First-time revision acetabular components have a 36% re-revision rate at 10 years in Australia, with subsequent revisions known to have even worse results. Acetabular component migration >1mm at two years following revision THA is a surrogate for long term loosening. This study aimed to measure the migration of porous tantalum components used at revision surgery and investigate the effect of achieving press-fit and/or three-point fixation within acetabular bone.

Between May 2011 and March 2018, 55 patients (56 hips; 30 female, 25 male) underwent acetabular revision THR with a porous tantalum component, with a post-operative CT scan to assess implant to host bone contact achieved and Radiostereometric Analysis (RSA) examinations on day 2, 3 months, 1 and 2 years. A porous tantalum component was used because the defects treated (Paprosky IIa:IIb:IIc:IIIa:IIIb; 2:6:8:22:18; 13 with pelvic discontinuity) were either deemed too large or in a position preventing screw fixation of an implant with low coefficient of friction. Press-fit and three-point fixation of the implant was assessed intra-operatively and on postoperative imaging.

Three-point acetabular fixation was achieved in 51 hips (92%), 34 (62%) of which were press-fit. The mean implant to host bone contact achieved was 36% (range 9-71%). The majority (52/56, 93%) of components demonstrated acceptable early stability. Four components migrated >1mm proximally at two years (1.1, 3.2, 3.6 and 16.4mm). Three of these were in hips with Paprosky IIIB defects, including 2 with pelvic discontinuity. Neither press-fit nor three-point fixation was achieved for these three components and the cup to host bone contact achieved was low (30, 32 and 59%).

The majority of porous tantalum components had acceptable stability at two years following revision surgery despite treating large acetabular defects and poor bone quality. Components without press-fit or three-point fixation were associated with unacceptable amounts of early migration.

First-time revision acetabular components have a 36% re-revision rate at 10 years in Australia, with subsequent revisions known to have even worse results. Acetabular component migration >1mm at two years following revision THA is a surrogate for long term loosening. This study aimed to measure the migration of porous tantalum components used at revision surgery and investigate the effect of achieving press-fit and/or three-point fixation within acetabular bone.

Between May 2011 and March 2018, 55 patients (56 hips; 30 female, 25 male) underwent acetabular revision THR with a porous tantalum component, with a post-operative CT scan to assess implant to host bone contact achieved and Radiostereometric Analysis (RSA) examinations on day 2, 3 months, 1 and 2 years. A porous tantalum component was used because the defects treated (Paprosky IIa:IIb:IIc:IIIa:IIIb; 2:6:8:22:18; 13 with pelvic discontinuity) were either deemed too large or in a position preventing screw fixation of an implant with low coefficient of friction. Press-fit and three-point fixation of the implant was assessed intra-operatively and on postoperative imaging.

Three-point acetabular fixation was achieved in 51 hips (92%), 34 (62%) of which were press-fit. The mean implant to host bone contact achieved was 36% (range 9–71%). The majority (52/56, 93%) of components demonstrated acceptable early stability. Four components migrated >1mm proximally at two years (1.1, 3.2, 3.6 and 16.4mm). Three of these were in hips with Paprosky IIIB defects, including 2 with pelvic discontinuity. Neither press-fit nor three-point fixation was achieved for these three components and the cup to host bone contact achieved was low (30, 32 and 59%).

The majority of porous tantalum components had acceptable stability at two years following revision surgery despite treating large acetabular defects and poor bone quality. Components without press-fit or three-point fixation were associated with unacceptable amounts of early migration.

Subjective outcomes used in THA show outstanding improvements in patient-reported outcomes. However, recent evidence suggests that there may be a disconnect between patient-reported and objectively measured function. The aim of this study was to investigate if physical activity and sleep patterns change from pre- to six months post primary THA.

54 patients scheduled for THA were recruited. Patients were given a wrist-worn accelerometer (GeneActiv, UK) to wear continuously for one week pre-operatively and six weeks, three months and six months post-operatively. The device was also fitted to the patient immediately following surgery to capture data for the first two post-operative weeks. The following parameters were calculated: (1) sleep efficiency; (2) the amount of time (and length of each bout and fragmentation of the activity) spent in sedentary activity; and (3) time spent in light, moderate and vigorous physical activity.

