Cornelia Lützner

Similar stability and range of motion between cruciate-retaining and cruciate-substituting ultracongruent insert total knee arthroplasty

AbstractPurpose The use of an ultracongruent (UC) insert with a standard femoral component for substitution of the posterior cruciate ligament (PCL) is a bone-preserving and therefore interesting alternative to the established box and cam mechanism of posterior-stabilized total knee arthroplasty (TKA). Despite the regular use of these UC inserts, there is little evidence about stability and range of motion (ROM).Methods The aim of this study was to evaluate the stability and ROM in standard cruciate-retaining (CR) and cruciate-substituting UC inserts of the same TKA. In 39 patients, intraoperative measurements of stability and ROM were taken (1) before soft tissue release and bone cuts, (2) after implantation of a CR TKA and (3) after resection of the PCL and substitution with an UC insert. All measurements were taken using a navigation system.ResultsStability measurements demonstrated no differences between CR (PCL intact) and UC TKA (PCL resected), but significantly increased anteroposterior translation at 60° and 90° of knee flexion compared with the preoperative condition. ROM measurements demonstrated improvement of knee flexion from preoperatively mean 105° (SD 14.1°) to intraoperative 120.2° (SD 6.7°) with the CR and 121.0° (SD 7.5°) with the UC insert and 113.5° (SD 14.0°) at the 1-year follow-up.ConclusionThis study demonstrates similar stability of an UC insert compared with a standard CR insert. UC inserts are therefore a bone-preserving solution if the PCL needs to be substituted. ROM was not improved after resection of the PCL and substitution with the UC insert.Level of evidenceII.

Placement makes a difference: Accuracy of an accelerometer in measuring step number and stair climbing

UNLABELLED Accurate and easy-to-use measurement tools are required to evaluate the effect of treatments on patient activity. Comfortable device placement and fixation are important for patient compliance. The aim of this study was the evaluation of the accuracy of an accelerometer at different placements and slow velocities. METHODS A total of 43 healthy volunteers were included for a literature-based treadmill protocol using five accelerometer positions; a subset of 18 volunteers performed an extended treadmill protocol with velocities between 0.1 and 2.6m/s and finally stair climbing. RESULTS An alternative accelerometer position at the anterolateral aspect of the middle shank did measure steps more accurately than at the manufacturer suggested position, especially during slow velocities. Participants preferred the alternative placement at the shank. The accuracy of different accelerometer positions was excellent at velocities between 1.0 and 2.2m/s. During slow velocities below 1.0m/s steps were recorded less accurately. Accepting an error of five percent, the accelerometer recorded steps accurately from 0.5m/s at the alternative placement and from 0.8m/s at the manufacturer suggested placement. Stair climbing was not recorded accurately by any accelerometer position. CONCLUSION For measuring step number during slow velocities, the alternative position should be favoured. Stair climbing was not recorded accurately by any tested placement.

Is Range of Motion After Cruciate-Retaining Total Knee Arthroplasty Influenced by Prosthesis Design? A Prospective Randomized Trial

Improvement in knee flexion is a major expectation for many patients undergoing total knee arthroplasty (TKA). One hundred and twenty two patients were randomized to receive a cruciate-retaining standard or high-flexion TKA. Range of motion (ROM) and functional outcomes were assessed. The high flexion implants had a greater intraoperative ROM than standard implants. The mean flexion preoperatively, intraoperatively and at the one year follow-up was 107.4°, 123.0° and 108.9° in the standard group and 109.9°, 129.1° and 109.7° in the high-flexion TKA group. These differences were not significant preoperatively and at follow-up, but intraoperatively (P < 0.001). In multivariate analysis preoperative knee flexion was the only significant factor influencing knee flexion at follow-up. No differences in the Knee Society Score or SF 36 were observed.

Midterm Results After Coated and Uncoated TKA: A Randomized Controlled Study.

Patients undergoing total knee arthroplasty (TKA) who have hypersensitivity to metals usually receive hypoallergenic TKA implants. Coating of a standard implant is a common solution. Although in vitro tests have demonstrated reduction in polyethylene wear for these coatings, it is unknown whether these costly implants have a clinical benefit for patients. One hundred twenty patients undergoing TKA were randomly assigned to receive a novel 7-layer-coating implant or a standard TKA implant. One revision occurred in the standard group, resulting in a calculated 5-year survival of 100% in the coated group and 98.1% in the standard group. The Oxford Knee Score improved substantially in both groups from a mean of 21.6 points preoperatively in the coated group and 21.9 points in the standard group to 39.2 points and 39.2 points, respectively. The current authors observed no adverse effects with the new coating during midterm follow-up. However, longer follow-up time is needed to evaluate possible advantages of this coating. [Orthopedics. 2016; 39(3):S13-S17.].

How Much Improvement in Patient Activity Can Be Expected After TKA

Most patients expect an improvement of physical activity after total knee arthroplasty (TKA). The aim of this study was to evaluate improvement in physical activity after TKA. An accelerometer was used to measure activity in 221 patients before and 1 year after TKA. The measurements included the total number of steps and time spent lying, sitting/standing, or walking. Threshold for achievement of health-enhancing physical activity (HEPA) guidelines and step-defined lifestyle were applied to the data. Measured steps per day improved from 5371 to 6587. Only 50 patients (22.6%) met the HEPA guidelines, whereas 31% achieved an active lifestyle. Improvement in daily step number was influenced by age (P<.001), body mass index (P<.001) and preoperative activity (P<.001). After TKA, patients improved in physical activity and one-third achieved an active lifestyle. Patient-specific characteristics and preoperative levels of physical activity had a relevant influence on activity after TKA. [Orthopedics. 2016; 39(3):S18-S23.].

TKA for Posttraumatic Osteoarthritis Is More Complex and Needs More Surgical Resources.

The purpose of this study was to evaluate the surgical effort of total knee arthroplasty (TKA) for posttraumatic osteoarthritis (PTOA) compared with primary osteoarthritis (OA). A total of 1841 TKAs were analyzed, including 170 patients with PTOA, that resulted from soft tissue trauma in 83 patients and fractures in 87 patients. Results showed that patients were significantly younger at the time of surgery in the posttraumatic group (62 vs 71 years; P<.001). Furthermore, fracture was associated with 3.7 years earlier need of TKA compared with soft tissue trauma. Operation time was significantly longer for both of the posttraumatic groups compared with OA (P<.001). Patients undergoing TKA after knee injuries are younger and surgical treatment is more challenging compared with TKA for OA. Extended operation time and implant systems with higher constraint and modular options are required. [Orthopedics. 2016; 39(3):S36-S40.].