OBJECTIVES

The use of a mobile bearing has been suggested to decrease the rate of patellar complications after total knee arthroplasty (TKA). However, to resurface or retain the native patella remains debated. Few long-term results have been documented. The present retrospective study was designed to evaluate the long-term (more than 10 years) results of mobile bearing TKAs on a national scale, and to compare pain results and survivorship according to the status of the patella.

The primary hypothesis of this study was that the 10 year survival rate of mobile bearing TKAs with patella resurfacing will be different from that of mobile bearing TKAs with native patella retaining.

Osteotomies for valgus deformity are much less frequent than those for varus deformity as evidenced by published series which are, on one hand, less numerous and on the other hand, based on far fewer cases. For genu varum deformity, it has been proved that navigation allows to reach easier the preoperative correction goal. Our hypothesis was that navigation for genu valgum could be as accurate as for genu varum deformity. The aim of this paper was to present the mid-term results of 29 computer-assisted osteotomies for genu valgum deformity performed between September 2001 and March 2013.

The series was composed of 27 patients (29 knees), 20 females and 7 males, aged from 15 to 63 years (mean age: 42.4+/−14.3 years). The preoperative functional status was evaluated according to the Lyshölm-Tegner score. The mean score was of 64+/−20.5 points (18–100). The stages of osteoarthritis were evaluated according to modified Ahlbäck's criteria. We operated on 12 stage 1, 9 stage 2, 5 stage 3 and 1 stage 4. 2 female patients had no osteoarthritis but a particularly unesthetic deformity (of which one was related to an overcorrected tibial osteotomy). The pre and postoperative HKA angle was measured according to Ramadier's protocol. We measured also the medial tibial mechanical angle (MTMA) and the medial femoral mechanical angle (MFMA). The mean preoperative HKA angle was 189.3°+/−3.9° (181° to 198°); the mean MFMA was 97.2° +/− 2.6° (93° to 105°) and the mean MTMA was 90.1° +/− 2.8° (86° to 95°). The goal of the osteotomies was to obtain an HKA angle of 179° +/− 2° and a MTMA of 90°+/2° in order to avoid an oblique joint line. We performed 24 femoral osteotomies (14 medial opening wedge and 10 lateral closing wedge) and 5 double osteotomies (medial tibial closing wedge + lateral opening wedge osteotomy). The functional results were evaluated according to Lyshölm-Tegner, IKS and KOO Scores, which were obtained after revision or telephone call.

We did not find any complication except a transient paralysis of the common fibular nerve. 23 patients (4 lost to follow-up) were reviewed at a mean follow-up of 50.9+/−38.8 months (6–144). The mean Lyshölm-Tegner score was 92.9+/−4 points (86–100), the mean KOO score 89.7+/−9.3 (68–100), the mean IKS ≪knee≫ score 88.7 +/−11.4 points (60 à 100) and the mean ≪function≫ score 90.6 +/−13.3 points (55–100). 22 of the 23 reviewed patients (25 knees) were very satisfied or satisfied of the result. Regarding the radiological results, the mean HKA angle was of 180.1°+/−1.9° (176° to 185°), the mean MFMA of 90.7°+/−2.5° (86°-95°) and the mean MTMA of 89.1°+/−1.9° (86°-92°). The preoperative goal was reached in 86.2% (25/29) of the cases for HKA angle and in 100% of the cases for MTMA when performing double level osteotomy (5 cases). At this follow-up, no patient was revised to TKA.

Computer-assisted osteotomies for genu valgum deformity lead to excellent results a mid-term follow-up. Navigation is very useful to reach the preoperative goal.

