Inaccuracy of Forefoot Axial Radiographs in Determining the Coronal Plane Angle of Sesamoid Rotation in Adult Hallux Valgus Deformity. A Study using Weight-Bearing CT Scanning

BACKGROUND:Hallux abducto valgus (HAV) is a triplane deformity with recent attention given to the significance of correcting the coronal plane component. This study explored the accuracy of the forefoot axial study as a standard radiographic assessment method compared to weight-bearing CT scanning.METHODS:Twelve feet with HAV from 12 subjects were included in this study. Three images of the affected foot were taken: 1) forefoot axial radiograph (FFA), 2) weight-bearing CT scan with the foot in a position of a) maximum pronation (Pronated CT) and b) maximum supination (Supinated CT). Five investigators (three faculty members and two podiatric16 medical students) determined the sesamoid rotation angle (SRA) from each of the images. The measurements from a single investigator were used to compare the SRA means from each of the image types, while those from all five investigators were used to determine reliability.RESULTS:The mean SRA for the pronated CT position was 22.1 {plus minus} 7.6 degrees, while that for the supinated CT image was 10.5 {plus minus} 5.0 degrees. In comparison, the mean SRA determined from the FFA image was 12.2 {plus minus} 9.4 degrees. The mean SRA from the Pronated CT was significantly greater than both the Supinated CT (p<0.001) and the FFA SRA (p<0.005). There were no significant differences in mean SRA between the FFA and Supinated CT images (p=1.000). Results indicated a high reliability in measurements between investigators.CONCLUSIONS:Using weight-bearing CT, the findings of this study indicate that the sesamoids significantly alter their position in the coronal plane, as determined by the SRA, with changes in weight-bearing subtalar joint position. Moreover, the affected foot positioning required for determining the SRA from the forefoot axial radiograph appears to significantly underestimate the true SRA value. Thus, the use of this image in surgical HAV planning is called into question.

The true axial shoulder projection: Diagnostic aid for acromioclavicular joint dislocation?

Introduction Acromioclavicular joint dislocations are common. Differentiating between horizontal and vertical instability is challenging, but possible to diagnose on axial radiographs. No clear consensus for axial radiograph parameters currently exists. We aim to establish a reproducible technique to assess whether an axial radiograph represents a true axial view of the shoulder. Methods One hundred CT scans of normal uninjured shoulders were examined using multiplanar reformatting to assess the distance between the anterior glenoid (reference line) and anterior-most aspect of the acromion in the axial plane. Measurements were repeated and performed by multiple observers to give of intra- and inter-observer reliability. Results The mean distance from the anterior acromion to the reference line was −2.6 mm (i.e. posteriorly placed) (SD = 5.8 mm, range −16.9–13.2 mm). Most (89%) of the measurements were between 9 and −9 mm to the reference line. Intra-observer reliability was high with Cronbach’s α measurement as 0.997. Inter-observer reliability gave a Cronbach’s α measurement of 0.959. Conclusion When the anterior aspect of the acromion lies within 10 mm either side of a line parallel to the scapula blade at the anterior aspect of the glenoid on an axial radiograph, it represents a true axial projection of the glenohumeral joint (GHJ). Level of evidence: IV, Case series

Agreement and Reliability of Lateral Patellar Tilt and Displacement following Total Knee Arthroplasty with Patellar Resurfacing

Patellar position and alignment may be measured on routine axial radiographs by various techniques; however, the agreement and reliability of such measurements with a resurfaced patella remain unknown. This study evaluated the range and reliability of lateral patellar tilt and lateral patellar displacement following total knee arthroplasty (TKA) with a resurfaced patella among three observers on 45° Merchant view in 139 TKAs. Intraclass correlation coefficient (ICCs) were used to evaluate intraobserver agreement (IOA) and inter-rater reliability (IRR). IRR was high between each of the observers for lateral patellar tilt (ICC = 0.8) and lateral patellar displacement (ICC = 0.87). IOA was also high upon repeat measurement for the same observer for lateral patellar tilt (ICC ≥ 0.90) and lateral patellar displacement (ICC ≥ 0.86). Therefore, lateral patellar tilt and lateral patellar displacement are reproducible measurements of patellar position on a Merchant axial radiograph following a well-functioning TKA with a resurfaced patella.

