Introduction. To evaluate the effect of hydroxyapatite coating, two same shape cementless stems were compared in this randomized control trial study. Methods. Between May 2003 and February 2010, 88 patients had a primary cementless total hip arthroplasty with two different types of cementless stems. Forty-three patients had Proarc stems (P group) (Kyocera Medical, Osaka, Japan), and Forty-five patients had Proarc HA stems (HA group) (Kyocera Medical, Osaka, Japan) which was coated with thin (20 micrometer) hydroxyapatite on Proarc rough porous coating. Gender distribution, average age at surgery, average weight and average follow-up period were same in the two groups. The average follow-up period was 8.5 years (range, 5 to 13 years). The average age at the time of surgery was 63 years. Porous acetabular shells and highly crosslinked polyethylene liners made by Kyocera Medical corporation were implanted into all hips. Stems were implanted with a modified Hardinge surgical approach without trochanteric osteotomy. Harris Hip Score was used for clinical evaluation. Post-op radiographs of these patients were evaluated. Fisher's exact probability test was used for statistical analysis. P values of less than 0.05 were considered to be significant. Results. The mean preoperative score and postoperative score of P group were 39 points and 86 points, respectively. The mean preoperative score and postoperative score of HA group were 46 points and 87 points, respectively. All stems were evaluated as bone-ingrown fixation in both groups. The rate of varus inclination was not different between two groups. The rate of severe stress shielding was not different. Discussion. However hydroxyapatite coating is useful for early fixation, the adverse effect, such as delamination for long-term in vivo situation is questionable. There was no significant difference between P-group and HA group in the present study. Longer follow-up is required to evaluate hydroxyapatite coating

Introduction and Aims: Titanium foam implants simulate the trabecular structure of bone to maximise porous space for bone ingrowth. Plasma-sprayed hydroxyapatite coatings work well on non-porous substrates but do not coat the inner surfaces of open-porous substrates. Chemical deposition is an attractive alternative that produces consistent coats on porous surfaces. Method: Titanium foam cylinders (5mm diameter by 25mm length) were implanted bilaterally in 40 rabbit femurs. Twenty implants were coated with 20 microns of hydroxyapatite (T-HA) by electrochemical deposition while 20 implants had no hydroxyapatite coat (T). Osseointegration was measured at six and 12 weeks by automated computerised histomorphometry of scanning electron microscopy images of sections taken through the implant at two levels: diaphyseal and metaphyseal. Bone ingrowth was quantified in the pores and was also measured up to 1mm beyond the surface of the implant to determine the pattern of bone growth. Results: For the T-HA surface, bone ingrowth increased from 35.0 ±8.5 % at six weeks to 41.5 ± 7.4 % at 12 weeks (p < 0.05). For the T surface, bone growth was 14.1 ± 8.8% at six weeks and 11.4 ± 4.2 % at 12 weeks. At both time points mean bone ingrowth was significantly different between hydroxyapatite-coated and non-hydroxyapatite-coated implants, (p< 0.01). No significant differences were noted between the diaphyseal and metaphyseal bone response. Conclusion: For the T-HA surface, bone ingrowth increased from 35.0 ±8.5 % at six weeks to 41.5 ± 7.4 % at 12 weeks (p < 0.05). For the T surface, bone growth was 14.1 ± 8.8% at six weeks and 11.4 ± 4.2 % at 12 weeks. At both time points mean bone ingrowth was significantly different between hydroxyapatite-coated and non-hydroxyapatite-coated implants, (p< 0.01). No significant differences were noted between the diaphyseal and metaphyseal bone response