Sedentary activities showed no change in the number, duration or fragmentation (p= 0.382, 0.288, 0.382, respectively). Patients were sedentary for 5–6 bouts/day with each bout lasting 50–76 minutes/day. A significant main effect was identified for time spent in light intensity activities (p=0.049). Prior to surgery, patients spent 201 minutes/day in light intensity activity. This decreased significantly to 133 minutes/day (p=0.025) in the first two postoperative weeks before returning close to pre-operative levels (192 minutes/day) at six weeks (p=0.025). No further changes were observed in light intensity activities. A significant main effect was identified for time spent in moderate intensity activities (p=0.003). Prior to surgery, patients spent 45 minutes/day in moderate intensity activities. This dropped to 18 minutes/day in the first two postoperative weeks (p=0.190). By three months this had increased to 66 minutes/day (p=0.049). No further changes were seen. There were no significant differences in time spent in vigorous intensity activities (p=0.244). Patients spent <1minute/day in vigorous intensity activities.

Sleep efficiency did not change significantly from pre- (82%) to six months post-operative (75%) (p=0.067) − 85% is typically considered good sleep efficiency. Patients discharged to a regional hospital had significantly poorer sleep efficiency than those discharged home (mean difference=14%, p=<0.001) or to a rehabilitation centre (mean difference=15%, p=0.001).

This patient cohort didn't demonstrate an overall improvement in objectively measured physical activity patterns from pre- to six months post-operative. Sleep efficiency, did not improve and remained sub-optimal.

Introduction

Severely comminuted, displaced acetabular fractures with articular impaction in the elderly population present significant treatment challenges. To allow early post-operative rehabilitation and limit the sequelae of immobility, treatment with acute total hip replacement (THA) has been advocated in selected patients. Achieving primary stability of the acetabular cup without early migration is challenging and there is no current consensus on the optimum method of acetabular reconstruction. We present clinical results and radiostereometric analysis of trabecular metal (TM) cup cage construct reconstruction in immediate THA without acetabular fracture fixation.

Acetabular components used to treat large defects are at greater risk of loosening. Porous tantalum acetabular components have reported the most promising early to midterm revision rates. Early stability of acetabular components used at revision THR was shown to be a good predictor of later loosening. The primary aim was to assess the migration of porous acetabular component used to reconstruct severe acetabular defects. Secondarily, we investigated the effect of acetabular defect severity and type of component fixation on migration.

Radiosterometric analysis was used to measure migration at a mean follow-up of four years, (range 2–10) in 59 reconstructions of severe acetabular defects with porous tantalum components. Acetabular component fixation was classified as superior if augmented with screws through cup, augments or cage in the ilium only. Fixation was classified as combined, superior and inferior, if flanges and/or screws were also placed in the ischium and or pubis. Acceptable limits of proximal migration were defined as ≤1mm within 2 years and ≤2.5mm at any time point.

Eight hips had reconstruction of Paprosky II defects with superior fixation only. The mean proximal migration of the eight acetabular components was 0.25mm (0.08–0.40) at 2 years and 0.29mm (0.10–0.81) at last follow-up.

Fifty-one hips had reconstruction of Paprosky III defects. Seven of these reconstructions exceeded the migration thresholds. Five reconstructions (four with superior fixation and one cup cage construct with no inferior screw fixation) of hips with pelvic discontinuity developed pain and were re-revised for loosening. Two reconstructions are asymptomatic and migrated 2.68mm (cup-cage construct with superior screws) and 2.86mm (no pelvic discontinuity, superior fixation) at final follow-up. The mean proximal migration of the 51 Paprosky III reconstructions was 0.99mm (0.03 to 16.4) at 2 years and 1.92mm (0.01 to 29.4) at last follow-up. The mean proximal translation at 2 years of the 11 reconstructions with inferior screw fixation was 0.2mm (−0.6 to 0.7mm), compared with 0.9mm (−0.6 to 16.4mm) for the reconstructions without inferior screw fixation.

In conclusion, when used to reconstruct Paprosky II defects, porous tantalum acetabular components provide component stability similar to a good performing primary THR. These implants achieve adequate stability when used to treat Paprosky III defects, including those with pelvic discontinuity. For the most severe defects, combined fixation with inferior screws is recommended, particularly when reconstructing hips with pelvic discontinuity.

