The Os Trigonum Syndrome

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Key Words: os trigonum syndrome (AND treatment NOT surgery, AND physical therapy), posterior ankle impingement, ballet dancers

Definition/Description

The Os Trigonum Syndrome refers to pain posterior of the ankle and reduced plantarflexion caused by “the nutcracker-phenomenon”. When an os trigonum is present, this accessory ossicle together with surrounding soft tissues can become wedged between the tibia, talus and calcaneus. This can lead to inflammation of the involved structures.

The os trigonum syndrome can also be named the symptomatic os trigonum, the talar compression syndrome or posterior tibial talar impingement syndrome.

Clinically Relevant Anatomy

Embryologically, the body of the talus and the posterior talar process are separate ossification centers. Between the 7th and the 13th year of life, the posterior talar process appears as a separate ossicle: the os trigonum. Normally, within a year of its appearance, it fuses with the talus, but about 7% of the adult population has still this os trigonum. It can be present unilaterally or bilaterally, with smooth or serrated margins. The os trigonum is usually seen as an individual bone, but can also exist of two or more pieces. It is less than 1cm in size, but this can vary.

The os trigonum is usually triangular with an anterior, inferior and posterior surface. The anterior surface connects with the lateral tubercle by cartilaginous synchondrosis. The inferior side may articulate with the calcaneus. The posterior surface is nonarticular, but is used as a point of attachment for capsuloligamentous structures. The os trigonum may also be round or oval.

The flexor hallucis longus tendon is situated medial to the os trigonum, in the sulcus between the medial and lateral tubercle.
 

Epidemiology /Etiology

There are three mechanisms for the development of an os trigonum:
1.fusion failure of an ossification center
2.fracture of the posterior margin of the tibia
3.fracture of the posterior process of the talus.

The presence of an os trigonum isn’t sufficient to create the syndrome. It must be combined with a traumatic event.

The os trigonum syndrome can be caused by overuse or trauma. When it’s due to overuse, it’s mostly found by ballet dancers and runners. The forceful plantar flexion that happens during an “en pointe” or “demi-pointe” position, as well as by running downhill, produces compression on the posterior aspect of the ankle joint. In cause of a trauma, the os trigonum can be displaced by forced plantarflexion.

Soft tissue structures, including the ankle joint capsule and surrounding ligaments, may react by forming a hypertrophic mass.

Characteristics/Clinical Presentation

A load-dependent, persistent pain between the Achilles tendon and the peroneal tendons is the first indicator of the syndrome. Stiffness, weakness and swelling can also be observed in this zone. The second main symptom is a decrease in plantarflexion compared with the unaffected ankle. In some cases the bony prominence may be palpable.

Eversion or inversion movements may cause discomfort. Pain at the posterior aspect of the ankle will be experienced by plantarflexion of the foot or dorsiflexion of the great toe.

Differential Diagnosis

The following diagnosis must be considered:

• Tendinitis flexor hallucis longus;
• Tarsal tunnel syndrome;
• Subtalar pathology;
• Achilles tendinopathy;
• Peroneal tendinopathy;
• Achilles tendon bursitis;
• Osteochondritis dissecans of the talus.

Diagnostic Procedures

1. MEDICAL DIAGNOSIS
A plain radiography or MRI is necessary to confirm the diagnose of a coccyx fracture. (level of evidence D)

2. CLINICAL DIAGNOSIS
The diagnose is made after rectal examination. (level of evidence D)iv By passing the finger up the rectum and then pressing the bone backwards and forward, the unnatural degree of motion will then be felt. Related to the age and sex of the patient must be remembered that in the female this bone naturally possesses more motion than in the male, and that in youth a degree of motion, that does not exist at a later period of life, is present, allowing the ossification being less complete. However the free motion of the bone is taken as a symptom. (level of evidence D)

Outcome Measures

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Examination

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Medical Management

1. COCCYGEOPLASTY
By applying the novel techniques that are used in vertebroplasty and sacroplasty, coccygeoplasty is introduced as a new percutaneous treatment modality for fractures of the coccyx. This procedure can be helpful for patients with refractory pain resulting from a fracture of the coccyx and can be performed quickly and safely with high-resolution c-arm fluoroscopy. The coccygeal fracture treated with an injection of polymethylmethacrylate cement can provide early symptom relief. Although the promising results, an experience with a larger patient population is warranted. ( level of evidence C)

2. COCCYGECTOMY
Literature reports suggest that coccygectomy, partial or total removal of the coccyx, has been beneficial with success rates as high as 60-91%. However, coccygectomy is a more invasive procedure, with a common complication rate as high as 22%, and is usually associated with perineal contamination of the wound. Other complications could include persistent bleeding from the hemorrhoidal venous complex of the rectum. (level of evidence C)ix

Physical Therapy Management

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Key Research

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Resources

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Clinical Bottom Line

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Recent Related Research (from Pubmed)

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References

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MOORE K.L., DALLEY A.F., AGUR A.M.R., Clinically oriented anatomy: chapter 3: Pelvis and perineum, Wolters Kluwer health, sixth edition, 2010, pag. 451-452, level of evidence D
YU-TSAI T., LI-WEN T., CHENG-HSIU L., SHIH-WEI C., The influence of human coccyx in body weight shifting, medicine and science in sport and exercise, 2011, Volume 43, Number 5, pag. 494-496, level of evidence B
MOORE K.L., DALLEY A.F., AGUR A.M.R., Clinically oriented anatomy: chapter 3: Pelvis and perineum, Wolters Kluwer health, sixth edition, 2010, pag. 332, level of evidence D
HAARMAN H.J.Th.M., Klinische traumatologie, Elsevier gezondheidszorg, 2006, pag. 117, level of evidence D
MOORE K.L., DALLEY A.F., AGUR A.M.R., Clinically oriented anatomy: chapter 3: Pelvis and perineum, Wolters Kluwer health, sixth edition, 2010, pag. 461, level of evidence D
TEKIN L. et al., Coccyx fracture in patients with spinal cord injury, European journal of physical and rehabilitation medicine, March 2010, Volume 46, Number 1, pag. 43-46, level of evidence C
RAISSAKI M.T.,Fracture dislocation of the sacro-coccygeal joint: MRI evaluation, Pediatric radiology, March 1999, pag. 642-643, level of evidence D
LONSDALE E.F., A practical treatise on fractures, Walton and Mitchell printers, 1838, pag. 269-270, level of evidence D
MIYAMOTO K. et al., Exposure to pulsed low intensity ultrasound stimulates extracellular matrix metabolism of bovine intervertebral dosc cells cultured in alginate beads, Spine, November 2005, level of evidence B
EBNEZAR J., Essentials of orthopaedics for physiotherapist, Jaypee, 2003, pag. 174, level of evidence D
DEAN L.M. et al., Coccygeoplasty : treatment for fractures of the coccyx, J. Vasc. Interv. Radiol, 2006, pag. 909-912, level of evidence C
COOPER G., HERRERA J.E., Manual of musculoskeletal medicine, Wolters kluwer, Lippincott Williams & Wilkins, 2008, pag. 144, level of evidence D