Purpose: The aim of this work was to assess retrospectively osteofixation and survival of a long custom-made femoral stem with complete hydroxyapatite coating and without locking for replacement of the femoral implant. Material and methods: From 1990 to 1999, 89 stems were implanted for revision total hip arthroplasty. Seventy-five hips were reviewed at one to ten years (mean four years). Radiographic analysis searched for bone damage, osteofixation and implant migration. All measures were taken on the AP views postoperatively and at last follow-up. Results: Revision was performed for aseptic loosening in 75%, for septic loosening in 12%, for fracture in 11% and for instability in 2%. Destruction was SOFCOT stage I in 36%, stage II in 44%, stage III in 17% and could not be assessed in 3%. The femorotomy approach was used in 60% and trochanterotomy in 32% and endofemoral assess in 8%. There were 18% intraoperative fractures, 4.8% postoperative infections and 2.4% dislocations. At last follow-up, the Postel Merle d’Aubigné score was 15.3 and the Harris Hip Score was 77.9. Thigh pain was present in 4%. Bone fixation was considered good in 48%, partial but better than 50% contact in 36% and could not be interpreted in 16%. Complete metaphyseal reconstruction was present in 8%. A piecemeal allograft was used in 89%. Between the postoperative and last follow-up films, 16% of the stems descended a mean 11 mm. Five percent of the stems were removed for infection and one (1.3%) for non-fixation. At five years, 95% of the stems was still in place and 80% at ten years, including removals for infection. All revisions for septic loosening had comparable clinical and radiological results in this series and did not develop secondary infection. Discussion: These results demonstrate the usefulness of the uncemented stems for replacement compared with cemented stems which have a 10% revision rate at five years (SOFCOT 1999). The complete hydroxyapatite coating improves distal fixation of the stem in a healthy zone without compromising secondary proximal fixation and authorising spontaneous metaphyseal bone reconstructions. This may explain the low rate of painful thighs. Modularity and locking could improve the primary fixation and limit descent

This study was conducted to evaluate the clinical and radiographic results on titanium stems that were similar in design but differed with regard to proximal grit-blasted surface texture with and without a hydroxy-apatite (HA) coating. We evaluated 40 patients who had undergone primary total hip replacement by a postero-lateral approach. The stems, all made of titanium alloy, tapered, grit-blasted, collarless, with anterior-posterior fins, did present some differences: in a group of 20 stems a proximal hydroxyapatite coating (thickness: 50 μm) was implanted; in another group of 20 stems the proximal surface was without HA coating. Clinical and radiographic evaluations were performed pre-operatively at 3, 6 and 12 mounths during the first year; than once for the following years.The mean duration of follow-up was 6 years. At the final follow-up examination the Harris hip scores in the HA-coated group (mean, 96 points) and non-HA coated group (mean, 94 points) were similar. Bone-remodelling patterns were similar in the groups and the fast bone integration of the HA coated group. In both groups only two cases of aseptic loosening of the stems were found. After 6 years of follow-up, the clinical and radiographic results among grit-blasted titanium tapered stems with or without Ha coating were perfectly similar. The optimum final bone integration was due just to the singular shape of femur (type B Dorr’s) with an excellent proximal bone stock. The micromotion of implants reduced the bony-anchored stems in two cases

Aims. Biofilm formation is intrinsic to prosthetic joint infection (PJI). In the current study, we evaluated the effects of silver-containing hydroxyapatite (Ag-HA) coating and vancomycin (VCM) on methicillin-resistant Staphylococcus aureus (MRSA) biofilm formation. Methods. Pure titanium discs (Ti discs), Ti discs coated with HA (HA discs), and 3% Ag-HA discs developed using a thermal spraying were inoculated with MRSA suspensions containing a mean in vitro 4.3 (SD 0.8) x 10. 6. or 43.0 (SD 8.4) x 10. 5. colony-forming units (CFUs). Immediately after MRSA inoculation, sterile phosphate-buffered saline or VCM (20 µg/ml) was added, and the discs were incubated for 24 hours at 37°C. Viable cell counting, 3D confocal laser scanning microscopy with Airyscan, and scanning electron microscopy were then performed. HA discs and Ag HA discs were implanted subcutaneously in vivo in the dorsum of rats, and MRSA suspensions containing a mean in vivo 7.2 (SD 0.4) x 10. 6.   or 72.0 (SD 4.2) x 10. 5.   CFUs were inoculated on the discs. VCM was injected subcutaneously daily every 12 hours followed by viable cell counting. Results. Biofilms that formed on HA discs were thicker and larger than those on Ti discs, whereas those on Ag-HA discs were thinner and smaller than those on Ti discs. Viable bacterial counts in vivo revealed that Ag-HA combined with VCM was the most effective treatment. Conclusion. Ag-HA with VCM has a potential synergistic effect in reducing MRSA biofilm formation and can thus be useful for preventing and treating PJI. Cite this article:Bone Joint Res. 2020;9(5):211–218

