Posterior condylar offset and flexion in posterior cruciate-retaining and posterior stabilized TKA.

BACKGROUND: Anterior tibial translation associated with posterior impingement has been reported to be one of the factors limiting flexion after posterior cruciate-retaining (CR) total knee arthroplasty (TKA), especially when posterior condylar offset is decreased postoperatively. On the other hand, its effect on postoperative motion in posterior-stabilized (PS) TKA remains unknown. It has been demonstrated that PS TKA exhibits a consistent posterior femoral rollback during flexion. Thus, we hypothesized that the problem of posterior impingement can be avoided by use of PS TKA. In this study, we examined the relationship between postoperative posterior condylar offset and knee flexion in CR and PS TKAs. METHODS: In this study, analysis was performed for 20 subjects who underwent bilateral TKAs (one CR and one PS TKA) as well as another group of 50 PS TKAs. All patients could be tracked for a minimum of 2 years. The range of flexion was measured before operation and at follow-up. Preoperative and postoperative posterior condylar offset was evaluated on true lateral radiographs. RESULTS: At the follow-up examination, the mean flexion angle was 123 degrees in the CR knees and 131 degrees in the PS knees with a significantly greater improvement observed for the latter group. In the roentgenographic measurement of the posterior condylar offset, no significant difference was observed between the preoperative and postoperative values both in the CR and PS knees. We divided the patients into two groups according to the change of posterior condylar offset. The first group (Group I) showed a decrease in the posterior condylar offset after surgery and the second group (Group II) showed no change or an increase. Subsequently, postoperative change in flexion was compared between Groups I and II for the CR and PS knees. A significant difference between Groups I and II was observed in the CR knees, while no difference was observed in the PS knees. The magnitude of postoperative posterior condylar offset did not correlate with an improvement in maximum flexion angle in the 50 PS knees. CONCLUSIONS: It was shown that the magnitude of posterior condylar offset correlated with a postoperative change in flexion angle in CR knees, while no such correlation was observed in PS knees.

Mechanical evaluation of a soft tissue interference screw with a small diameter: significance of graft/bone tunnel cross-sectional area ratio.

The purpose of this study is to evaluate the mechanical properties of a graft fixation using a small diameter soft tissue interference screw and analyze the factors affecting the fixation strength. Forty porcine knees were used. A bone tunnel, either 4.5 mm (n=40) or 5.0 mm (n=40) in diameter, was created in the bone block obtained from the proximal tibia or the distal femur. A patella-patellar tendon specimen with varied width was harvested, and the distal end of the patellar tendon was fixed within the bone tunnel using a small diameter soft tissue interference screw (4 x 15 mm). Then, the patella-patellar tendon-bone block complex was loaded until failure occurred and the maximum load was measured. As potential influential factors on the fixation strength, the insertion torque, bone mineral density of the bone block, and graft/tunnel cross-sectional area ratio (GTR) of each specimen were calculated. A significant correlation between the maximum failure load and the insertion torque was demonstrated. The quadratic regression analysis showed a statistically significant correlation between the failure load and the GTR. Optimal GTR for achieving high fixation strength was approximately 80%. When used in appropriate conditions, the mean failure load was 177 N for the 4.5 mm screw and 180 N for the 5 mm screw. The use of a small diameter interference screw for the fixation of a tendon graft to a bone is clinically feasible. Our research showed that the selection of appropriate fitting conditions is an important factor for optimizing the properties of the fixation.

In vivo kinematic comparison of posterior cruciate-retaining and posterior stabilized total knee arthroplasties under passive and weight-bearing conditions.

An in vivo comparison of flexion kinematics for posterior cruciate-retaining (PCR) and posterior stabilized (PS) total knee arthroplasty (TKA) was performed. Twenty patients who underwent bilateral paired TKAs were included in this prospective study. Both PCR and PS prostheses were from the same TKA series with comparable surface geometries, and all were implanted by a single surgeon. Of these 20 patients, 3-dimensional kinematics during flexion could be analyzed using a computer model fitting technique in 18 patients. The follow-up period ranged from 18 to 53 months. In the PCR TKA, an anterior femoral translation from 30 degrees to 60 degrees of flexion was observed in the weight-bearing condition. In contrast, flexion kinematics for the PS TKA was characterized by the maintenance of a constant contact position under weight-bearing conditions and posterior femoral rollback in passive flexion.

