Metaphyseal sleeves in arthroplasty of the knee

Background This study examined the clinical outcome following revision arthroplasty of the knee joint and severe arthrosis with metaphyseal bone defects and instability using metaphyseal sleeves. We analyzed the results based on established scores and recorded the complications occurring on revision arthroplasty. Material and methods Patients with revision arthroplasty of the knee and metaphyseal bone defects grade III according to the Anderson Orthopedic Research Institute (AORI) classification were included (16 patients, 9 females and 7 males). In all cases, surgery was performed using an endoprosthesis COMPLETE™ revision knee system with metaphyseal sleeves. Results All patients had a significant reduction in pain level after revision surgery. The median HSS score in the cohort with primary arthroplasty was 84 and in the cohort with revision arthroplasty 73 and the KSS was 83 and 55, respectively. According to the HSS an excellent result was achieved by 50% of the patients in the primary arthroplasty group and 25% in the revision group. Only three patients were considered to have an insufficient result. Postoperative pain was significantly reduced in both groups. The median ROM was 112° flexion in the primary arthroplasty group and 95° in the revision group. An extension deficit was observed in three patients and four patients showed prolonged wound healing postoperatively (25%), which was treated conservatively and did not lead to septic changes. Conclusion The use of metaphyseal sleeves in patients with bone defects is a suitable instrument with no negative impact on the outcome both in primary and revision arthroplasty. Further studies with larger study groups and analysis of long-term results after use of such endoprosthetic components should be conducted.


Introduction
With increasing numbers of primary total knee arthroplasty, the number of revision operations on the knee joint is increasing [6,25], often due to infections, wear of modular parts, periprosthetic fractures or aseptic loosening [18,20]. Periprosthetic osteolysis caused by polyethylene abrasion is one reason for bone defects, which are often seen in cases of loosening [10]. During revision surgery, explantation of components is usually accompanied by an increase of bone defects, especially in osteopenia or osteoporotic bones. In these situations, with significant bone loss in the metaphyseal part of the femur and/or the tibia, the exact positioning and permanent fixation of the revision components can be impaired. The management of these complicated cases can lead to longer operating times and thus to an increased risk of perioperative and postoperative complications [22]. Therefore, so-called metaphyseal sleeves are frequently used for the management of bone defects and have gained wide acceptance in revision arthroplasty of the knee [1]. These are cementless sleeves, which are anchored in the metaphysis of the femur and/or tibia as a modular part of the knee revision components. Combined with intramedullary stems, the sleeves are used to achieve a durable and stable anchorage situation in a deficient metaphyseal bone situation. The intramedullary stems are press-fitted into the medulla of the femur and/or tibia and provide additional stability in the diaphysis.
This study was carried out to examine the clinical outcome following revision arthroplasty of the knee joint and severe arthrosis with metaphyseal bone defects and instability using metaphyseal sleeves. We analyzed the results based on established scores and recorded the complications occurring with revision arthroplasty.

Material and methods
Prior to conducting this study a positive vote of the local ethics committee (Votum-No. 236/19-ek) was obtained. From May 2011 to March 2019, we identified patients who had undergone aseptic arthroplastic surgery of the knee with significant metaphyseal bone defects of the femur and/or tibia (. Fig. 1) or major proximal diaphyseal defects due to inlay wear (. Fig. 2). We evaluated patient data and conducted a clinical and radiological follow-up examination of the patients.
In order to have a homogeneous study group, we included patients with revision arthroplasty of the knee and metaphyseal bone defects grade III according to the AORI classification [9]. The major tibial and femoral bone deficiency situation and instability were intraoperatively confirmed as grade III. Patients with metaphyseal defects of class AORI I and II and patients with positive results for pathogens in the microbiological probe after explantation were excluded (. Fig. 3). Furthermore, we included patients with primary varus gonarthrosis who had primary major metaphyseal bone defects due to severe osteoporosis along with significant deformity and hence were treated primarily with semiconstrained or constrained total knee arthroplasty.
Altogether 16 patients (9 females and 7 males) were included: 12 patients after revision arthroplasty of the knee and 4 patients with primary arthrosis along with severe metaphyseal bone defects and varus deformity. In all cases we performed surgery using an endoprosthesis COMPLETE™ revision knee system with the tibial and femoral metaphyseal sleeves LCS ® valgus-varusconstrained VVC or S-ROM ® rotating hinge knee system (DePuy International, Leeds, UK). Clinical and radiological follow-up examinations were carried out. We evaluated the knee score according to Ranawat and Shine (HSS) and the functional and clinical knee society score according to Insall (KSS) [15]. Furthermore, we estimated the Numerical Rating Scale to compare the pain level and the preoperative and postoperative range of motion as well as the number of complications. The current radiological images were evaluated focusing on signs of loosening (e.g. radiolucent lines, changes of positioning). The data were evaluated with SPSS (IBM, Armonk, NY, USA) and Microsoft Excel 2019 (Microsoft, Redmond, WA, USA).

