Purpose: Porous tantalum has been shown to be very effective in achieving bone ingrowth. However, in some circumstances, bone quality or quantity is insufficient to allow adequate bone ingrowth. We hypothesized that the addition of alendronate to porous tantalum would enhance the ability of porous tantalum to achieve bone ingrowth in these challenging situations, such as when a gap exists between the implant and bone. We evaluated the effect of alendronate coated porous tantalum on new bone formation in an animal model incorporating a gap between implant and bone.

Method: Thirty-six cylindrical porous tantalum implants were bilaterally implanted into the distal femur of 18 rabbits for 4 weeks. There were 3 groups of implants inserted; a control group of porous tantalum with no coatings, porous tantalum with micro-porous calcium phosphate coating, and porous tantalum coated with micro-porous calcium phosphate and alendronate. Subcutaneous fluorescent labeling was used to track new bone formation. Bone formation was analyzed by backscattered electron microscopy and fluorescent microscopy on undecalcified samples.

Results: The relative increase in mean volume of gap filling, bone ingrowth and total bone formation was 143% (p< 0.001), 259% (p< 0.001) and 193% (p< 0.001) respectively in the alendronate coated porous tantalum compared with the uncoated porous tantalum controls. The relative increase in the percentage of new bone-implant contact length was increased by 804% on average in the alendronate coated porous tantalum compared with the uncoated tantalum controls.

Conclusion: This study demonstrated the significant enhancement of bone-implant gap filling and bone ingrowth which can be achieved by coating porous tantalum with alendronate. It is proposed that, when faced with the clinical problem of revision joint replacement in the face of bone loss (at the hip, knee or elsewhere), the addition of an alendronate-delivery surface coating would enhance biological fixation of the implant and promote the healing of bone defects.

We report the outcome at ten to 15 years of two-stage revision for hip infection in 99 patients using the Prostalac articulated hip spacer system.

All the patients were contacted to determine their current functional and infection status using the Oxford-12, Short form-12, and Western Ontario and McMaster University Osteoarthritis Index questionnaires. A total of 11 of the 99 patients had a further infection, of whom seven responded to repeat surgery with no further sequelae. The mean interval between the stages was five months (1 to 36). We were able to review 48 living patients, with a mean age of 72 years (46 to 86), 34 (71%) of whom provided health-related quality-of-life outcome scores.

The mean follow-up was 12 years (10 to 15). The long-term success rate was 89% and with additional surgery this rose to 96%. The mean global Western Ontario and McMaster University Osteoarthritis Index score was 80.6 (sd 18.3). The mean Oxford-12 score was 74.0 (sd 22.3), and the mean Short form-12 score was 53.1 (sd 9.4) (mental) and 33.5 (sd 13.5) (physical). The mean satisfaction score was 90.5 (sd 15.3).

Two-stage revision for hip infection using a Prostalac interim spacer offers a predictable and lasting solution for patients with this difficult problem.

Introduction: Achieving durable implant–host bone fixation is the major challenge in uncemented revision hip arthroplasty when significant bone stock deficiencies are encountered. The purpose of this study was 1) to develop an experimental model which would simulate the clinical revision hip scenario and 2) determine the effects of alendronate coating on porous tantalum on gap filling and bone ingrowth in the experimental model.

Methods: Thirty-six porous tantalum plugs were implanted into the distal femur, bilaterally of 18 rabbits for four weeks. There were 3 groups of plugs inserted; control groups of porous tantalum plugs (Ta) with no coating, a 2^nd control group of porous tantalum plugs with micro-porous calcium phosphate coating, (Ta-CaP) and porous tantalum plugs coated with alendronate (Ta-CaP-ALN). Subcutaneous fluorochrome labelling was used to track new bone formation. Bone formation was analysed by backscattered electron microscopy and fluorescence microscopy on undecalcified histological sections.

Results: The relative increase in mean volume of gap filling, bone ingrowth and total bone formation was 124 %, 232 % and 170 % respectively in Ta-CaP-ALN compared with the uncoated porous tantalum (Ta) controls, which was statistically significant. The contact length of new bone formation on porous tantalum implants in Ta-CaP-ALN was increased by 700% (8-fold) on average compared with the uncoated porous tantalum (Ta) controls.

Discussion: Alendronate coated porous tantalum significantly modulated implant bioactivity compared with controls. This study has demonstrated the significant enhancement of bone-implant gap filling and bone ingrowth, which can be achieved by coating porous tantalum with alendronate. It is proposed that, when faced with the clinical problem of revision joint replacement in the face of bone loss, the addition of alendronate as a surface coating would enhance biological fixation of the implant and promote the healing of bone defects.

