[More muscle mass in men: explanatory model for superior outcome after total hip arthroplasty]

BACKGROUND

Men show better functional results after total hip arthroplasty (THA). The aim of this study was a patient-specific analysis of the hip joint muscles in comparison to the joint geometry.

METHODS

In this study 93 computed tomography (CT) scans of the pelvis (45 men, 48 women) were analyzed to determine hip joint geometry and the volume of the gluteus medius (GMV), gluteus maximus (GXV) and tensor fasciae latae (TFL) muscles. The abduction muscle volumes were analyzed with respect to patient-specific adduction moments.

RESULTS

The absolute total volume of the hip muscular system (TMV) was larger in men than in women (1913 ccm vs. 1479 ccm; p <0.0001). Men exhibited a more progressive increase of muscle volume as the adduction moment increases.

CONCLUSIONS

Men have a greater abduction muscle mass in order to balance adduction moments occurring in the hip joint and therefore have more muscle mass to compensate the inevitable intraoperative muscle damage during THA. This argument supports the extraordinary importance of muscle sparing surgical techniques in women.

Wound drainage in primary knee arthroplasty--a prospective randomized study

PURPOUSE OF THE STUDY: Wound drainage in surgical interventions has a long tradition. Regarding the primary TKA there are no valid data concerning the ideal point of time for removal. The objective of this prospective randomized study was to investigate which drainage procedure should be given preference with regard to wound healing, blood loss, development of intraarticular hematomas and early postoperative function.

MATERIAL AND METHODS

We documented the ROM, the knee circumference at the upper patellar pole preoperatively and on days 2, 4 and 6 postoperatively. The blood volume and loss was calculated. As surrogate parameter for wound healing we counted the amount of days until no residual secretion was observed via the wound/drainage site.

RESULTS

The results of our investigation do not show any significant difference with regard to the mentioned parameters.

CONCLUSIONS

In our investigation, we were unable to find any significant advantage of intraarticular drainage for 48 hours over 24 hours after primary total knee arthroplasty. After uncomplicated total knee arthroplasty we recommend removing drainage after 24 hours.

[Extension first technique for TKA implantation]

OBJECTIVE

Surgical technique in total knee arthroplasty (TKA) to combine the femur first and tibia first techniques in order to reduce surgical mistakes regarding rotation and alignment.

INDICATIONS

Symptomatic arthritis of the knee.

CONTRAINDICATIONS

General contraindications for TKA.

SURGICAL TECHNIQUE

Osseous preparation starting with a distal femur cut. Then the proximal tibia cut is accomplished and the knee is balanced in extension after checking for correct alignment. Bone-referenced positioning of the femoral cutting block for further preparation of the femur. Finally, the rotation of the femur is checked in 90° of flexion by means of ligament tension. If required, the rotation is checked and the flexion gap balanced, respectively.

POSTOPERATIVE MANAGEMENT

Mobilization with weight bearing and range of motion as tolerated.

RESULTS

In a prospective study, 267 knees (160 women, 107 men, average age of 69.3 [46-89] years) were followed up preoperatively and after 6 weeks. The clinical results were based on the American Knee Society score. The scores were 48.9 (32-68) preoperatively and 86.5 (75-100) at follow-up. Radiologically 92.1% of the knees showed a malposition <3°.

Periprosthetic fractures around the knee: update on therapeutic algorithms for internal fixation and revision arthroplasty

Effective treatment of periprosthetic fractures following TKA continues to represent a surgical challenge. The incidence and frequency of these complicated type of fractures is expected to increase as the number of TKA as well as the activity level of these patients steadily rises. A careful and correct analysis of the fracture pattern, its classification, the quality of the existing bone stock and the fixation / loosening of the underlying prosthetic system has to precede decision making for successful conservative or surgical treatment. Therefore, improved diagnostic radiographic imaging of fracture patterns and reliable assessment of prosthesis loosening progressive development of new implant methods and refinement of soft tissue preserving surgical techniques will hold the key for regaining the functional level prior to the fracture.

