Nobuto Kitamura

Computed Tomography in the Assessment of Periacetabular Osteolysis

BACKGROUND Computed tomography recently has been proposed as an accurate method for diagnosing periacetabular osteolytic lesions. Several investigators have attempted to validate the accuracy of this technique, but they employed cadaveric and animal models, which cannot replicate the adaptive changes that occur over time in vivo. This study was performed to determine the accuracy of computed tomography in identifying and measuring periacetabular osteolytic lesions in hemipelves retrieved at autopsies of individuals with a previously well-functioning total hip prosthesis. METHODS We evaluated nine hemipelves, retrieved at autopsy, that contained a cementless porous-coated acetabular component. The fresh specimens were examined with conventional radiographs and computed tomography and then were embedded and sectioned into 1.5-mm slices for evaluation with slab radiographs. Anteroposterior and iliac oblique plain radiographs as well as axial, coronal, and sagittal computed tomography scans were reviewed to determine the presence and location of any periacetabular osteolytic lesions. These results were then compared with those identified on the slab radiographs. Lesion volume was calculated from computed tomography scans with use of post-processing software. RESULTS A total of twenty-three periacetabular osteolytic lesions were identified on the slab radiographs of the nine hemipelves. The plain radiographs identified twelve (52%) of the twenty-three lesions, and the computed tomography scans identified twenty (87%) of the twenty-three lesions. Three medial wall perforations were identified on the computed tomography scans but were not detected on the plain radiographs. Computed tomography was accurate in measuring the volume of the osteolytic lesions (r(2) = 0.997) but tended to overestimate the volumes measured on the slab radiographs. Periacetabular osteolytic lesions appeared on the computed tomography scans and slab radiographs as areas devoid of trabecular bone that were delineated by a sclerotic border and communicated with the joint space. CONCLUSIONS In this autopsy model, computed tomography was an accurate method for detecting the location and measuring the volume of periacetabular osteolytic lesions.

Proteoglycans and Glycosaminoglycans Improve Toughness of Biocompatible Double Network Hydrogels

Based on the molecular stent concept, a series of tough double-network hydrogels (St-DN gels) made from the components of proteoglycan aggregates - chondroitin sulfate proteoglycans (1), chondroitin sulfate (2), and sodium hyaluronate (3) - are successfully developed in combination with a neutral biocompatible polymer. This work demonstrates a promising method to create biopolymer-based tough hydrogels for biomedical applications.

Robust bonding and one-step facile synthesis of tough hydrogels with desirable shape by virtue of the double network structure

Robust bonding of a hydrogel in aqueous environment, either to another hydrogel or to a solid, is one of the major unsolved issues for the practical applications of hydrogels in various fields. Here we report robust bonding between a pair of hydrogel sheets, containing over 90 wt% of water, by applying the double-network (DN) structure. In the optimal condition, the peeling energy of the united gel sheets reaches 1200 J m−2, which is comparable to the bulk fracture energy of a normal type of tough DN gels. This hydrogel bonding technique is also applied to form tough bonding between hydrogel and plastic plates. Furthermore, based on this technique, we have developed a facile method to synthesize robust double network hydrogels with any desirable free-shape from micro-gel precursors. These novel techniques will substantially merit the applications of the tough hydrogels in various fields, such as an artificial meniscus.

Double-Network Hydrogels Strongly Bondable to Bones by Spontaneous Osteogenesis Penetration

On implanting hydroxyapatite-mineralized tough hydrogel into osteochondral defects of rabbits, osteogenesis spontaneously penetrates into the gel matrix owing to the semi-permeablility of the hydrogel. The gradient layer (around 40 μm thick) contributes quite strong bonding of the gel to bone. This is the first success in realizing the robust osteointegration of tough hydrogels, and the method is simple and feasible for practical use.

Characteristics of pelvic osteolysis on computed tomography after total hip arthroplasty.

We investigated the characteristics of pelvic osteolysis using computed tomography to assess osteolytic patterns associated with five acetabular cup designs. Additionally, we examined the relationship between polyethylene wear and volume of pelvic osteolysis. We measured defect volume on the computed tomography images of 126 hips at a mean of 10.9 years after arthroplasty. Defects were classified as osteolysis if there was: (1) a well-defined sclerotic border, (2) no radiographic evidence that the defect existed before hip arthroplasty, and (3) a clear communication between the defect and the joint space. We identified 225 bone defects in 116 hips. Of these, 184 defects in 101 hips fulfilled our criteria for osteolysis. We found that lesion size and the location of the communication pathways depended on the cup design. Osteolysis occurred primarily through central holes, and occurred only around the rim if there were no holes in the cup. The lesions that communicated only through central holes and those with multiple communications tended to be larger than rim-related lesions. There was a moderate correlation between volumetric polyethylene wear and osteolysis volume. Communication pathways between lesions and the joint space are valuable for diagnosing osteolysis on computed tomography. Lesion volume, location, and type of communication pathway to the joint are influenced by cup design. Level of Evidence: Therapeutic study, Level IV-1 (retrospective case series). See the Guidelines for Authors for a complete description of levels of evidence.

