Adolf Müller

The application of rapid prototyping techniques in cranial reconstruction and preoperative planning in neurosurgery.

The value of rapid prototype models of the skull in our craniofacial and neurosurgical practice was analyzed. Individual skull models of 52 patients were produced by means of rapid prototyping techniques and used in various procedures. Patients were divided into three groups as follows: group I (26 patients) requiring corrective cranioplasty 1) after resection of osseous tumors (15 patients) and 2) with congenital and posttraumatic craniofacial deformities (11 patients), group II (10 patients) requiring reconstructive cranioplasty, and group III (16 patients) requiring planning of difficult skull base approaches. The utility of the stereolithographic models was assessed using the Gillespie scoring system. The esthetic and clinical outcomes were assessed by means of the esthetic outcome score and the Glasgow Outcome Score, respectively. Simulation of osteotomies for advancement plasty and craniofacial reassembly in the model before surgery in group I reduced operating time and intraoperative errors. In group II, the usefulness of the models depended directly on the size and configuration of the cranial defect. The planning of approaches to uncommon and complex skull base tumors (group III) was significantly influenced by the stereolithographic models. The esthetic outcome was pleasing. The indications for the manufacture of individual three-dimensional models could be cases of craniofacial dysmorphism that require meticulous preoperative planning and skull base surgery with difficult anatomical and reconstructive problems. The stereolithographic models provide 1) better understanding of the anatomy, 2) presurgical simulation, 3) intraoperative accuracy in localization of lesions, 4) accurate fabrication of implants, and 5) improved education of trainees.

Meningiomas of the sellar region presenting with visual impairment: impact of various prognostic factors on surgical outcome in 62 patients.

Summary Background. Meningiomas of the supra- and parasellar region can cause insidious visual loss by optic nerve compression. 62 cases with such tumours affecting the anterior optic pathways were analysed to assess the surgical results and prognostic factors with particular attention to visual outcome. Method. In all patients, visual deterioration was the first clinical manifestation. Eleven lesions had their origin at the anterior clinoid process, 24 at the tuberculum sellae, 10 at the planum sphenoidale, two in the optic canal, 10 in the medial sphenoidal wing, and five in the olfactory groove. All patients underwent microsurgical tumour resection. Median age at the time of operation was 54 years, median duration of symptoms seven months. The mean follow-up time was 5.2 years (range 2 to 8 years). Statistical analysis of prognostic factors (gender, age, tumour location, tumour size, duration of symptoms, brain tumour interface, resection grade, preoperative visual loss, Glascow Outcome Score) was performed using univariate and multivariate analysis. Findings. The severe morbidity rate was 6,4%. Two patients died within the first 30 postoperative days. Overall, vision improved in 39 (65%) patients, in 11 (18%) it was unchanged, and worse in 10 (17%). Visual prognosis was favourably affected by age under 54 years (p<0,025), duration of symptoms of less than seven months (p<0,037), and the presence of an intact arachnoid membrane around the lesion (p<0,001). Severe preoperative loss of visual acuity (<0,02) appeared to be an unfavourable prognostic factor (p<0,047). Interpretation. Possible difficulties and surgical outcome in such patients can be predicted successfully. These facts in connection with new therapeutic modalities (radiosurgery, adjuvant therapies) will demand a careful risk assessment and should influence the treatment strategies and the degree of operative aggressiveness in the future.

A keyhole approach for endoscopically assisted pedicle screw fixation in lumbar spine instability.

