René Schmidt

Orthopädisch-Chirurgische Zentrum, Cham Regen, Bavaria, Germany

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Publications (31)66.11 Total impact

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    ABSTRACT: The decision of when to use selective thoracic fusion (STF) and the prediction of spontaneous lumbar curve correction (SLCC) remain difficult. Using a novel methodological approach, the authors yielded for a better prediction of SLCC and analyzed the efficacy of anterior scoliosis correction and fusion (ASF). A retrospective analysis of 273 patients treated with ASF for STF was performed. In total, 87 % of the patients showed a Lenke 1 curve pattern. The lumbar curve modifier was classified as A in 66 % of the patients, B in 21 % of the patients and C in 13 % of the patients. The fusion length averaged 6.7 levels. The analysis included an assessment of radiographic deformity and correction, surgery characteristics, complications and revisions and clinical outcomes to improve the prediction of SLCC. Patients with a Type A-L, Type B or Type C modifier were stratified into a target follow-up lumbar curve (LC) category of ≤20° or >20°. Linear regression analyses were performed to assess the accuracy of predicting LC magnitude, and a multivariate logistic regression model was built using the following preoperative (preop) predictors: main thoracic curve (MTC), LC, MTC-bending and LC-bending. The output variable indicated whether a patient had an LC >20° at follow-up. A variable selection algorithm was applied to identify significant predictors. Two thresholds (cut-offs) were applied to the test sample to create high positive and negative prediction values. The data from 33 additional patients were gathered prospectively to create an independent test sample to learn how the model performed with independent data as a test of the generalizability of the model. The average patient age was 17 years, and the average follow-up period was 33 months. The MTC was 53.1° ± 10.2° preoperatively, 29.8° ± 10.5° with bending and was 25.4° ± 9.7° at follow-up (p < 0.01). The LC was 35.7° ± 7.5° preoperatively, 8.9° ± 5.8° with bending, and 21.8° ± 7.0° at follow-up (p < 0.01). After applying a variable selection algorithm, the preop LC [p < 0.02, odds ratio (OR) = 1.09] and preop LC-bending (p < 0.009, OR = 1.14) remained in the model as significant predictors. The performance of the linear regression model was tested in an independent test sample, and the difference between the observed and predicted values was only 1° ± 4.5°. Based on the test sample, the lower threshold was set to 25 %, and the upper threshold was set to 75 %. Patients with prediction values of 25-75 % were identified by the model, but by definition of the model, no prediction was made. In the test sample, 87 % of the patients were correctly classified as having an LC ≤20° at follow-up, and 84 % of the patients were correctly classified as having an LC >20°. The model test in the independent test sample revealed that 100 % of the patients were correctly classified as having an LC ≤20°, and 86 % of the patients were correctly classified as having an LC >20°. After analyzing a sufficiently large sample of 273 patients who underwent ASF for STF, significant predictors for SLCC were established and reported according to the surgical outcomes. Application of the prediction models can aid surgeons in the decision-making process regarding when to perform STF. Our results indicate that with stratification of outcomes into target curves (e.g., an LC <20°), future benchmarks for STF might be more conclusive.
    European Spine Journal 03/2014; · 2.47 Impact Factor
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    ABSTRACT: There is sparse literature on how best to correct Scheuermann's kyphosis (SK). The efficacy of a combined strategy with anterior release and posterior fusion (AR/PSF) with regard to correction rate and outcome is yet to be determined. A review of a consecutive series of SK patients treated with AR/PSF using pedicle screw-rod systems was performed. Assessment of demographics, complications, surgical parameters and radiographs including flexibility and correction measures, proximal junctional kyphosis angle (JKA + 1) and spino-pelvic parameters was performed, focusing on the impact of curve flexibility on correction and clinical outcomes. 111 patients were eligible with a mean age of 23 years, follow-up of 24 months and an average of eight levels fused. Cobb angle at fusion level was 68° preoperatively and 37° postoperatively. Flexibility on traction films was 34 % and correction rate 47 %. Postoperative and follow-up Cobb angles were highly correlated with preoperative bending films (r = 0.7, p < 0.05). Screw density rate was 87 %, with increased correction with higher screw density (p < 0.001, r = 0.4). Patients with an increased junctional kyphosis angle (JKA + 1) were at higher risk of revision surgery (p = 0.049). 22 patients sustained complication, and 21 patients had revision surgery. 42 patients with ≥24 months follow-up were assessed for clinical outcomes (follow-up rate for clinical measures was 38 %). This subgroup showed no significant differences regarding baseline parameters as compared to the whole group. Median approach-related morbidity (ArM) was 8.0 %, SRS-sum score was 4.0, and ODI was 4 %. There was a significant negative correlation between the SRS-24 self-image scores and the number of segments fused (r = -0.5, p < 0.05). Patients with additional surgery had decreased clinical outcomes (SRS-24 scores, p = 0.004, ArM, p = 0.0008, and ODI, p = 0.0004). The study highlighted that AR/PSF is an efficient strategy providing reliable results in a large single-center series. Results confirmed that flexibility was the decisive measure when comparing surgical outcomes with different treatment strategies. Findings indicated that changes at the proximal junctional level were impacted by individual spino-pelvic morphology and determined by the individually predetermined thoracolumbar curvature and sagittal balance. Results stressed that in SK correction, reconstruction of a physiologic alignment is decisive to achieving good clinical outcomes and avoiding complications.
