Aims

It is not known whether change in patient-reported outcome measures (PROMs) over time can be predicted by factors present at surgery, or early follow-up. The aim of this study was to identify factors associated with changes in PROM status between two-year evaluation and medium-term follow-up.

Aims

The aim of this study was to report the implant survival and patient-reported outcome measures (PROMs) in a consecutive series of patients aged less than 50 years at the time of arthroplasty using the Birmingham Hip Resurfacing system (BHR), with a minimum follow-up of ten years.

The aim of this study was to report the procedure survival and patient-reported outcomes in a consecutive series of patients <50yrs at the time of hip arthroplasty with a metal-on-metal hip resurfacing system who have progressed to a minimum of 10yrs follow-up. Patients presenting for treatment of degenerative conditions of the hip electing to undergo hip resurfacing were included in a clinical registry (N=226 patients; 238 procedures). Procedure survival was confirmed by crosschecking to the Australian Orthopaedic Association National Joint Replacement Registry and comparing to all procedures by other surgeons nationwide. Kaplan-meier survival curves with 95% confidence intervals were constructed, while patient-reported outcome measures were compared with t-tests and postoperative scores assessed with anchor analysis to age and gender-matched normative data. At mean follow up of 12 years, six cases were revised with a cumulative survival rate of 96.8% (95%CI 94.2–99.4) at 15 years. Majority of revisions were early (<3yrs) and occurred in females (N=4). Patient-reported general health, disease state, hip function and activity level maintained large improvements beyond 10 years post-implantation and were equal to or exceeded age and gender-matched normative data. Metal-on-metal hip resurfacing in males and females aged <50 years at time of surgery demonstrated a high rate of cumulative survival beyond 10 years follow up. The results demonstrate excellent outcomes in this age group.

The Birmingham hip resurfacing (Smith & Nephew, Tennessee) (BHR) has been used in younger more active patients.

Aim

Adverse tissue reactions have been a concern in relation to metal components, particularly in hip replacements. We look at a possible correlation between hip joint effusion and metal ion levels.

There has recently been an increase in the number of hip replacement procedures performed through an anterior approach. Every procedure has a risk profile, and in the case of a new procedure or technique it is important to investigate the incidence of complications. The aim of this study is to identify the complications encountered in the first 100 patients treated with the minimally invasive anterior approach.

This is a case series of the first 100 hips treated and were assessed for complications. These were classified according to the severity and outcome [1]. The 100 hip comprised of 98 patients; 46 males and 52 females with an average operation age on 70.1 (±9.38) years. There were 2 bilateral procedures. Specific patient selection criteria were used. All complications occurred within one month of surgery. Complications such as fracture, deep vein thrombosis (DVT), cup malposition, femoral stem malposition, retained screw, excessive acetabular reaming and skin numbness were noted. Complications associated with fracture were characterized as either periprosthetic or trochanteric. Clinical outcome scores of SF36v2, WOMAC, Harris Hip and Tegner activity score were analysed at pre-operative, 6 months, 12 months 24 months and 36 months intervals.

A total of 13 early complications occurred. Of these 13 complications the most common complications were trochanteric fracture, 3 instances (3.00%), periprosthetic fracture, 2 (2.00%), DVT, 2 (2.00%), numbness, 2 (2.00%) and loosening. Other complications recorded were cup malposition, 1 (1.00%), femoral stem malpositon, 1 (1.00%), retained screw, 1 (1.00%) and excessive acetabular reaming, 1 (1.00%). All fractures occurred in patients over the age of 60 years.

Significant differences (p<0.05) were observed between all clinical outcomes measures pre-operatively and postoperatively (6, 12, 24 and 36 months). The unfamiliarity of the approach, however, increased operating time, and exposure problems, lead to trochanteric fracture.

Introduction

Dissatisfaction with the posterior approach to total hip replacement has led to the anterior approach being adopted with enthusiasm in some areas.

Introduction

The observation of elevated heavy metal ions in arthroplasty patients in association with complications has led to concern on the part of patients and surgeons. The aim of this study was to determine the levels of cobalt chromium ions in three compartments, the joint fluid, plasma, and CSF.

