Behavior of Hylamer polyethylene in hip arthroplasty: comparison of two gamma sterilization techniques.

Hylamer polyethylene was introduced in the 1990s as an alternative to conventional polyethylene. Its chemical and physical properties, and especially its high crystallinity, were claimed to improve resistance to wear. Initially Hylamer devices were sterilized by gamma radiation in air, then the technique was changed and gamma radiation was performed in the absence of oxygen. Clinical experience has shown the early loosening of some devices made from Hylamer. The aim of this study was to ascertain whether early wear and consequent osteolysis was linked to the sterilization method. We retrospectively compared 31 patients with hip prostheses with Hylamer liners sterilized by gamma radiation in air (group 1) with 30 patients with the same prosthesis, but sterilized in the absence of oxygen (group 2). The groups were similar for sex, age, disease, head diameter and material. Mean follow-up was 84 months and no clinical signs of failure were present. Radiographic measurement revealed that wear of group 1 was significantly greater than that of group 2 (0.23 mm/year vs 0.09 mm/year, p=0.001). Periacetabular and femoral osteolysis in group 1 was significantly greater than group 2. In conclusion, the method of sterilization might have influenced the outcome of Hylamer polyethylene liners.

Isolation and characterization of wear debris generated in patients wearing polyethylene Hylamer inserts, gamma irradiated in air.

Hylamer polyethylene was used in the early 1990s to make hip-joint components. Clinical experience has shown that these components, if sterilized by gamma rays in the presence of oxygen, are easily affected by wear, which then leads to osteolysis. The authors analyzed polyethylene wear particles in seven patients who had received Hylamer polyethylene implants sterilized by gamma rays in air and had suffered prosthetic loosening. The results were compared to those of six controls, who had received traditional polyethylene implants, sterilized by the same method. The frequency distribution of globular and fibrillar particles was similar in both groups (38.5% in Hylamer, 45.2% in controls). The globular particles in the Hylamer samples had a mean area of 0.12 microm2, which was significantly lesser than that of the controls (0.30 microm2). The width of fibrillar particles in the Hylamer samples was significantly lesser than that of the controls. Therefore, the two materials, despite undergoing the same type of sterilization, produced different types of wear, due to their different properties. In conclusion, the difference in the morphology of Hylamer polyethylene wear particles in comparison with PCA might have caused a more intensive biological response, early and massive osteolysis, and therefore, early loosening.

CT-based surgical planning software improves the accuracy of total hip replacement preoperative planning.

The present study is aimed to compare accuracy and the repeatability in planning total hip replacements with the conventional templates on radiographs to that attainable on the same clinical cases when using CT-based planning software. The sizes of the cementless components planned with new computer aided preoperative planning system called Hip-Op and with standard templates were compared to those effectively implanted. The study group intentionally included only difficult clinical cases. The most common aetiology was congenital dysplasia of hip (65.6%). The Hip-Op planning system allowed the surgeons to obtain a preoperative planning more accurate than with templates, especially for the socket. Assuming correct a size planned one calliper above or below that implanted the accuracy increased from 83% for the stem and 69% for the socket when using templates to 86% for the stem and 93% for the socket when using the Hip-Op system. The repeatability of the Hip-Op system was found comparable to that of the template procedure, which is much more familiar to the surgeons. Furthermore, the repeatability of the preoperative planning with the Hip-Op system was consistent between surgeons, independently from their major or minor experience. The study clearly shows the advantages of a three-dimensional computer-based preoperative planning over the traditional template planning, especially when deformed anatomies are involved. The surgical planning performed with the Hip-Op system is accurate and repeatable, especially for the socket and for less experienced surgeons.

Anatomic cementless total hip arthroplasty with ceramic bearings and modular necks: 3 to 5 years follow-up.

Reported here are the results obtained for 216 prosthetic implants in which cementless arthroplasty and a modular neck were used. The advantages to using this method are related to the fact that it may be adapted to a variety of anatomical conditions.

Cementless hip arthroplasty with a modular neck.

The authors report the preliminary results obtained in 347 prosthetic implants with hip arthroplasty with a modular neck. The advantages to using this method are related to the chance to adapt to different anatomical conditions: in particular, in primary arthroplasty a straight neck was used in the majority of cases (83%), while in dysplastic hips a straight neck was used in 47.5% of cases and a retroverse neck (8 degrees or 15 degrees) overall in 40% of cases.

The treatment of anterior recurrent dislocation of the shoulder: the Bankart-Delitala procedure.

The authors report the results of 110 shoulder capsulorrhaphies performed according to the Bankart-Delitala technique. After a mean period of 104 months +/- 63 the clinical results, evaluated on the basis of the Rowe method were excellent-good in 94.6% of cases, and fair-poor in 5.4%. In 83.6% of cases there was no deficit in motility of the shoulder submitted to surgery, in 16.4%, the shoulder presented deficit in extrarotation (exceeding 15 degrees in only 1 case, equal to 0.9%).