Correlation between Knee Kinematics and Patello-femoral Contact Pressure in Total Knee Arthroplasty

Transcription

1 Correlation between Knee Kinematics and Patello-femoral Contact Pressure in Total Knee Arthroplasty Takuya Konno, MD 1, Tomohiro Onodera, MD, PhD 1, Yasuhiko Kasahara, MD, PhD 1, Daisuke Takahashi 1, Norimasa Iwasaki 1, Eiji Kondo, MD, PhD 1, Tokifumi Majima, MD, PhD 2. 1 Hokkaido University Graduate School of Medicine, Sapporo, Japan, 2 International University of Health and Welfare, Nasushiobara, Japan. Disclosures: T. Konno: None. T. Onodera: None. Y. Kasahara: None. D. Takahashi: None. N. Iwasaki: None. E. Kondo: None. T. Majima: 1; None. 2; Depuy Japan, Smith & nephew. 3A; None. 3B; Robert Ried Inc.. 3C; None. 4; None. 5; Smith & Nepheus Japan, Depuy Japan. 6; None. 7; None. Introduction: Total knee arthroplasty (TKA) has proven to be highly successful at alleviating pain and improving function in patients with advanced knee arthritis. Patello-femoral problems are one of the common post-tka complications - and may result in revision surgery. [1, 2] Patello-femoral complications have been attributed to errors in operative technique, inferior prosthetic design, and excessive patello-femoral loads. However the etiology of these complications with patellar resurfacing is yet to be clearly established. Low patello-femoral pressure was considered to be advantageous as high pressures might account for anterior knee pain. Regarding to the tibio-femoral kinematics, large variations, including the medial pivot, and the lateral pivot, are known to exist after conventional TKA. The variation of knee kinematics may affect patello-femoral pressure after TKA. However, we have found no study of relationship between knee kinematic patterns after TKA and patello-femoral contact stress. Therefore, we hypothesized that tibio-femoral kinematic patterns after TKA will impact patello-femoral contact stress. Specifically, normal knee kinematics, like the medial pivot pattern, will reduce patello-femoral contact stress. The aim of this study was to intraoperatively evaluate the relationship between knee kinematics and patello-femoral contact stress in mobile bearing prosthesis with navigated TKA procedures. Methods: Approval for this experiment was obtained from our institutional investigational review board. All knees had a Kellgren-Lawrence grade of 4 in the medial compartment and underwent a primary posterior stabilized mobile bearing total knee arthroplasty (PFC Sigma RP-F; Depuy, Warsaw, IN, USA) between May 2007 and October A computed tomographyguided navigation system (Vector Vision 1.6, Brain LAB, Heimstetten, Germany) was used for accurate implantation with a standardized navigated TKA technique for all cases. Surgeries were performed using a subvastus approach. No patients received a lateral retinacular release. The flexion gap was applied to the navigation system. The amount of femoral osteotomy external rotation was adjusted by the navigation system with a balanced gap technique.the real-time assessment of femoral rotation, medial patellar shift, and lateral patellar tilt from knee extension to flexion was measured using the navigation system in the kinematic mode. The patella tracker (Brain Lab) was fixed onto the anterior aspect of the patella by small screws. The force exerted on the patellar component was measured directly using a uniaxial ultrathin (100 µm) force transducer (FlexiForce; NittaCorporation, Osaka, Japan) embedded between the backside of the patellar trial component and an originally developed metal plate fixed to the bony cut surface of the patella. Intraoperative knee kinematics were measured from 0 to 90 at 10 intervals after implantation. All positions of the surgical epicondylar axis were projected to the tibial axial plane. The node of the epicondylar axis of each 10 measurement was defined as the center of rotation. Patients with an average medial center of rotation between 0-90 knee flexion were defined as belonging to the medial pivot group (M group). Other kinematic patterns were defined as belonging to the non-medial pivot group (N group). The femoral component rotation (FCR) is defined as the span between the femoral component rotation planned for the surgical epicondylar axis before and that achieved after the operation. The patello-femoral contact stress data and complete kinematics data was obtained from 46 knees of 39 patient. All knees were divided into the M group (n = 19) or N group (n = 27). There were no significant differences in patient demographics between the two groups (Table1). Statistical comparison of the maximum value of femoral rotation, medial patellar shift, lateral patellar tilt and contact stress was made using an unpaired t test. All differences were considered significant at a probability level of 95% (P <.05) Results: The mean maximum patello-femoral stress in the M group was significantly lower than that of the N group (1.7 ± 1.7 MPa vs. 3.2 ± 2.7 MPa, P = 0.03). The mean patellar medial shift from knee extension to flexion demonstrated no significant difference between the M group and the N group (11.7 ± 12.4 mm vs. 8.9 ± 8.9 mm, P = 0.48). The mean lateral patellar tilt also revealed no significant difference between the M group and the N group (9.4 ± 5.2 vs ± 4.1, P = 0.33). FCR was 0.58

2 internal rotation in the M group and 1.97 internal rotation in the N group (P = 0.14) Discussion: We divided all samples into either a medial-pivot group or a non-medial-pivot group, finding significantly lower patello-femoral stress in the medial-pivot group than in the non-medial pivot group. Medial-pivot kinematics reduced patellofemoral contact pressure, suggesting that restoring normal tibio-femoral kinematics possibly results in a decreased risk of patello-femoral problems such as anterior knee pain after TKA. Previous reports revealed that external rotational femoral component alignment resulted in proper patellar tracking whereas internal femoral component rotation moves the center of the trochlear groove internally away from the patella and results in patello-femoral complications. [3, 4, 5] These results suggest that femoral component rotational alignment is an important factor in patello-femoral contact stress. In our results, there is a tendency that internal rotation of femoral component in the medial pivot group is less than that of the non-medial pivot group. Although the rotational alignment of femoral component is important for patellar tracking and patellar contact pressure, other various pre- and intraoperative factors such as soft tissue release, ligament balance and preoperative joint surface geometry, might affect the kinematics pattern and patellar contact pressure. Dynamic factors should be considered for the patello-femoral contact pressure after TKA. In conclusion, intraoperative medial pivot kinematic patterns resulted in significant reduction of patello-femoral contact pressure compared with knees demonstrating non-medial pivot kinematics patterns. The intentional achievement of medial-pivot kinematics pattern after TKA may reduce the risk of patello-femoral problems and anterior knee pain. Significance: intraoperative medial pivot kinematic patterns resulted in significant reduction of patello-femoral contact pressure compared with knees demonstrating non-medial pivot kinematic patterns. Acknowledgments: References: 1. Boyd AD, Jr., et al. J Bone Joint Surg Am, Skwara A, et al. Arch Orthop Trauma Surg, Berger RA, et al. Clin Orthop Relat Res, Kingsley R, et al. J Arthroplasty, Rhoads DD, et al. Clin Orthop Relat Res, 1993

3

4 ORS 2014 Annual Meeting Poster No: 1737

5