The Use of Advanced Semiautomated Bone Segmentation in Hallux Rigidus

Background: Weightbearing computed tomography (WBCT) measurements allow evaluation of several anatomical points for a correct clinical-radiographic diagnosis of pathologies, such as hallux rigidus (HR). In addition, a new semiautomatic segmentation software obtains automated 3D measurements from WBCT scan data sets, minimizing errors in reading angular measurements. The study’s objective was (1) to evaluate the reliability of WBCT semiautomatic imaging measures in HR, (2) to evaluate correlation and agreement between manual and semiautomatic measures in the setting of HR, and (3) to compare semiautomatic measurements between pathologic (HR) and standard control groups. Methods: A retrospective study of HR patients was performed including 20 feet with HR. WBCT manual and semiautomatic 3D measurements were performed using the following parameters: (1) first metatarsal-proximal phalanx angle (1stMPP), (2) hallux valgus angle (HVA), (3) first to second intermetatarsal angle (IMA), (4) hallux interphalangeal angle (IPA), (5) first metatarsal length (1stML), (6) second metatarsal length (2ndML), (7) first metatarsal declination angle (1stMD), (8) second metatarsal declination angles (2ndMD), and (9) metatarsus primus elevatus (MPE). The differences between pathologic and control cases were assessed with a Wilcoxon test. Results: Interobserver and intraobserver agreement for manual vs semiautomatic WBCT measurements demonstrated excellent reliability. According to the Pearson coefficient, there was a strong positive linear correlation between both methods for the following parameters evaluated: HVA (ρ = 0.96), IMA (ρ = 0.86), IPA (ρ = 0.89), 1stML (ρ = 0.96), 2ndML (ρ = 0.91), 1stMD (ρ = 0.86), 2ndMD (ρ = 0.95), and MPE (ρ = 0.87). Comparison between the pathologic group with HR and the control (standard) group allowed for the differentiating of the pathologic (HR) from the non-pathologic conditions for MPE (p < 0.05). Conclusion: Semiautomatic measurements are reproducible and comparable to measurements performed manually, showing excellent interobserver and intraobserver agreement. The software used differentiated pathologic from nonpathologic conditions when submitted to semiautomatic MPE measurements. Level of Evidence: Level III, retrospective comparative study.