Aims. Total knee arthroplasty (TKA) using functional alignment aims to implant the components with minimal compromise of the soft-tissue envelope by restoring the plane and obliquity of the non-arthritic joint. The objective of this study was to determine the effect of TKA with functional alignment on mediolateral soft-tissue balance as assessed using intraoperative sensor-guided technology. Methods. This prospective study included 30 consecutive patients undergoing robotic-assisted TKA using the Stryker PS Triathlon implant with functional alignment. Intraoperative soft-tissue balance was assessed using sensor-guided technology after definitive component implantation; soft-tissue balance was defined as intercompartmental pressure difference (ICPD) of < 15 psi. Medial and lateral compartment pressures were recorded at 10°, 45°, and 90° of knee flexion. This study included 18 females (60%) and 12 males (40%) with a mean age of 65.2 years (SD 9.3). Mean preoperative hip-knee-ankle deformity was 6.3° varus (SD 2.7°). Results. TKA with functional alignment achieved balanced medial and lateral compartment pressures at 10° (25.0 psi (SD 6.1) vs 23.1 psi (SD 6.7), respectively; p = 0.140), 45° (21.4 psi (SD 5.9) vs 20.6 psi (SD 5.9), respectively; p = 0.510), and 90° (21.2 psi (SD 7.1) vs 21.6 psi (SD 9.0), respectively; p = 0.800) of knee flexion. Mean ICPD was 6.1 psi (SD 4.5; 0 to 14) at 10°, 5.4 psi (SD 3.9; 0 to 12) at 45°, and 4.9 psi (SD 4.45; 0 to 15) at 90° of knee flexion. Mean postoperative limb alignment was 2.2° varus (SD 1.0°). Conclusion. TKA using the functional alignment achieves balanced mediolateral soft-tissue tension through the arc of knee flexion as assessed using intraoperative pressure-sensor technology. Further clinical trials are required to determine if TKA with functional alignment translates to improvements in patient satisfaction and outcomes compared to conventional alignment techniques. Cite this article: Bone Joint J 2021;103-B(3):507–514

The aim of this prospective multicentre study was to report the patient satisfaction after total knee replacement (TKR), undertaken with the aid of intra-operative sensors, and to compare these results with previous studies. A total of 135 patients undergoing TKR were included in the study. The soft-tissue balance of each TKR was quantified intra-operatively by the sensor, and 18 (13%) were found to be unbalanced. A total of 113 patients (96.7%) in the balanced group and 15 (82.1%) in the unbalanced group were satisfied or very satisfied one year post-operatively (p = 0.043).

A review of the literature identified no previous study with a mean level of satisfaction that was greater than the reported level of satisfaction of the balanced TKR group in this study. Ensuring soft-tissue balance by using intra-operative sensors during TKR may improve satisfaction.

Cite this article: Bone Joint J 2014;96-B:1333–8

Aims. Robotic arm-assisted surgery offers accurate and reproducible guidance in component positioning and assessment of soft-tissue tensioning during knee arthroplasty, but the feasibility and early outcomes when using this technology for revision surgery remain unknown. The objective of this study was to compare the outcomes of robotic arm-assisted revision of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) versus primary robotic arm-assisted TKA at short-term follow-up. Methods. This prospective study included 16 patients undergoing robotic arm-assisted revision of UKA to TKA versus 35 matched patients receiving robotic arm-assisted primary TKA. In all study patients, the following data were recorded: operating time, polyethylene liner size, change in haemoglobin concentration (g/dl), length of inpatient stay, postoperative complications, and hip-knee-ankle (HKA) alignment. All procedures were performed using the principles of functional alignment. At most recent follow-up, range of motion (ROM), Forgotten Joint Score (FJS), and Oxford Knee Score (OKS) were collected. Mean follow-up time was 21 months (6 to 36). Results. There were no differences between the two treatment groups with regard to mean change in haemoglobin concentration (p = 0.477), length of stay (LOS, p = 0.172), mean polyethylene thickness (p = 0.065), or postoperative complication rates (p = 0.295). At the most recent follow-up, the primary robotic arm-assisted TKA group had a statistically significantly improved OKS compared with the revision UKA to TKA group (44.6 (SD 2.7) vs 42.3 (SD 2.5); p = 0.004) but there was no difference in the overall ROM (p = 0.056) or FJS between the two treatment groups (86.1 (SD 9.6) vs 84.1 (4.9); p = 0.439). Conclusion. Robotic arm-assisted revision of UKA to TKA was associated with comparable intraoperative blood loss, early postoperative rehabilitation, functional outcomes, and complications to primary robotic TKA at short-term follow-up. Robotic arm-assisted surgery offers a safe and reproducible technique for revising failed UKA to TKA. Cite this article: Bone Joint J 2024;106-B(7):680–687

