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A Guide to the Cavus Foot

https://www.podiatrytoday.com/essential-guide-treating-cavus-foot-deformities

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Given the multifaceted nature of cavus foot deformities, these authors offer pertinent insights on the diagnostic workup, discuss keys to appropriate procedure selection and provide step-by-step pearls for surgical repair. 

Although an individual with a cavus foot type can present with many clinical signs and symptoms, the most common clinical presentation is a high plantar arch. Depending on the severity of the deformity, the patient can also complain of lateral foot pain, gait disturbances and a history of lateral ankle instability. Regardless of the presentation, a systematic approach to evaluating these patients will aid in identifying the appropriate diagnosis and facilitating individualized treatment. 

Prior to evaluating the patient’s lower extremities, a thorough history is necessary. Three main etiologies (neurologic, traumatic and congenital) contribute to most cavus foot types. Neurologic and congenital deformities typically present bilaterally while post-traumatic pathologies present unilaterally. A thorough family history is also important. A key point to identify through the history is whether the cavus foot type will progressively worsen (neurologic) or if it will remain static (trauma and congenital most often). 

Important findings include previous surgeries. Often, these patients have had a prior clubfoot correction or an Achilles lengthening, and documenting this is important. One should also note any information regarding complications or successes with previous surgeries or conservative treatments. 

Although each individual patient has unique characteristics, the cavovarus foot falls into one of three categories: anterior, posterior or mixed cavus. Anterior cavus will have an apex of deformity, typically in the midfoot, and be flexible or rigid. Posterior cavus will have an increased calcaneal pitch greater than 30 degrees from the weightbearing surface. A mixed type cavus will have a combination of both anterior- and posterior-driven deformities. Anterior cavus is often an overlooked physical exam finding and pathology. 

Cavus foot types are very often painful during gait and will continue to be painful after activity. During the physical exam, one must ensure pertinent exam tests and maneuvers specific to cavus feet. Gait analysis is a fundamental aspect of the patient visit and may involve a close inspection of shoe type, wear patterns and assistive devices. Examine each aspect of the gait cycle for at least five to eight stride lengths. Visualize from the anterior and posterior as well as the lateral aspect, shod and unshod. Pay close attention to any sort of deformity at the knee and take note of previous proximal limb deformity or arthroplasties as this can be an important aspect of surgical planning. 

Other key aspects of examination include: if the arch pronates or stays rigid through midstance of gait; early heel off during the propulsive stage of gait; and if the patient walks on the inside or outside of his or her foot. 

Often, large calluses are present on the lateral aspect of the foot, whether they are just on the fifth metatarsal head or on both the head and base of the fifth metatarsal. In strictly sagittal plane malalignment, for instance, the hyperkeratotic lesions typically exist across the entire forefoot at the metatarsophalangeal (MPJ) joints. 

Examination of the patient’s shoes should also reveal wear on the outside of the shoe if he or she repetitively strikes in a varus heel position during contact phase of gait. 

One should proceed to perform an extensive bilateral biomechanical exam, commonly starting proximal to distal. The clinician should examine the patient standing as well as seated on a table with the knees bent at 90 degrees. Assess active and passive range of motion at the ankle and subtalar joint along with any ankle laxity. Stressing the lateral ankle ligaments and peroneal tendons could reveal pain and instability. Peroneal tendons are a driving force in pain in these conditions and need close attention. It is beyond the scope of this article alone to discuss peroneal tendon repair and pathology. 

Next comes the hindfoot and midfoot exam. This should begin with the Coleman block test to identify if the deformity is forefoot- or hindfoot-driven.1 With this diagnostic test, the patient stands on a one-inch block with the first ray unsupported while the physician stands behind the patient, examining the heel and forefoot. This allows the medial forefoot or medial column to unload and plantarflex. If the patient’s hindfoot returns to neutral, then it is a forefoot-driven deformity. If the hindfoot remains in a rigid varus or inverted position, then it is at least rearfoot-driven.1 Again, this is important in surgical planning. 

Locking and unlocking of the midtarsal joint is important to note with a rigid midtarsal or Chopart joint being most common. One should also document the position of the first ray and forefoot valgus or varus. Clinicians may use the Silfverskiold test to evaluate for equinus. Pseudoequinus may also be present due to impingement of the talus on the distal tibia in dorsiflexion. Also be sure to document the presence of any digital contractures and hammertoes.2 

One should perform an extensive neurologic exam as well as order an electromyographic (EMG) study if there is concern for a peripheral nerve disorder. Be sure not to overlook muscle strength during this part of the exam as well. 

