Biomedical subjects

Andreas Eisenschenk

Publications and source records attributed to Andreas Eisenschenk.

4 recordsLinked to original sources

PubMed2007

Does chemotherapy impair the bone healing and biomechanical stability of vascularized rib and fibula grafts?

The purpose of this study was to observe the impact of chemotherapy on the healing and biomechanical properties of vascularized bone grafts. Ten male beagle dogs were divided into two experimental groups: a chemotherapy group (CH) and control group (C). Group CH received adjuvant and neo-adjuvant chemotherapy. Each animal of both groups underwent the following operative procedures. The 5th and 7th rib were removed and replaced by vascularized pedicle transfers of the adjacent 4th and 8th rib. Additionally, a free fibular flap was elevated and retransferred to the same anatomic position. The rate of bony union on plain x-ray was 100 percent in group C, 30 percent in the vascularized rib, and 80 percent in the fibula grafts of group CH. Microangiography demonstrated no avascular bone segments in group C and in the fibula flaps of group CH. The vascularized ribs of group CH presented with 20 percent avascular bone segments. Biomechanical tests focusing on the durability of the vascularized grafts against bending and torsion forces demonstrated a reduction of the average maximum bending times by 17 percent and 23.9 percent compared to the controls ( P < 0.05). The twisting times were reduced by 13.8 percent (n.s.) and 32.5 percent ( P < 0.05). The data demonstrated a clear worsening in bone healing and stability after simulated adjuvant and neo-adjuvant chemotherapy. Thus, a large animal model was established for the further determination of the effects of chemotherapy on different vascularized bone transfers.

Angiography↗

PubMed2006

Impact of radiation therapy on healing and stability of vascularized bone grafts in a dog model.

The purpose of the study was to observe the impact of radiation therapy on healing and biomechanical properties of vascularized bone grafts, and thus to establish an appropriate large animal model. Ten male beagles were divided into two experimental groups: radiation (R) and control (C). The left 5th to 7th ribs of the animals of group R were irradiated 3 and 2 weeks preoperatively, using a dose of 8 Gy each time. Each animal of both groups underwent the following operative procedures. The 5th and 7th ribs were removed, and the 5th rib was replaced by a vascularized pedicle transfer of the 4th rib. The 7th rib was reconstructed using a pedicle transplant of the 8th rib. The 5th and 7th ribs were used as nonvascularized bone grafts to replace the donor sites of the 4th and 8th ribs, respectively. Group R received two further irradiation cycles 2 and 3 weeks postoperatively. The vascularized rib grafts of group R demonstrated a higher number of delayed unions in plain x-rays and avascular bone segments in microangiography than the control group. The presence of vital osteocytes in histology was not significantly different between groups. Biomechanical tests focusing on the durability of vascularized ribs against bending and torsion forces demonstrated a reduction of average maximum bending moments by 56.6% after radiation compared to controls (P < 0.05). Twisting moments were reduced by 47.6% (P < 0.05). The data demonstrate a significant worsening in bone healing and stability after pre- and postoperative radiation therapy to the wound bed and bone grafts. Thus, a large animal model is established for further determination of different strategies of radiotherapy in combination with vascularized bone transfers.

Animals↗

PubMed2006

The application of vestibular-evoked myogenic potentials in otoneurosurgery.

OBJECTIVE: To evaluate the applicability of vestibular-evoked myogenic potentials (VEMPs) in the diagnostics, intraoperative monitoring, and postoperative follow-up of patients in otoneurosurgery. STUDY DESIGN: A prospective study of patients who underwent either cochlear implantation (CI, n = 18) or were diagnosed with an acoustic neuroma (AN, n = 9) or with neuro(micro)vascular compression of the VIIIth nerve (NVC, n = 27) in the period 2002 to 2004. The follow-up was 1 year for all patients. SETTING: A tertiary-referral unit. RESULTS: VEMPs could be recorded in 64% of all patients before CI and in 22% after surgery. The patients with AN had normal VEMPs in 22% of all cases when first diagnosed. Normal VEMPs were found in 37% of those patients with NVC. From the 5 AN patients who had to be operated, only 1 had intact VEMPs after surgery. In contrast, after microvascular decompression all patients (4) had normal VEMPs. CONCLUSIONS: VEMPs are helpful in diagnosing patients with vertigo to better identify saccular defects. They are highly sensitive in the early diagnosis of retrocochlear lesions. SIGNIFICANCE: VEMPs can help to reliably identify patients with a retrocochlerar lesion at an early stage and can be used in intraoperative, neurophysiological monitoring. EBM RATING: C-4.

Adolescent↗

PubMed2005

The "pull-back" technique for Nucleus 24 perimodiolar electrode insertion.

OBJECTIVE: To observe the influence of electrode pull-back after cochlear implant insertion of Nucleus 24 perimodiolar electrodes. STUDY DESIGN: In a prospective intraoperative study, we analyzed the impedances, neural response telemetry responses, and the spread of excitation after cochlear implant electrode insertion and compared these data to those obtained after a subsequent, controlled pull-back of the electrode. Postoperative depth of electrode insertion was controlled by x-ray. SETTING: Tertiary referral center. SUBJECTS: Six patients (4 male, 2 female; 18 to 69 years) were implanted with a Nucleus 24 (RCA) cochlear implant with a perimodiolar electrode. RESULTS: After a controlled pull-back, a significant decrease of the spread of excitation at the stimuli electrodes 5, 10, 15, and a nonsignificant decrease at stimuli electrode 20 compared to the recordings after the primary normal insertion procedure was found. The mean electric compound action potential amplitude was increased with an apical-to-basal tendency. Impedances remained unchanged by the pull-back. Mean insertion depth at the postoperative x-ray control was 372 degrees (+/- 10.2). CONCLUSION: Controlled cochlear implant electrode pull-back is a novel technique that optimizes objective intraoperative electrophysiological recordings in patients implanted with a Nucleus 24 perimodiolar cochlear implant by a greater approximation of the electrode to the modiolus.

Adolescent↗