MAGNETIC RESONANCE IMAGING FEATURES OF PROXIMAL METACARPAL AND METATARSAL INJURIES IN THE HORSE

Magnetic resonance (MR) imaging abnormalities in horses with lameness localized to the proximal metacarpal or metatarsal region have not been described. To accomplish that, the medical records of 45 horses evaluated with MR imaging that had lameness localized to either the proximal metacarpal or metatarsal region were reviewed. Abnormalities observed in the proximal suspensory ligament or the accessory ligament of the deep digital flexor tendon included abnormal high signal, enlargement, or alteration in shape. Twenty-three horses had proximal suspensory ligament desmitis (13 hindlimb, 10 forelimb). Sixteen horses had desmitis of the accessory ligament of the deep digital flexor tendon. One horse had desmitis of the proximal suspensory ligament and the accessory ligament of the deep digital flexor tendon on the same limb and one horse had desmitis of the proximal suspensory ligament on one forelimb and desmitis of the accessory ligament of the deep digital flexor tendon on the other forelimb. Four horses did not have abnormalities in the proximal suspensory ligament or accessory ligament of the deep digital flexor tendon. Eighty percent of horses with forelimb proximal suspensory ligament desmitis and 69% of horses with hindlimb proximal suspensory ligament desmitis returned to their intended use. Sixty-three percent of horses with desmitis of the accessory ligament of the deep digital flexor tendon were able to return to their intended use. MR imaging is a valuable diagnostic modality that allows diagnosis of injury in horses with lameness localized to the proximal metacarpal and metatarsal regions. The ability to accurately diagnose the source of lameness is important in selecting treatment that will maximize the chance to return to performance.     

Surgical treatment of a second metacarpal bone exostosis with associated desmitis of the body of the suspensory ligament in a horse

This report outlines the diagnosis, surgical treatment and successful outcome following treatment of second metacarpal bone exostosis with concurrent suspensory ligament desmitis, and lameness in a horse. Magnetic resonance imaging was useful in determining the extent of pathology within the suspensory ligament and site of proposed surgical resection. MRI was also utilised as a post-operative tool in determining the timescale for satisfactory healing to enable the horse to return to athletic work.     

Advanced imaging of an incomplete fracture and exostosis of the third metacarpal bone in a young Warmblood horse

A 5-year-old Hanoverian gelding with acute moderate right forelimb lameness underwent nuclear scintigraphy, which identified marked increase in radiopharmaceutical uptake of the proximomedial aspect of the right metacarpus. Ultrasonography and radiography identified sclerosis and exostosis of the proximomedial aspect of the metacarpal bone III in-between the suspensory ligament and the second metacarpal bone, and presence of a suspected fracture. The owner requested euthanasia of the gelding, and post-mortem computed tomography and magnetic resonance imaging identified marked bone sclerosis and thickening of the palmar cortex of the metacarpal III (McIII), presence of an incomplete fracture in the palmar cortex of McIII and expansive exostosis from McIII extending in a palmar direction between the suspensory ligament and the second metacarpal bone. Histopathological examination confirmed the imaging findings of sclerosis and led to final diagnosis of a fracture of the palmar cortex of the McIII associated with an exostosis encroaching the medial aspect of the suspensory ligament. No abnormalities were present in the suspensory ligament or metacarpal bone II (McII).     

Computed tomographic diagnosis of incomplete palmar cortical (fatigue) fracture of the third metacarpal bone in two young adult endurance horses

Two young adult endurance horses were presented for investigation of sudden-onset forelimb lameness during competition. Clinical examination revealed a severe forelimb lameness and pain on palpation of the proximal palmar metacarpal area. Initial radiographic survey of the affected forelimb was unremarkable in both cases. A week of box rest resulted in only a mild improvement in the lameness. A second radiographic examination did not reveal any significant abnormalities. In both cases, scintigraphic examination was suggested, but was declined by the owner, and the lameness had significantly improved after local infiltration of 3 mL of anaesthetic solution in the proximal suspensory region. Radiographic and ultrasonographic examinations of the carpus and proximal suspensory region were unremarkable in Case 2. Case 1 had increased thickness of the medial lobe of the proximal aspect of the suspensory ligament. A computed tomographic examination was performed and an incomplete longitudinal (fatigue) fracture of the proximal third metacarpal bone was detected. After 8 months of box rest and rehabilitation, re-examination revealed resolution of the lameness in both cases. Advanced diagnostic imaging should be considered in young endurance horses with severe lameness during competition or training, in which radiographic and ultrasonographic examinations are unremarkable or do not explain the severity of the lameness. Computed tomography imaging is considered a useful diagnostic imaging technique to detect incomplete longitudinal palmar metacarpal cortical (fatigue) fractures due to its ability to provide excellent bone detail.     

