Reactions of surrounding tissue to the cementless hip implant Ti-6Al-4V after an implantation period of several years. Autopsy studies in three cases

Thirty-Year Minimum Follow-Up Outcome of a Straight Cementless Rectangular Stem

BACKGROUND

Meta-diaphyseal fixation of straight, tapered, uncemented stems has been proven to be very reliable for total hip arthroplasty in 10 to 20 years of follow-up studies. The aim of the study was to evaluate whether the implant survival as well as radiological and functional outcome have changed in patients with a minimum follow-up of 30 years.

METHODS

From a total of 210 patients, who received a straight, rectangular, tapered cementless stem and a threaded cup, there were 37 total hip arthroplasties (33 patients) still available for follow-up after a minimum of 30 years. Patients were examined clinically and radiographically, and revision surgeries were recorded.

RESULTS

There was a low rate of revisions of the femoral stem with a survival probability of 0.92 (confidence interval 0.85 to 0.96) at 30 years. Survival probability of the acetabular component decreased drastically with 0.45 (confidence interval 0.30 to 0.59). Radiographic analysis of the stem revealed radiolucencies in 73% (n = 16), but only in the proximal/metaphyseal part and none of the stems were radiographically loose.

CONCLUSION

In this minimum 30-year follow-up study, a straight rectangular cementless implant continues to provide excellent implant survival and high patient satisfaction. However, survival rates of the whole total hip replacement system were reduced by a high revision rate due to wear-related problems.

Evaluation of peri-prosthetic radiolucent lines surrounding the cementless femoral stem using digital tomosynthesis with metal artifact reduction: a cadaveric study in comparison with radiography and computed tomography

Background

The traditional criterion for the diagnosis of implant loosening in total hip arthroplasty (THA) was once defined as a radiolucent line of >2 mm in width, based on plain radiography. Recent progress in imaging technology has allowed for the identification of complete radiolucent lines of ≤2 mm around the whole prosthesis as the basis for diagnosing component loosening in the absence of component migration. This study aimed to compare the sensitivity and specificity of digital tomosynthesis with metal artifact reduction with those of radiography and conventional computed tomography (CT) for detecting radiolucent lines of ≤2 mm surrounding cementless femoral stems of different widths.

Methods

The medullary canals of 4 cadaveric femurs were broached to 13 mm in diameter. Cylindrical cementless femoral stems with diameters of 9, 10, 11, 12, and 13 mm were sequentially inserted into each femur, creating 5 groups of radiolucent lines 2.0, 1.5-1.6, 1.1-1.2, 0.5-0.6, and 0 mm in diameter, respectively. Imaging by tomosynthesis, radiography, and CT was conducted for each radiolucent line model. The width information of the radiolucent line models was used as a reference standard for calculating sensitivity and specificity: observations in the group of 0 mm were used for calculating specificity, and those in the other four groups were used for sensitivity. The differences in sensitivity and specificity between the imaging methods were compared with chi-square test, and the 95% confidence intervals of improvements in the sensitivity and specificity of tomosynthesis compared with radiography and CT were calculated using mixed effects models.

Results

The overall sensitivity of tomosynthesis (63.3%) for detecting radiolucent lines ≤2 mm wide was significantly higher (P<0.017) than that of radiography (20.5%) and CT (50.2%), an improvement of 58.2%±3.1% (95% CI, P<0.001) and 21.7%±7.1% (95% CI, P<0.001) compared to radiography and CT, respectively. The sensitivity values for detecting radiolucent lines in all four groups by tomosynthesis and CT were significantly higher than those of radiography (P<0.017). Tomosynthesis also had significantly higher sensitivity than CT (P<0.017) in detecting radiolucent line ≤1.2 mm wide. The specificity of TMAR, radiography, and CT for detecting radiolucent lines was 87.5%, 92.5%, and 82.5%, respectively, with no significant difference (P>0.017).

Conclusions

Digital tomosynthesis with metal artifact reduction had significantly higher sensitivity than radiography for detecting radiolucent lines ≤2 mm wide surrounding cementless femoral stems. It also displayed higher sensitivity than CT for detecting radiolucent lines ≤1.2 mm in width. With a higher rate of detection for radiolucent lines narrower than 2 mm, tomosynthesis has the potential to improve the accuracy of early diagnosis of cementless THA stem loosening in clinical practice.

