Background:

Varus-valgus constrained (VVC) implants are used in cases of severe valgus deformity, attenuated medial collateral ligament and difficulty in balancing the medial and lateral gaps of the knee. The increased constraint has been postulated to lead to more stress at the bone-implant interface and early loosening. The objective of this study was to compare the wear characteristics of the polyethylene liner in VVC prosthesis with the posterior-stabilized (PS) prosthesis and identify the factors leading to more wear in the VVC tibial inserts.

Background:

Polyethylene wear in total knee arthroplasty (TKA) is influenced by patient, surgeon and implant factors. The objective of this study is to assess the effect of limb alignment, implant position and joint line position on the pattern of wear in posterior stabilized (PS) tibial inserts.

Purpose

The objective of this study was to compare the wear characteristics and damage scores in highly crosslinked (XLPE) and conventional polyethylene (CPE) acetabular liners.

In North America, and for the most part globally, a cementless acetabular component with adjuvant screw fixation is the preferred technique for revision total hip arthroplasty.

However, there are situations that involve massive pelvic bone loss that preclude the use of a cementless cup alone.

Options include: i)

Enhanced fixation components and augments

Complex acetabular revisions present the arthroplasty surgeon with challenges that require an approach with more than one solution for all scenarios. While structural allografts have recently fallen out of favour with the increasing use of enhanced fixation components, there would still appear to be a role in the case in which bone stock restoration is a primary goal. The role of bone graft substitutes remains unclear, with supportive basic science data, but limited clinical experience to date. An algorithm will be discussed to assist in prioritising the multiple goals of acetabular reconstruction and one stock restoration.

A conceptually new acetabular design is currently available when performing a total hip arthroplasty – the dual mobility socket. Essentially this is a press-fit acetabular component with a polished surface that articulates with a large polyethylene head with a 28 mm ball inserted into that polyethylene in a similar fashion to a bipolar design.

Proponents of this design advocate its use to reduce the risk of dislocation, and it is being offered as an alternative to constrained liners and also as a potential prophylactic application in revision and high risk patients.

The concerns regarding this construct include: 1.

Wear

A large polyethylene head articulating against a polished metal surface will have much greater wear than a conventional metal against poly bearing. Hip simulator data has shown this previously. To demonstrate a reduction in wear, one must compare unlike polyethylenes, or extremes in component positioning.

There are many options available to both manage and to prevent hip instability. Any new implant must show equivalence to current devices on the many fronts of wear, fixation, midterm results, complications and costs.

Pain following total hip arthroplasty is a relatively rare event. Several series place the incidence of some degree of pain post THA at approximately 5%.

A systematic approach to determining etiology will direct treatment. Hip pain can be categorised as:

Summary Sentence: Cementless solid tri-spiked titanium shells, with a polished inner surface and improved locking mechanism, demonstrated excellent fixation and survivorship at mid-term (minimum 5 years) follow-up.

Introduction: The tri-spiked Reflection cup (Smith & Nephew, Memphis) is a second-generation solid titanium shell with a polished inner surface, no screw holes and an improved locking mechanism. The purpose of this prospective study was to evaluate the minimum 5-year clinical & radiographic results and survivorship of this second-generation acetabular component.

Methods: Between 1997 and 2003, 659 primary THA were performed using the Reflection tri-spiked socket. None of the shells had adjuvant fixation with screws. The mean follow-up time was 7.0 years (5 to 11 yrs). The patients were followed prospectively using validated clinical outcome scores (WOMAC, SF-12, Harris Hip scores) and yearly radiographs.

Results: Twenty-seven patients had died before the minimum 5-year follow-up period. The mean Harris Hip and WOMAC scores were 89 and 79 respectively at last follow-up. Three sockets (0.6%) had been revised: two for infection, one for component malpositioning. No cup was revised for aseptic loosening. Six liners were exchanged: three for residual instability, 3 for wear associated with aseptic loosening of the stem. Radiographic review of remaining cups in-situ identified no cases of loosening and only a small number of cups (< 3%) with any osteolysis. The KM survivorship analysis with revision for any reason, was 97.5% and 97.4% at 5 and 10 years, while survivorship of the acetabular component was 99.8% at 5 and 10 years.

