SLR - July 2014 - Casey Ebert
The Mechanism of Action of Induced Membranes in Bone Repair
Reference: Aho OM, Lehenkari P, Ristiniemi J, Lehtonen S, Risteli J, Leskelä HV. The Mechanism of Action of Induced Membranes in Bone Repair. J Bone Joint Surg Am. 2013 Apr 3;95(7):597-604.
Reviewed By: Casey C Ebert, DPM
Residency Program: Franciscan Health System-St. Francis Hospital, Federal Way, WA
Podiatric Relevance: Large bone defects, while rare in the lower extremity, offer complexity to reconstruction and lack general consensus on treatment options. The two stage Masquelet technique utilizes the body’s own abilities for the treatment of large osseous defects. While the perceived benefits of this technique have a lot to offer the lower extremity surgeon, much is left to be investigated: indications, timing, and greater understanding of mechanisms of action. The reviewed article aims to biochemically and histologically evaluate human produced membranes to gain a greater understanding of induced membrane characteristics and their abilities within the human host.
Methods: Fourteen patients with lower extremity large segmental bone defects that underwent two stage induced membrane surgical intervention were included in the study. Membrane samples were harvested at each stage of surgery and appropriately prepared for various histological and biochemical evaluations. Membranes were co-cultured with mesenchymal stromal cells to investigate the ability of osseous formation. Osteoblastic differentiation was evaluated by measuring alkaline phosphatase activity. Subsequently, bone formation was quantified by aminoterminal propeptide of type I procollagen (PINP) and calcium deposition. Histological staining and image analysis were utilized to characterize older and newer membrane samples. Osseous formation was observed and the proportion of vascular tissue compared to membrane stroma was identified. Utilizing primers for Type I collagen, vascular endothelial growth factor (VEGF), and interleukin 6 (IL-6) quantitative reverse transcription polymerase chain reaction was utilized to compare the various gene expression activity with respect to membrane age.
Results: Cultured membranes with mesenchymal stromal cells induced alkaline phosphatase activity and calcium deposition. When comparing various sites of sampling within the membrane, the membranes from the sites of bone marrow and cancellous bones had increased PINP production, indicating greater osteoinductive properties at these sites. When comparing timing of the second stage of surgery, the one month samples spontaneously induced cell differentiation while the two month old membranes did not display this activity with levels less than two times lower of PINP and less than four times lower calcium deposition. Histological observations showed the induced membranes’ vascularity and ability to produce ossification. Additionally, newer membranes were described as having greater amounts of granulation tissue, whereas, older membranes displayed more uniform fibrous tissue implying decreased vascularity as maturation occurs. Compared to one month old samples, three month old samples had less than 60 percent of the vascularity. The expression of VEGF, IL-6 and Col-1 also decreased with the age of membrane as demonstrated by RTqPCR, with two month old membranes showing less than 40 percent of the gene expression exhibited by one month old membranes.
Conclusions: The results of the reviewed study indicate that first and foremost, the ability to produce a membrane with capabilities to increase vascularity and osteogenesis exists within human subjects. In addition, this study reveals that one month may be a prime age of membrane maturity as biological activity was found to decrease with respect to time greater than one month, furthermore implying that the second stage of the Masquelet technique is recommended to take place prior to one month from the primary operation. Overall this investigation aids in better understanding and implementation of the two-stage Masquelet technique for large bony defects. As further characterization of induced membranes occurs the utilization may become more wide spread, the indications may increase, and the patient outcomes may be optimized.