Contact stress in hips with osteonecrosis of the femoral head

The Effect of the Hip Flexion Angle in Osteonecrosis of the Femoral Head Based on China-Japan Friendship Hospital Classification - A Finite Element Study

OBJECTIVE

The alteration in the mechanical environment of the necrotic area is the primary cause of the collapse observed in osteonecrosis of the femoral head (ONFH). This study aims to evaluate the biomechanical implications of the China-Japan Friendship Hospital (CJFH) classification system and hip flexion angles on the necrotic area in ONFH using finite element analysis (FEA). The goal is to provide valuable guidance for hip preservation treatments and serve as a reference for clinical diagnosis and therapeutic interventions.

METHODS

Hip tomography CT scan data from a healthy volunteer was used to create a 3D model of the left hip. The model was preprocessed and imported into Solidworks 2018, based on the CJFH classification. Material parameters and boundary conditions were applied to each fractal model in ANSYS 21.0. Von Mises stresses were calculated, and maximum deformation values were obtained to evaluate the biomechanical effects of the load on the necrotic area and post-necrotic femur, as well as assess each fractal model's collapse risk.

RESULTS

(1) At the same hip flexion angle, maximum deformation followed this order: M Type < C Type < L Type. The L3 type necrotic area experienced the most significant deformation at 0, 60, and 110° angles (1.121, 1.7913, and 1.8239 mm respectively). (2) Under the same CJFH classification, maximum deformation values increased with hip flexion angle (0 < 60 < 110°), suggesting a higher risk of collapse at larger angles. (3) Von Mises stress results showed that the maximum stress was not located in the necrotic area but near the inner and outer edge of the femoral neck, indicating decreased stiffness and strength of the subchondral bone after osteonecrosis.

CONCLUSION

The study found that femoral head collapse risk was higher when the necrotic area was located in the lateral column under the same stress load and flexion angle. Mechanical properties of the necrotic area changed, resulting in decreased bone strength and stiffness. Large-angle hip flexion is more likely to cause excessive deformation of the necrotic area; thus, ONFH patients should reduce or avoid large-angle hip flexion during weight-bearing training in rehabilitation activities.

Pre-collapse femoral head necrosis treated by hip abduction: a computational biomechanical analysis

Background and objective

Clinical studies indicated that femoral head collapse (FHC) occurs in 90% of patients without intervention within five years after the diagnosis of femoral head necrosis (FHN). The management of the FHN is still a great challenging task. Clinical studies indicated that hip abduction as physical therapy represents an effective hip preservation method. However, the mechanism is unclear. In this study, we use computational biomechanical technology to investigate mechanical response in FHN patients with hip abduction and establish guide protocols for FHN rehabilitation.

Materials and methods

Thirty computational models were constructed for evaluating the safety of hip abduction and comparing the biomechanical performance of hip abduction for the treatment of different necrotic classifications. The distribution of principal compressive stress (PCS) and load share ratio (LSR) were computed and used for biomechanical evaluation.

Results

Before the start of physical therapy, when the size of necrotic segment is increased and located more laterally, the damage area of PCS enlarged and LSR of subchondral cortical to trabecular bone increased. As the increase of hip abduction angle, PCS of Type B transformed into Type A, PCS of Type C1 transformed into Type B, PCS of Type C2 transformed into Type C1; Except Type C2, the LSR return to normal level.

Discussion and conclusion

Stress transfer damaged pattern correlated significantly with necrotic classification. Hip abduction motions effectively enlarge the area of PCS and recover the LSR of different structures by altering motion posture during gait. The results indicated that hip abduction may be an effective physical therapy in improving hip function and interrupt the disease pathway of FHC and THA.

The Role of Structural Deterioration and Biomechanical Changes of the Necrotic Lesion in Collapse Mechanism of Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) is a crippling disease which is due to a lack of effective therapeutic measures. Its natural progression is rapid, the internal bone structure of the femoral head changes dramatically, and the subsequent fractures and collapse cause severe hip pain and loss of hip function. Femoral head collapse is a critical turning point in the development of ONFH and is related to the prognosis of patients. Early prevention and intervention help to preserve the hip joint and delay femoral head collapse. However, the mechanism of collapse still needs to be further studied because it is affected by different complex factors. This review discusses the underlying causes of femoral head collapse from two aspects: structural degradation and regional changes of biomechanical properties in the necrotic femoral head.