Conclusions: This second-generation cementless solid tri-spiked titanium shell, with a polished inner surface and improved locking mechanism, demonstrated excellent fixation and survivorship at mid-term follow-up.

Sixty four patients undergoing total hip replacement (THR) were randomized to receive a peri-articular intra-operative multi modal drug injection or to receive no injection. All patients received patient controlled analgesia (PCA) for 24 hours after surgery.

Patients receiving the peri-articular injection showed significantly less PCA consumption 6 hours postoperatively (P< 0.002). The 24 hour PCA requirement post surgery was also less (P< 0.009).

The VAS score for pain on activity in the post anaesthetic care unit (PACU) was significantly less for injected patients (P< 0.04). The VAS satisfaction score for injected patients in the PACU and 4 hours post-operatively showed no statistical difference.

Peri-articular intra-operative injection with multimodal drugs can significantly reduce post-operative patient controlled analgesia requirements and pain on activity in patients undergoing total hip replacement with no apparent increase in risk.

We performed a prospective, randomised, blinded clinical trial comparing metal versus polyethylene bearing surfaces in patients receiving a THA.

Forty-one patients were randomised to receive a metal (twenty-three) or a polyethylene (eighteen) insert with identical femoral and acetabular components. The metal bearing was a 28mm low carbon on high carbon couple. Patients were evaluated pre-operatively, at three, six, twelve months and annually thereafter, including an evaluation of erythrocyte and urine cobalt, chromium, and titanium, outcome measures (WOMAC, SF-12, Harris Hip Score) and radiographs.

No patients were lost to follow-up. At an average 7.2 (range 6.1 – 7.8) 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 most recent follow-up, compared to the polyethylene control group, patients receiving a metal on metal bearing had erythrocyte cobalt levels were eleven times elevated (median 1.4 μg/L (metal) vs 0.12 μg/L (poly), p< .001). Urine cobalt levels were thirty-nine times elevated (median 11.4 μg/L/day (metal) vs 0.29 μg/day (poly), p< .001) and urine chromium levels were twenty-eight times elevated (median 4.75 μg/day (metal) vs 0.17 μg/day (poly), p< .001). Additionally the metal ion levels reached an early steady state level and did not decrease over time. (Erythrocyte Co (μg/L): 1.29 (6 mos), 1.20 (1 yr), 1.0 (2 yr), 1.10 (3 yr), 1.35 (4 yr), 1.40 (5 yr)).

Both cobalt and chromium ion measurements were significantly elevated in the blood and urine of the patients randomised to receive the metal on metal THA at all time intervals. Contrary to previous reports, in 34% of patients with a metal liner, metal ion (erythrocyte cobalt) elevation was still increasing at latest follow-up, and in the overall metal on metal patient cohort, metal ion median levels were not decreasing over time. As in polyethylene wear data, metal ion results are not necessarily generalizable, but are bearing design specific.

There is an increasing trend towards performing a high tibial osteotomy (HTO) with a medial opening wedge technique. Amongst the potential advantages is easier conversion to a total knee replacement (TKR), although literature regarding this is scarce. We report our early clinical and radiological results, along with the technical issues encountered.

From our database, we identified thirty-one patients who had undergone thirty-two TKRs after medial opening wedge HTOs. Clinic and operative records were reviewed, and our database used for knee society scores. Those patients not seen in the last twelve months were reviewed in clinic. All pre- and postoperative radiographs were reviewed. The average age of the patients was fifty-seven years, and the average time from HTO to TKR was 4.5 years.

Difficulties with patella eversion were seen in 12.5%, and the knee balanced easily in 85% of cases. The tibia had minimal deformity in most cases, and all osteotomies were healed at the time of conversion. A stem was used in ten cases, and only if metalwork was removed at the time of conversion (which was done in twenty-three of the thirty-two). Minimum one year follow-up was available for twenty-six patients, with a mean follow-up time of twenty-eight months (range twelve to ninety-three months). The average Knee Society knee score was eighty-eight, function score seventy-five, and total score one hundred and sixty-two. Compared to non-matched group of 1149 primary TKRs (of older average age), the knee score was significantly lower, and there was a higher percentage of patients in the poor category. Poor results correlated strongly to the presence of chronic pain or workers compensation issues, and also to whether the knee had undergone revision HTO prior to TKR.

