Prospective, Randomized Evaluation of Optimal Implant Position of Gamma3 and PFNA for the Treatment of AO/OTA 31-A2 Fractures: Is Central Positioning Always the Best?

Results: 177 patients (Gamma3: 91; PFNA: 86) met all study criteria. Both implants showed a predilection for a central position on the AP radiograph with 83/91 (91.2%) for Gamma3 and 81/86 (94.2%) for the PFNA group. In the Gamma3 group, there were significantly higher reoperation rates for Parker’s ratio values less than 34 (inferior position) on the AP radiograph compared to values between 34 and 66 (central position; P = 0.035); this was not seen in the PFNA group. There was a significant association between implant type and reoperation, with Gamma3 having 11/91 (12.1%) reoperations and PFNA having 0/86 (0%) reoperations (P = 0.001). Predictive modeling of reoperation for Gamma3 was maximized when both TAD and Parker’s ratios from AP radiography were incorporated into the model. With Parker’s ratios subdivided into thirds (0-33, 34-66, 67-100), TAD categorized as 25 generated an ROC curve with AUC of 0.612 (P = 0.226). Although a higher risk for reoperation in the Gamma3 group was evident in cases with a lower-third Parker’s ratio, these criteria were not predictive of cut-out. There were no significant differences between the Gamma3 and PFNA in terms of Parker’s ratios and TAD. Conclusion: For the Gamma3 device, central position on AP radiographs resulted in significantly fewer reoperations compared to an inferior position. ROC analysis indicates that the combination of Parker’s ratio and TAD is a significant predictor of reoperation rate in Gamma3. It also indicates that TAD <20 mm is a better predictor of reoperation compared to 25 mm. The same criteria predicted reoperation, but not cut-out. If using a Gamma3