Alignment Of Femoral Component Research Articles

Rotational alignment of femoral component with different methods in total knee arthroplasty: a randomized, controlled trial

BackgroundFemoral component rotation (FCR) is one of the most important factors in total knee arthroplasty. In this prospective study, we used three different techniques for FCR and analyzed their accuracy with postoperative axial computed tomography (CT) images. We also evaluated effect of FCR to clinical outcome.MethodsOne hundred sixty-five patients were randomly allocated into three groups. In the measured resection group, FCR was set by externally rotating the axis 3° off the posterior femoral condylar axis. In the tensor group, a gap-tensioning device set at 20 lbf was used. In the block group, spacer blocks of various thicknesses were used. The FCR angle (FCRa) was measured on postoperative axial CT as an angle between the clinical transepicondylar and posterior condylar axes of the femoral component. Outliers were defined as FCRas deviated more than 3° either internally or externally. Postoperative 2 year clinical scores and knee range of motion were checked.ResultsThe tensor group had significantly better positioning of the femoral component to the neutral position compared with the measured resection group and the block group (mean FCRa: internal rotation 1.79, 0.43 and 2.63°, respectively, p < 0.001). The outliers were also least frequent in the tensor group (35, 16 and 40%, respectively, p = 0.02). There were no significant differences in postoperative 2 year clinical results among groups.ConclusionsGap technique with a 20-lbf tensor device was the most accurate and precise method for obtaining adequate FCR. Measured resection with 3° external rotation and gap technique with blocks could lead to internal rotation of the femoral component. Postoperative 2 year clinical results were not significantly different among groups with different techniques for FCR.Trial registrationThe study was registered in the Clinical Research information Service (trial number: KCT0000129) in Korea. Registration date is 23rd of June, 2011.

Efficacy of Patient-Specific Instruments in Total Knee Arthroplasty: A Systematic Review and Meta-Analysis.

Patient-specific instrumentation (PSI) was introduced with the aim of making the procedure of total knee arthroplasty more accurate and efficient. The purpose of this study was to compare PSI and standard instrumentation in total knee arthroplasty with regard to radiographic and clinical outcomes as well as operative time and blood loss. A meta-analysis was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. PubMed and Embase were searched from 2011 through 2015. We included randomized controlled trials and cohort studies that reported the effect of PSI on the aforementioned outcomes. The primary end point was deviation from the mechanical axis by >3°. Random and fixed-effect models were used for analysis. A total of 44 studies, which included 2,866 knees that underwent surgery with PSI and 2,956 knees that underwent surgery with standard instrumentation, were evaluated. The risk of mechanical axis malalignment was significantly lower for PSI, with a pooled relative risk of 0.79 (p = 0.013). The risk of tibial sagittal-plane malalignment was higher for PSI than for standard instrumentation (relative risk = 1.32, p = 0.001), whereas the risk of femoral coronal-plane malalignment was significantly lower (relative risk = 0.74, p = 0.043). The risk of tibial coronal-plane malalignment was significantly higher for PSI only when employing fixed-effect meta-analysis (relative risk = 1.33, p = 0.042). Minor reductions in total operative time (-4.4 minutes, p = 0.002) and blood loss (-37.9 mL, p = 0.015) were noted for PSI. PSI improves the accuracy of femoral component alignment and global mechanical alignment, but at the cost of an increased risk of outliers for the tibial component alignment. The impact of the increased probability of tibial component malalignment on implant longevity remains to be determined. Meta-analyses indicated significant differences with regard to operative time and blood loss in favor of PSI. However, these differences were minimal and, by themselves, not a substantial justification for routine use of the technology. Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Presence of rotational errors in long leg radiographs after total knee arthroplasty and impact on measured lower limb and component alignment.

