4.2 Navigation technology and musculoskeletal oncology
Navigation based technology in musculoskeletal oncology is an imaged-based system. This is in contrast to imageless systems which rely solely on the information obtained from registration of patient's anatomy intra-operatively following adequate surgical exposure. A hand-held mapping tool is used intraoperatively by the surgeon on various bony landmarks to provide the imageless-navigation system with sufficient data and a surgical plan is formulated intraoperatively.
Similar to 3DP, navigation technology requires pre-operative imaging (CT, MRI, PET-CT) to assess tumour size, soft tissue involvement, extent of intraosseous disease and anatomical relation to important neurovascular structures. CT is superior at imaging bone while MRI is superior at imaging soft tissues. PET-CT may provide additional value in distinguishing tumour tissue from scar tissue secondary to previous radiation/resection in cases of tumour recurrence. A technique described by Wong et al.
Image fusion for computer-assisted bone tumor surgery. Clinical Orthopaedics and Related Research.
describes the fusion of these imaging modalities to form a more accurate 3D representation of patient anatomy. This information is interpreted by a computer program and consequently utilized by the surgeon to develop a pre-operative plan.
Navigation technology in musculoskeletal oncology requires crucial extensive intraoperative registration of patient anatomy with information from the pre-operative imaging analyzed by the software. Intraoperative registration is operator dependent and the main determinant of navigation success. Bony landmarks (e.g. iliac crest tubercle, anterior superior iliac spine, spinous processes) have a fixed position and are hence used for registration as opposed to soft tissue landmarks. An infra-red camera captures information of the patient anatomy from a navigation probe used by the surgeon to complete the registration and calibration process. Once complete, an image of the fused CT/MRI/PET-CT is displayed with the real-time position of the navigation probe on the screen. If necessary, surgical instruments can be calibrated to display their 3D position as well. This potentially allows for more precise resection with real-time feedback.
Cartiaux et al. demonstrated that surgeons were unable to accurately and consistently obtain adequate resection margins for pelvic tumours despite ideal conditions. The probability of a surgeon obtaining a 10-mm surgical margin with a 5-mm tolerance above or below, was 52% and the resulting degree of contact at the host-graft junction was poor.
Surgical inaccuracy of tumor resection and reconstruction within the pelvis: an experimental study.
The group demonstrated significantly improved resection accuracy in a subsequent study using navigation
Computer-assisted planning and navigation improves cutting accuracy during simulated bone tumor surgery of the pelvis.
– 2.8 mm inaccuracy for the navigated procedure as compared to 11.2 mm for the conventional cutting procedure.
Jeys and colleagues demonstrated a reduction in intralesional resection rates from 29% to 8.7% with the use of intraoperative navigation in 31 patients with musculoskeletal tumours of the pelvis and sacrum.
Can computer navigation-assisted surgery reduce the risk of an intralesional margin and reduce the rate of local recurrence in patients with a tumour of the pelvis or sacrum?.
The registration error was <1 mm in all cases and no complications related to navigation use. The use of navigation allowed the preservation of sacral nerve roots (n = 13), resection of otherwise inoperable disease (n = 4) and the avoidance of hindquarter amputation (n = 3). When comparing the outcomes of navigation-guided resections with pre-operative planned resection, Aponte-Tinao et al. found a mean difference of 2.43 mm.
Multiplanar osteotomies guided by navigation in chondrosarcoma of the knee.
Cho et al. demonstrated clear resection margins in all 18 patients with metaphyseal or pelvic tumours.
The outcomes of navigation-assisted bone tumour surgery minimum three-year follow-up.
Local recurrence occurred in 2 patients who had tumours resected from the pelvis. Similarly, Young et al. demonstrated clear margins for 18 patients with diaphyseal and pelvic tumours undergoing navigation guided resection surgery.
- Young P.S.
- Bell S.W.
- Mahendra A.
The evolving role of computer-assisted navigation in musculoskeletal oncology.
Li et al. described the use of navigation technology and its utility in complex limb salvage surgery for tumours around the proximal humerus and knee with clear resection margins in all patients.
Precise resection and biological reconstruction under navigation guidance for young patients with juxta-articular bone sarcoma in lower extremity.
Image navigation assisted joint-saving surgery for treatment of bone sarcoma around knee in skeletally immature patients.
Irregular osteotomy in limb salvage for juxta-articular osteosarcoma under computer-assisted navigation.
Others reported similar results when using navigation surgery in complex joint preserving surgery.
Surgical technique: unicondylar osteoallograft prosthesis composite in tumor limb salvage surgery.
Joint-preserving limb salvage surgery under navigation guidance.
A study by Lall and colleagues demonstrated better fit and increased contact between allograft implant and resection planes during reconstructive surgery with the use of navigation technology.
Comparison of surface area across the allograft-host junction site using conventional and navigated osteotomy technique.
This could potentially result in improved bone healing and decreased non-union rates, which are reported to be as high as 27% in bulk allograft reconstruction.
Navigation provides real-time intraoperative feedback and allows for more accurate resection in complex musculoskeletal oncology cases with improved outcomes. However, some limitations prevent widespread adoption of this technology. They include the increased learning curve of utilizing this technology, the cost of the navigation systems, increased pre-operative planning time, potentially increased intra-operative surgical time (due to set up and utilization of the system), need for extra manpower within the operation theatre and registration errors which may potentially guide inaccurate or intralesional resection.
Joint-preserving limb salvage surgery under navigation guidance.
As mentioned above, PSI were introduced to replace navigation technology. When compared to computer-navigation assisted techniques which require navigation equipment and a machine operator, operating time with PSI could be potentially reduced.
Patient-specific instrument can achieve same accuracy with less resection time than navigation assistance in periacetabular pelvic tumor surgery: a cadaveric study.
PSI could be more cost effective as the technology is on a pay-per-use basis and has a minimal learning curve when compared to computer navigation. The use of custom PSI may produce more accurate results than the computer-navigation as computer navigation orientates the surgeon to the starting point of the resection cut, while custom PSI could potentially provide the trajectory for the entire cut.
Surgical technique: computer-generated custom jigs improve accuracy of wide resection of bone tumors.
Further studies comparing the use of computer navigation and PSI in musculoskeletal tumour resection are necessary before any conclusion can be made.
Navigation technology and PSI do not have to be mutually exclusive. A potential improvement could be the use of navigation technology to provide intraoperative real-time feedback and confirm accurate placement of PSI prior to resection, similar to the study by Chen et al. where navigation technology was utilized to complement the implantation of 3DP implants.
Image-guided installation of 3D-printed patient-specific implant and its application in pelvic tumor resection and reconstruction surgery.