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Biomedical subjects

R Verdonk

Publications and source records attributed to R Verdonk.

At least 55 records · Page 3Linked to original sources
PubMed2000

Anterograde femoral nailing with a reamed interlocking titanium alloy nail.

Intramedullary nailing has become the gold standard for treatment of femoral diaphyseal fractures. Between March 1995 and December 1998 we performed 40 intramedullary nailings using the ACE femoral nail (De Puy). The patients were followed for an average of 27.9 months (range: 6-54 months). The mean age was 33.2 years (range: 17-87 years); the sex distribution was 33 males and 7 females. All fractures were unilateral (right 18, left 22). Most of the fractures were caused by traffic accidents (35), the others originated from sports, work and gunshot (1). Thirty-five fractures were closed and 5 were open: 1 was grade I, 2 were grade II and 2 grade IIIa according to Gustilo's classification. According to the AO classification 18 fractures were type A, 13 type B and 9 type C. The majority of patients had associated injuries: neurotrauma 2, chest trauma 2, and other fractures e.g. of the clavicula, lumbar spine, patella, tibia. Immediate surgery was performed in 34 cases, delayed surgery in 6 cases. All fractures were treated on a fracture table, with closed reduction, reaming of the intramedullary canal, proximal and distal locking and intraoperative control of rotation and length. The mean time to healing was 17.85 weeks (range: 18-50 weeks). The following complications were observed: 3 delayed unions, which united after dynamisation, one malunion, which required corrective osteotomy, and one nonunion, which healed after exchange nailing. We encountered no rotational deformity and no clinically relevant shortening. Six nails were removed due to irritation by locking screws. These results are comparable with those of larger series in the literature with other types of interlocking nails. The union rate in this series was 97.5%.

Adolescent↗
PubMed1999

Jumper's knee: postoperative assessment. A retrospective clinical study.

Jumper's knee or infrapatellar insertional tendinopathy is a condition primarily found in athletes between 18 and 25 years of age who are engaged in explosive running and jumping sports. It is caused by microtears or partial macrotears through the patellar tendon. Conservative treatment is used as the primary approach. If conservative measures are insufficient or fail to relieve the symptoms, surgery is indicated. The patellar tendon is incised and the hyaline inflammatory tissue is removed. Twenty-six patients have been studied retrospectively, with specific attention to postoperative resumption of sports and residual subjective and objective findings. They all completed a detailed questionnaire and subsequently underwent a physical and ultrasound examination.

Adult↗
PubMed1999

Long-term results of tendon allografts for anterior cruciate ligament replacement in revision surgery and in cases of combined complex injuries.

We assessed the long-term validity of anterior cruciate ligament (ACL) reconstruction using tendon allografts. Nineteen patients were followed up for 8 years (mean 94 months) after tendon allograft replacement for ACL rupture. The evaluation used the International Knee Documentation Committee (IKDC) grades, the Lysholm score, and the Tegner scale. Two patients sustained a rerupture after a serious injury. Two others scored poorly because of associated proximal ipsilateral tibial and other fractures (IKDC grade D). Nine patients scored nearly normal (grade B) and six abnormal (grade C). The Lysholm score showed nine excellent (average 98), five good (average 87), and one fair result (70). Two of the excellent-rated patients were IKDC grade C solely because the X-rays showed a slight (1-mm) narrowing of the medial cartilage. One patient had 0.5-mm narrowing. The X-ray findings may indeed indicate future problems. On the Tegner scale the sports level decreased by an average of 2.1 points (from 6.87 to 4.73), and by 0.8 point compared to the level at which the patient had wished to perform. ACL repair using tendon allografts appears to provide satisfactory results on the Lysholm and Tegner scales. The IKDC scoring suggests future cartilage degeneration. Its value for knees with multiple ligament lesions and for revision cases is demonstrated. Only two reruptures were noted, suggesting good reliability of allografts on the long term.

Adult↗
PubMed1999

Function of the normal meniscus and consequences of meniscal resection.

