A comparison of 2 cementing techniques in hip resurfacing using human femoral heads.

INTRODUCTION: Hip resurfacing remains a valid option in young male patients. The creation of the optimum cement mantle aids fixation of the femoral component. If the cement mantle is too thick the prosthesis can remain proud leading to early failure or if it penetrates too far into the femoral head, it may cause osteonecrosis. METHOD: 18 of 96 femoral heads collected from patients undergoing total hip arthroplasty were matched for their surface porosity. They were randomly allocated into 2 different cementing groups. Group 1 had the traditional bolus of cement technique, while group 2 had a modified cementing technique (swirl) where the inside of the femoral component was lined with an even layer of low viscosity cement. RESULTS: The traditional bolus technique had significantly greater cement mantle thickness in 3 of 4 zones of penetration (p = 0.002), greater and larger air bubble formation (6 of 9 in bolus technique vs. 1 in 9 in swirl technique, p = 0.05) and more incomplete cement mantles compared with the swirl technique. There was no relationship to femoral head porosity. CONCLUSION: The swirl technique should be used to cement the femoral component in hip resurfacing. Long-term clinical studies would conform if this translates into increased survivorship of the femoral component.

The porosity of the bone cement interface of 96 human femoral heads prepared for hip resurfacing.

PURPOSE: The porosity of the femoral head prepared for hip resurfacing has not been previously described. This is important as greater pore size increases the penetration of bone cement and excessive cement penetration can cause osteonecrosis. METHODS: 96 osteoarthritic femoral heads were harvested at total hip arthroplasty and prepared for hip resurfacing. The porosity of the bone cement interface in hip resurfacing was calculated from digitised black and white photographs using MatLab software. RESULTS: The mean porosity was 0.63. Increased porosity was associated with larger femoral heads in both the coronal and sagittal dimensions and cysts in the femoral head. It was not associated with gender, age, body mass index (BMI), smoking, alcohol or corticosteroid consumption. CONCLUSION: The porosity of the femoral head has been shown to be 0.63. Future studies of cementing techniques in hip resurfacing should include this porosity in their designs. The surgeon prior to hip resurfacing should consider altering his cementing technique when cysts are present on the preoperative radiographs.

An 18-year comparison of hybrid total hip replacement and Birmingham hip resurfacing in active young patients.

AIM: To compare the long-term clinical and radiological results of metal-on-polyethylene hybrid total hip replacement (THA) with metal-on-metal Birmingham hip resurfacing (BHR) in young, active patients. PATIENTS AND METHODS: From the 1st consecutive 63 hips in young, active patients who underwent BHR by the senior author, 54 (51 patients) were matched to patients who had undergone THA with regard to age, gender, body mass index and preoperative levels of activity. Radiologically, all hips were assessed for migration and osteolysis, THAs for polyethylene wear and BHRs for a pedestal sign. Patient-reported outcomes, mortality and revision rates were compared. RESULTS: The mean follow-up of the patients with a hybrid THR was 19.9 years and for those with a BHR, 17.6 years. 13 patients with a hybrid THR and 5 with a BHR had died. 1 hybrid THR and 3 BHRs were lost to follow-up. The revision rate of the hybrid THRs was 14/54 and of the BHRs 6/54. Log rank comparison of Kaplan-Meier survival estimates demonstrated a significantly lower mortality in the BHR group (p = 0.039; hazard ratio [HR] = 0.37 [95% CI, 0.15-0.95]) but a non-significant difference in revision rates (p = 0.067; HR = 0.43 [95% CI, 0.18-1.06]). The BHRs recorded superior OHS (p = 0.03), UCLA (p = 0.0096), and EuroQol visual analogue scores (p = 0.03). Significantly more BHRs had run, played sport and undertaken heavy manual labour in the month preceding follow-up. CONCLUSION: After 18 years, patients with BHRs remained more active with a lower mortality rate but demonstrated no significant difference in revision rates. Both groups demonstrated progressive radiological changes at long-term follow-up.

Histology of failed metal-on-metal hip arthroplasty; three distinct sub-types.

