Femoral revision after cemented total hip arthroplasty (THA) might include technical difficulties, following essential cement removal, which might lead to further loss of bone and consequently inadequate fixation of the subsequent revision stem. Bone loss may occur because of implant loosening or polyethylene wear, and should be addressed at time of revision surgery. Stem revision can be performed with modular cementless reconstruction stems involving the diaphysis for fixation, or alternatively with restoration of the bone stock of the proximal femur with the use of allografts.

Impaction bone grafting (IBG) has been widely used in revision surgery for the acetabulum, and subsequently for the femur in Paprosky defects Type 1 or 2. In combination with a regular length cemented stem, impaction grafting allows for restoration of femoral bone stock through incorporation and remodeling of the proximal femur. Cavitary bone defects affecting the metaphysis and partly the diaphysis leading to a wide femoral canal are ideal indications for this technique. In case of combined segmental-cavitary defects a metal mesh is used to contain the defect which is then filled and impacted with bone grafts. Cancellous allograft bone chips of 2 to 4 mm size are used, and tapered into the canal with rods of increasing diameters. To impact the bone chips into the femoral canal a dummy of the dimensions of the definitive cemented stem is inserted and tapped into the femur to ensure that the chips are firmly impacted. Finally, a standard stem is implanted into the newly created medullary canal using bone cement. To date several studies from Europe have shown favorable results with this technique, with some excellent long-term results reported.

Advantages of IBG include the restoration of the bone stock in the proximal femur, the use of standard length cemented stems and preserving the diaphysis for re-revision. As disadvantages of the technique: longer surgical time, increased blood loss and the necessity of a bone bank can be mentioned.

Uncontained acetabular defects with loss of superior iliac and posterior column support (Paprosky 3) represent a reconstructive challenge as the deficient bone will preclude the use of a conventional hemispherical cup. Such defects can be addressed with large metallic constructs like cages with and without allograft, custom tri-flange cups, and more recently with trabecular metal augments. An underutilised alternative is impaction bone grafting, after creating a contained cavitary defect with a reinforcement mesh. This reconstructive option delivers a large volume of bone while using a small-size socket fixed with acrylic cement.

Between 2005 and 2014, 21 patients with a Paprosky 3B acetabular defect were treated with cancellous, fresh frozen impaction grafting supported by a peripheral reinforcement mesh secured to the pelvis with screws. A cemented all-polyethylene cup was used. Pre-operative diagnosis was aseptic loosening (15 cemented and 6 uncemented). The femoral component was revised in 10 patients. Post-operative course consisted of 3 months of protected weight bearing. Patients were followed clinically and radiographically.

One patient had an incomplete post-operative sciatic palsy. After a mean follow up of 47 months (13 to 128) none of the patients required re-revision of the acetabular component. One asymptomatic patient presented with aseptic loosening 9 years post-operatively. Hardware failure was not observed. All patients had radiographic signs of graft incorporation and bone remodeling. There were no dislocations.

The early and mid-term results of revisions of large acetabular defects with this technique are encouraging. Reconstitution of hip center of rotation and bone stock with the use of a small-size implant makes this technique an attractive option for large defects. Longer follow-up is needed to assess survivability.

The principles of acetabular reconstruction include the creation of a stable acetabular bed, secure prosthetic fixation with freedom of orientation, bony reconstitution, and the restoration of a normal hip centre of rotation with acceptable biomechanics.

Acetabular impaction grafting, particularly with cemented implants, has been shown to be a reliable means of acetabular revision. Whilst our practice is heavily weighted towards cementless revision of the acetabulum with impaction grafting, there is a large body of evidence from Tom Slooff and his successors that cemented revision with impaction grafting undertaken with strict attention to technical detail is associated with excellent long terms results in all ages and across a number of underlying pathologies including dysplasia and rheumatoid arthritis.

We use revision to a cementless hemispherical porous-coated acetabular cup for most isolated cavitary or segmental defects and for many combined deficiencies. Morsellised allograft is packed in using chips of varied size and a combination of impaction and reverse reaming is used in order to create a hemisphere. There is increasing evidence for the use of synthetic grafts, usually mixed with allograft, in this setting. The reconstruction relies on the ability to achieve biological fixation of the component to the underlying host bone. This requires intimate host bone contact, and rigid implant stability. It is important to achieve host bone contact in a least part of the dome and posterior column – when this is possible, and particularly when there is a good rim fit, we have not found it absolutely necessary to have contact with host bone over 50% of the surface.

