Are We Overutilizing the Cotton Osteotomy in Flexible Flatfoot Correction? A Case Report

Successful surgical management of the patient with a symptomatic flexible flatfoot is a difficult topic requiring a high level of understanding regarding the pathomechanics of the deformity. Despite its complexity, there are established algorithms that can help guide physicians in procedure selection. A standard options often include medializing calcaneal slide osteotomy, lateral column lengthening procedure (Evans), plantarflexory osteotomy of the first cuneiform (Cotton), posterior tibial tendon repair and spring ligament repair.¹ In the pre- and intraoperative evaluation of the adult flexible flatfoot, it is necessary to identify the presence or absence of a forefoot varus component. This finding guides surgeons in addressing medial column position and stability with procedures such as a plantarflexory first ray osteotomy, first metatarsocuneiform arthrodesis, or spring ligament reconstruction. Due to its triplanar nature, surgeons often incorporate these procedures after completing the Evans osteotomy. When a flexible, residual forefoot varus remains, performing a Cotton typically allows the first ray to purchase with the ground.^2-4 However, this does not take into consideration the altered soft tissue biomechanics at play as a result of other procedures performed, especially the Evans osteotomy.

In the case study presented, progressive correction and stability of the first ray was obtained without the addition of a Cotton osteotomy, in the presence of a flexible forefoot varus with a dorsiflexed first ray intraoperatively. This case study demonstrates that it is possible to achieve medial column correction and stability without the addition of a Cotton osteotomy and puts into question its potential overutilization.

Case Study: Is a Cotton Osteotomy Necessary?

A 55-year-old male presented to our clinic with a chief concern of painful flat feet worsening over the past several years. He attempted conservative management with a variety of over-the-counter orthotics, custom orthotics, bracing, and physical therapy, none of which were successful, and he expressed interest in surgical intervention. On physical exam, he had pain with range of motion through the subtalar joint bilaterally as well as with palpation of the insertion of the posterior tibial tendon. Upon weight-bearing, he exhibited calcaneal valgus, forefoot abduction, and a collapsed medial longitudinal arch, more severe on the left than on the right. Initial weight-bearing X-rays revealed a pes planus foot type, mild degenerative changes at the talonavicular joint and a moderate sized plantar calcaneal enthesophyte. Hindfoot alignment views demonstrated 27 degrees of lateral hindfoot angulation on the left and 17 degrees on the right.

We consented the patient for a medial calcaneal slide osteotomy, Evans osteotomy, Cotton osteotomy, spring ligament repair with posterior tibial tendon debridement and flexor digitorum longus transfer, and a gastrocnemius recession. Intraoperatively, we performed the gastrocnemius recession first, followed by the calcaneal slide, Evans osteotomy, and then posterior tibial tendon debridement and augmentation using the flexor digitorum longus. We then evaluated the position of the first ray and noted elevation with mild residual forefoot varus. However, this remaining varus was flexible in nature. As a result, we decided not to perform the Cotton osteotomy. Routine follow-up and serial post-operative X-rays helped us observe bony consolidation of the osteotomy sites as well as monitor the position of the first ray.

The post-operative course was uneventful with transition to partial weight-bearing at 6 weeks and full weight-bearing at 3 months, both in a CAM boot. Serial weight-bearing radiographs took place postoperatively at 3 months, 6 months, and 1 year. We evaluated the sagittal plane position of the first ray by measuring the angle of the bisection of the talus and the first metatarsal (ie, Meary’s angle⁵), the distance from the dorsal cortex of the first metatarsal to the dorsal cortex of the second metatarsal (ie, Seiberg’s index⁵), and the distance from the dorsal cortex of the first metatarsal 10mm proximal to the articular surface to the weight-bearing surface (see table below). Measurements at the 3-month follow-up were compared to the 6- and 12-month radiographs to observe any dynamic change. From the 3-month to the 12-month follow-up, there was a 0.7-degree change in Meary’s angle, a 1.8mm decrease of Seiberg’s index, and 8.3mm of correction of the first metatarsal to the weight-bearing surface.

