Abstract
This article provides an overview of the classification of progressive collapsing foot deformity (PCFD), along with a mnemonic aid for memorization. It also outlines the classification of spring ligament insufficiency, the surgical procedure selection process for stage 1 PCFD, and a detailed summary of surgical techniques, including key tips and potential pitfalls.
The surgical overview covers the following: patient positioning, evaluation of spring ligament insufficiency and procedure selection using tendoscopy, assessment and management timing of gastrocnemius–Achilles tendon contracture, preparation of the calcaneocuboid joint, and medial exposure for flexor digitorum longus tendon (FDLT) transfer. Two novel techniques developed by the author are introduced: corrective repair of the spring ligament (CORRS), a repair method addressing forefoot varus associated with spring ligament damage; and spring ligament reconstruction by remnant posterior tibial tendon (PTT) preservation (SREPP), a reconstruction technique that uses remnant PTT tissue to treat extensive spring ligament ruptures and concurrently correct forefoot varus. The article also offers surgical tips for FDLT transfer, bone grafting, and lateral column lengthening (LCL) via calcaneocuboid distraction arthrodesis (CCDA), with special attention to avoid residual forefoot varus.
Correction of midfoot and forefoot varus is emphasized as a crucial element in performing LCL for stage 1 PCFD. CORRS and SREPP are presented as effective adjunctive techniques that enhance the outcomes of CCDA by preventing over-lengthening and residual forefoot varus.
Introduction
In 2020, the Consensus Group established the concept and classification system for progressive collapsing foot deformity (PCFD).1 Since then, the condition formerly known as adult-acquired flatfoot deformity (AAFD) or posterior tibial tendon dysfunction (PTTD) has been increasingly referred to as PCFD in the orthopedic literature. PCFD primarily results from dysfunction of the spring and deltoid ligaments, and recent publications have highlighted the importance of repairing and reconstructing these key ligamentous structures.2-13 It is a complex, three-dimensional deformity characterized by three main components: hindfoot valgus, midfoot/forefoot abduction, and forefoot varus.1,14
The aim of this review is to present practical strategies for understanding and memorizing the PCFD classification system, elucidate the pathophysiology of spring ligament insufficiency, and share the author’s approach to surgical decision-making.14 Special emphasis is placed on the critical elements of successful surgical treatment, including two novel procedures developed by the author: corrective repair of the spring ligament (CORRS) and spring ligament reconstruction by remnant posterior tibial tendon (PTT) preservation (SREPP), both performed in conjunction with lateral column lengthening (LCL).14 In addition, surgical tips for LCL and flexor digitorum longus tendon (FDLT) transfer are discussed.
How to Understand the PCFD Classification
The classification system for PCFD consists of two axes: stage classification, based on deformity flexibility, and class classification, based on the type and anatomical location of the deformity.1
Stage Classification
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Stage 1: The deformity is flexible and manually correctable to a normal position.
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Stage 2: The deformity is rigid and not manually correctable.
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Class A: Hindfoot valgus.
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Class B: Midfoot or forefoot abduction.
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Class C: Forefoot varus or medial column instability.
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Class D: Peritalar subluxation or dislocation.
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Class E: Ankle valgus instability.
To facilitate memorization, two diagnostic anchors are emphasized: clinical symptoms and imaging findings.14
Clinical Symptoms
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Sinus tarsi pain because of talocalcaneal impingement resulting from forefoot abduction is characteristic of class B.
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Pain at the lateral tip of the fibula, caused by fibulocalcaneal impingement secondary to peritalar subluxation, suggests class D. Although fibulocalcaneal impingement is commonly seen in class D, it may also be found in class E.
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An increased talonavicular coverage (TNC) angle, associated with forefoot abduction, supports a diagnosis of class B.
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An increased lateral talus–first metatarsal (LTMT) angle, along with plantar gapping at the first tarsometatarsal (TMT) or cuneiform–navicular joint, indicates medial column instability, consistent with class C.
What Causes Abnormalities in the Spring Ligament?
Abnormalities of the spring ligament can be broadly categorized into primary and secondary causes.14 Primary causes include direct tears of the spring ligament and the presence of an accessory navicular, which may result in mechanical overload and subsequent tearing of the ligament, ultimately leading to progressive deformity. Secondary causes involve conditions that primarily affect the PTT, leading to increased stress on the spring ligament. These include narrowly defined PTTD, rheumatoid arthritis, trauma, os subtibiale, and other pathologies that cause degeneration or rupture of the PTT. The resulting mechanical imbalance places excessive load on the spring ligament, often leading to secondary tearing and progressive deformity.
