Current Concepts With The Lapidus Bunionectomy

When it comes to treating hallux valgus, the Lapidus arthrodesis can be an effective procedure. These authors discuss the evolution of the technique, offer a guide to key indications and contraindications, and provide essential step-by-step pearls for performing the procedure.

     Hallux valgus is one of the most common deformities we see as foot and ankle surgeons. There are over 100 different types of surgical procedures for this deformity.1,2 With the considerable variety of procedures, it is fairly evident that no one procedure has been able to provide excellent results in all patients and for all deformities.

     Most clinical studies of bunionectomies report a higher percentage of successful results than complications. However, there is no procedure that one can successfully apply to all bunion deformities. 3 Most procedures offered in the literature for the correction of hallux valgus do work if surgeons properly execute and perform the procedures for the right indications. 1,4 Research has shown that head osteotomies, base osteotomies and Lapidus arthrodesis procedures have similar rates of complications and similar needs for revision surgery. 5

     We have come from training environments where podiatric surgeons have utilized the first tarsometatarsal arthrodesis and variations of this procedure with much success. However, we are the first to recognize that this procedure is not the panacea for all feet with hallux valgus nor is the procedure without complications.

     Let us take a closer look at the Lapidus arthrodesis and the modifications of this procedure for correcting hallux valgus and first metatarsus primus varus deformity. While it is beyond the scope of this article to provide a comprehensive or authoritative article on the subject, we hope to provide valuable insight to foot and ankle surgeons who address these deformities in their practices.

A Closer Look At The Evolution Of The Lapidus Procedure

     In 1996, Hansen, a leader in the Lapidus arthrodesis surgical approach, reviewed the history behind the first tarsometatarsal arthrodesis as well as his rationale for using this procedure.

     He delineates how Dudley Morton, MD, an anatomist, recognized the anatomical variants that were often associated with the deformity to include a short first ray, atavistic cuneiform and equinus deformity. Paul Lapidus, MD, attempted to address the deformity where he felt the deformity originated at the first tarsometatarsal joint (TMTJ) area. Hansen explains how a lack of adequate internal fixation led to less than desirable outcomes and for a time, Lapidus abandoned the procedure. 6

     Hansen describes his own coming of age with the procedure and the evolution of the procedure in his hands. He concurs with Lapidus that one should address the deformity at its origin, the first TMTJ. Hansen also believes that to achieve success, surgeons must address significant associated pathology and biomechanical faults that contribute to the deforming force.

     As Hansen eloquently stated, “In my opinion, focusing on the bunion and discussing the advantages and disadvantages of various bunionectomies is an incredibly naïve and shortsighted approach to this problem.” 6 We believe most foot and ankle surgeons would agree with this statement.

     Focusing on reduction of the intermetatarsal angle and other measurable parameters via osteotomies or fusions is now the standard of care for bunion “correction.” Selecting the appropriate procedure based solely on radiographic parameters is inadequate. In order to facilitate appropriate procedure selection, one must obtain radiographs and ensure a thorough history and physical examination. (See “A Guide To Indications And Contraindications For The Lapidus Arthrodesis” on page 42.) A thorough discussion with the patient regarding his or her expectations and goals is vital to ensure that the patient’s needs and expectations are met. Also, a thorough discussion on the risks, benefits, possible complications and expected postoperative course facilitates improved patient satisfaction.

What Are The Pertinent Biomechanical Factors?

     The reliance of the body on normal first ray mechanics suggests that re-establishing normal function of the first ray is of paramount importance. During midstance, a cantilever load occurs on the first ray during normal physiologic loading. 7 It is well known that a structurally stable first ray is necessary for even distribution of weight across the forefoot. Its buttressing effect along the medial column of the foot also resists overpronation of the midfoot and collapse of the medial longitudinal arch. 8 This in turn helps prevent medial deflection of body weight and maintains appropriate alignment of the foot with the more proximal joints of the lower extremity.

     The properly functioning first ray provides stability through the windlass mechanism, offering a structurally sound platform during the midstance and propulsive phases of the gait cycle. 9,10 This is especially critical as the leg passes anteriorly over the ankle and the single foot’s first ray bears up to one third of the body’s weight during late midstance and push off. 11 It is easy to see how a dysfunctional first ray, with or without hallux valgus, can deleteriously affect the function of the whole foot and lower extremity.

