Adult Acquired Flatfoot Deformity

Adult acquired flatfoot deformity (AAFD), most commonly caused by posterior tibial tendon (PTT) insufficiency, consists of a spectrum of deformities. It typically consists of a combination of plantar sag, midfoot abduction, and heel valgus. It results from a combination of PTT insufficiency and failure of both capsular and ligamentous structures (spring ligament, deltoid ligament).

AAFD has a multifactorial etilogy. The primary risk factors include a pre-existing flatfoot, female gender, age (peak at 55), obesity, gastrocnemius contracture, ligamentous laxity, trauma, high impact sports and diabetes.

Staging

Johnson and Strom (1989)

Modified by Myerson (2007)

Diagnosis

Appropriate history with identification of risk factors, presence of medial sided pain, the intensity of pain may not necessarily reflect the severity of the stage, progressive lateral pain due to impingement.

A complete examination of the foot and ankle including toe-many toes sign, palpation along the distal portion of the PTT, pain at the lateral aspect of the hindfoot (suggestive of lateral impingement), pain on palpation of arthritic joints in stage III and IV (talonavicular, subtalar, calcaneocuboid, and ankle), inability to perform a single heel rise (highly suggestive of PTT insufficiency), range of motion of ankle must also be evaluated, gastrocnemius/Achilles tendon tightness (Silverskiold’s test).​

Weight-bearing plain AP and lateral radiographs of the foot ankle to assess arch collapse (by Meary’s or the lateral first tarsometatarsal angle), forefoot abduction (at the talonavicular joint), talar head uncoverage (>30%or <30%) and talar tilt (stage IV AAFD). Hindfoot valgus can be evaluated with either a hindfoot alignment view or long axial view. All radiographs should be carefully examined to identify arthritic changes that could substantially affect treatment choice.

MRI, although not essential but a very useful modality to assess the extent of cartilage, tendon, and ligament involvement, bone oedema (may reveal signs of lateral bony impingement) and spring ligament integrity.

Management

Conservative Management

Regardless of the stage, the first line of management for all patients is conservative before considering surgery. This includes physiotherapy, NSAIDs, orthotics, bracing (medial arch or ankle brace), a low-articulating ankle-foot orthosis (LAFO) or similar AFO, cast-boot (cam walker) or shoe modifications. In cases of stage I disease, Nielson et al. reported an 87 % success rate with these modalities defined as not requiring further surgical treatment. Similar results have been reported by other authors including Chao et al. Augustine et al. and Alvarez et al. (67%-90%) for stage I and II disease.​

Surgical Management

Stage I

In cases of disease progression with worsening symptoms after a period of at least 3 months, surgery may be considered. A combination of soft tissue and bony procedures is recommended instead of only soft tissue procedures. Preferred option in stage I is medializing calcaneal osteotomy with PTT procedures (tenosynovectomy, repair, or transfer).

Stage II

For stage IIa, medializing calcaneal osteotomy, flexor digitorum longus (FDL) transfer, and gastrocnemius recession or TA lengthening represent the treatment of choice in stage IIa AAFD. A medializing calcaneal osteotomy realigns the hindfoot, offloads the spring ligament and increases the inversion moment arm of the gastrocsoleus complex. The FDL transfer to the navicular compensates for the lost function of the degenerated PTT. An elevated medial column can be lowered to treat forefoot supination or varus persisting after hindfoot realignment. If the first TMT joint is not hypermobile, an opening wedge medial cuneiform osteotomy (Cotton osteotomy) can be performed to bring down the first ray. If the 1st TMT joint is hypermobile or arthritic, this can be addressed with a fusion of the joint in the desired position.

Myerson et al. reported the results of 129 patients treated with above combined procedure for stage II AAFD, with average age of 53 years and an average follow up of 5.2 years. Their results showed significant correction of radiographic parameters, 91% patient-satisfaction, 97% pain relief, 94% improvement of function, 87% improvement in the arch of the foot, and 84% patients were able to wear shoes comfortably without shoe modifications or orthotic arch support.

Deland et al. reported the results of the above procedure in 34 patients below 50 years of age (average 41 years), and average follow up of 44 months. Their results showed a significant improvement of functional scores (AOFAS).

Kou et al. reported excellent functional outcome and a high patient-satisfaction rate after medial calcaneal osteotomy, FDL transfer and gastrocnemius recession for stage II disease in 23 patients at 2-year follow up.

