High-flexion Total Knee Research Articles

Three- to six-year follow-up results after high-flexion total knee arthroplasty: can we allow passive deep knee bending?

We evaluated 3- to 6-year clinical and radiological follow-up results after NexGen® LPS-flex total knee arthroplasty (TKA). A retrospective evaluation was undertaken of 218 knees in 166 patients (22 males, 144 females) who were followed up for more than 3 years after TKA. Evaluations included preoperative and postoperative range of motion (ROM) measurement, Knee Society (KS) Score, tibiofemoral angle and assessment of postoperative complications. TKA resulted in a significant ROM increase from a mean flexion contracture of 9° (range 0°-20°) and further flexion of 117° (range 80°-155°) to a mean flexion contracture of 2° (range 0°-10°) and a further flexion of 131° (range 95°-155°). KS knee and function scores significantly improved from 52 and 38 before surgery to 87 and 82 after surgery, respectively. The tibiofemoral angle significantly improved from varus 5.7° to valgus 5.4°. Progressive radiolucent lines around the femoral component on radiographs were observed in 30 knees (13.8%, 27 patients), and more of those knees, could squat than non-radiolucent knees (76.7 vs. 20.2%; P<0.05). Seven knees (3.2%, 6 patients) were revised at a mean 49 months after the index operation. While NexGen® LPS-flex TKA satisfactorily improved ROM, it was associated with a relatively high incidence of early loosening of the femoral components. This might be associated with passive-maximal flexion activity, such as squatting or kneeling. The clinical relevance of this study is that squatting or kneeling, common activity in Asian, may not be allowed after NexGen® LPS-flex TKA.

Comparison of standard and gender-specific posterior-cruciate-retaining high-flexion total knee replacements

We undertook a study in which 138 female patients with a mean age of 71.2 years (51 to 82) received a standard NexGen CR-flex prosthesis in one knee and a gender-specific NexGen CR-flex prosthesis in the other. The mean follow-up period was 3.25 years (3.1 to 3.5). The aspect ratios of the standard and gender-specific prostheses were compared with that of the distal femur. The mean post-operative Knee Society knee scores were 94 (70 to 100) and 93 (70 to 100) points and the function scores were 83 (60 to 100) and 84 (60 to 100) points for the standard implants and the gender-specific designs, respectively. The mean post-operative Western Ontario and McMaster Universities score was 26.4 points (0 to 76). Patient satisfaction, the radiological results and the complication rates were similar in the two groups. In those with a standard prosthesis, the femoral component was closely matched in 80 knees (58.0%), overhung in 14 (10.1%) and undercovered the bone in 44 (31.9%). In those with a gender-specific prosthesis, it was closely matched in 15 knees (10.9%) and undercovered the bone in 123 (89.1%). Since we found no significant differences between the two groups with regard to the clinical and radiological results, patient satisfaction or complication rate, the goal of the design of the gender-specific CR-flex prosthesis to improve the outcome was not achieved in our patients.

High-Flexion Total Knee Replacement: Functional Outcome at One Year

Implants designed for enhanced flexion offer the prospect of improved function after total knee replacement (TKR). Whereas most studies evaluating these implants have focused on the range of knee flexion achieved, this study investigated the quality of function in deep knee flexion. The influences of residual pain and maximum flexion angle on function in deep knee flexion were also examined. Eighty-three patients (100 knees) were prospectively followed for 1year after TKR with a rotating-platform posterior-stabilized high-flexion prosthesis. Range of motion was measured and Knee Society scores were calculated. A questionnaire evaluated residual knee pain and function in high-flexion activities. Mean Knee Society score was 95, and mean knee flexion was 125°, yet 20% of patients could neither kneel, nor squat, nor sit on their heels. Fifty-seven percent were able to kneel without significant difficulty; 69% were able to squat without significant difficulty; and 46% were able to sit on their heels without significant difficulty. Function in deep flexion correlated with pain scores but did not correlate with knee flexion angles or Knee Society scores. Results 1year after TKR with a rotating-platform posterior-stabilized high-flexion prosthesis are encouraging, but one in five patients remain significantly limited in high-flexion activities.

Rehabilitative instruction for patients receiving high flexion total knee replacement

随着人口老龄化和社会经济的发展,采用人工全膝关节置换术(TKA)治疗膝关节疾病日益增多,但其功能仍不能与正常膝关节相媲美.膝关节活动度是评价TKA术后的-个重要指标,也是多个膝关节评分系统的主要组成部分。

Range of motion and function are similar in patients undergoing TKA with posterior stabilised and high-flexion inserts.

