Introduction: This biomechanical study evaluates the consequences of a mid-third BPTB-autograft excision on patellofemoral biomechanics and knee kinematics. Of particular interest was the potential role of a BPTB-autograft excision on postoperative anterior knee pain in ACL replacement surgery.

Methods: Isokinetic knee extension from 120 of flexion to full extension was simulated on 9 human knee cadaver specimens (5 male, 4 female, average age at death 43 years). Joint kinematics was evaluated by ultrasound sensors (CMS 100TM, Zebris, Isny, Germany), and retro-patellar contact pressure was measured using a thin-film resistive ink pressure system (K-ScanTM 4000, Tekscan, Boston). All data were taken before and after excision of a mid-third BPTB-autograft.

Results: Following excision of a mid-third patella tendon autograft we found a significant (p< 0.05) proximalization of the patella (average: 0.5 mm) and a significant decrease of patella flexion in the sagittal plane (average: 1). Patella tilt, -rotation (frontal plane), -translation (medial/lateral) and tibiarotation (external-/internal), -axis (varus-/valgus position) remained unchanged. Patellofemoral contact pressure and -area decreased significantly near knee extension (p< 0.05).

Conclusions: We conclude that an excision of a mid-third patella tendon autograft results in a lengthening of the tendon with a proximalization of the patella. As the patellofemoral pressure decreases and the patella remains centralized, postoperative anterior knee pain following ACL-replacement using a BPTB autograft can not be explained by the results of our study.

Aims: This biomechanical study was performed to evaluate the consequences of a total infrapatellar fat pad resection on knee kinematics and patellar contact pressure. Methods: Knee motion between 120∞ of flexion and full extension was performed in a knee kinemator on 10 fresh frozen knee specimens (6 male, 4 female, average age 44 years). The joint kinematics was evaluated by ultrasound sensors (Zebris-system), the patellar contact pressure was measured using a thin-film resistive ink pressure system (Tekscan). All data were taken before and after resection of the infrapatellar fat pad and statistically analyzed. Results: A total resection of the infrapatellar fat pad resulted in a significant (p< 0,05) decrease of the tibial external rotation in knee extension combined with a significant (p< 0,05) medial translation of the patella. The patellar contact pressure was significantly (p< 0,05) reduced, in knee flexion more than in knee extension. Conclusions: We conclude that a resection of the infrapatellar fat pad might reduce clinical symptoms in the anterior knee pain syndrome. A biomechanical function of the infrapatellar fat is suspected.