Sesamoid Bones In Horses Research Articles

Comparison of speed of onset and analgesic effect of 2% mepivacaine hydrochloride deposited within or outside the neurovascular bundle at the level of the proximal sesamoid bones in horses with naturally occurring forefoot-related lameness.

To compare the speed of onset and analgesic effect of mepivacaine deposited within or immediately outside the neurovascular bundle at the base of the proximal sesamoid bones in horses. 6 horses with naturally occurring forefoot-related lameness. In a crossover study design, horses were randomly assigned to receive 1 of 2 treatments first, with the second treatment administered 3 to 7 days later. Trotting gait was analyzed with an inertial sensor-based motion analysis system immediately before treatment to determine degree of lameness. Afterward, ultrasound guidance was used to inject 2% mepivacaine hydrochloride around the palmar digital nerves of the affected forelimb at the level of the base of the proximal sesamoid bones either within the subcircumneural space or outside the circumneural sheath. After injection, gait was reevaluated at 5-minute intervals for 45 minutes. Mepivacaine deposition outside the circumneural sheath did not resolve lameness in any horse; for 3 horses, the mean time to 70% reduction of initial vertical head movement was 13.3 minutes, and the remaining 3 horses had no such reduction at any point. Mepivacaine deposition within the subcircumneural space resulted in a mean time to 70% reduction of initial vertical head movement of 6.7 minutes and mean time to resolution of lameness of 21.7 minutes. Results suggested that when peripheral nerves of horses lie within a sheath, local anesthetic solution should be deposited within the sheath for an effective nerve block. If local anesthetic solution is deposited outside the sheath, the nerve block may yield erroneous results.

Ultrasound Assisted Arthroscopic Approach for Removal of Basilar Sesamoid Fragments of the Proximal Sesamoid Bones in Horses

To describe an ultrasound assisted arthroscopic approach for removal of non-articular basilar sesamoid fragments in Thoroughbred yearlings. Thoroughbred yearlings (n = 7). Basilar sesamoid fragments identified during pre-sale radiographic examination were removed using a palmar/plantar arthroscopic approach to the fetlock joint and ultrasonographic guidance. Complete fragment removal was confirmed by ultrasonography and radiography. Basilar sesamoid fracture fragments were localized and removed successfully using rongeurs and a radiofrequency probe for soft tissue dissection of the fragment. Complete fragment removal was confirmed by ultrasonography and radiography. No intra- or postoperative complications occurred. At 6-8 months follow-up, no fragments or bony proliferation at the base of the sesamoid was observed. Ultrasonographic guidance can be used to facilitate localization, dissection, and confirmation of removal of basilar fragments of the proximal sesamoid bone.

Computed Tomography to Identify Preoperative Guidelines for Internal Fixation of the Distal Sesamoid Bone in Horses: An In Vitro Study

To assess the reliability of computed tomography (CT) to identify the direction of implant insertion for cortical screws along the longitudinal axis of intact (nonfractured) distal sesamoid bones. In vitro study. Cadaveric paired equine forelimbs (n=16). Insertion of a cortical screw in lag fashion along the longitudinal axis of intact (nonfractured) distal sesamoid bones was evaluated in 2 groups (3.5 and 4.5 mm) of 8 paired limbs. In each group, the direction of the distal sesamoid bone was determined by CT (Equine XTC 3000 pQCT scanner). Screw placement was verified by specimen dissection. Implant direction was considered satisfactory if the entire screw length was within the distal sesamoid bone and not damaging the articular or flexural surfaces. In our sample and according to our criteria, the proportion of satisfactory direction of screws was 0.63 (5/8) for 4.5 mm implants, and 0.87 (7/8) for 3.5 mm implants. CT is a useful imaging modality to identify anatomic landmarks for insertion of a 3.5 mm cortical screw in the distal sesamoid bone.

