Malpositioning of the lag screws by 1- or 2-screw nailing systems for pertrochanteric femoral fractures: a biomechanical comparison of gamma 3 and intertan.

OBJECTIVES: The aim of this investigation was to perform a biomechanical comparison between 1- and 2-screw systems used for the treatment of intertrochanteric fractures for centralized and decentralized placement of femoral neck screws of failure loads, stiffness, survival rates, tip apex distance (TAD), and failure mode. METHODS: As fracture model, an AO 31A2.3 fracture was used. Twelve pairs of human cadaver femora were tested. Femoral neck screws were implanted in the femoral head in center/center, posterior/central, and anterior/superior position in axial/frontal plane. A single-screw system (Gamma 3 Locking Nail; Stryker GmbH & Co. KG) and a 2-screw system (Trigen-Intertan; Smith & Nephew GmbH) were used. To simulate the load in situ, a cyclic load was carried for 10,000 cycles in a material testing machine. If no cyclic failure occurred, femora were loaded until the failure. The systems were compared according to the stiffness, survivability through 10 k cycles, TAD, and load to failure. RESULTS: None of the tested bones failed at center/center location in the decentralized positions 3 Gamma Nail and 2 Intertan specimens failed during cyclic testing. The 2-screw system resisted higher forces in all positions (Gamma: 5370N ± 1924, Intertan: 7650N ± 2043; P = 0.014). CONCLUSIONS: Based on these data, it is clear that both the nail systems showed a higher biomechanical stability with a lower TAD. The 2 specimens that failed with the Intertan in the cyclic tests had a TAD ≥49 mm. The cutout failures that we detected during cyclic testing in the Gamma system had a TAD ≥30 mm. Thus, it is clear that the TAD affects failure independent of the implant used. With a less than ideal lag screw placement, however, the Intertan system with 2 integrated screws was able to withstand higher loads in this study.

Electromagnetic navigation provides high accuracy for transcoracoid-transclavicular drilling.

PURPOSE: A novel radiation-free electromagnetic navigation system (ENS)-based method was developed, and its feasibility and accuracy for transclavicular-transcoracoid drilling procedures were evaluated in an experimental setting. METHODS: Sixteen arthroscopically assisted electromagnetic navigated transcoracoid-transclavicular drilling procedures with subsequent TightRope device implantation were performed on eight human cadavers. Post-operative fluoroscopy and CT-scan analysis were acquired to determine tunnel placement accuracy. Optimal tunnel placement was defined as both the coracoid entry and exit point of the tunnel localized in the centre position of the coracoid base without cortical breach or fracture. RESULTS: Successful tunnel placement was accomplished in all 16 cases. The mean overall operation time was 30.3 ± 5.0 min. Regarding the coracoid exit point, 15 of 16 tunnels (93.8%) were localized in the desired base-centre position. During the navigated drilling procedure, no misguidance of the drill requiring directional readjustments or restarts occurred. No cortical breach, no fractures and no complications occurred. CONCLUSIONS: The electromagnetically navigated transcoracoid-transclavicular drilling procedure used in this study demonstrated high targeting accuracy, required no intraoperative radiographs, was associated with no complications and provided user-friendliness.

Radiological dorsal tilt analysis of AO type A, B, and C fractures of the distal radius treated conservatively or with extra-focal K-wire plus external fixateur.

OBJECTIVE: Fractures of the distal radius are amongst the most common injury patterns. The dorsal tilt represents an important co-factor determining functional outcome. The purpose of this study was to analyze the radiological dorsal tilt and identify critical time frames in conservative and operative treatment of distal radius fractures. MATERIALS AND METHODS: Eighty-seven conservatively treated (hematoma block assisted reduction and splinting) and 37 operatively treated (reduction, extra-focal K-wire fixation, bridging external fixateur) AO type A, B, and C fractures of the distal radius in 124 females were retrospectively analyzed. The dorsal tilt at the initial, post-reduction, and 2 weeks post-reduction stages was correlated with the final radiographic outcome at 6 weeks. RESULTS: Mean initial dorsal tilt was 16.53° in the conservatively treated group and 26.76° in the operatively treated group. Mean dorsal tilt after 6 weeks showed significant differences from the mean initial dorsal tilt at time of presentation within both groups (both groups p < 0.000). No significant differences between the two groups were found after 6 weeks of treatment (p = 0.194) regardless of the underlying AO fracture type. Conservatively treated radius fractures showed a significantly higher slip rate within the first 2 weeks (primary slip rate), whereas the operative group presented a significantly higher slip rate between the 2-week and 6-week radiographic checks (secondary slip rate). CONCLUSION: In terms of dorsal tilt, conservative (cast immobilization) and operative (K-wire fixation plus external fixateur) treatment demonstrated no significant differences at the final radiographic examination (6 weeks) regardless of the underlying AO fracture type. Both treatment groups showed treatment-associated different primary and secondary slip rates, indicating a need for more frequent radiographic checks within these critical time frames.

