Effect of quadriceps contraction on tangential patellar radiography.

This study examined whether the addition of quadriceps contraction to standard Merchant views provides additional useful information in the evaluation of patients with extensor mechanism malalignment. Fifteen patients (23 knees) with anterior knee pain due to lateral patellar compression syndrome and 22 control patients (44 knees) underwent standard Merchant views with the quadriceps relaxed and with an isometric isotonic contraction. Congruence and lateral patellar angles were measured for all groups. Although the congruence angle differed significantly between the control and symptomatic groups with the quadriceps contracted (P< or = .001), this difference also was seen without quadriceps contraction. There was also no significant difference within each group on addition of quadriceps contraction. No significant difference existed between the two groups for lateral patellar angle with quadriceps contraction. The addition of a controlled isometric quadriceps contraction did not add to the diagnostic yield of the standard Merchant view in terms of a predictable change in measured radiographic parameters.

Proximal and distal femoral centralizers in modern cemented hip arthroplasty.

Third generation cementing techniques using intramedullary restrictors, low porosity cement with pressurization, lavage, and cement-stem bond enhancement do not prevent implant malalignment and inadequate cement mantle thickness. This has led to the development of modular proximal and distal centralizers to control the alignment of the femoral component and maintain an adequate thickness of the cement, thereby theoretically decreasing the rate of aseptic loosening. A retrospective analysis was performed of 100 primary cemented centralized femoral components. At an average followup of 5.7 years (range, 4-8 years), the average Harris Hip Score was 90. There were no cases of aseptic loosening, osteolysis, or impending failure. Ninety-one percent of femoral stems were implanted with satisfactory alignment with an optimal cement thickness. However, six distal centralizers and one proximal centralizer fractured at the time of insertion and voids frequently were seen in and around the distal centralizer. Although centralizers improve prosthesis alignment and cement mantle thickness, the long term effects of centralizer fracture and distal cement voids need to be observed to determine if centralizers improve previous implant survival.