Surgical Approach for Removal of Nonarticular Base Sesamoid Fragments of the Proximal Sesamoid Bones in Horses

To describe a surgical approach for the removal of nonarticular base sesamoid fragments in performance horses and to report the outcome. Retrospective study. Horses (n=11), 7 months to 10 years of age, with lameness because of nonarticular base sesamoid fragments. Lameness was localized to the metacarpophalangeal/metatarsophalangeal region by clinical examination or response to diagnostic local anesthesia. Radiographs confirmed the diagnosis of a nonarticular base sesamoid fragment. Surgical removal was performed with an incision over the base of the affected sesamoid through the digital flexor tendon sheath. After identifying the fragment with the aid of needles, a small vertical incision was made in the straight distal sesamoidean ligament (SDSL) and the fragment was freed from its attachments and removed. Six months convalescence and rehabilitation was prescribed for all horses. Eleven horses had 16 nonarticular fragments of the base of the proximal sesamoid bones. Eleven (69%) fragments occurred in the forelimbs with the right front (82%) and medial sesamoid (73%) more commonly affected. Horses were treated by surgical fragment removal. In horses with follow-up, 9 of 10 returned to their intended use. Surgical removal of nonarticular base sesamoid fragments can be accomplished through a palmar/plantar approach through the digital flexor tendon sheath and SDSL. This "keyhole" approach minimizes damage to the distal sesamoidean ligament attachments to the sesamoid base and allows some horses to return to their intended use. Surgical removal of nonarticular base sesamoid fragments should be considered in horses with performance-limiting lameness as a result of the fragment.

Fungal osteomyelitis of the axial border of the proximal sesamoid bones in a horse

A 12-year-old Standardbred gelding was referred for swelling of the right metacarpophalangeal joint. Ultrasonography of the right metacarpal area revealed hypoechoic areas in the right digital sheath and metacarpophalangeal joint consistent with synovial effusion. Radiography of the right metacarpophalangeal joint revealed lysis of the axial border of the proximal sesamoid bones. Aspergillus fumigatus was detected on fungal culture of synovial fluid. Regional limb perfusion (150 mg of amikacin in 60 mL of saline [0.9% NaCl] solution perfused for 30 minutes) was performed 2 and 4 days after admission. Itraconazole (5 mg/kg [2.27 mg/lb], PO, q 24 h) was administered for approximately 9 weeks. Joint lavage with amikacin (500 mg) in 1 L of saline solution was performed 4 times. Three months after discharge, the owner reported that the horse was mildly lame during trotting but was moving freely and comfortably during all gaits and had gained a considerable amount of weight. Because the osteoarthritis was not expected to improve and because it was recommended that the horse not return to purposeful exercise, the owner decided to retire the horse from racing. Various diagnostic imaging methods and fungal cultures are useful for diagnosing fungal osteomyelitis of the axial borders of the proximal sesamoid bones in horses. Fungal osteomyelitis of the sesamoid bones and erosive arthritis should be considered as a differential diagnosis for horses in which corticosteroids have been administered intra-articularly.

Computer‐Assisted Surgery for Screw Insertion into the Distal Sesamoid Bone in Horses: An In Vitro Study

To compare the precision of computer-assisted surgery with a conventional technique (CV) using a special guiding device for screw insertion into the distal sesamoid bone in horses. In vitro experimental study. Cadaveric forelimb specimens. Insertion of a 3.5 mm cortex screw in lag fashion along the longitudinal axis of intact (non-fractured) distal sesamoid bones was evaluated in 2 groups (8 limbs each): CV and computer-assisted surgery (CAS). For CV, the screw was inserted using a special guiding device and fluoroscopy, whereas for CAS, the screw was inserted using computer-assisted navigation. The accuracy of screw placement was verified by radiography, computed tomography, and specimen dissection. Surgical precision was better in CAS compared with CV. CAS improves the accuracy of lateromedial screw insertion, in lag fashion, into the distal sesamoid bone. The CAS technique should be considered for improved accuracy of screw insertion in fractures of the distal sesamoid bone.

