The upper limb in human body is highly functional and mobile for positioning the hand in space. Humerus is the longest and largest bone of the upper limb which provides strength and resistance to both torsional and bending forces proximally and distally it tapers to triangular shape. The most proximal portion of the humerus is the head of the humerus, which forms a ball and socket joint with the glenoid cavity on the scapula by articulating proximally with the glenoid via the glenohumeral (GH) joint and distally with the radius and ulna at the elbow joint [1]. Shaft of humerus have cylindrical-shaped which contains a deltoid tubercle on its lateral aspect and a radial groove on its posterior aspect [2], extends from upper border of pectoralis major proximally to supracondylar ridge and is covered by strong muscles and a rather complicated arrangement of neurovascular structures [3].         

Pathophysiology of the Shaft of Humerus

Knowledge of the anatomy and pathophysiology of humeral shaft can facilitate the course and attachment of muscles and can explain the displacements of fractures and preoperative planning and fixation techniques. As the upper extremity functions with a long lever arm and highly exposed to external forces, it is predisposed to injuries frequently. They constitute approximately 3-5% of all fractures [4]. Diaphyseal fracture of humerus accounts for 20% of all humeral fractures [5].Pathological and open fractures of the humeral shaft are uncommon and accounts for 6%-8% and 2%-5% of all diaphyseal humeral fractures respectively [6].Holstein Lewis fracture is a special type of displaced spiral fracture of the distal humerus in which distal end deviating towards the radial side and proximally migrated .This result in increased risk of radial nerve palsy up to 7% due to entrapment of the radial nerve as it is fixed to the proximal fragment. The reason for high association with radial nerve palsy was that radial nerve come from posterior compartment to anterior compartment through the intermuscular septum and is relatively fixed and lies in direct contact with the bone and has limited mobility. The overall conclusion is that open reduction internal fixation should be the treatment of choice for this type of injuries. Fracture shaft of humerus has a bimodal distribution with first peak in young male patients of 20-30 years of age and second peak in older females from 60 to 80 years of age.

Mechanism of Injury to the Shaft of Humerus

The mechanism of injury for the occurrence of diaphyseal fractures vary and mainly depend on geographical and social parameters. Fall from height or level ground fall is the commonest cause followed by road traffic accident. In this situation humerus may be fractured by direct trauma to the arm or shoulder or by axial load transmitted through the elbow. The forces responsible for fracture shaft of humerus are torsional force that causes spiral fracture and bending force which is responsible for transverse fracture. The combination of these forces is responsible for oblique fractures, often with an associated butterfly segment. Other causes that account for less than 10% of humeral shaft fracture includes sporting activities, violence and bony pathology. Fracture shaft of humerus is classified according to anatomical site, fracture morphology, degree of comminution and associated soft tissue injuries. Garnavos classification takes morphology and topography of fractures into account to classify these fractures. Topographically the diaphysis of humerus is divided into three zones Proximal, Middle and Distal. Capital letters P, M and D describes the location of the fractures. Morphologically these fractures are divided into simple, intermediate and complex fractures. Simple fractures have no comminution; intermediate has one or two sizeable fragments and complex has three or more fragments or big comminution.

Classification of Injury

According to AO/OTA classification diaphyseal segment of humerus is designated as 12 and fractures of this segment are divided into three types. Type 12-A are simple fractures having two main fragments, type 12-B are wedge fractures and 12-C are the complex fractures. Depending upon the morphology of fractures these fractures are further divided into 3 groups from benign [1] to difficult [3,7].

