M. Schramme

Lameness associated with foot pain: results of magnetic resonance imaging in 199 horses (January 2001‐December 2003) and response to treatment

REASONS FOR PERFORMING STUDY The diagnosis of foot-related lameness often remains elusive and it can be difficult to offer rational treatment, or to predict outcome. OBJECTIVES To describe the spectrum of injuries of the foot identified using magnetic resonance imaging (MRI), to determine their relative prevalence among MRI diagnoses and to establish the long-term results of treatment. METHODS The MR images of horses examined from January 2001--December 2003 were reviewed. Horses were selected for MRI if the pain causing lameness was localised to the foot using perineural analgesia but any clinical, radiological or ultrasonographic abnormalities were insufficient to explain the degree of lameness. The clinical significance of lesions identified using MRI was determined with reference to the results of local analgesia, radiography, ultrasonography and nuclear scintigraphy. Follow-up information was obtained in January 2004 for horses which had been examined 6-36 months previously and the outcome classified as excellent (horse returned to full athletic function without recurrent lameness), moderate (sound, but only in light work), or poor (persistent or recurrent lameness). RESULTS One hundred and ninety-nine horses underwent MRI examinations. Deep digital flexor (DDF) tendonitis was the most common injury (59%) with primary injury in 65 horses (33%) and a further 27 horses (14%) having lesions of the DDF tendon and navicular bone. Seventeen percent of horses had injuries to multiple structures, including 24 with DDF tendonitis. Desmitis of a collateral ligament (CL) of the distal interphalangeal (DIP) joint was the second most common injury (62 horses, 31%), with primary injuries in 30 horses (15%) and a further 32 horses (16%) that had CL desmitis in conjunction with other injuries. Prognosis was best for horses with traumatic injuries of the middle or distal phalanges, with 5 of 7 horses (71%) having an excellent outcome. Horses with primary lesions of the DDF tendon or CL of the DIP joint had excellent results in only 13 of 47 (28%) and 5 of 17 horses (29%), respectively. Horses with combined injuries of the DDF tendon and navicular bone, or primary navicular bone abnormalities, had a poor outcome, with the majority of horses suffering persistent lameness. CONCLUSIONS A wide variety of lesions associated with foot pain were identified using MRI, a high proportion of which were primary soft tissue injuries with a guarded prognosis for return to full athletic function. POTENTIAL RELEVANCE It is now possible to propose more rational treatment strategies for the variety of foot injuries identified using MRI than had previously been possible; however, further information concerning aetiopathogenesis of these injuries is needed to improve their management.

Magnetic resonance imaging of the equine foot: 15 horses

REASONS FOR PERFORMING STUDY Foot pain is a common cause of equine lameness and there have been significant limitations of the methods available for the diagnosis of the causes of foot pain (radiography, nuclear scintigraphy and ultrasonography). Until recently, magnetic resonance imaging (MRI) in the horse has been limited to examination of cadaver limbs. OBJECTIVES Our purpose was to 1) describe MRI of the foot in live horses, 2) describe MRI findings in horses with foot pain in which a definitive diagnosis could not be established by alternative means and 3) correlate MRI findings with other methods of clinical investigation. METHODS The feet of 15 horses with unilateral (12) or bilateral (3), forelimb (14) or hindlimb (1) lameness associated with foot pain of previously ill-defined origin were examined using MRI. The horses were examined in right lateral recumbency under general anaesthesia, with the feet positioned in the isocentre of a flared end 1.5 Tesla GE Signa Echospeed magnet. Images were obtained in sagittal, transverse and dorsal planes using 3-dimensional (3D) T2* gradient echo (GRE), spoiled gradient echo, fat-saturated 3D T2* GRE and short inversion recovery sequences. Image acquisition took approximately 1 h. RESULTS Abnormalities of the distal interphalangeal joint (DIP) cartilage and/or subchondral bone, periarticular osteophyte formation, distension of the DIP joint capsule with or without synovial proliferation, distension of the navicular bursa with or without evidence of chronic inflammation, surface and core lesions in the deep digital flexor tendon, abnormal signal within the navicular bone, evidence of mineralised fragments in the distal sesamoidean impar ligament, irregular outline of and signal in the medial cortex of the distal phalanx, and an abnormal signal on the dorsal aspect of the distal phalanx consistent with laminitis were identified. CONCLUSIONS MRI permits the diagnosis of a variety of lesions involving different structures within the foot that cannot be diagnosed using other means, thus enhancing our knowledge of the causes of foot pain. POTENTIAL RELEVANCE With further experience it is likely that lesions involving other structures will also be identified. Long-term follow-up data is required to determine the prognosis for the injuries described.

