A longitudinal study was done assessing the latest radiographs available in a series of collarless Corail uncemented stems which have reported survival rates of 95% at 20 years. Parameters scored included the degree of “Ghosting” or delamination, the Gruen, the stem fit in the femoral canal and the degree of calcar resorption. Patient and implant demographics were noted.

At 3 years the loosening rate was 23% reaching 64% at 6 years after the index procedure. It was present in all age groups, with a peak in the 24 to 49 year age group. Males and females had the same occurrence. When it was present this was always in zone 1. It was present in 6% of patients in zone 7, but then always associated with zone 1 changes. High and standard off-set stems had the same loosening rates. The looser fit of the stem the higher the incidence of loosening. There was no correlation to the type of bearing surface or the degree of calcar resorption. Those patients with a BMI of 25 – 35 had lower loosening rates compared to those with higher or lower BMI's.

We postulate that cancellous bone on-growth onto the hydroxyapatite coating associated with loading flexural micro-motion leads to hydroxyapatite being pulled off the smooth stem substrate in zone 1. Progressive delamination of the hydroxyapatite then occurs. The triple-tapered design though imparts continued stability.

We report high loosening rates in the Corail stem and suggest a mechanism for its development.

Purpose Of Study

The study was started in 2004 to determine the best bearing surface in the long term, and to measure the metal ion levels generated by each of the bearing surfaces. We present the latest updated results.

Metal ion levels are used to track the performance of metal containing bearings in hip replacement patients. Changes in whole blood metal ion levels are indicators of wear rates in these bearings. Normal metal ion levels are variable, and range widely. Changes in these “non-bearing” levels over a period of time may influence the monitoring of these bearings.

Purpose of Study:

To look at the difference in metal ion levels using Ceramic on Metal (COM) and Metal on Metal (MOM) bearings in Total Hip Replacements, comparing the results between well placed and poorly placed cups.

Monitoring the performance of hip replacements post-operatively is tedious and costly, necessitating radiological examinations as well as other specialized examinations such as whole blood metal ion levels. In an effort to control escalating costs, we conducted an ethically approved clinical trial to assess the efficacy of basic acoustic monitoring equipment to asses these implants.

Purpose of Study

Multiple measurements have been described for the assessment of developmental dysplasia of the hip (DDH). In particular, the centre edge angle (CEA) has been described by Wiberg to assess the position of the femoral head in relation to the acetabular edge in patients over the age of five years. The purpose of this study is twofold. Firstly to assess the reliability of all measurements available in the literature and secondly to evaluate whether or not the CEA can be reliably measured below five years of age.

The search for the ideal bearing surface in Total Hip Replacements continues. The current ‘best’ materials are felt to be combinations of metal, ceramics and cross-linked polyethylene. Laboratory studies suggest that ceramic-on-metal articulations may provide distinct advantages. This study aims to identify the best bearing surface combination with the lowest adverse side effect profile.

Between February 2004 and September 2007, 164 hips were replaced in 142 patients. 39% were male and 69% were female. The average age at surgery was 53 years (17-72 years). Follow-up assessment included radiographs, the Harris Hip Score and whole blood samples for metal ion levels. Complications to date included 3 hips which needed femoral revision because of surgery related factors, and 3 cases of sepsis of which 1 settled and 2 needed revision. One hip needed revision of head and liner to a larger bearing size for recurrent dislocations, and is no longer being followed up for blood metal ions.

Post-operative whole blood metal ion levels were compared to pre-operative levels to determine the increase or decrease in metal ion levels. There were no changes in those patients with ceramic-on-ceramic and ceramic-on-polyethylene articulations. Moderately raised whole blood metal ion levels were noted at 3 months in the ceramic-on-metal group, while the metal-on-metal group show the greatest increase.

This study agrees with laboratory bearing surface wear studies demonstrating lower wear rates in the ceramic-on-metal group compared to the metal-on-metal group. With concerns related to high blood metal ion levels in metal-on-metal articulations, ceramic-on-metal bearing surfaces may well become a bearing surface of choice in the future, but progress needs to be monitored in the longer term.

