Kinematic factors affecting postoperative knee flexion after cruciate-retaining total knee arthroplasty

Purpose

The purpose of this study was to investigate kinematic factors affecting postoperative knee flexion after cruciate-retaining (CR) total knee arthroplasty (TKA) by analysing pre- and postoperative knee kinematics.

Methods

We retrospectively analysed 58 patients with osteoarthritis who received the same implant series. Pre- and postoperative kinematics were measured intraoperatively using a navigation system. As a clinical outcome, we measured the knee flexion angle before and one year after surgery. Correlations among pre- and postoperative kinematics and postoperative flexion were analysed using simple linear regression analyses.

Results

Preoperative knee kinematics, including tibial internal rotation and anterior translation (R?=?0.87, P?<?0.001; R?=?0.53, P?<?0.001, respectively), were significantly correlated with postoperative kinematics. Preoperative varus–valgus movements improved significantly postoperatively; however, tibial internal rotation remained unchanged. Furthermore, postoperative knee flexion angle was significantly correlated with postoperative tibial internal rotation (R?=?0.45, P?<?0.001).

Conclusions

Preoperative knee kinematics were unchanged even after CR-TKA. Postoperative tibial internal rotation is one of the most important factors affecting postoperative knee flexion.     

Computernavigierter Gelenkersatz am Knie mit dem Orthopilot®

Objective

Reproducible, precise implantation of a bicondylar knee prosthesis considering size of implant, axial conditions in coronal and sagittal planes, rotation, and ligament tension in extension and flexion.

Indications

Progressive painful gonarthrosis, when conservative treatment is no longer an option. Revision of unicondylar prosthesis.

Contraindications

General contraindications to bicondylar knee replacement. Revision after bicondylar replacement. Severe limitation of hip joint mobility, e.g., after arthrodesis of the hip joint or ipsilateral hip joint ankylosis. Morbid obesity.

Surgical Technique

Approach to the knee joint for alloarthroplasty. Placement of the screws and fixation of the infrared reflectors at femur and tibia. After adjustment of the double camera, collection of kinematic data via standardized motion patterns and identification of predetermined anatomic landmarks at the knee and ankle joint. By means of this data, controlled resection of the tibia, determination of the ligament tension in extension and flexion, planning of the femoral osteotomies, controlled distal resection of the femur. Following intraoperative verification of the distal femur resection, navigation of the position of the femur to complete femoral resection. Placement of the trial components, determination of the tibial onlay thickness, adjustment of the rotation of the tibial component, and final preparation of the tibial shaft. Preparation of the patella by resection of osteophytes, denervation, and possibly onlay patellar resection using a saw. Finally, implantation of the tibial component (cemented or noncemented), the tibial onlay, the femoral component (cemented or noncemented), and possibly cementation of the patellar onlay. After hardening, control of knee movement in straight position and wound closure in layers.

Postoperative Management

Early functional treatment using continuous passive motion device. Pain-adapted increase of weight bearing. Low-molecular-weight heparin for 5–6 weeks.

Results

Meanwhile, several studies have demonstrated that computer navigation helps to provide more accuracy in implant positioning, compared with conventional techniques in total knee replacement. Long-term survival of the implants promises to be superior after physiological leg axis restoration. Own results: 100 consecutive implantations: average duration of surgery 80 min, blood loss 360 ml, one deep infection (healed after early revision), one arthrofibrosis requiring revision surgery, average range of motion on the day of discharge 110° in flexion (90–120°) and full extension, after 3 months average 125° in flexion (90–140°) . No clinical signs of instability. Postoperative radiologic evaluation with standard radiographs of the knee joint in coronal and sagittal planes took place right after surgery and again after 3 months.     

The influence of the femoral force application point on tibial cementing pressure in cemented UKA: an experimental study

Background

Aseptic loosening is the major cause for implant failure in cemented unicompartmental knee arthroplasty (UKA). Central positioning of the femoral pressure during the tibial cementation process is recommended to achieve equal pressure and a good cementation result. The aim of this study was to verify the central position of the femoral force application point (FFAP) at 45° flexion of the knee and to investigate the influence of ligament tension and cement penetration pressure (CPP) for UKA.

Materials and methods

Cemented Oxford UKAs were performed in 24 human legs. CPP and ligament tension forces (LTF) were measured. The FFAP was measured in a standardised manner in relation to the tibial implant length on lateral digital X-rays.

