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The etymology of the word “orthopaedic” comes from the Greek words “orthos” – meaning “straight or correct” and “paedieia” – meaning “rearing of children”.

Limb discrepancies and deformities can occur in children as the result of a range of causes such as congenital, trauma, infection, growth disturbance and tumours. Limb deformities can present as bowed legs, knock-knees or a difference in limb lengths. Secondary symptoms include an awkward walking gait, short stature and, in rare instances, pain.

KK Women’s and Children’s Hospital (KKH) sees about 50 new cases of limb discrepancies and deformities each year. Of these, about 10 per cent are complex deformities, and 10 per cent as part of very rare conditions. Utilising 3D-printing technology, the paediatric Lower Limb Discrepancy (LLD) and Deformity Clinic at KKH is able to carry out a range of intervention and reconstruction options for a wide spectrum of complex and rare lower limb discrepancies and deformities in children.

Based on the patient’s actual limb, anatomically accurate 3D-printed limb models are reconstructed – enabling patients and their families to better visualise the discrepancy or deformity. The patient’s limb model is subsequently utilised in the assessment, planning, surgical simulation, family counselling and eventual surgical intervention for the patient. At KKH, this method has been successfully used in the planning and simulation of corrective surgeries, including:

• Fixation of a comminuted calcaneus fracture
• Hip arthroscopy in the resection of a cam lesion
• Valgus proximal femur osteotomy for a malunited femur neck fracture
• Arthroscopic resection of a physeal bar

Studies have shown that the use of 3D-printed limb models is helpful in improving patients’ appreciation and understanding of their anatomy^1,2. Additionally, being able to view a simulation of the entire corrective process and likely end result has greatly enhanced patient engagement and feedback. It also manages more accurately patient and parent expectations. This has led to greater patient satisfaction with the correction.

Case study: 3D-print-enabled intervention for an adolescent with complex foot deformity

An adolescent boy was diagnosed at birth with bilateral clubfoot deformities (Figure 1A) due to neuromuscular imbalances from an underlying spina bifida. The spinal cord condition also resulted in weak lower limb muscles.

Due to the boy’s feet deformities, he was unable to wear normal shoes or stand properly, and often developed painful calluses and ulcers on his feet. The boy underwent several operations to correct the deformities when he was younger in an attempt of an acute correction to allow for shoeing.

However, the deformity recurred after each surgery since the primary source of the deformity in the spinal cord remained. The condition progressively worsened.

Due to the severity and long-standing nature of the boy’s feet deformities in adolescence, surgical correction was not amenable using standard means. Correcting the deformities acutely could result in damage to the blood and nerve supply in the feet, possibly causing necrosis of the skin.

To assess the complexity of the deformities, the care team at the KKH LLD and Deformity Clinic created anatomically-correct, 3D-printed manipulable models of the boy’s feet (Figure 1B). The 3D-printed feet models were then used to simulate surgical correction via different techniques.

Clubfoot can be corrected gradually via Ilizarov frames, or a computer-based hexapod frame.

The completed simulated frame and model was shown and explained to the patient and his parents, enabling them to better understand the limb correction process, visualise the likely end result, and better prepare themselves for the surgery, as well as manage expectations.

During the actual surgery, the 3D-printed limb models were brought into the operating theatre to guide the positioning of the Taylor spatial frames (Figure 1C). Prior surgical simulations aided the team in achieving a satisfactory shape, alignment and size for the boy’s feet, as planned pre surgery (Figure 1D).

After being fitted with the Taylor spatial frames for close to five months, the frames were removed and the boy was fitted with ankle-foot orthoses, enabling him to wear normal sports shoes which he had not been able to do throughout his childhood.

He is currently undergoing physiotherapy and is able to stand with a walking frame. With continued follow up care at the LLD and Deformity Clinic, he is likely to progress to ambulatory exercises.

Benefits of 3D-model-guided simulation and surgery

The use of anatomically-correct, 3D-printed manipulable feet models enabled the team to better appreciate the limb deformities on all three planes, which can be more accurate in comparison to traditional modes of diagnostic and interventional imaging which are viewed on a two-dimensional screen.

Additionally, by simulating the feet models undergoing surgery with each of the frame techniques, the team was able to assess the feasibility of each construct, the ease of correction, and more importantly, the precision of the final correction. This aided the team in deciding on the hexapod Taylor spatial frame as the better option as well as examining the ideal level at which to perform the osteotomy (bone cuts).

