Hydroxyapatite-coated versus grit-blasted femoral stems. a prospective, randomised study using EBRA-FCA

Proximal Femoral Bone Regeneration After an Uncemented Hydroxyapatite-coated Long-stem in Revision Hip Surgery

Background:

Bone remodelling with lateral femoral cortex thinning is a major concern after extensively porous-coated long-stem in revision surgery. Extensive hydroxyapatite coated long-stems were introduced to improve osseointegration, but bone remodelling changes have not been quantified.

Objective:

The question of whether bone remodelling changes from extensive hydroxyapatite-coated long stems influence the durability of femoral revision, clinical outcome is assessed in follow-up radiographs.

Methods:

Uncemented straight monoblock hydroxyapatite-coated long-stems used in revision hip surgery for aseptic loosening were assessed in a consecutive series of 64 hips (60 patients). Mean follow-up was 8.6 years and the mean age at surgery was 70 years (27-91). The pre-operative bone defect was classified according to Paprosky. Cortical struts were not used in this series. Cortical index and femoral cortical width were measured at three different levels at different periods.

Results:

Four patients with pain under level 4 due to stem loosening needed an exchange surgery of their femoral component, but two patients rejected re-surgery. The cumulative probability of not having aseptic loosening was 91.2% (95% confidence interval 73.5-96.9) at 10 years according to Kaplan and Meier. Twenty-seven of 35 osteolytic lesions had disappeared or decreased at the last follow-up. The thickness of the lateral and medial cortex increased over the course of the study at different levels. Increases of femoral cortex thickness were greater in men and in cases with mild bone defects.

Conclusion:

Although clinical outcome of the hydroxyapatite-coated long stem in revision surgery is good but not outstanding, most osteolytic lesions heal and the femoral cortex thickness increases at different levels.

Development and validation of an automated and marker-free CT-based spatial analysis method (CTSA) for assessment of femoral hip implant migration: In vitro accuracy and precision comparable to that of radiostereometric analysis (RSA)

BACKGROUND AND PURPOSE

We developed a marker-free automated CT-based spatial analysis (CTSA) method to detect stem-bone migration in consecutive CT datasets and assessed the accuracy and precision in vitro. Our aim was to demonstrate that in vitro accuracy and precision of CTSA is comparable to that of radiostereometric analysis (RSA).

MATERIAL AND METHODS

Stem and bone were segmented in 2 CT datasets and both were registered pairwise. The resulting rigid transformations were compared and transferred to an anatomically sound coordinate system, taking the stem as reference. This resulted in 3 translation parameters and 3 rotation parameters describing the relative amount of stem-bone displacement, and it allowed calculation of the point of maximal stem migration. Accuracy was evaluated in 39 comparisons by imposing known stem migration on a stem-bone model. Precision was estimated in 20 comparisons based on a zero-migration model, and in 5 patients without stem loosening.

RESULTS

Limits of the 95% tolerance intervals (TIs) for accuracy did not exceed 0.28 mm for translations and 0.20° for rotations (largest standard deviation of the signed error (SD(SE)): 0.081 mm and 0.057°). In vitro, limits of the 95% TI for precision in a clinically relevant setting (8 comparisons) were below 0.09 mm and 0.14° (largest SD(SE): 0.012 mm and 0.020°). In patients, the precision was lower, but acceptable, and dependent on CT scan resolution.

INTERPRETATION

CTSA allows detection of stem-bone migration with an accuracy and precision comparable to that of RSA. It could be valuable for evaluation of subtle stem loosening in clinical practice.