Hip joint mechanics in patients with osteonecrosis of the femoral head following treatment by advanced core decompression

BACKGROUND

Osteonecrosis of the femoral head is a serious disease which, if left untreated, leads to destruction of the affected hip joint. For treatment of early stages of this disease, core decompression is the most common procedure. This study investigated the influence of the necrotic lesion and core decompression on the stress pattern in the hip joint using finite element analysis.

METHODS

Subject-specific models were generated from CT scan data of 5 intact hips. For each intact hip, twelve affected hip models were created by imposing a necrotic lesion in the femoral head, and four treated models were then created from four affected ones with central lesion, respectively. Treated models were created by supposing that the defect zone and the drill canal were filled with a bone substitute. Totally 105 hip models from three groups (intact, affected and treated) were simulated during normal walking activity.

FINDINGS

Necrotic lesion modified the stress distribution within the femoral head. Peak stress increased significantly up to 186% in mean in hips with a large lesion indicating an increased risk of femoral head collapse. Additionally, the presence of a medium to large necrosis altered significantly stress values (P < 0.05) and pattern in the articular cartilage. Our study revealed that advanced core decompression can recover normal cartilage stress values and pattern in treated joint.

INTERPRETATION

The presence of a large lesion increased the risk of femoral head collapse. Advanced core decompression with bone grafts can restore normal cartilage mechanics in hip postoperatively.

Combining frog-leg lateral view may serve as a more sensitive X-ray position in monitoring collapse in osteonecrosis of the femoral head

Load-bearing capacity of the bone structures of anterolateral weight-bearing area plays an important role in the progressive collapse in osteonecrosis of the femoral head (ONFH). The purpose of this study is to assess the efficacy of combined evaluation of anteroposterior (AP) and frog-leg lateral (FLL) view in diagnosing collapse. Between December 2016 and August 2018, a total of 478 hips from 372 patients with ONFH (268 male, 104 female; mean age 37.9 ± 11.4 years) were retrospectively evaluated. All patients received standard AP and FLL views of hip joints. Japanese Investigation Committee (JIC) classification system was used to classify necrotic lesion in AP view. Anterior necrotic lesion was evaluated by FLL view. All patients with pre-collapse ONFH underwent non-operative hip-preserving therapy. The collapse rates were calculated and compared with Kaplan–Meier survival analysis with radiological collapse as endpoints. Forty-four (44/478, 9.2%) hips were classified as type A, 65 (65/478, 13.6%) as type B, 232 (232/478, 48.5%) as type C1 and 137 (137/478, 28.7%) as type C2. Three hundred cases (300/478, 62.5%) were collapsed at the initial time point. Two hundred and twenty six (226/300, 75.3%) hips and 298 (298/300, 99.3%) hips collapse were identified with AP view and FLL view, respectively. An average follow-up of 37.0 ± 32.0 months was conducted to evaluate the occurrence of collapse in 178 pre-collapse hips. Collapses occurred in 89 hips (50.0%). Seventy-seven (77/89, 86.5%) hips were determined with AP view alone and 85 (85/89, 95.5%) hips were determined with the combination of AP and FLL views. The collapse rates at five years were reported as 0% and 0%, 16.2% and 24.3%, 58.3% and 68.1% and 100% and 100% according to AP view alone or combination of AP and FLL views for types A, B, C1 and C2, respectively. The collapse can be diagnosed more accurately by combination of AP and FLL views. Besides, JIC type A and type B ONFH can be treated with conservative hip preservation, but pre-collapse type C2 ONFH should be treated with joint-preserving surgery. Type C1 needs further study to determine which subtype has potential risk of collapse.