The principal functions of the meniscus are load transmission and shock absorption, based on the meniscal collagen architecture, the biochemical fluid composition, and the proteoglucan-collagen meshwork. The mobile menisci transmit 50-90% of load over the knee joint, depending on knee flexion angle, femoral translation and rotation. The meniscus contributes to knee joint proprioception and probably also to joint stability. Late consequences of total and partial meniscectomy are radiographic osteoarthritis, with a varying percentage of these patients having symptoms. Malalignment, concomitant articular cartilage lesions, and ligament instability are absolute risk factors, while age, lateral compartment, and continued sport activity are relative risk factors. Acute reinsertion of meniscal tears in the red-red or red-white zones can be performed successfully by arthroscopic technique. Also in chronic tears stable healing can be expected in most cases, if the scar tissue is resected.

Animals↗
PubMed1999

Meniscal substitutes--animal experience.

Animal studies have shown that meniscus allografts and tendon autografts generally heal to the capsule, are revascularized and repopulated with host cells. In animals, neither meniscal allografts nor tendon or fat autografts gain the properties of a normal meniscus. Meniscus allografts and tendon autografts are promising as both seem to offer some protection to the cartilage of the tibial plateau. There is no evidence that meniscal transplantation can prevent cartilage degenerative changes, and the long-term effect of meniscal transplantation on articular cartilage remains unknown. Whether cellular repopulation of the meniscal allograft is sufficient to restore its biomechanical properties is unknown. Collagen scaffolds and tissue engineered grafts are still under investigation, showing promising results especially for the former. Viable meniscal allografts should be implanted within 1 to 2 weeks after harvesting, as the production of proteoglycans decreases after 2 weeks.

Animals↗
PubMed1999

Meniscal substitutes--human experience.

A number of clinical series have described the effect of meniscus allograft replacement in humans. The general indication has been disabling pain following loss of a meniscus in a skeletally mature individual. Overall, healing of the graft to the capsule occurs in up to 80% of all transplants. Revascularization and cell repopulation is found in all grafts but is highly variable. The risk for graft failure seems to be greater with irradiated grafts and in patients with grade III or IV osteoarthritic changes. In most series, patients experienced a decrease in pain and an increase in activity level postoperatively. In many series, concominant surgery (cruciate ligament reconstruction or osteotomy) had been performed. Meniscus replacement with frozen or cryopreserved allografts seems to give the most promising short-term results in patients with post-meniscectomy pain. Controlled, randomized prospective studies are needed to confirm a long-term benefit and better define transplantation indications. Viable meniscus allografts seem to survive transplantation, as donor cells were found in the graft after 2 years. Clinically, pain was reduced and activity increased following transplantation, but after 4 years some of these gains were lost. There was no correlation between postoperative findings on MRI and clinical outcome. Meniscal replacement with a quadriceps tendon autograft in humans resulted in pain reduction, but at second-look arthroscopy, only 2 of 9 tendon autografts looked like a meniscus. Six were in position but still looked like tendons. Total medial meniscus replacement by quadriceps tendon autrograft is still an experimental procedure. There is no proof at present that meniscal substitutes (meniscus allografts or tendon autografts) in humans can protect the hyaline cartilage of the knee from the degeneration, following loss of a meniscus. There is some evidence in animal experiments that under circumstances not yet exactly known, a meniscus substitute can have a protective effect on articular cartilage. Three factors have been identified that prevent proper meniscal function: poor fixation of the meniscal horns, no contact of the graft with the articulating surfaces under load and incorrect positioning of the horns. Meniscal allograft transplantation sensitizes humoral and cell mediated immune systems. Bone plugs attached to meniscal allograft tissue may increase cell surface antigenicity. Deep freezing and especially freeze drying of meniscal tissue decreases host immunogenicity. Cryopreservation maintains the content of donor HLA encoded antigens and is likely more sensitizing to the host. The clinical importance of immune responses to meniscal allografts is not known, but it has not been shown to result in graft failure or rejection. Prospective studies are needed.

