Introduction: Differentially loaded radiostereometric analysis (DLRSA) uses RSA whilst simultaneously applying load to the bones under investigation. This technique allows measurement of interfragmentary displacements under measured weightbearing and joint movement. We have used this technique to prospectively monitor tibial plateau fractures and present the results of the first nine patients with six month follow up.

Method: Nine 41-B3 fractures were treated with open reduction internal fixation by one surgeon. At operation, RSA beads were inserted in the depressed osteochondral fragment and the adjacent non-fractured metaphysis. Postoperative weightbearing was restricted to 20kg and knee flexion to 60° for the first six weeks. Follow up included clinical and radiological examinations and patient reported outcome scores (Lysholm, KOOS). DLRSA examinations included RSA radiographs in 60° flexion and under measured weightbearing at six weekly intervals up to six months postoperatively. Significant interfragmentary displacement was defined as translations greater than 0.5mm and/or rotations greater than 1.5°.

Results: No postoperative displacement was identified on plain radiographs, except in one patient who fell two weeks postoperatively.

RSA: Longitudinal Results: In all patients, the osteo-chondral fragment continued to migrate up to six months, with one exception that stabilised at three months. At six months, the osteochondral fragment translated between 0.02 and 4.15 mm and rotated between 0.2 and 7.2° (> 0.5mm and/or > 1.5° in five cases).

Discussion: Tibial plateau fractures continue to migrate up to six months after treatment. Active range of motion, partial weightbearing to six weeks and weightbearing up to one body weight after six weeks was proven a safe postoperative regimen. Greater displacements recorded over time may be attributed to loading of more than one body weight, for example, the patient that fell recorded the largest amount of migration over time.

Introduction: Periacetabular osteotomy is a complex procedure which is associated with significant complications during the learning period and difficult to maintain such expertise when it is undertaken infrequently. Results were reviewed to determine if this difficult PAO procedure can be safely learnt by a process of mentoring and review.

Methods: A structured mentoring program was adopted by the senior author. A double approach was used in the first 11 cases to enhance exposure and minimise the risk of complications. Fifteen osteotomies have subsequently been undertaken using a single approach. The median patient age was 28 years (13–41 years). The median follow-up was 5 years (2–14 years). The clinical and radiographic results were examined.

Results: Two cases in the double approach series progressed to total hip replacement and there were two other major reoperations. Two cases in the single approach series had an ischial non-union not requiring reoperation. The median Harris hip score at latest review was 82 (35–100) and 80 (26–100) for the double and single approach series respectively. All radiographic indices indicated correction of the acetabulum for both series.

Discussion and Conclusion: A structured program of mentoring and review has allowed a complex surgical procedure to be learnt and surgical expertise maintained at a distant centre while avoiding the complications previously associated with the learning curve and achieving the acetabular correction similar to the originator of the procedure.

While computed tomography (CT) provides an accurate measure of osteolysis volume, it would be advantageous in general clinical practice if plain radiographs could be used to monitor osteolysis. This study determined the ability of plain radiographs to detect the presence of and determine the progression in size of osteolytic lesions around cementless acetabular components.

Nineteen acetabular components were diagnosed with osteolysis using a high-resolution multi-slice CT scanner with metal artefact suppression. Mean duration since arthroplasty was 14 years (range 10–15 years) at initial CT. Repeat CT scans were undertaken over a five year period to determine osteolysis progression. On anteroposterior pelvis (AP) radiographs and oblique radiographs of the acetabulum seen on the rolled lateral hip view, which were taken at the same time as the CT scans, area of osteolysis was measured manually correcting for magnification.

Osteolysis was detected on the AP radiographs in 8 of 19 hips (42%), on the oblique radiographs in 6 of 19 hips (32%) and on the combined AP and oblique radiographs in 8 of 19 hips (42%). Throughout the study period, osteolysis was detected on 31 of 76 AP radiographs (41%) and 22 of 75 oblique radiographs (29%). Osteolysis was more likely to be detected on plain radiographs if the lesion volume was greater than 10cm3 in size (p=0.005). On CT, osteolysis progressed by more than 1cm3/yr in 10 of 19 hips (55%). In these ten hips, osteolysis progression was detected on AP radiographs in six hips and on oblique radiographs in three hips. No correlation was found between osteolysis progression measured by CT and that measured on AP (r2=0.16, p=0.37) or oblique (r2=0.37, p=0.15) or AP and oblique radiographs (r2=0.34, p=0.17).

