TY - JOUR
T1 - Biomechanical Evaluation of the Medial Stabilizers of the Patella
AU - LaPrade, Matthew D.
AU - Kallenbach, Samantha L.
AU - Aman, Zachary S.
AU - Moatshe, Gilbert
AU - Storaci, Hunter W.
AU - Turnbull, Travis Lee
AU - Arendt, Elizabeth A.
AU - Chahla, Jorge
AU - LaPrade, Robert F.
PY - 2018/6/1
Y1 - 2018/6/1
N2 - Background: Quantification of the biomechanical properties of each individual medial patellar ligament will facilitate an understanding of injury patterns and enhance anatomic reconstruction techniques by improving the selection of grafts possessing appropriate biomechanical properties for each ligament. Purpose: To determine the ultimate failure load, stiffness, and mechanism of failure of the medial patellofemoral ligament (MPFL), medial patellotibial ligament (MPTL), and medial patellomeniscal ligament (MPML) to assist with selection of graft tissue for anatomic reconstructions. Study Design: Descriptive laboratory study. Methods: Twenty-two nonpaired, fresh-frozen cadaveric knees were dissected free of all soft tissue structures except for the MPFL, MPTL, and MPML. Two specimens were ultimately excluded because their medial structure fibers were lacerated during dissection. The patella was obliquely cut to test the MPFL and the MPTL-MPML complex separately. To ensure that the common patellar insertion of the MPTL and MPML was not compromised during testing, only one each of the MPML and MPTL were tested per specimen (n = 10 each). Specimens were secured in a dynamic tensile testing machine, and the ultimate load, stiffness, and mechanism of failure of each ligament (MPFL = 20, MPML = 10, and MPTL = 10) were recorded. Results: The mean ± SD ultimate load of the MPFL (178 ± 46 N) was not significantly greater than that of the MPTL (147 ± 80 N; P =.706) but was significantly greater than that of the MPML (105 ± 62 N; P =.001). The mean ultimate load of the MPTL was not significantly different from that of the MPML (P =.210). Of the 20 MPFLs tested, 16 failed by midsubstance rupture and 4 by bony avulsion on the femur. Of the 10 MPTLs tested, 9 failed by midsubstance rupture and 1 by bony avulsion on the patella. Finally, of the 10 MPMLs tested, all 10 failed by midsubstance rupture. No significant difference was found in mean stiffness between the MPFL (23 ± 6 N/mm2) and the MPTL (31 ± 21 N/mm2; P =.169), but a significant difference was found between the MPFL and the MPML (14 ± 8 N/mm2; P =.003) and between the MPTL and MPML (P =.028). Conclusion: The MPFL and MPTL had comparable ultimate loads and stiffness, while the MPML had lower failure loads and stiffness. Midsubstance failure was the most common type of failure; therefore, reconstruction grafts should meet or exceed the values reported herein. Clinical Relevance: For an anatomic medial-sided knee reconstruction, the individual biomechanical contributions of the medial patellar ligamentous structures (MPFL, MPTL, and MPML) need to be characterized to facilitate an optimal reconstruction design.
AB - Background: Quantification of the biomechanical properties of each individual medial patellar ligament will facilitate an understanding of injury patterns and enhance anatomic reconstruction techniques by improving the selection of grafts possessing appropriate biomechanical properties for each ligament. Purpose: To determine the ultimate failure load, stiffness, and mechanism of failure of the medial patellofemoral ligament (MPFL), medial patellotibial ligament (MPTL), and medial patellomeniscal ligament (MPML) to assist with selection of graft tissue for anatomic reconstructions. Study Design: Descriptive laboratory study. Methods: Twenty-two nonpaired, fresh-frozen cadaveric knees were dissected free of all soft tissue structures except for the MPFL, MPTL, and MPML. Two specimens were ultimately excluded because their medial structure fibers were lacerated during dissection. The patella was obliquely cut to test the MPFL and the MPTL-MPML complex separately. To ensure that the common patellar insertion of the MPTL and MPML was not compromised during testing, only one each of the MPML and MPTL were tested per specimen (n = 10 each). Specimens were secured in a dynamic tensile testing machine, and the ultimate load, stiffness, and mechanism of failure of each ligament (MPFL = 20, MPML = 10, and MPTL = 10) were recorded. Results: The mean ± SD ultimate load of the MPFL (178 ± 46 N) was not significantly greater than that of the MPTL (147 ± 80 N; P =.706) but was significantly greater than that of the MPML (105 ± 62 N; P =.001). The mean ultimate load of the MPTL was not significantly different from that of the MPML (P =.210). Of the 20 MPFLs tested, 16 failed by midsubstance rupture and 4 by bony avulsion on the femur. Of the 10 MPTLs tested, 9 failed by midsubstance rupture and 1 by bony avulsion on the patella. Finally, of the 10 MPMLs tested, all 10 failed by midsubstance rupture. No significant difference was found in mean stiffness between the MPFL (23 ± 6 N/mm2) and the MPTL (31 ± 21 N/mm2; P =.169), but a significant difference was found between the MPFL and the MPML (14 ± 8 N/mm2; P =.003) and between the MPTL and MPML (P =.028). Conclusion: The MPFL and MPTL had comparable ultimate loads and stiffness, while the MPML had lower failure loads and stiffness. Midsubstance failure was the most common type of failure; therefore, reconstruction grafts should meet or exceed the values reported herein. Clinical Relevance: For an anatomic medial-sided knee reconstruction, the individual biomechanical contributions of the medial patellar ligamentous structures (MPFL, MPTL, and MPML) need to be characterized to facilitate an optimal reconstruction design.
KW - biomechanics
KW - medial patellar ligaments
KW - medial patellar stabilizers
KW - patellofemoral
UR - http://www.scopus.com/inward/record.url?scp=85048026425&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85048026425&partnerID=8YFLogxK
U2 - 10.1177/0363546518758654
DO - 10.1177/0363546518758654
M3 - Article
C2 - 29554436
AN - SCOPUS:85048026425
SN - 0363-5465
VL - 46
SP - 1575
EP - 1582
JO - American Journal of Sports Medicine
JF - American Journal of Sports Medicine
IS - 7
ER -