Aims

Distal femoral resection in conventional total knee arthroplasty (TKA) utilizes an intramedullary guide to determine coronal alignment, commonly planned for 5° of valgus. However, a standard 5° resection angle may contribute to malalignment in patients with variability in the femoral anatomical and mechanical axis angle. The purpose of the study was to leverage deep learning (DL) to measure the femoral mechanical-anatomical axis angle (FMAA) in a heterogeneous cohort.

Aims

The primary objective of this study was to compare the five-year tibial component migration and wear between highly crosslinked polyethylene (HXLPE) inserts and conventional polyethylene (PE) inserts of the uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary objectives included clinical outcomes and patient-reported outcome measures (PROMs).

Aims

Knee arthroplasty surgery is a highly effective treatment for arthritis and disorders of the knee. There are a wide variety of implant brands and types of knee arthroplasty available to surgeons. As a result of a number of highly publicized failures, arthroplasty surgery is highly regulated in the UK and many other countries through national registries, introduced to monitor implant performance, surgeons, and hospitals. With time, the options available within many brand portfolios have grown, with alternative tibial or femoral components, tibial insert materials, or shapes and patella resurfacings. In this study we have investigated the effect of the expansion of implant brand portfolios and where there may be a lack of transparency around a brand name. We also aimed to establish the potential numbers of compatible implant construct combinations.

Aims

In patients with a “dry” aspiration during the investigation of prosthetic joint infection (PJI), saline lavage is commonly used to obtain a sample for analysis. The aim of this study was to investigate prospectively the impact of saline lavage on synovial fluid analysis in revision arthroplasty.

Metallosis is a rare cause of failure after total knee replacement and has only previously been reported when there has been abnormal metal-on-metal contact. We describe 14 patients (15 knees) whose total knee replacement required revision for a new type of early failure caused by extensive metallosis. A modification of a cementless rotating platform implant, which had previously had excellent long-term survival, had been used in each case. The change was in the form of a new porous-beaded surface on the femoral component to induce cementless fixation, which had been used successfully in the fixation of acetabular and tibial components. This modification appeared to have resulted in metallosis due to abrasive two-body wear. The component has subsequently been recalled and is no longer in use. The presentation, investigation, and findings at revision are described and a possible aetiology and its implications are discussed

A controlled study, comparing computer- and conventional jig-assisted total knee replacement in six cadavers is presented. In order to provide a quantitative assessment of the alignment of the replacements, a CT-based technique which measures seven parameters of alignment has been devised and used. In this a multi-slice CT machine scanned in 2.5 mm slices from the acetabular roof to the dome of the talus with the subject’s legs held in a standard position. The mechanical and anatomical axes were identified, from three-dimensional landmarks, in both anteroposterior and lateral planes. The coronal and sagittal alignment of the prosthesis was then measured against the axes. The rotation of the femoral component was measured relative to the transepicondylar axis. The rotation of the tibial component 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 radiation dose was 2.7 mSV. The computer-assisted total knee replacements showed better alignment in rotation and flexion of the femoral component, the posterior slope of the tibial component and in the matching of the femoral and tibial components in rotation. Differences were statistically significant and of a magnitude that support extension of computer assistance to the clinical situation

We undertook a prospective, randomised study using a non-invasive transcranial Doppler device to evaluate cranial embolisation in computer-assisted navigated total knee arthroplasty (n = 14) and compared this with a standard conventional surgical technique using intramedullary alignment guides (n = 10). All patients were selected randomly without the knowledge of the patient, anaesthetists (before the onset of the procedure) and ward staff. The operations were performed by a single surgeon at one hospital using a uniform surgical approach, instrumentation, technique and release sequence. The only variable in the two groups of patients was the use of single tracker pins of the imageless navigation system in the tibia and femur of the navigated group and intramedullary femoral and tibial alignment jigs in the non-navigated group. Acetabular Doppler signals were obtained in 14 patients in the computer-assisted group and nine (90%) in the conventional group, in whom high-intensity signals were detected in seven computer-assisted patients (50%) and in all of the non-navigated patients. In the computer-assisted group no patient had more than two detectable emboli, with a mean of 0.64 (SD 0.74). In the non-navigated group the number of emboli ranged from one to 43 and six patients had more than two detectable emboli, with a mean of 10.7 (. sd. 13.5). The difference between the two groups was highly significant using the Wilcoxon non-parametric test (p = 0.0003). Our findings show that computer-assisted total knee arthroplasty, when compared with conventional jig-based surgery, significantly reduces systemic emboli as detected by transcranial Doppler ultrasonography

