Die additive Zuggurtung der Rotatorenmanschette bei der winkelstabilen Plattenosteosynthese am proximalen Humerus

Suture Augmentation Neutralizes Deforming Muscular Forces in a Simulated 2-Part Osteoporotic Proximal Humeral Fracture Model

OBJECTIVES

To evaluate the contribution that tension-relieving sutures, placed between a proximal humeral locking plate and the rotator cuff muscles, had on preventing varus malalignment in an osteoporotic 2-part proximal humerus fracture model.

METHODS

A 2-part fracture model was created in 8 cadaveric specimens and then fixed with a lateral locking plate. A custom shoulder testing system was used to increase loading through the supraspinatus (SS) tendon to drive varus deformity. Trials were performed with no suture placement; SS only; SS and subscapularis (SB); and SS, SB, and infraspinatus. The primary outcome was contribution of each point of suture fixation to prevention of varus collapse.

RESULTS

Suture augmentation to the SS, SB, and infraspinatus significantly decreased humeral head varus collapse when compared with the plate alone at nearly all loads ( P < 0.05). There were no significant differences in humeral head varus collapse between the 3 suture constructs.

CONCLUSIONS

In our biomechanical evaluation of a simulated osteoporotic 2-part proximal humerus fracture with incompetent medial calcar, tension-relieving sutures placed between a lateral locked plate and the rotator cuff tendons prevented varus malalignment.

Nail Versus Plate: A Biomechanical Comparison of a Locking Plate Versus an Intramedullary Nail With an Angular Stable Locking System in a Shoulder Simulator With Active Muscle Forces Using a Two-Part Fracture Model

OBJECTIVES

To compare a locking compression plate versus an intramedullary nail with an angular stable locking system (ASLS) using a 2-part fracture model in a shoulder test bench.

METHODS

Twelve fresh frozen humeri were used for biomechanical testing in a shoulder simulator. A 2-part fracture model, with and without medial cortical support, was used to compare the locking plate and a nail with an ASLS. The varus impaction, varus per cycle motion, tilt, and tilt per cycle were analyzed.

RESULTS

No significant differences for the resulting forces in the glenoid fossa were evaluated. The stable fracture model showed no significant differences for the 2 groups. The median varus impaction was -0.96 degrees (range -0.55 to -4.26 degrees) in the plate group and 0.5 degrees (range -3.06 to 0.98 degrees) in the nail group, after 500 cycles of cyclic loading in the unstable fracture model. The plate group showed a significantly higher median varus impaction per cycle motion and median varus impaction at the 200th, 300th, and 400th cycle of physiological loading.

CONCLUSIONS

The intramedullary nail with the ASLS could be an alternative for patients suffering from osteoporosis and comorbidities.

Hybrid blade and locking plate fixation for proximal humerus fractures: a comparative biomechanical analysis

BACKGROUND

Open reduction and internal fixation of proximal humerus fractures can be difficult to achieve adequate, complication free results due to osteopenia of the proximal humerus and unstable fracture patterns. This study aimed to compare the biomechanical properties of a novel hybrid fixed angle blade plate (Fx plate) with an established fixed angle locking plate (PHILOS plate).

METHODS

A two-part fracture was simulated in synthetic composite humeri by creating a transverse osteotomy and 10 mm fracture gap at the surgical neck. After treating the fractures with either an Fx plate or a PHILOS plate, humeral head was fixed and the shaft was displaced in a cantilever fashion. For elastic tests, loading was along the frontal and sagittal plane to achieve varus/valgus and extension/flexion, respectively. In plastic tests, loading was in a varus direction to determine the constructs' resistance to varus collapse.

RESULTS

In elastic tests, both construct types had higher peak load and stiffness in extension/flexion than varus/valgus. Fx plate constructs were significantly stiffer than PHILOS constructs in varus/valgus (mean: 7.590/6.900 vs. 6.609/6.091 N/mm; p < 0.001 for both) but significantly less stiff in extension/flexion (8.770/9.541 vs. 9.533/9.997 N/mm; p < 0.001 for extension, p < 0.05 for flexion). In varus plastic tests, significantly higher peak loads were reported for Fx plate than PHILOS (134.391 vs. 115.531 N; p < 0.001).

