Tibial Head Research Articles

Osteocalcin enhances bone remodeling around hydroxyapatite/collagen composites

The effect of osteocalcin (OC), an extracellular bone matrix protein, on bone healing around hydroxyapatite/collagen composites was investigated. Cylindrical nanocrystalline hydroxyapatite implants of 2.5-mm diameter containing 2.5% biomimetically mineralized collagen type I were inserted press-fit into the tibial head of adult Wistar rats. To one implant group, 10 mug/g OC was added. Six specimens per group were analyzed at 2, 7, 14, 28, and 56 days. After 14 days, newly formed woven bone had reached the implant surface of the OC implants whereas a broad fibrous interface could still be observed around controls. Woven bone was formed directly around both implant groups after 28 days and had been replaced partially by lamellar bone around the OC implants only. No significant differences in total bone contact were seen between both groups after 56 days. The higher number of phagocytosing cells and osteoclasts characterized immunohistochemically with ED1, cathepsin D, and tartate-resistant alkaline phosphatase around the OC implants at the early stages of bone healing suggests an earlier onset of bone remodeling. The earlier and increased expression of bone-specific matrix proteins and multifunctional adhesion proteins (osteopontin, bone sialoprotein, CD44) at the interface around the OC implants indicates that OC may accelerate bone formation and regeneration. This study supports the observations from in vitro studies that OC activates both osteoclasts and osteoblasts during early bone formation.

Management of Concomitant Posterolateral Rotatory Instability and Anterior Cruciate Ligament Injuries of the Knee

Purpose: Many failures of anterior cruciate ligament (ACL) reconstruction are due to a failure to treat concomitant posterolateral rotatory instability (PLRI). We report the results of reconstruction in cases of combined PLRI and ACL injury. Materials and Methods: From January 1998 to December 2002, 24 patients were followed-up for a mean of 25 months (range, 12 to 58), postoperatively. PLRI was treated using a biceps tenodesis or posterolateral comer sling (PLCS), through a proximal tibial or fibular head obliquely anteroinferiorly to posterosuperiorly. ACLs were reconstructed using autogenous hamstring 4 bundles with RIGIDfix™ on the femoral side and Intrafix™ with additional staple fixation on the tibial side. Clinical results were evaluated using the Orthopadishe Arbeitsgruppe Knie (OAK) and International Knee Documentation Committee (IKDC) knee scoring system. Stability was measured on pull varus stress radiographs using a Telos stress device and by using the manual maximum displacement test using a KT-1000™ arthrometer with 30 degrees of knee flexion. Results: The mean side-to-side difference in anterior displacement measured on the pull stress radiographs was reduced from a preoperative 7.9±3.4 to 2.1±0.8 ㎜ at the last follow-up, from 2.1±0.8 to 0.4 ±0.7㎜ on varus stress radiographs, and from 6.5±1.3 ㎜ to 2.3±1.3 ㎜ as measured using the KT-1000 arthrometer. The average OAK score improved from 64.1±11.9 to 84.4±9.2 points over the same period. At the final evaluation, 22 of the 24 patients (92%) had a satisfactory result according to the IKDC system. Conclusion: Based on our experience, we recommend arthroscopically assisted ACL reconstruction and the correction of concomitant PLRI in cases of combined ACL and posterolateral rotatory instability.

An Alternative Method of Osteosynthesis for Distal Humeral Shaft Fractures

Treatment of extra-articular distal humerus shaft fractures with plating techniques is often difficult, as traditional centrally located posterior plates often encroach on the olecranon fossa, limiting distal osseous fixation. The use of a modified Synthes Lateral Tibial Head Buttress Plate (Synthes, Paoli, PA) allows for a centrally placed posterior plating of the humeral shaft that angles anatomically along the lateral column to treat far distal humeral shaft fractures. Fifteen patients treated in this manner were followed to radiographic and clinical union. There were no cases of instrumentation failure or loss of reduction.

Effect of high tibial flexion osteotomy on cartilage pressure and joint kinematics: a biomechanical study in human cadaveric knees. Winner of the AGA-DonJoy Award 2004.

