[Friction-assisted screw fixation after reorienting pelvic osteotomies : Current evidence and clinical implications].

Background

Internal fixation of the reoriented acetabular fragment is essential to maintain correction until osseous union. However, the underlying biomechanical principles of fixation stability remain insufficiently understood.

Objectives

To summarize the biomechanical evidence on fragment fixation following reorienting pelvic osteotomies and to derive clinically relevant fixation principles.

Materials And Methods

The results of a previously published biomechanical study using 12 synthetic hemipelvis models after triple pelvic osteotomy were combined with a structured literature review. A bidirectional construct with two axial screws and one transverse screw (group 1) was compared with a monoaxial construct using three long iliac screws (group 2).

Results

No significant differences were found between the two fixation concepts. Construct stiffness in group 1 and in group 2 was 56.5 ± 17.8 and 41.2 ± 9.5 N/mm, respectively, and corresponding failure loads were 255.3 ± 40.7 and 255.6 ± 61.7 N. Medialization and changes in acetabular anteversion and inclination increased significantly in both groups during progressively increasing cyclic loading, without significant differences between them at the assessed time points. Six additional biomechanical studies showed substantial methodological heterogeneity. Recurrent determinants of stability were osteotomy geometry, fragment contact, spatial screw distribution, and intraosseous anchorage.

Conclusions

Iliac screw fixation can be understood as a friction-assisted intraosseous interlocking construct. Long screws with favorable spatial distribution are more relevant than the isolated orientation of a single screw. In triple pelvic osteotomy, additional anterior fixation across the pubic osteotomy may further improve stability. Partial weight-bearing until radiographic consolidation and strict nicotine abstinence remain essential components of postoperative management.