Purpose: The current concern to achieve 120° postoperative flexion in certain patients raises the problems of polyethylene wear, prosthesis stability, and surgical technique. The purpose of this clinical and radiographic comparative study was to analyse pertinent factors

Material and methods: We studied two groups of posterior stabilised total knee prostheses with mobile plateaux. In group A (23 knees), the plateau had rotatory and translation mobility. In group B (36 knees) the plateaux only had rotatory mobility and the posterior condyle was long. We studied clinical flexion before surgery and postoperatively at one year. The radiographic analysis included: mechanical axis, height of the articular space, patellar height, anteroposterior prosthetic surface. In both groups the patients had undergone medial parapatellar arthrotomy and had participated in the same rehabilitation programme.

Results: There was no statistically significant difference between the two groups for age, gender, weight, height, pre-operative diagnosis, or preoperative flexion (mean 120.8°, range 90–130° in group A and mean 120.7°, range 90–140° in group B). Mean postoperative flexion was 114.8° (50–140°) in group A and 130.4° (90–150°) in group B. The difference was statistically significant. There were two episodes of instability in group A and none in group B. There was no difference concerning the pre- or postoperative axis or patellar height. There was a difference in articular space height and anteroposterior prosthetic surface.

Discussion: The gain in flexion achieved in group B is related to the smaller anteroposterior prosthetic surface and the more systematic use of distractors to clear the posterior part of the knee. The design of the posterior condyle could also be involved, allowing better congruence beyond 120°. The difference in stability between the two groups could be related to a difference in the distance between the apex of the tibial attachment and the posterior stabilisation cam. This study demonstrated that increased flexion is possible after total knee arthroplasty in certain patients. It is related to surgical technique but also has direct implications for prosthesis design.

Purpose: The Oxford unicompartmental prosthesis has congruent joint surfaces due to use of a mobile meniscus whose upper part matches the sphere constituted by the femoral component. The purpose of this work was to report results in a series of 75 prostheses studied with mean follow-up of 12.4 years (range 10–14 years).

Material and methods: Mean age of patients was 65 years (38–84), with 67% women and mean body mass index of 28.7 (21.2–40.6). Patients gave their subjective assessment of the arthroplasty and the IKS scores were determined. Radiographically, the mechanical alignment of the lower limb was evaluated pre- and postoperatively on the full stance images. The Kennedy classification (4 grades) was used to assess passage of the mechanical axis through the knee.

Results: At last follow-up, three patients were lost and eight had died. According to their subjective assessment, 84% of the patients were enthusiastic or satisfied. The overall IKS score showed that 52% of the patients were above 180 points, 25% above 150 points. Mean varus was 11° (2–24°) preoperatively and 5.7° (5° valgus to 14° varus) at last follow-up. The mechanical axis passed in the sufficient correction zone (c or 2) in 77% of the knees, undercorrection zone in 17% and in the overcorrection zone in 6%.Seven prostheses were revised for mechanical failure: four for loosening, two for extensive degeneration, and one for pain giving a survival curve of 90% at 12 years. It must be added that two meniscal dislocations occurred, one early due to wound dehiscence and infection and one late, both after a fall.

Discussion: Most loosenings occurred early and at the tibial level. Defective alignment could be incriminated in one case. The other knees exhibited a reactive line under the tibial plateau. The rate of dislocation should probably decline with the use of progressive reamers, not available at the time of this series. Finally none of the prostheses were revised for wear, confirming the proper prosthesis design.

This comparative clinical and radiographic study evaluates the role of implant design and positioning on maximum postoperative flexion after TKR.

Two groups of cemented posterostabilised mobile prosthesis were studied. In group A (23 cases) bearing mobility was possible in rotation and translation. In group B (36 cases) solely rotation was possible and the radius of the posterior femoral condyle was larger. In both groups the same medial transquadricipital approach was used and the postoperative rehabilitation was identical.

There were no significant difference between the two groups for patient age, sex, weight and etiology. The average preoperative flexion was 120.8° in group A and 120.7° in group B. The average postoperative flexion at one year was 114.8° in group A and 130.4° in group B. Instability was noted twice in group A and none in group B. Radiographically there was no difference in mechanical axis or patellar height. There was a difference in joint line elevation and anteroposterior joint size.

Higher flexion angle may be related to smaller antero-posterior joint size, better posterior osteophytes removal and larger posterior femoral condyle radius. Greater stability correlates with greater jumping distance over the tibial post. This study showed that deep flexion can be achieved in some patients after TKR, with implications on surgical technique and implant design.

The objective of the present study was to analyse kinematics of subjects having a UKA during stance phase of gait, where the ACL was intact at the time of the operative procedure.