We conclude that the conversion of a medial opening wedge HTO to a TKR is relatively straightforward technically, and some aspects are easier than performing a TKR after a lateral closing wedge osteotomy (using historical controls). The clinical results appear inferior to that of a TKR performed without a prior osteotomy, although the results in our osteotomy group were skewed by a small group of chronic pain and workers compensation cases.

Attempts have been made to develop standardise guidelines for knee implant wear testing of polyethylene (PE). The current ISO-14243-3 standard recommends the use “calf serum”, without giving ranges on the specific protein constituents and characteristics. In the present study, three types of frequently used calf sera with various protein constituents (albumin, globulins) were utilised. The effect of osmolality and hyaluronic acid (HA) was also assessed. An attempt was made to identify synovial fluid (SF) characteristics that may be responsible for the boundary lubrication in the joint with the goal to develop a more clinically relevant lubricant.

Twenty samples of SF were drawn from twenty patients and analyzed. Specific protein constituents and osmolality were then compared to three calf sera used for wear testing. Test One (six million cycles (Mc)): Bovine calf serum (BCS), newborn calf serum (NCS) and alpha-calf serum (ACS) were diluted with distilled water (DW). Test two (5.5Mc): ACS with an osmolality of 312 ± 1.00 mmol/kg (closest to clinical osmolality; diluted with phosphate buffered saline, PBS) and 145 ± 2.00 mmol/kg (diluted with DW) were consecutively tested. HA was added at a concentration of 1.5g/l. Modular total knee replacements of cruciate retaining design (GUR 1050, 10mm PE insert) were used.

ACS diluted with PBS appeared to be of closest specific protein constituents and osmolality when compared to SF. The wear rate for BCS was 21.81 ± 2.48 mg/Mc, 17.05 ± 3.25 mg/Mc for NCS, and 13.44 ± 0.79 mg/Mc for ACS (p < 0.016). Decreased osmolality amplified the PE wear by a factor of 2.3 (p = 0.020). Adding HA increased the PE wear by a factor of two (p = 0.002).

There was significant difference in PE wear rates between the three calf-sera. BCS and NBC did not have clinically relevant levels of specific protein constituents. This study strongly suggests that current standards for total knee wear testing should be revised to enable more controlled wear testing under more clinically relevant conditions. It is suggested to be of particular importance when new bearing materials, such as cross-linked PE’s, are evaluated and proposed for clinical application.

Patients with moderate to severe osteoarthritis of the knee, on a waiting list for total knearthroplasty, were recruited to a double-blind, randomized clinical trial evaluating neoprene knee braces containing high-power static magnets or sham magnets. Patients wore the brace for a minimum of six hours per day and were evaluated at baseline, two, six, twelve and twenty-four weeks. The subjective outcomes (MACTAR, WOMAC, KOOS, SF-36) and functional outcomes (six minute walk, thirty second stair climb) showed no statistically significant differences between the groups at any of the follow-up time periods.

The purpose of this study was to compare the effectiveness of neoprene knee braces containing high-power static magnets to sham magnets in the management of osteoarthritis of the knee

No statistically significant difference in patient-related quality-of-life and objective functional evaluation was found between groups.

This study provides patients and doctors with evidence as to the efficacy of this type of therapy. It will allow those individuals on fixed incomes to utilize their resources to the best advantage to minimize their symptoms related to osteoarthritis of the knee.

A prospective double-blinded randomized clinical trial was conducted. Ninety-five patients with moderate to severe osteoarthritis of the knee were randomized to receive a Magnet (M) or Sham (S) knee brace. Both groups were equal with regards to age (M = 71.1 yrs, S = 66.8yrs), severity of disease, gender and all baseline measures. No statistically significant difference in patient-related quality-of-life and objective functional evaluation was found between groups at any time interval.

All study patients were recruited from a knee arthroplasty waiting list. At baseline and at two, six, twelve and twenty-four weeks each patient completed a WOMAC, MACTAR, KOOS quality-of-life questionnaire, SF–36 global health measure, and six minute walk and thirty second stair climb after which they were asked to determine their general fatigue, pain and shortness of breath on a 100mm VAS scale. Patients were instructed to wear their brace at least six hours per day and when active (walking, shopping, golfing).

