Augmented cerclage wire improves the fixation strength of a two-screw construct for humerus split type greater tuberosity fracture: a biomechanical study

Management of greater tuberosity fracture dislocations of the shoulder

Background

Despite extensive literature dedicated to determining the optimal treatment of isolated greater tuberosity (GT) fractures, there have been few studies to guide the management of GT fracture dislocations. The purpose of this review was to highlight the relevant literature pertaining to all aspects of GT fracture dislocation evaluation and treatment.

Methods

A narrative review of the literature was performed.

Results

During glenohumeral reduction, an iatrogenic humeral neck fracture may occur due to the presence of an occult neck fracture or forceful reduction attempts with inadequate muscle relaxation. Minimally displaced GT fragments after shoulder reduction can be successfully treated nonoperatively, but close follow-up is needed to monitor for secondary displacement of the fracture. Surgery is indicated for fractures with >5 mm displacement to minimize the risk of subacromial impingement and altered rotator cuff biomechanics. Multiple surgical techniques have been described and include both open and arthroscopic approaches. Strategies for repair include the use of transosseous sutures, suture anchors, tension bands, screws, and plates. Good-to-excellent radiographic and clinical outcomes can be achieved with appropriate treatment.

Conclusions

GT fracture dislocations of the proximal humerus represent a separate entity from their isolated fracture counterparts in their evaluation and treatment. The decision to employ a certain strategy should depend on fracture morphology and comminution, bone quality, and displacement.

Greater tuberosity fractures of the humerus: complications and long-term outcomes after surgical treatment

BACKGROUND

Isolated greater tuberosity (GT) fractures typically occur in younger patients following high-energy trauma compared to humeral neck fractures. Surgical treatment is indicated when superior displacement is > 5 mm. This study aimed to assess the complications and long-term outcomes of surgically-treated GT fractures.

METHODS

A retrospective review of 39 patients who underwent surgery from 2010 to 2014 was conducted. The cohort comprised 54.6% females, with an average age of 56.74 years and a median follow-up of 6.71 years. Only 25 patients returned for reevaluation, with functional outcomes assessed using Constant-Murley score.

RESULTS

Women were older than men (63.00 ± 12.15 vs. 48.65 ± 16.93, p = 0.006). 18/39 patients (46.1%) sustained avulsion-type, 1 patient out of 39 (2.6%) depression-type, and 20/39 patients (51.3%) split-type fractures. The mean Constant-Murley score was 84.08 ± 18.36, with higher scores observed in men (p = 0.021). Avulsion-type fractures were related to higher postoperative scores compared to split fractures (p = 0.069). Post-surgical complications occurred in 20.5% of patients, with no differences noted between sexes, fracture types, or procedures.

CONCLUSION

This study enhances understanding of the long-term outcomes of surgically-treated GT fractures, aiding in treatment selection. Interfragmentary screws may be preferable in younger male patients, but are associated with the higher risk of reintervention, particularly in fragile bone. Prospective multicentric studies are warranted to further elucidate long-term results and treatment strategies.

Fracture Line Morphology of Greater Tuberosity Fragments of Neer Three- and Four-Part Proximal Humerus Fractures

OBJECTIVE

In complicated Neer three- and four-part proximal humerus fracture (PHF), greater tuberosity (GT) fragments are often comminuted, and the currently widely used locking plate may not fix GT fragments effectively. A further understanding of morphological characteristics of the GT fragments may help explore new fixation devices. This study aimed to determine the fracture line morphology of the GT fragment of Neer three- or four-part PHF and analyze the location relationship between the locking plate and the GT fragment.

METHODS

Seventy-one three-dimensional computed tomography scans of Neer three- and four-part PHF were retrospectively reviewed between January 2014 and June 2019. Fracture fragments were reconstructed and virtually reduced in the Mimics software, and fracture lines of GT fragments were depicted on a humerus template in the 3-matic software and then were superimposed altogether. The common sites of the GT fracture were identified, and the location relationship between the locking plate and GT fragments was analyzed in a computer-simulated scenario.

RESULTS

The fracture line morphology of GT fragments was similar between Neer three- and four-part PHF. The overall morphology of GT fragments was in a fan shape, which could be summarized as anterior, superior, posterior, and middle lines. Of these, we identified 51 split and 29 avulsion type GT fragments based on the Mutch classification, and they could occur simultaneously in a PHF. The overall morphology of split type fragments was in a fan shape, and avulsion type fragments showed a quite distinguishable distribution pattern. A GT fragment could be classified as anterior-split, posterior-split, complete-split, anterior -avulsion, and posterior-avulsion type based on its morphology and location. The median percentage of fragment area covered by the plate was 32.3% in all of the fragments, and it was 69.4%, 23.0%, 37.2%, 21.8%, 0.0% in anterior-split, posterior-split, complete-split, anterior-avulsion, and posterior-avulsion type GT fragments. We defined the posterior-split, anterior-avulsion, and posterior-avulsion type GT fragments as the risky GT fragments, and they occurred in 43 (60.6%) Neer three- and four-part PHFs.

CONCLUSION

The fracture line morphology of GT fragments of Neer three- and four-part PHF was in a fan shape. GT fragments could be classified based on their location and morphology. The extent of GT fragment coverage provided by the locking plate differed in various fragment types, and we identified the anterior-avulsion, posterior-avulsion, and posterior-split type fragments as the risky GT fragments with a high incidence rate in Neer three- and four-part PHFs.

Biomechanical comparisons of hook plate and screw fixations in split-type greater tuberosity fractures of the humerus

BACKGROUND

Screws and plate are commonly utilized for the fixation of split-type humeral greater tuberosity (GT) fractures. However, the mechanical properties of these 2 types of fixation methods have not been compared directly. The aim of the present study was to evaluate the classic 2 screws fixation with hook locking plate from a mechanical perspective.

METHODS

Sixteen synthetic humerii (Sawbones Pacific Research Laboratories, Vashon, WA, USA) were divided into 2 groups. An osteotomy was performed to simulate a split-type GT fracture. Group A (n = 8) was fixed with 2 standard parallel screws. Group B (n = 8) was fixed with a hook plate. Each specimen was tested with traction force at 45° shoulder abduction. Following the 20-N preload, a 500-cycle loading test was applied with a force ranging from 20 to 200 N (valley/peak), and the interfragmental displacement was measured periodically at intervals of 100 cycles. Finally, all the specimens were pulled with destructive force at a rate of 5 mm/min until catastrophic failure.

RESULTS

The hook plate exhibited greater construct stiffness than the screw fixation (63.2 ± 6.1 N/mm vs. 40.9 ± 3.4 N/mm, P < .001). All of the specimens completed the entire cyclic loading test without catastrophic failure, and the fragment displacement after 500 cycles was 0.4 ± 0.2 mm for the hook plate and 2.1 ± 0.3 mm for screw fixation, which was statistically lower in the plate group (P < .001). In terms of failure load, the hook plate group exhibited a significantly greater value than the screw group (770.6 ± 94.6 vs. 427.5 ± 45.1 N/mm, P < .001). The failure modes of both fixation methods were distinct.

CONCLUSION

In humeral GT fracture fixation, hook plate fixation appears to offer greater construct stiffness and failure load while maintaining fragment stability to resist a physiological traction force. The current study provides support from a mechanical perspective for the clinical application of the hook plate.