Introduction

Primary hip replacement in young active patients is on the increase. Due to the demands set by the patient, implants used in this patient group should have a proven long-term clinical and radiological outcome. We report our results in patients under the age of 50 using the C-Stem femoral component – a cemented triple tapered polished stem.

Introduction

Large acetabular bone defects caused by aseptic loosening are common. Reconstruction of large segmental defects can be challenging. Various implants and operative techniques have been developed to allow further acetabular revision in cases where bone stock is poor. Reconstitution of bone stock is desirable especially in younger patients. The aim of the study was to review the clinical and radiological results of hip revision with structural acetabular bone grafts using fresh frozen allograft and cemented components.

Introduction

Cross linked polyethylene (XLPE) has gained popularity as a bearing surface of choice for younger patients despite only medium term results being available for wear rates. Concern remains regarding the long-term stability and durability of these materials. In order to address these issues we present the longest radiological and clinical follow-up of XLPE.

Introduction

Severe osteolysis of the femur secondary to aseptic loosening in hip arthroplasty, remains a difficult revision scenario. Multiple techniques have been developed to aid the surgeon, including restoration of bone stock with impaction bone grafting or strut allografts, various distal fixation prostheses and mega-prostheses. Cemented femoral components, with integration of the cement into the cavitations, has largely fallen out of favour. We examined the long-term outcomes with this technique.

The C-Stem in its design as a triple tapered stem, is the logical development of the original Charnley flat-back polished stem. The concept, design and the surgical technique cater for a limited slip of the stem within the cement mantle transferring the load more proximally.

Five thousand two hundred and thirty three primary procedures using a C-stem have been carried out since 1993. We reviewed all 621 cases that had their total hip arthroplasty before 1998.

Sixty nine patients (70 hips) had died and 101 hips had not reached a ten-year clinical and radiological follow-up and had not been revised. Thirty-two hips had been revised before 10 years, none were revised for aseptic stem loosening and no stems. The indications for revision were Infection in 4, dislocation in 3, aseptic cup loosening in 24 and unexplained pain in 1.

The remaining 418 hips had a mean follow-up of 12 years (range 10–15 years). There were 216 women and 173 men, and 34 patients had bilateral LFAs. The patients' mean age at surgery was 53 years (range 16–83 years). Thirty four hips had been revised at the time of review. The reasons for revision were infection in 5, dislocation in 2, aseptic cup loosening in 24 and 1 for neuralgia paraesthetica where the stem was well fixed. Two hips were revised for stem fracture.

There were no revisions for stem loosening but 2 stems were revised for fracture - both with a defective cement mantle proximally. The clinical results are very encouraging and they support the concept of the Charnley cemented low friction arthroplasty, but place a demand on the understanding of the technique and its execution at surgery.

Introduction: Leg length discrepancy in general and leg lengthening in particular has emerged as a topic of interest and a common cause for litigation

Theoretical considerations: Painful mobile hip functions in abduction. The load on the hip is reduced by pelvic tilt to the symptomatic side. For this to be possible the proximal lever - the head neck and the acetabulum - must be relatively intact.

Methods: A method to identify patients at risk for limb lengthening after total hip arthroplasty by establishing the aetiology of abduction deformity of the osteoar-thritic hip.

Clinically: by pelvic tilt to the symptomatic side apparent limb lengthening, restriction of adduction.

Radiologically: by a relatively well preserved geometry of the hip and infero-medial femoral “head –drop” osteophyte.

Results: In a group of 5000 patients presenting for primary Charnley low-frictional torque arthroplasty: 182 (3.64%) 80 males, 102 females, mean age 63 (20–80) were identified as being at risk for post-operative limb lengthening.

Aetiology – Primary: Unilateral 130, Bilateral 10.

– Secondary: Post-surgery 23, post-trauma 10, spinal 6, mixed 3.

122 (67%) had apparent limb lengthening – mean 3.2% and in 43 (24%) limb lengths were equal, 91% had a well preserved architecture and the proximal lever system.

Discussion: The tell tale signs in patients at risk for limb lengthening after total hip arthroplasty are: pelvic tilt to the symptomatic side with apparent limb lengthening, restricted adduction, history of backache, well preserved hip structure and normal contralateral hip.

Conclusion: Awareness of the pattern identifying patients at risk, detailed pre-operative assessment, avoidance of capsule excision and tight hip reduction are essential.

With an increasing number of primary total hip arthroplasties being carried out worldwide, and a lack or inadequate follow-up leading to delays in revision surgery, more complex problems including periprosthetic fracture have to be dealt with at revision surgery.

Unawareness, that clinical results do not reflect the mechanical state of the arthroplasty, together with strain shielding in the femur, progressive endosteal cavitation and stem migration may result in deterioration of the periprosthetic bone stock and femoral fracture.

Acute onset due to the fracture, severe symptoms and poor medical status of the patient usually demands immediate surgical intervention.