The pathogenesis of osteolysis in failed total hip arthroplasty is not fully understood. The purpose of this study is to identify CD4+CD25+ Regulatory T cells in periprosthetic tissues in failed total hip replacements secondary to osteolysis. Intra-operative tissue samples and peripheral blood were collected from patients undergoing revision total hip arthroplasty surgery. Regulatory T cells were present in the tissues, and significantly increased in the peripheral blood in patients with failed total hips compared to normal controls. Further characterization of these regulatory T cells are warranted as they may play a role in osteolysis in loose total hip replacements.

Osteolysis remains the most common complication following total joint arthroplasty. To date, no authors have investigated the role of CD4+CD25+ regulatory T cells (T_REG) participating in the osteolytic pathogenesis. The purpose of this study is to quantitate the presence of T_REG cells in periprosthetic tissues in failed total hip replacements secondary to osteolysis.

Fifteen consecutive patients booked for revision total hip arthroplasty secondary to osteolysis were included. Tissue samples were collected: peripheral blood (PB), synovial fluid (SF), synovial tissue (ST), and interface tissue (IT) between the failed component and the bone defect. Total lymphocytes were isolated and analyzed using fluorescent-tagged antibody cell sorting (FACS) for the presence of T_REG cells. Frozen sections of ST and IT were analyzed with immunohistochemistry for T_REG cells.

T_REG cells were significantly upregulated (p< 0.01) in the PB (68%) of revision hip patients compared to normal controls PB (44%). In the synovial tissue (ST) and interface tissue (IT), 57% of the lymphocytes isolated were TREG cells. The presence of T_REG cells in the ST and IT were confirmed with immunohistochemistry.

T_REG cells are upregulated in the peripheral blood of patients with failed total hips secondary to osteolysis. The TREG cells are also present in the synovial tissue and interface tissue.

Evidence for involvement of regulatory T cells contribute to our understanding of this complex biologic response to artificial wear particles.

Functional studies of these T_REG cells are warranted as they are upregulated in patients with loose total hip replacements.

Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL^® (mobile bearing) versus the AMK^® and Genesis II^® (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System).

The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL^®, Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK^®, Depuy and Genesis II^®, Smith and Nephew).

Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.

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 6 months leaving eighty-seven 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 knee flexion at two years (SAL – 117^°, AMK – 115^°, GenesisII – 118^°).

No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

In this prospective randomized 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.

Funding: London Health Sciences Centre Internal Research Fund

Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL^® (mobile bearing) versus the AMK^® and Genesis II^® (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System).

The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL^®, Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK^®, Depuy and Genesis II^®, Smith and Nephew).

Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.

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 6 months leaving eighty-seven 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 knee flexion at two years (SAL – 117^°, AMK – 115^°, GenesisII – 118^°).

No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

In this prospective randomized 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.

Funding: London Health Sciences Centre Internal Research Fund

The Self Aligning (SAL I) total knee prosthesis (Sulzer, Winterthur) is a first generation cruciate retaining mobile bearing implant allowing unrestricted rotation and up to 5 mm. of translation. A consecutive series of two hundred and three SAL I components in one hundred and sixty- seven patients were implanted between 1990 and 1994 and were reviewed clinically and radiographically. Quality of life outcomes (SF-12 and WOMAC) were also reviewed pre-operatively and regular intervals. This first generation mobile bearing knee implant in this series, continues to function well at a minimum ten years follow-up, with a mechanical failure rate (8%) comparable to fixed bearing designs.

A consecutive series of SAL I total knee arthroplasties were performed between 1990 and 1994 and were reviewed clinically, radiographically and with standardized quality of life outcome tools, including the SF-12 and the Western Ontario MacMaster Osteoarthritis Index (WOMAC).

Patient demographics, radiographs, and multiple validated outcome measures (WOMAC, SF12, Knee Society Clinical Rating System) were evaluated pre-operatively, at three, twelve, and twenty-four months and every two years thereafter.

