Philipp Drees

Mechanisms of Disease: molecular insights into aseptic loosening of orthopedic implants

Despite the success of treating rheumatic disorders with biologic therapies, joint replacement surgery still remains the final treatment option in many cases. Approximately 1.5 million joint arthroplastic operations are performed annually worldwide. Implant failure due to massive bone loss and aseptic loosening of prostheses, however, is a major complication of joint replacement, which can lead to high socioeconomic burdens both for the individual patient and for health-care systems. To date, there is no approved drug therapy to prevent or inhibit periprosthetic osteolysis, and aseptic loosening of prostheses can only be overcome by surgical revision. Research during the past decade, however, has unravelled much of the pathogenesis of aseptic prosthesis loosening and preclinical studies have identified potential targets for pharmaceutical treatments. This article highlights the importance of a cooperative interaction between rheumatologists and orthopedic surgeons, and presents novel insights into the molecular mechanisms behind aseptic loosening of prostheses. In addition, we outline potential perspectives for the development of future therapeutic strategies for this devastating complication.

The internal calcar septum and its contact with the virtual stem in THR: A computer tomographic evaluation

The internal calcar septum is a ridge of cortical bone protruding from the inner cortical wall of the proximal femur into the medullary canal. It extends from the lesser trochanter into the femoral neck and narrows the femoral cavity in its dorsal third. This region is essential for THR stability, but the degree of contact between the septum and standard THR implants has never been studied. We obtained CT scans of 50 arthrotic hip joints from patients requiring THR. Virtual stems (50 straight/wedge-shaped and 50 anatomic stems) were placed in CT images of the femora using a PC-based preoperative planning unit. The dimensions of the septum, degree and location of contact between the septum and implants were recorded. A septum of cortical density was seen in 49/50 CT scans. It was 11 (2.9) mm long (medial-lateral), 3.5 (0.7) mm wide and 32 (10) mm high (caudal-cranial, mean (SD)). 94/100 implanted virtual stems showed direct contact with the septum. 31 straight stems and 5 anatomical stems were supported by the septum along their dorsal side. The internal calcar septum can be consistently seen on CT scans of patients needing THR and it probably contributes to THR stability.

The common occurrence of osteoarthritis and osteoporosis and the value of markers of bone turnover

