New technology in joint replacement design and materials adds cost which must be documented by improved outcomes. This is not always the case as the recent metal/metal data has shown. The current economics of arthroplasty surgery have put increasing financial pressure on hospitals and will progress under new health care legislation. New technology must be cost effective and this will be increasingly difficult in an era of outstanding long term results with current designs. Cost may necessitate less expensive alternatives, e.g. generic implants, in arthroplasty patients.

Joint replacement surgery has evolved over the past four decades into a highly successful surgical procedure. Earlier designs and materials which demonstrated inferior functional and long term results have disappeared in a Darwinian fashion. Through this evolutionary process many of the current designs have proven efficacy and durability. Current outcome data indicates that hip and knee designs demonstrate 90–95% success rates at 15 year follow-up. Technologic advances are necessary to improve implant design and materials, however, in an environment of reduced reimbursement to hospitals can the increase cost be justified.

The rationale that technology in medicine would be expensive at the outset yet be cost effective eventually has in many areas not been the case. Currently about one half of the rapid increase in health care costs in relation to GNP may be attributed to technology. Uwe Reinhardt, an economist at Princeton University, in referring to new technology has stated that the health care system provides misaligned incentives that create over-utilisation or misutilisation of everything that is new. It is now common knowledge among health care economists that if the cost of health care is to be controlled the growth of technology must be constrained.

Increasingly as new technology emerges the question will be: what is the cost-benefit analysis. A new era of comparative effectiveness research is being launched and will become predominant in medicine and arthroplasty surgery in the future. What is the newest may not always be the best. According to Reinhardt there is a need for comparative effectiveness studies of emerging and existing technology so that the new can be priced in a way that reflects its incremental value. New technology must demonstrate its benefit to justify its cost, often in arthroplasty there is little data available to document these better outcomes.

In a recent study by Bozic the cost effectiveness of new technologies were evaluated. Based on the authors' findings for an alternative bearing with an incremental cost of $2000 to be cost saving for a 50 year old there would have to be a 19% reduction in 20 year failure rates. The likelihood of cost savings for these alternate bearings in patients 63 or older is highly unlikely at current costs. Newer biomaterials (metal/metal, ceramic/ceramic, highly cross linked polyethylene) also have limited outcome analysis in patients beyond short to mid-term follow-up evaluation and all of these technologies add significant cost to the implant. With diminishing reimbursement careful analysis of utilisation of these newer technologies must be weighed if hospitals are to maintain economic viability.

The pharmaceutical, airline, and food industries have all moved toward generic products which are less costly and this will be the trend in the future in prosthetic implants as well. Newer technologies must demonstrate their efficacy in long term follow-up and be clearly superior to conventional implants. This is not always the case as new data on metal-metal implants is demonstrating. Change is not always progress.

For most revision total knee replacement there is associated soft tissue and bone loss. A constrained condylar implant can be useful in improving the stability of the knee after revision. Augmentation is commonly used to deal with bone loss on the femoral and tibial side of the joint. Stems are known to reduce the load at the interface of the femoral and tibial component and transfer the load into the medullary canals. There are problems with using stems in the revision setting, however, which include: (1) increased cost, (2) difficulty with removal should further revision be necessary, (3) violation of the intramedullary canals if infection occurs, (4) increased operating time. For these reasons a CCK implant was developed without stems in 1998. The use of this device must be very selective and it is primarily used for severe valgus deformity in elderly patients. In a revision setting where there is good preservation of femoral and/or tibial bone but the need for increased constraint is present (e.g. unicompartmental, cruciate retaining knee) a CCK without stems can be used with good results. We retrospectively reviewed 36 primary constrained condylar knee implants without stem extensions from 1998 to 2000 in 31 patients with knees in 15° valgus or greater. All patients were followed up for a minimum 10 years (range, 10 to 12 years). One patient had aseptic loosening and needed to be revised with stemmed components at nine years post-surgery. Wear was found in two patients. One patient, with severe rheumatoid arthritis, had infection and required a two-stage re-implantation procedure. Patients who are very active or heavy body weight where stresses may be excessive at the implant bone interface should have stems utilised.

Background: A navigated 8 in 1 femoral cutting guide for TKA that does not require primary fixation or intramedullary guides was developed. The hypothesis of our study were twofold: 1) the navigation system allows for precise alignment and adjustment of a new femoral 8 in 1 cutting guide with negligible variance in the initially planned vs. achieved implant position; 2) resulting femoral cuts are very accurate without relevant cutting errors.