Improvements in the surgical technique of total knee replacement (TKR) are continually being sought. There has recently been interest in three-dimensional (3D) pre-operative planning using magnetic resonance imaging (MRI) and CT. The 3D images are increasingly used for the production of patient-specific models, surgical guides and custom-made implants for TKR.

The users of patient-specific instrumentation (PSI) claim that they allow the optimum balance of technology and conventional surgery by reducing the complexity of conventional alignment and sizing tools. In this way the advantages of accuracy and precision claimed by computer navigation techniques are achieved without the disadvantages of additional intra-operative inventory, new skills or surgical time.

This review describes the terminology used in this area and debates the advantages and disadvantages of PSI.

The aim of this prospective single-centre study was to assess the difference in clinical outcome between total knee replacement (TKR) using computerised navigation and that of conventional TKR. We hypothesised that navigation would give a better result at every stage within the first five years. A total of 195 patients (195 knees) with a mean age of 70.0 years (39 to 89) were allocated alternately into two treatment groups, which used either conventional instrumentation (group A, 97 knees) or a navigation system (group B, 98 knees). After five years, complete clinical scores were available for 121 patients (62%). A total of 18 patients were lost to follow-up. Compared with conventional surgery, navigated TKR resulted in a better mean Knee Society score (p = 0.008). The difference in mean Knee Society scores over time between the two groups was not constant (p = 0.006), which suggests that these groups differed in their response to surgery with time. No significant difference in the frequency of malalignment was seen between the two groups.

In summary, computerised navigation resulted in a better functional outcome at five years than conventional techniques. Given the similarity in mechanical alignment between the two groups, rotational alignment may prove to be a better method of identifying differences in clinical outcome after navigated surgery.

We compared the performance of uncemented trabecular metal tibial components in total knee replacement with that of cemented tibial components in patients younger than 60 years over two years using radiostereophotogrammetric analysis (RSA). A total of 22 consecutive patients (mean age 53 years, 33 to 59, 26 knees) received an uncemented NexGen trabecular metal cruciate-retaining monobloc tibial component and 19 (mean 53 years, 44 to 59, 21 knees) a cemented NexGen Option cruciate-retaining modular tibial component.

All the trabecular metal components migrated during the initial three months and then stabilised. The exception was external rotation, which did not stabilise until 12 months. Unlike conventional metal-backed implants which displayed a tilting migration comprising subsidence and lift-off from the tibial tray, most of the trabecular metal components showed subsidence only, probably due to the elasticity of the implant.

This pattern of subsidence is regarded as being beneficial for uncemented fixation.

The rotational alignment of the tibia is an unresolved issue in knee replacement. A poor functional outcome may be due to malrotation of the tibial component. Our aim was to find a reliable method for positioning the tibial component in knee replacement.

CT scans of 19 knees were reconstructed in three dimensions and orientated vertically. An axial plane was identified 20 mm below the tibial spines. The centre of each tibial condyle was calculated from ten points taken round the condylar cortex. The tibial tubercle centre was also generated as the centre of the circle which best fitted eight points on the outside of the tubercle in an axial plane at the level of its most prominent point.

The derived points were identified by three observers with errors of 0.6 mm to 1 mm. The medial and lateral tibial centres were constant features (radius 24 mm (sd 3), and 22 mm (sd 3), respectively). An anatomical axis was created perpendicular to the line joining these two points. The tubercle centre was found to be 20 mm (sd 7) lateral to the centre of the medial tibial condyle. Compared with this axis, an axis perpendicular to the posterior condylar axis was internally rotated by 6° (sd 3). An axis based on the tibial tubercle and the tibial spines was also internally rotated by 5° (sd 10).

Alignment of the knee when based on this anatomical axis was more reliable than either the posterior surfaces or any axis involving the tubercle which was the least reliable landmark in the region.