Evaluation of complete and incomplete subscapularis tendon tear on preoperative magnetic resonance imaging.

BACKGROUND: This study aims to evaluate the significance of preoperative magnetic resonance imaging findings to predict subscapularis tear confirmed at arthroscopic surgery. METHODS: Sixty-four consecutive shoulders that underwent preoperative magnetic resonance imaging examination and arthroscopic shoulder operations were retrospectively reviewed. Under arthroscopic examination, complete subscapularis tear was defined as a full-thickness tear and incomplete subscapularis tear as tendon detachment larger than 5 mm from the insertion on the joint side. RESULTS: In arthroscopic findings, they were included 11 shoulders with complete subscapularis tear, 13 with incomplete subscapularis tear, and the remaining 28 shoulders without subscapularis tear. Subscapularis discontinuity by axial magnetic resonance imaging had the highest sensitivity and specificity in detecting complete subscapularis tear compared with other magnetic resonance imaging findings. Long head biceps subluxation or dislocation showed significantly higher prevalence in the complete and incomplete subscapularis tear groups than in the group with no tear. Incomplete subscapularis tear groups had a higher incidence of superior subscapularis recess fluid, and this fluid was present in all the shoulders with incomplete subscapularis tear. CONCLUSIONS: The presence of subscapularis discontinuity is useful for diagnosis of complete subscapularis tear. In addition, in cases of incomplete subscapularis tear, the presence of superior subscapularis recess fluid had 100% sensitivity. Thus, this finding may be a characteristic diagnosis of subscapularis tear including incomplete tear.

Is it possible to predict the final component gap in flexion before femoral posterior condylar osteotomy in cruciate-retaining and posterior-stabilized total knee arthroplasty?

BACKGROUND: In total knee arthroplasty (TKA) with posterior condylar osteotomy using anatomical landmarks, predicting the final flexion gap is impossible, as it differs with the presence or absence of the posterior cruciate ligament. We compared the predicted flexion gap, based on pre-femoral posterior condylar osteotomy measurements, with the postsurgical final flexion gap in cruciate-retaining (CR) and posterior-stabilized (PS) TKA. METHODS: One hundred knees of patients with osteoarthritis were included: 35 underwent CR, and 65 PS TKA. Distal femoral and proximal tibial osteotomy using the measured resection technique was performed. An anterior and posterior femoral osteotomy guide was set parallel to the surgical epicondylar axis, and the predicted flexion gap was measured using a seesaw tensor attached to the guide. After all procedures, the final component gap in flexion was measured using a similar seesaw tensor at the patella reduction position and was compared with the predicted gap. RESULTS: The correlation coefficients for predicted vs. final component gap were 0.45 (P < 0.05) in CR and 0.82 (P < 0.001) in PS. The mean differences between predicted and final gaps were 1.8 mm for CR and 1.0 mm for PS. In 34.3% of CR cases, the gap difference was more than 2 mm. CONCLUSION: It is possible to predict the final flexion gap before femoral posterior condylar osteotomy, with a strong correlation observed between predicted and final component gaps in PS TKA. However, in CR, more than 30% of the cases showed unexpectedly large final flexion gaps.

A Human Amnion-Derived Extracellular Matrix-Coated Cell-Free Scaffold for Cartilage Repair: In Vitro and In Vivo Studies.

