Joint Replacement

The use of, and interest in, total knee replacements (TKR) has been growing over the last few
decades. Loosening and migration of tibial components have been identified as one of the
primary causes of failure in the proximal tibia. Clinical studies show the use of metal
implants as one of the primary methods for the treatment of knee joints and associated bone
defects. Alignment and fixation techniques play an important role in achieving high success
rates. Defective bone stock requires the use of augments to stabilise the tibial plate. In these
cases, current clinical practice is to use an extended implant stem to ensure stability. The
problem with this is that it reduces the potential for future knee revision
In this research Finite Element Analysis (FEA) has been used to undertake virtual in-vivo
assessment of various configurations of augmented and non-augmented TKR that can be used
for the treatment of tibial defects. These configurations are based on a standard tibial insert,
namely a fixed bearing revision tibial tray. This has provided insight and information that can
be used to improve surgical decision making when dealing with defective bone stock.
The 3D FE models of a non-defect TKR with a fixed bearing tibial insert showed a stable
construct with stresses lying within an allowable threshold. The use of a stem extension
generally showed a reduction in stress levels in the cancellous bone contributing to an
increase in stress shielding and thus it is recommended that these are not used unless there is
some other overriding clinical requirement.
Further, the analysis demonstrated that, contrary to some clinical opinion, wedge
augmentation (rather than block augmentation) may provide a better approach to treat the
defect. This was largely due to improved cement stress distribution caused by a mechanism
termed “reverse-shear”.
The use of a cement augment was found to provide a more favourable stress distribution in
the cancellous bone. However, metal augments have been recommended as the cement
augment was shown to operate too close to its fatigue endurance limits.

Zirconia is widely used for load-bearing functional structures in medicine and dentistry. The quality of engineered zirconia surfaces determines not only the fracture and fatigue behaviour but also the low temperature degradation (ageing sensitivity), bacterial colonization and bonding strength of zirconia devices. This paper reviews the current manufacturing techniques for fabrication of zirconia surfaces in biomedical applications, particularly, in tooth and joint replacements, and influences of the zirconia surface quality on their functional behaviours. It discusses emerging manufacturing techniques and challenges for fabrication of zirconia surfaces in biomedical applications.

„ Silastic implants for the first metatarsophalangeal joint (MTPJ) have been in use for over 50 years. Initial reports were associated with high failure rates leading to development of new designs that are currently in use. „ The aim of this article is to review the historical evolution and the outcomes of silastic implants for the treatment of end-stage OA of the first MTPJ. Databases were searched for studies reporting the outcomes of silastic implants for the first MTPJ. Various relevant search terminologies were used. Studies reporting the outcomes of metallic implants or arthrodesis were excluded. „ The literature search revealed 522 studies, of which 28 were included. Eight studies used single-stemmed implants and 20 used double-stemmed implants for their patients. Twenty-eight studies had a total of 2354 feet with silastic replacements in 1884 patients (1968 to 2003) with an average age of 53 years and the average follow-up was 85.3 months. There were a total of 5.3% (124 feet) failed prostheses. Improvement in pain was reported in 76.6% (1804 feet) with an average patient satisfaction rate of 84%. Radiological changes around the implants were found to be significantly higher with single-stemmed implants (30.3%) compared to the double-stemmed implants (14.7%) (p < 0.05). „ Significantly more single-stemmed implants failed (11%) than the double-stemmed implants (3.6%) (p < 0.05). Despite the initial reports of failed implants and complications , first-and second-generation silastic implants were associated with high patient satisfaction and pain improvement. Current literature lacks long-term outcomes of implants currently in use.

Background: The purpose of this study was to review the survivorship, radiologic and clinical outcomes of reverse shoulder arthroplasty (RSA) used for the treatment of 3-part and 4-part proximal humeral fractures in the elderly. Methods: Between 2003 and 2009, 29 shoulders in 28 elderly patients (87% female) with a 3-part or 4-part fractures were managed with RSA in Brisbane, Australia. Clinical and radiologic outcomes of this continuous cohort were retrospectively reviewed at an average follow-up of 54.9 months. . Grade 1 scapular notching was observed radiologically in 4 shoulders. A scapular spur was observed in 7 shoulders. Class 1 heterotopic ossification was seen in 4 shoulders. Nonprogressive lucent lines were seen in 2 shoulders. Nonprogressive radiolucency was observed around the superior screw in 3 shoulders. No loosening of the glenoid baseplate or of the humeral component was observed. There was 1 complication of an axillary nerve palsy, which spontaneously resolved by 12 months after surgery. Conclusion: RSA using the shoulder technique described in this series provides good clinical and radiologic outcomes in elderly patients with 3-part and 4-part fractures.

The use of, and interest in, total knee replacements (TKR) has been growing over the last few
decades. Loosening and migration of tibial components have been identified as one of the
primary causes of failure in the proximal tibia. Clinical studies show the use of metal
implants as one of the primary methods for the treatment of knee joints and associated bone
defects. Alignment and fixation techniques play an important role in achieving high success
rates. Defective bone stock requires the use of augments to stabilise the tibial plate. In these
cases, current clinical practice is to use an extended implant stem to ensure stability. The
problem with this is that it reduces the potential for future knee revision
In this research Finite Element Analysis (FEA) has been used to undertake virtual in-vivo
assessment of various configurations of augmented and non-augmented TKR that can be used
for the treatment of tibial defects. These configurations are based on a standard tibial insert,
namely a fixed bearing revision tibial tray. This has provided insight and information that can
be used to improve surgical decision making when dealing with defective bone stock.
The 3D FE models of a non-defect TKR with a fixed bearing tibial insert showed a stable
construct with stresses lying within an allowable threshold. The use of a stem extension
generally showed a reduction in stress levels in the cancellous bone contributing to an
increase in stress shielding and thus it is recommended that these are not used unless there is
some other overriding clinical requirement.
Further, the analysis demonstrated that, contrary to some clinical opinion, wedge
augmentation (rather than block augmentation) may provide a better approach to treat the
defect. This was largely due to improved cement stress distribution caused by a mechanism
termed “reverse-shear”.
The use of a cement augment was found to provide a more favourable stress distribution in
the cancellous bone. However, metal augments have been recommended as the cement
augment was shown to operate too close to its fatigue endurance limits.