Patient-specific instrumentation improved three-dimensional accuracy in total knee arthroplasty: a comparative radiographic analysis of 1257 total knee arthroplasties

Functional knee phenotypes: A helpful classification tool for visualizing potential femoral varus in restricted kinematic alignment total knee arthroplasty in Japan

PURPOSE

Restricted kinematic alignment (rKA) is a modified technique of kinematically aligned total knee arthroplasty (TKA) within a safe alignment range for long-term implant survivorship. The purpose of this study was to clarify (1) the distribution of functional knee phenotypes in patients who underwent TKA in Japan and (2) whether the application of this classification results in anatomically neutral alignment after rKA TKA.

METHODS

Overall, 114 TKA surgeries (mechanical alignment [MA]: 49; rKA: 65) were performed. The joint line orientation angle (JLOA), hip-knee-ankle angle (HKA), femoral mechanical angle (FMA) and tibial mechanical angle (TMA) were obtained. The knees were categorized using a functional knee phenotype classification. Clinical evaluations, including the Knee Injury and Osteoarthritis Outcome, 12-question Forgotten Joint and Oxford Knee Scores, were performed 3 years postoperatively. Between-group comparisons were made.

RESULTS

The most common preoperative functional knee phenotype was VARHKA 3° + NEUFMA 0° + VARTMA 3° (11.4%). In the preoperative population, 51 knees (44.7%) had VARFMA  ≥ 3°. Postoperatively, the most common functional knee phenotype was NEUHKA 0° + VARFMA 3° + VALTMA 3° (14 knees, 28.6%) in the MA and NEUHKA 0° + NEUFMA 0° + NEUTMA 0° in the rKA group. The percentage of postoperative JLOA within ±3° from the floor was 27% and 72% in the MA and rKA groups, respectively (p < 0.001). The functional knee phenotype after rKA TKA was neutrally reproduced, and the joint line was more parallel to the ground in the standing position than that of MA. Between-group differences in clinical outcomes were not significant.

CONCLUSION

The application of functional knee phenotyping to knee osteoarthritis in Japan suggested the presence of racial morphological characteristics. This classification could help better visualize potential femoral varus, contributing to protocol deviation in applying restricted KA TKA.

LEVEL OF EVIDENCE

Level IV.

Ipsilateral Concurrent Knee Arthroplasty and Tibial Osteotomy with 3D-Printed Patient-Specific Instrumentation: A Case Report

CASE

A 70-year-old woman presented with knee pain and instability and was diagnosed with advanced knee osteoarthritis and bifocal tibial deformities. The complexity of the case challenged our team to perform a significant sagittal correction (>60°) and restore her ability to walk independently. We performed ipsilateral total knee arthroplasty and anterior closed wedge tibial osteotomy using virtual planning and 3D-printed patient-specific instrumentation.

CONCLUSION

Using 2 separate 3D-printed patient-specific cutting guides for this patient with a complex deformity and managing the whole planning process in close collaboration between the surgeons and engineers resulted in a satisfactory postoperative outcome, optimal implant positioning and leg alignment, and minimal soft-tissue damage.

Closed-leg standing long leg radiographs can be a useful tool to assess whether the joint line is parallel to the ground in restricted kinematic alignment total knee arthroplasty

PURPOSE

Restricted kinematic alignment (rKA) is a modified technique of kinematic alignment (KA) total knee arthroplasty (TKA) for patients with an outlier or atypical knee anatomy, striving to preserve the native knee joint line parallel to the ground in a bipedal stance. This study aimed to evaluate the accuracy of rKA TKA with a computed tomography (CT)-based patient-specific instrument (PSI) to achieve the preoperative plan with the joint line parallel to the ground level.

METHODS

Using a CT-based PSI, 74 closed-leg standing long-leg radiographs were obtained before and after rKA TKA. The hip-knee-ankle angle (HKA), joint line orientation angle (JLOA), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA) were measured. Bone resection accuracy was evaluated by postoperative HKA deviations from the planned alignment and joint line by postoperative JLOA deviations from the ground level.

RESULTS

The mean postoperative JLOA and HKA were 2.1° valgus (range, standard deviation: 6.0° valgus to 3.0° varus, 2.0) and 2.6° varus (3.5° valgus to 12.5° varus, 3.2), respectively. Postoperative JLOA and HKA were within ± 3° of the planned alignment for 69% and 86% of cases, respectively.

