Current Concepts In Surgery For Adult-Acquired Flatfoot

Although an abundance of research into the treatment of adult-acquired flatfoot (AAF) has led to improved standardization of surgical options, discrepancies still exist in how surgeons approach stage II flatfoot. These authors offer insights into surgical management of stage II AAF with a special emphasis on medial transpositional osteotomy of the posterior calcaneus and lateral column lengthening.

Adult-acquired flatfoot (AAF) is a common musculoskeletal condition that we encounter in day-to-day practice. There have been more articles published relating to AAF in peer-reviewed journals in the past 10 years than on virtually any other topic.

   Accordingly, once nebulous treatment options have become more formalized, especially with surgery. The surgical management of AAF has been enhanced by improved classification systems and advances in technology. However, in spite of this, differences exist among surgeons managing stage II AAF. These differences in surgical approaches appear to be based on geographic location, residency training, etc.

   Improved classification systems are a major reason for better procedure selection in managing stage II AAF. The original classification system proposed by Johnson and Strom in 1989 described three stages of AAF that we have used to guide us in choosing procedures.1 Myerson modified this classification system to include stage IV patients who present with ankle valgus in addition to a fixed flatfoot deformity.2 Stages I, III and IV are straightforward and clearly delineate pathology at each specific stage. However, this is not the case with stage II adult-acquired flatfoot. Stage II AAF is a continuum in which surgical therapy depends on when one encounters a patient in this temporal process.

   The clinical practice guidelines published by the American College of Foot and Ankle Surgeons in 2005 divided stage II AAF into early (II-A) and late (II-b) stages to clarify the specific findings associated with various stages.3 A recent classification published by Haddad and colleagues has divided stage II flatfoot into five different subcategories (A-E):4

A. hindfoot valgus;
B. flexible forefoot supinatus;
C. fixed forefoot supinatus;
D. forefoot abduction; and
E. medial ray instability.

   Our surgical approach to stage II AAF is based on this contemporary classification system, which appears more practical when choosing surgical procedures to address adult-acquired flatfoot.

A Closer Look At The Management Of Stage II AAF

Virtually all patients with stage II AAF have some degree of equinus that requires posterior muscle group lengthening, which will restore calcaneal inclination and maintain a plantigrade foot following osseous realignment. We typically perform a gastrocnemius recession, which seems sufficient in most cases of stage II AAF. There are times when gastrocnemius recession may not provide an adequate amount of dorsiflexion following realignment of a rather severe deformity. However, this is rare in stage II AAF. Rather, we have found an Achilles tendon lengthening to be necessary in some cases of stage III and IV AAF when the magnitude of deformity is large.

   We typically address hindfoot valgus associated with stage II AAF with a medial transpositional osteotomy of the posterior calcaneus. It has been well established that this osteotomy is effective in reducing hindfoot valgus by redirecting the coronal vector of the Achilles tendon from eversion to inversion.5-7 Although we routinely use a medial transpositional osteotomy of the posterior calcaneus to address hindfoot valgus, we rarely use the osteotomy as an isolated procedure in stage II AAF. While a medial transpositional osteotomy will have a direct effect on the subtalar joint, it has a much lesser effect on the midtarsal joint. Therefore, the majority of deformities in stage II AAF are often too severe to correct by an isolated medial transpositional osteotomy.

   Vora and co-workers compared the effectiveness of the medial transpositional osteotomy of the posterior calcaneus in correcting mild versus severe flatfoot.8 They concluded that one might treat less severe AAF by a medial transpositional osteotomy whereas more severe deformities may require an additional procedure.

   Bolt and colleagues compared lateral column lengthening and medial transpositional osteotomy of the posterior calcaneus for reconstruction of AAF.9 They found the rate of re-operation was twice as high for medial transpositional osteotomy. This was due to inadequate realignment. Therefore, we routinely use a medial transpositional osteotomy in conjunction with a lateral column lengthening.

