Kinematic femoral alignment with gap balancing and patient-specific instrumentation in total knee arthroplasty: a randomized clinical trial

Patient Specific Instruments and Patient Individual Implants—A Narrative Review

Joint arthroplasties are one of the most frequently performed standard operations worldwide. Patient individual instruments and patient individual implants represent an innovation that must prove its usefulness in further studies. However, promising results are emerging. Those implants seem to be a benefit especially in revision situations. Most experience is available in the field of knee and hip arthroplasty. Patient-specific instruments for the shoulder and upper ankle are much less common. Patient individual implants combine individual cutting blocks and implants, while patient individual instruments solely use individual cutting blocks in combination with off-the-shelf implants. This review summarizes the current data regarding the implantation of individual implants and the use of individual instruments.

Intra- and postoperative assessment of femoral component rotation in total knee arthroplasty: an EKA knee expert group clinical review

PURPOSE

Malrotation of the femoral component after primary total knee arthroplasty (TKA) is one of the most important problems leading to painful TKA requiring revision surgery.

METHODS

A comprehensive systematic review of the literature was performed to present current evidence on how to optimally place the femoral component in TKA. Several landmarks and techniques for intraoperative determination of femoral component placement and examination of their reliability were analyzed.

RESULTS

2806 articles were identified and 21 met the inclusion criteria. As there is no unquestioned gold standard, numerous approaches are possible which come along with specific advantages and disadvantages. In addition, imaging modalities and measurements regarding postoperative femoral component rotation were also investigated. Femoral component rotation measurements on three-dimensional (3D) reconstructed computerised tomography (CT) images displayed intraclass correlation coefficients (ICC) above 0.85, significantly better than those performed in radiographics or two-dimensional (2D) CT images. Thus, 3D CT images to accurately evaluate the femoral prosthetic component rotation are recommended, especially in unsatisfied patients after TKA.

CONCLUSION

The EKA Femoral Rotation Focus Group has not identified a single best reference method to determine femoral component rotation, but surgeons mostly prefer the measured resection technique using at least two landmarks for cross-checking the rotation.

LEVEL OF EVIDENCE

III.

Retention of Posterior Cruciate Ligament Alone May Not Achieve Physiological Knee Joint Kinematics After Total Knee Arthroplasty: A Retrospective Study

BACKGROUND

The apparently physiological kinematics of the bicruciate-stabilized total knee arthroplasty (BCS TKA) systems have been attributed to the anterior and posterior post-cam mechanism. Although comparisons between TKA designs with either a retained or a sacrificed cruciate ligament have been conducted, we are not aware of any analyses of 2 implants with identical bearing geometry but different cruciate-ligament strategies under equal loading conditions. Knowledge about the kinematic effect of the different cruciate ligament strategies would potentially be valuable to facilitate preoperative planning and decision-making with regard to selecting the most appropriate implant for a patient.

METHODS

This retrospective study included 20 patients: 10 treated with a BCS and 10 treated with a cruciate retaining (CR) TKA. Fluoroscopic analyses during high-flexion activities (unloaded flexion-extension and loaded lunge) were conducted at 24 months postsurgery. All patients completed the Knee Society Score, Forgotten Joint Score, and High-Flexion Knee Score questionnaires preoperatively and postoperatively.

RESULTS

The BCS cohort showed greater femoral lateral rollback as well as a medial pivot in both activities. In contrast, the CR cohort showed a significant increase in anterior translation on the medial compartment as well as almost absent femoral lateral rollback. Higher clinical scores were observed in the BCS cohort.

