A morphometric cadaver study of the anterior lumbar epidural space.

INTRODUCTION: Free disc fragments end often up in the concavity of the anterior epidural space. This space consists of two compartments. The discrepancy between the impressive magnetic resonance imaging findings, clinical symptoms in patients and the problem of treatment options led us to the anatomical determination of anterior epidural space volumes. MATERIALS AND METHODS: For the first time, the left and right anterior epidural volume between the peridural membrane and the posterior concavity of the lumbar vertebral bodies L3-S1 were determined for each segment. A CT scan and a polyester resin injection were used for the in vitro measurements. RESULTS: The volumes determined in human cadavers using this method ranged from 0.23 ccm for L3 to 0.34 ccm for L5. The CT concavity volume determination showed this increase in volume from cranial to caudal, as well. CONCLUSION: This volume is large enough to hold average-sized slipped discs without causing neurological deficits. A better understanding of the anterior epidural space may allow a better distinction of patient treatment options.

[Does osteoporosis lead to reduction the primary stability of cementless hip cups?]. / Führt Osteoporose zu einer Reduktion der Primärstabilität zementfreier Hüftpfannen?

BACKGROUND: Cementless hip cups require adequate primary stability in order to achieve osseointegration. Depending on implant design, a different biomechanical behavior in osteoporotic bone and in bone with normal bone mineral density might be expected. MATERIAL AND METHODS: The micromovement between bone and implant was determined in macerated human hip acetabula with reduced and with normal bone density for two different cementless screwed cups and two different cementless press-fit cups. The bone mineral density was assessed by means of Q-CT and 20 implantations were performed for each acetabulum with reduced and with normal bone density. RESULTS: Screwed cups showed significantly less micromovement than press-fit cups. The average micromovement of all cups, with the exception of the Monoblock cup, remained below the value of 100 µ, the upper limit for successful osseointegration. Values of over 200 µ were measured only for the Monoblock cup and only in some of the tests. There was no significant difference between the micro-movement in acetabula with reduced bone mineral density and with normal bone. CONCLUSION: Impaired osseointegration in osteoporotic bone because of increased micromovement is not to be expected in the investigated cementless hip cups as no relevant differences in micromovement were found between normal and osteoporotic bone stock. On the basis of the good clinical results with the Monoblock cup, the upper limit of 100 µ of micromotion for osseointegation in macerated bone is probably set too low.

[Rupture of the anterior cruciate ligament. Diagnostics and therapy]. / Ruptur des vorderen Kreuzbands. Diagnostik und Therapie.

Rupture of the anterior cruciate ligament (ACL) is the most common ligamentous knee injury. The knee is stabilized by the cruciate ligaments and the collateral ligaments. The ACL originates from the inner surface of the lateral condyle of the femur, runs in an anterior medial direction and inserts at the tibial plateau in the intercondyle area. The most common injury is an indirect knee trauma, typically a joint torsion in sports. Patients often describe a snapping noise followed by hemarthrosis. Concomitant injuries are lesions of the medial collateral ligament, the medial meniscus (unhappy triad) and chondral fractures. The age peak is between 15 and 30 years with a higher incidence in females. The cardinal symptom of the ACL rupture is the giving way phenomenon. The clinical diagnosis is provided by a positive Lachman test, a positive pivot shift test and the anterior drawer test. Fractures can be excluded by X-ray examination. Magnetic resonance imaging (MRI) allows the evaluation of the internal knee structures. ACL repair is carried out by arthroscopically assisted bone-tendon-bone or semitendinosus grafting techniques. Early rehabilitation is important for a good functional outcome.

Peri-implant reactivity and osteoinductive potential of immobilized rhBMP-2 on titanium carriers.

