Excessive flexed position of the femoral component was associated with poor new Knee Society Score after total knee arthroplasty with the Bi-Surface knee prosthesis.

AIMS This study aimed to evaluate the association between the sagittal alignment of the femoral component in total knee arthroplasty (TKA) and new Knee Society Score (2011KSS), under the hypothesis that outliers such as the excessive extended or flexed femoral component were related to worse clinical outcomes. METHODS A group of 156 knees (134 F:22 M) in 133 patients with a mean age 75.8 years (SD 6.4) who underwent TKA with the cruciate-substituting Bi-Surface Knee prosthesis were retrospectively enrolled. On lateral radiographs, γ angle (the angle between the distal femoral axis and the line perpendicular to the distal rear surface of the femoral component) was measured, and the patients were divided into four groups according to the γ angle. The 2011KSSs among groups were compared using the Kruskal-Wallis test. A secondary regression analysis was used to investigate the association between the 2011KSS and γ angle. RESULTS According to the mean and SD of γ angle (γ, 4.0 SD 3.0°), four groups (Extended or minor flexed group, -0.5° ≤ γ < 2.5° (n = 54)), Mild flexed group (2.5° ≤ γ < 5.5° (n = 63)), Moderate flexed group (5.5° ≤ γ < 8.5° (n = 26)), and Excessive flexed group (8.5° ≤ γ (n = 13)) were defined. The Excessive flexed group showed worse 2011KSSs in all subdomains (Symptoms, Satisfaction, Expectations, and Functional activities) than the Mild flexed group. Secondary regression showed a convex upward function, and the scores were highest at γ = 3.0°, 4.0°, and 3.0° in Satisfaction, Expectations, and Functional activities, respectively. CONCLUSION The groups with a sagittal alignment of the femoral component > 8.5° showed inferior clinical outcomes in 2011KSSs. Secondary regression analyses showed that mild flexion of the femoral component was associated with the highest score. When implanting the Bi-Surface Knee prosthesis surgeons should pay careful attention to avoiding flexing the femoral component extensively during TKA. Our findings may be applicable to other implant designs. Cite this article: Bone Joint J 2020;102-B(6 Supple A):36-42.

[1]  R. Hsu,et al.  Comparison of computer-assisted navigation and conventional instrumentation for bilateral total knee arthroplasty , 2019, Medicine.

[2]  N. Clement,et al.  Association Between Femoral Component Sagittal Positioning and Anterior Knee Pain in Total Knee Arthroplasty , 2019, The Journal of bone and joint surgery. American volume.

[3]  S. Otsuki,et al.  Sagittal Alignment of the Femoral Component and Patient Height Are Associated With Persisting Flexion Contracture After Primary Total Knee Arthroplasty. , 2019, The Journal of arthroplasty.

[4]  Hiroaki Nakamura,et al.  Two-dimensional measurement misidentifies alignment outliers in total knee arthroplasty: a comparison of two- and three-dimensional measurements , 2018, Knee Surgery, Sports Traumatology, Arthroscopy.

[5]  N. Clement,et al.  Three groups of dissatisfied patients exist after total knee arthroplasty: early, persistent, and late , 2018, The bone & joint journal.

[6]  S. Matsuda,et al.  Bone–femoral component interface gap after sagittal mechanical axis alignment is filled with new bone after cementless total knee arthroplasty , 2018, Knee Surgery, Sports Traumatology, Arthroscopy.

[7]  R. Gunaratne,et al.  Patient Dissatisfaction Following Total Knee Arthroplasty: A Systematic Review of the Literature. , 2017, The Journal of arthroplasty.

[8]  Hiromu Ito,et al.  Long-Term Durability of Ceramic Tri-Condylar Knee Implants: A Minimum 15-Year Follow-Up. , 2017, The Journal of arthroplasty.

[9]  K. Park,et al.  Femur bowing could be a risk factor for implant flexion in conventional total knee arthroplasty and notching in navigated total knee arthroplasty , 2016, Knee Surgery, Sports Traumatology, Arthroscopy.

[10]  Ju Hong Lee,et al.  Risk of Anterior Femoral Notching in Navigated Total Knee Arthroplasty , 2015, Clinics in orthopedic surgery.

[11]  S. Matsuda,et al.  Cross-cultural adaptation and validation of the Japanese version of the new Knee Society Scoring System for osteoarthritic knee with total knee arthroplasty , 2015, Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association.

[12]  Y. Iwamoto,et al.  Internal rotation of femoral component affects functional activities after TKA--survey with the 2011 Knee Society Score. , 2014, The Journal of arthroplasty.

[13]  K. Gromov,et al.  What is the optimal alignment of the tibial and femoral components in knee arthroplasty? , 2014, Acta orthopaedica.

[14]  Jinyu Zhu,et al.  Sagittal component alignment is less reliable than coronal component alignment in a Chinese population undergoing navigated TKA , 2014, Journal of Orthopaedic Surgery and Research.

[15]  H. Graichen,et al.  Influence of intentional femoral component flexion in navigated TKA on gap balance and sagittal anatomy , 2014, Knee Surgery, Sports Traumatology, Arthroscopy.

[16]  Jang-Won Park,et al.  The relationship between the survival of total knee arthroplasty and postoperative coronal, sagittal and rotational alignment of knee prosthesis , 2014, International Orthopaedics.

[17]  Tae Hyun Lee,et al.  Sagittal flexion of the femoral component affects flexion gap and sizing in total knee arthroplasty. , 2012, The Journal of arthroplasty.

[18]  P. Noble,et al.  The New Knee Society Knee Scoring System , 2012, Clinical orthopaedics and related research.

[19]  J P Cobb,et al.  The position and orientation of total knee replacement components: a comparison of conventional radiographs, transverse 2D-CT slices and 3D-CT reconstruction. , 2011, The Journal of bone and joint surgery. British volume.

[20]  Douglas A Dennis,et al.  The John Insall Award: Control-matched Evaluation of Painful Patellar Crepitus After Total Knee Arthroplasty , 2011, Clinical orthopaedics and related research.

[21]  K. Takaoka,et al.  TKA Sagittal Alignment with Navigation Systems and Conventional Techniques Vary Only a Few Degrees , 2009, Clinical orthopaedics and related research.

[22]  Georg Matziolis,et al.  A prospective, randomized study of computer-assisted and conventional total knee arthroplasty. Three-dimensional evaluation of implant alignment and rotation. , 2007, The Journal of bone and joint surgery. American volume.

[23]  Chiaki Hamanishi,et al.  An Anteroposterior Axis of the Tibia for Total Knee Arthroplasty , 2004, Clinical orthopaedics and related research.

[24]  F. C. Ewald The Knee Society total knee arthroplasty roentgenographic evaluation and scoring system. , 1989, Clinical orthopaedics and related research.

[25]  L. Dorr,et al.  Rationale of the Knee Society clinical rating system. , 1989, Clinical orthopaedics and related research.

[26]  K. Heiple,et al.  The influence of tibial-patellofemoral location on function of the knee in patients with the posterior stabilized condylar knee prosthesis. , 1986, The Journal of bone and joint surgery. American volume.

[27]  E. Salvati,et al.  Patella position in the normal knee joint. , 1971, Radiology.