ObjectiveTo investigate the pathological and microstructural features of the osteonecrosis samples from subjects with steroid-induced or alcohol-induced osteonecrosis of the femoral head (ONFH).MethodsThirty femoral head bone samples were collected from ONFH patients who underwent total hip arthroplasty between August 2015 and April 2016. There were 22 males and 8 females. The etiology of ONFH was alcohol-induced in 15 patients and steroid-induced in 15 patients. No significant difference of Association Research Circulation Osseous (ARCO) stage was found between alcohol-induced and steroid-induced ONFH (Z=2.143, P=0.143). The femoral head bone samples in different areas (necrosis, sclerosis, and normal) from involved subjects was taken, and gross observation, HE staining were carried out (the rate of empty lacunaes was calculated). The intact femoral head was scanned by Micro-CT and the parameters of bone microstructure were analyzed quantitatively. The parameters included bone volume to total volume (BV/TV), bone surface area to bone volume ratio (BS/BV), bone mineral density (BMD), bone mineral content (BMC), structural model index (SMI), trabecular plate number (Tb. N), trabecular plate thickness (Tb. Th), and trabecular spacing (Tb. Sp).ResultsAs observed in hard tissue slicing of both groups, the integrity of trabecular bone was destructed and cystic lesions left by the bone resorption was replaced by granulation tissues. Significant revascularization was found in granulation tissues of steroid-induced ONFH, but not in the alcohol-induced one. HE staining showed that the bone marrow structure was disordered in both group, as well as bone marrow necrosis and empty bone lacunaes noticed. The structure and integrity of trabecular bone of steroid-induced ONFH was far more severe whereas that of alcohol-induced one were thicker and better. The rate of empty bone lacunae in necrosis area of steroid-induced group was significantly higher than that of alcohol-induced one (P<0.05), but no significant difference was found in sclerotic and normal areas between 2 groups (P>0.05). Micro-CT showed that necrotic and sclerotic areas of both groups were low bone density. Bone structure in the former area was mostly heterogeneous. Further blood-rich granulation tissues formation was observed in the same places of hard tissue slicing, while the sclerotic one wasn’t. The results of quantitative bone structure analysis showed that BV/TV, BMD, BMC, Tb.N, and Tb.Th of the necrotic and sclerotic areas of steroid-induced ONFH were significantly lower than those of alcohol-induced one (P<0.01), BS/BV, SMI, and Tb.Sp of steroid-induced ONFH were significantly higher than those of alcohol-induced one (P<0.01). No significant difference among the indexes above was found in the normal areas of both groups (P>0.05).ConclusionThe integrity of trabecular bone was destroyed in necrotic area of steroid-induced or alcohol-induced ONFH. However, they performed different features of osteonecrosis and contrasted with each other. The steroid-induced ONFH was characterized by multiple " osteolytic bone destruction”, while the alcohol-induced one was manifested by some kinds of " coagulative destruction”.
Objective To analyze the femoral head collapse and the operation of osteonecrosis of the femoral head (ONFH) in different Japanese Investigation Commitee (JIC) types, in order to summarize the prognostic rules of each type of ONFH, and explore the clinical significance of CT lateral subtypes based on reconstruction of necrotic area of C1 type and verify their clinical effect. Methods A total of 119 patients (155 hips) with ONFH between May 2004 and December 2016 were enrolled in the study. The total hips consisted of 34 hips in type A, 33 in type B, 57 in type C1, and 31 in type C2, respectively. There was no significant difference in age, gender, affected side, or type of ONFH of the patients with differenct JIC types (P>0.05). The 1-, 2-, and 5-year femoral head collapse and operation of different JIC types were analyzed, as well as the survival rate (with femoral head collapse as the end point) of hip joint between different JIC types, hormonal/non-hormonal ONFH, asymptomatic and symptomatic (pain duration >6 months or ≤6 months), and combined preserved angle (CPA) ≥118.725° and CPA<118.725°. JIC types with significant differences in subgroup surgery and collapse and with research value were selected. According to the location of the necrotic area on the surface of the femoral head, the JIC classification was divided into 5 subtypes in the lateral CT reconstruction, and the contour line of the necrotic area was extracted and matched to the standard femoral head model, and the necrosis of the five subtypes was presented by thermography. The 1-, 2-, and 5-year outcomes of femoral head collapse and operation in different lateral subtypes were analyzed, and the survival rates (with collapse of the femoral head as the end point) between CPA≥118.725° and CPA<118.725° hip in patients with this subtype were compared, as well as the survival rates of different lateral subtypes (with collapse and surgery as the end points, respectively). ResultsThe femoral head collapse rate and operation rate in the 1-, 2-, and 5-year were significantly higher in patients with JIC C2 type than in patients with other hip types (P<0.05), while in patients with JIC C1 type than in patients with JIC types A and B (P<0.05). The survival rate of patients with different JIC types was significantly different (P<0.05), and the survival rate of patients with JIC types A, B, C1, and C2 decreased gradually. The survival rate of asymptomatic hip was significantly higher than that of symptomatic hip, and the survival rate of CPA≥118.725° was significantly higher than that of CPA<118.725° (P<0.05). The lateral CT reconstruction of type C1 hip necrosis area was selected for further classification, including type 1 in 12 hips, type 2 in 20 hips, type 3 in 9 hips, type 4 in 9 hips, and type 5 in 7 hips. There were significant differences in the femoral head collapse rate and the operation rate among the subtypes after 5 years of follow-up (P<0.05). The collapse rate and operation rate of types 4 and 5 were 0; the collapse rate and operation rate of type 3 were the highest; the collapse rate of type 2 was high, but the operation rate was lower than that of type 3; the collapse rate of type 1 was high, but the operation rate was 0. In JIC type C1 patients, the survival rate of the hip joint with CPA≥118.725° was significantly higher than that with CPA<118.725° (P<0.05). In the follow-up with femoral head collapse as the end point, the survival rates of types 4 and 5 were all 100%, while the survival rates of types 1, 2, and 3 were all 0, and the difference was significant (P<0.05). The survival rate of types 1, 4, and 5 was 100%, of type 3 was 0, and of type 2 was 60%, showing significant difference (P<0.05). Conclusion JIC types A and B can be treated by non-surgical treatment, while type C2 can be treated by surgical treatment with hip preservation. Type C1 was classified into 5 subtypes by CT lateral classification, type 3 has the highest risk of femoral head collapse, types 4 and 5 have low risk of femoral head collapse and operation, type 1 has high femoral head collapse rate but low risk of operation; type 2 has high collapse rate, but the operation rate is close to the average of JIC type C1, which still needs to be further studied.
