Biomedical subjects

Henrik Lauge-Pedersen

Publications and source records attributed to Henrik Lauge-Pedersen.

9 recordsLinked to original sources

PubMed2006

6 Weeks with the von Rosen splint is sufficient for treatment of neonatal hip instability.

BACKGROUND: There is no concensus on the optimal treatment time for unstable hips in the newborn. We analyzed the efficiency of a treatment program that has been used for 10 years at our hospital, in which all unstable hips (subluxatable, Barlow-positive and Ortolani-positive) are treated with the von Rosen splint for 6 weeks. PATIENTS AND METHODS: Between 1988 and 1997, 32,171 children were born alive at the hospital. During this period 247 children had a clinically unstable hip diagnosed. 223 of the 247 children underwent a radiographic follow-up after 5-15 years. RESULTS: 1 patient with bilateral instability and treated with a splint for 6 weeks showed a dislocated left hip at the radiographic examination at 8 months, which is part of the screening program, and needed operative treatment. 1 patient did not follow the treatment program and showed a dislocated hip at the age of 3. Another 4 patients required more treatment than the 6 weeks with the splint. We found no dysplastic hips at the radiographic follow-up. There was no late dysplasia and there were no late dislocations in children born in Lund between 1988 and 1997 who were diagnosed at other Swedish centers that treat developmental dysplasia of the hip (DDH). INTERPRETATION: We conclude that the present screening and 6-week treatment in a von Rosen splint prevent almost all cases of late dysplasia and late dislocation of the hip.

Adolescent↗

PubMed2006

Windswept hip deformity in children with cerebral palsy.

Windswept hip deformity describes an abduction and external rotation position of one hip with the opposite hip in adduction and internal rotation. Windswept hip deformity may occur in association with hip dislocation and scoliosis. We analysed the prevalence of this deformity in a total population of children with cerebral palsy, and the impact of hip prevention and early treatment of contractures on the prevalence and severity of windswept hip deformity. The frequency of windswept hip deformity was 12% in the control group and 7% in the study group, comprising children in the hip prevention programme. The children with this deformity in the study group had a lower frequency of scoliosis and none had hip dislocation. It thus seems that the hip prevention programme results in a decrease in the number of children with windswept hip deformity, and a decrease in the severity of the deformity.

Adolescent↗

PubMed2005

Prevention of severe contractures might replace multilevel surgery in cerebral palsy: results of a population-based health care programme and new techniques to reduce spasticity.

During the 1990s three new techniques to reduce spasticity and dystonia in children with cerebral palsy (CP) were introduced in southern Sweden: selective dorsal rhizotomy, continuous intrathecal baclofen infusion and botulinum toxin treatment. In 1994 a CP register and a health care programme, aimed to prevent hip dislocation and severe contractures, were initiated in the area. The total population of children with CP born 1990-1991, 1992-1993 and 1994-1995 was evaluated and compared at 8 years of age. In non-ambulant children the passive range of motion in hip, knee and ankle improved significantly from the first to the later age groups. Ambulant children had similar range of motion in the three age groups, with almost no severe contractures. The proportion of children treated with orthopaedic surgery for contracture or skeletal torsion deformity decreased from 40 to 15% (P = 0.0019). One-fifth of the children with spastic diplegia had been treated with selective dorsal rhizotomy. One-third of the children born 1994-1995 had been treated with botulinum toxin before 8 years of age. With early treatment of spasticity, early non-operative treatment of contracture and prevention of hip dislocation, the need for orthopaedic surgery for contracture or torsion deformity is reduced, and the need for multilevel procedures seems to be eliminated.

Anti-Dyskinesia Agents↗

PubMed2004

Initial stability of ankle arthrodesis with three-screw fixation. A finite element analysis.

OBJECTIVE: Compare the initial stability at the fusion site of ankle arthrodesis fixed with two and three screws. DESIGN: Finite element models of ankle arthrodesis were developed from computed tomography images. Two-screw constructs were augmented with a third screw in different orientations and subjected to loads likely to affect the ankle postoperatively. BACKGROUND: More stable fixation seems to increase the chance of fusion, as it minimises the motion between the tibiotalar interfaces. METHODS: Non-linear elastic finite element analyses were performed in external torsion and dorsiflexion. The micromotions at the tibiotalar interface were computed to compare the two- and three-screw fixation in intact and flat-cut arthrodesis. RESULTS: Adding a third screw reduced the micromotions at the fusion site. Inserting the third screw anteriorly predicted lower peak micromotions than inserting the screw posteriorly, except for the intact arthrodesis tested in dorsiflexion. Three-screw intact arthrodesis predicted lower peak micromotions than flat-cut arthrodesis. CONCLUSIONS: Better stability was predicted for three-screw ankle arthrodesis. In flat-cut arthrodesis, a third screw inserted anteriorly performed better than a posterior screw. In intact arthrodesis, a posterior screw seemed a better option when flexion stability was the main concern. Even with three-screw fixation, the configuration of the first two-crossed screws may still be important to improve the stability at the fusion site.

