Measured Resection Technique Research Articles

Kinematically aligned total knee arthroplasty reproduces more native rollback and laxity than mechanically aligned total knee arthroplasty: A matched pair cadaveric study

BackgroundA growing body of evidence supports that kinematically aligned (KA) total knee arthroplasty (TKA) provides superior clinical outcomes and satisfaction than mechanically aligned (MA) TKA. In theory, KA TKA would restore knee kinematics closer to the native condition than MA TKA, but the current biomechanical evidence is lacking. HypothesisKA TKA would restore knee biomechanics to the native condition better than MA TKA. MethodsSeven pairs of cadavers were tested. For each pair, one knee was randomly assigned to KA TKA and the other to MA TKA. During KA TKA, the sizes of femur and tibia resections were equivalent to implant thickness to align with the patient-specific joint line. MA TKA was performed using conventional measured resection techniques. All specimens were mounted on a customized knee-testing system and digitized. Knee motions measured during flexion included rollback, axial tibiofemoral rotation, and laxities, specifically varus-valgus laxity, anterior-posterior translation, and internal-external rotation. ResultsThe pattern of knee motion following KA TKA was similar to the native knee. However, following MA TKA, both medial and lateral rollback and tibiofemoral axial rotation were decreased relative to those of the native knee. Valgus laxity was restored only after KA TKA, whereas varus laxity was restored only after MA TKA. Anterior translation was increased regardless of the alignment strategy. In addition, rotational laxities were restored after KA TKA, but external rotation laxity increased after MA TKA. ConclusionKA TKA restores femoral rollback and laxity to the native condition better than MA TKA. KA TKA may enhance functional performance and provide a more normal knee sensation. Level of evidenceII, Controlled laboratory study.

The Effects of Resection Technique on Implant Migration in Single Radius Posterior-Stabilized Total Knee Replacement.

The purpose of the present study was to measure the effects of gap balancing and resection techniques on migration of a single total knee replacement implant design. A total of 23 patients (24 knees) were recruited on referral to either a surgeon performing gap balancing or a surgeon performing measured resection and followed prospectively. All patients received a fixed bearing, posterior stabilized total knee replacement implant of a single radius femoral component design with cement fixation, and all aspects of care outside of resection technique were identical. Patients underwent radiostereometric analysis (RSA) at 2 weeks (baseline), 6 weeks, 3 months, 6 months, 1 year, and 2 years. Migration of the tibial and femoral components was compared between groups. Tibial component migration was greater at 2 years in the gap balancing group (mean difference = 0.336 mm, p = 0.036), but there was no difference at 1 year. One measured resection and three gap balancing tibial components demonstrated continuous migration > 0.2 mm between years 1 and 2. There was no difference in femoral component migration. Small differences in tibial component migration were found between the gap balancing and measured resection techniques. However, comparing the migration to established predictive thresholds for long-term loosening risk, implants performed with both techniques were found to have equally low revision risk.

Association between limb alignment and patient-reported outcomes after total knee arthroplasty using an implant that reproduces anatomical geometry

BackgroundA kinematically aligned (KA) total knee arthroplasty (TKA) is expected to improve patient satisfaction, but its effect remains controversial. We investigated differences in patient-reported outcomes (PROs) between KA and non-KA TKAs using an implant that reproduces anatomical geometry.MethodsTKAs for varus deformity were performed in consecutive 129 patients (149 knees) via a measured resection technique with conventional instruments. The femorotibial angle (FTA), hip-knee-ankle angle (HKAA), and the angle between the joint line and the line perpendicular to the mechanical axis (AJLMA) were measured postoperatively (mean 13.6 months), and an AJLMA of ≥ 2° was defined as kinematic alignment. Patients were assigned to two or three alignment categories in each measurement method, and the Knee Society Scores (KSS) and Japanese Knee Injury and Osteoarthritis Outcome Scores (J-KOOS) was compared among the groups.ResultsFor patients assessed by FTA, an ADL-related J-KOOS subscale (J-KOOS-A) showed a significant difference between valgus and varus outliers (p < 0.05). When assessed by HKAA, neither the KSS nor J-KOOS subscales were significantly different among groups. When assessed by AJLMA, J-KOOS-A was significantly different between groups, and a group for AJLMA of ≥ 2° had higher scores than a group for AJLMA of < 2° (95% CI 0.323–7.763; p < 0.05).ConclusionsPatients with an AJLMA of ≥ 2° reported significantly higher patient’s satisfaction regarding ADL. This suggests the importance of restoration of the physiological joint line which can be achieved via KA TKAs.