OBJECTIVE: Extracellular matrix (ECM) derived from human amniotic mesenchymal cells (HAMs) has various biological activities. In this study, we developed a novel HAM-derived ECM-coated polylactic-co-glycolic acid (ECM-PLGA) scaffold, examined its property on mesenchymal cells, and investigated its potential as a cell-free scaffold for cartilage repair. MATERIALS AND METHODS: ECM-PLGA scaffolds were developed by inoculating HAM on a PLGA. After decellularization by irradiation, accumulated ECM was examined. Exogenous cell growth and differentiation of rat mesenchymal stem cells (MSCs) on the ECM-PLGA were analyzed in vitro by cell attachment/proliferation assay and reverse transcription-polymerase chain reaction. The cell-free ECM-PLGA scaffolds were implanted into osteochondral defects in the trochlear groove of rat knees. After 4, 12, or 24 weeks, the animals were sacrificed and the harvested tissues were examined histologically. RESULTS: The ECM-PLGA contained ECM that mimicked natural amniotic stroma that contains type I collagen, fibronectin, hyaluronic acid, and chondroitin sulfates. The ECM-PLGA showed excellent properties of cell attachment and proliferation. MSCs inoculated on the ECM-PLGA scaffold showed accelerated type II collagen mRNA expression after 3 weeks in culture. The ECM-PLGA implanted into an osteochondral defect in rat knees induced gradual tissue regeneration and resulted in hyaline cartilage repair, which was better than that in the empty control group. CONCLUSION: These in vitro and in vivo experiments show that the cell-free scaffold composed of HAM-derived ECM and PLGA provides a favorable growth environment for MSCs and facilitates the cartilage repair process. The ECM-PLGA may become a "ready-made" biomaterial for cartilage repair therapy.

Successful treatment of methicillin-resistant Staphylococcus aureus osteomyelitis with combination therapy using linezolid and rifampicin under therapeutic drug monitoring.

Linezolid is an effective antibiotic against most gram-positive bacteria including drug-resistant strains such as methicillin-resistant Staphylococcus aureus. Although linezolid therapy is known to result in thrombocytopenia, dosage adjustment or therapeutic drug monitoring of linezolid is not generally necessary. In this report, however, we describe the case of a 79-year-old woman with recurrent methicillin-resistant S. aureus osteomyelitis that was successfully treated via surgery and combination therapy using linezolid and rifampicin under therapeutic drug monitoring for maintaining an appropriate serum linezolid concentration. The patient underwent surgery for the removal of the artificial left knee joint and placement of vancomycin-impregnated bone cement beads against methicillin-resistant S. aureus after total left knee implant arthroplasty for osteoarthritis. We also initiated linezolid administration at a conventional dose of 600 mg/h at 12-h intervals, but reduced it to 300 mg/h at 12-h intervals on day 9 because of a decrease in platelet count and an increase in serum linezolid trough concentration. However, when the infection exacerbated, we again increased the linezolid dose to 600 mg/h at 12-h intervals and performed combination therapy with rifampicin, considering their synergistic effects and the control of serum linezolid trough concentration via drug interaction. Methicillin-resistant S. aureus infection improved without reducing the dose of or discontinuing linezolid. The findings in the present case suggest that therapeutic drug monitoring could be useful for ensuring the therapeutic efficacy and safety of combination therapy even in patients with osteomyelitis who require long-term antibiotic administration.

Intraoperative measurements of femoral anterior tangent (FAT) line for determining the rotational alignment of femoral component of total knee arthroplasty.

Previously, we reported using CT images that the anterior surface of the femur immediately proximal to the trochlea and its tangent line (femoral anterior tangent line; FAT line) could be used as a good index of the femoral rotation. In this study, we developed a jig that allowed us to measure the FAT line during surgery, and we examine the relation between preoperative and intraoperative measurement values. The results indicated that the average intraoperative measurement value of the 'surgical' FAT line was 9.8° ± 3.2° internally rotated using surgical transepicondylar axis reference. This value significantly correlated to preoperative FAT line/clinical transepicondylar axis angle. These findings demonstrated that FAT line is a useful index for appropriate rotational alignment of femoral component, both before and during TKA.

Effects of kneeling on tibiofemoral contact pressure and area in posterior cruciate-retaining and posterior cruciate-sacrificing total knee arthroplasty.

The objective of this study was to measure the effect of kneeling on tibiofemoral contact following cruciate-retaining and posterior-stabilized total knee arthroplasty. Five cadaveric knees were tested on a custom testing system that allowed physiologic muscle loading. Three forces were used to simulate nonkneeling, double-stance kneeling, and single-stance kneeling at flexion angles of 90°, 105°, 120°, and 135°. Tibiofemoral contact areas and pressures were measured using the Tekscan (South Boston, MA) system. Kneeling increased contact areas and pressures in both designs with variable significance (P < .05). Moving from double- to single-stance kneeling increased pressures in the cruciate-retaining group but decreased pressures in the posterior-stabilized group (P < .05). Chronic, repetitive kneeling after total knee arthroplasty may increase polyethylene wear due to increased contact areas and pressures.

