Basal Closing Wedge Osteotomy

♦ INTRODUCTION

Hallux valgus consists of a complex pathology with a multifactorial etiology involving anatomical, hereditary, and biomechanics factors.¹,² There are numerous surgical techniques described, including distal, diaphyseal, or proximal osteotomies. Regardless of the technique chosen, the multiple intrinsic factors involved in the pathophysiology of this disease must be corrected.³,⁴

The basal closing wedge osteotomy (BCWO) of the first metatarsal is a popular procedure used for years to treat hallux valgus associated with metatarsus primus varus.⁵,⁶ As a proximal metatarsal procedure, this osteotomy provides a great potential for correction and is traditionally recommended for moderate to severe hallux valgus with large intermetatarsal angle (IMA).⁵,⁶ This technique was first described in 1901 by Loison as a lateral basal closing wedge of the first metatarsal fixed with Kirschner wires (K-wires).⁷ Over time, this procedure underwent some modifications and was consolidated as an oblique wedge osteotomy with a medial hinge at the base of the first metatarsal fixed with screws.⁸,⁹,¹⁰ With the more recent introduction of minimally invasive surgery, this technique has once again evolved.¹¹ BCWO can be performed percutaneously, thus combining the benefits of a stable osteotomy fixed by screws with minimal soft-tissue manipulation.¹²,¹³ The purpose of this chapter is to present the general technical considerations for percutaneous BCWO.

♦ INDICATIONS AND CONTRAINDICATIONS

The indication for the percutaneous BCWO is moderate to severe hallux valgus cases with an incongruent first metatarsal phalangeal joint (1MTPJ) in patients with good bone quality. This technique is preferred over the distal osteotomies in those cases with a severe deformity due to a large IMA, in which the size of the first metatarsal head would not be wide enough to appropriately close the intermetatarsal space following a 100% lateral translation¹²,¹³ (Figure 3.1).

BCWO can also be performed in other circumstances. In patients with moderate to severe hallux valgus with congruent 1MTPJ due to a pathological distal metatarsal articular angle (DMMA), the percutaneous BCWO can be used as long as it is associated with a distal procedure.³,¹⁴ Hypermobility of the first tarsometatarsal joint (1TMTJ) is not necessarily a contraindication as with the percutaneous BCWO the proximal fragment is fixed in the most medialized position, as is done with the percutaneous chevron osteotomy.¹²,¹³,¹⁵ Because the BCWO resects a basal wedge, thus shortening the first metatarsal, in patients with associated transfer metatarsalgia with plantar callosities, the authors recommend adding a minimally invasive distal metatarsal osteotomy of the second, third, and fourth metatarsals.¹⁶ One of the limitations of the BCWO is the lack of rotational correction of the first ray in light of the integrity of the dorsomedial hinge. Given the attention that the three-dimensional correction of bunions is attracting the readers need to understand the implications of the BCWO and therefore the need to possibly having to add a distal metatarsal osteotomy to correct the sesamoid position.¹⁷,¹⁸

Figure 3.1 Schematic view of a severe hallux valgus with a large intermetatarsal angle in which the size of the first metatarsal head is not wide enough to cover the intermetatarsal space after a 100% lateral translation.

♦ PATIENT HISTORY AND PHYSICAL EXAMINATION

Patient history includes duration of symptoms, impact of the bunion on activity levels, footwear restrictions, and associated clinical comorbidities such as diabetes, vasculopathy, and rheumatologic conditions.

A comprehensive physical examination of a patient with hallux valgus should be carried out with the patient weight bearing as well as non-weight bearing and must include assessment of the gait, the hindfoot, midfoot, and forefoot alignment. Special attention should be directed toward the 1MTPJ evaluating its position, range of motion, deformity reducibility, and areas of tenderness. Any limitation in either dorsiflexion or plantarflexion of the 1MTPJ should be noted and compared to the contralateral foot as it can suggest intra-articular degeneration.¹⁹ The first ray hypermobility is clinically assessed through the first ray splay test (Figure 3.2A) and the range of motion analysis of the 1TMTJ.¹⁵ The associated lesser toe deformities, plantar callosities, metatarsalgia, and gastrocnemius contracture must also be documented.¹⁹

♦ IMAGING STUDIES

Weight-bearing three-view radiographs are crucial for the evaluation of hallux valgus and play an important role in classifying the severity of the deformity and its surgical treatment. The most commonly used measurements include the hallux valgus angle (HVA), the IMA between the first and second rays (IMA), the DMMA, and the sesamoids position according to the Hardy and Clapham classification.²⁰ The true IMA can be assessed with a radiographic splay test¹⁵ (Figure 3.2B).