[Embolisation of aneurysmal bone cysts as a minimally invasive treatment option - presentation of two cases]. / Die Embolisation stammnaher aneurysmatischer Knochenzysten als minimalinvasive Therapieoption - zwei Fallbeispiele.

AIM: The aim of this study was to evaluate embolisation as a therapy option for aneurysmal bone cysts of the trunk. METHOD: Case reports about two males with intermittent pseudo-radicular lumboischialgia and coxalgia are discussed. RESULTS: The diagnostic work-up and biopsies verified an aneurysmal bone cyst in both males. In one patient the tumour-like lesion was localised in the fifth lumbar vertebral body, in the other in the left ischium and pubis. Arterial embolisation was performed in both cases. Follow-up at 6 and 24 months after embolisation showed a significant increase of sclerosis and a reduced volume of the cysts. CONCLUSION: In accord with literature data, arterial embolisation seems to be a sufficient and minimally invasive therapy option in aneurysmal bone cysts of the spine and the pubis.

[The prognostic influence of primary tumour and region of the affected spinal segment in 217 surgical patients with spinal metastases of different entities]. / Der prognostische Einfluss von Primärtumor und Höhe des befallenen Wirbelsäulenabschnitts bei 217 operativen Patienten mit Wirbelsäulenmetastasen unterschiedlicher Entität.

AIM: A retrospective study to evaluate the prognostic influence of the primary tumour and the anatomic level of spinal metastases was carried out. MATERIAL AND METHODS: Between January 1984 and May 2005, 217 patients were surgically treated because of spinal metastases. The prognostic influence for the survival was analysed for the entity of the primary tumour and the localisation of the spinal metastases. RESULTS: The median survival of the study group was 8.0 months (range: 0-191.5 months). Mamma carcinoma was the most frequent primary tumour with 62 cases (28.6 %). The spinal level of the metastases did not influence the postoperative survival (p = 0.9058). The entity of the primary tumour showed a significant influence for the postoperative survival (p < 0.0001). CONCLUSION: In spinal metastases, the entity of the primary tumour was of prognostic value; the localisation of the spinal metastases at different spinal levels did not influence the postoperative survival. Therefore, the evaluation of the primary tumour is mandatory for an estimation of the expected survival.

Evaluation of the Tokuhashi prognosis score and its modifications in 217 patients with vertebral metastases.

AIM: The Tokuhashi prognosis score consists of six parameters. The sum of points rated for each parameter can be correlated with the prognosis. This study evaluates the score variations that have been done by different authors and Tokuhashi et al. themselves. METHODS: Two hundred and seventeen consecutive patients, surgically treated for vertebral metastases, were studied retrospectively. We calculated the original and modified score of Tokuhashi and evaluated the predictive value for the individual life expectancy. RESULTS: The original and modified Tokuhashi score assured a significant predictive value. Modified criteria by the authors showed the highest reliability between the predicted and real survival, and the patients could be allocated correctly to the desirable instrumentation. CONCLUSION: The original and modified Tokuhashi score showed a significant predictive value. The modified criteria by the authors showed the highest reliability between predicted and real survival.

Gait analysis and WOMAC are complementary in assessing functional outcome in total hip replacement.

OBJECTIVE: To investigate the correlation between objective and subjective evaluation of patients with total hip replacement. DESIGN: Prospective preliminary trial comparing the Western Ontario and McMaster University questionnaire (WOMAC) and gait analysis preoperatively and three months postoperatively. SETTING: A German academic orthopaedic centre specializing in total hip replacement surgery. SUBJECTS: Seventeen patients (median age 70 years) with hip osteoarthritis. INTERVENTION: All patients had had a primary unilateral total hip replacement. MAIN MEASURES: WOMAC questionnaire to assess self-perceived health status and gait analysis to determine objective gait parameters. RESULTS: Performance of walking as well as subjective judgement of health status improved following surgery (gait speed P = 0.0222; stride length P = 0.038; stance phase ratio P = 0.0466; WOMAC P < 0.0001). However, the correlation between gait parameters and WOMAC was poor (r = -0.27 or less). Correlation between changes of walking parameters and WOMAC was bad to good (r = 0.01 to r = -0.72). CONCLUSION: The WOMAC questionnaire might not reflect walking performance. The addition of gait analysis is recommended to gain objective information about the quality of gait.

