TY - JOUR A1 - Howell, Stephen M. A1 - Gill, Manpreet A1 - Shelton, Trevor J. A1 - Nedopil, Alexander J. T1 - Reoperations are few and confined to the most valgus phenotypes 4 years after unrestricted calipered kinematically aligned TKA JF - Knee Surgery, Sports Traumatology, Arthroscopy N2 - Purpose The present study determined the postoperative phenotypes after unrestricted calipered kinematically aligned (KA) total knee arthroplasty (TKA), whether any phenotypes were associated with reoperation, implant revision, and lower outcome scores at 4 years, and whether the proportion of TKAs within each phenotype was comparable to those of the nonarthritic contralateral limb. Methods From 1117 consecutive primary TKAs treated by one surgeon with unrestricted calipered KA, an observer identified all patients (N = 198) that otherwise had normal paired femora and tibiae on a long-leg CT scanogram. In both legs, the distal femur–mechanical axis angle (FMA), proximal tibia–mechanical axis angle (TMA), and the hip–knee–ankle angle (HKA) were measured. Each alignment angle was assigned to one of Hirschmann’s five FMA, five TMA, and seven HKA phenotype categories. Results Three TKAs (1.5%) underwent reoperation for anterior knee pain or patellofemoral instability in the subgroup of patients with the more valgus phenotypes. There were no implant revisions for component loosening, wear, or tibiofemoral instability. The median Forgotten Joint Score (FJS) was similar between phenotypes. The median Oxford Knee Score (OKS) was similar between the TMA and HKA phenotypes and greatest in the most varus FMA phenotype. The phenotype proportions after calipered KA TKA were comparable to the contralateral leg. Conclusion Unrestricted calipered KA’s restoration of the wide range of phenotypes did not result in implant revision or poor FJS and OKS scores at a mean follow-up of 4 years. The few reoperated patients had a more valgus setting of the prosthetic trochlea than recommended for mechanical alignment. Designing a femoral component specifically for KA that restores patellofemoral kinematics with all phenotypes, especially the more valgus ones, is a strategy for reducing reoperation risk. KW - phenotype KW - total knee arthroplasty KW - total knee replacement KW - kinematic alignment KW - calipered KW - reoperation Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265291 VL - 30 IS - 3 ER - TY - JOUR A1 - Nedopil, Alexander J. A1 - Shekhar, Adithya A1 - Howell, Stephen M. A1 - Hull, Maury L. T1 - An insert with less than spherical medial conformity causes a loss of passive internal rotation after calipered kinematically aligned TKA JF - Archives of Orthopaedic and Trauma Surgery N2 - Introduction In total knee arthroplasty (TKA), the level of conformity, a medial stabilized (MS) implant, needs to restore native (i.e., healthy) knee kinematics without over-tensioning the flexion space when the surgeon chooses to retain the posterior cruciate ligament (PCL) is unknown. Whether an insert with a medial ball-in-socket conformity and lateral flat surface like the native knee or a less than spherical medial conformity restores higher and closer to native internal tibial rotation without anterior lift-off, an over-tension indicator, when implanted with calipered kinematic alignment (KA), is unknown. Methods and Materials Two surgeons treated 21 patients with calipered KA and a PCL retaining MS implant. Validated verification checks that restore native tibial compartment forces in passive flexion without release of healthy ligaments were used to select the optimal insert thickness. A goniometer etched onto trial inserts with the ball-in-socket and the less than spherical medial conformity measured the tibial rotation relative to the femoral component at extension and 90° and 120° flexion. The surgeon recorded the incidence of anterior lift-off of the insert. Results The insert with the medial ball-in-socket and lateral flat surface restored more internal tibial rotation than the one with less than spherical medial conformity, with mean values of 19° vs. 17° from extension to 90° flexion (p < 0.01), and 23° vs. 20°-120° flexion (p < 0.002), respectively. There was no anterior lift-off of the insert at 90° and 120° flexion. Conclusion An MS insert with a medial ball-in-socket and lateral flat surface that matches the native knee's spherical conformity restores native tibial internal rotation when implanted with calipered KA and PCL retention without over-tensioning the flexion space. KW - calipered KW - medial stabilized KW - spherical KW - conforming KW - insert KW - rotation KW - total knee arthroplasty KW - total knee replacement KW - kinematic alignment Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-266710 SN - 1434-3916 VL - 141 IS - 12 ER - TY - JOUR A1 - Nedopil, Alexander J. A1 - Delman, Connor A1 - Howell, Stephen M. A1 - Hull, Maury L. T1 - Restoring the patient's pre-arthritic posterior slope is the correct target for maximizing internal tibial rotation when implanting a PCL