Corey Scholes

Unsatisfactory Accuracy as Determined by Computer Navigation of VISIONAIRE Patient-Specific Instrumentation for Total Knee Arthroplasty

This investigation evaluated the Smith and Nephew VISIONAIRE patient-specific cutting block (PSCB) system for total knee arthroplasty. A consecutive series of 60 patients was recruited. Intraoperative computer navigation was used to evaluate the accuracy of the cutting blocks in the coronal and sagittal planes for the tibia, as well as rotational plane for the femur. The PSCB would have placed 79.3% of the sample within ±3° of the preoperative plan in the coronal plane, while the rotational and sagittal alignment results within ±3° were 77.2% and 54.5% respectively. The VISIONAIRE PSCB system achieved unacceptable accuracy when assessed by computer navigation. There might be many sources of error, but caution is recommended before using this system routinely without objective verification of alignment.

Articular Cartilage Changes in Patients With Osteoarthritis After Osteotomy

Background: High tibial osteotomy (HTO) is a method used to treat medial compartmental osteoarthritis in the knee. The realignment of the knee changes the loading patterns within the joint and may allow for regeneration of articular cartilage. Magnetic resonance imaging methods can be used to assess the quality of the regenerated cartilage. Hypothesis: Altering mechanical alignment through HTO will have predictable effects on articular cartilage, allowing cartilage preservation and possible regeneration. Quality of regenerated cartilage will be inferior to normal articular cartilage. Study Design: Case series; Level of evidence, 4. Methods: Ten patients undergoing medial opening wedge HTO were evaluated using dGEMRIC methods (ie, delayed gadolinium-enhanced magnetic resonance imaging of cartilage) preoperatively and at 6 months, 1 year, and 2 years after HTO. Magnetic resonance images were evaluated by hand segmentation, and T1Gd relaxation times reflective of glycosaminoglycan content were determined for these regions of interest using magnetic resonance imaging analysis software. Results: The lateral compartment displayed higher T1Gd values than the medial compartment at baseline. Initially, a decrease in T1Gd values on the medial side were observed for all patients at 6 months and remained reduced for all but 2 participants at 1 year and 2 years after HTO. However, on the medial side after 6 months, the rate of change for T1Gd values shifted from being negative (−9.6 milliseconds per month) to being positive (1.7 milliseconds per month). A positive change in the T1Gd of the medial tibial plateau was responsible for the positive overall change in the medial compartment. There was no significant difference in the rate of change on the lateral side (P = .141), with the average over the 2-year period being a decrease of 2.28 milliseconds per month. Conclusion: Medial opening wedge HTO provides subjective improvements in pain and quality of life, but the potential benefit of allowing articular cartilage preservation and possible regeneration is not well established. Results showed that after a nonweightbearing period, the rate of change in the medial compartment changes from negative to positive, indicating the potential for articular cartilage recovery secondary to an improved mechanical environment.

Incidence and severity of complications due to femoral nerve blocks performed for knee surgery

BACKGROUND While single shot femoral nerve blocks and indwelling femoral nerve catheters provide significant peri-operative analgesia, there are small but serious risks of neurovascular complications. We aimed to determine the incidence and characterise the nature of neural complications arising from femoral nerve blocks performed for knee surgery. METHODS One thousand eight hundred and two patients receiving a femoral nerve block for knee surgery during the study period were screened. Patients with possible neurological symptoms were evaluated with a detailed physical examination and self-report questionnaires. Also measures of depression, anxiety and tension/stress were collected. RESULTS In the patients screened, an incidence of 1.94% was found. Of the 24 patients available for testing, 4 had bilateral symptoms following bilateral nerve blocks. All had sensory abnormalities in the distribution of the femoral nerve. The incidence was significantly higher in females (females=2.5%, males=0.83% p=0.01) and in patients receiving a single shot block (single shot=2.66%, femoral catheter=0.93, p=0.01). CONCLUSIONS The incidence of neurological complication after FNB was higher in this series than typically reported and the symptoms significantly influenced the quality of life in the affected cases. The decision to include a femoral nerve block in the peri-operative analgesic regimen should be made on an individual basis considering the risks and benefits.