[Surgical treatment and evaluation of prognostic factors in spinal metastases of renal cell carcinoma]. / Chirurgische Therapie und Evaluation von Prognosefaktoren bei Wirbelsäulenmetastasen durch Nieren-Zell-Karzinome.

AIM: The aim of this study was the evaluation of surgical results and prognostic factors in spinal metastases of renal cancer. METHODS: 37 surgical patients with spinal metastases of renal cell carcinoma were retrospectively analysed. In 2 patients the cervical, in 16 patients the thoracic, in 4 patients the thoraco-lumbar and in 16 patients the lumbar spine was involved. RESULTS: In 11 cases (29.7 %) a combined posterior-anterior spondylodesis with vertebral body replacement, in 26 cases (70.3 %) a single posterior instrumentation was done. Perioperatively, 24 complications appeared, 4 of them were lethal. Postoperatively, the neurological situation was unchanged in 26 patients, dischanged in 4 patients and improved in 7 patients. The level of pain was unchanged in 10 patients, dischanged in 3 patients and improved in 24 patients. The mean postoperative survival was 13.6 months. For the postoperative survival the Karnofsky-Index and the Frankel-Score were univariate highly significant, the factors nutritional condition and latency between the primary tumor and the development of spinal metastases showed a lower significancy. No prognostical influence for the postoperative survival could be detected for the factors gender, age, localisation of the metastases, type of operation and the factor solitary/multiple metastases. The multivariate analyses did not attempt any of the univariate significant prognostic factors for the postoperative survival. The postoperative survival was significantly (p: 0.0030) influenced by postoperative adjuvant therapy (radio- and/or chemotherapy). The analysis of each adjuvant therapy form (i. e. chemo-, radio- and combined therapy) attempts this prognostic effect (p: 0.0229). CONCLUSION: In most patients with spinal metastases of renal cell carcinoma, the singular posterior intrumentation combined with a decompression is a sufficient therapy. To avoid posterior implant failure, in patients with a prognosticated survival of more than one year, a combined posterior-anterior spondylodesis with vertebral body replacement should be done. The prognostic influence of an adjuvant postoperative treatment in the present study must be interpreted in the context of this small, highly selected patient collective. Further standardized studies should be performed to evaluate the prognostic influence of an adjuvant therapy.

[Surgical treatment and prognosis factors in spinal metastases of breast cancer]. / Chirurgische Behandlung und Prognosefaktoren von Wirbelsäulenmetastasen bei Mamma-Karzinom.

AIM: The aim of this study was the evaluation of surgical therapy results and prognosis factors in patients with spinal metastases of breast cancer. METHODS: 55 patients with spinal metastases of breast cancer who were treated surgically were retrospectively evaluated. In 11 patients the cervical, in 27 patients the thoracic and in 17 patients the lumbar spine was affected. RESULTS: Postoperatively, 45 patients (81.8 %) described a reduction in pain and 5 patients (50 %) reported a neurological improvement. Perioperative complications appeared in 27 patients (49.1 %), 2 patients died. For the entire group, the mean postoperative survival was 27.2 +/- 28.6 months and the median survival 16.2 months. In patients with solitary metastasis the univariate analysis did not show a significantly longer postoperative survival than in patients with additional visceral metastases (p = 0.0659), but patients with solitary metastasis showed a significantly longer survival than those with multiple osseous and/or visceral metastases (p = 0.0325). In the univariate analysis, the classification of the primary tumour, the duration of symptoms, the localisation of the metastases, the patient's age and the kind of surgical procedure (posterior stabilising instrumentation versus combined posterior-anterior treatment with intralesional resection of the affected vertebra and vertebral body replacement) did not show a significant influence on the postoperative survival. The multivariate analysis did not show a significant prognostic influence for the potentially prognostic factors, however, solitary and multiple metastasis showed the highest statistical influence for the prognosis (p = 0.1187), followed by the classification of the primary tumour (p = 0.1243). CONCLUSION: Pain reduction and neurological improvement can be reached by a stabilisation of the diseased spinal region. Patients with spinal metastases due to breast cancer showed a relatively long postoperative median and mean survival. Therefore, the preoperative evaluation of extent of the disease and the therapy concept should be individually adapted. The surgical procedure (posterior stabilising instrumentation versus combined posterior-anterior approach with vertebrectomy and vertebral body replacement) does not significantly influence the survival.

