Bone impaction grafting and anti-protrusio cages in high-grade acetabular defects: a 22-year single centre experience.

PURPOSE: Report clinical and radiological long-term follow-up (FU) outcome of bone impaction grafting (BIG) and anti-protrusio cage (APC) technique in hip revision surgery. MATERIALS AND METHODS: We analysed data on complications, as well as the clinical and radiological outcome of patients treated using this technique at our institution. We evaluated the acetabular bone stock renovation, acetabular component stability and its radiological migration. The clinical parameters considered were the Visual Analogue Scale (VAS) and the modified Harris Hip Score (mHHS). RESULTS: Forty hips, with a mean 14.3-year FU, were included. This technique showed good clinical long-term results in an elderly and low-demanding population (mean age at surgery 71.4 ± 12.1 years). The radiological results were not as good as clinical results: 67.5% of cases had a radiographic evidence of resorption of less than 1/3 of the bone graft; 27.5% had a resorption ranging from 1/3 and ½ of the graft, and 5% had more than ½ of the graft. Paprosky type III B reported worse results in terms of graft resorption and a greater migration of the APC (p < 0.001). The survival rate was 95% and a 2.5% rate of septic failure was recorded. CONCLUSION: Impaction grafting with femoral head and APC is an effective technique for treating high-grade acetabular defects. APC reconstructs the hip centre of rotation, avoiding loading forces on the underlying bone graft that can be correctly integrated. At long-term FU, satisfactory clinical results, not strictly correlated to radiological signs of integration, were observed; Paprosky type III B reported worse results in terms of graft resorption and a greater migration of the APC.

On the energy transfer to small scales in a discrete model of one-dimensional turbulence.

We consider a discrete one-dimensional model that was investigated numerically by Daumont and Peyrard [Chaos 13, 624 (2003)] as a model for turbulence in fluids, i.e., for the energy transfer from large to small scales. They found numerically that there exist two different regimes for the energy spectrum at high energies and low energies, respectively, and gave an analytical explanation for the high-energy spectrum. An analytical explanation is given here for the low-energy spectrum, which corresponds to the laminar regime.

Regeneration of large bone defects in sheep using bone marrow stromal cells.

Bone repair was addressed in a critical-sized defect model in sheep, combining a ceramic biomaterial and mesenchymal progenitor cells. The defects in the tibial mid-diaphysis were treated with autologous bone or with a silicon-stabilized tricalcium phosphate biomaterial, implemented or not by the addition of expanded bone marrow stromal cells. An internal locking compression plate and an external fixator were applied for stabilization. Radiographies were taken during the 8 months follow-up: the pixel grey levels of the lesion areas were determined to evaluate the repair process radiologically. Microradiography, histology and vascular density tests were performed. The autologous bone-treated group performed best, as assessed radiologically, within 20-24 weeks after surgery. Very limited healing was detected in the other experimental group: a partial bone deposition occurred at the periphery of the bony stumps only in the cell-seeded scaffolds. Interestingly, this effect ended within 20-24 weeks, as for the autologous bone, suggesting similar kinetics of the repair processes involved. Moreover, bone deposition was located where a significant reduction of the ceramic scaffold was detected. Faxitron microradiography and histology data confirmed these results. Vascular density analysis evidenced that cell-seeded scaffolds supported an increased vascular ingrowth. Thus, the interactions with the proper microenvironment and the oxygen and nutrient supply in the inner part of the constructs seem fundamental to initiate scaffold substitution and to improve cell performance in tissue-engineered approaches to bone repair.

Integrin synthesis and utilization in cultured human osteoblasts.