CONCLUSIONS

Despite a static verification, we clarified how the joint line after rKA TKA was reproduced in the closed-leg long leg radiographs to mimic the limb position during gait. However, this imaging method is not well-established, and lack of long-term survivorship and the relationship between joint line inclination and clinical outcomes represented limitations of this study.

LEVEL OF EVIDENCE

Level IV.

Research Advances in the Application of AI for Preoperative Measurements in Total Knee Arthroplasty

Total knee arthroplasty (TKA) is widely used in clinical practice as an effective treatment for end-stage knee joint lesions. It can effectively correct joint deformities, relieve painful symptoms, and improve joint function. The reconstruction of lower extremity joint lines and soft tissue balance are important factors related to the durability of the implant; therefore, it is especially important to measure the joint lines and associated angles before TKA. In this article, we review the technological progress in the preoperative measurement of TKA.

Trends in Computer-Assisted Surgery for Total Knee Arthroplasty in Germany: An Analysis Based on the Operative Procedure Classification System between 2010 to 2021

Alignment strategies for primary total knee arthroplasty (TKA) have changed significantly over time with a shift towards a more individualized alignment goal. At the same time, computer-assisted surgery (CAS) has gained interest for intraoperative control and accuracy in implant positioning and limb alignment. Despite the often discussed benefits and drawbacks of robotics and navigation for TKA, the routine use of these new devices on a day-to-day basis remains obscure. Therefore, nationwide hospital billing data based on the Operation Procedure Classification System (OPS) were retrieved from the Federal Statistical Office of Germany for the period from 2010 to 2021. OPS codes for primary total knee arthroplasty (OPS code: 5-822*) were further analyzed regarding the usage of computer navigation (additional OPS code: 5-988) or robotic devices (additional OPS code: 5-987). Gender and age at the time of surgery were also assessed. The results show a total of 2,226,559 primary TKAs were implanted between 2010 and 2021, of which 2,044,914 were performed conventionally (91.84% of all TKAs). A total of 170,276 TKAs were performed using navigation technique (7.65% of all TKAs) and another 11,369 TKAs were performed using robotics (0.51% of all TKAs). For the period from 2018 to 2021, a substantial increase in robot-assisted TKA (R-TKA) was observed, with an average increase rate of 84.74% per year, while the number of navigated TKAs declined (-3.67% per year). Computer-assisted surgery, and particularly robotics for TKA, are seeing growing popularity and stepwise translation into routine clinical use in Germany, with a steep increase rate of more than 80% per year since 2018. Nevertheless, the majority of TKAs are still performed using manual instrumentation, rendering conventional TKA the currently unchanged gold standard.

Accuracy of a Three-Dimensional (3D)-Printed Patient-Specific (PS) Femoral Osteotomy Guide: A Computed Tomography (CT) Study

Femoral neck osteotomy creates a critical anatomical landmark for surgeons performing primary Total Hip Arthroplasty (THA); it affects the final height and position of the femoral component. Patient Specific Instrumentation (PSI) has been developed to guide the osteotomy. We aimed to assess the accuracy of a patient-specific (PS) femoral osteotomy guide in primary THA using three-dimensional (3D) computed tomography (CT) analysis. We included pre- and post-operative CT data of 103 THAs. All patients underwent 3D planning to define the optimal femoral neck osteotomy level. Our primary objective was to quantify the discrepancy between the achieved and planned osteotomy level; our secondary objective was to evaluate the clinical outcome. The median (Interquartile Range—IQR) discrepancy between the achieved and planned osteotomy level was 0.3 mm (−1 mm to 2 mm). We found a strong positive correlation between the planned and achieved osteotomy level (R2 = 0.9, p < 0.001). A satisfactory clinical outcome was recorded. Our findings suggest that surgeons can use 3D-printed PS guides to achieve a femoral neck osteotomy with a high level of accuracy to the plan.

Patient-specific instrumentation for total knee arthroplasty improves reproducibility in the planned rotational positioning of the tibial component

Background

The purpose of this study was to evaluate the reproducibility of planned component positioning including tibial rotational alignment in patient-specific instrumentation (PSI) for total knee arthroplasty (TKA).

