Mechanical stretching induces calcification and cartilage matrix metabolism, causing degeneration of the acetabular labrum.

PURPOSE: The acetabular labrum plays an important role in joint lubrication, and damage to this structure leads to osteoarthritis. This study aimed to histologically classify the degree of degeneration of the acetabular labrum and to investigate the changes in gene expression induced by mechanical stretching. METHODS: We obtained acetabular labrum cells from patients with hip osteoarthritis during total hip arthroplasty (n = 25). The labrum was stained with safranin O, and images were histologically evaluated using a new parameter, the red/blue (R/B) value. The samples were divided into the degenerated group (D group: n = 18) and the healthy group (H group: n = 7) in accordance with the Kellgren-Lawrence (KL) grade. The cultured acetabular labral cells were subjected to loaded uniaxial cyclic tensile strain (CTS). After CTS, changes in gene expression were examined in both groups. RESULTS: Spearman's correlation analysis revealed that the R/B value was significantly correlated with the KL grade and the Krenn score. The expression levels of genes related to cartilage metabolism, osteogenesis and angiogenesis significantly increased after CTS in the H group, while gene expression in the D group showed weaker changes after CTS than that in the H group compared to the nonstretched control group. CONCLUSIONS: The degree of labral degeneration could be classified histologically using the R/B value and the KL grade. Mechanical stretching caused changes in gene expression that support the pathological features of labral degeneration.

Bipolar Hip Arthroplasty Using a Conjoined Tendon-preserving Posterior Approach in Geriatric Patients.

In bipolar hemiarthroplasty (BHA), it is important to preserve soft tissue to reduce the risk of postoperative dislocation. A variety of surgical approaches for BHA are available, but extra care is needed with muscle- and tendon-preserving approaches in geriatric patients. We investigated the usefulness of BHA using a conjoined tendon-preserving posterior (CPP) approach, in which only the external obturator muscle is dissected, in geri-atric patients. We retrospectively analyzed the cases of 40 femoral neck fracture patients (10 men, 30 women) aged ≥ 80 years who underwent BHA using the CPP approach. The patients' average age was 85.8 years (80-94 years). We examined the operation time, bleeding, preservation of short external rotator muscles, complica-tions, and stem alignment and subsidence from postoperative radiographs. Although gemellus inferior muscle injury was detected in 4 patients (10%), the hip joint stability was very excellent in all cases. There was no intraoperative fracture or postoperative dislocation. On postoperative radiographs, all femoral stems were in a neutral position. There was no stem subsidence in all 40 patients. BHA using the CPP approach appeared to be useful even in geriatric patients.

The Thickness of the Medial Wall of the Acetabulum Prevents Acetabular Fracture during the Insertion of a Cementless Cup in Total Hip Arthroplasty: A Biomechanical Study.

Intra-operative acetabular fracture is a total hip arthroplasty complication that can occur during cementless cup insertion, especially in osteoporotic patients. We conducted this biomechanical study to investigate the impact resistance of the acetabulum with simulated bones of different density by drop-weight impact testing. Low- and high-density polyurethane foam blocks were used as osteoporotic and healthy bone models, respectively. Polyurethane blocks were used as the acetabular cancellous bone. Composite sheets were used as the acetabu-lum's medial cortex. The testing revealed that the osteoporotic bone model's impact resistance was significantly lower than that the healthy bone model'. In the healthy bone model, even thin acetabular cancellous bone with ≥ 1 mm acetabulum medial cortex was less likely to fracture. In the osteoporotic bone model, fracture was pos-sible without ≥ 1 mm medial cortex of the acetabulum and thick acetabular cancellous bone. Although impac-tion resistance differs due to bone quality, the impaction resistance in this osteoporotic bone model was equiv-alent to that healthy bone model's when a thick medial wall was present. To avoid intra-operative acetabulum fracture, surgeons should consider both the bone quality and the thicknesses of the medial cortex and acetabu-lar cancellous bone.