Material and Methods: We demonstrate our approach with the Universal Knee Instrument (UKI, Precimed Inc. USA), a versatile 8 in 1 TKA guide designed to perform all femoral cuts with a single jig. We integrated an array of “adjustable constraints” into the UKI by machining four threaded holes directly through the template. Adaptation to a navigation system has been performed by integrating the adjustable constraints protocol on the open platform Surgetics Station (PRAXIM-medivision, France), which uses image-free BoneMorphing technology. Based on navigated bone morphing the required preadjustment of the guide was done mechanically, with depth control by mini screws. Testings on 10 cadavers compared the planned vs. achieved positions of the jig before, after fixation, final implant position and planned vs. achieved cutting procedures.

Results: Results revealed for valgus/varus deviations before fixation −0.1°±0.7°, after 0.0°±0.8° (p=0.51), final implant position 0.9°±1.7° (p=0.93). For flexion before fixation −0.3°±1.3° after −0.3°±1.8° (p=0.44), final position 2.9°±2.5° (p=0.65). Distal cut height before fixation 0.0°±0.4°, after 0.1°±0.3° (p=0.61), final position 0.3°±1.0° (p=0.1). Axial rotation before −0.3°±1.1°, after fixation 0.2°±1.4° (p=0.57), final implant position 0.8°±2.7° (p=0.89). Anterior-posterior positions before fixation 0.7°±1.4°, after 1.0°±1.6° (p=0.27), final position 3.4°±1.3° (p=0.13). Highest deviations in the planned vs. actual cut position was found for the posterior cut −3.1°±2.4° in sagittal and anterior cut 0.8°±1.9° in the coronal plane. The highest mean errors in the final implant position where on the order of 3 degrees/mm in flexion and anterior-posterior positioning.

Conclusion: A novel ‘CAS-enabled 8 in 1 jig’ has been developed and validated. The system allows for direct execution of a complex, multi-planar CAS plan with single navigated device. The instrumentation is considerably simplified and eliminates the problems associated with sequential jigs.

Particles generated at the non articulating surface (backside) of modular acetabular components have been implicated in the development of periprosthetic osteolysis after total hip arthroplasty. Several design changes have been introduced in modern uncemented acetabular cups in an attempt to reduce backside wear, including the use of so called “non-modular cups”. We compared the backside wear of retrieved cementless non-modular cups, with modular cups of first and second generation designs.

Nine retrieved non-modular cups (Implex) were match paired for time in situ, patient age and weight, with 9 retrieved Trilogy cups, 9 Harris-Galante 1, and 9 Harris-Galante 2. The average time in situ was 2.5 years (1 to 7). The backside was divided in quadrants and each rated utilizing a score with a value from 0 (absence of wear) to 3 (severe backside wear) for a total ranging from 0 to 12. The score was validated for intra and inter observer reproducibility.

Among 36 quadrants in the HG1 group there were 3 rated 1, 23 rated 2, and 10 rated 3. In the HG2 group, there was 1 quadrant rated 0, 16 rated 1, 14 rated 2, and 5 rated 3. In the Trilogy group, there were 6 quadrants rated 0, 27 rated 1, and 3 rated 2. In the Implex group, there were 15 quadrants rated 0, 21 rated 1. The average total backside wear score and 95%CI were 8.4 (7.6–9.3); 7.3 (5.5–9.1); 3.7 (3.2–4.1); and 2.3 (1.3–3.4) respectively. The HG1 and HG2 groups demonstrated similar backside wear scores (p=0.3). The HG1 and HG2 designs demonstrated significantly more backside wear than the Trilogy and Implex (p< 0.01). The differences between the Trilogy and the Implex were not significant in this cohort.

A comparison of the “in vivo” backside wear of first generation and modern acetabular cups has not been published to date. Despite the limitations imposed by the small sample studied, the presence of multiple screw holes in the HG retrievals, and sub-optimal matching for sex, height, and varied indication for revision, we detected significant reduction in the backside wear of modern modular and non-modular acetabular cups when compared to first generation modular designs.

