Evaluation of the Foot Arch in Partial Weightbearing Conditions

Background: Weightbearing plain radiography or computed tomography (CT) is used for diagnosis or treatment selection in foot disorders. This study compared foot alignment between full weightbearing (50% body weight [BW] per foot) plain radiography and nonweightbearing (0% BW) or partial weightbearing (10% BW per foot) CT scans. Methods: Subjects had both full (50% BW per foot) weightbearing plain radiographs and either a nonweightbearing (0% BW) or a partial weightbearing (20% BW or 10% BW per foot) CT scan. Feet (n = 89) had been previously classified as pes cavus (n = 14/17 [subjects/feet]), neutrally aligned (NA; 20/30), asymptomatic pes planus (APP; 18/24), and symptomatic pes planus (SPP; 15/18). Lateral talometatarsal angle (LTMA) and calcaneal pitch angle were compared between weightbearing radiography and maximum-intensity projection images generated from CT. Results: Significant differences in LTMA were found between nonweightbearing CT scans and full (50% BW per foot) weightbearing plain radiographs: the mean difference was 6.6 degrees in NA, 9.2 degrees in APP, and 11.3 degrees in SPP ( P < .0001); no significant difference in LTMA was found for pes cavus. Although the interaction of foot type ( P = .084) approached statistical significance, pairwise differences between 10% weightbearing and 50% weightbearing images by foot type were significant but small. The 50% weightbearing condition resulted in calcaneal pitch angles the same or slightly lower or higher than those of the 10% weightbearing and nonweightbearing images. LTMA and calcaneal pitch angle measurements made on full (50% BW per foot) weightbearing plain radiographs and non- (0%) or partial (10% BW per foot) weightbearing angles from CT scans were strongly correlated. Conclusion: Different foot types have similar 2-dimensional sagittal plane morphologies with partial weightbearing (10% BW per foot) CT scans and, to a lesser degree, nonweightbearing (0%) neutral-position CT scans when compared to full weightbearing (50% BW per foot) plain radiographs. Level of Evidence: Level III Retrospective case control study.

Comparative Reliability of a Novel Electromechanical Device and Handheld Ruler for Measuring First Ray Mobility

Background: Quantifying first ray mobility is crucial to understand aberrant foot biomechanics. A novel device (MAP1st) that can perform measurements of first ray mobility in different weightbearing conditions, foot alignments, and normalization was tested. The reliability of these measurement techniques was assessed in comparison to a handheld ruler considered representative of the common clinical examination. Methods: The study included 25 participants (50 feet). Two independent raters performed baseline, test-retest, and remove-replace measurements of first ray mobility with MAP1st and the handheld device. The effects of non-, partial, and full weightbearing in subtalar joint neutral and the resting calcaneal stance position were assessed. Measurement normalization relative to foot size was also investigated. Intra- and interclass correlation coefficients (ICCs) were calculated for each device between the 2 raters. In addition, Bland-Altman plots were constructed to determine if fixed biases or substantial outliers were present. Results: Similar intrarater ICC values were found for both devices (≥0.85). However, interrater ICC values were substantially improved by MAP1st compared with the handheld device (0.58 vs 0.06). Bland-Altman plots demonstrated biases of 1.27 mm for the handheld ruler, and 2.88 to 0.05 mm and −1.16 to 0.00 for linear and normalized MAP1st measurements, respectively. Improved reliability was achieved with MAP1st for normalized assessments of first ray mobility while the foot was placed in partial- and full-weightbearing resting calcaneal stance positions. Conclusion: MAP1st provided reliable assessments of partial- and full-weightbearing first ray mobility. It should help investigators to explore the potential relationships between first ray function and aberrant foot biomechanics in future research. Level of Evidence: Level II, prospective cohort study.

Asymmetric Lambda Sign on Axial Weightbearing CT Scans of the Foot: An Indicator to Aid in the Diagnosis of Subtle Lisfranc Instability?

Category: Trauma; Midfoot/Forefoot Introduction/Purpose: Subtle Lisfranc instability, a spectrum of conditions resulting from trauma of individual structures within the Lisfranc ligamentous complex (LLC) including the dorsal- (DLL), interosseous- (ILL), and plantar Lisfranc ligaments (PLL) remain challenging to effectively diagnose. The current standard to asses these injuries is through bilateral weightbearing radiography. However, weight bearing computed tomography (WBCT), which provides a clearer visualization of osseous structures, joint spaces, and instability could also be utilized for evaluation. This study aims to define and report the occurrence rate of an ‘asymmetric lambda sign’ observed on axial WBCT imaging secondary to simulated purely ligamentous Lisfranc injuries of various severities subjected to increasing magnitudes of weightbearing conditions. It is hypothesized that this sign will be a reliable aid in detecting subtle Lisfranc instability, clinically. Methods: The asymmetric lambda sign was assessed on 24 match-paired cadaveric legs (mean age, 46.0 +- 14.8 years; mean weight, 80.2 +- 17.4 kg; mean body mass index, 25.3 +- 4.2 kg/m2). Dissection groups were described as follows: control intact LLC (group 1), dissection of the DLL (group 2), dissection of the DLL and ILL (group 3), dissection of the DLL, ILL, and PLL (group 4). After each dissection, CT scans were acquired in non- (NWB, 0 kg), partial- (PWB, 40 kgs), and full-weightbearing (FWB, 80 kgs) conditions. In a standardized axial view, the lambda sign was appreciated by visualizing the joint spaces between the medial cuneiform and the second metatarsal base (C1-M2), the medial and middle cuneiform (C1-C2), and the second metatarsal base and middle cuneiform (M2-C2). The asymmetric lambda sign was defined by a widening of the C1-M2 joint space relative to the C1-C2 or M2-C2 joint space (Fig). Results: The asymmetric lambda sign was observed in 25.6% (221/864) of all studies. This sign was not found in any intact specimens regardless of the weightbearing status. In group 2, this sign was observed in 4.2% of NWB, 15.3% of PWB, and 16.7% of FWB conditions. With the DLL and ILL dissected, simulating a more developed subtle LLC injury (group 3), this sign was observed in 15.3%, 27.8%, and 38.9% in NWB, PWB and FWB conditions, respectively. Additionally, the fully dissected specimens (group 4), demonstrated this specific sign in 33.3%, 72.2%, and 83.3% in NWB, PWB, and FWB conditions, respectively. The inter- and intra- observer reliability was calculated to a kappa value of .843 and .912. Conclusion: An asymmetric lambda sign viewed through axial WBCT imaging is a reliable indicator in the diagnosis of a complete Lisfranc ligamentous injury with secondary joint instability in partial and full weightbearing conditions as demonstrated using a cadaveric model. Clinically, this simple sign can be utilized as an aid to accurately evaluate and diagnose patients presenting with subtle Lisfranc instability.

