Citation: Presti ML, Francesco I, Sharma B, Raspugli GF, Bignozzi S, et al. Reasons for Early Failure in Medial Unicondylar Arthroplasty. Radiographic Analysis on the Importance of Joint Line Restoration. J Orthopedics Rheumatol. 2014;2(1): 5. J Orthopedics Rheumatol January 2015 Vol.:2, Issue:1 © All rights are reserved by Presti et al. Reasons for Early Failure in Medial Unicondylar Arthroplasty. Radiographic Analysis on the Importance of Joint Line Restoration Keywords: UKA; Knee; Joint line; Alignment; Failure mechanism Abstract Background: Survivorship of Unicompartimental Knee Arthroplasty (UKA) remains a drawback, especially compared to the outcome of Total knee Arthroplasty (TKA). However, this could be improved by identifying and correcting failure mechanisms. To this purpose, this study aims at exploring failure modalities of UKA, with particular focus on the role of Joint Line (JL) position and alignment as variable to be optimized for a successful outcome Material & methods: This study explores modes of failure in 266 medial UKAs, by analyzing the correlation between changes in the obtained alignment and the ideal JL position. In detail, a radiological comparison was performed between 24 failures and 24 matched controls, to determine the importance of UKA positioning in terms of femoro-tibial angle (FTA), tibial plateau angle (TPA), and posterior tibial slope (PTS). Results: Failure occurred for subsidence of the tibial component in two knees, unexplained pain in seven patients, aseptic loosening of the tibial component in eight, aseptic loosening of the femoral component in three, medial tibial fracture in one, and overall osteoarthritis progression in three. The radiographic analysis showed that statistically signifcant differences could be found in the failure group in terms of higher variation of FTA, PTS, and JL height with respect to the control group. Conclusion: A successful outcome after UKA is determined by a correct alignment in all planes, as demonstrated by the failures analyzed in our series: not appropriate coronal alignment, distal JL line positioning, and abnormal PTS were observed and correlated with the failed cases. Thus, based on the results of this study, it could be recommended that the JL position should be carefully controlled while implanting a UKA not only with regard to the coronal plane: in fact, attention should be paid on the implant component positioning in all planes. Introduction In recent years unicondylar knee replacement (UKA) has come forth as a plausible alternative to total knee Arthroplasty (TKA) for specifc patient categories [1-5]. Tis success of surgical option has been favoured by increasing awareness on the importance of proper selection criteria, as well as by advances in prosthesis design and surgical technique. Compared to TKA, UKA is less traumatic, conserves more bone stock and preserves native knee kinematics; resulting in earlier convalescence and better subjective outcome [6- 8]. Tese advantages have expanded its indications to include primary osteonecrosis, younger and more active populations [9-11]. And have also inspired research in bicondylar UKA replacement. However, unexplained UKA failures [12-24], presenting as aseptic component loosening, polyethylene wear, and antero-medial pain, suggest the existence of not yet well identifed parameters that, once addressed, could help to further improve the results, which currently present a slightly poorer long-term survivorship in comparison to TKA [25,26]. Tis represents a sizable population of patients, whose failure cannot be attributed to infection, progression of osteoarthritis, tibial plateau fracture, instability, and metabolic diseases [12-24]. A variety of factors may play a role in these failures. Patient selection, [18,27] implant design, [22,28] and surgical technique [18,21,22,27,29] have been considered among the factors playing a major role in earlier publications [21,28,29]. However, failures have been reported also in cases presenting optimal characteristics in terms of demographic parameter and postoperative alignment [12,13,15,17]. Earlier failure rate unrelated to change in coronal alignment was reported to range from 3.6% to 28.6%: with either unexplained femoral [12,15,17] or tibial loosening [13]. Among the failure mechanisms that should be explored to understand the high failure rate still attributed to unknown factors, prosthetic component positioning deserves further attention. In fact, success may be not only related to the coronal alignment, but could also depend on the appropriateness of JL restoration in terms of UKA positioning in diferent planes. Tus, the aim of this study was to evaluate, in a large cohort of patients, how changes in terms of JL level restoration in the diferent planes may determine failures in UKA. Materials and Methods Te study cohort consisted of 246 patients (men/women: 87/159), who underwent 266 medial UKAs. UKAs were implanted in 187 pa- tients (70.3 %) for osteoarthritis isolated to medial compartment and in 79 (29.7 %) for primary osteonecrosis of medial femoral condyle. Mirco Lo Presti*, Iacono Francesco , Bharat Sharma, Giovanni Francesco Raspugli, Simone Bignozzi, Bruni Danilo, Stefano Zaffagnini, Maria Pia Neri and Maurilio Marcacci 2 nd Orthopaedic and Traumatology Clinic and Biomechanics Laboratory, Codivilla-Putti Research Center Istituto Ortopedico Rizzoli, University of Bologna, Italy *Address for Correspondence Mirco Lo Presti, 2 nd Orthopaedic and Traumatology Clinic and Biomechanics Laboratory, Codivilla-Putti Research Center Istituto Ortopedico Rizzoli, University of Bologna, 1/10 – 40100 – Bologna, Italy, Tel: +051 6366507; E-mail: m.lopresti@biomec.ior.it Submission: 10 July 2014 Accepted: 06 January 2015 Published: 12 January 2015 Copyright: © 2015 Presti ML, et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 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