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Background: First metatarsal pronation angle (MPA) is increasingly relevant in the management of hallux valgus and is assessed on weightbearing computed tomography (WBCT) and sesamoid-view weightbearing radiography (WBR). The purpose of this study is to compare MPA measured by WBCT against WBR to determine if any systematic discrepancy in MPA measurement exists between the 2 modalities., Methods: A total of 40 patients with 55 feet were included for study. MPA was measured in all patients by 2 independent readers on both WBCT and WBR with an appropriate washout period between measurement modalities. Mean MPA by WBCT and WBR were analyzed; interobserver reliability was calculated with an intraclass correlation coefficient (ICC) value., Results: Mean MPA as measured by WBCT was 3.7 ± 7.9 degrees (95% CI, 1.6-5.9; range -11.7 to 20.5). Mean MPA measured on WBR was 3.6 ± 8.4 degrees, (95% CI, 1.4-5.8; range -12.6 to 21.4). There was no difference in MPA as measured by WBCT compared to WBR ( P = .529). Interobserver reliability was excellent with an ICC of 0.994 for WBCT and 0.986 for WBR., Conclusion: Measurement of first MPA by WBCT and WBR was not significantly different. In our cohort of patients with and without forefoot pathology, we found that either sesamoid view weightbearing radiographs or weightbearing CT can be used reliably to measure first MPA and will generate similar values., Level of Evidence: Level IV, case series.

Background: There is increased evidence of first metatarsal hyperpronation in patients with hallux valgus, but its impact on the stability of the first metatarsophalangeal and metatarsosesamoid joints is unknown. A previous biomechanical study showed that an increase in hallucal pronation might lead to medial soft tissue failure of the first metatarsophalangeal joint. Conversely, dynamic studies on hallux valgus have shown that the first tarsometatarsal joint moves in supination during weightbearing, and supination was associated with an increase in the intermetatarsal angle (IMA) and hallux valgus angle (HVA)., Questions/purposes: (1) Does an increase in first metatarsal pronation cause an increase in hallucal pronation? (2) Can an intrinsic increase in first metatarsal pronation lead to first ray supination during weightbearing? (3) Can a combination of intrinsic first metatarsal hyperpronation and first metatarsophalangeal medial soft tissue failure increase supination of the first ray during weightbearing? (4) Is first ray supination during weightbearing associated with an increase in the IMA and HVA?, Methods: Twelve transtibial, nonpaired cadaver specimens without deformities were used. Each specimen underwent six weightbearing CT scans under different conditions. The first three CT examinations were performed without any osteotomy of the first metatarsal. The first was a simulated nonweightbearing condition. The second was a simulated weightbearing condition. The third was a simulated weightbearing condition with medial soft tissue release. Subsequentially, a 30° pronation osteotomy of the first metatarsal was performed, and the same sequence of weightbearing CT images was obtained. On each weightbearing CT image, the HVA, IMA, sesamoid rotation angle, metatarsal pronation angle (MPA), metatarsosesamoid rotation angle, and hallucal pronation (HP) were measured. Motions were calculated based on the differential values of these angular measurements produced by the six different conditions (weightbearing, medial soft tissue release, 30° pronation osteotomy, and combinations of these conditions). We compared means using a t-test for normally distributed variables and the Mann-Whitney U test for nonnormally distributed variables. Correlations were assessed with Pearson product-moment correlation coefficients., Results: We found that 30° pronation osteotomy of the first metatarsal increased the MPA and HP by 28° ± 4° and 26° ± 6°, respectively, in the nonweightbearing condition. No differences between the increase in MPA and the increase in HP were noted (mean difference 2° [95% CI -1° to 5°]; p = 0.20). Therefore, an increase in first metatarsal pronation caused an increase in hallucal pronation. When a 30° pronation osteotomy of the first metatarsal was performed, the first ray motion during weightbearing went from pronation to supination (4° ± 2° in pronation without osteotomy versus 4° ± 2° in supination after the osteotomy, mean difference 8° [95% CI 6° to 9°]; p < 0.001). Therefore, an intrinsic increase in pronation of the first metatarsal led to a first ray supination motion during weightbearing. When a first metatarsophalangeal medial soft tissue release was performed in addition to the 30° osteotomy of the first metatarsal, the supination motion of the first ray increased (4° ± 2° without medial soft tissue release versus 11° ± 7° after the release, mean difference 8° [95% CI 3° to 12°]; p = 0.003). Therefore, a combination of intrinsic first metatarsal hyperpronation and first metatarsophalangeal medial soft tissue failure increased supination of the first ray during weightbearing. Regarding static angular measurements, the HVA and IMA were not correlated with the MPA (ρ = 0.20; p = 0.09 and ρ = 0.22; p = 0.07, respectively). Regarding motions, as the HVA and IMA increased from nonweightbearing to weightbearing the pronation decreased, with strong correlations (ρ = -0.82; p < 0.001 and ρ = -0.77; p < 0.001, respectively). Therefore, a first ray supination during weightbearing was associated with an increase in the HVA and IMA., Conclusion: The combination of first metatarsal intrinsic hyperpronation and first metatarsophalangeal medial soft tissue failure led to a hallux valgus deformity in this cadaveric study. The static measurement of first metatarsal head pronation relative to the ground (MPA) did not reflect the real intrinsic pronation of the first ray, and foot and ankle specialists should be careful when interpreting these measurements. Hallux valgus is a dynamic condition, and the deformity could be more correlated with motions during weightbearing than with plain static measurements., Clinical Relevance: First ray supination compensating for first metatarsal intrinsic hyperpronation might be an important factor in the hallux valgus pathogenesis. Further in vivo studies involving nonweightbearing and weightbearing comparative assessments of hallux valgus and controls should be performed to confirm this pathomechanism., Competing Interests: All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request., (Copyright © 2022 by the Association of Bone and Joint Surgeons.)

