of 0.75–1 mm/day, frequency of 0.25 mm 6–8 hourly) using a ring external fixator (e.g. Ilizarov) or monolateral external fixator until it meets and docks with the distal fragment. During this process regenerate bone forms behind the segment and matures into mechanically stable bone. Bone graft may be required at the docking site.
Bifocal treatment Bifocal treatment uses bone transport principles to manage bone defects in a process of ‘compression-distraction’ (see Fig. 4.6). Acute closure of the gap brings
the bone ends together and leads to a leg length discrepancy. Secondary lengthening is undertaken using callotasis, through a corticotomy performed away from the site of non-union. The maximum safe degree of shortening (and therefore lengthening) is approximately 5 cm in the femur and 3 cm in the tibia. This should ideally not exceed 20 per cent of the original bone length because of the risk of neurovascular and soft tissue compromise, with resulting joint instability or stiffness.
the decision-making process, with early involvement of prosthetic and rehabilitation services.
MALUNION
INCIDENCE
Although incidence data are not readily available, malunion is a relatively common complication, particularly in fractures treated non-operatively.
AETIOLOGY
The healing of bone in an abnormal position commonly results from an initial lack of adequate fracture reduction. Alternatively, inadequate fixation, fracture comminution or poor bone quality may lead to collapse and displacement during the early stages of the healing process.
DIAGNOSIS
A comprehensive history is required with emphasis on adjacent joint pain, functional deficit, limp and cosmesis.
Physical examination includes assessment of true (and apparent) limb length discrepancy and comparison with the contralateral limb, with documentation of varus/valgus, recurvatum/procurvatum and rotation deformities.
Radiographs may reveal impending malunion at an early subclinical stage and are key to early identification of displacement or malalignment during the first 3 weeks of fracture healing. In the lower limb, long-leg standing radiographs are obtained with the patellae facing forward and the pelvis balanced by using appropriately sized blocks to address leg length discrepancy. This method also allows
assessment of anatomical and mechanical axes. Subsequent radiographs should employ the same technique to allow comparison, whereas computed tomography scanning allows assessment particularly of versional, torsional and rotational malalignment.
TREATMENT
Non-operative treatment
Many cases of malunion do not require any form of intervention. This is especially the case in the absence of functional or cosmetic problems. In the lower limb, malunions close to the hip or ankle cause much less mechanical axis deviation (MAD) than those near the knee (Fig. 4.7) and so are less likely to require intervention.
Children have great potential for remodelling while bones are growing and can therefore frequently be treated expectantly. Remodelling occurs for deformities of angulation and length, but not rotation. Remodelling potential is greatest in younger children, in the upper limb, near the physis (an active area of osteogenesis) and in the same plane of motion as an adjacent joint. In the upper limb most growth and therefore remodelling occur in the proximal humerus and distal radius, whereas in the lower limb it is around the knee. Acceptable malalignment for radius and ulna shaft fractures is shown in Table 4.7. Even if remodelling is incomplete, there may be no residual cosmetic or functional deficit.
In adults in whom the deformity is not severe enough to impair function, surgical intervention is not indicated. For example, a malunited diaphyseal fracture of the humerus with angular or rotational deformity often has minimal effect on limb function, on account of the ball-and-socket nature of the glenohumeral joint.
Table 4.7 Acceptable malalignment for radial and ulnar shaft fractures
Age Angulation Malrotation Displacement Loss of radial bow
<9 yr 15° 45° 100% Yes
>9 yr 10° 30° 100% Partial
Acceptable ranges for malunion have reduced with advances in internal fixation techniques. In diaphyseal fractures such as the tibia, no more than 5° of angular or rotational deformity and 1 cm of shortening are now considered acceptable. In the distal radius, up to 10° of dorsal or 15° of volar angulation is usually tolerated fairly well. A 1–2-mm step may be acceptable for intra-articular fractures.
Malunion may be accepted beyond these criteria if the risks of surgical intervention outweigh the theoretical advantages of anatomical reduction (e.g. in elderly patients), and clearly the functional demands of each patient must be individually assessed. A simple measure such as a shoe raise is an effective way of managing leg length discrepancy and avoiding surgical morbidity.
Operative treatment
Symptomatic malunion requires surgical intervention, most obviously in the case of functional or cosmetic defects, but also with
deformities outside acceptable ranges and MAD (see Fig. 4.7). There is a paucity of data, and no consensus on the long-term effects of diaphyseal fracture malunion on joint function.
Malalignment greater than 15° may load the joints above and below asymmetrically and cause secondary osteoarthritis. However, more recent long-term studies have shown that malunion following tibial and femoral fractures at 30 and 22 years of follow-up, respectively, are not significantly associated with an increased incidence of knee osteoarthritis, although some patients do report pain and stiffness.
Treatment therefore aims to restore functional alignment and achieve nearly anatomical reduction. In children, the chief indication is malunion exceeding the capacity for remodelling. In adults, broad indications include angulation greater than 15° in a long bone or a visible rotational deformity.
Management strategies may broadly be subdivided into acute (osteotomy) (Figs. 4.8 and 4.9) and gradual (corrective distraction osteogenesis) (Fig. 4.10).
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Date: 14.04.2014 Fig No: 7.4 Cat #/Author: K17090 - Dawson-Bowling, Achan, Briggs, Ramachandran Proof Stage: 1
Proximal anatomic and mechanical axis
MAD
= 41mm
MAD LDFA=92°
CORA
Distal anatomical and mechanical axis
(a)
(b)
Figure 4.7. Biomechanical parameters used for assessing and managing non-union. (a) Mechanical axis deviation (MAD) and (b) centre of rotation of angulation (CORA).
