Posterior cruciate ligament resection under minimum medial collateral ligament release changes tibial internal rotation, joint center gap, and varus ligament balance on joint distraction force at flexion in total knee arthroplasty.

BACKGROUND: The purpose of this study was to assess the effect of posterior cruciate ligament resection under minimum medial collateral ligament release on the joint center gap, varus ligament balance, and the rotational change of the femur and tibia. METHODS: This study included 75 knees with varus osteoarthritis that underwent total knee arthroplasty. After minimum medial collateral ligament releases and bone resection of the distal femur and proximal tibia, the joint center gap and varus ligament balance were measured before and after posterior cruciate ligament resection using a digital tensor with a joint distraction force of 89, 133, 178 N. The rotational changes under a distraction force of 200 N were captured using a navigation system. FINDINGS: The joint center gap and varus ligament balance at 90° and 120° of flexion significantly increased after posterior cruciate ligament resection with distraction forces of 89 N (90°: 0.4 mm / 0.9° and 120°: 0.5 mm / 0.8°), 133 N (90°: 0.9 mm / 1.3° and 120°: 0.9 mm / 1.1°), 178 N (90°: 1.5 mm / 1.9° and 120°: 1.5 mm / 1.5°). Tibial internal rotation significantly increased after posterior cruciate ligament resection at 90° (1.9°) and 120° (2.2°). INTERPRETATION: Joint distraction forces after posterior cruciate ligament resection increased the tibial internal rotation, joint center gap, and varus ligament balance at flexion. These findings indicate that posterior cruciate ligament resection should increase the lateral gap more than the medial gap due to tibial internal rotation at flexion. (245 words).

Cartilage assessment using preoperative planning MRI for femoral component rotational alignment.

BACKGROUND: Surgical planning of posterior referencing total knee arthroplasty (TKA) using computed tomography (CT) might lead to over-rotation of the femoral component because CT could not detect cartilage thickness of the posterior femoral condyle. The purpose of this study was to examine the rotational alignment difference of the femoral component between magnetic resonance imaging (MRI) and CT. METHODS: For elderly varus osteoarthritic patients, 66 varus osteoarthritic knee patients that underwent primary TKA were selected. Twenty-seven young patients who underwent primary anterior cruciate ligament reconstruction were selected as control. After the transepicondylar axis (CEA), the surgical epicondylar axis (SEA) and the posterior femoral condylar line (PCL) were drawn on CT and on MRI at the same angles as CT. Then, the practical PCL was drawn on MRI considering the cartilage thickness (the cartilage PCL). The angle between the SEA and the cartilage PCL (the cartilage posterior condylar angle (PCA)) was measured as preoperative planning. To investigate the accuracy of preoperative MRI measurement, the cartilage thickness on posterior femoral condyles was directly measured during TKA. RESULTS: The cartilage PCA for varus osteoarthritic patients averaged 1.3 ± 1.3°. The cartilage PCA was 1.8 ± 1.0° significantly smaller than the bone PCA (the PCA measured on CT). Meanwhile, the cartilage PCA was 0.2 ± 0.4° significantly larger than the bone PCA in young people. The preoperative angle measurement on MRI strongly correlated with the direct measurement of cartilage thickness during TKA. CONCLUSION: There was 1.8° of divergence between MRI and CT in varus osteoarthritic patients due to cartilage degeneration of the medial femoral condyle. Cartilage assessment using MRI was useful for femoral component rotational alignment.

In vitro cartilage formation using TGF-beta-immobilized magnetic beads and mesenchymal stem cell-magnetic bead complexes under magnetic field conditions.

