Skip to main content
Download PDF
  • Research article
  • Open access
  • Published:

Enhancing total knee arthroplasty outcomes: the role of individualized femoral sagittal alignment in robotic-assisted surgery - A randomized controlled trial

Journal of Orthopaedic Surgery and Research volume 19, Article number: 558 (2024) Cite this article

Abstract

Background

Optimal sagittal alignment of the femoral prosthesis is critical to the success of total knee arthroplasty (TKA). While robotic-assisted TKA can improve alignment accuracy, the efficacy of default femoral alignment versus individualized alignment remains under scrutiny. This study aimed to compare the differences in prosthetic alignment, anatomical restoration, and clinical outcomes between individualized femoral sagittal alignment and default sagittal alignment in robotic-assisted TKA.

Methods

In a prospective randomised controlled trial, 113 patients (120 knees) underwent robotic-assisted TKA were divided into two groups: 61 with individualized femoral flexion (individualized alignment group) and 59 with default 3–5° flexion (default alignment group). The individualized alignment was based on the distal femoral sagittal anteverted angle (DFSAA), defined as the angle between the mechanical and distal anatomical axes of the femur. The radiographic and clinical outcomes were compared.

Results

Despite similar postoperative femoral flexion angles between groups (P = 0.748), the individualized alignment group exhibited significantly lower incidences of femoral prosthesis extension and higher rates of optimal 0–3° prosthesis flexion (9.8% vs. 27.1%, P = 0.014,78.7% vs. 55.9%, p = 0.008, respectively). The individualized alignment group also demonstrated more favourable changes in sagittal anatomy, with higher maintenance of postoperative anterior femoral offset within 1 mm (54.1% vs. 33.9%, P = 0.026) and posterior condylar offset within 1 mm and 2 mm (44.3% vs. 25.4%, p = 0.031,73.8% vs. 50.8%, p = 0.010, respectively). Although slight improvement in the Hospital for Special Surgery Knee Score (HSS) at three months was observed (P = 0.045), it did not reach a minimal clinically important difference.

Conclusion

Individualized tailoring of femoral sagittal alignment in robotic-assisted total knee arthroplasty (TKA) enhances prosthetic alignment and anatomical restoration, suggesting potential improvements in postoperative outcomes.

Introduction

The sagittal alignment of the femoral prosthesis is crucial for both function and the long-term survival of total knee arthroplasty (TKA) [1,2,3]. Femoral prosthesis extension increases patellofemoral forces, potentially leading to postoperative anterior knee pain [4]. Hyperflexion of the femoral prosthesis, conversely, significantly heightens the risk of subsequent failure [5]. Therefore, most surgeons recommend a femoral prosthesis with mild flexion of 0°-3° [1, 6, 7]. Femoral flexion varies greatly in conventional TKA [8], but robotic-assisted TKA offers a means to precisely achieve the desired sagittal alignment.

In robotic-assisted TKA, the femoral mechanical axis (from the femoral head centre to the intercondylar notch apex) serves as a common reference for sagittal alignment, however, this may not align with the postoperative anatomical assessment, which utilizes the femur’s distal anatomical axis [9,10,11,12]. The distal femoral sagittal anteverted angle (DFSAA), the angle between the mechanical and distal anatomical axes in the sagittal plane, reconciles these differences and serves as a sagittal alignment reference [13, 14]. Notably, the DFSAA varies considerably amongst individuals due to differences in femoral morphology and ethnicity, with values ranging from 1.72° extension to 8.5° flexion within the general population [15, 16], challenging the one-size-fits-all approach of setting femoral flexion between 3–5° [17, 18]. Emerging evidence suggests that default femoral flexion significantly raises the incidence of femoral prosthesis extension and notching [9, 17, 19, 20]. On the contrary, aligning femoral flexion to account for individual anatomy can optimize joint gap balance and sagittal diameter restoration [21].

The restoration of femoral anatomy, including anterior femoral offset (AFO) and posterior condylar offset (PCO), is crucial for replicating native joint mechanics and enhancing patient satisfaction [22,23,24]. Although the relationship between femoral flexion and changes in AFO and PCO is established [4], the efficacy of individualized sagittal alignment in bettering the restoration of femoral anatomy and improving patient outcomes warrants further investigation.

The prospective randomized controlled trial aimed to compare individualized and default femoral sagittal alignment in robotic-assisted TKA. The primary objective was to assess the distribution of DFSAA in patients with knee osteoarthritis and explore potential postoperative sagittal alignment differences between individualized and default alignment groups. The secondary objective was to compare sagittal anatomy restoration and short-term postoperative clinical outcomes between the two groups.

