The relationship between cup design and the radiological signs of aseptic loosening in total hip arthroplasty

We assessed differences in the incidence and appearance of the radiological signs of loosening of the cup for various types of design. This was an observational study based on hip registry data of 15,340 patients with 17,951 total hip arthroplasties collected over a period of 33 years in 49 hospitals in Central Europe. The threaded and the press-fit titanium cups showed significantly less aseptic loosening than the other systems. The direction of migration and the frequency of the radiological signs of loosening differed between the cup systems and were time-dependent. Our findings indicate the superiority of uncemented threaded cups and press-fit titanium cups over other designs of cup.

[First trimester fetal sex determination in maternal serum using real-time PCR]

OBJECTIVE

Fetal sex prediction can be achieved using PCR targeted at the SRY gene by analyzing cell-free fetal DNA in maternal serum. Unfortunately, the results reported to date, show lack of sensitivity, especially in the first trimester of pregnancy. Therefore, determination of fetal sex by maternal serum analysis can not replace caryotype analysis following chorionic villus sampling.

PATIENTS AND METHODS

A new highly sensitive real-time PCR was developed to detect a SRY gene sequence in maternal serum. Analysis was performed on 121 pregnant women during their first trimester of pregnancy (mean gestational age: 11.8 weeks). Among them, 61 had at least one previous male-bearing pregnancy. Results were compared to fetal sex.

RESULTS

SRY PCR analysis of maternal serum was in complete concordance with fetal sex. Among the 121 pregnant women, 61 were bearing a male fetus and 60 a female fetus No false negative results were observed. Furthermore, no false positive results results occurred although 27 women carried female fetus during the current pregnancy, had at least one previous male-bearing pregnancy.

DISCUSSION AND CONCLUSION

This study demonstrates that a reliable, non-invasive sex determination can be achieved by PCR analysis of maternal serum during the first trimester of pregnancy. This non-invasive approach for fetal sex prediction should have great implications in the management of pregnant women carriers of an X-linked genetic disorder. Prenatal diagnosis is thus performed for male fetuses only, avoiding invasive procedures and the risk of fetal loss for female fetuses.

Treatment of cartilage defects of the talus by autologous osteochondral grafts

We reviewed retrospectively 11 patients who had been treated surgically by open autologous osteochondral grafting for symptomatic chondral or osteochondral defects of the dome of the talus between 1996 and 1999. The mean ages of the eight men and three women were 34.2 and 25.9 years, respectively, with a mean time to follow-up of 24 months. The results of functional outcome were prospectively obtained using the MODEMS AAOS foot and ankle follow-up questionnaire, the AOFAS ankle-hindfoot scale and the Hannover scores for the ankle.

The grafts were harvested from the ipsilateral knee. Good to excellent results were obtained for the ankle without adverse effects on the knee. We believe that autologous osteochondral grafting should be considered for the patient with a symptomatic osteochondral defect of the talus.

Treatment of cartilage defects of the talus by autologous osteochondral grafts

We reviewed retrospectively 11 patients who had been treated surgically by open autologous osteochondral grafting for symptomatic chondral or osteochondral defects of the dome of the talus between 1996 and 1999. The mean ages of the eight men and three women were 34.2 and 25.9 years, respectively, with a mean time to follow-up of 24 months. The results of functional outcome were prospectively obtained using the MODEMS AAOS foot and ankle follow-up questionnaire, the AOFAS ankle-hindfoot scale and the Hannover scores for the ankle. The grafts were harvested from the ipsilateral knee. Good to excellent results were obtained for the ankle without adverse effects on the knee. We believe that autologous osteochondral grafting should be considered for the patient with a symptomatic osteochondral defect of the talus.

