RESUMO
Due to the compromised bone situation revision implants need extended fixation options in order to achieve good long-term survival. Over decades this has been achieved with stems, either cemented or uncemented. In the last decade additional fixation options in terms of cementless metaphyseal sleeves or metaphyseal cones have been introduced and widely accepted. Revision of such implants is challenging, in particular if those porous coated parts are well integrated. Therefore, partial revision leaving the well-fixed parts in place can be an option if the indication is allowing it. This can help to preserve bone. In this study we show 2 cases with metaphyseal sleeves, in which we demonstrate when and how revision can be performed leaving sleeves in place. Meticulous pre-Op analysis of the failure mechanism is mandatory to find those few cases in which a partial revision can be recommended. In our cases, it was one patient with persistent tibia stem pain and another patient with secondary instability. In both cases implant fixation was not the problem, and therefore leaving the well-fixed sleeves in place was considered. Before final decision was made, specific information on implants sizes and constraint are needed. In our tibial revision stem thickness was less than 14 mm decision, in this situation the stem can be removed through the sleeve, leaving the sleeve in place. The technique how to do it, is shown in this study. In the second case a traumatic MCL rupture was leading to a secondary instability, needing a revision from a VVC constraint to a rotating hinge. Again, pre-Op analysis and the surgical technique of femoral component removal are described. In the great majority of cases a full revision with complete implant removal is required. In a few cases a partial revision with maintenance of implant parts can be considered but only after careful analysis of the failure mode. Even if the failure mode allows a partial revision specific implant information need to be obtained to clarify whether it is really possible. If it is possible, a specific surgical technique is recommended and described in this study.
RESUMO
Metaphyseal sleeves have shown an improved fixation in Revision Total Knee Arthroplasty (R-TKA) leading to a reduced aspetic loosening rate compared to other stem based fixation options. In the majority of these studies sleeve have been used with stems. Due to that is was not clear how much of this improved fixation could be rated to the sleeve and how much to the additional sleeves. In this review article we analysed the results of sleeve-only obtained in in-vitro or in-vivo studies. In Vitro models showed independent of the set-up a dominant fixation of the sleeve, an additional stem was not adding a lot to the overall fixation. Undersized additional stems showed an increased micromotion and the stem tip, while distal engaging stems showed a proximal stress shielding effect. Very interestingly an increased BMI had not a significant effect on primary fixation of the sleeve. Reduced bone quality on the other hand had and this effect was increased in cases with an increased BMI. In vivo results of sleeve-only patients showed comparable good results to sleeve and stem constructs. In particular on the femoral side the use of an additional stem is required only in a few scenarios. It has to be stated that the numbers of sleeves-only in rotating hinges is too low, to give any recommendation for this high constraint implants. Majority of cases was done with PS and VVC constraint. So far no in vivo data exist on the limitations of sleeve-only in patients with reduced bone quality and increased body weight. In conclusion we can state, that Sleeve-only is an option for R-TKA. In majority of cases the aspetic loosening rate is as low as with additional stems. The borderlines in terms of constraint, bone quality and body weight need to be investigated in future in vivo studies. The in vitro results look so far encouraging.
RESUMO
OBJECTIVE: Primary and long-term fixation of cementless metaphyseal implants in knee revision arthroplasty cases with large bone defects. INDICATIONS: All tibial and femoral bone defects AORI grade 2 and 3. CONTRAINDICATIONS: Cases where stable uncemented fixation of the metaphyseal implant is not possible. SURGICAL TECHNIQUE: Pre-operative evaluation of the failure mode and implant fixation planning. After opening the joint, a synovectomy and mobilisation of medial and lateral recesses routinely performed. Testing of ligamentous stability and implant fixation undertaken before explantation. Removal of the bearing, femoral and tibial components with osteotomes or oscillating saw. Tibial diaphysis prepared with reamers, and metaphyseal preparation with broaches and stem extension. Placement of the metaphyseal broach for height with respect to the tibial joint line and rotational stability assessed. Tibial tray size and position determined before implanting the sleeve, stem and tray trial. The tibial trial provides a stable platform for analysis of the extension and flexion gaps with spacer blocks. Diaphyseal reamers used to identify the anterior femoral bow. Metaphyseal broaches used to achieve stable fixation up to the resection line marked on the handle. Distal femoral freshening cut in 5° or 7° of valgus made to accommodate distal augments as needed. Positioning of the 4-in-1 block with reconstruction of the posterior off-set and cutting for posterior augmentation. Selection of a box cut corresponding to the amount of constraint needed. Trial insert with appropriate, stem, sleeve, condylar femur and augments introduced. Bearing size, joint stability and ROM assessed. Patella alignment and the need for patella replacement or revision determined. The definitive implants are cemented at the joint surface, with metaphyseal sleeves and diaphyseal stems are uncemented. POSTOPERATIVE MANAGEMENT: Full weight bearing as tolerated, physiotherapy, lymph drainage and pain therapy are routine with no specific post-operative management required. RESULTS: Between 2007 and 2011, 193 sleeves (119 tibial/74 femoral) were implanted in 121 aspetic knee revision arthroplasties. After average of 3.6 years they were analysed clinically and radiographically. The AKSS (American Knee Society Score) increased from 88 ± 18 to 147 ± 23 points (p < 0.01). ROM (range of motion) increased from 89 ± 6° to 114 ± 4°. Overall revision rate was 11.6 %. Only 4 sleeves revised for aseptic loosening (2 % of total sleeves). An additional 10 revisions performed mainly for infection (3.3 %) or ligament instability (3.3 %).