    European Spine Journal 07/2013; · 2.47 Impact Factor
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    ABSTRACT: Aims and background. Kyphoplasty is an effective procedure providing structural stability and pain alleviation in vertebral metastases. To prevent early regrowth, patients typically receive postoperative fractionated radiotherapy, which is associated with long treatment duration. Therefore, we established a new approach to deliver intraoperative radiotherapy during kyphoplasty to shorten the treatment time and reach structural stability and sterilization of the metastases (Kypho-IORT). Methods and study design. For Kypho-IORT, a 50 kV X-ray source with a specially designed applicator was used. A radiation dose of 8 Gy in 5 mm distance was delivered. After radiation the device was removed and the kyphoplasty was completed according to the standard procedure. Since August 2009, 18 patients with instable or painful spinal metastases received Kypho-IORT. The median age was 63 years (range, 43-73). Results. Kypho-IORT was successfully performed in 18 of 21 vertebral lesions (86%). No severe complications occurred during or early after IORT. The median pain score using a visual analogue scale decreased from 5/10 before the procedure to 2.5/10 at day 1 (P <0.001) and to 0/10 six weeks after the procedure (P = 0.001). Imaging studies were available for 15 of 18 patients. Stable disease within the irradiated vertebral body was seen in 14 patients (93%) and local progressive disease in one patient (7%). No re-irradiation due to local progressive disease or pain recurrence was necessary within the median follow-up of 4.5 months. Conclusions. Kypho-IORT is well tolerated without severe side effects and provides fast improvement of pain. Although stable disease was seen in 93% of the patients, a longer follow-up is necessary to assess the effectiveness. A dose escalation study to establish the maximally tolerated dose has been initiated.
    Tumori. 07/2012; 98(4):434-40.
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    ABSTRACT: To evaluate whether this new method is clinically applicable after theoretical and cadaver testing. The incidence of spinal metastases requiring therapy is increasing, due to enhanced life expectancy. Due to results from studies with epidural compression a combined surgical and radiation therapy is often chosen. Minimal invasive cement augmentation is an increasingly used technique, due to fast pain relief and immediate stabilisation. On the other hand, stereotactic radiosurgery is considered to provide a more durable response and better local disease control than conventional radiotherapy with the application of higher doses. Therefore the combination of cement stabilisation and simultaneous intra-operative radiation with immediate stabilisation and high-dose radiation could be an interesting therapeutic option. The results of a clinical feasibility study are presented. 17 patients could be treated with the new method. In two patients (10%) intra-operative radiation could not be applied. No surgical interventions for complications were required. Summarizing Kypho-IORT is technically feasible with an intra-operative risk profile comparable to sole kyphoplasty and a shorter treatment time and hospitalisation for the patients compared to conventional multifraction radiation. Radiation could not be applied in 10% of cases due to technical difficulties. The results of this feasibility study permit further evaluation of this new technique by a dose escalation study which is currently in preparation.
