Medial Double Arthrodesis and Medial Displacement Calcaneal Osteotomy for Adult-Acquired Flatfoot Deformity

Adult-acquired flatfoot deformity (AAFD) is a complex and progressive deformity. To varying degrees, abduction of the midfoot, peritalar subluxation (subtalar eversion, talar plantarflexion, and forefoot abduction), forefoot varus, and hindfoot valgus comprise this deformity. Over the decades, the many attempts at staging these deformities and their associated treatments continue to evolve as we gain new insight into the underlying complexities. The most prevalent classification for AAFD is the system Johnson and Strom introduced in 1989¹ and that Myerson modified in 1997.²

At its most basic interpretation, AAFD consists of:^1,2  

• Stage 1: posterior tibial tendon (PTT) tenosynovitis without deformity;
• Stage 2: reducible hindfoot valgus; and
• Stage 3: rigid hindfoot valgus.

Myerson then added Stage 4, consisting of ankle valgus.² Efforts to expand on the AAFD staging also arose with Weinraub and Heilala in 2000 and Haddad and colleagues in 2011.^3,4 More recently a new classification system and terminology has been developed and introduced and is termed progressive collapsing foot deformity (PCFD).⁵

Regardless of the classification, it is important to understand the complex 3-dimensional nature of this deformity. While proper diagnosis and staging is vital, it is critical to understand what impact certain procedures have on the underlying deformity. A combination of clinical examination and imaging analysis can help to ascertain these underlying components and assist with appropriate surgical planning. X-rays, magnetic resonance imaging (MRI), computed tomography (CT) and weight-bearing CT can all provide critical information when considering deformity staging, surgical planning, and procedure selection.

Weight-bearing CT is not yet widely available for many providers, but recent literature has been positive regarding its use in surgical planning and deformity analysis.⁶ Standard foot and ankle radiographs with hindfoot alignment and calcaneal axial views are the minimum images one should obtain when considering surgical management of AAFD.

A Closer Look at Medial Double Arthrodesis

Late- and end-stage surgical management of AAFD has historically led to triple arthrodesis, with subtalar joint (STJ), talonavicular joint (TNJ), and calcaneocuboid joint (CCJ) fusions. This is a classic option for addressing rigid AAFD, although not without potential complications. Traditionally, one employs a 2-incision approach with the medial incision used to access the TNJ and the lateral incision to access the CCJ and STJ. Some potential downsides to this approach center around lateral incision wound healing complications, sural nerve injury/neuritis, prolonged operative times, and potential nonunion concerns (specifically at the CCJ). A double arthrodesis (STJ and TNJ) performed through a single medial incisional approach, in our experience, offers comparable levels of correction and outcomes to the triple arthrodesis while decreasing operative times, providing fewer wound complications, and potentially fewer issues with nonunions by bypassing fusion of the CCJ. Studies show that after TNJ fusion there is only approximately 2 degrees of motion at the CCJ.⁷ O’Malley and team demonstrated that forefoot rotation and restoration of medial arch height did not require CCJ arthrodesis.⁸

In studying the medial double versus triple arthrodesis for AAFD, DeVries and colleagues concluded there was statistically significant improvement in pre- and postoperative radiographic angles in both groups and no statistical difference in postop radiographic angles between groups, indicating comparable levels of deformity correction for the two approaches.⁹ The medial double arthrodesis may also provide increased benefit by decreasing the occurrence of postoperative ankle valgus. Hyer and coworkers demonstrated a statistically significant increase (3.64 times greater) in postoperative ankle valgus after triple arthrodesis compared to medial double arthrodesis.¹⁰

Understanding the Surgical Technique

The medial incision begins just posterior and inferior to the medial malleolus coursing distally along the posterior tibial tendon to just distal to the navicular tuberosity. One then carries dissection down in the same surgical plane at the superior margin of the posterior tibial tendon. At this point, the surgeon inspects that tendon and places a self-retaining retractor between the posterior tibial tendon and the medial malleolus. This not only pulls the tendon out of the surgical field, but also helps protect the posterior neurovascular bundle. Next, one directs attention to the distal aspect of the incision.

