Comparative Study of Pinless Navigation System versus Conventional Instrumentation in Total Knee Arthroplasty

Bridging theory and practice: A comprehensive algorithm for imageless total knee arthroplasty

Total knee arthroplasty (TKA) is a surgical procedure to treat severe knee osteoarthritis. Among several techniques available for performing TKA, imageless TKA is known for achieving precise alignment while minimizing invasiveness. This work proposes a comprehensive algorithm for imageless TKA device to calculate the varus/valgus and flexion/extension angles, as well as resection depths for cutting planes at distal femur and proximal tibia. Moreover, the algorithm calculates the hip-knee-ankle (HKA) and flexion angles of the leg. Initially, the proposed algorithm was validated in a virtual environment using a CT-scanned bone model in Solidworks. Subsequently, for the real-world validation, a SoftBone model was resected with conventional intra and extramedullary rods and cross-checked with the proposed algorithm. For the third validation, another SoftBone model was resected with the proposed algorithm and cuts were measured with a vernier caliper. During this experiment, there was an error of approximately 1 mm for both femoral and tibial resection cases when using an infrared camera with an accuracy of ±0.5 mm. However, this error could be reduced using an infrared camera with higher accuracy.

No differences in long-term clinical outcomes and survival rate of navigation-assisted versus conventional primary mobile-bearing total knee arthroplasty: A minimum 10-year follow-up

PURPOSE

This study aimed to compare long-term clinical and radiographic outcomes and survival rates between navigation-assisted (NAV) total knee arthroplasty (TKA) and conventional (CON) TKA using a mobile-bearing insert.

METHODS

From May 2008 to December 2009, 45 and 63 mobile-bearing TKA patients were enroled in the CON- and NAV-TKA groups with 146.8 months follow-up, respectively. Clinical outcomes (Western Ontario and McMaster University Osteoarthritis Index and Knee Society Scores), radiographic outcomes (hip-knee-ankle [HKA], lateral distal femoral, medial proximal tibial, γ, and δ angles), and survivorship were compared between both groups.

RESULTS

The number of HKA angle outliers (more than 3 degrees or less than -3 degree) was significantly lower in the NAV-TKA group (24.4% vs. 9.5%, p = 0.036) than in the CON-TKA group. However, long-term clinical outcomes were similar between both groups. The cumulative survival rate (best-case scenario) was 98.3% in the CON-TKA group and 97.5% in the NAV-TKA group, with no significant difference between the groups (p = 0.883).

CONCLUSION

Long-term clinical outcomes and survival rates were similar between the two groups despite fewer outliers of postoperative lower-limb alignment in the NAV-TKA group. Excellent survival rates were observed in both groups using mobile-bearing inserts.

LEVEL OF EVIDENCE

Level IV, case series.

Accuracy of Advanced Active Robot for Total Knee Arthroplasty: A Cadaveric Study

Although the accuracy of other types of robotic systems for total knee arthroplasty (TKA) has been assessed in cadaveric studies, no investigations have been performed to evaluate this newly advanced active robotic system. Therefore, the authors aimed to analyze the accuracy of bone resection in terms of thickness and alignment in a cadaveric study. Three cadaveric specimens (six knees) and an active robotic system (CUVIS Joint, CUREXO) were used in the study. Three surgeons with different experiences in robotic TKAs performed this cadaveric study using the same robotic protocol with two different implant designs. The thickness and angle of bone resection planes obtained from the optical tracking system and the difference between resection planes and the planning data were assessed to determine accuracy. With respect to the overall resection accuracy compared to the plan, the cutting depth accuracy was within 1.0 mm mean of root mean square (RMS), and the resection angle accuracy in terms of sagittal, coronal, and axial planes was within 1.0 degree mean RMS. In contrast, no significant differences were observed between the planned and measured values in terms of the resection angles and cutting thickness. The hip-knee-ankle angle at postoperative evaluation was 0.7 degrees ± 0.7 degrees (RMS 1.0 degrees). This in vivo study suggests that the use of this newly advanced active robotic system for TKA demonstrates a high degree of accuracy in terms of resection thickness and alignment. This finding supports the clinical application of this advanced robotic system. LEVEL OF EVIDENCE:  Cadaveric study, Level V.

