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Replacement of the Medial Tibial Plateau by a Metal ... · replacement of the medial tibial plateau...

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Replacement of the Medial Tibial Plateau by a Metal Implant in a Goat Model + 1 Custers R J H; 1 Saris D B F; 1 Creemers L B; 1 Verbout A J; 1 van Rijen M H P; 2 Mastbergen S C; 2 Lafeber F P J G; 1,3 Dhert W J A + 1 Dept. Orthopaedics, University Medial Center Utrecht, The Netherlands 2 Dept. Rheumatology & Clin. Immunol., University Medial Center Utrecht, The Netherlands 3 Faculty of Veterinary Medicine, Utrecht University, The Netherlands [email protected] Introduction Damage to, or removal of the menisci alters static load transmission across the knee joint and is associated with degeneration of the articular cartilage of the knee, especially the tibial cartilage. Although very promising, the replacement options of the meniscus are limited. The purpose of the present study was to explore the surgical possibilities for replacement of the medial tibial plateau by a metal implant and to examine the implications for the opposing cartilage. Materials and Methods In 6 adult Dutch milk goats, the medial tibia plateau of the right knee was replaced by a cobalt-chromium (CoCr) implant, using PMMA bone cement for fixation. During the procedure, the anterior part of the medial meniscus was dissected, without damaging the integrity of both cruciate ligaments, the collateral ligaments and the femoral cartilage. The un- operated left knee served as a control. After a follow-up period of 26 weeks the animals were sacrificed. The joint was evaluated macroscopically (Macroscopic Articular Evaluation 1 ) and the cartilage quality was analysed macroscopically (Macroscopic Cartilage Score 2 ) and microscopically using the OARSI Osteoarthritis Cartilage Histopathology Assessment System 3 (OOCHAS) and the modified Histological Histochemical Grading System 4,5 (HHGS). Cartilage proteoglycan turnover and content were determined biochemically. From each of the three separate regions of the knee cartilage explants were cultured during 4 hours in the presence of 35 SO4 2- . After 4 hours, the samples were cultured for another 72 hours in the absence of 35 SO4 2- . Incorporation was measured by liquid scintillation analysis of tissue digests. GAG release and total GAG content of explants were measured by Alcian blue assay in conditioned medium and tissue extracts, respectively (Figure 1). Results Surgery was performed without complications. All animals were able to move and load the knees without any limitations. The macroscopic articular evaluation scores showed worsening 26 weeks after inserting the implant (p < 0.05). Macroscopic and microscopic scores showed more cartilage degeneration of the opposing medial femoral condyle in the experimental knee compared to the control knee (p < 0.05) (Figure 2). Biochemical analyses showed higher 35 SO4 2- incorporation at the medial femoral condyle cartilage in the experimental knees (p < 0.05). GAG content and release were not significantly different in experimental knees from controls for any of the compartments (Figure 3). Conclusions As demonstrated by macro- and microscopical analysis, the replacement of a medial tibia plateau by an implant induced considerable damage to the cartilage of the opposing medial femur. Surprisingly, this damage was only partly reflected by biochemical parameters. Synthetic activity of GAGs seemed to be stimulated in this compartment, although this did not affect final GAG content of the cartilage. Possibly the increased synthesis indicates some compensatory response to the tissue damage induced. Given the results obtained, the current model is a viable tool in the evaluation of bearing materials for implants. However, the introduction of tibial implants in a human clinical setting for the treatment of post-meniscectomy cartilage degeneration of the medial tibial plateau currently does not seem a realistic option. References 1 O’Driscoll SW et al. J Bone Jt Surg. 68A 1986. 2 Mastbergen SC et al. Rheumatology 45 2005. 3 Pritzker KPH et al. Osteoarthritis&Cartilage 14 2006. 4 Mankin HJ et al. J Bone Jt Surg 53A 1971. 5 Lafeber FP et al. Am J Pathology 140 1992. Poster No. 2061 55th Annual Meeting of the Orthopaedic Research Society
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Page 1: Replacement of the Medial Tibial Plateau by a Metal ... · replacement of the medial tibial plateau by a metal implant and to examine the implications for the opposing cartilage.

