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Paper # 11: Biomechanical Comparison of Anatomic Double-Bundle, Anatomic Single-Bundle and Non-Anatomic Single-Bundle Anterior Cruciate Ligament Reconstructions
ABSTRACTS nant preservation group showed less instability than total tear group (12% v 20% of Gr I instability, p⫽0.04). Mean side to side differences, measured using the Telos® device also showed better stability in remnant preservation than total tear group (1.2 v 2.4mm, p⫽0.03). Conclusions: ACL reconstruction with remnant preservation shows better pivot-shift outcomes and instrumented stability compared to ACL reconstruction without remnant preservation. Summary: The clinical results of ACLR with or without remnant preservation after 2 year follow up were compared. Remnant preservation ACLR shows better clinical outcome & stability compared to total tear ACLR. Paper # 10: The Quantitative Analysis of Mechanoreceptors in the Tibial Remnants of the Ruptured Anterior Cruciate Ligament in Human Knees LIN SHA, CHINA JINZHONG ZHAO, MD, CHINA · Shanghai 6th People’s Hospital Affiliated to Shang Shanghai, CHINA Summary: The residual mechanoreceptors in a rupture ACL have a long-term survival and show no obvious withering within 1 year. Abstract: A morphologic and quantitative evaluation was performed in order to evaluate the survival condition of mechanoreceptors in the tibial remnant of ruptured anterior cruciate ligament (ACL) in human knees. 60 patients who underwent arthroscopic ACL reconstruction with existing free tibial remnant were included and divided into 4 groups according to the time of injury, with 15 patients in each group. The time duration between injury and surgery was no more than 3 months, 3 to 6 months, 6 to 1 year and more than 1 year, respectively in Group 1, 2, 3, and 4. In each patient, a piece of specimen about 5mm wide, 7mm long and 5mm thick was removed from the anteromedial side of the ACL tibial remnant. The specimens were cut into 20 um thick sections, stained via immunohistochemical method, and observed under microscope to evaluate the three types of mechanoreceptors, Ruffni-like corpuscle, Pacini-like corpuscle and Golgi organ-like corpuscles. Results showed that mechanoreceptors were found in 9, 8, 9, and 6 patients, and totally 31, 22, 23, and 12 mechanoreceptors were found, respectively in Group 1, 2, 3, and 4. ANOVA analysis showed no statistically significant differences were found among the number of mechanoreceptors found in the four groups (p⫽0.285).
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However, the number in Group 4 was lower compared to the other groups and LSD analysis showed a trend towards significant difference between Group 1and Group 4 (p⫽0.055). Although some degenerative and atrophic changes could be observed in Group 4, no obvious variation was observed regarding the size of the Ruffini-like endings among four groups. So we consider that the residual mechanoreceptors in a rupture ACL survive for a long time and show no obvious withering. This implies that the ACL remnant may attribute the restoration of proprioceptive function, because of the viability of the mechanoreceptors. Paper # 11: Biomechanical Comparison of Anatomic Double-Bundle, Anatomic Single-Bundle and NonAnatomic Single-Bundle Anterior Cruciate Ligament Reconstructions EIJI KONDO, MD, PHD, JAPAN AZHAR M. MERICAN, BM, MSORTH, UNITED KINGDOM KAZUNORI YASUDA, MD, PHD, JAPAN ANDREW A. AMIS, DSC, UNITED KINGDOM · Imperial College London London, UNITED KINGDOM Summary: The anterior translation during the pivot-shift and internal rotational laxity after the anatomic double-bundle and the laterally placed single-bundle ACL reconstructions were significantly better than after the single-bundle reconstruction placed in the femoral anteromedial bundle attachment with hamstrings tendon grafts. Abstract: Introduction: Recently, several trials have compared the clinical results between anatomic double-bundle and single-bundle ACL reconstructions [1-3]: their anatomic double-bundle procedures were significantly better than their single-bundle procedures concerning the pivot-shift test and/or the anterior laxity. However, it remains controversial whether the anatomic double-bundle procedure is superior [4,5]. Biomechanical studies have found that the double-bundle procedure in cadaveric knees can achieve better results in both anterior and rotatory laxity than the single-bundle procedure [6,7]. However, it is possible that tunnel positions created with clinical double-bundle procedures in patients are different from those created with controlled experimental procedures, because it is not always straightforward to create tunnels using a specific device in the clinical setting. To address this, a biomechanical comparison of the various clinical double-bundle procedures with single-bundle procedures, using cadaveric knees is required. However, such studies have not yet been performed. This study aimed to
