Cholinergic nerve fibers in bone defects of a rat osteoporosis model and their regulation by implantation of bone substitution materials

OBJECTIVES

Bone is innervated by autonomic nervous system that consists of sympathetic and parasympathetic nerves that were recently identified in bone. Thus we asked whether parasympathetic nerves occur in bone defects and at the interface of substitution materials that were implanted for stabilization and improvement of healing in an osteoporosis animal model.

METHODS

Osteoporosis was induced in rats by ovariectomy and deficiency diet. A wedge-shaped osteotomy was performed in the metaphyseal area of femur. Eight different implants were inserted that were based on calcium phosphate cement, iron, silica-mineralized collagen, and modifications with strontium. Nerves were identified by immunohistochemistry with antibodies against vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH) and protein gene product 9.5 (PGP 9.5) as neuronal marker.

RESULTS

Cholinergic nerves identified with VAChT immunostaining were detected in defects filled with granulation tissue and in surrounding mast cells. No immunolabeling of cholinergic nerves was found after implantation. The general presence of nerves was reduced after implantation as shown by PGP 9.5. Sympathetic nerves identified by TH immunolabeling were increased in strontium functionalized materials.

CONCLUSION

Since cholinergic innervation was diminished after implantation a further increase in the compatibility of substitution materials to nerves could improve defect healing especially in osteoporotic bone.

mRNA expression and protein distribution of fibronectin splice variants and high-molecular weight tenascin-C in different phases of human fracture healing

Fracture healing is a reparative physiological process, which proceeds in stages, each characterized by the predominant tissue in the fracture gap. The tissue matrix is continuously reorganized by cell migration, proliferation, and differentiation. Adhesive proteins such as fibronectin and tenascin transmit information between matrix and cells. As a result of alternative splicing of pre-RNA, EDA + fibronectin, EDB + fibronectin, and high-molecular weight (hm) tenascin-C are generated. By definition, EDB + fibronectin is an oncofetal protein because it is extremely rare in normal adult tissue and plasma, whereas it is expressed in fetal and tumor tissues and during wound healing. In this study, we for the first time describe EDA + fibronectin, EDB + fibronectin, and hm tenascin-C expression in human fracture gap tissue during various stages of differentiation. We demonstrate mRNA expression of all three splice variants in the initial fibrin matrix with upregulation in the enchondral ossification/osteoid and woven bone stages. Of all variants, EDA + fibronectin mRNA has the highest concentration in all stages. For the analysis, we used LightCycler-based relative mRNA quantification and immunohistochemistry. Our data demonstrate that EDA + fibronectin and hm tenascin-C show a diffuse distribution pattern in fracture gap connective tissue, while EDB + fibronectin is focally concentrated in osteoblastic cells at the margins of woven bone. EDA + fibronectin and hm tenascin represent markers for active granulation processes, whereas EDB + fibronectin is specific for cells forming the enchondral and osteoid matrix. The possibility of stimulating fracture healing by EDB + fibronectin-cytokine complexes should be tested in further investigations.

[Biochemical bone resorption markers during the healing of osteoporotic fractures]

BACKGROUND

This study investigated the progression and clinical relevance of biochemical resorption marker values during fracture healing in osteoporosis.

PATIENTS AND METHODS

In 44 patients with distal radius fractures and 29 patients without fractures, the blood and urine concentrations of pyridinoline (PYD), deoxypyridinoline (DPD), N-telopeptides (NTx), and bone sialoprotein (BSP) were recorded on the day of trauma as well as during further progression. All postmenopausal patients underwent bone density measurement. Accordingly, patients were divided into premenopausal, postmenopausal osteoporotic, and postmenopausal nonosteoporotic groups.

RESULTS

Between the groups, PYD, DPD, and NTx showed significant differences in their initial values. However, their further relative progression was primarily affected by the chosen therapy.

CONCLUSION

Bone resorption markers can diagnostically point to osteoporosis and are significant parameters in fracture healing.

