Femoral cement extraction in revision total hip arthroplasty--an in vitro study comparing computer-assisted freehand-navigated cement removal to conventional cement extraction.

BACKGROUND: Revision surgery of cemented femoral stems in total hip arthroplasty is gaining more and more importance, but cement removal in revision hip arthroplasty may be technically challenging. Conventional manual cement removal can be time consuming and be associated with complications such as cortical perforation, fracture, or bone loss. The aim of this study was to investigate the practicability of computer-navigated cement removal. MATERIAL AND METHODS: In an in vitro study, we examined the removal of the bone cement out of composite bones. To evaluate accuracy, the bones were scanned before and after cement removal with the ISO-C three-dimensional C-arm computed tomography system to determine the amount of unremoved cement and the loss of bone stock. The data of freehand-navigated cement removal is compared to conventionally extracted cement using levers and drills under X-ray control. RESULTS: The mean time for cement removal was 29 ± 5 min for the conventional method and 32 ± 8 min for the freehand-navigated cement removal. Here, excepting the preparatory examinations, the navigated cement removal only took 13 ± 5 min. The measured temperature during polymerization was 36 ± 5 °C and during navigated cement removal was 37 ± 8 °C. In the distal part of the femur, cement removal was more accurate with the conventional method compared to the navigated one. CONCLUSION: The freehand-navigated cement removal, with the exception of the preparatory examinations, is time saving compared to the conventional method. However, a potential for technical development especially for the milling device and accuracy exist.

Endoglin (CD105) expression differentiates between aseptic loosening and periprosthetic joint infection after total joint arthroplasty.

The differentiation between aseptic loosening and periprosthetic joint infection (PJI) after total joint arthroplasty is essential for successful therapy. A better understanding of pathogenesis of aseptic loosening and PJI may help to prevent or treat these complications. Previous investigations revealed an increased vascularization in the periprosthetic membrane in cases of PJI via PET signals. Based on these findings our hypothesis was that PJI is associated with an increased neovascularization in the periprosthetic membrane. Tissue samples from periprosthetic membranes of the bone-implant interface were investigated histologically for inflammation, wear particles, vascularization and fibrosis. To identify vascular structures antibodies against CD 31, CD 34, factor VIII and CD 105 (endoglin) were applied for immunohistochemical investigations. According to a consensus classification of Morawietz the tissue samples were divided into four types: type I (wear particle induced type, n = 11), type II (infectious type, n = 7), type III (combined type, n = 7) and type IV (indeterminate type, n = 7). Patients with PJI (type II) showed a pronounced infiltration of neutrophil granulocytes in the periprosthetic membrane and an enhanced neovascularization indicated by positive immunoreaction with antibodies against CD 105 (endoglin). Tissue samples classified as type I, type III and type IV showed significantly less immune reaction for CD 105. In cases of aseptic loosening and PJI vascularization is found in different expression in periprosthetic membranes. However, in aseptic loosening, there is nearly no neovascularization with CD 105-positive immune reaction. Therefore, endoglin (CD 105) expression allows for differentiation between aseptic loosening and PJI.

A cell-free collagen type I device for the treatment of focal cartilage defects.

The purpose of this study was to evaluate the potential value of a cell-free collagen type I gel plug for the treatment of focal cartilage defects. Cellular migration and proliferation was addressed in vitro, and the formation of repair tissue in a nude mouse-based defect model. A cell-free plug made of collagen type I was placed in the center of an incubation plate. Surrounding space was filled with a collagen type I gel (Arthro Kinetics, Esslingen, Germany) seeded with 2 x 10(5) human articular chondrocytes/mL gel. After cultivation for up to 6 weeks in vitro, samples were subject to histological and immunohistochemical staining and gene expression analysis. Subsequently, chondral defects of human osteochondral blocks were treated with the plug, and specimens were cultivated subcutaneously in nude mice for 6 weeks. The repair tissue was evaluated macroscopically, and collagen type II production was investigated immunohistochemically. In vitro, morphology of immigrated cells did not show any differences, as did collagen type II gene expression. After 4 weeks, the plug was homogeneously inhabited. After 6 weeks of cultivation in nude mice, collagen gel plug treatment led to a macroscopically excellent repair tissue. Histological staining revealed a tight bonding, and the collagen gel plug started to be remodeled. We conclude that the novel collagen gel plug device offers an environment favorable for the migration of articular chondrocytes and leads to a good-quality repair tissue in the nude mouse model. The arthroscopic transplantation of a collagen gel plug may be one option in the treatment of focal cartilage defects.