    International Orthopaedics 01/2012; 36(6):1255-60. · 2.32 Impact Factor
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    ABSTRACT: Clinical studies reported frequent failure with anterior instrumented multilevel cervical corpectomies. Hence, posterior augmentation was recommended but necessitates a second approach. Thus, an author group evaluated the feasibility, pull-out characteristics, and accuracy of anterior transpedicular screw (ATPS) fixation. Although first success with clinical application of ATPS has already been reported, no data exist on biomechanical characteristics of an ATPS-plate system enabling transpedicular end-level fixation in advanced instabilities. Therefore, we evaluated biomechanical qualities of an ATPS prototype C4–C7 for reduction of range of motion (ROM) and primary stability in a non-destructive setup among five constructs: anterior plate, posterior all-lateral mass screw construct, posterior construct with lateral mass screws C5 + C6 and end-level fixation using pedicle screws unilaterally or bilaterally, and a 360° construct. 12 human spines C3–T1 were divided into two groups. Four constructs were tested in group 1 and three in group 2; the ATPS prototypes were tested in both groups. Specimens were subjected to flexibility test in a spine motion tester at intact state and after 2-level corpectomy C5–C6 with subsequent reconstruction using a distractable cage and one of the osteosynthesis mentioned above. ROM in flexion–extension, axial rotation, and lateral bending was reported as normalized values. All instrumentations but the anterior plate showed significant reduction of ROM for all directions compared to the intact state. The 360° construct outperformed all others in terms of reducing ROM. While there were no significant differences between the 360° and posterior constructs in flexion–extension and lateral bending, the 360° constructs were significantly more stable in axial rotation. Concerning primary stability of ATPS prototypes, there were no significant differences compared to posterior-only constructs in flexion–extension and axial rotation. The 360° construct showed significant differences to the ATPS prototypes in flexion–extension, while no significant differences existed in axial rotation. But in lateral bending, the ATPS prototype and the anterior plate performed significantly worse than the posterior constructs. ATPS was shown to confer increased primary stability compared to the anterior plate in flexion–extension and axial rotation with the latter yielding significance. We showed that primary stability after 2-level corpectomy reconstruction using ATPS prototypes compared favorably to posterior systems and superior to anterior plates. From the biomechanical point, the 360° instrumentation was shown the most efficient for reconstruction of 2-level corpectomies. Further studies will elucidate whether fatigue testing will enhance the benefit of transpedicular anchorage with posterior constructs and ATPS.
    European Spine Journal 04/2011; · 2.47 Impact Factor
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    ABSTRACT: Preoperative embolization of vertebral metastases has been shown to lower intraoperative blood loss. Nevertheless, excessive up to life-threatening blood loss can occur despite embolization. We therefore decided to evaluate possible parameters for predicting significant blood loss in a surgically homogeneous group of patients with vertebral metastases. Patients with vertebral metastases of the thoracic and thoracolumbar spine who underwent preoperative embolization were included. All patients had existing or impending neurological deficit as the main indication for direct metastasis reduction. The parameters evaluated were the technical feasibility of embolization, vascularization grade of metastasis, success of embolization, tumor type in relation to blood loss, and interval between embolization and surgery. Twenty-seven patients fullfilled the inclusion criteria. Technically complete embolization was feasible in 14 patients (52%) and fully successful embolization was obtained in 10 patients (37%). Eighty-three percent of the renal cell carcinomas were hypervascularized, but also 67% of the breast carcinoma patients had hypervascularized tumors. No permanent complications occurred during embolization, but two patients had pain and another two experienced a transient burning sensation. A significant difference in intraoperative blood loss was only found between patients achieving partially or fully successful embolization in the subgroup of hypervascularized grade III metastases. The success of embolization in the group of hypervascularized grade III metastases was the only predictor for the extent of blood loss in our study. Due to the inaccuracy of predicting high blood loss in general all possible precautions for excessive blood loss should be taken despite preoperative embolization. Further randomized studies to determine the indications and results of embolization seem desirable.
