Take preoperative, intraoperative steps to minimize dislocation following THR

Using pre-emptive preoperative/intraoperative measures can reduce the risk of postoperative dislocation following total hip arthroplasty, according to an orthopedic surgeon in private practice.

Dislocation following total hip replacement (THR) “is the bane of the hip surgeon,” according to John M. Cuckler, MD, of Birmingham, Ala. He cited the inevitable “Friday-night telephone call,” most often from an emergency room which can leave an orthopedist wondering, “Where did I go wrong and what do I do next?”

The risk of dislocation can be minimized by “proper patient selection, appropriate component position and selection of components that are likely to be most resistant to dislocation in the individual patient,” Cuckler told Orthopedics Today. The choices for surgeons include a large diameter femoral head, a tripolar-type design, a constrained component and occasionally, trochanteric advancement.

The dislocation etiologies “are really pretty simple,” Cuckler, an Orthopedics Today Editorial Board member, said. “The majority are malposition of the components or soft-tissue imbalance usually associated with shortening.”

Causes of dislocation

Causes of early dislocation — those within the first 6 to 8 weeks — include acetabular retroversion or femoral retroversion, or a combination of the two. “Even excessive anteversion can contribute,” Cuckler said. Impingement should also be examined after implanting the final components by performing a complete range of motion to detect impingement, especially in flexion/internal rotation and extension with external rotation.

John M. Cuckler

Late dislocation, which occurs after years of successful function, is usually related to component wear or loosening of the implant. Trauma can also produce dislocation. Additionally, years after THR patient noncompliance can lead to dislocation, stemming from everything from substance abuse to progressive senility.

Overall, women are at greater risk for early and late dislocation, “probably because they acquire better motion as time goes by, whereas men are subject to things like impingement,” he said.

Addressing the dislocation

When dislocation first appears, a closed reduction is warranted. The surgeon should evaluate the stability of the hip after reduction with fluoroscopy. “I want to observe where the hip begins to sublux, so I can begin to consider if the problem is impingement or component malposition, as well as the likelihood of recurrence of dislocation,” Cuckler said.

He then places the patient in a THR orthosis at 15° abduction, and allows only 30° to 60° of motion. “I ask patients to wear the orthosis full time for 6 weeks, and during the day only for the following 12 weeks,” he said. “However, if wear, loosening or component malposition are thought to be the cause of the dislocation, revision will probably be necessary.”

Three dislocations constitute the need for a revision, according to Cuckler. “If all implants are well fixed and well aligned, and leg lengths are equal, your strategies may include procedures such as trochanteric advancement or use of a larger diameter femoral head, both accompanied by capsular repair.”

Chronic bracing “is the final salvage solution in some cases,” Cuckler said at the 11th Annual Current Concepts in Joint Replacement Spring Meeting (CCJR) in Las Vegas.

When performing a revision for recurrent dislocation, “it is important that you rigidly fix the pelvis,” Cuckler said. “The surgeon needs to know how the pelvis is aligned on the operating table in order to judge component position, especially the acetabular component.”

Large femoral heads should be generally selected to enhance stability. “The use of tripolar-type components is occasionally helpful, especially in a patient who may not be able to comply with restrictions in postoperative motion of the implant,” Cuckler said.

Cuckler said he uses constrained components in 10% to 20% of his revision cases. “The problem, though, is that the lever arm is so strong that there is really no locking mechanism to prevent recurring dislocation,” he said. The range of motion is also decreased by the constraining mechanism, which can lead to increased impingement and dislocation.

On the other hand, trochanteric advancement “works well for well-positioned implants and in cases where the limb lane has been optimally restored,” Cuckler said. Cuckler add that he braces all revisions for dislocation for 12 weeks after surgery in a THR orthosis, as described above. – by Bob Kronemyer

Reference:

• Cuckler JM. The chronic dislocator: The 3 a.m. phone call. Paper 82. Presented at the 11th Annual Current Concepts in Joint Replacement Spring Meeting. May 23-26. Las Vegas.

• John M. Cuckler, MD, can be reached at Suite 164, 100 Club Dr., Burnsville, AL 28714; 205-936-9199; e-mail: jcuckler@charter.net. He receives grant and research support, royalties and is on the speakers bureau for Biomet Orthopedics.