Methods and materials

This study represents a partial data analysis from a prospective randomised controlled trial conducted on robotic-assisted TKA. Ethical approval was obtained from the Ethics Committee of the First Affiliated Hospital of Chongqing Medical University (Approval No. 2022 − 176), and the trial was registered with the Chinese Clinical Trial Register (Registration number. ChiCTR2200063223). Informed consent was obtained from all participants. Enrolment spanned from November 2022 to June 2023, involving patients scheduled for TKA. Inclusion criteria included age 21–80 years, suitability for surgery, ability to attend follow-up visits and no vascular or neurological injury. Exclusion criteria encompassed previous hip arthroplasty on the same side, significant deformities (> 15° valgus or varus), knee infection, tumours, or ankylosing deformities of the hip or ankle.

A total of 155 patients were initially assessed, with 121 qualifying for the study and were subsequently randomly grouped using a random number table method. The patient flow is detailed in Fig. 1. Finally, data from 58 patients (61 TKAs) in the individualized alignment group and 55 patients (59 TKAs) in the default alignment group were subjected to analysis. Baseline characteristics, including demographics, DFSAA measurements, and preoperative functional scores showed no significant difference between groups (Table 1).

Fig. 1
figure 1

Flow diagram showing recruitment and allocation of patients

Full size image
Table 1 Details of the patients in the study
Full size table

All patients underwent full-length CT scanning of both lower extremities (scanning protocol: 200 mA, 130KV, slice spacing of 0.6 mm), facilitating the bilateral assessment of DFSAA in all cases (comprising 211 femurs). Utilizing these scans, three-dimensional models of the femur were reconstructed by trained orthopaedic surgeons using Mimics 21.0 (Materialise, Leuven, Belgium). The surgical transepicondylar axis (sTEA) was defined as the line between the medial epicondylar sulcus and the lateral epicondylar prominence. The sagittal plane of the femur was defined as the plane through the centre of the femoral head and perpendicular to the sTEA (Fig. 2a). Additionally, the mechanical axis of the femur was defined as the line connecting the centre of the femoral head to the apex of the intercondylar notch. The anatomical axis of the femur was defined as the line connecting the geometric centres of the femoral medullary cavity at 5 cm and 10 cm from the knee joint line. Subsequently, the femoral mechanical and anatomical axes were projected onto its sagittal plane to measure their intersecting angle, known as the DFSAA (Fig. 2b).

Fig. 2
figure 2

Establishment of the coordinate system and definition of the femoral axis and angle. Figure 2a. Establishment of the coordinate system and projection plane. The sagittal plane was defined as the plane perpendicular to the surgical transepicondylar axis and passing through the centre of the femoral head. Figure 2b. Definition of the femoral axis and angle. The femoral mechanical axis is determined by connecting the centre of the femoral head to the apex of the intercondylar notch. The anatomical axis of the femur is determined by connecting the midpoint of the femoral medullary cavity. Both the femoral mechanical axis and the distal femoral anatomical axis are projected onto the femur’s sagittal plane. The angle formed between these two axes is identified as the distal femoral sagittal anteverted angle (DFSAA). If the femoral mechanical axis was extended relative to the distal femoral anatomical axis, the value of DFSAA was assigned a positive value. DFSAA, distal femoral sagittal anteverted angle

Full size image

All operations were performed by a unified team led by a senior orthopaedic surgeon (W.H) using the KUNWU-TKA (Yuanhua Intelligent Technology, Shenzhen, China). This system, proven effective in previous studies [25, 26], employs functional alignment with a fixed-platform posterior cruciate ligament sacrificing prosthesis (Unique knee, Zhengtian, Tianjin, China). Preoperative plans were based on Shatrov et al.‘s procedure [27]. Prosthesis size was determined based on matching the prosthesis model to the bone model, avoiding anterior notching and patellofemoral joint overfilling. Prosthesis adjustments in the coronal plane were made according to the lateral angle of the distal femur and medial angle of the proximal tibia, targeting a final limb alignment between 3° valgus and 6° varus. In the axial plane, the femoral prosthesis was aligned parallel to the sTEA with up to a 3° adjustment, while the tibial prosthesis followed the Akagi line. In the sagittal plane, the individualized alignment group matched the distal anatomical axis and allowed 0–3° of flexion according to the DFSAA; the default alignment group set 3–5° of flexion relative to the mechanical axis, and the tibial prosthesis was set to match the patient’s native posterior tibial slope.