Uncemented fully hydroxyapatite-coated hip stem for intracapsular femoral neck fractures in osteoporotic elderly patients: a multicenter study

There is still debate over the limits of age and bone stock quality of patients on whom to use an un-cemented straight stem coated with hydroxyapatite (HA). We studied a group of 244 patients with a displaced intracapsular fracture of the femoral neck who underwent cementless hemiarthroplasty or total hip arthroplasty. 143 patients were reviewed at the two-year follow up. A fully HA-coated stem for intracapsular hip fracture results in a satisfactory return to pre-injury mobility and a low complications rate. The advantage reported in the literature of a low mortality rate with use of an un-cemented implant in elderly patients was shown to be greater still on finding an immediate primary stability and rapid osteointegration of the implant.

Biomineral/Agarose Composite Gels Enhance Proliferation of Mesenchymal Stem Cells with Osteogenic Capability

Hydroxyapatite (HA) or calcium carbonate (CaCO₃) formed on an organic polymer of agarose gel is a biomaterial that can be used for bone tissue regeneration. However, in critical bone defects, the regeneration capability of these materials is limited. Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into bone forming osteoblasts. In this study, we loaded MSCs on HA- or CaCO₃-formed agarose gel and cultured them with dexamethasone, which triggers the osteogenic differentiation of MSCs. High alkaline phosphatase activity was detected on both the HA- and CaCO₃-formed agarose gels; however, basal activity was only detected on bare agarose gel. Bone-specific osteocalcin content was detected on CaCO₃-formed agarose gel on Day 14 of culture, and levels subsequently increased over time. Similar osteocalcin content was detected on HA-formed agarose on Day 21 and levels increased on Day 28. In contrast, only small amounts of osteocalcin were found on bare agarose gel. Consequently, osteogenic capability of MSCs was enhanced on CaCO₃-formed agarose at an early stage, and both HA- and CaCO₃-formed agarose gels well supported the capability at a later stage. Therefore, MSCs loaded on either HA- or CaCO₃-formed agarose could potentially be employed for the repair of critical bone defects.

Does hydroxyapatite coating have no advantage over porous coating in primary total hip arthroplasty? A meta-analysis

There are some arguments between the use of hydroxyapatite and porous coating. Some studies have shown that there is no difference between these two coatings in total hip arthroplasty (THA), while several other studies have shown that hydroxyapatite has advantages over the porous one. We have collected the studies in Pubmed, MEDLINE, EMBASE, and the Cochrane library from the earliest possible years to present, with the search strategy of “(HA OR hydroxyapatite) AND ((total hip arthroplasty) OR (total hip replacement)) AND (RCT* OR randomiz* OR control* OR compar* OR trial*)”. The randomized controlled trials and comparative observation trials that evaluated the clinical and radiographic effects between hydroxyapatite coating and porous coating were included. Our main outcome measurements were Harris hip score (HHS) and survival, while the secondary outcome measurements were osteolysis, radiolucent lines, and polyethylene wear. Twelve RCTs and 9 comparative observation trials were included. Hydroxyapatite coating could improve the HHS (p < 0.01), reduce the incidence of thigh pain (p = 0.01), and reduce the incidence of femoral osteolysis (p = 0.01), but hydroxyapatite coating had no advantages on survival (p = 0.32), polyethylene wear (p = 0.08), and radiolucent lines (p = 0.78). Hydroxyapatite coating has shown to have an advantage over porous coating. The HHS and survival was duration-dependent—if given the sufficient duration of follow-up, hydroxyapatite coating would be better than porous coating for the survival. The properties of hydroxyapatite and the implant design had influence on thigh pain incidence, femoral osteolysis, and polyethylene wear. Thickness of 50 to 80 μm and purity larger than 90% increased the thigh pain incidence. Anatomic design had less polyethylene wear.

On the fate of particles liberated from hydroxyapatite coatings in vivo

PURPOSE

Hydroxyapatite (HA) has been used as a coating for orthopaedic implants for over 30 years to help promote the fixation of orthopaedic implants into the surrounding bone. However, concerns exist about the fate of the hydroxyapatite coating and hydroxyapatite particles in vivo, especially in the wake of recent concerns about particulates from metal-on-metal bearings.

