## 3 Results
The group with preoperative diagnosis of instability included 9 patients; in this group, according to AORI classification: 0 patients had bone defects classified as AORI I, 2 patients had bone defects classified as AORI IIA, 6 patients had bone defects classified as AORI IIB, and 1 patient had bone defects classified as AORI III. The group with preoperative diagnosis of periprosthetic fracture included 7 patients; in this group, according to AORI classification: 0 patients had bone defects classified as AORI I, 2 patients had bone defects classified as AORI IIA, 4 patients had bone defects classified as AORI IIB, and 1 patient had bone defects classified as AORI III. In Table 4, we report the type of bone defects according to the AORI Classification System. The group with preoperative diagnosis of aseptic loosening included 25 patients (29% of the total); in this group the femoral long stem was implanted in 23 patients (92% of the total), the femoral short stem was implanted in 2 patients (8% of the total), the tibial long stem was implanted in 24 patients (96% of the total), the tibial short stem was implanted in 24 patients (96% of the total), the tibial short stem was implanted in 3 patients (12.5% of the total), and the tibial cone was implanted in 3 patients (12.5% of the total). The group with preoperative diagnosis of infection included 20 patients; in this group the femoral long stem was implanted in 16 patients (80% of the total), the femoral short stem was implanted in 4 patients (20% of the total), the tibial long stem was implanted in 15 patients (75% of the total), the tibial short stem was implanted in 5 patients (25% of the total), the femoral cone was implanted in 4 patients (20% of the total), and the tibial cone was implanted in 7 patients (35% of the total). \begin{table}
\begin{tabular}{c c c c c c} \hline  & \(\mathbf{N}^{\circ}\) & **AORI I** & **AORI IIA** & **AORI IIB** & **AORI III** \\ \hline \hline \begin{tabular}{c} Aseptic \\ loosening \\ \end{tabular} & 25 & / & 6 & 12 & 7 \\ \hline \hline \begin{tabular}{c} Malpositioning \\ \end{tabular} & 24 & 16 & 8 & / & / \\ \hline \hline Infection & 20 & / & 7 & 8 & 5 \\ \hline \hline \
\begin{tabular}{c} Instability \\ \end{tabular} & 9 & / & 2 & 6 & 1 \\ \hline \hline
\begin{tabular}{c} Periprosthetic fracture \\ \end{tabular} & 7 & / & 2 & 4 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Type of bone defects in each subgroup according to AORI Classification. The group with preoperative diagnosis of instability included 9 patients; in this group the femoral long stem was implanted in 9 patients (100% of the total), the femoral short stem was implanted in 0 patients, the tibial long stem was implanted in 9 patients (100% of the total), the tibial short stem was implanted in 0 patients, the femoral cone was implanted in 0 patients, and the tibial cone was implanted in 2 patients (22% of the total). The group with preoperative diagnosis of peripro prosthetic fracture included 7 patients; in this group the femoral long stem was implanted in 7 patients (100% of the total), the femoral short stem was implanted in 0 patients, the tibial long stem was implanted in 3 patients (43% of the total), the tibial short stem was implanted in 2 patients (29% of the total), the femoral cone was implanted in 2 patients (29% of the total), and the tibial cone was implanted in 3 patients (43% of the total). Other techniques such as impaction grafting or cancellous allograft were used to fill the femoral and tibial defects when cones were not used. All the cones were tantalum (Trabecular Metal; Zimmer, Warsaw, Indiana, USA). The number and type of stems and cones (Figure 1(a),b) used for each group of patients are summarized in Table 5.