Pelvic stability during simulated total hip arthroplasty motions: Comparing different hip positioners.

Introduction: Total hip arthroplasty (THA) requires forceful maneuvers that can cause the pelvis to shift from its original position. Various methods for stabilizing the pelvis in the lateral decubitus position exist, but there is limited data quantifying the relative stability of each hip positioner. We sought to quantify the pelvic movement that occurred in four commercially available hip positioners during surgeon induced motion of the hip. Methods: An infrared marker was attached to the ilium of a cadaver secured in the lateral decubitus position. Four commercially available hip positioners were used for positioning: Beanbag, Pegboard, Stulberg, and ExactFit. Rotation and translation was captured using an infrared marker and camera system while the hip was moved through six motions (Flexion, Extension, Internal Rotation, External Rotation, Push, and Pull). Results: The Beanbag had the greatest amount of rotation and translation of the pelvis, with maximum hip rotation of 41.5°. The Stulberg and Pegboard positioners showed intermediate stability, with a maximum rotation of 7.8° and 17.1°, respectively. The ExactFit hip positioner resulted in the least amount of motion of the pelvis, with a maximum rotation of the pelvis of up to 3.2°. Of the simulated motions performed, internal rotation and flexion of the hip led to the greatest changes in pelvic rotation and translation. Conclusion: The ExactFit positioner was associated with the smallest amount of pelvic motion during simulated motions of hip arthroplasty, followed by the Stulberg, Pegboard, and Beanbag positioners. Further studies are required to correlate this information with clinical outcomes following total hip arthroplasty.

Prophylactic Cerclage With Braided Polyblend Suture During Femoral Broaching.

Femur fractures occur during broaching and impaction of the implant during hip arthroplasty. Prophylactic cerclage of the proximal femur with braided cable and steel wire has been shown to decrease hoop stresses and has been posited as a way to decrease the incidence of intraoperative fracture. In this biomechanical study, the authors investigated the strain across the proximal femur during broaching after the application of stainless steel wire, comparing it with that for braided polyblend suture. Nine femur models were prepared, and strain gauges were applied to each of 3 groups. The control group received no cerclage, the second group received a double loop of suture, and the third group received a single loop of steel wire. A broach was firmly seated in each femur and sequentially increasing axial loads were applied at 1000 N, 2000 N, 3000 N, 4000 N, 5000 N, and 6000 N and to failure. Strain at all loads was lower in both cerclage groups than in the control group. Strain was 28.6%±12.4% lower in the suture group than in the control group (P=.0003). Strain was 30.8%±10.7% lower in the steel wire group than in the control group (P=.0011). There was no statistically significant difference between suture cerclage and steel wire cerclage (P=.7367). When used for prophylactic cerclage of the proximal femur, braided polyblend suture increases hoop stress resistance, decreases strain, and may play a clinically useful role in decreasing intraoperative proximal femur fractures during hip arthroplasty. [Orthopedics. 2016; 39(6):e1183-e1187.].

Development of a surgical skills curriculum for the training and assessment of manual skills in orthopedic surgical residents.

OBJECTIVE: To develop and conduct a pilot study of a curriculum of 4 surrogate bone training modules to assess and track progress in basic orthopedic manual skills outside the operating room. DESIGN: Four training modules were developed with faculty and resident input. The modules include (1) cortical drilling, (2) drill trajectory, (3) oscillating saw, and (4) pedicle probing. Orthopedic resident's performance was evaluated. Validity and reliability results were calculated using standard analysis of variance and multivariate regression analysis accounting for postgraduate year (PGY) level, number of attempts, and specific outcome target results specific to the simulation module. SETTING: St. Mary's Medical Center in San Francisco, CA. PARTICIPANTS: These modules were tested on 15 orthopedic surgery residents ranging from PGY 1 to PGY 5 experience. RESULTS: The cortical drilling module had a mean success rate of 56% ± 5%. There was a statistically significant difference in performance according to the diameter of the drill used from 33% ± 7% with large diameter to 70% ± 6% with small diameter. The drill trajectory module had a success rate of 85% ± 3% with a trend toward improvement across PGY level. The oscillating saw module had a mean success rate of 25% ± 5% (trajectory) and 84% ± 6% (depth). We observed a significant improvement in trajectory performance during the second attempt. The pedicle probing module had a success rate of 46% ± 10%. CONCLUSION: The results of this pilot study on a small number of residents are promising. The modules were inexpensive and easy to administer. Conclusions of statistical significance include (1) residents who could easily detect changes in surrogate bone thickness with a smaller diameter drill than with a larger diameter drill and (2) residents who significantly improved saw trajectory with an additional attempt at the module.

Achilles allograft reconstruction for recurrent dislocation in total hip arthroplasty.

Recurrent dislocation secondary to posterior soft tissue deficiency is a challenging complication of total hip arthroplasty. We describe the use of an Achilles allograft sling to improve hip stability. Eight patients treated with the sling were followed an average of 5 years. Seven patients had no recurrent instability and good postoperative range of motion. One graft failed in a patient with a neuropathic hip. Cadaveric biomechanical testing was also performed to investigate the stiffness and torque to failure of the sling in 6 specimens. Allograft slings can be used to improve hip stability. The technique is relatively easy to perform and does not limit postoperative range of motion. The graft decreases joint stiffness and has a greater torque to failure than the intact capsule.