Influence of intra-operative joint gaps on post-operative flexion angle in posterior cruciate-retaining total knee arthroplasty

Addressing sagittal plane imbalance in primary total knee arthroplasty

Aims

Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies.

Methods

In 137 robotic-assisted TKAs, extension and flexion stressed gap laxities and bone resections were measured. The primary outcome was the proportion and magnitude of medial and lateral SPI (gap differential > 2.0 mm) for KA, MA, and FA. Secondary outcomes were the proportion of knees with severe (> 4.0 mm) SPI, and resection thicknesses for each technique, with KA as reference.

Results

FA showed significantly lower rates of medial and lateral SPI (2.9% and 2.2%) compared to KA (45.3%; p < 0.001, and 25.5%; p < 0.001) and compared to MA (52.6%; p < 0.001 and 29.9%; p < 0.001). There was no difference in medial and lateral SPI between KA and MA (p = 0.228 and p = 0.417, respectively). FA showed significantly lower rates of severe medial and lateral SPI (0 and 0%) compared to KA (8.0%; p < 0.001 and 7.3%; p = 0.001) and compared to MA (10.2%; p < 0.001 and 4.4%; p = 0.013). There was no difference in severe medial and lateral SPI between KA and MA (p = 0.527 and p = 0.307, respectively). MA resulted in thinner resections than KA in medial extension (mean difference (MD) 1.4 mm, SD 1.9; p < 0.001), medial flexion (MD 1.5 mm, SD 1.8; p < 0.001), and lateral extension (MD 1.1 mm, SD 1.9; p < 0.001). FA resulted in thinner resections than KA in medial extension (MD 1.6 mm, SD 1.4; p < 0.001) and lateral extension (MD 2.0 mm, SD 1.6; p < 0.001), but in thicker medial flexion resections (MD 0.8 mm, SD 1.4; p < 0.001).

Conclusion

Mechanical and kinematic alignment (measured resection techniques) result in high rates of SPI. Pre-resection angular and translational adjustments with functional alignment, with typically smaller distal than posterior femoral resection, address this issue.

Higher use of fixed-bearing over mobile-bearing and posterior-stabilized over medial pivot designs in total knee arthroplasty (TKA): a systematic comparative analysis using worldwide arthroplasty registers from England and Wales, Australia, Norway, New Zealand, Germany and Switzerland

INTRODUCTION

The aim of this study was to compare the use of mobile-bearing, fixed-bearing, posterior-stabilized (PS) and medial pivot design to describe epidemiological differences and subsequent outcomes.

MATERIALS AND METHODS

A systematic literature search was performed using the NORE website to identify the relevant arthroplasty registers. Inclusion criteria were the following: (1) reports had to be publicly available, (2) reports had to be written in German or English language, (3) differentiation between mobile- and fixed-bearing, posterior-stabilized, and if possible, medial pivot designs had to be possible from the present reports, and (4) data had to be reported for at least three consecutive years and the latest report had to be from the year 2020 to retrieve recent data.

RESULTS

Six registries (England and Wales, Australia, Norway, New Zealand, Germany, Switzerland) offered sufficient data according to the inclusion criteria. In all countries, the dominant type of bearing used for total knee arthroplasty (TKA) was fixed-bearing, with percentages ranging from 60.8% to 84.1% in 2018, 63.6% to 85.7% in 2019 and 66.2% to 87.4% in 2020. A large variation was observed concerning mobile-bearing design, which showed a range from 2.8% to 39.2% in 2018, 2.6% to 36.4% in 2019 and 2.9% to 33.8% in 2020. Some variation was found regarding the use of PS TKA, as its percentage frequency ranged from 9.7% to 29.2% in 2018, 9.8% to 29.4% in 2019 and 10.1% to 28.5% in 2020. Medial pivot design had a share of 9.1% in 2018, 8.6% in 2019 and 8.4% in 2020 in Australia, while it only accounted for 1.4% in 2018, 2.1% in 2019 and 2.5% in 2020 in Germany.

CONCLUSION

The comparison of arthroplasty registers from England and Wales, Australia, Norway, New Zealand, Germany and Switzerland revealed large differences regarding the application of posterior-stabilized designs, but also common ground considering the overwhelming use of fixed-bearing inserts, which, when inserted correctly, eradicate the potential complication of bearing dislocation. Arthroplasty registers offer a real-world clinical perspective with the aim to improve quality and patient safety.

