Calcaneal Autograft: Can It Facilitate Salvage Of A Failed First MPJ Implant?
- Volume 23 - Issue 3 - March 2010
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Use a sagittal saw or osteotome to cut the outline of the graft. Take care to ensure accuracy with the space between the parallel cuts. Also remember the depth should be no greater than half the width of the calcaneus. Make the inferior transverse cut last. The resulting block graft is approximately 2 cm tall by 1 cm wide. Insert a curved 1 cm osteotome at the midline of the calcaneus from the superior aspect and drive it plantarly to separate the block of bone from its bed. One may insert allogenic cancellous cubes or another bone substitute into the defect to encourage union prior to weightbearing.
Additionally, surgeons may insert a 7.3 mm screw across the harvest site to discourage a potential postoperative fracture. In most cases, full weightbearing is contraindicated for six to eight weeks.
Cut and contour the bicortical calcaneal bone graft to fill the defect and restore a plantigrade hallux with normal parabolic length and alignment. When the calcaneal bone graft is in the desired corrected position, insert one 0.062-inch Kirschner wire obliquely from the medial aspect of the metatarsal neck across the graft and into the lateral aspect of the proximal phalanx to stabilize the graft temporarily. The surgeon can later utilize this hole as a guide for a 3.5 mm compression screw if he or she desires.
However, in most circumstances, a low-profile locking plate is preferrable. Contour one or two small fragment, low-profile locking plates and place the plate(s) dorsally, overlying the midline of the first MPJ. Generally, one would place two to four screws in the metatarsal, one in the graft and two in the proximal phalanx in a polyaxial configuration.
Often it is necessary to lengthen the extensor hallucis tendon of the first MPJ through a Z-step tendon lengthening and stitch it with a non-absorbable 4-0 suture at the end of the procedure if you see considerable clawing.6 Additionally, one may perform concurrent surgery to the forefoot if desired.
Surgeons may utilize intraoperative C-arm fluoroscopy prior to closure to reaffirm the position of the hallux and the placement and fixation of the calcaneal bone graft. Compare the restoration of the length of the first metatarsal to that of the lesser metatarsals. Ideally the center of the first and second metatarsal heads should be on the same line. Proceed to close the extensor tendon over the plate and close the remaining layers.
Keys To The Postoperative Protocol
Postoperatively, have the patient use a modified Jones compression splint for 10 to 14 days. At this time, remove the sutures. One should subsequently ensure non-weightbearing for two weeks. Once you see radiographic consolidation, gradually promote the patient to full weightbearing in a walking boot and finally into regular shoe gear.
Schedule quarterly follow-up visits with accompanying weightbearing radiographs for the first year postoperatively. Be advised that radiographic healing with complete incorporation of the graft can take up to a year. External bone stimulators are routinely recommended given the high risk of delayed union or nonunion. Researchers have also recommended that physicians routinely give a low molecular weight heparin such as enoxaparin 40 mg (Lovenox, Sanofi Aventis) for four to six weeks in patients who are at a higher risk of deep venous thrombosis.4,6