[One-year outcomes after proximal humeral fractures : A risk-adjusted regression analysis of routine data based on 17,322 cases]. / Einjahresverläufe nach proximalen Humerusfrakturen : Eine risikoadjustierte Regressionsanalyse mittels Routinedaten anhand von 17.322 Fällen.

BACKGROUND: Proximal humeral fractures (PHF) are the third most common fracture in geriatric traumatology. No standard evidence-based treatment has been established so far. The epidemiology and economic burden highlight the importance of a targeted treatment strategy. OBJECTIVE: Epidemiology of PHF and analysis of the influence of preoperative length of stay, comorbidities and quality of patient life. Additionally, a comparison to the more frequently studied proximal femoral fractures. MATERIAL AND METHODS: A routine data analysis of 17,322 cases admitted for inpatient treatment with an observational period of 1 year was performed following an established model. Descriptive statistics included comorbidities, treatment procedures and mortality. Analytical statistics using logistic regression with the primary endpoints of early revision, mortality and decubitus within 1 year. RESULTS: In the investigated PHFs there was a mortality of 13% within 1 year, which is increased three-fold in patients with comorbidities such as cancer. There was an increase of 57% in patients who first received a care level following PHF. A preoperative care level in general significantly decreased survival. The most frequently used surgical procedure was fixation via stable-angle plate (used in 43%). The preoperative length of stay did not impact survival. DISCUSSION: Intrinsic factors such as preoperative comorbidities are crucial for the mortality after PHF. The PHF affects patients' lives less than proximal femoral fractures. With comparable comorbidity profiles, possible reasons are the lower levels of immobilization and less dependency on care before the fracture in comparison to proximal femoral fractures.

[Development of the inpatient quality of care of surgically treated patients with a proximal femoral fracture in North Rhine-Westphalia : Analysis of 61,249 treatment courses based on data from external inpatient quality assurance]. / Entwicklung der stationären Versorgungsqualität operativ behandelter Patienten mit einer proximalen Femurfraktur in Nordrhein-Westfalen : Eine Analyse über 61.249 Behandlungsverläufe auf Grundlage der Daten der externen stationären Qualitätssicherung.

BACKGROUND AND OBJECTIVE: Every year in Germany over 100,000 people, mostly of older age, suffer a proximal femoral fracture. Increasing case numbers in connection with an aging population and a relatively large number of concomitant diseases requiring treatment make everyday care more difficult. It is therefore of great importance to observe the quality of care for these patients using relevant quality parameters in order to be able to derive implications for everyday treatment practice. MATERIAL AND METHODS: The data of the external inpatient quality assurance from North Rhine-Westphalia for the years 2007-2008 and 2017-2018 were analyzed and the time periods compared. In addition, based on the documented secondary diagnosis and other influencing parameters, a risk adjustment was carried out with the aid of a logistic regression model with respect to the outcomes of general and surgical complications and mortality. Both osteosynthetically and endoprosthetically treated patients were taken into account. A total of 61,249 cases were included in the study. RESULTS: Positive developments could be observed in the area of surgical complications and wound infections with decreases of 1.2% and 0.8%, respectively. Patients with cardiovascular diseases had a particularly poor outcome. Here, improvements in the subcategory of cardiovascular events were found for general complications. The mortality remained unchanged at 6%. Operative activity on the weekends increased significantly. Patients whose hospital admission was related to the weekend did not show an increased risk of complications or mortality. Although the proportion of patients who were operated on after more than 48 h was reduced from 11.4% to 8.2%, the operation (> 24 h) was still delayed in 26.8% of cases. CONCLUSION: Against the background of increasing performance demands on the healthcare system, the results document improvements in some central areas of inpatient treatment. Nevertheless, the development of strategies for the further reduction of the preoperative waiting times in a medically justifiable manner is required. Internal concomitant diseases have a decisive influence on patient outcome. Thus, an adequate treatment of the multimorbid patient collective is to be established in everyday practice on the basis of close cooperation between geriatric traumatology and geriatric internal medicine departments.

[Subtrochanteric femur fractures-epidemiology, surgical procedures, influence of time to surgery and comorbidities on complications : A risk-adjusted regression analysis of routine data from 2124 cases]. / Subtrochantäre Femurfrakturen ­ Epidemiologie, Operationsverfahren sowie Einfluss der präoperativen Verweildauer und von Nebendiagnosen auf Komplikationen : Eine risikoadjustierte Regressionsanalyse mittels Routinedaten anhand von 2124 Fällen.