Recombinant human BMP-2 (rhBMP-2) was immobilized non-covalently and covalently as a monolayer on plasma vapour deposited (PVD) porous commercially pure titanium surfaces in amounts of 5-8 µg cm(-2), providing a ca. 10-fold increase vs. previously reported values. Dissociation of the immobilized [125I]rhBMP-2 from the surface occurred in a two-phase exponential decay: a first rapid phase (ca. 15% of immobilized BMP-2) with a half-life of 1-2 days and a second slow sustained release phase (ca. 85% of immobilized BMP-2) with a half-life of 40-60 days. Dissociation rate constants of sustained release of k(-1)=1.3-1.9 x 10(-7)s(-1) were determined, allowing an estimation of the binding constants (K(A)) for the adsorbed rhBMP-2 monolayer, to be around 10(12) M(-1). The rhBMP-2-coated surfaces showed a high level of biological activity, as demonstrated by in vitro epifluorescence tests for alkaline phosphatase with MC3T3-E1 cells and in vivo experiments. In vivo osteoinductivity of rhBMP-2-coated implants was investigated in a gap-healing model in the trabecular bone of the distal femur condylus of sheep. Healing occurred without inflammation or capsule formation. The calculated concentration of released rhBMP-2 in the 1mm gap ranged from 20 to 98 nM--well above the half-maximal response concentration (K(0.5)) for inducing alkaline phosphatase in MC3T3-E1 cells. After 4, 9 and 12 weeks the bone density (BD) and bone-to-implant contact (BIC) of the explanted implants were assessed histomorphometrically. Implants with immobilized rhBMP-2 displayed a significant (2- to 4-fold) increase in BD and BIC values vs. negative controls after 4-9 weeks. Integration of implants by trabecular bone was achieved after 4 weeks, indicating a mean "gap-filling rate" of ∼250 µm week(-1). Integration of implants by cortical bone was observed after 9 weeks. Control implants without rhBMP-2 were not osseointegrated. This study demonstrates the feasibility of enhancing peri-implant osseointegration and gap bridging by immobilized rhBMP-2 on implant surfaces which may serve as a model for future clinical applications.

[Cement-in-cement hip revision with a long-stemmed femoral component]. / Zement-in-Zement-Hüftrevision mit einem zementierten langen Prothesenstiel.

Revision hip surgery often requires individualized techniques and implants. We report on a case of failed femoral revision in an extensively cemented femur with a concomitant proximal and dorsal femoral bone defect. We advocate the clinically effective revision procedure of antegrade drilling of the stable cement mantle and use of a cemented long-stemmed femoral component. This cement-in-cement revision technique is discussed along with the pertinent literature.

[Uncemented arthroplasty of the hip]. / Zementfreie Endoprothetik des Hüftgelenks.

Prognosis of cemented total hip replacement seems to be excellent for elderly patients. In younger age the outcome is less favourable and early revision is more common. Thus, different concepts with better prognosis and preservation of bone stock for possible revisions were needed. After more than 30 years of application with excellent short-term and long-term results, uncemented total hip arthroplasty is nowadays generally regarded as the standard procedure for younger patients. New bone-preserving implants, such as surface replacement or short-stemmed femoral shaft prostheses, have been introduced especially for younger patients. Some of these new procedures are still under development, and the long-term results of new implant concepts have to be evaluated over the next decades. Regarding recently published scientific studies an overview about non-cemented total hip arthroplasty is given and current concepts and developments are presented.

[Rotating platform spinout in LCS knee arthroplasty]. / Spinout der rotierenden Plattform bei der LCS-Knieendoprothese.

In knee arthroplasty, a lax flexion gap may cause flexion instability. Subsequently, the operated knee may subluxate or dislocate. We report on a case of recurrent subluxations with malrotation of the rotating platform (spinout) after primary LCS total knee arthroplasty. Potential causes for spinout, therapy procedures, and consequences for the primary surgical technique are discussed. In the LCS rotating platform knee arthroplasty, the flexion gap must not be laxer than the extension gap. In such an instance, we recommend a higher rotating platform and a more proximal distal transverse femoral osteotomy.

[Ultrasound in the early diagnosis of congenital dislocation of the patella]. / Sonographische Frühdiagnose der kongenitalen Patellaluxation.

