Sealing effect of hydroxyapatite coating: a 12-month study in canines

This study addresses the clinical problems regarding access of wear debris to the bone-implant interface and the possible dissemination of polyethylene (PE) particles to distant organs. We inserted two implants into each knee of 7 dogs allowing access of joint fluid to the bone-implant interface with a 0.75 mm initial gap around the implant. Hydroxyapatite (HA)-coated and non-coated (Ti) titanium alloy implants were randomly allocated to each distal femoral condyle. PE particles were repeatedly injected into the right knee joint 3 weeks after surgery for a period of 49 weeks, while only vehicle was injected into the left knee joint. We found huge amounts of PE particles mainly in the bone-implant interface around Ti implants. Infiltration of mononuclear inflammatory cells was present around 3 of 7 Ti implants in relation to PE particles. HA implants had approximately 70% bone ongrowth. In contrast, no bone ongrowth was seen on any Ti implants, all being surrounded by a fibrous membrane. The number of PE particles was evaluated semi-quantitatively. More PE particles were found around Ti implants than with HA implants (p < 0.002). Specimens from iliac lymph nodes, liver, spleen and lung were examined and showed dissemination of PE particles only in regional lymph nodes.     

Sealing effect of hydroxyapatite coating on peri-implant migration of particles. An experimental study in dogs

We have studied the beneficial effects of a hydroxyapatite (HA) coating on the prevention of the migration of wear debris along the implant-bone interface. We implanted a loaded HA-coated implant and a non-coated grit-blasted titanium alloy (Ti) implant in each distal femoral condyle of eight Labrador dogs. The test implant was surrounded by a gap communicating with the joint space and allowing access of joint fluid to the implant-bone interface. We injected polyethylene (PE) particles into the right knee three weeks after surgery and repeated this weekly for the following five weeks. The left knee received sham injections. The animals were killed eight weeks after surgery. Specimens from the implant-bone interface were examined under plain and polarised light. Only a few particles were found around HA-coated implants, but around Ti implants there was a large amount of particles. HA-coated implants had approximately 35% bone ingrowth, whereas Ti implants had virtually no bone ingrowth and were surrounded by a fibrous membrane. Our findings suggest that HA coating of implants is able to inhibit peri-implant migration of PE particles by creating a seal of tightly-bonded bone on the surface of the implant.     

A retrospective 12-month study of conversion to everolimus in lung transplant recipients

Background

Everolimus has potent antifibrotic effects that may potentially affect the clinical course of bronchiolitis obliterans syndrome (BOS) or provide nephroprotective immunosuppressive regimens for lung transplantation.

Methods

We retrospectively assessed the 12-month outcomes of the conversion to everolimus among lung recipients in six Spanish centers.

Results

From March 2005 to December 2007, 65 lung recipients who were at a mean posttransplantation time of 10.2 ± 7.9 months were converted to everolimus, mainly because of BOS (64.6%) or renal insufficiency (RI; 12.3%). The initial dose of everolimus was 1.9 ± 0.6 mg/d and the mean blood trough levels were stable over time (6.4 ± 2.8 ng/mL at 12 months). Conversion to everolimus allowed us to eliminate the calcineurin inhibitor (CNI) in 21% of patients. Among the overall population, the forced expiratory volume at 1 second (FEV₁) and renal function remained stable. Mean FEV₁ did not change among the 35 (81%) patients surviving BOS at 12 months: preconversion FEV₁: 1.449.5 ± 641.9 mL vs 12-month FEV₁: 1420.0 ± 734.6 mL (P = .866). There was a significant improvement in renal function among the RI patients with mean glomerular filtration rates of 42.2 ± 15.2 mL/min/1.73 m² (P = .043) at 6 and 44.4 ± 18.8 mL/min/1.73 m² at 12 months, (P = .063) and a decrease in the use of CNIs from 1% of RI patients preconversion to 57% at 6 and 75% at 12 months. With a mean of 8.1- months follow-up (range: 1–31.3) overall survival was 84.6% at 1 year and 50% at 22.3 months. Progressive BOS was the main cause of death. Reasons for everolimus discontinuation were patient death (n = 10), lack of efficacy (n = 4), gastrointestinal adverse events (n = 2), and edema (n = 2).

Conclusions

BOS and RI were the main indications for conversion to everolimus among lung recipients. Conversion to everolimus improved renal function among patients converted because of RI. The present results were inconclusive regarding effects of everolimus on BOS.     

