Influence of the posterior tibial slope on the flexion gap in total knee arthroplasty

BackgroundAdjusting the joint gap length to be equal in both extension and flexion is an important issue in total knee arthroplasty (TKA). It is generally acknowledged that posterior tibial slope affects the flexion gap; however, the extent to which changes in the tibial slope angle directly affect the flexion gap remains unclear. This study aimed to clarify the influence of tibial slope changes on the flexion gap in cruciate-retaining (CR) or posterior-stabilizing (PS) TKA.MethodsThe flexion gap was measured using a tensor device with the femoral trial component in 20 cases each of CR- and PS-TKA. A wedge plate with a 5° inclination was placed on the tibial cut surface by switching its front–back direction to increase or decrease the tibial slope by 5°. The flexion gap after changing the tibial slope was compared to that of the neutral slope measured with a flat plate that had the same thickness as that of the wedge plate center.ResultsWhen the tibial slope decreased or increased by 5°, the flexion gap decreased or increased by 1.9 ± 0.6 mm or 1.8 ± 0.4 mm, respectively, with CR-TKA and 1.2 ± 0.4 mm or 1.1 ± 0.3 mm, respectively, with PS-TKA.ConclusionsThe influence of changing the tibial slope by 5° on the flexion gap was approximately 2 mm with CR-TKA and 1 mm with PS-TKA.Clinical relevanceThis information is useful when considering the effect of manipulating the tibial slope on the flexion gap when performing CR- or PS-TKA.     

In vivo kinematic analysis of posterior-stabilized total knee arthroplasty for the valgus knee operated by the gap-balancing technique

BackgroundMost in vivo kinematic studies of total knee arthroplasty (TKA) report on the varus knee. The objective of the present study was to evaluate in vivo kinematics of a posterior-stabilized fixed-bearing TKA operated on a valgus knee during knee bending in weight-bearing (WB) and non-weight-bearing (NWB).MethodsA total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis and that were operated on using the gap balancing technique were evaluated. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimensional to 3-dimensional registration technique.ResultsThe average flexion angle was 111.3° ± 7.5° in WB and 114.9° ± 8.4° in NWB. The femoral component demonstrated a mean external rotation of 5.9° ± 5.8° in WB and 7.4° ± 5.2° in NWB. In WB and NWB, the femoral component showed a medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion. The medial condyle moved similarly in the WB condition and in the NWB condition. The lateral condyle moved posteriorly at a slightly earlier angle during the WB condition than during the NWB condition.ConclusionsWe conclude that similar kinematics after TKA can be obtained with the gap balancing technique for the preoperative valgus deformity when compared to the kinematics of a normal knee, even though the magnitude of external rotation was small. Level of evidence: IV.     

Recutting the distal femur to increase maximal knee extension during TKA causes coronal plane laxity in mid-flexion

BackgroundThe aim of this study was to quantify the effects of distal femoral cut height on maximal knee extension and coronal plane knee laxity.MethodsSeven fresh-frozen cadaver legs from hip-to-toe underwent a posterior stabilized TKA using a measured resection technique with a computer navigation system equipped with a robotic cutting guide. After the initial femoral resections were performed, the posterior joint capsule was sutured until a 10° flexion contracture was obtained with the trial components in place. Two distal femoral recuts of + 2 mm each were then subsequently made and the trials were reinserted. The navigation system was used to measure the maximum extension angle achieved and overall coronal plane laxity [in degrees] at maximum extension, 30°, 60° and 90° of flexion, when applying a standardized varus/valgus load of 9.8 [Nm] across the knee.ResultsFor a 10 degree flexion contracture, performing the first distal recut of + 2 mm increased overall coronal plane laxity by approximately 4.0° at 30° of flexion (p = 0.002) and 1.9° at 60° of flexion (p = 0.126). Performing the second + 2 mm recut of the distal femur increased mid-flexion laxity by 6.4° (p < 0.0001) at 30° and 4.0° at 60° of flexion (p = 0.01), compared to the 9 mm baseline resection (control). Maximum knee extension increased from 10° of flexion to 6.4° (± 2.5° SD, p < 0.005) and to 1.4° (± 1.8° SD, p < 0.001) of flexion with each 2 mm recut of the distal femur.ConclusionsRecutting the distal femur not only increases the maximum knee extension achieved but also increases coronal plane laxity in midflexion.     

