery initially warranted sedation for trimming and shoeing were reviewed. All 11 horses had a history of chronic lameness that was mild to moderate, but foot pain was the presenting complaint in only seven horses - all with chronic laminitis. The other four horses had abnormal foot conformation (long-toe, low-heel, or “club foot), but the lameness had not been attributed to the foot. All 11 horses showed improvement in gait with corrective trimming and shoeing. In each case, sedation for farriery could be discontinued after one to six visits, concurrent with the improvements in gait and foot pathology. On the basis of the survey results from 17 professional farriers, an ethogram of farriery-related undesirable horse behavior was developed.     

Shoeing principles for the management of navicular disease in horses

Navicular disease was diagnosed in 36 horses. Each horse was treated, using shoeing as the only major means of treatment. Phenylbutazone was used initially for 10 days after shoeing. Shoeing was designed to correct preexisting problems, enhance physiologic function of the foot, and ease breakover of the foot. The horses were evaluated over a period ranging from 12 to 54 months. The lameness improved in all horses. Thirty-one of the 36 horses treated were not lame when last evaluated. Shoeing was most effective when performed within 8 months of the first signs of lameness. Also, horses used for show ring performance classes had a better response to treatment than did horses used for gaming or jumping.     

Hoof growth between two shoeing sessions leads to a substantial increase of the moment about the distal, but not the proximal, interphalangeal joint

REASONS FOR PERFORMING STUDY: There is little insight into the effects of routine farriery on the internal structures of the distal limb in sound horses. OBJECTIVES: To measure the effect of change in hoof conformation during a shoeing interval on the moments about the proximal and distal interphalangeal joints (PIPJ, DIPJ) and to determine whether and how the horse compensates for this change in hoof conformation. METHODS: Both front feet of 9 sound Warmblood horses were measured while standing on a pressure-force measuring system and radiographed in a lateromedial direction shortly after shoeing and 8 weeks later. From these data, ground reaction forces (GRF) and lever arms were measured in order to calculate joint moments. RESULTS: After 8 weeks, the moment about the PIPJ did not increase significantly, but the moment about the DIPJ did so, indicating a compensatory mechanism for a change in hoof conformation in the DIPJ. CONCLUSIONS: Standing horses compensate for hoof conformation change during an 8-week shoeing interval, which leads to increased DIPJ extension and consequently an increased loading of the deep digital flexor tendon. POTENTIAL RELEVANCE: This study quantifies the effect of a shoeing interval on the internal structures of the foot and helps to determine an appropriate shoeing interval for individual horses in which the hoof with the lowest hoof angle is the best indicator. The exact determination of an optimal individual shoeing interval requires further study.     

The Use of Intraneural Doxorubicin in Association with Palmar Digital Neurectomy in 28 Horses

Painful neuroma formation after palmar digital neurectomy in the horse is common. Experimentally, injection of doxorubicin (Adriamycin) into the proximal transected nerve stump has been shown to prevent axon sprouting and neuroma formation for up to 5 months. This procedure was used in 28 horses with navicular disease, preexisting painful neuroma, or wing fractures of the distal phalanx. At 1 month, 16 horses had incisional complications. At 1 year, 15 horses were sound. Eight horses were lame, although three were improved. Three horses required a second surgical procedure, two of which became sound. Follow-up was not available in two horses. The technique used in this study has an unacceptable rate of wound complications and no benefit over other palmar digital neurectomy techniques currently in use.     

The force and contact stress on the navicular bone during trot locomotion in sound horses and horses with navicular disease

Mechanical overload due to poor conformation or shoeing has been suggested to contribute to the development of navicular disease. While studies have determined the compressive force exerted on the navicular bone in normal horses, this has not been reported for horses with navicular disease. Also, the force has not been converted to stress by correction for contact area. In this study we developed a technique for the determination of the contact area between the deep digital flexor tendon and the navicular bone in vivo, and used a forceplate system to determine the force and stress on the bone at trot in 6 normal and eight diseased horses. The mean +/- s.d. peak force and peak stress were 5.62+/-1.45 N/kg and 2.74+/-0.76 MPa for the normal group and 6.97+/-1.50 N/kg and 3.07+/-0.55 MPa for the navicular disease group. The peak force and peak stress were similar for both groups but the force and stress in the horses with navicular disease were approximately double control group values early in the stance phase. This was due to a higher force in the deep digital flexor tendon, which was attributed to a contraction of the deep digital flexor muscle in early stance in an attempt to unload the heels.     