Effects on tibiofemoral biomechanics from kneeling.

BACKGROUND: Repetitive kneeling in certain occupations, hobbies and cultures is associated with tibiofemoral joint osteoarthritis. The biomechanics of kneeling is therefore of interest. This cadaveric study investigated tibiofemoral joint contact areas, pressures, and kinematics in response to kneeling. METHODS: Five human cadaveric knees were subjected to simulated kneeling at flexion angles of 90°, 105°, 120°, and 135°. Different anterior forces were applied to the knee to simulate crouching (no force), double stance kneeling (339N of force), and single stance kneeling (678N of force). Tibiofemoral joint kinematics, contact areas, and pressures were measured. FINDINGS: Kneeling produced tibial posterior translation and external rotation. Posterior translation was significantly less at 90° than at higher flexion angles (P<0.05). Posterior translation and external rotation were significantly greater moving from crouching to double stance kneeling when compared to moving from double to single stance kneeling (P<0.05). Double and single stance kneeling increased contact areas and pressures significantly when compared to crouching (P<0.05). Pressures also increased significantly moving from double to single stance kneeling (P<0.05). INTERPRETATION: Kneeling produces less tibial posterior translation at 90° than at higher flexion angles primarily due to posterior cruciate ligament biomechanics. Tibial external rotation results from posterior cruciate ligament biomechanics and differences between medial and lateral compartment anatomy. Different anatomical constraints allow significantly less posterior translation and external rotation moving from double to single stance kneeling is a result of increased pressure with kneeling likely contributes to the development of tibiofemoral osteoarthritis, and single stance kneeling may be more deleterious than double stance kneeling.

Activities of daily living after total hip arthroplasty. Is a 32-mm femoral head superior to a 26-mm head for improving daily activities?

Range of motion (ROM) of the hip joint after total hip arthroplasty (THA) could be increased by using a larger prosthetic femoral head, but it is not known whether the activities of daily living (ADL) are influenced by THA with different head sizes. Our objective was to compare postoperative ADL in patients who underwent THA using a head diameter of 26 mm or 32 mm. We assessed the range of motion and the mode of ADL after cementless primary THA. Comparison was performed between 25 joints of 24 patients who underwent THA with a 26-mm femoral head (26-mm group) and 24 joints of 20 patients with a 32-mm head (32-mm group). The postoperative range of flexion and abduction was significantly larger in the 32-mm group than in the 26-mm group. With respect to the mode of performing selected ADL such as putting on and removing pants, socks, and cutting toenails, many patients adopted the compensatory position of lumbar flexion with hip flexion plus knee extension in the 26-mm group, while a majority of the patients from the 32-mm group employed the mode of hip flexion with knee flexion. Patients with the 32-mm head showed better postoperative ADL of the ipsilateral side compared with the 26-mm head.

Femoral anterior tangent line of the osteoarthritic knee for determining rotational alignment of the femoral component in total knee arthroplasty.

Several reference axes have been used to establish femoral rotational alignment during total knee arthroplasty. The current study examined the configuration of the anterior surface of the femur immediately proximal to the trochlea as an alternative rotational landmark. An analysis of computed tomographic images of 150 knees with osteoarthritis indicated that the configuration of the surface is mostly flat or slightly depressed, and the line tangential to the surface (femoral anterior tangent line; FAT line) was consistently determined to be 12.2° ± 3.6° internally rotated to the transepicondylar axis. This value was relatively constant and as reliable as the femoral anteroposterior axis for determining rotational alignment. In addition, the FAT line was not affected by the degree of the varus-valgus deformity of the osteoarthritic knees.

Biomechanical effects of patellar positioning on intraoperative knee joint gap measurement in total knee arthroplasty.

