Session II - Tibia

Fri., 10/8/04 Tibia, Paper #10, 11:04 am

Augmentation of Tibial Plateau Fractures with Calcium Phosphate Cement: A Randomized Study Using Radiostereometry

Sune Larsson, MD (n); Per Berg, MD (n); Marcus Sagerfors, MD (n);
Department of Orthopedics, Uppsala University Hospital, Uppsala, Sweden

Purpose: One problem with tibial plateau fractures that involve a depressed articular fragment is the difficulty of maintaining reduction until healing. The conventional method is to fill the subchondral void with autologous bone transplant followed by restricted weightbearing for 8 to 12 weeks. Recently, biomaterials have been introduced that might overcome several problems associated with bone transplant. The purpose of this study was to evaluate an injectible calcium-phosphate cement when used as a bone graft substitute in lateral tibial plateau fractures, with special emphasis on the stability of the elevated articular fragment.

Methods: Twenty-four patients with a lateral tibial plateau fracture type 41-B2 or 41-B3 (OTA classification) were included. The authors operated on all patients. Conventional metal fixation was used to fix the fracture following elevation of the articular fragment. The subchondral void was filled with injectable calcium-phosphate cement (Norian SRS, Synthes) or conventional iliac bone graft according to randomization during surgery. There were 12 patients in each group with an average age of 50 and 52 years, respectively. During surgery, tantalum markers were inserted for subsequent radio stereometry (RSA) (RSA Biomedical Innovation, Umeå, Sweden), a radiologic technique that enables measurement of movement along and around three orthogonal axes with a precision of less than 0.5 mm and 0.7°. Continuous passive motion was begun immediately after surgery. Weightbearing was restricted to 20 kg for 6 weeks in the SRS group and for 12 weeks in the control group. Radio stereometry was performed before weightbearing and at 1, 6, and 12 weeks and at 6 and 12 months. Conventional radiographs were used for assessment of reduction and healing. Clinical evaluation (Lysholm score and a visual analog scale score of 0 to 10 for pain) was conducted by a physiotherapist. For assessment of compliance with regard to weightbearing, patients were examined with F Scan (Tecscan, Inc., Boston, Massachusetts, USA) at each time point.

Results: No patients were lost but two were excluded from the RSA evaluation due to technical problems. All fractures healed. There was one deep infection (SRS). At 6 weeks, average weightbearing was 22 kg in the SRS group and 19 kg among the controls (NS); at 12 weeks, 66 kg vs. 28 kg (P <0.001); and at 6 and 12 months, on average, between 66 and 72 kg with no difference between groups. Pain during activity was lower in the SRS group at 1 week (P <0.01), 6 weeks (P <0.004), 3 months (P <0.005), and at 6 months (P <0.02), with no difference at 1 year. The Lysholm knee score was better at 6 weeks (P <0.01), 12 weeks (P <0.002), and 6 months (P <0.02) in the SRS group, and there was no significant difference at 1 year. Radio stereometry revealed movement of the articular fragment in all patients. The total translation was, on average, 1.41 mm in the SRS group and 3.88 mm in the controls (P <0.001). In both groups the most significant movement occurred during the first 6 weeks, and there was no significant movement of the articular fragment from 6 to 12 months, indicating stable healing. The most typical pattern of movement was subsidence along the vertical axis or rotation in the transversal axis (forward tilt) or both, and as toe-out rotation around the vertical axis. One patient from the SRS group had a migration exceeding 3 mm, and two controls had a migration exceeding 5 mm.

Conclusion/Significance: Injectable calcium-phosphate cement provided a more stable fixation of the elevated articular fragment in lateral tibial plateau fractures when compared with conventional bone graft, despite the fact that cement-augmented patients were allowed earlier weightbearing. Patients treated with cement also had less pain during the entire course of healing when compared with controls. Bone graft substitutes can offer new perspectives for treatment of fractures involving metaphyseal defects, without the side effects associated with bone grafting.