POSITIVE CONTRAST MAGNETIC RESONANCE BURSOGRAPHY FOR ASSESSMENT OF THE NAVICULAR BURSA AND SURROUNDING SOFT TISSUES

Magnetic resonance (MR) imaging is often performed to determine the cause of palmar heel pain. We evaluated how distension of the navicular bursa affected the MR appearance of the navicular bursa and associated structures. An MR evaluation was performed on normal cadaver limbs and cadaver limbs from horses with lameness localized to the foot. The normal navicular bursae were injected with 2, 4, or 6 ml of solution. The bursae of the feet from lame horses were injected with 4 or 6 ml, and the MR study was repeated. All bursae were examined grossly to verify the presence or absence of adhesions. Clinical patients that had initial MRI abnormalities suggesting adhesions were also evaluated. Distension of the proximal recess of the normal navicular bursa, proximal to the collateral sesamoidean ligament was achieved with 2 ml. Separation of the collateral sesamoidian ligament from the deep digital flexor tendon (DDFT) was achieved with 4 ml. The separation of the navicular bone from the DDFT and distal sesamoidian impar ligament required 6 ml. Adhesions were more clearly defined in the bursa of the two pathologic cadaver limbs following distension. MR bursography used on clinical patients allowed the determination of the presence or absence of adhesions. In these horses, this determination could not have been definitively made without this technique. MR bursography is useful in horses where the presence of adhesions cannot be clearly defined by MRI.     

Magnetic resonance imaging changes of the navicular bursa following navicular bursoscopy in seven horses

Navicular syndrome is a multifactorial disease process in horses with multiple structures in the foot contributing to lameness. Surgical debridement is a treatment option for lesions of the navicular bursa and deep digital flexor tendon. This retrospective case series describes the magnetic resonance imaging (MRI) appearance of the navicular bursa following bursoscopy. Seven horses (three being bilaterally affected) with forelimb lameness isolated to the foot, and pre- and post-operative MRI were included. All limbs had concurrent lesions associated with the deep digital flexor tendon, navicular bone, impar ligament, collateral sesamoidean ligament and/or distal interphalangeal joint. All bursae developed or had progression of proliferative bursal tissue following surgery. At recheck MRI, following rehabilitation protocols, almost all horses had improved to resolved lameness with relatively unchanged concurrent lesions despite the navicular bursa appearance worsening. Outcomes for return to work were poor with only two horses going back to the previous level of work.     

Magnetic resonance imaging of navicular bursa adhesions

Adhesions occur in the navicular bursa between the deep digital flexor tendon (DDFT) and other structures. Our objectives were to describe the appearance of navicular bursa adhesions on high-field magnetic resonance (MR) images, to compare these findings to findings at navicular bursoscopy, and to determine the prevalence of lesions in the remainder of the podotrochlear apparatus. Sixteen forelimbs from 14 horses that underwent MR imaging and navicular bursoscopy were evaluated. Adhesions were considered type 1 when characterized by a discontinuity in the navicular bursa fluid signal between two structures, type 2 when the navicular bursa fluid signal was disrupted and ill-defined tissue was present between two structures, and type 3 when the fluid signal was disrupted and well-defined tissue was present between two structures. Twenty-six adhesions were suspected on MR images and nineteen were visualized at surgery. The positive predictive value was 50% for type 1 adhesions, 67% for type 2 adhesions, and 100% for type 3 adhesions. Additional lesions were detected in the navicular bursa in 15 limbs, the DDFT in 13, the navicular bone in 15, the collateral sesamoidean ligaments in 9, and the distal sesamoidean impar ligament in 8. A discontinuity in the navicular bursa fluid signal with well-defined tissue between two structures detected on high-field MR images is diagnostic for a navicular bursa adhesion. Additional lesions in the podotrochlear apparatus are common in horses with navicular bursa adhesions.     