Management And Clinic-o-Radiological Outcome

These fractures are unique among all long bone fractures in having good results with non-operative methods. However, all fractures are not amenable to conservative method of treatment as acceptable reduction cannot be achieved in many patients. Though a wide range of radio graphic malunion of 20 degrees of angular ion,30 degree of rotation and up to 3 cm of shortening can be accepted with little functional deficit due to extensive range of motion of shoulder and elbow. Historically, the treatment of choice for such fractures has been functional bracing and studies have found that the fractures heal quickly with an acceptable functional outcome [8], but non operative management requires a long period of immobilization resulting in shoulder stiffness and also inconvenience to the patient. Moreover, studies have indicated that the incidence of non-union after non-operative treatment is higher in certain patterns of fracture and that not all patients recover fully after non-operative treatment [9]. It has also been reported that the non-union of fracture after conservative management of these fracture does occur in 10 percent of the cases, thus making treatment of these cases very difficult [10].

Currently, there are no defined gold standards for the treatment of humeral shaft fractures [11]. While on one hand, nonoperative treatment has had a long and successful history in certain cases [12], on the other hand new surgical treatment methods have been developed to reduce soft tissue damage, improve early training and prevent long uncomfortable periods of immobilization, which can be associated with nonoperative treatment [13]. 

Hence, the trend of treatment of diaphyseal humerus fractures has now shifted from conservative cast/brace to internal fixation with plate and screws and intramedullary nail. Each of these techniques has its own benefits and drawbacks. There is increase interest in treating fracture shaft humerus by surgical modalities in order to avoid these problems, to allow earlier mobilization and rapid return to work of the patients. Various modalities are available for surgical treatment of humerus shaft fractures but plate osteosynthesis and intramedullary nail are the commonest one. Intramedullary nail has benefit of smaller incisions, preserved fracture site biology and load sharing properties [14,15], but have disadvantage due to concern of non-union, higher reoperation rate, stiffness, fracture at the insertion point and adjacent joint pain. There is hypothesis that fractures managed by Intramedullary nail would have shorter hospital stay but with more shoulder problems. 

Because of the above-described drawbacks open reduction and internal fixation with plate and screws continues to be gold standard for surgical treatment given its lower complication rate, shorter time to union, lower re-operational rate and avoidance of adjacent joint discomfort [16,17]. For open reduction and internal fixation, the humerus has traditionally been approached posteriorly. The posterior approach offers biomechanical advantages due to the ability to apply the plate on the tension side of the humerus [18]. There is substantial variability in plating that allows the surgeons to modify the construct to the personality of the fracture. The anterolateral approach and its modifications have also been widely employed for exposure of the humerus in various pathological conditions [19]. Though, the anterolateral approach allows supine positioning, which is the most notable advantage for patients with multiple injuries it also includes the risk of secondary nerve injury [20]. In general, the incidence of radial nerve palsy after plating ranges from 0 to 5.1% but most commonly it is neuropraxia due to manipulation during surgery which usually recovers with time [21]. 

So, when operative treatment is required plate osteosynthesis with open reduction has offered a successful result, with the advantages of anatomical fracture reduction. Plate osteosynthesis has distinct advantages in the fracture shaft of humerus and compression plating has been established as a successful modality for the surgical treatment of humerus fractures [7].The conventional plates used for fracture shaft of humerus has drawback that screws are in tension, plate-bone friction, screw interface loosening but these drawbacks can be prevented by using Locking Compression Plates which are non-contact plates and blood supply to the bone is preserved. In Locking Compression Plates, the screw head engages in the plate hole and the load transfer from the bone to the plate is provided by the locking mechanism of the screw within the plate hole.

Locking the screws ensures both angular and axial stability and thus reduces the risk of postoperative loss of reduction. These plates form stable construct with less chances of implant failure thus improving clinical and radiological results. The stability does not depend on the tight fit of the plate on the bone surface and locking plates do not need to be individually contoured, but rather can be used in their manufactured pre-contoured shape. All locked screws act together and distribute the load more uniformly over the length of the plate in comparison to the screws in conventional plating. These features aim at rigid stability to allow early postoperative mobilization and early return to function as well as adequate stiffness to stimulate fracture healing of complex multi fragmentary shaft [21]. 

Locking the screws ensures both angular and axial stability and thus reduces the risk of postoperative loss of reduction. The Locking Compression Plates allow better fixation even in osteoporotic bones having less complication plus better clinic radiological results.

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