Eero Waris

Bioabsorbable miniplating versus metallic fixation for metacarpal fractures.

Bioabsorbable implants offer an attractive alternative to metallic implants to stabilize small bone fractures in the hand. Self-reinforced bioabsorbable miniplating for metacarpal fractures was studied in bones from cadavers and compared with standard metallic fixation methods. One hundred twelve fresh-frozen metacarpals from humans had three-point bending and torsional loading after transverse osteotomy followed by fixation using seven methods: (1) dorsal and (2) dorsolateral 2-mm self-reinforced polylactide-polyglycolide 80/20 plating, (3) dorsal and (4) dorsolateral 2-mm self-reinforced poly-L/DL-lactide 70/30 plating, (5) dorsal 1.7-mm titanium plating, (6) dorsal 2.3-mm titanium plating, and (7) crossed 1.25-mm Kirschner wires. In apex dorsal and palmar bending, dorsal self-reinforced polylactide-polyglycolide and poly-L/DL-lactide plates provided stability comparable with dorsal titanium 1.7-mm plating. When the bioabsorbable plates were applied dorsolaterally, apex palmar rigidity was increased and apex dorsal rigidity was decreased. Bioabsorbable platings resulted in higher torsional rigidity than 1.7-mm titanium plating and in failure torque comparable with 2.3-mm titanium plating. Low-profile selfreinforced polylactide-polyglycolide and poly-L/DL-lactide miniplates provide satisfactory biomechanical stability for metacarpal fixation. These findings suggest that bioabsorbable miniplating can be used safely in the clinical stabilization of metacarpal and phalangeal fractures.

Bioabsorbable fixation devices in trauma and bone surgery: current clinical standing

Bioabsorbable fixation devices are increasingly used in trauma, orthopedic and craniomaxillofacial surgery. The devices are essentially made of polylactic acid and/or polyglycolic acid polymers. Ultra-high-strength implants are manufactured from such polymers using self-reinforcing techniques. Implants are available for stabilization of fractures, osteotomies, bone grafts and fusions, as well as for reattachment of ligaments, tendons, meniscal tears and other soft tissue structures. As these implants are completely absorbed, the need for a removal operation is overcome and long-term interference with tendons, nerves and the growing skeleton is avoided. The risk of implant-associated stress shielding, peri-implant osteoporosis and infections is reduced. Implants do not interfere with clinical imaging. Current clinical use of bioabsorbable devices is reviewed.

Poly-L/D-lactide (PLDLA) 96/4 fibrous implants: histological evaluation in the subcutis of experimental design.

Poly-L/D-lactide (PLDLA) 96/4 fibrous implants have been introduced to engineer functional fibrous constructions in situ. The current study was undertaken to evaluate the guidance of the fibrous tissue formation and the tissue reaction of porous PLDLA 96/4 scaffolds implanted in subcutaneous tissue. Three various PLDLA 96/4 knitted-mesh scaffolds (Loose, Ordinary, and Dense) were implanted subcutaneously in 32 rats, and followed-up from 3 days until 48 weeks postsurgery. Histological examination showed that PLDLA 96/4 scaffolds provided a structurally supporting element for 48 weeks. They were filled with fibrous tissue by 3 weeks. During the follow-up, loose connective tissue was organized into dense connective tissue with thick collagen bundles. At 48 weeks, no statistically significant difference was found in the amount of loose or dense connective tissue between the scaffold groups of various porosities, although the tendency for higher amounts of loose connective tissue was seen in the Loose type scaffolds. PLDLA filament diameters were 121 &mgr;m at 2 weeks, 119 &mgr;m at 24 weeks and 116 &mgr;m at 48 weeks (P = 0.03 between 2 and 48 weeks). Porous PLDLA scaffold induced fibrous tissue formation in situ. This can be exploited in engineering fibrous tissue constructs in vivo for tissue support or replacement purposes.

