Operative Techniques in Orthopaedic Surgery (4 Volume Set) 1st Edition

419. Lapidus Procedure

Ian L. D. Le and Sigvard T. Hansen, Jr.

DEFINITION

 Paul W. Lapidus originally described a procedure for the correction of hallux valgus in 1934.

 This procedure was founded on the premise that hallux valgus was a secondary phenomenon to metatarsus primus varus arising from first tarsometatarsal (TMT) hypermobility and a medially oriented first TMT joint.

 The original Lapidus procedure entailed excision of the lateral aspect of the medial cuneiform and first TMT arthrodesis coupled with a distal first metatarsophalangeal (MTP) capsulorrhaphy.

 Many modifications of the original Lapidus procedure have been made, primarily advocating rigid internal fixation as a means for maintenance of reduction, lower nonunion rates, and earlier healing and mobilization.

ANATOMY

 The goal of foot surgery is to obtain a plantigrade position with normal underlying mechanical alignment to allow for weight bearing, shock absorption, accommodation, and power for efficient painless gait.

 Weight should be evenly distributed across the six weightbearing surfaces, consisting of the paired sesamoids underlying the first metatarsal head, the lesser metatarsals, and the calcaneus.

 The lateral column of the foot is designed for mobility to accommodate to uneven surfaces while the medial column, including the first TMT joint, is more rigid to allow efficient power for push-off.

 The first TMT joint is typically 30 mm deep.

PATHOGENESIS

 Equinus is often an underlying pathologic feature predisposing the midfoot to increased repetitive tension and subsequent longitudinal collapse and instability.

 In particular, patients develop first TMT hypermobility potentially in both the axial and sagittal planes.

 Axial instability presents as metatarsus primus varus and resultant hallux valgus.

 Sagittal instability presents as a dorsiflexed first metatarsal with predisposition to dorsolateral peritalar subluxation.

 Furthermore, many patients have a medially oriented first TMT joint and tendency toward metatarsus primus varus.

NATURAL HISTORY

 Symptomatic hallux valgus associated with metatarsus primus varus with underlying first TMT hypermobility and equinus presents with progressive deformity and pain.

 In the face of underlying pathologic first TMT hypermobility or equinus, the hallux valgus deformity will inevitably progress over time in both symptomatology and degree of deformity.

 Consequently, it is imperative to treat any underlying pathology concomitantly with treatment of the hallux valgus deformity.

PATIENT HISTORY AND PHYSICAL FINDINGS

 Physical examination methods include:

 First TMT hypermobility. The examiner rests the index and middle finger of one hand over the dorsal aspect of the first TMT joint to monitor motion. The thumb of that hand rests under the lesser metatarsals. The other hand grasps the first metatarsal between the thumb and fingers and moves it up and down and side to side. Minimal motion should be palpated at this joint. Excessive motion or translation is pathologic and indicative of first TMT hypermobility and instability. Occasionally intercuneiform instability is noted.

 Equinus/Silfverskiöld test. The examiner corrects the hindfoot to neutral subtalar position and checks dorsiflexion range of motion both with the knee in straight extension and flexed 30 degrees. The forefoot appears wide and splayed with a narrow hindfoot. An inability to obtain neutral dorsiflexion with the knee in straight extension that corrects with flexion is indicative of isolated gastrocnemius equinus. An inability to obtain neutral dorsiflexion in both knee extension and flexion is indicative of soleus and gastrocnemius equinus.

 First MTP range of motion. The examiner assesses flexion and extension of the first MTP and repeats the test with the first metatarsal held in a corrected position out of varus. Loss of significant range of motion in a corrected position is indicative of loss of congruency at the MTP joint. Consideration may be needed for additional distal metatarsal osteotomy.

 Lesser metatarsalgia. With hypermobility of the first TMT joint, the first metatarsal is relatively elevated compared to the adjacent lesser metatarsals, resulting in pain and callosities. Callosities are seen beneath the lesser metatarsals, and the skin under the first metatarsal head is often soft from lack of weight bearing. Claw toes and extensor recruitment can result in distal migration of the plantar forefoot fat pad, exacerbating lesser metatarsalgia.

IMAGING AND OTHER DIAGNOSTIC STUDIES

 Plain weight-bearing radiographs including AP, lateral, and oblique views of the foot should be obtained. Every effort should be made to obtain a true lateral radiograph with talar dome overlap.

 Features of first TMT hypermobility

 Signs of second and third metatarsal overload (hypertrophied cortical thickening, stress fracture)

 Dorsal translation or dorsiflexion of first metatarsal

 Plantar widening at the first TMT joint

 First, second, third TMT arthrosis

 First MTP dorsal osteophytes

 Occasionally plain radiographs of the ankle are needed to rule out adjacent involvement.