OBJECTIVE Increasing bone mineral density (BMD) has been found in several studies in patients with osteoarthritis. Therefore, many clinicians deny the simultaneous occurrence of osteoporosis (OP) and osteoarthritis (OA). Because of our clinical impression however, we suggested that we have to consider a common occurrence. Furthermore, the value of markers of bone turn over with a view to early diagnosis of OP and or as an assessment for bone metabolism in OA is still a matter debate and their clinical use has not been clearly defined in the management of the individual patient. METHOD The BMD of the lumbar spine and the proximal femur of 119 OA patients (83 postmenopausal female patients aged 50-83 and 35 male patients aged 36-86 years) who subsequently required hip or knee replacements, but were otherwise healthy, were measured by dual energy X-ray absorption (DXA), Hologic QDR-2000. We also measured biochemical markers of bone turn over, i. e., CICP, ICTP, DPD, PTH, estrogen, testosterone, bAP, hydroxy vitamin D and the normal blood count. RESULTS There was a high occurrence of a low BMD among the patients. A total of 28.9% of women were affected by OP and 52.9% by osteopoenie. This reflects the normal distribution of OP in the female population. Of the male patients 20% had OP and 38.8% osteopoenie. This is astonishing high. Age proved to be a significant factor in the degree of BMD. An association between disuse osteoporosis and degree of BMD in the OA affected joint could not be proven. The use of the biochemical markers for an earlier diagnosis or to assess bone metabolism in OP and OA was not possible. CONCLUSION We can not support the hypotheses that OA prevents OP. Moreover, the occurrence of OP in our study reflected the incidence of OP in the average female and the astonishingly high incidence in the male population; however does not mean that the two conditions are mutually exclusive. We did not find that the biochemical markers of bone turn over could deliver additional information with respect to bone metabolism and an earlier diagnosis of OP.ZusammenfassungFragestellungDas häufig in der Literatur in Frage gestellte gemeinsame Auftreten von Osteoporose und Arthrose sowie der Einsatz von Knochenstoffwechselparametern als ergänzendes Diagnostikum sollte untersucht werden.Material und Methode119 primär knochengesunde Patienten (83 postmenopausale Frauen im Alter von 50–83 und 36 Männer im Alter von 36–86 Jahren) mit einer operationsbedürftigen Arthrose des Hüft- oder Kniegelenkes wurden hinsichtlich der Knochendichte an Lendenwirbelsäule und proximalem Femur mittels Dual X-ray Absorptiometrie (DXA) untersucht. Hierbei erfolgte die Auswertung gemäß der Forderungen der WHO und der Leitlinien des Dachverbandes Osteologie (DVO). Weiterhin wurden neben dem Basislabor die gängigen Knochenstoffwechselparameter in Abhängigkeit von Knochendichte, Geschlecht und Alter untersucht.ErgebnisseEs zeigte sich ein unerwartet hoher Anteil an Patienten mit einer geminderten Knochendichte. Der Anteil von 28,9% der weiblichen Patienten mit Osteoporose entspricht dem geschätzten Prozentsatz in der Normalbevölkerung in Deutschland. Überraschend hoch ist mit 20% die Zahl der Männer, die eine Osteoporose aufwiesen, sie waren im Durchschnitt 4 Jahre jünger als die Frauen. Weiterhin wurde bei 38,8% der Männer und bei 52,9% der Frauen eine Knochendichte im Sinne einer Osteopenie gemessen. Die Altersabhängigkeit der Osteoporose konnte wie die Abhängigkeit der Osteoporose vom Body-Mass-Index bei Frauen bestätigt werden, eine Inaktivitätsosteoporose ausgeschlossen. Die Knochenstoffwechselmarker lieferten in dem selektionierten Patientengut keine ergänzenden Informationen zur Knochendichte und konnten Patienten mit erniedrigter Knochendichte nicht identifizieren.SchlussfolgerungDie Hypothese, dass Arthrose vor Osteoporose schützt, konnte von uns nicht bestätigt werden. Vielmehr entsprach die Osteoporoseinzidenz der in der Normalbevölkerung. Weiterhin überraschte die hohe Anzahl an männlichen Patienten mit Osteoporose. Auch kann somit nicht von einer geringeren Frakturgefährdung für Arthrosepatienten ausgegangen werden. Die Knochenstoffwechselparameter konnten bei unserem selektioniertn Patientengut keine zusätzlichen Informationen liefern.SummaryObjectiveIncreasing bone mineral density (BMD) has been found in several studies in patients with osteoarthritis. Therefore, many clinicians deny the simultaneous occurrence of osteoporosis (OP) and osteoarthritis (OA). Because of our clinical impression however, we suggested that we have to consider a common occurrence. Furthermore, the value of markers of bone turn over with a view to early diagnosis of OP and or as an assessment for bone metabolism in OA is still a matter debate and their clinical use has not been clearly defined in the management of the individual patient.MethodThe BMD of the lumbar spine and the proximal femur of 119 OA patients (83 postmenopausal female patients aged 50–83 and 35 male patients aged 36–86 years) who subsequently required hip or knee replacements, but were otherwise healthy, were measured by dual energy X-ray absorption (DXA), Hologic QDR-2000. We also measured biochemical markers of bone turn over, i. e., CICP, ICTP, DPD, PTH, estrogen, testosterone, bAP, hydroxy vitamin D and the normal blood count.ResultsThere was a high occurrence of a low BMD among the patients. A total of 28.9% of women were affected by OP and 52.9% by osteopoenie. This reflects the normal distribution of OP in the female population. Of the male patients 20% had OP and 38.8% osteopoenie. This is astonishing high. Age proved to be a significant factor in the degree of BMD. An association between disuse osteoporosis and degree of BMD in the OA affected joint could not be proven. The use of the biochemical markers for an earlier diagnosis or to assess bone metabolism in OP and OA was not possible.ConclusionWe can not support the hypotheses that OA prevents OP. Moreover, the occurrence of OP in our study reflected the incidence of OP in the average female and the astonishingly high incidence in the male population; however does not mean that the two conditions are mutually exclusive. We did not find that the biochemical markers of bone turn over could deliver additional information with respect to bone metabolism and an earlier diagnosis of OP.