Ultrasonographic Evaluation of the Distal Extremity

Despite the increasing use of magnetic resonance imaging (MRI), ultrasound remains a valuable tool to diagnose injuries that cause distal extremity lameness in the horse. The key to a successful examination is a strong knowledge of anatomy in combination with proper ultrasonographic technique and the patience and dedication to learn these skills. Similar to all imaging modalities, it is equally important to recognize and consider the limitations of ultrasound in this region so that findings can be interpreted appropriately. Ultrasound can be used to diagnose injuries to the deep digital flexor tendon (DDFT), straight distal sesamoidean ligament and branches of the superficial digital flexor tendon using standard pastern ultrasonographic technique. The addition of newer techniques to image the DDFT at the level of P2, the navicular bursa and the collateral sesamoidean ligament can enhance the diagnostic utility of ultrasound in horses with distal extremity lameness. Although visibility is limited, ultrasound can be used to diagnose collateral ligament injuries of the coffin joint in many affected horses. Transcuneal imaging may be useful in some horses to detect abnormalities of the distal sesamoidean impar ligament and navicular bone, but evaluation of the DDFT is limited. Ultrasound should be considered in all horses with distal extremity lameness, regardless of the ability to perform advanced imaging procedures. Information gained is often complementary to other imaging modalities and may provide the basis for recheck examination purposes.     

Current concepts of navicular disease

Navicular disease is unlikely to be a single disease. The close anatomical and functional relationships between the navicular bone, collateral sesamoidean ligament, distal sesamoidean impar ligament, deep digital flexor tendon, navicular bursa and distal interphalangeal joint result in the frequent occurrence of combinations of injuries. There are a number of different pathological processes that affect the navicular bone, which probably have different aetiopathogeneses. While there is strong evidence that biomechanical forces may result in failure of functional adaptation and excessive modelling, it is likely that each disease or injury type has a multifactorial cause.     

Ultrasonographic diagnosis of injuries to the deep digital flexor tendon and associated structures in the equine foot (suprasesamoidean area)

Foot pain is the most common cause of lameness in horses. In sport horses, podotrochlear syndrome (‘navicular syndrome’) is reported to be the most frequent condition affecting the front foot. Ultrasonography has the potential to detect damage to the soft tissues as well as the bone surfaces; in some clinics it has become the technique of choice for the identification and documentation of many podotrochlear injuries. The purpose of this paper is to review the main pathological conditions of the proximal part of the podotrochlear apparatus (PTA) that can be diagnosed ultrasonographically, focusing on the deep digital flexor tendon (DDFT), podotrochlear bursa (PTB) and distal digital annular ligament (DDAL). Potentially significant ultrasonographic findings of the DDFT include thickening of one or both lobes, longitudinal tears, focal or diffuse changes in echogenicity, irregularities of the dorsal border and adhesions between the DDFT and the proximal sesamoidean ligament and/or distal sesamoid bone. Deep digital flexor tendon injuries are often associated with concurrent lesions of the PTB (acute to chronic bursitis) and of the DDAL (desmopathy). Both feet should be routinely examined as lesions of the PTA are often bilateral. We currently consider that ultrasonography should be routinely employed as the primary diagnostic procedure to complement radiography of the equine foot.     

CHARACTERIZATION OF THE MAGIC ANGLE EFFECT IN THE EQUINE DEEP DIGITAL FLEXOR TENDON USING A LOW-FIELD MAGNETIC RESONANCE SYSTEM

Three isolated equine limbs were imaged with a low-field magnetic resonance system with a vertical magnetic field. Each limb was scanned in multiple positions with mild variation of the angle between the magnetic field and the long axis of the limb. When the long axis of the limb was not perpendicular to the magnetic field, a linear hyperintense signal was present at the palmar aspect of one of the deep digital flexor tendon lobes, at the level of the navicular bone and collateral sesamoidean ligaments, in proton density and T1-weighted pulse sequences. With increased angulation of the limb, the palmar hyperintense signal extended farther distally and proximally and additional signal hyperintensity was present at the dorsal aspect of the distal part of the other lobe of the deep digital flexor tendon. Increased signal intensity was also present in the collateral ligament of the distal interphalangeal joint on the same side as the palmar hyperintense signal in the tendon. The changes in the deep digital flexor tendon are due to the specific orientation of fibers at the palmar and dorsal aspect of the tendon, which is responsible for focal manifestation of the magic angle effect. Careful positioning of the limb perpendicular to the magnetic field can prevent this phenomenon. The association of palmar increased signal intensity in the deep digital flexor tendon with increased signal in the collateral ligament of the distal interphalangeal joint on the same side should be recognized as manifestations of the magic angle effect.     

