Date Published: January 19, 2017
Publisher: Public Library of Science
Author(s): Benjamin Panzram, Ines Bertlich, Tobias Reiner, Tilman Walker, Sébastien Hagmann, Marc-André Weber, Tobias Gotterbarm, Carlos M. Isales.
Tibial radiolucent lines (RL) are commonly seen in cemented unicompartmental knee replacement (UKR). In the postoperative course, they can be misinterpreted as signs of loosening, thus leading to unnecessary revision. Since 2004, a cementless OUKR is available. First studies and registry data have shown equally good clinical results of cementless OUKR compared to the cemented version and a significantly reduced incidence of RL in cementless implants.
This single-centre retrospective cohort study includes the first 30 UKR (27 patients) implanted between 2007 and 2009 with a mean follow-up of 5 years. Clinical outcome was evaluated using the OKS, AKS, range of movement (ROM) and level of pain (VAS). Standard radiologic evaluation was performed at three months, one and five years after surgery. The results five years after implantation were compared to a group of 27 cemented Oxford UKR (OUKR) in a matched-pair-analysis.
Tibial RL were seen in 10 implants three months after operation, which significantly decreased to five after one year and to three after five years (p = 0.02). RL did not have a significant influence on revision (p = 1.0) or clinical outcome after five years. RL were always partial, never progressive and strictly limited to the tibia. There was no significant difference in the incidence of tibial RL five years after implantation between cemented and cementless implants (cemented: 4, cementless: 3, p = 1.0).
After cementless implantation RL were limited to the tibia, partial and never progressive. During short term follow-up the incidence of RL decreased significantly. RL seem to have no influence on clinical outcome and revision.
Cemented medial unicondylar knee replacement is the gold standard for the therapy of anteromedial osteoarthritis of the knee. It has proven excellent long-term survival rates and has many advantages compared to total knee replacement such as smaller incision, minor loss of blood, preservation of bone stock and physiological knee kinematics, shorter hospital stay and rapid recovery.[1–3] The main causes of revision in national joint registries are aseptic loosening of the implant and pain.[4, 5] When pain is associated with physiological radiolucent lines, it might be misinterpreted as a sign of loosening and thereby may lead to unnecessary revisions. 
This single-centre cohort study includes the first 30 cementless OUKR (27 patients), consecutively implanted between 2007 and 2009 in our clinic.
The mean follow-up of this study was 60.0 months (range, 47–69; SD, 8.3) and included 30 cementless OUKR from 27 patients (15 male, 12 female). Mean age at surgery was 62.5 years (range, 49–76; SD, 8.3).
This single-centre cohort study assessed the incidence of RL and their influence on clinical outcome in the first 27 consecutive patients (15 male, 12 female, 30 knees) that were treated with cementless, medial OUKR in our institution between 2007 and 2009. Mean follow-up time was 60.0 months (47–69; SD 8.3) and mean age at surgery was 62.5 years (range 49–76).
RL after cementless OUKR implantation demarcate within the first months after operation and significantly regress over time. They are limited to the tibia, partial and do not progress. As important notion, they seem to have no influence on clinical outcome and revision.