Operations were conducted using a medial parapatellar approach with a tourniquet. Adjustments occurred at 0° of extension and 90° of flexion to balance the medial-lateral knee gap. The individualized alignment group aligned with the distal anatomical axis, permitting 0–3° of flexion, while the default alignment group adjusted femoral flexion as directed by the system prompts to prevent anterior notching. Appropriate flexion and extension gaps were obtained by fine-tuning the position of the femoral and tibial prostheses, and subsequent osteotomies were performed according to the intraoperative plan without the need to loosen the soft tissues. Postoperatively, all patients received antibiotics and anticoagulation therapy, without drain placement, and began passive and active knee exercises immediately.

Anterior-posterior and lateral knee radiographic imaging were performed pre-surgery and during the final postoperative evaluation. Following the technique described by Pierson et al [28], two authors (DHW and KL) independently evaluated, basing their analyses on the average of both sets of measurements. The femoral flexion angle was defined as the angle between the anatomic axis of the distal femur and the anterior flange of the femoral prosthesis, minus a 3° adjustment for the prosthesis’s design-induced tilt (Fig. 3a). The AFO was defined as the distance between the anterior edge of the femoral cortex and the anterior aspect of the femoral condyle, corrected for magnification differences using a scale and standardized to a radiographic distance of 1.5 m. The change in AFO was calculated as the preoperative AFO minus the postoperative AFO. Similar measurements were made for PCO as shown in Fig. 3b and c. As previous studies indicate the cartilage thickness of the distal femur averages 2.0 ± 0.4 mm [29], the cartilage thickness was standardized at 2 mm for all patients.

Fig. 3
figure 3

Radiographic analysis. Figure 3a Measurement of femoral prosthesis flexion angle. According to the design of the prosthesis, the femoral prosthesis flexion angle = β -3°. (+): flexion, (–): extension. Figure 3b and c Measurement of AFO and PCO. The preoperative(b) and postoperative(c) measurements on lateral radiographs. A cartilage thickness of 2 mm was considered when evaluating the preoperative AFO and PCO. AFO anterior femoral offset; PCO posterior condylar offset

Full size image

Clinical outcomes were evaluated preoperatively, 6 weeks and 3 months postoperatively by a trained orthopaedic surgeon using the Visual Analogue Scale (VAS) for pain, the Hospital for Special Surgery Knee Score (HSS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) for overall joint assessment. In order to comprehensively assess the postoperative knee range of motion (ROM) in both groups, ROM was collected at 6 weeks and 3 months postoperatively. Measurements were taken with the patients prone on a rigid bed, the knee extended to its maximum angle of flexion, and the angle between the longitudinal axis of the femur and the longitudinal axis of the tibia was measured in the sagittal plane.

Statistical analysis. Data analysis was performed using GraphPad Prism 9 version 9.4.0 (GraphPad Software, USA). Descriptive statistics were presented as mean ± standard deviation. The Kolmogorov-Smirnov test was employed to assess the normal distribution of data. Differences between groups were compared using the independent samples t-test. Count data were described as rates, and the chi-square test was used for comparisons between groups. p < 0.05 was considered statistically significant. With a power of 95%, α level of 0.05, and 95% confidence level, the number of subjects needed was calculated as 37 per group.

Results

The analysis of the 211 knees revealed the mean DFSAA was found to be 4.2° ± 1.7°, ranging from 0.7° to 8.7°. Notably, only 41.3% of cases fell within the traditionally targeted DFSAA range of 3° to 5° (Fig. 4).

Fig. 4
figure 4

The distribution of DFSAAs in study patients. n = 211 knees

Full size image

While the mean postoperative femoral flexion angles did not significantly differ between the Individualized and Default alignment groups (1.9 ± 1.7° vs. 1.6 ± 2.7°, p = 0.748), the Individualized alignment group presented a significantly lower incidence of femoral extension (9.8% vs. 27.1%, p = 0.014). Moreover, within the Individualized alignment group, there was a substantial increase in the occurrence of the femoral component within the desired mild flexion range of 0° to 3° (78.7% vs. 55.9%, p = 0.008), as detailed in Fig. 5.

Fig. 5
figure 5

The distribution of femoral prosthesis flexion angle between the two groups. *P < 0.05. ** P < 0.01

Full size image

Analysis of AFO and PCO showed no significant difference in preoperative values between the groups. Postoperatively, the Individualized alignment group achieved better AFO restoration, with 54.1% maintaining an offset within 1 mm of preoperative measurements, significantly higher than the Default alignment group’s 33.9% (p = 0.026). In terms of PCO, an improvement was also observed in the Individualized alignment group, where postoperative measurements within 1 mm and 2 mm of preoperative values were seen in 44.3% and 73.8% of patients, respectively, compared to 25.4% and 50.8% in the Default alignment group (p = 0.031 for 1 mm, p = 0.010 for 2 mm), as reported in Table 2.