Navigation makes more accurate femur resection compared to conventional total knee arthroplasty in lateral femoral bowing greater than 5º

There are many disagreements about the merits of navigation in total knee arthroplasty (TKA). We compared and analyzed the difference in the accuracy of femoral resection according to the degree of lateral femoral bowing in 2 surgical methods (conventional and navigation-assisted TKA). A total of 238 (100 who underwent navigation TKA and 138 who underwent conventional TKA from 2016 to 2021) were included in this study. The surgeon first performed TKA as the main operator in 2016. Most of the TKAs were navigation-assisted between 2016 and 2018, and most of the TKAs were conventional between 2019 and 2021. For more accurate distal femoral cutting in patients with lateral femoral bowing, a preoperative scanogram was used to set up the insertion point of the IM rod in conventional TKA. Femoral lateral bowing was divided into 3 groups based on the angle. Group 1 was divided into groups with negative values, group 2 into mild bowing of 0° to 5°, and group 3 into groups with moderate bowing of ≥ 5°. The postoperative mechanical hip knee ankle angle and mechanical lateral distal femoral angle (mLDFA) were aimed to be 0° and 90°. The allowable ranges of these values were set as 0° ± 3° and 90° ± 3°, respectively. The distribution of outliers of the mLDFA in the 3 groups divided according to lateral femoral bowing in the navigation-assisted group was not statistically significant difference (P = .59). On the other hand, the distribution of outliers of mLDFA was statistically significant difference in the conventional method group (P = .01). The odds ratio of the outlier occurrence of mLDFA in the conventional method was 2.50, which was statistically significant (P = .03). Also, when the lateral femoral bowing value was moderate; i.e., ≥5°, the odds ratio was 4.20, which was statistically significant (P = .003). In the case of navigation-assisted TKA, the accuracy of femur resection was consistent regardless of the degree of lateral femoral bowing. However, in conventional TKA, the outlier of femur resection increased as lateral femoral bowing increased. Especially, for patients with lateral femoral bowing >5°, navigation-assisted TKA allows for more accurate femur resection compared to conventional TKA.

Prior tuberosity screw fixation of the osteotomized tubercle can lead to favorable outcomes in retro-tubercular bi-planar opening wedge high tibial osteotomy

BACKGROUND

Exact information regarding fixing the tuberosity screw during retro-tubercular opening-wedge high tibial osteotomy (RT-OWHTO) is still lacking. The purpose of this study was to determine whether prior tuberosity screw fixation before plate fixation of main osteotomy fragment can prevent complications associated with tuberosity screw.

METHODS

From 2019 to 2021, patients who underwent RT-OWHTO were divided into two groups (group I, prior tuberosity screw fixation; group II, later tuberosity screw fixation). A total of 49 and 44 knees were included in groups I and II, respectively. Plain radiographs and computed tomography (CT) were used to analyze the parameters of tuberosity screw fixation, neurovascular (NV) safety and osteotomy configurations. Clinical outcomes and post-operative complications were assessed.

RESULTS

The delta (Δ) of the deformation angle of the tuberosity (P = 0.002), delta (Δ) of the posterior tibial slope (PTS) (P < 0.001), extruded screw length (P < 0.001), and retro-tuberosity tip distance (P < 0.001) of group I were significantly smaller than those of group II. All tuberosity screws were fixed medially to the NV structures. Post-operative tuberosity fracture occurred in one knee (2%) in group I and in 10 knees (23%) in group II (P = 0.003).

CONCLUSIONS

RT-OWHTO with prior tuberosity screw fixation can minimize the risk of tuberosity fracture and an increase in the PTS. It can also prevent NV injuries by reducing extruded tuberosity screw length and fixing it medially from the NV structures.

Effect of mediolateral gap difference on postoperative outcomes in navigation-assisted total knee arthroplasty using an ultracongruent insert and the medial stabilising technique

PURPOSE

This study was aimed to compare the clinical, functional, and radiographic outcomes between symmetric and asymmetric extension and mediolateral gap balance after navigation-assisted (NA) total knee arthroplasty (TKA) using ultracongruent (UC) insets and the medial stabilising technique (MST).

METHODS

In all, 363 knees of 275 patients who underwent mechanical alignment-target NA TKA with MST between January 2015 and December 2017 were analysed. Patients were divided into balanced (extension mediolateral gap difference ≤ 2 mm) and tight medial (difference ≥ 3 mm) groups. Pre- and postoperative clinical, functional (range of motion, Western Ontario and McMaster University Osteoarthritis [WOMAC] index, Knee Society Knee Score [KSKS], and Knee Society Function Score [KSFS]) and radiographic (hip-knee-ankle [HKA] angle, femoral condylar offset, extension angle [a minus indicates hyperextension], and joint line distance) outcomes were compared between the groups. Student's t- or Chi-squared test was used to compare the outcomes.