CONCLUSIONS

At 24 months postsurgery, despite equal bearing geometry, retention of the posterior cruciate ligament in the CR cohort apparently was insufficient to reduce anterior shift. The BCS cohort showed expected knee joint kinematics; however, the kinematics in this cohort could eventually benefit from a smooth transition between the interchanging surfaces. Further investigation should be focused on the surgical technique and its interaction with the TKA design.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Gap balancing versus measured resection for primary total knee arthroplasty: a meta-analysis study

INTRODUCTION

To achieve the most desirable post-operative results, operation techniques and procedures for total knee arthroplasty (TKA) are highly standardized. However, debates persist whether patients having undergone a gap balancing technique (GB) perform better than those having undergone measured resection (MR) technique. Therefore, a meta-analysis study was conducted to investigate advantages of GB compared to the MR. The focus of the present study was on clinical and functional scores, radiological measurements and further complications.

MATERIALS AND METHODS

The present meta-analysis was conducted according to the PRISMA checklist. In November 2019, literature search was performed. All clinical studies comparing measured resection technique versus gap balancing technique for primary total knee arthroplasty were considered for inclusion. Only articles reporting quantitative data under the outcomes of interest were eligible for inclusion. The methodological quality assessment and statistical analyses were performed through the Review Manager Software version 5.3 (The Cochrane Collaboration, Copenhagen).

RESULTS

Data from 25 clinical trials (2971 procedures) were collected. Patient baseline demonstrated a good comparability. No difference among the two cohorts was found in terms of SF-12 Mental and Physical, ROM, KSS, KSS Function, OKS, WOMAC. No difference was found in the alignment of mechanical axis and femoral rotation. During the knee motion, no difference was found between the medial and lateral gaps among the two techniques. The GB showed a significant elevated joint line (P < 0.0001), along with a longer duration of the operating time (P = 0.001). No differences were found in terms of revision surgery, aseptic loosening or prosthetic infections.

CONCLUSION

GB and MR achieve similar outcomes for TKA. In the GB group, a proximalisation of the joint line and extended operating time was detected. Regarding the additional outcomes of interest, the present analysis showed comparability between both groups, MR and GB.

Contralateral preoperative templating of lower limbs' mechanical angles is a reasonable option

PURPOSE

In cases where the femur or tibia exhibits abnormal mechanical angulation due to degenerative changes or fracture, the contralateral leg is often used to complete preoperative templating. The aim of this study was to determine the degree of asymmetry between knee joints in healthy individuals and to determine whether it is affected by differing demographic parameters.

METHODS

A CT scan-based modelling and analysis system was used to examine the lower limb of 233 patients (102 males, 131 women; mean age 61.2 ± 15.2 years, mean body mass index 24.9 ± 4.4 kg/m²) The hip-knee angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), posterior proximal tibial angle (ppta) and posterior distal femoral angle (PDFA) were then calculated for each patient. Results were then analysed to calculate femoral symmetry based on absolute differences (AD) and percentage asymmetry (%AS) using a previously validated method.

RESULTS

Our results do not demonstrate any considerable asymmetry (percentage of asymmetry > 2%) for all the anatomical parameters analysed: HKA (mean AD = 1.5°; mean AS % = 0.8, n.s), MPTA (AD = 1.1°; AS % = 1.3, n.s), PPTA (AD = 1.4°; AS % = 1.0, n.s), LDFA (AD = 1.2 mm; AS % = 1.4, n.s) and PDFA (AD = 0.9°; AS % = 1.0, n.s). Gender and ethnicity were not associated with significantly higher AD asymmetry. A significant correlation of AD asymmetry was observed between BMI and HKA, BMI and MPTA, and between patients' age and the MPTA.

CONCLUSION

This data demonstrate that there is a non-statistically significant mechanical angle asymmetry between the two lower limbs. In cases where contralateral templating is used, such asymmetry will induce minimal (if any) clinical differences.

LEVEL OF EVIDENCE

IV.

The fate of Baker's cysts at mid-term follow-up after total knee arthroplasty

AIMS

We report the natural course of Baker's cysts following total knee arthroplasty (TKA) at short- and mid-term follow-up.

