How to Quantitatively Balance a Total Knee? A Surgical Algorithm to Assure Balance and Control Alignment

Varus-valgus native knee laxity in extension displays an almost rectangular pattern and does not correlate with lower limb alignment

Optimal ligament balance is crucial for successful total knee arthroplasty (TKA), which is a standard procedure for managing end-stage knee osteoarthritis. However, the reported values of ligament balance vary due to different methodologies and population differences, which requires further studies. This study aimed to investigate the varus-valgus ligament balance in healthy knees of Japanese individuals and its relationship with lower limb alignment. The studyanalyzed64 knees from 33 healthy young adults using stress radiographs to measure varus-valgus laxity. The mechanical hip-knee-ankle angle, medial proximal tibial angle, and lateral distal femoral angles were determined using digital long-leg radiographs. Varus and valgus laxities were compared, and the relationship between ligament balance and alignment parameters was analyzed. Mean varus laxity (3.6°± 1.3°) was significantly greater than mean valgus laxity(2.9°± 1.0°) (p<0.0001). No significant association was observed between ligament balance and alignment parameters. Healthy knees of Japanese individuals exhibited slightly greater varus laxity (0.7°) than valgus laxity, with no correlation observed between ligament balance and lower limb alignment. The finding underscores the importance of recognizing alignment diversity while noting that alignment does not influence ligament balance; this is particularly relevant in modern TKA techniques focusing on patient-specific joint and ligament reconstructions. The study's findings could help formulate strategies benefiting knee osteoarthritis management.

Precision soft tissue balancing: grid-assisted pie-crusting in total knee arthroplasty

Introduction

The varus and valgus knee deformities result from imbalance in tension between medial and lateral soft tissue compartments. These conditions need to be addressed during total knee arthroplasty (TKA). However, there is no consensus on optimal soft-tissue release techniques for correcting varus and valgus deformities during TKA. We assessed the efficacy of a novel grid-based pie-crusting technique on soft-tissue release.

Methods

Cadaver knees were dissected, leaving only the femur and tibia connected by an isolated MCL or the femur and fibula connected by an isolated LCL. Bone cuts were made as performed during primary TKA. Mechanical testing was performed using an MTS machine. A 3D-printed 12-hole grid was placed directly over the MCL and LCL. Using an 18-gauge needle, horizontal in-out perforations were made 3 mm apart. Deformation and stiffness of the ligaments were collected after every 2 perforations. Means were calculated, and regression analyses were performed.

Results

A total of 7 MCL and 6 LCL knees were included in our analysis. The mean medial femorotibial (MFT) space increased from 6.018 ± 1.4 mm-7.078 ± 1.414 mm (R2 = 0.937) following 12 perforations. The mean MCL stiffness decreased from 32.15 N/mm-26.57 N/mm (R2 = 0.965). For the LCL group, the mean gap between the femur and fibula increased from 4.287 mm-4.550 mm following 8 perforations. The mean LCL stiffness decreased from 29.955 N/mm-25.851 N/mm. LCL stiffness displayed a strong inverse relationship with the number of holes performed (R2 = 0.988).

Discussion

Our results suggest that using this novel grid for pie-crusting of the MCL and LCL allows for gradual lengthening of the ligaments without sacrificing their structural integrity. Our proposed technique may serve as a valuable piece in the soft-tissue release toolkit for orthopaedic surgeons performing TKA in varus and valgus deformed knees.

Using sequential bone cutting to titrate soft tissue balance in total knee arthroplasty effectively minimizes soft tissue release

BACKGROUND

Achieving soft tissue balance while maintaining limb alignment within acceptable boundaries is crucial for successful total knee arthroplasty (TKA). We proposed a sequential bone cutting (SBC) technique to titrate the soft tissue balance in robot-assisted TKA to achieve the desired balance with minimum soft tissue release.

METHODS

In total, 106 robot-assisted TKAs using the SBC technique were included. The preoperative hip-knee-ankle angle (HKA) was < 10° in 76 and ≥ 10° in 30 knees. The gaps were initially balanced with the help of the pre-resection balancing provided by the robotic system. Soft tissue balance and alignment were quantitatively measured after the initial bone cutting and final bone cutting. Additional adjustments (bone recuts and soft tissue releases) required to address soft tissue imbalance after initial bone cutting were recorded. The frequencies of soft tissue releases, soft tissue balance, and resultant alignment ≤ 3° were compared between non-severe (HKA < 10°) and severe deformity (HKA ≥ 10°) groups.