Condensed cellular seeded collagen gel as an improved biomaterial for tissue engineering of articular cartilage.

Three-dimensional autologous chondrocyte implantation based on collagen gel as matrix scaffold has become a clinically applied treatment for focal defects of articular cartilage. However, the low biomechanical properties of collagen gel makes intraoperative handling difficult and creates the risk of early damages to the vulnerable implant. The aim of the study was to create a stabilized form of collagen gel and to evaluate its biomechanical and biochemical properties.Collagen type-I gel was seeded with human articular chondrocytes. 20 samples were subject to condensation which was achieved mechanically by compression and filtration. Control samples were left uncondensed. From both types of gels 10 samples were used for initial biomechanical evaluation by means of unconfined compression and 10 samples were cultivated under standard conditions in vitro. Following cultivation the samples were evaluated by conventional histology and immunohistochemistry. The proliferation rate was calculated and matrix gene expression was quantified by real-time PCR.The biomechanical tests revealed a higher force carrying capacity of the condensed specimens. Strain rate dependency and relaxation was seen in both types of collagen gel representing viscoelastic material properties. Cells embedded within the condensed collagen gel were able to produce extracellular matrix proteins and showed proliferation.Condensed collagen gel represents a mechanically improved type of biomaterial which is suitable for three-dimensional autologous chondrocyte implantation.

[Surgical principles and clinical experiences with the DUROM hip resurfacing system using a lateral approach]. / Operationstechnik und klinische Ergebnisse des DUROM-Hip-Resurfacing-Systems mit dem lateralen Zugang.

OBJECTIVE: Objective Bone-preserving hip resurfacing in young and active patients using a soft-tissue-sparing, modified transgluteal, lateral approach. INDICATIONS: Primary hip osteoarthritis in physically active, working patients aged < 65 years (males) and < 60 years (females). Good bone quality. CONTRAINDICATIONS: Male patients > or = 65 years of age, female patients > or = 60 years of age. Necrosis of the femoral head. Varus deformity of the femoral neck with a reduced horizontal femoral offset. Femoral head cysts (> 1 cm in diameter). Infection. Osteoporosis. Rheumatoid arthritis. Tumor. Reduced renal function. Leg length difference (> or = 1 cm). Metal allergy. Previous femoral neck fracture. Previous intertrochanteric femoral osteotomies. SURGICAL TECHNIQUE: Supine position of the patient. Modified transgluteal, lateral approach to the hip joint. Luxation of the femoral head. First, reaming of the femoral head to improve visualization of the acetabular cup. Central positioning of the guide wire in the femoral neck in a slight valgus position of approximately +5 degrees to the anatomic collodiaphyseal (CCD) angle using the mechanical targeting device. Overdrilling of the central guide wire to the appropriate depth for the implant. Central insertion of the guide rod. Preparation of the femoral head over the guide rod using cylinder cutters one or two sizes larger than the smallest possible femoral component. Cement-free implantation of the acetabular component according to the predetermined definitive size of the femoral component. Final preparation of the femoral head using profile, surface and forming cutter. Following cemented implantation of the femoral component, repositioning of the hip joint and conclusion of the surgical procedure. POSTOPERATIVE MANAGEMENT: Mobilization of the patient using two forearm crutches as of the 1st day after surgery. Removal of the Redon drains after 24 h. Partial weight bearing of 20 kg for 3 weeks under continuation of thrombosis prophylaxis. Limitation of hip flexion to 90 degrees during the first 6 postoperative weeks, and no adduction and forced external rotation allowed in order to avoid luxation. Avoidance of sports involving the loads of jumping and axial impact loading for 12 postoperative months. RESULTS: Analysis involved the pre- and postoperative functions of 72 patients with a total of 82 prostheses and a mean durability time of 29.2 +/- 11 months based on the Harris Hip Score (HHS), the modified UCLA (University of California, Los Angeles) activity index, and the Merle d'Aubigné Score. Postoperatively, prosthetic angle and femoral offset as well as periprosthetic signs of loosening/lytic areas were assessed by means of radiology and compared with the preoperative CCD angle and femoral offset. Compared to the preoperative evaluation, follow-up yielded a significant increase in the average HHS values (94 +/- 4.6 vs. 40.1 +/- 7 points), the modified UCLA activity index (8.9 +/- 2.6 vs. 4.6 +/- 2.2), and the Merle d'Aubigné Score (17.9 +/- 1.9 vs. 7.3 +/- 2.4; p < or = 0.05). In 98.8%, a solid osteointegration of the cup and femoral components was observed. The average deviation of the physiological CCD angle (136.6 degrees +/- 3.6 degrees ) from the postoperative angle of the prosthesis (142.6 degrees +/- 4.9 degrees ) was 6 degrees +/- 2.8 degrees . The postoperative femoral offset was reduced by an average of 2.3 mm compared to the preoperative offset. During clinical follow-up n = 2 prostheses (2.5%) required revision (one femoral neck fracture; one periarticular ossification [Brooker III]).