INTRODUCTION: Congenital dislocation of the patella is defined as lateral dislocation of the patella present at birth, impossibility of closed reduction and diagnosis before the age of 10 years. We report about a rare case of a bilateral congenital dislocation of the patella. CASE REPORT: Physical examination of an eight-month- old boy showed bilateral knee flexion contractures associated with moderate genu varum. On both sides the patella could not be palpated easily. Radiographic diagnosis could not show the patella as the patella normally ossifies later. Ultrasound examination located the patella lateral to the lateral femoral condyle on both sides. Closed reduction was impossible. An open reduction with division of the lateral soft tissues, lateral release, and derotation of the quadriceps femoris and refining of the medial structures was performed. After cast removal the patellae were both located in the intercondylar grooves as confirmed by clinical and ultrasound examinations of both knees. Active and passive exercises were started. CONCLUSION: Failure of internal rotation of the myotome which contains the quadriceps femoris and the patella is the etiology of congenital dislocation of the patella. The quadriceps acts as flexor, exerting a valgus stress on the knee, causing external rotation of the tibia. Diagnosis is often delayed because of the lack of pathological findings on plain radiographs. Early diagnosis is enabled by ultrasonography. Surgical treatment is necessary and results are good, as long as there are no secondary changes.

[Unusual course of sacrococcygeal chordoma]. / Ungewöhnlicher Verlauf eines sacrococcygealen Chordoms.

Observation of a sacrococcygeal chordoma with exceptional long survival of now 17 years after incomplete surgery with following additional resection and adjuvant radiotherapy. Local recurrence occurred after more than 10 years, metastases after 15 years.

[Survival rate of a cement-free cup of titanium with laser structured surface]. / Uberlebensrate einer zementfreien Pfanne aus Reintitan mit laserstrukturierter Oberfläche.

PURPOSE: So far no clinical results concerning the survival rates of cementless pure titanium cups with laser-structured surfaces exist. This study was performed to evaluate our results for the Alphasegment acetabular component (Alphanorm). METHOD: Retrospective analysis of 50 cups in 45 patients was performed (operations performed between November 1995 and January 1998). The average age at the time of the implantation was 65.1 years. Dysplastic hips and revisions were excluded. The survival rate was calculated according to the Kaplan-Meier analysis with the end point defined as the revision surgery of the cup. RESULTS: The average follow-up period was 2.9 (0.6-4.0) years. Two patients (i.e., two implants) died during the observation period, none were lost for follow-up. Six of the cups had to be revised due to aseptic loosening. The survival rate at 3.2 years after implantation was 87%. None of the stems had to be revised. CONCLUSIONS: Further use of the cementless hemispherical pure titanium cup with laser-structured surface cannot be recommended. The observed prevalence of loosening for the Alphasegment acetabular components was higher than for other cups. Close follow-up of patients with this type of implant is necessary.

The low-molecular-mass subunit of the cell wall channel of the Gram-positive Corynebacterium glutamicum. Immunological localization, cloning and sequencing of its gene porA.

The 5-kDa protein PorA of the Gram-positive bacterium Corynebacterium glutamicum is the subunit of the cell wall channel. Antibodies raised against PorA specifically detected the protein on the cell surface. PorA was sequenced using Edman degradation and a gas phase sequencer. The primary sequence was used to create degenerate oligonucleotide primers. The gene of the channel-forming protein and its flanking regions were obtained by PCR followed by inverse PCR. The gene porA comprises 138 bp and encodes a 45-amino-acid-long acidic polypeptide with an excess of four negatively charged amino acids in agreement with the high cation selectivity of the PorA cell wall channel. PorA does not contain an N-terminal extension. A ribosomal-binding site was recognized 6 bp before the start codon ATG of porA. It codes for the smallest subunit of a membrane channel known so far and for the first cell wall channel protein of a corynebacterium. Southern blots demonstrated that only the chromosomes of corynebacteria contain homologous sequences to porA; no hybridization could be detected with DNA from other mycolata.

[Complete dislocation of the polyethylene inlay after internal hemipelvectomy and individually fitted tumor endoprosthesis]. / Komplette Luxation des PE-Inlays nach innerer Hemipelvektomie und individueller Tumorendoprothese.

