Martin Pietsch

Introduction The present study aimed to assess the postoperative alignment and clinical outcomes of patients with complex extra-articular deformities (EADs) undergoing computer-assisted surgery (CAS) for constrained total knee arthroplasty (TKA) with modular stem extensions. Materials and methods From May 2015 to July 2018, ten patients with EADs scheduled for constrained TKA were enrolled retrospectively. The preoperative average deviation from neutral (= 180°) mechanical axis was 15.3° (range of coronal alignment: 150.9° varus–202.9° valgus). Alignment was assessed using an accelerometer-based handheld CAS system. On long-leg films, the positions of the components and possible stems were analysed and templated preoperatively. The average follow-up was 3.3 years (range: 2.0–4.6 years). Results The postoperative mechanical axis was within ± 3.0° from neutral in nine patients. In all patients, the Knee Society score (KSS) and range of motion improved significantly. A constrained condylar and a rotating hinge prosthesis were used in five patients each. In eight patients, the 100-mm cementless stem that was preferred by the authors was found to be unusable for the femur or the tibia in the planning stage. For the femur, a cementless 100-mm stem was used in three, and a cemented 30-mm stem in five patients; a femoral stem was not usable in two patients. For the tibia, a cementless 100-mm stem was used in six, and a cemented 30-mm stem in two patients; a monoblock rotating hinge tibia was used in two patients. Conclusions Complex EADs were excellently managed during constrained TKA implantation using the handheld CAS system. Templating allowed the possible stem lengths to be identified and prevented anatomical conflict with the CAS-configured mechanical alignment. Limb alignment and function improved significantly after surgery. No intra- or postoperative complications occurred. Level of evidence Level IV, retrospective study.

Purpose: The treatment of an infected arthritic knee might be challenging. The failure rate has been reported to be high for open or arthroscopic debridement. A subsequently high rate of infection has been noted in these patients undergoing primary total knee arthroplasty (TKA). In the present study, a two‐stage approach using an articulating spacer was used. The hypothesis was that the procedure would eradicate the infection and improve pain and function in these patients.Methods: A total of 16 consecutive patients were enrolled in this retrospective study. The mean follow‐up time was 6.1 years (range 2.0–9.9 years). Patients with advanced osteoarthritis and infection of the knee were included. All patients had previously undergone one or more failed arthroscopic or open procedures for the eradication of infection. All patients received the same homemade metal‐on‐plastic articulating antibiotic spacer. Double antibiotic therapy was given for 2 weeks intravenously and orally for 4 weeks. TKA implantation was performed 6 weeks after the first stage.Results: The infection was eradicated without recurrence in all patients. The functional results were significantly improved, and pain was significantly reduced after spacer and TKA implantation. The mean amount of knee flexion was 95 ± 30° preoperatively, and it increased to 109 ± 14° (p = 0.012) after spacer implantation and to 119 ± 10° (p = 0.002) after TKA implantation. The mean KSS objective was 58 ± 12 preoperatively, and it increased to 75 ± 14 (p < 0.0001) after spacer implantation and to 96 ± 3 (p < 0.0001) after TKA implantation. The mean KSS function was 17 ± 11 preoperatively, and it increased to 46 ± 10 (p < 0.0001) after spacer implantation and to 86 ± 6 (p < 0.0001) after TKA implantation. The mean VAS score was 65 ± 11 preoperatively, and it decreased to 2 ± 4 (p < 0.0001) after spacer implantation and to 1 ± 2 (p < 0.0001) after TKA implantation.Conclusion: The two‐stage procedure for the treatment of infected arthritic knees after failed eradication surgery was effective in all patients. Using an antibiotic articulating metal‐on‐plastic cement spacer showed improved functional results between the stages and at the final follow‐up. No intra‐ or postoperative complications occurred.

