A 28-year clinical and radiological follow-up of alumina ceramic-on-crosslinked polyethylene total hip arthroplasty: a follow-up report and analysis of the oxidation of a shelf-aged acetabular component.

AIMS: Our aim in this study was to describe a continuing review of 11 total hip arthroplasties using 22.225 mm Alumina ceramic femoral heads on a Charnley flanged femoral component, articulating against a silane crosslinked polyethylene. PATIENTS AND METHODS: Nine patients (11 THAs) were reviewed at a mean of 27.5 years (26 to 28) post-operatively. Outcome was assessed using the d'Aubigne and Postel, and Charnley scores and penetration was recorded on radiographs. In addition, the oxidation of a 29-year-old shelf-aged acetabular component was analysed. RESULTS: The mean clinical outcome scores remained excellent at final follow-up. The mean total penetration remained 0.41 mm (0.40 to 0.41). There was no radiographic evidence of acetabular or femoral loosening or osteolysis. There was negligible oxidation in the shelf-aged sample despite gamma irradiation and storage in air. CONCLUSION: These results highlight the long-term stability and durability of this type of crosslinked, antioxidant containing polyethylene when used in combination with a small diameter alumina ceramic femoral head. Cite this article: Bone Joint J 2017;99-B:1286-9.

Fate of the unrevised cemented stem following cup only revision: 227 hips at an average of 6 years follow-up.

BACKGROUND: After primary total hip replacement, aseptic loosening of the acetabular cup is more common than loosening of the femoral stem. Removal of a well-fixed stem adds to operative time, blood loss, risk of bone loss and fracture. There is limited evidence that isolated cup revision can be a safe option in revision hip arthroplasty. We question the following regarding the unrevised cemented stem after isolated cup revision: 1) Does the unrevised stem require revision after isolated cup revision? 2) When is the stem subsequently revised? 3) Why is the stem subsequently revised? 4) Do unrevised stems exhibit radiographic loosening? HYPOTHESIS: We hypothesise that after isolated cup revision most unrevised stems do not need subsequent revision, and that most do not exhibit evidence of radiographic loosening. PATIENTS AND METHODS: A retrospective analysis of all patients who underwent revision of the acetabular component only during revision hip arthroplasty between March 1970 and July 2013 was carried out. We assessed survival of the unrevised stem, reasons for subsequent revision, plus radiographic analysis for stem loosening. RESULTS: Two hundred and twenty-seven hips were included [215 patients with an average age at the time of primary surgery was 47 (13-70) years]. The Charnley stem was used in 161 cases; C-stem 65, Howse 1. Average time between primary surgery and cup revision was 15.9 (1.6-33.4) years. Average follow-up for all stems post-isolated cup revision was 6.1 (0.1-30.7) years. Twenty-eight stems (12.3%) were subsequently revised 5.1 (0.1-12.6) years after the isolated cup revision. Reasons for subsequent revision were: aseptic loosening (10); infection (8); dislocation (6); unreconstructable joint post-loose cup removal (2); fracture (2). Radiographic review was possible on 140 cases. Five femoral stems were revised and 2 others showed evidence of possible radiological loosening but were not revised. CONCLUSION: To our knowledge this is the largest series showing that isolated cup revision in the place of a well-fixed cemented stem is safe and is associated with ongoing good long-term survival of the stem. LEVEL OF EVIDENCE: Level IV, retrospective case series.

Microseparation, fluid pressure and flow in failures of metal-on-metal hip resurfacing arthroplasties.

OBJECTIVES: Metal-on-metal (MoM) hip resurfacing was introduced into clinical practice because it was perceived to be a better alternative to conventional total hip replacement for young and active patients. However, an increasing number of reports of complications have arisen focusing on design and orientation of the components, the generation of metallic wear particles and serum levels of metallic ions. The procedure introduced a combination of two elements: large-dimension components and hard abrasive particles of metal wear. The objective of our study was to investigate the theory that microseparation of the articular surfaces draws in a high volume of bursal fluid and its contents into the articulation, and at relocation under load would generate high pressures of fluid ejection, resulting in an abrasive water jet. METHODS: This theoretical concept using MoM resurfacing components (head diameter 55 mm) was modelled mathematically and confirmed experimentally using a material-testing machine that pushed the head into the cup at a rate of 1000 mm/min until fully engaged. RESULTS: The mathematical model showed the pattern but not the force of fluid ejection, the highest pressures were expected when the separation of the components was only a fraction of one millimetre. The experimental work confirmed the results; with the mean peak ejection pressure of 43 763 N/m(2) equivalent to 306 mmHg or 5 psi. CONCLUSIONS: The mechanical effect of the high-pressure abrasive water jet is the likely cause of the spectrum of complications reported with metal-on-metal resurfacing. Investigating serum levels of metallic elements may not be the best method for assessing the local mechanical effects of the abrasive water jet.