Outcome of desmoplasty and fasciotomy for desmitis involving the origin of the suspensory ligament in horses: 27 cases (1995-2004)

OBJECTIVE: To determine outcome of percutaneous ultrasound-guided desmoplasty with simultaneous fasciotomy for proximal suspensory desmitis (ie, desmitis of the origin of the suspensory ligament) in horses that have not responded to stall rest. DESIGN: Retrospective case series. ANIMALS: 27 horses. PROCEDURES: Medical records of horses with proximal suspensory desmitis treated by means of desmoplasty with fasciotomy were reviewed. Follow-up information was obtained through telephone conversations with owners and trainers of the horses or by examination of horses at the hospital. RESULTS: 23 of the 27 (85%) horses, including 3 of 4 horses with forelimb lesions and 20 of 23 horses with hind limb lesions, were able to return to full work after surgery and rehabilitation. All horses had ultrasonographic evidence of healing of suspensory ligament lesions. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that desmoplasty with fasciotomy is a viable treatment option in horses with proximal suspensory desmitis that have not responded to stall rest.     

Disorders of the origin of the suspensory ligament in the horse: a diagnostic challenge

Lameness in horses due to pain originating from the proximal metacarpal/metatarsal region remains a diagnostic challenge. In cases of obvious lameness the pain can be localised to this region by diagnostic anaesthesia. Because a variety of disorders can cause lameness in this region different imaging modalities including radiography, ultrasonography and scintigraphy should be used to arrive at an accurate diagnosis. Even though a precise anatomic-pathologic diagnosis can still be an enigma, because not only bone and joints, but also soft tissue structures including the proximal suspensory ligament, its origin at the proximal metacarpus/ metatarsus, its fascia, the superficial fascia, as well as the intermetacarpal/metatarsal ligaments, the accessory ligament of the deep digital flexor tendon and both digital flexor tendons may be involved. Magnet resonance tomography (MRT) shows a high diagnostic sensitivity in imaging soft tissue structures and bone. In horses MRT is still at the beginning. The MRT appearance of the proximal metacarpal/metatarsal region has not yet been evaluated in detail and there are only few anatomic studies of the origin of the suspensory ligament in horses. The first experiences showed, that more gross and histologic examinations are necessary to fully interpret MRT-images and to differentiate pathologic alterations from clinically not relevant variations.     

Hindlimb lameness associated with proximal suspensory desmopathy and injury of the accessory ligament of the suspensory ligament in five horses

The accessory ligament of the hindlimb suspensory ligament arises from the plantar aspect of the calcaneus and fourth tarsal bones and blends with the suspensory ligament in the proximal aspect of the metatarsus. The accessory ligament of the suspensory ligament of both hindlimbs of 12 mature horses, with no history of hindlimb lameness, was assessed ultrasonographically. The ligament comprised linear parallel echoes which were consistently shorter than those of the lateral digital flexor tendon; the dorsal and plantar borders were parallel. Lameness associated with injury of the accessory ligament of the suspensory ligament was identified in 6 of 8 lame hindlimbs of 5 horses, unilaterally in 4 horses and bilaterally in one horse. In all horses there was concurrent proximal suspensory desmopathy. There was localised oedematous swelling on the distal medial aspect of the chestnut extending distally in 2 horses. Lameness was best identified when the horses were ridden. Perineural analgesia of the deep branch of the lateral plantar nerve abolished lameness in 3 horses but perineural analgesia of the tibial nerve was required to abolish lameness in the hindlimb with injury of the accessory ligament of the suspensory ligament in 2 horses. Injury of the accessory ligament of the suspensory ligament was characterised by marked decrease in echogenicity of the ligament and loss of parallel alignment of the linear echoes, which were shorter than normal in longitudinal images.     