[Prognosis, surgical therapy and progression in cervical and upper-thoracic tumor osteolysis]. / Prognose, operative Therapie und Verlauf bei zervikalen und hochthorakalen Tumorosteolysen.

INTRODUCTION: This study analyzes the early and mid-term results of our modular rod-screw implant system for the posterior instrumentation of the occipito-cervical, cervical and cervico-thoracic spine (neon occipito-cervical system, Ulrich, Germany) in patients with tumor osteolysis. The prognosis of the patients was evaluated using the Tokuhashi score. METHODS: The cervical and upper thoracic spines of 14 patients (7 males, 7 females, mean age 61 years, range 40-77 years) with osteolysis due to plasmocytoma (n = 2), bronchial (n = 3), mamma (n = 4), thyroid (n = 2), esophageal (n = 1) and pancreatic (n = 1) carcinomas as well as melanoma (n = 1) were instrumentated between June 2001 and April 2004. RESULTS: A stable fixation without loosening or failure of the fixator system was achieved in all cases. No impairment of the neurological status was observed. In our cohort different prognosis scores failed to make a reliable estimate of the expected survival at the time of surgery. CONCLUSION: Posterior instrumentation of the cervical spine including the occipito-cervical and the cervico-thoracic regions with a modular angle-stable rod-screw implant system (neon) offers good stabilization and allows simultaneous decompression. Since tumor masses are predominantly located in the anterior portion of the spine, blood loss can be controlled well. In this patient collective appears difficult to estimate the time of survival by a scoring system.

Sports activities 5 years after total knee or hip arthroplasty: the Ulm Osteoarthritis Study.

OBJECTIVE: To analyse sports activities of patients with hip or knee osteoarthritis (OA) over lifetime, preoperatively, and 5 years after arthroplasty. METHODS: In a longitudinal four centre study, 809 consecutive patients with advanced OA of the hip (420) or the knee (389) joint under the age of 76 years who required total joint replacement were recruited. A completed questionnaire about sports activities at 5 year follow up was received from 636 (79%) of the 809 patients. RESULTS: Although most patients with hip (97%) and knee (94%) OA had performed sports activities during their life, only 36% (hip patients) and 42% (knee patients) had maintained sports activities at the time of surgery. Five years postoperatively, the proportion of patients performing sports activities increased to 52% among patients with hip OA, but further declined to 34% among those with knee OA. Accordingly, the proportion of patients with hip OA performing sports activities for more than 2 hours a week increased from 8 to 14%, whereas this proportion decreased from 12 to 5% among patients with knee OA. Pain in the replaced joint was reported by 9% of patients with hip and by >16% with knee OA. CONCLUSION: Differences in pain 5 years after joint replacement may explain some of the difference of sports activities between patients with hip and knee OA. Reasons for reduction of sports activities may include the increasing age of the patients, their worries about an "artificial joint", and the advice of their surgeon to be cautious.

[Reliability of transcutaneous measurement of oxygen tension on the lower leg]. / Reliabilität der transkutanen Sauerstoffpartialdruckmessung an der unteren Extremität.

