Influence of preoperative factors on the gain in flexion after total knee arthroplasty.

UNLABELLED: Final flexion mobility after a total knee arthroplasty is an important factor in patient comfort. Some patients gain in flexion mobility, others do not. Is it possible to identify the clinical factors related to the patient that predicted the final gain in flexion? MATERIALS AND METHODS: A multicenter retrospective study directed by the Société française de la hanche et du genou (SFHG) was conducted on 1601 cases of total knee arthroplasty that had presented no complications and a minimal follow-up of 2 years. The gain in flexion was assessed by the difference between the preoperative and the final range of flexion. The range of the gain in flexion was tested based on eight factors: age, gender, etiology, body mass index, frontal deformity, preoperative flexum deformity and four levels of preoperative mobility: < 90°, 90°-109°, 110°-129°, and ≥ 130°. RESULTS: A mean gain in flexion of 8.4°±14° was found for the overall series. In 66% of cases, we found an increase of flexion and in 19% a loss of flexion. In cases with BMI higher than 35, varus deformity with an HKA angle<166°, or flessum greater than 5°, the gain in flexion was significantly higher. A significantly different gain in flexion (P<0.0001) was found in the four levels of preoperative flexion: the greatest gain in flexion was found in the "<90°" group, then this gain was less in the next two groups, to become a significant decrease in the "≥130°" group. A decrease in flexion was noted in 51% of the cases in the latter group. Other factors such as age, sex, and etiology had no influence on the gain in flexion. DISCUSSION: After TKA, a gain in flexion was often noted. The amount of gain depended on the preoperative range of flexion: the lower this level was, the more flexion increased. The presence of a varus deformity, morbid obesity, or flessum was associated with greater gain in flexion, even if the final flexion was lower than the mean flexion in the overall population. The search for these factors made it possible to predict a gain in flexion and discuss this with the patient. LEVEL OF EVIDENCE: Level IV. Multicenter retrospective study.

Survival analysis of total knee arthroplasty at a minimum 10 years' follow-up: a multicenter French nationwide study including 846 cases.

INTRODUCTION: Survivorship for modern total knee arthroplasties (TKA) is not precisely known from large series, other than registries. The present retrospective study therefore analyzed 846 TKAs at a minimum 10 years' follow-up. HYPOTHESIS: Ten-year survivorship for TKAs in a multicenter study exceeds 90%, independently of design and level of prosthetic constraint. MATERIALS AND METHODS: Eight hundred and twenty-eight patients (846 TKAs) were assessed on the Knee Society score. Mean age was 71 years (range, 41-93 years); 274 males and 554 females (67%); 496 patients (60%) were active; diagnosis was principally osteoarthritis (n=752 [89%]). Most TKAs were cemented (n=704 [83%]), replacing the patella (n=668 [79%]) and sacrificed the posterior cruciate ligament (PCL) (n=707 [84%]), 65% being posterior-stabilized and 35% ultracongruent, with fixed (39%) or mobile bearing (61%). RESULTS: At a minimum 10 years' follow-up, mean knee score rose from 35 (15-55) to 83 points (74-95), and functional score from 24 (5-45) to 74 points (60-90); mean flexion rose from 105° (25-125°) to 112° (25-125°). Mean hip-knee-ankle angle was 179.5° (169-189°). Sixty-three (7.5%) revision surgeries were required, mainly for loosening (n=18 [2%]) or infection (n=18 [1.8%]). Overall 10-year survivorship was 92% (95% CI: 0.90-0.94). There was no significant difference in survivorship according to implant design or PCL retention. Activity level correlated with revision rate; mechanical complications were more frequent in active and infectious complications in sedentary subjects. Revision was not more frequent in TKA aligned outside the 177-183° range. DISCUSSION: Ten-year TKA survivorship was 92%, independently of design and level of mechanical stress. Revision was mainly for infection or loosening, and not for greater than 3° axis misalignment. Mechanical complications were more frequent in younger and more active subjects, for whom therefore other treatment options or technical improvements should be sought. LEVEL OF EVIDENCE: Level IV. Retrospective study.

A prospective clinical and radiological study comparing hydroxyapatite-coated with cemented tibial components in total knee replacement.

This prospective study compares the outcome of 157 hydroxyapatite (HA)-coated tibial components with 164 cemented components in the ROCC Rotating Platform total knee replacement in 291 patients. The mean follow-up was 7.6 years (5.2 to 11). There were two revisions for loosening: one for an HA-coated and one for a cemented tibial component. Radiological evaluation demonstrated no radiolucent lines with the HA-coated femoral components. A total of three HA-coated tibial components exhibited radiolucent lines at three months post-operatively and these disappeared after three further months of protected weight-bearing. With HA-coated components the operating time was shorter (p < 0.006) and the radiological assessment of the tibial interface was more stable (p < 0.01). Using revision for aseptic loosening of the tibial component as the end point, the survival rates at nine years was identical for both groups at 99.1%. Our results suggest that HA-coated components perform at least as well as the same design with cemented components and compare favourably with those of series describing cemented or porous-coated knee replacements, suggesting that fixation of both components with hydroxyapatite is a reliable option in primary total knee replacement.

