Surgical treatment of fragility sacrum fractures with percutaneous sacroiliac (SI) screw fixation is associated with high failure rates in terms of screw loosening, cut-through and turn-out. The latter is a common cause for complications, being detected in up to 20% of the patients. The aim of this study was to develop a new screw-in-screw concept and prototype implant for fragility sacrum fracture fixation and test it biomechanically versus transsacral and SI screw fixations.

Twenty-seven artificial pelves with discontinued symphysis and a vertical osteotomy in zone 1 after Denis were assigned to three groups (n = 9) for implantation of their right sites with either an SI screw, the new screw-in-screw implant, or a transsacral screw. All specimens were biomechanically tested to failure in upright position with the right ilium constrained. Validated setup and test protocol were used for complex axial and torsional loading, applied through the S1 vertebral body. Interfragmentary movements were captured via optical motion tracking. Screw motions in the bone were evaluated by means of triggered anteroposterior X-rays.

Interfragmentary movements and implant motions in terms of pull-out, cut-through, tilt, and turn-out were significantly higher for SI screw fixation compared to both transsacral screw and screw-in-screw fixations. In addition, transsacral screw and screw-in-screw fixations revealed similar construct stability. Moreover, screw-in-screw fixation successfully prevented turn-out of the implant, that remained at 0° rotation around the nominal screw axis unexceptionally during testing.

From biomechanical perspective, fragility sacrum fracture fixation with the new screw-in-screw implant prototype provides higher stability than with the use of one SI screw, being able to successfully prevent turn-out. Moreover, it combines the higher stability of transsacral screw fixation with the less risky operational procedure of SI screw fixation and can be considered as their alternative treatment option.

Open reduction and internal fixation of proximal humerus fractures with angular stable plates is, beside antegrade nailing of the humerus, a standard procedure. A retrograde nail has been developed to avoid penetrating the rotator cuff and to avoid opening the fracture side during osteosynthesis.

The aim of our biomechanical study was to evaluate if retrograde nailing of proximal humerus fractures is as stable as locking plate osteosynthesis.

The biomechanical properties of 2 implants were tested in 11 human fresh frozen cadaveric humeri pairs. The Retron Nail® and the Philos® plate were implanted after osteotomy. All specimens were suspected to axial and torque load for 1000 cycles in a servo pneumatic testing apparatus.

The Philos® plate had greater torsion stiffness than the Retron® nail, but we found no significance. The Retron® nail had greater axial stiffness but our findings were not statistically significant.

Our study showed, that there are no significant differences between a retrograde nail and locking plate osteosynthesis for proximal humerus fractures concerning axial and torsion deformities. Therefore the retrograde nail is a suitable alternative for fixation of proximal humerus fracture.

The aim of our biomechanical study was to find out whether the prosthetic design, especially of the metaphyseal part, and the type of tuberosity fixation influences the primary stability in shoulder arthroplasty.

Materials and Methods: 16 fresh frozen human cadaveric humeri were dissected until only the rotator cuff remained. A four-part fracture was simulated by osteotomy. In a first step two types of shoulder prosthesis (open stem versus closed stem) were used. The Tornier Aequalis prosthesis (open stem) using suture fixation and the Mathys Affinis fracture prosthesis (closed stem) using cable fixation were implanted according to standard techniques. The specimens were then loaded into a servo-pneumatic testing device in 25° of abduction. In 20 consecutive cycles traction of 40 Newton was alternating exerted on the subscapularis and infraspinatus tendon, while a continuous force of 40 Newton was exerted on the greater tuberosity to simulate the pull of the m. supraspinatus. The motion of the fragments was recorded by 2 high speed cameras. The following parameters were investigated : Failure of osteosynthesis, intertuberosity motion, motion lesser tuberosity-shaft, motion greater tuberosity-shaft, motion metaphysis-shaft. After completing the first series the cable fixation exposed to be more stable. In a second series we compared cable versus suture fixation in the Affinis fracture prosthesis to find out whether the stability was depending on the prosthesis design.

Results:

Series 1: The intertuberosity motion was significantly lower in the cable prosthesis. The tuberosity-shaft motion was significantly lower in the cable group for greater and lesser tuberosity. The metaphysis - shaft motion did not significantly differ in both groups.

Conclusion: Highest primary stability of tuberosity fixation in trauma-arthroplasty of the shoulder was measured in cable fixation and closed stem. We proved that the kind of fixation was the most important factor determing the stability. Metaphyseal design was less important.

Background: The purpose of this study was to compare the stability of the 2.4 mm palmar locking compression plate (LCP) and a new intramedullary nail-plate-hybrid Targon DR (TDR) for dorsally comminuted distal radius fractures.

