Carlos J. Marques

Does the brake response time of the right leg change after left total knee arthroplasty? A prospective study

Patients undergoing total knee arthroplasty often ask when they can safely resume car driving. There is little evidence available on which physicians can rely when advising patients on this issue. In a prospective study we assessed the brake response time of 24 patients admitted to the clinic for left total knee arthroplasty preoperatively and then 10 days after surgery. On each measurement day the patients performed two tasks, a simple and a complex brake response time task in a car simulator. Ten days after left TKA the brake response time for the simple task had decreased by 3.6% (p=0.24), the reaction time by 3.1% (p=0.34) and the movement time by 6.6% (p=0.07). However, the performance improvement was not statistically significant. Task complexity increased brake response time at both time points. A 5.8% increase was significant (p=0.01) at 10 days after surgery. Based on our results, we suggest that patients who have undergone left total knee arthroplasty may resume car driving 10 days after surgery as long as they drive a car with automatic transmission.

The Effects of Task Complexity on Brake Response Time Before and After Primary Right Total Knee Arthroplasty

OBJECTIVE To study the effects of an increase in task complexity on brake response time (BRT) in patients undergoing total knee arthroplasty (TKA). DESIGN A prospective repeated-measures design was used. The measurements took place 1 day before and 10 and 30 days after surgery. SETTING Clinic. PARTICIPANTS The data of patients (N=21) who were admitted for primary total arthroplasty of the right knee were pooled for analysis. INTERVENTIONS On each measurement day patients performed 5 practice and 10 test trials for 2 tasks (1 simple, 1 complex) in a car simulator. Task complexity was increased by adding a second movement to the first task performed. MAIN OUTCOME MEASURES BRT, reaction time (RT), and movement time were assessed. RESULTS An increase in task complexity increased BRT, RT, and movement time at all measurement times. Right TKA increased BRT by increasing movement time. Thirty days after surgery BRT was no longer increased compared with preoperative values in both tasks. CONCLUSIONS Task complexity consistently increased BRT and its components. The effects of task complexity remained constant throughout the 3 measurements. After right TKA, we suggest patients should be advised to wait 30 days after surgery before resuming driving.

Do Well-Balanced Primary TKA Patients Achieve Better Outcomes Within the First Year After Surgery?

Some surgically modifiable factors are related to soft tissue balance. With computer-assisted surgery, it is possible to access these variables quantitatively. The aim of this analysis was to study the influence of gap balance on clinical outcomes within the first year after computer-navigated total knee arthroplasty (TKA). Based on navigation data, 3 independent variables reflecting gap balance were used to split the patients in 2 groups. The Knee Society Scores (Function [KSS-F] and Knee [KSS-K]) and the maximal knee flexion (MKF) measured preoperatively and at 3, 6 and 12 months were compared using analyses of variance (2×4 design) for repeated measures. Higher flexion-extension gap equality led to statistically higher KSS-F and KSS-K scores at 1 year (P=.02). Higher medial-lateral flexion gap equality led to superior mean MKF at all measurement points; however the differences were statistically only significant at 3 months (P=.01). The coefficients of variation of the variables used to select the patients were overall very low. With computer-assisted navigation, it is possible to access quantitatively the size of the medial and lateral flexion and extension gaps. Higher flexion-extension gap equality values led to statistically significant better KSS-F and KSS-K scores at 1 year. Higher medial-lateral flexion gap equality values led to better MKF values; however the differences were only statistically significant at 3 months. [Orthopedics. 2016; 39(3):S6-S12.].

BIOSIGNALS EVENTS DETECTION - A Morphological Signal-independent Approach

This study presents a signal-independent algorithm, which detects significant events in a biosignal, without previous knowledge or specific pre-processing steps. From a morphological analysis, the algorithm computes the instants when the most significant standard deviation discontinuities occur. An iterative optimization step is then applied. This assures that a minimal error is achieved when modeling the signal segments (between the detected instants) with a polynomial regression. The detection scale can be modified by an optional input scale factor. An objective algorithm performance evaluation procedure was designed, and applied on two types of synthetic signals, for which the events instants were previously known. An overall mean error of 20.32 ( 16.01) samples between the detected and the real events show the high accuracy of the proposed algorithm. The algorithm was also applied on accelerometry and electromyography raw signals collected in different experimental scenarios. The fact that this approach does not require any previous knowledge and the good level of accuracy represents a relevant contribution in events detection and biosignal analysis.