Table 2 Comparison of offset between the two groups
Full size table

After 3 months, an analysis of functional outcomes revealed a marginal but statistically significant increase in the HSS in the Individualized alignment group in comparison to the Default alignment group (p = 0.045). This finding, though notable, did not achieve the threshold of a minimal clinically important difference [30]. The two groups did not exhibit significant differences in other clinical measures at the 6-week and 3-month follow-up points (Table 3). There was no significant difference in ROM between the individualized alignment group and the default alignment group at 6 weeks and 3 months postoperatively. At 6 weeks postoperatively, the mean ROM was 104.7 ± 7.4° in the individualized alignment group compared with 104.1 ± 8.2° in the default alignment group. At 3 months postoperatively, the ROMs were 118.2 ± 6.8° and 117.5 ± 7.5° in the two groups, respectively, p > 0.05.

Table 3 Comparison of clinical outcomes between the two groups
Full size table

Discussion

This study presents pioneering insights into the high variability of DFSAA in patients with knee osteoarthritis and underscores the potential advantages of individualized sagittal femoral alignment in robotic-assisted TKA. Alignment of femoral flexion to each patient’s unique anatomy, alignment with the femoral axis and anatomical restoration are markedly improved.

Recent advancements in robotic-assisted TKA have demonstrated improved accuracy in component placement and alignment. Studies have shown that individualized alignment strategies can lead to better anatomical and functional outcomes compared to conventional methods. For example, Mancino et al. and Rossi et al. highlighted the enhanced accuracy of robotic-arm knee arthroplasty systems, which significantly improve prosthetic alignment and patient outcomes [31, 32]. Similarly, studies by Rossi et al. and Mancino et al. have demonstrated that accounting for individual anatomical variations can optimize joint mechanics and reduce postoperative complications [33, 34].

The risks associated with extension of femoral prostheses in robotic-assisted TKA have received increasing attention [9]. Such risks can be mitigated by individualized alignment strategies during surgery. To counteract this issue and ensure alignment with the anatomic axis, distal femoral resection is typically executed at 3–5° of flexion [1, 17, 18]. The findings resonate with those reported by Chung et al., who observed a broad DFSAA range [15], and Hood et al., who noted a minority of healthy individuals conforming to the conventional 3°-5° DFSAA range [16]. This mirrors the observation that only 41.3% of osteoarthritis knees lay within this range, suggesting the necessity of individualized alignment adjustments to achieve more accurate reconstruction.

Given the sagittal alignment of the femoral prosthesis depends on the variable distal femoral anatomy, adjusting this alignment to match the distal femoral anatomy during computer-assisted TKA may be crucial for improved clinical outcomes. Roßkopf et al. found that intentional flexion of the femoral prosthesis during navigated TKA improved the restoration of the sagittal diameter and was critical in establishing flexion-extension balance [21]. Similarly, Kuriyama et al. reported that aligning the sagittal of the femoral prosthesis with the anatomical axis during navigated TKA enhanced bone-to-prosthesis matching [18]. Numerous studies have demonstrated that 0–3° flexion of the femoral prosthesis leads to improved postoperative function [35, 36]. The data from this study adds to this narrative by showcasing a higher frequency of femoral prosthesis alignments within the optimal mild flexion range when using individualized settings.

Alterations in AFO after TKA can influence the biomechanical integrity of the knee joint, potentially leading to complications such as patellar malalignment and anterior knee pain [37]. Postoperative changes in AFO are common in conventional TKA. Matz et al. reported that only 13.4% of 970 patients maintained an AFO change within 1 mm in postoperative lateral X-ray analysis [38]. Similarly, Chloe et al. identified femoral prosthesis extension leading to anterior femoral overfilling as a significant cause of postoperative anterior patellofemoral pain [4]. These findings suggest that individualized femoral alignment more effectively preserves AFO, thus potentially minimizing these postoperative challenges.

Similarly, restoring the PCO is crucial for promoting stability and range of motion after TKA. Matziolis et al. analyzed intraoperative data from 42 patients undergoing navigated TKA and found that variations in PCO exceeding 2 mm were associated with midflexion instability [39]. Van et al. analysed 98 cases of TKA and found that maintaining PCO resulted in improved postoperative flexion angles and functionality [36]. However, restoring the posterior femoral condylar anatomy remains challenging, even with the posterior reference technique [40]. In line with Popat et al., who championed the precision of robotic-assisted TKA for PCO [41], the data affirms that individualized alignment approaches can optimize PCO restoration and potentially enhance overall postoperative function.

