Category: Basic Sciences/Biologics; Midfoot/Forefoot Introduction/Purpose: Spring ligament is a principle static stabilizer of the medial longitudinal arch. There is a triangular facet of fibrocartilage in its superomedial bundle that articulates with the talar head which is poorly described in the literature. The aim of this study was to carry out a formal anatomical and radiological description of the spring ligament articular facet (SLAF). Methods: Anatomically, we dissected 10 normally aligned cadaveric lower limbs. The spring ligament was approached from the superior direction. The talus was disarticulated and high-resolution images were taken of the ligament complex. ImageJ and Tracker software was used to calculate the surface area and the maximum linear measurements of the spring ligament articular facet (SLAF). 22 normally aligned feet were analysed on reformatted PD space sequences on MRI using PACS. Results: The meniscus was consistently trapezoid in shape in all specimens. The mean area of the SLAF was 203.31 mm2. The average longest proximal to distal length was 11.93 mm and at the shortest plantar and lateral margin was 5.34 mm. The attachment of the SLAF with calcaneum and navicular articular surface was defined by a distinct thick fibrous ligamentous structure that measured 3.67 and 1.69 mm at its medial and lateral margin on the calcaneal side and 2.72 and 2.87 mm respectively on the navicular side. SLAF was visible on MRI but it was not possible to differentiate between SLAF and its investing ligaments. MRI measurements showed a mean surface area of 354 mm2 with mean thickness of 2.7 - 4.3 mm throughout its course. Conclusion: The paper describes the anatomical and radiological parameters of SLAF, a constant fibrocartilaginous structure within the superomedial portion of the spring ligament, as well as its ligamentous attachments.

Category: Other Introduction/Purpose: Radiographic angles and measurements are widely used in foot and ankle pathologies to define normal and abnormal skeletal alignment. In spite of this the inter-observer reliability of these parameters is debatable. The aim of this study was to determine the inter-observer reliability of various radiographic angles and measurements in flat foot deformity. Methods: Antero-posterior (AP) and lateral foot radiographs of 18 patients with flatfoot deformity were analysed by eight clinicians of various grade of experience (2 consultants, 4 fellows / registrars and 2 core training grades) with 11 different radiological parameters. A digital presentation demonstrating the method of measurement of all parameters using same software was provided to the participants. The inter-observer reliability was analysed using interclass correlation (ICC) model mixed for reliability at 95% confidence interval for individual parameters and different grade of experience. Results: The inter-observer reliability was excellent (>0.9) in calcaneal pitch angle (CPA), medial cuneiform height (C1H) and lateral incongruency angle (LIA). It was good (0.75 - 0.90) in talo-navicular angle (TNA), medial cuneiform articular angle (CAA), medial arch sag angle (MASA), medial cuneiform - 1st MT angle (C1MTA), talonavicular coverage angle (TNCA)andtalar - 1st MT angle on AP radiograph (T1MTA). The inter-observer reliability was moderate (0.5 - 0.75) in Meary's angle and talo-navicular uncoverage percentage (TNUP). The reliability did not differ with the grade of surgeon on sub-group analysis. Conclusion: This is first study to analyse the interobserver reliability of radiographic measurements in a flatfoot deformity, including grade of surgeon. The results suggest that these radiological parameters can be reliably used in clinical practice if standard measurement techniques are followed by clinicians of all grades.

Category: Midfoot/Forefoot Introduction/Purpose: Progressive Collapsing Foot Disorder (PCFD) is caused by failure of both dynamic and static structures. The aim of this study was to identify the anatomical location of the medial longitudinal arch break in symptomatic flat foot deformity and analyze its relationship with Meary's angle. Methods: We analyzed weight-bearing radiographs of 81 patients [mean age 53.7 years (range, 18-81) with 101 flat feet. The apex of the medial arch break was determined on the lateral foot radiographs as the intersection of the anatomical axis of the talus and the first metatarsal. Therefore, the overall centre of rotation of angulation (CORA) of the medial arch break was documented as the angle at its apex (Meary's angle). Each separate joint angulation was then calculated to determine if the overall CORA was made of separate CORAs. Correlations between the apex location, and the number of apices, with Meary's angle were conducted. Results: There was an isolated apex of deformity in 50.4% (51/101) of cases. These were localised at talonavicular joint (TNJ) in 47% (24/51), the naviculocuneiform joint (NCJ) in 52.9% (27/51) and none at the cuneiform-first metatarsal joint (C-1MTJ). The remaining 49.5% (50/101) had combination apices with the primary deformity being at TNJ in 58% (29/50), the NCJ in 40% (20/50), and 2% (1/50) at the C-1MTJ. The mean Meary's angle was -17.9° for isolated and -18° for combination which was not statistically significant (p=0.92). There was no statistical difference in the talonavicular uncoverage angle between the single and combination apices group (p= 0.99). Conclusion: The apex of the medial arch break occurs distal to the talonavicular joint in the majority of cases, and thereby the main insertion points of the posterior tibial tendon and spring ligament. In 52.9% (27/51) of cases, the deformity occurs solely distal to the TNJ and in 58% (29/50) cases, it involves joints in addition to the TNJ. These will involve pathology of other structures, including the naviculocuneiform ligament. Surgical strategies in successfully correcting Progressive Collapsing Foot Disorder will therefore need to address joints distal to the TNJ in the majority of cases.