Molekulare Signalwege der aseptischen Endoprothesenlockerung (Molecular pathways in aseptic loosening of orthopaedic endoprosthesis)

Zusammenfassung Die Behandlung von immobilisierenden degenerativen und entzündlichen Gelenkerkrankungen mit der Implantation von Endoprothesen ist ein großer Erfolg und Fortschritt in der Medizin und hat stark zur Verbesserung der Lebensqualität der betroffenen Patienten beigetragen. Jährlich werden weltweit ca. 1,3 Mio. Endoprothesen implantiert, davon allein 500.000 in den USA. Dennoch sind die einmal implantierten Prothesen nicht von lebenslanger Dauer und unterliegen multiplen Einflüssen. Trotz immer neuer Entwicklungen müssen innerhalb der ersten 15 Jahre bis zu 10% der Implantate aufgrund vorzeitiger Prothesenlockerung gewechselt werden. Bei vorzeitiger Lockerung ohne Infekt oder Trauma spricht man von aseptischer Lockerung. Es ist allgemein bekannt, dass durch Abrieb entstandene Kleinstpartikel und aktivierte Makrophagen die Hauptrolle im Prozess der aseptischen Lockerung spielen. Die Pathophysiologie ist jedoch noch nicht vollständig erklärt. Die vorliegende Arbeit gibt eine Übersicht über die anerkannten molekularen Mechanismen und die Signalwege, die zur aseptischen Prothesenlockerung führen. Außerdem werden neue Therapieoptionen zur Vermeidung der aseptischen Lockerung diskutiert. Abstract Operative joint replacement to treat disabling joint conditions secondary to degenerative and inflammatory arthritides has become one of the most efficacious and cost-effective procedures to relieve pain and restore joint function. However, prosthetic implants are not built to last forever and osteolysis and aseptic loosening has been associated with prosthetic arthroplasties since their introduction. The functional life of a synthetic joint is influenced by many factors including the material of the implant, operation procedures and the surgeon involved, as well as patient-related factors. Although promising developments have been achieved in this field, more than 10% of all implants still have to undergo operative revision within 15 years after the initial operation. Failure due to sepsis, fractures and dislocations has become rare; premature loosening of implants on the other hand is becoming much more important. Prosthetic loosening without concurrent infection or trauma is called aseptic loosening. It is generally accepted that small particles (“wear debris”) and activated macrophages play a key role in aseptic loosening. The pathophysiology of this condition, however, is still not very well characterized. In this article, we review the molecular mechanisms and signal pathways that were unravelled as responsible factors for loosening orthopaedic implants. Finally, we discuss possible novel strategies for future therapeutic approaches.

Das gemeinsame Auftreten von Osteoporose und Arthrose und der Nutzen der Knochenstoffwechselmarker