Particles generated at the non articulating surface (backside) of modular acetabular components have been implicated in the development of periprosthetic osteolysis after THA. Several design changes have been introduced in modern acetabular cups in an attempt to reduce backside wear, including the use of “non-modular cups”. We compared the backside wear of retrieved cementless non-modular cups, with modular cups of first and second generation designs. Nine retrieved non-modular cups (Implex) were match-paired for time-in-situ, patient age and weight, with 9 retrieved Trilogy cups, 9 Harris-Galante 1, and 9 Harris-Galante 2. The average time in situ was 2.5 years (1–7). The backside was divided in quadrants and each rated with a value from 0 (absence of wear) to 3 (severe backside wear) for a total ranging from 0 to 12. This new score was validated for intra and inter observer reproducibility. Among 36 quadrants in the HG1 group there were 3 rated 1, 23 rated 2, and 10 rated 3. In the HG2 group, 1 quadrant was rated 0, 16 rated 1, 14 rated 2, and 5 rated 3. In the Trilogy group, 6 quadrants were rated 0, 27 rated 1, and 3 rated 2. In the Implex group, 15 quadrants were rated 0, 21 rated 1. The average backside wear score and 95%CI were 8.4 (7.6–9.3); 7.3 (5.5–9.1); 3.7 (3.2–4.1); and 2.3 (1.3–3.4) respectively. The HG cups demonstrated more severe backside wear than the Trilogy and Implex (p< 0.02). There was a tendency towards less backside wear in the Implex cup when compared to the Trilogy (p=0.04). The difference between the HG1 and HG2 was not significant. We detected significant reduction in the backside wear of modern modular and non-modular acetabular cups when compared to first generation modular designs.

Introduction: Patello-femoral complications are a major problem after total knee arthroplasty (TKA). Purpose of the present study was to analyze patello-femoral complications and function after two different posterior-stabilized TKA designs (Optetrak 913 vs IB-II).

Materials and Methods: This study was performed in two consecutive phases. In the first phase 1410 TKA’s performed by the senior author between 1994 and 1998 were considered for chart review. Within this period, the last 300 IB-II and the first 300 913 performed were analyzed for patello-femoral complication rate. In the second phase, of the 600 charts analyzed, two matched groups (50 patients each of IB-II and 913), were selected for a clinical (Knee Society score), functional (HSS Patellar score) and radiological assessment (AP, Lateral, Merchant, modified-wb Merchant views).

Results: A lateral retinacular release was performed in 30% for the IB-II and 16% for the 913 (p=0.02). The following patello-femoral complications were encountered (phase-1):

IB-II 913

Patellar clunk 3.5% 0.3%

Dislocation 0% 0.3%

Fracture 0% 0.3%

Loosening 0% 0%

Clinical results at follow-up (phase-2) did not show any significant difference between the two matched groups in terms of Knee and Function scores (p=0.7). Patellar score showed a higher rate of excellent and good results in the 913 group (88% vs 81%: p=.043). Anterior knee pain was only mild and activity related in 26% of the IB-II and 14% of the 913 (p=.025). In a multivariate regression analysis, radiographic patellar tilt, subluxation, and height, did not correlate with clinical outcomes, whilst bone-implant contact showed a trend towards a higher incidence of pain, particularly when associated with asymmetric patellar resection.

Discussion: At an intermediate follow-up, the Optetrak 913 prostheses showed fewer complications and an improved patello-femoral function compared to the IB-II prosthesis.

Introduction: Patello-femoral evaluation after total knee arthroplasty (TKA) is not addressed by most knee scoring systems. Patellar radiographic assessment after TKA is obtained with static, unloaded views that may not reproduce the in-vivo patello-femoral kinematics. The purpose of this study was to develop and validate new reliable and reproducible clinical and radiographic assessment tools for analysis of the patello-femoral joint in TKA.

Materials and Methods: The existing axial Merchant view was modified by positioning the standing patient in the semi-squatted position with the knees at 45°. Relationship between X-ray source, the angle of incidence on the joint, and the cassette position, were kept unchanged from the original view. The standing position and consequent muscle involvement were the only differences. The quality of the view was confirmed on a cadaveric knee model with multiple markers. Safety, reproducibility and clinical reliability were obtained in 100 posterior-stabilized TKA’s. These patients were assessed by a new Patella Scoring System (0–100 points). This system considers anterior knee pain, crepitus, stair performance and quadriceps strength. Radiographic abnormalities are calculated as deductions. Intra- and inter-observer variability were obtained comparing the results of two different investigators.

Results: The modified Merchant view showed significant patello-femoral tracking changes in 68% of patients. Twenty-one cases of bone-implant contact were observed when load was applied. Correlation between excellent-good clinical outcome and excellent patello-femoral performance was significantly higher for the Patellar Score compared to Knee Society Clinic or Function scores (p=.022, p=.014). Multivariate regression analysis of radiographic tilt, subluxation, and height, did not correlate with clinical outcomes, whilst bone-implant contact showed higher incidence of pain, particularly when associated with asymmetric patellar resection.

