BACKGROUND: Traditionally, the placement of the tibial component in total knee arthroplasty (TKA) has focused on maximizing coverage of the tibial surface. However, the degree to which maximal coverage affects correct rotational placement of symmetric and asymmetric tibial components has not been well defined and might represent an implant design issue worthy of further inquiry. QUESTIONS/PURPOSES: Using four commercially available tibial components (two symmetric, two asymmetric), we sought to determine (1) the overall amount of malrotation that would occur if components were placed for maximal tibial coverage; and (2) whether the asymmetric designs would result in less malrotation than the symmetric designs when placed for maximal coverage in a computer model using CT reconstructions. METHODS: CT reconstructions of 30 tibial specimens were used to generate three-dimensional tibia reconstructions with attention to the tibial anatomic axis, the tibial tubercle, and the resected tibial surface. Using strict criteria, four commercially available tibial designs (two symmetric, two asymmetric) were placed on the resected tibial surface. The resulting component rotation was examined. RESULTS: Among all four designs, 70% of all tibial components placed in orientation maximizing fit to resection surface were internally malrotated (average 9°). The asymmetric designs had fewer cases of malrotation (28% and 52% for the two asymmetric designs, 100% and 96% for the two symmetric designs; p < 0.001) and less malrotation on average (2° and 5° for the asymmetric designs, 14° for both symmetric designs; p < 0.001). CONCLUSIONS: Maximizing tibial coverage resulted in implant malrotation in a large percentage of cases. Given similar amounts of tibial coverage, correct rotational positioning was more likely to occur with the asymmetric designs. CLINICAL RELEVANCE: Malrotation of components is an important cause of failure in TKA. Priority should be given to correct tibial rotational positioning. This study suggested that it is easier to balance rotation and coverage with asymmetric tibial baseplates; clinical research will need to determine whether the observed difference affects patellar tracking, loosening rates, or the likelihood of revisions after TKA.
BACKGROUND: Traditionally, the placement of the tibial component in total knee arthroplasty (TKA) has focused on maximizing coverage of the tibial surface. However, the degree to which maximal coverage affects correct rotational placement of symmetric and asymmetric tibial components has not been well defined and might represent an implant design issue worthy of further inquiry. QUESTIONS/PURPOSES: Using four commercially available tibial components (two symmetric, two asymmetric), we sought to determine (1) the overall amount of malrotation that would occur if components were placed for maximal tibial coverage; and (2) whether the asymmetric designs would result in less malrotation than the symmetric designs when placed for maximal coverage in a computer model using CT reconstructions. METHODS: CT reconstructions of 30 tibial specimens were used to generate three-dimensional tibia reconstructions with attention to the tibial anatomic axis, the tibial tubercle, and the resected tibial surface. Using strict criteria, four commercially available tibial designs (two symmetric, two asymmetric) were placed on the resected tibial surface. The resulting component rotation was examined. RESULTS: Among all four designs, 70% of all tibial components placed in orientation maximizing fit to resection surface were internally malrotated (average 9°). The asymmetric designs had fewer cases of malrotation (28% and 52% for the two asymmetric designs, 100% and 96% for the two symmetric designs; p < 0.001) and less malrotation on average (2° and 5° for the asymmetric designs, 14° for both symmetric designs; p < 0.001). CONCLUSIONS: Maximizing tibial coverage resulted in implant malrotation in a large percentage of cases. Given similar amounts of tibial coverage, correct rotational positioning was more likely to occur with the asymmetric designs. CLINICAL RELEVANCE: Malrotation of components is an important cause of failure in TKA. Priority should be given to correct tibial rotational positioning. This study suggested that it is easier to balance rotation and coverage with asymmetric tibial baseplates; clinical research will need to determine whether the observed difference affects patellar tracking, loosening rates, or the likelihood of revisions after TKA.
Authors: Bradley P Graw; Alexander H Harris; Krishna R Tripuraneni; Nicholas J Giori Journal: Clin Orthop Relat Res Date: 2010-03-30 Impact factor: 4.176
Authors: Arnd Steinbrück; Andreas Fottner; Christian Schröder; Matthias Woiczinski; Markus Schmitt-Sody; Tatjana Müller; Peter E Müller; Volkmar Jansson Journal: Knee Surg Sports Traumatol Arthrosc Date: 2015-11-03 Impact factor: 4.342
Authors: Ingrid Dupraz; Christoph Thorwächter; Thomas M Grupp; Florian Hammerschmid; Matthias Woiczinski; Volkmar Jansson; Peter E Müller; Arnd Steinbrück Journal: Arch Orthop Trauma Surg Date: 2021-05-22 Impact factor: 3.067