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Review Article: Principles of Fracture Management in the Immature Patient.

 
 

There are several unique characteristics of young bone which should be considered when assessing fractures in patients less than 12 months of age:- 

fig. 1a - caudo cranial view of distal femoral Salter Harris type I fracture in an eight-month-old DSH.

fig. 1b - post-op view showing reduction and stabilisation with crossed arthrodesis wires

(i) a structural weakness through the metaphyseal growth plate predisposes towards Salter Harris fractures (see figs. 1a & 1b),   

   (ii) soft, thin cortices are inherently poor at holding implants, but the presence of a thick, fibrous periosteum explains the high incidence of incomplete fractures and,.    

   (iii) the rapid rate of metabolism results in exuberant callus formation.  This, combined with low mechanical loading, results in early (mal)union.    

It is also important to consider any potential paediatric complications such as hypoglycaemia, hypothermia and a relatively naïve immune response.  In addition, metabolic bone disease must be considered as an underlying factor with immature patients fed sub-optimal diets, as this will need to be addressed (possibly whilst cage-resting the animal) before successful bone-healing can occur.     

Due to the high metabolic rate of juveniles, it is essential to manage cases as soon as the health status of the patient permits – joint alignment and restoration of limb length should ideally be performed within 2-3 days, or profuse fibrous callus formation will hinder reduction.  This phenomenon is also responsible for ‘quadriceps tie-down’, occasionally encountered in young patients suffering femoral fractures.  The risk of developing this potentially devastating complication may be reduced by minimal disturbance of the fracture callus and passive physiotherapy following stabilisation to maintain the range of stifle motion during recovery. 

Diaphyseal Fractures

fig. 2a - comminuted diaphyseal fracture of the tibia with intact fibula in a 12 month-old terrier. The fracture was managed with a modified Robert-Jones dressing.

fig. 2b - one-month films show bridging callus.

The splinting provided by an intact periosteum allows for less rigid methods to be used in the majority of juvenile patients (see figs. 2a & 2b).  In very young patients, where external coaptation is used, dressings should be changed at least weekly to allow for the rapid growth of the bone; Robert Jones-type dressings may be more suitable in this regard, as opposed to rigid casting materials used in the mature patient.      

 

 

 

 

 

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fig. 4a - lateral condylar fracture (Salter Harris type IV) in a five-month-old Labrador retriever. There is a suspicion of a folding-fracture of the medial epicondyle, which was managed conservatively.

fig. 4b - postoperative view showing reduction and stabilisation with a 4.5mm lag-screw and de-rotational arthrodesis wire.

fig. 5a - Ce2 body fracture with stepping of neural canal

fig. 5b. reduction and stabilisation with screws and bone cement

A good rule of thumb is ‘the younger the patient, the less metalwork required’.  However, notable exceptions to this rule include fractures extending through articular surfaces (figs 4a & 4b) or those involving the CNS (figs. 5a & b).  These should be critically assessed in accordance with general orthopaedic principles: Anatomical reduction and rigid internal fixation should be considered here to minimise the risk of long term complications.  Nevertheless, young joints have a greater capacity to remodel where joint congruity has been lost, or perfect reduction was not achieved.     

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 Metaphyseal fractures

fig. 6a - Proximal, articular ulnar fracture in a seven-month-old Italian Greyhound.

Fig. 6b –repair using tension band wire to restore elbow congruency

Great care must be taken when manipulating fragments to minimise the risk of crushing the germinal layer of the metaphyseal growth plates or fragmentation of relatively soft bone.
Open physes should not be bridged with rigid fixation devices where possible. Where it is unavoidable, implants should be removed as soon as clinical union has been achieved. Intramedullary implants that do cross the physis should be placed perpendicular to the plane of the physis and occupy less than 20% of its diameter.  They should ideally be smooth, especially when used to compress the fragments  – e.g. lag-screw/ tension band wire (see figs. 6a & 6b).     

Any injury involving a growth plate has the potential for future limb shortening and/ or angular limb deformity.  Significant, long-term sequelae are more likely to be seen in younger patients, with appreciable physeal growth potential remaining.  The prognosis is also worse where the injury involves a limb segment comprising paired bones (radius & ulna/ tibia & fibula) with the potential for mismatched growth rates resulting in a ‘bow-string’ effect.  Truncated growth of a single long bone is rarely clinically significant with compensatory overgrowth of  bones elsewhere in the limb and increased extension of the joints.     

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fig. 7c - two week films show periosteal bridging - implants removed

fig. 7b - post op view shows good alignment with stack-pinning

fig. 7a - short, oblique humeral fracture in a 15-week old DSH

For the majority of fractures, the stability of the callus should be checked weekly so as to facilitate early implant removal.  This is especially important for devices which do not accommodate growth — e.g. bone plates and external fixators.  In contrast, non-threaded, intramedullary pins/ wires placed perpendicular to the physis/ long axis of the bone will have the least potential for causing significant growth disturbances.     

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fig. 8a - Salter Harris fracture of the left femoral head in a six-month-old DSH

fig. 8b - reduction maintained with divergent arthrodesis wires via a limited, craniolateral approach

In summary, the range of techniques applicable to most cases, in order of simplicity include:     

(i) intramedullary pinning, including. Kirschner/ arthrodesis wires,

(ii) parallel or ‘stack pins’(see figs. 7a, 7b & 7c, above).— these counter rotational forces and may be countersunk to reduce soft tissue irritation and left in place (but they are often overgrown anyway, precluding removal)

(iii) cross-pinning, though divergent pins may interfere with longitudinal growth (see figs. 8a & 8b)

(iv) external fixators; usually a single 1/2 pin per major fragment is sufficient to  counter the forces of rotation and compression.  They may be tied into an intramedullary pin to prevent migration (see figs. 8c & 8d, below)

(v) tension-band wires specifically to counter distraction (figs. 6).

……………………………………………………………..(vi) biodegradable pins

fig. 8c - comminuted humeral fracture from same case, fig 7.

fig. 8d - Post-op view of IM-pin tied-in to 2-pin external fixator - N.B: no attempt is made to reconstruct the fragments.

Other methods of rigid internal fixation such as bone plating (‘biological healing’, DCP or locking-type) and interlocking nails might be considered in specific, highly comminuted fracture configurations, but early implant removal is again recommended so as to minimise the risk of growth disturbance.  However, this may result in increased morbidity as compared to retrieval of simpler devices, especially where screws and plates become incorporated into the fracture callus.  In practice, indications for the use of such fixation systems are few as simpler solutions will usually suffice.     

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