In general, secondary cases tend to exhibit smaller, localized tears of the spring ligament, whereas primary cases typically demonstrate more extensive ligamentous damage.14
How is the Surgical Procedure for PCFD Determined?
Surgical treatment for PCFD involves a combination of soft tissue procedures and osseous realignment techniques. In stage 2 deformities, rigid and uncorrectable alignment typically necessitates hindfoot fusion procedures such as triple arthrodesis. In contrast, stage 1 deformities, which remain flexible, are commonly treated with realignment procedures such as LCL or medial displacement calcaneal osteotomy (MDCO). However, clear criteria for selecting between these two procedures have not been well established.
In PCFD, the midfoot and forefoot are typically positioned in varus relative to the hindfoot at the Chopart joint. Therefore, accurate assessment and correction of forefoot varus are critical components of surgical planning. The Consensus Group previously noted that “no previous clinical staging classification has mentioned the spring ligament.”1 In contrast, the author has long emphasized that AAFD originates primarily from spring ligament abnormalities and that surgical decision-making should be based on the pathophysiology of these abnormalities.14 Accordingly, in stage 1 PCFD, surgical procedures should be selected according to the presence and severity of spring ligament insufficiency. Since 2014, the author’s treatment algorithm has undergone multiple revisions. However, since 2018—before the widespread acceptance of the PCFD classification—a stable treatment selection algorithm has been applied (Figure 1).14 Notably, this algorithm, which centers on spring ligament pathology, did not require modification after the PCFD classification was introduced.
Before surgery or immediately after anesthesia induction, the patient’s leg is suspended freely from the examination or operating table. The examiner then manually corrects hindfoot valgus to a neutral position and evaluates the presence and degree of midfoot/forefoot varus.14 The algorithm begins by assessing the presence of mobile hindfoot valgus, midfoot abduction, and/or forefoot varus (Figure 1).
The author identifies three levels of forefoot varus: absent, fully correctable, and partially correctable.14
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If no forefoot varus is present, MDCO combined with FDLT transfer, is indicated.
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If the forefoot varus is fully correctable, radiological parameters are used to further guide procedure selection:
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For mild deformity (LTMT < 25°, TB-C < 15°), MDCO + FDLT transfer is recommended.15
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For more severe deformity (LTMT ≥ 25°, TB-C ≥ 15°), LCL + FDLT transfer is indicated.
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If the forefoot varus is only partially correctable preoperatively, an intraoperative decision is required:
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If CORRS or SREPP results in a fully correctable forefoot varus, LCL is performed.
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If forefoot varus remains partially correctable after spring ligament correction, medial column rebalancing procedures may be necessary.
In addition, gastrocnemius recession or heel cord lengthening should be performed according to the degree of equinus contracture.
Ultimately, surgical decision-making involves a combination of preoperative and intraoperative manual assessment and imaging, with the degree of forefoot varus being the most critical determinant, particularly, when considering the indication for LCL.
Outline of the Surgery and Tips and Pitfalls for Each Technique
Because CORRS and SREPP are not required in stage 1 cases amenable to MDCO, this section focuses on stage 1 PCFD treated with CORRS or SREPP, FDLT transfer, and LCL using calcaneocuboid distraction arthrodesis (CCDA). An outline of the surgical procedure along with critical technical tips and common pitfalls is subsequently presented. The author routinely performs LCL through the CCDA technique, which is described in the subsequent nine steps.
1. Positioning
Because CCDA is performed on the lateral aspect of the foot and FDLT transfer on the medial side, the patient should be positioned to allow easy and simultaneous access to both sides without the need for intraoperative repositioning.
2. Evaluation of Spring Ligament Insufficiency and Surgical Procedure Selection Using Tendoscopy14
Preoperative MRI is essential for evaluating spring ligament insufficiency. Preoperative MRI often reveals discontinuity, thinning, thickening, or signal alteration of the spring ligament, especially in the superomedial portion, which should be carefully evaluated when planning surgical intervention.