First-trimester fetal sex determination in maternal serum using real-time PCR

Fetal sex prediction can be achieved using PCR targeted at the SRY gene by analysing cell-free fetal DNA in maternal serum. Unfortunately, the results reported to date show a lack of sensitivity, especially during the first trimester of pregnancy. Therefore, determination of fetal sex by maternal serum analysis could not replace karyotype analysis following chorionic villus sampling. A new highly sensitive real-time PCR was developed to detect an SRY gene sequence in maternal serum. Analysis was performed on 121 pregnant women during the first trimester of pregnancy (mean gestational age: 11.8 weeks). Among them, 51 had at least one previous male-bearing pregnancy. Results were compared with fetal sex. SRY PCR analysis of maternal serum was in complete concordance with fetal sex. Among the 121 pregnant women, 61 were bearing a male fetus and 60 a female fetus. No false-negative results were observed. Furthermore, no false-positive results occurred, even though 27 women carrying a female fetus during the current pregnancy had at least one previous male-bearing pregnancy. This study demonstrates that a reliable, non-invasive sex determination can be achieved by PCR analysis of maternal serum during the first trimester of pregnancy. This non-invasive approach for fetal sex prediction should have great implications in the management of pregnant women who are carriers of an X-linked genetic disorder. Prenatal diagnosis might thus be performed for male fetuses only, avoiding invasive procedures and the risk of the loss of female fetuses.

Accuracy of computer-guided screw fixation of the sacroiliac joint

Computer-assisted image guidance allows precise preoperative planning and intraoperative localization of surgical instruments. The technique recently was validated for the insertion of pedicle screws. In the laboratory, the precision of a surface-matching algorithm was evaluated for registration and accuracy and safety of screw placement into the vertebral bodies of S1 and S2 for fixation of the sacroiliac joint. Using six plastic pelves, 24 screw holes were made through the sacroiliac joint into the vertebral body of S1, and 12 holes were made through the sacroiliac joint into S2. The accuracy of the hole position was evaluated using a postoperative computed tomography examination. The safety factor was assessed by analysis of the remaining bone stock around the holes calculating a theoretical cylindrical volume being outside bone with increasing bore hole diameters. The registration was accurate with a mean error less than 1.4 mm in the posterior parts of the pelvis. The drilling followed precisely the preoperatively planned trajectories; perforation of the cortex of the sacrum was not observed. The safety factor of the S1 vertebral body is higher than that of S2 allowing larger diameter screw insertion into S1. This technique provides a safe and precise guide for transcutaneous or open insertion of iliosacral screws in cases of iliosacral dislocation or sacral fracture.

Surgical dislocation of the adult hip

Surgical dislocation of the hip is rarely undertaken. The potential danger to the vascularity of the femoral head has been emphasised, but there is little information as to how this danger can be avoided. We describe a technique for operative dislocation of the hip, based on detailed anatomical studies of the blood supply. It combines aspects of approaches which have been reported previously and consists of an anterior dislocation through a posterior approach with a ‘trochanteric flip’ osteotomy. The external rotator muscles are not divided and the medial femoral circumflex artery is protected by the intact obturator externus. We report our experience using this approach in 213 hips over a period of seven years and include 19 patients who underwent simultaneous intertrochanteric osteotomy. The perfusion of the femoral head was verified intraoperatively and, to date, none has subsequently developed avascular necrosis. There is little morbidity associated with the technique and it allows the treatment of a variety of conditions, which may not respond well to other methods including arthroscopy. Surgical dislocation gives new insight into the pathogenesis of some hip disorders and the possibility of preserving the hip with techniques such as transplantation of cartilage.

Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis

Surgical dislocation of the hip is rarely undertaken. The potential danger to the vascularity of the femoral head has been emphasised, but there is little information as to how this danger can be avoided. We describe a technique for operative dislocation of the hip, based on detailed anatomical studies of the blood supply. It combines aspects of approaches which have been reported previously and consists of an anterior dislocation through a posterior approach with a 'trochanteric flip' osteotomy. The external rotator muscles are not divided and the medial femoral circumflex artery is protected by the intact obturator externus. We report our experience using this approach in 213 hips over a period of seven years and include 19 patients who underwent simultaneous intertrochanteric osteotomy. The perfusion of the femoral head was verified intraoperatively and, to date, none has subsequently developed avascular necrosis. There is little morbidity associated with the technique and it allows the treatment of a variety of conditions, which may not respond well to other methods including arthroscopy. Surgical dislocation gives new insight into the pathogenesis of some hip disorders and the possibility of preserving the hip with techniques such as transplantation of cartilage.

