Is there an association between ossification of the cartilages of the foot and collateral desmopathy of the distal interphalangeal joint or distal phalanx injury?

Reasons for performing study: Associations between degree of ossification of the cartilages of the foot and injuries to other structures of the foot have been suggested, but have not been investigated by large scale studies. Objectives: To describe the frequency of grade >3 ossification of the cartilages of the foot (possibly significant ossification, PSO), mediolateral symmetry of ossification and left‐right symmetry between feet; and to investigate associations between PSO and injury of either the collateral ligaments (CLs) of the distal interphalangeal (DIP) joint or the distal phalanx. Hypotheses: Possibly significant ossification of the cartilages of the foot is associated with CL and distal phalanx injury. Distal phalanx injury is associated with a mediolateral difference in ossification grade of ≥2. Methods: Horses were examined for lameness localised to the foot by perineural analgesia, and underwent radiographic and magnetic resonance imaging examinations. Age, breed, occupation, duration of lameness, lame(st) limb, primary cause of lameness, and presence or absence of CL injury were recorded. Dorsopalmar (dorsoplantar) radiographs were examined and ossification of the cartilages of the foot graded using a modification of a previously published scale. Results: One foot from each of 462 horses was included for analysis. There was left‐right symmetry of ossification between feet, and significant association between grades of each foot, with lateral ≥medial cartilages. Possibly significant ossification occurred in the maximally ossified cartilage in 59 (12.8%) feet. There were significant associations between PSO of the maximally ossified cartilage of the foot and injuries of both the CLs of the DIP joint and the distal phalanx. There was no association between distal phalanx injury and marked asymmetry of the ossified cartilages of the foot. Conclusions and clinical relevance: Extensively ossified cartilages of the foot are significantly associated with CL or distal phalanx injury. Markedly asymmetric ossification did not increase the likelihood of distal phalanx injury and should be considered at a prepurchase examination.     

INJURY OF THE COLLATERAL LIGAMENTS OF THE DISTAL INTERPHALANGEAL JOINT DIAGNOSED BY MAGNETIC RESONANCE

We describe the clinical, imaging, and necropsy findings of two horses with severe injury of the collateral ligaments of the distal interphalangeal (DIP) joint diagnosed using magnetic resonance (MR) imaging. In MR images it was possible to examine the collateral ligaments of the DIP joint from the origin at the middle phalanx to the insertion on the distal phalanx. Both horses in this report had abnormal high signal intensity within the collateral ligaments of the DIP joint, and one horse had abnormal high signal intensity within the bone of the distal phalanx on short tau inversion recovery (STIR) and T2-weighted imaging sequences. High signal intensity on STIR and T2-weighted images represents abnormal fluid accumulation indicative of inflammation, within ligament, tendon, or bone on these imaging sequences. Abnormalities were confirmed on necropsy in both horses. Injury of the collateral ligaments of the DIP joint should be considered as a source of pain in horses with lameness localized to the foot.     

Arthroscopically assisted arthrodesis of the distal interphalangeal joint with transarticular screws inserted through a dorsal hoof wall approach in a horse

CASE DESCRIPTION: A 16-year-old Thoroughbred gelding was examined because of chronic right forelimb lameness. CLINICAL FINDINGS: On radiographs of the right front foot, the distal interphalangeal (DIP) joint space was narrow, and osteophytes and periarticular bony proliferation indicative of severe osteoarthritis were seen. Arthrodesis of the right DIP joint was recommended to improve the horse's comfort on the limb. TREATMENT AND OUTCOME: The horse was anesthetized, and palmar and dorsal arthroscopic approaches were used to remove as much of the articular cartilage as was accessible. Holes were then drilled through the dorsal aspect of the hoof wall, and 3 transarticular, 5.5-mm cortical screws were placed in lag fashion through these holes across the distal phalanx and into the middle phalanx. Defects in the hoof wall were filled with gentamicin-impregnated polymethyl methacrylate plugs and sealed with cyanoacrylate. Eight months after surgery, fusion of the DIP joint was evident radiographically and the horse was sound at a walk. CLINICAL RELEVANCE: Transarticular placement of cortical screws through a dorsal hoof wall approach combined with arthroscopically guided cartilage removal can result in fusion of the DIP joint in horses.     