Charnley low-friction arthroplasty in teenage patients: the ultimate challenge.

Increasing follow-up identifies the outcome in younger patients who have undergone total hip replacement (THR) and reveals the true potential for survival of the prosthesis. We identified 28 patients (39 THRs) who had undergone cemented Charnley low friction arthroplasty between 1969 and 2001. Their mean age at operation was 17.9 years (12 to 19) and the maximum follow-up was 34 years. Two patients (4 THRs) were lost to follow-up, 13 (16 THRs) were revised at a mean period of 19.1 years (8 to 34) and 13 (19 THRs) continue to attend regular follow-up at a mean of 12.6 years (2.3 to 29). In this surviving group one acetabular component was radiologically loose and all femoral components were secure. In all the patients the diameter of the femoral head was 22.225 mm with Charnley femoral components used in 29 hips and C-stem femoral components in ten. In young patients who require THR the acetabular bone stock is generally a limiting factor for the size of the component. Excellent long-term results can be obtained with a cemented polyethylene acetabular component and a femoral head of small diameter.

The principle of low frictional torque in the Charnley total hip replacement.

The design of the Charnley total hip replacement follows the principle of low frictional torque. It is based on the largest possible difference between the radius of the femoral head and that of the outer aspect of the acetabular component. The aim is to protect the bone-cement interface by movement taking place at the smaller radius, the articulation. This is achieved in clinical practice by a 22.225 mm diameter head articulating with a 40 mm or 43 mm diameter acetabular component of ultra-high molecular weight polyethylene. We compared the incidence of aseptic loosening of acetabular components with an outer diameter of 40 mm and 43 mm at comparable depths of penetration with a mean follow-up of 17 years (1 to 40). In cases with no measurable wear none of the acetabular components were loose. With increasing acetabular penetration there was an increased incidence of aseptic loosening which reflected the difference in the external radii, with 1.5% at 1 mm, 8.8% at 2 mm, 9.7% at 3 mm and 9.6% at 4 mm of penetration in favour of the larger 43 mm acetabular component. Our findings support the Charnley principle of low frictional torque. The level of the benefit is in keeping with the predicted values.

Charnley low-frictional torque arthroplasty: follow-up for 30 to 40 years.

Of the 11 054 Charnley low-frictional torque arthroplasties carried out at our hospital between 1962 and 1977, 110 (94 patients) had a minimum follow-up of 30 years with a mean of 32.3 years (30.0 to 40.5). The mean age of the patients at operation was 43.3 years (17.0 to 65.0) and 75.7 years (51.0 to 97.0) at follow-up. Overall, 90% of hips (99) were free from pain and activity was reported as normal in 58% of the patients. A total of 13 hips (11.8%) were revised at a mean follow-up of 32.3 years (30.0 to 39.5), with wear and loosening of the acetabular component as the main indications. The clinical results did not reflect the mechanical state of the implant. Follow-up with sequential radiographs of good quality is essential. Revision for radiological changes alone must be accepted if gross loss of bone stock is to be avoided. Improvements in the design, materials and operative technique, based on the long-term outcome, are highlighted.

Increasing patients' body mass. Are the criteria for testing stemmed femoral components in total hip arthroplasty still valid?

The increasing incidence of obesity in the population is a topic of current interest. This trend is reflected in patients undergoing primary Charnley hip replacement. Over a 21 year period from January 1986 to October 2006, during which 6910 primary operations were performed, the body mass of patients increased at a mean rate of 0.48 kg/year. The findings suggest that the test criteria for the endurance of stemmed femoral components be modified. The maximum load should be increased from 2.3 kN to 2.5 kN to reflect patients' increasing weight. The duration of the test should be increased from 5 x 10(6) cycles during which the 'femoral component shall not fracture' to 10 x 10(6) cycles in order to reflect not only the patients' activity level but also the 4-11 year period at risk for stem fracture, and so 'reflect developing clinical experience'.

Charnley low-friction arthroplasty: survival patterns to 38 years.