Ceramic-on-metal (COM) bearings have shown reduced wear and friction compared with metal-on-metal (MOM) bearings in-vitro. Lower wear has been attributed to a reduction in corrosive wear, smoother surfaces, improved lubrication and differential hardness reducing adhesive wear. Clinical studies have also shown reduced metal ion levels in-vivo compared with MOM bearings. The aim of this study was to examine two explanted COM bearings (one head and cup, one head only), and to assess the effect of in-vivo changes on the wear performance of the COM bearings by comparing the wear of the explanted bearings with three new COM implants in a hip wear simulator.

Two 28mm diameter COM bearings were provided for analysis. These were visually examined and surface profilometry was performed using a 2-D contacting profilometer (Form Talysurf, Taylor Hobson, UK). Scanning electron microscopy was used to image the regions of transfer on the ceramic heads, and EDX to assess the transfer composition (Philips XL30 ESEM).

Hip simulator testing was conducted for 2 million cycles (Mc) comparing the explanted bearings with three new 28mm COM bearings. Tests were performed in a Prosim simulator (SimSol, UK), which applied a twin peak loading cycle, with a peak load of 3kN. Flexion-extension of − 15 to 30 degrees was applied to the head and internal-external rotation of +/− 10 degrees was applied to the cup, components were mounted in the anatomical position. The lubricant was 25% (v/v) calf serum supplemented with 0.03% (w/v) sodium azide and was changed approximately every 0.33Mc. Wear was measured gravimetrically at 0.5, 1 and 2 Mc.

Regions of material transfer, identified on both ceramic explant heads, were shown to be CoCr material by EDX analysis, suggesting metallic transfer from the metal cup. Profilometry traces across metallic transfer showed comparable surface roughness measurements compared to unworn material.

The overall mean wear rate for the new COM bearings at 2Mc was 0.047 ± 0.06mm3/Mc. The mean wear rate for the explanted head articulated with a new cup was slightly lower at 0.034mm3/Mc. The mean wear rate for the explanted head and cup was highest at 0.15mm3/Mc. It was noted that the explanted head/cup had higher bedding in wear compared with the other bearings, but still significantly less than a new MOM bearing (mean bedding-in wear rate 2.03 ± 2.59 mm3/Mc). The steady-state wear was comparable with the new bearings. As the orientation of these implants in-vivo was unknown, it is proposed that the elevated wear during bedding-in of the explanted head/cup bearing may be due to the alignment of the components. The wear rates of the explanted ceramic head against a new cup were comparable with the new bearings, suggesting that the presence of metallic transfer on the ceramic head does not adversely affect the wear behaviour of COM bearings.

The combination of a ceramic head articulating against a metal acetabular liner (CoM) has shown reduced metal ion levels compared with a metal-on-metal bearing (MoM) in hip simulator studies. A randomized prospective clinical trial was undertaken using CoM and MoM bearings in an otherwise identical total hip procedure. The initial clinical results were encouraging. This report comprises a further review of metal ion data.

Patients received identical components with the exception of the bearing surface material but all were 28mm diameter. All components were supplied by DePuy International Ltd. Patients were assessed pre-operatively, 3m, 12m and > 24m (median 32m). Whole blood samples were collected at regular follow-ups, frozen and analysed in batches using high resolution Inductively Coupled Plasma – Mass Spectrometry (ICP-MS). All recruited patients are included irrespective of outcome. However some patients failed to attend specific follow-ups and some contaminated samples had to be discarded. Statistical significance was analyzed using a non-parametric comparison (Mann-Whitney test). After 3m and 12m implantation there were between 21 and 24 patients available for analysis in both the CoM and MoM cohort and after > 24m point 10 and 9 respectively.

There were four outliers (either Cr or Co > 10ug/l) in both the CoM and MoM groups. In common with previous studies (with the exception of two marginal outliers), these were related to component position. They were implanted with either a cup abduction angle of > 55°, an anteversion angle of > 30° or both. Other studies with the same design of component have reported no significant outliers.

