Nailing vs. plating in comminuted proximal ulna fractures - a biomechanical analysis.

BACKGROUND: Comminuted proximal ulna fractures are severe injuries with a high degree of instability. These injuries require surgical treatment, usually angular stable plating or double plating is performed. Nailing of proximal ulna fracture is described but not performed regularly. The aim of this study was to compare a newly developed, locked proximal ulna nail with an angular stable plate in an unstable fracture of the proximal ulna. We hypothesize, that locked nailing of the proximal ulna will provide non-inferior stability compared to locked plating. METHODS: A defect fracture distal to the coronoid was simulated in 20 sawbones. After nailing or plate osteosynthesis the constructs were tested in a servo-pneumatic testing machine under physiological joint motion (0°-90°) and cyclic loading (30 N - 300 N). Intercyclic osteotomy gap motion and plastic deformation of the constructs were analyzed using micromotion video-analysis. RESULTS: The locked nail showed lower osteotomy gap motion (0.50 ± 0.15 mm) compared to the angular stable plate (1.57 ± 0.37 mm, p < 0.001). At the anterior cortex the plastic deformation of the constructs was significantly lower for the locked nail (0.09 ± 0.17 mm vs. 0.39 ± 0.27 mm, p = 0.003). No statistically significant differences were observed at the posterior cortex for both parameters. CONCLUSIONS: Nail osteosynthesis in comminuted proximal ulna fractures shows lower osteotomy gap motion and lower amount of plastic deformation compared to locking plate osteosynthesis under laboratory conditions.

Complex radial head and neck fractures treated with modern locking plate fixation.

BACKGROUND: Internal fixation of complex radial head and neck (CRHN) fractures is difficult, and postoperative complications are common. This study evaluated elbow function and patient clinical status after internal fixation of CRHN fractures with modern locking plates. METHODS: We included 40 patients with 41 fractures (1 bilateral lesion). In 25 patients (61%), a concomitant injury was found. Patients were an average age of 46 years (range, 22-70 years). The mean follow-up time was 36 months (range, 2-70 months). Postoperative assessments included evaluation of range of motion, functional scores, and radiologic findings. We assessed fracture healing, surgical complications, revision surgery, and the need for metal removal. RESULTS: Of the 34 fractures available for follow-up, 33 (97%) healed well. The mean extension deficit was 6° (range, 0°-30°). The average elbow flexion was 134° (range, 90°-160°), pronation was 70° (range, 30°-90°), and supination was 64° (range, 20°-90°). The Mayo Elbow Performance Score showed a mean of 90 points (range, 65-100 points). We observed no "poor" results. The mean Disability of Arm, Shoulder and Hand score was 16.5 (range, 2.5-58.3; n = 29). All patients continued activity without daily analgesics. There were 12 (34%) complications. In 11 (32%) patients, the plate was removed. CONCLUSIONS: CRHN fractures fixed with modern locking plates and treated as an osseoligamentous lesion exhibited promising midterm results. The new fixation devices represent an improvement in the treatment of this difficult and common fracture while reducing the need for joint replacement or radial head resection. Diagnosis and treatment of concomitant injuries should be emphasized.

Space available for trans-sacral implants to treat fractures of the pelvis assessed by virtual implant positioning.

INTRODUCTION: The use of trans-sacral implants to treat fractures of the sacrum is limited by the variable pelvic anatomy. We were interested in how many trans-sacral implants can be placed per pelvis? If a trans-sacral implant cannot be placed in S1, where is the cortex perforated, and is the use of sacroiliac screws safe in these pelves? MATERIALS AND METHODS: 3D pelvic models were created from CT scans of 156 individuals without fractures (92 European and 64 Japanese, 79 male and 77 female, mean age 66.7 ± 13.7 years). Trans-sacral implants with a diameter of 7.3 mm were positioned virtually with and without a surrounding safe zone of 12 mm diameter. RESULTS: Fifty-one percent of pelves accommodated trans-sacral implants in S1 with a safe zone. Twenty-two percent did not offer enough space in S1 for an implant even when ignoring the safe zone. Every pelvis had sufficient space for a trans-sacral implant in S2, in 78% including a safe zone as well. In S1, implant perforation was observed in the sacral ala and iliac fossa in 69%, isolated iliac fossa perforation in 23% and perforation of the sacral ala in 8%. Bilateral sacroiliac screw placement was always possible in S1. CONCLUSIONS: The use of trans-sacral implants in S1 requires meticulous preoperative planning to avoid injury of neurovascular structures. S2 more consistently offers space for trans-sacral implants.