Intraoperatively, tendoscopy is used to assess the extent of ligament damage. If the torn ends approximate with passive forefoot adduction (“small tear”), CORRS is indicated. If the torn ends remain widely separated (“extensive tear”), SREPP is selected. This real-time evaluation is critical for determining the most appropriate surgical technique.
3. Do Not Overlook Gastrocnemius–Achilles Tendon Shortening14
Tightness of the gastrocnemius–Achilles tendon complex is a key factor in the pathogenesis and persistence of PCFD. Precise intraoperative assessment of dorsiflexion with the knee extended (DKE) and flexed (DKF) is necessary. Based on the findings, additional procedures such as gastrocnemius recession or Achilles tendon lengthening via the Hoke’s procedure (Achilles triple hemisection lengthening)16 may be required (Figure 1).
These adjunctive procedures are critical components of PCFD correction and should be part of every surgeon’s skill set. Importantly, they should be performed before corrective fixation or immediately after anesthesia induction because post-correction release increases the risk of implant-related complications and may impair the evaluation of intraoperative alignment.
4. Expansion of the Calcaneocuboid Joint (CCJ) and Optimal LCL
To optimize operative efficiency, the author performs preparation of the CCJ before addressing the medial structures during CCDA.
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A lateral incision is made along a line connecting the base of the fourth metatarsal to the tip of the fibula, approximately 5 cm from the center of the CCJ.
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The fascia of the extensor digitorum brevis is incised carefully and preserved for later repair. The extensor digitorum brevis muscle is detached from its calcaneal origin and retracted distally to expose the CCJ.
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The joint capsule is excised, and the articular surfaces of the calcaneus and cuboid are minimally and parallelly resected using a micro bone saw, with care taken to preserve the inferior ligament.
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This next step is critical: while applying plantar pressure to the cuboid to align the plantar margins of the calcaneus and cuboid, a 2-mm K-wire is inserted into the dorsolateral cortex of each bone at a 45° angle to the plantar surface (Figure 2a). A wire spreader is then used to distract the CCJ (Figure 2b), allowing correction of forefoot abduction and varus at the Chopart joint (Figure 2c). Ideally, the K-wires remain parallel in the frontal plane during distraction. Any angular deviation suggests improper alignment and risks residual forefoot varus, which may lead to lateral foot pain postoperatively.
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When LCL is performed correctly, the plantar surface of the foot becomes perpendicular to the long axis of the tibia (Figure 2d), and the longitudinal arch is restored (Figure 2c).
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After confirming proper alignment, the spreader is removed. The procedure then proceeds to spring ligament repair or reconstruction and FDLT transfer.
A medial incision is made extending from the posterior-superior aspect of the medial malleolus to the navicular tuberosity and continuing distally to the medial base of the first metatarsal. After identifying the PTT, dissection is carried out in the same fascial plane from the navicular to the first metatarsal base. The abductor hallucis muscle is mobilized as a single unit and retracted plantarly without opening its fascia. The dissection is extended to expose the tendon sheaths of the FDLT and flexor hallucis longus tendon (FHLT). A practical technique for exposing the FDLT and FHLT involves first identifying the FDL tendon sheath proximal to the PTT. By incising this sheath distally with scissors, the FDLT can be exposed rapidly and accurately. Caution is warranted around the knot of Henry because of its rich vascularity, necessitating meticulous hemostasis. Before transecting the FDLT, a continuous suture is placed between the proximal stump of the PTT and the FDLT. At the same time, a single suture is placed distal to the crossing point between the FDLT and FHLT. The FDLT is then transected proximally to this distal suture site. Proximal suturing between the PTT and FDLT is essential because the FDLT is approximately one-third the thickness of the PTT, and the remaining PTT muscle serves as an auxiliary motor source post-transfer. The harvested FDLT must be long enough to allow passage through the navicular bone tunnel with adequate length to ensure secure fixation.
6. Evaluation of the Spring Ligament and Spring Ligament Repair/Reconstruction
The author performs spring ligament repair using the CORRS technique or reconstruction using the SREPP technique in all cases where CCDA is indicated. The author has performed CORRS in 35 cases with an average follow-up of 8.5 years and SREPP in 13 cases with an average follow-up of 6 years. No cases showed residual forefoot varus, and no major complications were observed.
CORRS (Corrective Repair of the Spring Ligament)14
CORRS is a technique for repairing the spring ligament while simultaneously correcting forefoot varus (Figure 3).
