Introduction
Proximal humeral fractures account for 4–5 % of all fractures. Several classification systems exist, the most commonly referred to is the Neer classification, which describes the site of fracture and thenumber of parts involved based displacement.
Undisplaced fractures are usually treated conservatively. Operative treatment is recommended for the displaced fractures, as non-operative management often results mal-union, non-union and stiffness.
Various surgical techniques and implants are available, each with their own set of advantages and disadvantages. The main concern in the majority of those cases is the amount of soft tissue dissection involved, increasing the risk of avascular necrosis
The Palm Tree technique was developed as a minimally invasive percutaneous approach for the fixation of 2 and 3 part proximal humeral fractures, using three wires inserted retrograde. This technique was later extended to include 4 part fractures and fracture dislocation.
Technique
The patient is positioned in the beach chair position with the arm draped free. The fracture is reduced closed under image intensifier control. This is usually achieved by reducing the humeral shaft onto the rotated humeral head with abduction and external rotation.
Fig1: Closed reduction technique
A stab incision is then made just distal to the deltoid insertion within a 3-4cm window of safety between the axillary and radial nerves.
The instruments needed for this procedure are minimal as seen in the figure below.
Fig 2: Instruments for palm tree fixation
The lateral cortex is approached by blunt dissection and an oblique hole is made in the lateral cortex using a 4.5mm drill.
Three divergent pre-bent 1.8mm wires are introduced through the drill hole across the fracture into the humeral head as follows.
Fig 3: Insertion of Wire
The blunt end of the first wire is bent and a gentle curve is made in the wire. Mounted on a T handle on a Jacob's chuck, the wire is introduced into the medullary cavity via the drill hole and is passed in a retrograde direction towards the humeral head. By introducing the blunt end of the wire there is smooth passage of the wire proximally as it "bounces off" the medial cortex. The direction of the wire is dictated by the rotation of the T handle. The wire is then impacted into the subchondral bone. The second wire is bent in a similar fashion, introduced blunt end first through the same drill hole and is made to diverge from the first by controlling rotation of the T handle. The third wire is introduced sharp end first by sliding it on the two wires in situ. Atight interference fit is achieved at the lateral cortex. This third wire is made to diverge from the other two by controlling rotation of the T handle. The wires are cut and buried but remain fairly superficial.
Fig 3: Fixation completed
With 4-part fractures, the fracture is approached through an antero-superior approach (Neviaser-Mackenzie). The head fragment and the tuberosities are reduced. The tuberosities are reapproximated and held with sutures against the reduced head ('Closing the book') and if there is a significant void, this is filled with bone graft substitute. By this, we transform the 4-part fracture into a '2-part' fracture. The reconstructed proximal fragment is then reduced onto the shaft of the humerus and the pre-bent wires are inserted in the manner described above.
Post-operatively, the patient is immobilised in a sling for three weeks at which point radiographs are taken. If there is any sign of callus formation at this stage, passive mobilisation is begun. If there is not, the patient is immobilised for a further three weeks. The wires are removed under general anaesthetic at six weeks and rehabilitation programme commence.
This method of fixation works on the basis of achieving good angular stability but maintaining axial elasticity. There is no or minimal disruption of the soft tissue envelope.
Three-point fixation is achieved for each of the wires: laterally at the tight-fit entry point in the lateral cortex, medially where the wire "bounces off" the medial cortex, and superiorly where the wire is impacted into the subchondral / subcortical bone.