The durability of the intrascaphoid compression of headless compression screws: in vitro study.

PURPOSE: To test a new generation of compression screws: the Acumed Acutrak 2 Mini (AA; Acumed, Hillsboro, OR), the Stryker TwinFix (ST; Stryker, Kalamazoo, MI), and the Synthes 3.0 headless compression screw (SH; Synthes, Solothurn, Switzerland). METHODS: We used 40 fresh-frozen human scaphoids for this study. Bone density was measured. A K-wire was inserted centrally. A perpendicular osteotomy was created in the middle third (Herbert B2 fracture). A custom-made load sensor was placed between the bone fragments. All screws were implanted according to the manufacturers' instructions. The Synthes 2.0 cortical screw (SC), implanted as a lag screw, was used as a reference. The compression force during each experiment was digitally monitored for 12 hours while the data were acquired. The data were analyzed using analysis of variance with the Bonferroni correction. RESULTS: Immediately after screw insertion, ST reached 226 N, followed by AA with 191 N, SH with 137 N, and SC with 72 N. After 12 hours, ST displayed the highest residual compression force, 141 N, followed by AA with 121 N, SH with 78 N, and SC with 32 N. The differences were significant for ST and AA compared to SC. The loss of compression force over 12 hours was 39% for ST, 42% for AA, 49% for SH, and 55% for SC. CONCLUSIONS: The new generation of headless compression screws, especially ST and AA, provided significantly higher compression forces after 12 hours, as well as the least loss of compression force over time, in comparison to a classic cortical lag screw. CLINICAL RELEVANCE: A new generation of headless compression screws, by producing higher compression forces, increase stability at the fracture site and might thereby promote bone healing.

[Fractures of the elbow joint]. / Frakturen des Ellenbogengelenkes.

Fractures around the elbow joint comprise fractures of the distal humerus, the radial head, the olecranon and the coronoid process. Combined lesions are particularly demanding for the surgeon. Accurate knowledge of the anatomy and of the biomechanics is an essential requirement for a specific diagnosis and therapy. A stable and painless movable elbow joint is essential for most of the activities of daily living. Risk factors for the development of posttraumatic elbow joint arthrosis are non-anatomically reconstructed joint surfaces, axial malalignment of the joint axis and untreated concomitant injuries. Modern angular stable and anatomically preshaped implants facilitate a biomechanically adequate osteosynthesis and avoid or decrease functional impairment. In consideration of an increasing number of osteoporotic elbow joint fractures, endoprosthetic replacement has gained significance.

Distal humerus fractures in the elderly: osteosynthesis or endoprosthesis? Review of the literature.

Fractures of the distal humerus in adults are rare but challenging for the orthopaedic trauma surgeon. The bimodal distribution reflects the trauma mechanism. While distal humerus fractures are caused by high-energy traumata in young male adults, a fall from a standing height is the most common reason for humerus fractures among elderly females. As a rule, fractures of the distal humerus are treated surgically. In young patients, open reduction and internal fixation (ORIF) with anatomic locking plates are the gold standard. In elderly patients, reconstruction is not always possible, and total elbow arthroplasty (TEA) becomes necessary. The present article provides an overview of the current diagnostic and treatment recommendations. The current literature is reviewed and the results discussed.

[Fractures of the distal humerus in the elderly. Pros and cons of endoprosthetic replacement]. / Distale Humerusfraktur beim älteren Menschen. Pro und Contra endoprothetischer Ersatz.

The intraarticular fracture of the distal humerus in an elderly patient remains a challenge for trauma surgeons. In case of severe co-morbidities and/or osteoporosis stable fixation with screws and plates is difficult and in some cases can be impossible. Even if osteosynthesis is feasible the clinical outcome is still incalculable due to delayed or non-union of the fracture fragments. Endoprosthetic replacement of the elbow joint for comminuted distal humerus fractures has been used for almost 20 years. The clinical results are predominantly excellent or good and better predictable than those of osteosynthesis. There still is no guideline when a prosthesis for the elbow joint should be used. We reviewed the literature and outline the current recommendations for diagnostics and surgical therapy for distal humerus fractures in the elderly.

Traumatic damage to the cartilage influences outcome of anatomically reduced acetabular fractures: a medium-term retrospective analysis.

