Additive fiber-cerclages in proximal humeral fractures stabilized by locking plates: no effect on fracture stabilization and rotator cuff function in human shoulder specimens

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.

The addition of cerclage wiring does not improve proximal bicortical fixation of locking plates for Type C periprosthetic fractures in synthetic humeri

BACKGROUND

Treatment of proximal humerus periprosthetic fractures is challenging. It remains difficult to achieve robust fixation of the proximal fragment to the locking plate using cerclage wiring and/or unicortical screws. Use of polyaxial tangentially directed bicortical locking screws increases screw purchase, but it is unclear if this option provides robust fixation. This biomechanical study compares fixation of constructs using cerclage wires, bicortical locking screws, and a hybrid method utilizing both methods.

METHODS

Uncemented humeral stems were implanted into synthetic humeri and Type C periprosthetic fractures were simulated with a 1 cm transverse osteotomy. Distal ends of locking plates were secured with bicortical non-locking screws. The proximal ends were supported by either isolated cerclage wires, polyaxial locking screws, or a hybrid combination of both (n = 6 for each group). A universal test frame was used for non-destructive torsion and cyclic axial compression tests. 3-D motion tracking was employed to determine stiffnesses and relative interfragmentary motions.

FINDINGS

Isolated screw constructs showed significantly increased resistance against torsional movement, bending, and shear, (p < 0.05) in comparison to cerclage constructs. The hybrid construct provided no significant changes in stability over the isolated screw construct.

INTERPRETATION

Addition of cerclage wires in this synthetic bone model of Type C periprosthetic humerus fractures did not add significant stability to proximal bicortical locking plate fixation. Considering risks of tissue stripping and nerve injury, usage of cerclage wires in a similar clinical setting should be chosen carefully, especially when bicortical fixation around the prosthetic stem can be achieved.

The forgotten fragment: additional lesser tuberosity fixation of 4-part proximal humeral fractures-a biomechanical investigation

BACKGROUND

Fractures of the proximal humerus are common. The most frequent surgical treatment option is open reduction and locking plate fixation. Multifragmentary fractures, including 3- and 4-part fractures, are especially challenging to treat because they correlate with an increased risk of fixation failure. In the past, several mechanisms of additional fixation were investigated, but none directly addressed the lesser tuberosity (LT). The goal of this study was to investigate the biomechanical impact of additional anterior fracture fixation in lateral locked plating (LLP) of 4-part proximal humeral fractures (PHFs).

METHODS

Twenty-seven fresh frozen human shoulder specimens (mean age, 80 years) with intact rotator cuffs (RCs) were randomized into 4 groups: 3-part PHF with LLP and RC cerclage (n = 6); 4-part PHF with LLP and RC cerclage as standard of care (n = 7); 4-part PHF with LLP, RC cerclage, and 2 anterior 3.5-mm cortical screws (n = 7); and 4-part PHF with LLP, RC cerclage, and additional anterior one-third tubular plate (additional anterior plating [AAP], n = 7). Static load of the RC was simulated with weights. A force-controlled cyclic loading test was performed with a servo-hydraulic testing machine, followed by load-to-failure testing. An optical motion capture system recorded humeral head range of motion.

RESULTS

LLP of a 4-part PHF showed more humeral head motion than LLP of a 3-part PHF without fracture of the LT (P < .001). Fixing the LT to the humeral head with two 3.5-mm screws significantly reduced humeral head motion compared with LLP with RC cerclage alone (P < .006). Using AAP significantly increased the construct stiffness compared with the standard of care (P = .03).

CONCLUSION

LLP of a 4-part PHF is biomechanically less stable than LLP of a 3-part PHF without fracture of the LT. Additional screw fixation of the LT in 4-part PHFs improves stability compared with LLP alone. In case of metaphyseal comminution, AAP is favorable from a biomechanical perspective.