Kinematically aligned total knee arthroplasty reproduces native patellofemoral biomechanics during deep knee flexion.

The implant positioning for kinematically aligned total knee arthroplasty (TKA) differs fundamentally from conventional mechanically aligned TKA. This difference may affect patellofemoral (PF) biomechanics after TKA. This cadaveric study tested the hypothesis that kinematically aligned TKA would restore PF biomechanics to the native condition better than mechanically aligned TKA. Seven pairs (14 knees) of fresh-frozen cadavers were tested. All specimens were mounted on a customized knee-testing system and digitized using a Microscribe 3DLX instrument (Revware Inc., Raleigh, NC, USA) to measure patellar kinematics in terms of patellar varus/valgus rotation, medial/lateral position, flexion/extension rotation and proximal/distal position at knee flexion angles of 0°, 30°, 60°, 90°, and 120°. The medial and lateral PF joint contact pressure distributions at 120° of knee flexion were measured using a K-scan system (Tekscan Inc., Boston, MA, USA). All patellae remained unresurfaced. For each pair, one knee was randomly assigned to kinematically aligned TKA and the other to mechanically aligned TKA performed using the conventional measured resection technique. During kinematically aligned TKA, the amount of femur and tibia resected was equivalent to implant thickness to maintain the patient-specific joint line. All patellar kinematics were measured and compared between the native condition and after surgery. The patellae of mechanically aligned TKA rotated more valgus and was positioned more laterally compared with those of kinematically aligned TKA at knee flexion angles ≥ 90°. Neither the patellar flexion/extension rotation nor the proximal/distal position differed between either prosthetic knee design and the native knee at all flexion angles. The contact pressure distribution between the medial and lateral PF joint after kinematically aligned TKA were similar to those of the native knee, while the lateral PF joint contact pressure after mechanically aligned TKA was higher than that of the native knee (p = 0.038). Kinematically aligned TKA better restores patellar kinematics and PF contact pressure distribution to the native condition than mechanically aligned TKA during deep knee flexion. These findings provide clues to understand why kinematically aligned TKA is associated with less anterior knee pain and better PF functional performance compared to mechanically aligned TKA. Patients undergoing kinematically aligned TKA may experience a more normal feeling during deep knee flexion activities.

Computed tomography confirmation of component rotation in nanosensor-balanced total knee arthroplasty.

Balanced gaps and proper rotation are felt to be essential for optimum range of motion, stability, and patellar tracking in total knee arthroplasty. The purpose of this study is to assess, using computed tomography, the rotation of femoral and tibial components in fresh-frozen human cadaver knees that have been balanced using nanosensor trials while also observing how this rotation affects measured compartment loads and requirement for ligament balancing adjustment. We found that minor degrees of rotational malalignment of the femur and tibia were common using standard instrumentation and measured resection technique. Quantitative balance and rotational congruence are aided by nanosensor guidance, and femoral malrotation of up to 8° does not appear to affect compartment loads significantly as long as rotational congruity is present.

Selection of Reference Axis for Distal Femoral Rotation in TKA: A Literature Review

Total knee arthroplasty (TKA) is widely accepted and standard surgical procedure for osteoarthritis. Most patients are able to recover their preoperative pain completely and achieve a good range of motions to perform daily tasks after TKA. However, there is a number of patients who remained unsatisfied with the result after TKA and often complain pain in performing daily task. Exploring reason behind post-operative pain and failure of TKA; researchers had found that in 31.2% of these cases; failure is due to aseptic loosening. Aseptic loosening is closely related to improper component placement. Orienting component in the axial direction is critical for proper outcome of TKA. Measured resection and gap balancing are two methods used for rotational alignment of component. Studies have shown that the measured resection technique has an advantage over gap balancing. However, the outcome of measured resection technique depends on the proper selection of reference axis. Transepicondyle axis, Whiteside line and Posterior condyle line are mostly used for setting the component rotation in TEA. All three rotational axis has its own advantages and pitfalls, therefore selection of reference should be based upon knee bone morphology and diseased condition. Malalignment of component placement in the axial plane may cause patella maltracking, anterior knee pain, aseptic loosening and also it could be one of the reasons behind TKA revision. The Success of rotational alignment depends upon proper preoperative planning and accurately selection of landmarks involved in creating axis. In this review paper, Pros and cons of reference axis are discussed individually and their correlations with each other are explored based on existing literature.

