In Asia and the Middle-East, people often flex their knees deeply
in order to perform activities of daily living. The purpose of this
study was to investigate the 3D kinematics of normal knees during
high-flexion activities. Our hypothesis was that the femorotibial
rotation, varus-valgus angle, translations, and kinematic pathway
of normal knees during high-flexion activities, varied according
to activity. We investigated the Aims
Materials and Methods
We investigated whether an asymmetric extension
gap seen on routine post-operative radiographs after primary total
knee replacement (TKR) is associated with pain at three, six, 12
and 24 months’ follow-up. On radiographs of 277 patients after primary
TKR we measured the distance between the tibial tray and the femoral
condyle on both the medial and lateral sides. A difference was defined
as an asymmetric extension gap. We considered three groups (no asymmetric
gap, medial-opening and lateral-opening gap) and calculated the
associations with the Western Ontario and McMaster Universities
osteoarthritis index pain scores over time. Those with an asymmetric extension gap of ≥ 1.5 mm had a significant
association with pain scores at three months’ follow-up; patients
with a medial-opening extension gap reported more pain and patients
with a lateral-opening extension gap reported less pain (p = 0.036).
This effect was still significant at six months (p = 0.044), but had
lost significance by 12 months (p = 0.924). When adjusting for multiple
cofounders the improvement in pain was more pronounced in patients
with a lateral-opening extension gap than in those with a medial-opening extension
gap at three (p = 0.037) and six months’ (p = 0.027) follow-up. Cite this article:
We measured the contact areas and contact stresses at the post-cam mechanism of a posterior-stabilised total knee arthroplasty when a posterior force of 500 N was applied to the Kirschner Performance, Scorpio Superflex, NexGen LPS Flex Fixed, and NexGen LPS Flex Mobile knee systems. Measurements were made at 90°, 120°, and 150° of flexion both in neutral rotation and 10° of internal rotation of the tibial component. Peak contact stresses at 90°, 120°, and 150° were 24.0, 33.9, and 28.8 MPa, respectively, for the Kirschner; 26.0, 32.4, and 22.1 MPa, respectively, for the Scorpio; and 34.1, 31.5, and 32.5 MPa, respectively, for the NexGen LPS Flex Fixed. With an internally rotated tibia, the contact stress increased significantly with all the fixed-bearing arthroplasties but not with the NexGen LPS Flex Mobile arthroplasty. The post-cam design should be modified in order to provide a larger contact area whilst avoiding any impingement and edge loading.
This study evaluated the effect of limb lengthening
on longitudinal growth in patients with achondroplasia. Growth of
the lower extremity was assessed retrospectively by serial radiographs
in 35 skeletally immature patients with achondroplasia who underwent
bilateral limb lengthening (Group 1), and in 12 skeletally immature
patients with achondroplasia who did not (Group 2). In Group 1,
23 patients underwent only tibial lengthening (Group 1a) and 12 patients
underwent tibial and femoral lengthening sequentially (Group 1b). The mean lengthening in the tibia was 9.2 cm (59.5%) in Group
1a, and 9.0 cm (58.2%) in the tibia and 10.2 cm (54.3%) in the femur
in Group 1b. The mean follow-up was 9.3 years (8.6 to 10.3). The
final mean total length of lower extremity in Group 1a was 526.6
mm (501.3 to 552.9) at the time of skeletal maturity and 610.1 mm
(577.6 to 638.6) in Group 1b, compared with 457.0 mm (411.7 to 502.3)
in Group 2. However, the mean actual length, representing the length
solely grown from the physis without the length of distraction,
showed that there was a significant disturbance of growth after
limb lengthening. In Group 1a, a mean decrease of 22.4 mm (21.3
to 23.1) (4.9%) was observed in the actual limb length when compared
with Group 2, and a greater mean decrease of 38.9 mm (37.2 to 40.8)
(8.5%) was observed in Group 1b when compared with Group 2 at skeletal
maturity. In Group 1, the mean actual limb length was 16.5 mm (15.8 to
17.2) (3.6%) shorter in Group 1b when compared with Group 1a at
the time of skeletal maturity. Premature physeal closure was seen
mostly in the proximal tibia and the distal femur with relative
preservation of proximal femur and distal tibia. We suggest that significant disturbance of growth can occur after
extensive limb lengthening in patients with achondroplasia, and
therefore, this should be included in pre-operative counselling
of these patients and their parents.
We performed a prospective, randomised trial of 44 patients to compare the functional outcomes of a posterior-cruciate-ligament-retaining and posterior-cruciate-ligament-substituting total knee arthroplasty, and to gain a better understanding of the At follow-up at five years, no statistically significant differences were found in the clinical outcome measurements for either design. The prevalence of radiolucent lines and the survivorship were the same. In a subgroup of 15 knees, additional image-intensifier analysis in the horizontal and sagittal planes was performed during step-up and lunge activity. Our analysis revealed striking differences. Lunge activity showed a mean posterior displacement of both medial and lateral tibiofemoral contact areas (roll-back) which was greater and more consistent in the cruciate-substituting than in the cruciate-retaining group (medial p <
0.0001, lateral p = 0.011). The amount of posterior displacement could predict the maximum flexion which could be achieved (p = 0.018). Forward displacement of the tibiofemoral contact area in flexion during stair activity was seen more in the cruciate-retaining than in the cruciate-substituting group. This was attributed mainly to insufficiency of the posterior cruciate ligament and partially to that of the anterior cruciate ligament. We concluded that, despite similar clinical outcomes, there are significant kinematic differences between cruciate-retaining and cruciate-substituting arthroplasties.
