Isolated liner and head exchange procedure has been an established treatment method for polyethylene wear and osteolysis when the acetabular component remains well-fixed. In this study, its mid-term results were evaluated retrospectively in 34 hips. Among the consecutive patients operated upon from September 1995, 2 patients (3 hips) were excluded because of inadequate follow-up and the results of remaining 34 hips of 34 patients were evaluated. They were 20 men and 14 women with a mean age of 49 years at the time of index surgery. Conventional polyethylene liner was used in 26 cases and highly cross-linked polyethylene liner was used in 8 cases. In 3 cases, liner was cemented in the metal shell because compatible liner could not be used. After a minimum follow-up of 5 years (range, 5∼20.2), re-revision surgery was necessary in 10 cases (29.4%); 8 for wear and osteolysis, 2 for acetabular loosening. In all re-revision cases, conventional polyethylene was used. There was no failure in the cases in which highly cross-linked polyethylene was used. There was no case complicated with dislocation. The results of this study suggest more promising results with the use of highly cross-linked polyethylene in isolated liner exchange.
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. Since February 2014, 44 consecutive patients (39 female, 5 male) with primary arthritis of the knee were enrolled in this prospective, randomized controlled study. 24 patients underwent TKA (Vanguard RP or PS, Biomet Japan) using the navigation device for the distal femoral resection (Navigated Group), and 20 patients with conventional femoral IM alignment guide. The proximal tibial resection was performed using an extramedullary guide. All the operation was performed by a single senior surgeon (YK) with the same gap balancing technique except for the use of the navigation system for the femur. Accuracy of femoral implant positioning was evaluated on 2 weeks postoperative standing anteroposterior (AP) hip to ankle radiographs.INTRODUCTION
MATERIALS & METHODS
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. Eighty-four knees which underwent primary TKA for the varus osteoarthritis of the knee were analyzed. Those knees were chosen by the retrospective confirmation of the precise rotational alignments of both femoral and tibial components by postoperative computed tomography (with ±3 degrees to the targeted reference lines described below). The femoral reference line was the surgical epicondylar axis and the tibial reference line was Akagi's line; a line connecting the midpoint of the tibial insertion of the posterior cruciate ligament and the medial border of patellar tendon. Intraoperative, dynamic evaluations of the rotational mismatch between femoral and tibial components was performed with a special device attached to the mobile-bearing trials at full extension and in neutral, passive external rotation and passive internal rotation.INTRODUCTION
SUBJECTS & METHODS
We prospectively studied the use of intercostal EMG monitoring as an indicator of the accuracy of the placement of pedicle screws in the thoracic spine. We investigated 95 thoracic pedicles in 17 patients. Before insertion of the screw, the surgeon recorded his assessment of the integrity of the pedicle track. We then stimulated the track using a K-wire pedicle probe connected to a constant current stimulator. A compound muscle action potential (CMAP) was recorded from the appropriate intercostal or abdominal muscles. Postoperative CT was performed to establish the position of the screw. The stimulus intensity required to evoke a muscle response was correlated with the position of the screw on the CT scan. There were eight unrecognised breaches of the pedicle. Using 7.0 mA as a threshold, the sensitivity of EMG was 0.50 in detecting a breached pedicle and the specificity was 0.83. Thoracic pedicle screws were accurately placed in more than 90% of patients. EMG monitoring did not significantly improve the reliability of placement of the screw.
