Yes. Although a joint-sparing procedure such as the Cotton osteotomy may hold appeal for surgeons and patients, this author says the first tarsometatarsal arthrodesis provides a more direct, superior option to address deformities associated with forefoot varus.
By J.P. McAleer, DPM, FACFAS
Forefoot varus is a malalignment of the medial column, which produces excessive forefoot inversion in relation to the hindfoot in a non-weightbearing limb.1 Estimates suggest that 8.8 to 15 percent of the general population has forefoot varus.2 In describing this condition, Michaud noted both flexible and fixed deformity variants impacting the first ray and medial column’s ability to contact the weightbearing surface when maintaining the subtalar joint in neutral position.3 In cases of forefoot varus, arguments exist for multiple surgical treatment options. However, when specifically evaluating the first tarsometatarsal arthrodesis versus a Cotton osteotomy, there are aspects of forefoot varus that a first tarsometatarsal fusion addresses that a Cotton osteotomy simply does not.
One can observe this aberrant positioning of forefoot varus in congenital, arthritic or traumatically-induced rigid fixed subtypes, or in flexible variants that one may see with forefoot supinatus and early adult-acquired flatfoot.4 However, the true differentiation of forefoot varus and forefoot supinatus is that the former is a rigid osseous deformity that induces subtalar joint pronation whereas the latter develops secondary to subtalar joint pronation.5
There are compensatory biomechanical mechanisms that may offset this abnormal foot position and help achieve a plantigrade medial column.6 This includes closed-chain subtalar joint pronation during gait to promote metatarsal head purchase at the weightbearing surface.7 A study evaluating weightbearing measurements and gait analysis in a cohort of 54 patients showed a positive correlation between the presence of forefoot varus and increased subtalar pronation in weightbearing circumstances.8
Various pathologic changes can occur as the degree of forefoot varus malalignment and associated compensation increase. This is in part due to a retrograde hindfoot eversion response resulting in ankle equinus that predisposes the patient to Achilles tendon injury as well as posterior tibial tendon dysfunction, leading to hypertrophy and degeneration.9-10
One can assess functional instability of the first tarsometatarsal joint (TMT) and naviculocuneiform (NC) joint clinically. However, clinicians can also view this radiographically with plantar joint gapping and arthritic changes on weight-bearing projections.11 This frank global adaptation of the foot can also influence joint subluxation at the medial column as one sees in the development of flatfoot and hallux valgus.11
Assessing The Surgical Options For Forefoot Varus
There are various treatment options to address forefoot varus and the associated complex deformities that follow. One such procedure is the Cotton opening wedge osteotomy. This procedure provides foot and ankle surgeons with a powerful technique to restore the plantigrade position of the first ray via angular correction of the medial column through the creation of an opening wedge osteotomy at the medial cuneiform. The introduction and incorporation of a bone graft or its analog to plantarflex and lengthen the first ray is an attractive option when hallux valgus is absent and the adjacent joints are healthy and functional.