BACKGROUND: Balancing both the lateral/medial and extension/flexion joint gaps is a prerequisite for soft tissue balance in total knee arthroplasty. The purpose of this study was to quantify the effects of patellar positioning and quadriceps load during total knee arthroplasty on knee joint gap measurements. METHODS: Eight fresh-frozen cadaveric knees ranging in age from 65 to 85 years old were used. Using a medial parapatellar approach, posterior cruciate ligament sacrificing total knee arthroplasty was performed. The specimens were mounted on a custom knee testing system that allowed the femur to be locked in position for knee extension or flexion. Patellar positions of eversion, reduction, and following repair of the arthrotomy were examined. The influence of quadriceps muscle load was investigated by varying the quadriceps load from 0 to 125N. The lateral and medial joint gaps, represented by the distance from the implanted femoral component surface to the cut tibia surface, were measured with 100N tibial distraction force using a 3D digitizer in both extension (0 degrees ) and flexion (90 degrees ). FINDINGS: Both the medial and lateral joint gaps with patella eversion were significantly smaller than those with patellar reduction and arthrotomy repair (extension: all quadriceps loads, P<0.0002; flexion: quadriceps loads less than 75N, P<0.0002). In patella eversion, quadriceps loading decreased the lateral joint gap more than the medial joint gap in both extension and flexion; however, the effect was greater in knee flexion with significant differences seen at all quadriceps loads, whereas in extension significant differences were only seen for quadriceps loading of 75N and greater. Patella eversion also caused a lateral-posterior shift and external rotation of the tibia compared to the other conditions (P<0.005). With patella reduction and repair of the arthrotomy lower quadriceps loading decreased the extension gap significantly more than the flexion gap (P<0.01). Following repair of the arthrotomy higher quadriceps loading significantly decreased the flexion gap more than the extension gap (P<0.04). INTERPRETATION: The patellar positioning and quadriceps muscle loading in total knee arthroplasty have a strong influence on intraoperative joint gap measurements.

Intraoperative patellar tendon strain: predicting the range of knee flexion after total knee arthroplasty.

BACKGROUND: The preoperative range of motion is an important factor that influences the range of motion after total knee arthroplasty. Because the length and tightness of the extensor mechanism are extracapsular elements with an influence on knee flexion, it is reasonable to assume that the tension of the knee extensor mechanism during surgery has a considerable impact on the postoperative range of motion. The purpose of this study was to determine the influence of the tightness of knee extensor mechanism on postoperative knee flexion. METHODS: In 18 knees undergoing posterior-stabilized type total knee arthroplasty, we measured the longitudinal strain on the patellar tendon with all the components in position during passive knee flexion up to 135 degrees . The patellar tendon strains measured during surgery were compared with the preoperative maximum knee flexion angle and postoperative maximum knee flexion angle at 1 year. RESULTS: There was a significant inverse correlation between the patellar tendon strain during surgery at 60 degrees (r = -0.54, P < 0.05), 90 degrees (r = -0.55, P < 0.05), or 135 degrees of flexion (r = -0.65, P < 0.05) and postoperative knee flexion. CONCLUSIONS: The results indicated that subjects with high intraoperative patellar tendon strain during passive flexion of the knee had more restricted postoperative knee flexion. Therefore, the tightness of the knee extensor mechanism measured at total knee arthroplasty is a good predictor of maximum postoperative range of flexion.

Joint gap changes with patellar tendon strain and patellar position during TKA.

UNLABELLED: Balancing of the joint gap in extension and flexion is a prerequisite for success of a total knee arthroplasty. The joint gap is influenced by patellar position. We therefore hypothesized the state of the knee extensor mechanism (including the patellar tendon) would influence the joint gap. In 20 knees undergoing posterior-stabilized type total knee arthroplasties, we measured the joint gap and the patellar tendon strain from 0 degrees to 135 degrees flexion with the femoral component in position. When the patella was reduced, the joint gap was decreased at 90 degrees and 135 degrees (by 1.9 mm and 5.5 mm, respectively) compared with the gap with the patella everted. The patellar tendon strain increased with knee flexion. Patellar tendon strain at 90 degrees flexion correlated with the joint gap difference with the patella in everted and reduced positions. This suggests that in addition to the collateral ligaments, the knee extensor mechanism may have an influence on the joint gap. Therefore, accounting for extensor mechanism tightness may be important in achieving the optimal joint gap balance during total knee arthroplasty. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Severe bone defects and reduced mineralization caused by massive metallosis after total knee arthroplasty: histopathologic and bone morphometric findings.

