Summary

A modified suture bridge technique for tibial eminence fracture fixation provides stable fixation and maintains fracture reduction allowing for early post-operative rehabilitation.

Abstract

Background

Surgical management with anatomic reduction and rigid fragment fixation is often required for displaced tibial eminence fractures. Early rehabilitation while avoiding post-operative fracture migration is important for successful functional outcomes.

Purpose

To determine differences in stiffness, cyclic elongation, and fragment displacement in type III tibial eminence fractures for various suture configurations. It was hypothesized that a modified suture bridge technique would exhibit higher stiffness, less cyclic elongation, and less fracture displacement compared to a suture sling technique.

Methods

Twenty-nine fresh frozen porcine knees were dissected with the exception of the ACL to form a femur-ACL-tibia complex (FATC). A 2 cm x 2cm x 0.5 cm type III tibial eminence fracture was created using an oscillating bone saw. For the modified suture bridge technique, individual sutures were passed through each ACL bundle with suture ends passing through one lateral tunnel and two medial tunnels. For the suture sling technique, one suture was passed through and looped around the ACL prior to passing the ends through one lateral and one medial tunnel. #2 braided suture and #2 suture tape were utilized and secured with a button fixation device on the anteromedial tibia.
Four configurations were used: bridge technique with suture tape (n=7), sling technique with suture tape (n=7), bridge technique with braided suture (n=7), and sling technique with braided suture (n=8). Each specimen was loaded onto a materials testing machine with the ACL in vertical alignment and the following loads were applied consecutively: (1) 2N preload, (2) 30 cycles of 2-10 N loads for preconditioning, and (3) 500 cycles of cyclical loading from 2-50 N. An optical tracking system (DMAS, Spica Technology Corporation, Kihei, HI; 0.01 mm accuracy) was used to measure the 3D motion of the fracture fragment relative to the tibia. Linear region stiffness and cyclic elongation were calculated at the last completed cycle. Kruskal-Wallis test with post-hoc analysis was performed to evaluate differences in structural properties among configurations. Significance was set at p < 0.05.

Results

Bridge-tape (42.4 ± 1.0 N/mm) and sling-tape (42.6 ± 3.9 N/mm) exhibited significantly higher stiffness with a 29% and 30% difference compared to sling-braided (31.5 ± 8.2 N/mm), respectively (both p < 0.05). Both bridge-tape (2.0 ± 0.3 mm) and bridge-braided (2.3 ± 1.0 mm) resulted in significantly less elongation with >70% difference when compared to sling-tape (5.5 ± 1.0 mm) and sling-braided (4.9 ± 1.4 mm) (all p < 0.05). Regarding fracture motion, bridge-tape (1.8 ± 1.0 mm) resulted in 118% and 119% less vertical displacement compared to sling-tape (7.0 ± 2.2 mm) and sling-braided (7.1 ± 2.5 mm), respectively (both p < 0.05). Additionally, bridge-braided (0.2 ± 0.6 mm) resulted in 189% less vertical displacement compared to both sling techniques (both p < 0.05).

Conclusion

Compared to suture sling, modified suture bridge exhibited significantly higher stiffness, less elongation, and less fracture displacement. Modified suture bridge is a stable fixation technique that may facilitate early progressive rehabilitation while preserving fracture reduction.