Navigation-assisted surgery for bone and soft tissue tumors with bony extension

Computerized surgical navigation resection of pelvic region simulated bone tumors using skin fiducial marker registration: an in vitro cadaveric study

INTRODUCTION

Computerized surgical navigation system guidance can improve bone tumor surgical resection accuracy. This study compared the 10-mm planned resection margin agreement between simulated pelvic-region bone tumors (SPBT) resected using either skin fiducial markers or Kirschner (K)-wires inserted directly into osseous landmarks with navigational system registration under direct observation. We hypothesized that skin fiducial markers would display similar resection margin accuracy.

METHODS

Six cadaveric pelvises had one SPBT implanted into each supra-acetabular region. At the left hemi-pelvis, the skin fiducial marker group had guidance from markers placed over the pubic tubercle, the anterior superior iliac spine, the central and more posterior iliac crest, and the greater trochanter (5 markers). At the right hemi-pelvis, the K-wire group had guidance from 1.4-mm-diameter wires inserted into the pubic tubercle, and 3 inserted along the iliac crest (4 K-wires). The senior author, a fellowship-trained surgeon performed "en bloc" SPBT resections. The primary investigator, blinded to group assignment, measured actual resection margins.

RESULTS

Twenty of 22 resection margins (91%) in the skin fiducial marker group were within the Bland-Altman plot 95% confidence interval for actual-planned margin mean difference (mean = -0.23 mm; 95% confidence intervals = 2.8 mm, - 3.3 mm). Twenty-one of 22 resection margins (95%) in the K-wire group were within the 95% confidence interval of actual-planned margin mean difference (mean = 0.26 mm; 95% confidence intervals = 1.7 mm, - 1.1 mm).

CONCLUSION

Pelvic bone tumor resection with navigational guidance from skin fiducial markers placed over osseous landmarks provided similar accuracy to K-wires inserted into osseous landmarks. Further in vitro studies with different SPBT dimensions/locations and clinical studies will better delineate use efficacy.

Advances in Virtual Cutting Guide and Stereotactic Navigation for Complex Tumor Resections of the Sacrum and Pelvis: Case Series with Short-Term Follow-Up

Primary malignancies of the sacrum and pelvis are aggressive in nature, and achieving negative margins is essential for preventing recurrence and improving survival after en bloc resections. However, these are particularly challenging interventions due to the complex anatomy and proximity to vital structures. Using virtual cutting guides to perform navigated osteotomies may be a reliable method for safely obtaining negative margins in complex tumor resections of the sacrum and pelvis. This study details the technique and presents short-term outcomes. Patients who underwent an en bloc tumor resection of the sacrum and/or pelvis using virtual cutting guides with a minimum follow-up of two years were retrospectively analyzed and included in this study. Preoperative computer-assisted design (CAD) was used to design osteotomies in each case. Segmentation, delineating the tumor from normal tissue, was performed by the senior author using preoperative CT scans and MRI. Working with a team of biomedical engineers, virtual surgical planning was performed to create osteotomy lines on the preoperative CT and overlaid onto the intraoperative CT. The pre-planned osteotomy lines were visualized as "virtual cutting guides" providing real-time stereotactic navigation. A precision ultrasound-powered cutting tool was then integrated into the navigation system and used to perform the osteotomies in each case. Six patients (mean age 52.2 ± 17.7 years, 2 males, 4 females) were included in this study. Negative margins were achieved in all patients with no intraoperative complications. Mean follow-up was 38.0 ± 6.5 months (range, 24.8-42.2). Mean operative time was 1229 min (range, 522-2063). Mean length of stay (LOS) was 18.7 ± 14.5 days. There were no cases of 30-day readmissions, 30-day reoperations, or 2-year mortality. One patient was complicated by flap necrosis, which was successfully treated with irrigation and debridement and primary closure. One patient had local tumor recurrence at final follow-up and two patients are currently undergoing treatment for metastatic disease. Using virtual cutting guides to perform navigated osteotomies is a safe technique that can facilitate complex tumor resections of the sacrum and pelvis.

What to choose in bone tumour resections? Patient specific instrumentation versus surgical navigation: a systematic review

Patient specific instrumentation (PSI) and intraoperative surgical navigation (SN) can significantly help in achieving wide oncological margins while sparing bone stock in bone tumour resections. This is a systematic review aimed to compare the two techniques on oncological and functional results, preoperative time for surgical planning, surgical intraoperative time, intraoperative technical complications and learning curve. The protocol was registered in PROSPERO database (CRD42023422065). 1613 papers were identified and 81 matched criteria for PRISMA inclusion and eligibility. PSI and SN showed similar results in margins (0-19% positive margins rate), bone cut accuracy (0.3-4 mm of error from the planned), local recurrence and functional reconstruction scores (MSTS 81-97%) for both long bones and pelvis, achieving better results compared to free hand resections. A planned bone margin from tumour of at least 5 mm was safe for bone resections, but soft tissue margin couldn't be planned when the tumour invaded soft tissues. Moreover, long osteotomies, homogenous bone topology and restricted working spaces reduced accuracy of both techniques, but SN can provide a second check. In urgent cases, SN is more indicated to avoid PSI planning and production time (2-4 weeks), while PSI has the advantage of less intraoperative using time (1-5 min vs 15-65 min). Finally, they deemed similar technical intraoperative complications rate and demanding learning curve. Overall, both techniques present advantages and drawbacks. They must be considered for the optimal choice based on the specific case. In the future, robotic-assisted resections and augmented reality might solve the downsides of PSI and SN becoming the main actors of bone tumour surgery.

Accuracy of bony resection under computer-assisted navigation for bone sarcomas around the knee

BACKGROUND

Computer-assisted navigation has made bone sarcoma resections more precise. However, further clinical studies involving accuracy analyses under navigation are still warranted.

METHODS

A retrospective study for analysis of computer-assisted navigation accuracy was carried out. Between September 2008 and November 2017, 39 cases of bone sarcomas around the knee joint were resected under computer-assisted navigation. The control group comprised 117 cases of bone sarcomas around the knee treated by limb salvage surgery wherein bony cutting was achieved freehand. The length difference (LD) was defined as the specimen length minus the planned resection length. The LDs were detected in both groups and compared. The margin accuracy (MA) was defined as the achieved margin minus the desired margin at the bone cutting site and was detected in the navigation group.