[TKA revision of semiconstraint components using the 3-step technique]

OBJECTIVE

The surgical goal is to achieve a pain free and stable knee joint after revision total knee arthroplasty in three steps. An important component of the technique is the reproducible restoration of the joint line.

INDICATIONS

Revision total knee arthroplasty.

CONTRAINDICATIONS

Complete bone loss at the knee joint (epicondyles and tibia plateau), persistent joint infection, loss of the extension apparatus, and neurological disease with progressive ligament instability.

SURGICAL TECHNIQUE

Implantation of revision components is performed in three steps. The first step is the positioning of the tibia component at the correct height and rotation. As the position of the tibial articular surface is independent of the knee position, the tibia serves as a reference both in extension and in flexion. The second step consists of balancing the knee joint in flexion and, thereby, definition of the flexion gap and the rotation of the femoral component. In the third step, the reconstruction and balancing of the knee joint in extension is performed.

POSTOPERATIVE MANAGEMENT

Mobilization with weight bearing and range of motion as tolerated depending on osseous and soft tissue condition at surgery. The surgical technique does not influence the further treatment.

RESULTS

In a prospective study, 168 consecutive knee revisions operated by the first author were examined clinically and radiologically preoperatively and at a mean follow-up of 38 months (range 22-61 months). There were 96 knees from women and 72 were from men with an average age of 74.6 years (range 51-92 years). Clinical results were based on the American Knee Society score. The score showed 47.6 (range 32-63) preoperatively and 81.5 (range 62-95) at follow-up. Radiologically, 92.7% of the knees showed a malposition <3°. The joint line was correctly reconstructed in 86.3% based on the preoperative plan; 89% of the patella showed correct tracking in the patella tangential view.

Induced apoptosis of chondrocytes by Porphyromonas gingivalis as a possible pathway for cartilage loss in rheumatoid arthritis

The role of bacterial infections in the pathogenesis of rheumatoid arthritis (RA) has gained increasing interest. Patients with RA often exhibit periodontal disease, which is associated with pathogens like Porphyromonas gingivalis. The present study examines the direct effects of P. gingivalis on apoptosis of human chondrocytes (a feature of inflammatory joint diseases) as one can assume an interrelation of pathogenesis of RA and P. gingivalis infections. Primary chondrocytes were infected with P. gingivalis. Early apoptotic and dead cell analysis was performed using Annexin-V, 7AAD, and propidium iodide and examined by flow cytometry and fluorescence microscopy. Caspase activation and DNA fragmentation were determined by western blot analysis and TUNEL reaction. Flow cytometry and fluorescence microscopy demonstrated an increase of Annexin-V-positive early apoptotic chondrocytes after infection. Western blot showed upregulation of activated caspase-3 expression, and TUNEL reaction revealed considerable DNA fragmentation following infection. The data show that P. gingivalis promotes early and later stages of apoptosis of primary human chondrocytes, which might contribute to the joint damage seen in the pathogenesis of RA.

Effects of celecoxib on the expression of osteoprotegerin, energy metabolism and cell viability in cultured human osteoblastic cells

BACKGROUND AND OBJECTIVE

The selective COX-2 inhibitor celecoxib is widely used to treat pain and inflammation in rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis. The drug has well-known important effects on immune cells but its direct and/or indirect influence on osteoblasts has not yet been explored in detail. This study aimed to investigate the dose-dependent effects of celecoxib on cell viability, energy metabolism and bone remodeling processes in cultured human osteoblastic cells.

METHODS

Primary human osteoblasts and MG-63 cells were incubated with celecoxib (2, 10, 50microM). Cell viability and apoptosis were determined by trypan blue, 7AAD and Annexin-V staining. Effects on cellular oxygen consumption were measured amperometrically using a Clark electrode. mRNA expression of GLUT-1 and OPG was determined by RT-PCR; OPG protein secretion by ELISA and HIF-1alpha protein expression by immunoblotting.

