Yasukazu Yonetani

Differential and collaborative actions of Rad51 paralog proteins in cellular response to DNA damage

Metazoan Rad51 plays a central role in homologous DNA recombination, and its activity is controlled by a number of Rad51 cofactors. These include five Rad51 paralogs, Rad51B, Rad51C, Rad51D, XRCC2 and XRCC3. We previously hypothesized that all five paralogs participate collaboratively in repair. However, this idea was challenged by the biochemical identification of two independent complexes composed of either Rad51B/C/D/XRCC2 or Rad51C/XRCC3. To investigate if this biochemical finding is matched by genetic interactions, we made double mutants in either the same complex (rad51b/rad51d) or in both complexes (xrcc3/rad51d). In agreement with the biochemical findings the double deletion involving both complexes had an additive effect on the sensitivity to camptothecin and cisplatin. The double deletion of genes in the same complex, on the other hand, did not further increase the sensitivity to these agents. Conversely, all mutants tested displayed comparatively mild sensitivity to γ-irradiation and attenuated γ-irradiation-induced Rad51 foci formation. Thus, in accord with our previous conclusion, all paralogs appear to collaboratively facilitate Rad51 action. In conclusion, our detailed genetic study reveals a complex interplay between the five Rad51 paralogs and suggests that some of the Rad51 paralogs can separately operate in later step of homologous recombination.

Repair of meniscal lesions using a scaffold-free tissue-engineered construct derived from allogenic synovial MSCs in a miniature swine model

The menisci of the knee are fibro-cartilaginous tissues and play important roles in the joint, and the loss of the meniscus predisposes the knee to degenerative changes. However, the menisci have limited healing potential due to the paucity of vascularity. The purpose of the present study was to test the feasibility of a scaffold-free tissue-engineered construct (TEC) derived from synovial mesenchymal stem cells (MSCs) to repair incurable meniscal lesions. Porcine synovial MSCs were cultured in monolayers at high density in the presence of ascorbic acid followed by the suspension culture to develop a three-dimensional cell/matrix construct (TEC). A 4-mm cylindrical defect was created bilaterally in the medial meniscus of skeletally mature miniature pigs. The defects were implanted with an allogenic TEC or were left empty. After 6 months, the TEC-treated defects were consistently repaired by a fibro-cartilaginous tissue with good tissue integration to the adjacent host meniscal tissue, while the untreated were either partially or not repaired. The ratio of Safranin O positive area within the central body of the meniscus adjacent to the original defect was significantly higher in the TEC-treated group than in the control group. Moreover, TEC treatment significantly reduced the size and severity of post-traumatic chondral lesions on the tibial plateau. These results suggest that the TEC could be a promising stem cell-based implant to repair meniscal lesions with preventive effects from meniscal body degeneration and the development of post-traumatic arthritis.

Histological evaluation of juvenile osteochondritis dissecans of the knee: a case series

Osteochondritis dissecans (OCD) is an acquired, potentially reversible idiopathic disease of subchondral bone resulting in delamination and sequestration. Although juvenile-type OCD lesions typically appear stable on superficial examination, conservative treatment results in cure in approximate 50% of patients. We hypothesized that juvenile-type OCD lesions exhibit an underlying instability despite stability at the articular surface and this underlying instability might underlie the lack of effectiveness of conservative treatment. In this study, osteochondral cylindrical tissue samples obtained from stable juvenile OCD lesions located at the medial femoral condyle (classical site) were examined. Eight patients with symptomatic juvenile-type OCD at the classical site underwent arthroscopy. Osteochondral cylindrical tissue samples were obtained from the central portion using a biopsy needle. The samples underwent macroscopic and microscopic examination. All cylindrical samples demonstrated macroscopic separation. On microscopic examination, no degenerative changes in articular cartilage and no bone necrosis were observed. Histological examination revealed two distinct patterns in the samples: (1) thick homogeneous hyaline cartilage alone with little fibrous tissue surrounding areas of separation and (2) nearly normal, thin hyaline cartilage above a mixed layer of hyaline cartilage and subchondral trabeculae and fibrous/fibro-cartilaginous tissue at the areas of separation, indicating delayed or nonunion. Pathological findings in stable juvenile OCD lesions indicate an underlying instability at deeper layers of articular cartilage and poor healing at areas of separation. Improved knowledge of the histology of juvenile-type OCD lesions may support surgical treatment. Early marrow stimulation and/or fixation may be the treatment of choice to promote healing even in macroscopically stable juvenile-type OCD lesions.