In vitro evaluation of the tension band suture method for proximal humerus fracture treatment

Background

Proximal humeral fractures are common, and more than half occur in patients over 65 years of age. Operative treatment may be recommended for displaced, complicated fractures; however, surgery may lead to displacement of the greater tuberosity or humeral head. Supplemental tension band sutures have been recommended to prevent such a complication. In this study, we investigate the best combination of suture, washer, and threading angle for proximal humeral fractures from a mechanical view.

Methods

The mechanical durability of 18 combinations of suture materials (Fiberwire, Ethibond, and Surgilon), threading washers (ring washer, disc washer), and threading angles (15 or 45°) were examined via a cyclic loading test.

Results

The most durable combination in the cyclic loading test consisted of threading the Fiber Wire to the washer ring using only one hole (ring washer-1) at 45°. In contrast, the most vulnerable combination was threading Ethibond to the washer disc at 15°. Breakage of all suture materials occurred at the suture-washer interface, and no failure or loosening of the knots was observed. FiberWire gradually eroded until the loss of equilibrium; whereas the rupture of Ethibond and Surgilon occurred suddenly.

Conclusions

From a mechanical viewpoint, we demonstrated that applying a supplemental tension band suture using FiberWire with a single-hole ring washer threaded at a wider angle is recommended.

Arthroscopic Repair of a Displaced Tuberosity Fragment After Proximal Humerus Locking Plate Fixation: A Case Report

CASE

Locking plate fixation of proximal humerus fractures is known to have high complication rates. Even a technically well-performed surgery can be subject to loss of reduction, which can lead to an adverse functional outcome for the patient. In this case report, we describe a patient who underwent open reduction and internal fixation of a proximal humerus fracture complicated by delayed loss of reduction of a greater tuberosity fragment that was revised using arthroscopic techniques.

CONCLUSION

Arthroscopic repair of displaced greater tuberosity fragments after failed locking plate fixation of proximal humerus fractures can lead to good functional outcomes at 1-year follow-up.

Surgical Considerations in the Treatment of Osteoporotic Proximal Humerus Fractures

Proximal humerus fractures in the setting of osteoporosis can be technically challenging. Intraoperative challenges include comminution, thin cortical bone, and crushed cancellous bone that lead to difficulties in obtaining and maintaining a reduction and hardware fixation. Loss of fixation and varus collapse continue to be problems despite the utilization of modern locking plate fixation. A clearer understanding of predictors of fixation failure and the encouraging early results of reverse total shoulder arthroplasty (RTSA) have resulted in increased utilization of RTSA for the primary treatment of proximal humerus fractures.

The elderly have similar outcomes compared to younger patients after ORIF with locking plate for comminuted proximal humerus fracture

Objective

The aim of this study was to compare clinical and radiological outcomes of elder and younger patients with comminuted proximal humerus fracture treated with osteosynthesis with locking plate.

Methods

A total of 70 patients (30 males and 40 females; mean age 65.4 years) operated on for Neer 3- or 4-part proximal humeral fractures between 2010 and 2016 and followed for at least one-year were included in the study. The reduction was achieved through intraosseous window to minimize soft tissue stripping in all patients and structural allograft at metaphyseal diaphyseal junction was used aggressively to resist varus force. Group 1 consisted of 32 patients aged 70 or older (14 males and 18 females; mean age: 77.8 ± 5.1), while Group 2 consisted of 38 patients younger than 70 (16 males and 22 females; mean age: 58.2 ± 9.3). The groups were compared for their clinical and radiological outcomes.

Results

There was no significant difference in clinical outcomes by Oxford score (54.8 ± 2.7 vs 56.6 ± 3.4, p = 0.13) and ASES score (89.7 ± 5.7 vs 90.8 ± 8.2, p = 0.68). Two groups had similar radiological outcomes regarding neck shaft angle, greater tip height and offset. However, group 2 had better final shoulder forward elevation (162.6 ± 8.7 vs 135.4 ± 14.7ß, p < 0.05) and shorter duration to achieve maximal range of motion (4.37 ± 2.37 vs 8.14 ± 3.25 months, p < 0.05) than group 1. Two groups had similar complication rates (9.4% vs 7.9%). All the complications were related to greater tuberosity including mal-reduction and avulsion.