The median Cr and the Co levels are lower with the CoM bearing compared with the MoM at all measurements points following implantation. The median background (pre-operative) levels for the combined CoM and MoM group were Cr: 0.22ug/l and Co: 0.49ug/l. These were significantly different (p=0.006).

In the CoM group, the median 12m Cr and Co values were 0.43ug/l and 0.72ug/l respectively. The comparable values for MoM are 0.68ug/l and 0.83ug/l. Increases in metal ion levels from pre-operative levels are used as the primary ion level outcome in this study because the background level will comprise of the order of 30–50% of the overall value. The increase in Cr for CoM and MoM from pre-op levels to 12m significantly different for Cr (p=0.015). It has a lower significance for combined metal ion levels (p=0.029). This difference in not significant for Co (p=0.195).

In agreement with predictions from hip simulator studies, CoM bearings in this study produced lower levels of metal ions than comparable MoM bearings at all time points. However the difference is less than that predicted in the laboratory and is much more pronounced with Cr than with Co.

Purpose: Whole blood metal ion levels remain a concern in those patients undergoing total hip replacement with metal bearing surfaces. The determination of baseline reference levels are essential if useful information can be gleaned from in vivo studies of functioning implants. We set out to prospectively determine chromium and cobalt metal ion concentrations in patients undergoing total hip replacement to determine reference levels of these metal ions.

Method: 100 patients with normal renal function, no occupational or environmental exposure to cobalt and chromium, and an absence of implanted metals were recruited into the study. Metal ion levels were determined using two different assay methods. Both ICP-MS (Inductively Coupled Plasma Mass Spectroscopy) and GFAAS (Graphite Furnace Atomic Adsorption Spectroscopy) are well recognized analytical techniques for the quantification of trace elements. Levels were correlated with gender, age and place of residence.

Results: There was considerable variability in whole blood metal ion levels, with the ICP-MS being more sensitive and consistent than the GFAAS method. Direct comparison of concentration levels determined by the two methods revealed no significant correlation. There was no correlation with age, gender and place of residence.

Conclusion: Our findings would favour the use of the ICP-MS to determine reference levels and as a baseline for metal ion surveillance pre-operatively in patients undergoing metal-on-metal total hip replacements. We also determined that changes in whole blood metal ion levels are more significant than actual levels in patients who have undergone total hip replacement.

Recurrent patellar dislocation is a relatively common disorder in young patients. Historically, treatment options have been based on the underlying disorder predisposing the patient to the dislocation. This has resulted in various soft tissue reefing procedures, patella tendon realignment procedures and boney realignment procedures.

Further research has shown that the medial patello-femoral ligament (MPFL) is the primary restraint to lateral patella subluxation and dislocation. Many authors have published their successful treatment of recurrent patella dislocation by reconstruction of the medial patellofemoral ligament. The most widely used is autologous semitendinosis tendon grafts, as well as synthetic materials, and MPFL reconstructions may be combined with boney procedures. Varieties of fixation techniques have been described involving both the patella and femoral sides.

We present a technique of MPFL reconstruction using the autologous ipsilateral quadriceps tendon. Our technique avoids the morbidity associated with semitendinosis graft harvesting and the drill holes in, and potential resulting fracture of, the patella. The technique is also simple and is associated with decreased procedure costs.

We present the technique and a series of six patients (seven knees) with follow up ranging from eight months to nine years. The average age of patients at the time of surgery 16 to 28 years (mean = 20 years). There have been no redislocations. The median Kujala patellofemoral knee score at follow up was 97 out of 100 (Range 69–100). The results compare very favorably to published results using other techniques.

Our technique of reconstructing the MPFL is reliable, produces good results using an objective knee score, and is cost effective.

Seventy staff members participated from a potential pool of approximately one hundred staff on duty at the time. Of the seventy staff who participated in this research project a total of three staff members were within 50 mls of the correct amount for each of the three samples. Overall staff were very poor at estimating blood loss.

