Migration of press-fit cups fixed with poly-L-lactic acid or titanium screws: A randomized study using radiostereometry

The early migration of porous acetabular cups was studied in 43 patients with osteoarthrosis. The patients were randomly allocated to additional fixation of the cup with either biodegradable poly-L -lactic acid screws or titanium screws. Radiostereometric evaluation was done during the first 2 years after the procedure in 43 hips (23 with poly-L -lactic acid screws and 20 with titanium screws). At the 2-year follow-up, cups fixed with poly-L-lactic acid screws had migrated significantly more in the proximal-distal (p < 0.05) and medial-lateral (p < 0.05) directions. Cups with titanium screws displayed more pronounced rotations around the longitudinal axis (p < 0.05). Postoperatively, on the lateral view, there was an increased occurrence of radio-lucencies at the dome of the cups fixed with poly-L -lactic acid screws (p < 0.05). The clinical result did not differ between the two groups. Inferior implant-bone contact in the poly-L -lactic acid group, local changes of the bone quality, and diminishing support of the poly-L -lactic acid screws caused by their degradation with time could be reasons for the different pattern of migration observed.     

In vivo wear and migration of highly cross-linked polyethylene cups a radiostereometry analysis study

In 50 cemented hip arthroplasties, wear and migration of the polyethylene (PE) cups were measured with radiostereometric analysis for a period of 2 years. Twenty had a normal gamma-in-air-sterilized PE, another 20 had a PE sterilized with 30000 Gy followed by heat stabilization (Duration; Stryker Orthopaedics, Mahwah, NJ), and 10 had highly cross-linked PE cups irradiated with 100000 Gy (Crossfire; Stryker Orthopaedics). In the initial 2 months, head penetration (creep) was 63 microm on average for the 3 groups. From 2 to 24 months, the mean proximal head penetration (wear) was 156 microm for standard PE, 138 microm for stabilized PE (P = .45), and 23 microm for highly cross-linked PE (P < .001; analysis of variance). The low in vivo wear rate for highly cross-linked cups was not at the expense of higher migration or less favorable clinical outcome and looks promising.     

Less wear with aluminium-oxide heads than cobalt-chrome heads with ultra high molecular weight cemented polyethylene cups: A ten-year follow-up with radiostereometry

Purpose  

Wear is a major contributor to osteolysis and aseptic loosening of total hip replacements (THR). Both alumina (Al₂O₃) and cobalt-chrome (CoCr) femoral heads are commonly used. We investigated wear comparing alumina heads to cobalt-chrome heads against conventional cemented polyethylene (PE) cups for up to ten years.     

Femoral remodeling after porous-coated total hip arthroplasty with and without hydroxyapatite-tricalcium phosphate coating: a prospective randomized trial

We prospectively assessed femoral bone remodeling using dual-energy x-ray absorptiometry for 2 years after total hip arthroplasty. Thirty-nine hips were randomized to receive a titanium proximally porous-coated femoral component with or without hydroxyapatite-tricalcium phosphate coating. Although both stems resulted in alterations in the periprosthetic bone mineral density, the hydroxyapatite-tricalcium phosphate coated stems had significantly less femoral bone loss than the uncoated stems at 2-year follow-up. This reduced femoral bone loss may provide short-term and long-term advantages over noncoated stems.     

Inferior stabilization of cementless compared with cemented dual-mobility cups in elderly osteoarthrosis patients: a randomized controlled radiostereometry study on 60 patients with 2 years’ follow-up

Background and purpose — Elderly patients may benefit from a dislocation low-risk dual-mobility (DM) articulation in total hip arthroplasty, but the best cup fixation method is unknown. We compared cup migration for cemented and cementless DM cups using radiostereometry.Patients and methods — In a patient-blinded randomized trial, 60 patients (33 female) with osteoarthritis were allocated to cemented (n = 30) or cementless (n = 30) Avantage DM cup fixation. Criteria were age above 70 years, and T-score above –4. We investigated cup migration, periprosthetic bone mineral density (BMD), and patient-reported outcome measures (PROMs) until 24 months postoperative follow-up.Results — At 24 months mean proximal cup migration was 0.11 mm (95% CI 0.00–0.23) for cemented cups and 0.09 mm (CI –0.09 to 0.28) for cementless cups. However, cementless cups generally migrated more than cemented cups at 12 and 24 months. Cemented cups had no measurable migration from 3 months’ follow-up, while cementless cups had not yet stabilized at 24 months in all rotations. Cementless cups showed statistically significantly more maximum total point motion (MTPM) at 12- and 24-month follow-up compared with cemented cups in patients with low systemic BMD (p = 0.01). Periprosthetic BMD changes did not statisticially significantly correlate to proximal migration in either cup fixation group (p > 0.05). PROMs improved similarly in both groups.Interpretation — Cemented cups were well fixed at 3 months. The cementless cups migrated more in patients with low BMD, showed an inconsistent pattern of migration, and migrated in different directions during the first and second year without tendency to stabilization. Cemented fixation of the Avantage DM cup seems safer in elderly patients