Histopathology in horses with chronic palmar foot pain and age-matched controls. Part 1: Navicular bone and related structures

REASONS FOR PERFORMING STUDY: Causes of palmar foot pain and the aetiopathogenesis of navicular disease remain poorly understood, despite the high incidence of foot-related lameness. HYPOTHESES: Abnormalities of the collateral sesamoidean ligaments (CSLs), distal sesamoidean impar ligament (DSIL), deep digital flexor tendon (DDFT), navicular bone, navicular bursa, distal interphalangeal (DIP) joint or collateral ligaments (CLs) of the DIP joint may contribute to palmar foot pain. METHODS: Feet were selected from horses with a history of unilateral or bilateral forelimb lameness of at least 2 months' duration that was improved by perineural analgesia of the palmar digital nerves, immediately proximal to the cartilages of the foot (Group 1, n = 32); or from age-matched control horses (Group 2, n = 19) that were humanely destroyed for other reasons and had no history of forelimb foot pain. Eight units of tissue were collected for histology: the palmar half of the articular surface of the distal phalanx, including the insertions of the DDFT and DSIL; navicular bone and insertion of the CSLs; DDFT from the level of the proximal interphalangeal (PIP) joint to 5 mm proximal to its insertion; synovial membrane from the palmar pouch of the DIP joint and the navicular bursa; CLs of the DIP joint and DSIL. The severity of histological lesions for each site were graded. Results were compared between Groups 1 and 2. RESULTS: There was no relationship between age and grade of histological abnormality. There were significant histological differences between groups for lesions of the flexor aspect, proximal and distal borders, and medulla of the navicular bone; the DSIL and its insertion and the navicular bursa; but not for lesions of the CSLs, the dorsal aspect of the navicular bone, distal phalanx and articular cartilage, synovium or CLs of the DIP joint. CONCLUSIONS: Pathological abnormalities in lame horses often involved not only the navicular bone, but also the DSIL and navicular bursa. Abnormalities of the navicular bone medulla were generally only seen dorsal to lesions of the FFC. POTENTIAL RELEVANCE: Adaptive and reactive change may be occurring in the navicular apparatus in all horses to variable degrees and determination of the pathogenesis of lesions that lead to pain and biomechanical dysfunction should assist specific preventative or treatment protocols.     

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.     

Effect of contact stress in bones of the distal interphalangeal joint on microscopic changes in articular cartilage and ligaments

OBJECTIVE: To examine articular cartilage of the distal interphalangeal (DIP) joint and distal sesamoidean impar ligament (DSIL) as well as the deep digital flexor tendon (DDFT) for adaptive responses to contact stress. SAMPLE POPULATION: Specimens from 21 horses. PROCEDURE: Pressure-sensitive film was inserted between articular surfaces of the DIP joint. The digit was subjected to a load. Finite element models (FEM) were developed from the data. The navicular bone, distal phalanx, and distal attachments of the DSIL and DDFT were examined histologically. RESULTS: Analysis of pressure-sensitive film revealed significant increases in contact area and contact load at dorsiflexion in the joints between the distal phalanx and navicular bone and between the middle phalanx and navicular bone. The FEM results revealed compressive and shear stresses. Histologic evaluation revealed loss of proteoglycans in articular cartilage from older horses (7 to 27 years old). Tidemark advancement (up to 14 tidemarks) was observed in articular cartilage between the distal phalanx and navicular bone in older clinically normal horses. In 2 horses with navicular syndrome, more tidemarks were evident. Clinically normal horses had a progressive increase in proteoglycans in the DSIL and DDFT. CONCLUSIONS AND CLINICAL RELEVANCE: Load on the navicular bone and associated joints was highest during dorsiflexion. This increased load may be responsible for microscopic changes of tidemark advancement and proteoglycan depletion in the articular cartilage and of proteoglycan production in the DSIL and DDFT Such microscopic changes may represent adaptive responses to stresses that may progress and contribute to lameness.     

