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Purpose: The goal of this study was to investigate whether a new posterior cruciate ligament (PCL) balancing approach with a spacer technique during total knee arthroplasty (TKA) reproduced the correct tibiofemoral contact point (CP) location. It was hypothesized that it should be possible to adequately balance the PCL with this geometrical technique, obtaining correct position and stability of the medial femoral condyle, independent of insert shape. Methods: Nine fresh-frozen full-leg cadaver specimens were used. After native testing, prototype components of a new PCL-retaining implant were implanted using navigation and a bone-referencing technique. After finishing the bone cuts, the spacer technique was used to ascertain balancing of the PCL and the tibial cut was corrected if necessary. Passive and squat motions were performed before and after TKA using a dynamic knee simulator while tibiofemoral kinematics were recorded using six infrared cameras. CPs (native and implant) were calculated as the projections of the femoral condylar centres on the horizontal plane of the tibia. Results: The spacer technique resulted in correct PCL balancing in all specimens. The kinematic patterns of native and replaced knees showed no statistically significant differences in passive and squat motions. The medial CP after TKA was at the same position as in the native knee. No paradoxical sliding forward was seen after TKA, supporting our hypothesis. Conclusions: The spacer technique can be applied by surgeons during PCL-retaining TKA and will lead to good PCL balancing, indicated by a correct CP, no lift-off in flexion and no posterior sag. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to describe the intra- and inter-observer variability of the registration of bony landmarks and alignment axes on a Computed Axial Tomography (CT) scan. Six cadaver specimens were scanned. Three-dimensional surface models of the knee were created. Three observers marked anatomic surface landmarks and alignment landmarks. The intra- and inter-observer variability of the point and axis registration was performed. Mean intra-observer precision ranks around 1 mm for all landmarks. The intra-class correlation coefficient (ICC) for inter-observer variability ranked higher than 0.98 for all landmarks. The highest recorded intra- and inter-observer variability was 1.3 mm and 3.5 mm respectively and was observed for the lateral femoral epicondyle. The lowest variability in the determination of axes was found for the femoral mechanical axis (intra-observer 0.12° and inter-observer 0.19°) and for the tibial mechanical axis (respectively 0.15° and 0.28°). In the horizontal plane the lowest variability was observed for the posterior condylar line of the femur (intra-observer 0.17° and inter-observer 0.78°) and for the transverse axis (respectively 1.89° and 2.03) on the tibia. This study demonstrates low intra- and inter-observer variability in the CT registration of landmarks that define the coordinate system of the femur and the tibia. In the femur, the horizontal plane projections of the posterior condylar line and the surgical and anatomical transepicondylar axis can be determined precisely on a CT scan, using the described methodology. In the tibia, the best result is obtained for the tibial transverse axis. [Copyright &y& Elsevier]

Conclusions: In a cadaver model, posterior transosseous repair provides superior stability of a total hip replacement. Optimal surgical technique with a slightly modified approach allows greater retention of capsule and tendon length and a more anatomical reinsertion of the soft tissues. [ABSTRACT FROM AUTHOR]

The aim of this study was to measure and compare the ultimate failure strengths and cyclic fatigue strengths of currently available meniscal suturing devices. No statistically significant difference in failure load was found between a vertical loop suture (mean 46.3 N), a horizontal mattress suture (52.5 N), the T-fix Device® (47.5 N), and the 16-mm (39.2 N) and 13-mm (32.8 N) Bionix Arrow®. Statistically inferior results were seen with the 10-mm Bionix Arrow® (18.8 N), the S.D. Sorb Stapler® (4.3 N), and the 12-mm Arthrex Meniscal Dart® (10.5 N) (P<0.01). The Mitek Meniscal Repair System® (28.1 N) performed intermediate, with significantly better results than the S.D. Sorb Stapler® and the 12-mm Arthrex Dart®, but significantly worse than the vertical and horizontal sutures, the T-fix® and Bionix 16-mm Device® (P<0.01). Cyclic fatigue strength was significantly less for the 10-mm Bionix Arrow®, the S.D. Sorb Stapler®, and the 12-mm Arthrex Meniscal Dart® (P<0.01) compared to all other devices. We conclude that the 13- and 16-mm Bionix Arrow® and the T-fix Device® have comparable ultimate failure strengths and cyclic fatigue strengths to conventional meniscal suturing techniques. The 10-mm Bionix Arrow®, S.D. Sorb Stapler®, and the 12-mm Arthrex Meniscal Dart®, however, have far inferior failure and cyclic fatigue strengths and their clinical application should be questioned. [Copyright &y& Elsevier]