The most common indication for revision of a conventional primary total hip arthroplasty (THA) is aseptic loosening of the components (SHAR 2016, NJR 2017, DHAR 2018).Implant fixation method (i.e., cemented or cementless) in primary THA seems mainly based on the surgeon’s preference and national trends. The Danish Hip Replacement Registry report shows a decrease in the use of cemented cup fixation in osteoarthrosis (OA) patients above 70 years (DHAR 2018). This trend has also been described in the United Kingdom (UK) and Australian Joint Registries, while in Sweden and Norway cemented cup fixation is still the preferred fixation method in elderly patients (SHAR 2016, NAR 2017, NJR 2017).The dual-mobility (DM) concept, with 2 articulation surfaces and increased jump distance, may decrease the dislocation rate and increase range of motion compared with standard single mobility (SM) THAs. The long-term survival and the best fixation method of the newer Avantage Reload DM cup in elderly patients is currently unknown but retrospective studies on other types of primary DM THAs suggest acceptable survival rates (Batailler et al. 2017) .Excessive early (2-year) implant micromotion measured with radiostereometric analysis (RSA) is a strong predictor for later implant loosening and poor survival (Karrholm et al. 1997, Nieuwenhuijse et al. 2012, Pijls et al. 2012), and our primary aim was to investigate the early RSA-measured migration of cemented and cementless Avantage DM cups in elderly (> 70 years old) OA patients until 24 months’ follow-up. Secondary endpoints included systemic and periprosthetic bone mineral density (BMD) measurements, and clinical outcome scores.     

Hydroxyapatite and tricalcium phosphate-coated cups with and without screw fixation: a randomized study of 64 hips

Sixty-two patients (64 hips) were provided with porous press-fit cups (Trilogy), plasma-sprayed with a coating consisting of 70% hydroxyapatite and 30% tricalcium phosphate. The patients were randomized to a cup with cluster holes for adjunctive screw fixation (n = 30) or to a cup without holes (n = 34). Radiostereometry was used to study migration and wear. Up to 2 years median translations and rotations <0.2 mm and <0.2 degrees were recorded in the 2 groups, without any difference. The median annual proximal wear (0.11 and 0.12 mm) was within the expected range despite the use of a ceramic coating, and it did not differ between the 2 designs. Radiolucent lines were frequently seen postoperatively but diminished during the follow-up without any sign of migration into the gaps. At 2 years, the median Harris scores were 99 points (range, 51-100 points) in the group with and 98 points (range, 69-100 points) in the group without screws. The results indicate that early fixation can be achieved for ceramic-coated press-fit cups without using additional screw fixation.     

Split liver transplantation and risk to the adult recipient: analysis using matched pairs

BACKGROUND: The technique of liver splitting is an effective way of increasing the donor pool and reducing pediatric waiting list mortality. But the procedure is still not fully accepted because of concerns that it may cause complications in adult recipients. STUDY DESIGN: Fifty-nine adult recipients of primary extended right split liver transplantations (SLTs) were matched to recipients of whole liver transplantations (WLTs) according to the following criteria: 1) United Network for Organ Sharing (UNOS) status, 2) donor age, 3) recipient age, 4) total cold ischemic time, 5) indication for liver transplantation, 6) Child-Pugh class, and 7) year of transplantation. A WLT-recipient match was identified in 40 adult recipients of primary SLT. RESULTS: Fifteen percent of the recipients in our study were highly urgent cases (UNOS 1), and 85% were UNOS status 3-4. The 3- and 12-month patient survival rates after SLT and WLT were 82.5% and 77.1%, and 92.5% and 87.5%, respectively (log rank p = 0.358). The 3- and 12-month graft survival rates showed no significant difference in either group (80% and 74% in SLT and 87.5% and 77.4% in WLT [log rank p = 0.887]). The rates of primary nonfunction, primary poor function, biliary and vascular complications, intra- and postoperative blood transfusion, and intensive care stay were comparable for SLT and WLT. CONCLUSIONS: SLT, using the extended right hepatic lobe, does not notably differ from WLT with regard to initial graft function, postoperative complications, or patient and graft survival. Based on this, the liver can be considered a paired organ, and mandatory splitting of good-quality livers can be recommended.     