Rotation of the lower limb in weight bearing long leg radiographs has a great impact on measured component and lower limb alignment parameters. We asked which rotational errors of long leg radiographs are present in a high volume centre and which radiological and clinical consequences arise regarding measured coronal component and lower limb alignment after total knee arthroplasty. In 100 long leg radiographs coronal femoral and tibial component alignment and hip knee ankle angle (HKA) were measured. Present rotational errors in long leg radiographs were determined by fibular overlap and its impact on alignment parameters calculated. A mean internal rotation of 8.1° (9.3 SD) with a range between 36° of internal and 16° of external rotation was found in long leg radiographs. This resulted in mean differences between measurements before and after rotational correction regarding femoral and tibial component alignment and HKA of 0.6-0.8° (range 3.5° valgus and 1.6° varus error). Clinically, 11 out of 100 patients were wrongly assigned to either mal- or well-alignment (neutral mechanical alignment within ±3° varus or valgus). Surgeons should be aware of potential rotational errors in long leg radiographs after total knee arthroplasty resulting in wrong measurements. In case of rotational errors, radiographs should be repeated or rotational corrections calculated. For study purposes only radiographs after rotational correction should be accepted.

Cortical Strut Allograft Support of Modular Femoral Junctions During Revision Total Hip Arthroplasty

BackgroundThere is risk of junction failure when using modular femoral stems for revision total hip arthroplasty (THA), especially with loss of bone stock in the proximal femur. Using a cortical strut allograft may provide additional support of a modular femoral construct in revision THA. MethodsWe reviewed prospectively gathered clinical and radiographic data for 28 revision THAs performed from 2004 to 2014 using cementless modular femoral components with cortical strut allograft applied to supplement proximal femoral bone loss: 5 (18%) were fluted taper designs and 23 (82%) were porous cylindrical designs All the patients had a Paprosky grade IIIA or greater femoral defect. The mean follow-up was 5.4 ± 3.9 years. ResultsThe Harris Hip Scores improved from 26 ± 10 points preoperatively to 71 ± 10 points at final follow-up (P < .001). The Western Ontario McMaster Universities Osteoarthritis Index scores improved from 45 ± 12 points preoperatively to 76 ± 12 points at final follow-up (P < .001). Eighty-nine percent (25 hips) of all revision or conversion THAs were in place at final follow-up. Three (11%) patients underwent reoperations, 2 for infection and 1 for periprosthetic fracture. There was no statistical significant change in femoral component alignment (P = .161) at final follow-up. Mean subsidence was 1.8 ± 1.3 mm at final follow-up. Femoral diameter increased from initial postoperative imaging to final follow-up imaging by a mean of 9.1 ± 5.1 mm (P < .001) and cortical width increased by a mean of 4.5 ± 2.2 mm (P < .001). Twenty-seven hips (96%) achieved union between the cortical strut allograft and the host femur. ConclusionThe use of a modular femoral stem in a compromised femur with a supplementary cortical strut allgraft is safe and provides satisfactory clinical and radiological outcomes.

Does final component alignment correlate with alignment of the bone resection surfaces in cemented total knee arthroplasty?

To examine, with a navigation, whether the final component alignments correlate with alignment of the bone resection surfaces in cemented total knee arthroplasty (TKA), and to evaluate the factors affecting alignment deviation. A total of 222 patients (276 knees) who underwent navigation-assisted TKA between September 2012 and January 2014 due to osteoarthritis were retrospectively reviewed. The deviation between the alignment of bone resection surfaces and the final alignment of femoral and tibial components was measured. Factors associated with alignment deviation of greater than 2° (outliers) were evaluated. These included age, sex, body mass index, bone mineral density (T score), preoperative and postoperative mechanical femorotibial angle, preoperative and postoperative flexion contractures, and the difference between medial and lateral gaps in knee extension or flexion. Outliers consisted of 24 cases (8.6%) on the femoral coronal plane, 4 cases (1.4%) on the tibial coronal plane, and 48 cases (17.4%) on the tibial sagittal plane. In the coronal plane (femur and tibia), the outliers were associated with preoperative [p<0.001; odds ratio (OR) 0.774; 95% confidence interval (CI) 0.672-0.891] and postoperative (p<0.001; OR 0.240; 95% CI 0.123-0.468) flexion contractures; a difference of 3mm or more between the medial and lateral gaps in knee extension (p<0.041; OR 5.805; 95% CI 1.075-31.343); and a T score of less than -2.5(p<0.024; OR 5.899; 95% CI 1.258-27.664). In the sagittal plane of the tibia, the outliers were associated with preoperative (p<0.001; OR 0.886; 95% CI 0.829-0.946) and postoperative (p<0.031; OR 0.803; 95% CI 0.659-0.980) flexion contractures. There was a deviation between the alignments of the bone resection surfaces and the final alignments of components. With larger preoperative and postoperative flexion contractures in the coronal and sagittal planes, there were more outlier risks. The outliers in the coronal plane were associated with a difference of 3mm or more between the medial and lateral gaps in knee extension and poor bone quality. Awareness of such alignment deviation and related factors can help diminish the outliers after TKA. IV.

