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Paper 113: Size Variability of the Human Anterior Cruciate Ligament Insertion Sites: A Prospective Study
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ABSTRACTS
Methods: Animal anatomy was studied on freshly frozen specimens. The ACL anatomy was studied by MR imaging, followed by dissection. Bones from different species were studied by using three-dimensional laser photography and 3D CT scans and measurements were done on specific software. Results: We have found a large variety of ACL anatomy in the Animal Kingdom. The Nubian goat (Capra hircus), the springbok (Antidorcas marsupialis), the pig (Sus scrofa domestica) and the Rhesus monkey (Macaca mulatta) have three ACL bundles (AM, IM, PL). Human (Homo sapiens) has 2 bundles. The ostrich (Struthio camelus) and the chicken (Gallus gallus) have only one bundle. Discussion/Conclusion: By studying the complexities of functional morphologic features of the knee in different animal species we can help surgeons better understand knee kinematics and the role of each ACL bundle in human being and this knowledge will help surgeons reconstruct anatomy more accurately and therefore perform a more precise knee surgery. Paper 112: Anatomical Description and Quantitative Analysis of the Anterior Cruciate Ligament of the Goat Knee MARIO RONGA, MD, ITALY, PRESENTING AUTHOR MUTURI G. MURIUKI, PHD, USA MAX EKDAHL, MD, CHILE PATRICK J. SMOLINSKI, PH.D., USA FREDDIE H. FU, MD, USA ABSTRACT Purpose: The goat knee has been widely used for anterior cruciate ligament (ACL) reconstruction models, including biomechanical and biological studies. The purpose of this study was to perform a detailed qualitatively and quantitatively assessment of the ACL, its bundles and its insertion site in the goat knee. Materials and Methods: Ten fresh-frozen non-paired adult goat knees were used in this study. We measured the insertion site area of each bundle, the distances between the center of these areas and the anatomy landmarks. Moreover, we analyzed the ratio between the femoral and tibial insertion site areas and the midsubstance cross-sectional area of the ACL. A digitizing systems, Microscribe 3D and 3D-laser camera, were used to record the data. Statistical analysis was performed using a t test with p ⬍ 0.05 being considered statistically significant. Results: Three bundles could be clearly identified in each ACL: anteromedial (AM), intermediate (IM) and posterolateral (PL) bundle. Interestingly, the anterior horn attachment of the lateral meniscus divides the an-
terior portion of the tibial ACL insertion into AM and IM/PL bundles. On the tibial side, the insertion of the IM and PL bundles could not be identified separately. On the femoral side, each insertion were clearly identified separately. On the femur, the area of insertion site, represented as a percentage of the entire footprint, was 54.3 ⫾ 7.8% for AM, 9.9 ⫾ 3.8% for IM and 35.8 ⫾ 4.4% for PL bundle. The area of tibial insertion was 68.6 ⫾ 4.7% for AM and 31.4 ⫾ 4.7% for IM/PL bundle. The differences between the entire femoral (51.9 ⫾ 4.6 mm2) and tibial (81.1 ⫾ 11.9 mm2) footprint areas and between each bundle were statistical significant (p ⬍ 0.05). All insertions had significantly larger areas than the ligament midsubstance cross-sectional area (21.76 ⫾ 7.26 mm2) (p ⬍ 0.05). Conclusion: The precise knowledge of the ACL anatomy in the goat knee is necessary when a goat model is planned. Our study provides valuable information about the ACL, its bundles and its femoral and tibial insertion sites. Although it shares some similarities with the human ACL, the goat has some specific features that must be considered. Further investigation should be conducted in order to determine the biomechanical role of each bundle in the goat knee. Paper 113: Size Variability of the Human Anterior Cruciate Ligament Insertion Sites: A Prospective Study SEBASTIAN KOPF, M.D., USA, PRESENTING AUTHOR MATHEW WILLIAM POMBO, M.D., USA