Session VII - Tibia

*The Less Invasive Stabilization System for Bicondylar Fractures of the Proximal Tibia

Thomas Gosling, MD; Mathias Müller, MD; Martinus Richter, MD; Tobias Hüfner, MD; Christian Krettek, MD, FRACS; Hannover Medical School, Hannover, Germany (a-AO Clinical Investigation and Documentation)

Purpose: For most bicondylar tibial fractures, dual plating has been the treatment of choice so far. Recently, a fixation device called the Less Invasive Stabilization System (LISS) has been developed. Rather than relying on maximal interfragmentary compression, the LISS implant acts as an internal fixator. Monocortical self-drilling screws are locked in an anatomically pre-shaped plate to provide angular stability and to fix the fragments after reduction has been performed. The plate is inserted percutaneously. This system may offer some advantages, especially in fractures with soft tissue injury, fracture comminution, or osteopenic bone.

Methods: In a prospective multicenter study including 13 level-1 trauma centers, all 41-C type fractures treated with the LISS from July 1, 1998 to September 30, 2000 were evaluated in a standardized matter. Patients returned to follow-up with clinical as well as radiological evaluation after 3, 6, and 12 months from the day of operation. Special emphasis was placed on secondary loss of reduction, which was defined to be more than 5° of angulation resp. 2 mm of subsidence on planar radiographs. The Lysholm, Tegner, and Rasmussen scores were used for assessment.

Results: A total of 75 patients (29 women, 46 men) with a median age of 50 years (range, 18 to 89) were included; 16 patients had open fractures, 59 had closed fractures. Fracture types were 8 C1, 35 C2, and 32 C3. The operations were performed by 42 surgeons, averaging 1.8 operations per surgeon. Fourteen primary bone grafts were performed. One deep infection and four superficial infections occurred, and one peroneal palsy and one compartment syndrome were recorded postoperatively. At the latest follow-up, the Lysholm Score averaged 86. The mean loss in the Tegner Activity Score was 1.5. The Rasmussen score revealed 78% good-to-excellent results. Six delayed unions were observed; four of them healed after secondary bone grafting, two still have the tendency to heal, with the patients free of any pain under full weight-bearing. Nine patients had secondary loss of reduction, caused by an incorrect technique in eight. Typical technical failures included missing of additional screw osteosynthesis to build the proximal block, too short metaphyseal screws, and too anterior placement of the LISS.

Discussion: In spite of the high rate of open and comminuted fractures, the incidence of infection was small in this group. This result could be attributed to the minimally invasive unilateral placement of the LISS. Primary bone grafting was rarely necessary, which left the metaphyseal-diaphyseal junction untouched. The functional results were good to excellent in most of the patients. A learning curve seems to be inevitable, but if the LISS is used correctly, secondary loss of reduction seldom occurs.

Conclusion: The LISS is a good alternative to double plating in the treatment of bicondylar proximal tibial fractures, especially for those fractures with a high degree of soft tissue damage or extensive comminution or both.