Cutting and implanting errors in minimally invasive total knee arthroplasty using a navigation system

The Adjustment of the Rotational Alignment of the Distal End of the Extramedullary Guide to the Anteroposterior Axis of the Proximal Tibia in Total Knee Arthroplasty

The optimal placement within 3 degrees in coronal alignment was reportedly achieved in only 60 to 80% of patients when using an extramedullary alignment guide for the tibial side in total knee arthroplasty (TKA). This probably occurs because the extramedullary alignment guide is easily affected by the position of the ankle joint which is difficult to define by tibial torsion. Rotational direction of distal end of the extramedullary guide should be aligned to the anteroposterior (AP) axis of the proximal tibia to acquire optimal coronal alignment in the computer simulation studies; however, its efficacy has not been proven in a clinical setting. The distal end of the guide can be overly displaced from the ideal position when using a conventional guide system despite the alignment of the AP axis to the proximal tibia. This study investigated the effect of displacement of the distal end of extramedullary guide relative to the tibial coronal alignment while adjusting the rotational alignment of the distal end to the AP axis of the proximal tibia in TKA. A total of 50 TKAs performed in 50 varus osteoarthritic knees using an image-free navigation system were included in this study. The rotational alignment of the proximal side of the guide was adjusted to the AP axis of the proximal tibia. The position of the distal end of the guide was aligned to the center of the ankle joint as viewed from the proximal AP axis (ideal position) and as determined by the navigation system. The tibial intraoperative coronal alignments were recorded as the distal end was moved from the ideal position at 3-mm intervals. The intraoperative alignments were 0.5, 0.9, and 1.4 degrees in valgus alignment with 3-, 6-, and 9-mm medial displacements, respectively. The intraoperative alignments were 0.7, 1.2, and 1.7 degrees in varus alignment with 3-, 6-, and 9-mm lateral displacements, respectively. In conclusion, the acceptable tibial coronal alignment (within 2 degrees from the optimal alignment) can be achieved, although some displacement of the distal end from the ideal position can occur after the rotational alignment of the distal end of the guide is adjusted to the AP axis of the proximal tibia.

The use of augmented reality for limb and component alignment in total knee arthroplasty: systematic review of the literature and clinical pilot study

PURPOSE

A systematic review of the literature has been carried out to assess the actual evidence of the use of augmented reality in total knee arthroplasty (TKA). We then conducted a pilot clinical study to examine the accuracy of the Knee + augmented reality navigation in performing TKA. The present augmented reality (AR) system allows the surgeon to view the tibial and femur axis superimposed on the surgical field through the smart glasses. It provides real-time information during surgery and intraoperative feedback.

METHODS

A systematic review of the PubMed, MEDLINE, and Embase databases up to May 2021 using the keywords "augmented reality", "knee arthroplasty", "computer assisted surgery", "navigation knee arthroplasty" was performed by two independent reviewers. We performed five TKAs using the Knee + system. Patients were 4 females, with mean age of 76.4 years old (range 73-79) and mean Body Max Index (BMI) of 31.9 kg/m2 (range 27-35). The axial alignment of the limb and the orientation of the components were evaluated on standardized pre and postoperative full leg length weight-bearing radiographs, anteroposterior radiographs, and lateral radiographs of the knee. The time of tourniquet was recorded. The perception of motion sickness was assessed by Virtual Reality Sickness Questionnaire (VRSQ) subjected to surgeon immediately after surgery.

RESULTS

After duplicate removal, a total of 31 abstracts were found. However, only two studies concerned knee arthroplasty. Unfortunately, both were preclinical studies. Knee + system is able to perform a cutting error of less than 1° of difference about coronal alignment of femur and tibia and less than 2° about flexion/extension of femur and posterior tibial slope. The absolute differences between the values obtained during surgery and the measurement of varus femur, varus tibia, posterior slope, and femur flexion angle on post-operative radiographs were 0.6° ± 1.34°, 0.8° ± 0.84°, 0.8° ± 1.79°, and 0.4 mm ± 0.55 mm, respectively.

CONCLUSIONS

On light of our preliminary results, the Knee + system is accurate and effective to perform TKA. The translation from pilot study to high-level prospective studies is warranted to assess accuracy and cost-effective analysis compared to conventional techniques.

LEVEL OF EVIDENCE

IV.