Posterior Reference Position Affects Intraoperative Kinematic and Soft Tissue Balance in Navigated Posterior-Stabilized Total Knee Arthroplasty

BackgroundThe importance of medial compartment stability is recognized in total knee arthroplasty (TKA). To manage the medial extension-flexion gap, the posterior reference position can be changed from conventional posterior center to posterior medial in measured resection techniques. This study aimed to compare the intraoperative soft tissue balance and rotational kinematics between the posterior medial and posterior center reference groups. MethodsWe enrolled 57 consecutive patients with varus osteoarthritis undergoing posterior-stabilized (PS) TKA using an image-free navigation system. The detailed surgical plan in both groups and intraoperative kinematics were recorded using navigation, and soft tissue balance measured with an offset-type tensor was statistically compared between groups. ResultsPatients were divided into the posterior center reference group (n = 32) and posterior medial reference group (n = 25). The posterior medial and posterior lateral condyles were significantly thicker in the posterior center reference group (P < .05). Although preoperative rotational kinematics were comparable between groups, the tibial rotational position was significantly more externally rotated in the posterior center reference group than in the posterior medial reference group at 45°, 60°, and 90° of flexion (P < .05). The varus angle and joint component gap were significantly smaller in the posterior medial reference group than in the posterior center reference group at 60° and 90° of flexion (P < .05). ConclusionThe posterior reference position affects intraoperative kinematics and soft tissue balance in navigated PS TKA. Posterior medial reference PS TKA decreases the excessive tibial external rotation during midflexion and increases the flexion stability compared with conventional posterior center reference PS TKA.

Intraoperative soft tissue balance using novel medial preserving gap technique in posterior-stabilized total knee arthroplasty: comparison to measured resection technique.

To investigate intraoperative soft tissue balance with femoral component trial in place using a novel medial preserving gap technique, focusing on medial compartment stability and allowing lateral physiological laxity, with compared with using a measured resection technique in posterior-stabilized (PS) total knee arthroplasty (TKA). Primary PS TKA, using either medial preserving gap technique (n = 127) or measured resection technique (n = 148), was performed in 275 subjects with varus knee osteoarthritis. Intraoperative soft tissue balance with femoral component in place was assessed using Offset Repo-Tensor with 40 lbs. of joint distraction force throughout the range of motion, and medial and lateral compartment gaps (mm) were calculated. Medial and lateral joint gap changes (mm) were calculated by subtracting the medial/lateral compartment gap at 0° from the medial/lateral compartment gap at each knee flexion angle, respectively. Medial and lateral joint gap changes in medial preserving gap technique were significantly smaller than measured resection technique respectively (mean difference between two procedures: medial; 0.9 ± 0.2mm, lateral; 1.0 ± 0.3mm). Medial and lateral joint gaps were significantly changed during knee flexion in measured resection technique, whereas medial and lateral joint gaps were not significantly changed during mid-to-deep knee flexion (30°-90° in medial, 30°-120° in lateral) in medial preserving gap technique. Medial preserving gap technique provided more consistent intraoperative soft tissue balance during knee flexion than the measured resection technique, suggesting that this novel technique can be utilized to obtain a more stable joint gap in PS TKA. III.

Three-dimensional limb lengthening after total knee arthroplasty in a simulation study

Objectives: Limb lengthening after total knee arthroplasty (TKA) has been reported in some cases, all of which were evaluated using two-dimensional images. To our knowledge, no case has been evaluated using three-dimensional (3D) images. We investigated 3D limb lengthening after TKA.Methods: We simulated 100 varus knees using 3D templating software. Virtual TKA was performed to maintain the original joint line by conducting a measured-resection technique. We examined the relationships of 3D distance between the femoral head center and ankle center before and after TKA, degree of hip–knee–ankle angle (HKA) improvement, and degree of flexion contracture angle improvement.Results: All cases showed limb lengthening (average, 9.4 ± 6.0 mm). The coefficients of correlation with limb lengthening and the degree of HKA improvement and the degree of flexion contracture angle improvement were good (0.730 and 0.751, respectively). The correlation between the degree of total improvement (the degree of HKA improvement + the degree of flexion contracture angle improvement) and limb lengthening was strong (r = 0.896).Conclusion: The expected limb lengthening when performing measured-resection TKA is expressed as 0.58 × (the degree of HKA improvement + the degree of flexion contracture angle improvement) mm and is a useful index.