The histological specimens from 29 failed metal-on-metal (MoM) hip arthroplasties treated at our institution were reviewed. Five patients had a failed MoM total hip arthroplasty (THA), and 24 patients a failed hip resurfacing. Clinical and radiographic features of each hip were correlated with the histological findings. We report three major histological subtypes. Patients either have a macrophage response to metal debris, a lymphocytic response (ALVAL) or a mixed picture of both. In addition we observe that the ALVAL response is located deep within tissue specimens, and can occur in environments of low wear debris. The macrophage response is limited to the surface of tissue specimens, with normal underlying tissue. Patients with subsequently confirmed ALVAL underwent revision surgery sooner than patients whose histology confirms a macrophage response (3.8 vs. 6.9 years p<0.05). Both histological subtypes (ALVAL and macrophage dominant) are responsible for abnormal soft tissue swellings.

The thermal effects of lavage on 57 ox femoral heads prepared for hip resurfacing arthroplasty.

BACKGROUND AND PURPOSE: Previously, we have documented surface temperatures recorded by thermography great enough to cause osteonecrosis of the femoral head during hip resurfacing. We now performed an in vitro investigation with 3 questions: (1) whether water irrigation reduced bone surface temperature, (2) whether external bone temperatures were similar to core temperatures, and (3) whether blunting of the reamer affected temperature generation. METHODS: Using an ox-bone model, 57 femoral heads were peripherally reamed. The surface temperatures of bone were measured using a thermal camera and internal bone temperatures were measured using 2 theromocouples. We measured the effects of cooling with water at room temperature and with ice-cooled water. Progressive blunting of reamers was assessed over the 57 experiments. RESULTS: Mean and maximum temperatures generated during peripheral reaming were greater when no irrigation was used. Ice-cold saline protected femoral heads from thermal damage. External bone temperatures were much greater than internal temperatures, which were not sufficiently elevated to cause osteonecrosis regardless of lavage. Blunting of the reamer was not found to have a statistically significant effect in this study. INTERPRETATION: Cooling with ice-cooled water is recommended. Internal bone temperatures are not elevated despite the high surface temperatures reached during femoral head resurfacing.

Blood levels of cobalt and chromium are inversely correlated to head size after metal-on-metal resurfacing arthroplasty.

Resurfacing arthroplasty has fallen out of favour in recent years due to unfavourable survivorship in joint registries and alarming reports of soft tissue reactions around metal on metal prostheses. Our aim was to assess the effect of head size, implant design and component positioning on metal production by resurfacing arthroplasties. We measured whole blood cobalt and chromium and component position in matched populations implanted with two designs of resurfacing arthroplasty over a two-year period. Both implants resulted in a significant increase in blood metal levels (p<0.001) though the ASR design generated significantly higher metal levels (p = 0.041). A significant inverse correlation was seen between component size and blood cobalt levels (p = 0.032) and blood chromium levels (p<0.001). No correlation was identified between component position and blood metal levels. Small diameter metal resurfacing components result in increased metal generation compared with larger components. As increased metal generation has been correlated to wear and therefore failure, caution must be used on implantation of smaller components and indeed, in those who require smaller components, alternative bearing materials should be considered. These results contrast with recent findings which have demonstrated early failure for larger diameter stemmed metal-on-metal prostheses.

The medium term outcome of the Omnifit constrained acetabular cup.

Recurrent dislocation requiring revision surgery occurs in approximately 4% of primary total hip arthroplasties (THAs). To reduce this risk, or to treat those patients who recurrently dislocate, a constrained acetabular component may be used, however there are concerns over the success of such components due to increased mechanical stresses. The purpose of this study was to analyse the survivorship and radiological results for the Omnifit constrained acetabular component, providing a longer patient reported outcome follow-up than previous studies. 117 patients (median age 82 years) underwent a THA with an Omnifit constrained acetabular component. Of these, 45 were primary replacements and 72 were revisions. Survivorship analysis was performed and patients were assessed both radiologically and functionally. At follow-up, 53 patients (45.3%) had died at a median time of 33 months from operation. The median overall follow-up was 7.0 (5.5-8.2) years. Survivors (median age 83 years) reported a median Oxford Hip Score (OHS) of 16.6 (0-48), 87.8% were satisfied with their surgery. 45 (91.8%) of the acetabular components were stable radiologically, 48 (96%) of the femoral components were stable (5 uncemented, 43 cemented) and two possibly unstable. Four of the 117 patients underwent further surgery. Only one required revision of the prosthesis and this was for a periprosthetic fracture. In the medium term the Omnifit constrained acetabular component prevents dislocation and does not cause excessive loosening of either the acetabular or femoral components in our patient population. Our results support the use of the Omnifit constrained acetabular component in elderly patients at risk of dislocation with low functional demand.