The accelerometer-based navigation system demonstrated superior radiological outcomes in restoring mechanical alignment and component sagittal positioning in total knee arthroplasty

Background

This study aimed to determine whether the accelerometer-based navigation (ABN) could improve the accuracy of restoring mechanical axis (MA), component positioning, and clinical outcomes compared to conventional (CON) total knee arthroplasty (TKA).

Methods

A total of 301 consecutive patients (ABN: 27, CON: 274) were included. A 1:4 propensity score matching (PSM) was performed between the two groups according to preoperative demographic and clinical parameters. The postoperative MA, femoral coronal angle (FCA), femoral sagittal angle (FSA), tibial coronal angle (TCA) and tibial sagittal angle (TSA) were compared. Absolute deviations of aforementioned angles were calculated as the absolute value of difference between the exact and ideal value and defined as norms if within 3°, otherwise regarded as outliers. Additional clinical parameters, including the Knee Society knee and function scores (KSKS and KSFS) and range of motion (ROM), were assessed at final follow-up (FU) (mean FU was 21.88 and 21.56 months respectively for ABN and CON group). A secondary subgroup analysis and comparison on clinical outcomes were conducted between norms and outliers in different radiological parameters.

Results

A total of 98 patients/102 knees were analyzed after the PSM (ABN: 21 patients/24 knees, CON: 77 patients/78 knees). In the ABN group, the mean MA, FCA and TSA were significantly improved (p = 0.019, 0.006, < 0.001, respectively). Proportions of TKAs within a ± 3°deviation were significantly improved in all the postoperative radiological variables except for TCA (p = 0.003, 0.021, 0.042, 0.013, respectively for MA, FCA, FSA, and TSA). The absolute deviations of FSA and TSA were also significantly lower in the ABN group (p = 0.020, 0.048, respectively). No significant differences were found in either mean value, absolute deviation or outlier ratio of TCA between two groups. On clinical outcomes, there were no significant differences between two groups, although KSKS, KSFS and ROM (p < 0.01, respectively) dramatically improved compared to baseline. The subgroup analysis also demonstrated no statistical difference on clinical outcomes between the outliers and norms in varied radiological parameters.

Conclusions

The ABN could improve the accuracy and precision of mechanical alignment and component positioning without significant improvement of clinical outcomes. Further high quality studies with long term FU are warranted to comprehensively evaluate the value of the ABN.

Conventional instruments are more accurate for measuring the depth of the tibial cut than computer-assisted surgery in total knee arthroplasty: a prospective study

INTRODUCTION

The most commonly used tool for implant positioning are conventional instruments (CI) followed by computer-assisted surgery (CAS). A number of studies have investigated the cutting error of the tibial component when CAS is used, but most of them were focused on the cutting angles. The accuracy of CAS to determine the depth of the cut has not received much attention, even though implications are similar or worse, than with an angle mismatch.

MATERIALS AND METHODS

This was an ethics board approved, prospective study of 23 consecutive varus TKAs by a single surgeon. Implant positioning was performed using CAS; however, the depth of the tibial cut was determined with both CAS and CI. Targeted alignment was the mechanical axis and 3° of posterior slope. The planned and the achieved cut, as determined by CAS needed to match. The achieved cut was then measured using a caliper and compared to the depth of the cut as per CAS. Medial and lateral cuts were analyzed separately. Analysis of variance and Bland-Altman plots were used for the comparison.

RESULTS

Mean medial navigated cut was 6.3 (± 2.2) mm, mean measured medial cut was 6.6 (± 2.3) mm. Mean lateral navigated cut was 8.9 (± 1.8) mm, mean measured lateral cut was 8.8 (± 1.5) mm. There was a statistical significance for both the medial (p < 0.001) and the lateral (p = 0.004) navigated and measured cuts.

CONCLUSIONS

The results of this study suggest that the tibial cut depth, measured by the navigation, does not match the actual bony cuts performed, even if a perfect cut was achieved in both sagittal and coronal plane. Surgeons should be aware of the measurement error in the navigation system and potentially add an additional step for verifying the achieved depth of the cut.

Augmented reality-based navigation system applied to tibial bone resection in total knee arthroplasty

Background

This pilot study was performed to examine the accuracy of the AR-KNEE system, an imageless navigation system using augmented reality (AR) technology for total knee arthroplasty. The AR-KNEE system enables the surgeon to view information from the navigation superimposed on the surgical field on a smartphone screen in real time.