The series included two hundred and three SAL I implants in one hundred and sixy-sevenpatients. There have been sixty-nine patient deaths (eighty-five procedures), nine patients (eleven procedures) now reside in nursing homes and are unable to return due to medical complications, two patients (three procedures) could not be located. Nine-teen patients/procedures have had revision surgery. Therefore, seventy-six patients (ninety-three procedures) were evaluated with over ten year follow-up (average 10.89 years, range 10.03–13.72). Indications for revision included, sepsis (three), aseptic loosening (eight), instability (two) and poly-wear (six). The KSCRS was assessed for all remaining patients at greater than ten years including pain (45.83), function(65.60), range of motion extension(0.13) and flexion(113.82) as well as the results of the WOMAC (pain-4.36, joint stiffness-2.29, function-18.66, total- 15.92) and SF-12 (Mental-55.37 Physical- 34.99).

The SAL I mobile bearing implant continues to perform comparably to fixed bearing cruciate retaining designs.

This first generation mobile bearing knee implant continues to function well at a minimum ten years follow-up, with a mechanical failure rate (8%) comparable to fixed bearing designs.

The Genesis II total knee prosthesis was a successor to the Genesis I TKR in which three degrees of external rotation was built into the femoral component to improve patellofemoral tracking and eliminate rotational incongruity. The midterm (minimum five year) results of three hundred and forty-three Genesis II cemented components were reviewed in three hundred and twenty-four patients. Kaplan-Meier survivorship was 98% at a mean 7.6 years.

The focus of this study was to analyze the minimum five- year results of patients receiving either a cruciate-retaining, posterior stabilizing, or mobile bearing Genesis II TKR. Further analysis was performed to delineate differences between subsets of this population.

Data from a consecutive series of three hundred and twenty-four patients receiving three hundred and sixty-seven Genesis II TKR’s between February 1996 and July 1999 was collected. Patients were evaluated pre-operatively, at six weeks, three months, six months and annually thereafter, using the Knee Society Clinical Rating System and the Western Ontario MacMaster Osteoarthritis Index. A Kaplan-Meier Survivorship was performed on the consecutive series. Statistical analyses were used to delineate significant differences between subsets of patients.

There were three hundred and sixty-seven procedures (one hundred and sixty-nine cruciate-retaining, one hundred and sixty-six posterior stabilized and six mobile bearing designs) performed on three hundred and twenty-four patients. At the time of evaluation, forty-five (13%) patients were deceased, twenty-four (7%) patients were unavailable for evaluation and nine (2%) knees had been revised. A 98% implant survivor-ship was calculated at a mean time of 7.6 years.

These are the first mid-term (minimum five year) clinical results of the Genesis II TKR, which continues to function well. Kaplan-Meier survivorship was 98% at a mean 7.6 years.

Isolated liner exchange in revision total hip arthroplasty for the treatment of polyethylene wear is an increasingly common surgical procedure. Twenty-four hips underwent this procedure via the direct lateral approach and were prospectively followed clinically and radiographically. Accessible osteolytic lesions were curetted and bone grafted. At a mean follow-up of forty months, a significant clinical improvement was observed. One cup collapsed into an osteolytic lesion postoperatively; all other lesions regressed. No dislocations have occurred. Isolated liner exchange via the direct lateral approach may reduce dislocation rates while avoiding the morbidity associated with the removal of well-fixed components.

The purpose of this study was to evaluate the clinical and radiographic results of isolated liner exchange in revision total hip arthroplasty (THA) for osteolysis and polyethylene wear via the direct lateral surgical approach.

Retention of well-fixed implants avoids unnecessary bone loss at revision surgery. Previous studies report a significant dislocation rate with isolated liner exchange. Revision via the direct lateral surgical approach may reduce the dislocation rate in surgery for acetabular osteolysis.

Twenty-four hips that underwent an isolated liner exchange revision procedure via the direct lateral approach were prospectively followed. Accessible osteolytic lesions were curetted and bone grafted. Harris Hip Score, WOMAC Index, and radiographic analysis were recorded. The area of osteolytic lesions was calculated using a computer imaging technique.

At mean follow-up of forty months, all except one of the osteolytic lesions had regressed in size. Mean Harris Hip scores improved from sixty-nine to eighty-three and WOMAC indices improved from thirty-seven to twenty-four. No dislocations have occurred. One cup collapsed into an osteolytic lesion postoperatively, requiring an acetabular revision procedure.

Isolated liner exchange is a promising technique that avoids the removal of well-fixed acetabular implants. The increased dislocation rate associated with revision THA may be reduced and osteolytic lesions may be debrided and bone grafted through the direct lateral approach.