Fragility fractures of the sacrum occur in elderly patients with severe loss of sacral bone mass.

INTRODUCTION: Patients suffering from osteoporosis-associated fragility fractures of the sacrum (FFS; also termed sacral insufficiency fractures) are increasingly observed. They have typical fracture patterns with fracture lines located in the sacral ala. When treating these patients operatively, iliosacral screw loosening is not uncommon. We aimed to study the sacral bone mass in patients presenting with a FFS using 3D statistical models. MATERIALS AND METHODS: 3D models of averaged Hounsfield units (HU) were generated based on CT scans from 13 patients with a unilateral FFS (mean age 79.6 years; 11 females, 2 males). The control group without fractures consisted of 28 males and 32 females (mean age of 68.3 years). A virtual bone probe along the trans-sacral corridors S1 and S2 was taken. RESULTS: The bone mass distribution in the fractured sacra was similar to the control group, however, with overall lower HU. Large zones of negative HU were located in the sacral ala. In the fractured sacra, the HU in the sacral ala was significantly lower on the non-injured side when comparing to the fractured side (p < 0.001) as well as compared to the non-fractured group (p < 0.001). Low bone mass was observed in sacral body S1 (40 HU) and S2 (20 HU). CONCLUSIONS: The extensive area of negative HU may explain the fracture location in the sacral ala. The low HU in the sacral bodies advocates the use of trans-sacral implants or augmented iliosacral screws to enhance the strength of fracture fixation. The increased HU in the fractured ala could be explained by fracture-asssociated hemorrhage and can be used as a diagnostic tool.

Is the novel olecranon tension plate a valid alternative to tension band wiring of olecranon fractures? A biomechanical study on cadaver bones.

INTRODUCTION: Tension band wiring (TBW) used for olecranon fractures is afflicted with a high rate of complications. The aim of this study was to compare the stability of the TBW versus an alternative, novel low-profile olecranon tension plate (OTP) with angular stable screws in a simulated complex fracture model. MATERIALS AND METHODS: Nine fresh-frozen pairs of cadaver proximal ulnae with an oblique osteotomy and an additional wedge fragment simulating an unstable fracture were tested. The TBW and OTP were implanted pairwise. The elbow motion was simulated in a single-muscle model and ranged from full extension to 90° of flexion. The pulling force of the triceps tendon ranged from 50 to 200 N. The displacement of the fracture fragments was measured with a video motion analysis system over 304 cycles. Data were assessed statistically using the Wilcoxon signed-rank test. RESULTS: The cyclic loading tests showed mean loosening of the fracture fragments at the articular surface of 0.56 mm using TBW (SD 0.65) and 0.15 mm for OTP (SD 0.39). There was no statistical significance in loosening between the two constructs (p = 0.31). No plate breakage or screw loosening occurred. CONCLUSIONS: The low-profile OTP, using the principles of pre-tensioning, lag, cortical, and angular stable screws together, demonstrated similar stability after olecranon fracture fixation when compared with the TBW technique and a lag screw in the olecranon fracture model with a third wedge fragment.

Results Of The Treatement Of Intracapsular Femoral Neck Fractures With A New Dynamic Locking Plate.

The purpose of this study was to evaluate the outcomes in patients with intracapsular femoral neck fractures treated with the novel Targon FN implant. Sixty two patients (mean age: 57 years) were included. The clinical and radiological results were investigated. Radiological and clinical followup (mean time: 21,2 months) was available for 51 patients; in 36 patients, Harris Hip Score (HHS) outcome data were additionally assessed. The overall complication rate was 8%. The median Harris Hip Score was 92 (range 30-100). The results of the Harris Hip Score were rated excellent or good in 26 (72%) patients and fair or poor in 10 (28%). The HHS was correlated significantly with age at trauma, time from admission to operation, preexisting cardiovascular risk factors and disease of the ipsilateral leg. The positive experience with Targon FN suggests that this implant is an advance in treatment of intracapsular femoral neck fractures with head-preserving surgery.

Olecranon tension plating or olecranon tension band wiring? A comparative biomechanical study.