Direct arthroscopic cartilage assessment remains the gold standard. It is recommended by the International Cartilage Repair Society (ICRS) to systematically assess cartilage status during arthroscopy but this examination is highly subjective, poorly reproducible, time-consuming and lacks precision. US has shown good potential for cartilage evaluation but is limited in extra-articular conditions. It is also difficult to manually maintain a perfect perpendicularity between the ultrasound beam and the curved surface of the cartilage. Therefore, we have developed a navigated intra-articular US probe (NIAUS). The NIAUS probe could contribute to a more exhaustive and direct intra-articular evaluation of cartilage integrity. Navigation enables control of the US echo pulse perpendicularity and its localisation relative to the joint. Our objectives were (1) to evaluate automatic cartilage thickness measurement with the NIAUS probe in comparison to high definition MRI on cartilage samples, (2) to generate a real-time 3D map of the thickness parameter on samples, and (3) to demonstrate the feasibility of a full NIAUS probe cartilage scan on a specimen distal femur in arthroscopic conditions.

The NIAUS probe is a 4.5mm probe consisting of a 64 element linear array transducer with a central frequency of 13 MHz and a motorised head. The NIAUS probe is navigated. The rotating US head position is controlled by navigation in order to enable constant perpendicular acquisition of cartilage. The NIAUS probe thickness measurement (1) was evaluated on bone and cartilage samples of 9 tibial plateaus. The cartilage thickness was measured via automatic segmentation. Each sample was also scanned in a high resolution MRI (4,7 Tesla) and cartilage thickness was semi-automatically extracted for comparison. During NIAUS scan, (2) a visual 3D map was generated. Finally (3), we scanned two distal femurs with the NIAUS probe in arthroscopic navigated conditions on one specimen and a 3D map of the distal femur thickness was generated in real time.

NIAUS thickness measurement (1) absolute error compared to MRI for 9 plateaus ranged from 0.15mm to 0.32mm in median, p25=0.07 and 0.18, p75=0.28 and 0.5 respectively. 3D maps of the sample cartilage thickness (2) were generated in real time during the NIAUS scan. The cadaveric procedure (3) was conducted without incident via the two anterior portals and a 3D map of the distal femurs cartilage thickness was generated.

A precise US arthroscopic grading and scoring of cartilage during surgery could help for better standardisation, prediction of results and making “live” decisions. Our in vitro experiment shows good results compared to MRI for NAIUS cartilage thickness measurement, and our cadaveric study demonstrate the feasibility of a NIAUS scan in arthroscopic conditions. Our results are encouraging and a clinical trial is currently being designed for preliminary in vivo NIAUS evaluations of cartilage thickness compared to MRI.

INTRODUCTION

Polyethylene wear is one of the reasons for failure of total knee replacement (TKR). There are several reasons for wear, and the femoro-tibial contact area is an important factor. Mobile bearing, highly congruent prostheses might be more resistant to polyethylene wear than fixed bearing, incongruent prostheses. We evaluated the 5- to 8-year experience of three university departments by using an original system with following highlights: implantation with a navigation system, extended congruency up to 90° of flexion, floating polyethylene component with non-limited movements of rotation, antero-posterior translation and medio-lateral translation.

Polyethylene wear is one of the reasons for failure of total knee replacement (TKR). There are several reasons for wear, and the femoro-tibial contact area is an important factor. Mobile bearing, highly congruent prostheses might be more resistant to polyethylene wear than fixed bearing, incongruent prostheses. We evaluated the five- to eight-year experience of three university departments by using an original system with following highlights: implantation with a navigation system, extended congruency up to 90° of flexion, floating polyethylene component with non-limited movements of rotation, antero-posterior translation and medio-lateral translation.

347 patients have been operated on in the three participating departments with this new prosthesis system between 2001 and 2004, and have been prospectively followed with clinical and radiologic examination with a minimal follow-up time of five years. There were 246 women and 101 men, with a mean age of 67 years.

Clinical and functional results have been analyzed according to the Knee Society scoring system. Accuracy of implantation has been assessed on post-operative long leg antero-posterior and lateral X-rays. Survival rate up to eight years has been calculated according to Kaplan and Meier, with mechanical revision or any revision as end-points.