We have developed a modular cemented femoral component for revisions where deficiency of the proximal femur, or the femoral fracture, demands a variable extra-femoral portion of the stem. The shaft of the stem is 200mm or longer allowing the extra-medullary position to vary up to 15cm. It has a double polished taper

Between 1985 and 2007 the stem has been used in 79 revisions where there was a periprosthetic fracture. The mean age at surgery was 70 years (37–93) and the mean follow-up was 4 years (0–14 years 10 months). In 86% the primary surgery had been performed at another hospital. In 80% the fracture had united at one year. The main post-operative problem was dislocation in 10 cases between 7 days and 9 years after revision and was most common where the abductors were absent. 2 patients died in the post-operative period. Five hips have been re-revised, 3 for dislocation, 1 for Infection and 1 stem loosening.

Overall revision for periprosthetic fracture using this implant has given good results.

Although the results of this type of surgery are encouraging, this must not be considered as an alternative to regular follow-up and early intervention in cases where progressive loosening and deteriorating bone stock are likely to lead to a more demanding surgery.

Introduction: The triple tapered polished cemented C-stem has evolved from the study on long-term results of the Charnley design, when first fractures of the stem and then proximal strain shielding of the femur and stem loosening were identified as the continuation of the same process. The design utilises the common engineering principle of male (stem) and female (cement) tapers engaging under load, loading the proximal femur.

Methods and Results: The C-stem was tested extensively and introduced into clinical practice in December 1993. Up to the end of October 2007, 4558 have been implanted in primary operations.

None of the 4558 stems have been revised for aseptic loosening or fracture.

The patient’s mean age at surgery was 48 years (range 15–76), and 171 hips with a mean follow-up of 11 years (range 10–13.7) have now passed 10 years. There were 97 females and 64 males in this group with 10 patients having bilateral C-stems. The main underlying pathologies were Primary Osteoarthritis 30%, Developmental Dysplasia of the hip 27% and Avascular Necrosis of the hip 19%.

Clinical outcome graded according to d’aubigne and postel for pain, function and movement has improved from 3.1, 3.1 and 2.9 to 5.9, 5.7 and 5.6 respectively.

A good quality proximal femur had been maintained in 47.1% and improved in a further 29.9%.

Discussion: The results achieved with the C-Stem design and technique are encouraging and support the concept of loading the proximal femur, but place a demand on the understanding of the technique and its execution at surgery.

Introduction. Presentation of results by survivorship analysis method offers uniformity of terminology and comparability of results, an essential aspect of scientific communication. The Swedish National Total Hip Arthroplasty Register (SNTHAR) has set the standards with revision as the failure endpoint.

We set out to examine the survivorship after primary Charnley low-frictional torque arthroplasty (LFA) with revision as the end point, but documenting all the operative findings.

Methods & Results. Between November 1962 and June 2005, 22,066 primary operations in 17409 patients had been carried out at the author’s hospital by over 330 surgeons. By June 2006, 1001 (4.5%) hips have been revised.

Survivorship with revision as the end point was: infection 95%, dislocation 98%, fractured stem 88.6%, loose stem 72.5%, loose cup 53,7%.

Infection and dislocation are early problems. With improved cementing techniques stem loosening does not become a problem until 11 years after the primary. Loosening and wear of the ultra high molecular weight polyethylene cup is a significant long-term problem.

Discussion. Since revision is an event interrupting a process, its timing will influence the survivorship analysis pattern and indications and detailed operative findings will become important issues. Since clinical results do not reflect the mechanical state of the arthroplasty to await symptoms would invariably mean that revisions are likely to be carried out late and as such the complexity of complications are likely to increase. Furthermore, if information gathered is of a single “indication for revision”, and not of the operative findings at revision, the information would be of limited value.

Our conclusion is that regular follow-up after hip replacement is essential. The frequency, judged from the revision patterns, would suggest that every two years would not be unreasonable. Recording of all operative findings at revision is essential.

Introduction: Bone stock and cement-bone interface in revision total hip replacement (THR) for deep infection have never been investigated in the literature, while they are known to be important for aseptic loosening. The purpose of this study was to assess preoperative bone stock and immediate postoperative cement-bone interface as factors affecting infection control and mechanical outcome after revision THR for deep infection.

Methods: This study included 115 cases in which revision THR with antibiotic-loaded cement was operated for infected hip replacement by a single surgeon with minimal follow-up of five years (range 5–27 years). Preoperative bone stock was classified into four grades (Grade 0: No bone loss, Grade 1: Demarcation, Grade 2: Localized cavitation, Grade 3: Extensive bone loss). The immediate postoperative cement-bone interface was also graded into four categories (Grade A: White-out, obscure interface, Grade B: Clear line, no measurable gap, Grade C: Gap> 1mm, Grade D< 1mm). These two factors were analysed with regard to infection control and mechanical survival of implants after surgery.

Results: Bone stock did not have significant influence on infection control while it affected mechanical outcome. The cement-bone interface was an affecting factor for not only the mechanical survival of implants but also the cure of infection.

Discussion: There was a good chance of curing the infection even with extensive bone loss. Good cement fixation was an important factor with regard to infection control as well as the mechanical survival of implants. The results suggested that it might be important to shield the medullary space from the infected joint space with antibiotic-loaded cement.

Introduction: We describe the association between postoperative femoral stem radiological appearances and aseptic failure of THA (total hip arthroplasty).

