Purpose: A three-year evaluation of long-term clinical efficacy of Characterized Chondrocyte Implantation (CCI) compared to microfracture (MF), in the repair of symptomatic cartilage defects of the femoral condyles at 36 months post-surgery.

Materials and Methods: In a prospective, randomized, controlled, multicenter trial, CCI was compared to MF in patients aged 18–50 years with a single symptomatic ICRS grade III–IV lesion of the knee. Clinical outcome was measured 36 months after surgery by means of the KOOS, VAS for pain and ARS, with a non-inferiority margin preset at 9 % points for KOOS and VAS. Furthermore, response to treatment and progression of knee symptoms were assessed. Treatment failure was monitored throughout the study.

Results: Improvement from baseline was higher in the CCI group (N = 41) compared to the MF group (N = 49) for all clinical outcome parameters. Mean improvement from baseline for Overall KOOS was 22.14 vs. 14.48, respectively, with VAS and ARS scores revealing a similar trend. Responder analysis showed 83% of the patients treated with CCI improving vs. 61% after MF. Additionally, we observed a shift in the proportion of knee symptoms over time (52% vs. 35% of asymptomatic knees at 36 months compared to 2% vs. 8% at baseline in the CCI and MF group respectively). At 36 months, failure rates were low in both groups (n=2 in CCI vs. n=7 in MF).

Conclusions: Previous data have described a superior structural repair after CCI compared to MF at 1 year post-surgery. Continued clinical improvement as well as a favorable responder analysis was demonstrated for CCI compared to MF at 36 months.

INTRODUCTION: The techniques to stabilize the patella can be divided into two groups: the first group seeks to change the direction of the extensor mechanism in order to medialize the extending force vector of the quadriceps muscle, e.g. by a distal medialization of the tibial tuberosity or a proximal realignment; the second seeks to reconstruct the medial patellofemoral ligament (MPFL). The goal of this study was therefore to measure changes in patellofemoral kinematics in the intact, MPFL deficient knee, after medial transfer of the tibial tuberosity, after proximal realignment as well as after reconstruction of the MPFL.

METHODS: Eight fresh frozen right knee specimens were mounted in a knee simulator in which isokinetic flexion-extension motions were simulated. Extension cycles were simulated from 120° flexion to full knee extension with an extension moment of 31 Nm. Movement of the patella relative to the femur was measured using an ultrasound based 3D motion analysis system (Zebris, Isny, Germany). During the first test cycles, patellar movement under intact knee conditions were measured, while a constant 100 N laterally oriented force was applied by means of a steel cable attached to the patella. Subsequently, patellar movement was again measured after: transecting the MPL (deficient knee), performing a medialization of the tibial tuberosity, after reconstruction of the transected MPL using a semitendinosus autograft and after proximal realignment.

RESULTS: The patella of the intact knee moved along a medial path with a maximum attained position of 8.8 mm at 25° of knee flexion. The patella of the deficient knee moved up to 4.6 mm (p=0.04) in the medial direction at maximal extension at 30° of knee flexion. After medial transfer of the tibial tuberosity patellar movement reached a maximum medial position of 12.8 mm (p=0.04) at 22° of knee flexion with the laterally oriented force. With a reconstructed MPL, the patella attained a maximum medial position 14.8 mm (p=0.04) at 24.0° of knee flexion. Following proximal realignment, the patella moved on a medial, but significant (p=0.03) different path up to 13.8 mm medially at 30° of knee flexion. In addition, following medialization of the tibial tuberosity and proximal realignment, the center of the patella was significantly (p=0.03) more internally rotated (tilted) than the physiologic patella.

DISCUSSION: The shape of the movement curves after the stabilizating procedures resulted in a medialization relative to intact and deficient conditions. With the reconstructed medial patellofemoral ligament, the patella moved along the most medially oriented path with physiologic tilting. The results suggest that a semi-tendinous autograft can provide sufficient stabilization to prevent lateral displacement or subluxation with physiologic patellar tilt.

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.

Purpose: The study was designed to evaluate the biomechanical and neurohistological properties of the infrapatellar fat especially concerning its potential role in the anterior knee pain syndrome.

Methods: Isokinetic knee extension from 120 of flexion to full extension was simulated on 10 human knee cadaver specimens (6 male, 4 female, average age at death 44 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). The infrapatellar tissue pressure was analyzed using a closed sensor cell. The patellar contact pressure was measured before and after resection of the infrapatellar fat pad. The distribution of nerve fibres in the infrapatellar fat pad was assed immunohistologically in a second part of the study.

Results: Infrapatellar tissue pressure significantly increased during knee extension < 20 and flexion > 100 ranging from 343 (223) mbar at O- to 60 (64) mbar at 60 of flexion. Total resection of the infrapatellar fat pad resulted in a significant decrease in tibial external rotation of 3° in full knee extension (p=0.011), combined with a significant medial translation of the patella between 29 and 69° knee flexion (p=0.017 to 0.028). Retropatellar contact pressure was significantly (p< 0.05) reduced at all flexion angles, at 120° knee flexion more than in full knee extension. Studying all the detectable nerves present in 50 fields (x200 objective) we found an average of 6.4 substance-P- (25%) of a total of 24.7 nerve fibres in the infrapatellar fat pad. There was a significantly (p< 0.01) higher number of substance-P-fibers (24.4 (28%) of 105.7) in the superficial synovial tissue. The number of S-100-fibers was significantly (p< 0.05) higher in the central and lateral part of the fat pad.

Conclusions: Based on these results, we conclude that resection of the infrapatellar fat pad could potentially reduce clinical symptoms in the anterior knee pain syndrome, and that, contrary to commonly believed, the infrapatellar fat pad may have a biomechanical function and play a role in the anterior knee pain syndrome.

Aims: The purpose of the study was to determine the distribution and speciþcation of nerve þbers in the infrapatellar fat pad especially concerning nociceptive substance-P þbres. Methods: The infrapatellar fat pad was taken as a fresh specimen out of 21 patients (4 male, 17 female, mean age 69 years) during total knee arthroplasty. It was dissected in þve deþned parts, þxed and embedded in parafþn. Immunohistochemical techniques using antibodies against S-100 protein and substance-P were employed to determine and specify the nerve þbres. Results: Studying all the detectable nerves present in 50 þelds (x200 objective) we found an average of 6,4 substance-P- (25%) of a total of 24,7 nerve þbres in the infrapatellar fat pad. There was a significantly (p< 0,01) higher number of substance-P-þbers (24,4 (28%) of 105,7) in the surfacing synovial tissue. The number of S-100-þbers was signiþcantly (p< 0,05) higher in the central and lateral part of the fat pad. Conclusions: The occurance and distribution of nerve þbres in the infrapatellar fat pad suggests a nociceptive function. A neurohistological role in the anterior knee pain syndrome is assumed.

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.