A posterior-stabilized total knee arthroplasty shows condylar lift-off during deep knee bends.

This prospective randomized study was done to examine whether any difference in presentation of condyler lift-off exists between posterior cruciate-retaining and posterior-stabilized total knee arthroplasties. Fluoroscopic analysis of flexion kinematics under weightbearing condition was done for 18 patients who had bilateral paired total knee arthroplasties. The posterior cruciate-retaining and posterior-stabilized prostheses were from the same total knee arthroplasty series with comparable surface geometries and were implanted by one surgeon. At evaluation, five of 18 patients (28%) with posterior cruciate-retaining total knee arthroplasties had condylar lift-off, compared with 12 of 18 patients (67%) with posterior-stabilized total knee arthroplasties. Consequently, a significant difference in its incidence was seen between the groups. Condylar lift-off in posterior-stabilized knees was observed at various flexion angles, and one knee in this group had lift-off laterally and medially at different flexion angles. These findings raise concern that the higher incidence of condylar lift-off in posterior-stabilized total knee arthroplasty may lead to an increased wear rate of polyethylene associated with long-term prosthetic loosening.

Magnetic resonance delineation of the anterior cruciate ligament of the knee: flexed knee position within a surface coil.

The purpose of this study was to evaluate the effect of the knee position at three different flexion angles in magnetic resonance (MR) delineation of the anterior cruciate ligament (ACL) in the knee and to determine the optimal knee position. Thirteen knees of normal volunteers were examined at 15 degrees, 30 degrees, and 45 degrees of flexion with a surface coil, and three sets of obtained oblique sagittal MR images were evaluated by four observers. MR images at 30 degrees of knee flexion most clearly delineate compared with those at 15 degrees and 45 degrees of knee flexion. We recommended examining the knee in 30 degrees of flexion.

Expression of transcription factor Sox9 in rat L6 myoblastic cells.

Muscle-derived cells can differentiate into chondrogenic cells. In our present study, we investigated the pattern of expression of Sox9, a transcription factor known to play a key role in chondrogenesis, in a rat myoblastic cell line, L6. In addition, we evaluated expression of type II collagen and myogenic regulatory markers by reverse-transcript polymerase chain reaction. We also investigated the effect of transforming growth factor (TGF)-beta3, which is known to induce chondrogenesis, on Sox9 mRNA expression. On the first day of culture, we observed a high expression of Sox9. However, on the seventh day of culture, there was a decline in the level of Sox9 and type II collagen mRNAs and an increased expression of Myf5 and myogenin mRNAs. Sox9 mRNA expression was increased after stimulation of TGF-beta3 at 2, 6, and 24 hr. Cartilage nodules were observed in L6 cells treated with TGF-beta3 and dexamethasone. These results indicated that L6 myoblasts originally possess the capacity to differentiate into chondrogenic cells, but that capacity is lost as the cells differentiate toward the myogenic lineage. In addition, TGF-beta3 may modulate Sox9 mRNA expression in L6 cells and retain the capacity to differentiate into chondrogenic lineage.

Evaluation of hamstring strength and tendon regrowth after harvesting for anterior cruciate ligament reconstruction.

BACKGROUND: It is generally thought that tissue regeneration and good functional recovery can be expected after anterior cruciate ligament reconstruction using the hamstring tendons. However, persistent strength deficit in deep knee flexion has also been reported. HYPOTHESIS: Morphologic regeneration of the harvested hamstring tendon is not necessarily associated with its functional recovery. STUDY DESIGN: Retrospective follow-up study. METHOD: Twenty-eight patients who underwent anterior cruciate ligament reconstruction with hamstring graft were evaluated after a minimum period of 2 years. Status of tendon regrowth was assessed by magnetic resonance imaging. To specifically analyze the functional deficit after graft harvest, the isometric hamstring strength was examined in a sitting position at 90 degrees of flexion and a prone position at 90 degrees and 110 degrees of flexion. Then, the strength data were correlated with the extent of tendon regeneration. RESULTS: In 22 of the 28 patients, a regrowth of the semitendinosus tendon was found, whereas regeneration of the gracilis tendon was observed in 13 patients. In the evaluation of hamstring strength, the isometric peak torque was reduced to 86.2%, 54.6%, and 49.1%, respectively, in the aforementioned 3 postures as compared with the contralateral side. CONCLUSIONS: Significant functional deficit of hamstring strength remains regardless of morphologic regeneration.

