One cementless cup which had porous outer surface with Apatite-Wollastonite glass ceramic (AWGC) coating, was revised 13 years after primary THA because of massive osteolysis expanded to medial iliac wall along the screws. While many retrieved studies of hydroxyapatite-coated cup have been reported, there has been no report on the retrieved cup with AWGC coating. The purpose of this study was to describe this rare case in detail, confirm the bone ingrowth to the porous cup, and discuss on the effectiveness of porous surface with AWGC coating. The patient was a 64 old woman and complained of chronic mild pain around her left groin region. X-ray examination revealed that osteolysis had been expanding around the screws and extended proximally. The revision surgery was performed for the massive osteolysis through Hardinge antero-lateral approach. The retrieved implants included a cementless cup made of titanium alloy (QPOC cup, Japan Medical Materirals Inc.(JMM) Osaka, Japan), the outer surface of which was plasma-sprayed with titanium for porous formation and coated with AWGC in the deep layer. It was found that the polyethylene liner was destructed partially in the supero-lateral portion, but the cup was well fixed to the bone. The bone-attached area was found to be dispersed over the porous surface of the hemispherical cup. Histological examination revealed that matured bony tissue intruded into the porous surface of the cup, and contacted to bone directly, which was also demonstrated in the back-scattered electron image. It was also demonstrated that there were residual silicon (Si) rich regions on the porous surface by the SEM-EDX analysis, which indicated that constituents of AWGC still remained on the surface. On the other hand, the results of elementary analyses in the Si rich regions varied among the sections, which probably indicated that the extent of degradation and absorption of AWGC varied among the sections. AWGC was one of the bioactive ceramics and reported to have an ability to bond to bone earlier than hydroxyapatite (HA). In the present case, though massive osteolysis occurred with aggressive wear, it did not expand on the porous surface, and rather progressed along the smooth surface of the screws. Considering that there are many clinical studies reporting poor clinical results of HA-coated smooth cups, bioactive ceramic coating may function well and bring superior clinical results when combined with porous coated substrate. In our study, though the cause of massive polyethylene wear and intrapelvic giant osteolysis could not be revealed, the porous cup with AW-GC bottom coating was well fixed and gained bone-ingrowth at the porous surface under osteolytic conditions, which may demonstrate the long-term durability of this surface treatment.Case
Poly-L-lactic acid (PLLA) is characterized by its biocompatibility and biodegradability, and is used clinically. In our hospital, we started to use PLLA screws instead of metallic or ceramic screws in the fixation of acetabular bone grafts in total hip arthroplasty (THA) in 1990, because there were concerns about the use of rigid and nonbioabsorble screws, which might contribute to the absorption of the grafted bone and induce metallosis or third-body wear when breakage of the screws occurs. The purpose of this study was to review a series of cemented THA for dysplasia, with structural autograft fixed with PLLA screws. We focused on the survival rate of the acetabular component and radiological change of the grafted bone–socket interface. This study included 104 consecutive cemented total hip arthroplasties (80 patients) performed between July 1990 and December 1995 in our hospital. All patients were followed over 10 years and reviewed retrospectively. The grafted bone trimmed from the excised femoral head was fixed rigidly with 1 or 2 PLLA screws (cancellous lag screws 6.5 mm in bore diameter and 4.1 mm in grove diameter) (Fixsorb; Takiron Co., Ltd., Osaka, Japan). X-ray photographs taken just after the primary operation showed an obscure but still visible radiolu-cent region corresponding to the inserted PLLA screws in many cases. However, X-ray photographs at the final follow-up showed an unclear radiolucent zone at the sites of the PLLA screws, and the osteosclerotic line surrounding the site where the radiolucent zone had been found was confirmed in only 4 cases. Bone union was confirmed radiologically at the grafted site in every case, and there were no cases of early collapse or extravasation of the grafted bone. No positive resorption of the grafted bone was observed in any case. Kaplan–Meier survivorship analysis of socket revision, radiological loosening of the socket, and the appearance of a radiolucent line >
1 mm in the graft–socket interface as the endpoints indicated survival rates of 99%, 97.1%, and 63.5% at 10 years, and 96.6%, 90.2%, and 56.1% at 15 years, respectively. The results of this study indicated that PLLA screws are safe and useful for the fixation of acetabular bone graft concomitant to cemented THA with a careful rehabilitation program. However, because of concern about the mechanical insufficiency of the PLLA screws for THA with an early weight-bearing rehabilitation program, we have used mechanically stronger and bioabsorbable screws made of forged composites of hydroxyapatite and PLLA since 2003.