HOW DOES MAGNETIC RESONANCE IMAGING REPRESENT HISTOLOGIC FINDINGS IN THE EQUINE DIGIT?

Magnetic resonance (MR) imaging is increasingly used in the diagnosis of equine foot pain, but improved understanding of how MR images represent tissue-level changes in the equine foot is required. We hypothesized that alterations in signal intensity and tissue contour would represent changes in tissue structure detected using histologic evaluation. The study objectives were to determine the significance of MR signal alterations in feet from horses with and without lameness, by comparison with histopathologic changes. Fifty-one cadaver feet from horses with a history of lameness improved by palmar digital analgesia (n = 32) or age-matched control horses with no history of lameness (n = 19) were stored frozen before undergoing MR imaging and subsequent histopathological examination at standard sites (deep digital flexor tendon, navicular bone, distal sesamoidean impar ligament, collateral sesamoidean ligament, and navicular bursa). Using MR images, signal intensity and homogeneity, size, definition of anatomic margins, and relationships with other structures were described. Alterations were graded as mild, moderate, or severe for each structure. For each anatomic site examined histologically the structures were described and scored as no changes, mild, moderate, or severe abnormalities, also taking into account adhesion formation within the navicular bursa detected on macroscopic examination. Alterations in MR signal intensity were related to changes at the tissue level detected by histologic examination. A sensitivity and specificity comparison of MR imaging with histologic examination was used to evaluate the significance of MR signal alterations for detection of moderate-to-severe lesions of the deep digital flexor tendon (DDFT), navicular bone, distal sesamoidean impar ligament (DSIL), collateral sesamoidean ligament (CSL) and navicular bursa. Agreement between the MR and histologic grading was assessed for each structure using a weighted kappa agreement. Direct comparison between histology and MR imaging for individual limbs revealed that signal alterations on MR imaging did represent tissue-level changes. These included structural damage, fibroplasia, fibrocartilaginous metaplasia, and hemosiderosis in ligaments and tendons; trabecular damage, osteonecrosis, fibroplasia, cortical defects, and increased vascularity in bone; and fibrocartilage defects. MR imaging had a high sensitivity and specificity for most structures. MR imaging had high specificity for lesions of the DDFT, CSL and navicular bursa, quite high specificity for lesions of the medulla of the navicular bone and its proximal aspect, with moderate specificity for the DSIL, and distal, dorsal and palmar aspects of the navicular bone, and was sensitive for detection of abnormalities in all structures except the dorsal aspect of the navicular bone. When MR and histologic grades alone were compared, there was good agreement between MR and histologic grades for the navicular bursa, DDFT, navicular bone medulla and CSL; moderate-to-good agreement in grades of the distal and palmar aspects of the navicular bone; fair to moderate in grades of the DSIL, and poor agreement for the dorsal and proximal aspects of the navicular bone. The results of this study support our hypothesis and indicate the potential use and limitations of MR imaging for visualization of structural changes within osseous and soft tissue structures of the equine foot.     

Standing MRI lesions of the distal interphalangeal joint and podotrochlear apparatus occur with a high frequency in warmblood horses

Foot pain is a common presenting complaint in Warmblood horses. The aim of this retrospective, cross‐sectional study was to determine the spectrum of foot lesions detected by magnetic resonance imaging (MRI) in Warmblood horses used for dressage, jumping, and eventing. The medical records of 550 Warmblood horses with foot pain that were scanned using standing MRI were reviewed and the following data were recorded: signalment, occupation, lameness, diagnostic analgesia, imaging results, treatments, and follow‐up assessments. Associations between standing MRI lesions and chronic lameness following treatment were tested. Abnormalities of the navicular bone (409 horses, 74%), distal interphalangeal joint (362 horses, 65%), and deep digital flexor (DDF) tendon (260 horses, 47%) occurred with the highest frequency. The following abnormalities were significantly associated (P < .05) with chronic lameness following conservative therapy: moderate to severe MRI lesions in the trabecular bone of the navicular bone, mild or severe erosions of the flexor surface of the navicular bone, moderate sagittal/parasagittal DDF tendinopathies, and moderate collateral sesamoidean desmopathies. Also, identification of concurrent lesions of the DDF tendon, navicular bone, navicular bursa, and distal sesamoidean impar ligament was associated with chronic lameness after conservative therapy. Development of effective treatment options for foot lesions that respond poorly to conservative therapy is necessary.     

