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Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 83 - 83
1 Mar 2008
Comley A McCalden R Rorabeck C MacDonald S Bourne R
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Constrained acetabular components are a useful adjunct for the potentially unstable hip arthroplasty. There have been concerns over implant failure and early acetabular component loosening secondary to the increased implant constraint. We report the results of a constrained ace-tabular component used as treatment for dislocating hips and as prophylaxis against dislocation in high risk primary and revision hip arthroplasty. At average 3.1 years follow-up only one insert of eighty-nine inserted had failed. No cups have demonstrated radiographic or clinical evidence of loosening. We conclude this implant is safe and effective for both the prevention and treatment of hip instability.

To review the effectiveness and durability of a constrained acetabular component used to treat and prevent recurrent dislocation after total hip arthroplasty

Constrained acetabular components of this type provide both an excellent treatment and preventative option in total hip arthroplasty. There is no evidence of accelerated cup loosening and the implant failure rate remains acceptable despite the increased constraint.

Constrained acetabular components have been mainly used as a salvage option for dislocating hip arthroplasty. There have been concerns over implant failure and early acetabular component loosening secondary to the increased implant constraint. Use of this implant can prevent dislocation in high risk patient groups (eg: revision surgery) without compromising implant longevity. This significantly reduces the potential morbidity associated with hip instability.

Eighty-nine patients received the tripolar constrained acetabular component. Fifteen were inserted for recurrent dislocation whilst seventy-two were inserted in patients felt to be at high risk of dislocation (forty-nine for intra-operative instability at revision surgery, twenty-five for primary THA in patients with poor compliance, neurological conditions or deficient abductor mechanism). One implant failed by component dissociation at eighteen months. All other recurrent dislocators remained stable. There was no evidence of accelerated component loosening at medium term review (range twelve – eighty three months, average thirty-seven months)

Radiographic and clinical data was prospectively collected on eighty-nine patients who had the constrained acetabular component inserted.

Funding: The primary author’s fellowship position is partially funded by Smith and Nephew Richards Inc.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 144 - 144
1 Mar 2008
Kearns S Jamal B Burns A Skutek M Bourne R MacDonald S McCalden R Rorabeck C
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Purpose: The young patient with hip arthritis remains one of the biggest challenges to arthroplasty surgeons. The difficulty of providing a long-lasting total hip arthroplasty (THA) has been clearly documented in the literature. The aim of this study was to assess the outcomes of uncemented THA’s performed in our unit in patients aged under 50.

Methods: In our unit information on all patients is recorded prospectively on an arthroplasty database. From this database we identified 273 uncemented THAs in 237 patients under the age of 50 performed in our unit between 1985 and 2000 with a minimum of 5 year follow up. Outcomes were assessed in terms of 10 and 15-year survival with revision for any reason as the endpoint. Hip scores at routine and most recent follow-up were also reviewed. All surviving implants were radiographically assessed for acetabular wear, component loosening and for the presence of osteolysis.

Results: The mean age of patients at the time of surgery was 41.1 years. 36 patients had bilateral THA. The overall 10 and 15 year survival was 88.7 ± 2.4% and 65.6 ± 4.8 % respectively. Femoral stem survival was significantly higher at 100 % and 98.4 ± 1.6% at 10 and 15 years. Acetabular component survival was 88.6 ± 2.5 % at 10 years and 65.9 ± 4.8 % at 15 years. In unrevised THA’s 56.9% had asymmetric polyethylene wear > 2mm. 2% had definite evidence of acetabular loosening. 25.5% had radiographic evidence of femoral cortical hypertrophy or spot-welds. The mean HHS pre–operatively, at 5 and 10-year follow-up was 46.4 ± 13, 90.7 ± 12.2 and 87.9 ± 14.7 respectively.

Conclusions: Uncemented THA is effective even in young active patients. The main challenges remain ace-tabular polyethylene wear and loosening. Femoral uncemented stems provide long-term functional fixation. Contemporary bearing surfaces in association with such stems may provide long lasting THA’s even in young active patients.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 96 - 96
1 Mar 2008
MacDonald S Roabeck C Bourne R McCalden R Cleland D
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Controversy continues to exist regarding the choice of a cementless femoral component in a primary total hip arthroplasty. Both proximally coated tapered stems and fully coated cylindrical stems have excellent clinical results. The incidence of both thigh pain and proximal femoral stress shielding and multiple validated outcome measures were evaluated in a prospective randomized clinical trial with a minimum of two year follow-up comparing a proximally coated tapered femoral stem to a fully coated cylindrical femoral stem.

