Biomedical subjects

Andreas Wentzensen

Publications and source records attributed to Andreas Wentzensen.

5 recordsLinked to original sources

PubMed2004

C-arm based navigation in total hip arthroplasty-background and clinical experience.

After experimental and preclinical evaluation of a CT-free image guided surgical navigation system for acetabular cup placement, the system was introduced into clinical routine. The computation of the angular orientation of the cup is based on reference coordinates from the anterior pelvic plane concept. A hybrid strategy for pelvic landmark acquisition has been introduced, involving percutaneous pointer-based digitization with the noninvasive bi-planar landmark reconstruction using multiple registered fluoroscopy images. From January 2001 to October 2003, a total of 236 consecutive patients (mean age 66 years, 144 male, 92 female, 124 left and 112 right hip joints) were operated on with the hybrid CT-free navigation system. During each operation, the angular orientation of the inserted implant was recorded. To determine the placement accuracy of the acetabular components, the first 50 consecutive patients underwent a CT scan 7-10 days postoperatively to analyze the cup position relative to the anterior pelvic plane. This procedure was done blinded and with commercial planning software. There was no significant learning curve observed for the use of the system. Mean values for postoperative inclination read 42 degrees (SD 3.6, range (37-49)) and anteversion 21 degrees (SD 3.9, range (10-28)). The resulting system accuracy, ie, the difference between intraoperatively calculated cup orientation and postoperatively measured implant position shows a maximum error of 5 degrees for the inclination (mean 1.5 degrees, SD 1.1) and 6 degrees for the anteversion (mean 2.4 degrees, SD 1.3). An accuracy of better than 5 degrees inclination and 6 degrees anteversion was achieved under clinical conditions, which implies that there is no significant difference in performance from the established CT-based navigation methods. Image-guided CT-free cup navigation provides a reliable solution for future total hip arthroplasty (THA).

Aged↗

PubMed2004

Polymorphonuclear neutrophils in posttraumatic osteomyelitis: cells recovered from the inflamed site lack chemotactic activity but generate superoxides.

The pathogenesis of posttraumatic osteomyelitis, one of the major complications after orthopedic surgery, is not yet understood. Formation of bacterial biofilms on the implant is presumed, conferring resistance to antibiotic therapy and probably also to the host defense mechanisms. In that context, the polymorphonuclear neutrophils (PMN) having infiltrated the infected site were recovered and characterized phenotypically and functionally. Loss of CD62L and upregulation of CD14 were seen, as was expression of CD83. Expression of the latter is dependent on de novo protein synthesis and thus is indicative of an extended life span and a transdifferentiation of the PMN at the infected site. The infiltrated PMN had lost their chemotactic activity, whereas the capacity to produce superoxides was preserved and in some patients even enhanced. In vitro experiments done in parallel showed that long-term culture with interferon-gamma resulted in similar alterations of PMN: loss of chemotactic activity, whereas other functions of PMN, such generation of superoxides and phagocytosis of opsonized bacteria, were preserved or even enhanced. The loss of the migratory capacity of PMN having already emigrated from the blood vessel to the infected site is not expected to affect the host defense negatively. Assuming, however, that bacteria are organized as a biofilm and that infiltration into this biofilm is required for phagocytosis of the bacteria, our data could to some extent explain why despite being activated, the PMN are not able to control the infection. By releasing their cytotoxic, proteolytic, and collagenolytic potential, PMN might instead contribute to tissue destruction and eventually to osteolysis.

Adult↗

PubMed2003

Post-traumatic osteomyelitis: analysis of inflammatory cells recruited into the site of infection.

Device-associated infections after implants or endoprostheses inflict local inflammation and ultimately osteolysis, a clinical entity referred to as posttraumatic osteomyelitis. The underlying molecular mechanisms are not yet known; formation of bacterial biofilms on the implant is presumed, conferring resistance to antibiotics and to host defense mechanisms as well. To gain insight into the pathogenesis of post-traumatic osteomyelitis, the infected site was analyzed for the presence of immunocompetent cells. In 18 patients, the infected site was rinsed intraoperatively. This so-called lavage contained 1-2 x 107 leukocytes, predominantly highly activated polymorphonuclear neutrophils (PMNs), as characterized by low expression of CD62L (selectin), and high expression of the adhesion protein CD18, of the high-affinity immunoglobulin (IgG) receptor CD64, and of the LPS-receptor CD14. CD16, the low-affinity IgG receptor, was affected in some patients only. Because the majority of infections were caused by staphylococci species, the effect of bacteria-derived lipoteichoic acid on PMN of healthy donors was tested in vitro. A similar activation pattern was found: rapid down-regulation of CD62L, a slower loss of CD16, and upregulation of CD18, CD64, and CD14. Lipoteichoic acid signaling required p38 mitogen-activated protein kinase and resulted in induction of CD14-specific mRNA and de novo protein synthesis. We conclude that PMNs infiltrate the infected site, but despite local activation they are unable to clear the bacteria, presumably because of biofilm formation. Our data are consistent with the hypothesis that during the ineffective "frustrated" attempt to phagocytose, PMNs release cytotoxic and proteolytic entities that in turn contribute to the progression of tissue injury and ultimately to osteolysis.

