Spring Ligament Insufficiency

The plantar calcaneonavicular ligament (spring ligament) is a critical static restraint to medial longitudinal arch collapse. While isolated injury is rare, spring ligament insufficiency is present in 90% of patients with Stage II or higher posterior tibial tendon dysfunction (PTTD). The ligament acts as a hammock supporting the talar head, resisting approximately 50% of the load transmitted through the medial arch during weight bearing.

The topic repeatedly describes the spring ligament as a "hammock" and "static keystone" suspending the talar head. That imagery is best understood through the concept of the acetabulum pedis (also called the coxa pedis) — the ball-and-socket cradle that receives the talar head, functionally analogous to the acetabulum of the hip. Understanding this socket explains why spring ligament failure produces the specific deformity seen radiographically, rather than a vague "arch collapse."

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When the spring ligament attenuates, the medial-plantar floor of the acetabulum pedis fails and the talar head rotates plantar-medially out of its socket — true peritalar (peritalar/subtalar) subluxation. The navicular and midfoot swing into abduction and dorsiflexion around the sagging head, generating the talonavicular uncoverage and the break in Meary's line measured on weight-bearing films. Reframing flatfoot as subluxation of the talus out of the acetabulum pedis (rather than passive arch sag) clarifies why surgical reconstruction targets restoration of the socket floor and talonavicular coverage, not merely arch height.

Spring ligament insufficiency develops through a progressive degenerative process, nearly always in the context of posterior tibial tendon dysfunction:

Spring ligament insufficiency presents as medial-sided foot pain with arch collapse. The key task is distinguishing it from other causes of acquired flatfoot and medial foot pain, and recognising that it usually coexists with posterior tibial tendon dysfunction rather than occurring in isolation.

The Controversies section names synthetic suture-tape (internal brace) augmentation as an option but does not develop it. Because this is an increasingly discussed spring-ligament-specific adjunct, it warrants explanation.

What it is. A high-strength non-absorbable suture tape (for example a braided FiberTape-type construct) is anchored bone-to-bone from the sustentaculum tali / medial calcaneus to the navicular tuberosity, running along the anatomic course of the superomedial band, and tensioned with the foot held in the corrected position (talar head reduced, hindfoot neutral).

Crucially, tape augmentation follows the same rule as every soft-tissue step in this operation: it does not substitute for a medializing (or lateral column lengthening) osteotomy when fixed hindfoot valgus or forefoot abduction is present. Bony realignment restores alignment; the internal brace protects the medial soft-tissue reconstruction that maintains it.

Spring ligament insufficiency is managed within the broader framework of adult acquired flatfoot deformity (AAFD), now increasingly termed progressive collapsing foot deformity (PCFD). There is no isolated society guideline for the spring ligament itself; practice is guided by foot-and-ankle society consensus on flatfoot and by the underlying evidence.

Global epidemiology

• AAFD predominantly affects middle-aged women (typical onset 40 to 65 years), with a strong female preponderance.
• Spring ligament pathology is identified in the large majority of advanced (flexible stage II and beyond) flatfeet at surgery; isolated rupture with a normal PTT is rare but real and under-recognised.
• Obesity, hypertension, diabetes and seronegative inflammatory arthropathy are recognised associations with degenerative medial-arch failure.

Registry note. No arthroplasty-style registry tracks spring ligament reconstruction; it is a soft-tissue procedure with no implant. Evidence is therefore confined to small retrospective and prospective series rather than registry survivorship data, which is why recommendations remain level IV.