Purpose of the study: In vivo kinematics of the knee joint (anteroposterior translation or rollback, axial rotation, elevation of the femoral condyle, range of motion) was determined for the knees of 30 subjects with a total knee prosthesis with a fixed or mobile plateau and also for the normal knees.

Material and methods: Videofluoroscopic images were recorded during gait and maximal flexion. An automatic 3D adaptation-modelling process was then applied to the fluoroscopic images to determine knee kinematics.

Results: For the normal knee, a certain degree of femoral rollback was noted for the lateral compartment (4.2 mm on average) while minimal translation was observed medially. The femoral rollback increased laterally during maximal flexion (14.4 mm on average) while the medial translation was minimal (1.5 mm on average). Thus, the average movement, which was not observed for all normal knees tested, was a pivot movement centred medially. The variability observed during maximal flexion was wide for all knee prostheses with a fixed or mobile plateau which do not have a stabilising system substituting for the absent posterior cruciate. During flexion, the normal knees exhibited mean 10° external rotation of the over the tibia. All of the rotational knee prostheses presented external rotation (mean 5°, ragne 0–10°). Inversely, the posterostabilised prostheses exhibited medial rotation of the femur over the tibia (mean 5°, range 0–10°), i.e. paradoxical movement.

Discussion: Unlike the normal knee where femoral rollback occurs during maximal flexion, paradoxical anterior translation of the femorotibial point of contact after arthroplasty, in particular in subjects with a fixed plateau prosthesis. For prostheses substituting for the posterior cruciate, femoral rollback involving the lateral condyle occurs regularly with minimal variability in the femorotibial contact point due to the regular engagement of the cam and cam follower mechanism during maximal flexion.

Purpose of the study: This retrospective analysis compared surgical treatments of femoral neck fractures in patients aged over 80 years.

Material and methods: Two hundred femoral neck fractures (Garden 3 and 4) were treated in three different manners: total prosthesis with a retaining cup (74 patients), intermediary prosthesis (58 patients), and osteosynthesis (68 patients). Indications were the same, but the periods of treatment were successive. Study variables were: mortality, number of revisions, duration of hospital stay, discharge to home or rehabilitation center, cost per hospital day. Follow-up was at least two years. The chi-square test was applied with p< 0.05.

Results: Mortality was similar for the three groups: eight deaths during stay in orthopedic unit (4%), three after total prosthesis (4%), three after osteosynthesis (5%) and two after intermediary prosthesis (3%). The difference was nonsignificant (p=0.24). Among the total prostheses, five dislocations (6.7%) required anesthesia despite the retaining cup. The rate of dislocation was 12% for intermediary prostheses and to avoid recurrence four revisions were needed to totalize an intermediary prosthesis with a retaining cup. Among the osteosynthesis cases, the rate of revision was 25%; transformation to a total prosthesis was necessary for 17% and material removal with resection of the head and neck was necessary in 8%. One total prosthesis and one intermediary prosthesis had to be removed because of infection. Resection of the head and neck for infection also occurred in one patient with an intermediary prosthesis. The rate of revision for an orthopedic problem was significantly less (p< 0.01) in the total prosthesis group. At last follow-up, or before death, patients with a total prosthesis were more independent and returned to their home significantly more often than patients treated with osteosynthesis. The economic cost of these interventions were not significantly different, the cost of the implant being insignificant compared with the cost of hospitalization and reeducation of this very elderly population.

Discussion: Total hip arthroplasty is a recognized treatment for painful degenerative hip disease. Historically, the total prosthesis was not considered as a first-intention treatment for fractures of the femoral neck in elderly subjects due to the risk of intraoperative blood loss, the risk of infection, and the risk of dislocation if a hip stabilization mechanism was not applied. This study demonstrated that, in light of the complications observed with the other methods, progress in anesthesia and use of implants avoiding dislocation can be proposed as first-intention treatment for total prosthesis patients who suffer a fracture of the femoral neck.

Purpose of the study: The aim of this study was to analyze rotation of the normal and prosthetic distal femur as well as the spaces from 90 to 130 degrees flexion.

Material and methods: Torsion scans were obtained preoperatively and postoperatively for 44 total knee prostheses. The difference in femoral torsion between the pre- and postoperative image was used to assess the rotation in which the femoral component was implanted. The prostheses were divided into two groups: group I when the femoral implant was implanted with external rotation of more than 5°; group II when the femoral implant was implanted with external rotation less than 5°. A preoperative stress scan was obtained in 20 patients then repeated during the year following implantation. Stress images with knee flexion at angles from 90° to 130° were obtained. The patient was installed in the ventral supine position. 8mm scan slices were centered on the lower end of the femur, ten 50ms images were acquired during flexion movement from 90° to 130°. This enabled determination of the knee flexion axis preoperatively and postoperatively, to measure the variation in the epicondylar axis compared with the mechanical axis of the tibia between 90° and 130° flexion and finally to deduct change in the femorotibial space in flexion from 90° to 130°.

