Investigation of contact behavior on a model of the dual-mobility artificial hip joint for Asians in different inner liner thicknesses

BACKGROUND The four components that make up the current dual-mobility artificial hip joint design are the femoral head,the inner liner,the outer liner as a metal cover to prevent wear,and the acetabular cup.The acetabular cup and the outer liner were constructed of 316L stainless steel.At the same time,the inner liner was made of ultra-high-molecular-weight polyethylene(UHMWPE).As this new dual-mobility artificial hip joint has not been researched extensively,more tribological research is needed to predict wear.The thickness of the inner liner is a significant component to consider when calculating the contact pressure.AIM To make use of finite element analysis to gain a better understanding of the contact behavior in various inner liner thicknesses on a new model of a dual-mobility artificial hip joint,with the ultimate objective of determining the inner liner thickness that was most suitable for this particular type of dual-mobility artificial hip joint.METHODS In this study,the size of the femoral head was compared between two diameters(28 mm and 36 mm)and eight inner liner thicknesses ranging from 5 mm to 12 mm.Using the finite element method,the contact parameters,including the maximum contact pressure and contact area,have been evaluated in light of the Hertzian contact theory.The simulation was performed statically with dissipated energy and asymmetric behavior.The types of interaction were surface-to-surface contact and normal contact behavior.RESULTS The maximum contact pressures in the inner liner(UHMWPE)at a head diameter of 28 mm and 36 mm are between 3.7-13.5 MPa and 2.7-10.4 MPa,respectively.The maximum von Mises of the inner liner,outer liner,and acetabular cup are 2.4–11.4 MPa,15.7–44.3 MPa,and 3.7–12.6 MPa,respectively,for 28 mm head.Then the maximum von Mises stresses of the 36 mm head are 1.9-8.9 MPa for the inner liner,9.9-32.8 MPa for the outer liner,and 2.6-9.9 MPa for the acetabular cup.A head with a diameter of 28 mm should have an inner liner with a thickness of 12 mm.Whereas the head diameter was 36 mm,an inner liner thickness of 8 mm was suitable.CONCLUSION The contact pressures and von Mises stresses generated during this research can potentially be exploited in estimating the wear of dual-mobility artificial hip joints in general.Contact pressure and von Mises stress reduce with an increasing head diameter and inner liner’s thickness.Present findings would become one of the references for orthopedic surgery for choosing suitable bearing geometric parameter of hip implant.

Traumatic isolated bilateral gluteus minimus injuries misdiagnosed as lumbar radiculopathy:A case report

BACKGROUND The tear of the gluteus medius and minimus tendons can cause chronic buttock pain,especially in middle-aged individuals;these tears occur mostly in association with degenerative changes in the muscles and tendons.Chronic injuries are more common than acute injuries,and concurrent injuries to the gluteus medius and minimus tendons without chronic pain are rare,especially isolated injuries to both sides of the gluteus minimus;such a case has not yet been reported.CASE SUMMARY The authors present a case of bilateral acute traumatic injuries to the gluteus minimus during buttock strengthening exercises in a 75-year-old male patient.The patient completely returned to his pre-injury lifestyle after 8 weeks of injury,with no limitations,but the diagnosis was initially delayed due to misdiagnosis as lumbar radiculopathy,resulting in unnecessary socio-economic burden on the patient.CONCLUSION When treating patients who complain of hip pain,it is important to consider various causes to make a correct diagnosis.

Characterisation of wear particles from biomedical carbon/carbon composites with different preforms in hip joint simulator

A hip joint simulator was employed to predict the clinical wear behaviour of carbon/carbon （C/C） composites with needled carbon cloth preform and carbon felt preform. Wear particles generated from the two kinds of C/C composites were isolated and characterised by the size distribution and morphology. The evolvement of wear particles in the hip joint simulator was proposed. The results show that the wear particles from two kinds of C/C composites have a size ranging from submicron to tens of micrometers. The wear particles have various morphologies including broken fiber, fragment fiber, slice pyrolytic carbon and spherical pyrolytic carbon. C/C composites with needled carbon cloth preforms have larger size range and more broken fiber particles and slice pyrolytic carbon particles in comparison with C/C composites with carbon felt preforms. The evolvement of pyrolytic carbon particles is caused by surface regularization, whereas, the evolvement of carbon fiber particles is related to stress direction in the hip joint simulator.