Enhancing proximal femoral pressure during cemented stem insertion.

BACKGROUND: Poor proximal femoral pressures during a cemented primary hip replacement may compromise proximal fixation and cause early aseptic loosening. Occlusion of the calcar, during stem insertion, achieves a uniform and sustained rise in the proximal intra-medullary pressure, which should enhance cement penetration into bone and improve long-term survival of the prosthesis. METHODS: 54 Exeter stems were cemented into femoral moulds prepared from plaster of Paris. Pressure transducers were connected to the proximal, middle and distal zones of the mould. After cement insertion, stems were implanted with occlusion of the calcar by either nothing, a thumb placed medially or an Exeter horse-collar. 18 stems each were inserted into Palacos-R at 3½-4 minutes and 4-4½ minutes after mixing and Simplex-P 6-6½ minutes after mixing and the intra-medullary pressures were measured. Data were subjected to regression analysis using SPSS. RESULTS: Proximal and distal intra-medullary pressures were significantly higher (P < 0.01-0.001) with proximal occlusion in all cements. The highest pressures were achieved with Palacos-R at 4-4½ minutes after mixing, with proximal thumb occlusion. Stem insertion into Palacos-R at 3½-4 min. or 4-4½ min. after mixing, gave higher pressures than into Simplex-P regardless of the method of occlusion. With Simplex-P, there was a trend to higher proximal intra-medullary pressures with the horse-collar. CONCLUSION: Occluding the calcar during stem insertion into cement achieves and sustains high intra-medullary pressures in both the proximal and distal femur. The highest pressures are obtained with stem insertion into Palacos-R at 4-4½ minutes after mixing, with proximal thumb occlusion. A horse-collar achieves slightly higher pressures with Simplex-P.

Reducing the risk of surgical site infection: a case controlled study of contamination of theatre clothing.

Surgical site infections are one of the most important causes of healthcare associated infections (HCAI), accounting for 20% of all HCAIs. Surgical site infections affect 1% of joint replacement operations. This study was designed to assess whether theatre clothing is contaminated more inside or outside the theatre suite. Petri dishes filled with horse blood agar were pressed on theatre clothes at 0, 2, 4, 6 and 8 hours to sample bacterial contamination in 20 doctors whilst working in and outside the theatre suite. The results showed that there was greater bacterial contamination when outside the theatre suite at 2 hours. There were no differences in the amount of contamination at 4, 6 and 8 hours. This study suggests that the level of contamination of theatre clothes is similar both inside and outside the theatre setting.

A comparison of neck movement in the soft cervical collar and rigid cervical brace in healthy subjects.

OBJECTIVE: The soft cervical collar has been prescribed for whiplash injury but has been shown to be clinically ineffective. As some authors report superior results for managing whiplash injury with a cervical brace, we were interested in comparing the mechanical effectiveness of the soft collar with a rigid cervical brace. Therefore, the purpose of this study was to measure ranges of motion in subjects without neck pain using a soft cervical collar and a rigid brace compared with no orthosis. METHODS: Fifty healthy subjects (no neck or shoulder pain) aged 22 to 67 years were recruited for this study. Neck movement was measured using a cervical range of motion goniometer. Active flexion, extension, right and left lateral flexion, and right and left rotation were assessed in each subject under 3 conditions: no collar, a soft collar, and a rigid cervical brace. RESULTS: The soft collar and rigid brace reduced neck movement compared with no brace or collar, but the cervical brace was more effective at reducing motion. The soft collar reduced movement on average by 17.4%; and the cervical brace, by 62.9%. The effect of the orthoses was not affected by age, although older subjects had stiffer necks. CONCLUSION: Based on the data of the 50 subjects presented in this study, the soft cervical collar did not adequately immobilize the cervical spine.

