Sebastian Warwas

Advanced core decompression, a new treatment option of avascular necrosis of the femoral head--a first follow-up.

Aseptic necrosis of the femoral head (AVN) leads to destruction of the affected hip joint, predominantly in younger patients. Advanced core decompression (ACD) is a new technique that may allow better removal of the necrotic tissue by using a new percutaneous expandable reamer. A further modification is the refilling of the drill hole and the defect with an injectable, hard‐setting, composite calcium sulphate (CaSO4)–calcium phosphate (CaPO4) bone graft substitute. Compression tests were performed on seven pairs of femoral cadaver bones. One femur of each pair was treated with ACD, while the opposite side remained untreated. Clinically, the postoperative outcome of 27 hips in 23 patients was performed by physical examination 6 weeks after ACD and at average follow‐up of 9.69 months, and compared with the preoperative results. MRI was used to assess the removal of the necrotic tissue, any possible progression of AVN and evaluation of collapse. In the biomechanical analysis, the applied maximum compression force that caused the fracture did not significantly differ from the untreated opposite side. The overall results of postoperative physical examinations were significantly better than preoperatively. Five hips (18.5%) were converted to a total hip replacement. The follow‐up MRIs of the other patients showed no progression of the necrotic area. The first follow‐up results of ACD have been encouraging for the early stages of aseptic necrosis of the femoral head. In our opinion, an assured advantage is the high stability of the femoral neck after ACD, which allows quick rehabilitation. Copyright

Osteogenic differentiation and proliferation of bone marrow-derived mesenchymal stromal cells on PDLLA + BMP-2-coated titanium alloy surfaces.

RhBMP-2 is clinically applied to enhance bone healing and used in combination with titanium fixation implants. The purpose of this in vitro study was to compare the osteogenic differentiation and proliferation of hMSC on native polished versus sandblasted titanium surfaces (TS) and to test their behavior on pure poly-D,L-lactide (PDLLA) coated as well as PDLLA + rhBMP-2 coated TS. Furthermore, the release kinetics of PDLLA + rhBMP-2-coated TS was investigated. Human bone marrow cells were obtained from three different donors (A: male, 16 yrs; B: male, 27 yrs, C: male, 49 yrs) followed by density gradient centrifugation and flow cytometry with defined antigens. The cells were seeded on native polished and sandblasted TS, PDLLA-coated TS and PDLLA + rhBMP-2-coated TS. Osteogenic differentiation (ALP specific activity via ALP and BCA assay) and proliferation (LDH cytotoxicity assay) was examined on day 7 and 14 and release kinetics of rhBMP-2 was investigated on day 3, 7, 10, and 14. We found significant higher ALP specific activity and LDH activity on native polished compared to native sandblasted surfaces. PDLLA led to decreased ALP specific and LDH activity on both surface finishes. Additional rhBMP-2 slightly diminished this effect. RhBMP-2-release from coated TS decreased nearly exponentially with highest concentrations at the beginning of the cultivation period. The results of this in vitro study suggest that native TS stimulate hMSC significantly stronger toward osteogenic differentiation and proliferation than rhBMP-2 + PDLLA-layered TS in the first 14 days of cultivation. The PDLLA-layer seems to inhibit local hMSC differentiation and proliferation.

Experimental and computational studies on the femoral fracture risk for advanced core decompression.

BACKGROUND Two questions are often addressed by orthopedists relating to core decompression procedure: 1) Is the core decompression procedure associated with a considerable lack of structural support of the bone? and 2) Is there an optimal region for the surgical entrance point for which the fracture risk would be lowest? As bioresorbable bone substitutes become more and more common and core decompression has been described in combination with them, the current study takes this into account. METHODS Finite element model of a femur treated by core decompression with bone substitute was simulated and analyzed. In-vitro compression testing of femora was used to confirm finite element results. FINDINGS The results showed that for core decompression with standard drilling in combination with artificial bone substitute refilling, daily activities (normal walking and walking downstairs) are not risky for femoral fracture. The femoral fracture risk increased successively when the entrance point is located further distal. The critical value of the deviation of the entrance point to a more distal part is about 20mm. INTERPRETATION The study findings demonstrate that optimal entrance point should locate on the proximal subtrochanteric region in order to reduce the subtrochanteric fracture risk. Furthermore the consistent results of finite element and in-vitro testing imply that the simulations are sufficient.

Two-year follow-up after advanced core decompression

The so‐called “Advanced Core Decompression” (ACD) is a new option that tries to remove the necrotic tissue in patients with osteonecrosis of the femoral head (AVN) in a minimally invasive way by the use of a percutaneous expandable reamer and refilling with a resorbable and osteoinductive bone‐graft substitute. Seventy‐two hips of sixty patients with a mean follow‐up of 29.14 months after ACD have been included in this study. Patients underwent physical examination preoperatively and six weeks after surgery as well as at two further follow‐ups. Certain phases in disease progression and size of the necrotic lesion were differentiated on the basis of the classification of osteonecrosis of the femoral head by Steinberg.The femoral heads had collapsed in 24 cases (33%). Analysis of the survival rates with regard to defect size revealed that the largest defects had a significantly higher rate of femoral head collapse than the smaller defects. Clinical scores were also depending on defect size but also on disease stage. The current ACD technique has not yet achieved any significant improvement in the success rate of core decompression procedures. It can be concluded that the success of ACD depends especially on the defect size. Copyright