RESULTS

The LDs between the postoperative specimen length and the preoperative planned length were compared. In the navigation group, the LD was 0.5 ± 2.5 mm (range, - 5 to 5 mm), while in the freehand group, the LD was 3.4 ± 9.6 mm (range, - 20 to 29 mm), with a significant difference (P < 0.01). In the absolute value analysis, the LD absolute value was 2.0 ± 1.6 mm in the navigation group and 8.3 ± 6.0 mm in the freehand group, with a significant difference (P < 0.01). In the navigation group, the MA was 0.3 ± 1.5 mm (range, - 3 to 3 mm) and the MA absolute value was 1.1 ± 1.0 mm.

CONCLUSIONS

Better accuracy can be achieved when computer-assisted navigation is conducted for bone sarcoma resection around the knee.

LEVEL OF EVIDENCE

IV.

Fluorescence guidance improves the accuracy of radiological imaging-guided surgical navigation

BACKGROUND

Imaging-based navigation technologies require static referencing between the target anatomy and the optical sensors. Imaging-based navigation is therefore well suited to operations involving bony anatomy; however, these technologies have not translated to soft-tissue surgery. We sought to determine if fluorescence imaging complement conventional, radiological imaging-based navigation to guide the dissection of soft-tissue phantom tumors.

METHODS

Using a human tissue-simulating model, we created tumor phantoms with physiologically accurate optical density and contrast concentrations. Phantoms were dissected using all possible combinations of computed tomography (CT), magnetic resonance, and fluorescence imaging; controls were included. The data were margin accuracy, margin status, tumor spatial alignment, and dissection duration.

RESULTS

Margin accuracy was higher for combined navigation modalities compared to individual navigation modalities, and accuracy was highest with combined CT and fluorescence navigation (p = 0.045). Margin status improved with combined CT and fluorescence imaging.

CONCLUSIONS

At present, imaging-based navigation has limited application in guiding soft-tissue tumor operations due to its inability to compensate for positional changes during surgery. This study indicates that fluorescence guidance enhances the accuracy of imaging-based navigation and may be best viewed as a synergistic technology, rather than a competing one.

Outcomes and Complications of Pelvic Chondrosarcomas Treated Using Navigation Guidance and Multidisciplinary Approach: Is the Tumor Volume a Prognostic Factor?

(1) Background: Pelvic Chondrosarcomas (CS) have a poor prognosis. The grade is the most important survival predictor; other factors are periacetabular location and Dedifferentiated CS subtype. The aim of the study is to investigate a series of CS of the pelvis, to analyze the prognostic factors that affect outcomes and to demonstrate how the use of intraoperative navigation can reduce the complications without worse outcomes. (2) Methods: Retrospective study on 35 patients (21 M, 14 F), median age at surgery 54 years (IQR 41−65), with pelvic CS, treated with hemipelvectomy under navigation guidance. (3) Results: 30 high-grade CS and 5 low-grade CS; mean follow-up 51.4 months. There was a positive linear correlation between the tumor volume and the presence of local recurrence at follow-up. The mean survival time of patients with larger chondrosarcoma volume was lower, but not significantly so. Lower MSTS score was associated with significantly lower survival time (p < 0.001). (4) Conclusion: in this series overall survival, LR and distant metastasis were comparable with recent literature, while complication rate was lower compared to similar series without the use of navigation. There was a correlation between tumor volume and local recurrence rate but not with the presence of metastasis at follow up.

Percutaneous Image-guided Needle Biopsy of Musculoskeletal Tumors: Technical Tips

With recent advances in imaging technology, the frequency of detecting musculoskeletal lesions has also increased. Percutaneous image-guided needle biopsy is occasionally required for the diagnosis of such lesions. Moreover, in the era of personalized cancer care, chances in histopathological diagnosis and the importance of histopathological diagnosis by percutaneous needle biopsy are increasing. However, as percutaneous needle biopsy is not a common procedure for musculoskeletal lesions, careful planning and the application of adequate techniques such as hydrodissection and the trans-osseous approach are occasionally required. In this review, we have summarized the indications and techniques for percutaneous image-guided needle biopsy for musculoskeletal lesions, including lymphatic lesions.

The role of imaging in computer assisted tumor surgery of the sacrum and pelvis

The use of a navigation system allows precise resection of a tumor and accurate reconstruction of the resultant defect thereby sparing important anatomical structures and preserving function. It is an "image-based" system where the imaging (computed tomography and magnetic resonance imaging) is required to supply the software with data. The fusion of the preoperative imaging provides pre-operative information about local anatomy and extent of the tumor, so that it allows an accurate preoperative planning. Accurate pre-operative imaging is mandatory in order to minimize CATS errors, thus performing accurate tumor resections.

Intrapelvic melanocytic schwannoma resection with computer-assisted navigation

Melanocytic schwannoma is a rare nerve tumor characterized by melanin-producing neoplastic Schwann cells. Wide surgical resection is the management of choice for this tumor; however, anatomical location and proximity to nerve roots can make locating this tumor and the surgical resection challenging. Here we describe the case of 49-year-old male with a melanocytic schwannoma in the presacral area adjacent to the second sacral nerve root that was managed by wide resection aided by computer-assisted navigation due to the difficulty in identifying its location intraoperatively. The utilization of computer-assisted navigation improves accuracy and precision through the creation of a virtual continuous tridimensional map, particularly useful when oftentimes tumor margins may seem equivocal and further resection would compromise the patient's functionality. The value of computer-assisted navigation for soft tissue tumor resections in orthopedic oncology is still in its infancy, though, in certain scenarios it may advance the technique for some soft tissue resections.

Computer-assisted surgery (CAS) in orthopedic oncology. Which were the indications, problems and results in our first consecutive 203 patients?

AIMS

to review a group of patients with primary bone tumors treated with intraoperative navigation and analyze: (1) The technical problems; (2) Indications for Computer Assisted Surgery (CAS); (3) Oncological results; (4) Non oncological complications.

MATERIALS AND METHODS

All patients from a single institution who had preoperative virtual planned for an oncological primary bone resection assisted with navigation between May 2010 and July 2017 were enrolled in the study (203 patients). The use of computer-assisted surgery (CAS) was classified according to the oncologic procedure performed: (1) intralesional resections, (2) en-block resections, and (3) en-block resections + navigated allograft reconstructions.

