Summary Statement

Our data suggest that postoperative component positioning in TKA with PSPG is not consistent with pre-operative software planning. More studies are needed to rule out possible learning curve in this study.

Background

Tranexamic acid (TA) in total knee replacement surgery (TKR) has shown marked reduction in bleeding and blood transfusion. There are little data on TA in revision TKR. From February 2008 all patients having primary or revision TKR received TA 10mg/kg × 2. We whished to evaluate the effect and possible complications of TA.

Background

There are few studies of total knee replacements with cemented tibia and uncemented femur (hybrid). Previous studies have not shown any difference in revision rate between different fixation methods, but these studies had few hybrid prostheses. This study evaluates the results of hybrid knee replacements based on data from the Norwegian Arthroplasty Register (NAR).

Introduction Impaction grafting in revision hip arthroplasty has now been used with a number of cemented stem designs. Follow-up has been short/intermediate with variable results due to pronounced stem subsidence and incomplete cement mantles. This study investigated the performance of a cementless, HA-coated stem used with the impaction grafting technique.

Methods We performed revision hip arthroplasty on a series of 16 stems for mechanical loosening (majority type II) in 14 patients (mean age 64 years). An uncemented Anatomic® stem was inserted into a neomedullary canal of impacted fresh frozen allograft bone. Stem migration was assessed with RSA. Graft and host cortical bone remodeling were evaluated radiographically as was the quality of the impaction grafting and amount of radiographic bone ingrowth. Bone mineral density (BMD) was assessed with DEXA at two and 10 years. Harris Hip Score was recorded for clinical assessment.

Results At six months the stems had subsided 0.78 mm (−7.78 – 0.22). Thereafter, the majority stabilized (6 months vs. 12 years: p=0.3). The graft had a homogenous distribution proximally, but to a lesser extent distally. Remodeling of graft was frequently seen at two years, especially proximally. There were no signs of graft resorption and no change in BMD in any Gruen zone between two and 10 years (P=0.15 – 0.54). About one third of patients had evidence of cortical restitution. In most cases there were no radiolucencies at all between the HA-fiber mesh and the bone. Slight cortical erosion at the stem tip was observed in nine cases but none progressed after two years. These parameters (remodeling, ingrowth and radiolucencies) changed minimally between the two and 12 years. At two years, the Harris Hip (50 to 85) and pain scores (20 to 40) had increased (p = 0.001). Thereafter the scores remained stationary. One hip dislocated during the first year. Heterotopic ossification occurred in three cases. One case underwent two stage revision at 30 months for late infection. One fracture was detected post-operatively. This stem subsided 16.2 mm at two years requiring revision. One patient died due to unrelated causes. Early migration was seen. Radiographs suggest much of the graft was substituted with living bone with no deterioration between two and 12 years.

Conclusions Our findings are sufficiently encouraging to initiate trials of uncemented stems with extended HA coatings.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction Wear particle induced osteolysis is regarded as the main reason for aseptic loosening of hip replacements. Crosslinked polyethylene show extremely low wear in lab studies and is routinely used today, though with very little clinical testing. We report wear, migration and function for uncemented cups with a crosslinked poly.

Methods Twelve hips in 12 patients with mean age of 70 years were operated with uncemented cups (Reflection), cemented stems and metal heads. Five Mrad cross linked liners annealed below melt temperature were used in all hips (XLPE, Smith & Nephew). Tantalum markers were inserted in liners and acetabular bone for RSA measurements and migration and wear measured over two years. The result was compared to matched controls from a study of 80 cups with the same implant and non cross linked poly, operated by the same surgeon. X-rays, WOMAC and Sf-36 were performed pre-operatively and at two years.

Results The mean proximal head penetration at two months was 0.09 mm. This was thought to be mainly due to the creep of the polyethylene and was equal to “normal” poly. At the one year follow-up the mean proximal wear had increased with 0.02 mm and at two years 0.03 mm. This compares with the 0.33 mm recorded for the old poly (p=0.001, Mann Whitney U test.). The cups migrated 0.2 mm proximally and showed a normal migration profile, comparable to the cups with non cross-linked poly. The accuracy of measuring proximal wear, in this study, was found to be 0.07 mm (95% CI). No differences in radiolucent lines or clinical scores were found.

