Discrepancy in the Distribution Patterns of Subchondral Bone Density Across the Ankle Joint After Medial Opening-Wedge and Lateral Closing-Wedge High Tibial Osteotomy

Background: High tibial osteotomy (HTO) changes the alignment and dynamics of the ankle joint; however, differences in the stress distribution of the ankle joint after opening-wedge HTO (OWHTO) and closing-wedge HTO (CWHTO) are not understood. It is believed that subchondral bone density of the articular surface reflects the pattern of cumulative stress distribution across the joint surface. Purpose: To clarify the effects of OWHTO and CWHTO on the distribution patterns of subchondral bone density across the ankle joint using computed tomography (CT)–osteoabsorptiometry. Study Design: Cohort study; Level of evidence, 4. Methods: Radiographic and CT data of 18 cases who underwent OWHTO (OW group), 12 cases who underwent CWHTO (CW group), and 11 cases with unilateral anterior cruciate ligament injury serving as controls were retrospectively reviewed. The subchondral bone density of the distal tibia was assessed in the 3 groups using CT-osteoabsorptiometry. The distal tibial surface of the ankle joint was divided into 4 parts in the coronal direction, and the percentage of the high-density area (%HDA) to each subregion was compared before and after HTO. Results: Preoperatively, comparing %HDA among the 3 groups, there were no significant differences in any regions. In the OW group, postoperative %HDA in the most medial region was significantly increased compared with preoperative %HDA (49.3% to 53.0%; P = .011), and postoperative %HDA in the most lateral region was significantly decreased (21.4% to 17.2%; P = .003). On the other hand, in the CW group, postoperative %HDA in the most medial region was significantly decreased (55.7% to 35.7%; P = .001), and %HDA in the second lateral region was significantly increased (23.6% to 29.2%; P = .002). Conclusion: The ankle distribution pattern of subchondral bone density shifted significantly medially after OWHTO without fibular osteotomy, whereas the distribution pattern shifted laterally after CWHTO with fibular osteotomy. When the OWHTO is performed for patients with medial ankle osteoarthritis, surgeons should pay attention to potential postoperative progression of ankle osteoarthritis due to medial shift of the stress distribution in the ankle joint.

CT Osteoabsorptiometry Assessment of Subchondral Bone Density Predicts Intervertebral Implant Subsidence in a Human ACDF Cadaver Model

Study Design: Cadaveric biomechanics study. Objective: Subchondral bone mineral density (sBMD) reflects the long-term mineralization and distribution of stress on joints. The use of 3-dimensional (3-D) methods to evaluate sBMD, including computed tomography osteoabsorptiometry (CT-OAM), enables the assessment of density distribution with emphasis on subchondral bone. This study sought to measure the sBMD of cervical endplates using CT-OAM and correlate it to mechanical implant subsidence in a cadaveric model. Methods: Fourteen fresh human cadaveric cervical spines were subjected to dynamic testing after single level discectomy and instrumentation using a PEEK interbody spacer. Specimens were imaged with CT 3 times: 1st) whole intact cervical spine, 2nd) after implantation, and 3 rd) after testing. These images were used to assess sBMD distributions using CT-OAM directly underneath the spacer. Subsidence was defined as the displacement of the device into the endplates. Results: The observed “failure mode” was consistently recorded as subsidence, with a mean of 0.45 ± 0.36 mm and 0.40 ± 0.18 mm for the C4-5 and C6-7 levels, respectively. There were no differences by level. The experimental cyclic test showed that denser endplates experienced less deformation under the same load. Conclusions: This study achieved its stated aim of validating the use of CT-OAM as a method to analyze the sBMD of the cervical endplates. Studies such as this are providing new information on available technology such as CT-OAM, providing new tools for clinicians treating spinal conditions in need of augmentation and stabilization via interbody devices.