Individualized sagittal alignment of the femur provides better restoration of the femoral anatomy, potentially due to the effects of sagittal osteotomies on prosthesis sizing [42]. Flexing the femoral prosthesis by a few degrees can effectively reduce its size while preventing an excessive increase in the flexion gap [21].

The significance of sagittal femoral alignment in enhancing postoperative functionality is well-supported in the literature. For instance, Nishitani et al. observed that patients with mildly flexed femoral prostheses achieved higher scores in functional assessments one year after TKA compared to those with extended or hyperflexed prostheses [6]. Similarly, Hassan et al., after a two-year follow-up, reported that femoral prosthesis flexion of 0–3° was associated with a knee that felt ‘always normal‘ [1]. Although the data indicate enhanced functionality with individualized alignment, as suggested by increased HSS scores, the observed differences did not reach the threshold of minimal clinically important differences after TKA. Despite the theoretical benefits of individualized alignment, the results did not demonstrate a significant improvement in postoperative ROM. This stands in contrast to Zhou et al.’s findings, where the ROM in the mildly flexed group was significantly better than that in the extended or hyperflexed groups after one year. This may indicate that the measurement of ROM in the early postoperative period fails to adequately reflect long-term functional recovery and the effectiveness of alignment strategies. Given these observations, subsequent long-term assessments are essential to more fully understand these effects.

However, it is crucial to acknowledge certain limitations. Firstly, the follow-up period duration of only 3 months, restricting the ability to evaluate sustained clinical outcomes consequent to individualized femoral alignment. Therefore, it is intended that prospective patient follow-ups continue, with plans to publish longer-term data in the future. Secondly, the use of lateral radiographs and standardization of 2 mm cartilage thickness for assessing the AFO and PCO may not fully capture cartilage thickness. Future studies need to measure cartilage thickness more accurately. Lastly, although employing a single knee design enhanced the study’s internal validity, it may limit the generalizability of the findings to other prosthesis designs.

Conclusion

In conclusion, the study demonstrates that robotic-assisted TKA employing individualized femoral sagittal alignment can significantly reduce the occurrence of femoral prosthesis extension. Furthermore, it markedly enhances the precision in postoperative prosthetic alignment and anatomical restoration. These findings suggest the utility of an individualized approach to femoral prosthesis alignment in TKA, which may have implications for refining surgical techniques and guiding future orthopaedic research.

Data availability

No datasets were generated or analysed during the current study.

Abbreviations

TKA:

Total knee arthroplasty

DFSAA:

Distal femoral sagittal anteverted angle

AFO:

Anterior femoral offset

PCO:

Posterior condylar offset

BMI:

Body Mass Index

VAS:

Visual Analogue Score

HSS:

Hospital for Special Surgery Knee Score

WOMAC:

Western Ontario and McMaster Universities Osteoarthritis Index

sTEA:

surgical transepicondylar axis

ROM:

range of motion

SD:

Standard deviation

References

  1. Farooq H, Deckard ER, Arnold NR, Meneghini RM. Machine learning algorithms identify optimal Sagittal component position in total knee arthroplasty. J Arthroplast. 2021;36(7):S242–9.

    Article  Google Scholar 

  2. Farooq H, Deckard ER, Carlson J, Ghattas N, Meneghini RM. Coronal and Sagittal Component Position in contemporary total knee arthroplasty: targeting native alignment optimizes clinical outcomes. J Arthroplasty. 2023;38(7 Suppl 2):S245–51.

    Article  PubMed  Google Scholar 

  3. Kim YH, Park JW, Kim JS, Park SD. The relationship between the survival of total knee arthroplasty and postoperative coronal, sagittal and rotational alignment of knee prosthesis. Int Orthop. 2014;38(2):379–85.

    Article  PubMed  Google Scholar 

  4. Scott CEH, Clement ND, Yapp LZ, MacDonald DJ, Patton JT, Burnett R. Association between femoral component Sagittal Positioning and anterior knee Pain in total knee arthroplasty: a 10-Year case-control follow-up study of a cruciate-retaining single-Radius Design. J bone Joint Surg Am Volume. 2019;101(17):1575–85.

