Use Of Computer-assisted Surgery Research Articles

Femoral bowing in the Arab population: A cross-sectional study and literature review

BackgroundThe femur normally has a degree of bowing that could influence the performance and outcome of some surgical procedures like intra-medullary nailing and hip replacement. This article aimed at evaluating the anterior femoral bowing angle in the Arab population, determining if age and sex are potential influencing factors, and reviewing the literature for identifying possible risk factors. MethodsMeasuring the anterior bowing of 116 Arab femora was done using lateral radiographs. The relationship between age and femoral bowing was done using the Pearson correlation coefficient, while an independent t-test was used to compare the bowing angles in males and females. A literature review was done to identify similar studies using PubMed and the references included in the identified papers. ResultsFrom the 116 femora, of which 37 (32%) belonged to male individuals and 79 (68%) to females, the mean femoral bowing angle was 8.13° with a standard deviation of 1.87°. Weak positive correlation was found between age and the bowing angle (r = 0.09, 95%CI [-0.09 to 0.27], p-value = 0.312). However, the angle of femoral bowing was greater in males than females by a mean of 0.76° (95%CI [0.04 to 1.49], p-value = 0.04) when compared using the independent t-test. ConclusionIt appears that anterior femoral bowing is more pronounced in the Arab population, compared to other ethnicities. We encourage more research to define the possible outcomes in patients with severe femoral deformity and to assess the use of computer-assisted surgery in these cases.

Use of computer-assisted surgery in the orbit

ABSTRACT Purpose To present the application of computer-assisted surgery (CAS) in pre-operative planning, intra-operative navigation, and post-operative assessment as an adjunct tool in orbital surgery. Methods An IRB-approved, retrospective review was performed to identify patients who had undergone orbital surgery by a single surgeon from July 2013 to December 2019 with attention to pre-operative virtual surgical planning, intra-operative navigation, and post-operative assessment. The reasons and methods of CAS use were classified. Results The use of computer-assisted technologies was identified in 91 cases out of 464 orbital surgeries (19.6%). This included 23 (25.3%) orbital decompression surgeries, 39 (42.9%) fracture repairs, and 25 (27.5%) orbital tumors. In all cases, pre-, intra-, and post-operative CAS allowed for increased operative efficiency and safety with good outcomes. Conclusions Use of CAS in orbital surgery can allow for complex radiographic analysis and in select cases is a great tool to add to the orbital surgeon’s armamentarium.

Computer navigation does not improve 10-year functional outcomes following total knee arthroplasty: A randomised clinical trial

Purpose: The use of computer-assisted surgery (CAS) in total knee arthroplasty (TKA) has been widely shown to be beneficial in improving prostheses alignment. The evidence of correlation to superior functional result, however is both sparse and conflicting. Methods: TKA participants were randomised into one of three trial arms to compare implantation techniques; CAS, intramedullary instrumentation guides for femur and tibia or intramedullary guides for femur and extramedullary tibial jigs. This was a single centre trial, with one senior surgeon performing all surgeries through a standardised medial parapatellar approach and cemented prostheses. Participants were blinded to surgical technique, and post-operatively followed up for 10 years. Outcome measures included a Numerical Knee Pain Rating, Oxford Knee Score and Short Form Health Survey and Likert satisfaction score. Results: 107 patients were successfully randomised for age, body mass index and knee function. Mean surgical times were 112 minutes for CAS, 82 minutes for EM/IM and 79 minutes for IM/IM. 68 patients completed 10-year follow-up. We failed to find significant differences in knee pain (p=0.11), knee function (p=0.24), satisfaction (p=0.43) or health status physical component score (p=0.06) or mental component score (p=0.29) at 10 years. Conclusion: 10-year results of this study indicate that compared to conventional techniques, CAS fails to provide superior long-term functional outcomes for patients undergoing TKA.

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

Aimsto 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 methodsAll 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. ResultsFour 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%. ConclusionThe 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 evidenceIV.

