The Lapidus Procedure

Abstract

The Lapidus procedure and its modification perform the correction of the deformity as close to the center of rotation axis (CORA) as can be performed for any deformity. It is able to correct deformity in all three planes including the frontal plane, which is not possible with any translational or angular metatarsal osteotomy. With newer methods of fixation, this is a far more reliable procedure and can be used to treat all deformities with a minimum of complications and initiate bearing of weight far earlier than had been used historically.

Key Words

Lapidus, bunion, hallux valgus, first tarsometatarsal, arthrodesis, instability

Overview

It is important to distinguish between the procedure as originally described by Paul Lapidus, which included an arthrodesis between the base of the first and second metatarsals, and the modified Lapidus procedure, which stabilizes only the first metatarsocuneiform (MC) joint. The true Lapidus procedure is indicated primarily when significant transverse plane instability is present. This instability may be at the MC joint, or between the medial and middle columns, extending into the interspace between the medial and middle cuneiforms. In general, we perform the modified Lapidus procedure, with addition of stabilization between the first and second metatarsals only if persistent instability is present after arthrodesis of the MC joint. The indications for the Lapidus bunionectomy therefore include hypermobility and instability of the first metatarsal in either the sagittal or the transverse plane.

Examination for sagittal plane instability or hypermobility is best performed by stabilizing the lateral aspect of the foot and then manipulating the medial column in a dorsal or plantar direction ( Fig. 2.1 ). There is obviously a “feel” to this examination, and although objective interobserver reliability may not be achievable among surgeons who examine the foot for instability, each surgeon should establish personal criteria for what is normal and what is abnormal. An important component of this test for increased first ray mobility is to establish that it is only the first metatarsal and not the entire medial column that is mobile. By pushing the lateral column into maximum dorsiflexion and then testing the first ray, a more accurate result will be obtained. Radiographic parameters of instability are helpful but unreliable in planning this operation; however, instability in the transverse plane is easy to document ( Fig. 2.2 ).

Patients with arthritis of the first or second metatarsal cuneiform joint associated with hallux valgus are best treated with an extended Lapidus procedure to include the second MC joint. Arthritis of the second tarsometatarsal (TMT) joint usually is the result of the instability of the first metatarsal, with hypermobility leading to overload of the second metatarsal and, ultimately, arthritis. Frequently, patients with arthritis of the second metatarsal cuneiform joint have associated arthritis of the first metatarsal cuneiform joint as well, but the Lapidus procedure is indicated nonetheless in the absence of arthritis of the first metatarsal cuneiform joint.

The Lapidus procedure is an important adjunct to the correction of the flatfoot deformity when instability of the first MC joint is present.

Incision and Joint Preparation

Two main approaches have been used for exposure of the first TMT and medial aspect of the first metatarsophalangeal (MTP) joint. Either a dorsal, dorsomedial, or medial incision may be used according to the method of fixation or surgeon preference.

The dorsal approach is based off the incision for the first webspace distal soft tissue and adductor release, the incision is then extended proximally, lateral to the extensor hallucis longus tendon, without injury to the deep peroneal nerve ( ). In our experience, this single midline incision is cosmetically acceptable and facilitates exposure of the TMT joint proximally. The exostectomy is not performed at this time because supination of the metatarsal is essential to correct the pronation that is invariably present. This will change the axis of the exostectomy, and if the arthrodesis is performed correctly, it is often not necessary to do an exostectomy. The extensor hallucis longus tendon is retracted medially, and with subperiosteal dissection, the dorsal surface of the articulation is identified and opened. The key to the joint debridement is restraint , because only the articular cartilage and minimal subchondral bone should be removed. Excessive bone removal will result in significant shortening that may cause transfer metatarsalgia. Although some compensation of the shortening will occur will plantar translation, this maneuver has its limits. ( Fig. 2.3 ).