METHODS

Here, we assess the mechanisms of particle detachment from coated orthopaedic devices as well as the safety and performance concerns and biomedical implications arising from the liberation of the particles by review of the literature.

FINDINGS

The mechanisms that can result in the detachment of the HA coating from the implant can be mechanical or biochemical, or both. Mechanical mechanisms include implant insertion, abrasion, fatigue and micro-motion. Biochemical mechanisms that contribute to the liberation of HA particles include dissolution into extra-cellular fluid, cell-mediated processes and crystallisation of amorphous phases. The form the particles take once liberated is influenced by a number of factors such as coating method, the raw powder morphology, processing parameters, coating thickness and coating structure.

CONCLUSIONS

This review summarises and discusses each of these factors and concludes that HA is a safe biomimetic material to use as a coating and does not cause any problems in particulate form if liberated as debris from an orthopaedic implant.

Hydroxyapatite-coated femoral stems in primary total hip arthroplasty: a meta-analysis of randomized controlled trials

BACKGROUND

Controversy exists over the use of hydroxyapatite (HA)-coated femoral stems in primary total hip arthroplasty (THA). We conducted a meta-analysis of randomized controlled trials (RCT) to compare the clinical and radiologic outcomes of primary THA using HA-coated versus non-HA-coated femoral stems.

METHODS

Databases including MEDLINE, EMBASE and the Cochrane Library were searched to find relevant RCTs comparing HA-coated versus non-HA-coated femoral stems in primary THA. Data analyses were performed using RevMan 5.0 (The Cochrane Collaboration).

RESULTS

Seven studies (792 hips) met the inclusion criteria. The pooled weighted mean difference (WMD) for the postoperative Harris hip score was 3.04 (95% CI: -4.47 to 10.54, P = 0.43). The cumulative risk ratios (RR) for the presence of endosteal condensation and radioactive lines were 1.02 (95% CI: 0.93 to 1.12, P = 0.64) and 1.01 (95% CI: 0.90 to 1.14, P = 0.81), respectively.

CONCLUSIONS

This meta-analysis demonstrates that the use of HA-coated femoral stems in primary THA has no clinical or radiological benefits.

Local inhibition of 5-lipoxygenase enhances bone formation in a rat model

Objectives

Recent studies have shown that modulating inflammation-related lipid signalling after a bone fracture can accelerate healing in animal models. Specifically, decreasing 5-lipoxygenase (5-LO) activity during fracture healing increases cyclooxygenase-2 (COX-2) expression in the fracture callus, accelerates chondrogenesis and decreases healing time. In this study, we test the hypothesis that 5-LO inhibition will increase direct osteogenesis.

Methods

Bilateral, unicortical femoral defects were used in rats to measure the effects of local 5-LO inhibition on direct osteogenesis. The defect sites were filled with a polycaprolactone (PCL) scaffold containing 5-LO inhibitor (A-79175) at three dose levels, scaffold with drug carrier, or scaffold only. Drug release was assessed in vitro. Osteogenesis was assessed by micro-CT and histology at two endpoints of ten and 30 days.

Results

Using micro-CT, we found that A-79175, a 5-LO inhibitor, increased bone formation in an apparent dose-related manner.

Conclusions

These results indicate that 5-LO inhibition could be used therapeutically to enhance treatments that require the direct formation of bone.

Analysis of bone formation on porous and calcium phosphate-coated acetabular cups: a randomised clinical [18F]fluoride PET study