    Tumori 01/2011; 97(1):66-73. · 0.92 Impact Factor
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    ABSTRACT: Clinical studies reported frequent failure with anterior instrumented multilevel cervical corpectomies. Hence, posterior augmentation was recommended but necessitates a second approach. Thus, an author group evaluated the feasibility, pull-out characteristics, and accuracy of anterior transpedicular screw (ATPS) fixation. Although first success with clinical application of ATPS has already been reported, no data exist on biomechanical characteristics of an ATPS-plate system enabling transpedicular end-level fixation in advanced instabilities. Therefore, we evaluated biomechanical qualities of an ATPS prototype C4-C7 for reduction of range of motion (ROM) and primary stability in a non-destructive setup among five constructs: anterior plate, posterior all-lateral mass screw construct, posterior construct with lateral mass screws C5 + C6 and end-level fixation using pedicle screws unilaterally or bilaterally, and a 360° construct. 12 human spines C3-T1 were divided into two groups. Four constructs were tested in group 1 and three in group 2; the ATPS prototypes were tested in both groups. Specimens were subjected to flexibility test in a spine motion tester at intact state and after 2-level corpectomy C5-C6 with subsequent reconstruction using a distractable cage and one of the osteosynthesis mentioned above. ROM in flexion-extension, axial rotation, and lateral bending was reported as normalized values. All instrumentations but the anterior plate showed significant reduction of ROM for all directions compared to the intact state. The 360° construct outperformed all others in terms of reducing ROM. While there were no significant differences between the 360° and posterior constructs in flexion-extension and lateral bending, the 360° constructs were significantly more stable in axial rotation. Concerning primary stability of ATPS prototypes, there were no significant differences compared to posterior-only constructs in flexion-extension and axial rotation. The 360° construct showed significant differences to the ATPS prototypes in flexion-extension, while no significant differences existed in axial rotation. But in lateral bending, the ATPS prototype and the anterior plate performed significantly worse than the posterior constructs. ATPS was shown to confer increased primary stability compared to the anterior plate in flexion-extension and axial rotation with the latter yielding significance. We showed that primary stability after 2-level corpectomy reconstruction using ATPS prototypes compared favorably to posterior systems and superior to anterior plates. From the biomechanical point, the 360° instrumentation was shown the most efficient for reconstruction of 2-level corpectomies. Further studies will elucidate whether fatigue testing will enhance the benefit of transpedicular anchorage with posterior constructs and ATPS.
    European Spine Journal 12/2010; 19(12):2137-48. · 2.47 Impact Factor
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    ABSTRACT: Only a few reports exist concerning biomechanical challenges spine surgeons face when treating Parkinson's disease (PD) patients with spinal deformity. We recognized patients suffering from spinal deformity aggravated by the burden of PD to stress the principles of sagittal balance in surgical treatment. Treatment of sagittal imbalance in PD is difficult due to brittle bone and (the neuromuscular disorder) with postural dysfunction. We performed a retrospective review of 23 PD patients treated surgically for spinal disorders. Mean ASA score was 2.3 (2-3). Outcome analysis included review of medical records focusing on failure characteristics, complications, and radiographic analysis of balance parameters to characterize special risk factors or precautions to be considered in PD patients. The sample included 15 female and 8 male PD patients with mean age of 66.3 years (57-76) at index surgery and 67.9 years (59-76) at follow-up. 10 patients (43.5%) presented with the sequels of failed previous surgery. 18 patients (78.3%) underwent multilevel fusion (C3 level) with 16 patients (69.6%) having fusion to S1, S2 or the Ilium. At a mean follow-up of 14.5 months (1-59) we noted medical complications in 7 patients (30.4%) and surgical complications in 12 patients (52.2%). C7-sagittal center vertical line was 12.2 cm (8-57) preoperatively, 6.9 cm postoperatively, and 7.6 cm at follow-up. Detailed analysis of radiographs, sagittal spinal, and spino-pelvic balance, stressed a positive C7 off-set of 10 cm on average in 25% of patients at follow-up requiring revision surgery in 4 of them. Statistical analysis revealed that patients with a postoperative or follow-up sagittal imbalance (C7-SVL >10 cm) had a significantly increased rate of revision done or scheduled (p = 0.03). Patients with revision surgery as index procedure also were found more likely to suffer postoperative or final sagittal imbalance (C7-SPL, 10 cm; p = 0.008). At all, 33% of patients had any early or late revision performed. Nevertheless, 78% of patients were satisfied or very satisfied with their clinical outcome, while 22% were either not satisfied or uncertain regarding their outcome. The surgical history of PD patients treated for spinal disorders and the reasons necessitating redo surgery for recalcitrant global sagittal imbalance in our sample stressed the mainstays of spinal surgery in Parkinson's: If spinal surgery is indicated, the reconstruction of spino-pelvic balance with focus on lumbar lordosis and global sagittal alignment is required.