Once the decision to attempt a cementless reconstruction is made, hemispherical reamers are used to prepare the acetabular cavity. Sequentially larger reamers are used until there is three-point contact with the ilium, ischium and pubis. Acetabular reaming should be performed in the desired orientation of the final implant, with approximately 200 of anteversion and 400 of abduction (or lateral opening). Removing residual posterior column bone should be avoided. Reaming to bleeding bone is desirable. Morsellised allograft is inserted and packed and/or reverse reamed into any cavitary defects. This method can also be applied to medial wall uncontained defects by placing the graft onto the medial membrane or obturator internus muscle, and gently packing it down before inserting the cementless acetabular component. Either the reamer heads or trial cups can be used to trial prior to choosing and inserting the definitive implant. The fixation is augmented with screws in all cases. Incorporation of the graft may be helped by the use of autologous bone marrow.

Cementless acetabular components with impaction grafting should not be used when the host biology does not allow for stability or for bone ingrowth. This includes the severely osteopenic pelvis, pelvic osteonecrosis after irradiation, tumours, and metabolic bone disorders. They should also not be used in the presence of pelvic discontinuity unless the structure of the pelvic ring has been restored with a plate, or specialised materials/porous metals are used.

The challenge of reconstituting the acetabulum depends on the degree and type of bone loss. The principles of maximising host bone-implant contact and implant stability have borne fruit in our experience with cementless revision. The advantages of bone grafting in acetabular reconstruction include the ability to restore bone stock, to rebuild a normal hip center and hip biomechanics and to increase bone stock for future revisions.

The technique involves impaction of cancellous bone into a cavitary femur. If segmental defects are present, the defects can be closed with stainless steel mesh. The technique requires retrograde fill of the femoral cavity with cancellous chips of appropriate size to create a new endomedullary canal. By using a set of trial impactors that are slightly larger than the real implants the cancellous bone is impacted into the tube. Subsequent proximal impaction of bone is performed with square tip or half moon impactors. A key part of the technique is to impact the bone tightly into the tube especially around the calcar to provide optimal stability. Finally a polished tapered stem is cemented using almost liquid cement in order to achieve interdigitation of the implant to the cancellous bone.

The technique as described is rarely performed today in many centers around the world. In the US, the technique lost its interest because of the lengthy operative times, unacceptable rate of peri-operative and post-operative fractures and most importantly, owing to the success of tapered fluted modular stems. In centers such as Exeter where the technique was popularised, it is rarely performed today as well, as the primary cemented stems used there, rarely require revision.

There is ample experience from around the globe, however, with the technique. Much has been learned about the best size and choice of cancellous graft, force of impaction, surface finish of the cemented stem, importance of stem length, and the limitations and complications of the technique. There are also good histology data that demonstrate successful vascularization and incorporation of the impacted cancellous bone chips and host bone.

Our experience at the clinic was excellent with the technique as reported in CORR in 2003 by M Cabanela. The results at mid-term demonstrated minimal subsidence and good graft incorporation. Six of 54 hips, however, had a post-operative distal femoral fracture requiring ORIF. The use of longer cemented stems may decrease the risk of distal fracture and was subsequently reported by the author after reviewing a case series from Exeter.

Today, I perform this technique once or twice per year. It is an option in the younger patient, where bone restoration is desired. Usually in a Paprosky Type IV femur, where a closed tube can be recreated and the proximal bone is reasonable. If the proximal bone is of poor quality, then I prefer to perform a transfemoral osteotomy, and perform an allograft prosthetic composite instead of impaction grafting, and wrap the proximal bone around the structural allograft. I prefer this technique as I can maintain the soft tissues over the bone and avoid the stripping that would be required to reinforce the bone with struts or mesh. Another indication for its use in the primary setting is in the patient with fibrous dysplasia.