Diagnostic analgesia of the equine digit

Analgesia usually occurs within 5 min after administration of local anaesthetic solution into joints or around nerves in the distal portion of the limb. Gait should be assessed within 10 min after diagnostic regional analgesia of the distal portion of the limb because rapid diffusion of anaesthetic solution can result in anaesthesia of other nerve branches, thus confusing results of the examination. A palmar digital nerve block (PDNB) anaesthetises most of the foot, including the distal interphalangeal (DIP) joint (coffin joint), rather than just the palmar half of the foot, as was once commonly believed. To avoid partially anaesthetising the proximal interphalangeal joint (pastern joint), the palmar digital nerves should be anaesthetised near or distal to the proximal margin of the collateral cartilages. Clinicians should be aware that an abaxial sesamoid nerve block (ASNB) may ameliorate or abolish pain within the metacarpo/metatarso‐phalangeal joint (fetlock joint). Mepivacaine administered into the DIP joint desensitises the DIP joint and probably the palmar digital nerves to also cause anaesthesia of the navicular bursa, the navicular bone, the toe region of the sole, the digital portion of the deep digital flexor tendon (DDFT) and the distal portions of the collateral ligaments of the DIP joint. When a large volume of mepivacaine HCl (e.g. 10 ml) is administered, the heel region of the sole may also be desensitised. Only a small percentage of horses with disease of the collateral ligament(s) of the DIP joint show a significant improvement in lameness after intra‐articular analgesia of the DIP joint, and no horse is likely to improve after intrabursal analgesia of the navicular bursa. A PDNB, however, improves lameness substantially in most horses that are lame because of disease of the collateral ligament(s) of the DIP joint, and all affected horses are likely to become sound after an abaxial sesamoid nerve block. The degree of improvement in lameness associated with injury to one or both collateral ligaments of the DIP joint after PDNB is determined by the extent of the injury and the level at which the palmar digital nerves are anaesthetised. The further proximal the level of the injury within the collateral ligament, the less likely that lameness is ameliorated by analgesia of the DIP joint or a PDNB. Verschooten's technique appears to be the most accurate technique for centesis of the navicular bursa. Even though analgesia of the DIP joint results in analgesia of the navicular bursa, analgesia of the navicular bursa does not result in analgesia of the DIP joint. Pain arising from the DIP joint can probably be excluded as a cause of lameness when lameness is attenuated by analgesia of the navicular bursa. Analgesia of the digital flexor tendon sheath (DFTS) is likely to desensitise only structures that are contained within or border on the sheath itself (i.e. the superficial and deep digital flexor tendons, the straight and oblique distal sesamoidean ligaments, the annular ligaments of the fetlock and pastern, and the portion of the DDFT that lies within the foot). Because lameness caused by disease of the DDFT within the foot may fail to improve appreciably after analgesia of the palmar digital nerves, the DIP joint, or the navicular bursa, a portion of the DDFT within the foot and distal to the DFTS probably receives its sensory supply from more proximal deep branches of the medial and lateral palmar digital nerves that enter the DFTS. Performing intrathecal analgesia of the DFTS on horses with lameness that is unchanged after anaesthesia of the palmar digital nerves but resolves after an ASNB, may be useful in localising lameness to that portion of the DDFT that lies within the foot. Resolution of lameness after intrathecal analgesia of the DFTS justifies suspicion of a lesion within the digital portion of the DDFT or within structures contained within the DFTS. The belief that concurrent or sequential intra‐articular administration of medication substantially increases the risk of joint infection or that inflammation caused by the local anaesthetic solution may dampen the therapeutic response to intra‐articular medication appears to be unfounded.     