Methods

A total of 100 knees of 100 patients underwent TKA using PSI (n = 50) or the conventional method (n = 50). Full-length anteroposterior radiographs of the lower limb were taken in the standing position, and the coronal alignments of the femoral and tibial components were measured. Computed tomography (CT) images of the lower limb were obtained preoperatively and postoperatively, and the rotational alignments of the femoral and tibial components were measured. The difference from the preoperative planning in tibial rotational alignment was measured using three-dimensionally merged pre- and postoperative images. The mean values and rates of outliers in each measurement were compared between the PSI group and the conventional group.

Results

There were no significant differences in coronal alignment of the femoral and tibial components and rotational alignment of the femoral component between the two groups. With respect to rotational alignment of the tibial component from the preoperatively planned reference axis, the PSI group showed a lower rate of outliers (internal rotation > 10°) than the conventional group (p < 0.05).

Conclusions

This study demonstrated that the difference from the preoperative planning in tibial rotational positioning was accurately evaluated using novel three-dimensional measurement method, and PSI could reduce outliers in rotational alignment of the tibial component (internal rotation > 10°). PSI is a useful technique for improving the reproducibility of the planned tibial rotational positioning in TKA.

A new robotically assisted technique can improve outcomes of total knee arthroplasty comparing to an imageless navigation system

BACKGROUND

Robotic assisted total knee arthroplasty (RTKA) has shown improved knee alignment and reduced radiographic outliers. However, there remains debate on functional outcomes and patient-reported outcomes (PROMs). This study compares the 1-year clinical outcomes of a new imageless robotically assisted technique (ROSA Knee System, Zimmer Biomet, Warsaw, IN) with an imageless navigated procedure (NTKA, iAssist Knee, Zimmer, Warsaw, IN).

METHODS

The study is a retrospective analysis of prospectively collected data that compared the functional outcomes and PROMs of 50 imageless RTKA with 47 imageless NTKA at 1-year follow-up. Baseline characteristics, intraoperative and postoperative information were collected including complications, revisions, Knee Society Score (KSS), Knee injury and Osteoarthritis Outcome Score (KOOS) score, and Forgotten Joint Score (FJS-12). Radiographic analysis of preoperative and postoperative images evaluating hip-knee-ankle (HKA) angle was performed.

RESULTS

There was no difference regarding baseline characteristics between the groups. Mean operative time was significantly longer in the RTKA group (122 min vs. 97 min; p < 0.0001). Significant differences were reported for the "Pain" (85 [RTKA] vs 79.1 [NTKA]; p = 0.0283) subsection of the KOOS score. In addition, RTKA was associated with higher maximum range of motion (119.4° vs. 107.1°; p < 0.0001) and better mean improvement of the arc of motion by 11.67° (23.02° vs. 11.36°; p < 0.0001). No significant differences were noted for other subsections of KOOS, KSS, FJS-12, complications, or limb alignment at 1-year follow-up.

CONCLUSIONS

Imageless RTKA was associated with longer surgical time, better pain perception and improved ROM at 12-month follow-up compared with NTKA. No significant differences were reported on other PROMs, complication rates and radiographic outcomes.

LEVEL OF EVIDENCE

III.

Patient-specific instrumentation makes sense in total knee arthroplasty

INTRODUCTION

Patient-specific instrumentation (PSI) for total knee arthroplasty (TKA) surgery was initially developed to increase accuracy. The potential PSI benefits have expanded in the last decade, and other advantages have been published. However, different authors are critical of PSI and argue that the advantages are not such and do not compensate for the extra cost. This article aims to describe the recently published advantages and disadvantages of PSI.

AREAS COVERED

Narrative description of the latest publications related to PSI in accuracy, clinical and functional outcomes, operative time, efficiency, and other benefits.

EXPERT COMMENTARY

We have published high accuracy of the system, with a not clinically relevant loss of accuracy, significantly higher precision with PSI than with conventional instruments, and a high percentage of cases in the optimal range and similar to that obtained with computer-assisted navigation, greater imprecision for tibial slope, a significant blood loss reduction, and time consumption, an acceptable and non-significant increase in the cost per procedure and no difference in complications during hospital admission and at 90 days. We think that PSI will not follow the Scott Parabola and that it will continue to be a valuable type of device in some instances of TKA surgery.

