Lapidus Arthrodesis by an Anatomic Dorsomedial Plate

Abstract

Background: 

Arthrodesis of the first tarsometatarsal joint (Lapidus arthrodesis) is a powerful modality for correction of a bunion deformity because it both addresses the instability of the first tarsometatarsal joint and fuses the base of first and second metatarsal. The Lapidus arthrodesis can be modified to fuse only the first tarsometatarsal joint. A comprehensive clinical evaluation and appropriate imaging modalities are essential to ensure the right indications for Lapidus arthrodesis and to provide an excellent surgical outcome.

Objectives: 

The purpose of our study was to present an anatomic dorsomedial low-profile locked compression plate with a dorsal crossing screw, which can be used for both the original and modified Lapidus arthrodesis.

Patients and Methods: 

In total, 24 Lapidus arthrodesis were performed at our institution with the APTUS dorsomedial anatomic angular stable Lapidus plate (Medartis, Switzerland) for the correction of symptomatic bunion deformity. Severity of HV deformity was determined by the Hallux Valgus angle and the Intermetatarsal angle.

Results: 

All original and modified Lapidus arthrodesis healed postoperatively within 3 months. There was significant improvement of radiographic parameters postoperatively with a P-value of <0.05.

Conclusions: 

The Lapidus arthrodesis allows for long-term bunion correction and contributes to the correction of a possible concomitant Pes planovalgus. Modifications to the surgical technique and use of a stable, novel, anatomic locking plate fixation provide high union rates with minimal postoperative complications.

Hallux valgus (HV) correction is a technically demanding surgery and might have high complication rates and recurrence if performed incorrectly. Poor surgical outcomes can be expected for a moderate deformity [hallux valgus angle (HVA)<40 degrees and intermetatarsal angle (IMA)>13 degrees, incongruent joint] or a severe deformity (HVA>40 degrees and IMA>20 degrees, incongruent joint)¹ if associated with first ray instability or Pes planovalgus. Lapidus arthrodesis provides a potent surgical correction of such moderate or severe HV deformities with first ray instability.

Arthrodesis of the first tarsometatarsal (TMT) joint to treat HV was popularized by Lapidus in 1934,² although it was described earlier by Albrecht,³ Truslow,⁴ and Kleinberg.⁵ The rationale for this intervention is based on the principle that metatarsus primus varus and first ray instability need to be realigned and stabilized in order to obtain a satisfactory correction of HV. Lapidus believed that congenital or atavistic oblique orientation of the first metatarsal cuneiform (MTC) joint is a main causative factor of HV deformities. Compared to distal procedures, Lapidus arthrodesis can provide a high degree of correction as it addresses the deformity proximally at the base.^6,7 The original Lapidus fuses both first TMT joints and the base of first and second metatarsal and is performed concurrently with a distal soft tissue procedure.² In his original paper, the fusion was held with a strong chromic catgut suture. The term “modified” Lapidus indicates arthrodesis of the first TMT joint without fusion of the base of first and second metatarsals.⁸ Since Lapidus described the procedure, the surgical technique has been modified by several authors as they have attempted to reduce or obviate postoperative complications, especially nonunion. Numerous fixation methods have been promoted using a variety of different implants and internal fixation constructs.

In a normal foot, the first metatarsophalangeal (MTP) joint is stabilized by ligamentous, tendinous, and bony structures that maintain its alignment by a delicate balance between medial and lateral forces. However, an imbalance of these forces leads to a contraction of the lateral soft tissue structures and an attenuation of the medial soft tissue structures, causing a HV deformity. As the deformity progresses, instability of the first ray occurs because of the deforming forces of the intrinsic musculature and loss of the windlass mechanism. The concept of hypermobility of the first ray was introduced by Morton in 1928⁹ and later popularized by Lapidus, who suggested that it contributes to lateral ray metatarsalgia and symptomatic excessive pronation.

