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Arthrosc Tech
Arthrosc Tech
Arthroscopy Techniques
2212-6287
Elsevier

S2212-6287(24)00134-8
10.1016/j.eats.2024.103025
103025
Technical Note
Knee
Navigation in Multiligament Knee Reconstruction: A Proof-of-Concept Study on a Femoral Sawbones Model
Wilson William T. F.R.C.S.(Orth.)
Feller Julian A. F.R.A.C.S.
Batty Lachlan M. F.R.A.C.S. lbatty@osv.com.au
∗
OrthoSport Victoria, Melbourne, Victoria, Australia
∗ Address correspondence to Lachlan Batty, F.R.A.C.S., 89 Bridge Rd., Richmond, Victoria, 3121, Australia. lbatty@osv.com.au
16 5 2024
8 2024
16 5 2024
13 8 10302511 12 2023
9 3 2024
© 2024 The Authors
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Multiligament knee reconstruction surgery is technically challenging, requiring careful planning and execution. Accurate placement of bone tunnels is important for graft function and there is an inherent risk of tunnel collision, which can compromise graft integrity. In this proof-of-concept study, we present a technique using computer navigation to help optimize tunnel placement and to avoid collision during multiligament knee reconstruction. A computed tomography (CT)-based navigation system was used to plan and execute femoral tunnel placement on a Sawbones model, for a Schenck KD-IV multiligament knee reconstruction. After CT scanning of the Sawbones model, commercially available software was used to plan tunnel trajectories for reconstruction of the posterolateral corner, medial ligament complex, and both cruciate ligaments. Tunnel entry points and trajectories were based on bony landmarks as identified on CT. The model was successfully registered with an accuracy of <0.5 mm. Execution of tunnel drilling was carried out for 7 femoral tunnels, guided by computer navigation. A postprocedure CT scan was then performed and superimposed over the preoperative planning scan. This demonstrated excellent correlation between planned and executed tunnels with no evidence of tunnel collision. This study supports the idea of using computer navigation to plan and execute tunnels in multiligament knee reconstruction.

Technique Video

Video 1

Demonstration of the technique described in this study, using an adaption of commercially available computer navigation to assist with planning and drilling of femoral tunnels in the setting of multiligament knee reconstruction surgery.
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pmcMultiligament knee injuries are a serious clinical problem, and the treatment presents several challenges to clinicians. The mechanism of injury often involves high-energy trauma, and there are high rates of complications and concomitant injuries.1 Surgical treatment has been associated with improved outcomes when compared with nonoperative management.2, 3, 4, 5 Surgical options include acute ligamentous repair, reconstruction, or a combination of both. A ligament reconstructive approach using grafts is favored in many circumstances.6 Reconstructive surgery, however, is technically demanding and requires detailed planning and careful execution.7 Accurate placement of bone tunnels is important to optimize surgical outcomes and restore knee stability.7 Tunnel entry points must be located anatomically to ensure that the graft functions to restore stability without overconstraining the knee. With high-grade injuries, there is potential for up to 7 reconstruction tunnels to be drilled in the distal femur.8 The requirement for several multidirectional tunnels has an inherent risk of tunnel collision9 (Fig 1). Tunnel collision can compromise graft integrity, damage fixation devices, or prevent graft passage and fixation, thereby increasing the complexity of the procedure and potentially increasing failure rates.7 Furthermore, insufficient bone stock between tunnels may affect graft incorporation.7 To mitigate against tunnel collision, technical guides have been produced to help plan tunnel entry point and trajectories.8,10 These act to guide the surgeon during drilling, but despite this, tunnel collision is still encountered frequently in these complex cases.11Fig 1 Arthroscopic photograph looking up the femoral anterior cruciate ligament tunnel with a 30° arthroscope. This demonstrates tunnel collision between the anterior cruciate ligament tunnel (with the green passing suture running to the exit) and lateral collateral ligament tunnel (white hamstring graft crossing deep in the tunnel) during a multiligament knee reconstruction.

One option to help plan and execute surgical techniques is computer navigation, which has been shown to improve accuracy in areas such as knee arthroplasty.12 Computer navigation has been used sparingly in knee ligament reconstruction surgery with no effect demonstrated on clinical outcomes; however, there are data to show that it allows more accurate placement of the femoral tunnel position in isolated anterior cruciate ligament reconstruction.13,14

In this proof-of-concept study, we present a technique using computer navigation to assist with tunnel placement during multiligament knee reconstruction in Sawbones model. Potential benefits of this approach include advanced preoperative computed tomography (CT) planning to guide tunnel starting points based on anatomical bony landmarks and the ability to preoperatively manipulate tunnel trajectories to avoid collision. The navigation system can be used to execute this plan.

Surgical Technique

In this technique, we use a commercially available, image-based computer navigation system (SpineMap 3D NAV3i Platform; Stryker, Kalamazoo, MI) to plan and execute femoral tunnel placement on a Sawbones model (Sawbones, Pacific Research Lab, Vachon Island, WA), in the setting of a worst-case scenario (Schenck KD-IV) multiligament injury (Video 1).