Results

The FFAP at 45° of knee flexion is located at 53.5?% and is not significantly different from the FFAP at 0° (p?=?0.768). The CPP shows mean values at the anterior portion of 13.97?kPa (SD 16.11), at the implant keel of 24.34?kPa (SD 25.21) and at the posterior portion of 36.58?kPa (SD 26.51). The LTF shows a mean value of 194.35?N (SD 83.77).

Conclusion

The central position of the FFAP for the investigated cemented UKA with single radius femoral component at 45° flexion of the knee could be confirmed. A flexion angle of <45° does not influence the position of the FFAP significantly. More than 45° of flexion should be avoided because the FFAP shifts backwards significantly and may cause increased pressures posteriorly and therefore tilting of the component occurs during the cementation process.     

Aufklappende Osteotomie des Tibiakopfes

Background

Lesions of the popliteal artery during high tibial osteotomy are rare complications, consequently the majority of publications are case related. The interval between surgery and diagnosis is reported to be as long 3 years; therefore, the current literature probably does not reflect the true incidence of vascular injuries.

Objective

The case reports published in the literature were further evaluated. The focus was on the normal vascular anatomy of the popliteal region and anatomical deviations that predispose to vascular injury. As the flexion angle of the knee joint is considered to be decisive for vascular injury, this aspect was also an additional focus. For the unlikely event of a vascular injury, recommendations are presented which indicate diagnostic and therapeutic decisions.

Methods

We analyzed the available literature and present own magnetic resonance imaging (MRI) investigations of the popliteal artery with different angles of flexion in six healthy volunteers.

Results and discussion

A variation of the origin of the anterior tibial artery with a course between the posterior tibial cortex and the popliteal muscle was found in 6?% of all patients and predisposes to an accidental injury during osteotomy. The results in the literature and our own MRI findings suggest that a flexion angle of 90° facilitates anatomical dissection and osteotomy but cannot be regarded as a reliable protection against vascular injury.     

Navigierte Implantation weichteilbalancierter Knieendoprothesen

Objective

Implantation of a total knee arthroplasty with a correct mechanical axis, a rectangular joint gap and a reconstructed joint line by use of an imageless computer navigation device

Indications

Symptomatic gonarthrosis if non operative treatment or joint preserving operations remains ineffective

Contraindications

Infections; soft tissue damage in the approach area; massive instability of the collateral ligaments

Surgical Technique

Medial parapatellar approach to the knee joint; diminution of the patella; fixation of the reference arrays in tibia and femur; registration of leg axis, ligament balance and surface of the knee joint by use of the navigation system; tibial resection perpendicular to the mechanical axis; ligament balancing to achieve a rectangular extension gap; femoral implant planning to maintain the original joint line and reconstruct an equal joint gap in extension and flexion; femora resection perpendicular to the mechanical axis; reconstruction of the rectangular flexion gap by rotation of the femoral resection; two stage cementing technique for fixation of the original implants; check of the final mechanical axis and symmetry of the joint gap over the whole range of motion; wound closure.

Postoperative Management

Physiotherapy; continuous passive motion treatment; mobilization with 20?kg weight bearing with 2 crutches for 2?weeks, thereafter with 2 crutches and incremental full weight bearing for 4?weeks.

Results

The analysis of 582 consecutive navigated total knee arthroplasties showed one case of extension gap instability ?>?3?mm (0.2%) and 8?patients with flexion gap instability? >?3?mm (1.4%). A too tight flexion gap was registered in 23?patients (4.4%), a too wide flexion gap in 13 cases (2.5%). The joint line was reconstructed with an average inaccuracy of 0?mm, in 17?patients the joint line was elevated ?>?3?mm (2.9%).     

Knie-TEP-Revision auf ein halbgekoppeltes Prothesensystem mit der 3-Schritt-Technik

Objective

The surgical goal is to achieve a pain free and stable knee joint after revision total knee arthroplasty in three steps. An important component of the technique is the reproducible restoration of the joint line.

Indications

Revision total knee arthroplasty.

Contraindications

Complete bone loss at the knee joint (epicondyles and tibia plateau), persistent joint infection, loss of the extension apparatus, and neurological disease with progressive ligament instability.

Surgical technique

Implantation of revision components is performed in three steps. The first step is the positioning of the tibia component at the correct height and rotation. As the position of the tibial articular surface is independent of the knee position, the tibia serves as a reference both in extension and in flexion. The second step consists of balancing the knee joint in flexion and, thereby, definition of the flexion gap and the rotation of the femoral component. In the third step, the reconstruction and balancing of the knee joint in extension is performed.

