Therapeutic study, Level III.

Aims Patellofemoral problems are a common complication of total knee arthroplasty. A high compressive force across the patellofemoral joint may affect patient-reported outcome. However, the relationship between patient-reported outcome and the intraoperative patellofemoral contact force has not been investigated. The purpose of this study was to determine whether or not a high intraoperative patellofemoral compressive force affects patient-reported outcome. Patients and Methods This prospective study included 42 patients (42 knees) with varus-type osteoarthritis who underwent a bi-cruciate stabilized total knee arthroplasty and in whom the planned alignment was confirmed on 3D CT. Of the 42 patients, 36 were women and six were men. Their mean age was 72.3 years (61 to 87) and their mean body mass index (BMI) was 24.4 kg/m 2 (18.2 to 34.3). After implantation of the femoral and tibial components, the compressive force across the patellofemoral joint was measured at 10°, 30°, 60°, 90°, 120°, and 140° of flexion using a load cell (Kyowa Electronic Instruments Co., Ltd., Tokyo, Japan) manufactured in the same shape as the patellar implant. Multiple regression analyses were conducted to investigate the relationship between intraoperative patellofemoral compressive force and patient-reported outcome two years after implantation. Results No patient had anterior knee pain after total knee arthroplasty. The compressive force across the patellofemoral joint at 140°of flexion was negatively correlated with patient satisfaction (R 2 = 0.458; β = –0.706; p = 0. 041) and Forgotten Joint Score-12 (FJS-12; R 2 = .378; β = –0.636; p = 0. 036). The compressive force across the patellofemoral joint at 60° of flexion was negatively correlated with the patella score (R 2 = 0.417; β = –0.688; p = 0. 046). Conclusion Patient satisfaction, FJS-12, and patella score were affected by the patellofemoral compressive force at 60° and 140° of flexion. Reduction of the patellofemoral compressive forces at 60° and 140° of flexion angle during total knee arthroplasty may improve patient-reported outcome, but has no effect on anterior knee pain.

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Case series, Level IV.

Purpose. To compare bone mineral density (BMD) in patients with or without weekly injection of teriparatide to promote bone ingrowth after cementless total knee arthroplasty (TKA). Methods. Records of 8 men and 32 women (mean age, 75.6 years) who underwent cementless TKA for medial knee osteoarthritis with (n=20) or without (n=20) once-weekly subcutaneous/hypodermic injection of teriparatide for 48 weeks were reviewed. BMD and bone volume/total volume (BV/TV) of the bone-prosthesis interface of the proximal tibia in 6 regions of interest (ROI) were assessed at 3, 6, 9, and 12 months using multi-detector computed tomography. Results. Patients with or without weekly injection of teriparatide after cementless TKA were comparable in terms of baseline characteristics and pre-and postoperative knee range of motion and Knee Society knee and function scores. In ROI 1 (medial), ROI 3 (anteromedial), and ROI 4 (posteromedial), the BV/TV Weekly injection of teriparatide for bone ingrowth after cementless total knee arthroplasty increased throughout the postoperative period in patients with weekly injection of teriparatide and declined after 6 months in patients without weekly injection of teriparatide. These 3 ROIs of the 2 groups differed significantly only in BMD at 6, 9, and 12 months. In ROI 2 (lateral), ROI 5 (anterolateral), and ROI 6 (posterolateral), both BV/TV and BMD showed a decreasing trend, and these 3 ROIs of the 2 groups did not differ significantly. Conclusion.Weekly injection of teriparatide after cementless TKA promoted bone ingrowth mostly in the medial aspect of the bone-prosthesis interface.

Objective: Insall advocated that a successful clinical outcome of total knee arthroplasty (TKA) depends on soft tissue balance procedure. Spacer blocks, balancer, and instrumented tibial sensor (VERESENSE, OrthoSensor, Dania, Florida, USA) are the current methods of soft tissue balancing during TKA. The purpose of the study is to assess intraoperative medial and lateral tibiofemoral compressive force (TFCF) using novel insert sensor and investigate the relationship between TFCF and patient-reported outcome measurements (PROMs). Methods: Twenty-five patients who underwent bicruciate stabilized (BCS) TKA were evaluated retrospectively. We measured intraoperative medial and lateral TFCF in neutral position as well as the force ratio (FR %:medial TFCF/medial + lateral TFCF) in varus and valgus position using the novel insert sensor throughout the range of motion (ROM) and assessed the relationship between intraoperative medial and lateral TFCF and PROM at 6 months after TKA. Results: Medial TFCF increased and lateral TFCF decreased throughout ROM. The mean FR was 0.44% ± 0.22 throughout ROM. Medial and lateral TFCF differences at 60° of ROM in neutral position showed a positive correlation with physical function in Western Ontario and McMaster Universities scores ( r = 0.60, p < 0.05). Medial and lateral TFCF differences at 30° and 140° of ROM in valgus stress test showed a positive correlation with symptoms in 2011 Knee Society Scores ( r = 0.49, p < 0.05; r = 0.51, p < 0.05). Conclusion: The present study revealed that BCS TKA reproduces the coronal laxity, which is similar to healthy knee. These results suggest that intraoperative medial stability is important for function and symptoms, therefore, surgeons should not release medial soft tissue for achieving better clinical outcomes after BCS TKA. Level of Evidence: II

Porous tantalum tibial component is durable with excellent bone ingrowth, higher knee scores, and long-term survivorship. However, to our knowledge, the effect of posterior cruciate-retaining (CR) and posterior cruciate-substituting (PS) porous tantalum tibial component has not been reported. The aim of the current study was to investigate the prosthetic bone quality between CR porous tantalum tibial component and PS using three-dimensional multi-detector-row computed tomography (3D-MDCT). Porous twenty-two (22) CR total knee arthroplasties and 22 PS received 3D-MDCT at every 6 months up to 5.5 years postoperatively to assess prosthetic bone quality (bone marrow contents/tissue volumes [BMC/TV, mg/cm3]) underneath the pegs of porous tantalum modular tibial component. Clinical outcomes (Knee Society score [KSS], Western Ontario and McMaster Universities (WOMAC), FJS-12, Patella score) were evaluated at a minimum follow-up period of 5.5 years. No statistically significant differences were found in age, gender, body mass index, KSS, and BMC/TV volumes in the proximal tibia between the two groups before total knee arthroplasty (TKA). There were also no significant differences between the CR and PS groups with regard to BMC/TV at every 6 months up to 5.5 years after TKA. At 5.5 years postoperatively, there was no significant difference between the two groups in terms of the KSS, WOMAC, forgotten joint score (FJS-12), and Patella score. The present study revealed that the prosthetic bone quality of the CR porous tantalum tibial component and PS were equivalent at every 6 months up to 5.5 years after TKA. This study reflects level II evidence.