Valgus high tibial osteotomy is an established treatment for unicompartmental varus osteoarthritis. However, only little is known about the effect of osteotomy in the sagittal plane on biomechanical parameters such as cartilage pressure and joint kinematics. This study investigated the effects of high tibial flexion osteotomy in a human cadaver model. Seven fresh human cadaveric knees underwent an opening wedge osteotomy of the proximal tibia in the sagittal plane. The osteotomy was opened anteriorly, and the tibial slope of the specimen was increased gradually. An isokinetic flexion-extension motion was simulated in a kinematic knee simulator. The contact pressure and topographic pressure distribution in the medial joint space was recorded using an electronic pressure-sensitive film. Simultaneously the motion of the tibial plateau was analyzed three-dimensionally by an ultrasonic tracking system. The traction force to the quadriceps tendon which was applied by the simulator for extension of the joint was continuously measured. The experiments were carried out with intact ligaments and then after successively cutting the posterior and anterior cruciate ligaments. The results demonstrate that tibial flexion osteotomy leads to a significant alteration in pressure distribution on the tibial plateau. The tibiofemoral contact area and contact pressure was shifted anteriorly, which led to decompression of the posterior half of the plateau. Moreover, the increase in the slope resulted in a significant anterior and superior translation of the tibial plateau with respect to the femoral condyles. Posterior subluxation of the tibial head after cutting the posterior cruciate ligament was completely neutralized by the osteotomy. The increase in slope resulted in a significant higher quadriceps strength which was necessary for full knee extension. We conclude from these results that changes in tibial slope have a strong effect on cartilage pressure and kinematics of the knee. Therapeutically a flexion osteotomy may be used for decompression of the degenerated cartilage in the posterior part of the plateau, for example, after arthroscopic partial posterior meniscectomy. If a valgus osteotomy is combined with a flexion component of the proximal tibia, complex knee pathologies consisting of posteromedial cartilage damage and posterior and posterolateral instability can be addressed in one procedure, which facilitates a quicker rehabilitation of these patients.

Plasma transglutaminase factor XIII induces microvessel ingrowth into biodegradable hydroxyapatite implants in rats

Coagulation factor XIII is a member of the transglutaminase-family. Transgluaminases cross-link either fibrin monomers in blood coagulation or extracellular proteins in extracellular matrix formation. In early stages of bone healing migration and proliferation of endothelial cells lead to formation of new vessels. The aim of this study was to investigate the angiogenetic activity of plasma factor XIII in bone defects filled with nanoparticulate hydroxyapatite paste. A critical size defect was created in the tibial head of rats which was not filled in group I. In group II the defect was filled with hydroxyapatite paste, and in group III with hydroxyapatite paste enriched with factor XIII. Ten days after surgery angiogenesis in the defects was assessed using immunohistochemistry and confocal laser scanning microscopy. Ac16 antibody was used to detect activation of factor XIII into factor XIIIA. In defects without biomaterial (group I) vessel-rich connective tissue and diffuse distribution of capillaries was observed. In defects filled with pure hydroxyapatite (group II) formation of capillaries was limited to the host bone-hydroxyapatite interface. In contrast, addition of plasma factor XIII to hydroxyapatite (group III) stimulated formation of vessels within the biomaterial. The current study reveals that factor XIII can improve angiogenesis in hydroxyapatite.

Bone morphogenetic protein 2 accelerates osteointegration and remodelling of solvent-dehydrated bone substitutes.

lt was the purpose of this study to investigate how bone morphogenetic protein 2 (BMP-2) influences remodelling and the biomechanics of solvent-dehydrated bone in the long run. Furthermore, the early influence of this growth factor on the substitute was investigated. Using a weight-bearing animal model, solvent-dehydrated bone was implanted in the tibial head of merino sheep ( n=12) after being loaded with BMP-2 (100 microg/100 microl). At 4 weeks ( n=6) and 9 months ( n=6) after surgery, histomorphological, histomorphometrical and biomechanical investigations were performed. At 9 months after implantation of BMP-2-loaded specimens, the bone per tissue volume was high, with levels above those of physiological cancellous bone. The amount of remaining solvent-dehydrated bone was markedly decreased, and in contrast, the amount of newly formed bone was extremely high. The specimen degradation had already occurred within the first 4 weeks after implantation, showing no further impact throughout the 9-month period. Biomechanical investigations at 9 months after implantation demonstrated a yield strength which achieved levels at least equivalent to physiological cancellous bone. BMP-2 showed no significant impact on the biomechanical properties after 4 weeks, compared to specimens prior to implantation. BMP-2 predominantly has an impact on the early implant degradation as well as bone formation, which leads to an almost completed bone remodelling of the solvent-dehydrated specimen within the study period of 9 months.