Results
The average follow-up period was 79.5 months in the primary arthroplasty group and 31 months in the revision arthroplasty group. The average age at surgery of the patients was 76.5±12 years and 79 ±7 years, respectively (. Tables 1  and 2). The median duration of surgery in the primary group was 259±26 min and in the revision group 151±57 min.
The median HSS score in the cohort with primary arthroplasty at the last time of examination (median follow-up 79.5 months, range 63-93 months) was 84 (±11) and in the cohort with revision arthroplasty 73 (±18) (median followup 31 months, range 24-94 months) and the KSS was 83 (±23) and 55 (±34), respectively. According to the HSS 50% of the patients achieved an excellent result in the primary arthroplasty group and 25% in the revision group. 25% received a "good" result respectively 33% in the revision group and 25% received a "mediocre" result respectively 17%. Only three patients were considered to have an insufficient result (. Table 3).
Four patients had no specific postoperative complications (25%), two out of these four underwent previous knee surgery (50%). Four patients showed prolonged wound healing postoperatively (25%), which was treated con-servatively and did not lead to septic changes. A postoperative hematoma had to be treated by puncture or surgical revision in two cases (12.5%). Of the patients two suffered from recurrent effusions until the last follow-up (12.5%). In one case (6.25%) a patellar tendon rupture occurred, which had to be treated with a patellar tendon graft 17 months after the initial revision operation. After 44 months the same patient received a retropatellar replacement due to retropatellar arthrosis. One patient (6.25%) with a known peroneal lesion showed increasing weakness of dorsiflexion and toe lifter from muscular strenght grade 3/5 (flexion against gravity feasible) according to Janda to 1/5 (muscular twitches) 14 days postoperatively and was treated conservatively. At the last follow-up the lesion was still present with only slight improvement (Janda 2/5 flexion under suspension of gravity feasible).
Two independent examiners found no radiological signs of aseptic loosening such as radiolucent zones, endoprosthetic shift or dislocation or localized cortical hypertrophy [16] in any of the cases (0%).

Abstract
Background. This study examined the clinical outcome following revision arthroplasty of the knee joint and severe arthrosis with metaphyseal bone defects and instability using metaphyseal sleeves. We analyzed the results based on established scores and recorded the complications occurring on revision arthroplasty. Material and methods. Patients with revision arthroplasty of the knee and metaphyseal bone defects grade III according to the Anderson Orthopedic Research Institute (AORI) classification were included (16 patients, 9 females and 7 males). In all cases, surgery was performed using an endoprosthesis COMPLETE™ revision knee system with metaphyseal sleeves.
Results. All patients had a significant reduction in pain level after revision surgery. The median HSS score in the cohort with primary arthroplasty was 84 and in the cohort with revision arthroplasty 73 and the KSS was 83 and 55, respectively. According to the HSS an excellent result was achieved by 50% of the patients in the primary arthroplasty group and 25% in the revision group. Only three patients were considered to have an insufficient result. Postoperative pain was significantly reduced in both groups. The median ROM was 112°flexion in the primary arthroplasty group and 95°in the revision group. An extension deficit was observed in three patients and four patients showed prolonged wound healing postoperatively (25%), which was treated conservatively and did not lead to septic changes. Conclusion. The use of metaphyseal sleeves in patients with bone defects is a suitable instrument with no negative impact on the outcome both in primary and revision arthroplasty. Further studies with larger study groups and analysis of long-term results after use of such endoprosthetic components should be conducted.