BACKGROUND: There are approximately 12,000 subtrochanteric femur fractures in Germany per year with a rising trend but studies about the epidemiology and the surgical outcome are rare. Furthermore, there are no guidelines from expert societies and there is no adequate quality assurance. OBJECTIVE: Presentation of the epidemiology and the current treatment situation with respect to the patient collective, comorbidities, time to surgery and surgical procedures used as well as the identification of modifiable risk factors with respect to complications. MATERIAL AND METHODS: Analysis of routine data based on an established data model in 2124 cases. The descriptive statistics contain data on basic patient characteristics, such as age, comorbidities, surgical procedure, time to surgery and mortality. In the analytical statistics the impact of risk factors (surgical procedure, time to surgery etc.) on the endpoints mortality, complications and decubitus was investigated by logistical regression analyses. RESULTS: Of the patients 55% were operated on within the first 24h. Intramedullary osteosynthesis (89%) is the most frequently used surgical method (prostheses 2%, extramedullary procedures 5%). Within the first postoperative year 37% of the patients received a higher level of care, where the care was moved from outpatient to inpatient treatment. The mortality in the first postoperative year was 26%, while early complications were observed in 6%. A delay in surgical treatment was associated with an increased mortality and intrinsic factors, which were difficult to influence. Intramedullary osteosynthesis had the lowest mortality and revision rates. CONCLUSION: Concerning the epidemiological data, the patient collectives of subtrochanteric fractures and femoral neck or pertrochanteric fractures were very similar. Major delays in the time to surgery of subtrochanteric fractures can be associated with increased complication rates and mortality. Therefore, programs to prevent older patients from falling have a high priority.

[One-year outcomes for proximal femoral fractures: Posthospital analysis of mortality and care levels based on health insurance data]. / Einjahresverläufe nach proximalen Femurfrakturen: Poststationäre Analyse von Letalität und Pflegestufen durch Kassendaten.

BACKGROUND: Proximal femur fractures are common and treatment is expensive. The aim of the present study was - after matching of hospital and health insurance data - to evaluate the influence of early operation on certain outcome parameters. Data from a German health insurance were used to identify then influence of the day of operation after admittance on the rate of mortality, decubitus, and revision surgery during the hospital stay and on the care level of the patients up to 1 year and in some cases longer after operation. MATERIALS AND METHODS: In all, 7905 patients were included. The descriptive data, specifying the given population, described the hospital stay (occurrence, surgical procedures, early complications, secondary diagnoses, length of stay) and the course of patient recovery up to 1 year after the hospital stay (care level, late complications). The calculated data (analytical statistics) give correlations evaluating the influence of the length of the preoperative hospital stay on the outcome parameters mentioned above. Risk adjustment was performed by using secondary diagnoses. RESULTS: The study included more women (mean age 81.5 years). Most common was the femoral neck fracture. Of the operations 77% were carried out on the first day after admission; dominating procedures were intramedullary nails and prostheses. Most common secondary diagnoses were diabetes, dementia, ischemic heart disease, and chronic heart insufficiency. Descriptive data revealed 6% early as well as late complications. In all, 50% of patients had a higher care level after operation. Almost 40% of patients changed from outpatient care to inpatient care. The time interval between admission and operation negatively influenced all outcome parameters. The relative risk to die, to develop decubitus, or to receive early revision was increased by approximately one third when patients were operated on later than the first day after admission. A total of 3172 patients died during the study period. Mortality after operation reached 9.9% within 30 days and 26.9% at 1 year. The mortality of patients operated after the first day was increased by more than 6% compared to patients treated within the first 24 h. CONCLUSION: The present study clearly presents the importance of analysis of routine records after discharge and it demonstrates that longer periods up to 1 year and more can be evaluated. The data show that a longer time period between hospital admission and operation negatively influences all outcome parameters. The care data give impressive evidence for a significant loss of quality of life and the importance of intense postoperative rehabilitation.

[More patients in a shorter inpatient stay with better outcome in treatment of femoral neck fracture: external quality assurance in Westfalia-Lippe on 50,354 patients]. / Mehr Patienten in kürzerer Zeit bei besserer Qualität in der Behandlung der Schenkelhalsfraktur : Externe chirurgische Qualitätssicherung in Westfalen-Lippe an über 50.354 Patienten.