JAMES J. IRRGANG, PHD, PT, ATC, USA MICHAL SZCZODRY, MD, USA WEI SHEN, M.D., USA FREDDIE H. FU, MD, USA ABSTRACT Background: Current trends in anterior cruciate ligament reconstruction (ACL-R) have been towards a more anatomic reconstruction that restores the normal size and location of the ACL insertions. This has resulted in a more individualized approach to ACL-R. Several studies have shown that the size of the ACL insertion sites is variable, however these studies are limited by relatively small sample sizes. The purpose of this prospective study is to evaluate the size of the ACL insertion sites at the time of arthroscopic ACL-R. Methods: 60 patients with an average age of 22.9 years (SD 9.8, range 13.6 to 55.3) undergoing anatomic ACL-R with identifiable insertion sites from November of 2007 to February 2008 were included in this study. Time from injury to surgery averaged 60.9 days (SD 74, range 15 to 369). Demographic data from
ABSTRACTS each patient was recorded prior to surgery. Under arthroscopic visualization the tibial and femoral ACL insertion sites, as well as the two bundle anatomy, were identified using the ACL injury pattern, the soft tissue remnants, and bony landmarks. After marking the insertion sites with electrocautery, the total length and width of the femoral and tibial insertion sites and the two ACL bundles were measured using an arthroscopic ruler. The distance between the centers of the two bundles was also recorded. The reliability of insertion site measurements was blindly tested by a second surgeon. Results: The tibial insertion sites had a mean length of 16.8 mm (SD 2, range 12-20 mm). The tibial AM bundle had a mean length of 8.7 mm (SD 1.1, range 7-11 mm) and a mean width of 9.2 mm (SD 1.1, range 10, 7-11 mm). The tibial PL bundle had a mean length of 7.4 mm (SD 1.1, range 5-9 mm) and a mean width of 6.6 mm (SD 1, range 4-8 mm). The distance between the centers of the tibial AM and PL bundles averaged 8.7 mm (SD 1.5, range 7-10 mm). The femoral insertion sites had a mean length of 16.7 mm (SD 2.2, range 12-20 mm). The femoral AM bundle had a mean length of 9.7 mm (SD 1.2, range 7-12 mm) and a mean width of 8.6 mm (SD 0.9, range 7-10 mm). The femoral PL bundle had a mean length of 7.1 mm (SD 1.1, range 4-9 mm) and a mean width of 6.6 mm (SD 1.1, range 4-9 mm). Statistical evaluation of patient demographics revealed a positive correlation in regard to patient height and weight (p⬍0.05) for femoral and tibial ACL length, tibial PL bundle length, femoral AM bundle length, and tibial AM and PL bundle areas. Conclusions: This study is the only arthroscopic in vivo study of ACL insertion site anatomy and has the largest sample size reported in the literature. The results of this study clearly support a large variation in ACL insertion site sizes, but are the first to show a positive correlation with patient weight and height. With current trends in ACL-R supporting a more anatomical approach, knowledge of the insertion site sizes and locations are keys to the restoration of native ACL anatomy. Paper 114: Anatomical and Histological Study of the Anterior Cruciate Ligament: Is There an Intermediate Bundle? MARIO FERRETTI, MD, PHD, BRAZIL, PRESENTING AUTHOR MARIA TEREZA SEIXAS ALVES, MD, PHD, BRAZIL FRANK BERETTA MARCONDES, MD, BRAZIL JOICEMAR SAROUCO AMARO, MD, BRAZIL FREDDIE H. FU, MD, USA MOISES COHEN, MD, PHD, BRAZIL
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ABSTRACT Introduction: The anatomy of the anterior cruciate ligament (ACL) is divided in two functional bundles, anteromedial (AM) and posterolateral (PL) bundles. However, there is a controversy about the number of anatomic bundles that constitute the ACL. This subject is controversy in the literature. We can find studies where the ACL is made by only one bundle, or by two bundles, and even three bundles. The third bundle described is the intermediate bundle (IM). Another important subject that needs to be clarified is the microscopic features of