Conclusion: These new patello-femoral clinical and radiological assessment methods employed in the study represent additional valuable tools for the comprehensive evaluation of results in TKA.

We evaluated the safety and efficacy of a multimodal approach for prophylaxis of thromboembolism after THA, which includes preoperative autologous blood donation; hypotensive epidural anesthesia; intravenous administration of heparin during surgery, before femoral preparation when the thrombogenesis is maximally activated; expeditious surgery, minimizing femoral vein occlusion and blood loss; pneumatic compression; and early mobilization after surgery. 1946 consecutive, non-selected patients (2016 THAs) who received multimodal thromboembolic prophylaxis were followed prospectively for 3 months. Only patients with history of thrombocytopenia (platelet count < 100.000) or adverse reaction to heparin were excluded. The average age was 65 years (14 to 93), ASA classification was 1 in 14%, 2 in 48%, 3 in 37% and 4 in 1% of patients. There was a history of DVT in 86 patients and PE in 35. After surgery, the patients also received pharmacologic prophylaxis for 6 weeks (aspirin 83%; warfarin 17%). The incidence of asymptomatic DVT assessed by ultrasound in the first 198 consecutive patients was 7.1% (14 of 198). The incidence of clinical DVT in the subsequent 1748 patients was 1.8% (32 of 1748). Symptomatic PE occurred in 0.56% (11 of 1946), none of them fatal. The rate of PE in patients receiving aspirin was 0.49% (8 of 1615) and warfarin 0.9% (3 of 331). There was 1 PE among 95 patients with a prior history of PE or DVT (1%). One morbidly obese patient died of a cardiac arrhythmia confirmed by autopsy. There was only one major bleeding complication: one patient with a history of coagulopathy developed hematuria requiring a bladder flush and five units of blood, with an uneventful recovery. No patients developed epidural hematoma following administration of intraoperative heparin. A multimodal approach to prevent thromboembolic disease, showed results that compare favorably with the literature, and with our historic control of 2592 THRs without intraoperative heparin (PE rate of 1%; 0.04% fatal). This multimodal approach appears safe and efficacious as thromboembolic prophylaxis. Our low rate of PE does not support routine anticoagulation prophylaxis with drugs with a significant risk of bleeding.

Introduction and Aims: Retroacetabular osteolysis is a common cause of failure of hip replacements. Polyethylene wear particles from the joint are often present in osteolytic lesions. We investigate three theories that describe how fluid and debris could be pumped from the joint space through the holes in the shell to the retroacetabular bone.

Method: We report three experiments that investigate this question. We performed an in vivo study where we measured pressures in the hip joint and in the osteolytic lesion while cyclically loading the hip in 10 patients. We performed a series of biomechanical studies, where we model diaphragm pumping and piston pumping of the polyethylene liner within the metal shell in the laboratory. We also carried out a finite element analysis showing how loading of the hip affects the size of an osteolytic lesion and the pressure of fluid within an osteolytic lesion.

Results: In the in vivo study, loading of the hip produced a pressure increase in each of the four contained osteolytic lesions (mean 68mmHg), but not in the six uncontained osteolytic lesions. This pressure rise was independent of hip joint pressure, demonstrating that there is a pumping mechanism in the artificial hip joint that is independent of hip joint pressure. In the diaphragm pumping experiment, the pressure produced by the non-congruent liners (4030 ±1250mmHg) was six times the pressure produced by the congruent liners (670 ±240mmHg). In the piston pumping experiment, the pressure produced by the pistoning liners (5140 ±330mmHg) was eight times the pressure produced without pistoning (650 ±300mmHg). FEA demonstrates that loading of the hip may reduce the volume and, therefore, increase pressure in a contained osteolytic lesion.

Conclusion: The prosthetic hip contains a complex system of pumps transporting fluid and particles and generating pressures. The importance of each pumping mechanism varies with patient activity and with implant design features. These pumping mechanisms may contribute to the pathogenesis of osteolysis.

