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Biomedical subjects

R P Jakob

Publications and source records attributed to R P Jakob.

At least 19 recordsLinked to original sources
PubMed2006

Repair of superficial osteochondral defects with an autologous scaffold-free cartilage construct in a caprine model: implantation method and short-term results.

OBJECTIVE: To compare four different implantation modalities for the repair of superficial osteochondral defects in a caprine model using autologous, scaffold-free, engineered cartilage constructs, and to describe the short-term outcome of successfully implanted constructs. METHODS: Scaffold-free, autologous cartilage constructs were implanted within superficial osteochondral defects created in the stifle joints of nine adult goats. The implants were distributed between four 6-mm-diameter superficial osteochondral defects created in the trochlea femoris and secured in the defect using a covering periosteal flap (PF) alone or in combination with adhesives (platelet-rich plasma (PRP) or fibrin), or using PRP alone. Eight weeks after implantation surgery, the animals were killed. The defect sites were excised and subjected to macroscopic and histopathologic analyses. RESULTS: At 8 weeks, implants that had been held in place exclusively with a PF were well integrated both laterally and basally. The repair tissue manifested an architecture similar to that of hyaline articular cartilage. However, most of the implants that had been glued in place in the absence of a PF were lost during the initial 4-week phase of restricted joint movement. The use of human fibrin glue (FG) led to massive cell infiltration of the subchondral bone. CONCLUSIONS: The implantation of autologous, scaffold-free, engineered cartilage constructs might best be performed beneath a PF without the use of tissue adhesives. Successfully implanted constructs showed hyaline-like characteristics in adult goats within 2 months. Long-term animal studies and pilot clinical trials are now needed to evaluate the efficacy of this treatment strategy.

Animals↗
PubMed2005

Impact loading of articular cartilage during transplantation of osteochondral autograft.

Surgical reconstruction of articular surfaces by transplantation of osteochondral autografts has shown considerable promise in the treatment of focal articular lesions. During mosaicplasty, each cylindrical osteochondral graft is centred over the recipient hole and delivered by impacting the articular surface. Impact loading of articular cartilage has been associated with structural damage, loss of the viability of chondrocytes and subsequent degeneration of the articular cartilage. We have examined the relationship between single-impact loading and chondrocyte death for the specific confined-compression boundary conditions of mosaicplasty and the effect of repetitive impact loading which occurs during implantation of the graft on the resulting viability of the chondrocytes. Fresh bovine and porcine femoral condyles were used in this experiment. The percentage of chondrocyte death was found to vary logarithmically with single-impact energy and was predicted more strongly by the mean force of the impact rather than by the number of impacts required during placement of the graft. The significance of these results in regard to the surgical technique and design features of instruments for osteochondral transplantation is discussed.

Animals↗
PubMed2004

[Closing wedge osteotomy of the tibial head in treatment of single compartment arthrosis].

Closing wedge high tibial osteotomy is an efficient method for the treatment of medial osteoarthritis of the knee. Prerequisites of successful surgery are proper indication and planning as well as the understanding of biomechanics and pathophysiology. The technique of osteotomy to choose (opening or closing wedge) depends on the type of malalignment and on additional pathologies. The surgical technique demands high precision to realize the planned correction and to avoid complications. Implants with angular stability provide advantages compared to traditional implants. Correct indication and surgical technique results in a desirable follow-up, which often lasts for at least 10 years. The effect on the prognosis of the young patient with cartilage damage is still unclear.

Bone Malalignment↗
PubMed2003

Short-term load bearing capacity of osteochondral autografts implanted by the mosaicplasty technique: an in vitro porcine model.

