Modified fourth-generation minimally invasive technique with a modified K-wire fixation technique for hallux valgus: a biomechanical and clinical study

Abstract Background Minimally invasive techniques have become prominent in hallux valgus (HV) correction. However, prevalent third and fourth-generation methods using the “in-out-in” screw fixation often involve extensive intraoperative fluoroscopy, a steep learning curve, and higher costs. This study introduces and evaluates a modified fourth-generation technique featuring an extra-articular transverse osteotomy combined with a modified Kirschner wire (K-wire) fixation technique and the concept of “fourth-dimensional correction” (dynamic and static assessment). Methods The study comprised two parts. First, a finite element analysis (FEA) model was developed to compare the biomechanical performance (bone/implant stress, stability) of the modified K-wire fixation technique versus the standard “in-out-in” K-wire fixation at different lateral translation distances (4, 8, 12 mm). Second, a prospective case series of 108 patients (164 feet) with mild to severe HV who underwent the modified technique was analyzed. Outcomes included radiographic parameters (HVA, IMA, DMAA), the AOFAS score, complications, and intraoperative fluoroscopy usage. Results FEA demonstrated that the modified K-wire fixation technique provided stability comparable to the “in-out-in” technique while exhibiting significantly lower stress on the K-wires, suggesting a reduced risk of pin fracture. Clinically, all osteotomy sites achieved bony union. Significant improvements were observed in the entire cohort: mean HVA corrected from 36.93°±9.32° to 9.57°±4.88°, mean IMA from 14.86°±3.82° to 6.08°±3.43°, and mean AOFAS score from 61.26 ± 6.97 to 88.90 ± 4.68 (all P < 0.01). Excellent correction was maintained across all severity subgroups. The mean intraoperative fluoroscopy shots were 4.14 ± 3.04 per foot, showing a distinct learning curve that stabilized after approximately 25 cases, with usage significantly lower than rates reported for traditional “in-out-in” methods. Conclusion The modified fourth-generation minimally invasive technique with the modified K-wire fixation technique is biomechanically sound and clinically effective. It provides reliable radiographic and functional outcomes for HV of varying severities while substantially reducing intraoperative radiation exposure, offering a valuable alternative in the minimally invasive HV correction arsenal.