We studied survival to 38 years after Charnley low-friction arthroplasty of the hip. We used revision as an end-point, while adopting a policy of regular follow-up and early revision for radiological changes alone if indicated. Between November 1962 and June 2005, 22,066 primary low-friction arthroplasties (17,409 patients) had been performed at Wrightington Hospital by more than 330 surgeons. By June 2006, 1001 (4.5%) hips had been revised and 1490 patients (2662 hips, 12%) had died. At 31 years, where a minimum of 40 hips were still attending follow-up, survival with revision for infection as an endpoint was 95%, for dislocation 98%, for a fractured stem 88.6%, for a loose stem 72.5% and for a loose acetabular component 53.7%. Wear and loosening of the ultra-high-molecular-weight polyethylene acetabular component were the main long-term problems. We conclude that regular follow-up after hip replacement is essential and that all operative findings should be recorded at revision.

The Charnley hip replacement -- 43 years of clinical success.

The Charnley low-frictional torque arthroplasty of the hip with 22.225 mm diameter head and thick ultra high molecular weigh polyethylene cup, both components grouted with cold curing acrylic cement, has reached 43 years of clinical success. Follow-up past 30 years is now available. Over 96% of patients are satisfied with the result. Post operative activity level is a reflection of patient selection. The neuropathic nature of the new joint does not reflect the mechanical state of the arthroplasty: regular follow-up with good quality radiographs is essential. Revisions may have to be undertaken for asymptomatic radiographic changes: a principle that must be understood and accepted before the primary procedure. The long-term problems are wear and cup loosening and strain shielding of the proximal femur. Long-term success will be further extended by understanding and practical application of the principles at the primary procedure and use of low wear materials for the articulation. The operation of total hip arthroplasty marks the beginning and not the end of treatment.

The angle-bore acetabular component and dislocation after revision of a failed total hip replacement.

We reviewed 1039 revision total hip replacements where an angle-bore acetabular component was used. After a mean follow-up of nine years (0 to 20.6), the incidence of revision for dislocation was 2.1% (22 revisions), a success rate of 97.9%. In 974 revisions, where the indication was other than dislocation, the success rate was 98.5%. Of the 65 revisions for dislocation, 58 (89.2%) were successful after the first revision and a further five after the second revision, an overall success of 96.9%. Two patients elected to have their implants removed. Dislocation after revision of failed total hip replacement is a complex issue. There is often no single cause and no simple solution. The angle-bore acetabular component, in combination with a 22.225-mm diameter femoral head, offers a high level of success.

Low-friction arthroplasty of the hip using alumina ceramic and cross-linked polyethylene. A 17-year follow-up report.

We report the results of our continued review of 11 total hip arthroplasties using 22.225 mm alumina ceramic femoral heads on a Charnley flanged stem, articulating with chemically cross-linked polyethylene. There was an initial bedding-in of up to 0.41 mm at the articular surface in the first two years. This had not progressed further, at a minimum follow-up of 15 years. Radiographically no femoral or acetabular component showed loosening or osteolysis.

Wear of the cup in the Charnley LFA in the young patient.

Since wear and loosening of the ultra-high-molecular-weight polyethylene cup are factors which limit the life of an arthroplasty we have attempted to identify factors associated with either low wear (0.02 mm/year or less) or high wear (0.2 mm/year or more). In a series of 1434 Charnley low-friction arthroplasties (1092 patients) 190 (13.2%) showed low wear while 149 (10.4%) showed high wear. We used chi-squared test to assess the significance of various factors. The significant factors of the low-wear group were female gender (p = 0.042), rheumatoid arthritis (p = 0.014), Charnley grade C (p = 0.03) and varus position of the stem (p = 0.003). The use of acetabular cement pressurisation (p = 0.07) and medialisation of the cup (p = 0.07) approached significance. In the high-wear group there was a predominance of men (p = 0.042) with osteoarthritis (p = 0.006) as the underlying hip pathology, and the stem in a valgus position (p = 0.023). Support of the cup by the rim of the acetabulum approached significance (p = 0.07). There was no statistical significance between the two groups for revision for aseptic loosening of the stem or fracture of the stem (p = 0.49). There was a highly significant difference (p < 0.0001) between the two groups for revision for wear and aseptic loosening of the cup, 5.3% compared with 39%. Changes in the cup geometry are probably sufficient to explain the increasing incidence of loosening and revisions with the increasing depth of penetration of the cup. There is much to be gained from the use of a low-wearing ceramic-ultra-high-molecular-weight combination. Tissue reaction to the polyethylene particles cannot be the cause of aseptic loosening of the stem.

Determination of the trabecular bone direction from digitised radiographs.

