Proximal Metatarsal Region Research Articles

Magnetic Resonance Imaging Findings in the Proximal Metacarpal Region of 359 Horses and Proximal Metatarsal Region of 64 Horses Acquired Under Standing Sedation

Standing magnetic resonance (MR) images of proximal metacarpal/metatarsal regions are increasingly being acquired. This study aimed at describing ranges of abnormalities detected in sport/racehorses, using retrospective evaluation of magnetic resonance imaging (MRI) reports from horses with lameness isolated to proximal metacarpal/metatarsal regions with images acquired standing. It was hypothesized that MRI features are different between metacarpal and metatarsal regions and between horses doing different sports. Reports from 359 forelimbs and 64 hindlimbs were included. Palmar/plantar metacarpal/metatarsal bone injury and suspensory desmopathy, which often occurred concurrently, were most frequently reported. Third metacarpal abnormalities were more likely at palmar/medial locations, including cortical (86.4%) and trabecular (38.2%) pathology with frequent thickening, irregularity, and periosteal/endosteal abnormalities. Fluid signal was reported in cortical (38.7%) and trabecular (22.6%) bone. Medial intermetacarpal articulation abnormalities were more frequently reported (52.5%) than lateral. Suspensory ligament pathology was reported in 83.8% forelimbs, frequently with cortical (74.1%) or trabecular (32.9%) pathology. Tarsal-joint abnormalities were significantly more likely than carpal-joint abnormalities. Third metatarsal cortical (57.8%) and trabecular (20.3%) pathology was most frequently plantar, but significantly more likely to be dorsal than forelimbs. Metatarsal fluid signal was significantly less likely than metacarpal. Lateral intermetatarsal articulation pathology (23.4%) was more frequent than medial; medial was significantly more likely in forelimbs. Suspensory ligament abnormalities were reported in 64.1% hindlimbs, 39.1% having concurrent cortical pathology. Metacarpal fluid signal was significantly more likely in endurance/racehorses than dressage/show jumping horses. Dressage was overrepresented in hindlimb suspensory origin pathology. These findings indicate different pathology patterns between forelimb/hindlimb and between different sports and may be useful for MRI interpretation.

Ultrasonography of the hock

The hock is a complex joint comprising a number of low-motion joints and a single high-motion joint, together with a large number of soft tissues consisting of ligaments and tendons with their own tendon sheaths and bursae. The hock, including the proximal metatarsal region, is considered the most common site for hindlimb lameness and so ultrasound offers significant diagnostic benefit for this area. The indications for ultrasound examination of the hock are soft tissue swellings in the region of the hock (including effusions of the tarsoscrural joint, tendon sheaths and bursae), wounds including detection of foreign bodies, and lameness localised to the tarsal region. This article describes the ultrasonographic technique and normal ultrasonographic anatomy, and shows examples of the most common pathologies encountered.

Standing repair of a proximal, incomplete, articular fracture of the third metatarsal bone

SummaryA 5‐year‐old National Hunt Thoroughbred mare presented with sudden onset left hindlimb lameness after race training on the gallops. Clinical examination revealed a marked painful reaction over the proximal metatarsal region but no other obvious abnormalities were detected. Survey radiographs at the yard did not reveal any abnormalities. Nuclear scintigraphic examination 3 days after injury revealed focal marked increased radiopharmaceutical uptake in the proximal metatarsal region. Subsequent radiography revealed an incomplete, articular fracture of the proximal left third metatarsal bone. Repair of the fracture using 3 × 4.5 mm cortical screws placed in lag fashion was performed under standing sedation following perineural analgesia. Follow‐up radiographs demonstrated progressive healing of the fracture. The mare returned to race training 8 months after the fracture was repaired and raced successfully 12 months post injury.

The angle contrast ultrasound technique in the flexed limb improves assessment of proximal suspensory ligament injuries in the equine pelvic limb

SummaryDiagnosis of proximal suspensory ligament (PSL, third interosseous muscle) injuries in equine hindlimbs can be challenging because of the complex anatomy of the proximal metatarsal region. Ultrasonographic examination of the PSL using the angle contrast ultrasound technique in the flexed limb facilitates assessment of PSL desmopathies and enthesopathies, with subjectively improved sensitivity compared with the standard approach. The main limitation of ultrasonography is identification of deep osseous injuries, but combined with other imaging procedures, ultrasonography provides valuable diagnostic information of the injured structures. Ultrasonography also helps to specify the stage of a lesion. The repair process can be monitored, helping the clinician to adapt the rehabilitation programme and establish a prognosis for the horse to return to its previous level.

In Vitro Evaluation of a Single Injection Technique for Diagnostic Analgesia of the Proximal Suspensory Ligament of the Equine Pelvic Limb

To examine the anatomic relationship of the deep branch of the lateral plantar nerve (DBLPN) with structures of the proximal metatarsal region, and to define the anatomic location of a solution injected using a single injection technique for diagnostic analgesia of the proximal suspensory ligament (PSL). Descriptive study. Cadaveric equine pelvic limbs (n=29). The proximal metatarsal region of both pelvic limbs (n=5 horses, 10 limbs) was dissected and measurements were made of anatomic structures relative to the head of the 4th metatarsal bone (HMT4). A single injection technique was used to inject dye 15 mm distal to the HMT4, axial to the MT4 at a depth of 25 mm in each limb from 10 equine cadavers (19 limbs). Hindlimbs were dissected and the position of the dye was recorded. DBLPN branched from the lateral plantar nerve (LPN) at a mean distance of 30 mm proximal to the HMT4 and entered the PSL at a mean distance of 17 mm distal to the HMT4. A 2nd DBLPN was observed in 1 of 10 dissected limbs. Blue dye surrounded the DBLPN in 18 limbs (95%). A single injection technique was likely to have resulted in desensitization of the DBLPN in 18 of 19 limbs (95%). This technique provides a reliable method using a single needle puncture for perineural analgesia of the DBLPN for diagnosis of proximal suspensory desmitis of the pelvic limb with a minimal risk of inadvertently desensitizing structures within the tarsal sheath and the tarsometatarsal joint.