RESULTS

While celecoxib at a concentration of 2 and 10microM showed only marginal effects, a suprapharmacological concentration of 50microM influenced viability and energy metabolism, as well as OPG expression and secretion of osteoblastic cells. Cell viability was significantly reduced by celecoxib treatment. Celecoxib at 50microM stimulated oxygen consumption significantly. Corresponding experiments with the protonophore FCCP suggest that this effect is due to mitochondrial uncoupling. After 24h, GLUT-1 mRNA expression was significantly increased. HIF-1alpha protein was not expressed under any of our experimental conditions. We also showed that celecoxib at 50microM significantly inhibits OPG protein secretion leading to a compensative increase of mRNA expression.

CONCLUSION

Pronounced effects of celecoxib on cell viability (reduction), oxygen consumption (stimulation), GLUT-1 mRNA expression (stimulation) and OPG protein secretion (inhibition) in osteoblastic cells were observed only at 50microM-a concentration not reached by therapeutic doses giving plasma concentrations less than 10microM. On the contrary, celecoxib at 2 and 10microM showed only marginal effects, suggesting that celecoxib administration is probably safe with respect to bone metabolism in cases requiring potent treatment of pain and inflammation. However, higher intracellular concentrations, which might occur through accumulation, necessitate investigations with high concentrations.

Effects of Porphyromonas gingivalis on cell cycle progression and apoptosis of primary human chondrocytes

BACKGROUND

It has been suggested that bacterial infections have a role in the pathogenesis of rheumatoid arthritis (RA). P gingivalis, a Gram-negative, anaerobic rod, is one of the major pathogens associated with periodontal disease.

OBJECTIVE

To examine P gingivalis infection and its effects on cell cycle progression and apoptosis of human articular chondrocytes.

METHODS

Primary human chondrocytes cultured in monolayers were challenged with P gingivalis. Infection and invasion of P gingivalis into chondrocytes was analysed by scanning electron microscopy, double immunofluorescence and by antibiotic protection and invasion assay. Cell cycle progression of infected chondrocytes was evaluated by flow cytometry. Also, cell apoptosis was visualised by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) of DNA strand breaks and by western blot analysis.

RESULTS

Data showed that P gingivalis could adhere and infect primary human chondrocytes. After chondrocyte infection, intracellular localisation of P gingivalis was noted. Flow cytometry analyses demonstrated affected cell cycle progression, with an increase of the G(1) phase and a significant decrease of the G(2) phase after infection. In addition, increased apoptosis of P gingivalis-infected chondrocytes was visualised by TUNEL assay and by upregulation of caspase-3 protein expression.

CONCLUSION

These data demonstrate that P gingivalis infects primary human chondrocytes and affects cellular responses, which might contribute to the tissue damage seen in the pathogenesis of rheumatoid arthritis.

[Promotion of bone healing through clinical application of autologous periosteum derived stem cells in a case of atrophic non-union]

This case report describes the application of periosteum-derived mesenchymal stem cells in a patient with atrophic non-union of the distal femur after correction osteotomy. While biomechanical treatment devices for various bone defects are available in abundance, biological promoters for clinical application in situations of critical bone healing are still scarce. We showed radiographically that cultivated autologous periosteal bone precursor cells on a three-dimensional matrix can promote bone healing in a defect where numerous established methods had failed to lead to consolidation. To the best of our knowledge, this is the first clinical application of in-vitro cultivated autologous periosteum-derived cells for the healing of a large bone defect in humans.

[Musculoskeletal biomechanics of the knee joint. Principles of preoperative planning for osteotomy and joint replacement]