Postoperative management

Mobilization with weight bearing and range of motion as tolerated depending on osseous and soft tissue condition at surgery. The surgical technique does not influence the further treatment.

Results

In a prospective study, 168 consecutive knee revisions operated by the first author were examined clinically and radiologically preoperatively and at a mean follow-up of 38?months (range 22?C61?months). There were 96 knees from women and 72 were from men with an average age of 74.6?years (range 51?C92?years). Clinical results were based on the American Knee Society score. The score showed 47.6 (range 32?C63) preoperatively and 81.5 (range 62?C95) at follow-up. Radiologically, 92.7% of the knees showed a malposition <3°. The joint line was correctly reconstructed in 86.3% based on the preoperative plan; 89% of the patella showed correct tracking in the patella tangential view.     

Tuberositasosteotomie in der Knieendoprothetik

Objective

Tibial tubercle osteotomy facilitates access to the knee joint without excessive tension of the extensor apparatus with the lateral parapatellar approach and the medial parapatellar approach in case of contracture or revision arthroplasty.

Indications

Inadequate exposure of the knee joint with the lateral parapatellar approach and inadequate exposure of the knee joint with the medial parapatellar approach in case of contracture and revision arthroplasty.

Contraindications

Severe periarticular osteoporosis or bone atrophy after knee arthroplasty and damage to the patella tendon insertion due to previous operations.

Surgical technique

A bone block 8?C10?cm long is excised with the tibial tubercle using an oscillating saw. A step cut inferior to the tibial plateau is created with a chisel. Refixation is performed with two cortical screws. Alternatively, in case of poor bone quality, refixation is accomplished with two cerclage wires.

Postoperative management

In case of stable refixation, full weight bearing is allowed with an extension brace for 2?C4?weeks and passive flexion is increased as tolerated. In case of poor bone quality, it is recommended that full weight bearing be postponed for 6?weeks, whereby full flexion is regained in 30° steps at 2, 4, and 6?weeks postoperatively.

Results

From 2001?C2004, 67 osteotomies of the tibial tubercle were performed for revision arthroplasty. During follow-up in 2010, no pseudarthrosis or dislocation was noticed. Postoperatively, two hematoma and one skin necrosis had to be revised. The risk of hematoma and pseudarthrosis or dislocation of the fragment can be minimized by using the correct operative technique.     

Are We Subluxating Knees in Total Knee Arthroplasty? A Cadaveric Investigation

Background

In comparison to coronal, sagittal, and rotational alignment, translational alignment parameters have been widely neglected in total knee arthroplasty (TKA) so far. As there is a certain variable range of possible component placement in mediolateral, ventrodorsal, and proximodistal direction, we hypothesized that relative positions between the femoral and tibial bones are changed after TKA, resulting in a subluxation of knees.

Mid-term results of a new cementless hydroxyapatite coated anatomic unicompartmental knee arthroplasty

Introduction

We report the mid term results of a cement less HA coated unicompartmental knee prosthesis.

Material and methods

One hundred and fifty-nine Unicompartmental knee arthroplasties were done between 1995 and 2000 with ALPINA^® UNI, a cementless HA coated anatomic prosthesis. One hundred and twenty knees were available for the mid-term follow-up at a mean of 6.5 years.

Results

The mean IKS improved from 87.1 ± 22.1 points preoperatively to 168.2 ± 26.1 at the latest follow-up (P < 0.001). Ninety-four percent of the knees were rated good and excellent. The mean knee flexion has significantly improved from 120° preoperatively to 126° at the latest follow-up (P < 0.001). Ten knees were revised: three for degeneration of osteoarthritis in the opposite compartment of the knee, four for polyethylene insert fracture, one for severe polyethylene wear and two for tibial component loosening. When revision for any reason was defined as the end point, the 5-year Kaplan–Meier survival rate was 95.7% (95% confidence interval, 90.1–98.2%) and when revision due to implant mechanical failure (excluding degeneration of osteoarthritis in the opposite compartment of the knee) was defined as the end point, the 5-year survival rate was 96.6% (95% confidence interval, 91.2–98.7%).

Conclusion

This study confirms the reliability of HA coated unicompartimental knee replacement. With careful indications it seems to be a good alternative to osteotomy of total arthroplasty.     

