Purpose

Surgeons sometimes encounter moderate or severe varus deformed osteoarthritic cases in which medial substantial release including semimembranosus is compelled to appropriately balance soft tissues in total knee arthroplasty (TKA). However, medial stability after TKA is important for acquisition of proper knee kinematics to lead to medial pivot motion during knee flexion. The purpose of the present study is to prove the hypothesis that step by step medial release, especially semimembranosus release, reduces medial stability in cruciate-retaining (CR) total knee arthroplasty (TKA).

Patients planning to undergo total knee arthroplasty (TKA), especially in Asian and Middle Eastern countries, usually expect to be able to perform activities requiring knee flexion such as sitting cross-legged or kneeling with ease after the surgery. Postoperative range of motion (ROM) can be affected by multiple factors such as the patient's gender, age, preoperative ROM, diagnosis, the surgeon's technique, the pre- and post-operative rehabilitation program, and the design of the prosthesis. Among these, the choice of the prosthesis depends on the surgeon's preference. As a result, several trials and studies have been conducted to improve postoperative ROM by modifying prosthesis design. The present study aimed to examine the results of TKA with the NexGen LPS-Flex system (Zimmer, Warsaw, Indiana), which is one of several high-flexion total knee prostheses that were designed to achieve a wide ROM for osteoarthritis in the valgus knee. A total of 27 primary TKAs in 26 osteoarthritis patients with valgus knee deformities (femorotibial angle (FTA) ≤ 170°) were performed using the NexGen LPS-Flex fixed prosthesis between July 2003 and December 2011. The patients included 2 men (7.7%, 2 knees) and 24 women (92.3%, 25 knees) with a mean age of 72.6 years (range, 59 to 83 years) at the time of the surgery. The mean duration of follow-up after surgery was 50.1 months (range, 24 to 126 months). Knee Society Knee Score (KSKS), Knee Society Function Score (KSFS), maximum flexion angle, maximum extension angle, and radiological femorotibial angle (FTA) were evaluated pre- and post-operatively. The mean preoperative KSKS and KSFS were 42.6 points (SD 7.5) and 41.1 points (SD 8.6), respectively, which improved after surgery to 82.2 points (SD 8.2) and 80.9 points (SD 7.6), respectively (P < 0.01). The maximum flexion angle improved from 109.1° (SD 23.1) to 117.3° (SD 12.4) postoperatively, but it did not reach statistical significance (P = 0.097). The preoperative maximum extension angle improved from −9.7° (SD 10.8) to −3.6° (SD 4.9) postoperatively (p < 0.05). The mean radiological FTA was 166.4° (SD 4.2; range: 155° − 170°) preoperatively and 172.4° (SD 2.7; range: 168° − 178°) at the final follow-up, and the difference was statistically significant (P < 0.01). None of the patients had undergone revision surgery by the final follow-up. As a conclusion, the results of the present study showed that the use of NexGen LPS-Flex implant in TKA for knee osteoarthritis with valgus deformity produced a satisfactory improvement in the clinical and radiological outcomes. Further studies on the outcomes of other prosthesis are needed to determine whether the NexGen LPS-Flex implant is advantageous for osteoarthritis patients with valgus knees who undergo TKA, and further large-scale studies with longer term follow-up are necessary to verify our results.

Background:

The axis of the fibula in the sagittal plane are known as a landmark for the extramedullary guide in order to minimize posterior tibial slope measurement error in the conventional total knee arthroplasty (TKA). However, there are few anatomic studies about them. We also wondered if the fibula in the coronal plane could be reliable landmark for the alignment of the tibia. This study was conducted to confirm whether the fibula is reliable landmark in coronal and sagittal plane.

Thirty-three knees in thirty-three patients who underwent ACLR using four-strand semitendinousus and gracilis tendon in our hospital were included in this study. In 17 knees, we use a fluoroscopic-based navigation system (Vector Vision ACL, BrainLab. Inc.) for positioning of the tunnels (Group 1). In the remaining 16 knees, positioning of the femoral and tibial tunnels was done without navigation (Group 2).

In navigation operation, anteroposterior and lateral images of the knee were taken with a fluoroscope and captured into the computer. The optimal target points for bone tunnels were semi-automatically calculated and displayed on the screen. Femoral placement was determined based on the quadrant method. The target for tibial tunnel was set at 43% of tibial plateau AP length. Intraoperatively, positions of the drill guides were decided referring to both navigation image and arthroscopic image. We evaluated Lysholm score, International Knee Documentation Committee (IKDC) subjective score, Lachman test and pivot shift test at 1 year after operation and calculated bone tunnel position on the postoperative lateral x-ray films and expressed them as relative values against total AP length of the Blumensaat's line and of the tibia plateau.

Lysholm score, IKDC subjective score, Lachman test and pivot shift test were not significantly differed between the groups. The femoral tunnels were 74.2±3.3% in Group 1 and 71.7±6.0% in Group 2 along and the tibial tunnels were 42.1±1.4% in group 1 and 43.0±4.6% in group 2 along the tibia plateau. Although femur and tibial tunnel positions were not significantly differed between the groups, variation of bone tunnel position was significantly smaller in Group 1, indicating a good reproducibility. One pin tract infection occurred in Group 1. This case successfully treated with debridment and antibiotics containing cement filling.

Fluoroscopic navigation system is quite helpful for precise and reproducible creation of both femur and tibial tunnel. The results encourage us to use this system for double-bundle anatomical ACLR. However, a special care must be taken to avoid complication caused by tracker pin placement.