A prospective randomized clinical trial (RCT) was performed comparing a cylindrical cobalt chrome fully coated femoral stem (Prodigy, Depuy, Warsaw, IN) to a tapered, titanium, proximally porous coated stem (Synergy, Smith & Nephew,

Memphis, TN) with respect to thigh pain, femoral stress shielding and multiple outcome measures.

One hundred and ninety-four patients were enrolled and evaluations were performed pre-operatively, three months, six months and annually. Multiple outcome measures (Harris Hip Score, SF12, WOMAC, Patient Satisfaction Questionnaire, Thigh Pain Questionnaire) were obtained. Sixty-one of these patients were randomized to receive a bone density scan pre-operatively, two weeks post-operatively, six months and annually.

Twelve patients were unavailable for two-year follow-up, leaving one hundred and eighty-two patients evaluated. No significant differences were demonstrated in thigh pain incidence or the multiple outcome measures. Bone density scans demonstrated significantly greater bone density (p< 0.005) in the tapered stem versus the cylindrical stem patients at two-week evaluations from distal femoral reaming. Both stem designs demonstrated statistically significant bone loss in Gruen zones one, six, seven between the two-week and one and two-year evaluations. There were no differences between stem designs although the Prodigy stem demonstrated trends towards greater bone loss in Gruen zones six and seven.

This prospective RCT demonstrated no difference in thigh pain incidence and multiple outcome measures between patients receiving a proximally coated tapered versus a fully coated cylindrical femoral component. Both stem designs demonstrated statistically significant proximal femoral bone loss between the post-operative and two-year evaluations; however, there were no differences between stem designs.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 121 - 121
1 Mar 2008
Shore B Busch C Bhandari R Ganapathy S MacDonald S Rorabeck C Bourne R McCalden R
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This Blinded Randomized Clinical Trial outlines: how peri-articular intra-operative multimodal analgesia significantly reduces post-operative analgesia requirement. Sixty-four patients undergoing total knee replacement were randomised to receive a peri-articular intra-operative injection containing ropivacaine, ketorolac, epimorphine and epinephrine or nothing. Patients who received the injection demonstrated greater satisfaction and pain relief. Finally, patients in the injected group did not show any signs of cardio and central nervous system toxicity.

Post-operative analgesia can be associated with troublesome side effects. Good peri-operative analgesia facilitates rehabilitation, improves patient satisfaction and may reduce hospital stay. The purpose of this study was to assess a novel cocktail for peri-articular analgesia after total knee replacement.

Sixty-four patients undergoing total knee replacement were randomised to receive a peri-articular intra-operative injection containing ropivacaine, ketorolac, epimorphine and epinephrine or nothing. The anaesthetic analgesic regime was standardised. All patients received patient controlled analgesia (PCA) for twenty-four hours post surgery, followed by standard analgesia. VAS pain scores during activity and at rest and patient satisfaction scores were recorded pre and post operatively and at six week follow up. PCA consumption and overall analgesic requirement were measured.

PCA use at six, twelve and over twenty-four hours post surgery was significantly less in patients receiving the injection (p< 0.01, p=0.016, p< 0.01). Patient satisfaction in PACU and four hours post operation was greater (p=0.016, p=0.013). VAS for pain during activity in PACU and at four hours were significantly less (p=0.04, p=0.007) in the injected group. The average ROM at six weeks was no different. Overall hospital stay and the incidence of wound complications were not different between the two groups.

Peri-articular intra-operative multimodal analgesia significantly reduces post-operative analgesia requirement. Patient satisfaction and pain relief is greater in the injection group. No cardio and central nervous system toxicity was observed.

Our novel cocktail of ketorolac, epimorphine, epinephrine and ropivacaine provides superior pain relief with no adverse side effects.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 102 - 102
1 Mar 2008
Busch CA Bourne R MacDonald S McCalden R Martell J Rorabeck C
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Despite favourable wear characteristics of compression molded HMWPE in vitro preliminary data show no statistical difference in wear between RAM extruded HMWPE and compression moulded polyethylene. This study reviews AP and lateral radiographs for wear using the Martell technique at two, five years and maximum follow up (mean 88.2 months).

Reduced implant survivorship due to aseptic loosening has prompted research into alternative bearing materials. Simulator testing is useful but clinical studies are the gold standard to evaluate the wear characteristics of new bearing materials.