Ankle Joint↗

PubMed2004

The effect of bone quality on the stability of ankle arthrodesis. A finite element study.

BACKGROUND: Despite uniform operating techniques, lack of fusion still occurs after ankle arthrodesis. Differences in the biological healing potential may be a factor but the mechanical performance of the arthrodesis construct because of varying bone quality also may be important. Internal compression techniques are preferred because of higher union rates, shorter fusion times, and fewer complications. A three-screw configuration has been shown to be more stable than a two-screw configuration, but it is not obvious when it should be used. METHODS: Three-dimensional finite element models of intact and flat-cut ankle arthrodeses were built, using two and three screws in different configurations. Poor bone quality was simulated by decreasing Young's modulus of the bone. The constructs were loaded in torsion and dorsiflexion, and micromotions at the fusion site were measured. RESULTS: Bone quality had a marked effect on the stability at the arthrodesis site. Inserting two screws at 30 degrees relative to the longitudinal axis of the tibia in an intact arthrodesis seemed the best option, especially as bone quality worsened. The addition of a third screw increased the stability at the arthrodesis site. CONCLUSIONS: Overall, intact joint surfaces and three-screw fixation, with the lateral and medial screws inserted produced the most stable arthrodesis constructs when bone quality was poor. CLINICAL RELEVANCE. Ankle arthrodeses are technically demanding because of the shape and small size of the talus. Preoperative planning is an absolute necessity to determine placement and number of screws. This study shows that poor bone quality decreases the stability of the arthrodesis constructs, suggesting that an attempt should be made to create the most stable three-screw configuration. Finite element models can be used as an effective preoperative tool for planning screw number and placement.

Ankle Joint↗

PubMed2003

Synovial fluid depletion: successful arthrodesis without operative cartilage removal.

Operative arthrodesis has been thought to require surgical removal of remaining joint cartilage, but we have found in rabbits that even a joint with intact cartilage can fuse if rigidly fixed. This may enable new percutaneous techniques for arthrodesis. Rigid adaptation of the joint surfaces deprives the cartilage of mechanical stimulation and depletes the cells of synovial fluid transport of oxygen and nutrition. To better understand the requirements for successful arthrodesis, we studied the histological consequences of the complete absence of mechanical stimulation alone or in combination with synovial depletion by placing a metal cap over part of the joint cartilage in rabbits. The cap was either closed or had an opening to permit synovial fluid to reach the cartilage. We also studied if penetration of the bone-cartilage junction by a drill hole would facilitate cartilage resorption. Synovial fluid depletion in combination with a drill hole through the bone-cartilage junction led to disappearance of all cartilage matrix after 7 weeks. Synovial fluid depletion with an intact bone-cartilage junction led to complete disappearance of the cartilage matrix in four of seven rabbits after 7 weeks. With a hole in the cap for synovial fluid, the cartilage matrix was still present to varying degrees after 7 weeks in all the rabbits. In conclusion, percutaneous arthrodesis by rigid adaptation may lead to cartilage disappearance due to synovial depletion rather than due to the absence of mechanical stimulation. A combination with perforation of the bone-cartilage junction appears to lead to reasonably quick removal of the cartilage matrix.

Animals↗

PubMed2003

Finite element analysis of the initial stability of ankle arthrodesis with internal fixation: flat cut versus intact joint contours.

OBJECTIVE: Qualitative comparison of the initial stability provided by two joint preparation techniques and various screw configurations in ankle arthrodesis, using the finite element method.Design. A three-dimensional model of a healthy ankle was developed from computed tomography images. Two groups of models were built, one with the joint contours resected to produce flat surfaces, and the second with the joint contours preserved. In each case, a variety of screw orientations were examined. BACKGROUND: Despite the improved results of ankle arthrodesis, failure rates due to non-union are still reported. The initial stability of the arthrodesis construct seems important in the final outcome of the fusion. METHODS: Non-linear contact finite element analyses were performed in the arthrodesis constructs subjected to internal/external torsion and dorsiflexion. Micromotions at the bone-to-bone interface were calculated for frictionless and Coulomb friction contact, and compared for the two joint preparation techniques and screw configurations. RESULTS: Overall lower peak micromotions were predicted when preserving the joint contours both in torsion and dorsiflexion. For both preparation techniques, the lowest micromotions tended to occur with the screws inserted at 30 degrees with respect to the long axis of the tibia, crossing above the fusion site. Inclusion of friction in the models caused a general decrease on the magnitude of the micromotions as compared to the frictionless case, but did not affect the ranking of the models. CONCLUSIONS: The finite element method can be used as a qualitative tool to study the initial stability of ankle arthrodesis, overcoming the difficulties of measuring bone-to-bone interface micromotions experimentally. Better initial stability was predicted for ankle arthrodesis when the joint contours were preserved rather than resected. Crossing the screws above the fusion site at a steeper angle also tended to increase the stability at the fusion site. RELEVANCE: Finite element analyses can help during the pre-operative planning of ankle arthrodesis. When bone density is not compromised, preserving the joint contour and inserting the screws at less than 45 degrees to the long axis of the tibia, crossing over the arthrodesis site, may offer better initial stability.