Percutaneous, Intramedullary Fracture Reduction and Extension Block Pinning for Dorsal Proximal Interphalangeal Fracture-Dislocations

PURPOSE A percutaneous, intramedullary fracture reduction technique for treatment of unstable dorsal fracture-dislocation of the proximal interphalangeal (PIP) joint is described and the clinical and radiological results are reported. METHODS We conducted a retrospective clinical follow-up of 16 patients with 18 dorsal fracture-dislocations of the PIP joint. After closed joint reduction, we used an extension block K-wire to maintain the joint reduction. Impacted volar articular fragments were reduced percutaneously under fluoroscopy control using a pre-bent K-wire inserted through the intramedullary canal of the middle phalanx. The patients initiated passive range of motion exercises immediately after surgery. After a mean of 3 weeks, we removed the extension block K-wire and allowed free mobilization. We examined 13 patients with 15 injured fingers at a mean 5-year follow-up (range, 1-8 y). RESULTS Radiographic reduction of the joint dislocation was achieved and maintained. The mean articular step-off decreased from 2.1 mm (range, 1.6-3.1 mm) to 0.5 mm (range, 0.0-1.2 mm). At the final follow-up, active PIP motion averaged 83° (range, 65° to 97°) with a mean flexion contracture of 3° (range, 0° to 15°). The mean visual analog scale score for digit pain was 1/10. The mean Disabilities of the Shoulder, Arm, and Hand score of 4/100 indicated little functional impairment. CONCLUSIONS Percutaneous, intramedullary reduction of the impacted volar articular fragments associated with unstable, dorsal fracture-dislocation of the PIP joint restores joint congruence and function. TYPE OF STUDY/LEVEL OF EVIDENCE Therapeutic IV.

Transphyseal bioabsorbable screws cause temporary growth retardation in rabbit femur.

A self-reinforced bioabsorbable poly-L-lactide/polyglycolide (SR-PLGA) 80/20 screw 2.0 mm in diameter was implanted transphyseally across the distal growth plate of the right femur in 24 immature rabbits. Radiologic evaluation revealed a mean shortening of 3.1 mm at 3 weeks, 11.1 mm at 6 weeks, 9.3 mm at 24 weeks, 9.0 mm at 48 weeks, and 12.6 mm at 72 weeks compared with the intact contralateral femur. In 13 control rabbits, drilling without screw placement did not cause any statistically significant femoral shortening. Therefore, the transphyseal SR-PLGA 80/20 screw caused growth retardation for 6 weeks postoperatively, after which the normal growth tendency was recovered until the growth plate was closed. The duration of temporary growth retardation correlated with that of strength retention of the SR-PLGA 80/20 copolymer. These findings suggest that SR-PLGA 80/20 screws can be applied in transphyseal bone fixation. The use of bioabsorbable screws for temporary epiphysiodesis seems attractive but requires further study.

Long-term bone tissue reaction to polyethylene oxide/polybutylene terephthalate copolymer (Polyactive®) in metacarpophalangeal joint reconstruction

The poly-L/D-lactide 96/4 joint scaffolds are used to engineer fibrous tissue joints in situ for the reconstruction of metacarpophalangeal joints. In this experimental study, a supplementary elastomeric stem made of Polyactive 1000PEO70PBT30 (a segmented block copolymer of polyethylene oxide and polybutylene terephtalate with 70/30 PEO/PBT ratio) was used to anchor the joint scaffold in the arthroplasty space. Eleven resected fifth metacarpophalangeal joints of minipig were reconstructed and evaluated radiologically and histologically for 3 years. Plain joint scaffold and Swanson silicone implant arthroplasties (11 of each) in metacarpophalangeal joints of minipig served as controls. Altogether fore limbs of eighteen minipigs were operated for the study. Deleterious tissue reaction with dramatic signs of osteolysis and inflammatory foreign-body reaction was observed around the Polyactive stems. The mean maximum diameter of the osteolytic stem cavity was statistically wider when compared to the mean maximum diameter of Swanson implant group during the first postoperative year. Numerous osteoclasts were found at the margins of the osteolytic areas. No direct bone contact could be seen. At 1 year osteoblastic regeneration and formation of new trabecular bone followed. Finally the foreign-body reaction settled, but the adjoining bones were at this stage highly sclerotic and composed of coarse trabeculae. In contrary to previous in vivo studies suggesting biocompatibility, osteoconductivity and capability to bond to bone, Polyactive 1000PEO70PBT30 stem in this setting caused massive osteolytic lesions and foreign-body reactions.

Alloplastic injectable biomaterials for soft tissue augmentation: a report on two cases with complications associated with a new material (DermaLive) and a review of the literature

A wide variety of biological and alloplastic injectable biomaterials are available for soft tissue augmentation, but the ideal material has not yet been discovered. Biological materials such as collagen and hyaluronan yield temporary results, while injectable alloplasts are apt to cause varying degrees of foreign body reactions that may result in lumps and chronic inflammation.We present two cases (one is the first filed case in the world) of migratory subcutaneous inflammatory masses secondary to injection of acrylic hydrogel (DermaLive), which is an alloplastic biomaterial recently introduced into the market in Europe. Histology revealed foreign body reaction to acrylic hydrogel with granuloma formation containing multinucleated giant cells. Following this, further reports on complications have been reported elsewhere in Europe. The use and development of injectable materials, as well as alternative methods and future directions are reviewed.