We present a study using Fluoride-Positron Emission Tomography (F-PET/CT) to analyse new bone formation in periacetabular bone adjacent to press fit cups following THA. In 16 THA (8 patients) with bilateral hip osteoarthritis simultaneous bilateral total hip arthroplasty (THA) was performed, employing electrochemically applied calcium phosphate coated (HA) cups or porous-coated (PC) cups allocated at random to compare the two sides. A reference group of 13 individuals with a normal healthy hip was used to determine 'normal' bone metabolism. [18F]fluoride -PET/CT was used to analyze bone formation adjacent to the cups 1 week, 4 months and 12 months after surgery. Clinical and radiographic evaluation was performed preoperatively, postoperatively and at 2 years. Bone forming activity had a mean of 5.71, 4.69 and 3.47 SUV around the HA- and 5.04, 4.80 and 3.50 SUV around the PC-cups at 1 week, 4 months and 12 months respectively. Normal bone metabolism was 3.68 SUV. After 1 year activity had declined to normal levels for both groups. The clinical results were good in all cases. HA coating resulted in higher uptake indicating higher bone forming activity after 1 week. F-PET/CT is a valuable tool to analyse bone formation and secondary stabilisation of an acetabular cup.

High incidence of migration with poor initial fixation of the Accolade stem

BACKGROUND

Numerous cementless femoral stem design variations are in clinical use. Because initial implant instability and micromotion are associated with aseptic loosening of the femoral component, migration analysis provides an early assessment of implant survivorship.

QUESTIONS/PURPOSES

We determined the (1) migration pattern of the Accolade cementless femoral stem; (2) clinical factors predisposing to stem migration; (3) self-reported patient outcomes; and (4) our current rate of aseptic stem loosening.

METHODS

We retrospectively analyzed 81 femoral stems for aseptic migration using Ein-Bild-Roentgen-Analyse-femoral component analysis. Postoperatively, patients completed the WOMAC and SF-12 questionnaires. We assessed radiographic factors potentially associated with subsidence: indices of bone shape and quality, canal fill of the implant, and radiographic signs of loosening. Minimum followup was 24 months (mean, 29 months; range, 24-48 months).

RESULTS

The average subsidence at 24 months was 1.3 mm (range, 0-1.5 mm). In the first 2 years, 36% of stems subsided more than 1.5 mm. Large stem size was associated with subsidence. Radiolucent lines (> 1.5 mm in three zones) were present in 10% of stems and associated with lower questionnaire scores. The 5-year survivorship for aseptic loosening of the 367 stems was 97% with revision as end point and 95% for radiographic failure.

CONCLUSIONS

The high incidence of migration and stems with radiographic failure raises concerns about patient clinical function and long-term survivorship of this stem design. This migration pattern may be due to poor initial stability with a subsequent lack of osseointegration. Our results differ from radiographic findings and clinical durability of other similar cementless stem designs.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Total hip arthroplasty in the ankylosed hip

Altered biomechanics secondary to hip ankylosis often result in degeneration of the lumbar spine, ipsilateral knee, and contralateral hip and knee. Symptoms in these joints may be reduced with conversion total hip arthroplasty (THA) of the ankylosed hip. THA in the ankylosed hip is a technically challenging procedure, and the overall clinical outcome is generally less satisfactory than routine THA performed for osteoarthritis and other etiologies. Functional integrity of the hip abductor muscles is the most important predictor of walking ability following conversion THA. Many patients experience persistent limp, and it can take up to 2 years to fully assess final functional outcome. Risk factors cited for increased risk of failed THA include prior surgical ankylosis and age <50 years at the time of conversion THA.

Digital comparison of planned and implanted stem position in total hip replacement using a program form migration analysis

AIM

One main goal in primary total hip replacement is the reconstruction of preoperative biomechanical conditions by adequate implant positioning. Our aim was to compare the planned and effectively implanted stem position in using a program for digital migration measurement.

PATIENTS

We examined 120 cases with this new method based on a modification of the EBRA-FCA program and compared these results to direct plain radiographic methods. In addition, the intra- and inter-observer reliability was determined in 50 cases.

RESULTS

We observed a rate of correct prediction of 80% for the size of the stem. The new method revealed a good correlation (0.95 and 0.64 for the position along the stem axis and 0.84 for the stem angle) to direct plain radiographic methods. Regarding the intraclass correlation coefficient for intra- and inter-observer reliability, the results were superior (0.97 vs. 0.81-0.84 and 0.90 vs. 0.74-0.88) compared with direct plain radiographic methods.

