In this study, researchers from the Gait and Posture Lab at the University of Montreal in Canada compare walking patterns between patients who had a total hip replacement versus a surface replacement arthroplasty. An earlier study by Mont et al comparing these two groups reported a slower walking speed and decreased muscle force in the hip abductor muscle of the hip.
Results for the patients in the previous study were reported for six to 18 months after surgery. The effects of different implants on gait pattern were measured six to eight months after surgery in this study. The authors thought that a tighter time frame might give them a better way to compare these two patient groups.
Hip joint resurfacing was introduced several years ago to help younger patients who are more active and who would likely dislocate or wear out a total hip replacement. Surgeons found a way to replace the surface of the joint without removing the bone and replacing the entire joint. Bone is saved because the femoral head (round ball at the top of the thighbone) isn't cut off. And it isn't necessary to put a long stem down into the canal of the femur since the head isn't replaced.
All of these features of joint resurfacing make it possible for patients to extend the life of their own joint before a full joint replacement is needed. There is also some thought that joint resurfacing may preserve a more normal load transfer during gait (walking). If that is true, gait recovery could be added to the list of advantages for joint resurfacing over total hip replacement.
The researchers repeated many of the study features of the Mont et al group but the shorter time period and closer attention paid to the speed of walking set this study apart. Since speed affects how people walk, this factor is important. Three groups of 10 subjects were compared. One group of 10 received a total hip replacement. The second group of 10 had hip joint resurfacing. And the third group was the control group -- volunteers who were healthy and did not have any hip surgery. All 30 participants were similar in age, height, weight, and body mass index (BMI).
They tried to keep the surgical groups fairly simple in order to make clean comparisons. For example, no one in the surgical groups had any other hip or knee problems that could affect the way they walked. No one was obese, had a neurologic problem of any kind, or had back pain (all of which could also affect how they walked).
X-rays were taken before and after surgery and compared. Special computer software (Imagika) was used to measure various angles, centers of rotation, and differences in leg length between the operated hip and the other (normal) side. A daily rehab program under the supervision of a physical therapist helped patients regain motion and strength.
Each patient was evaluated individually and given a program that best suited their needs. Special attention was paid to the muscles surrounding the hip. All exercises were progressed over a period of 12 weeks until the patients could return to normal, unrestricted activities (including high-impact sports such as basketball, football, or hockey).