Biocompatibility and osseointegration of beta-TCP: histomorphological and biomechanical studies in a weight-bearing sheep model.

The aim of the study was to investigate the biocompatibility, degradation, and biomechanical properties of beta-TCP (Cerasorb) in a weight-bearing sheep model. beta-TCP implant prototypes were implanted in the tibial head of adult merino sheep. After 6 and 12 months material explants were harvested for biomechanical, histological, and histomorphometrical analysis. Corresponding bone specimens of the intact bone of the contralateral leg were used as controls in the biomechanical test. Compression tests showed higher values for maximum fracture load, yield strength, and compression modulus after 6 and 12 months compared to control. Microscopically, the implants showed good osteoconduction and were incorporated into the bone; however, relevant amounts of beta-TCP were still present after 12 months. Histomorphological results revealed that beta-TCP had partially degraded between implantation and 6 months, but its share remained constant between 6 and 12 months. The bone volume fraction in the area of the implant (46% +/- 6.5%) was initially higher than in the corresponding bone area of the contralateral leg (31% +/- 9.6%), but after 12 months declined to 29% +/- 9.4% (control: 33% +/- 8.3%), while the share of beta-TCP remained constant at 36% +/- 12.2%. These findings were supported by microradiographic data. In conclusion, in a weight bearing implantation model beta-TCP showed good biocompatibility, osseointegration and beginning degradation, even though it was not further degraded between 6 and 12 months.

Stability, bone healing and loss of correction after valgus realignment of the tibial head. A roentgen stereometry analysis

In high tibial closing-wedge osteotomies (HTO), closure of an osteotomy gap after resection of a bony wedge can be associated with a fissure of the medial cortex of the tibial head (MCT). The effect of a broken MCT on the recurrence of varus deformity is disputed. In this study, serial roentgen stereometric analysis (RSA) was used to determine the fixation stability of a rigid internal "L" plate after HTO. Full weight lower limb radiographs were used to determine the sagittal alignment in patients with varying degrees of varus malalignment and correction over time. Forty-two patients with varus gonarthrosis stage I-III (Ahlback) were treated with HTO and internal fixation with an L-shaped rigid plate. Patients were followed by serial RSA, conventional radiographs, and clinical evaluation (Hospital of Special Surgery score) over a 12-month period. In 19 of 42 successive patients, an average wedge size of 6.9 degrees was resected leaving the MCT intact (group 1). In 23 of 42 of patients, the MCT was unintentionally fissured during surgery when an average 10.3 degrees -wedge was resected (group 2). In group 2, RSA revealed a fivefold increase in lateral displacement of the distal tibial segment within 3 weeks after HTO. Twelve weeks after HTO, translations between tibial segments were below the accuracy of the RSA setup in the majority of patients. Group 1 patients demonstrated a higher initial fixation stability, less occurrence of varus deformity, and a higher HSS score compared to patients with larger wedge sizes and frequent fracture of the MCT (group 2). Before bone healing is achieved, the integrity of the MCT plays a crucial role for the clinical and radiological outcome after HTO.

Prevention of thromboembolism with low-molecular-weight heparin in orthopedic surgery: a 5-year experience.

A regimen of prophylaxis of thromboembolism with low molecular weight heparin (LMWH) and unfractionated heparin (UFH) in orthopedic surgery is presented. Over a 5-year period, 11,905 patients have been operated in all fields of orthopedic surgery in a big trauma center. In 498 cases, deep vein thrombosis (DVT) was clinically suspected and phlebography was performed: 122 patients had confirmed DVT (rate 0.98%); 59.8% of the DVT were limited to the calf. Nineteen pulmonary embolisms (rate 0.16%) were diagnosed (3 lethal). Heparin-induced thrombocytopenia type II was diagnosed in 12 of 122 patients. Only one of these had received LMWH. The related rates of DVT were highest for tibial head fractures (12.4%), total knee replacement (6.7%), and multiple trauma (6.4%). The extent of DVT was most severe in multiple trauma. The results proved the regimen to be of good clinical use and showed that more attention has to be paid to fractures, especially of the knee; and to patients with multiple injuries.

Complications in high tibial (medial opening wedge) osteotomy.

