Six year old TB-cross mare (dressage horse) with nail puncture to medial frog of LH foot 1 week earlier. Horse was started on antibiotics (trimethoprim-sulfamethoxazole) after owner removed nail. Horse became toe-touching lame LH limb the day after the injury. Horse was referred for further evaluation, MRI, and treatment. MRI Scan of LH Foot: nail hole is clearly seen penetrating the frog, digital cushion, deep digital flexor tendon, and impar ligament of the navicular bone. Effusion of the coffin joint was present. No obvious effusion of the navicular bursa was present, but the distal aspect of the navicular bursa had been completely penetrated by the nail. Synoviocentesis (joint tap) of the LH coffin joint showed mildly turbulent synovial fluid, with a moderately elevated white cell count, that grew E. coli on culture. No synovial fluid could be obtained from the navicular bursa.
Amikacin was instilled into both the coffin joint and navicular bursa after both were lavaged. Antibiotics were switched to Chloramphenicol. Initially improved, then toe-touching lame again on LH 1 week later. Contrast Digital Radiography of the nail puncture wound confirmed continued communication with the navicular bursa. Repeat joint tap of the coffin joint showed clear joint fluid with a normal cell count and protein.
A minimally invasive (minimal tissue removal) surgical “Streetnail Procedure” was then performed to provide adequate drainage and treatment of the navicular bursa. We were able to perform a minimally invasive procedure because of the information provided by the MRI Scan. This scan provided us with a perfect surgical roadmap, allowing us to remove only the smallest amount of damaged tissue created by the original nail puncture wound. Removal of only damaged deep digital flexor tendon, instead of unnecessarily resecting more healthy tendon, should significantly increase the chance of future athletic soundness.
Antibiotic PMMA impregnated beads were placed into the surgical defect in the digital cushion. These beads will release high levels of broad-spectrum antibiotics into the local tissues of the navicular bursa for 4-6 weeks, where they are most needed. Culture of the navicular bursa yielded infection with 3 different bacteria.