The surgeon incises the talonavicular capsule at the level of the joint and carries this plantarly and proximally under the talar head and down into the STJ. Careful use of a straight or curved osteotome can then transect the interosseous ligament. Introduction of a lamina spreader into the joint can allow visualization of and access to the subtalar joint. Alternatively, Steinmann pins with a self-retaining retractor can distract the subtalar joint.

STJ preparation can take place with a combination of curettes, sharp osteotomes, and/or a high-speed rotary burr. Addressing 3 facets and complete removal of all articular cartilage is critical for ensuring fusion. Anecdotal teaching is that “all you need is one joint to heal,” but ensuring preparation of all 3 joints increases those chances, in our experience. Fenestration further prepares the joint with an appropriately sized drill and a sharp osteotomy can fish-scale/further break up the subchondral plate.

Moving to the talonavicular joint, Steinmann pins and a self-retaining retractor can again distract the joint for appropriate preparation, using a similar technique as with the subtalar joint. One should exercise care when addressing the medial aspect of the talar head, as we find this is often significantly softer due to medial talar head uncoverage and lack of force through this portion of the joint. A high-speed drill with a football burr can be useful here as well, if one is careful not to aggressively shorten the joint or dig in to the softer medial aspect. Curved osteotomes and angled curettes can allow for improved cartilage removal from the lateral aspect of the talonavicular joint. Subchondral joint preparation is next, with fenestration and fish scaling with appropriate drill bit and osteotome respectively.

Provisional STJ fixation takes place with guidewires for the appropriate size screws that one will use for definitive fixation. Typically, one uses 2 (6.5, 7.0 or 7.3mm) cannulated compression screws. It is critical to place the STJ in neutral position with proper alignment and reduction of the valgus deformity with intraoperative fluoroscopy confirmation. The surgeon places these guidewires in the lateral view in the same orientation as the anticipated screws. Checking AP and calcaneal axial projections can ensure proper reduction and orientation of the guidewires. A 2-screw configuration provides multiplanar stability. A parallel or delta screw configuration is often utilized, oriented from the posterior plantar calcaneus, across the STJ into the talar body. Alternatively, a counter parallel configuration is an option, with 1 screw oriented from the plantar posterior calcaneus into the talar body and the other screw oriented from the proximal talar neck into the plantar posterior calcaneus. Thread length should allow for all threads to cross the joint to allow for appropriate compression of the joint surfaces.

The TNJ joint should then be reduced anatomically, restoring proper sagittal and transverse plane relationship of the talar-first metatarsal axis. Fixation is with 2 or 3 5.0mm compression screws oriented distally from the anterior navicular across the joint into the talar head. Conversely, compression staples or a small plate may provide fixation or supplement screw fixation. Fixation placement is important as it should fixate the lateral and medial aspects of the joint. One may place the lateral screw percutaneously to ensure proper orientation.

Examining the Medial Displacement Calcaneal Osteotomy (MDCO)

The main indication for this procedure is correcting the valgus hindfoot in flexible/reducible AAFD. One may utilize this in conjunction with arthrodesis in the correction of stages 3 and 4 AAFD/residual hindfoot valgus. Biomechanically speaking, the MDCO changes the axis of the calcaneus, allowing ground reactive forces to impart a supinatory force on the heel and preventing it from going into a valgus orientation. It additionally moves the line of pull of the Achilles tendon medial to the STJ axis, altering the force vector and imparting an inversion pull on the heel.

Nyska and colleagues showed that the Achilles tendon’s pull on a valgus-oriented hindfoot increased the collapse of the medial arch of the foot.¹¹ After the addition of a 1-cm MDCO, the Achilles pull resulted in decreased flattening of the arch. Hadfield and team demonstrated that the MDCO resulted in significantly decreased plantar pressure under the first and second metatarsals, indicating significant forefoot inversion.¹² Arangio and Salathe demonstrated that with an MDCO, forces shift laterally, significantly offloading the medial arch.¹³ If a surgeon questions whether to choose MDCO over a realignment STJ fusion, MRI can be an important tool in determining STJ condition when plain radiographs are not helpful.