Antibody Formation↗
PubMed1999

Harvest and conservation of meniscal allografts.

Meniscal allografts can be harvested and preserved in different ways. A technique for harvesting and conserving viable allografts is described. The meniscus should be harvested within 12 h after the start of ischaemia. The ideal time for implantation of the viable graft is 10 to 14 days after harvest, in which time a recipient should be identified. Frozen grafts are avital. Cryopreserved grafts are not avital, as 10-30% of the fibrochondrocytes are preserved. Frozen and cryopreserved grafts can be stored for a long time and if a graft bank is established, grafts are always readily available. There is no proven advantage of one graft type over others.

Cryopreservation↗
PubMed1999

Meniscus transplantation: preoperative planning.

Precise preoperative planning is mandatory to obtain good results of meniscus transplantation. Any pathology in addition to the missing meniscus should be detected, including malalignment, and ligament instability. A full status of the changes in the cartilage should be made. It is unknown how precisely the donor meniscus needs to fit the size of the original meniscus to allow healing and regeneration. The effect of incongruency and wrong insertion of the meniscal horns has been investigated in an animal experiment. The incongruous grafts did not entirely avoid chondromalacia after meniscectomy, but provided some chondroprotective effect. A wrong bony insertion of the meniscal horns leads to even more serious chondral damage than meniscectomy.

Animals↗
PubMed1999

Arthroscopic and open surgical techniques for meniscus replacement--meniscal allograft transplantation and tendon autograft transplantation.

Open, arthroscopically assisted and arthroscopic methods for lateral and medial meniscus allograft transplantation with bone plug fixation are described. An open technique for medial and lateral meniscus transplantation without bone plug fixation, as well as an open technique for autograft quadriceps tendon replacement of the medial meniscus are described.

Arthroscopy↗
PubMed1999

Postoperative follow-up and rehabilitation after meniscus replacement.

Even though basic scientific knowledge about the meniscal loading pattern may advocate restrictive rehabilitation after meniscus repair, experience and one controlled study favour accelerated rehabilitation. The current protocols for rehabilitation after meniscal substitution follow personal experience with parameters such as pain, effusion, locking, and gait pattern used as clinical guidance. Controlled clinical studies on rehabilitation should be encouraged. An example of a rehabilitation protocol is given. As meniscus replacement is a new treatment option, it is essential to document details about the graft, the knee status at operation and the surgical procedure. The goal of a postoperative follow-up is to control quality, to measure patient satisfaction and to show whether meniscus replacement is beneficial in relation to the natural history of meniscectomy cases. There is a need for a standard follow-up evaluation of patients after meniscus replacement, and the development of a meniscus transplantation score including subjective and objective data is suggested.

Humans↗
PubMed1999

Future research in meniscal replacement.

To study the remodelling process after meniscus replacement and to learn how to control it will be a key topic for future research. Not enough is known about the importance of precision in meniscal fixation and how to make the insertions as strong as in the normal meniscus. Methods to measure load-distribution, mechanical properties of the graft and status of the cartilage should be developed. A number of different auto- and allografts have been shown to heal and revascularize, but whether the grafts are functioning is not known. Meniscal scaffolds, which can be used for replacement of partial meniscal loss, need to be tested. Scaffolds and tissue engineering will be the subject of intensive research in the future.

Cryopreservation↗
PubMed1997

Current status and imaging of allograft meniscal transplantation.

The authors present an overview of the current indications, techniques, results and complications of allograft meniscal transplantation. The radiologist's role in pre- and postoperative imaging is described. The spectrum of magnetic resonance imaging findings of meniscal allografts are illustrated.

Arthroplasty↗
PubMed1996

Human meniscal proteoglycan metabolism in long-term tissue culture.

