Background

The goal of this study was (1) to investigate the relationships between the bony contours of the knee and the popliteus tendon before and after TKA and (2) to analyse the influence of implant sizing. Our hypothesis was that an apparently well-sized prosthesis, will modify the position or the tracking of popliteus tendon.

Purpose

Analysis of the morphology of the distal femur, and by extension of the femoral components in total knee arthroplasty (TKA), has been related to the aspect ratio, which represents the width of the femur. Little is known about variations in trapezoidicity (i.e whether the femur is more rectangular or more trapezoidal). This study aimed to quantify additional morphological characteristics of the distal femur and identify anatomical features associated with higher risks of over- or under-sizing of components in TKA.

To determine the mechanisms and extents of popliteus impingements before and after TKA and to investigate the influence of implant sizing. The hypotheses were that (i) popliteus impingements after TKA may occur at both the tibia and the femur and (ii) even with an apparently well-sized prosthesis, popliteal tracking during knee flexion is modified compared to the preoperative situation.

The location of the popliteus in three cadaver knees was measured using computed tomography (CT), before and after implantation of plastic TKA replicas, by injecting the tendon with radiopaque liquid. The pre- and post-operative positions of the popliteus were compared from full extension to deep flexion using normosized, oversized and undersized implants (one size increments).

At the tibia, TKA caused the popliteus to translate posteriorly, mostly in full extension: 4.1mm for normosized implants, and 15.8mm with oversized implants, but no translations were observed when using undersized implants. At the femur, TKA caused the popliteus to translate laterally at deeper flexion angles, peaking between 80º-120º: 2.0 mm for normosized implants and 2.6 mm with oversized implants. Three-dimensional analysis revealed prosthetic overhang at the postero-superior corner of normosized and oversized femoral components (respectively, up to 2.9 mm and 6.6 mm).

A well-sized tibial component modifies popliteal tracking, while an undersized tibial component maintains more physiologic patterns. Oversizing shifts the popliteus considerably throughout the full arc of motion. This study suggests that both femoro- and tibio-popliteus impingements could play a role in residual pain and stiffness after TKA.

Analysis of the morphology of the distal femur, and by extension of the femoral components in total knee arthroplasty (TKA), has largely been related to the aspect ratio, which represents the width of the femur. Little is known about variations in trapezoidicity (i.e. whether the femur is more rectangular or more trapezoidal). This study aimed to quantify additional morphological characteristics of the distal femur and identify anatomical features associated with higher risks of over- or under-sizing of components in TKA.

We analysed the shape of 114 arthritic knees at the time of primary TKA using the pre- operative CT scans. The aspect ratio and trapezoidicity ratio were quantified, and the post- operative prosthetic overhang was calculated. We compared the morphological characteristics with those of 12 TKA models.

There was significant variation in both the aspect ratio and trapezoidicity ratio between individuals. Femoral trapezoidicity was mostly due to an inward curve of the medial cortex. Overhang was correlated with the aspect ratio (with a greater chance of overhang in narrow femurs), trapezoidicity ratio (with a greater chance in trapezoidal femurs), and the tibio- femoral angle (with a greater chance in valgus knees).

This study shows that rectangular/trapezoidal variability of the distal femur cannot be ignored. Most of the femoral components which were tested appeared to be excessively rectangular when compared with the bony contours of the distal femur. These findings suggest that the design of TKA should be more concerned with matching the trapezoidal/ rectangular shape of the native femur.

Analysis of the morphology of the distal femur, and by extension of the femoral components in total knee arthroplasty (TKA), has largely been related to the aspect ratio, which represents the width of the femur. Little is known about variations in trapezoidicity (i.e. whether the femur is more rectangular or more trapezoidal). This study aimed to quantify additional morphological characteristics of the distal femur and identify anatomical features associated with higher risks of over- or under-sizing of components in TKA.