Monosodium Iodoacetate Induced Subchondral Bone Microstructure and Inflammatory changes in an Animal Model of Osteoarthritis

Objective: To verify the presence of histopathological injury and cartilage degeneration in MIA induced joints. To investigate the correlation between inflammatory reaction and subchondral bone remodeling in a rodent osteoarthritic model.Method: Intra-articular injection of MIA was performed in Wistar rats to induce OA. After 4 weeks intervention, the animals were sacrificed, changes in intrinsic structural properties of the subchondral bones were measured using micro-CT scanning. Moreover, the histological evaluation and biochemical analysis was conducted using histochemical staining, immunofluorescence, real-time polymerase chain reaction, and western blot analysis.Results: This study demonstrated that intra-articular injection of MIA increased chondrocyte apoptosis and promoted cartilage matrix degradation, such as cartilage surface defects and shallow or even disappeared staining. MIA also induced the inflammatory process, improved the expression of IL-1β, TNF-α, matrix metalloproteinase, and decreased the expression of cartilage specific proteins with the extension of modeling time. Meanwhile, the MIA also significantly accelerated the subchondral bone remodeling at both week two and week four, as shown by the decreased subchondral bone density, thinning of trabeculae, disordered cartilage structure and morphology.Conclusion: Intra-articular injection of MIA can lead to articular cartilage degeneration and subchondral bone remodeling in the rat model of OA. MIA induced rodent osteoarthritic model would cause decreased subchondral bone density, sparse trabecular bone, and other manifestations of osteoporosis accompanied by an inflammatory response, which would worsen with the progression of modelling time.

Effect of High Tibial Osteotomy on the Distribution of Subchondral Bone Density Across the Proximal Tibial Articular Surface of the Knee With Medial Compartment Osteoarthritis

Background: The effect of high tibial osteotomy (HTO) on the stress distribution across the knee joint is not completely understood. Subchondral bone density is considered to reflect the pattern of stress distribution across a joint surface. Purpose: To assess the distribution of subchondral bone density across the proximal tibia in nonarthritic knees and in the knees of patients with osteoarthritis (OA) before and after HTO. Study Design: Cohort study; Level of evidence, 3. Methods: We retrospectively collected radiological and computed tomography data from 16 patients without OA (control group) and 17 patients with OA. Data from the OA group were collected before and 1.5 years after HTO. Subchondral bone density of the proximal tibia was assessed with computed tomography–osteoabsorptiometry. The locations and percentages represented by high-density areas (HDAs) on the articular surface were quantitatively analyzed. Results: The ratio of the HDA of the medial compartment to the total HDA (medial ratio) was significantly higher in the preoperative OA group (mean, 80.1%) than in the control group (61.3%) ( P < .001). After HTO, the medial ratio decreased significantly to 75.1% ( P = .035 in comparison with preoperative values) and was significantly correlated with the hip-knee-ankle angle in both groups: control ( r = −0.551; P = .033) and OA ( r = −0.528; P = .043). The change in medial ratio after HTO was significantly correlated with the change in hip-knee-ankle angle ( r = 0.587; P = .035). In the medial compartment, the HDA in the most lateral region of 4 subregions increased after HTO, but that in 3 medial subregions decreased. Conclusion: In this exploratory study, HTO shifted the HDA of the medial compartment of the proximal tibial articular surface toward the lateral compartment. In contrast, the HDA of the most lateral region of the medial compartment increased after HTO. This change in subchondral bone density may result from the change in stress distribution.

Changes in the Contact Stress Distribution Pattern of the Patellofemoral Joint After Medial Open-Wedge High Tibial Osteotomy: An Evaluation Using Computed Tomography Osteoabsorptiometry