A preoperative CT scan of the Sawbones model is uploaded and the software used to plan tunnel trajectories for reconstruction of the posterolateral corner (lateral collateral ligament and popliteus), medial collateral ligament (superficial medial collateral ligament and posterior oblique ligament) and bicruciate injuries (anterior cruciate ligament and double bundle posterior cruciate ligament). This equates to 7 femoral tunnels in total. Entry points are based on predetermined anatomical bony landmarks and trajectories planned according to published recommendations8 (Fig 2). Cross-sectional and 3-dimensional images are checked, and trajectories altered to avoid tunnel collisions. Diameter and length of the tunnels are set based on the anticipated graft diameter and importantly can be adjusted intraoperatively for the actual graft sizes when known. In Video 1, it is demonstrated that despite using published entry points and trajectories,8,9 a tunnel collision would occur between the anterior cruciate ligament and lateral collateral ligament tunnels (Fig 3). The 3-dimensional preoperative planning allows alteration of the planned trajectories to prevent collision and accommodates the specific bony anatomy of the individual patient. In total, 7 tunnels are added to the plan and the positions checked before proceeding to the next stage (Fig 4).Fig 2 Screenshot from the computer navigation software user interface showing the planned entry point and trajectory for the lateral collateral ligament (LCL) tunnel on left distal femur computed tomography–based model. The entry point and trajectory can be checked on cross-sectional and 3-dimensional imaging. (A) axial, (B) sagittal, (C) coronal, and (D) 3-dimensional views.

Fig 3 After adding the anterior cruciate ligament tunnel trajectory (purple) to the computer navigation plan for left knee reconstruction, it is evident that a collision would occur with the lateral collateral ligament tunnel (green). This is shown on cross-sectional images: (A) coronal, (B) sagittal, (C) axial, and (D) 3-dimensional and the collision is highlighted in the red oval.

Fig 4 Computed tomography image showing completed 3-dimensional virtual plan with all seven femoral tunnels now in place for multiligament reconstruction and no evidence of tunnel collision.

The technology uses standard techniques for computer navigation of the lower limb and spinal surgery. The specific system used is an adaption of a system used for spinal pedicle screws. An optical navigation system is positioned 3 meters from the model and the pointer and drill instruments calibrated with the camera to define their position in space. An active optical tracker is fixed to the model femoral diaphysis using two 3.2-mm pins. Once the planning phase is completed, the Sawbones model is registered against the computer system by the identification of 4 predefined anatomical points: the proximal extent of the medial and lateral trochlea chondral surfaces, trochlear point, and medial epicondyle. These points are chosen on the basis that they can potentially be identified and registered arthroscopically or percutaneously. The registration is then refined with surface mapping of the femoral condyles and notch area, which confirms a registration accuracy of <0.5 mm in this model. Once the bone model is registered against the computer model, execution of the tunnel drilling is carried out. Once calibrated, the 2.4-mm diameter drill pin tip and trajectory are visualized on the user interface (Fig 5). The surgeon uses this to align the drilling trajectory with the planned tunnel trajectory and once this is achieved, performs the drilling of the tunnel. The tunnels are then reamed according to the planned length and diameter using conventional cannulated reamers.Fig 5 Image showing computer navigated drilling of anterior cruciate ligament femoral tunnel trajectory. A screenshot from the navigation software shows the drill tip and drill trajectory in real time; the blue solid line in A and B shows the drill and the dotted blue line represents the trajectory in real time. (A) Axial, (B) sagittal, (C) coronal, (D) crosshair mechanism that will change from orange (on screen) to green when the trajectory aligns with the plan, and (E) clinical photograph demonstrating drilling technique guided by computer navigation on Sawbones model.

After completion of the procedure, a postoperative CT scan of the Sawbones model is performed and overlaid with the preoperative planning to assess accuracy in execution of the plan. There is very acceptable correlation between what was planned and executed with one outlier tunnel deviating 2 mm from the plan (purple posteromedial bundle tunnel of posterior cruciate ligament, Fig 6). This outlier was due to skiving of the guidewire at initiation of drilling. In this Sawbones model, the technique was successful in planning and executing femoral tunnel placement and in avoiding any tunnel collision in a worst-case, KD-IV scenario with 7 femoral tunnels.Fig 6 Axial image from postprocedure computed tomography scan with overlay of planned tunnels (colored) demonstrating the relationship between planned and drilled tunnels. The popliteus (aqua) and posterior cruciate ligament (PCL) anterolateral bundle (orange) show less than 1 mm of deviation to the plan. The largest deviation in this model was for the posteromedial bundle of PCL (purple) and was 2 mm off the planned tunnel. This deviation was due to surgeon error with the wire skiving at the start of drilling causing an incorrect starting point.