On hundred and twelve patients matched for sex, age, body mass index, primary pathology, Charnley grade, and follow up underwent uncemented total hip replacement using an identical implant. Group One (sixty-four patients) had a RAM extruded liner (GUR 4150 HP) and Group Two (forty-eight patients) had a compression molded liner (Montell H 1900). HMWPE sterilisation regimes were identical. AP and lateral radiographs were analysed for wear using the Martell technique at two, five years and maximum follow up (mean 88.2 months).

Preliminary data show a linear and volumetric wear rate in Group One of 0.067 mm/yr and 26 mm3/year respectively between two years to maximum follow up. Similarly, the wear rates for Group Two were 0.132 mm/yr and 45 mm3/year respectively. There was no statistical difference in acetabular osteolysis between Group One (16.3%) and Group Two (15%) patients at maximum follow up.

Despite favourable wear characteristics of compression molded HMWPE in vitro preliminary data show no statistical difference in wear between RAM extruded HMWPE and compression moulded polyethylene. Quality of the wear debris is more likely to be important in producing aseptic loosening than actual wear rate.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 103 - 103
1 Mar 2008
Bow J Summers K Singh B MacDonald S
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T cells have been implicated in the pathogenesis of osteolysis. The goal of this study was to compare the ratios of CD4+ T cell populations in total hip arthroplasty (THA) patients with and without osteolysis. We found no significant differences in the frequency of peripheral blood CD4+CD25+ regulatory and effector T cells, serum IL-10 and TGF-β concentrations, and immuno-suppressive ability of regulatory T cells from patients with osteoarthritis prior to THA, and THA patients with and without radiographic evidence of osteolysis.

CD4+ T cells are critical in regulating immune-mediated conditions. This study compared the frequency of CD4+ T cell subpopulations in the peripheral blood of patients with and without osteolysis following total hip arthroplasty (THA).

Numbers of CD4+CD25hi regulatory T cells, CD4+CD25moderate effector T cells, and CD4+CD25+ T cells in the peripheral blood of thirty patients with osteoarthritis prior to primary THA, thirty patients with asymptomatic THAs and no radiographic evidence of osteolysis, nineteen patients with asymptomatic THAs with radiographic evidence of early osteolysis (not requiring revision surgery) and nine patients scheduled for revision THA for osteolysis were determined by flow cytometry. Serum IL-10 and TGF-β levels were measured using ELISA kits. Results were compared by t-test and rank sum test. CD4+ CD25hi regulatory T cells and CD4+ CD25neg T cells were isolated from blood using a MACS cell isolation kit, co-cultured for three days, and T cell proliferation determined by [3H]-thy-midine uptake.

The frequency of CD4+CD25hi regulatory T cells, CD4+CD25moderate effector T cells, and CD4+CD25+ T cells were similar in each study group. Regulatory T cells from patients with and without osteolysis had a normal functional ability to inhibit CD4+ T cell proliferation. Serum levels of the regulatory T cell-derived cytokines IL-10 and TGF-β were also comparable between groups.

Our data suggests that CD4+ T cell immune responses are normal in THA regardless of the level of osteolysis, in contrast to previous studies that have implicated T cell hypersensitivity in the pathogenesis of osteolysis surrounding THA.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 127 - 127
1 Mar 2008
Shore B Bourne R MacDonald S McCalden R Busch C Rorabeck C Bhandari R Ganapathy S
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Purpose: Post-operative analgesia using opioids or epidural analgesia can be associated with troublesome side effects. Effective peri-operative analgesia facilitates rehabilitation, improves patient satisfaction and may reduce hospital stay. Locally administered analgesia is effective, avoids systemic drug related side-effects and may be of benefit in minimally invasive joint replacement. This study compares the effects of a peri-articular injection cocktail in patients undergoing total knee and hip replacement surgery

Methods: 128 patients undergoing total knee (TKR) and hip (THR) replacement were randomised to receive a peri-articular intra-operative injection containing ropivacaine, ketorolac, epimorphine and epinephrine or nothing. The anaesthetic analgesic regime was standardised. All patients received patient controlled analgesia (PCA) for 24 hours post surgery, followed by standard analgesia. VAS pain scores during activity and at rest and patient satisfaction scores were recorded pre and post operatively and at 6 week follow up. PCA consumption and overall analgesic requirement were measured.