AIM: Measurement of transcutaneous oxygen tension is increasingly used to determine the appropriate level of amputation in patients with vascular disease. The purpose of the present study was to analyze the intra- and interrater reliability of transcutaneous oxygen [tcpO (2)] measurements in a homogeneous study group. METHOD: Five investigators assessed the transcutaneous oxygen tension of both lower legs of seven persons in a fixed setting. Assessment was repeated with the same examiners and the same examinees after 24 hours. TcpO (2) was measured at the posterior aspect of the lower leg twenty centimeters below the knee joint line. The TCM 400 Monitoring System (Radiometer Medical AIS, Bronshoj, Denmark) was used. Statistical analysis of the intra- and interrater reliability was performed with the Spearman coefficient of correlation. RESULTS: An overall mean of 56.2 +/- 10.6 mmHg was found. For the first examination, a mean of 55.3 +/- 10.6 mmHg was observed, whereas for the second examination it was 57.0 +/- 10.5 mmHg. Analysis of intrarater reliability showed a coefficient of correlation of r (s) = 0.56 (p < 0.0001). For interrater reliability, we found coefficients of correlation ranging from r (s) = 0.20 (p = 0.20) to r (s) = 0.69 (p = 0.0004). CONCLUSION: Analysis of transcutaneous oxygen tension measurements performed by different investigators in a fixed setting revealed a non- homogeneous intra- and interrater reliability, which should be taken into account prior to initiating therapy.

[Diabetic muscle infarction-an orthopedic disease pattern?]. / Der diabetische Muskelinfarkt-ein orthopädisches Krankheitsbild?

Diabetic muscle infarction (DMI) is a largely unfamiliar disease. It affects mainly patients around 40 years of age with long-standing diabetes and concomitant end-organ complications. The symptoms represent a classic pattern of a musculoskeletal disease with muscle pain without trauma, swelling, and functional impairment. Although its short-term prognosis is good, with improvement of the symptoms over weeks or months under analgesia and rest, a high recurrence rate of up to 60% can be observed. Additionaly, the long-term survival of patients after DMI is reduced mostly due to major vascular complications. Since many diabetic patients are in orthopedic care for musculoskeletal disorders, the orthopedic surgeon should be aware of this disease to avoid unnecessary invasive diagnostic procedures and initiate suitable therapy. Furthermore, a better knowledge of the disease could lead to definite conclusions regarding its real incidence and aid in establishing new therapeutic measures for prophylaxis and better long-term survival.

[Calcaneal cyst: a classical simple bone cyst?]. / Die Kalkaneuszyste: eine klassische solitäre Knochenzyste?

INTRODUCTION: In the calcaneus differentiation between a solitary cyst and intraosseus lipoma is difficult. Radiologists frequently diagnose an intraosseus lipoma, whereas histology shows the classical signs of a solitary bone cyst. We present 12 cases of a solitary cyst of the calcaneus. MATERIAL AND METHODS: Between 1993 and 2001 we operated on 12 patients (8 men, 4 women, median age 28 +/- 14 years) with calcaneal cysts. 9 patients received a curretage and an autologous, one patient a homologous, one patient a mixed autologous-homologous bone-grafting and one patient only a curretage (due to the small diameter of the cyst) of their cysts. RESULTS: No case revealed the histological picture of a fatty formation, which appears to be typical for an intraosseus lipoma. All of the microscopic findings resembled the characteristics seen in cysts of the long bones. A pathological fracture has not been observed. CONCLUSION: The histologically confirmed calcaneal cysts showed the radiological signs that are supposed to be typical for an intraosseous lipoma. It cannot be decided whether the histologically diagnosed calcaneal lipomas described by others can be interpreted as fatty degeneration of a calcaneal cyst, or whether fatty areas of the bone marrow have given a wrong impression. Since the literature only describes single isolated cases of a pathological fracture of the calcaneal cyst or lipoma, asymptomatic patients should be treated non-operatively.

[Minimally invasive therapy for osteoid osteoma]. / Minimalinvasive Therapie bei Osteoidosteom.