Intraoperative assessment of midflexion laxity in total knee prosthesis

BackgroundSoft-tissue balancing of the knee is fundamental to the success of a total knee arthroplasty (TKA). In posterior-stabilized TKA, there is no stabilizer of the anterior–posterior translation in the midflexion range in which the cam-post mechanism does not engage yet. Therefore, instability in the midflexion range is suspected to occur in posterior-stabilized TKA. The purpose of this study was to measure the joint gap throughout a full range of motion and to analyze the joint gap laxity in the midflexion range after implantation of a mobile-bearing posterior-stabilized total knee prosthesis.MethodsJoint gap kinematics in 259 knees with varus osteoarthritis were measured during TKAs using a tensor device with the same shape of a total knee prosthesis of the same design was used. After the implantation of a mobile-bearing posterior-stabilized prosthesis and the reduction of the patellofemoral joint, the joint gap was measured at 0°, 30°, 60°, 90°, 120°, and 145° of flexion.ResultsThe center size of the joint gap was tight in extension and deep flexion and loose at midflexion ranges, especially at 30° of flexion (p < 0.001). The symmetry of the joint gap was varus at 0° and 145° of flexion (p < 0.001).ConclusionsOur results showed the joint gap laxity in the midflexion range after the implantation of a mobile-bearing posterior-stabilized prosthesis. Our new tensor device, which can attach the polyethylene insert trial, will provide the important information about the joint gap kinematics after implantation of total knee prostheses.Level of evidenceIV.     

Does flexion of the femoral implant in total knee arthroplasty increase knee flexion: A randomised controlled trial

IntroductionProsthetic and operative modifications in total knee arthroplasty (TKA) have been proposed to maximise post-operative knee flexion as it is essential in routine functional activities.MethodsWe performed a double blind randomised controlled trial to compare clinical outcomes of primary cruciate-retaining TKA for osteoarthritis with the femoral component implanted in either 4° flexion in the sagittal plane (F) or in a neutral position (C). The primary outcome of knee flexion and secondary outcomes knee extension, quadriceps strength, WOMAC, SF-12v2, timed stand test, stair climb test and satisfaction were assessed at 1 year. Knee flexion and extension were also assessed intra-operatively. Implant flexion was measured from true lateral radiographs.ResultsThirty-nine participants (40 knees) were recruited, 20 knees per group. Three subjects from the control group and two from the flexed group were lost to 1 year follow-up but numbers were sufficient to satisfy the sample size calculation. Significant differences were found between the groups in knee flexion (F: 113.6 ± 8.8° pre-operative, 122.4 ± 6.0° intra-operative, 110.2 ± 7.5° 1 year, C: 117.4 ± 11.7°, 117.4 ± 7.6°, 103.5 ± 10.7°. p = 0.031) and mental component score of the SF12-v2 (F 53.3 ± 13.2, C 61.1 ± 7.3, p = 0.009) but there were no significant differences in other outcomes and patients were equally satisfied.ConclusionFlexing the femoral implant in this cruciate retaining TKA system provided a significant difference in knee flexion compared to a neutral position. The improvement appears to occur predominantly at surgery and was not associated with a clinical or functional benefit at 1 year. (ACTRN12606000325505). Level of evidence: Level 1; randomised controlled trial.     

