We present a new technique for TKA implantation which utilizes patient-specific femoral and tibial positioning guides developed from MRI to offer an individualized approach to total knee replacement.

This is a prospective non controlled study which aims to analyse the precision of this technique, its advantages and inconvenients in comparison with the conventional instrumented technique.

Purpose of the study: How does a total knee arthroplasty (TKA) function? Do all prostheses provide the excellent results reported in the literature? This gait analysis compared patients with a TKA versus normal subjects in order to obtain a 3D quantification of the kinematic and dynamic differences between patients with a very good functional result and controls.

Material and methods: Twenty patients who had a TKA for less than one year and whose functional outcome was scored very good (KSS knee > 85/100, VAS ≤1/10) were compared in a double blind study with 20 normal controls. The knees were masked so that the investigators were unaware of the type of subject (operated or not), the side operated, or the type of implant. The analysis as performed on an AMTI platform with six infrared cameras which followed the displacements of 36 reflectors. Motion Analysis software was applied. The gait parameters recorded were: speed, step length, flexion angle, duration of weight bearing/oscillation phases, and dynamic variables: flexion-extension moment, varus-valgus moment, internal/external rotation moment.

Results: Adjusted for age and height, step length, walking speed, and duration of the weight bearing phase were identical in the operated and control populations. Kinematic and dynamic variables demonstrated significant differences. At lift-off, all of the TKA subjects were in functional permanent flexion (m=10); the flexion moment of the quadriceps was less than in the non-operated subjects. In the frontal plane, the weight-bearing phase was identical between the operated subjects and controls, but with a varus dynamic (m=4) during the oscillating phase. In the horizontal plane, there was an external rotation of the tibia (m=+5) during weight bearing.

Discussion: Gait analysis provides quantitative information which is not perceptible at physical examination nor with videoscopic explorations. Even patients with an excellent KSS score exhibit important anomalies despite the fact that the physical exam finds a normal range of motion and normal muscle force. The degree by degree 3D gait analysis reveals the difference.

Conclusion: Despite a clinical score considered to be very good, patients with a TKA have a functional deficit of the extensor system during take-off, even when the knee has complete active extension; the weight-bearing phase of the step is in external rotation and the oscillating phase exhibits varus laxity.

This study aims to compare the gait pattern of patients operated with a TKA versus a normal population in order to evaluate if the excellent function of TKA reported in the literature corresponds to objectively measured parameters.

20 patients operated of TKA with a follow up > 1 year, all patients rated with a very good functional result (Knee Society Knee score > 85/100 – VAS < = 1/10) were compared with a group of 20 “ normal” persons.

The study was blind: the examiner did not know whether the person was a normal, or which knee was operated.

The test consisted in an 11 meters walk, on an AMTI force platform; the movements of the body were recorded with 6 IR cameras and analysed with the “Motion Analysis” software.

The implant was a mobile bearing AP stabilised knee.

The measured parameters were kinematic : speed, step length, flexion angle, duration of stance /WB phase and dynamic : flexion/extension, varus/valgus, internal/ external moments and resultant force direction. When matched with age and BMI, all kinematic parameters of the TKA group are equal to that of the normals.

However, dynamic parameters differ significantly between both groups: At the end of stance phase and heel strike the operated patients have a lack of extension of 10° despite a clinical measurement of full extension (0°) In the frontal plane, all patients exhibited a valgus walking pattern but the mechanical axis measured on long standing radiographs was 180°+/−1°. In the horizontal plane, all operated patients had an external rotation of +8° compared to the normals.

Despite excellent clinical scores and radiologic positioning, gait analysis demonstrates important dynamic differences between the TKA and the normal group. The extension lag at heel strike may be related to either quad weakness, or an insufficient extension gap at surgery; The valgus resultant pattern occurs despite a perfect alignment of the mechanical axis (180°) on the operated patients: this rises the question whether this alignment is the goal or if an undercorrection would be more physiologic. External rotation is superior to the normal group : it is in relation with the external rotation of the femoral and tibial components.

Conclusion. Gait analysis of the TKA group of patients compared to normal demonstrates important dynamic differences in relation with the surgical positioning of the implant.

This is a prospective gait laboratory case matched cohort study of patients after total knee arthroplasty.

20 patients who had TKA with a good functional result and a follow-up superior to 2 years were compared with 20 “normal” knees.

The examiners were blinded to the group. A standardized gait analysis was performed, measuring gait kinematics, kinetics and force plate recordings using Motion Analysis computer software.

All patients had a single surgeon and the same brand mobile bearing platform.

The kinematics parameters were identical in both groups

However the dynamic parameters showed a statistically significant difference

At terminal swing and heel strike the operated patients had a 10-degree extension deficit in their gait analysis, despite of the fact that clinically all patients had a full extension with no quadriceps lag.

The coronal plane kinetics of TKA showed valgus moment in stance despite having radiological normal (180° +/−1°) mechanical axis. (p< 0,02)

In the axial plane, all operated patients had an external rotation moment greater than normals. (p< 0,01)

Despite good clinical ROM and quadriceps strength, the TKA demonstrated a lack of extension in early stance.