Is Femoral Component Rotation in a TKA Reliably Guided by the Functional Flexion Axis

BackgroundThe position of the femoral component in a TKA in the axial plane influences patellar tracking and flexion gap symmetry. Errors in femoral component rotation have been implicated in the need for early revision surgery. Methods of guiding femoral component rotation at the time of implantation typically are derived from the mean position of the flexion-extension axis across experimental subjects. The functional flexion axis (FFA) of the knee is kinematically derived and therefore a patient-specific reference axis that can be determined intraoperatively by a computer navigation system as an alternative method of guiding femoral component rotation. However, it is unclear whether the FFA is reliable and how it compares with traditional methods.Question/purposesWe asked if the FFA could be measured reproducibly at different stages of the operative procedure; (2) where it lies in relation to a CT-derived gold standard; and (3) how it compares with more traditional methods of judging femoral component rotation.MethodsThirty-seven patients undergoing elective TKAs were recruited to the study. Preoperative CT scans were obtained and the transepicondylar axis (TEA) was identified. The TKA then was performed using computer navigation. The FFA was derived before incision and again after the surgical approach and osseous registration. The navigation system was used to register the surgical TEA. The FFA and surgical TEA then were compared with the CT-derived TEA.ResultsThe mean preincision FFA was similar to the intraoperative FFA and therefore deemed reproducible. We observed no differences in variability between surgical TEA and preincision FFA. The FFA was different from the CT-TEA and judged similar in accuracy to the surgical TEA.ConclusionThe reliability and accuracy of the FFA were similar to those of other intraoperative methods. Further evaluation is required to ascertain whether the FFA improves on currently available methods for determining the ideal rotation of the femoral component during TKA.

Is Femoral Nerve Block Necessary During Total Knee Arthroplasty?: A Randomized Controlled Trial

There remains a lack of randomized controlled trials comparing methods of perioperative analgesia for total knee arthroplasty. To address this deficiency, a blinded, randomized controlled trial was conducted to compare the use of femoral nerve block (group F) and local anesthetic (group L). A sample of 55 patients who met the inclusion criteria were randomized to either group. No significant differences in the most severe pain score or 36-Item Short Form Health Survey, The Western Ontario and McMaster Universities Arthritis Index (WOMAC), or Oxford scores were observed between groups. However, the Knee Society score was significantly higher in group F. In addition, group F used significantly fewer micrograms of intravenous fentanyl in the first 24 hours. Balancing the risks of femoral nerve block with those of increased systemic narcotic delivery should be performed on a case-by-case basis.

Tibial Fixation in Anterior Cruciate Ligament Reconstruction A Prospective Randomized Study Comparing Metal Interference Screw and Staples With a Centrally Placed Polyethylene Screw and Sheath

Background: The use of hamstring tendons for anterior cruciate ligament reconstruction has increased in popularity over recent years. However, concerns with the stability of graft fixation on the tibial side remain. Centrally placed interference screw/sheath implants have demonstrated promising results in biomechanical studies. Hypothesis: Centrally placed, polyethylene screw and sheath implants will provide clinically equivalent fixation to the standard metal interference screw and supplemental staple fixation. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: A total of 113 consecutive patients undergoing isolated, unilateral, primary anterior cruciate ligament reconstruction with hamstring autografts were randomized to tibial fixation with metal interference screw and staples (RCI) or with a centrally placed polyethylene screw and sheath implant (INTRAFIX). Prospective assessment of subjective outcomes was performed using Lysholm, Mohtadi, and International Knee Documentation Committee (IKDC) scores. Results: At minimum 2-year follow-up, there were no significant differences between the 2 groups in terms of instrumented stability testing (KT-1000 arthrometer) or subjective assessment of knee outcomes (IKDC, Lysholm, Mohtadi). Both fixation methods demonstrated a significant, but not different, increase in outcomes scores from preoperative to postoperative evaluation. There were 7 failures (5 INTRAFIX, 2 RCI) caused by reinjury, but no statistically significant differences were observed between the 2 fixation methods. Conclusion: The centrally placed polyethylene screw and sheath provided equivalent clinical outcomes at minimum 2-year follow-up to standard tibial fixation with metal interference screw and staples.

Intraoperative computer navigation parameters are poor predictors of function 1 year after total knee arthroplasty.