However, surgeons cannot address the presence of plantar gapping and instability at the first tarsometatarsal joint or more proximal joints through a joint-preserving technique such as the Cotton osteotomy. An increase of the lateral talar-first metatarsal angle radiographically and the presence of first ray elevation clinically are possible indicators for isolated medial column joint fusions.12 When there are preoperative findings of concomitant hallux valgus deformity, surgeons may achieve more optimal outcomes with arthrodesis of the first tarsometatarsal joint.4
Lapidus first described arthrodesis of the first tarsometatarsal joint in 1934 for the treatment of metatarsus primus varus.13 Although the procedure’s original intent was for isolated hallux valgus correction, surgeons have subsequently expanded the indications of the Lapidus procedure by using it to address medial column pathology, including joint instability and arthritis.14 First ray shortening and nonunion rates are commonly cited concerns with the Lapidus procedure.15 However, a study by Ray and colleagues reported a 1.6 percent symptomatic non-union rate in a cohort of 57 patients (62 feet) allowed to weightbear within two weeks following first tarsometatarsal joint arthrodesis using a biplanar plating technique.16
Medial column instability with subsequent arch collapse and rotation of the hallux, as one sees in cases of adult-acquired flatfoot, may influence the propagation of hallux valgus.17 Recurrence of hallux valgus after isolated surgical correction is more likely in feet with flatfoot than without, and in those with severe pes planus to a greater degree than those with milder forms.17
The benefits of medial column arthrodesis with lateral column lengthening to treat flatfoot improve osseous and soft tissue foot balancing.18 This approach and postoperative protocol may prove to be advantageous over the Cotton osteotomy in certain populations with forefoot varus. The first tarsometatarsal joint arthrodesis is particularly useful in foot width reduction in populations with hallux valgus and for those in need of weightbearing tripod restoration.11 A study by Vaida and colleagues showed an average forefoot bone width reduction of 10.4 mm (10.8 percent) and soft tissue width decrease of 7.3 mm (6.8 percent) postoperatively after triplanar first tarsometatarsal arthrodesis in 148 feet.19
The frank loss of ligamentous stabilization at the tarsometatarsal, naviculocuneiform or talonavicular joints, and the subsequent development of associated adaptive, structural and arthritic changes have a significant risk of progressive symptomatology and patient dissatisfaction if one does not identify and manage these issues.11,20 Hallux valgus is one such potential byproduct of forefoot varus and subsequent flatfoot requires a thorough level of assessment. In addition, chronic degenerative joint changes such as cartilaginous eburnation, subchondral sclerosis, osteophyte formation and cystic bone loss dictate the need for a procedure that offers stabilization through joint elimination.
The first tarsometatarsal arthrodesis procedure offers direct surgical management and correction of compensatory pathologic change that can address the severity of the foot deformities present in cases of forefoot varus, deformities that the Cotton osteotomy cannot legitimately resolve.
Dr. McAleer is a shareholder partner at the Jefferson City Medical Group (JCMG) in Jefferson City, Mo. He is on staff at SSM Health St. Mary’s Hospital in Jefferson City, Mo., and serves as the Vice Chief of Staff at the JCMG Surgical Center. He is a Diplomate of the American Board of Foot and Ankle Surgery, and a Fellow of the American College of Foot and Ankle Surgeons.
Dr. McAleer has disclosed that he is a medical device consultant for Treace Medical Concepts, Inc.
No. Noting the preservation of first ray mobility and reduced complication rate in comparison to the first tarsometatarsal arthrodesis, these authors maintain the Cotton osteotomy offers an advantageous adjunctive procedure to address persistent forefoot supinatus/varus at the navicular-medial cuneiform joint.
By H. John Visser, DPM, FACFAS, Blake T. Savage, DPM and Kiera Benge-Shea, DPM
Initially describing his namesake Cotton osteotomy procedure in 1936, Cotton called the foot a “triangle of support.”1 He noted that when one’s transmission of weight through the leg falls outside or inside this “neat” triangle, mechanical trouble or dysfunction likely follows.1 Over the years, surgeons increasingly recognize rearfoot varus as a pertinent consideration in the treatment of patients with posterior tibial tendon dysfunction (PTTD). For the purposes of this discussion, let us take a closer look at the utility of the Cotton osteotomy to address compensatory changes of the medial column in adult-acquired flatfoot secondary to posterior tibial tendon dysfunction.