The high tibial (medial opening wedge) osteotomy (HTO) is a standard procedure in the treatment of varus gonarthrosis. This is potentially associated with various complications. The aim of this study was an analysis of complications and potential technical mistakes. A total of 85 patients (49 male and 36 female) suffering from varus gonarthrosis underwent a medial opening wedge HTO. The osteotomy was fixed in 55 patients by a spacer plate (Puddu plate; group A). In group B (n=30), the osteotomies were fixed by C-plate. The rate of complications was 43.6% in group A and 16.7% in group B (p<0.05). Infraction of the lateral tibial head is a possible intraoperative complication. This was seen in 11.7%. An additional osteosynthesis was required in group A. In contrast, the C-plate can solve this problem without additional measures. General complications of the HTO were seen: infection (4.7%), hematoma (4.7%), and thrombosis (2.3%). In every case of a severe deep infection, the osteotomy space was filled with synthetic bone graft. These grafts were used only in group A. Failure of the implants is a potential cause of loss of correction. This complication was seen nine times in group A but never in group B. A diligent surgical technique and a convenient implant are obligatory in (medial opening wedge) HTO.

Proximal tibial fracture stability with intramedullary nail fixation using oblique interlocking screws.

The purpose of this study was to evaluate the mechanical stability of oblique interlocking screws in supplementing intramedullary nail fixation of high proximal tibial fractures. In vitro experimental testing. SETTING Orthopaedic biomechanics laboratory, Sunnybrook and Women's College Health Sciences Center. Ten paired fresh-frozen human cadaver tibiae. One tibia of each pair was randomized to be instrumented with an intramedullary nail (M/DN; Zimmer, Warsaw, Indiana), while the other was stabilized with a 13-hole stainless steel lateral tibial head plate (Synthes AO/ASIF). Specimens were tested in varus-valgus (v/v), flexion-extension (f/e) and torsion, before and after a 2-cm gap osteotomy was performed in the proximal segment. Testing of the nailed tibiae was performed with and without oblique proximal screws. Bone density was physically determined by removing a core of trabecular bone from the distal end of each tibia following testing. Biomechanical construct stability. The addition of the proximally placed oblique screws increased the stability of the nail construct in v/v by 50% (6.8 mm, P < 0.05), in f/e by 47% (7.2 mm, P < 0.05), and in torsion by 18% (3.0 degrees, P < 0.05). There was no significant difference observed between the stability of the intramedullary nail construct with oblique screws and the plated construct. Trabecular bone density had a significant effect in reducing stability (P < 0.05) in nail and plate fixation. The addition of oblique interlocking screws significantly improves the stability of a nailed proximal tibia fracture and provides comparable stability to a plate osteosynthesis.

Paper #146 Intra-articular osteotomies for malunited tibial head fractures: operative technique and long-term follow-up results

Paper #146 Intra-articular osteotomies for malunited tibial head fractures: operative technique and long-term follow-up results

Abstracts

Efficacy of magnets for the treatment of traumatic reticuloperitonitis in cows Gandini, G., Cizinauskas, S., Lang, J., Fatzer, R. & Jaggy, A. (2003) Radiographic findings before and after oral administration...

Gait-analytical studies in patients treated by valgus tibial head osteotomy

So far, the use of imaging methods has been the only way of evaluating unicompartmental gonarthritis caused by malalignment of lower extremity axes and the results of operative correction. Unfortunately, radiological visualization does not give any information about the actual loads on the joint, i.e.the forces and moments acting on it under dynamic conditions. These can be determined by means of gait-analytical measurements. The authors explain how the anomalous loading that occurs in the knee joint in the case of varus gonarthritis can be calculated and assessed. The mean maximum varus moment of knee joints in a group of patients with varus deformity was 0.74 Nm\kg, which was significantly higher than that in a control group (0.63 Nm\kg). Even after correction of the axes, increased maximum moments--some of them independent of the angle of the knee and of the correction angle--were observed in 30% of the cases investigated. These cases were found to be characterized by a predisposition to revarization. Knee joints in which the preoperative varus moment was significantly high or there was a tendency to under-correction were especially likely to show these features. For these reasons, valgus tibial head osteotomies should generally be performed with slight overcorrection. If the preoperative gait analysis has already confirmed that significantly increased varus forces are in play, a definite overcorrection to about 5 degrees beyond the physiological angle should be the aim.