One-level cervical spine fusion: A randomized study, with or without plate fixation, using radiostereometry in 27 patients

We randomized 27 consecutive patients undergoing 1 -level cervical disc surgery to surgery with or without anterior plate fixation. The patients were studied with radiostereometry and clinically with visual analogue scores (VAS) for arm and neck pain. After 2 years, 1 patient had developed pseudoarthrosis, all other fusions were healed, but 1 patient showed substantial motions in the fusion area between the 1- and 2-year follow-ups. The 12 patients operated on without a plate had increased rotations around the transverse axis, corresponding to deformation towards kyphosis. Clinically, there was no difference in outcome between the two groups, as assessed by VAS.

The use of an anterior plate in 1 -level degenerative disc surgery in the cervical spine seems to prevent rotational deformation, without affecting the clinical outcome or fusion healing.     

Uncemented cups with and without screw holes in primary THA: a Swedish Hip Arthroplasty Register study with 22,725 hips

Background and purpose — Uncemented cups in total hip arthroplasty (THA) are often augmented with additional screws to enhance their primary stability. We investigated whether there is a difference in the risk for revision between cups with screw holes and cups without screw holes.

Patients and methods — We analyzed the risk for cup revision of uncemented cups registered in the Swedish Hip Arthroplasty Register (SHAR) between 2000 and 2017 with respe ct to the presence of screw holes. Only patients with primary osteoarthritis (OA) were included. 22,725 cups, including 12,354 without screw holes and 10,371 with screw holes, were evaluated. Revision rates at 2 and 10 years after the primary operation were analyzed.

Results — At a median follow-up time of 3.4 years (0–18), 459?cup revisions were reported. The main reasons for cup revision during the whole observation time were infection, 52% of all cup revisions, and dislocation, 26% of all cup revisions. The survival rate with cup revision due to aseptic loosening as endpoint was 99.9% (95% CI 99.8–99.9) at 2 years for both cups with and cups without screw holes, and the survival rates at 10 years were 99.5% (CI 99.3–99.7) and 99.1% (CI 98.6–99.5), respectively. Cups without screw holes showed a decreased risk of revision due to any reason at both 2 years (adjusted hazard ratio [HR] 0.6, CI 0.5–0.8) and 10 years (HR 0.7, CI 0.5–0.9).

Interpretation — We found a very low revision rate for aseptic loosening with modern, uncemented cup designs. Cups with screw holes had an increased risk of revision due to any reason in patients with primary OA     

Long-term clinical outcome of acetabular cup revision surgery: comparison of cemented cups,cementless cups,and cemented cups with reinforcement devices

The aim of the present study was to analyze the clinical and radiographic outcomes and Kaplan–Meier survivorship of patients who underwent revision surgeries of the acetabular cup that had sustained aseptic loosening. We reviewed 101 consecutive patients (120 hips; 10 men 11 hips; 91 women 109 hips; age at surgery 66 years; range 45–85) who underwent acetabular component revision surgery, at a follow-up period of 15.6 years (range 10–32). To evaluate the state of the acetabulum, acetabular bony defects were classified according to the AAOS classification based on intraoperative findings: type I (segmental deficiencies n = 24 hips), type II (cavity deficiency n = 48), type III (combined deficiency n = 46), and type IV (pelvic discontinuity n = 2). The Harris hip score improved from 42.5 ± 10.8 (mean ± SD) before surgery to 74.9 ± 14.6 points at follow-up. The survival rates of the acetabular revision surgery with cemented, cementless, and cemented cups plus reinforcement devices were 74, 66, and 82 %, respectively. The difference in the survival rate between the cemented and cementless group was marginal (p = 0.048 Gehan–Breslow–Wilcoxon, p = 0.061 log-rank), probably due to the early-stage failure cases in the cementless group. The cementless and reinforcement groups included nine early-stage failure cases. To prevent early-stage failure, we recommend the cementless cups for types I and II acetabular bone defects with adequate contact between host bone and acetabular component, and the cemented cup with or without reinforcement devices, together with restoration of bone stock by impaction or structured bone grafting, for cases lacking such contact.     

