Promotion of bone formation by simvastatin in polyethylene particle-induced osteolysis

The effects of statins on bone formation in periprosthetic osteolysis have not been determined to date. We investigated the effect of the HMG-CoA reductase inhibitor simvastatin on osteoblastic bone formation under conditions of ultra-high molecular weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 21 C57BL/J6 mice randomized to three groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III, particles and simvastatin treatment. After 2 weeks, calvaria were processed for histomorphometry and stained with Giemsa dye. New bone formation was measured as osteoid tissue area within the midline suture. Bone thickness was quantified as indicator of net bone growth. Statistical analysis was performed using one-way ANOVA and a Student's t-test. New bone formation and bone thickness were significantly enhanced following simvastatin treatment. New bone formation was 0.008+/-0.008 mm2 in sham controls (group I), 0.015+/-0.012 mm2 after particle implantation without further intervention (group II), compared to 0.083+/-0.021 mm2 with particle implantation and simvastatin treatment (group III) (p=0.003). The bone thickness was 0.213+/-0.007 mm in group I, 0.183+/-0.005 mm in group II, and 0.238+/-0.009 mm in group III (p=0.00008). In conclusion, simvastatin treatment markedly promoted bone formation and net bone growth in UHMWPE particle-induced osteolysis in a murine calvarial model. These new findings indicate that simvastatin may have favorable osteoanabolic effects on wear debris-mediated osteolysis after total joint arthroplasty, involving local stimulation of osteoblastic bone formation.     

Assessment and management of chronic pain in patients with stable total hip arthroplasty

Total hip arthroplasty (THA) is one of the most successful operations that can restore function and relieve pain. Although a majority of the patients achieve significant pain relief after THA, there are a number of patients that develop chronic pain for unknown reasons. A literature search was performed looking for chronic pain after total hip arthroplasty and stable THA. Major causes of chronic pain include aseptic loosening or infection. However, there is a subset of patients with a stable THA that present with chronic pain which can have several aetiologies. These include soft tissue, bony, neurological, vascular and psychological causes. Essential for successful treatment is the ability to make the correct diagnosis. Thus therapy may be either non-operative or operative. In addition, diagnosis and management often may require multidisciplinary approaches to successfully alleviate chronic pain in these patients with a stable prosthesis.     

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 © 2015 John Wiley & Sons, Ltd.     

Tartrate-resistant acid phosphatase 5b and C-terminal telopeptides of type I collagen as markers for diagnosis of aseptic loosening after total hip replacement

Introduction  

Plain radiography, bone scintigraphy, digital subtraction arthrography and various other techniques can be used to evaluate loosening of hip replacements. These methods are associated with radiation exposure and some of them have an increased morbidity. Furthermore, in some cases the results are not conclusive.     

Fixation method does not affect restoration of rotation center in hip replacements: A single-site retrospective study

ABSTRACT: BACKGROUND: Aseptic loosening is one of the greatest problems in hip replacement surgery. The rotation center of the hip is believed to influence the longevity of fixation. The aim of this study was to compare the influence of cemented and cementless cup fixation techniques on the position of the center of rotation because cemented cup fixation requires the removal of more bone for solid fixation than the cementless technique. METHODS: We retrospectively compared pre- and post-operative positions of the hip rotation center in 25 and 68 patients who underwent artificial hip replacements in our department in 2007 using cemented or cementless cup fixation, respectively, with digital radiographic image analysis. RESULTS: The mean horizontal and vertical distances between the rotation center and the acetabular teardrop were compared in radiographic images taken pre- and post-operatively. The mean horizontal difference was 2.63 mm (range: -11.00 mm to 10.46 mm, standard deviation 4.23 mm) for patients who underwent cementless fixation, and 2.84 mm (range: -10.87 to 5.30 mm, standard deviation 4.59 mm) for patients who underwent cemented fixation. The mean vertical difference was 0.60 mm (range: -20.15 mm to 10.00 mm, standard deviation 3.93 mm) and 0.41 mm (range: -9.26 mm to 6.54 mm, standard deviation 3.58 mm) for the cementless and cemented fixation groups, respectively. The two fixation techniques had no significant difference on the position of the hip rotation center in the 93 patients in this study. CONCLUSIONS: The hip rotation center was similarly restored using either the cemented or cementless fixation techniques in this patient cohort, indicating that the fixation technique itself does not interfere with the position of the center of rotation. To completely answer this question further studies with more patients are needed.     

Hip imaging of avascular necrosis at 7 Tesla compared with 3 Tesla

Objectives

To compare ultra-high field, high-resolution bilateral magnetic resonance imaging (MRI) of the hips at 7 Tesla (T) with 3 T MRI in patients with avascular necrosis (AVN) of the femoral head by subjective image evaluations, contrast measurements, and evaluation of the appearance of imaging abnormalities.