A randomized clinical trial of cementless femoral stems with and without hydroxyapatite/tricalcium-phosphate coating: an 8- to 12-year follow-up study

To evaluate the effect of hydroxyapatite coating on cementless femoral stem, a prospective randomized clinical trial was conducted. A total of 84 hips from 69 patients were assigned to a hydroxyapatite/tricalcium-phosphate-coated group or a noncoated group. Thirty-two patients (37 hips) who received hydroxyapatite/tricalcium-phosphate-coated stems and 31 patients (38 hips) who received noncoated stems were followed for an average of 127 months. Forty-nine patients (78%) were men, and the average age was 45.5 years. Preoperative diagnosis was osteonecrosis in 62 hips (83%). The mean Harris hip score at the time of final follow-up was 91 points in the coated group and 90 points in the noncoated group. Six acetabular components (3 in each group) were revised. One femoral stem in the noncoated group was loose. There was no statistical difference in the survival distributions of the implants between the 2 groups.     

The effect of hydroxyapatite coating on the fixation of hip prostheses

The efficacy of a total hip replacement with a hydroxyapatite-coated hip prosthesis was compared with that of an uncoated, cementless prosthesis of the same type. Preoperatively, there was no difference in the patient's diagnosis, hip score, age, and sex. All operations were performed by one surgeon in a standardized manner. The choice of the implant was randomized, and the follow-up period was equal for both types. The implant used was associated with a poor outcome due to a high incidence of early aseptic loosening. Probably because of a poor initial fixation, there was a significant difference in the clinical results after a short follow-up period when an additional HA layer was used. According to the patients' pain, migration of the implant, and presence of a progressive radiolucent line, use of the HA-coated prosthesis led to a significantly better result; however, we also found an increased rate of heterotopic bone formation in the HA-coated group. It was concluded that the HA coating improves the initial fixation of a hip prosthesis.     

A 12-month prospective study of gasserian ganglion stimulation for trigeminal neuropathic pain

AIMS: Trigeminal neuropathic pain is a broad diagnostic category that includes pain of several etiologies and excludes trigeminal neuralgia. The authors report a prospective series of percutaneous gasserian ganglion stimulation for trigeminal neuropathic pain. METHODS: Patients who experienced >50% reduction in pain from a 7- to 10-day trial period underwent permanent implantation and were prospectively followed. RESULTS: Eight of 10 trialed patients received a permanent implant. At the 12-month follow-up, 2 patients had been explanted and 1 was lost to follow-up. Three (all working at that the time) continued to experience >50% improvement in pain. DISCUSSION: The results in this series were variable but 3 patients showed long-term improvements. Patients who continued to work responded better to treatment.     

Protein and amino acid status before and after bariatric surgery: A 12-month follow-up study

BackgroundPatients with obesity submitted to bariatric surgery present altered ingestion of macronutrient and micronutrient levels and nutrients deficiency. The objective of this study was to evaluate the protein and amino acid nutritional status of obese adults before and after bariatric surgery, with emphasis on plasma free amino acids.MethodsThirty obese women were submitted to Roux-en-Y gastric shunt (bariatric surgery). Food and protein intake, anthropometric and bioimpedance data (body composition analysis), and serum total protein, albumin, and plasma amino acids levels were collected before the surgery (preoperative) and 3, 6, and 12 months after the surgical procedure.ResultsThe mean protein intake was 47±2 g/day. The total weight loss during the study period was 39±8 kg; the fat-free mass decreased 7±5 kg. The amino acid profile showed increased concentrations of most amino acids 3 months after surgery; at 6 months, glutamic acid, serine, arginine, alanine, methionine, valine, phenylalanine, isoleucine, and tyrosine concentrations decreased. The total protein and albumin concentrations dropped along the 12-month follow-up.ConclusionThe amino acid profile changes after RYGB are evidence that total protein and albumin levels may not be good indicators of protein profile after the surgery.     

Recurrence of duodenal ulceration in patients on maintenance sucralfate. A 12-month follow-up study

A single-blind, 1-year follow-up study of 70 patients with recently healed duodenal ulcers was undertaken to assess the value of sucralfate (Ulsanic; Continental Ethicals) in preventing recurrence and to establish the lowest dose required to achieve this. Endoscopy was repeated on clinical relapse and routinely at 6 and 12 months. Fifty of the 70 patients were followed up for 12 months or to recurrence proved on endoscopy; the remaining 20 patients were excluded from analysis because of default or protocol violation. Endoscopic evidence of recurrence was found in 6 of 19 patients (32%) given sucralfate 1 g twice a day (group B), in 7 of 15 (47%) on sucralfate 1 g at night (group A), and in 13 of 16 controls (81%). The recurrence rates in groups A and B were significantly lower than in the control group (P less than 0,05 and P less than 0,005 respectively), and there was a significant gradient between the number of patients in remission at 12 months and the amount of medication (P less than 0,05).     