Plain radiographs are poor in monitoring progression in size of periacetabular osteolytic lesions. Plain radiographs may detect lesions more than 10cm3 in size, but are unreliable.

Computed tomography (CT) provides a sensitive and accurate measure of periacetabular osteolytic lesion volume, however, there may remain a role for plain radiographs in monitoring osteolysis. This study aimed to compare CT and plain radiographs for determining the progression in size of osteolytic lesions around cementless acetabular components.

A high-resolution multi-slice CT scanner with metal artefact suppression was used to determine the volume and progression of osteolysis around 19 cementless Harris Galante-1 and PCA acetabular components. The mean duration since arthroplasty was 14 years (range 10–15 years) at initial CT. Repeat scans of the hip were undertaken over a five year period to determine the progression in size of osteolytic lesions over time. A second blinded observer manually measured the area of osteolytic lesions off anteroposterior pelvis radiographs and oblique radiographs of the acetabulum that were taken at the same time as the CT scan.

All 19 hips had CT detected osteolysis. Osteolysis was detected on one or both of the anteroposterior pelvis or oblique radiographs from at least one time point in eight of 19 hips (42%). Osteolysis was detected on 31 of 76 anteroposterior pelvis radiographs (41%) and on 22 of 75 oblique radiographs (29%) (p=0.140). Osteolysis was more likely to be detected on plain radiographs if the lesion volume was greater than 10cm3 in size compared to those 5–10cm3 and less than 5cm3 in size (p=0.009). In 10 of 19 hips (55%), CT determined that osteolytic lesions progressed in size by more than 1cm3/yr. The mean volume of osteolysis progression was 3.2cm3/yr (range 1.1–7.5cm3/yr). Progression in size of osteolytic lesions was significantly associated with hips with larger osteolytic lesions at the initial CT (p=0.0004). Radiographic measurements detected progression of osteolytic lesions in 5 of the 10 hips (50%) that progressed. No correlation was found between progression in size of osteolytic lesions as measured by CT and progression in size of osteolytic lesions as measured off the anteroposterior pelvis (r2 = 0.16, p=0.37), oblique (r2=0.37, p=0.15) and combined anteroposterior pelvis and oblique radiographs (r2=0.34, p=0.17).

Periacetabular osteolytic lesions are more likely to be detected on plain radiographs if they are more than 10cm3 in size. Plain radiographs may therefore provide some monitoring value as lesions more than 10cm3 are more likely to be progressive. However, plain radiographs should not be relied upon to monitor the progression of these lesions.

Differentially loaded radiostereometric analysis (DLRSA) uses RSA whilst simultaneously applying load to the bones under investigation. This technique allows measurement of interfragmentary translations and rotations under measured weight bearing and joint movement. We have recently introduced this technique to monitor tibial plateau fracture healing. This paper presents our preliminary results.

Twelve patients with a 41 B2, B3, C2, or C3 fracture were followed for a minimum of three months. RSA beads were inserted in the largest osteochondral fragment and the adjacent metaphysis. Knee flexion was restricted to 60° for 6 weeks. After partial weight bearing (20kg) between 2 and 6 weeks, patients progressed to full weight bearing. Follow up included clinical and radiological examinations and patient reported outcome scores (Lysholm, KOOS). DLRSA examinations included RSA radiographs in 60° flexion and under measured weight bearing. Significant interfragmentary displacement was defined as translations greater than 0.5mm and/or rotations greater than 1.5°.