Interobserver agreement of sensor-derived compartmental pressure measurements in computer-assisted total knee arthroplasty

BackgroundSensor-guided compartmental pressure measurements are becoming increasingly utilized in total knee arthroplasty (TKA) to objectively confirm intraoperative knee balance. We aimed to determine agreement of pressure measurements between two observers when performing sensor-guided TKA with the use of computer-assisted surgery (CAS). MethodsOne-hundred and eighteen consecutive patients undergoing 130 TKAs were analysed. Femoral and tibial trial implants were inserted prior to performing knee balancing. We compared the reliability of sensor pressure compartmental measurements between two observers at 10, 45 and 90° of flexion using intraclass correlation coefficient (ICC) estimates and the 95% limits of agreement (Bland–Altman plots). ResultsThe interobserver agreement between sensor pressure measurements was excellent at 10° of knee flexion, with ICCs of 0.93 and 0.91 in the medial and lateral compartments, respectively (P < 0.001). At 45°, medial and lateral compartment ICCs were 0.91 and 0.76, respectively (P < 0.001). At 90°, the ICC was 0.88 medially and 0.76 laterally (P < 0.001). Although the agreement decreased at higher knee flexion, it remained good to excellent. The 95% limits of agreement at each angle were all within 20 psi and 11 psi for the medial and lateral compartments, respectively. ConclusionsThere was excellent interobserver agreement of sensor pressure measurements at 10° of knee flexion with computer-assisted TKA. Interobserver agreement decreased slightly as knee flexion angles increased, particularly in the lateral compartment. It is likely that interobserver agreement and hence reliability of sensor pressure measurements in TKA has some dependence on accurate angular positioning of the knee.

Consensus statement for perioperative care in total hip replacement and total knee replacement surgery: Enhanced Recovery After Surgery (ERAS®) Society recommendations

Background and purpose — There is a large volume of heterogeneous studies across all Enhanced Recovery After Surgery (ERAS®) components within total hip and total knee replacement surgery. This multidisciplinary consensus review summarizes the literature, and proposes recommendations for the perioperative care of patients undergoing total hip replacement and total knee replacement with an ERAS program.Methods — Studies were selected with particular attention being paid to meta-analyses, randomized controlled trials, and large prospective cohort studies that evaluated the efficacy of individual items of the perioperative treatment pathway to expedite the achievement of discharge criteria. A consensus recommendation was reached by the group after critical appraisal of the literature.Results — This consensus statement includes 17 topic areas. Best practice includes optimizing preoperative patient education, anesthetic technique, and transfusion strategy, in combination with an opioid-sparing multimodal analgesic approach and early mobilization. There is insufficient evidence to recommend that one surgical technique (type of approach, use of a minimally invasive technique, prosthesis choice, or use of computer-assisted surgery) over another will independently effect achievement of discharge criteria.Interpretation — Based on the evidence available for each element of perioperative care pathways, the ERAS® Society presents a comprehensive consensus review, for the perioperative care of patients undergoing total hip replacement and total knee replacement surgery within an ERAS® program. This unified protocol should now be further evaluated in order to refine the protocol and verify the strength of these recommendations.

Virtual 3D planning of osteotomies for craniosynostoses and complex craniofacial malformations

Introduction and objectivesComputer-assisted surgery has been more and more widely used in craniofacial surgery in recent years. It is useful in many situations: stereolithographic models, surgical simulations of osteotomies and bone repositioning, and cutting guides and customized implants. The present paper argues that computer-assisted surgery is particularly useful in complex cases such as rare malformations, or to address the sequelae of previous surgeries. The various advantages of the technique are emphasized from a surgical and from a teaching standpoint. Materials and methodsForty cases of various computer-assisted surgeries were analyzed, allowing a comprehensive review of outcomes in cases such as craniosynostosis, complex craniosynostosis, hypertelorism, craniosynostosis sequelae and cranio-facial and orbital trauma. ResultsResults were promising in all of the cases reviewed, except in a few cases for which computer-assisted surgery with cutting guides may not be necessary. In these specific cases, the pedagogical input is nevertheless interesting for residents and students. ConclusionComputer-assisted surgery is revolutionizing the surgical approach to complex craniofacial malformations, as well as easing management of less complex ones. It is likely that in the years to come this technique will supersede previous ones. However, using this technique implies being willing to rely on a non-human device. We need to consider computer-assisted surgery as a tool that can change surgical practices. The surgeon can rely on it, yet nothing will replace his/her eye and experience. It is the combination of both this experience and the appropriate use of computer-assisted surgery that, ultimately, leads to successful surgery.