A Biomimetic Hip Joint Simulator and its Application in in vitro Study of the Integrity of Replacement Cemented Hip

A biomimetic hip joint simulator that can be used to evaluate the outcome of the cemented total hip replacement has been designed, manufactured and evaluated. The simulator produces motion in the extension/flexion plane, with a socket to rotate internal/externally. At the same time a dynamic loading cycle is applied. A validation test was performed on a cemented femoral stem within a novel composite femur. The hone quality has a strong effect on the stem migration and on the integrity of the interfaces. The migration of the stem is a combination of 3-D translation and rotation of the stem. Under the same loading conditions, weak bone allows more stem migration than strong bone. There is a great decrease in the strength of the stem-cement interface after the dynamic test, and the weak bone composite exhibited a greater reduction in interfacial strength than the strong bone composite. The decrease of the interfacial strength indicates that the primary bonding between the stem and the cement mantle had deteriorated and the integrity of stem-cement interface was damaged. The study demonstrates the value of using a hip joint simulator to investigate stem migration and interface integrity within the cemented hip replacement, suggesting that method can be used for in vitro evaluation of the biomaterials used in the cemented hip replacements.

One-stage total hip arthroplasty for advanced hip tuberculosis combined with developmental dysplasia of the hip:A case report

BACKGROUND A patient with advanced tuberculosis of the hip joint combined with Crowe type IV developmental dysplasia of the hip(DDH)and a drainage sinus is a rare condition.There are no previous reports of this condition,and it is a complex challenge for surgeons to develop a treatment scheme.CASE SUMMARY We report a 73-year-old male patient with severe hip pain and drainage sinus of the left hip for one month.Approximately 40 years ago,a drainage sinus occurred at the lateral left hip was healed at the local hospital with anti-infectious therapy.After the sinus healed,gradual pain occurred in the left hip for 40 years.Approximately one month prior,hip pain was sharply aggravated,and a drainage sinus reoccurred in the left hip.The X-ray and computed tomography examinations showed destruction of the head and neck of the left femur,as well as an acetabular deformity.The results of Mycobacterium tuberculosis antibody and Xpert were positive.Therefore,the patient was diagnosed with advanced TH combined with Crowe type IV DDH.After 22 d of treatment with anti-tuberculosis chemotherapy,the sinus healed,and the patient underwent one-stage total hip arthroplasty(THA)surgery consisting of debridement,osteotomy,and joint replacement.After surgery,the patient received anti-tuberculosis chemotherapy drugs for nine months,with no recurrent infection.After one year of follow-up,the Harris score of the patient increased from 21 pre-THA to 86.CONCLUSION Although drainage sinuses are a contraindication to one-stage THA,one-stage THA is still an effective and safe surgical method after the sinus heals.

Chromium Content in the Human Hip Joint Tissues

Objective Chromium has many important functions in the human body. For the osseous tissue, its role has not been clearly defined. This study was aimed at determining chromium content in hip joint tissues. Methods A total of 91 hip joint samples were taken in this study, including 66 from females and 25 from males. The sample tissues were separated according to their anatomical parts. The chromium content was determined by the AAS method. The statistical analysis was performed with U Mann-Whitney＇s non-parametric test, P〈0.05. Results The overall chromium content in tissues of the hip joint in the study subjects was as follows： 5.73 μg/g in the articular cartilage, 5.33 μ/g in the cortical bone, 27.86 μ/g in the cancellous bone, 5.95 μg/8 in the fragment of the cancellous bone from the intertrochanteric region, and 2.28 μ/g in the joint capsule. The chromium contents were observed in 2 group patients, it was 7.04 μ/g in people with osteoarthritis and 22.59 μ/g in people with fractures. Conclusion The observed chromium content was highest in the cancellous bone and the lowest in the joint capsule. Chromium content was significantly different between the people with hip joint osteoarthritis and the people with femoral neck fractures.