Background: Tibial valgus, a known complication of leg lengthening by external fixation, has been related to stability of the bonefixator system and, in particular to pin loosening. Hydroxyapatite coating has been reported to enhance the quality of the bone-pin interface. The aim of this study was to compare the incidence of axial deformity between tibial lengthening procedures with hydroxyapatite-coated and non-coated external-fixation pins. Methods: A prospective trial was conducted on 34 symmetrical tibial lengthenings in 17 pathologically-short patients. For each pair of bones, one side to be lengthened with hydroxyapatite-coated pins and the other with standard uncoated pins were randomly selected. The bone angle in the frontal plane was measured before the operation and at the end of the fixation period. The difference was calculated and compared between lengthenings performed with coated and uncoated pins. Results: Mean deviation into valgus of the tibiae was 6.5° with hydroxyapatite-coated pins and 12.5° with uncoated pins (p=0.023). Other factors previously related to valgus deformity did not significantly differ between groups. Conclusions: Tibial lengthenings performed with hydroxyapatite-coated external-fixation pins are less prone to axial deviation in the frontal plane than those without it

Purpose of the study: Locked implants have yielded favourable results for femoral bone reconstruction for revision total hip arthroplasty, but defective integration has also been reported due to insufficient bioactive coating. The purpose of this work was to evaluate a locked pivot with a two-third proximal hydroxyapatite coating. Material and methods: From 1996 to 2007, 158 femoral implants (Linea™) were implanted for hip arthroplasty revision. The 143 cases with more than one year follow-up were reviewed (14 deaths, 1 lost to follow-up); 83 revisions for aseptic loosening, 41 periprosthetic fractures, 19 revisions in an infected context. Patients were reviewed retrospectively by a non-operator observer. These were older patients (mean age 68 years, range 31–93) and 36 patients had complex situations requiring at least two prior prostheses; 25% had severe grade 3 or 4 (SOFCOT) bone lesions and 59% diaphyseal damage. Results: Clinical improvement was significant, the Postel Merle d’Aubigné score improved from 7.7 + 4.3 (0–17) to 15.6 + 2.2 (8–18) at mean 50 months (14–131) (p< 0.001). At last follow-up, 14 patients (10%) reported thigh pain and only seven pivots (5%) had not achieved Engh osteointegration (five with thigh pain two without). There were no fractures. There was on non-union of the femorotomy. According to the Hoffman index, femoral bone regeneration was significant at the metaphyseal and diaphyseal levels. Eighteen of the 19 infections cured, all periprosthetic fractures healed. The implant survival was 88.9% at 91 months (65–96.7%). There were five pivot replacements for non integration and/or thigh pain which resolved in all cases; there were no other pivot replacements. The quality of the metaphyseal and diaphyseal filling was predictive of the quality of the bone fixation of the pivot (p< 0.01). Discussion: Compared with older models of locked pivots, this implant reduced the rate of thigh pain while allowing constantly satisfactory bone reconstruction. The metaphyseal and diaphyseal filling index is the main factor predictive of clinical and radiological success by favouring osteointegration. Maximal filling, obtained with a full range of implant diameters and lengths, contributes to this good result

Purpose: Extracortical bone bridging and ingrowth have been shown to reduce stresses on the stem and cement mantle of tumor endoprostheses. The purpose of this study was to assess the effect of bone morphogenetic protein 7 (BMP-7) delivered by Peri-Apatiteâ (PA, Stryker Orthopaedics) hydroxyapatite coating on porous segmental replacement prostheses. Method: Eighteen mature mongrel canines were implanted with unilateral segmental replacement prostheses made of a cobalt-chromium (Co-Cr) alloy and coated with two layers of sintered Co-Cr alloy beads (diameter 600 to 800mm). The control group consisted of a plain porous coated segmental prosthesis without any PA coating. Group 2 consisted of a PA-coated segmental prosthesis coated with buffer solution. Group three consisted of a PA-coated segmental prosthesis loaded with rhBMP-7 (Stryker Biotech) in a buffer solution carrier. Group 1 had the implant only. Group 2 had the buffer solution evenly applied to the porous coat and group 3 had 2.9 mg of BMP-7 in liquid buffer solution evenly applied. The canines were allowed to fully bear weight without restrictions. The femurs were retrieved at twelve weeks for radiographic and histologic analysis. Results: Gross and radiographic data of the retrieved specimens showed that all six PA-coated implants augmented with BMP-7 had complete bone bridging; only one of the PA-coated implants and only two of the plain porous implants were completely bridged. There was a greater percentage of bone apposition for the BMP-7 augmented PA-coated group compared to both the plain (p=0.0026) and the PA-coated (p=0.0001). There was no difference in bone formation or bone apposition between the plain and PA-coated groups. Histology revealed greater depth of bone ingrowth in the BMP-7 augmented PA-coated group as compared to the plain (p< 0.0001) and the PA-coated (p< 0.0001) groups. There was also significantly greater bone apposition in the BMP-7 augmented PA coated groups as compared to the plain (p=0.0014) and PA-coated (p=0.0067) groups. There was no significant difference in depth of bone ingrowth or bone apposition between the plain and PA-coated groups. Conclusion: BMP-7 when used to augment PA-coated prostheses in a canine segmental defect model can significantly improve extracortical bone bridging and bone ingrowth. PA-coated implants may be considered to deliver the exogenous biological growth factors