RESULTS

Soft tissue balance was achieved in 45 knees (42.5%) after initial bone cutting and in 93 knees (87.7%) after final balancing. The postoperative alignment was within 3° from neutral in 87 knees (82.1%) and 3-5° in 17 knees (16.0%). For unbalanced knees (n = 61) after initial bone cutting, soft tissue release was avoided by SBC in 37 knees (60.7%) and was deemed necessary in 24 knees (39.3%). Soft tissue release was more likely to be avoided in the non-severe deformity cohort (86.8% [33 of 38]) than in the severe deformity cohort (17.4% [4 of 23]; p < 0.001). The non-severe deformity cohort showed a significantly higher rate of resultant alignment ≤ 3° from neutral than the severe deformity cohort (90.8% vs. 60.0%; p < 0.001).

CONCLUSION

Pre-resection balancing is inappropriate to ensure soft tissue balance. The SBC technique is effective in minimizing soft tissue release while maintaining overall alignment within acceptable boundaries.

Incidence of soft tissue releases in robotic assisted cementless TKA with mechanical alignment and flexion gap balancing

BACKGROUND

To ensure the success of total knee arthroplasty (TKA), precise bone cuts and a well-balanced soft tissue envelope are crucial. Soft tissue release may be necessary, subject to various factors. Therefore, documenting the type, frequency, and necessity of soft tissue releases can establish a benchmark for comparing different alignment techniques and philosophies and evaluating their outcomes. The purpose of this study was to demonstrate that robotic-assisted knee surgery requires minimal soft tissue release.

METHODS

We prospectively documented and retrospectively reviewed the soft tissue releases employed in securing ligament balance in the first 175 patients who received robotic-assisted TKAs at Nepean Hospital. ROSA was utilized in all surgeries with the aim of restoring mechanical coronal alignment, with a flexion gap balancing technique. Surgeries were performed between December 2019 to August 2021 by a single surgeon who used a standard medial parapatellar approach without a tourniquet, and the cementless persona prosthesis. All patients were followed up for a minimum of 6 months post-surgery. Soft tissue releases included any form of medial release for varus knee, posterolateral release for valgus knee and PCL fenestration or sacrifice.

RESULTS

There were 131 female and 44 male patients, aged between 48 to 89 years (average 60 years). The preoperative HKA ranged from 22 degrees varus to 28 degrees valgus, with 71% of patients presenting with a varus deformity. For the whole group, the no need for soft tissue release was documented in 123 patients (70.3%), small fenestrated releases of PCL in 27 (15.4%), sacrifice of PCL in 8 (4.5%), medial releases in 4 (2.3%) and posterolateral releases in 13 (7.4%). In 29.7% of patients in whom a soft tissue release was necessary for balance, over half were/received minor fenestrations of the PCL. Outcomes to date included no revisions or impending revisions, 2 MUAs (1%), and Oxford knee scores averaged 40 at 6 months.

CONCLUSION

We concluded that Robot technology enhanced the precision of bone cuts and allowed for titration of required soft tissue releases to achieve optimal balance.

Pie-Crusting Technique of Medial Collateral Ligament for Total Knee Arthroplasty in Varus Deformity: A Systematic Review

Background

We aimed to better understand the outcomes/complications of pie-crusting technique using blade knife during total knee arthroplasty (TKA) in patients with knee genu varum deformity.

Materials and Methods

A systematic search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. English and Persian language articles were considered on the use of pie-crusting technique during TKA in patients with knee genu varum/varus deformity using related keywords and Medical Subject Headings terms with reported postoperative complications and outcomes.

Results

Primary search resulted in 81 studies of them 9 included in our study (ages ranged: 19 years to 62 years). No perioperative complications and/or any significant differences between pie-crusting and control group were observed. Except for two studies that found no significant positive effect for the use of pie-crusting, other studies found pie-crusting a useful and promising technique. Four studies found significant improvement in pie-crusting group compared to control in terms of functional Knee Society Score (KSS), range of motion (ROM), medial gap, and the knee-specific KKS. Three records found no significant differences in terms of functional KSS, ROM; however, they reported fewer use of constrained inserts or a reasonable correction of femoral tibial angle. No serious complications were reported.

Conclusions

Due to the inconsistency of the results on the efficiency and outcomes of pie-crusting, we cannot make a firm conclusion and more high-quality studies are needed in this regard. However, this method can be considered as a safe method which depends on the skill of surgeon.

Robotic-assisted revision total knee arthroplasty: a novel surgical technique

BACKGROUND

Revision total knee arthroplasty is a challenging procedure. The robotic-assisted system has been shown to enhance the accuracy of preoperative planning and improve reproducibility in primary arthroplasty surgeries. The aim of this paper was to describe the surgical technique for robotic-assisted revision total knee arthroplasty and the potential benefits of this technique.