Table 1: Meary’s angle, Seiberg’s index, and the distance from the first metatarsal head to the weight-bearing surface.

What Does the Literature Reveal?

Some refer to the Evans osteotomy as the workhorse of flatfoot reconstruction due to the triplanar correction it provides, which includes plantarflexion of the first ray. Because there is often a forefoot varus component to this deformity, the triplanar corrective nature of the Evans is crucial. In cases where the Evans osteotomy does not provide adequate correction of the first ray, one may consider a plantarflexory osteotomy of the first ray. One determines the necessity of such an addition by intraoperative evaluation of the first ray position and relative flexibility of the forefoot after the Evans osteotomy is complete. This evaluation involves applying pressure under the first metatarsal head intraoperatively to simulate loading and observing the position first ray in the sagittal plane.³ Johnson and colleagues published a clinical consensus regarding the indications for a Cotton osteotomy and the role it plays in flatfoot correction.² They recommend that selection of a Cotton procedure should be clinically, not radiographically driven. Their recommended technique involves pushing up on the head of the first metatarsal and observing its position in comparison to the fifth metatarsal head. Using this maneuver, the surgeon can determine if a Cotton is indicated.²

In his original 1975 article, Evans referred to the lateral column as the foundation of the osseous structure of the foot. He stated that the lateral column doesn’t change much in shape, but often varies in length. In addition, he noticed that by lengthening the lateral column, he could obtain restoration of the medial arch, but did not theorize as to the mechanics through which this correction occurred.³

The correction of the first ray achieved after an Evans osteotomy is often attributed to the reduction of the abductory force on the forefoot.^1-4 As the forefoot adducts back into the normal plane, the medial column will theoretically reform. However, the literature does not address the exact process by which this occurs. One popular explanation behind this correction is that after the lateral column has been brought out to length, there is an increased mechanical advantage of the peroneus longus tendon. It is well known that the peroneus longus tendon plays a significant role in supporting the medial longitudinal arch due to its plantarflexory pull of the first metatarsal.⁵ However, in order for soft tissue to have an impact on deformity correction, the underlying deformity has to be flexible. These dynamic corrections will not present in a rigid deformity. If this theory is correct, as the patient transitions to a weight-bearing status, the mechanical advantage provided to the peroneus longus tendon should continue to plantarflex the first ray and potentially correct any remaining forefoot varus. However, there are no current studies evaluating the long-term radiographic correction of the position of the first ray after flexible flatfoot correction.^6-7

In 2007, Hix and team discussed calcaneal osteotomies and their role in the correction of flexible flatfoot. In their article, they reference the triplanar correction provided by the Evan’s osteotomy, as well as the supinatory effect it has on the subtalar joint. They also specifically mention the change in mechanical advantage of the peroneus longus, but do not provide any supporting evidence for this claim.⁴

Sanhuda and colleagues (2019) identified the impact that the peroneus longus can have on the dynamic correction of the flexible flatfoot via peroneus brevis-to-longus tendon transfer. They presented this transfer as an alternative to medial column procedures, citing potential avoidance of more osteotomies, hardware, and no additional incisions. They noted a decrease in abduction forces on the forefoot as well as strengthening of the peroneus longus tendon and its first ray plantarflexory function. This observation and technique tip are helpful in the identification of the important role the peroneus longus plays in the correction of the flexible flatfoot. In their study, however, they do not address long-term follow-up of the twelve patients to indicate whether the dynamic correction of the first ray continued as the patients began weight-bearing.⁸

Concluding Thoughts

In the case study presented above, dynamic correction of the first ray occurred over the course of one year after flexible flatfoot correction without the addition of a Cotton osteotomy. There was 1.8mm of correction of Seiberg’s index and 8.3mm of correction of the first metatarsal height to the weight-bearing surface. There was no obvious change seen in Meary’s angle over the post-operative period. There was a change from the pre-operative X-ray to the 3-month x-ray, but this is a well-known and documented benefit of the Evans osteotomy. However, two of the three metrics evaluated appear to indicate that there is potentially a change in mechanical forces resulting in plantarflexion of the first ray post-operatively. It is the opinion of these authors that the correction observed is a result of the increased mechanical advantage provided to the peroneus longus muscle after the lateral column is lengthened.