Short-term effect of therapeutic shoeing on severity of lameness in horses with chronic laminitis

OBJECTIVE: To evaluate the short-term effects of 4 therapeutic shoeing systems on lameness and voluntary limb-load distribution in horses with chronic laminitis. ANIMALS: 10 horses with chronic laminitis. PROCEDURES: A clinical trial was conducted that used a concurrent control, crossover design to evaluate the relative effectiveness of a standard flat shoe, fullered egg-bar shoe, heart-bar shoe, and modified equine digital support system to alleviate chronic lameness in horses. Therapeutic success was assessed during a 7-day period by use of subjective (Obel grade and clinical score) and objective (force-plate data) evaluations. RESULTS: Comparison of pretreatment and intertreatment control data indicated that disease status of the horses did not change during the course of the study. None of the therapeutic shoeing treatments used resulted in a significant change in severity of lameness. CONCLUSIONS AND CLINICAL RELEVANCE: Results were interpreted to imply that substantial clinical improvement should not be expected during the first 7 days after therapeutic shoeing for the specific shoes tested in this study. On the basis of our results, we hypothesize that when used as the lone indicator of therapeutic success, severity of lameness may not be a valid indicator.     

Evaluation of Stainless Steel Nerve Caps for Palmar Digital Neurectomy

Stainless steel nerve caps for application to the proximal nerve stump during palmar digital neurectomy were examined. Six experimental horses and three clinical patients underwent palmar digital neurectomy using the capping technique. Good results were obtained on the experimental horses; however, when the caps were used on the clinical patients, lameness appeared in two of three horses after hard work. The caps were considered unacceptable for clinical use.     

Palmar digital neurectomy using the GaAlAs diode laser

Palmar digital neurectomy is typically performed as a treatment for palmar foot pain that is unresponsive to medical treatment and therapeutic shoeing. Although it is useful for the elimination of pain related to navicular disease or wing fractures of the distal phalanx, a number of potential complications can occur after this procedure, including painful neuroma formation, persistence of skin sensation, reinnervation, and rupture of the deep digital flexor tendon. Over the years, surgical techniques have been developed to minimize complications associated with digital neurectomy, including sharp dissection (the guillotine method), epineural capping, and cryosurgical treatment of the nerve, using a double freeze-thaw cycle. Alternatively, lasers may be used to divide the palmar digital nerve with coagulation of the nerve endings. The thermal effects of the laser theoretically help to minimize the potential for painful neuroma formation and reinnervation by sealing the cut surface of the nerve endings, preventing adhesion formation with surrounding soft tissues, and delaying the reanastomosis of the proximal and distal nerve segments.     

Outcome of medical treatment for horses with foot pain: 56 cases

Reasons for performing study: Currently, there are limited data regarding the long‐term outcome of horses with foot pain treated with corrective shoeing, rest and rehabilitation, and intrasynovial anti‐inflammatory medication to target lesions detected with MRI. Objective: To report the long‐term (≥12 months) outcome of horses with foot lesions following medical therapy. Hypotheses: 1) There is no association between clinical parameters considered and a poor response to therapy. 2) Horses with a deep digital flexor tendinopathy are less likely to respond to medical therapy than horses without a deep digital flexor tendinopathy. Methods: The medical records of horses with foot pain subjected to MRI examination and medical therapy (2005–2007) were evaluated retrospectively. Data collected included history, signalment, occupation, duration and severity of lameness at the time of MRI, radiological and MRI abnormalities. Number of treatments, complications and long‐term response to treatment were obtained by detailed telephone questionnaires. Association between clinical and MRI findings and long‐term lameness were investigated. Results: Frequent abnormal structures included the navicular bone, the deep digital flexor tendon, the navicular bursa and the distal interphalangeal joint. Thirty‐four of 56 horses (60.7%) failed to return to previous level of exercise due to persistent or recurrent lameness or owners' decision to decrease the horse's athletic level; however, 11 horses (32.3%) were being used for light riding. Prognosis for horses with concurrent deep digital flexor tendon, navicular bone and navicular bursa lesions was worse than horses with individual lesions. Deep digital flexor tendinopathy was strongly associated with persistent or recurrent lameness. Conclusions: Horses with multiple foot lesions managed with conservative therapy have a guarded prognosis for long‐term soundness. Deep digital flexor tendinopathies negatively influence prognosis.