In vitro effects of particulate bone substitute materials on the resorption activity of human osteoclasts.

Much research has been done on bone cells, but only a few studies deal with biomaterial-induced effects on human osteoclasts, which may take on an important role in the successful regeneration of bone. In order to highlight such effects, human peripheral blood mononuclear cells (PBMCs) were extracted from venous blood, differentiated to osteoclasts and then cultured in, the presence of five particulate hydroxyapatite (HA)/ß-tricalcium phosphate (TCP) biomaterials, on bovine bone slices and glass cover slips. The biomaterials, AlgOSS 50/50 (50 % HA/50 % TCP), AlgOSS 20/80 (20 % HA/80 % TCP), Algipore (98 % HA), Cerasorb (100 % TCP) and Bio-Oss (100 % HA) were chosen to assess their influence on cell morphology and numbers. Light microscopic evaluation was performed during ongoing cell culture. After 21 d of cultivation, the biomaterial-induced effects on osteoclastic resorption of the bone slices were evaluated by scanning electron microscopy (SEM). Osteoclast-like cells were identified by TRAP staining. All five biomaterials showed larger area fractions of resorbed bone than the control (5.6 ± 6.8 %), as measured on SEM images. The purely hydroxyapatite-based Algipore (9.8 ± 9.7 %) and Bio-Oss (7.9 ± 8.8 %) showed significantly elevated area fraction rates (p ≤ 0.05) of bone resorption. Light microscope evaluation revealed a significant, but inhibiting effect of Cerasorb (p = 0.05). These data indicated that introducing of small biomaterial hydroxyapatite particles may have improved the performance of bone substitute materials.

Volume changes occurring in postoperative below-knee residual limbs.

Comparative maturation rates of 36 below-knee postoperative, healed amputation residual limbs were observed. Measured were the limb volumes and circumferences. Three methods of residual limb stabilization were employed: 1) elastic wrap; 2) plaster cast and pylon; and, 3) plastic laminate socket and pylon. The limbs receiving the plastic laminate showed the most rapid stabilization, while the elastic wrap did not stabilize. Considerable variance existed in relations between variables. Correlation between limb circumference and volume was poor. However, in general, the rates of change, i.e., the relations between volume and time, and circumference and time, were statistically significant (p less than .05).

Protection of the deltoid to triceps tendon transfer repair sites.

The posterior deltoid muscle was used to replace lost elbow extension in 11 patients with C5 or C6 level tetraplegia. During surgery stainless steel sutures were inserted into the donor muscle, graft, and tendon insertion sites. Over the succeeding time periods (1 month to 2 years) the distances between the various markers were measured. Significant tendon elongation of 23.1 +/- 4.8 mm (mean +/- SEM; n = 6) was observed in patients receiving traditional postoperative care. To reduce the tendon elongation observed, a specially designed armrest was developed and applied the first postoperative day. The armrest was designed to maintain the elbow in 20 degrees flexion and to prevent shoulder adduction. The addition of this armrest to the traditional postoperative protocol resulted in a dramatic decrease of tendon elongation to only 8.4 +/- 3.0 mm (n = 5). Elongation occurred within the first 6 postoperative weeks in the armrest group; in the nonprotected group, elongation continued for several additional months. The majority of the elongation in both groups occurred in the proximal portion of the tendon-graft-tendon unit. Although this study did not explicitly measure strength, we conclude that preventing excessive muscle length change is required to protect repair sites in posterior deltoid to triceps transfer. (J Hand Surg 2000; 25A:144-149.

Regional variation in shear strength of the bone-polymethylmethacrylate interface.

Many investigators consider the polymethylmethacrylate-bone interface the weakest link in the bone-cement-implant system. Push-out tests, frequently used for in vitro evaluation of the bone-cement interface, produced inconsistent results of shear strength. Therefore, a more reliable model for testing the shear failure of the interface was developed. Better understanding of intrinsic variations in bone quality and geometry of endosteal bone at the interface may yield important insight into the patterns of clinical failure of cemented total joint prostheses.