Radiographs Over-Estimates Joint Space Narrowing in Hallux Rigidus in Comparison to Weight-Bearing Computed Tomography

Category: Other; Bunion Introduction/Purpose: Twenty years ago, Coughlin and Shurnas proposed a clinical and radiographic classification grading scale for hallux rigidus (HR). Radiographic grading was based on weight-bearing anteroposterior and lateral conventional radiographs. Radiographic metrices include joint space width, a narrowing percentage of the dorsal joint space, and sesamoidal changes such as enlargement, irregularities, and sclerosis. Dorsal osteophytes were the main findings in all grades. The aim of this study was to compare hallux rigidus radiographic findings between conventional and weight-bearing computed tomography (WBCT). We hypothesized that radiographs overestimate joint space narrowing due to bone overlap and osteophytes. Methods: In this IRB approved study, all patients who had weight-bearing radiographs and WBCT for HR were included. Patients with previous hallux surgeries or associated severe hallux valgus were excluded. The first metatarsophalangeal joint (1st MTPJ) was measured using the summation method. (figure1) Dorsal osteophytes were measured. We measured the percentage of narrowing of the dorsal articular surface on a weight-bearing lateral/sagittal view. We evaluated the proximal phalanx (P1), first metatarsal (M1), and sesamoids (SS) for cysts. (Figure 1) All measurements were performed by two fellowship-trained orthopaedic foot and ankle surgeons. A comparison between groups was performed using the t-test or the Mann-Whitney U test according to data normality. Inter-rater reliability was evaluated using inter class correlation coefficient. Significant differences were established for p-values under 0.05. Results: The study included 21 patients; 13 were males. The average age was 55.9 ± 12.5 and the BMI was 28.9 ± 6.5. The joint space width was significantly larger on WBCT (1.9mm ± 0.44) vs. (0.92mm ± 0.53) (P < 0.001). WBCT showed less narrowing of the dorsal articular surface (46.59% ± 18.8%) vs. (22.78% ± 8.71). There was no difference in the size of dorsal spurs (4.57 mm ± 1.49) vs. (4.39 mm ± 1.56) (P = 0.684). WBCT detected loose bodies in nine patients, while radiographs detected them only in six patients. Sesamoid changes were appreciated on the WBCT image of all patients. Conclusion: Radiographic parameters of the Coughlin classification of hallux rigidus are better evaluated with WBCT. WBCT showed less narrowing of the dorsal joint space as it’s not affected by the overlap of other bones. Dorsal spurs may give the false impression of joint space narrowing on radiographs. Dedicated radiographic sesamoid views (not routinely ordered) are required to study sesamoid changes. The detection of less joint space affection could potentially lead to more joint sparing surgeries.