Revision of a failed acetabular reconstruction in total hip arthroplasty (THA) can be challenging when associated with significant bone loss. In cementless revision THA, achieving initial implant stability and maximising host bone contact is key to the success of reconstruction. Porous tantalum acetabular shells may represent an improvement from conventional porous coated uncemented cups in revision acetabular reconstruction associated with severe acetabular bone defects.

Methods: We reviewed the clinical and radiographic results of 46 acetabular revisions with Paprosky 2 and 3 acetabular bone defects done with a hemispheric, tantalum acetabular shell (Trabecular Metal Revision Shell, Zimmer, Warsaw, USA) and multiple supplementary screws for fixation.

Results: At a mean follow-up of 40 (24–51) months, one acetabular shell had been revised in a patient with a Paprosky 3B defect. Two liner revisions were performed for recurrent instability, without porous tantalum shell revision. The clinical outcome showed significant postoperative improvement in all measured sub-scales, compared with baseline pre-operative scores (mean improvement in Oxford Hip Score of 40.0, p < 0.001, in WOMAC of 36.7, p < 0.001, Physical component SF-12 of 12.3, p =0.0003, mental component of SF-12 of 6.8, p = 0.006). Radiographic evidence of osseointegration using validated criteria (Moore’s criteria) was demonstrated in 39 of the 40 hips available for radiographic analysis at a mean of 30.9 months, by two independent observers. Of the remaining six hips, five hips were lost to follow-up and one radiograph demonstrated failure of the hip reconstruction secondary to loss of fixation and superior migration of the component.

Discussion: Cementless acetabular revision with the porous tantalum acetabular shell demonstrated excellent early clinical and radiographic results in a series of complex revision acetabular reconstruction associated with severe bone defects. The evidence of radiographic osseointegration suggests that outcome should remain favourable, however, further longer-term evaluation is warranted.

Introduction: Deep infection in total hip replacement can be devastating. We report the outcomes 10–15 years after two stage revision for hip infection in 103 patients using the PROSTALAC (prosthesis of antibiotic-loaded acrylic cement) hip.

Methods: All patients or their next of kin were contacted to determine their current functional status and whether they had required repeat surgery or had recurrent infection. The Oxford-12, SF-12, and WOMAC questionnaires were administered. A comprehensive chart review was undertaken to review the infective organisms, surgery, approach, complications, and need for further revision surgery.

Results: 11 patients had re-infection, 7 of whom responded to repeat surgery with no further sequelae. Two patients required resection arthroplasty, one patient underwent hip disarticulation after eventual failure of treatment and bone loss, and one immuno-compromised patient developed osteomyelitis and was subsequently lost to follow-up. Long-term success rate for two stage-revision is thus 89%, or 96% with additional surgery. Since then, 3 patients required revisions for aseptic loosening, 1 for recurrent dislocation. We were able to follow up 45 patients, 75 % of whom provided health-related quality of life outcome scores. 39 patients were deceased, with their outcome confirmed via their last follow-up or with family members, for a total follow-up rate of 85 %. 15 patients were lost to follow-up, but did not undergo further surgery or have reinfections treated at our centre.

Discussion: Two-stage revision for hip infection, which includes an interim prosthesis of antibiotic loaded cement, offers a predictable and lasting solution for patients with this difficult problem.

Introduction: The aims of this study were to

determine predictors of pain, function and activity level 1–2 years after revision hip arthroplasty and

Methods: A prospective cohort of 222 patients who underwent revision hip arthroplasty were evaluated. Predictive models were developed and proportional odds regression analyses were performed to identify factors that predict quality of life outcomes at 1 and 2 years post surgery. The dependent outcome variables were WOMAC function, pain and UCLA activity. The independent variables included patient demographic, surgery specific and objective parameters including baseline Western Ontario McMaster Universities (WOMAC) osteoarthritis index, and the Short Form-12 mental component. The Loess method was used to plot the change of WOMAC and SF-12 scores over time.

Results: There was a significant improvement (p< 0.001) in all patient quality of life scores from baseline with results plateauing at 1 year. UCLA activity remained static between 1 and 2 years. In the predictive model, higher baseline WOMAC function (p < 0.001), age between 60–70 (p< 0.037), male gender (0.017), lower Charnley class (p < 0.001) and diagnosis of aseptic loosening (p < 0.003) were significant predictors of improved function.

When considering WOMAC pain as an outcome variable, factors predictive of improving category outcome included baseline WOMAC function (p= 0.001), age between 60–70 (p< 0.004), male gender (p= 0.005), lower Charnley class (p< 0.001) and no previous revisions (p < 0.023). Baseline WOMAC pain did not predict final pain outcome. Baseline WOMAC function (p=0.001), the indication for the operation (p=0.007), and the operating surgeon were significant predictors of UCLA activity at follow up. Peri or post-operative complications were not an adverse predictor of physical function, pain or activity.

