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

419. Lapidus Procedure

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

DEFINITION

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

images 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.

images 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.

images 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

images 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.

images 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.

images 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.

images The first TMT joint is typically 30 mm deep.

PATHOGENESIS

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

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

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

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

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

NATURAL HISTORY

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

images 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.

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

PATIENT HISTORY AND PHYSICAL FINDINGS

images Physical examination methods include:

images 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.

images 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.

images 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.

images 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

images 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.

images Features of first TMT hypermobility

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

images Dorsal translation or dorsiflexion of first metatarsal

images Plantar widening at the first TMT joint

images First, second, third TMT arthrosis

images First MTP dorsal osteophytes

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

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

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

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

DIFFERENTIAL DIAGNOSIS

images Hallux rigidus

images Metatarsosesamoid arthrosis

images Lesser metatarsalgia

images Interdigital neuroma

images Gout or other inflammatory arthropathy

NONOPERATIVE MANAGEMENT

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

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

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

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

SURGICAL MANAGEMENT

images Indications

images Hallux valgus with associated metatarsus primus varus and first TMT hypermobility

images Hallux valgus with first TMT arthrosis

images Revision of failed hallux valgus surgery

images Contraindication

images Open physeal growth plates

Preoperative Planning

images AP foot plain radiographs are reviewed for:

images Hallux valgus angle (normal less than 15 degrees)

images Intermetatarsal angle (normal less than 9 degrees)

images Angle of first TMT joint

images Proximal phalangeal articular angle (normal less than 10 degrees)

images Degree of sesamoid subluxation

images Relative lengths of metatarsal heads

images Lateral foot plain radiographs are reviewed for:

images Talar first metatarsal angle

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

images Degree of correction

images Need to excise lateral wedge from medial cuneiform

images Need for concomitant second or third metatarsal shortening

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

Positioning

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

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

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

images 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

CORRECTION OF METATARSUS PRIMUS VARUS AND PREPARATION OF FIRST TARSOMETATARSAL JOINT

images  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).

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

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

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

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

images 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.

images 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.

images  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.

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

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

images

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

DISTAL SOFT TISSUE PROCEDURE

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

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

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

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

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

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

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

images  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.

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

images

TECH FIG 2  Step 2, distal soft tissue release.

STABILIZATION

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

images  Temporary Kirschner wires may be helpful if assistance is unavailable.

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

images  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).

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

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

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

images

TECH FIG 3  Step 3, fixation.

BONE GRAFTING

images  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).

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

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

images

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

INTRAOPERATIVE RADIOGRAPHS

images  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).

images

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

WOUND CLOSURE

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

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

images  Close the remaining incisions in layers.

ADDITIONAL PROCEDURES TO CONSIDER

images  Gastrocnemius slide or percutaneous Achilles tendon lengthening

images Persistent equinus and forefoot overload

images  Akin osteotomy

images Presence of associated hallux valgus interphalangeus

images  Second or third metatarsal shortening

images Loss of metatarsal head parabola

images Particularly problematic in patients wearing highheeled shoes

images

POSTOPERATIVE CARE

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

images The cast is overwrapped with fiberglass before discharge.

images Analgesia is best managed with a popliteal peripheral nerve catheter.

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

images The patient is mobilized on a knee scooter.

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

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

OUTCOMES

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

images Recurrence of hallux valgus is rare.

COMPLICATIONS

images 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.



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