Although dynamic hip screw (DHS) is considered the treatment of choice for pertrochanteric fractures, we theorized that external fixation would produce clinical outcomes equal to, if not better than, outcomes obtained with conventional treatment. As external fixation is minimally-invasive, we expected a lower rate of morbidity and a reduced need for blood transfusions. We compared fixation with DHS vs. Orthofix pertrochanteric fixator (OPF) in elderly pertrochanteric fracture patients. Forty consecutive pertrochanteric fracture patients were randomized to receive either 135A1 4-hole DHS (Group A) or OPF with 4 HA-coated pins (Group B). Inclusion criteria were: female, age B3 65 years, AO type A1 or A2 and BMD less than −2.5 T score. There were no differences in patient age, fracture type, BMD, ASA, hospital stay or quality of reduction. Operative time was 64 B1 6 minutes in Group A and 34 B1 5 minutes in Group B (p < 0.005). Average number of post-operative blood transfusions was 2.0 B1 0.1 in Group A, and none in Group B (p < 0.0001). Pain was measured 5 days post-operatively and was lower in Group B (p < 0.005). Fracture varization at 6 months was 6 B1 8A1 in Group A and 2 B1 1A1 in Group B (p = 0.002). In Group B, no pin-tract infections occurred. Pin fixation improved over time, as shown by pin extraction torque (2770 B1 1710 N/mm) greater than insertion torque (1967 B1 1254 N/mm), (p= 0.001). Harris hip score at 2 years was 62 B1 20 in Group A and 63 B1 17 in Group B. This study shows that OPF with HA-coated pins is an effective treatment for this patient population. Operative time is brief, blood loss is minimal, fixation is adequate and the reduction is maintained over time.

Background: Hydroxyapatite (HA) coating is widely used for total hip arthroplasty as it has been suggested to improve implant ingrowth and long-term stability. However, the evidence behind the use of HA in femoral stems is ambiguous. Methods: We investigated a non-cemented, tapered titanium femoral stem that was available either with or without HA coating. This stem had been used in 3,116 total hip arthroplasties (THAs) in 2,608 patients registered in the Swedish Hip Arthroplasty Register (1992–2007). Kaplan-Meier survival analysis and a Cox regression model including type of coating, age, sex, primary diagnosis, and the type of cup fixation were used to calculate adjusted risk ratios (RR) of the risk for revision for various reasons. Results: 63.7% of the stems were coated with HA, 36.3% were uncoated. It was found that the investigated HA-coated stem had an excellent 10-year survivorship of 97.7% (95% CI 96.5–98.9), and that the stem without HA coating had a 10-year survivorship of 97.6% (95% CI 96.2–99.0) when revision due to any reason was defined as the endpoint. There was no significant difference between these two groups (p> 0.05, log rank Mantel-Cox). A Cox regression model showed that the presence of HA coating did not significantly influence the risk of stem revision due to any reason (RR 1.3; 95% CI 0.7–2.4), or due to aseptic loosening (RR 1.0; 95% CI 0.3–3.4). The risk for revision due to infection, dislocation, or fracture was also not affected by the presence of HA coating. Interpretation: Our results show HA coating of this non-cemented tapered stem with excellent 10-year survivorship does not affect the risk for revision. The assumed beneficial effect of HA coating of femoral stems in total hip arthroplasty is thus questionable

The purpose of this study was to evaluate the clinical outcome of a hydroxyapatite (HA)-coated tapered stem and to assess bone remodelling of the proximal femur using quantitative computed tomography osteodensitometry.