Diagnostic features of pelvic osteolysis on computed tomography: the importance of communication pathways.

BACKGROUND Progressive periacetabular osteolysis following total hip arthroplasty may require revision surgery. The purpose of this study was to use computed tomography scans of hemipelves retrieved at autopsy from patients who had had a total hip arthroplasty, to define the radiographic characteristics that differentiate clinically important osteolytic lesions from osteoarthritic bone cysts. METHODS We analyzed forty-four hemipelves that had been retrieved at autopsy at a mean of eight years after a total hip arthroplasty with an uncemented acetabular component. Computed tomography images were analyzed to identify the location, volume, and presence of cortical erosion and/or communication pathways with the joint space for all periacetabular bone defects. Lesions that were not present on preoperative or immediate postoperative plain radiographs were defined as new lesions. These new lesions were compared with those that were present on preoperative or immediate postoperative plain radiographs, which were defined as preexisting lesions. RESULTS Forty-six lesions were identified on computed tomography, and sixteen of them were preexisting lesions. The mean volume of the preexisting lesions was 1.5 +/- 1.5 cm(3), which was significantly smaller than the mean volume of 5.6 +/- 11.4 cm(3) of the thirty new lesions (p = 0.034). Twenty-eight of the thirty new lesions had a clear communication pathway with the joint space, while thirteen of the sixteen preexisting lesions demonstrated no communication pathway. New lesions were significantly more likely to communicate with the joint space than were preexisting lesions (p < 0.001). Cortical erosion was seen in sixteen of the thirty new lesions; none of the sixteen preexisting lesions exhibited cortical erosion (p < 0.001). CONCLUSIONS The most important difference between osteolytic lesions and preexisting bone defects was the presence of a communication pathway to the joint space. Lesions that did not have an identifiable communication to the joint space were smaller and were not associated with cortical erosion. Lesions with communication to the joint through multiple pathways or through a central dome hole were larger and more likely to be associated with cortical erosion.

Effects of Remnant Tissue Preservation on Clinical and Arthroscopic Results After Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction

Background: Clinical utility of remnant tissue preservation after single-bundle anterior cruciate ligament (ACL) reconstruction has not been established. In addition, no studies have evaluated the clinical utility of remnant preservation after anatomic double-bundle ACL reconstruction. Hypothesis: The study hypotheses were as follows: (1) Subjective and functional clinical results may be comparable between anatomic double-bundle reconstructions that preserve the remnant tissue and those that resect the remnant tissue, (2) postoperative knee stability and the second-look arthroscopic evaluation may be significantly more favorable with the remnant-preserving reconstruction, and (3) the degree of the initial graft coverage may significantly affect postoperative knee stability. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 179 patients underwent anatomic double-bundle ACL reconstruction. Based on the Crain classification of ACL remnant tissue, 81 patients underwent the remnant-preserving procedure (group P) and the remaining 98 patients underwent the remnant-resecting procedure (group R). There were no differences between the 2 groups concerning all background factors, including preoperative knee instability and intraoperative tunnel positions. The patients were followed for 2 years or more. Results: The subjective and functional clinical results were comparable between the 2 reconstruction procedures. Side-to-side anterior laxity was significantly less (P = .0277) in group P (0.9 mm) than in group R (1.5 mm). The pivot-shift test was negative in 89% of group P and 78% of group R patients; the result for group R was significantly lower (P = .0460). In the arthroscopic observations, results for group P were significantly better than for group R concerning postoperative laceration and fibrous tissue coverage of the grafts (P = .0479). Conclusion: Remnant preservation in anatomic double-bundle ACL reconstruction did not significantly improve subjective and functional results in the short-term evaluation, but it significantly improved postoperative knee stability. The degree of initial graft coverage significantly affected postoperative knee stability.

Induction of Spontaneous Hyaline Cartilage Regeneration Using a Double-Network Gel Efficacy of a Novel Therapeutic Strategy for an Articular Cartilage Defect