OBJECTIVE Increasing bone mineral density (BMD) has been found in several studies in patients with osteoarthritis. Therefore, many clinicians deny the simultaneous occurrence of osteoporosis (OP) and osteoarthritis (OA). Because of our clinical impression however, we suggested that we have to consider a common occurrence. Furthermore, the value of markers of bone turn over with a view to early diagnosis of OP and or as an assessment for bone metabolism in OA is still a matter debate and their clinical use has not been clearly defined in the management of the individual patient. METHOD The BMD of the lumbar spine and the proximal femur of 119 OA patients (83 postmenopausal female patients aged 50-83 and 35 male patients aged 36-86 years) who subsequently required hip or knee replacements, but were otherwise healthy, were measured by dual energy X-ray absorption (DXA), Hologic QDR-2000. We also measured biochemical markers of bone turn over, i. e., CICP, ICTP, DPD, PTH, estrogen, testosterone, bAP, hydroxy vitamin D and the normal blood count. RESULTS There was a high occurrence of a low BMD among the patients. A total of 28.9% of women were affected by OP and 52.9% by osteopoenie. This reflects the normal distribution of OP in the female population. Of the male patients 20% had OP and 38.8% osteopoenie. This is astonishing high. Age proved to be a significant factor in the degree of BMD. An association between disuse osteoporosis and degree of BMD in the OA affected joint could not be proven. The use of the biochemical markers for an earlier diagnosis or to assess bone metabolism in OP and OA was not possible. CONCLUSION We can not support the hypotheses that OA prevents OP. Moreover, the occurrence of OP in our study reflected the incidence of OP in the average female and the astonishingly high incidence in the male population; however does not mean that the two conditions are mutually exclusive. We did not find that the biochemical markers of bone turn over could deliver additional information with respect to bone metabolism and an earlier diagnosis of OP.ZusammenfassungFragestellungDas häufig in der Literatur in Frage gestellte gemeinsame Auftreten von Osteoporose und Arthrose sowie der Einsatz von Knochenstoffwechselparametern als ergänzendes Diagnostikum sollte untersucht werden.Material und Methode119 primär knochengesunde Patienten (83 postmenopausale Frauen im Alter von 50–83 und 36 Männer im Alter von 36–86 Jahren) mit einer operationsbedürftigen Arthrose des Hüft- oder Kniegelenkes wurden hinsichtlich der Knochendichte an Lendenwirbelsäule und proximalem Femur mittels Dual X-ray Absorptiometrie (DXA) untersucht. Hierbei erfolgte die Auswertung gemäß der Forderungen der WHO und der Leitlinien des Dachverbandes Osteologie (DVO). Weiterhin wurden neben dem Basislabor die gängigen Knochenstoffwechselparameter in Abhängigkeit von Knochendichte, Geschlecht und Alter untersucht.ErgebnisseEs zeigte sich ein unerwartet hoher Anteil an Patienten mit einer geminderten Knochendichte. Der Anteil von 28,9% der weiblichen Patienten mit Osteoporose entspricht dem geschätzten Prozentsatz in der Normalbevölkerung in Deutschland. Überraschend hoch ist mit 20% die Zahl der Männer, die eine Osteoporose aufwiesen, sie waren im Durchschnitt 4 Jahre jünger als die Frauen. Weiterhin wurde bei 38,8% der Männer und bei 52,9% der Frauen eine Knochendichte im Sinne einer Osteopenie gemessen. Die Altersabhängigkeit der Osteoporose konnte wie die Abhängigkeit der Osteoporose vom Body-Mass-Index bei Frauen bestätigt werden, eine Inaktivitätsosteoporose ausgeschlossen. Die Knochenstoffwechselmarker lieferten in dem selektionierten Patientengut keine ergänzenden Informationen zur Knochendichte und konnten Patienten mit erniedrigter Knochendichte nicht identifizieren.SchlussfolgerungDie Hypothese, dass Arthrose vor Osteoporose schützt, konnte von uns nicht bestätigt werden. Vielmehr entsprach die Osteoporoseinzidenz der in der Normalbevölkerung. Weiterhin überraschte die hohe Anzahl an männlichen Patienten mit Osteoporose. Auch kann somit nicht von einer geringeren Frakturgefährdung für Arthrosepatienten ausgegangen werden. Die Knochenstoffwechselparameter konnten bei unserem selektioniertn Patientengut keine zusätzlichen Informationen liefern.SummaryObjectiveIncreasing bone mineral density (BMD) has been found in several studies in patients with osteoarthritis. Therefore, many clinicians deny the simultaneous occurrence of osteoporosis (OP) and osteoarthritis (OA). Because of our clinical impression however, we suggested that we have to consider a common occurrence. Furthermore, the value of markers of bone turn over with a view to early diagnosis of OP and or as an assessment for bone metabolism in OA is still a matter debate and their clinical use has not been clearly defined in the management of the individual patient.MethodThe BMD of the lumbar spine and the proximal femur of 119 OA patients (83 postmenopausal female patients aged 50–83 and 35 male patients aged 36–86 years) who subsequently required hip or knee replacements, but were otherwise healthy, were measured by dual energy X-ray absorption (DXA), Hologic QDR-2000. We also measured biochemical markers of bone turn over, i. e., CICP, ICTP, DPD, PTH, estrogen, testosterone, bAP, hydroxy vitamin D and the normal blood count.ResultsThere was a high occurrence of a low BMD among the patients. A total of 28.9% of women were affected by OP and 52.9% by osteopoenie. This reflects the normal distribution of OP in the female population. Of the male patients 20% had OP and 38.8% osteopoenie. This is astonishing high. Age proved to be a significant factor in the degree of BMD. An association between disuse osteoporosis and degree of BMD in the OA affected joint could not be proven. The use of the biochemical markers for an earlier diagnosis or to assess bone metabolism in OP and OA was not possible.ConclusionWe can not support the hypotheses that OA prevents OP. Moreover, the occurrence of OP in our study reflected the incidence of OP in the average female and the astonishingly high incidence in the male population; however does not mean that the two conditions are mutually exclusive. We did not find that the biochemical markers of bone turn over could deliver additional information with respect to bone metabolism and an earlier diagnosis of OP.