Fifty consecutive hips were managed with total hip replacement using the Cerafit Multicone H-A.C. stem with HA coating and the Cerafit Triradius-M press-fit cup (Ceraver Osteal, Paris, France). The mean follow-up was 3 years (range, 2.9 to 4 years). Current criteria were used for clinical and radiological assessment.

Forty-nine hips (98%) were clinically rated good or excellent. The mean preoperative Harris Hip Score was rated 57, and it has improved to 96 at the time of follow-up. The radiographs showed stable fixation by bone ingrowth in all hips. Fifteen patients (15 hips) were eligible for osteodensitometry. The mean decrease of the overall bone density (BD) in the metaphyseal portion of the femur 3 years after insertion of the stem was rated 14.21%, and the mean decrease of the cortical BD was rated 15.52%. The mean decrease of the overall BD in the diaphyseal portion of the femoral component was rated 10.00%, and the mean decrease of cortical BD was rated 7.76%. Little changes were observed underneath the tip of the stem.

The clinical and radiological outcomes of the tapered stem with HA coating at a mean follow-up of 3 years compares favourably with other reports. Results of osteodensitometry show less proximal femur BD loss in comparison to similar investigations performed using uncemented stems.

Problems

Biofilm infections are increasingly associated with orthopedic implants. Bacteria form biofilms on the surfaces of orthopedic devices. The biofilm is considered to be a common cause of persistent infections at a surgical site. The growth and the maturation of biofilm are enhanced by the flow of broth in culture environment. In order to reduce the incidence of implant-associated infections, we developed a novel coating technology of hydroxyapatite (HA) containing silver (Ag). We previously reported that the Ag-HA coating inhibits biofilm formation under flow condition of Trypto Soy Broth + 0.25% glucose for 7 days. In this study, we evaluated whether the Ag-HA coating continuously inhibits the biofilm formation on its surface under flow condition of fetal bovine serum, which contains many in vivo substrates such as proteins.

Purpose of the study: The objective of this retrospective analysis was to examine the functional and radiographic results of 33 resvisions for femoral implants using a long locked stem inserted without cement and coated with hydroxyapatite.

Material and methods: Mean follow-up was two years for 33 patient who underwent revison total hip arthroplasty (rTHA) with implantation of a press-fit long locked hydroxyapatite coated femoral stem (Aura or Linea) between 2000 and 2004. The explanted prosthesis was cemented in 23 cases. The reason for revision was femoral loosentng for 60%, femoral fracture for five pateints, and infection for two. According to the SOFCOT 1999 criteria, ten patients had bone defects score grade III or IV. Femorotomy was performed in 21 cases. Patients were reviewed clinically and radiologically. Function was assessed with the Postel-Merle-d’Aubligné (PMA) score and radiographic analysis determined the quality of osteointegration of the implants and the restitution of bone stock.

Results: There were six early complications (one death, one disloction with sciatic paralysis), and six late complications, mainly related to defective locking. The PMA score was less than 3 for only three patients. Twenty-six patients were satisfied or very satisfied and seven patients reported thigh pain which was generally moderate. The locking was released for five prostheses because of failure or pain (relief observed in three cases). Migration was noted in three cases, illustrating their non-integration. For 15 patients, corticalisation around the lower part of the prosthesis suggested implant mobility. This image was observed in all patients who complained of thigh pain (p=0.057). There was a significant increase in the cortical index, reflecting progression of the bone stock favoring the internal cortex.

Conclusion: This type of implant has provided a solution for the difficult problems of explantation and reimplantation of THA. These prostheses provide satisfactory short-term results and a significant improvement in bone stock. There remains the problem of osteointegration of certain implants. Technical factors can contribute to improved clinical results.