We evaluated the efficacy of transforming growth factor (TGF)-beta-immobilized magnetic beads for chondrogenesis in vitro using a mesenchymal stem cell (MSC) delivery system and an external magnetic force (EMF). MSCs isolated from the bone marrow of Sprague Dawley rats were mixed with carboxyl group-combined magnetic beads (Ferri Sphere 100C) coated with anti-rat CD44 mouse monoclonal antibodies. TGF-beta3 (10 and 1 ng/mL) was attached magnetically to such other Ferri Sphere 100C beads via an amide bond formed between a primary amino group on the TGF-beta3 and the carboxyl groups on the surface of the beads. MSC-magnetic bead complexes were centrifuged to form a pellet and cultured in chondrogenic differentiation medium (CDM) supplemented with either 10 or 1 ng/mL TGF-beta-immobilized magnetic beads (10 or 1 ng/mL TGF-beta-immobilized magnetic bead groups) or in CDM supplemented with 1 or 10 ng/mL TGF-beta (1 or 10 ng/mL TGF-beta group). TGF-beta-immobilized magnetic beads were gathered effectively under an EMF. Chondrogenesis was achieved from the MSC-magnetic bead complexes in the presence of 1 ng/mL TGF-beta-immobilized magnetic beads.

Functional and radiographic outcome of stable juvenile osteochondritis dissecans of the knee treated with retroarticular drilling without bone grafting.

PURPOSE: The purpose of this study was to evaluate the functional and radiographic outcome of retroarticular drilling for patients with juvenile osteochondritis dissecans after 6 months of unsuccessful nonoperative treatment. METHODS: A total of 20 osteochondritis dissecans lesions in 12 skeletally immature patients were treated with retroarticular drilling without bone grafting. There were 10 boys and 2 girls with a mean age of 12.0 years (range, 9 to 15 years). The functional outcomes were evaluated by use of the Lysholm score at a mean follow-up of 2.7 years after drilling, and healing of the lesions was confirmed by use of plain radiographs and magnetic resonance imaging. RESULTS: The mean Lysholm score significantly improved postoperatively (from 72.3 to 95.8). All lesions except 1 healed after retroarticular drilling. Healing was achieved at a mean of 4.4 months on plain radiographs and 7.6 months on magnetic resonance imaging. CONCLUSIONS: This study shows that retroarticular drilling without bone grafting leads to improved clinical outcomes and high healing rates. We advocate retroarticular drilling for patients with stable juvenile osteochondritis dissecans of the knee whose initial nonoperative treatment has failed.

Articular cartilage injury of the posterior lateral tibial plateau associated with acute anterior cruciate ligament injury.

Thirty-nine knees in 39 patients with recent anterior cruciate ligament (ACL) rupture (age 14-55 years; with a mean age of 22.8 years) were selected from our cases of ACL reconstruction from July 2005 to June 2006, to take part in a study on articular cartilage injury of the posterior lateral tibial plateau associated with acute ACL injury and on the correlation between bone bruises depicted on MRI and cartilage injury of the posterior lateral tibial plateau detected at arthroscopic ACL reconstruction. Using preoperative MRI, we evaluated whether there were bone bruises or not in the lateral compartment of the knee and divided them accordingly into two groups: the bone bruise positive group and the negative group. The differences in the proportions of the lateral meniscus (LM) tears and the cartilage injuries in the two groups were evaluated using Fisher's exact probability test. Thirty-five cases out of 39 arthroscopic ACL reconstructions (89.7%) were regarded as bone bruise positive in the lateral compartment and four cases (10.3%) were regarded as negative. At arthroscopic ACL reconstruction, 33 cases (84.6%) had tears in the LM posterior horn, 34 cases (87.2%) had articular cartilage injuries in the lateral femoral condyle and 29 cases (74.3%) had articular cartilage injuries in the posterior lateral tibial plateau. From 35 bone bruise positive cases, 32 cases (91.4%) had tears in the LM posterior horn, 33 cases (94.3%) had articular cartilage injuries in the lateral femoral condyle and 28 cases (80%) had articular cartilage injuries in the posterior lateral tibial plateau. Of four bone bruise negative cases, one case (25%) had a tear in the LM posterior horn, articular cartilage injury of the lateral femoral condyle and of the posterior lateral tibial plateau. There was a statistically significant correlation between the proportion of bone bruise and cartilage injury of the lateral femoral condyle (P = 0.004), that of the posterior lateral tibial plateau (P = 0.04) and that of tears in the LM posterior horn (P = 0.008). This current study has demonstrated that we need to pay attention to cartilage damage of the posterior lateral tibial plateau as well as to posterior horn tears in LM, when acute ACL injury is shown. We also have to ensure that we follow the long-term progress of cartilage injuries, with the aim of preventing these injuries becoming osteoarthritis after ACL reconstruction.