Effects of medial patellofemoral ligament reconstruction on patellar tracking

PurposeMedial patellofemoral ligament (MPFL) reconstruction has been performed to treat recurrent patellar dislocation. However, the effects on patellar tracking have not been well documented, particularly in patients. The purpose of this study is to compare patellar tracking pattern and chondral status at MPFL reconstruction with those at second-look arthroscopy.MethodsBetween 1999 and 2008, 71 patients with recurrent patellar dislocation underwent MPFL reconstruction using a double-looped semitendinosus tendon. Of these, 25 knees in 24 patients underwent second-look arthroscopy (at 6–26xa0months after initial surgery), forming the subject for the present study. No other surgical procedures such as tibial tuberosity transfer, lateral release, or osteotomy were performed in any patients. To assess the patellar tracking pattern, the position of the patella on femoral groove was evaluated arthroscopically during passive knee motion through lateral suprapatellar portal.ResultsBefore MPFL reconstruction, the patella in all patients was shifted laterally throughout the entire range of knee motion. Immediately after MPFL reconstruction, patellar malalignment was corrected in all cases. On second-look arthroscopy, two different patellar tracking patterns were observed. In 9 knees, the patella was located on the center of the femoral groove throughout the range of motion. Meanwhile, in the remaining 16 knees, the patella was shifted laterally at knee extension and migrated to the center of femoral groove with increased knee flexion. No significant deteriorations in chondral status were seen on second-look arthroscopy.ConclusionThe present study revealed that not all improved patellar trackings after MPFL reconstruction remained intact at follow-up. Chondral status in patellofemoral joint was not aggravated by MPFL reconstruction.Level of evidenceTherapeutic studies, Level IV.

Histological evaluation of spontaneous osteonecrosis of the medial femoral condyle and short-term clinical results of osteochondral autografting: A case series

Although many surgical modalities for spontaneous osteonecrosis of the knee (SONK) of the medial femoral condyle have been reported, few reports have described these treatment options from the etiological point of view. Recently, osteochondral autografting has gained popularity for use in small cartilage injuries. The aims of this study were to characterize the SONK lesion histopathologically and to report on preliminary clinical results of autogenous osteochondral grafting for SONK. Six patients with SONK of the medial femoral condyle underwent osteochondral autografting. Average age was 54.2 years (range, 50-57 years). Using Koshinos classification, three patients lesions were classified as stage III and three as stage IV. Classical histological investigation of the lesions was performed in all cases. All the patients achieved favorable pain relief after osteochondral autografts. The mean duration of follow-up was 27.7 months (range, 23-45 months). An increase in the average Lysholm score was found, ranging from 54.7 preoperatively to 92.3 postoperatively. Histological investigation of the lesions revealed articular bone plate fracture with enchondral ossification, reactive cartilage tissue formation, and proliferation of fibrous tissue. An area of osteonecrosis was observed in detached or fragmented osteochondral lesions. Osteochondral autografting was performed on six patients for the SONK and the short-term clinical results were favorable. Histological results give support to subchondral fracture as the etiological mechanism underlying SONK.