Comparisons of blood metal ion levels of cobalt and chromium (CoCr) between metal-on-metal total and resurfacing hip arthroplasties are limited. High levels of CoCr may result in long-term adverse biological effects. We compare metal ions levels between total and resurfacing implants.

70 patients (28 males and 42 females) had a total hip arthroplasty using the Birmingham (Smith & Nephew) modular femoral component and a variety of stems, articulating with the Birmingham resurfacing component. The average age was 65.5 (±6.8) years and an average follow-up of 6.0 (±2.2) years. 170 patients (145 male and 25 female had a Birmingham resurfacing arthroplasty with an average age of 54.7 (±9.9) years and an average follow-up of 5.9 (±3.0) years. CoCr levels were measured. Bivariate correlations and independent samples t-tests were applied to determine similarities and differences within and between groups.

Average ion levels in total arthroplasty patients were: Co 114.17 (±94.01) nmol/L (range 2–414); and Cr 75.12 (±68.45) nmol/L (range 10–312). Average levels in hip resurfacing arthroplasty were: Co 55.98 (±79.5) nmol/L (range 7–505); and Cr 70.77 (±87.41) nmol/L (range 5–751). Both total and resurfacing groups showed significant correlations (p<0.01) between Co and Cr levels. A significant difference was observed between the total and resurfacing group Co levels (p<0.0001). No significant difference was shown between group Cr levels (p>0.672).

The average total hip replacement CoCr levels were higher than the hip resurfacing levels. While the overall activity level may be higher in the resurfacing group, possibly the incidence of stop/start frequency may be higher in the total hip replacement group.

Hip resurfacing arthroplasty average CoCr levels are lower than those of total hip replacement patients. Associations between Co and Cr metal ion levels are shown within each group. Co levels differ significantly between groups where Cr does not. Long-term follow-up of CoCr levels are required.

The Repicci modification of the Marmor unicompartmental arthroplasty (UKA) has provided a minimally invasive alternative to proximal tibial osteotomy for localised osteoarthritis. Advantages of UKA include preservation of bone, faster rehabilitation and maintained function. This study analyses the survivorship of the Repicci medial compartment arthroplasty with a minimum 10-year follow-up.

438 medial UKR procedures were performed between 01/01/1998 and 01/07/2001 included 68 bilateral procedures in 370 patients. The patients comprised of 229 males and 141 females. A specific set of selection criteria were used, including clinical, radiological, an arthroscopic data. The average age at operation was 66.7 years. The average follow-up was 12.8 years. For the patients who are not reachable, we sought the help of the Australian joint replacement registry. All revisions were identified. Procedures were reviewed to determine survivorship and function. Clinical outcomes scores of SF36v2. WOMAC and Oxford Knee were analysed at pre-operative, 1, 3, 5 and 10 year intervals.

In 54 patients (64 procedures) the implant was in situ at the time of death. Revision was carried out in 37 knees (8.5%) at a mean time period of 7.8 years (1–13) post-operatively. Of the revisions, the commonest cause was progression of arthritic changes in the lateral compartment, 25 patients. Loosening of the tibial component was present in six patients and for six patients whose data was obtained from the registry, revision was documented, but no cause was identified. Kaplan-Meier investigation showed survivorship of 91.6% to 12.5 years. Average pre-operative, 1, 3, 5 and 10 years SF36v2 Total scores were 107.80, 124.57, 124.83, 111.14 and 121.47. WOMAC Total scores for pre-operative, 1, 3, 5 and 10 years were 51.96, 83.34, 80.59, 82.00 and 78.54. Oxford Knee scores for pre-operative, 1, 3, 5 and 10 years were 35.76, 20.99, 19.28, 19.61 and 21.16.

Significant differences (p<0.0001) were observed between all pre-operative and post-operative 1, 3, 5 and 10 year outcomes of SF36v2, WOMAC and Oxford Knee scores.