Results: The 18 total knee prostheses with a femoral component implanted with external rotation greater than 5° (group I) showed significantly greater range of flexion (p< 0.05) (mean 120°, range 110°–130°) than the 26 prostheses in group II with a femoral component implanted in external rotation less than 5° (mean 100°, range 80°–115°. For the 20 knees with stress scans, the preoperative images showed an epicondylar axis about 5° fro the mechanical axis of the tibia when the knee flexed in the 90°–130° range. After surgery, the stress scans showed that this epicondylar axis of rotation of the prosthesis-bearing knees occurred especially for knees with a wide range of flexion. The 20 knees with flexion limited to 100° did not present an epicondylar rotation axis compared with the mechanical axis of the tibia. The 15 knees with 125° flexion or more had an epicondylar axis of rotation after 90° flexion. Rotation of the epicondylar axis in relation to the mechanical axis of the tibia between 90° and 130° flexion was the consequence of a femorotibial space which changed in the medial and laeral femorotibial compartments between 90° and 130° flexion: after 90° flexion, the medial femorotibial space decreased and the lateral femorotibial space increased. This explains why movement from 90° flexion to 130° flexion was facilitated by placing the femoral piece in external rotation.

Discussion: Search for ligament balance for knee flexion above 90° is logical only if the goal is to obtain knee stability in extension and flexion at 90°. It is probably no rational if the goal is to allow the knee to reach flexion in the 120°–130° range. Ligament balance in flexion above 90° is important and should be maintained up through 130° flexion. The other solution is to empirically increase external rotation of the femoral component a few degrees in order to allow greater range of flexion.

Purpose of the study: The humeral head is the second most frequent localization of non-traumatic osteonecrosis. For certain etiologies, for example sickle-cell anemia, the frequency is similar to that observed for the femoral head. There have nevertheless been very few publications on this pathology and its treatment. The purpose of this study was to assess outcome in a series of 771 cases of humeral head osteonecrosis in order to establish the natural history of the disease, criteria predictive of outcome, and therapeutic options.

Material and methods: The diagnosis of osteonecrosis of the humeral head was established for 771 humeri in 424 patients between 1981 to 2000. Minimum follow-up was five years (maximum 23 and mean 13 years). Outcome was assessed in terms of the clinical course, specifically the need for surgery due to pain or functional impotency. The radiological assessment was made on serial AP and lateral views taken every year or two years. The extent of the osteonecrosis was assessed on the basis of the magnetic resonance imaging (MRI) findings when available (after 1985). The ARlet and Ficat classification established for the femoral head was adapted to the shoulder: grade I: osteonecrosis of the humeral head visualized solely with MRI; grade II: radiologically detectable osteonecrosis; grade III: subchondral dissection without loss of spherical shape: grade IV: loss of spherical shape without visible osteoarthritis: grade V: osteoarthritis.

Results: Bilateral osteonecrosis was observed in 82% of the 424 patients. This gave 771 cases of humeral head necrosis. There was no gender predominance. Mean age at diagnosis was 32 years (range 18–57 years). The most frequent etiology was sickle-cell anemia (307 patients), followed by corticosteroid therapy (80 patients). Other etiologies were much less frequent: alcohol abuse, Gaucher’s disease, hyperlipidemia. Osteonecrosis of the humeral head was generally associated with another localization, particularly involving the hip and the knee joints. Multifocal osteonecrosis was also a common finding. Among the patients whose dignosis of osteonecrosis was established before symptom onset (scintigraphy or MRI performed in patients with multifocal osteonecrosis), the natural history was on average three years between MRI diagnosis and onset of pain. For 46% of the cases, pain appeared at grade I, before the development of radiographic signs. In 54% of the cases, grade II occurred before pain. It took six years before all of the cases with osteonecrosis diagnosed in a non-symptomatic phase produced pain. Factors affecting the rapidity of the radiological course were: etiology, size of the necrotic focus, presence and rapidity of osteonecrosis in other localizations (hip and knee). The humeral head lost its spherical shape on average four to five years after the diagnosis of osteoarthritic degradation of the joint, at about seven to eight years of evolution. Among the 256 patients followed for more than ten years, 51% required surgery. These 131 operations were for: drilling with bone marrow grafting (grade I or II) (n=62), cimentoplasty after loss of spherical shape but before glenohumeral osteoarthritis (n=15), resection of sequestered necrosis after loss of spherical shape (n=12), shoulder arthroplasty (n=42).