Articular surface congruency and graft stability are considered essential factors in the success of osteochondral grafting; however, quantitative measures of short-term load bearing capacity of grafts implanted by the mosaicplasty technique have not been reported. The purpose of this study was to develop a live tissue in vitro model to examine short-term fixation strength of mosaicplasty autografts immediately after and 1 week following graft implantation. Cylindrical osteochondral autografts were implanted in vitro by the mosaicplasty technique on five pairs of porcine femoral condyles within one and a half hours of animal sacrifice. Immediately following the surgical procedure, graft push-in and pull-out strength tests as well as indentation tests to determine modulus of the surrounding cancellous bone were performed on half of the specimens from the distal femurs of each animal. The remaining specimens, matched for location in the contralateral leg, were incubated in culture medium for 7 days prior to performing the same set of mechanical tests. Averaged push-in and pull-out graft fixation strength decreased 44% from 135.7 to 75.5N over the 7-day period, while no change in modulus was detected in the surrounding cancellous bone. These in vitro results demonstrate a substantial deterioration of short-term fixation strength of mosaicplasty grafts from the immediate post-operative state. Such a reduction in short-term graft load bearing capacity may pose a threat to the surgically established articular surface congruency and blood vessels formed during the early stages of the healing response.

Animals↗
PubMed2003

Ten-year patient and prosthesis survival after unipolar hip hemiarthroplasty in female patients over 70 years old.

We found that 162 unipolar hemiarthroplastics of the hip were performed between 1989 and 1995 on women over 70 years of age in our institution. The mean age was 84 years (70 to 99). Cumulative survival of the prostheses was 98% at 1 year and 94% after 5 and 10 years. Of the original patients, 137 have died. Survival rate for patients was 73% at 1 year, 23% at 5 years, and 6% at 10 years. Eighteen patients could be accounted for, with a mean follow-up time of 7.7 years (5.5-11.3 years). The mean Harris hip score was 80 points (55-100). Protrusion was observed in 3 patients. The treatment of cervical neck fracture with unipolar hip prostheses is a valuable method, with a low complication rate, particularly in women over 70 years for whom life expectancy may be short.

Aged↗
PubMed2002

Treatment of cartilage defects of the talus by autologous osteochondral grafts.

We reviewed retrospectively 11 patients who had been treated surgically by open autologous osteochondral grafting for symptomatic chondral or osteochondral defects of the dome of the talus between 1996 and 1999. The mean ages of the eight men and three women were 34.2 and 25.9 years, respectively, with a mean time to follow-up of 24 months. The results of functional outcome were prospectively obtained using the MODEMS AAOS foot and ankle follow-up questionnaire, the AOFAS ankle-hindfoot scale and the Hannover scores for the ankle. The grafts were harvested from the ipsilateral knee. Good to excellent results were obtained for the ankle without adverse effects on the knee. We believe that autologous osteochondral grafting should be considered for the patient with a symptomatic osteochondral defect of the talus.

Adolescent↗
PubMed2001

In situ compressive stiffness, biochemical composition, and structural integrity of articular cartilage of the human knee joint.

OBJECTIVE: Reduction of compressive stiffness of articular cartilage has been reported as one of the first signs of cartilage degeneration. For the measurement of in situ compressive stiffness, a hand-held indentation probe has recently been developed and baseline data for macroscopically normal knee joint cartilage were provided. However, the histological stage of degeneration of the measured cartilage was not known. The purpose of this study was to investigate whether there is a relationship between the in situ measured compressive stiffness, the histological stage of degeneration, and the biochemical composition of articular cartilage. DESIGN: Instantaneous compressive stiffness was measured for the articular cartilage of 24 human cadaver knees. Additionally, biochemical composition (total proteoglycan and collagen content) and histological appearance (according to the Mankin score) were assessed for each measurement location. RESULTS: Despite visually normal surfaces, various histological signs of degeneration were present. A high correlation between Mankin score and cartilage stiffness was observed for the lateral patellar groove (R(2)=0.81), the medial (R(2)=0.83) and the lateral femoral condyle (R(2)=0.71), whereas a moderate correlation was found for the medial patellar groove (R(2)=0.44). No correlation was observed between biochemical composition and cartilage compressive stiffness. CONCLUSIONS: Our results are in agreement with others and show that the instantaneous compressive stiffness is primarily dependent on the integrity of the extracellular matrix, and not on the content of the major cartilage constituents. The high correlation between stiffness and Mankin score in mild osteoarthrosis suggests that the stage of cartilage degeneration can be assessed quantitatively with the hand-held indentation probe. Moderate and severe case of osteoarthrosis remains to be investigated.

