Principles of ACL graft fixation

29 Pages·2016·1.51 MB·English

Principles of ACL graft fixation
Ph. Landreau

Aspetar

Doha

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Introduction
The success of ACL surgery relies on patient selection,
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graft selection, fixation method, surgical technique
(position, tensioning and surgical approach) and
postoperative rehabilitation program.
ACL graft fixation: major factor influencing the graft’s
•
mechanical properties in the immediate postoperative
period. ==> Physiotherapy timing and protocol.
Industry
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Numerous publications
ACL and Graft strength Noyes 1984
BTB = mean strength of 159 to 168 % of that of ACL.
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Estimation of the ACL in vivo loading during “normal
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activity,” on average, of 454 N.
Graft fixation Kurosaka 1987
Better mechanical properties on BPTB grafts fixed with
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interference screw than staples or sutures tied over
buttons
The fixation site is the weakest link of ACL reconstruction
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ACL reconstruction decision
1. Graft choice
Biomechanical Properties of Selected ACL Graft Tissues
Tissue Ultimate tensile load N Stiffness (N/ Cross-sectional area
mm) (mm2)
(% ACL)
Intact ACL 2160 (100%) 242 44
BTB 10 mm 2977 (138%) 620 35
Quadruple hamstring 4090 (189%) 776 53
Quadriceps tendon 2352 (109%) 463 62
West et al.
2. Fixation choice
Fixation is the weakest link
Fixation Characteristics
Strength: Load that causes permanent displacement of
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the graft fixation complex. Measured in newtons (N)
Stiffness: Amount of strain or displacement produced by
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a given load. Measured in N/mm
Slippage: Change in position of the initial graft fixation
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position at a specific number of submaximal load cycles
Strength: Activities of daily living and rehabilitation
Minimum must be: 454 N (native ACL)
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Noyes FR, Butler DL, Grood ES, Zernicke RF, Hefzy MS.
Biomechanical analysis of human ligament grafts used in knee-ligament
repairs and reconstructions.
J Bone Joint Surg Am. 1984; 66:344-352
Characteristics of the fixation devices
Jackson DW, Grood ES, Goldstein JD, et al:
Acomparison of patellar tendon autograft and
allograft used for anterior cruciate ligament
reconstruction in the goat model.
Am J Sports Med 1993;21: 176-185.
Kousa P, Jarvinen TL, Vihavainen M, Kannus P,
Jarvinen M: The fixation strength of six hamstring
tendon graft fixation devices in anterior cruciate
ligament reconstruction: I. Femoral site.
Am J Sports Med 2003;31:174-181.
Kousa P, Jarvinen TL, Vihavainen M, Kannus P,
Jarvinen M: The fixation strength of six hamstring
tendon graft fixation devices in anterior cruciate
ligament reconstruction: II. Tibial site.
Am J Sports Med 2003;31:182-188.
Exceed the 450-N safe early
physiological loading threshold
proposed by Noyes et al.
West et al.
Stiffness and Slippage
Stiffness: Aperture fixation (joint line) > nonaperture (at
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distant site)
Ishibashi Y, Rudy TW, Livesay GA, Stone JD, Fu FH, Woo SL. Scheffler SU, Sudkamp NP, Gockenjan A, Hoffmann RF,
The effect of anterior cruciate ligament graft fixation site at the Weiler A. Biomechanical comparison of hamstring and patellar
tibia on knee stability:evaluation using a robotic testing system. tendon graft anterior cruciate ligament reconstruction
Arthroscopy. 1997; 13:177-182 techniques: the impact of fixation level and fixation method
under cyclic loading.
Arthroscopy. 2002; 18:304-315.
Slippage: 6 weeks of activities of daily living corresponds
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to approximately 220,000 cycles to the ACL.
Grover DM, Howell SM, Hull ML.
Early tension loss in an anterior cruciate ligament graft. A
cadaver study of four tibial fixation devices.
J Boint Joint Surg Am. 2005; 87:381-390
Graft fixation must be:
Strong enough to avoid failure.
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Stiff enough to restore load displacement response and
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allow biological incorporation of the graft into the bone
tunnels.
Secure enough to resist slippage under cyclic loading
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(during the first 1 to 2 months when conversion from
mechanical to biologic fixation is occurring).