Causes and management of prosthesis dislocation after artificial hip replacement

Objective To explore the causes and management of prosthesis disocation after artificaial hip replacement (AHR).Methods Seventeen patients with prosthesis dislocation after AHR during January 2000 to July 2010 were studied

Hip prosthetic loosening and periprosthetic osteolysis:A commentary

Prosthetic loosening and periprosthetic osteolysis have been debated for decades,both in terms of the timing and nature of the triggering events.The hypothesis of wear-particle-induced loosening states that wear particles cause a foreign-body response leading to periprosthetic osteolysis and ultimately to late prosthetic loosening,i.e.,that the osteolysis precedes the loosening.The theory of early loosening,on the other hand,postulates that the loosening is already initiated during or shortly after surgery,i.e.,that the osteolysis is secondary to the loosening.This commentary focuses on the causal relationship between prosthetic loosening and periprosthetic osteolysis.

Hip prosthetic loosening:A very personal review

Hip prosthetic loosening is often difficult to detect at an early stage,and there has been uncertainty for a long time as to when the loosening occurs and thus to the basic causes.By comparing different diagnostic methods,we found that loosening is best defined as prosthetic migration and measured by radiostereometric analysis.Convincing evidence indicates that poor interlock,poor bone quality,and resorption of a necrotic bone bed may initiate loosening during or shortly after surgery;this forms the basis of the theory of early loosening.Biomechanical factors do affect the subsequent progression of loosening,which may increase subclinically during a long period of time.Eventually,the loosening may be detected on standard radiographs and may be interpreted as late loosening but should to be interpreted as late detection of loosening.The theory of early loosening explains the rapid early migration,the development of periprosthetic osteolysis and granulomas,the causality between wear and loosening,and largely the epidemiology of clinical failure of hip prostheses.Aspects discussed are definition of loosening,the pattern of early migration,the choice of migration threshold,the current understanding of loosening,a less exothermic bone cement,cemented taper-slip stems,a new exciting computed tomography-based technique for simpler implant migration studies,and research suggestions.

Preliminary Report on Phenom^®Femoral Component in Total Hip Replacement: The Correlation between Outcome Scores in a Cross-Seccional Study

Background: The main purpose of the present study was to assess the short term performance of a cementless femoral stem in total hip replacement. Methods: Cross-sectional observational study of a 48-patient cohort with Phenom? femoral stems implanted between June 1, 2014 and September 1, 2018, to determine clinical performance, stability, and radiographic osseointegration. Patients were followed-up from 13 to 76 months (mean: 44.5 months) and assessed using the Harris Hip Score-HHS, the Hip Disability and Osteoarthritis Outcome Score-HOOS and radiographs. Results: All stems were radiologically stable. Mean Harris Hip Score was 89.8 and the HOOS was 80.4. No statistical differences were observed among patients with different diagnoses. Conclusions: The short-term results revealed satisfactory clinical outcomes and radiological signs of implant stability in all cases. Using two functional scores was useful in detecting biases and a low to moderate agreement was found between the scores.

A Novel Engineering Spherical Bearing, with Potential Application for a Hip Implant

It is a research which could enter into contradiction with the current trend concerning the hip implants. It is known as sliding friction, which is characteristic of present artificial hip joints, is higher than in the case of rolling friction. The paper reports the studies of the functioning mode of a novel spherical bearing MoM （metal on metal） with rolling friction, with potential application for an artificial hip joint obtained by introducing a number of balls between the femoral head and the acetabular cup. After over 15 years of research upon the functional principle and constructive solution, a version that offered a coefficient of minimum friction in the hip joint came to light. This version was based on a constructive solution of motion with lower friction, ＂Omnitrack~ movement solutions＂, which has been modified and rebuilt to be used as a joint of a total hip prosthesis--MOMJ. The joint was built entirely in stainless steel, SS316L medical grade. Tests have been carried out on the experimental laboratory devices that showed very low values of the coefficient of friction （μ = 0.0225）. For validation, the prosthesis had to be put through tests for 500,000 cycles, in terms of physiological motion and dynamic loading, according to ISO 14242-3. Testing was conducted on a multiaxial dynamics machine, MTS Bionix, equipped with system for hip implant testing. The testing results of this total hip prosthesis with rolling friction have been successful in signing up for a friction moment of 0.525 kNmm which means a coefficient of friction la = 0.0143, for a joint with femoral head diameter 28 mm.

Friction and Wear Behavior of Ti-6Al-7Nb Biomaterial Alloy

Titanium has been increasingly applied to biomedical application because of its improved mechanical characteristics, corrosion resistance and biocompatibility. However their application remains limited, due to the low strength and poor wear resistance of unalloyed titanium. The purpose of this study is to evaluate the friction and wear behavior of high-strength titanium alloys: Ti-6Al-7Nb used in femoral stem (total hip prosthesis). The oscillating friction and wear tests have been carried out in ambient air with oscillating tribotester in accord with standards ISO 7148, ASTM G99-95a, ASTM G 133-95 under different conditions of normal applied load (3, 6 and 10 N) and sliding speed (1, 15 and 25 mm.s-1), and as a counter pair we used the ball of 100C 6, 10 mm of diameter. The surface morphology of the titanium alloys has been characterized by SEM, EDAX, micro hardness, roughness analysis measurements. The behavior observed for both samples suggests that the wear and friction mechanism during the test is the same for Ti alloys, and to increase resistance to wear and friction of biomedical titanium alloys used in total hip prosthesis (femoral stems) the surface coating and treatment are required.