Methods: A retrospective review of records and radiographs of all patients attending for follow-up between August 2002 and August 2003 who had a cemented Charnley femoral stem and either a cemented polyethylene acetabular cup inserted. Femoral stem aseptic loosening was defined either by findings at revision surgery, the definite radiographic loosening criteria of Harris or progressive endosteal cavitation across zones as described by Gruen. Well-fixed control THA’s were defined as those that demonstrated none of the radiographic features of aseptic loosening or ‘at risk’ signs as described by Wroblewski. Parameters measured were: Alignment, Barrack grade of cementation, cement mantle width of the cement mantle and the presence and width of any radiolucent lines

Results: 63 hips were entered into the aseptic failure group and 138 into the control group. The alignment of the femoral stem was not associated with failure (p=0.283). Thickness of the cement mantle was statistically associated with failure in Gruen zones 6 (p=0.040) and Gruen zone 7 (p=0.003). A significant association for the presence of radiolucent lines was found for Gruen zones 3 (p=0.0001) and 5 (p=0.0001). The grade of cementation as measured by the Barrack grade was strongly associated with failure for grades C (p=0.001) and D (p=0.001).

Discussion and conclusion: This study has demonstrated that easily applied radiological criteria can be used to identify ‘at risk’ Charnley THA’s from the immediate post-operative AP radiograph.

Introduction. Preoperative bone stock and cement-bone interface in revision total hip replacement (THR) for deep infection have never been investigated while they are both well known to be important for mechanical outcome after revision THR for aseptic loosening.

Purpose. The purpose of this study was to assess pre-operative bone stock and immediate postoperative cement-bone interface as factors affecting infection control after one stage revision THR for deep infection.

Material and methods. This study included 115 cases which satisfied following conditions; a) One stage revision THRs for deep infection were carried out by a single surgeon. b) Follow-up of more than five years was done. Preoperative bone stock was classified into four grades (Grade 0: No bone loss, Grade 1: Demarcation, Grade 2: Localized cavitation, Grade 3: Extensive bone loss). Immediate postoperative cement-bone interface was also graded into four categories (Grade A: White-out, obscure interface, Grade B: Clear line, no measurable gap, Grade C: Gap within 1mm, Grade D: Gap more than 1mm). These two factors were analyzed in view of infection control after surgery.

Results. Preoperative bone stock did not show significant influence on infection control. Immediate postoperative cement-bone interface was an affecting factor for cure of infection.

Conclusion. There was a good chance of cure of infection even in cases with significant bone loss. Good cement fixation appeared to be important in view of infection control. The results suggested the importance of shielding of medullary space with antibiotic-loaded cement from infected joint space in revision THR for infection.

A single dislocation after total hip arthroplasty may not be a problem, once it becomes recurrent it rapidly undermines patients’ confidence. With an increasing number of revisions the problem of dislocations is likely to increase. The study and development of methods of prevention and management must proceed in pace with revision surgery.

We have designed a new cup: the angle-bore cup – to simulate both the structure and the function of the natural acetabulum with freedom of flexion, adduction, internal rotation and stability in the opposite direction. In its manufacture the centre of the hemisphere of the plastic is approached at an acute, less than 90 degrees angle, to the face of the cup creating a chamfer anteriorly and a recess postero-superiorly. The cup is side specific and cannot be reversed.

The angle-core cup was used in conjunction with a 22.225mm diameter head of the Charnley design with the exposure by trochanteric osteotomy. One thousand and thirty nine revisions were carried out: 505 were males and 534 females, mean age 65 (22.2 – 93.3): 66% were referred from other units. The indications for revision were: loose and worn cup 740, loose stem 553, deep infection 212, dislocation 65, fractured stem 51, bent stem 3, unexplained pain 17. There were 30 post-operative dislocations 2.9%; 22 (2.1%) had to be revised for recurrent dislocation. Of the 65 cases where dislocation was the original indication for revision 7 (10.8%) had to have further revision for dislocation.

(In 2330 primary Charnley low frictional torque arthroplasty with 22.225 mm diameter head and the angle-bore cup, there were 17 dislocations (0.73%); seven having to have revision for dislocation – a revision rate of 0.3% with a mean follow-up of 6.2 years.)

Full exposure, preservation of soft tissues, correct placement of components ensures stability in primary total hip arthroplasty. The same principles apply to revisions where the first attempt produces best results.

Dislocation after revision of 2.9% and re-revision for dislocation of 2.1% has been achieved with the 22.225 mm head and angle-bore cup. Advantages of the low-frictional torque can be maintained and low rate of dislocation achieved, even in revision surgery, using a 22.225 mm diameter head and the angle-bore cup.

We describe the association between immediate postoperative radiological appearances and early aseptic failure of THA having compensated for the methodological flaws in previous similar studies. 63 hips were entered into the aseptic failure group and 138 into the control group. Alignment of the femoral stem was not associated with failure (p=0.283). Thickness of the cement mantle was associated with failure in Gruen zones 6 (p=0.040) and 7 (p=0.003). A significant association for the presence of radiolucent lines was found for Gruen zones 3 (p=0.0001) and 5 (p=0.0001). Grade of cementation was associated with failure for Barrack grades C (p=0.001) and D (p=0.001). This study has demonstrated that easily applied radiological criteria can be used to identify at risk THAs from the immediate post-operative AP radiograph.