Regulation of phosphate transport by fibroblast growth factor 23 (FGF23): implications for disorders of phosphate metabolism

There are a number of hypophosphatemic disorders due to renal phosphate wasting that cannot be explained by elevated levels of parathyroid hormone. The circulating factors responsible for the phosphaturia have been designated as phosphatonins. Studies of patients with tumor-induced osteomalacia and other genetic diseases of phosphate metabolism have resulted in the identification of a number of hormones that regulate phosphate homeostasis, including matrix extracellular phosphoglycoprotein (MEPE), secreted frizzled-related protein 4 (sFRP-4), dentin matrix protein 1 (DMP1), fibroblast growth factor 7 (FGF7), fibroblast growth factor 23 (FGF23), and Klotho. Our understanding of the actions of these hypophosphatemic peptides has been enhanced by studies in mice either overexpressing or not expressing these hormones. This review focuses on FGF23 since its regulation is disordered in diseases that affect children, such as X-linked hypophosphatemia, autosomal dominant and recessive hypophosphatemic rickets as well as chronic kidney disease. Recent studies have shown that FGF23 is unique among the FGFs in its requirement for Klotho for receptor activation. Here, we also discuss new potentially clinically important data pointing to the receptor(s) that mediate the binding and action of FGF23 and Klotho.     

Unstable trochanteric fractures augmented with calcium phosphate cement. A prospective randomized study using radiostereometry to measure fracture stability.

BACKGROUND AND AIMS: Internally fixed unstable trochanteric fractures might be difficult to retain in position during healing. Secondary displacement might lead to malunion and poor functional result. The aim with this study was to measure whether augmentation with resorbable calcium-phosphate cement could improve fracture stability as shown in biomechanical studies. MATERIAL AND METHODS: 26 ambulatory patients with an unstable trochanteric fracture were randomized to treatment with a sliding screw device alone (Controls) or the same device combined with calcium-phosphate cement for augmentation (Augmented). All patients were allowed unrestricted weight bearing after surgery. Fracture movement was measured with radiostereometry (RSA) at 1 and 6 weeks and at 6 months. RESULTS: Two patients died during the study period due to unrelated causes and another three were excluded due to technical problems with the RSA in two and concomitant illness in one. 21 patients (11 Augmented and 10 Controls) were followed according to the study protocol. At 1 week the augmented fractures had moved on average 1.9+/-1.7 mm while movement in the controls was 4.0+/-2.4 mm (p < 0.05). The average total movement from the day after surgery until 6 months, when all fractures had healed, was 7.8+/-6.2 mm for the augmented fractures and 13.2+/-4.3 mm for the controls (p < 0.05). Varus angulation was the most pronounced rotational movement for both groups although augmented fractures revealed less varus angulation compared with controls at all time points. Rotation around the longitudinal and transversal axes were small with no significant differences between treatment groups. CONCLUSION: Augmentation with calcium-phosphate cement improved the stability of unstable trochanteric fractures fixed with a sliding screw device. The improvement was most pronounced for varus angulation and lateral and distal migration of the head and neck fragment.     

Autograft versus interbody fusion cage without plate fixation in the cervical spine: a randomized clinical study using radiostereometry

A primary object with a fusion cage is avoidance of graft collapse with subsequent subsidence and malalignment of the cervical spine that is observed after bone grafting alone. No randomized studies exist that demonstrate the difference between these two methods in terms of graft subsidence and angulation of the fused segment. The size of the study population was calculated to be 24 patients to reach a significant difference at the 95% CI level. Patients with one-level cervical radiculopathy scheduled for surgery were randomized to anterior discectomy and fusion (ACDF) with autograft or to fusion cage, both without plate fixation. Tantalum markers were inserted in the two adjacent vertebrae at the end of surgery. Radiostereometry was performed immediately postoperatively and at regular intervals for 2 years. Questionnaires were used to evaluate the clinical outcome and an unbiased observer graded the outcome after 2 years. No significant differences were found between the two methods after 2 years in regard of narrowing of the disc space (mean 1.7 and 1.4 mm, respectively) or deformation of the fused segment into flexion (mean 7.7° and 4.6°, respectively). Patients in the cage group had a significantly better clinical outcome. The findings of subsidence and flexion deformation of the fused segment after 2 years seem to be of no clinical importance after one-level cervical disc surgery. However, in multi-level surgery using the same methods, an additive effect of the deformations of the fused segments may affect the clinical outcome.     