Conclusions: Predictors of quality of life outcomes after revision hip replacement-showed that although some patient specific and surgical specific variables were important, age, gender, Charnley class and baseline WOMAC function had the most robust associations with outcomes.

Introduction: This single incision, anterolateral intermuscular approach (AL-IM) utilizes the interval between gluteus medius and tensor fascia lata. The aims of the study were to compare the quality of life, satisfaction and complications of this approach with two of the most commonly used limited incision transmuscular (TM) approaches, namely the mini-posterior (P-TM) and the mini-direct lateral (L-TM).

Methods: 199 patients receiving MIS THA surgical procedures were evaluated prospectively (63 AL-IM, 68 P-TM and 68 L-TM). The outcome variables were WOMAC function, pain, stiffness, SF-12 (physical & mental), Oxford-12, satisfaction and radiological outcome. Parametric and non-parametric analyses were performed.

Results: There were no significant differences between groups in baseline characteristics including age, sex, BMI, co-morbidity, or pre-op WOMAC, SF-12, Oxford-12 (p> .05). However, the AL-IM group was associated with superior outcomes (p< .05) in WOMAC function, WOMAC pain, global WOMAC, Oxford-12 and SF-12 physical component.

Conclusion: In the short term the AL-IM approach provides significant improvements in quality of life scores over other limited incision approaches. It provides minimal soft tissue disruption and maintains the abductor musculature and posterior soft tissue envelope, with similar complications and radiological outcomes.

A prospective cohort of 222 patients who underwent revision hip replacement between April 2001 and March 2004 was evaluated to determine predictors of function, pain and activity level between one and two years post-operatively, and to define quality of life outcomes using validated patient reported outcome tools. Predictive models were developed and proportional odds regression analyses were performed to identify factors that predict quality of life outcomes at one and two years post-operatively. The dependent outcome variables were the Western Ontario and McMaster Osteoarthritis Index (WOMAC) function and pain scores, and University of California Los Angeles activity scores. The independent variables included patient demographics, operative factors, and objective quality of life parameters, including pre-operative WOMAC, and the Short Form-12 mental component score.

There was a significant improvement (t-test, p < 0.001) in all patient quality of life scores. In the predictive model, factors predictive of improved function (original regression analyses, p < 0.05) included a higher pre-operative WOMAC function score (p < 0.001), age between 60 and 70 years (p < 0.037), male gender (p = 0.017), lower Charnley class (p < 0.001) and aseptic loosening being the indication for revision (p < 0.003). Using the WOMAC pain score as an outcome variable, factors predictive of improvement included the pre-operative WOMAC function score (p = 0.001), age between 60 and 70 years (p = 0.004), male gender (p = 0.005), lower Charnley class (p = 0.001) and no previous revision procedure (p = 0.023). The pre-operative WOMAC function score (p = 0.001), the indication for the operation (p = 0.007), and the operating surgeon (p = 0.008) were significant predictors of the activity assessment at follow-up.

Predictors of quality of life outcomes after revision hip replacement were established. Although some patient-specific and surgery-specific variables were important, age, gender, Charnley class and pre-operative WOMAC function score had the most robust associations with outcome.

We studied various aspects of graft impaction and penetration of cement in an experimental model. Cancellous bone was removed proximally and local diaphyseal lytic defects were simulated in six human cadaver femora. After impaction grafting the specimens were sectioned and prepared for histomorphometric analysis.

The porosity of the graft was lowest in Gruen zone 4 (52%) and highest in Gruen zone 1 (76%). At the levels of Gruen zones 6 and 2 the entire cross-section was almost filled with cement. Cement sometimes reached the endosteal surface in other Gruen zones. The mean peak impaction forces exerted with the impactors were negatively correlated with the porosity of the graft.

Revision of a total knee arthroplasty may require an extensile approach to permit a satisfactory exposure without compromising the attachment of the patellar tendon. It has been assumed that a rectus snip is a relatively benign form of release, but the effect of using this approach on function, pain and patient satisfaction is not known.

From January 1997 to December 1999, 107 patients who underwent revision of total knee arthroplasty were followed up at a minimum of two years (mean 40.5 months) and assessed by the Oxford Hip Score, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Short-Form (SF)-12 and patient satisfaction. Co-morbidity, surgical exposure, the Hospital for Special Surgery (HSS) knee scores and the range of movement were also used. A standard medial parapatellar approach was used in 57 patients and the rectus snip in 50. The two groups were equivalent for age, sex and co-morbidity scores. The WOMAC function, pain, stiffness and satisfaction scores demonstrated no statistical difference. The use of a rectus snip as an extensile procedure has no effect on outcome.

