الفهرس 
Evolution of knee arthroplastyOnly 14 pages are availabe for public view
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Abstract
T
he medial Oxford unicompartmental knee replacement is a valid option for the treatment of advanced bone on bone medial compartment knee arthritis. It has good mid-term survival at five years and achieves excellent patient-reported functional outcomes. The indications and criteria for its use are critical for achieving good results.
The cementless design has significantly improved the incidence of radiolucent lines associated with the cemented tibial component. This may lead to reducing the rate of revisions by avoiding the misinterpretation of radiolucency with aseptic loosening. The radiolucency observed underneath the cementless tibial component appears on the post-operative films possibly due to incomplete seating of the component. This corrects to the desired position with weight-bearing in the first three months following surgery. Also, the persistence of radiolucent lines may occur and is usually not related to the functional outcomes of patients. Therefore, the assessment of painful knees following medial cementless OUKR should aim to specify the cause of the symptoms.
Tibial subsidence is not an uncommon complication following the cementless OUKR. It is one of the causes of persistent pain following surgery. Tibial component subsidence is best assessed using fluoroscopy aligned imaging. Consequently, obtaining fluoroscopic films post-operatively is beneficial for further evaluation. The subsidence in most cases is non-progressive after three months as the tibial component integrates with the bone. It may be classified into posterior subsidence, valgus subsidence, or combined. This could be related to the cause of subsidence but still requires further research to confirm these findings. The diagnosis of this complication is based on radiograph measurements with comparison to the initial post-operative films and is ideally done by fluoroscopy.
Patients’ factors may play an important role in the choice of the tibial prosthesis fixation method for this prosthesis. Elderly patients with poor tibial metaphysis bone quality due to periarticular osteoporosis, associated with reduced loading in the arthritic knee, may be at higher risk for tibial component subsidence. These patients may benefit more from receiving a cemented tibial implant.
In general, this complication is usually non-progressive and the treatment is in the form of pain management, offloading, and monitoring with repeated radiographs. These patients tend to recover fully and achieve excellent outcomes following the osteointegration of the implants with no further interventions required. Revision surgery for these knees is unnecessary.
Tibial implant subsidence may in some cases be progressive and pain persists longer than three months. The progression of subsidence can be evaluated by measurements on follow-up radiographs. Besides, clinical examination may reveal MCL stretch or insufficiency.
Progressive subsidence may lead to the progression of OA with deformity and instability. The treatment of this type of subsidence is usually by a revision to TKR and may require tibial augments for bone loss. Another important factor for the planning for revision surgery of knees with progressive tibial component subsidence is the evaluation of the MCL. In the event of MCL insufficiency, the choice of TKR prosthesis design will change to a more constraint implant.
Tibial component subsidence and fracture are uncommon complications of the cementless OUKR, but have been recorded with a higher incidence than has been seen with the cemented prosthesis. However the risk of radiolucency with the cemented OUKR and the potential for that leading to a revision procedure needs to be balanced against this risk. Our current strategy is to use the cementless prosthesis in the vast majority of cases, but with occasional use of a cemented tibial component if we have concerns about the quality of the proximal tibial bone at the time of surgery.