Education and reducing the learning curve

There is a need for better education on hip resurfacing in residency training programs. The learning curve for most surgical procedures occurs during residency. When metal-metal resurfacing became available, a paucity of practicing orthopedic surgeons had prior training in hip resurfacing. There are limitations on surgical training outside academic programs. Education for metal-metal resurfacing was primarily through industry-sponsored courses, with a variable degree of supervised surgery on actual patients. All orthopedic residents receive training in total hip replacement, but training in hip resurfacing is not available to many. Residency training should include the fundamentals of patient selection for resurfacing, preoperative planning, and avoidance and management of complications. The greatest benefit of residency training, however, is in the operating room. The best way to learn surgical skills is through direct observation and repetition of the correct technique under the guidance of an experienced mentor. This deficit in residency training should be considered when comparing community results (ie, joint registries) of total hip replacement with hip resurfacing. Regardless of technological evolution, the outcomes of community hip resurfacings would be improved if the steep portion of the learning curve occurs during residency training.

Surgical technique, component positioning, and instrumentation

Most short-term complications associated with resurfacing, including femoral neck fractures, dislocation, loosening, accelerated wear, and ALTRs, are related to surgical technique or component position. On the femoral side, varus component orientation, neck notching, overpenetration of cement, and vigorous femoral impaction should be avoided. The currently available mechanical means for femoral guide pin placement have a learning curve. Computer-assisted (navigation) femoral guide pin placement improves accuracy when compared with mechanical means. Preoperative 3-dimensional analysis of the proximal femur using computed tomography or magnetic resonance imaging creates a shape-matching guide for femoral pin placement. This methodology is more time efficient than intraoperative computer navigation.

The prime problem in hip arthroplasty today is acetabular component positioning. Because of the relatively small head to neck ratio of resurfacing compared with modern total hip replacement, the window for proper component position is smaller. There are 2 challenges: determining the desired component positions for a specific hip and being able to reliably implant the components in that position. Current evidence indicates that the determination of satisfactory femoral-acetabular mating includes consideration of the native femoral valgus and the corresponding acetabular component lateral opening and the native femoral version and the corresponding acetabular component version. To achieve adequate bearing contact area, a femur with increased valgus needs a correspondingly lower acetabular component lateral opening angle. Similarly, a femur with increased anteversion needs a correspondingly lower acetabular component anteversion.

Inserting the acetabular component into the desired position requires identification of the pelvic plane or the use of validated surrogates. Innovations to accomplish this positioning include mechanical guides, intraoperative imaging, computer-assisted surgery (navigation), and pelvic/acetabular shape-matching guides.

Monoblock acetabular components with a cobalt-chromium alloy substrate are more difficult to properly seat than modular titanium alloy total hip replacement components. This disparity is because of the increased stiffness of the cobalt chrome components, the absence of a dome hole to visually assess the seating, and the relatively bulky monoblock insertion devices, which limit peripheral visualization and impinge on adjacent tissues. Future innovations include alternative means to assess seating and debulking with easily reattachable insertion/extraction instrumentation.

Surgical technique, component positioning, and instrumentation

Most short-term complications associated with resurfacing, including femoral neck fractures, dislocation, loosening, accelerated wear, and ALTRs, are related to surgical technique or component position. On the femoral side, varus component orientation, neck notching, overpenetration of cement, and vigorous femoral impaction should be avoided. The currently available mechanical means for femoral guide pin placement have a learning curve. Computer-assisted (navigation) femoral guide pin placement improves accuracy when compared with mechanical means. Preoperative 3-dimensional analysis of the proximal femur using computed tomography or magnetic resonance imaging creates a shape-matching guide for femoral pin placement. This methodology is more time efficient than intraoperative computer navigation.

The prime problem in hip arthroplasty today is acetabular component positioning. Because of the relatively small head to neck ratio of resurfacing compared with modern total hip replacement, the window for proper component position is smaller. There are 2 challenges: determining the desired component positions for a specific hip and being able to reliably implant the components in that position. Current evidence indicates that the determination of satisfactory femoral-acetabular mating includes consideration of the native femoral valgus and the corresponding acetabular component lateral opening and the native femoral version and the corresponding acetabular component version. To achieve adequate bearing contact area, a femur with increased valgus needs a correspondingly lower acetabular component lateral opening angle. Similarly, a femur with increased anteversion needs a correspondingly lower acetabular component anteversion.

Inserting the acetabular component into the desired position requires identification of the pelvic plane or the use of validated surrogates. Innovations to accomplish this positioning include mechanical guides, intraoperative imaging, computer-assisted surgery (navigation), and pelvic/acetabular shape-matching guides.

Monoblock acetabular components with a cobalt-chromium alloy substrate are more difficult to properly seat than modular titanium alloy total hip replacement components. This disparity is because of the increased stiffness of the cobalt chrome components, the absence of a dome hole to visually assess the seating, and the relatively bulky monoblock insertion devices, which limit peripheral visualization and impinge on adjacent tissues. Future innovations include alternative means to assess seating and debulking with easily reattachable insertion/extraction instrumentation.