Reconstructive orbital surgery

In complex orbital reconstructions ideal positioning of the bony buttress and surrounding soft tissue is aprerequisite for an aesthetic and functional result. The use of computer-assisted surgery can support the surgeon before and during the reconstruction procedure and facilitate quality control processes. This is illustrated using three clinical examples. The areas of interest (bony defect areas, surrounding tissues) are segmented in a3D image series. In most cases, the contralateral non-affected side can serve as the reference in virtual reconstruction. The virtual model obtained can now be used for the manufacturing of patient specific models and implants, as well as for intraoperative navigation or direct quality control with the use of intraoperative cone beam computed tomography (CBCT). For the reconstruction of primary and secondary traumatic defects as well as for congenital malformations or neoplastic diseases, the presented workflow can be used. Preoperative virtual visualization, patient specific reconstruction and direct quality control using intraoperative CBCT ensure that the preoperatively planned result can be achieved. Together with the interplay of hard and soft tissue the best possible results can be achieved. Computer-assisted surgery has been continuously further developed over the last two decades and is currently used in the clinical routine. Patient specific implants in combination with the use of direct intraoperative quality control facilitate the reconstruction of complex orbital injuries and defects and enable the ideal reconstruction from both aesthetic and functional aspects.

Perceptions and use of computer-assisted surgery (CAS) in the orbit

ABSTRACT Computer-assisted surgery (CAS) plays a prominent role in certain surgical disciplines. We investigated the current perceptions and use of this technology for orbital surgery. An online survey was emailed to members of the American Society of Ophthalmic Plastic and Reconstructive Surgery, Canadian Society of Oculoplastic Surgery, and British Oculoplastic Surgery Society. Respondents were asked to describe their practice type and seniority, their frequency of orbital surgery, experience, use, and accessibility of CAS, and their opinion on the technology. There were a total of 151 responses across the societies. 105 respondents (69.5%) had been in attending/consultant practice for over 10 years, with over half (54.7%) working in academic/teaching hospitals. The majority (66.7%) had superficial or no experience with CAS. In total, 84.8% of respondents rarely or never use CAS for orbital surgery (n = 128). Posterior orbital surgery (64.2%) and orbital decompression (49.0%) were the two most useful reasons to implement CAS. Longer operating time (58.3%) and cost (54.8%) were the two most selected weaknesses for CAS, whereas improved accuracy in attaining surgical end point(s) (80.8%) and patient safety (63.6%) were the principal advantages. Type of practice was significantly associated with CAS availability/accessibility (p < 0.05). Proportion of orbital surgery performed in practice was significantly associated with both CAS experience and use (p < 0.05). Our study confirms an expected variation in the perception and use of CAS for orbital surgery. Demonstrated patient benefit and integration of refined and cost-effective CAS systems into operating room environments may influence its future role.

Navigated versus conventional total knee arthroplasty: A prospective study at three years follow-up

ObjectiveComputer-assisted surgery application in total knee arthroplasty (TKA) has shown more accurate implant alignment compared with conventional instrumentation and is associated with more homogeneous alignment results. Although longer implant survival and superior clinical outcomes should be expected from navigated TKA, currently available evidence does not support this hypothesis. The aim of this study was to compare navigated TKA with conventional TKA regarding clinical and radiological outcomes after a 3-year follow-up under the hypothesis that navigated TKA would provide better outcomes than conventional TKA. Material and methodIn a prospective multicentre study, 119 patients underwent navigated TKA and 80 patients received conventional instrumentation. Patients were evaluated at the baseline and at postoperative months 3, 12, 24, and 36. Analysis included the American Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Short Form-12 (SF12) Health Survey, and radiographic assessment. ResultsAll clinical scores improved significantly for all patients during the follow-up but were significantly better in the navigation group.The percentage of patients showing a mechanical axis between 3° of varus and 3° of valgus was significantly higher in the ATR group (93%) than in the conventional TKA group (71%) (p<.01). ConclusionsThe use of computer-assisted surgery in TKA provides more accurate mechanical alignment and superior short-term functional outcomes compared to conventional TKA.