Preoperative Measurement of Tibial Resection in Total Knee Arthroplasty Improves Accuracy of Postoperative Limb Alignment Restoration.

Background:Accuracy of implant placement in total knee arthroplasty (TKA) is crucial. Traditional extramedullary alignment instruments are fairly effective for achieving the desired mean tibial component coronal alignment. We modified the traditional tibial plateau resection technique and evaluated its effect on alignment restoration.Methods:Two hundred and eighty-two primary TKAs in our hospital between January 2013 and December 2014 were enrolled in this retrospective study. Group A consisted of 128 primary TKAs performed by one senior surgeon. Preoperative measurement of the tibial resection was conducted on radiographs, and the measured thicknesses of the lateral and medial plateau resection were used to place the tibial alignment guide. Group B consisted of 154 primary TKAs performed by the other senior surgeon, using a traditional tibial plateau resection technique. In all patients, an extramedullary guide was used for tibial resection, and preoperative and postoperative full-leg standing radiographs were used to assess the hip-knee-ankle angle (HKA), femoral component alignment angle (FA), and tibial component alignment angle (TA). A deviation ≥3° was considered unsatisfactory. Data were analyzed by unpaired Student's t-test.Results:The mean postoperative HKA and TA angles were significantly different between Groups A and B (178.2 ± 3.2° vs. 177.0 ± 3.0°, t = 2.54, P = 0.01; 89.3 ± 1.8° vs. 88.3 ± 2.0°, t = 3.75, P = 0.00, respectively). The mean postoperative FA was 88.9 ± 2.5° in Group A and 88.9 ± 2.6° in Group B, and no significant difference was detected (t = 0.10, P = 0.92). There were 90 (70.3%) limbs with restoration of the mechanical axis to within 3° of neutral alignment and 38 (29.7%) outliers (>3° deviation) in Group A, whereas there were 89 (57.8%) limbs with restoration of the mechanical axis to within 3° of neutral alignment and 65 (42.2%) outliers (>3° deviation) in Group B. The severity of the preoperative alignment deformity was a strong predictor for postoperative alignment.Conclusions:Using conventional surgical instruments, preoperative measurement of resection thickness of the tibial plateau on radiographs could improve the accuracy of conventional surgical techniques.

Measuring the effect of femoral malrotation on knee joint biomechanics for total knee arthroplasty using computational simulation.