RESULTS

Among the 363 knees analysed, 279 (77%) were assigned to the balanced group and 84 (23%) to the tight medial group. The preoperative HKA angle was significantly greater in the tight medial group than in the balanced group (9.7° ± 4.1° vs 14.3° ± 4.7°, P < 0.001). The postoperative WOMAC index, KSKS, and KSFS were similar between the groups. The change in the joint line distance was not significantly different (1.5 ± 3.7 vs 2.0 ± 3.3; n.s).

CONCLUSION

The clinical, functional, and radiographic outcomes, including joint line distance, were comparable between the tight medial and balanced group after mechanical alignment-targeted UC TKA with MST.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

The Usefulness of a Simplified Navigation-Based Instrumentation for a Novice Surgeon in Primary Total Knee Arthroplasty: A Retrospective Analysis of a Randomized Controlled Trial

Background

A novel simplified navigation-based instrumentation system has been developed. It simplifies the existing navigation system and facilitates convenient bone cutting by positioning the tracker on an existing cutting block without additional pin fixation. This study aimed to compare the outcomes of this newly developed simplified navigation-based instrumentation system in primary total knee arthroplasty (TKA) performed by a novice surgeon with those of conventional surgical techniques.

Methods

From January 2020 to July 2020, 67 knees that underwent primary TKA using the ExactechGPS TKA Plus (group A) were compared to 68 knees that underwent primary TKA using a conventional technique (group B). All patients had a minimum follow-up of 24 months. The operative details such as tourniquet time were investigated. Postoperative hip-knee-ankle (HKA) angle and component position angles in the coronal and sagittal planes (α, β, γ, and δ angles) were evaluated. The outlier rates were compared between the groups as those lying outside ± 3°. Knee Injury and Osteoarthritis Outcome Score for Joint Replacement, the Western Ontario and McMaster Universities Osteoarthritis Index for pain and function, and range of motion were compared.

Results

There was no statistically significant difference in average tourniquet time between the groups (74.3 vs. 70.3 minutes, p = 0.061). Outlier rates for HKA angle (7.5% vs. 23.5%, p = 0.010) and β angle (1.5% vs. 22.1%, p < 0.001) in group A were significantly lower than those in group B. There were no significant differences in clinical outcomes between the groups.

Conclusions

Primary TKA performed by a novice surgeon using a simplified navigation-based instrumentation system did not significantly increase the operation time, and more accurate lower extremity mechanical alignment and tibial component alignment in the coronal plane could be obtained.

Learning curve of robot-assisted total knee arthroplasty and its effects on implant position in asian patients: a prospective study

BACKGROUND

Robot-assisted total knee arthroplasty (r-TKA) can reportedly achieve more accurate implant positioning than conventional total knee arthroplasty (c-TKA), although its learning curve is controversial. Moreover, few studies have investigated r-TKA in Asians, who have different anatomical characteristics. This study aimed to determine the learning curve for r-TKA and compare implant positions between r-TKA and c-TKA according to the learning curve in Asian patients.

METHODS

This prospective study included 50 consecutive c-TKAs (group C), followed by 50 consecutive r-TKAs conducted using the MAKO robotic system (Stryker, USA). Cumulative summation analyses were performed to assess the learning curve for operative time in r-TKA. Accordingly, the r-TKA cases were divided into the initial (group I) and proficiency cases (group P). The femoral and tibial component positions in the coronal, sagittal, and axial planes and lower limb alignment were compared among the three groups.

RESULTS

r-TKA was associated with a learning curve for operative time in 18 cases. The operative time was significantly shorter in groups C and P than that in group I, with no significant difference between groups C and P. Groups I and P demonstrated fewer outliers with respect to lower limb alignment, femoral component coronal position, axial position, and tibial component sagittal position than those in group C, with no significant difference between groups I and P.

CONCLUSION

The operative time did not differ significantly between r-TKA and c-TKA after the learning curve. Surgeons could expect more accurate and reproducible lower limb alignment and implant positioning with r-TKA in Asian patients, irrespective of the learning curve.