the ACL, mainly regarding to the mechanoreceptors and vascularity of the ACL. In this study we performed an anatomical and histological evaluation of the ACL in order to determine: 1) the gross anatomy of the ACL regarding the number of bundles and its tibial and femoral insertion; 2) the histology of the ACL regarding the number of bundles in the tibial insertion part of the ACL, in the midsubstance and in the femoral insertion part; 3) the presence of mechanoreceptors and vascularity in the ACL regarding the anatomical position of the ACL. Methods: Twenty eight knees were used in this study. The knees were dissected and the gross anatomy was observed regarding the numbers of bundles and its tibial and femoral insertion. Eight ACLs with three distinct bundles were removed, divided in three bundles in order to measure the length and diameter of each bundle. Twenty ACLs were removed, divided in three transverse part (1/3 tibial part, 1/3 midsubstance, and 1/3 femoral part) and subjected to histological process. Coronal and transverse sections were stained with haematoxilin & eosin in order to identify different bundles of the ACL. Immunohistochemestry with S100 antiprotein was performed to identify the presence of mechanoreceptors regarding the type of the mechanoreceptors and its location in the ACL. Results: Gross anatomy: The ACL usually contains three distinct bundles, AM, IM and PL. The bundles were identified by invagination of the synovial membrane into the ligament. We found 24 out of 28 ACLs composed of three bundles. The distinction between bundles varies from each ACL, with some ACL having well distinct three bundles. In 4 ACLs we could not observe the presence of three bundles, but two bundles were observed (AM and PL). The length and the larger diameter was respectively 36.4⫾2.8 and 8.2⫾1.2 mm for the AM bundle, 30.7⫾2.7 and 6.3⫾1.1 mm for IM bundle, and 25.1⫾2.2 and 4.5⫾1 mm for PL bundle. The tibial insertion has a triangular shape and the femoral insertion has a semicircular shape. Histology: The histological sections demonstrated that the ACL changes its config-
ABSTRACTS
Methods: Animal anatomy was studied on freshly frozen specimens. The ACL anatomy was studied by MR imaging, followed by dissection. Bones from different species were studied by using three-dimensional laser photography and 3D CT scans and measurements were done on specific software. Results: We have found a large variety of ACL anatomy in the Animal Kingdom. The Nubian goat (Capra hircus), the springbok (Antidorcas marsupialis), the pig (Sus scrofa domestica) and the Rhesus monkey (Macaca mulatta) have three ACL bundles (AM, IM, PL). Human (Homo sapiens) has 2 bundles. The ostrich (Struthio camelus) and the chicken (Gallus gallus) have only one bundle. Discussion/Conclusion: By studying the complexities of functional morphologic features of the knee in different animal species we can help surgeons better understand knee kinematics and the role of each ACL bundle in human being and this knowledge will help surgeons reconstruct anatomy more accurately and therefore perform a more precise knee surgery. Paper 112: Anatomical Description and Quantitative Analysis of the Anterior Cruciate Ligament of the Goat Knee MARIO RONGA, MD, ITALY, PRESENTING AUTHOR MUTURI G. MURIUKI, PHD, USA MAX EKDAHL, MD, CHILE PATRICK J. SMOLINSKI, PH.D., USA FREDDIE H. FU, MD, USA ABSTRACT Purpose: The goat knee has been widely used for anterior cruciate ligament (ACL) reconstruction models, including biomechanical and biological studies. The purpose of this study was to perform a detailed qualitatively and quantitatively assessment of the ACL, its bundles and its insertion site in the goat knee. Materials and Methods: Ten fresh-frozen non-paired adult goat knees were used in this study. We measured the insertion site area of each bundle, the distances between the center of these areas and the anatomy landmarks. Moreover, we analyzed the ratio between the femoral and tibial insertion site areas and the midsubstance cross-sectional area of the ACL. A digitizing systems, Microscribe 3D and 3D-laser camera, were used to record the data. Statistical analysis was performed using a t test with p ⬍ 0.05 being considered statistically significant. Results: Three bundles could be clearly identified in each ACL: anteromedial (AM), intermediate (IM) and posterolateral (PL) bundle. Interestingly, the anterior horn attachment of the lateral meniscus divides the an-