ObjectivesMalrotation of the femoral component can result in post-operative complications in total knee arthroplasty (TKA), including patellar maltracking. Therefore, we used computational simulation to investigate the influence of femoral malrotation on contact stresses on the polyethylene (PE) insert and on the patellar button as well as on the forces on the collateral ligaments.Materials and MethodsValidated finite element (FE) models, for internal and external malrotations from 0° to 10° with regard to the neutral position, were developed to evaluate the effect of malrotation on the femoral component in TKA. Femoral malrotation in TKA on the knee joint was simulated in walking stance-phase gait and squat loading conditions.ResultsContact stress on the medial side of the PE insert increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. There was an opposite trend in the lateral side of the PE insert case. Contact stress on the patellar button increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. In particular, contact stress on the patellar button increased by 98% with internal malrotation of 10° in the squat loading condition. The force on the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) increased with internal and external femoral malrotations, respectively.ConclusionsThese findings provide support for orthopaedic surgeons to determine a more accurate femoral component alignment in order to reduce post-operative PE problems.Cite this article: K-T. Kang, Y-G. Koh, J. Son, O-R. Kwon, C. Baek, S. H. Jung, K. K. Park. Measuring the effect of femoral malrotation on knee joint biomechanics for total knee arthroplasty using computational simulation. Bone Joint Res 2016;5:552–559. DOI: 10.1302/2046-3758.511.BJR-2016-0107.R1.

Reference axes for optimal femoral rotational alignment in varus osteoarthritic Indian knees - A CT based study.

Optimal rotational alignment of femoral component is important for longevity and success of total knee replacement. Whiteside line (WL), posterior condylar axis (PCA) and femoral transepicondylar axis are various intra-operative landmarks to guide femoral rotation. Each of these has its pros and cons. The aims of our study were to assess the relationship of posterior condylar axis and the antero-posterior axis of femur with the surgical epicondylar axis and evaluate whether degree of deformity or severity of osteoarthritis alters the rotational alignment of the femur when posterior condylar axis is taken as a reference. Are we justified in using a 3° external rotation with respect to posterior condylar axis in each knee? The study is a single-centre, CT-based, cross-sectional, radiological study in 56 bilateral osteoarthritic varus Indian knees. The following were deduced using a uniform standardised method: Whiteside-surgical transepicondylar angle and posterior condylar angle. The study population was subdivided based on age, sex, deformity and grade of osteoarthritis. The mean posterior condylar angle (N=112) was 3.25±1.379° (95% CI). The posterior condylar angle ranged from '0' degrees to '6' degrees with only 27.7% having an angle of 3°. The mean Whiteside-transepicondylar angle (N=112) is 89.72±3.537° (95% CI). PCA and the WL are comparable in establishing the rotational alignment of the femoral component with respect to the surgical transepicondylar axis. A fixed, 3° external rotation with respect to the PCA is an oversimplification and rotational alignment of the knees should be individualised.

Technical Considerations and Accuracy Improvement of Accelerometer-Based Portable Computer Navigation for Performing Distal Femoral Resection in Total Knee Arthroplasty

BackgroundAccelerometer-based computer navigation has been shown to be highly accurate for performing distal femoral and proximal tibial component alignment in total knee arthroplasty (TKA), although the procedure for the femoral component is less accurate than for the tibial component. MethodsFirst, 30 knees without hip osteoarthritis or proximal femoral surgeries were selected. Sequential hip adduction, abduction, and flexion were performed, and the femoral head was monitored fluoroscopically in the coronal plane before TKA. Significantly more movement was detected during hip adduction than during abduction and flexion. Then, postoperative femoral and tibial component alignment was retrospectively evaluated in 48 TKAs before fluoroscopic monitoring (early group) and in the next 61 TKAs with femoral registration using smaller adduction movements to avoid large femoral head movements (later group). Another 47 TKAs treated with the conventional intramedullary method for the distal femoral component and the extramedullary method for the proximal tibial component were also analyzed (IM and EM group) for historic control. ResultsSignificantly large variances in the femoral component implantation of the early group were detected in both the coronal and sagittal planes. The sagittal femoral implantation angle of the early group (4.6 ± 3.0°) was significantly larger than that of the later group (3.2 ± 1.8°) when 3.5° was the target for both groups. No significant difference was detected in the variances of either the coronal or sagittal tibial component implantation, although the coronal tibial implantation angle was significantly smaller (−1.3 ± 1.3°valgus) in the early group than in the other groups. ConclusionAccelerometer-based navigation sometimes has technical issues during registration associated with hip adduction. We showed that femoral registration without large adduction movements will enable more accurate femoral implantation. Surgeons should also keep in mind that the coronal tibial component is likely to be in valgus alignment (about 1°) even if a neutral angle (0°) is selected with this particular device.