Femoral revision in cemented THA might include some technical difficulties, based on loss of bone stock and cement removal, which might lead to further loss of bone stock, inadequate fixation, cortical perforation or consequent fractures. Femoral impaction grafting, in combination with a primary cemented stem, allows for femoral bone restoration due to incorporation and remodelling of the allograft bone by the host skeleton. Historically it has been first performed and described in Exeter in 1987, utilizing a cemented tapered polished stem in combination with morselised fresh frozen bone grafts. The technique was refined by the development of designated instruments, which have been implemented by the Nijmegen group from Holland. Indications might include all femoral revisions with bone stock loss, while the Endo-Clinic experience is mainly based on revision of cemented stems. Cavitary bone defects affecting meta- and diaphysis leading to a wide or so called “drain pipe” femora, are optimal indications for this technique, especially in young patients. Contraindications are mainly: septical revisions, extensive circumferential cortical bone loss and noncompliance of the patient.

Generally, the technique creates a new endosteal surface to host the cemented stem by reconstruction of the cavitary defects with impacted morselised bone graft. This achieves primary stability and restoration of the bone stock. It has been shown, that fresh frozen allograft shows superior mechanical stability than freeze-dried allografts. Incorporation of these grafts has been described in 89%. Technical steps include: removal of failed stem and all cement, reconstruction of segmental bone defects with metal mesh (if necessary), preparation of fresh frozen femoral head allografts with bone mill, optimal bone chip diameter 2–5 mm, larger chips for the calcar area (6–8 mm), insertion of an intramedullary plug including central wire, 2 cm distal the stem tip, introduction of bone chips from proximal to distal, impaction started by distal impactors over central wire, then progressive larger impactors proximal, insertion of a stem “dummy” as proximal impactor and space filler, removal of central wire, retrograde insertion of low viscosity cement (0.5 Gentamycin) with small nozzle syringe, including pressurization, and insertion of standard cemented stem. The cement mantle is of importance, as it acts as the distributor of force between the stem and bone graft and seals the stem. A cement mantle of at least 2 mm has shown favorable results. Post-operative care includes usually touch down weightbearing for 6–8 weeks, followed by 4–6 weeks of gradually increased weightbearing with a total of 12 weeks on crutches.

Relevant complications include mainly femoral fractures due to the hardly impacted allograft bone. Subsidence of tapered polished implants might be related to cold flow within the cement mantle, however, could also be related to micro cement mantle fractures, leading to early failure. Subsidence should be less than 5 mm. Survivorship with a defined endpoint as any femoral revision after 10-year follow up has been reported by the Exeter group being over 90%, while survivorship for revision as aseptic loosening being above 98%. Within the last years various other authors and institutions reported about similar excellent survivorships, above 90%. In addition, a long-term follow up by the Swedish arthroplasty registry in more than 1180 patients reported a cumulative survival rate of 94% after 15 years.

Impaction grafting might technically be more challenging and more time consuming than cement-free distal fixation techniques. It, however, enables a reliable restoration of bone stock which might especially become important in further revision scenarios in younger patients.

Femoral revision in cemented THA might include some technical difficulties, based on loss of bone stock and cement removal, which might lead to further loss of bone stock, inadequate fixation, cortical perforation or consequent fractures. Femoral impaction grafting, in combination with a primary cemented stem, allows for femoral bone restoration due to incorporation and remodeling of the allograft bone by the host skeleton. Historically, it has been first performed and described in Exeter in 1987, utilizing a cemented tapered polished stem in combination with morselised fresh frozen bone grafts. The technique was refined by the development of designated instruments, which have been implemented by the Nijmegen group from Holland.

Indications might include all femoral revisions with bone stock loss, while the ENDO-Klinik experience is mainly based on revision of cemented stems. Cavitary bone defects affecting meta- and diaphysis leading to a wide or so called “drain pipe” femora, are optimal indications for this technique, especially in young patients. Contraindications are mainly: septical revisions, extensive circumferential cortical bone loss and noncompliance of the patient.

Generally the technique creates a new endosteal surface to host the cemented stem by reconstruction of the cavitary defects with impacted morselised bone graft. This achieves primary stability and restoration of the bone stock. It has been shown, that fresh frozen allograft shows superior mechanical stability than freeze-dried allografts. Incorporation of these grafts has been described in 89%.