Introduction and Aims: The aim of this study was to evaluate the efficacy of one stage revision THA for deep infection with a long-term follow-up.

Method: One stage revision THA for deep infection was carried out in 273 joints on 262 patients by the senior author between 1974 and 2000. All infected hip replacements were primarily treated with one stage revision THA, regardless of microorganisms at the authors’ unit unless bone stock in the hips was too poor for implant fixation. This study included 162 revisions in 154 patients for which a minimum follow-up of five years (range 5.1 to 27.6 years; average 12.3 years) had been done. Fifty-two cases (32.1 %) had had discharging sinus by the time of revision surgery for infection.

Results: One hundred and thirty eight (85.2 %) hips were free of infection at the time of the latest follow-up. Twenty cases (12.3 %) had reoperation for recurrent infection. Four hips (2.5%) maintained their implants with the evidence of infection. Twenty-two cases (13.6 %) showed radiological loosening. Thirteen cases (8.0 %) were revised again for reasons other than infection (12 for aseptic loosening and one for dislocation).

Conclusion: Deep infection is one of the most serious complications after total hip arthroplasty (THA). This study presented the longest follow-up, with a large number of cases in revision THA for deep infection. The results suggested that one stage revision was an effective treatment for deep infection of hip arthroplasty.

Introduction and Aims: The purpose of this study was to assess pre-operative bone stock and immediate postoperative cement-bone interface as factors affecting infection control and mechanical outcome after one stage revision THR for deep infection.

Method: This study included 115 cases which satisfied the following conditions: 1) One stage revision THR for deep infection was the primary intervention for infected hip replacement by a single surgeon (BMW) unless the bone stock was too poor for fixing implants; 2) follow-up of more than five years; 3) A complete series of radiographs was available for radiological study including pre-operative and immediate post-operative ones. Pre-operative bone stock was classified into four grades (Grade 0: No bone loss, Grade 1: Demarcation, Grade 2: Localised cavitation, Grade 3: Extensive bone loss). The immediate post-operative cement-bone interface was also graded into four categories (Grade A: White-out, obscure interface, Grade B: Clear line, no measurable gap, Grade C: Gap> 1mm, Grade D< 1mm). These two factors were analysed with regard to infection control and the mechanical survival of implants after surgery.

Results: Bone stock did not have significant influence on infection control, while it did affect mechanical outcome. The cement-bone interface was an affecting factor for not only the mechanical survival of implants but also the cure of infection.

Conclusion: There was a good chance of curing the infection even with extensive bone loss. Good cement fixation was an important factor with regard to infection control, as well as the mechanical survival of implants. The results suggested that it was important to shield the medullary space from the infected joint space with antibiotic-loaded cement in revision THR for deep infection.

We explored the association of post-operative pyrexia following hip arthroplasty and the development of deep infection Method: The postoperative temperature records of 80 patient’s following primary hip replacement were retrospectively analysed. Thirty-one patients had revision surgery at a mean time interval of 37.2 months (range 5–74 months) for confirmed deep prosthetic infection. The control group of patients were asymptomatic at a mean follow-up of 31.5 months. There were 28 patients with an uneventful clinical outcome following surgery and 21 patients who had developed a systemic infection during their stay in hospital. The maximum daily temperature of each patient was recorded. Results: The mean peak temperature of patients with deep prosthetic infection was significantly lower then patients with a systemic infection or a normal clinical recovery following surgery (p=0.01). The difference between the peak post-operative temperature and the preoperative temperature was also significantly lower in patients who subsequently required revision surgery for prosthetic infection (p=0.007). Conclusion: Patients with deep prosthetic infection have a lower pyrexia response then patients with either an uneventful clinical recovery or the development of a systemic infection following total hip replacement. Pyrexia is part of the acute phase response following surgery is mediated by cytokines including IL-1 and IL-6, which are also involved in activation of the patients cellular and humoral immune response. A low pyrexia response following surgery may therefore also be suggestive of reduced acute phase response to the potential wound contamination produced during surgery with a consequence of subsequent prosthetic infection.

Pyrexia in the post-operative setting has often been associated with a possible systemic or wound infection. We assessed whether there is any justification for our concern regarding post-operative pyrexia following hip arthroplasty and subsequent deep prosthetic infection.

We undertook an assessment of the clinical outcome of 97 sequential patients who underwent 103 primary hip arthroplasty for primary osteoarthritis replacements. Daily temperature and systemic complications in the post-operative period were recorded. Clinical outcome was measured using an Oxford hip questionnaire.

Patients had a mean follow-up of 5.2 years (range 3.5–7.2years)

We reviewed the postoperative temperature records of 80 patients who had undergone primary total hip replacement. Thirty-one patients had required revision surgery at a mean time interval of 37.2 months (range 5–74 months) for confirmed deep prosthetic infection. The remaining Forty-nine patients were asymptomatic at a mean follow-up of 31.5 months.

Study 1

Post-operative pyrexia of 38 degrees Celsius was present in 51% of patients undergoing primary hip replacement in the first post-operative week but in 21.1% no etiological cause could be identified. Clinical outcome measured by an Oxford hip questionnaire was not influenced by the post-operative temperature pattern.

