Traumatic Hallux Valgus due to Medial Collateral Ligament Injury of the First Metatarsophalangeal Joint: A Comprehensive Review

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Introduction

Traumatic hallux valgus, particularly when caused by injury to the medial collateral ligament (MCL) of the first metatarsophalangeal (MTP) joint, represents a rare but clinically significant condition. Unlike idiopathic hallux valgus, which is commonly associated with genetic predisposition, footwear, or chronic biomechanical stresses, traumatic hallux valgus results from acute injury mechanisms. This column aims to provide an expert-level synthesis of current evidence on the pathophysiology, epidemiology, clinical presentation, imaging features, differential diagnosis, management, and prognosis of this condition, while integrating case-based imaging findings. All figures are drawn from the attached case review for educational illustration.

Pathophysiology

Hallux valgus is defined as a lateral deviation of the great toe relative to the first metatarsal. In traumatic hallux valgus, the deformity arises acutely following disruption of stabilizing structures of the MTP joint. The medial collateral ligament (MCL) plays a critical role in resisting valgus stress. When ruptured, typically due to hyperabduction or hyperextension mechanisms, the joint loses medial restraint, allowing lateral deviation of the hallux.

Other contributing factors include:

  • Injury to the plantar plate, leading to dorsiflexion instability.

  • Associated contusion or marrow edema of the first metatarsal head.

  • Secondary tendinopathy of the abductor hallucis or flexor hallucis brevis.

Epidemiology

Traumatic hallux valgus is rare. Most documented cases appear in isolated case reports or small series, often involving athletes exposed to high-impact or turf-related injuries. Unlike idiopathic hallux valgus, which is more common in women and older populations, traumatic hallux valgus can affect younger, active males, particularly in sports such as football, rugby, or martial arts.

Clinical Presentation

Patients typically present with:

  • Acute pain in the first MTP joint following trauma.

  • Swelling, ecchymosis, and medial tenderness.

  • A subjective sense of instability of the great toe.

  • Visible lateral deviation of the hallux.

On examination, valgus stress testing may demonstrate excessive medial joint opening compared to the contralateral side, confirming ligamentous laxity.

Imaging Features

Radiographs

  • Often normal but important for excluding fractures.

  • May show soft tissue swelling, mild lateral deviation of the hallux, or associated sesamoid malalignment.

[Figure 1] Right foot X-ray: Mild hallux valgus with soft tissue thickening around the bunion region. No fracture or dislocation.

MRI

MRI is the gold standard for assessment of MCL integrity and associated soft tissue injuries.

  • MCL: Thickening, discontinuity, or increased T2 signal intensity suggest tear.

  • Bone marrow edema: Seen in the metatarsal head or proximal phalanx.

  • Associated tendon changes: Tendinosis of the abductor hallucis or extensor hallucis longus.

[Figure 2] Right foot MRI: Hallux valgus with near full-thickness tear of the medial collateral ligament (white arrow). Tendinosis of the abductor hallucis tendon with increased T2 signal (red arrow). Marrow edema of the first metatarsal head without cortical fracture. Medial soft tissue edema present.

Differential Diagnosis

  • Turf toe (plantar plate tear)

  • Sesamoid fractures

  • Stress fractures of the metatarsal head

  • Flexor hallucis longus tendon rupture

  • Neuropathic joint changes

Diagnosis

The diagnosis of traumatic hallux valgus relies on:

  1. Clinical history of acute trauma with localized pain and swelling.

  2. Physical examination revealing medial tenderness and valgus instability.

  3. Imaging findings confirming MCL disruption with or without associated injuries.

Definitive diagnosis is made when MRI shows MCL tear correlating with clinical instability.

Treatment

Conservative

  • Immobilization with orthosis or stiff-soled shoe.

  • Physical therapy focusing on restoring joint stability.

  • NSAIDs for pain and inflammation.

Surgical

Indicated when:

  • Complete MCL rupture with persistent instability.

  • Progressive hallux valgus deformity.

  • Failed conservative treatment.

Procedures include direct MCL repair, reconstruction with tendon graft, or corrective osteotomy if deformity progresses.

Prognosis

Early recognition and stabilization improve outcomes. With appropriate management, many patients return to sports without long-term sequelae. However, delayed or missed diagnosis may lead to chronic hallux valgus deformity, functional impairment, and need for corrective surgery.

Quiz

Question 1: Which of the following best describes the primary injured structure in traumatic hallux valgus?

A) Plantar plate

B) Medial collateral ligament

C) Extensor hallucis longus tendon

D) Sesamoid bone

Question 2: On MRI, which feature most strongly supports the diagnosis of traumatic hallux valgus?

A) Bone marrow edema of the second metatarsal 

B) Thickened and hyperintense medial collateral ligament on T2

C) Joint effusion in the first MTP joint

D) Flattening of the longitudinal arch

Question 3: Which of the following is NOT typically a differential diagnosis for traumatic hallux valgus?

A) Turf toe

B) Sesamoid fracture

C) Flexor hallucis longus tendon rupture

D) Achilles tendon rupture

Answer & Explanation

1. Answer: B) Medial collateral ligament. Explanation: Traumatic hallux valgus is defined by disruption of the MCL, leading to acute lateral deviation of the hallux.

2. Answer: B) Thickened and hyperintense medial collateral ligament on T2. Explanation: Increased T2 signal intensity in the MCL indicates acute injury, which is the hallmark of this condition.

3. Answer: D) Achilles tendon rupture. Explanation: While Achilles rupture is a common foot injury, it does not mimic hallux valgus deformity and is not considered in its differential diagnosis.

References

[1] J. M. Linklater, "Imaging of sports injuries in the foot," AJR Am J Roentgenol, vol. 199, no. 3, pp. 500-508, 2012.
[2] C. R. Hood and J. R. Miller, "Post-traumatic hallux valgus – a rupture of the medial collateral ligament," FAOJ, vol. 9, no. 1, pp. 1-6, 2016.
[3] T. S. Watson, R. B. Anderson, and D. W. Hunt, "Periarticular injuries to the hallux metatarsophalangeal joint in athletes," Foot Ankle Clin, vol. 5, no. 3, pp. 687-713, 2000.
[4] P. C. McKeon and M. Hertel, "Biomechanics of foot injuries in sports," Clin Sports Med, vol. 24, no. 4, pp. 679-700, 2005.
[5] N. Shibuya and K. Jupiter, "Epidemiology and treatment outcomes of hallux valgus injuries," J Foot Ankle Surg, vol. 52, no. 6, pp. 701-706, 2013.
[6] B. L. Clanton and A. J. Coupe, "Turf toe injury mechanisms and management," Sports Med Arthrosc Rev, vol. 14, no. 1, pp. 30-35, 2006.
[7] D. L. Sobel, "Surgical management of hallux valgus in athletes," Clin Orthop Relat Res, vol. 468, no. 6, pp. 1673-1679, 2010.

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