The letter raises concerns about registration drift in pinless navigation. Our clinical experience presents a different perspective. During our early experience with pin-mounted fixation, we encountered registration drifts or mismatches. When these were detected through our verification protocol (correlating patient anatomy clinically with navigation images and comparing planned versus actual starting points), we did not proceed with screw placement. Instead, we performed reregistration or repeat O-arm scans. This experience taught important lessons about pin limitations and the critical importance of robust verification protocols.

The literature acknowledges that registration errors and equipment challenges remain concerns even with bone-mounted systems [2]. Our experience revealed that rotations and drifts can still occur even with pins if adequate precautions are not taken, potentially arising through several mechanisms: patient gliding on the table (micromotion that is not easily perceived), patient sagging further into the table as weight settles, or changes in anesthesia depth. A single clamp or pin cannot be relied upon to prevent any motion of the whole body when the patient is not properly secured to the table. Pin insertion may create a false sense of security. The pin may not provide adequate stability in osteoporotic bone, and frequently interferes with screw trajectories, necessitating additional handling near the pin site to accommodate caudal trajectories. This paradoxically creates more opportunities for interference and patient movement rather than preventing it.

After recognizing these problems and gaining experience, we transitioned away from pins. Pins were already not being used for kyphoplasty cases, and occasionally required mid-procedure removal to allow trajectories to caudal screws such as S1 or ilium. The rationale for eliminating the pin was to remove the source of these complications. Additionally, pin insertion increases patient morbidity due to placement at a site distant from the surgical field, whilst still not providing complete assurance of patient immobilization.

Instead, proper patient immobilization to the table was emphasized. Our operating table (Allen Advance table) features wedge-shaped bolsters with an open frame construct, which provides superior immobilization compared to pin mounting. In our comparative study of 750 patients, the pinless group (550 cases, 3,034 screws) achieved 99.40% clinically acceptable screw placement, which was comparable to the pin-mounted group’s 99.55% (200 cases, 890 screws), with no statistically significant difference (p>0.05). In our pinless series, now exceeding 1,000 cases, zero registration drift events have occurred that resulted in malpositioned screws. This finding is consistent with published reports demonstrating that the Mazor X Stealth Edition system, which integrates navigation without requiring a percutaneous pin, can achieve 100% Grade A accuracy on the Gertzbein-Robbins scale [3]. Similarly, studies utilizing floor-mounted robotic systems without pin fixation have demonstrated 96.4% pedicle screw accuracy rates with negligible screw-related complications and robot abandonment rates [4].

The letter suggests our cohort may not represent sufficient anatomical complexity. We would respectfully argue that morphological complexity is not the relevant variable for the pinless versus pin debate. Our emphasis is that pin fixation is not the solution to minimize motion regardless of case complexity. The pin cannot immobilize the entire spine, nor can it counteract gross motion due to patient weight and improper positioning. A more robust mechanism is required that protects patients from movement during robotic procedures whilst facilitating workflow efficiency.

Whether addressing a simple degenerative case or a complex deformity, the fundamental question remains: can adequate patient immobilization be achieved? If so, the pinless approach is viable. In our study, analysis of all 22 breaches (four in pin-mounted, 18 in pinless) revealed that the vast majority were attributed to anatomical challenges, particularly hypoplastic or small pedicle dimensions (77% of breaches), followed by sclerotic bone, soft tissue pressure, and planning errors. These reflect anatomical challenges that neither pin fixation nor its absence would address, requiring instead surgical technique refinement. As robotic technology has evolved, little margin for error exists with pedicle screw placement, as screw malposition may lead to serious complications, making accuracy paramount regardless of the fixation method employed [5].

We concur that motion detection capabilities should be available in addition to current technology, with the ability to adjust robotic action accordingly. However, achieving this is not straightforward. Tracking motion across multiple vertebral levels would require a comprehensive solution. Until such technology matures, the most effective approach is proper patient immobilization using less invasive solutions such as described in our technique.

Artificial intelligence (AI) features cannot be institute-specific and will affect costs universally. High cost, along with registration failures and logistical complexities, has already been acknowledged as one of the significant challenges in robotic spine surgery adoption [2]. Our technique, now applied in more than 1,000 pinless cases, demonstrates that whilst equipping robots with advanced features would be beneficial, understanding what factors are important, how features impact outcomes, and recognizing their limitations are equally critical. Patient movement was successfully addressed not through extensive fixation using pins and clamps that could impede surgery, but through relatively cost-effective workflow innovations.

The literature demonstrates that robotic spine surgery presents a learning curve, with studies showing that surgical times may initially increase but subsequently decrease once the learning curve is reached [6,7]. These workflow innovations may become obsolete once robots achieve sufficient sophistication to visualize the patient in real time, map internal structures externally, and adjust trajectories accordingly. However, until that time, safe practice must be maintained, and pin mounting is neither the only solution nor, in our experience, necessarily the optimal one.

We believe that both robotic systems and surgeons must advance in parallel. Until robotic technology achieves greater sophistication, surgeons must actively address existing limitations, including accuracy verification, patient movement monitoring, registration maintenance, skiving detection, and navigation error recognition. Continuous study of all cases and ongoing learning are essential to help this technology reach its maximum potential.

This represents not resistance to innovation but pragmatic problem-solving based on real-world experience. Our comparative study of 750 patients with 3,924 screws demonstrated that pinless navigation with proper immobilization technique achieved accuracy comparable to pin-mounted methods (99.40% vs. 99.55%, p>0.05), validating that pinless navigation is both safe and offers practical advantages: less invasive approach, streamlined workflow, elimination of trajectory interference, and reduced per-case costs.

We welcome the vision of advanced motion-integrated systems and anticipate their clinical availability. However, we caution against the assumption that pinless navigation is inherently risky or requires AI augmentation to be viable. Our practical experience, supported by both our data and emerging literature, suggests that proper immobilization technique renders pinless navigation effective and safe presently, whilst surgeons and engineers collaborate to develop the next generation of truly intelligent robotic systems.

The future may indeed bring self-correcting, computationally intelligent systems. However, the present has already demonstrated that thoughtful workflow optimization and understanding of fundamental principles can achieve excellent outcomes with existing technology. We believe this represents a more accessible and immediately applicable pathway to improving patient care whilst advanced technologies continue to develop.