Frequently Asked Questions About Hip Replacement Surgery

Total hip joint replacement (or total hip arthroplasty) is a treatment for degenerative arthritis in the hip joint, during which damaged bone and cartilage is removed and replaced with prosthetic components.

Within the hip, the femoral head (ball at the top of the femur, or thigh bone) is connected to the acetabulum or “hip socket” of the pelvis bone. This connection is much like a ball and socket and like all joints, there is a layer of cartilage on the ends of the bones where they make contact. Synovial fluid surrounds the hip joint and acts as a lubricant to reduce friction, allowing the hip to move and swivel smoothly.

When the cartilage that provides padding starts to breaks down, eventually causing direct bone-on-bone contact is when, aches, pains, stiffness, swelling and decreased range of motion and flexibility can occur. This occurrence is called, degenerative arthritis.

Total hip replacement surgery involves the following components:

• Femoral Stem – Once the damaged femoral head is removed a metal component is placed into the hollow center or canal of the femur (thigh bone). The femoral stem may be either cemented or wedged into the bone creating a “press fit” to hold the prosthesis in place.
• Femoral Head (Ball) – A metal or ceramic ball is placed on the upper part of the femoral stem component. This ball replaces the damaged femoral head that was removed.
• Acetabular Cup (Socket) – The damaged cartilage surface of the acetabulum (hip socket) is removed and replaced with a metal or polyethylene cup or socket. Screws or cement are sometimes used to hold the cup in place.
• Cup Liner – A plastic or ceramic spacer is inserted between the new ball and the cup to allow for a smooth gliding surface.

In the Partial Hip Replacement surgical procedure, only the femoral head (ball) of the damaged hip joint is replaced with a prosthetic implant. The hip socket is not substituted or replaced allowing the femoral head prosthetic to articulate with the native acetabular anatomy. A partial hip replacement can also be called a hemi-arthroplasty.

Traumatic hip injuries (broken and fractured hips) are the primary reason for partial hip replacement. It is not typically a treatment for degenerative arthritis of the hip joint.

During traditional hip replacement surgery, surgeons typically select standard replacement parts for the femoral stem and acetabular cup from several available sizes. If the standard parts are too big or too small, then surgeons can choose a size up or down as needed, by trial and error, they find the size that fits the   patient’s anatomy most appropriately.

Conformis has designed a 3D (3-dimensional) patient specific hip system to improve upon the traditional surgical process and provide a unique implant for each individual.

The Conformis Hip System is the first ever and only 3D (3-dimensional) designed custom primary total hip replacement system.

The Conformis Hip System uses individualized implants intended to replicate the structure and function of each patient’s natural anatomy. The system reduces estimation during surgery using 3D surgical planning by targeting the precise position for those individualized implants.

With the Conformis Hip System, computed tomography (CT) scans of patients’ hips are converted into 3D virtual computer models, taking into account the unique measurements of their anatomy. Surgeons may then make adjustments and corrections – such as, widening or narrowing the hip, also known as the “offset.”

Once surgeons complete their virtual review, they approve the final individualized implant design. The new personalized design is then sent to Conformis engineers, who create the implant parts out of titanium alloy, along with customized 3D-printed tools and guides for the surgical procedure.

Conformis develops a comprehensive, individualized, pre-operative surgical plan (iView^®) that is delivered to the surgeon well in advance of the operation. The iView^® shows surgeons the pre-planned positioning of each implant. This allows the surgeons to visualize the placement of the implant within each patient’s actual anatomy in 3D, enabling better positioning of the implant.

Traditional implant systems use a 2D (2-dimensional) templating technique for standard implant size and positioning. 2D templating and standard implant sizes make traditional hip replacement an unguided surgery with some estimation required by surgeons during their surgical planning and procedure. If the prostheses are not properly placed, the length of the leg and/or hip offset could be shortened or lengthened causing the patient’s gait to be compromised and at increased risk for dislocation of the joint.

In contrast, Conformis’ 3D (3-dimensional) Hip System is designed to address many of the short comings of traditional primary hip replacements today because it is personalized. It is all about the individual:

1. Personalized components are designed in 3D from patients’ computed tomography (CT) scans to replicate the structure and function of each patient’s natural anatomy

2. Surgeons leverage the 3D models to adjust and correct the design of each personalized implant to minimize the risk of leg length and hip offset discrepancies

3. Individualized pre-operative surgical plans enable surgeons to accurately position the hip implants

4. Conformis’ personalized instruments (iJigs^®) enable proper placement and orientation of both the femoral stem and acetabular cup implants

5. A groundbreaking acetabular cup reaming system adds efficiency and accuracy

The Conformis Hip System is the first hip system to provide orthopedic surgeons with guided placement of custom implants, designed to address the wide variations in anatomy presented across patient demographics.

In general, many hip replacement surgeries range from 1-2 hours in length. However, the length of a hip replacement surgery depends on several factors – the surgeon, how complicated the specific case is, the patient’s physical condition and weight, the severity of the patient’s joint osteoarthritis, the type of replacement received, and whether the surgery is a partial (hip hemiarthroplasty) or full hip replacement.

As prescribed by surgeons, physical therapy is an important step to help restore hip joint motion and strength, and to decrease the risk of dislocating new hip replacements. Physical therapy often begins the day after surgery and, within days, patients can typically walk with a walker, crutches, or a cane. Physical therapy usually continues for weeks to months following the surgery. The focus of therapy is often on increasing the range of motion in the new joint as well as strengthening the muscles surrounding the hip. Balance exercises are also commonly performed to help decrease the risk of falling. Patients are advised to speak to their doctor or therapist to identify precautions to minimize the risk of hip dislocation.

Immediately after surgery, scar tissue begins to form. This scar tissue will form not only at the incision site, but also deep within the joint. It is common at this point for patients to still have a feeling of stiffness, particularly if they have stayed in one position for too long. Physical therapists usually prescribe exercises to stretch out scar tissue while it is still pliable, and thereafter patients typically continue to gain motion for up to 12 months.

Hip replacement recovery time varies from person to person. Because individual circumstances, medical conditions, and pain tolerance are different for each patient, there is no definitive timeline for the length of pain after surgery. Everyone is different. Some hip patients report that their arthritis pain is gone immediately after total hip replacement surgery but, even in these instances, it is typically replaced by surgical pain for about 4-6 weeks (1 – 1.5 months), the time at which many patients begin reporting improved pain control.

Hip replacement recovery time varies from person to person. When a surgeon clears hip replacement patients to return to work depends on both the pace of the patients’ individual recoveries and the types of duties required by their jobs. In general, many patients are not advised to return to work until at least 6-8 weeks (1.5 – 2 months) after their hip replacement. However, some surgeons may clear patients to return to work earlier if their job primarily involves sitting.

Hip replacement recovery time varies from person to person. Everyone is different. Many patients can walk with assistance on the same day as surgery, or on the day after surgery. Then, many patients can resume routine activities within 10-12 weeks (2.5 – 3 months) after hip surgery. However, full recovery from a hip replacement typically takes up to 12 months, but this is dependent on each patient’s specific circumstances.