Smith & Nephew Hip Replacements
Smith & Nephew is a British-based multinational company with more than 11,000 employees in 90 countries. The annual sales in 2012 were more than $4.1 billion. The company specializes in orthopedic reconstruction, sports medicine, trauma and advanced wound management.
- ANTHOLOGYS Hip System
- BHRS Birmingham Hip Resurfacing
- R3 Acetabular System
- REDAPT Revision Femoral System
- SMFS Short Modular Femoral Hip
- VERILASTS Technology
- EMPERION Modular Hip System
- SPECTRON Hip System
- ECHELON Hip System
- CONQUEST FX Femoral Hip Implant
- TANDEM Hip System
- REFLECTION Acetabular Cup System
R3 acetabular system
The R3 acetabular system is the latest hip implant product introduced by Smith & Nephew in 2007. The acetabular system in combination with stems was designed to provide greater stability, wider range of movement, longevity and address the revision in case of failures. The R3 acetabular system consists of acetabular cup with a liner.
The complete hip replacement system comprises of:
- Hip stem
- Femoral head
- Acetabular cup
The R3 Acetabular component consists of an enhanced porous ingrowth surface to satisfy the needs of both primary and revision hip surgery. It has an optimized locking mechanism and the ability to accommodate polyethylene, metal, or ceramic liners. A study on the safety and efficacy of the new StikTite porous ingrowth surface claims to provide a superior “scratch-fit” due to its greater coefficient of friction and less micro motion. The high porosity StikTite and lower porosity Roughcoat surfaces provide excellent “biologic fixation”. The StikTite coating is designed to provide proper fixation and enhance the stability. This not only helps holding the weakened bone but also allows the normal growth of the bone. The R3 Acetabular Cup is designed for multiple weight bearing. The multi-bearing cup is engineered in a way to reduce wear and increase the life of the apparatus. The cup can support CoCr, OXINIUM and Biolex femoral heads and can hold larger cups for greater range of movements. The internal surface is usually lined by the Cross-linked polyethylene (XLPE) for reducing the friction, enhancing the stability and resilience. The R3 acetabular system allow the surgeon to select the material according to the need of patients.
Following are the important features of acetabular cup:
- Accommodation of Larger femoral heads for greater range of movements.
- Complementation between neck geometry and liner allow maximum head/shell ratios for optimal functioning.
- The liner equally surrounds the head from all sides, thus enabling the enhanced range of motions which ultimately reduces the risk of joint subluxation, nerve impingement, and prosthetic loosening—all contributors to revision surgery.
Recent modifications to R3 acetabular system include multi-hole shells with Constrained Liners and Big Femoral Heads.
The Liner is an articular surface between the head of femur and the acetabular cup. A good liner should be resilient, tough, erosion-free, and provide enough room for the femoral head. Smith & Nephew recommends the liner made of Polyethylene (XLPE or PEX) which is thicker at the apex and load-bearing areas. According to a 5 year study, the head penetration of a second-generation XLPE liner remained low at 5 years and the wear rate calculated after the first year was “low in all directions”. The liner is also engineered in a way to allow repositioning during the surgery.
When are hip replacements recommended?
Initially, treatment for degenerative joint diseases deals with the pain and other symptoms common for these types of joint problems. The initial treatment for pain management consists of steroids, anti-inflammatory drugs, pain killers and local injections. After failure of all these treatments, total hip replacement is the last resort to rehabilitate the patients suffering from:
- Osteoarthritis as a result of antigen-antibody reaction
- Traumatic arthritis as a result of inflammation after trauma
- Avascular necrosis due to compromise in blood supply
- Fused hip joint due to inflammatory scarring or any other cause
- Slipped capital epiphysis due to shear stress
- Fracture of the pelvis and diastrophic variant.
The diverse varieties of Hip components are also used for degenerative joint diseases which include:
- Rheumatoid arthritis (an autoimmune attack)
- Arthritis secondary to a variety of diseases and anomalies, and congenital dysplasia;
- Treatments of non-union
- Femoral neck fracture (trauma)
- Fractures of the trochanter of femur along with head involvement
- Fracture-dislocation of the hip
- Correction of deformity
Harmful Effects of R3 Acetabular System
The harmful effects of R3 acetabular system with metallic liner are diverse and include:
It is very common complication especially in the younger patients. Almost 20% of patients complain of post-operative pain at the site of implantation. It is usually associated with signs of inflammation i.e. redness, tenderness, swelling, warmth etc.
The deposition of metal debris resulting in increased plasma concentration of metals, results from shaving off metals by friction. In a recent study, it was demonstrated that almost all the patients suffer from severe metallosis after 10 year of metal-on-metal implant. The larger cup size increases the likelihood of developing severe metallosis.
Revision Surgery After Device Failure:
There are a variety of problems than can lead to revision surgery. Mechanical failure, infection and recurrent hip dislocation can all prompt a doctor to consider a revision surgery. Often the revision surgery is more dangerous than the initial surgery and can further damage the area of the implant.