[Pseudoaneurysm - a rare complication after insertion of a distal locking bolt of an intramedullary femur nail]

A pseudoaneurysm is caused by an extravasal hematoma after vessel injury. Persistent blood supply via the afferent artery can lead to aneurysm growth with potential rupture of the lesion. We present a case of a 27-year-old man who developed three independent pseudoaneurysms after insertion of percutaneous distal locking bolts for static locking of an intramedullary femur nail. Color-coded Doppler sonography and intraarterial subtraction angiography were used to detect the lesion. Successful treatment consisted of endovascular embolization (coiling) with injection of a platinum coil into the aneurysm's supplying vessel. Pseudoaneurysm after fracture or fracture fixation represents a rare complication, but the risk of acute bleeding by pseudoaneurysm rupture should not be neglected.

[Elution kinetics and antimicrobial effects of gentamicin- and clindamycin-loaded bone cements in vitro]

AIMS

In arthroplasty and particulary in revision surgery antibiotic-loaded bone cements are applied. The purpose of the current study was to analyse the kinetics of antibiotic release and antimicrobial effects of the gentamicin- and clindamycin-loaded bone cement Versabond.

MATERIALS AND METHODS

Test cylinders of bone cements, containing gentamicin and clindamycin in different concentrations, were investigated in vitro with regards to the kinetics of antibiotic release by applying static and continuous elution methods. Antimicrobial effects of antibiotic-loaded bone cement were tested in an infection model with different strains of Staphylococcus aureus and Staphylococcus epidermidis and live/dead dye plus fluorescence microscopy. For the surface analysis of antibiotic-loaded test cylinders contaminated with Staphylococcus epidermidis, scanning electron microscopy was used.

RESULTS

The measurement of static and continuous elution revealed initially higher rates of gentamicin release in comparison with clindamycin. The gentamicin amount decreased within 24 h, whereas clindamycin-loaded test cylinders showed a prolonged release. After 24 h exclusive avital bacteria on antibiotic-loaded cement cylinders were seen, after 72 h on gentamicin-loaded cement bacterial growth was again detected. Application of antibiotics in bone cement revealed an inhomogeneous surface of the bone cement cylinder.

CONCLUSIONS

On application of clindamycin in bone cement the features of increased antibiotic uptake and antimicrobial effect compared with gentamicin-loaded bone cement are observed.

Neurovaskuläre Lappenplastiken zum Verschluss problematischer Weichteildefekte am Unterschenkel

AIM OF THE STUDY

Soft tissue covering on the lower leg is a difficult challenge. A plastic surgical method for covering of these soft tissue defects is presented.

PATIENTS AND METHODS

From May 1997 until May 2003 36 patients were treated using neurovascular flaps. Above the sural or the saphenous nerve an adipo-facial flap is dissected, rotated into the defect and fixed without tension. Wound closure of the donor-site defect is done primarily or by mesh-graft.

RESULTS

In 35 cases the flap healed without functional impairment. Primary healing was achieved in 30 patients. In 5 cases partial loss of the skin island was registered, whereby subcutaneous tissue remained vital. Revision by mesh-graft transplantation led to successful healing in these patients. In only one patient necrosis of the flap was seen.

CONCLUSION

Neurovascular flaps usually result in reliable and complete healing of soft tissue defects of the lower extremity.