    European Spine Journal 10/2010; 19(10):1785-94. · 2.47 Impact Factor
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    ABSTRACT: A total of 12 human cervical spines were tested in vitro in a biomechanical nondestructive set-up to compare the primary stability of different posterior cervical instrumentations after a bilevel corpectomy. To evaluate the primary 3-dimensional stability with special focus on the impact of cervical pedicle screws. Cervical pedicle screw fixation gains popularity due to supposed higher stability. However, biomechanical studies are rare. Especially the impact of a combination of lateral mass and pedicle screws on stability in multilevel posterior stabilizations has not been evaluated until now. A total of 12 human cervical specimens were loaded with pure moments and unconstrained motion between C4 and C7 was measured. The specimen were tested in the intact state, all lateral mass screws (all LMS) from C4-C7, cervical pedicle screws (CPS) C4 and C7 left, LMS C4-C7 right, C5+C6 left, CPS C4+C7 bilateral, LMS C5+C6, and a anterior-posterior instrumentation (360°). All instrumentations showed a higher stability compared with the intact state. No difference was found for uni- or bilateral applied CPS. The all LMS showed comparable stability than the CPS instrumentations. From a biomechanical primary stability point it seems unnecessary to add CPS in a bilevel corpectomy model. If CPS are added, the unilateral application seems sufficient.
    Spine 10/2010; 35(22):E1167-71. · 2.16 Impact Factor
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    ABSTRACT: The purpose of this study was to evaluate the influence of different implant designs of total lumbar disc replacements on the segmental biomechanics of the lumbar spine. The unconstrained Charité, the semi-constrained Prodisc and a semi-constrained Prototype with more posterior centre of rotation than the Prodisc were tested in vitro using six human, lumbar spines L2-L5. The segmental lordosis was measured on plain radiographs and the range of motion (ROM) for all six degrees of freedom with a previously described spine tester. All prostheses were implanted at level L3-L4. Compared with the intact status all prostheses resulted in a significant increase of segmental lordosis (intact 5.1°; Charité 10.6°, p = 0.028; Prodisc 9.5°, p = 0.027; Prototype 8.9°, p = 0.028), significant increase of flexion/extension (intact 6.4°, Charité 11.3°, Prodisc 12.2°, Prototype 12.2°) and axial rotation (intact 1.3°, Charité 5.4°, Prodisc 3.9°, Prototype 4.2°). Lateral bending increased significantly only for the Charité (intact 7.7°; Charité 11.6°, p = 0.028; Prodisc 9.6°, Prototype 9.8°). The segmental lordosis after Prototype implantation was significantly lower compared with Charité (p = 0.024) and Prodisc (p = 0.044). No significant difference could be observed for segmental lordosis between Charité and Prodisc and for ROM between the two semi-constrained prosthesis Prodisc and Prototype. The axial rotation for the unconstrained Charité was significantly higher than for the semi-constrained prosthesis Prodisc and Prototype, flexion/extension and lateral bending did not differ. Summarizing, the unconstrained prosthesis design increased segmental lordosis and showed a tendency towards higher ROM for axial rotation/lateral bending and lower ROM for flexion/extension than a semi-constrained prosthesis. A more anterior centre of rotation in a semi-constrained prosthesis resulted in a higher increase of segmental lordosis after TDR than a semi-constrained prosthesis with more posterior centre of rotation. The location of the centre of rotation in a semi-constrained prosthesis did not alter the magnitude of ROM. Despite the different alterations of ROM and segmental lordosis due to implant design, these differences were negligible compared with the overall increase of ROM and segmental lordosis by the implantation of a TDR compared with the physiologic state.
    European Spine Journal 09/2010; 21 Suppl 5:S577-84. · 2.47 Impact Factor
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    ABSTRACT: The concept of total lumbar disc replacement (TDR) is gaining acceptance due to good clinical short-term outcome. Standard implantation is strict anterior, which poses especially above the segment L5/S1 sometimes difficulties due to the vessel configuration. Therefore, oblique implantable TDR have been invented. In oblique implantation the anterior longitudinal ligament (ALL) is only partially resected, with additional partial resection of lateral annulus fibers. This could have an impact on biomechanical properties, which has not been evaluated until now. We therefore compared the standing ap and lateral X-rays pre- and postoperative after anterior and oblique implantation of TDR in segment L4/5. Significant differences between the groups were not found. In both the anterior and oblique group, segmental lordosis showed a significant increase, whereas total lordosis as well as ap balance were unchanged. The absolute segmental lordosis increase was nearly double in the anterior group. In conclusion, both anterior and oblique implanted TDR significantly increase segmental lordosis while retaining total lordosis and ap balance. The segmental increase is lower in the oblique implanted group which is probably due to the remaining ALL. Further studies should evaluate whether this finding has any implication for the long-term outcome.