METHODS

In this prospective case series, 105 TKA patients were included. All patients who received surgery had a diagnosis of primary osteoarthritis and had preoperatively presented with a Baker's cyst. Sonography and MRI were performed to evaluate the existence and the gross size of the cyst before TKA, and sonography was repeated at a mean follow-up time of 1.0 years (0.8 to 1.3; short-term) and 4.9 years (4.0 to 5.6; mid-term) after TKA. Symptoms potentially attributable to the Baker's cyst were recorded at each assessment.

RESULTS

At the one-year follow-up analysis, 102 patients were available. Of those, 91 patients were available for the 4.9-year assessment (with an 86.7% follow-up rate (91/105)). At the short- and mid-term follow-up, a Baker's cyst was still present in 87 (85.3%) and 30 (33.0%) patients, respectively. Of those patients who retained a Baker's cyst at the short-term follow-up, 31 patients (35.6%) had popliteal symptoms. Of those patients who continued to have a Baker's cyst at the mid-term follow-up, 17 patients (56.7%) were still symptomatic. The mean preoperative cyst size was 14.5 cm² (13.1 to 15.8). At the short- and mid-term follow-up, the mean cyst size was 9.7 cm² (8.3 to 11.0) and 10.4 cm² (9.8 to 11.4), respectively. A significant association was found between the size of the cyst at peroperatively and the probability of resolution, with lesions smaller than the median having an 83.7% (36/43) probability of resolution, and larger lesions having a 52.1% (25/48) probability of resolution (p < 0.001). At the mid-term follow-up, no association between cyst size and popliteal symptoms was found.

CONCLUSION

At a mean follow-up of 4.9 years (4.0 to 5.6) after TKA, the majority (67.0%, 61/91) of the Baker's cysts that were present preoperatively had disappeared. The probability of cyst resolution was dependent on the size of the Baker's cyst at baseline, with an 83.7% (36/43) probability of resolution for smaller cysts and 52.1% (25/48) probability for larger cysts. Cite this article: Bone Joint J. 2020;102-B(1):132-136.

Weight Bearing Activities change the Pivot Position after Total Knee Arthroplasty

The knee joint center of rotation is altered in the absence of the anterior cruciate ligament, which leads to substantially higher variance in kinematic patterns. To overcome this, total knee arthroplasty (TKA) designs with a high congruency in the lateral compartment have been proposed. The purpose of this study was to analyze the influence of a lateral pivot TKA-design on in-vivo knee joint kinematics. Tibiofemoral motion was retrospectively addressed in 10 patients during unloaded flexion-extension and loaded lunge using single plane fluoroscopy. During the unloaded flexion-extension movement, the lateral condyle remained almost stationary with little rollback at maximum flexion. The medial condyle exhibited anterior translation during the whole flexion cycle. During the loaded lunge movement, a higher degree of rollback compared to the unloaded activity was observed on the lateral condyle, whereas the medial condyle remained almost stationary. The results showed a clear lateral pivot during the unloaded activity, reflective of the implant’s geometric characteristics, and a change to a medial pivot and a higher lateral rollback during the weight-bearing conditions, revealing the impact of load and muscle force. It remains unclear if the kinematics with a lateral TKA design could be considered as physiological, due to the limited knowledge available on native knee joint kinematics.

Clinical Outcomes of Gap Balancing vs Measured Resection in Total Knee Arthroplasty: A Systematic Review and Meta-Analysis Involving 2259 Subjects

BACKGROUND

The argument on the clinical effects between gap balancing (GB) and measured resection (MR) in total knee arthroplasty remains to be resolved. A systematic review and meta-analysis was performed to investigate which technique in total knee arthroplasty has better clinical effect.

METHODS

A total of 20 studies involving 2259 cases were included in the meta-analysis. The primary outcome measure was Knee Society Score (KSS), whereas the secondary outcomes included other function assessment systems (eg, range of motion, Western Ontario and McMaster University Osteoarthritis Index), radiological outcomes (eg, femoral component rotation, total outliers), revision rate, complications (eg, infection, loosening, instability), and surgical time.

