INTRODUCTION

The literature suggests a survivorship of unicompartmental knee arthroplasties (UKA) for spontaneous osteonecrosisof the knee range from 93% to 96.7% at 10 to 12 years. However, these data arise from series reporting 23 to 33 patients, jeopardizing meaningful conclusions.

Background

The reported outcomes of unicompartmental knee replacement (UKR) for spontaneous osteonecrosis of the knee (SPONK) often derive from small series with an average followup of 5 years, enabling to generate meaningful conclusions. Therefore, we determined the long-term functional results and the 10-years survivorship of the implant in all patients with advanced SPONK of the medial tibio-femoral compartment treated with a unicompartmental knee arthroplasty at our institute.

Arthroscopic selective resurfacing of the knee may be considered a treatment option for selected patients with focal articular damage.

From more than 2 years in IX Division of Rizzoli Orthopaedics Institute(Bologna- Italy) we use, in selected cases with only one articular compartment damaged, an innovative resurfacing prosthesis.

We mad a new design of focal resurfacing (MAIOR) that is possible to implant with arthroscopic technique and that realize both mini-invasive and mini-traumatic surgery.

The fixation method of the MAIOR allows higher osteointegration by biomaterials and hydrossiapatite of new generation that permit a press-fit fixation of the implant.

The new philosophy of this implant consist of early focal treatment with low compromise of bone. Many surgeons, in case of focal articular damage, prefer to attend to made an unique definitive surgical operation when the degenerative changes are more severe.

This new implant permit to substitute, also in arthroscopic technique, only the articular damage and to avoid to attend a more important and diffuse articualr damage.

It is an uncemented, focal resurfacing prosthesis that requires minimal bone sacrifice and utilizes a minimal invasive surgical (MIS) approach with or without arthroscopic assistance.

In a prospective and consecutive study, 78 patients were followed up at least for 12 months. Subjective pain and joint function were assessed using Visual analogue scale (VAS) and Knee society scores respectively. The preliminary results are interesting and encouraging with subjective evaluation equal to 85% of normal knee.

Significant reduction of pain and improvement in joint function was observed. Although, long term study will determine the real performance of the prosthesis, trend seems to be positive.

Introduction: Anterior Cruciate Ligament (ACL) is primary constrain to anterior displacement of tibia with respect to the femur and secondary to internal/external (IE) and varus/valgus (VV) rotations; an ACL reconstruction should thus control not only AP but also IE and VV laxities. For this reasons, more attention has given to residual rotational instability. This study aims to verify if those subjects with high of pre-op knee laxities has also high post-op laxity after an ACL reconstruction.

Material and Methods: The study includes 115 patients, that underwent ACL reconstructions between January 2005 and September 2007. Patients with associated severe ligaments tears or severe chondral defects were excluded. The joint passive kinematics was intra-operatively assessed using the BLU-IGS system (Orthokey, Delaware). We evaluated, before and after the reconstruction, the manual maximum IE rotation at 30° and 90° of flexion, VV rotation at 0° and 30° of flexion and AP displacement at 30° and 90° of flexion. We used the k-means algorithm applied to pre-op values to create two groups among the patients: the GROUP H, with higher pre-op laxity and the GROUP L, with lower pre-op laxity. The pre-op groups were compared for each test using independent Student’s t-test (p=0.01) in order to assess their difference. Student’s t-test (p=0.01) was performed on the corresponding post-op values in order to verify if the difference between H and L was maintained after the reconstruction.

Results: Mean pre-op VV at 0° was 7.1±0.9° for group H and 4.7±0.8° for group L (p< 0.01), post-op was 3.2±0.8° for group H and 2.5±0.8° for group L (p< 0.01). Mean pre-op VV at 30° was 6.2±1.5° for group H and 3.4±0.7° for group L (p< 0.01), post-op was 3.4±1.3° for group H and 2.2± 0.9° for group L (p< 0.01). Mean pre-op IE at 30° was 28.3±3.5° for group H and 19.2±3.1° for group L (p< 0.01), post-op was 21.5±3.8° for group H and 14.7±3.7° for group L (p< 0.01). Mean pre-op IE at 90° was 31.3±2.8° for group H and 22.4±3.5° for group L (p< 0.01), post-op was 22.3±4.0° for group H and 17.0±4.4° for group L (p< 0.01). Mean pre-op AP at 30° was 14.5±2.1mm for group H and 8.9±1.6mm for group L (p< 0.01), post-op was 6.2±1.6mm for group H and 4.2±1.6mm for group L (p< 0.01). Mean pre-op AP at 90° was 11.2±1.7mm for group H and 6.7±1.4mm for group L (p< 0.01), post-op was 5.4±1.8mm for group H and 3.4±1.3mm for group L (p< 0.01).

Discussion: The comparison between group H and group L showed that those patients with higher pre-op laxity had maintained higher post-op values mainly for all the tests. This finding is probably correlated to the possible presence of different tears affecting soft structures of the joint and to the proper and specific anatomy of each patient.

Aims: In Revision Total Knee Arthroplasty (RTKA), bone deficiencies and lack of anatomical references make it difficult to understand the normal knee kinematic and adequately plan the intervention. To our knowledge there are no data about computer assisted navigation system specifically developed for RTKA in the literature and existing navigated techniques for RTKA use navigation systems developed for primary TKA. A new computer assisted technique for RTKA is presented.

Methods: This technique is based on the use of a navigation system, RTKANav consisting of an optical localizer, a dedicated software and some navigated tools specifically done for RTKA. The system doesn’t use medical images, and patient anatomy model is represented with dots and lines corresponding to acquired landmarks, providing the surgeon with the main references for the intervention monitored in real-time. During the most critical steps of the intervention (soft tissue balancing and the consequent choice of implant size, and joint line height restoration), the system provide the surgeon with graphical and numerical tools to improve the surgical outcome. Several criteria to set each degree of freedom of prosthetic components are considered and compared, and even if some required landmarks can not be identified, the system is always able suggest an intervention plan. The surgeon is provided with tools to analyze and modify the proposed plan, and to reproduce it on the patient.

Results: Till now the presented technique was used on five patients by an expert surgeon. Qualitative results, collected after the intervention through a questionnaire on surgeon feelings, in order to assess the functionality, user friendliness and the data visualization criteria implemented were very satisfying. System reliability was assessed intraoperatively analyzing joint line height, limb alignment and knee stability using trial components: based on his experience, the surgeon checked some acceptable components combination and compared the corresponding outcome with the one provided by the implant planned by the system. In three out five cases the suggested implant was considered the best by the surgeon, while in one case he decided to change the tibial insert of one size because of knee instability and in another case he changed the tibial component of one size because the planned one was too small. Final limb alignment evaluated with postoperative x-rays, was satisfactory in all cases.

Conclusions: Presented navigation system showed early promising results providing the surgeon with intraoperative quantitative and qualitative information on the main surgical parameters, useful to achieve a satisfactory prosthesis implant. Moreover this system use anatomical patient specific landmarks acquired after prosthesys removal, while navigation systems developed for primary TKA use both reference taken from preoperative x-rays and anatomical references acquired on metal component to be removed. Therefore in this case the operation planning is based on rough anatomical landmarks that do not reflect patients original anatomy.