Abstract Whether there are differences in knee anthropometry between Asian and white knees remains unclear. Three-dimensional knee models were constructed using computed tomography or magnetic ...resonance imaging of healthy Chinese and white subjects. The morphologic measurements of the femur included mediolateral, anteroposterior dimensions, and aspect ratio. The tibial measurements included mediolateral, medial/lateral anteroposterior dimension, aspect ratio, and posterior slope of medial/lateral plateau. The results showed that Chinese knees were generally smaller than white knees. In addition, the femoral aspect ratio of Chinese females was significantly smaller than that of white females (1.24 ± 0.04 vs 1.28 ± 0.06). Tibial aspect ratio differences between Chinese and white males (1.82 ± 0.07 vs 1.75 ± 0.11), though significant, were likely a reflection of differences in knee size between races. These racial differences should be considered in the design of total knee arthroplasty prosthesis for Asian population.
Abstract Lack of ACL and non-anatomic articular surfaces in contemporary total knee implants result in kinematic abnormalities. We hypothesized that such abnormalities may be addressed with a ...biomimetic bi-cruciate retaining (BCR) design having anatomical articular surfaces. We used dynamic computer simulations to compare kinematics among the biomimetic BCR, a contemporary BCR and cruciate-retaining implant for activities of daily living. During simulated deep knee bend, chair-sit and walking, the biomimetic BCR implant showed activity dependent kinematics similar to healthy knees in vivo. Restoring native knee geometry together with ACL preservation provided these kinematic improvements over contemporary ACL-preserving and ACL-sacrificing implants. Further clinical studies are required to determine if such biomimetic implants can result in more normal feeling knees and improve quality of life for active patients.
Abstract Background Modular dual taper femoral neck designs have been associated with taper corrosion requiring revision surgery. However, outcomes after revision dual taper total hip arthroplasty in ...patients with symptomatic adverse local tissue reaction due to taper corrosion remain largely unknown. Methods A total of 198 revision surgeries in 187 patients with dual taper femoral stem total hip arthroplasty with minimum 12-month follow-up were evaluated. Results At mean follow-up of 18 months, at least 1 complication had occurred in 39 patients (20%) of 198 revisions. Single episode of dislocation, treated with close reduction, occurred in 16, whereas 2 patients required rerevision due to multiple dislocations. Infection requiring rerevision occurred in 3 patients. Adverse local tissue reaction recurrence requiring reoperation occurred in 6 patients. Implant survivorship for revision for any cause was 86% at 30 months. The reoperation rate of revised dual taper was 8% (16 out of 198 hips). The median serum levels of cobalt, chromium, and cobalt/chromium ratio decreased ( P < .01) from 5.3 μg/L (range: 2.3-48.5 μg/L), 2.6 μg/L (range: 0.2-64 μg/L), and 4.7 (range: 2.1-35) prerevision to 1.4 μg/L (range: 0.2-8.8 μg/L), 0.7 μg/L (range: 0.1-3.9 μg/L), and 2.2 (range: 0.4-8.8) postrevision, respectively. Conclusion This pilot study demonstrates that intraoperative tissue necrosis was associated with a high rate of early complications (20%) and revisions (8%), suggesting the importance of a systematic evaluation of these patients including metal ion levels and metal artifact reduction sequence magnetic resonance imaging in optimizing revision outcome, as early diagnosis will facilitate the initiation of appropriate treatment before significant adverse tissue necrosis.
Abstract Alterations in normal knee kinematics following total knee arthroplasty (TKA) arise in part from the non-anatomic articular geometry of contemporary implants. In this study, the kinematics ...of a novel posterior cruciate-retaining (CR) implant with anatomic (biomimetic) articular surface, were compared to that of contemporary CR implants during various simulated activities. Across different simulated activities the biomimetic-CR mimicked normal kinematic patterns more closely than contemporary CR implants. In particular, during deep knee bend and chair-sit, the biomimetic-CR showed medial pivot motion, while other CR implants showed abnormal motion including lateral pivot or no pivot, and paradoxical anterior sliding. Further in vivo and clinical studies are needed to determine whether such biomimetic implants can truly help to achieve a more normal feeling knee and improved patient satisfaction.
