DOES LESS MEDIAL TIBIAL PLATEAU RESECTION MAKE A DIFFERENCE IN UKA

Potential benefits of an inlay design of UKA compared to onlay components include less post-operative pain and quicker recovery due to a lower volume of bone removed, in particular preservation of the densely innervated periosteum and medial tibial plateau periphery. This study assesses the clinical consequences of removing less tibial bone in UKA. Seventy-nine UKA patients from a single surgeon were included in this study, 45 patients receiving a standard onlay UKA and 34 receiving an inlay UKA implanted using a robotically guided system. A radiographic technique was developed to measure the depth of resection of tibial bone stock relative to the initial medial joint line. All patients received the same pain management and rehabilitation protocol and the length of hospital stay was measured. The average depth of medial tibial plateau resection was significantly less with inlay tibial components (3.7 ± 0.8mm) relative to onlay tibial components (6.5 ± 0.8mm, p<0.0001). While the average length of hospital stay was the same for both onlay (LOS = 1.0 ± 0.2days) and inlay (LOS = 0.9 ± 0.5days) UKA procedures, a significantly higher percentage of inlay patients went home the day of surgery (18% vs. 2%, p<0.0001). The depth of medial tibial plateau resection with a typical fixed bearing onlay UKA design is twice as much as an inlay tibial UKA. This has significant consequences for potentially using only primary components at future conversion to total TKA. Likely due to the less invasive (from a host bone perspective) nature of inlay UKA, a significantly higher percentage of these patients are able to be treated as outpatients.