MRI analysis of single-, double-, and triple-bundle anterior cruciate ligament grafts

PurposeThe purpose of the study was to evaluate the entire course of ACL grafts on coronal oblique MR images, focusing on differences in graft morphology and graft-to-tunnel healing among single-bundle (SB), double-bundle (DB), and triple-bundle (TB) reconstructions. MethodsEighty-three patients underwent anatomical ACL reconstruction using the semitendinosus tendon. SB reconstruction was performed on 20 patients, DB on 29 patients, and TB on 34 patients. The anteromedial-bundle (AMB) and posterolateral-bundle (PLB) images were extracted from coronal oblique images of grafts at 6xa0months to visualize their entire course. Signal intensity of grafts was measured independently in three regions: (1) intra-femoral tunnel region, (2) intra-articular region, and (3) intra-tibial tunnel region, followed by calculation of the signal-to-noise quotient (SNQ). To evaluate graft-to-tunnel healing, T2-weighted images were examined for the presence of a high signal-intensity lesion between the graft and bone tunnel around the tunnel aperture.ResultsAMB images showed that SB graft was thick throughout the entire course, while DB graft was thinner than SB graft. TB graft showed a fan shape approaching the tibial tunnels. The SNQ in the femoral tunnel of SB graft was significantly lower than in the DB and TB grafts. High signal-intensity lesions were frequently observed around the femoral tunnel aperture in PLB images of DB and TB grafts compared to SB grafts.ConclusionGross morphology of TB grafts resembled that of the natural ACL. However, the graft-to-tunnel healing around the femoral tunnel seemed to be insufficient in PLB images of DB and TB compared to SB grafts.Level of evidenceIII.

MRI analysis of the attachment of the anteromedial and posterolateral bundles of anterior cruciate ligament using coronal oblique images

PurposeThe purpose of this study was to evaluate the course of the anteromedial bundle (AMB) and the posterolateral bundle (PLB) of the anterior cruciate ligament (ACL) with magnetic resonance imaging (MRI) in order to clarify the relationship between the bundles and surrounding anatomic landmarks.MethodsEighty-eight knees with intact ACLs were included in this study. MRI coronal oblique images were obtained with the knee in extension and used to assess the following characteristics of the AMB and PLB: (1) course of the ligament, (2) location of the tibial attachment, and (3) femoral attachment and geometry of the lateral femoral condyle inner wall.ResultsIn terms of the tibial attachment, the AMB was confluent with the apex of the medial intercondylar ridge (MIR) in all cases. Sixty-five PLBs (74%) inserted into the region between the apex and the slope of the MIR. The resident’s ridge was detected in 91% of the knees in the AMB image, whereas the ridge was clearly visualized in only 17% of the knees in the PLB image. A bony eminence was observed at the inner articular margin of the lateral femoral condyle in the PLB image.ConclusionIn terms of the tibial attachment, the AMB was confluent with the apex of the medial intercondylar ridge in all cases. Most of the PLBs attached to the region between the apex and the slope of the MIR. Because the bone tunnel location influences clearance between the grafts and the surrounding tissues, these results should be considered during anatomic double-bundle ACL reconstruction.Level of evidenceStudy of nonconsecutive patients without a universally applied gold standard, Level III.

Fixation of Detached Osteochondritis Dissecans Lesions With Bioabsorbable Pins: Clinical and Histologic Evaluation

PURPOSEnThe purpose was to evaluate the effect of fixation of detached free fragments of osteochondritis dissecans (OCD) (International Cartilage Repair Society OCD IV) on not only the clinical outcome, including functional and radiographic assessment, but also postoperative second-look arthroscopic and histologic evaluation.nnnMETHODSnNine International Cartilage Repair Society OCD IV fragments were fixed with bioabsorbable pins made of poly-L-lactic acid after curettage of the bed and bone grafting. In 4 cases with severe cartilage damage in the fragments, after resection of the damaged part, trimmed fragments were fixed and osteochondral autologous transplantation was performed to cover the remaining defects. The follow-up period was at least 2 years (range, 2 to 3 years). Lysholm score and computed tomography (CT)/magnetic resonance imaging (MRI), second-look arthroscopy, and biopsy findings were examined postoperatively.nnnRESULTSnAll patients ultimately could return to previous sports activity, and the mean postoperative Lysholm score was 97 (range, 90 to 100). At 6 months, CT/MRI scans showed complete union and smooth continuity of articular surface in all cases. Second-look arthroscopy in 7 cases showed that fixed fragments were stable and that there were no progressive degenerative changes in the cartilage. Postoperative histologic examination in 4 cases showed almost normal cartilage from surface to bottom in terms of viability and quality. In addition, new bone trabeculae were covering dead bone trabeculae, which is called creeping substitution.nnnCONCLUSIONSnOur study shows good short-term clinical results, as well as confirmation of healing on CT/MRI and second-look arthroscopy.nnnLEVEL OF EVIDENCEnLevel IV, therapeutic case series.

