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The role of the medial capsule and transverse metatarsal ligament in hallux valgus deformity including stability of the first metatarsophalangeal and adjacent joints was investigated in vitro. The three-dimensional positions of the proximal phalanx, first metatarsal, and second metatarsal before and after sectioning the medial capsule and metatarsal ligament were measured using a magnetic tracking system. Valgus deformity of the hallux increased with medial capsule sectioning an average of 22.3 degrees +/- 6 degrees. Valgus deformity of the hallux increased with medial capsule and metatarsal ligament sectioning an average of 27.4 degrees +/- 9.1 degrees. Valgus deformity of the hallux did not change significantly after sectioning the metatarsal ligament only. No significant changes were found in varus and eversion of the first metatarsal, in valgus of the second metatarsal, in the distance between first and second metatarsal heads after sectioning the medial capsule, or in the metatarsal ligament. This study shows the importance of the medial capsule in hallux valgus deformity. The transverse ligament did not contribute substantially to cause the deformity.

This study compares the standardized measurements of the foot in nonweight-bearing and weight-bearing radiographs. Both normal and hallux valgus patients were studied. The results show that some changes thought to occur with weight-bearing cannot be consistently demonstrated. Obtaining both weight-bearing and nonweight-bearing views may not be routinely indicated in all patients.

The pathomechanics for the development of the hallux valgus deformity takes place at the first metatarsophalangeal joint--the sesamoid complex. The sesamoid complex consists of seven muscles, eight ligaments, and two sesamoid bones. When the first metatarsal escapes the complex and drifts medially, the sesamoids remain twisted in situ, several of the ligaments "fail," and others contract. The authors propose reduction of the metatarsus primus varus by first metatarsal osteotomy and appropriate ligament releases and plications to restore alignment. A detailed understanding of the pathomechanics is essential for proper interpretation of the problems and anticipated lasting surgeries.

The first metatarso-sesamoid joint is separately identified from the first metatarso-phalangeal joint and its anatomical characteristics are described from a study of one hundred anatomical specimens of normal adult and children's feet and two hundred radiographs of patients' feet. The author finds that the metatarso-sesamoid joint is assymmetrical both in children and adults, the medial surface being larger than the lateral. The medial sesamoid lies centrally, and the lateral sesamoid lies laterally, under the head of the first metatarsal. A knowledge of the shape and function of this joint is important in understanding the pathology as well as the therapeutic indications of various conditions of forefoot imbalance, mainly of hallux valgus.

Dissection and roentgenographic findings in 35 nonoperative cadaveric and freshly amputated feet were correlated with disorders of the first day--specifically the sesamoids. There are four noteworthy factors associated with first ray pathology. The most significant are axial rotation of the first metatarsal bone and degenerative changes at the first metatarsophalangeal joint. Significant anatomic variations can be correlated with failed bunion surgery.

The normal characteristics of the hallux sesamoid bones were studied in 200 toes (100 dissections and 100 radiographs from patients with hallux valgus), and pathological changes were recorded. Normally each sesamoid articulated with a separate groove on the plantar surface of the first metatarsal head. A bony ridge on the head separated these grooves. Bipartite sesamoids were found in 4% of the toes. Osteoarthritic changes manifested by deformity, irregularity, lipping, cysts in the sesamoids and in the heads of the first metatarsal, and erosions in the articular surfaces were present in 32% of the dissected toes. Fusion of the sesamoids was found in 6%. Ankylosis between the sesamoids and the head of the metatarsal was observed in 4%. In the toes affected by hallux valgus the sesamoids, together with the plantar pad and the tendon of the flexor hallucis brevis, were displaced laterally to a variable degree. In severe deformities the lateral sesamoid was dislocated lateral to the first metatarsal head and the medial sesamoid occupied the groove originally corresponding to the lateral sesamoid, while the metatarsal ridge separating the two sesamoids tended to disappear. Osteoarthritis of the metatarsophalangeal joint frequently accompanied hallux valgus.

The authors investigated the statistical relationship and significance between the transverse and sagittal plane proximal articular set angles both radiographically and intraoperatively. The analysis revealed a highly significant difference between the means of the respective measurements. Although the radiographic and intraoperative findings were found to be related for the transverse plane proximal articular set angle, the transverse plane PASA was approximately 7 degrees greater when measured intraoperatively. The concept of a sagittal plane PASA was also introduced. The significance of accurate measurements in the surgical correction of hallux valgus was also examined.