    European Spine Journal 09/2010; 19(9):1534-9. · 2.47 Impact Factor
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    ABSTRACT: Instable and painful vertebral metastases in patients with progressive visceral metastases present a common therapeutic dilemma. We developed a novel approach to deliver intraoperative radiotherapy (IORT) during kyphoplasty and report the first treated case. 60 year old patient with metastasizing breast cancer under chemotherapy presented with a newly diagnosed painful metastasis in the 12th thoracic vertebra. Under general anaesthesia, a bipedicular approach into the vertebra was chosen with insertion of specially designed metallic sleeves to guide the electron drift tube of the miniature X-ray generator (INTRABEAM, Carl Zeiss Surgical, Oberkochen, Germany). This was inserted with a novel sheet designed for this approach protecting the drift tube. A radiation dose of 8 Gy in 5 mm distance (50 kV X-rays) was delivered. The kyphoplasty balloons (KyphX, Kyphon Inc, Sunnyvale) were inflated after IORT and polymethylmethacrylate cement was injected. The whole procedure lasted less than 90 minutes. In conclusion, this novel, minimally invasive procedure can be performed in standard operating rooms and may become a valuable option for patients with vertebral metastases providing immediate stability and local control. A phase I/II study is under way to establish the optimal dose prescription.
    Radiation Oncology 02/2010; 5:11. · 2.11 Impact Factor
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    ABSTRACT: With regard to the literature, several factors are considered to have an impact on postoperative mobility after lumbar total disc replacement (TDR). As TDR results in a distraction of the ligamentous structures, theoretically the postoperatively disc height and ligamentous integrity have also an influence on biomechanics of a treated segment. The purpose of the study was to evaluate the influence of posterior longitudinal ligament (PLL) resection and segmental distraction on range of motion (ROM). Six human, lumbar spines (L2-L3) were tested with pure moments of ±7.5 Nm in a spine loading apparatus. The ROM was determined in all three motion planes. Testing sequences included: (1) intact state, (2) 10 mm prosthesis (PLL intact), (3) 10 mm prosthesis (PLL resected), (4) 12 mm prosthesis (PLL resected). The prosthesis used was a prototype with a constrained design using the ball-and-socket principle. The implantation of the 10 mm prosthesis already increased the disc height significantly (intact: 9.9 mm; 10 mm prosthesis: 10.6 mm; 12 mm prosthesis: 12.7 mm). Compared to the intact status, the implantation of the 10 mm prosthesis resulted in an increase of ROM for flexion/extension (8.6° vs 10.8°; P = 0.245) and axial rotation (2.9° vs 4.5°; P = 0.028), whereas lateral bending decreased (9.0° vs 7.6°; P = 0.445). The resection of the PLL for the 10 mm prosthesis resulted in an increase of ROM in all motion planes compared to the 10 mm prosthesis with intact PLL (flexion/extension: 11.4°, P = 0.046; axial rotation: 5.1°, P = 0.046; lateral bending: 8.6°, P = 0.028). The subsequent implantation of a 12 mm prosthesis, with resected PLL, resulted in a significant decrease of ROM in all motion planes compared to the 10 mm prosthesis with intact PLL (flexion/extension: 8.4°, P = 0.028; axial rotation: 3.3°, P = 0.028; lateral bending: 5.1°, P = 0.028). Compared to the intact status, the 12 mm prosthesis with resected PLL only decreased lateral bending significantly while the 10 mm prosthesis with intact PLL increased axial rotation significantly. The resection of the PLL during TDR results in a significant increase of ROM in all three principle motion planes. But it still remains unclear if this increase which is in median not more than 1° may alter the clinical results. Moreover, the destabilizing effect of PLL resection can be reversed using a higher implant. The prosthesis height seems more crucial than PLL preservation to maintain the primary stability after TDR.
