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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

AC angle (in degrees) in the original and optimal orientations of the acetabulum for (A) linear and (B) non-linear DEA. The graph displays mean ± standard deviation of measurements for each group. The groups denoted by (i), (ii), (iii), (iv), and (v) represent the original alignment and the optimal alignments found using uniform, p-b dysplastic, p-b normal, and CT-based cartilage thickness models, respectively. The black line marks the border between normal and dysplastic values for the AC angle. Optimal orientation of the acetabulum results in improvement (decrease) of AC angle.
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Figure 10: AC angle (in degrees) in the original and optimal orientations of the acetabulum for (A) linear and (B) non-linear DEA. The graph displays mean ± standard deviation of measurements for each group. The groups denoted by (i), (ii), (iii), (iv), and (v) represent the original alignment and the optimal alignments found using uniform, p-b dysplastic, p-b normal, and CT-based cartilage thickness models, respectively. The black line marks the border between normal and dysplastic values for the AC angle. Optimal orientation of the acetabulum results in improvement (decrease) of AC angle.

Mentions: Different cartilage thickness models and DEA techniques resulted in similar improvements in radiological angles, all of which saw increased lateral coverage of the femoral head in the optimized location. Across the eight combinations of cartilage model and DEA technique, the average increase in CE angle from preoperative to optimal was 19.0 ± 2.2°, ranging from 14.7° to 21.5° (Figure 9). Similarly, the average decrease in AC angle was 19.5 ± 2.4°, ranging from 15.3° to 22.4° (Figure 10). Of the 22 cases with CE angle in the dysplastic range, 91.5% moved to normal range (CE >25°) and 8.5% moved to borderline range (20° < CE < 25°) after realignment.


Biomechanical factors in planning of periacetabular osteotomy.

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

AC angle (in degrees) in the original and optimal orientations of the acetabulum for (A) linear and (B) non-linear DEA. The graph displays mean ± standard deviation of measurements for each group. The groups denoted by (i), (ii), (iii), (iv), and (v) represent the original alignment and the optimal alignments found using uniform, p-b dysplastic, p-b normal, and CT-based cartilage thickness models, respectively. The black line marks the border between normal and dysplastic values for the AC angle. Optimal orientation of the acetabulum results in improvement (decrease) of AC angle.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 10: AC angle (in degrees) in the original and optimal orientations of the acetabulum for (A) linear and (B) non-linear DEA. The graph displays mean ± standard deviation of measurements for each group. The groups denoted by (i), (ii), (iii), (iv), and (v) represent the original alignment and the optimal alignments found using uniform, p-b dysplastic, p-b normal, and CT-based cartilage thickness models, respectively. The black line marks the border between normal and dysplastic values for the AC angle. Optimal orientation of the acetabulum results in improvement (decrease) of AC angle.
Mentions: Different cartilage thickness models and DEA techniques resulted in similar improvements in radiological angles, all of which saw increased lateral coverage of the femoral head in the optimized location. Across the eight combinations of cartilage model and DEA technique, the average increase in CE angle from preoperative to optimal was 19.0 ± 2.2°, ranging from 14.7° to 21.5° (Figure 9). Similarly, the average decrease in AC angle was 19.5 ± 2.4°, ranging from 15.3° to 22.4° (Figure 10). Of the 22 cases with CE angle in the dysplastic range, 91.5% moved to normal range (CE >25°) and 8.5% moved to borderline range (20° < CE < 25°) after realignment.

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