Addressing Deltoid Ligament Insufficiency In Stage III/IV Adult-Acquired Flatfoot

Given the importance of the deltoid ligament for patients with stages III and IV adult-acquired flatfoot, numerous authors have proposed surgical solutions. Accordingly, these authors offer a thorough review of the literature and share surgical pearls from their experience.

Adult-acquired flatfoot deformity is a challenging clinical condition. It has been well classified, defined and documented as a dynamic failure of the posterior tibial tendon and ligaments that support the medial longitudinal arch.

Johnson and Strom originally classified adult-acquired flatfoot deformity into three stages with Myerson adding a fourth stage.^1,2 Stage I is characterized by symptoms of pain and swelling along the posterior tibial tendon without visible changes of foot malalignment. Stage II deformity shows asymmetrical alignment with flexible hindfoot valgus and forefoot abduction. These patients have weakness with inversion and difficulty when performing a single heel raise. Stage III represents a progression of the longstanding deformity in which the deformity becomes fixed and rigid.

In 1996, Myerson recognized the presence of deltoid ligament failure in late stage adult-acquired flatfoot deformity and added a fourth stage to the original classification.² This is visible on a weightbearing AP X-ray by valgus tilt of the talus within the ankle mortise and is associated with deltoid insufficiency.

The deltoid ligament is a triangular structure that attaches the medial malleolus to multiple osseous areas of the medial ankle and is composed of both superficial and deep layers. The superficial components prevent excessive eversion of the ankle and consist of the tibionavicular, tibiocalcaneal and superficial posterior tibiotalar ligaments. The deep components are composed of the anterior tibiotalar and the deep posterior tibiotalar ligaments that prevent axial rotation of the talus.

Each layer of the deltoid ligament provides a specific supportive function to the ankle joint while collectively preventing lateral subluxation of the talus. The deltoid ligament plays an important role in preventing valgus deformity by acting as the primary stabilizer of the ankle joint while also restricting excessive eversion. It is a passive, load-bearing structure that is mainly protected by an active and intact posterior tibial tendon. As adult-acquired flatfoot deformity progresses, transverse plane deviation of the forefoot on the hindfoot occurs with lateral talar tilting secondary to attenuation of the medial structures, especially the deltoid ligament.

As hindfoot valgus progresses, the mechanical axis of the leg assumes a medial position relative to the foot. This results in increased tension on the medial soft tissue structures of the ankle. This process leads to progressive attenuation and failure of the static stabilizers including the spring ligament, plantar fascia and deltoid ligament complex. In cases of advanced flatfoot, the spring ligament complex often attenuates or ruptures. Failure of this ligament allows the talus to shift medial and plantar relative to the navicular while increasing tension on the medial ankle. As the deltoid ligamentous complex fails, the talus may assume a valgus position within the ankle mortise. Deltoid ligament insufficiency may decrease tibiotalar contact area and increase peak pressures within the lateral ankle mortise.^3-4 This will ultimately result in rapid degeneration of the ankle joint if left unresolved.  

How To Handle The Deltoid Ligament In Stage IV Adult-Acquired Flatfoot Repair

Authors have described various techniques for deltoid ligament reconstruction.^5-9 Patients with stage IV-A adult-acquired flatfoot have hindfoot valgus and a flexible ankle valgus without significant tibiotalar arthritis. Accordingly, authors usually recommend joint preservation procedures. Patients with stage IV-B flatfoot have a rigid ankle valgus with significant tibiotalar arthritis. These patients often require ankle arthrodesis or total ankle replacement.  

The ultimate surgical goal for stage IV-A adult-acquired flatfoot deformity is anatomic restoration of both deep and superficial layers of the deltoid ligament in order to correct talar tilt and preserve ankle motion. Techniques to address deltoid insufficiency include primary repair of the host tissue, advancement of regional host tissue or reconstruction with an autograft or allograft tendon. Additionally, surgeons can also use non-biologic, long-chain polyethylene materials for reconstruction. Several repair procedures have had good short-term results although chronically diseased and attenuated deltoid ligament tissue does not allow for a durable, direct repair.^7-9 As such, autograft or allograft tendon-enhanced deltoid reconstruction of ankle valgus is often favored over poor quality regional tissue.

Deltoid ligament repair is invariably a component of stage III or IV flatfoot reconstruction. Therefore, surgeons should perform hindfoot arthrodesis as well as other standard procedures to address stage III or IV adult-acquired flatfoot deformity in conjunction with deltoid ligament repair to obtain a plantigrade foot. Otherwise, residual valgus deformity will result in continued stress on the deltoid ligament reconstruction with recurrent attenuation and failure.