Background: A double-network (DN) gel, which was composed of poly-(2-acrylamido-2-methylpropanesulfonic acid) and poly-(N,N′-dimetyl acrylamide) (PAMPS/PDMAAm), has the potential to induce chondrogenesis both in vitro and in vivo. Purpose: To establish the efficacy of a therapeutic strategy for an articular cartilage defect using a DN gel. Study Design: Controlled laboratory study. Methods: A 4.3-mm-diameter osteochondral defect was created in rabbit trochlea. A DN gel plug was implanted into the defect of the right knee so that a defect 2 mm in depth remained after surgery. An untreated defect of the left knee provided control data. The osteochondral defects created were examined by histological and immunohistochemical evaluations, surface assessment using confocal laser scanning microscopy, and real-time polymerase chain reaction (PCR) analysis at 4 and 12 weeks. Samples were quantitatively evaluated with 2 scoring systems reported by Wayne et al and O’Driscoll et al. Results: The DN gel–implanted defect was filled with a sufficient volume of the hyaline cartilage tissue rich in proteoglycan and type 2 collagen. Quantitative evaluation using the grading scales revealed a significantly higher score in the DN gel–implanted defects compared with the untreated control at each period (P < .0001). The mean relative values of type 2 collagen mRNAs in the regenerated tissue were obviously higher in the DN gel–implanted defect than in the untreated control at each period. The mean surface roughness of the untreated control was significantly higher than the normal cartilage at 12 weeks (P = .0106), while there was no statistical difference between the DN gel–implanted and normal knees. Conclusion: This study using the mature rabbit femoral trochlea osteochondral defect model demonstrated that DN gel implantation is an effective treatment to induce cartilage regeneration in vivo without any cultured cells or mammalian-derived scaffolds. Clinical Relevance: This study has prompted us to develop a potential innovative strategy to repair cartilage lesions in the field of joint surgery.

Spontaneous hyaline cartilage regeneration can be induced in an osteochondral defect created in the femoral condyle using a novel double-network hydrogel

BackgroundFunctional repair of articular osteochondral defects remains a major challenge not only in the field of knee surgery but also in tissue regeneration medicine. The purpose is to clarify whether the spontaneous hyaline cartilage regeneration can be induced in a large osteochondral defect created in the femoral condyle by means of implanting a novel double-network (DN) gel at the bottom of the defect.MethodsTwenty-five mature rabbits were used in this study. In the bilateral knees of each animal, we created an osteochondral defect having a diameter of 2.4-mm in the medial condyle. Then, in 21 rabbits, we implanted a DN gel plug into a right knee defect so that a vacant space of 1.5-mm depth (in Group I), 2.5-mm depth (in Group II), or 3.5-mm depth (in Group III) was left. In the left knee, we did not apply any treatment to the defect to obtain the control data. All the rabbits were sacrificed at 4 weeks, and the gross and histological evaluations were performed. The remaining 4 rabbits underwent the same treatment as used in Group II, and real-time PCR analysis was performed at 4 weeks.ResultsThe defect in Group II was filled with a sufficient volume of the hyaline cartilage tissue rich in proteoglycan and type-2 collagen. The Waynes gross appearance and histology scores showed that Group II was significantly greater than Group I, III, and Control (p < 0.012). The relative expression level of type-2 collagen, aggrecan, and SOX9 mRNAs was significantly greater in Group II than in the control group (p < 0.023).ConclusionsThis study demonstrated that spontaneous hyaline cartilage regeneration can be induced in vivo in an osteochondral defect created in the femoral condyle by means of implanting the DN gel plug at the bottom of the defect so that an approximately 2-mm deep vacant space was intentionally left in the defect. This fact has prompted us to propose an innovative strategy without cell culture to repair osteochondral lesions in the femoral condyle.

A Novel Medial Collateral Ligament Reconstruction Procedure Using Semitendinosus Tendon Autograft in Patients With Multiligamentous Knee Injuries: Clinical Outcomes

Background: Several new procedures for medial collateral ligament (MCL) reconstruction using a hamstring tendon graft have been reported in the 2000s. However, the midterm and long-term clinical outcomes of these procedures have not been reported. Hypothesis: Postoperative medial stability of the knee that underwent our MCL reconstruction may not be significantly different from that of the noninjured knee. Study Design: Case series; Level of evidence, 4. Methods: A total of 37 patients who sustained multiligamentous knee injuries underwent combined MCL and cruciate ligament reconstruction at our institution between 1994 and 2007. Thirty of the 37 patients were clinically evaluated at least 2 years after surgery. Sixteen had combined MCL and anterior cruciate ligament (ACL) reconstruction, 5 had combined MCL and posterior cruciate ligament (PCL) reconstruction, and 9 had combined MCL, ACL, and PCL reconstruction. The International Knee Documentation Committee (IKDC) evaluation form and Lysholm score were used to evaluate postoperative knee function. Anteroposterior knee laxity was examined with a KT-2000 arthrometer. To assess objective medial instability, we performed a stress radiograph examination under valgus stress with the knee at 20° of flexion. Results: At the final follow-up, 1 patient showed a loss of knee extension of more than 3°. Five patients revealed a loss of knee flexion of 6° to 15° and 2 patients of 16° to 25°. Lysholm scores averaged 94.8 points. In the IKDC evaluation, 9 patients were graded as A, 17 were graded as B, 3 were graded as C, and 1 was graded as D. In the stress radiograph examination, the mean medial joint opening was 8.5 ± 1.6 mm in the reconstructed knee and 8.0 ± 1.2 mm in the healthy opposite knee. There was no significant difference in the medial joint opening between reconstructed and intact knees. Conclusion: Medial collateral ligament reconstruction for chronic combined knee instabilities can be safely performed using hamstring tendon autografts, and the clinical outcome with a minimum 2-year follow-up was favorable with satisfactory stability.