Conclusion

With the prerequisite of good alignment with robust medial cortical support and untouched soft tissue over medial metaphysis area via intra-osseous reduction, comminution of proximal humeral fracture can achieve satisfactory result and low complication rate by osteosynthesis with locking plate system, regardless of age. In addition, we suggested to use structural bone graft for comminuted medial cortex fracture with multiple fragments or bony defect more than 2 cm.

Level of evidence

Level III Therapeutic study.

Biomechanical analysis of plate systems for proximal humerus fractures: a systematic literature review

BACKGROUND

Proximal humerus fractures are the third most common in the human body but their management remains controversial. Open reduction and internal fixation with plates is one of the leading modes of operative treatment for these fractures. The development of technologies and techniques for these plates, during the recent decades, promise a bright future for their clinical use. A comprehensive review of in vitro biomechanical studies is needed for the comparison of plates' mechanical performance and the testing methodologies. This will not only guide clinicians with plate selection but also with the design of future in vitro biomechanical studies. This review was aimed to systematically categorise and review the in vitro biomechanical studies of these plates based on their protocols and discuss their results. The technologies and techniques investigated in these studies were categorised and compared to reach a census where possible.

METHODS AND RESULTS

Web of Science and Scopus database search yielded 62 studies. Out of these, 51 performed axial loading, torsion, bending and/or combined bending and axial loading while 11 simulated complex glenohumeral movements by using tendons. Loading conditions and set-up, failure criteria and performance parameters, as well as results for each study, were reviewed. Only two studies tested four-part fracture model while the rest investigated two- and three-part fractures. In ten studies, synthetic humeri were tested instead of cadaveric ones. In addition to load-displacement data, three-dimensional motion analysis systems, digital image correlation and acoustic emission testing have been used for measurement.

CONCLUSIONS

Overall, PHILOS was the most tested plate and locking plates demonstrated better mechanical performance than non-locking ones. Conflicting results have been published for their comparison with non-locking blade plates and polyaxial locking screws. Augmentation with cement [calcium phosphate or poly(methyl methacrylate)] or allografts (fibular and femoral head) was found to improve bone-plate constructs' mechanical performance. Controversy still lies over the use of rigid and semi-rigid implants and the insertion of inferomedial screws for calcar region support. This review will guide the design of in vitro and in silico biomechanical tests and also supplement the study of clinical literature.

Cement augmentation of humeral head screws reduces early implant-related complications after locked plating of proximal humeral fractures

Background

Cement augmentation (CA) of humeral head screws in locked plating of proximal humeral fractures (PHF) was found to be biomechanically beneficial. However, clinical outcomes of this treatment have not been well evaluated to date.

Objectives

To assess outcomes of locked plating of PHF with additional CA and to compare them with outcomes of conventional locked plating without CA.

Methods

24 patients (mean age, 74.2 ± 10.1 years; 22 female) with displaced PHF were prospectively enrolled and treated with locked plating and additional CA. The Constant score (CS), the Simple Shoulder Test (SST), and the Simple Shoulder Value (SSV) were assessed 3 and 12 months postoperatively. Fracture healing and potential complications were evaluated on postoperative radiographs. The CS and complications were compared with the outcomes of a matched group of 24 patients (mean age, 73.9 ± 9.4 years; 22 female) with locked plating of displaced PHF without CA.