Superior femoral component alignment can be achieved with Oxford microplasty instrumentation after minimally invasive unicompartmental knee arthroplasty.

Oxford microplasty (MP) instrumentation has been developed to facilitate the reproducible and consistent performance of minimally invasive unicompartmental knee arthroplasty (MI-UKA) operation. The aim of this study was to compare the clinical and radiographic results of two groups of patients implanted using either a conventional instrumentation technique or an MP technique. A prospective cohort study of 108 knees in 108 patients who underwent an MI-UKA procedure using either conventionally instrumented UKA (CI-UKA) (52 knees of 52 patients) or MP-assisted UKA (MP-UKA) (56 knees of 56 patients). The clinical assessment included the Oxford Knee Score (OKS), the Knee Society Score (KSS), a visual analogue scale (VAS) for pain, and range of motion (ROM). Complications were also recorded. No significant differences were observed between the two groups regarding OKS, KSS, VAS, and ROM. There were also no significant differences in terms of mechanical limb alignment and tibia implant alignment. However, the MP-UKA group showed significantly more accurate positioning of the femoral component than the CI-UKA group. Additionally, the MP-UKA group had more femoral prostheses implanted in the "satisfactory" range and fewer "outliers" than the CI-UKA group. No significant difference in complications was noted between the two groups. This study suggested that compared with CI-UKA, MP-UKA provides significant improvements in increasing the accuracy of sagittal and coronal implantation of the femoral component and in reducing the numbers of outliers for femoral prosthetic alignment. It is advocated that the MP system should be considered when MI-UKA is performed. Therapeutic study, Level IV.

Mathematical analysis of the influences of femoral and tibial bone cuts on the dynamic alignment in total knee arthroplasty

To investigate the influences of the distal femoral cut, the anterior and posterior femoral cuts, the proximal tibial cut on the dynamic alignment of the lower extremity in total knee arthroplasty. Based on the three-dimensional geometric model, imitating the flexion movement of the knee without axial rotation after total knee arthroplasty, the influence of each of the three bone cuts on the dynamic alignment was analyzed with the assumption of standard bone cuts of the other two and equality of the medial and lateral soft tissue balancing. The dynamic alignment was defined as the angle between the mechanical axis of the tibia and the sagittal plane of the body when the knee was in any angle of flexion. With two of the three major bone cuts standard, the track of the tibial movement was established when the other one bone cut deviated from the ideal section of angle A. Based on the principle of geometry, the mathematical formula were established to present the influences of three bone cuts on the dynamic alignment of the lower extremity. All of the three kinds of bone cuts in total knee arthroplasty influenced the dynamic alignment of the lower extremity not just in one static position, but during the whole range of motion. At the θ angle of knee flexion, the alignment of the lower extremity was arcsin(cosθsinA) when the varus/valgus femoral component alignment was A; the alignment of the lower extremity was arcsin(sinθsinA) when the rotational femoral component alignment was A; the alignment of the lower extremity was A when the varus/valgus tibial component alignment was A. The influences of the distal femoral cut, the anterior and posterior femoral cuts, the proximal tibial cut on the dynamic alignment of the lower extremity in total knee arthroplasty are dynamically changed during the flexion movement of the knee.

Does Use of a Variable Distal Femur Resection Angle Improve Radiographic Alignment in Primary Total Knee Arthroplasty?