There was no loss to follow-up. Longitudinal RSA follow-up: Follow-up RSA radiographs were compared to postoperative examinations. Osteochondral fragment depression was less than 0.5mm in seven patients and between 2 and 4mm in the remaining five patients. Significant interfragmentary displacement after three months was recorded in three patients. DLRSA flexion results: Under 60° of flexion, translations over 0.5mm were recorded in five patients (one postoperatively; one at 2 weeks; two at 6 weeks; and one postoperatively, at 2 weeks and at 3 months). Rotations over 1.5° were recorded in six patients (one postoperatively; two at 2 weeks; one at 6 weeks; one at 2 weeks, 3 months and 4.5 months; and one postoperatively, at 2 weeks, 3 months and 6 months). DLRSA weight bearing results: Under partial weight bearing at two weeks, two patients recorded significant translations, one involving a significant rotation. Under weight bearing as tolerated, three patients recorded significant translations (one at 6 weeks; and two at 18 weeks) and four patients recorded significant rotations (one at 6 weeks; one at 18 weeks; and two at 12 and 18 weeks). Patient Reported Outcomes: Both the Lysholm and KOOS scores improved between 6 weeks and 3 months. DLRSA provides new insight and perspective in tibial plateau fractures. Some fractures take more than three months to heal. Our current rehabilitation protocol was safe in most patients, however significant interfragmentary displacement was encountered in 17% at the 2 week followup, raising questions about the quality of the initial stability.

Differentially loaded radiostereometric analysis (DLRSA) uses RSA whilst simultaneously applying load to the bones under investigation. This technique allows measurement of interfragmentary translations and rotations under measured amounts of weight bearing. The aim of this paper was to measure the mechanical stiffness of distal femoral fractures during healing.

Six patients with a 33A2, 33A3, 33B2 and 33C2 fracture were treated with open reduction, internal fixation using a long bridging plate. All patients had a DLRSA examination at 6, 12, 18 and 26 weeks postoperatively. Each DLRSA examination consisted of RSA radiographs taken without load (pre-load), under different increments of load, and finally, without load (post-load). The direction and magnitude of the interfragmentary displacements in six degrees of freedom were recorded at each examination.

DLRSA examinations were able to monitor the inter-fragmentary displacements of the distal femoral fragment relative to the femoral shaft. The interfragmentary displacement recorded, progressively increased as more load was applied in all patients, at all follow-up time points. The two dimensional (2D) translations under maximum tolerated load, progressively decreased over time in three patients. The 2D translations recorded under 60 kg of load at 26 weeks for these patients was 0.18, 0.21 and 0.27mm. The 2D translations of two patients did not decrease progressively between 6 and 18 weeks but did decrease at 26 weeks to 0.47 and 0.75mm. One patient recorded 2D translations of 4.11, 3.48 and 4.53mm under 30kg at 12, 18 and 26 weeks respectively. In the majority of examinations, post-load radiographs enabled the interfragmentary displacements under load to be identified as elastic in nature.

The DLRSA stiffness data confirmed that at 26 weeks three patients had united; two were delayed but improving; and one was a clear non-union without progression. DLRSA examinations may be used as a clinical research tool. to monitor in vivo the stiffness of healing femoral fractures fixed with “relative stability”.

Irradiating allograft bone may compromise the mechanical stability of the prosthesis-bone construct, potentially having adverse effects on the outcome of femoral impaction grafting at revision hip replacement. This in vitro study aimed to determine the effect of irradiation of allograft bone used in femoral impaction grafting on initial prosthesis stability.

Morsellised ovine femoral head bone was irradiated at 0 kGy (control), 15 kGy and 60 kGy. For each group, six ovine femurs were implanted with a cemented polished double taper stem following femoral impaction bone grafting. Dynamic hip joint loading was applied to the femoral head using a servo-hydraulic materials testing machine. The primary outcome was stem micromotion. Tri-axial micromotion of the stem relative to the bone at two sites was measured using linear variable differential transformers and non-contact laser motion transducers. Statistical analysis was performed using SPSS.

Compared to the control and 15 kGy groups, specimens in the 60 kGy group demonstrated statistically significant greater micromotion in the axial, antero-posterior and medio-lateral axes. A multi-factorial post-hoc power analysis based on the overall effect of group size indicated a power of 0.7. There was no difference in micromotion between the control and 15 kGy groups. The average micromotion in the axial axes was 63μm in the control and 59μm in the 15 kGy group.

The results of this study suggest that a maximum irradiation dose of 15 kGy may not affect initial prosthesis stability following femoral impaction grafting in this model and provide the basis for us to now proceed to in-vivo studies examining the effect of irradiated bone on implant stability over time.