Intraoperative navigation data were collected prospectively for 134 knees undergoing cemented, posterior-stabilized total knee arthroplasty. Partial least squares regression analysis was used to test the association between patient demographics and intraoperative data collected with a computer-assisted navigation system (coronal alignment, ligament balance, range of motion, external tibiofemoral rotation) with 1-year outcomes (36-item Short-Form Health Survey, Oxford Knee Score, range of motion). Age at surgery displayed the largest coefficients of any other predictor. In contrast, navigation coefficients were variable in the strength and direction of their association with the outcome variables. Static knee alignment data obtained intraoperatively have limited capacity to explain the variance in functional outcome at 1 year. Although alignment and component position can be precisely measured intraoperatively, intrinsic patient factors remain dominant in determining the outcome.

Unsatisfactory Accuracy With VISIONAIRE Patient-Specific Cutting Jigs for Total Knee Arthroplasty

This investigation evaluated the Smith and Nephew VISIONAIRE patient-specific cutting block (PSCB) system for total knee arthroplasty. A consecutive series of 60 patients were recruited. Intraoperative computer navigation was used to evaluate the accuracy of the cutting blocks in the coronal and sagittal planes for the tibia, as well as rotational plane for the femur. The PSCB would have placed 79.3% of the sample within +3° of neutral in the coronal plane, while the rotational and sagittal alignment results within +3° were 77.2% and 54.5% respectively. The VISIONAIRE PSCB system achieved unacceptable accuracy in the coronal plane and even less in the sagittal and rotational planes compared to computer navigation. Caution is recommended before PSCB are used routinely without objective verification of alignment.

In Vivo Assessment of Weight-Bearing Knee Flexion Reveals Compartment-Specific Alterations in Meniscal Slope

PURPOSE The purpose of this study was to determine the effects of flexion angle on meniscal slope during partial weight-bearing knee flexion. METHODS Forty-eight sagittal sequences were performed on 12 patients (6 male patients, 6 female patients; 25.7 ± 10.5 years) during partial weight bearing in an open magnetic resonance imaging (MRI) scanner at full extension, 60°, 90°, and maximum knee flexion. A previously published method was used to measure the meniscal slope for each compartment using manual digitalization. A general linear model was used to test for effects of compartment and flexion angle on meniscal slope. RESULTS The mean maximum flexion angle achieved was 125° ± 10.5°. A significant main effect of compartment (P < .01) and flexion angle (P < .01) on meniscal slope was observed. A significant interaction between compartment and angle was also detected (P < .01). Specifically, the lateral meniscal slope was significantly more horizontal than the medial meniscus slope at full extension (P = .017) but significantly more posterior at all other angles. In addition, the lateral meniscus displayed a greater change in posterior slope across the range of motion compared with the medial meniscus. Significant correlations were found in medial meniscal slope at full extension and at maximum knee flexion (P = .031). CONCLUSIONS The results showed that meniscal slope in healthy knees increased significantly with knee flexion for both menisci, with significantly greater changes in the lateral meniscus. Furthermore, a lack of correlation was observed between the meniscal slope in extension and the meniscal slope at increasing flexion angles, questioning the efficacy of measuring the meniscal slope only in extension as commonly described. Overall, this study has provided valuable insight into how meniscal slope changes with knee motion.

Multiobjective optimization of cartilage stress for non-invasive, patient-specific recommendations of high tibial osteotomy correction angle – a novel method to investigate alignment correction

Medial opening wedge high tibial osteotomy (MOWHTO) is a surgical procedure to treat knee osteoarthritis associated with varus deformity. However, the ideal final alignment of the Hip-Knee-Ankle (HKA) angle in the frontal plane, that maximizes procedural success and post-operative knee function, remains controversial. Therefore, the purpose of this study was to introduce a subject-specific modeling procedure in determining the biomechanical effects of MOWHTO alignment on tibiofemoral cartilage stress distribution. A 3D finite element knee model derived from magnetic resonance imaging of a healthy participant was manipulated in-silico to simulate a range of final HKA angles (i.e. 0.2°, 2.7°, 3.9° and 6.6° valgus). Loading and boundary conditions were assigned based on subject-specific kinematic and kinetic data from gait analysis. Multiobjective optimization was used to identify the final alignment that balanced compressive and shear forces between medial and lateral knee compartments. Peak stresses decreased in the medial and increased in the lateral compartment as the HKA was shifted into valgus, with balanced loading occurring at angles of 4.3° and 2.9° valgus for the femoral and tibial cartilage respectively. The concept introduced here provides a platform for non-invasive, patient-specific preoperative planning of the osteotomy for medial compartment knee osteoarthritis.