Ring-Pins combined with cable cerclage for the fixation of displaced inferior patellar pole fractures

ObjectiveThe study aimed to present the clinical results and complication rates of ring-pins with cable cerclage for treating the inferior pole of patella fracture.MethodA study that retrospectively reviewed consecutive patients of the displaced inferior pole of patella fracture (AO/OTA 34-A1) operated with a ring-pin tension band using cable cerclage between October 2015 and October 2017 was performed. The duration of surgery, motion range of the knee, function outcomes, and complications were recorded.ResultsThe average follow-up of 31 patients was 21 months. The mean operation time was 50 min. Fractures in all 31 patients healed at a mean duration of 8 weeks. There was no infection, no withdrawing of ring-pins, no implant breakage, and no loss of fracture reduction. The mean range of motion was 120°, and no patient complained of implant irritation at the final follow-up. The average Bostman score was 29.0 points, and 28 patients graded clinical outcomes excellent and 3 patients graded clinical outcomes good at the last follow-up.ConclusionsRing-pin combined with cable cerclage for treating the displaced inferior pole of patellar fracture is simple, and the postoperative internal fixation-related complication rate is low. It is a good choice for treating the displaced inferior pole of the patellar fracture

The mechanical benefit of medial support screws in locking plating of proximal humerus fractures.

BACKGROUND: The purpose of this study was to evaluate the biomechanical advantages of medial support screws (MSSs) in the locking proximal humeral plate for treating proximal humerus fractures. METHODS: Thirty synthetic left humeri were randomly divided into 3 subgroups to establish two-part surgical neck fracture models of proximal humerus. All fractures were fixed with a locking proximal humerus plate. Group A was fixed with medial cortical support and no MSSs; Group B was fixed with 3 MSSs but without medial cortical support; Group C was fixed with neither medial cortical support nor MSSs. Axial compression, torsional stiffness, shear stiffness, and failure tests were performed. RESULTS: Constructs with medial support from cortical bone showed statistically higher axial and shear stiffness than other subgroups examined (P<0.0001). When the proximal humerus was not supported by medial cortical bone, locking plating with medial support screws exhibited higher axial and torsional stiffness than locking plating without medial support screws (P ≤ 0.0207). Specimens with medial cortical bone failed primarily by fracture of the humeral shaft or humeral head. Specimens without medial cortical bone support failed primarily by significant plate bending at the fracture site followed by humeral head collapse or humeral head fracture. CONCLUSIONS: Anatomic reduction with medial cortical support was the stiffest construct after a simulated two-part fracture. Significant biomechanical benefits of MSSs in locking plating of proximal humerus fractures were identified. The reconstruction of the medial column support for proximal humerus fractures helps to enhance mechanical stability of the humeral head and prevent implant failure

Titanium Elastic Nail (TEN) versus Reconstruction Plate Repair of Midshaft Clavicular Fractures: A Finite Element Study.

The biomechanical characteristics of midshaft clavicular fractures treated with titanium elastic nail (TEN) is unclear. This study aimed to present a biomechanical finite element analysis of biomechanical characteristics involved in TEN fixation and reconstruction plate fixation for midshaft clavicular fractures.Finite element models of the intact clavicle and of midshaft clavicular fractures fixed with TEN and with a reconstruction plate were built. The distal clavicle displacement, peak stress, and stress distribution on the 3 finite element models were calculated under the axial compression and cantilever bending.In both loading configurations, TEN generated the highest displacement of the distal clavicle, followed by the intact clavicle and the reconstruction plate. TEN showed higher peak bone and implant stresses, and is more likely to fail in both loading configurations compared with the reconstruction plate. TEN led to a stress distribution similar to that of the intact clavicle in both loading configurations, whereas the stress distribution with the reconstruction plate was nonphysiological in cantilever bending.TEN is generally preferable for treating simple displaced fractures of the midshaft clavicle, because it showed a stress distribution similar to the intact clavicle. However, TEN provides less stability, and excessive exercise of and weight bearing on the ipsilateral shoulder should be avoided in the early postoperative period. Fixation with a reconstruction plate was more stable but showed obvious stress shielding. Therefore, for patients with a demand for early return to activity, reconstruction plate fixation may be preferred

The results under four different load tests for the three groups (±sd, n = 10).

a<p>compared with group A, P<0.05;</p>b<p>compared with group B, <i>P</i><0.05.</p

Division of the proximal humerus fracture models.

<p>In group A, proximal humerus fractures were fixed without MSSs (Fig.2a); transverse osteotomies were created along a horizontal line (line A) (Fig. 2d). In group B, proximal humerus fractures were fixed with 3MSSs(Fig.2b); wedge osteotomies were created along a horizontal line(line A) and an oblique line (line B) to simulate medial comminution of the proximal humerus(Fig. 2e). In group C, proximal humerus fractures were fixed without medial cortical support or MSSs(Fig.2c); wedge osteotomies were created identical to group B (Fig. 2f).</p

Shear Failure Mode: humeral shaft fracture (A), humeral head fracture (B) and specimens failed by significant plate bending (C).

<p>Shear Failure Mode: humeral shaft fracture (A), humeral head fracture (B) and specimens failed by significant plate bending (C).</p

von Mises stress distribution in the bone of the three finite element models under both loading conditions.

<p>von Mises stress distribution in the bone of the three finite element models under both loading conditions.</p

Comparison of stiffness tests among three groups under four load steps (a,b) axial stiffness test, (c, d) torsional stiffness test, (e, f) shear stiffness test, (g) failure test.

<p>Fig(Group A> Group B> Group C; <i>P</i>≤0.0207) Fig 4 c Torsional stiffness data for all subgroups. The maximum load of Group C was statistically different from both Group A and Group B, (Group A> Group C, Group B> Group C; *,#, <i>P</i><0.0001). The comparisons of Groups A and B for maximum load were not significantly different (<i>P</i> = 0.6086). Fig 4 d Torsional stiffness data for all subgroups. The torsional stiffness of Group C was statistically different from both Group A and Group B (Group A> Group C, Group B> Group C; *,#, <i>P</i><0.0001). The comparisons of Groups A and B for torsional stiffness were not significantly different (<i>P</i> = 0.2738). Fig 4 e Shear stiffness data for all subgroups. The maximum load showed statistical differences between the groups (Group A> Group B> Group C; <i>P</i>≤0.0044). Fig4 f Shear stiffness data for all subgroups. The shear stiffness of Group A was statistically different from both Group B and Group C (Group A> Group B, Group A> Group C; *,#, <i>P</i><0.0001). The comparisons of Groups B and C for shear stiffness were not significantly different (<i>P</i> = 0.0561). Fig 4 g The load-to-failure of Group A was statistically different from both Group B and Group C (Group A> Group B, Group A> Group C; *,#, <i>P</i>≤0.0131); however, no statistical differences were noted between Group B and Group C (<i>P</i> = 0.3655).</p

The proximal screw distribution and the medial support screws (MSS) for the locking proximal humerus plate.

<p>The proximal screw distribution and the medial support screws (MSS) for the locking proximal humerus plate.</p

Mechanical test modes used to assess the (A) axial stiffness; (B) torsional stiffness; and (C) shear stiffness and load-to-failure of the plated humeral constructs.

<p>Mechanical test modes used to assess the (A) axial stiffness; (B) torsional stiffness; and (C) shear stiffness and load-to-failure of the plated humeral constructs.</p