PURPOSE: The complication rate of a tension band wiring (TBW) used for the internal fixation of olecranon fractures remains high. The aim of this study was to compare the stability of a novel olecranon tension plate (OTP) with TBW in a simulated fracture model. METHODS: We tested 12 fresh frozen-pairs of cadaver proximal ulnae treated with OTP and TBW under cyclic loading. The elbow motion ranged from full extension to 90° of flexion, and the pulling force of the triceps tendon ranged from 50 to 350 N. The displacement of the fracture fragments was measured continuously. Data were assessed statistically using the Wilcoxon test with significance level of p < 0.05. RESULTS: The cyclic loading tests showed median displacements of the fracture fragments of 0.25 mm using OTP and 1.12 mm for TBW. Statistical analysis showed the difference to be substantial (p = 0.086) but not statistically significant. No plate breakage or screw loosening occurred. CONCLUSIONS: The concept of replacing prominent K-wires at the proximal end of the ulna using an low-profile plate with classical lag and multidirectional angle-stable screws demonstrated biomechanical advantages over TBW.

Distal humerus hemiarthroplasty of the elbow for comminuted distal humeral fractures in the elderly patient.

BACKGROUND: The purpose of our study was to evaluate the objective and subjective outcomes, as well as the radiographic results after elbow hemiarthroplasty (HA) for comminuted distal humerus fractures in elderly patients. METHODS: Ten female patients with a mean age of 75.2 years were treated with elbow HA either for osteoporotic, comminuted distal humerus fractures (n = 8) or for early failed osteosynthesis of distal humerus fractures (n = 2). The mean follow-up period was 12.1 months. All patients were examined and evaluated using the Mayo Elbow Performance Score and the Disabilities of the Arm, Shoulder, and Hand score. Radiographic postoperative outcomes were assessed performing anteroposterior and lateral radiographs of the injured elbow. RESULTS: According to the Mayo Elbow Performance Score, nine patients achieved "good" to "excellent results" and only one patient revealed a "fair" clinical outcome. The mean Disabilities of the Arm, Shoulder, and Hand score was 11.5 (range, 0-30). The flexion of the affected elbow was 124.5° (range, 95-140°), the extension deficit was 17.5° (range, 5-30°), the pronation was 80.5° (range, 60-90°), and the supination was 79.5° (range, 50-90°). The following postoperative complications were seen: one triceps weakness, one transient ulnar nerve irritation, one superficial wound infection, and two heterotopic ossifications. None of the patients required explantation of the prosthesis. There was no evidence of loosening, radiolucency, or proximal bone resorption, whereas one patient developed progressive osteoarthritis of the proximal ulnar and radial articulation. CONCLUSIONS: Elderly patients treated with elbow HA revealed good to excellent short-term clinical outcomes. A high rate of complications occurred but most complications found were minor and reoperation rate was low. Our results must be regarded as a report on our first experience with HA. As cartilage wear is just a question of time especially in active patients, we cautiously recommend HA only for elderly and multimorbid low-demand patients.

Nailing of proximal ulna fractures: biomechanical comparison of a new locked nail with angular stable plating.

PURPOSE: Proximal ulna fractures are common injuries and frequently treated with angular stable plating. This surgical option shows good functional results. Relevant drawbacks such as large soft tissue exposure, compromised blood supply of fracture fragments and disturbing osteosynthetic material are described. The aim of this study was to compare a new locked proximal ulna nail with angular stable plating in a biomechanical testing setup for extraarticular proximal ulna fractures. METHODS: Ten pairs of sawbones with a Jupiter type IIB proximal ulna fracture (OTA 2U1A3.1) were tested after osteosynthesis with the mentioned implants in a servo-pneumatic testing machine. The testing setup simulates physiological joint motion (0°-90°) under cyclic loading (30-300 N). Primary stability and loosening of both constructs were quantified using micromotion video-analysis after 608 test cycles. RESULTS: The micromotion analysis showed significantly higher primary stability of the locked nail (0.29 ± 0.13 mm) compared to the angular stable plate (0.97 ± 0.30 mm, p < 0.001). Both implants showed a low amount of loosening after completion of the test cycles. The construct with the locked nail (0.08 ± 0.06 mm) showed significantly lower dislocation of the fragments measured at the anterior cortex (plate 0.24 ± 0.13 mm, p < 0.001). CONCLUSION: Nailing of proximal ulna fractures shows significantly higher primary stability and lower loosening compared to angular stable plating in our testing setup.

Nailing of diaphyseal ulna fractures in adults-biomechanical evaluation of a novel implant in comparison with locked plating.