Background: Medial open-wedge high tibial osteotomy (OWHTO) theoretically causes distalization and lateralization of the tibial tuberosity and the patella. Purpose/Hypothesis: The purpose of the study was to identify any changes in the stress distribution of subchondral bone density across the patellofemoral (PF) joint before and after OWHTO through the use of computed tomography (CT) osteoabsorptiometry. We hypothesized that OWHTO would alter the distribution of contact stress in the PF joint. Study Design: Case series; Level of evidence, 4. Methods: A total of 17 patients (17 knees) who underwent OWHTO were enrolled in this study between September 2013 and September 2015. All patients underwent radiologic examination preoperatively and at 1 year postoperatively, and the distribution patterns of subchondral bone density through the articular surface of the femoral trochlea and patella were assessed preoperatively and >1 year postoperatively using CT osteoabsorptiometry. The quantitative analysis of the obtained mapping data focused on location of the high-density area (HDA) through the articular surface of the PF joint. The percentage of HDA at each divided region of the articular surface of the femoral trochlea and the patella was calculated. Results: In the radiologic evaluation, the Blackburne-Peel ratio was significantly reduced ( P < .001) after surgery, and the tilting angle of the patella was significantly decreased ( P < .001). On CT evaluation, the percentage of HDA in the lateral notch and lateral trochlea of the femur and in the medial portion of the lateral facet of the patella increased significantly after OWHTO surgery ( P ≤ .038). Conclusion: OWHTO significantly increased the stress distribution pattern of the lateral trochlea of the femur and the medial portion of the lateral facet of the patella. The procedure significantly lowered the patellar height and significantly decreased the patellar tilting angle after surgery.

Stress Distribution Patterns Across the Shoulder Joint in Gymnasts: A Computed Tomography Osteoabsorptiometry Study

Background: The distribution pattern of subchondral bone density is an indicator of stress distribution over a joint surface under long-term physiologic loading. The biomechanical characteristics of the articular surfaces of the shoulder joint in gymnasts can be determined by measuring this distribution pattern. Purpose: To evaluate the distribution of subchondral bone density across the shoulder joint in male collegiate gymnasts and to determine the effects of gymnastic activities on its articular surfaces under long-term loading conditions using computed tomography osteoabsorptiometry (CTOAM). Study Design: Descriptive laboratory study. Methods: CT image data were obtained from both shoulders of 12 asymptomatic male collegiate gymnasts (gymnast group; mean age, 19.4 years; range, 18-22 years) and 10 male collegiate volunteers (control group; mean age, 20.2 years; range, 18-22 years). The distribution pattern of subchondral bone density across the articular surfaces of each shoulder joint was assessed by CTOAM. Quantitative analysis was performed of the locations and percentages of high-density areas on the articular surface. Results: Stress distribution patterns over the articular surfaces differed between the gymnasts and the controls. In the gymnasts, high-density areas were detected on the posterosuperior articular surface of the humeral head and the anterosuperior and/or posterosuperior articular surface of the glenoid. Mean bone density was greater in the gymnasts than in the controls ( P < .0001). Conclusion: Stress distribution over the articular surfaces of the shoulder joint was affected by gymnastic activities. Stress was concentrated over the superior part of the glenohumeral joint in male collegiate gymnasts. Clinical Relevance: The present findings suggest that gymnastic activities increase stress to the articular surfaces of the superior glenohumeral joint. This supports the notion that mechanical conditions play a crucial role in the origin of disorders particular to gymnastic activities.

Long-term Stress Distribution Patterns Across the Ankle Joint in Soccer Players: A Computed Tomography Osteoabsorptiometry Study

Background: The distribution pattern of subchondral bone density is considered to accurately reflect the stress distribution over a joint under long-term physiologic loading. The biomechanical characteristics of the surface of the ankle joint in soccer players can be determined by measuring this distribution pattern under long-term loading. Purpose: To evaluate the distribution of subchondral bone density across the ankle joint in soccer players and to determine the effects of soccer activities, including kicking motion, on the ankle joint surface under long-term loading conditions by computed tomography (CT) osteoabsorptiometry (CTOAM). Study Design: Cross-sectional study; Level of evidence, 3. Methods: CT imaging data were obtained from both ankles of 10 soccer players (soccer group) and 10 nonathletic volunteers (control group). The distribution patterns of subchondral bone density across the articular surface of the ankle joints were assessed by CTOAM. Quantitative analysis was performed of the locations and percentages of high-density areas on the articular surface. Results: Stress distribution patterns over the ankle joint differed between the soccer players and controls. In the soccer players, the high-density areas were found in the anterior part of the distal tibia and proximal talus as well as the distal fibula. The percentages of high-density areas were greater in the soccer players compared with controls ( P < .0001). Conclusion: Stress distribution over the articular surface of the ankle joint was affected by soccer activities. A high stress concentration was seen in soccer players in the anterior part of the tibia and talus and in the fibula; such excessive stress may lead to anterior impingement.