It is debatable whether high-flexion (HF) total knee arthroplasty (TKA) designs will improve postoperative flexion and function or will diminish the need for manipulation under anaesthesia (MUA). We retrospectively analysed range of motion (ROM), flexion, Knee Society Score (KSS), and rate of MUA in a consecutive group of patients who underwent TKA with a conventional posterior stabilised (PS) insert or an HF insert using identical surgical technique, implant design, and postoperative care. Fifty TKAs with a standard PS insert were matched for patient's age, gender, preoperative ROM, and KSS with 50 TKA performed with an HF insert. The patient's ROM and KSS were evaluated at six weeks, four months, and one year postoperatively. The outcome variables (flexion, ROM, KSS, and manipulation rate) in both groups were compared using the generalised estimating equations method. A second analysis of patients with preoperative flexion ≥120° was performed. The ROM, flexion, and patient-reported KSS was similar in both groups at each time period. The rate of MUA was also similar. Patients with a preoperative ROM of at least 120° showed similar results. Our study found that one year after surgery, patients who underwent TKA with a PS or an HF insert achieved similar flexion, ROM, and function.

Comparison of In Vivo Patellofemoral Kinematics for Subjects Having High-Flexion Total Knee Arthroplasty Implant With Patients Having Normal Knees

This study compares the in vivo patellar kinematics of high-flexion posterior cruciate ligament-retaining and posterior-stabilized total knee arthroplasty (TKA) implants with that of the healthy knee. Twenty-seven subjects performing weight-bearing deep knee bends were analyzed under fluoroscopic surveillance from full extension to maximum flexion. The patellofemoral contact positions and patellar flexion were similar for both TKAs. At low flexion, the patellofemoral contact was significantly more distal on the healthy patella than on the TKA patella, but in deeper flexion, there was no difference among the 3 groups. The tibiopatellar angle was similar for all 3 groups, except at deep flexion where the healthy patella rotated significantly more than the implanted ones. Patellofemoral separation was observed in some TKA knees, whereas it was absent in the healthy knees.

Thigh–calf contact: Does it affect the loading of the knee in the high-flexion range?

Recently, high-flexion knee implants have been developed to provide for a large range of motion (ROM>120°) after total knee arthroplasty (TKA). Since knee forces typically increase with larger flexion angles, it is commonly assumed that high-flexion knee implants are subjected to larger loads than conventional knee implants. However, most high-flexion studies do not consider thigh–calf contact which occurs during high-flexion activities such as squatting and kneeling. In this study, we hypothesized that thigh–calf contact reduces the knee forces during deep knee flexion as the tibio-femoral load shifts from occurring inside the knee towards the thigh–calf contact interface. Hence, the effect of thigh–calf contact on the knee loading was evaluated using a free body diagram and a finite element model and both the knee forces and polyethylene stresses were analyzed. Thigh–calf contact force characteristics from an earlier study were included and a squatting movement was simulated. In general, we found thigh–calf contact considerably reduced both the knee forces and polyethylene stresses during deep knee flexion. At maximal flexion (155°), the compressive knee force decreased from 4.89 to 2.90 times the bodyweight (BW) in case thigh–calf contact was included and the polyethylene contact stress at the tibial post decreased from 49.3 to 28.1 MPa. Additionally, there was a clear correlation between a subject's thigh and calf circumference and the force reduction at maximal flexion due to thigh–calf contact ( R=0.89). The findings presented in this study can be used to optimize the mechanical behavior of high-flexion total knee arthroplasty designs.

High-Flexion Total Knee Arthroplasty

High-flexion total knee arthroplasty is considered flexion beyond 125°. Certain activities and a number of workplace demands benefit from this greater range of motion. Some cultures and religions place more emphasis on deep knee flexion. Important patient factors include preoperative motion, body mass index, and previous knee surgery. Component design modifications focus on lengthening the radius of curvature through the posterior condyles, increasing the posterior condylar offset, recessing the tibial insert, lengthening the trochlear groove, and altering the cam-post design. These changes allow increased femoral rollback, translation, and thus clearance in deep flexion. Surgical techniques focus on soft tissue balancing, component sizing and position, removal of impinging osteophytes, and reestablishment of the flexion gap. A number of outcome studies have demonstrated benefits for high flexion after standard total knee and high-flexion designs.

