Liquid dextran does not increase the elution rate of different antibiotics from bone cement.

PURPOSE: To investigate the possibility of increasing elution of fosfomycin, gentamicin, clindamycin, and vancomycin by the addition of dextran fluid during the cement-mixing phase. METHODS: In 12 test series, we produced standardized, antibiotic-loaded test specimens of cement, with and without addition of dextran, and determined their effectiveness against three reference pathogens in agar diffusion and elution tests. RESULTS: In the test series using combined agents, Refobacin(®)-Palacos(®)R plus fosfomycin continuously produced the largest zone of inhibition, both against methicillin-sensitive Staphylococcus aureus (p = 0.009) and against methicillin-resistant Staphylococcus aureus (p = 0.009). The addition of dextran to the various test series had no useful effect on the size of the zone of inhibition for any of the antibiotics tested. CONCLUSIONS: Dextran supplementation in Refobacin(®)-Palacos(®)R bone cement did not have the hope for positive effect on the elution rate of bound antibiotics.

[Nerve injuries in total hip arthroplasty--prophylactic strategies--quality assurance and risk management in orthopaedic and trauma surgery]. / Nervenläsionen bei der Hüft-TEP-Implantation--Strategien zur Lähmungsprophylaxe--Qualitätssicherung und Risk-Management in der Operativen Orthopädie und Unfallchirurgie.

AIM: Nerve lesions are a serious complication of total hip arthroplasty. The incidence of lesions of large nerves exceeds those of luxation and septic loosening. An analysis of damage causes should lead to prophylactic strategies and improvement of operative technique. Patients are more aware of this complication and malpractice cases are increasing. Between 1977 and 2001 the medical association of North Rhine dealt with 126 cases of nerve lesions. METHOD: All potential intraoperative causes for nerve damage are investigated. RESULTS: Incorrectly placed Hohmann retractors offer the largest damage potential. Electro surgery and self-cutting screws have a hazardous potential. Sharp injuries, retractor damage and leg lengthening are infrequent causes for nerve lesions. Positioning devices such as leg holders used for robotic hip surgery might damage the peroneal nerve. CONCLUSION: Risk management is necessary for medico-legal quality control and gives protection for patient and surgeon. Risk management may prevent damage in advance. The head of the department is in charge of internal quality control. Systematic evaluations of operative techniques and damage possibilities are necessary to avoid future malpractice. Guidelines give a good support, but cannot replace teaching on the patient. Operation reports offer the surgeon the chance to document cautious and nerve protecting techniques.

Individual bone cement spacers (IBCS) for septic hip revision-preliminary report.

BACKGROUND: Two-stage septic hip revision with intermediate resection arthroplasty leads to temporary poor function and difficult reimplantation. Antibiotic-loaded cement spacers improve patient mobility and maintain stability of the joint as well as length of the limb. Prefabricated spacers are readily available but lack adaptability. We developed modular moulds separately for stem and head to create more individual spacers with optimised femoral press-fit and smooth head surface. METHODS: Moulds are fabricated preoperatively by forming 4 mm polyethylene over trial stems and cups under vacuum (MS 30, Centerpulse, Switzerland). After gas sterilization, Refobacin Palacos (Merck, Darmstadt, Germany) is poured into stem and head moulds of appropriate size. A double K-wire is inserted as a rod. Fluoroscopy is used to check for air inclusions, which might impair resistance. For mechanical resistance testing trials, 5 spacers were resin-fixed with 80% stem insertion and loaded in a craniocaudal direction at 20 N/s (universal testing machine, Zwick, Germany) until failure. RESULTS: The static testing showed an average failure load of 1550 N (range 1350-2000 N). The K-wires prevented complete dislocation of the fragments. CONCLUSION: Partial weight-bearing is possible with this system, but a fall might lead to an acute fracture. New materials for the core can be tested with our biomechanical model. Following the presented craniocaudal static testing, torsion testing and dynamic testing in Ringer's solution are planned.

Preserving the abductor mechanism in robotic THR: the influence of stem design and cutterpath.

OBJECTIVE: The tip of the greater trochanter is the attachment site for the abductor muscles of the hip joint. Its preservation in robotic and conventional THR is important for normal gait. The effect of different stem designs and robotic cutterpaths on the preservation of the trochanter tip is examined. MATERIALS AND METHODS: One anatomical stem, one straight stem, and one stem specifically designed for robotic THR were implanted virtually in CT scans of osteoarthrotic hip joints using the Torch preoperative planning unit (URS-ortho). In transverse sections of the trochanter tip, dimensions of the trochanter area removed by the milling tool were recorded for each stem design and different cutterpaths (3-axis versus 5-axis milling). RESULTS: Five-axis milling showed significantly better results than 3-axis milling. For straight stems, more bone was removed than for anatomic stems. The most favorable results were achieved with 5-axis milling and a curved stem specifically designed for robotic THR. CONCLUSIONS: The introduction of 5-axis milling in robotic THR is an improvement of the technique and makes preservation of the abductor mechanism at the tip of the greater trochanter easier for the surgeon.

[High energy extracorporeal shockwave therapy (ESWT) in pseudarthrosis]. / Die hochenergetische extrakorporale Stosswellentherapie (ESWT) bei Pseudarthrose.

