Introduction 6 6 11 6 2  2 11 6 11 19 13 3 8 ® However, it is unknown if the femoral resurfacing device leads to increased peak contact pressure to the opposing biological structures such as meniscus and articular cartilage of the tibial plateau. ® Materials and methods Knee joints A total of eight fresh-frozen knee cadaver specimens (3 pairs, 2 single) were used for data collection in this study. The specimens were obtained from donors, who consented in writing during their lifetime to the use of their body for research and education. The average age of the seven male and one female specimen was 71 years (range 61–81) with an average weight of 71 kg (range 62–85). Specimens were selected after inspection of the medial compartment according to the following criteria: Intact femorotibial cartilage, intact meniscus, and intact collateral and cruciate ligaments. Thirteen specimens were excluded following these criteria. Another six specimens were excluded due to specimen failure during the testing procedure: The reason for exclusion was fracture of the femur or tibial plateau (2 specimens), rupture of the anterior cruciate ligament (2 specimens) or rupture of the patella tendon (2 specimens). All specimen failures were female human cadaver knees. Technology 1 28 Fig. 1 Schematic drawing of the knee simulator that was used for this study  2 18 21 25 31 ® Testing protocol The specimens were aligned using a fixed laser beam to achieve correct alignment in the mechanical axis of the lower limb. The mechanical axis was defined by a line through the center of the head of the artificial hip joint, the center of the knee joint and the center of the hinge joint representing the artificial ankle. For calibration of the sensor the ankle hinge joint was secured with two aluminum plates perpendicular to the ground. Thereby the knee was fixed in full extension. Each sensor was individually preconditioned and calibrated intra-articulary with a two-point calibration method at 700 and 1,500 N according to manufacturer’s guidelines. Definitions of the correct angles of the actual knee position were adjusted with a custom-made goniometer and by the displacement-controlled main rod. During the test cycles the cadaver were sprayed with saline solution to prevent dehydration. ® 2 Fig. 2 a b c d  Operative technique 2 2 2 Data analysis t P Results Continuous data were obtained at every trial. No difference in the quality of data collection was seen comparing the stance positions or dynamic testing. 3 1 P P P 3 1 Fig. 3 Mean peak contact pressures with one standard deviation  Table 1 Peak contact pressures at different testing conditions Testing position Testing condition Peak contact pressure (Mpa) Mean difference to untreated (%) P 5° Untreated 3.09 ± 0.86 (3.05, 1.92–4.86) N/A N/A Flush 3.98 ± 2.19 (3.59, 2.15–9.02) 29 NS 1 mm proud 9.80 ± 4.37 (9.36, 4.70–18.37) 217 ≤0.004 Defect 3.35 ± 1.39 (3.39, 1.90–5.83) 8 NS 15° Untreated 3.01 ± 0.81 (2.95, 2.01–4.11) N/A N/A Flush 3.69 ± 1.79 (3.89, 1.38–7.06) 23 NS 1 mm proud  9.19 ± 9.27 (5.87, 2.10–30.49) 205 NS Defect 2.94 ± 1.07 (2.84, 1.69–5.09) −2 NS 30° Untreated 3.18 ± 0.94 (3.52, 1.46–4.26) N/A N/A Flush 2.89 ± 0.85 (3.02, 1.03–3.83) −9 NS 1 mm proud  7.07 ± 5.97 (5.24, 1.03–19.81) 122 NS Defect 3.31 ± 1.06 (3.11, 2.05–5.34) 4 NS 45° Untreated 4.77 ± 1.85 (4.23, 2.66–7.90) N/A N/A Flush 4.96 ± 2.02 (4.18, 2.79–7.92) 4 NS 1 mm proud  5.79 ± 2.76 (5.54, 2.01–11.82) 21 NS Defect 4.94 ± 1.81 (4.65, 2.05–7.54) 4 NS Dynamic Untreated 5.84 ± 2.12 (5.14, 3.85–9.82) N/A N/A Flush 6.02 ± 2.05 (5.21, 3.46–8.97) 3 NS 1 mm proud  11.61 ± 6.39 (10.50, 6.22–25.46) 99 ≤0.02 Defect 5.68 ± 1.76 (5.11, 3.76–8.24) −3 NS 30° 2tBW Untreated 6.57 ± 2.31 (6.01, 4.09–11.15) N/A N/A Flush 6.05 ± 1.40 (5.82, 4.68–8.97) −8 NS 1 mm proud  12.49 ± 8.02 (9.67, 5.83–30.49) 90 ≤0.03 Defect 7.38 ± 4.68 (5.31, 4.75–17.70) 12 NS Values given as mean ± SD (median, range) NS 1 4 5 Fig. 4 color red blue a b c d b  Fig. 5 a b arrow 4  1 Discussion The patient aged over 40 years with a full thickness chondral or osteochondral defect reflects a serious problem for the orthopedic surgeon. Considered as being too old for biological repair of the defect, primarily the patients are mostly managed with conservative, non-surgical treatment including weight reduction, physical therapy to increase and support musculature, unloading braces and medications such as NSAID’s, intraarticular injections (Corticosteroids, Hyaluronic acid, etc.) and dietary supplements. 4 7 17 5 14 5 5 14 2 7 ® 15 15 14 29 9 12 16 17 2 20 22 23 5 5 16 4 5 7 16 17 26 17 26 24 7 30 10 18 21 31 10 27 1 ®