Instability of the first ray is believed to contribute to both deformity and pain. The first ray plays a significant role in the transfer of weight-bearing forces during mid-stance and toe-off phases. Thus, if the first ray is unstable, the weight will transfer to the lateral aspect of the forefoot causing a callus beneath the lesser metatarsal head consequently presenting as a transfer metatarsalgia, hammertoe, or metatarsal stress fracture.¹⁰

The main joint where first ray mobility occurs is at the TMT joint, with its motion occurring in three planes.¹¹ Normally, the first TMT joint axis orientation is 45 degrees from the sagittal and frontal plane and parallel to the transverse plane. Accordingly, in HV deformities with pronation of the first ray, the dominant plane of instability becomes the transverse (mediolateral) plane, followed by the sagittal (dorsoplantar) and frontal (rotational) plane, respectively.^12,13

Since first ray instability is more prominent in the transverse and sagittal planes, it makes sense to stabilize them both for an optimal outcome. However, current designs of Lapidus plates allow the plates to be placed dorsally, medially or plantarly. Hypothetically, to resist these forces, we should consider 90-90 plating (ie, an arrangement of two plates placed at a relative 90 degrees angle medially and dorsally) with a medial plate to resist the transverse mobility and a dorsal plate to withstand sagittal instability. Recently, an anatomic dorsomedial plate has been designed to improve the success of the Lapidus arthrodesis based on the above concept. The design also provides the flexibility to perform the original Lapidus if required. This present article will detail our experiences in the management of HV by Lapidus arthrodesis using this dorsomedial anatomic plate that offers stability in both planes (APTUS Medartis, Basel, Switzerland).

INDICATIONS AND CONTRAINDICATIONS

The Lapidus arthrodesis is a technique for the treatment of the following pathologic conditions:

• Severe HV deformity.
• Moderate or severe HV deformity with hypermobility of the first ray (excessive movement of the first ray in relation to the lesser metatarsal).
• Recurrent HV or salvage procedure for failed bunion surgery.
• HV deformity with Pes planovalgus.
• Degenerative osteoarthritis or posttraumatic arthritis of the first TMT joint.
• Comminuted Fractures of the first TMT.

The main contraindications are the following pathologic conditions:

• General contraindications including acute or chronic infection with or without osteomyelitis.
• Juvenile HV deformity with an open epiphysis of the first metatarsal base.
• Degenerative arthritis of the first MTP joint.
• Significantly short first metatarsal is considered a relative contraindication.
• Smoking (relative contraindication).
• Charcot arthropathy of the midfoot with or without non-well controlled diabetes.

PREOPERATIVE PLANNING

Clinical Evaluation

Clinical evaluation of the foot consists of focused history-taking and clinical examination. This includes a history of the patient’s pain, previous related surgeries, patient’s general health, occupation, activity of daily living, and level of sporting activity. A comprehensive assessment of the hindfoot, midfoot and forefoot is required to avoid any pitfalls. Clinical examination begins with a gait analysis followed by inspection of the patient in both standing and sitting positions to assess for foot deformities (eg, Pes Planovalgus), plantar keratoses, pseudoexostosis, or surgical scars. It is important to evaluate for tenderness over the first TMT joint and the first MTP joint.

First ray mobility should be assessed clinically in both sagittal and transverse planes with special attention to the transverse one. Although seated with the ankle in the neutral position, the examiner first stabilizes the lateral aspect of the forefoot with one hand and grasps the first ray with the other hand. The examiner then attempts to translate the first ray in a dorsal-plantar and lateral-medial direction. Comparison to the contralateral foot is essential.¹⁴

Shibuya et al¹⁵ found significantly increased first ray motion in patients with HV deformity compared with those without HV deformity (mean difference was 3.62 mm in sagittal plane). However, attempting to quantify this motion clinically can be difficult and depends on the surgeon’s experience. Thus, efforts to accurately measure first ray mobility have evolved to the use of external calipers (eg, Klaue device).¹⁶ When using this device, HV patients with >9 mm of mobility in the sagittal plane are defined as having first ray instability. More recently, 3-dimensional estimation of the first ray mobility using a computed tomography (CT) scan has been also undertaken.¹⁷

Generalized joint hyperlaxity should be ruled out with Beighton’s score. It is also important to evaluate for intrinsic muscle contraction (hammer or claw toe), posterior tibial tendon dysfunction (PTTD), medial ankle instability, and gastrocnemius or Achilles tendon contraction.