For the purpose of human meniscal allografting, menisci have been maintained viable in in vitro culture. The influence of long-term tissue culture on the extracellular matrix metabolism of the meniscus has been studied. Fetal calf serum (FCS) was used as a supplement for the growth factors necessary to maintain optimal meniscal cell metabolism. A series of semilunar cartilage samples was cultured under serum-free conditions since foreign proteins could be responsible for immunological problems after eventual allografting. The proteoglycan metabolism in human menisci cultured in FCS-supplemented and in serum-free culture media was compared. To rule out any influence of topographical variations in glycosaminoglycan (GAG) content on proteoglycan (PG) metabolism, GAG concentrations within the tissue were determined, and sulphate (35S) incorporation was studied in tissue samples with a comparable biochemical composition. Sulphate incorporation was preserved when 20% FCS was added to the nutrient medium. The meniscal tissue fibroblasts continued to produce 35S-PG during 4 weeks of culture. The PG molecules were shown to consist of PG-aggregates, monomers and a low molecular-weight PG population. Newly synthesized GAG consisted of approximately 55% chondroitin 4- and 6-sulphate and 33% dermatan sulphate. In the presence of serum, 35S incorporation in PG and in the PG-aggregate fraction significantly increased during the first 2 weeks and then decreased during the following 2 weeks of in vitro culture. Newly synthesized PG-aggregates were almost entirely accumulated in the tissue during these weeks. In the 3rd week the values for this parameter decreased slightly. 35S-PG synthesis dramatically declined after 4 weeks of in vitro culture. Catabolism probably resulted in increased proportions of 35S-PG in the incubation media. In the absence of serum, 35S-PG production also increased in the 2nd week of culture. However, 35S activity was almost exclusively found in small PG, and this material apparently diffused to the incubation media. Consequently, catabolism is higher, and the immobilization of 35S-PG is poor when FCS is not added to the culture media. Our findings suggest that menisci are maintained in viable condition and may serve for allografting at least during 2 weeks of tissue culture.

Adult↗
PubMed1996

Intramedullary fixation of forearm fractures in adults.

The authors present a retrospective study of acute fractures of the diaphysis of the radius or ulna, or both, in adults treated by intramedullary nailing. Seventy diaphyseal fractures in 38 patients (30 men and 8 women) were treated by intramedullary fixation. The mean age of the patients was 31.5 years. Union occurred in 66 fractures (94%). The average union-time was 73 days. Compared with the results published by other authors, using the same evaluation criteria, union-time with the intramedullary technique was shorter than with other techniques. Union-rates and functional results were similar to those in comparable studies. Closed nailing does have many advantages, including early union, low incidence of infection, small scars, less blood loss, and short operating time with minimal surgical trauma.

Adolescent↗
PubMed1995

Phase I and pharmacokinetic study of KW-2149 given by 24 hours continuous infusion.

KW-2149 is a new mitomycin C (MMC) analog, forming DNA-DNA and DNA-protein crosslinking 20-fold more effectively than MMC. Because of its equal or superior in vitro and in vivo activity compared to MMC, a phase I study was initiated with an intravenous bolus injection every three weeks. This study was interrupted after dose escalation from 5 mg/m2 to 100 mg/m2 because of subacute and dose dependent pulmonary toxicity. Because of the lack of other end-organ toxicity, the moderate hematological toxicity and the observed antitumor effect, a second phase I study was initiated with a 24 hour continuous infusion. The starting dose was 50 mg/m2 and further escalation depended on observed pulmonary toxicity. Four patients were entered into this study and the received in total 17 courses. Toxicity was again mainly restricted to the lungs with one patient suffering grade 2 dyspnoe and another one grade 1 dyspnoe. Three patients had a substantial change in the carbon monoxide (CO) diffusion capacity. Pharmacokinetic data from these patients showed very low plasma levels both for KW-2149, as for both known metabolites M-16 and M-18. This study demonstrates that pulmonary toxicity continues to occur with KW-2149, in spite of the assurance of low plasma levels of both the parent compound and the known metabolites. The interesting activity of this compound has stimulated further in-depth research towards mechanisms of pulmonary toxicity and means of preventing them.

Antineoplastic Agents↗