The role of biomechanical forces and MALAT1/miR-329-5p/PRIP signalling on glucocorticoid-induced osteonecrosis of the femoral head

Glucocorticoid‐induced osteonecrosis of the femoral head (GIONFH) is a common orthopaedic disease. GIONFH primarily manifests clinically as hip pain in the early stages, followed by the collapse of the femoral head, narrowing of the hip joint space and damage to the acetabulum, resulting in severely impaired mobility. However, the pathogenesis of GIONFH is not clearly understood. Recently, biomechanical forces and non‐coding RNAs have been suggested to play important roles in the pathogenesis of GIONFH. This study aimed to evaluate the role of biomechanical forced and non‐coding RNAs in GIONFH. We utilized an in vivo, rat model of GIONFH and used MRI, μCT, GIONFH‐TST (tail suspension test), GIONFH‐treadmill, haematoxylin and eosin staining, qRT‐PCR and Western blot analysis to analyse the roles of biomechanical forces and non‐coding RNAs in GIONFH. We used RAW264.7 cells and MC3T3E1 cells to verify the role of MALAT1/miR‐329‐5p/PRIP signalling using a dual luciferase reporter assay, qRT‐PCR and Western blot analysis. The results demonstrated that MALAT1 and PRIP were up‐regulated in the femoral head tissues of GIONFH rats, RAW264.7 cells, and MC3T3E1 cells exposed to dexamethasone (Dex). Knockdown of MALAT1 decreased PRIP expression in rats and cultured cells and rescued glucocorticoid‐induced osteonecrosis of femoral head in rats. The dual luciferase reporter gene assay revealed a targeting relationship for MALAT1/miR‐329‐5p and miR‐329‐5p/PRIP in MC3T3E1 and RAW264.7 cells. In conclusion, MALAT1 played a vital role in the pathogenesis of GIONFH by binding to (‘sponging’) miR‐329‐5p to up‐regulate PRIP. Also, biomechanical forces aggravated the pathogenesis of GIONFH through MALAT1/miR‐329‐5p/PRIP signalling.

Discrete element and finite element methods provide similar estimations for hip joint contact mechanics during walking gait

Finite element analysis (FEA) provides a powerful approach for estimating the in-vivo loading characteristics of the hip joint during various locomotory and functional activities. However, time-consuming procedures, such as the generation of high-quality FE meshes and setup of FE simulation, typically make the method impractical for rapid applications which could be used in clinical routine. Alternatively, discrete element analysis (DEA) has been developed to quantify mechanical conditions of the hip joint in a fraction of time compared to FEA. Although DEA has proven effective in the estimation of contact stresses and areas in various complex applications, it has not yet been well characterised by its ability to evaluate contact mechanics for the hip joint during gait cycle loading using data from several individuals. The objective of this work was to compare DEA modelling against well-established FEA for analysing contact mechanics of the hip joint during walking gait. Subject-specific models were generated from magnetic resonance images of the hip joints in five asymptomatic subjects. The DEA and FEA models were then simulated for 13 loading time-points extracted from a full gait cycle. Computationally, DEA was substantially more efficient compared to FEA (simulation times of seconds vs. hours). The DEA and FEA methods had similar predictions for contact pressure distribution for the hip joint during normal walking. In all 13 simulated loading time-points across five subjects, the maximum difference in average contact pressures between DEA and FEA was within ±0.06 MPa. Furthermore, the difference in contact area ratio computed using DEA and FEA was less than ±6%.

Prognostic analysis of different morphology of the necrotic-viable interface in osteonecrosis of the femoral head

PURPOSE

The purpose of this study was to investigate the collapse progression in different morphologies of the necrotic-viable interface in osteonecrosis of the femoral head (ONFH).

METHODS

A total of 168 patients (202 hips) with Association Research Circulation Osseous (ARCO) stage II ONFH were included. Ending with the collapse of the femoral head, all patients received conservative treatment but without surgical intervention and were followed for three to 91 months. Bilateral hip-joint radiographs and magnetic resonance imaging (MRI) were examined, and the largest layer of necrosis within the coronal section of MRI images was selected together with its anteroposterior radiograph to observe the morphology of the necrotic-viable interface. The morphology was divided into four types: I, type transverse; II, type "V"; III, type zigzag; IV, type closed. The collapse rate and the time to collapse in different morphologies were assessed.

RESULTS

A total of 120 hips collapsed in two years or less, 61 were type-I, 51 were type-II, and 8 were type-III. Non-collapse occurred in all 17 hips with type-IV ONFH during long-term follow-up. In 202 hips with ARCO stage-II ONFH, the collapse rate in type-I ONFH was significantly higher than that of type-II and type-III ONFH (P < 0.01 for both). The time to collapse was markedly shortened.