Removal of femoral bone cement is required for preparation of proper implant bed for reimplantation of a new femoral component in revision total hip arthroplasty. Several devices and procedures have been developed for cement removal, including an extracorporal shock-wave lithotripter and YAG laser, as well as a high-powered drill or burr under the control of conventional fluoroscopic images and an intrafemoral endoscopy. Ultrasonic tools are efficient for removal of bone cement with minimal damage to bone. We use a high-powered burr to remove the deep femoral bone cement under the control of conventional fluoroscopic images, although the problem of this procedure is large exposure of X-ray and two dimensional viewing of burr position which can result in perforation in the third plane. Computer-assisted fluoroscopic navigation system allows the surgeons to provide positional information about surgical instrument to target bones during operations. Two-dimensional image data are obtained using the fluoroscope with a reference frame and stored on a computer workstation. A camera interfaced with the computer then tracks the position of the patient and registered surgical instruments during the procedure. Taking advantage of the real-time guidance of computer-assisted fluoroscopic navigation system, we introduce a valuable technique using computer-assisted fluoroscopic navigation system for performing removal of the cement of the femoral canal in revision cemented total hip arthroplasty.
Kokubo and one of the present authors (T.N) have developed a new technique of bioactive coating using alkaline and heat treatment, which induces the formation of a thin HA layer on the surface of titanium after implantation in the body. This new coating technique is not associated with degradation or separation of the HA coating, because a bone-like apatite layer of 1 μm in width begins to form in the body tissue after implantation. Chemically and thermally treated titanium possesses bone-bonding ability, which has been confirmed by detachment tests. Bone ingrowth into bioactive titanium continues to increase throughout the 26 weeks of implantation, whereas bone ingrowth into non-treated or HA plasma coating implants tends to decrease between 6 and 12 weeks. These findings suggest the long-term stability and osteoconduction of the bioactive layer of chemically and thermally treated titanium. We carried out a series of 70 cementless primary total hip arthroplasties using this coating technique on a porous titanium surface, and followed up the patients for a mean period of 4.8 years. There were no instances of loosening or revision, or formation of a reactive line on the porous coating. Although radiography just after surgery showed a gap between the host bone and the socket in 70% of cases, all the gaps disappeared within a year, indicating the good osteoconduction provided by the coating. Alkaline-heat treatment of titanium to provide a HA coating has several advantages over plasma-spraying, including no degeneration or absorption of the HA coating, simplicity of the manufacturing process, and cost effectiveness. In addition, this method allows homogeneous deposition of bone-like apatite within a porous implant. Although this was a relatively short-term study, treatment that creates a bioactive surface on titanium and titanium alloy implants has considerable promise for clinical application.
We have developed bioactive bone cements manufactured from bioactive glass-ceramic powder and BIS-GMA resin, which has the bone-bonding ability. In the present clinical trial, this bioactive bone cement was used for fixation of total hip arthroplasty (THA) and the clinical results were investigated Two types of bioactive bone cements (high- and low- viscosity type cements) were prepared (Nippon Electric Glass Co. Ltd.). Inorganic filler contained 72.0 wt% AW-GC (apatite and wollastonite containing glass-ceramic) and 27.0 wt% SiO2 powder. All surgery was performed at Kyoto University Hospital between February and October 1996. 20primary THA (20 patients) were performed using bioactive bone cement as a clinical trial. The average age of the patients was 58 years. The average follow-up period was 6 years, 9 months. The diagnosis for 18 hips at the operation was osteoarthritis and 2 hips were rheumatoid arthritis. All sockets and one stem were fixed by bioactive cement, and all but one stem were fixed by PMMA cement. In all cases all polyethylene socket and titanium stem were used (14 KC type THA and 8 KMAX type THA). For the femoral head 22 mm diameter alumina head was used in all cases. If the bone cement is bioactive and shows direct bonding with the bone, wear particles can’t enter the interface and thus prevention of loosening due to bone resorption would be expected. This cement demonstrated satisfactory clinical results, proving to be a promising material for implant fixation.
Zirconia ceramic femoral head has better mechanical properties than those alumina head has. However, it is concerning whether the wear of UHMWPE against zirconia head is as low as that of alumina head. We compared polyethylene wears against 22.225mm alumina and zirconia heads in total hip arthroplasties (THA) occupied in our hospital. Kobelco hip prostheses (Kobelco, Kobe, Japan) were used. Titanium alloy stem was cement-fixed and all-polyethylene acetabular components were articulated with alumina or zirconia femoral heads. In the cases from February 1996 to December 1998, 96 primary cemented total hip arthroplasties (THA) in 87 patients of osteoarthritis were observed with a minimum follow-up of five years. The clinical results were evaluated using JOA hip score (100 in normal hip). There were 46 hips with alumina heads and mean follow-up of 6.2 years, and 51 hips with zirconiaheads and mean follow-up of 5.2 years. Mean ages at operation were 58 years. For each patient, the initial postoperative and the latest anterior-posterior radiographs of the pelvis were selected. With the custom software Image-Pro Plus version 4.0, linear wear and volumetric wear were measured. Clinical results of both heads showed no difference. Linear wear rate of alumina is 0.080±0.047mm/year, while it is 0.147±0.069mm/year for zirconia, significantly higher than alumina (p?0.0001). Volumetric wear rate of zirconia (42.499±20.233mm3/year) is also significantly higher than alumina (27.049±17.216mm3/year) (p?0.0001). The low thermal conductivity of zirconia is thought to cause local high temperature, leading to the phase transformation and lower-temperature aging degeneration (LTAD) of zirconia head surface. In order to solve this problem, alumina-adding zirconia compound ceramics with lower phase transformation were developed. Hip simulator test revealed much lower wear rate of improved zirconia. This will be discussed.
