Prashant Deshmane

Flexion instability in posterior-stabilized total knee arthroplasty is a relatively uncommon but distinct problem that is often underdiagnosed and may require surgical management. This retrospective study evaluated the authors' management strategy and assessed the results of revision surgery. The authors identified 19 knees that underwent revision for isolated flexion instability after primary posterior-stabilized total knee arthroplasty. All patients had typical symptoms and signs of flexion instability, which include diffuse pain, especially when negotiating stairs, a sense of instability without giving way, recurrent joint effusions, and…

Accurate component placement in joint replacement cannot be overemphasized; despite many re-engineering efforts over the past 3 decades, failure rates at 10 years for total hip arthroplasty (THA) and total knee arthroplasty (TKA) remain constant. Intraoperative decisions with joint replacement have been facilitated with manual instrumentation and are affected by the surgeon's intuition, instinct, and experience. Current technology allows the development and use of high-tech instrumentation, which, irrespective of surgeon-dependent variables, gives intraoperative quantitative information on which precise placement of hip and knee components can be done. Component placement is the single most important technical maneuver the surgeon accomplishes to prevent mechanical complications, which will nearly eliminate outliers from very good and excellent results and revision as a consequence of technical errors; computer navigation has almost made it possible. In knees it gives precise component placement in the coronal and sagittal planes, and in hips it particularly improves acetabular component position by numerical control of inclination, anteversion, and most importantly center of rotation. Precision is enhanced even more when computer navigation is elevated to the next level, which is robotic guidance. The preoperative plan set by the surgeon is executed by the robotic tool while the surgeon manually controls the robotic arm. Bone preparation cannot exceed the boundaries the surgeon has set, as the surgeon's manual force will stop the robot and the error cannot be made. Robotic surgery has progressed in the unicompartmental knee, and this innovation is in the final stages of development in THA.

Newer surgical approaches to THA, such as the direct anterior approach, may influence a patient's time to recovery, but it is important to make sure that these approaches do not compromise reconstructive safety or accuracy. We compared the direct anterior approach and conventional posterior approach in terms of (1) recovery of hip function after primary THA, (2) general health outcomes, (3) operative time and surgical complications, and (4) accuracy of component placement. In this prospective, comparative, nonrandomized study of 120 patients (60 direct anterior THA, 60 posterior THAs), we assessed functional recovery using the VAS pain score, timed up and go (TUG) test, motor component of the Functional Independence Measure™ (M-FIM™), UCLA activity score, Harris hip score, and patient-maintained subjective milestone diary and general health outcome using SF-12 scores. Operative time, complications, and component placement were also compared. Functional recovery was faster in patients with the direct anterior approach on the basis of TUG and M-FIM™ up to 2 weeks; no differences were found in terms of the other metrics we used, and no differences were observed between groups beyond 6 weeks. General health outcomes, operative time, and complications were similar between groups. No clinically important differences were observed in terms of implant alignment. We observed very modest functional advantages early in recovery after direct anterior THA compared to posterior-approach THA. Randomized trials are needed to validate these findings, and these findings may not generalize well to lower-volume practice settings or to surgeons earlier in the learning curve of direct anterior THA.

This follow-up study reports on 69 patients at mean 13 years with total hip arthroplasty using 28-mm Metasul (Zimmer, Winterthur, Switzerland) metal-on-metal articulation. These results are not transferable to large-diameter head metal-on-metal articulations. Four new revisions, 3 for disassociation of the liner and 1 for mechanical loosening of the acetabulum, occurred since the previous report of mean 7.3 years. The prevalent cause of late revision is disassociation, which suggests a high frictional torque or impingement in these articulation surfaces. No revision was done for osteolysis. Overall, of the original 127 hips, 116 (91%) were known to have maintained their original components.

The intraoperative estimation of the anteversion of the femoral component of a total hip arthroplasty is generally made by the surgeon's visual assessment of the stem position relative to the condylar plane of the femur. Although the generally accepted range of intended anteversion is between 10 degrees and 20 degrees, we suspected that achieving this range of anteversion consistently during cementless implantation of the femoral component was more difficult than previously thought. We prospectively evaluated the accuracy of femoral component anteversion in 109 consecutive total hip arthroplasties (ninety-nine patients), in which we implanted the femoral component without cement. In all hips, we measured femoral stem anteversion postoperatively with three-dimensional computed tomography reconstruction of the femur, using both the distal femoral epicondyles and the posterior femoral condyles to determine the femoral diaphyseal plane. The bias and precision of the measurements were calculated. The surgeon's estimate of femoral stem anteversion was a mean (and standard deviation) of 9.6 degrees +/- 7.2 degrees (range, -8 degrees to 28 degrees). The anteversion of the stem measured by computed tomography was a mean of 10.2 degrees +/- 7.5 degrees (range, -8.6 degrees to 27.1 degrees) (p = 0.324). The correlation coefficient between the surgeon's estimate and the computed tomographic measurement was 0.688; the intraclass coefficient was 0.801. Anteversion measured by computed tomography found that forty-nine stems (45%) were between 10 degrees and 20 degrees of anteversion; forty-three stems (39%) were between 0 degree and 9 degrees of femoral anteversion; eight stems (7%) were in anteversion of >20 degrees; and nine stems (8%) were in retroversion. The surgeon's estimation of the anteversion of the cementless femoral stem has poor precision and is often not within the intended range of 10 degrees to 20 degrees of anteversion. The implications of this finding increase the importance of achieving a safe range of motion by evaluating the combined anteversion of the stem and the cup.