Purpose We hypothesized that a side-to-side (STS) tendon repair has biomechanical characteristics that match those of a Pulvertaft (PT) weave. Methods Thirty extensor tendons were harvested (4 ...extensor digitorum communis and 1 extensor indicis proprius from 6 cadaver arms). Three hand surgery fellows with similar backgrounds of training under the same conditions and precise standardized technique performed the repairs (5 PT and 5 STS per surgeon). After the repairs, the tendons were passed through a graft-sizing guide to determine bulk and results were expressed as a repaired versus native diameter ratio. The specimens were then tested for ultimate strength and fatigue properties. Failure type and mechanical properties were recorded and compared with those of the native tendon. Results The average peak force to failure was 93 ± 20 N for the STS and 62 ± 32 N for PT group. Relative strength ratio (repair strength compared with native tendon strength) was 37% ± 21% for the STS and 22% ± 11% for the PT group. In the STS group, all failures occurred as a result of tissue failure; however, in the PT, suture failures occurred in 3 tendons before tissue failure. The mean bulk ratio of the repaired site versus native proximal tendon was 37 ± 14% and 40% ± 22% more for the STS and PT groups, respectively. These values for native distal tendon were 28% ± 9.9% and 26% ±24 %, respectively for STS and PT repair. Furthermore, the bulk of the repaired site for the STS and PT groups was 4.2 ± 0.50 and 4.7 ± 1.2 mm, respectively. Conclusions Side-to-side repair technique showed superior biomechanical properties while demonstrating comparable repair bulk of the tendon coaptation compared with the Pulvertaft weave. Clinical relevance The results of this study may help guide a surgeon’s choice of repair technique when addressing tendon injuries or tendon transfers.
Abstract Biomechanical studies have shown that external rotation of the femoral TKA component improves patellar tracking but does not restore it to physiologic values. We hypothesized that this could ...be due to differences in the trochlear groove geometry of TKA and normal knees. This was investigated via a virtual TKA procedure that mounted femoral components on to 3-dimensional models of healthy femurs, followed by measurement of the trochlear geometry before and after the simulated TKA. The results showed that (1) external rotation of the component brought the trochlear groove closer to normal anatomy than no external rotation; (2) however, even with external rotation, the trochlear anatomy was only partially restored to normal. Further work is needed to determine implications for patellofemoral complications observed with current TKA designs.
Abstract Background context Previous studies have reported position-dependent changes of the lumbar intervertebral foramen (LIVF) dimensions at different static flexion-extension postures. However, ...the changes of the LIVF dimensions during dynamic body motion have not been reported. Purpose The objective of this study was to investigate the in vivo dimensions of the LIVF during a dynamic weight-lifting activity. Study design/Setting This was a retrospective study. Methods Ten asymptomatic subjects were recruited for this study. Three-dimensional (3D) vertebral models of the lumbar segments from L2 to S1 were constructed for each subject using magnetic resonance images. The lumbar spine was then imaged using a dual fluoroscopic imaging system as the subject performed a dynamic weight-lifting activity from an upper body position of 45° to a maximal extension position. The in vivo positions of the vertebrae along the motion path were reproduced using the 3D vertebral models and the fluoroscopic images. The minimal area, height, and width of each LIVF during the dynamic body motion were analyzed. Results The LIVF area and width monotonically decreased with lumbar extension at all levels except L5–S1 (p<.05). On average, the LIVF area decreased by 7.4±6.7%, 10.8±7.7%, and 10.0±8.0% at the L2–L3, L3–L4, and L4–L5 levels, respectively, from the flexion to the upright standing position, and by 6.4±5.0%, 7.7±7.4%, and 5.1±5.1%, respectively, from the upright standing to the extension position. The LIVF height remained relatively constant at all segments during the dynamic activity. The foramen area, height, and width of the L5–S1 remained relatively constant throughout the activity. Conclusions Human lumbar foramen dimensions show segment-dependent characteristics during the dynamic weight-lifting activity.