Isolated liner exchange via the direct lateral approach reduces the dislocation rate in THA. Retention of wellfixed implants and bone grafting is a procedure that preserves bone stock and addresses osteolytic lesions at revision surgery.

The purpose of this study was to determine contact patterns in cementless acetabular cups using a novel computed tomography (CT) scan analysis technique. Eighteen embalmed cadaveric hemipelvis specimens were randomly assigned to receive one of three cup designs. A custom CT platform was designed to optimize imaging of the acetabular cups. After cup implantation, specimens were mounted on the platform and imaged in a spiral CT scanner. Contact analysis was preformed using custom-developed imaging software. The hemisphere, dual geometry and spiked cup designs analyzed using this CT analysis technique demonstrate differences in the amount and distribution of bone pros-thesis contact.

The purpose of this study was to determine contact patterns in cementless acetabular cups using computed tomography (CT) scan analysis.

Eighteen embalmed cadaveric hemipelvis specimens were randomly assigned to receive a hemispherical cup, a dual geometry cup, or a spiked cup. After radiographic templating, an experienced orthopaedic team prepared the specimens and implanted the acetabular cups. A custom CT platform was designed to optimize imaging of the acetabular cups. After cup implantation, specimens were mounted on the platform and imaged in a spiral CT scanner. Contact analysis was preformed using custom-developed imaging software. Contact was defined as a bone-prosthesis distance of 0.5 mm or less.

The mean amount of cup contact was 40.4% (SD=8.2%) in the hemisphere group, 24.7% (SD=2.3%) in the dual geometry group, and 29.7% (SD=9.5%) in the spiked group. Colour mapping of the bone-prosthesis gap was used to identify contact/non-contact regions along the acetabular contour for all cup designs.

Preliminary work with this CT analysis technique demonstrates differences in the amount and distribution of contact in the acetabular cup designs. Future work will involve development of an imaging phantom to clarify error, use of the technique with different cup designs and reaming techniques, and comparison of this technique with conventional CT scan techniques.

This study outlines a novel CT analysis technique for quantitatively determining bone-prosthesis contact for cementless acetabular cups.

The hemisphere, dual geometry and spiked cup designs analyzed using this CT analysis technique demonstrate differences in the amount and distribution of bone prosthesis contact.

Funding: Smith and Nephew

One hundred and thirty-one cemented femoral stems inserted during revision total hip arthroplasty were reviewed to determine component survival. Harris Hip scores and complete radiographs were analysed. Survival at 10.5 years was 86.9%. Radiographically, 76.9% of the remaining components were classified as stable or possibly loose. Chi-square analysis of demographic and surgical factors determined age < 60 years, male gender and stems > 200 mm in length contributed significantly to failure (p < 0.05). Contrary to published results, we found that longer stems were more susceptible to failure. Revision femoral THA to a cemented component is an effective procedure that exhibits good long-term survival.

The purpose of this study was to determine the long-term survival of cemented femoral components in revision total hip arthroplasty (THA) and to identify factors significant to implant failure.

Cemented femoral components demonstrate good long-term survival and remain a suitable option for revision THA for hips with an intact cortical tube.

We report high long-term survival for this increasingly popular procedure, and contradict published results regarding the relationship between stem length and failure.

A consecutive series of one hundred and thirty-one THA revisions using a cemented femoral component were reviewed. Ninety-four hips in eighty-five patients alive > six years post-operatively were studied with a mean follow-up of 10.5 years. Hips excluded from analysis were thirty deceased and seven lost to follow-up before six years post-operatively. Implant success was graded radiographically and by comparing pre-operative to recent Harris Hip scores.

Of the ninety-four hips, fifteen (16%) femoral components were subsequently revised; nine (9.6%) for aseptic loosening, three (3.2%) for periprosthetic fracture, and one (1.1%) for each of stem fracture, instability, and sepsis. Survival at 10.5 years was 86.9% for all reasons and 91.0% for aseptic loosening as an endpoint. 76.9% of the retained components were radiologically classified as stable or possibly loose at follow-up. Factors significant for failure included age at revision < sixty years (p = 0.003), male patients (p = 0.036) and stems > 200 mm in length (p = 0.024).