Fitzpatrick Referrals Oncology and Soft Tissue, University of Surrey School of Veterinary Medicine, Guildford, UK
Tumours of the digits commonly encountered include melanoma, osteosarcoma, squamous cell carcinoma, mast cell tumour, haemangiopericytoma, and other malignancies. It is normally only affecting one toe, but very occasionally several can be involved. Surgery is the mainstay of therapy and positively impacts survival. Other factors, such as patient age, tumour type, site, and stage, were not as important as a curative-intent surgical procedure and so that is where attention should be focused.
Concern exists in surgery of the foot regarding appropriate margins to take, and how the resulting amputation is likely reconstructed. A number of options exist for surgery ranging from removal of P3 through to partial foot amputation.
Staging is recommended prior to surgery and consists of foot radiographs, local lymph node palpation and aspiration, and chest radiographs.
Techniques which will be covered in the lecture include:
Named after August Bier, this is an intravenous regional anesthesia technique in which the foot is anaesthetized for digit surgery. A distal vein is catheterized, the foot exsanguinated by use of an Esmarch tourniquet secured just proximal to the carpus or the hock, and then local anesthetic solution instilled intravenously to infuse the tissues of the foot. The tourniquet ensures the local anesthetic does not leave the foot, as well as ensuring a bloodless field to work in, making for faster, more precise surgery.
The beauty is also patients do not need full general anesthesia, but heavy sedation is often sufficient. In an elderly patient, this can offer some real advantages and allows the surgery to be performed on an out-patient basis.
It is a useful, versatile, easily learnt technique.
Partial Foot Amputation
It is widely believed that only lateral toes can be removed, and amputation of even one central toe will result in lameness and decreased function. Partial foot amputation is used in reference to removal of typically two or more toes, including, at times, the two central toes. When this is performed, the remaining lateral and medial toes are partially filleted and the remaining skin dorsally and palmar/plantarly sutured together, including the pads.
A technique to preserve the skin over the digit, when it is not necessary to be excised in terms of achieving margins. It can be preserved with as wide a base as possible and used to rotate into defects or to cover exposed phalangeal bone.
Mast cell tumours, fibrosarcomas and melanomas and other malignancies are seen within pad tissue. The dense fibrous nature of pad tissue means that achieving margins can be simpler than expected even with limited pad 'space.' Reconstruction techniques for pads include partial excision and fusion, undermining, and simple resection/repair.
Typically when the central toes are removed, this is an alternative to the fusion podoplasty described above, and places less axial stress on the metacarpo/metatarsophalangeal joints than the fusion. Concerns exist re function given the subsequent 'splaying' of the foot, but walking and running are still possible and largely normal.