We analysed the shape of 114 arthritic knees at the time of primary TKA using the pre- operative CT scans. The aspect ratio and trapezoidicity ratio were quantified, and the post- operative prosthetic overhang was calculated. We compared the morphological characteristics with those of 12 TKA models.

There was significant variation in both the aspect ratio and trapezoidicity ratio between individuals. Femoral trapezoidicity was mostly due to an inward curve of the medial cortex. Overhang was correlated with the aspect ratio (with a greater chance of overhang in narrow femurs), trapezoidicity ratio (with a greater chance in trapezoidal femurs), and the tibio- femoral angle (with a greater chance in valgus knees).

This study shows that rectangular/trapezoidal variability of the distal femur cannot be ignored. Most of the femoral components which were tested appeared to be excessively rectangular when compared with the bony contours of the distal femur. These findings suggest that the design of TKA should be more concerned with matching the trapezoidal/ rectangular shape of the native femur.

Goals of the study

(1) to investigate the relationships between the bony contours of the knee and the Popliteus Tendon (PT) in the healthy knee and after implantation of a TKA and (2) to analyze the influence of implant sizing.

Purpose of the study: The results of the first total ankle arthroplasties (TAA) using the Salto™ prosthesis were published in 2004 with mean 35 months follow-up. The purpose of this work was to update the results of the initial multicentric series.

Material and methods: From 1997 to 2000, 98 TAA were performed with a Salto™ prosthesis in three centres: 62 women, 36 men, mean age 56 years, age range 26–81 years, mean BMI 24.3 kg/m². The patients had osteoarthritis (n=65; posttraumatic 43, post-instability 8, primary 14), rheumatoid arthritis (n=29), and sequel of septic arthritis (n=4). At last follow-up, nine patients had died (none had had revision surgery of the ankle) and one patient had been amputated for an unrelated reason. The remaining patients (88 TAA) were reviewed in an outpatient clinic with a mean 102 months follow-up (range 65–134). None of the patients were lost to follow-up.

Results: Seven prostheses were replaced by an arthrodesis (six osteoarthritis and one rheumatoid arthritis): three for defects at 44, 72 and 101 months after implantation, two for unexplained pain after 32 and 57 months, one for tibial loosening after 62 months and one for infection after six months. One tibial piece was changed for loosening and fracture of the polyethylene insert after 100 months (revision with a longer anchor piece). Two 3 mm polyethylene inserts were changed alone for fracture after 72 and 122 months. Five TAA were reoperated for stiffness: removal of bone fragments±synovectomy. Four TAA were grafted for secondary defects (two tibia and two talus). One lateral maleolar piece was removed for loosening after 88 months. There were two infections treated by synovectomy, wash-out and antibiotic therapy. The survival rates were 92% for failure=removal of the prosthesis; 91% for removal or replacement of one component; 89% for removal or replacement of one piece, including the polyethylene insert. The survival rate (prosthesis removal) was better for rheumatoid disease (97%). The AOFAS score at last follow-up was 81.5±12 (80.5±10.3 for osteoarthritis and 76.4±14.8 for rheumatoid disease).

Conclusion: These results underscore: the importance of rigorous technique and careful patient selection (five revisions for defective technique); the higher risk of infection (three cases); the importance of the thickness of the poly-ethylene insert (three fractures on 3mm inserts). Seven patients underwent revision to graft defects, four successfully and three failures (secondary arthrodesis).

Purpose of the study: Compar the position of the femoral piece in relation to the transepicondylar axis (TEA) using four different techniques for regulating rotation:

cut parallel to the posterior bicondylar line (BCL),

Material and methods: One hundred patients who underwent total knee arthroplasty (TKA) had a preoperative computed tomography (CT) scan. The surgical transepicondylar axis (TEA) and the BCL were drawn on the horizontal slices. The angle measured between these two lines (1.56°–2.5°) determined the theoretical angle of external rotation for aligning the femoral piece on the TEA. During the operation, femoral valgus was set to the HKS angle, measured by goniometry. The knife of the distal femoral cut, materializing the line perpendicular to the mechanical femoral axis, came in contact with the most distal femoral condyle (generally the medial condyle but occasionally the lateral condyle for varus femurs). The distance d between the knife and the most distal point of the condyle which remained distant was then measured. The external rotation was set at 0° and 3° with the techniques 1) and 2). For the technique 3), the asymmetry of the distal cut was projected on the posterior cut leading to an automatic rotation at an angle calculated trigonometrically. For the technique 4), the rotation was calculated as a function of the distance d. The difference between the external rotation obtained for each of these techniques and the theoretical rotation was calculated for each patient.

Results: The mean error of rotation obtained for the four techniques was respectively: 2.2–1.9°; 2–1.7°; 1.8–2.2°; and 1.5–1.4° (p< 0.05). The rate of malrotations greater than 1° for the four techniques was respectively: 60%, 58%, 41% and 36%. The rate of malrotations greater than 2° was respectively: 45%, 44%, 27% and 21%. This rate varied according to the femoral morphotype. The percentage of malrotations greater than 2° by technique was as follows for femoral morphotypes normal, varus, and valgus: technique 1: 37,34,58%; technique 2: 37,53,40%; technique 3: 7.5,9,26%; technique 4:22,30,40%.

Conclusion: Interindividual variations in the TEA-BCL angle explain the high rate of malrotation after regulated rotation. An adapted regulation will enable lesser risk of error. An adaptation taking into consideration the results of the preoperative CT scan appear to provide the most reliable results.

Purpose: The purpose of this work was to assess results of total ankle arthroplasty (TAA) for rheumatoid arthritis and determine the technical difficulties.

Material and methods: Between 1993 and 1999, 32 TAA were performed for rheumatoid arthritis: 26 women and 16 men, mean age at implantation 55 years, age range 32 – 81 years, disease duration 17 years (range 2 – 35 years), long-term corticosteroid treatment 18, metotrex-ate 17. Non-cemented prostheses with a mobile insert were implanted: Buechel-Pappas (n=7), STAR (n=5), Salto (n=20). For 21 patients, subtalar and mediotarsal arthrodesis was associated with the TAA because of associated subtalar deterioration or valgus tilt due to tendiopathy of the posterior tibial tendon. All patients were seen at three, six and twelve months then every year for physical examination and x-rays. None of the patients were lost to follow-up. Mean follow-up was 57 months (range 26 – 90 months). Clinical outcome was assessed with the AOFAS.

Results: There were two failures requiring revision: one loose talar piece migrated four years after implantation requiring arthrodesis; one over-sized talar piece leading to pain had to be changed after one year with good results (AOFAS = 92). Among the other 30 patients, the mean overall score and the pain score were 82/100 (73–92) and 35/40 (20–40) respectively. Several complications were observed: wound necrosis (n=2), impaction of the talar piece (n=1), and impaction of the tibial piece (n=2) which developed at weight bearing then remained unchanged. One anterior translation of the tibial piece was asymptomatic at two years, fractures of the medial malleolus healed without difficulty.

Discussion: TAA is the treatment of choice for rheumatoid tibiotarsal degeneration. Associated lesions of the hind foot influence prognosis and results. Preoperative analysis of the deformation and loss of bone stock must be achieved with careful physical examination and appropriate x-ray or computed tomography imaging. Subtalar valgus deformation or tendinopathy of the posterior tibial tendon require an associated subtalar and mediotarsal arthrodesis.

Purpose: The transepicondylar axis (TECA) is an important landmark for positioning the femoral component in correct the rotation during total knee arthroplasty. In vivo studies have shown that the TECA corresponds to the flexion-extension axis of the knee joint. Two TECA have been defined in the literature depending on the landmark used for the medial epicondyle: the eminence for the “clinical” TECA and the depression for the “surgical” TECA. The purpose of the present study was to investigate in vivo the relations between the TECA and the mechanical axis of the femur (FA) and the tibia (TA) measured on computed tomography (CT) scans of the flexed knee, analysing separately the two TECAs.