Is it possible to predict the final component gap in flexion before femoral posterior condylar osteotomy in cruciate-retaining and posterior-stabilized total knee arthroplasty?

BACKGROUND

In total knee arthroplasty (TKA) with posterior condylar osteotomy using anatomical landmarks, predicting the final flexion gap is impossible, as it differs with the presence or absence of the posterior cruciate ligament. We compared the predicted flexion gap, based on pre-femoral posterior condylar osteotomy measurements, with the postsurgical final flexion gap in cruciate-retaining (CR) and posterior-stabilized (PS) TKA.

METHODS

One hundred knees of patients with osteoarthritis were included: 35 underwent CR, and 65 PS TKA. Distal femoral and proximal tibial osteotomy using the measured resection technique was performed. An anterior and posterior femoral osteotomy guide was set parallel to the surgical epicondylar axis, and the predicted flexion gap was measured using a seesaw tensor attached to the guide. After all procedures, the final component gap in flexion was measured using a similar seesaw tensor at the patella reduction position and was compared with the predicted gap.

RESULTS

The correlation coefficients for predicted vs. final component gap were 0.45 (P < 0.05) in CR and 0.82 (P < 0.001) in PS. The mean differences between predicted and final gaps were 1.8 mm for CR and 1.0 mm for PS. In 34.3% of CR cases, the gap difference was more than 2 mm.

CONCLUSION

It is possible to predict the final flexion gap before femoral posterior condylar osteotomy, with a strong correlation observed between predicted and final component gaps in PS TKA. However, in CR, more than 30% of the cases showed unexpectedly large final flexion gaps.

Intraoperative physiological lateral laxity in extension and flexion for varus knees did not affect short-term clinical outcomes and patient satisfaction

PURPOSE

Medial release during total knee arthroplasty (TKA) is used to correct ligament imbalance in knees with varus deformity. However, questions remain on whether residual ligament imbalance would be related to inferior clinical results. The purposes of the present study were to measure the intraoperative joint gap and to evaluate the effect of intraoperative soft tissue condition on the new Knee Society Score (KSS 2011) at 2-year follow-up, without the maneuver of additional medial release to correct the asymmetrical gap balance.

METHODS

Varus-valgus gap angle and joint gap were measured using a tensor device without medial release for 100 knees with preoperative varus deformity. The knees were categorized according to the varus-valgus gap angle and the laxity. The preoperative and postoperative clinical outcomes using KSS 2011 were compared between the groups.

RESULTS

The average varus-valgus angles had a residual imbalance of 2.8° varus and 1.3° varus in extension and flexion, respectively. In comparison, according to varus-valgus joint gap angle and knee laxity in extension and flexion, no significant differences were found in postoperative range of motion and subscale of KSS 2011 among the groups.

CONCLUSION

Intraoperative asymmetrical joint gap and physiological laxity do not affect early clinical results after TKA.

LEVEL OF EVIDENCE

III.

Joint distraction force changes the three-dimensional articulation of the femur and tibia in total knee arthroplasty: a cadaveric study

PURPOSE

The purpose of this study was to test the hypotheses that the joint distraction force changes the three-dimensional articulation between the femur and the tibia and that the presence of posterior cruciate ligament (PCL) affects the three-dimensional articulation during joint gap evaluation in total knee arthroplasty (TKA).

METHODS

Cruciate-retaining TKA procedures were performed on 6 cadaveric knees using a navigation system. The joint center gap and varus ligament balance were measured using Offset Repo-Tensor^® with the knee at 90° of flexion before and after PCL resection for joint distraction forces of 89, 178, and 266 N. The three-dimensional location of the tibia relative to the femur and the axial rotational angle of the tibia were also assessed.

RESULTS

Regardless of PCL resection, the joint center gap became larger (p = 0.002, p = 0.020) and varus ligament balance became more varus (p = 0.002, p = 0.002) with increasing joint distraction force, whereas the tibia was more internally rotated (p = 0.015, p = 0.009) and more anteriorly located (p = 0.004, p = 0.009). The tibia was more internally rotated (p = 0.015) and more posteriorly located (p = 0.026) after PCL resection than before resection.

CONCLUSIONS

Joint distraction force changed three-dimensional articulation regardless of PCL preservation. PCL function was revealed as a factor restraining both tibial posterior translation and internal rotation. Surgeons should recognize that joint gap evaluation using a tensor device is subject to three-dimensional changes depending on the magnitude of the joint distraction force.