RADIOGRAPHIC APPEARANCE OF THE NAVICULAR BONE AND DISTAL INTERPHALANGEAL JOINT AND THEIR RELATIONSHIP WITH OSSIFICATION OF THE COLLATERAL CARTILAGES OF THE DISTAL PHALANX IN FINNHORSE CADAVER FOREFEET

Radiographic findings in the navicular bone and distal interphalangeal joint as well as the ossification status of the collateral cartilages of the distal phalanx were evaluated in 100 Finnhorse cadaver forefeet. The most common shapes of the proximal articular margin of the navicular bone were convex and straight. Remodeling of the navicular bone was common, especially on the lateral extremity. No bony fragments were identified at the distal flexor margin even though this area appeared irregular in several feet. Several large, rounded or lollipop-shaped synovial invaginations were identified in only six feet. The thickness of the flexor cortex varied considerably, and the corticomedullary junction was uni- or bilaterally indistinct in nine feet. The shape of the sagittal ridge of the flexor cortex was commonly flat but varied. It appeared locally irregular or indistinct in 17 feet, but changes elsewhere along the flexor cortex were rare. Osteophytosis on the dorsal and palmar margins of the distal interphalangeal joint and entheseophytosis on the dorsal aspect of the middle phalanx and on the extensor process of the distal phalanx were common. "Possibly significant" ossification of the collateral cartilages (high side-bones or separate centers of ossification) was present in 36 feet; all grades of ossification in the proximal/ palmaroproximal direction as well as palmar ossification were seen. A statistically significant relationship was found between entheseophytosis on the proximal flexor margin of the navicular bone and "possibly significant" ossification. Osteophytosis on the palmarodistal margin of the middle phalanx was more common in feet with a relatively long distal phalanx, suggestive of palmar ossification. Radiographic changes in the navicular bone or in the distal interphalangeal joint did not otherwise appear to be associated with ossification of the collateral cartilages of the distal phalanx in Finnhorses.     

Use of standing low‐field magnetic resonance imaging to diagnose middle phalanx bone marrow lesions in horses

Bone marrow lesions (BMLs) (also known as ‘bone bruises’, ‘bone oedema’, ‘bone contusions’ and ‘occult fractures’) within the middle phalanx were diagnosed by standing low field magnetic resonance imaging (MRI) in 7 horses. The lesions were characterised by low signal intensity on T1‐ and T2*‐weighted gradient echo sequences, mildly increased signal intensity on T2 fast spin echo sequences, and high signal intensity on short tau inversion recovery (STIR) sequences. Four distinct patterns of abnormal signal were identified: BML associated with osteoarthritis of either the proximal or distal interphalangeal joints; BML associated with soft tissue injury; BML associated with acute trauma; and BML unassociated with any other injury or lameness (assumed to represent bone response to biomechanical stress). Repeat MRI was undertaken in 4 cases. In most cases the BML resolved with rest and time, although lameness was persistent in 2 horses (one of which had an associated osteoarthritis of the proximal interphalangeal joint).     

Chronic proliferative synovitis of the equine metacarpophalangeal joint

Chronic proliferative synovitis of 27 metacarpophalangeal joints in 16 horses is described. The diagnosis was based on a history of lameness and, or, poor performance, pain on flexion of the metacarpophalangeal joint, the response to intra-articular anaesthesia, and plain and contrast radiography. Radiographic findings included concavity of the distal dorsal metacarpus proximal to the sagittal ridge, and an increase in size of the synovial tissue adjacent to the proximal, dorsal attachment of the joint capsule. Mineralisation of the synovial tissue was present in some joints, and chip fractures from the dorsal aspect of the proximal phalanx were also occasionally seen. Treatment by arthroscopic resection of the tissue gave excellent results.     

Osseous abnormalities associated with collateral desmopathy of the distal interphalangeal joint: Part 1

