Altering spacer material affects bone regeneration in the Masquelet technique in a rat femoral defect

Abstract

The Masquelet technique depends on pre-development of a foreign-body membrane to support bone regeneration with grafts over three times larger than the traditional maximum. To date, the procedure has always used spacers made of bone cement, which is the polymer polymethyl methacrylate (PMMA), to induce the foreign-body membrane. This study sought to compare (i) morphology, factor expression, and cellularity in membranes formed by PMMA, titanium, and polyvinyl alcohol sponge (PVA) spacers in the Masquelet milieu and (ii) subsequent bone regeneration in the same groups. Ten-week-old, male Sprague-Dawley rats were given an externally stabilized, 6 mm femur defect, and a pre-made spacer of PMMA, titanium, or PVA was implanted. All animals were given 4 weeks to form a membrane, and those receiving an isograft were given 10 weeks post-implantation to union. All samples were scanned with microCT to measure phase 1 and phase 2 bone formation. Membrane samples were processed for histology to measure membrane morphology, cellularity, and expression of the factors BMP2, TGFβ, VEGF, and IL6. PMMA and titanium spacers created almost identical membranes and phase 1 bone. PVA spacers were uniformly infiltrated with tissue and cells and did not form a distinct membrane. There were no quantitative differences in phase 2 bone formation. However, PMMA induced membranes supported functional union in 6 of 7 samples while a majority of titanium and PVA groups failed to achieve the same. Spacer material can alter the membrane enough to disrupt phase 2 bone formation. The membrane's role in bone regeneration is likely more than just as a physical barrier. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Masquelet Technique: Effects of Spacer Material and Micro-topography on Factor Expression and Bone Regeneration

“…It may be worth conducting subtractive comparisons between the PMMA and TI groups with more in depth techniques even though TI has repeatedly performed poorly. 39 …”

“…39 Briefly, an external fixator was installed using a lateral approach. After assuring stable placement, a 6mm defect was created at approximately the bone mid-point, a cylindrical spacer (3.2mmØ × 6mm) was placed in the defect, and the skin was closed.…”

“…This is a timepoint shown previously to clearly result in union (or non-union) for this technique in rats. 20,39 …”

“…To qualitatively assess union, composites of each animal’s microCT scout view, anterior reconstruction, and lateral reconstruction (Figure 5) was blindly graded by an orthopaedic surgeon (DN) as united, delayed, or non-union as done previously for this animal model. 39 …”

Preclinical induced membrane model to evaluate synthetic implants for healing critical bone defects without autograft

“…Despite promising results, epoxy spacers are not currently FDA approved for clinical use and thus, translation of this protocol is limited. Recently, McBride‐Gagyi et al used an induced membrane rat model with a similar segmental femoral defect to investigate the ability of alternative foreign materials (titanium and polyvinyl alcohol) to induce a membrane and heal critical sized bone defects . At 4 weeks post index procedure, a second surgery was performed whereby the membrane was incised, the intercalary spacer was removed, and allogenic bone graft from euthanized rats was implanted to fill the defect.…”