Role and regulation of VEGF and its receptors 1 and 2 in the aseptic loosening of total hip implants

It was hypothesized that vascular endothelial growth factor (VEGF) in fibroblasts participates in aseptic loosening of total hip replacement (THR) implants. Therefore, osteoarthritic (OA) samples (n = 11) were compared with synovial membrane‐like interface tissues from revision THR (n = 10). VEGF‐A and its receptors were stained using streptavidin‐immunoperoxidase method. Their regulation by hypoxia and cytokines were studied in cultured fibroblasts using quantitative real‐time polymerase chain reaction (qRT‐PCR). VEGFR1+ lining cells (p < 0.01), stromal fibroblast‐like cells (p = 0.001) and stromal macrophage‐like cells (p < 0.05) were more numerous in rTHR than in OA. As to VEGFR2+, only stromal fibroblast‐like cells in rTHR outnumbered those found in OA (p < 0.05). VEGFRs in synovial fibroblasts were not affected by hypoxia, but VEGF increased 2.4‐fold (p < 0.05). Interleukin‐4 up‐regulated VEGFR1 expression 23‐fold. This is the first study to describe a difference between rTHR and OA in VEGF receptors, particularly VEGFR1. Hypoxia increased VEGF, but the VEGFR1 increase in the lining and stroma is probably IL‐4 driven, in accordance with the M2‐type macrophage dominance in interface tissues. VEGF/VEGFR system is also affected by hypoxia and may play a role in angiogenesis and bone pathology in aseptic loosening of total hip implants.

Expression of epidermal growth factor and transforming growth factor α in interfacial membranes retrieved at revision total hip arthroplasty

BACKGROUND The interfacial membrane between bone and implant has been shown to be a key tissue in the process of aseptic loosening of total hip arthroplasty. The cells within the interfacial membrane produce numerous inflammatory mediators which, through complex mechanisms, cause periprosthetic osteolysis and aseptic loosening. Both epidermal growth factor (EGF) and transforming growth factor α (TGFα) have similar biological functions. They have been found to stimulate bone resorption. OBJECTIVE To investigate the presence, cellular localisation, and extent of expression of EGF and TGFα in interfacial membrane retrieved from revision total hip arthroplasty and compare it with that in synovial membrane from primary total hip arthroplasty. METHODS Ten interfacial membranes and 10 synovial membranes were stained with avidin-biotin-peroxidase complex for EGF and TGFα. The staining process was done using the Lab Vision Autostainer. The results were measured by a semiautomatic VIDAS image analysis system. RESULTS Immunoreactivity for both EGF and TGFα was found in the endothelial cells of blood vessels, macrophages, and fibroblasts, both in interfacial membranes and synovial membranes. However, the number of EGF (980 (370)) and TGFα (1070 (360)) positive cells per mm2 was greater in interfacial membranes than in the synovial membranes (220 (200), 270 (100); p<0.01). CONCLUSION It is suggested that owing to their increased expression in interfacial membrane, EGF and TGFα may have an important pathogenetic role in stimulating periprosthetic bone resorption in aseptic loosening of total hip arthroplasty.

Unfavourable short-term outcomes of a poly-L/D-lactide scaffold for thumb trapeziometacarpal arthroplasty.

The bioabsorbable poly-L-D-lactide joint scaffold arthroplasty is a recent attempt in the reconstruction of small joints in rheumatoid patients. In this study, we analysed the 1-year clinical, functional and radiologic results of partial trapeziectomy with the poly-L-D-lactide (96/4) joint scaffold in 23 patients with isolated trapeziometacarpal osteoarthritis. The results showed that the procedure provided pain relief and improvement in overall function according to the Quick Disabilities of the Arm, Shoulder and Hand score in most patients. However, radiographs demonstrated a high frequency of osteolysis around the implant. Seven patients developed clinically manifested foreign-body reactions 6 months to 1 year after surgery. The reason for the unexpected tissue reactions may relate to excessive mechanical cyclic loading of the implant. The outcomes of this implant in our patients have not been sufficiently beneficial and we have discontinued use of this implant in isolated trapeziometacarpal osteoarthritis.