European Database of Explanted UHMWPE Liners from Total Joint Replacements: Correlations among Polymer Modifications, Structure, Oxidation, Mechanical Properties and Lifetime In Vivo

This contribution lays the foundation for the European database of explanted UHMWPE liners from total joint replacements. Three EU countries (Czech Republic, Italy and Spain) have joined their datasets containing anonymized patient data (such as age and BMI), manufacturer data (such as information on UHMWPE crosslinking, thermal treatment and sterilization), orthopedic evaluation (such as total duration of the implant in vivo and reasons for its revision) and material characterization (such as oxidative degradation and micromechanical properties). The joined database contains more than 500 entries, exhibiting gradual growth, and it is beginning to show interesting trends, which are discussed in our contribution, including (i) strong correlations between UHMWPE oxidative degradation, degree of crystallinity and microhardness; (ii) statistically significant differences between UHMWPE liners with different types of sterilization; (iii) realistic correlations between the extent of oxidative degradation and the observed reasons for total joint replacement failures. Our final objective and task for the future is to continuously expand the database, involving researchers from other European countries, in order to create a robust tool that will contribute to the better understanding of structure-properties-performance relationships in the field of arthroplasty implants.

Long-term outcomes of a new model of anatomical hydroxyapatite-coated hip prosthesis

This prospective study was designed to evaluate 196 Anatomique Benoist Giraud (ABG II) total hip arthroplasties which were implanted between September 1999 and December 2000. A minimum 11 years follow up was completed in 183 cases. The bearing surfaces were polyethylene-zirconia in 84 cases, polyethylene-metal in 42 and ceramic-ceramic in 57. Changes in the femoral stem design, in relation to the previous ABG I model, have led to a significant improvement in stress-shielding. Polyethylene wear rate was lower by more than 50% compared with non-crosslinked polyethylene. Excellent and good results were obtained in 90.32% of cases, and implant survival was 98.39% at the end of follow-up.

Comparison between DEXA and finite element studies in the long-term bone remodeling of an anatomical femoral stem

The implantation of a cemented or cementless femoral stem changes the physiological load transfer on the femur producing an effect on the bone called adaptative remodeling. The patterns of this remodeling are attributed to mechanical and biological factors, and those changes in bone mineral density have been determined in long-term densitometry studies. This technique has proved to be a useful tool able to quantify small changes in bone density in different femoral areas, and it is considered to be ideal for long-term studies. On the other hand, the finite element (FE) simulation allows the study of the biomechanical changes produced in the femur after the implantation of a femoral stem. The aim of this study was to contrast the findings obtained from a 5 year follow-up densitometry study that used a newly designed femoral stem (73 patients were included in this study), with the results obtained using a finite element simulation that reproduces the pattern of load transfer that this stem causes on the femur. In this study we have obtained a good comparison between the results of stress of FE simulation and the bone mass values of the densitometry study establishing a ratio between the increases in stress (%) versus the increases in bone density (%). Hence, the changes in bone density in the long term, compared with the healthy femur, are due to different load transfers after stem implantation. It has been checked that in the Gruen zone 7 at 5 years, the most important reduction in stress (7.85%) is produced, which coincides with the highest loss of bone mass (23.89%). Furthermore, the simulation model can be used with different stems with several load conditions and at different time periods to carry out the study of biomechanical behavior in the interaction between the stem and the femur, explaining the evolution of bone density in accordance to Wolff's law, which validates the simulation model.

Bone remodelling after total hip arthroplasty using an uncemented anatomic femoral stem: a three-year prospective study using bone densitometry

PURPOSE

To evaluate the clinical, radiological, and densitometric changes in the bone-remodelling patterns of femoral stems aligned in neutral, valgus, or varus positions.

