How To Salvage A Failed First MPJ Implant
- Volume 18 - Issue 5 - May 2005
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In many of these cases, one will observe varus malposition of the hallux and second and third digits. These digits can usually be anatomically aligned after the hallux is anatomically positioned.
Step-By-Step Pearls For Distraction Arthrodesis
For the salvage procedure, one should ensure the patient is in a supine position and proceed to prepare and drape the foot and ipsilateral hip. If the heel is the site for bone harvesting, place a bump under the hip. If possible, make the incision over the first metatarsophalangeal joint over any existing scars. The dorsal linear incision usually measures 7 to 8 cm in length and one should make this incision just medial to the extensor tendon of the big toe. Carry the incision to bone and enter the joint. Remove the implant and debride the synovitis. Resect the bone interfaces with an oscillating saw and a high speed burr until one sees bleeding. Depending on the type of implant the patient has, erosion of the medullary canal of the first metatarsal head or proximal base may occur. This erosion can be extensive and require extensive burring until one achieves a healthy “bleeding” bone interface.
After removing the sclerotic margins, pack the defects with cancellous bone and products that promote osteogenesis. Proceed to fashion the structural graft to fit the defect, restoring a plantigrade hallux with good length.
When the graft is in place and is of appropriate length, proceed to fit the graft by using an obliquely placed 3.5-mm AO positional screw and a five- to seven-hole, one-third tubular dorsal neutralization plate. One can usually select a screw measuring 40 to 60 mm in length. Proceed to direct the screw from the medial aspect of the first metatarsal head through the graft to the lateral aspect of the base of the proximal phalanx. Position the plate slightly lateral to the midline of the metatarsal and hallux for coverage with the extensor tendon. One should engage at least four cortices proximal and distal to the graft piece. However, this goal is not always achievable given the extent of sclerosis in the proximal phalanx and the fact that bone length after resection can be extremely short. Proceed to close the extensor tendon over the plate and close the remaining layers.
Pertinent Postoperative Pointers
Postoperatively, one should have the patient wear a modified Jones compression splint for 10 to 14 days and then remove the sutures. Apply a short-leg non-weightbearing cast for four more weeks. Take non-weightbearing radiographs of the foot at six weeks postoperatively.
Depending on the radiographic evidence of healing, one may advance patients to a removable fiberglass walking boot with partial weightbearing for two weeks and follow up with two weeks of full weightbearing in the walking boot. Evidence of radiographic consolidation determines the advancement to regular shoes.
Repeat follow-up visits and weightbearing radiographs of the foot at three and six months postoperatively. Given the higher risk of delayed union or nonunion, utilizing external bone stimulation is routinely recommended, particularly if the length of the structural graft piece exceeds 2 cm.