Role of the intrinsic subtalar ligaments in subtalar instability

Key points

1. 01The cervical ligament (CL) and interosseous talocalcaneal ligament (ITCL) contribute importantly to normal subtalar kinematics and stability, alongside the calcaneo-fibular ligament (CFL).
2. 02Subtalar instability (STI) is estimated to be involved in about 25% of cases presenting with talocrural instability.
3. 03Diagnosis requires a step-by-step approach: clinical signs, MRI assessment of subtalar ligaments, and intraoperative evaluation.
4. 04Intrinsic subtalar ligament injuries are probably underreported due to small ligament size and frequent partial ruptures that may preserve anatomical continuity while losing tensile strength.
5. 05In complex cases of STI, cervical ligament reconstruction in addition to ATFL and CFL reconstruction is recommended based on recent clinical and biomechanical evidence.

How it was conducted

Design

Narrative/comprehensive literature review

Databases searched

PubMed, Web of Science, Embase

Focus

Pathophysiology, anatomy, and biomechanics of intrinsic subtalar ligaments; diagnosis and surgical treatment of subtalar instability

Ligaments assessed

Cervical ligament (CL), interosseous talocalcaneal ligament (ITCL), anterior capsular ligament (ACaL), calcaneo-fibular ligament (CFL), anterior talo-fibular ligament (ATFL)

What they found

• CFL failure load is higher than ATFL failure load across multiple biomechanical studies, supporting its role as an important subtalar stabilizer (Attarian et al.; Siegler et al.; Rochelle et al., 2020).
• The CL has a low failure load similar to the ATFL (Michels et al., 2022a), making it vulnerable to injury during inversion ankle sprains.
• The ACaL-ITCL complex has a relatively high failure load and high stiffness compared to the CL (Michels et al., 2022a).
• MRI footprint analysis showed the ITCL footprints are very close to the subtalar axis of rotation, consistent with its role as a central pivot (Goto et al., 2009).
• Tochigi et al. found intrinsic subtalar ligament lesions on MRI after acute ankle sprain and a significant relationship between ITCL or CL lesions and instability complaints at follow-up.
• Lee et al. found additional CL insufficiency in some patients with combined ATFL and CFL lesions, and CL insufficiency was correlated with radiographic signs of STI (Lee et al., 2016).
• Combined ATFL and CFL lesion occurrence varies from 20% to 65% (Broström, 1965; van den Hoogenband et al.).
• A recent MRI study reported ATFL lesions in 96.3% of all included patients with CFL lesions (Debieux et al.).
• Non-anatomical tenodesis techniques result in disturbed joint biomechanics, restricted range of motion, inferior functional results, and increased risk of degenerative changes over time.

Limitations

• This is a narrative review; no systematic meta-analysis was performed, and findings depend on the authors' selection and interpretation of existing studies.
• Many of the underlying biomechanical studies used cadaveric models, which may not fully replicate in vivo conditions during dynamic ankle sprain.
• Intrinsic subtalar ligament injuries are probably underreported due to small ligament size and the difficulty of detecting partial ruptures on MRI and intraoperatively.
• Clinical outcome data for cervical ligament reconstruction are limited to small series with selected complex cases, so generalizability is unclear.

Why it matters

For patients

Patients with chronic ankle instability who have not responded to standard treatment may have undiagnosed subtalar ligament injuries that require targeted surgical reconstruction.

For clinicians

Clinicians should use a step-by-step diagnostic algorithm including MRI of the intrinsic subtalar ligaments and intraoperative assessment, and should consider cervical ligament reconstruction alongside CFL repair in complex instability cases.

For readers

This review consolidates recent anatomical and biomechanical evidence to reframe subtalar instability as a multi-ligament problem, shifting surgical strategy beyond the traditional ATFL-CFL focus.