The gold standard for treatment of pseudarthrosis is operation with osteosynthesis and grafting. More than 10 years ago, extracorporeal shock wave therapy (ESWT) was additionally introduced as a noninvasive and low-risk treatment for pseudarthrosis. The aim of our prospective study was to analyze the treatment effect in a homogeneous group of patients and to develop prognostic factors. Forty-three consecutive patients were included in this study. All patients had been operated on for trauma or undergone selective osteotomy and had developed pseudarthrosis that persisted for 9 months. All patients received high-energy ESWT (0.6 mJ/mm2) with 3000 impulses (Siemens Osteostar) in one session under regional anesthesia. To differentiate active from inactive pseudarthrosis, a bone scintigraphy was compulsory. Clinical and radiological follow-ups were done at 4-week intervals starting 8 weeks after ESWT for 9 months. Cortical bridging was found in 31 of 43 (72.1%) pseudarthroses at 4.0 +/- 0.6 months after ESWT. Of 31 (80.6%) successfully treated patients, 25 had a positive scintigraphy compared to 4 of 12 (33.3%) treatment failures. Of 35 (82.9%) patients with a positive bone scintigraphy, 29 had bony healing compared to 2 of 8 (25%) patients with a negative bone scintigraphy. Six of these eight patients smoked more than 20 cigarettes a day. ESWT is still a clinically experimental treatment method. The absence of complications justifies its use for pseudarthrosis treatment. Further controlled studies are mandatory.

[Pregnancy-associated symphysis damage from the orthopedic viewpoint--studies of changes of the pubic symphysis in pregnancy, labor and post partum]. / Der schwangerschaftsassoziierte Symphysenschaden aus orthopädischer Sicht--Untersuchungen zu Veränderungen an der Symphysis pubica in der Schwangerschaft, unter der Geburt und post partum.

AIM: Is the sonographic measurement of the symphysis pubis enough to enable a prognosis of the occurrence of symphyseal pain during pregnancy and birth? METHOD: First of all, a simplified definition of symphyseal pain was categorized in order to make the classification more easy. The symphyseal widths of 171 pregnant women were measured during pregnancy and after birth. Our control group consisted of 25 non-pregnant women. 15 of the 171 patients suffered from symphyseal pain; however, 156 of the 171 did not. Additionally, we measured the intrapartal symphyseal width in 11 of the women. RESULTS: The average symphyseal width of non-pregnant women was 4.07 mm (s = 0.79; n = 25). Pre- and postpartally we measured 6.32 mm (s = 1.71; variation of 3 to 16 mm) in pregnant asymptomatic women. A significant increase in width was recorded in the 15 women with pain in the symphysis: the symphyseal width was 10.62 mm (s = 2.37; Variation from 6.7 to 15.25 mm). Intrapartally the symphyseal width varied between 5.8 and 1.2 mm. CONCLUSION: Ultrasound measurement of the symphyseal width shows around 4 mm in non-pregnant women. Asymptomatic pregnant women have an average width of 6.3 mm. The majority of pregnant women with 9.5 mm or more have symphyseal pain. If that is the case then conservative treatment is usually sufficient to cure this complaint.

[Digital planimetry for exact assessment of peri-articular ossification]. / Die digitalisierte Planimetrie zur exakten Erfassung von periartikulären Ossifikationen.

PROBLEM: Currently, non-steroidal anti-inflammatory drugs (NSAID) and radiation have become established as methods of choice in the prevention of ectopic ossifications after total hip replacement. The most effective doses is still not known exact for both. Conventional classification systems only permit a rough distinction of ossifications, so they cannot be used for an exact quantitative measuring. Further, only a limited number of categories can be distinguished. We wanted to find out whether a quantitative measurement of ossifications can be realized, and if small differences in prophylactic effect can be detected in this way. METHOD: By computerized digitized planimetry, we measured ossifications of patients after total hip replacement on plain X-rays of the pelvis. We followed 57 patients for up to 2 years after operation. After marking the ossifications they were measured by drawing the outline with a magnifying glass-mouse. We checked all aspects of precision and reproducibility of the measurements and the comparability with an established classification method (Brooker). RESULTS: The digitized planimetry could be performed on all patients X-rays. It gave a much more differentiated picture compared to the method of Brooker. The method is simple and reproducible, but time consuming. CONCLUSIONS: Digitized planimetry allows a very exact measurement of ectopic bone formation. Compared to conventional classification systems, it differentiates more subtly. In limited, well controlled studies slight differences of prophylactic methods on ossifications can be evaluated. New developments in X-ray technology will make the handling of this method even easier.

[Pedestal cup operation in acetabular defects after hip cup loosening. A progress report]. / Die Sockelpfannenoperation bei acetabulären Defekten nach Hüftpfannenlockerung. Ein progress report.

PURPOSE: An extreme extent of acetabular bone loss makes a primary stable cup fixation very difficult to achieve. No reliable operation method is as yet available. Defect filling with bone cement or bone grafts gives a high long-term failure rate. Further revisions are programmed. METHODS: The titanium pedestal cup possibly offers a solution to these situations. It is fixed in the load-carrying upper vital part of the pelvis. A guide is necessary for this step. The tapered pedestal is reinforced by two large wings for rotational and structural stability. The physiological load transfer goes entirely through the pedestal. Thus, the cup serves only for articulation, sometimes without any contact to bone. Structural bone grafts are not implanted. Due to its modular length the pedestal very often allows a cup position at the original center of rotation. RESULTS: A total of 139 pedestal cups have been implanted. Within a prospective study 51 hip revisions have been followed over 1-5 years. The indications include acetabular defects and resection arthroplasty. Implant related complications were few and consisted of a first generation screw failure and malpositioning of the pedestal. CLINICAL RELEVANCE: After complete removal of all granulomatous tissue and restoration of physiological joint forces we observed early and spontaneous bone regeneration. CONCLUSION: We doubt that a bony reconstruction exclusively happens after massive bone grafting. The acetabulum can recover even in catastrophic cases of pelvic discontinuity without allografts. Nearly all revision cases and rim defects can be managed with the pedestal cup.