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Indication: If forefoot adduction brings the torn ends of the spring ligament into contact, CORRS is considered feasible.
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Partial Resection: In cases without frank rupture, where the ligament is merely elongated (Figure 3a), a partial resection is performed on the navicular-side insertion—approximately 2 cm in the plantar-to-dorsal direction and 5 mm in the anterior-posterior direction—to freshen the tissue (Figure 3b).
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Anchor Placement: With the forefoot adducted and pronated, both ends of the ligament are aligned and three corresponding points are marked (Figure 3c). Suture anchors are then inserted into the medial border of the navicular at the marked sites (Figure 3d). While maintaining the forefoot in the corrected position (Movie S1), plication is performed by suturing the proximal spring ligament to match the marks (Figure 3e).
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Confirmation of Arch Restoration: Successful repair results in visible reconstitution of the medial longitudinal arch (Movie S2). The correction is deemed adequate if the plantar line from the first to fifth metatarsal heads is perpendicular to the tibial axis.
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Lateral Column Lengthening: The decision regarding the extent of LCL is made after completion of CORRS.
SREPP is a reconstruction technique using the remnant PTT to restore the spring ligament, indicated in cases of extensive spring ligament rupture with loss of tissue continuity (Figure 4a, b; Movie S3-S7).
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Indication: When the spring ligament ends do not approximate, even with forefoot adduction, SREPP is indicated (Movie S3).
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Use of Degenerated PTT: The degenerative remnant PTT, often compressed by the talar head in chronic cases, lacks gliding motion and retains sufficient integrity to serve as a biological graft for ligament reconstruction (Movie S4).
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Tunnel Pathway: After transection posterior to the medial malleolus, the PTT is passed beneath the tibiocalcaneal component of the deltoid ligament (Movie S5), providing medial coverage of the talar head.
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Fixation Technique: Three suture anchors are inserted along the medial border of the anterior to middle facets of the calcaneus, and the plantar side of the PTT is secured to the calcaneus (Figure 4a). During suturing (Figure 4b), the forefoot is held in an adducted and pronated position, whereas the remnant PTT is pulled proximally under tension and sutured to maintain appropriate correction. Postoperatively, residual midfoot/forefoot varus must be avoided.
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Tendon Fold-Back: The remnant PTT is folded back distally to complete the construct. Although artificial ligaments have been recently reported in this context,2,5,6,8,11 the author discourages the use of artificial ligaments because of concerns over the potential loss of flexibility essential for normal foot function (Movie S6).
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Completion with FDLT Transfer: The procedure concludes with FDLT transfer to support medial column function (Movie S7).
After completing the spring ligament procedure—either CORRS or SREPP—the FDLT transfer is performed as prepared in the earlier medial dissection (step 5). The procedure is carried out as follows:
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Bone Tunnel Creation: A needle is used to accurately localize the navicular bone by referencing the Chopart joint and naviculocuneiform joint. To maximize the mechanical efficiency of the transferred FDLT, the bone tunnel should be created as close as possible to the medial edge of the navicular. However, care must be taken not to place it too medially because this may cause fracture. The tunnel is first drilled with a 3.2-mm drill, then gradually expanded using a 4.5-mm drill to minimize fracture risk.
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Tendon Passage: The PTT sheath behind the medial malleolus is partially repaired to prevent escape of the transferred FDLT (Figure 5). The FDLT is then passed dorsally through the tunnel from the plantar side of the navicular.
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Fixation and Tensioning: The FDLT is securely sutured into the navicular bone tunnel. A critical technical point is achieving appropriate tendon tension during fixation. The foot is positioned midway between maximum inversion and the neutral position of the foot and ankle. Under moderate tension, the FDLT is fixed to the navicular. Tension is evaluated post-fixation by moving the foot from neutral to maximum inversion using a retractor. Optimal tension is characterized by firm resistance at neutral and slight elasticity at maximum inversion (Movie S8).
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Closure and Consideration of Indications: Upon completion of CORRS or SREPP and the FDLT transfer, all exposed tendon sheaths are closed, completing the medial procedure. It is important to emphasize that FDLT transfer alone is insufficient to correct deformities severe enough to warrant CCDA.17 Therefore, this procedure is performed in combination with osseous realignment techniques.14,17 After completion of the medial soft tissue reconstruction, the distraction gap at the CCJ is measured to determine the appropriate length of LCL. At this stage, the tourniquet is released, and iliac bone graft harvesting or molding for artificial graft material is performed.