Results: Both TKR and THR patients used significantly less PCA 6 hours after surgery (p = 0.02 THR, p< 0.01 TKR). TKR patients receiving the injection used significantly less PCA use over 24 hours post surgery (p = 0.013). VAS for pain at 4 hrs post operation was significantly lower in the both groups (p = 0.003 TKR)(p = 0.017 THR). VAS for pain during activity at 24 hours was significantly less (p = 0.001) in the injected TKR group. Overall hospital stay and wound complications were not different between the groups.

Conclusions: Peri-articular analgesia significantly reduces post-operative analgesia requirement in TKR and THR patients. Greater satisfaction and pain relief was seen in TKR patients compared with THR.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 111 - 111
1 Mar 2008
O’Brien D Bourne R MacDonald S McCalden R Rorabeck C
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Fifty-one prospectively followed Contour_ acetabular reconstruction cages, inserted through the direct lateral approach, were reviewed at three years minimum follow-up (range 3 to 6.4 yrs.). To date, four reoperations were required (two each for sepsis and instability) with no failures due to aseptic loosening. The Kaplan-Meier Survival Rate for any reoperation was 87% at 6.4 years. Short to mid-term follow-up of a single type of acetabular reconstruction cage, inserted through the lateral approach, demonstrated this to be a successful reconstruction option in the management of large acetabular bone defects.

This study reports the mid-term results of a single design of acetabular reconstruction cage inserted through the direct lateral approach.

At minimum three years follow-up (range 3 to 6.4 yrs.), there were no failures due to aseptic loosening with only four of fifty-one cases requiring reoperation (two sepsis, two instability).

This review supports the use of the reconstruction cage, inserted through the lateral approach, for large defects that cannot be managed with a hemispherical porous implant.

The use of the reconstruction cage in our center is reserved for large defects that cannot be managed with a hemispherical porous implant because of insufficient bone stock for initial implant stability and/or host bone contact for in-growth. Fifty-one consecutive prospectively followed Contour_ (Smith and Nephew) acetabular reconstruction cages, inserted through the direct lateral approach, were reviewed at three years minimum follow-up (range 3 to 6.4 yrs.). The majority of cases were AAOS Type Three and Four defects in which morsellized allograft was used in forty-nine cases and structural graft in three cases. Harris hip scores improved from 32.1±17.8 pre-op to 65.3±24.1 at most recent follow-up. Defining any acetabular reoperation as a failure, four of the fifty-one cages were considered to have failed giving a Kaplan-Meier Cumulative Survival Rate of 87% at 6.41 years. Two reoperations were for recurrent dislocation and the other two for sepsis. None of the fifty-one cages have been revised for aseptic loosening to date.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 90 - 90
1 Mar 2008
Mehin R Yuan X Haydon C Rorabeck C Bourne R McCalden R MacDonald S
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The timing of liner exchange for retroacetabular oste-olysis in THA remains uncertain. Liner exchange should be done before the shell becomes loose. The purpose of this study was to determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell. Osteolytic lesions were quantified radiographically using three different measures. Implant stability was confirmed intraoperatively. Percent of shell circumference with surrounding osteolysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than fifty percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.

The timing of liner exchange for retroacetabular osteolysis in cementless THA remains uncertain. Liner exchange should be done before the shell becomes loose.

To determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell.

Osteolytic areas differ between loose and stable shells.

Between 1992 to 2002, seventy-one cementless shells of the same design were revised at our institution; forty-six were for aseptic retroacetabular osteolysis. Radiographs and a computer-assisted technique were used to quantify osteolytic areas and percent of shell circumference associated with lesions. Implant stability was confirmed intraoperatively.

Of twenty-six stable and twenty loose shells, the average area of osteolysis on AP radiographs showed no significant difference (Stable 591mm2, Loose 630 mm2, p greater than 0.05); whereas, lateral radiographs demonstrated a significant difference (Stable 546 mm2, Loose 837 mm2, p 0.05). The percentage of shell circumference with associated osteolysis on AP and lateral films demonstrated a significant difference (AP: Stable 60, Loose 75, p 0.042; LATERAL: Stable 49, Loose73, p 0.016). Diagnostic criteria of fifty percent shell circumference associated with osteolysis on AP films has sensitivity 1, specificity 0.27 while the same criteria on lateral films has sensitivity 0.84, specificity 0.54 for shell loosening.

Percent of shell circumference with surrounding oste-olysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than fifty percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_I | Pages 29 - 29
1 Mar 2006
Busch C Shore B Bhandari R MacDonald S Rorabeck C Bourne R McCalden R
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Introduction: Post-operative analgesia using parenteral opioids or epidural analgesia can be associated with troublesome side effects. Good peri-operative analgesia facilitates rehabilitation, improves patient satisfaction and may reduce hospital stay. Locally administered pre-emptive analgesia is effective, reduces central hyper-sensitisation and avoids systemic drug related side-effects and may be of benefit in minimally invasive joint replacement.

