Analyzing Treatment Outcomes in Scaphoid Nonunion: A Comparative Study of Humpback Deformity versus Dorsal Translation

Scaphoid nonunion has the potential to advance into scaphoid nonunion advanced collapse (SNAC), causing alterations in biomechanics of the carpal joint, arthritis, and deformities arising from malunion. The position of the fracture about the apex of the dorsal scaphoid ridge serves as a dependable indicator for assessing progression of scaphoid nonunion deformity. Due to the dorsal intercarpal ligament (DIC) attaches to apex of the scaphoid dorsal ridge, after fracture distal then apex, causing volar flexion of the distal pole fragment leading to humpback deformity. More proximal fracture lines than dorsal apex exhibit relative stability with mild dorsal translation due to connection with lunate and ligament. However, the anatomical similarity to proximal pole fractures raises concerns about reduced blood flow. For this reason, this study aims to compare and analyze the treatment results and characteristics accord to the type of deformity in groups that performed same cancellation auto bone graft and screw fixation.

A retrospective analysis was conducted , 70 patients were included, and the clinical assessment encompassed Modified Mayo Wrist Score (MMWS), DASH score, range of motion, and complications. Radiological evaluations involved examining bone union status, as well as parameters such as lateral intra-scaphoid angle (LISA), scapholunate angle (SLA), radiolunate angle (RLA), scaphoid length, and SL ratio.

Among the patients included in the study, there were 65 males and 5 females, with an average age of 36.8 years. The analysis involved 33 cases of Humpback-like deformity and 37 cases of Dorsal translation deformity. In cases of Humpback-like deformity, 7 exhibited a notable humpback deformity with LISA greater than 40 degrees. Bone union occurred in 32 cases, with an average union time of 4.5 months. 3 cases resulted in nonunion, with 2 being asymptomatic, and 1 requiring additional quadruple joint fusion due to pain and swelling. For cases of Dorsal translation deformity, 31 exhibited bone union, and the average union time was 5.8 months. 8 cases resulted in nonunion, with 7 being asymptomatic, and 1 causing pain, leading to an additional procedure.

In the analysis of this study, bone union was successfully attained in the majority of cases presenting both groups, with few complications observed. Nevertheless, in instances of dorsal translation deformity, the duration required for bone union was comparatively longer than that for humpback-like deformity. This discrepancy may be attributed to the fracture line being situated more proximally, reduced blood flow in that region.

Keywords: Scaphoid, Non-union, Deformity, Osteosynthesis