retaining TKA with calipered kinematic alignment JF - Journal of Personalized Medicine N2 - Introduction: The calipered kinematically-aligned (KA) total knee arthroplasty (TKA) strives to restore the patient's individual pre-arthritic (i.e., native) posterior tibial slope when retaining the posterior cruciate ligament (PCL). Deviations from the patient's individual pre-arthritic posterior slope tighten and slacken the PCL in flexion that drives tibial rotation, and such a change might compromise passive internal tibial rotation and coupled patellofemoral kinematics. Methods: Twenty-one patients were treated with a calipered KA TKA and a PCL retaining implant with a medial ball-in-socket and a lateral flat articular insert conformity that mimics the native (i.e., healthy) knee. The slope of the tibial resection was set parallel to the medial joint line by adjusting the plane of an angel wing inserted in the tibial guide. Three trial inserts that matched and deviated 2°> and 2°< from the patient's pre-arthritic slope were 3D printed with goniometric markings. The goniometer measured the orientation of the tibia (i.e., trial insert) relative to the femoral component. Results: There was no difference between the radiographic preoperative and postoperative tibial slope (0.7 ± 3.2°, NS). From extension to 90° flexion, the mean passive internal tibial rotation with the pre-arthritic slope insert of 19° was greater than the 15° for the 2°> slope (p < 0.000), and 15° for the 2°< slope (p < 0.000). Discussion: When performing a calipered KA TKA with PCL retention, the correct target for setting the tibial component is the patient's individual pre-arthritic slope within a tolerance of ±2°, as this target resulted in a 15–19° range of internal tibial rotation that is comparable to the 15–18° range reported for the native knee from extension to 90° flexion. KW - total knee replacement KW - total knee arthroplasty KW - kinematic alignment KW - slope KW - rotation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-240996 SN - 2075-4426 VL - 11 IS - 6 ER - TY - JOUR A1 - Arnholdt, Jörg A1 - Kamawal, Yama A1 - Horas, Konstantin A1 - Holzapfel, Boris M. A1 - Gilbert, Fabian A1 - Ripp, Axel A1 - Rudert, Maximilian A1 - Steinert, Andre F. T1 - Accurate implant fit and leg alignment after cruciate-retaining patient-specific total knee arthroplasty JF - BMC Musculoskeletal Disorders N2 - Background For improved outcomes in total knee arthroplasty (TKA) correct implant fitting and positioning are crucial. In order to facilitate a best possible implant fitting and positioning patient-specific systems have been developed. However, whether or not these systems allow for better implant fitting and positioning has yet to be elucidated. For this reason, the aim was to analyse the novel patient-specific cruciate retaining knee replacement system iTotal (TM) CR G2 that utilizes custom-made implants and instruments for its ability to facilitate accurate implant fitting and positioning including correction of the hip-knee-ankle angle (HKA). Methods We assessed radiographic results of 106 patients who were treated with the second generation of a patient-specific cruciate retaining knee arthroplasty using iTotal\(^{TM}\) CR G2 (ConforMIS Inc.) for tricompartmental knee osteoarthritis (OA) using custom-made implants and instruments. The implant fit and positioning as well as the correction of the mechanical axis (hip-knee-ankle angle, HKA) and restoration of the joint line were determined using pre- and postoperative radiographic analyses. Results On average, HKA was corrected from 174.4 degrees +/- 4.6 degrees preoperatively to 178.8 degrees +/- 2.2 degrees postoperatively and the coronal femoro-tibial angle was adjusted on average 4.4 degrees. The measured preoperative tibial slope was 5.3 degrees +/- 2.2 degrees (mean +/- SD) and the average postoperative tibial slope was 4.7 degrees +/- 1.1 degrees on lateral views. The joint line was well preserved with an average modified Insall-Salvati index of 1.66 +/- 0.16 pre- and 1.67 +/- 0.16 postoperatively. The overall accuracy of fit of implant components was decent with a measured medial overhang of more than 1 mm (1.33 mm +/- 0.32 mm) in 4 cases only. Further, a lateral overhang of more than 1 mm (1.8 mm +/- 0.63) (measured in the anterior-posterior radiographs) was observed in 11 cases, with none of the 106 patients showing femoral notching. Conclusion The patient-specific iTotal\(^{TM}\) CR G2 total knee replacement system facilitated a proper fitting and positioning of the implant components. Moreover, a good restoration of the leg axis towards neutral alignment was achieved as planned. Nonetheless, further clinical follow-up studies are necessary to validate our findings and to determine the long-term impact of using this patient- specific system. KW - total knee replacement KW - knee axis KW - patient-specific knee arthroplasty KW - knee osteoarthritis KW - implant positioning Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230012 VL - 21 ER -