     Researchers have shown that feet with hallux valgus carry less than normal loads under the first metatarsal with a subsequent relative increased load under the lesser metatarsals. 12 A malaligned first metatarsal may adversely affect overall foot function. Conversely, a properly aligned first metatarsal can improve alignment of the hindfoot and affect proximal deformity. 13-15

     In normal walking, the greatest loads are beneath the first metatarsal. The metatarsals must resist bending and shear forces during forefoot loading. Otherwise, flattening of the medial longitudinal arch, lesser metatarsal stress fractures and metatarsalgia may ensue. 12

     It is clear the first ray must bear its appropriate load during midstance and propulsion. 12 If it cannot sufficiently do so, this may have profound effects on the rest of the foot. A hypermobile or unstable first ray is functionally similar to a short or elevated first ray. Appropriate length, alignment and stability of the first ray are essential to activation of the windlass mechanism. 10,14 According to Stainsby, restoring this function “must surely be one of the main aims of surgery for hallux valgus.” 14

Key Insights On Associated Pathology

     In addition to correcting the bunion with the surgical treatment of hallux valgus, one must also address the associated pathology caused or aggravated by the bunion deformity.

     Authors have shown that concomitant pes planovalgus, overpronation of the midfoot or hypermobility of the first ray play etiologic roles in the development of hallux valgus. Moreover, researchers have blamed their continued presence for a higher rate of complications following surgery. 16,17 The first ray is vital to the overall function of the foot and lower extremity so dysfunction in the form of hallux valgus is often only part of the picture. One can consider hallux valgus as a symptom of a more complicated dysfunctional foot. If one does not address the cause of the symptom, then a less than satisfactory result may occur.

     Concomitant pes planovalgus, lesser metatarsalgia, hammertoes and hallux limitus are often associated with a dysfunctional first ray and these dilemmas can complicate the clinical picture. When it comes to isolated hallux valgus, the type of procedure one performs is not as critical as long as the patient maintains a normal length and alignment. Of course, if normal anatomic restraints or weightbearing distribution are disrupted, then associated pathology can develop as a result of the incorrect bunion procedure.

     One must take extra care in the surgical decision-making process when associated pathology is present. Flatfoot deformity not only increases the likelihood of hallux valgus development but renders successful correction much more difficult. Since overpronation of the midfoot leads to increased medial deflection of body weight, the biomechanical forces going through the first metatarsal create a bending moment in the medial column. This results in elevation of the first ray and increases the likelihood of recurrence if the first metatarsal cannot act as a stable buttress. 9

     A similar scenario ensues if the first metatarsal is congenitally or iatrogenically short, elevated or hypermobile. In this case, the insufficient first ray can cause collapse of the medial longitudinal arch. Perhaps this is a desired effect in correcting hallux valgus in a cavus foot. However, in a normal or flat foot, this only increases dysfunction and deformity.

     Lesser metatarsal overload can be secondary to a poorly functioning first ray. Hypermobility can be a predisposing factor in lesser metatarsalgia. Whether the lesser metatarsal symptoms manifest as pain, synovitis, predislocation syndrome, a plantar plate tear, stress fracture or a simple callus, an insufficient first ray can be the cause. Procedure selection, in most cases, is limited to those procedures that address the cause of the lesser metatarsal overload. Stabilizing the first ray is of paramount importance.

A Step-By-Step Guide To The Lapidus Procedure

     Lapidus originally resected the cortices of adjacent surfaces of the first and second metatarsals, and the first tarsometatarsal joint. We have been utilizing a modified Lapidus arthrodesis that emphasizes fusion of only the first tarsometatarsal joint with some variations, depending on surgeon preference.

     Make a longitudinal incision from the first cuneiform to the base of the proximal phalanx of the hallux. Proximally, the incision curves laterally to avoid the dorsomedial cutaneous nerve and to gain more central exposure over the first metatarsocuneiform joint. The remainder of the incision lies medial to the extensor hallucis longus tendon. Address the first MPJ first. Resect the hypertrophic medial eminence if it is present. One would usually accomplish this with a rongeur and a high speed burr. Avoid over-aggressive eminence resection. For this reason, one usually does not utilize a saw blade. Preserve as much joint surface as possible to avoid varus subluxation once you have laterally translated the metatarsal.