We report about an exceptional complication after internal hemipelvectomy and replacement of the defect with a custom-made endoprosthesis. A complete luxation of the PE-inlay out of the metal cup occurred. Radiologically we assumed a luxation of the femoral head in dorsal direction. Revision after a failed attempt of closed reposition showed a complete luxation of the inlay, which was caused by deficient fixation in the acetabular component. The absence of a contrast wire in the PE-inlay delayed the right diagnosis and made it difficult to find the dislocated inlay in the large wound.

Biochemical identification and biophysical characterization of a channel-forming protein from Rhodococcus erythropolis.

Organic solvent extracts of whole cells of the gram-positive bacterium Rhodococcus erythropolis contain a channel-forming protein. It was identified by lipid bilayer experiments and purified to homogeneity by preparative sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). The pure protein had a rather low molecular mass of about 8.4 kDa, as judged by SDS-PAGE. SDS-resistant oligomers with a molecular mass of 67 kDa were also observed, suggesting that the channel is formed by a protein oligomer. The monomer was subjected to partial protein sequencing, and 45 amino acids were resolved. According to the partial sequence, the sequence has no significant homology to known protein sequences. To check whether the channel was indeed localized in the cell wall, the cell wall fraction was separated from the cytoplasmic membrane by sucrose step gradient centrifugation. The highest channel-forming activity was found in the cell wall fraction. The purified protein formed large ion-permeable channels in lipid bilayer membranes with a single-channel conductance of 6.0 nS in 1 M KCl. Zero-current membrane potential measurements with different salts suggested that the channel of R. erythropolis was highly cation selective because of negative charges localized at the channel mouth. The correction of single-channel conductance data for negatively charged point charges and the Renkin correction factor suggested that the diameter of the cell wall channel is about 2.0 nm. The channel-forming properties of the cell wall channel of R. erythropolis were compared with those of other members of the mycolata. These channels have common features because they form large, water-filled channels that contain net point charges.

[Early loosening of a cemented hip endoprosthesis stem of titanium]. / Frühlockerungen eines zementierten Hüftendoprothesenstiels aus Titan.

Up to now there are no facts concerning the loosening rate of the cemented titanium stem (Trios). The central guiding canula and the longitudinal drilled stem shall ensure a symmetric cement mantle. In order to estimate the risk of aseptic loosening all Trios prostheses implanted in our clinic (n = 67; operations 1/95-11/96; max. follow-up: 3.1 years) were examined in a retrospective study and compared with a conventional femoral component (n = 141; Müller special; CoCr; operations 1977-1982). We used survivorship analysis to assess the results (Kaplan-Meier method; end point: revision). Compared to the conventional femoral stem the survival rate of the Trios prostheses was significantly worse (p = 0.0001). The probability of no revision after 3 years was 72% (conventional femoral component: 96%). Preoperative x-rays showed radiolucent lines surrounding the cement mantle. These findings as well as the loosening at the cement metal interface were confirmed intraoperatively. The explanted stems showed corresponding signs of abrasion on the surface. Our results prove that the application of cemented titanium stems might be problematic. With regard to the Trios prosthesis we recommend close routine check-ups to keep the chance of an early revision.

Evidence for a small anion-selective channel in the cell wall of Mycobacterium bovis BCG besides a wide cation-selective pore.

Two channels were observed in extracts of whole Mycobacterium bovis BCG cells using organic solvents and detergents. The channels derived from organic solvent treatment had a single-channel conductance of about 4.0 nS in 1 M KCl in lipid bilayer membranes with properties similar to those of the channels discovered previously in Mycobacterium smegmatis and Mycobacterium chelonae. The channel was in its open configuration only at low transmembrane potentials. At higher voltages it switched to closed states that were almost impermeable for ions. Lipid bilayer experiments in the presence of detergent extracts of whole cells revealed another channel with a single-channel conductance of only 780 pS in 1 M KCl. Our results indicate that the mycolic acid layer of M. bovis BCG contains two channels, one is cation-selective and its permeability properties can be finely controlled by cell wall asymmetry or potentials. The other one is anion-selective, has a rather small single-channel conductance and is voltage-insensitive. The concentration of channel-forming proteins in the cell wall seems to be small, which is in agreement with the low cell wall permeability for hydrophilic solutes.