Expression of EDA+ and EDB+ fibronectin splice variants in bone

The extracellular matrix component fibronectin (fn) has fundamental functions in cell attachment, differentiation, proliferation, and migration. Isoforms of cellular fibronectin, named EDA+ fibronectin or embryonal EDB+ fibronectin, are generated by alternative splicing of its mRNA precursors. Little is known about the expression of EDA+ and EDB+ fibronectin splice variants in human bone. The aim of this study was to investigate the expression pattern of fibronectin splice variants in bone cell lines and in different human bone tissue samples (mature bone, early stages of fracture healing, hypotrophic nonunion, osteosarcoma). Analysis was done by immunostaining with recombinant and monoclonal antibodies, qualitative RT-PCR and LightCycler-based real-time quantitative RT-PCR assay. In osteoblast and osteosarcoma cell lines, abundant expression of EDA+ and EDB+ fibronectin was found in immunocytochemistry. High transcription levels of both splice variants mRNA were seen in quantitative RT-PCR in osteosarcoma cell lines. In mature bone, EDA+ and EDB+ were not detectable in immunohistochemistry. Transcription of mRNA in both splice variants was absent in these samples. Early stages of fracture healing and osteosarcoma cell samples exhibited extensive staining for EDA+ and EDB+ fibronectin, and high mRNA levels were found. Both osteosarcoma and bone fracture healing tissue expressed high mRNA levels of the fibronectin splice variants independent of benign or malignant behavior. Low level of EDA+ fibronectin mRNA transcription and focal immunohistochemical staining of EDA+ fibronectin was found in hypotrophic nonunions, whereas EDB+ fibronectin was not detected by immunohistochemistry and qualitative or quantitative PCR. EDA+ fibronectin was found in granulation tissue-forming processes in bone independent from bone-forming activity. EDB+ fibronectin was seen only in high-turnover new osteoid-forming processes like early stages of fracture healing and osteosarcoma and was absent in low-turnover processes like mature bone and hypotrophic nonunion. Both EDA+ and EDB+ fibronectin mark active processes in bone without differentiation between malignant or benign activity. In conclusion, EDA+ and EDB+ fibronectin splice variants are strong markers for active fibrogenetic and osteoid-forming processes in human bones.

In vivo mechanisms of hydroxyapatite ceramic degradation by osteoclasts: fine structural microscopy

In the present study the in vivo mechanism of calcium-phosphate (CaP) ceramic degradation has been investigated by means of transmission electron microscopy. The results revealed osteoclast-mediated degradation of hydroxyapatite ceramic implanted into sheep bone by simultaneous resorption and phagocytosis. After 6 weeks of implantation, osteoclasts were localized immediately beneath the ceramic surface. They had formed resorption lacunae and exhibited typical ultrastructural features, such as the ruffled border, the clear zone, and the dorsal microvilli. Their resorption capacity also had become evident by alterations of the electron density and the shape of the CaP crystals localized within the acidic microenvironment of the ruffled border. Moreover, the osteoclasts simultaneously were capable of phagocytosing the resorbed CaP crystals. The formation of endophagosomes was performed (1) by the uptake of particles into large intracellular vacuoles, which were generated by deep invagination of the membranes of the osteoclastic ruffled border, and (2) by the encircling of particles due to the development of pseudopodia-like plasmaprotrusions of the ruffled border. The formation of endophagosomes was followed by the in situ fragmentation of the inclusion material, which subsequently was released into the extracellular space and phagocytosed by macrophages.

Effects of platelet growth factors on human mesenchymal stem cells and human endothelial cells in vitro

The aim of the present in vitro study has been to investigate the effects of a enriched platelet derived growth factors on proliferation and migration of human endothelial and mesenchymal stem cells and on osteogenic differentiation of stem cells. Platelet rich plasma has been produced, yielding a four time higher number of thrombocytes than normal plasma. Degranulation of platelets has been performed by means of calcium and thrombin. Plasma has served as a control, whereas plasma in combination with calcium and thrombin was used to distinguish the difference between calcium and/or thrombin mediated effects and growth factor induced effects on the cells. The observed enhanced proliferation and migration of endothelial cells towards the platelet derived growth factors was driven by the plasma component of these preparations. However PDGF solely stimulated the migration and proliferation of mesenchymal stem cells. The increased osteogenic differentiation of growth factor treated mesenchymal stem cells was mostly driven by the high level of calcium used for the platelets degranulation. In summery, the different components of platelet derived growth factors work together to influence human endothelial and mesenchymal stem cells. This is of special clinically interest regarding the stimulation of bone healing in orthopaedic and traumatic surgery.