Results

At the 3‑month follow-up, the mean CS was 59.9 ± 15.6 points, the mean SST was 7.5 ± 2.7 points, and the mean SSV was 63.9 ± 21.7%. All scores significantly improved by the 12-month follow-up (p < 0.05; CS, 72.9 ± 17.7; SST, 9.2 ± 3.2; SSV, 77.2 ± 17.3%). There were two cases (8%) of biological complications (n = 1 varus malunion and n = 1 humeral head necrosis). Compared with locked plating without CA, no significant differences were observed between the CS at the 3‑ (57.8 ± 13.4 points; p = 0.62) and 12-month (73.0 ± 12.8 points; p = 0.99) follow-up. However, patients without CA had a significantly increased risk of early loss of reduction and articular screw perforation (p = 0.037).

Conclusion

Locked plating of proximal humeral fractures with trauma cement augmentation of humeral head screws could be translated from the ex-vivo lab setting into the clinical situation without additional complications. Locked plating of displaced PHF with additional cement augmentation showed similar clinical outcomes but reduced the rate of early implant-related complications compared to locked plating without additional CA.

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).

Complications of locked plating for proximal humeral fractures-are we getting any better?

BACKGROUND

Complication rates reported after locking plate fixation of proximal humeral fractures still range up to 40%. Whether modifications of surgical techniques, use of primary shoulder arthroplasty, or a fracture-specific management resulted in decreased complication rates during recent years remains unclear. Therefore, the aim of this long-term observation study was to analyze the incidence of complications and revision surgery after locked plating.

METHODS

Between February 2002 and December 2013, 788 patients (aged 67.4 ± 17.3 years) with displaced proximal humeral fractures were treated with locking plate, primary hemiarthroplasty (HA), or reverse shoulder arthroplasty (RSA). Standardized follow-up included radiographs at 1 day, 6 weeks, and 3, 6, and 12 months. Complications and unplanned revision surgery were prospectively recorded over the complete follow-up.

RESULTS

Of 788 patients, 646 (82%) were treated with locking plate, 82 (10.4%) with HA, and 60 (7.6%) with RSA. Mean follow-up was 14.8 ± 3.8 months. The mean complication rate associated with locked plating was 12.8%, and revision surgery was necessary in 11.6%. Within the last 5 years, the loss of fixation rate markedly decreased from 14.3% to 4.8%; simultaneously, an increased use of RSA was observed.

CONCLUSION

The overall complication rate of locking plate osteosynthesis for proximal humeral fractures has been decreasing considerably within the last years. Among others, this might be due to an increased use of primary RSA for complex fracture types. In addition to a precise surgical technique, choosing the adequate treatment for each individual fracture to avoid complications and revision surgery is of utmost importance.

Biomechanical Contribution of Tension-Reducing Rotator Cuff Sutures in 3-Part Proximal Humerus Fractures

OBJECTIVES

Using a cadaveric 3-part fracture model and cyclic loading protocol, our study objectives were to quantify the stabilizing effect of tension-reducing rotator cuff sutures in terms of fracture displacement across the surgical neck and greater tuberosity compared with a control group in which no sutures were used.

METHODS

Six matched pairs of fresh frozen specimens underwent a standardized, 3-part, proximal humerus fracture and were split into 2 groups. The control group had the fracture fixed with a plate and screw construct only while the experimental group had additional suture fixation through the plate to each rotator cuff tendon. Active abduction through the rotator cuff was simulated for 100, 200, 300, and 400 cycles and to failure at 1000 N. A Mann-Whitney U test compared cyclic displacement of the greater tuberosity and surgical neck fracture gaps and load to failure between the 2 groups.

RESULTS

There was no significant difference (P > 0.05) in fracture gap between fixation methods at the surgical neck at 100 (P = 0.13), 200 (P = 0.07), 300 (P = 0.49), and 400 (P = 0.07) cycles. There was no significant difference (P > 0.05) between fixation methods in the fracture gap at the greater tuberosity at 100 (P = 0.39), 200 (P = 1.00), 300 (P = 0.31), and 400 (P = 0.59) cycles. There was no significant difference (P > 0.5) at 1000 N at the surgical neck (P = 0.70) or the greater tuberosity (P = 0.39).