    European Spine Journal 10/2009; 21 Suppl 5:S592-8. · 2.47 Impact Factor
  • Orthopedics 09/2009; 32(8):589. · 1.05 Impact Factor
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    ABSTRACT: Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its superior biomechanical pull-out characteristics compared with vertebral body screws and the accuracy of inserting ATPS using a manual fluoroscopically assisted technique. Although accuracy was high, showing non-critical breaches in the axial and sagittal plane in 78 and 96%, further research was indicated refining technique and increasing accuracy. In light of first clinical case series, the authors analyzed the impact of using an electronic conductivity device (ECD, PediGuard) on the accuracy of ATPS insertion. As there exist only experiences in thoracolumbar surgery the versatility of the ECD was also assessed for posterior cervical pedicle screw fixation (pCPS). 30 ATPS and 30 pCPS were inserted alternately into the C3-T1 vertebra of five fresh-frozen specimen. Fluoroscopic assistance was only used for the entry point selection, pedicle tract preparation was done using the ECD. Preoperative CT scans were assessed for sclerosis at the pedicle entrance or core, and vertebrae with dense pedicles were excluded. Pre- and postoperative reconstructed CT scans were analyzed for pedicle screw positions according to a previously established grading system. Statistical analysis revealed an astonishingly high accuracy for the ATPS group with no critical screw position (0%) in axial or sagittal plane. In the pCPS group, 88.9% of screws inserted showed non-critical screw position, while 11.1% showed critical pedicle perforations. The usage of an ECD for posterior and anterior pedicle screw tract preparation with the exclusion of dense cortical pedicles was shown to be a successful and clinically sound concept with high-accuracy rates for ATPS and pCPS. In concert with fluoroscopic guidance and pedicle axis views, application of an ECD and exclusion of dense cortical pedicles might increase comfort and safety with the clinical use of pCPS. In addition, we presented a reasonable laboratory setting for the clinical introduction of an ATPS-plate system.
    European Spine Journal 08/2009; 18(9):1300-13. · 2.47 Impact Factor
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    ABSTRACT: Retrospective radiographic analysis of lumbar spine range of motion (ROM) after monosegmental fusion and posterior dynamic stabilization at the level L4-L5. Comparison of segmental ROM at the index level and the cranial and caudal adjacent levels and of global lumbar spine ROM after monosegmental fusion and posterior dynamic stabilization. The postulated advantage of nonfusion technology compared with fusion is based on the assumption that preservation of motion at the treated segment reduces the incidence of adjacent segment effects. Therefore, it is imperative to provide evidence that dynamic stabilization devices avoid hypermobility at the adjacent segments because this might substantiate a protective effect on the adjacent segments. Twenty-six patients with low back pain and claudication due to degenerative instability at the level L4-L5 with concomitant spinal stenosis were treated either with decompression and Dynesys (n = 11) or with decompression and fusion (n = 15). All patients underwent flexion/extension radiographs before surgery and at latest follow-up. ROM was assessed at the index level (L4-L5), the cranial/caudal adjacent levels (L3-L4/L5-S1), and at the lumbar spine from L2 to S1. There was a significant reduction of the global ROM of the lumbar spine (L2-S1) and the segmental ROM at the index level (L4-L5) in the fusion group, whereas adjacent level ROM did not change significantly. In the Dynesys group, no significant changes of global lumbar spine ROM (L2-S1) and segmental ROM (index level and cranial/caudal adjacent levels) were seen. This study shows that neither monosegmental instrumented fusion nor monosegmental posterior dynamic stabilization with Dynesys alter the ROM of the cranial and caudal adjacent levels. Consequently, monosegmental posterior dynamic stabilization with Dynesys has no effect with regard to adjacent segment mobility compared with monosegmental fusion.
    Spine 06/2009; 34(12):1287-91. · 2.16 Impact Factor
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    ABSTRACT: Analysis of segmental and total lumbar range of motion (ROM) before and after total lumbar disc replacement. To examine the relationship between absolute segmental and total lumbar ROM and evolution of ROM on clinical outcome. At the moment, data are scarce with regard to the evolution of total lumbar ROM (t-ROM) and segmental ROM (s-ROM) after total lumbar disc replacement. Moreover, the influence of ROM on clinical outcome still is unclear and remains a matter of controversial debate. METHODS.: Forty patients operated on for mono- or bisegmental symptomatic degenerative disc disease with a total of 45 artificial discs (ProDisc-L, Synthes) were analyzed. Pre- and postoperative s-ROM and t-ROM were measured on flexion/extension radiographs. The Oswestry Low Back Pain Disability Questionnaire and the Short Form 36 Health Survey were obtained pre- and postoperatively with a minimum follow-up of 3 years (37-64 months). Neither the s-ROM (pre-/postoperatively: 6.9 degrees/7.3 degrees) nor the t-ROM (pre-/postoperatively: 34.9 degrees/35.8 degrees) did change significantly after implantation of an artificial disc. Postoperatively, there was an increase of s-ROM (t-ROM) in 40% (40%), a decrease in 35% (30%), and no change in 25% (30%) of the patients. A significant inferior clinical outcome only was observed in patients with decreased t-ROM. The resulting postoperatively s-ROM had no significant impact on outcome. Neither the absolute s-ROM nor the evolution of s-ROM (increase, decrease, unchanged) was positively correlated with better clinical outcome. Although a positive correlation was observed with regard to t-ROM.