terior portion of the tibial ACL insertion into AM and IM/PL bundles. On the tibial side, the insertion of the IM and PL bundles could not be identified separately. On the femoral side, each insertion were clearly identified separately. On the femur, the area of insertion site, represented as a percentage of the entire footprint, was 54.3 ⫾ 7.8% for AM, 9.9 ⫾ 3.8% for IM and 35.8 ⫾ 4.4% for PL bundle. The area of tibial insertion was 68.6 ⫾ 4.7% for AM and 31.4 ⫾ 4.7% for IM/PL bundle. The differences between the entire femoral (51.9 ⫾ 4.6 mm2) and tibial (81.1 ⫾ 11.9 mm2) footprint areas and between each bundle were statistical significant (p ⬍ 0.05). All insertions had significantly larger areas than the ligament midsubstance cross-sectional area (21.76 ⫾ 7.26 mm2) (p ⬍ 0.05). Conclusion: The precise knowledge of the ACL anatomy in the goat knee is necessary when a goat model is planned. Our study provides valuable information about the ACL, its bundles and its femoral and tibial insertion sites. Although it shares some similarities with the human ACL, the goat has some specific features that must be considered. Further investigation should be conducted in order to determine the biomechanical role of each bundle in the goat knee. Paper 113: Size Variability of the Human Anterior Cruciate Ligament Insertion Sites: A Prospective Study SEBASTIAN KOPF, M.D., USA, PRESENTING AUTHOR MATHEW WILLIAM POMBO, M.D., USA JAMES J. IRRGANG, PHD, PT, ATC, USA MICHAL SZCZODRY, MD, USA WEI SHEN, M.D., USA FREDDIE H. FU, MD, USA ABSTRACT Background: Current trends in anterior cruciate ligament reconstruction (ACL-R) have been towards a more anatomic reconstruction that restores the normal size and location of the ACL insertions. This has resulted in a more individualized approach to ACL-R. Several studies have shown that the size of the ACL insertion sites is variable, however these studies are limited by relatively small sample sizes. The purpose of this prospective study is to evaluate the size of the ACL insertion sites at the time of arthroscopic ACL-R. Methods: 60 patients with an average age of 22.9 years (SD 9.8, range 13.6 to 55.3) undergoing anatomic ACL-R with identifiable insertion sites from November of 2007 to February 2008 were included in this study. Time from injury to surgery averaged 60.9 days (SD 74, range 15 to 369). Demographic data from
ABSTRACTS each patient was recorded prior to surgery. Under arthroscopic visualization the tibial and femoral ACL insertion sites, as well as the two bundle anatomy, were identified using the ACL injury pattern, the soft tissue remnants, and bony landmarks. After marking the insertion sites with electrocautery, the total length and width of the femoral and tibial insertion sites and the two ACL bundles were measured using an arthroscopic ruler. The distance between the centers of the two bundles was also recorded. The reliability of insertion site measurements was blindly tested by a second surgeon. Results: The tibial insertion sites had a mean length of 16.8 mm (SD 2, range 12-20 mm). The tibial AM bundle had a mean length of 8.7 mm (SD 1.1, range 7-11 mm) and a mean width of 9.2 mm (SD 1.1, range 10, 7-11 mm). The tibial PL bundle had a mean length of 7.4 mm (SD 1.1, range 5-9 mm) and a mean width of 6.6 mm (SD 1, range 4-8 mm). The distance between the centers of the tibial AM and PL bundles averaged 8.7 mm (SD 1.5, range 7-10 mm). The femoral insertion sites had a mean length of 16.7 mm (SD 2.2, range 12-20 mm). The femoral AM bundle had