The surgical simulation further enabled the team to identify, pre-empt and overcome technical challenges which, previously, would have been discovered intra-operatively. This included the issue of the distal ring abutting a proximal U-ring due to the severity of the deformity, which would have obstructed the correction of the connecting struts. In this instance, a ¾ distal ring was chosen for its decreased rigidity, allowing just enough pliability to avoid abutment of both rings.

Multidisciplinary care for limb deformities in children

To help each child develop to their fullest potential, it is crucial for limb discrepancies and deformities to be assessed and corrected before secondary complications such as contractures, arthritis or scoliosis develop.

Through the sharing of knowledge and best practices amongst larger centres around the world, the repertoire of skills and surgical options is increasing. Today, most limbs can be reconstructed and deformities that were once thought to be too severe, or trivial can be addressed. Patients can be offered a wider range of options in limb reconstruction.

For the child with a limb discrepancy or deformity, the aim of treatment is to have a limb with aligned mechanical axes, functional, pain-free and equal in limb length. Most patients will need a detailed surgical life-plan. Appropriate surgical procedures are planned at certain stages in their life such that they can achieve the above aims by the time they reach skeletal maturity.

If the deformities are part of a physiological spectrum (e.g. physiological bow-leggedness in children less than two years old), reassurance is often all that is needed. However, any child with unequal limb length, or with obvious limb deformities (e.g. a varus or valgus deformity, flexion or extension deformity or even a rotational deformity) can be referred for assessment by the KKH LLD and Deformity Clinic.

The KKH LLD and Defomity Clinic

The LLD and Deformity Clinic at KKH sees and manages a wide range of paediatric conditions, which can include rare and complex conditions such as fibula and tibia hemimelias, congenital femoral deficiencies, osteogenesis imperfecta (brittle-bone disease), congenital pseudarthrosis of tibia, arthrogryposis, Blount’s disease, rickets, skeletal dysplasias, resistant clubfeet and multiple exostoses.

Upper limb conditions such as unusually short arm lengths, or deformed elbows and forearms due to previous infection, trauma or growth disturbance and tumours are also seen at the clinic.

Due to the complex nature of limb deformities, the clinic is staffed by a multidisciplinary care team, and designed to provide patients and families time and information to understand and appreciate the problem and treatment options available.

Following a consultation with the orthopaedic surgeon, a physiotherapist and an occupational therapist are also in a room adjacent to the consultation room to advise patients and their families on rehabilitation requirements and equipment that they would require post-surgery.

Patients who need to be put in external fixation frames for a period of time would also be counselled by specialty care nurses who would review pin site wounds and offer advice such as special clothing and home modifications.

The clinic has also successfully incorporated the use of growth modulation, Ilizarov frames, advanced hexapod frame technology and internal lengthening rods to surgically correct these deformities. These advanced techniques make surgical correction safer and more precise, and in some cases, provide a better cosmetic result.

In conclusion, almost all limb deformities can now be managed and reconstructed. Any limb deformity should not be trivialised. With currently available technology and expertise, there is no reason for patients to live with a limb discrepancy or deformity if they choose not to.

​Dr Lam Kai Yet, Consultant, Department of Orthopaedic Surgery, KK Women’s and Children’s Hospital Dr Lam Kai Yet obtained his basic medical and postgraduate qualifications from the National University of Singapore and the Royal College of Surgeons of Edinburgh, United Kingdom. He also has a Diploma in Children’s Orthopaedics from the European Paediatric Orthopaedic Society. Upon completion of his specialist training in orthopaedic surgery, Dr Lam joined KKH in 2014, and is actively involved in research in 3D-printing, paediatric trauma, and sports injuries. Dr Lam's areas of interest include children and adolescent sports injuries, patella dislocations, hip dysplasia, osteogenesis imperfecta, and limb deformity correction and limb lengthening. He has since completed an arthroscopy and knee fellowship at the Centre of Albert Trillat, Hospital de la Croix-Rousse, France, and a paediatric orthopaedics fellowship at the Great Ormond Street Hospital, London, and University College Hospital London. Dr Lam is currently an Adjunct Assistant Professor at the Lee Kong Chian School of Medicine, and a Senior Clinical Lecturer at the Yong Loo Lin School of Medicine. A member of the Singapore Orthopaedic Association Humanitarian and Outreach Subcommittee, Dr Lam compassionately cares for the underprivileged in Singapore and regional countries.