From a dermatological perspective, evaluating for hyperkeratotic lesions on the plantar foot is relevant as the tripod foot is exaggerated in a cavus foot type,. This can potentially lead to callus development under the calcaneus as well as the fifth and first metatarsal heads. Sub-fifth metatarsal head lesions are common with forefoot varus deformities. 

What To Look For In Diagnostic Imaging 

Imaging should begin with standard weightbearing radiographs of the foot and ankle. There are not too many updates in the literature as it pertains to imaging except for weightbearing computed tomography (CT), which is helpful for evaluating mechanical complex deformities. 

Long leg axial and calcaneal axial X-ray images are beneficial when evaluating hindfoot deformities. One should first identify the apex of the deformity on a lateral foot or ankle X-ray view. Important radiographic signs one should evaluate include Meary’s angle, talar declination, calcaneal inclination, talar head coverage and the sinus tarsi bullet hole sign. The goal is to find the center of rotation of angulation (CORA) on a lateral view and determine what type of osteotomy, fusion or other ancillary procedures to perform. If there is metatarsus adductus or severe forefoot deformity present, this is also a consideration. Advanced imaging may be indicated if there is concern about tarsal coalitions, peroneal tendon tears, arthritic changes or to evaluate previous surgical correction. 

Key Considerations In Surgical Planning 

Conservative care will typically consist of custom orthotics, ankle/foot bracing and various analogs of injections. If the patient does not have relief of pain and symptoms with conservative care, one should discuss and contemplate surgical treatment options. Generally speaking, the greater degrees of deformity and the more rigid deformities do not do well with conservative treatment, depending on the age and activity level of the patient. 

The surgeon should pose several pertinent questions during surgical planning. Is the deformity forefoot- or rearfoot-driven? Is the deformity rigid or flexible? What is the age and occupation of the patient? Is there lateral ankle instability or proximal limb deformity? Is there peroneal tendon injury? Is there equinus or pseudoequinus? What is the pain generator? Answering these questions will guide your preoperative procedure selection. 

A Stepwise Approach To Surgical Repair Of Cavus Deformities 

There are key procedures that each surgeon should have the basic knowledge to discuss and interpret. Most often, a combination of procedures is useful for selection (e.g. gastrocnemius recession, lateral ankle ligament repair, calcaneal osteotomy, posterior tibial tendon transfer and first metatarsal osteotomy). The surgeon should consider each segment of the leg/ankle/foot as he or she works through the procedure selection. 

Starting proximally with a posterior muscle group release is most common for these deformities. We typically perform an open gastrocnemius recession with a 2.5 cm incision on the posterior medial leg, just distal to the gastrocnemius muscle belly. With the patient in a lateral position, a single operating surgeon can easily perform this procedure. One then carries the incision down through subcutaneous tissues, avoiding the sural nerve and lesser saphenous vein. At this point, utilizing an Army-Navy retractor medially and laterally helps to visualize the fascia. Upon sharply opening the fascia, one can inspect the aponeurosis. In an open manner, the surgeon can clearly see the myotendinous junction and transect the gastrocnemius aponeurosis alone with the knee extended just distal to the muscle fibers. Most often, the surgeon can feel an palpable release to appreciate at least 10 degrees of dorsiflexion past neutral with the knee extended. Endoscopic releases are common and recent research does show less overall complications with an endoscopic approach.3 

Next, one can perform a Dwyer calcaneal osteotomy or lateralizing calcaneal osteotomy. Surgeons can perform a lateral calcaneal osteotomy for a rearfoot-driven deformity when the calcaneus is in a varus position.4 This converts the Achilles tendon from an inverting force to an everting force while also reducing the calcaneal inclination angle.5 

Schmid and colleagues found that a five mm and 10 mm lateral shift of the calcaneus resulted in a two mm and three mm shift in force distribution, and 41 and 49 percent reduction in peak pressure at the ankle respectively.5 The senior author will utilize a wedge resection with a lateral base, a true Dwyer osteotomy, when significant calcaneal varum is present only. In the senior author’s experience, the key with this osteotomy is twofold: make certain to have an adequate skin bridge between any lateral ankle incision and perform the osteotomy halfway between the subtalar joint and posteroinferior calcaneal margin. 

