Pertinent Insights On Treating Lapidus Nonunions

By Graham A. Hamilton, DPM

What You Should Know About Fixation

     In the aforementioned multicenter review, surgeons achieved fixation either with long solid screws or screws and a plate depending on the surgeons’ preference. They used a minimum of two solid screws. In 13 patients (76 percent), surgeons used two solid crossed and stacked, fully-threaded 3.5 mm cortex or 4.0 mm cancellous positional screws. The screws crossed the joint and graft in the sagittal plane, and thereby resist cantilever loads applied to the first metatarsal during the midstance phase of the gait cycle. Orientation of screws in this manner allows one to disperse the force through the length of the screws.      In cases in which surgeons noted intraoperative transverse or sagittal plane hypermobility after the standard crossed two-screw fixation, they stabilized the intercuneiform joint by inserting a third screw from the medial base of the first metatarsal to the second cuneiform. For primary Lapidus arthrodesis, Sangeorzan and Hansen used two 3.5 mm cortical screws for fixation.3 A 3.5 mm cortical screw crossed the first metatarsocuneiform joint to provide compression whereas the second screw served as a derotational screw, crossing from the first metatarsal base to the second cuneiform.      In a biomechanical study, Cohen, et al., compared load to failure with a dorsal locking plate design versus standard crossed screw fixation. Screw fixation for first tarsometatarsal arthrodesis created a stronger and stiffer construct than did the dorsal H-locking plate.8 For four patients, surgeons used a single 3.5 mm or 4.0 mm positional screw along with a dorsal or dorsomedial four- or five-hole neutralization plate. Plate designs consisted of a standard 1/3 tubular compression plate or a reconstruction plate.

A Guide To Post-Op Care And Contraindications

     In our study, 13 patients (76 percent) undergoing revision received immediate post-op bone stimulation. Twelve patients received external bone stimulation while one received internal bone stiumulation. Four patients received no bone stimulation and all of these went on to solid union. While there are various arguments on bone stimulation technology, a subject for another discussion, this modality is a useful adjunct for revision cases. However, one cannot use this as an alternative to meticulous surgical technique.      In regard to postoperative care, all patients wore a short-leg, non-weightbearing cast for six weeks. If early radiographic consolidation occurred at this time, we had the patients progress to a removable walking boot for four more weeks.      Patients demonstrating incomplete radiographic consolidation at six weeks remained non-weightbearing in a short-leg cast for at least four more weeks. At an average of 10 weeks postoperatively, patients advanced to regular supportive shoes with a gradual return to regular activities as tolerated.

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