Discussion and conclusion: This study demonstrated that the natural history of osteonecrosis of the humeral head has a poor long-term outcome. Shoulder arthroplasty is rarely required during the first decade of the disease. Other therapeutic alternatives can help avoid or retard the need for shoulder arthroplasty in these very young patients.

Purpose of the study: It is currently accepted that ligament balance should be one of the goals for total knee arthroplasty (TKA) and that this balance should be obtained by correct bone cuts or appropriate ligament procedures. There is however no standard way of assessing this balance. The purpose of this study was to define limit values for knee laxity observed in a series of normal knees and in a series of 54 TKA reviewed at more than ten years.

Material and methods: Laxity in extension of normal knees was measured on forced varus and valgus films using the contralateral knees of patients who had undergone knee surgery for osteotomy or prosthesis implantation. Laxity in extension of TKA knees was measured the first postoperative year and at last follow-up by measuring the decoaptation between the tibial and femoral pieces on single-leg stance films. The change in decoaptation over time was compared with the postoperative and last follow-up goniometry figures, the IKS knee score, the number of loosenings and the number of lucent lines. Multifactorial analysis was considered significant at p< 0.05.

Results: For the normal knees in extension, the medial compartment gap was 2 mm on average (range 1.5–3.5 mm) on the forced valgus images and the lateral compartment gap was 3 mm on average (range 2–4 mm) on the forced varus images. The corresponding angular value was 1° decoaptation on the forced valgus images and 1.5° on the forced varus images. Among the 54 knees with a TKA, the first postperative single-leg stance image revealed a lateral decoaptation _ 3° for 12 knees considered to present laxity, and was _ 2° for 42 knees considered not to present laxity. At last follow-up (13 years on average, range 11–14 years) the 42 knees without laxity remained unchanged without decoaptation, including the 34 normocorrected knees (±3°) and the eight undercorrected knees presenting more than 3° varus (mean undercorection 5°, range 3–7°). The 12 knees presenting postoperative radiographic decoaptation _ 3° showed at last follow-up a significant increase in laxity (p< 0.05) and 2.5° further increase in decoaptation. The increase in decoaptation occurred on normocorrected (n=7) or undercorrected (n=5) knees. This increase in decoaptation was greater with greater residual genu varum. Four groups of knees could be distinguished: normocorrected and stable; normocorrected and unstable; undercorrected and stable; overcorrected and unstable. The number of loosenings requiring revision and the number of progressive lucent lines were significantly greater among unstable knees (two loosenings, and five progressive lucent lines) than among stable knees (no loosening or lucent lines). They were also greater in the group of normocorrected and unstable knees (one loosening and two lucent lines) than in the group of undercorrected and stable knees (no loosening or lucent line). The IKS knee score of stable knees was higher than that of unstable knees irrespective of the correction (p< 0.05).

Discussion: Postoperative laxity in varus with angular decoaptation greater than 3° corresponds to a lateral compartment gap and should be avoided even if the knee is properly aligned postoperatively. If the knee is stable, moderate undercorrection (3–5° varus) does not appear to have an unfavorable long-term effect on knee laxity or on the femoral and tibial pieces.

Conclusion: For knees with constitutional genu varum, moderate undercorrection with a stable knee is preferable to normocorrection at the cost of lost stability.

The purpose was to assess the effect of the posterior slope on the long-term outcome of unicompartmental arthroplasty in knees with intact and deficient anterior cruciate ligaments.

We retrospectively reviewed ninety-nine unicompartmental arthroplasties after a mean duration of follow-up of sixteen years (12 to 20 years). At the time of the arthroplasty, the anterior cruciate ligament was considered to be normal in fifty knees, damaged in thirty-one, and absent in eighteen. At the most recent follow-up, we measured the posterior tibial slope and the anterior tibial translation on standing lateral radiographs.

In the group of seventy-seven knees that had not been revised by the time of the most recent follow-up, there was a significant linear relationship between anterior tibial translation (mean, 3.7 mm) and posterior tibial slope (mean, 4.3) (p = 0.01). The mean posterior slope of the tibial implant was significantly less in the group of seventy-seven knees without loosening of the implant than it was in the group of seventeen knees with loosening of the implant (p = 0.03). Five ruptures of the anterior cruciate ligament occurred in knees in which the ligament had been considered to be normal at the time of implantation; the posterior tibial slope in these five knees was greater than 13 degrees. Clinical evaluation revealed normal or nearly normal anteroposterior stability at the time of the most recent follow-up in all sixty-six unrevised knees in which the anterior cruciate ligament had been present at the time of implantation. Of the eighteen knees in which the anterior cruciate ligament had been absent at the time of the arthroplasty, eleven still had the implant in situ at the time of the most recent follow-up; the mean posterior tibial slope in these 11 knees was less than 5 degrees. Seven knees in which the anterior cruciate ligament had been absent at the time of the arthroplasty were revised. In these 7 knees, the tibial prosthesis was implanted with a posterior slope greater than 8 degrees.