OBJECTIVE The standard approach for dorsal transpedicular fixation in lumbar spine instability requires extensive exposure of the vertebral column. This increases the risk of potential complications and possibly destabilizes healthy neighboring segments because of the dissection and denervation of paravertebral muscles. The majority of spinal disorders are currently treated successfully via limited and tailored approaches. Accordingly, a keyhole approach for dorsal fusion of the lumbar spine was developed on the basis of an anatomic study. METHODS The new endoscopic technique entails the transmuscular insertion of a pedicle screw-rod fixation device via a rigid operating sheath. As a prerequisite, the endoscopic microanatomy of the target area, as visible through the operating sheath, was first evaluated on lumbar bone specimens. To localize the exact screw entry point into the pedicle, we identified the bony and ligamentous landmarks on partly macerated specimens. To determine the course of the pedicle screws, we deduced the corresponding angles of convergence from transparent polyester casting models of average vertebrae from T12 to S1. These angles were transferred into the operative situation and measured on-line with an inclinometer. The approach was finally tested on 12 cadavers for clinical feasibility and accuracy of screw placement and then successfully implemented in patients. RESULTS After extracutaneous localization of the pedicles at lateral fluoroscopy, paramedian skin incisions were made above the pedicles of the motion segment to be stabilized. The operative windows were exposed by use of a rigid operating sheath (length, 50 mm; diameter, 15 mm), which was inserted transmuscularly in the pedicle axis. The screw entry point into the pedicles was localized by endoscopic dissection of the mamilloaccessory ligament, bridging the mamilloaccessory notch. The pilot holes were created via insertion of a blunt-tipped pedicle probe. The adequate angles of convergence were constantly controlled during hollowing of the pedicles by an inclinometer mounted to the pedicle probe handle. The pedicle screws were then inserted through the operating sheaths. After removal of the operating sheaths, the connecting rods were inserted transmuscularly and anchored in the pedicle screw heads. Posterior bone grafting was performed after completion of the dorsal instrumentation. The dorsal fusion site was exposed by reinserting the operating sheath and tilting it medially. CONCLUSION This new approach significantly reduces surgical traumatization and destabilization of adjacent motion segments. An endoscopic operating sheath, adopted from thoracoscopic surgery, creates space for visualization and surgical manipulations. The newly defined anatomic landmarks provide guidance to the screw entry point into the pedicle in the center of the exposure. Observation of the exact corresponding angles of convergence during screw insertion by an inclinometer facilitates correct screw placement. In accordance with the initial anatomic studies, this approach was successfully performed on 12 cadavers and then used in six patients. Two illustrative cases are presented.

A paramedian tangential approach to lumbosacral extraforaminal disc herniations.

OBJECTIVE Extraforaminal disc herniations today are operated on via the so-called lateral approach. Clinical experience has shown that in contrast to levels L2/3-L4/5, this approach may become extremely difficult at the L5-S1 level. According to new microanatomic studies, the previous lateral approaches at this level often do not allow access to the neuroforamen without partial or total destruction of the L5-S1 facet joint. Postoperatively, this may lead to joint irritation with consecutive low back and pseudoradicular pain. To preserve the facet joint, a new approach was developed based on an anatomic study. METHODS The approach was first considered with the help of bone specimens including ilium, vertebra 5, and sacrum. Thereafter, lumbar maceration specimens were prepared leaving ligaments, intervertebral discs, and joints intact. From these specimens, bony and ligamentous landmarks were deduced. Finally, the approach was tested on seven cadavers. Subsequently, the approach was performed on 13 patients and the intraoperative findings, the clinical feasibility, and the postoperative results were analyzed. APPROACH After a transverse skin incision above the dorsal curvature of the ilium, the paravertebral muscles are dissected from the ilium medially toward the spinous process. Lateral from the apophyseal joint, a canal is drilled through the spongiosa of the sacrum. Primarily, a thin layer of inner cortex is spared to protect the content of the neuroforamen. Subsequently, it can easily be removed with the dissector to enter the extraforaminal space. In the depth of the drilled canal, the nerve root is found, because it is fixed at the sacrum near the disc space by the anterior lumbosacral ligaments. Riding on the nerve root, the intertransverse ligament and muscle can be removed with the punch. It is then possible to see the neuroforamen and extraforaminal space in front of the joint. Free fragments and contained discs can then easily be found and removed. CONCLUSION Using this new approach, the L5-S1 joint remains intact. Space for instrumental manipulations is created in areas not essential for joint function. For this procedure, newly defined anatomic landmarks, such as the ileolumbar ligament, upper edge of the sacrum, lateral rim of the apophyseal joint, and para-articular notch, guide the operative route. In accordance with the preliminary anatomic studies, this approach was successfully used in 13 patients, and we think that it is a promising alternative that helps to preserve joint function and dorsal root ganglion integrity.