Anti-embolism stockings and proximal indentation.

The authors of this study noticed that the elastic garters of below knee anti-embolism stockings (AES) were indenting the proximal calves of patients after application and feared this might be interrupting venous return. This was lower on one ward which had a rigorous standardized protocol for sizing and checking stockings. Hypotheses were that proximal indentation caused higher proximal than distal pressures (reverse gradients) and that by adopting the standardized protocol throughout the unit, proximal indentation could be reduced. Fifty-seven patients were recruited after total hip replacement (THR) or total knee replacement (TKR) in a regional orthopaedic centre. The authors implemented the standardized protocol for sizing stockings and measured the pressures under them. After implementation of the standardized protocol, proximal indentation fell from 53% to 19% (p<0.05), incorrectly sized stockings from 74% to 34% (p<0.05) and removal of stockings by patients from 32% to 0% (p<0.05). In total, 21% of patients had reverse gradients which occurred in 41% of legs with proximal indentation and 8% without. When reverse gradients or proximal indentation exist, AES may not be as effective and may be counterproductive. A standardized protocol of nursing practice is critical to optimizing AES after THR and TKR. More in-vivo research is needed on AES after hip and knee replacement.

Meta-analysis of low molecular weight heparin versus placebo in patients undergoing total hip replacement and post-operative morbidity and mortality since their introduction.

OBJECTIVES: 1) To establish the clinical validity for in-patient low molecular weight heparin (LMWH) following total hip replacement (THR) through a meta-analysis of peer reviewed and published randomised placebo controlled trials (RCTs). 2) To establish whether modern peri-operative practices were associated with changes in rates of clinical venous thromboembolic (VTE) and all-cause mortality after THR by review of series of patients receiving in-patient LMWH published between 1985 and 2000. DATASOURCES: Medline and Embase (from 1980 to 2005), Datastar and Proquest databases were searched and references from bibliographies traced. REVIEW METHODS: Studies of adult patients receiving in-patient LMWH following elective primary or revision THR were sought and data abstracted. The first part of our analysis included only randomised placebo controlled trials. For the second part, randomised control trials were included and divided by their year of completion into three groups. RESULTS: We found no difference between LMWH and placebo in the risk of fatal pulmonary embolism (PE), other deaths, all cause mortality or major bleeding. LMWH reduced non-fatal PE (OR=0.14, 95%CI 0.03 to 0.74, p=0.029) at the expense of haematoma formation (7/147 vs 0/149, p=0.015). 35 studies were included in the second part of our analysis. Point estimates of rates of fatal and non-fatal pulmonary embolism and other deaths suggest a decline over time but fell short of statistical significance. CONCLUSION: Clinically relevant VTEs are a rare complication following THR. The lower risk of VTE narrows the risk benefit of potent pharmacological thromboprophylaxis. We do not support their use in patients undergoing THR without additional thromboembolic risk factors.

Cemented polished tapered stems in patients less than 50 years of age: a minimum 10-year follow-up.

We report the outcome of 58 consecutive polished tapered stems in 47 patients younger than 50 years, with a minimum of 10 years of follow-up. No stems were revised for aseptic loosening or osteolysis. The Harris hip scores were good or excellent in 76% of the patients. There was excellent preservation of proximal bone. Despite higher patient weight and frequent previous surgery, the outcome of polished tapered stems in patients younger than 50 years is comparable to the general population undergoing total hip arthroplasty and superior to other non-polished tapered stem designs in young patients. Cup wear and cup failure were significantly worse in this group, with a higher incidence of periarticular osteolysis. Polished tapered stem designs are the benchmark for comparison to other arthroplasty options in young patients.

Revision for recurrent dislocation of total hip replacement.