Ultrasonographic examination of the palmar aspect of the pastern of the horse: Sesamoidean ligaments

The suspensory apparatus is composed of the third interosseous muscle (TIOM) or suspensory ligament, the proximal sesamoid bones, palmar ligament and distal sesamoidean ligaments (DSL). Of these structures, the suspensory ligament is the most frequently implicated in conditions seen in race and sport horses; nevertheless, DSL lesions are not rare and often associated with other injuries that can modify patient prognosis and management. Ultrasonography has been shown to be valuable in the assessment of DSL desmitis. In contrast to the metacarpal area, the pastern region has been considered technically more difficult to scan because of the small and irregular contact surface and frequent artefacts. Advances in imaging techniques with adapted ultrasound probes and the use of magnetic resonance imaging (MRI) for equine lameness evaluation have revealed that distal sesamoidean ligament injuries are more frequently implicated in lameness than previously suspected.     

SCINTIGRAPHIC EVALUATION OF THE PROXIMAL METACARPAL AND METATARSAL REGIONS OF HORSES WITH PROXIMAL SUSPENSORY DESMITIS

The aim of the study was to characterize radiopharmaceutical uptake patterns in horses with clinical and ultrasonographic evidence of proximal suspensory desmitis. It was hypothesized that radiopharmaceutical uptake in the proximal palmar (plantar) aspect of the third metacarpal (metatarsal) bone would be greater in lame limbs of horses with proximal suspensory desmitis than in sound limbs and that there would be a positive correlation between the severity of ultrasonographic abnormalities and the degree of radiopharmaceutical uptake. Nuclear scintigraphic evaluation of the proximal metacarpal or metatarsal regions of 126 horses with ultrasonographic evidence of proximal suspensory desmitis was performed. In all horses lameness was substantially improved by perineural analgesia of the palmar metacarpal (subcarpal) or plantar metatarsal (subtarsal) nerves. Scintigraphic images were assessed subjectively, by profile analysis and using region of interest analysis. Associations between the degree of ultrasonographic abnormality and radiopharmaceutical uptake ratios and the presence of radiographic abnormalities and radiopharmaceutical uptake ratios were analyzed. Subjectively, the majority of horses had normal radiopharmaceutical uptake. Profile analysis provided little additional information. However with region of interest analysis there was greater radiopharmaceutical uptake ratios in plantar images in the proximal metatarsal regions of lame limbs compared with nonlame limbs. There was no association between radiological abnormalities and radiopharmaceutical uptake ratios. In forelimbs there was no association between ultrasonographic lesion grade and radiopharmaceutical uptake ratios, however in hindlimbs there was a significant relationship between ultrasonographic grade and radiopharmaceutical uptake ratios.     

Proximal suspensory desmitis: clinical, ultrasonographic and radiographic features

Clinical, ultrasonographic and radiographic features of proximal suspensory desmitis in the forelimb and the hindlimb are described. Acute cases may present with slight, localised, oedematous swelling, heat, distension of the medial palmar (plantar) vein and/or pain, whereas chronic cases or those rested immediately after onset of lameness usually have no detectable clinical signs suggestive of the source of pain. In these cases local analgesia is required to identify pain in the proximal metacarpal (metatarsal) region. Transverse ultrasonographic images of the suspensory ligament usually yield the most information and a variety of abnormalities of the proximal suspensory ligament have been identified including i) enlargement ii) poor definition of one or more of the margins of the suspensory ligament, especially dorsally iii) a well circumscribed, central hypoechoic area iv) one or more poorly defined hypoechoic areas, central or more peripheral v) a larger area of diffuse decrease in echogenicity (such lesions were seen most commonly in the hindlimb and appeared to warrant a more guarded prognosis than focal lesions). Radiographic abnormalities were identified in hindlimbs more often than in forelimbs and were usually seen in a dorsopalmar (dorsoplantar) view, and/or a lateromedial projection. Radiographic abnormalities included sclerosis of the trabeculae, a change in orientation of the trabeculae and entheseophyte formation. The most extensive radiographic abnormalities were seen together with an ultrasonographic type v lesion. The prognosis for return to full athletic function and sustained future soundness was better for forelimbs than hindlimbs, especially if the lesion, identified ultrasonographically, resolved.     

