Biomedical subjects

Philippe Merloz

Publications and source records attributed to Philippe Merloz.

5 recordsLinked to original sources

PubMed2006

Femoral nerve palsy following mini-open extraperitoneal lumbar approach: report of three cases and cadaveric mechanical study.

Anterior extraperitoneal exposures to the lumbar spine are being increasingly used owing to the expanding use of novel technologies to treat degenerative disc disease. Lumbar plexus injuries are potential, albeit uncommon, complications of such exposures and can lead to significant perioperative morbidity. In this report, we present three patients with thoracolumbar fractures who sustained isolated femoral nerve palsies after a mini-open extraperitoneal approach to the midlumbar spine was undertaken to perform a partial corpectomy. To further understand the pathophysiology of this nerve injury, we conducted a cadaveric experiment to evaluate the effect of performing this approach and the effect of hip positioning on linear displacement of the femoral nerve. The displacement of the femoral nerve during the anterolateral extraperitoneal exposure through a 4- to 6-cm incision was equal to 6.6% of the full femoral nerve length. Relaxation of the femoral nerve was equal to 25% of the full nerve length when the hip was flexed to 90 degrees in neutral abduction-adduction. We conclude that the anterolateral extraperitoneal exposure of the midlumbar spine can potentially stretch the femoral nerve beyond its physiologic limits, particularly in trauma cases where exposure of the lateral vertebral body necessitates substantial retraction of the psoas muscle. The avoidance of self-retaining retractors for prolonged periods of time and the positioning of the hip in flexion may help to avoid such nerve injuries.

Adult↗

PubMed2006

Anterior cruciate ligament reconstruction using navigation: a comparative study on 60 patients.

BACKGROUND: Poor outcome in anterior cruciate ligament reconstruction is often related to tunnel position. HYPOTHESIS: Improving accuracy of the tunnel position will lead to improved outcome. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: Sixty patients were randomized to either standard instrumentation or computer-assisted guides to position the tibial and femoral tunnels. The results were evaluated on clinical outcome based on International Knee Documentation Committee form (laxity) and radiologic assessment: radiologic Lachman (Telos at 150 and 200 N) and analysis of the tunnel positions. RESULTS: International Knee Documentation Committee laxity was level A in 22 knees in the conventional group (mean, 1.5 mm at 200 N) compared with 26 navigated knees (mean laxity, 1.3 mm; P = .49). Laxity was less than 2 mm in 96.7% of the navigated group and 83% of the conventional group (P = .292). The variability of laxity in the navigated group was significantly less than in the conventional group, with the standard deviation of the navigated group being smaller than that in the conventional group (P = .0003 at 150 N and .0005 at 200 N Telos). A significant difference (P = .03) was found between the groups in the ATB value (distance between the projection of the Blumensaat line on the tibial plateau and the anterior edge of the tibial tunnel), characterizing the sagittal position of the tibial tunnel (negative ATB values imply graft impingement in extension). In the conventional group, mean ATB was -0.2 (-5 to +4), whereas it was 0.4 (0 to 3) in the navigated patients. There were no negative ATB values in the navigated group. CONCLUSION: This study confirms that the accuracy and consistency of tibial tunnel position can be improved by the use of computer-assisted navigation and that the clinical result in terms of laxity is more reliable.

Adolescent↗

PubMed2006

[Basic concept in computer assisted surgery].

OBJECTIVE: To investigate application of medical digital imaging systems and computer technologies in orthopedics. METHODS: The main computer-assisted surgery systems comprise the four following subcategories. RESULTS: (1) A collection and recording process for digital data on each patient, including preoperative images (CT scans, MRI, standard X-rays), intraoperative visualization (fluoroscopy, ultrasound), and intraoperative position and orientation of surgical instruments or bone sections (using 3D localises). Data merging based on the matching of preoperative imaging (CT scans, MRI, standard X-rays) and intraoperative visualization (anatomical landmarks, or bone surfaces digitized intraoperatively via 3D localiser; intraoperative ultrasound images processed for delineation of bone contours). (2) In cases where only intraoperative images are used for computer-assisted surgical navigation, the calibration of the intraoperative imaging system replaces the merged data system, which is then no longer necessary. (3) A system that provides aid in decision-making, so that the surgical approach is planned on basis of multimodal information: the interactive positioning of surgical instruments or bone sections transmitted via pre- or intraoperative images, display of elements to guide surgical navigation (direction, axis, orientation, length and diameter of a surgical instrument, impingement, etc. ). And (4) A system that monitors the surgical procedure, thereby ensuring that the optimal strategy defined at the preoperative stage is taken into account. CONCLUSION: It is possible that computer-assisted orthopedic surgery systems will enable surgeons to better assess the accuracy and reliability of the various operative techniques, an indispensable stage in the optimization of surgery.