Die Problematik der Hoffa-Fraktur

To study the outcome in Hoffa fractures regarding the type of fracture, concomitant injuries, and different treatments. From January 1996 until December 2002, 7 Hoffa fractures (6 patients) from a total of 79 distal femoral fractures were treated in the Department of Trauma Surgery, University Hospital of Giessen. The results were evaluated by Neer's score. For the evaluation of postoperative vascularization of the distal femur, clinical and radiological findings were compared with anatomical studies of the bone arteries by corrosion preparations. Fracture consolidation was seen in all cases. Patients with an isolated Hoffa fracture achieved a score of 89.0 (82-97) according to Neer. One patient suffering initially from nonunion achieved 68 points after bone union. One polytraumatized patient with bilateral Hoffa fracture achieved a satisfying result (score value of 72) and a bad result (score value of 38). Multiple small nutrient arteries of the distal femur originate from the "rete articulare genus." They can be expected to ensure the arterial blood supply. Hoffa fracture is a very rare injury. In our patients, careful surgical treatment with open reduction and safe screw fixation yielded good to very good results.

[Ultrastructural examination of cell-mediated degradation of a calcium phosphate ceramic]

Up to now little is known about cell-mediated degradation of biomaterial surfaces, especially as methodologically significant studies are not available. Therefore, the present study focused on ultrastructural details of cells involved in degradation of calcium phosphate ceramics. For the experimental procedure six adult sheep were used. At the medial aspect of the left hindlimb a cylindrical defect was created at the level of the proximal epiphysis of the tibia. Subsequently, a calcium phosphate paste was packed into the defect. Six weeks after implantation, specimens from the implants fixed by perfusion were examined histologically and by transmission electron microscopy. The results of light microscopy revealed substitution of the ceramic by newly formed lamellar bone. Electron microscopy indicated multinucleated cells localized at the implantation site and the bone surface, corresponding to osteoclasts. They formed resorption lacunae and revealed typical ultrastructural features such as the ruffled border and the sealing zone. Osteoclast-mediated degradation was performed by simultaneous resorption and phagocytosis. For the first time this degradation mechanism was documented in vivo. It confirms the notion that osteoclasts are members of the monocyte/macrophage family.

[Vacuum mixing systems for bone cement completion - comparison of different systems]

INTRODUCTION

The use of vacuum mixing systems when mixing bone cement reduces its porosity and hereby significantly improves the features of the material. The currently available mixing systems are compared with regard to handling, mechanical properties and economical aspects.

METHODS

In 8 vacuum mixing systems the handling, pump performance, system tightness, the used air volume, the filter efficiency, the remaining amounts in the mixing system and the porosity of the cements are shown in comparison.

RESULTS

All vacuum mixing systems reduce the porosity of the cement in comparison to hand mixed cements significantly if used correctly. The individual examinations, though, show enormous differences, which can be of significance to the user in the individual choice of system and, depending on the individual circumstances, can influence the quality of the mixed cement.

CONCLUSION

The results enable the user to choose and handle a vacuum mixing system which is optimally suitable for the individual circumstances in respect to the characteristics examined.

["Biorigid" interlocking after unreamed intramedullary nailing of tibial shaft fractures]

Between April 1996 and December 1999, 76 tibial shaft fractures were treated at the Department of Trauma Surgery of the Justus-Liebig-University in Giessen, Germany and the Department of Orthopedic Surgery of the University of Louisville, USA with a newly developed, unreamed, solid, small diameter tibial nail interlocked "biorigidly" with screws in grooves of the nail. 69 Patients were reviewed with a minimal follow-up period of 16 months. In 65 patients, the fractures united without exchange nailing, although four of these fractures showed a delay of healing. In further four cases, non-union occurred, one of which was associated with the only break of a nail located at a distal interlocking groove of the nail. In one patient, a late medullary infection so far has not recurred following treatment. In 358 implanted interlocking screws, no implant failure was observed. First clinical experience suggests that, especially due to the low rate of material fatigue, the biorigid nail is an alternative to other implants for unreamed intramedullary nailing of the tibia.