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test the hypothesis that using a commercially available aiming device, better rotational stability can be achieved with anatomic double-bundle and laterally placed singlebundle procedures compared to conventional single-bundle procedure. Methods: Eight fresh-frozen cadaveric knees were used. The knee was mounted in a 6 degrees of freedom rig and laxity testing was performed using the following: 90-N anterior tibial loads, 5-Nm internal and external tibial torques, and a simulated pivot-shift test (50N-iliotibial tract loading, 5-Nm valgus moment, and 1-Nm internal tibial torque). Knee kinematics was recorded with an active optical tracking system (Polaris, NDI, Canada) for (1) the intact, (2) ACL-deficient, (3) anatomic doublebundle (DB) reconstruction, (4) conventional single-bundle (CSB) and (5)laterally placed single-bundle (LSB) reconstructions. ACL reconstruction was performed three times in each knee by filling the tunnels with polyester resin using the same hamstring tendon graft. In the DB, the 4 tunnels that passed through the anatomical attachment of the AM and PL bundles on the tibia and the femur, respectively, were created using the anatomic ACL guide system (S&N). In the CSB, the tibial tunnel that passed through the posterior aspect of the normal ACL attachment was created. Then, the femoral tunnel was drilled into the center of the AM bundle attachment. In the LSB, the tibial and the femoral tunnel were created at the center of the normal ACL insertions between AM and PL bundles. The graft was simultaneously fixed at 20 degrees of knee flexion, applying a total initial tension of 60 N, while a 40N posterior tibial load was applied. Each graft was secured with endobuttons (S&N) on the femur and with screws (DSP plate, S&N) on the tibia. The kinematic data were analyzed using a two-way repeatedmeasures ANOVA. Significance was set at p⬍0.05. Results: The anterior translation-versus-flexion curves were significantly different among the ACL-deficient, DB, CSB and LSB (p⬍0.0001). The anterior translations in DB, CSB and LSB were significantly less than in the ACL-deficient knee. There were no significant differences among DB, CSB and LSB. Tibial internal rotation increased significantly (p⬍0.0182) after the ACL was cut, from 0 to 110 degrees of knee flexion. The internal rotation-versus-flexion curves were significantly different among the ACL-deficient, DB, CSB and LSB (p⬍0.0001). The internal rotational laxities in DB and LSB were significantly less than in CSB (p⫽0.0375, and p⫽0.0006, respectively). There were no significant differences between the ACL-deficient and CSB. Transection and the reconstructions of the ACL did not cause significant changes in tibial external rotation laxity. Under the simulated pivot-shift test, tibial anterior transla-
tion increased significantly near extension after the ACL was sectioned. The anterior translation-versus-flexion curves were significantly different among the ACL-deficient, DB, CSB and LSB (p ⬍0.0005). The anterior translation was significantly less in DB, and LSB than in CSB (p ⬍0.0001, and p ⬍0.0001, respectively). Discussion: This study showed that internal rotational laxity under tibial torque and anterior translation laxity under pivot-shift loading were significantly less after DB and LSB than after CSB. However, there were no significant differences between the three procedures with anterior translation load, or tibial external rotation torque. In addition, there were no significant differences between DB and LSB with all loading conditions. Although the present study showed promising results of the DB procedure, further clinical studies, including quantitative evaluation of the effects on the rotatory stability and long-term survival of the graft functions, are needed to establish the clinical utility of the DB for the ACLdeficient knee. This study did not find any significant differences between DB and LSB, where the tibial and the femoral tunnel were placed at the center of the anatomical attachment area. This might suggest that there is no justification for using the more complex double-bundle method, and so further understanding of the clinical and biomechanical performance is required.