CONCLUSIONS

In this fracture gap model, humeri implanted with a novel Fx plate provided higher varus/valgus stiffness but lower extension/flexion stiffness than a more traditional proximal humeral locking plate design (PHILOS).

Biomechanical comparison of an angular stable plate with augmented and non-augmented screws in a newly developed shoulder test bench

BACKGROUND

The proximal humeral fracture is one of the most common fractures. Although there are a number of treatment options available, the clinical outcomes in geriatric patients are still unsatisfactory. Therefore, the aim of this study was to investigate the biomechanical behaviour of an angular stable plate with either augmented or non-augmented screws using two different fracture models in a shoulder test bench with active muscle forces.

METHODS

Six paired fresh-frozen humeri were loaded into a shoulder test bench simulating ab- and adduction between 15 and 45° induced by active muscle forces. The bone mineral density was measured by a quantitative CT. A two-part fracture model (stable and an unstable) was used to investigate the different biomechanical behaviours of the PHILOS plate, either utilising cannulated screws, allowing in situ augmentation, or without utilising augmented screws. Four screws were augmented with 0.5ml PMMA cement.

FINDINGS

The in vitro-measured resulting forces in the glenoid fossa were comparable to the in vivo forces generated in shoulder arthroplasties. Under stable conditions, the per cycle motion and varus impaction tilting showed no significant difference. In the unstable state, the augmented group showed a maximum of 0.81° per cycle motion and a maximum varus impaction of -1.46° compared to the non-augmented maximum of 2.31° per cycle motion and maximum varus impaction of -4.26° (P<0.05).

INTERPRETATION

In an unstable fracture model under dynamic testing conditions, augmentation leads to a decreased per cycle motion and varus impaction of the humeral head.

Are polyaxially locked screws advantageous in the plate osteosynthesis of proximal humeral fractures in the elderly? A prospective randomized clinical observational study

OBJECTIVES

To evaluate the results of plate osteosynthesis using either polyaxial or nonpolyaxially locked screw-plate systems in proximal humeral fractures in the elderly.

DESIGN

Prospective, randomized.

SETTING

Level I trauma center.

METHODS

Fifty-six patients (older than 60 years) with isolated, displaced three- and four-part fractures were included. Twenty-five patients (median age, 75.5 years) were randomized to a polyaxial locking screw plate (Group 1), whereas 31 patients (median age, 72 years) were treated with a locking screw plate (Group 2). Follow-up evaluations were performed 3, 6, and 12 months postoperatively using the Simple Shoulder Test, Disabilities of the Arm, Shoulder and Hand score, and Constant score as well as radiographs. The results and the complications were compared between both groups.

RESULTS

Forty-eight patients were available for follow-up (Group 1, 20 of 25; Group 2, 28 of 31). The Simple Shoulder Test, Disabilities of the Arm, Shoulder and Hand, and Constant score improved significantly from 3 to 12 months and did not differ between groups. Twelve months after the index procedure, the Simple Shoulder Test score was 8.6 ± 3.2 points in Group 1 and 9.7 ± 1.8 points in Group 2. The Disabilities of the Arm, Shoulder and Hand score was 17.8 ± 16.2 in Group 1 and 15.7 ± 11.8 in Group 2. The mean Constant score amounted to 73% ± 17% in Group 1 and 81% ± 13% in Group 2. There were six complications in Group 1 and eight in Group 2.

CONCLUSIONS

Both the functional outcomes and the rate of complications after polyaxial locked plate osteosynthesis of proximal humeral fractures in elderly patients were comparable to those treated with nonpolyaxial implants. Despite the theoretical advantages of polyaxial locked plating in proximal humerus fractures, this study could not show a verifiable clinical advantage of these plates.