BackgroundThe distal femur resection in total knee arthroplasty (TKA) is commonly made using a fixed angle relative to an intramedullary rod. This study’s purpose was to assess if a variable distal femur resection angle technique improves femoral component alignment in TKA. MethodsThis was a review of primary TKAs performed by 2 surgeons. One surgeon used a fixed resection angle of 5° for varus and 3° for valgus knees (“fixed” cohort). The second used hip-knee-ankle (HKA) radiographs to measure the angle between the femoral anatomic axis and a line perpendicular to the femoral mechanical axis, which was used as the resection angle for each patient (“variable” cohort).Femoral component and HKA alignment were measured from standing HKA radiographs by 2, independent, blinded observers. Two hundred ninety patients were needed for power to detect a 15% difference in femoral component “outliers” (target of 0° ± 2°; significance = P < .05). ResultsThree hundred twenty consecutive patients were included with no differences in age, body mass index, or preoperative deformity (P = .3-.8). A 5° resection angle was used in 46.3% of the variable and 80.0% of the fixed cohort patients.A total of 80.2% of femoral components in the variable and 63.1% in the fixed cohort were within 0° ± 2° (P = .002; 84.6% of variable and 56.3% of fixed for valgus knees, P < .001). The mean HKA alignment was improved in the variable cohort (−1.4° ± 3.3° vs −2.6° ± 3.3°, P = .001). ConclusionUse of a variable distal femur resection angle improves femoral component alignment after TKA.

Measuring long radiographs affects the positioning of femoral components in total knee arthroplasty: a randomized controlled trial.

The aim of this study was to investigate if preoperative measurements of the femoral valgus angle (FVA) affected the mechanical alignment, individual component positions and clinical outcome in total knee arthroplasty (TKA). 120 patients were randomized into two groups. In one group (control), a fixed FVA for the intramedullary femoral guide was set at 7°, whereas in the other group (measured) FVA was measured preoperatively on long hip-knee-ankle radiographs, and the angle for the distal femoral cut was set accordingly. Preoperatively and 1year after TKA, range of motion (ROM) and Knee Society Score (KSS) were assessed. Postoperatively, the coronal alignments of the components and the mechanical alignment were measured comparing the rate of outliers which deviated more than 3° from the neutral mechanical axis. 104 patients remained for the radiological analysis (52 in each group). There were no significant differences either in the mean preoperative or postoperative mechanical alignment, or femoral or tibial component alignment; also, there were no differences in the number of postoperative mechanical axis or tibial component alignment outliers. However, the number of femoral component alignment outliers was significantly higher in the control group. 97 patients were available for clinical outcome analysis. Preoperatively, the groups did not differ significantly with respect to KSS or ROM. The postoperative ROM and KSS functional subscale scores were similar between the groups. However, there was slightly but significantly better postoperative KSS objective subscale score in the measured group. Preoperative FVA measurement and following femoral distal cut adjustments did not affect overall leg alignment postoperatively, while positioning of femoral component was improved together with minor improvements in objective KSS subscale scores.

The Impact of Imaging Modality on the Measurement of Coronal Plane Alignment After Total Knee Arthroplasty

BackgroundThe optimal coronal alignment after total knee arthroplasty (TKA) has become an area of increased debate. Sources of variability among investigations include the radiographic technique used for both preoperative surgical planning and postoperative alignment assessments. This study’s purpose was to assess the impact of the imaging modality used on the measurement of coronal plane alignment after TKA. MethodsA consecutive series of patients undergoing TKA using the same cruciate-retaining prosthesis were included for analysis. Postoperatively, all patients received both a rotationally controlled, scout computed tomography scan and a hip–knee–ankle (HKA) image using the EOS Imaging system (EOS Inc., Paris, France). Two, independent observers measured the HKA angle, and femoral and tibial component alignment from each image. ResultsAfter classifying overall and component alignment as neutral, varus, or valgus, 40.6% (65 of 160) of knees had a discordant alignment classification for HKA, 28.1% (45 of 160) for femoral component alignment, and 26.9% (43 of 160) for tibial component alignment between their computed tomography and EOS images. Overall, 24.4% (39 of 160) of patients had a HKA difference of ≥3° between the 2 images, whereas 18.8% (30 of 160) and 20.0% (32 of 160) of patients had a femoral and tibial component alignment difference of ≥2°, respectively. ConclusionSignificant differences are present when comparing 2 measurement techniques of mechanical alignment after TKA. The impact of imaging modality on postoperative assessments must be accounted for and be consistent when comparing the results of different investigations.

