Keywords

Lumbar Spine, skin strain, scarring, wound healing, surgery, infection, suture, preoperative incision planning, motion capture, Activities Daily Living

Abstract

Introduction: When mechanical stimulation of the skin, post-surgery, is kept at a minimum, the risk for hypertrophic scarring is reduced. Therefore, surgeons have utilized different tools for optimal scar outcomes such as cutting along or perpendicular to the Langers lines or collagen fiber orientation1,2. However, biomechanical strains induced in the skin during activities of daily living (ADL) are the primary mechanism for suture opening, and increased awareness of these strains may provide informative insights to both pre-operative incision planning, as well as post-operative counseling with the patient regarding specific activities that may lead to wound re-opening.

Methods: Data were collected for a healthy young cohort of 28 people (25.2 ± 9.3 years, BMI: 23.3 ± 3.3). For each subject, 8 motion tracking markers were placed on the S2 and L5-T11 spinous processes. 16 additional markers were then placed 1.75” laterally. 12 more markers were placed in the S2/L5 region for increased width and resolution, resulting in a total of 36 markers in a 3.5-inch-wide rectangle between S2 and T11 and a 7.5-inch-wide rectangle in the S2/L5 region. 3D coordinates of each marker were measured by 10 cameras for a predefined set of subject movements (flexion, extension, right/left rotation, and standing up from a sitting position), repeated 3 times. Marker coordinates were used to generate strain magnitudes and strain field maps of the lumbar region using finite deformation theory.

Results: Table 1 shows maximum principal skin strains at each lumbar level for 4 different activities, which roughly correlated with either a superior-inferior (SI) or medial-lateral (ML) orientation.

Table 1: Maximum principal skin strains at each lumbar level are reported, corresponding to either a roughly superior-inferior (SI) or roughly medial-lateral (ML) axis.

Flexion (SI)

Extension (SI)

Rotation Right/Left (ML)

Standing up From Chair (SI)

L1-T11

22.8%

-13.7%

9.3%

-1.2%

L3-L1

40.7%

-15.9%

6.9%

-5.6%

L5-L3

60.3%

-14.7%

4.7%

-9.9%

S2-L5

58.8%

-11.4%

5.1%

-9.4%

Conclusion/Discussion: Based on our results, lower lumbar incisions are exposed to high SI-oriented tensile strains, especially during high-flexion activities. Upper lumbar incisions are exposed to more moderate SI tensile strains, but experience more severe ML-oriented tensile strains during high-rotation activities. Suture orientations which are perpendicular to the direction of high strain may be more sensitive to suture pullout, wound opening, or tissue damage. High-extension activities, including sit to stand, resulted in negative strains (i.e., “buckling” of the skin), which is unlikely to induce direct skin damage or suture pullout, but may provide opportunities for suture loosening.

1. Rennekampff HO, Tenenhaus M. Theoretical basis for optimal surgical incision planning to reduce hypertrophic scar formation. Medical Hypotheses. 2020/07/01/ 2020;140:109672.

2. Wong VW, Akaishi S, Longaker MT, Gurtner GC. Pushing Back: Wound Mechanotransduction in Repair and Regeneration. Journal of Investigative Dermatology. 2011/11/01/ 2011;131(11):2186-2196.

Document Type

Poster

Publication Date

2022-09-10

Language

English

College

Ira A. Fulton College of Engineering

Department

Mechanical Engineering

University Standing at Time of Publication

Graduate Student

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