Introduction

Periprosthetic femur fractures are a serious complication after hip replacement surgery. In an aging population these fractures are becoming more and more common. Open reduction and plate osteosynthesis is one of the available treatment options.

Periprosthetic femur fractures are severe complications after hip arthroplasty. There is a high re-operation rate due to malunion, refracture and stem loosening. Fixation is more rigid when screws are used for proximal fixation of the plate instead of cables. Screws penetrating the cement mantle may damage it and induce loosening of the prosthesis stem.

Objectives

Overlap between the distal tibia and fibula has always been quoted to be positive. If the value is not positive then an injury to the syndesmosis is thought to exist. Our null hypothesis is that it is a normal variant in the adult population.

Introduction: Surgical treatment of most displaced proximal humerus fractures is challenging due to osteoporosis, which makes stable fixation difficult. Locking plates are intended to provide superior mechanical stability. The NCB^® -PH (Non-Contact-Bridging for the Proximal Humerus) plate is a locking plate of the latest generation that allows both open and minimally invasive (MI) application.

Methods: In a prospective multicenter study 131 patients were treated (n = 78 open, n = 53 MI). The open procedure was performed using a standard deltopectoral approach; the MI technique involved percutaneous reduction and an anterolateral deltoid split approach. Clinical and radiological follow-up was obtained 6 weeks, 3, 6 and 12 months after surgery. An iADL (instrumental activities of daily living) score was used for functional assessment, the subjective outcome was measured using VAS (Visual Analogue Scale) for pain and mobility.

Results: Improvement in function (ROM) was statistically significant in both groups (open and MI) postoperatively. Fracture type had the most significant impact on the complication rate. The most frequent complication was intraarticular screw perforation. The open treated group showed a higher complication rate. However, more C-type fractures (AO) were treated with this technique.

Conclusion: The NCB-PH is suitable as a routine method of treatment for proximal humerus fractures. Complication rate and functional outcome are comparable to the literature. The MI technique, which is limited by percutaneous fracture reduction, provides a less invasive option for patients requiring fast recovery. Complex fractures should preferably be treated with the open technique.

Introduction: Since the introduction of locked implants new possibilities in the treatment of proximal humeral fractures have evolved. Despite the success using locked plates recent publications report the cutting of screws through the humeral head in up to 30% of the cases. The distribution of the bone strength in the humeral head is not linear. Can polyaxial screw positioning in areas with higher bone strength reduce the “cutout” rate? Which effect has an inferomedial screw if the medial hinge is not restored?

Methods: 4 groups were formed from 31 fresh frozen proximal humeral cadavers. A polyaxial proximal humeral locking plate was used to perform the tests. A standardised unstable intraarticular fracture was created. Main Outcome measure was the load and cycle where at least one screw was cutting through the cartilage.

Results: Polyaxial screw placement in areas of incresead bone strength compared to random screw placement had no effect on the cutout behaviour (p=0.7). Increased screw number (3 vs. 5) significantly increases the resistance against cutout (p< 0.04). An inferomedial screw significantly increases the resistance to develop a cutout compared to the control groups(p=0.03 and p< 0.05).

Discussion: The placement of an inferomedial screw significantly increases the resistence to develop a cutout in proximal humeral fractures without a medial hinge independently of the total screw number. In addition we could also show that the number of screws in the humeral head has a significant effect on cutout resistance in a human cadaver setup.

Introduction In a Finite Element Analysis we calculated that in order to obtain a dynamic plate osteosynthesis a long plate with few screws and if possible no lag screw must be applied. These principles were employed in most shaft fractures at our institution since January 1999. We present the preliminary results of tibial shaft fractures treated with dynamic plate osteosynthesis.

Methods Forty-seven consecutive patients treated from January 1999 until August 2001 were followed clinically and radiologically. Fractures of the distal third and mid-shaft not suitable for a nail such as anatomical bends or narrow intramedullary canal were fixed with a long plate (titanium LCDCP) and few screws. In eight cases no lag screws were used. Six fractures were open fractures. Two cases needed a local flap for coverage of the defect.

Results There were no deep infections. There was one delayed union necessitating re-osteosynthesis and cancellous bone graft after four months. All other fractures healed within six months. No axis deviation was noticed. Due to the dynamic osteosynthesis all cases without lag screws healed with visible callus formation. However, breakage of three screws was seen.

Conclusion Intramedullary nails have become the gold standard for most tibial shaft fractures. However, a significant risk of malunion is associated with nails and in some anatomical instances a nail is not feasible. Dynamic plate osteosynthesis allows good bone healing with callus formation and restores length, axis and rotation of the bone. We consider it a safe and biological method for the treatment of most tibial shaft fractures.