Intraoperative Comparison of Measured Resection and Gap Balancing Using a Force Sensor: A Prospective, Randomized Controlled Trial

BackgroundFor establishing femoral component position, gap-balancing (GB) and measured resection (MR) techniques were compared using a force sensor. MethodsNinety-one patients were randomized to undergo primary total knee arthroplasty using either MR (n = 43) or GB (n = 48) technique using a single total knee arthroplasty design. GB was performed with an instrumented tensioner. Force sensor data were obtained before the final implantation. ResultsGB resulted in greater range of femoral component rotation vs MR (1.5° ± 2.9° vs 3.1° ± 0.5°, P < .05) and posterior condylar cut thickness medially (10.2 ± 2.0 mm vs 9.0 ± 1.3 mm) and laterally (8.5 ± 1.9 mm vs 6.4 ± 1.0 mm). Force sensor data showed a decreased intercompartmental force difference at full flexion in GB (.8 ± 2.3 vs 2.0 ± 3.3u, 1u ≈ 15 N, P < .05). ConclusionGB resulted in a greater range of femoral component rotation and thicker posterior condylar cuts resulting in an increased flexion space relative to MR. Intercompartmental force difference trended toward a more uniform distribution between full extension and full flexion in the GB vs MR group.

The comparison of femoral component rotation in the total knee arthroplasty

AbstractIntroduction Background:Optimal femoral component rotation in total knee arthroplasty (TKA) is crucial to establish a balanced knee reconstruction. Unbalanced knees can lead to instability, patellofemoral problems, persistent pain, stiffness, and generally poorer outcomes including early failure. There are several methods to achieve the femoral component rotation such as balanced gap technique, measured resection technique, and bone landmarks such as transepicondylar line (TEA) and Whiteside line. The purpose of this study was to compare the balan ced gap technique with the TEA technique.Materials and Methods:This randomised prospective study compares the femoral component rotation obtained with the use of balanced gap technique and the TEA, as well as compares the differences due to preoperative knee desaxations. The study includes 50 knees, 19 with neutral alignment, 22 with varus, and 9 with valgus desaxation. The femoral component rotation was measured postoperatively on photodocumentation taken after determining the TEA and balanced gap technique line peroperatively. These lines were compared to the posterior femoral condyles obtaining the degree of rotation. In case of transepicondylar line it is condylar twist angle (CTA) and in case of ligament balancer rotation axis it is ligament balancer angle (LBA).Results:The statistically significant differences in femoral component rotation using the techniques mentioned above as well as differences in individual knee desaxations were observed. The average LBA was 3.42 degrees and average CTA 3.58 in neutral knees group, but in the varus knees the average CTA value was 2.27 degrees and LBA value was 1.05 degrees. The average CTA value in patients with valgus desaxation is 4.78 degrees and LBA value is 5.22 degrees. According to Tukey Post Hoc test a statistically significant difference in LBA value is between neutral and varus knees with a significance level of p = 0.000022 and the most significant difference between varus and valgus knees with a significance level of p = 0.000011.Conclusion:The statistically significant differences in femoral component rotation using the techniques mentioned above as well as differences in individual knee desaxations were observed.

Columbus® computer navigated total knee arthroplasty: Gap balancing versus measured resection

BackgroundThe aim of this study was to compare the medium term functional outcome and patient satisfaction of gap balanced (GB) with measured resection (MR) total knee arthroplasty (TKA) using computer navigation. MethodsA cohort of 144 consecutive computer navigated TKA were retrospectively identified from an arthroplasty database. Functional assessment using the Oxford Knee Score (OKS) and patient satisfaction were obtained from 113 patients at a mean follow-up of 5.4 (range four to seven) years. There were 44 patients in the GB group and 69 patients in the MR group. ResultsThe mean OKS for the GB group was 36.9 (SD 9.2) and for the MR was 33.6 (SD 9.8), with a difference of 3.3 (95% CI 0.3 to 6.3) points, which was statistically significant (p=0.01). Linear regression analysis confirmed the independent effect of surgical technique when adjusting for confounding factors and surgeon, with the GB group achieving a greater post-operative OKS (R2=0.39, 3.0 points, 95% CI 1.2 to 4.8, p=0.001). There was a greater rate of patient satisfaction in the GB group (88.6%, n=39/44) compared to the MR group (81.1%, n=56/69), but this was not statistically significant (odds ratio 1.8, 95% CI 0.6 to 5.5, p=0.31). ConclusionComputer navigated Columbus® TKA using a GB technique results in a statistically significantly greater functional outcome but no significant difference in patient satisfaction in the medium term compared to patients undergoing a MR technique.