What to Know for Selecting Cruciate-Retaining or Posterior-Stabilized Total Knee Arthroplasty

There has been continuing debate about the superiority of cruciate-retaining (CR) total knee arthroplasty (TKA) versus posterior-stabilized (PS) TKA for obtaining knee joint stability with functional improvement. Many surgeons tend to select the type of prosthesis on the basis of their own training and experience. However, the selection must be based on a great store of knowledge rather than on the surgeon's preconceptions or preferences. CR TKA may not be feasible in certain settings: posterior cruciate ligament insufficiency, severe deformity, and history of trauma or surgery. The risk of conversion from a CR type prosthesis to a PS type prosthesis might be high in patients with severe flexion contracture, steep posterior slope, and small femoral component size. The above factors should be carefully considered for an appropriate selection of the type of prosthesis. The surgeon should have a clear understanding on the technical differences between CR and PS TKAs. The amount of distal femoral resection, femoral component size, and tibial slope are particularly crucial for successful TKA. Unless they are meticulously determined, stiffness or instability will ensue, which can be difficult to resolve afterwards. There was no notable difference in functional outcome, range of motion, kinematics, and survival rate between CR and PS TKAs in most previous studies. Strict adherence to surgical indications and solid understanding of differences in surgical principles might be more important than the selection of either a CR or PS prosthesis.

Posterior condylar offset influences the intraoperative soft tissue balance during posterior-stabilized total knee arthroplasty

PURPOSE

This study aimed to clarify the influence of the posterior condylar offset (PCO) on intraoperative soft tissue balance including the joint component gap and varus ligament balance measured by an offset-type tensor during posterior-stabilized (PS) total knee arthroplasty (TKA).

METHODS

In this study, 35 patients with osteoarthritis of the knee underwent PS TKA. Intraoperative soft tissue balance including the joint component gap and varus/valgus ligament balance were assessed at 0°, 10°, 45°, 90°, and 135° of flexion with an offset-type tensor that could be used with the femoral component placement and patellofemoral joint reduction. The correlations between the postoperative PCO and the intraoperative soft tissue balance parameters were assessed using simple regression analysis.

RESULTS

The joint component gap at 0° extension was inversely correlated with the PCO (R = -0.41, p < 0.05). The joint component gap of 10°-0° was positively correlated with the PCO (R = 0.35, p < 0.05). No other soft tissue balance parameters were correlated with the PCO.

CONCLUSIONS

A larger PCO was confirmed to reduce joint component gap in extension but not always in flexion in PS TKA.

Influence of soft tissue balancing and distal femoral resection on flexion contracture in navigated total knee arthroplasty

PURPOSE

The purpose of this study was to evaluate the influence of intra-operative soft tissue balancing and distal femoral cutting on flexion contracture in navigated TKA.

METHODS

This was a prospective cohort study. Fifty-nine patients of primary navigation-assisted TKA were included with over 15° of flexion contracture and excluded valgus knees. Among the cases, 43 cases were performed with soft tissue balancing procedures only, and 16 cases were performed with soft tissue balancing and additional distal femoral bone cutting. The mean preoperative flexion contracture was 17.5° ± 2.7°. The angles of flexion contracture were recorded at each surgical step with navigation.

RESULTS

The mean difference in flexion contracture angle between initial angle and angle after medial release was 5.2° ± 2.8°. The mean difference in flexion contracture angle between medial release step and after posterior cruciate ligament (PCL) release was 2.5° ± 2.2°. The mean difference in flexion contracture angle between PCL release step and after routine bone cutting was 3.1° ± 3.2°. The mean difference in flexion contracture angle between after trial insertion and after posterior clearing procedure was 2.7° ± 1.9°. Among the cases, TKA with 2 mm additional bone cutting were performed in 16 cases. The mean difference in flexion contracture angle after additional femoral bone cutting was 4.8° ± 2.1°.

CONCLUSION

The medial release and 2 mm additional bone cutting could correct flexion contracture by 5°. The appropriate soft tissue balancing and bone cutting could correct flexion contracture intra-operatively up to 5° in each step.

LEVEL OF EVIDENCE

II.