Reasons for performing study: Osseous abnormalities. associated with collateral ligament (CL) injury of the distal interphalangeal (DIP) joint have been documented using magnetic resonance imaging (MRI) but there is currently limited information about the frequency of osseous pathology associated with CL injury. Objectives: To determine the frequency of occurrence of osseous abnormality coexistent with CL injury of the DIP joint and describe the distribution and character of osseous lesions; and to establish if there was an association between osseous abnormality and increased radiopharmaceutical uptake (IRU). Hypotheses: There would be a higher incidence of osseous abnormality at the insertion of an injured CL than at the origin; and a relationship between the presence of osseous abnormality and duration of lameness. Materials and methods: Magnetic resonance images of 313 feet of 289 horses with foot pain and a definitive diagnosis of collateral desmopathy of the DIP joint were analysed retrospectively for presence and type of osseous abnormality in the middle and distal phalanges. Scintigraphic images were examined and the presence of IRU in the middle or distal phalanges recorded. Results: Osseous abnormalities were detected in 143 (45.7%) feet, 27 (18.8%) of which had osseous and CL injury alone, while the remaining 116 had CL related osseous injury and multiple injuries within the hoof capsule. Entheseous new bone and endosteal irregularity of the middle and distal phalanges were the most frequent types of osseous abnormality. There was a higher incidence of osseous abnormalities medially than laterally and at the ligament insertion than at the origin. There was a significant association between presence of IRU and osseous injury. Conclusions: A variety of osseous lesions of differing severity are associated with CL injury. Normal radiopharmaceutical uptake does not preclude significant osseous pathology associated with CL injury. Clinical relevance: Further studies are necessary in order to determine if osseous abnormalities associated with CL injury influence prognosis for return to performance.     

Pedal bone fractures

Fractures of the pedal bone are usually the result of direct trauma, and are relatively commonly encountered in equine practice. Either front or hind feet may be affected. Seven distinct fracture types are recognised. Type I fractures involve the palmar/plantar process and do not enter the distal interphalangeal (DIP) joint. Type II fractures are oblique or parasagittal fractures that are articular but are not on the midline. Type III fractures are midline articular fractures that bisect the pedal bone into 2 equal halves. Type IV fractures involve the extensor (pyramidal) process of the pedal bone. Type V fractures are comminuted and split the pedal bone into multiple fragments. Type VI fractures are solar margin fractures. Type VII fractures are exclusive to foals and are also fractures of the solar margin. In most cases the onset of clinical signs is acute. The diagnosis is usually achieved by radiography, although computed tomography or magnetic resonance imaging can be helpful in some cases. Treatment options include surgical and nonsurgical therapies. The prognosis for articular fractures (Types II and III) is worse than for nonarticular fractures (Types I, IV, VI and VII) because of the likelihood of osteoarthritis within the DIP joint. Nonarticular fractures carry a good prognosis if a long enough convalescence is undertaken. Comminuted fractures (Type V) carry a poor, but not hopeless, prognosis.     

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.     

Verification of scintigraphic imaging for injury diagnosis in 264 horses with foot pain

REASONS FOR PERFORMING STUDY: Nuclear scintigraphy is commonly used as a diagnostic aid for foot pain, but there is limited information about different patterns of radiopharmaceutical uptake (RU) and their correlation with the results of other imaging modalities. OBJECTIVES: To describe patterns of RU in horses with foot pain. MATERIALS AND METHODS: Scintigraphic images of the feet of 264 horses with front foot pain were analysed subjectively and using region of interest analysis. Magnetic resonance images of all feet were analysed prospectively; the navicular bones were reassessed retrospectively and assigned a grade. A Spearman rank correlation test was used to test for a relationship between the scintigraphic grade of the navicular bone and magnetic resonance imaging (MRI) grade. Sensitivity and specificity of scintigraphy for detection of lesions in the deep digital flexor tendon (DDFT), the collateral ligaments (CL) of the distal interphalangeal (DIP) joint and the navicular bone were determined. RESULTS: Increased radiopharmaceutical uptake (IRU) was detected in: a) the navicular bone (36.6%); b) pool phase images in the DDFT (13.0%); and c) at the insertion of the DDFT on the distal phalanx (14.3%). There was focal IRU at the insertion of the medial or lateral CL of the DIP joint in 9.4% and 1.5% of limbs, respectively. There was IRU in the medial and lateral palmar processes in 7.6% and 3.4% of limbs, respectively. There was a significant positive correlation between the scintigraphy grade and total MRI grade for the navicular bone and no difference between either focal or diffuse IRU and total MRI grade. There was high specificity, but low sensitivity of scintigraphy for detection of MR lesions of the navicular bone, the DDFT and the CLs of the DIP joint. CONCLUSIONS: Positive nuclear scintigraphic results are good predictors of injury or disease of the navicular bone, DDFT and CLs of the DIP joint. However, a negative scintigraphic result does not preclude significant injuries. CLINICAL RELEVANCE: Nuclear scintigraphy is a useful tool in the investigation of foot lameness and may help to determine the significance of MR lesions, especially if >1 lesion is identified that may be contributing to lameness.     

