Knee joint contact stresses : the influence of deformity and muscle activity

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dc.contributor.advisorVaughan, Christopher Leonard (Kit)en_ZA
dc.contributor.advisorLearmonth, I Den_ZA
dc.contributor.authorSchmotzer, Hansen_ZA
dc.date.accessioned2017-12-14T14:20:45Z
dc.date.available2017-12-14T14:20:45Z
dc.date.issued1991en_ZA
dc.description.abstractStudies have shown that the alignment of the knee in the coronal plane has a significant effect on the joint contact stress. However, gait analysis demonstrated that factors other than alignment contributed significantly to the outcome of corrective surgery. It was therefore hypothesized that muscle contraction can alter the stress distribution within the knee joint and that overloading can occur in the absence of a deformity. Six normal knees were harvested from different donors. The exact orientation of all muscle groups was recorded and their tendinous insertions carefully preserved. Custom built pressure transducers (6 per compartment, 0.5 mm thick, 10 mm diameter) were inserted through 2 small, posterior, capsular incisions and placed on the tibial surface and the menisci. The knees were mounted in a loading system which allowed free self-alignment of the joint under load. All muscles were replaced by wire cables instrumented with force transducer, tensioner and grip. Several alignment models (5, 10 degree varus, neutral, 5 degree valgus and 15 degree of flexion) as well as the effect of contraction of all major muscles crossing the knee joint were tested. An even pressure distribution was seen in neutral alignment. In a varus deformity the peak pressure shifted medially and laterally in valgus. Unloading of the opposite compartment was seen for deformities as small as 5 degrees. A flexion deformity produced a postero-lateral shift of the peak pressure area. Muscle contraction increased the pressure significantly in a region next to the muscle. Generally, unloading - though less significant - was seen in a region diagonally across the joint. These results suggest that muscular hyperactivity may considerable increase the contact stresses. However, muscle weakness or lack of muscular contraction may indirectly play a significant role in affecting the contact pressure distribution. If the muscle force is insufficient to counterbalance the external moment condylar lift-off occurs. This increases the angulation between femur and tibia thereby overloading the compartment where contact takes place; One can therefore conclude that abnormal gait patterns or neuromuscular control mechanisms may result in unphysiologically high contact stresses which may cause the development of unicompartmental osteoarthritis and subsequently, a deformity.en_ZA
dc.identifier.apacitationSchmotzer, H. (1991). <i>Knee joint contact stresses : the influence of deformity and muscle activity</i>. (Thesis). University of Cape Town ,Faculty of Health Sciences ,Division of Biomedical Engineering. Retrieved from http://hdl.handle.net/11427/26674en_ZA
dc.identifier.chicagocitationSchmotzer, Hans. <i>"Knee joint contact stresses : the influence of deformity and muscle activity."</i> Thesis., University of Cape Town ,Faculty of Health Sciences ,Division of Biomedical Engineering, 1991. http://hdl.handle.net/11427/26674en_ZA
dc.identifier.citationSchmotzer, H. 1991. Knee joint contact stresses : the influence of deformity and muscle activity. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Schmotzer, Hans AB - Studies have shown that the alignment of the knee in the coronal plane has a significant effect on the joint contact stress. However, gait analysis demonstrated that factors other than alignment contributed significantly to the outcome of corrective surgery. It was therefore hypothesized that muscle contraction can alter the stress distribution within the knee joint and that overloading can occur in the absence of a deformity. Six normal knees were harvested from different donors. The exact orientation of all muscle groups was recorded and their tendinous insertions carefully preserved. Custom built pressure transducers (6 per compartment, 0.5 mm thick, 10 mm diameter) were inserted through 2 small, posterior, capsular incisions and placed on the tibial surface and the menisci. The knees were mounted in a loading system which allowed free self-alignment of the joint under load. All muscles were replaced by wire cables instrumented with force transducer, tensioner and grip. Several alignment models (5, 10 degree varus, neutral, 5 degree valgus and 15 degree of flexion) as well as the effect of contraction of all major muscles crossing the knee joint were tested. An even pressure distribution was seen in neutral alignment. In a varus deformity the peak pressure shifted medially and laterally in valgus. Unloading of the opposite compartment was seen for deformities as small as 5 degrees. A flexion deformity produced a postero-lateral shift of the peak pressure area. Muscle contraction increased the pressure significantly in a region next to the muscle. Generally, unloading - though less significant - was seen in a region diagonally across the joint. These results suggest that muscular hyperactivity may considerable increase the contact stresses. However, muscle weakness or lack of muscular contraction may indirectly play a significant role in affecting the contact pressure distribution. If the muscle force is insufficient to counterbalance the external moment condylar lift-off occurs. This increases the angulation between femur and tibia thereby overloading the compartment where contact takes place; One can therefore conclude that abnormal gait patterns or neuromuscular control mechanisms may result in unphysiologically high contact stresses which may cause the development of unicompartmental osteoarthritis and subsequently, a deformity. DA - 1991 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1991 T1 - Knee joint contact stresses : the influence of deformity and muscle activity TI - Knee joint contact stresses : the influence of deformity and muscle activity UR - http://hdl.handle.net/11427/26674 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/26674
dc.identifier.vancouvercitationSchmotzer H. Knee joint contact stresses : the influence of deformity and muscle activity. [Thesis]. University of Cape Town ,Faculty of Health Sciences ,Division of Biomedical Engineering, 1991 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/26674en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDivision of Biomedical Engineeringen_ZA
dc.publisher.facultyFaculty of Health Sciencesen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherKnee Joint - physiopathologyen_ZA
dc.subject.otherBiomedical Engineeringen_ZA
dc.titleKnee joint contact stresses : the influence of deformity and muscle activityen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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