MAGNETIC RESONANCE IMAGING FINDINGS IN THE EQUINE DEEP DIGITAL FLEXOR TENDON AND DISTAL SESAMOID BONE IN ADVANCED NAVICULAR DISEASE—AN EX VIVO STUDY

We describe the abnormal magnetic resonance (MR) imaging findings in the deep digital flexor tendon (DDFT) and distal sesamoid bone in horses with radiographic changes compatible with navicular syndrome. Thirteen postmortem specimens were examined using a 1.5-T magnetic field, with spin echo (SE) T1-weighted, turbo SE (TSE) proton density-weighted (with and without fat saturation), and fat saturation TSE T2-weighted sequences. The limbs were then dissected to compare the MR findings with the gross assessment and histologic examination of the DDFT and distal sesamoid bones. Tendonous abnormalities were detected by MR imaging in 12 DDFTs and confirmed at necropsy. Most tendon lesions were located at the level of the distal sesamoid bone and the proximal recess of the podotrochlear bursa. Tendon lesions were classified based on their MR imaging features as core lesions, dorsal lesions, dorsal abrasions, and parasagittal splits. Areas of increased MR signal in the DDFTs were characterized by tendon fiber disturbance and lack of continuity of the collagen fibers, foci of edema, hemorrhages, and formation of lakes containing eosinophilic plasma-like material or amphophilic material of low density. Bone marrow signal alterations in the distal sesamoid bone were seen in all digits. Two main phenomena were responsible for the abnormal signal, respectively, in T1-weighted (decreased signal) and in T2-weighted fat-suppressed images (increased signal): a decrease in the fat marrow content in the trabecular spaces and an increase in the fluid content. Histologic examination revealed foci of bone marrow edema, hemorrhage, necrosis, and fibrosis. Cyst formation and trabecular abnormalities (disorganization, thinning, remodelling) were also observed in areas of abnormal signal intensity. Increased bone density because of trabecular thickening induced a decrease in signal in all sequences.

Arthroscopic removal of fracture fragments involving a portion of the base of the proximal sesamoid bone in horses: 26 cases (1984-1997).

To determine the outcome of horses with basal fractures of the proximal sesamoid bone from which a fracture fragment involving a portion of the base of the bone was removed arthroscopically and to determine whether fragment size was associated with outcome. Retrospective study. 26 horses. Dorsopalmar and axial-abaxial lengths of the fracture fragment were measured on the dorsopalmar and mediolateral radiographic views, respectively, and percentage of the base of the sesamoid bone involved was estimated. Fractures were classified as grade 1 (< or = 25% of the base involved) or grade 2 (> 25% but < 100% of the base involved). Outcome was classified as successful if the horse started at least 2 races or unsuccessful if the horse started only 1 race or failed to return to racing. There were 24 racehorses and 2 nonracehorses. Twelve (50%) of the racehorses returned to racing and started at least 2 races. Eight of 14 horses with grade-1 fractures and 4 of 10 horses with grade-2 fractures had a successful outcome. Ten of 16 horses without associated articular disease had successful outcomes, compared with 2 of 8 horses with associated articular disease. However, fragment size and presence of associated articular disease were not significantly associated with outcome. Horses with basal fractures of the proximal sesamoid bone from which a fracture fragment involving a portion of the base of the bone is removed arthroscopically have a fair prognosis for return to racing.

A Finite Element Model of the Proximal Sesamoid Bones of the Horse Under Different Loading Conditions

SummaryFracture of the proximal sesamoid bones is a common injury of racing horses, usually resulting from over-dorsiflexion of the metacarpophalangeal joint. The purpose of this study was to develop a computer-aided method utilizing stereo-radiography, computed tomography, and finite element method to determine three-dimensional stress distribution in the proximal sesamoid bones during metacarpophalangeal joint dorsiflexion. The stress pattern was characterized by a compressive component on the articular part of the bone and a tensile component on the non-articular part of the bone. Maximum principal stresses were 2.5, 9.1 and 15.5 MPa and minimum principal stresses were -1.9, -9. 2 and -14. 9 MPa for metacarpophalangeal joint angles of 140°, 125° and 110°, respectively. The distal portion of the articular part of the bone experienced the largest compressive stress. In this study changes in the orientation and magnitude of the ligament force vectors did not significantly change stress patterns of the proximal sesamoid bone.This study was designed to determine stress patterns of the proximal sesamoid bones in horses. Stress patterns were determined by finite element method analysis. Compressive stresses were present on the articular side, and tensile stresses were present on the nonarticular side of the bones. The magnitude of load applied to the bone did not appreciably change the pattern of stresses.