Adolescent↗

PubMed2003

Image-based hip navigation.

After experimental and preclinical evaluation (HAP Paul Award 2001) of a CT-free image-guided surgical navigation system for acetabular cup placement, the system was introduced into clinical routine. The computation of the angular orientation of the cup is based on reference coordinates from the anterior pelvic plane (APP) concept. A hybrid strategy for pelvic landmark acquisition has been introduced involving percutaneous pointer-based digitization with the noninvasive biplanar landmark reconstruction using multiple registered fluoroscopy images. From January 2001 to May 2002, 118 consecutive patients (mean age 68 years, 82 male, 36 female, and 62 left and 56 right hip joints) were operated on with the hybrid CT-free navigation system. During each operation, the angular orientation of the inserted implant was recorded. To determine the placement accuracy of the acetabular components, the first 50 consecutive patients underwent a CT scan 7-10 days postoperatively to analyze the cup position relative to the APP. This was done blinded with commercial planning software. There was no significant learning curve observed for the use of the system. Mean values for postoperative inclination read 43 degrees (SD 3.0, range 37-49) and anteversion 19 degrees (SD 3.9, range 10-28). The resulting system accuracy, i.e., the difference between intraoperatively calculated cup orientation and postoperatively measured implant position, shows a maximum error of 5 degrees for the inclination (mean 1.5 degrees, SD 1.1) and 6 degrees for the anteversion (mean 2.4 degrees, SD 1.3). An accuracy of better than 5 degrees inclination and 6 degrees anteversion was achieved under clinical conditions, which implies that there is no significant difference in performance from the established CT-based navigation methods. Image-guided CT-free cup navigation provides a reliable solution for future total hip arthroplasty (THA).

Acetabulum↗

PubMed2002

Recombinant human bone morphogenetic protein-2 for treatment of open tibial fractures: a prospective, controlled, randomized study of four hundred and fifty patients.

BACKGROUND: The treatment of open fractures of the tibial shaft is often complicated by delayed union and nonunion. The objective of this study was to evaluate the safety and efficacy of the use of recombinant human bone morphogenetic protein-2 (rhBMP-2; dibotermin alfa) to accelerate healing of open tibial shaft fractures and to reduce the need for secondary intervention. METHODS: In a prospective, randomized, controlled, single-blind study, 450 patients with an open tibial fracture were randomized to receive either the standard of care (intramedullary nail fixation and routine soft-tissue management [the control group]), the standard of care and an implant containing 0.75 mg/mL of rhBMP-2 (total dose of 6 mg), or the standard of care and an implant containing 1.50 mg/mL of rhBMP-2 (total dose of 12 mg). The rhBMP-2 implant (rhBMP-2 applied to an absorbable collagen sponge) was placed over the fracture at the time of definitive wound closure. Randomization was stratified by the severity of the open wound. The primary outcome measure was the proportion of patients requiring secondary intervention because of delayed union or nonunion within twelve months postoperatively. RESULTS: Four hundred and twenty-one (94%) of the patients were available for the twelve-month follow-up. The 1.50-mg/mL rhBMP-2 group had a 44% reduction in the risk of failure (i.e., secondary intervention because of delayed union; relative risk = 0.56; 95% confidence interval = 0.40 to 0.78; pairwise p = 0.0005), significantly fewer invasive interventions (e.g., bone-grafting and nail exchange; p = 0.0264), and significantly faster fracture-healing (p = 0.0022) than did the control patients. Significantly more patients treated with 1.50 mg/mL of rhBMP-2 had healing of the fracture at the postoperative visits from ten weeks through twelve months (p = 0.0008). Compared with the control patients, those treated with 1.50 mg/mL of rhBMP-2 also had significantly fewer hardware failures (p = 0.0174), fewer infections (in association with Gustilo-Anderson type-III injuries; p = 0.0219), and faster wound-healing (83% compared with 65% had wound-healing at six weeks; p =0.0010). CONCLUSIONS: The rhBMP-2 implant was safe and, when 1.50 mg/mL was used, significantly superior to the standard of care in reducing the frequency of secondary interventions and the overall invasiveness of the procedures, accelerating fracture and wound-healing, and reducing the infection rate in patients with an open fracture of the tibia.

Adolescent↗