Valgus malalignment of the distal femur may be treated with corrective osteotomy. The purpose of this study was to compare the primary stability of a lateral opening-wedge osteotomy (LOWO) using a uniplanar compared to a biplanar technique. A study was carried out to test both surgeries, with both an intact medial cortex and with a deliberate attached cut of the medial cortex simulating a fracture. The primary hypothesis was that the biplanar technique provides higher axial and torsional stiffness. It was further hypothesized that the mechanical superiority of the biplanar technique would not be affected in the case of breakage of the far medial cortex.

Purpose: The purpose of the study was to evaluate the accuracy of the planning of the patient‐specific pin guides in total knee arthroplasty (TKA). This planning was performed primarily by a technician of the company and offered to the surgeon. All parameters of the implantation can either be modified or accepted by the surgeon. The hypothesis was that the plan needs preoperative intervention by the surgeon. Methods: A prospective study in 50 patients was carried out. All patients received the same posterior‐stabilised implant with patient‐specific instrumentation. All surgical parameters (coronal, sagittal, rotational alignment, femoral and tibial resection levels and implant sizes) were checked by the orthopaedic surgeon and changed if necessary.Results: Preoperatively, the femoral size was changed in 8 patients (16 %), the femoral flexion in 23 patients (46 %), the femoral shift in 34 patients (68 %), the tibial size in 24 patients (48 %) and the tibial rotation in all patients. The epicondylar axis was accepted in 47 patients (94 %) in the technician plan. Mean planning time was 8 ± 4 min. Intraoperatively, the femoral anterior–posterior size was in 50 patients (100 %) the same as in the surgeon and in 42 patients (84 %) the same as in the technician plan (p = 0.003). The tibial component implanted was in 42 patients (84 %) the same as in the surgeon and in 19 patients (38 %) the same as in the technician plan (p < 0.0001). A femoral distal recut was necessary in 31 patients (62 %) and a change of the tibial proximal cut in 17 patients (34 %) during surgery. Intraoperatively, no changes of the femoral and tibial alignment, the femoral anterior–posterior size, the femoral flexion, the femoral shift, the femoral and tibial rotation were necessary. Postoperatively, the coronal mechanical overall axis was within ±3° in 47 patients (94 %) with a maximum deviation of 5.6°.Conclusions: Significant changes of the technician plan were necessary to get an accurate preoperative plan. Intraoperative changes were significant less compared to the surgeon than to the technician plan. No major changes (alignment, femoral anterior–posterior size and rotation) of the surgeon plan were necessary. Surgeons using patient‐specific pin guides in TKA may verify the default plan provided by the technician. A blind reply on the technician plan may be not recommended.Level of evidence: Therapeutic study, Level III.

Purpose: In this prospective study, we determined whether corrective surgery for isolated rotational malalignment of femoral prosthesis components would benefit patients previously treated with total knee arthroplasty. The symptoms, amount of malrotation and type of constraint necessary for the revision prosthesis were investigated.Methods: Seventy‐two patients were screened with computed tomography; of these, 14 had isolated internal malrotation of the femoral component with no other malpositions and were included in the study. A complete exchange arthroplasty with the correction of the malrotated femoral component was performed within 3 years of primary arthroplasty. Mean follow‐up was 57 months.Results: At the time of revision, patients suffered either from instability in flexion with good range of motion (ROM) (flexion ≥90°) and pain on the lateral side of the distal femur and proximal tibia (n = 8) or from stiffness with pain on the medial side of the proximal tibial and poor ROM (flexion n = 6). One patient showed no patellar maltracking, six patients, patellar tilt and six patients, patellar subluxation. Median internal rotation of the femoral component was 7.1° (4.1–10.0°). A condylar‐type revision implant with a posterior‐stabilized insert was used in all patients. The corrective surgery resulted in an increase in the mean Knee Society Score from 52/65 to 85/84 points and an improvement in the mean Hospital for Special Surgery knee score from 63 to 83 points.Conclusions: Correction of isolated internal malrotation of the femoral component ≥4° improves patient outcome.