Plastic Surgery Research Council

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Mechanical Analysis of Reduction Mammoplasty Effects on Spinal Musculature
George Kamel, MD, Jonathan Morris, MD, Jinesh Shah, MD, Amanda Rizzo, BA, Oren Tepper, MD, Katie Weichman, MD, Evan Garfein, MD.
Montefiore Medical Center, Bronx, NY, USA.

Purpose: Breast weight places a considerable burden on the spine, and can lead to back pain and postural changes. Reduction mammoplasty improves these physical symptoms, but the mechanical effect of the change in breast mass is unknown. The purpose of the study is to examine the mechanical effects of reduction mammoplasty on the forces across erector spinae muscles. It is hypothesized that the patientŐs body habitus, breast size and level of ptosis will affect forces across the erector spinae muscles.
METHODS: Using a cantilever model, the sum of the forces and moments were solved in using static modeling parameters. Mechanical models composed thick and thin body width with high mass and low mass grade III ptotic breasts were created. The variables included were body thickness, mass of the breast, and center of gravity of the breast. It was assumed breasts were homogenous and symmetric. The forces were uniformly distributed across the spine and absorbed by the muscles attached to the spinous process. The mass of the breasts and their center of gravity were altered. The reaction forces across the spine was calculated for each combination of body width, change in breast mass, and change in breast center of gravity.
RESULTS: Independent of body habitus, the percentage of breast tissue mass resected was directly proportional to the decrease in forces on the spinae erectae muscles. Decreasing the amount of breast tissue below the inframammary fold raised the center of the gravity of the breast. The thinner a patientŐs trunk the greater the effect raising the center of gravity had on the forces on the spinal muscles.
CONCLUSION: Reduction mammoplasty reduces the force across the spinal muscles. In thin patients reducing the ptotic grade had a greater effect than in overweight patients. Further studies are needed to correlate the results of this mechanical model with clinical findings.


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