Abstract
Introduction
Early complication post total knee replacement reported to be higher in obese patient in general. Also the outcome of cruciate retaining and PS knee has been fully discussed before and there was no major difference in the outcome. However, the purpose of this paper is to find out if early complication postTKR such as fracture and instability is more common in PS implant than in CR knee. This is a retrospective study comparing two groups of obese patients. The first using PS implant and the other using CR implant. These two groups were matched for age, body mass and severity of deformity. We clearly showed that there is significant increase in peri-prosthetic fracture and instability in the group that use PS implant.
Materials & Methods
At our institution we have been using Persona implant which has the option of using PS insert or a CR. The decision to proceed with CR or PS mainly depends on the availability of the implant and also the ability to well balance the knee in patients. In most patients we try to proceed with CR implant. However, the flow of implant sometime sometimes limit us from using CR or the imbalance in the ligament force us to process with PS implant.
We have reviewed a chart of over 200 patients in each group of obese patient they were done within the last three years. All cases had a minimum follow up of 6 months. Those groups were matched for body mass, age and severity of deformity. After matching the groups we documented knee score, blood loss, post – operative pain and complications. All surgeries were performed by the same surgeon.
Results
We had 7 cases of per-prosthetic fracture in the PS group and non in the CR implant. We had 3 revisions in the PS group for instability and MCL insufficiency. We had non in the CR implant. Infection, wound complication, blood loss, knee score and patient satisfaction were same in both groups.
Discussion
Our study clearly show that the decrease incidence of peri-prosthetic fracture in the CR implant which could be easily explained by the fact that a good cortical bone is resected in order to make room for the PS spine. Also, the fact that resecting the posterior cruciate ligament might cause more stress on the implant versus the CR. Instability also were more common in the PS group. We believe this has to do with the fact that the PCL serve as a secondary constraint to the MCL. The presence of the PCL help maintain the stability in case of incidental injury to the MCL during surgery which was reported to be higher in obese patients. Practically the same in both group shows there is no apparent advantage of either implant.
Conclusion
There is clear advantage of decreasing the early postoperative complications in obese patient using CR knee and we strongly recommend using CR implant in obese patients in order to reduce the incidence of peri-prosthetic fracture and the revision for instability.