Jumbo cup in hip joint renovation may cause the center of rotation to increase

BACKGROUND Utilizing the large jumbo cup in revision total hip arthroplasty is an effective approach to cure many lacunar and segmental peripheral bone defects.However,with the use of the jumbo cup,the center of the hip joint may become elevated relative to the primary acetabulum,and the diameter of the large cup is greater.AIM To study the height and the significance of the elevation of the hip joint center.METHODS Eighty-eight patients matched the criteria for this condition and were included in the study.The center height of the hip joint was measured relative to the opposite normal hip joint.The diameter of the jumbo cup was measured and checked according to operation notes,and the diameter of the jumbo cup was measured with a prosthesis label.Then,the horizontal and vertical centers of rotation were measured on the surgical side and opposite side.The average center height of the hip joint on the renovated side and the opposite side and the position of the hip cup relative to the teardrop were compared using a paired t-test.RESULTS Radiometric analysis showed that the average hip joint center was elevated by 7.6 mm.The rotational center height delta of the renovated hip was 7.6±5.6 mm,and there was an obvious difference between the two groups(P=0.00).The difference in horizontal distance was 0.5±5.1 mm(-11.5-14.0 mm),and there was no obvious difference between the two groups(P=0.38).According to the foreign standard,the rotational center height delta of the renovated hip was 7.5±6.2 mm,and there was a significant difference between the two groups(P=0.00).There was no obvious difference between the domestic and foreign standards(P>0.05)between the two groups.CONCLUSION The application of the jumbo cup elevates the rotational center of the hip joint,but it is feasible and effective to use the jumbo cup.

ANALYSIS AND RESEARCH OF COMPUTER-AIDED MODEL OF HIP JOINT BASED ON REVERSE ENGINEERING

Former research work about the modeling of hip joint focus on the uppersegment of femoral, and assumes the acetabulum cup is sphere concave, and the acetabulum prosthesesis semisphere. A method of acquiring the point data on the surface of the hipbone using the reverseengineering technology is presented. After analyzing the acetabulum surface fitting error, arotation ellipsoid CAD model is applied to fit the acetabulum surface, and then optimizationtechnique is used to find the geometric parameters of the model. The fitting error between thesphere and rotation ellipsoid is compared and gets the result that the fitting error of rotationellipsoid is smaller than sphere, and the rotation ellipsoid can describe the shape of theacetabulum better.

The Developmentand Clinical Application of Acoustical Technique in Hip Joint

A non- invasive acoustical system was developed for the measurement of transmission properties of acoustic waves in the hip joints.The instrumentation consisted of three sub- system s. An excitation system employed a vibratory force at the sacrum of the test subjects.A transduction system included a pair of identical microphones installed in the tubes of two stethoscopes,which were placed at the greater trochanters on both sides for picking up the acoustical signals transm it- ted across the hip joints.The data acquisition and analysis system was a portable signal analyzer with a program of dual channel digital filter for m easuring the power of acoustical signal in 1/ 3- oc- tave frequency bands.2 7normal adults,2 0 normal pre- school children and 4 0 norm al neonates were random ly selected for testing.Coherence function (CF) and discrepancy(D) was measured during the testing.Results from the three groups showed that there was a high coherence of the signals (CF>0 .9) and a sm all discrepancy(D<3d B) between bilateral hips in the frequency range of2 0 0— 315 Hz.For normal neonates,there was a wider frequency range of16 0 - 315 Hz in which the acoustical signals m aintained a high coherence (CF>0 .93) and a smaller discrepancy (D <2 d B) was observed.This study showed that the development of the acoustical technique pro- vided a practical m ethod with objective parameters.The results obtained in this study can offer a baseline for further investigation of hip disorders particularly those related to structural abnorm ali- ties of the hip.