The long-term clinical outcome of surgical interventions at the knee is dependent upon the quality of the restoration of normal function, together with moderate musculoskeletal loading conditions. In order to achieve this, it is essential to consider biomechanical knowledge during the planning and execution of the procedures. Until now, such knowledge has only been available in books and journal manuscripts and is merely considered during preoperative planning. Its transfer into the specific intraoperative situation is, however, primarily dependent upon the surgeon's skills and understanding. Mathematical models hold the potential to provide the surgeon with detailed, patient-specific information on the in vivo forces, as well as their spatial and temporal distribution. Their application in clinical routine, however, requires a comprehensive validation. Based on a model validated against patient data, it has been shown that - mainly as a result of the action of the muscles - both the tibiofemoral as well as the patellofemoral joints experience substantial mechanical loads even during normal activities of daily living. The calculations further indicate that malalignment at the knee in the frontal plane of more than approximately 4 degrees results in considerably increased forces across the tibiofemoral joint. The actual change in force to a given degree of malalignment might, however, vary greatly between subjects. In order to additionally determine the distribution of the forces in more detail, a sufficiently accurate model of knee joint kinematics is required. In combination with MR-based in vivo imaging techniques, new mathematical models offer the possibility to capture the individual characteristics of knee kinematics and might additionally allow the effect of muscle activity on joint kinematics to be considered. By implementing these technologies in preoperative planning and navigation systems, up-to-date biomechanical knowledge can be made available at the surgeons' fingertips. We propose that optimizing the biomechanical conditions through using these approaches will allow the long-term function of the replaced joint to be significantly enhanced.

[Implant with a mobile or a fixed bearing in unicompartmental knee joint replacemen]

Although the goal of anatomical and functional joint reconstruction in unicompartmental knee replacement is well defined, no uniform implant design has become established. In particular, the differential indications for implantation of an implant with a mobile or a fixed bearing are still not clear. The long-term results of mobile and with fixed bearings are comparable, but there are significant differences in resulting knee joint kinematics, tribological properties and implant-associated complications. In unicompartmental knee replacement mobile bearings restore the physiological joint kinematics better than fixed implants, although the differences to total knee arthroplasty seem minor. The decoupling of mobile bearings from the tibia implant allows a high level of congruence with the femoral implant, resulting in larger contact areas than with fixed bearings. This fact in combination with the more physiological joint kinematics leads to less wear and a lower incidence of osteolyses with mobile bearings. Disadvantages of mobile bearings are the higher complication and early revision rates resulting from bearing dislocation and impingement syndromes caused by suboptimal implantation technique or instability. Especially in cases with ligamentous pathology fixed bearings involve a lower complication rate. It seems their use can also be beneficial in patients with a low level of activity, as problems related to wear are of minor importance for this subgroup. The data currently available allow differentiations between various indications for implants with mobile or fixed bearings, so that the implants can be matched to the patient and the joint pathology in unicompartmental knee joint replacement.

[Musculoskeletal load analysis. A biomechanical explanation for clinical results--and more?]

Mechanical loading of the lower extremities due to muscle and joint contact forces plays an important role in orthopaedic and trauma surgery. Detailed, patient specific information on the in vivo forces and their distribution is, however, currently not readily available to the surgeon in clinical routine. The goal of this study was to elucidate the relationship between the position of the cup and the musculoskeletal loading conditions at the hip using validated analyses, and further, to evaluate the predictions of the biomechanical conditions against the results of a clinical study. The results indicate that restoring the anatomical hip centre to its anatomical mediolateral position could help to reduce joint loads and add to the longevity of the reconstruction. The routine use of validated analyses of musculoskeletal loading conditions, such as in the presented example using standardised pre-operative planning and sound intra-operative decision support systems, could contribute to securing a high standard in patient treatment.

[The reconstruction of extended acetabular bone defects in revision hip arthroplasty--risk factors for migration and loosening using the pedestal cup]

AIM

For the reconstruction of extended acetabular bone defects in revision hip arthroplasty different implants and techniques are available.However, in cases with a broad operative range of new implants, specific indications must be determined. The aim of this study is to determine the risk factors for migration and loosening associated with implantation of the pedestal cup.

METHOD

In a retrospective study the first 50 implantations of the pedestal cup in our hospital for high-grade acetabular defects (Paprosky classification II and III) were examined after a medium period of 26 months. Differences between radiologically loosened and osteal integrated implants in consideration of the preoperative osseous situation(defect size and morphology, bone density)as well as the implant positioning were determined as risk factors of an implant failure.