AIM: We describe a minimally invasive procedure for the treatment of osteoidosteoma and present the outcome of the treatment in our collective. Additionally, a review of the literature for minimally invasive therapy for osteoidosteoma was performed. METHODS: Within approximately three years, ten male patients with the clinical and radiological diagnosis of osteoidosteoma were treated. First, during the procedure for the purpose of orientation, a CT scan of the affected area was performed. Then, under CT-guidance, the nidus of the osteoidosteoma was marked with a k-wire and destroyed with a drill, moulding cutter or the k-wire. The patients' charts and films were reviewed in a retrospective manner, all patients participated in a personal telephone interview. RESULTS: In all cases the intraoperative course was free of complications. After surgery 90 % of the patients were free of pain, in 10 % a significant reduction of the pain was reported. Both in those 10 % and the whole collective there were no clinical symptoms of relapse, the average follow-up in all cases was 19 months. Our results are in accord with data in the literature. CONCLUSION: In our collective the CT-guided, percutaneous removal of osteoidosteoma has been shown to be a safe and effective method. Under DRG conditions it can be performed within a short period of hospitalization or in the out-patient clinic.

[Vertebral body replacement with expandable titanium cages]. / Wirbelkörperersatz durch expandierbare Titan-Cages.

OBJECTIVES: The aim of vertebral body replacement is the stabilisation and restoration of the anterior column of the spine with removal of the diseased region. We present our results of stabilisation, pain reduction and neurological improvement using vertebral-body replacement systems METHODS: Between April 1997 and December 2002, 53 patients with malignant vertebral destruction or instability due to traumatic and osteoporotic fracture were treated. We evaluated the results after vertebrectomy and vertebral body replacement by using expandable titanium cages in a retrospective study. RESULTS: The average follow-up time was 18.9 +/- 19.9 months. The mean operation time was 173.2 +/- 77.4 minutes. Intraoperatively, we saw no implant-related complications. Perioperatively, complications appeared in 18 patients (34.0 %). 4 of them were severe, with 2 patients dying. In the total follow-up, 16 patients died, 10 of them (62.5 %) due to tumour progression. Pain reduction was reported in 52.7 %, neurological improvement in 48.0 %. One patient had a loosening of his posterior instrumentation in the further follow-up due to tumour growth with dislocation of the cage and a deterioration of his neurological deficit. CONCLUSION: By using vertebral body replacement systems, sufficient stabilisation of the vertebral column, pain reduction and neurological improvement can be achieved with an acceptable perioperative risk.

[Sagittal alignment and segmental range of motion after total disc replacement of the lumbar spine]. / Sagittales Alignement und segmentale Beweglichkeit nach endoprothetischer Versorgung lumbaler Bewegungssegmente.

AIM: To evaluate changes in static and dynamic values, X-rays of patients who underwent total disc replacement for degenerative disc disease were analyzed. METHOD: An analysis of pre- and postoperative lateral X-rays in 22 patients with 24 total disc replacements (Prodics, Spine Solutions) was performed. The total lumbar lordosis, the segmental lordosis angle, the disc height and the range of motion in the operated level were measured. RESULTS: Postoperatively a significant increase was observed for the following parameters: the anterior (pre: 9.0 +/- 3.4 mm; post: 16.7 +/- 2.4 mm; p < 0.001) and posterior (pre: 4.4 +/- 1.3 mm; post: 8.8 +/- 1.3 mm; p < 0.001) disc height and the segmental lordosis angle (pre: 20 degrees +/- 7.2 degrees; post: 27.7 degrees +/- 7.4 degrees; p < 0.001). Statistically no significant changes could be observed postoperatively for the total lumbar lordosis (pre: 56.2 degrees +/- 10.7 degrees; post: 58.6 degrees +/- 9.3 degrees; p = 0.196) and the range of motion (pre: 5.0 degrees +/- 4.0 degrees; post: 5.9 degrees +/- 3.5 degrees; p = 0.293). CONCLUSION: Total disc replacement for degenerative disc disease of the lumbar spine with the current concept does not alter the range of motion but significantly increases the disc height. The significant increase in segmental lordosis without a change in the total lumbar lordosis accounts for a change in lordosis in adjacent segments.

A new dorsal modular fixation device allows a modified approach in cervical and cervico-thoracic neoplastic lesions.