Aims. The diagnosis of periprosthetic joint infection (PJI) continues to present a significant clinical challenge. New biomarkers have been proposed to support clinical decision-making; among them, synovial fluid alpha-defensin has gained interest. Current research methodology suggests reference methods are needed to establish solid evidence for use of the test. This prospective study aims to evaluate the diagnostic accuracy of high-performance liquid chromatography coupled with the mass spectrometry (LC-MS) method to detect alpha-defensin in synovial fluid. Methods. Between October 2017 and September 2019, we collected synovial fluid samples from patients scheduled to undergo revision surgery for painful total knee arthroplasty (TKA). The International Consensus Meeting criteria were used to classify 33 PJIs and 92 aseptic joints. LC-MS assay was performed to measure alpha-defensin in synovial fluid of all included patients. Sensitivity, specificity, positive predictive value, negative predictive value, and the area under the receiver operating characteristic curve (AUC) were calculated to define the test diagnostic accuracy. Results. The AUC was 0.99 (95% confidence interval (CI) 0.98 to 1.00). Receiver operating characteristic (ROC) analysis showed that the optimal cut-off value of synovial fluid alpha-defensin was 1.0 μg/l. The sensitivity of alpha-defensin was 100% (95% CI 96 to 100), the specificity was 97% (95% CI 90 to 98), the positive predictive value was 89.2% (95% CI 82 to 94), and negative predictive value was 100% (95% CI 96 to 100). ROC analysis demonstrated an AUC of 0.99 (95% CI 0.98 to 1.0). Conclusion. The present study confirms the utility of alpha-defensin in the synovial fluid in patients with painful TKA to select cases of PJI. Since LC-MS is still a time-consuming technology and is available in highly specialized laboratories, further translational research studies are needed to take this evidence into routine procedures and promote a new diagnostic approach. Cite this article: Bone Joint J 2022;104-B(9):1047–1051

Aims. Alternative alignment concepts, including kinematic and restricted kinematic, have been introduced to help improve clinical outcomes following total knee arthroplasty (TKA). The purpose of this study was to evaluate the clinical results, along with patient satisfaction, following TKA using the concept of restricted kinematic alignment. Methods. A total of 121 consecutive TKAs performed between 11 February 2018 to 11 June 2019 with preoperative varus deformity were reviewed at minimum one-year follow-up. Three knees were excluded due to severe preoperative varus deformity greater than 15°, and a further three due to requiring revision surgery, leaving 109 patients and 115 knees to undergo primary TKA using the concept of restricted kinematic alignment with advanced technology. Patients were stratified into three groups based on the preoperative limb varus deformity: Group A with 1° to 5° varus (43 knees); Group B between 6° and 10° varus (56 knees); and Group C with varus greater than 10° (16 knees). This study group was compared with a matched cohort of 115 TKAs and 115 patients using a neutral mechanical alignment target with manual instruments performed from 24 October 2016 to 14 January 2019. Results. Mean overall patient satisfaction for the entire cohort was 4.7 (SE 0.1) on a 5-point Likert scale, with 93% being either very satisfied or satisfied compared with a Likert of 4.3 and patient satisfaction of 81% in the mechanical alignment group (p < 0.001 and p < 0.006 respectively). At mean follow-up of 17 months (11 to 27), the mean overall Likert, Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, Western Ontario and McMaster Universities Osteoarthritis Index, Forgotten Joint Score, and Knee Society Knee and Function Scores were significantly better in the kinematic group than in the neutral mechanical alignment group. The most common complication in both groups was contracture requiring manipulation under anaesthesia, involving seven knees (6.1%) in the kinematic group and nine knees (7.8%) in the mechanical alignment group. Conclusion. With the advent of advanced technology, and the ability to obtain accurate bone cuts, the target limb alignment, and soft-tissue balance within millimetres, using a restricted kinematic alignment concept demonstrated excellent patient satisfaction following primary TKA. Longer-term analysis is required as to the durability of this method. Cite this article: Bone Joint J 2021;103-B(6 Supple A):59–66

