This study aimed to investigate the dimensions and types of the os trigonum and evaluate their relationship with various pathologic conditions on the posterior ankle using ankle MRI images. A total of 124 non-contrast-enhanced ankle and foot MR images of 123 consecutive patients were included in this retrospective study. The images were presented randomly, and they contained no patient information. The MR images were retrospectively and independently reviewed by two reviewers with a fellowship-trained musculoskeletal radiologist. The images were classified as type I and II based on the ossicle\'s medial border overlying the talus\'s posterior process and the groove for the flexor hallucis longus tendon (FHL). The study revealed that patients with type II os trigonum had a longer transverse diameter of the ossicle than type I, and there were statistically significant differences. Detachment status tended to be less in type I than in type II os trigonum, and the differences between the groups were statistically significant. There were no significant differences between type I and II os trigonum regarding posterior talofibular ligament (PTFL) abnormality, bone marrow edema, FHL tenosynovitis, and posterior synovitis. The study concluded that the os trigonum is a common cause of posterior ankle impingement, and type II os trigonum has a longer transverse diameter of the ossicle than type I.

BACKGROUND: Accessory ossicles, sesamoid bones, and biphalangism of toes are the most common developmental variations of the foot. These bones may be associated with painful syndromes; however, their clinical importance is not well understood because the reported prevalence varies widely. Therefore, we aimed to investigate these variants in Turkish subjects.
METHODS: A total of 1651 foot radiographs were retrospectively assessed. Radiographs of feet were examined regarding the prevalence, sex, and bilaterality of accessory ossicles, sesamoid bones, and biphalangism in Turkish subjects.
RESULTS: Accessory ossicles (26.1%) and sesamoid bones (8%) were detected. The most common accessory ossicles were os trigonum (9.8%), accessory navicular bone (7.9%), and os peroneum (5.8%). Also, we detected os supratalare (0.48%), os calcanei secundarium (0.42%) os subfibulare (0.42%), os supranaviculare (0.36%), os vesalianum (0.30%), os subtibiale (0.24%), os intermetatarseum (0.12%), and os subcalcis (0.12%). We observed bipartite hallux sesamoid in 1.8% and interphalangeal sesamoid bone of the hallux in 0.7% of radiographs. Incidences of metatarsophalangeal sesamoid bones were found as 0.6%, 0.06%, 0.6%, and 5.8% in the second, third, fourth, and fifth digit, respectively. We observed biphalangeal toe in 0.5%, 1.7%, 3.5%, and 37.6% in the second, third, fourth, and fifth toe, respectively.
CONCLUSIONS: This study is the first detailed report on the incidence of the most common variants of the foot and ankle in a wide-ranging patients\' series in Turkish subjects. Our study\'s findings will contribute to reducing misdiagnosis.
CONCLUSIONS: The results of this study may provide anatomical data that could help clinicians in the diagnosis and management of disorders that present with pain and discomfort in the feet. Knowledge of these variants is important to prevent misinterpreting them as fractures.

OBJECTIVE: The aim of the study was to examine the ligaments of the os trigonum.
METHODS: The ankle joint magnetic resonance imaging (MRI) of 104 patients with the os trigonum (experimental group) and 104 patients without the os trigonum (control group) were re-reviewed. The connections of the os trigonum and posterior talofibular ligament (PTFL), the fibulotalocalcaneal ligament (FTCL), the paratenon of the Achilles tendon, the posterior talocalcaneal ligament (PTCL), the osteofibrous tunnel of the flexor hallucis longus (OF-FHL) and the flexor retinaculum (FR) were studied.
RESULTS: The os trigonum is connected to structures. The posterior part of the PTFL inserted on the os trigonum in 85.6% of patients, whereas in all patients in the control group, the posterior part of the PTFL inserted on the posterior talar process (p < 0.05). The connection of the PTCL was seen in 94.2% of patients in the experimental group, while it was seen in 90.4% of patients in the control group (p > 0.05). The connection to the FTCL in the experimental group was 89.4%, while in the control group, it was 91.3% (p > 0.05). The communication with the paratenon was seen more often in the control group compared to that in the experimental group (31.7% vs. 63.8%, p < 0.001). The FTCL was prolonged medially into the FR in 85.6% of patients in the experimental group and in 87.5% of patients in the control group (p > 0.05). The flexor hallucis longus (FHL) run at the level of articulation between the os trigonum 63.5% and the posterior process of the talus 25% and less often on the os trigonum 11.5%.
CONCLUSIONS: The os trigonum is connected with all posterior ankle structures and more connections than previously reported.

