Hallux valgus interphalangeus: reliability of radiological assessment
Introduction
Hallux valgus interphalangeus (HVI) is a deformity of the first ray, characterised by valgus angulation of the distal phalanx on the proximal phalanx. It is considered present if the hallux interphalangeus angle exceeds 10° [1], [2], [3], [4]. Recent epidemiological studies suggest a high prevalence of HVI in patients presenting to foot and ankle surgeons [5].
HVI can present as an isolated deformity, it has been described in the adolescent population without traumatic precipitant and can develop after trauma to the interphalangeal joint [6], [7]. More commonly, however it is seen in combination with hallux valgus deformity. Strydom et al. demonstrated that a hallux valgus interphalangeus deformity (>10°) was seen in 56% of patients with hallux valgus angulation greater than or equal to 15°, and HVI contributed significantly, with a positive linear relationship to total valgus deformity of the hallux.
The concept of correcting the total valgus deformity of the hallux has led to the practise of addressing both the hallux valgus angulation via osteotomy and soft tissue procedures, but also the hallux valgus interphalangeus deformity, most commonly via medial closing wedge osteotomy of the proximal phalanx and fixation (Akin osteotomy) [8], [9], [10].
Reliable radiographic measurement of hallux valgus interphalangeus deformity therefore has a role in guiding surgical management decisions, assessing post-operative outcomes, and building a robust evidence base for ongoing practise.
There have been studies that determine the reliability of radiological measurements in the context of hallux valgus, showing good inter-observer and intra-observer reliability for many of the commonly utilised parameters [11], [12], [13], [14], [15], [16], [17], [18], [19].
These studies, showed good reliability of measurements such as hallux valgus angle, intermetatarsal angle when measured on weight bearing radiographs of feet, in a variety of patients with and without clinically diagnosed hallux valgus deformity. Both D’Arcangelo and Menz et al. demonstrated that these measurements correlate well with non-radiographic clinical severity scores of the deformity e.g. Manchester scale [20].
Of these studies, five included reliability analysis of measurement angles of hallux valgus interphalangeus deformity specifically. Three looked at the hallux interphalangeus angle [13], [14], [17] and two looked at both the hallux interphalangeus angle and the distal articular set angle [16], [19].
The most commonly assessed angle was the angle between the long axis of the two phalanges of the hallux, the hallux interphalangeus angle (Fig. 1a). These studies showed a reasonable level of intra and inter-observer reliability for this angle with intra-class correlation co-efficients (ICC) ranging from 0.66 to 0.98 [13], [14], [16], [17], [19].
The distal articular set angle is measured between a line perpendicular to the longitudinal axis of the proximal phalanx and a line delineating the orientation of the proximal phalangeal base articular surface (Fig. 1b). Balding and Sorto published a radiological study in 1985 popularising the use of this angle, after initially being described by Piggott in 1960 [21], [22]. Of the studies listed above, reasonable inter and intra-observer reliability for measurement of the distal articular set angle was found (ICC ranging from 0.72 to 0.82). [N.B Lee et al. refer to the distal articular set angle as PPAA.]
However, these studies measured angles in radiographs of non-operated feet in either normal volunteers or patients presenting with clinically diagnosed hallux valgus, with no reliability analysis of their application to post-operative imaging. Furthermore, there have been no reliability analyses of another angle utilised in our department to assess interphalangeus deformity, the proximal to distal phalangeal articular angle. This is the angle between the effective articular surface of the proximal and distal articular ends of the proximal phalanx of the hallux (Fig. 1c). It is unclear when this angle was first described, however it has been adopted by other authors to assess HVI [23].
The aim of the study is to investigate the reliability of measurements of these three angles, (hallux interphalangeus angle, distal articular set angle and the proximal to distal phalangeal articular angle) in the assessment of hallux valgus interphalangeus in both the preoperative and post-operative radiographs.
Section snippets
Material and methods
This retrospective observational radiological study was approved by our local research and development department.
Results
A total of 70 radiographs from 28 patients were included in the study (7 patients with bilateral radiographs). The 35 feet were x-rayed at two separate time points; pre and post hallux valgus surgery. There were 4 males and 24 females (M: 14%, F: 86%), with a mean age of 54 years (range 20–80).
17 patients underwent Chevron osteotomy; out of them fifteen had an adjunct Akin osteotomy, while 18 patients underwent SCARF osteotomy and all of them had an adjunct Akin osteotomy.
Inter-observer
Discussion
Hallux valgus deformity is one of the most common musculoskeletal disorders in the orthopaedic foot and ankle clinic. A recent survey in the United Kingdom suggested that 28.4% of adults have hallux valgus deformity [24].
It occurs frequently with a medial deviation of the first metatarsal bone, a deformity on the phalangeal bone and interphalangeal joint, and pronation with sesamoid subluxation.
A thorough knowledge and understanding of the pathologic conditions present with hallux valgus
Conclusion
Hallux interphalangeus angle and proximal to distal phalangeal articular angle measurements of hallux valgus interphalangeus have excellent intra and inter-observer reliability, both pre and post hallux valgus surgery. The distal articular set angle has lesser agreement within and between observers but remains at acceptable levels.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Conflict of interest
The authors declare that they have no conflict of interest.
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2021, Foot and Ankle SurgeryCitation Excerpt :which is formed by a line perpendicular to the midshaft axis of the proximal phalanx and the line running through the edges of the distal articular surface of the proximal phalanx of the greater toe. Therefore, the PDPAA might describe HVI deformity more precisely and reliably than does the HIA [13–15]. In contrast, the PPAA and the DPAA describe parts of the phalangeal deformity only.