Methods

Using the AR-KNEE system, one surgeon resected 10 tibial sawbones with viewing the tibial axis and aiming varus/valgus, posterior slope, internal/external rotation angles, and resection level superimposed on the surgical field. We performed computed tomography of the resected sawbones and measured the varus/valgus, posterior slope, and internal/external rotation angles using a designated computer software. The thickness of the resected bone was measured using digital calipers.

Results

The absolute differences between the values displayed on the smartphone screen and the measurement values for varus/valgus, posterior slope, internal/external rotation angles, and thickness of the resected bone were 0.5° ± 0.2°, 0.8° ± 0.9°, 1.8° ± 1.5°, and 0.6 mm ± 0.7 mm, respectively.

Conclusions

This pilot study using sawbones suggested that the AR-KNEE system may provide reliable accuracy for coronal, sagittal, and rotational alignment in tibial bone resection during total knee arthroplasty.

Accuracy of medial-side cutting guide compared to anterior cutting guide in distal femoral osteotomy of total knee arthroplasty

INTRODUCTION

Minimally invasive surgery (MIS) in total knee arthroplasty has the benefits of less postoperative pain and a faster recovery time. An MIS instrument was designed to help surgeons perform this procedure under reduced visualization conditions. A medial cutting guide of the distal femur is used to cut the distal femoral bone without patella subluxation. This study aimed to compare the accuracy of the distal femoral bone cut between the medial and standard anterior cutting guides.

MATERIALS AND METHODS

Two orthopedic surgeons, who specialize in total knee arthroplasty and are familiar with both of these cutting guides, performed the procedures. Forty-eight synthetic saw bones were used, and five-degree valgus medial and anterior cutting guides were randomly assigned to the surgeons. After the osteotomies were performed, the synthetic saw bones were investigated via plain radiographs. Two independent radiologists measured the medial distal femoral angle (MDFA) and the posterior distal femoral angle (PDFA).

RESULTS

The MDFA in the medial cutting group was statistically significantly different from that of the anterior cutting group (94.18° ± 1.47° vs. 94.98° ± 1.14°, P = 0.041). However, the PDFA was not different between the two groups. Likewise, the number of outliers was not different between the groups when a ± 2° error was defined as an outlier (P = 0.609 for MDFA and P = 0.359 for PDFA). Moreover, a high degree of reliability was found in both MDFA and PDFA measurements (intraclass correlation coefficients = 0.813 and 0.824, respectively).

CONCLUSIONS

In this experimental study, the MIS medial cutting guide was less accurate than the standard cutting guide in the distal femoral cut.

Case-related factors affecting cutting errors of the proximal tibia in total knee arthroplasty assessed by computer navigation

PURPOSE

The aim of this study was to determine factors that contribute to bone cutting errors of conventional instrumentation for tibial resection in total knee arthroplasty (TKA) as assessed by an image-free navigation system. The hypothesis is that preoperative varus alignment is a significant contributory factor to tibial bone cutting errors.

METHODS

This was a prospective study of a consecutive series of 72 TKAs. The amount of the tibial first-cut errors with reference to the planned cutting plane in both coronal and sagittal planes was measured by an image-free computer navigation system. Multiple regression models were developed with the amount of tibial cutting error in the coronal and sagittal planes as dependent variables and sex, age, disease, height, body mass index, preoperative alignment, patellar height (Insall-Salvati ratio) and preoperative flexion angle as independent variables.

RESULTS

Multiple regression analysis showed that sex (male gender) (R = 0.25 p = 0.047) and preoperative varus alignment (R = 0.42, p = 0.001) were positively associated with varus tibial cutting errors in the coronal plane. In the sagittal plane, none of the independent variables was significant.

CONCLUSION

When performing TKA in varus deformity, careful confirmation of the bone cutting surface should be performed to avoid varus alignment. The results of this study suggest technical considerations that can help a surgeon achieve more accurate component placement.

LEVEL OF EVIDENCE

IV.

Comparison of Midterm Outcomes of Minimally Invasive Computer-Assisted vs Minimally Invasive Jig-Based Total Knee Arthroplasty

BACKGROUND

Minimally invasive surgery (MIS) has perceived advantages in the early postoperative stage for total knee arthroplasty (TKA). It is not clear whether the improved radiographic alignment achieved by computer-assisted navigation surgery (CAS) improves midterm clinical outcomes. The aim of this study was to compare patient outcomes of MIS TKA performed with and without CAS after a minimum follow-up of 7 years.