RESULTS

Four patients (4/203, 2%) of the series presented technical problems which came from 2 software and 2 hardware crashes. Eight (4%) procedures were intralesional resections and no local recurrences or complications were reported in this group. Ninety-eight surgeries (49%) were pure en block resection. The pelvis and sacrum were the main location in this group (57%). All bone margins were defined negative but 2 patients presented a positive resection in the soft tissues. Infection was the most prevalent complication (16/23). Ninety-three procedures were done for en block resections + allograft reconstruction (all extremities tumor). All margins were free of tumor and non oncological rate for this group was 28%.

CONCLUSION

The main indications for CAS were malignant bone tumors resection. The technical failures precluded navigation use in 2%. CAS for pure en-block resections were mainly indicated in pelvic and sacrum tumors while en-block resection + allograft reconstruction assisted with navigation were only indicated in extremities tumors.

LEVEL OF EVIDENCE

IV.

Are Skin Fiducials Comparable to Bone Fiducials for Registration When Planning Navigation-assisted Musculoskeletal Tumor Resections in a Cadaveric Simulated Tumor Model?

BACKGROUND

To improve and achieve adequate bony surgical margins, surgeons may consider computer-aided navigation a promising intraoperative tool, currently applied to a relatively few number of patients in whom freehand resections might be challenging. Placing fiducials (markers) in the bone, identifying specific anatomical landmarks, and registering patients for navigated resections are time consuming. To reduce the time both preoperatively and intraoperatively, skin fiducials may offer an efficient and alternative method of navigation registration.

QUESTIONS/PURPOSES

(1) Does preoperative navigation using skin fiducials for registration allow the surgeon to achieve margins similar to those from bone fiducial registration in a simulated lower extremity tumor resection model in cadavers? (2) Does the use of preoperative navigation using skin fiducials for registration allow the surgeon to achieve similar bony margins in pelvic resections of simulated tumors as those achieved in long-bone resections using only skin fiducials for navigation in a cadaver model?

METHODS

Simulated bone tumor resections were performed in three fresh-frozen cadavers with intact pelvic and lower-extremity anatomy using navigation guidance. We placed 5-cm intraosseous cement simulated bone tumors in the proximal/distal femur (n = 12), and proximal/distal tibia (n = 12) and pelvis (supraacetabular; n = 6). After bone tumor implantation, CT images of the pelvis and lower extremities were obtained. Each planned osseous resection margin was set at 10 mm. Navigation registration was performed for each simulated tumor using bone and skin markers that act as a point of reference (fiducials). The simulated bone tumor was resected based on a resection line that was established with navigation, and the corresponding osseous margins were calculated after resection. These margins were determined by an orthopaedic surgeon who was blinded to resection planning by the removal of cancellous bone around the cement simulated tumor. The shortest distance was measured from the cement to the resection line. Smaller mean differences between planned and postoperative margins were considered accurate. Independent t-tests were conducted to assess measurement differences between planned and postoperative margins at the 95% CI. Bland-Altman analyses were conducted to compare the deviation in margin difference between planned and postoperative margins in skin and bone fiducial registration, respectively.

RESULTS

In all, 84 total resection margins were measured with 48 long bone and 20 pelvic obtained with skin fiducials and 16 long bone obtained with bone fiducials. The planned mean margin was 10 mm for all long bone and pelvic resections. We found that skin fiducial and bone fiducial postoperative margins had comparable accuracy when resecting long bones (10 ± 2 mm versus 9 ± 2 mm, mean difference 1 [95% CI 0 to 2]; p = 0.16). Additionally, skin fiducial long bone postoperative margins were comparable in accuracy to pelvic supraacetabular postoperative margins obtained with skin fiducials (10 ± 2 mm versus 11 ± 3 mm, mean difference -1 mm [95% CI -3 to 1]; p = 0.22). When comparing the deviation in margin difference between planned and postoperative margins in skin and bone fiducial registration, 90% (61 of 68) of skin fiducial and 100% (16 of 16) bone fiducial postoperative margins fell within 2 SDs.

CONCLUSIONS

In this pilot study, skin fiducial markers were easy to identify on the skin surface of the cadaver model and on CT images used to plan margins. This technique appears to be an accurate way to plan margins in this model, but it needs to be tested thoroughly in patients to determine if it may be a better clinical approach than with bone fiducials.

CLINICAL RELEVANCE

The margins obtained using skin fiducials and bone fiducials for registration were similar and comparable in this pilot study with a very small effect size. Boundaries of the simulated tumors were not violated in any resections. Skin fiducials are easier to identify than bone fiducials (anatomic landmarks). If future clinical studies demonstrate that margins obtained using skin fiducials for registration are similar to margins obtained with anatomical landmarks, the use of navigation with skin fiducials instead of bone fiducials may be advantageous. This technique may decrease the surgeon's time used to plan for and localize registration points and offer an alternative registration technique, providing the surgeon with other registration approaches.

Treatment of Post-traumatic Pediatric Ankle Varus Deformity with Physeal Bar Resection and Hemi-Epiphysiodesis

Children presenting with partial physeal arrest and significant remaining growth may benefit from physeal bar resection, although the operation is a technique demanding procedure. This study evaluates the treatment of post-traumatic pediatric ankle varus deformity using physeal bar resection and hemi-epiphysiodesis with the assistance of two operative methods. Forty-five patients presenting with a distal tibial medial physeal bridge as well as ankle varus deformity following traumatic ankle physeal injury between 2009 and 2017 were followed. These patients were treated with physeal bar resection and hemi-epiphysiodesis, with the assistance of either fluoroscopy (10 cases) or intraoperative three-dimensional navigation (35 cases). Of the 45 cases, the median age was 9.0 years (range: 3-14 years) with 28 male and 17 female patients. The median of pre-operation ankle varus angle was 20 degrees (IQR 15-25) and 5 degrees (IQR 0-20) at the time of final follow up, representing a statistically significant difference (P<0.05). No differences were observed with regards to age, gender, and surgical history between effective group and ineffective group (P>0.05). The median of pre-operative ankle varus angles of the navigation and fluoroscopy groups were both 20 degrees (P>0.05). The median correction angle of the navigation and fluoroscopy groups was 10 and 15 degrees, respectively (P>0.05). Our results indicate that physeal bar resection and hemiepiphysiodesis are effective treatments for correcting ankle varus deformity due to traumatic medial physeal arrest of the distal tibia. We observe no difference in outcome between fluoroscopy group and three-dimensional navigation group during the procedures.