The major failure mode of cemented or non-cemented acetabular fixation is osteolysis produced by polyethylene debris and biologic reaction to this material. A monoblock acetabular non-cemented component offers advantages in reducing the failure mechanism of acetabular cups. First, because the polyethylene is fixed to the metal shell there is no motion between the shell and the liner as is seen with modular components. Therefore extra-articular polyethylene wear debris is not generated. Secondly, there is no need for a locking mechanism which may fail and from which metallic debris may be produced. Thirdly, no screw holes are present on the back of the monoblock cup increasing the surface area for ingrowth and eliminating an entrance point for wear debris to access the floor of the acetabulum. Avoidance of the use of screws also prevents the possibility of neurovascular injury during screw insertion. Fourthly, by adding an elliptical configuration to a monoblock cup the dome of the shell is the same dimension as the reamed diameter allowing for improved coaptation of shell to acetabular floor. By increasing the diameter at the rim secure press fit is achieved without sacrificing contact at the dome.

There are disadvantages to a monoblock cup and these include the need for a revision liner mechanism should there be a need to replace the polyethylene liner. Additionally, if secure stabilisation is not achieved, the cup cannot be converted to screw fixation.

In a radiologic review of 661 acetabular components, 5.1% of cups were noted to have a polar dome acetabular gap of greater than 1.5 mm on the immediate postoperative radiograph. These patients were followed for a minimum of two years and there was noted shift in implant position in only one patient. Gaps tended to lessen in degree and fill in with bone in almost all cases. The clinical result was not compromised by the presence of a dome gap.

In a short-term follow-up of 6 years, 1843 elliptical monoblock acetabular cups have been inserted with greater than two-year follow-up in 972 hips. There have been no mechanical failures requiring revision. Two patients have been revised for instability and one for infection. The need to convert to a cup with screw fixation because of poor press fit is less than 2%.

Inciting events leading to deep vein thrombosis occur primarily intraoperatively. Therefore, if at all possible, intervention should be performed at the time of the operative procedure. It has been demonstrated in hip replacement surgery that DVT is significantly reduced with epidural hypotensive anaesthesia, which may or not be augmented with intraoperative small doses of heparin (500–1000 units). Reduction of extreme limb position with occlusion of the femoral vein during hip replacement surgery reduces the stasis effect, which promotes clotting. In the hip, overall DVT rates have been reduced to 7% and proximal DVT rates to 2% using these intraoperative techniques.

Mechanical devices work by a myriad of mechanisms: 1.) venous turbulence is created in valve pocket areas and this reduces clot formation; 2.) there is an increase release of endothelial relaxing factor (EDRF) which inhibits platelet aggregation; 3.) intermittent compression stimulates fibrinolysis by inducing release of urokinase and tissue plasminogen from the venous endothelium. Randomised trials have demonstrated a reduction in DVT to levels similar to pharmacologic agents (20–27%) without the risk of postoperative haemorrhage. However, compliance with use of these devices is crucia1, as a positive relationship has been demonstrated between time of use and DVT rates. Although plantar pump devices tend to be well tolerated with occasional complaints of foot and skin irritation, calf compression devices with or without sequential foot compression applying at least 50 mmHg of external pressure at a frequency of at least once per minute and an inflation rate of less than 1 second tend to be the ideal device for DVT prophylaxis.

The indications for unicompartmental replacement are quite specific. Overall there should be involvement of one tibiofemoral compartment, mild malalignment, and ligamentous stability. In a review of 250 osteoarthritic knees these pathologic findings were present in 9% of patients. If the average orthopaedic surgeon performs 25 total knee replacements per year only 2–3 patients will be ideally suited for this procedure. Technique, despite improvement in instrumentation, is still more demanding than tricompartmental knee replacement and therefore failure to achieve an optimal arthroplasty is higher. Overall results with unicompartmental replacement in the literature have been inferior to tricompartmental replacement (82% versus 97%). The concept that unicompartmental replacement is a temporising procedure is not a valid one in that the patient has to undergo another arthroplasty with all the risks of revision arthroplasty surgery. Tibial osteotomy remains the procedure of choice in the younger, active patient with unicompartmental replacement and tricompartmental replacement in the older, lower demand patient.

A multi-centre clinical trial of ICLH (Freeman-Swanson) arthroplasty has been in progress since 1971. In this paper the results up to two years after operation are reported in seventy-one knees displaying at least 30 degrees of fixed flexion, 25 degrees of valgus or 20 degrees of varus, before operation. It has been found that knees displaying 70 degrees of fixed flexion, 70 degrees of valgus, 30 degrees of varus or 50 degrees of valgus/varus instability can be satisfactorily aligned and stabilised with acceptable function. Three knees required revision. The other complications are listed and were unremarkable in nature. These results depend upon the prosthesis and upon the operative technique. The latter avoids damage to healthy bone but does involve the replacement of the tissues in the midline of the knee.