Stem cell factor receptor KIT (CD117) in aseptic hip prosthesis loosening

Objective: This study aimed to investigate specific inflammatory pathomechanisms, i.e. the expression of the stem cell factor receptor KIT (CD117) in tissue specimens from patients with aseptic hip prosthesis loosening (AHPL) with special emphasis on colocalization with the mast cell specific marker tryptase. Methods: Immunohistochemical analysis of CD117 was performed in tissue specimens from 10 patients with aseptically loos- ened acetabular components of failed non-cement total hip replacements and compared to control samples obtained at primary hip surgery (n=4). The CD117 expressing cells were characterized further with mast cell tryptase (MCT) by serial section analy- sis and a double staining method. CD117 and MCT expression was examined by semi-quantitative analysis. Additionally, double labeling of the CD117 or MCT expression by immunohistochemistry and of polyethylene (PE) particles by Oil Red reac- tion was performed. Results: In AHPL, CD117 was almost exclusively detected in MCT positive cells. Co-expression tended to be highly correlated (r=0.86, p<0.01). CD117 was found mainly in two regions: first, in perivascular lymphocyte-rich areas and; secondly, near macrophages and multinucleated giant cells (MGC). PE particles were not detected in CD117 and MCT positive cells. In con- trol samples, CD117/MCT positive cells were less frequent. Conclusion: This is the first report on CD117 expression in AHPL. CD117 is almost exclusively expressed in a distinct mast cell subgroup. As an important growth factor receptor, CD117 could play a major role in recruitment and activation of mast cells in AHPL. Furthermore, mast cells do not contain significant amounts of PE particles. However, it remains to be investi- gated whether this cell population could influence phagocytosis of PE particles. (Journal of Applied Biomaterials & Biome- chanics 2005; 3: 11-7)

The learning curve in short-stem THA: influence of the surgeon’s experience on intraoperative adjustments due to intraoperative radiography

IntroductionShort-stem THA has become increasingly popular over the last decade. However, implantation technique differs from conventional THA and thus possibly involves a distinct learning curve. The purpose of this study was to evaluate the value of intraoperative radiography and the influence of the surgeon’s experience on intraoperative adjustments in short-stem THA.MethodsA total of 287 consecutive short-stem THAs, operated by a total of 24 senior consultants, consultants and residents in training, were prospectively included. Intraoperative radiography was performed after trial reduction. Preoperative planning and intraoperative outcome with regard to positioning, sizing of components as well as resulting offset and leg length were compared. Frequency, reason and type of intraoperative adjustments were documented in relation to the surgeon’s experience. Operation time was assessed.ResultsOne hundred and fifty-six (54.4%) procedures were carried out by one of three senior consultants, and a total of nine consultants and 12 residents in training performed 105 (36.6%) and 26 (9.0%) operations, respectively. In 121 cases (42.2%), intraoperative adjustments were made following intraoperative radiography. Intraoperative adjustments of one or more components were made by senior consultants in 51 cases (32.7%), by consultants in 53 cases (50.5%) and by residents in 17 cases (65.4%), respectively. The most common cause was undersizing of the stem. Operation time varied markedly between groups of surgeons.DiscussionShort-stem THA involves a learning curve. Intraoperative radiography is decisive for prevention of malpositioning and undersizing of components, as well as loss of offset and leg length discrepancies. Hence, it should be considered mandatory, especially for less experienced surgeons.

Das gemeinsame Auftreten von Osteoporose und Arthrose und der Nutzen der Knochenstoffwechselmarker@@@The common occurrence of osteoarthritis and osteoporosis and the value of markers of bone turnover