A comparative biomechanical analysis of fixation devices for unstable femoral neck fractures: the Intertan versus cannulated screws or a dynamic hip screw.

BACKGROUND: First introduced in 2005, the "Intertan" (IT), an intramedullary nail with two cephalocervical screws, has become an increasingly popular option for treating intertrochanteric fractures. The purpose of this study was to identify the utility of this device for stabilization of unstable femoral neck fractures compared with cannulated screws (CS) and a dynamic hip screw (DHS). METHODS: Twenty-four human cadaveric femurs were harvested and assigned to three groups that were matched with regard to bone mineral density (BMD). Standardized Pauwels-Type-III fractures were osteomized with a custom-made saw guide and fixated by an "IT," three CS, or a DHS. All constructs were biomechanically tested in a servohydraulic testing machine with a physiologic mechanical axis loading of the femoral head (700 N), cyclical compression to 1,400 N (10,000 cycles; 2 Hz), and loading to failure. All specimens were compared with respect to the number of survived cycles, mechanical strength, head displacement, load to failure, and failure mechanism. RESULTS: Regardless of the fixation, the mechanical strength of the stabilized femurs was significantly decreased to 71% compared with the intact femurs (100%). During cyclical testing 46% of the constructs (6 CS, 4 DHS, and 1 IT) failed. There was no difference between the mechanical strength of all survived constructs regarding the BMD, but the BMD of the failed specimens was significantly reduced compared with the surviving femurs (0.71 g/cm² ± 0.18 g/cm² vs. 1.07 g/cm² ± 0.33 g/cm²; p < 0.05). IT femurs survived significantly longer than CS specimens (IT, 9,063 cycles ± 2,480 cycles vs. CS, 3,325 cycles ± 3,885 cycles vs. DHS, 5,716 cycles ± 4,448 cycles; p < 0.01), endured higher failure loads (IT, 4,929 N ± 1,105 N vs. CS, 3,421 N ± 20 N vs. DHS, 3,505 N ± 905 N; p < 0.05), and presented a less inferior head displacement (IT, 8.5 mm ± 1.6 mm vs. CS, 16.4 mm ± 6.7 mm vs. DHS, 14.5 mm ± 6.4 mm; p < 0.05). CONCLUSION: Our results suggest that (1) none of the tested devices restore a comparable mechanical strength in the fractured specimens compared with the intact femurs, and (2) the "IT" possesses some biomechanical benefits for internal fixation of unstable femoral neck fractures compared with DHS and CS. Because the IT constructs failed with an inferior femoral neck fracture, complicating the mandatory anchorage of a prosthetic stem in a revision operation, more biomechanical experiments using the IT in the presence of a posterior comminution defect are required, along with clinical outcome studies.

3D fluoroscopic navigated reaming of the glenoid for total shoulder arthroplasty (TSA).

Survival rates for total shoulder arthroplasty are critically dependent on the correct placement of the glenoid component. Especially in osteoarthritis, pathological version of the glenoid occurs frequently and has to be corrected surgically by eccentric reaming of the glenoid brim. The aim of our study was to evaluate whether eccentric reaming of the glenoid can be achieved more accurately by a novel computer assisted technique. Procedures were conducted on 10 paired human cadaveric specimens presenting glenoids with neutral version. To identify the correction potential of the navigated technique compared to the standard procedure, asymmetric reaming of the glenoid to create a version of -10° was defined as the target. In the navigated group, asymmetric reaming was guided by a 3D fluoroscopic technique. Postoperative 3D scans revealed greater accuracy for the eccentric reaming procedure in the navigated group compared to the freehand group, resulting in glenoid version of -9.8 ± 3.8° and -5.1 ± 4.1°, respectively (p < 0.05). Furthermore, deviation from preoperative planning was significantly reduced in the navigated group. These data indicate that our navigated procedure offers an excellent tool for supporting glenoid replacement in TSA.

The treatment of intertrochanteric fractures: results using an intramedullary nail with integrated cephalocervical screws and linear compression.