Materials and methods: 64 patients undergoing total knee replacement were randomised to receive a peri-articular intra-operative injection containing ropiva-caine, ketorolac, epimorphine and epinephrine. The anaesthetic analgesic regime was standardised. All patients received patient controlled analgesia (PCA) for 24 hours post surgery, followed by standard analgesia. VAS pain scores during activity and at rest and patient satisfaction scores were recorded pre and post operatively and at 6 week follow up. PCA consumption and overall analgesic requirement were measured.

Results: PCA use over 24 hours post surgery was significantly less in patients receiving the injection (P=0.013). Patient satisfaction at 4 hrs post operation was greater (P=0.003). VAS for pain during activity at 4 hrs and 24 hours were significantly less (P=0.001) in the injected group. The average ROM at 6 weeks was no different. Overall hospital stay and the incidence of wound complications was not different between the 2 groups.

Discussion: Peri-articular intra-operative multimodal analgesia significantly reduces post-operative analgesia requirement. Patient satisfaction is greater in the injection group. No cardio and central nervous system toxicity was observed.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 342 - 342
1 Sep 2005
Comley A MacDonald S McCalden R Rorabeck C Bourne R
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Introduction and Aims: To compare the results of patients treated with articulating versus static antibiotic-impregnated spacers for infected knee arthroplasty.

Method: All patients undergoing two-stage revision knee arthroplasty for sepsis in the last five years were reviewed. Twenty-six patients had been treated with articulating spacers. This group was compared to 36 patients treated with static spacers. The articulating spacer technique had been adopted more recently than the static technique. Minimum follow-up was 12 months from second stage re-implantation (average 22 months articulating, 40 months static). Patients were compared in terms of the need for extensile exposures required for re-implantation, range of motion at most recent review, eradication of infection and augmentation required on revision implants.

Results: In the articulating group, fewer extensile exposure methods were required at second-stage prosthesis re-implantation (19% vs 36%). No tibial tuberosity osteotomies have been required since using the articulating spacer. The articulating group demonstrated a significantly improved range of flexion compared to the static group (106 vs 97 degrees – p=0.045) and had fewer patients with significant loss of extension or quadriceps lag. Eradication of infection was improved in the articulating group (92% vs 82%) but at shorter average follow-up. The need for augments and stabilised prostheses at revision surgery as a measure of bone loss was no different between the groups but was related to the number of prior surgical procedures.

Conclusion: Articulating cement spacers facilitate reimplantation surgery by maintaining tissue planes and joint mobility without compromising joint stability or eradication rate of infection. Patients demonstrate better range of motion and less complications related to the extensor mechanism with the articulated spacer.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 353 - 353
1 Sep 2005
Mehin R Yuan X Haydon C Burnett S Rorabeck C Bourne R McCalden R MacDonald S
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Introduction and Aims: Problem: The timing of liner exchange for retroacetabular osteolysis in THA remains uncertain. Liner exchange should be done before the shell becomes loose.

Purpose: To determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell.

Hypothesis: Osteolytic areas differ between loose and stable shells.

Method: Between 1992 and 2002, 71 cementless shells of the same design were revised at our institution; 46 were for aseptic retroacetabular osteolysis. Radiographs and a computer-assisted technique were used to quantify osteolytic areas and percent of shell circumference associated with lesions. Implant stability was confirmed intra-operatively.

Results: Of 26 stable and 20 loose shells, the average area of osteolysis on AP radiographs showed no significant difference (Stable 591mm2, Loose 630 mm2, p greater than 0.05); whereas, lateral radiographs demonstrated a significant difference (Stable 546 mm2, Loose 837 mm2, p 0.05). The percentage of shell circumference with associated osteolysis on AP and lateral films demonstrated a significant difference (AP: Stable 60, Loose 75, p 0.042; LATERAL: Stable 49, Loose 73, p 0.016). Diagnostic criteria of 50 percent shell circumference associated with osteolysis on AP films has sensitivity 1.0, specificity 0.27, while the same criteria on lateral films has sensitivity 0.84, specificity 0.54 for shell loosening.