Conclusions The first two years proximal wear was 0.03 mm compared to the 0.33 mm found for non crosslinked poly. This is a reduction with 90% which certainly looks promising.

Aim: Investigate wear and performance of high cross linked plastic cups in vivo. Methods: Thirty cemented total hip arthroplasties done in patients with a mean age of 67 years (49–81) and weight of 74 kg (45–98). In twenty hips a standard gamma in air sterilized polyethylene plastic cup was used and in 10 hips a high cross linked plastic, (7.5 Mrad cold irradiated, sub melt annealed and gamma sterilized in inert (Crossfire®)). Exeter stems with 28 mm metal heads and Palacos-G cement were used in all. RSA measurement of wear and cup migration was done over 2 years and standard radiographs and Harris hip score also followed. Results: The cups had a similar head penetration the first 2 months, 46 and 61 um, and mainly due to plastic creep. Between 2 and 24 months the mean proximal wear (head penetration) was 156 um for Exeter and 13 um for Crossfire. (p< 0.001. T-test).

The mean vectorial migration was 0.31 and 0.24 mm and change in inclination 0.2° and 0.2° for the groups. (p> 0.8) Harris Hip Score was 92/96 and the radiological and clinical performance was equal after 2 years. Conclusion: High cross linked polyethylene showed a wear reduction of 90% compared to standard polyethylene after 2 years. The reduced wear was not at the expense of increased migration or radiolucences. High cross linked plastic looks promising but to what extent the decrease in wear reflects a decrease in clinical loosening and osteolyses remains to be shown.

Post operative stability is of paramount importance to obtain bone in growth and a tight interface in uncemented implants. Although hemispherical press fit cups are widely used different opinions exists according optimal fixation and a variety of principles are preferred. Lab studies show better stability if a cup is augmented by screws or pegs. However, cups with screws and holes increases penetration of joint fluid, pressure and particles to the interface with a risk for osteolyses. HA coating is in many studies favourable to obtain a quick in growth but is by many regarded unnecessary or even a risk for increased wear. This RSA studie was done to investigate stability and wear in cups with different fixation.

Material: 80 hips in 75 patients with a mean age of 58 years (36–70) were operated with a cemented Spectron stem and a porous coated Reflection cup of titanium (Smith a Nephew) All cups were oversized 1–2 mm and fixed with press fit by experienced surgeons. Great care was taken to achieve a good rim fit. They hips were by randomisation allocated to one of four groups with different fixation methods. One group was done with only press fit technique, one with additional screws, one additional pegs and another with HA coating on the porous surface. Migration and wear was investigated with RSA at 2, 12 and 24 months and standard radiography was done post op and at 2 years.

Mann-Whitneys U-test was used on signed values for evaluation of group differencies.

Results: At 2 years the mean cup migration for the whole group was 0.2 mm longitudinally, 0.3 mm horizontally and 0.3 mm anterior-posteriorly. (SEM 0.03–0.05) The inclination changed 0.4 dgr and anteversion 0.4 dgr as well. Most cups moved laterally, proximally and anteriorly with increased anteversion and decreased inclination. No major differences in mean values were found between the groups according translations or rotations and no significant differences. Nor did we find differences between the press fit only and the augmented cups.

Wear was 0.45 mm proximally and in total 0. 6 mm without any sign of differences between the HA and porous coated groups. HA coated cups had less radiolucent lines after 2 years. (p=0.01)

Discussion: The Reflection cups were stable fixed ad we found no indication of inferior stability for cups without augmentation as might have been anticipated. The reason is probably the firm press fit fixation obtained with a stable cup, good bone and forceful impaction. Many use screws for safety but such cups are not sealed for leakage of joint fluid and pressure gradients and the risk for backside osteolyses is higher… Pegs are easier and safer to insert and tighten the holes better. A tight, no hole cup with HA is preferred by us in normal younger patients since HA gave a better interface. Such a solution should minimise the risk for penetration of particles and pressure gradients with less risk for lyses.