Deland described a technique using peroneus longus tendon autograft that surgeons transect proximally and pass through a tunnel in the talus from lateral to medial.^7,10 One passes the tendon through the medial malleolus from medial to lateral to replicate the deep structures of the deltoid ligament. This procedure has faced criticism for its failure to address the superficial fibers of the deltoid ligament, which research has shown to be the primary restraint to valgus ankle angulation.¹¹ Donor site morbidity is a concern with this technique and the study authors have now modified their technique by using Achilles tendon allograft as an alternative.

In 2011, Jeng and colleagues reported outcomes of a minimally invasive technique using allograft hamstring tendon to reconstruct the deep and superficial fibers of the deltoid ligament.¹² Surgeons split a 20 cm graft longitudinally to create two limbs with about 6 cm remaining intact as the single limb. The surgeon would pass the single limb of the graft through a tibial tunnel parallel to the ankle joint, which he or she would fixate with a bioabsorbable interference screw. One would subcutaneously pass the graft distally, securing one limb of the graft through a talar tunnel to recreate the deep deltoid fibers. The surgeon would then pass the remaining graft limb through a calcaneal tunnel and secure fixation with an interference screw to recreate the superficial deltoid. The authors concluded that this procedure is appropriate in a carefully selected population of patients with stage IV adult-acquired flatfoot deformity and a valgus talar tilt of less than 10 degrees.

Understanding The Impact Of The Deltoid Ligament In Stage III Adult-Acquired Flatfoot Repair

Although authors have described deltoid ligament repair for stage IV adult-acquired flatfoot deformity, the role of addressing the deltoid ligament in a stage III deformity has not been thoroughly addressed in the literature. Patients with stage III flatfoot will demonstrate a dysfunctional, degenerated posterior tibial tendon. Clinically, this reflects an inability to perform a single heel rise with evidence of a talar bulge. Patients will also demonstrate a “too many toes sign” with symptoms along the medial hindfoot secondary to medial ligamentous attenuation and the lateral hindfoot due to calcaneofibular impingement. These patients might also have non-reducible deformities with end-stage arthritis. These deformities include hindfoot valgus, fixed forefoot varus and forefoot abduction accompanied by gastrocnemius-soleus equinus. This may lead to deltoid ligament insufficiency with subsequent valgus deformity of the ankle.

We believe that a number of patients with stage III adult-acquired flatfoot likely have some component of deltoid ligament degeneration and attenuation yet demonstrate a congruent ankle on an AP weightbearing radiograph. Although the deltoid ligament is mechanically competent in static stance, the disease process has begun and may continue, especially if there is residual valgus within the foot following hindfoot arthrodesis.

The surgical techniques described for double and triple arthrodesis usually recommend positioning the hindfoot in 5 degrees of valgus. There is concern that this residual deformity will cause continued stress on an already diseased deltoid ligament complex and result in a valgus ankle. Furthermore, there have been reports that describe the deltoid ligament complex being stressed even after a properly aligned triple arthrodesis.^13-15 An isolated AP weightbearing radiograph of the ankle might be insufficient to assess the deltoid ligament complex adequately in late stage III adult-acquired flatfoot.

Preoperative imaging of the stage III adult-acquired flatfoot is necessary to assess the deltoid ligamentous structures. This should include weightbearing radiographs of the foot and ankle as well as magnetic resonance imaging (MRI) or diagnostic ultrasound. Weightbearing views of the ankle are necessary to evaluate the presence of valgus deformity and degenerative changes while long leg calcaneal axial and hindfoot alignment views provide information regarding frontal plane alignment. The most important angles to assess for ligamentous injury are the calcaneal pitch angle, Meary’s angle and abnormal talonavicular coverage.¹⁶

Lin and coworkers stated that a calcaneal pitch angle less than 19 degrees provides the best assessment of injury to the supporting structures of the medial longitudinal arch, including the deltoid ligament.¹⁶ Consider an MRI to evaluate the soft tissue structures contributing to the stage III adult-acquired flatfoot. According to Crim and colleagues, MRI findings of discontinuity or non-visualization of discrete fibers of the deltoid ligament yield a sensitivity of 96.3 percent and specificity of 97.9 percent.¹⁷ Song and coworkers have recommended routine preoperative MRI on patients undergoing stage III adult-acquired flatfoot deformity reconstruction.⁶ We do this routinely as part of our preoperative evaluation.

Alternatively, if patients are precluded from an MRI for other reasons, a diagnostic ultrasound can ascertain disease within the deltoid ligament complex. We will also consider a deltoid stress test if our suspicion for deltoid ligament disease is high but MRI and/or diagnostic ultrasound is negative.

