How To Handle Lapidus Complications
The lapidus arthrodesis for the treatment of symptomatic hallux valgus remains a controversial subject in foot surgery. Since its inception in the early 1900s, the lapidus arthrodesis has been abandoned by many surgeons mainly due to its high complication rate, particularly nonunion. However, it has regained popularity in recent years due to better fixation techniques and an improved understanding of first ray biomechanics.
The major advantage of performing a metatarsocuneiform arthrodesis is it allows you to realign the first metatarsal at the apex of the deformity along with stabilizing the first ray. Moreover, the efficiency of peroneus longus in stabilizing the medial column is enhanced as well. The procedure also enhances the efficiency of the peroneus longus in stabilizing the medial column. The indications for lapidus are hallux valgus with an increased intermetatarsal angle, metatarsocuneiform joint arthrosis, hypermobility of the medial column and/or lesser metatarsal overload. It is also used as a salvage procedure for recurrent hallux valgus after a failed metatarsal osteotomy. One may treat some cases of hallux limitus secondary to a long metatarsal by shortening the metatarsal through the arthrodesis site.
In 1935, Dudley Morton described a foot type in which first ray hypermobility is associated with ankle equinus and a short first ray and/or long second metatarsal. The concept of first ray hypermobility is difficult to quantify. However, its existence becomes obvious with certain clinical scenarios. You will typically see lesser metatarsalgia associated with discrete callosities in cases of first ray insufficiency. Radiographic features suggestive of hypermobility include metatarsocuneiform joint obliquity greater than 30 degrees, diastasis at the first metatarsocuneiform intercuneiform joint, cortical thickening of the lesser metatarsal shafts and a dorsal metatarsocuneiform traction spur.
Longstanding hypermobility results in altered weightbearing mechanics and the ground reactive forces are transferred onto the lesser metatarsals and midfoot. In the early stages, one may see rupture of the second metatarsophalangeal plantar plate with digital dislocation. Stress fracture of the second and/or third metatarsal shafts is also an indicator of first ray insufficiency. Arthritis of the midfoot is typically an end-stage manifestation of untreated hypermobility.
Using Two-Screw Fixation In First Metatarsocuneiform Joint Arthrodesis
While there are several fixation techniques described for first metatarsocuneiform joint arthrodesis, two-screw fixation is required for a stable construct and is considered the standard of care.
We utilize long cross screw fixation with 3.5-mm cortical screws, a technique advocated by Hansen. You would insert the first screw approximately 2 cm distal to the fusion site along the dorsal aspect of the midshaft region of the first metatarsal. One should position the screw’s long axis almost perpendicular to the fusion site. Doing so increases the screw’s compressive force. This orientation also resists the cantilever bending moment of the first ray. Place the second screw from the dorsal lateral aspect of the medial cuneiform into the metatarsal base.
A third screw may be used if additional stability is needed. There are several options in regard to the alignment of subsequent screws. Patients with a wider first metatarsal may accommodate a third screw directly across the fusion site. Other options include placing a temporary screw from the first metatarsal base into either the second metatarsal base or intermediate cuneiform. This technique is often used to add stability to the construct during the bone healing process.
A previous cadaveric study performed by the senior author demonstrated greater medial column stiffness with the second metatarsal screw when compared to the intermediate cuneiform screw. However, this finding was not statistically significant. Removing the second metatarsal screw does involve a risk for a stress fracture so one should closely monitor the patient’s progress after screw removal.