REFERENCES: 1. 2. 3. 4. 5. 6. 7.
Aglietti et al. CORR 2007 Yagi et al. CORR 2007 Kondo et al. AJSM 2008 Lewis et al. AJSM 2008 Meredick et al. AJSM 2008 Yagi et al. AJSM 2002 Yamamoto et al. AJSM 2004
Paper # 12: Biomechanical Comparison of Bioabsorbable Suture Anchor Fixation on Tibial Side for ACL Reconstruction Using Free Soft Tissue Graft Experimental Laboratory Study on Porcine Bone MYUNG KU KIM, MD, KOREA SUNG WOOK CHOI, MD, SOUTH KOREA MAN HEE WON, SOUTH KOREA DONG SUK YOO, MD, SOUTH KOREA · Inha University Hospital Incheon, SOUTH KOREA Summary: We hypothesize that bioabsorbable suture anchor (BSA) as additional soft tissue grafts fixation devices would have a adequate pullout strength as much as
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However, the number in Group 4 was lower compared to the other groups and LSD analysis showed a trend towards significant difference between Group 1and Group 4 (p⫽0.055). Although some degenerative and atrophic changes could be observed in Group 4, no obvious variation was observed regarding the size of the Ruffini-like endings among four groups. So we consider that the residual mechanoreceptors in a rupture ACL survive for a long time and show no obvious withering. This implies that the ACL remnant may attribute the restoration of proprioceptive function, because of the viability of the mechanoreceptors. Paper # 11: Biomechanical Comparison of Anatomic Double-Bundle, Anatomic Single-Bundle and NonAnatomic Single-Bundle Anterior Cruciate Ligament Reconstructions EIJI KONDO, MD, PHD, JAPAN AZHAR M. MERICAN, BM, MSORTH, UNITED KINGDOM KAZUNORI YASUDA, MD, PHD, JAPAN ANDREW A. AMIS, DSC, UNITED KINGDOM · Imperial College London London, UNITED KINGDOM Summary: The anterior translation during the pivot-shift and internal rotational laxity after the anatomic double-bundle and the laterally placed single-bundle ACL reconstructions were significantly better than after the single-bundle reconstruction placed in the femoral anteromedial bundle attachment with hamstrings tendon grafts. Abstract: Introduction: Recently, several trials have compared the clinical results between anatomic double-bundle and single-bundle ACL reconstructions [1-3]: their anatomic double-bundle procedures were significantly better than their single-bundle procedures concerning the pivot-shift test and/or the anterior laxity. However, it remains controversial whether the anatomic double-bundle procedure is superior [4,5]. Biomechanical studies have found that the double-bundle procedure in cadaveric knees can achieve better results in both anterior and rotatory laxity than the single-bundle procedure [6,7]. However, it is possible that tunnel positions created with clinical double-bundle procedures in patients are different from those created with controlled experimental procedures, because it is not always straightforward to create tunnels using a specific device in the clinical setting. To address this, a biomechanical comparison of the various clinical double-bundle procedures with single-bundle procedures, using cadaveric knees is required. However, such studies have not yet been performed. This study aimed to
e76
ABSTRACTS
test the hypothesis that using a commercially available aiming device, better rotational stability can be achieved with anatomic double-bundle and laterally placed singlebundle procedures compared to conventional single-bundle procedure. Methods: Eight fresh-frozen cadaveric knees were used. The knee was mounted in a 6 degrees of freedom rig and laxity testing was performed using the following: 90-N anterior tibial loads, 5-Nm internal and external tibial torques, and a simulated pivot-shift test (50N-iliotibial tract loading, 5-Nm valgus moment, and 1-Nm internal tibial torque). Knee kinematics was recorded with an active optical tracking system (Polaris, NDI, Canada) for (1) the intact, (2) ACL-deficient, (3) anatomic doublebundle (DB) reconstruction, (4) conventional single-bundle (CSB) and (5)laterally placed single-bundle (LSB) reconstructions. ACL