Background: The association between forefoot and hindfoot position for planus and cavus feet is fundamental to the treatment of these deformities. However, no studies have evaluated the association between hindfoot alignment and first metatarsal (M1) axial rotation. Understanding this possible relationship may help to understand the deformity and improve patient care. The purpose of this study is to determine a correlation between hindfoot alignment and metatarsal rotation as assessed by weightbearing computed tomography (WBCT)., Methods: Patients who underwent weightbearing plain radiography (WBPR) and WBCT between 2015 and 2018 were evaluated. Hindfoot alignment was measured with the calcaneal moment arm (CMA). M1 rotation was measured using the Kim and Saltzman angles. Patient subgroups were created according to the severity of valgus/varus hindfoot alignment. Statistical analyses were performed to evaluate for association between variables., Results: Among the 196 patient feet included in the study, the average CMA was 6.0 ± 16.2 mm. The average Kim and Saltzman angles were 7.7 ± 12.9 degrees and 2.8 ± 13.1 degrees, respectively. The average Meary angle was 182.0 ± 11.9 degrees. A moderately strong association was found between the CMA and the Saltzman ( r = 0.641, P < .01) and Kim angles ( r = 0.615, P < .01). Hindfoot valgus was associated with M1 pronation and hindfoot varus with M1 supination. Additionally, inverse relationships between the Meary angle and the Saltzman ( r = -0.600, P < .01) and Kim angles ( r = -0.529, P < .01) were identified., Conclusion: In this well-defined cohort, we found substantial correlation between hindfoot alignment and M1 rotation. Hindfoot valgus was associated with M1 pronation, and hindfoot varus was associated with M1 supination. Surgeons correcting cavovarus/planovalgus deformities should be aware of this association and evaluate the need for first-ray derotation., Level of Evidence: Level III, retrospective cohort study.

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, retrospective cohort study.

Rotation of the first metatarsal (M1) as a potential etiological factor of hallux valgus (HV) deformity was described relatively early in the description of HV pathoanatomy. However, because biplanar radiographs have been the standard method for imaging HV, clinicians primarily developed measurement methods and corrective operations confined to 2 dimensions, medial-lateral and inferior-superior. Recently, as our understanding of HV pathoanatomy has further developed, aided in part by advanced imaging technology, M1 rotation about its axis ("axial rotation") and its implications for HV deformity and treatment has reemerged. The goal of this review is to summarize M1 rotation in HV from a historical perspective, to present the current understanding of its potential role in the etiology/pathogenesis of HV, and to summarize relevant imaging and operative considerations with respect to M1 rotation. Level of Evidence: Level III, systematic review.

