Hip replacements can be preformed through a direct anterior approach, an anterior lateral approach, a lateral approach, a posterior approach, and a superior approach. Some surgeons will use 2 incisions, both the anterior and superior approach. Each approach has advantages and disadvantages.
Types of Hip Replacement (Approach)
The superior approach is a relatively new approach that has recently been developed in Boston by Dr. Stephen Murphy. This superior approach is my preferred approach because I feel it offers the most advantages and the least disadvantages. Most notably, the hip stability after a superior approach is remarkable because neither the anterior nor posterior capsule is cut during this approach. In addition, the leg is never dislocated during the entire procedure and typically the hip can not be dislocated on the operating table even with the patient pharmacologically paralyzed and the leg in the most compromising positions. The excellent stability typically allows patients to move their leg after surgery without any restrictions on their motion. The leg is held in a normal position during the entire operation, so the blood vessels and nerves are not stretched and twisted like during other approaches. The femoral canal is prepared prior to the femoral neck is cut, so the femur is structurally more sound during the preparation of the canal. This fact may decrease the risk of femoral fractures during the canal preparation. Preparing the femoral canal before cutting the femoral neck also allows the surgeon to use a special leg length measuring device to recreate the patient's leg length and offset. Although larger body size makes any joint replacement a little harder, the superior approach seems to be easier than other approaches at dealing with the difficulties of joint replacement in larger patients. The relative easy with the superior approach in larger patients is because of the special leverage retractors and the inherent femoral stability while preparing the femoral canal. The disadvantages of the superior approach is that the surgeon can not deliberately lengthen a patient more than 1-2 cm because the intact joint capsule will not stretch more than about 1 cm. Another disadvantage of the superior approach is that it is more difficult to insert screws into the acetabular component, although I routinely do insert screws. Special equipment and training is required to perform this technique. The superior approach can easily be extended into a posterior approach if the surgeon needs more access to the femur or pelvis. The superior approach is most similar to the posterior approach without cutting the posterior capsule or short external rotator muscles and without dislocating the joint.
The direct anterior (Smith-Peterson) and anterior lateral (Watson Jones) approach have the advantage of not violating the posterior muscles (Gluteus Maximus). There is often less damage to the posterior capsule as well. The intact gluteus maximus muscle is the main purposed reason for the quicker recovery touted by some doctors. I personally think that the rate of recovery between my anterior approach hip replacements and my superpath approach hip replacements are very similar. The direct anterior approach is the most direct approach to the hip joint going through a thinner amount of soft tissue (2-3") than the posterior approach (3-5"). Most (90%) of hip dislocations occur posteriorly, and therefore the anterior approach likely has lower dislocation rate than a traditional posterior approach, although the dislocation rate is not zero. Most surgeons do not restrict their patients' hip motion after an anterior approach.
The anterior approach has the disadvantage of possibly injuring the lateral femoral cutaneous nerve, which can cause lateral thigh numbness. This numbness usually does not bother patients much. Surgeons often use a special operating table (Hanna table) to force the leg in a hyper-extended and externally rotated position in order to insert the femoral component into the femoral canal. This extreme leg position is not something the patient could do while they were awake. The anterior approach often requires using curved, tapered style femoral component because there is a limit to the amount of hip extension the surgeon can force the patient's leg into. The patient's body and limited hip extension can make it difficult to get a straight femoral component down the femoral canal. This is similar to a professional golfer deliberately hitting a slice onto the green to avoid a tree that blocks his direct shot. Because of the stress on the femoral bone by all of the attached muscles and the extreme leg position, there is a slightly higher rate of intra-operative femoral fractures with the anterior approach. The anterior approach is definitely easier at inserting the socket component and more difficult at inserting the femoral component.
The lateral approach (Hardinge) has the advantage of not cutting the posterior capsule and muscles (lower dislocation rate) and not inadvertently injuring the abductor muscles. The anterior 1/3 of the abductor muscles are dissected off the femur and then repaired at the end of the operation. The muscle belly is retracted and protected during the insertion of the femoral component. The disadvantage of the lateral approach is that the repaired abductor muscles must be protected after the surgery by limiting the patient's weight bearing status. The patient may also limp if the abductor muscles do not heal or are damaged from the dissection.
The posterior approach (Kocher-Langenbock) has the advantage of not injuring the abductor muscles and the dissection can be extended in case more access to the femur or pelvis is necessary. The posterior approach is probably the most popular approach for a total hip replacement today. The disadvantage of the posterior approach is that the posterior capsule and muscles are cut during the approach. They are typically repaired at the end of the case which helps prevent dislocations, but the posterior approach does have a higher dislocation rate than the other approaches. Most surgeons limit the patient's motion after surgery with a posterior approach to prevent any compromising leg positions that might cause a hip dislocation. Because the abductor muscles are spared, most patients have historically had the lowest rate of limping with the posterior approach.
The two incisions technique combines the anterior approach and the superior approach. The acetabular component is inserted through a traditional anterior incision and the femoral component is inserted through a superior incision. Advocated of this approach claimed that the two incisions approach offered the hip stability of an anterior approach and the abductor protection of a posterior approach. Skeptics of the two incisions approached have published high complications rates and claimed damage to the abductor muscles from the blind preparation of the femoral canal and insertion of the femoral prosthesis without protecting the abductor muscles. Initially, there was considerable marketing and publicity surrounding this approach, but recent reports are mixed.
Good results after a total hip replacement can be achieved with any of the above approaches. Patients should allow the surgeon to perform the approach the surgeon is most comfortable with.