Acta chirurgiae orthopaedicae
et traumatologiae Čechoslovaca

Acta Chir Orthop Traumatol Cech. 2006; 73(4):243-250 | DOI: 10.55095/achot2006/035

Metodika sledování distribuce otěrových částic UHMWPE v okolních tkáních u TEP kyčelního kloubuPůvodní práce

D. POKORNÝ^1,*, M. ŠLOUF², Z. HORÁK², D. JAHODA¹, G. ENTLICHER³, S. EKLOVÁ³, A. SOSNA¹

¹ Ortopedická klinika 1. LF UK a FN Motol, Praha

² Ústav makromolekulární chemie AV ČR, Praha

³ Katedra biochemie, Přírodovědecká fakulta UK, Praha

PURPOSE OF THE STUDY:
Aseptic loosening of implants is the main complication affecting the longevity of joint prostheses. The highest proportion of loosening occurs due to osteolysis produced by the presence of ultra-high molecular weight polyethylene (UHMWPE) wear particles smaller than 1 μm. These can be identified by microscopic, spectroscopic or light-scattering methods. Here we describe our method for counting wear particles, based on the principle of light scattering.

MATERIAL AND METHODS:
Between 2002 and 2004, we collected samples of polyethylene granuloma in 19 patients who underwent revision total hip arthroplasty (THA) for aseptic loosening. The samples were obtained from strictly defined areas corresponding to the radiographic presentation of periprosthetic zones describes by Gruen and DeLee in THA.
The frozen samples were lyophilized and subjected to delipidation and hydrolyzation procedures in 65 % HNO₃. The top part of solution containing wear particles was blended with isopropanol, and the mixture was filtered through a 10-μm polycarbon membrane. Subsequently, the filtrate was filtered through a 0.1-μm membrane. Membranes with trapped particles, 0.1 to 1.0 μm in size, were sent for particle characterization and quantification.
The number of wear particles was measured by the method based on light scattering with calibration (LSC), using a Beckman Coulter LS230 analyzer that can express particle size distribution in a given volume in percent. The method was based on the fact that each particle reflects rays that can be measured. The medium measured contained an unknown number of UHMWPE particles and a known number of calibration glass beads varying in size. The number of UHMWPE particles was calculated from the known number of calibration beads.

RESULTS:
Because the collected samples were also used to develop the method, comprehensive data was obtained in six patients only.
Particle distribution recorded in the periprosthetic zones in THA varied greatly; up to a five-fold difference in particle concentration was observed between the zones. In five of the six patients, the highest particle concentration was found in zone III.

DISCUSSION:
Seeking a method that would be exact, quick and cheap and would eliminate particle aggregation remains the subject of study for researchers cooperating with clinical practice. At present methods based on weighing isolated particles are used most frequently. We developed the LSC method that, for quantification, utilizes the ability of particles to disperse light, and allows us to calculate the real numbers of UHMWPE wear particles in a medium containing a known number of calibration particles. Although this is an indirect method, it gives more accurate results than the direct weighing of particles.
The advantages of the LSC method involve less demand on sample purity, greater speed and low limits of detection. The method is useful for statistical evaluation of a larger number of samples. The variation in particle distribution in THA found in this study is in agreement with the relevant literature data; it is also in agreement with our assumptions and clinical findings.

CONCLUSIONS:
The authors developed an original method for assessment of UHMWPE wear particles in tissue samples, which is quicker than the methods so far used. In the periprosthetic tissues studied, particles about 1 μm in size were detected; their numbers (about 10¹⁰ particles per gram dry tissue) are in agreement with the literature data. The distribution of particles in periprosthetic zones in THA was uneven. The highest number of particles was found in the neighboring zone III and zone 7, as described by Gruen and DeLee.

Klíčová slova: wear, polyethylene, total hip arthroplasty, light scattering, aseptic loosening, wear particles

Přijato: 2. květen 2006; Zveřejněno: 1. srpen 2006  Zobrazit citaci