How do you diagnose an unstable turf toe?

Diagnosing Unstable Turf Toe

MRI is the preferred imaging method to diagnose an unstable turf toe by directly evaluating the capsuloligamentous complex, plantar plate integrity, and associated chondral or osteochondral lesions. 1

Clinical Assessment and Imaging Strategy

Initial Radiographic Evaluation

Stress radiography with forced dorsiflexion is the critical first step to assess instability. 1 The key radiographic finding that indicates instability is:

• Sesamoid-phalangeal distance increase of ≥3 mm compared to the intact/contralateral side on dorsiflexion stress views is highly predictive of severe plantar plate injury involving at least 3 of 4 ligaments. 2
• This quantitative measurement provides objective evidence of instability and helps distinguish stable from unstable injuries 2
• Proximal migration of one or both sesamoids indicates plantar plate disruption 2

Advanced Imaging for Definitive Diagnosis

MRI directly visualizes the soft-tissue structures of the capsuloligamentous complex and is superior to radiography for determining the extent of plantar plate injury. 1 The ACR guidelines specifically recommend MRI as the preferred method for evaluating suspected turf toe and plantar plate injuries 1

• MRI allows assessment of the degree of plantar plate tear (partial vs. complete rupture) 3
• MRI identifies associated injuries including sesamoid fractures, chondral lesions, and osteochondral defects that may not be visible on radiographs 1
• Complete plantar plate disruption on MRI indicates an unstable injury requiring surgical consideration 3

Ultrasound as an Alternative

US can be used to evaluate plantar plate integrity with 96% sensitivity, though it is less comprehensive than MRI 1

• US visualizes the plantar plate in the sagittal plane between the tendon and hyaline cartilage of the metatarsal head 1
• US has the advantage of dynamic assessment but lower accuracy (63%) for identifying the exact location of injury compared to MRI (93%) 1

Clinical Indicators of Instability

Beyond imaging, clinical examination findings suggesting instability include:

• Inability to bear weight or push off during gait 3
• Gross deformity or hyperextension of the hallux MTP joint 3
• Positive stress testing with palpable joint laxity or frank separation 3

Treatment Algorithm Based on Stability

Stable injuries (intact or minimally disrupted plantar plate on imaging) are managed conservatively with immobilization, stiff-soled shoes, and gradual weight-bearing. 3

Unstable injuries (complete plantar plate disruption or ≥3 mm sesamoid migration on stress views) require surgical intervention with plantar plate repair to restore optimal function. 3

Common Pitfalls

• Relying solely on standard radiographs without stress views will miss unstable injuries, as routine films may only show soft-tissue swelling 4
• Failing to obtain comparison views of the contralateral foot makes it difficult to quantify sesamoid migration 2
• Underestimating the severity based on clinical examination alone can lead to prolonged recovery if an unstable joint is treated conservatively 2