RESULTS

Three (6%) intraoperative implant-associated complications occurred, which were in the phase of the initial learning curve. In the early postoperative period 10 hip dislocations (20%)occurred. Two septic loosenings (4%) and 6 aseptic loosenings (12%) were observed. In 7 further cases a significant migration of the implant was assessed in the first months after surgery, a solid osteal integration did not appear. As risk factors for an implant loosening were determined:a missing reconstruction of the defect behind the pedestal cup with allogenous bone graft(p = 0.002), a lateralisation of the rotation centre(p = 0.023), the absence of the craniolateral wall (p = 0.002) and the presence of osteoporosis(p = 0.026).

CONCLUSION

The pedestal cup is an implant that is well usable in many high-grade acetabular defect situations with good mid-term results; however,contraindications do exist. In cases with a significant osteoporosis, a missing sclerosis of the cranial acetabulum as well as extended damage of the lateral ilium and its absence, respectively, alternative procedures should be considered.

Rekonstruktion des Streckapparats mittels freiem, allogenem, gefriergetrocknetem Patellatransplantat

Allograft reconstruction of a deficient extensor mechanism is sufficient using an allogenic, freeze-dried patellar graft sterilized with peracetic acid. The reduced risk of infection is an advantage over fresh-frozen grafts.

[Reduction of arthrosis associated knee pain through a single intra-articular injection of synthetic hyaluronic acid]

AIM

Conventional hyaluronic acids need three to five injections for therapeutic success, whereas Durolane), a synthetic hyaluronic acid, needs only a single injection. Clinical outcome using Durolane should be compared with the results of studies using hyaluronic acids or glucocorticoids.

METHOD

Fifty patients with primary gonarthrosis stages I-III (Kellgren Score) were investigated for knee function, pain intensity, and quality of life. The knee and osteoarthritis outcome score (KOOS), visual analogue scale (VAS), and European quality of live score (EQ-5D), as well as motion of the knee were measured. Patients were investigated before, and 2, and 24 weeks after injection.

RESULTS

Two weeks after injection, the subjective function of knee and quality of life had increased significantly. In the following 22 weeks, all parameters increased significantly (quality of life and activity +19%; range of motion active 109 vs. 115 degrees ; pain, 55 vs. 41 mm (VAS); all p<0.01).

CONCLUSION

We conclude that a single injection of Durolane can reduce arthrosis associated knee pain sufficiently. Our data are comparable with those published in clinical studies using other hyaluronic acids. The effects of Durolane are delayed but more sustained compared than those found for glucocorticoids. Because of the single injection, we see an advantage in using Durolane compared to other conventional hyaluronic acids and glucocorticoids.

Computer tomographically determined design parameters for optimized fit of an acetabular reconstruction cage

PURPOSE OF THE STUDY

Reinforcement rings are widely used for treatment of large acetabular defects but significant migration due to a lack of implant integration into the bone is a common problem. Although insufficient congruence between implant and acetabular bone has been identified main factor in early implant loosening, there are no reconstruction ring design parameters based upon anatomical data of the pelvis available.

MATERIAL

In this study such parameters were calculated on the basis of standardized computer tomograms of the hip region of 10 male and 10 female patients (40 data sets).

METHODS

The center of rotation, the acetabular entrance plane and the geometry of a simulated cranial and caudal flange of a reconstruction ring were determined. The flanges geometry was defined by the angles between the flanges and the entrance plane, the angle between the flange projections onto the entrance plane, the torsion and the width of each flange depending on the distance to the center of rotation, and the flanges torsion and width at their origin at the acetabular circumference.

RESULTS

An optimal alignment between reconstruction ring and the periacetabular bone could be achieved with a medial angulation of 19.9 degrees +/- 19.4 degrees of the cranial and 14.7 degrees +/- 7.1 degrees of the caudal flange against the entrance plane. The angle between the flanges projections onto the entrance plane was calculated to be 162.2 degrees +/- 6.4 degrees . At its origin from the acetabular circumference the cranial flange is twisted 28.5 degrees , the caudal flange -0.8 degrees against the entrance plane. The maximal flanges widths were calculated to 21-54 mm for the cranial and 22-25 mm for the caudal flange depending on the distance from the acetabular circumference.