This may be due to insufficient extension gap at surgery.

The valgus resultant pattern poses a more challenging question:

Are we aiming for the wrong goals in the mechanical axis, or should we consider undercorrection?

Gait analysis of the TKA patients compared to normals demonstrates dynamic differences in relation with the surgical positioning of the implant.

Which parameters are related with a forgotten knee after TKA?

The operated knee was said forgotten when it was similar to the normal controlateral knee in all situations.

When a restriction existed, the knee was considered as not forgotten.

470 patients operated with a stabilised mobile bearing knee were examined with a minimal follow up of 5 years and answered to this question.

4 groups of parameters: patient, prosthesis, surgery and post operative care were compared to the binary answer to the forgotten knee question.

48% of the patients had a forgotten knee one year after the TKA;

The following factors had a significant negative correlation with the forgotten knee:

low SF12 psychological profile; Patellofemoral dysplasic arthritis (p = 0,01);

We found no correlation between the following factors and the forgotten knees:

gender, BMI, approach, cemented or not, patellar resurfacing; preoperative Oxford and Knee Society knee scores;

The forgotten knee is a simple objective clinical item because the answer to the question is binary and does not accept any unprecision. It is highly correlated with surgical scores and patients expectation scores (p = 0,0001).

The forgotten knee is a painless and asymptomatic knee identical to a normal knee.

Surgical factors have the highest infiuence on this parameter compared to patient or prosthetic related factors.

Purpose: From 1985 to 2001, 31 total knee arthroplasties were performed for 17 adolescents or young adults with idiopathic juvenile osteoarthritis. The purpose of this work was to evaluate functional and radiological outcome.

Material and methods: Overall functional outcome was assessed with the Steinbrocker classification. Knee function was evaluated with the IKS score. Several types of prostheses were implanted: constrained GSB (n=14), cemented semi-constrained tri-CCC tri-compartment with a rotatory platform (n=10), non-cemented semi-constrained ROCC (n=1), LCS (n=2) including non-cemented, and FINN (n=2) (two custom-made rotation hinge prostheses implanted in the same patient). Fourteen prostheses involved bilateral implants, including three dual implantation procedures.

Results: Mean age at implantation was 20 years five months (14–29). There were fourteen girls and three boys. Eight had systemic idiopathic juvenile osteoarthritis and nine a polyarticular form. The Steinbrocker staging was: II (n=5,) III (n=6), IV or bedridden (n=4). Ten patients had two hip prostheses before bilateral knee arthroplasty. Mean follow-up was 4.5 years (1–12). Among the 31 operated knees, 16 were pain free, 14 minimally painful, and one painful due to loosening. The joint score was very good (n=18), good (n=4), and poor (n=5). Radiographically, normal alignment was found for 29 knees. Lucent lines were observed for 10 of the 14 GSB constrained prostheses. We did not observe any evidence of lucent lines for the non-cemented tri-compartment prostheses. Complications were: limited skin necrosis (n=1), bilateral supracondylar fracture one year after implantation (n=1).

Discussion: Outcome has been encouraging for total knee prostheses in patients with idiopathic juvenile osteoarthritis. These arthroplasties allow spectacular functional improvement. The few series reported have also reported very good results. Cemented tri-compartment semi-constrained implants appear to provide better stability at five years. Biologically sealed tri-compartment prostheses would be a very satisfactory solution due to the preservation of bone stock.

Purpose: We expose technical problems encountered for prosthesis replacement in osteoarthrosis juvenilis (OJ). The characteristic feature of this disease is early joint destruction during growth.

Material and methods: Total knee arthoplasty (TKA) was performed in 17 severely disabled patients (31 knees): Steinbrocker stage II=30%, stage III=30%, stage IV=40%. Mean age at operation was twenty years (14–29). Technical difficulties were related to the following combinations: 1) multidirectional malformations, generally in valgus (mean 16°, range 5–30°) in 30% of the knees associated with external rotation (mean 20°, range 5–50) and sagittal deformation with permanent flexion (mean 31°, range 5–60°) with external or posterior tibia dislocation; 2) limited joint motion: 71° (0–115°); 3) extraarticular deformations with permanent flexion or vicious hip rotation, tibial or femoral callus; 4) major condyle dysplasia due to growth deficiency (3/31 or necrosis (3/31); 5) low patella (100%) and subluxation; 6) weak bone and fragile skin related to corticosteroid therapy; 7) persistent growth cartilage in four patients. We tried to implant the most adapted prosthesis in each individual situation, favouring the least constrained implant possible.

Results: We used fifteen mobile plateau prostheses including five pure gliding TKA and ten posterostabilised TKA with a mobile plateau and 16 hinge prostheses with two rotators. Thirty of the 31 TKA were custom-made.

Discussion: Our different approaches enabled us to propose the following: correction of extra-articular deformations by TKA, after tenotomy and traction, or after concomitant osteotomy; primary approach after checking the vasculonervous bundle (popliteal sciatic); sub-periosteal dissection preserving the lateral ligaments searching to achieve ligament balance when possible in order to implant the least constrained implant possible; non-cemented implants, especially for “soft” or “fatty” bone; no patellar resurfacing when there is a risk of an overly thick low and subluxed patella.