The effect of graft sizing on osteochondral transplantation.

PURPOSE: The goal of this study was to analyze the effect of graft sizing on the histologic property of articular cartilage in autologous osteochondral transplantation. TYPE OF STUDY: Histologic analysis using an animal model. METHODS: Eighteen skeletally mature female Japanese white rabbits were used in this study and divided into 2 groups based on the surgical procedure. Group I: A cylindrical fragment (7 mm in diameter and 5 mm in depth) was harvested at the femoral condyle using the Osteochondral Autograft Transfer System (Arthrex, Naples, FL), then precisely returned to the defect from which the fragment was originally harvested. This surgical model supposes that the articular surface geometry of the osteochondral graft exactly matches that of the cartilage lesion; however, the osteochondral graft is not the same size as the defect in this model because of the surrounding gap that corresponds to the blade thickness of the chisel used to take the graft. Group II: A 1-mm larger osteochondral fragment (8 mm in diameter and 5 mm in depth) taken from the contralateral femoral condyle was transplanted to the osteochondral defect made as in group I, achieving a tight fit. Specimens were stained with Safranin-O fast green and analyzed microscopically at 4, 12, and 24 weeks after surgery. RESULTS: In group I, histologic examination revealed an increase in cartilage thickness and cell density during the implantation period. Round and polygonal hypertrophic clusters of chondrocytes with cytoplasmic vacuoles were observed. By contrast, in group II, the thickness of the articular cartilage was almost the same as that of the normal adjacent cartilage with no significant change observed. CONCLUSIONS: It is suggested that sizing of the implanted osteochondral fragment plays an important role in preserving the histologic properties of cartilage. CLINICAL RELEVANCE: This study suggests that osteochondral graft stability may influence the histologic properties of the repaired cartilage. It is preferable to implant the slightly oversized graft into the cartilage lesion in autologous osteochondral transplantation to preserve the histologic properties of cartilage.

Revision anterior cruciate ligament reconstruction using the regenerated semitendinosus tendon: analysis of ultrastructure of the regenerated tendon.

In this report, we present a case of a college skier who sustained a rerupture of the reconstructed anterior cruciate ligament (ACL) 8 months after surgery in which an autogenous semitendinosus tendon graft was used. At the revision surgery, the harvested semitendinosus tendon appeared to be regrown. Thus the regenerated tendon was reharvested, and in combination with the gracilis tendon, was used as a graft. The electron microscopic examination revealed a difference in fibril diameter between the regenerated tissue and the normal tendon. Although the regenerated semitendinosus tendon could be reharvested, the feasibility of its use for revision surgery is still to be determined.

Functional comparison of posterior cruciate-retaining versus posterior stabilized total knee arthroplasty.

A prospective, randomized comparison of posterior cruciate-retaining (PCR) and posterior stabilized (PS) total knee arthroplasties (TKAs) was conducted in 20 patients who underwent bilateral TKAs for osteoarthritis. All procedures were performed by a single surgeon. One knee was implanted with a PCR TKA, and a contralateral knee with a PS TKA. Both prosthetic designs were of the same TKA series, with comparable surface geometries. Patients had a clinical and radiographic evaluation at a mean of 31.7 months for PCR TKAs and 30.6 months for PS TKAs postoperatively. There were no significant differences between the PCR and PS TKAs in postoperative knee scores. However, postoperative improvement in range of motion was significantly superior in the PS group.

Ultrasound treatment of nonunion of the hook of the hamate in sports activities.