CONCLUSION

We concluded that the comparison of the planned and implanted stem position using a modified EBRA-FCA method is more reproducible than direct radiographic measurements.

Porous-coated femoral components with or without hydroxyapatite in primary uncemented total hip arthroplasty: a systematic review of randomized controlled trials

The purpose of this systematic review was to determine the clinical and radiologic benefit of hydroxyapatite coating in uncemented primary total hip arthroplasty. A database of Medline articles published up to September 2007 was compiled and screened. Eight studies involving 857 patients were included in the review. Pooled analysis for Harris hip score as a clinical outcome measure demonstrated no advantage of the hydroxyapatite coating (WMD: 1.49, P = 0.44). Radiologically, both groups showed equal presence of endosteal bone ingrowth (RR: 1.04, P = 0.66) and radioactive lines (RR: 1.02, P = 0.74) in the surface area of the prosthesis. This meta-analysis demonstrates neither clinical nor radiologic benefits on the application of a hydroxyapatite coating on a femoral component in uncemented primary total hip arthroplasty.

Enhanced osseointegration of grit-blasted, NaOH-treated and electrochemically hydroxyapatite-coated Ti-6Al-4V implants in rabbits

Osseointegration, in terms of the bone apposition ratio (BAR) and the new bone area (NBA), was measured by backscattered electron imaging. The results were compared for four implant types: grit-blasted and NaOH-treated Ti-6Al-4V (Uncoated-NaOH), electrodeposited with hydroxyapatite without alkali treatment (ED-HAp), electrodeposited with hydroxyapatite after alkali treatment (NaOH-ED-HAp), and plasma sprayed with hydroxyapatite (PS-HAp). No heat treatment was done after soaking in NaOH. The implants were press fitted into the intramedullary canal of mature New Zealand white rabbits and analyzed, both at the diaphyseal and at the metaphyseal zones, either 1week or 12weeks after surgery. NaOH-ED-HAp already exhibited a higher BAR value than the ED-HAp at 1week, and was as good as the commercial PS-HAp at 12weeks. The NBA value for NaOH-ED-HAp at 12weeks was the highest. The higher content of octacalcium phosphate in NaOH-ED-HAp, as evident from the X-ray photoelectron spectroscopy analysis of the oxygen shake-up peaks, and the associated increase in the solubility of this coating in vivo are considered responsible for the enhanced osseointegration. Taking into account also the reduced occurrence of delamination and the inherent advantages of the electrodeposition process, electrodeposition of HAp following soaking in NaOH may become an attractive alternative for the traditional plasma-sprayed process for coating of orthopedic and dental implants.

Uncemented stems in hip replacement--hydroxyapatite or plain porous: does it matter? Based on a prospective study of HA Omnifit stems at 15-years minimum follow-up

For many years, acrylic cement has been regarded as the unique available means for a long term and secure fixation of components in hip arthroplasty. A new generation of uncemented implants coated in hydroxyapatite (HA) has arisen since the mid-1980s, aiming to provide a 'biological interface' between metal and surrounding bone, and thus the hydroxyapatite interface was defined some years ago as a distinct entity from both cemented and 'plain porous' fixation. Based upon our 20-year experience with the HA Omnifit stem, this paper aims to discuss the efficiency of hydroxyapatite as a means of fixation for femoral components in hip arthroplasty, then examine whether the addition of a calcium phosphate layer induces any adverse effects, and finally make comparisons between HA-coated versus porous hip stems reported in the literature. With respect to fixation of femoral components in hip arthroplasty we report excellent results from the partially coated HA Omnifit stem in our series, with 99.20% of survival rate at 17-year follow-up, these results being consistent and similar to other HA series in the literature. HA 'uncemented' fixation can therefore be considered reliable and efficient. Furthermore, two decades of hydroxyapatite coatings have resulted in the identification of no major adverse effects. In fact calcium phosphate ions participate in the physiological turn-over of bone remodelling, and the HA coating is replaced by new bone formation without any fibrous tissue layer. Since HA particles are biodegradable and do not produce any inflammatory reaction in the surrounding bone, fears of osteolysis or third body wear due to HA debris have not been confirmed. Finally, comparison between HA versus plain porous femoral components through the literature has demonstrated better results with HA than porous alone both in terms of the quantity and quality of bone remodelling, and the potential migration and subsidence of the stem.