    Spine 05/2009; 34(9):917-23. · 2.16 Impact Factor
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    ABSTRACT: The Tomita prognosis score consists of the following 3 parameters: growth behavior, evidence of visceral metastases, and/or evidence of bony metastases. 217 consecutive patients, surgically treated for vertebral metastases of different entities, were studied retrospectively. The score according to Tomita was determined. In the study group, the Tomita score showed significant results for the estimation of life expectancy of the different prognostic groups (p < 0.0001), but the analysis showed a low reliability, i.e. correlation between predicted prognosis and real survival. A modified division of the patients based on the total sum of points allowed a significant separation (p < 0.0001) of patients into 2 prognostic groups with a real survival of more or less than 12 months. In our study, the original Tomita score was not reliable to predict the life expectancy of cancer patients with spinal metastases. Our modification allows a significant differentiation of patients with spinal metastases with a prognosis of more or less than 12 months.
    Onkologie 09/2007; 30(8-9):414-8. · 1.00 Impact Factor
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    ABSTRACT: Retrospective evaluation of the prognosis scores of Tokuhashi and Tomita for life expectancy in 37 consecutive patients with spinal metastases secondary to renal cancer who underwent surgery. The score of Tokuhashi, composed of six parameters, each rated from zero to two, has been proposed in 1990 for the prognostic assessment of patients with spinal metastases. In 2001, Tomita et al. created another prognostic score, composed of three parameters, growth behaviour of the primary tumor (slow, moderate and rapid) and the evidence of visceral and bony metastases. Thirty-seven patients, surgically treated for vertebral metastases secondary to renal cancer were studied. The scores according to Tokuhashi and Tomita were calculated for each patient. Applying the Tokuhashi Score for the estimation of life expectancy of renal cancer patients with vertebral metastases was found to provide very reliable results with a statistically high significance. The analysis according to Tomita showed no correlation between predicted and real survival. The statistical analysis did not show any significance. For surgical decisions in renal cancer patients with spinal metastases, the prognostic score of Tokuhashi appears to be much more valuable than the Tomita score.
    Annals of Surgical Oncology 03/2007; 14(2):998-1004. · 4.12 Impact Factor
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    ABSTRACT: This study analyzed the outcome of patients treated with total disk replacement and posterior dynamic stabilization. For pathologies of different origin, dynamic stabilization of the lumbar spine is a novel alternative to fusion surgery. Although a physiological reconstruction of the sagittal profile was not always achieved, improvement was seen in all subscales of the clinical outcome measures in both treatment groups. Posterior dynamic stabilization and total disk replacement are promising alternatives to fusion with acceptable morbidity for strictly defined indications.
    Orthopedics 09/2006; 29(8):716-22. · 1.05 Impact Factor

Publication Stats

400 Citations
66.11 Total Impact Points

Institutions

  • 2013
    • Orthopädisch-Chirurgische Zentrum
      Cham Regen, Bavaria, Germany
  • 2010–2012
    • Universität Mannheim
      Mannheim, Baden-Württemberg, Germany
  • 2011
    • Paracelsus Medical University Salzburg
      • University Clinic of Nuclear Medicine and Endocrinology
      Salzburg, Salzburg, Austria
  • 2010–2011
    • Universitätsklinikum Freiburg
      • Department of Orthopedics and Traumatology
      Freiburg, Lower Saxony, Germany
  • 2002–2009
    • Universität Ulm
      • Institute of Orthopaedic Research and Biomechanics
      Ulm, Baden-Wuerttemberg, Germany
  • 2005
    • St. Josefs-Hospital Wiesbaden
      Wiesbaden, Hesse, Germany