Lapidus Bunionectomy: First Metatarsal-Cuneiform Arthrodesis
Lawrence A. DiDomenico
Metatarsus primus varus and hallux abducto valgus (HAV) have been used to correct HAV since originally described by Albrecht (1) in 1911. Truslow (2) followed with a version of the procedure in 1925 that involved a wedged resection of bone from the first metatarsocuneiform joint. The procedure was later popularized by and named after Paul Lapidus. In 1930, he proposed a first metatarsal-cuneiform arthrodesis paired with arthrodesis of the second metatarsal as well as resection of the dorsomedial eminence of the first metatarsal head and distal soft tissue repositioning for metatarsus primus varus. He believed that metatarsus primus varus was the result of an underdeveloped atavistic foot type. He hypothesized that hypermobility of the first metatarsal-cuneiform joint combined with an increased first to second intermetatarsal (IM) angle caused by an oblique joint axis predisposes the foot to HAV and metatarsus primus varus. Lapidus concluded that the apex of the deformity, the first metatarsal-cuneiform joint, needed to be addressed or a “bayonet-shaped” deformity would result (3).
While many techniques have been described modifying the original Lapidus procedure, all use arthrodesis of the metatarsal-cuneiform joint (4,5,6,7,8,9,10 and 11). The procedure allows for triplanar correction of first metatarsal pathology, increases the biomechanical advantage of the peroneus longus, and has the ability to stabilize the medial column. The first metatarsal-cuneiform arthrodesis, while controversial, is a versatile procedure that can correct numerous pathologies.
Traditionally, the first metatarsal-cuneiform arthrodesis has been used to correct for a hypermobile first ray. When the first metatarsal possesses increased motion of the first metatarsalcuneiform joint, the metatarsal elevates during gait, making the first ray unstable and unable to maintain its position against ground reaction forces throughout the gait cycle (12). Numerous attempts have been made to define hypermobility in both the sagittal and transverse planes although no standardized values exist. Clinical assessment of the first ray range of motion is still currently the most accepted method to diagnose hypermobility of the first ray. Root described normal first ray motion as equal dorsal and plantar range of motion and hypermobility as anything beyond equal motion in the sagittal plane. He placed the ankle joint and subtalar joints in neutral position and then stabilized metatarsal heads 2 to 5 with one hand and the first metatarsal head with the other hand, while taking the first metatarsal through its range of motion (13,14). Later, one thumb’s breadth of dorsal motion was described as hypermobile when using Root’s technique (15). Roukis et al have promoted the “dynamic Hicks test,” in which the foot is tested with the hands positioned in the same manner as Root described. The hallux is then fully dorsiflexed at the first metatarsophalangeal joint, and dorsal and plantar pressures are then applied to the metatarsal head. The results of the “dynamic Hicks test” are then compared with those of Root’s; they believe that true hypermobility of the first ray exists when both tests show a positive result of hypermobility (16). Radiographically, hypermobility is frequently distinguished on anteroposterior radiograph as an increased first to second IM angle with medial cortical thickening of the second metatarsal, which is believed to be due to second metatarsal overload (17). Clinically, this can be accompanied with a hyperkeratotic lesion plantar to the second metatarsal head (18). Some advocate the test for evaluation of transverse plane hypermobility, which entails wrapping an ACE wrap across the forefoot while applying moderate tightness (19,20). Radiographs with the ACE wrap applied are compared with normal weight-bearing radiographs to assess if hypermobility of the joint occurs in the transverse plane, which can be seen with a decreased IM angle with the apex of deformity at the first metatarsal-cuneiform joint. Hypermobility is frequently concomitant with a large HAV deformity, although mild to moderate cases of HAV have been treated successfully when first ray hypermobility is present (5,12,21,22 and 23). The procedure is also indicated when generalized ligamentous laxity is seen with HAV.
