Alignment accuracy and functional outcomes between hand-held navigation and conventional instruments in TKA: a randomized controlled trial

Total knee replacement with an accelerometer-based, hand-held navigation system improves knee alignment: reliable in all patients

BACKGROUND

Achieving adequate alignment has traditionally been an important goal in total knee arthroplasty to achieve long-term implant survival. While accelerometer-based hand-held navigation systems (ABN) has been introduced as a way to achieve alignment, there is a limited body of evidence on its accuracy, especially in patients under 65 years with differing etiologies for knee arthritis. This study aimed to assess the precision of a specific ABN system in restoring the mechanical axis and report surgical variables and complications, with particular attention to younger patients.

METHODS

We conducted a retrospective review of 310 primary TKA performed with ABN from May 2016 to February 2021. The mean patient age was 67.4 (SD 8.9) years, with 43% under 65 years and mean body mass index of 33.2 (SD 6.8). The average surgical time was 96.8 min (57-171) and the average follow-up was 3.3 years (1.9-6.7). Data regarding length of stay, pain, range of motion (ROM), complications, and reinterventions were collected from the institutional joint arthroplasty registry and the medical records. Preoperative mechanical axis measurements and postoperative radiological data, including mechanical axis, component alignment and mechanical alignment outliers were analyzed.

RESULTS

The mean preoperative mechanical axis was 175.4° (SD 7.6), with 248 knees (80%) in preoperative varus. The mean postoperative mechanical axis was 179.5° (SD 1.96) with 98% of knees falling within ± 3° of the neutral mechanical axis. Only 6 knees (2 varus, 4 valgus) fell outside the ± 3° range. And 3 knees (1 varus, 2 valgus) fell outside the ± 5° range. In the sagittal plane, 296 knees (95.5%) knees were within ± 3° of goal of 3 degrees of femoral flexion and 302 (97.4%) knees were within ± 2° of goal 1° of slope for tibial component. Far outliers (alignment outside ± 5° of targeted position) were found in 3 knees. Factors such as posttraumatic arthrosis, previous surgery, presence of retained hardware, and age below 65 years were not associated with increase in alignment outliers and far outliers. No complications related to the navigation system were observed. There were 22 complications and 20 reoperations, including 2 revisions for periprosthetic joint infection and 1 revision for flexion instability. Patients that required knee manipulation achieved an ultimate flexion of 110° (SD 14.1).

CONCLUSIONS

The ABN system proved to be user-friendly and accurate in reducing alignment outliers in both coronal and sagittal planes in all patient populations. It offers a straightforward navigation solution while preserving surgeon autonomy and the use of traditional surgical tools. These findings advocate for the integration of this navigation system as a valuable tool to enhance the precision of TKA surgery in all patient groups.

Navigated Versus Conventional Total Knee Arthroplasty: A Systematic Review and Meta-analysis of Prospective Randomized Controlled Trials

Background

Recent evidence on the cost-effectiveness of technology in total knee arthroplasty (TKA) demonstrated that navigated computer-assisted methods (N-TKA) is likely to be most cost-effective in the clinical setting. The aim of the current meta-analysis is to compare radiographic, clinical and functional outcomes between conventional TKA (C-TKA) and N-TKA methods.

Methods

All prospective randomized controlled trials (pRCTs) comparing primary TKA performed using C-TKA and N-TKA techniques were eligible for inclusion. Radiographic outcomes included postoperative coronal, sagittal and axial component alignment. Clinical outcomes included all-cause revision and aseptic revision. Functional outcomes were analyzed when reported. A random-effects meta-analysis of all available cases was performed. This allowed for all missing data.

Results

Normal coronal mechanical alignment of the tibial (p < 0.001) and femoral (p = 0.001) components was achieved more frequently with N-TKA. Normal sagittal mechanical alignment of the tibial component was achieved significantly more with N-TKA (p < 0.010). There was no difference in short-term clinical survivorship (all-cause, p = 0.649; aseptic, p = 0.79) or in functional outcomes reported between groups. There was a clinically significant reduction in the mean C-TKA operative time (87 min, σ = 16.6, 95% CI 76.4-98.8) compared N-TKA (97.6 min, σ = 16.9, 95% CI 86.2-109.1) (p = 0.17).

Conclusion

Navigated TKA achieves superior radiographic alignment for femoral and tibial components in both the coronal and sagittal plane. Operative times are 10 min longer in the N-TKA group. Functional outcomes are similar between navigated and conventional groups. Clinical outcomes reported in Level I studies are limited to short-term follow-up so future prospective studies are required.

[Trends in navigation-handheld systems]

Navigation-assisted surgical procedures in orthopedics and trauma surgery have become increasingly widespread over the last 20 years. In addition to applications in spinal surgery, they are primarily available for knee and hip endoprosthetics. On the one hand, computer-assisted procedures have been increasingly expanded with robotic assistance systems in recent years, and on the other hand, so-called handheld navigation systems have been developed, which enable specialized use directly in the operating field at lower acquisition costs. The aim of this overview is to describe current handheld systems and to present the respective technical principles and the available scientific results. Three handheld systems for TKA use, two for THA use and one system to support pedicle screw placement on the spine are presented.

Concordance in Radiological Parameters of Different Knee Views After Total Knee Arthroplasty

Background Total knee arthroplasty (TKA) is a cost-effective treatment for the end-stage of knee osteoarthritis. Despite the improvements in this surgery, a significant percentage of patients still report dissatisfaction after knee arthroplasty. Radiological results have been used to predict clinical outcomes and satisfaction after knee replacement. This study aims to evaluate the concordance of a set of radiographic views to assess alignment on total knee arthroplasty. Methods A concordance study was designed with 105 patients (130 TKA) that underwent conventional total knee arthroplasty cruciate-retaining design recruited for the study and scheduled for their annual radiograph control. Measurements were performed on the following radiograph after total knee replacement: full-length standing anteroposterior and lateral radiograph, anteroposterior standing, lateral and axial knee view, and the knee "seated view". A musculoskeletal radiologist and a knee surgeon were recruited to perform the radiological measurement and then estimate the interobserver agreement.  Results There was an excellent correlation between Limb Length (LL), Hip-knee-ankle angle (HKA), Sagittal mechanical tibial component alignment (smTA), extension lateral and medial joint space (eLJS and eMJS), 90º flexion lateral and medial joint space (fLJS and fMJS) and Sagittal anatomic lateral view tibial component alignment (saLTA); the good correlation between Mechanical lateral femoral component alignment (mLFA), Sagittal anatomic tibial component alignment (saTA), Sagittal anatomic lateral view femoral component alignment 2 (saLFA2), Patella Height (PH); and moderate to poor correlation for the rest of measurements. Conclusion Excellent and good concordance can be achieved for radiographic measurements in different knee views to assess results after TKA. These findings must encourage future studies to address functional and survival outcomes using all knee views and not just one plane.