Technical steps include: removal of failed stem and all cement, reconstruction of segmental bone defects with metal mesh (if necessary), preparation of fresh frozen femoral head allografts with bone mill, optimal bone chip diameter 2 – 5 mm, larger chips for the calcar area (6 – 8 mm), insertion of an intramedullary plug including central wire, 2 cm distal to the stem tip, introduction of bone chips from proximal to distal, impaction started by distal impactors over central wire, then progressively larger impactors proximal, insertion of a stem “dummy” as proximal impactor and space filler, removal of central wire, retrograde insertion of low viscosity cement (0.5 Gentamycin) with small nozzle syringe, including pressurization, insertion of standard cemented stem. The cement mantle is of importance, as it acts as the distributor of force between the stem and bone graft and seals the stem. A cement mantle of at least 2 mm has shown favorable results. Originally the technique is described with a polished stem. We use standard brushed stems with comparable results. Postoperative care includes usually touch down weight bearing for 6–8 weeks, followed by 4–6 weeks of gradually increased weightbearing with a total of 12 weeks on crutches.

Survivorship with a defined endpoint as any femoral revision after 10 year follow up has been reported by the Exeter group being over 90%. While survivorship for revision related to aseptic loosening being above 98%. Within the last years various other authors and institutions reported similar excellent survivorships, above 90%. In addition a long term follow up by the Swedish arthroplasty registry in more than 1180 patients reported a cumulative survival rate of 94% after 15 years.

Impaction grafting might technically be more challenging and more time consuming than cement free distal fixation techniques. It, however, enables a reliable restoration of bone stock which might become important in further revision scenarios in younger patients.

Introduction

The reconstructive hip surgeon is commonly faced with complex cases where severe bone loss makes conventional revision techniques difficult or impossible. This problem is likely to increase in future, as there is a good correlation between the degree of bone loss seen and number of previous total hip operations. In such situations, one alternative is the use impaction allografting with cement. This has captured the attention of the orthopaedic community because of its potential for reconstituting femoral bone stock.

Introduction:

The reconstructive hip surgeon is commonly faced with complex cases where severe bone loss makes conventional revision techniques difficult or impossible. This problem is likely to increase in future, as there is a good correlation between the degree of bone loss seen and number of previous total hip operations. In such situations, one alternative is the use of impaction allografting with cement.

Introduction

The reconstructive hip surgeon is commonly faced with complex cases where severe bone loss makes conventional revision techniques difficult or impossible. This problem is likely to increase in future, as there is a good correlation between the degree of bone loss seen and number of previous total hip operations. In such situations, one alternative is the use impaction allografting with cement. This has captured the attention of the orthopaedic community because of its potential for reconstituting femoral bone stock.

The reconstructive hip surgeon is commonly faced with complex cases where severe bone loss makes conventional revision techniques difficult or impossible. This problem is likely to increase in future, as there is a good correlation between the degree of bone loss seen and number of previous total hip operations. In such situations, one alternative is the use impaction allografting with cement. This has captured the attention of the orthopaedic community because of its potential for reconstituting femoral bone stock.

The first clinical reports of impaction allografting on the femoral side were in relation to revision with cementless stems. The use of morsellised bone with cement on the femoral side was first reported by the Exeter group. The great enthusiasm with which this technique has been received is related to its biological potential to increase bone stock. The rapid revascularisation, incorporation and remodelling of morsellised compacted cancellous allograft differs dramatically from structural allografting where bone ingrowth usually is limited to 2–3mm. Histological evidence for bony reconstitution has been presented from postmortem retrievals, and from biopsies at the time of trochanteric wire removal.

The size of the bone chips used as morsellised allograft is important. The graft behaves as a friable aggregate and its resistance to complex forces depends on grading, normal load and compaction. It is recommended that particles of 3–5mm in diameter make up the bulk of the graft. A bone slurry, such as that produced by blunted bone mills, or by the use of acetabular reamers or high speed burrs would not give satisfactory stability. A wide range of particle sizes is recommended in order to achieve the greatest stability. Future considerations will include the potential for either adding biomaterials to the allograft, or ultimately substituting it completely.

A satisfactory cement mantle is required to ensure the longevity of any cemented stem. The primary determinant of cement mantle thickness is the differential between the graft impactors and the final stem. All femoral impaction systems require careful design to achieve a cement mantle that is uninterrupted in its length and adequate in its thickness.

