Abstract
Introduction
Various implant designs and bearing surfaces are used in TKR. The use of All Poly Tibia and poly moulded on Tibial metal base plate has been in practice since long. Recently due to the reports on wear and osteolysis in modular articulations, these components have generated significant interest.
Aim
To report early medium term results in elderly (>70 years) patients.
Method
Study of 130 cases done between 2005–2009. All cases were performed by the author.
Inclusion Criteria:
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Patients with physiological age > 70 years
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Patients with low functional demand.
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Good bone quality.
Exclusion Criteria: Inflammatory arthropathy
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Osteoporosis and poor bone quality.
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High functional demand.
All Poly Tibial component/ Moulded Metal back Tibia implantations were performed. A PS design was used in all cases fixed with CMW 1 gentamicin cement.
Results
12 cases were lost to follow up. 11 patients deceased due to medical conditions. This left us with 107 cases at the time of the last follow up.
Mean age at index surgery was 72.5 years.(70–91 years)
Preop KSS average was 42 (25–62). Post operative at the latest Follow up was 89 (68–97).
Of 107 cases there were 4 revisions - two for deep sepsis and two for periprosthetic fractures.
There were no revisions for aseptic loosening or osteolysis. All 103 cases are performing well functionally and clinically. 19 cases have a nonprogressive radiolucent line beneath the Tibial component.
Discussion
Use of Monobloc Tibia is somewhat controversial. The first Total condylar Knee was an all poly design in early 70s1. The monobloc tibia eliminates backside wear. The overall thickness of polyethylene in this implant is 2 to 4mm thicker in allpoly tibia design. The metal base plate with compression moulded polyethylene dissipates stresses evenly in osteopaenic bones.
The polywear and osteolysis are two most important factors for aseptic loosening. If Symptomatic, loosening warrants a revision surgery. Metal back fixed bearing implant has a disadvantage that it wears from both the surfaces. The highly polished trays are supposed to reduce the wear but it is too early for a statistically significant conclusion. Functionally low demand patients have lesser stresses as compared to their counterparts. The surgical technique for insertion of these implants is slightly demanding as compared to modular implants.
The combination of perfect alignment and soft tissue balance creates an environment for a successful TKR. The choice of Monobloc Tibial component for functionally low demand age group patients reduce the chances of premature wear and osteolysis. In elderly patients the implant should outlive the patient. Here it is observed that at early medium term (5 to 9 yr.s) aseptic loosening and subsequent revision chances are low. The Monobloc Tibial component is cheaper as compared to its metal back counterpart.
Conclusion
An excellent clinical result in our hands for this group of patients supports the continued use of this implant strongly.