Replacement of the Medial Tibial Plateau by a Metal Implant in a Goat Model

+1Custers R J H; 1Saris D B F; 1Creemers L B; 1Verbout A J; 1van Rijen M H P; 2Mastbergen S C; 2Lafeber F P J G; 1,3Dhert W J A

+1 Dept. Orthopaedics, University Medial Center Utrecht, The Netherlands 2 Dept. Rheumatology & Clin. Immunol., University Medial Center Utrecht, The Netherlands

3 Faculty of Veterinary Medicine, Utrecht University, The Netherlands [email protected]

Introduction Damage to, or removal of the menisci alters static load transmission across the knee joint and is associated with degeneration of the articular cartilage of the knee, especially the tibial cartilage. Although very promising, the replacement options of the meniscus are limited. The purpose of the present study was to explore the surgical possibilities for replacement of the medial tibial plateau by a metal implant and to examine the implications for the opposing cartilage. Materials and Methods In 6 adult Dutch milk goats, the medial tibia plateau of the right knee was replaced by a cobalt-chromium (CoCr) implant, using PMMA bone cement for fixation. During the procedure, the anterior part of the medial meniscus was dissected, without damaging the integrity of both cruciate ligaments, the collateral ligaments and the femoral cartilage. The un-operated left knee served as a control. After a follow-up period of 26 weeks the animals were sacrificed. The joint was evaluated macroscopically (Macroscopic Articular Evaluation1) and the cartilage quality was analysed macroscopically (Macroscopic Cartilage Score2) and microscopically using the OARSI Osteoarthritis Cartilage Histopathology Assessment System3 (OOCHAS) and the modified Histological Histochemical Grading System4,5 (HHGS). Cartilage proteoglycan turnover and content were determined biochemically. From each of the three separate regions of the knee cartilage explants were cultured during 4 hours in the presence of 35SO4

2-. After 4 hours, the samples were cultured for another 72 hours in the absence of 35SO4

2-. Incorporation was measured by liquid scintillation analysis of tissue digests. GAG release and total GAG content of explants were measured by Alcian blue assay in conditioned medium and tissue extracts, respectively (Figure 1).

Results Surgery was performed without complications. All animals were able to move and load the knees without any limitations. The macroscopic articular evaluation scores showed worsening 26 weeks after inserting the implant (p < 0.05). Macroscopic and microscopic scores showed more cartilage degeneration of the opposing medial femoral condyle in the experimental knee compared to the control knee (p < 0.05) (Figure 2). Biochemical analyses showed higher 35SO4

2- incorporation at the medial femoral condyle cartilage in the experimental knees (p < 0.05). GAG content and release were not significantly different in experimental knees from controls for any of the compartments (Figure 3).

Conclusions As demonstrated by macro- and microscopical analysis, the replacement of a medial tibia plateau by an implant induced considerable damage to the cartilage of the opposing medial femur. Surprisingly, this damage was only partly reflected by biochemical parameters. Synthetic activity of GAGs seemed to be stimulated in this compartment, although this did not affect final GAG content of the cartilage. Possibly the increased synthesis indicates some compensatory response to the tissue damage induced. Given the results obtained, the current model is a viable tool in the evaluation of bearing materials for implants. However, the introduction of tibial implants in a human clinical setting for the treatment of post-meniscectomy cartilage degeneration of the medial tibial plateau currently does not seem a realistic option. References 1 O’Driscoll SW et al. J Bone Jt Surg. 68A 1986. 2 Mastbergen SC et al. Rheumatology 45 2005. 3 Pritzker KPH et al. Osteoarthritis&Cartilage 14 2006. 4 Mankin HJ et al. J Bone Jt Surg 53A 1971. 5 Lafeber FP et al. Am J Pathology 140 1992.

Poster No. 2061 • 55th Annual Meeting of the Orthopaedic Research Society

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