BACKGROUND: We show a comparison between two patient groups of the inpatient population suffering from femoral neck fractures registered in the external quality assurance between 1993 and 1997 and between 2005 and 2009. RESULTS: The comparison between two patient groups showed the following developments: an increase in patient numbers per year from 4,229 to 5,842 where the average age remained constant but the proportion of elderly patients over 70 years old increased; the period of hospitalization was clearly shorter (from 27 days to 18 days); an increase in comorbidities (according to the ASA classification) with simultaneous decrease of the complication rate (from 11.1% to 7.6%). The inhospital mortality remained constant at 5.3%. At the same time the number of hospitals which treat patients with femoral neck fractures decreased from 166 to 150. Concurrently the number of patients per hospital and year increased from 23.6 to 41.3 cases. CONCLUSION: The technique of operative treatment changed and while during the 1990s many patients with femoral neck fractures were treated by implanting a total endoprosthesis, in the 2000s treatment was dominated by the hemi prosthesis. During the two periods of study use of the osteosynthesis technique decreased. In conclusion, the study showed an obvious compression of performance in trauma surgery but despite everything there was a clear improvement of treatment quality with respect to complication rates.

[Pertrochanteric fractures. What impact do surgical timing and implant choice have on the outcome?]. / Pertrochantäre Frakturen. Welchen Einfluss haben Operationszeitpunkt und Implantatwahl auf das Outcome?

Pertrochanteric fractures are grouped together with femoral neck fractures to represent the most frequent femur fractures in the region of the hip joint and usually occur in elderly people with preexisting conditions. Analysis of the data from the 2004/2005 quality assurance program of North Rhine-Westphalia shows, just as is the case for medial femoral neck fractures, that not only does delayed management increase risk-adjusted general and surgical complications but also mortality.

[The influence of timing of surgery on mortality and early complications in femoral neck fractures, by surgical procedure: an analysis of 22,566 cases from the German External Quality Assurance Program]. / Einfluss des Operationszeitpunkts und -verfahrens auf Mortalität und Frühkomplikationen der Schenkelhalsfraktur : Eine Analyse von 22.566 Fällen der verpflichtenden externen Qualitätssicherung.

BACKGROUND: The current S2 guideline recommends treatment of a femoral neck fracture within the first 24 h; this becomes evident by the significant rise in general and early surgical complications, when the surgical treatment was delayed for more than 48 h. The influence of different surgical procedures was investigated. PATIENTS UND METHODS: A total of 22,566 records from the external Quality Assurance Program in North Rhine-Westphalia for treatment of femoral neck fractures in 2004/2005 (BQS specification 7.0 and 8.0) were risk-adjusted and evaluated. RESULTS: Surgery was performed within 48 h in 83.9% of the patients. A significant rise in general and early surgical complications was registered when the surgical treatment was delayed for more than 48 h. Mortality and general complications were significantly lower for percutaneous screw fixation. All kinds of joint replacement show significantly higher general and surgical complications. CONCLUSION: The analyzed data support the rating of femoral neck fracture as requiring the intervention of urgent early surgery, as stated in the guideline. Percutaneous screw fixation can be considered for immobile and multimorbid patients with undislocated fractures. Advantages of total hip replacement compared to hemiarthroplasty cannot be supported by the QS-NRW data.

[Influence of operation time point on the frequency of early complications after surgical femoral neck fracture treatment]. / Frühkomplikationen nach Versorgung der Schenkelhalsfraktur. Einfluss des Operationszeitpunktes -- Analyse von 30.254 Fällen der externen Qualitätssicherung in Westfalen-Lippe.

AIM: The current publication deals with surgically treated medial and lateral femoral neck fracture of patients aged 60 and older. MATERIAL/METHODS: All patients were evaluated who received operative treatment between day of trauma and day 14 after trauma. Therefore, 30,254 patients (77,44%) were included. All early complications observed during hospital treatment were recorded as general and special complications, and we calculated whether the day of operation influenced the occurrence of early complications. Statistically significant differences were gained for revision operations. RESULTS: If the primary operation was performed on days 2 to 3 or 4 to 5 after trauma, fewer revisions necessary. Similar results were gained for revisions due to seroma and haematoma or postoperative bleeding. In these cases, fewer revision operations were performed when primary treatment was achieved on day 2 or 3. CONCLUSIONS: From the data presented, it is postulated that early complications provide no decisive reason for treating femoral neck fracture as an emergency. However, considering late complications such as the rate of femoral head necrosis, treatment for retaining the femoral head should be performed as early as possible. German guidelines suggest early but not emergency treatment in case of operations not saving the femoral head. Emergency operation within 6 h is not mandatory.