    Article  Google Scholar 

  5. Nishitani K, Kuriyama S, Nakamura S, Song YD, Morita Y, Ito H, Matsuda S. Excessive flexed position of the femoral component causes abnormal kinematics and joint contact/ ligament forces in total knee arthroplasty. Sci Rep. 2023;13(1):6356.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  6. Nishitani K, Kuriyama S, Nakamura S, Umatani N, Ito H, Matsuda S. Excessive flexed position of the femoral component was associated with poor new Knee Society Score after total knee arthroplasty with the Bi-surface knee prosthesis. bone Joint J. 2020;102–b(6SuppleA):36–42.

    Article  PubMed  Google Scholar 

  7. Kang KT, Koh YG, Son J, Kwon OR, Park KK. Flexed femoral component improves kinematics and biomechanical effect in posterior stabilized total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2019;27(4):1174–81.

    Article  PubMed  Google Scholar 

  8. Koenen P, Ates DM, Pfeiffer TR, Bouillon B, Bathis H. Femoral flexion position is a highly variable factor in total knee arthroplasty: an analysis of 593 conventionally aligned total knee replacements. Knee Surg Sports Traumatol Arthrosc. 2020;28(4):1014–22.

    Article  PubMed  Google Scholar 

  9. An HM, Gu W, Nan SK, Liu Z, Li R, Chai W. Sagittal Alignment in total knee arthroplasty: are there any discrepancies between robotic-assisted and Manual Axis Orientation? J bone Joint Surg Am Volume. 2023;105(17):1338–43.

    Article  Google Scholar 

  10. Roche M. The MAKO robotic-arm knee arthroplasty system. Arch Orthop Trauma Surg. 2021;141(12):2043–7.

    Article  PubMed  Google Scholar 

  11. Ewald FC. The Knee Society total knee arthroplasty roentgenographic evaluation and scoring system. Clin Orthop Relat Res. 1989;248:9–12.

    Article  Google Scholar 

  12. An HM, Wen JX, Gu W, Chen JY, Chai W, Li R. Discrepancies in Sagittal Alignment of the lower extremity among different brands of robotic total knee Arthroplasty systems. J Arthroplasty 2024.

  13. Shah MR, Patel JP, Patel CR. Optimal flexion for the femoral component in TKR: a study of Angle between Mechanical Axis and Distal Anatomic Intramedullary Axis using 3D reconstructed CT scans in 407 osteoarthritic knees studied in India. Indian J Orthop. 2020;54(5):624–30.

    Article  PubMed  PubMed Central  Google Scholar 

  14. Ke S, Ran T, He Y, Lv M, Song X, Zhou Y, Xu Y, Wang M. Does patient-specific instrumentation increase the risk of notching in the anterior femoral cortex in total knee arthroplasty? A comparative prospective trial. Int Orthop. 2020;44(12):2603–11.

    Article  PubMed  Google Scholar 

  15. Chung BJ, Kang YG, Chang CB, Kim SJ, Kim TK. Differences between sagittal femoral mechanical and distal reference axes should be considered in navigated TKA. Clin Orthop Relat Res. 2009;467(9):2403–13.

    Article  PubMed  PubMed Central  Google Scholar 

  16. Hood B, Blum L, Holcombe SA, Wang SC, Urquhart AG, Goulet JA, Maratt JD. Variation in Optimal Sagittal Alignment of the femoral component in total knee arthroplasty. Orthopedics. 2017;40(2):102–6.

    Article  PubMed  Google Scholar 

  17. Lee SH, Cho YJ, Choi WK. Comparison of femoral sagittal axis between navigated total knee arthroplasty and conventional total knee arthroplasty in patients with knee osteoarthritis. Medicine. 2022;101(33):e30085.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  18. Kuriyama S, Hyakuna K, Inoue S, Kawai Y, Tamaki Y, Ito H, Matsuda S. Bone-femoral component interface gap after sagittal mechanical axis alignment is filled with new bone after cementless total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2018;26(5):1478–84.

    Article  PubMed  Google Scholar 

  19. Ko JH, Han CD, Shin KH, Nguku L, Yang IH, Lee WS, Kim KI, Park KK. Femur bowing could be a risk factor for implant flexion in conventional total knee arthroplasty and notching in navigated total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2016;24(8):2476–82.

    Article  PubMed  Google Scholar 

  20. Friedman RJ. Navigation in total knee arthroplasty: a Procedure whose time has not come: Commentary on an article by Young-Hoo Kim, MD, et al.: the clinical outcome of computer-navigated compared with conventional knee arthroplasty in the same patients. A prospective, randomized, Double-Blind, long-term study. J bone Joint Surg Am Volume. 2017;99(12):e64.