Periprosthetic osteolysis is a serious medium to long-term complication of total hip arthroplasty. Interobserver reliability of detecting osteolysis around cementless ace-tabular components is reported to be poor using plain radiographs. Quantitative computed tomography (CT) provides sensitive and accurate measures of osteolytic lesion volume, however, there may remain a role for plain radiographs in monitoring progression of osteolysis. The aim of this study was to use quantitative CT to monitor the progression of osteolytic lesions around cementless acetabular components and to compare plain radiographs and CT in determining the progression of osteolysis.

A high-resolution multi-slice quantitative CT scanner with metal artefact suppression was used to determine the volume of osteolysis around 18 cementless acetabular components. The mean time since arthroplasty was 14 years (range 10–15 years) at the initial CT. Repeat scans of the hip were undertaken over a five-year period to determine progression of osteolysis with time. A second blinded observer examined anteroposterior and lateral plain radiographs taken at the same time as the CT scans and measured the location and area of osteolytic lesions.

CT measurements determined that in ten of 18 hips (56%), osteolytic lesions progressed by more than 1cm3/yr. Progression in size of osteolytic lesions was significantly associated with hips with larger osteolytic lesions at the initial CT (p=0.0005). The mean volume of osteolysis progression was 4.9cm3/year (range 2.8–7.5cm3/yr) for cases with osteolysis volumes greater than 10cm3 at the initial CT, and 0.7cm3/yr (range 0–2.3cm3/yr) for cases with osteolysis volumes smaller than or equal to 10cm3 at the initial CT (p=0.002). Importantly, the rate of osteolysis progression between CT scans varied greatly in some hips. In contrast, using plain radiograph assessment, progression in the area of osteolytic lesions was only detected in 10% of hips.

In conclusion, quantitative CT provides new insights into the natural history of periacetabular osteolysis. Total osteolysis volume greater than 10cm3 is associated with a high risk of progression and progress, on average, at a greater rate than those less than 10cm3. Plain radiographs, including a lateral view, are an unreliable clinical diagnostic tool to predict substantial progression of periacetabular osteolytic lesions.

Relatively high rates of fracture of the femoral stem of total hip replacements were seen with early designs manufactured with stainless steel. Improvements in metallurgy, alloy chemistry, materials and stem design have led to a reduction in the incidence of this complication and the occurrence of fracture with modern femoral stems is a now a rare event. However, the implantation of modern stems into heavy patients and the use of higher offset stems leads to considerable testing of the mechanical capabilities of some stem designs.

We present ten cases of fracture of modern stainless steel polished tapered stems. The fractures occur either in the neck, or in the distal half of the stem. Our clinical data suggests that heavy patients with small stems and high offsets are at risk of breaking their implants. Varus positioning of the stem in a number of cases further increases the bending moment of the stems, and the sacrifice of cement mantle thickness for implant size within narrow medullary canals may lead to the loss of proximal support. Failure analysis of the retrieved high nitrogen stainless stems also suggests there may be metallurgical factors that contribute to their failure.

On the basis of our findings, careful consideration is required when using high offset stainless steel stems in large patients.

Introduction and Aims: This paper presents a treatment plan for femoral stem revision that has been developed based on long-term studies of revision total hip replacement (THR) using cemented stems, cementless proximal fixation stems, cemented stems with impaction grafting and modular titanium long stems.

Method: The clinical and radiographic results of femoral stem revision were compared using the following techniques: 1) a standard or long cemented collarless double taper Exeter or CPT stems (CCDT stems) [n=190]; 2) a proximally porous coated mid to long cementless stem [n=56]; 3) two series of CCDT stems with impaction grafting n=34]; and 4) a modular grit-blasted titanium taper stem [n=13] used for severe cortical damage. Treatment decisions were made based on the age of the patient, the appearance of the pre-operative radiograph and the extent of bone deficiency at surgery. Follow-up was from 17 to two years.