CONCLUSIONS

The risk of ONFH-induced collapse is influenced by the morphology of the necrotic-viable interface. Effective mechanical support for preventing the collapse of the femoral head is necessary when the morphology of the necrotic-viable interface is type transverse.

A method to investigate the biomechanical alterations in Perthes' disease by hip joint contact modeling

Perthes' disease is a destructive hip joint disorder characterized by malformation of the femoral head in young children. While the morphological changes have been widely studied, the biomechanical effects of these changes still need to be further elucidated. The objective of this study was to develop a method to investigate the biomechanical alterations in Perthes' disease by finite element (FE) contact modeling using MRI. The MRI data of a unilateral Perthes' case was obtained to develop the three-dimensional FE model of the hip joint. The stress and contact pressure patterns in the unaffected hip were well distributed. Elevated concentrations of stress and contact pressure were found in the Perthes' hip. The highest femoral cartilage von Mises stress 3.9 MPa and contact pressure 5.3 MPa were found in the Perthes' hip, whereas 2.4 MPa and 4.9 MPa in the healthy hip, respectively. The healthy bone in the femoral head of the Perthes' hip carries additional loads as indicated by the increase of stress levels around the necrotic-healthy bone interface. Identifying the biomechanical changes, such as the location of stress and contact pressure concentrations, is a prerequisite for the preoperative planning to obtain stress relief for the highly stressed areas in the malformed hip. This single-patient study demonstrated that the biomechanical alterations in Perthes' disease can be evaluated individually by patient-specific finite element contact modeling using MRI. A multi-patient study is required to test the strength of the proposed method as a pre-surgery planning tool.

Patient-specific hip geometry has greater effect on THA wear than femoral head size

In vivo linear penetration in total hip arthroplasty (THA) exhibits similar values for 28mm and 32mm femoral head diameter with considerable variations between and within the studies. It indicates factors other than femoral head diameter influence polyethylene wear. This study is intended to test the effect of patient׳s individual geometry of musculoskeletal system, acetabular cup orientation, and radius of femoral head on wear. Variation in patient׳s musculoskeletal geometry and acetabular cup placement is evaluated in two groups of patients implanted with 28mm and 32mm THA heads. Linear wear rate estimated by mathematical model is 0.165-0.185mm/year and 0.157-0.205mm/year for 28 and 32mm THA heads, respectively. Simulations show little influence femoral head size has on the estimated annual wear rate. Predicted annual linear wear depends mostly on the abduction angle of the acetabular cup and individual geometry of the musculoskeletal system of the hip, with the latter having the greatest affect on variation in linear wear rate.

Unfavorable hip stress distribution after Legg-Calvé-Perthes syndrome: a 25-year follow-up of 135 hips

To study the effect of hip and pelvis geometry on development of the hip after Perthes disease, we determined the resultant hip force and contact hip stress distribution in a population of 135 adult hips of patients who had been treated for Perthes disease in childhood. Contra-lateral hips with no record of disease were taken as the control population. Biomechanical parameters were determined by mathematical models for resultant hip force in one-legged stance and for contact hip stress, which use as an input the geometrical parameters assessed from anteroposterior radiographs. The mathematical model for stress was upgraded to account for the deviation of the femoral head shape from spherical. No differences were found in resultant hip force and in peak contact hip stress between the hips that were in childhood subject to Perthes disease and the control population, but a considerable (148%) and significant (p < 0.001) difference was found in the contact hip stress gradient index, expressing an unfavorable, steep decrease of contact stress at the lateral acetabular rim. This finding indicates an increased risk of early coxarthritis in hips subject to Perthes disease.

Impact of triple pelvic osteotomy on contact stress pressure distribution in the hip joint

PURPOSE

We studied changes of contact stress distribution in the hip joint after Tonnis triple pelvic osteotomy applied in the treatment of dysplasia and hip joint incongruence in adolescents.

METHODS

In a group of 75 patients, 54 (72 %) female, who underwent surgery by triple pelvic osteotomy in adolescence for developmental disorder of the hip and avascular necrosis of the femoral head, a three-dimensional hip joint model was used based on the radiography of the pelvis with hips. The following biomechanical parameters were calculated: resultant hip force normalised to body weight (R/Wb), inclination of the resultant hip force (θ-R), the position of the stress pole (θ), peak contact hip stress (Pmax), and peak contact hip stress normalised to body weight (Pmax/Wb). Gait quality was also assessed.