Discussion
The most remarkable results of this retrospective follow-up examination were the significant postoperative pain relief and the absence of postoperative loosening. The average value of the HSS was 84 (±11) and in the cohort with revision arthroplasty 73 (±18) and can overall be One specification of our study is the investigation of sleeve-stem systems in purely aseptic revision arthroplasty of the knee joint. According to our literature research, no prior study has exclusively evaluated the outcome after aseptic revision arthroplasty of the knee using metaphyseal sleeve-stem systems. The use of metaphyseal sleeves has already been in- vestigated in other studies with different follow-up times, patient numbers and results with septic as well as aseptic cases ( [2,5,8,14]; . Table 4). When comparing clinical and functional scores, the results of the present study are comparable with those of other studies [4,12].
Another specific feature of our study is that all patients included in the study had severe metaphyseal bone defects of the AORI classification grade III [9,21]. This distinguishes this patient population from other studies that included patients of all AORI grades in their study.
In the literature there are different results concerning septic or aseptic loosening of sleeve-stem systems. For example, results of the studies by Graichen et al., Bugler et al. and Watters et al. [7,11,24] showed loosening rates below 10%. Rosso et al. [19] documented a loosening rate of up to 41.5%. Graichen et al. [11] and Bugler et al. [7] had similar follow-up periods compared to this study (3.6 years, range 2-6.2 years and 3.2 years, range 2-5.1 years, respectively). Watters et al. [24] had a follow-up period of 5.3 years (range 2-9.6 years). Graichen [19] only used sleeves in patients with defects of AORI classification III, but also included patients with preoperative infections, which was an exclusion criterion in the present study. The absence of loosening in our work could then be an explanation of the fact that the pain level of the patients in this study was significantly lower after surgery was performed.
A limitation of this study lies in the small number of cases (n = 16); however, no study group with purely aseptic replacement surgery using sleeves for AORI III defects in revision knee arthroplasty has ever been investigated. Metaphyseal sleeves showed no negative impact on patient outcome: pain levels were significantly reduced (NRS preoperative 7.7 ± 1.4 vs. postoperative 2.7 ± 1.9; p > 0.001), the median range of motion was 112°and 95°flexion (median; ±27°), repectively and extension deficit was observed only in three patients (18.75%; 30°-5°extension deficit). Two patients (12.5%) showed postoperative swelling of the knee joint and no patient suffered from postoperative instability. It is remarkable that patients with primary arthroplasty had a significantly longer operating time but, in the end, slightly better average scores in HSS and KSS and 50% of them showed no specific complication at all.
There are different ways of treating metaphyseal bone defects in revision arthroplasty of the knee, for example the use of bone cement for defect augmentation. This is only recommended for patients with AORI grades I and II [23]. Likewise, so-called wedges, bone chips or autologous bone blocks can be used as augmentation for bone defects, but these show only moderate long-term Table 1 Preoperative profiles of patients with a list of previous operations, age, pre-existing condition category (ASA classification according to the American Society of Anesthesiologists), duration of surgery and outcome (ROM range of motion, pain level and complications). The mean flexion was 95°. Almost every patient was able to perform a full extension (0° Ex extension, flex flexion, zero zero position Ex extension, flex flexion, zero zero position  [13]. Especially in the mentioned case 1 (. Fig. 1) the use of a so-called metaphyseal cone would be another adequate option for treating metaphyseal defects like this [19]. These cones may be also useful to achieve a good metaphyseal fixation in the presence of poor bone quality. The choice for one or the other option depends on the surgeon's experience, type, size and location of the defect and on the quality of the bone. For larger bone defects, the use of distal femoral replacement sets should be mentioned; however, the use of such megaimplants is associated with significantly higher intraoperative and perioperative complication rates [26].
Overall, the results of this study as well as comparable studies [3] indicate a positive benefit of metaphyseal fixation using

Conclusion
Revision arthroplasty of the knee increasingly confronts patients as well as surgeons. Large metaphyseal bone defects are of particular significance. The use of metaphyseal sleeves in patients with bone defects is a suitable instrument, which has no negative impact on outcome both in primary arthroplasty and in revision arthroplasty. Further studies with larger study groups and analysis of long-term results after use of such endoprosthetic components should be conducted.