J Orthopaed Traumatol (2011) 12:131–136 Table 1 Comparison between patellar resurfaced and unresurfaced total knee arthroplasty (P value [ 0.05 for all items) Total HSS Pain ROM Functionality Quadriceps force Flexion deformity Instability CI conﬁdence interval Results Follow-up concluded in December 2009. From the initial 233 implants, the right knee was replaced in 116 cases (49.8%) and the left knee in 117 (50.2%) cases . Forty-nine arthroplasties were implanted in men (21.1%) and 184 (78.9%) in women. The average age at surgery was 68.4 (95% CI 52.7–84.1) years. A femoral or tibial stem was used in ﬁve cases (2.1%); the patella was replaced in 144 cases (72.9%). During the follow-up period, 15 patients died without signs or symptoms of failure. In addition, 37 patients did not match the follow-up protocol for almost 2 years and were therefore considered to be lost. Finally, 179 implants (76.8% of implanted prosthesis) in 176 patients were evaluated (107 with patellar resurfaced and 72 with patella not resurfaced). The telephonic eval- uation was applied in seven cases. Average follow-up was calculated with respect to the last clinical control (includ- ing deceased and lost patients, with shorter follow-up) and was equal to approximately 13.5 years (162.1 months; 95% CI 132.3–191.9 months). Clinical results All HSS score items of the 176 patients had a statistically signiﬁcant improvement from preoperative to postoperative analysis (P \ 0.05). The total average score increased from 61.5 (95% CI 60.4–62.7) to 89.4 (95% CI 87.7–93.5) points. Pain at rest improved from 4.4 (severe; 95% CI 4.1–4.8) to 12.4 (absent; 95% CI 11.9–12.9), pain marching from 8.4 (95% CI 7.9–8.8) to 13.4 (95% CI 12.9–13.8) points, functionality from 6.5 (95% CI 6.2–6.9) to 9.7 (95% CI 9.4–10.1) points; range of motion increased from 86.5 (95% CI 84.8 –88.2 ) before surgery to 108 (95% CI 106.1 –109.9 ). Patellar resurfaced and unresurfaced TKAs were compared, and no statistically signiﬁcant difference (P [ 0.05) was observed between the two groups for all HSS items (Table 1). Complications A complication after surgery occurred in 36 cases (20.2%): 18 (10.1%) incomplete cicatrisation of the surgical wound, Patella resurfaced 85.9 (95% CI 83.8–88.1) 24.2 (95% CI 22.6–25.9) 106.3 (95% CI 102.7 –110.1 ) 17.8 (95% CI 16.8–18.8) 9.4 (95% CI 9.2–9.6) 9.9 (95% CI 9.8–9.9) 9.5 (95% CI 9.3–9.7) Patella not resurfaced 81.7 (95% CI 78.6–84.9) 26.7 (95% CI 25.7–27.8) 109.1 (95% CI 106.4 –111.7 ) 16.8 (95% CI 15.6–18.1) 9.1 (95% CI 8.7–9.4) 9.8 (95% CI 9.6–9.9) 9.4 (95% CI 9.1–9.6) 133 P value 0.1053 0.0636 0.0647 0.5911 0.3646 0.3699 0.0699 Number of radiolucent lines 40 37 17 34 14 14 40 6 2 2 123 in absence of signs of infection, treated with a superﬁcial revision; nine (5.0%) postoperative haematoma, redness, swelling and temperature, treated with an immediate articular washing and polyethylene exchange; two (1.1%) postoperative periprosthetic incomplete tibial fractures, treated with immobilisation followed by complete ﬁnal healing; four (2.3%) periarticular calciﬁcations and three (1.7%) peroneal nerve palsy, which were not treated. Radiographic results X-rays of 140 patients (78.2% of the patients who underwent clinical evaluation) were analysed. Radiolucent lines were found in 71 cases (50.7%), but progression of the radiolucent space (index of mobilisation) was observed only in 20 cases (14.3%). These 20 cases underwent a revised implant. A signiﬁcant correlation between progressive radiolucent lines and failure (revision) was found. Distribution of the radio- lucent lines in the tibial and femoral areas is reported in Table 2. The angles described by Ewald [12] were measured: the average a angle was 94.4 , the b angle 89.1 , the c angle 3.6 and the d angle 88.6 (95% CI are reported in Table 3). Comparison was made between alignment of implants that were revised for failure and nonrevised implants: no statis- tically signiﬁcant differences were found (Table 3). Table 2 Radiolucent line distribution in the different zones of the anteroposterior (AP) and laterolateral (LL) view of the tibia, and of the LL view of the femur, according to the Knee Society Roentgen- ographic Evaluation System [11] Tibia AP Tibia LL Femur (LL) Zone 1 4 6 1 2 3 1 2 3 6