Abstract
Introduction: Soft tissue balancing is an important factor in the success of TKA, but if extensive may necessitate the use of thicker tibial inserts with the risk of creating a Pseudo-patella baja (PPB), which describes narrowing between the patella and the tibia without shortening of the PT, and occurs when the tibial prosthesis plus insert are thicker than the resected tibia.
Hypothesis: Patients who undergo extensive soft tissue releases during TKA, with resultant use of thicker tibial inserts will develop a PPB, with increased risk of patella pathology.
Method: 506 patients aged 40–90 years underwent 526 Kinemax TKAs, between 1999 and 2002. The extent of soft tissue releases and thickness of tibial inserts were recorded. Patella height was measured on pre and postoperative radiographs by an independent observer. Outcome was assessed using the Oxford Knee Score and the American Knee Society Clinical Rating System, with a minimum follow-up of 12 months.
Results:
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TKA surgery creates a Pseudo-Patella Baja. PPB was introduced into 26.7% of patients. (p=0.000).
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The incidence of pseudo patella baja increased with the extent of soft tissue release. (p=0.000).
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The incidence of pseudo-patella-baja increased with increases in insert thickness. (p=0.035).
There was no correlation between the incidence of PPB and changes in outcome, as measured using the OKS and AKSS.
Conclusion: Pseudo patella baja occurs in 26% of all patients following TKA, and in 46% of patients in whom extensive soft tissue releases have been performed and/or large tibial inserts have been used. AT 12 months, no detrimental outcomes were attributable to the incidence of pseudo patella baja.
Correspondence should be addressed to Mr Tim Wilton, BASK at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