UKR is an operation which is often regarded as a temporising procedure, on the way to a total knee replacement, the attrition rate is less than 1% per year, indicates that long-term function is a goal which may be achievable.

UKR provides satisfactory function, with a low revision rate, and a minimally invasive approach does not decrease the efficacy, while currently, improving function, speed of recovery, and patient satisfaction. Patient selection, particularly in relation to the status of the lateral compartment articular surface may be an important aspect in minimising revision incidence.

The Birmingham mid-head hip resurfacing arthroplasty (Smith & Nephew, Tennessee) (BMHR) is designed for use in patients with avascular necrosis of the femoral head. The BMHR has limited short-mid term follow-up results. We report the experience of 27 consecutive BMHR procedures with a minimum two year follow-up.

23 patients (20 males and 3 females) with an average operation age of 49.8 years (SD ±10.9) (22–65) were investigated. The mean follow-up period was 3.0 years (SD ±0.77). The operations were between April 2008 and November 2011 by one surgeon. Data and outcome measurements were collected prospectively and analysed retrospectively. Procedures were reviewed to determine function. We evaluated Harris Hip Scores, Short Form-36 (SF-36v2) Scores, Tegner Activity Score Scores and McMaster Universities Osteoarthritis Index Scores (WOMAC) comparatively at preoperative, six month and yearly intervals. Paired samples t-tests were applied to determine improvements where p<0.05 was deemed as significant.

There were no patient deaths. There were no revisions. Harris Hip scores for pre-operative 6, 12, 24 and 36 month intervals were: 52.30, 84.14, 83.07, 87.50 and 89.50. Average pre-operative 6, 12, 24 and 36 month SF36v2 Total scores were: 116.54, 124.32, 130.44, 135.97 and 133.18. Tegner scores for pre-operative 2.75, 3.29, 3.00, 3.67 and 3.01. WOMAC Total scores for aforementioned intervals for the posterior approach were: 59.51, 84.22, 90.30, 86.86 and 92.25.

The mean Harris Hip scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.001). The mean SF-36v2 physical scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.016). WOMAC scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.017).

The presence of avascular necrosis significantly increases the revision rate for hip resurfacing surgery. The BMHR prosthesis, in this short term follow-up, appears to avoid the main cause of failure, femoral component loosening. Longer term efficacy remains to be seen. We plan to continue close supervision of these patients.

Gentamicin sulphate is a potent antibiotic, widely used by clinicians to treat Staphylococcus aureus bacterial complications in orthopaedic surgery and osteomyelitis. Antibiotics as administered are poorly localised and can accumulate with toxic effects. Achieving a better targeted release and controlled dosage has been an ongoing unmet microengineering challenge.

In this study we evaluated the antibiotic release potential of beta tricalcium phosphate (β-TCP) micro and macrospheres to eradicate Staphylococcus aureus and maintain osteoblast biocompatibility. Gentamicin was absorbed onto and within the spheres at an average amount of 4.2 mg per sample. Human osteoblast cell studies at five days incubation showed attachment and growth on the spheres surface with no detrimental effect on the cell viability. A time delayed antibacterial efficacy test was designed with the bacteria introduced at predetermined time intervals from 0–60 minutes.

We demonstrated that hydroxyapatite covered Foraminifera nano-, micro- macrospheres facilitated the slow release of the encapsulated pharmaceutical agent. Principally, this arises owing to their unique architecture of pores, struts and channels, which amplifies physiological degradation and calcium phosphate dissolution to release attached pharmaceuticals in a controlled manner. The Staphylococcus aureus growth response following exposure to the gentamicin incorporated microspheres at various time intervals showed the complete elimination of the bacteria within 30 minutes. Gentamicin release continued with no re-emergence of bacteria.

β-TCP nano to macro size spheres show promise as potential bone void filler particles with, in this case, supplementary delivery of antibiotic agent. Owing to their unique structure, excellent drug retention and slow release properties, they could be used in reconstructive orthopaedics to treat osteomyelitis caused by Staphylococcus aureus and possibly other sensitive organisms.