INTRODUCTION: The aim of this study was to improve the management of cervical tumor osteolysis. A new modular rod-screw implant system for the posterior instrumentation of the occipito-cervical, cervical and cervico-thoracic spine (neon occipito cervical system, Ulrich, Germany) is available since 2000. K-wire guided pedicle screws are used, CT-guided instrumentation is possible. Previous studies have demonstrated increased biomechanical stability compared to established posterior cervical systems. METHODS: The cervical and cervico-thoracic spine of 8 patients (6 males, 2 females, mean age 62 years, range 48-77 years) with osteolysis due to plasmocytoma (n=2), bronchial (n=2), mammary (n=2), esophageal (n=1) and pancreatic (n=1) carcinoma were instrumentated since June 2001. RESULTS: A stable fixation without loosening or failure of the fixation system was achieved in all cases. No impairment of the neurogical status was observed. CONCLUSION: Posterior instrumentation of the cervical spine including the occipito-cervical and the cervico-thoracic region with a new modular angle-stable rod-screw implant system offers good stabilization and allows simultaneous decompression. Since tumor masses are predominantly located in the anterior portion of the spine blood loss can be reduced.

[Posterior dynamic stabilization as an alternative for dorso-ventral fusion in spinal stenosis with degenerative instability]. / Dorsale dynamische Stabilisierung als Alternative zur dorso-ventralen Fusion bei Spinalkanalstenose mit degenerativer Instabilität.

AIM: Our retrospective study analyzed the outcome of patients with degenerative lumbar instability with spinal stenosis, who underwent decompression surgery with dorsoventral fusion (Group I) and decompression surgery with posterior dynamic stabilization (Group II). METHOD: For 10 patients in each group intra- and postoperative data were obtained and the functional outcome was evaluated with the "Oswestry Low Back Pain Disability Questionnaire" (OQ) and the "Short Form 36 Health Survey Questionnaire" (SF-36). The average follow up was 14.4 months in Group I, 15.2 months in Group II. RESULTS: In Group I the OQ averaged postoperatively 32 points (preoperatively 46 points), the "Physical Component Summary" (PCS) of SF-36 averaged 34 points (preoperatively 24 points), the "Mental Component Summary" (MCS) averaged 43 points (preoperatively 36). In Group II the values at follow up were as follows: OQ 33 points (preoperatively 54), PCS 34 points (preoperatively 28) and MCS 46 points (preoperatively 36). The average hospitalization was 28.4 days in Group I, 19.3 days in Group II and the average operation time was 218 minutes in Group I, 163 minutes in Group II. CONCLUSION: When compared the functional outcome, the dynamic stabilization seems to be a promising alternative to fusion in patients with degenerative lumbar instability with spinal stenosis.

Expression of collagen type I, II, X and Ki-67 in osteochondroma compared to human growth plate cartilage.

In order to characterize the consequences for the process of endochondral ossification we performed an immunohistochemical study and compared the expression of collagen type I, II and X as markers of cartilage differentiation and Ki-67 as a marker of cell proliferation in solitary (7-26 years, n=9) and multiple (11-42 years, n=6) osteochondromas with their expression in human fetal and postnatal growth plates. In fetal and young postnatal controls, we found a thin superficial layer of articular cartilage that stained positive for collagen type I while collagen II was expressed in the rest of the cartilage and collagen type X was restricted to the hypertrophic zone. Osteochondromas from children showed lobular collagen type II-positive areas surrounded by collagen type I. In adults, the separation of collagen type I- and type II-positive areas was more blurred, or the cartilaginous cap was missing. Collagen type X was detected in a pericellular distribution pattern within hypertrophic zones but also deeper between bone trabecula. The proliferative activity of osteochondromas from children younger than 14 years of age was comparable to postnatal growth plates, whereas in cartilage from individuals older than 14 years of age, we could not detect significant proliferative activity.

[Review and comparison of culture-techniques for articular chondrocytes]. / Vergleichender Uberblick über Verfahren zur Kultivierung artikulärer Chondrozyten.