Return to Weightbearing and High-Impact Activities Following Jones Fracture Intramedullary Screw Fixation

Background: Although the benefit of primary intramedullary (IM) screw fixation of fifth metatarsal Jones fractures in athletes is clear, limited data support its use in conventional patient populations. This study evaluated radiographic and functional outcomes following primary IM screw fixation in a series of Jones fractures to determine if similar excellent outcomes were achievable. Methods: We reviewed the data of 32 consecutive patients who underwent Jones fracture primary IM screw fixation by a single surgeon. Demographic risk factors of interest (age, gender, tobacco use, pertinent medical comorbidities, military service status, and prior nonoperative management) were collected prospectively. Primary outcomes included times to return to full weightbearing, radiographic union, and resumption of high-impact or restriction-free activities. Complications including reoperations were recorded. Categorical data are reported as frequencies, and statistical means with P values are reported for continuous variables. Mean age for the 32 patients was 33.4 years. Results: All 32 fractures healed uneventfully, and at mean follow-up time of 24.2 months, overall patient-reported satisfaction was 100%. Overall mean postoperative outcomes are as follows: 3.7 weeks return to full weightbearing, 10.8 weeks to radiographic union, and 13.0 weeks to resumption of restriction-free activities. Among the risk factors assessed, only preoperative peripheral vascular disease (PVD) and/or diabetes mellitus (DM) and active duty military service resulted in significantly increased and decreased time to resumption of restriction-free activities, respectively, but did not impact overall weightbearing or union times. Patient age, gender, and tobacco use had no effects on radiographic or functional outcomes. Conclusion: Primary IM screw fixation was a safe, reliable option for all appropriate operative candidates with Jones fractures and may result in similar early weightbearing, osseous healing, and expeditious return to full activities consistently reported in high-level athletes. Level of Evidence: Level IV, case series.

Three-dimensional kinematic change of hindfoot during full weightbearing in standing: an analysis using upright computed tomography and 3D-3D surface registration

Background Weightbearing of the hindfoot affects positional changes of the ankle joint and subtalar joint (ankle-joint complex [AJC]). However, it is difficult to assess the kinematic changes in the hindfoot in a natural full weightbearing condition using conventional CT or cone beam computed tomography (CT) due to limitations of acquiring foot images under a physiological weightbearing condition using those imaging modalities. Analysis of AJC kinematics using fluoroscopy and 2D-3D registration technique requires data on the number of steps and amount of time to build and match the bones. This study aimed to analyze the effect of full weightbearing on hindfoot motion when standing using upright CT and 3D-3D surface registration. Methods Forty-eight AJCs of 24 asymptomatic volunteers (13 women, 11 men) were examined under no weightbearing, 50% weightbearing, and single leg full weightbearing conditions while standing. The CT images were acquired from the distal femur to the whole foot using a 320-row upright CT scanner. The condition of each weightbearing stance was measured using a pressure mat. Bone-to-bone rotations of the talus relative to the tibia and calcaneus relative to the talus were evaluated using the surface registration technique. Image quality of the CT and intra- and interobserver reliabilities of the rotation angle were also evaluated. Results All CT images were excellent or good quality and the intra- and interobserver correlation coefficients for the angle were 0.996 and 0.995, respectively. The motion of the ankle joint and subtalar joint under 50% and 100% weightbearing were as follows (in degrees); the talus plantarflexed (5.1 ± 4.5 and 6.8 ± 4.8), inverted (1.3 ± 1.4 and 2.0 ± 1.6), and internally rotated (2.4 ± 4.2 and 4.3 ± 4.6) relative to the tibia, and the calcaneus dorsiflexed (2.8 ± 1.4 and 3.8 ± 1.7), everted (5.3 ± 2.6 and 8.0 ± 3.6), and externally rotated (3.0 ± 2.0 and 4.1 ± 2.4) relative to the talus, respectively. Conclusions The effect of weightbearing was clearly identified using an upright CT and the 3D-3D registration technique. Three-dimensional kinematics under static full weightbearing were opposite between the ankle and subtalar joints on their respective axes.