Cruciate retaining versus posterior stabilized total knee arthroplasty for the treatment of valgus osteoarthritis?

Abstract

Aims and Objectives: The debate of cruciate retaining (CR) versus posterior stabilized (PS) designs in total knee arthroplasty (TKA) is ongoing. With the posterior cruciate ligament retained, the TKA is supposed to function better in terms of proprioception, balance and kinematics. In contrast to that, PS designs are supposed to lead to higher degrees of flexion and a better femoral rollback. It is known, that the preoperative deformity negatively correlates with inferior results following TKA. When balancing a valgus knee, Ranawat et al. suggest to address the PCL in the first place. It is known that in 60% of valgus knees 1-2 soft tissue releases are necessary in order to achieve neutral alignment. Up to date no study exists, reporting the outcome of CR versus PS TKA in valgus knees. Thus, it was purpose of this study to evaluate the mid term outcome of CR versus PS TKA for the treatment of valgus OA in groups between 3°-6° of valgus, 7-10° of valgus and >10° of valgus. Materials and Methods: With the KOOS score as the primary endpoint, a sample size of 117 cases (78 CR and 39 PS) was needed in order to get a statistical power of 80%.Between 01-2011 and 03-2014 a total of 248 patients with a preoperative valgus >3° were treated with a CR TKA (167 cases) or a PS TKA (81 cases) of the same manufacturer (Stryker Triathlon, Stryker, Kalamazoo USA). CR patients were divided into the following groups: Preoperative valgus >3°-6°, 7°-10° and >10°. PS patients were divided into the following groups: Preoperative valgus >3°-6°, 7°-10° and >10°. The KOOS Score and the Oxford Knee score was collected at the time of follow up. For the CR and PS group failure rates and failure etiologies were analyzed. Patients demographics and were collected as well. Results: 141 patients were included into this study (97 CR and 44 PS cases). The CR group had a mean follow up of 57 weeks, the PS group had a follow up of 52weeks. In the CR group, 11/97 (11%) patients were revised due to a.p. instability, whereas 2/44 (5%) patients were revised in the PS group due to infection or aseptic loosening. There was no difference regarding OKS and the KOOS score between the two groups. Further, there was no difference regarding patients demographics and no correlation between the BMI and the clinical outcome. Conclusion: The most important findings of this study are that the CR group showed a significant higher early revision rate, whereas the clinical mid term follow up results are equal. The CR version of the used system showed significantly higher early failure due to a.p. instability.