Wrist arthroplasty using prosthesis as an alternative to arthrodesis: design, outcomes and future

We developed an uncemented screw-shaped ball-and-socket wrist prosthesis and modified it during a decade of trails from 1996 to 2005. The final Motec® wrist prosthesis was launched in 2006. Since then we have used this prosthesis in 110 wrists (110 patients) from 2006 to 2018. This article reviews the design, functional outcomes, complications, clinical usefulness and possible future modifications of the Motec® wrist prosthesis.

Late removal of titanium hardware from the elbow is problematic

A retrospective review of 21 patients that underwent bone screw removal from the elbow was studied in relation to the type of metal, duration of implantation, and the location of the screws about the elbow. Screw failure during extraction was the dependent variable. Five of 21 patients experienced hardware failure during extraction. Fourteen patients had titanium alloy implants. In four cases, titanium screws broke during extraction. Compared to stainless steel, titanium screw failure during removal was not statistically significant (P = 0.61). Screw removal 12 months after surgery was more likely to result in broken, retained screws in general (P = 0.046) and specifically for titanium alloy (P = 0.003). Bone screws removed from the distal humerus or proximal ulna had an equal chance of fracturing (P = 0.28). There appears to be a time-related association of titanium alloy bone screw failure during hardware removal cases from the elbow. This may be explained by titanium's properties and osseointegration.

Excellent long-term survival of an uncemented press-fit stem and screw cup in young patients: follow-up of 75 hips for 15-18 years

BACKGROUND

The long-term results of uncemented total hip arthroplasties vary widely due to differences in design, metal alloy, coating, surface structure, and porosity.

PATIENTS AND METHODS

We retrospectively studied 75 cementless Zweymuller SL stems in combination with Endler titanium-backed threaded cups (Z-E) in 70 patients. 35 patients were women, and the mean age at surgery was 52 (24-68) years. 16 patients died and 1 emigrated, 7 patients (of which 1 later died) subsequently underwent revision, and the remaining 47 patients with 50 original arthroplasties were followed up after a median of 16 (15-18) years.

RESULTS

Revision of 8 hips resulted in an 18-year Kaplan-Meier estimated overall survival rate of 88% (CI: 79-96). 6 of 7 cup revisions were due to liner wear and osteolysis, and 1 was due to aseptic loosening. 2 of 3 stem revisions were due to femoral loosening and 1 was due to fracture of the neck of the stem. The clinical results were good, with a mean Harris hip score of 89 (54-100). Half of 70 hips in 65 patients had ectopic bone formation. All unrevised implants were radiographically stable, with a mean liner wear of 0.07 mm/year.

INTERPRETATION

These long-term results demonstrate that the combination of a Zweymuller SL stem and an Endler titanium-backed screw cup is a good hip arthroplasty in young and active patients. A prefixed polyethylene liner is a drawback, necessitating exchange of the whole cup in cases with polyethylene wear.

Characterization, quantification, and isolation of aluminum oxide particles on grit blasted titanium aluminum alloy hip implants

BACKGROUND

This study was undertaken to verify whether or not the microstructure of aluminum alloy implants interferes with the characterization and quantification of aluminum inclusions on their surfaces, resulting from grit blasting.

METHODS

Four factory-fresh prostheses were investigated by scanning electron microscopy and X-ray microanalysis. Specimens were cut out of the stems and the cross-sections analyzed. The specimens were etched in hot 25% hydrochloric acid. The hydrochloric acid was subsequently filtered with a 0.2-microm-pore filter. The filters were scanned using electron microscopy and X-ray microanalysis.

RESULTS

Aluminum oxide particles were found on all investigated stems; the diameter of the particles ranged from 4 to 100 microm. One hundred fifty-four particles were counted per mm(2). No particles were seen on the cross-sections of the implants. Scanning electron microscopy of the Millipore filters revealed aluminum oxide particles.

CONCLUSION

Remnants of grit blasting were found only on the surfaces; none were observed on cross-sections. We conclude that the microstructure of titanium aluminum alloy does not interfere with the identification and quantification of particles. Particles were identified on the filters by electron microscopy and X-ray microanalysis. Aluminum oxide on the surface of grit-blasted titanium aluminum alloy implants is, in fact, a residue of grit blasting.

