Fixation of rotationally unstable extracapsular proximal femoral fractures

It was thought that the AO types A1.2 and A1.3 fractures are rotationally stable; however, it revealed instability when fixed using the dynamic hip screw. Therefore, we hypothesized that these fractures should be treated as rotationally unstable.

A series of 83 fractures of the AO types A1, A2, and B2.1 were treated using dynamic hip screw with derotation screw (DHS/DRS) composite and then prospectively followed for 24 months. Adequacy of reduction and fixation were immediately assessed after surgery, and fracture collapse was assessed at six months or when fractures healed. To investigate the feasibility of our hypothesis, fractures were classified into two groups: 1) the inevitably unstable group (IUG) included the AO types A1.1, A2.1, A2.2, A2.3, and B2.1 fractures and 2) the potentially unstable group (PUG) included the AO types A1.2 and A1.3 fractures. The results were statistically analyzed.

Adequate reduction was achieved in 77 and adequate fixation in 71 fractures. All fractures healed in a mean time of 13.5 weeks, and the amount of the fracture collapse averaged 5.8 mm. Equalization of the lower limbs was achieved in 66 patients, and hip motion range equalized the healthy contralateral in 80 patients. Re-operation was performed in one case with AO type A1.2. Comparison of IUG and PUG using the outcomes revealed insignificant differences.

Using the DHS/DRS composite, anatomical features of the proximal femoral end were restored and maintained during the follow-up period. Insignificant differences between outcomes of IGU and PGU render the addition of the AO types A1.2 and A1.3 to the rotationally unstable fractures reasonable.