Surgical Technique

One performs the MDCO from the lateral aspect of the calcaneus. Anatomic landmarks include the lateral aspect of the distal fibula, the peroneal tendons, the inferior and superior aspects of the calcaneus, and the anterior aspect of the Achilles tendon. Incision placement is between the peroneal tendons and the anterior aspect of the Achilles tendon at a 45-degree angle to the weight-bearing surface. To ensure proper orientation, under lateral fluoroscopy, one may use a Freer elevator, Kirschner wire, or osteotome to properly plan where the incision and osteotomy will lay within the anatomic safe zone and avoid the sural nerve. Once one carefully carries the incision down to the lateral wall of the calcaneus, the surgeon exposes the wall and incises the periosteum in the same surgical plane. A Freer elevator or small Key elevator can fully free the superior and inferior margins of the calcaneus along the planned osteotomy to allow for easier translation. Hohmann retractors placed to the superior and inferior aspects of the planned incision aid in retraction/protection of the soft tissues and provide landmarks for the osteotomy. To facilitate visualization of the planned osteotomy, one may score the lateral wall of the calcaneus with electrocautery.

The recommended orientation of the osteotomy begins at the posterosuperior calcaneal tuberosity, extending to just distal to the origin of the plantar fascia and the safe zone for the osteotomy extends distally approximately 1cm from this line. One should make sure to create the cut perpendicular to the lateral wall of the calcaneus, maintaining this orientation while advancing the saw blade from the lateral to medial aspect, not deviating anteriorly or posteriorly. Care to avoid the medial neurovascular bundle and surrounding soft tissue is paramount as the saw blade approaches the medial wall of the calcaneus. Often an osteotome can finish the osteotomy to avoid any iatrogenic damage to the medial structures.

After completing the osteotomy, one may introduce a smooth lamina spreader to distract the osteotomy and help loosen soft tissues to aid in appropriate translation as necessary. After removing the lamina spreader, the surgeon then manually shifts the calcaneal tuberosity medially. It is wise to have the foot in a plantarflexed position while translating the osteotomy as the gastroc-soleus complex is in a relaxed position, which will allow for easier translation. Typically, we find the amount of medial shift should be in the range of a minimum of 5mm to 15mm with improved hindfoot and midfoot alignment seen with a greater amount of medial translation.

Of note, unlike with a lateral translation osteotomy, the medially shifted osteotomy has shown to not increase chances of developing tarsal tunnel syndrome.¹⁴ Once achieving the appropriate shift, placing the foot in a dorsiflexed position allows the tension of the gastroc-soleus complex to assist in holding the osteotomy in place. Confirmation of the osteotomy translation takes place under intraoperative fluoroscopy and subsequent fixation is with cannulated guide wires. Intraoperative lateral and calcaneal axial images are essential to obtaining proper translation and fixation orientation.

A 2-screw configuration for fixation is preferred to allow for appropriate stability and resistance to rotational forces. The starting point for these screws should be slightly superior to the weight-bearing surface of the posterior calcaneal tuberosity and oriented as perpendicular as possible to the osteotomy. Placing the screw starting point at this location helps avoid screw prominence and painful ambulation. Studies show that using larger screws (>6.5mm) compared to smaller diameters (4.0mm, 4.5mm, 5.0mm) resulted in increased incidence of hardware removal secondary to pain and discomfort.¹⁵ We have found that 5.0mm to 5.5mm cannulated headless fully-threaded screws offer excellent fixation without need for removal after the osteotomy has healed. Intraoperatively, one should assess the prominence of the lateral wall of the calcaneus after translation and fixation. In larger translations, if this prominence has not been assessed and smoothed down with a bone tamp or rongeur, it can remain prominent and cause the patient discomfort.