Distal splint bone fractures in the horse: an experimental and clinical study

An experimental and clinical study to investigate the aetiology of distal splint bone fractures is described. In vitro, extension of the fetlock did not appear to alter the position of the distal ends of the splint bones, although tension in the interosseous tendons increased. Flexion of the fetlock resulted in slight outward displacement of the distal ends of the splint bones. It is suggested that concurrent desmitis of the suspensory ligament can cause movement of the ends of the splint bones thus predisposing to a fatigue fracture. In a clinical study of 87 horses, 114 splint bone fractures were identified. In at least 70 per cent of horses, suspensory desmitis was present. Follow up information was available in 24 horses in which more than 80 per cent of the fractures healed spontaneously. Non-union fractures were not painful and did not cause lameness.     

Incomplete Longitudinal Fracture of the Proximal Palmar Cortex of the Third Metacarpal Bone in Horses

Seven horses, 2 to 4 years of age, were examined because of moderate-to-severe forelimb lameness, mild effusion of the middle carpal joint (3 horses), and pain on palpation of the origin of the suspensory ligament (4 horses). The lameness was abolished by anesthetic infiltration of the middle carpal joint in six horses. In four of them, a high palmar nerve block also abolished the lameness. A linear radiolucency in the proximal end of the third metacarpal bone (McIII) was interpreted as an incomplete longitudinal fracture. In one horse, distinct intramedullary sclerosis limited to the palmar cortex was indicative of an incomplete fracture confined to the palmar cortex. No osteoproliferative lesions were identified on the dorsal cortex of any of the horses. Surgical treatment with cortical screws in lag fashion accompanied by a rest period was successful in one horse. In four horses, rest for at least 3 months resulted in clinical soundness. In two horses, a shorter rest period resulted in recurrence of the lameness even though the horses were sound when put back into training. Careful clinical and radiographic examinations helped differentiate incomplete longitudinal fractures from lesions involving the carpus and proximal aspect of the suspensory ligament.     

Normal ultrasonographic anatomy and injury of the patellar ligaments in the horse

The purposes of this study were to investigate the ultrasonographic appearance of the patellar ligaments in clinically normal horses and to describe the clincical features, diagnosis and outcome of patellar ligament injury. The medial, middle and lateral patellar ligaments of 5 Thoroughbred and 5 Warmblood horses, free from lameness and in full work, were examined ultrasonographically. The ligaments were all of uniform echogenicity and each ligament was fairly consistent in its shape. The size of the ligaments of the Warmblood horses tended to be bigger than the lighter bodyweight Thoroughbred horses. The bone surfaces were smooth at the ligament insertions on the patella and tibia. Nine horses, including 7 showjumpers, were identified with a unilateral hindlimb lameness associated with ultrasonographic evidence of damage to one or more patellar ligaments. Four horses had primary desmitis of the middle patellar ligament, one of which had concurrent intermittent upward fixation of the patella and a second had abnormal movement of the patella. Two additional horses had desmitis of the middle patellar ligament associated with previous medial patellar desmotomy. Two horses had desmitis of both the middle and lateral patellar ligaments, and one horse had desmitis of the lateral patellar ligament alone. None of the 9 horses were able to return consistently to their former level of competition. Careful clinical evaluation and ultrasonographic examination of the patellar ligaments should be considered in horses with hindlimb lameness of otherwise undetermined cause.     

Treatment of chronic or recurrent proximal suspensory desmitis using radial pressure wave therapy in the horse

REASONS FOR PERFORMING STUDY: Proximal suspensory desmitis (PSD) is diagnosed with increasing frequency in horses and radial pressure wave therapy (RPWT) is a widely used therapy for painful orthopaedic conditions in man and dogs. There are, however, few published data as to the outcome of its use in PSD. OBJECTIVE: To evaluate the use of RPWT in the treatment of chronic or recurrent PSD in the horse, an injury which carries a poor prognosis for return to athletic function with conservative management alone. HYPOTHESIS: RPWT and controlled exercise improves the prognosis of chronic or recurrent PSD in the horse when compared to previously published results of controlled exercise alone. METHODS: The use of RPWT in the management of chronic or recurrent proximal suspensory desmitis (PSD) was evaluated in 65 horses. Diagnosis was based on response to local analgesia, ultrasonography and radiography. Horses were classified according to severity of ultrasonographic lesions, whether fore- or hindlimbs were affected, and duration of lameness prior to diagnosis. Horses were treated 3 times at 2-week intervals and followed a controlled exercise programme; they were reassessed clinically and ultrasonographically 10-12 weeks after diagnosis, when further exercise recommendations were made dependent upon the animal's progress. RESULTS: Forty-one percent of horses with hindlimb lameness and 53% with forelimb lameness were nonlame and returned to full work 6 months after diagnosis. The prognosis was significantly affected by the ultrasonographic grade at the time of diagnosis and by ultrasonographic evidence of resolution of the lesion in hindlimb cases. CONCLUSIONS: These findings, when compared to previously published results of treatment using controlled exercise alone, suggest that RPWT improves the prognosis for PSD in the hindlimb. POTENTIAL RELEVANCE: RPWT is a useful treatment modality for chronic or recurrent PSD when combined with controlled exercise. Further studies are required on the effect of RPWT employing histology and biomechanics in order to fully evaluate its use on equine tissues.     