Stress Analysis and Shape Design of a Femoral Hip Prosthesis

Objective： To study the stress distribution of the femoral hip prosthesis after the hip joint replacement. Methods： After the hip joint replacement, when the fenmr and prosthesis are considered as concentric cylinders with perfectly banded interface, a relatively perfect theoretical model of simulating the interracial stress transfer is established. Results： The maximum interfaeial shear stress oeeured at Z=O. At the cross-section of the femoral neck, interfacial shear stress decreased exponentially with the increases of the Z. Shear stress became very small at Z〉0. 1 m, which meant that the shear stress at the far end of the femoral hip prosthesis was very small. In order to avoid the stress concentration and femoral hip prosthesis sinking, interracial stress must remain constant and balanced with the pressure load at Z=O. The radius of the femoral hip prosthesis changed with interfacial shear stress. The maximum value of the radius occured at Z=O, then it decreased at m. Specially, a=18.2 mm at Z=10 ram, a=5.36 mm at Z=98 ram, these are ideal radius. Conclusion： A theoretical model of simulating the interfacial stress is established when the femur and prosthesis are considered as concentric cylinders. The distributions of the interfacial shear and radial stresses with the axial positions are obtained. A theoretical reference for the design of the prosthesis is provided.

3D Finite Element Analysis of a Man Hip Joint Femur under Impact Loads

Objective： The biomechanical characters of the bone fracture of the man femoral hip joint under impact loads are explored. Methods ：A biosystem model of the man femoral hip joint by using the GE （ General Electric） lightspeed multi-lay spiral CT is conducted. A 3D finite element model is established by employing the finite element software ANSYS. The FE analysis mainly concentrates on the effects of the impact directions arising from intense movements and the parenchyma on the femoral hip joint on the stress distributions of the proximal femur. Results：The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. Conclusion：Effects of the angle δ of the impact load to the anterior direction and the angle γ of the impact load to the femur shaft on the bone fracture are given;δ has larger effect on the stress and strain distributions than the angle γ,which mainly represents the fracture of the upper femur including the femoral neck fracture when the posterolateral femur is impacted, consistent with the clinical resuits.

Effects of alendronate sodium combined with InterTan on osteoporotic femoral intertrochanteric fractures and fracture recurrence

BACKGROUND Osteoporosis is a global disease affecting 6.6%of the total population.Osteoporosis complications include fractures,increased bone fragility,and reduced bone strength.The most commonly affected parts are the vertebral body,hip,and wrist.AIM To examine the effect of alendronate sodium combined with InterTan for osteoporotic femoral intertrochanteric fractures on bone and fracture recurrence METHODS In total,126 cases of osteoporotic femoral intertrochanteric fractures were selected and divided into two groups according to the 1:1 principle by the simple random method.They were admitted to the Department of Orthopedics,First Affiliated Hospital of Xingtai Medical College,from January 2018 to September 2020.The control group was treated with InterTan fixation combined with placebo,and the observation group with alendronate sodium based on InterTan fixation.Operation-related indicators,complications,and recurrent fractures were compared between the groups.Changes in bone metabolism markers,t value for hip bone mineral density,and Harris Hip Score were observed.RESULTS Operation time,intraoperative blood loss,postoperative ambulation time,and complications were compared between the groups,and no significant difference was found.The fracture healing time was significantly shorter in the observation group than in the control group.β-Collagen-specific sequence(β-CTX)and total aminoterminal propeptide of type I procollagen(T-PINP)in the control group at 3 mo after operation were compared with those before operation,and the difference was not significant.Six months after the operation,theβ-CTX level decreased and T-PINP level increased.β-CTX level at 3 and 6 mo in the observation group after operation was lower,and TPINP level was higher,than that before operation.Compared with the control group,T-PINP level of the observation group was significantly higher andβ-CTX level was significantly lower at 3 and 6 mo after operation.The t value of hip bone mineral density was compared in the control group before and 1 mo after operation,and significant difference was not found.Compared with the control group,the t value of hip bone mineral density in the observation group was significantly higher at 1,3,6,and 12 mo after operation.Compared with the control group,the Harris score of the observation group was significantly higher at 1,3,6,and 12 mo after operation.The recurrence rate of fractures in the observation group within 12 mo was 0.00%,which was significantly lower than 6.35%in the control group.CONCLUSION Alendronate sodium combined with InterTan in the treatment of osteoporotic femoral intertrochanteric fractures can increase bone mineral density,improve hip joint function,promote fracture healing,and reduce fracture recurrence.