Background: As the understanding of bone repair mechanics has advanced the integrity of the bone pin interface has emerged as a key factor in determining the success of external fracture fixation. The benefits of using pins coated with Hydroxyapatite (HA) are well documented however the thickness of the conventional plasma spray coating precludes its use for modification of the surface of fine features in implants. Consequently new electro-chemical techniques for pre-coating implants with a ‘biomimetic’ HA layer using simulated body fluids (SBF) have been pioneered. In this study we test the hypothesis that varying the technique for deposition of HA by electrolysis of SBF alters the morphology of the HA surface which will modify the level of osseointegration. Method: Three alternative methods of HA coating the Barerre, Redepenning and Kumar techniques were compared. Tantalum coated stainless steel pins were coated then used to stabilise a mid-diaphyseal osteotomy in three sheep using an orthofix fixator for a period of ten weeks. Insertion and extraction torques were measured to calculate the pin performance index (PPI). Sections of the bones were then examined using scanning electron microscopy to determine the percentage of bone in contact with the pin surface and the percentage of new bone formation. Results: The different coating protocols resulted in different HA crystal morphologies. The extraction torque exceeded the insertion torque for both the Barerre and Redepenning methods and their PPI exceeds that of plasma spray coatings. The Redepenning technique was shown to perform sig-nificantly better than both the Barerre (p=0,001) and Kumar (p=0,001) techniques with 49.4% of the pin surface in contact with bone. These results were mirrored on analysis of new bone formation with the Redepen-ning technique showing 70.2% of new bone formation compared to the Barerre (55.4%) and Kumar (53.8%) methods. Conclusion: These results indicate that the Redepenning technique is the most effective for creating a bio mimetic HA coating in terms of bonding to bone and promoting new bone formation. This technique holds significant advantages over the conventional plasma spray technique for example the coating thickness can be easily controlled and additional proteins such as bone morphogenic proteins and antibiotics can be incorporated. It may therefore represent a new era in the use of HA coating.

Osseointegration has been shown to be directly affected by surface roughness and bioactive coatings. This report compares bone response to hydroxyapatite coatings on differing substrate treatments. Titanium cylinders was implanted bilaterally in the distal femora of 30 rabbits. One of three surface treatments was applied to each implant: plasma sprayed titanium surface without hydroxyapatite coating (P), plasma sprayed titanium surface with hydroxyapatite coating (PHA), and acid-etched surface with hydroxyapatite coating (CHA). Osseointegration was measured at 6 and 12 weeks, by histomorphometry of scanning electron microscopy images of histologic sections taken through the implant at three levels: diaphysis, metaphysis, and intermediate. Bone growth was measured up to 3 mm from the edge of the implant to determine changes in patterns of bone growth. Overall, bone response was greatest in the diaphyseal sections. Mean osseointegration was significantly different between hydroxyapatite coated and non-hydroxyapatite coated implants (CHA: 74+10%, PHA: 65+12%, and P: 39+10%, p< 0.01). Both hydroxyapatite coated implants demonstrated increased bone growth closer to the implant which dropped off with increasing distance from the implant. Lower and relatively unchanging levels of bone growth were seen in non-hydroxyapatite coated implants. Osseointegration and bone growth was higher in both hydroxyapatite coated surfaces confirming previous reports. The differences in substrates (acid etched vs. plasma sprayed titanium) did not yield a significant difference in bone growth, suggesting that the hydroxyapatite coating provided a much larger benefit. This study supports the hypothesis that enhanced osseointegration is primarily due to the bioactive coating

Polyimide (MP-1, MMATech, Haifa, Israel), is a high performance aerospace thermoplastic used for its lubricity, stability, inertness and radiation resistance. A wear resistant thin robust bearing is needed for total hip arthroplasty (THR). After independent laboratory testing, in 2006, the author used the material as a bearing in two Reflection (Smith and Nephew, USA) hip surgeries. The first, a revision for polyethylene wear, survives with no evidence of wear, noise, new osteolysis or complications related to the MP-1 bearing after 16 yrs. The second donated his asymptomatic MP-1 hip at 6.5yrs for post-mortem examination. There were no osteoclasts, cellular reaction bland in contrast to that of polyethylene. In 2013 a clinical study with ethical committee approval was started using a Biolox Delta (Ceramtec, Germany) head against a polyimide liner in 97 patients. MMATech sold all liners, irradiated: steam 52:45. Sixteen were re-machined in New Zealand. Acetabular shells were Delta PF (LIMA, Italy). The liner locked by taper. The cohort consisted of 46:51 M:F, and ages 43 to 85, mean 65. Ten received cemented stems. For contralateral surgery, a ceramic or polyethylene liner was used. Initial patients were lower demand, later, more active patients, mountain-biking and running. All patients have on-going follow up, including MP-1 liner revision cases. There has been no measurable wear, or osteolysis around the acetabular components using weight-bearing radiographs. Squeaking within the first 6 weeks was noted in 39 number of cases and subtle increase in palpable friction, (passive rotation at 50 degrees flexion), but then disappeared. There were 6 revisions, four of which were related to cementless Stemsys implants (Evolutis, Italy) fixed distally with proximal linear lucencies in Gruen zones 1 and 7, and 2 and 6. No shells were revised and MP-1 liners were routinely changed to ceramic or polyethylene. The liners showed no head contact at the apex, with highly polished contact areas. There were no deep or superficial infections, but one traumatic anterior dislocation at 7 years associated with 5 mm subsidence of a non-collared stem. The initial squeaking and increased friction was due to the engineering of the liner / shell composite as implanted, not allowing adequate clearance for fluid film lubrication and contributed to by shell distortion during impaction. The revised bearings were “equatorial” rather than polar, and with lack of wear or creep this never fully resolved. Where the clearance was better, function was normal. The “slow” utilization was due to my ongoing concern with clearances not being correct. The revision of 4 Stemsys stems, tribology issues may have contributed, but non “MP-1” / Stemsys combinations outside this study have shown the same response, thought to be due to de-bonding of the hydroxyapatite coating. With correct engineering and clearances, a 3.6 mm thick MP-1 bearing, a surface Ra<0.5, steam sterilized, shows no appreciable wear, and with confidence, can be used as a high performance THR bearing