BACKGROUND AND PURPOSE: Dislocation is one of the commonest complications of total hip arthroplasty with an incidence of between 0.5 and 9.2%. Despite this, little is known of the outcome of treatment strategies for dislocation. The aim of this study was to establish the optimal strategy for the operative management of recurrent dislocation following THA taking account of the surgical approach employed in the replacement that became unstable and the direction of the instability that followed. METHODS: We reviewed 70 patients who underwent revision surgery for recurrent dislocation after total hip arthroplasty (THA), 38 through the transgluteal (Hardinge) and 32 through the posterior approach.52 of these followed primary and 18 followed revision THA for reasons other than instability.We recorded the surgical approach, the direction of dislocation and the operative strategy employed for each case. RESULTS: We achieved stability in 75% of patients who dislocated after primary and 50% after revision THA. 77% of dislocations performed initially through the transgluteal approach were anterior and 88% through the posterior approach were posterior. Following the transgluteal approach, we stabilised anterior dislocation in 54% of cases. Following the posterior approach we stabilised posterior dislocation in 79%. The most successful operative strategy overall was cup augmentation which conferred stability in 90% of cases. INTERPRETATION: Instability after primary total hip replacement is easier to treat (75% chance of success) than after revision total hip replacement (50% chance of success). Although previous studies have shown that the posterior approach has a slightly higher risk of dislocation, this study has shown that achieving stability after a posterior dislocation is more likely than after an anterior dislocation. The outcome of revision for instability depends on the surgical approach used initially, and the direction of dislocation.

The effect of a modified posterior approach on blood flow to the femoral head during hip resurfacing.

The deep branch of the medial femoral circumflex artery is vulnerable to injury during posterior approaches to the hip. We modified the posterior approach during hip resurfacing in 10 patients by dividing the short external rotators 2 cm from their insertion into the femur. The cefuroxime concentrations in bone samples from the femoral heads were compared with results for the extended posterolateral approach from previous published work. There was no difference between the concentration of cefuroxime in bone when using the modified posterior approach (mean 5.6 mg/kg; CI 3.6 - 7.8) compared to the extended posterolateral approach (mean 5.6 mg/kg; CI 3.5 - 7.8; p=0.95). The similarity in femoral head perfusion between approaches suggests that the blood supply may be impaired further by capsulotomy and capsulectomy rather than by damage to the deep branch of the MFCA alone.

Impaction bone grafting of the acetabulum at hip revision using a mix of bone chips and a biphasic porous ceramic bone graft substitute.

BACKGROUND AND PURPOSE: One of the greatest problems of revision hip arthroplasty is dealing with lost bone stock. Good results have been obtained with impaction grafting of allograft bone. However, there have been problems of infection, reproducibility, antigenicity, stability, availability of bone, and cost. Thus, alternatives to allograft have been sought. BoneSave is a biphasic porous ceramic specifically designed for use in impaction grafting. BoneSave is 80% tricalcium phosphate and 20% hydroxyapatite. Previous in vitro and in vivo studies have yielded good results using mixtures of allograft and BoneSave, when compared with allograft alone. This study is the first reported human clinical trial of BoneSave in impaction grafting. METHODS: We performed a single-institution, multi-surgeon, prospective cohort study. 43 consecutive patients underwent revision hip arthroplasty using BoneSave and allograft to restore missing bone in the acetabulum. 9 patients had cemented acetabular components implanted and 34 uncemented. 10 patients had cemented femoral components implanted and 1 had an uncemented femoral component. 32 patients did not have their femoral component revised. RESULTS: No patients were lost to follow-up. At a mean follow-up of 24 (11-48) months, there were no re-revisions and there was no implant migration. 1 acetabular component had confluent lucent lines at the implant-graft interface. Complications were rare (1 fracture, 2 dislocations). Patient satisfaction with the procedure was high. INTERPRETATION: Short-term results indicate that impaction grafting of BoneSave and allograft is an effective method of dealing with loss of bone stock at revision hip surgery.

Primary total knee replacement: is suction a portal of infection?