Methods: An extraarticular 10 mm dorsally open wedge osteotomy was created in 8 pairs of fresh frozen distal radii to simulate an AO-A3-fracture. The fractures were stabilized with one of the fixation constructs. The specimens were loaded axially with 200 N and dorsal-excentically with 150 N. Cyclic loading with 2000 cycles as well as loading to failure were performed under axial loading.

Results: Axial loading revealed that intramedullary osteosynthesis (Targon DR: 369N/mm) was significantly (p=0.017) stiffer than plate osteosynthesis (LCP: 131 N/mm). With 214 N/mm the intramedullary nail was also more stable during dorsal excentric loading than the LCP with 51 N/mm (p=0.012). After the 2000 cycles of axial loading with 150 N the Targon group was still significant stiffer than the LCP group under both loading patterns. Neither group showed a significant change in stiffness after the 2000 cycles. The Targon DR group even showed a slight increase with 435,22 N/mm (p = 0.161), while the LCP group showed a slight decrease with 122.24 N/mm (p = 0.575) during axial loading. Under dorsal excentric loading the Targon group was still significant stiffer with 212.46 N/mm than the LCP group with 44.96 N/mm (p=0.012). The load to failure tests demonstrated again the superiority of intramedullary nailing (625N) when compared to plate osteosynthesis (403N) (p< 0.025).

Conclusions: The study shows that both implants are able to withstand physiological loads occuring under unloaded wrist motion. Neither implant showed a significant loss of stability after 2000 cycles long-term loading. Intramedullary nailing with the Targon DR of a distal A3 radial fracture is biomechanically more stable than volar fixed angle plating with the 2.4 mm LCP under axial and dorsal-excentric loads in our experimental setup.

Introduction: Radial Head Arthroplasty is considered the treatment of choice for unreconstructable radial head fractures. Short-term results in the current literatue are promising. Due to the lack of long-term results, radial head arthroplasty is looked at critically by many surgeons. In our the study we provide the 8.4 years results after treatment with the floating radial head prosthesis by Judet (Tornier, France).

Methods: In our department 19 patients were treated with bipolar radial head arthroplasty between 1997 and 2001. 11 prostheses were implantated primary and 6 secondary. The other two were implanted because of a loosening of a prior implanted prosthesis and one after resection of a vast chondrosarcoma. 12 of these patients − 10 men and 2 women – were now examined retrospectively after 101 months (78–132).

Results: 6 Patients were treated primary, 5 secondary and one was treated because of a vast chondrosarcoma. There were 5 proximal ulna fractures and 8 processus coronoideus fractures as concomitant injuries of the elbow. Following complications were seen: 2 dislocations, 2 capitellar erosions and 4 cases of heterotopic ossifications. According to the Mayo Elbow Performance Score 4 patients achieved an excellent result, 7 a good, and one a satisfactory result. The mean DASH was 13.7 (0–44). No differences were seen between primary and secondary implantation. The flexion arc was 123° (110–140°), the extension deficit was 20° (0–40°), pronation 61° (30–90°) and supination 62° (40–90°).

Conclusion: Our 8.4 years results show that radial head arthroplasty with Judet’s bipolar prosthesis leads to mostly excellent and good – subjective as well as objective – results.

Introduction: The aim of this study was to evaluate the efficacy of the treatment of vertebral burst fractures with kyphoplasty. This minimal-invasive technique has been established for the treatment of osteoporotic compression fractures. The value for the treatment of burst fractures is still under research.

Materials and Methods: Between 2003 and 2006, 31 patients presenting a traumatic vertebral burst fracture Magerl Type A3 of the thoraco-lumbar junction were treated with balloon kyphoplasty. All had a normal neurological examination. Assessment of the patients outcome included subjective evaluation of pain (VAS), evaluation of the clinical function (Oswestry-Score), SF-36 Medical Outcome Survey and radiologic evaluation.

Results: The patients experienced an early pain relief and early mobilisation. Complications such as constriction of the spinal channel were not observed. The morphology of the vertebral body showed minor correction of the malposition.

Conclusion: Kyphoplasty represents an efficient and minimal-invasive alternative for the treatment of burst fractures of the thoraco-lumbar junction. This technique allows an early return to daily activities with almost pain relief and with a low incidence of complications.

Introduction: The aim of this study was to analyze the periprosthetic bone remodeling of the femoral component after implantation of an uncemented taper-design stem using CT-assisted osteodensitometry. This method allows accurate three-dimensional evaluation of cortical and cancellous bone with high resolution.

Material and methods: We followed 21 consecutive Patients with osteoarthritis who received primary total hip replacement using 21 uncemented three-dimensionally shaped taper stems (TiAl6V4-Cerafit, Ceraver, France). CT-evaluation was performed 2 weeks, 1 and 6 years post-op. Bone mineral density (BMD) [mg/ml] was determined separately for both cortical and cancellous bone using a special software.