Conclusion: Percent of shell circumference with surrounding osteolysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than 50 percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 357 - 357
1 Sep 2005
Haydon C Mehin R Burnett S Rorabeck C Bourne R McCalden R MacDonald S
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Introduction and Aims: Cemented femoral revision total hip arthroplasty has been associated with early mechanical failure by aseptic loosening. This study was performed to determine the long-term survival of cemented femoral revision arthroplasty and to identify factors predictive of failure.

Method: One hundred and twenty-nine cemented femoral revision cases were reviewed to determine component survival. Ninety-seven hips with a minimum follow-up of five years were included for survival analysis and tests of significance. Harris hip scores were used to quantify clinical outcomes. Complete radiographic series were reviewed. Kaplan-Meier survival curves were calculated. Clinical and surgical factors were analysed to determine if they were predictive of failure.

Results: Individual Harris hip scores improved to a mean of 71 at the most recent follow-up from a mean pre-operative score of 52 (p< 0.001). Kaplan-Meier survival at 10 years was 91%, with revision for aseptic loosening of the femoral component as the endpoint and 71% with mechanical failure as the endpoint. Patients older than 60 years experienced greater long-term component survival and less pain than patients younger than sixty years (p< 0.05). Good quality post-operative cement mantles were associated with better long-term radiographic fixation (p< 0.001). Poor femoral bone quality was significantly associated with an increased rate of re-revision for aseptic loosening (p=0.021).

Conclusion: Revision femoral THA with cement remains an option in selected patients with acceptable 10-year survival and fair radiographic fixation. Patients demonstrated acceptable clinical outcomes at 10 years and few experienced significant pain. The best results may be achieved in older patients with adequate bone stock and modern cementing techniques.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 339 - 339
1 Sep 2005
MacDonald S Rorabeck C Marr J Clark C Swafford J Macdonald D
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Introduction and Aims: The dilemma to retain or sacrifice the posterior cruciate ligament in a primary total knee arthroplasty continues to be an area of discussion. A randomised clinical trial was performed comparing clinical, radiographic and quality of life outcomes between patients receiving a posterior cruciate sparing versus posterior cruciate substituting knee implants.

Method: A multi-centred, prospective, randomised, blinded, clinical trial was performed to compare posterior cruciate retaining (CR) versus posterior cruciate substitution (PS) in osteoarthritic patients with an intact posterior cruciate ligament, undergoing total knee arthroplasty using the AMK® (Depuy®, Warsaw, Indiana) component. One hundred and fifty-two patients were randomised to receive one of the two devices. Patients were evaluated pre-operatively, at three, six, 12 months and annually thereafter. Patient demographics, radiographs, and multiple validated, outcome measures (WOMAC, SF-12, the Knee Society Clinical Rating System, and a stair climbing test) were evaluated. Patients and assessors were blinded to the implant design.

Results: One hundred and fifty-two patients were randomised at three centres; 72 in the CR group and 80 in the PS group. One patient was revised due to instability. Average follow-up was 5.14 years (range 2.97–6.99 years). There were no significant differences in baseline patient demographics between groups. There were no significant differences in outcome measures or radiographic findings. There were no significant differences in the Knee Society Clinical Rating System (CR- 159.18 versus PS- 156.49). There were no differences in knee extension at latest follow-up (CR- 1.02) and (PS- 1.10). There were no differences in knee flexion at latest follow-up (CR-111.00 ) and (PS- 113.61). No differences were noted in the WOMAC and SF-12 scores between the two groups.

Conclusion: In this prospective randomised clinical trial no significant differences involving radiographs and multiple outcome measures could be seen between a cruciate retaining versus a posterior stabilised total knee prostheses at a mean follow-up of 5.14 years. Long-term evaluation is necessary to comment on wear, osteolysis and implant longevity.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 358 - 359
1 Sep 2005
Burnett S O’Brien J Haydon C McCalden R MacDonald S Bourne R Rorabeck C Yuan X
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Introduction and Aims: Polyethylene wear in total hip arthroplasty (THA) is frequently associated with wellfixed cementless implants. Purpose: To evaluate the clinical and radiographic results of the isolated liner exchange (ILE) procedure in revision THA via the direct lateral surgical approach.

Method: A prospective study of 24 hips that underwent an ILE revision procedure via the direct lateral approach was conducted. Accessible osteolytic lesions were managed with curettage and bone grafting. Clinical data including Harris hip score, WOMAC Index, SF-12, and radiographic analysis were recorded. The area of osteolytic lesions was calculated using a new software program.