Can tibio-femoral kinematic and kinetic parameters reveal poor functionality and underlying deficits after total knee replacement? A systematic review

BackgroundExtensive efforts have been made to understand joint kinematics and kinetics in total knee arthroplasty (TKA) in subjects with satisfactory outcomes during daily functional activities and clinical tests, but it remains unclear whether such movement characteristics hold the potential to indicate the underlying aetiology of unsatisfactory or bad TKA outcomes.PurposeTo investigate which kinematic and kinetic parameters assessed during passive clinical tests and functional activities of daily living are associated with poor functionality and underlying deficits after total knee replacement.MethodsWe focused on studies characterizing the kinematic or kinetic parameters of the knee joint that are associated with poor clinical outcome after TKA. Seventeen articles were included for the review, and kinematic and kinetic data from 719 patients with minimal follow up of 6 months were extracted and analyzed.ResultsPassive posterior translation at 90° flexion exhibited good potential for differentiating stable and unstable TKAs. Anterior-posterior (A-P) translation of the medial condyle at 0–30° and 30–60° flexion, A-P translation of the lateral condyle at 60–90° during closed chain exercises, as well as knee extension moment during stair ascent and descent, knee abduction moment during stair descent, knee internal rotation moment and plantar flexion moment during walking, 2nd peak ground reaction force during stair ascent and walking showed the greatest promise as functional biomarkers for a dissatisfied/poor outcome knee after TKA.ConclusionIn this study, we systematically reviewed the state-of-the-art knowledge of kinematics and kinetics associated with functional deficits, and found 11 biomechanical parameters that showed promise for supporting decision making in TKA.     

Reliability of stress radiography in the assessment of coronal laxity following total knee arthroplasty

BackgroundStress radiography is used in the valuation of soft tissue laxity following total knee arthroplasty (TKA). However, reliability and agreement is largely unknown.MethodsIn this prospective reliability study, we included 15 participants with prior TKA. Standardized coronal stress radiographs were obtained in both extension and flexion and with both varus and valgus stress. All radiographs were repeated (test–retest). In extension the Telos stress device was used, and flexion radiographs were obtained using the epicondylar-view. Three independent raters measured angulation between femoral and tibial component from all radiographs. Reliability was assessed by intra-class correlation coefficient (ICC) and agreement visualized with Bland–Altman plots and by mean difference and limits of agreement (LOA).ResultsStress radiography in extension showed excellent reliability with ICC = 0.96 (0.95–0.98) and LOA of ± 1.2°. Stress radiography at 80–90° of flexion showed good to excellent reliability when measuring medial laxity with ICC = 0.94 (0.89–0.97) and LOA of ± 1.7°; however, when measuring lateral laxity the reliability was only moderate to good with ICC = 0.70 (0.51–0.84) and LOA of ± 6.3°.ConclusionStress radiography is clinically applicable and the methods described in this study provide excellent reliability for measurement of laxity in extension. The reliability of measurements in flexion is good to excellent when measuring medial laxity but only moderate to good when measuring lateral laxity.     

Measuring patellar height using the lateral active flexion radiograph: Effect of total knee implant design

Patellar position during knee flexion was studied in 41 patients with bicruciate substituting (BCS), 41 patients with posterior cruciate retaining (CR) and 41 patients with posterior stabilized (PS) TKA's. The perpendicular height of the patella above the tibial tubercle was compared to the length of the patellar tendon on maximum flexion lateral radiographs. BCS knees had greater active flexion compared to PS and CR knees (BCS = 124 ± 9.8, PS = 112 ± 9.5, CR = 110 ± 10.9). In flexion, apparent patella infera (API) or the height of the patella above the tibial tubercle was 3.5% lower than the patellar tendon length for BCS knees, 1.7% lower in PS knees and 0.5% lower in CR knees. API in PS and BCS knees correlated with active knee flexion, but not in CR knees. Our findings indicate that an apparent inferior position of the patella occurs in BCS knees during deep flexion which is not caused by significant patellar ligament shortening or joint line elevation, but associated with normal posterior rollback of the femur.     