[Nerve lesions after hip prosthesis implantation--fate or treatment error?]. / Nervenläsionen nach Hüftprothesenimplantation--Schicksal oder Behandlungsfehler?

INTRODUCTION: Nerve lesions after hip arthroplasty are common complications which may imply the reproach of a treatment mistake. Thus, the decisive question to the expert runs: fate or treatment mistake? METHODS: Retrospective analysis of all cases dealt with at the medical expert commission of the General Medical Council Nordrhein during 1977-1997 in respect of the damage mechanisms and expert judgments. RESULTS: As long as diagnosis and therapy were set on time, nerve lesions after hip arthroplasty due to extension, pressure or placement of the leg were evaluated as fateful (81%). Delayed treatment as well as incorrect operation technique, -indication, or inadequate documentation were judged as a treatment mistake (19%). CONCLUSION: Nerve lesions after hip arthroplasty cannot always be avoided and thus do not directly imply a treatment mistake. Immediate therapy and precise documentation are important to minimize the damage.

[Quality and management of preoperative patient information. Results of conventional and computer based documentation]. / Qualität und Management der Patientenaufklärung. Ergebnisse konventioneller und computergestützter Dokumentation.

INTRODUCTION: Analysis of the quality of different modes of preoperative information management on the example of primary total hip arthroplasty. Comparison between a since 10 years used, computer based system and a conventional procedure with additional hand-written notes. METHODS: Retrospective analysis of respectively 50 with conventional and computer based system written preoperative patient information. The completeness of the documentation is examined according to the demands of current judgement. RESULTS: The results confirm, independent from the level of education, a complete documentation of all risks by applying the computer based system, whereas the conventional method leads to considerable lacks of documentation. DISCUSSION: The computer based system guarantees a high quality of preoperative patient information which cannot be obtained by the conventional method and therefore offers a protection against unjustified claims of liability.

The cell wall porin of the gram-positive bacterium Nocardia asteroides forms cation-selective channels that exhibit asymmetric voltage dependence.

Detergent-solubilized cell wall extracts of the gram-positive, strictly aerobic bacterium Nocardia asteroides contain channel-forming activity as judged from reconstitution experiments using lipid bilayer membranes. The cell wall porin was identified as a protein with an apparent molecular mass of about 84 kDa based on SDS-PAGE. The porin was purified to homogeneity using preparative SDS-PAGE. The 84-kDa protein was no longer observed after heating in SDS buffer. The presumed dissociation products were not observed on SDS-polyacrylamide gels. The cell wall porin increased the specific conductance of artificial lipid bilayer membranes from phosphatidylcholine/phosphatidylserine mixtures by the formation of cation-selective channels, which had an average single-channel conductance of 3.0 nS in 1 M KCl. The single-channel conductance was only moderately dependent on the bulk aqueous KCl concentration, which indicated negative point charge effects on the channel properties. The analysis of the concentration dependence of the single-channel conductance using the effect of negative charges on channel conductance suggested that the diameter of the cell wall channel is about 1.4 nm. Asymmetric addition of the cell wall porin to lipid bilayer membranes resulted in an asymmetric voltage dependence. The cell wall channel switched into substates, when the cis side of the membrane, the side of the addition of the protein, had negative polarity. Positive potentials at the cis side had no influence on the conductance of the cell wall channel.

Improvement of the cement mantle of the acetabular component with bone cement spacers. A retrospective analysis of 200 cemented cups.

A discontinuous or thin cement mantle of a socket is associated with increased polyethylene wear and cement fractures. In a retrospective radiological analysis we examined the quality of the cement mantle in cups without (group I = 100 Charnley-Mueller cups) and with (group II = 100 Contemporary cups, Howmedica) bone cement spacers. Under-filling (0-2 mm) and over-filling (> 8 mm) of the cement mantle were noted and classified. Statistics show significantly less under-filling of the cement mantle in group II than in group I (P = 0.001), in particular when comparing separate cup regions (thirds: P << 0.001). Furthermore, there is no significant difference in the frequency of overfilling with cement between groups I and II (P = 0.108). To sum up, utilization of an acetabular component with performed bone cement spacers considerably improves the quality of the cement mantle without additional cost.