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

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

Postoperative Knee Flexion Angle Is Affected by Lateral Laxity in Cruciate-Retaining Total Knee Arthroplasty

BACKGROUND

Although many studies have reported that postoperative knee flexion is influenced by preoperative conditions, the factors which affect postoperative knee flexion have not been fully elucidated. We tried to investigate the influence of intraoperative soft tissue balance on postoperative knee flexion angle after cruciate-retaining (CR) total knee arthroplasty (TKA) using a navigation and an offset-type tensor.

METHODS

We retrospectively analyzed 55 patients with osteoarthritis who underwent TKA using e.motion-CR (B. Braun Aesculap, Germany) whose knee flexion angle could be measured at 2 years after operation. The exclusion criteria included valgus deformity, severe bony defect, infection, and bilateral TKA. Intraoperative varus ligament balance and joint component gap were measured with the navigation (Orthopilot 4.2; B. Braun Aesculap) while applying 40-lb joint distraction force at 0° to 120° of knee flexion using an offset-type tensor. Correlations between the soft tissue parameters and postoperative knee flexion angle were analyzed using simple linear regression models.

RESULTS

Varus ligament balance at 90° of flexion (R = 0.56; P < .001) and lateral compartment gap at 90° of flexion (R = 0.51; P < .001) were positively correlated with postoperative knee flexion angle. In addition, as with past studies, joint component gap at 90° of flexion (R = 0.30; P < .05) and preoperative knee flexion angle (R = 0.63; P < .001) were correlated with postoperative knee flexion angle.

CONCLUSION

Lateral laxity as well as joint component gap at 90° of flexion is one of the most important factors affecting postoperative knee flexion angle in CR-TKA.

Intraoperative joint gaps and mediolateral balance affect postoperative knee kinematics in posterior-stabilized total knee arthroplasty

BACKGROUND

Adjusting joint gaps and establishing mediolateral (ML) soft tissue balance are considered essential interventions for better outcomes in total knee arthroplasty (TKA). However, the relationship between intraoperative laxity measurements and weightbearing knee kinematics has not been well explored. This study aimed to quantify the effect of intraoperative joint gaps and ML soft tissue balance on postoperative knee kinematics in posterior-stabilized (PS)-TKA.

METHODS

We investigated 44 knees in 34 patients who underwent primary PS-TKA by a single surgeon. The central joint gaps and ML tilting angles at 0°, 10°, 30°, 60°, 90°, 120° and 135° flexion were measured during surgery. At a minimum of two year follow-up, we analyzed in vivo kinematics of these knees and examined the influence of intraoperative measurements on postoperative kinematics.

RESULTS

Gap difference of knee flexion at 135° minus 0° was correlated with the total posterior translation of lateral femoral condyle (r=0.336, p=0.042) and femoral external rotation (r=0.488, p=0.002) during squatting, anteroposterior position of lateral femoral condyle (r=-0.510, p=0.001) and maximum knee flexion (r=0.355, p=0.031) in kneeling. Similar correlations were observed between deep flexion gap differences with respect to the 90° reference and postoperative knee kinematics. Well-balanced knees showed less anterior translation of medial femoral condyle in mid- to deep flexion, consistent femoral external rotation, and the most neutral valgus/varus rotation compared with unbalanced knees.

CONCLUSION

These findings indicate the importance of adequate intraoperative joint gaps in deep flexion and ML soft tissue balance throughout the range of motion.

Ligament balancing in total knee arthroplasty-Medial stabilizing technique

Ligament balancing is one of the most important surgical techniques for successful total knee arthroplasty. It has traditionally been recommended that medial and lateral as well as flexion and extension gaps are equal. This article reviews the relevant literature and discusses the clinical importance of the aforementioned gaps. Current evidence indicates that achieving medial stability throughout the range of motion should be a high priority in ligament balancing in total knee arthroplasty. Finally, the medial stabilising surgical technique, which aims to achieve good medial stability in posterior cruciate-retaining total knee arthroplasty, is introduced.

Intra-operative gaps affect outcome and postoperative kinematics in vivo following cruciate-retaining total knee arthroplasty

PURPOSE

The following investigation evaluates the effect of intra-operative gaps after posterior cruciate ligament-retaining total knee arthroplasty using two-dimensional/three-dimensional registration and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

METHODS

Patients were divided into two groups according to their 90°-0° component gap changes using a device designed by our laboratory. The wide gap group was defined as more than 3 mm (4.3 ± 0.7 mm), and the narrow gap group was defined as less than 3 mm (1.3 ± 1.3 mm).