Stability of capsule closure and postoperative anterior knee pain after medial parapatellar approach in TKA

Anterior knee pain after total knee arthroplasty (TKA) remains a widely discussed postoperative complication. In contrast to sports traumatology, the role of the dissected medial patellofemoral ligament (MPFL) using a medial parapatellar approach in TKA has not been discussed so far. In the present study, it was hypothesized that the attempted repair of the MPFL in TKA by simple closure of the joint capsule may not be successful in some cases, causing anterior knee pain. Furthermore, it was hypothesized, that the success of repair might be influenced by femoral component rotation. Forty patients received their TKA in a ligament-balanced and forty patients in a conventional measured-resection technique. After implantation of the TKA using a medial parapatellar approach, two titan clips were attached on both sides of the capsule incision. 3days and 3 months after surgery, the dehiscence of the two clips was measured on skyline patella radiographs; additionally patellar tilt, shift, the Knee Society Score and the Feller Score were obtained. 48 patients showed an increase of capsule dehiscence. Patients with a capsule dehiscence of more than 4mm showed significantly less improvement in the Feller score 3months postoperatively than patients with a capsule dehiscence≤4mm. Regarding the radiological measurements and the clinical outcome, no significant difference between the ligament-balanced and the measured-resection group was found. The present results suggest that the successful repair of the MPFL after using a medial parapatellar approach in TKA could reduce the high rate of postoperative anterior knee pain. Furthermore, the appearance of capsule dehiscence and anterior knee pain does not seem to be dependent on the used operative technique.

Outcome &amp; Survival Analysis of Conventional Measured Resection, Neutral Alignment Attune TKA vs CAS Anatomic Tibia, Balanced Femur, Constitutional Alignment Attune TKA

Objectives:Arthroplasty knee surgeons have traditionally performed a measured resection technique with a neutral mechanical axis. We have recently developed a new total knee arthroplasty technique whereby the tibia is cut anatomically and the femoral component position is determined using a balanced approach utilizing a computer assisted ligament tension device with aim of restoring constitutional alignment. This study compares the Oxford scores and survival of these two techniques for Attune TKA’s.Method:The New Zealand Joint Registry has requested Oxford Knee Scores at six months on all Attune Total Knee Replacements performed. 1088 scores have been returned. 716 have been performed using a conventional measured resection technique aiming for a neutral mechanical axis. 362 have been performed using the CAS anatomic tibia, balanced femur (ATBF) technique aiming for constitutional alignment. Oxford scores are compared alone and with a multivariate analysis including age, sex, surgeon level, fixed vs mobile, public vs private, operative time and cruciate retaining vs cruciate substitutingResults:Mean Oxford Conventional TKA univariate Oxford Score is 38.1 Mean Oxford CAS ATBF TKA univariate Oxford Score is 40.7 p=<0.001 Mean Oxford Conventional TKA multivariate Oxford Score is 36.9 Mean Oxford CAS ATBF TKA multivariate Oxford Score is 39.1 p=<0.001 The CAS ATBF had 10% less poor and fair scores and 15% more excellent scores Non infection conventional TKA has 0.71 failures per 100 component years Non infection CAS ATBF TKA has 0.25 failures per 100 component years.Conclusion:The CAS assisted anatomic tibia balanced femur TKA has a significantly higher Oxford score with a three times lower non infection failure rate at three years

Meta-analysis of gap balancing versus measured resection techniques in total knee arthroplasty.