Ankle Joint↗

PubMed2003

Percutaneous arthrodesis.

It has been generally accepted that residual cartilage and subchondral bone has to be removed in order to get bony fusion in arthrodeses. In 1998 we reported successful fusion of 11 rheumatoid ankles, all treated with percutaneous fixation only. In at least one of these ankle joint there was cartilage left. This was confirmed by arthrotomy in order to remove an osteophyte, which hindered dorsiflexion. More than 25 rheumatoid patients with functional alignment in the ankle joint have subsequently been operated on with the percutaneous technique, and so far we have had only one failure. Patients with rheumatoid arthritis are known to sometimes fuse at least their subtalar joints spontaneously, and the destructive effect of the synovitis on the cartilage could contribute to fusion when using the percutaneous technique. In a rabbit study we therefore tested the hypothesis that even a normal joint can fuse merely by percutaneous fixation. The patella was fixated to the femur with lag screw technique without removal of cartilage, and in 5 of 6 arthrodeses with stable fixation bony fusion followed. Depletion of synovial fluid seemed to be the mechanism behind cartilage disappearance. The stability of the fixation achieved at arthrodesis surgery is an important factor in determining success or failure. Dowel arthrodesis without additional fixation proved to be deleterious. A good fit of the bone surfaces appears necessary. In the ankle joint, it would be technically demanding to retain the arch-shaped geometry of the joint after resection of the cartilage. Normally the joint surfaces are resected to produce flat osteotomy surfaces that are thus easier to fit together, encouraging healing to occur. On the other hand it is considered an advantage to preserve as much subchondral bone as possible, as the strong subchondral bone plate can contribute to the stability of the arthrodesis. Ankle arthrodesis can be successfully performed in patients with rheumatoid arthritis by percutaneous screw fixation without resection of the joint surfaces. This procedure has two advantages: first, it is less surgically traumatic, second, both the arch-shaped geometry and the subchondral bone are preserved, and thus both could contribute to the postoperative stability of the construct. Intuitively, preservation of the arch-shape should increase rotational stability. The results of our experimental sawbone study indicate that the arch shape and the subchondral bone should be preserved when ankle arthrodesis is performed. The importance of this is likely to increase in weak rheumatoid bone. In a finite element study the initial stability provided by two different methods of joint preparation and different screw configurations in ankle arthrodesis, was compared. Better initial stability is predicted for ankle arthrodesis when joint contours are preserved rather than resected. Overall, inserting the two screws at a 30-degree angle with respect to the long axis of the tibia and crossing them above the fusion site improved stability for both joint preparation techniques. The question rose as to whether patients with osteoarthritis could also be operated on solely by percutaneous fixation technique. The first metatarsophalangeal joint in patients with hallux rigidus was chosen as an appropriate joint to test the percutaneous technique. In this small series we have shown that it is possible to achieve bony fusion with a percutaneous technique in an osteoarthrotic joint in humans, but failed to say anything about the fusion rate.

Aged↗

PubMed2002

Arthrodesis by percutaneous fixation: patellofemoral arthrodesis in rabbits without debridement of the joint.

Arthrodesis is usually performed with joint resection or at least with removal of cartilage. Our recent experience with successful fusion in all 11 rheumatoid ankles treated only with percutaneous fixation questions the necessity of debridement of the joint before arthrodesis. In this rabbit study we tested the hypothesis that joints fuse because of rigid fixation. 9 skeletally mature loop-ear dwarf female rabbits were operated on. With the knee in about 45 degrees of flexion, two 1.5 mm cortical screws were inserted through the patellofemoral joint in an anterior-posterior direction with the lag screw technique. 3 rabbits were excluded due to technical problems. Of the remaining 6 rabbits, 5 underwent bony fusion and 1 fibrous healing. Fusion was confirmed with Micro-CT in 2 cases and by histological examination in all 5 cases. In those 5 cases, bony fusion was seen in almost all areas with close contact. Therefore, fusion occurred not only in relation to the screws, but also between the screws and in the periphery of the patella. Our findings show that bony fusion can occur in a healthy joint without joint resection or debridement.

Animals↗