OBJECTIVE: A new device for the treatment of intertrochanteric fractures that uses 2 cephalocervical screws in an integrated mechanism allowing linear intraoperative compression and rotational stability of the head/neck fragment has been developed. The aim of this study was to describe the results using this device for the treatment of stable and unstable intertrochanteric fractures. DESIGN: Prospective, consecutive. SETTING: Academic Trauma Center. METHODS: Between March 1, 2005, and July 31, 2006, 100 consecutive patients with an intertrochanteric fracture were treated with a new trochanteric antegrade nail (InterTan; Smith-Nephew, Memphis, TN). All living patients were followed up for a minimum of 1 year postoperatively (range 12-27 months). Clinical and radiographic examinations were performed until healing and at the 1-year anniversary of the index procedure. Healing, pain with ambulation, return to activities of daily living, the modified Harris hip score, and Barthel Index were used to evaluate outcomes. RESULTS: The mean age of the patients was 81.2 (+/-11.3) years. Thirty-seven patients died, 12 were too infirmed for follow-up, and 3 could not be located, leaving 48 patients available for final evaluation. The average surgical time was 41 minutes (13-95 minutes). This rose significantly with the complexity of the fracture (OTA/AO classification: A1 versus A3, P = 0.016). All fractures healed within 16 weeks (range 10-16 weeks). Radiographic analysis at healing revealed no loss of reduction, no uncontrolled collapse of the neck, no nonunions, no femoral shaft fractures, and no implant failures. Two cases in the series were poorly reduced and settled into varus malalignment. There was no varus malposition seen in the remaining 46 fractures. The mean prefracture Harris hip score (75.1 +/- 13.4) was significantly reduced at the time of follow-up (70.3 +/- 14.5, P = 0.003); 58% of the patients recovered their prefracture status. No significant difference was seen for the Barthel Index. CONCLUSIONS: The InterTan device appears to be a reliable implant for the treatment of intertrochanteric femoral fractures. Its design provides for stability against rotation and minimizes neck malunions (shortening) through linear intraoperative compression of the head/neck segment to the shaft. As a result of the negligible complication rate and improved clinical outcomes, this implant is now the standard treatment for all intertrochanteric fractures at our institution.

Distal Tibial Fractures: Intramedullary Nailing.

The tibia is an exposed bone with vulnerable soft tissue coverage and is therefore predisposed to local soft tissue problems and delayed bone healing. The objective in distal tibial fracture treatment is to achieve stable fixation patterns with a minimum of soft-tissue affection. Thus, the risk of soft tissue breakdown and bone healing complications is more likely related to open reduction and plating. Percutaneous, minimally invasive intramedullary nailing is a proven fixation mode for fracture stabilization in tibial shaft fractures. Anticipating the pitfalls, intramedullary nailing meets the requirements of the method of choice in distal tibial fracture fixation. In conclusion, intramedullary nailing of distal tibial fractures is a reliable method of fixation, possessing the advantages of closed reduction and symmetric fracture stabilization of an area with a delicate soft tissue situation, but prospective randomized trials are needed to compare modern intramedullary fracture fixation with modern plate fixation in distal tibial fractures.

Mechanical evaluation of different techniques for Achilles tendon repair.

INTRODUCTION: One aim of the surgical treatment of acute Achilles tendon ruptures is to obtain a maximum primary stability of the sutured tendon. Therefore, we investigated the primary stability of sutured human Achilles tendons depending on different applied techniques. METHODS: The strength of 60 repaired cadaveric human Achilles tendons was tested depending on either the suture technique (Bunnell or Kessler), the suture material (PDS-thread or PDS-cord) or an additional plantaris tendon augmentation (PDS-thread with or without augmentation). Following anatomic reconstruction the repaired specimens were loaded to failure. RESULTS: The use of Bunnell's technique resulted in a stronger primary suture stability compared to Kessler's technique. Sutures carried out with a PDS-thread were of lower strength than those accomplished with a PDS-cord (Bunnell: thread 139 N +/- 29.8; cord 291 N +/- 55.2/Kessler: thread 137 N +/- 37.3; cord 180 N +/- 41.1). Sutures performed according to Bunnell's technique with a PDS-thread and an additional autologous plantaris tendon augmentation reached the highest primary stability (326 N +/- 124.9). CONCLUSIONS: The findings identify the Achilles tendon suture with a PDS-cord according to Bunnell's technique as a mechanically strong method. A plantaris tendon augmentation in addition to a PDS-thread can even add more stability to the Achilles tendon suture.