Staff working in the operating theatre, no matter what their affiliation or years of experience, are not accurate when estimating blood loss spilt into a patients bed. A tool that aids in blood loss estimation is a valuable addition to the theatre resource manual.

Dislocations remain a significant problem, especially after revision hip surgery. Revision of components, particularly in elderly patients with co-morbidities, can be fraught with complications. The surgeon’s options are sometimes restricted, particularly when the acetabular and femoral components are well fixed. Increased head lengths are often utilised to increase tissue tension, and thus improve stability.

As a niche solution we have designed a low cost modular femoral neck extender. They are manufactured from medical grade Cobalt-Chrome, conforming to ISO 200, CE mark and EN46001 standards. Available in three incremental lengths and with different connecting Morse tapers, increases in effective neck lengths of up to 49 mms can be achieved. When both the original acetabular and femoral components are well orientated, the resultant increased tissue tension imparts stability to the hip.

We present a series of five patients where we have used a femoral neck extender to achieve stability of a total hip replacement. Four patients had had multiple previous dislocations. One patient was unstable at the time of revision surgery because of a high hip centre. The average age of the patients was 72 years, and the number of previous dislocations averaged four. The average follow-up after surgery was 22 months. No patients have redislocated their hips.

We present our novel femoral neck extenders as an elegant and cost effective solution to convert an unstable hip to a stable hip, especially when the patient has well fixed and orientated components not in themselves requiring revision.

A randomised prospective study of four bearing surfaces in hip replacements is being conducted. The primary objective is to identify the best long term bearing surf ace clinically and radiographically, and metal ion levels have been measured in all cases.

Patients have been randomised to the four bearing surfaces viz. Ceramic-on-XLinked Polyethelene, Ceramic-on-Ceramic, Metal-on-Metal and Ceramic-on-Metal. Pre-operative blood samples and follow-up blood samples for metal ion analysis using ICP-MS method have been taken in all patients. As at February 2008 187 patients have been recruited, and metal ion levels at one year are available in 52 patients.

Metal ion levels are not increased with Ceramic-on-XLPE or Ceramic-on-Ceramic bearings. At one year follow-up the metal ion levels in Ceramic-on–Metal bearings is half that of Metal-on-Metal bearings using mean levels, and one third using median levels. Of note is that chromium levels in Ceramic-on-Metal bearings is the least elevated.

Due to the laboratory evidence that ceramic-on-metal bearings have the best surf ace wear characteristics with no head stripe wear on a ceramic head, and the laboratory and clinic al evidence of lower metal ion levels, Ceramic-on-Metal hip replacements could be one of the bearing surfaces of the future.

Recurrent patellar dislocation is a relatively common disorder in young patients. Historically, treatment options have been based on the underlying disorder predisposing the patient to the dislocation. This has resulted in various soft tissue reefing procedures, patella tendon realignment procedures and boney realignment procedures.

Further research has shown that the medial patellofemoral ligament (MPFL) is the primary restraint to lateral patella subluxation and dislocation. Many authors have published their successful treatment of recurrent patella dislocation by reconstruction of the medial patellofemoral ligament. The most widely used is autologous semitendinosis tendon grafts, as well as synthetic materials, and MPFL reconstructions may be combined with boney procedures. Varieties of fixation techniques have been described involving both the patella and femoral sides.

We present a technique of MPFL reconstruction using the autologous ipsilateral quadriceps tendon. Our technique avoids the morbidity associated with semitendinosis graft harvesting and the drill holes in, and potential resulting fracture of, the patella. The technique is also simple and is associated with decreased procedure costs.

We present the technique and a series of 6 patients (7 knees) with follow up ranging from 8 months to 9 years. The average age of patients at the time of surgery 16–28 years (mean = 20years). There have been no redis-locations. The median Kujala patellofemoral knee score at follow up was 97 out of 100 (Range 69–100). The results compare very favourably to published results using other techniques.

Our technique of reconstructing the MPFL is reliable, produces good results using an objective knee score, and is cost effective.