Assessment of the ultrasonographic characteristics of the podotrochlear apparatus in clinically normal horses and horses with navicular syndrome

OBJECTIVE: To characterize the normal ultrasonographic appearance of the podotrochlear apparatus in horses by use of standardized measurements and identify soft tissue changes associated with navicular syndrome. DESIGN: Prospective study. ANIMALS: 7 clinically normal horses and 28 horses with navicular syndrome. PROCEDURE: The feasibility of identifying and measuring the soft tissue structures of the podotrochlear apparatus ultrasonographically via the transcuneal approach was assessed in 2 additional horses without navicular syndrome; both horses were euthanatized, and the structures identified ultrasonographically were confirmed at necropsy. Ultrasonographs were obtained in the study horses. Objective and subjective data were obtained to characterize ultrasonographic changes associated with navicular syndrome. RESULTS: Abnormalities of the flexor surface of the distal sesamoid (navicular) bone, the impar ligament, the distal digital annular ligament, deep digital flexor tendon (DDFT), and the podotrochlear (navicular) bursa were assessed via the transcuneal ultrasonographic approach. No significant differences were found between the measurements of the podotrochlear apparatus in normal horses and those with navicular syndrome; however, important subjective differences were detected ultrasonographically in horses with navicular syndrome. In horses with navicular syndrome, ultrasonographic findings were indicative of navicular bursitis, dystrophic mineralization of the DDFT and impar ligament, tendonitis and insertional tenopathy of the DDFT, desmitis of the impar ligament, and cortical changes in the flexor surface of the navicular bone. CONCLUSIONS AND CLINICAL RELEVANCE: Findings of ultrasonographic evaluation of the hoof appear to be useful in determining the cause of caudal heel pain and characterizing the components of navicular syndrome in horses.     

Collateral desmitis of the distal interphalangeal joint in conjunction with concurrent ossification of the cartilages of the foot in nine horses

The purpose of this study was to describe the frequency of occurrence of severe ossification of the collateral cartilages (sidebone) coexistent with collateral desmitis of the distal interphalangeal joint (DIPJ) in lame horses. Sidebone was diagnosed and graded on standard radiographs and soft tissue injuries of the foot were diagnosed using standing low‐field magnetic resonance imaging (MRI). Of 15 horses with forelimb lameness and severe sidebone, 9 had evidence of concurrent collateral desmitis of the DIPJ. All 15 horses had damage to other structures (including the deep digital flexor tendon, distal sesamoidean impar ligament, collateral sesamoidean ligament, navicular bone and distal phalanx) within the affected feet as identified on MRI. The clinical and pathophysiological significance of concurrent collateral desmitis of the DIPJ and sidebone is currently uncertain. However, this study shows that injuries to multiple structures within the foot are common and that collateral desmitis of the distal interphalangeal joint is frequently seen in lame horses in conjunction with severe ossification of the collateral cartilages.     

Histopathology in horses with chronic palmar foot pain and age-matched controls. Part 2: The deep digital flexor tendon

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 deep digital flexor tendon (DDFT) may contribute to palmar foot pain; ageing degenerative changes may be seen in horses free from lameness; and horses with lameness are likely to have a greater severity of abnormalities than age-matched horses with no history of foot pain. METHODS: Feet were selected from horses with a history of uni- or bilateral forelimb lameness of at least 2 months' duration. Histology of the DDFT from the level of the proximal interphalangeal joint to its insertion were examined and the severity of lesions for each site graded. Associations between lesions of the navicular bone, collateral sesamoidean ligaments (CSL), distal sesamoidean impar ligament, navicular bursa, distal interphalangeal (DIP) joint synovium and collateral ligaments of the DIP joint and DDFT were assessed. RESULTS: There was no relationship between age and grade of histological abnormality of the DDFT. There were significant histological differences between groups for lesions of the dorsal layers of the DDFT, but not for lesions of the palmar aspect. There were significant associations between histological grades for the superficial dorsal layer of the DDFT and flexor aspect of the navicular bone; and between the deep dorsal layer of the DDFT and the proximal border and medulla of the navicular bone. The navicular bursa grade was correlated with grades for the superficial dorsal, deep dorsal and deep palmar layers of the DDFT. The histological grades for the CSL and the superficial dorsal layer of the DDFT were also associated. CONCLUSIONS: Pathological abnormalities in lame horses often involved the DDFT in addition to the navicular bone. Vascular and matrix changes may precede changes in the fibrocartilage of the navicular bone. POTENTIAL RELEVANCE: Identification of factors leading to vascular changes within the interstitium of the DDFT and changes in matrix composition, may help in future management of palmar foot pain.     