Discussion

This study has demonstrated that it is possible to use computer navigation technology to assist with planning and drilling of tunnels in multiligament knee reconstruction on a Sawbones model. Tunnel entry points can be planned based on predetermined bony landmarks, which helps to ensure grafts are positioned correctly for optimal function. A major advantage of this technique is the ability to plan the case ahead of time and adjust tunnels prior to the case commencing. Despite the initial plan being based on published techniques,8,9 the computer-navigated planning screen demonstrated that a tunnel collision would have occurred between the anterior cruciate ligament and lateral collateral ligament tunnels. This could have caused damage to a graft or fixation device if not identified intraoperatively and can be a challenging situation to overcome. Camarda et al.11 demonstrated that tunnel collision between the anterior cruciate ligament and lateral collateral ligament tunnels can occur in up to 75% of cases. Likewise, tunnels for posterior cruciate ligament reconstruction can often collide with those of the medial ligament reconstruction.10 Although guidelines for altering tunnel trajectories can reduce this risk, they do not eliminate it.9 The computer navigation technique allows identification of tunnel collision before drilling, such that the plan can be altered and checked to ensure that it does not occur intraoperatively.

The hardware and software used with this technique are already commercially available to guide implant placement in other surgical techniques, such as knee arthroplasty and spinal pedicle screw placement. As many surgeons are already skilled in the use of computer guided surgery, it is envisaged that this technique would be straightforward to apply, if it evolved to clinical adoption. The planning is based on a CT scan of the knee, which will often be performed as part of routine clinical practice in many of the patients suffering this kind of severe multiligament knee injury, negating the need for additional imaging. Most of the planning can be performed preoperatively, with additions and small amendments possible intraoperatively based on the size of grafts being used. Although the registration process and navigated drilling may add time, this is small in the context of what are often lengthy procedures. It is possible that using this technique may make drilling of tunnels quicker and easier, minimizing the potential to have to redrill if a tunnel collision occurs. Advantages and disadvantages of this technique as well as pearls and pitfalls are outlined in Tables 1 and 2, respectively.Table 1 Potential Advantages and Disadvantages of Computer Navigation for Multiligament Knee Reconstruction

Advantages	Disadvantages	
Preoperative, image-based, planning of tunnels with the ability to fine tune the plan intraoperatively.	May add time and complexity to the procedure
The requirement for femoral pins to mount the tracker array (however, if applicable, existing external fixator pins could be used).	
CT-based real-time navigation can augment arthroscopic or open anatomical landmarks to facilitate execution of anatomic tunnel placement.	Not all surgeons are familiar with use of navigation and there may be associated learning curve	
May help to reduce the chance of tunnel collision or tunnel malposition.	The accuracy of the CT registration and stability of the optical tracker is critical to accuracy and in executing the plan	
CT, computed tomography.

Table 2 Pearls and Pitfalls of Computer Navigation for Multiligament Knee Reconstruction

Pearls	Pitfalls	
Plan tunnels in advance using preferred technique for each reconstruction	Computer navigation is not a substitute for careful surgical technique or anatomical knowledge in this complex surgery. Image-based guidance must be correlated and checked against intraoperative anatomical landmarks.	
Check the plan on all views to ensure anatomical starting points based on bony landmarks and no tunnel collisions	Fix optical trackers securely to ensure no movement during procedure	
Diameter and length of tunnels can be edited in the plan intraoperatively based on actual graft dimensions. Trajectories can still be altered if required.	Registration of the knee to the CT scan needs to be accurate. The system will advise of any discrepancy between the registration and the CT, in this case it was under 0.5 mm	
CT, computed tomography.

We acknowledge that this study has limitations, in that it was a single technical demonstration carried out on a Sawbones model by a single surgeon. The next phase of development will be to execute a computer-navigated reconstruction on a human cadaver knee, to ensure that arthroscopic registration of bony landmarks is possible, prior to clinical use. The ability to accurately register the knee is critical to the utility of this technique and needs to be confirmed in cadavers and clinically. In terms of planning, it is likely that anatomical landmarks may be easier to define on a human knee CT compared with the ill-defined landmarks of a Sawbones model. Most importantly, computer navigation may be an augment to, but will never be a substitute for, careful surgical technique and anatomical knowledge in this complex surgery. Nonetheless, this technique shows potential to optimize multiligament knee reconstruction, with benefits for both patients and surgeons. This study supports future investigation into the role of computer navigation in multiligament knee reconstruction surgery.

Disclosures

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: J.F. reports speaking and lecture fees from and consultant or advisor for Smith & Nephew. L.B. reports consultant or advisor for 10.13039/100007307 Arthrex and speaking and lecture fees from 10.13039/100009026 Smith & Nephew and Device Technologies. W.W. declares that he has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary Data

Video 1

Demonstration of the technique described in this study, using an adaption of commercially available computer navigation to assist with planning and drilling of femoral tunnels in the setting of multiligament knee reconstruction surgery.
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