The Cotton osteotomy is useful to increase plantarflexion of the first ray. This provides tension forces on the plantar fascia and thereby improves the effect of the windlass mechanism. This in turn affects elevation of the longitudinal arch.2 Hicks noticed that with relative extension of the hallux, shortening of the plantar aponeurosis was analogous to “winding up a cable.”3 This leads to shortening of the foot, raising of the longitudinal arch and supination of the rearfoot via closed kinetic chain supination along with associated external leg rotation. Abyar and colleagues showed that performing an isolated Cotton osteotomy provided correction of arch sag but did not improve Meary’s angle.4
The Cotton osteotomy had a resurrection with its use for medial column correction in patients with adult-acquired flatfoot. Stage II PTTD, originally described by Johnson and Strom, indicates a flexible deformity with rearfoot valgus, forefoot supination, abduction and corresponding pain of the posterior tibial tendon.5 Hansen introduced this resulting position as a dorsolateral peritalar subluxation (subluxation talar pedal lateralis).6 There is increased awareness of the importance of forefoot varus in patients with PTTD. With this in mind, Tankson further divided stage II PTTD into the following three categories: stage IIA (rearfoot valgus); stage IIB (rearfoot valgus and flexible forefoot varus); and stage IIC (rearfoot valgus and fixed forefoot varus).7
Recognizing The Difference Between Forefoot Varus And Forefoot Supinatus
It is important to understand that forefoot varus differs from forefoot supinatus as many use the terms incorrectly and interchangeably. Forefoot supinatus represents an acquired soft tissue adaptation in which the forefoot inverts relative to the rearfoot. The “degree” of forefoot supination is a function of calcaneal eversion and gastrocnemius-soleus equinus compensation.8 The chronicity of the condition is a function of adaptive muscular and osseous changes with long-term significant adaptive alterations involving muscle, ligaments and articular surfaces. Supinatus becomes difficult to differentiate from forefoot varus.8
Forefoot varus represents a congenital osseous deformity centered at the talar neck that induces subtalar joint (STJ) pronation. Forefoot supinatus is acquired and develops because of STJ pronation.9 Excessive inversion of the foot along the longitudinal midtarsal joint axis occurs secondary to calcaneal eversion. In cases in which further compensation is necessary (forefoot flat on the floor) for pathologic heel eversion, dorsal displacement of the first ray (medial cuneiform-navicular) will occur in the sagittal plane. One can see this radiographically as a navicular-medial cuneiform fault. The result is a lateral peritalar subluxation as evidenced by an increased lack of talar coverage medially and associated midfoot abduction.
When There Is A Loss Of Medial Column Support
Paradoxically, Hansen felt that resultant rearfoot deformity was secondary to the loss of forefoot stability caused by a loss of medial column support.6,10 Forefoot supinatus radiographically is represented by “thinning” of the tarsus where the metatarsals “pile up.” This is due to inversion rotation (secondary to heel eversion) about the talonavicular joint or the longitudinal midtarsal joint axis. Here the first through third metatarsals, their respective cuneiforms and the navicular become parallel to the fourth and fifth metatarsals at the cuboid articulation via rotation about the talus. Further metatarsus primus elevatus will often represent compensation for further eversion at the first ray axis.10
Resultant medial column collapse may then appear with single or multiple sagittal apices. These can involve the talonavicular, navicular-medial cuneiform and first tarsometatarsal joints.11-14 In PTTD, faults along the medial column most commonly occur at the navicular-medial cuneiform joint or first ray. The navicular-medial cuneiform joint is the epicenter of the lever arm of the foot where significant bending and moment stresses occur. It represents the apex of a “truss” created by two beams (medial column osseous structures supported by the “tie rod” (plantar fascia)). A fault at the talonavicular joint is quite rare in cases of PTTD. It can, however, present subtly with the talar articular surface one to two mm plantar to the navicular articulation. This may represent a spring ligament tear.
The first metatarsal-medial cuneiform-navicular sag can also occur as a combined fault. It normally occurs with long-standing PTTD complicated by obesity when first ray compensation (navicular-medial cuneiform) cannot withstand STJ peritalar subluxation and equinus forces. The fault at the first metatarsal-medial cuneiform appears as plantar gapping on the lateral view. One may also see this with a high intermetatarsal angle and associated hallux abductovalgus deformity.15 The reverse Coleman block test can determine where the primary medial fault manifests. The clinician places blocks under the forefoot until calcaneal eversion is brought to vertical. Doing so enables one to identify if there is a primary medial fault.15
Keys To Ascertaining The Correct Substage Of Stage II PTTD
During physical examination of a patient with stage II PTTD, the clinician should differentiate between the exact substages of the deformity in order to determine the best surgical intervention. With the rearfoot corrected to neutral STJ position, one should assess the forefoot for compensation and reducibility of forefoot supination (supinatus).