Aseptic stem loosening in primary THA: migration analysis of cemented and cementless fixation

Early migration has reportedly been predictive for later implant failure. Using four different migration patterns, this study aimed to analyse migration behaviour of the two types of implant fixation--cemented and cementless--throughout the process of loosening. Migrational behaviour of 69 revised stems (49 cemented, 20 uncemented) was analysed retrospectively with EBRA-FCA (Einzel-Bild-Röntgen-Analyse, Femoral Component Analysis). Uncemented stems failed after early and late onset migration alike, while late migration was the predominant pattern in cemented stems. Mean prosthetic failure after early migration occurred 5.8 (+/-4.4) years postoperatively due to insufficient primary stability. Initially stable stems with late onset migration were revised after 12.4 (+/-4.5) years. Measurement of early migration was found to be a valuable tool to screen short-term and mid-term failure. In the long run the method's sensitivity decreased. Late onset migration, however, preceded long-term failure by a mean of three years.

Results of a hydroxyapatite-coated modular femoral stem in primary total hip arthroplasty. A minimum 5-year follow-up

The use of a modular metaphyseal-diaphyseal femoral stem in primary total hip arthroplasty is infrequent. We analyze 94 ESOP (Fournitures Hospitalieres, Heimsbrunn, France) cementless 2-piece modular stems after a minimum 5 years of follow-up. There were 2 aseptic femoral stem loosenings and no cases with thigh pain. Mean femoral canal filling was 90%. Radiographic ingrowth was obtained in 83 (P < .001). At 7 years, the survival rate for femoral aseptic loosening was 97.8% and no stem was at risk for revision (95% confidence interval, 94.8%-100%). This prosthesis provides good clinical results with absence of pain and excellent radiographic results. It is an option in femora with good bone quality. Femoral osteopenia and cortical widening were infrequent, and the modular metaphyseal-diaphyseal junction was not a problem in vivo.

Bioactive borate glass coatings for titanium alloys

Bioactive borate glass coatings have been developed for titanium and titanium alloys. Glasses from the Na(2)O-CaO-B(2)O(3) system, modified by additions of SiO(2), Al(2)O(3), and P(2)O(5), were characterized and compositions with thermal expansion matches to titanium were identified. Infrared and X-ray diffraction analyses indicate that a hydroxyapatite surface layer forms on the borate glasses after exposure to a simulated body fluid for 2 weeks at 37 degrees C; similar layers form on 45S5 Bioglass((R)) exposed to the same conditions. Assays with MC3T3-E1 pre-osteoblastic cells show the borate glasses exhibit in vitro biocompatibility similar to that of the 45S5 Bioglass((R)). An enameling technique was developed to form adherent borate glass coatings on Ti6Al4V alloy, with adhesive strengths of 36 +/- 2 MPa on polished substrates. The results show these new borate glasses to be promising candidates for forming bioactive coatings on titanium substrates.