There is increasing evidence for monitoring the bone trabecular structure to explain, in part, the mechanical properties of bone. Despite the emergence of Computed Tomography, a radiograph is the standard format as it is cheap and used for assessing implant performance. Furthermore, various image-processing techniques developed to assess the trabecular structure from radiographs have regained interest owing to improvements in imaging equipment. This study assessed the precision and accuracy of the Co-occurrence and Run-length matrix, Spatial-frequency and Minkowski-fractal techniques to infer the trabecular direction from radiographs. Ten clinical images of femoral neck regions were obtained from digitised pelvic radiographs and subsequently analysed. These data were also used to generate synthetic images where the trabecular thickness, separation and directions were controlled in order to calculate the accuracy of the techniques. Additionally, a Laplacian noise was added in order to infer the precision of the techniques. All methods assessed the trabecular direction with a high degree of accuracy in these synthetic images including a single direction and no noise. However, only the Spatial-frequency and Co-occurrence matrix methods performed well on the clinical and heavily corrupted synthetic images. This demonstrated the possibility of inferring a linear trabecular direction in clinical conditions.

Wear of enhanced ultra-high molecular-weight polyethylene (Hylamer) in combination with a 22.225 mm diameter zirconia femoral head.

We have prospectively studied the wear of enhanced ultra-high molecular-weight polyethylene (Hylamer) in combination with a zirconia femoral head of 22.225 mm diameter on a cemented, triple-tapered, collarless, polished stem, the C Stem. The 71 patients who underwent total hip arthroplasty had a mean follow-up of six years (3 to 8). No patient died or was lost to follow-up. The clinical results were excellent with 96% of patients satisfied. There were no revisions. Two cups were considered to be loose radiologically. One was avulsed from the cement in a skiing accident, with a periprosthetic fracture of the femur, but has remained stable for more than seven years. One femur shows radiological appearances which are compatible with a healing infection. One femoral component is at risk of loosening. The mean rate of penetration of the cup was 0.22 mm/year (0.06 to 0.55). Our results appear to be within the guidelines set by the National Institute of Clinical Excellence. We have discontinued the use of Hylamer despite excellent clinical results and no revisions to date because the high initial rates of penetration did not settle to the expected low levels within the anticipated time.

Charnley low-frictional torque arthroplasty in patients under the age of 51 years. Follow-up to 33 years.

Between November 1962 and December 1990 a group of 1092 patients, 668 women and 424 men, under the age of 51 years at the time of surgery, underwent 1434 primary Charnley low-frictional torque arthroplasties and are being followed up indefinitely. Their mean age at operation was 41 years (12 to 51). At the latest review in June 2001 the mean follow-up had been for 15 years 1 month. Of the 1092 patients 54 (66 hips) could not be traced, 124 (169 hips) were known to have died and 220 (248 hips) had had a revision procedure. At a mean follow-up of 17 years and 5 months, 759 patients (951 hips) are still attending. In this group satisfaction with the outcome is 96.2%. The incidence of deep infection for the whole group was 1.67%. It was more common in patients who had had previous surgery (hemi- and total hip arthroplasties excluded), 2.2% compared with 1.5% in those who had not had previous surgery, but this difference was not statistically significant (p = 0.4). There were fewer cases of deep infection if gentamicin-containing cement was used, 0.9% compared with 1.9% in those with plain acrylic cement, but this was not also statistically significant (p = 0.4). There was a significantly higher rate of revision in patients who had had previous hip surgery, 24.8% compared with 14.1% in those who had not had previous surgery (p < 0.001). At the latest review, 1.95% are known to have had at least one dislocation and 0.4% have had a revision for dislocation. The indication for revision was aseptic loosening of the cup (11.7%), aseptic loosening of the stem (4.9%), a fractured stem (1.7%), deep infection (1.5%) and dislocation (0.4%). With revision for any indication as the endpoint the survivorship was 93.7% (92.3 to 95.0) at ten years, 84.7% (82.4 to 87.1) at 15 years, 74.3% (70.5 to 78.0) at 20 years and 55.3% (45.5 to 65.0) at 27 years, when 55 hips remained 'at risk'.

Triple taper polished cemented stem in total hip arthroplasty: rationale for the design, surgical technique, and 7 years of clinical experience.

Successful long-term clinical results with the Charnley low-friction torque arthroplasty have identified proximal femoral strain shielding as a long-term problem to be addressed. The problem has arisen because of the load transfer by a distally supported stem that is no longer subject to fracture. To overcome this problem and improve proximal load transfer to the femur, a continuous triple-tapered stem--the C stem--was designed. This article describes the first 500 primary hip arthroplasties at a mean follow-up of 3 years, 5 months (range, 1-7 years). There have been no revisions for aseptic stem loosening, and no stem is considered to be at risk for loosening. In 20% of cases, there was subjective radiologic improvement of the bone-cement interface.

