[Use of an new modular revision arthroplasty system for the knee reconstruction]. / Einsatz eines neuen modularen revisionsendoprothetischen Systems zur Kniegelenksrekonstruktion.

OBJECTIVE: Reconstruction of stable knee joint kinematics using modular axis-guided revision implants after failed knee arthroplasty surgery. INDICATIONS: Revision implant for bone defects (type Anderson Orthopaedic Research Institute [AORI] III) in case of revision arthroplasty. Primary implant in case of mediolateral instability (>grade I) or multidirectional instability. CONTRAINDICATIONS: Persistent or current joint infection, general infection (e.g. pneumonia), missing metaphysis femoral and/or tibial, insufficient extensor apparatus. SURGICAL TECHNIQUE: Standard approach extending the previously used skin incision. Arthrotomy, synovectomy and collection of multiple samples for microbiological and histopathological analyses. Preparation of the femur with reamers of increasing diameter. Subsequently, a reference stem is anchored and after referencing the correct rotation and joint line height; the femoral osteotomy is performed after fixation of the 5­in­1 cutting block. Following the femoral osteotomy, the box of the femoral prosthesis is prepared. In addition, the tibia is prepared using an intramedullary reference system. Level of constraint and additional tibial augmentation is chosen according to the amount of defect bone and according to ligament stability. POSTOPERATIVE MANAGEMENT: Full load bearing; standard wound control and sterile dressings; limitation of active/passive range of motion only in case of weakened extensor apparatus. RESULTS: Between 03/2011 and 05/2018, a total of 48 patients underwent revision arthroplasty using the described system. The mean follow-up was 24 months (range 21-35 months). In 30 of the 48 cases, a rotating hinge variant was implanted, while in 18 cases a semiconstrained variant was implanted. Indications to revision arthroplasty: infection (n = 22), aseptic loosening (n = 11), instability (n = 11), periprosthetic fracture (n = 3) and PMMA allergy (n = 1). In 11 cases, revision had to be performed due to persistent infection (n = 6) and aseptic loosening (n = 5): 9 cases could be successful treated by a two-step revision procedure, while in 2 cases it was necessary to perform an arthrodesis. The 2­year implant survival rate was 77%.

[Distal femur replacement in extensive defects of the distal femur in revision arthroplasty]. / Distaler Femurersatz bei ausgedehnten femoralen Defekten in der Revisionsendoprothetik.

OBJECTIVE: Use of distal femur replacement implants in advanced bone defects after multiple bone-damaging revision surgery on the knee joint. INDICATIONS: Advanced femoral bone defects (AORI IIb and III defects) in revision arthroplasty of the knee joint. CONTRAINDICATIONS: Persistent or current joint infection, general infection, defect and/or nonreconstructable insufficient extensor apparatus. SURGICAL TECHNIQUE: Standard access including existing skin scars, arthrotomy, removal of cement spacer if necessary and removal of multiple tissue samples; preparation of tibia first to define the joint line, then preparation of the femur. Determining the resection height of the remaining femur corresponding to the preoperative planning. Gradual drilling using flexible medullary drills and then preparation by femoral rasps. Two stem systems are available for coupling to the distal femur (MUTARS). First there is the standard MUTARS stem (available lengths of 90, 120 and 160 mm); if longer shafts are required, so-called revision shaft (RS) stems are necessary (stems available in 150, 200 and 250 mm). In case of extensive femoral defects extension sleeves in different lengths can be used to reconstruct the femur. After preparation the implant position and the joint line height is checked. POSTOPERATIVE MANAGEMENT: Full weight bearing, in case of existing bony defects possibly partial load of a maximum of 10 kg für 6 weeks; regular wound control; limitation of the degree of flexion only with weakened or reconstructed extensor apparatus. RESULTS: Between February 2015 and August 2018, a total of 34 distal femurs were implanted. In 19 patients, the implantation was performed after septic and aseptic loosening of a knee prosthesis. All patients had an intraoperative AORI III defect of the femur. Of the 19 patients who underwent a distal femur implantation, 7 had to be revised due to a persistent infection; 4 of these 7 patients had to be revised several times and, finally, had a conversion to a knee arthrodesis. One patient had to undergo a revision with a stem change due to a secondary aseptic loosening of the cemented stem. The mean follow-up period was 11.2 months (range 4-29 months). The follow-up included clinical examination, KSS (Knee Society Score) and X­ray analysis. A significant improvement in range of motion from 65 ± 16° to 83 ± 14° (p < 0.01) was noted. The KSS improved significantly from 69 ± 9 points preoperatively to 115 ± 15 points postoperatively. Four patients complained of persistent symptoms during exercise after 9 months; femoral shaft pain was denied by all patients. After about 11 months, an implant survival rate of 73.7% was observed in the patient collective.

[Clinical results after replacement of comminuted radial head fractures (Mason III and IV) by the bipolar radial head prosthesis of Judet]. / Endoprothetischer Ersatz der nicht rekonstruierbaren Radiuskopffraktur (Mason III und IV) mit der bipolaren Radiuskopfprothese nach Judet - Klinische Ergebnisse.

AIM: Long-term results after resection of comminuted fractures of the radial head (Mason III and IV) may lead to valgus elbow instability, radius proximalisation and rotatory instability. Radial head replacement has been used to prevent and treat these complications. The aim of this study was to define the value of the bipolar radial head prosthesis of Judet for treating comminuted fractures of the radial head. METHOD: Over a 5-year period, 14 radial head prosthesis were implanted in 12 patients. Retrospectively, we studied the clinical and radiological results. RESULTS: Eleven patients with thirteen implants were analysed at a mean follow-up of 33.4 +/- 20.4 months. In all patients, the elbow was stable. Subjectively, we found good and excellent results with one exception. Compared to the pre-trauma status, the subjective rate was 78 +/- 12 %. According to the score of Radin and Riseborough, five of the results were found to be good and eight to be fair. According to the Broberg and Morrey score, one result was found to be very good, seven to be good and five to be fair. The mean DASH score was 10.2 +/- 10.1 points. Two temporary nerve lesions were observed. CONCLUSION: In comminuted fractures of the radial head (Mason III and IV), bipolar radial head replacement with the Judet prosthesis leads subjectively to very good and good and functionally to good and fair results on the medium-term view. Joint stability is achieved and secondary complications like valgus elbow deformity and proximal radial migration are prevented. Patients must be informed about the possibility of temporary nerve lesions, heterotopic ossification causing limitation of motion and the lack of long-term results.