The incidence of acetabular fractures has increased in China during the last 20 years . The primary goals of acetabular fracture surgery are anatomical reduction and strong fixation , which ensure early postoperative mobilization and reduce the incidence of traumatic arthritis or hip ankyloses. The ALP facilitates strong fracture fixation and early mobilization. However, because of the fixation of the locking screw, use of the ALP incurs a risk of the screw entering the acetabulum, as with other non-locking plates. Furthermore, the shape of the ALP and the angle of the screw may limit the compression of the fracture ends, leaving a residual gap .
The NALP consists of an inverted Y-shaped structure that matches the inverted Y-shaped structure of the acetabulum  (Fig. 3). The NALP is anatomically contoured to match the surface of the posterior column of the acetabulum of Chinese patients; therefore, this plate can be used directly without the need for manual precontouring, which reduces the surgical time . The NALP has a fan-shaped wing guard in the region of the acetabular top with the largest load; this wing guard structure and locking screw helps obtain more stable fixation in patients with a fixed femolar top comminuted. The guide holes in the NALP were designed to guarantee the appropriate starting points for the anterior column screws and the Magic screws, respectively, making it easier to safely place minimally invasive screws. These two screws pressurize the fracture line of the anterior column, while the posterior column is pressurized via the single Kocher–Langenbeck approach.
In the present study, the ALP group tended to have a shorter operation time than the NALP group, but this difference was not significant. The NALP group had a significantly larger mean intraoperative blood loss volume than the ALP group. For many patients in the NALP group, the time from injury to the operation was longer than 3 weeks; i.e., many patients in the NALP group had older fractures. Bicolumnar fractures were also more common in the NALP group. These fractures were more difficult to treat, which delayed the surgery.
The NALP group had significantly higher fracture gaps than the ALP group. The rates of excellent and good radiographic results based on the Matta scores in the NALP and ALP groups were 90% and 58.3%, respectively. In the NALP group, the Matta scores indicated that 10% of patients achieved fair results and that no patients achieved poor results. In the ALP group, the Matta scores indicated that 16.7% of patients achieved fair results and 25% achieved poor results. The NALP group achieved superior radiographic results because the compression screw enables the NALP to pressurize the fracture ends, reduce the gap at the fracture ends, and improve the reduction outcome.
The rates of excellent and good functional results based on the Harris hip scores in the NALP and ALP groups were 90.0% and 66.6%, respectively. Each group contained one patient with a poor result due to osteonecrosis of the femoral head; both patients had posterior dislocation. The Harris hip scores indicated that three patients in the ALP group achieved fair results. The Harris hip scores indicated that the hip function tended to be superior in the NALP group than in the ALP group, but this difference was not significant. Although the reduction of the acetabular fracture strongly influences the functional score of the hip, the Harris hip score is also affected by many other factors.
When the ALP was used for fixation, acetabular anatomical reduction was required, and the fracture ends could not be compressed after plate fixation. When using the NALP, the compression screws were driven into the anterior and posterior columns through the plate to compress the acetabular fracture ends. However, although the auxiliary insertion point was provided when the NALP was used, the correct implantation was also dependent on the combined application of the guide module and the perspective, which increased the operation time [21, 22].
In our experience, several important aspects must be considered when using the NALP for acetabular fractures. (1) Because the structure of the NALP is designed based on the posterior acetabular morphology of Chinese patients, the Kocher–Langenbeck approach or the combined anterior and posterior approach must be used. (2) Neither the NALP nor ALP must necessarily totally fit the contour of the patients. The locking feature provides adequately stable fixation for rehabilitation. (3) After the NALP is placed, the best compression is achieved by inserting the anterior column screws and Magic screws before inserting the other locking screws.
The present study had some limitations, including the retrospective study design and relatively small sample size. The present findings require confirmation in prospective randomized controlled trials with large sample sizes.