Christof Meyer

Bone ingrowth in bFGF-coated hydroxyapatite ceramic implants.

This experimental study was performed to evaluate angiogenesis, bone formation, and bone ingrowth in response to osteoinductive implants of bovine-derived hydroxyapatite (HA) ceramics either uncoated or coated with basic fibroblast growth factor (bFGF) in miniature pigs. A cylindrical bone defect was created in both femur condyles of 24 miniature pigs using a saline coated trephine. Sixteen of the 48 defects were filled with HA cylinders coated with 50 microg rhbFG, uncoated HA cylinders, and with autogenous transplants, respectively. Fluorochrome labelled histological analysis, histomorphometry, and scanning electron microscopy were performed to study angiogenesis, bone formation and bone ingrowth. Complete bone ingrowth into bFGF-coated HA implants and autografts was seen after 34 days compared to 80 days in the uncoated HA group. Active ring-shaped areas of fluorochrome labelled bone deposition with dynamic bone remodelling were found in all cylinders. New vessels could be found in all cylinders. Histomorphometric analysis showed no difference in bone ingrowth over time between autogenous transplants and bFGF-coated HA implants. The current experimental study revealed comparable results of bFGF-coated HA implants and autogenous grafts regarding angiogenesis, bone synthesis and bone ingrowth.

Treatment of periprosthetic femoral fractures by effective lengthening of the prosthesis.

The increasing number of hip and knee arthroplasties implies a greater likelihood of periprosthetic fractures and need for successful treatment options. We asked whether in situ effective lengthening of the indwelling prosthesis by a custom-made slotted hollow intramedullary nail provided a reasonable alternative to the established internal fixation techniques and prosthesis exchange. Between 1994 and 2005, we treated 25 patients (four male and 21 female; average age, 80 years) with a hip or knee periprosthetic fracture using this technique. Preconditions included a well-fixed prosthesis with a conical tip. In 23 hip cases a retrograde femur nail and in two knee fracture cases an antegrade nail were used for in situ lengthening of a femoral hip or knee implant stem. In all 25 cases, we used a preoperatively manufactured custom-made implant; in 20 patients, we recommended immediate mobilization by partial or full weightbearing. Eighteen of 25 patients were followed a minimum of 7 months (mean, 25 months; range, 7-31 months). Three patients died and four were lost to followup. We observed fracture healing in all patients, but one female patient had subsequent prosthesis loosening. The major complication rate was 6% (one of 18). We believe effective lengthening of the indwelling prosthesis by a custom-made slotted hollow intramedullary nail is a reasonable option for treating periprosthetic femoral fractures.Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Elastic stable intramedullary nailing in pediatric femur and lower leg shaft fractures: intraoperative radiation load.

Background: Elastic stable intramedullary nailing (ESIN) is currently the therapy of choice in unstable, transverse and short oblique femoral and tibial-fibular shaft fractures in childhood and adolescence. As with every intramedullary technique, it requires a greater intraoperative reliance on radiological imaging. Literature concerning intraoperative radiation load in ESIN is rare, results having a wide range from less than 1 minute to more than 15 minutes. Methods: We performed a retrospective analysis of 53 femoral and 24 tibial shaft fractures. In addition, image intensifier times of several steps of the operative procedure in 10 femoral shaft fractures were evaluated prospectively. Results: The average radiation time in femoral fractures was 70.3 (range, 12-193) seconds, in tibial shaft fractures, 42.4 (range, 16-108) seconds. The prospective analysis of femur shaft fractures was able to show the most intense use of imaging during fracture passage (43.2%) and placement of the nail tips (26.6%). Image intensifier times in educational operations were not significantly higher than in operations performed by experienced surgeons. Conclusions: The actual intraoperative radiation load is influenced by bone mass and soft tissue coverage. Surgeons are able to reduce it only by decreasing the fluoroscopy time. According to our results, image intensifier time should not exceed 3 minutes in ESIN of femoral shaft fractures and 2 minutes in ESIN of lower-leg fractures. Low intraoperative radiation times are a mark of quality with respect to the interests of patients, surgeons, and operation theater staff.

