Abstract
Recommendation:
Forefoot varus is a physical and radiographic examination finding associated with the Progressive Collapsing Foot Deformity (PCFD). Varus position of the forefoot relative to the hindfoot is caused by medial midfoot collapse with apex plantar angulation of the medial column. Some surgeons use the term forefoot supination to describe this same deformity (see Introduction section with nomenclature). Correction of this deformity is important to restore the weightbearing tripod of the foot and help resist a recurrence of foot collapse. When the forefoot varus deformity is isolated to the medial metatarsal and medial cuneiform, correction is indicated with an opening wedge medial cuneiform (Cotton) osteotomy, typically with interposition of an allograft bone wedge from 5 to 11 mm in width at the base. When the forefoot varus is global, involving varus angulation of the entire forefoot and midfoot relative to the hindfoot, other procedures are needed to adequately correct the deformity.
Level of Evidence:
Level V, consensus, expert opinion.
Keywords
Consensus Statements Voted:
Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.
(Unanimous, strongest consensus)
Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.
(Unanimous, strongest consensus)
Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.
(Unanimous, strongest consensus)
Delegate vote: agree, 89% (8/9); disagree, 0%; abstain, 11% (1/9).
(Strong consensus)
Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.
(Unanimous, strongest consensus)
Rationale
Forefoot varus is a component of the multiplanar Progressive Collapsing Foot Deformity (PCFD), as well as in some cases of developmental pes planovalgus and osteoarthritis of the medial column of the foot. This deformity is not corrected by hindfoot procedures such as a lateral column lengthening, medial displacement calcaneal osteotomy, or repositional subtalar arthrodesis.
Forefoot varus is characterized by a spectrum of physical examination findings from elevation of the first ray (only in the sagittal plane) or rotation of the entire forefoot around the central longitudinal axis of the foot toward the midline in the coronal plane with deformity at the talonavicular joint, midtarsal joints, or tarsometatarsal joints. The deformity may be fixed or flexible and the diagnosis is made by physical examination in the nonweightbearing position, with the hindfoot corrected to a neutral hindfoot alignment reference position. This examination will indicate the location, magnitude, and flexibility of the deformity as well as indicate when the deformity has been adequately corrected intraoperatively. First-ray elevation is typically related to dorsal instability of the first tarsometatarsal (TMT) or first-second intercuneiform joint with dorsal angulation at the naviculocuneiform joint.
A lateral weightbearing radiograph will help determine the presence of dorsal instability, plantar first TMT joint gapping, osteoarthritis, as well as location of the apex of the deformity along the medial column as being at the talonavicular, naviculocuneiform, or TMT joints.6,12 Reconstruction of the PCFD begins in the proximal aspect of the foot and ankle and proceeds distally because each level of correction is determined by aligning it to the next most proximal segment. Therefore, forefoot varus is often the last portion of the deformity to be corrected during the bony realignment portion of the procedure. Occasionally, once the hindfoot deformity correction has been performed, the apparent forefoot varus that was present preoperatively has been improved sufficiently that osteotomy of the medial cuneiform is not required.
Correction of this deformity with an opening wedge, plantarflexion, medial cuneiform osteotomy was described by Cotton in 1936 to restore the “static triangle of support.” 4 However, the Cotton osteotomy did not gain widespread use until decades later, when surgeons began using joint-preserving osteotomies, especially lateral column lengthening (LCL) procedures, and noted that residual forefoot varus was limiting the complete correction of many feet with PCFD. 5 Currently, osteotomy of the medial cuneiform is a commonly used technique to correct forefoot varus, with the concept that restoring the weightbearing tripod of the foot will help resist recurrent foot collapse. Benthien et al, in a cadaveric biomechanical study, demonstrated that LCL increased lateral forefoot pressures in a severe PCFD model. 2 The authors demonstrated that an added Cotton osteotomy provided increased deformity correction and decreased pressure under the lateral forefoot, thereby suggesting that the Cotton osteotomy could help restore a more normal loading pattern of the foot.
