Introduction: Differentially loaded radiostereometric analysis (DLRSA) uses RSA whilst simultaneously applying load to the bones under investigation. This technique allows measurement of interfragmentary displacements under measured weightbearing and joint movement. We have used this technique to prospectively monitor tibial plateau fractures and present the results of the first nine patients with six month follow up.
Method: Nine 41-B3 fractures were treated with open reduction internal fixation by one surgeon. At operation, RSA beads were inserted in the depressed osteochondral fragment and the adjacent non-fractured metaphysis. Postoperative weightbearing was restricted to 20kg and knee flexion to 60° for the first six weeks. Follow up included clinical and radiological examinations and patient reported outcome scores (Lysholm, KOOS). DLRSA examinations included RSA radiographs in 60° flexion and under measured weightbearing at six weekly intervals up to six months postoperatively. Significant interfragmentary displacement was defined as translations greater than 0.5mm and/or rotations greater than 1.5°.
Results: No postoperative displacement was identified on plain radiographs, except in one patient who fell two weeks postoperatively.
RSA: Longitudinal Results: In all patients, the osteo-chondral fragment continued to migrate up to six months, with one exception that stabilised at three months. At six months, the osteochondral fragment translated between 0.02 and 4.15 mm and rotated between 0.2 and 7.2° (>
0.5mm and/or >
1.5° in five cases).
DLRSA: Flexion Results: During 60° of flexion, translations exceeding 0.5mm were recorded in only one patient (0.7 mm at 2 weeks). Rotations exceeding 1.5° were recorded in three patients (1.6°, 2° and 2.1° all at six months).
DLRSA: Weightbearing Results: Translations exceeding 0.5mm were recorded in four patients whilst full weightbearing (0.7mm in two patients at three months, and 0.6mm and 0.8 mm at 18 weeks). Rotations exceeding 1.5° were recorded in two patients. One patient recorded 2.3° under full weightbearing at three months. Another recorded 2.3° under 20kg of weight at two weeks and 1.8° under full weightbearing at 18 weeks. Patient reported outcomes improved progressively. At six months, five patients reported excellent results, two good and two fair. The two patients reporting fair results recorded low interfragmentary displacements.
Discussion: Tibial plateau fractures continue to migrate up to six months after treatment. Active range of motion, partial weightbearing to six weeks and weightbearing up to one body weight after six weeks was proven a safe postoperative regimen. Greater displacements recorded over time may be attributed to loading of more than one body weight, for example, the patient that fell recorded the largest amount of migration over time.