Complete patient history was obtained by 319 cases (92%). The mean clinical score was 93 points. The mean pain score was 47 points. The mean flexion angle was 118°. The mean functional score was 87 points. An optimal correction of the coronal femoro-tibial axis was obtained in 94% of the cases. Survival rate after eight years was 98.8% for mechanical revisions and 95.5% for all revisions.

We confirmed the influence of the navigation system on the accuracy of implantation. The clinical and functional results after five to eight years are in line with the better results of the current literature after conventional implantation of non-congruent prostheses. The survival rate is comparable to the current standards. The influence of the design on polyethylene wear will need a longer follow-up.

Double level osteotomy (DLO) for severe genu varum is not a common technique. We performed our first computer-assisted double level osteotomy (CADLO) in March 2001 and we published our preliminary results in 2005 and 2007. The rationale to perform this procedure is to avoid oblique joint line in order to have less difficulty in case of revision to a total knee arthroplasty (TKA). The goal of this paper is to present the results of 37 cases operated on between August 2001 and January 2010.

The series was composed of 35 patients (two bilateral), nine females and 26 males, aged from 39 to 64 years old (mean age: 50.5 +/− 7.5). We operated on 20 right knees and 17 left ones. The mean BMI was 29.3 +/− 4.3 for a mean height of 1.71 m and a mean weight of 85.8 kg. The functional status was evaluated according to the LYSHÖLM and TEGNER score. The mean score was of 42.4 +/− 8.9 points (22–69). According to modified AHLBÄCK criteria we operated on seven stage 2, 22 stage 3, five stage 4 and two stage 5. We measured HKA (Hip-Knee-Ankle) angle using RAMADIER's protocol and we also measured the femoral mechanical axis (FMA) and the tibial mechanical axis (TMA) to pose the right indication. These measures were respectively: 168° +/− 3.4° (159°–172°), 87.5° +/− 2.1 (83°–91°) for the FMA and 83.7° +/− 2.6° (78°–88°) for the TMA.

The inclusion criteria were a patient younger than 65 years old with a severe varus deformity (more than 8° − HKA angle ≤ to 172°) and a FMA at 91° or less. All the osteotomies were navigated using the ORTHOPILOT® device (B-BRAUN-AESCULAP, TUTTLINGEN, GERMANY). The procedure was performed as follows: after inserting the rigid-bodies and calibrating the lower leg, we did first the femoral closing wedge osteotomy (from 4 to 7 mm) which was fixed by a an AO T-Plate, and secondly, after checking the residual varus, the high tibial opening wedge osteotomy using a BIOSORB® wedge (Tricalcium phosphate) and a plate (AO T-plate or C-plate). The goals of the osteotomy were to achieve an HKA angle of 182° +/− 2° and a TMA angle of 90° +/− 2°.

The functional results were evaluated using the LYSHÖLM-TEGNER score and the KOOS score. The patients answered the questionnaire at revision or by phone, and the radiological results were assessed by plain radiographs and standing long leg X-Rays between three and six months postoperatively.

We had no complication in this series but one case of recurrence of the deformity related to an impaction of the femoral osteotomy on the medial side. Two patients were lost to follow-up after removing of the plates (24 months) but were included in the results because the file was complete at that date. All the patients were assessed at a mean follow-up of 43 +/− 27 months (12–108). The mean LYSHÖLM-TEGNER score was 78.7 +/− 7.5 points (59–91) and the mean KOOS score was 94.9 +/− 3.3 points (89–100). Thirty-five patients were satisfied (18) or very satisfied (17) of the result. Only two were poorly satisfied. Regarding the radiological results, if we exclude the patient who had a loss of correction, the goals were reached in 32 cases (89%) for the HKA angle and in 31 cases (86%) for the TMA with only one case at 93°. The mean angles were: 181.97° +/− 1,89° (177°–185°) for HKA, 89.86° +/− 1,85° (85°–93°) for TMA and 93.05° +/− 2.3° (89°–99°) for FMA. At that mid-term follow-up no patient had revision to a total knee arthroplasty.