Alternative Technique
A closing wedge osteotomy for correction of forefoot varus performed from a plantar approach to the medial cuneiform has been described and has the advantage of direct bone healing without a need for graft, no implant interposition, ability to perform the procedure through a single plantar incision used for the medial soft tissue repair, and the ability to slightly adduct the foot through the osteotomy. 10 However, the amount of correction is more difficult to titrate for a given deformity, and closing a significant wedge resection to achieve apposition of the cuneiform can be challenging.
Multiple fixation techniques for Cotton osteotomies have been described, using specialized wedge plates, screws,5,11 Kirschner wires, 11 and no fixation.3,11,15 Alternatives to allograft or autografting methods include use of trabecular metal wedges,13,14 or metal wedges attached to thin dorsal plates. A dorsal wedge plate has been found to be as effective as a bone graft wedge in a cadaver model. 9 Potential advantages include no donor site morbidity seen with autograft, no potential risk of disease transmission with allograft and easier availability for outpatient surgical centers. In a series of patients that received trabecular metal wedges, 2 nonunions were identified, but only 1 was found to be symptomatic at 35.4 months postoperation. 14
The disadvantage of plates and screws is that they may create a painful prominence on the dorsum of the foot requiring an additional surgical procedure for hardware removal,5,11,15 and metal wedges may confound any future revision surgery. The metallic wedges need to be removed with a saw if revision of the osteotomy is needed and they are difficult to drill across or place a screw through them if an extended medial column fusion is required later. Long-term studies evaluating the durability of these nonbiologic implants are lacking.
Extraosseous and intraosseous blood supply to the medial cuneiform is robust and does not exhibit consistent watershed areas of hypovascularity. 7 Predictable osteotomy healing rates using allograft wedges, of up to a 100%, has been reported by many authors, and they do not seem to be related to type of fixation or whether any fixation is utilized.1,3,5,11,15
Quantifying the contribution of the Cotton osteotomy to the overall radiographic changes from preoperative to postoperative is difficult given that multiple procedures are usually preformed at the time of surgery. Numerous radiographic measurements have been used to describe the correction that is observed following Cotton osteotomy including the lateral talus-first metatarsal angle, lateral medial cuneiform metatarsal angle, calcaneal pitch, medial cuneiform distance, 5 medial arch sag angle (MASA), 1 and cuneiform articular angle (CAA). 3 Using a multivariate linear regression model, Kunas et al demonstrated that the Cotton osteotomy graft size was significantly associated with changes in the CAA, calcaneal pitch, lateral talonavicular Cobb angle, and lateral naviculomedial cuneiform angle. 8 However, the authors emphasized that the Cotton graft size was the only factor found to significantly predict a change in the CAA. Therefore, preoperative measurement of the cuneiform articular angle (CAA) can help predict the graft size intraoperatively. Each millimeter of the width of the base of the wedge-shaped graft corresponds to an approximately 2.1-degree decrease of the CAA. 8 However, intraoperative clinical examination is best used to confirm the proper graft size that provides satisfactory correction of the deformity. Typically, a graft size of 5-11 mm width at the base of the wedge is needed to correct most deformities.
The indication for performing a Cotton osteotomy should be determined clinically, not radiographically, and is dependent on the presence of residual forefoot varus after hindfoot deformity correction.6,12 By pushing up on the bottom of the forefoot, the surgeon can feel the balance of the first ray in relation to the lateral rays by placing one thumb of each hand on the first and fifth metatarsal heads, respectively. This maneuver will indicate which metatarsals are elevated relative to the fifth metatarsal and help determine whether a Cotton osteotomy, alone, is indicated or whether a more global correction of the midfoot is needed.
Supplemental Material
FAI950739_disclosures – Supplemental material for Consensus on Indications for Medial Cuneiform Opening Wedge (Cotton) Osteotomy in the Treatment of Progressive Collapsing Foot Deformity
Supplemental material, FAI950739_disclosures for Consensus on Indications for Medial Cuneiform Opening Wedge (Cotton) Osteotomy in the Treatment of Progressive Collapsing Foot Deformity by Jeffrey E. Johnson, Bruce J. Sangeorzan, Cesar de Cesar Netto, Jonathan T. Deland, Scott J. Ellis, Beat Hintermann, Lew C. Schon, David Thordarson and Mark S. Myerson in Foot & Ankle International
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
References
Supplementary Material
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