Essential Treatment Tips For Flexible Flatfoot

Author(s): 
By Richard O. Lundeen, DPM, and Stephen M. Offutt, DPM, MS

The treatment of symptomatic flexible pes planovalgus is a topic that stirs up considerable controversy among practitioners. This is especially true in the pediatric arena where there is a common belief that the child will “grow out of it.” For many foot specialists who see the damaging effects of excessive pronation among adults, the realization is all too obvious that much of this pathology can be curbed if it is addressed in childhood. Shockingly, some even deny the existence of the condition. Etiological factors of flexible pes planovalgus fall into two broad categories: pediatric and adult. Pediatric flexible pes planovalgus is typically congenital. Torsional abnormalities, muscular imbalance, ligamentous laxity, neuropathy, obesity, agenesis of the sustentaculum tali, calcaneovalgus, equinus, varus or valgus tibia, compensated forefoot varus, limb length discrepancy and os tibiale externum are just some of the possible causes. On the other hand, adult flexible pes planovalgus is nearly always an acquired condition that is often secondary to posterior tibial tendon dysfunction (PTTD). In this circumstance, the clinical presentation is synonymous with a Johnson and Strom late stage I and stage II. Biomechanically, the condition hinges around the cornerstone of peritalar subluxation. Peritalar subluxation occurs secondarily to excessive pronation of the subtalar joint, which is often associated with posterior contractures of the triceps surae. The foot functions on a maximally pronated subtalar joint which, upon weightbearing, unlocks the midtarsal joint. This results in an unstable forefoot, making efficient weightbearing and load transfer impossible. The forefoot proceeds to dorsiflex on a plantarflexing rearfoot, which leads to collapse of the arch. The concept of planal dominance should be addressed. A high subtalar joint axis will primarily compensate in the transverse plane. Conversely, the low subtalar joint axis will compensate more in the frontal plane. Reviewing Pertinent Diagnostic Findings Understanding the clinical presentation of the flexible pes planovalgus is paramount when it comes to appropriate treatment selection. A closed kinetic chain exam will reveal collapse of the longitudinal arch with concomitant internal tibial rotation, heel valgus and forefoot abduction. You’ll see tibial rotation during the gait examination as demonstrated by patellar “squinting” or medial deviation through the midline. Often, you’ll observe medial talar bulging. You may also see pronation continue throughout midstance with little resupination. The “too many toes sign,” as described by Johnson, is indicative of the forefoot abduction.1 You should also note a positive Hubscher maneuver. An open kinetic chain examination often will demonstrate an arch while subtalar joint range of motion will display excessive eversion. In the case of PTTD, you will surely note edema and pain along the posterior tibial tendon course. You may see radiographic deviations of some or perhaps all of the following angles: talocalcaneal (Kite’s), cuboid adduction, talometatarsal angle and talonavicular congruity. Lateral radiographs will show deviations in calcaneal inclination, lateral talocalcaneal, talar declination, Meary’s angle, cyma line break and medial column sag at the talonavicular and/or naviculocuneiform joints. Axial projections may demonstrate calcaneal valgus and you should use them to rule out ankle valgus, which may have a similar presentation. In the juvenile or the adult patient, you may also note adaptive changes due to the deforming pronatory forces. Taking A Closer Look At Potential Orthotic Solutions With an understanding of the preceding review of flexible pes planovalgus, you can now consider the treatment options. Initially, we will look at the functional foot orthosis as described by Root. This device is designed to place the subtalar joint in its neutral position via rigid control of the rearfoot and allowing the foot to function around this neutral joint. This modality is an excellent starting point for the supple deformity. However, you should not post all the supinatus deformity out of the pediatric device as this may encourage the forefoot to mature in this supinated position. As opposed to the functional foot orthosis, which can only function during stance, an ankle foot orthosis (AFO) can function in stance and throughout the swing phase as well. Unlike the foot orthosis, the AFO can provide direct control on the ankle and the tibia. The AFO also applies forces above and below the axis of rotation of the rearfoot throughout