Comparison of new bone formation, implant integration, and biocompatibility between RGD-hydroxyapatite and pure hydroxyapatite coating for cementless joint prostheses—An experimental study in rabbits

This is the first work to report on additional Arginin-Glycin-Aspartat (RGD) coating on precoated hydroxyapatite (HA) surfaces regarding new bone formation, implant bone contact, and biocompatibility compared to pure HA coating and uncoated stainless K-wires. There were 39 rabbits in total with 6 animals for the RGD-HA and HA group for the 4 week time period and 9 animals for each of the 3 implant groups for the 12 week observation. A 2.0 K-wire either with RGD-HA or with pure HA coating or uncoated was placed into the intramedullary canal of the tibia. After 4 and 12 weeks, the tibiae were harvested and three different areas of the tibia were assessed for quantitative and qualitative histology for new bone formation, direct implant bone contact, and formation of multinucleated giant cells. Both RGD-HA and pure HA coating showed statistically higher new bone formation and implant bone contact after 12 weeks than the uncoated K-wire. There were no significant differences between the RGD-HA and the pure HA coating in new bone formation and direct implant bone contact after 4 and 12 weeks. The number of multinucleated giant did not differ significantly between the RGD-HA and HA group after both time points. Overall, no significant effects of an additional RGD coating on HA surfaces were detected in this model after 12 weeks.

Enhancement of bone formation in hydroxyapatite implants by rhBMP-2 coating

The combination of hydroxyapatite (HA) implants serving as osteoconductive scaffold with growth factors is an interesting approach for the improvement of bone defect healing. The purpose of this study was to test whether recombinant human bone morphogenetic protein-2 (rhBMP-2) coating of solid HA-implants improves bone formation in a cortical bone defect. Cylindrical trephine mill defects (diameter: 9.8 mm, depth: 10 mm) were created into the cortical tibia shaft of minipigs and subsequently filled either by plain HA cylinders (Endobon) or by rhBMP-2-coated HA cylinders. Fluorochrome labeling for the evaluation of time-dependent bone formation was done on days 8, 9, and 10 postsurgery with tetracyclin-100, at days 25 and 30 with alizarin-komplexon, and finally on days 32, 37, 73, and 79 with calcein green. Twelve weeks after implantation, the tibiae were harvested and were prepared for standard histological staining, fluorochrome analysis, and histomorphometry. Coating of HA implants with rhBMP-2 led to significant enhanced new bone formation of 84.7% (+/-4.6%) of the implant area with almost complete bony incorporation compared with only 27.7% (+/-8.5%) in the uncoated HA implants (p = 0.028). In both types of implants, osteoconduction of HA led to bone ingrowth of the surrounding host bone into the implants. However, only rhBMP-2-coated implants showed multitopic de novo bone formation reflecting the osteoinductive properties of rhBMP-2 in all areas of the HA implant. This study showed that the coating of HA ceramic implants with rhBMP-2 can significantly enhance new bone formation attributable to its osteoinductive effects.

Frequency and Effects of Intratendinous and Peritendinous Calcifications after Open Achilles Tendon Repair

Background: Although calcification of the Achilles tendon has been described by several authors, a detailed evaluation of its frequency and effects on clinical outcome has not been reported. The purposes of this work were to determine the frequency of calcifications in the Achilles tendon after open repair and their effects on clinical outcomes and to identify possible risk factors for postoperative calcification. Methods: Thirty-six patients with open Achilles tendon repair were evaluated at an average followup of 19 months. Evaluation included a self-assessment questionnaire concerning treatment outcomes, clinical examination, and radiographic and ultrasonographic examinations. Results: No patient had calcifications in the Achilles tendon area before surgery. Postoperatively, intratendinous or peritendinous calcifications, ranging in size from 3 mm to 37 mm, were found in 10 (28%) of the 36 patients. The development of calcifications was associated with chronic swelling, decreased range of motion of the ankle joint, and increase pain, especially with calcifications larger than 10 mm. No association was found between the development of calcifications and the surgical technique, suture materials, time from injury to surgery, or postoperative management, and no risk factors could be identified. Conclusions: Calcifications of the Achilles tendon appear to be frequent after open tendon repair and to have a negative effect on clinical outcome.