[Atypical HHS-syndrome--a rare differential diagnosis of circulatory disorders of the hand]. / Das atypische Hypothenar-Hammer-Syndrom--eine seltene Differenzialdiagnose der akralen Durchblutungsstörung der Hand.

We report on an acral circulatory disorder of the hand, representing a Hypothenar-Hammer-Syndrome (HHS) with atypical symptoms. The patient suffered from a radial circulatory disorder of his right hand, clinically representing a secondary M. Raynaud. The symptoms occurred after a single severe trauma of the right hand and after using both hands like a hammer. Angiography showed a cork-screw sign of the A. ulnaris at the typical area and an open Arcus palmaris superficialis as well as occlusions of multiple finger arteries. Symptoms improved significantly after lysis. The most important differential diagnosis is endangiitis obliterans according to angiography. If symptoms occur again, histology is recommended to exclude vasculitis. Surgery should be discussed if the HHS is confirmed, since a cork-screw morphology of the A. ulnaris exists as well as perfusion of the fingers mainly via the A. ulnaris. Also a radial circulatory disorder of the hand combined with typical anamnesis may represent a HHS.

[Madreporic hydroxyapatite granulates for filling bone defects]. / Madreporische Hydroxylapatitgranulate zur Füllung ossärer Defekte.

Two macrocrystalline madreporic granular hydroxyapatite implants of different size range (single crystal size within both implants 1-3 microns) were implanted for 7, 28, 84 and 168 days into the trabecular bone of the distal femur epiphysis of rabbits. Both materials were investigated histologically. For testing of granular materials a new animal model has been developed. The drill hole was closed by reimplantation of an autologeous chondrocortical tissue slice to prevent loss of particles into the knee-joint. Both of the granular materials tested developed increasing bone bonding from the 7th day on to outer surfaces and pore surfaces. The degradation of both of the materials affected the superficial implant layers in soft-tissue interfaces exclusively and was mainly due to passive processes, e.g. leaching, fragmentation of granules after crack-production, particulate degradation and subsequent phagocytosis of liberated implant particles by macrophages and foreign body giant cells. Zones of superficial implant degradation were bonded partially to bone a second time. A possible low-degree, active superficial degradation by foreign body giant cells is discussed. Osteoclasts of typical morphology as being observed on other hydroxyapatite implant surfaces were not demonstrated. This was related to the low degradation rate of the implants. Both of the granular materials tested are useful in filling bone defects. A guided tissue regeneration due to partial implant degradation and subsequent bone formation seems to be impossible since the degradation rate of the materials is too low.

In vivo comparison of bioactive glass particles in rabbits.

Bioglass particles of the compositions 45s5, 52s and 55s were implanted in the distal femoral epiphysis of rabbits. Animals were sacrificed at 7, 28, and 84 d postoperatively and specimens investigated using light microscopy and histomorphometry. Bone bonding occurred in a zentripetal fashion and fastest for 45s5. Bone formation was hampered at the core of the implantation bed where bone bonding showed a peak at 28d and diminished at 84d (except for 55s). This went along with a significant increase in numerous multinuclear giant cells (MNGC). Implantation model, particle size and surface-area-to-volume ratio are discussed as possible parameters determining bone regeneration.

Procollagen alpha 1(I) transcripts in cells near the interface of coralline implants in rats, detected by in situ hybridization.

Cells procollagen alpha 1(I) transcripts were demonstrated at the interface of natural coral mineral implanted in the femur of rats after 7, 14, 21 and 28 days by in situ hybridization with digoxigenin-labelled RNA probes. Procollagen alpha 1(I) transcripts were detectable in osteoblasts between 7 and 28 days after implantation. As early as 7 days after implantation, procollagen alpha 1(I) RNA expression was also demonstrated in fibroblasts; the transcripts steady state levels decreased until the 28th day, when they subsided completely. The development of bone was significantly during the 4 weeks of implantation. Inhibition of bone development by the coralline material could not be recorded.

Nanoapatite and organoapatite implants in bone: histology and ultrastructure of the interface.