DLO is a very demanding technique. Navigation can improve the accuracy of the correction compared to non computer-assisted osteotomies. The functional results are satisfying and the satisfaction of the patients is very high. Despite the difficulty of the procedure, complications are, in our hands, very rare. We recommend DLO for severe genu varum deformity in young patients to avoid oblique joint line, which will be difficult to revise to TKA.

Navigation of Uni knee arthroplasty (UKA) is not common. Usually the software includes navigation of the tibial as well as the femoral implant. In order to simplify the surgical procedure we thought that navigation of the tibial plateau alone could be a good option. Since 2005 we have been using a mobile bearing UKA of which the ancillary is based on dependent bone cuts. The tibial cut is made first and the femoral cut is automatically performed using cutting blocks inserted between the tibial cut and the distal end of the femur. Although we are satisfied with this procedure, it is not rare we have some difficulties getting the right under correction needed to get a good long-term result. The aim of this paper was to present our computer-assisted UKA technique and our preliminary radiological results in genu varum (17 cases) as well as genu valgum (6 cases) deformities.

The series was composed of 23 patients, 10 females and 13 males, aged from 63 to 88 years old (mean age: 75 +/− 8). The mean preoperative HKA (Hip-Knee-Ankle) angle was: 172.35° +/− 2.31° (167° to 176°) for the genu vara and 186.33° +/− 2.87° (182° to 189°) for the genu valga.

The goal of the navigation was to get an HKA angle of 177° +/− 2° for genu varum deformity and 183° +/− 2° for genu valgum.

We used the SURGETICS® device (PRAXIM, GRENOBLE, FRANCE) in the first six cases and the ORTHOPILOT® device (B-BRAUN-AESCULAP, TUTTLINGEN, GERMANY) in the other cases. The principles are the same for both devices. The 1rst step consists in inserting percutaneously the rigid-bodies on the distal end of the femur and on the proximal end of the tibia. Then, we locate the center of the hip by a movement of circumduction, the center of the ankle by palpating the malleoli and the center of the knee by palpating intra articular anatomic landmarks to get the HKA angle in real time. This step is probably the most important because it allows checking the reducibility of the deformity in order to avoid an over correction when inserting a mobile bearing prosthesis. The 3^rd step consists in navigation of the tibial cut such as the height of the resection, the tibial slope (3 to 5° posterior tibial slope) and the varus of the implant (2 to 3°). Once the tibial cut was done, we must use the conventional ancillary to perform the femoral bone cuts (distal and chamfer). The last step consists in inserting the trial implants and checking the HKA angle and the laxity of the medial or lateral side.

We used postoperative long leg X-Rays to evaluate the accuracy of navigation and plain radiographs to evaluate the right position of the implant.

As far as genu varum deformity was concerned, the mean postoperative HKA angle was 177.23° +/− 1.64° (173°–179°). The preoperative goal was reached in 94% of the cases. Moreover, this angle could be superimposed on the peroperative computer-assisted angle, which was 177° +/− 1.43° (p>0.05). For genu valgum, the mean postoperative HKA angle was 181° +/− 1.41° (179°–183°). The preoperative goal was reached in 66% of the cases but the series is too short to give any conclusion.

The navigation of tibial plateau alone can be used with accuracy, provided one has the right ancillary to use dependent bone cuts. The procedure is quick and needs only one tibial cutting guide equipped with a rigid-body. Our results, especially in genu varum deformity, are quite remarkable. Regarding genu valgum, the results seem to be less accurate, but the software was designed for medial UKA and the series is short, so, it is too soon to extrapolate any conclusion. The main interest in this navigation is to avoid too much under correction and even better to avoid over correction when the deformity is over reducible. Indeed, when one uses a mobile bearing plateau, the risk is to have a dislocation of the meniscus. So, when tightening the collateral ligaments, checking the lower limb axis may persuade not to use a mobile bearing plateau but rather a fixed plateau.