Results: Only one hip was lost to follow-up. In the CCDT group, at a median follow-up of five years (range 2–17 years), two standard length stems and one long stem had been re-revised for loosening (1.5%) and seven stems had been re-revised for other reasons. Survivorship to re-revision for loosening at eight years was 95% (95%CI=85–100%) for both standard and long stems. There was a trend for better longer-term results for long stems. The extent of pre-operative bone loss did not influence results. For the cementless proximal fixation group, at a median follow-up of 10 years, re-revision of the stem for loosening occurred in 20%. Importantly, these poor results could have been predicted from short-term results. The initial series of femoral impaction grafting with CCDT stems and irradiated bone had a small incidence of stem loosening and periprosthetic fracture. The majority of stems subsided, but at a median follow-up of eight years there were no further re-revisions. In the second series, usually with non-irradiated allograft with mesh containment, there was minimal stem subsidence and no re-revision. The grit blasted titanium taper stem has dealt with periprosthetic fratures and severe proximal cortical loss, but with some cases of subsidence and femoral fracture.

Conclusion: Based on these results, our treatment plan for routine femoral revision in middle-aged and elderly patients without severe proximal deficiency is a polished CCDT long stem. In younger patients, impaction grafting is recommended, provided deficient bone is protected. Cementless modular stems are reserved for femurs with severe proximal cortical deficiency.

Introduction and Aims: To aid the comparison of results of different techniques of femoral revision at total hip replacement and in choosing types of revision, a number of radiographic classifications have been proposed. We aimed to determine the reliability of five popular radiographic classification systems for grading the extent of femoral bone deficiency.

Method: Twenty pre-revision total hip replacement femoral radiographs were assessed by a senior consultant specialist in revision surgery, a junior consultant, a fellow and a trainee registrar. The femoral bone deficiency was classified using the systems of the American Academy of Orthopaedic Surgeons (AAOS) and EndoKlinik, and those described by Paprosky, Gross and Gustillo. Intra-observer agreement and inter-observer agreement between assessors were determined using the kappa coefficient. Radiographs were reassessed after a minimum of two weeks. Kappa coefficients of 0.6–0.8 (substantial) or > 0.8 (almost perfect) were considered to indicate acceptable agreement. Intra-operative measurement of deficiency was also undertaken.

Results: Intra-oberser agreement was rated as acceptable for the Paprosky, Gross and Gustillo systems, each giving substantial agreement, but was unacceptable for the AAOS and EndoKlinik systems. Inter-observer agreement was unacceptable for all systems except the Gross classification system, which was rated as having substantial agreement.

Conclusion: Comparing results of femoral revision between different surgeons based on bone deficiency according to the most popular radiographic classification systems is doubtful because of poor reliability. These classifications can be used by an individual surgeon as a guide to management, but most classifications should not be used to recommend the type of femoral revision to other surgeons.

Introduction and Aims: The usefulness of bone graft substitutes and growth factors to promote bone graft incorporation and prosthesis fixation in hip replacement should be examined in a loaded model, as results from cortical defect models may not apply. This paper reviews the results of femoral impaction grafting using these materials in an ovine hip replacement model.

Method: At cemented hemiarthroplasty, sheep femurs were impacted with allograft bone (control group n=23) or with allograft mixed with: 1) corglaes bioglass (n=12); 2) a synthetic hydroxyapatite (HA) (n=6) or the bone morpohogenetic protein OP-1 (n=6) (study groups) and implanted with a cemented double taper femoral stem. Sheep were sacrificed at between six and 26 weeks. The primary outcome was femoral stem subsidence, as determined more recently by the development of clinical radiostereometric analysis (RSA) in this model. Femoral fixation, as assessed by ex-vivo mechanical testing, and bone graft incorporation, as assessed by histological review and histoquantitation, were also key outcomes.

Results: In the control groups, there was a consistent response with bone graft incorporation by new bone advancing proximal to distally in the femur and advancing from the endocortex towards the cement mantle. Mineralised bone apposition occurred by six weeks and this was preceeded by partial resorption of the graft. Complete graft incorporation, with subsequent remodelling of bone, was evident proximally by 26 weeks. Bone graft incorporation in femurs impacted with a 1:1 allograft: bioglass mix was minimal and there was often partial or complete resorption of the graft with replacement by fibrous tissue, resorption of endocortical bone and instability of the femoral prosthesis. Supplementation of allograft with OP-1 promotes initial graft resorption, thus hastening bone graft incorporation and remodelling but one case of stem subsidence, that may have been associated with early resorption seen in the OP-1 group, reinforces the need for further studies examining dose response. There was excellent incorporation of the allograft and HA, with new woven bone directly apposing the HA surface and integrated into the larger porous spaces of the HA. There was no adverse response to the HA and there was minimal to no subsidence of the stem at the cement-bone interface, as determined by RSA.