This article reports on the reaction of bone to a new family of nanocrystalline hydroxyapatite biomaterials with crystal sizes similar to those of human bone. Pure nanoapatite cylinders and organoapatite cylinders containing a synthetic nanopeptide were analyzed 28 days after implantation into the spongy bone of Chinchilla rabbits. The experimental techniques used for analysis were light microscopy, scanning electron microscopy, and transmission electron microscopy. Both implant types were well incorporated, and interface events were found to be similar to those observed on human bone surfaces with regard to resorption by osteoclast-like cells and bone formation by osteoblasts. Different types of giant cells were observed resorbing the outermost surfaces of implants. There seemed to be both dissolution of the implant and particulate biodegradation leading to less dense implant regions near the interface, whereas the bulk of the implants remained denser. Transmission electron micrographs revealed that bone bonding occurred with and without an afibrillar intervening layer. Given the biologic reaction observed, these implant materials should be suitable for bone replacement and the organoapatite form could be useful for additional functions such as the release of drugs and optimized release of antibiotics, growth factors, or other substances. The organic component can also be used to control physical properties in a bony implantation bed.

Modulation of matrix vesicle enzyme activity and phosphatidylserine content by ceramic implant materials during endosteal bone healing.

This study examined effects of bone bonding and nonbonding implants on parameters associated with matrix vesicle-mediated primary bone formation, matrix vesicle alkaline phosphatase and phospholipase A2 specific activities, and phosphatidylserine content. Tibia marrow ablation followed by implantation of KG-Cera, Mina 13 (bonding), KGy-213, or M 8/1 (nonbonding) was used as the experimental model. Postsurgery, matrix vesicle-enriched microsomes (MVEM) were isolated from implanted and contralateral limbs. MVEM alkaline phosphatase and phospholipase A2 were stimulated adjacent to bonding implants with similar, though reduced, effects contralaterally. Alkaline phosphatase exhibited slight stimulation in nonbonding tissue; phospholipase A2 was inhibited or unchanged in treated and contralateral limbs. Phosphatidylserine content of MVEM was differentially affected by the implant materials. Thus, MVEM are modulated by implant materials locally and systemically. The data demonstrate that the model is a biologically relevant diagnostic for assessing the tissue/implant interface, primary calcification is affected by implant materials, and implant-specific effects are detected in the contralateral unimplanted limb.

In vivo regulation of matrix vesicle concentration and enzyme activity during primary bone formation.

In vivo regulation of matrix vesicles (MV) during primary bone formation was examined using tibial marrow ablation in rats as the experimental model. The effects of bone-bonding and nonbonding implants on the number of MV/micron 2 of matrix and the alkaline phosphatase (ALPase) and phospholipase A2 (PA2) activities of MV-enriched microsomes (MVEM) isolated from the healing bone were studied. MV concentration, ALPase, and PA2 were increased by bone-bonding implants by day 3 post-surgery; a similar effect was seen in the contralateral limb, but at a lower magnitude. Nonbonding implants had no effect at day 3 and decreased MV concentration and PA2 activity at later time points; the same behavior was observed in the contralateral limb. These results demonstrate that MVs are influenced in a differential manner by implant materials, both locally and systemically, and can be regulated during primary mineralization.

The early host and material response of bone-bonding and non-bonding glass-ceramic implants as revealed by scanning electron microscopy and histochemistry.

The interface of bone-bonding and non-bonding glass-ceramics in the femur of of rats with the concomitant material and host response has been investigated by scanning electron microscopy (SEM) and histochemistry after transverse fractures in the interface level. During wound healing around these implants, four overlapping phases could be distinguished: (1) blood clot formation, (2) formation of organization tissue, (3) formation of primary bone and calcification, and (4) remodelling which lasts from months to years. This sequence of healing was disturbed around metal ions containing non-bonding implants, as shown by a longer settlement of acid phosphatase positive macrophages and a disturbed calcification at the surface of the material. Only bone-bonding implants developed considerable changes in surface morphology due to leaching and corrosion phenomena. A preferential leaching of the glass moiety, starting at the phase transition between glass and ceramic, contributes to the production of surface elevations which provide adhesion points for fibres and fibrils. Subsequent mineralization of inserting fibres contributes to a tensile strength at the interface. These findings are essential for further understanding of bone-bonding mechanisms and for further development of surface-reactive materials.

Matrix vesicle enzyme activity in endosteal bone following implantation of bonding and non-bonding implant materials.

