Biomedical subjects

Jens Geerling

Publications and source records attributed to Jens Geerling.

7 recordsLinked to original sources

PubMed2006

Intraoperative pedography: a validated method for static intraoperative biomechanical assessment.

BACKGROUND: A new device was developed to perform intraoperative static pedography. The purpose of this study was to validate the introduced method by a comparison with the standard method for dynamic and static pedography. METHODS: A device known as Kraftsimulator Intraoperative Pedographie (KIOP) was developed for intraoperative placement of standardized forces to the sole of the foot. Pedographic measurements were done with a custom-made mat that was inserted into the KIOP (Pliance, Novel Inc., St. Paul, MN, USA). Validation was done in two steps: (1) comparison of standard dynamic pedography walking on a platform, standard static pedography in standing on a platform, and pedography with KIOP in supine position in 30 healthy volunteers, and (2) comparison of static pedography in standing position, pedography with KIOP supine awake, and pedography with KIOP supine with 30 patients under anesthesia. Individuals who had operative procedures at the knee or distal to the knee were excluded. The different measurements were compared (one-way ANOVA, t-test; significance level 0.05). RESULTS: No significant differences were found among all measurements for the hindfoot compared to midfoot-forefoot force distribution. For the medial compared to lateral force distribution and the 10-region-mapping, significant differences were found when comparing all measurements (steps 1 and 2) and when comparing the measurements of step 1 only. No differences were found for these distributions when comparing the measurements of step 2 alone or when comparing the measurements of step 1 and 2 without the platform measurements of step 1 (dynamic walking pedography and static standing pedography). No significant differences in the force distributions were found in step 2 when comparing subjects without anesthesia, with general anesthesia, and with spinal anesthesia. CONCLUSIONS: The KIOP device allows a valid static intraoperative pedography measurement. No statistically significant force distribution differences were found between standing subjects and anesthetized subjects in the supine position.

Adult↗

PubMed2006

Differences in the mechanical properties of calcaneal artificial specimens, fresh frozen specimens, and embalmed specimens in experimental testing.

BACKGROUND: Artificial calcanei, fresh-frozen cadaver specimens, and embalmed cadaver specimens were compared in experimental testing under biocompatible loading to clarify the biocompatibility of artificial calcaneal specimens for implant testing. METHODS: Two different artificial calcaneal bone models (Sawbone, Pacific Research Laboratories, Vashon, WA, and Synbone, Synbone Inc., Davos, Switzerland), embalmed cadaver calcaneal specimens (bone density, 313.1 +/- 40.9 g/cm2; age, 43.8 +/- 7.9 years), and fresh-frozen cadaver calcanei (bone density, 238.5 +/- 30.0 g/cm2; age, 44.4 +/- 8.2 years) were used for testing. Seven specimens of each model or cadaver type were tested. A mechanical testing machine (Zwick Inc., Ulm, Germany) was used for loading and measurements. Cyclic loading (preload 20 N, load was increased every 100 cycles by 100 N from 1,000 to 2,500 N, 0.5 mm/s) and load to failure (0.5 mm/s) were performed. The loads were applied through an artificial talus in a physiological loading direction. The displacement of the posterior facet in the primary loading direction was measured. RESULTS: The four different specimen groups showed different stability and different displacement in the primary loading direction during cyclic loading. The variation of the maximal displacement in the primary loading direction for the entire cyclic loading was higher in artificial specimens than in the cadaver specimens. CONCLUSIONS: Artificial calcanei (Sawbone, Synbone) showed different biomechanical characteristics than cadaver bones (embalmed and fresh-frozen) in this experimental setup with biocompatible cyclic loading. These results do not support the use of artificial calcanei for biomechanical implant testing. Fresh-frozen and embalmed specimens seem to be equally adequate for mechanical testing. The low variation of mechanical strength in the unpaired cadaver specimens suggests that the use of PAIRED specimens is not necessary.

Adult↗

PubMed2005

Intraoperative three-dimensional imaging with a motorized mobile C-arm (SIREMOBIL ISO-C-3D) in foot and ankle trauma care: a preliminary report.

OBJECTIVE: The aim of the study was to assess the feasibility and benefit of the intraoperative use of a mobile C-arm with 3-dimensional imaging (ISO-C-3D). DESIGN: Prospective consecutive clinical study. SETTING: University hospital, level I trauma center. METHODS: The ISO-C-3D was used for intraoperative visualization in foot and ankle trauma care. Conventional C-arms were used to judge the reduction and implant position before the ISO-C-3D was used. Time spent, changes resulting from use of the ISO-C-3D, and surgeons' ratings (visual analogue scale, 0-10 points) were recorded. PATIENTS: Between January 1, 2003 and March 15, 2004, the ISO-C-3D was used in 62 cases (factures: pilon, n = 1; Weber-C ankles, n = 7; isolated dorsal Volkmann, n = 1; talus, n = 3; calcaneus, n = 20; navicular, n = 1; cuboid, n = 1; Lisfranc fracture-dislocation, n = 6; hindfoot arthrodesis with or without correction, n = 12). RESULTS: On average, the operation was interrupted for 440 seconds (range 330-700); 120 seconds, on average, for the ISO-C-3D scan and 210 seconds, on average, for evaluation of the images by the surgeon. In 39% of the cases (24 of 62), the reduction and/or implant position was corrected during the same procedure after the ISO-C-3D scan. The ratings of the 8 surgeons who used the ISO-C-3D were 9.2(5.2-10) for feasibility, 9.5 (6.1-10) for accuracy, and 8.2 (4.5-10) for clinical benefit. CONCLUSION: Intraoperative 3-dimensional visualization with the ISO-C-3D can provide useful information in foot and ankle trauma care that cannot be obtained from plain films or conventional C-arms. During the same procedure, after conventional C-arm scans judged the positioning to be correct and an ISO-C-3D scan was done, the reduction and/or implant position was corrected in 39% of the cases in this study, although not unnecessarily prolonging the operation. The ISO-C-3D appears to be most helpful in procedures with a closed reduction and internal fixation, and/or when axial reformations provide information that is not possible to obtain with a conventional C-arm and/or direct visualization during open reduction and internal fixation.