With rigid deformities, surgeons can perform a Cole midfoot osteotomy through a dorsal foot incision.6 We typically perform this with other osseous procedures to reduce forefoot pressure and reduce the apex of deformity in the sagittal plane. Making a five cm incision over the central naviculocuneiform joint, the surgeon would carry this down to the periosteum. Then the surgeon drives two Steinmann pins from the dorsal navicular and the intermediate cuneiform to the plantar aspect of this joint. One confirms pin placement on fluoroscopy and adjusts as necessary. Following pin placement, the surgeon may use a large sagittal saw to resect a dorsal-based wedge, taking care to excise the appropriate amount from the mid-cuboid. Otherwise, the surgeon will create a varus foot type by elongating the lateral column. Fixation for the osteotomy consists of crossed screws and or staples. 

Tendon transfers are also common with cavus foot deformities. One of the more productive transfers is the peroneal switch or transfer, whereby one sutures the peroneus longus side by side to the peroneus brevis in order to reduce the deforming force of the medial column and improve eversion power. A posterior tibial tendon transfer is a workhorse for a hindfoot- or rearfoot-driven deformity, which one may see with excessive talar coverage and inversion of the talus. 

Lateral ankle reconstruction is paramount with a high degree of chronic ankle instability in this patient cohort. An open or arthroscopic approach is possible based on surgeon preference. For simplicity and reproducibility, we typically perform an arthroscopic, double-row repair, and have had great outcomes anecdotally with this approach. 

What About Adjunctive Procedures? 

If the first metatarsal remains plantarflexed after the aforementioned procedures, surgeons may perform a dorsiflexory first metatarsal osteotomy or first tarsometatarsal joint fusion. This may be the case with forefoot-driven deformities and one can perform the procedure in a joint preserving or destructive manner.7 

If the patient continues to have a high plantar arch after an osteotomy, the plantar soft tissue structures are likely preventing the arch from collapsing. Performing a Steindler stripping will free the soft tissue attachments at the calcaneus, allowing the arch to collapse and often assisting with offloading the forefoot. 

Although this is not fully within the scope of this article, coexisting tibial or tibiotalar deformities in cavus feet may require a tibial osteotomy, which the senior author discussed in another Podiatry Today article.8 

Many patients with cavus deformity will have hammertoe deformities and pain associated with digital contractures. Often, in these cases, one performs intramedullary fixation with an extensor tendon lengthening or flexor tendon transfer. 

In a patient with a rigid, arthritic cavus foot deformity, a triple arthrodesis should be a strong consideration. These deformities are most often present in patients who had previously corrected clubfoot with subsequent relapse.9 

In patients with ankle arthritis and a concomitant cavus or cavovarus foot type, sound surgical planning is essential to ensure a high degree of successful outcomes. Malleolar osteotomies, calcaneal osteotomies and medial column osteotomies are standard staged procedures to ensure adequate survivorship of ankle implants. The key here is not to ignore or under-appreciate the degree of coronal plane deformity, which could inherently ruin the foot and ankle mechanics, and lead to edge loading and subsequent implant failure. 

For additional surgical considerations, see the sidebar “What Recent Research Has Revealed About Cavus Foot Reconstruction” by clicking here.

Postoperative Principles: What You Should Know 

Postoperatively, one applies a bulky Jones dressing and non-weightbearing posterior splint for two weeks. Suture removal takes place when the skin heals. The patient then remains non-weightbearing in a short-leg boot or cast. Weightbearing can start at six to eight weeks post-op, depending on the radiographs and healing process. By obtaining serial X-rays throughout the postoperative course, one can confirm healing of osteotomies and fusions. 

Early physical therapy can begin at six weeks and continue until the patient is comfortable with weightbearing in supportive shoes. A custom orthotic is important postoperatively. In regard to activity limitations and exercise progression, one would make these decisions based on osteotomy healing and pain. In the senior author’s experience, the recovery for cavus foot procedures can often exceed six months to a year. 