[Fluoroscopic navigation versus conventional manual positioning of the femoral component for hip resurfacing: first experimental trial]. / Fluoroskopische Navigation versus konventionelle manuelle Positionierung der Femurkomponente beim Oberflächenersatz der Hüfte: erste experimentelle Erprobung.

BACKGROUND: The most essential improvement of modern hip resurfacing arthroplasty is the metal-on-metal bearing as well as the integration of a procedure for the exact and repeatable positioning of the femoral component through a specific mechanical alignment instrument. Nevertheless, the main reasons for early implant failure are mal-positioning of the femoral component and notching of the femoral neck during femoral head preparation. MATERIALS AND METHODS: In the context of an in vitro study, in each case six DUROM-Hip resurfacing prostheses were implanted in artificial femora with the prosthesis-specific mechanical alignment instrument, as well as under navigation control. The aim of the study was to evaluate the functionality and accuracy of a computer-assisted planning and navigation system on the basis of a navigation module library from Surgitaix AG (Aachen, Germany), as well as a comparison with the prosthesis-specific mechanical alignment instrument. RESULTS: The main angulation error between planning and navigation of the stem-shaft angle was 0.2+/-1.2 degrees for the navigation system and 6.5+/-4.1 degrees for the mechanical alignment instrument, the main anterior offset error was 1.2+/-1.2 mm vs. -0.83+/-4.1 mm. The mean time for all five planning and navigation steps was 17+/-1.2 min vs. 14+/-0.8 min. The main distance error between planning and navigation was 1.9+/-0.6 mm for the navigation system, and 5.3+/-2.4 mm for the mechanical alignment instrument. Femoral notching was not observed for navigational or conventional positioning. CONCLUSION: The computer-assisted fluoroscopic planning and navigation system for hip resurfacing showed, within the scope of this in vitro study, first promising experiences. The system approves a practicable planning with a high accuracy in implementation. Nevertheless, the potential benefit has to be evaluated in further clinical studies, especially from the perspective of a possible integration of this navigation system into the clinical workflow. Further studies should consider a fluoroscopy-assisted range of motion assessment under consideration of an additional cup-module to enhance the postoperative range of motion after hip resurfacing procedures.

Assessment of leech therapy for knee osteoarthritis: a randomized study.