OBJECTIVE Increasing bone mineral density (BMD) has been found in several studies in patients with osteoarthritis. Therefore, many clinicians deny the simultaneous occurrence of osteoporosis (OP) and osteoarthritis (OA). Because of our clinical impression however, we suggested that we have to consider a common occurrence. Furthermore, the value of markers of bone turn over with a view to early diagnosis of OP and or as an assessment for bone metabolism in OA is still a matter debate and their clinical use has not been clearly defined in the management of the individual patient. METHOD The BMD of the lumbar spine and the proximal femur of 119 OA patients (83 postmenopausal female patients aged 50-83 and 35 male patients aged 36-86 years) who subsequently required hip or knee replacements, but were otherwise healthy, were measured by dual energy X-ray absorption (DXA), Hologic QDR-2000. We also measured biochemical markers of bone turn over, i. e., CICP, ICTP, DPD, PTH, estrogen, testosterone, bAP, hydroxy vitamin D and the normal blood count. RESULTS There was a high occurrence of a low BMD among the patients. A total of 28.9% of women were affected by OP and 52.9% by osteopoenie. This reflects the normal distribution of OP in the female population. Of the male patients 20% had OP and 38.8% osteopoenie. This is astonishing high. Age proved to be a significant factor in the degree of BMD. An association between disuse osteoporosis and degree of BMD in the OA affected joint could not be proven. The use of the biochemical markers for an earlier diagnosis or to assess bone metabolism in OP and OA was not possible. CONCLUSION We can not support the hypotheses that OA prevents OP. Moreover, the occurrence of OP in our study reflected the incidence of OP in the average female and the astonishingly high incidence in the male population; however does not mean that the two conditions are mutually exclusive. We did not find that the biochemical markers of bone turn over could deliver additional information with respect to bone metabolism and an earlier diagnosis of OP.ZusammenfassungFragestellungDas häufig in der Literatur in Frage gestellte gemeinsame Auftreten von Osteoporose und Arthrose sowie der Einsatz von Knochenstoffwechselparametern als ergänzendes Diagnostikum sollte untersucht werden.Material und Methode119 primär knochengesunde Patienten (83 postmenopausale Frauen im Alter von 50–83 und 36 Männer im Alter von 36–86 Jahren) mit einer operationsbedürftigen Arthrose des Hüft- oder Kniegelenkes wurden hinsichtlich der Knochendichte an Lendenwirbelsäule und proximalem Femur mittels Dual X-ray Absorptiometrie (DXA) untersucht. Hierbei erfolgte die Auswertung gemäß der Forderungen der WHO und der Leitlinien des Dachverbandes Osteologie (DVO). Weiterhin wurden neben dem Basislabor die gängigen Knochenstoffwechselparameter in Abhängigkeit von Knochendichte, Geschlecht und Alter untersucht.ErgebnisseEs zeigte sich ein unerwartet hoher Anteil an Patienten mit einer geminderten Knochendichte. Der Anteil von 28,9% der weiblichen Patienten mit Osteoporose entspricht dem geschätzten Prozentsatz in der Normalbevölkerung in Deutschland. Überraschend hoch ist mit 20% die Zahl der Männer, die eine Osteoporose aufwiesen, sie waren im Durchschnitt 4 Jahre jünger als die Frauen. Weiterhin wurde bei 38,8% der Männer und bei 52,9% der Frauen eine Knochendichte im Sinne einer Osteopenie gemessen. Die Altersabhängigkeit der Osteoporose konnte wie die Abhängigkeit der Osteoporose vom Body-Mass-Index bei Frauen bestätigt werden, eine Inaktivitätsosteoporose ausgeschlossen. Die Knochenstoffwechselmarker lieferten in dem selektionierten Patientengut keine ergänzenden Informationen zur Knochendichte und konnten Patienten mit erniedrigter Knochendichte nicht identifizieren.SchlussfolgerungDie Hypothese, dass Arthrose vor Osteoporose schützt, konnte von uns nicht bestätigt werden. Vielmehr entsprach die Osteoporoseinzidenz der in der Normalbevölkerung. Weiterhin überraschte die hohe Anzahl an männlichen Patienten mit Osteoporose. Auch kann somit nicht von einer geringeren Frakturgefährdung für Arthrosepatienten ausgegangen werden. Die Knochenstoffwechselparameter konnten bei unserem selektioniertn Patientengut keine zusätzlichen Informationen liefern.SummaryObjectiveIncreasing bone mineral density (BMD) has been found in several studies in patients with osteoarthritis. Therefore, many clinicians deny the simultaneous occurrence of osteoporosis (OP) and osteoarthritis (OA). Because of our clinical impression however, we suggested that we have to consider a common occurrence. Furthermore, the value of markers of bone turn over with a view to early diagnosis of OP and or as an assessment for bone metabolism in OA is still a matter debate and their clinical use has not been clearly defined in the management of the individual patient.MethodThe BMD of the lumbar spine and the proximal femur of 119 OA patients (83 postmenopausal female patients aged 50–83 and 35 male patients aged 36–86 years) who subsequently required hip or knee replacements, but were otherwise healthy, were measured by dual energy X-ray absorption (DXA), Hologic QDR-2000. We also measured biochemical markers of bone turn over, i. e., CICP, ICTP, DPD, PTH, estrogen, testosterone, bAP, hydroxy vitamin D and the normal blood count.ResultsThere was a high occurrence of a low BMD among the patients. A total of 28.9% of women were affected by OP and 52.9% by osteopoenie. This reflects the normal distribution of OP in the female population. Of the male patients 20% had OP and 38.8% osteopoenie. This is astonishing high. Age proved to be a significant factor in the degree of BMD. An association between disuse osteoporosis and degree of BMD in the OA affected joint could not be proven. The use of the biochemical markers for an earlier diagnosis or to assess bone metabolism in OP and OA was not possible.ConclusionWe can not support the hypotheses that OA prevents OP. Moreover, the occurrence of OP in our study reflected the incidence of OP in the average female and the astonishingly high incidence in the male population; however does not mean that the two conditions are mutually exclusive. We did not find that the biochemical markers of bone turn over could deliver additional information with respect to bone metabolism and an earlier diagnosis of OP.