Soft tissue balancing in total condylar knee arthroplasty

Soft tissue balancing and correct bone cuts are an entity in correcting malalignment in total knee arthroplasty, and cannot be considered isolated. Distinct bony deformations/deviations need enlarged soft tissue management. The extent of resection of the bone stock has to be planned exactly before the operation. Exact soft tissue balancing is necessary to stabilize the corrected knee. Soft tissue balancing has to be done primarily on the side of the contracture by lengthening of the shortened and contracted structures. After balancing the ligaments should have the same tension in extension and flexion together with the same height of the extension and flexion gap. Because of the classic resection of the tibial head, the femoral resection must follow the Insall-Line, that means 3 degrees to 5 degrees outer rotation in relation to the condyles. Only in this way a symmetric flexion gap can be achieved in combination with ligamentous stability in extension and flexion.

Bone Substitution and Augmentation in Trauma Surgery Using a Degradable Calcium Phosphate Bone Cement

The purpose of this prospective, uncontrolled clinical multicenter study was to prove the safety and performance of a new resorbable bone substitute material. The injectable microcrystalline hydroxyapatite cement-like material (α-BSM/Biobon®) hardens in an endothermal reaction at about 37 °C after implantation. Its chemical composition and the crystalline structure appear essentially identical to the calcium phosphate component of natural bone and due to this it is highly biocompatible. This bone substitute material was used in cases of operative treatment of mainly cancellous bone defects in 49 patients. 51 bone defects in 49 patients (age 22-73) were filled with 0.5 up to 20 g (median 5.5 g) of bone cement (α-BSM/Biobon®). 39 trauma defects were treated (calcanear fractures 12, tibial head fractures 10, distal radial fractures 10, others 7, 2 patients with 2 implantation sites). In 12 patients bone defects originated from benign tumors, bone cysts and defects of donor sites after bone transplantation were filled by calcium phosphate cement. The radiological and clinical follow-up was performed after 1, 3, 6 and 12 months. This bone substitute material was easy to prepare and easy to apply, manually or by syringe, in the operating theatre. After hardening, the calcium phosphate bone substitute material could withstand moderate compression forces associated with normal treatment of patients with properly reduced and stabilized bone fracture defects. There were no signs of fracture dislocation or complications related to the calcium phosphate implant. Except for one soft tissue infection primary wound healing was observed in all cases. The radiographs showed indistinct outlines of the calcium phosphate bone substitute material with increasing time as a sign of osseous integration and resorption. All patients recovered in a way which can be expected in these type of fractures or bone defects treated by autologous bone grafting. This calcium phosphate bone substitute material appeared safe and osteoconductive and was suitable for filling bone defects and bone cavities for selected clinical cases showing slow resorption and a rapid osseous integration.

Prophylaxe thromboembolischer Komplikationen in der Unfallchirurgie mit niedermolekularem Heparin - Klinische Ergebnisse nach Anwendung bei über 11 000 Patienten -

Es wird ein differenziertes Thromboembolie-Prophylaxeschema unter überwiegender Verwendung des niedermolekularen Heparins Dalteparin (NMH) sowie von unfraktioniertem Heparin (UFH) vorgestellt und über die klinischen Ergebnisse aus 5 Jahren Anwendung an einem rein traumatologischen Patientengut berichtet. Bei 11 905 operativ behandelten Patienten wurden 122 tiefe Beinvenenthrombosen (TVT) (Rate 0,98 %) und 19 Lungenembolien (LE) (Rate 0,16 %) klinisch diagnostiziert. Die TVT wurden phlebographisch verifiziert. 59,8 % der TVT waren auf den Unterschenkel begrenzt. Der Zeitraum zwischen Trauma/OP und Diagnose der TVT/LE betrug  10,7 Tage (1 - 42). 12-mal fand sich eine HIT Typ II (nur 1 × unter NMH). Die höchsten diagnosebezogenen Thromboseraten zeigten sich nach Tibiakopffrakturen (12,4 %), Knie-TEP (6,7 %), Polytraumen (6,5 %) und Hüft-TEP (2,6 %), wobei die Anzahl proximaler TVT bei Polytraumen am höchsten war. Das Prophylaxeschema war praktikabel. Unsere Ergebnisse zeigen, dass sich auch im klinischen Alltag die medikamentöse Thromboembolieprophylaxe mit NMH bewährt und dass vor allem den frischen Frakturen am Knie besondere Aufmerksamkeit geschenkt werden muss.