Ultrastructural and immunocytochemical evaluation of the effects of extracorporeal shock wave treatment in the hind limbs of horses with experimentally induced suspensory ligament desmitis

OBJECTIVE: To evaluate the effects of extracorporeal shock wave therapy (ESWT) on affected ligaments in the hind limbs of horses with experimentally induced suspensory ligament desmitis by use of ultrasonographic, ultrastructural, and immunocytochemical techniques. ANIMALS: 10 horses. PROCEDURE: Suspensory ligament desmitis was induced in both hind limbs of each horse by use of 2 collagenase injections (administered 2 weeks apart) in each suspensory ligament. Two weeks after the second injection, the right hind limb of each horse was treated with ESWT (3 treatments at 3-week intervals); the left hind limb was not treated (control limb). Periodically during the study, the healing process was monitored ultrasonographically and the proportions of ligaments affected with lesions were assessed. Four weeks after the last ESWT treatment, biopsy specimens were collected from all ligaments for ultrastructural evaluation and immunocytochemical analysis of transforming growth factor beta-1. RESULTS: The difference in the proportion of the lesion-affected ligament between ESWT-treated and control limbs was significant (P < 0.05) from 3 weeks after the second ESWT treatment to the end of the study. Compared with control ligaments, ESWT-treated ligaments had more small, newly formed collagen fibrils and greater expression of transforming growth factor beta-1 4 weeks after the last ESWT treatment was administered. CONCLUSIONS AND CLINICAL RELEVANCE: Results have indicated that ESWT appears to facilitate the healing process in horses with experimentally induced hind limb suspensory ligament desmitis.     

MRI FINDINGS IN 232 HORSES WITH LAMENESS LOCALIZED TO THE METACARPO(TARSO)PHALANGEAL REGION AND WITHOUT A RADIOGRAPHIC DIAGNOSIS

Two hundred and thirty‐two horses with lameness localized to the metacarpo(tarso)phalangeal (MCP/MTP) region without a radiographic diagnosis were evaluated. All horses had high‐field magnetic resonance (MR) imaging of the MCP/MTP region performed for the lame limb and the contralateral limb for comparison. There were 46 horses that had bilateral abnormalities in the forelimbs; 27 of these horses were not lame in the contralateral limb at the time of examination. Bilateral hind limb abnormalities were observed in 37 horses; 22 horses were not lame in the contralateral limb. Soft tissue abnormalities alone were observed in 218 limbs (162 horses). Subchondral bone and articular cartilage abnormalities alone were observed in 43 limbs (34 horses). A combination of soft tissue, subchondral bone, and cartilage abnormalities were observed in 64 limbs (36 horses). The distribution of primary abnormalities was as follows; oblique distal sesamoidean ligament desmitis (73 limbs in 56 horses), straight distal sesamoidean ligament desmitis (44 limbs in 38 horses), chronic subchondral bone injuries (15 limbs in 12 horses), suspensory ligament branch desmitis (14 limbs in 12 horses), collateral ligament desmitis (12 limbs in 12 horses), tendonitis of the superficial and deep digital flexor tendons (10 limbs in 10 horses), osteochondral defects greater than 1 cm (nine limbs in six horses), osteochondral defects less than 1 cm (eight limbs in seven horses), bone marrow lesions (six limbs in five horses), intersesamoidean ligament desmitis (five limbs in four horses). MR imaging is useful in diagnosing bone and soft tissue injuries when radiographs and ultrasound fail to yield a diagnosis.     