(a)
(b)
(c) (d)
Figure 4.8. Malalignment of a non- union of the tibia treated with dome osteotomy. (a) Lateral radiograph of the malunion; (b) dome osteotomy and bone graft; and (c) and (d) healed bone.
Osteotomy
Acute correction using an osteotomy at the site of deformity (i.e. CORA) allows restoration of alignment in mild deformities without translation. Opening wedge, closing wedge or dome osteotomy (see Fig. 4.9) may be used.
Possible fixation methods are summarized in Table 4.8.
• Closing wedge – A wedge of bone is excised. Bone healing is more predictable, with greater stability allowing for early weightbearing. This procedure leads to shortening of the bone and is potentially
more technically challenging than an open wedge.
• Opening wedge – An osteotomy is created and the bony angulation then corrected, creating a defect filled with bone graft that lengthens the bone. Potential delayed healing can lead to a loss of reduction.
• Dome osteotomy – This is usually performed in large cancellous metaphyseal areas
to minimize the risk of non-union. The osteotomy does not alter the structure of nearby joints, but it requires immobilization and protected weightbearing. Bone length is maintained (see Fig. 4.8).
Table 4.8 Methods of osteotomy fixation with advantages and disadvantages
Method Advantages Disadvantages
Non-locking plate • Ease of use.
• Ready availability.
• Low cost.
• Allows interfragmentary compression.
• Absolute stability.
• Open approach.
• Periosteal stripping.
• Disruption of haematoma.
• Risk of failure with poor bone quality.
• Neurovascular complications of rapid correction.
Locking plate • Ease of use.
• Ready availability.
• Use in osteoporotic bone.
• Minimally invasive device.
• Bridging construct.
• Open approach.
• Periosteal stripping.
• Disruption of haematoma.
• Cost.
• Overly rigid fixation.
• Lack of interfragmentary compression.
• Neurovascular complications of rapid correction.
Intramedullary device • Minimally invasive device.
• Relative stability.
• Allows dynamic compression.
• Allows early weightbearing.
• Allows for reaming.
• Possible need to remove because of morbidity.
• Lack of rotational control.
• Need for minimum intramedullary canal diameter.
• Risk of compartment syndrome.
External fixator • Percutaneous.
• Allows correction of complex deformities.
• Fewer soft tissue complications because of gradual correction.
• Enables lengthening.
• Allows early weightbearing.
• Relative stability.
• Pin site care/infection.
• Cosmetic appearance.
• Prolonged treatment duration.
• Further procedure to remove.
• Risk of neurovascular damage.
• Risk of compartment syndrome.
Distraction osteogenesis
The principle of distraction osteogenesis uses external fixation to distract the callus (callotasis) formed at an osteotomy site (see Fig. 4.10). This allows gradual correction of length and angulation in more severe deformities, thus significantly reducing tension on neurovascular structures.
The osteotomy can be performed at the CORA using an opening wedge, to achieve alignment of the mechanical axis without translation. Alternatively, osteotomy performed away from the CORA creates alignment with translation. In either case the hinge of the external fixator should be placed at the bisector line of the CORA; otherwise, translation will occur irrespectively. If both osteotomy and hinge are away from the CORA, translation will occur without mechanical axis realignment.
REFERENCES AND FURTHER READING
Einhorn TA. Enhancement of fracture-healing. J Bone Joint Surg Am 1995;77:940–56.
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Date: 14.04.2014 Fig No: 4.9 Cat #/Author: K17090 - Dawson-Bowling, Achan, Briggs, Ramachandran Proof Stage: 1
(a)
(b)
(c)
Figure 4.9. Types of osteotomy used in the proximal tibia for malunion. (a) Closing wedge, (b) opening wedge and (c) dome osteotomies with correction of anatomical axes at the centre of rotation of angulation to achieve alignment.
(b)
Date: 14.04.2014 Fig No: 4.10a Cat #/Author: K17090 - Dawson-Bowling, Achan, Briggs, Ramachandran Proof Stage: 2
(a)
Figure 4.10. Malunion of the tibia treated with a circular Taylor Spatial Frame (TSF). (a) Long-leg alignment radiograph showing the mechanical axes (blue lines) and mechanical axis deviation on the right; (b) correction of deformity and mechanical axis.
Marsh D. Concepts of fracture union, delayed union, and non-union. Clin Orthop Relat Res 1998;355(Suppl):S22–30.
Masquelet AC, Begue T. The concept of induced membrane for reconstruction of long bone defects. Orthop Clin North Am 2010;41:27–37.
Paley D. Principles of Deformity Correction. New York: Springer, 2005.
Weber BG, Cech O. Pseudarthrosis: Pathology, Biomechanics, Therapy, Results. Bern: Hans Huber, 1976.
Wilkins KE. Principles of fracture remodelling in children. Injury 2005;36(Suppl 1):A3–11.
MCQs
1. Which of the following substances is osteoinductive?
a. Calcium phosphate.
b. Hydroxyapatite.
c. Collagen-based matrix.
d. Cancellous allograft.
e. Cancellous autograft.
2. Which of the following is not contained in demineralized bone matrix?
a. Bone morphogenic proteins.
b. Collagen.
c. Transforming growth factor β.
d. Residual calcium.
e. Mesenchymal precursor cells.
Viva questions
1. What are the stages of fracture healing?
Which of these arrests, leading to non-union?
Mention the cytokines involved.
2. How do you treat non-union of a mid-shaft clavicle and scaphoid waist fracture?
3. What are BMPs, and what is their effect on bone?
4. What is bone graft used for, and what types of bone graft are there? Mention storage, sterility and antigenicity.
5. What causes bone defects in the diaphysis of long bones, and how can they be treated?