Dislocation after long-necked total hip arthroplasty.

Dislocation after total hip arthroplasty is problematic and not completely understood. Skirted long-necked implants have been used to reestablish soft tissue tension with the assumption that their use will reduce dislocation. It is unknown whether the dislocation rates with long-necked implants are different than those with standard neck length devices. The records of 250 consecutive total hip arthroplasties were reviewed, 125 primary and 125 revision, in which long-necked femoral prostheses were used. A matched control sample with standard neck length prostheses was defined. Dislocation rates and radiographic indices of leg length were calculated and compared with the control group. Dislocation rates in the long-necked groups were 10.6% and 18% for primary and revision surgeries, respectively. These rates were significantly higher than the rates seen in standard neck length controls (1.6% and 10%, respectively). There was no difference in leg-length discrepancy between long-necked prostheses and standard neck length matched controls. Long-necked prostheses are associated with higher rates of dislocation after total hip arthroplasty. The higher rates may be attributable to impingement of the neck, inadequate restoration of soft tissue tension, and/or other factors. Although this study cannot claim to have shown a cause and effect relationship between the skirted neck and dislocation, the association between the two variables is clearly shown.