Intraneural ganglion cyst of the lumbosacral plexus mimicking L5 radiculopathy:A case report

BACKGROUND Intraneural ganglion cysts are benign gelatinous masses that form within the epineurium of a peripheral nerve.Only few cases of intraneural ganglion cyst arising from the hip joint have been reported.CASE SUMMARY A previously healthy 65-year-old woman who had been experiencing left buttock pain radiating to the dorsum of the foot for 2 years visited our clinic.Prior to visiting the clinic,she underwent lumbar spine magnetic resonance imaging and received physiotherapy,pain killers,and epidural injections based on a presumptive diagnosis of spinal stenosis for 2 years in other hospitals.Repeat magnetic resonance imaging revealed joint connection of the articular branch of the hip joint and rostral extension of the cyst along the L5 spinal nerve near the L5-S1 neural foramen.The patient was diagnosed with intraneural ganglion cyst arising from the articular branch of the hip joint based on high-resolution magnetic resonance neurography.Using the arthroscopic approach,a cystic opening within the intra-articular space was detected,and cyst decompression was then performed.The pain in the left leg was significantly relieved during the 6-mo follow-up.CONCLUSION Although intraneural ganglion cysts arising from the hip joint are rare,they can cause typical radicular pain and mimic common L5 radiculopathy.Typical cyst ascent phenomenon starting from the termination of the articular branch on magnetic resonance imaging is a crucial finding indicative of intraneural ganglion cysts arising from the hip joint.

Simultaneous laparoscopic and arthroscopic excision of a huge juxta-articular ganglionic cyst compressing the sciatic nerve:A case report

BACKGROUND A large ganglionic cyst extending from the hip joint to the intrapelvic cavity through the sciatic notch is a rare space-occupying lesion associated with compressive lower-extremity neuropathy.A cyst in the pelvic cavity compressing the intrapelvic-sciatic nerve is easily missed in the diagnostic process because it usually presents as atypical symptoms of an extraperitoneal-intrapelvic tumor.We present a case of a huge ganglionic cyst that was successfully excised laparoscopically and endoscopically by a gynecologist and an orthopedic surgeon.CASE SUMMARY A 52-year-old woman visited our hospital complaining of pain and numbness in her left buttock while sitting.The pain began 3 years ago and worsened,while the numbness in the left lower extremity lasted 1 mo.She was diagnosed and unsuccessfully treated at several tertiary referral centers many years ago.Magnetic resonance imaging revealed a suspected paralabral cyst(5 cm×5 cm×4.6 cm)in the left hip joint,extending to the pelvic cavity through the greater sciatic notch.The CA-125 and CA19-9 tumor marker levels were within normal limits.However,the cyst was compressing the sciatic nerve.Accordingly,endoscopic and laparoscopic neural decompression and mass excision were performed simultaneously.A laparoscopic examination revealed a tennis-ball-sized cyst filled with gelatinous liquid,stretching deep into the hip joint.An excisional biopsy performed in the pelvic cavity and deep gluteal space confirmed the accumulation of ganglionic cysts from the hip joint into the extrapelvic intraperitoneal cavity.CONCLUSION Intra-or extra-sciatic nerve-compressing lesion should be considered in cases of sitting pain radiating down the ipsilateral lower extremity.This large juxta-articular ganglionic cyst was successfully treated simultaneously using laparoscopy and arthroscopy.