A randomized trial comparing TVT with TVT-O: 12-month results

The aim of this randomized clinical trial was to compare the cure rate and the rate of complications of the tension-free vaginal tape (TVT) with those of the tension free vaginal tape obturator (TVT-O) procedure after one year of follow-up. The study was powered to show a ten per cent difference in cure rate and/or rate of complications. Of the initially treated 267 women 134 in the TVT group and 131 in the TVT-O group were evaluated. A cough stress test and a 24 h pad test were used as objective outcome measures. Subjective outcome was assessed by different condition-specific quality of life questionnaires and general health by the EQ-5D questionnaire. Objective cure rate was 95.5% in the TVT patients and 93.1% in TVT-O patients. Subjective cure rates showed significant improvement at one the year follow up in both groups. No significant differences in cure rates between groups were seen. The complication rate was equal in both groups.     

Improved bone-screw interface with hydroxyapatite coating: an in vivo study of loaded pedicle screws in sheep

STUDY DESIGN: An in vivo sheep model with loaded pedicle screws was used, wherein each animal served as its own control. OBJECTIVES: To examine the effects of hydroxyapatite (HA) coating on the bone-to-implant interface in loaded spinal instrumentations. SUMMARY OF BACKGROUND DATA: Spinal instrumentation improves the healing rate in spinal fusion, but screw loosening constitutes a problem. HA coating of other implants has resulted in favorable effects on the bone-to-implant interface. METHODS: Nine sheep were operated on with destabilizing laminectomies at two levels: L2-L3 and L4-L5. Each level was stabilized separately with a four-screw instrumentation. Uncoated screws (stainless steel) or the same type of screws coated with plasma-sprayed HA were used in either the upper or the lower instrumentation in a randomized fashion. The animals were killed at 6 or 12 weeks after surgery. The specimens were embedded in resin, ground to approximately 10 microm, and stained with toluidine blue. Histomorphometric evaluation was carried out in a Leitz Aristoplan (Wetzlar, Germany) light microscope equipped with a Leitz Microvid unit. RESULTS: The average percentage of bone-to-implant contact after 6 weeks was 69 +/- 10 for the HA-coated screws and 18 +/- 11 for the uncoated screws (P < 0.03), and after 12 weeks 64 +/- 31 (HA-coated) and 9 +/- 13 (uncoated, P < 0.02). The average bone volume in the area close to the screw was significantly higher for the HA-coated screws at both 6 and 12 weeks. CONCLUSIONS: HA coating improved the bone-to-implant interface significantly, indicating that HA coating can become useful for improving the purchase of pedicle screws.     

The effect of hydroxyapatite coating on bone growth into porous titanium alloy implants

In rabbits and goats, test implants with a porous surface of two layers of Tl-6A;-4V beads were examined at intervals for bond strength with bone. Half of the implants were coated with hydroxyapatite by plasma spray. The bonding strength with bone in the coated specimens was about four times greater than that of the uncoated specimens at two weeks, and twice as strong at six weeks. Twelve weeks after implantation, the strengths were similar. The hydroxyapatite coating of the beads provided earlier and stronger fixation.     

Effects of hydroxyapatite coating of cups used in hip revision arthroplasty: A Swedish Hip Arthroplasty Register study of 1,780 revisions

Background and purpose

Coating of acetabular revision implants with hydroxyapatite (HA) has been proposed to improve ingrowth and stability. We investigated whether HA coating of revision cups can reduce the risk of any subsequent re-revision.

Methods

We studied uncemented cups either with or without HA coating that were used at a primary acetabular revision and registered in the Swedish Hip Arthroplasty Register (SHAR). 2 such cup designs were identified: Harris-Galante and Trilogy, both available either with or without HA coating. These cups had been used as revision components in 1,780 revisions of total hip arthroplasties (THA) between 1986 and 2009. A Cox proportional hazards model including the type of coating, age at index revision, sex, cause of cup revision, cup design, the use of bone graft at the revision procedure, and the type of cup fixation at primary THA were used to calculate adjusted risk ratios (RRs with 95% CI) for re-revision for any reason or due to aseptic loosening.

