PurposeRecent reports have highlighted the importance of an anatomic tunnel placement for anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the effect of different tunnel positions for single-bundle ACL reconstruction on knee biomechanics.MethodsSixteen fresh-frozen cadaver knees were used. In one group (n = 8), the following techniques were used for knee surgery: (1) anteromedial (AM) bundle reconstruction (AM–AM), (2) posterolateral (PL) bundle reconstruction (PL–PL) and (3) conventional vertical single-bundle reconstruction (PL-high AM). In the other group (n = 8), anatomic mid-position single-bundle reconstruction (MID–MID) was performed. A robotic/universal force-moment sensor system was used to test the knees. An anterior load of 89 N was applied for anterior tibial translation (ATT) at 0°, 15°, 30° and 60° of knee flexion. Subsequently, a combined rotatory load (5 Nm internal rotation and 7 Nm valgus moment) was applied at 0°, 15°, 30° and 45° of knee flexion. The ATT and in situ forces during the application of the external loads were measured.ResultsCompared with the intact ACL, all reconstructed knees had a higher ATT under anterior load at all flexion angles and a lower in situ force during the anterior load at 60° of knee flexion. In the case of combined rotatory loading, the highest ATT was achieved with PL-high AM; the in situ force was most closely restored with MIDMID, and the in situ force was the highest AM–AM at each knee flexion angle.ConclusionAmong the techniques, AM–AM afforded the highest in situ force and the least ATT.

Triaxial accelerometer could serve as a quantitative evaluation of rotational instability. The present study demonstrated that PL bundle has the most important contribution for rotational instability (80.4%) when compared to IM bundle (0.01%) and AM bundle (19.5%) in porcine knee model.

Purpose To evaluate clinical outcomes and radiographic changes in patellofemoral (PF) joint congruity between open wedge high tibial osteotomy (OWHTO) and hybrid closed wedge HTO (HCWHTO). Methods From 2011 to 2013, 36 knees in 31 patients who underwent OWHTO and 21 knees in 17 patients who underwent HCWHTO were evaluated in this retrospective study with a minimum 5-year follow-up. Radiological outcomes including hip-knee-ankle angle (HKA), femoral patellar height index (FPHI), preoperative PF osteoarthritis (OA) grade, medial and lateral joint spaces of the PF joint, and congruence angle were measured. Clinical parameters including the Knee injury and Osteoarthritis Outcome Score (KOOS) and the Oxford Knee Score (OKS) were also evaluated. Preoperative and final follow-up values for each procedure were compared in outcome analyses. Results Mean preoperative HKA and the degree of PF-OA were significantly more severe for patients treated with HCWHTO compared with those treated with OWHTO (p = 0.001, p = 0.0001). Mean postoperative FPHI was significantly decreased with proximalization of the patella in HCWHTO (p = 0.01) but showed no significant change in OWHTO (n.s.). Regarding PF joint congruity after HCWHTO, lateral joint space and congruence angle were significantly improved (p = 0.0001, p = 0.005), while medial joint space was not significantly changed (n.s.). After OWHTO, congruence angle showed no significant difference (n.s.), but medial and lateral joint spaces were significantly decreased (p = 0.0001, p = 0.018). There were no significant differences in KOOS and OKS between the groups (n.s., n.s.). Conclusions Although degrees of varus knee and PF-OA were more severe in HCWHTO than those in OWHTO, HCWHTO led to improved PF joint congruity, and its mid-term clinical outcomes were equivalent to those of OWHTO. Therefore, in patients with varus knee combined with PF-OA preoperatively, HCWHTO is a more effective treatment than OWHTO. Level of evidenceTherapeutic level III. Keywords Open wedge high tibial osteotomy • Hybrid closed wedge high tibial osteotomy • Patellofemoral joint congruity • Osteoarthritis • Knee * Tetsuro Ishimatsu

Our previous studies showed that a mechano-active scaffold made of poly(L-lactide-co-epsilon-caprolactone) (PLCL) exhibited a high potential to realize the formation of a functional, engineered cartilage in vitro. This animal study therefore was designed to investigate the feasibility of repairing on osteochondral defect with the use of bone marrow-derived mesenchymal stem cells (BMSCs) incorporated with a PLCL scaffold. Rabbit BMSCs, isolated and subsequently cultured in monolayer, were seeded into a porous PLCL scaffold sponge following an implantation onto a full-thickness osteochondral defect (diameter of 4.5 mm, depth of 5 mm) that was artificially created on the medial femoral condyles at a high load-bearing site on a rabbit's knee joint. Time-dependent healing of the defect was evaluated by macroscopic, histological examinations at both 3- and 6-month-implantations, respectively. A PLCL sponge incorporated with BMSCs exhibited sufficient structural support, resulting in new osteochondral tissue regeneration: a physiologically well-integrated subchondral bone formation, a hyaline cartilage-like morphology containing chondrocytes surrounded by abundant cartilaginous matrices. In addition, quantitative biochemical assays also demonstrated high potential for the synthesis of sulfated glycosaminoglycan and collagen, both of which are biomolecules essential to extracelluar matrix in normal cartilage tissue. In contrast, defects filled with cell-free PLCL scaffold or left empty showed a very limited potential for regeneration. Our findings suggest that a composite of PLCL-based sponge scaffold and BMSCs promote the repair of osteochondral defects at high load-bearing sites in adult rabbits.

Hip instability is increased in proportion to the degree of dysplasia. Triaxial accelerometry is helpful in the evaluation of dynamic instability of the dysplastic hip. The center-edge angle can be used as an indicator of hip instability.