Guided-Motion Bicruciate-Stabilized Total Knee Arthroplasty Reproduces Native Medial Collateral Ligament Strain

Background and Objectives: Guided-motion bicruciate-stabilized (BCS) total knee arthroplasty (TKA) includes a dual cam-post mechanism with an asymmetric bearing geometry that promotes normal knee kinematics and enhances anterior-posterior stability. However, it is unclear whether the improved biomechanics after guided-motion BCS TKA reproduce soft tissue strain similar to the strain generated by native knees. The purpose of this cadaveric study was to compare medial collateral ligament (MCL) strain between native and guided-motion BCS TKA knees using a video extensometer. Materials and Methods: Eight cadaver knees were mounted onto a customized knee squatting simulator to measure MCL strain during flexion in both native and guided-motion BCS TKA knees (Journey II-BCS; Smith & Nephew, Memphis, TN, USA). MCL strain was measured using a video extensometer (Mercury® RT RealTime tracking system, Sobriety s.r.o, Kuřim, Czech Republic). MCL strain level and strain distribution during knee flexion were compared between the native and guided-motion BCS TKA conditions. Results: The mean and peak MCL strain were similar between native and guided-motion BCS TKA knees at all flexion angles (p > 0.1). MCL strain distribution was similar between native and BCS TKA knees at 8 of 9 regions of interest (ROIs), while higher MCL strain was observed after BCS TKA than in the native knee at 1 ROI in the mid portion of the MCL at early flexion angles (p < 0.05 at ≤30° of flexion). Conclusions: Guided-motion BCS TKA restored the amount and distribution of MCL strain to the values observed on native knees.

Comparison of Survival Rate and Outcomes Between Conventional and Navigation-Assisted Primary Total Knee Arthroplasty in Severe Varus Knees: A Minimum 10-Year Follow-Up

BACKGROUND

This study aimed to compare the long-term clinical and radiographic outcomes and survival rates between navigation-assisted (NAV) total knee arthroplasty (TKA) and conventional (CON) TKA in patients with preoperative severe varus deformity.

METHODS

From January 2005 to December 2011, 152 TKAs and 62 TKAs with preoperative hip-knee-ankle (HKA) angles more than 15° were enrolled in the CON-TKA and NAV-TKA group with 135.7 months follow-up. Clinical outcomes (Western Ontario and McMaster University Osteoarthritis Index and Knee Society Scores), radiographic outcomes (HKA, α, β, γ, and δ angles), and survivorship were compared between the groups.

RESULTS

The mean value of radiographic outcomes was not statistically different; however, outliers of the HKA angle were significantly higher in the CON-TKA group (18.4% versus 8.1%, P = .04). However, long-term clinical outcomes were similar between both groups. The cumulative survival rate was 96.1% in the CON-TKA group and 96.8% in the NAV-TKA group, with no difference between the groups (P = .962).

CONCLUSION

NAV-TKA showed fewer outliers in the HKA angle for severe preoperative varus deformity compared with CON-TKA. The long-term clinical outcomes and survival rates were similar between the 2 techniques. A survival rate of more than 96% was observed in both groups.

STUDY DESIGN

Level III, retrospective comparative study.

Restoration of the Joint Line Configuration Reproduces Native Mid-Flexion Biomechanics after Total Knee Arthroplasty: A Matched-Pair Cadaveric Study

Background: Recent evidence supports that restoration of the pre-arthritic condition via total knee arthroplasty (TKA) is associated with improved post-TKA performance and patient satisfaction. However, whether the restored pre-arthritic joint line simulates the native mid-flexion biomechanics remains unclear. Objective: We performed a matched-pair cadaveric study to explore whether restoration of the joint line via kinematically aligned (KA) TKA reproduced native knee biomechanics more accurately than the altered joint line associated with mechanically aligned (MA) TKA. Methods: Sixteen fresh-frozen cadaveric knees (eight pairs) were affixed onto a customized knee-squatting simulator for measurement of femoral rollback and medial collateral ligament (MCL) strain during mid-flexion. One knee from each cadaver was randomly designated to the KA TKA group (with the joint line restored to the pre-arthritic condition) and the other to the MA TKA group (with the joint line perpendicular to the mechanical axis). Optical markers were attached to all knees and rollback was analyzed using motion capture cameras. A video extensometer measured real-time variations in MCL strain. The kinematics and MCL strain prior to and following TKA were measured for all specimens. Results: KA TKA was better for restoring the knee kinematics to the native condition than MA TKA. The mid-flexion femoral rollback and axial rotation after KA TKA were consistently comparable to those of the native knee. Meanwhile, those of MA TKA were similar only at ≤40° of flexion. Furthermore, KA TKA better restored the mid-flexion MCL strain to that of the native knee than MA TKA. Over the entire mid-flexion range, the MCL strain of KA TKA and native knees were similar, while the strains of MA TKA knees were more than twice those of native knees at >20° of flexion. Conclusions: The restored joint line after KA TKA effectively reproduced the native mid-flexion rollback and MCL strain, whereas the altered joint line after MA TKA did not. Our findings may explain why patients who undergo KA TKA experience superior outcomes and more natural knee sensations during daily activities than those treated via MA TKA.