Background: Surgical correction of deformity plays a central role in the treatment of hallux valgus deformity. However, complications or unintended outcomes are frequently noted in clinical series. There has been no rigorous systematic review of studies reporting outcomes of surgical treatment for hallux valgus deformity, to the best of our knowledge., Methods: We performed a systematic review of studies reporting the outcomes of surgical correction for hallux valgus deformity., Results: A total of 229 studies met the inclusion criteria. The pooled rates of postoperative patient dissatisfaction and postoperative first metatarsophalangeal pain were 10.6% and 1.5%, respectively. The overall rate of recurrent deformity was 4.9%., Conclusions: Hallux valgus surgery has been reported to have fairly consistent results and rates of complications or unfavorable outcomes., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background: Patients with ankle arthritis often present with concomitant hindfoot deformity, which may involve the tibiotalar and subtalar joints. However, the possible compensatory mechanisms of these two mechanically linked joints are not well known., Questions/purposes: In this study we sought to (1) compare ankle and hindfoot alignment of our study cohort with end-stage ankle arthritis with that of a control group; (2) explore the frequency of compensated malalignment between the tibiotalar and subtalar joints in our study cohort; and (3) assess the intraobserver and interobserver reliability of classification methods of hindfoot alignment used in this study., Methods: Between March 2006 and September 2013, we performed 419 ankle arthrodesis and ankle replacements (380 patients). In this study, we evaluated radiographs for 233 (56%) ankles (226 patients) which met the following inclusion criteria: (1) no prior subtalar arthrodesis; (2) no previously failed total ankle replacement or ankle arthrodesis; (3) with complete conventional radiographs (all three ankle views were required: mortise, lateral, and hindfoot alignment view). Ankle and hindfoot alignment was assessed by measurement of the medial distal tibial angle, tibial talar surface angle, talar tilting angle, tibiocalcaneal axis angle, and moment arm of calcaneus. The obtained values were compared with those observed in the control group of 60 ankles from 60 people. Only those without obvious degenerative changes of the tibiotalar and subtalar joints and without previous surgeries of the ankle or hindfoot were included in the control group. Demographic data for the patients with arthritis and the control group were comparable (sex, p=0.321; age, p=0.087). The frequency of compensated malalignment between the tibiotalar and subtalar joints, defined as tibiocalcaneal angle or moment arm of the calcaneus being greater or smaller than the same 95% CI statistical cutoffs from the control group, was tallied. All ankle radiographs were independently measured by two observers to determine the interobserver reliability. One of the observers evaluated all images twice to determine the intraobserver reliability., Results: There were differences in medial distal tibial surface angle (86.6°±7.3° [95% CI, 66.3°-123.7°) versus 89.1°±2.9° [95% CI, 83.0°-96.3°], p<0.001), tibiotalar surface angle (84.9°±14.4° [95% CI, 45.3°-122.7°] versus 89.1°±2.9° [95% CI, 83.0°-96.3°], p<0.001), talar tilting angle (-1.7°±12.5° [95% CI, -41.3°-30.3°) versus 0.0°±0.0° [95% CI, 0.0°-0.0°], p=0.003), and tibiocalcaneal axis angle (-7.2°±13.1° [95% CI, -57°-33°) versus -2.7°±5.2° [95% CI, -13.3°-9.0°], p<0.001) between patients with ankle arthritis and the control group. Using the classification system based on the tibiocalcaneal angle, there were 62 (53%) and 22 (39%) compensated ankles in the varus and valgus groups, respectively. Using the classification system based on the moment arm of the calcaneus, there were 68 (58%) and 20 (35%) compensated ankles in the varus and valgus groups, respectively. For all conditions or methods of measurement, patients with no or mild degenerative change of the subtalar joint have a greater likelihood of compensating coronal plane deformity of the ankle with arthritis (p<0.001-p=0.032). The interobserver and intraobserver reliability for all radiographic measurements was good to excellent (the correlation coefficients range from 0.820 to 0.943)., Conclusions: Substantial ankle malalignment, mostly varus deformity, is common in ankles with end-stage osteoarthritis. The subtalar joint often compensates for the malaligned ankle in static weightbearing., Level of Evidence: Level III, diagnostic study.

The hypermobile first ray has been implicated as contributing to the cause and progression of hallux valgus deformity. Deformity of the hallux is often accompanied by an enlarged first intermetatarsal (IM 1-2) angle. It has been hypothesized that subjects having an abnormally large IM 1-2 angle have laxity of the first ray. Objectives of this study were to compare dorsal mobility of the first ray in subjects with hallux valgus to asymptomatic controls, and to investigate the relationship between dorsal mobility and the IM 1-2 angle. Fourteen subjects (age 23-81) with hallux valgus were matched by gender and age to control subjects. The IM 1-2 angle was measured from radiographs. A load-cell device measured dorsal mobility of the first ray under a standard load of 55 N. Pearson's correlation coefficient identified a marginal correlation (r = .51) between IM 1-2 angle and dorsal mobility. An independent t-test showed a statistically (P < 0.01) larger amount of dorsal mobility in the group of subjects having hallux valgus. Mobility of the first ray was increased in subjects with hallux valgus and a large IM 1-2 angle may be an indicator of increased dorsal mobility.