Cardiovascular effects of SL65.0472, a 5-HT receptor antagonist

In this study, we describe the cardiovascular effects of SL65.0472 (7-fluoro-2-oxo-4-[2-[4-(thieno[3,2-c] pyridin-4-yl) piperazin-l-yl] ethyl]-1, 2-dihydroquinoline-1-acetamide), a novel 5-hydroxytryptamine (5-HT) receptor antagonist developed for the treatment of cardiovascular disease, in several in vivo models. The haemodynamic profile of SL65.0472 was evaluated in anaesthetised dogs. Following i.v. bolus doses of 0.03 mg/kg i.v. and 0.3 mg/kg, no significant changes in cardiac output, contractility or rate, systemic and pulmonary pressures, regional blood flows and vascular resistances or electrocardiogram were noted. After 1 mg/kg i.v. SL65.0472 significantly reduced arterial blood pressure. In conscious spontaneously hypertensive rats administration of SL65.0472 0.5 mg/kg p.o. had no effect on mean arterial blood pressure or heart rate. Vasoconstriction produced by 5-HT results primarily from the stimulation of two receptor subtypes, 5-HT(1B) and 5-HT(2A) receptors. In anaesthetised dogs SL65.0472 antagonised sumatriptan-induced decreases in saphenous vein diameter (5-HT(1B)-receptor mediated) with an ID(50) of 10.1 microg/kg i.v. (95% c.l. 8.3-12.4). In anaesthetised pithed rats SL65.0472 inhibited 5-HT pressor responses (5HT(2A)-receptor mediated) with ID(50) values of 1.38 microg/kg i.v. (95% c.l. 1.15-1.64) and 31.1 microg/kg p.o. (95% c.l. 22.6-42.6). The duration of the 5-HT(2A)-receptor antagonist effect of SL65.0472 following oral administration was evaluated in conscious rats. SL65.0472 (0.1 mg/kg p.o.) markedly inhibited 5-HT pressor responses 1 and 6 h after administration. Therefore, in vivo, SL65.0472 potently antagonises vasoconstriction mediated by 5-HT(1B) and 5-HT(2A) receptors but has minimal direct haemodynamic effects.

Prenatal diagnosis of congenital toxoplasmosis by duplex real-time PCR using fluorescence resonance energy transfer hybridization probes

The diagnosis of congenital toxoplasmosis frequently relies on PCR tests of amniotic fluid (AF). A duplex real-time quantitative PCR test based on fluorescence resonance energy transfer was developed to quantify the parasite load and to decrease the risk of contamination. An internal control based on the detection of 10 pg mouse DNA added to the AF was included to check for PCR efficiency. The relationship between the parasite load and the occurrence of ultrasonographic abnormalities in 87 samples of AF was analyzed. Seven AF (8%) had a parasitic load > 10(3); 14 (16%) had > 10(2)-< or =10(3); 26 (30%) had > 10-< or = 10(2); and 40 (46%) had < or = 10 parasites/ml. Four of the six AF with cerebral ventriculomegaly had >10(3) parasites/ml. The other two had 130 and 24 parasites/ml, respectively. No parasitic loads of > 10(3) parasites/ml and no ultrasonographic abnormalities were observed in the 11 AF with maternal toxoplasmosis in the third trimester. Therefore, there is a trend to associate high parasite count with ultrasonographic abnormality, but the main concern remains early maternal infection. The importance of quantification should be better evaluated with postnatal studies. The duplex LightCycler PCR test currently provides rapid and safe results.