Preoperative Medial Tightness and Narrow Medial Joint Space Are Predictive Factors for Lower Extremity Alignment Change Toward Varus After Opening-Wedge High Tibial Osteotomy

Background:

Time-dependent changes in lower extremity alignment after an opening-wedge high tibial osteotomy (OWHTO) have been poorly investigated. Moreover, few studies have investigated risk factors of postoperative alignment change.

Purposes:

To investigate time-dependent alignment changes and identify predictive factors for postoperative alignment change after OWHTO.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

This study included patients who underwent OWHTO between March 2010 and September 2018. A total of 142 knees with a mean follow-up of 42 months were included and classified as the change group when the amount of hip-knee-ankle (HKA) angle change was >1°; if otherwise, then as the no-change group. HKA angle was obtained at 6 time points: preoperatively and at 3 months, 6 months, 1 year, 2 years, and final follow-up postoperatively. Multiple regression analysis was performed to identify the factors that were correlated with the changes in the HKA angle from 3 months to the final follow-up.

Results:

Among the 142 knees, 59 (42%) were included in the change group. The overall postoperative HKA angles progressed serially toward varus after OWHTO. The mean angles of the 6 time points were 8.5°, –3.7°, –3.6°, –3.3°, –3.1°, and –2.7°, respectively. The mean HKA angles of the change and no-change groups were 9.1°, –4.3°, –3.4°, –2.8°, –2.0°, and –1.4° and 8.1°, –3.3°, –3.8°, –3.6°, –3.8°, and –3.7°, respectively. Greater change in the HKA angle was predicted by preoperatively greater valgus stress joint line convergence angles and less medial joint space width.

Conclusion:

Of the cases of OWHTO, 42% showed correction loss of >1° at a mean follow-up of 42 months. The overall postoperative HKA angles progressed serially to varus angles after OWHTO. Preoperative greater valgus stress joint line convergence angles and less medial joint space width were predictive factors for greater change in alignment toward varus after OWHTO.

Avoiding Overcorrection to Increase Patient Satisfaction After Open Wedge High Tibial Osteotomy

BACKGROUND

Achieving the postoperative mechanical axis passing through 62.5% of the tibial plateau is considered successful osteotomy surgery. Despite precise preoperative planning and surgical techniques, some procedures result in under- or overcorrection. Few studies have investigated the relationship between clinical outcomes and unintentional under- or overcorrection after open wedge high tibial osteotomy (OWHTO) using whole-leg standing radiographs.

PURPOSE

To investigate the relationship between postoperative alignment using whole-leg standing radiographs and clinical outcomes after OWHTO.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 89 knees (72 patients) that underwent OWHTO between October 2013 and September 2018 were included. Patients with postoperative weightbearing line (WBL) ratios within 57% to 67% were classified as appropriate correction (group A; 45 cases), whereas ratios <57% and >67% were classified as undercorrection (group U; 20 cases) and overcorrection (group O; 24 cases), respectively. The following patient-reported outcomes (PROs) were investigated: International Knee Documentation Committee (IKDC) subjective score, Kujala score, and Knee injury and Osteoarthritis Outcome Score (KOOS). The correlation between postoperative WBL and PROs was analyzed. PROs were compared among the 3 groups.

RESULTS

Regarding the correlation between postoperative WBL ratio and PROs, a larger postoperative WBL ratio was significantly correlated with a poor IKDC subjective score (P = .002), Kujala score (P = .009), and KOOS. Group O showed inferior postoperative PRO scores when compared with group A or U, whereas group U showed a similar result to group A (mean IKDC subjective scores: group U, 62.0; group A, 61.2; group O, 47.6; P = .004).

CONCLUSION

Overcorrection after OWHTO surgery correlated with inferior PROs; therefore, overcorrected alignment should be avoided for patient satisfaction. Knees with an undercorrected alignment showed clinical results similar to those with appropriate correction.