When math meets surgery: how to improve femoral interference screw alignment in ACL reconstruction. A cadaveric study.

Transtibial femoral tunnel drilling is still an alternative technique in ACL reconstruction. Femoral interference screw divergence is a potential pitfall associated with transtibial tunnel technique, as angles greater than 15° jeopardize graft fixation. Our mathematical model theorizes the proper degrees of knee flexion during femoral screw insertion and the correct screwdriver position to obtain a minimal divergence of the screw in the femoral tunnel. The cadaveric study confirms our method. Mathematical model: using rototranslation matrices, a correlation is demonstrated between the ACLtibial- guide angle, the knee flexion, and the screwdriver position. A theoretical minimal divergence between femoral interference screw and the femoral tunnel is obtainable following these assumptions: 1) knee hyperflexion during femoral screw insertion is obtained adding a flexion corresponding to the ACL-tibial-guide angle to the flexion while drilling the femoral tunnel; 2) screwdriver position (through the AM portal) is kept parallel to tibial plateau at a rotation of 15° medial to tibial sagittal plane. Cadaveric study: 24 cadaver knees were used. The transtibial tunnel was drilled with an 8 mm drill bit with the help of an ACL tibial guide set at 55°. To simulate femoral tunnel direction, a 2.4 mm K. wire was drilled through the femur with a transtibial 7 mm offset femoral drill guide. To simulate the femoral screw direction, a second 2.4 mm K. wire was drilled from the femoral entry point of the first wire through the femur, with a cannulated screwdriver. Screwdriver direction and knee flexion during the simulation were obtained following two different methods: GROUP A (mathematical model group, 12 knees), screwdriver direction and knee flexion were calculated following the mathematical model; in GROUP B (control group, 12 knees), knee hyperflexion and screwdriver medialization were manually obtained by a senior surgeon. The divergence between the femoral interference screw and the femoral tunnel was identified as the angle formed by the two wires, measured on the plane formed by the direction of the wires. Mean divergence angles between the K. wires were significantly different (p< 0.05) between the groups: GROUP 1 (mathematical rule): 7.25° (SD 2.2); GROUP 2 (free-hand technique): 17.3° (SD 2.9). Our study shows that a minimal divergence between the femoral tunnel and the screwdriver can be achieved simply by following a mathematical rule for correct intraoperative knee flexion and screwdriver position without the need for any specialized instrumentation. Namely, during femoral interference screw insertion through the anteromedial portal: 1) the correct knee flexion is the sum between the knee flexion angle while drilling the transtibial femoral tunnel AND the ACL tibial guide angle used during tibial tunnel drilling; 2) Correct screwdriver position is parallel to the tibial plateau, engaging the femoral tunnel with a position of 15° medial to tibial sagittal plane. This simple concept has clinical relevance in helping the surgeons in obtaining an optimal alignment between the femoral tunnel and the femoral interference screw during transtibial ACL reconstruction. Furthermore, following the assumptions of this study, a starting knee flexion angle around 70° during femoral tunnel drilling seems preferable for ACL reconstruction when the transtibial tunnel technique is used. Indeed, because ACL-tibial-guide angles range commonly from 50° to 60° and in vivo, the maximal intraoperative knee flexion attainable is 130°, a starting knee flexion around 70° is optimal to allows for adding flexion angles up to 60° before reaching the physiological limit value of 130°.

Periprosthetic osteolysis: a narrative review.

Periprosthetic osteolysis is still one of the major limitations of prosthetic joints longevity. The process of this "silent" iatrogenic disease involves both mechanical and biological factors that initiate a local immune response in the periprosthetic tissue that eventually lead to implant loosening and failure. There are many causes of the primary aseptic loosening inside the periprosthetic microenvironment, but the most important elements are the wear debris and the cell-particle interactions. Together with implant position, micromotion, bearings, joint fluid pressure, and increased load on the joints drive the pathogenesis of the disease. This narrative review aims to summarise recent studies describing the biological and mechanical factors in the pathogenesis of osteolysis and some of the current pharmacological attempts to "rescue" a failing implant.

Comparing different approaches in robotic-assisted surgery for unicompartmental knee arthroplasty: outcomes at a short-term follow-up of MAKO versus NAVIO system.