The technique of impaction allografting on the femoral side was first and most successfully reported using a highly polished stem with a double tapered geometry and no collar. It is thought to be ideal for this technique as it can subside within the cement mantle, thus generating hoop stresses on the cement which creeps, potentially maintaining physiological loads on the supporting bone. The extension of this technique to other stems has led to some controversy. Confounding factors such as surgical technique, the impaction system available, the type and size of allograft bone used, and the extent of the pre-operative bone loss, will undoubtedly continue to influence such comparisons. It appears that the exact stem configuration may not be as critical as its surface finish, the amount of graft impaction possible and the cement mantle produced.

Impaction allografting is the only technique currently available that reverses the loss of bone stock seen in a revision hip arthroplasty. Moreover, this technique does not sacrifice host tissue, and could facilitate further surgery. Impaction allografting, performed with great attention to detail using appropriate equipment, represents an exciting reconstructive solution for contained femoral defects. Its role in larger and combined defects remains open to scrutiny. Careful observation and cautious optimism are necessary as further refinements may well improve the predictability of the clinical results and expand the indications for this important addition to the armamentarium of the revision surgeon.

Purpose:

Tuberosity healing in hemiarthroplasty for proximal humerus fractures remains problematic. Improved implant design and better techniques for tuberosity fixation have not been met with improved clinical results. The etiology for tuberosity failure is multifactorial; however thermal injury to host bone is a known effect of using polymethylmethacrylate for implant fixation. We hypothesized that the effect of thermal injury at the tuberosity shaft junction could be diminished by utilizing an impaction grafting technique for hemiarthroplasty stems.

Femoral revision in cemented THA might include some technical difficulties, based on the loss of bone stock and cement removal, which might lead to further loss of bone stock, inadequate fixation, cortical perforation or consequent fractures. Femoral impaction grafting, in combination with a primary cemented stem, allows for femoral bone restoration by incorporating and remodeling the allograft bone of the host skeleton. Historically, this was first performed and described in Exeter in 1987.

Indications might include all femoral revisions with bone stock loss, while the Endo-Clinic experience is mainly based on revision of cemented stems. Nowadays our main indication is the Paprosky Type IIIb and Type IV. Contraindications are mainly: septical revisions, extensive circumferential cortical bone loss and noncompliance of the patient. Generally the technique creates a new endosteal surface to host the cemented stem by reconstruction of the cavitary defects with impacted morselised bone graft. This achieves primary stability and restoration of the bone stock. It has been shown, that fresh frozen allograft shows superior mechanical stability than freeze-dried allografts.

Technical steps include: –

removal of failed stem and all cement rests

The cement mantle is of importance as it acts as the distributor of force between the stem and bone graft while sealing the stem. A cement mantle of at least 2 mm has shown favourable results. Post-operative care includes usually touch down weight bearing for 6–8 weeks, followed by 4–6 weeks of gradually increased weightbearing with a total of 12 weeks on crutches. Relevant complications include mainly femoral fractures due to the hardly impacted allograft bone. Subsidence of tapered polished implants might be related to coldflow within the cement mantle, however, it could also be related to micro cement mantle fractures, leading to early failure. Subsidence should be less than 5 mm.

Survivorship with a defined endpoint as any femoral revision after 10-year follow-up has been reported by the Exeter group at over 90%. While survivorship for revision defined as aseptic loosening is even greater at above 98%. Within the last years various other authors and institutions reported similar excellent survivorships, above 90%. In addition a long-term follow-up by the Swedish arthroplasty registry in more than 1180 patients reported a cumulative survival rate of 94% after 15 years and 99% with the endpoint aseptic loosening.

Impaction grafting is technically more challenging and more time consuming than cement free distal fixation techniques. However, it enables a reliable restoration of bone stock.

Uncontained acetabular defects with loss of superior iliac and posterior column support (Paprosky 3B) represent a reconstructive challenge as the deficient bone will preclude the use of a conventional hemispherical cup. Such defects can be addressed with large metallic constructs like cages with and without allograft, custom tri-flange cups, and more recently with trabecular metal augments. An underutilised alternative is impaction bone grafting, after creating a contained cavitary defect with a reinforcement mesh. This reconstructive option delivers a large volume of bone while using a small-size socket fixed with acrylic cement.