RESULTS

After surgery the Wiberg CE angle was increased by 17.85° (114 %), resultant hip force normalised to body weight (R/Wb) was decreased by 0.107 (3.3 %), the position of the stress pole was shifted medially by 27.59° (63.5 %), and peak contact hip stress normalised to body weight (Pmax/Wb) was decreased by 2249.74 (55.9 %). Waddling gait was reduced from 17 (23.9 %) to four cases (5.6 %). All changes were statistically highly significant (p<0.01).

CONCLUSIONS

The effect of Tonnis triple pelvic osteotomy lies in the improvement of stress distribution across the acetabular cartilage of the hip joint, thus slowing down the degenerative damage of the hip joint.

Dynamic expression of Runx2, Osterix and AJ18 in the femoral head of steroid-induced osteonecrosis in rats

OBJECTIVE

To study dynamic changes in gene expression and protein synthesis of runt-related transcription factor-2 (Runx2), Osterix and AJ18 in the femoral head of steroid-induced osteonecrosis in rats.

METHODS

Forty mature Wistar rats, 250-270 g (mean, 260 g) in weight, were randomly divided into model (30 rats) and control groups (10 rats). An early rat model of femoral head necrosis (FHN) was created by weekly injections of dexamethasone (20 mg/kg) into alternate sides of the gluteus maximus and twice-weekly training on a laboratory animal treadmill for 8 weeks. Hematoxylin and eosin (HE) staining was used to determine whether osteonecrosis had been successfully induced, and the model was then divided into equal 8, 10 and 12 week groups. At the end of the appropriate time period, total RNA and total protein were extracted from the femoral heads, and then real-time quantitative polymerase chain reaction and Western blot were performed to detect dynamic changes in the expression of Runx2, Osterix and AJ18 and protein synthesis in femoral heads with steroid-induced osteonecrosis in rats.

RESULTS

At the post-modeling eighth, tenth and twelfth week, expression of Runx2 mRNA, Osterix mRNA and related protein synthesis were significantly down-regulated compared to that of the control group, which showed a downward trend with time; while expression of AJ18 mRNA and protein synthesis in the model group was much higher than in the control group, which showed an upward trend with time.

CONCLUSION

Glucocorticoids may induce femoral head osteonecrosis by down-regulating Runx2/Osterix mRNA and up-regulating AJ18 mRNA.

Pathological gait in children with Legg-Calvé-Perthes disease and proposal for gait modification to decrease the hip joint loading

PURPOSE

Legg-Calvé-Perthes disease (LCP) severely limits the range of hip motion and hinders a normal gait. Loading of the hip joint is a major consideration in LCP treatment. The aim of this study was to evaluate gait patterns in LCP and identify gait modifications to decrease the load on the affected hip.

METHODS

Forty children with unilateral LCP were divided into three groups based on the time base integral of the hip abductor moments during single stance on the affected side acquired during instrumented 3D gait analysis. X-rays of the affected hip were classified according to Herring and Catterall.

RESULTS

Children in the "unloading" group spontaneously adopted a Duchenne-like gait with pelvis elevation, hip abduction and external rotation during single support phase. The "normal-loading" group showed pelvis elevation with a neutral hip position in the frontal plane. In the "overloading" group the pelvis dropped to the swinging limb at the beginning of stance accompanied by prolonged hip adduction. The time base integral of the hip abductor moments during single stance correlated positively with the X-ray classifications of Herring and Catterall, hip abduction angle and age. Older children preferred to walk in hip adduction during single stance, had more impaired hips and tended to overload them.

CONCLUSION

The hip overloading pattern should be avoided in children with LCP. Gait training to unload the hip might become an integral component of conservative treatment in children with LCP.

Quality of life following femoral osteotomy and total hip arthroplasty for nontraumatic osteonecrosis of the femoral head

BACKGROUND

Nontraumatic osteonecrosis of the femoral head (NOFH) frequently develops in active young persons. The affected femoral head collapses owing to weight-bearing, and the individual's quality of life (QOL) can be predicted to deteriorate greatly with time. We undertook to determine the efficacy of surgery and to clarify whether patient QOL differs according to differences in the surgical method employed.