This study used model-based radiostereometric analysis (MBRSA) to compare migration of a recently introduced cementless hip stem to an established hip stem of similar design. Novel design features of the newer hip stem included a greater thickness of hydroxyapatite coating and a blended compaction extraction femoral broach. Fifty-seven patients requiring primary total hip arthroplasty (THA) were enrolled at a single centre. Patients were randomized to receive either an Avenir collarless stem and Trilogy IT cup (ZimmerBiomet) or a Corail collarless stem and Pinnacle cup (DePuy Synthes) via a posterior or lateral approach. Both stems are broach-only femoral bone preparation. RSA beads (Halifax Biomedical) were inserted into the proximal femur during surgery. Patients underwent supine RSA imaging a 6 weeks (baseline), 6, 12, and 24 months following surgery. The primary study outcome was total subsidence of the hip stem from baseline to 24 months as well as progression of subsidence between 12 and 24 months. These values were compared against published migration thresholds for well-performing hip stems (0.5mm). The detection limit, or precision, of MBRSA was calculated based on duplicate examinations taken at baseline. Patient reported outcome measures were collected throughout the study and included the Oxford-12 Hip Score (OHS), EuroQoL EQ-5D-5L, Hip Osteoarthritis Score (HOOS) as well as visual analogue scales (VAS) for thigh pain and satisfaction. Analysis comprised of paired and unpaired t-tests with significance set at p≤0.05. Forty-eight patients (30 males) were included for analysis; 7 patients received a non-study hip stem intra-operatively, 1 patient suffered a traumatic dislocation within three weeks of surgery, and 1 patient died within 12 months post-surgery. RSA data was obtained for 45 patients as three patients did not receive RSA beads intra-operatively. Our patient cohort had a mean age of 65.9 years (±;7.2) at the time of surgery and body mass index of 30.5 kg/m2 (±;5.2). No statistical difference in total stem migration was found between the Avenir and Corail stems at 12 months (p=0.045, 95%CI: −0.046 to 0.088) and 24 months (p=0.936, 95% CI: −0.098 to 0.090). Progression of subsidence from 12-24 months was 0.011mm and 0.034mm for the Avenir and Corail groups which were not statistically different (p=0.163, 95%CI: −0.100 to 0.008) between groups and significantly less than the 0.5mm threshold (pNo statistically significant differences existed between study groups for any pre-operative function scores (p>0.05). All patients showed significant functional improvement from pre- to post-surgery and no outcome measures were different between study groups with exception of EQ-5D-5L health visual analogue scale at 12 months which showed marginally superior (p=0.036) scores in the Avenir group. This study was not powered to detect differences in clinical outcomes. This study has demonstrated no statistical difference in subsidence or patient-reported outcomes between the Corail hip stem and the more recently introduced Avenir hip stem. This result is predictable as both stems are of a triple-tapered design, are coated with hydroxyapatite, and utilize a broach-only bone preparation technique. Both stem designs demonstrate migration below 0.5mm suggesting both are low-risk for aseptic loosening in the long-term