The Birmingham Hip Resurfacing (BHR) has been used in the younger more active patient for the treatment of advanced osteoarthritis. Long-term follow-up of the BHR is limited. The Australian national joint replacement registry shows that failure rates vary greatly, depending on implant types. 77 consecutive BHR procedures with a minimum ten year follow-up are reported.

There were 70 patients (44 males and 26 females) with an average operation age of 57.4 years (SD ±12.6). All patients were evaluated, including the “learning curve” patients. The mean follow-up period was 11.42 years (SD ±0.50). The arthroplasties were performed between April 1999 and December 2000 by one surgeon, with a standardised patient selection set of criteria. Data and outcome measurements were collected prospectively and analysed retrospectively. We evaluated Harris Hip Scores, Short Form-36 (SF-36v2) Scores, Tegner Activity Score Scores and McMaster Universities Osteoarthritis Index Scores (WOMAC) comparatively at preoperative, six month and yearly intervals

In 8 patients (10 procedures) the implant was in situ at the time of death. Revision was carried out in 6 hips (7.8%) at a mean time period of 2.5 years (0–10) post-operatively. Failure was due to femoral neck fracture in four patients, acetabular loosening in one and avascular necrosis of the femoral head, leading to loosening, in one patient. Kaplan-Meier analysis showed survivorship of 92.2% to 10 years. The mean Harris Hip scores (paired t-test, p<0.05) improved significantly from 59.7 preoperatively to 80.1 at ten years. The mean SF-36v2 physical scores (paired t-test, p<0.05) improved significantly from 35.09 preoperatively to 47.83 at ten years. WOMAC scores (paired t-test, p<0.05) improved significantly from 54.61 preoperatively to 85.89 at ten years.

The BHR prosthesis, in this series, has been shown to be effective, reliable, and durable in this group of highly active, relatively young patients. Problems with metallic debris, sensitivity reactions, and osteolysis have not been seen. However, we believe that with better selection criteria, improved understanding of component positioning and surgical techniques, results can be improved.

There is a report that higher failure rate in uncemented total knee replacement components due to loosening. However, uncemented fixation has been an attractive concept because of bone preservation and revision surgery, potential improved load transfer, and decreased surgical time. “Regenerex” is a porous titanium layer with excellent initial fixation, and the promise of providing favourable biological fixation. This is used with the Biomet Vanguard total knee replacement.

14 patients had undergone total knee replacement surgery comprising 11 men and three women with an average age of 63.07 years, and a body mass index of 30.33. Three of these patients required revision, because of tibial component loosening within 12 months of surgery. There were two men and one woman with an average age of 63.33 and BMI of 34.55. Clinically, patients developed pain and a gradual deformity as a result of a symmetrical collapse of the proximal tibial bony support surface.

Histopathology on the removed specimens shows the development of fibre cartilaginous metaplasia with evidence of necrotic bone. This was similar in all patients. There was no foreign body giant cell reaction, and no evidence of infection. The appearance was suggested of osteonecrosis, occurring gradually.

The incidence of frequency of this complication with this component in our experience is of concern, and the aim of this presentation is to determine whether this is a more widespread phenomenon.

There has recently been an increase in the number of hip replacement procedures performed through an anterior approach. Every procedure has a risk profile, and in the case of a new procedure or technique it is important to investigate the incidence of complications. The aim of this study is to identify the complications encountered in the first 100 patients treated with the minimally invasive anterior approach.

This is a case series of the first 100 hips treated and were assessed for complications. These were classified according to the severity and outcome [1]. The 100 hip comprised of 98 patients; 46 males and 52 females with an average operation age on 70.1 (±9.38) years. There were 2 bilateral procedures. Specific patient selection criteria were used. All complications occurred within one month of surgery. Complications such as fracture, deep vein thrombosis (DVT), cup malposition, femoral stem malposition, retained screw, excessive acetabular reaming and skin numbness were noted. Complications associated with fracture were characterised as either periprosthetic or trochanteric. Clinical outcome scores of SF36v2, WOMAC, Harris Hip and Tegner activity score were analysed at pre-operative, 6 months, 12 months 24 months and 36 months intervals.