The Burch-Schneider antiprotrusio cage in acetabular revision surgery: a mean follow-up of 12 years

A total of 38 acetabular revisions using a Burch-Schneider antiprotrusio cage in 37 patients (18 women and 19 men), with a mean age at surgery of 75 years (range, 55-88 years), were evaluated retrospectively with a mean follow-up of 12 years (range, 8-21 years). In 2 cases with total hip dislocation and in 1 case with a deep infection, revision of the antiprotrusio cages was required. Defining every revision of the antiprotrusio cage as the endpoint of survivorship, the antiprotrusio cage showed a survival rate of 92% after 21 years. Clinical evaluation of the surviving patients showed a mean Harris hip score of 76 points (range, 20-96). Radiologic evaluation revealed that 1 antiprotrusio cage was loose and that 4 femoral stems were loose. The Burch-Schneider antiprotrusio cage compares favorably with other devices with regard to long-term implant survival rate.

Strain distribution in plated and unplated sheep tibia an in vivo experiment

After plate osteosynthesis changes in bone biology and bone mechanics are observed in the plated bone segment. Compromise of the vascular supply in the plate bed leads to a remodelling process and to a temporary porosity in the bone cortex underneath the plate. In addition, the plate takes over some of the physiological loading of the bone, which in turn alters the normal strain distribution of the cortical bone tissue. The aim of the present study is to determine the tissue deformation of the sheep tibia in vivo and the changes in tissue strain due to plating with plates of different rigidities. Measurements were performed on the intact bone at the mid diaphysis using the strain gauge technique. With different connections on the tension bridge (Wheatstone bridge), the strain was measured separately for pure axial loading, bending, and torsion before and after plating with a 4.5 mm stainless steel or titanium DCP. Under physiological load the sheep tibia is mainly deformed in torsion (62%) and bending (33%), and much less in axial loading (5%). Plating with a steel plate reduces the overall tissue strain by 18%, with a titanium plate by 13%. This reduction is mainly due to a reduction in axial tissue strain due to axial loading and bending and less to the reduction of tissue strain under torsion. In our in vivo model, plating with steel or titanium plates leads to a reduction of the physiological tissue strains. The difference between the different plates is small due to the fact that the high tissue strain under torsion is only slightly affected by plating. Thus, from the purely mechanical point of view and with regard to preserving normal tissue strains as much as possible, titanium plates offer little advantage compared with stainless steel plates. But, titanium as an implant material may offer advantages with respect to tissue compatibility and infection resistance.

Effect of plate position relative to bending direction on the rigidity of a plate osteosynthesis. A theoretical analysis

Mechanical unloading of the plated bone segment is observed after plate osteosynthesis because the implant takes over a part of the physiological loading. Strain reduction in the bony tissue depends on the rigidity of the plate (cross-sectional area, geometrical form, and modulus of elasticity). The aim of the present study was to calculate theoretically the effect of plate position relative to bending direction on the overall bending stiffness of the composite system plate-bone. To calculate the rigidity, a cylindrical bone model with mechanical characteristics similar to a sheep tibia and a rectangular plate cross-section corresponding to a DC-plate with either a modulus of elasticity of steel or titanium was used. Calculations under different bending directions were performed according to the laws of the linear bending theory and the composite beam theory. The bending stiffness of a plate osteosynthesis reaches a minimum and a maximum respectively, in cases in which the bending moment acts in the direction of the main axis of the area moment of inertia of the plate. The minimum is present with the plate bent vertically, the maximum with the plate bent horizontally, e.g. on the tension side of the composite system--on the assumption that the bone structure opposite the plate is capable of withstanding compressive loading. For steel and titanium plates, factors of 2 and 2.25 respectively were calculated between the minimum and the maximum bending stiffnesses of the osteosynthesis. The bending rigidity of the plate alone has only a minimal effect on the total stiffness of the osteosynthesis. With a plate bent vertically, the difference between steel and titanium plates was 18%, with the plate bent horizontally (situated on the tension side), it was only 7%. The bending stiffness of a plate osteosynthesis depends on the cross-section, the geometrical form, and the modulus of elasticity of the plate, as well as on the plate position relative to the bending direction of the composite system. The modulus of elasticity of the plate is relatively unimportant, while with a given plate the individual plate position relative to the bending direction is of crucial importance. Thus, changing the modulus of elasticity of the plate cannot solve the problem of implant induced unloading of the bone cortex because the bending stiffness of the composite system depends much more on the plate position relative to the bending direction.