Pertinent Pitfalls In The Treatment Of Cavus Foot 

In the senior author’s experience, common mistakes in cavus foot correction and treatment can include: 

• Resection of the fifth metatarsal base, leading to a severe midfoot rotational deformity; 

• Resection of the fifth metatarsal head alone, which can cause continued pain and transfer forefoot lesions; 

• Not addressing posterior muscle group contractures; 

• Not addressing ankle deformity when it is present; and 

• Ignoring the rigid hindfoot deformity and only correcting the forefoot. 

In Conclusion 

Cavus feet are complex. Cavus foot treatment always begins with aggressive conservative care but often transitions to the operating room quickly. The more active patients may be more suitable to undergo osteotomies versus fusions. The key to cavus foot reconstruction is not avoiding certain stepwise procedures and leaving the patient with residual deformity.  

Dr. McAlister is a fellowship-trained foot and ankle surgeon. He is the founder of the Phoenix Foot and Ankle Institute (www.phoenixfai.com), and is in private practice in Scottsdale and Phoenix, Ariz. Dr. McAlister is a Fellow of the American College of Foot and Ankle Surgeons. One can reach Dr. McAlister at jeff.mcalister@phoenixfai.com. 

Dr. Danesh is a third-year resident with the Carl T. Hayden Phoenix VA Podiatric Residency Program in Phoenix, Ariz. 

References

1. Coleman SS, Chestnut WJ. A simple test for hindfoot flexibility in the cavovarus foot. Clin Orthop Relat Res. 1977;123:60-62. 

2. Goss DA Jr, Long J, Carr A, Rockwell K, Cheney NA, Law TD Sr. Clinical implications of a one-hand versus two-hand technique in the Silfverskiöld test for gastrocnemius equinus. Cureus. 2020;12(1):e6555. 

3. Brandão RA, So E, Steriovski J, Hyer CF, Prissel MA. Outcomes and incidence of complications following endoscopic gastrocnemius recession: a systematic review. Foot Ankle Spec. 2020. doi: 10.1177/1938640019892767. Accessed January 11, 2021. 

4. Dwyer FC. Osteotomy of the calcaneum for pes cavus. J Bone Joint Surg Br. 1959;41- B(1):80-86. 

5. Schmid T, Zurbriggen S, Zderic I, Gueorguiev B, Weber M, Krause FG. Ankle joint pressure changes in a pes cavovarus model: supramalleolar valgus osteotomy versus lateralizing calcaneal osteotomy. Foot Ankle Int. 2013;34(9):1190-1197. 

6. Cole WH. The classic. The treatment of claw-foot. By Wallace H. Cole. 1940. Clin Orthop Relat Res. 1983;181:3-6. 

7. Pirozzi K, Meyr AJ. Using geometry for the dorsiflexory wedge osteotomy of the first metatarsal. J Foot Ankle Surg. 2014;53(3):295- 297. 

8. McAlister JE, Philbin TM. A closer look at the distal tibial osteotomy for ankle varus. Podiatry Today. 2012;25(11). Available at: https://www. podiatrytoday.com/closer-look-distal-tibial-osteotomy-ankle-varus . Published October 29, 2012. Accessed January 11, 2021. 

9. DeVries JG, McAlister JE. Corrective osteotomies used in cavus reconstruction. Clin Pod Med Surg. 2015;32(3):375-387. 

10. Weinheimer K, Campbell B, Roush EP, Lewis GS, Kunselman A, Aydogan U. Effects of variations in Dwyer calcaneal osteotomy determined by three-dimensional printed patient-specific modeling. J Orthop Res. 2020;38(12):2619- 2624. 

11. Dash KK, Bradley R, Stavrakakis I, Shah K. Medial soft-tissue release for lateralising calcaneal osteotomy: a cadaveric study. Indian J Orthop. 2020;54(1):49-54. 

12. Li S, Myerson MS. Failure of surgical treatment in patients with cavovarus deformity: why does this happen and how do we approach treatment? Foot Ankle Clin. 2019;24(2):361-370. 

13. Lintz F, Jepsen M, De Cesar Netto C, Bernasconi A, Ruiz M, Siegler S, International Weight- Bearing CT Society. Distance mapping of the foot and ankle joints using weightbearing CT: the cavovarus configuration. Foot Ankle Surg. 2020. doi: 10.1016/j.fas.2020.05.007. Accessed January 11, 2021. 

 

Author
Jeffrey E. McAlister DPM

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