[Long-term results in the surgical treatment of pilon tibial fractures. A retrospective study]

BACKGROUND

While Pilon fractures of the tibia have been treated for decades by primary open reduction and internal fixation by plate osteosynthesis, during the last 10 years differential treatment was developed: After primary open reduction nowadays patients are treated with (according to type of fracture and tissue damage). As well as primary open reduction and internal fixation a two-step treatment (primary external fixator and delayed ORIF) or consolidation by external fixator combined with minimal invasive osteosynthesis (cannulated screws and K-wires) has been implemented. Furthermore, the significance of primary bone grafting in comminuted fractures to prevent aseptic pseudarthrosis has been acknowledged.

METHODS

Of 151 patients with 160 pilon fractures treated from January 1979 to May 1995, 107 patients (113 fractures) were evaluated. Only the results of C2 and C3 fractures could be compared, as only in these groups were all three types of treatment used.

RESULTS

Over 75% of the treated fractures were closed fractures, most of them being fractures with a soft tissue damage grade 2 of the Oestern and Tscherne classification. In the open fractures we found mainly grade 3 fractures according to the Gustilo and Anderson classification. In 54.9% of all pilon tibial fractures we observed an uncomplicated course of healing. Early complications (25.7%) were mainly soft tissue infections, whereas we found pseudarthrosis to be the most frequent late complication. Highest infection rate (55.5%) was in the two-step treatment group (primary external fixator and delayed ORIF) and lowest in the primary internal stabilization group, although especially in the C2 and C3 fractures best clinical late results were obtained with the two-step procedure.

CONCLUSION

The complication rate in the treatment of pilon fractures depends mainly on the type of fracture, the soft tissue damage and the type of treatment. The results of primary ORIF varied. In the case of low-grade soft tissue damage, good to excellent results were accomplished. In the case of higher-grade soft tissue damage, the problem of soft tissue coverage and reconstruction of the joint surface could be solved with good results by the two-step treatment. Herewith it is important to use limited open reduction of displaced fragments and fixation by cannulated screws and K-wires. We consider ORIF of the fibula necessary as stabilization of the second column of the ankle joint.

[The frozen shoulder. Arthroscopy, histological findings and transmission electron microscopy imaging]

INTRODUCTION

During a period of 17 months (February 1998 to July 1999) arthroscopy was performed in 172 patients because of pathologic changes of the shoulderjoint.

METHODS

From the history and clinical examination, only eleven patients fulfilled the criteria for primary frozen shoulder set up by Lundberg in 1969. Further investigations such as X-ray examination, ultrasonography and MRI scanning showed no changes that could explain the clinical picture of shoulder stiffness. Of the eleven patients with frozen shoulder. additionally in two cases hyperthyroidism, in five cases diabetes type II and in a further five cases a Dupuytren's contracture could be found. Based on the operative procedure, recently published by Habermeyer, Ogilvie and Warner we carried out an arthroscopic arthrolysis of the stiff shoulder.

RESULTS

Diagnostic arthroscopy demonstrated synovialitis in the upper and ventral areas of the joint in over 50% of the patients. Interestingly, intraarticular adhesions were not found in any of our patients; in particular, no obliteration of the axillary recess could be seen. Altogether, in seven of the eleven patients with frozen shoulder, a notably contracted biceps tendon was found which obviously applied increased the force on the humeral head, as in corresponding areas cartilage damage could be demonstrated arthroscopically. A significant increase in fibroblast cells next to loose areas of connective tissue could be shown in histological examinations of biopsies of the capsule in the rotatorer interval. We noted thickened vessel walls and an augmentation of the synovial surface, whereas typical inflammation could not be demonstrated in any of the histological specimens. In the transmission-electron microscope examination (TEM) of samples taken from the capsule in the rotatorer interval, structural changes in collagenous tissue were discernible. Typically, a loss of fibril order and a twisting of collagen fibrils were seen. This twirling led to an up to fourfold diameter of the collagenous fibrils, whereby thin, elastin-like filaments could be seen between the thickened bundles of collagen fibrils.