Improved bone ingrowth and fixation with a thin calcium phosphate coating intended for complete resorption

Bonit is claimed to be a resorbable electrochemically deposited calcium phosphate coating consisting mainly of brushite, which is a hydroxyapatite precursor. This study involved a comparison of Ti6Al4V screw-shaped implants with and without a 15 +/- 5 microm Bonit coating in rabbit tibia and femur, after 6 and 12 weeks of insertion. The biomechanical removal torque test showed significantly increased values for the coated implants after 12 weeks (p < 0.05) but not after 6 weeks of integration. Higher bone-implant contact was found for the coated implants in the tibia after 6 weeks and for both tibial and femoral screws after 12 weeks (p < 0.05). There was no difference in the inflammatory reaction around the implants, and possible grains of the coating could be detected after 6 weeks, but not after 12 weeks of follow-up. This unloaded short-term study has shown promising results for the easily applicable and resorbable coat (Bonit) compared to uncoated titanium-alloy implants.

Radiolucent lines and osteolysis along tapered straight cementless titanium hip stems: a comparison of 6-year and 10-year follow-up results in 95 patients

BACKGROUND

The progress of radiolucent lines (RLs) around the stems of cementless hip endoprostheses and their implications for implant survival are unclear.

PATIENTS AND METHODS

150 consecutive total hip replacements (THRs) were performed between January and July 1993. The presence and development of RLs and osteolyses were monitored with a standardized special radiographic technique, and the results were compared at 6 and 10 years of follow-up in 95 patients.

RESULTS

At 6 years, RLs were detectable in 43 of 95 patients. RLs with an extension of 50% of the respective zone were present in 35 patients, almost all in Gruen zones 1 and 7. 2 patients presented with osteolysis. At 10 years, the RLs were almost identical--both in number and thickness. Only 1 additional osteolytic lesion had developed; no cup osteolyses were detected, and there was no significant polyethylene wear.

INTERPRETATION

The RLs detected at 6 years were virtually unchanged at 10 years. As they did not progress, they would not jeopardize implant stability. However, the osteolyses seen in 3 patients emphasize the importance of follow-up examinations.

Effect of the initial implant fitting on the predicted secondary stability of a cementless stem

A numerical model able to investigate the influence of biomechanical factors on the long-term secondary stability of implants would be extremely useful for the design of new cementless prosthetic devices. A purely biomechanical model of osseo-integration has been developed, formulated as a rule-based adaptation scheme. Due to its complexity, the problem was divided into three steps: preliminary implementation of the model (proof of concept); implementation of the complete model and investigation of the model solution; and model validation. The paper describes the first of these three steps. The model was implemented as a discrete-states machine, and the few parameters required were derived from the literature. It was then applied to a real clinical case. The study was conducted using the frictional contact finite element model of a human femur implanted with a cementless anatomical stem. A stable solution was achieved after between three and 15 iterations for all initial positions considered. Similar initial conditions yielded similar final configurations. The model predicted all initial configurations, with the exception of a partial osseo-integration, ranging between 62% (distal fit) and 78% (proximal fit) of the viable interface. This is in good agreement with the values reported in the literature that never exceed 75%, even in the best conditions, and report better clinical results for proximal fit. For the varus configuration, which lacks cortical support, the algorithm predicted a completed loosening.

Cementless total hip arthroplasty with a tapered, rectangular titanium stem and a threaded cup: a minimum ten-year follow-up

BACKGROUND

We report the results of cementless total hip arthroplasty with a tapered, rectangular titanium stem that was introduced in 1979 and continues to be used today with only minor changes. The aim of the design is to achieve primary stability to resist rotational and axial forces through precision rasping and press-fit implantation of a tapered, rectangular femoral component.

METHODS

Between October 1986 and November 1987, 208 total hip arthroplasties with insertion of a tapered, rectangular titanium stem and a threaded cup without cement were performed in 200 consecutive patients (average age, sixty-one years; range, twenty-two to eighty-four years).

RESULTS

At the time of the latest follow-up, fifty-one patients (fifty-two hips) had died and sixteen patients had been lost to follow-up, leaving 133 patients. Twelve hips had been revised, two in patients who subsequently died, leaving 123 living patients without revision. The median follow-up time was 120.7 months. Five cups needed revision surgery because of aseptic loosening; two, because of massive polyethylene wear; one, because of posttraumatic migration; and one, because of breakage. Three femoral stems were revised: one because of malpositioning (the reoperation was done five days after implantation); one, because of infection; and the third, after multiple failed acetabular revisions. The mean Harris hip score for the patients who did not have revision was 85.4 points (range, 46 to 100 points) at the time of the latest follow-up. Four patients (3%) complained of thigh pain that was not associated with another disorder. According to the criteria of Engh et al., all femoral implants were graded as stable bone-ingrown. The probability of survival of both the femoral and the acetabular component at ten years, with any revision as the end point, was 0.92 (95% confidence interval, 0.88 to 0.97). The probability of survival of the cup was 0.93 (95% confidence interval, 0.89 to 0.97), and that of the stem was 0.99 (95% confidence interval, 0.97 to 1.00).