INTRODUCTION: Pulsed lavage during a total knee replacement usually leaves a pool of fluid on the surgical drapes. It is common practice to suck away this fluid using the same suction device used intra-operatively. This could be a cause of direct wound contamination. We hypothesised that bacteria contaminate fluid that collects around the foot in total knee replacement surgery and that suction equipment could be a portal of contamination. We also hypothesised that bacterial count in the fluid is lower if chlorhexidine, rather than saline, is used in the pulsed lavage. PATIENTS AND METHODS: Forty patients undergoing primary total knee replacement were divided into two groups. The first group had pulsed lavage with normal saline and the second with 0.05% chlorhexidine. RESULTS: At the end of the operation, 20 ml of fluid, pooled on the surgical drapes was aspirated and cultured for bacterial growth. None of the fluid samples showed bacterial growth. CONCLUSIONS: Suction device used peri-operatively during knee replacement is unlikely to be a cause of wound contamination. Pulsed lavage with normal saline is as effective as lavage with chlorhexidine.

Patient-reported outcomes after total hip and knee arthroplasty: comparison of midterm results.

The aim of this study was to compare the midterm functional outcomes of total knee arthroplasty (TKA) and total hip arthroplasty (THA). A cross-sectional postal audit survey of all consecutive patients who had a primary joint replacement at one orthopedic center 5 to 8 years ago was conducted. Participants completed an Oxford hip score or Oxford knee score, which are self-report measures of functional ability. Completed questionnaires were returned from 1112 THA patients and 613 TKA patients, giving a response rate of 72%. The median Oxford knee score of 26 was significantly worse than the median Oxford hip score of 19 (P < .001). In conclusion, TKA patients experience a significantly poorer functional outcome than THA patients 5 to 8 years postoperatively.

Dislocation following total hip replacement: the Avon Orthopaedic Centre experience.

INTRODUCTION: The aim of this study was to determine the incidence and outcome of dislocation after total hip arthroplasty at our unit. PATIENTS AND METHODS: In total, 1727 primary total joint arthroplasties and 305 revision total hip arthroplasties were performed between 1993 and 1996 at our unit. We followed up 1567 (91%) of the primary hip arthroplasties and 284 (93%) of the revision hip arthroplasties at 8-11 years after surgery. Patients were traced by postal questionnaire, telephone interview or examination of case notes of the deceased. RESULTS: The dislocation rates by approach were 23 out of 555 (4.1%) for the posterior approach, 0 out of 120 (0%) for the Omega approach and 30 out of 892 (3.4%) for the modified Hardinge approach. Of dislocations after primary total hip arthroplasty, 58.5% were recurrent. The mean number of dislocations per patient was 2.81. Overall, 8.1% of revision total hip arthroplasties dislocated. 70% of these became recurrent. The mean number of dislocations per patient was 2.87. The vast majority of dislocations occurred within 2 months of surgery. DISCUSSION: To our knowledge, this is the largest multisurgeon audit of dislocation after total hip arthroplasty published in the UK. The follow-up of 8-11 years is longer than most comparable studies. The results of this study can be used to inform patients as to the risk and outcome of dislocation, as well as to the risk of further dislocation.

Adherence to recommendations designed to decrease intra-operative wound contamination.

INTRODUCTION: The incidence of wound infection following total hip and knee arthroplasty has fallen with the introduction of laminar vertical laminar airflow, occlusive clothing and prophylactic antibiotics. However, infection still occurs after prosthetic joint replacement and can have devastating consequences. Intra-operative wound contamination is the major source of infection. Measures proven to decrease intra-operative wound contamination include chlorhexidine lavage, removal of jewellery, covering old jewellery, ears, nose, mouth and hair and wearing theatre clothing in an occlusive manner. PATIENTS AND METHODS: Posters explaining this practice were placed at eye level in the scrub area of orthopaedic theatres and adoption of these techniques was observed covertly before and after. RESULTS: Eighty-two personnel were audited before the poster was erected and 90 afterwards. Only 2 of 12 observed standards were adhered to 100% of the time. CONCLUSIONS: Education by posters did not significantly improve adherence to protocols. Compliance with protocols was worse amongst non-scrubbed theatre personnel.