For stage IIb, more severe flexible deformity, the treatment strategy is the same as above, with an addition of lateral column lengthening, however, it is controversial. It achieves correction of TN abduction and increases the arch. It can be performed either by an Evan’s procedure or CC distraction. Some studies have reported an incidence of lateral sided foot pain in up to 45% cases after lateral column lengthening.

Stage III

Stage III AAFD consists of fixed deformity involving the subtalar, calcaneocuboid and talonavicular joints. Correction is achieved by fusing the talonavicular and subtalar joints, where most of the deformity occurs and the calcaneocuboid joint may be spared, unless arthritic and symptomatic. Triple arthrodesis causes difficulty to adapt to uneven ground and increases the risk of developing ankle arthritis.

The heel should be fused in ≤5° of valgus with the forefoot in neutral, avoiding supination, pronation or elevation of the first ray. If heel valgus persists after achieving neutral of the forefoot and triple-joint complex, then a medializing calcaneal osteotomy may be needed additionally. It is important to avoid overcorrection of the deformity as lateral overload can result from fixed supination deformity. If the first ray is elevated, a first TMT procedure (fusion or osteotomy) may need to be added.

Stage IV

Stage IVa deformity can potentially be treated with foot reconstruction without requiring fusion or replacement of the ankle joint. Deltoid ligament reconstruction can be performed with a variety of techniques employing autografts, allografts, or tendon transfers. The correction of deformity in the foot must be done at the same time so the first ray is stable and the valgus of the heel and ankle are corrected. The only available study is by Deland et al., which described long-term clinical and radiographic results. In a small cohort of patients at 9 years follow-up, the results were encouraging.

Stage IVb deformity may be treated in different ways. If the patients fulfil the criteria for an ankle replacement, this can be combined with triple arthrodesis. Patients not eligible for ankle replacement are treated with pantalar fusion.

References

  • Ettore Vulcano & Jonathan T. Deland & Scott J. Ellis; Approach and treatment of the adult acquired flatfoot deformity; Curr Rev Musculoskelet Med (2013) 6:294–303, DOI 10.1007/s12178-013-9173-z.

  • Bluman EM, Title CI, Myerson MS. Posterior tibial tendon rupture: a refined classification system. Foot Ankle Clin. 2007;12:233–49.

  • Deland JT. Adult-acquired flatfoot deformity. J Am Acad Orthop Surg. 2008;16:399–406.

  • Mann RA. Flatfoot in adults. In: Mann RA, Coughlin MJ, editors. Surgery of the foot and ankle. 7. St. Louis: Mosby; 1999. p. 733–67.

  • Adult acquired flatfoot. Available at http://orthoinfo.aaos.org/topic.cfm?topic=a00173. Accessed January 2013.

  • Johnson KA, Strom DE. Tibialis posterior tendon dysfunction. Clin Orthop Relat Res. 1989;239:196–206.

  • Deland JT, Page A, Sung I-H, O'Malley MJ, Inda D, Choung S. Posterior tibial tendon insufficiency results at different stages. HSS J. 2006;2:157–60

  • Nielsen MD, Dodson EE, Shadrick DL, Catanzariti AR, Mendicino RW, Malay DS. onoperative care for the treatment of adultacquired flatfoot deformity. J Foot Ankle Surg. 2011;50:311–4.

  • Alvarez RG, Marini A, Schmitt C, Saltzman CL. Stage I and II posterior tibial tendon dysfunction treated by structured nonoperative management protocol: an orthosis and exercise program. Foot Ankle Int. 2006;27:2e8.

  • Myerson MS, Badekas A, Schon LC. Treatment of stage II posterior tibial tendon deficiency with flexor digitorum longus tendon transfer and calcaneal osteotomy. Foot Ankle Int. 2004; 25:445–50.

  • Kou JX, Balasubramaniam M, Kippe M, Fortin PT. Functional results of posterior tibial tendon reconstruction, calcaneal osteotomy, and gastrocnemius recession. Foot Ankle Int. 2012;33:602–11. Twenty-four patients with stage II flatfoot were treated with FDL transfer, double calcaneal osteotomy, and gastrocnemius recession. Twenty-three patients had 2-year follow-up. Patients were highly satisfied with the results of their surgery.

Last Updated: Jan 2018

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Date First Published - March 4, 2018

Date Last Updated - Jan 12, 2019