The ROCC® prosthesis is a stabilised posterior cruciate ligament-sacrificing rotating mobile bearing knee. It contains a press-moulded polyethylene insert (Arcom®). It has high coronal conformity during gait and lift-off, and sagittal conformity during the weight-bearing phase. It also has a central concave-convex saddle-horse stabilisation mechanism with a progressive stop. Preferential gliding kinematics optimise the wear factor. A deep anatomical trochlea permits good patellar tracking at every degree of flexion with both resurfaced and unresurfaced patellae. The tibiofemoral displacement of the prosthesis approximates normality.

In 175 primary TKAs with the ROCC® knee, at two-year follow-up the objective measurement of pain was 8.7 out of 10 (7 to 10) in 94% of patients. In 89% of patients, the range of flexion was 128° (95° to 145°). At 3 months, the Knee Society Score was 175 in 87% of patients (function score 80), at 6 months 185 in 89% of patients (function score 90) and at 12 months 200 in 94% of patients (function score 100).

In 98% the femoral component was not cemented and there were no femoral radiolucent lines. The tibial component was not cemented in 30% and two patients in this group needed revision for loosening of the tibial plateau. There were no complications such as persistent pain, flexion contracture, Sudeck’s syndrome, instability or dislocation. Mechanical tests did not show any wear or cold flow deformation of the polyethylene insert after 3 million cycles.

Purpose: This comparative study of femoropatellar function in four types of total knee arthroplasty (TKA) was conducted to demonstrate the relation between the form of the femoropatellar articulation and the function outcome achieved with these prostheses.

Material and methods: Forty patients who had undergone first-intention TKA for primary degenerative joint disease were selected at random. Minimum follow-up was one year. The functional IKDC score was greater than 85/100. All TKA had been inserted without preservation of the posterior cruciate ligament. Four types of prostheses were used:

- posterior stabilised prosthesis with a fixed plateau, toric trochlea, cemented dome patella (n=10);

The following parameters were studied prospectively:

- pain assessed on a visual analogue scale;

Results: The kinematic data demonstrated a significant difference between:

- TKAs with a dome patella and those with an anatomic patella;

This difference basically involved the patellar tilt, lateral subluxation of the patella, and especially, the patellar trajectory between 20° and 90°, the toric trochlae with a dome patella having a more anterior trajectory than the normal knee.

The clinical and functional study showed that:

- the percentage of totally pain-free femoropatellar articulations was higher for the hollow anatomic trochlae (96%) than for the three other types (75%) (p = 0.04);

Discussion and conclusion: This study confirms the theoretic work reported by Walker and the clinical work reported by Andriacchi on the anterior curvature of the trochlae and the kinematic work reported by Stichl on the advantage of anatomic trochlae. These findings point out the advantage of the hollow anatomic trochlae where the patella is applied on the trochlear groove situated at the same depth as the normal trochlae, which is not the case with most TKAs. This advantage is seen by the absence of pain and by the propulsion when climbing stairs.

Purpose: The purpose of this work was to compare polyethylene (PE) wear between prostheses with similar function but different congruency of the femoral implant / PE insert and, as a corollary, the mobility of the plateau.

Material and methods: We studied two groups of knee prostheses: prostheses preserving both cruciate ligaments (n = 20), and stabilised prostheses without preservation of the cruciate ligaments (n = 20). Four representative samples of ten patients by type of total knee arthroplasty (TKA) were selected at random among a cohort of 105 patients operated on between 1994 and 1996 with a mean follow-up of five years. All patients were reviewed with AP and lateral radiographs, a view in the plateau plane, and goniometry. Using this random selection, patients in the two groups were comparable for operative age (69 years), diagnosis (degenerative disease), sex ratio, IKS score (> 80/100), and follow-up. The only difference between the two groups was the postoperative goniometry: 180±2° for fixed plateau; 178±3° for mobile plateau (p< 0.05).

Result: Penetration of the femur in the PE insert (U) (after correction for radiographic magnification) was: TKA two cruciates fixed plateau: U=3.5±1.5mm; TKA two cruciates mobile plateau: U=0±1mm (p< 0.001); TKA posterior stabilisation fixed plateau: U=2.5±1mm; TKA posterior stabilisation mobile plateau: U=0 mm (p< 0.001). A difference of more than 3° in the mechanical axis did not show detectable wear in the group of congruent prostheses while for fixed plateau prostheses, wear appeared when the mechanical axis was 180°.

Discussion: Few studies have compared PE wear of TKAs with identical form and function. The random selection allowed us to compare homogeneous groups of patients eliminating selection bias of the retrospective analysis and of the effect of patients lost to follow-up. The highly significant difference between the groups compared avoided potential ß risk. However the quality of the PE and its mode of sterilisation were not known with certainty for the tested implants.

Conclusion: This study demonstrates the importance of congruency as a factor reducing PE wear in TKA. This parameter is more favourable when the postoperative mechanical axis is perfectly corrected.