PurposeTo report second‐look arthroscopic assessment after all‐arthroscopic autologous chondrocyte implantation (ACI) for articular cartilage defects at the patella. MethodsA second‐look arthroscopy after all‐arthroscopic ACI using chondrospheres® (ACT3D) was performed in 30 patients with 30 full‐thickness retropatellar cartilage defects. The mean time from ACI to second‐look arthroscopy was 14.9 ± 16.3 (6–71) months. The quality of cartilage regeneration was evaluated by the International Cartilage‐Repair Score (ICRS)—Cartilage Repair Assessment (CRA). ResultsEleven lesions (36.7%) were classified as CRA grade I (normal) and 19 lesions (63.3%) as grade II (nearly normal). Concerning the degree of defect repair, 25 lesions (83.3%) were repaired up to the height of the surrounding articular retropatellar cartilage. Five lesions (16.7%) showed 75% repair of defect depth. The border zone was completely integrated into the surrounding articular cartilage shoulder in 28 lesions (93.3%) and demarcated within 1 mm in 2 lesions (6.7%). Macroscopically and by probing, 12 lesions (40%) had intact smooth surface, 17 lesions (56.7%) had fibrillated surface and 1 lesion (3.3%) had small, scattered fissures. A negative correlation was found between the overall repair assessment score and the defect size (r2 = − 0.430, p = 0.046) and between integration into border zone and defect size (r2 = − 0.340, p = 0.045). A positive correlation was found between macroscopic appearance and age (r2 =  + 0.384, p = 0.036). ConclusionsAll‐arthroscopic ACI using chondrospheres® (ACT3D) for full‐thickness retropatellar articular cartilage defects proved to be reproducible and reliable. The advantage of the procedure is that it is minimal invasive. Arthroscopic second‐look demonstrated a high grade of normal or nearly normal cartilage regeneration. Although statistically significant differences were not observed, larger defect size and younger age may compromise the result of overall repair. Level of evidenceIII.

Recent anatomical studies show clear evidence that the anterior cruciate ligament (ACL) has a ribbon like structure from its femoral origin to its tibial attachment. The femoral bony origin of the ACL is half-moon like and the tibial attachment is duck-foot like. On the femoral side the flat midsubstance raise from its origin in a straight line and on the tibial side in a "C"-shaped way. Twisting of the flat ACL from extension to flexion gives the impression of separate bundles. However, no bundles could be found in recent studies. Based on above findings this article introduce a new technique for a flat ACL reconstruction. It was developed to reproduce the native "ribbon like" morphology of the ACL, with a rectangular femoral-and a C-shaped tibial socket.