Imaging Modalities

Radiographic examination includes weight-bearing dorsoplantar and lateral plain radiographs of the foot, ankle mortise, and hindfoot alignment view (Saltzman view).¹⁸ Parameters to be analyzed from the radiographs include the following:

• Radiographic angles are used to measure the severity of HV deformities and are helpful in preoperative planning and evaluating postoperative outcomes [Hallux Valgus angle (HVA), Intermetatarsal angle (IMA), Distal metatarsal articular angle (DMAA), interphalangeal angle (IPA)].¹⁹
• Assessment of the congruity of the sesamoids.²⁰
• Assessment of the congruity of the first MTP joint.
• Osteoarthritis in the first TMT joint, the first MTP joint, or the Lisfranc joint.
• Hypertrophy of the second MT head or cortical thickening of the first and second MT indicates a possible first TMT joint instability.
• Sloping of the first TMT joint with excessive medial inclination will manifest as metatarsus primus varus deformity.
• Any contraindication findings (eg, an open growth plate).
• Gaping of the plantar aspect of the first TMT joint on the lateral standing view is associated with HV or first MTC joint instability in about 20% of the patients.²¹
• Metatarsophalangeal break to exclude abnormal metatarsal parabola.

A CT scan might be needed in certain cases to assess the configuration and variation of the bony anatomy. Single photon emission CT (SPECT-CT) scan is useful for assessing the extent of active degeneration in different foot joints and the need for surgical intervention in the neighboring joints.²² Magnetic resonance imaging (MRI) is helpful for assessing soft tissue pathologies that might be associated with HV deformity (eg, PTTD).

SURGICAL PROCEDURE

Patient Setup

The patient is placed in a supine position and the foot is positioned at the most distal edge of the bed. A well-padded pneumatic thigh tourniquet is wrapped around the marked extremity. The procedure is typically performed under spinal anesthesia; however, regional anesthesia, like popliteal or ankle blocks, can also be used. The operative foot is prepped and draped up to the knee level following aseptic surgical principles. After exsanguination of the lower limb, the tourniquet is elevated 100 to 150 mm Hg above systolic pressure. Before skin incision, WHO surgical time-out is performed to ensure patient safety and prevent surgical errors, such as wrong-site surgery.

Surgical Approach

A dorsomedial longitudinal skin incision is centered over the first TMT joint and extended as a medial incision to the level of the first MTP joint and the proximal phalanx. The interval is between the Tibialis Anterior tendon and the Extensor Hallucis Longus (EHL) tendon. Proximally, the incision is deepened in the same plane straight down to the base of first metatarsal periosteum. Care should be taken to protect the dorsal cutaneous nerves. All bleeders are identified with hemostasis achieved. The dorsal tarsal-metatarsal ligaments at the TMT joint are resected. Periosteal flaps are raised all around the first TMT joint.

At the distal portion of the approach, the incision is extended over the medial eminence to the level of the MTP joint. The deep fascia is incised in line with the incision, raising the dorsal and planter flaps. The EHL is identified and retracted laterally. The dorsomedial digital branch of the medial cutaneous nerve and the medial branch of the common digital artery which can be injured are identified and protected. A Y-shape or longitudinal capsulotomy of the first MTP joint is performed. Using a sharp dissection, the capsule is freed dorsally, laterally, and plantarly to gain access to the lateral MTP structures and sesamoids. The approach can be extended distally if the Akin osteotomy is indicated.

Surgical Techniques

Distal soft tissue release is an essential step to allow for correction of the IMA. It includes releasing the capsule, adductor tendon, lateral collateral ligament, and transverse metatarsal ligament lateral to the first metatarsal head. Following this, the first TMT joint is exposed. Two Hohmann retractors are used for protection of the dorsal and plantar soft tissue and prepared for articular cartilage denudation. On the basis of our experience, it is difficult to realign the joint by only removing the cartilage from the surface. Therefore, our joint preparation is made with a saw blade. The initial joint resection is performed on the first metatarsal articular surface border parallel to the first metatarsal base and perpendicular to the long axis of the first metatarsal bone. The resection is made taking only a small sleeve of subchondral bone to prevent shortening.

The medial cuneiform articular resection is made perpendicular to the axis of the second metatarsal bone in the coronal plane, that is, cutting a lateral wedge of the medial cuneiform. It is crucial to start the cuneiform cut inside the cuneiform cartilage area to avoid over shortening of the first ray. The wedge is performed biplanarly by removing more bone on the plantar side than dorsally; this helps plantarflexing the first ray during arthrodesis. Both arthrodesis surfaces are debrided and drilled down to healthy bleeding subchondral bone several times with a small drill bit. Occasionally, a lateral bone resection with debridement at the proximal base of the first metatarsal is required to get a good valgisation correction.

