Normative Distribution of First Metatarsal Axial Rotation

Abstract

Background: First metatarsal (M1) axial rotation is recognized as a clinically relevant component of hallux valgus deformity. Methods to realign the M1 in 3 dimensions have been developed. One goal of these operations is to restore normal rotation of the first ray. The aim of this study is to provide estimates for the normal distribution of M1 rotation in patients without relevant anatomic pathology. Methods: Using stringent clinical and radiographic criteria, we evaluated a set of plain radiograph and weightbearing computed tomography (WBCT) images of 62 feet from a consecutive patient database. Subjects included had normal foot alignment without bunion symptoms. M1 rotation of each foot was measured using 2 unique methods (Saltzman et al and Kim et al methods). Measurement of rotation was performed by 2 observers from coronal WBCT images. Mean values and confidence intervals (CIs) of M1 rotation were calculated for each method. Inter- and intraobserver reliability values were also reported. Results: Mean M1 rotation values of 2.1 degrees (95% CI: 0.9-3.4) and 6.1 degrees (95% CI: 4.4-7.8) were identified using the Saltzman et al and Kim et al methods, respectively. Inter- and intraobserver reliability values were interpreted as excellent for both methods. Conclusion: In this study, we describe the natural distribution of the M1 axial rotation in subjects without bunion or other identifiable bony foot deformities. This information should provide a normative reference for surgeons correcting rotational issues of the first metatarsal. Level of Evidence: Level III.

Distal Metatarsal Articular Angle in Hallux Valgus Deformity. Fact or Fiction? A 3-Dimensional Weightbearing CT Assessment

“…Two recent articles evaluated the mean α angle in a normal population. 21,35 It appears that the mean value in a control population is around 6 degrees in pronation. Therefore, 6 degrees may be a better correction target.…”

“…It is currently unknown which measurement is appropriate for assessing first ray pronation, and the different measurements currently available give different values. 4,35,36 We choose the α angle because this measurement is relative to the ground, it is one of the first described in WBCT assessment, 16 and has proven reliability. 4,16,20,36 However, choosing another measurement might give us different results.…”

Intraoperative checking of the first ray rotation and sesamoid position through sonographic assistance

“…Second, the learning curve, the correct patient selection, and the availability of sonographic assistance could be some of the obstacles to its generalization. On the other hand, the coronal rotation of the first metatarsal has been reported in the literature to be significantly different in the same foot between full weight-bearing status and non-weight-bearing status [17][18][19]. Thus, performing the ultrasound on the operating table is a limitation that although we have tried to solve by performing simulated weight-bearing with the linear ultrasound probe, it should be taken into account.…”

Imaging Findings and First Metatarsal Rotation in Hallux Valgus

“…In 2 recent papers looking at first metatarsal rotation using WBCT, the mean MPA in the normal population is between 2.1 and 5.5 degrees, and the mean alpha angle is between 6.1 and 6.9 degrees. 27,39 Najefi et al 27 demonstrated that the normal range (representing 2 standard deviations (SDs) from the mean) of MPA is between −5 and 16 degrees for the MPA and −4 and 18 degrees for the alpha angle, whereas Steadman et al 39 identified the normal range as between −7.7 and 11.9 degrees for the MPA and −7.1 and 19.3 degrees for the alpha angle. The degree of first metatarsal pronation has, however, been found to be higher in patients with hallux valgus, although the reasons for this have not yet been fully established.…”

“…13,31 Nevertheless, the severity of first metatarsal rotation does not appear to correlate with the hallux valgus angle (HVA) nor with abnormal sesamoid position in patients with hallux valgus. 3,20,36 In a normal patient cohort using WBCT, Steadman et al 39 did show that there was a relationship between first metatarsal axial rotation and intermetatarsal angle (IMA); however, Najefi 27 et al found no correlations between MPA or alpha angle and IMA or HVA.…”