Results

71% of the cups were coated with HA and 29% were uncoated. At a mean follow-up time of 6.9 (0–24) years, 159 (9%) of all 1,780 cups had been re-revised, mostly due to aseptic loosening (5%), dislocation (2%), or deep infection (1%). HA coating had no significant influence on the risk of re-revision of the cup for any reason (RR = 1.4, CI: 0.9–2.0) or due to aseptic loosening (RR = 1.1, 0.6–1.9). In contrast, HA coating was found to be a risk factor for isolated liner re-revision for any reason (RR = 1.8, CI: 1.01–3.3). Age below 60 years at the index cup revision, dislocation as the cause of the index cup revision, uncemented cup fixation at primary THA, and use of the Harris-Galante cup also increased the risk of re-revision of the cup. In separate analyses in which isolated liner revisions were excluded, bone grafting was found to be a risk factor for re-revision of the metal shell due to aseptic loosening (RR = 2.1, CI: 1.05–4.2).

Interpretation

We found no evidence to support the notion that HA coating improves the performance of the 2 studied cup designs in revision arthroplasty. In contrast, patient-related factors such as younger age and dislocation as the reason for cup revision, and technical factors such as the choice of revision cup were found to influence the risk of subsequent re-revision of the cup. The reason for inferior results after revision of uncemented cups is not known, but it is possible that these hips more often had pronounced bone loss at the index cup revision.The most common cause of re-revision of the hip after revision surgery is failure of the acetabular component (Swedish Hip Arthrolasty Register (SHAR) 2010). Acetabular revision with cemented implants has shown up to 20% failure at 10 years of follow-up, whereas contemporary designs of uncemented acetabular cups have substantially reduced this failure rate (Callaghan et al. 1985, Kavanagh et al. 1985, Katz et al. 1997, Lie et al. 2004). Loosening of the primary acetabular component often leaves substantial bone loss and a sclerotic acetabular bed. Fixation of revision cups is therefore demanding, and several techniques have been used to restore bone loss and achieve long-term fixation of the revision cup—such as screw fixation, bone grafting, and different cup designs (Palm et al. 2007, Pulido et al. 2011). The use of hydroxyapatite (HA) coating on cups used as revision implants has been proposed to be an improvement over uncoated cups (Dorairajan et al. 2005, Geerdink et al. 2007).HA is the main inorganic component of human bone. It has therefore been hypothesized that coating of metallic implants with HA enhances ingrowth of bone and thus leads to improved stability (Soballe et al. 1999). Indeed, some HA-coated cups perform well and are still in use, while other HA-coated cups have shown high failure rates in the long term. For instance, inferior results were achieved with the Romanus cup where the combination of an inferior locking mechanism of the liner with an inferior type of polyethylene resulted in excessive osteolysis in the acetabular region (Puolakka et al. 1999, Lyback et al. 2004, Lazarinis et al. 2010, SHAR 2010). Due to the relatively small numbers of revision procedures, very few authors have reported results after hip revision arthroplasty using HA-coated implants. To our knowledge, there have been no registry studies specifically investigating the performance of HA-coated hip revision implants. Thus, the question of whether the use of HA coating on revision cups is beneficial remains to be answered.In this study, we analyzed the outcome of acetabular revision surgery using uncemented cups with or without HA coating recorded in the Swedish Hip Arthroplasty Register (SHAR). Our hypothesis was that coating of revision acetabular cups with HA reduces the risk of re-revision of the acetabular component inserted. The primary endpoint was re-revision of the acetabular component for any reason and the secondary endpoint was re-revision of the cup due to aseptic loosening.     

The effect of substrate roughness and hydroxyapatite coating thickness on implant shear strength

This study examined the role of substrate preparation and hydroxyapatite (HA) coating thickness on bone ongrowth and shear strength in a bilateral bicortical sheep model. Plasma-sprayed and grit-blasted titanium implants with different thickness HA coatings were examined at 4, 8, 12, and 26 weeks after implantation. Shear strength increased with time for all implants. Plasma-sprayed implants were superior to grit-blasted implants at all time points. The 100-microm-thick HA layer used in the present study provided greater fixation and ongrowth and less resorption compared with the 50-microm-thick layer. We did not observe any advantage in using a thicker HA coating for the titanium substrates examined.     

The effect of hydroxyapatite coating on ingrowth of bone into cavities in an implant.