Incidence of loose bodies in an osteoarthritic hip.

In a prospective study of 75 consecutive primary Charnley low friction arthroplasties carried out for osteoarthritis, loose bodies were found in nine hip joints; an incidence of 12%. Whether their presence is the cause or the effect of the condition remains unclear. Their discoid or spherical shape suggests that they were free and had been subjected to sliding or rolling motion. Those of irregular shape may have remained partly attached within the capsule, or become confined to a space.

The effect of activity levels of total hip arthroplasty patients on socket penetration.

Survivorship of total hip arthroplasties (THAs) has been linked to penetration of the femoral head into the polyethylene acetabular cup and to polyethylene wear. The activity level of patients with THAs is considered to be an important factor affecting wear, and the purpose of this study was to explore the relationship between activity as recorded by pedometers and cup penetration. The measurement of daily activity levels of normal subjects and THA patients of various ages are discussed in another article ([1]). Subjects were monitored continuously during 2- to 4-week periods using simple pedometer devices. Patients (n = 54; mean age, 58 years) from the Centre for Hip Surgery at Wrightington Hospital for whom the penetration data also were available were included in the study. The average activity level for the patient group was 1.426 million loading cycles on each hip joint per year. Radiographic penetration measurements were compared for 81 hips in 54 patients with a mean follow-up of 13.1 years (range, 1.3-26.4 years). The overall correlation of penetration with implantation period is known to be poor, however, and did not improve significantly when the penetration was plotted against a new parameter that took account of not only implant life, but also the level of activity and patient weight. The considerable scatter of penetration levels was noted to increase with increasing implantation period, which indicates that in the multifactorial problem of polyethylene wear, other factors, particularly femoral head surface finish or polyethylene deterioration, may predominate.

Comparative study of the activity of total hip arthroplasty patients and normal subjects.

The walking activity of normal subjects and total hip arthroplasty (THA) patients from the Wrightington Hospital for Joint Disease and The General Infirmary at Leeds was assessed by means of electronic pedometers. The principal objectives were to establish the extent to which joint arthroplasty patients recover their activity relative to normal subjects and to establish the number of loading cycles to which prostheses should be subjected in joint simulator studies of implant performance. A further objective was to establish an experimental procedure for the assessment of the role of activity in contributing to the well-known scatter in the measurements of femoral head penetration into acetabular cups in in vivo studies of implant performance. The last-mentioned issue is addressed in another article ([1]). The walking activity of 2 normal subjects of disparate ages was assessed during 1 full year. It was concluded that fair estimates of activity could be achieved by recording pedometer readings during successive 2- to 4-week periods. This approach was adopted in the full assessment of the walking activity of cohorts of normal subjects and THA patients. Linear regression expressions relating the number of steps taken daily and the annual number of loading cycles on each leg to age are presented for normal subjects and THA patients. In all cases, activity declines with age, but it is shown that total joint arthroplasty is not at all restrictive on walking activity-a remarkable testimony to the efficacy of total joint arthroplasty. Attention is drawn, however, to different levels of activity of THA patients recorded in the present United Kingdom study and a similar survey conducted in California.

The calcar femorale in cemented stem fixation in total hip arthroplasty.

The calcar femorale is a vertical plate of bone lying deep to the lesser trochanter and is formed as a result of traction of the iliopsoas which separates the femoral cortex into two distinct layers, the calcar femorale and the medial femoral cortex. They fuse together proximally to form the medial femoral neck. A stem placed centrally will abut against the calcar femorale with little or no space for cement. Clearing of the calcar will offer space for a cement layer, which will support the stem proximally on the posterior aspect. We compared two consecutive groups of Charnley low-friction arthroplasties, with and without clearing of the calcar. In 330 patients who had an arthroplasty without clearing the calcar, there were ten revisions for aseptic loosening of the stem and six other stems were considered 'definitely loose', giving a rate of failure of 4.8%. In 111 patients in whom the calcar was cleared there was only one revision for aseptic loosening and no stems were classed as 'definitely loose', giving a rate of failure of 0.9%. Survivorship analysis has again shown the need for long-term follow-up; the differences became clear after ten years but because of the relatively small numbers, statistical analysis is not yet applicable. We now clear the calcar femorale routinely and advocate optimal access to the medullary canal and insertion of the stem in the area of the piriform fossa.