Comparison of the accuracy of CT- and accelerometer-based navigation systems for cup orientation in total hip arthroplasty.

BACKGROUND: The accuracies of various navigation systems in total hip arthroplasty (THA) have been described; however, the accuracy of cup orientation with an accelerometer-based navigation system has not been reported. The purpose of this study was to compare the accuracies of computed tomography (CT)- and accelerometer-based navigation systems for cup orientation in THA. METHODS: In this prospective study, 30 patients who underwent cementless THA via anterolateral approach in the lateral decubitus position were analysed. A CT-based navigation system (30 hips) and an accelerometer-based navigation system (30 hips) were used simultaneously. The accuracy of cup orientation (absolute difference between intraoperative vs. postoperative measurements) was compared between the navigation systems using postoperative CT. RESULTS: The accuracy of cup inclination was 3.2 ± 2.4° in the CT-based navigation group and 4.1 ± 3.7° in the accelerometer-based navigation group (p = 0.3035). The accuracy of cup anteversion was 3.0° ± 2.5° in the CT-based navigation group and 6.8° ± 4.8° in the accelerometer-based navigation group. Cup anteversion was significantly more accurate with the CT-based navigation system than with accelerometer-based navigation (p = 0.0009). Multiple regression analysis demonstrated that the malposition in cup anteversion was positively correlated with the change in pelvic tilt and loosening of the reference antenna. CONCLUSIONS: Although, these results are only true for this specific accelerometer system, cup positioning was significantly more accurate with the CT-based navigation system than an accelerometer-based navigation in the lateral decubitus position. This is because of considerable discrepancies in the sagittal pelvic tilt, resulting in variability in cup anteversion angle with the use of an accelerometer-based navigation system.

Acetabular depth, an early predictive factor of acetabular development: MRI in patients with developmental dysplasia of the hip after open reduction.

Early prediction of future acetabular development is important to determine an additional surgery for developmental dysplasia of the hip (DDH). The purpose of this study was to investigate the predictive factors of acetabular development using MRI. We retrospectively investigated dislocated 40 hips and 34 normal hips in 37 pediatric patients (9 males and 28 females) with DDH who underwent open reduction after walking age. We evaluated the cartilaginous acetabulum and labrum of the patients using coronal MRI T2*-weighted images at 5 years of age. The mean age at the time of surgery was 22 months, and the mean age at the final survey was 19 years. We divided patients into two groups in accordance with the Severin classification at the final follow-up. Groups with good outcomes (affected 26 hips and unaffected 27 hips) and poor outcomes (14 hips and 7 hips) were compared using the MRI parameters on each side. Predictive factors of acetabular development were identified using univariate and multiple logistic regression analyses. Using multiple logistic regression analysis, labral acetabular roof depth and labral hip center distance at 5 years of age represented predictors after open reduction (odds ratio 0.27, P = 0.035; odds ratio 3.4, P = 0.028, respectively) on the affected side, and bony hip center distance represented a predictor on the unaffected side (odds ratio 2.6, P = 0.049). Acetabular development in the unaffected side could be predicted by bony assessment, while acetabular development in the affected side had to be assessed by labrum using MRI.

An accelerometer-based navigation system provides acetabular cup orientation accuracy comparable to that of computed tomography-based navigation during total hip arthroplasty in the supine position.