BACKGROUND AND PURPOSE: Symptomatic treatment of osteoarthritis of the knee with leeches is presently undergoing a renaissance. Previous studies have shown methodical weaknesses. In the present study patients were blinded regarding the treatment, and a control group was included to explore possible differences in various subjective clinical scores and intake of pain medication over time between leech therapy and placebo control. PATIENTS AND METHODS: 113 patients with advanced osteoarthritis of the knee were included. The patients were randomized to a single treatment group, group I (single leech application, n = 38), a double treatment group, group II (double application, n = 35), and a control group (n = 40). The second treatment in group II took place after an interval of 4 weeks. The treatment in the control group was simulated with the help of an "artificial leech". Results were documented with the KOOS and WOMAC scores and also a visual analog scale (VAS) for pain. Changes in the use of pain medication were monitored over 26 weeks. RESULTS: An improvement in KOOS and WOMAC scores, and also in VAS, was found in all 3 groups following treatment. These improvements were statistically significant for treatment groups I and II during the complete follow-up period. The reduction in individual requirements for pain medication was also statistically significant. The greatest improvement was seen in the group treated twice with the leeches, with a long-term reduction of joint stiffness and improved function in the activities of daily living. INTERPRETATION: Leech therapy can reduce symptoms caused by osteoarthritis. Repeated use of the leeches appears to improve the long-term results. We have not determined whether the positive outcome of the leech therapy is caused by active substances released during the leeching, the placebo effect, or the high expectations placed on this unusual treatment form.

Amphiphilic bonder improves adhesion at the acrylic bone cement-bone interface of cemented acetabular components in total hip arthroplasty: in vivo tests in an ovine model.

INTRODUCTION: Even following the introduction of the "third generation" cementing technique, an improvement of the fixation of the acetabular component similar to that of the femoral has not been shown in clinical studies. The goal of the present study was to achieve a better stability with the use of an amphiphilic bonder while preserving the mechanically important subchondral sclerosis. MATERIALS AND METHODS: In a total of 20 sheep, a cemented total hip replacement was implanted. In the treatment group (n = 10), the implantation was carried out following surface conditioning of the acetabular bed with an amphiphilic bonder. All the sheep were followed for 9 months. To assess the biocompatibility, the osseous ingrowth at the cement-bone interface was depicted with the help of an in vivo fluorescent marking of the osteoblasts. Additionally, conventional radiographs were obtained over the course of treatment. Finally, the ovine pelvic regions were split following a standardized technique allowing for histological evaluation of the cement-bone interfaces. RESULTS: The acetabular components of the treatment group revealed a stable cement-bone compound. In the control group, the implants were easily dislodged from their beds. This finding was consistent with the radiological and histological results, which had revealed increased, progressive lytic radiolucent lines and the interposition of fibrous tissue at the cement-bone interface in the control group compared to the treatment group. The bonder was biocompatible. CONCLUSION: Following the application of the bonder, the cemented acetabular components revealed an improved stability without signs of inflammation or neoplasia in a viable acetabular osseous bed. With the help of this technique, the in vivo longevities of cemented acetabular components can be increased in the clinical setting without sacrificing the biomechanical relevant subchondral sclerosis.

[ Improvement of femoral bone-cement adhesion in cemented revision hip arthroplasty by application of an amphiphilic bonder in a dynamic femur expulsion testing in vitro ]. / Steigerung der femuralen Knochen-Knochenzement-Verbundfestigkeit in der zementierten Revisionshüftendoprothetik durch einen amphiphilen Knochenhaftvermittler im dynamischen in-vitro Ausstossversuch.

Cemented femoral stems have shown decreased longevity compared to cementless implants in hip revision arthroplasty. The aim of this study was to evaluate the effect of an amphiphilic bonder on bone cement stability in a biomechanical femur expulsion test. A simplified hip simulator test setup with idealised femur stem specimens was carried out. The stems were implanted into bovine femurs (group 1: no bonder, n=10; group 2: bonder including glutaraldehyde, n=10; group 3: bonder without glutaraldehyde, n=10). A dynamic loading (maximum load: 800 N; minimum load: 100 N; frequency: 3 Hz; 105 cycles) was performed. Subsequently, the stem specimens were expulsed axially out of their implant beds and maximum load at failure was recorded. The static controls showed a mean maximum load to failure of 4123 N in group 1, 8357.5 N in group 2 and 5830.8 N in group 3. After dynamic loading, the specimens of group 2 reached the highest load to failure (8191.5 N), followed by group 3 (5649.5 N) and group 1 (3462 N), respectively. In group 2, we observed nine periprosthetic fractures at a load of 8400 N without signs of interface loosening. Application of an amphiphilic bonder led to a significant improvement of bonding stability, especially when glutaraldehyde was added to the bonder. This technique might offer an increased longevity of cemented femur revision stems in total hip replacement.