METHODS

We cross-sectionally compared QOL in NOFH patients treated with femoral osteotomy, total hip arthroplasty (THA), or nonoperatively. A total of 81 cases were available for study, comprising 41 with osteotomy, 19 with THA, and 21 in the nonoperative group. The mean age was significantly higher in the THA group than in the other two groups. The Japanese Orthopaedic Association (JOA) hip score and Visual Analogue Scale (VAS) regarding hip pain were compared among the groups. These groups were also analyzed for their health-related QOL using the Short Form Health Survey (SF-36) with analysis of variance for age adjustment.

RESULTS

The mean JOA score was significantly lower in the nonoperative group than in the osteotomy group. The mean VAS scores showed no significant difference between any of the three groups. Regarding the subscales of SF-36, the physical functioning subscale in the nonoperative group showed a significantly lower value than was seen in the osteotomy group (P = 0.003). The physical component summary (PCS) scores were 39.4 (osteotomy group), 39.1 (THA group), and 27.8 (nonoperative group), with a significant difference between the osteotomy and nonoperative groups (P = 0.027). There was also a trend for a better PCS scores in the THA group than in the nonoperative group (P = 0.056). The mental component summary scores were 49.6 (osteotomy group), 50.3 (THA group), and 48.3 (nonoperative group), with no significant difference found among any of the three groups.

CONCLUSIONS

Among patients with NOFH, physical function impairment was a more potent factor than pain for decreasing QOL in the nonoperative group than in the surgical groups. Furthermore, osteotomy and THA were similar in regard to the evaluation of the postoperative QOL score if the indications for osteotomy were strictly applied.

Higher peak contact hip stress predetermines the side of hip involved in idiopathic osteoarthritis

BACKGROUND

Biomechanical parameters of the hip have been suggested to have an important influence on the development of osteoarthritis. We aimed to find out whether higher stress is generated in a hip that subsequently results in earlier hip arthroplasty compared to the contralateral hip in the same subject.

METHODS

Standard anterior-posterior pelvic radiographs with no or subtle radiological signs of hip osteoarthritis, of 59 female patients, who underwent hip arthroplasty for primary osteoarthritis years later, were selected from the archives. For each subject peak contact hip stress of the hip with earlier arthroplasty and of the contralateral hip (pair of hips), was calculated from the radiographically obtained geometrical parameters with the HIPSTRESS program, which is based on a three-dimensional biomechanical model of the resultant hip force in the one-legged stance and a three-dimensional mathematical model of the contact hip stress distribution. Differences in peak contact hip stress within pairs of hips were determined for subjects with unilateral (22 pairs of hips) and bilateral disease (37 pairs of hips) by using paired-samples T-test.

FINDINGS

In the population of subjects with unilateral osteoarthritis, average peak contact hip stress was significantly higher (P = 0.007) in hips with arthroplasty (2.44 kPa/N) than in contralateral hips (2.32 kPa/N). In the population of subjects with bilateral osteoarthritis, average peak contact hip stress was significantly higher (P<0.001) in hips with earlier arthroplasty (2.54 kPa/N) than in contralateral hips (2.35 kPa/N).

INTERPRETATION

Results are consistent with the hypothesis that higher peak contact hip stress results in earlier hip arthroplasty due to faster development of idiopathic osteoarthritis.

Repairing defect and preventing collapse of canine femoral head using titanium implant enhanced by autogenous bone graft and rhBMP-2

There is a direct relationship between mechanical stress and the progressive collapse of the necrotic region in osteonecrosis of the femoral head. The titanium implant combined with autogenous bone graft and recombinant human bone morphogenetic protein (rhBMP)-2 to repair the defect and prevent collapse of the femoral head was investigated. The femoral head defects were made by the trapdoor procedure and then the defects were filled, respectively, with the titanium implant combined with autogenous bone graft and rhBMP-2, with autogenous bone graft and rhBMP-2, and with autogenous bone graft alone. Roentgenographic and histological examinations were performed at various times postoperatively. The defects were repaired completely and the titanium implant was integrated with the surrounding bone tissues. The defects healed faster than did without rhBMP-2. No trapdoor cartilage collapsed and joint space narrowed. The titanium implant combined with autogenous bone graft and rhBMP-2 can enhance the repairing procedure and prevent the collapse of the femoral head.