How to avoid unintended valgus alignment in distal femoral derotational osteotomy for treatment of femoral torsional malalignment - a concept study

Abstract Background Defining the optimal cutting plane for derotational osteotomy at the distal femur for correction of torsion in cases of patellofemoral instability is still challenging. This preliminary study investigates changes of frontal alignment by a simplified trigonometrical model and demonstrates a surgical guidance technique with the use of femur cadavers. The hypothesis was that regardless of midshaft bowing, a cutting plane perpendicular to the virtual anatomic shaft axis avoids unintended valgus malalignment due to derotation. Methods A novel mathematical model, called the Pillar-Crane-Model, was developed to forecast changes on frontal alignment of the femur when a perpendicular cutting plane to the virtual anatomical shaft was chosen. As proof of concept, eight different torsion angles were assessed on two human cadaver femora (left and right). A single cut distal femoral osteotomy perpendicular to the virtual anatomical shaft was performed. Frontal plane alignment (mLDFA, aLDFA, AMA) was radiographically analyzed before and after rotation by 0°, 10°, 20°, and 30°. Measurements were compared to the model. Results The trigonometrical equation from the Pillar-Crane-Model provides mathematical proof that slight changes into varus occur, seen by an increase in AMA and mLDFA, when the cutting plane is perpendicular to the virtual anatomical shaft axis. A table with standardized values is provided. Exemplarily, the specimens showed a mean increase of AMA from 4.8° to 6.3° and mLDFA from 85.2° to 86.7 after derotation by 30°. Throughout the derotation procedure, aLDFA remained at 80.4° ± 0.4°SD. Conclusions With the use of this model for surgical guidance and anatomic reference, unintended valgus changes on frontal malalignment can be avoided. When the cutting plane is considered to be perpendicular to the virtual anatomical shaft from a frontal and lateral view, a slight increase of mLDFA results when a derotational osteotomy of the distal femur is performed

The Potential Negative Effects of Smoking on Cervical and Lumbar Surgery beyond Pseudoarthrosis: A Michigan Spine Surgery Improvement Collaborative (MSSIC) Study

OBJECTIVE: The study was designed to review the Michigan Spine Surgery Improvement Collaborative (MSSIC) registry to investigate the long-term associations between current smoking status and outcomes after elective cervical and lumbar spine surgery. METHODS: Utilizing MSSIC we captured all cases from 01/01/17-11/21/20 with outcomes data available. 19,251 lumbar cases and 7,936 cervical cases were included. Multivariate regression analyses were performed to assess the relationship of smoking with the clinical outcomes. RESULTS: Current smoking status was associated with lower urinary retention and satisfaction for lumbar surgery patients and was also associated with less likelihood of achieving minimal clinically important difference (MCID) in Patient-Reported Outcomes Measurement Information System (PROMIS), back pain, leg pain, and EQ5D at 90 days and 1 year after surgery. Current smokers were also less likely to return to work at 90 days and 1 year after surgery. For cervical patients, current smokers were less likely to have urinary retention and dysphagia postoperatively. They were less likely to be satisfied with the surgery outcome at 1 year. Current smoking was associated with lower likelihood of achieving MCID in PROMIS, neck pain, arm pain, and EQ5D at various time points. There was no difference in return-to-work status. CONCLUSION: Our analysis suggests that smoking is negatively associated with functional improvement, patient satisfaction, and return-to-work after elective spine surgery