Expression of stem cell factor receptor KIT (CD117) in aseptic hip prosthesis loosening

OBJECTIVE This study aimed to investigate specific inflammatory pathomechanisms, i.e. the expression of the stem cell factor receptor KIT (CD117) in tissue specimens from patients with aseptic hip prosthesis loosening (AHPL) with special emphasis on colocalization with the mast cell specific marker tryptase. METHODS Immunohistochemical analysis of CD117 was performed in tissue specimens from 10 patients with aseptically loosened acetabular components of failed non-cement total hip replacements and compared to control samples obtained at primary hip surgery (n=4). The CD117 expressing cells were characterized further with mast cell tryptase (MCT) by serial section analysis and a double staining method. CD117 and MCT expression was examined by semi-quantitative analysis. Additionally, double labeling of the CD117 or MCT expression by immunohistochemistry and of polyethylene (PE) particles by Oil Red reaction was performed. RESULTS In AHPL, CD117 was almost exclusively detected in MCT positive cells. Co-expression tended to be highly correlated (r=0.86, p<0.01). CD117 was found mainly in two regions: first, in perivascular lymphocyte-rich areas and; secondly, near macrophages and multinucleated giant cells (MGC). PE particles were not detected in CD117 and MCT positive cells. In control samples, CD117/MCT positive cells were less frequent. CONCLUSION This is the first report on CD117 expression in AHPL. CD117 is almost exclusively expressed in a distinct mast cell subgroup. As an important growth factor receptor, CD117 could play a major role in recruitment and activation of mast cells in AHPL. Furthermore, mast cells do not contain significant amounts of PE particles. However, it remains to be investigated whether this cell population could influence phagocytosis of PE particles. (Journal of Applied Biomaterials and Biome-chanics 2005; 3: 11-7).

Preserving the abductor mechanism in robotic THR: the influence of stem design and cutterpath.

Objective: The tip of the greater trochanter is the attachment site for the abductor muscles of the hip joint. Its preservation in robotic and conventional THR is important for normal gait. The effect of different stem designs and robotic cutterpaths on the preservation of the trochanter tip is examined. Materials and Methods: One anatomical stem, one straight stem, and one stem specifically designed for robotic THR were implanted virtually in CT scans of osteoarthrotic hip joints using the Torch preoperative planning unit (URS-ortho). In transverse sections of the trochanter tip, dimensions of the trochanter area removed by the milling tool were recorded for each stem design and different cutterpaths (3-axis versus 5-axis milling). Results: Five-axis milling showed significantly better results than 3-axis milling. For straight stems, more bone was removed than for anatomic stems. The most favorable results were achieved with 5-axis milling and a curved stem specifically designed for robotic THR. Conclusions: The introduction of 5-axis milling in robotic THR is an improvement of the technique and makes preservation of the abductor mechanism at the tip of the greater trochanter easier for the surgeon.