Comparative Study of Patients Treated with the Original Lapidus Procedure That Evolved with and without Fusion Between the First and Second Metatarsals
Authors: Nishikawa Danilo Ryuko , Duarte Fernando A. , Miranda Bruno R. , Saito Guilherme H. , Mendes Alberto , Prado Marcelo P. 
Published: November 2022

Category: Midfoot/Forefoot; Bunion Introduction/Purpose: The Original Lapidus procedure (OLP) consists of realigning the varus of the first metatarsal (M1) present in the hallux valgus (HV) deformities, by fusing the first tarsometatarsal joint (TMJ) and the M1 to the second metatarsal (M2). Compared to its modified version, some studies support that the OLP is more stable with less motion around the TMJ, which may prevent complications such as recurrence. However, fusion between M1 to M2 may not occur and its clinical and radiographic impact is still unknown. The aim of this study was to compare clinical, functional and radiographic outcomes in patients who underwent the OLP that evolved with and without fusion between the M1 and M2. Our null hypothesis was that they would have the same results. Methods: A retrospective and comparative study of twenty-nine patients (thirty-eight feet) with a mean follow-up of 18.03 (range, 6-51) months who underwent the OLP. They were divided in two different groups based on the presence of fusion and non-fusion between the M1 and M2 (Figure1). Twenty-three patients were included in the first group and fifteen in the second. Their average age was 48.74 (range,18-73) years. Twenty-five patients were female and four, male. Their mean body mass index (BMI) was 25.6 (range, 19.13-31.64). Clinical and functional data were assessed with the VAS for pain, AOFAS, LEFS and SF-12. SF- 12 comprises physical and mental health scales (PCS-12 and MCS-12). Radiographic parameters assessed were bony and soft tissue forefoot widths (BSFW), intermetatarsal-angle(IMA) and HV-angle(HVA). Intraclass Correlation Coefficients (ICC) were calculated for all radiographic measurements. Clinical, functional and radiographic measurements were compared between the two groups pre- and postoperatively using Student t Test. Results: The two groups were demographically similar in terms of mean age, BMI and follow-up time (p=.28, p=.84 and p=.06, respectively). Separately, patients from both groups presented significant improvements in all questionnaires (p<.001), except on MCS-12 (fusion p=.08 and non-fusion p=.27). Concerning radiographic parameters, they improved significantly in all measures (p<.001). When comparing the two groups, patients with fusion had higher scores only on the AOFAS questionnaire compared to those without (Table1). They improved from 37.61 preoperatively to 87.26 postoperatively and those without fusion improved from 44.47 to 82.80 (p<.05). Regarding radiographic parameters, there were no differences between both groups. They showed the same improvements on bony and soft tissue width, IMA and HVA (p=.09, p=16, p=.52 and p=.63, respectively), meaning that even when there is no fusion between M1 and M2, satisfactory radiographic corrections can be achieved (Table2). Pre- and postoperative ICC was good to excellent for most measurements (Table3). Conclusion: The present study showed that there was no difference in the amount of correction of HV deformities between patients who evolved with and without fusion between M1 and M2 after the OLP. However, patients with fusion may have better postoperative function when considering AOFAS scores. Further prospective and comparative studies with larger populations are required to assess the role of non-union between M1 and M2 in the outcomes of the OLP.