A medially-based approach is also an effective method to perform a Lapidus procedure. The major disadvantage to this approach is the need for a second incision if a formal soft tissue release is performed. However, given the power of correction, we have not found a formal release necessary in most patients and perform an intraarticular release of the lateral capsule for most patients. The benefit of this approach is the avoidance of the dorsomedial branch of the superficial peroneal nerve, which may be encountered and is at risk during a dorsal approach. Visualization of the joint is quite easy, specifically the plantar surface, in addition to ease of medial or plantar-based plating techniques to transfix the first TMT joint. The anterior tibial tendon is not at risk with a dorsal approach to the joint, however, with a medially based approach, the risk of injury does appear to be higher. Care must be taken proximally to identify the anterior tibialis and ensure that it is not transected with aggressive soft-tissue dissection and that the plantar attachment is left in place ( Figs. 2.4 and 2.5 ; ).

Although the first metatarsal is moved laterally during the procedure, translation and rotation of the metatarsal base are preferable. The ease of this manipulation will depend on the configuration of the articulation, which is typically saddle shaped and may not be amenable to this translational movement. In the situation where rotation is not possible, minimal wedge resection of the proximal cuneiform is a very powerful and effective maneuver. Although this can be performed freehand, the use of a Kirschner wire (K-wire) that is placed transversely in the medial cuneiform to guide the osteotomy is more precise. We prefer using fluoroscopy and place the guidewire at the most distal aspect of the medial cuneiform directed proximal and lateral, so that it is parallel to the second metatarsal. A pin distractor along with soft tissue retractors dorsally and plantarly is important to minimize the risk of injury to the dorsal neurovascular bundle, extensor hallucis longus and flexor hallucis longus. A flat cut is made along the first metatarsal, taking care to remove only the subchondral bone. A 9- by 30-mm saw is ideal when performing this wedge resection and to minimize heat necrosis; we no longer use a tourniquet for this procedure. If this is not preferred, liberal use of irrigation is encouraged.

A smooth laminar spreader is inserted into the TMT articulation, and the joint is distracted to provide visualization of the plantar surface of the first metatarsal. The joint is much deeper than might be expected, and for prevention of a dorsal malunion, the entire joint must be denuded. A chisel is used to denude the articular cartilage, and then we perforate the joint multiple times using a small drill bit to drill down to healthy bleeding subchondral bone on both the metatarsal and cuneiform surfaces. The perforation of the joint surfaces is probably an important component of the procedure, and with this minor change to technique, we have rarely encountered a nonunion over the recent past. Local bone graft from the calcaneus or allograft may be used to improve the rate of arthrodesis. There is no data to state concretely that this is required, however, given the ease of local graft from the calcaneus, we have used this more liberally over the last few years. The medial eminence is not removed until the completion of the procedure, as in many cases, the deformity will completely resolve following a well-done Lapidus.

Correction of Deformity

Restoration of the normal intermetatarsal angle is the most difficult part of a Lapidus procedure. Although achieving a union is critical, leaving the first metatarsal adducted compromises the outcome for the patient, and a large medial eminence resection does not solve this problem appropriately.

The metatarsal deformity is corrected with a maneuver that includes adduction and simultaneous supination. The use of supination to correct deformity is a more widely accepted method to correct deformity over the last few years, as opposed to a uniplanar correction. Despite the fact that when we open the first TMT joint, there does not appear to be a rotational deformity, a supination maneuver clearly is very effective to reduce the sesamoid complex.

Manual reduction can be attempted; we prefer to dorsiflex the hallux to force the first metatarsal into slight plantar flexion. The first metatarsal is then squeezed to the second metatarsal, and the combination of hallux dorsiflexion and adduction of the metatarsal serves to correct the deformity. The articular surface should be nicely impacted, and both the base of the first metatarsal and the articular surface of the medial cuneiform should be well apposed. If the alignment is corrected and no instability remains, then the fixation is planned between the first metatarsal and the medial cuneiform only. Temporary fixation with two K-wires is performed with intraoperative fluoroscopic assessment of the reduction of the intermetatarsal (IM) angle and the sesamoids. We have used this method for many years with success; however, in some situations, we have noted difficulty in achieving the reduction manually ( Fig. 2.6 ).