Conclusion: This model is extremely valuable for investigating new biological approaches to reconstruction of major bone deficiency at revision hip replacement and demonstrates clear differences between materials used to supplement allograft, with HA and OP-1 giving encouraging results. RSA is an essential outcomes tool for this model.

Introduction There are currently hundreds of total hip replacement (THR) prosthesis designs in use. In practice the decision to use a THR prosthesis should be based on published long-term outcomes. This study provides a critical analysis of the literature to determine what prostheses have successful published results.

Methods The Medline (Ovid) database was searched for English text publications on primary THR published between 1975 and 2002. The search produced 12219 publications with 1400 (11.5%) reporting an incidence of revision or survivorship. Criteria for potentially successful designs were applied to the percentage of hips unrevised or survivorship data. Success was defined as less than 1% revised for any cause or less than 0.5% revised due to aseptic loosening. Using reported loss to follow-up, worst case analysis was performed to divide successful prostheses into definitely (DS), probably (PB) or possibly successful (PS).

Results Only 404 (23%) of the 1404 publications reviewed were methodologically adequate. The cemented acetabular prostheses had 39 (26.5%) reports of success (46%DS, 26%PB, 28%PS) at greater than 10 years and 80 (54%) reports of failure. The cement-less acetabular prostheses had 12 (10%) reports of success (42%DS, 42%PB, 16%PS), and 55 (46%) reports of failure. For cemented femoral prostheses 50 (30%) (62%DS, 18%PB, 20%PS) reports were successful, and 86 (51%) were failures. For cementless femoral prostheses 16 (18%) (69%DS, 25%PB, 6%PS) reports were successful and 38 (42%) were failures. Nineteen different cemented acetabular designs, and 34 different cementless acetabular designs had reports of success. For the femoral prostheses there were 27 different cemented designs and 26 different uncemented designs with reports of success. Thirty-two (18.2%) prostheses designs had reports of both success and failure, 71 (40%) had reports of failure only and 73 (41.5%) had reports of success only. It was not possible to identify what design alterations, if any, were attributed to a prosthesis being classified as both a success and a failure, because the technical details of the prosthesis were often not reported.

Conclusions Only 22% of prostheses reported were successful at greater than 10 years. High loss to follow-up meant only 56% of the potentially successful prostheses were definitely successful. The reporting of prosthesis manufacturer and catalogue numbers, and the publication of good and poor results are recommended to better gauge the success of designs.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction This study reviews the mid to long term results of revision THR with cemented, collarless double-tapered (CCDT) stems.

Methods We prospectively studied 192 revisions, in 183 patients, of femoral stems using standard (42%) or long (58%) Exeter and CPT CCDT stems. Results were analysed according to the length of stem, extent of pre-operative deficiency (Paprosky I:II:IIIa:IIIb:IV = 4:20:44:20:12%) and intra-operative bone loss. Postoperative radiographs were independently analysed for loosening and stress shielding. Risk factors of poor outcome were examined by multivariate logistic regression. The median follow-up was six years (2 to 17 years) with 55 patients having died (28%) and no cases lost to follow-up.

Results There were four stem re-revisions for sepsis (2%), three for aseptic loosening (1.5%) and three for component malpositioning (1.5%). The survivorship to femoral re-revision for aseptic loosening at eight years was 95% (95%CI=90–100%) for standard and 95% (90 – 100%) for long stems (p=0.674). Migration was less than five millimetre in unrevised stems. Survivorship and outcomes was independent of the Paprosky grade. There was a trend for better longer-term results in hips with long stems. Major stress shielding was not seen and thigh pain was not a problem.

Conclusions CCDT long stems are suitable for most femoral revisions in patients without severe segmental deficiency.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction Early complications of revision total hip replacement (rTHR) with femoral impaction allografting have included stem subsidence and loosening. In this comparative study, the impact of new techniques, including the use of longer stems, non-irradiated washed allograft, larger bone chips and medial mesh, on early clinical and radiographic outcomes was examined.