The primary aim of this study was to determine dislocation and revision total hip replacement (THR) up to ten years following primary THR, as well as rates of polyethylene wear, in patients previously enrolled in a randomised controlled trial (RCT) which compared 28 mm and 36 mm metal on highly cross-linked polyethylene (XLPE) articulations.

328 primary THR patients were enrolled in the RCT in Australia. Dislocation was identified from hip instability and hospital visit questionnaires completed by patients or, if they were unable to do so, by their next of kin or primary carer, or General Practitioner. All reported dislocations were confirmed radiographically. Patients' names were cross-matched with the Australian National Joint Replacement Registry to determine whether the index hip had undergone revision THR. Linear wear was measured on plain radiographs using PolyWare (Rev 5, Draftware Developers, Vevay IN, USA). A separate RCT examined the mean proximal wear rate of 28 and 36 mm articulations using radiostereometric analysis (RSA).

At 10 years, 110 patients were deceased and 3 patients were lost to follow-up. Overall, dislocation was identified in 8 of 167 (5%) patients with a 28 mm articulation and 2 of 158 (1%) patients with a 36 mm articulation. Three patients experienced recurrent dislocation; all had a 28 mm articulation. 320 (163 28 mm; 157 36 mm) patients were successfully cross-matched with Registry data to identify revision THR. Three patients, all with a 28 mm articulation, underwent revision because of dislocation. Other reasons for revision were infection (1:2), periprosthetic fracture (0:3), loosening/lysis (1:2) and liner fracture (0:1). Adequate radiographs were available to measure wear in 122 hips (67:55) using PolyWare. Excluding bedding in, the mean annual linear wear rate from 1–10 years was 0.04 mm/yr for both 28 and 36 mm articulations (p=0.48). The more sensitive RSA data indicated that at 7 years following primary THR, the mean annual wear rate did not exceed 0.02 mm/yr with either articulation.

Up to 10 years following primary THR, 36 mmm articulations were associated with fewer dislocations and revisions for dislocation and did not increase the mean annual linear wear rate.

There has not been any published work quantifying the volume cement used/needed for knee arthroplasty. The number of mixes of cement used is at the discretion of the surgeon, based on their own experience/training.

The objective of this study was to quantify the volume of cement used for knee arthroplasty in our institution, and to observe variations between surgeons and implant size. The study then aimed to calculate the theoretical volumes required and observe the volume of cement actually implanted before commenting on cost implications of cement usage.

Prospective data for 85 consecutive knee arthroplasties performed by 9 consultants was examined. A single mix in this institution refers to 40g of Palacos R+G. Significant variation between surgeons was seen, with a range of one to three mixes being used. Several surgeons used one mix exclusively, independent of implant size, whilst others exclusively used two mixes. The departmental average was 1.4 mixes per knee. The total surface area of our largest implants (Size 8 Triathlon Femoral and Tibial components) was measured-108cm² and compared to the volume of a single mix of cement −49 cm³. Even using the largest component size, a single mix will provide 4.5mm of uniform cement coverage. The volume of cement actually implanted during 10 knee arthroplasties was examined by weighing the residual cement. The average volume of cement implanted was 18cm³ per knee.

In 2009 1085 knee replacements were performed in this institution. If all surgeons in the department used a single mix of cement this could potentially save £16,357.46 per year. (Presuming average usage was 1.4 mixes per knee, 434 ‘extra’ mixes were used, costing £37.69 each) We conclude that a single mix of cement will cover the area required for all Triathlon implants and that less than half a mix (on average) is actually implanted.

Introduction

To evaluate the clinical success and hip pain and function of patients with infected hip replacement treated by two-stage exchange using a temporary implant with high dose vancomycin added to the antibiotic cement at the first stage revision.

Introduction

There has been almost universal adoption of highly cross-linked polyethylene as the polyethylene of choice in metal-on-polyethylene articulations in total hip replacement (THR). Although wear of conventional polyethylene has been shown to be related to periprosthetic osteolysis, the relationship between wear of highly cross-linked polyethylene and osteolysis remains uncertain. Our aim was to determine the incidence and volume of periacetabular osteolysis at a minimum of seven years following primary THR with metal on highly cross-linked polyethylene articulations.