Aims. Despite new technologies for total knee arthroplasty (TKA), approximately 20% of patients are dissatisfied. A major reason for dissatisfaction and revision surgery after TKA is persistent pain. The radiological grade of osteoarthritis (OA) preoperatively has been investigated as a predictor of the outcome after TKA, with conflicting results. The aim of this study was to determine if there is a difference in the intensity of pain 12 months after TKA in relation to the preoperative radiological grade of OA alone, and the combination of the intensity of preoperative pain and radiological grade of OA. Methods. The preoperative data of 300 patients who underwent primary TKA were collected, including clinical information (age, sex, preoperative pain), psychological variables (depression, anxiety, pain catastrophizing, anticipated pain), and quantitative sensory testing (temporal summation, pressure pain thresholds, conditioned pain modulation). The preoperative radiological severity of OA was graded according to the Kellgren-Lawrence (KL) classification. Persistent pain in the knee was recorded 12 months postoperatively. Generalized linear models explored differences in postoperative pain according to the KL grade, and combined preoperative pain and KL grade. Relative risk models explored which preoperative variables were associated with the high preoperative pain/low KL grade group. Results. Pain 12 months after TKA was not associated with the preoperative KL grade alone. Significantly increased pain 12 months after TKA was found in patients with a combination of high preoperative pain and a low KL grade (p = 0.012). Patients in this group were significantly more likely to be male, younger, and have higher preoperative pain catastrophizing, higher depression, and lower anxiety (all p ≤ 0.05). Conclusion. Combined high preoperative pain and low radiological grade of OA, but not the radiological grade alone, was associated with a higher intensity of pain 12 months after primary TKA. This group may have a more complex cause of pain that requires additional psychological interventions in order to optimize the outcome of TKA. Cite this article: Bone Joint J 2022;104-B(11):1202–1208

Aims. A significant percentage of patients remain dissatisfied after total knee arthroplasty (TKA). The aim of this study was to determine whether the sequential addition of accelerometer-based navigation for femoral component preparation and sensor-guided ligament balancing improved complication rates, radiological alignment, or patient-reported outcomes (PROMs) compared with a historical control group using conventional instrumentation. Methods. This retrospective cohort study included 371 TKAs performed by a single surgeon sequentially. A historical control group, with the use of intramedullary guides for distal femoral resection and surgeon-guided ligament balancing, was compared with a group using accelerometer-based navigation for distal femoral resection and surgeon-guided balancing (group 1), and one using navigated femoral resection and sensor-guided balancing (group 2). Primary outcome measures were Patient-Reported Outcomes Measurement Information System (PROMIS) and Knee injury and Osteoarthritis Outcome (KOOS) scores measured preoperatively and at six weeks and 12 months postoperatively. The position of the components and the mechanical axis of the limb were measured postoperatively. The postoperative range of motion (ROM), haematocrit change, and complications were also recorded. Results. There were 194 patients in the control group, 103 in group 1, and 74 in group 2. There were no significant differences in baseline demographics between the groups. Patients in group 2 had significantly higher baseline mental health subscores than control and group 1 patients (53.2 vs 50.2 vs 50.2, p = 0.041). There were no significant differences in any PROMs at six weeks or 12 months postoperatively (p > 0.05). There was no difference in the rate of manipulation under anaesthesia (MUA), complication rates, postoperative ROM, or blood loss. There were fewer mechanical axis outliers in groups 1 and 2 (25.2%, 14.9% respectively) versus control (28.4%), but this was not statistically significant (p = 0.10). Conclusion. The sequential addition of navigation of the distal femoral cut and sensor-guided ligament balancing did not improve short-term PROMs, radiological outcomes, or complication rates compared with conventional techniques. The costs of these added technologies may not be justified. Cite this article: Bone Joint J 2020;102-B(6 Supple A):24–30