Humans↗

PubMed2005

Detection of the center of the hip joint in computer-assisted surgery: an evaluation study of the Surgetics algorithm.

OBJECTIVE: The aim of this paper is to assess the accuracy of an algorithm implemented by PRAXIM in the SURGETICS navigation station for detection of the hip center. This study will assess the robustness and accuracy of the algorithm in various clinical situations such as those involving non-sphericity of the femoral head, motion of the pelvis during hip center detection, and restricted range of motion. MATERIALS AND METHODS: The localization of the hip center, based on kinematics, relies on the recording of n successive positions of the femoral rigid body in the localizer reference system during a passive circumduction motion of the hip joint. Therefore, the shape of the clouds of points acquired may vary from one acquisition to the next. To allow a comprehensive study of the consequences of these variations for hip center detection, we developed a simulator to generate numerous clouds of points. Results given subsequently for each test are the values of the difference between the femoral mechanical axis computed with C(c), the computed hip center, and the same axis computed with C(o), the reference hip center. RESULTS: Test 1: Sensitivity to noise. The errors ranged from 3.33 E - 12 (SD 3.29E - 12) for a noise of 0 mm to 8.18E - 1 (SD - 7.05E - 1) for a noise of 15 mm. Test 2: Sensitivity to the shape of the acquisition motion. All trajectories gave an error < 1 degrees . Test 3: Sensitivity to restricted range of motion. No value > 1 degrees was found during this test. Test 4: Sensitivity to the distance between two points of the cloud. No value > 0.5 degrees was found during this test. Test 5: Sensitivity to the number of points included in the cloud. No value > 1 degrees was found during this test. CONCLUSIONS: The Surgetics algorithm is robust to noise, can compensate for pelvic motion, and can be used even in the case of restricted range of motion.

Algorithms↗

PubMed2004

Compliance with guidelines on antibiotic prophylaxis in total hip replacement surgery: results of a retrospective study of 416 patients in a teaching hospital.

OBJECTIVE: To assess compliance of anesthesiologist practices in antibiotic prophylaxis during total hip replacement (THR) surgery with the French Society of Anesthesiology and Intensive Care consensus-based guidelines. DESIGN: Retrospective review of medical records. Compliance of anesthesiologist practices with the guidelines was assessed according to antibiotic prophylaxis use, antimicrobial agent, dosage of first injection, time from first dose to incision, and total duration of antibiotic prophylaxis. SETTING: Orthopedic surgery wards in a 2,200-bed French teaching hospital. PATIENTS: A random sample of 416 patients undergoing THR from January 1999 to December 2000. RESULTS: Three hundred eighty-six (93%) of the sampled medical records were usable. Antibiotic prophylaxis was used for 366 (95%) of the patients. Total duration of prophylaxis did not exceed 48 hours in 98% (359 of 366) of the patients. Drug selection complied with national guidelines in 259 (71%) of the patients. Dosage and timing of the first injection were appropriate in 98% (290 of 296) and 80% (236 of 296) of the patients, respectively, who received one of the recommended antibiotics. Overall, 53% (203 of 386) of the patients met all five criteria. In multivariate analysis, there was a significant anesthesiologist effect on overall compliance with the guidelines (likelihood ratio chi-square with 9 degrees of freedom, 25.7; P < .01). Undergoing surgery during 2000 was the only patient characteristic associated with an increased rate of appropriate practices (adjusted OR, 1.56; CI95 1.02-2.38). CONCLUSION: The overall compliance rate should be improved by disseminating the guidelines and the results of this study following audit and feedback.

Adult↗