Material and methods: CT scans of the right knees of ten volunteers were studied. Goniometric data was acquired on the scans. Five controls with genu varum and five with genu valgum were also studied. Images were acquired at 0°, 45° and 90° flexion. The epicondyles were identified on the horizontal sections and three frontal sections parallel to the posterior cortical of the tibia were reconstructed. Superoposition of these three sections, for each flexion angle, gave a frontal section with TECA-clin, TECAsurg, TA, and the posterior bicondylar line (PBL). The angles between TECA and TA, FA and PBL were analysed during flexion. Angles were measured by the medial side.

Results: TECAsurg remained perpendicular to the TA throughout flexion but with considerable interindividual variability. The mean variation during flexion was 3.4±1.5°. The FA-TECA angle was 88.5±0/8° and did not vary with morphotype. The TECA/PBL and TECA/TA angles varied with morphotype but less with flexion.

Conclusion: The surgical TECA maintains constant relations with the tibial axis during knee flexion. It can thus be used as a landmark for positioning the femoral component for total knee arthroplasty in order to optimise femorotibial kinematics. The relations between the clinical TECA and the TA are variable and preoperative identification on the main medial epicondylar eminence may give variable results.

Purpose of the study: We reviewed 69 consecutive cases of total knee arthroplasty revisions to analyze the causes of failure.

Material and methods: Sixty-nine total knee arthroplasty revisions were required between 1990 and 1997 for non-septic failure. Five categories of failures were identified: 30 loosenings including 11 with an initial malposition (varus position of the tibial component in 8 cases), 14 laxities (medial in 5, lateral in 5 and anteroposterior in 4), 11 stiff knees with no other clinical or radiological anomaly, 6 patellar failures (2 dislocations, 2 cases of excessive wear, 2 painful knees with a Freeman prosthesis), and 8 cases of painful knees with no other detectable anomaly.

Results: A three-phase reconstruction procedure was used after removing the failing TKA:1) reconstruction of the tibia with replacement of lost bone, 2) reconstruction of the femur with balanced flexion determining the size of the implant, 3) balanced extension determining the distal/proximal position of the femoral component. A “simple” sliding prosthesis was used in 16 cases, a modular reconstruction prosthesis in 40 cases and a hinge prosthesis in 13 cases. Mean follow-up for functional and radiographic assessment after revision surgery was 37 months (59 cases) with a minimum follow-up of 1 year. The best outcome was observed in the “loosening”, “laxity”, and “stiffness” patients. Outcome was less favorable for the group “isolated pain” with IKS functional scores of 35.5 ± 16 and 52.5 ± 21.

Discussion: In 36 p. 100 of cases, TKA failure was related to a technical mistake (component malposition, poor ligament alignment). In 33 p. 100, failure was patient related (multiple procedures, congenital hip dysplasia, rheumatoid arthritis...). Outcome after revision TKA was less favorable than after primary TKA, particularly in case of painful knees with no other detectable anomaly.

Conclusion: Surgical revision of TKA must follow a rigorous procedure with a detailed preoperative work-up. The decision for revision must not be made unless a precise anomaly has been identified.

Anterior tibial translation was measured in both knees using the radiological Lachman test and the lateral monopodal stance tests in 281 patients with unilateral anterior cruciate ligament (ACL) rupture. Measurements of translation in the medial compartment were more useful than those in the lateral compartment. Measurement of anterior tibial translation in the medial compartment using the radiological Lachman test showed ACL rupture in 92% of cases compared with 70% for the lateral monopodal stance test. In normal and in ACL-ruptured knees the monopodal stance test showed that every 10 degrees increase in posterior inclination of the tibial plateau was associated with a 6 mm increase in anterior tibial translation; the radiological Lachman test showed a 3 mm increase for every 10 degrees increase in tibial slope.