Study 2

The mean peak temperature on the first post-operative day was significantly lower in patients with deep prosthetic infection then patients with a clinically normal outcome (p=0.01).

Post-operative pyrexia is clearly not uncommon following primary arthroplasty and its presence should not be regarded as detrimental. Pyrexia in the postoperative setting is a component of the acute phase response to trauma and study 2 demonstrates patients who develop a low-grade infection following arthroplasty may have a diminished febrile response to surgical trauma which may be an indirect representation of a diminished immune response to surgical trauma or infection

Deep infection is one of the most serious complications after total hip replacement (THR). The aim of this study is to evaluate the efficacy of one stage revision THR for deep infection with a long-term follow-up.

One stage revision THR for deep infection was carried out in 285 joints on 274 patients by a single surgeon (BMW) between 1974 and 2001. All infected hip replacements are primarily treated with one stage revision THR at the authors’ unit unless bone stock is extremely poor. This study included a review of 162 revisions in 154 for which a minimum follow-up of five years had been done. The mean duration of follow-up was 12.3 years.

Trochanteric osteotomy was done for extensive resection of infected tissue and removal of cement. Both cups and stems were revised with bone cement. Antibiotic-loaded cement was used in 152 cases (93.8%). Further antibiotics were commenced systemically for 6–12 weeks postoperatively.

Failure of infection control was defined as a) reoperation for recurrent infection or b) clinically persistent infection. Infection control. One hundred and thirty eight hips (85.2%) were free of infection at the time of the latest follow-up. 1) No sinus group (N=110): Success rate was 82.7 %. 2) Sinus group (N=52): Success rate was 90.4 %.

This study presents the longest follow-up with a large number of cases in revision THR for deep infection. At least, history of discharging sinus was not considered as a contraindication. The results suggested that one stage revision was an effective treatment for deep infection of hip replacement in the long term.

Ultra high molecular weight polyethylene (UHMWPE) was introduced into clinical practice by Charnley in November 1962 and has remained the standard material for the hip and other total joint arthroplasties.

Wear of the UHMWPE cup, although studied from the beginning, did not appear to be a clinical problem although Charnley suspected that this would be so in the long term.

A review of the outcome of the Charnley low-friction arthroplasty in patients under the age of 40 years at the time of the operation has shown that the incidence of cup migration was exponentially related to the depth of cup penetration. A prospective study using 22.225 mm alumina ceramic (Al 20 3 ) head articulating with cross linked polyethylene was set up with the initial penetration of 0.2 – 0.4 mm in about 2.5 years with no further penetration. The clinical results mirrored closely the experimental results obtained with the identical set of materials and design. The clinical results have now reached 14 year follow-up and the initial total penetration of 0.2 – 0.4mm has remained unchanged.

Review of long term results of the Charnley LFA has shown a mean penetration rate of 0.1 mm/year (0.02 – 0.6). With a mean penetration rate of 0.1 mm/year, the revision rate for cup wear and loosening in patients under the age of 50 at the time of the LFA, and with a follow-up to 32 years, is in the region of 10%. If the penetration rate remained at 0.02 mm/year or less then no cups have been revised for aseptic loosening. Ceramic / UHMWPE articulation is the next stage of evolution of the Charnley LFA. A prospective study using zirconia 22.225 mm head is approaching 7 year follow-up in over 1000 cases.

A prospective study of Charnley low friction arthroplasty in patients under the age of 51 at the time of surgery.

1092 patients, 668 women and 424 men, mean age 41 years (12–51) at the time of surgery had 1434 Charnley low-friction arthroplasties carried out between November 1962 and December 1990. At mean follow-up 14.2 years (1 – 32), 742 patients (973 hips) are still attending and patients’ satisfaction with the outcome is 96.2%. Survivorship was 95.24% at 10 years and 58.67% at 27 years.

Patients who had had previous hip surgery had revision rate 24.8% compared with 14.1%. Patients with rheumatoid arthritis had fewer revisions than those with developmental hip dysplasia or primary osteoarthritis. Large 43 mm diameter cup gave lower revisions for aseptic cup loosening as compared with 40mm cup. Presence and preservation of subchondral plate, rim support compared to medialization of the cup, use of acetabular cement pressurizer and the reduced diameter neck (10mm) all made a contribution to reducing the incidence of revisions for aseptic cup loosening. Closing the medullary canal with bone block reduced the incidence of aseptic stem loosening. Use of the brace reamers did not affect the outcome and there appears to have been no advantage with the flanged stem.

The long-term problem was the increasing incidence of revisions for aseptic cup loosening. This was exponentially related to the depth of cup penetration by the head of the femoral component.

The long term clinical results of the Charnley LFA remain excellent even in young patients. Rim support of the cup, preservation of the subchondral bone of the acetabulum, cup flange and pressurising of the acetabular cement all make a significant contribution. Distal closure of the medullary canal and central position of the stem are of benefit, but reaming the medullary canal to cortex must be avoided. The long-term problem has been highlighted again as: wear and cup loosening.