Aims. This aim of this study was to assess the feasibility of designing and introducing generic 3D-printed instrumentation for routine use in total knee arthroplasty. Materials and Methods. Instruments were designed to take advantage of 3D-printing technology, particularly ensuring that all parts were pre-assembled, to theoretically reduce the time and skill required during surgery. Concerning functionality, ranges of resection angle and distance were restricted within a safe zone, while accommodating either mechanical or anatomical alignment goals. To identify the most suitable biocompatible materials, typical instrument shapes and mating parts, such as dovetails and screws, were designed and produced. Results. Before and after steam sterilization, dimensional analysis showed that acrylonitrile butadiene styrene could not withstand the temperatures without dimensional changes. Oscillating saw tests with slotted cutting blocks produced debris, fractures, or further dimensional changes in the shape of Nylon-12 and polymethylmethacrylate (MED610), but polyetherimide ULTEM 1010 was least affected. Conclusion. The study showed that 3D-printed instrumentation was technically feasible and had some advantages. However, other factors, such as whether all procedural steps can be accomplished with a set of 3D-printed instruments, the logistics of delivery, and the economic aspects, require further study. Cite this article: Bone Joint J 2019;101-B(7 Supple C):115–120

Aims. The objectives of this study were to assess the effect of anterior cruciate ligament (ACL) resection on flexion-extension gaps, mediolateral soft tissue laxity, maximum knee extension, and limb alignment during primary total knee arthroplasty (TKA). Methods. This prospective study included 140 patients with symptomatic knee osteoarthritis undergoing primary robotic-arm assisted TKA. All operative procedures were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess study outcomes pre- and post-ACL resection with knee extension and 90° knee flexion. This study included 76 males (54.3%) and 64 females (45.7%) with a mean age of 64.1 years (SD 6.8) at time of surgery. Mean preoperative hip-knee-ankle deformity was 6.1° varus (SD 4.6° varus). Results. ACL resection increased the mean extension gap significantly more than the flexion gap in the medial (mean 1.2 mm (SD 1.0) versus mean 0.2 mm (SD 0.7) respectively; p < 0.001) and lateral (mean 1.1 mm (SD 0.9) versus mean 0.2 mm (SD 0.6) respectively; p < 0.001) compartments. The mean gap differences following ACL resection did not create any significant mediolateral soft tissue laxity in extension (gap difference: mean 0.1 mm (SD 2.4); p = 0.89) or flexion (gap difference: mean 0.2 mm (SD 3.1); p = 0.40). ACL resection did not significantly affect maximum knee extension (change in maximum knee extension = mean 0.2° (SD 0.7°); p = 0.23) or fixed flexion deformity (mean 4.2° (SD 3.2°) pre-ACL release versus mean 3.9° (SD 3.7°) post-ACL release; p = 0.61). ACL resection did not significantly affect overall limb alignment (change in alignment = mean 0.2° valgus (SD 1.0° valgus; p = 0.11). Conclusion. ACL resection creates flexion-extension mismatch by increasing the extension gap more than the flexion gap. However, gap differences following ACL resection do not create any mediolateral soft tissue laxity in extension or flexion. ACL resection does not affect maximum knee extension or overall limb alignment. Cite this article: Bone Joint J 2020;102-B(4):442–448

Aims

To identify unanswered questions about the prevention, diagnosis, treatment, and rehabilitation and delivery of care of first-time soft-tissue knee injuries (ligament injuries, patella dislocations, meniscal injuries, and articular cartilage) in children (aged 12 years and older) and adults.

Aims

The use of cementless total knee arthroplasty (TKA) components has increased during the past decade. The initial design of cementless metal-backed patellar components had shown high failure rates due to many factors. The aim of this study was to evaluate the clinical results of a second-generation cementless, metal-backed patellar component of a modern design.