Methods The initial series of rTHRs with femoral impaction allografting comprised 20 hips (19 patients, median age 68 years) with a median follow-up of eight years. In the current series where the new techniques were used, there are 11 hips (11 patients, median age 69 years) with a median follow-up of 1.5 years. Three surgeons at one hospital undertook all rTHRs using a polished cemented collarless double tapered stem. Patients were mobilised on day one with partial weight bearing for 12 weeks. The femoral deficiencies commonly comprised extensive cavitatory loss combined with segmental deficiencies. Regular clinical and radiographic assessment was undertaken.

Results In the initial series, there were three early rerevisions for subsidence and stem loosening and one rerevision for infection. Periprosthetic fracture occurred early in three hips. EBRA FCA was used to assess stem subsidence. By two to four years, nine femoral stems had subsided more than five millimetres. At mid-term follow-up of eight years there have been no further rerevisions. In comparison, there has been minimal stem subsidence in the current series, with no stems subsiding more than five millimetres. To-date there have been no periprosthetic fractures and no complications requiring re-revision.

Conclusions Prospective monitoring of rTHR is important to identify factors that may be associated with poor outcome. Current techniques of femoral impaction grafting at rTHR, that includes washing of allograft and the use of long length stems and proximal mesh support yield good early-term radiographic and clinical results.

Introduction Peri-acetabular osteolysis is a serious complication of total hip arthroplasty (THA). The aim of this study was to determine, using quantitative computed tomography (CT), the location, volume and rate of progression of peri-acetabular osteolytic lesions, and to determine the validity of this CT technique with intra-operative measurements.

Methods High-resolution spiral multislice CT scan (Somatom Volume Zoom, Siemens, Munich, Germany), with metal-artefact suppression protocol, was used to measure the volume of osteolytic lesions around 47 cementless THAs in 36 patients (median age 73 years, duration 14 years, range five to 24 years). In vitro validation was undertaken. CT scans were taken from the top of sacroiliac joint down to two centimetres below the end of the prosthesis. Reconstruction images were analysed by two different observers and progression of osteolysis with time was determined. In some patients, subsequently revised, in-vivo CT measurements were compared to intra-operative measurements. The rate of progression of osteolytic lesions was calculated. The technique was optimised and validated by extensive in-vitro studies, using bovine and human pelves.

Results The incidence of lesions located in each site was: the ilium, 65%; around fixation screws, 20%; in the anterior column, nine percent; and in the medial wall, six percent. Some lesions were shown to be relatively quiescent, while others were aggressively osteolytic. Intra and inter-observer error for the CT measurement technique was four percent and 2.8%, respectively. In vitro volumetric measurements of simulated bone defects adjacent to the acetabular component and fixation screw were accurate to within 96% and precise to 98%. In addition, preliminary data obtained intra-operatively indicate the accuracy of CT in identifying the sites of osteolysis.

Conclusions CT is thus a valid and reliable technique for investigating the natural history of osteolysis and the factors that may influence its progression. It will also enable assessment of non-surgical treatments of osteolysis.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

The purpose of health outcomes monitoring is to assess the benefits and risks of health care processes, to enable benchmarking and to allow comparative studies of new technologies and variations in clinical practice. This paper critically reviews the discipline of health outcomes monitoring in joint replacement surgery. We reviewed over 250 papers published over the last 20 years in the major English speaking journals were reviewed. We conclude that there are considerable shortcomings of clinical studies which make it difficult to determine the results of different joint replacement designs. The shortcomings include inadequate study design and the lack of comparative data. Despite repeated calls for standardisation of outcome measures, this has yet to be achieved. Considerable resources are often invested in outcomes monitoring programs.It is therefore important that instruments are selected based on them meeting strict psychometric criteria, that adequate follow-up is achieved and that appropriate data analysis techniques are utilised, otherwise interpretation of results is difficult. We have found that patients’ reporting of symptoms and outcomes after hip arthroplasty were found to be consistent with those reported by their reviewing doctor. We therefore suggest that for uncomplicated joint arthroplasty cases, the marginal costs of their regular review in outpatients probably outweighs the marginal benefits and important resources and doctors time would be made available for other patient care activity if these patients were reviewed by patient self-administered questionnaires. Our studies have shown that SF-36 health survey and the WOMAC instruments are useful when administered by mailed survey, however, the cost-benefits of using these outcomes instruments is an important consideration. The lack of comparable outcomes data should encourage greater orthopaedic participation in multi-centre outcomes studies including randomised trials.