Between 2006 and 2014, sixteen patients with a Paprosky 3B acetabular defect were treated with cancellous, fresh frozen impaction grafting supported by a peripheral reinforcement mesh secured to the pelvis with screws. A cemented all polyethylene cup was used. Preoperative diagnosis was aseptic loosening (10 cemented and 6 non-cemented). The femoral component was revised in 9 patients. Postoperative course consisted of 3 months of protected weight bearing. Patients were followed clinically and radiographically.

One patient had an incomplete postoperative sciatic palsy. After a mean follow up of 40 months (24 to 104) none of the patients required re-revision. One asymptomatic patient presented with aseptic loosening 9 years postoperatively. Hardware failure was not observed. All patients had radiographic signs of graft incorporation and bone remodeling. There were no dislocations.

The early and mid-term results of revisions for large acetabular defects with this technique are encouraging. Reconstitution of hip center of rotation and bone stock with the use of a small-size implant make this technique an attractive option for these large defects. Longer follow-up is needed to assess survivability.

Impaction grafting is an excellent option for acetabular revision. It is technique specific and very popular in England and the Netherlands and to some degree in other European centers. The long term published results are excellent. It is, however, technique dependent and the best results are for contained cavitary defects. If the defect is segmental and can be contained by a single mesh and impaction grafting, the results are still quite good. If, however, there is a larger segmental defect of greater than 50% of the acetabulum or a pelvic discontinuity, other options should be considered.

Segmental defects of 25–50% can be managed by minor column (shelf) or figure of 7 structural allografts with good long term results. Porous metal augments are now a good option with promising early to mid-term results. Segmental defects of greater than 50% require a structural graft or porous augment usually protected by a cage. If there is an associated pelvic discontinuity then a cup cage is a better solution.

An important question is does impaction grafting facilitate rerevision surgery? There is no evidence to support this but some histological studies of impacted allograft would suggest that it may. On the other hand there are papers that show that structural allografts do restore bone stock for further revision surgery. Also the results of impaction grafting are best in the hands of surgeons comfortable with using cement on the acetabular side, and one of the reasons why this technique is not as popular in North America.

Acetabular impaction grafting (AIG) for the reconstruction of acetabular defects in total hip arthroplasty has the potential to recreate anatomy whilst also allowing the restoration of bone stock. The incorporation of impacted, morcellised bone graft has been demonstrated in histological studies and is a well established technique in revision hip surgery where there is loss of bone stock. We have studied our results of fullAIG when used in primary total hip arthroplasty, with particular emphasis on the results of AIG in cavitary and segmental defects.

Between 1995 and 2003, 129 cemented primary THAs were performed using full acetabular impaction grafting to reconstruct acetabular deficiencies. These were classified as cavitary in 74 and segmental in 55 hips. Eighty-one patients were reviewed at mean 9.1 (6.2–14.3) years post-operatively. There were seven acetabular component revisions due to aseptic loosening, and a further 11 cases that had migrated »5 mm or tilted »5° on radiological review — ten of which reported no symptoms. Kaplan–Meier analysis of revisions for aseptic loosening demonstrates 100% survival at nine years for cavitary defects compared to 82.6% for segmental defects. Our results suggest that the medium-term survival of this technique is excellent when used for purely cavitary defects but less predictable when used with large rim meshes in segmental defects.

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.

Femoral impaction grafting with cancellous bone and cement is an important technique in reconstituting deficient bone stock in revision hip arthroplasty. We report the medium to long term results of 75 consecutive patients using a collarless, polished, tapered femoral stem with an average age of 68 (±11.4) years and a mean follow up of 10.5 (±2.4) years (range 6.3 to 14.1 years).

The median Endoklinik pre-operative bone defect score was 3 (IQR: 2–3) with a median subsidence at 1 year of 2mm (IQR: 1–3mm). At the most recent follow-up (mean 10.5±2.4 years), the median Harris Hip Score (HHS) was 80.6 (IQR: 67.6–88.9) and median subsidence 2mm (IQR: 1–4mm). Ten-year survivorship with any further femoral operation as an endpoint was 92%. Four prostheses required further revision.