Posterior femoral condylar offsets of a Chinese population

BackgroundThe effect of posterior condylar offset (PCO) on maximal flexion of the knee after TKA is controversial. Another parameter, the posterior condylar offset ratio (PCOR), has been recently introduced to describe the posterior condylar geometry. This study measured the posterior femoral condyle geometry of a Chinese population and compared with those of a Western population published in the literature.MethodsWe measured the PCO and PCOR of 100 Chinese knees (50 males, 50 females). The distances from the anterior and posterior femoral shaft cortex line to the most posterior femoral condyle tangent line were defined as the anterior–posterior dimension (ACP) and posterior condylar offset (PCO). The PCOR was calculated as PCO/ACP. The measured PCO and PCOR were compared to those of a Western population reported in the literature.ResultsThe PCOs were 25.80 ± 2.71 and 27.32 ± 2.34 mm for the Chinese females and males, respectively, where the PCO of the females was significantly smaller than that of the males (p < 0.05). The PCORs were 0.47 ± 0.04 and 0.46 ± 0.03 for the Chinese females and males, respectively, where the PCORs were similar among the Chinese males and females (p > 0.05).ConclusionsWhile the PCO of the Chinese females was smaller than that of the males, their PCORs were similar. Compared to the data of a Western population reported in literature, the PCO of the Chinese population is significantly smaller, but the PCOR is significantly larger.     

Numerical analysis of variations in posterior cruciate ligament properties and balancing techniques on total knee arthroplasty loading

Total knee arthroplasty (TKA) is a widely used and successful orthopaedic procedure. During TKA, the posterior cruciate ligament (PCL) can either be retained or substituted by a post-cam mechanism. One of the main functions of the PCL is to facilitate femoral rollback during knee flexion. For adequate PCL functioning, the PCL should be balanced correctly after TKA. A tight PCL leads to more femoral rollback at the expense of a higher joint compression and potential polyethylene wear. Frequently used surgical techniques to balance a tight PCL are PCL release and increasing the posterior tibial slope. The objective of this study was to evaluate the effects of variations in PCL properties and balancing techniques on the mechanical outcome of a total knee replacement during a weight-bearing squatting movement (flexion range = 45–150°). For this purpose, a prosthetic finite element knee model was developed including a PCL having adjustable properties. Varying the PCL stiffness and PCL steepness (elevation angle) with respect to the tibial plateau considerably affected the TKA loading characteristics. Both a relatively high PCL stiffness and a low elevation angle at the start of the flexion cycle led to a high PCL force (1400–1500 N) and a high peak polyethylene contact stress of roughly 52 MPa during deeper knee flexion (120°). Releasing the PCL with roughly 4 mm or increasing the posterior tibial slope to 7° reduced the PCL force to 300–400 N and the polyethylene peak contact stress to 35–42 MPa at 120° of flexion. The femoral rollback patterns during deep knee flexion were only marginally affected when extra posterior tibial slope was added, whereas additional PCL release resulted in paradoxical anterior movement of the femur.     

Physical examination and in vivo kinematics in two posterior cruciate ligament retaining total knee arthroplasty designs

The aim of this study was to investigate anteroposterior instability in the CKS and the PFC total knee arthroplasty (TKA) designs. Physical examinations, including VAS, IKS and WOMAC were performed in combination with a detailed fluoroscopic measurement technique for three-dimensional kinematic assessment of TKA design function. Anteroposterior instability rated with the IKS was not significantly different (p = 0.34), but patients with a CKS design showed more limitations according to the WOMAC joint stiffness total score, and for items regarding higher flexion activities in the WOMAC score for knee disability. Kinematic analyses showed that the CKS design tended to have more anterior sliding of the femur on the tibia during mid- and deep flexion activities. The sliding distance was larger at the medial than at the lateral side. This phenomenon has also been described for posterior cruciate ligament deficient knees. Furthermore, the CKS design showed a significantly lower range of tibial rotation (p < 0.05) from maximum extension to maximum flexion during deep knee bend activities. Kinematic differences can be ascribed to posterior cruciate ligament deficiency/laxity or differences in TKA designs.     