Surgeon Dominated Design Can Improve the Accuracy of Patient-Specific Instruments in Kinematically Aligned TKA

Precise bone resection is mandatory for kinematically aligned total knee arthroplasty (KA-TKA). This study is to investigate whether surgeon-dominated design can alter the accuracy of patient-specific instrumentation (PSI) in KA-TKA compared with the engineer design. A total of 24 patients (24 knees) who underwent KA-TKA in our institution were assigned to an engineer design group (10 knees) and surgeon design group (14 knees) chronologically. A novel portable medical-engineer interactive application can greatly enhance the surgeon’s participation in PSI design. The bone resection discrepancies were used to evaluate the accuracy of PSI in bone resection. The overall discrepancy of bone resection was reduced by surgeon-designed PSI compared to engineer-designed PSI by 0.33 mm. Surgeon-designed PSI seems to reduce the outliers in terms of relative discrepancies in bone resection as well, but it does not reach statistical significance. Moreover, surgeon-designed PSI could significantly improve the accuracy of PSI in the restoration of the joint line in terms of medial proximal tibial angle and mechanical lateral distal femoral angle. This study indicates that the dominance of surgeons in both PSI design and subsequent surgical operation should be emphasized in efforts to improve the accuracy of PSI.

Extreme Hinge Axis Positions Are Necessary to Achieve Posterior Tibial Slope Reduction With Small Coronal-Plane Corrections in Medial Opening Wedge High Tibial Osteotomy

Background:

Both coronal- and sagittal-plane knee malalignment can increase the risk of ligamentous injuries and the progression of degenerative joint disease. High tibial osteotomy can achieve multiplanar correction, but determining the precise hinge axis position for osteotomy is technically challenging.

Purpose:

To create computed tomography (CT)–based patient-specific models to identify the ideal hinge axis position angle and the amount of maximum opening in medial opening wedge high tibial osteotomy (MOWHTO) required to achieve the desired multiplanar correction.

Study Design:

Descriptive laboratory study.

Methods:

A total of 10 patients with lower extremity CT scans were included. Baseline measurements including the mechanical tibiofemoral angle (mTFA) and the posterior tibial slope (PTS) were calculated. Virtual osteotomy was performed to achieve (1) a specified degree of PTS correction and (2) a planned degree of mTFA correction. The mean hinge axis position angle for MOWHTO to maintain an anatomic PTS (no slope correction) was 102.6° ± 8.3° relative to the posterior condylar axis (PCA). Using this as the baseline correction, the resultant hinge axis position and maximum opening were then calculated for each subsequent osteotomy procedure.

Results:

For 5.0° of mTFA correction, the hinge axis position was decreased by 6.8°, and the maximum opening was increased by 0.49 mm for every 1° of PTS correction. For 10.0° of mTFA correction, the hinge axis position was decreased by 5.2°, and the maximum opening was increased by 0.37 mm for every 1° of PTS correction. There was a significant difference in the trend-line slopes for hinge axis position versus PTS correction (P = .013) and a significant difference in the trend-line intercepts for maximum opening versus PTS correction (P < .0001).

Conclusion:

The mean hinge axis position for slope-neutral osteotomy was 102.6° ± 8.3° relative to the PCA. For smaller corrections in the coronal plane, more extreme hinge axis positions were necessary to achieve higher magnitudes of PTS reduction.

Clinical Relevance:

Extreme hinge axis positions are technically challenging and can lead to unstable osteotomy. Patient-specific instrumentation may allow for precise correction to be more readily achieved.

Patient-Specific Instrumentation Accuracy Evaluated with 3D Virtual Models

There have been remarkable advances in knee replacement surgery over the last few decades. One of the concerns continues to be the accuracy in achieving the desired alignment. Patient-specific instrumentation (PSI) was developed to increase component placement accuracy, but the available evidence is not conclusive. Our study aimed to determine a PSI system’s three-dimensional accuracy on 3D virtual models obtained by post-operative computed tomography. We compared the angular placement values of 35 total knee arthroplasties (TKAs) operated within a year obtained with the planned ones, and we analyzed the possible relationships between alignment and patient-reported outcomes. The mean (SD) discrepancies measured by two experienced engineers to the planned values observed were 1.64° (1.3°) for the hip–knee–ankle angle, 1.45° (1.06°) for the supplementary angle of the femoral lateral distal angle, 1.44° (0.97°) for the proximal medial tibial angle, 2.28° (1.78°) for tibial slope, 0.64° (1.09°) for femoral sagittal flexion, and 1.42° (1.06°) for femoral rotation. Neither variables related to post-operative alignment nor the proportion of change between pre-and post-operative alignment influenced the patient-reported outcomes. The evaluated PSI system’s three-dimensional alignment analysis showed a statistically significant difference between the angular values planned and those obtained. However, we did not find a relevant effect size, and this slight discrepancy did not impact the clinical outcome.