We have been using a Charnley type hip prosthesis with an alumina ceramic head. Three sizes of alumina head, 28, 26 and 22mm, were employed and the Ortron 90 Charnley total hip prosthesis was used at the same period. The objective of this study was to compare the survival rate and the wear rate of those four groups. There were 90, 62, 322 and 88 hips in 28, 26, 22mm alumina head and 0rtron 90 head group. Average age at operation was 49.5, 57.8, 58.0 and 60.6, respectively. A 28 mm prosthesis was indicated for relatively young patients. The mean duration of follow-up was 156, 97, 49 and 110 months, respectively. Twenty patients were chosen at random for each of four groups and the linear wear as seen on X-ray film was measured every two years with a computer and scanner.
The objective of this study was to compare the wear mode of 100 Mrad PE cups run in a hip simulator to retrieved 100 Mrad PE cups, and to evaluate the efficacy of the PE wear model. 15 In-vitro PE cups: 3 each 0,2.5.50,100 and 150 Mrad (9 channel hip simulator, 6.2 million cycle duration, physiological load profile by Paul, 2000N maximum load at 1Hz using 30% bovine serum). 5 Retrieved PE cups: three SOM cups (Mizuho Medical Instrument Co., COP alloy 28 mm head)-0 Mrad after 8 years of clinical use, two 100 Mrad cups after 15 years of clinical use, two T28 PE 2.5 Mrad cups (Zimmer): 18 years and 13 years of clinical use. The cups were examined using a SEM (Philip XL30 FEG) for wear scar locations and PE wear-topography. Original machine marks were observed in the weight-bearing areas of the highly cross-linked in-vitro PE. No machine marks were observed for the 0 and 2.5 Mrad in-vitro cups and none were seen in any of the retrieved cups. The formation of more nodules and fibrils in the 0Mrad cups compared to the extensivley cross-linked cups (in-vitro and retrieved) was striking. The frequency of occurrence and length of the fibrils and nodules was dependent on the dose of gamma irradiation. More ripples were formed in the 2.5 Mrad and higher cups compared to the non-irradiated cups (in-vitro and retrieved). The in-vitro cups formed more ripples than the retrieved cups. In general, the SEM features for in-vitro Mrad cups appeared similar to those of the retrieved Mrad cups. The in-vitro Mrad cups accurately reflected the conditions of the artificial joint in living body. Therefore, comparisons of retrieved PE cups with simulator PE cups appeared to be a very powerful research tool. (2) SEM observation demonstrated far less wear damage in the extensively cross-linked cups than in the non-extensively cross-linked PE. Thus the extensive cross-linked PE cups appeared to be a significant improvement over conventional PE cups in terms of wear resistance.
The results of 278 consecutive primary total hip arthroplasties performed with bone grafting for ace-tabular bone deficiencies were reviewed at an average of 9.0 years (range, 5–23) after surgery. All patients had underlying developmental dysplasia of the hip. For all hips, the grafts used were from the patients’ own resected femoral heads. All but three grafts were screwed to the supero-lateral aspect of the acetabular roof, the exceptions being grafts without internal fixation. Kaplan-Meier survivorship analysis predicted a rate of survival of the acetabular component at 10 years of 97% (95% confidence interval (CI), 94–100%) with revision for aseptic loosening as the endpoint, and of 82% (95% CI, 76–89%), when radiological loosening was used. Trabecular reorientation, as an indicator of graft incorporation, was seen in 89% of the joints between 1.5 and 5 years (mean 3 years), and delayed up to 7 years. Parametric survivorship analysis using the Cox proportional-hazards model indicated that trochanteric non-union, lateral placement of the socket, and delayed trabecular re-orientation of the bone graft, were risk factors for loosening of the acetabular component. Autogenous acetabular bone grafting will be of value for long-term success and has good potential for additional improvement of the results, provided these three risk factors are reduced. In order to promote the trabecular reorientation, we have gradually improved the surgical technique including sizing of bone graft and adaptation technique. By these alterations of the surgical technique, trabecular reorientation of the 51 joints operated after 1993 was completed by 4 years after surgery.