RESULTS

Under non-WB (weight bearing) conditions, the wide flexion gap group (N = 10) showed a significant anterior displacement of the medial femoral condyle as compared with the narrow flexion gap group (N = 20). Despite no significant differences observed under WB conditions, both femoral condyle positions during flexion were significantly more posterior than during extension. WOMAC of the tight gap group showed worse scores for two functional items demanding knee flexion (bending to floor and getting on/off toilet).

CONCLUSION

The large flexion gap could influence the late rollback under non-WB conditions and better WOMAC functional scores in the flexion items. Three to four millimetre laxity at 90°-0° component gaps may be adequate and might be necessary to carry out daily life activities.

Influence of Intraoperative Soft Tissue Balance on Postoperative Active Knee Extension in Posterior-Stabilized Total Knee Arthroplasty

We evaluated the influence of intraoperative soft tissue balance on postoperative active knee extension using Offset Repo-Tensor® among 73 varus osteoarthritic knees underwent primary posterior-stabilized total knee arthroplasty. The joint center gap between osteotomized surfaces and the component gap after femoral trial component placement were measured using a joint distraction force of 40lb. The active knee extension angle was measured 4weeks after surgery. The postoperative extension angle was not correlated with the joint center gap at 0°, but positively correlated with the component gap at 0°, and the joint looseness at 0° which was calculated by subtracting insert thickness from the component gap. Thus, intraoperative soft tissue measurement with femoral trial component placement would be useful to predict the postoperative knee extension angle.

The influence of the tibial slope on intra-operative soft tissue balance in cruciate-retaining and posterior-stabilized total knee arthroplasty

PURPOSE

This study aims to make clear the influence of the tibial slope on intra-operative soft tissue balance measurements using a tensor in cruciate-retaining and posterior-stabilized total knee arthroplasty (TKA).

METHODS

Forty patients with osteoarthritis of the knee received TKAs (20 cruciate-retaining TKAs and 20 posterior-stabilized TKA). Soft tissue balance was measured using an offset type tensor at 0, 10, 45, 90, 135 degrees of knee flexion. The tibial slopes were measured by post-operative lateral radiograph. The correlation between the tibial slope and values of soft tissue balance were assessed.

RESULTS

Joint component gap at 90° (R = 0.537, p < 0.01) and 135° (R = 0.463, p < 0.05) of flexion and joint component gap change value of 90-0° (R = 0.433, p < 0.05) showed positive correlations with tibial slope in posterior-stabilized TKA. There was no relationship between the tibial slope and the value of soft tissue balances in cruciate-retaining TKA.

CONCLUSIONS

In the present study, we confirmed that increasing the tibial slope resulted in a larger flexion gap compared to extension gap in posterior-stabilized TKA. Surgeons should be aware that increasing the tibial slope is one factor responsible for widening the flexion-extension gap difference in posterior-stabilized TKA.

Tibial internal rotation is affected by lateral laxity in cruciate-retaining total knee arthroplasty: an intraoperative kinematic study using a navigation system and offset-type tensor

PURPOSE

The purpose of this study was to test the hypothesis that intraoperative soft-tissue balance assessed by an offset-type tensor influences post-operative knee kinematics after cruciate-retaining (CR) total knee arthroplasty (TKA).

METHODS

The influence of intraoperative soft-tissue balance on knee kinematics in CR-TKA was retrospectively analysed in 30 patients. Intraoperative soft-tissue balance parameters such as varus angle (varus ligament balance), joint component gap (centre gap), and medial and lateral compartment gaps were measured in the navigation system while applying 40-lb joint distraction force at 0°, 10°, 30°, 60°, 90°, and 120° of knee flexion using an offset-type tensor with the patella reduced. Tibial internal rotation and tibial anterior translation were measured as the differences between the values at 60° and 120° of flexion using the navigation system. Correlations between the soft-tissue parameters and post-operative knee kinematics were analysed.

RESULTS

The varus ligament balance was positively correlated with tibial internal rotation at 60° and 90° of flexion (R = 0.54, P < 0.05; R = 0.60, P < 0.01, respectively). Furthermore, the joint component gap was positively correlated with tibial internal rotation at 90° of flexion (R = 0.44, P < 0.05), and the lateral compartment gap was positively correlated with tibial internal rotation at 60°, 90°, and 120° of knee flexion.

CONCLUSIONS

The intraoperative varus ligament balance and joint component gap values were factors that predicted post-operative knee kinematics after CR-TKA. Lateral laxity at mid-to-deep knee flexion plays a significant role in tibial internal rotation.