[Evaluation of laxity, rigidity and compliance of the normal and pathological knee. Application to survival curves of ligamentoplasties]. / Evaluation de la laxité, de la rigidité et de la compliance du genou normal et pathologique. Application à la courbe de survie des ligamentoplasties.

PURPOSE OF THE STUDY: The aim of this prospective study was to measure the stiffness of the ACL in normal knees, ACL deficient knees and after ACL reconstructions or meniscectomies. Stiffness is a physical quantity which expresses objectively the mechanical efficiency of the ACL. MATERIAL AND METHODS: 1502 tests were performed on: 480 normal control knees, 191 acute tears and 171 chronic instabilities pre and post-operatively, 60 extra-articular plasties, 30 meniscectomies and 64 arthritic knees before and after a cruciate sparing arthroplasty. The force displacement measurements were made on radiograms of the medial and lateral compartment of each knee at 20 degrees flexion by applying a postero anterior force from 0 to 300 N with increments of 50 N. The stiffness is the slope of the F/dl curve. RESULTS: In the normal knee the medial compartment is fixed. Its stiffness is 13.8 x 10(4) N/m and does not depend on age and sex. The diagnosis of ACL rupture is made when the right/left difference on the medial compartment is at least 4 mm at 250 N. The lowest level for an accurate diagnostic is 180 N. The positive predictive value is 99 per cent. In acute tears the stiffness is 2.5 x 10(4) N/m. It is 3.4 x 10(4) N/m in chronic instability (p = 0.0001). When a meniscectomy was performed in chronic instability the stiffness decreases significantly (M+: 3.7 x 10(4) N/m; M-: 2.1 x 10(4) N/m) (p = 0.03). After a bone-patellar tendon-bone plasty (BPTB) the stiffness was 6.0 x 10(4) N/m and did not decrease with the passage of time but after the extra-articular plasty (EAP) the stiffness was 4.7 x 10(4) N/m after 24 months and 3.0 x 10(4) N/m after 60 months. Meniscectomy decreases the stiffness in both procedures, however it remains stable after BPTB, but decreases with the passage of time after EAP. DISCUSSION: Stiffness is a biomechanical parameter of knee ligaments. It is highly correlated with the clinical symptoms of instability (p = 0.0001). It is more accurate than laxity which is a numerical value without mechanical significance. CONCLUSION: This method gives functional information on the ACL deficient knee. It is the more precise method for the diagnostic of ACL rupture with an efficiency of 98.5 per cent. It has a high prognostic value after ACL surgery and can be considered as the mechanical survival of the plasty.

[Biomechanics of the normal and prosthetic knee]. / Biomécanique du genou normal et prothétique.

The knee joint is characterized by particular kinetics due to asymmetry of the femoral condyles and to angulation of the extensor system. During flexion, this results in a rolling/sliding movement in which the upper surface of the tibia recoils under the femoral condyles, combined with an automatic movement of medial rotation from extension towards flexion of the tibia beneath the femur. The articular contact areas are very small, ranging from 10 to 20 cm2 for the femorotibial articulation and barely reaching 4 cm2 for the femoropatellar articulation. These areas are subjected to extremely strong pressures amounting to 7 times the body weight in the femorotibial articulation during walking, and up to 1500 N (20 times the body weight) during simple flexion. However, the most fundamental element of biomechanics is the instability of the knee joint which is dependent on its menisco-ligamentous system. In addition, the menisci increase the femorotibial contact area, thereby relieving some of the pressure. The knee prosthesis concept is based on the stability of the prosthetic knee. In patients with healthy ligaments, non-strained prosthesis can be used, in which case part of the forces proceeds directly from one bone to the other via the ligaments, and there are only minimal stresses between the two prosthetic pieces and at the prosthesis/bone interface. But when the ligamentous system is defective or incomplete, or when the axial alignment is so upset that ligaments must be severed, one must use prostheses that are partly or totally constrained.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon-PGLA prostheses for ligament reconstruction. Experimental basis and short-term results in man.