Anatomy of the medial femoral circumflex artery and its surgical implications

The primary source for the blood supply of the head of the femur is the deep branch of the medial femoral circumflex artery (MFCA). In posterior approaches to the hip and pelvis the short external rotators are often divided. This can damage the deep branch and interfere with perfusion of the head.

We describe the anatomy of the MFCA and its branches based on dissections of 24 cadaver hips after injection of neoprene-latex into the femoral or internal iliac arteries.

The course of the deep branch of the MFCA was constant in its extracapsular segment. In all cases there was a trochanteric branch at the proximal border of quadratus femoris spreading on to the lateral aspect of the greater trochanter. This branch marks the level of the tendon of obturator externus, which is crossed posteriorly by the deep branch of the MFCA. As the deep branch travels superiorly, it crosses anterior to the conjoint tendon of gemellus inferior, obturator internus and gemellus superior. It then perforates the joint capsule at the level of gemellus superior. In its intracapsular segment it runs along the posterosuperior aspect of the neck of the femur dividing into two to four subsynovial retinacular vessels. We demonstrated that obturator externus protected the deep branch of the MFCA from being disrupted or stretched during dislocation of the hip in any direction after serial release of all other soft-tissue attachments of the proximal femur, including a complete circumferential capsulotomy.

Precise knowledge of the extracapsular anatomy of the MFCA and its surrounding structures will help to avoid iatrogenic avascular necrosis of the head of the femur in reconstructive surgery of the hip and fixation of acetabular fractures through the posterior approach.

Anatomy of the medial femoral circumflex artery and its surgical implications

The primary source for the blood supply of the head of the femur is the deep branch of the medial femoral circumflex artery (MFCA). In posterior approaches to the hip and pelvis the short external rotators are often divided. This can damage the deep branch and interfere with perfusion of the head. We describe the anatomy of the MFCA and its branches based on dissections of 24 cadaver hips after injection of neoprene-latex into the femoral or internal iliac arteries. The course of the deep branch of the MFCA was constant in its extracapsular segment. In all cases there was a trochanteric branch at the proximal border of quadratus femoris spreading on to the lateral aspect of the greater trochanter. This branch marks the level of the tendon of obturator externus, which is crossed posteriorly by the deep branch of the MFCA. As the deep branch travels superiorly, it crosses anterior to the conjoint tendon of gemellus inferior, obturator internus and gemellus superior. It then perforates the joint capsule at the level of gemellus superior. In its intracapsular segment it runs along the posterosuperior aspect of the neck of the femur dividing into two to four subsynovial retinacular vessels. We demonstrated that obturator externus protected the deep branch of the MFCA from being disrupted or stretched during dislocation of the hip in any direction after serial release of all other soft-tissue attachments of the proximal femur, including a complete circumferential capsulotomy. Precise knowledge of the extracapsular anatomy of the MFCA and its surrounding structures will help to avoid iatrogenic avascular necrosis of the head of the femur in reconstructive surgery of the hip and fixation of acetabular fractures through the posterior approach.

Treatment of proximal humerus fracture using multiple intramedullary flexible nails

A total of 61 patients with a proximal humeral fracture was treated between January 1996 and March 1998 by closed reduction and fracture fixation with intramedullary Prévot (or Nancy) nails. Of these, 28 female and 25 male patients with a mean age of 52 years (range 3-91 years) were reviewed clinically and radiologically with a mean follow-up of 17 months (range 4-30 months). The mean Constant score was 63, the mean Neer score 74 and the mean visual analogue scale (VAS) 73. The 14 patients under 24 years old achieved a Constant score of 86, a Neer score of 99 and a VAS of 97, while 13 patients aged between 25 and 60 years had a Constant score of 67, a Neer score of 75 and a VAS of 71. The 26 patients older than 61 years had a Constant score of 48, a Neer score of 61 and a VAS of 61. One patient with total and 6 with partial humeral head necrosis as well as 5 pseudarthroses were noted. Proximal nail perforation of the humeral head due to fracture collapse was seen in 22 cases. Complications were more frequently observed in the elderly. End results were not related to the type of fracture. This minimally invasive technique decreases the rate of occurrence of avascular necrosis of the humeral head. However, fractures are not sufficiently stabilised, mainly because of bone loss induced by impaction and osteoporosis. Bone loss remains an unsolved problem, and alternative methods such as the use of bone substitute combined with minimally invasive techniques should be studied.