METHODS

Between 2007 and 2009, 50 patients underwent CAS and MIS TKA, and 50 patients underwent jig-based MIS TKA in this prospective study. Ninety-six patients were evaluated after a mean follow-up of 7.7 years, and clinical and radiological evaluations were performed.

RESULTS

Midterm results demonstrated that the Knee Society knee score, function score, and range of motion were comparable in the 2 groups. The percentage of patients with the mechanical axis within ±3° of neutral was significantly higher in the CAS group than in the jig-based group (94% vs 79%, respectively; P = .038). No knees had loosening after TKA. However, 1 patient in the CAS group demonstrated late infection 4 years postoperatively.

CONCLUSION

CAS did not improve midterm outcomes after MIS TKA compared with jig-based surgery, although CAS reduced outliers in coronal alignment.

Twice cutting method reduces tibial cutting error in unicompartmental knee arthroplasty

BACKGROUND

Bone cutting error can be one of the causes of malalignment in unicompartmental knee arthroplasty (UKA). The amount of cutting error in total knee arthroplasty has been reported. However, none have investigated cutting error in UKA. The purpose of this study was to reveal the amount of cutting error in UKA when open cutting guide was used and clarify whether cutting the tibia horizontally twice using the same cutting guide reduced the cutting errors in UKA.

METHODS

We measured the alignment of the tibial cutting guides, the first-cut cutting surfaces and the second cut cutting surfaces using the navigation system in 50 UKAs. Cutting error was defined as the angular difference between the cutting guide and cutting surface.

RESULTS

The mean absolute first-cut cutting error was 1.9° (1.1° varus) in the coronal plane and 1.1° (0.6° anterior slope) in the sagittal plane, whereas the mean absolute second-cut cutting error was 1.1° (0.6° varus) in the coronal plane and 1.1° (0.4° anterior slope) in the sagittal plane. Cutting the tibia horizontally twice reduced the cutting errors in the coronal plane significantly (P<0.05).

CONCLUSION

Our study demonstrated that in UKA, cutting the tibia horizontally twice using the same cutting guide reduced cutting error in the coronal plane.

Do manual cutting guides for total knee arthroplasty introduce systematic error?

INTRODUCTION

Conventional cutting guides in total knee arthroplasty can potentially cause unintentional deviation from the planned direction and depth of bone resection resulting in malaligned components. The purpose of this study was therefore to investigate the accuracy of bone cutting jigs for both the femur and tibia using imageless navigation.

MATERIAL AND METHODS

A total of 125 patients with a mean age of 66.7 ± 9.9 years underwent primary total knee arthroplasty with a Stryker Triathlon™ fixed bearing posterior cruciate retaining implant using imageless navigation. Coronal and sagittal position of the secured cutting jig was recorded and bone resection was checked with a rectangular probe attached to a navigation tracker.

RESULTS

There were significant within group differences for the femoral sagittal cut (mean δ = 0.9° [31 %]; p = 0.00001), femoral depth medial compartment (mean δ = 0.5 mm [5 %]; p = 0.001), femoral depth lateral compartment (mean δ = 0.7 mm [7 %]; p = 0.00001), proximal tibial cut (mean δ = 0.3 mm [25 %]; p = 0.001), tibial depth medial compartment (mean δ = 0.6 mm [10 %]; p = 0.0001) and tibia depth lateral cut (mean δ = 0.4 mm [5 %]; p = 0.002). Deviation of more than 2° was observed for the distal cut in the sagittal plane in 17 % and in 9.6 % for the proximal tibial cut in the sagittal plane of all patients.

CONCLUSION

The results of this study demonstrated significant differences between the dialed in cut and "actual" bone resection achieved for all planes for both the femur and tibia. The femur sagittal cut demonstrated a tendency for an extended cut and the tibia showed a tendency for varus.

Pinless navigation in total knee arthroplasty: navigation reduced by the maximum?

PURPOSE

Restoring a neutral mechanical axis in total knee arthroplasty (TKA) (within ±3° of varus/valgus) is associated with superior functional outcome and reduced early implant failure. Using conventional alignment jigs results in malalignment in >20 % of cases. In this study, we investigated the reduction of outliers within the threshold of ±3° of leg alignment using a "pinless" navigation system in comparison with conventional alignment jigs investigated.