LEVEL OF EVIDENCE

III.

Posterior cruciate-retaining versus posterior stabilized total knee arthroplasty: a meta-analysis of randomized controlled trials

PURPOSE

To compare the outcomes between posterior cruciate-retaining and posterior stabilized total knee arthroplasty (TKA) in order to evaluate which approach is superior.

METHODS

Randomized controlled trials (RCTs) comparing posterior cruciate-retaining with posterior stabilized TKA were reviewed which were published up to August 2011. Methodological quality of each included RCT was assessed using the Physiotherapy Evidence Database (PEDro) scale. The relevant data were analysed using Review Manager 5.1. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to determine the quality of the evidence.

RESULTS

Eight RCTs involving 888 patients with 963 knee joints met predetermined inclusion criteria. The postoperative range of motion (ROM) and flexion angle were 11.07° and 2.88° higher for patients with a posterior stabilized TKA than those with a posterior cruciate-retaining TKA, respectively [weighted mean difference (WMD), -11.07; 95% confidence interval (CI), -18.06 to -4.08; p < 0.01 and WMD, -2.88; 95% CI, -5.63 to -0.12; p = 0.04]. No statistical differences were observed between the two designs for knee society pain score, extension angle, 2- and 5-year knee society score, 2- and 5-year knee society function score and complications after primary TKA.

CONCLUSION

Posterior cruciate-retaining and posterior stabilized TKA have similar clinical outcomes with regard to knee function, postoperative knee pain and the other complications. Prosthesis survivorship for both posterior cruciate-retaining and posterior stabilized TKA is satisfactory, and there are no differences between them at short- and middle-term follow-up.

LEVEL OF EVIDENCE

II.

Significant effect of the posterior tibial slope and medial/lateral ligament balance on knee flexion in total knee arthroplasty

PURPOSE

The intra-operative femorotibial joint gap and ligament balance, the predictors affecting these gaps and their balances, as well as the postoperative knee flexion, were examined. These factors were assessed radiographically after a posterior cruciate-retaining total knee arthroplasty (TKA). The posterior condylar offset and posterior tibial slope have been reported as the most important intra-operative factors affecting cruciate-retaining-type TKAs. The joint gap and balance have not been investigated in assessments of the posterior condylar offset and the posterior tibial slope.

METHODS

The femorotibial gap and medial/lateral ligament balance were measured with an offset-type tensor. The femorotibial gaps were measured at 0°, 45°, 90° and 135° of knee flexion, and various gap changes were calculated at 0°-90° and 0°-135°. Cruciate-retaining-type arthroplasties were performed in 98 knees with varus osteoarthritis.

RESULTS

The 0°-90° femorotibial gap change was strongly affected by the posterior condylar offset value (postoperative posterior condylar offset subtracted by the preoperative posterior condylar offset). The 0°-135° femorotibial gap change was significantly correlated with the posterior tibial slope and the 135° medial/lateral ligament balance. The postoperative flexion angle was positively correlated with the preoperative flexion angle, γ angle and the posterior tibial slope. Multiple-regression analysis demonstrated that the preoperative flexion angle, γ angle, posterior tibial slope and 90° medial/lateral ligament balance were significant independent factors for the postoperative knee flexion angle. The flexion angle change (postoperative flexion angle subtracted by the preoperative flexion angle) was also strongly correlated with the preoperative flexion angle, posterior tibial slope and 90° medial/lateral ligament balance.

CONCLUSION

The postoperative flexion angle is affected by multiple factors, especially in cruciate-retaining-type TKAs. However, it is important to pay attention not only to the posterior tibial slope, but also to the flexion medial/lateral ligament balance during surgery. A cruciate-retaining-type TKA has the potential to achieve both stability and a wide range of motion and to improve the patients' activities of daily living.

Different pattern in gap balancing between the cruciate-retaining and posterior-stabilized total knee arthroplasty

PURPOSE

In order to permit soft tissue balance under more physiological conditions during total knee arthroplasties (TKAs), an offset-type tensor was developed to obtain soft tissue balancing throughout the range of motion with reduced patello-femoral (PF) and aligned tibiofemoral joints. The main purpose of the present study was to assess intra-operative soft tissue balance using a navigation system with the offset-type tensor in both cruciate-retaining (CR) and posterior-stabilized (PS) TKAs.