AIM: In-vitro techniques for articular chondrocytes allow the analysis of their metabolism in the presence and absence of mediators or drugs against osteoarthritis or rheumatoid arthritis, as well as the synthesis of de-novo cartilage tissue for implantation into articular defects in vivo. This review aims to give an overview about the basics of different methods of cultivation of articular chondrocytes and about several specific demands (e.g., phenotypical stability with synthesis of aggrecan and type-II collagen, no cell-to-cell contact, low proliferation rates, low matrix molecule turn-over) to such methods. METHOD: Current techniques for the cultivation of articular chondrocytes and their development were identified via "medline". Their evaluation was based on our own experience and on data from the literature. RESULTS: Two- and three-dimensional culture systems are employed to maintain articular chondrocytes in vitro. Two-dimensional cultures (monolayer) support the proliferation of articular chondrocytes, but lead to a de-differentiation to fibroblast-like cells. Three-dimensional set-ups (e.g., organ, alginate, agarose cultures) not only maintain the articular cartilage phenotype, but they also support the re-differentiation of de-differentiated chondrocytes. CONCLUSION: The choice of a culture system for in-vitro studies with articular chondrocytes should be adapted to the question asked.

Lipofection of rabbit chondrocytes and long lasting expression of a lacZ reporter system in alginate beads.

OBJECTIVE: Our aim was to investigate the maintenance of the transfection status of non-viral transfected chondrocytes in an alginate culture system. DESIGN: Chondrocytes harvested from rabbit knees were isolated by sequential digestion and cultivated in monolayer culture. At 60-70% cell density, chondrocytes were transfected with different transfection systems (FuGENE6, CaCl2, Lipofectin). A lac Z expression vector (pcDNA 3.1/Myc-His+ lacZ) was used as a reporter system. In order to improve transfection rates, hyaluronidase (4 U/ml) was used prior and during the transfection procedure. Thereafter, transfected cells were either kept in monolayer culture or embedded in alginate beads and kept in culture for up to the next 30 weeks. RESULTS: Transfection efficiency was maximal using FuGENE6TM/DNA at a ratio of 3:2 and hyaluronidase (4 U/ml). Transfection efficiency reached up to 40.8% (+/- 3.2%) after 36 h. In alginate beads lac Z positive cells declined to 8.5% +/- 3.3% after 4 weeks and to 4.6% +/- 3.2% after 12 weeks of culturing. After 30 weeks 3% of chondrocytes still expressed lac Z. In contrast, during culturing in monolayer, no lac Z expression was detectable after 4 weeks. Differentiation status of the chondrocytes was confirmed by histology and immunohistochemistry methods. CONCLUSIONS: After successful gene transfer to rabbit chondrocytes the alginate system made it possible to culture lipofected chondrocytes phenotypically stable. Genetically engineered chondrocytes express the lac Z reporter gene over a period of at least 30 weeks. This transfection and culture system provides a promising tool to further investigate the over-expression of growth factors and enzyme inhibitors.

Long-term effects of osteogenic protein-1 on biosynthesis and proliferation of human articular chondrocytes.

OBJECTIVE: To study the long-term effects of OP-1 on the biosynthesis and proliferation of human articular chondrocytes. METHODS: Chondrocytes were released from human cartilage from 10 organ donors of different ages and cultured in alginate. They were exposed to OP-1 (0-200 ng/ml) for 3 to 60 days. Proteoglycan (35S-sulfate) and collagen (3H-proline) synthesis were measured by radiolabeling. Proteoglycan content was determined by a dimethylmethylenblue assay, hydroxyproline content by a colorimetric assay, and DNA content by a fluorometric assay. RESULTS: Long-term (60 days) cultures of human adult articular chondrocytes stimulated by OP-1 (50 ng/ml) revealed a relative decrease of proteoglycan and collagen synthesis. However, proteoglycan (5-fold) and collagen (1.4-fold) content were increased even after 60 days in culture when compared to controls. Maintaining the chondrocyte phenotype (aggrecan synthesis as the main proteoglycan) in long-term culture, OP-1 (50 ng/ml) stimulated proliferation up to 2.4-fold. CONCLUSION: Maintaining a stable phenotype and accelerating matrix assembly and proliferation in long-term culture OP-1 might support the tissue engineering of human cartilage.