the entire gait cycle. One situation where the AFO has proven more efficacious than the traditional foot orthosis is in the treatment of late stage II PTTD. At this point, a disruption in the ligamentous attachments between the foot and the leg has occurred. Therefore, the ability of the traditional foot orthotic to direct the ground reactive force to stabilize against the resulting internal tibial rotation is greatly challenged.2 However, the AFO excels in this regard. Functional orthoses are best used in patients over the age of six when a flexible deformity becomes adaptively more rigid and a supinatus has formed in the forefoot to rearfoot relationship. You can effectively use heel stabilizers in younger patients from the time walking starts until about the age of three to four. You can modify the forefoot of the device to induce in-toe (Type B) or out-toe (Type C) as well as treat forefoot supinatus (Type A) or splayfoot (Type D). Roberts or Whitman-Roberts devices offer another alternative for patients ranging in age from five to 10. These are “active” devices in that flanges irritate the foot in gait to initiate active supination during the gait cycle. You can modify the Roberts devices to induce out-toeing as well (Reverse Roberts). These orthoses are made around a “rectus” cast that enables you to maintain the rearfoot in neutral and reduce the forefoot deformity while casting. This prevents a forefoot supinatus from becoming a fixed varus deformity as the child grows. When You Should Consider Surgical Treatment When external support and stabilization by either a functional foot orthosis or AFO proves inadequate in treating flexible pes planovalgus, you should consider surgical intervention. When you’re treating the juvenile patient or the adult with minimal adaptation and/or degeneration, a subtalar joint arthroereisis is the next logical step in the treatment continuum. Subtalar arthroereisis is a time-tested therapeutic option that has been finely revised over its beginnings in 1946 with Chambers. Several implant designs are currently on the market. All work under the similar principle of limiting excess pronation without limiting the necessary subtalar joint range of motion. However, each design offers slight nuances in form and function. The implants most commonly used at this time are the STA-Peg (Dow Corning), MBA (KMI) and Kalix (New Deal). While arthroereisis procedures can be utilized alone, they are usually combined with ancillary heel cord lengthening and/or medial arch stabilizing procedures. Arthroeresis, when compared to arthrodesis and osteotomy combinations, is reversible with little residual sequelae if the patient does not tolerate the procedure. Weighing The Pros And Cons Of Commonly Used Implants Arthroeresis selection can be difficult. The Lundeen Subtalar Implant (Sgarlato Labs) is a design that is derivative of the original device created by Steve Smith, DPM. The Lundeen device offers three sizes to help ensure better fit in the calcaneal sulcus and the superior surface of the device was angled at 6 degrees to better block motion of the lateral talar process on the implant. In addition, the stem of the device was enlarged to fit a 3/16-inch drill hole in the floor of the sinus tarsi. This allows you to “press fit” the implant in the calcaneus and obviates the need for polymethylmethacrylate cement. The implant itself is milled from a block of ultra high-density polyethylene (UHDPE). A study was performed on 49 patients and 96 feet with an average 46-month follow-up.3 Researchers reported 78 percent good results (resolution of symptoms and no deformity). The remainder of the study consisted of 19 percent fair results (resolution of symptoms, but residual deformity) and 3 percent poor results (residual symptoms and deformity). It must be noted that out of the three poor results, two patients suffered from trauma unrelated to the procedure and the third had a loose implant, which was resolved with re-implantation.3 The MBA prosthesis is easier to use than the STA-Peg, is placed into the sinus tarsi through a smaller incision and does not require opening of the subtalar joint, nor does it come in direct contact with the joint. Radiographic-guided placement makes it easier as well. When treating adult patients, Maxwell recommends that the MBA not be a solitary procedure and that you should always direct attention toward the medial column intraoperatively.4 However, be aware that problems can arise as the device is cylindrical in shape, making it somewhat prone for loosening or lateral extrusion upon weightbearing. It can also present a problem when you’re trying to control excess pronation following the resection of a CN