Ankle Injuries↗

PubMed2005

A comparison of plates with and without locking screws in a calcaneal fracture model.

BACKGROUND: We compared different plates in an experimental calcaneal fracture model under biocompatible loading. METHODS: Four plates were tested: a plate without locked screws (Synthes), and three different plates with locked screws (Newdeal, Darco, Synthes). Synthetic calcanei (Sawbone) were osteotomized to create a fracture model, and the plates were fixed onto them. Seven specimens for each plate model were subjected to cyclic loading (preload 20 N, 1,000 cycles with 800 N, 0.75 mm/s), and load to failure (0.75 mm/s). Motion, forces, plastic deformation of the plate, and consequent depression of the posterior joint facet were analyzed. RESULTS: During cyclic loading, all plates with locked screws showed statistically significant lower displacement in the primary loading direction than the plates without locked screws. Mean values (mm) of maximal displacements for each plate during cyclic loading were as follows: Synthes, 3.5; Darco, 4.5; Newdeal, 5.0; Synthes without locked screws, 7.5; (p < 0.001). No statistically significant differences between the plates were found in relation to loads to failure and corresponding displacement. CONCLUSION: This is the first biomechanical study to assess the stability of different plates currently in use in our practice for the fixation of calcaneal fractures. Our results showed that plates with locked screws provided greater stability during cyclic loading than the plate without locked screws.

Biomechanical Phenomena↗

PubMed2005

Navigated Iso-C3D-based percutaneous osteoid osteoma resection: a preliminary clinical report.

Minimally invasive osteoid osteoma resection under computer tomography (CT) guidance has yielded good results and has become a viable alternative to open surgical procedures. Limited visualization of the actual drill position under CT guidance can frequently result in inadequate and malpositioned drilling, especially at lesions located in less accessible anatomic regions. With the conventional CT-guided drilling technique, sterility and general operative management poorly correlate with standard operating room conditions, and are at risk of intra- and postoperative complications. The new Iso-C(3D) imaging device provides intraoperative multiplanar reconstructions. Adequate image quality and implementation in navigation systems were described for numerous indications. On the basis of multiplanar reconstructions, minimally invasive navigated techniques under three-dimensional surgical tool control become possible, which is not the case under fluoroscopic or CT-based navigation. We report on our first three cases of navigated Iso-C(3D) osteoid osteoma resection. A minimally invasive resection of the nidus was possible under permanent multiplanar image control. No complications were encountered and all patients reported successful outcomes. Minimally invasive-based navigation offered an effective and reproducible surgical approach. Dependence on CT imaging for proper positioning and complications associated with use away from the operating room environment can be avoided.

Bone Neoplasms↗

PubMed2004

Computer aided tumor resection in the pelvis.

Surgical treatment of malignant tumors within the pelvis is a complex problem due to the anatomy and biomechanics. There are standardized preoperative diagnostic tools like computed tomography (CT) or magnetic resonance imaging (MRI) that provide multidimensional information. However, this information cannot be transferred intraoperatively. Computer aided orthopedic surgery (CAOS) may be a solution for precise intraoperative accuracy for these indications. We report on two patients with tumors within the pelvis. In one patient, an infiltrating recurrent chordoma within the sacrum was resected with CAOS. The other patient presented with a periacetabular chondrosarcoma. Resection was done with navigation so precise that a custom-made hemipelvis prosthesis with a special coating fit. In both patients, a complete resection was achieved with tumor-free resection margins. Navigation may be helpful in tumor surgery within the pelvis.

Bone Neoplasms↗

PubMed2003

Computer assisted pelvic surgery: registration based on a modified external fixator.

A fundamental step in Computer Assisted Surgery (CAS) is the registration, when the preoperative virtual data and the corresponding operative anatomy of the region of interest are merged. To provide exact landmarks for anatomical registration, a tubular external fixator was modified. Two intact pelvic bones (one artificial foam pelvis and one cadaver specimen) were used for the experimental setup. Registration was carried out using a standardized protocol for anatomy-based registration in the control group; anatomical registration was achieved using a modified external fixator in the study group. This external fixator had titanium fiducials wedged into the fixator carbon tubes serving as landmarks for paired-point registration. The tubes were used for surface registration. The standard anterior pelvis fixator assembly was augmented with additional bilateral tubes oriented towards the posterior, enabling registration of the sacroiliac areas. The accuracy of registration was checked by "reversed verification", where the examiner used only the screen display to control the virtual position of the pointer tip in relation to selected landmarks. By virtual matching, the real distance was measured with a digital caliper. We defined the verification as "accurate" when the residual distance was less than 1 mm; "acceptable" when it was between 1 mm and 2 mm; and "insufficient" when it exceeded 2 mm. The paired T-test with significance levels of p < 0.05 was used for statistical analysis. The anatomical registration based on the external fixator landmarks was statistically as accurate as that obtained using anatomical landmarks on the pelvic bone. This study concludes that the external fixator, a conventional tool in the management of acute traumatic pelvic instability, can also be useful for landmark registration in CAS.

External Fixators↗