Retear of anterior cruciate ligament grafts in female basketball players: a case series

BackgroundIncidence of anterior cruciate ligament (ACL) injuries in young female basketball players is higher than that in male basketball players. Graft retears are more frequent with the increasing number of ACL reconstructions. The present study aimed to examine the incidence of retears in competitive female basketball players.MethodsSixty-four female basketball players (aged 12 to 29 years) who underwent primary anatomic double-bundle ACL reconstruction using hamstring grafts participated in the study. We investigated incidence, mechanism, and patient characteristics of ACL graft retears. Mann-Whitney U test was used for statistical analysis, and the level of significance was determined at P < 0.05.ResultsSix patients suffered from ACL graft retear (9.4%). Mean duration between primary ACL reconstruction and incidence of retears was 11.7 months. However, there were no other postoperative graft ruptures after 24 months. Primary injury and retear mechanisms varied by patient. At six months after the primary ACL reconstruction surgery, mean quadriceps and hamstring strengths were 81% and 87%, respectively, indicating favorable recovery of muscle strength. However, preoperative quadriceps and hamstring strength in the retear group were 65% and 71%, respectively. In particular, preoperative quadriceps strength in the retear group demonstrated a lower value than that in the uninjured group (P < 0.05).ConclusionsWe observed a high incidence of ACL graft retears in competitive female basketball players, as previously reported. Considering the timing of graft retear occurrences, an early return to playing basketball should be avoided following ACL reconstruction. Closer attention should be paid to player preoperative condition, as well as muscle strength and postoperative status.

The use of MRI in pre-operative evaluation of anterior talofibular ligament in chronic ankle instability

Objectives To evaluate the applicability of MRI for the quantitative assessment of anterior talofibular ligaments (ATFLs) in symptomatic chronic ankle instability (CAI). Methods Between 1997 and 2010, 39 patients with symptomatic CAI underwent surgical treatment (22 male, 17 female, mean age 25.4 years (15 to 40)). In all patients, the maximum diameters of the ATFLs were measured on pre-operative T2-weighted MR images in planes parallel to the path of the ATFL. They were classified into three groups based on a previously published method with modifications: ‘normal’, diameter = 1.0 - 3.2 mm; ‘thickened’, diameter > 3.2 mm; ‘thin or absent’, diameter < 1.0 mm. Stress radiography was performed with the maximum manual force in inversion under general anaesthesia immediately prior to surgery. In surgery, ATFLs were macroscopically divided into two categories: ‘thickened’, an obvious thickened ligament and ‘thin or absent’. The imaging results were compared with the macroscopic results that are considered to be of a gold standard. Results Agreement was reached when comparison was made between groups, based on MRI and macroscopic findings. ATFLs were abnormal in all 39 cases and classified as ten ‘thickened’ and 29 ‘thin or absent’. As to talar tilt stress radiography, a clear cut-off angle, which would allow discrimination between ‘thickened’ and ‘thin or absent’ patients, was not identified. Conclusion MRI is valuable as a pre-operative assessment tool that can provide the quantitative information of ATFLs in patients with CAI. Cite this article Bone Joint Res 2014;3:241–5.