Objective To establish finite element models of different preserved angles of osteonecrosis of the femoral head (ONFH) for the biomechanical analysis, and to provide mechanical evidence for predicting the risk of ONFH collapse with anterior preserved angle (APA) and lateral preserved angle (LPA). Methods A healthy adult was selected as the study object, and the CT data of the left femoral head was acquired and imported into Mimics 21.0 software to reconstruct a complete proximal femur model and construct 3 models of necrotic area with equal volume and different morphology, all models were imported into Solidworks 2022 software to construct 21 finite element models of ONFH with LPA of 45°, 50°, 55°, 60°, 65°, 70°, and 75° when APA was 45°, respectively, and 21 finite element models of ONFH with APA of 45°, 50°, 55°, 60°, 65°, 70°, 75° when LPA was 45°, respectively. According to the physiological load condition of the femoral head, the distal femur was completely fixed, and a force with an angle of 25°, downward direction, and a magnitude of 3.5 times the subject’s body mass was applied to the weight-bearing area of the femoral head surface. The maximum Von Mises stress of the surface of the femoral head and the necrotic area and the maximum displacement of the weight-bearing area of the femoral head were calculated and observed by Abaqus 2021 software. ResultsThe finite element models of ONFH were basically consistent with biomechanics of ONFH. Under the same loading condition, there was stress concentration around the necrotic area in the 42 ONFH models with different preserved angles composed of 3 necrotic areas with equal volume and different morphology. When APA was 60°, the maximum Von Mises stress of the surface of the femoral head and the necrotic area and the maximum displacement of the weight-bearing area of the femoral head of the ONFH models with LPA<60° were significantly higher than those of the models with LPA≥60° (P<0.05); there was no significant difference in each index among the ONFH models with LPA≥60° (P>0.05). When LPA was 60°, each index of the ONFH models with APA<60° were significantly higher than those of the models with APA≥60° (P<0.05); there was no significant difference in each index among the ONFH models with APA≥60° (P>0.05). Conclusion From the perspective of biomechanics, when a preserved angle of ONFH is less than its critical value, the stress concentration phenomenon in the femoral head is more pronounced, suggesting that the necrotic femoral head may have a higher risk of collapse in this state.
Objective To investigate the impact of the bone mass and volume of the low-density area under the tibial plateau on the lower limb force line by finite element analysis, offering mechanical evidence for preventing internal displacement of the lower limb force line in conjunction with knee varus in patients with knee osteoarthritis (KOA) and reducing bone mass under the tibial plateau. Methods A healthy adult was selected as the study subject, and X-ray film and CT imaging data were acquired. Mimics 21.0 software was utilized to reconstruct the complete knee joint model and three models representing low-density areas under the tibial plateau with equal volume but varying shapes. These models were then imported into Solidworks 2023 software for assembly and verification. Five KOA finite element models with 22%, 33%, 44%, 55%, and 66% bone mass reduction in the low-density area under tibial plateau and 5 KOA finite element models with 81%, 90%, 100%, 110%, and 121% times of the low-density area model with 66% bone mass loss were constructed, respectively. Under physiological loading conditions of the human lower limb, the distal ends of the tibia and fibula were fully immobilized. An axial compressive load of 1 860 N, following the lower limb force line, was applied to the primary load-bearing area on the femoral head surface. The maximum stress within the tibial plateau, as well as the maximum displacements of the tibial cortical bone and tibial subchondral bone, were calculated and analyzed using the finite element analysis software Abaqus 2022. Subsequently, predictions regarding the alteration of the lower limb force line were made based on the analysis results. Results The constructed KOA model accorded with the normal anatomical structure of lower limbs. Under the same boundary conditions and the same load, the maximum stress of the medial tibial plateau, the maximum displacement of the tibial cortical bone and the maximum displacement of the cancellous bone increased along with the gradual decrease of bone mass in the low-density area under the tibial plateau and the gradual increase in the volume of the low-density area under tibial plateau, with significant differences (P<0.05). ConclusionThe existence of a low-density area under tibial plateau suggests a heightened likelihood of knee varus and inward movement of the lower limb force line. Both the volume and reduction in bone mass of the low-density area serve as critical initiating factors. This information can provide valuable guidance to clinicians in proactively preventing knee varus and averting its occurrence.