Abstract Background Current guidelines recommend longitudinal monitoring of at-risk metal-on-metal (MoM) arthroplasty patients with cross-sectional imaging such as metal artifact reduction sequence ...(MARS) magnetic resonance imaging (MRI) or ultrasound. During follow-up evaluations, the clinical focus is on the relative interval changes in symptoms, radiographs, laboratory tests, and cross-sectional imaging modalities. Although MRI has the capacity for the detection of adverse local soft tissue reactions (ALTRs), the potential disadvantages of MARS MRI include the obscuration of periprosthetic tissues by metal artifacts and the cost. The aim of this study was to evaluate the diagnostic accuracy of ultrasound in comparison with MARS MRI in detecting ALTR in MoM patients during consecutive follow-up. Methods Thirty-five MoM patients (42 hips) were recruited prospectively to evaluate the sensitivity and specificity of the ultrasound for detecting ALTR in relation to MARS MRI during 2 longitudinal follow-up scans. The agreement between ultrasound and MARS MRI in ALTR grade, size, and size change was calculated. Results At the initial evaluation and at the subsequent follow-up, ultrasound had a sensitivity of 81% and 86% and a specificity of 92% and 88%, respectively. At the follow-up evaluations, ultrasound was able to detect the “change” in the lesions size with −0.3 cm2 average bias from the MARS MRI with higher agreement (k = 0.85) with MARS MRI compared to the initial evaluation in detecting any “change” in ALTR size or grade. Conclusion Ultrasound detected the interval change in the ALTR size and grade with higher accuracy and higher agreement with MARS MRI compared with the initial evaluation, suggesting ultrasound is a valid and useful.
Abstract Background Component malalignment in unicompartmental knee arthroplasty (UKA) has been associated with contact stress concentration and poor clinical outcomes. However, there is a paucity of ...data regarding UKA component alignment and in vivo articular contact in weight-bearing position. This study aims to (1) quantify three-dimensional UKA component alignment and (2) evaluate the association between the component alignment and in vivo articular contact in standing position. Methods Seventy-seven UKAs in 68 consecutive patients were imaged in standing position using a biplanar X-ray imaging acquisition system. The UKA models were imported into a virtual imaging environment and registered with component silhouette on X-ray image for determination of component position and contact location. Anatomic bony landmarks of the lower limb were digitized for quantification of the bone alignment. Results The femoral component (FC) showed 1.6° ± 3.3° valgus, 6.5° ± 6.4° external rotation, and 2.4° ± 4.6° flexion. The tibial component (TC) showed 3.9° ± 4.5° varus, 4.4° ± 6.7° internal rotation, and 10.1° ± 4.6° tibial slope. The average contact point was located medially and posteriorly by 7.8 ± 7.6% and 0.7 ± 7.7% of TC dimensions to its center. Multiple regression analysis identified FC flexion as a significant variable affecting UKA anterior and/or posterior contact position (R = 0.549, P < .001). Conclusion This study demonstrated the highest variability of UKA component positioning in axial plane rotation for FC and TC. The association between FC flexion and anterior contact position suggests accurate implant positioning may be important in optimizing in vivo UKA contact behavior. Further studies are required to gain understanding of the influence of axial rotation variability on in vivo UKA contact kinematics during functional activities.
Background The suprascapular nerve (SSN) carries sensory fibers which may contribute to shoulder pain. Prior anatomic study demonstrated that alteration in SSN course with simulated rotator cuff ...tendon (RCT) tears cause tethering and potential traction injury to the nerve at the suprascapular notch. Because the SSN has been implicated as a major source of pain with RCT tearing, it is critical to understand nerve anatomy during shoulder motion. We hypothesized that we could evaluate the SSN course with a novel technique to evaluate effects of simulated RCT tears, repair, and/or release of the nerve. Methods The course of the SSN was tracked with a dual fluoroscopic imaging system in a cadaveric model with simulated rotator cuff muscle forces during dynamic shoulder motion. Results After a simulated full-thickness supraspinatus/infraspinatus tendon tear, the SSN translated medially 3.5 mm at the spinoglenoid notch compared to the anatomic SSN course. Anatomic footprint repair of these tendons restored the SSN course to normal. Open release of the transverse scapular ligament caused the SSN to move 2.5 mm superior-posterior out of the suprascapular notch. Conclusion This pilot study demonstrated that the dynamic SSN course can be evaluated and may be altered by a RCT tear. Preliminary results suggest release of the transverse scapular ligament allowed the SSN to move upward out of the notch. This provides a biomechanical proof of concept that SSN traction neuropathy may occur with RCT tears and that release of the transverse scapular ligament may alleviate this by altering the course of the nerve.
PDF