The case study presented demonstrates a change in first metatarsal position during the postop weight-bearing period after an Evans osteotomy. We attribute this change to the increased mechanical advantage provided to the peroneus longus as a result of the lateral column lengthening procedure. Our hope is to stimulate debate on whether inclusion of a Cotton osteotomy is necessary to produce the desired correction of a flexible forefoot varus. Further research is required to further assess dynamic forefoot varus correction that can occur after an Evans osteotomy in patients with known flexible forefoot varus.

Dr. Ptak is a second-year resident with the Podiatric Medicine and Surgery Residency Program at Intermountain Medical Center in Murray, UT.

Dr. Mallory is a staff physician at the George E. Wahlen VA Medical Center and adjunct faculty of the Podiatric Medicine and Surgery Residency Program at Intermountain Medical Center in Murray, UT.

References

1.     Hentges MJ, Moore KR, Catanzariti AR, Derner R. Procedure selection for the flexible adult acquired flatfoot deformity. Clin Podiatr Med Surg. 2014;31(3):363-379. doi: 10.1016/j.cpm.2014.03.003.

2.     Johnson JE, Sangeorzan BJ, de Cesar Netto C, et al. Consensus on indications for medial cuneiform opening wedge (Cotton) osteotomy in the treatment of progressive collapsing foot deformity. Foot Ankle Int. 2020;41(10):1289-1291. doi: 10.1177/1071100720950739. Epub 2020 Aug 28. PMID: 32856482.

3.     Evans D. Calcaneo-valgus deformity. J Bone Joint Surg Br. 1975;57(3):270-278.

4.     Hix J, Kim C, Mendicino RW, Saltrick K, Catanzariti AR. Calcaneal osteotomies for the treatment of adult-acquired flatfoot. Clin Podiatr Med Surg. 2007;24(4):699-719, viii-ix. doi: 10.1016/j.cpm.2007.07.002.

5.     Johnson CH, Christensen JC. Biomechanics of the first ray. Part I. The effects of peroneus longus function: a three-dimensional kinematic study on a cadaver model. J Foot Ankle Surg. 1999;38(5):313-321. doi: 10.1016/s1067-2516(99)80002-7.

6.     Chan F, Bowlby MA, Christensen JC. Medial column biomechanics: Nonsurgical and Surgical Implications. Clin Podiatr Med Surg. 2020;37(1):39-51. doi: 10.1016/j.cpm.2019.08.004. Epub 2019 Oct 21.

7.     Sangeorzan BJ, Mosca V, Hansen ST Jr. Effect of calcaneal lengthening on relationships among the hindfoot, midfoot, and forefoot. Foot Ankle. 1993;14(3):136-141. doi: 10.1177/107110079301400305.

8.     Sanhudo JAV. Dynamic correction for forefoot varus in stage II-A adult flatfoot: Technique tip. Foot Ankle Surg. 2019 Oct;25(5):698-700. doi: 10.1016/j.fas.2018.05.007. Epub 2018 Jun 3.

9.     Bolt PM, Coy S, Toolan BC. A comparison of Evan’s osteotomy and medial translational osteotomy of the calcaneus for the reconstruction of adult acquired flatfoot. Foot Ankle Int. 2007;28(11):1115-1123. doi: 10.3113/FAI.2007.1115.

10.  Doğan A, Albayrak M, Akman YE, Zorer G. The results of calcaneal lengthening osteotomy for the treatment of flexible pes planovalgus and evaluation of alignment of the foot. Acta Orthop Traumatol Turc. 2006;40(5):356-366.

11.  Hunt KJ, Farmer RP. The Undercorrected Flatfoot Reconstruction. Foot Ankle Clin. 2017;22(3):613-624. doi: 10.1016/j.fcl.2017.04.003.