    Article  Google Scholar 

  21. Roßkopf J, Singh PK, Wolf P, Strauch M, Graichen H. Influence of intentional femoral component flexion in navigated TKA on gap balance and sagittal anatomy. Knee Surg Sports Traumatol Arthrosc. 2014;22(3):687–93.

    Article  PubMed  Google Scholar 

  22. Almaawi AM, Hutt JRB, Masse V, Lavigne M, Vendittoli PA. The impact of mechanical and restricted kinematic alignment on knee anatomy in total knee arthroplasty. J Arthroplasty. 2017;32(7):2133–40.

    Article  PubMed  Google Scholar 

  23. Geijsen GJ, Heesterbeek PJ, van Stralen G, Anderson PG, Wymenga AB. Do tibiofemoral contact point and posterior condylar offset influence outcome and range of motion in a mobile-bearing total knee arthroplasty? Knee Surg Sports Traumatol Arthrosc. 2014;22(3):550–5.

    Article  CAS  PubMed  Google Scholar 

  24. Gupton M, Johnson JE, Cummings GR, Deivaraju C. Overstuffing the patellofemoral compartment in total knee arthroplasty: a systematic review. EFORT open Reviews. 2023;8(8):597–605.

    Article  PubMed  PubMed Central  Google Scholar 

  25. Xu J, Li L, Fu J, Xu C, Ni M, Chai W, Hao L, Zhang G, Chen J. Early clinical and radiographic outcomes of Robot-assisted Versus Conventional Manual total knee arthroplasty: a randomized controlled study. Orthop Surg. 2022;14(9):1972–80.

    Article  PubMed  PubMed Central  Google Scholar 

  26. Lai YH, Xu H, Su Q, Wan XF, Yuan MC, Zhou ZK. Effect of tourniquet use on blood loss, pain, functional recovery, and complications in robot-assisted total knee arthroplasty: a prospective, double-blinded, randomized controlled trial. J Orthop Surg Res. 2022;17(1):118.

    Article  PubMed  PubMed Central  Google Scholar 

  27. Shatrov J, Battelier C, Sappey-Marinier E, Gunst S, Servien E, Lustig S. Functional alignment philosophy in total knee arthroplasty - rationale and technique for the varus morphotype using a CT based robotic platform and individualized planning. SICOT J. 2022;8:11.

    Article  PubMed  PubMed Central  Google Scholar 

  28. Pierson JL, Ritter MA, Keating EM, Faris PM, Meding JB, Berend ME, Davis KE. The effect of stuffing the patellofemoral compartment on the outcome of total knee arthroplasty. J bone Joint Surg Am. volume 2007;89(10):2195–203.

  29. Turan K, Camurcu Y, Kezer M, Uysal Y, Kizilay YO, Temiz A. Preliminary outcomes of kinematically aligned robot-assisted total knee arthroplasty with patient-specific cartilage thickness measurement. J Robotic Surg. 2023;17(3):979–85.

    Article  Google Scholar 

  30. Fan XY, Ma JH, Wu X, Xu X, Shi L, Li T, Wang P, Li C, Li Z, Zhang QY, et al. How much improvement can satisfy patients? Exploring patients’ satisfaction 3 years after total knee arthroplasty. J Orthop Surg Res. 2021;16(1):389.

    Article  PubMed  PubMed Central  Google Scholar 

  31. Mancino F, Rossi SMP, Sangaletti R, Caredda M, Terragnoli F, Benazzo F. Increased accuracy in component positioning using an image-less robotic arm system in primary total knee arthroplasty: a retrospective study. Arch Orthop Trauma Surg. 2024;144(1):393–404.

    Article  PubMed  Google Scholar 

  32. Rossi SMP, Sangaletti R, Perticarini L, Terragnoli F, Benazzo F. High accuracy of a new robotically assisted technique for total knee arthroplasty: an in vivo study. Knee Surg Sports Traumatol Arthrosc. 2023;31(3):1153–61.

    Article  PubMed  Google Scholar 

  33. Rossi SMP, Benazzo F. Individualized alignment and ligament balancing technique with the ROSA® robotic system for total knee arthroplasty. Int Orthop. 2023;47(3):755–62.

    Article  PubMed  Google Scholar 

  34. Mancino F, Rossi SMP, Sangaletti R, Lucenti L, Terragnoli F, Benazzo F. A new robotically assisted technique can improve outcomes of total knee arthroplasty comparing to an imageless navigation system. Arch Orthop Trauma Surg. 2023;143(5):2701–11.

