Fracture of the humerus shaft comprises a break of the long humeral bone between its extremities: the humeral head, joining at the shoulder joint with the glenoid fossa of the scapula, and the distal humeral head forming the elbow joint. The humeral shaft is the middle portion of the bone.
The fractures of the humerus shaft represent 3-5% of all fractures. They can occur at any level of the humerus shaft including the proximal, middle, or distal humerus. The involvement of the radial nerve is critical in humerus shaft fractures. This nerve travels along the humerus from the humerus neck to the hand, and spirals closely around the bone shaft. Fractures of the humeral shaft can damage the radial nerve causing the inability to extend (bend) the wrist and the fingers backwards (drop hand). Injury to this nerve is caused by its entrapment within the bone break.
Fractures of the humerus shaft can display various patterns: transverse, oblique, spiral, and comminuted. In addition they are differentiated depending on whether the fracture is displaced or undisplaced, relative to the loss of bone alignment and closed or open fracture. The AO classification is one of most used systems available to characterise humerus shaft fractures. According to the AO humerus shaft fractures are divided into their level of comminution:
Type A - No comminution
Type B - Presence of butterfly fragment (wedge-shaped fragment of bone)
Type C - Comminution
Grade 2: formation of pretendinous and cords, limited finger extension
Grade 3: permanent contracture of the affected finger(s)
Fractures to the humerus shaft are mostly caused by trauma with only a small percentage due to underlying conditions that weaken the bone density (osteoporosis, cancer, Paget’s disease). This type of fractures is common amongst middle-aged and elderly people, mostly women, due to low energy falls. More commonly in younger males, humerus fractures often result from high-energy impact injuries with direct trauma to the arm and torsion of the upper extremity. They often coexist with a shoulder dislocation. In this young population humerus shaft fractures are caused by road traffic accidents and sport injuries.
The most frequent risk factors leading to a humerus shaft fracture include:
Tendency to fall in elderly individuals (poor vision, lack of physical exercise)
Medical conditions (diabetes, seizure)
Sports (bicycle, horse riding)
Contact sports (football, rugby)
Post-menopausal age in women
The symptoms arising from a humerus shaft fracture are quite evident:
Sudden sharp pain on the upper arm at time of injury
Deformity of the upper arm
Shortening of the upper arm
Crepitus with arm movement and palpation
Inability to raise the arm
Increasing pain when attempting to move the arm
Radial nerve palsy
Clinical examination begins by discussing the medical history including the causes leading to a humerus shaft fracture. The main scope of the diagnosis is to determine the type of humerus shaft fracture to develop an optimal treatment plan suitable to the specific fracture. It is critical for the examiner to assess potential damage caused to the radial nerve and the vasculature. Clinical examination will determine:
Changes in the anatomy of the upper arm and bone deformities
Presence of bruises and lacerations in case of open fractures
Functional restriction in the range of movement of the arm
Increasing pain while moving the arm
Neurological symptoms relative to the radial nerve
Peripheral pulses to evaluate possible vascular injury
X-rays are taken under different angles to ascertain the type of humerus shaft fracture and whether the elbow and shoulder joints have been affected by the injury. A CT scan and MRI may be requested in more complex cases. Severe multiple injuries to the humerus shaft can lead to secondary complications and require immediate attention at the Emergency Department including the examination by an orthopaedic surgeon.
In case of undisplaced or minimally displaced humeral fractures conservative treatment is standard management. Nonoperative treatment is also accepted in case of relatively small displacement with a 30-40° angulation of the bone extremities. Standard management involves the use of a sling, cast, splint or brace and arm immobilisation for a few weeks. A coaptation splint may be used initially until swelling has subsided and then replaced with a rigid cast or a brace after 1-2 weeks. A hanging arm cast may also be used to keep the arm bone in alignment.
Surgery is required in significantly displaced, comminute and in open fractures. This treatment option will depend on the age, general health and the osteoporotic nature of the bone. Several approaches are available to repair the humeral shaft fracture including:
Intramedullary rod or nail involves the use of a metal rod introduced in the canal of the bone shaft that is fixed on the outer bone extremities with screws. The rod can be inserted either from the proximal or distal end of the humerus
Open reduction and internal fixation (ORIF) consists of accessing the humerus with a large skin incision to allow the insertion of a metal plate along the fracture length, which is fixed with multiple screws
External fixation with percutaneous screws is a temporary fixation of the humerus fracture with screws inserted through the skin to maintain the anatomical bone alignment while the fracture is healing. This procedure is often followed by permanent internal fixation within 14 days after the injury. This treatment is used in situations where an immediate internal fixation cannot be performed, eg. multiple injured patients or severe soft tissue damage. In rare cases the external fixator remains in place until the fracture has healed completely.
With either conservative or surgical treatments, complications after the repair of humerus shaft fracture can occur. The most frequent complications include:
Non-union of the fracture (when the gap between the bone extremities is not closed)
Mal-union when the fracture heals with abnormal bone alignment
Temporary damage to the radial nerve
Joint stiffness of the shoulder and elbow
A humerus shaft fracture requires approximately three months to heal. Major attention is drawn to restore the function of the elbow and shoulder joints that may have stiffened during the immobilisation phase. Rehabilitation will begin as soon as the fracture has become stable as recommended by the orthopaedic surgeon. Physical exercise is gradually increased in intensity to regain strength, flexibility and range of movement of the elbow and shoulder. The prognosis of humerus shaft fracture is usually good. Standard rehabilitative therapy includes:
Activity modification advice
Return to sport/work plan
The main preventative measures aim at reducing the risk of falls and use a protecting gear during contact sports, biking/motor biking protect the arm in case of collision and accident. Other common preventive strategies include:
Use of walking devices to improve stability and avoid falls in elderly patients
Modification of physical activities
Regular physical exercise to maintain muscle strength, joint flexibility and correct posture