Ventral cervical fusion at multiple levels using free vascularized double-islanded fibula - a technical report and review of the relevant literature.

Abstract. Reconstruction of the cervical spine using free vascularized bone flaps has been described in the literature. The reports involve either one level or, when multiple levels, they describe en bloc resection and reconstruction. Stabilization of different levels with a preserved intermediate segment with a single vascularized flap has not been described. We report on the case of a 55-year-old man, who had been operated several times using conventional techniques for cervical myelopathy and instability, who presented to us with severe neck pain. Diagnostic procedures showed pseudarthrosis of C3/4 and stress-overload of the C3/4 and C5/6 segments. The C4/5 fusion was adequately rigid, but avascular. We performed anterior cervical fusion at the C3/4 and C5/6 levels with a vascularized fibula flap modified as a double island. The rigidly fused C4/5 block was preserved and vascularized with the periosteum bridging the two fibular islands. The method and technique are described in detail. Fusion was adequate. Donor site morbidity was minimal and temporary. The patient is symptom free to date (25 months). The suggested method provides the possibility of vertebral fusion at different levels using a single vascularized flap. The indications for this procedure are (1) repeated failure of conventional methods, (2) established poor bone healing and bone non-union with avascular grafts and (3) a well-fused or preserved intermediate segment. The relevant literature is reviewed.

Closure of Recurrent Frontal Skull Base Defects with Vascularized Flaps – A Technical Case Report

Summary Techniques for vascularized reconstruction of the anterior cranial fossa floor defects causing recurrent cerebrospinal fluid fistula are discussed in this report. The closure employs the use of local random- or axial-pattern vascularized flaps in simple cases. In complicated cases (for instance, status after repeated exploration) the tissue of the cranial base is severely compromised and shows low potential for healing. Non-vascularized grafts only add avital scars to the already present ones leading to recurrent fistulas. Free vascularized flaps show more mechanical strength and less scar contraction, resistance to infections and survive better in a compromised surrounding, thus leading to long term sealing in such cases. The technical issues of vascularized closure of defects of the frontal skull base are discussed in this report.

Complex wound-healing problems in neurosurgical patients: risk factors, grading and treatment strategy

BackgroundWound-healing problems in the neurosurgical patient can be particularly bothersome, owing to various specific risk factors involved. These may vary from simple wound dehiscence to complex multi-layer defects with cerebrospinal fluid (CSF) leakage and contamination. The latter is quite rare in practice and requires an individually titrated reconstruction strategy. The objective is to retrospectively analyze neurosurgical patients with complex, recalcitrant wound-healing problems we had treated in our department, attempt to develop a grading system based on the risk factors specific to our specialty and adapt a surgical reconstruction algorithm.MethodsDuring an 11-year period, 49 patients were identified to have had complex, recalcitrant wound-healing problems involving the cranial vault (n = 43) and the skull base (n = 6) that required an adapted surgical wound-management strategy. The etiologies of wound healing problems were aftermaths of surgical treatment of: (1) brain tumors (nine cases), (2) aneurysm clipping (ten cases), (3) trauma (27 patients), and (4) congenital malformations (three patients). Local rotational advancement flaps were performed in 18 patients and free microvascular tissue transfer was performed in 37 cases.ResultsMajor risk factors leading to recalcitrant wound healing problems in the presented group were: prolonged angiographic interventions (20%), ongoing chemotherapy or radiotherapy (47%), prolonged cortisone application (51%), CSF leak (76%) and, above all, multiple failed attempts at wound closure (94%). Stable long-term wound healing was achieved in all patients using vascularized tissue coverage. A ternary grading system was developed based on various risk factors in the presented cohort. Accordingly, the algorithm for reconstruction in neurosurgical patients was adapted.ConclusionsPrimary disease, treatment history, and distorted anatomical structures are major concerns in the management of complex wound-healing problems in neurosurgical patients. The higher the risk factors involved, the more complex is the surgical strategy. Free microvascular tissue transfer offers stable long-term results in recalcitrant cases. However, this may be indicated only in patients with a good prognosis of the underlying disease.