Hindfoot arthrodesis (double or triple arthrodesis) is indicated for stage III and stage IV adult-acquired flatfoot deformity. Intraoperative realignment is critical. Precise positioning of the calcaneus collinear with the tibia is necessary to avoid residual valgus deformity, which will predispose the deltoid ligament to attenuation with ensuing degenerative changes within the ankle.

We avoid leaving the hindfoot in residual valgus, depending on the suprastructural skeleton as well as other factors. We try to ensure placement of the calcaneus in a vertical position to the lower leg with the subtalar joint in neutral. Confirm this with an intraoperative axial image, which should demonstrate the calcaneus parallel to the tibia. Lateral images should show restoration of the calcaneal inclination angle as well. One would fixate this using two large diameter cannulated screws.

Realign the talonavicular joint by adducting the forefoot on the hindfoot while dorsiflexing the first metatarsophalangeal joint to engage the windlass mechanism. This maneuver will restore transverse and sagittal plane alignment. The end result will consist of a parallel forefoot to hindfoot relationship in the frontal and transverse planes. The talar head will demonstrate complete coverage by the navicular with the talo-first metatarsal angle being reduced to 0 degrees on an AP radiograph. An adequately aligned arthrodesis procedure will result in normal physiologic contact pressures throughout the ankle. This will prevent soft tissue attenuation of the medial soft tissue constraints leading to ankle valgus deformity. The primary goal of realignment arthrodesis of the hindfoot is long-term protection of the ankle.

What You Should Know About The Medial Calcaneal Displacement Osteotomy

We also perform the medial calcaneal displacement osteotomy as an ancillary procedure to protect the deltoid ligament in late stage III adult-acquired flatfoot deformity. We consider medial calcaneal displacement osteotomy in patients with MRI or ultrasound evidence of deltoid ligament attenuation, regardless of whether the ankle is congruent on preoperative ankle radiographs. We also consider this osteotomy for rather severe deformities.

Medial translation of the calcaneal tuber segment will alter the mechanical axis of the lower limb and reduce the valgus thrust on the hindfoot. The Achilles insertion translates to a more medial position, which converts the posterior muscle group into an inverter of the hindfoot. This reduces stress through the deltoid ligament.

Resnick and coworkers demonstrated that a triple arthrodesis in combination with a medial calcaneal displacement osteotomy reduces the deltoid ligament forces by 56 percent.⁵ Song and colleagues suggested that medializing the calcaneus with an Achilles tendon lengthening serves to protect the deltoid complex.⁶

We routinely include medial calcaneal displacement osteotomy as a component part of all stage IV adult-acquired flatfoot reconstruction. Additionally, we consider a medial calcaneal displacement osteotomy in those cases of stage III adult-acquired flatfoot deformity if the preoperative MRI is consistent with deltoid ligament disease or a preoperative deltoid stress test is positive.

A Closer Look At The Influence Of Equinus On Hindfoot Valgus

Equinus deformity also plays a key role in hindfoot valgus and deltoid insufficiency. Loss of the primary inverter, observed in stage III adult-acquired flatfoot deformity, leaves the peroneus brevis unopposed to evert the foot. The Achilles tendon then creates excessive hindfoot valgus because the insertion is now lateral to the subtalar joint axis, which further increases eversion force.

A gastrocnemius recession or Achilles tendon lengthening is necessary to obtain adequate length and restore sagittal plane position. We also include transfer of the peroneus brevis to peroneus longus tendon as a component part of stage III/IV flatfoot reconstruction to help restore muscle balance.

In Conclusion

Stage III adult-acquired flatfoot deformity is characterized by a rigid, fixed deformity. This may eventually progress to deltoid attenuation or rupture with subsequent stage IV deformity. While studies have investigated various techniques of deltoid fixation in stage IV-A adult-acquired flatfoot deformity, there are few studies with long-term outcomes. There has been no consensus on the ideal procedure for deltoid ligament repair.

We believe the deltoid ligament may be diseased from longstanding valgus stress in stage III adult-acquired flatfoot. Therefore, one should give special consideration to precise positioning of the hindfoot to avoid residual valgus as well as to ancillary procedures that can alter contact pressures within the ankle and provide protection to the deltoid ligament. We perform direct deltoid ligament repair as a supplemental procedure for stage IV deformity but do not directly repair the deltoid ligamentous structures in in stage III deformity. Rather, we rely on osseous procedures to offload the deltoid ligament for stage III deformities.

One may use imaging modalities to assess the soft tissue structures and aid in surgical planning. A meticulous and precise triple or double arthrodesis allows for adequate realignment, which ultimately decreases the amount of medial ligamentous strain. Combining this technique with a medial calcaneal displacement osteotomy and posterior muscle group lengthening will further offload the deltoid ligament complex from valgus stress, and protect the ankle over the long term.