[Clinical evaluation tools of total hip arthroplasties]

Total hip arthroplasty is one of the most efficient hip surgery procedures enabling improved function in the vast majority of operated patients. The major long-term complication is aseptic loosening due to an inflammatory response to particle wear debris coming from the bearings. Polyethylene is the key culprit. Currently two solutions are proposed: eliminating polyethylene from the prosthetic articulation or reducing material wear. This leads to the need for reliable tools for evaluating short-term results, predictive of long-term outcome. When the innovation concerns reduction of polyethylene wear, short-term wear should be measured with software methods or radiostereometry. If the innovation concerns improvement of polyethyleneless implants, then short-term migration should be measured with EBRA or radiostereometry. In addition, the long-term retrospective evaluation of large series of patients remains of major interest provided that it is performed with survival analysis. These different methods are detailed in this study, indicating the pros and cons for each solution.

Cementless hemiarthroplasty in femoral neck fractures: evaluation of clinical results and measurement of migration by EBRA-FCA

Aim of the present study was to evaluate migration rates of cementless primary hemiarthroplasty in acute femoral neck fractures. In a longitudinal, prospective study 46 patients were treated by cementless hemiarthroplasty. Clinical follow up was correlated with the EBRA-FCA method. In 30% of all patients stem migration amounted to more than 2 mm; further, these patients were seen to have a high level of activity. A high degree of migration in more than 30% of all patients requires critical scepticism toward further use of the investigated cementless stem as hemiarthroplasty. According to literature, migration of more than 2 mm suggests a high probability of early aseptic loosening. In patients with a low degree of activity good results could be observed; nevertheless, in patients with a high level of activity the combination of the investigated cementless stem with a solid fracture head cannot be recommended.

Tapered hydroxyapatite-coated press-fit stems: any added value?

This study compares the efficacy of hydroxyapatite (HA)-coated press-fit stems versus porous coated press-fit stems with a minimum 2-year follow up. Of the 1152 patients in the study, 69 had an HA-coated grit blasted cemented stem inserted (6%), whereas 1083 (94%) had a porous coated stem inserted. A detailed clinical and radiographic analysis demonstrated that there was no clinical difference at an average 4-year follow up. Similarly, there was no radiographic difference when the HA group was compared with the porous coated group. Thus, there is no need for HA coating on a tapered titanium stem in primary total hip arthroplasty in patients with osteoarthritis.

Long-term results of uncemented acetabular cups with an ACS polyethylene liner. a 14-16-year follow-up study

We assessed the clinical and radiographic results of 40 porous-coated acetabular cups with an Acetabular Cup System polyethylene liner over a minimum 14-year follow-up. Femoral head penetration was estimated using a software package. Fifteen cups were revised, 11 due to polyethylene liner rupture. All cups but two were radiographically stable, and 11 hips showed acetabular osteolysis. The overall femoral head penetration rate in hips without liner fracture with reference to the early penetration point was 0.1188+/-0.070 mm per year. Polyethylene liner fractures were associated with higher early femoral head penetration (P<0.0001) and a vertical cup position (P=0.0016). The 14-year survival without cup revision for any reason was 63.9%, 71.8% with no ACS polyethylene liner fracture and 65.3% with no acetabular osteolysis. Most cups showed a good clinical outcome in general, but major Acetabular Cup System liner failure and osteolysis were frequent. Patients with the ACS cups still in place should be monitored closely.

Total hip arthroplasty with an uncemented hydroxyapatite-coated tapered titanium stem: results at a minimum of 10 years' follow-up in 104 hips

BACKGROUND

The purpose of this study was to evaluate the minimum 10-year results of primary total hip arthroplasty using an uncemented, hydroxyapatite-coated tapered stem. Radiological signs of bone remodeling are also presented.

METHODS

We followed a consecutive series of 105 patients (115 hips), who had had an uncemented, proximally hydroxyapatite-coated Bi-Metric femoral component for a mean of 12.2 years (range 10.0-14.9 years). The average age at operation was 52 years. Detailed clinical and radiological analyses were performed after a minimum of 5 and 10 years. Eight patients (10 hips) had died, and one patient was lost to follow-up, leaving 104 hips for final evaluation. The clinical result was evaluated by the Harris Hip Score, complications, and thigh pain.