A canine implant study was performed to assess whether hydroxyapatite (HA) could induce bone to close gaps at the bone-prosthesis junction. Titanium alloy (TiAlV) plates with varying grooves cut into them (1, 2, and 3 mm deep) and identical on both sides were sprayed on one side with HA and left as bare metal on the other. These were then implanted into the distal femora of dogs that were killed 4 and 8 weeks afterwards. Specimens were analyzed using optical microscopy and microradiography. Results show that the presence of HA induces bone to grow almost completely down the deepest groove by 8 weeks. In the 1- and 2-mm grooves at 4 weeks the depth of penetration of bone into the grooves was greater on the HA coated side (but the actual volume of bone in the grooves was greater on the TiAlV side because the bone present was more dense). We conclude that the presence of HA induces bone to close relatively large gaps. Although bone does not grow all the way into uncoated defects there can be more bone here in the short term. This feature of HA may be of great value in hip implant fixation.     

Unilateral stimulation of the subthalamic nucleus in Parkinson disease: a double-blind 12-month evaluation study

OBJECT: Bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been established as an effective treatment for Parkinson disease (PD). Nevertheless, bilateral surgical procedures can be associated with frequent and severe complications. The aim in the present study was to assess the safety and efficacy of unilateral STN stimulation, and the need for a second procedure. METHODS: Twelve patients with PD underwent unilateral DBS of the STN and were followed up for 12 months. Patients were assessed at baseline and at each visit in a double-blind fashion by analyzing the Unified PD Rating Scale (UPDRS), ambulation speed, and home diaries. Levodopa-off/stimulation-on UPDRS motor scores were improved by 26 +/- 8% (p < 0.05, mean +/- standard deviation [SD]) compared with the baseline levodopa-off score; there was a 50% improvement in contralateral features, a 17% improvement ipsilaterally, and a 36% improvement in axial features. The mean ambulation speed increased by 83 +/- 44% (p < 0.01, mean +/- SD). The medication-on time with dyskinesias was significantly reduced (p < 0.01) and the daily levodopa dose was reduced by 19 +/- 6% (p < 0.05, mean +/- SD). There were no clinically significant side effects. CONCLUSIONS: Unilateral DBS of the STN is safe and well tolerated, and may provide sufficient benefit so that additional surgery is not required.     

A back-scattered electron microscopy (BSEM) study of the tight apposition between bone and hydroxyapatite coating

We performed a back-scattered electron microscopy analysis of the interface between newly formed bone and hydroxyapatite coating, in an experimental rabbit model. Twenty cylinders made of Ti6A14V and coated with hydroxyapatite at different crystallinity were implanted in the distal femural canal and retrieved at 4, 8, 26 an 34 weeks. Crystallinity of the coating varied from 90% to 60% and thickness varied between 50 and 100 μm. Osteocytes were detectable a few micrometers in proximity of the coating. They produced new bone which was so tightly apposed to the coating that high magnification BSEM did not resolve any discontinuity at the interface. This was not observed in uncoated implants. Degradation of the hydroxyapatite coating is not a simple hydrolytic process because newly formed bone is remodelled in areas were a tight apposition with hydroxyapatite is present. The coatint itself is likely to be attacked by the resorptive action of multinucleated giant cells and osteoclasts. In conclusion, response to coated samples is morphologically characterized by tight apposition with bone. The substitution of areas of the coating by newly formed bone is possible. Received: 28 April 2000/Accepted: 2 June 2000     

羟基磷灰石涂层镁铝合金的体外生物相容性研究

目的：评价羟基磷灰石（HA）涂层镁铝合金（AZ31B）的体外生物相容性。方法实验分为3组：HA涂层AZ31B浸提液组（H组）、阳性对照组（P组）和空白对照组（N组）。将L929细胞与各组混合液培养3、5和7 d,采用WST-1法检测细胞活力并进行细胞毒性分级。各组混合液与稀释兔血混匀,测定吸光度（OD）并计算溶血率。采用各组混合液对白化豚鼠分别进行皮内诱导、局部诱导和激发,观察去除贴敷片24、48、72 h动物激发部位皮肤情况。结果3、5和7dN组和H组细胞毒性反应分级为0级,P组部分细胞毒性反应分级为3级;各时间点H组、N组细胞活力均高于P组,差异有统计学意义（P ＜0.05）。H组、P组和N组OD值分别为（0.004±0.001）、（0.648±0.050）和（0.008±0.003）;H组溶血率为-0.6%,无溶血反应。去除贴敷片24、48、72 h H组皮肤无明显改变,P组可见中度至重度融合性红斑。结论体外实验提示HA涂层镁铝合金具有良好的体外生物相容性。