Evaluation of joint awareness after acetabular fracture:Validation of the Forgotten Joint Score according to the COSMIN checklist protocol

BACKGROUND A fracture of the acetabulum is an uncommon,but serious injury.Established outcome tools do not reflect the patient’s perspective after fracture of the hip joint.Originally designed for post-arthroplasty patients,the Forgotten Joint Score(FJS)is a patient-reported outcome measurement(PROM)tool evaluating the diseasespecific health-related quality of life(HR-QoL).AIM To validate the FJS in patients after acetabular fracture.METHODS In a prospective mono-centric cohort study,we evaluated 100 patients at mean 5.2±3.6 years after a fracture of the acetabulum.The validation study followed the complete COSMIN checklist protocol.For calculation of convergent validity,we used the Tegner-Activity Scale,the Western Ontario and McMaster Universities Osteoarthritis Index,the EuroQol-5D,and a subjective rating of change as an anchor variable.RESULTS We confirmed good internal consistency with a Cronbach‘s alpha of 0.95.With an intraclass correlation coefficient of 0.99(95%CI:0.97,0.99),test-retest reliability of the FJS was excellent.Correlation coefficients between the questionnaires were moderate to high ranging from|0.56|to|0.83|(absolute value).No relevant floor or ceiling effects occurred.Standard error of measurement was 3.2 and smallest detectable change(SDC)was 8.8.Thus,changes greater than 8.8 points between two assessments denote a real change in FJS.CONCLUSION The FJS is a valid and reliable tool for evaluation of patient-reported outcome in posttraumatic condition after acetabular fracture.The SDC indicating a real clinical improvement was 8.8 points in the FJS.We could confirm responsiveness of the FJS and found no relevant floor-or ceiling effects.

Evaluation of P-POSSUM scoring system in predicting mortality in patients with hip joint arthroplasty

Objective. To evaluate the applicability of Porthsmouth modified physiological and operative severity score for the enumeration of mortality and morbidity （ P- POSSUM） in predicting the mortality of the patients undergoing hip joint arthroplasty. Methods： A total of 141 patients （75 males and 66 females, aged 63.22 years ± 14.45 years on an average ） undergoing hip joint arthroplasty during January 2002 and March 2005 were studied retrospectively with P-POSSUM. Their average physiological score and operative severity score were 17.48 ±5.16 and 12.43 ±3.05, respectively. The predicted postoperative mortality with P-POSSUM was compared with the observed value. Subgroup analysis was performed to investigate the predictive capability of P- POSSUM. POSSUM scoring system was used as the control. Results： Three patients died after operation in this study actually. The average physiological scores were 32.33±9.87 in the death group and 17.16±4.56 in the survival group. The former was obviously higher than the latter, which showed statistical difference between the two groups （Wilcoxon rank sum test, P〈0.05）. Perfect agreement was found between the observed death number and the predicted death number calculated by P-POSSUM （ Cochran-ManteI-Haenszel %2 test, P 〉 0.05）, though POSSUM overestimated the overall mortality. Conclusions ： P-POSSUM can predict the mortality accurately in the patients undergoing hip joint arthroplasty, which is superior to POSSUM.

Total hip arthroplasty for patients with osteoarthritis secondary to hip pyogenic infection

Background Pyogenic hip arthritis occurs most often in young patients. Delayed treatment causes significant anatomical deformation of bony and soft tissue structures leading to premature onset of secondary osteoarthritis. Total hip arthroplasty （THA） in patients who had osteoarthritis secondary to hip pyogenic infection has been associated with high complication rates. Methods We analyzed 19 THAs performed from April 2003 to July 2008 in adults with osteoarthritis secondary to hip pyogenic infection （average age 40.7 years; range 34-52 years）. There were 7 males and 12 females, the average age of infection was 10.6 years （range 7-13 years） and the average quiescent period of infection was 29.5 years （range 22-41 years）. The count of white blood cell （WBC）, erythrocyte sedimentation rate （ESR） and C-reactive protein （CRP） were examined routinely before surgery. The duration of followup was 34 months （range 6-52 months）. Results There was no evidence of infection according to laboratory values, intraoperative exploration and bacterial culture of joint fluids and synovial tissues. Split fracture above the lesser trochanter occurred in two hips and healed without adverse sequelae after fixation with wires. One patient with sciatic nerve palsy was successfully treated by positioning the hip in extension and the knee in flexion with complete resolution of motor symptoms one month later. There were no cases of dislocation, deep vein thrombosis, or postoperative reinfection. The symptoms and hip joint activities were significantly improved. The median Harris hip score improved from 47.3 preoperatively to 89.7 and the median range of motion from 53% to 125%. Conclusions It is safe and efficient to perform THA in patients who had osteoarthritis secondary to pyogenic hip arthritis when the infection is quiescent. The key points of successful surgery are exclusion of active infection preoperatively, quiescent period of infection more than ten years and adequate intraoperative soft tissue releases.