METHOD

This single-centre retrospective study included a total of 19 patients recruited from April 1, 2021 to April 30, 2022. Inclusion criteria were patients who had Mako™ robotic-assisted revision total knee arthroplasty done within the study period with a more than 6 months follow-up. Statistical analysis was done using Microsoft Excel 16.0.

RESULTS

All 19 patients were followed up for 6 to 18 months. All patients in this study had uneventful recoveries without needing any re-revision surgery when reviewed to date.

CONCLUSION

With the development of dedicated revision total knee software, robot-assisted revision TKA can be a promising technique that may improve surgical outcomes by increasing the accuracy of implant placement, and soft tissue protection and achieving a better well-balanced knee.

Popliteus Avulsion Fracture After Unicompartmental Arthroplasty: A Case Report

CASE

An active 64-year-old patient presented with new-onset lateral knee pain 42 days after an uncomplicated medial unicompartmental knee arthroplasty (UKA). Magnetic resonance imaging and diagnostic injection of local anesthetic identified an avulsion fracture of the popliteus tendon as the source of discomfort. Repair of the tendon to its native footprint was performed with suture anchor fixation. The patient was pain-free and returned to work without restrictions at 12 weeks.

CONCLUSION

We identify a unique cause of knee pain after UKA-avulsion of the popliteus tendon. Successful management of this condition included anatomic repair of the tendon with suture anchor fixation.

Assistive technologies in knee arthroplasty: fashion or evolution? Rate of publications and national registries prove the Scott Parabola wrong

PURPOSE

Most opponents of assistive technologies in orthopedic surgery consider them as a marketing ruse or fashion. Our hypothesis was that many innovations in modern knee arthroplasty are not following the Scott Parabola. This parabola represents the visual curve of a procedure or therapy showing great promise at the beginning, becoming the standard treatment after reports of encouraging results, only to fall into disuse due to adverse outcome reports. This study aimed to assess the interest in these assistive technologies by (1) their number of publications/year and (2) their actual surgical use reported in the National Joint Registries.

METHODS

The search was performed through PubMed, EMBASE, and MEDLINE databases from 1997 to 2021 inclusive to identify all available literature that described the use and results of assistive technologies or new surgical techniques in knee arthroplasty. In the Australian and Norwegian registries, the number of cases performed with these techniques in knee arthroplasty has been quantified year by year.

RESULTS

Following the initial online search, a total of 4085 articles was found. After the assessment mentioned above, 2106 articles were included in the study. The orthopedic techniques assessed in this study are not following the "Scott's parabola" in the literature. Computer-assisted knee arthroplasty and patient-specific instrumentation have increased quickly to have reached a plateau, with a stable number of publications over the last 6 years. The number of publications concerning robotic surgery, accelerometers and sensors continue to rise. In the Australian registry, the proportion of primary TKA performed by computer-assisted systems increased from 2.4% in 2003 to 32% in 2019. In the Norwegian registry, the proportion of computer-assisted TKA remained between 8 and 12% of primary TKA since 2007.

CONCLUSION

Most of the innovations in modern knee arthroplasty are not following the Scott Parabola. After a fast rise, these techniques do not disappear but continue to evolve. Their evolution is synergistic, and techniques appeared to be linked to each other's. Despite persisting concerns about the cost-efficiency of assisting technologies in knee arthroplasties, the interest and use do not decrease and seems to be directly linked to an exponential increase in interest for a better understanding of alignment targets and improved functional recovery.

The MAKO robotic-arm knee arthroplasty system

INTRODUCTION

The Mako robotic arm knee arthroplasty system was initially indicated in unicompartmental knee arthroplasty followed by bicompartmental and total knee arthroplasty techniques. The system utilizes three elements: (1) Pre-op 3D CT based planning and image based intra-op navigation. (2) Pre-resection implant modifications with integrated alignment, implant position and gap data, and (3) A semi-constrained robotic arm assisted execution of bone resection with "haptic" boundaries, and cemented implants.

MATERIALS AND METHODS

This paper evaluates variable pre-op implant placement, and anatomic reference positioning; data entry with incorporation of alignment, implant congruency through range of motion, and gaps; bone resection with "haptic" boundaries, and final implant evaluation with kinetic sensors.

RESULTS

The Mako system allowed for improved implant placement utilizing CT guidance, bone resection accuracy, flexibility for functional implant placement with gap balancing. When combined with kinetic sensors, there was improved rotation and soft tissue balance.

CONCLUSION

The MAKO robotic system can assist the surgeon with anatomic landmarks, provides the flexibility for independent gap balance through implant and alignment refinement, and three-dimensional soft tissue balancing data to achieve functional stability. Registry data has shown improved outcome survivorship irrespective of the surgeons' volumes and learning curves.