Does soft tissue balancing using intraoperative pressure sensors improve clinical outcomes in total knee arthroplasty? A protocol of a multicentre randomised controlled trial.

INTRODUCTION: Soft tissue imbalance is considered to be a major surgical cause of dissatisfaction following total knee arthroplasty (TKA). Surgeon-determined manual assessment of ligament tension has been shown to be a poor determinant of the true knee balance state. The recent introduction of intraoperative sensors, however, allows surgeons to precisely quantify knee compartment pressures and tibiofemoral kinematics, thereby optimising coronal and sagittal plane soft tissue balance. The primary hypothesis of this study is that achieving knee balance with use of sensors in TKA will improve patient-reported outcomes when compared with manual balancing. METHODS AND ANALYSIS: A multicentred, randomised controlled trial will compare patient-reported outcomes in 222 patients undergoing TKA using sensor-guided balancing versus manual balancing. The sensor will be used in both arms for purposes of data collection; however, surgeons will be blinded to the pressure data in patients randomised to manual balancing. The primary outcome will be the change from baseline to 1 year postoperatively in the mean of the four subscales of the Knee Injury and Osteoarthritis Outcome Score (KOOS4) that are most specific to TKA recovery: pain, symptoms, function and knee-related quality of life. Secondary outcomes will include the surgeon's capacity to determine knee balance, radiographic and functional measures and additional patient-reported outcomes. Normality of data will be assessed, and a Student's t-test and equivalent non-parametric tests will be used to compare differences in means among the two groups. ETHICS AND DISSEMINATION: Ethics approval was obtained from South Eastern Sydney Local Health District, Approval (HREC/18/POWH/320). Results of the trial will be presented at orthopaedic surgical meetings and submitted for publication in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: ACTRN#12618000817246.

Image intensifier distortion influences a surgeon's ability to aim guidewires during orthopaedic procedures.

OBJECTIVE: Accurate insertion of a guidewire under image intensifier guidance is a fundamental skill required by orthopaedic surgeons. This study investigated how image intensifier distortion, which is composed of pin-cushion and sigmoidal components, changed the apparent trajectory of a guidewire, and the resulting deviation between the intended and actual guidewire tip position. MATERIALS AND METHODS: Intraoperative image intensifier images for 220 consecutive patients with hip fractures were retrospectively corrected for distortion using a global polynomial method. The deviation between the intended and actual guidewire tip positions was calculated. Additional distortion parameters were tested using an image intensifier produced by a different manufacturer, and a flat-panel c-arm. RESULTS: Deviation was approximately 1 cm if the guidewire was aimed from the extremity of the image and almost 0 if the entry point was only 20% from the centre (p < 0.001). The direction of deviation was different for left and right hips, with average deviations measuring 3 mm proximal and 5 mm distal respectively (p < 0.001). The flat-panel c-arm almost completely eliminated distortion. CONCLUSIONS: Image intensifier distortion significantly altered the intended trajectory of a guidewire, with guidewires aimed from the image periphery more affected than guidewires aimed from the centre. Furthermore, for right hips, guidewires should be aimed distal to their intended position, and for left hips they should be aimed proximal to achieve their desired position. The flat-panel c-arm eliminated the effect of distortion; hence, it may be preferable if precision in guidewire positioning is vital.

Tibial rotation kinematics subsequent to knee arthroplasty.

BACKGROUND: The use of computer assisted joint replacement has facilitated precise intraoperative measurement of knee kinematics. The changes in "screw home mechanism" (SHM) resulting from Total Knee Arthroplasty (TKA) with different prostheses and constraints has not yet been accurately described. METHODS: A pilot study was first completed. Intraoperative kinematic data was collected two groups of 15 patients receiving different prostheses. RESULTS: On average, patients lost 5.3° of ER (SD = 6.1°). There was no significant difference between the prostheses or different prosthetic constraints. CONCLUSIONS: There significant loss of SHM after TKA. Further research is required to understand its impact on patient function.

The Australian arthroplasty thromboprophylaxis survey.

Previous surveys of orthopedic surgeons have shown considerable variation in thromboprophylaxis for venous thromboembolism after joint arthroplasty. This survey aimed to determine the current practice among Australian orthopedic surgeons. A questionnaire regarding the duration, reasons, and methods of chemical and mechanical prophylaxis for hip and knee arthroplasty patients was sent to the 1082 surgeons identified; 593 (55%) members completed the questionnaire. The survey revealed that 98% of surgeons used chemical thromboprophylaxis, mainly low-molecular-weight heparin (84% hip and 79% knee). Those who use low-molecular-weight heparin were more likely to prescribe anticoagulants in fear of litigation (19.2% vs 10.1%, P = .04) and more likely to rely on protocols or guidelines (32.2% vs 17.2%, P = .004) instead of basing their decision on their own reading (52.4% vs 71.3%, P = .001). Most orthopedic surgeons in our survey have indicated that they would welcome guidelines from their association or college regarding thromboprophylaxis in arthroplasty.

Minimally invasive imageless computer-navigated knee surgery: initial results.

The combination of imageless computer-aided surgery (CAS) and minimally invasive surgery (MIS) for total knee arthroplasty (TKA) has not been reported. This study presents the initial 30 procedures in which imageless CAS was combined with MIS for TKA by the senior author. Coronal alignment of femoral and tibial components with respect to the mechanical axis of the lower limb was measured when patients could achieve full extension. Component position was acceptable for all implants. The mean coronal tibial alignment was 90.35 degrees (range, 88 degrees -93 degrees ) and mean coronal femoral alignment 90.10 degrees (range, 88 degrees -93 degrees ) to the mechanical axis. Tourniquet time averaged 90 minutes (range, 60-118 minutes). There was no significant reduction in tourniquet time with increasing familiarity with the technique. Our results demonstrate that CAS combined with MIS for TKA maintains the accuracy of component alignment despite the minimally invasive approach. These initial results demonstrate no significant learning curve associated with the technique.

Open reduction of intracapsular hip fractures using a modified Smith-Petersen surgical exposure.

The Smith-Petersen or modified direct anterior hip surgical exposures have not previously been described for open reduction of femoral neck fractures. This technique of reduction provides a direct approach to the femoral neck and hip joint. Displaced fractures of the femoral neck can easily be reduced through this approach, local osseus defects resulting from impaction can be supported with bone graft, and fracture fixation is then placed through a separate lateral exposure or through small stab incisions. The technique of reduction is presented.