2002 - University of Washington Bone and Joint Sources

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Figure 2: Loaded- 36 Newtons. Partial un-crimping- 12X. (Figure 2 and 3). The 67, 100, and 220 N loaded specimens displayed no evidence of crimping in any region (Figure 4). The blinded observer correctly identified the loading history in 14/16 specimens. Two of the 9N loaded specimens were incorrectly identified as un-loaded specimens. Collagen Fiber Interaction Loading the uncut ligaments at 150N resulted in complete un-crimping of the ligament. “Deep” section through the anterior 1/3 of the patellar ligament resulted in a crimping of the cut fibers which was visible to the full depth of the incision, and which was visible from insertion to insertion (Figure 5). The uncut fibers immediately deep to the incision were loaded and completely un-crimped (Figure 5). The cut fibers at the deepest point of the incision were retracted to approximately the same distance as the superficial fibers. Superficial section, partially through the superficial band of the patellar ligament, resulted in a localized retraction and crimping of fibers near the cut site (Figure 6). However, the cut fibers remained uncrimped along the majority of the length of the ligament. A triangular shaped lesion was visible on SEM, as the cut fibers adjacent to the loaded fibers were not as retracted, nor as crimped as the superficial cut fibers (Figure 7). Figure 3: Loaded- 36 Newtons. Partial un-crimping- 60X. Figure 4: Loaded- 67 Newtons. No Crimp 12X. DISCUSSION This study shows that freezefixation can preserve ligament collagen in an un-crimped state, and thus loaded fibers can be distinguished from nonloaded fibers in which a crimp remains. Using this technique, the rabbit patellar ligament showed a consistent pattern of strain dispersion with increasing load. Under these loading conditions, the central 1/3 of the ligament uncrimped at lower applied loads than the deep and superficial regions. The crimp in the entire specimen was extinguished at approximately 67N which, based upon ligament cross-sectional estimates, correlates closely with the previously reported toe-region of the stress strain curve of the rabbit patellar ligament (approx 4.5 MPa) (Woo et al, 1993). The strength of this technique is that it enables investigators to examine entire ligaments or tendons preserved in a functionally loaded state using various forms of microscopy, including the potential use of high 2002 ORTHOPAEDIC RESEARCH REPORT 33
Figure 5: Deep cut in loaded ligament. 12X. resolution electron microscopy. This study also confirms that the patellar ligament is composed of independent parallel units. When transected, the anterior third of the ligament remains fully crimped even when the intact ligament is under sufficient tension to completely ablate crimp. This condition would not occur in the face of any functional crossover between cut and uncut segments. It also strongly implies that mechanical coupling between collagen fibrils does exist within the anterior band, since partial section of that segment does not cause full recoil of the transected part. Collagen fiber recruitment is thought to be important to how ligaments resist elongation under load. This evidence for lateral support between collagen fibers further advances our understanding of the functional ultrastructure of normal ligaments. RECOMMENDED READING Gathercole and Keller, Matrix, 1991 Woo et al. J. Orthop Res., 1993 Figure 6: Superficial cut in loaded ligament. 60X. Figure 7: SEM superficial cut in loaded ligament. 34 2002 ORTHOPAEDIC RESEARCH REPORT
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Page 35 and 36: The Role of Fusion Protein-Induced
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Page 45 and 46: Evidence that FGF-18 is a Growth Fa
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Page 73 and 74: Friends of Orthopaedics Richard M.
Page 75 and 76: 1983 E. Anne O. Elliot, M.D. Edward

2002 - University of Washington Bone and Joint Sources

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