Aims. The aim of this study was to assess the effect of posterior cruciate ligament (PCL) resection on flexion-extension gaps, mediolateral soft-tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilized (PS) total knee arthroplasty (TKA). Patients and Methods. This prospective study included 110 patients with symptomatic osteoarthritis of the knee undergoing primary robot-assisted PS TKA. All operations were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps before and after PCL resection in extension and 90° knee flexion. Measurements were made after excision of the anterior cruciate ligament and prior to bone resection. There were 54 men (49.1%) and 56 women (50.9%) with a mean age of 68 years (. sd. 6.2) at the time of surgery. The mean preoperative hip-knee-ankle deformity was 4.1° varus (. sd. 3.4). Results. PCL resection increased the mean flexion gap significantly more than the extension gap in the medial (2.4 mm (. sd. 1.5) vs 1.3 mm (. sd. 1.0); p < 0.001) and lateral (3.3 mm (. sd. 1.6) vs 1.2 mm (. sd. 0.9); p < 0.01) compartments. The mean gap differences after PCL resection created significant mediolateral laxity in flexion (gap difference: 1.1 mm (. sd. 2.5); p < 0.001) but not in extension (gap difference: 0.1 mm (. sd. 2.1); p = 0.51). PCL resection significantly improved the mean FFD (6.3° (. sd. 4.4) preoperatively vs 3.1° (. sd. 1.5) postoperatively; p < 0.001). There was a strong positive correlation between the preoperative FFD and change in FFD following PCL resection (Pearson’s correlation coefficient = 0.81; p < 0.001). PCL resection did not significantly affect limb alignment (mean change in alignment: 0.2° valgus (. sd. 1.2); p = 0.60). Conclusion. PCL resection creates flexion-extension mismatch by increasing the flexion gap more than the extension gap. The increase in the lateral flexion gap is greater than the increase in the medial flexion gap, which creates mediolateral laxity in flexion. Improvements in FFD following PCL resection are dependent on the degree of deformity before PCL resection. Cite this article: Bone Joint J 2019;101-B:1230–1237

Aims

The aim was to assess whether robotic-assisted total knee arthroplasty (rTKA) had greater knee-specific outcomes, improved fulfilment of expectations, health-related quality of life (HRQoL), and patient satisfaction when compared with manual TKA (mTKA).

Aims

The primary aim was to assess whether robotic total knee arthroplasty (rTKA) had a greater early knee-specific outcome when compared to manual TKA (mTKA). Secondary aims were to assess whether rTKA was associated with improved expectation fulfilment, health-related quality of life (HRQoL), and patient satisfaction when compared to mTKA.

Patient specific instrumentation (PSI) uses advanced imaging of the knee (CT or MRI) to generate individualised cutting blocks aimed to make the procedure of total knee arthroplasty (TKA) more accurate and efficient. However, in this era of healthcare cost consciousness, the value of new technologies needs to be critically evaluated. There have been several comparative studies looking at PSI versus standard instrumentation. Most compare PSI with conventional instrumentation in terms of alignment in the coronal plane, operative time and surgical efficiency, cost effectiveness and short-term outcomes. Several systematic reviews and meta-analyses have also been published. PSI has not been shown to be superior compared with conventional instrumentation in its ability to restore traditional mechanical alignment in primary TKA. Most studies show comparative efficacy and no decrease in the number of outliers in either group. In terms of operative time and efficiency, PSI tended towards decreasing operative time, saving a mean of five minutes per patient (0 to 20). Furthermore, while some cost savings could be realised with less operative time and reduced instrumentation per patient, these savings were overcome by the cost of the CT/MRI and the cutting blocks. Finally, there was no evidence that PSI positively affected clinical outcomes at two days, two months, or two years. Consequently, current evidence does not support routine use of PSI in routine primary TKA. Cite this article: Bone Joint J 2016;98-B(1 Suppl A):78–80

Aims

Intraoperative pressure sensors allow surgeons to quantify soft-tissue balance during total knee arthroplasty (TKA). The aim of this study was to determine whether using sensors to achieve soft-tissue balance was more effective than manual balancing in improving outcomes in TKA.

Aims

Thresholds of acceptable early migration of the components in total knee arthroplasty (TKA) have traditionally ignored the effects of patient and implant factors that may influence migration. The aim of this study was to determine which of these factors are associated with overall longitudinal migration of well-fixed tibial components following TKA.

Aims

The aim of this study was to compare any differences in the primary outcome (biphasic flexion knee moment during gait) of robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) at one year post-surgery.

Aims

The aim of this study was to compare the clinical outcomes of robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) during the first six weeks and at one year postoperatively.

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