After measurement of the distraction gap at the CCJ, an autologous iliac bone graft is harvested to match the required dimensions. A tricortical graft is preferred to provide sufficient mechanical strength and structural stability during arthrodesis. Although the necessary depth of the bone block may vary depending on the patient’s body habitus and the extent of lateral column lengthening, a depth of approximately 2 cm is generally considered adequate.
In cases where autologous bone graft harvesting is contraindicated or not feasible—such as in patients with comorbidities, previous iliac crest surgery, or patient preference—an artificial bone substitute may be used. The selected substitute should possess adequate osteoconductive and load-bearing properties and must be shaped to conform precisely to the CCJ distraction gap.
9. CCDA-Guided LCL
After correction of forefoot varus through CORRS or SREPP, the lateral column is lengthened under the guidance of the CCDA technique.
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Distraction of the CCJ: 2.0-mm K-wires are reinserted into the calcaneus and cuboid (Figure 2a). To maintain alignment and prevent residual forefoot varus, the cuboid is pressed plantarly with the thumb during distraction (Figure 2b, c). Using a wire spreader, the CCJ is gradually distracted while ensuring that the K-wires remain parallel in the frontal plane (Figure 2d). After lengthening, adequate forefoot adduction and pronation should be confirmed (Figure 2c). In addition, mobility at the cuboid–fifth metatarsal articulation is assessed by grasping the fifth metatarsal head and applying dorsoplantar stress while distracting the CCJ (Movie S9). A marked decrease in joint play at this site suggests over-lengthening, a key intraoperative cue to avoid.
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Graft Insertion and Temporary Stabilization: Once the appropriate distraction length is achieved, a tricortical iliac bone graft (or artificial bone substitute) is inserted into the CCJ gap. The wire spreader is then gradually released to seat the graft securely. A 2.0-mm K-wire is inserted from the calcaneal tuberosity to temporarily fix the graft and maintain CCJ alignment during definitive fixation.
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Definitive Fixation with Locking Plate: A locking plate is applied to the dorsolateral aspect of the lengthened segment for final fixation. The calcaneal neck may be pre-contoured to facilitate optimal plate placement. Before wound closure, it is essential to confirm the adequacy of the LCL. The plantar plane of the forefoot—defined as a line connecting the heads of the first through fifth metatarsals—should be perpendicular to the longitudinal tibial axis (Figure 2d). Persistent midfoot or forefoot varus at this stage will compromise proper plantar loading, potentially leading to postoperative lateral foot pain, a known source of patient dissatisfaction. Finally, the extensor digitorum brevis muscle is reapproximated over the plate and sutured to the calcaneal neck. The fascia is repaired, and the incision is closed in anatomical layers.
Conclusion
Correction of midfoot and forefoot varus is the cornerstone of successful LCL in stage 1 PCFD. Techniques such as CORRS and SREPP play a vital role in achieving medial stability and facilitate safe and effective CCDA-guided LCL. Notably, these techniques help to prevent over-lengthening and reduce the risk of residual forefoot varus, thereby minimizing postoperative complications such as lateral column overload and foot pain. Future studies are warranted to validate the long-term outcomes of CORRS and SREPP and further refine surgical indications and biomechanical evaluation methods.
Author Contributions
Hisateru Niki conceived and designed the study, developed the original surgical techniques, and drafted the manuscript. Hiroyuki Mitsui contributed substantially to the acquisition and interpretation of clinical data and participated in the critical revision of the manuscript for important intellectual content. Kai Suzuki assisted in figure preparation, and provided critical feedback on the surgical concepts and their presentation. All authors have read and approved the final version of the manuscript and agree to be accountable for all aspects of the work.
Conflicts of Interest
The authors declare that there are no conflicts of interest.
Informed Consent Statement
Informed consent was obtained from all individual participants included in the study.
Disclaimer
Hisateru Niki is one of the Associate Editors of Journal of Orthopaedic Foot and Ankle Science and on the journal’s Editorial Board. This author was not involved in the editorial evaluation or decision to accept this article for publication at all.
Supplementary Material
Supplementary Material accompanies this article: https://doi.org/10.64079/jofas.2025-0006
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