bar or in a very hypermobile flatfoot deformity. You know the phrase, “easy in, easy out.” The Kalix prosthesis, on the other hand, is more difficult to insert (it has a higher learning curve) but is more anatomical in its fit into the sinus tarsi, and is harder to displace or extract. There are two ways to insert the device. You can fill the lateral opening of the sinus tarsi with the implant, as most European surgeons do, or use a smaller device and place it under the talar neck. We prefer the latter method as the device is more stable in its placement and offers a higher degree of control of the total range of subtalar motion, especially eversion. At our institution, we have inserted 41 Kalix implants to date with only one reported complication. One patient suffered from lateral impingement pain and was treated conservatively with a corticosteroid injection and orthotic therapy. No implants have been removed to date. Other Key Treatment Considerations When significant joint adaptation and/or degeneration have occurred, arthroereisis is no longer a viable option unless one uses the procedure to block most of the subtalar motion in order to prevent a fusion. In these cases, you can employ the arthroeresis to control the rearfoot and then use combinations of arthrodeses and/or osteotomies to control the mid- and forefoot. It should be mentioned that if significant joint degeneration is present, you are no longer dealing with a flexible pes plano valgus, but a rigid deformity which requires various osteotomy and arthrodesis procedures. When you’re dealing with semi-rigid deformities or partially compensated deformities that are still reducible, you need to take a different approach. One can often treat these with a combination of a calcaneal osteotomy (Evans), medial column procedure (navicular cuneiform or Lapidus fusions), heel cord lengthening (endoscopic gastroc recession) and tendon transfer (FDT to PT tendon transfer). Common calcaneal osteotomies, such as the Dwyer and the Koutsogiannis, can be employed to medialize the calcaneus out of valgus and return the pull of the triceps to a supinatory force. Medial column procedures often consist of talonavicular or Miller types of arthrodesis. These procedures correct for any medial column fault and help restore the arch. Heel cord lengthening comes in the form of either a tendo Achilles lengthening or some type of gastrocnemius recession to release the deforming force of the equinus. You can perform the Young tenosuspension to help restore the longitudinal arch but soft tissue correction alone is rarely used. Invariably, you can obtain the best results by performing an arthroeresis or arthrodesis along with different types of soft tissue procedures. Common tendon transfers include the flexor digitorum longus to posterior tibial tendon transfer (thereby increasing the diameter of the PT tendon, which increases its mechanical pull) and the Cobb procedure. Both of these procedures are utilized when one is dealing with an attenuated posterior tibial tendon. The Kidner procedure is often combined with the tendon transfer to redirect the pull of the posterior tibial tendon. When dealing with a primarily transverse plane or high subtalar joint axis presentation, then you should consider the Evans procedure. You should also consider using the Evans procedure if the midtarsal joint is unable to lock when the subtalar joint is in its realigned position. While we cannot comfortably recommend one particular combination, we do encourage you to mold the procedure selection around the patient’s pathomechanics. In Conclusion There is no doubt that every practitioner sees these patients on an all too regular basis. While the preceding paragraphs are not an exhaustive discussion on the topic of flexible pes planovalgus, the article does reflect our approach and treatment rationale when we are confronted with such a clinical scenario. Hopefully, this will be a catalyst for further study of this condition. Dr. Lundeen is Residency Director of the Winona Hospital Podiatric Residency Program in Indianapolis, Ind. Dr. Offutt is a first-year resident at the same institution.
 

 

References:

References 1. Johnson KA: Tibialis posterior tendon rupture. Clin Orthop. 177:140-147, 1983. 2. Richie D: Exploring the potential of AFO devices. Pod Today. January, 2003. pp 26-36. 3. Lundeen RO: The Smith STA-Peg operation for hypermobile pes planovalgus in children. J Am Pod Med Assoc. 75:177-183, 1985. 4. Maxwell JR, Carro A, Sun C: Use of the maxwell-brancheau arthroereisis implant for the correction of posterior tibial tendon dysfunction. Clin Pod Med Surg. 16:479-489, 1999.

 

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