Long-term outcomes after an initial experience of computer-navigated resection of primary pelvic and sacral bone tumours

Aims

The aim of this study was to investigate the local recurrence rate at an extended follow-up in patients following navigated resection of primary pelvic and sacral tumours.

Patients and Methods

This prospective cohort study comprised 23 consecutive patients (nine female, 14 male) who underwent resection of a primary pelvic or sacral tumour, using computer navigation, between 2010 and 2012. The mean age of the patients at the time of presentation was 51 years (10 to 77). The rates of local recurrence and mortality were calculated using the Kaplan–Meier method.

Results

Bone resection margins were all clear and there were no bony recurrences. At a mean follow-up for all patients of 59 months (12 to 93), eight patients (34.8%) developed soft-tissue local recurrence, with a cumulative rate of local recurrence at six-years of 35.1% (95% confidence interval (CI) 19.3 to 58.1). The cumulative all-cause rate of mortality at six-years was 26.1% (95% CI 12.7 to 49.1).

Conclusion

Despite the positive early experience with navigated-assisted resection, local recurrence rates remain high. With increasing knowledge of the size of soft-tissue margins required to reduce local recurrence and the close proximity of native structures in the pelvis, we advise against compromising resection to preserve function, and encourage surgeons to reduce local recurrence by prioritizing wide resection margins of the tumour. Cite this article: Bone Joint J 2019;101-B:484–490.

Navigation-Guided Endoscopy Combined with Deep Lateral Orbitotomy for Removal of Small Tumors at the Lateral Orbital Apex

Purpose

To evaluate the efficacy, feasibility, and safety of the navigation-guided endoscopy combined with deep lateral orbitotomy for removal of small tumors at the lateral orbital apex.

Design

A retrospective, noncomparative case series.

Methods

Retrospective analysis of ten patients (10 eyes) with small tumors at the lateral orbital apex comprised navigation-guided endoscopy combined with deep lateral orbitotomy at the Eye Hospital of Wenzhou Medical University from November 2015 to November 2017. In each case, the indication of surgery was existing or imminent visual impairment due to the tumor. The removal was believed to be complete if the mass was removed intactly during the surgery. The tumor character was confirmed by pathological examination after surgery. Patients were followed up to 3 months after surgery. Best corrected visual acuity before and after surgery was compared.

Results

All tumors were completely removed by the navigation-guided endoscopic approach. The mean preoperative best corrected visual acuity was 6/15 (95% confidence interval (95% CI) 6/40–6/8.5), and the mean postoperative best corrected visual acuity was 6/10 (95% CI 6/15–6/7.5). 5 of 7 (71%) patients with vision loss gained visual improvement in different degrees after surgery, and the rest of the patients had preoperative best corrected visual acuity. Visual field of all patients also improved. 8 cavernous hemangiomas and 2 schwannomas were confirmed postoperatively by pathology. 4 patients accompanied with limitation of eye abduction, which recovered spontaneously in an average of 4 weeks. No other serious complications occurred.

Conclusions

Navigation-guided endoscopy combined with deep lateral orbitotomy seems to be a feasible, efficient, and safe approach for removing small tumors at the lateral orbital apex. This trial is registered with ChiCTR1800019244.

A Cadaveric Comparative Study on the Surgical Accuracy of Freehand, Computer Navigation, and Patient-Specific Instruments in Joint-Preserving Bone Tumor Resections

Orthopedic oncologic surgery requires preservation of a functioning limb at the essence of achieving safe margins. With most bone sarcomas arising from the metaphyseal region, in close proximity to joints, joint-salvage surgery can be challenging. Intraoperative guidance techniques like computer-assisted surgery (CAS) and patient-specific instrumentation (PSI) could assist in achieving higher surgical accuracy. This study investigates the surgical accuracy of freehand, CAS- and PSI-assisted joint-preserving tumor resections and tests whether integration of CAS with PSI (CAS + PSI) can further improve accuracy. CT scans of 16 simulated tumors around the knee in four human cadavers were performed and imported into engineering software (MIMICS) for 3D planning of multiplanar joint-preserving resections. The planned resections were transferred to the navigation system and/or used for PSI design. Location accuracy (LA), entry and exit points of all 56 planes, and resection time were measured by postprocedural CT. Both CAS + PSI- and PSI-assisted techniques could reproduce planned resections with a mean LA of less than 2 mm. There was no statistical difference in LA between CAS + PSI and PSI resections (p=0.92), but both CAS + PSI and PSI showed a significantly higher LA compared to CAS (p=0.042 and p=0.034, respectively). PSI-assisted resections were faster compared to CAS + PSI (p < 0.001) and CAS (p < 0.001). Adding CAS to PSI did improve the exit points, however not significantly. In conclusion, PSI showed the best overall surgical accuracy and is fastest and easy to use. CAS could be used as an intraoperative quality control tool for PSI, and integration of CAS with PSI is possible but did not improve surgical accuracy. Both CAS and PSI seem complementary in improving surgical accuracy and are not mutually exclusive. Image-based techniques like CAS and PSI are superior over freehand resection. Surgeons should choose the technique most suitable based on the patient and tumor specifics.

Toward Holographic-Guided Surgery

The implementation of augmented reality (AR) in image-guided surgery (IGS) can improve surgical interventions by presenting the image data directly on the patient at the correct position and in the actual orientation. This approach can resolve the switching focus problem, which occurs in conventional IGS systems when the surgeon has to look away from the operation field to consult the image data on a 2-dimensional screen. The Microsoft HoloLens, a head-mounted AR display, was combined with an optical navigation system to create an AR-based IGS system. Experiments were performed on a phantom model to determine the accuracy of the complete system and to evaluate the effect of adding AR. The results demonstrated a mean Euclidean distance of 2.3 mm with a maximum error of 3.5 mm for the complete system. Adding AR visualization to a conventional system increased the mean error by 1.6 mm. The introduction of AR in IGS was promising. The presented system provided a solution for the switching focus problem and created a more intuitive guidance system. With a further reduction in the error and more research to optimize the visualization, many surgical applications could benefit from the advantages of AR guidance.

Can Navigation-assisted Surgery Help Achieve Negative Margins in Resection of Pelvic and Sacral Tumors?

BACKGROUND

Navigation-assisted resection has been proposed as a useful adjunct to resection of malignant tumors in difficult anatomic sites such as the pelvis and sacrum where it is difficult to achieve tumor-free margins. Most of these studies are case reports or small case series, but these reports have been extremely promising. Very few reports, however, have documented benefits of navigation-assisted resection in series of pelvic and sacral primary tumors. Because this technology may add time and expense to the surgical procedure, it is important to determine whether navigation provides any such benefits or simply adds cost and time to an already complex procedure.