Lateralization of Femoral Entry Point to Improve the Coronal Alignment During Total Knee Arthroplasty in Patients With Bowed Femur

BackgroundIntramedullary jigs are most often used for distal femoral bone cuts in total knee arthroplasty (TKA). However, the accuracy of bone cuts in the distal femur may be affected by the presence of diaphyseal deformities of the femur. MethodsSixty-three patients (88 knees) with lateral bowing of the femur underwent primary TKA using a lateralized femoral entry point for intramedullary femoral guide. The following measurements were obtained on the preoperative and postoperative scanograms–mechanical axis deviation, degree of femoral bowing, femoral entry point from the intercondylar sulcus, distance from the center of the knee to the mechanical axis, and coronal alignment of femoral and tibial components. ResultsIn 48.8% of cases, the femoral entry point was 3-5 mm lateral to the intercondylar notch, in 44.4% of cases, it was 6-10 mm lateral to the notch, and in 6.8% of cases, it was 10-15 mm lateral to the intercondylar notch. Postoperatively the tibiofemoral angle was 6-10 degrees of valgus in 96% of cases. The postoperative mechanical axis was within 3 mm from the center of the knee in 80 of the 88 knees (90.9%). For every 1° increase in femoral bowing, the entry point was lateralized by an average of 1.04 mm. ConclusionThe location of femoral entry point is important in TKA in patients with coronal plane deformity of the femur. In patients with lateral femoral bowing of 5° or more, a lateralized femoral entry point is useful in allowing straighter passage of long intramedullary femoral rod and this resulted in good mechanical axis alignment and femorotibial component alignment in over 90% of patients in our series.

Computer-assisted surgery does not improve the rotational alignment of the femoral component in total knee arthroplasty for severe genu varus deformity

Background: Accurate femoral rotational alignment is critical for successful total knee arthroplasty (TKA). Debates exist about whether computer-assisted surgery-TKA (CAS-TKA) improves the accuracy of femoral rotational alignment. We hypothesize that it is related to the severity of the preoperative genu varus deformity and that CAS-TKA is beneficial under certain circumstances. Methods: Patients who had osteoarthritis with genu varus deformity and underwent conventional TKA or CAS-TKA between January 2007 and July 2013 at our hospital were enrolled. Based on the degree of preoperative deviation from the mechanical axis (MA), the patients were divided into three subgroups at 5-degree intervals: (1) varus deformity of ＜ 10 degrees, (2) 10–14.9 degrees, and (3) ≥ 15 degrees. Computed tomography was used to determine whether CAS-TKA provided better femoral rotational alignment than did conventional TKA. Component and limb alignment were also radiographically compared. Results: One hundred seventy-three knees on 128 patients met the inclusion criteria. For patients in the ＜ 10 degrees and 10–14.9 degrees groups, the component alignments and postoperative mechanical axes were not significantly different between conventional and CSA-TKA. For patients in the ≥ 15 degrees group, however, the femoral flexion angle was significantly (p ＜ 0.001) better for CSA-TKA, but not for the femoral valgus, tibial valgus, tibial flexion, or femoral rotational angles. Conclusions: CAS-TKA does not improve the accuracy of rotational alignment of the femoral component in patients with genu varus deformity. Level of Evidence: Therapeutic Level III.

Radiological Outcomes and Operative Time following Total Knee Arthroplasty using Accelerometer-based, Portable Navigation versus Conventional Inter-Medullary Alignment Guides