Use of Body-Mounted Inertial Sensors to Objectively Evaluate the Response to Perineural Analgesia of the Distal Limb and Intra-articular Analgesia of the Distal Interphalangeal Joint in Horses With Forelimb Lameness

Diagnostic analgesia of the distal interphalangeal (DIP) joint is theoretically helpful to localize the source of pain in the foot to the joint and/or navicular bursa. However, it has been suggested that potential diffusion of local anesthetic agent to nearby distal limb nerves may anesthetize other areas of the foot. The objective of this study was to compare the results of palmar digital (PD) and abaxial sesamoid (AS) nerve blocks to intra-articular anesthesia of the DIP joint in horses with distal forelimb lameness. Palmar digital nerve block (group 1) or PD and AS nerve blocks (group 2) were used to abolish digital pain in 22 horses. The following day lameness was again evaluated in all horses before and 2, 5, and 10 minutes after DIP joint anesthesia. All lameness evaluations were performed objectively with a body-mounted inertial sensor system (Lameness locator; Equinosis LLC, Columbia, MO). In group 1 horses, overall improvement in group lameness was the same after DIP joint block, but only six showed positive response after DIP joint analgesia, five after 2 minutes, and one after 5 minutes. In group 2 horses, overall improvement in lameness was less after DIP joint block, with seven showing a positive response after DIP joint analgesia, one after 2 minutes, four after 5 minutes, and two after 10 minutes. Intra-articular analgesia of the DIP joint and perineural analgesia of the digit result in overlapping but unequal areas of analgesia. In addition, a time-dependent response was observed after DIP joint block with full effect requiring 5–10 minutes.     

An investigation of the relationships between angles and shapes of the hoof capsule and the distal phalanx

Reasons for performing study: There is little scientific evidence to support the premise that poor foot conformation predisposes to foot pain and lameness. Objectives: To determine relationships between external characteristics of the hoof capsule and angles of the distal phalanx; to determine variability in shape of the distal phalanx; and to investigate association between distal phalanx angles and the injury causing lameness. Materials and methods: Feet were documented photographically and radiographically. Linear and angle measurements were obtained for the hoof capsule and distal phalanx and compared statistically. Horses were categorised according to injury group, and angles and linear ratios were compared between groups. Results: There was modest correlation between hoof wall and heel angles and angles of the distal phalanx. There was variation in shape of the distal phalanx. There was no significant association between injury type and angles of the distal phalanx, although there was a trend for the angle of the dorsal aspect of the distal phalanx with the horizontal to be smaller in horses with injuries of the podotrochlear apparatus or deep digital flexor tendon compared with other groups. Conclusions: There are variations in shape of the distal phalanx largely due to differences in orientation of the concave solar border and the solar border to the horizontal. Variations in shape of the distal phalanx were not accurately correlated with external characteristics of the hoof capsule. There were weak associations between injury groups and angles of the distal phalanx. Clinical relevance: Further work is required to elucidate risk factors for foot‐related lameness.     

Septic Arthritis of the Distal Interphalangeal Joint in 12 Horses

The medical records of 12 horses with septic arthritis of a distal interphalangeal joint were reviewed to determine clinical features and response to treatment. Sepsis was caused by trauma or an injection that resulted in an open or contaminated distal interphalangeal joint. All horses were severely lame. Treatment included broad-spectrum parenterally administered antimicrobial drugs (ten horses), percutaneous through-and-through joint lavage (eight horses), indwelling drains (three horses), immobilization of the limb in a cast (three horses), intraarticular injection of sodium hyaluronate (one horse), intraarticular injection of antimicrobial drugs (five horses), curettage of the distal phalanx (one horse), and cancellous bone grafting to promote fusion (one horse). Five horses were euthanatized. Ankylosis of the affected joint developed in five horses, four of which are pasture sound. Two horses treated medically are sound although one underwent subsequent palmar digital neurectomy for treatment of navicular syndrome.     