Sixty-two consecutive primary total hip arthroplasties were prospectively randomized to receive either hydroxyapatite coated (thirty-five hips) or nonhydroxy-apatite coated (twenty-seven hips) femoral prostheses. At a minimum eleven-year followup fifty-one hips (forty-four patients) were evaluated. Only one femoral stem had been revised (secondary to traumatic periprosthetic fracture). Radiographs were available for thirty-nine hips. None of these femoral stems were loose. Harris Hip scores were evaluated for thirty-six unrevised hips and did not differ significantly between the two groups. There appears to be no significant advantage to hydroxyapatite coating for this femoral prosthesis at an average follow-up of thirteen years. There are a paucity of long term randomized controlled trials on results of hydroxapatite coating of femoral prostheses. The purpose of this study was to update the results of a prospective randomized study of a proximally pourous coated, tapered titanium femoral component with and without hydroxyapatite coating. Sixty-two consecutive primary total hip arthroplasties done by one surgeon in fifty-five patients were prospectively randomized to receive either hydroxyapatite coated (thirty-five hips) or nonhydroxyapatite coated (twenty-seven hips) femoral prostheses. At a minimum eleven year followup, three hips (three patients) were lost to followup, and a further eight patients had expired (eight hips). The remaining surviving cohort of fifty-one hips (forty-four patients) were evaluated clinically, including Harris Hip Scores, and radiographically. At an average of thirteen years followup, only one femoral stem had been revised (secondary to traumatic periprosthetic fracture), that being in the hydroxyapatite group. There were eight acetabular revisions in the hydroxyapatite group (thirty-four percent) and four acetabular revisions in the nonhydroxyapatite group (sixteen percent). Radiographs were available for thirty-nine hips. None of these femoral stems were loose. Harris Hip scores were evaluated for thirty-six unrevised hips and did not differ significantly between the two groups. Using endpoints of femoral revision, radiographic loosening, and Harris Hip Scores there appears to be no significant advantage to hydroxyapatite coating for this femoral prosthesis at an average follow-up of thirteen years. Funding: Biomet, Warsaw IN

Aims. Coatings for endo-osseous implants have been developed based on phospholipids. Such coatings promote the formation of a very thin superficial layer which is highly enriched with calcium phosphates. Aim of this study is a comparison of such coatings with an hydroxyapatite coating. Methods. Two phospholipid-based preparations have been compared with a standard hydroxyapatite coating. Preparation S was based on phosphatidyl-serine; preparation C was based on a mixture of phosphatidyl-serine, phosphatidyl-choline and cholesterol. Titanium cylinders wrapped with titanium foam were the metallic substrate for the coatings; they were implanted in the femural canal of New Zealand White rabbits and retrieved after 4, 8 and 26 weeks. A Back Scattered Electron Microscopy analysis followed. Results. Both phospholipid preparations showed to have no inhibitory action on bone apposition and growth and did not elicit any adverse fibrous reaction. Pictures of bone in-growth into the cavities of the titanium foam were present. A tight apposition between bone and coating was evident only in the comparative group sprayed with hydroxyapatite, but this latter coating was often fragmented and its constituent granules were evident. Conclusion. Phospholipid-based coatings showed no inhibitory action on bone apposition and growth and did not elicit any adverse fibrous reaction

Aims: The results of the Mallory Head prosthesis were already described after 10 years. About the hydroxy-apatite coated Mallory Head prosthesis almost no literature is known. We chose a hydroxyapatite coating because of the sealing effect according to Soballe. Methods: In this þrst European study, we followed 152 consecutive primary hip replacements in 126 patients with a proximal hydroxyapatite coated femoral prosthesis for 5.2 to 11.1 years. Results: All but two prostheses showed osseointegration. No osteolysis was seen even in cases with PE-wear. The mean Harris Hip Score increased from 40 (16 Ð 48) to 92 (10 Ð 100). No or only mild pain reported 97%, limping reported 11% postoperatively (90% preop). There was a very low incidence in thigh pain: 3.2%. The morphology of positive bone remodeling depended on the stem þt in the medullary canal. The correlation between tight stem þt and symmetrical cortical thickening was signiþcant (p ≤ 0.001 chi-square test). The same correlation existed between non tight þt and cancellous densiþcations. There was no correlation between the clinical parameters and the radiological phenomena. The 11 year survival was 98.7 (±6.4)%. Conclusion: TheMallory Head hydroxyapatite coated femoral stem has a reliable long-term survival and clinical and radiological result. The hydroxyapatite coating has a protective effect against wear particle migration. The morphology of remodeling depends on stem þt