RESULTS

All patients still had their femoral components in place at the final follow-up. The average Harris Hip Score after 10 years was 92 (range 50-100) with no deterioration over time. Radiologically, several signs of progressive remodeling were identified, but no stem showed signs of loosening.

CONCLUSIONS

The intermediate clinical and radiological results with this stem are encouraging. In the hands of various surgeons, the stem has performed well in a young, high-risk population.

Tissue engineered ceramic artificial joint--ex vivo osteogenic differentiation of patient mesenchymal cells on total ankle joints for treatment of osteoarthritis

Total joint arthroplasty is the common treatment of severe cases of osteoarthritis. However, complications involving failure of the bone-prosthesis interface are significant, especially in ankle arthroplasty. To prevent this complication, we attempted a tissue engineering approach using the mesenchymal cells of the patient. We collected a small amount of fresh bone marrow cells from the patient's iliac crest and expanded the number of mesenchymal cells. We then applied the mesenchymal cells to a ceramic ankle prosthesis and cultured them to form an osteoblasts/bone matrix on the prosthesis. We used tissue engineered prostheses on three patients suffering from ankle arthritis and followed their progress for at least 2 years. Follow-up X-ray examinations revealed early radiodense appearance (bone formation) around the cell-seeded areas of the prostheses about 2 months after the operation after which a stable host bone-prosthesis interface was established. All patients showed high clinical scores after the operation and did not exhibit inflammatory reactions. These preliminary results indicate that the tissue engineering approach using autologous cultured marrow mesenchymal cells might prevent aseptic loosening of the total ankle arthroplasty.

Effects of calcium ion implantation on osseointegration of surface-blasted titanium alloy femoral implants in a canine total hip arthroplasty model

Osteoconductivity of titanium-alloy implants may be improved when surface-modified by calcium ion (Ca2+) implantation. We studied the effects of Ca2+ implantation on osseointegration of a grit-blasted titanium-alloy stem using a canine total hip arthroplasty model. Fifteen dogs underwent bilateral hip arthroplasties and were sacrificed at 1, 6, and 12 months postoperatively. The hip components were evaluated by radiographic, qualitative, and quantitative histology methods. Radiographically and histologically, both Ca(2+)-implanted and non-Ca(2+)-implanted stems were well integrated. Ca(2+)-implanted stems had greater new bone apposition than non-Ca(2+)-implanted stems, although the difference was significant only at 1 month (15.8% +/- 3.5% of the implant perimeter for non-Ca(2+)-implanted, 25.4% +/- 4.7% for Ca(2+)-implanted, P< .05). This result could be related to chronological decrease of the dissolution rate of calcium ions from Ca(2+)-implanted surface. Although further improvement of the Ca2+ implantation technique for a sustained osteoconductive effect is necessary, Ca2+ implantation may be beneficial for early fixation of titanium-alloy implants.

Hip arthrodesis: current indications and techniques

The management of young adults with severe osteoarthritis of the hip remains a problem because of the increased failure rates of total hip arthroplasty (THA) as well as the prospect of multiple revisions in this population. Although hip arthrodesis is not perceived favorably as an alternative by most orthopaedic surgeons or patients because of the presumption of less than optimal functional outcomes, it is a viable technique, especially for younger patients with a recent history of local infection and/or trauma. With current internal fixation techniques, a fusion rate >80% can be achieved with maximal preservation of bone stock. Proper patient selection and optimal arthrodesis position (flexion of 20 degrees to 30 degrees, adduction of 5 degrees, external rotation of 5 degrees to 10 degrees, and limb-length discrepancy <2 cm) are essential for a successful, long-term result. Back and ipsilateral knee pain are the most common complaints leading to secondary conversion of a hip fusion to a THA. Symptoms improve markedly after conversion. Survivorship of the conversion THA is comparable to that of a primary THA when the patient is older than 50 years of age and multiple surgical procedures have been avoided. However, the procedure can be technically challenging and has a high risk of postoperative complications.