Successful hip revision surgery following refracture of a modern femoral stem using a cortical window osteotomy technique:A case report and review of literature

BACKGROUND The ExeterTM Universal cemented femoral component is widely used for total hip replacement surgery.Although there have been few reports of femoral component fracture,removal of a broken femoral stem can be a challenging procedure.CASE SUMMARY A 54-year-old man with a Dorr A femur sustained a refracture of a primary ExeterTM stem,two years after receiving a revision using a cement-within-cement technique(CWC)through an extended trochanteric osteotomy(ETO).The technical problems related to the CWC technique and the ETO played a major role in the stem fatigue refracture.We performed revision surgery and removed the distal cement using a cortical femoral window technique,followed by reimplantation with an uncemented,modular,distally-fixed uncemented stem.The patient experienced an uneventful postoperative recovery.CONCLUSION Re-fracture of a modern femoral ExeterTM stem is a rare event,but technical complications related to revision surgery can lead to this outcome.The cortical window osteotomy technique can facilitate the removal of a broken stem and cement,allowing for prosthetic reimplantation under direct vision and avoiding ETO-related complications.

Mid-term survival of the Optimys short stem: A prospective case series of 500 patients

BACKGROUND In recent years,there has been an increase in the number of total hip arthroplasty procedures in the younger patient population.This active group has higher expectations of their prosthesis in comparison to the older population,and there is a greater physical demand for the prosthesis.Short femoral stems were in-troduced to retain proximal bone stock and joint biomechanics and became more common to implant in this specific population.Currently,the long-term survival and functional outcomes of various short stems are still being investigated in different clinics.AIM To determine the 5-year survival of the Optimys hip stem.METHODS This was a prospective multicenter cohort study of 500 patients conducted in two hospitals in the Netherlands.All patients received the Optimys short stem(Mathys Ltd,Bettlach,Switzerland).The primary outcome measure was survival of the hip stem,with revision as the endpoint.The secondary outcome measurements included patient-reported outcome measures(PROMs).Kaplan-Meier analysis was used to calculate the 5-year survival rate.Log-minus-log transformation was performed to calculate the 95%confidence interval(95%CI).Mixed model analyses were performed to assess the course of the PROMs during the 1st 2 years after surgery.Analyses were modeled separately for the 1st and 2nd years to calculate the yearly change in PROMs during both follow-up periods with accompanying 95%CIs.RESULTS The mean age of the total 500 patients was 62.3 years(standard deviation:10.6)and 202 were male(40%).At a median follow-up of 5.5 years(interquartile range:4.5-6.7),7 patients were deceased and 6 revisions were registered,for infection(n=3),subsidence(n=2)and malposition(n=1).This resulted in an overall 5-year survival of 98.8%(95%CI:97.3-99.5).If infection was left out as reason for revision,a stem survival of 99.4%(95%CI:98.1-99.8)was seen.Baseline questionnaires were completed by 471 patients(94%),317 patients(63%)completed the 1-year follow-up questionnaires and 233 patients(47%)completed the 2-year follow-up.Both outcome measures significantly improved across all domains in the 1st year after the operation(P<0.03 for all domains).In the 2nd year after surgery,no significant changes were observed in any domain in comparison to the 1-year follow-up.CONCLUSION The Optimys stem has a 5-year survival of 98.8%.Patient-reported outcome measures increased significantly in the 1st postoperative year with stabilization at the 2-year follow-up.

Biomechanical Optimization of Elastic Modulus Distribution in Porous Femoral Stem for Artificial Hip Joints

Long-term loosening is the major cause of failure of arthroplasty. One of the major causes is stress shielding, initiated by the large stiffness difference between prosthesis and bone tissue. Therefore, prosthesis with reduced stiffness properties to match those of the bone tissue may be able to minimize such a problem. Design with porous structure is believed to reduce the stiffness of the prosthesis, however at the cost of decreased strength. In this study, a patient-specific bone-implant finite element model was developed for contact mechanics study of hip joint, and algorithms were developed to adjust the elastic modulus of elements in certain regions of the femoral stem, until optimal properties were achieved according to the pre-defined criterions of the strength and stability of the system. The global safety factor of the optimized femoral stem was 11.3, and 26.4% of elements were designed as solid. The bone volume with density loss was reduced by 40% compared to the solid stem. The methodology developed in this study provides a universal method to design a patient-specific prosthesis with a gradient modulus distribution for the purposes of minimizing the stress shielding effect and extending the lifespan of the implant.

Effect of morselized bones on binding of the canine hydroxyapatite-coated femoral stem

Background Non-cement femoral stems are recognized in clinical use, but there are still some problems. The aim of this research was to make non-cement femoral stems to be press-fit with the medullary cavity. Methods Twenty-four healthy adult mongrel dogs were randomly divided into experimental and control groups. In the right hip joint, an artificial femoral bone replacement surgery was conducted. For the experimental group, the replacement surgery of hydroxyapatite （HA）-coated femoral stems was done, while autogeneous morselized bone was implanted into the medullary cavity. For the control group, morselized bone was not implanted. At postoperative 1, 3, 6 months, a test for interfacial shear characteristics was conducted in the MTS810 Tester. The comparison between the two groups＇ bone-prostheses in shear strength for their interface from shearing destruction was made. A histological observation to check prosthesis-bone interface contact ratios and bone growth was carried out. Results For the experimental group, shear strength was 0.317 MPa in 1 month, 1.447 MPa in 3 months, and 1.621 MPa in 6 months. For the control group, shear strength was 0.195 MPa in 1 month, 1.023 MPa in 3 months, and 1.483 MPa in 6 months. The difference was statistically significant. Stereomicroscope-based observation showed that the number of trabecular bones in the experimental group was larger than that of the control group, and bone growth of the former group was better than that of the latter group. Inverted microscopic observation showed that the binding degree between the prosthesis and trabecular bone of the experimental group was higher than that of the control group. Comparatively, the experimental group＇s trabecular bone had more stromal cells. Conclusions The morselized bones can effectively improve the biological bonding strength and bone-contact ratios in the short term for the HA-coated femoral stem and accelerate the bonding process. The use of morselized autogenous bones played a good role in bone in-growth of the femoral bone stem surface.

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.

Fracture of Extensively Porous-Coated Cylindrical Femoral Stem Following Revision Total Hip Arthroplasty

Total hip arthroplasty （THA） is one of the most clinically successful surgeries. Despite the prevalence of THA, the number of revisions for septic or aseptic reasons continues to increase.