The effect of bone bonding (KGy-Cera) and non-bone bonding (KGy-213) implant materials on primary mineralization was examined in endosteal bone repair following marrow ablation. Comparisons were made to determine implant effect on concentration and biochemical parameters of matrix vesicles, as contrasted to vesicles in normal bone healing. Matrix vesicle number was determined by high-resolution computerized morphometric analysis, and implant effect on the specific activity of alkaline phosphatase and phospholipase A2 was measured. Bone responses differed according to the composition of the implant material. The bone bonding implant in this study stimulated matrix vesicle formation, alkaline phosphatase specific activity, and, to a lesser extent, phospholipase A2 activity. The effect of the non-bonding implant on healing bone was of suppression of enzyme specific activities and reduced matrix vesicle production. The results indicate that the bone bonding implant material (KGy-Cera) promotes the initiation of primary mineralization, whereas failure of the KGy-213 to bond may be related to toxic materials that leach from the implant and inhibit the normal sequence of events in the mineralization cascade. The results also demonstrate that the implant materials alter the healing process distal to the injury site. Changes observed in the contralateral control limb mimic the changes observed in the injured limb, but at lower magnitude.

Histological and ultrastructural observations at the interface of expanded polytetrafluorethylene anterior cruciate ligament implants.

Anterior cruciate ligament (ACL) grafts made from expanded polytetrafluorethylene (ePTFE) were examined after failure (n = 7; 3 instabilities, 2 partial ruptures, and 2 complete ruptures) to provide information about secondary fixation mechanisms via ingrowth of the different tissues. The ultrastructural evaluation clearly evidenced the existence of two main interface areas of ePTFE ACL-replacement: First, in areas without a dense cellular infiltrate there was interdigitating collagen producing a dense ePTFE-collagen network. Additionally, in a few areas of the graft/bone-tunnel interface a fibrous cartilage or bone regenerate could be demonstrated to be in contact with the prosthesis. Second, there was a dense infiltration of macrophages and multinuclear giant cells, partially containing birefringent material of implant origin, with and without a neosynovia-like reaction product, indicating a disturbance of tissue integration of the prosthesis. In areas of inflammation there was no bone development and only few collagen interdigitation with the graft material. This study provides further knowledge about mechanisms of secondary graft fixation due to tissue ingrowth. The interdigitation of collagen fibers and ePTFE filaments provides interfaces which should be at least partially resistant against load.

The effect of glass-ceramic implants on matrix vesicle calcification after two weeks of rat tibial bone healing.

Type, size and distribution of extracellular matrix vesicles (MV), known mediators of primary calcification, were studied around bone-bonding and metal-oxide containing, nonbonding, glass-ceramic implants. This was performed in order to further understand the different effects of implants on bone healing. At 14 days after implantation in adult rat tibial bone the effects of different implants on MV were studied by transmission electron microscopy and computerized morphometry. A total number of 4607 MV in 245 electron micrographs were counted and grouped according to diameter, distance from the calcifying front, and classified as four types: "empty," "amorphous," "crystal," and "rupture." The sequence of types according to diameter and distance was recorded as follows around both implants tested: "rupture" MV were the closest to the front with the largest diameter, followed by "crystal," "amorphous," and "empty," MV with the largest distance from the front and the smallest diameter. Most vesicles were concentrated in a distance of less than 2.4 microns from the front and between diameters of 0.06 microns and 0.22 microns. The noncalcified extracellular matrix around bone-bonding implants contained more MV than the matrix around the nonbonding type (26.24 MV/10 microns2 and 18.76 MV/10 microns2). MV distribution according to types showed that around bonding implants there was a higher percentage of "crystal" and a lower percentage of "rupture" when compared to the nonbonding type. These results indicate that bonding implants affect osteoblastic function by increasing the vesicular number and retardation of intravesicular crystal formation. It might be suggested that bonding implants induce an increase in the process of primary calcification and a decreased rate of crystal formation resulting with the highest organization of the healing bone.

Incorporation and degradation of hydroxyapatite implants of different surface roughness and surface structure in bone.

The interface of dense hydroxyapatite (HA) implants with different surface roughness was investigated after implantation into the spongy bone of the distal femur of rabbits by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) following transverse fractures in the interface. Each implant displayed considerable changes in surface morphology caused by leaching (increasing pore diameter), corrosion (particulate disintegration), and active resorption by osteoclasts. Macrophages were involved in "cleaning" the surface via phagocytosis of loose implant particles. Newly formed surface elevations provided adhesion points for fibers and fibrils. Subsequent mineralization of these areas stabilized the interdigitation of surface elevations and extracellular matrix with adhering fibers and contributed to the tensile strength in the interface. This investigation provides further knowledge about HA implants, which seem to be partially resorbed by osteoclast-like cells.