QUESTIONS/PURPOSES

(1) What proportion of pelvic and sacral bone sarcoma resections utilizing a computer-assisted resection technique achieves negative margins? (2) What are the oncologic outcomes associated with computer-assisted resection of pelvic and sacral bone sarcomas? (3) What complications are associated with navigation-assisted resection?

METHODS

Between 2009 and 2015 we performed 24 navigation-assisted resections of primary tumors of the pelvis or sacrum. Of those, four were lost to followup after the 2-year postoperative visit. In one patient, however, there was a failure of navigation as a result of inadequate imaging, so nonnavigated resection was performed; the remaining 23 were accounted for and were studied here at a mean of 27 months after surgery (range, 12-52 months). During this period, we performed navigation-assisted resections in all patients presenting with a pelvis or sacral tumor; there was no selection process. No patients were treated for primary tumors in these locations without navigation during this time with the exception of the single patient in whom the navigation system failed. We retrospectively evaluated the records of these 23 patients and evaluated the margin status of these resections. We calculated the proportion of patients with local recurrence, development of metastases, and overall survival at an average 27-month followup (range, 12-52 months). We queried a longitudinally maintained surgical database for any complications and noted which, if any, could have been directly related to the use of the navigation-assisted technique.

RESULTS

In our series, 21 of 23 patients had a negative margin resection. In all patients the bone margin was negative, but two with sacral resections had positive soft tissue margins. Six of 23 patients experienced local recurrence within the study period. Three patients died during the study period. Seventeen patients demonstrated no evidence of disease at last recorded followup. We noted three intraoperative complications: one dural tear, one iliac vein laceration, and one bladder injury. Eight patients out of 23 had wound complications resulting in operative débridement. Two patients in the series developed transient postoperative femoral nerve palsy, which we believe were caused by stretch of the femoral nerve secondary to the placement of the reference array in the pubic ramus.

CONCLUSIONS

Navigation-assisted resection of pelvic and sacral tumors resulted in a high likelihood of negative margin resection in this series, and we observed relatively few complications related specifically to the navigation. We have no comparison group without navigation, and future studies should indeed compare navigated with nonnavigated resection approaches in these anatomic locations. We did identify a potential navigation-related complication of femoral nerve palsy in this series and suggest careful placement and observation of the reference array during the operative procedure to lessen the likelihood of this previously unreported complication. We suggest it is worthwhile to consider the use of navigation-assisted surgery in resection of tumors of the pelvis and sacrum, but further study will be needed to determine its precise impact, if any, on local recurrence and other oncologic outcomes.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Computer navigation-assisted surgery for musculoskeletal tumors: a closer look into the learning curve

BACKGROUND

Computer navigation-assisted surgery for musculoskeletal tumors has shown to reduce the risk of intra-lesional margins in resection. Experiences with this method are still limited to smaller case series.

METHOD

We reviewed our first experiences in 24 patients in whom computer navigation-assisted surgery had been performed. In 7 of these patients (6 male and 1 female), this has influenced the surgical treatment plan and navigation was used for both tumor resection and reconstruction. Three of the patients suffered from a chondrosarcoma, 2 from an osteosarcoma, 1 from a fibrosarcoma and 1 from an Ewing's sarcoma. Tumors were localized in the femur (n = 2), the tibia (n = 1), the sacrum (n = 1), the humerus (n = 1), the ilium (n = 1) and in the gluteal region (n = 1).

RESULTS

The mean registration error was 0.9 mm. No intra-operative complications occurred. Two postoperative complications were observed which required revision surgery. Except for one marginal resection, all tumors were excised with wide margins. One patient suffered from a local recurrence, and one patient died of disease after distant metastatic dissemination.

CONCLUSION

Computer navigation-assisted surgery represents a safe and helpful tool for the resection of musculoskeletal tumors and may influence surgical treatment plans in selected cases to provide more limited resections. Surgeons should be aware of risks considering biomechanical and oncological consequences in doing so. Further investigations and the evaluation of newer techniques (e.g., computed tomography-guided navigation) are needed to assess long-term outcomes of computer navigation assistance in musculoskeletal tumor surgery.

Preoperative Magnetic Resonance and Intraoperative Computed Tomography Fusion for Real-Time Neuronavigation in Intramedullary Lesion Surgery

BACKGROUND

Image-guided surgery techniques in spinal surgery are usually based upon fluoroscopy or computed tomography (CT) scan, which allow for a real-time navigation of bony structures, though not of neural structures and soft tissue remains.

OBJECTIVE

To verify the effectiveness and efficacy of a novel technique of imaging merging between preoperative magnetic resonance imaging (MRI) and intraoperative CT scan during removal of intramedullary lesions.

METHODS

Ten consecutive patients were treated for intramedullary lesions using a navigation system aid. Preoperative contrast-enhanced MRI was merged in the navigation software, with an intraoperative CT acquisition, performed using the O-arm TM system (Medtronic Sofamor Danek, Minneapolis, Minnesota). Dosimetric and timing data were also acquired for each patient.

RESULTS

The fusion process was achieved in all cases and was uneventful. The merged imaging information was useful in all cases for defining the exact area of laminectomy, dural opening, and the eventual extension of cordotomy, without requiring exposition corrections. The radiation dose for the patients was 0.78 mSv. Using the authors' protocol, it was possible to merge a preoperative MRI with navigation based on intraoperative CT scanning in all cases. Information gained with this technique was useful during the different surgical steps. However, there were some drawbacks, such as the merging process, which still remains partially manual.

CONCLUSION

In this initial experience, MRI and CT merging and its feasibility were tested, and we appreciated its safety, precision, and ease.

What Is the Expected Learning Curve in Computer-assisted Navigation for Bone Tumor Resection?

BACKGROUND

Computer navigation during surgery can help oncologic surgeons perform more accurate resections. However, some navigation studies suggest that this tool may result in unique intraoperative problems and increased surgical time. The degree to which these problems might diminish with experience-the learning curve-has not, to our knowledge, been evaluated for navigation-assisted tumor resections.

QUESTIONS/PURPOSES

(1) What intraoperative technical problems were observed during the first 2 years using navigation? (2) What was the mean time for navigation procedures and the time improvement during the learning curve? (3) Have there been any differences in the accuracy of the registration technique that occurred over time? (4) Did navigation achieve the goal of achieving a wide bone margin?