Human hip joint center analysis for biomechanical design of a hip joint exoskeleton

We propose a new method for the customized design of hip exoskeletons based on the optimization of the humanmachine physical interface to improve user comfort. The approach is based on mechanisms designed to follow the natural trajectories of the human hip as the flexion angle varies during motion. The motions of the hip joint center with variation of the flexion angle were measured and the resulting trajectory was modeled. An exoskeleton mechanism capable to follow the hip center＇s movement was designed to cover the full motion ranges of flexion and abduction angles, and was adopted in a lower extremity assistive exoskeleton. The resulting design can reduce human-machine interaction forces by 24.1% and 76.0% during hip flexion and abduction, respectively, leading to a more ergonomic and comfortable-to-wear exoskeleton system. The humanexoskeleton model was analyzed to further validate the decrease of the hip joint internal force during hip joint flexion or abduction by applying the resulting design.

Running-in friction of hip joint replacements can be significantly reduced:The effect of surface-textured acetabular cup

Hip joint replacements represent the most effective way of treatment for patients suffering from joint diseases.Despite the rapid improvement of implant materials over the last few decades,limited longevity associated with wear-related complications persists as the main drawback.Therefore,improved tribological perfor-mance is required in order to extend the service life of replacements.The effect of surface texturing of ultra-high molecular weight polyethylene(UHMWPE)acetabular cup was investigated in the present study.Unique tilling method was utilized for manufacturing the dimples with controlled diameter and depths on the contact surface of the cup.The experiments with four commercial femoral components and two model lubricants were realized.The main attention was paid to a coefficient of friction considering the differences between the original and the dimpled cups.Results showed remarkable lowering of friction,in general.Focusing on the simulated human synovial fluid,friction was reduced by 40%(alumina ceramic),38.8%(zirconia toughened ceramic),25.5%(metal),and 9.9%(oxinium).In addition,the dimples helped to keep the friction stable without fluctuations.To conclude,the paper brings a new insight into frictional behaviour of the hip replacements during running-in phase which is essential for overall implant lifespan.It is believed that proper surface texturing may rapidly improve the life quality of millions of patients and may lead to considerable financial savings.

Radiological Assessment of the Sacrofemoral Angle： A Novel Method to Measure the Range of Hip Joint Flexion

Background： A quantitative and accurate measurement of the range of hip joint flexion （RHF） is necessarily required in the evaluation of disordered or artificial hip joint function. This study aimed to assess a novel method to measure RHF more accurately and objectively. Methods： Lateral radiographs were taken of 31 supine men with hip joints extended or flexed. Relevant angles were measured directly from the radiographs. The change in the sacrofemoral angle （SFA） （the angle formed between the axis of the femur and the line tangent to the upper endplate of S1） from hip joint extension to hip joint flexion, was proposed as the RHF. The validity of this method was assessed via concomitant measurements of changes in the femur-horizontal angle （between the axis of the femur and the horizontal line） and the sacrum-horizontal angle （SHA） （between the line tangent to the upper endplate of S 1 and the horizontal line）, the difference of which should equal the change in the SFA. Results： The mean change in the SFA was 112.5 ± 7.4°, and was independent of participant age, height, weight, or body mass index. The mean changes in the femur-horizontal and SHAs were 123.0±6.4° and 11.4 ± 3.0°, respectively. This confirmed that the change of SFA between hip joint extension and hip joint flexion was equal to the difference between the changes in the femur-horizontal and SHAs. Conclusions： Using the SFA, to evaluate RHF could prevent compromised measurements due to the movements of pelvis and lumbar spine during hip flexion, and is, therefore, a more accurate and objective method with reasonable reliability and validity.