In 1992, my nan received a “simultaneous bilateral total hip replacement”, meaning both hips were replaced during the same surgery. The surgeon had only performed this type of surgery once before her, as this was a newer type of surgery in the UK. She’s had a total of 4 hip replacements, 2 on each hip, all of which were metal-on-polyethylene implants. Unfortunately, she’s suffered from numerous complications both in and out of surgery.
First of all, both hips were cemented in. I wasn’t sure why this decision was made, so I was encouraged to investigate the pros and cons of cemented hips, which I’ve summarised into the table below [1].
| Cement Pro | Cement Con | Cementless Pro | Cementless Con |
|---|---|---|---|
| Cement holds the implant to the bone Faster Recovery Hardens fast Mouldable material so well fixated Good for those with bone strength issues (osteoarthritis) | Can crack Some people are allergic, which you would only discover after getting the implant If allergies exist, the implant must be completely removed and redone, extending recovery time | Bone grows into the implant Stronger connection No concern over cement in the body Lasts longer than cemented on average | Long recovery as bone needs time to grow into the implant Longer and more difficult rehabilitation |
My nan was in her 50s at the time of the operation. A cementless implant would be a favourable choice for someone her age, especially considering cementing hips in makes replacing them later more difficult. However, the reason she was having her hips replaced was due to having level 4 osteoarthritis in her hips, so her bones may not have been strong enough for a cementless replacement. Unfortunately, her left hip had dislocated 3 months after the operation. This meant more bone had to be removed to replace the dislocated hip.
After the operation, they insisted she stay in the hospital for a few days. This saved her life, she proceeded to suffer from a pulmonary embolism (see image to left). This is when a blood clot blocks a blood vessel in your lungs and can be fatal if not treated quickly. They proceeded to find numerous clots throughout her body as a complication of the surgery.
Simultaneous hip replacements have a higher risk of blood clots compared to staged replacements due to the increased time on the operating table [3]. The increased risk of complications means this surgery is typically saved for younger patients in good health. However, simultaneous hip replacements have their advantages, as you only need to enter the operating room once. This means only one dose of anaesthesia, shorter overall recovery time and is less expensive than staged operations [4].
Implants have seen drastic improvement since my nan’s surgery, especially for polyethylene. While 3-4mm of polyethylene is still used, the standard polyethylene wears 0.2mm annually, meaning after 15-20 years, the polyethylene would be completely worn away [5]. The new cross-linked polyethylene only wears 0.04mm annually, meaning it’d take over 75 years to wear [5]. This allows younger patients to get their hip replacements sooner without worry of needing another replacement. The cross-linked polyethylene is more robust due to the additional bonding between chains, which we can see in the diagram to the right. This allows patients to perform high-demand activities after surgery without increasing further complications. If my nan had access to cross-linked polyethylene, she might not have dislocated her new hip nor needed any further hip replacements.
My nan’s hips have once again degraded, but as she is now in her 90s, she’s too old to be operated on again. However, with materials and technology used in hip replacements rapidly advancing, we are getting closer to prosthetics that won’t need replacing. The next generation will have access to safer and more efficient surgeries thanks to her and the millions of others who have undergone joint replacement surgeries.
References
[1] El_Paso_Manual_Physical_Therapy. YouTuber [Video]. 2023 21/09/2023 [accessed 25/03/2024]; Available from: https://youtu.be/OvWXltT6zoU?si=gGals_WT9svuWXON.
[2] Lear, S. Can Pulmonary Embolism Cause PH? Lung Sounds and More. 2023 [accessed 25/03/2024]; Available from: https://www.myphteam.com/resources/can-pulmonary-embolism-cause-ph-lung-sounds-and-more.
[3] Zhang, Z.-h., et al., Risk factors for venous thromboembolism of total hip arthroplasty and total knee arthroplasty: a systematic review of evidences in ten years. BMC Musculoskeletal Disorders, 2015. 16(1): p. 24.
[4] Yale Medicine, Simultaneous Bilateral Total Hip Replacement. [accessed 25/03/2024]; Available from: https://www.yalemedicine.org/conditions/simultaneous-bilateral-total-hip-replacement.
[5] Andrew_Yun_MD. YouTube [Video]. 05/11/2021 [cited 25/03/2024]; Available from: https://youtu.be/IQloOIiZvQI?si=2_R-vfoO24C85Kkk.
[6] Thomas, J., M.E. Thomas, and S. Thomas, Crosslinked Polyethylene: State-of-the-Art and New Challenges, in Crosslinkable Polyethylene: Manufacture, Properties, Recycling, and Applications, J. Thomas, S. Thomas, and Z. Ahmad, Editors. 2021, Springer Singapore: Singapore. p. 1-15.
I’ve linked further reading to key words – these will aid in understanding and provide some context. I really recommend checking out the YouTube video embedded to cross-linked polyethylene!
