Leg lengthening after routine hip replacement surgery should be rare, but it is sometimes necessary. When the operative hip is lengthened, making it longer than the non-affected hip, it improves the stability of the hip and reduces the risk of dislocation. This increases the muscle tension around the hip and reduces the risk of impingement of the ball against the socket and thus improves the overall stability of the hip. Lengthening most commonly occurs with more complex procedures or during revision hip replacement.
For a routine hip replacement, there are numerous safety checks that are used to attempt to make your leg lengths normal. To start with, many surgeons will template your X-rays (place transparent pictures of different sized implants over the X-ray films) before surgery to plan what size implants will be needed and how they need to be positioned. At the time of surgery, trial implants are used prior to placing the final implants to test your hip stability through a functional range of motion and evaluate your leg lengths. Lastly, your surgeon will be able to clinically assess your leg lengths to ensure there is no additional lengthening prior to completion of the procedure. As a result, “true” lengthening of the leg is uncommon after hip replacement.
However, it’s not uncommon for patients to feel like their leg is too long after hip replacement. This is what we consider an apparent leg length discrepancy. Your operative leg is not actually longer after surgery. This apparent leg length discrepancy results from a contracture in your arthritic hip (pre-surgery) that limits your hip range of motion. As a result, your pelvis must accommodate and tilts down on the arthritic side.
Once your hip has been replaced, the contracture in the hip will be resolved and your motion improved. However, your pelvis is still tilted down on the operative side. This pelvic tilting is flexible and with time should balance out. As it does, your leg lengths should equalise. In some cases, this process can take several months.
Your surgeon may give you exercises to help correct this pelvic tilt. But, it’s critical that you don’t use shoe inserts unless directed by your surgeon. A shoe insert will make you feel more balanced from a leg length standpoint; however, it will prevent your pelvis from correcting to a more balanced position.
Another reason patients may feel like their leg is too long after hip replacement is due to their former arthritis. With advanced hip arthritis, oftentimes there’s some shortening of the affected leg, in addition to the wear of the joint. The leg lengths will be evaluated during surgery to account for this shortening, but it can feel strange immediately afterward.
In short, your leg lengths should be the same after surgery, but don’t be surprise if the operative leg feels too long initially. This is common and should correct with time. If you’re considering hip replacement surgery, talk to your surgeon about these concerns. He or she will be able to provide guidance specific to your condition.
Written by Thomas J. Aleto, M.D.
Paid Consultant of Zimmer Biomet
Thomas J. Aleto, M.D. is a board-certified, fellowship-trained Orthopaedic Surgeon in Columbia, Missouri. He specialises in hip and knee replacement surgery.