There are two techniques widely used to determine the rotational alignment of the components in total knee arthroplasty (TKA); gap balancing (GB) and measured resection (MR). Which technique is the best remains controversial. We aimed to investigate this in a systematic review and meta-analysis. In accordance with the methods of Cochrane, databases were searched for all randomised controlled trials in the literature between January 1986 and June 2015 comparing radiographic and clinical outcomes between the use of these two tecniques. Meta-analysis involved the use of the Revman5.3 software provided by Cochrane collaboration. A total of 1464 papers were initially identified, and after the application of rigourous inclusion and exclusion critera, eight were included in the study. In total they inolved 980 TKAs. The meta-analysis showed that GB techniques resulted in statistically significant improvements in the restoration of mechanical and rotational alignment and mean Knee Society Scores and Knee Society Function scores two years post-operatively, but resulted in greater elevation of the position of the joint line. There is no significant difference in the other radiographic data. This study suggests that GB may provide better radiographic and clinical outcomes than MR when used to determine mechanical rotation in TKAs. Cite this article: Bone Joint J 2017;99-B:151-8.

Contact Kinematic Differences Between Gap Balanced vs Measured Resection Techniques for Single Radius Posterior-Stabilized Total Knee Arthroplasty

BackgroundMeasured resection (MR) and gap balancing (GB) are common surgical techniques for total knee arthroplasty (TKA). Controversy has arisen as each conceptually differs in how the knee is balanced through bone and soft tissue management. The objective of the present study was to compare both the frequency of condylar liftoff and the location of femorotibial contact from extension through midflexion between patients undergoing GB or MR TKA. MethodsA total of 24 knees (23 patients) were randomly assigned at referral to either a surgeon performing MR or GB TKA with the same single radius, posterior-stabilized implant (12 per cohort). At 1-year postoperation, patients underwent biplanar radiographic imaging at 0°, 20°, 40°, and 60° of flexion. Condylar liftoff, contact location, and magnitude of excursion on each condyle were measured. Preoperative and postoperative clinical outcome scores were also collected. ResultsThere was no difference (P = .41) in the frequency of liftoff between cohorts. The MR cohort had more posterior contact on the medial condyle (P < .01) and more anterior contact on the lateral condyle (P < .01) throughout flexion. Motion patterns were similar between cohorts, with similar medial (P = .48) and lateral (P = .44) excursion, which was equal in magnitude between condyles for both MR (P = .48) and GB (P = .73). There was no difference in clinical outcome scores between groups. ConclusionFor this particular implant system, GB and MR appear to produce similar kinematic and patient-reported outcome results.

Bi-cruciate substituting total knee arthroplasty improved medio-lateral instability in mid-flexion range

PurposeAppropriate medio-lateral (ML) stability is an important factor of good clinical outcome following total knee arthroplasty (TKA). We hypothesized that a newly introduced Bi-Cruciate Stabilized substituting (BCS) prosthesis reduces the medio-lateral instability in mid-flexion range. The purpose of this study was to measure the ML stability (varus ligament balance) using a new tensor device after implantation of BCS TKA and to analysis the association between varus ligament balance and clinical results after TKA. Materials and methodsWe evaluated 33 patients who underwent 39 Journey. 2. BCS TKA using the measured resection technique. We measured the gaps after implantation from extension to full flexion with reduced patella by constant distraction force with 120N. The varus ligament balance gap was defined as the gap calculated by subtracting from Lateral to medial component gap. The clinical results at 2years after operation was compared with intraoperative varus ligament balance. ResultsVarus ligament balance showed its maximum gap at full knee extension and 120° flexion. Varus ligament balance at 30°, 60° and 90° of flexion were significant differences in the varus ligament balance at full extension. (* p<0.05). The varus ligament balance gap was negatively corrected with postoperative 2011 Knee society score (patient’s satisfaction) (r=0.661, p=0.001). ConclusionsThe most important findings of the present study are that BCS TKA can reduces the ML instability in mid-flexion range, and improve simultaneously the patient’s satisfaction. Level of evidenceTherapeutic study, Level III.

Navigation assisted total knee arthroplasty - Evaluation of correction of clinico - Radiololgical parameters in substantial varus deformity

