Aims

The mid-term results of kinematic alignment (KA) for total knee arthroplasty (TKA) using image derived instrumentation (IDI) have not been reported in detail, and questions remain regarding ligamentous stability and revisions. This paper aims to address the following: 1) what is the distribution of alignment of KA TKAs using IDI; 2) is a TKA alignment category associated with increased risk of failure or poor patient outcomes; 3) does extending limb alignment lead to changes in soft-tissue laxity; and 4) what is the five-year survivorship and outcomes of KA TKA using IDI?

Aims

The aim of this study was to report patient and clinical outcomes following robotic-assisted total knee arthroplasty (RA-TKA) at multiple institutions with a minimum two-year follow-up.

Abstract

Introduction and aims

Robotic Assisted Arthroplasty (RAA) is increasingly proliferative in the international orthopaedic environment. Traditional bibliometric methods poorly assess the impact of surgical innovations such as robotic technology. Progressive Scholarly Acceptance (PSA) is a new model of bibliographic analysis which quantitatively evaluates the impact of robotic technology in the orthopaedic scientific community.

Introduction and aims

The International Orthopaedic community is eagerly adopting Robotic Assisted Arthroplasty (RAA) technology. However, the evidence for the benefits of this technology are unproven and at best equivocal. This study is a comprehensive bibliometric analysis of all published research in the field of RAA.

Background

In suspected scaphoid fracture the initial scaphoid series plain radiographs are 84-94% sensitive for scaphoid fractures. Patients are immobilised awaiting diagnosis. Unnecessary lengthy immobilisation leads to lost productivity and may leave the wrist stiff. Early accurate diagnosis would improve patient management. Although Magnetic Resonance Imaging (MRI) has come to be regarded as the gold standard in identifying occult scaphoid injury, recent evidence suggests Computer Tomography (CT) to be more accurate in identifying scaphoid cortical fracture. Additionally CT and USS are frequently a more available resource than MRI.

We hypothesised that 16 slice CT is superior to high spatial resolution Ultrasonography (USS) in the diagnosis of radiograph negative suspected cortical scaphoid fracture and that a 5 point clinical examination will help to identify patients most likely to have sustained a fracture within this group.

This study was to assess the accuracy of fixed posterior condylar referencing cutting blocks to the accuracy of combined epicondylar/AP axis referencing in femoral component rotation using a computer navigation system.

Seventy-five consecutive patients undergoing TKRs were randomized into two groups. The first received femoral component rotation by a computerized method that combined the epicondylar axis and Whitesides AP axis measurements to determine rotation. The second group had a zero or three-degree posterior referencing external rotation block, depending on which was closest to the epicondylar axis. All patients underwent axial CT scans of the distal femur to determine component rotation around the surgical epicondylar axis.

Femoral component alignment with the combined method as compared to fixed posterior alignment guides is statistically improved (p=0.001). In the posterior referencing group 43% were correctly rotated to the epicondylar axis but another 43% were malrotated by 3 degrees or more. The mean malrotation was 1.72 degrees (range 0–5) In the combined group 82% were correctly rotated and 11% were malrotated by 3 degrees or more. The mean malrotation was 0.51 degrees (range 0–4).

Conclusion: A combined computerized method of using the surgical epicondylar axis and Whitesides AP axis produces superior results when aiming for neutral femoral component rotation. Fixed posterior referencing blocks will produce errors in malrotation in over 50% of cases.

Plain radiographs are a poor indication of the overall coronal, sagittal and axial alignment of a total knee arthroplasty (TKA). We describe a new CT method that allows the mechanical axis in both planes to be defined and seven alignment characteristics to be defined.

A GE Light Speed multislice CT scanner performed a high-speed helical scan from the acetabular roof to the talus in 100 patients following TKA. The knees were scanned in a supine position with the legs in a neutral position. The images were reformatted in coronal, sagittal and axial planes and the mechanical and anatomical axes identified. The femoral component (varus/ valgus, flexion/extension, rotation) as well as the tibial – (varus/valgus, posterior slope and rotation) are measured. Coupled femoro-tibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The accuracy of this technique has been checked by using a mechanical FARO-arm.

The technique has a low intraobserver error rate of 9% (in each case less than 1 degree) and an accuracy of 3mm in a three-dimensional plane, as determined against an independent FARO arm technique. The CT analysis of 100 patients shows normal tibial baseplate rotation to be 8–12 degrees from the tibial tuberosity.

Conclusion: The CT protocol is the first single radiographic investigation that characterizes all the alignment parameters of a TKA. It sets an excellent standard in planning revision knee surgery and provides a valuable tool in assessing alignment of painful knee replacements as well as in outcome measures of TKA.

Introduction: We describe a CT method that allows the seven alignment characteristics of a knee arthroplasty to be defined in a single investigation.

Method: A multislice CT scanner, scans in 2.5mm slices from the acetabular roof to the dome of the talus with the legs in a standard position.

The mechanical and anatomical axes are identified, from 3 dimensional landmarks, in both AP and lateral planes. The coronal and sagittal alignment of the pros-theses is then measured against the axes.

The rotation of the femoral component is measured relative to the transepicondylar axis. Tibial rotation was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images.

The results of 100 scans show a low inter and intra observer error rate whilst independent assessment shows a mean measurement error of 3mm in a three dimensional plane. The radiation dose is 2.7mSV.

Conclusions: The technique provides the only currently available measure of all the alignment characteristics required to assess the quality of a knee arthroplasty. It will become a gold standard in planning revision surgery and provide a valuable tool in assessing alignment of painful knee replacements.

Introduction: The epicondylar axis is often cited as a guide to rotation of the femoral component in total knee arthroplasty. Our aimwas to accurately identify with digital palpation, the epicondyles in 14 cadaveric knees Method: Each cadaveric knee had a midline parapatellar approautil ch and the patella was everted. The epicondyles where palpated and the position of the epicondyles was marked by inserting a pin in each epicondyle. All cadavers had a CT scan to identify the position of the epicondyles and pins. The angular difference was calculated with computer-guided measurements. Results: Of the seven right knees, þve had perfect epicondylar identiþcation, whilst two had inaccurate placement of pins. In both cases of error the medial epicondyle had a sulcus conþguration as opposed to a prominent ridge. This resulted in internal rotation of 2 degrees and 3 degrees. Of the seven left knees, þve had perfect epicondylar identiþcation, whilst two had inaccurate pin placement. In both cases this was inaccurate placement of the medial epicondylar pin in a sulcus conþguration. In both this resulted in extra external rotation of the component to 6 degrees. Overall four out of 14 knees had inaccurate placement and in each the medial epicondyle had a sulcus conþguration.

Introduction: Plain radiographs are a poor indication of the overall axial and rotational alignment of a total knee replacement. A CT method is described to overcome these problems. Method: A multislice CT scanner took 1mm contingous slices from the acetabular roof to the dome of the talus with the legs immobile in a standard position. The scans are stored and reformatted to allow axial, coronal and sagittal images. The centre of femoral head, distal femur, tibial plateau and ankle joints are identiþed in three dimensions. The mechanical and anatomical axes are identiþed. The alignment of the prostheses is then measured against the mechanical axis in both AP and lateral planes. The rotation of the femoral component is measured relative to the transepicondylar axis. Tibial rotation was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The accuracy of this technique has been checked by using a Ferro Arm which mechanically validates the mechanical axis. Results: The technique provides the only currently available measure of all the alignment characteristics required to assess the quality of a knee replacement. Conclusions: The Perth protocol provides an accurate assessment of alignment of the femoral and tibial components to a measured mechanical axis and rotational measurements of both components both individually and