The popularity of unicompartmental knee arthroplasty (UKA) continues to grow among orthopaedic surgeons and robotic surgery may be helpful in obtaining a precise placement of the prosthetic components, thanks to the meticulous intra-operative computer study for simulating the prosthetic positioning. This may lead to longer implant survivorship as well as a reduction in intermediate and long-term prosthetic complications, despite the initial greater costs than those of manual UKA. In this preliminary study, from January 2017 and October 2017, 18 patients underwent UKA with MAKO robotic system assistance and 10 patients received UKA with NAVIO robotic system assistance. The two groups were homogeneous by age, BMI, degree of osteoarthritis involvement, and postoperative program. Patients were followed both clinically (Numeric Rating Scale NRS and Knee Injury Osteoarthritis Outcome Scores KOOS) and radiographically. At the end term follow up (2 years), no significant difference was observed for NRS and KOOS as well as for clinical parameters as an active range of motion. A significant discrepancy was detected regarding the duration of the surgery and time of using the robotic system, that appeared to be longer in the NAVIO group than that of MAKO group, likely due to the specific technical aspects that characterize these two different robotic systems. The main finding of this study is that favorable clinical and radiographical results may be obtained using a robotic approach (MAKO or NAVIO) for UKA positioning at a short follow up. Due to the lack of significant clinical differences observed between the two groups of patients at end term follow up, the "concept" of a robotic approach, more than a specific patented system, may be considered the key element for improving UKA technique and it is likely that in the near future the choice of a single specific robotic system will still be a "surgeon's preference". The results of the study add scientific evidence regarding the effective improvement of UKA results using different robotic approaches. They also show possible economic sustainability of this therapeutic strategy related to the optimal patients' performance obtained at short term follow up, suggesting that the robotic assistance may really become a key element for better long-term survivorship of unicompartmental knee arthroplasty.

Endoftalmitis endógena por Nocardia asteroides en un paciente con lupus eritematoso sistémico / Endogenous Nocardia asteroides endophthalmitis in a patient with systemic lupus erythematosus

We report a case of endogenous nocardial endophthalmitis in a 32-year-old man with systemic lupus erythematosus. The patient developed pulmonary and ocular disease while on systemic corticosteroid and cyclophosphamide treatment. The intraocular infection progressed to a scleral fistula, and was treated with pars plana vitrectomy, lensectomy, intravitreous and intravenous antibacterial therapy. The diagnosis of Nocardia asteroides was made by isolation and growth of colonies from samples of a vitreous specimen and bronchioloalveolar aspirates. The eye became phthisical, it was eviscerated, and histopathogical examination was carried out.

Se describe un caso de endoftalmitis endógena por nocardia en un varón de 32 años con diagnóstico de lupus eritematoso sistémico. El paciente desarrolló compromiso pulmonar y ocular luego de meses de tratamiento con corticoides y ciclofosfamida. La infección intraocular, de rápida evolución a fístula escleral, recibió tratamiento con vitrectomía, lensectomía y terapia antibacteriana intravítrea y endovenosa. Se aislaroncolonias de Nocardia asteroides a partir de material vítreo y aspirado bronquioloalveolar. El ojo afectado evolucionó a ptisis bulbi y fue posteriormente eviscerado, y se realizó el estudio histopatológico.

Endoftalmitis endógena por Nocardia asteroides en un paciente con lupus eritematoso sistémico / Endogenous Nocardia asteroides endophthalmitis in a patient with systemic lupus erythematosus

We report a case of endogenous nocardial endophthalmitis in a 32-year-old man with systemic lupus erythematosus. The patient developed pulmonary and ocular disease while on systemic corticosteroid and cyclophosphamide treatment. The intraocular infection progressed to a scleral fistula, and was treated with pars plana vitrectomy, lensectomy, intravitreous and intravenous antibacterial therapy. The diagnosis of Nocardia asteroides was made by isolation and growth of colonies from samples of a vitreous specimen and bronchioloalveolar aspirates. The eye became phthisical, it was eviscerated, and histopathogical examination was carried out.(AU)

Se describe un caso de endoftalmitis endógena por nocardia en un varón de 32 años con diagnóstico de lupus eritematoso sistémico. El paciente desarrolló compromiso pulmonar y ocular luego de meses de tratamiento con corticoides y ciclofosfamida. La infección intraocular, de rápida evolución a fístula escleral, recibió tratamiento con vitrectomía, lensectomía y terapia antibacteriana intravítrea y endovenosa. Se aislaroncolonias de Nocardia asteroides a partir de material vítreo y aspirado bronquioloalveolar. El ojo afectado evolucionó a ptisis bulbi y fue posteriormente eviscerado, y se realizó el estudio histopatológico.(AU)