We retrospectively analysed three hundred and one infected total hip replacements. Infection was defined on the basis of the surgeons clinical impression. This included a thorough history and physical examination, laboratory and radiographic evaluation. Peri operative findings were also taken into consideration.

Despite the overt appearances of sepsis fifty seven of these three hundred and one cases demonstrated no bacterial growth. These were excluded from the microbiological analysis.

The remaining two hundred and forty four cases oven bacteriological evidence of deep infection. Thirty seven cases grew two different organisms both of which were felt to be clinically significant. The remainder grew a single organism. Hence a total two hundred and eighty one bacteriological isolates were grown.

Coagulase negative staphylococcus accounted for 54.8%, staphylococcus aureus 13.5%, streptococci 8.9%, Escherichia coli 6.1% and diptheroids 2.5%.These organisms were plated out in a standard fashion against a variety of antimicrobial agents.

We analysed ten antibiotics and their sensitivity profiles against the spectrum of organisms demonstrated by this series.

Best antimicrobial coverage by a single antibiotic was afforded by fucidic acid (85.3%) and erythromycin (79.6%). Gentamicin was found to be sensitive to only 76.1% of the bacteria present at the time of revision for deep infection.

Combining gentamicin with other antibiotics improved the theoretical coverage. A combination of gentamicin and fucidic acid demonstrated a 97.5% coverage. Gentamicin with erythromycin gave 95.2%.

When treating the infected arthroplasty it may be beneficial to add extra antibiotics to bone cement. This may either be to the cement spacer in a two stage revision or to the definitive cement in a single stage revision. We would suggest that fucidic acid or erythromycin would be good candidates for this. These candidates should also be considered when designing the next generation of combination antibiotic acrylic bone cements.

Bacterial resistance in joint replacement surgery is an emerging problem. A review of the bacteriology from infected revisions performed at Wrightington over the past 5 years has shown that the most common organism is coagulase negative staphylococcus (59%), followed by staphylococcus aureus (17%).

The sensitivity profiles are shown below.

Gentamicin is the most commonly pre formulated antibiotic added to acrylic bone cement. The above data clearly demonstrates that for 32% of infected cases gentamicin alone is inadequate prophylaxis. As a consequence of this the use of additional antibiotics for resistant cases is becoming commonplace.

The aim of this study was to investigate the mechanical properties of additional antibiotics in acrylic bone cement.

The 7 antibiotics listed above were selected on the basis of sensitivity to organisms isolated at revision for deep infection. Each was added at a loading of 1g active to CMW1 RO (plain) and CMW1 G (gentamicin). The antibiotics were mixed with the polymer by hand. The cement was then mixed as per manufacturer’s instructions.

Dough and setting times were noted. Standard samples were produced using ISO approved moulds. Each antibiotic/cement combination was tested for compression strength, impact strength and flexural strength.

All antibiotic/cement combinations performed as well as the control mix when tested for compression and impact strength. The flexural strength results for fusidic acid and erythromycin when added to acrylic cement were comparable to the control mix. Flucloxacillin, clindamycin and teicoplanin did lower the flexural strength to just below acceptable limits. However Vancomycin when added at 1g active reduced the flexural strength of acrylic bone cement significantly.

Although vancomycin may remain one of the last bastions of antibiotic therapy our study suggests that’s its addition to acrylic bone cement significantly weakens its mechanical properties. We would advise caution in its use as this may reduce the chances of long term success when undertaking revision for deep infection.

Objective: To study the incidence of MRSA (Methicillin resistant Staphylococcus aureus) at pre-operative screening and relate this to positive cultures of the tissue in joint replacement surgery.

Setting: Elective joint replacement centre with routine MRSA screening facility.

Design: Retrospective review of MRSA screening and positive tissue samples taken during one year period from 1.11.99 to 31.10.00 in hip and knee replacements.

Results: Eighteen (18) out of the 2867(0.7%) screens performed on patients undergoing joint replacement surgery had MRSA isolated from one source or other. However, no MRSA was found from tissue samples taken during the surgery. But 63 isolates from 499 tissue samples (12.6%) were reported as coagulase negative staphylococcus, out of which 28(44%) were resistant to Methicillin.

After observing the incidence of Methicillin resistant coagulase negative staphylococcus during one year, we reviewed the tissue culture reports in revision hip replacements from May 1974 till July 1999. Two hundred ninety-one (291) positive organisms were isolated from 337 cultures, out of which 57.5% were coagulase negative staphylococcus 11.9% staphylococcus aureus. Methicillin resistance was noted in 30.8% of coagulase negative staphylococcus as opposed to 6% of staphylococcus aureus.

Conclusion: Staphylococcus epidermidis is the most prevalent and persistent species on human skin and mucous membranes, constituting 65–90% of all staphylococci (Mandell, Douglas & Bennett, 2000). Since a majority of isolation in tissue samples constitute methicillin resistant coagulase negative staphylococcus, would it be more appropriate to screen for Methicillin resistant Staphylococcus epidermidis (MRSE), rather than MRSA, in patients undergoing joint replacement surgery?

We reviewed prospectively cemented stem revision in 106 patients with severe femoral endosteal bone lysis without infection. Bone grafts were not used in any of the patients. The minimum follow-up was three years (mean 6 years 4 months). At the last review 76.4% of the patients were free of pain and 17.9% had only mild or occasional discomfort; radiographs showed well-fixed stable stems in 101 (95.3%). An intramedullary cement plug was used at revision to improve stability in 97.7%. There was new endosteal osteolysis after revision in 17 patients; only two had severe changes. Seven hips (6.6%) required a second revision; only four of these (3.8%) were for stem loosening. Survivorship of the revised stem, using radiological evidence of stem loosening as the end point, was 95.8% at seven years. The results of stem revision arthroplasty using cement in the presence of massive endosteal cavitation are satisfactory.

We reviewed the records and radiographs of 387 cemented revisions of aseptic loose sockets after total hip replacement at a mean follow-up of 5.5 years. The clinical results were satisfactory, but at the last radiological assessment 38 sockets (9.8%) had a continuous zone of demarcation greater than 1 mm thick and another 35 (9%) showed migration. Poor acetabular bone stock had a profound influence on the outcome of revision surgery, but the results of cemented revision were comparable to those reported for cementless revision at similar mean follow-up.

We reviewed 54 patients at a mean follow-up of 4 years 4 months after rerevisions for failure of Charnley low-friction arthroplasty. Rerevision for aseptic loosening in 26 hips was satisfactory; there were no clinical failures and at the latest radiological assessment only one stem and three sockets showed signs of loosening. By contrast, nine of 20 multiple revisions for recurrent dislocation failed, as did five of eight multiple revisions for deep infection. There was radiological evidence of loosening in one stem and nine sockets in the former group and in three stems and five sockets in the latter.

We reviewed 351 cemented revisions of femoral stems performed for aseptic loosening. At a mean of six years after the revision operation 72.1% of the patients were pain-free and 21.4% had only mild or occasional discomfort. The latest radiographs showed definite stem loosening in 10 (2.8%) and 20 hips (5.7%) had required rerevision, only nine (2.6%) of which were for mechanical failure of the stem. Survivorship analysis, taking the end point as rerevision of the stem, gave 97.0% survival at eight years and 91.6% at 11 years. Excellent results both clinically and radiologically can be achieved by cemented revision of the femoral stem for aseptic loosening.

We assessed 41 patients with rheumatoid arthritis (47 hips) who had had revision hip arthroplasty, at an average follow-up of 7 years 4 months (2 to 19). The clinical results were excellent or satisfactory in 43 hips. Radiologically, 45 stems were secure. Fifteen sockets (36.6%) were radiologically loose. Three hips required rerevision. Socket failure is the predominant problem in rheumatoid patients after cemented revision arthroplasty.

We report a prospective study of 57 one-stage cemented revisions of total hip replacement for deep infection with an actively discharging sinus. The average follow-up was 7 years 4 months. Seven patients had required rerevisions, but at latest follow-up, infection was under control in 49 (86%). A discharging sinus is not, in itself, a contraindication to one-stage revision of a hip replacement.

A flanged socket was introduced by Sir John Charnley for use in his low-friction hip arthroplasty in 1976. Experimental evidence has suggested that the flange offers an advantage in terms of cement pressurisation at the time of implantation. We have reviewed 302 primary Charnley arthroplasties followed for 9 to 11 years to determine the effect of the flanged socket on the radiological appearance. The incidence of radiological demarcation at the cement-bone interface is significantly reduced in early radiographs after the use of a flanged socket, and the advantage is maintained in the long-term results.

Laboratory wear testing of ultra high molecular weight polyethylene from 12 Charnley acetabular cups, removed after periods of up to 17.5 years showed that the large patient-to-patient variations in clinical penetration rate cannot be explained by batch-to-batch variation in the wear resistance of the material. Nor was there any evidence of a time-dependent degradation in wear resistance of the material.

In a prospective study, a double crossover wire with a compression spring was used to re-attach 52 un-united trochanters at revision operations on total hip arthroplasties. Bony union was achieved in 42 (81%) and was not influenced by the duration of the nonunion or the separation gap. The new method compared favourably with earlier revisions at which other methods of trochanteric re-attachment had been used.

A retrospective review of 72 cases of Charnley low friction arthroplasty revised for stem loosening, has identified a number of "at risk" factors. These were: previous hip surgery and, in radiographs taken at one year, demarcation of the distal cement and fracture of the cement near the tip of the stem. Separation of the back of the stem from the cement, as an isolated feature, was not considered significant. Endosteal cavitation of the femoral shaft, rare in the first year, indicated loosening of some duration. Patients whose radiographs show the "at risk" changes, should be followed-up indefinitely in order to plan timely revision and avoid gross loss of the femoral bone stock.

An experimental evaluation was made of the efficacy of an unflanged cup, an ogee-flanged cup and the Exeter pressuriser in the pressurisation of acetabular cement. Only a very modest injection pressure could be generated through an unflanged socket and even this was readily lost as the socket "bottomed out". The ogee-flanged socket gave a consistently high injection pressure which could be maintained throughout the process of polymerisation. The Exeter pressuriser gave marginally better results. Of the two cements tested, Palacos with gentamicin showed better intrusion than CMW Type 1 cement, but it also allowed greater extrusion once pressure was released. The importance of maintaining a continuous pressure on the cement throughout polymerisation is emphasised.

We report a retrospective review of 127 low friction arthroplasties carried out for the failure of a previous hip operation. After an average follow-up of 10.4 years, 20% of cases required further revision, over half of them for deep infection. We estimated from the radiographic appearances that eventual failure by loosening was probable in 58% on the femoral side and 56% on the acetabular side of the arthroplasties.

A retrospective review of 1542 Charnley low-friction arthroplasties was carried out to compare the incidence of deep infection arising after plain and gentamicin-containing acrylic cement. There was no significant difference between the two series in primary operations, the infection rate being 1.72% and 1.65% respectively. However, in secondary operations (conversions and revisions) the gentamicin-containing cement gave significantly better results--a 0.81% infection rate as compared with 3.46%. All operations were performed in a clean air enclosure using total-body exhaust suits. Radiological diagnosis of deep infection was possible within one year of operation in all cases. Late haematogenous infection occurred in one case and was related to a skin lesion.

We examined 59 cemented high density polyethylene sockets removed at revision hip arthroplasty. Of these 19 showed areas of wear between the outside of the socket and the acetabular bone. This was associated with lack of acrylic cement in those areas and was also related to the depth of the wear on the articulating surface of the socket. It is suggested that, in some cases, changes at the bone-cement junction are secondary to socket loosening and abrasion against the bone of the acetabulum, rather than to particles migrating from the metal-polyethylene interface. It is therefore important that impingement of the neck of the femoral stem on the edge of the cup be avoided and that, when the socket is inserted, it is not in direct contact with the bone.

Twenty-two high-density polyethylene sockets from Charnley low-friction arthroplasties have been studied. Acrylic casts and shadowgraph techniques were used to measure both the real and radiographic rates of wear; these rates showed a significant correlation. In the sagittal plane, nine of the sockets had worn lateral to a line drawn vertically from the centre of curvature of the socket, 12 had worn medial to that line and only one was worn exactly in the line. In the coronal plane, nine sockets had worn in front of a similar vertical line, two behind that line and 11 had worn exactly in the line. Evidence of impingement of the neck of the stem onto the rim of the socket was found in 14 patients; this is considered to be one of the causes of socket loosening. The obvious solution is to reduce the diameter of the neck of the stem from 12.5 mm to 10 mm; provided that it is made of cold-formed, high nitrogen-content stainless steel, this narrower neck is strong enough not to fracture.

A method of performing a biplanar intracapsular trochanteric osteotomy with a Gigli saw was designed and tested prospectively in 431 cases of Charnley low friction arthroplasty. Three methods of trochanteric reattachment were tested, and a double cross-over wire with a compression spring was best; this method was successful in 222 out of 226 patients (98.2%), of which half were revision operations. Adduction seemed to be the main movement leading to trochanteric detachment.

In order to improve the fixation of the stem in primary Charnley low-friction arthroplasty, the medullary canal was routinely closed off with a cancellous bone block. A prospective study of 611 consecutive arthroplasties were carried out between 1 and 5 1/2 years (average 2 years and 9 months) after operation. There were two cases of radiological loosening of the stem, both of which could have been avoided. Five other patients showed demarcation of the bone-cement junction at the calcar; two of these are considered to be "at risk" of loosening. There was no evidence of radiological loosening of the stem in 604 cases and the method is recommended for routine use in primary total hip arthroplasty.

A retrospective study of 44 diabetic patients who, between them, had 62 Charnley low-friction arthroplasties, showed a superficial-infection rate of 9.7 per cent and a deep-infection rate of 5.6 per cent. All the operations were carried out in the Charnley clear-air enclosure and prophylactic antibiotics were not used. A statistically significant increase in the overall rate of infection was found in diabetic patients when compared with non-diabetic osteoarthritic patients (P less than 0.001) and rheumatoid patients (P less than 0.01). Hence it is suggested that in diabetic patients there may well be a place for prophylactic antibiotics in hip replacement surgery in addition to the use of the clean-air enclosure.

Twenty-one cases of the Charnley low-friction arthroplasty were revised because of recurrent or irreducible dislocation. Three main reasons for this revision, usually in combination, were identified: loss of the abductor mechanism due to trochanteric detachment; shortening of the limb due to high placement of the socket or low section of the femoral neck; and malorientation of the components. Sixteen patients had no further problems after revision. One patient had a single dislocation, four had more than one dislocation although they managed to cope with them and did not require a further revision.

A series of 400 patients (average age 57.7 years) with bilateral low-friction arthroplasties of the hip has been reviewed. Comparison was made with similar unilateral operations. The results showed that the bilateral arthroplasties can be carried out as a single operation without higher risk of local or general complications. However, this excludes the incidence of pulmonary embolism which is higher for the bilateral replacements.

Wear of high-density polyethylene on bone and cartilage has resulted in a large volume of plastic particles being shed into the two knees and two hips studied. The giant-cell foreign-body reaction of the synovium may not be sufficient to cope with the amount of debris presented and the destruction of the endosteal bone in one hip, caused by the wear particles and movement of the prosthesis, has made revision impossible. Articulation of high-density polyethylene against bone or cartilage either by design or by the failure of alignment of the component must be avoided.