Reconstruction of the lower leg with the sural artery flap.

Abstract Background. Soft tissue covering on the lower leg is frequently a difficult challenge and causes increasing problems for treatment in smaller hospitals. We introduce a plastic surgery method for covering these soft tissue defects. Method. An island of skin, centered above the sural nerve, is cut out in the middle dorsal area of the lower leg. The subcutaneous vascular pedicle is prepared along the nerve. The gained skin flap is rotated into the defect site and fixed without tension. The wound of the donor-site defect is usually closed primarily, and the flap pedicle is covered with Meshcraft. Results. In 18 of the 21 patients treated by this method the flap healed without functional impairment, one patient experienced a necrosis leading to the loss of the flap. And a partial loss of the skin island was recorded in two cases, complete healing was achieved by means of Meshcraft transplantation. Conclusions. The superficial sural artery flap usually results in a reliable and complete healing of soft tissue defects within the area of the lower legs with justifiable operational expenditures also for elderly patients and those with vascular ailments.

Biomechanische Analysen zur Verbundfestigkeit eines bioresorbierbaren Knochenklebers: experimentelle Untersuchungen am Schafsmodell / Bond strength of a bioresorbable bone adhesive: results of a biomechanical study in a sheep model

Zusammenfassung Ziel dieser Arbeit war die Überprüfung der Verbundfestigkeit eines Knochenklebstoffes, basierend auf einer Ethylenglykol-Oligolactid-Bismethacrylat-Verbindung, in einem Osteotomiesegmentmodell an der Schafsulna durch die 4-Punkt-Biegung. Ergänzende morphologische sowie radiologische Analysen wurden durchgeführt. 36 Merinolandschafe wurden in eine Kleber- und Kontrollgruppe mit jeweils 18 Tieren eingeteilt und einseitig an der Ulna operiert, indem bei jedem Tier an der Ulna des linken Vorderlaufes ein 2 cm langes Segment entfernt und mit/ohne Klebstoff refixiert wurde. Die Beobachtungszeiträume des In-vivo-Versuches waren mit 21, 42 und 84 Tagen festgelegt, an denen jeweils 6 Tiere euthanasiert wurden. Während der mittelfristige Untersuchungszeitraum von 42 Tagen eine nicht signifikant höhere Biegefestigkeit der Kontrollgruppe aufwies, zeigten die kurz- und langfristigen Analysen nach 21 und 84 Tagen eine höhere Biegefestigkeit der Klebergruppe (p=0,25), welche im Langzeitversuch mit 102,83 N/mm2 (Klebergruppe) zu 58,48 N/mm2 (Kontrolle) besonders deutlich wurde. Die histomorphometrischen Untersuchungen der Osteotomiequerschnitte nach 84 Tagen zeigten, dass diese höhere Biegefestigkeit der Klebergruppe (p=0,25) mit einer geringeren Kallusbildung der Kleber- gegenüber der Kontrollgruppe (p=0,04) einher ging. Der dem In-vivo-Versuch angeschlossene In-vitro-Versuch zeigte nach Polymerisationszeiten von 10, 60 und 360 Minuten, nach denen jeweils 3 geklebte Ulnasegmente in der gleichen Versuchsanordnung getestet wurden, einen Anstieg der Biegefestigkeit auf 17,32 N/mm2 nach 360 Minuten (p=0,59). Abstract The purpose of this study was to investigate the bond strength of a new bone adhesive based on ethylene glycol-oligolactide-bismethacrylate on 36 sheep. A 2-cm metaphysial segment was produced on the ulna of each sheep by an oscillating saw and it was not stabilized by any type of additional osteosynthesis. Adhesive was applied to the osteotomy gaps in 18 sheep, the remaining 18 animals served as controls. A total of 6 animals with glue and 6 controls were euthanized after 21, 42 and 84 days. The bond strength after repair of the gaps through bone adhesive compared to a control group was studied by using a four-point bending test. There was a continual increase of bending stiffness from 21 to 84 days in all sheep, with the highest bending stiffness of 102.83 N/mm2 by the glue group after 84 days as opposed to the control group with 58.48 N/mm2 (p=0.25). Morphological investigations showed more callus formation by the control group than the adhesive group after 84 days (p=0.04). In addition, an in vitro gluing of the ulna segment was performed with a four-point bending test after 10, 60 and 360 min polymerization time. The in vitro gluing of the ulna segment showed a continual increase of bending stiffness to 17.32 N/mm2 after 360 min (p=0.59).