Artroplastia total de rodilla navegada versus convencional; estudio prospectivo a 3 años de seguimiento

ObjectiveComputer-assisted surgery application in total knee arthroplasty (TKA) has shown more accurate implant alignment compared with conventional instrumentation and is associated with more homogeneous alignment results. Although longer implant survival and superior clinical outcomes should be expected from navigated TKA, currently available evidence does not support this hypothesis. The aim of this study was to compare navigated TKA with conventional TKA regarding clinical and radiological outcomes after a 3-year follow-up under the hypothesis that navigated TKA would provide better outcomes than conventional TKA. Material and methodIn a prospective multicentre study, 119 patients underwent navigated TKA and 80 patients received conventional instrumentation. Patients were evaluated at the baseline and at postoperative months 3, 12, 24, and 36. Analysis included the American Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Short Form-12 (SF12) Health Survey, and radiographic assessment. ResultsAll clinical scores improved significantly for all patients during the follow-up but were significantly better in the navigation group.The percentage of patients showing a mechanical axis between 3° of varus and 3° of valgus was significantly higher in the ATR group (93%) than in the conventional TKA group (71%) (P<.01). ConclusionsThe use of computer-assisted surgery in TKA provides more accurate mechanical alignment and superior short-term functional outcomes compared to conventional TKA.

Use of Computer Assistance in Lumbar Fusion Surgery: Analysis of 15 222 Patients in the ACS-NSQIP Database.

Study Design:Retrospective cohort study.Objective:Several studies have shown that the accuracy of pedicle screw placement significantly improves with use of computer-assisted surgery (CAS). Yet few studies have compared the incidence of postoperative complications between CAS and conventional techniques. The objective of this study is to determine the difference in postoperative complication rates between CAS and conventional techniques in spine surgery.Methods:The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was used to identify patients who underwent posterior lumbar fusion from 2011 to 2013. Multivariate analysis was conducted to demonstrate the difference in postoperative complication rates between CAS and conventional techniques in spine surgery.Results:Out of 15 222 patients, 14 382 (95.1%) were operated with conventional techniques and 740 (4.90%) were operated with CAS. Multivariate analysis showed that patients in the CAS group had fewer odds to experience adverse events postoperatively (odds ratio [OR] = 0.57, P < .001). Minor adverse events occurred in 2905 (20.2%) patients in the conventional group and in 98 (13.2%) patients in the CAS group (OR = 0.57, P < .001). Blood transfusion was present in 2488 (17.3%) of the patients in the conventional group compared to 81 (11.0%) of the patients in the CAS group (OR = 0.56, P < .001). The mean operative time in the conventional group was 205.2 ± 106.1 minutes, and it was 227.0 ± 111.9 minutes in the CAS group. This difference was statistically significant (r = 20.14, P < .001).Conclusion:This article examined the complications in lumbar spinal surgery with or without the use of CAS. These results suggest that CAS may provide a safer technique for implant placement in lumbar fusion surgeries.

The use of computer-assisted surgery as an educational tool for the training of orthopedic surgery residents in pedicle screw placement: a pilot study and survey among orthopedic residents.

The training of orthopedic residents in adequate pedicle screw placement is very important. We sought to investigate orthopedic residents' perspectives on the use of computer-assisted surgery (CAS) in a training trial. Orthopedic residents were randomly assigned to independently place a screw using the free-hand technique and the CAS technique on 1 of 3 cadavers (Cobb angles 5º, 15º and 67º) at randomly selected thoracolumbar vertebral levels. All residents were blinded to their colleagues' pedicle screw placements and were asked to complete a short questionnaire at the end of the session to evaluate their experience with CAS. We obtained CT images for each cadaver to assess pedicle screw placement accuracy and classified placement as A) screw completely in pedicle, B) screw < 2 mm outside pedicle, C) screw 2-4 mm outside pedicle, or D) screw > 4 mm outside pedicle. Twenty-four orthopedic residents participated in this trial study. In total, 65% preferred using the free-hand technique in an educational setting even though most (60%) said that CAS is safer. The main reason for free-hand technique preference was the difficult technical aspects encountered with CAS. In addition, accuracy of pedicle screw placement in this trial showed that 5 screws were classified as A or B (safe zone) and 19 as grade C or D (unsafe zone) using the free-hand technique compared with 15 and 9, respectively, using CAS (p = 0.008). Orthopedic residents perceived CAS as safe and demonstrated improved accuracy in pedicle screw placement in a single setting. However, the residents preferred the free-hand technique in an educational stetting owing to the difficult technical aspects of CAS.