Angiosarcoma around Hip Joint Prosthesis

Angiosarcoma,a rare and malignant tumor,is known to be associated with prosthesis and trauma.Up to now,only a few cases related to knee prosthesis and fewer cases related to hip prosthesis have been reported.

Observational study of a new modular femoral revision system

BACKGROUND The uncemented ArcosTM Modular Femoral Revision System(ARCOS)is a new comprehensive,press-fit revision design.The modular design offers a wide range of possible combinations to accommodate different variations of anatomy and bone stock.The ARCOS is made by a proximal body and a distal stem.As probably the only ones worldwide we predominantly use a combination of body and stem which supports proximal fixation and load,since this mimics the concept of the primary total hip arthroplasty with proximal weight-bearing,leading to bone stock preservation and no stress shielding or thigh pain.AIM To evaluate the early results after femoral revision in a consecutive series of patients undergoing surgery over 3 years.METHODS We included 116 patients in the study.They were operated in the period August 2011 to December 2014 and we got a clinical mean observation time of 4(0.5-6)years.Clinical and radiographical follow-up included present function of the hip assessed by Harris Hip Score,Oxford Hip Score,and EQ5D(measure of health outcome).Of the 116 patients,17 died in the interim and were consequently included only in the implant survivorship analysis;46 patients attended the follow-up control.RESULTS In total 6(5%)hips were re-revised due to infection(n=3),fracture(n=2)or subsidence(n=1).No patient was re-revised due to aseptic loosening.The 1-,2-and 5-year probability of implant survival(95%CI)were 97%(93%-100%),97%(93%-100%)and 96%(92%-99%),respectively.In this cohort 95 patients received a combination of a proximal broach and a distal curved and slotted stem(BS),aiming for proximal fixation and load bearing;21 patients received a different combination.When comparing these two groups the BS-group had a 5-year implant survival probability(95%CI)of 97%(93%-100%)compared with the group of other combinations with a 5-year implant survival probability(95%CI)of 90%(78%-100%)(P=0.3).Our regression analysis showed that periprosthetic fracture as an indication for the ARCOS operation was the only significant negative outcome predictor.The mean Harris Hip Score result(100 points being best)was 83(range 5-98).The mean Oxford Hip Score result(48 points being best)was 40(range 19-48).CONCLUSION The early results of the ARCOS are promising compared with similar studies.We encourage the use of the BS combination whenever the bone stock proximally is adequate.

Total hip arthroplasty with cementless cups and femoral head autografts for patients with hip dysplasia and osteoarthritis

Objective: To evaluate the outcome of total hip arthroplasty (THA) with cementless cups and femoral head autografts for patients with hip dysplasia and osteoarthritis. Methods: Between 1995 and 2002, we implanted 23 cementless cups and femoral head autografts in 20 patients with hip dysplasia and osteoarthritis. In this study, a retrospective study was made on 21 hips in 20 patients (18 females and 2 males, aged 50 years on an average) with developmental hip dysplasia treated by THA with a cementless cup and femoral head autograft. The acetabular cup was placed at the level of the true acetabulum and all the patients required autogenous femoral head grafts due to acetabular deficiency. The average rate of the acetabular cup covered by the femoral head autograft was 31% (ranging from 10% to 45%). Eight hips had less than 25% cup coverage and thirteen between 25% and 50%. The average follow-up period was (4.7) years (range, 1-8 years). The replacing outcome was evaluated by modified Harris hip score. Preoperative and follow-up radiographs were made. Results: All the autografts were united to the host bones. No autograft was collapsed or no component from the hip was loosed in all the patients. According to the modified Harris hip score, the average hip score increased from 46 before operation to 89 at the final review. Before operation, the leg-length discrepancy was greater than 2 cm in all the patients except one with bilateral hip dysplasia. After operation, only 2 out of 20 patients had a leg-length discrepancy greater than 1 cm. Three hips showed minor bone resorption in the lateral portion of the graft, which did not support the cup. Three hips developed Grade 1 Brooker heterotopic ossification and one developed Grade 2. Conclusions: THA with a cementless cup and a femoral head autograft for patients with osteoarthritis resulted from hip dysplasia can result in favorable outcomes. This method can provide reliable acetabular fixation and restore the acetabular bone stock in patients with developmental hip dysplasia when the cementless cup covered by the graft does not exceed 50%.