Comparisons of computed tomography, contrast enhanced computed tomography and standing low-field magnetic resonance imaging in horses with lameness localised to the foot. Part 1: anatomic visualisation scores

Reasons for performing study: To date, few reports exist comparing magnetic resonance imaging (MRI) and computed tomography (CT) for imaging of the equine distal limb, yet clinicians are required to decide which modality to use regularly. Objectives: To report and compare anatomic visualisation scores obtained for CT, contrast enhanced CT (CECT) and standing low‐field MRI (LFMRI) in the equine foot. Hypothesis: Anatomic visualisation score discrepancies would exist between CT, CECT and LFMRI. Methods: Images of 22 lame horses (31 limbs) undergoing both CT and LFMRI of the foot were reviewed. When available, CECT images were reviewed. The deep digital flexor tendon (DDFT) was categorised into proximal to distal levels (A–D), structures were assigned visualisation scores (Grades 0–3) and technique comparisons were made using the paired marginal homogeneity test. Results: Computed tomography and LFMRI had similar visibility scores for the navicular bone, middle phalanx, DDFT‐B, collateral ligaments of the distal interphalangeal joint and collateral sesamoidean ligament of the navicular bone. The proximal and distal phalanx had lower visibility scores with LFMRI. The distal DDFT (C–D), distal sesamoidean impar ligament and synovial structures had higher scores with LFMRI. Contrast enhanced CT lowered DDFT and collateral sesamoidean ligament scores and raised distal interphalangeal synovium CT visualisation scores. Conclusions and potential relevance: Visualisation scores differ depending on imaging technique and anatomic structure of interest. This information increases our understanding of the limitations of CT, CECT and LFMRI to visualise anatomy in clinical cases.     

Ultrasonographic examination of the distal podotrochlear apparatus of the horse: A transcuneal approach

In the diagnostic work‐up of lameness originating from the foot, ultrasonographic examination is an essential complement to radiography for the detection of soft tissue lesions of the podotrochlear apparatus (PTA). The infrasesamoidean part of the deep digital flexor tendon, distal sesamoidean ligament and distal sesamoid bone can be accurately assessed using a transcuneal approach. This paper describes the ultrasonographic technique and presents normal and abnormal ultrasound images of the infrasesamoidean part of the PTA.     

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.     

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.     

Comparison of two techniques for injection of the podotrochlear bursa in horses

OBJECTIVE: To compare accuracy of 2 methods for injection of the podotrochlear bursa in horses. DESIGN: Observational study. ANIMALS: 17 French Standardbreds. PROCEDURE: In each horse, contrast medium was injected into the podotrochlear bursa of 1 foot by use of a distal palmar approach with the needle inserted parallel to the sole (DPPS) and into the podotrochlear bursa of the other foot by use of a distal palmar approach to the navicular position (DPNP). Podotrochlear bursa injection was evaluated by means of radiographic examination in all horses and postmortem examination in 6. RESULTS: Contrast medium was successfully injected into the podotrochlear bursa in 6 of 16 feet in which the DPPS method was used and 14 of 17 feet in which the DPNP method was used; these results were significantly different. Failure was attributed to contrast medium invading the distal interphalangeal joint, contrast medium pooling palmar to the deep digital flexor tendon, contrast medium located in the podotrochlear bursa and the distal interphalangeal joint, contrast medium located in the podotrochlear bursa and the area palmar to the deep digital flexor tendon, and an inability to inject contrast medium despite adequate needle placement. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the DPNP technique can be used successfully for injection into the podotrochlear bursa in horses. However, radiographic assessment should be used to confirm that material was injected into the bursa.