Component malalignment has long been implicated in poor implant survival in Total Knee Arthroplasty (TKA). Malalignment can occur in orientation of bony cuts, and in component cementation/implantation. Several systems exist to aid bony cut alignment (navigation, shape matching), but final implantation technique is common to all TKA. Correction of errors in bony cut alignment at cementation/implantation by surgeons has been described. Changes in alignment at this stage are likely to result in asymmetrical cement penetration, which is implicated in early failure.

This study reviewed a consecutive series of 150 primary cemented TKAs using an imageless navigation system (aiming for neutral overall limb alignment). Deviation at implantation was calculated by comparing limb alignment recorded using the trial components with limb alignment recorded with the final implanted components, prior to closure.

136 patients (91%) had a final overall limb alignment within 2° of neutral. Three patients (2%) had a final overall limb alignment greater than 3° from neutral. Deviation occurring at implantation is shown in Figure 1 with deviations distributed around zero (mode 0, median 0.3, range −2 to +4,)

The aim of this study was to examine the progression of osteolytic lesions following liner exchange surgery and relate this to the size of the lesion prior to surgery, and whether the defect underwent curettage and bone grafting during surgery.

Six patients with well-fixed Harris-Galante-1 acetabular components underwent liner exchange surgery for excessive polyethylene wear and osteolysis. The mean interval from primary arthroplasty to revision was 14 years (range 11–17 years). All patients underwent a CT scan pre-operatively to identify the location and size of the osteolytic lesions and during surgery, accessible lesions were curetted and bone grafted. One patient had recurrent dislocations and the acetabular component was revised one year following liner exchange surgery. The remaining five patients had CT scans taken at a mean of five months (range 3–5 months) and 5 years (range 3.4–8.2 years) following surgery. Osteolytic lesion volume with or without bone grafting was measured.

Of the 19 osteolytic lesions detected pre-operatively, the first post-operative CT scan showed that four lesions were fully bone-grafted, ten lesions were partially bone-grafted and five lesions had no bone grafting during surgery. At a minimum of three years following surgery, all fully bone-grafted lesions remained full of bone- graft. Of the ten partially bone-grafted lesions, the osteolytic non-grafted zone decreased in volume in five lesions and five lesions remained unchanged. Of the five osteolytic lesions with no bone grafting, one lesion increased in volume, one lesion decreased in volume and three lesions remained unchanged. No new lesions were detected in any of the hips.

These preliminary results suggest that liner exchange surgery is effective in treating periacetabular osteolysis. Although bone grafting appears to aid in restoring bone stock, it is not essential in halting the progression of osteolysis, which likely results from the ongoing production of polyethylene particles in the joint.

Sensitive and accurate measures of osteolysis around TKR are needed to enhance clinical management and assist in planning revision surgery. Therefore, our aim was to examine, in a cadaver model of osteolysis around TKR, the sensitivity of detection and the accuracy of measuring osteolysis using Xray, CT and MRI.

Fifty-four simulated osteolytic lesions were created around six cadaver knees implanted with either a cemented or cementless TKR. Twenty-four lesions were created in the femur and thirty in the tibia ranging in size from 0.7 cm3 to 14 cm3. Standard anteroposterior and lateral fluoroscopically guided radiographs, CT and MRI scans with metal reduction protocols were taken of the knees prior to the creation of lesions and at every stage as the lesion sizes were enlarged. The location, number and size of the lesions from images obtained by each method were recorded.

The sensitivity of osteolytic lesion detection was 44% for plain radiographs, 92% for CT and 94% for MRI. On plain radiographs, 54% of lesions in the femur and 37% of lesions in the tibia were detected. None of the six posterior lesions created in the tibia were detected on the AP radiographs; however, three of these six lesions were detected on the lateral radiographs. CT was able to detect lesions of all sizes, except for four lesions in the posterior tibia (mean volume of 1.2 cm3, range 1.06–1.47 cm3). Likewise, MRI was very sensitive in detecting lesions of all sizes, with the exception of three lesions, two of which were in the femur and one was in the medial condyle of the tibia (mean volume of 1.9 cm3, range 1.09–3.14 cm3). Notably, all six posterior tibial lesions, which could not be detected using AP radiographs, were detected by MRI.