Measures for reducing ultra-high-molecular-weight polyethylene wear in total knee replacement: a simulator study.

Wear of ultra-high-molecular-weight polyethylene (UHM-WPE) inlays is associated with aseptic loosening in total knee replacement (TKR). The aim of this study was to investigate the in vitro performance of a TKR system that combines several measures to decrease UHMWPE wear. Tests were carried out on a BPK-S Integration system (R&D, P. Brehm Chirurgie-Mechanik, Weisendorf, Germany) according to ISO 14,243-1 in a knee joint simulator. Calf serum with a high protein concentration of 30 g/l was chosen as the test lubricant. PE wear was measured gravimetrically. Particle analysis was performed by scanning electron microscopy, with measurement of particle size and shape. Low mean wear rates of 1.20 mg per million cycles were found for the fixed bearing type and 2.47 mg per million cycles for the rotating-platform bearing design. Anteroposterior deflection was low. The contact areas for both types of bearings were large and showed a constant pattern throughout the test. Backside wear was obvious on rotating platforms. Particle analysis revealed equally sized and round-shaped particles in both types of bearings (fixed, 0.35 microm; mobile, 0.32 microm). In conclusion, the combination of design features and surface modifications of the BPK-S integration TKR system leads to low gravimetric UHMWPE wear.

Uncemented femoral revision arthroplasty using the modular revision prosthesis MRP-TITAN revision stem.

OBJECTIVE: Restoration of a painless hip joint capable of bearing weight by uncemented implantation of a rotationally stable, modular revision stem anchored in the diaphysis. INDICATIONS: Prosthetic stem loosening with osteolytic bone defects (defect classification types I-III according to Paprosky). Material failure with broken prosthesis. Sub- and/or periprosthetic femoral fractures. Tumors. CONTRAINDICATIONS: Extensive osteolysis preventing diaphyseal anchorage of the prosthesis. SURGICAL TECHNIQUE: Transgluteal approach to the hip joint. Removal of the loose prosthetic stem and, if cemented, the bone cement as well. Excision of intramedullary granulation tissue. Reaming of the medullary cavity with flexible reaming shafts and form-fit, uncemented implantation of the star-shaped modular revision stem with diaphyseal press fit. If there is extensive loss of metaphyseal bone stock, augmentation with autogenous/allogenic bone should be performed. POSTOPERATIVE MANAGEMENT: Mobilization on two underarm crutches from the 1st postoperative day. Removal of the Redon drains after 48 h. Partial loading with 20 kg for 6 weeks postoperatively. If plain radiographs show unchanged seating of the prosthesis after 6 weeks, loading can be increased by 10 kg per week until full weight bearing is achieved; thrombosis prophylaxis is continued throughout. Radiologic checkups after 3, 6, and 12 months. After that, the patient should be checked annually. RESULTS: 45 patients (n = 48 prostheses) with an average age of 67.2 years (min.-max. 42.4-87.4 years) were investigated. The average implantation time of the Modular Revision Prosthesis MRP-TITAN revision stem was 4.7 years (min.-max. 1.0-9.0 years). The Harris Hip Score for Paprosky bone defect types I-III had increased from 25.6 preoperatively to 71.4 postoperatively at the time of the final follow-up (< or = 0.05). Extensively defective bone was diagnosed preoperatively in 32 patients (> or = Paprosky IIB). Plain radiographs showed stable anchorage without migration in 44 patients. In one case, the stem (implantation time 2.36 years) was replaced due to increasing axial subsidence (> or = 5 mm). Good integration of bone graft with subsequent defect regeneration was seen in all patients with bone transplant (n = 30). Postoperative dislocation occurred in six patients and required closed reduction in four cases. Open reduction was performed in two patients, whereby the external rotation angle of the prosthetic neck was corrected without dismantling the distally anchored prosthetic stem components. The mechanical failure rate over the follow-up period of 9 years was one out of the 48 prospectively investigated prostheses. Rate of survival according to Kaplan-Meier was 97%.