Influence of Foot Position on the Measurement of First Metatarsal Pronation Using the First Metatarsal Axial Radiographs

Category: Other Introduction/Purpose: In hallux valgus (HV) surgery, the importance of correcting first metatarsal (1MT) pronation, as well as correcting adduction, has been increasingly recognized. A 1MT axial radiograph is a simple method to quantify 1MT pronation (see figure). However, this view does not provide the exact axial projection, and 1MT is angled on the image. Furthermore, the 1MT angle is dependent on the foot position and alignment. Therefore the measured pronation angle on the radiograph may not be the same as the “true” pronation along the 1MT long axis. The purposes of this study were to 1) quantify the difference between the measured 1MT pronation on the axial radiograph and the true pronation angle, and 2) determine the influence of foot position on the measurement. Methods: CT images of 10 feet from HV patients (HV group; age, 58 years; HV angle, 44°) and 10 feet from those without HV (non-HV group; age, 47years; HV angle, 12°) were obtained. Digitally reconstructed radiographs of the 1MT were generated from the CT images in a three-dimensional virtual space (see figure). 1MT was pronated along the long axis (true pronation angle). Then, images with different plantarflexion (25° to 35° in 5° increments) and adduction (-10° to 10°) angles were created. This procedure was repeated for different pronation angles (-10° to 30°), and 135 simulated 1MT axial radiographs were obtained from each bone. We measured the 1MT pronation angles in all images. Differences in the measured pronation angle and true pronation angle were calculated for each group. Correlations between the measurement difference and 1MT plantarflexion/adduction angles were assessed using the Spearman correlation coefficient. Results: The mean measurement differences were 0.7° and 1.0° for the HV group and non-HV group, respectively. The standard errors of the measurement were 0.5° and 0.6° for the HV group and non-HV group, respectively. There was no significant correlation between the measurement difference and plantarflexion angle (P = 0.92 and P = 0.92 for the HV group and non-HV group, respectively), nor between the measurement difference and adduction angle (P = 0.82 and P = 0.74). Conclusion: The measurement differences were low in both HV and non-HV feet, indicating that the 1MT pronation angle measured on the axial radiograph represented the true pronation angle along the long axis of 1MT. The measurement differences were consistent regardless of plantarflexion and adduction angles. Therefore, a variation of 1MT angle on the image, which can be caused by the misalignment of foot position while taking the radiograph and difference in foot alignment (such as flatfeet and cavus feet), did not affect the measurement. 1MT axial radiograph could be used as a valid and robust method to quantify 1MT pronation.

Measuring Sesamoid Position in Hallux Valgus

Measuring tibial sesamoid position is an important component of the preoperative radiographic evaluation of hallux valgus as it helps guide the surgeon in surgical selection. Tibial sesamoid position is typically measured on an anteroposterior (AP) radiograph on a scale from 1 to 7 as described by Hardy and Clapham. Some authors have advocated measuring the position on the sesamoid axial view, noting that the AP and axial views often yield different measurements. There is no consensus as to which view is more helpful in guiding the surgeon’s surgical decision. Weightbearing radiographs of 99 feet in patients with a clinical diagnosis of hallux valgus were retrospectively reviewed. Tibial sesamoid position was measured on the AP view using the 7-point scale of Hardy and Clapham. Tibial sesamoid position was also measured on the axial radiograph. Cohen’s kappa statistic was used to assess agreement of measurements obtained on the 2 views. There was poor agreement of the AP and axial views, with a kappa of 0.31. In our analysis of the data, it was determined that the lack of agreement was due mainly to X-rays showing tibial sesamoid positions of 4 and 5. A subgroup analysis of all X-rays with tibial sesamoids in positions other than 4 or 5 showed excellent agreement, with a kappa of 0.95. Anteroposterior and sesamoid axial views of feet with hallux valgus show excellent agreement in patients with the tibial sesamoid in positions other than 4 or 5. If the tibial sesamoid has a position of 4 or 5 on the AP, an axial view may be warranted to further understand the extent of deformity. Levels of Evidence: Diagnostic, Level IV: Case series