Objectives:Accelerometer-based, portable navigation instrumentation is a new method of achieving desired resection alignments in total knee arthroplasty (TKA).Methods:After randomisation and the application of exclusion criteria, 79 knees were analysed. 42 patients which underwent TKA using conventional intra-medullary (IM) alignment guides were compared to 37 patients with the use of accelerometer-based, portable navigation device (KneeAlign; OrthoAlign Inc, Aliso Viejo, California). Radiographic results were obtained from post-operative computer-tomography following the CT Perth Protocol.Results:In the IM cohort, 81.0% of patients had a coronal alignment within 3° of a neutral mechanical axis (vs 83.8% with KneeAlign, p=0.74), 81.0% had a femoral coronal alignment within 2° of perpendicular to the femoral mechanical axis (vs 89.2% with KneeAlign, p=0.31), and 92.9% had a tibial coronal alignment within 2° of perpendicular to the tibial mechanical axis (vs 81.1% with KneeAlign, p=0.12). Regarding sagittal alignment, the IM cohort had 90.5% of patients with femoral component alignment within 2° of optimum (vs 91.9% with KneeAlign, p=0.83) and 92.9% had a tibial component alignment within 2° of the optimal tibial slope (vs 89.2% with KneeAlign, p=0.57). The mean tourniquet time (from incision to completion of coronal bone resections) in the IM cohort was 16.5± 8.9 minutes vs 22.2 ± 7.6 minutes in the KneeAlign cohort (p<0.003).Conclusion:Accelerometer-based, portable navigation has a statistically similar outcome in alignment following TKA as IM guides. It is noted that using the portable navigation device does prolong surgical time compared to conventional IM surgery and this may be due to the learning curve.

Changes in sagittal component alignment alters patellar kinematics in TKA: an in vitro study.

Patellar maltracking due to incorrect component alignment is considered as a main reason for anterior knee pain after total knee arthroplasty (TKA). In contrast to coronal and axial component placement, the influence of sagittal component alignment on patellar kinematics has not been investigated so far. In ten lower cadaveric limbs, TKAs were implanted using a commercial computer navigation system. In six knees, the femoral component was aligned in 5° and in four knees in 0° of flexion, respectively. Patellar kinematics were registered by means of a computer navigation system using an additional patella tracking array and correlated with femoral and tibial sagittal component alignment. Sagittal component alignment significantly altered patellar mediolateral shift (p<0.05). In contrast, patellar epicondylar distance, rotation and tilt were not significantly influenced. Sagittal component alignment in TKA has a major impact on patellar kinematics and should therefore be considered while addressing tibiofemoral kinematics intraoperatively.

Rotational alignment of the femoral component in total knee arthroplasty.

We describe here various surgical options to obtain a correct rotational alignment of femoral component in total knee arthroplasty (TKA). The correct rotational alignment is the key point to obtain a rectangular balanced flexion gap as well to have a good patellar tracking. For that reason, rotation alignment largely affects postoperative kinematic results particularly during flexion.

Comparison of Postoperative Alignment Using Fixed vs Individual Valgus Correction Angle in Primary Total Knee Arthroplasty With Lateral Bowing Femur

BackgroundLateral bowing of the femur, commonly observed among Asian populations, may cause malalignment after primary total knee arthroplasty (TKA). Therefore, in this study, a fixed valgus correction angle (VCA) technique for TKA was compared with individual VCA to determine which surgical technique leads to better limb and component alignment. MethodsPatients with primary TKAs with lateral bowing femurs (n = 133) were randomized to 2 groups: individual VCA (group A) and fixed VCA (group B). Full-length standing hip-knee-ankle radiographs were used to measure the VCA and limb alignment. The postoperative mechanical axis, femoral component, and tibial component alignment were measured and compared between the 2 groups. ResultsThe mean postoperative mechanical axis and femoral component alignment were 178.1° and 88.3°, respectively, in group A, compared with 175.9° and 86.4°, respectively, in group B (P < .05). There were 52 (77.6%) knees with ±3° mechanical axis deviation from the neutral axis in group A, compared with 19 (28.8%) in group B (P < .001). There were 56 (83.6%) knees with femoral component alignment deviation within ±3° in group A, compared with 26 (39.4%) in group B (P < .001). ConclusionThe individual VCA achieves a better radiographic limb and femoral component alignment than fixed VCA in our study patients. Preoperative hip-knee-ankle radiographs are imperative for distinguishing a bowing femur and performing accurate planning of the distal femoral resection.