Radiological study of Os trigonum and its clinical significance

Background: Os trigonum (OST) is commonly located on the posterior aspect of the talus. It occurs as a result of secondary ossification center failing to fuse with the lateral tubercle of the posterior process of the talus; its incidence varies between 2 and 25%, and is more often bilateral. It occurs as an intra-articular Os, which is most often securely rooted to the lateral tubercle of the talus by a fibrocartilaginous synchondrosis. Aims and Objective: To determine the incidence, morphology, and distribution of Os Trigonum (OST). Materials and Methods: Retrospective 500 lateral foot radiographs view were studied to determine the incidence, morphology, and distribution of OST. Results: Incidence of OST in the present study was 6.6%, with predominantly round or ovoid in shape. OST was located on the posterolateral aspect of the talus. Conclusion: OST can be one of the causative factor responsible for Flexor hallucis longus tendonitis, OST syndrome, which occur in plantarflexion of the ankle, leading to compression of the OST between the distal tibia and the calcaneus. Hence, knowledge regarding the incidence, morphology, and distribution of OST is important for the radiologist, orthopedic surgeons to arrive at a correct diagnosis, which aids in the management of cases presenting with complaints of posterior ankle pain.

Double Posteromedial Portals for Excision of a Symptomatic Os Trigonum With Ankle Arthroscopy in Supine Position

Background: The existence of abnormal os trigonum often causes posterior ankle impingement syndrome, the commonly used method for excision of symptomatic os trigonum is standard arthroscopic approach when posterior and anterior abnormalities appear in one patient. However, the arthroscopy of posterior and anterior compartement of the ankle joint must be undertaken in one surgical position. In most cases, when adopting the standard arthroscopic approach, the patient has to be firstly positioned supine to perform the anterior procedure, and then re-positioned prone to operate on the posterior compartment. Material and Methods: To simplify this process and shorten operation time, we describe a double posteromedial ankle portals procedure, which provides access to reach both the posterior and anterior compartment without changing position, to exam both symptomatic compartement. Standard operation are conducted by changing position to reach both compartement. Standard operation and double posteromedial ankle portals procedure were conducted to 46 patients (standard approach 23, 2 posteromedial portals 23). Operation time, AOFAS score, KAF score and VAS score were analyzed.Results: It shows operation time reduced from 69.78±5.24 min to 36.61±3.63 min (P<0.05) and postoperative recovery index of novel method including AOFAS score, KAF score and VAS score were better than that in standard way one month after operation, but there was no significance difference after one month. Conclusion: The figures strongly suggest that the double posteromedial portals approach is better than the standard procedures in operation time, short-term postoperative recovery.

Arthroscopic os trigonum en-bloc removal outcomes at 6-month follow-up are better compared to Stieda’s process resection in patients with posterior ankle impingement syndrome: a prospective comparative study

ObjectiveTo evaluate the potential differences in American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score and Foot Function Index (FFI) at 6-month and 12-month postoperative follow-up of arthroscopic treatment for posterior ankle impingement (PAIS) between os trigonum (OT) and Stieda’s process (SP) patients.MethodsThirty consecutive patients (32 ankles) treated in our Institution for PAIS with posterior arthroscopy were prospectively enrolled in the study from December 2012 to July 2019. Indications were patients with PAIS with persistent symptoms following conservative management. Exclusion criteria were the coexistence of concomitant pathologies and patients who underwent additional surgical procedures. An independent investigator interviewed and evaluated the patients according to the AOFAS hindfoot score and FFI preoperatively, at 6-month and 12-month follow-up.ResultsExcept for AOFAS scores in the SP group (MD (mean difference) 11.28, p=0.08), patients undergoing arthroscopic treatment for bony PAIS had an overall significant improvement in AOFAS score (OT MD 22.29, p<0.05) and FFI (OT MD −70.07, p<0.05; SP MD −50.96, p<0.05) from their preoperative scores at 6-month follow-up. Similarly, a significant improvement in AOFAS score (OT MD 5.78, p=0.01; SP MD 12.14, p<0.05) and FFI (OT MD −9.36, p=0.04; SP MD −26.43, p<0.05) was observed from the 6-month to 12-month follow-up in all groups. At 6-month follow-up, the OT group had significantly better FFI outcomes (MD −33.57, p=0.04) compared with the SP group. No differences were found by group when comparing AOFAS score and FFI score at 12-month follow-up.ConclusionsWhen comparing patients undergoing OT excision or SP resection, better FFI outcomes were observed in the OT group at 6-month follow-up.Level of evidenceProspective comparative study. Level II.

Chronic Fracture of the Posteromedial Tubercle of the Talus Masquerading as Os Trigonum Syndrome

Posterior ankle impingement syndrome (PAIS) can be caused by osseous pathology from the posterior aspect of the talus. The commonest cause is an os trigonum, an accessory ossicle arising from the lateral tubercle of the posterior talus. We have observed cases where the osseous impingement is due to a chronic fracture nonunion of the medial tubercle of the posterior talus with unique symptoms, differentiating this clinical syndrome from the more common os trigonum syndrome. These can be readily overlooked on imaging and confused with an often coexisting os trigonum. Awareness of these lesions is paramount to ensure appropriate management and safe surgery. We describe a series of patients presenting to the senior author with this clinical syndrome, discuss its unique clinical and radiological features, and describe our surgical technique.