In Vivo Comparison of Knee Kinematics for Subjects Having Either a Posterior Stabilized or Cruciate Retaining High-Flexion Total Knee Arthroplasty

The objective of this study was to determine the in vivo kinematics for subjects having either a fixed posterior stabilized (PS) or cruciate retaining (CR) high-flexion total knee arthroplasty (TKA). Three-dimensional kinematics from full extension to maximum flexion were determined for 30 subjects (15 PS, 15 CR) using fluoroscopy. On average, the PS subjects demonstrated 112° of weight-bearing (WB) flexion, −6.4 mm of posterior femoral rollback, and 2.9° of axial rotation. The CR subjects averaged 117° of WB flexion, −4.9 mm of posterior femoral rollback, and 4.8° of axial rotation. Posterior femoral rollback of the lateral condyle occurred for all PS TKAs and in 93% of the CR TKAs. Only 2 subjects in each group experienced greater than 1.0 mm of condylar lift-off. Subjects in both TKA groups demonstrated excellent WB ranges of motion and kinematic patterns similar to the normal knee, but less in magnitude.

A mechanical comparison of high-flexion and conventional total knee arthroplasty

The question addressed in this study was whether high-flexion total knee arthroplasty (TKA) designs improve the mechanical behaviour of TKAs in high flexion and whether they maintain the mechanical performance of conventional TKAs at normal flexion angles. A finite element study was performed in which the mechanical behaviour of the conventional Sigma RP and the new high-flexion Sigma RP-F were compared, during a dynamic simulation of a high-flexion squatting activity. Forces, stresses, and contact positions were calculated during different stages of the simulations. In general, higher stresses were found with larger flexion angles for both designs. Mechanical parameters were similar in normal flexion. In high flexion, lower stress and deformation values were found for the high-flexion Sigma RP-F, except for the contact stress at the post of the insert. This study confirms that a high-flexion design can improve mechanical behaviour at high-flexion without changing the performance in normal flexion. Hence, although a high-flexion TKA may show a similar or better performance in comparison with a conventional TKA, high-flexion activities still cause an increase in the implant stress levels. Therefore, the patient's demand for large flexion angles may reduce the longevity of TKA implants.

Factors Affecting Flexion after Total Knee Arthroplasty

Results of total knee arthroplasty have demonstrated excellent pain relief and increased patient function, particularly in activities such as walking. This procedure has not always met the needs of certain ethnic and religious groups as well as younger patients who require greater magnitudes of knee flexion. This has resulted in the introduction of new implant designs engineered to improve postoperative flexion. We reviewed factors known to influence postoperative flexion after total knee arthroplasty. An in vivo, weightbearing fluoroscopic kinematic analysis of multiple high-flexion total knee arthroplasty designs was performed, and demonstrated high levels of weightbearing flexion (125 degrees) can be obtained in some, but not all, evaluated designs. Multiple evaluations of the same high-flexion total knee arthroplasty design performed by different surgeons and involving different patient populations revealed one study group with high weightbearing flexion and other groups that did not achieve high flexion. This suggests numerous factors other than implant design influence eventual flexion, including the patient, surgical technique, knee kinematics, perioperative complications, and postoperative physiotherapy. Level V, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

A High Flexion Total Knee Arthroplasty Design Replicates Healthy Knee Motion

Deep flexion affects both femorotibial contact pattern and the patellofemoral articulation. The purpose of this study was to compare the patellofemoral motion of nonimplanted and implanted knees and to analyze femorotibial kinematics after total knee replacement designed for deep flexion. Three-dimensional patellofemoral kinematics were evaluated during a deep knee bend using fluoroscopy for five control patients with a healthy knee, five patients with an anterior-cruciate-ligament-deficient knee, and 20 patients who had a high flexion total knee arthroplasty. Less translation of patellofemoral contact position was seen in patients who had knee replacements than in patients with healthy knees, but the average motion and the patella tilt angles were similar to the healthy knees. On average, patients who had a total knee arthroplasty had 4.9 degrees normal axial rotation, and all patients had at least -4.4 mm of posterior femoral rollback. The average weightbearing range of motion of the patients in the total knee arthroplasty group was 125 degrees . In this study, patients implanted with a high-flexion knee replacement design had kinematic patterns that were similar to the healthy knee. It can be hypothesized that forces acting on the patella were not substantially increased for patients who had a total knee arthroplasty compared with the control patients.