The main problem of modern total hip replacement is the reduction of wear debris. Hence, new tribological partners such as ceramic on ceramic, metal on highly crosslinked polyethylene and metal on metal have evolved. Of these new combinations metal on metal has the longest history. The early problems of high friction using a “micro-fit” between acetabulum and femoral head have been solved by introducing an optimal clearance between the head and the cup to allow for small deformations of the acetabulum during activities without locking. The annual wear rate of metal on metal combinations has been shown to be extremely low ranging from 2 to 5 micrometers/year only. A further advantage of Metasul may be the “wearing in of small scratches” as well as forgiving slight malpositions of the acetabulum, which is not the case in ceramic – ceramic combinations. However, Metasul should not be implanted in patients with renal failure or severe allergies. Metal-metail pairing has proven a valuable alternative in young and active patients over the last 10 years.

Introduction: For plate osteosynthesis (OS) many surgeons use a rigid fixation which prevents callus formation. The present paper applies biomechanical laws and a FE analysis for optimal screw placement to turn a rigid plate OS into a dynamic and biological OS.

Methods: A Finite Element Analysis was performed. The bone was modeled as a cylinder with an outer diameter of 30 mm and an inner diameter of 22 mm. An E-modul of 18 GPa was assumed for cortical bone. A DC steel plate was modeled with a preload of 300 N for each screw. Fracture motion and stress on the screw head was calculated for different screw placements and a load of 300 N angulated at 30 deg.

Results: The number of screws did not influence fracture motion. This could only be controlled by the distance of the first screw to the fracture site, the use of a lag screw and the material of the plate. When one screw hole was omitted close to the fracture site, motion doubled. Using A lag screw reduced fracture motion dramatically. The stress was greatest at the screw closest to the fracture site.

Conclusions: In order to achieve a dynamic plate OS with callus formation a long plate with a minimal amount of screws and no lag screws should be used. To adjust the flexibility of the OS, the distance of the first screw to the fracture site is the most crucial parameter. Additional screws do not influence the stiffness. The stress is highest at the screw head close to the fracture site. This screw is endangered for fatigue failure. To reduce the stress on this screw it must not be placed oblique and also not eccentric. However, the last screw has little stress and should be placed oblique to increase the pull out strength.

Introduction: There is little data available about numerical analysis of polyethylene particles from regions with different degrees of osteolysis in aseptic loosening of total hip replacements. Hence, it was the purpose of the present study to investigate, whether particles from large ostolitic lesions are different in size or shape to particles from regions with little or no osteolysis.

Methods: during hip revision surgery tissue samples from regions with maximal and minimal osteolysis at the stem and acetabulum were collected in five patients. The samples were examined histologically and numerically for each region. The polyethylene particles were isolated from one gram soft tissue by papain digestion and analyzed with a scanning electron microscope (SEM). Size, elongation, area, form factor and perimeter were calculated for a total of 6526 particles.

Results: The histological examination showed significantly more lymphocytes (p < 0,001), histiocytes (p < 0,01) und giant cells (p < 0,001) in large osteolitic lesions. The numerical SEM analysis also revealed significantly larger particles (p< 0,001) in regions with maximal osteolysis (Median acetabulum 1,44mmm und femur 1,89mmm) than in regions with minimal osteolysis (acetabulum 1,21mmm und femur 0,76mmm).

Discussion: Presently only the small micro particles were thought of importance for aseptic loosening. The present paper showed, that regions with large osteolitic lesions have not only more but also larger particles than small osteolitic lesions. The question arises whether the larger particles and giant cells may have an influence on the progression of osteolysis or not. Furthermore, periprosthetic tissue for wear particle analysis in revision surgery must be harvested from the same region in order to obtain conclusive results.

Fracture healing results in increased markers of bone turnover and callus formation. The exact patterns of these changes after different type and locations of fractures as well as weight bearing are unknown.

Bone markers and the callus index were measured prospectively for 6 month following osteosynthesis of different fractures of the lower limb. Serum and urin samples were collected at day 0, 1, 3, 7 and after 2, 6, 12 and 24 weeks. X-rays were taken direct postoperatively and after 6 and 24 weeks. Labarotory parameters for bone formation were: bone-specific alkaline phosphatase (BnAP), Osteocalcin (OC), procollagen type I N- and type III C-terminal propeptide (PINP, PIIICP); markers for bone resorption were: free and peptid-bound forms of urinary pyridinium crosslinks (Dpd, Pyr,), N – terminal propeptides of type I collagen (NTx). All fractures healed within 6 month without complications.

Results: We present preliminary data obtained from 12 adults (10 male, 2 female, mean age 45±15 years). a great variability of bone formation and resorption markers was observed during the first two weeks, probably due to the type trauma and amount of soft tissue injury. Accelerated bone resorption, and a decrease of bone formation was observed during the first week. Thereafter, an increase in OC and BnAP was noted despite persistently elevated bone resorption markers. With increasing weigth bearing, a decrease of bone resorption markers with unchanged or slightly increasing levels of bone formation markers occured.

Conclusions: No fracture specific trends for changes in bone remodelling markers were observed. Accelerated bone resorption is followed by increased bone formation; the longer and steeper the increase on bone resorption, the later and more pronounced the increase in bone formation. For further evaluation of the relationship between changes in bone remodeling markers and fracture healing, more patients will be included into the ongoing study.