Lameness in 46 horses associated with deep digital flexor tendonitis in the digit: diagnosis confirmed with magnetic resonance imaging

REASONS FOR PERFORMING STUDY The differential diagnosis of foot pain has long proved difficult and the use of magnetic resonance imaging (MRI) offers the opportunity to further the clinical understanding of the subject. OBJECTIVES To determine the incidence of deep digital flexor tendon (DDFT) injuries in a series of 75 horses with lameness associated with pain localised to the digit, with no significant detectable radiographic or ultrasonographic abnormalities, using MRI; and to describe a variety of lesion types and relate DDF tendonitis with anamnesis, clinical features, response to local analgesic techniques and nuclear scintigraphic and ultrasonographic findings. METHODS All horses undergoing MRI of the front feet between January 2001 and October 2002 were reviewed and those with DDFT injuries categorised according to lesion type; horses with primary tendonitis (Group I) and those with concurrent abnormalities of the navicular bone considered to be an important component of the lameness (Group II). The response to perineural analgesia of the palmar digital nerves and palmar (abaxial sesamoid) nerves, intra-articular analgesia of the distal interphalangeal (DIP) joint and analgesia of the navicular bursa were reviewed. The result of ultrasonography of the pastern and foot was recorded. Lateral, dorsal and solar pool and bone phase nuclear scintigraphic images were assessed subjectively and objectively using region of interest (ROI) analysis. RESULTS Forty-six (61%) of 75 horses examined using MRI had lesions of the DDFT considered to be a major contributor to lameness. Thirty-two horses (43%) had primary DDFT injuries and 14 (19%) a combination of DDF tendonitis and navicular bone pathology. Lesions involved the insertional region of the tendon alone (n = 3), were proximal to the navicular bone (n = 23) or were at a combination of sites (n = 20). Lesion types included core lesions, focal and diffuse dorsal border lesions, sagittal plane splits, insertional injuries and lesions combined with other soft tissue injuries. Many horses had a combination of lesion types. Lameness was abolished by palmar digital analgesia in only 11 of 46 horses (24%). Twenty-one of 31 horses (68%) in Group I showed > 50% improvement in lameness after intra-articular analgesia of the DIP joint, whereas 11 of 12 horses (92%) in Group II had a positive response. Twelve of 18 horses (67%) in Group I had a positive response to analgesia of the navicular bursa. Nineteen horses had lesions of the DDFT extending proximal to the proximal interphalangeal joint seen using MRI, but these were identified ultrasonographically in only 2 horses. Scintigraphic abnormalities suggestive of DDFT injury were seen in 16 of 41 horses (41%), 8 in pool phase images and 8 in bone phase images. CONCLUSIONS AND POTENTIAL RELEVANCE DDFT injuries are an important cause of lameness associated with pain arising from the digit in horses without detectable radiographic abnormalities. Lameness is not reliably improved by palmar digital analgesia, but may be improved by intra-articular analgesia of the DIP joint in at least 68% of horses. Ultrasonography is not sensitive in detecting lesions of the DDFT in the distal pastern region, but a combination of pool and bone phase scintigraphic images of the digit is helpful in some horses. Further follow-up information is required to determine the prognosis for horses with lesions of the DDFT in the digit and to establish whether this is related to lesion severity and/or location.

Collateral desmitis of the distal interphalangeal joint in 18 horses (2001–2002)

REASONS FOR PERFORMING STUDY There have been no previously published case series of horses examined using either scintigraphy or MRI to diagnose collateral ligament injuries not detectable using ultrasonography or radiography, nor have other concurrent soft tissue lesions been described. OBJECTIVES To describe the clinical features of horses with desmitis of the collateral ligaments of the distal interphalangeal (DIP) joint and to evaluate the results of radiographic, ultrasonographic, scintigraphic and magnetic resonance imaging (MRI) examinations. METHODS Horses were examined between January 2001 and January 2003 and were selected for inclusion in the study if there was unequivocal evidence of collateral desmitis of the DIP joint based on ultrasonography or MRI. Subject details, case history, results of clinical examination and responses to local analgesic techniques were reviewed. The results of radiographic, ultrasonographic, scintigraphic and MRI examinations were assessed. RESULTS Eighteen horses were identified with desmitis of a collateral ligament of the DIP joint, 3 horses (Group 1) based on ultrasonography alone, 7 (Group II) with positive ultrasonographic and magnetic resonance images and 8 (Group III) with no lesion detectable using ultrasonography, but lesions identified using MRI. Seventeen horses had forelimb injuries and one a hindlimb injury. The medial collateral ligament was injured most frequently (13 horses). In the majority of horses, no localising clinical signs were seen. Lameness was invariably worse in circles compared with straight lines. Lameness was improved by palmar digital analgesia in 16 horses (87%), but only 6 were nonlame. Intra-articular analgesia of the DIP joint produced improvement in lameness in 6/15 horses (40%). In 16 horses, no radiographic abnormality related to the DIP joint or collateral ligament attachments was identified. Eight of 14 horses (57%) had focal, moderately or intensely increased radiopharmaceutical uptake (IRU) at the site of insertion of the injured collateral ligament on the distal phalanx. Alteration in size and signal in the injured collateral ligament was identified using MRI. In addition, 5 horses had abnormal mineralisation and fluid in the distal phalanx at the insertion of the ligament. Eleven horses had concurrent soft tissue injuries involving the deep digital flexor tendon, distal sesamoidean impar ligament, navicular bursa or collateral ligament of the navicular bone. CONCLUSIONS AND POTENTIAL RELEVANCE Collateral desmitis of the DIP joint should be considered as a cause of foot lameness. Although some injuries are detectable ultrasonographically, false negative results occur. Focal IRU at the ligament insertion on the distal phalanx may be indicative of injury in some horses. MRI is useful for both characterisation of the injury and identification of any concurrent injuries. Further follow-up information is required to determine factors influencing prognosis.