This study demonstrates the high sensitivity of both CT and MRI (which uses no ionising radiation) to detect simulated knee osteolysis and can therefore be used to detect and monitor progression of osteolysis around TKR. The study also shows the limitations of plain radiographs to assess osteolysis.

Large articulations are increasingly being used to reduce dislocation, the most common early complication following THR. However, potential benefits of large articulations in reducing dislocation have not been proven in a well-controlled clinical trial.

The aim of our randomised controlled trial was to compare the one-year incidence of dislocation between 36 and 28 mm metal on highly cross-linked polyethylene articulations.

Patients were excluded if they had a high risk of dislocation due to, for example, abnormal anatomy, neuromuscular disease, previous infection or dislocation. Eligible patients were stratified according to a number of other factors which may influence dislocation risk, including primary or revision THR and, if primary THR, by surgeon, age, diagnosis, sex and Charnley grade. Patients were randomised intra- operatively to either a 28 or 36 mm articulation. Dislocation incidence was determined using a hip instability questionnaire and a hospital visit questionnaire. A dislocation was diagnosed if there was radiological evidence and reduction by a doctor was required. Six-hundred-and-forty-four patients undergoing primary or revision THR were entered into the study.

Overall, the incidence of dislocation at one year following THR was 5.4% with a 28 mm articulation and 1.3% with a 36 mm articulation (p=.004). Incidence in primary THR patients was 4.4% with a 28 mm articulation, compared to 0.8% with a 36 mm articulation (p=.007). Incidence in revision THR patients was 12.2% and 4.9% with 28 and 36 mm articulations, respectively. For both primary and revision THR patients, sex distribution, age and BMI of patients who dislocated were similar to those of the total samples of primary or revision patients.

This large randomised study unequivocally shows for the first time that, compared to a 28 mm articulation, a 36 mm articulation in THR is efficacious in reducing the incidence of dislocation in the first year following THR.

The purpose of this paper is to review the early results of Prostalac system under licence from Therapeutic Goods Administration for Professor Howie in the management of two stage exchange hip arthroplasty for infection (restricted to Royal Adelaide Hospital) and the addition of vancomycin and teicoplanin powder to tobramycin cement without additional tobramycin.

Thirteen patients were treated for an infected THR with the Prostalac system. Preoperative and intra-operative cultures were taken to identify the infective organisms. Vancomycin 3 gm was added to the Prostalac cement mantle per 40 gm packet of antibiotic bone cement containing tobramycin 1 gm. Teicoplanin 2.4 gm was used in one case where the patient had a known vancomycin allergy. Postoperatively patients underwent six weeks of IV antibiotics followed by four to six weeks of oral.

A short term successful clinical outcome was determined by implantation of a total hip prosthesis at the time of second stage operation and no reoperations resulting from recurrent infection and off antibiotics for â□¥ 6 months with normal clinical and CRP lab values.

Thirteen patients received the Prostalac system. No patient was lost to follow-up. Nine have progressed to second stage revision, eight of which had femoral impaction grafting. Two deaths occurred not attributed to the Prostalac system. Three superficial wound infections and two required washout and debridement. One Prostalac stem subsidence. There has been no recurrence of deep joint infection. Retention of the second stage prosthesis has been 100% at 17 months.

The PROSTALAC system with the addition of vancomycin or teicoplanin to the tobramycin antibiotic cement has encouraging short-term results for treatment of deep joint infection. Complication rate has been well within the range reported in literature. Successful early outcomes are encouraging with all patients in the Prostalac study having retained their permanent hip prosthesis following second stage surgery.

This study aimed to compare the early clinical results and stem subsidence between three consecutive series of revision hip replacement cases with femoral impaction bone grafting to evaluate the effects of developments in technique. In the original series 1 (n=23), bone graft was irradiated at 25kG. I n series 2 (n=12) non-irradiated double washed graft and long stems were used as required.

In series 3 (n=21) modular tamps were used. Sensitive radiographic analysis techniques, EBRA and RSA, were used to measure stem subsidence. Major stem re-revision was required in five hips in series one, one hip in series two and no hips in series three. Two periprosthetic fractures occurred in series one. There was a statistically significant reduction in stem subsidence at the cement-bone interface at 12 months between series one and series two and three (p<0.05). In series three there was negligible stem subsidence at the cement-bone interface.