Two cases of nonunion of the hook of the hamate were treated with low-intensity pulsed ultrasound. The patients were baseball players and had been injured as a result of hitting repeatedly. Nonunion was detected on computed tomography (CT) and was exposed to ultrasound for 20 min a day for 4 months. In both cases pain at the hypothenar eminence disappeared, and bone union was confirmed on CT at the end of the ultrasound treatment.

Analysis of the thickness and curvature of articular cartilage of the femoral condyle.

PURPOSE: To develop an optimal autologous osteochondral transplantation technique, we analyzed the thickness and curvature of the femoral condyle. TYPE OF STUDY: Basic research for surgical technique, anatomic study. METHODS: Eight cadaveric femoral condyles were sectioned sagittally into 8 slices. Photographs of each slice were digitized, and the thickness and curvature of the overlaying cartilage were analyzed using a National Institutes of Health image program. RESULTS: The average thickness of the cartilage was 1.69 mm. The minimum and maximum values were measured at 0.22 mm and 3.65 mm, respectively, with the thinnest part seen in the sulcus terminalis (the groove for meniscus). The average curvature of the cartilage was 4.4 m(-1). The minimum and maximum values were measured at -20.0 m(-1) and 27.2 m(-1), respectively. CONCLUSIONS: When the chondral lesion is assumed at the weight bearing area of the medial or lateral femoral condyle, the anterior portion of the sulcus terminalis (the groove for meniscus) in the middle section of the lateral condyle is considered to be the optimal donor site.

An intraligamentous ganglion cyst of the anterior cruciate ligament after a traumatic event.

An unusual case of intraligamentous ganglion cyst of the anterior cruciate ligament after a traumatic event in a 12-year-old boy is presented. Magnetic resonance imaging was helpful in delineating the lesion. An arthroscopic aspiration of the cyst material resulted in resolution of symptoms to preserve satisfactory knee function. The patient remains asymptomatic 25 months after surgery.

Isolated suprapatellar bursitis: Computed tomographic and arthroscopic findings.

A rare case of compartmentalized suprapatellar bursitis in the left knee of an 80-year-old man is presented. Computed tomographic (CT) scans following intravenous administration of contrast media showed a cystic mass between the quadriceps tendon and the anterior surface of the femur. Multiplanar reconstruction CT scans showed a mass superior to the patella, the wall of which was enhanced. Arthroscopic examination of the knee revealed a complete suprapatellar septum that separated the suprapatellar bursa from the knee joint cavity. Surgical excision of the bursa was curative. To our knowledge, multiplanar reconstruction CT and arthroscopic features of the isolated suprapatellar bursitis have not been illustrated previously.

Solitary intra-articular tumoral calcinosis of the knee.

An unusual case of symptomatic, solitary, intra-articular tumoral calcinosis of the knee in a 39-year-old man is presented. This is the first reported case of intra-articular tumoral calcinosis with no associated underlying systemic diseases. Magnetic resonance imaging was helpful in delineating the lesion. Surgical excision resulted in resolution of symptoms and was not followed by recurrence of the lesion.

The effect of the small and unstable autologous osteochondral graft on repairing the full-thickness large articular cartilage defect in a rabbit model.

We have investigated the effect of the insufficient autologous osteochondral graft on healing of the large articular cartilage defect using a rabbit model. An osteochondral defect, 7 mm in diameter, was made on the patellar groove of the femoral condyle and repaired with two surgical procedures: Group I, the osteochondral fragment as half as the defect was grafted. The graft was unstable and the size of the graft was smaller than the defect. This is a model of the insufficient autologous osteochondral graft to the large articular cartilage defect; Group II, the defect was left empty. At 2, 4, 12, and 24 weeks after the surgery, the specimens were analyzed macroscopically and histologically. To evaluate the microscopic morphology, a histologic grading scale composed of 5 categories was used. In Group I, although the graft sank a little, a grafted cartilage survived and the reparative fibrous tissue filled the defect covering implanted cartilage. In contrast, in Group II, the defect was only partially covered by fibrocartilaginous tissue with a faintly staining matrix. Throughout the entire observed periods, the scores of the repaired cartilage in Group I are significantly higher than those in Group II. Even the half size of osteochondral graft has an effect to reduce the size of the cartilage defect such as the spacer and leads to better healing compared to the cartilage defect untreated. In case that it is hard to transplant an optimal osteochondral graft because of large cartilage lesion, even the small and unstable osteochondral plug should be transplanted.