No difference between computer-assisted and conventional total knee arthroplasty: five-year results of a prospective randomised study

The use of computer-assisted surgery (CAS) in total knee arthroplasty (TKA) results in better limb and implant alignment compared to conventional TKA; however, it is unclear whether this translates to better mid- to long-term clinical outcome. This prospective randomised study comparing CAS and conventional TKA reports the functional and patient perceived outcomes at a follow-up of 5 years. The hypothesis was that there would be a difference in functional outcome or quality of life after mid-term follow-up. Sixty-seven patients were available for physical and radiological examination at 5 years. The Knee Society Score (KSS) was used to describe functional outcome and the Euroquol questionnaire for quality of life. The mean total KSS for the CAS group improved from 91.1 (SD 22.3) points preoperatively to 157.4 (SD 21.9) and 150.2 (SD 30.4) points at 2 and 5 years, respectively. In the conventional group, the mean total KSS was 99.6 (SD 18.6) points preoperatively and 151.1 (SD 26.0) and 149.0 (SD 28.0) points at 2 and 5 years, respectively. The mean quality of life score improved from 48.2 (SD 16.5) points preoperatively to 67.4 (SD 16.3) and 66.8 (SD 22.2) points at 2 and 5 years in the CAS group, and from 52.2 (SD 17.1) points preoperatively to 65.6 (SD 14.6) and 61.7 (SD 19.3) points at 2 and 5 years, respectively, in the conventional TKA group. These differences were not statistically significant. There were radiolucent lines up to 2 mm in 11 knees (four CAS, seven conventional), but there were no changes in implant position. There were no significant differences in functional or patient perceived outcome after mid-term follow-up in this study. I.

Clinical Outcomes After Computer-assisted Versus Conventional Total Knee Arthroplasty

The purpose of this study was to determine whether the use of computer-assisted surgery can improve the clinical results in total knee arthroplasty (TKA) compared with conventional methods of TKA.A literature search of PubMed (1966 to August 2011), CENTRAL (Cochrane Controlled Trials Register; issue 3, 2011), and EMBASE (1984 to August 2011) was conducted. Randomized, controlled trials detecting the clinical outcomes of TKA with or without the use of computer-assisted surgery were identified. A meta-analysis of these clinical trials was then performed. Twenty-one articles were included in the meta-analysis. The results confirmed that operative time was significantly increased with the use of computer-assisted TKA (mean standard difference, 14.68; 95% confidence interval [CI], 11.74 to 17.62; P<.00001], whereas no significant difference existed between the 2 groups regarding the total operative blood loss (mean standard difference, -54.38; 95% CI, -119.76 to 11.00; P=.10). As for other clinical outcomes, including the Knee Society Score (mean standard difference, 4.47; 95% CI, -1.05 to 9.99; P=.36) and range of motion (mean standard difference, 1.38; 95% CI, -1.43 to 4.18; P=.34), the use of computer-assisted TKA did not help to improve function recovery postoperatively.

Short-term outcome of 1,465 computer-navigated primary total knee replacements 2005–2008

Background and purpose Improvement of positioning and alignment by the use of computer-assisted surgery (CAS) might improve longevity and function in total knee replacements, but there is little evidence. In this study, we evaluated the short-term results of computer-navigated knee replacements based on data from the Norwegian Arthroplasty Register.Patients and methods Primary total knee replacements without patella resurfacing, reported to the Norwegian Arthroplasty Register during the years 2005–2008, were evaluated. The 5 most common implants and the 3 most common navigation systems were selected. Cemented, uncemented, and hybrid knees were included. With the risk of revision for any cause as the primary endpoint and intraoperative complications and operating time as secondary outcomes, 1,465 computer-navigated knee replacements (CAS) and 8,214 conventionally operated knee replacements (CON) were compared. Kaplan-Meier survival analysis and Cox regression analysis with adjustment for age, sex, prosthesis brand, fixation method, previous knee surgery, preoperative diagnosis, and ASA category were used.Results Kaplan-Meier estimated survival at 2 years was 98% (95% CI: 97.5–98.3) in the CON group and 96% (95% CI: 95.0–97.8) in the CAS group. The adjusted Cox regression analysis showed a higher risk of revision in the CAS group (RR = 1.7, 95% CI: 1.1–2.5; p = 0.02). The LCS Complete knee had a higher risk of revision with CAS than with CON (RR = 2.1, 95% CI: 1.3–3.4; p = 0.004)). The differences were not statistically significant for the other prosthesis brands. Mean operating time was 15 min longer in the CAS group.Interpretation With the introduction of computer-navigated knee replacement surgery in Norway, the short-term risk of revision has increased for computer-navigated replacement with the LCS Complete. The mechanisms of failure of these implantations should be explored in greater depth, and in this study we have not been able to draw conclusions regarding causation.