METHODS

Between February and October 2000, 70 patients underwent unilateral total hip arthroplasty for primary osteoarthritis using an uncemented Anatomique Benoist Girard (ABG) II stem. 69 patients (30 males and 39 females) with a mean age of 59 years (range, 38-76 years) and a mean body weight of 79.3 kg (range, 29-110 kg) completed 3 years' follow-up on bone remodelling. The clinical, radiological, and densitometric changes of the neutral, valgus, and varus groups were evaluated, and the difference in bone-remodelling patterns between the 3 groups was analysed.

RESULTS

54 patients had neutrally placed stems, while varus and valgus malalignment occurred in 6 and 9 patients, respectively. Clinical and radiological evaluations were very similar among the 3 groups. Only densitometry could detect traceable changes resulting from the differing biomechanics of the neutral, varus, and valgus stem alignments.

CONCLUSION

The ABG II stem design made moderate errors in alignment biomechanically tolerable. Alignment defects had no clinical consequences and resulted in minimal differences in bone remodelling.

The floating metatarsal: first metatarsophalangeal joint dislocation with associated Lisfranc dislocation

The authors report a case of an irreducible dorsal dislocation of the first metatarsophalangeal joint, with concomitant Lisfranc dislocation and fractures of the second, third, and fourth metatarsals. This combination has been reported only once in the literature. This extremely rare combined injury results in a floating metatarsal. Open reduction of the metatarsophalangeal joint dislocation and fixation of Lisfranc joint and metatarsal fractures with Kirschner wires was performed. One year after surgery, the patient is active and the first metatarsophalangeal joint is asymptomatic, but there is mild pain in the Lisfranc joint.

Comparison of two different posterior approachs for hemiarthroplasty of the hip

A prospective study was undertaken on 183 patients who had suffered a femoral neck fracture between 1998 and 1999. The aim was to compare the complication rates for the classical posterior approach and the modified posterior approach. The modified posterior approach used was the one described by Williams et al., which preserved the pyriformis, the labrum and the capsule. Group 1 included 95 patients, who were operated on by the posterior approach. Group 2 included 88 patients, who were operated on by the modified posterior approach. The dislocation rate for the posterior approach was 7.4% (7 cases), and 1.1% (1 case) for the modified posterior approach. This difference was statistically significant (p < 0.05). There were no significant differences in the incidences of other intraoperative and postoperative complications. We concluded that the modified posterior approach significantly increases the stability of a hemiarthroplasty in relation to the classical posterior approach.

Marchetti-Vicenzi nailing of humeral shaft fractures

Between 1995 and 1999, 46 acute nonpathological humeral shaft fractures were treated with retrograde Marchetti-Vicenzi humeral nailing. The mean healing time of all fractures was 10.8 weeks. Forty-five fractures (97.9%) united primarily, and one needed bone grafting (2.1%). Function of the shoulder was excellent in 35 patients (76.1%) and moderate in 11 (23.9%). Elbow function was also excellent in 35 patients and moderate in 11. Global functional results were excellent in 16 patients (34.8%), good in 22 (47.8%) and fair in 8 (17.4%). There were 4 cases of 10 degrees varus malunion (8.6%), one case of 15 degrees varus malunion (2.1%), and one case of 15 degrees anterior angulation malunion (2.1%). These malunions were clinically well tolerated. Four patients required removal of the nail because of posterior elbow pain. Retrograde Marchetti-Vicenzi nailing is an acceptable alternative for the treatment of acute humeral shaft fractures with a low complication rate.

Changes in the morphology of hip fractures within a 10-year period

The objective of this study was to find out whether the morphology of various types of hip fractures and the mean ages of the patients had changed in a recent 10-year period. All patients aged 65 years or more with acute hip fracture admitted to Miguel Servet University Hospital in 1989-1990 (n = 457) and in 1999-2000 (n = 518) were studied. The results showed a significant increase in the incidence of displaced cervical fractures (P < 0.001) and a decrease in the incidence of nondisplaced cervical fractures (P < 0.001) in women. The incidence of different types of trochanteric fractures did not vary. No change was observed in the mean age of patients with cervical fractures, but the mean age of women with A12 trochanteric fractures was significantly higher in 1999-2000 than in 1989-1990 (P < 0.05).