Femorotibial contact positions for nineteen subjects (15 medial UKA (MUA); 14 lateral UKA (LUA); HSS > 90, post-op > 3 yrs) were analysed using video fluoroscopy.

During stance-phase of gait, on average, subjects having a medial UKA experienced 0.8 mm of anterior motion (7.7 to – 2.3 mm), while subjects having a lateral UKA experienced −0.4 mm (0.9 to – 2.1 mm) of posterior femoral rollback (PFR). Eight of 15 subjects having a medial UKA and two out of four lateral UKA experienced PFR. Eight of 15 subjects having a medial UKA experienced normal axial rotation (average = 0.9 degrees) and one out of four subjects having a lateral UKA experienced normal axial rotation (average = −6.0 degrees).

High variability in the kinematic data for subjects experiencing an anterior slide and opposite axial rotation suggests that these subjects had an ACL that was not functioning properly and was unable to provide an anterior constraint force with the necessary magnitude to thrust the femur in the anterior direction at full extension. Progressive laxity of the ACL may occur over time, and at least in part, lead to premature polyethylene wear occasionally seen in UKA. Our results support the findings of other studies that the ACL plays a significant role in maintaining satisfactory knee kinematics, which may also, in part, contribute to UKA longevity.

The objective of this present study was to determine the in vivo kinematic patterns for subjects implanted with a patellofemoral arthroplasty (PFA).

Twenty subjects, all having a PFA, were studied (< 2 years post-op) under fluoroscopic surveillance to determine patellofemoral contact positions, sagittal plane, and medial/lateral translation using a skyline view.

The patellofemoral contact patterns for each subject having a PFA was highly variable, 11.9 mm of translation. The average amount of patella rotation during the full flexion cycle was 26.3 degrees, while one subject experienced 48.6 degrees. The average amount of medial/lateral translation was 3.8 mm (5 > 5 mm). Five subjects experienced grater than 5 mm of motion.

This was the first study to ever determine the in vivo kinematics for subjects having a PFA and the in vivo medial/lateral translation patterns of the patellofemoral joint. Subjects in this study experienced high variability and some abnormal rotational patterns. Most of the subjects who underwent PFA in this study had a previous history of subluxed or dislocated patella which affects the normal patella tracking, especially regarding tilting and translation. This tracking may also be directly affected by patellofemoral conformity, a consequence of femoral implant design. Finally, after PFA the patello-tibial tilt angle is influenced by the anteroposterior positioning of the femoral component.

The results of this very first in vivo kinematic study may play an important role, not only for design consideration of patellofemoral replacement but also for surgical technique in order to obtain optimal implant positioning.

Purpose: Implantation of a prosthesis on a remodelled femur can cause technical difficulties affecting the outcome of the arthroplasty. We performed a tridimensional study of the femoral anatomy before prosthesis implantation for sequelar congenital hip dislocation.

Material and method: The series included 312 hips in 262 patients. The same radiography and computed tomography work-up was perfomred in all patients. There were 288 women and 84 men, men age 56 years. Mean weight was 66 kg and mean height was 163 cm. The crowe classification was 195 dysplasia, 123 dislocations (41% class I, 27% class II, 13% class III, 19% class IV). Telemetric measurements were: femoral isthma, the centre of the lesser trochanter, limb length discrepancy, the cephalo-cervico-diaphyseal angle. Computed tomographic measurements were: anterio-posterior and mediolateral dimensions and femur funneling, helitorsion between the bichondylar plane and the upper femur, anteroposterior diameter of the acetabulum.

Results: The mean mediolateral and anteroposterior diameters of the femoral canal at the isthma were 9.8 and 13.1 cm respectively in dysplasia and 9.3 and 12.6 cm, 9.4 and 12.7, and 9.7 and 13.6 cm in I, II, and III–IV congenital dislocations respectively. The femoral funneling index varied from 1.9 to 7.6 in dysplasia and from 2.6 to 7.9, 2.1 to 8.4 and 2.1 to 8.7 in I, II, and III–IV congenital dislocations respectively. The mean cephalo-cervico-diaphyseal angle was 129.3°, 131.9°, 136.8°, and 127.4° respectively. Maximal leg length discrepancy was 45, 57, 71, and 82 cm respectively. Mean helitorsion was 22.9° (1°–52°), 36.4° (8°–86°), 43.2° (2°–82°- and 38.4° (6°–68°) respectively. The mean anteroposterior diameter of the acetabulum was 52, 51.2, 53.1; and 49.6 cm respectively.

Discussion and conclusion: The dysplastic or dislocated femur is narrower than the normal femur with wide variations in funneling and cephalo-cervico-diphyseal angle. The mean difference in leg length increases gradually with helitorsion but with wide individual variability, irrespective of the grade. These tridimensional anatomic data can be useful for predicting difficulties in prosthetic treatment of these patients.