Intraoperative changes in medial joint gap after posterior femoral condylar resection,posterior osteophyte removal,and femoral component placement during primary total knee arthroplasty

Background“Mid-flexion stability” is important for superior patient satisfaction following total knee arthroplasty (TKA). Thus, it is important to control medial joint gap intraoperatively as a countermeasure. However, reports on the precise intraoperative changes in medial joint gap during TKA are scarce. This study evaluated the intraoperative changes in medial joint gap during TKA.MethodsWe studied 167 knees with varus osteoarthritis that underwent 80 cruciate-retaining (CR) and 87 posterior-stabilized (PS) TKAs between January 2018 and December 2020. We measured the intraoperative changes in medial joint gap with a tensor device at 137.5 N.ResultsThe medial joint gap after posterior femoral condylar resection was significantly increased not only at 90° of flexion but also at 0° of extension in CR and PS TKAs (p < 0.01). The medial joint gap after posterior osteophyte removal was significantly increased not only at 0° of extension but also at 90° of flexion in CR and PS TKAs (p < 0.01). The medial joint gap at 0° of extension was reduced by 0.60 mm after femoral component placement in PS TKA.ConclusionSurgeons need to pay close attention to these intraoperative changes in medial joint gap by measuring the medial joint gap before and after each procedure or assuming the changes in those values before bone cutting to achieve superior patient satisfaction following TKA.     

Range of motion and function are not affected by increased post constraint in patients undergoing posterior stabilized total knee arthroplasty

BackgroundConstrained primary total knee arthroplasty (TKA) can provide stability in the face of incompetent collateral structures or irreconcilable flexion–extension imbalances. However, little is known about its effect on overall knee range of motion (ROM). This study determines whether TKA with increased constraint affects postoperative ROM.MethodsPatients undergoing primary TKA using either posterior stabilized (PS) or constrained condylar knee (CCK) inserts were match-paired based on body mass index, preoperative ROM, and direction and severity of the coronal deformity, yielding 68 pairs. ROM and Knee Society Score (KSS) were obtained preoperatively and at 6 weeks, 4 months, and 1 year.ResultsWhen the 68 matched pairs were considered, all outcome variables related to ROM between the PS and CCK groups at each of the postoperative intervals were similar. Additionally, both the individual items and combined scores of the KSS were similar between groups at all time points.ConclusionsWe demonstrate that the use of increased constraint does not affect ROM, relief of pain, or function after TKA.Level of evidenceLevel III (retrospective case-controlled study, based on prospectively collected data).     

Knee kinematics after cruciate retaining highly congruent mobile bearing total knee arthroplasty: An in vivo dynamic RSA study

PurposeThis work presents a kinematic evaluation of a cruciate retaining highly congruent mobile bearing total knee arthroplasty design using dynamic Roentgen sterephotogrammetric analysis. The aim was to understand the effect of this implant design on the kinematics of prosthetic knees during dynamic activities.MethodsA cohort of 15 patients was evaluated at nine month follow-up after surgery. The mean age was 74.8 (range 66–85) years.The kinematics was evaluated using the Grood and Suntay decomposition and the Low-Point (LP) methods.Results?tlsb=-0.15pt?>From sitting to standing up position, the femoral component internally rotated (from − 11.3 ± 0.2° to − 7.0 ± 0.2°). Varus–valgus rotations were very close to 0° during the whole motor task.LP of medial condyle moved from an anterior position of 12.0 ± 0.2 mm to a posterior position of − 12.4 ± 0.2 mm; LP of the lateral condyle moved from an anterior position of 8.1 ± 0.2 mm to a posterior position of − 12.4 ± 0.2 mm, showing a bi-condylar rollback where both condyles moved parallel backward. Moreover, the femoral component showed anterior translation with respect to the tibia from 80° to 20° (from − 4.9 ± 0.2 mm to 3.3 ± 0.2 mm), then a posterior translation from 20° to full extension was identified (from 3.3 ± 0.2 mm to 0.5 ± 0.2 mm).ConclusionsParadoxical anterior femoral translation and absence of medial-pivoting motion were recorded, highlighting the role of the symmetric deep dishes insert as main driver of the kinematic of this TKA design.     