[Micro-CT analysis of cancellous bone fragments from the distal radius fracture zone in osteoporosis].

Zusammenfassung Angesichts der zu erwartenden demographischen Entwicklung und der veränderten Lebensbedingungen muss auch künftig mit einer starken Zunahme der Häufigkeit von Osteoporose gerechnet werden. Bei der Diagnose des Schweregrades der Osteoporose kommt der Untersuchung der dreidimensionalen Knochenstruktur die gleiche Bedeutung zu wie der Bestimmung der Knochenmasse oder des Mineralgehalts. Aus den Frakturzonen am distalen Radius wurden bei verunfallten Patienten intraoperativ spongiöse Kleinfragmente entnommen und im Mikro-CT untersucht. Die errechneten 3-dimensionalen Rekonstruktionen zeigten bei den Patienten, bei denen eine Osteoporose durch Osteodensitometrie an der Lendenwirbelsäule nachgewiesen werden konnte, auch eine deutlich verminderte Knochenmasse, -dichte und Trabekeldicke am distalen Radius. Die Trabekelbrüche, die sich in der 2D-Analyse bei den nicht osteoporotischen Patienten auch im Bereich dicker Trabekel fanden, zeigten sich hier regelmäßig im Bereich der dünnsten Stellen und Aufzweigungen. Trotz der teilweise sehr kleinen Fragmente konnten in der Mikro-CT Analyse die Unterschiede in der Histomorphometrie und der Qualität der Trabekelbrüche bei osteoporotischen und nicht osteoporotischen Patienten sehr gut dargestellt werden. Abstract The incidence and prevalence of osteoporosis must be considered to continue to increase significantly due to the expected demographic development and environmental changes. In the diagnosis and staging of osteoporosis the three-dimensional bone structure should be as important as the bone mass or the mineral content of the bone. In this study, microfragments were taken from distal radius fracture zones and investigated in Micro-CT scans. Patients in which osteodensitometry of the lumbal spine had revealed osteoporosis in were found to have significantly reduced bone mass, bone density and trabecular thickness. Trabecular fractures which were found in non-osteoporotic patients even in robust trabeculae were detected by the two-dimensional analysis in thin locations and arborizations. Despite some trabeculae turned out to be very small the differences in the histomorphometry and the quality of trabecular fractures in osteoporotic as well as non-osteoporotic patients could be visualized very good in the Micro-CT analysis.

Triple fracture during rehabilitation after revision total knee arthroplasty

PurposeThe incidence of periprosthetic fractures after knee-joint implant revisions is increasing in prevalence. We present a method of treatment for a patient who sustained a triple fracture—a periprosthetic femur fracture, a patella fracture, and a tibial shaft fracture.MethodsThe femoral fracture was treated with a specially designed intramedullary nail, the patella fracture with a figure-of-eight suture, and the tibial shaft fracture by a minimal-invasive plate osteosynthesis using a percutaneous plating technique.ResultsOsseous consolidation was confirmed, and the patient presented a satisfying range of movement under full-weight-bearing conditions after mobilisation.ConclusionsSimultaneous multiple periprosthetic fractures are a special challenge, and in situ coupling of the endoprosthesis with a slotted hollow nail presents a valuable option for the treatment.Level of evidenceLevel V, Expert opinion.