We encountered a patient who developed metallosis after total knee arthroplasty (TKA), resulting in loosening of the implant, bone resorption, reduced bone formation, and fracture. The implant was replaced with a NexGen modular revision TKA system after autologous bone and hydroxyapatite granule grafting. Histopathologic examination showed accumulation of metallic debris and tartrate-resistant acid phosphatase-positive cells around the trabecular and cortical bone. Examination of hard tissue specimens showed a reduced bone volume (determined by bone histomorphometry) and an increase of all osteoid parameters, indicating disturbance of mineralization in addition to increased bone resorption.

Efficient gene delivery to articular cartilage using electroporation.

Abstract Effective in vivo gene transfer into articular cartilage has not yet been established. Since chondrocytes are embedded within a rich extracellular matrix, various gene transfer methods have failed to introduce genes into deeper layers of the articular cartilage. In this study, we developed new superfine pointed needle electrodes for in situ electroporation (EP), and investigated the efficiency of gene transfer into articular cartilage with different degrees of degeneration. Full-thickness articular cartilage slices were obtained from the knee joint of a 3-4-month-old rabbit. The cartilage tissues were treated briefly with trypsin to partly remove matrix proteoglycan. Human articular cartilage with different grades of degeneration was also used. For EP, the articular cartilage surface was soaked in a solution containing green fluorescent protein (GFP) plasmid. Then, the superfine pointed 7-needle electrodes were gently stabbed into the surface layer of the articular cartilage and the gene was transfected by an electroporator. GFP expression was examined by immunohistochemical analysis. Cartilage tissue was successfully transfected with the GFP gene by the electrodes and EP. Transfection efficiency was enhanced by depleting the matrix proteoglycan in rabbit articular cartilage. Chondrocytes in the deeper layer of the articular cartilage were also transfected and expressed GFP. In human osteoarthritic cartilage, ca. 30% of the cells in the deeper layer were transfected by selecting optimal EP conditions. No adverse effects of EP on damaged articular cartilage were obvious from histological analysis or TUNEL staining. The results indicated that EP-mediated in vivo gene transfer into articular cartilage may provide a useful therapeutic strategy to treat cartilage degeneration.

Quantitative analysis of the effect of lumbar orthosis on trunk muscle strength and muscle activity in normal subjects.

We studied the effect of lumbar orthosis on trunk muscle strength and muscle activity during flexion-extension bending of the trunk in 31 male volunteers. Trunk muscle strength was measured with a kinetic measurement system. Peak torque was calculated by using the mean torque of five repetitions. Trunk muscle activity was measured with commercially available equipment that has portable EMG data-collection units. The maximum level of the EMG signal was evaluated by employing the analyzing part of the computer's measuring program. With the application of the lumbar orthosis, the strength of the abdominal muscle and the back muscle increased; conversely, the activities of both muscles were decreased significantly. This might imply that lumbar orthosis reduces the load of the trunk muscles during performance.

Fixation of the NexGen HA-TCP-coated cementless, screwless total knee arthroplasty: comparison with conventional cementless total knee arthroplasty of the same type.

We performed a 12-month prospective study on 59 patients (92 knees) who underwent NexGen (Zimmer Inc, Warsaw, IN) cruciate-retaining total knee arthroplasty. In the control group, uncoated components were fixed using screws, whereas the hydroxyapatite-tricalcium phosphate (HA-TCP) group underwent screwless fixation of coated components. At 12 months postoperatively, there was a radiographic clear zone around the femoral and tibial components of 56.5% and 32.6% of the knees in the control group. The HA-TCP group showed a clear zone at the medial aspect of the tibial component in only 1 knee. These results suggested that HA-TCP-coated articular components show good initial fixation without using screws. The NexGen coated knee arthroplasty may be useful for solving the problems of cementless fixation.