Aims

A fracture of the medial tibial plateau is a serious complication of Oxford mobile-bearing unicompartmental knee arthroplasty (OUKA). The risk of these fractures is reportedly lower when using components with a longer keel-cortex distance (KCDs). The aim of this study was to examine how slight varus placement of the tibial component might affect the KCDs, and the rate of tibial plateau fracture, in a clinical setting.

The kinematic alignment (KA) approach to total knee arthroplasty (TKA) has recently increased in popularity. Accordingly, a number of derivatives have arisen and have caused confusion. Clarification is therefore needed for a better understanding of KA-TKA. Calipered (or true, pure) KA is performed by cutting the bone parallel to the articular surface, compensating for cartilage wear. In soft-tissue respecting KA, the tibial cutting surface is decided parallel to the femoral cutting surface (or trial component) with in-line traction. These approaches are categorized as unrestricted KA because there is no consideration of leg alignment or component orientation. Restricted KA is an approach where the periarthritic joint surface is replicated within a safe range, due to concerns about extreme alignments that have been considered ‘alignment outliers’ in the neutral mechanical alignment approach. More recently, functional alignment and inverse kinematic alignment have been advocated, where bone cuts are made following intraoperative planning, using intraoperative measurements acquired with computer assistance to fulfill good coordination of soft-tissue balance and alignment. The KA-TKA approach aims to restore the patients’ own harmony of three knee elements (morphology, soft-tissue balance, and alignment) and eventually the patients’ own kinematics. The respective approaches start from different points corresponding to one of the elements, yet each aim for the same goal, although the existing implants and techniques have not yet perfectly fulfilled that goal.

The meniscus is a fibrocartilaginous tissue that plays an important role in controlling the complex biomechanics of the knee. Many histological and mechanical studies about meniscal attachment have been carried out, and medial meniscus (MM) root repair is recommended to prevent subsequent cartilage degeneration following MM posterior root tear. However, there are only few studies about the differences between meniscus root and horn cells. The goal of this study was to clarify the differences between these two cells.

Tissue samples were obtained from the medial knee compartments of 10 patients with osteoarthritis who underwent total knee arthroplasty. Morphology, distribution, and proliferation of MM root and horn cells, as well as gene and protein expression levels of Sry-type HMG box (SOX) 9 and type II collagen (COL2A1) were determined after cyclic tensile strain (CTS) treatment.

Horn cells had a triangular morphology, whereas root cells were fibroblast-like. The number of horn cells positive for SOX9 and COL2A1 was considerably higher than that of root cells. Although root and horn cells showed similar levels of proliferation after 48, 72, or 96 h of culture, more horn cells than root cells were lost following 2-h CTS (5% and 10% strain). SOX9 and COL2A1 mRNA expression levels were significantly enhanced in horn cells compared with those in root cells after 2- and 4-h CTS (5%) treatment.

This study demonstrates that MM root and horn cells have distinct characteristics and show different cellular phenotypes. Our results suggest that physiological tensile strain is important for activating extracellular matrix production in horn cells. Restoring physiological mechanical stress may be useful for promoting healing of the MM posterior horn.

Aims

Cementless unicompartmental knee arthroplasty (UKA) has advantages over cemented UKA, including improved fixation, but has a higher risk of tibial plateau fracture, particularly in Japanese patients. The aim of this multicentre study was to determine when cementless tibial components could safely be used in Japanese patients based on the size and shape of the tibia.

Introduction

In most cases of stable type medial femoral neck fracture and some cases of dislocated medial femoral neck fracture, internal fixation was undertaken. Dual SC Screw (DSCS) System is an internal fixation device which has sliding mechanism and preventing mechanism of back out of the screw. The purpose of this study is to evaluate the results and complication of medial femoral neck fracture treated with DSCS.

Introduction

Plate fixations have been recommended for dislocated clavicle fractures. However, existing plates are inadequate for morphological compatibility with the clavicle. The aim of this study is to measure the anatomical shape of the clavicle and to compare the radiographical and clinical outcomes of our tree-dimensional (3D) reconstruction plate with conventional straight plate.

Aims

Dual SC Screw (DSCS) is a novel fixation device for the femoral neck fracture. DSCS is comprised of screw and barrel allowing sliding of the screw and preventing protrusion of the screw end. Two types of the barrels are available, threaded barrel (TB) and plate barrel (PB). Ordinarily, both barrels are implanted. Concept of the design is that the PB contributes stability to the screw against the varus force of the femoral head while the additional screw with TB prevents rotational deformity. The aim of this study was to represent clinical results after DSCS operation in patients with femoral neck fracture.

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.

The ligament balance as well as the alignment is essential for successful total knee arthroplasty (TKA). However it is usually assessed and adjusted only at 0? and 90?. In order to evaluate the ligament balance at the other angles we have used a navigation system. Twenty-one patients underwent posterior stabilised mobile bearing TKA using a CT-based navigation system were included in this study. Immediately post-operation and still under anaesthesia, varus and valgus stresses were applied on operated knees manually at 0?, 30?, 60?, 90? and 120?. The ligament balance was calculated based on the angles under varus and valgus stress displayed on the navigation screen, presenting a relationship between the femoral and tibial cutting planes. The mean ligament balance angle at 0?, 30?, 60?, 90? and 120? were −2? ± 3.6?, −5.8? ± 7.9?, 5.0? ± 6.9?, −1.3? ± 5.4?, 7.9? ± 7.2?, respectively. At 0? and 90? balance was well adjusted, however in the other angles, it was quite varied. At 30? and 120?, the lateral side was loose, on the other hand, medial side was looser at 60? knee flexion angle. The good balance at 0? and 90? is understandable because the balance is assessed and adjusted in these angles. Regarding the other angles, the 30? and 120? results corresponded with previous studies; however, the 60? results did not correlate. Although the reason is unknown, it must be aware the mid-flexion and deep flexion instability is quite common. Further investigations about the impact on clinical outcomes of such instabilities and how to adjust them if they are critical are needed.