Symmetry and reliability of the anterior distal tibial angle and plafond radius of curvature

Mechanical Ankle Joint Axis Point on a Hip-to-Calcaneus Long Leg View Correlates Significantly With SPECT/CT Activation in Symptomatic Asymmetric Ankle Osteoarthritis

BACKGROUND

Asymmetric joint load is the main cause of development of ankle osteoarthritis (OA). Realignment surgery aims to transfer ankle joint load from the degenerative area toward the uninvolved area. Determination of the optimal shift is still challenging. When the degenerative area is correlated to the ankle joint mechanical axis establishing an optimal target angle for corrective surgery may become more feasible. The primary aim of our study was to investigate if the area of ankle joint activation on single-photon emission computed tomography and conventional computed tomography (SPECT/CT) imaging correlates with the mechanical ankle joint axis point (MAJAP).

METHODS

In this cross-sectional study, patients 18 years or older with symptomatic asymmetric ankle OA and a hip-to-calcaneus long leg view with SPECT/CT of the affected ankle were eligible for inclusion. Primary outcome was MAJAP divided into 3 alignment categories (medial shift, neutral, lateral shift). SPECT/CT activation was determined in 8 different areas of the ankle joint. A Spearman rho correlation coefficient was calculated to investigate the relationship between the alignment categories and SPECT/CT activation in the 8 areas.

RESULTS

Forty-nine patients (mean age 58.8 [SD 10.0] years) with 52 ankles with moderate to severe asymmetric OA were included. A significantly (Spearman rho -0.379 [P = .006] and Spearman rho -0.279 [P = .045]) higher proportion of ankles with radioisotope uptake in the anteromedial ankle joint areas (zones 1 and 5) was seen in the medial shift category. A significantly (Spearman rho .312 (P = .025)) higher proportion of ankles with radioisotope uptake in the anterolateral ankle joint area (zone 8) was seen in the lateral shift category.

CONCLUSION

We found in this patient group that the area of SPECT/CT uptake in asymmetric ankle OA was associated to MAJAP measured on hip-to-calcaneus weightbearing views, although the strength of the correlation is weak to moderate. Consequently, nonweightbearing metabolic SPECT/CT radiotracer uptake has the potential to help determine the area to unload in ankle joint-preserving alignment surgery.

Evaluation of distal tibia slope in pilon fractures after surgical fixation

INTRODUCTION

Alteration of sagittal alignment during fracture fixation directly impacts ankle motion in dorsiflexion and plantarflexion. Previously research measured the anterior distal tibia angle (ADTA) in a normal healthy population. The null hypothesis for this study is that ADTA is restored to normal range following unstable pilon fractures. The aim of this study is to identify the range of the ADTA in distal tibia fractures after surgical fixation, compared to a previously published normal population.

MATERIAL AND METHODS

A retrospective review of operative distal tibia fractures (AO/OTA classification 43A and 43C - 43B were excluded due to lower likelihood of fracture changing the ADTA) was performed. ADTA on lateral radiograph was measured as the angle relative to the tibia shaft.

RESULTS

100 patients with post-operative radiographs that met inclusion criteria were analyzed. The average ADTA was 6.9° (⌠=4.62°) with a maximum slope of 19.2° (i.e. anterior orientation) and a minimum of -3.3° (i.e. posterior orientation). The uninjured population had an average ADTA of 6.0° (range -2.0°-14°, ⌠=3.0°).

CONCLUSION

This analysis shows the average distal tibia sagittal alignment in the post-surgical group is similar to a normal, uninjured population. Large alterations in ADTA would directly impact the ankle in the plane of motion (i.e. negative ADTA would decrease ankle dorsiflexion). Considering ADTA as an objective intra-operative parameter optimizes sagittal plane alignment.

Symmetry of the left and right tibial plafond; a comparison of 75 distal tibia pairs

PURPOSE

Tibia plafond or pilon fractures present a high level of complexity, making their surgical management challenging. Three-Dimensional Virtual Planning (3DVP) can assist in preoperative planning to achieve optimal fracture reduction. This study aimed to assess the symmetry of the left and right tibial plafond and whether left-right mirroring can reliably be used.

METHODS

Bilateral CT scans of the lower limbs of 75 patients without ankle problems or prior fractures of the lower limb were included. The CT images were segmented to create 3D surface models of the tibia. Subsequently, the left tibial models were mirrored and superimposed onto the right tibia models using a Coherent Point Drift surface matching algorithm. The tibias were then cut to create bone models of the distal tibia with a height of 30 mm, and correspondence points were established. The Euclidean distance was calculated between correspondence points and visualized in a boxplot and heatmaps. The articulating surface was selected as a region of interest.

RESULTS

The median left-right difference was 0.57 mm (IQR, 0.38 - 0.85 mm) of the entire tibial plafond and 0.53 mm (IQR, 0.37 - 0.76 mm) of the articulating surface. The area with the greatest left-right differences were the medial malleoli and the anterior tubercle of the tibial plafond.

CONCLUSION

The tibial plafond exhibits a high degree of bilateral symmetry. Therefore, the mirrored unfractured tibial plafond may be used as a template to optimize preoperative surgical reduction using 3DVP techniques in patients with pilon fractures.