In Summary

Both the medial double arthrodesis and MCDO play a significant role in AAFD correction surgery. The surgeon needs to be aware of the proper sequence of examination and palliative care techniques to ensure when and if surgery becomes necessary. Once this is ascertained, in our experience, the aforementioned stepwise approaches can contribute to successful outcomes. We feel that AAFD correction has very predictable and rewarding results when performed correctly and with the right combination of procedures.

Dr. Marshall is the current Fellow at the Pennsylvania Intensive Lower Extremity Fellowship in Malvern, PA in association with Premier Orthopedics and Sports Medicine.

Dr. Miller is an Adjunct Associate Professor in the Department of Surgery at Temple University School of Podiatric Medicine, the Founder and Director of the Tower Health/Phoenixville Hospital residency program (PMSR/RRA), and the Founder and Director of the Pennsylvania Intensive Lower Extremity Fellowship Program.

References

1. Johnson KA, Strom DE. Tibialis posterior tendon dysfunction. Clin Orthop Relat Res. 1989;239:196-206.
2. Myerson MS. Adult acquired flatfoot deformity: treatment of dysfunction of the posterior tibial tendon. Instr Course Lect. 1997;46:393-405.
3. Weinraub GM, Heilala MA. Adult flatfoot/posterior tibial tendon dysfunction: outcomes analysis of surgical treatment utilizing and algorithmic approach. J Foot Ankle Surg. 2000;39(6):359-364.
4. Haddad SL, Myerson MS, Younger A, et al. Adult acquired flatfoot deformity. Foot Ankle Int. 2011;32(1):95-111.
5. Myerson MS, Thordarson DB, Johnson JE, et al. Classification and nomenclature: progressive collapsing foot deformity. Foot Ankle Int. 2020 Oct;41(10):1271-1276.
6. de Cesar Netto C, Myerson MS, Day J, et al. Consensus for the use of weightbearing CT in the assessment of progressive collapsing foot deformity. Foot Ankle Int. 2020;41(10):1277-1282.
7. Astion DJ, Deland JT, Otis JC, Kenneally S. Motion of the hindfoot after simulated arthrodesis. J Bone Joint Surg Am. 1997;79(2):241-246.
8. O’Malley MJ, Deland JT, Lee KT. Selective hindfoot arthrodesis for treatment of adult acquired flatfoot deformity: an in vitro study. Foot Ankle Int. 1995;16(7):411-417.
9. DeVries JG, Scharer B. Hindfoot deformity corrected with double versus triple arthrodesis: radiographic comparison. J Foot Ankle Surg. 2015;54(3):424-427.
10. Hyer CF, Galli MM, Scott RT, Bussewitz B, Berlet GC. Ankle valgus after hindfoot arthrodesis: a radiographic and chart comparison of the medial double and triple arthrodesis. J Foot Ankle Surg. 2014;53(1):55-58.
11. Nyska M, Parks BG, Chu IT, et al. The contribution of the medial calcaneal osteotomy to the correction of flatfoot deformities. Foot Ankle Int. 2001;22(4):278-282.
12. Hadfield MH, Snyder JW, Liacouras PC, et al. Effects of medializing calcaneal osteotomy on achilles tendon lengthening and plantar foot pressures. Foot Ankle Int. 2003;24(7);523-529.
13. Arangio GA, Salathe EP. Medial displacement calcaneal osteotomy reduces the excess forces in the medial longitudinal arch of the flatfoot. Clin Biomech (Bristol, Avon). 2001;16(6):535-539.
14. Bruce BG, Bariteau JT, Evangelista PE, Arcuri D, Sandusky M, DiGiovanni CW. The effect of medial and lateral calcaneal osteotomies on the tarsal tunnel. Foot Ankle Int. 2014;35(4):383-388.
15. Lucas DE, Simpson GA, Berlet GC, Philbin TM, Smith JL. Screw size and insertion technique compared with removal rates for calcaneal displacement osteotomies. Foot Ankle Int. 2015;36(4):395-399.