Partial hip replacement, also called hip hemiarthroplasty, is a surgical procedure where only the femoral head (the ball) of the damaged hip joint is replaced. The acetabulum (the socket) is not replaced. Basically, a partial hip replacement (hemiarthroplasty) is performed to treat femoral neck fractures which are a type of hip fracture. During a partial hip replacement, only the head of the femur (thigh bone) is replaced and the new prosthetic head rotates in the body’s own natural hip socket. The ceramic or metal ball is attached to a metal stem. This is called a hip implant. The stem is set down into the core of the thighbone (femur).

By comparison, a Total Hip Replacement involves replacing the femoral head and resurfacing the socket. With this procedure, the prosthetic femoral head moves within the prosthetic socket. Total hip replacements most often are performed when there is cartilage damage on both the femoral head and within the socket, which occurs from degenerative osteoarthritis of the hip. There is, however, an increasing trend to treat some hip fractures with total hip replacements.

Usually, patients who are considered good candidates for partial hip replacement have no underlying hip arthritis and have healthy acetabular cartilage. This is often the case for someone who has fractured the femoral neck after a fall but did not have troublesome hip symptoms or hip arthritis prior to their injury.

Hip fractures most commonly occur from a fall or from a direct blow to the side of the hip. Some medical conditions such as osteoporosis, cancer, or stress injuries can weaken the bone and make the hip more susceptible to breaking. In severe cases, it is possible for the hip to break with the patient merely standing on the leg and twisting. Osteoporosis is the most common bone disease. Osteoporosis is characterized by progressive bone loss that leads to brittle, thin and weak bones. The term osteoporosis (AH-stee-oh-por-OH-sis) literally means “porous bone”. In the United States, more than 53 million people either already have or are at high risk of developing osteoporosis. Half of all women and a quarter of all men over the age of 50 years will suffer a bone fracture caused by osteoporosis during their lifetime. Osteoporosis will contribute to an estimated 2 million bone fractures this year, and the National Osteoporosis Foundation estimates that number will increase to over 3 million by the year 2025. Osteoporosis is a disease that can be prevented and treated.

Basically there are four different categories or “grades” of fracture. Grades 1, 2 and 3 – subtrochanteric, intertrochanteric and fractured neck – don’t interfere with the joint at all and will generally be repaired with pins or nailing devices. Grade 4 – subcapital fracture – is graded into four “types”, according to the amount of displacement at the fracture site. Type 1 is a stable fracture with impaction, meaning the bones are pressed together. Type 2 is complete but non-displaced, meaning the bones remain aligned as they were pre-fracture. Type 3 is displaced but the two bone fragments have some contact with one another. Type 4 is completely displaced and there is no contact between the fracture fragments. Types 1, 2 and 3 can be fixed with pins or a nailing device. Type 4 will involve disruption of the blood supply to the femoral head with early bone death. This fracture is highly unlikely to heal if it is pinned like the other categories. In this situation, partial hip replacement or hemiathroplasty is required. Again, hemiarthroplasty simply involves removing the broken femoral head, trimming the fractured end of the neck and inserting a one piece prosthesis of stem and ball. The socket or acetabulum is never interfered with as it is still in very good condition.

The patient with a hip fracture will have pain over the outer upper thigh or in the groin. There will be significant discomfort with any attempt to flex or rotate the hip. If the bone has been weakened by disease (such as a stress injury or cancer), the patient may notice aching in the groin or thigh area for a period of time before the break. If the bone is completely broken, the leg may appear to be shorter than the non-injured leg. The patient will often hold the injured leg in a still position with the foot and knee turned outward (external rotation).

Because younger people can sometimes suffer a Type 4 subcapital fracture, a hemiarthroplasty is not normally used because metal prosthesis bearing against bone is not the optimal solution. It can result in wear on the bone and possibly even to the point of wearing away the base of the socket. For this reason, certain patients – young patients and also very able and active older patients – may have a total hip replacement performed as an emergency procedure, rather than a partial hip replacement.Even in the event of this type of hip fracture, a partial hip replacement is only recommended on occasion and generally only when the patient is elderly and in poor health.

Usually, patients who are considered good candidates for partial hip replacement have no underlying hip arthritis and have healthy acetabular cartilage. This is often the case for someone who has fractured the femoral neck after a fall but did not have troublesome hip symptoms or hip arthritis prior to their injury.

For a variety of reasons, your surgeon may decide it is more suitable to treat your fractured hip with a total hip replacement rather than a partial hip replacement, even if you have no evidence of osteoarthritis. Your surgeon may feel a total hip replacement would be in your best interest if you have other conditions, such as thin bone in the socket, a bone cyst in the femur or pelvis, or an additional fracture elsewhere around your hip joint. As with any orthopedic surgery and, certainly, with any hip replacement surgery, patients are best-advised to speak with an experienced, board-certified orthopedic surgeon about all available surgical and conservative options. He or she will give you a recommendation based upon your specific circumstances and their history and familiarity with certain implants and procedures.

A partial hip replacement removes and replaces the ball of the hip joint. It does not replace the socket. This surgery is most often done to repair certain types of hip fractures.The ceramic or metal ball is attached to a metal stem. This is called a hip implant. The stem is set down into the core of the thighbone (femur).

Source: American Academy of Orthopaedic Surgeons, https://orthoinfo.aaos.org/; American Association of Hip and Knee Surgeons, https://hipknee.aahks.org/total-hip-replacement/; BoneSmart, https://bonesmart.org/hip/partial-hip-replacement-surgery/