Removal of well-fixed, cementless, acetabular components during revision arthroplasty remains a challenging problem. Further damage to host bone may limit options for reconstruction and compromise the long-term result of the revision operation. We report the results of 31 hips with well-fixed, cementless sockets which were removed using a new cup extraction system. In all hips the socket was removed without difficulty and with minimal further bone loss.

There are few medium- and long-term data on the outcome of the use of proximal femoral structural allografts in revision hip arthroplasty. This is a study of a consecutive series of 40 proximal femoral allografts performed for failed total hip replacements using the same technique with a minimum follow-up of five years (mean 8.8 years; range 5 to 11.5 years). In all cases the stem was cemented into both the allograft and the host femur. The proximal femur of the host was resected in 37 cases.

There were four early revisions (10%), two for infection, one for nonunion of the allograft-host junction, and one for allograft resorption noted at the time of revision of a failed acetabular reconstruction. Junctional nonunion was seen in three patients (8%), two of whom were managed successfully by bone grafting, and bone grafting and plating respectively. Instability was observed in four (10%). Trochanteric nonunion was seen in 18 patients (46%) and trochanteric escape in ten of these (27%). The mean Harris hip score improved from 39 to 79. Severe resorption involving the full thickness of the allograft was seen in seven patients (17.5%). This progressed rapidly and silently, but has yet to cause failure of any of the reconstructions.

Profound resorption of the allograft may be related to a combination of factors, including a slow form of immune rejection, stress shielding and resorption due to mechanical disuse with solid cemented distal fixation, and the absence of any masking or protective effect which may be provided by the retention of the bivalved host bone as a vascularised onlay autograft. Although continued surveillance is warranted, the very good medium-term clinical results justify the continued use of structural allografts for failed total hip replacements with severe loss of proximal femoral bone.

The PROSTALAC functional spacer is made of antibiotic-loaded acrylic cement but has a small metal-on-polythene articular surface. We have used it as an interim spacer in two-stage exchange arthroplasty for infected total knee replacement. PROSTALAC allows continuous rehabilitation between stages as it maintains good alignment and stability of the knee and a reasonable range of movement. It also helps to maintain the soft-tissue planes, which facilitates the second-stage procedure.

We reviewed 45 consecutive patients, treated over a period of nine years. The mean follow-up was for 48 months (20 to 112). At final review, there was no evidence of infection in 41 patients (91%); only one had a recurrent infection with the same organism. There was improvement in the Hospital for Special Surgery knee score between stages and at final review. The range of movement was maintained between stages. Complications were primarily related to the extensor mechanism and stability of the knee between stages. Both of these problems decreased with refinement of the design of the implant.

The rate of cure of the infection in our patients was similar to that using other methods. Movement of the knee does not appear to hinder control of infection.

We describe a U-shaped approach to the distal femur which, having divided the extensor mechanism and elevated the entire quadriceps muscle, gives excellent exposure and allows a number of reconstructive options. It was used in 14 patients, 13 of whom were followed up for a mean of 3.5 years (1 to 11). There was no case of flap necrosis, and complications related to the reconstruction were acceptable.

An analysis of the cement mantle obtained with the Exeter impaction allografting system at one centre showed that it was either deficient or absent in almost 47% of Gruen zones. We therefore examined the mantle obtained using this system at another hospital and compared the results with those from the CPT and Harris Precoat Systems at other centres.

The surgical indications for the procedure and the patient details were broadly similar in all four hospitals. There was some variation in the frequency of use of cortical strut allografts, cerclage wires and wire mesh to supplement the impaction allograft. Analysis of the cement mantles showed that when uncertain Gruen zones were excluded, the incidence of zones with areas of absence or deficiency of the cement was 47% and 50%, respectively, for the two centres using the Exeter system, 21% for the CPT system and 18% for the Harris Precoat system.

We measured the difference in size between the proximal allograft impactors and the definitive prosthesis for each system. The Exeter system impactors are shorter than the definitive prosthesis and taper sharply so that the cavity created is inadequate, especially distally. The CPT proximal impactors are considerably longer than the definitive prosthesis and are designed to give a mantle of approximately 2 mm medially and laterally and 1.5 mm anteriorly and posteriorly. The Harris Precoat proximal impactors allow for a mantle with a circumference of 0.75 mm in the smaller sizes and 1 mm in the larger.

Many reports link the longevity of a cemented implant to the adequacy of the cement mantle. For this reason, femoral impaction systems require careful design to achieve a cement mantle which is uninterrupted in its length and adequate in its thickness. Our results suggest that some current systems require modification.