The deformity correction maneuver includes first metatarsal adduction, supination, and simultaneous maintenance of neutral plantarflexion, combined with axial compression of the MTP joint. Special attention should be given to correct the pronation of the first metatarsal which brings back the sesamoids to their anatomic articulations; this can be achieved with the assistant dorsiflexing the first MTP joint and applying supination, adduction, and plantearflexion with axial loading. The desired position is held temporarily by one K-wire. After confirmation with fluoroscopy, a cortical screw is inserted with a lag technique from dorsal to plantar and from the middle of the dorsum of the first metatarsal to the medial cuneiform to hold the position.

The Medartis plate (Fig. 1) is a low-profile, locked plate that is placed anatomically from dorsal at the medial cuneiform to medial at the base of the first metatarsal. The plate allows the option of inserting olive k-wires through plate holes and achieving with foceps further compression at the arthrodesis site. Screws are placed over the proximal cuneiform plate holes first. A compression screw is placed distally in the metatarsal metaphysis in the dynamic slot to provide further compression at the arthrodesis side. Following that, the remaining screws are inserted into the plate with locking and/or nonlocking screws depending on surgeon preference and the patient’s bone quality. This is called the “modified” Lapidus arthrodesis technique (Fig. 2).

FIGURE 1: A, Dorsomedial locked plate (Medartis, Basel, Switzerland) that not impinging Anterior Tibialis tendon (illustrated), B, Intraoperative photo of the plate.

FIGURE 2: Modified Lapidus Arthrodesis using a dorsomedial locked plate and axially crossing screw (preoperative and postoperatives views). Dorsoplantar views (A, B), Lateral views (C, D). In this case Akin and Weil osteotomies were indicated.

After performing the “modified” Lapidus arthrodesis, it is imperative to examine for instability between the first and second ray. This can be done by performing a First web space compression stress test under fluoroscopy (Fig. 3). This test was described by Victor Valderrabano: a pretest fluoroscopy image centered over the base of first and second metatarsals is taken. The surgeon dynamically compresses the first web space with his thumb and index finger and a second image is taken. If the IMA opens up excessively, this suggests a first-second ray instability. The “original” Lapidus procedure with fusion of the first to the second metatarsal base is therefore indicated. This can be done by denuding the cortices of the first and second metatarsals. An additional screw is inserted through a specially designed hole in the plate for the “original” Lapidus from the first towards the second MT (Fig. 4). In the first-second metatarsal fusion space, a piece of bone can be inserted (eg, from Akin osteotomy or medial eminence bunionectomy) to promote bone healing. Reexamination of the first ray instability is performed again with the above described test after internal fixation.

FIGURE 3: First web space compression stress test. A, Modified Lapidus arthrodesis in dorsoplantar x-ray view. B, Compression of the first web space reveals increase IMA after modified Lapidus arthrodesis. C, Reexamination of the first ray instability after original Lapidus arthrodesis with no opening up of IMA.

FIGURE 4: Original Lapidus Arthrodesis using a dorsomedial locked plate and crossing screw (preoperative and postoperatives views). Dorsoplantar views (A, B), Lateral views (C, D). In this case Akin and Weil osteotomies were indicated.

At the first MTP joint, the medial eminence is resected (bunionectomy) by an oscillating saw from dorsal to plantar to create a flushed proximal surface of the bunionectomy in line with the metatarsal shaft. Finally, a medial capsular plication at the MTP joint is performed and the soft tissue is closed in layers. Dressings and a splint are applied to the foot.

Adjunct Procedures

Lapidus arthrodesis has been associated with other adjunct procedures. Akin osteotomy is the most commonly combined procedure used to correct interphalangeal angle (IPA) and pronation of the proximal phalanx. Akin osteotomy could be done by extending the approach distally or through a separate incision. A closing wedge osteotomy is performed at the first proximal phalanx and is held with a 3.0 mm cannulated compression screw (Medartis APTUS CCS).