Subluxation of the metatarsosesamoid joints frequently occurs with the development of hallux valgus deformity, and the restoration of a normal metatarsosesamoid articulation has been proposed as essential for achieving a biomechanically sound operative result. The position of the sesamoid bones on the AP radiograph is used often to assess the pre- and postoperative relationship between the hallucal sesamoids and the metatarsal sulci. We evaluated the validity of this approach. Thirty subjects with hallux valgus and 30 control subjects participated in this study by undergoing both AP and tangential weightbearing radiographs. The sesamoid station on the AP radiographs was compared with the position of the sesamoids on tangential radiographs, using a new continuous measure to estimate subluxation. In approximately half of the cases, we found a difference between the apparent sesamoid station on the AP radiograph and the true position on the tangential one. Increased metatarsal rotation was associated with misclassification of the sesamoid station on the AP radiograph. We conclude that the standard method for measuring the sesamoid station on the AP radiograph is not valid. Surgeons wishing to evaluate the metatarsosesamoid joint should obtain weightbearing tangential radiographs.

A method for measuring hallucal rotation or weightbearing tangential radiographs is described. Under controlled conditions using cadaver specimens, 10 degree changes in hallucal rotation were associated with a mean change in radiographically measured rotation of 10.6 degrees (S.D. = 2.3 degrees). A clinical study of 30 control patients and 39 patients presenting with a chief complaint of a bunion deformity was undertaken to assess the reliability of the measurement method. The overall reliability was high for both groups (r = 0.98). A significant difference was found between mean values for hallucal rotation in the two groups (P < 0.005). There is a modest association between increasing valgus deviation and increasing rotation of the hallux (r = 0.43, P < 0.01). This study suggests that bunion deformities involve variable degrees of axial and coronal plane rotations of the first metatarsophalangeal joint and that the concept of a planar "hallux valgus" deformity may insufficiently describe this three-dimensional clinical condition.

A laboratory cadaver model was used to assess the effects of the major anatomic components of hallux valgus deformity on first metatarsophalangeal flexion moments. The individual components of the flexor hallucis longus' effective tendon moment arm were evaluated as a function of imposed hallux valgus, of hallux pronation, and of combined hallux valgus and pronation. To simulate the effects of distal first metatarsal surgery, the components' changes after metatarsal head lateral translation or supination were assessed. Significant changes in effective tendon moment arm occurred with increases in the hallux valgus angle, with changes in the hallux pronation angle, and with combined increases in the hallux valgus angle and hallux pronation angles. The changes involved primarily were a redirection of the moment vector's projection within the superior and inferior plane or medial and lateral plane, rather than an appreciable alteration of the magnitude of the resultant. By contrast, neither translational nor rotational displacements of the metatarsal head influenced any of the individual components of the effective tendon moment arm.

A method for measuring first metatarsal rotation on weightbearing tangential radiographs is described. Under controlled conditions using cadaver specimens, 5 degree changes in first metatarsal rotation were associated with a mean change in radiographically measured rotation of 5.4 degrees (SD = 1.7 degrees). A clinical study of 30 hallux valgus and 30 control patients was undertaken to assess the reliability of the method of measurement. The overall reliability was high for both hallux valgus and control patients (r = 0.93 and 0.95, respectively). In these two groups, no significant difference was found between the mean values for first metatarsal rotation. Likewise, we found no correlation between first metatarsal rotation measured on tangential standing ("sesamoid" view) radiographs and the first metatarsophalangeal angle or the intermetatarsal 1-2 angle measured on anteroposterior standing radiographs.

The chevron osteotomy for hallux valgus was modified by addition of screw fixation and change of the osteotomy angle. Thirty-six patients underwent this modified osteotomy. All had mild to moderate symptomatic hallux valgus deformities. No other forefoot procedures were performed. Standing radiographs were taken before surgery, at 1 month after surgery, and, for the 15 patients who returned for long-term follow-up, at 1 year or more after surgery. Overall, 35/42 procedures were rated as satisfactory without reservations and 7 were rated as satisfactory with mild reservations. All patients stated that they had some improvement in their preoperative symptoms, which included pain, cosmetic concerns, and shoe wear difficulties. Radiographically, none of the capital fragments displaced and there were no malunions, nonunions, nor evidence of avascular necrosis. The average metatarsophalangeal-1 angle improved 8 degrees and the average intermetatarsal 1-2 angle improved 4 degrees. This modification is relatively simple, increases stability, and allows early weightbearing. In our experience, the modified chevron osteotomy has been a very reliable procedure for mild to moderate symptomatic hallux valgus deformity.