Discussion
UC knee, pain, UC
COMPLICATION
The most important finding of this study was that the hypothesis was confirmed: the clinical and radiographic outcomes achieved with these devices would be equivalent at 5 years, with a trend favoring the UC group. The ROM, Knee Society Pain/Motion Score, LEAS, SF-36 scores, and radiographic outcomes are all statistically similar. However, the KSS Pain-only and the KSS Function scores favored the non-PS groups, primarily favoring the UC group. Additionally, the tourniquet and total operative times were longer for the PS group compared to the CS and UC groups.There was only one device-related complication, in the UC group: one participant whose polyethylene insert locking bolt was found to be loose at the 3-year follow-up visit, requiring reoperation. This issue has been addressed with a modification in the instrumentation to include an anti-rotational handle to ensure full torque application during assembly of the locking bolt, without affecting tibial baseplate stability and cement fixation during the cement curing process.Hofmann, et al. [In a randomized study of 107 knees receiving either a fixed-bearing UC or PS device at 5-year follow-up, it was found that surgical time was 10 min shorter in the UC group (A 2016 prospective computer-aided navigation study of a UC device and a PS rotating platform device correlated passive kinematics to clinical outcomes [A report [Illustrating this point that stability in mid-flexion is more relevant clinically than stability in 90º of flexion, Jang performed a study [In another dynamic fluoroscopy evaluation, Khasian found that patients with a UC device experienced femoral rollback of the lateral condyle and a normal pattern of axial rotation with flexion, although lower in magnitude than the normal knee. Most importantly, these authors reported minimal dynamic mid-flexion laxity with this UC device [The kinematic alignment approach used in this study may affect the results in a manner that might not be directly comparable to a more traditional mechanical alignment and/or gap balancing surgical approach. It is possible that the UC knee design is better suited for use with kinematic alignment, which preserves the native knee anatomy of each individual patient more closely than other alignment techniques. Perhaps, the PS and CS knee would perform better with a different surgical technique such as mechanical alignment. It is also theoretically possible that the results seen with this specific implant may not be translated to other brands of UC, CS, and/or PS knee systems. To the best of our knowledge, this is the first study reporting the results with a UC device implanted with kinematic alignment.The main limitation of this study is that we did not include the Forgotten Joint Score, which may help discriminate between these implant designs, since kinematic alignment in and of itself provides a high ceiling effect for other scoring schemes such as the Knee Society Score. Another limitation is that the UC group was not part of the randomized CS vs PS group, but instead it was a consecutive group of subjects enrolled after the CS and PS subjects. This could theoretically influence the data in that there might be some subtle differences in various factors such as rehabilitation, pain management, etc.; however, the surgical technique employed was identical. Another limitation is that our enrollment numbers are modest in size, especially at the longer follow-up periods, and that it is possible that with a greater number of patients enrolled statistically significant differences in outcomes might be detected.The PS knee design has several negative attributes not shared with other designs, including a greater incidence of the presence of mechanical sensations [