Key Takeaways & Executive Findings
- •• Mixed reality (HoloLens 2) significantly improves the accuracy of acetabular cup placement compared with freehand technique, reducing variability in both experienced and inexperienced surgeons. • With HoloLens 2 assistance, junior surgeons achieved cup placement accuracy comparable to that of senior surgeons, effectively shortening the learning curve. • The technology provides real-time 3D holographic navigation, enabling precise alignment within the Lewinnek safe zone (abduction 40°±10°, anteversion 15°±10°). • Mixed reality offers a promising tool for surgical training and intraoperative guidance, potentially reducing complications and improving long-term implant survival.
Abstract
BACKGROUND: There is a long surgical learning curve for safe and accurate placement of the acetabular prosthesis in hip replacement surgery. Mixed reality technology can fuse virtual image data models with real patient entities, which can help operations such as virtual surgery and intraoperative navigation, potentially improving the accuracy of acetabular prosthesis placement and shortening the learning curve for junior surgeons. OBJECTIVE: To use HoloLens 2 to develop a system that overlays the correct placement data of the acetabular prosthesis onto a 3D-printed pelvic model, and to evaluate the effect of mixed reality technology in training and guiding hip replacement surgery. METHODS: Senior orthopedic surgeons with experience in joint replacement and junior surgeons without experience in cup placement were selected. They performed simulated hip replacement surgery on 3D-printed pelvic models either freehand or with the guidance of HoloLens 2 head-mounted device. The abduction and anteversion angles of the acetabular cup were measured and recorded, and the accuracy of cup placement was compared between groups. RESULTS AND CONCLUSION: (1) Under freehand conditions, the experienced group had cup abduction angle of (41.52±3.76)° and anteversion angle of (21.35±3.63)°; the inexperienced group had abduction angle of (44.29±7.62)° and anteversion angle of (21.55±7.82)°, with significant differences between the two groups (P < 0.05). (2) With HoloLens assistance, the inexperienced group achieved abduction and anteversion angles of (41.10±1.28)° and (20.09±0.53)°, respectively, while the experienced group achieved (41.08±1.09)° and (20.28±0.65)°, with no significant difference between the two groups. (3) These findings indicate that for total hip replacement, the use of mixed reality technology significantly improves the accuracy of cup placement compared with freehand operation, and has obvious clinical auxiliary value in precise reaming and cup placement, shortening the learning curve for orthopedic surgeons.
1. Introduction
Joint replacement surgery is an effective treatment for end-stage bone and joint diseases. Accurate placement of the prosthesis is crucial for its wear behavior, stability, and longevity. Poor placement can lead to component impingement, dislocation, accelerated wear, and loosening, which are important factors causing prosthesis dislocation and premature revision [1-8]. LEWINNEK et al. [6] proposed the concept of a "safe zone" for cup placement: abduction angle within (40±10)° and anteversion angle within (15±5)° can significantly reduce the risk of dislocation [2,7,9]. However, hip replacement surgery has a long learning curve, and beginners often face complications such as prolonged operation time, increased blood loss, nerve injury, and dislocation due to poor prosthesis placement [10-12].
To optimize the procedure and outcomes of joint replacement surgery, various assistive technologies have emerged, including preoperative navigation devices, 3D-printed models, surgical robots, and augmented reality [4,5,13-14]. Compared with traditional freehand techniques, computer navigation and robotic assistance can improve accuracy, but they often have drawbacks such as prolonged surgical time, high cost, and complex operation. Mixed reality technology (e.g., HoloLens) reconstructs patient CT/MRI data into a 3D holographic model and precisely overlays it onto the real surgical field, giving surgeons "X-ray vision" [5,9,15-19], significantly enhancing surgical planning accuracy and intraoperative safety, providing an innovative solution to these challenges. Devices like Microsoft HoloLens 2 are portable, wearable, and intuitive, offering surgeons "holographic vision" that can theoretically provide precise guidance without interrupting the surgical workflow [16-18], improving the precision of joint replacement and shortening the learning curve. Mixed reality systems also create immersive simulation environments where trainees can practice repeatedly without risk, effectively shortening the learning curve and reducing the risk of operating on real patients during early training [20-21].
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Xia Qingquan, Wu Xuhua, Yin Yelin, Xu Qing, Meng Xiangchao, Rong Ke (2026). Impact of HoloLens 2–assisted navigation for precision acetabular cup placement on the learning curve of surgeons with different levels of experience. Chinese Journal of Tissue Engineering Research. https://doi.org/10.12307/2026.21620
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Frequently Asked Questions
What is the Lewinnek safe zone for acetabular cup placement?
The Lewinnek safe zone is a classic standard for cup placement in hip replacement, defined as an abduction angle of (40±10)° and an anteversion angle of (15±10)°. Adherence to this zone significantly reduces the risk of postoperative dislocation, with dislocation rates dropping from 6.5% to 1.5%.
How does HoloLens 2 assist in acetabular cup placement?
HoloLens 2 overlays a 3D holographic model of the patient's anatomy onto the real surgical field, allowing surgeons to visualize the correct cup position in real time. This guidance helps achieve precise alignment within the safe zone, reducing variability and improving accuracy compared with freehand techniques.
Can mixed reality technology shorten the learning curve for junior surgeons?
Yes. In this study, junior surgeons using HoloLens 2 achieved cup placement accuracy comparable to that of experienced surgeons, with no significant difference between the groups. This indicates that mixed reality can effectively shorten the learning curve by providing real-time visual guidance.
What are the potential limitations of using HoloLens 2 in surgery?
Potential limitations include the need for stable registration markers, which may shift during surgery, and the reliance on CT data that may not account for anatomical variations. Future developments may include markerless registration and diverse pelvic models to enhance applicability.
What is the clinical significance of this study?
The study demonstrates that mixed reality technology can significantly improve the accuracy of acetabular cup placement, potentially reducing complications such as dislocation and implant loosening. It also offers a valuable training tool, helping junior surgeons achieve proficiency faster and improving overall surgical outcomes.
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