Results: This is the first study to our knowledge to report on the results of the ILE procedure performed via the direct lateral surgical exposure. Twenty-three patients underwent 24 revisions with an ILE. At mean follow-up of 40 months, all osteolytic lesions had regressed. Harris hip scores improved from 69 to 83. WOMAC indices improved from 37 to 24. No dislocations have occurred. Two patients have required revision. Isolated liner exchange for polyethylene wear is a promising technique that avoids the removal of well-fixed acetabular implants. The increased dislocation rate associated with this revision THA procedure may be reduced and osteolytic lesions may be successfully debrided and bone grafted through the direct lateral approach.

Conclusion: The ILE procedure, when performed via the direct lateral surgical approach, may reduce the dislocation rate commonly reported via the posterolateral exposure with this procedure. Retention of well-fixed implants and bone grafting preserves bone stock and adequately addresses osteolytic lesions at revision surgery through this exposure.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 351 - 351
1 Sep 2005
McCalden R MacDonald S Rorabeck C Bourne R Chess D Saleh A
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Introduction and Aims: While highly cross-linked polyethylene has achieved widespread clinical use based on laboratory testing showing significant wear reduction, there is little clinical information demonstrating its benefits in vivo. This study reports the early clinical and wear performance of a prospective randomised controlled trial comparing highly cross-linked to standard polyethylene.

Method: One hundred patients were enrolled in a prospective randomised controlled trial in which all patients received a hybrid THR (cemented Versys stem, Triology cementless acetabulum). The two groups were virtually identical in terms of age, weight, male/female ratio and received identical hip implants, except that one half (50 patients) randomly received a highly cross-linked polyethylene liner. Clinical outcomes were determined using Harris hip, WOMAC and SF-12 scores. Two-dimensional (2D) and three-dimensional (3D) wear rates were determined using a validated radiographic technique based on AP and lateral radiographs at six weeks and one, two and three years post-operatively.

Results: At two years minimum follow-up (range two to four years), there were no differences in Harris hip, WOMAC or SF-12 scores. No patients were lost to follow-up, although five patients had died of unrelated causes. There were no infections, dislocations or revisions to date. Wear analysis at one-year post-op showed high penetration rates for both groups (mean 3D wear approximately 0.25 mm/year) consistent with the bedding-in phenomena. At most recent radiographic follow-up (two or three years), there was a statistically significant although modest difference in wear rates between the two groups with a 2D and 3D wear rate of 0.14±0.10 mm/yr and 0.15±0.02 mm/yr respectively for conventional polyethylene compared to 0.09±0.04 mm/yr and 0.11±0.02 mm/yr for cross-linked polyethylene. This represented a 32 and 29 percent reduction in 2D and 3D wear rates respectively with cross-linked polyethylene.

Conclusion: At early follow-up, there were no clinical differences. There was a modest wear reduction (approximately 30%) with highly cross-linked polyethylene, considerably less than expected based on laboratory testing. Longer follow-up, after the bedding-in process is completed, is required to demonstrate the wear reduction afforded by highly cross-linked polyethylene.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 321 - 321
1 Sep 2005
MacDonald S Bourne R Rorabeck C Cleland D Chess D McCalden R
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Introduction and Aims: Polyethylene wear continues to be the most significant issue following total hip arthroplasty (THA), leading to the current increase in use of alternative bearing surfaces. We performed a prospective, randomised, blinded clinical trial comparing metal versus polyethylene bearing surfaces in patients receiving THA.

Method: Forty-one patients were randomised to receive a metal (23) or a polyethylene (18) insert with identical femoral and acetabular components. Patients were evaluated pre-operatively at three, six, 12 months and annually thereafter, including an evaluation of erythrocyte and 24-hour urine cobalt, chromium and titanium metal ion levels, validated outcome measures (WOMAC, SF-12, Harris Hip Score) and radiographs.

Results: No patients were lost to follow-up. One patient died of unrelated causes. At an average 4.4 (range 3.3–5.1) years follow-up there were no differences in any outcome measures or radiographic findings. Patients receiving metal liners had significantly elevated metal ion measurements. At the latest follow-up erythrocyte cobalt levels were seven times elevated (median 1.2μg/l (metal) Vs 0.18μg/l (poly), p< .001). Urine cobalt levels were 41 times elevated (median 11.9μg/day (metal) Vs 0.29μg/day (poly), p< .001) and urine chromium levels were 14 times elevated (median 4.9μg/day (metal) Vs 0.36μg/day (poly), p< .001). Erthrocyte chromium, titanium and urine titanium were not significantly different between groups. As well, contrary to previous reports, there was not a significant trend towards decreasing ion levels over time.