What You Should Know About Lateral Column Lengthening

We prefer lateral column lengthening as our primary procedure for most cases of stage II AAF. A lateral column lengthening will reduce inversion demand on the posterior tibial tendon, reduce the Achilles force required to achieve a heel rise position, and adduct and plantarflex the midfoot relative to the hindfoot. Lengthening the lateral column also creates a “bowstringing” effect on the peroneus longus tendon, which might be responsible for clinical restoration of the longitudinal arch.10-12

   One can perform a lateral column lengthening through an osteotomy of the anterior calcaneus or an interpositional bone block arthrodesis of the calcaneocuboid joint. Our preference is an anterior calcaneal osteotomy. We performed calcaneocuboid joint bone block arthrodesis from 1996 to 2001 but abandoned this procedure due to a relatively high number of complications. Furthermore, the literature has clearly shown that it is best to perform lateral column lengthening with a calcaneal osteotomy rather than a bone block arthrodesis because of the high complication rate.13-19

Emerging Insights On Fixation And Avoiding Displacement

We have used allograft as our choice of bone graft. Research has shown allograft to be an acceptable form of graft for lateral column lengthening.20-23 In a retrospective analysis of anterior calcaneal osteotomies using allograft bone, Shine and colleagues demonstrated that allograft bone was a safe and effective biomaterial for lateral column lengthening in adults.22

   We fixate our lateral column lengthening procedures with one small diameter screw. We have been fixating these osteotomies over the last several years. However, the senior authors did not use fixation for this procedure in their first 25 years of practice. We place these bone grafts with a large amount of tension and displacement is unlikely. Nonetheless, fixation will secure the bone graft and diminish micromotion at the host-graft interface. Our goal with fixation is to expedite bone graft incorporation and lessen the risk of nonunion. Furthermore, surgeons must consider whether fixation of these osteotomies is the standard of care in their specific region of practice.

   Dunn and Meyer evaluated displacement of the anterior process of the calcaneus after lateral column lengthening.24 They found that fixation captured a statistically significant amount of early sagittal plane displacement whereas the amount of displacement was insignificant when surgeons used no fixation. Therefore, the decision to use fixation is based on surgeon preference.

   Researchers have described lateral column pain as a potential complication following lengthening and attribute this to inappropriate graft size.25-30 Graft sizing can be an intraoperative challenge and there are no guidelines for estimating the amount of lateral column lengthening necessary to reduce the deformity. We have found the magnitude of deformity and suppleness of soft tissues to be important factors that influence graft size. In the past, the senior authors would place as large a graft as possible. However, this often resulted in hindfoot stiffness and lateral column pain. These were cases in which we performed lateral column lengthening without a medial transpositional osteotomy of the posterior calcaneus. We tried to achieve complete realignment with one osteotomy.

   However, with the addition of the medial transpositional osteotomy to lateral column lengthening, we can now control the amount of displacement and lengthening at both osteotomy sites. In other words, we can use a smaller size graft for the lateral column lengthening by increasing the displacement at the medial transpositional osteotomy site. The risk of lateral column pain diminishes with a smaller size bone graft. We also test the amount of remaining eversion following graft placement. We will move to a smaller graft size if eversion is severely limited.

   We also use trial wedges when ascertaining graft size. One can take the tritarsal complex through a range of motion after the wedge is in place to evaluate remaining eversion. Additionally, we obtain intraoperative images to evaluate realignment with the wedge in place. Placement of the trial wedges, however, can weaken the osteotomy but this is not an issue when one is using fixation. In addition to evaluating the clinical position of the foot and range of motion, we often obtain intraoperative images with simulated weightbearing to confirm restoration of angular relationships.

