CT measurements prior to computer-assisted total knee arthroplasty do not improve rotational placement of the femoral component.

PURPOSE: The aim of this study is to determine whether computer-assisted surgery (CAS) can gain more precision by utilizing information from pre-operative computed tomography (CT). METHODS: Sixty-five patients undergoing total knee arthroplasty in 2008 were included. On pre- and post-operative CT, epicondylar and posterior condylar lines were drawn and the posterior condylar angle between these two lines measured. During the surgery, epicondylar and posterior condylar lines were also registered before and after CAS-guided cuts were made. CAS was used to fix the orientation of the cutting guide on the distal femur at 3° of external rotation from the posterior condylar line. RESULTS: There was no correlation between CT measurements and CAS measurements. All orientations of the lines (relative to the horizontal) and angles measured using CT were significantly different (p < 0.05). CONCLUSION: No relationship was found between pre-operative CT measurements and peri-operative CAS measurements used to orient the femoral component. Data obtained from CT cannot be used peri-operatively with CAS to improve rotational setting of the femoral component. LEVEL OF EVIDENCE: Therapeutic study, Level II.

[Influence of the tibial slope on tibial translation and mobility of non-constrained total knee prosthesis]. / Influence de la pente tibiale sur la translation tibiale et la mobilité d'une prothèse totale du genou non contrainte.

PURPOSE OF THE STUDY: We determined retrospectively the influence of posterior tibial slope and anterior cruciate ligament (ACL) sparing on anterior tibial translation in 68 Cloutier total knee prosthesis. We also precised the influence of posterior tibial slope on knee functional score and appearance of tibial prosthetic interfaces. MATERIAL: 38 Cloutier total knee prosthesis (62 patients mean aged 62 +/- 10 years (36-76) at surgery) reviewed at systematic follow-up control, after a mean period of 5.5 +/- 3 years (2-15), were included in the study. The ACL was preserved in 38 knees and sacrified in 30 knees, the posterior cruciate ligament was preserved in all cases. The prosthetic design was the same whatever the number of cruciate ligament preserved. Osteoarthritis was the reason for surgery in 54 knees, and rheumatoid arthritis in 14 knees. Mean HSS knee score was 54 +/- 10 (29-80) before surgery and 89 +/- 10 (35-100) at follow-up. The mean range of motion was 103 +/- 24 degrees (30-130) before surgery and 110 +/- 14 degrees at follow-up (40-130). METHODS: Anterior tibial translation was determined on two profil x-rays (non weight bearing and weight bearing) at 20 degrees of flexion by comparing the position of tibial tray with regard to posterior edge of femoral prosthesis. Tibial slope was measured on lateral view with regard to peroneus axis. Appearance of tibial prosthetic interface was studied in 48 knees on AP and lateral x-rays orientated with an image intensifier in order to obtain the x-ray would be parallel to the tibial interface. RESULTS: Posterior tibial slope (mean value 6.2 degrees +/- 4.2 degrees) was the main factor influencing the anterior tibial translation (mean value 3.9 +/- 4.6 mm) (p = 0.0007). A 10 degree increase of posterior tibial slope makes the anterior tibial translation rise by 5.6 mm in weight bearing situation. When ACL was preserved, the anterior tibial translation was lower but the decrease was not significant. Likewise, preservation of ACL or the degree of posterior tibial slope had no influence on: 1) HSS knee functional score, 2) range of motion. Radiolucent lines were observed in 18 out of 48 knees, but their occurrence was not influenced by the degree of posterior tibial slope or preservation of ACL. DISCUSSION: Posterior tibial slope has a higher influence than ACL preservation on anterior tibial translation. The increase of posterior tibial slope in order to improve range of motion and to protect the bone-prosthetic tibial interface appeared unjustified with this non-constrained prosthesis. Moreover, implantation of tibial tray (whatever the preservation of ACL) with an important posterior inclination exposes to high anterior tibial translation in weight bearing situation. This last condition could reduce the survivorship of tibial polyethylene.

[Recurvatum in arthritic genu valgum. Contraindication for osteotomy and unicompartmental prosthesis]. / Le recurvatum du genu valgum arthrosique. Conséquences dans les ostéotomies et les prothèses unicompartimentales.

Nine lateral gonarthroses were accompanied by a preoperative recurvatum. The recurvatum of arthritic origin is rare. It appears only at a late stage of the arthritis evolution in the genu valgum. Considering the series results, it constitutes a contraindication to the treatment by osteotomy or by unicompartmental prosthesis.

[Anatomy of the trochleo-condylar junction and its consequences on the femoro-patellar joint in single-compartment prostheses]. / Anatomie de la jonction trochléo-condylienne et ses conséquences sur l'articulation fémoro-patellaire des prothèses unicompartimentales.

A search was made for impingement of the femoral part upon the patella on femoropatellar axial views made at a 90 degree angle of flexion in 81 cases of unicondylar arthroplasty (46 medial and 35 lateral). The patients were followed up during a period ranging from 5 to 10 years. 16 cases of impingement between the condyle part and the patella were found. Radiologically, this resulted in a notch on the patella. Clinical symptoms were usually moderate. The anomaly most often found at the onset of this complication was faulty positioning of the condyle part. The complication was more frequently observed in lateral femorotibial arthroplasty (10 cases out of 35) than in medial one-compartment arthroplasty (6 cases out of 46). This variation can be explained on the basis of morphological differences between the medial and lateral sides of the trochleocondylar junction. A study carried out using anatomical specimens, X-rays and scanner sections was used to define the differences.