Biomedical subjects

C Krettek

Publications and source records attributed to C Krettek.

237 records · Page 14Linked to original sources

PubMedDate not supplied

[Induction of bone tissue on different matrices: an in vitro and a in vivo pilot study in the SCID mouse].

AIM: Three resorbable biomaterials were evaluated regarding proliferation and osteogenic differentiation of human bone marrow stromal cells (BMSC) in vitro. In a second step, the new biomaterial, calcium-deficient hydroxyapatite (CDHA), was tested in a pilot in vivo study by subcutaneous implantation in the severe combined immunodeficiency (SCID) mouse. METHODS: CDHA, beta-tricalcium phosphate (beta-TCP), and demineralized bone matrix (DBM) were seeded with human BMSC and cultured in osteogenic supplements for 3 weeks. In the pilot in vivo study, CDHA was seeded with BMSC and kept in osteogenic media for 2 weeks (group A) before subcutaneous implantation in 8 SCID mice for 3 and 8 weeks. In addition, CDHA seeded with BMSC without prior osteogenic induction (group B) and empty ceramics were implanted in each mouse. RESULTS: Total protein content and the values for specific alkaline phosphatase (ALP) increased significantly in vitro on all matrices, but no significant difference between the groups was noted. In the pilot in vivo study all ceramics were well penetrated by cells. After 8 weeks 2 of 4 samples in group B and 1 of 4 samples in group A revealed cells resembling hypertrophic chondrocytes. Specific ALP was higher in the group B (p = 0.012, Z = - 2.5) compared to empty ceramics. There were no significant differences between groups A and B. Differences between group A and the empty control did not become significant (p = 0.069, Z = - 1.8). CONCLUSION: All three matrices promoted BMSC proliferation and differentiation to osteogenic cells in vitro. Human BMSC on CDHA showed signs of osteogenic differentiation after subcutaneous implantation into SCID mice.

Adolescent↗

PubMedDate not supplied

Surgical options for the treatment of severe tibial pilon fractures: a study of three techniques.

OBJECTIVE: To determine whether long-term results of one of three different management protocols for severe tibial pilon fractures offer advantages over the other two. DESIGN: In a retrospective study, patients were examined clinically and radiologically after internal fixation of severe tibial plafond fractures (i.e., 92 percent Type C fractures according to the AO-ASIF classification). SETTING: Department of Traumatology, Hanover Medical School. Level I trauma center. PATIENTS: Fifty-one of seventy-seven patients treated between 1982 and 1992 were examined clinically and radiologically at an average of sixty-eight months (range 13 to 130 months) after injury. INTERVENTIONS: The patients were treated in three different ways: primary internal fixation with a plate following the AO-ASIF principles (n = 15), which was reserved for patients with closed fractures without severe soft tissue trauma; one-stage minimally invasive osteosynthesis for reconstruction of the articular surface with long-term transarticular external fixation of the ankle for at least four weeks (n = 28); and a two-stage procedure entailing primary reduction and reconstruction of the articular surface with minimally invasive osteosynthesis and short-term transarticular external fixation of the ankle joint followed by secondary medial stabilization with a plate using a technique requiring only limited skin incisions (a reduced invasive technique) (n = 8). MAIN OUTCOME MEASUREMENTS: Objective evaluation criteria were infection rate, amount of posttraumatic arthritis, range of ankle movement, and number of arthrodeses. Subjective criteria were pain, swelling, and restriction of work or leisure activities. RESULTS: Because only closed fractures were treated by primary internal fixation with a plate, there was a statistically significant difference (p < 0.005) in the distribution of open fractures between the three treatment groups. Fracture classification in these groups were not significantly different. All but four fractures were classified as Type C lesions according to the AO-ASIF system. The soft tissue was closed in 63 percent (n = 32) and open in 37 percent (n = 19). No significant relationship could be found between the soft tissue damage and degree of arthritis or between the type of surgical treatment and extent of posttraumatic arthritis. However, none of the patients who required secondary arthrodesis (23 percent of all cases) were in the group who had undergone two-step surgery (p < 0.05). The range of ankle movement was much greater in the two-step group than in the others; these patients also had less pain, more frequently continued working in their previous profession, and had fewer limitations in their leisure activities. These differences did not reach statistical significance. The incidence of wound infection did not differ significantly among the three groups. CONCLUSIONS: On the basis of our results, we now prefer a two-step procedure for the treatment of severe tibial pilon fractures with extensive soft tissue damage. In the first stage, primary reduction and internal fixation of the articular surface is performed using stab incisions, screws, and K-wires. Temporary external fixation is applied across the ankle joint. After recovery of the soft tissues, the second stage entails internal fixation with a medial plate using a reduced invasive technique.

Adolescent↗

PubMedDate not supplied

Accuracy study of computer-assisted drilling: the effect of bone density, drill bit characteristics, and use of a mechanical guide.

OBJECTIVE: This study was designed to determine the clinical relevant accuracy of CT-based navigation for drilling. DESIGN: Experimental model. SETTING: Laboratory. METHODS: Twelve drills of varying lengths and diameters were tested with 2 different set-ups. Group 1 used free-hand navigated drilling technique with foam blocks equipped with titanium target points. Group 2 (control) used a newly developed 3-dimensional measurement device equipped with titanium target points with a fixed entry for the navigated drill to minimize bending forces. One examiner performed 690 navigated drillings using solely the monitor screen for control in both groups. The difference between the planned and the actual starting and target point (up to 150 mm distance) was measured (mm). STATISTICS: Levene test and a nonpaired t test. Significance level was set as P < 0.05. RESULTS: The core accuracy of the navigation system measured with the 3-dimensional device was 0.5 mm. The mean distance from planned to actual entry points in group 1 was 1.3 (range, 0.6-3.4 mm). The mean distance between planned and actual target point was 3.4 (range, 1.7-5.8 mm). Free-hand navigated drilling showed an increased difference with increased length of the drill bits as well as with increased drilling channel for drill bits 2.5 and 3.2 mm and not for 3.5 and 4.5 mm (P < 0.05). CONCLUSIONS: The core accuracy of the navigation system is high. Compared with the navigated free-hand technique, the results suggest that drill bit deflection interferes directly with the precision. The precision is decreased when using small diameter and longer drill bits.

Bone Density↗