The spatiotemporal expression of TGF-beta1 and its receptors during periosteal chondrogenesis in vitro.

Transforming growth factor-beta1 (TGF-beta1) has been shown to stimulate chondrogenesis in periosteal explants cultured in agarose suspension. TGF-betas exert their cellular effects through a heteromeric cell membrane receptor complex consisting of TGF-beta type I and type II receptors. In this study, the spatial and temporal expressions of the type I receptor (TbetaR-I), type II receptor (TbetaR-II) and endogenous TGF-beta1 in periosteal explants cultured in vitro were examined using reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry. The temporal changes in the expression of the TbetaR-I and TbetaR-II mRNAs correlated with that of TGF-beta1. Exogenous administration of TGF-beta1 upregulated the expression of both receptors and of the TGF-beta1 ligand in a biphasic pattern. The earlier peak of upregulation was observed at 7 days in culture. A later peak of upregulation was seen at 42 days, at which time cartilage formation reached a maximum. Immunohistochemical studies demonstrated co-localization of TbetaR-I and TbetaR-II simultaneously among the same cells expressing TGF-beta1. TGF-beta1 treatment increased the expression of TGF-beta1, TbetaR-I and TbetaR-II in mesenchymal cells in the cambium layer at 7 days in culture. Small round chondrocytes showed widely distributed immunoreactivity of TGF-beta1, TbetaR-I and TbetaR-II in the 42-day explants treated with TGF-beta1. These observations support the hypothesis that TGF-beta1 regulates the initiation and formation of cartilage during periosteal chondrogenesis.

Low-intensity pulsed ultrasound enhances early healing of medial collateral ligament injuries in rats.

OBJECTIVE: To investigate the effect of low-intensity pulsed ultrasound exposure on the healing of injured medial collateral ligaments. METHODS: Thirteen male Sprague Dawley rats were used in the study. After surgical transection of the bilateral medial collateral ligaments, the ligament of 1 knee received low-intensity pulsed ultrasound exposure (30 mW/cm2 for 20 minutes daily), whereas no ultrasound was applied to the contralateral knee (control side). Eight rats were killed at 12 days after surgery, and 5 rats were killed at 21 days. The bilateral knees of 5 rats were used for mechanical testing at each of the 2 periods, and 12-day specimens of the remaining 3 rats were prepared for the electron microscopic examination. The knees of 5 additional rats were used to obtain mechanical data of the normal uninjured medial collateral ligament. RESULTS: On the 12th day, the low-intensity pulsed ultrasound-treated side exhibited significantly superior mechanical properties when compared with the control side in ultimate load, stiffness, and energy absorption (P < .05). However, the treatment did not afford any mechanical advantage when tested on the 21st day. The mean diameter of the fibril was significantly larger on the treatment side than on the control side (P < .05). CONCLUSIONS: Low-intensity pulsed ultrasound exposure is effective for enhancing the early healing of medial collateral ligament injuries.

Repeat tears of repaired menisci after arthroscopic confirmation of healing.

We undertook 114 arthroscopic meniscal repairs in 111 patients and subsequently carried out second-look arthroscopy to confirm meniscal healing at a mean of 13 months after repair. Stable healing at the repaired site was seen in 90. Of these, however, 13 had another arthroscopy later for a further tear. The mean period between the repair and the observation of a repeat tear was 48 months. Of the 13 patients, 11 had returned to high activity levels (International Knee Documentation Committee level I or II) after the repair. An attempt should be made to preserve meniscal function by repairing tears, but even after arthroscopic confirmation of stable healing repaired menisci may tear again. The long-term rate of healing may not be as high as is currently reported. Second-look arthroscopy cannot predict late meniscal failure and may not be justified as a method of assessment for meniscal healing. Young patients engaged in arduous sporting activities should be reviewed regularly even after arthroscopic confirmation of healing.