Clinical Heritage: Success of the MRK™
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Clinical Heritage: Success of the MRK™
The MRK™, also manufactured by MatOrtho® (previously Finsbury), is the original 1994 ‘medial ball-and-socket knee’ and remains in popular use. The clinical success of the MRK™ has strong relevance as a ‘proof of concept’ to the expected long-term outcomes for the SAIPH® Knee, which is an evolution of the original design.
Overall, the MRK™ has been shown to provide greater inherent stability than comparator devices18,19,20. Patients with a medially stabilised knee notice the difference, and express that they prefer the design over posterior substituting (PS), cruciate retaining (CR) and mobile designs, citing feelings of stability, normality and strength on stairs as reasons for their preference21,22. With its lateralised trochlea11 the MRK™ exhibits a more normal patellar function12. It provides better restoration of ROM when compared to a standard PS knee design23 and mean ROM is equal that of a ‘high-flex’ knee24.
When compared to all other TKR designs, NJR collected patient reported outcome measures (PROMs) show that the benefits of the MRK™ are reflected in higher functional scores22,23 and improved rates of success and satisfaction when compared to other TKRs20,22. The MRK™ also provides better high-end function for categories of daily living, sport and exercise, movement and lifestyle included in the total knee function questionnaire (TKFQ). In this questionnaire, patients who received an MRK™ have scored significantly better 1 and 2 years postoperatively than counterparts who had received the most commonly used standard PS knee in the UK at the time23.
Survivorship for the MRK™ is the best of all TKR devices available: it has been reported with the LOWEST revision rate of ALL TKRs in the NJR more times than any other brand – 50% of all reporting instances since the NJR started reporting device brands in its 2009 Annual Report16,24. In the most recent 18th Annual Report (2021), the MRK™ has the lowest revision rate of all TKR brands at 17 years, the longest time point reported by the NJR, with a revision rate of 3.23% (95% CI: 2.69-3.87)17.
The MRK™ has an ODEP 15A rating for its use with and without the saddle-shaped patella25.
The MRK™ has the LOWEST revision rate of all TKR brands at 17 years: 3.23% (95% CI 2.69-3.87) 17 and is awarded an ODEP 15A rating25.
References
16. National Joint Registry. Implant Summary Report for the MRK. Summary.Report.KP_Femoral_MRK.18/02/2022.
17. National Joint Registry for England, Wales, Northern Ireland and the Isle of Man. 18th Annual Report, 2021: Surgical data to 31 December 2020. www.njrreports.org.uk.
18. Moonot P, Mu S, Railton GT, Field RE, Banks SA. Tibiofemoral kinematic analysis of knee flexion for a medial pivot knee. Knee Surg Sports Traumatol Arthrosc. 2009; 17(8):927-34.
19. Moonot P, Shang M, Railton GT, Field RE, Banks SA. In vivo weight-bearing kinematics with medial rotation knee arthroplasty. Knee. 2010; 17(1):33-7.
20. Molloy D, Jenabzadeh R, Walter W and Hasted T. Sagittal Stability in Three Different Knee Designs. A Single Centre Independent Review. Bone Joint J 2013; 95-B SUPP 15 85. Presented ISTA, Sydney, 2012 and The Great Debate, London, 2013.
21. Pritchett JW. Patients prefer a bicruciate-retaining or the medial pivot total knee prosthesis. J Arthroplasty. 2011; 26(2): 224-8.
22. Jonas SC, Argyropoulos M, Al-Hadithy N, Korycki M, Lotz B, Deo SD, Satish V. Knee arthroplasty with a medial rotating total knee replacement. Midterm clinical findings: A district general experience of 38 cases. The Knee. 2015; 22(2): 122-5.
23. Hossain F, Patel S, Rhee SJ, Haddad FS. Knee arthroplasty with a medially conforming ball-and-socket tibiofemoral articulation provides better function. Clin Orthop Relat Res. 2011; 469(1):55-63.
24. Kooijman CM and van Stralen GMJ. Having the confidence to change for a more stable future. Presented at The Great Debate, London, 2013.
25. Orthopaedic Data Evaluation Panel (ODEP). Latest ODEP ratings can be found at www.odep.org.ukResources
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Clinical Function of the SAIPH® Knee
Balancing stability with freedom of movement is a principal goal of TKR design. How well a TKR achieves this can be determined by evaluating the pattern of movement in patients’ knees during well- elected activities.