Results: Mean decrease of cortical BMD in the proximal (metaphyseal) area 6 years post-op was −25%, (1 year post-op −15%). Only slight changes of BMD were observed in the distal (diaphyseal) area. Cancellous BMD decreased progressively from −26% 1 year post-op to −49% 6 years after index operation in the proximal area. Cortical bone density loss was lower and non-progressive at the diaphysis (Ø −7% 1 year, −9% 6 years post-OP) and the distal region (Ø −6% 1 year, −4% 6 years post-OP) of the stem. All stems showed no signs of loosening on plain radiography and good clinical results according to the Harris hip score.

Conclusion: Computertomography assisted osteoden-sitometry is the only method which allows discrimination between periprosthetic cortical and cancellous bone density changes in vivo. The analyzed uncemented stem is anchored at the diaphysis and distal region. Due to the changed biomechanical loading after stem implantation, progressive proximal cancellous bone density loss was measured for the first time in vivo. Its role in the pathogenesis of implant loosening is still unknown and needs to be further elucidated.

Introduction: There is an increasing tendency for internal fixation of proximal metaphyseal fractures. Intra-medullary nailing only recently has been considered to be a valuable option in these cases. Through the development of new reliable implant types, nailing finds increasing acceptance.

Questions: Is intramedually nailing with a new angle stable titanium nail a safe procedure in the treatment of proximal humeral fractures and is it combined with a good outcome?

Material and methods: A prospective international mul-ticenter study with standardized study control focused on the “Proximal Humeral Nail (PHN–Synthes Inc.), possible complications and clinical outcome. 151 fractures had been treated in 11 hospitals, where 72 were A-type, 67 B-type and 12 C-type (AO). There were 37 male, 114 female patients, median age 66 years ranging from 16 to 97 years. The outcome had been measured through Constant-Morley scores and DASH scores. 108 patients could be followed up until 1 year postoperatively.

Results: Important complications were perforation of the articular surface by screw or spiral blade (n=8), pain due to the implant (n=10), dislocation of fragments (n=2), non union (n=2), humeral head necrosis (n=3) and wound infection (n=1). The Constant-Morley score shows in total mean values one year postoperatively 75.3 in the injured and 89.9 in the non-injured side. The DASH score pre-operatively was in total 5.9 and 9.3 one year postoperatively, where the best results could achieve 0 points, the worst 100 points.

Discussion: Analyzing the complications, perforation of the articular surface by screw or spiral blade and pain due to the implant or impingement at the nail base are clearly related the technical failure in performing nailing. Here or the nail has not been introduced profoundly enough or the length for the spiral blade was not determined exactly and probably not controlled intraoperatively. This is due to the individual accuracy of the surgeon. The development of non-union (2/108) shows a ratio equal or even better to what is reported in conservative treatment or plate osteosynthesis. Dislocation of fragments n the other side, show the limit of this procedure, where in multifragmentary fracture type one spiral blade will not be able to fix a fragments. Using additional hardware is possible, but might reduce the effect of an initially low invasive approach. Constant score and Dash-score results perform similar to plate osteosynthesis, where clearly C-type-fractures present the worst prognosis.

Conclusion: Proximal humeral nailing seems to be beneficial in A-type metaphyseal fractures. Even in many B-type fractures it is still a good alternative with limited incision to the plate osteosynthesis.

In C-type fractures it is not advisable as a standard routine, only for experienced surgeons it might be a possible solution in selected cases.

Introduction: The Expert Tibia Nail was designed to address proximal, shaft, segmental and distal tibia fractures in one implant. Multiple locking options in various directions provide more stability and reduce the risk of secondary malalignment. Angle stable cancellous bone locking screws in the tibia head also improve fixation.

We evaluated this new implant in our series in a prospective, multicenter setting.

Methods: 190 patients were treated in 10 participating centers using the Expert Tibia Nail (Synthes). 127 patients suffered polytrauma, 58 presented as open fractures. Within the framework of the study 5 cases were proximal tibia fractures, 108 shaft fractures, 56 distal fractures, and 21 segmental fractures. These were followed-up postoperatively, after 3 months and one year and evaluated radiologically and clinically with regard to malalignment, union rate and complications.

Results: Non union occurred in 9 cases after one year of follow up (n=150). 20 patients showed delayed union. The rate of open and complex fractures was high in this group. Dynamisation was performed in 10 cases. Valgus/varus and recurvatum/antecurvatum malalignment of more than 5 degrees occurred in 13 cases. Stable reduction was achieved in 144 cases. In 4 complex fractures, initial reduction went into malalignment. 2 patients developed a deep infection after 3rd degree open fractures. 34 patients suffered from pain in the operated area. 6 screws broke during the follow-up.

