Initial treatment
Initial treatment consisted of surgical excision of the osteosarcoma under general anaesthesia and local injection of carboplatin eleven weeks after surgery. For the surgery, the horse was positioned in left lateral recumbency and an Esmarch tourniquet was placed proximal to the carpus. After surgical preparation and draping, an elliptical incision was made around the tumour and the central part of the skin (3 cm wide) was removed. The incision was extended 4 cm proximal and distal of the tumour. Soft tissues were dissected distally and proximally of the mass until the level of the bone. With a periosteal elevator the mass was separated from the underlying bone cortex and removed. At the palmaromedial aspect of the third metacarpal bone and the dorsal aspect of the second metacarpal bone, a depression filled with soft bone-like tissue was present. This was excised and a sample was taken for histopathology. The remaining irregular bone was curetted, resulting in a crater of approximately 5 cm long, 1 cm width and 1 cm deep. The bone and soft tissues were flushed and a Penrose drain was inserted from the crater towards a stab incision distal to the initial incision. The subcutaneous tissue and skin were sutured in a simple continuous pattern, and the wound was covered with an antimicrobial, non-adhesive dressing (Zorbopad1), secured with cotton and an elastic bandage. During the recovery from anaesthesia, radial paralysis of the contralateral front limb was noted. A medical treatment consisting of both local (Ekyflogyl2) (topical gel containing 1.8 mg/ml prednisolone, 8.7 mg/ml lidocaine and 968 mg/ml DMSO applied topically b.i.d. during seven days) and systemic (0.01 mg/kg btw dexamethasone, i.v., q. 24 h during three days) steroidal anti-inflammatory drugs was initiated. The paralysis gradually improved in the hours following surgery and full resolution was obtained after one week.