     Resect the conjoined adductor tendon in the first interspace along with the sesamoid ligaments. Identify the dorsomedial cutaneous nerve and medially retract it. Expose the first tarsometatarsal joint through a transverse capsulotomy. Remove the cartilage with a sharp osteotome and leave the subchondral plate intact.

     Insert a laminar spreader to gain access to the cartilage at the deeper part of the joint. Newer pin type distracters are also available to allow for excellent visualization. One must visualize the joint, approximately 3 cm deep, to ensure adequate removal of the deeper cartilaginous surfaces. Fenestrate the subchondral bone and “scallop” it to promote bleeding. One can perform this with a curved osteotome, drill bit or both.

     Preserve the peripheral rim of subchondral bone to retain as much length as possible and to provide added stability for internal fixation. 6 In most cases, one can reduce the first metatarsal in the transverse and sagittal planes by simply “dialing in” the amount of correction. In a foot with a medially angulated or atavistic cuneiform, one would plane or “feather” the lateral aspect of the joint to accommodate appropriate correction of the deformity with a small sagittal saw, osteotome or burr. Fix the joint with two crossed and stacked 3.5-mm or 4.0-mm cortical solid screws by placing these across the fusion site in lag fashion.

What You Should Know About Compression And Screw Orientation

     Compression across a fusion site provides stabilization and reduces shear forces across the bony interface. This allows the extremity to undergo functional loading without osseous or fixation failure. The surgeon can achieve the greatest amount of compression by placing the screw perpendicular to the fusion site. However, it offers inadequate resistance to axial loading. The surgeon should take both of these factors into account when it comes to the orientation of interfragmentary screws. Often, placement of the screw halfway in between being perpendicular to the joint line and perpendicular to the long axis of the bone provides maximal stability against the major forces acting on the bone.

     Place the first screw, the “home run screw,” axially from the dorsomedial surface of the first metatarsal base to the plantar surface of the medial cuneiform. This screw is usually 45 to 50 mm in length. Place the second screw from the dorsal aspect of the medial cuneiform to the plantar lateral aspect of the first metatarsal. This screw is usually 36 to 45 mm long. Certain authors have found that a positional screw is adequate for a second screw but we would not recommend it. 18 The plantar compression afforded with the second lag screw facilitates a more predictable union rate.

     The use of cannulated screws has become increasingly popular over the years. Guide wires allow accurate placement, especially when one uses them under fluoroscopic guidance. However, remember that the mechanics of cannulated screws differ from standard, solid screws. Cannulated screws are approximately 1.7 times weaker than a solid, cortical screw of the same diameter. They are inferior in both bending and pullout strength. Therefore, one should utilize a larger diameter screw to compensate when inserting a cannulated screw. For healthy patients, these implants will usually work quite nicely. However, if any comorbidity exists, the surgeon should employ solid lag screws.

     Currently, there are also specific “Lapidus” locking plates available that are designed for this fusion. Cohen, et al., in a biomechanical study, compared load to failure with a dorsal locking plate design versus standard cross-screw fixation. Screw fixation for the first TMTJ arthrodesis created a stronger and stiffer construct than the dorsal H-locking plate. 19

     The authors would also not recommend a locking plate in this location for the primary fusion as the bone is subcuticular and the patient would most likely feel the prominent plate, which would likely require removal.

     After placing the two crossed and stacked screws, the surgeon should place an index finger in the first inner space and apply a varus stress test to the first metatarsal. One could also employ a small bone hook. If the surgeon can medially translate the first metatarsal with minimal effort and reproduce the intermetatarsal (IM) angle, then the first ray is still hypermobile and one should insert a third positional screw. The position of the screw can vary. A positional screw from the medial base of the first metatarsal to the second cuneiform or from the first metatarsal base across the second metatarsal base provides further stability and closes down the intermetatarsal angle.

     Take care not to over-tighten this screw as a negative IM angle and a varus malposition of the first MPJ can result. Perform the varus stress test again to assess stability. In rare circumstances, a fourth screw is required. If this is the case, place this screw from the medial cuneiform to the intermediate cuneiform.