Prostacyclin Suppresses Twist Expression in the Presence of Indomethacin in Bone Marrow-Derived Mesenchymal Stromal Cells

Background Iloprost, a stable prostacyclin I2 analogue, seems to have an osteoblast-protective potential, whereas indomethacin suppresses new bone formation. The aim of this study was to investigate human bone marrow stromal cell (BMSC) proliferation and differentiation towards the osteoblastic lineage by administration of indomethacin and/or iloprost. Material/Methods Human bone marrow cells were obtained from 3 different donors (A=26 yrs/m; B=25 yrs/f, C=35 yrs/m) via vacuum aspiration of the iliac crest followed by density gradient centrifugation and flow cytometry with defined antigens (CD105+/73+/45−/14−). The cells were seeded and incubated as follows: without additives (Group 0; donor A/B/C), with 10−7 M iloprost only (Group 0+ilo; A/B), with indomethacin only in concentrations of 10−6 M (Group 1, A), 10−5 M (Group 2, B), 10−4 M (Group 3, A/B), and together with 10−7 M iloprost (Groups 4–6, A/B/C). On Day 10 and 28, UV/Vis spectrometric and immunocytochemical assays (4 samples per group and donor) were performed to investigate cell proliferation (cell count measurement) and differentiation towards the osteoblastic lineage (CD34−, CD45−, CD105+, type 1 collagen (Col1), osteocalcin (OC), alkaline phosphatase (ALP), Runx2, Twist, specific ALP-activity). Results Indomethacin alone suppressed BMSC differentiation towards the osteoblastic lineage by downregulation of Runx2, Col1, and ALP. In combination with indomethacin, iloprost increased cell proliferation and differentiation and it completely suppressed Twist expression at Day 10 and 28. Iloprost alone did not promote cell proliferation, but moderately enhanced Runx2 and Twist expression. However, the proliferative effects and the specific ALP-activity varied donor-dependently. Conclusions Iloprost partially antagonized the suppressing effects of indomethacin on BMSC differentiation towards the osteoblast lineage. It enhanced the expression of Runx2 and, only in the presence of indomethacin, it completely suppressed Twist. Thus, in the treatment of avascular osteonecrosis or painful bone marrow edema, the undesirable effects of indomethacin might be counterbalanced by iloprost.

A multicenter approach evaluating the impact of vitamin E-blended polyethylene in cementless total hip replacement

Since polyethylene is one of the most frequently used biomaterials as a liner in total hip arthroplasty, strong efforts have been made to improve design and material properties over the last 50 years. Antioxidants seems to be a promising alternative to further increase durability and reduce polyethylene wear in long term. As of yet, only in vitro results are available. While they are promising, there is yet no clinical evidence that the new material shows these advantages in vivo. To answer the question if vitamin-E enhanced ultra-high molecular weight polyethylene (UHMWPE) is able to improve long-term survivorship of cementless total hip arthroplasty we initiated a randomized long-term multicenter trial. Designed as a superiority study, the oxidation index assessed in retrieval analyses of explanted liners was chosen as primary parameter. Radiographic results (wear rate, osteolysis, radiolucency) and functional outcome (Harris Hip Scores, University of California-Los Angeles, Hip Disability and Osteoarthritis Outcome Score, Visual Analogue Scale) will serve as secondary parameters. Patients with the indication for a cementless total hip arthroplasty will be asked to participate in the study and will be randomized to either receive a standard hip replacement with a highly cross-linked UHMWPE-X liner or a highly cross-linked vitamin-E supplemented UHMWPE-XE liner. The follow-up will be 15 years, with evaluation after 5, 10 and 15 years. The controlled randomized study has been designed to determine if Vitamin-E supplemented highly cross-linked polyethylene liners are superior to standard XLPE liners in cementless total hip arthroplasty. While several studies have been started to evaluate the influence of vitamin-E, most of them evaluate wear rates and functional results. The approach used for this multicenter study, to analyze the oxidation status of retrieved implants, should make it possible to directly evaluate the ageing process and development of the implant material itself over a time period of 15 years.

Correction: Partial Hemiresurfacing of Osteochondral Defects of the Talus? Surgical Technique and Preliminary Report from Four Patients

Background: Osteochondral lesions of the medial talus (OLT) frequently lead to chronic ankle pain and osteoarthritis. Arthroscopic debridement, subchondral bone stimulation by drilling, and microfracturing are options for primary therapy in small lesions. In larger lesions, restoration of the talar dome contour seems to be a mandatory course of action. Methods: In a case series, we followed up four patients being treated with a focal resurfacing prosthetic due to large osteochondral talar lesions. In contrast to other studies, we can report on an off-label application to restore defects of the lateral talar dome with two patients for the first time. At follow-up, three patients reported a remarkable reduction in pain and were able to return to sports activities. One patient developed pseudarthrosis of the medial malleolar osteosynthesis. Conclusions: With selected patients, focal resurfacing appears to be an option for large osteochondral defects of the talus.