DISCUSSION & CONCLUSION

The given design parameters may result in optimized implants respecting the pelvic anatomy and possibly providing improved fixation.

[Accuracy of determination of the hip centre in navigated total knee arthroplasty]

AIM

In navigated knee arthroplasty the hip centre is determined by rotary motion of the femur (pivoting). The accuracy of this functional hip centre determination in vivo is unclear. In the following paper the accuracy of pivoting in the determination of the hip centre was examined.

METHODS

Navigated (TC-PLUS, Solution, PLUS Orthopedics) total knee arthroplasty (PI Galileo, PLUS Orthopedics) was performed on 25 patients with primary arthritis of the knee joint. The position of the femoral component and the hip centre were postoperatively determined by computer tomography. Through comparison with the intraoperatively documented data, the deviation of the pivoted from the true hip centre in the frontal and sagittal planes was calculated. The degree of arthritis of the hip was determined on plain radiographs according to Kellgren.

RESULTS

The mean deviation was determined to 1.0 +/- 0.7 degrees in the frontal plane and 2.5 +/- 1.6 degrees in the sagittal plane (p = 0.002). This corresponds to a mean overall deviation of 20 +/- 10 mm. The data were continuously, non-parametrically distributed without any outliers. A great range of motion (ROM) in the frontal as well as sagittal planes during pivoting resulted in a less accurate determination of the hip centre. There was no correlation to the degree of arthritis of the hip.

CONCLUSION

The results indicate a recommendable ROM during pivoting for maximal accuracy of hip centre determination of 20 to 30 degrees in the sagittal plane and 30 to 40 degrees in the frontal plane. Arthritis of the hip is not a contraindication for functional determination of the hip centre.

Varianz der Epikondylenerfassung bei der navigierten Knieendoprothesenimplantation

BACKGROUND

The aims of this study were the quantification of the accuracy of registration of the epicondylar axis (EA) in navigated total knee arthroplasty (TKA) and the identification of presumed factors influencing this accuracy.

METHODS

A total of 32 navigated TKAs were performed and the surgical EA registered. Postoperatively, the difference from the surgical EA determined by computed tomography was calculated. Presumed factors influencing the accuracy were sex, preoperative malalignment, stability and range of motion, operated side, body mass index, and component size.

RESULTS

The absolute error was calculated to be 1.4+/-1.3 degrees . Alignment according to the intraoperatively defined axes would have resulted in three outliers (>3 degrees malalignment). The operated side was the only factor showing a significant effect on the accuracy. The absolute error in left knee joints was calculated to be 0.9+/-0.7 degrees (max. 2.4 degrees ) and in right knee joints to be 2.0+/-1.5 degrees (max. 5 degrees, p=0.021).

CONCLUSIONS

The surgeon stood on the patient's right side in every case, so that right knee joints were operated from the lateral and left ones from the medial side. A medial position of the surgeon to the knee joint during registration of EA is recommended because it results in a higher accuracy than a lateral position.

Effects of dexamethasone and celecoxib on calcium homeostasis and expression of cyclooxygenase-2 mRNA in MG-63 human osteosarcoma cells

OBJECTIVE

Glucocorticoids and selective COX-2 inhibitors are potent anti-inflammatory agents. They are also suggested to influence bone physiology and remodeling. Here we searched for effects of dexamethasone and celecoxib on crucial parameters of bone physiology that could be therapeutically relevant.

METHODS

The human osteosarcoma cell line MG-63 was used to measure effects of these drugs on (i) intracellular calcium concentration ([Ca2+]i) using a microfluorometric technique, (ii) alkaline phosphatase and osteocalcin levels (EIA) and (iii) the expression of cox-2 mRNA (quantitative real time PCR). Measurements were performed in Vitamine D-incubated quiescent cells and in cells stimulated with TNF-alpha and IL-1beta.