METHODS

All patients who underwent preoperative virtual planning for tumor bone resections and operated on with navigation assistance from 2010 to 2012 were prospectively collected. Two surgeons (GLF, LAA-T) performed the intraoperative navigation assistance. Both surgeons had more than 5 years of experience in orthopaedic oncology with more than 60 oncology cases per year per surgeon. This study includes from the very first patients performed with navigation. Although they did not take any formal training in orthopaedic oncology navigation, both surgeons were trained in navigation for knee prostheses. Between 2010 and 2012, we performed 124 bone tumor resections; of these, 78 (63%) cases were resected using intraoperative navigation assistance. During this period, our general indications for use of navigation included pelvic and sacral tumors and those tumors that were reconstructed with massive bone allografts to obtain precise matching of the host and allograft osteotomies. Seventy-eight patients treated with this technology were included in the study. Technical problems (crashes) and time for the navigation procedure were reported after surgery. Accuracy of the registration technique was defined and the surgical margins of the removed specimen were determined by an experienced bone pathologist after the surgical procedure as intralesional, marginal, or wide margins. To obtain these data, we performed a chart review and review of operative notes.

RESULTS

In four patients (of 78 [5%]), the navigation was not completed as a result of technical problems; all occurred during the first 20 cases of the utilization of this technology. The mean time for navigation procedures during the operation was 31 minutes (range, 11-61 minutes), and the early navigations took more time (the regression analysis shielded R² = 0.35 with p < 0.001). The median registration error was 0.6 mm (range, 0.3-1.1 mm). Registration did not improve over time (the regression analysis slope estimate is -0.014, with R² = 0.026 and p = 0.15). Histological examinations of all specimens showed a wide bone tumor margin in all patients. However, soft tissue margins were wide in 58 cases and marginal in 20.

CONCLUSIONS

We conclude that navigation may be useful in achieving negative bony margins, but we cannot state that it is more effective than other means for achieving this goal. Technical difficulty precluded the use of navigation in 5% of cases in this series. Navigation time decreased with more experience in the procedure but with the numbers available, we did not improve the registration error over time. Given these observations and the increased time and expense of using navigation, larger studies are needed to substantiate the value of this technology for routine use.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

A computer-assisted navigation technique to perform bone tumor resection without dedicated software

PURPOSE

In oncological orthopedics, navigation systems are limited to use in specialized centers, because specific, expensive, software is necessary. To resolve this problem, we present a technique using general spine navigation software to resect tumors located in different segments.

MATERIALS AND METHODS

This technique requires a primary surgery during which screws are inserted in the segment where the bone tumor is; next, a CT scan of the entire segment is used as a guide in a second surgery where a resection is performed under navigation control. We applied this technique in four selected cases. To evaluate the procedure, we considered resolution obtained, quality of the margin and its control.

RESULTS

In all cases, 1 mm resolution was obtained; navigation allowed perfect control of the osteotomies, reaching the minimum wide margin when desired. No complications were reported and all patients were free of disease at follow-up (average 25.5 months).

CONCLUSIONS

This technique allows any bone segment to be recognized by the navigation system thanks to the introduction of screws as landmarks. The minimum number of screws required is four, but the higher the number of screws, the greater the accuracy and resolution. In our experience, five landmarks, placed distant from one another, is a good compromise. Possible disadvantages include the necessity to perform two surgeries and the need of a major surgical exposure; nevertheless, in our opinion, the advantages of better margin control justify the application of this technique in centers where an intraoperative CT scanner, synchronized with a navigation system or a dedicated software for bone tumor removal were not available.

Patient-specific instrument can achieve same accuracy with less resection time than navigation assistance in periacetabular pelvic tumor surgery: a cadaveric study

PURPOSE

Inaccurate resection in pelvic tumors can result in compromised margins with increase local recurrence. Navigation-assisted and patient-specific instrument (PSI) techniques have recently been reported in assisting pelvic tumor surgery with the tendency of improving surgical accuracy. We examined and compared the accuracy of transferring a virtual pelvic resection plan to actual surgery using navigation-assisted or PSI technique in a cadaver study.

METHODS

We performed CT scan in twelve cadaveric bodies including whole pelvic bones. Either supraacetabular or partial acetabular resection was virtually planned in a hemipelvis using engineering software. The virtual resection plan was transferred to a CT-based navigation system or was used for design and fabrication of PSI. Pelvic resections were performed using navigation assistance in six cadavers and PSI in another six. Post-resection images were co-registered with preoperative planning for comparative analysis of resection accuracy in the two techniques.

RESULTS

The mean average deviation error from the planned resection was no different ([Formula: see text]) for the navigation and the PSI groups: 1.9 versus 1.4 mm, respectively. The mean time required for the bone resection was greater ([Formula: see text]) for the navigation group than for the PSI group: 16.2 versus 1.1 min, respectively.

CONCLUSIONS

In simulated periacetabular pelvic tumor resections, PSI technique enabled surgeons to reproduce the virtual surgical plan with similar accuracy but with less bone resection time when compared with navigation assistance. Further studies are required to investigate the clinical benefits of PSI technique in pelvic tumor surgery.

Does intraoperative navigation assistance improve bone tumor resection and allograft reconstruction results?

BACKGROUND

Bone tumor resections for limb salvage have become standard treatment. Recently, computer-assisted navigation has been introduced to improve the accuracy of joint arthroplasty and possible tumor resection surgery; however, like with any new technology, its benefits and limitations need to be characterized for surgeons to make informed decisions about whether to use it.

QUESTIONS/PURPOSES

We wanted to (1) assess the technical problems associated with computer-assisted navigation; (2) assess the accuracy of the registration technique; (3) define the time required to perform a navigated resection in orthopedic oncology; and (4) the frequency of complications such as local recurrence, infection, nonunion, fracture, and articular collapse after tumor resection and bone reconstruction with allografts using intraoperative navigation assistance.

METHODS

We analyzed 69 consecutive patients with bone tumors of the extremities that were reconstructed with massive bone allografts using intraoperative navigation assistance with a minimum followup of 12 months (mean, 29 months; range, 12-43 months). All patients had their tumors reconstructed in three-dimensional format in a virtual platform and planning was performed to determine the osteotomy position according to oncology margins in a CT-MRI image fusion. Tumor resections and allograft reconstructions were performed using a computer navigation system according to the previously planned cuts. We analyzed intraoperative data such as technical problems related to the navigation procedure, registration technique error, length of time for the navigation procedure, and postoperative complications such as local recurrence, infection, nonunion, fracture, and articular collapse.