Complex Primary Total Knee Arthroplasty in a Patient with Achondroplasia, Osteoarthritis, and Severe Coronal Instability

Genu varum in patients with achondroplasia is common and is often exacerbated by the associated generalized ligamentous laxity. Despite this, development of knee osteoarthritis is rare. There are only a few previously published case reports of total knee arthroplasty in this population. We present 2-year follow-up of a patient with achondroplasia who underwent staged bilateral primary total knee arthroplasties using hinged components. Technical considerations and careful preoperative planning are required in patients with achondroplasia given their small skeletal stature, metaphyseal deformities, and ligamentous laxity.

[Clinical application of distal femoral patient-specific cutting guide based on knee CT and full-length X-ray film of lower extremities]

OBJECTIVE

To discuss the feasibility and accuracy of distal femoral patient-specific cutting guide in total knee arthroplasty (TKA) based on knee CT and full-length X-ray film of lower extremities.

METHODS

Between July 2016 and February 2017, 20 patients with severe knee joint osteoarthritis planned to undergo primary TKA were selected as the research object. There were 9 males and 11 females; aged 53-84 years, with an average of 69.4 years. The body mass index was 22.1-31.0 kg/m 2, with an average of 24.8 kg/m 2. The preoperative range of motion (ROM) of the knee joint was (103.0±19.4)°, the pain visual analogue scale (VAS) score was 5.4±1.3, and the American Hospital of Special Surgery (HSS) score was 58.1±11.3. Before operation, a three-dimensional model of the knee joint was constructed based on the full-length X-ray film of lower extremities and CT of the knee joint. The distal femoral patient-specific cutting guide was designed and fabricated, and the thickness of the distal femoral osteotomy was determined by digital simulation. The thickness of the internal and external condyle of the distal femur osteotomy before operation and the actual thickness of the intraoperative osteotomy were compared. The intraoperative blood loss, postoperative drainage loss, and hidden blood loss were recorded. The ROM of knee joint, VAS score, and HSS score at 3 months after operation were recorded to evaluate effectiveness. The position of the coronal and sagittal plane of the distal femoral prosthesis were assessed by comparing the femoral mechanical-anatomical angle (FMAA), anatomical lateral distal femoral angle (aLDFA), mechanical femoral tibial angle (mFTA), distal femoral flexion angle (DFFA), femoral prosthesis flexion angle (FPFA), anatomical lateral femoral component angle (aLFC), and the angle of the femoral component and femoral shaft (α angle) between pre- and post-operation.

RESULTS

TKA was successfully completed with the aid of the distal femoral patient-specific cutting guide. There was no significant difference between the thickness of the internal and lateral condyle of the distal femur osteotomy before operation and the actual thickness of the intraoperative osteotomy ( P>0.05). All patients were followed up 3 months. All incisions healed by first intention, and there was no complications such as periarticular infection and deep vein thrombosis. Except for 1 patient who was not treated with tranexamic acid, the intraoperative blood loss of the rest 19 patients ranged from 30 to 150 mL, with an average of 73.2 mL; the postoperative drainage loss ranged from 20 to 500 mL, with an average of 154.5 mL; and the hidden blood loss ranged from 169.2 to 1 400.0 mL, with an average of 643.8 mL. At 3 months after operation, the ROM of the knee was (111.5±11.5)°, and there was no significant difference when compared with the preoperative one ( t=-1.962, P=0.065). The VAS score was 2.4±0.9 and HSS score was 88.2±7.5, showing significant differences when compared with the preoperative ones ( t=7.248, P=0.000; t=-11.442, P=0.000). Compared with the preoperative measurements, there was a significant difference in mFTA ( P<0.05), and there was no significant difference in aLDFA, FMAA, or DFFA; compared with the preoperative plan, there was no significant difference in FPFA, aLFC, or α angle ( P>0.05).

CONCLUSION

The use of distal femoral patient-specific cutting guide based on knee CT and full-length X-ray film of lower extremity can achieve precise osteotomy, improve coronal and sagittal limb alignment, reduce intraoperative blood loss, and obtain satisfactory short-term effectiveness.