We reviewed 77 patients with an acetabular fracture, treated operatively through a non-extensile approach after an average time of 45 months. The ilioinguinal approach was chosen in 41, the Kocher-Langenbeck approach in 36 patients. Following the Letournel classification, the most frequent lesions were posterior wall (26%), two-column (22.1%) and anterior column (14.3%) fractures. Subchondral impaction, intra-articular fracture fragments and fracture comminution, called modifiers, could be identified in the preoperative CT-data of 38 patients (49.4%). Patients were operated after an average of 4 days. Average hospital stay was 19 days. Sciatic nerve and peroneal nerve palsy were registered in 5.6%. Deep venous thrombosis was seen in 10.4%, peri-articular ossifications in 7.8%. During the 45-months follow-up, 10.4% patients needed secondary total hip arthroplasty. Using the Merle d'Aubigné score, 15 patients had an excellent, 39 a good, 15 a moderate, and 8 a bad result. In accordance with the Harris Hip Score, 29 patients achieved an excellent, 26 a good, 9 a moderate and 13 a bad result. Twenty of twenty-three (Merle d'Aubigné score) and twenty of twenty-two (Harris Hop Score) patients with moderate or bad results had one or more modifiers. Patients with operatively treated acetabular fractures, who had CT-findings such as subchondral impaction, fracture comminution or intra-articular fracture fragments in their preoperative examination, score significantly lower at middle term in the Harris Hip and Merle d'Aubigné scoring systems.

[Periprosthetic femoral bone reaction after total hip arthroplasty with preservation of the collum femoris : CT-assisted osteodensitometry 1 and 3 years postoperatively]. / Periprothetische femorale Knochenreaktion nach schenkelhalserhaltender Hüftendoprothetik : CT-gestützte Osteodensitometrie 1 und 3 Jahre postoperativ.

BACKGROUND: Short-stemmed cementless femoral components in total hip arthroplasty have been designed to preserve the proximal femoral bone stock by load transfer to the femoral metaphysis. An in vivo method of computed tomography-assisted (CT) osteodensitometry after total hip arthroplasty is presented which differentiates between cortical and cancellous bone density (BD) changes around uncemented femoral components. PATIENTS AND METHODS: Cortical and cancellous periprosthetic femoral BD (mg Ca HA/ml) was determined prospectively in 31 patients at day 10, 1 year and 3 years after total hip arthroplasty with preservation of the collum femoris (C.F.P.-stem, Link, Hamburg, Germany) using computed tomography-assisted osteodensitometry. Clinical results (Harris hip score) and plain x-rays were assessed in all cases. RESULTS: Progressive proximal cortical BD loss was observed between the 1 year (Ø -8%) and 3 year (Ø -22%) postoperative measurements. Distal to the trochanter minor no significant cortical BD changes were observed. Proximal cancellous BD decreased progressively between the 1 year (Ø -33%) and 3 year (Ø -45%) analyses. The Harris hip score improved from 45 points pre-operatively to 93 points at the 3 year follow-up. All x-rays showed signs of stable ingrowth. CONCLUSION: Periprosthetic CT osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling. Progressive proximal cortical and cancellous BD loss indicates that metaphyseal fixation cannot be achieved with the analyzed C.F.P. stem design. The lack of cortical BD loss below the trochanter minor suggests diaphyseal fixation of the implanted stem.

Dynamic biomechanical analysis of different olecranon fracture fixation devices--tension band wiring versus two intramedullary nail systems: an in-vitro cadaveric study.

BACKGROUND: The aim of this study was to develop a test-setup with continuous angle alteration to imitate joint motion for the evaluation of 3 different olecranon fracture fixation devices. METHODS: Twenty-one fresh cadaver upper extremities underwent olecranon fracture by the means of transverse osteotomy and received 3 different fixation systems. Group 1: Tension band wiring according to Weber. Group 2: XS-nail with 9 holes, all locked with 2mm threaded K-wires. Group 3: Olecranon Nailing System with 90 mm length, locked with 2.7 mm screws, a variable angle locking hole for the proximal fragment and a proximal locking end cap. The servo-pneumatical test stand worked with a rotational angle-adjusted and a linear force-adjusted engine. The fracture model was dynamically tested under cyclic loading imitating elbow motion. There was a continuous angle alteration between 0 degrees and 100 degrees of flexion with continuous changing pull force between 25 N and 150 N. Two steel pins were placed in the proximal, two in the distal olecranon fragment for video analysis of the motion between the two pairs of pins. Displacement in the fracture gap was determined after 4 and 300 cycles. FINDINGS: After 300 cycles the displacement in the fracture fixation model was significantly higher in the tension-band-wiring-group than in the XS-nail group and the olecranon-nailing-system-group. INTERPRETATION: Other studies evaluating biomechanical properties of olecranon-osteosynthesis with joint-involvement did not change the force-direction dynamically. We introduce a test-setup with continuous angle alteration to imitate joint motion. This is an important step for accurate biomechanical evaluation of the treatment of different fixation methods in olecranon fractures. The tested nailing systems showed a higher stability in comparison to tension band wiring.