RESULTS

The GB technique was associated with statistically significant increases in the primary outcomes of KSS-function in 1 year. However, a mean difference of 2.12 points was below the minimal clinically important difference of 6 points. No differences were found in the analyses of KSS-knee and KSS-function in any other follow-up periods. Secondary outcome assessments showed significant decreased surgical time (mean difference, 16.18; P < .00001) for MR. Although statistically significant difference in favor of GB was identified in total outliers (risk ratio, 1.72, P = .0004), the 2 techniques were comparable in range of motion, Western Ontario and McMaster University Osteoarthritis Index, femoral component rotation, complications, and revision rate.

CONCLUSION

We conclude that both techniques can result in equivalent results when done properly, and each surgeon must understand the strengths and weaknesses of each technique.

Small Improvements in Postoperative Outcome with Gap Balancing Technique Compared with Measured Resection in Total Knee Arthroplasty

Background:

There is ongoing debate about how to obtain correct rotational alignment in total knee arthroplasty (TKA). Two commonly used techniques are the measured resection (MR) and the gap balancing (GB) technique.

Objective:

The objective of the present study was to analyze which of these two techniques confers a clinical advantage up to 10 years postoperatively.

Methods:

Two hundred patients were randomized to either MR or GB. The primary outcome was the Knee Society Knee Score (KS) 10 years postoperatively. Secondary outcomes were passive range of motion, the Knee Society Function Score (FS), and the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC), along with implant survival. We employed a two one-sided test (TOST) and linear mixed models to assess clinical outcomes.

Results:

Mean KS was 82 (95% confidence interval (CI), 80 – 83) and 77 (95% CI, 76 – 79) in the GB and MR group, respectively. The TOST test and linear mixed model both revealed statistical significance (p < 0.001). In addition, GB yielded better postoperative FS and WOMAC. However, between-group differences were consistently small. Implant survival rates at 10 years, with survival for any reason as the endpoint of interest, were 93.7% (95% CI, 86.4% and 97.1%) and 89.8% (95% CI, 81.9% - 94.4%) for the GB group and the MR group, respectively (p = 0.302).

Conclusion:

Gap-balancing is a safe and reliable technique. KS for the two study groups at 10 years can be considered equivalent, and the small postoperative advantages may not extend beyond clinical relevance.

Early Outcomes of Kinematic Alignment in Primary Total Knee Arthroplasty: A Meta-Analysis of the Literature

BACKGROUND

Kinematic alignment in total knee arthroplasty (TKA) seeks to more anatomically align the knee prosthesis to promote more physiological kinematics. However, there are questions about the durability, function, and complication rate of a non-mechanically aligned TKA. Therefore, the purpose of this study is to perform a systematic review and meta-analysis to evaluate early outcomes after kinematic alignment.

METHODS

Two independent reviewers performed a systematic review of the English literature using both the MEDLINE and Embase databases searching for studies on kinematic TKA. Of the initial 839 published reports, 9 studies were included in the review. Four randomized, controlled trials comparing outcomes of kinematic and conventional alignment TKA were identified. Data were extracted and aggregated using inverse variance and Mantel-Haenszel fixed effects meta-analysis.

RESULTS

Of an aggregated 877 kinematic TKAs, the cumulative survivorship was 97.4% at a weighted mean follow-up of 37.9 months. The most common reasons for revision were patellofemoral problems in 8 patients (1.2%). We found no difference in the complication rate between the 229 kinematic and 229 conventional TKA patients (3.9% vs 4.4%; P = .83). The kinematic TKA group had a higher combined postoperative Knee Society Score than the conventional TKA group (mean difference, 9.1 points; 95% confidence interval, 5.2-13.0 points; P < .001).

CONCLUSION

Small deviations from the traditional mechanical axis alignment in TKA do not appear to impact overall survivorship or complication rates at short-term follow-up. Functional outcome as measured by the Knee Society Score favored kinematic alignment. These preliminary results illustrate the concept that there may be more than a single alignment target for all patients undergoing primary TKA.