Using bilateral data in controls and patients with bilateral and unilateral pathology requires increased scrutiny

In many aspects of human research, capturing multiple measures from the same participant is common due to the symmetric nature of the human body (e.g., two eyes, ten fingers, two legs, etc.). This has established a concerning paradox in biomedical and clinical research. When the same condition exist bilaterally (controls or bilateral pathology), researchers often blindly include both (or multiple) measures into the statistical analysis. This assumes that measures between the two sides are statistically independent (uncorrelated). However, there are certain inherent factors within an individual (e.g., age, sex, physical activity, gait pattern, tissue characteristics, hormonal status, pain thresholds, etc.) that would point to a statistical dependence between bilateral measures. Conversely, in unilateral pathology, it is common practice to use the contralateral side as the comparator. This assumes the exact opposite, that sans pathology, bilateral measures are perfectly correlated without bias. Both of these assumptions can lead to errors in the study conclusions. Few studies have explored the statistical dependence between multiple measures from the same participant. Thus, the purpose of this perspective is to explore the statistical considerations associated with analyzing multiple measures from the same participant and provide recommendations for navigating the use of multiple, non-temporal, data points from the same participant. To give context for these recommendations, an example dataset involving patellofemoral kinematics is provided. Due to the prevalent use of bilateral data in the current literature and the resulting potential for invalid study conclusions, we recommend that future research use caution when using multiple measures from the same participant and apply proper statistical analysis (e.g., generalized estimating equations) when these measures are not independent. If the contralateral limb is used as a comparator in unilateral pathology, strong evidence must exist that the underlying pathology has not altered the measures of interest in this contralateral limb.

Distal Tibia Apex Posterior Angulation: A Normal Anatomic Variant Related to Hindfoot Alignment With Side-to-Side Symmetry

OBJECTIVES

The sagittal plane of the distal tibia has not been well-described. This study sought to characterize sagittal plane morphology, determine symmetry from side to side, and identify differences based on hindfoot alignment.

METHODS

One hundred twelve bilateral lateral weight-bearing ankle radiographs were retrospectively evaluated (224 ankles). Hindfoot alignment was classified as neutral, planus, or cavus using the Meary angle. The angle between the diaphyseal and distal tibia axes was measured, and the apex location relative to the plafond was recorded.

RESULTS

A mean distal tibia apex posterior angulation (DTAPA) of 2.0° (range -2° to 7°, SD = 2.06°) was located 8.0 cm proximal to the plafond. No difference was observed from side to side in DTAPA magnitude (P = 0.36) or location (P = 0.90). Planus alignment was associated with a significantly greater DTAPA (3.05°) as compared with neutral (1.89°) (P = 0.002) and cavus (1.25°) (P < 0.001) alignment.

CONCLUSION

The distal tibia has an apex posterior angulation, suggesting that the true anatomic axis of the tibia terminates just posterior to the plafond center. Hindfoot alignment is related to distal tibia morphology. DTAPA symmetry indicates that contralateral imaging can be used to guide reconstruction of patient-specific anatomy and alignment. Knowledge of the DTAPA may help mitigate sagittal malalignment during distal tibia fracture surgery.

Application of symmetry evaluation to deep learning algorithm in detection of mastoiditis on mastoid radiographs

As many human organs exist in pairs or have symmetric appearance and loss of symmetry may indicate pathology, symmetry evaluation on medical images is very important and has been routinely performed in diagnosis of diseases and pretreatment evaluation. Therefore, applying symmetry evaluation function to deep learning algorithms in interpreting medical images is essential, especially for the organs that have significant inter-individual variation but bilateral symmetry in a person, such as mastoid air cells. In this study, we developed a deep learning algorithm to detect bilateral mastoid abnormalities simultaneously on mastoid anterior-posterior (AP) views with symmetry evaluation. The developed algorithm showed better diagnostic performance in diagnosing mastoiditis on mastoid AP views than the algorithm trained by single-side mastoid radiographs without symmetry evaluation and similar to superior diagnostic performance to head and neck radiologists. The results of this study show the possibility of evaluating symmetry in medical images with deep learning algorithms.

Increasing grades of frontal deformities in knee osteoarthritis are not associated with ligamentous ankle instabilities

PURPOSE

Varus or valgus deformities in knee osteoarthritis may have a crucial impact on ankle subtalar range of motion (ROM) and ligamentous stability. The purpose of this study was to assess whether the grade of ankle eversion and inversion rotation stability was influenced by frontal deformities of the knee joint.

METHODS

Patients who were planned to undergo total knee arthroplasty (TKA) were prospectively included in this study. Patients were examined radiologically (mechanical tibiofemoral angle (mTFA), hindfoot alignment view angle (HAVA), anterior distal tibia angle (ADTA)) and clinically (ROM of the knee and ankle joint, foot function index, knee osteoarthritis outcome score). Ankle stability was assessed using an ankle arthrometer (AA) to test inversion/eversion (ie) rotation and anterior/posterior (ap) displacement stability of the ankle joint. Correlations were calculated using Pearson's coefficient, and differences between two independent groups of nonparametric data were calculated using a two-sided Wilcoxon signed rank test.

RESULTS

Eighty-two (varus n = 52, valgus n = 30) patients were included. The preoperative mTFA significantly correlated with the HAVA (Pearson's correlation = - 0.72, p < 0.001). Laxity testing of the ankle demonstrated that in both varus and valgus knee osteoarthritis, higher grades of mTFA did not correlate with the inversion or eversion capacity of the ankle joint. The ADTA significantly correlated with the posterior displacement of the ankle joint (cor = 0.24, p = 0.049).

CONCLUSIONS

This study could not confirm that higher degrees of frontal knee deformities in osteoarthritis were associated with increasing grades of ligamentous ankle instabilities or a reduced ROM of the subtalar joint.

LEVEL OF EVIDENCE

II.