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Purpose: Starting from the hypothesis that a deep-dished highly congruent tibial insert in cruciate-retaining total knee arthroplasty would prevent the increase in patellar tendon angle and anterior patellar translation by reducing the paradoxical anterior femoral translation, the main purpose of the present study was to investigate the effect of this prosthesis design, and secondary to assess the clinical outcomes at 6-month follow-up. Methods: Twenty patients treated with cruciate-retaining total knee arthroplasty with navigation technique were enrolled and prospectively followed up at 6 months. The median value of age was 71 years (57-83). Before and after surgery, the following parameters were calculated: patellar tendon angle, anterior-posterior and medio-lateral patellar translation, patellar height and range of motion. All patients were assessed with the SF-36 Physical Functioning and the Knee injury and Osteoarthritis Outcome Score ADL scores. Results: Patellar tendon angle and anterior patellar translation significantly increased in post-operative conditions ( p < 0.0001); a statistically significant medial patellar translation was found ( p < 0.0001), while patellar height did not show any difference between pre- and post-operative conditions (n.s). A significant correlation was found between patellar tendon angle and anterior patellar translation and the clinical scores ( p < 0.0417). There was a significant post-operative decrease ( p < 0.0033) in the range of motion. Conclusions: The present study failed to demonstrate that deep-dished highly congruent tibial insert prevents the anterior translation of the patella in cruciate-retaining total knee arthroplasty, thus causing inferior clinical scores. It provided useful information about the biomechanical role of the patella in total knee arthroplasty, allowing to choose the most appropriate surgical approach. Level of evidence: Case series, Level IV. [ABSTRACT FROM AUTHOR]

We performed a retrospective clinical and radiographic evaluation of 83 nonconsecutive patients operated in our institute between February 1996 and March 2003 with a mean follow-up of 60 months to assess the efficiency of unicompartmental knee replacement (UKR) performed with a minimally invasive technique. The aim of this study was to correlate the clinical outcome with the pre- and post-operative alignment and with implant positioning on coronal and sagittal plane. Eighty-three nonconsecutive patients (60 males, 23 females) underwent cemented UKR (De Puy Preservation Uni with all-poly tibial component), for both medial OA (80 patients) and AVN of the medial femoral condyle (3 patients). All patients were available at final follow-up evaluation, and they all presented an evident varus alignment at pre-operative clinical and radiographic evaluation. At radiographic measurement, we considered a knee with femoro-tibial angle (FTA) > 175° as varus knee, 170° < FTA < 175° as normal knee and a knee with a FTA < 170° as a valgus knee. Moreover, we considered a tibial plateau angle (TPA) > 90° for valgus knee and a TPA < 90° for varus knee. According to Hospital for Special Surgery (HSS) scoring system, at a mean follow-up of 60 months, 61 (74%) cases were excellent (100-85 points), 15 (18%) cases were good (84-70 points) and 7 cases (8%) had fair results (<70 points). In our series, patients with an excellent clinical result presented a mean varus deformity of 7.2° (3.6°–10.8°) pre-operatively. According to literature, we demonstrated that a small amount of undercorrection with a small amount of residual varus deformity of 3°–5° is the goal to be reached in order to avoid both rapid degeneration of the nonreplaced compartment and the premature loosening of the replaced compartment. We performed a mean axial correction of 5° (SD 3.9°), leaving a mean axial varus deformity of 2.2° in the excellent group. In our series, the group with excellent results also showed a post-operative PTS of 7° (2.4°–11.6°), while mean pre-operative PTS was 6.5° (2.7°–10.3°). In this study, results have shown that minimally invasive UKR producing a small amount of varus undercorrection in selected patients with medial tibio-femoral osteoarthritis or moderate avascular necrosis of the medial femoral condyle provides excellent clinical and functional results. Overcorrection of varus malalignment with a UKR may produce both rapid degeneration of the lateral tibio-femoral compartment and the early failure of the replaced compartment. [ABSTRACT FROM AUTHOR]

Surgical navigation systems are currently used to guide the surgeon in the correct alignment of the implant. The aim of this study was to expand the use of navigation systems by proposing a surgical protocol for intraoperative kinematics evaluations during knee arthroplasty. The protocol was evaluated on 20 patients, half undergoing unicondylar knee arthroplasty (UKA) and half undergoing posterior-substituting, rotating-platform total knee arthroplasty (TKA). The protocol includes a simple acquisition procedure and an original elaboration methodology. Kinematic tests were performed before and after surgery and included varus/valgus stress at 0 and 30° and passive range of motion. Both UKA and TKA improved varus/valgus stability in extension and preserved the total magnitude of screw-home motion during flexion. Moreover, compared to preoperative conditions, values assumed by tibial axial rotation during flexion in TKA knees were more similar to the rotating patterns of UKA knees. The analysis of the anteroposterior displacement of the knee compartments confirmed that the two prostheses did not produce medial pivoting, but achieved a postoperative normal behavior. These results demonstrated that proposed intraoperative kinematics evaluations by a navigation system provided new information on the functional outcome of the reconstruction useful to restore knee kinematics during surgery. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:202-207, 2009 [ABSTRACT FROM AUTHOR]

Abstract: Revision total knee arthroplasty (RTKA) is a skill-demanding intervention presenting several technical challenges to the surgeon due to bone deficiencies and lack of anatomical references. Computer-assisted navigation systems can potentially solve these problems. An innovative computer-assisted surgical technique for RTKA is presented. The system is image free. Based on anatomical landmarks acquired on the patient, the system automatically plans the intervention, and provides the surgeon with tools to analyse and modify the proposed plan and to accurately reproduce it on the patient. Although we performed few cases with this navigated procedure, early results obtained demonstrated to be very promising. [Copyright &y& Elsevier]