   The combination of lateral column lengthening and medial transpositional osteotomy is enough to restore transverse plane deformity in most cases of stage II AAF. However, there are times when severe medial column instability may result in residual transverse deformity, even after lateral column lengthening and medial transpositional osteotomy. Image intensification will demonstrate the talar head to be only partially covered by the navicular in these cases. We will add a naviculocuneiform arthrodesis to help restore transverse plane alignment. The naviculocuneiform arthrodesis will improve talonavicular subluxation, address forefoot supinatus and impart stability to the medial column.31-33

Evaluating And Managing Forefoot Supinatus And First Ray Instability

We proceed to evaluate forefoot supinatus following the restoration of transverse plane alignment. Forefoot supinatus can be supple or fixed. The naviculocuneiform arthrodesis is our procedure of choice for fixed forefoot supinatus. Sagittal plane correction occurs by a combination of plantar rotation of the cuneiforms and wedge resection. We employ an opening wedge cuneiform osteotomy to address a supple forefoot supinatus. The medial cuneiform osteotomy is effective at reducing forefoot supinatus and restoring medical column stability.25,33 This procedure is technically simple and has a low complication rate.

   We also take a critical look at first ray instability, especially when forefoot supinatus is absent. Patients with first ray instability are at risk for developing lateral forefoot overload following lateral column lengthening and medial transpositional osteotomy of the posterior calcaneus. These patients will develop symptoms when they resume their normal activity level. We perform an opening wedge cuneiform osteotomy to impart first ray stability in this group of patients. This procedure restores first ray weightbearing and restores balance to the forefoot, thereby offloading the lateral column. First tarsometatarsal arthrodesis is also an option in these patients.

Essential Pointers On Soft Tissue Reconstruction

We perform soft tissue reconstruction last. This occurs through a medial incision directed over the posterior tibial tendon. Explore the posterior tibial tendon and repair it as necessary. Consider a flexor digitorum longus (FDL) tendon transfer when the posterior tibial tendon is severely degenerated and tendinosis is pronounced. We usually perform tenodesis of the flexor digitorum longus to the navicular with a biotenodesis screw.

   In the past, we would routinely transfer the flexor digitorum longus for stage II AAF. However, we now perform fewer flexor digitorum longus tendon transfers and preserve this tendon whenever possible. Realignment is the most important factor relative to outcome. Adequate realignment will support the medial soft tissues (spring ligament, posterior tibial tendon, etc.) and prevent attenuation over the long term. The pathomechanics of a preexisting flatfoot likely contribute to dysfunction of the posterior tibial tendon.34-36

   Arrangio and Salathe conducted a biomechanical analysis of posterior tibial tendon dysfunction, medial transpositional osteotomy and flexor digitorum longus transfer in AAF.38 They concluded that flexor digitorum longus transfer did little when they combined it with a medial displacement osteotomy with regard to reducing load on the medial column of the foot. However, the osteotomy itself greatly reduced the load.

   DiDomenico and colleagues performed a retrospective study of 34 patients with stage II AAF who had surgery without a flexor digitorum longus transfer.39 They noted statistically significant changes in structural realignment and concluded that surgeons can avoid flexor digitorum longus transfer without compromising the outcome when surgically treating stage II AAF. Therefore, we focus primarily on osseous reconstruction to address stage II AAF and secondarily on soft tissue reconstruction.

In Summary

Surgical management of stage II adult-acquired flatfoot is important in preventing progression of the deformity, adaptation of the osseous and soft tissue structures, end-stage arthritis and ankle malalignment. The surgical approach and procedure selection should be based on the pathology one encounters at any given time. Surgeons should be familiar with a set of procedures that address all pathological components of stage II AAF.

   Dr. Catanzariti is the Director of Residency Training and the Chair of the Division of Foot and Ankle Surgery at the Western Pennsylvania Hospital in Pittsburgh. He is a Fellow of the American College of Foot and Ankle Surgeons.

   Dr. Mendicino is a Foot and Ankle Surgeon at Pinnacle Orthopedics Associates in Salisbury, N.C. He is a Fellow and Past President of the American College of Foot and Ankle Surgeons.

   Dr. Hentges is a second-year foot and ankle surgery resident in the Division of Foot and Ankle Surgery at the Western Pennsylvania Hospital in Pittsburgh.

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