Joint gap measurement in total knee arthroplasty using a tensor device with the same articulating surface as the prosthesis

Background

We developed a new tensor to measure the joint gap throughout knee flexion during total knee arthroplasty (TKA). This tensor has the same articular shape as that of the tibial liner, including the post structure and the curvature of femorotibial articular surface, to measure the gap intraoperatively under the same conditions as after TKA. The present study aimed to examine the precision of the new tensor for gap measurement after implantation.

Methods

We performed TKA using the modified gap technique in four cadaveric knees and measured the gaps using the new tensor. The intra-observer and inter-observer error of the tensor was analyzed using 168 measurements of the gaps as determined at least twice by two surgeons. In addition, the gaps in rotating-platform posterior-stabilized TKA were measured at seven positions with the knee bending from extension to full flexion.

Results

The inter-observer and intra-observer errors were 0.8 and 0.3 mm, respectively, indicating precise and reproducible gap measurement. The gaps before implantation in reduced patellar position were 12.1 mm at extension and 12.5 mm at 90° flexion. The gaps after implantation were 9.1, 12.9, 13.1, 13.5, 13.8, 13.3, and 10.1 mm at 0°, 30°, 45°, 60°, 90°, 120°, and full flexion, respectively.

Conclusions

The new tensor provides precise and reproducible measurements. Although the joint gap before implantation was parallel and equal at extension and 90° flexion, the joint gap after implantation was variable throughout knee flexion. This feature of the gap should be considered during the operation.     

The rectangular flexion gap is associated with an increased knee flexion angle in a cruciate-sacrificing rotating platform mobile-bearing total knee arthroplasty

Background

The knee flexion angle after a total knee arthroplasty is an important indicator of clinical outcome. However, there is little appropriate information about the correlation between the ligament balancing and knee flexion angle after total knee arthroplasty. The purpose of this study was to investigate the effect of the ligamentous balance in extension and flexion on knee flexion angle one year after posterior cruciate ligament sacrificing rotating platform total knee arthroplasty.

Erfahrungen mit lateralen unikondylären Prothesen

Background

Unicompartmental osteoarthritis of the knee joint affects the medial compartment more often than the lateral compartment whereby the lateral is solely affected in only 5–10?% of cases. In this case unicompartmental knee arthroplasty has been shown to be an effective alternative to total knee arthroplasty. There are some basic anatomical and biomechanical differences between the medial and lateral compartment of the knee joint which directly influence modern surgery techniques and implant design. In general, kinematics and design are fundamentally different in mobile-bearing compared to fixed-bearing prostheses.

Objectives

This article presents a summary of outcome and survival rates after unicompartmental knee arthroplasty in the lateral compartment.

Methods

This article is based on a literature search in the PubMed database for clinical results after lateral unicompartmental knee arthroplasty.

Results

The results demonstrate that lateral unicompartmental knee arthroplasty with a mobile-bearing implant and a domed tibial plateau design gives an excellent clinical outcome while reducing the dislocation rate to an acceptable level in the short and mid-term. Published data on the clinical outcome of fixed-bearing lateral unicompartmental knee arthroplasty prostheses revealed heterogeneous results due to the inclusion of different implant designs and relatively small patient cohorts. Nevertheless, most of them demonstrated good clinical results with a longer follow-up than current studies concerning mobile-bearing prostheses.

Conclusion

Based on the published data it is not possible to demonstrate precise differences in clinical outcome and survival rates after mobile-bearing and fixed-bearing unicompartmental knee arthroplasty or to make clear recommendations on the use of each type of prosthesis.     

Popliteal vessels in knee surgery. A magnetic resonance imaging study.

Popliteal artery injury during surgery of the knee is rare but can have devastating consequences. The position of knee flexion has been thought to be protective for the popliteal artery, allowing it to fall back from the knee joint. No prior study has provided in vivo cross sectional evidence of the behavior of the popliteal vessels during knee flexion with the effect of gravity. Magnetic resonance imaging was used in nine volunteers to measure the distance of the popliteal artery and veins from the posterior proximal tibia at two levels corresponding to the levels of osteotomy in total knee arthroplasty and in high tibial osteotomy. Scans were taken with the knee in full extension and at 90 degrees flexion with the patient in the supine position, allowing for the effect of gravity. Considerable variation in behavior of the vein and the artery was observed at the high tibial osteotomy cross sectional level and the total knee arthroplasty cross sectional level. In two knees at the high tibial osteotomy cross sectional level and in two knees at the total knee arthroplasty cross sectional, level the artery moved closer to the posterior tibia with knee flexion. Even with the effect of gravity included, knee flexion does not guarantee removal of the popliteal vessels from potential harm during surgery of the knee.     