a mean length of 9.7 mm (SD 1.2, range 7-12 mm) and a mean width of 8.6 mm (SD 0.9, range 7-10 mm). The femoral PL bundle had a mean length of 7.1 mm (SD 1.1, range 4-9 mm) and a mean width of 6.6 mm (SD 1.1, range 4-9 mm). Statistical evaluation of patient demographics revealed a positive correlation in regard to patient height and weight (p⬍0.05) for femoral and tibial ACL length, tibial PL bundle length, femoral AM bundle length, and tibial AM and PL bundle areas. Conclusions: This study is the only arthroscopic in vivo study of ACL insertion site anatomy and has the largest sample size reported in the literature. The results of this study clearly support a large variation in ACL insertion site sizes, but are the first to show a positive correlation with patient weight and height. With current trends in ACL-R supporting a more anatomical approach, knowledge of the insertion site sizes and locations are keys to the restoration of native ACL anatomy. Paper 114: Anatomical and Histological Study of the Anterior Cruciate Ligament: Is There an Intermediate Bundle? MARIO FERRETTI, MD, PHD, BRAZIL, PRESENTING AUTHOR MARIA TEREZA SEIXAS ALVES, MD, PHD, BRAZIL FRANK BERETTA MARCONDES, MD, BRAZIL JOICEMAR SAROUCO AMARO, MD, BRAZIL FREDDIE H. FU, MD, USA MOISES COHEN, MD, PHD, BRAZIL
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ABSTRACT Introduction: The anatomy of the anterior cruciate ligament (ACL) is divided in two functional bundles, anteromedial (AM) and posterolateral (PL) bundles. However, there is a controversy about the number of anatomic bundles that constitute the ACL. This subject is controversy in the literature. We can find studies where the ACL is made by only one bundle, or by two bundles, and even three bundles. The third bundle described is the intermediate bundle (IM). Another important subject that needs to be clarified is the microscopic features of the ACL, mainly regarding to the mechanoreceptors and vascularity of the ACL. In this study we performed an anatomical and histological evaluation of the ACL in order to determine: 1) the gross anatomy of the ACL regarding the number of bundles and its tibial and femoral insertion; 2) the histology of the ACL regarding the number of bundles in the tibial insertion part of the ACL, in the midsubstance and in the femoral insertion part; 3) the presence of mechanoreceptors and vascularity in the ACL regarding the anatomical position of the ACL. Methods: Twenty eight knees were used in this study. The knees were dissected and the gross anatomy was observed regarding the numbers of bundles and its tibial and femoral insertion. Eight ACLs with three distinct bundles were removed, divided in three bundles in order to measure the length and diameter of each bundle. Twenty ACLs were removed, divided in three transverse part (1/3 tibial part, 1/3 midsubstance, and 1/3 femoral part) and subjected to histological process. Coronal and transverse sections were stained with haematoxilin & eosin in order to identify different bundles of the ACL. Immunohistochemestry with S100 antiprotein was performed to identify the presence of mechanoreceptors regarding the type of the mechanoreceptors and its location in the ACL. Results: Gross anatomy: The ACL usually contains three distinct bundles, AM, IM and PL. The bundles were identified by invagination of the synovial membrane into the ligament. We found 24 out of 28 ACLs composed of three bundles. The distinction between bundles varies from each ACL, with some ACL having well distinct three bundles. In 4 ACLs we could not observe the presence of three bundles, but two bundles were observed (AM and PL). The length and the larger diameter was respectively 36.4⫾2.8 and 8.2⫾1.2 mm for the AM bundle, 30.7⫾2.7 and 6.3⫾1.1 mm for IM bundle, and 25.1⫾2.2 and 4.5⫾1 mm for PL bundle. The tibial insertion has a triangular shape and the femoral insertion has a semicircular shape. Histology: The histological sections demonstrated that the ACL changes its config-