Arthroscopic removal of palmar intermediate carpal bone fracture fragments in four horses using a transthecal approach through the carpal flexor tendon sheath.

OBJECTIVE: To describe the removal of palmar intermediate carpal bone (ICB) fracture fragments using a transthecal approach through the carpal flexor tendon sheath. STUDY DESIGN: Case series. ANIMALS: Four horses with fractures of the palmar aspect of the ICB. METHODS: Two horses were injured when falling and two during recovery from general anesthesia. Three horses underwent MRI to supplement conventional imaging. Three horses had concurrent fractures of the radial and/or accessory carpal bones. Conventional proximolateral carpal sheath arthroscope and instrument portals were used, supplemented with a medial instrument portal through the carpal flexor retinaculum to access the palmar carpal ligament. Optimized dissection through the latter was facilitated by needle guidance and radiography. The fragment was dissected from the soft tissue attachments and the palmar ICB fragments retrieved through the carpal sheath in all horses. Surgery time was 85 to 142 min. RESULTS: Limitations of this technique include a long surgery time and the potential for hemorrhage to impair visibility during surgery. All four horses were discharged 3 to 8 days postoperatively. Three horses returned to full athletic work within 9 months postoperatively and one horse was euthanized due to persistent lameness. CONCLUSION: A tenoscopic transthecal carpal flexor tendon sheath approach provides access for removal of palmar ICB fracture fragments but should be viewed as an advanced arthroscopic procedure. CLINICAL SIGNIFICANCE: A transthecal approach through the carpal flexor tendon sheath offers an alternative technique for removal of palmar ICB fracture fragments.

Preliminary study of proton magnetic resonance spectroscopy to assess bone marrow adiposity in the third metacarpus or metatarsus in Thoroughbred racehorses.

BACKGROUND: Magnetic resonance spectroscopy (MRS) has been used to investigate metabolic changes within human bone. It may be possible to use MRS to investigate bone metabolism and fracture risk in the distal third metacarpal/tarsal bone (MC/MTIII) in racehorses. OBJECTIVES: To determine the feasibility of using MRS as a quantitative imaging technique in equine bone by using the 1H spectra for the MC/MTIII to calculate fat content (FC). STUDY DESIGN: Observational cross-sectional study. METHODS: Limbs from Thoroughbred racehorses were collected from horses that died or were subjected to euthanasia on racecourses. Each limb underwent magnetic resonance imaging (MRI) at 3 T followed by single-voxel MRS at three regions of interest (ROI) within MC/MTIII (lateral condyle, medial condyle, proximal bone marrow [PBM]). Percentage FC was calculated at each ROI. Each limb underwent computed tomography (CT) and bone mineral density (BMD) was calculated for the same ROIs. All MR and CT images were graded for sclerosis. Histology slides were graded for sclerosis and proximal marrow space was calculated. Pearson or Spearman correlations were used to assess the relationship between BMD, FC and marrow space. Kruskal-Wallis tests were used to check for differences between sclerosis groups for BMD or FC. RESULTS: Eighteen limbs from 10 horses were included. A negative correlation was identified for mean BMD and FC for the lateral condyle (correlation coefficient = -0.60, p = 0.01) and PBM (correlation coefficient = -0.5, p = 0.04). There was a significant difference between median BMD for different sclerosis grades in the condyles on both MRI and CT. A significant difference in FC was identified between sclerosis groups in the lateral condyle on MRI and CT. MAIN LIMITATIONS: Small sample size. CONCLUSIONS: 1H Proton MRS is feasible in the equine MC/MTIII. Further work is required to evaluate the use of this technique to predict fracture risk in racehorses.