Discussion: The Expert Tibia Nail proved to be an excellent tool to treat tibia fractures. Not only shaft fractures but also complex fractures in the proximal and distal metaphyseal area can be successfully stabilized due to advanced locking options and design of the nail. The rate of malalignment, non-union and complications was low.

The science of tribology concerning hip arthroplasty has mainly dealt with total endoprostheses, whereas measurement values of hemiendoprosthetic implants are rare. The small amount of experimental tribologic data concerning hemiendoprosthetic implants in the form of pendulum trials, animal experiments, in-vivo measurements on human hip joints and pin on disc studies will be reviewed in the following work. The reported frictional coefficients in these studies were between 0,014-0,07. In order to test the friction coefficients of different femur head hemiendoprostheses (ceramic-cobalt chrome – and titanium heads and bipolar endoprostheses) against fresh cadaveric acetabula, the HEPFlEx-hip simulator (Hemi-EndoProsthesis Flexion Extension) was developed. In the simulator, the various hemiendoprosthetic heads are placed on a special cone and tested against a human cadaver acetabulum cast in MCP 47 woodmetal. The plane of movement of the apparatus is uniaxial with a rotating movement of +/− 35 degrees. The force is produced pneumatically dynamic with amounts of up to 5 kN. Newborn calf serum served as a lubricant. Preliminary results showed that the mean friction coefficient at 3 kN loading was μ=0.032–0.07 for ceramic against cartilage and μ=0.024–0.153 for metal against cartilage.

Objective: to study the clinical performance of a new intramedullary nail, which is introduced in a retrograde way, for the treatment of humeral shaft fractures.

Design: prospective, non-randomized multicentrical clinical study.

Setting: Level I trauma centers in 4 European countries.

Patients: In a two year period, 102 humeral shaft fractures in 102 patients were nailed. Seventy-three fresh fractures, 12 pseudarthroses, 3 refractures and 14 pathological fractures were involved. Decision for nailing was taken by each surgeon individually. The diaphysis was defined as the part of the humerus between two centimetres below the surgical neck and five centimetres above the olecranon fossa. Sixty-six fractures were closed: 62 grade I and 4 closed grade II and III. There were also 7 open fractures, 4 grade I, 2 grade II and one grade III.

Intervention: all fractures were stabilized with the new unreamed humeral nail (UHN), which was introduced in a retrograde way.

Main outcome measurements: 42,5% of operations were performed in less than one hour, 82,4% in less than 90 minutes (skin to skin). In four patients (3,9%), additional fissures or fractures occurred on the entry portal, in one patient (1%) an additional diaphyseal fracture occurred during nail insertion. There were 4 (3,9%) secondary radial nerve palsies. Seventy-five fractures could be followed up until fracture healing, 58 fresh fractures, 9 pseudarthroses, 2 refractures and 6 pathological fractures. Five fractures needed more than 8 months for fracture healing, in all these patients (5/75 = 6,7%) secondary surgery was necessary. In three patients, inter-fragmentary compression was used with the UHN, once cancellous bone grafting was performed and in one patient changement of procedure to plate and screw osteosynthesis was considered necessary. Sixty-seven patients (89,4%) showed an excellent shoulder function and 7 (9,3%) an acceptable one, 66 (88,0%) an excellent elbow function and 7 (9,3%) an acceptable one at the time of fracture healing.

Conclusions: The unreamed humeral nail (UHN) is a very elegant device for intramedullary stabilization of fresh and pathological fractures and pseudarthroses. The retrograde approach is safe when the nail is introduced carefully through an appropriate entry portal. In case of good fragment adaptation and sufficient stability, an unproblematic fracture healing can be expected.

We treated 39 patients with fractures of the humeral shaft by closed retrograde locked intramedullary nailing, using Russell-Taylor humeral nails. The mean healing time of all fractures was 13.7 weeks. After consolidation, shoulder function was excellent in 92.3% and elbow function excellent in 87.2%. Functional end-results were excellent in 84.6% of patients, moderate in 10.3% and bad in 5.1%. One patient had a postoperative radial nerve palsy, which recovered within three months. There was additional comminution at the fracture site in three patients (7.7%) which did not affect healing, and slight nail migration in two older patients (5.1%). Two patients (5.1%) needed a second procedure because of disturbed fracture healing. One screw breakage was seen in a patient with delayed union. Retrograde locked humeral nailing appears to be a better solution for the stabilisation of fractures of the humeral shaft than anterograde nailing or plate and screw fixation. We found the complication rate to be acceptable and shoulder and elbow function to recover rapidly in most cases.