A total of 13 early complications occurred. Of these 13 complications the most common complications were trochanteric fracture, 3 instances (3.00%), periprosthetic fracture, 2 (2.00%), DVT, 2 (2.00%), numbness, 2 (2.00%) and loosening. Other complications recorded were cup malposition, 1 (1.00%), femoral stem malpositon, 1 (1.00%), retained screw, 1 (1.00%) and excessive acetabular reaming, 1 (1.00%). All fractures occurred in patients over the age of 60 years. There were no dislocations.

Significant differences (p<0.05) were observed between all clinical outcomes measures pre-operatively and postoperatively (6, 12, 24 and 36 months). The unfamiliarity of the approach, however, increased operating time, and exposure problems, lead to trochanteric fracture.

The Birmingham Hip Mid Head Resection (BMHR) was designed to accommodate patients with lower quality bone in the proximal half of the femoral head. It is a relatively new conservative hip implant with promising early results. Finite element modelling may provide an insight into mid-term results.

A cadaveric femur was CT scanned and 3D geometry of the intact femur constructed. The correctly sized BMHR implants (with and without visual stop) were positioned and these verified by a surgeon; hence constructing the post-operative models. Walking loads were applied and contact surfaces defined.

Stress analyses were performed using the finite element method and contact examined. Also, a strain-adaptive bone remodelling analysis was run using 45% gait hip loading data. Virtual DEXA images were computed and were analysed in seven regions of the bone surrounding the implants.

The BMHR was found to be mechanically stable with all surfaces indicating micromotion less than the critical 150 microns. Stress distribution was similar to the intact femur, with the exception of the head-neck region where some stress/strain shielding occurs. This is mirrored in the bone remodelling results, which show some bone resorption in this region. The visual stop, which is designed to ensure that the stem is not overdriven during implantation, did not affect the stress/strain results; only on a very local scale.

There is minimal data available in the literature regarding conservative hip implants and no data regarding the BMHR. This study is the first to look at the mechanical response of the bone to this implant.

The major advantage of hip resurfacing is the decreased amount of bone resection compared with a standard total hip replacement. Fracture of the femoral neck is the most common early complication and poor bone quality is a major risk factor. We undertook a prospective consecutive case control study examining the effect of bone mineral density changes in patients undergoing hip resurfacing surgery. A total of 423 patients were recruited with a mean age of 54 years (24 to 87). Recruitment for this study was dependent on pre-operative bilateral femoral bone mineral density results not being osteoporotic. The operated and non-operated hips were assessed. Bone mineral density studies were repeated over a two-year period. The results showed no significant deterioration in the bone mineral density in the superolateral region in the femoral neck, during that period.

These findings were in the presence of a markedly increased level of physical activity, as measured by the short-form 36 health survey physical function score.

Introduction: High ion release along with bone resorption at the bone/implant interface is still a problem, leading to pain, poor function and the possibility of bone fracture. Treatment of a loose implant is not easy and can lead to less than satisfactory revision surgery. The reason for ion release, loosening or periprosthetic fracture of an implant is multifactorial. One factor for ion release that has been reported is inclination angle. Another can be the version angle of the implant and subjecting it to an abnormal loading environment. Few studies have been reported in the literature on hip resurfacing performance based on implant orientation. More studies are required into investigating the use of this predictive technique in orthopaedics to investigate the bearing behaviour and potential ion release due to implant surgical positioning. In this study we modeled a number of different version angles and investigated the contact area, stress and wear characteristics using the finite element method.

Methods: CT scans were used to reconstruct the part of the femur and pelvic geometry. A 3D finite element mesh was created using PATRAN (MSC Software, Santa Ana, CA). The femur loading was taken at peak load position of the gait cycle. The loading was applied to the femur and pelvis was fixed. Material properties were applied using the Hounsfield units from the CT file. Two models were generated, a preoperative and a postoperative state model. The post operative model was reconstructed using the Birmingham Hip Replacement (BHR) system (Smith & Nephew Inc, Memphis, TN). The BHR acetabular cup was oriented at different anteversion angles (5°, 30° & 45° to the saggital plane) to investigate the contact mechanics between the head and cup. Serum ion levels were taken from 12 patients and the change in ion levels over the first 12 month period were analysed statistical to investigate the correlation with anteversion angle. Radiographs from the same patients were analysed to determine the cup anteversion angle using image analysis and edge matching techniques.