METHODS

One hundred and twenty TKAs--80 CR and 40 PS--were performed in patients with varus-type osteoarthritis using a computed tomography-free navigation system. The offset-type TKA tensor with a reduced and repaired PF joint and femoral component in place was used with the tibia first gap technique to balance soft tissues (joint component gap and ligament balance) at 0°, 10°, 30°, 60°, 90°, and 120° of flexion. The achievement in equalized rectangular gap at extension and flexion--joint component gap within ±3 mm between extension and flexion and ligament balance within ±3° at extension and flexion--was assessed retrospectively.

RESULTS

Both types of implants showed similar patterns of soft tissue balance throughout the range of motion, whereas PS TKA had larger values especially at 60° or 90° of flexion than did CR TKA. In the achievement of equalized rectangular gaps at extension and flexion, CR TKA was superior to PS TKA.

CONCLUSION

Using the tibia first gap technique with the tensor allows appropriate soft tissue balancing, especially in CR TKA.

LEVEL OF EVIDENCE

Therapeutic studies, Level II.

Influence of intra-operative parameters on postoperative early recovery of active knee flexion in posterior-stabilized total knee arthroplasty

PURPOSE

Active knee flexion is more important for daily activities than passive knee flexion. The hypothesis is that the intra-operative parameters such as osteotomized bone thickness and soft tissue balance affect the postoperative active flexion angle in total knee arthroplasty (TKA). Therefore, we evaluate the influence of intra-operative parameters on postoperative early recovery of active flexion after posterior-stabilized (PS) TKA.

METHODS

The subjects were 45 osteoarthritic knees undergoing primary PS TKA with anterior-reference technique. Intra-operative soft tissue balance was measured using an offset type tensor, and each osteotomized bone thickness was also measured. Pre- and postoperative active knee flexion angles were measured using lateral radiographs. Liner regression analysis was used to determine the influence of these intra-operative parameters on postoperative active flexion angles or recovery of active flexion angles.

RESULTS

Pre-operative flexion angle was positively correlated with postoperative flexion angle (R = 0.52, P = 0.0002). Postoperative flexion angle was negatively correlated with the osteotomized bone thickness of femoral medial posterior condyle (R = -0.37, P = 0.012), and femoral lateral posterior condyle (R = -0.36, P = 0.015). Recovery of flexion angle was slightly negatively correlated with gap difference calculated by subtracting joint gap at extension from that at flexion between osteotomized surfaces (R = -0.30, P = 0.046).

CONCLUSIONS

The osteotomized bone thickness of the femoral posterior condyle is a significant independent factor of postoperative flexion angles. This indicates that the restoration of the posterior condyle offset may lead to larger postoperative active flexion angles in PS TKA.

Lateral soft tissue laxity increases but medial laxity does not contract with varus deformity in total knee arthroplasty

BACKGROUND

In TKA, soft tissue balance (the joint gap) depends on the amount of resected bone and soft tissue release. Some studies report preoperative bony deformity correlates with soft tissue balance evaluated intraoperatively and that the medial tissues are contracted with varus deformity. However, these studies did not take into account the amount of resected bone and did not describe whether the soft tissue was tight or loose. Therefore, it remains unclear whether in varus deformity the soft tissues on the medial side are contracted.

QUESTIONS/PURPOSES

We compared (1) intraoperative joint gap, (2) amount of resected bone, and (3) intraoperative soft tissue laxity on the lateral and medial sides according to severity of preoperative varus deformity.

METHODS

We retrospectively reviewed 70 patients with osteoarthritis and varus deformities who underwent 90 TKAs. We retrospectively divided the 90 knees into three groups according to degree of preoperative alignment: mild varus group (<10°), moderate varus group (10°-20°), and severe varus group (>20°). To evaluate intraoperative soft tissue tension, we calculated the soft tissue gap by subtracting the thickness of the resected bone from the joint gaps on the medial and lateral sides, respectively. We then explored the relationship between the soft tissue gap and preoperative alignment.

RESULTS

The lateral soft tissue gap was larger in the severe varus group than in the mild and moderate varus groups. The medial soft tissue gap was larger in the severe varus group than in the mild varus group, but there were no differences in the medial joint gaps among the groups.

CONCLUSIONS

After the bone is resected, the soft tissue on the lateral side is more lax; however, the soft tissue on the medial side is not shorter with greater preoperative varus deformity.

