Less-invasive stabilization of rib fractures by intramedullary fixation: a biomechanical evaluation.

BACKGROUND: This study evaluated intramedullary fixation of rib fractures with Kirschner wires and novel ribs splints. We hypothesized that rib splints can provide equivalent fixation strength while avoiding complications associated with Kirschner wires, namely wire migration and cutout. METHODS: The durability, strength, and failure modes of rib fracture fixation with Kirschner wires and rib splints were evaluated in 22 paired human ribs. First, intact ribs were loaded to failure to determine their strength. After fracture fixation with Kirschner wires and rib splints, fixation constructs were dynamically loaded to 360,000 cycles at five times the respiratory load to determine their durability. Finally, constructs were loaded to failure to determine residual strength and failure modes. RESULTS: All constructs sustained dynamic loading without failure. Dynamic loading caused three times more subsidence in Kirschner wire constructs (1.2 mm +/- 1.4 mm) than in rib splint constructs (0.4 mm +/- 0.2 mm, p = 0.09). After dynamic loading, rib splint constructs remained 48% stronger than Kirschner wire constructs (p = 0.001). Five of 11 Kirschner wire constructs failed catastrophically by cutting through the medial cortex, leading to complete loss of stability and wire migration through the lateral cortex. The remaining six constructs failed by wire bending. Rib splint constructs failed by development of fracture lines along the superior and interior cortices. No splint construct failed catastrophically, and all splint constructs retained functional reduction and fixation. CONCLUSIONS: Because of their superior strength and absence of catastrophic failure mode, rib splints can serve as an attractive alternative to Kirschner wires for intramedullary stabilization of rib fractures, especially in the case of posterior rib fractures where access for plating is limited.

Anatomically contoured plates for fixation of rib fractures.

BACKGROUND: : Intraoperative contouring of long bridging plates for stabilization of flail chest injuries is difficult and time consuming. This study implemented for the first time biometric parameters to derive anatomically contoured rib plates. These plates were tested on a range of cadaveric ribs to quantify plate fit and to extract a best-fit plating configuration. METHODS: : Three left and three right rib plates were designed, which accounted for anatomic parameters required when conforming a plate to the rib surface. The length lP over which each plate could trace the rib surface was evaluated on 109 cadaveric ribs. For each rib level 3-9, the plate design with the highest lP value was extracted to determine a best-fit plating configuration. Furthermore, the characteristic twist of rib surfaces was measured on 49 ribs to determine the surface congruency of anatomic plates with a constant twist. RESULTS: : The tracing length lP of the best-fit plating configuration ranged from 12.5 cm to 14.7 cm for ribs 3-9. The corresponding range for standard plates was 7.1-13.7 cm. The average twist of ribs over 8-cm, 12-cm, and 16-cm segments was 8.3 degrees, 20.6 degrees, and 32.7 degrees, respectively. The constant twist of anatomic rib plates was not significantly different from the average rib twist. CONCLUSIONS: : A small set of anatomic rib plates can minimize the need for intraoperative plate contouring for fixation of ribs 3-9. Anatomic rib plates can therefore reduce the time and complexity of flail chest stabilization and facilitate spanning of flail segments with long plates.

Evaluation of intramedullary rib splints for less-invasive stabilisation of rib fractures.

BACKGROUND: Intramedullary fixation of rib fractures with generic Kirschner wires has been practiced for over 50 years. However, this technique has not been advanced to address reported complications of wire migration and cut-out. This biomechanical study evaluated a novel rib splint designed to replicate the less-invasive fixation approach of Kirschner wires while mitigating their associated complications. METHODS: The durability, strength, and failure mode of rib fracture fixation with intramedullary rib splints were evaluated in 27 cadaveric ribs. First, intact ribs were loaded to failure to determine their strength and to induce realistic rib fractures. Subsequently, fractures were stabilised with a novel rib splint made of titanium alloy with a rectangular cross-section that was secured with a locking screw. All fixation constructs were dynamically loaded to 360,000 cycles at five times the respiratory load magnitude to determine their durability. Finally, constructs were loaded to failure to determine their residual strength and failure modes. RESULTS: Native ribs had a strength of 9.7+/-5.0 N m, with a range of 3.5-19.6 N m. Fracture fixation with rib splints was uneventful. All 27 splint constructs sustained dynamic loading without fixation failure, implant migration or implant cut-out. Dynamic loading caused no significant decrease in construct stiffness (p=0.85) and construct subsidence remained on average below 0.5 mm. The residual strength of splint constructs after dynamic loading was 1.1+/-0.24 N m. Constructs failed by splint bending in 44% of specimens and by developing fracture lines along the superior and inferior cortices in 56% of specimens. Regardless of the failure mode, all rib splint constructs recoiled elastically after failure and retained functional reduction and fixation. No construct exhibited implant cut-out or migration through the lateral cortex. CONCLUSIONS: Rib splints can provide sufficient stability to support respiratory loading throughout the healing phase, but they cannot restore the full strength of native ribs. Most importantly, rib splints mitigated the complications reported for rib fracture fixation with generic Kirschner wires, namely implant cut-out and migration through the lateral cortex. Therefore, rib splints may provide an advanced alternative to the original Kirschner wire technique for less-invasive fixation of rib fractures.