Mechanical alterations in the avascular region of the meniscus following partial meniscectomy: A cadaveric porcine longitudinal meniscal tear model
Introduction
The meniscus is a wedge-shaped structure that distributes joint loads over the entire articular cartilage surface and improves the stability of the joint movements in the knee. Tears in the meniscus, caused by traumas or age-related degenerative processes, are one of the most common type of knee injuries. Numerous studies have reported a significant relationship between meniscal tears and the development of post-injury osteoarthritis (OA) (Englund et al., 2009a, Englund et al., 2009b; Katz et al., 2013; Murphy et al., 2019b; Sharma et al., 2008). Damages in the mechanical functions of torn menisci are believed to significantly impair the weight-bearing capacities of the knee joint, which may result in an early onset of OA (Marchetti et al., 2017; Song et al., 2006, Song et al., 2014).
Partial meniscectomy has been a popular treatment for torn menisci due to its minimal invasiveness, fast and convenient surgical procedure, and short recovery periods (Fox et al., 2015). Although partial resection of the torn meniscus can effectively reduce pain, restore functions, and minimize tear progression, clinical studies have reported that meniscectomy tends to promote articular cartilage degenerations (Murphy et al., 2019b; Rockborn and Messner, 2000; Stein et al., 2010). Post-meniscectomy articular cartilage degradations may be caused by mechanical alterations in the magnitude and distribution of articular cartilage contact stresses (Bedi et al., 2010, Bedi et al., 2012; Dong et al., 2014; Lee et al., 2006; Song et al., 2006, Song et al., 2014). Meniscectomy was found to concentrate joint loadings on localized areas, which results in greater articular cartilage consolidations (Song et al., 2008). Increased cartilage deformation may lead to chronic dehydration in the extracellular matrix of the articular cartilage, which is detrimental to maintaining healthy articular cartilage structures. Thus, the use of meniscectomy treatments is limited due to the risk of mechanically-induced articular cartilage degenerations.
Recent treatments of meniscal tears include surgical repairs to maintain the native biomechanical conditions in the knee joint (Fox et al., 2015; Marchetti et al., 2017; Murphy et al., 2019a). Although meniscal repairs have been reported to significantly reduce the risk of post-surgery OA developments (Weber et al., 2018), the outcome of the surgeries depends on the healing ability of the meniscus. Because vascular supply is limited in the outer 1/3 portion of the meniscus, meniscal repairs in this well-vascularized region have been reported to be successful (Murphy et al., 2018; Noyes and Barber-Westin, 2010). However, the tears in the inner 1/3 portions of meniscus may not be healed properly due to the limited blood supply (Murphy et al., 2018; Noyes and Barber-Westin, 2010; Weber et al., 2018). Clinical studies reported that healing rates in the avascular inner 1/3 region of the meniscus were much lower than the healing rates in well-vascularized portions of the meniscus (the middle and outer 1/3 regions) (Bombelli et al., 1997; Weber et al., 2018). Repairs in the avascular inner regions might result in the need for multiple revision surgeries or cause an eventual failure in healing (Mordecai et al., 2014).
Repair surgeries are prescribed as an optimal treatment for meniscal tears. However, partial meniscectomy is still the preferred option for tears in the avascular region in spite of the risk of mechanically-induced OA (Jeong et al., 2012; Murphy et al., 2019b). Thus, the purpose of this study was to examine the risk of mechanical alterations following partial meniscal resection surgeries in the avascular inner region. Porcine cadaveric knee models with a longitudinal tear in the medial menisci were tested. We measured the articular cartilage contact pressure distributions in the knees with surgically repaired and partially resected menisci in the avascular region at various flexion angles. We then compared the magnitudes and the locations of the contact pressures in repaired and meniscectomized knees to estimate the risk of mechanically-induced articular cartilage degenerations following each treatment.
Section snippets
Sample preparation
Fourteen healthy cadaveric porcine knees were tested. The pigs weighted approximately 100 kg. We chose the porcine model due to its anatomical and functional similarities to human knees (Hennerbichler et al., 2007). Joint capsules and collateral ligaments were carefully removed while both cruciate ligaments remained intact. This was done to exclude the effect of soft tissues on articular cartilage contact mechanics. Circumferential attachments of the meniscus were removed to insert pressure
Maximum contact pressure
A representative image of the Tekscan pressure measurements in one of the tested knees is shown in Fig. 4. Variations in the maximum articular cartilage contact pressure between the knees with intact, torn, repaired, and partially resected menisci in the White-White regions were only significant at flexion angles of 20° and 35° (one-way ANOVA, p < 0.05), and no pairwise differences were found between the groups (Fig. 5a). However, variations in the maximum contact pressure for the tears in the
Discussion
Although repair surgeries are one of the common treatments for meniscal tears, partial meniscectomy has been popular for the tears in avascular regions of the meniscus because meniscal tissues in the avascular areas may not be completely healed due to the poor blood supply. However, total or partial resection of the meniscus has been shown to alter articular cartilage contact stress distributions and may initiate the onset of OA (Bae et al., 2012; Englund and Lohmander, 2006). In this study, we
Conclusions
In this study, we measured articular cartilage contact pressures using Tekscan pressure sensors to examine the mechanical alterations following partial meniscectomy in the avascular region of the meniscus because surgical outcomes of meniscal repair surgeries in the avascular regions have not been successful due to the limited healing ability. Our results revealed that partial meniscectomy in the avascular region did not statistically alter the maximum contact pressures and the average
Declaration of competing interest
The authors declare that they have no conflict of interest.
Acknowledgments
This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MEST) (NRF-2015R1C1A1A02037088).
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