reconstruction was performed three times in each knee by filling the tunnels with polyester resin using the same hamstring tendon graft. In the DB, the 4 tunnels that passed through the anatomical attachment of the AM and PL bundles on the tibia and the femur, respectively, were created using the anatomic ACL guide system (S&N). In the CSB, the tibial tunnel that passed through the posterior aspect of the normal ACL attachment was created. Then, the femoral tunnel was drilled into the center of the AM bundle attachment. In the LSB, the tibial and the femoral tunnel were created at the center of the normal ACL insertions between AM and PL bundles. The graft was simultaneously fixed at 20 degrees of knee flexion, applying a total initial tension of 60 N, while a 40N posterior tibial load was applied. Each graft was secured with endobuttons (S&N) on the femur and with screws (DSP plate, S&N) on the tibia. The kinematic data were analyzed using a two-way repeatedmeasures ANOVA. Significance was set at p⬍0.05. Results: The anterior translation-versus-flexion curves were significantly different among the ACL-deficient, DB, CSB and LSB (p⬍0.0001). The anterior translations in DB, CSB and LSB were significantly less than in the ACL-deficient knee. There were no significant differences among DB, CSB and LSB. Tibial internal rotation increased significantly (p⬍0.0182) after the ACL was cut, from 0 to 110 degrees of knee flexion. The internal rotation-versus-flexion curves were significantly different among the ACL-deficient, DB, CSB and LSB (p⬍0.0001). The internal rotational laxities in DB and LSB were significantly less than in CSB (p⫽0.0375, and p⫽0.0006, respectively). There were no significant differences between the ACL-deficient and CSB. Transection and the reconstructions of the ACL did not cause significant changes in tibial external rotation laxity. Under the simulated pivot-shift test, tibial anterior transla-
tion increased significantly near extension after the ACL was sectioned. The anterior translation-versus-flexion curves were significantly different among the ACL-deficient, DB, CSB and LSB (p ⬍0.0005). The anterior translation was significantly less in DB, and LSB than in CSB (p ⬍0.0001, and p ⬍0.0001, respectively). Discussion: This study showed that internal rotational laxity under tibial torque and anterior translation laxity under pivot-shift loading were significantly less after DB and LSB than after CSB. However, there were no significant differences between the three procedures with anterior translation load, or tibial external rotation torque. In addition, there were no significant differences between DB and LSB with all loading conditions. Although the present study showed promising results of the DB procedure, further clinical studies, including quantitative evaluation of the effects on the rotatory stability and long-term survival of the graft functions, are needed to establish the clinical utility of the DB for the ACLdeficient knee. This study did not find any significant differences between DB and LSB, where the tibial and the femoral tunnel were placed at the center of the anatomical attachment area. This might suggest that there is no justification for using the more complex double-bundle method, and so further understanding of the clinical and biomechanical performance is required.
REFERENCES: 1. 2. 3. 4. 5. 6. 7.
Aglietti et al. CORR 2007 Yagi et al. CORR 2007 Kondo et al. AJSM 2008 Lewis et al. AJSM 2008 Meredick et al. AJSM 2008 Yagi et al. AJSM 2002 Yamamoto et al. AJSM 2004
Paper # 12: Biomechanical Comparison of Bioabsorbable Suture Anchor Fixation on Tibial Side for ACL Reconstruction Using Free Soft Tissue Graft Experimental Laboratory Study on Porcine Bone MYUNG KU KIM, MD, KOREA SUNG WOOK CHOI, MD, SOUTH KOREA MAN HEE WON, SOUTH KOREA DONG SUK YOO, MD, SOUTH KOREA · Inha University Hospital Incheon, SOUTH KOREA Summary: We hypothesize that bioabsorbable suture anchor (BSA) as additional soft tissue grafts fixation devices would have a adequate pullout strength as much as