Introduction: The purpose of this study was to evaluate the micromotion of a femoral prosthesis relative to the femur in a revision hip replacement model.

Methods: A series of Ovine hip hemiarthroplasties were mechanically tested to detect micromotion of the femoral prosthesis relative to the femur 12 weeks following implantation. A mechanical testing device utilising muscle simulation of the major groups around the femur was designed. A 3D targeting system was developed using non-contact LASER transducers on the implant referenced to a second target on the overlying femur. Movement of this second target was measured with three LVDT’s (linear variable differential transformers).

Results: The system error was quantified in each femur to a resolution of the order of 15 microns. The mean micromotion, in 3D at two points assuming rigid body mechanics, was less than 50 microns for clinically stable implants. One stem was determined to be clinically loose and had a corresponding mean micromotion of 150 microns.

Conclusion: The method enabled measurement of 3Dmicromotion of a femoral prosthesis within the femur, during a laboratory approximation of normal physiological load cycles. The micromotion values corresponded to clinical outcomes, in a manner consistent with other reports in the literature. This system can be modified to allow targeting of different implants within a variety of bone types.

Reported rates of dislocation after primary and revision total hip replacement (THR) vary widely, whereas subluxation after THR is not commonly reported. Importantly, it is now recognised that reported dislocation rates are likely to be an underestimate of the true dislocation rate. The primary aim of this study was to develop and validate a Patient Hip Instability Questionnaire and subsequently to use this questionnaire to determine the incidence of dislocation, subluxation and symptoms due to hip instability following primary and revision THR. In addition the associated costs, morbidity, disability and effects on health-related quality of life were examined.

A retrospective review of dislocation rates from 1996 to 1998 identified problems in determining the true dislocation rate from standard hospital and database records. Therefore, a patient-completed Hip Instability Questionnaire was developed and validated to monitor dislocation and subluxation rates. This was then mailed to patients three and 12 months following primary or revision THR. All dislocations were then confirmed by telephone interview and radiographs. Telephone interviews and patient completion of the SF-36 questionnaire were used to assess morbidity, disability and quality of life. Costs of treating patients with hip dislocation were also determined.

The response rate to the mailed questionnaire was greater than 95%. The questionnaire was shown to be a valid measure of the true rate of dislocation following THR and confirmed the inaccuracies in previous methods of determining dislocation rate based on hospital and database records. Using this questionnaire, the rate of subluxation was higher than previously reported and the significant morbidity and health care costs associated with with this complication were identified.

The use of this questionnaire will allow better assessment of morbidity and costs due to complications following THR.

Aim: To compare the outcomes of cemented and uncemented primary total hip arthroplasty and to report the radiological features of 41 Exeter polished tapered stems which demonstrate good clinical scores at long-term review.

Methods: We set up a randomised trial, involving two surgeons, Twenty stems were modular and 21 were monoblock. The radiographic measurements, made using templates adjusted for magnification, included vertical subsidence of the stem, scoring of cement mantle thickness, analysis of the p-c and cement-bone (c-b) radiolucencies, and cement fracture in each of the Gruen zones on AP and lateral views.

Loosening was classified as possible if there was between 50 and 99 percent c-b radiolucency, probable when there was complete radiolucency, or definite when vertical subsidence was more than 5mm. The presence and type of radiological features analysed according to surgeon and whether a centraliser was utilised.

Results: There were no failures of the polished stems with 100% survival at 11 years. At the latest review, none of the polished cemented stems demonstrated definite or possible loosening. Osteolysis was found proximally in two cases and more distally in one case and each of these stems was implanted without a centraliser. Incomplete cement mantles and the presence of radiolucencies were more common around stems without centralisers, however the differences in results according to surgeon is a potential confounder and requires investigation in a larger series.

Conclusion: This study demonstrated excellent radiological results of the polished Exeter stem at mid to long-term follow-up.