RESULTS

We found the cytokine-stimulation to increase [Ca2+]i which was prevented by dexamethasone already after 30 min and still after 48 h. Dexamethasone was without any effect on [Ca2+]i in quiescent cells. Celecoxib had no measurable short-term or long-term effects neither in quiescent nor in stimulated cells. Vitamin D stimulated the expression of cox-2 mRNA which was further enhanced by TNF-alpha/IL-1beta. Dexamethasone did not have any measurable effects on COX-2 expression after 30 min, but a pronounced inhibition was seen after 48 h. In contrast, celecoxib had no effect on COX-2 expression. Neither of the drugs had any effect on the secretion of alkaline phosphatase and osteocalcin.

CONCLUSION

We found dexamethasone to inhibit the [Ca2+]i increase in MG-63 cells following stimulation and to reduce considerably COX-2 expression via the genomic pathway. In contrast, celecoxib did not show any measurable short-term or long-term effects on the parameters of bone physiology measured.

Achskorrektur bei Knietotalendoprothesenrevisionen

Implant malalignment is a major cause for early loosening, increased wear, painful limitation of motion, and patient dissatisfaction in total knee arthroplasty. Validated diagnostic algorithms and a deeper understanding of the pathological mechanisms underlying functional deficits and pain resulting from malalignment explain the increasing number of revision operations on unloosened prostheses, which are now nearly as common as revisions for implant loosening. Common reasons are component malpositioning are a shifted joint line, or a non-physiological patella position. The success of any revision procedure basically depends on: (1) correct component positioning, (2) equal and symmetrical flexion and extension gaps, (3) restoration of joint line, and (4) a physiological patella height. The adequate grade of implant constraint has to be determined intra-operatively. A higher loosening rate of constrained implants as well as increased wear and painful limitation of motion in case of instability have to be taken into account. In the present work, a diagnostic and therapeutic algorithm for malalignment of knee prostheses is presented.

The management of necrosis-associated and idiopathic bone-marrow oedema of the proximal femur by intravenous iloprost

Bone-marrow oedema can occur both in isolation and in association with necrosis of bone, but it has not been shown whether each respond to the same methods of treatment.

We treated 16 patients with isolated oedema and 17, in which it was associated with necrosis of the proximal femur, with the prostacyclin derivative iloprost, which has been shown to be effective in the idiopathic form. The Harris hip score, the range of movement, the extent of the oedema as measured by MRI, pain on a visual analogue scale and patient satisfaction were recorded before and subsequent to treatment.

In both groups, we were able to show a significant improvement (p < 0.001) in these observations during the period of follow-up indicating that iloprost will produce clinical improvement in both circumstances.

Endothelin-1 is secreted after total knee arthroplasty regardless of the use of a tourniquet

Early infections and wound healing disorders after implantation of a total knee replacement occur regardless of the intraoperative use of a tourniquet. The biochemical regulatory processes responsible for the disturbances in microcirculation and thus the potential therapeutic options have yet to be elucidated. The hypothesis of the present paper was that endothelin-1 (ET-1), a mediator of microcirculation disturbances in parenchymatous organs, also is released after major operations on peripheral joints. The concentration of ET-1 in the plasma was determined preoperatively and at 10 postoperative time points (5 min-48 h) with (group A, n=10) and without the use of a tourniquet (group B, n=10). The ET-1 concentration achieved its maximum 6h after opening the tourniquet, which corresponded to 3.3 times the preoperative value. Without a tourniquet, the concentration maximum (2.9 times the baseline value) was achieved already 1.5 h after the end of the operation. However, the total amount of ET-1 secreted over 24 h was identical in both groups (p>0.5). We conclude that the tissue hypoxia resulting from the use of a tourniquet modulates ET-1 secretion, but that traumatization during the operation has a much stronger influence on the total amount secreted. ET-1 antagonists thus should be discussed for the drug prophylaxis of wound healing disorders, regardless of the use of a tourniquet.