Analysis of trabecular bone texture by modified Hurst orientation transform method.

There is a growing need for noninvasive and inexpensive methods that can effectively be used on a large scale, to detect an onset of early osteoarthritis in human knee joints. Of many possible options, fractal analysis of two-dimensional projection x-ray images of trabecular bone (TB) texture, appears as one of the best approaches. However, there are some problems associated with the characterization of the roughness and anisotropy of the bone texture. To resolve these problems, a modified Hurst orientation transform (HOT) method, previously developed by the authors, has been used in this study. The advantages of the HOT method over other techniques used to analyze bone texture, are that it calculates a two-dimensional fractal dimension in all possible directions and also provides a measure of anisotropy for both surfaces exhibiting strong anisotropy and surfaces exhibiting weak anisotropy. In this study, the accuracy of the HOT method in measuring the bone texture roughness and anisotropy; together with the effects of image noise, blur, exposure, magnification, and projection angle on its performance were investigated. Computer-generated images of fractal surfaces and x-ray images obtained for a human tibia head were used. Results obtained show that the HOT method can effectively be used to characterize the roughness and anisotropy (isotropy) of TB texture.

Histomorphological, histomorphometrical and biomechanical analysis of ceramic bone substitutes in a weight-bearing animal model.

It was the purpose of this investigation to prove the biomechanical properties, the osteoconductive capacity and the degradation rate of alpha tricalcium phosphate (alpha TCP), a neutralized glass ceramics (GB9N) and a composite material (GB9N+copolymers). In a weight-bearing animal model six substitutes each were implanted in the medial tibial head of the right lower leg of adult Merino-sheep in a standardized surgical technique. After nine months the implants were harvested and prepared for histomorphological and histomorphometrical investigations (undecalcified Masson Goldner staining). For additional biomechanical testing of the specimens, non-operated bone blocks from the contralateral tibia as well as native implants served as controls. No significant differences for the maximum fracture load as well as for the yield strength were detected between harvested specimens and bone blocks from the contralateral tibia. However there were marked differences to ceramics that were not implanted. All substitutes showed osteoconduction, leading to a continuous ingrowth of new formed bone. However in the composite material soft tissue could be identified within the scaffold and there were signs of ongoing bone remodeling, nine months after implantation. The bone per tissue volume of alpha-TCP in conjunction to new bone (=percentage of trabecular bone volume plus percentage of residual substitute) was higher than for GB9N and the composite material. Nine months after implantation the percentage of residual alpha-TCP was 48%, it was 32% for GB9N and 28% for the composite. The intention of further studies should be to accelerate the degradation rates of substitutes and to improve biomechanical properties of implants by either modifying the chemical composition or combining materials with agents as, e.g. growth factors.

Degradation characteristics of α and β tri‐calcium‐phosphate (TCP) in minipigs

In seven Goettingen minipigs 3.5--4.7-ml cancellous bone defects were created in the area of the tibial head on both sides. The defects were filled with alpha-TCP or beta-TCP (tricalciumphosphate). ITI implants (Straumann, Freiburg, Germany) of 3.2 x 12-mm length were inserted into the underlying ceramic substitutes. Two additional pigs were used as control. Within the periods of observation (4, 16, 20, 28, 46, 68, and 86 weeks) fluorescent dyes were applied. Nondecalcified thin-sliced sections were examined by means of light and fluorescence microscopy. In addition microangiography and microradiography were performed. Bony regeneration occurred basally and on the sides of the defect according the angiogenetic reossification pattern. Resorption was due to a hydrolytic and cellular degradation process. After 46 weeks histomorphological evaluation showed an incomplete osseointegration of the simultaneously implanted dental implants. The bone contact surface ratio was lower than 25%. After 86 weeks 95--97% of both alpha- and beta-TCP were resorbed. Ceramic residuals stayed within the newly formed trabeculae thus resisting further degradation until remodeling occurred. Both alpha- and beta-TCP show a comparable degradation process. At the 86-week postoperative point only small residuals of the ceramic can be found. These residuals stay within the newly formed trabeculae, which show a functional orientation. In comparison control defects showed only sparse reossification. The beta-TCP material shows an accelerated degradation mode and has an optimal reactivity with the surrounding tissues. According to the results of this animal experiment both materials can be classified as bone-rebuilding materials.