CONCLUSIONS

Tension-relieving rotator cuff sutures do not add stability to the repair of 3-part proximal humerus fractures. Varus collapse and greater tuberosity displacement are common complications associated with 3-part fractures. No mechanical data exist to demonstrate benefit of adding suture to a plate and screw construct for limiting fracture displacement.

Stainless steel wire versus FiberWire suture cerclage fixation to stabilize the humerus in total shoulder arthroplasty

HYPOTHESIS

No. 5 FiberWire (Arthrex, Naples, FL, USA) cerclage (FWC) and 1.25-mm stainless steel wire cerclage (SSWC) are biomechanically similar in resistance to prosthetic subsidence in shoulder arthroplasty.

METHODS

In this laboratory bench study, 3 different surgical knot configurations (4-throw knot, cow hitch, and simple hitch) using a No. 5 FWC were evaluated and compared with a 1.25-mm SSWC. First, distraction tests were performed using bovine femoral cortical half shells mounted on a testing jig. Cerclage tightening, load to a 3-mm gap opening, and load to total failure were measured. Second, uncemented humeral prosthetic stems were inserted into an experimentally split humeral medullary canal, secured by the cerclage. After 100 N of preloading, the prosthesis was advanced into the humerus at a speed of 0.2 mm/s, and resistance during subsidence up to a penetration depth of 10 mm, as well as gap opening, was measured.

RESULTS

Tightening force showed higher values for SSWC (618 N) than FWC (131-137 N) (P < .001). Load to total failure was comparable among the 3 different FWC knots (2,642-2,804 N), which were significantly stronger than SSWC (1,775 N, P < .001). At 3 mm of distraction, SSWC (1,820 N), cow hitch (1,803 N), and single-throw hitch (1,709 N) performed significantly better than a 4-throw knot (1,289 N) (P < .01). Subsidence testing showed no difference in force restraint or gap opening between the best FWC and SSWC.

CONCLUSIONS

FWCs appear, in vitro, equally suitable to steel wires to stabilize nondisplaced periprosthetic humeral fractures. To actively reduce a displaced fracture, steel wires may still be the first choice.

No Contribution of Tension-Reducing Rotator Cuff Sutures on Locking Plate Fixation in a 2-Part Proximal Humerus Fracture Model

OBJECTIVES

Varus failure is a well-known complication of open reduction internal fixation of proximal humeral fractures. The addition of tension-reducing sutures from the plate to the rotator cuff may attenuate the deforming forces of the rotator cuff resulting in decreased varus failure. In this study, we investigate the biomechanical contributions of tension-reducing sutures to a locked plate construct in a 2-part proximal humerus fracture model.

METHODS

Two fixation techniques were tested in 12 matched fresh frozen humeri in which standard 2-part fractures of the surgical neck were created with a gap simulating surgical neck medial comminution. In group 1, fractures were fixed with a standard proximal humerus locking plate. In group 2, the plate fixation was similar, and additionally, tension-reducing sutures were applied from the plate to the rotator cuff. Active abduction was simulated for 400 cycles with force applied through the rotator cuff tendons. Intercyclic fracture motion, change in displacement, and load to failure were recorded.

RESULTS

The addition of tension-reducing sutures did not lead to significant differences in intercyclic fracture motion. The mean change in displacement and load to failure were similar in both groups. Failure typically occurred in both groups at the rotator cuff testing clamp interface.

CONCLUSIONS

Tension-relieving rotator cuff sutures added to locking plate fixation did not lead to a change in fracture gap with cyclic loading or an increase in ultimate failure load in a 2-part surgical neck proximal humerus fracture model without medial support.

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.