Juvenile HAV frequently is accompanied by hypermobility at the first metatarsal-cuneiform joint. Adolescent HAV differs from adult HAV in that a smaller dorsomedial eminence is present and less valgus rotation of the hallux occurs (24,25). If hypermobility is present and not addressed, recurrence of the deformity may result, as juvenile HAV frequently is a structural problem that can persist throughout adulthood and progress (12,22). It has been demonstrated that the angle created by the axis of the first metatarsal and the distal surface of the medial cuneiform is increased with statistical significance in Juvenile HAV, supporting that varus angulation occurs proximal to the metatarsal at the level of the first metatarsal-cuneiform joint. A positive correlation also exists between the angle created by the distal surface of the medial cuneiform and the axis of the second metatarsal and an increased IM angle (26). Lower recurrence rates have been achieved with this procedure as it addresses the deformity at its apex and eliminates first ray hypermobility (17,22,27). Juvenile HAV corrected with other procedures has been noted to have recurrence rates as high as 35% (27,28). The procedure is an excellent option for correction of Juvenile HAV as it can be performed successfully without resection of the medial eminence and distal soft tissue release (17).
Moderate to severe HAV can be treated effectively with this procedure without the presence of hypermobility. IM angles ranging from 14 to 30 degrees on anteroposterior radiograph have been used as a baseline for the procedure (24,29). Etiology of an increased IM angle may be due to the shape of the first MC joint itself, as a positive correlation exists between the obliqueness of the joint and increased first to second IM angle (30). Surgical correction of large IM angles needs to be addressed with proximal procedures, as the long lever arm allows for a higher level degree of correction as opposed to distal procedures. The procedure has the ability to restore first metatarsophalangeal joint congruency and realign the sesamoid apparatus in addition to correction of the IM angle. The closing base wedge osteotomy (CBWO) and the modified Lapidus were compared and both procedures demonstrated significant first to second IM correction, with the Lapidus maintaining a greater degree of correction postoperatively, the CBWO losing an average of 2.55 degrees of correction and the Lapidus losing only an average of 1.08 degrees (31).
More recently, the procedure has been used in conjunction with other procedures as a practical option for treatment of medial column insufficiency and flatfoot deformity. Addressing the medial column for these pathologies is vital as the first metatarsal can accommodate up to 50% of the stress experienced through gait and provides a paramount role in stabilizing the medial longitudinal arch (32). It is important to note that the procedure is not advocated for primary correction of these pathologies. Morton described what has become known as a “Morton’s foot” in which the first metatarsal is anatomically or functionally short, leading to rotation about the axis of the forefoot causing pronation (33,34,35,36 and 37). The goal of surgical correction of a “Morton’s foot” is to stabilize the medial column and realign the parabola of the metatarsal heads to distribute weight-bearing evenly. The peroneus longus muscle gains mechanical advantage following a Lapidus procedure contributing to functional stability of the medial column, which is lost with pronation of the foot (38,39). In 2008, Avino et al performed radiographic analysis on 39 feet in which an isolated Lapidus was performed to review the effects of the arthrodesis to the medial column in the sagittal plane. Postoperatively, the mean cuneiform increase in height was 3.44 mm and Meary’s angle decreased by a mean of 2.97 degrees (40). Logel et al examined the effects of calcaneocuboid arthrodesis and first metatarsal-cuneiform arthrodesis on lateral column pressure as well as radiographic correction of flatfoot deformity on 10 fresh frozen cadaver limbs. They found that with the lateral column lengthening procedure alone there was improved radiographic measurements when evaluating lateral talus-first metatarsocuneiform angle, talonavicular coverage angle, medial column height, lateral talus-calcaneal angle, and calcaneal pitch; however, increased lateral column pressures were noted. They subsequently performed a first metatarsalcuneiform arthrodesis on the same limbs, which decreased pressure of the lateral column and the radiographic values demonstrated additional increased correction (41). This procedure has been successfully used when medial column insufficiency is present in conditions such as Charcot-Marie-Tooth and postpolio when restoration and stability of the medial column is essential to restore function of the foot (4,42).
Degenerative joint disease (DJD) of the first metatarsal-cuneiform joint can be successfully treated with arthrodesis of the joint. DJD can be the result of arthritides, trauma, and long-standing biomechanical abnormalities (11,17,43). The pain experienced with the DJD is corrected with arthrodesis of the joint.
Failed HAV procedures may also elicit the need of arthrodesis of the Lapidus procedure as it can maintain good functional results (44). If the deformity returns following initial surgical correction, hypermobility of the first metatarsal-cuneiform joint needs to be assessed as well as generalized ligamentous laxity to determine if excessive movement of the joint was etiology of recurrence. A bone graft may need to be incorporated into the joint to maintain length and restore function as the prior procedure may have shortened the first metatarsal.