Measurement of migration of a humeral head resurfacing prosthesis using radiostereometry without implant marking: an experimental study

Introduction

Standard radiostereometric analysis of prosthetic migration requires that tantalum beads are inserted into the implant. For manufacturing reasons, this is not possible for humeral head resurfacing implants. We therefore used marker-free radiostereometry, developed for metal-backed acetabular cups, on a dummy model to validate the method for a humeral head resurfacing prosthesis.

Material and methods

3 hemispherical resurfacing prostheses of different sizes were marked with tantalum beads and mounted in a sawbone. Standard and marker-free radiostereometry was then done repeatedly with gradual shifts of position of the prosthesis between each analysis. The marker-free algorithm was then compared to the standard to determine the accuracy.

Results

The accuracy for marker-free radiostereometry was 0.22–0.47 mm for translations and 0.92–1.56 degrees for rotations.

Interpretation

Based on our results, marker-free radiostereometry can be used to measure migration of humeral head resurfacing prostheses. This indicates that implant marking is not required when doing radiostereometry on humeral head resurfacing in clinical trials.Radiostereometric analysis (RSA) (Selvik 1989) is the standard for measuring micromotion of orthopedic implants. With RSA, it is possible to get highly accurate three-dimensional (3-D) measurements from calibrated stereo radiographs. By making measurements over time, implant migration can be quantified and loosening predicted with high sensitivity (Kärrholm et al. 1994, Ryd et al. 1995). The method requires the insertion of tantalum markers into the skeleton and the implant to create 2 rigid bodies, called segments. The migration of the implant segment in relation to the skeleton segment for translation and rotation around the x-, y-, and z-axes (the 6 degrees of freedom) is then calculated.Marking of an implant requires modification of the implant design. This is costly, and can potentially adversely affect the performance of the implant being studied. In many countries, the marking of implants is therefore prohibited by the regulatory authorities. The high density of the implant metal can also obscure the tantalum markers, resulting in loss of migration data (Kaptein et al. 2005).For hemispherical metal-backed acetabular cups, an implant marker-free RSA algorithm (marker-less RSA) has been developed to address these problems. It has been found to be accurate in assessing penetration of femoral heads in hip arthroplasty and has also been used to determine acetabular cup migration (Valstar et al. 1997, Börlin et al. 2006, Zhou et al. 2006). To our knowledge, the method has not been used previously for migration analysis of a resurfacing prosthesis.We determined the accuracy of marker-less RSA when used on a humeral head resurfacing prosthesis.     

Comparison of porous-coated titanium femoral stems with and without hydroxyapatite coating

BACKGROUND: The purpose of this prospective, randomized study was to evaluate the clinical and radiographic results associated with proximally porous-coated titanium stems that were identical in geometry but differed with regard to proximal surface treatment (with or without hydroxyapatite coating). METHODS: A prospective, randomized study was performed to evaluate fifty patients (100 hips) who had undergone sequential bilateral primary total hip replacement. A proximally porous-coated titanium stem with hydroxyapatite coating was implanted on one side and a proximally porous-coated titanium stem without hydroxyapatite coating was implanted on the other side during the same operative setting in all fifty patients. A cementless acetabular component made of titanium was used in all hips. There were thirty-six men and fourteen women; the mean age at the time of the operation was 45.3 years. The mean duration of follow-up was 6.6 years. Clinical and radiographic evaluations were performed preoperatively; at six weeks; at three, six, and twelve months; and yearly thereafter. RESULTS: The Harris hip scores in the hydroxyapatite-coated group (mean, 94 points) and non-hydroxyapatite-coated group (mean, 92 points) were similar at the final follow-up examination. The prevalence of transient pain in the thigh was 4% in each group. No acetabular or femoral component demonstrated aseptic loosening. Bone-remodeling patterns, including calcar atrophy, were similar in the two groups. No acetabular or femoral osteolysis was seen. CONCLUSIONS: At a mean of 6.6 years postoperatively, the clinical and radiographic results associated with proximally porous-coated femoral prostheses with identical geometries that differed only with regard to the presence or absence of hydroxyapatite coating were similar.