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Biomechanical factors in planning of periacetabular osteotomy.

Niknafs N, Murphy RJ, Armiger RS, Lepistö J, Armand M - Front Bioeng Biotechnol (2013)

Bottom Line: For each combination of thickness distribution and compressive properties, the optimal alignment of the acetabulum was found; the resultant geometric and biomechanical characterization of the hip were compared among the optimal alignments.The optimal alignment increased the lateral coverage of the femoral head and decreased the obliqueness of the acetabular roof in all patients.However, in all groups the biomechanically predicted optimal alignment resulted in decreased joint contact pressure and improved acetabular coverage.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Johns Hopkins University , Baltimore, MD , USA.

ABSTRACT

Objective: This study addresses the effects of cartilage thickness distribution and compressive properties in the context of optimal alignment planning for periacetabular osteotomy (PAO).

Background: The Biomechanical Guidance System (BGS) is a computer-assisted surgical suite assisting surgeon's in determining the most beneficial new alignment of a patient's acetabulum. The BGS uses biomechanical analysis of the hip to find this optimal alignment. Articular cartilage is an essential component of this analysis and its physical properties can affect contact pressure outcomes.

Methods: Patient-specific hip joint models created from CT scans of a cohort of 29 dysplastic subjects were tested with four different cartilage thickness profiles (one uniform and three non-uniform) and two sets of compressive characteristics. For each combination of thickness distribution and compressive properties, the optimal alignment of the acetabulum was found; the resultant geometric and biomechanical characterization of the hip were compared among the optimal alignments.

Results: There was an average decrease of 49.2 ± 22.27% in peak contact pressure from the preoperative to the optimal alignment over all patients. We observed an average increase of 19 ± 7.7° in center-edge angle and an average decrease of 19.5 ± 8.4° in acetabular index angle from the preoperative case to the optimized plan. The optimal alignment increased the lateral coverage of the femoral head and decreased the obliqueness of the acetabular roof in all patients. These anatomical observations were independent of the choice for either cartilage thickness profile, or compressive properties.

Conclusion: While patient-specific acetabular morphology is essential for surgeons in planning PAO, the predicted optimal alignment of the acetabulum was not significantly sensitive to the choice of cartilage thickness distribution over the acetabulum. However, in all groups the biomechanically predicted optimal alignment resulted in decreased joint contact pressure and improved acetabular coverage.

No MeSH data available.


Related in: MedlinePlus

The hip joint coordinate frame with the X (red), Y (green), and Z (blue) axes pointing from left to right, posterior to anterior, and inferior to superior, respectively.
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Figure 1: The hip joint coordinate frame with the X (red), Y (green), and Z (blue) axes pointing from left to right, posterior to anterior, and inferior to superior, respectively.

Mentions: Each patient scan was performed in the supine orientation and covered the entire joint region (the acetabulum and proximal femur) in axial slices. Axial slices comprising the scanned volume had variable and sometimes non-uniform spacing; however, the maximum slice spacing was smaller than 1.6 mm in the entire scan volumes and the hip joint was usually scanned at higher resolution compared to the rest of the scan volume. For consistency, the scan volumes were re-sampled at 1 mm spacing and realigned such that the X axis contained the centers of the femoral heads (Figure 1).


Biomechanical factors in planning of periacetabular osteotomy.

Niknafs N, Murphy RJ, Armiger RS, Lepistö J, Armand M - Front Bioeng Biotechnol (2013)

The hip joint coordinate frame with the X (red), Y (green), and Z (blue) axes pointing from left to right, posterior to anterior, and inferior to superior, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126379&req=5

Figure 1: The hip joint coordinate frame with the X (red), Y (green), and Z (blue) axes pointing from left to right, posterior to anterior, and inferior to superior, respectively.
Mentions: Each patient scan was performed in the supine orientation and covered the entire joint region (the acetabulum and proximal femur) in axial slices. Axial slices comprising the scanned volume had variable and sometimes non-uniform spacing; however, the maximum slice spacing was smaller than 1.6 mm in the entire scan volumes and the hip joint was usually scanned at higher resolution compared to the rest of the scan volume. For consistency, the scan volumes were re-sampled at 1 mm spacing and realigned such that the X axis contained the centers of the femoral heads (Figure 1).

Bottom Line: For each combination of thickness distribution and compressive properties, the optimal alignment of the acetabulum was found; the resultant geometric and biomechanical characterization of the hip were compared among the optimal alignments.The optimal alignment increased the lateral coverage of the femoral head and decreased the obliqueness of the acetabular roof in all patients.However, in all groups the biomechanically predicted optimal alignment resulted in decreased joint contact pressure and improved acetabular coverage.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Johns Hopkins University , Baltimore, MD , USA.

ABSTRACT

Objective: This study addresses the effects of cartilage thickness distribution and compressive properties in the context of optimal alignment planning for periacetabular osteotomy (PAO).

Background: The Biomechanical Guidance System (BGS) is a computer-assisted surgical suite assisting surgeon's in determining the most beneficial new alignment of a patient's acetabulum. The BGS uses biomechanical analysis of the hip to find this optimal alignment. Articular cartilage is an essential component of this analysis and its physical properties can affect contact pressure outcomes.

Methods: Patient-specific hip joint models created from CT scans of a cohort of 29 dysplastic subjects were tested with four different cartilage thickness profiles (one uniform and three non-uniform) and two sets of compressive characteristics. For each combination of thickness distribution and compressive properties, the optimal alignment of the acetabulum was found; the resultant geometric and biomechanical characterization of the hip were compared among the optimal alignments.

Results: There was an average decrease of 49.2 ± 22.27% in peak contact pressure from the preoperative to the optimal alignment over all patients. We observed an average increase of 19 ± 7.7° in center-edge angle and an average decrease of 19.5 ± 8.4° in acetabular index angle from the preoperative case to the optimized plan. The optimal alignment increased the lateral coverage of the femoral head and decreased the obliqueness of the acetabular roof in all patients. These anatomical observations were independent of the choice for either cartilage thickness profile, or compressive properties.

Conclusion: While patient-specific acetabular morphology is essential for surgeons in planning PAO, the predicted optimal alignment of the acetabulum was not significantly sensitive to the choice of cartilage thickness distribution over the acetabulum. However, in all groups the biomechanically predicted optimal alignment resulted in decreased joint contact pressure and improved acetabular coverage.

No MeSH data available.


Related in: MedlinePlus