Femoral impaction bone grafting (IBG) may be used to restore bone stock in revision total hip arthroplasty (THA) and allow use of a shorter, than otherwise, length prosthesis. This is most beneficial in young patients who are more likely to require further revision surgery. This study aimed to assess the results of femoral IBG for staged revision THA for infection. A prospective cohort of 29 patients who underwent staged revision THA for infection with femoral IBG and a cemented polished double-tapered (CPDT) stem at the final reconstruction was investigated.

The minimum follow-up was two years (2 – 10 years, median 6 years). Stem subsidence was measured with radiostereometric analysis. Clinical outcomes were assessed with the Harris Hip, Harris Pain, and and Société Internationale de Chirurgie Orthopédique et de Traumatologie Activity (SICOT) Scores. The original infection was eradicated in 28 patients. One patient required a repeat staged revision due to re-infection with the same organism. At two-year follow-up, the median subsidence at the stem-bone interface was −1.70 mm (−0.31 to −4.98mm). The median Harris Hip Score improved from 51 pre-operatively to 80 at two years (p=0.000), the Harris Pain Score from 20 to 44 (p=0.000) and the SICOT Score from 2.5 to 3 (p=0.003).

As successful eradication of infection was achieved in the majority of patients and the stem migration was similar to that of a primary CPDT stem, this study supports the use of femoral IBG during the final reconstruction of the femur after staged revision THA for infection.

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.

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.

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.

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.

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.

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 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.