Outcomes evaluation of locking plate osteosynthesis in displaced fractures of the proximal humerus

Objective

To evaluate functional outcomes, radiographic findings and complications of proximal humeral fractures treated with locking plates and to determine prognostic factors for successful clinical outcomes.

Methods

Forty patients undergoing internal fixation of fractures of the proximal humerus with the Philos^® plate were included in the study. The surgeries were performed between 2004 and 2011 and the patients underwent radiographic and clinical evaluation, by Constant–Murley and Dash score. Outcomes were analyzed by use of multivariate regression with several different variables.

Results

Patients were on average of 61.8 ± 16.28 years, and most were female (70%). The Constant–Murley score was 72.03 ± 14.01 and Dash score was 24.96 ± 19.99. The postoperative radiographs showed a head-shaft angle of 135.43° ± 11.82. Regression analysis showed that the patient's age and the Hertel classification influenced the Constant–Murley scale (p = 0.0049 and 0.012, respectively). Other prognostic criteria such as Neer and AO classification, head-shaft angle, the presence of metaphyseal comminution and extension of the humeral metaphyseal fragment showed no effect on prognosis. Complications occurred in four patients (10%).

Conclusion

The fixation with the Philos^® plate provided good clinical and radiographic results in fractures of the proximal humerus, with a low complication rate. Patient's age and Hertel classification were defined as prognostic factors that led to worse functional outcomes.

Does a critical rotator cuff tear stage exist?: a biomechanical study of rotator cuff tear progression in human cadaver shoulders

BACKGROUND

It is unknown at which stage of rotator cuff tear the biomechanical environment is altered. The purpose of this study was to determine if a critical rotator cuff tear stage exists that alters glenohumeral joint biomechanics throughout the rotational range of shoulder motion, and to evaluate the biomechanical effect of parascapular muscle-loading.

METHODS

Eight cadaver shoulders were used with a custom testing system. Four progressive rotator cuff tear stages were investigated on the basis of footprint anatomy. Three muscle-loading conditions were examined: rotator cuff only; rotator cuff with deltoid muscle; and rotator cuff, deltoid, pectoralis major, and latissimus dorsi muscles. Testing was performed in the scapular plane with 0°, 30°, and 60° of shoulder abduction. The maximum internal and external rotations were measured with 3.4 Nm of torque. The position of the humeral head apex with respect to the glenoid was calculated with use of a MicroScribe 3DLX digitizing system throughout the rotational range of motion. The abduction capability was determined as the abduction angle achieved with increasing deltoid load.

RESULTS

Tear of the entire supraspinatus tendon significantly increased maximum external rotation and significantly decreased abduction capability with higher deltoid loads (p < 0.05). Tear of the entire supraspinatus tendon and half of the infraspinatus tendon significantly shifted the humeral head apex posteriorly at the midrange of rotation and superiorly at maximum internal rotation (p < 0.05). Loading the pectoralis major and latissimus dorsi muscles decreased the amount of humeral head elevation due to deltoid loading.

CONCLUSIONS

Tear of the entire supraspinatus tendon was the critical stage for increasing rotational range of shoulder motion and for decreased abduction capability. Further tear progression to the infraspinatus muscle was the critical stage for significant changes in humeral head kinematics. The pectoralis major and latissimus dorsi muscles played an important role in stabilizing the humeral head as the rotator cuff tear progressed.

New trends in fixation of proximal humeral fractures: a review

Surgical treatment of proximal humeral fractures continues to be a challenge especially in osteoporotic patients. Locking plates and intramedullary nails have been used with satisfactory results but the previous reported complications have not been substantially reduced. Most of the existing studies involve a small number of patients followed up for a rather short period of time. Since proximal humeral fractures constitute a heterogenous group of complex fractures in an even more heterogenous population, no single fixation method is a panacea. Choice of implant and method of fixation should be selected according to individual patient and fracture pattern characteristics based on clearly defined indications and contraindications. Based on the findings of the existing clinical studies the authors propose a treatment algorithm.