Relationship of the posterior femoral axis of the “kinematically aligned” total knee arthroplasty to the posterior condylar,transepicondylar, and anteroposterior femoral axes

BackgroundA recent proposed modification in surgical technique in total knee arthroplasty (TKA) has been the introduction of the “kinematically aligned” TKA, in which the angle and level of the posterior joint line of the femoral component and joint line of the tibial component are aligned to those of the “normal,” pre-arthritic knee. The purpose of this study was to establish the relationship of the posterior femoral axis of the “kinematically aligned” total knee arthroplasty (TKA) to the traditional axes used to set femoral component rotation.MethodsOne hundred and fourteen consecutive, unselected patients with preoperative MRI images undergoing TKA were retrospectively reviewed. The transepicondylar axis (TEA), posterior condylar axis (PCA), antero-posterior axis (APA) of the trochlear groove, and posterior femoral axis of the kinematically aligned TKA (KAA) were templated on axial MRI images by two independent observers. The relationships between the KAA, TEA, APA, and PCA were determined, with a negative value indicating relative internal rotation of the axis.ResultsOn average, the KAA was 0.5° externally rotated relative to the PCA (minimum of − 3.6°, maximum of 5.8°), − 4.0° internally rotated relative to the TEA (minimum of − 10.5°, maximum of 2.3°), and − 96.4° internally rotated relative to the APA (minimum of − 104.5°, maximum of − 88.5°). Each of these relationships exhibited a wide range of potential values.ConclusionsUsing a kinematically aligned surgical technique internally rotates the posterior femoral axis relative to the transepicondylar axis, which significantly differs from current alignment instrument targets.     

3D in vivo femoro-tibial kinematics of tri-condylar total knee arthroplasty during kneeling activities

BackgroundKneeling position can serve as an important posture, providing stability and balance from a standing position to sitting on the floor or vice-versa. The purpose of the current study was to determine the kinematics during kneeling activities after subjects were implanted with a tri-condylar total knee arthroplasty.Materials and methodsKinematics was evaluated in 54 knees using fluoroscopy and a three-dimensional model fitting approach.ResultsThe average knee flexion at before contact status, at complete contact and at maximum flexion was 98.1 ± 9.0°, 107.2 ± 6.7°, and 139.6 ± 12.3°, respectively. On average, there was no gross anterior displacement from before contact status to complete contact. Only slight posterior rollback motion of both condyles from complete contact to maximum flexion was observed. Three of 39 (7.7%) knees experienced anterior movement of both condyles more than 2 mm from before contact status to complete contact. Reverse rotation pattern from before contact status to complete contact and then normal rotation pattern from complete contact to maximum flexion were observed. Condylar lift-off greater than 1.0 mm was observed in 45 knees (83.3%).ConclusionThe presence of the ball-and-socket joint articulation provides sufficient antero-posterior stability in these designs to enable the patients to kneel safely without the incidence of any dislocation.Clinical relevanceThis study suggests a safe implant design for kneeling.     

Does cruciate-retaining total knee arthroplasty enhance knee flexion in Western and East Asian patient populations? A meta-analysis

IntroductionThis study analyzed the published data to examine if CR TKAs can enhance the flexion and functional outcomes of the knee in the Western and East Asian populations using a meta-analysis approach.Materials and methodsA systematic review of literature published through Medline and EMBASE was conducted. The inclusion criteria were: primary TKA, follow up duration greater than one year, a fixed bearing CR prosthesis, and data for maximum pre- and post-operative flexion along with standard deviations or errors. We estimated the weighted mean differences between pre- and post-operative flexion, extension and knee scores (KSS and HSS) via a random effect model.ResultsSeventeen articles were selected and reviewed among 1229 studies that included 1090 knees of the Western and 516 knees of the East Asian. No significant difference was noted in maximal knee flexion pre- and post-operatively, when all the studies were pooled together (? 0.17°, p = 0.93, post-operative < pre-operative). The mean difference in flexion was ? 1.87° (p = 0.2) and 2.03° (p = 0.17), respectively in the both populations. However, the extension angle was significantly improved by ? 5.49° and ? 13.05° (p < 0.05), respectively. KSS scores were significantly improved by 46.39 and 51.63, and HSS scores by 36.65 and 30.67 (p < 0.05), respectively in the both populations.ConclusionThe meta-analysis indicated that contemporary CR TKAs have not been shown to enhance post-operative flexion capability in the Western and East Asian. The extension angles of the knee and the knee scores were significantly improved in both populations.     