Retrograde Marknagelung bei periprothetischen Frakturen des distalen Femurs

Objective

Intramedullary stabilization of periprosthetic distal femoral fractures by interlocking nailing. Closed reduction by retrograde nail can be combined with the use of transmedullary support screws (TMS principle of Stedtfeld).

Indications

Supracondylar fractures above stable knee arthroplasty (Rorabeck types I and II), femoral shaft fractures ipsilateral of stable hip and/or knee arthroplasty, contraindications for antegrade nailing

Contraindications

Closed box design of femoral implant, intercondylar distance of the femoral component smaller than nail diameter, more than 40° flexion deficit of the knee, inability to place two bicortical distal interlocking screws. Relative contraindication: insufficient overlap with proximal implants

Surgical technique

Supine position and knee flexion of approximately 45°. Fluoroscopy should be possible between the knee and hip. Longitudinal skin incision into the pre-existing scar over the patellar tendon which is then split. The nail entry point is located in the intercondylar groove at the deepest point of Blumensaat’s line, often predetermined by the femoral arthroplasty component. Reaming is rarely necessary. Transmedullary support screws may correct axial malalignment during nail insertion. Static interlocking in a direction from lateral to medial by the aiming device. Insertion of locking cap.

Postoperative management

Retrograde nailing normally allows full weight bearing. Range of motion does not need to be restricted.

Results

Out of 101 fractures treated between 2000 and 2013 with a Targon RF nail (Aesculap, Tuttlingen, Germany) 10 were periprosthetic, all were classified as Rorabeck type II and of these 6 fractures were metaphyseal and 4 were diaphyseal. In four cases proximal implants were present. The mean operative time for periprosthetic fracture fixation did not significantly differ from that for normal retrograde femoral nailing. There were no postoperative infections, fixation failures or delayed unions. There was one revision for secondary correction of maltorsion.     

Influence of intra-operative parameters on postoperative early recovery of active knee flexion in posterior-stabilized total knee arthroplasty

Purpose

Active knee flexion is more important for daily activities than passive knee flexion. The hypothesis is that the intra-operative parameters such as osteotomized bone thickness and soft tissue balance affect the postoperative active flexion angle in total knee arthroplasty (TKA). Therefore, we evaluate the influence of intra-operative parameters on postoperative early recovery of active flexion after posterior-stabilized (PS) TKA.

Methods

The subjects were 45 osteoarthritic knees undergoing primary PS TKA with anterior-reference technique. Intra-operative soft tissue balance was measured using an offset type tensor, and each osteotomized bone thickness was also measured. Pre- and postoperative active knee flexion angles were measured using lateral radiographs. Liner regression analysis was used to determine the influence of these intra-operative parameters on postoperative active flexion angles or recovery of active flexion angles.

Results

Pre-operative flexion angle was positively correlated with postoperative flexion angle (R?=?0.52, P?=?0.0002). Postoperative flexion angle was negatively correlated with the osteotomized bone thickness of femoral medial posterior condyle (R?=??0.37, P?=?0.012), and femoral lateral posterior condyle (R?=??0.36, P?=?0.015). Recovery of flexion angle was slightly negatively correlated with gap difference calculated by subtracting joint gap at extension from that at flexion between osteotomized surfaces (R?=??0.30, P?=?0.046).

Conclusions

The osteotomized bone thickness of the femoral posterior condyle is a significant independent factor of postoperative flexion angles. This indicates that the restoration of the posterior condyle offset may lead to larger postoperative active flexion angles in PS TKA.     

In vivo kinematics of a robot-assisted uni- and multi-compartmental knee arthroplasty

Background

There is great interest in providing reliable and durable treatments for one- and two-compartment arthritic degeneration of the cruciate-ligament intact knee. One approach is to resurface only the diseased compartments with discrete unicompartmental components, retaining the undamaged compartment(s). However, placing multiple small implants into the knee presents a greater surgical challenge than total knee arthroplasty, so it is not certain that the natural knee mechanics can be maintained or restored. The goal of this study was to determine whether near-normal knee kinematics can be obtained with a robot-assisted multi-compartmental knee arthroplasty.

