Session X1 - Tibia

The Tibial Less Invasive Stabilization System (LISS) and Its Relationship to the Posteromedial Fragment in Bicondylar Tibial Plateau Fracture Patterns

David P. Barei, MD; Timothy O'Mara, MD; Alexis Falicov, MD;

Lisa A. Taitsman, MD; Sean E. Nork, MD; (n-all authors)

Harborview Medical Center, Seattle, Washington, USA

Purpose: Tibial LISS is often used for treating bicondylar tibial plateau fractures. These fractures may have medial articular injury. Our purpose is to describe the medial articular injury, its frequency, and the relationship of the tibial LISS screws relative to these fragments.

Methods: Between May 2000 and March 2003, we identified 170 OTA 41 C-type bicondylar tibial plateau fractures using an orthopaedic database. 146 salvageable fractures had computed tomographic scans (CTs) performed prior to definitive fixation. Radiographic data were available using the picture archiving and communication system (PACS). 66 injuries (45.2%) involved the medial articular surface. Nine of these had technically poor CTs precluding accurate measurements, leaving a total of 57 injuries for review. All CTs were felt to be interpretable and were reviewed by 2 observers. Agreement was by consensus. Using PACS, the major medial articular fracture line angle was identified relative to the posterior femoral condylar axis (PFCA) on the axial view. A scatter diagram demonstrated a clustering of angles between 20° and -45° to the PFCA. This defined the boundaries of the posteromedial fragment (PMF). The surface area of the major fragments and entire tibial plateau were obtained. On sagittal reformats, the maximum posterior cortical height (PCH) of the PMF and the angle subtended by the articular surface and major fracture plane (sagittal fracture angle) were obtained. A sample of injuries with PMF had CTs mapped (Surfdriver Software, Kailua, HI) to a normal human tibia (NIH Human Body Project), and virtual surgery with a 9-hole uniformly applied LISS plate was performed via 3-dimensional CAD software (Cinema 4d, Maxon Computer Inc). The PMF was captured if at least one screw obtained 5 mm of penetration within the fragment.

Results: 39 of 57 injuries (68.4%) had a PMF. The PMF involved an average of 23% of the entire tibial plateau (range, 8% to 47%). The mean PCH was 43 mm (range, 16 to 59 mm), and mean sagittal fracture angle was 83°
(range, 33° to 112°). The PMF in 6 of 11 sample fractures was not captured with the virtual LISS plate. No single fracture characteristic was predictive of capture.

Conclusions/Significance: Medial articular injury is frequent in bicondylar plateau fractures. Nearly two thirds of those with medial injuries demonstrated a PMF. The proximal tibial LISS screws do not reliably penetrate this fragment. Implant and fracture variables are codependent in the successful neutralization of the PMF. When using LISS to manage those injuries with significant medial articular fractures, alternate or supplementary fixation methods should be considered.