Medial sesamoid position in moderate to severe hallux valgus: Correlation between three radiographic measurements

Hallux valgus, one of the most common causes of forefoot pain, is characterized by pain in the first metatarsophalangeal (MTP) joint concomitant with an increase in the hallux valgus and intermetatarsal angles (IMAs), lateral subluxation of the sesamoids, and protonation of the great toe [[1], [2], [3]]. Several authors have reported that lateral subluxation or displacement of the sesamoids is correlated with the severity of hallux valgus deformity [1,4,5]. Furthermore, when the sesamoids are displaced laterally due to the valgus angulation and protonation of the first MTP joint, the flexor and extensor hallucis longus tendons are also displaced. These tendons place a dynamic, laterally directed force on the hallux and may contribute to a progressive hallux valgus deformity or postoperative recurrence [6,7]. Therefore, the hallux valgus correction and reduction of the subluxated sesamoids are important for the successful surgical intervention for hallux valgus deformities. In previous studies, the incomplete reduction of the sesamoids after corrective metatarsal osteotomy has been considered a risk factor for the recurrence of hallux valgus deformities [[8], [9], [10], [11], [12], [13]]. However, in general, the degree of subluxation of the sesamoids during the hallux valgus surgery is relatively not well recognized compared to the hallux valgus angle (HVA) and IMA. Hence, it is important to assess the status of the sesamoid subluxation preoperatively and the extent of sesamoid reduction postoperatively.

Several radiographic methods are available for evaluating the degree of subluxation and sesamoid reduction. The radiographic weight-bearing foot anteroposterior (AP) and tangential sesamoid views are often used to assess the relationship between the sesamoid and metatarsal bone [14]. However, these methods have limitations pertaining to the evaluation of the position of the sesamoid. Weight-bearing AP radiographs are misrepresentative due to the rotational component of hallux valgus deformity [[15], [16], [17]]. Simultaneously, the tangential sesamoid view requires the dorsiflexion of the hallux, and the sesamoid position varies with the degree of hallux dorsiflexion. Consequently, the prevalence of sesamoid subluxation may be underestimated [14]. Moreover, correctly determining the position of the sesamoid with severe varus of the first metatarsal is difficult using the tangential sesamoid view [5]. Recently, full or partial weight-bearing computed tomography (CT) scans have been used to assess the sesamoid-first metatarsal head complex. CT makes it possible to reconstruct the images in any plane, allowing for a more detailed assessment of the sesamoid position. However, it is difficult to perform a CT scan with full weight bearing [1,5,18]. Consequently, it is challenging to determine the most accurate test owing to the limitations of each method; hence, several methods should be utilized concomitantly. However, there has been little research on the correlation between these radiographic measurements.

This study aimed to evaluate the degree of reduction of the medial sesamoid through three various radiographic measurements pre- and postoperatively in patients with moderate-to-severe hallux valgus and investigate the correlation between imaging methods in the evaluation of medial sesamoids. We conducted a preoperative and postoperative assessment of the medial sesamoid position (MSP) using weight-bearing AP, tangential sesamoid, and semi-weight-bearing CT axial views in patients who had undergone surgery for hallux valgus. The correlation between these three radiographic methods was analyzed, and the degree of postoperative reduction in the medial sesamoid was measured.

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