Computed tomography to identify preoperative guidelines for internal fixation of the distal sesamoid bone in horses: an in vitro study.

OBJECTIVE: 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. STUDY DESIGN: In vitro study. SAMPLE POPULATION: Cadaveric paired equine forelimbs (n=16). METHODS: 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. RESULTS: 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. CONCLUSIONS: CT is a useful imaging modality to identify anatomic landmarks for insertion of a 3.5 mm cortical screw in the distal sesamoid bone.

Use of computed tomography to diagnose new bone formation associated with desmitis of the proximal aspect of the suspensory ligament in third metacarpal or third metatarsal bones of three horses.

CASE DESCRIPTION: 3 horses with lameness localized to the proximal aspect of the metacarpus or metatarsus. CLINICAL FINDINGS: All horses had evidence of problems that originated from the proximal aspect of the suspensory ligament (PASL), including signs of pain on palpation, positive results of diagnostic nerve blocks, ultrasonographic detection of enlargement and diffuse areas of reduced echogenicity in the proximal region of insertion of the ligament, and radiographic detection of increased mineral opacity in the proximal aspect of the metacarpus or metatarsus. Desmitis of the PASL was diagnosed in each horse; however, conservative treatment failed to improve the lameness. The horses were taken to surgery for splitting of the PASL and osteostixis of the proximal aspect of the third metacarpal or metatarsal bone. At that time, the proximal aspect of the metacarpus or metatarsus was evaluated via computed tomography (CT), which identified new bone formation at the proximal aspect of the third metacarpal or metatarsal bone that had not already been identified. TREATMENT AND OUTCOME: In all horses, the newly formed bone was removed surgically under radiographic and CT guidance, and the splitting and osteostixis that had been planned were performed. After rehabilitation, all horses returned to full training at 6 months after surgery. All horses responded well to the surgical treatment and were sound 8 months afterward. CLINICAL RELEVANCE: Use of CT imaging should be considered in lame horses with pain associated with the proximal aspect of the third metacarpal or metatarsal bones that does not improve with conservative treatment.

Use of computed tomography in standing position to identify guidelines for screw insertion in the distal phalanx of horses: an ex vivo study.

OBJECTIVES: To compare the precision of radiography and computed tomography (CT) preoperatively in the standing position for identification of guidelines for screw insertion in the distal phalanx, and to identify whether standing CT might improve operative time compared with preoperative radiographic planning. STUDY DESIGN: Experimental ex vivo study. ANIMALS: Cadaveric equine thoracic limb pairs (n=10). METHODS: Insertion of a 4.5 mm cortex screw in lag fashion into an intact distal phalanx was evaluated in 2 groups (n=10) of cadaveric equine thoracic limbs. In 1 group, the site, direction, and length of the implant were determined by radiography, and in the other group, by CT. Accuracy of screw placement was verified by specimen dissection. Outcomes were (1) absence of penetration of the articular surface, the solar surface, or the semilunar canal (2) appropriate length and direction of the screw. Surgical time was also measured. RESULTS: No screw penetrated the articular surface, the solar surface, or the semilunar canal in either group. CT was more accurate to identify guidelines for screw insertion (U=23.50, P=.049). With CT, surgical time (mean, 7.7 minutes) was significantly shorter (U=0.000, P=.000) than with radiography (mean, 12.7 minutes). CONCLUSION: Standing CT can be used to accurately determine anatomic landmarks for screw insertion in lag fashion in sagittal fractures of the distal phalanx. CLINICAL RELEVANCE: This study has a clear clinical relevance for improved internal fixation of sagittal fractures of the distal phalanx.

Endoscopic resection of dorsal spinous processes and interspinous ligament in ten horses.

OBJECTIVE: To describe endoscopic surgical subtotal resection of the dorsal spinous processes (DSP) and interspinous ligament in horses. STUDY DESIGN: Descriptive clinical study. ANIMALS: Adult horses (n=10) with back pain and impinging dorsal spinous processes METHODS: Diseased portions of DSP and interspinous ligament were resected by endoscopic surgery, using Destandau Endospine to create a surgical space and provide triangulation for the endoscope, suction cannula, and surgical instruments. Medical records of 10 horses with pain attributable to DSP pathology treated by endoscopic resection of DSP were reviewed to determine intra- and postoperative complications and outcome. RESULTS: Affected portions of DSP were successfully resected with minimal hemorrhage. Limited periosteal reaction was noticed after 3 months in 2 horses. Nine horses had no complications and returned to full work within 8 weeks; 1 developed a subcutaneous abscess, which was successfully managed, and returned to work after 3 months. Surgical resection improved presenting clinical signs and owner's complaint although 2 horses did not return to previous performance levels. CONCLUSION: Resection of DSP and interspinous ligament can be successfully performed endoscopically in horses. Hemorrhage was minimal but reduced visibility. Complications were minimal and most horses returned to work by 8 weeks. CLINICAL RELEVANCE: Endoscopic resection of DSP is a safe and reliable surgical procedure in horses.