These findings suggest that more than 7 degrees of posterior slope of the tibial implant should be avoided, particularly if the anterior cruciate ligament is absent at the time of implantation. An intact anterior cruciate ligament, even when partly degenerated, was associated with the maintenance of normal anteroposterior stability of the knee for an average of sixteen years following unicompartmental knee arthroplasty.

We studied hips with these two different ceramics during the same period and with a minimum follow-up of 15 years. Because the sizes of the alumina and zir-conia heads were different, hips with 32 mm alumina heads and those with 28 mm zirconia heads were compared with control hips with stainless-steel heads of the same sizes. The same stem and the same PE cup were implanted with cement at the same period. The femoral head was made of alumina with a diameter of 32 mm in 62 cases, and made of yttrium-oxide-partially-stabilized zirconia with a diameter of 28 mm in 40 cases. These ceramic heads were compared with 32 and 28 mm stainless steel heads (40 hips)

There was an increased linear rate of penetration of the femoral heads into the liner between years five and 15 for the zirconia and the stainless-steel groups. This was severe in the zirconia group (0.4 mm/year compared with 0.13 mm/year for the stainless-steel group). During the same 15-year period there was, however, no significant change in the rate of wear in the alumina group (0.07 mm/year). The mean wear at the most recent follow-up was 1740 mm3 for the 28 mm zirconia group, 842 mm3 for the 28 mm stainless-steel group, 825 mm3 for the 32 mm alumina group and 1416 mm3 for the 32 mm stainless-steel group. The three femoral heads retrieved in the zirconia group were analysed using x-ray diffraction. The transformation rate of the tetragonal to the monoclinic crystal was 19 mol%, 25 mol% and 30 mmol% respectively. By comparison, the percentage of monoclinic phase was 4 mol% on a non-implanted femoral head at its surface. Their surface roughness was increased. Scanning electron microscopy of the surface of the retrieved heads showed more craters than on the zirconia heads before implantation. Changes were observed in the volume and sphericity of the retrieved heads. Their volume was measured by fluid displacement and had increased respectively by 0.5%, 0.7% and 1.1%. This variation was greater than that due to manufacturing tolerances . The morphological appearance of the surface of the retrieved cups was inspected. The most surprising change was found on the periphery of one cup with an increase in volume of the polyethylene on the non-articular surface of the liner as if the polyethylene had melted and then cooled. Although experimental studies have shown encouraging results, the long term clinical results of zirconia are not favorable.

In a society dependent upon the motor car, impaired driving ability is a significant disability which may affect patients with total knee replacement during the postoperative rehabilitation. Recently, there has been much interest in minimally invasive surgery for total knee arthroplasty (TKA). This study evaluated the hypothesis that a minimally invasive technique using a small incision (7 to 10 cm), and a minimal quadriceps muscle splitting without eversion of the patella (MIS approach) would have a beneficial effect on driving reaction time.

15 patients undergoing a primary TKA with the MIS approach were compared with 15 TKAs using a standard approach. An experimental car was used to measure the force and timing of pressure by the foot on accelerator and break pedals. The mean reaction time for normal adults was 0.442 s to go from the accelerator to the brake pedal. This time falls well within the code guideline of 0.7 s. The driving reaction times of the patients with knee arthroplasty were measured at one, two and three months after the operation. The ability to perform an emergency stop was assessed as the time taken to achieve a brake pressure of 100 N after a visual stimulus.The patients have an actual follow-up of 2 years. A clinical and radiological evaluation was performed. Radiographic analysis included evaluation of postoperative alignment variables and progressive radioluciencies.

Over all 27 among the 30 knees have good and excellent objective knee Society Scores and patient satisfaction indices. The patients in the MIS group had a statistically shorter time until they could straight leg raise, used less epidural analgesia, used less overall analgesics and had a more rapid regaining of flexion. Patients with standard approach and technique for total knee replacement recovered sufficient knee function to return to driving at only three months after the operation according to the time and the force necessary to the brake pedal. Patients with mini invasive surgery approach have recovered sufficient knee function to return driving at one month after the operation. There was no significant difference in alignment of implants and in alignment of the knee between the two groups. Three knees had radioluciencies (two with a standard incision and one with a MIS approach).

Using a small incision without patellar eversion does not jeopardize the alignment of the implants and improves postoperative rehabilitation.