CONCLUSIONS

The results of arthroplasty with a tapered, rectangular titanium stem combined with a conical threaded cup inserted without cement were excellent at a minimum of ten years. Our data suggest that femoral stem fixation continues to be secure, while the threaded cup is prone to aseptic loosening.

The outcome of cemented vs. cementless fixation of a femoral component in total knee replacement (TKR) with the identification of radiological signs for the prediction of failure

A survival analysis and radiological review were performed on a series of femoral total knee arthroplasty (TKA) prostheses either cemented (150 cases) or cementless, press-fit (201 cases). The internal surface of the femoral components were shot-blast CoCr alloy. The incidence of loosening of the femoral component at 6 years was 9.8% with cementless fixation and 0.6% with cement (P<0.05) at 6 years. Amongst uncemented prostheses, there was no difference in the survival or radiological outcome with the use of a stem as against two condylar pegs. The clinical need for revision may be predicted radiologically 3 years after operation in symptomless patients by noting a change in component position combined with progressive radiolucent lines and osteolysis. Thus, radiological follow-up should be continued for a minimum of 3 years after knee replacement. The use of a stem enabled the detection of radiolucent lines which we believe were missed around prostheses with condylar pegs. Thus, the use of a stem improves the prediction of failure (but does not improve fixation).

Human postmortem retrieval of total hip arthroplasty

Postmortem retrieval of well-functioning prostheses from total hip arthroplasty is essential in determining the quality and success of the implant, implant fixation, and operative technique. This report describes the retrieval procedure, including details on informed consent, retrieval procedure, and types and benefits of specimen analysis. Bone densitometry, roentgenography, and microscopy studies permit a level of assessment of operative and prosthetic performance not obtainable from clinical and in vivo roentgenographic evaluation alone. Findings from these techniques yielding data on stress shielding, bone mineral density, extent of bone-prosthesis apposition and osseointegration, and histologic activity are ultimately of considerable clinical significance. The implementation of retrieval programs, along with establishing early family and patient cooperation and proper planning practices, will continue to contribute invaluably to advances in orthopaedic science.

Femoral remodeling after arthroplasty of the hip. Prospective randomized 5-year comparison of 120 cemented/uncemented cases of arthrosis

We compared radiographically the femurs for 5 years after cemented (Landos Titane) and uncemented (Zweymüller/Endler) hip arthroplasty (THA) for coxarthrosis in 120 patients. The bone changes followed a characteristic time-course with rapid initial remodeling and almost no further changes after 3-4 years. No association between bone changes and clinical results was found. The groups did not differ in bone atrophy and ectopic bone formation, whereas the incidence of distal cortical hypertrophy and proximal radio-opaque double line was higher around uncemented stems. The age and body weight of the patients and the stem size did not affect the bone changes, but women with uncemented stems developed more bone atrophy than did men.

Histological patterns of bone and articular tissues after orthopaedic reconstructive surgery (artificial joint implants)

Revision surgery after failures of joint replacements leads to histological studies on joint and bone tissues close to the implanted material. Aspectic loosening is the main complication. The surgical pathologist has to identify wear debris (metal, polyethylene, polymethylmethacrylate, chiefly) which promotes a histiocytic granuloma. Some surgical procedures such as cup or resurfacing arthroplasties create a new articular surface and a bone remodeling or necrosis. Cemented joint prostheses show various membrane structures between bone and the cement mantle while there is an association of bone resorption and formation. Non-cemented, porous-coated joint prostheses induce little bone ingrowth, even in satisfactory clinical results. Mechanical factors are predominant in massive limb prostheses. For silicone elastomer implants or artificial ligaments, wear of material promotes many tissular reactions. Often used bone grafts show little creeping substitution process in case of homografts, even well-incorporated on X-rays. More retrieval specimen studies are necessary to delineate precise topographical histological lesions, including non-loosened joint implants.