If the first MTP joint remains incongruous after Lapidus arthrodesis, a Chevron osteotomy may be performed. If the patient has symptomatic metatarsalgia and abnormal metatarsal parabola, Weil osteotomies might be indicated. A Weil osteotomy of the lesser metatarsal will additionally lengthen the short first ray. If needed, the pes planovalgus deformity, posterior tibial tendon dysfunction, and contraction of gastrocnemius complex should be addressed along with HV correction.

Postoperative care

During the first postoperative week, the physiotherapy program focuses on lymphatic drainage and gently improving the range of motion of the first MTP joint and hindfoot. Early weight bearing with a stabilizing walker is allowed with 15 kg of partial weight bearing for 6 weeks. After 6 weeks, we recommend progressing into full weight bearing and using a more flexible stabilizing shoe for another 6 weeks.

Possible complications

• Nerve injury.
• Delayed union, especially in smokers.
• Nonunion: significantly lower in this technique.
• Malunion: more common in noncompliant patients and smokers.
• Prominent hardware that might require removal at a later date. However, this is a low-profile anatomic plate and rarely causes irritation in our experience.
• Iatrogenic hallux varus because of excessive correction or soft tissue release.

PATIENTS AND METHODS

Between January and December 2017, we performed 24 Lapidus arthrodesis (15 original and 9 modified Lapidus arthrodesis) at our institution with the APTUS dorsomedial anatomic angular stable Lapidus plate (Medartis, Switzerland) for the correction of symptomatic bunion deformity. Severity of HV deformity was determined by the HVA and the IMA.

RESULTS

All original and modified Lapidus arthrodesis healed postoperatively within 3 months and showed the following radiologic improvements (Table 1).

TABLE 1: Radiological Angles

DISCUSSION

Lapidus arthrodesis is a powerful modality to correct HV deformities and lower recurrence rate because it addresses both the instability of the first ray and the metatarsus primus varus. The progression of a HV deformity worsens with instability of the first ray, leading to an increase in deformity severity and forefoot disorders such as metatarsalgia. Metatarsus primus varus malalignment is the most proximal promoter of the HV deformity.

The main advantages of our technique with a modern dorsomedial plate are the following:

• Easy plate placement because of its conformity to the local anatomy.
• The dorsomedial plate position results in high stability as it prohibits pathologic movement of the first MTC joint in all planes (transverse, sagittal and frontal).
• No hardware irritation or impingement on the anterior tibialis tendon and easy placement of the crossing lag screw.
• Plate designed to have an integrated hole for placing an original Lapidus screw.

Since the Lapidus arthrodesis was first described, several methods of internal fixation have been used for HV correction. The most recent studies recommend using a combination of locking plate systems and an intrafragmentary/interfragmentary compression screw (Table 2).

TABLE 2: Recent Studies of Locking Plate Fixation With Compression Screw in Lapidus Arthrodesis

Although the most common complication after Lapidus arthrodesis is nonunion, several factors can improve bone healing to mitigate this risk. In general, a more stable fixation results in higher union rates and reduced postoperative complications because of improved primary bone healing. The Medartis locking plate we used is designed to offer stability, avoid impingement of the soft tissue, and allow maximal compression at the fusion site (by combination of compression over olive k-wires, a TriLock Plus locking compression hole in the plate, and the possibility to place a crossing lag screw). Joint preparation techniques, bone autograft, and increased surface area by drilling holes are essential to encourage biological healing. Even with meticulous surgical technique, patient related factors such as smoking, medical comorbidities, and medications (eg, NSAIDs) can still cause nonunion.

Postoperatively, we encourage patients to mobilize early with 15 kg weight bearing for the first 6 weeks; afterwards, they are allowed to gradually increase to full weight bearing. We believe this protocol reduces the risk of nonunion but also allows the patient to start early functional rehabilitation.

Shortening of the first ray after Lapidus arthrodesis can lead to complications such as transfer metatarsalgia. This complication can be avoided by reducing the bone loss with minimal bone resection and using the medial eminence bone as autograft.

CONCLUSIONS

Lapidus arthrodesis is a powerful modality for correction of a bunion deformity. However, the Lapidus arthrodesis can be unpopular because of perceived high rates of nonunion from previous poor internal fixation modalities. With a novel anatomic dorsomedial locking plate as well as a good surgical technique, the Lapidus arthrodesis can provide a successful outcome with statistically significantly reduced postoperative complications (eg, nonunion) but still allows early postoperative mobilization.