Becker's ASC Review

49 Executive Briefing Rajeev Jain, MD: The Mpact Double Mobility Cup has become an integral part of my hip implant armamentarium to address patients who have a high risk of dislocation. Let me elaborate on some indications where I like to have the Mpact DM at my disposal. I have found that the effect of spinopelvic mobility challenges traditional thinking on acetabular component positioning. The traditional safe zone for acetabular component inclination and anteversion, as proposed by Lewinnek, may need to be reconsidered in some patients. 5 For example, patients with stiff hips, limited spinopelvic motion, have the greatest risk for dislocation. It is in these situations that I like to increase my "safe zone" by using the Mpact DM double mobility cup. The one- piece Mpact DM cup allows me a femoral head that is 8 mm smaller than the shell size. For example, a 54 mm cup allows for a 46 mm double articulating femoral head. Displaced femoral neck fractures treated with total hip arthroplasty have been associated with higher dislocation rates. There are many potential factors that can lead to instability, including an inability to evaluate the preexisting spinopelvic mobility. In these patients, I find the Mpact DM cup to be invaluable. In addition, I find that the high coefficient of friction of the plasma spray coating of the Mpact cup really grabs the acetabulum when implanting, even in these osteoporotic hip fracture patients. Patients with CDD tend to lack functional anteversion that contributes to posterior hip dislocation, because there is less posterior coverage of the acetabular component to stabilize the femoral head in sitting position. 7 Besides maximizing the size of the articulating femoral head, the Mpact DM has a 5 degree raise on the shell that I can position posterior for additional head coverage for these circumstances. Finally, younger patients suffering from hip arthritis who still participate in martial arts, gymnastics and dance refuse to give up their activities. The Mpact DM affords increased range of motion to accommodate these activities. Your choice of implants can improve functional outcomes and reduce the risk of dislocation. Femoral stem implants that maximize your options to restore femoral offset without changing leg length can optimize hip joint biomechanics. For certain patient indications, a double mobility cup that increases the "safe zone" by providing a larger jump height and greater ROM can reduce the risk of dislocation. n References: 1. Kwon MS, et al. Does surgical approach affect total hip arthroplasty dislocation rates? Clin Orthop Relat Res. 2006;447:34–38. 2. Gwam CU, et al. Current epidemiology of revision total hip arthroplasty in the United States: National Inpatient Sample 2009 to 2013. J Arthroplasty 2017;32:2088e92. https://doi.org/10.1016/j. arth.2017.02.046. 3. Forde B., et al. Restoring femoral offset is the most important technical factor in preventing total hip arthroplasty dislocation. Journal of Orthopaedics 15 (2018) 131-133 4. M.M. Innmann et al. Additive influence of hip offset and leg length reconstruction on postoperative improvement in clinical outcome after total hip arthroplasty. The Journal of Arthroplasty 33 (2018) 156-161 5. Lewinnek GE, et al. Dislocations after total hip- replacement arthroplasties. J Bone Joint Surg Am 1978;60:217-20. 6. Buckland AJ, et al. Dislocation of a primary total hip arthroplasty is more common in patients with a lumbar spinal fusion. Bone Joint J 2017;99-B: 585-91. 7. C.I. Esposito et al. Total hip arthroplasty patients with fixed spinopelvic alignment are at higher risk of hip dislocation. J Arthroplasty article in press (2017) 1-6 8. Burroughs BR, et al. Range of motion and stability in total hip arthroplasty with 28-, 32-, 38-, and 44-mm femoral head sizes. J Arthroplasty 2005, 20(1):11–19 9. Heffernan C, et al. Does dual-mobility cup geometry affect posterior horizontal dislocation distance? Clin Orthop Relat Res 2014;472:1535-44 10. D'Apuzzo MR, et al. Relative head size increase using an anatomic dual mobility hip Prosthesis compared to traditional hip arthroplasty: impact on hip stability. J Arthroplasty 2014;29:1854-6 11. Epinette JA, et al. Early experience with dual mobility acetabular systems featuring highly cross- linked polyethylene liners for primary hip arthroplasty in patients under fifty-five years of age: an international multi-centre preliminary study. Int Orthop 2016 12. Ko LJ, et al. Serum metal ion levels following total hip arthroplasty with modular dual mobility components. J Arthroplasty. 31 (2016) 186–189 13. Nam D. Metal ion levels in young, active patients receiving a modular, dual mobility total hip arthroplasty. J Arthroplasty 32 (2017) 1581-1585 14. Friction testing of the Mpact and Versafitcup coating samples. Data on file Medacta. 15. Robotti P, et al. Macroporous titanium coatings , by thermal plasma spray. ITSC 2013, International Thermal Spray Conference, May 13 –15, 2013, Busan, Korea. 16. Biemond JE, et al, In vivo assessment of bone ingrowth potential of 3-dimensional E-beam produced implant surfaces and the effect of additional treatments by acid-etching and Hydroxyapatite coating. J Biomat Appl, published on line January 27, 2011, 0885328210391495. 17. Ferro de Godoy R., et al., In vivo evaluation of titanium macro-porous structures manufactured through an innovative powder metallurgy approach. Proceedings CM XIII: Bone Fixation, Repair & Regeneration, June 24–26, 2012, Davos, Switzerland. 18. Goodship A, et al. In-vivo assessment of the ingrowth potential of engineered surface topographies produced by spark plasma sintering, Proceedings 9th World Biomaterial Congress, June 1-5, 2012, Chengdu, China. 19. Data on file Medacta Medacta® International is a world leading manufacturer of orthopedic implants, neurosurgical systems, and instrumentation. Medacta's revolutionary approach and responsible innovation have resulted in standard of care breakthroughs in hip replacement with the AMIS® system and total knee replacement with MyKnee® patient matched technology. Over the last 10 years, Medacta has grown dramatically by taking a different approach and placing value on all aspects of the care experience from design to training to sustainability. Medacta is headquar- tered in Castel San Pietro, Switzerland, and operates in over 30 countries. To learn more about Medacta International, please visit www.medacta.com or follow @Medacta on Twitter. Rajeev Jain, MD

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