 Axial sesamoid view can be helpful to assess the extent of metatarsosesamoid arthrosis and degree of sesamoid subluxation.

 Full-length hip-to-ankle radiographs are obtained if there is suspicion of an underlying lower extremity malalignment.

 Seldom is a CT scan, MRI, or other imaging modality needed.

DIFFERENTIAL DIAGNOSIS

 Hallux rigidus

 Metatarsosesamoid arthrosis

 Lesser metatarsalgia

 Interdigital neuroma

 Gout or other inflammatory arthropathy

NONOPERATIVE MANAGEMENT

 Many patients with hallux valgus and hypermobility of the first TMT joint are asymptomatic.

 However, once symptoms develop, progression is inevitable, in particular in patients with underlying equinus contractures.

 Initially management can be directed at resolving local symptoms, including nonsteroidal anti-inflammatories, activity modification, rest, weight loss, shoe modifications, and orthotics.

 In patients with equinus, a well-directed physiotherapy stretching protocol can be helpful.

SURGICAL MANAGEMENT

 Indications

 Hallux valgus with associated metatarsus primus varus and first TMT hypermobility

 Hallux valgus with first TMT arthrosis

 Revision of failed hallux valgus surgery

 Contraindication

 Open physeal growth plates

Preoperative Planning

 AP foot plain radiographs are reviewed for:

 Hallux valgus angle (normal less than 15 degrees)

 Intermetatarsal angle (normal less than 9 degrees)

 Angle of first TMT joint

 Proximal phalangeal articular angle (normal less than 10 degrees)

 Degree of sesamoid subluxation

 Relative lengths of metatarsal heads

 Lateral foot plain radiographs are reviewed for:

 Talar first metatarsal angle

 Based on the above, the surgeon formulates an operative plan, including:

 Degree of correction

 Need to excise lateral wedge from medial cuneiform

 Need for concomitant second or third metatarsal shortening

 Intraoperatively the surgeon assesses for equinus and the need for percutaneous Achilles tendon lengthening or gastrocnemius slide.

Positioning

 The patient is placed supine on a radiolucent table with a padded wedge or bump under the ipsilateral hip to correct external rotation.

 The arm is placed across the chest and the ulnar nerve is padded.

 A tourniquet is applied to the thigh proximal enough to allow access to the proximal tibia for possible bone graft.

 Once the limb is prepared and draped, a towel bump is placed beneath the knee to allow access to the dorsum of the foot.

TECHNIQUES

  Make an incision about 8 cm long between the extensor hallucis longus and brevis, roughly in line with the lateral aspect of the first metatarsal and medial cuneiform (TECH FIG 1A,B).

  Protect the deep peroneal nerve, dorsalis pedis artery, and dorsal cutaneous nerves.

  Identify the first TMT joint by moving the first metatarsal, and reflect the capsule sharply off bone using the Henry angle of dissection.

  Using a quarter-inch osteotome, remove the dorsal osteophytes over the first TMT joint and save them for bone graft.

  At this point, the joint is prepared in one of two ways:

 If there is a need to correct a medially angled first TMT joint, use an oscillating saw. First insert an elevator to determine the slope of the joint. Resect a lateral wedge of bone from the medial cuneiform. Remove the piece and check it to ensure that adequate plantar bone was removed. Resect a minimal amount of bone from the first metatarsal base, again ensuring that enough plantar bone is removed. Avoid excessive metatarsal shortening.

 If there is no medially angled first TMT joint or if there is an excessively short first metatarsal, then prepare the joint using a series of curved osteotomes and curettes. This will give two congruent opposing surfaces for arthrodesis.

  Use an oblong curette to ensure there is no residual plantar lip resulting in excessive dorsiflexion. The first TMT joint is 28 to 30 mm deep.

  Drill each side of the joint with a 2.0-mm drill (TECH FIG 1C).

  This should leave a lateral gap in the first TMT joint.

TECH FIG 1 • A. Planned incisions. B. Step 1, incision between extensor hallucis longus and extensor hallucis brevis. C. Step 1, joint preparation.

  Extend the dorsal incision down to the first web space, taking care to avoid the digital nerves.

  Deep to the attenuated intermetatarsal ligament is the fibular sesamoid and adductor hallucis tendon; leave it intact.

  Protect the fibular sesamoid, identify the first MTP capsule, and incise it longitudinally (TECH FIG 2).