METHODS

In this randomised prospective study, 80 patients were randomly assigned/allocated to the pinless or conventional control group. After surgery, the two groups were compared regarding outliers > ±3° by means of hip-knee-ankle angle (HKA), mechanical medial proximal tibia angle (mMPTA), mechanical lateral distal femoral angle (mLDFA) and duration of surgery. Student's unpaired t test was used for quantitative variables, Fisher's exact test compared groups (pinless vs. control) and a two-sided p value of ≤0.05 was considered statistically significant.

RESULTS

In the pinless group, outliers regarding HKA and mLDFA > ±3° was significantly reduced (p = 0.025 and p = 0.002 respectively). In the pinless group, the surgery duration was significantly longer (75.6 vs. 64.5 minutes, p < 0.001).

CONCLUSION

Pinless navigation is effective in reducing outliers > ±3° regarding HKA without risking pin-related complications, such as fractures, infections or breaking screws. However, not all tools for conventional navigation in TKA, such as real-time measurements of the tibiofemoral axis and gap balancing, are available.

Navigated total knee arthroplasty: is it error-free?

PURPOSE

The aim of this study was to determine whether errors do occur in navigated total knee arthroplasty (TKAs) and to study whether errors in bone resection or implantation contribute to these errors.

METHODS

A series of 20 TKAs was studied using computer navigation. The coronal and sagittal alignments of the femoral and tibial cutting guides, the coronal and sagittal alignments of the final tibial implant and the coronal alignment of the final femoral implant were compared with that of the respective bone resections. To determine the post-implantation mechanical alignment of the limb, the coronal alignment of the femoral and tibial implants was combined.

RESULTS

The median deviation between the femoral cutting guide and bone resection was 0° (range -0.5° to +0.5°) in the coronal plane and 1.0° (range -2.0° to +1.0°) in the sagittal plane. The median deviation between the tibial cutting guide and bone resection was 0.5° (range -1.0° to +1.5°) in the coronal plane and 1.0° (range -1.0° to +3.5°) in the sagittal plane. The median deviation between the femoral bone resection and the final implant was 0.25° (range -2.0° to 3.0°) in the coronal plane. The median deviation between the tibial bone resection and the final implant was 0.75° (range -3.0° to +1.5°) in the coronal plane and 1.75° (range -4.0° to +2.0°) in the sagittal plane. The median post-implantation mechanical alignment of the limb was 0.25° (range -3.0° to +2.0°).

CONCLUSIONS

When navigation is used only to guide the positioning of the cutting jig, errors may arise in the manual, non-navigated steps of the procedure. Our study showed increased cutting errors in the sagittal plane for both the femur and the tibia, and following implantation, the greatest error was seen in the sagittal alignment of the tibial component. Computer navigation should be used not only to guide the positioning of the cutting jig, but also to check the bone resection and implant position during TKA.

LEVEL OF EVIDENCE

IV.

Fibula head is a useful landmark to predict the location of posterior cruciate ligament footprint prior to total knee arthroplasty

PURPOSE

The hypothesis of our study is that a routine tibial cut during cruciate retaining TKA may result in a partial or a total removal of the PCL footprint. Therefore providing a reliable landmark is essential to estimate the probability of PCL damage with a tibial cut and to enable the surgeon to decide pre-operatively whether a cruciate retaining implant design is suitable.

METHODS

In a case series of 175 cruciate retaining TKA, the routinely made standing postoperative AP-view radiographs were evaluated to determine the distance between fibula head and tibial cutting plane. In a second case series knee MRI of 223 subjects were consecutively used to measure the vertical distance between tibial attachment of PCL and fibula head. The probability of partial or total PCL damage was calculated for different vertical distances between tibial cut and fibula head.

RESULTS

The vertical distance between the tibial cut and the most proximal point of the fibula head averaged 6.1 mm ±4.8 mm. The mean vertical distance from fibula head to proximal and to distal PCL footprint revealed to be 11.4 mm ±3.7 mm and 5.4 mm ±2.9 mm, respectively. The location of the insertion was not significantly different between subgroups such as age (<50 or >50 years), gender and side. Based on our results 11 (7%) knees were considered at high risk of an entire PCL removal after implantation of a cruciate retaining TKA design.

CONCLUSIONS

Currently available routine tibial preparation techniques result in partial or total posterior cruciate ligament detachment. Fibula head as a landmark aids to predict the PCL location and to estimate its disruption pre- and postoperatively on AP-view radiographs.