Computer-Assisted Surgery

Implant-supported prostheses are a predictable treatment of totally edentulous patients. Progresses in implantology allowed realizing prostheses that are supported by immediately loading implants. Implants can be inserted in the healed site as fresh extraction sites, without differences about long-term results. Using computer-assisted surgery, it is possible to insert implants in a predetermined position and to create a prostheses, which can be immediately fixed on the implants. Patients have major comfort and an immediate aesthetic and functional result. The use of computer-assisted surgery in fresh extraction sites is a procedure that has not been evaluated because of technical difficulties: teeth extraction eliminates references for surgical guides. The absence of guidelines to treat dentulous areas is often likely caused by lack of computer-assisted surgery: we attempted to use this procedure to replace residual teeth with an immediate implant prosthetic rehabilitation. The aim of this clinical report was to show the possibility to apply computer-assisted surgery in dentulous patient using a double surgical template: one before extraction and the other after extraction of selected teeth.

Zygomatic and Maxillary Implants Inserted by Means of Computer-Assisted Surgery in a Patient With a Cleft Palate

This report describes the possibility of treating a patient affected by unilateral cleft palate and an extremely atrophied edentulous maxilla using zygomatic implants inserted in a conventional manner and maxillary implants inserted by means of a computer-assisted surgery. A cross-arch prosthesis supported by 4 maxillary and 2 zygomatic implants may be an ideal mode of prosthetic rehabilitation for these kinds of patients. The use of zygomatic implants is essential to optimize load distribution and to increase prosthesis stability, whereas the use of computer-assisted surgery facilitates surgical procedures and makes it possible to improve patient satisfaction.

Stellenwert emissarischer Venen bei der operativen Therapie temporaler Paragangliome

With the surgical removal of temporal paraganglioma, possible changes of the cerebral blood pathways of the Circle of Willis should be considered. If the cerebral blood drains dominates unilaterally and the pathway of drainage over the Bulbus venae jugularis is inadequate due to vessel malformation or variations or by intraluminal tumor growth, as for instance of temporal paragangliomas, collateral emissary vessels can take over this function by an extraordinary large lumen extension. Ignorance of such a characteristic venous drainage can lead to hemorrhagic apoplexia when such originally redundant veins are sacrificed. A presurgical angiography is, therefore, indicated. In case of vessel malformations or variations the use of computer-assisted surgery could be helpful to preserve such native emissary veins at the bony skull base, such as the condylar emissary vein in the case of a transcondylar infralabyrinthine approach.

Does Computer-Assisted Surgery Improve Accuracy and Decrease the Learning Curve in Hip Resurfacing? A Radiographic Analysis

Hip resurfacing is a technically demanding procedure in which accurate positioning of the femoral component is critical to the avoidance of early implant failures. The purpose of this study was to assess the accuracy of computer-assisted placement of the femoral component and to evaluate the impact of computer-assisted surgery on the learning curve associated with this procedure. The accuracy of positioning the femoral component was analyzed radiographically in hips undergoing resurfacing procedures performed by surgeons assigned to four different study groups: Group 1, in which the operations were performed with use of computer-assisted surgery by a fellowship-trained surgeon who was experienced in performing resurfacing arthroplasty (surgical experience, more than 250 hip resurfacings); Group 2, in which the operations were performed with use of computer-assisted surgery by senior residents who were inexperienced in performing resurfacing arthroplasty and who were closely supervised by faculty; Group 3, in which the operations were performed with use of conventional instruments by fellowship-trained faculty members; and Group 4, in which the operations were performed with use of computer-assisted surgery by a lesser experienced fellowship-trained faculty member (surgical experience, more than forty but less than seventy-five hip resurfacings) from Group 3. The range of error in varus or valgus angulation that was observed for navigated procedures was 6 degrees in Group 1, 7 degrees in Group 2, and 5 degrees in Group 4. Compared with the preoperative neck-shaft angle value, the mean postoperative stem-shaft angle value increased by a mean of 4.7 degrees in Group 1, 7.2 degrees in Group 2, 6.5 degrees in Group 3, and 11.6 degrees in Group 4. When compared with the use of standard instrumentation, the use of computer-assisted surgery reduced the number of outliers and facilitated valgus insertion. In the present study, computer-assisted surgery resulted in improved accuracy and precision in positioning the femoral component. In addition, computer-assisted surgery led to a reduction in the length of the learning curve for beginners in hip resurfacing and improved the surgeon's ability to perform this procedure safely.