Equinus has been shown to be present in up to 96% of biomechanically induced foot pain [6]. Equinus has shown to be pathologic and present in the development of the pathologic flatfoot. Compensation for ankle equinus often results in midtarsal and subtalar pronation with a demonstrated three fold arch deforming force of the Achilles tendon over the posterior tibial tendon by Thordarson and colleagues [7]. Hibbs was the first to advocate a tendo-Achilles lengthening procedure as part of the treatment for pes planus deformity. An unaddressed equinus forces the calcaneus into a valgus position and limits subtalar joint inversion. Therefore, in order to get the calcaneus into a rectus position a posterior muscle group lengthening procedure should be considered. Failure to identify the equinus component when surgically reconstructing the symptomatic flatfoot predisposes the surgeon to less than desirable results.

While there are many options for surgical reconstruction of PTTD refractory to conservative care one of the most common complications encountered is undercorrection of the deformity. Undercorrection can occur with joint sparing as well as joint destructive procedures. Failure to correct the deformity leads to continued pain and disability and further progression of PTTD. Identifying all planes of deformity is important in the reconstruction of PTTD.

Undercorrection in the transverse plane can lead to continued pain along the posterior tibial tendon and lateral impingement of the subtalar joint (Fig. 22.1). Procedures commonly used for the correction of transverse plane deformity focus on lengthening of the lateral column. This is commonly approached through either an Evans osteotomy or calcaneocuboid distraction arthrodesis (CCJ) (Fig. 22.2).

In situ/undercorrected triple arthrodesis of a stage IIIC PTTD does not correct for any deformity and often leads to continued pain and disability. In situ fusion is often multiplanar and results in a post-operative foot that is malaligned and stiff. Revision of an in situ arthrodesis often requires takedown of the existing fusion and techniques to realign the hindfoot in a rectus position. Multiple examples can be seen below on management strategies for malaligned double or triple arthrodesis.

When confronted with a “mal-aligned in-situ” arthrodesis requiring revision, the authors have had good success with an intra-operative protocol that entails initial takedown of the previous fusion sites, followed by a realignment lateral column lengthening (either Evans or CCJ distraction) that essentially “dials in” the correction in all three planes in the same manner a virgin lateral column lengthening procedure does. The talonavicular and subtalar joints are then fixated in this new revised alignment (Fig. 22.3).

Surgical approach for an end stage PTTD typically involves doing a triple or double arthrodesis. Traditionally a triple arthrodesis is approached through a lateral primary incision. Joint resection occurs laterally as well as positioning the foot for final alignment and fixation. The end stage PTTD that requires triple or double arthrodesis will have a hindfoot valgus and surgical resection laterally can make it hard to place the foot into correct alignment and avoid a valgus malalignment. The author routinely performs a medial approach—double arthrodesis for end stage PTTD (Fig. 22.4). This allows adequate correction of the valgus component of the hindfoot through medial joint resection. Astion and colleagues have shown that after isolated arthrodesis of the talonavicular and subtalar joints there is no motion left in the calcaneocuboid joint [8, 9].

When addressing transverse plane deformities through lateral column lengthening procedures there are a number of complications that can occur. Evans osteotomy is a calcaneal osteotomy performed through the anterior aspect of the calcaneus utilizing either an allograft of autograft as a wedge to elongate the calcaneus. The same principle is applied with a CCJ arthrodesis with the exception that this is a joint destructive procedure. Both procedures involve lengthening the lateral column to correct for transverse plane deformity associated with PTTD.

Graft subsidence is a cause of undercorrection when performing an Evans osteotomy or CCJ arthrodesis (Fig. 22.5a, b). If subsidence does occur, performing revision lateral column procedures is acceptable but utilizing adequate fixation is preferred to avoid the complication again. Locked plating techniques to bridge the osteotomy can be performed for stabilization and successful union (Fig. 22.5c, d).