Distal fixation modular prosthesis for Paprosky type ⅢA/ⅢB femoral bone defect in revision total hip replacement： a short-term clinical follow-up study
Authors: Sun Xiaoyu , Yang Dinglong , Yan Chaochao , Wang Fan , Jiao Qiang 
Published: March 2023

Objective
To evaluate the short-term clinical results of using distal fixation modular prosthesis to reconstruct Paprosky type ⅢA/ⅢB femoral bone defect in revision total hip replacement.
Methods
From December 2017 to December 2022, a group of 30 patients with Paprosky type ⅢA、ⅢB femoral defect were selected in this study. They were divided into two groups according to the type of implanted prosthesis. Distal fixation modular prosthesis was used in the treatment group (n = 16), and distal fixation all-coated prosthesis was used in the control group (n = 14). Harris hip score, VAS (visual analog scale) score, leg length discrepancy value (D-value), and prosthesis settlement value were recorded, the complications were evaluated at follow-up.
Results
All included patients were followed up for 17 ~ 56 months, average (31 ± 15) months, and no patients were lost to follow-up. Clinical evaluation: There were no significant differences in Harris score and VAS score between the two groups before the operation (P > 0.05). Harris score and VAS score at the last follow-up were significantly improved than the preoperative score in both groups (P < 0.05), and the postoperative Harris scores of treatment group were significantly improved than control group (P < 0.05). No significant difference was embodied in VAS score between two groups up to the last follow-up (P > 0.05). Radiological Evaluation: compared the postoperative radiological data with those at the last follow-up. D-value and prosthesis settlement value in control group was greater than that intreatment group (P < 0.05). The preoperative D-value in both groups was no significant difference (P > 0.05). Up to the last follow-up, the D-value was significantly improved compared with that before operation, and it was higher in control group (P < 0.05). All femoral prostheses were well fixed without loosening at last follow-up in treatment group, showed sufficient bone ingrowth, and no sclerosis band or > 1mm radiolucent lines. In the control group, one patient showed a > 2mm radiolucent line and the prosthesis subsidence was > 6mm, which could be considered as prosthesis “reloosening”. Two patients showed a radiolucent line of about 1 ~ 2mm. Although all of them showed no significant clinical symptoms currently, the imaging suggested an increased likelihood of the stem shift and loosening, and the long-term survival rate is disturbing. Postoperative complications: In control group, one patient experienced postoperatively hip dislocation after 15 days that was resolved after a closed reset, until the last follow-up, the dislocation did not recur. Other patients did not have any complications such as peri-prosthetic infection, peri-prosthetic fracture, or sciatic nerve injury.
Conclusion
Distal fixation modular prosthesis can obtain significant clinical effects for the reconstruction of Paprosky type IIIA and IIIB femoral bone defects. It shows superior clinical outcomes than distal fixation all-coated prosthesis, can reach reliable initial stability and long-term stability, besides, it has a more obvious functional improvement of the hip.