Adult↗
PubMed2001

Articular cartilage repair using a tissue-engineered cartilage-like implant: an animal study.

OBJECTIVE: Because articular cartilage has limited ability to repair itself, treatment of (osteo)chondral lesions remains a clinical challenge. We aimed to evaluate how well a tissue-engineered cartilage-like implant, derived from chondrocytes cultured in a novel patented, scaffold-free bioreactor system, would perform in minipig knees with chondral, superficial osteochondral, and full-thickness articular defects. DESIGN: For in vitro implant preparation, we used full-thickness porcine articular cartilage and digested chondrocytes. Bioreactors were seeded with 20x10(6) cells and incubated for 3 weeks. Subsequent to culture, tissue cartilage-like implants were divided for assessment of viability, formaldehyde-fixed and processed by standard histological methods. Some samples were also prepared for electron microscopy (TEM). Proteoglycans and collagens were identified and quantified by SDS-PAGE gels. For in vivo studies in adult minipigs, medial parapatellar arthrotomy was performed unilaterally. Three types of defects were created mechanically in the patellar groove of the femoral condyle. Tissue-engineered cartilage-like implants were placed using press-fit fixation, without supplementary fixation devices. Control defects were not grafted. Animals could bear full weight with an unlimited range of motion. At 4 and 24 weeks postsurgery, explanted knees were assessed using the modified ICRS classification for cartilage repair. RESULTS: After 3-4 weeks of bioreactor incubation, cultured chondrocytes developed a 700-microm- to 1-mm-thick cartilage-like tissue. Cell density was similar to that of fetal cartilage, and cells stained strongly for Alcian blue and safranin O. The percentage of viable cells remained nearly constant (approximately 90%). Collagen content was similar to that of articular cartilage, as shown by SDS-PAGE. At explantation, the gross morphological appearance of grafted defects appeared like normal cartilage, whereas controls showed irregular fibrous tissue covering the defect. Improved histologic appearance was maintained for 6 months postoperatively. Although defects were not always perfectly level upon implantation at explanation the implant level matched native cartilage levels with no tissue hypertrophy. Once in place, implants remodelled to tissues with decreased cell density and a columnar organization. CONCLUSIONS: Repair of cartilage defects with a tissue-engineered implant yielded a consistent gross cartilage repair with a matrix predominantly composed of type II collagen up to 6 months after implantation. This initial result holds promise for the use of this unique bioreactor/tissue-engineered implant in humans.

Animals↗
PubMed2001

Low reoperation rate with the Medoff sliding plate: 1 technical failure in 63 trochanteric hip fractures.

The Medoff sliding plate was designed to treat unstable intertrochanteric and subtrochanteric fractures. This plate has a dual sliding capability along both the femoral shaft and neck in order to improve bone coaptation, interfragment compression and hence load-sharing between bone and implant in hip fractures. In a retrospective study of 63 patients (mean age 82 (51-98) years) with intertrochanteric (n 44) and high subtrochanteric fractures (n 19), we assessed the results with the Medoff sliding plate. All patients, except 1 lost to follow-up, were examined clinically and radiographically. 14 patients died within 1 year, and in the other, the mean follow-up was 15 (6-30) months. 1 technical failure occurred, leading to a single reoperation. The low technical failure rate suggests that the Medoff sliding plate with combined compression modus is suitable for treating intertrochanteric and high subtrochanteric fractures.

Aged↗
PubMed2000

The effect of knee position on the reproducibility of measurements taken from stress films: a comparison of four measurement methods.

We evaluated the accuracy of four different means of radiographic measurement of anteroposterior translation in the knee joint. The tests were performed in normal knees, in knees lacking the anterior cruciate ligament, and in knees lacking both anterior and posterior cruciate ligaments; the knees were obtained from cadavers. It is difficult to define landmarks and to perform exact measurements, and we sought to determine which of the four methods is the most accurate. In particular, we examined the effect of various degrees of rotation and flexion on the positional relationships of the landmarks of the tibia and the femur.