No improvement in reducing outliers in coronal axis alignment with patient-specific instrumentation

Purpose and hypothesisPatient-specific instrumentation (PSI) uses 3D preoperative imaging to produce individualized cutting blocks specific to patients’ anatomy and according to the preoperative plan with the aim to reduce the number of mechanical leg alignment (MLA) outliers, to improve implant positioning and to decrease surgery time. The primary purpose of this study was to investigate the efficacy of a specific PSI in comparison with standard instrumentation (SI) in reducing the number of MLA outliers. It was hypothesized that the number of MLA outliers would be significantly lower in the PSI group.MethodsA multicenter randomized controlled trial was implemented. There were 59 patients in the PSI group and 66 in the SI group. The absolute number of outliers outside the ± 3° target neutral MLA was compared between the groups with a Chi-square test. As secondary outcomes, the Knee Society Score (KSS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were compared between the groups preoperatively and at 90-day follow-up.ResultsThere were 15 (26.3%) MLA outliers in the PSI group and 8 (12.3%) in the SI group. The number of outliers was not independent from the group (X2(1) = 3.8, p = 0.04; Relative risk = 1.5). Preoperatively, there were no significant differences between the groups when comparing their KSS and KOOS sub-scores. At 90 days postoperatively, the patients in the SI group showed better KOOS-Quality of Life (KOSS-QOL) in comparison with the PSI group (p < 0.0001).ConclusionThe use of PSI did not significantly reduce the number of MLA outliers in comparison with SI. There were no differences when comparing the achieved mean MLA of both groups.Level of evidenceLevel I, prospective randomized controlled trial.

Intra- and Inter-rater Reliability of Navigated Ultrasound in the Assessment of Pelvic Tilt in Symptom-Free Young Adults: Navigated Ultrasound and Pelvic Tilt Assessment

Pelvic tilt is the angle between the anterior pelvic plane and the coronal plane. It affects cup positioning in total hip arthroplasty. The primary objective of this study was to test the intra‐ and inter‐rater reliability of a navigated smart device–based ultrasound system for pelvic tilt assessment. The secondary objective was to test the inter‐rater variability of the measurements on a hip phantom.

Pelvic Tilt Angle Differences Between Symptom-Free Young Subjects and Elderly Patients Scheduled for THA: The Rationale for Tilt-Adjusted Acetabular Cup Implantation

Background: The question whether Pelvic Tilt (PT) angles measured in the supine position are adequate for the alignment of the acetabular cup without an adjustment for anatomical differences between patients is of clinical importance. The aim of this work was to test for factors that can significantly affect PT angles. Methods: In the present retrospective cohort comparison, the PT angles of 12 Symptom-Free Young Subjects (SFYS) and 45 patients scheduled for Total Hip Arthroplasty (THA) were compared. The data was collected during two studies with the use of a novel smartphone-based navigated ultrasound measurement system. Multi-factorial analysis of variance was run to determine which factors significantly affect PT. Results: Body position (F= 126.65; P< 0.001) and group (SFYS vs. THA patients) (F= 17.52; P< 0.001) had significant main effects on PT. There was also a significant interaction between body position and group (F= 25.59; P< 0.001). The mean PT increased by 8.1° from an interiorly to a neutral tilted position (P< 0.001) and 21.4° from a neutral to a posteriorly tilted position (P< 0.001) with the transition from the supine into the upright position for the SFYS and THA patients, respectively. Conclusion: In both groups, PT changed significantly with a transition from the supine to the upright position. A position-dependent mean PT increase in the patient group showed that acetabular cup alignment based on PT in the supine position is not reliable without taking into consideration the inclination of the pelvis in standing position. This may lead to instability and dislocations.

Software and instrument improvements reduced significantly navigation acquisition time in computer assisted TKA: A cadaveric study

Abstract Purpose: Computer navigation in total knee arthroplasty (TKA) has proven to significantly reduce the number of outliers in prosthesis positioning and to improve mechanical leg alignment. Despite these advantages the acceptance of navigation technologies is still low among orthopaedic surgeons. The time required for navigation might be a reason for the low acceptance. Objective: The aim was to test whether software and instrument improvements made in an established navigation system could lead to a significant navigation acquisition time reduction. Materials and methods: An improved and the current version of the TKA navigation software were used to perform surgery trials on a human cadaveric specimen by two experienced orthopedic surgeons. Results: A significant effect of the “procedure” (navigation software version) on the navigation time (p < 0.001) was found, whereas the difference between surgeons was not significant (p = 0.2). There was no significant interaction between surgeon and navigation software version (p = 0.5). The improved version led to a significant navigation acquisition time reduction of 28%. Conclusions: Software and instrument improvements led to a statistically significant navigation acquisition time reduction. The achieved navigation acquisition time decrease was independent from surgeon. Specific instrument and software improvements in established navigation systems may significantly decrease the surgery time segments where navigation takes place. However, the total navigation acquisition time is low in comparison to the total surgery time.