BACKGROUND: Adult forearm fractures require surgical treatment in most cases. Open reduction and internal fixation with plate osteosynthesis is the therapy of choice. Intramedullary fixation offers several advantages compared to plate fixation but is not routinely used. The aim of our study was to compare a newly designed ulna nail with angular stable plating in a biomechanical testing setup of an ulna shaft fracture with a diaphyseal defect. METHODS: Ten pairs of sawbones with a defect osteotomy of the ulna shaft (OTA 2U2C3) were fixed with an interlocked nail or locked plate osteosynthesis. The constructs were tested under four-point bending, torsional loading and axial loading in a servo-pneumatic testing machine to compare the stiffness of both stabilization methods. RESULTS: The nail constructs show lower yet sufficient bending stiffness (62.25 ± 6.64 N/mm) compared to the plate constructs (71.2 ± 5.98 N/mm, p = 0.005). The torsional loading test shows superior stiffness of the plate constructs (0.24 ± 0.03 Nm/deg vs. 0.1 ± 0.01 Nm/deg; p < 0.001), while the axial loading shows superior stiffness of the nail constructs (1028.9 ± 402.1 N/mm vs. 343.9 ± 112.6 N/mm; p < 0.001). CONCLUSIONS: Intramedullary nailing of ulna shaft fractures obtains sufficient but lower stability in bending and torsional loading when compared to rigid angular stable plating and could be an alternative technique to plate fixation. The lower stability and the closed stabilization technique allow for a rapid periosteal healing, which is not present in stiffer constructs.

Impact of Different Screw Designs on Durability of Fracture Fixation: In Vitro Study with Cyclic Loading of Scaphoid Bones.

PURPOSE: The use of new headless compression screws (HCSs) for scaphoid fixation is growing, but the nonunion rate has remained constant. The aim of this study was to compare the stability of fixation resulting from four modern HCSs using a simulated fracture model to determine the optimal screw design(s). METHODS: We tested 40 fresh-frozen cadaver scaphoids treated with the Acumed Acutrak 2 mini (AA), the KLS Martin HBS2 midi (MH), the Stryker TwinFix (ST) and the Synthes HCS 3.0 with a long thread (SH). The bones with simulated fractures and implanted screws were loaded uniaxially into flexion for 2000 cycles with a constant bending moment of 800 Nmm. The angulation of the fracture fragments was measured continuously. Data were assessed statistically using the univariate ANOVA test and linear regression analysis, and the significance level was set at p < 0.05. RESULTS: The median angulation of bone fragments φ allowed by each screw was 0.89° for AA, 1.12° for ST, 1.44° for SH and 2.36° for MH. With regards to linear regression, the most reliable curve was achieved by MH, with a coefficient of determination of R2 = 0.827. This was followed by AA (R2 = 0.354), SH (R2 = 0.247) and ST (R2 = 0.019). Data assessed using an adapted ANOVA model showed no statistically significant difference (p = 0.291) between the screws. CONCLUSIONS: The continuous development of HCSs has resulted in very comparable implants, and thus, at this time, other factors, such as surgeons' experience, ease of handling and price, should be taken into consideration.

Mobilization of CD34+-progenitor cells in patients with severe trauma.

Circulating CD34+ progenitor cells () gained importance in the field of regenerative medicine due to their potential to home in on injury sites and differentiate into cells of both endothelial and osteogenic lineages. In this study, we analyzed the mobilization kinetics and the numbers of CD34+, CD31+, CD45+, and CD133+ cells in twenty polytrauma patients (n = 13 male, n = 7 female, mean age 46.5±17.2 years, mean injury severity score (ISS) 35.8±12.5 points). In addition, the endothelial differentiation capacity of enriched CD34+cells was assessed by analyzing DiI-ac-LDL/lectin uptake, the expression of endothelial markers, and the morphological characteristics of these cells in Matrigel and spheroid cultures. We found that on days 1, 3, and 7 after a major trauma, the number of CD34+cells increased from 6- up to 12-fold (p<0.0001) over the number of CD34+cells from a control population of healthy, age-matched volunteers. The numbers of CD31+ cells were consistently higher on days 1 (1.4-fold, p<0.01) and 7 (1.3-fold, p<0.01), whereas the numbers of CD133+ cell did not change during the time course of investigation. Expression of endothelial marker molecules in CD34+cells was significantly induced in the polytrauma patients. In addition, we show that the CD34+ cell levels in severely injured patients were not correlated with clinical parameters, such as the ISS score, the acute physiology and chronic health evaluation II score (APACHE II), as well as the sequential organ failure assessment score (SOFA-2). Our results clearly indicate that pro-angiogenic cells are systemically mobilized after polytrauma and that their numbers are sufficient for the development of novel therapeutic models in regenerative medicine.