Current Concepts in Treatment of Ligament Incompetence in the Acquired Flatfoot

Incidence and predictors of valgus tibiotalar tilt after progressive collapsing foot deformity reconstruction using subtalar fusion with concomitant procedures

PURPOSE

Development of valgus tibiotalar tilt is a significant complication after subtalar fusion for progressive collapsing foot deformity (PCFD) correction. However, its incidence and etiologic factors have not been extensively studied. The purpose of this study was to define the incidence of valgus tibiotalar tilt after subtalar fusion for PCFD reconstruction, and to determine predictors of this complication.

METHODS

This study included 59 patients who underwent PCFD reconstruction with subtalar fusion. Patients with tibiotalar tilt prior to surgery were excluded. On standard weightbearing radiographs, the talonavicular coverage angle, talo-1st metatarsal angle, calcaneal pitch, hindfoot moment arm (HMA), and medial distal tibial angle were measured. Weightbearing computed tomography (WBCT) was used to determine the presence of lateral bony impingement. A radiologist evaluated the superficial and deep deltoid ligaments using magnetic resonance imaging (MRI). Univariate regression analysis was used to identify the factors associated with development of postoperative valgus tibiotalar tilt, defined as tilt > 2 degrees.

RESULTS

Seventeen patients (28.8%) developed postoperative valgus tibiotalar tilt at a mean of 7.7 (range 2-31) months. Eight (47.1%) of these patients developed valgus tibiotalar tilt within 3 months. Univariate logistic regression demonstrated association between preoperative HMA and postoperative valgus tibiotalar tilt (odds ratio 1.06, P = 0.026), with a 6% increase in risk per millimeter of increased HMA. Deltoid ligament status and concomitant procedures on other joints did not correlate with postoperative valgus tilt.

CONCLUSION

Our findings indicate that surgeons should be cognizant of patients with a greater degree of preoperative hindfoot valgus and their propensity to develop a valgus ankle deformity. Additionally, our relatively high incidence of valgus tibiotalar tilt suggests that weightbearing ankle radiographs should be included in the initial and subsequent follow-up of PCFD patients with hindfoot valgus treated with subtalar fusion.

The impact of ligament tears on joint contact mechanics in progressive collapsing foot deformity: A finite element study

BACKGROUND

Patients with longstanding progressive collapsing foot deformity often develop osteoarthritis of the ankle, midfoot, or hindfoot joints, which can be symptomatic or lead to fixed deformities that complicate treatment. The development of deformity is likely caused by ligament degeneration and tears. However, the effect of individual ligament tears on changes in joint contact mechanics has not been investigated.

METHODS

A validated finite element model of the foot was used to compare joint contact areas, forces, and pressures between the intact and collapsed foot, and to evaluate the effect of individual ligament tears on joint contact mechanics.

FINDINGS

Collapsing the foot resulted in an increase in contact pressure in the subtalar, calcaneocuboid, tibiotalar, medial naviculocuneiform, and first tarsometatarsal joints but a decrease in contact pressure in the talonavicular joint. Rupture of the spring ligament was the main contributor to increased calcaneocuboid and subtalar joint contact pressures and decreased medial naviculocuneiform and first tarsometatarsal joint contact pressures, as well as talonavicular subluxation. Deltoid ligament rupture was the primary source of increased contact pressure in the medial naviculocuneiform, first tarsometatarsal, and tibiotalar joints.

INTERPRETATION

Degenerative tearing of the ligaments in flatfoot deformity leads to increased joint contact pressures, primarily in the calcaneocuboid, subtalar, and tibiotalar joints, which has been implicated in the development of osteoarthritis in these joints. An improved understanding of the relationship between ligament tears and joint contact pressures could provide support for the use of ligament reconstructions to prevent the development of arthrosis.

The Importance of the Medial Column in Progressive Collapsing Foot Deformity: Osteotomies and Stabilization

Adult acquired flatfoot deformity is a complex pathologic condition that requires considerate and thoughtful surgical solutions. Medial column procedures are often supplemented by a medializing calcaneal osteotomy and/or a lateral column lengthening because of the complex nature of progressive collapsing foot deformity and its resultant peritalar instability. Other osteotomies and fusions include a Cotton osteotomy and first tarsometatarsal fusion.