Technique developments in femoral impaction grafting, including the use of modular tamps designed to simply the procedure, yields excellent early clinical and radiographic results. Using RSA, we have shown that the fixation of the stems in bone is comparable to that achieved in primary hip replacement.

Background: Our multi-centre international randomized controlled trial compared the one-year incidence of dislocation between a 36 mm and 28 mm metal on highly cross-linked polyethylene articulation in primary and revision total hip replacement (THR).

Patients: 644 patients were entered into the study. Surgical approach was posterior in primary THR and posterior, transfemoral or transtrochanteric in revision THR. Patients were stratified according to a number of factors which may influence dislocation risk and polyethylene wear. Patients were randomized intra-operatively to either a 28 or 36 mm articulation.

Results: The 12-month incidence of dislocation was statistically significantly lower in patients undergoing THR with a 36 mm articulation than in those with a 28 mm articulation (1.3% vs 5.4%, p=.004). When primary and revision THR were examined separately, the 12-month incidence of dislocation was statistically significantly lower in patients undergoing primary THR with a 36 mm articulation than in those with a 28 mm articulation (0.8% vs 4.4%, p=.007). Of the 12 primary THR patients with a 28 mm articulation who dislocated within one year, four experienced recurrent dislocation and two were revised for dislocation. Two patients with a 36 mm articulation dislocated, one of whom experienced recurrent dislocation and was revised. The incidence of dislocation after revision THR with a 36 mm articulation was 4.9%, compared to 12.2% with a 28 mm articulation. Three of the five patients who dislocated following revision THR with a 28 mm articulation experienced recurrent dislocation and were revised within one year of surgery. Two patients dislocated following revision THR with a 36 mm articulation but neither experienced recurrent dislocation or further revision.

This large randomized study unequivocally shows for the first time that, compared to a 28 mm articulation, a 36 mm articulation in THR is efficacious in reducing the incidence of dislocation in the first year following THR.

Background: Good results have been reported for cemented femoral total hip arthroplasty in young patients from centres with expert surgeons but what is unknown are the results when surgeries are performed by a group of surgeons with varying experience in total hip replacement. The purpose of this study was to evaluate the outcome of primary total hip arthroplasty using a polished cemented polished collarless double tapered stem in young patients aged less than 55 years performed by a group of surgeons with varying experience in total hip replacement.

Methods: One hundred and ninety seven arthroplasties in 169 patients were performed between 1988 to 2005. The procedures were performed by surgeons with varying arthroplasty experience. Follow-up was 2 to 19 years (median 8 years). Clinical outcomes, radiographic evaluations and survivorship analyses were undertaken.

Results: Of the 197 femoral stems, eight were revised, but none for aseptic loosening. Four stems underwent cement within cement revision for recurrent dislocation, leg length discrepancy, infection and to assist cup revision. Two stems were revised for periprosthetic fractures. Two stems were revised for infection. No stems were classified as probably or possibly loose. Median stem within cement subsidence was 1.0mm. Two stems have more than 5mm vertical subsidence and in the absence of radiolucent lines or associated pain they were not considered loose. At long term follow-up the overall incidence of femoral osteolysis was 7% (n=13 hips). At latest patient follow-up the median Harris Hip and pain scores were respectively 81 (range 34 to 100) and 40 (range 10 to 44). Survivorship of the polished collarless double tapered stems at 13 years using the endpoint revision for aseptic loosening was 100% (worst case analysis 96.5%).

Conclusion: This study confirms that good results of cemented polished collarless double tapered stems in the younger patient can be achieved by a group of surgeons with varying experience in total hip replacement. The ability to perform a minor stem revision, cement within cement, for other reasons than aseptic loosening further strengthens the indications for these type of implants in young patients.

Early revision is an important risk factor for repeated revision and poor results after primary total hip replacement and instability is a major cause of early revision. Larger articulations with cross-linked polyethylene are proposed as a solution, but these are not without risk, including fracture of the thin polyethylene rim of the liner. The aim of our study was to examine implant-related revisions among primary total hip replacement patients with up to six year follow-up in a randomized controlled trial which compared 28 mm and 36 mm metal on highly cross-linked polyethylene articulations in total hip replacement.

557 patients undergoing primary total hip replacement were included in this study. Risk factors for dislocation and wear were controlled by stratification and patients were then randomized intra-operatively to either a 28 or 36 mm articulation.