CONCLUSION

In stage of the primary frozen shoulder exclusive fibrosis of the joint capsule was found. Electronmicroscopic twists of collagen fibrills were marked.

[A benign form of osteopetrosis. Case report]

Osteopetrosis is a disease in which a disturbance in the resorption of bone formed by endochondral ossification takes place. The cause of the osteoclast insufficiency is unknown. In the literature, the etiology of the disease is discussed in relation to the complete absence of cathepsin K synthesis, a cysteine protease. In our case report, we demonstrated cathepsin K expression in the osteoclast cells of the benign form of osteopetrosis. We also found the macrophage marker CD 68 in these osteoclast cells, whereas other mononuclear phagocytic cells were not present in the vicinity of osteoclasts. The inhibition of osteoclast cells by phagocytes is unlikely.

[Correction of malunited distal radius fractures by osteotomy and interposition of iliac crest bone spain in the radio-palmar position. A retrospective study of 42 patients]

The retrospective study included 42 patients who have been treated with a palmar opening wedge osteotomy after malunion of distal radius fracture. 31 patients could be reexamined clinically and radiologically. The corrective osteotomy on the distal radius was done only radiopalmar with an insertion of a corticocancellous iliac graft. Radiological and functional findings as well as the subjective judgement of the patient have been commented pre- and after surgically according to the assessment scheme of Pechlaner and were then compared with the contra lateral wrist. The evaluation of the x-ray pictures showed an improvement from 3.7 to 1.9 points, the functional improvement from 3.7 to 2.6 points. The improvement of the subjective complaints results in a diminution of 3.3 to 2.2 points.

[A semiquantitative rapid test for cysteine: possible use for monitoring the ascorbic acid therapy in cystinuria and cystine lithiasis]

A semiquantitative method is presented for the determination of cysteine in urine, based on the formation of a red cysteine/nitroprusside salt. The method is suitable as a rapid test for checking the progress of ascorbic acid therapy of cystinuria and cystine urolithiasis. It guarantees acceptable reproducibility of values and can be easily carried out in any clinical chemical laboratory. With the K2CO3/nitroprusside test described and an additional colorimetric determination of cystine (CN-/nitroprusside), a separate semiquantitative differentiation of cysteine and cystine in fresh (!) urine is possible.

Investigations on the early diagnosis of cystinuria in children

The procedure described confirms that the Ni2+/S2O4(2-) tablet test is a suitable quick cystine screening test for large groups. In 16 (0.67%) of 2,395 one- to three-year-old crèche children significantly enhanced cystine levels of 0.60-0.96 mmol/l were found. The corresponding creatinine values (mmol/l) did not reveal any significant deviations from the normal values. In a preliminary group of 9 children, enhanced lysine levels support the suspicion of the existence of cystinuria without clinical symptoms. This also forms the basis for further necessary family histories as well as for prophylactic measures.

[Simple rapid test with carbonate/nitroprusside for the semiquantitative determination of cysteine in the urine--possible use for control of ascorbic acid therapy in cystine urolithiasis]

In this paper a method of semiquantitative cysteine determination is presented, which is based on the formation of a red cysteine-Na-nitroprusside salt. The method is a suitable rapid test for checking the process of ascorbic acid therapy in cystinuria and cystine urolithiasis patients. It guarantees acceptable reproducibility of values and can be easily carried out in every clinicochemical laboratory. With the K2CO3/nitroprusside test described and an additional cystine rapid test (Ni2+/S2O4(2-) tablet reagency) a separate semiquantitative differentiation of cysteine and cystine in fresh (!) urine is possible.

[Modified rapid test for the semiquantitative determination of cystine in the urine]

The present study describes a modified method of the semiquantitative determination of cystine in the urine which is based on the decomposition of cystine by dithionite ions and formation of a mixed nickel/cystein/sulfide-complex. The method is suitable as rapid and search test, it guarantees an acceptable reproducibility as well as the exactness of the values and is simply to be performed in every clinical-chemical laboratory. The criteria of analytic applicability are confirmed in comparisons of methods. It must be urged to treat fresh urines.