FRACTURES OF THE DISTAL PHALANX AND ASSOCIATED SOFT TISSUE AND OSSEOUS ABNORMALITIES IN 22 HORSES WITH OSSIFIED SCLEROTIC UNGUAL CARTILAGES DIAGNOSED WITH MAGNETIC RESONANCE IMAGING

Ungual cartilage ossification in the forelimb is a common finding in horses. Subtle abnormalities associated with the ungual cartilages can be difficult to identify on radiographs. Magnetic resonance (MR) imaging findings of 22 horses (23 forelimbs) with a fracture of the distal phalanx and ossified ungual cartilage were characterized and graded. All horses had a forelimb fracture. Eleven involved a left forelimb (seven medial; four lateral), and 12 involved a right forelimb (five medial; seven lateral). All fractures were nonarticular, simple in configuration, and nondisplaced. The fractures were oriented in an axial proximal to abaxial distal and palmar to dorsal direction, and extended from the base of the ossified ungual cartilage into the distal phalanx. The fracture involved the fossa of the collateral ligament on the distal phalanx in 17 of 23 limbs. The palmar process and ossified ungual cartilage was abnormally mineralized in all horses. Ligaments and soft tissues adjacent to the ossified ungual cartilages were affected in all horses. The routine site of fracture in this study at the base of the ossified ungual cartilage extending into the distal phalanx suggests a biomechanical cause or focal stress point from cycling. The ligamentous structures associated with the ungual cartilages were often affected, showed altered signal intensity as well as enlargement and were thought to be contributing to the lameness. In conclusion, ossified ungual cartilages may lead to fracture of the palmar process of the distal phalanx and injury of the ungual cartilage ligaments.     

Radiographic, scintigraphic and magnetic resonance imaging findings in the palmar processes of the distal phalanx

REASON FOR PERFORMING STUDY: Increased radiopharmaceutical uptake (IRU) in the palmar processes of the distal phalanx is recognised but its clinical significance has not been established. OBJECTIVES: To investigate the relationship between radiographic, scintigraphic and MRI findings in the palmar processes of the distal phalanx. HYPOTHESES: Increased radiopharmaceutical uptake in the palmar processes of the distal phalanx is associated with MRI abnormalities; IRU and MRI abnormalities are over-represented in lame limbs. METHODS: Clinical data, radiographic, scintigraphic and MRI findings of 258 horses with unilateral or bilateral foot pain were recorded. Scintigraphic images were assessed subjectively and using region of interest and profile analysis, and intensity of IRU graded. Alteration in signal intensity in T1 and T2 weighted and short tau inversion recovery (STIR) MR images was documented, and MRI abnormalities graded. Relationships between scintigraphic, MRI, radiographic and clinical findings were assessed. RESULTS: Focal IRU was over-represented in palmar processes with most MRI abnormalities. There was a significant correlation between IRU and MRI grades and IRU was over-represented in palmar processes with MRI Grades 2 and 3. Both IRU and MRI abnormalities occurred most frequently in the medial palmar process. MRI abnormalities were generally over-represented in lame limbs. The most common MRI abnormality was mild diffuse decreased signal intensity in T1 and T2 weighted images, which was associated with mild generalised IRU. CONCLUSIONS: There was considerable variation in the radiographic, scintigraphic and MRI appearance of palmar processes of the distal phalanx. Focal IRU in a palmar process was seen in association with MRI abnormalities and lameness or as an incidental finding. Magnetic resonance imaging abnormalities occurred more frequently in lame limbs, either contributing to lameness or as a consequence of lameness. POTENTIAL RELEVANCE: Further investigation is needed to establish the clinical significance of MRI abnormalities in the palmar processes of the distal phalanx and their relationship with lesions in adjacent structures.