Conclusion: In this prospective randomised blinded clinical trail comparing metal to polyethyle bearing surfaces, both cobalt and chromium ion levels were significantly elevated in the blood and urine of the patients randomised to receive the metal on metal THA.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 362 - 362
1 Sep 2005
MacDonald S
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Introduction: A review of the concept of metal-on-metal bearings is presented.

Method: The material is based on a review of the literature and personal experience.

Results: The metal-on-metal bearing couple is enjoying a resurgence in clinical applications seen in both total hip and hip resurfacing technologies. The most significant advantage of a metal-on-metal implant is the improved wear characteristics seen both in vitro on wear simulators and in vivo with retrieved implants. All bearings have disadvantages and a metal-on-metal bearing is no exception. Concerns exist regarding the generation of metal ions seen in both the blood and urine of patients with metal-on-metal implants. These elevated metal ions have theoretical, although not proven, risks related to carcinogenic and biological concerns. In addition, concerns exist regarding hypersensitivity, increased incidence of instability and increased costs. As well, specific patient selection issues arise with metal-on-metal implants and with the current generation of implants only early and mid-term results are available, with no long-term series yet published.

Conclusions: Therefore, while a metal-on-metal bearing may be considered a viable alternative to either polyethylene or ceramic implants, outstanding and unresolved issues continue to exist.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 337 - 337
1 Sep 2005
MacDonald S Marr J Bourne R McCalden R Rorabeck C
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Introduction and Aims: Fixed bearing and mobile bearing knee designs are currently used in clinical practice with little evidence based research available to determine superiority of one system. The purpose of this study was to compare the results between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

Method: We performed a prospective, randomised, blinded clinical trial to compare a mobile bearing to two standard fixed-bearing implants. We evaluated the short- and long-term outcomes of the SAL® (Sulzer) mobile bearing versus the AMK® (Depuy) and Genesis II® (Smith & Nephew) fixed bearing, total knee joint replacements. Ninety patients were randomised to receive one of the three prostheses. Patients were evaluated pre-operatively, at three, 12 months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated. A single observer was used to measure range of motion scores.

Results and Discussion: No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two-year follow-up, and one patient was revised for infection at six months, leaving 87 patients at an average follow-up of 3.37 years (range 2.91–4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL – 167, AMK – 158, GenesisII – 166 ). There were no differences in WOMAC scores or SF-12 survey scores. There were no differences in knee flexion at two years (SAL – 117°, AMK – 115°, GenesisII – 118°). Therefore, no differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

Conclusion: In this prospective randomised clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.


Orthopaedic Proceedings
Vol. 85-B, Issue SUPP_II | Pages 166 - 166
1 Feb 2003
Patel J Masonis J McCalden R MacDonald S Bourne R Rorabeck C
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Our aim was to evaluate the functional outcome of extensile revision knee exposure techniques.

166 revision total knee arthroplasties requiring an extensile exposure with 2 year minimum follow-up were prospectively studied {81 rectus snips (RS), 42 tibial tubercle osteotomies (TTO), and 43 quadriceps turn-downs (QT)}. Patients were clinically evaluated for knee society score, range of motion (ROM) and extensor lag comparing pre-op and 24 month follow-up appointment findings. Radiological evidence of avascular necrosis (AVN) pre & post operation was recorded. The TTO group was further examined for proximal migration of the tubercle post op.

Pre-operative knee motion (75° & 71°) and knee scores (74 & 70) were lower in revision total knee arthroplasties requiring QT & TTO than those requiring a RS (91° & 84). Post op flexion and knee scores were greater in the RS group (102° & 131) than in the QT (81° & 114) and TTO (84° & 111) groups in whom there was no significant difference. Avascular necrosis of the patella was most commonly seen following QT. In both QT & TTO groups performing a lateral release was significantly associated with AVN of the patella. Extensor lag (> 10°) was seen only in the QT & TTO groups (11% & 8%) in whom there was no significant difference. Tubercle escape (> 2mm) in the TTO group was significantly greater (54%) in those where circlage wires only had been used than in those where a proximal transfixation wire was used (11%).

In conclusion, both QT & TTO groups had similarly poor knee scores & ROM pre & post operation. AVN of the patella for both groups was similar and significantly associated with performing a lateral release. Finally we would conclude that the use of a through wire significantly reduces tubercle escape in TTO fixation.