Purpose: Posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs.Methods: All prostheses were fixed on custom-designed metal fixtures and mounted in a knee rig and five sequential-loaded squats were performed between 30° and 130° of flexion. Contact pressure and contact area were measured using pressure-sensitive Tekscan sensors on the posterior face of the post. Kinematics was recorded with reflective markers and infrared light-capturing cameras.Results: The post-cam mechanisms analyzed in this study are very variable in terms of design features. This leads to large variations in terms of the flexion angle at which the post and cam engage maximal contact force, contact pressure and contact area. We found that more functional post-cam mechanisms, which engage at lower flexion angle and have a similar behavior as normal PCL function, generally show more normal rollback and tibial rotation at the expense of higher contact forces and pressures. All designs show high contact forces. A positive correlation was found between contact force and initial contact angle.Conclusion: Post-cam contact mechanics and kinematics were documented in a standardized setting. Post-cam contact mechanics are correlated with post-cam function. Outcomes of this study can help to develop more functional designs in future. Nevertheless, a compromise will always be made between functional requirements and risk of failure. We assume that more normal knee kinematics leads to more patient satisfaction because of better mobility. Understanding of the post-cam mechanism, and knowing how this system really works, is maybe the clue in further development of new total knee designs. [ABSTRACT FROM AUTHOR]

Abstract: In many cases knee osteoarthritis leads to total knee replacement surgery (TKR) even if the lateral compartment is not involved. More recently, a bicompartmental knee replacement system (BKR) (Journey Deuce, Smith & Nephew Inc., Memphis, TN, USA) has been developed that only replaces the medial tibiofemoral and the patellofemoral compartments, thus preserving both cruciate ligaments with its associated benefits. However information on the effect of BKR on in vivo knee joint kinematics is not widely available in the literature. Therefore, this study analyzed full three-dimensional knee joint kinematics in 10 postoperative BKR-subjects for a broad spectrum of relevant daily life activities: walking, walking followed by a cross-over or sidestep turn, step ascent and descent, mild squatting and chair rise. We analyzed to what extent normal knee motion is regained through comparison with their non-involved limb as well as a group of matched controls. Furthermore, coefficients of multiple correlation were calculated to assess the consistency of knee joint kinematics both within and between subject groups. This analysis demonstrated that, despite the presence of differences indicative for retention of pre-operative motion patterns and/or remaining compensations, knee joint kinematics in BKR limbs replicate, for a large range of daily-life motor tasks, the kinematics of the contra-lateral non-affected limbs and healthy controls to a similar extent as they are replicated within both these control groups. [Copyright &y& Elsevier]

Purpose: Long-term success of contemporary total knee replacements relies to a large extent on proper implant alignment. This study was undertaken to test whether specimen-matched cutting blocks based on computed axial tomography (CT) scans could provide accurate rotational alignment of the femoral component. Methods: CT scans of five fresh frozen full leg cadaver specimens, equipped with infrared reflective markers, were used to produce a specimen-matched femoral cutting block. Using those blocks, the bone cuts were made to implant a bi-compartmental femoral component. Rotational alignment of the components in the horizontal plane was determined using an optical measurement system and compared with all relevant rotational reference axes identified on the CT scans. Results: Average rotational alignment for the bi-compartmental component in the horizontal plane was 1.9° (range 0°-6.3°; standard deviation 2.6°). One specimen that showed the highest deviation from the planned alignment also featured a completely degraded medial articular surface. Conclusions: The CT-based specimen-matched cutting blocks achieved good rotational alignment accuracy except for one specimen with badly damaged cartilage. In such cases, imaging techniques that visualize the cartilage layer might be more suitable to design cutting blocks, as they will provide a better fit and increased surface support. [ABSTRACT FROM AUTHOR]

Background Eccentric exercises have proven to be an effective management option and prevention strategy in tendon overuse injuries (a challenging sport pathology). However, till date, these exercise protocols are undifferentiated and certainly don't take subregional stress and strain differences, which have frequently been mentioned as important etiological factors, in account. Knowledge on these biomechanical parameters, obtained by in vivo experiments, could optimise the exercise protocols. Objective The present experiment evaluates the feasibility of automatic, intensity-based, spatio-temporal elastic registration for non-invasive local strain measurement by speckle tracking on dynamic ultrasound movies. Methods An isolated porcine patellar tendon (tendon length of 60 mm) with bone parts at each side was placed in a loading frame with an ultrasound transducer orientated along the long axis of the tendon. Ultrasound recordings were made while the tendon was cyclically loaded at two different velocities (1 mm/s and 2 mm/s) and three different displacements (1.5 mm, 3 mm and 5 mm). Afterwards a precalibrated strain-gauge extensometer was inserted in the central 2.5 cm of the tendon and the same loading scheme was applied while recording ultrasound movies. The movies were processed, based on non-rigid elastic registration and speckle tracking, and these results were compared with the extensometer data. Results Ultrasound strain values were comparable to extensometer strain data in four measurements (a- velocity 1.0 mm/s, displacement 1.5 mm: 0.8% strain difference; b- velocity 1.0 mm/s, displacement 3.0 mm: 0.6% strain difference; c- velocity 1.0 mm/s displacement 5.0 mm: 0.7% strain difference; d- velocity 2.0 mm/s, displacement 1.5 mm: strain difference 0.1%) resulting in a mean strain difference of 0.55%. The measurements at velocity 2 mm/s and 3.00 and 5.00 mm displacement were left out because of poor tracking in these recordings due to more out of plane movement. Conclusion It seems feasible to obtain comparable strain values between extensometer measurements and speckle tracking on non-invasive ultrasound recordings. [ABSTRACT FROM PUBLISHER]