Dr. Wilder is a first-year resident at the Western Pennsylvania Hospital in Pittsburgh.

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

References

1.     Johnson KA, Strom DE. Tibialis posterior tendon dysfunction. Clin Orthop. 1989;239:196–206.
2.     Myerson MS. Adult acquired flatfoot deformity. J Bone Joint Surg. 1996;78A:780-792.
3.     Jahss MH, Gee RO, Kummer F. Deltoid insufficiency: part II. Anatomy of the deltoid. Presented at the American Orthopaedic Foot and Ankle Society ninth annual summer meeting, 1993.
4.     Panchani PN, Chappell TM, Moore GD, et al. Anatomic study of the deltoid ligament of the ankle. Foot Ankle Int. 2014; 35(9):916-21.
5.     Resnick RB, Jahss MH, Choueka J, et al. Deltoid ligament forces after tibialis posterior tendon rupture: effects of triple arthrodesis and calcaneal displacement osteotomies. Foot Ankle Int. 1995; 16(1):14–20.
6.     Song, SJ, Lee S, O’Malley MJ, et al. Deltoid ligament strain after correction of acquired flatfoot deformity by triple arthrodesis. Foot Ankle Int. 2000;21(7):573-7.
7.     Deland JT, de Asla RJ, Segal A. Reconstruction of the chronically failed deltoid ligament: a new technique. Foot Ankle Int. 2004;25(11):795–9.
8.     Lack W, Phisitkul P Femino J. Anatomic deltoid ligament repair with anchor-to-post suture reinforcement: technique tip. Iowa Orthoped J. 2012; 32:227-30.
9.     Hintermann B, Valderrabano V, Boss A, et al. Medial ankle instability: an exploratory, prospective study of fifty-two cases. Am J Sports Med. 2004;32(1):183–90.
10.     Deland JT, de Asla RJ, Sung IH, et al. Posterior tibial tendon insufficiency: which ligaments are involved? Foot Ankle Int. 2005;26(6):427–35.
11.     Balen PF, Helms CA. Association of posterior tibial tendon injury with spring ligament injury, sinus tarsi abnormality, and plantar fasciitis on MR imaging. AJR Am JRoentgenol. 2001;176(5):1137–43.
12.     Jeng CL, Bluman EM, Myerson MS. Minimally invasive deltoid ligament reconstruction for stage IV flatfoot deformity. Foot Ankle Int. 2011;32(1):21–30.
13.     Catanzariti AR, Mendicino RW, Maskill MP. Posterior tibial tendon dysfunction. In: Southerland JT (ed.) McGlamry’s Comprehensive Textbook of Foot and Ankle Surgery. Lippincott, Williams & Wilkins, Philadelphia, 2012. p. 636-69.
14.     Catanzariti AR, Adeleke AT. Double arthrodesis through a medial approach for end-stage adult-acquired flatfoot. Clin Podiatr Med Surg. 2014; 31(3):435-44.
15.     Fortin PT, Walling AK. Triple Arthrodesis. Clin Orthop Relat Res. 1999;365:91-9.
16.     Lin YC, Mhuircheartaigh JN, Lamb J, et al. Imaging of adult flatfoot: correlation of radiographic measurements with MRI. AJR Am J Roentgenol. 2015; 204(2):354-59.
17.     Crim J, Longenecker L. MRI and surgical findings in deltoid ligament tears. AJR Am J Roentgenol. 2015; 204(1):W63–9.                            

Additional References

 18.   Otis JC, Deland JT, Kenneally S, Chang V. Medial arch strain after medial displacement calcaneal osteotomy: an in vitro study. Foot Ankle Int. 1999; 20(4):222–226.
 19.   Deland JT. The acquired flatfoot and spring ligament complex. Foot Ankle Clin. 2001;6(1):129–35.
 20.   Yao L, Gentili A, Cracchiolo A. MR imaging findings in spring ligament insufficiency. Skeletal Radiol. 1999;28(5):245–50.
 21.   Gazdag AR, Cracchiolo A 3rd. Rupture of the posterior tibial tendon. Evaluation of injury of the spring ligament and clinical assessment of tendon transfer and ligament repair. J Bone Joint Surg Am. 1997;79(5):675– 81.
 22.   Okereke E, Wang CY, Jahss MH, Kummer F. Tibialis posterior tendon forces following calcaneal osteotomies. Submitted for publication.
 23.    Nyska M, Parks BG, Chu IT, Myerson MS. The contribution of the medial calcaneal osteotomy to the correction of flatfoot deformities. Foot Ankle Int. 2001; 22(4):278-82.
 24.   Raikin SM, Myerson MS. Surgical repair of ankle injuries to the deltoid ligament. Foot Ankle Clin. 1999;4(4):745–53.