Horizontal platform supported total hip replacement

Objective To investigate the effect of horizontal platform supported (HPS) prosthesis on cementless total hip replacement for surgical treatment of arthritis in a long-term follow-up study.Methods Clinical and radiographic follow-up of 65 consecutive primary cementless porous coated HPS total hip replacements, which were implanted in 60 patients between 1982 and 1989, was carried out.Results The 53 hips in 50 patients were evaluated both clinically and radiographically. The average follow-up was 6.8 years (range: 5 to 12 years). According to the Harris hip score, 52 (98%) of the hips had sustained an excellent or good result with an average score of 92. At the time of final assessment, no patient experienced anterior thigh pain. There were two revisions performed early in the series due to technical failures. Radiographically, osteolysis and bone re-modelling were assessed. Conclusion The findings suggest that the clinical and radiographic results after cementless total hip replacement for primary hip arthroplasty may be favourably influenced by the use of the proximal stress loaded HPS femoral component.

Analysis of prosthetic replacement in treatment of femoral neck fracture on the hemiplegia side in the elderly

Objective: To study the effect of prosthetic replacement in treatment of femoral neck fractures on the hemiplegia side in the elderly. Methods: From May 1990 to May 2000, 189 elderly patients with femoral neck fractures were treated with prosthetic replacement in my hospital. Twenty-nine hemiplegia patients, who suffered from stroke previously, had Garden type III and type IV femoral neck fractures on the hemiplegia side. Thirty non-hemiplegia patients were chosen randomly. The two groups were followed-up for 27-98 months (average: 59 months). The age, hospitalization days, operating time, blood loss, blood transfusion, complications during perioperative period and long-term complications were compared between the two groups and the results of femoral head replacement and total hip replacement in the hemiplegia group were also compared. Results: All the patients of the two groups survived the perioperative period. No significant difference was found in the age, hospitalization days, operation time, blood loss and blood transfusion and long-term complications between the two groups (P> 0.05). However there was significant difference in complications during perioperative period between the two groups (P< 0.05). Five patients died in the hemiplegia group with the mortality of 17.2% and two died in the non-hemiplegia group with the mortality of 6.7% 11 months to 5 years after operation. There was significant difference in long-term complications between the femoral head replacement and the total hip replacement in the hemiplegia group (P< 0.05). The result of the total hip replacement was better than that of the femoral head replacement. Conclusions: Prosthetic replacement is a reliable method in treatment of Garden type III and type IV femoral neck fractures on the hemiplegia side in the elderly, and patients are safe during perioperative period. More complications during perioperative period occur in the hemiplegia group, and long-term complications are insignificantly different between the two groups. The mortality rate is higher in the hemiplegia group than in the non-hemiplegia group within 5 years after operation. Since the result of the total hip replacement is better than that of the femoral head replacement, total hip replacement should be chosen firstly to treat Garden type III and type IV femoral neck fractures on the hemiplegia side in the elderly if the muscular strength of the hip is beyond IV degree.

Center of Gravity Estimation Using a Reaction Board Instrumented With Fiber Bragg Gratings

The purpose of the present work is to construct a reaction board based on fiber Bragg gratings （FBGs） that could be used for estimation of the 2D coordinates of the projection of center of gravity （CG） of an object. The apparatus is consisted of a rigid equilateral triangular board mounted on three supports at the vertices, two of which have cantilevers instrumented with FBGs. When an object of known weight is placed on the board, the bending strain of the cantilevers is measured by a proportional wavelength shift of the FBGs. Applying the equilibrium conditions of a rigid body and proper calibration procedures, the wavelength shift is used to estimate the vertical reaction forces and moments of force at the supports and the coordinates of the object＇s CG projection on the board. This method can be used on a regular basis to estimate the CG of the human body or objects with complex geometry and density distribution. An example is provided for the estimation of the CG projection coordinates of two orthopaedic femur bone models, one intact, and the other with a hip stem implant encased. The clinical implications of changing the normal CG location by means of a prosthesis have been discussed.

Femoral component revision using extensively porous-coated cementless stem

To evaluate the clinical and radiographic results of extensively porous-coated femoral stem in revision of total hip arthroplasty （THA）. Methods： From January 1999 to December 2003, fifteen hips of fifteen cases received revision of THA with extensively porous-coated femoral stem. There were six males and nine females. The average age was 66 years （ranging 58-82 years ）. The reason for the revision was aseptic loosening in 10 cases, septic loosening in 2, femoral shaft fracture around loose implant in 2, and femoral revision for malposition of the femoral component in 1. All the patients were clinically evaluated using Harris hip score and radiographically evaluated both preoperatively and postoperatively at regular follow-up intervals. Results： No patients were lost for follow-up. The average length of follow-up was 2.3 years （ range, 1-5 years）. The average preoperative Harris hip score was 42 points, which was improved to 89 points at latest follow-up. The latest follow-up showed that bone in-growth occurred in fourteen stems and solid fibrous fixation in one. Complications consisted of femoral shaft fracture in two cases （1 undisplaced distal femur fracture and 1 cortical perforation at the tip of the prosthesis）, and postoperative dislocation in one. There was no mechanical failure of the stem in this study. Conclusions ： Satisfactory results of short-term clinical and radiographic follow-up have been achieved in using extensively porous-coated femoral stem for revision of THA. It should be noticed that the straight, 203 mm stem should be used with caution in short people.