The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: Prospective control trial

BackgroundThe purpose of this study was to assess whether custom cutting blocks improve accuracy of component alignment compared to conventional TKA instrumentation.MethodsEighty primary TKA patients were enrolled in an open-label randomized prospective clinical trial and were divided into two groups, 40 custom cutting blocks and 40 conventional TKA instrumentations. The primary outcome was prosthetic alignment with respect to mechanical axis and epicondylar axis. Secondary outcomes included operative time, 24-hour postoperative blood loss and hemoglobin at discharged.ResultsThere were no statistical significant differences in the postoperative mechanical axis between the custom cutting blocks group and conventional TKA group, (95% vs. 87.5% within 3° of neutral mechanical alignment, p = 0.192). The average rotational alignment was statistically significantly different in the custom cutting blocks group (1.0° ± 0.6° vs. 1.6° ± 1.8° external rotation from epicondylar axis, p < 0.001). There were statistical significant differences in operation time between custom cutting blocks group and conventional group, skin to skin [57.5 ± 2.3 min vs. 62.1 ± 1.5,p < 0.001]. We found an improvement in group 1 compared with group 2 regarding the proportion of patients with postoperative blood loss within 24 h.ConclusionsCustom cutting blocks technique was a surgical procedure which provided better accuracy in rotational alignment but no statistical differences in mechanical axis, less operative time and reduced blood loss than the conventional TKA instrumentation in the majority of patients.     

The use of navigation to achieve soft tissue balance in total knee arthroplasty — A randomised clinical study

BackgroundAchieving soft tissue balance is an operative goal in total knee arthroplasty. This randomised, prospective study compared computer navigation to conventional techniques in achieving soft tissue balance.MethodsForty one consecutive knee arthroplasties were randomised to either a non-navigated or navigated group. In the non-navigated group, balancing was carried out using surgeon judgement. In the navigated group, balancing was carried out using navigation software. In both groups, the navigation software was used as a measuring tool.ResultsBalancing of the mediolateral extension gap was superior in the navigation group (p = 0.001). No significant difference was found between the two groups in balancing the mediolateral flexion gap or in achieving equal flexion and extension gaps.ConclusionsComputer navigation offered little advantage over experienced surgeon judgement in achieving soft tissue balance in knee replacement. However, the method employed in the navigated group did provide a reproducible and objective assessment of flexion and extension gaps and may therefore benefit surgeons in training.Level of evidenceLevel I, RCT.     

The medial gap is a reliable indicator for intraoperative soft tissue balancing in posterior-stabilized total knee arthroplasty

BackgroundAppropriate soft tissue balance and accurate alignment are important for successful total knee arthroplasty (TKA). However, the optimal technique for establishing and measuring soft tissue balancing remains unclear. The aim of this study was to analyze the intraoperative medial and lateral gap pattern using digital knee balancer in posterior-stabilized (PS) TKA.MethodsThis study involved 55 patients with medial osteoarthritis who underwent a primary TKA using an image-free navigation system. The extension gap and the flexion gap at 90° knee flexion were assessed using an offset seesaw-type digital balancer. Continuous joint distraction force from 10 lb to 60 lb was applied. Medial gap, lateral gap, and varus angle were measured.ResultsThe medial bone gap difference between extension and flexion was constant regardless of the distraction force from 20 lb to 60 lb. The lateral bone gap was significantly greater than the medial bone gap in extension and flexion from 30 lb to 60 lb (P < 0.05). The varus angle changed depending on the distraction force, especially in flexion. The varus angle in flexion was significantly greater than that in extension from 40 lb to 60 lb (P < 0.05).ConclusionsThe medial bone gap is a reliable indicator unaffected by the distraction force during surgery and is useful for adjusting the medial gap in extension and flexion appropriately to ensure medial stability in PS-TKA. The digital knee balancer and navigation system support both precise gap assessment and surgery.