If reduction occurs, the patient has a flexible forefoot. If the forefoot requires ankle plantarflexion for reduction, then an equinus release determined by the Silfverskiöld test is necessary.7 A rearfoot reconstruction that may include a posterior, anterior or double (posterior and anterior) calcaneal osteotomy or arthroeresis will restore talonavicular and STJ congruity. A flexor digitorum longus (FDL) tendon transfer is all that stage IIB PTTD cases require. If forefoot supination remains fixed, noted by the lateral border of the forefoot not passively correlating to a plane perpendicular to the long axis of the tibia, a medial column procedure is indicated.
Current Insights On The Cotton Osteotomy
One may employ the Cotton opening wedge medial cuneiform osteotomy for stage IIC PTTD medial column conditions. This presents as a navicular-medial cuneiform fault radiographically. Other operative options for medial longitudinal arch collapse at this level include: plantar closing wedge osteotomy of the medial cuneiform; first tarsometatarsal joint arthrodesis (modified sagittal plane Lapidus procedure); navicular-medial cuneiform arthrodesis (Hoke); and extended medial column arthrodesis of the first metatarsal-medial cuneiform-navicular joints (Miller procedure).16
The Cotton osteotomy is clearly indicated for persistent forefoot supinatus/varus that centers at the navicular-medial cuneiform joint. This sag or fault of the medial column at this apex is consistent with stage IIC PTTD. One determines the residual forefoot supination clinically, not by radiographs. Loading the forefoot, the surgeon can determine the relationship between the first and fifth metatarsals to determine the needed correction.4 Typical wedge sizes for the Cotton osteotomy range from five to 11 mm. The surgeon may use autograft, allograft or cancellous titanium wedges with or without internal fixation.
Hirose and Johnson concluded that the Cotton cuneiform osteotomy was superior to first tarsometatarsal joint arthrodesis due to its preservation of first ray mobility and ease of operation.17 Kadakia and colleagues warned that utilization of the first tarsometatarsal joint arthrodesis as a proxy for navicular-medial cuneiform joint instability does not provide a long-term solution.18 Certainly, significant instability of the first tarsometatarsal joint, signified by plantar gapping and hallux abductovalgus with a high intermetatarsal angle, would require arthrodesis at the first tarsometatarsal joint. A combined faulting of the first tarsometatarsal joint and navicular-medial cuneiform joint may benefit from a first tarsometatarsal joint arthrodesis combined with a Cotton osteotomy. Extensive arthrosis of these joints and/or significant instability best respond to a Miller-type arthrodesis.
Regarding complications of the Cotton osteotomy, Hirose and Johnson’s case series involving 15 patients (16 feet) noted one screw causing symptoms and no non-unions or residual pain.17 In a 2011 study of opening wedge osteotomies of the medial cuneiform in 86 patients (101 feet), Lutz and Myerson noted 10 post-operative complications: three symptomatic screws, two bony exostoses, one case of sesamoid pain, one instance of plantar fasciitis, two patients with lateral column overload and one recurrent flatfoot.19 Tarsometatarsal joint arthrodesis has rates of non-union of up to 12 percent.17
Postoperative care primarily depends upon equinus release and rearfoot correction. The Cotton osteotomy can depend on the wedge composition, which includes autograft, allograft or cancellous titanium with associated internal fixation. Generally, allografts require six weeks of non-weightbearing and autograft with cancellous titanium requires four weeks of non-weightbearing. Internal fixation, which one may or may not use, does not lessen the required time of non-weightbearing.
The Cotton opening wedge medial cuneiform osteotomy is a common adjunctive procedure for type IIC PTTD. The procedure is safe, easy to perform, maintains mobility and offers significant correction for faults at the naviculocuneiform joint by plantarflexing the first metatarsal. The concept of forefoot varus versus supinatus still remains in dispute. However, the Cotton osteotomy for the medial column in PTTD is effective with benefits beyond that of an isolated first tarsometatarsal arthrodesis.
Dr. Visser is the Director of the Podiatric Residency Program at SSM Health DePaul Medical Center in St. Louis. He is a Fellow of the American College of Foot and Ankle Surgeons, and a Diplomate of the American Board of Foot and Ankle Surgery.
Dr. Savage is a second-year resident at SSM Health DePaul Medical Center in St. Louis.
Dr. Benge-Shea is a first-year resident at SSM Health DePaul Medical Center in St. Louis.
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