INTRODUCTION

Although the most commonly used method of femoral component alignment in total knee arthroplasty (TKA) is an intramedullary (IM) guides, this method demonstrated a limited degree of accuracy. The purpose of this study was to assess whether a portable, accelerometer-based surgical navigation system (Knee Align 2 system; Orth Align, Inc, Aliso Viejo, Calif) improve accuracy of the post-operative radiographic femoral component alignment compared to conventional IM alignment guide.

INTRODUCTION

Rotational alignment of the femoral and tibial component in total knee arthroplasty (TKA) are separately determined based on the anatomy of each bone. Popular references are the transepicondylar axis (TEA) for femoral component, and medial one-third of the tibial tubercle for the tibial component. It was reported that these references are not in accordance with each other in osteoarthritic (OA) knees and rotational mismatch could occur even when the components were accurately aligned. There has been, however, a paucity of data as for the rotational mismatch after TKA for OA knees. The purpose of this study was to evaluate the rotational mismatch between the femoral and tibial component after TKA for OA knees.

INTRODUCTION:

It has been reported that rotational deformity is present in varus osteoarthritis (OA) of the knee and the tibia rotates externally as the varus deformity progresses. Although many studies addressed the rotational alignment of the femoral and tibial component in total knee arthroplasty (TKA), the pre-and postoperative changes of the rotational alignment in varus OA knee has not been evaluated. The purpose of this study was to quantitatively analyze the alteration of rotational deformity after TKA for the varus OA knee.

Over the past decade, there has been an increase in the number of total knee arthropalsty (TKA). Demand of TKA for the young patients who often have high physical demands is also increasing. However, the revision rate in such young patients is much higher due to polyethylene (PE) wear and instability (Julin J, Acta Orthop 2010). Therefore, next generation total knee prostheses are expected to decrease PE wear and to provide stability.

Although in vitro study such as wear simulator test provides important information about PE wear, we have often encountered the discrepancy between the in vitro results and in vivo results. Thus we have performed in vivo PE wear particle analysis, and showed that in vivo PE wear was affected by the design of articulating surface and the materials of femoral component and PE insert (Minoda Y, JBJS Am 2009). Medial pivot design, ceramic femoral component, and highly cross-linked PE decreased in vivo PE wear particle generation.

Patients who underwent bilateral staged TKAs were more likely to prefer medial pivot prosthesis or ACL-PCL retaining prosthesis than the other types of prostheses, because they feels “more stable overall” (Pritchett JW, J Arthroplasty 2011). In vivo fluoroscopic 3D analysis showed that medical pivot and bi-cruciate substituting designs restored physiological knee motion and provided higher reproducibility (Mueller J. Komistek RD, Trans ORS 2009, Iwakiri K, Trans ORS 2007).

The excellent mid-term clinical results of those newly introduced total knee prosthesis, such as alumina medial pivot TKA (Iida T, ORS 2008), medial pivot TKA (Mannan K, JBJS Br 2009, Kakachalions T, Knee 2009), ACL-PCL retaining TKA (Clouter JM, JBJS Am 1999), and highly cross-linked PE (Hodrick JT, CORR 2008), have been reported.

From the point of view of in vivo PE wear, in vivo stability, and the mid-term clinical results, we suspect that medial pivot prosthesis is one of the prostheses which meet the demand in future especially for young active patients.