To date, 10 hips have been revised for implant-related problems following primary total hip replacement. Seven hips with a 28 mm articulation were revised to a larger articulation because of instability. Four of these were for recurrent dislocation, one for an irreduceable first dislocation and two for subluxation. In contrast, only one patient who had undergone total hip replacement with a 36 mm articulation was revised for recurrent dislocation. One hip with a 36 mm articulation in a well-positioned cup was revised to a 32 mm articulation because of elevated lip liner fracture. Another 36 mm articulation hip was revised for acetabular component loosening.

This study shows that a 36 mm metal on highly cross-linked polyethylene articulation reduces the need for early revision for instability after primary total hip replacement. However, these benefits need to be weighed against the potential risks associated with these articulations, including rare fracture of the relatively thin poly-ethylene liner.

Large articulations using cross-linked polyethylene and other alternate bearings are increasingly being used to reduce the incidence of dislocation, the most common early complication following total hip replacement. While indirect evidence has suggested the potential benefits of a large articulation in reducing dislocation risk, this has not been proven in a well-controlled clinical trial. The primary objective of our multi-centre international randomized controlled trial was to compare the one-year incidence of dislocation between a 36 mm and 28 mm metal on highly cross-linked polyethylene articulation in primary and revision total hip replacement.

644 patients were entered into the study. Patients were stratified according to a number of factors which may influence dislocation risk, including primary or revision total hip replacement, age, sex, Charnley grade, diagnosis and stem type. Patients were randomized intra-operatively to either a 28 or 36 mm articulation.

The 12-month incidence of dislocation was statistically significantly lower in patients undergoing total hip replacement with a 36 mm articulation than in those with a 28 mm articulation (1.3% vs 5.2%, p< .05). A total of 6 dislocations occurred in the 4 patients who dislocated with a 36 mm articulation, compared to a total of 36 dislocations in the 17 patients who dislocated with a 28 mm articulation. When primary and revision THR were examined separately, the 12-month incidence of dislocation was statistically significantly lower in patients undergoing primary total hip replacement with a 36 mm articulation than in those with a 28 mm articulation (0.7% vs 4.2%, p< .05). A total of 4 dislocations occurred in two patients with a 36 mm articulation, compared to a total of 19 dislocations in 12 patients with a 28 mm articulation. The incidence of dislocation after revision total hip replacement with a 36 mm articulation was 4.8%, compared to 11.1% with a 28 mm articulation.

This large randomized study unequivocally shows for the first time that, compared to a 28 mm articulation, a 36 mm articulation in total hip replacement is efficacious in reducing the incidence of dislocation in the first year following hip replacement.

Introduction: In the past, surgeons have found impaction bone grafting technically difficult leading to its limited use. This paper reviews the long term results and developments in instrumentation and techniques aimed at simplifying femoral impaction grafting at revision hip replacement. The expanded indications for this procedure are reviewed and recent results of stem fixation using radiostereometric analysis (RSA) are reported.

Methods: The impaction bone grafting procedure, using a cemented collarless polished double taper stem, has been used in 66 hips (median patient age 63yrs) since 1993. The technique has undergone numerous developments. Modular tamps have been used in the last 29 hips and in the last seven hips, a pneumatic mechanical vibration device has been used in place of manual impaction. Stem subsidence at both the prosthesis-cement and cement-graft/bone interfaces was measured, more recently using radiostereometric analysis.

Results: There was a high early incidence of failure in the initial cases but there have been no further revisions for mechanical failure at up to 15 years. Technique developments have resulted in dramatic improvements in stem fixation achieved. In the modular tamp cases, the mean stem subsidence at the cement-bone interface at 12 months was 0.07mm (0 to 0.7mm) at 12 months. The stem subsidence in the hips where the mechanical vibration device was used was 0.05mm (0 to 0.06mm). Femoral impaction grafting offers special advantages in younger patients include standard femoral stem revision and at the second stage of two stage revision for infection.

Discussion and Conclusion: A stable cement-bone interface is achieved using advanced techniques of femoral impaction grafting that includes the use of modular impaction instruments. Early results of mechanical vibration impaction are encouraging. Femoral impaction grafting restores bone and new techniques simplify the femoral revision procedure.