Methods

Thirteen patients with 15 multi-compartmental knee arthroplasties using haptic robotic-assisted bone preparation were involved in this study. Nine subjects received a medial unicompartmental knee arthroplasty (UKA), three subjects received a medial UKA and patellofemoral (PF) arthroplasty, and three subjects received medial and lateral bi-unicondylar arthroplasty. Knee motions were recorded using video-fluoroscopy an average of 13 months (6–29 months) after surgery during stair and kneeling activities. The three-dimensional position and orientation of the implant components were determined using model-image registration techniques.

Results

Knee kinematics during maximum flexion kneeling showed femoral external rotation and posterior lateral condylar translation. All knees showed femoral external rotation and posterior condylar translation with flexion during the step activity. Knees with medial UKA and PF arthroplasty showed the most femoral external rotation and posterior translation, and knees with bicondylar UKA showed the least.

Conclusions

Knees with accurately placed uni- or bi-compartmental arthroplasty exhibited stable knee kinematics consistent with intact and functioning cruciate ligaments. The patterns of tibiofemoral motion were more similar to natural knees than commonly has been observed in knees with total knee arthroplasty. Larger series are required to confirm these as general observations, but the present results demonstrate the potential to restore or maintain closer-to-normal knee kinematics by retaining intact structures and compartments.     

Comparisons of tunnel-graft angle and tunnel length and position between transtibial and transportal techniques in anterior cruciate ligament reconstruction

Purpose

Our aim was to evaluate tunnel-graft angle, tunnel length and position and change in graft length between transtibial (30 patients) and anteromedial (30 patients) portal techniques using 3D knee models after anterior cruciate ligament (ACL) reconstruction.

Methods

The 3D angle between femoral or tibial tunnels and graft at 0° and 90° flexion were compared between groups. We measured tunnel lengths and positions and evaluated the change in graft length from 0° to 90° flexion.

Results

The 3D angle at the femoral tunnel with graft showed a significant difference between groups at 0° flexion (p?=?0.01) but not at 90° flexion (p?=?0.12). The 3D angle of the tibial tunnel showed no significant differences between groups. Femoral tunnel length in the transtibial group was significantly longer than in the transportal group (40.7 vs 34.7 mm,), but tibial tunnel length was not. The relative height of the lateral femoral condyle was significantly lower in the transportal than the transtibial group (24.1 % vs 34.4 %). No significant differences were found between groups in terms of tibial tunnel position. The change in graft length also showed no significant difference between groups.

Conclusion

Even though the transportal technique in ACL reconstruction can place the femoral tunnel in a better anatomical position than the transtibial technique, it has risks of a short femoral tunnel and acute angle at the femoral tunnel. Moreover, there was also no difference in the change of the graft length between groups.     

The relationship between the survival of total knee arthroplasty and postoperative coronal,sagittal and rotational alignment of knee prosthesis

Purpose

Our study sought to address four issues: (1) the relationship between postoperative overall anatomical knee alignment and the survival of total knee prostheses; (2) the relationship between postoperative coronal alignment of the femoral and tibial component and implant survival; (3) the relationship between postoperative sagittal alignment of the femoral and tibial components and implant survival; and (4) the relationship between postoperative rotational alignment of the femoral and tibial component and implant survival.

Methods

We reviewed 1,696 consecutive patients (3,048 knees). Radiographic and computed tomographic examinations were performed to determine the alignment of the femoral and tibial components. The mean duration of follow-up was 15.8 years (range, 11–18 years).

Results

Thirty (1.0 %) of the 3,048 total knee arthroplasties failed for a reason other than infection and periprosthetic fracture. Risk factors for failure of the components were: overall anatomical knee alignment less than 3° valgus, coronal alignment of the femoral component less than 2.0° valgus, flexion of the femoral component greater than 3°, coronal alignment of the tibial component less than 90°, sagittal alignment of the tibial component less than 0° or greater than 7° slope, and external rotational alignment of the femoral and tibial components less than 2°

Conclusion

In order to improve the survival rate of the knee prosthesis, we believe that a surgeon should aim to place the total knee components in the position of: overall anatomical knee alignment at an angle of 3–7.5° valgus; femoral component alignment, 2–8.0° valgus; femoral sagittal alignment, 0–3°; tibial coronal alignment, 90°; tibial sagittal alignment, 0–7°; femoral rotational alignment, 2–5° external rotation; and tibial rotational alignment, 2–5° external rotation.