Dislocations remain a significant problem, especially after revision hip surgery. Revision of components, particularly in elderly patients with co-morbidities, can be fraught with complications. The surgeon’s options are sometimes restricted, particularly when the acetabular and femoral components are well fixed. Increased head lengths are often utilized to increase tissue tension, and thus improve stability.

As a niche solution we have designed a low cost modular femoral neck extender. They are manufactured from medical grade Cobalt-Chrome, conforming to ISO 200, CE mark and EN46001 standards. Available in 3 incremental lengths and with different connecting Morse tapers, increases in effective neck lengths of up to 49 mm can be achieved. When both the original acetabular and femoral components are well orientated, the resultant increased tissue tension imparts stability to the hip.

We present a series of 5 patients where we have used a femoral neck extender to achieve stability of a total hip replacement. 4 patients had had multiple previous dislocations. 1 patient was unstable at the time of revision surgery because of a high hip centre. The average age of the patients was 72 years, and the number of previous dislocations averaged 4. The average follow-up after surgery was 22 months. No patients have redislocated their hips.

We present our novel femoral neck extenders as an elegant and cost effective solution to convert an unstable hip to a stable hip, especially when the patient has well fixed and orientated components not in themselves requiring revision.

Whole blood metal ion levels remain a concern in those patients undergoing total hip replacement with metal bearing surfaces. The determination of baseline reference levels are essential if useful information can be gleaned from in vivo studies of functioning implants. We set out to prospectively determine chromium and cobalt metal ion concentrations in patients undergoing total hip replacement to determine reference levels of these metal ions.

100 patients with normal renal function, no occupational or environmental exposure to cobalt and chromium, and an absence of implanted metals were recruited into the study. Metal ion levels were determined using two different assay methods. Both ICP-MS (Inductively Coupled Plasma Mass Spectroscopy) and GFAAS (Graphite Furnace Atomic Adsorption Spectroscopy) are well recognized analytical techniques for the quantification of trace elements. Levels were correlated with gender, age and place of residence.

There was considerable variability in whole blood metal ion levels, with the ICPMS being more sensitive and consistent than the GFAAS method. Direct comparison of concentration levels determined by the two methods revealed no significant correlation. There was no correlation with age, gender and place of residence

Our findings would favour the use of the ICP-MS to determine reference levels and as a baseline for metal ion surveillance pre-operatively in patients undergoing metal-on-metal total hip replacements. We also determined that changes in whole blood metal ion levels are more significant than actual levels in patients who have undergone total hip replacement.

A randomised prospective study of 4 bearing surfaces in hip replacements is being conducted. The primary objective is to identify the best long term bearing surface clinically and radiographically, and metal ion levels have been measured in all cases.

Patieents have been randomised to the 4 bearing surfaces viz. Ceramic on XLinked Poly, Ceramic on Ceramic, Metal on Metal and Ceramic on Metal. Pre operative blood samples and follow up blood samples for metal ion analysis using the ICPMS method have been taken in all patients. As at February 2008 187 patients have been recruited, and metal ion levels at 1 year are available in 52 patients.

Metal ion levels are not increased with Ceramic on XLinked Poly or Ceramic on Ceramic bearings. At 1 year follow up the metal ion levels in Ceramic on Metal bearings is half that of Metal on Metal bearings using the mean levels, and one third using the madian levels. Of note is that the chromium levels in Ceramic on Metal bearings is the least elevated.

Due to laboratory evidence that Ceramic on Metal bearings have the best surface wear characteristics with no head stripe wear, and laboratory and clinical evidence of lower metal ion blood levels, Ceramic on Metal hip replacements could be a bearing surface of the future.

Whole blood metal ion levels remain a concern in those patients undergoing total hip replacement with metal bearing surfaces. The determination of baseline reference levels are essential if useful information can be gleaned from in vivo studies of functioning implants. We set out to prospectively determine chromium and cobalt metal ion concentrations in patients undergoing total hip replacement to determine reference levels of these metal ions.

