Dislocation following total hip replacement

Abstract

Background: Hip replacement ranks among the more successful operations on the musculoskeletal system, but it can have serious complications. A common one is dislocation of the total hip endoprosthesis, an event that arises in about 2% of patients within 1 year of the operation. Physicians should be aware of how this problem can be prevented and, if necessary, treated, so that the degree of trauma due to hip dislocation after hip replacement surgery can be kept to a minimum.

Methods: The authors searched Medline selectively for pertinent publications and analyzed the annual reports of international endoprosthesis registries.

Results: The rate of dislocation of primary hip replacements ranges from 0.2% to 10% per year, while that of artificial hip joints that have already been surgically revised can be as high as 28%, depending on the patient population, the follow-up interval, and the type of prosthesis. Patient-specific risk factors for displacement of a hip endoprosthesis include advanced age, accompanying neurologic disease, and impaired compliance. Patients should scrupulously avoid hip movements such as bending far forward from a standing position, or internal rotation of the flexed hip. Operation-specific risk factors include suboptimal implant position, insufficient soft-tissue tension, and inadequate experience of the surgeon. Conservative treatment is justified the first time dislocation occurs without any identifiable cause. If a mechanical cause of instability is found, then operative revision should be performed as recommended in a standardized treatment algorithm, because, otherwise, dislocation is likely to recur.

Conclusion: The dislocation of a total hip endoprosthesis is an emotionally traumatizing event that should be prevented if possible. Preoperative risk assessment should be performed and the operation should be performed with optimal technique, including the best possible physical configuration of implant components, soft-tissue balance, and an adequately experienced orthopedic surgeon.

Figure 1

Pelvic radiograph after total hip arthroplasty. To restore hip joint kinematics, implant positioning is characterized by secure bone support, reconstruction of cup inclination (1) and anteversion (2), antetorsion of the stem and reconstruction of the rotational center of the hip, offset (3), and leg length (4)

Figure 2

Radiograph of a THA dislocation on the left side, resulting from loosening of the acetabular component. In this case, prosthesis infection led to loosening of the acetabular component and secondary dislocation

Figure 3

Extended prosthetic heads. Extended prosthetic heads are used to improve the soft-tissue tension of a total hip arthroplasty and thereby its stability. They feature a shoulder (arrow) in the area of head-neck junction which can – subject to the position of the acetabular component (cup) and the extent of motion – cause the shoulder to collide with the rim of the cup, thereby promoting the levering of the prosthetic head out of the cup eFigure: Directions of dislocation after total hip arthroplasty.

Figure 4

Diagnostic and therapeutic algorithm for THA dislocation. a.p., anterior-posterior; THA, total hip arthroplasty; CT, computed tomography; yrs, years

eFigure

Directions of dislocation after total hip arthroplasty. a) In cups opening excessively towards anterior (anteversion), b) external rotation and adduction of the extended hip joint may lead to dislocation. c) In case of excessively steep cup positioning (inclination) and abductor insufficiency, d) adduction of the extended leg may lead to dislocation. e) In cups opening excessively towards dorsal (retroversion), f) internal rotation and adduction of the flexed hip joint may lead to dislocation