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Design process of cementless femoral stem using a nonlinear three dimensional finite element analysis.

Baharuddin MY, Salleh ShH, Zulkifly AH, Lee MH, Noor AM, A Harris AR, Majid NA, Abd Kader AS - BMC Musculoskelet Disord (2014)

Bottom Line: This present study proposed a new design process of the cementless femoral stem using a three dimensional model which provided more information and accurate analysis compared to conventional methods.The results showed better total fit (53.7%) and fill (76.7%) canal, with more load distributed proximally to prevent stress shielding at calcar region.The stem demonstrated lower displacement and micromotion (less than 40 μm) promoting osseointegration between the stem-bone and providing primary fixation stability.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Biomedical Engineering Transportation Research Alliance, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia. hussain@fke.utm.my.

ABSTRACT

Background: Minimal available information concerning hip morphology is the motivation for several researchers to study the difference between Asian and Western populations. Current use of a universal hip stem of variable size is not the best option for all femur types. This present study proposed a new design process of the cementless femoral stem using a three dimensional model which provided more information and accurate analysis compared to conventional methods.

Methods: This complete design cycle began with morphological analysis, followed by femoral stem design, fit and fill analysis, and nonlinear finite element analysis (FEA). Various femur parameters for periosteal and endosteal canal diameters are measured from the osteotomy level to 150 mm below to determine the isthmus position.

Results: The results showed better total fit (53.7%) and fill (76.7%) canal, with more load distributed proximally to prevent stress shielding at calcar region. The stem demonstrated lower displacement and micromotion (less than 40 μm) promoting osseointegration between the stem-bone and providing primary fixation stability.

Conclusion: This new design process could be used as a preclinical assessment tool and will shorten the design cycle by identifying the major steps which must be taken while designing the femoral stem.

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Related in: MedlinePlus

Cementless femoral stem design according to the femur morphology (a) mediolateral view (b) anteroposterior view (c) cross section view.
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Figure 4: Cementless femoral stem design according to the femur morphology (a) mediolateral view (b) anteroposterior view (c) cross section view.

Mentions: In general, custom made stems are used for their shape which is designed in line with the patient’s hip morphology [23]. However, manufacturing costs and time consumed are major topics of discussion within the orthopedic community. As standard, off the shelve implants do not cater to all types of femora, a few modifications from the implant’s manufacturer have been done, especially on size and the metaphyseal region. Kaya et al. [24] reported the modification of Anatomic Medullary Locking (AML) stem (Depuy, Warsaw, IN, USA) especially at the metaphyseal, called medial modified aspects (MMA) due to narrower and shorter hips of Japanese. The AML-A was made from cobalt chromium with porous coating circumferentially at proximal region. Another question was whether the smaller size implant solved the problem or was the profile used as a guideline not similar to the Asian femora. We have computed the descriptive statistics for each parameter used in the stem design profile from the dataset as shown in Table 2. In addition to mean, minimum, maximum, and range values, we also reported inter quartile range (IQR) values as a resistance statistic toward outliers compared to the range and standard deviation. The “average” morphology could be used as a guideline for the implant’s design, which better addresses the population diversity. The assumptions made regarding size selection and implant design were based on this “average” femur provides the actual figure of the bone itself. The best fit and fill were considered to contribute to the fixation stability of the implant. Combining the parameters acquired from periosteal and endosteal canal, the stem design was done carefully as shown in Figure 4. The basic principles were used in the design are as follows:


Design process of cementless femoral stem using a nonlinear three dimensional finite element analysis.

Baharuddin MY, Salleh ShH, Zulkifly AH, Lee MH, Noor AM, A Harris AR, Majid NA, Abd Kader AS - BMC Musculoskelet Disord (2014)

Cementless femoral stem design according to the femur morphology (a) mediolateral view (b) anteroposterior view (c) cross section view.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3924227&req=5

Figure 4: Cementless femoral stem design according to the femur morphology (a) mediolateral view (b) anteroposterior view (c) cross section view.
Mentions: In general, custom made stems are used for their shape which is designed in line with the patient’s hip morphology [23]. However, manufacturing costs and time consumed are major topics of discussion within the orthopedic community. As standard, off the shelve implants do not cater to all types of femora, a few modifications from the implant’s manufacturer have been done, especially on size and the metaphyseal region. Kaya et al. [24] reported the modification of Anatomic Medullary Locking (AML) stem (Depuy, Warsaw, IN, USA) especially at the metaphyseal, called medial modified aspects (MMA) due to narrower and shorter hips of Japanese. The AML-A was made from cobalt chromium with porous coating circumferentially at proximal region. Another question was whether the smaller size implant solved the problem or was the profile used as a guideline not similar to the Asian femora. We have computed the descriptive statistics for each parameter used in the stem design profile from the dataset as shown in Table 2. In addition to mean, minimum, maximum, and range values, we also reported inter quartile range (IQR) values as a resistance statistic toward outliers compared to the range and standard deviation. The “average” morphology could be used as a guideline for the implant’s design, which better addresses the population diversity. The assumptions made regarding size selection and implant design were based on this “average” femur provides the actual figure of the bone itself. The best fit and fill were considered to contribute to the fixation stability of the implant. Combining the parameters acquired from periosteal and endosteal canal, the stem design was done carefully as shown in Figure 4. The basic principles were used in the design are as follows:

Bottom Line: This present study proposed a new design process of the cementless femoral stem using a three dimensional model which provided more information and accurate analysis compared to conventional methods.The results showed better total fit (53.7%) and fill (76.7%) canal, with more load distributed proximally to prevent stress shielding at calcar region.The stem demonstrated lower displacement and micromotion (less than 40 μm) promoting osseointegration between the stem-bone and providing primary fixation stability.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Biomedical Engineering Transportation Research Alliance, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia. hussain@fke.utm.my.

ABSTRACT

Background: Minimal available information concerning hip morphology is the motivation for several researchers to study the difference between Asian and Western populations. Current use of a universal hip stem of variable size is not the best option for all femur types. This present study proposed a new design process of the cementless femoral stem using a three dimensional model which provided more information and accurate analysis compared to conventional methods.

Methods: This complete design cycle began with morphological analysis, followed by femoral stem design, fit and fill analysis, and nonlinear finite element analysis (FEA). Various femur parameters for periosteal and endosteal canal diameters are measured from the osteotomy level to 150 mm below to determine the isthmus position.

Results: The results showed better total fit (53.7%) and fill (76.7%) canal, with more load distributed proximally to prevent stress shielding at calcar region. The stem demonstrated lower displacement and micromotion (less than 40 μm) promoting osseointegration between the stem-bone and providing primary fixation stability.

Conclusion: This new design process could be used as a preclinical assessment tool and will shorten the design cycle by identifying the major steps which must be taken while designing the femoral stem.

Show MeSH
Related in: MedlinePlus