The Masquelet or induced membrane technique (IMT) is a two-stage surgical procedure used for the treatment of segmental bone defects. In this technique, the defect is first filled with a polymethyl methacrylate (PMMA) spacer, which triggers the formation of a membrane that will encapsulate the defect. During the second surgery, the spacer is carefully removed and replaced by autologous bone graft while preserving the membrane. This membrane is vascularized, contains growth factors, and provides mechanical stability to the graft, all of which are assumed to prevent graft resorption and promote bone healing. The technique is gaining in popularity and several variations have been introduced in the clinical practice. For instance, orthopaedic surgeons now often include antibiotics in the spacer to treat or prevent infection. However, the consequences of this approach on the properties of the induce membrane are not fully understood. Accordingly, in a small animal model, this study aimed to determine the impact on the induced membrane of impregnating spacers with antibiotics frequently used in the IMT. We surgically created a five-mm segmental defect in the right femur of 25 adult male Sprague Dawley rats. The bone was stabilized with a plate and screws before filling the defect with a PMMA spacer. Animals were divided into five equal groups according to the type and dose of antibiotics impregnated in the spacer: A) no antibiotic (control), B) low-dose tobramycin (1.2 g/40 g of PMMA), C) low-dose vancomycin (1 g/40 g of PMMA), D) high-dose tobramycin (3.6 g/40 g of PMMA), E) high-dose vancomycin (3 g/40 g of PMMA). The animals were euthanized three weeks after surgery and the induced membranes were collected and divided for analysis. We assessed the expression of selected genes (Alpl, Ctgf, Runx2, Tgfb1, Vegfa) within the membrane by quantitative real-time PCR. Moreover, frozen sections of the specimens were used to quantify vascularity by immunohistochemistry (CD31 antigen), proliferative cells by immunofluorescence (Ki-67 antigen), and membrane thickness. Microscopic images of the entire tissue sections were taken and analyzed using FIJI software. Finally, we measured the concentration of vascular endothelial growth factor (VEGF) in the membranes by ELISA. No significant difference was found among the groups regarding the expression of genes related to osteogenesis (Alpl, Runx2), angiogenesis (Vegfa), or synthesis of extracellular matrix (Ctgf, Tgfb1) (n = four or five). Similarly, the density of proliferative cells and blood vessels within the membrane, as well as the membrane thickness, did not vary substantially between the control, low-dose, or high-dose antibiotic groups (n = four or five). The concentration of VEGF was also not significantly influenced by the treatment received (n = four or five). The addition of tobramycin or vancomycin to the spacer, at the defined low and high doses, does not significantly alter the bioactive characteristics of the membrane. These results suggest that orthopaedic surgeons could use antibiotic-impregnated spacers for the IMT without compromising the induced membrane and potentially bone healing.
It may not be possible to undertake revision total hip arthroplasty
(THA) in the presence of massive loss of acetabular bone stock using
standard cementless hemispherical acetabular components and metal
augments, as satisfactory stability cannot always be achieved. We
aimed to study the outcome using a reconstruction cage and a porous
metal augment in these patients. A total of 22 acetabular revisions in 19 patients were performed
using a combination of a reconstruction cage and porous metal augments.
The augments were used in place of structural allografts. The mean
age of the patients at the time of surgery was 70 years (27 to 85)
and the mean follow-up was 39 months (27 to 58). The mean number
of previous THAs was 1.9 (1 to 3). All patients had segmental defects
involving more than 50% of the acetabulum and seven hips had an
associated pelvic discontinuity. Aims
Patients and Methods
An uncemented hemispherical acetabular component
is the mainstay of acetabular revision and gives excellent long-term
results. Occasionally, the degree of acetabular bone loss means that a
hemispherical component will be unstable when sited in the correct
anatomical location or there is minimal bleeding host bone left
for biological fixation. On these occasions an alternative method
of reconstruction has to be used. A major column structural allograft has been shown to restore
the deficient bone stock to some degree, but it needs to be off-loaded
with a reconstruction cage to prevent collapse of the graft. The
use of porous metal augments is a promising method of overcoming
some of the problems associated with structural allograft. If the defect
is large, the augment needs to be protected by a cage to allow ingrowth
to occur. Cup-cage reconstruction is an effective method of treating
chronic pelvic discontinuity and large contained or uncontained
bone defects. This paper presents the indications, surgical techniques and
outcomes of various methods which use acetabular reconstruction
cages for revision total hip arthroplasty. Cite this article:
