Osteonecrosis with the use of polymethylmethacrylate cement for hip replacement: thermal-induced damage evidenced in vivo by decreased osteocyte viability.

Thermal damage to host bone is a possible source of compromise of fixation in patients undergoing cemented total hip replacement (THR). Data on the subject to date are derived from mathematical modelling powered by animal studies. The aim of this study was to assess the effect of cement thickness on osteocyte viability in a population of patients undergoing cemented THR. An in vivo model was designed and validated by means of a finite element analysis. During standard hip joint replacement in 14 patients, the femoral necks were exposed before final resection to the heat of a curing cement mantle equivalent to 2.5 (Group 1) or 5 mm (Group 2) in vivo in the cemented acetabulum. Matched controls were collected for each patient. Osteocyte counts and viability were assessed by means of haematoxylin and eosin (H&E) stain and lactate dehydrogenase (LDH) assay. Ex vivo experiments were performed to determine the extent of thermal insult. H&E staining proved unreliable for assessing thermal insult in the short term. The LDH assay was reliable and demonstrated a significant reduction in osteocyte viability to a depth of 2.19 mm in group 1 and 9.19 mm in group 2. There was a significant difference between the groups at all depths. The ex vivo experiments revealed thermoclines indicating that host bone in the population undergoing cemented THR is more sensitive to the thermal insult delivered by curing polymethylmethacrylate cement than previously believed. This thermal insult may weaken the fixation between bone and cement and contribute towards aseptic loosening, the commonest cause of failure of THRs.

Role of early intravenous to oral antibiotic switch therapy in the management of prosthetic hip infection treated with one- or two-stage replacement.

OBJECTIVES: To determine outcomes for an antibiotic regimen using early switch to oral antibiotics for treatment of infected total hip replacement (THR) treated by either a one-stage or two-stage procedure. METHODS: Cases of infected THR were identified from the microbiology records on all orthopaedic infections in a 24 month period. Diagnosis was made by microbiological culture of theatre specimens and findings at the time of surgery. A standard approach of 10-14 days intravenous (iv) antibiotic followed by a switch to oral antibiotics either for 6-8 weeks until second-stage re-implantation or for up to 3 months following a one-stage procedure was used. The exact date of oral switch and antibiotic duration was determined by clinical resolution and C-reactive protein (CRP). Outcome was recorded as no microbiological or clinical evidence of relapse of infection or relapse after completing the antibiotic course. Follow-up duration for all cases at the time of study was 24-36 months after completion of antibiotic treatment. RESULTS: In 24 months, 19 patients underwent two-stage THR for infection, of which 17 were treated with oral antibiotics after a median of 14 days initial iv antibiotics. None relapsed. Four patients underwent one-stage THR and had 12-20 days iv then 6-26 weeks oral antibiotics with no relapse. CONCLUSIONS: Early oral antibiotic switch therapy was effective in patients treated at the Avon Orthopaedic Centre with infected THR and plays an important role in enabling patients to return to independence after revision surgery and avoid complications of prolonged iv access.

Prevalence and functional impact of patient-perceived leg length discrepancy after hip replacement.

The aim of this postal survey was to determine the prevalence and impact of patient-perceived leg length discrepancy (LLD) at 5-8 years after primary total hip replacement (THR). A postal audit survey was undertaken of all consecutive patients who had a primary unilateral THR at one elective orthopaedic centre between April 1993 and April 1996. The questionnaire included the Oxford hip score (OHS) and questions about LLD. Questionnaires were received from 1,114 patients. In total, 329 THR patients (30%) reported an LLD, although radiographic analysis revealed that only 36% of these patients had anatomical LLD. Patients with a perceived LLD had a significantly poorer OHS (p < 0.001) and reported more limping than those patients without a perceived LLD. This study found that a third of patients perceived an LLD after THR and that perceived LLD was associated with a significantly poorer midterm functional outcome.

Ten-year life expectancy after primary total hip replacement.

We determined the ten-year life expectancy of 5831 patients who had undergone 6653 elective primary total hip replacements at a regional orthopaedic centre between April 1993 and October 2004. Using hospital, general practitioner and the local health authority records, we recorded the dates of death for those who died following surgery. The mean age at operation was 67 years (13 to 96) with a male:female ratio of 2:3. Of 1154 patients with a ten-year follow-up 340 (29.5%) had died a mean of 5.6 years (0 to 10) after surgery. Using Kaplan-Meier curves, the ten-year survival was 89% in patients under 65 years at surgery, 75% in patients aged between 65 and 74 years, and 51% in patients over 75. The standardised mortality rates were considerably higher for patients under 45 years, 20% higher for those between 45 and 64 years, and steadily reduced in patients aged 65 and over. The survival of cemented hip replacement derived from the Swedish Hip Arthroplasty Register Annual Report 2004 exceeds the life expectancy of patients over the age of 60 in our area, suggesting that cemented hip replacement is the procedure of choice in this population.

Omnifit acetabular component: a solution to preventing and treating dislocation.

PURPOSE: To assess short- to medium-term outcome of the Omnifit constrained acetabular component in preventing dislocation in at-risk patients after total hip arthroplasty (THA). METHODS: 81 patients (mean age, 77 years) underwent either primary or revision THA with an Omnifit constrained acetabular component and were followed up clinically and radiologically for a mean period of 24 months. RESULTS: There was one dislocation and one revision for avulsion of the acetabulum. The remaining prostheses remained well fixed. CONCLUSIONS: In the short- to medium-term, the Omnifit constrained acetabular component is effective in preventing primary and recurrent dislocation in at-risk patients. Long-term follow-up is needed to assess whether good fixation is maintained. The Omnifit acetabular cup is recommended for elderly patients with limited life expectancy and functional demands.

Should finger rings be removed prior to scrubbing for theatre?

Finger rings increase surface bacterial counts. Although scrubbing reduces these (P=0.05), there are more bacteria under rings than on adjacent skin or the opposite hand. If rings are removed before scrubbing, bacterial counts are reduced but remain higher than on adjacent skin or the opposite hand. Ideally, finger rings should not be worn by theatre staff. However, if they are, they should be removed prior to scrubbing for surgical operations.

Total hip arthroplasty and hemiarthroplasty in mobile, independent patients with a displaced intracapsular fracture of the femoral neck. A randomized, controlled trial.

BACKGROUND: Hemiarthroplasty and total hip arthroplasty are commonly used to treat displaced intracapsular fractures of the femoral neck, but each has disadvantages and the optimal treatment of these fractures remains controversial. METHODS: In the present prospectively randomized study, eighty-one patients who had been mobile and lived independently before they had sustained a displaced fracture of the femoral neck were randomized to receive either a total hip arthroplasty or a hemiarthroplasty. The mean age of the patients was seventy-five years. Outcome was assessed with use of the Oxford hip score, and final radiographs were assessed. RESULTS: After a mean duration of follow-up of three years, the mean walking distance was 1.17 mi (1.9 km) for the hemiarthroplasty group and 2.23 mi (3.6 km) for the total hip arthroplasty group, and the mean Oxford hip score was 22.3 for the hemiarthroplasty group and 18.8 for the total hip arthroplasty group. Patients in the total hip arthroplasty group walked farther (p=0.039) and had a lower (better) Oxford hip score (p=0.033) than those in the hemiarthroplasty group. Twenty of thirty-two living patients in the hemiarthroplasty group had radiographic evidence of acetabular erosion at the time of the final follow-up. None of the hips in the hemiarthroplasty group dislocated, whereas three hips in the total hip arthroplasty group dislocated. In the hemiarthroplasty group, two hips were revised to total hip arthroplasty and three additional hips had acetabular erosion severe enough to indicate revision. In the total hip arthroplasty group, one hip was revised because of subsidence of the femoral component. CONCLUSIONS: Total hip arthroplasty conferred superior short-term clinical results and fewer complications when compared with hemiarthroplasty in this prospectively randomized study of mobile, independent patients who had sustained a displaced fracture of the femoral neck.

The Exeter Universal stem: a minimum ten-year review from an independent centre.

We reviewed 142 consecutive primary total hip replacements implanted into 123 patients between 1988 and 1993 using the Exeter Universal femoral stem. A total of 74 patients (88 hips) had survived for ten years or more and were reviewed at a mean of 12.7 years (10 to 17). There was no loss to follow-up. The rate of revision of the femoral component for aseptic loosening and osteolysis was 1.1% (1 stem), that for revision for any cause was 2.2% (2 stems), and for re-operation for any cause was 21.6% (19 hips). Re-operation was because of failure of the acetabular component in all but two hips. All but one femoral component subsided within the cement mantle to a mean of 1.52 mm (0 to 8.3) at the final follow-up. One further stem had subsided excessively (8 mm) and had lucent lines at the cement-stem and cement-bone interfaces. This was classified as a radiological failure and is awaiting revision. One stem was revised for deep infection and one for excessive peri-articular osteolysis. Defects of the cement mantle (Barrack grade C and D) were found in 28% of stems (25 hips), associated with increased subsidence (p = 0.01), but were not associated with endosteal lysis or failure. Peri-articular osteolysis was significantly related to the degree of polyethylene wear (p < 0.001), which was in turn associated with a younger age (p = 0.01) and male gender (p < 0.001). The use of the Exeter metal-backed acetabular component was a notable failure with 12 of 32 hips (37.5%) revised for loosening. The Harris-Galante components failed with excessive wear, osteolysis and dislocation with 15% revised (5 of 33 hips). Only one of 23 hips with a cemented Elite component (4%) was revised for loosening and osteolysis. Our findings show that the Exeter Universal stem implanted outside the originating centre has excellent medium-term results.

Treatment of the young active patient with osteoarthritis of the hip. A five- to seven-year comparison of hybrid total hip arthroplasty and metal-on-metal resurfacing.

We compared the five- to seven-year clinical and radiological results of the metal-on-metal Birmingham hip resurfacing with a hybrid total hip arthroplasty in two groups of 54 hips, matched for gender, age, body mass index and activity level. Function was excellent in both groups, as measured by the Oxford hip score, but the Birmingham hip resurfacings had higher University of California at Los Angeles activity scores and better EuroQol quality of life scores. The total hip arthroplasties had a revision or intention-to-revise rate of 8%, and the Birmingham hip resurfacings of 6%. Both groups demonstrated impending failure on surrogate end-points. Of the total hip arthroplasties, 12% had polyethylene wear and osteolysis under observation, and 8% of Birmingham hip resurfacings showed migration of the femoral component. Polyethylene wear was present in 48% of the hybrid hips without osteolysis. Of the femoral components in the Birmingham hip resurfacing group which had not migrated, 66% had radiological changes of unknown significance.

The effects of Scaphoid and Colles casts on hand function.

Although necessary for bone healing, immobilisation temporarily prevents hand function and may necessitate corrective physiotherapy later. Scaphoid and Colles casts are both commonly used to immobilize scaphoid fractures. Non-union rates are comparable with both casts. The Scaphoid cast incorporates the thumb, whereas the Colles cast leaves the thumb free. We compared the effect of the two casts on hand function in 20 healthy right-hand-dominant volunteers using the Jebsen-Taylor Hand Function Test. Data were obtained through a mixed between and within subject design. Both casts prolonged the time taken to complete the hand function test compared to controls. Testing in the Scaphoid cast took significantly longer than in the Colles cast.

The importance of leg length discrepancy after total hip arthroplasty.

We assessed leg length discrepancy and hip function in 90 patients undergoing primary total hip arthroplasty before surgery and at three and 12 months after. Function was measured using the Oxford hip score (OHS). After surgery the mean OHS improved by 26 points after three months and by 30 points after 12. After operation 56 (62%) limbs were long by a mean of 9 mm and this was perceived by 24 (43%) patients after three months and by 18 (33%) after 12. The mean OHS in patients who perceived true lengthening was 27% worse than the rest of the population after three months and 18% worse after 12. In 55 (98%) patients, lengthening occurred in the femoral component. Appropriate placement of the femoral component could significantly reduce a patient's perception of discrepancy of length.

Source of bacterial shedding in laminar flow theatres.

In a previous unpublished observation, unacceptably high bacterial counts, presumably due to shedding episodes, occurred in two of 56 (3.57%) slit-air samples during arthroplasty surgery in a laminar flow operating theatre. The isolates matched those cultured from swab samples taken from the skin of one of the surgeons's foreheads on each of the two occasions. These findings occurred despite scrub staff wearing standard occlusive gowns, hats and masks with visors. In order to localize the potential source of such shedding more accurately, 20 members of theatre staff underwent anonymous microbiological swabbing from the facial areas not covered by theatre clothing, namely their foreheads, eyebrows and ears. These swabs were cultured and the growths were compared statistically. Significantly more colonies were cultured from swabs taken from the theatre staff's ears (P = 0.047, Freidman's test) compared with the other two facial areas studied. These data support the use of exhaust helmets in arthroplasty surgery, or at least mandatory coverage of the ears with theatre hats for scrub staff.

Perioperative wound infection in elective orthopaedic surgery.

Between 1981 and 1987, 12,907 [corrected] consecutive open elective orthopaedic procedures were performed. The in-patient infection rate was 1.43%. There was a significantly greater risk of infection in revision total knee replacement (15.3%), ankle fusion (9.3%), subtalar fusion (5.8%), primary total knee replacement (5.7%), spinal fusion (5.7%) and revision total hip replacement (4.5%). Revision surgery carried approximately a threefold greater risk than primary procedures. Staphylococci were present in 83% of positive wound cultures. Infection rates varied among surgeons but when number and type of procedure were taken into account only two surgeons differed significantly from that expected. Patients undergoing spinal and hindfoot fusion suffered considerable morbidity as a consequence of wound infection. Antibiotic prophylaxis may be helpful in these procedures.

Assessment of airborne bacterial contamination of clean wounds: results in a tissue model.

Ovine skeletal muscle was used as a model wound and inoculated with airborne bacteria collected from a busy communal room. A specialized counting technique involving agar overlay and post-incubation tetrazolium staining was developed to allow accurate counting of small numbers of bacteria on the surfaces of muscle and membrane filters coated with substantial quantities of muscle and fat debris. Two techniques of recovering the inoculated airborne bacteria from the model wound were compared. Pulsed jet lavage with membrane filtration of the recovered fluid showed substantially better recovery, less variability and correlated more closely with controls than a tetrazolium stained 5 microns membrane filter imprint technique. Pulsed jet lavage with membrane filtration is likely to be the more appropriate technique in the assessment of contamination of wounds created in ultraclean air.

Wound disinfection with ultraviolet radiation.

Bacteria were counted concurrently in the air and wounds during the first 20 min of total joint arthroplasty procedures in two theatres: a conventional plenum ventilated theatre with ultraviolet C (UVC) tubes installed and a filtered vertical laminar flow theatre. Four theatre environments were tested: conventional theatre and clothing; conventional theatre with UVC protective clothing, with UVC set to produce 100 or 300 microW cm-2 s-1 irradiation; and filtered vertical laminar flow air with staff wearing cuffed cotton/polyester clothing. When used, the UVC was activated 10 min after starting an operation to assess the effect of UVC clothing alone, and of UVC radiation on bacteria already present in the wound. Compared with conventional theatres, UVC clothing reduced air counts by 38%, UVC at 100 microW cm-2 s-1 by 81%, at 300 microW cm-2 s-1 by 91%, and laminar flow by 92%. Wounds counts fell correspondingly by 66% with UVC clothing, 87% with UVC at 100 microW cm-2 s-1 and 92% both with UVC at 300 microW cm-2 s-1 and laminar flow. In conventional and laminar flow theatres air and wound counts correlated closely but in UVC theatres wound counts were lower than levels expected from prevailing air counts suggesting that UVC kills bacteria in wounds as well as in air.

Importance of air quality and related factors in the prevention of infection in orthopaedic implant surgery.

Small numbers of organisms can cause orthopaedic implant infections, which give rise to a considerable degree of morbidity and also mortality. The periprosthetic infection rates have been shown to correlate with the number of airborne bacteria within 30 cm of the wound. This is influenced by factors such as the number of operating theatre personnel, their clothing and the type of ventilation system used. Guidance on routine bacteriological monitoring of ultraclean air theatres, based on the Department of Health document Health Technical Memorandum 2025, is discussed. Factors important in minimizing the number of postoperative implant infections such as the use of ultraclean air, ultraviolet radiation, different types of surgical clothing, prophylactic antibiotics and host-related factors are also discussed. The importance of proper scientific investigation into the effectiveness of practical preventative measures in the operating room is emphasized.

Effect of jewellery on surface bacterial counts of operating theatres.

Twenty items of three jewellery types were studied. Finger rings, nose and ear piercings increased local surface bacterial counts when in situ, and especially after removal (P<0.0001). Although in the UK the National Association of Theatre Nurses' guidelines suggest that all jewellery should be removed before scrubbing, we suggest that jewellery worn on noses and ears should be left in situ and covered by masks and hats, respectively. The effect of jewellery on skin disinfection needs further study before guidelines can be made concerning finger rings.

Clothing in laminar-flow operating theatres.

Bacterial shedding, wound contamination and clinical-infection rates in clean wounds are influenced by operating-theatre dress. The aim of this study was to clarify the relative contribution of hats, masks and clothing to the control of wound contamination in both ultraclean (enclosed vertical laminar-flow) and conventional (plenum ventilated) airflow theatres. Personnel wore varying combinations of dress in both types of theatre. Colony forming units (cfus) were measured on settle plates at head and waist height, and in the air by a centrifugal air sampler. Bacterial counts in conventional theatres were consistently high and were not significantly influenced by theatre dress. There was a 22-fold increase in cfus on settle plates at waist height when neither hat nor mask were worn, a 15-fold increase when a hat but no mask was worn and a fourfold increase with a mask but no hat in vertical laminar airflow enclosures, although air sample counts remained low. When balloon-cotton clothing was worn, rather than cuffed polyester with microfilament barrier-fabric gowns, cfu counts rose by a factor of six. The bacterial inoculum in conventionally ventilated theatres, or in ultraclean theatres if hat or mask are omitted or balloon-cotton clothing worn, is theoretically sufficient to infect a prosthetic arthroplasty. Theatre-air sampling alone does not reflect local contamination when a surgeon stands over a wound in a vertical laminar-flow enclosure, and both hats and masks are an important part of dress in such environments.

Direct measurement of bacterial penetration through surgical gowns: a new method.

There is a paucity of data on the penetration of bacteria through surgical gowns during operations. A simple new method was developed, using Petri dishes filled with horse blood agar that were attached to the outside of the gown material. This was used to assess bacterial penetration through disposable spun-bonded polyester gowns and re-usable woven polyester gowns during normal use. There was a significant difference between the two gown types when tested in the axilla (P = 0.02), the groin (P = 0.02) and the peri-anal region (P < 0.01), with the disposable gowns performing to a higher standard. Re-usable gowns demonstrated variation in penetrability, and for this reason, may be unsuitable for use in orthopaedic implant surgery.