Biomechanical Phenomena↗
PubMed2000

Treatment of proximal humerus fracture using multiple intramedullary flexible nails.

A total of 61 patients with a proximal humeral fracture was treated between January 1996 and March 1998 by closed reduction and fracture fixation with intramedullary Prévot (or Nancy) nails. Of these, 28 female and 25 male patients with a mean age of 52 years (range 3-91 years) were reviewed clinically and radiologically with a mean follow-up of 17 months (range 4-30 months). The mean Constant score was 63, the mean Neer score 74 and the mean visual analogue scale (VAS) 73. The 14 patients under 24 years old achieved a Constant score of 86, a Neer score of 99 and a VAS of 97, while 13 patients aged between 25 and 60 years had a Constant score of 67, a Neer score of 75 and a VAS of 71. The 26 patients older than 61 years had a Constant score of 48, a Neer score of 61 and a VAS of 61. One patient with total and 6 with partial humeral head necrosis as well as 5 pseudarthroses were noted. Proximal nail perforation of the humeral head due to fracture collapse was seen in 22 cases. Complications were more frequently observed in the elderly. End results were not related to the type of fracture. This minimally invasive technique decreases the rate of occurrence of avascular necrosis of the humeral head. However, fractures are not sufficiently stabilised, mainly because of bone loss induced by impaction and osteoporosis. Bone loss remains an unsolved problem, and alternative methods such as the use of bone substitute combined with minimally invasive techniques should be studied.

Activities of Daily Living↗
PubMed2000

[Knee injuries in general practice].

Careful technique of examination of the knee joint allows to establish the diagnosis of the most frequent knee joint injuries already through simple clinical and radiological evaluation: Recurrent dislocation of the patella with the Apprehension sign; meniscal injuries with the test of McMurray, pain on the joint line and pain on passive hyperextension; the anterior cruciate ligament tear with Lachman's sign and the Pivot Shift test and posterior cruciate injury with the Sag sign. Further imaging techniques allow to establish a definite diagnosis, which has replaced in many cases the classical, purely diagnostic arthroscopy. Thanks to careful aspiration of the knee joint the patient can be referred with a more precise diagnosis to the traumatologist and orthopaedic surgeon. Meniscal lesions don't have to be treated as emergencies with exception of the locked knee. Equally, in presence of a fresh tear of the anterior cruciate ligament a delay of surgery for eight weeks may be beneficial, be it only to rehab and prepare the knee joint for surgery. Posterior cruciate ligament tears should only be treated by a few centers, since they demand a high degree of experience. The same accounts for the new techniques for the treatment of cartilage lesions like the mosaicplasty or the autologous chondrocyte implantation.

Emergencies↗
PubMed2000

The Burch-Schneider antiprotrusio cage in acetabular revision surgery: a mean follow-up of 12 years.

A total of 38 acetabular revisions using a Burch-Schneider antiprotrusio cage in 37 patients (18 women and 19 men), with a mean age at surgery of 75 years (range, 55-88 years), were evaluated retrospectively with a mean follow-up of 12 years (range, 8-21 years). In 2 cases with total hip dislocation and in 1 case with a deep infection, revision of the antiprotrusio cages was required. Defining every revision of the antiprotrusio cage as the endpoint of survivorship, the antiprotrusio cage showed a survival rate of 92% after 21 years. Clinical evaluation of the surviving patients showed a mean Harris hip score of 76 points (range, 20-96). Radiologic evaluation revealed that 1 antiprotrusio cage was loose and that 4 femoral stems were loose. The Burch-Schneider antiprotrusio cage compares favorably with other devices with regard to long-term implant survival rate.

Aged↗
PubMed1999

Knee joint simulator: an anatomical reconstruction of the joint surfaces and of the ligamentous structures of the knee joint for teaching purposes.

A knee joint simulator with anatomical reconstruction of the joint surfaces and of the ligamentous structures was built for teaching purposes. With this simulator it is possible to demonstrate the anatomy, physiology and kinematics of knee ligaments, to teach and learn how to conduct ligamentous instability tests and to demonstrate the effect of knee ligament reconstructive surgery.

Education, Medical↗