Results: The contact areas increased with increasing anteversion angle, 137.3, 165.3 and 169.9mm2 respectively. As a consequence, the contact pressure decreased. The change in ion levels for the patients over the first 12 month period correlated significantly (p< .05) with the anteversion angle using Pearson’s r test.

Discussion: Statistical analysis showed a good Pearson’s correlation of anteversion angle to a change in serum ion levels, 0.867 and 0.734 with p values of 0.001and 0.012 respectively. Acetabular version angle appears to be, at the least, important in determining serum metal ion levels and in evaluating causes of metallosis, the influence of anteversion angle needs to be considered when using metal on metal bearing technology when placing the cup in the acetabulum.

The aim of the study was to develop a simple and effective method of determining acetabular component ante-version at the time of surgical implantation. A technique using a laser beam was developed, and put into practice.

Ante-version and closure of the component determine the three-dimensional position. Ante-version is particularly difficult to judge because of lack of perspective from the surgeons position. Using a standard industrial laser, a protractor and a tripod, a beam is projected across the operative field, allowing the acetabular impactor handle to be lined up, at predetermined angle. The patient needs to be positioned accurately preoperatively, and secured in a stable fashion to the operating table. The operating table needs to be parallel to the floor.

We have found this technique easy-to-use. It is less invasive than the computer navigation techniques requiring skeletal fixation, but it does not provide as much information. It is simple, inexpensive, easily transportable. As far as anteversion measurement is concerned, because of the longer distance of projection it provides a greater degree of confidence in alignment, than the standard short jigs which attach to the handle of the acetabular impactor.

The aim of the study was to examine the stress and strain relationships in proximal femurs, using finite element analysis techniques. We looked at normal, osteoporotic and osteoarthritic models, to detect any differences, and specifically, in relation to neutral or valgus alignments of the femoral components in a cemented prosthetic femoral head resurfacing situation. A CAD model of a third-generation composite femur was virtually operated upon to implant the femoral component. The femoral component, geometry was of a 54 mm Birmingham hip resurfacing. A 1 mm cement mantle was allowed for. Finite element model is were generated with 10 node tetrahedral elements. The material properties of both cortical and cancellous bone were assigned according to standard parameters.

Our analysis of the stress and strain in the resurfaced femoral head under the implant showed significant reductions in the stress and strain compared to the intact femur and this was the case for all stem-bone interface conditions. This region of high stress and strain was not seen in the model with the stem was overreamed and there was no bone contact with the stem. The stress and strain levels were generally higher when osteoporotic bone was modelled. The peak maximum tensile stress and strain in the cortical bone at the superolateral femoral neck was 4% to 24% greater in the resurfaced femur for all by the conditions with valgus implant positioning experiencing high at peak stresses and strain then neutral alignment. Maximum tensile stress in the cement at the had- implant rim junction was not greatly different for the different bone conditions except for osteoporosis where the stress was almost 50% greater than the other bone conditions. Generally the highest tensile stresses occurred anteroinferiorly and were greater in the neutral alignment than in the valgus alignment. The superolateral offset associated with a valgus orientation, rather than the valgus orientation itself maybe what reduces the stress and strain in the neck leading to a lower incidence of fracture. Stresses were lower than 8 MPa, the fatigue strength of cement, for all the valgus models except osteoporosis. All neutral models contained some locations where the tensile stress exceeded 8 MPa.

The postoperative stress and strain in the femoral head and neck maybe increased in comparison to the intact femur. Under the component there may be significant reduction in stress and strain, causing resorbtion. The biomechanical reason why a more valgus orientation protects against femoral neck fracture is more complex, sends in some critical locations stress and strain has reduced but in others it is increased. Further study is being planned.