BACKGROUND: Inadequate acetabular component orientation is associated with postoperative impingement, dislocation, and accelerated polyethylene wear. Computed tomography (CT)-based navigation systems provide accuracy for total hip arthroplasty (THA) but are not available in all facilities. Accelerometer-based navigation systems are inexpensive, but their accuracy remains undetermined. This study compares the accuracy of cup orientation in THA using CT-based and accelerometer-based navigation systems. METHODS: This retrospective study included 35 consecutive patients (11 males, 24 females; mean age, 65 years) who underwent primary cementless THA via an anterolateral approach in the supine position. Both CT-based and accelerometer-based navigation systems were used simultaneously. The accuracy of cup orientation was compared between the two systems using postoperative CT. RESULTS: The accuracy of cup inclination was 2.7° ± 2.0° in the CT-based group and 3.3° ± 2.4° in the accelerometer-based group. The accuracy of cup anteversion was 2.8° ± 2.6° in the CT-based group and 3.4° ± 2.2° in the accelerometer-based group. No significant difference was observed in cup inclination (p = 0.29) or cup anteversion (p = 0.34) between CT-based and accelerometer-based navigation. CONCLUSIONS: The accuracy of cup positioning did not differ significantly between CT-based and accelerometer-based navigation systems.

Ten-Year Outcomes of Total Hip Arthroplasty Using Fit-and-Fill Type Cementless Collared Straight Stem Implants: Relationship between the Initial Contact Status and Stress Shielding.

We investigated the relationship between the initial contact status and stress shielding in total hip arthroplasty (THA) using fit-and-fill type straight-stem implants. In addition we evaluated the clinical and radiographic outcomes. Subjects were 100 hips of 94 patients who underwent THA and were followed-up for ≥10 years. Contact areas with the femoral cortical bone were investigated according to the zonal distribution of Gruen using postoperative CT images. Depending on the number of contact areas, the patients were classified into high contact [HC], medium contact [MC], and low contact [LC] groups. Radiographic and clinical outcomes were evaluated. In the HC group (20 hips), severe stress shielding was observed in 12 hips, which was statistically significant (p=0.008). In the LC group (29 hips), mild stress shielding was observed in 27 hips which was statistically significant (p<0.001). No significant differences were observed among the 3 groups in clinical outcomes, Harris hip score (p=0.719) or Japanese Orthopedic Association (JOA) score (p=0.301). In insertion of cementless collared fit-and-fill type straight-stem implants, severe late stress shielding of the femoral bone may occur if high contact of the femoral component is achieved. However, the degree of stress shielding does not result in adverse clinical outcomes.

Idiopathic Chondrolysis of the Hip Treated by Immunosuppressive Therapy and Arthroscopic Intervention.

Idiopathic chondrolysis of the hip (ICH), a very rare disorder of unknown etiology, occurs mainly in female adolescents. Characterized by pain, limp, stiffness and radiological narrowing joint space from the rapid destruction of the articular cartilage, ICH sometimes results in ankyloses. We present the case of a 10-year-old girl diagnosed with ICH based on arthroscopic inspection and synovium biopsy. The femoral deformity appeared gradually, like a cam-type femoroacetabular impingement. She was treated with intensive rehabilitation and immunosuppressive drug. We later performed an arthroscopic bumpectomy for residual symptoms. She achieved a favorable outcome as a 15-year-old at the latest follow-up.

Changes in acetabular component alignment due to screw fixation in patients with hip dysplasia.

INTRODUCTION: Adequate initial stability of the acetabular cup is essential for total hip arthroplasty (THA). However, changes in the alignment of the acetabular component caused by screw fixation are concerning in patients with inadequate bone stock. This study aimed to investigate the effects of screw fixation on the alignment of the acetabular component in THA patients with hip dysplasia. METHODS: We retrospectively examined 256 hips (range 28-87 years) that underwent THA using a navigation system. Patients were divided into 2 groups based on the presence or absence of changes in the alignment of the intraoperative acetabular cup, and univariate and multivariate analyses were performed to identify factors that were predictive of changes in acetabular component alignment after screw fixation in 2 dimensions: inclination and anteversion. RESULTS: Screw fixation led to a mean change in inclination of 1.6° (range 0-10°) and a mean change in anteversion of 1.4° (range 0-14°). The Crowe classification, the presence of bone cysts, and the use of an inferior quadrant screw were identified as factors that correlated with acetabular cup alignment changes in inclination (odds ratios, 6.01, 5.94 and 0.03, respectively). Only the Crowe classification was identified as a factor that correlated with intraoperative alignment changes in anteversion (odds ratio, 2.08). CONCLUSIONS: Screw fixation altered the acetabular cup alignment. The inclination changes were related to the extent of the dysplasia, and the risk was reduced when the inferior quadrant screw was used. Surgeons should use caution during screw fixation in THAs performed on severely dysplastic hips.