BACKGROUND: Open surgical excision of the os trigonum has been the traditional treatment for posterior ankle impingement syndrome (PAIS). However, the endoscopic excision has recently become quite popular. Purpose/Hypothesis: The purpose of our study was to compare the results of endoscopic versus open excision of a symptomatic os trigonum for the treatment of PAIS in an athletic population. It was hypothesized that the endoscopic technique would be superior to the open technique regarding functional outcomes, pain, and time to return to training and the previous sports level.
METHODS: Randomized controlled trial; Level of evidence, 2.
METHODS: From 2008 to 2011, 52 athletes underwent a symptomatic os trigonum excision; 26 athletes had an open procedure (group A) and 26 had an endoscopic procedure (group B). The American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score and the Visual Analog Score-Foot and Ankle (VAS-FA) were obtained, and the time to return to training and to previous sports level was recorded.
RESULTS: Patients in group B appeared to have significant improvement of AOFAS hindfoot score compared with those in group A ( P < .05), whereas no statistical significance was found for the postoperative VAS-FA scores between the 2 groups. The mean ± SD time to return to training was 9.58 ± 3.98 weeks for group A and 4.58 ± 1.47 weeks for group B ( P < .001). The time to return to previous sports level was 11.54 ± 3.89 weeks for group A and 7.12 ± 2.25 weeks for group B ( P < .001). The overall complication rate was 23% for group A (6 cases) and 3.8% for group B (1 case).
CONCLUSIONS: Both the open procedure and the endoscopic approach yielded acceptable outcomes in terms of function and pain. However, complication rates were remarkably lower with endoscopic treatment, and the time to return to full activities was much shorter. Endoscopic excision of the os trigonum is a safe and effective treatment option for athletes who require early return to their previous sports level.

BACKGROUND: Arthroscopic management of the posterior ankle impingement with the patient in supine position has the advantage of dealing with anterior ankle pathology at the same time without the need to change position of the patient. This study aims at evaluation of the safety of portal establishment and instrumentation of this technique.
METHODS: Sixteen fresh-frozen cadaver specimens were used. The relationships of the posteromedial and posterolateral portals to the adjacent tendons and nerves and the relationship of the coaxial portal tract with the posterior ankle capsule and the flexor hallucis longus tendon were studied.
RESULTS: Angle θ1 between the intermalleolar line and the posterior ankle coaxial portal tract averaged 1° (-10° to 22°). Angle θ2 between the intermalleolar line and the metal rod where the neurovascular bundle started to move averaged 19° (10° to 30°). Angle θ3 between the intermalleolar line and the metal rod where it reached the lateral border of the Achilles tendon was larger than angle θ2 in all specimens. The angle of safety (θs) averaged 18° (-1° to 26°).
CONCLUSIONS: Injury to the tendon, nerves or vessels is possible during establishment of the portals and resection of the os trigonum.

BACKGROUND: Both subtalar arthroscopic and posterior endoscopic techniques are used to treat posterior ankle impingement syndrome (PAIS). However, there have been no studies comparing the 2 procedures.
OBJECTIVE: Both arthroscopic and endoscopic excisions of the os trigonum are safe and effective in treating PAIS.
METHODS: Cohort study; Level of evidence, 3.
METHODS: Twenty-eight patients were treated with excision of the os trigonum either by an arthroscopic (16 patients) or endoscopic (12 patients) technique. The mean patient age was 29.8 years (range, 17-55 years), and the mean follow-up period was 30 months (range, 18-58 months). Preoperative and postoperative visual analog scale (VAS) score for pain, American Orthopaedic Foot and Ankle Society (AOFAS) score, and Maryland Foot Score (MFS) were used to analyze the functional results. Duration of surgery, time to return to sports (RTS), and patient satisfaction were evaluated as well. The size of the os trigonum was measured using T1-weighted sagittal magnetic resonance imaging (MRI). The clinical and MRI results were compared between the 2 groups.
RESULTS: The VAS score, AOFAS score, and MFS for both the arthroscopic group (preoperative: 6.3, 63.8, and 61.5, respectively; postoperative: 1.2, 89.9, and 89.6, respectively) and endoscopic group (preoperative: 6.7, 64.8, and 62.5, respectively; postoperative: 1.2, 89.9, and 88.4, respectively) improved significantly (P < .01). The mean surgery and RTS times were 39.4 minutes and 7.5 weeks in the arthroscopic group and 34.8 minutes and 8.0 weeks in the endoscopic group, respectively (P > .05). All patients were satisfied with the results. There were no significant differences between the 2 groups in the preoperative and postoperative VAS score, AOFAS score, or MFS (P > .05). The mean size of the os trigonum was 11.1 × 8.8 mm(2) in the arthroscopic group and 12.6 × 10.4 mm(2) in the endoscopic group, and the difference was significant (P < .05). Two patients underwent both arthroscopic and endoscopic procedures because of technical difficulty in removing the large os trigonum arthroscopically.
CONCLUSIONS: Both arthroscopic and posterior endoscopic excisions of the os trigonum were safe and effective in treating PAIS. The arthroscopic procedure was more demanding, especially in cases of a large os trigonum. The posterior endoscopic approach had the advantage of addressing problems in the posterior ankle joint and allowed a more extensive release of the flexor hallucis longus.