Essential Tips On Postoperative Management

     Patients who have undergone a modified Lapidus arthrodesis wear a modified Jones compression splint with posterior splinting or fracture boot for 14 days.

     Patient adherence and the amount of edema dictate the type of immobilization. For adherent patients, one can utilize an Ace wrap and fracture boot, which allows for ankle range of motion. This also enhances and accelerates the recovery period. Non-adherent patients will need cast immobilization to help protect them from themselves.

     Following suture removal, the patient will continue strict non-weightbearing for an additional four weeks. At this time, one should obtain radiographs to evaluate the arthrodesis. If the arthrodesis is stable and healing, then weightbearing commences in a fracture boot with transition to full weightbearing taking place over the next two weeks. At that point, the patient returns to supportive athletic footgear. The surgeon determines further follow-up and advancement to full activities on an individual basis.

What About The Potential Complications?

     Multiple studies have reviewed the nature and rate of complications with the Lapidus arthrodesis. The most publicized complication with the Lapidus arthrodesis is nonunion.

     Catanzariti, et al., reported primary arthrodesis in 42 of 47 (10.6 percent) feet.20 Sangeorzan reported non-union in four of 40 (10 percent) fusions.21 In the largest series to date looking at the rate of nonunion in Lapidus arthrodesis, Patel, et al., noted 12 out of 227 (5.3 percent) fusions went on to nonunion. 22

     Revisional surgery for these patients can be challenging. We recommend structural grafting with autogenous tricortical iliac crest, plate fixation and the use of bone growth stimulators to achieve fusion.

     Other complications include but are not limited to:
     • recurrent hallux valgus;
     • hallux varus;
     • first ray elevation and subsequent first MPJ arthrosis and lesser metatarsal symptoms; and
     • plantarflexed first ray with associated sesamoiditis.

In Conclusion

     Lapidus arthrodesis is a powerful option we have in correcting hallux valgus. When we use appropriate technique and emphasize proper patient selection, we can provide durable correction of the deformity and excellent, longstanding symptomatic relief.

     However, the Lapidus arthrodesis is not the panacea for bunion correction. If one performs this procedure inadequately or for patients in whom the procedure is not indicated, debilitating symptoms and poor outcomes will occur.

     Dr. Hamilton practices in the Department of Orthopedics and Podiatric Surgery at Kaiser Permanente in Antioch, Calif. He is a member of the attending staff with the San Francisco Bay Area Foot and Ankle Residency. Dr. Hamilton is a Fellow of the American College of Foot and Ankle Surgeons.

     Dr. Sautter practices in the Department of Orthopedics and Podiatric Surgery at Kaiser Permanente in Antioch, Calif. He is a member of the attending staff with the San Francisco Bay Area Foot and Ankle Residency. Dr. Sautter is an Associate of the American College of Foot and Ankle Surgeons.

     Dr. Ford practices in the Department of Orthopedics and Podiatric Surgery at Kaiser Permanente in Oakland, Calif. He is the Residency Director of the San Francisco Bay Area Foot and Ankle Residency Program. Dr. Ford is an Fellow of the American College of Foot and Ankle Surgeons.

References:

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Foot Ankle Int 29(2):155-63, 2008 39. Ressegul B, Cusack J. Current concepts in foot function supplementary notes. Langer group pp. 2,3,6, 12-14, 1984. 40. Roukis TS, Landsman AS. Hypermobility of the first ray: a critical review of the literature. JFAS 42(6):377-90, 2003 41. Scranton PE. Principles in bunion surgery: Current concepts review. J Bone Joint Surg Am 65(7):1026-28. 42. Stienstra JJ, Lee JA, Nakadate DT. Large displacement distal chevron osteotomy for the correction of hallux valgus deformity. JFAS 41(4):213-20, 2002 43. Stokes IAF, Hutton WC, Evans MJ. The effects of hallux valgus and Keller’s operation on the load-bearing function of the foot during walking. Acta Orthop Belgica 41:695-704, 1975. 44. Vianna VF, Myerson MS. Complications of hallux valgus surgery. Management of the short first metatarsal and the failed resection arthroplasty. Foot & Ankle Clinics 3(1):33-49, 1998. 45. Yamamoto H, Muneta T, Asahina S, Furuya K. 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