The anatomy and function of the gluteus minimus muscle

In order to investigate the functional anatomy of gluteus minimus we dissected 16 hips in fresh cadavers. The muscle originates from the external aspect of the ilium, between the anterior and inferior gluteal lines, and also at the sciatic notch from the inside of the pelvis where it protects the superior gluteal nerve and artery. It inserts anterosuperiorly into the capsule of the hip and continues to its main insertion on the greater trochanter. Based on these anatomical findings, a model was developed using plastic bones. A study of its mechanics showed that gluteus minimus acts as a flexor, an abductor and an internal or external rotator, depending on the position of the femur and which part of the muscle is active. It follows that one of its functions is to stabilise the head of the femur in the acetabulum by tightening the capsule and applying pressure on the head. Careful preservation or reattachment of the tendon of gluteus minimus during surgery on the hip is strongly recommended.

The anatomy and function of the gluteus minimus muscle

In order to investigate the functional anatomy of gluteus minimus we dissected 16 hips in fresh cadavers. The muscle originates from the external aspect of the ilium, between the anterior and inferior gluteal lines, and also at the sciatic notch from the inside of the pelvis where it protects the superior gluteal nerve and artery. It inserts anterosuperiorly into the capsule of the hip and continues to its main insertion on the greater trochanter.

Based on these anatomical findings, a model was developed using plastic bones. A study of its mechanics showed that gluteus minimus acts as a flexor, an abductor and an internal or external rotator, depending on the position of the femur and which part of the muscle is active. It follows that one of its functions is to stabilise the head of the femur in the acetabulum by tightening the capsule and applying pressure on the head. Careful preservation or reattachment of the tendon of gluteus minimus during surgery on the hip is strongly recommended.

Strain gauges used in the mechanical testing of bones. Part I: Theoretical and technical aspects

The internal restructuring of bone as a reaction to physiological load described by Wolff's law is related to both stress and strain in the bone. Bone is a rather brittle material, with nearly equal properties in tension and in compression: Elastic modulus E = 20 Gpa, tensile strength sigma tens = 200 Mpa (cortical bone). In biomechanics, it is very easy to assess strain using strain gauges. The theoretical and technical aspects specific to the use of strain gauges on bones are presented in this paper including how the measurements are taken and how the data is analyzed.

Strain gauges used in the mechanical testing of bones. Part II: "In vitro" and "in vivo" technique

How to choose and prepare the strain gauges for bonding on bones "in vitro" and "in vivo"? This communication aims to elucidate technical details and some applications: direct assessment of the axial load, the bending moment, and the torque applied to long bones by the physiological loads. As a typical example of application, we will show the assessment of stress protection due to plates on the bones in the sheep tibia.

Strain gauges used in the mechanical testing of bones. Part III: Strain analysis, graphic determination of the neutral axis

The problem addressed in this part is the analysis of the strain pattern within the bone, when the strain has been measured using strain gauges along the long axis of the diaphysis of a bone subjected to axial load, bending, or eccentric axial load. It is first necessary to obtain the position of the strain gauges using, for instance, computed tomography. The linear bending theory is then used to determine graphically the position of the neutral axis in a cross section and the strain field within the bone. An example of application is taken from the literature: Rybicky et al. (1) measured the reduction of strain within a plated horse metatarsus, relative to that of the intact bone. They made an analytical strain analysis. A comparison is made between the analytical results and the graphic ones, validating the graphic method.