Background: In the present scenario arthritis of knee joint is inevitable. Total- knee replacement is the final solution in severely deformed joints for pain free mobility. Longevity of the replaced joint is mainly dependent on good mechanical alignment. The navigation system was introduced with a claim to achieve near normal parameters of weight bearing axis thereby increasing the life of implanted knee. Material and Method: This was a prospective study from January 2012 to August 2015 done in Department of Orthopaedics at our institute. A cohort of 20 patients were taken with varus deformity more than 15 degree and operated with the help of navigation system. The result were compared with a cohort of 20 patients suffering from more than 15 degree varus deformity and operated without navigation. Informed consent was taken. Clearance from ethical committee of the institute was taken. Patients were evaluated pre operatively and post operatively at 1, 3, 6 and12 months post operatively with the help of knee society knee score and function score and radiographically. Results: Using computer assisted navigation and measured resection technique of ligament balancing in total knee replacement, mean tibio-femoral angle of 16.40 degrees varus preoperatively (range, 15degrees -24 degrees) was corrected to 2.4 degrees varus (range 5 degree valgus- 4 degree varus) postoperatively. Mean Knee Society score improved from 23.4 (range 0-44) to 86 (range 72 -98), and function score from 21 (range, 0-46) to 98.50 (range 55-100) at 12 months (range 12 month -34 months).No patient reported significant instability. Correction of severe varus deformity by the technique reported can successfully restore alignment, pain free motion, and stability. Conclusion: Substantial Varus knee deformity is very well corrected when total knee arthroplasty is done with the help of navigation system. Here, in our study, either no varus or residual varus deformity was 1-2 degree. Navigation system assisted surgery produces good functional outcome and near normal radiological parameters.

Comparison of soft tissue balancing, femoral component rotation, and joint line change between the gap balancing and measured resection techniques in primary total knee arthroplasty: A meta-analysis.

This meta-analysis was designed to compare the accuracy of soft tissue balancing and femoral component rotation as well as change in joint line positions, between the measured resection and gap balancing techniques in primary total knee arthroplasty. Studies were included in the meta-analysis if they compared soft tissue balancing and/or radiologic outcomes in patients who underwent total knee arthroplasty with the gap balancing and measured resection techniques. Comparisons included differences in flexion/extension, medial/lateral flexion, and medial/lateral extension gaps (LEGs), femoral component rotation, and change in joint line positions. Finally, 8 studies identified via electronic (MEDLINE, EMBASE, and the Cochrane Library) and manual searches were included. All 8 studies showed a low risk of selection bias and provided detailed demographic data. There was some inherent heterogeneity due to uncontrolled bias, because all included studies were observational comparison studies. The pooled mean difference in gap differences between the gap balancing and measured resection techniques did not differ significantly (-0.09 mm, 95% confidence interval [CI]: -0.40 to +0.21 mm; P = 0.55), except that the medial/LEG difference was 0.58 mm greater for measured resection than gap balancing (95% CI: -1.01 to -0.15 mm; P = 0.008). Conversely, the pooled mean difference in femoral component external rotation (0.77°, 95% CI: 0.18° to 1.35°; P = 0.01) and joint line change (1.17 mm, 95% CI: 0.82 to 1.52 mm; P < 0.001) were significantly greater for the gap balancing than the measured resection technique. The gap balancing and measured resection techniques showed similar soft tissue balancing, except for medial/LEG difference. However, the femoral component was more externally rotated and the joint line was more elevated with gap balancing than measured resection. These differences were minimal (around 1 mm or 1°) and therefore may have little effect on the biomechanics of the knee joint. This suggests that the gap balancing and measured resection techniques are not mutually exclusive.

Functional ligament-guided femoral rotation with patient-specific instruments: description of a new surgical technique

Background: There are two basic implantation philosophies in total knee arthroplasty that essentially determine the rotational alignment of the femur. One method, the measured resection technique, uses bony landmarks to determine alignment, while the other, the gap-balancing technique, uses soft-tissue tension as the reference. The use of patient-specific instrumentation (PSI) has so far only been employed in cases where alignment is based on bony landmarks; alignment of the femoral rotation applying the gap-balancing technique is not currently possible. Methods: This paper describes the use of PSI with alignment using a balancer device in 25 patients, corresponding to the gap-balancing technique. The average age of the study population was 67.6±6.7 yr. The Knee Society Score (KSS) and flexion of the knee joint were recorded preoperatively and then at 3 and 12 mo postoperatively. Postoperatively, function was determined based on the Forgotten Joint Score (FJS), and any complications were documented. Deviation to the neutral mechanical leg axis also was determined based on long-standing radiographs of the lower extremity. Results: The KSS and flexion improved after 3 and 12 mo compared with preoperative results. The FJS was 34.4±4.2 points after 3 mo and 57.8±8.4 points after 12 mo. There were no complications. The deviation of the neutral mechanical axis averaged 1.5 degrees±1.8 degrees. Conclusions: The data show that the alignment of the PSI also can be achieved functionally, which will extend the range of application of PSI, especially in complex anatomical situations and after previous surgery.