Current Concepts In Surgery For Adult-Acquired Flatfoot
The combination of lateral column lengthening and medial transpositional osteotomy is enough to restore transverse plane deformity in most cases of stage II AAF. However, there are times when severe medial column instability may result in residual transverse deformity, even after lateral column lengthening and medial transpositional osteotomy. Image intensification will demonstrate the talar head to be only partially covered by the navicular in these cases. We will add a naviculocuneiform arthrodesis to help restore transverse plane alignment. The naviculocuneiform arthrodesis will improve talonavicular subluxation, address forefoot supinatus and impart stability to the medial column.31-33
Evaluating And Managing Forefoot Supinatus And First Ray Instability
We proceed to evaluate forefoot supinatus following the restoration of transverse plane alignment. Forefoot supinatus can be supple or fixed. The naviculocuneiform arthrodesis is our procedure of choice for fixed forefoot supinatus. Sagittal plane correction occurs by a combination of plantar rotation of the cuneiforms and wedge resection. We employ an opening wedge cuneiform osteotomy to address a supple forefoot supinatus. The medial cuneiform osteotomy is effective at reducing forefoot supinatus and restoring medical column stability.25,33 This procedure is technically simple and has a low complication rate.
We also take a critical look at first ray instability, especially when forefoot supinatus is absent. Patients with first ray instability are at risk for developing lateral forefoot overload following lateral column lengthening and medial transpositional osteotomy of the posterior calcaneus. These patients will develop symptoms when they resume their normal activity level. We perform an opening wedge cuneiform osteotomy to impart first ray stability in this group of patients. This procedure restores first ray weightbearing and restores balance to the forefoot, thereby offloading the lateral column. First tarsometatarsal arthrodesis is also an option in these patients.
Essential Pointers On Soft Tissue Reconstruction
We perform soft tissue reconstruction last. This occurs through a medial incision directed over the posterior tibial tendon. Explore the posterior tibial tendon and repair it as necessary. Consider a flexor digitorum longus (FDL) tendon transfer when the posterior tibial tendon is severely degenerated and tendinosis is pronounced. We usually perform tenodesis of the flexor digitorum longus to the navicular with a biotenodesis screw.
In the past, we would routinely transfer the flexor digitorum longus for stage II AAF. However, we now perform fewer flexor digitorum longus tendon transfers and preserve this tendon whenever possible. Realignment is the most important factor relative to outcome. Adequate realignment will support the medial soft tissues (spring ligament, posterior tibial tendon, etc.) and prevent attenuation over the long term. The pathomechanics of a preexisting flatfoot likely contribute to dysfunction of the posterior tibial tendon.34-36
Arrangio and Salathe conducted a biomechanical analysis of posterior tibial tendon dysfunction, medial transpositional osteotomy and flexor digitorum longus transfer in AAF.38 They concluded that flexor digitorum longus transfer did little when they combined it with a medial displacement osteotomy with regard to reducing load on the medial column of the foot. However, the osteotomy itself greatly reduced the load.