MRI FEATURES OF METACARPO(TARSO)PHALANGEAL REGION LAMENESS IN 40 HORSES

Lameness originating from the metacarpo(tarso)phalangeal (MP) joint has a significant effect on the use and athletic competitiveness of a horse. The identification of the cause of lameness originating from the MP joint can be challenging, given the limitations of radiography, ultrasonography, and nuclear scintigraphy. Our purpose was to describe the injury types and incidence in magnetic resonance imaging (MRI) studies from 40 horses with lameness attributable to the MP joint region where it was not possible to reach a clinically plausible diagnosis using other imaging modalities. Horses were examined in a 1.5 T magnet (Siemens Medical Solutions) under general anesthesia. The frequency of occurrence of MR lesions was subchondral bone injury (19), straight or oblique distal sesamoidean desmitis (13), articular cartilage injury and osteoarthritis (eight), suspensory branch desmitis (seven), osteochondral fragmentation (seven), proximal sesamoid bone injury (seven), intersesamoidean desmitis (four), deep digital flexor tendonitis (four), collateral desmitis (three), superficial digital flexor tendonitis (two), enostosis‐like lesions of the proximal phalanx or MCIII (two), desmitis of the palmar annular ligament (one), desmitis of the proximal digital annular ligament (one), and dystrophic calcification of the lateral digital extensor tendon (one). Twenty‐five horses had multiple MR abnormalities. MRI provided information that was complementary to radiography, ultrasonography, and nuclear scintigraphy and that allowed for a comprehensive evaluation of all structures in the MP joint region and a diagnosis in all 40 horses.     

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.     

Histological Changes in the Deep Branch of the Lateral Palmar Nerve of Horses With Induced Proximal Suspensory Desmitis

Desmitis of the proximal aspect of the suspensory ligament, or interosseus medius muscle, of the pelvic or thoracic limb is a commonly diagnosed cause of lameness of performance horses. Despite medical treatments available for horses with proximal suspensory desmitis (PSD), most horses treated medically for PSD of a pelvic limb remain persistently lame; this persistent lameness may be the result of a neuropathy caused by compression of nerves by an enlarged suspensory ligament. Few horses with PSD of a thoracic limb remain persistently lame. Based on the results of reports citing successful treatment of horses chronically lame because of PSD of a pelvic or thoracic limb, by excising a portion of the deep branch of the lateral plantar or palmar nerve (DBLPlN/DBLPaN), we theorized that persistent lameness of horses caused by PSD of a thoracic limb may also be due to compression of nerves that supply the ligament. The aim of this study was to determine if histological signs of compression neuropathy of the DBLPaN are present in horses with PSD in a thoracic limb. To test this hypothesis, we induced PSD by instilling collagenase into the ligament and then examined the DBLPaN after harvesting this nerve 2 months later. We found that the DBLPaNs of all treated limbs showed histologic changes suggestive of nerve compression. We conclude that studies examining the DBLPaN of horses with naturally occurring PSD for histological evidence of neuropathy are warranted.     

Treatment of chronic proximal suspensory desmitis in horses using focused electrohydraulic shockwave therapy

The objective of the present clinical report was to investigate the short- and long-term outcomes of chronic proximal suspensory desmitis (PSD) treated with Extracorporeal Shockwave Treatment (ESWT). Fifty-two horses with chronic PSD in the forelimb (34 cases) or hindlimb (22 cases) were included in the study. Three horses had lesions in both hindlimbs and one in both forelimbs. The origin of the suspensory ligament was treated every three weeks for a total of three treatments using 2000 impulses applied by a focused ESWT device (Equitron) at an energy flux density of 0.15 mJ/ mm2. This treatment regime was followed by box rest and a controlled exercise program of 12 weeks duration. The horses were assessed 3, 6, 12, 24 weeks and one year after the first treatment. Of the 34 cases with forelimb PSD, 21 (61.8%) had returned to full work by six months after diagnosis and 19 cases (55.9%) were still in full work one year after ESWT. Of the 22 horses with hindlimb PSD, 9 (40.9%) had returned to full work by six months and 4 (18.2%) were still in full work one year after diagnosis. There was no association (chi-square test) between the outcome and the severity of the initial ultrasonographic and/or radiographic findings. Compared with the results of other clinical studies, these findings suggest that in horses with PSD of fore- and hindlimb, the prognosis for returning to full work six months after diagnosis can be improved when ESWT and a controlled exercise program are used. However, a high rate of recurrence occurred in the hindlimb despite treatment.