Subsidence of the Exeter stem continued, albeit at a slower rate after the first year and was related to the Endoklinik pre-operative bone loss (p=0.037). The degree of subsidence at 1 year was a strong predictor of long term subsidence (p<0.001). Neither subsidence nor bone stock were related to long term outcome (HHS). There was a correlation between previous revision surgery and a poor Harris Hip Score (p=0.028) and those who had undergone previous revision surgery for infection had a higher risk of complications (p=0.048).

The good long term results of this technique commend its use in revision hip arthroplasty for patients with poor femoral bone stock.

Acetabular reconstruction with impaction bone grafting and a cemented polyethylene aims to reconstitute the bone stock in hip revision. This is an effective but expensive, resource intensive and time consuming technique. Most surgeons remove the articular cartilage from the femoral head allograft. The aim of this study is to reproduce the results using the whole femoral head with the articular cartilage for acetabular impaction grafting.

38 acetabular revisions using impacted morselised bone graft retaining the articular cartilage and a cemented cup were studied retrospectively. The operations were performed by the senior author in Wrightington Hospital, UK with a posterior hip approach. The mean follow up was 4.1 years (range, 1–10 years). Clinical and radiological assessment was made using the Oxford hip score, Hodgkinson's criteria (1988) for socket loosening and the Gie classification (1993) for evaluation of allograft incorporation.

Thirty-six (94.7%) sockets were considered radiologically stable (type 0, 1, 2 demarcations) and two (5.3%) sockets were radiologically loose (type 3 demarcations) but there was no socket migration. Twenty-one (55.3%) cases showed good trabecular remodeling (grade 3). Fourteen (36.8 %) cases showed trabecular remodeling (grade 2). Only three (7.9%) cases showed poor allograft incorporation (grade 1). Mean pre-operative hip score was 41 and post-operative hip score was 21. There was one (2.6%) wound infection treated with oral antibiotics and one (2.6%) periprosthetic femoral fracture treated with cables. Furthermore, there was one (2.6%) case of pulmonary embolism and three (7.89%) cases of asymptomatic heterotopic ossification. One year mortality rate was 2.6% (one case) from heart failure but not associated with the surgery. There have been no socket re-revisions (100% survival) at an average of 4 years.

At a mean follow up of 4 years, results with the aforementioned technique are comparable to other major studies. Compared to the 40% of minimal loss in obtaining pure cancellous graft less than 10% of initial graft mass is lost without removing the articular cartilage. Particularly when the supply of allograft and operative time are limited retaining the articular cartilage of the femoral head is a safe and effective alternative to be considered.

The process of femoral impaction grafting requires vigorous impaction to obtain adequate stability but the force of impaction has not been determined. This process has been reported to result in femoral fractures with rates reaching 16%. The aims of this study were to determine the threshold force required for femoral impaction grafting, to determine the affect cortical thickness, canal diameter and bone mineral density (BMD) have on this threshold force and to measure subsidence of an Exeter prosthesis following impaction at the threshold force.

Adult sow femurs were prepared and placed through a DEXA scanner and the BMD and canal diameter measured. Thirty five femurs were impacted with morsellised bone chips and an increasing force of 0.5kN was applied until the femur fractured. Using callipers the cortical thickness of the bone was measured along the fracture line. Once the threshold force was determined 5 femurs were impacted to this threshold force and an Exeter stem was cemented into the neomedullary canal and a 28mm Exeter head attached. Axial cyclic loading was performed between 440N (swing phase of gait) and 1320N (stance phase of gait) for 150,000 cycles at a frequency of 3Hz. The position sensor of the hydraulic testing machine measured the subsidence.

29 tests were successfully completed. The threshold force was found to be 4kN. There was no significant correlation between the load at fracture and the cortex: canal ratio or the bone mineral density. Following impaction with the maximum force of 4kN the average subsidence for the 5 femurs was 0.276mm (range 0.235 – 0.325mm). In this animal study the threshold force was 4kN. Minimal axial subsidence of the implant occurred when impacting the graft with this threshold force. We therefore achieved a stable construct without fracture which is the ultimate goal for the revision hip surgeon.

Introduction

Modern processing techniques in bone banking are thought to decrease the presence of allogenic material in bone. This project was performed to observe any changes in peripheral blood lymphocyte subsets in response to allografted bone used in revision hip replacement.