Intraoperative soft tissue tension and postoperative range of motion in posterior stabilized total knee arthroplasty

BACKGROUND

Intraoperative soft tissue tension can significantly impact the range of motion following total knee arthroplasty (TKA). However, the level of impact remains unclear. The purpose of this study was to investigate the relationship between intraoperative soft tissue tension and postoperative range of motion.

METHODS

This retrospective study included 504 patients operated with posterior stabilized TKA. During surgery, we adjusted the soft tissue tension from 80 to 160 N for both flexion and extension with the tensor/balancer device and torque driver. Patients were grouped into three categories based on intraoperative soft tissue tension and analyzed with the 1-year postoperative range of motion using one-way analysis of variance (ANOVA). In addition, Pearson's correlation coefficients were determined to assess the association between intraoperative soft tissue tension and postoperative range of motion.

RESULTS

The absolute tension value at 90° flexion did not affect the postoperative flexion angle (p = 0.61). The absolute tension value at 0° extension did not affect the postoperative extension angle (p = 0.91). Likewise, the difference of tension between flexion and extension did not affect the postoperative flexion angle (p = 0.86). All comparisons did not have the differences in sex, height, weight, body mass index, diagnosis and preoperative range of motion between three groups. No significant correlation was found in each comparison (r = 0.078, r = 0.031, r = -0.052, respectively).

CONCLUSIONS

We did not observe a correlation between intraoperative soft tissue tension adjusted from 80 to 160 N and 1-year postoperative range of motion in posterior stabilized TKA.

The influence of patella height on soft tissue balance in cruciate-retaining and posterior-stabilised total knee arthroplasty

PURPOSE

Although the patella reduced or everted position has recently been recognised as an important factor influencing soft tissue balance during assessment in total knee arthroplasty (TKA), the influence of patella height on soft tissue balance has not been well addressed. Therefore, the relationship between soft tissue balance and patella height was investigated and differences between cruciate-retaining (CR) and posterior-stabilised (PS) TKA were compared.

METHODS

Forty consecutive patients blinded to the type of implant received, were randomised prospectively. Using lateral radiographs, pre-operative patella height was measured. Using an offset-type tensor designed to measure the soft tissue balance with a reduced patellofemoral (PF) joint and femoral component in place, soft tissue balance was intra-operatively assessed in CR TKA (n = 20) and PS TKA (n = 20) in osteoarthritic patients. The joint component gap and varus ligament balance at zero, ten, 45, 90 and 135° of knee flexion with the patella reduced were measured.

RESULTS

In PS TKA, the joint component gap positively correlated with patella height at 90 and 135° of knee flexion. However, there was no correlation between joint component gap and patella height at other flexion angles in PS TKA and any flexion angle in CR TKA. Varus ligament balance showed no significant correlation with patella height in either CR or PS TKA.

CONCLUSION

Analysis of soft tissue balance and patella height only showed a positive correlation in joint component gap at a high flexion angle (90 and 135°) in PS TKA but not in other parameters examined. Pre-operative measurement of patella height may be an important factor for predicting an intra-operative flexion gap in PS TKA.

The influence of patella height on intra-operative soft tissue balance in posterior-stabilized total knee arthroplasty

PURPOSE

Although the patella reduced or everted position has recently been recognized as an important factor in influencing soft tissue balance during the assessment in total knee arthroplasty (TKA), the influence of patella height on soft tissue balance has not been well addressed. We therefore investigated the effect of patella height by comparing soft tissue balance between high [Insall-Salvati index (ISI) > 1] and low patella patients (ISI ≦ 1).

METHODS

Using a tensor designed to facilitate soft tissue balance measurements with a reduced patellofemoral joint and femoral component in place, we intra-operatively assessed the joint component gap and ligament balance of posterior-stabilized (PS) TKAs in 30 osteoarthritic patients performed at 0, 10, 45, 90, and 135° of flexion, with the patella reduced.

RESULTS

When comparing the two groups, the component gaps of the higher patella group showed a larger trend than those of the lower patella group, with significant differences at 90 and 135° of knee flexion. Moreover, the joint component gap positively correlated with ISI at 90 and 135° of knee flexion.

CONCLUSION

Patella higher group showed significant larger component gaps than patella lower group in high flexion angles (90 and 135°). Pre-operative measurement of patellar height can help predict intra-operative soft tissue balance in PS TKA.

LEVEL OF EVIDENCE

III.