RESULTS

In three patients (4%), the navigation was not carried out as a result of technical problems. Of the 66 cases in which navigation was performed, the mean registration error was 0.65 mm (range, 0.3-1.2 mm). The mean required time for navigation procedures, including bone resection and allograft reconstruction during surgery, was 35 minutes (range, 18-65 minutes). Complications that required a second surgical procedure were recorded for nine patients including one local recurrence, one infection, two fractures, one articular collapse, and four nonunions. In two of these nine patients, the allograft needed to be removed. At latest followup, three patients died of their original disease.

CONCLUSIONS

The navigation procedure could not be performed for technical reasons in 4% of the series. The mean registration error was 0.65 mm in this series and the navigation procedure itself adds a mean of 35 minutes during surgery. The complications rate for this series was 14%. We found a nonunion rate of 6% in allograft reconstructions when we used a navigation system for the cuts.

LEVEL OF EVIDENCE

Level IV, case series. See the Guidelines for Authors for a complete description of levels of evidence.

Assessment of registration accuracy during computer-aided oncologic limb-salvage surgery

PURPOSE

Computer-aided surgery is used in musculoskeletal tumor procedures to improve the surgeon's orientation to local anatomy during tumor resection. For the navigation system to function correctly, preoperative imaging (e.g., CT, MR) must be registered to the patient in the operating room. The goals of this study were (1) to directly quantify registration accuracy in computer-aided tumor surgery and (2) to validate the "system reported error" (SRE) of the navigation system.

METHODS

Registration accuracy was evaluated in eight bone sarcoma cases by determining the location of the anatomical paired-points used for registration following surface matching. Coordinates of specific intraoperative post-registration points were compared with the corresponding coordinates in preoperative CT scans to determine the measurement error (ME).

RESULTS

The mean difference between post-registration points and planned registration points was 12.21±6.52 mm significantly higher than the mean SRE (0.68 ± 0.15 mm; p = 0.002; 95 % CI 6.11-16.96 mm). The SRE poorly correlated with the calculated ME (R(2) = 0.040). Anatomical paired-point registration with surface matching results in a substantial shift in the post-registration coordinates of the same paired-points used for registration, and this shift is not represented by the SRE.

CONCLUSION

The SRE of a surgical navigation system was poorly correlated with direct measurements obtained in musculoskeletal tumor surgery. Improvement in registration accuracy is needed to better navigate tumor boundaries and ensure clear margins while maximally preserving the unaffected tissues and reducing operative morbidity.

Radiation dosimetry of intraoperative cone-beam compared with conventional CT for radiofrequency ablation of osteoid osteoma

BACKGROUND

Radiofrequency (RF) ablation is the standard of care for the surgical treatment of non-spinal osteoid osteoma and has greatly reduced morbidity associated with surgical excision. Precise placement of the RF ablation probe is necessary to avoid incomplete ablation. Limiting radiation exposure is especially advantageous in the pediatric population in whom osteoid osteoma frequently occurs. The aim of this study was to compare the radiation dosimetry and clinical outcomes among patients treated with RF ablation using three different localization techniques.

METHODS

Case-control methods were used to analyze sixty-six cases. Patients were categorized into three treatment groups: (1) intraoperative three-dimensional cone-beam CT (computed tomography) imaging (O-Arm) with surgical navigation (StealthStation S7), (2) intraoperative three-dimensional imaging (O-Arm) only, and (3) radiology suite-based diagnostic CT imaging. Radiation dosimetry and clinical outcome were analyzed with use of the dose-length product and local-relapse-free survival, respectively.

RESULTS

Mean age was nineteen years for the twenty-three patients in group 1, twenty years for the seven patients in group 2, and nineteen years for the thirty-six patients in group 3. Mean follow-up was fifty-three months. The mean radiation dose for groups 1, 2, and 3 was 446.62, 379.78, and 1058.83 mGy-cm, respectively. Significant (p < 0.05) differences in the radiation dose existed between groups 1 and 3 and between groups 2 and 3, whereas no difference was found between groups 1 and 2. Local-remission-free survival at three years for groups 1, 2, and 3 was 84.7% (95% confidence interval [CI], 64.5% to 100%), 100% (95% CI, 100% to 100%), and 90.7% (95% CI, 80.7% to 100%), respectively. Fifty-eight (92%) of the sixty-three followed patients were asymptomatic at the latest follow-up visit.

CONCLUSIONS

RF ablation using intraoperative cone-beam CT imaging, with or without surgical navigation, was associated with a significantly lower radiation dose compared with ablation using a radiology suite-based CT technique. Ablation using each of the three imaging techniques was equally effective in treating osteoid osteomas with a similar risk of relapse.

Use of Computer Navigation in Orthopedic Oncology

The use of computer navigation was first described in the surgical resection of pelvic tumors in 2004. It was developed to improve surgical accuracy with the goal of achieving clear resection margins and better oncologic results. During the past few years, there has been tremendous advancement of computer-assisted tumor surgery (CATS) in the field of orthopedic oncology. Currently, CATS with image fusion offers preoperative three-dimensional surgical planning and allows surgeons to reproduce the intended bone resections in musculoskeletal tumors. The technique is reported to be useful in technically demanding resections, such as in pelvic and sacral tumors; joint-preserving intercalated and multiplanar tumor resection; and complex reconstruction with custom computer-aided design prostheses or allografts. This article provides an up-to-date review of the recent developments and key features in CATS, its current status in clinical practice, and future directions in its development.

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?

We hypothesised that the use of computer navigation-assisted surgery for pelvic and sacral tumours would reduce the risk of an intralesional margin. We reviewed 31 patients (18 men and 13 women) with a mean age of 52.9 years (13.5 to 77.2) in whom computer navigation-assisted surgery had been carried out for a bone tumour of the pelvis or sacrum. There were 23 primary malignant bone tumours, four metastatic tumours and four locally advanced primary tumours of the rectum. The registration error when using computer navigation was < 1 mm in each case. There were no complications related to the navigation, which allowed the preservation of sacral nerve roots (n = 13), resection of otherwise inoperable disease (n = 4) and the avoidance of hindquarter amputation (n = 3). The intralesional resection rate for primary tumours of the pelvis and sacrum was 8.7% (n = 2): clear bone resection margins were achieved in all cases. At a mean follow-up of 13.1 months (3 to 34) three patients (13%) had developed a local recurrence. The mean time alive from diagnosis was 16.8 months (4 to 48). Computer navigation-assisted surgery is safe and has reduced our intralesional resection rate for primary tumours of the pelvis and sacrum. We recommend this technique as being worthy of further consideration for this group of patients.