This study describes the adhesion of human osteoblasts, cultured in vitro, to proteins of the extracellular matrix, the biosynthesis of integrins, their topography and organization in focal contacts. The adhesion of osteoblasts to laminin, type I collagen, vitronectin and fibronectin was 77-100%, in 2 h and at 55 nM substrata concentration, and it was accompanied by spreading of the cells. Adhesion to fibronectin (FN), laminin (LN) and type I collagen (COL) was inhibited by antibodies to the beta 1 integrin and antibodies to the alpha 5 chain affected adhesion only to fibronectin. Using a panel of polyclonal antibodies against alpha 2, alpha 3, alpha 5, alpha v, beta 1 and beta 3 integrins we detected synthesis of alpha 3 beta 1, alpha 5 beta 1, alpha v beta 3, and an alpha v beta 1-like dimer by immunoprecipitation of metabolically labelled cell lysates. Studies of immunolocalization demonstrated the presence of the same integrins identified in lysates, plus alpha 4, alpha 1 and beta 5 subunits. In cells adhering in the presence of serum we showed organization of beta 3 and alpha v integrins in focal contacts. In cells adhering to fibronectin alpha 5 and beta 1 integrins were localized in focal contacts. In cells spread on laminin or type I collagen none of the integrins investigated was localized in focal contacts.

Considerations on seven cases of breakage of the polyethylene acetabular cup.

The authors describe seven cases of breakage of the polyethylene acetabular cup observed in 6 patients (5 females and 1 male) after a period of time ranging from 2 to 11 years postsurgery. By comparing the results obtained with those reported in the literature the authors analyze the possible etiopathogenesis of this rare late complication in total hip arthroplasty, which they particularly believe to be caused by hyperwear and fatigue phenomena of the acetabular cup, in turn caused by mechanical overloading.

Differential expression of alkaline phosphatase in clones of human osteoblast-like cells.

We established cultures of cells growing out from adult bone chips and maintained them through 12 passages in culture. The cultures showed osteoblastic phenotype accompanied by synthesis of collagen type I, osteonectin, alkaline phosphatase, and osteocalcin. We report the characterization of 21 clones obtained from three different individual primary cultures. We studied the expression of osteonectin, alkaline phosphatase, collagen, and osteocalcin in the clones. Metabolic labeling showed production of type I collagen and of osteonectin in all clones studied. In two-thirds of the clones and in mass cultures alkaline phosphatase was not detected at passage 2, but it was detected in increasing amounts at later passages in culture. The clones attained different but detectable levels of expression of this marker by passage 8. The different levels in the expression of alkaline phosphatase in positive clones may be because they were derived from cells at different stages of osteoblastic maturation or due to small changes in microenvironment. The alkaline phosphatase-positive clones were tested for osteocalcin, and they showed measurable expression only at passage 10. A third of the clones obtained were negative for alkaline phosphatase during 12 passages in culture. The obtainment of clones unable to produce alkaline phosphatase may be due to loss of differentiating potential under the in vitro culture conditions. The growth rate and potential of all clones studied were similar through 12 passages in culture, regardless of their potential for expression of alkaline phosphatase.

The closed treatment of severe malleolar fractures.

The authors studied, with clinical and radiological criteria the results of closed treatment (reduction by manipulation and immobilization in a plaster cast for 7 or 8 weeks) of severe displaced malleolar fractures. Of 145 patients who had suffered an ankle fracture and were treated with closed methods between 1979 and 1989, 78 were reviewed, with an average follow-up of 6.2 years. The main difficulties of closed treatment concerned reduction of the fractures; anatomical reduction was achieved only in 32.4% of the cases, and deterioration of the position achieved often occurred (26.2%). Although some joints healed in a fair position, subjective and objective late results were excellent or good in 77% of the cases, fair in 20.5% and poor in 2.6%. The most common clinical outcome was a slight decrease of the range of motion in the injured ankle, which was found in 68% of the cases. Arthritis developed in 28.2% of the reviewed ankles, both after an initial good reduction as well as after an initial poor reduction. A complete failure of closed treatment occurred in 8.3% of the cases, caused by an interpositioning of soft tissues among bone fragments leading to unsuccessful manipulation or by late deterioration of the initial position of reduction causing healing of the fracture in a poor position (severe talar shift).