The metatarsaus adductus effect by the syndesmosis procedure for hallux valgus correction

Abstract

Aims: The purpose of this study is to examine the adductus impact on the second metatarsal by the nonosteotomy nonarthrodesis syndesmosis procedure for the hallux valgus deformity correction, and how it would affect the mechanical function of the forefoot in walking. For correcting the metatarsus primus varus deformity of hallux valgus feet, the syndesmosis procedure binds first metatarsal to the second metatarsal with intermetatarsal cerclage sutures.

Methods: We reviewed clinical records of a single surgical practice from its entire 2014 calendar year. In total, 71 patients (121 surgical feet) qualified for the study with a mean follow-up of 20.3 months (SD 6.2). We measured their metatarsus adductus angle with the Sgarlato's method (SMAA), and the intermetatarsal angle (IMA) and metatarsophalangeal angle (MPA) with Hardy's mid axial method. We also assessed their American Orthopaedic Foot & Ankle Society (AOFAS) clinical scale score, and photographic and pedobarographic images for clinical function results.

Results: SMAA increased from preoperative 15.9° (SD 4.9°) to 17.2° (5.0°) (p < 0.001). IMA and MPA corrected from 14.6° (SD 3.3°) and 31.9° (SD 8.0°) to 7.2° (SD 2.2°) and 18.8° (SD 6.4°) (p < 0.001), respectively. AOFAS score improved from 66.8 (SD 12.0) to 96.1 (SD 8.0) points (p < 0.001). Overall, 98% (119/121) of feet with preoperative plantar calluses had them disappeared or noticeably subsided, and 93% (113/121) of feet demonstrated pedobarographic medialization of forefoot force in walking. We reported all complications.

Conclusion: This study, for the first time, reported the previously unknown metatarsus adductus side-effect of the syndesmosis procedure. However, it did not compromise function restoration of the forefoot by evidence of our patients' plantar callus and pedobarographic findings. Level of Clinical Evidence: III Cite this article: Bone Jt Open 2021;2(3):174-180.

Keywords: Bunion; Hallux valgus; Metatarsus adductus; Metatarsus primus varus; Syndesmosis procedure.

Fig. 1

Sgarlato’s metatarsus adductus angle measurement method: Line A extends between the most lateral point of the fourth metatarso-cuboid and the calcaneo-cuboid joints. Line B extends between the most medial point of the talo-navicular and the medial cuneiform-first metatarsal joints. Line C extends between midpoints of lines A and B. Line D represents the longitudinal axis of the second metatarsal bone. Line E is perpendicular to line C and represents the longitudinal axis of the lesser tarsus. Sgarlato's angle is between the lines D and E.

Fig. 2

Schematic illustration of key features of the syndesmosis procedure.

Fig. 3

Cross-section of themetatarsus primus varus deformity demonstrating the failure of its tie-barsystem at the medial metatarsosesamoid ligament.

Fig. 4

a) Preoperative standing radiograph of a 55-year-old femalewith bilateral severe hallux valgus deformity Sgarlato’s metatarsus adductus angle (SMAA) 17° and 14.5°, intermetatarsal angle (IMA) 17.8° and 19.3°, and metatarsophalangeal angle (MPA) 35.6° and 48.1° of her left and right foot respectively. There was also overlapping toes with both second metatarsophalangeal joint (MPJ) dorsally subluxated. b) Her two-year postoperative standing radiograph showed the SMAA was 20° and 16.5°, IMA 7.2°and 6.3°, and MPA 19.9° and 13.7° of her left and right foot respectively. Both overlapping toes deformity and subluxated second MPJs were reduced and maintained. Preoperative metatarsosesamoid dissociation was also much improved. Both metatarsophalangeal joints and metatarsocuneiform joints’ congruences were improved. There was increased 2-3 intermetatarsal space from Figure 4a. c) Her preoperative pedobarographic study by F-scan revealed that most plantar force concentrated under midmetatarsal heads (red) during walking instead of the first ray (first metatarsal head and hallux) of normal feet. d) Her two-year postoperative pedobarographic F-scan revealed reduced mid metatarsal pressure bearing and increased first ray function.