    Article  PubMed  Google Scholar 

  35. Zhou H, Wu ZR, Chen XY, Zhang LS, Zhang JC, Hidig SM, Feng S, Yang Z. Does mild flexion of the femoral prosthesis in total knee arthroplasty result in better early postoperative outcomes? BMC Musculoskelet Disord. 2023;24(1):711.

    Article  PubMed  PubMed Central  Google Scholar 

  36. Van de Kelft AS, De Mulder K, De Schepper J, Victor J, Vundelinckx B. Balancing the flexion gap first in total knee arthroplasty leads to better preservation of posterior condylar offset resulting in better knee flexion. Knee Surg Sports Traumatol Arthrosc. 2023;31(9):3792–8.

    Article  PubMed  Google Scholar 

  37. Tanikawa H, Tada M, Harato K, Okuma K, Nagura T. Influence of total knee arthroplasty on Patellar Kinematics and Patellofemoral pressure. J Arthroplasty. 2017;32(1):280–5.

    Article  PubMed  Google Scholar 

  38. Matz J, Howard JL, Morden DJ, MacDonald SJ, Teeter MG, Lanting BA. Do changes in Patellofemoral Joint Offset lead to adverse outcomes in total knee arthroplasty with patellar resurfacing? A Radiographic Review. J Arthroplasty. 2017;32(3):783–e787781.

    Article  PubMed  Google Scholar 

  39. Matziolis G, Brodt S, Windisch C, Roehner E. Changes of posterior condylar offset results in midflexion instability in single-radius total knee arthroplasty. Arch Orthop Trauma Surg. 2017;137(5):713–7.

    Article  PubMed  Google Scholar 

  40. Familiari F, Mercurio M, Napoleone F, Galasso O, Giuzio E, Simonetta R, Palco M, DePhillipo NN, Gasparini G. Anterior referencing versus posterior referencing in primary total knee arthroplasty: a Meta-analysis of Randomized controlled trials. J Clin Med 2023, 12(23).

  41. Popat R, Albelooshi A, Mahapatra P, Bollars P, Ettinger M, Jennings S, Van den Berg JL, Nathwani D. Improved joint line and posterior offset restoration in primary total knee replacement using a robotic-assisted surgical technique: an international multi-centre retrospective analysis of matched cohorts. PLoS ONE. 2022;17(8):e0272722.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  42. Nakahara H, Matsuda S, Okazaki K, Tashiro Y, Iwamoto Y. Sagittal cutting error changes femoral anteroposterior sizing in total knee arthroplasty. Clin Orthop Relat Res. 2012;470(12):3560–5.

    Article  PubMed  PubMed Central  Google Scholar 

Download references

Acknowledgements

None.

Funding

Chongqing Science and Health Joint Medical Research Program(2022DBXM002); Key Project of Technical Innovation and Application Development in Chongqing (CSTB202ITIAD-KPX0069); Chongqing Medical University Academic Peak Project (cyyy-xkdfjh-lcyj-202304).

Author information

Author notes

  1. Dehua Wang and Yu Ye contributed equally to this work.

  2. Ke Li and Wei Huang have equal contribution as co-corresponding authors

Authors and Affiliations

  1. Department of Orthopaedics, the First Affiliated Hospital of Chongqing Medical University, 1 Youyi Road, Yuanjiagang Yuzhong District, Chongqing, 400016, China

    Dehua Wang, Xi Liang, Ke Li & Wei Huang

  2. Orthopaedic Laboratory of Chongqing Medical University, Chongqing, China

    Dehua Wang, Xi Liang, Ke Li & Wei Huang

  3. Department of Orthopaedics, The Second People’s Hospital of Yubei District, Chongqing, China

    Yu Ye

Authors
  1. Dehua Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Yu Ye
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Xi Liang
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Ke Li
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Wei Huang
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

DHW, YY, LX, KL and WHcontributed to the study conception and design. DHW and YY performed material preparation, data collection and analysis. The first draft of the manuscript was written by DHW and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding authors

Correspondence to Ke Li or Wei Huang.

Ethics declarations

Ethics approval and consent to participate

The First Affiliated Hospital of Chongqing Medical University (IRB approval number: 2022 − 176) approved this study. Informed consent was obtained from all participants.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Wang, D., Ye, Y., Liang, X. et al. Enhancing total knee arthroplasty outcomes: the role of individualized femoral sagittal alignment in robotic-assisted surgery - A randomized controlled trial. J Orthop Surg Res 19, 558 (2024). https://doi.org/10.1186/s13018-024-05027-w

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s13018-024-05027-w

Keywords

Journal of Orthopaedic Surgery and Research

ISSN: 1749-799X