Predicting acetabular growth in developmental dysplasia of the hip following open reduction after walking age.

BACKGROUND: Acetabular dysplasia of the hip following open reduction can complicate the treatment of developmental dysplasia of the hip (DDH). The purposes of this retrospective study were to investigate the long-term results of open reduction performed via an extensive anterolateral approach for DDH after walking age and to predict acetabular development using postoperative radiographs and arthrograms. METHODS: From 1973 to 2001, we performed open reduction for 131 hips in 119 pediatric patients with DDH after failed closed reduction. Of these, 85 hips of 73 patients who underwent arthrography at 5 years old were followed-up radiologically until skeletal maturity. Mean age at the time of surgery was 17 ± 4.6 months (range, 10-33 months), and mean age at final survey was 19 ± 5.7 years (range, 14-33 years). Mean follow-up time was 17.7 ± 5.8 years (range, 13-32 years). Groups with satisfactory outcomes (66 hips) and unsatisfactory outcomes (19 hips) according to the Severin classification were compared. Factors predicting acetabular development were identified using univariate and multiple logistic analyses. RESULTS: Univariate analysis showed a significant between-group difference in acetabular index (AI) at 2 months postoperatively, and in center-edge (CE) angle, cartilaginous AI (CAI), and cartilaginous CE angle at 5 years old (p < 0.05 each). In multiple logistic regression analysis, CAI at 5 years old represented a predictor of acetabular development after open reduction for DDH (odds ratio, 1.81; 95% confidence interval (CI), 1.04-3.13; p < 0.05). Area under the receiver operating characteristic curve for CAI at 5 years old was 0.93 (95%CI, 0.85-1.0), and the optimal cut-off was 10° (81.8% sensitivity, 92% specificity). CONCLUSIONS: A CAI ≥10° on hip arthrograms at 5 years old may offer a useful indicator of the need for corrective surgery following open reduction after walking age.

Accuracy of Cup Positioning With the Computed Tomography-Based Two-dimensional to Three-Dimensional Matched Navigation System: A Prospective, Randomized Controlled Study.

BACKGROUND: The accuracy of various navigation systems used for total hip arthroplasty has been described, but no publications reported the accuracy of cup orientation in computed tomography (CT)-based 2D-3D (two-dimensional to three-dimensional) matched navigation. METHODS: In a prospective, randomized controlled study, 80 hips including 44 with developmental dysplasia of the hips were divided into a CT-based 2D-3D matched navigation group (2D-3D group) and a paired-point matched navigation group (PPM group). The accuracy of cup orientation (absolute difference between the intraoperative record and the postoperative measurement) was compared between groups. Additionally, multiple logistic regression analysis was performed to evaluate patient factors affecting the accuracy of cup orientation in each navigation. RESULTS: The accuracy of cup inclination was 2.5° ± 2.2° in the 2D-3D group and 4.6° ± 3.3° in the PPM group (P = .0016). The accuracy of cup anteversion was 2.3° ± 1.7° in the 2D-3D group and 4.4° ± 3.3° in the PPM group (P = .0009). In the PPM group, the presence of roof osteophytes decreased the accuracy of cup inclination (odds ratio 8.27, P = .0140) and the absolute value of pelvic tilt had a negative influence on the accuracy of cup anteversion (odds ratio 1.27, P = .0222). In the 2D-3D group, patient factors had no effect on the accuracy of cup orientation. CONCLUSION: The accuracy of cup positioning in CT-based 2D-3D matched navigation was better than in paired-point matched navigation, and was not affected by patient factors. It is a useful system for even severely deformed pelvises such as developmental dysplasia of the hips.