100 patients with normal renal function, no occupational or environmental exposure to cobalt and chromium, and an absence of implanted metals were recruited into the study. Metal ion levels were determined using two different assay methods. Both ICP-MS (Inductively Coupled Plasma Mass Spectroscopy) and GFAAS (Graphite Furnace Atomic Adsorption Spectroscopy) are well recognised analytical techniques for the quantification of trace elements. Levels were correlated with gender, age and place of residence.

There was considerable variability in whole blood metal ion levels, with the ICP-MS being more sensitive and consistent than the GFAAS method. Direct comparison of concentration levels determined by the two methods revealed no significant correlation. There was no correlation with age, gender and place of residence.

Our findings would favour the use of the ICP-MS to determine reference levels and as a baseline for metalion surveillance pre-operatively in patients undergoing metal-on-metal total hip replacements. We also determined that changes in whole blood metal ion levels are more significant than actual levels in patients who have undergone total hip replacement.

This study reports on ceramic-on-metal (CoM) bearings in total hip replacement. Whole blood metal ion levels were measured. The median increase in chromium and cobalt at 12 months was 0.08 μg/1 and 0.22 μg/1, respectively, in CoM bearings. Comparable values for metal-on-metal (MoM) were 0.48 μg/1 and 0.32 μg/1. The chromium levels were significantly lower in CoM than in MoM bearings (p = 0.02). The cobalt levels were lower, but the difference was not significant. Examination of two explanted ceramic heads revealed areas of thin metal transfer. CoM bearings (one explanted head and acetabular component, one explanted head and new acetabular component, and three new heads and acetabular components) were tested in a hip joint simulator. The explanted head and acetabular component had higher bedding-in. However, after one million cycles all the wear rates were the same and an order of magnitude less than that reported for MoM bearings. There were four outliers in each clinical group, primarily related to component malposition.

The search for the ideal bearing surfaces to be used in Total Hip Replacement continues. The current “best” materials are felt to be various combinations of metal, ceramics and cross-linked polyethylene. Laboratory studies suggest that ceramic-on-metal articulations may provide distinct advantages. This study aims to identify the best combination with the lowest side effect profile.

In February 2004 a prospective randomised trial on different bearing surfaces was started. The combinations selected were ceramic-on-cross-linked polyethylene, ceramic-on-ceramic, metal-on-metal and ceramic-on-metal. Institutional ethics clearance was obtained. In all patients uncemented femoral stems are used, with an uncemented porocoated acetabular shell. A uniform 28mm femoral head size was selected. Blood samples have been taken to measure the metal ion concentrations in all patients. These are measured pre operatively, and repeated at follow up visits at 3 months and 1 year, with further follow up at 3,5 and 10 years post operatively. Whole blood ion levels are measured using a graphite furnace atomic absorption spectrometer.

Between February 2004 and April 2006 one hundred and ten hips have undergone total hip replacement. There are 105 patients (5 bilateral). 40% are males and 60% female. The average age at operation is 52 years (17 to 72). 49% hips are left and 51% right. Follow up includes blood samples and the Harris Hip Score. Complications to date have been surgeon related, with three femoral components needing early revision for technical reasons. This has not affected the bearing surfaces. Radiological and clinical assessment shows no difference between the different bearing surface groups.

Post operative whole blood metal ion levels are compared to the patient’s pre operative level. To date there is no increase in the metal ion levels for the ceramic-on-cross linked polyethylene and ceramic-on-ceramic articulations. The ceramic-on-metal group is providing moderately raised metal ion levels, and the highest metal ion levels are in the metal-on-metal articulation group. At one year, the ceramic-on-metal group demonstrates a drop to close to pre-operative levels and these are still significantly lower than the metal-on-metal group. This confirms laboratory studies on the ceramic-on-metal articulation, which demonstrate significantly lower wear than comparable metal-on-metal articulations. The high level of metal ions in the latter groups has always been of concern.

This study demonstrates a lower blood level of metal ions in the ceramic-on-metal group. If the in vivo wear rate in this group continues to replicate the laboratory wear studies, this articulation becomes a very attractive bearing surface in younger active patients, and may well become a bearing surface of choice in the future.