SCINTIGRAPHIC EVALUATION OF THE PROXIMAL METACARPAL AND METATARSAL REGIONS IN CLINICALLY SOUND HORSES

In recent years, pain arising from the proximal metacarpal and metatarsal regions has become well recognized as a cause of lameness and various disease entities have been identified. However, our knowledge of normal patterns of radiopharmaceutical uptake is limited, making interpretation of images problematic. It is therefore important to characterize normal patterns of radiopharmaceutical uptake at specific sites to ensure valid interpretation of images in clinical cases with subtle lesions. The purpose of this study was to describe the pattern of radiopharmaceutical uptake in the proximal metacarpal and proximal metatarsal regions in clinically sound horses. Scintigraphic images from 64 clinically normal horses were evaluated. All the images were assessed subjectively. The lateral, dorsal, and plantar scintigraphic images were assessed qualitatively using horizontal line profiles through the proximal metacarpal and proximal metatarsal regions. Mean ratios of radiopharmaceutical uptake were calculated from three regions of interest sited over the proximal metacarpal and proximal metatarsal regions and a reference site. In 78% of forelimbs the peak of radiopharmaceutical activity was at the dorsal to central portion of the proximal metacarpal region. Seventy-five per cent of the dorsal plane profiles of activity were symmetrical, with the highest peak over the medial to central portion of the proximal metacarpal region. In 80% of hindlimb lateral images the peak radiopharmaceutical activity was at the central to plantar aspect of the proximal metatarsal region. All (100%) plantar image profiles of activity were symmetrical, with the highest peak being over the lateral portion of the proximal metatarsal region. There was no significant left and right variation between sites for mean ratios on the lateral and dorsal images of the proximal metacarpal region. However, using lateral images the mean ratios from all regions of the right proximal metatarsal were greater than left (dorsal P = 0.003, plantar P < 0.0001 and whole proximal metatarsal, P = 0.0006). There was no significant variation in mean ratios between left and right on plantar images. However, the mean ratio for the lateral proximal metatarsal region was significantly greater than for the medial proximal metatarsal regions (P < 0.0001). There was no significant effect of age. Left/right symmetry of radiopharmaceutical uptake was shown in the proximal metacarpal region. However, there was a significant difference between left and right proximal metatarsal regions. There was higher radiopharmaceutical uptake in the right proximal metatarsal region than the left, which agrees with previous studies of the tarsal and metatarsophalangeal joints. There were differences in the pattern of radiopharmaceutical uptake between the forelimbs and hindlimbs. In the forelimbs maximum radiopharmaceutical uptake was located at the dorsal to central portion of the proximal metacarpal region in the lateral image, with peak activity over the medial to central portion of the proximal metacarpal region on dorsal images. In the hindlimbs the maximum radiopharmaceutical uptake was at the central to plantar aspect of the proximal metatarsal region in the lateral image, with peak activity over the lateral portion of proximal metatarsal region on plantar images. The results of this study support the hypothesis that there would be a standard pattern of radiopharmaceutical uptake across the proximal metacarpal and l metatarsal regions, but the pattern of uptake observed would be different in the proximal metacarpal region compared with the proximal metatarsal region. There was left/right symmetry of radiopharmaceutical uptake in the proximal metacarpal region. However, there was a significant difference between left and right proximal metatarsal regions, with higher radiopharmaceutical uptake in the right. There was no variation of radiopharmaceutical uptake pattern with age.

CRANIAL TIBIAL ARTERY CATHETER FOR MONITORING PRESSURES AND SAMPLING

A technique for placement of a long‐term arterial catheter that the author developed was used in 20 canine patients. The catheter was used for pressure monitoring and arterial blood sampling. The technique involved the following steps post‐sedation and placement of a local anesthetic: Clipping and prepping of the medial aspect of the distal tibia and proximal metatarsal region; Incision over the medial tibial malleolus just caudal to the cranial tibial muscle‐tendon; Blunt dissection of the space just caudal to the cranial tibialis tendon; Isolation of the cranial tibial artery and loop placement proximally and distally; Placement of a 3 Fr. polyurethane 4–8 cm catheter using a Seldinger wire technique; Placement of a suture in the periosteium of the distal tibia and anchoring of the catheter with this suture; Closure of the skin incision with sutures or staples; Bandage application to hold the catheter in place. The entire surgical procedure was done using sterile technique. The catheter was able to be kept in place and working for up to 9 days (averaged 4 days). This compared favorably retrospectively over dorsalis pedis catheters that lasted only a maximum of 4 days. (average 1.5 days). Because of the size of the catheter (3 Fr.) it provided improved waveforms over that observed with the dorsalis pedis catheter (22 g) and its occlusion rate was very low (2 in 20). The cranial tibial artery catheter was found to be particularly effective because the catheter was able to be inserted several cm up the artery and the catheter was able to be anchored well. No major complications were observed with this technique. Because of its effectiveness it is recommended to be used routinely over femoral artery and dorsal pedis artery catheters.