How intraoperative navigation is changing musculoskeletal tumor surgery

Computer-assisted orthopedic surgery (CAOS) was introduced, developed, and implemented in musculoskeletal tumor surgery recently to enhance surgical precision in resecting malignant and benign tumors. The origins of computer-assisted surgery were in other subspecialties including maxillofacial surgery, spine surgery, and arthroplasty. Early studies have shown that CAOS can also be used safely for bone tumor resection surgery. Additional technological improvements may allow use of CAOS in soft tissue tumor surgery. It has the potential to improve surgical precision and accuracy, but more study is needed to evaluate clinical efficacy and long term results.

Accuracy of 3-D planning and navigation in bone tumor resection

Surgical precision in oncologic surgery is essential to achieve adequate margins in bone tumor resections. Three-dimensional preoperative planning and bone tumor resection by navigation have been introduced to orthopedic oncology in recent years. However, the accuracy of preoperative planning and navigation is unclear. The purpose of this study was to evaluate the accuracy of preoperative planning and the navigation system. A total of 28 patients were evaluated between May 2010 and February 2011. Tumor locations were the femur (n=17), pelvis (n=6), sacrum (n=2), tibia (n=2), and humerus (n=1). All resections were planned in a virtual scenario using computed tomography and magnetic resonance imaging fusion. A total of 61 planes or osteotomies were performed to resect the tumors. Postoperatively, computed tomography scans were obtained for all surgical specimens, and the specimens were 3-dimensionally reconstructed from the scans. Differences were determined by finding the distances between the osteotomies virtually programmed and those performed. The global mean of the quantitative comparisons between the osteotomies programmed and those obtained through the resected specimen was 2.52±2.32 mm for all patients. Differences between osteotomies virtually programmed and those achieved by navigation intraoperatively were minimal.

Computer-assisted tumor surgery in malignant bone tumors

BACKGROUND

Small recent case series using CT-based navigation suggest such approaches may aid in surgical planning and improve accuracy of intended resections, but the accuracy and clinical use have not been confirmed.

QUESTIONS/PURPOSES

We therefore evaluated (1) the accuracy; (2) recurrences; and (3) function in patients treated by computer-assisted tumor surgery (CATS).

METHODS

From 2006 to 2009, we performed CATS in 20 patients with 21 malignant tumors. The mean age was 31 years (range, 6-80 years). CT and MR images for 18 cases were fused using the navigation software. Reconstructed two-dimensional/three-dimensional images were used to plan the bone resection. The achieved bone resection was compared with the planned one by assessing margins, dimensions at the level of bone resection, or fitting of CAD custom prostheses. Function was assessed with the Musculoskeletal Tumor Society (MSTS) score. The minimum followup was 31 months (mean, 39 months; range, 5-69 months).

RESULTS

Histological examination of all resected specimens showed a clear tumor margin. The achieved bone resection matched the planned with a difference of ≤ 2 mm. The achieved positions of custom prostheses were comparable to the planned positions when merging postoperative with preoperative CT images in five cases. Three of the four patients with local recurrence had tumors at the sacral region. The mean MSTS score was 28 (range, 23-30).

CONCLUSION

CATS with image fusion allows accurate execution of the intended bone resection. It may be beneficial to resection and reconstruction in pelvic, sacral tumors and more difficult joint-preserving intercalated tumor surgery. Comparative clinical studies with long-term followup are necessary to confirm its efficacy.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Computer-assisted planning and navigation improves cutting accuracy during simulated bone tumor surgery of the pelvis

BACKGROUND

Resection of bone tumors within the pelvis requires good cutting accuracy to achieve satisfactory safe margins. Manually controlled bone cutting can result in serious errors, especially due to the complex three-dimensional geometry, limited visibility, and restricted working space of the pelvic bone. This experimental study investigated cutting accuracy during navigated and non-navigated simulated bone tumor cutting in the pelvis.

METHODS

A periacetabular tumor resection was simulated using a pelvic bone model. Twenty-three operators (10 senior and 13 junior surgeons) were asked to perform the tumor cutting, initially according to a freehand procedure and later with the aid of a navigation system. Before cutting, each operator used preoperative planning software to define four target planes around the tumor with a 10-mm desired safe margin. After cutting, the location and flatness of the cut planes were measured, as well as the achieved surgical margins and the time required for each cutting procedure.

RESULTS

The location of the cut planes with respect to the target planes was significantly improved by using the navigated cutting procedure, averaging 2.8 mm as compared to 11.2 mm for the freehand cutting procedure (p < 0.001). There was no intralesional tumor cutting when using the navigation system. The maximum difference between the achieved margins and the 10-mm desired safe margin was 6.5 mm with the navigated cutting process (compared to 13 mm with the freehand cutting process).

CONCLUSIONS

Cutting accuracy during simulated bone cuts of the pelvis can be significantly improved by using a freehand process assisted by a navigation system. When fully validated with complementary in vivo studies, the planning and navigation-guided technologies that have been developed for the present study may improve bone cutting accuracy during pelvic tumor resection by providing clinically acceptable margins.

CT-guided stereotactic targeting accuracy of osteoid osteoma

BACKGROUND

The aim of this study was to evaluate the CT-guided stereotactic targeting accuracy for radiofrequency ablation of osteoid osteoma (OO), a small, benign but painful osseous lesion.

METHODS

Patient and extremity were fixed in a vacuum cushion. The OO was targeted using an optical navigation system with a stereotactic targeting device. For evaluation of targeting errors, the control CT with the needle in place was fused with the planning CT.

RESULTS

In 16 consecutive patients, nine OOs in the femur, four in the tibia, one in the spine, one in the ulna and one in the pubic bone were successfully targeted without complications. The mean ± SD lateral targeting error was 2.6 ± 1.7 mm at the needle entry and 1.9 ± 1.2 mm at the needle tip, and the mean angular error was 2.0 ± 1.3°.

CONCLUSION

Stereotaxy allows for accurate and safe targeting of OOs in various bone regions.