The efficiency of a pure carbon prosthesis to reconstruct intra-articular ligamentous loss of substance was evaluated on 14 sheep with an 18-month follow-up study of recent and old ACL experimental injuries. Functional results showed a correlation between a tightened implant, the stability of the knee, and the absence of severe arthritis. The rupture strength of the newly formed ligament amounts to about 300 Newtons (N). That of the normal ACL amounts to 250-550 N. The structure gives a viscoelastic behavior to the prosthesis. This tissue was made of collagen fibers surrounding the carbon fibers and running generally in the direction of the ligament. In the osseous tunnels, the newly formed lamellar bone invaded and surrounded the implant. Carbon fiber fragmentation occurred, and fibers were found in the synovia and in the homolateral, inguinal, and paraaortic lymph nodes. No degeneration, necrosis of tissue, or cellular toxicity was found. On these bases, the carbon prosthesis was modified by adding a resorbable copolymer of polyglycollic (PGA) and polylactic acid (PLA) around the fibers and a resorbable sheath of the same polymer. This carbon-PGA/PLA prosthesis was used in 23 patients with a three- to 12-month follow-up period. Patients were evaluated by clinical tests and by functional control of the ligament. The indications for prosthetic replacement were: recent mop-end tears of the ACL, cruciate ligament reconstruction in chronic knee instability, and wide rotator cuff loss of substance. Five complications occurred because of hematomas and/or sepsis and prosthesis breakage. Eighteen of 23 patients had good clinical results with good function in five. The conclusions are that PGA/PLA produces a clean and flexible ligament, thus eliminating carbon fiber articular deposits and allowing a normal function. Inflammatory postoperative reactions seem to be more frequent than with other procedures and call for operative and clinical care in order to eliminate hematoma and sepsis. The efficiency of a rehabitable carbon-PGA/PLA prosthesis in intra-articular ligamentous defects in man will be confirmed only by controlled long-term clinical observations.

Harmonic and impulse rheological tests of biomaterials.

Up to now, not so much attention has been paid concerning the dynamic rheological behaviour of soft tissues although non linear viscoelastic effects have often been reported when mechanical properties of biomaterials are concerned. In order to characterize such properties different rheological tests have been proposed, the two principal being the study of the sample stresses responses to applied strains which are either harmonic with time or of step function type. Two different apparatus have been designed in our laboratory which allow specific rheological tests on biological materials under controlled environmental conditions. With one of them, harmonic uniaxial extension tests are performed in a large domain of frequencies (.001 Hz to 100 Hz) and forces (up to 20 daN); with the other, the samples are submitted to relaxation tests in uniaxial elongation up to 5 cm deformation within time duration of the order of 20 ms. The principal characteristics, limitations and performances of such apparatus are presented and few examples of data thus obtained are given. On the basis of quasi linear viscoelasticity models, it can be shown that both two types of tests with their proper limitations are leading to the same rheological parameters.

[Replacement of the anterior cruciate ligament by carbon fibers. An experimental study]. / Remplacement du ligament croisé antérieur par des fibres de carbone. Etude expérimentale.

The authors have excised the anterior cruciate ligament in 14 sheep and replaced it by carbon fibres. The animals were sacrificed after 12 to 18 months. Eight had a satisfactory new ligament without any evidence of arthrosis and with stability of the knee. In 2 cases, there was moderate instability and arthrosis associated with a lax ligament and in 3 cases the new ligament had ruptured with severe instability and arthrosis. Microscopic examination shows a satisfactory acceptance of the carbon filament both inside the bone as well as in the joint. There was no difference between cases repaired immediately or 6 months after excision of the ligament. A study of aortic lymph nodes showed the presence of carbon particles. The rupturing strength of the new ligaments and of normal ligaments were similar. The visco-elasticity of the new ligaments was also studied and was found to be satisfactory. It was considered that the use of carbon fibre may be valuable but more studies should be done to improve the elasticity and to decrease the migration of carbon material.

[Value of deliberate normovolemic hemodilution associated with a capillary vasoconstrictor, ornipressin, in surgery of the spine]. / Intérêt de l'hémodilution normovolémique intentionnelle associée à un vaso-constricteur capillaire, l'ornipressine, dans la chirurgie du rachis.

This study of sixty-seven children divided in two groups compared the blood loss and the amount of blood transfused during and after the operation. The operations were carried out without haemodilution nor the local injection of vasoconstrictor (twenty-four patients) and following haemodilution and the local injection of vasoconstrictor (forty-three patients). The blood loss during operation was 344 +/- 455 ml per vertebra in the first group, and 151 +/- 54 ml in the second. The blood loss in the post operative period did not seem to be modified by haemodilution, as the level of hemoglobulin was virtually the same in the two groups eleven days after the operation. A mean of seven units of blood were transfused to the first group, whilst only three in the second group. In the post-operative period, both groups received a mean of one unit each. Associating haemodilution and a vasoconstrictor, ornipressin, reduced very significantly the need for homologous blood.

[Epiphysiodesis in the treatment of discrepancies in length of the lower extremities (author's transl)]. / L'épiphysiodèse dans le traitement des inégalités de longueur des membres inférieurs.

Thirteen children treated only by epiphysiodesis for inequality in the length of lower limbs were reviewed after maturity. The intention was to estimate the value of the predictions of growth used in this work and the effectiveness of the operation. The result of this procedure depends upon the accuracy in predicting the further growth in order to determine at what age the operation should be performed. The imperfect results of epiphysiodesis are attributable to prediction errors and to operation delay in some cases. Prediction can be made using only roentgenographic measurement of the femur and the tibia, skeletal age and growth charts of Green and Anderson. It is not necessary to make use of others factors such as the size of the child.