Materials and Methods

Thirteen subjects with avascular necrosis treated using advanced core decompression underwent MRI at both 7 T and 3 T. Sequence parameters as well as resolution were kept identical for both field strengths. All MR images (MEDIC, DESS, PD/T2w TSE, T1w TSE, and STIR) were evaluated by two radiologists with regard to subjective image quality, soft tissue contrasts, B1 homogeneity (four-point scale, higher values indicating better image quality) and depiction of imaging abnormalities of the femoral heads (three-point scale, higher values indicating the superiority of 7 T). Contrast ratios of soft tissues were calculated and compared with subjective data.

Results

7-T imaging of the femoral joints, as well as 3-T imaging, achieved “good” to “very good” quality in all sequences. 7 T showed significantly higher soft tissue contrasts for T2w and MEDIC compared with 3 T (cartilage/fluid: 2.9 vs 2.2 and 3.6 vs 2.6), better detailed resolution for cartilage defects (PDw, T2w, T1w, MEDIC, DESS?>?2.5) and better visibility of joint effusions (MEDIC 2.6; PDw/T2w 2.4; DESS 2.2). Image homogeneity compared with 3 T (3.9–4.0 for all sequences) was degraded, especially in TSE sequences at 7 T through signal variations (7 T: 2.1–2.9); to a lesser extent also GRE sequences (7 T: 2.9–3.5). Imaging findings related to untreated or treated AVN were better delineated at 3 T (≤1.8), while joint effusions (2.2–2.6) and cartilage defects (2.5–3.0) were better visualized at 7 T. STIR performed much more poorly at 7 T, generating large contrast variations (1.5).

Conclusions

7-T hip MRI showed comparable results in hip joint imaging compared with 3 T with slight advantages in contrast detail (cartilage defects) and fluid detection at 7 T when accepting image degradation medially.     

Prevalence of CAM deformity and its influence on therapy success in patients with osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) and CAM‐type femoroacetabular impingement (FAI) present two different pathologies of the hip joint. The aim of this study is to describe the prevalence of CAM‐FAI in a collective of ONFH hips and to evaluate its influence on ONFH therapy outcome. A cohort of 86 ONFH hips with a mean follow‐up of 46.7 months (±20.5) after advanced core decompression (ACD) was evaluated regarding CAM deformity by measuring the alpha angle (α) and head–neck offset. The influence of CAM‐type FAI was investigated using the Kaplan–Meier estimator and the Cox regression model. The mean α was 60.4° (±13.8) with 41 hips (47.7%) being ≥60°. The mean head–neck offset was 4.5 mm (±3.2), with 78 hips (90.7%) being ≤9 mm. Survival analysis indicated noticeably better ACD results for α < 60° versus α ≥ 60° (p = 0.07). Treatment failure within the first 2 years was statistically estimated as 27.7% for α < 60° versus 40.7% for α ≥ 60°: The hazard ratio for α ≥ 60° was 1.94. Head–neck offset‐dependent survival showed better, though not significant, results for offset >9 mm (p = 0.38, hazard ratio 1.89 for offsets ≤9 mm). The prevalence of CAM‐type deformity is greatly increased in patients with concomitant ONFH. There is a strong indication that CAM‐type FAI has a negative influence on ONFH therapy outcome. The risk that ONFH treatment will fail seems to be twice as high for α ≥ 60° as for α < 60°. We recommend cotreatment of pathological head–neck offset in patients with ONFH.     

Suppression of polyethylene particle-induced osteolysis by exogenous osteoprotegerin

Alterations of the key regulators of osteoclastogenesis, receptor activator of NF-kappaB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) have been implicated in wear particle-induced osteolysis, the most common cause for implant failure in total joint replacements. This study investigated the effect of exogenous OPG on ultra-high-molecular-weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 28 C57BL/6J mice randomized to four groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III and IV particles and subcutaneous OPG starting from day 0 (group III) or day 5 (group IV) until sacrifice. After 2 weeks, calvaria were prepared for histology and histomorphometry. Bone resorption was measured within the midline suture using Giemsa staining and osteoclast numbers were determined using TRAP staining. UHMWPE particle implantation resulted in grossly pronounced osteoclastogenesis and bone resorption. Both immediate and delayed treatment with OPG counteracted these particle-induced effects significantly, suppressing osteoclast formation and bone resorption (p < 0.001 and p < 0.001, respectively). In conclusion, exogenous OPG markedly suppressed UHMWPE particle-induced osteolysis in a murine calvarial model. This important finding underscores the crucial significance of the OPG-RANKL-RANK signaling in wear particle-induced osteolysis. Exogenous OPG may prove an effective treatment modality for wear debris-mediated periprosthetic osteolysis after total joint arthroplasty.