3D-Printed Custom Implants for Severe Hip Bone Loss

We look at the X-ray to see whether the hip joint space is maintained. If pain has started but mobility is still there and the joint space and cartilage are maintained, we don't straight away advise hip replacement — we have other options, such as the arthroscopic method, where we clean up osteochondral extra bone formation or damaged cartilage and repair it with stem cell therapy. That is a good option instead of hip replacement. Once the cartilage is completely damaged on CT or MRI, with no blood flow to the femoral head, then the only answer is hip replacement.

For sickle cell disease in children, bone marrow transplant is the standard treatment, with the best results when done early while the patient is still a child — my colleague Dr. Dharma Choudhary's centre specialises in this. As for hip arthroplasty itself, it is not recommended below 17–18 years of age because the hip does not develop enough. Below that age we instead use arthroscopy to clean up damage, or osteotomies — we change the weight-bearing surface of the hip with procedures like valgus or varus osteotomy — based on where the MRI shows the main damage, which relieves pain much better.

After hip replacement, certain things are not recommended: sitting on the floor, sitting cross-legged, and squatting, as these positions can damage the implant and cause loosening. High-energy sport activity should also be avoided. Following these recommendations, a well-fitted hip can last 30–35 years, and since most hip replacement candidates are of an older age profile, most patients will not need it again in their lifetime.

Stem cells are osteoprogenitor or osteopotent cells that can convert into osteoblasts, osteoclasts, or chondroblasts. For hip cartilage damage, we clean the damaged islands of cartilage with hip arthroscopy and inject stem cells; over time, review MRIs show the cartilage growing back, like grass growing, with less damage and fewer symptoms after about 6 months — though it does take time. In orthopaedics we harvest stem cells from the iliac crest, using a Jamshidi needle, taking around 120 ml of blood from the marrow (posterior or anterior, near the spine). This is then put into a centrifuge machine for about 45 minutes to 1 hour to concentrate the stem cells before injection.

Earlier, international companies like Johnson, Stryker and Zimmer supplied all the revision and complex hip replacement implants, but they have since withdrawn much of their hardware because of government policies and duties. Luckily we now have two or three Indian companies that have come up very well and collaborated to produce cost-effective implants. Earlier a hip replacement used to cost around $10,000–$12,000; now that has come down to between $7,000 and $8,000. Where there are problems, I also try to reduce my own surgical fees to help the patient.

Custom implants become necessary when a patient's hip anatomy is too severely altered for standard implants to fit, often the result of a childhood problem that changed how the hip grew. In some cases the internal diameter of the femoral canal is found to be less than six millimetres, which makes fitting a standard stem impossible.

The implant is designed from the patient's own CT scan. A 3D CT scan is used to plan the reconstruction, and this data is sent to specialised implant companies who manufacture a custom implant matched to the patient's own anatomy, with artificial intelligence tools now helping to visualise in advance how the implant will sit once placed.

For hips where a large part of the acetabulum, such as the entire anterior wall, is missing, a 3D-printed metal model is used to plan reconstruction precisely around the remaining bone. This deliberate, patient-specific approach is central to managing the most severe cases of hip arthroplasty.

Taking the necessary time is standard practice for these cases, sometimes four to five days of discussion and planning using a bone model and 3D imaging, because the hardware required is highly specific and has to be confirmed as available before the case is scheduled.