  Make a separate medial incision over the first MTP joint, again watching for the crossing dorsal cutaneous nerves.

  Develop a flap superficial to the first MTP capsule, taking care to avoid thinning the capsule itself.

  Sharply incise the capsule full thickness longitudinally and reflect it plantar and dorsal.

  Tease back the capsular reflections to the first metatarsal head proximally to release the scarred synechiae and allow the sesamoid to move independently.

  Grasp the plantar capsule with a Kocher. With gentle pressure, the metatarsal head should be easily reducible over the sesamoids while simultaneously correcting the intermetatarsal angle and closing the gap at the first TMT joint.

  Resect a minimal amount of medial eminence with a rongeur to allow shaping of the medial metatarsal head into a rounded surface.

TECH FIG 2 • Step 2, distal soft tissue release.

  Before stabilization, hold the foot in a reduced position and palpate the forefoot to ensure it is plantigrade.

  Temporary Kirschner wires may be helpful if assistance is unavailable.

  Burr a bone trough in the mid-dorsal aspect of the first metatarsal about 2 cm away from the joint and tapering out distally.

  Place a 4.0-mm screw after drilling in a lag screw fashion with a 4.0-mm and then a 2.9-mm drill (TECH FIG 3).

  Place a second 4.0-mm lag screw from the dorsal medial cuneiform to the plantar aspect of the first metatarsal base.

  Stabilize this construct by placing a last 4.0-mm screw from the first metatarsal into the base of the second metatarsal.

  Drill this last screw in a lag manner but avoid excessive tightening to prevent overcorrection of the intermetatarsal angle.

TECH FIG 3 • Step 3, fixation.

  Use a 5.0-mm burr to create two small troughs on the dorsomedial and dorsolateral aspects of the first TMT joint to serve as sites for shear-strain-relieving bone graft (TECH FIG 4A,B).

  Also place bone graft in any gaps at the arthrodesis site.

  Bone graft is obtained from the local procedure or proximal tibial bone graft.

TECH FIG 4 • A. Step 4, bone graft trough. B. Step 4, shear strain relieving bone graft.

INTRAOPERATIVE RADIOGRAPHS

  Obtain AP, lateral, and oblique films to ensure appropriate positioning and correction, which is often not seen in detail under C-arm fluoroscopy (TECH FIG 5A,B).

TECH FIG 5 • A. Final AP radiograph. B. Final lateral radiograph.

  Plicate the medial first MTP capsule. Excessive capsule may be excised if redundant.

  It should not be necessary to overtighten the capsule to correct the hallux valgus.

  Close the remaining incisions in layers.

  Gastrocnemius slide or percutaneous Achilles tendon lengthening

 Persistent equinus and forefoot overload

  Akin osteotomy

 Presence of associated hallux valgus interphalangeus

  Second or third metatarsal shortening

 Loss of metatarsal head parabola

 Particularly problematic in patients wearing highheeled shoes

POSTOPERATIVE CARE

 A well-molded below-knee plaster cast is applied with a single anterior univalve to accommodate postoperative swelling.

 The cast is overwrapped with fiberglass before discharge.

 Analgesia is best managed with a popliteal peripheral nerve catheter.

 Six weeks of heel weight bearing in static stance phase only is prescribed.

 The patient is mobilized on a knee scooter.

 Progressive weight bearing is allowed between 6 to 12 weeks in a removable boot.

 The patient is weaned out of the removable boot into standard shoes at 12 weeks.

OUTCOMES

 With appropriate surgical indications, surgical technique, and patient compliance, the patient satisfaction rate is greater than 90%.

 Recurrence of hallux valgus is rare.

COMPLICATIONS

 See the Pitfalls section.

REFERENCES

· Bendnarz PA, Manoli A. Modifed Lapidus procedure for the treatment of hypermobile hallux valgus. Foot Ankle Int 2000;21:816–821.

· Coetzee JC, Wickum D. The Lapidus procedure: a prospective cohort outcome. Foot Ankle Int 2004;25:526–531.

· Hansen ST. Hallux valgus surgery: Morton and Lapidus were right. Clin Podiatr Med Surg 1996;13:347–354.

· Lapidus PW. The author's bunion operation from 1931 to 1959. Clin Orthop 1960;12:119–135.

· Morton DJ. The Human Foot. Morningside Heights, NY: Columbia University Press.

· Morton DJ. Evolution of the longitudinal arch of the human foot. J Bone Joint Surg 1924;22:56–90.

· Sangeorzan BJ, Hansen ST Jr. Modified Lapidus procedure for hallux valgus. Foot Ankle Int 1989;9:262–266.