Comparison of anatomic axes with a navigated functional rotation axis determined by ligament tension for rotational femoral component alignment in cadaver knee arthroplasty.

INTRODUCION: The malimplantation of the total knee arthroplasty (TKA) components is one of the main reasons for revision surgery. For determining the correct intraoperative femoral rotation several anatomic rotational axes were described in order to achieve a parallel, balanced flexion gap. In this cadaveric study prevalent used rotational femoral axes and a navigated functional rotational axis were compared to the flexion-extension axis defined as the gold standard in rotation for femoral TKA component rotation. MATERIALS AND METHODS: Thirteen body donors with knee osteoarthritis (mean age: 78.85 ± 6.09; eight females and five males) were examined. Rotational computer tomography was performed on their lower extremities pre- and postoperatively. Knee joint arthroplasties were implanted and CT diagnostics were used to compare the preoperatively determined flexion-extension axis (FEA). The FEA is the axis determined by our surgical technique and serves as an internal reference. It was compared to other axes such as (i) the anatomical transepicondylar axis (aTEA), (ii) the surgical transepicondylar axis (sTEA), (iii) the posterior condylar axis (PCA) and (iv) the functional rotation axis (fRA). RESULTS: Examination of 26 knee joint arthroplasties revealed a significant angular deviation (p*** < 0.0001) for all axes when the individual axes and FEA were compared. aTEA show mean angular deviation of 5.2° (± 4.5), sTEA was 2.7° (± 2.2), PCA 2.9° (± 2.3) and the deviation of fRA was 4.3° (± 2.7). A tendency towards external rotation was observed for the relative and maximum axis deviations of the aTEA to the FEA, for the sTEA and the fRA. However, the rotation of the posterior condylar axis was towards inwards. CONCLUSIONS: All axes showed a significant angular deviation from the FEA. We conclude that the presented technique achieves comparable results in terms of FEA reconstruction when compared with the use of the known surrogate axes, with certain deviations in terms of outliers in the internal or external rotation.

Clinical outcome after dorso-ventral stabilization of the thoracolumbar and lumbar spine with vertebral body replacement and dorsal stabilization.

PURPOSE: Surgical stabilization of the spine by vertebral body replacement (VBR) is used for spinal disorders such as traumatic fractures to provide an anatomical re-adjustment of the spine to prevent late detrimental effects and pain [1-4]. This study addresses the clinical outcome after a ventral intervention with VBR and bisegmental fusion. METHODS: The study includes 76 patients (mean age: 59.34 ± 15.97; 34 females and 42 males) with fractures in the lower thoracic and lumbar spine. They were selected from patients of our hospital who received an anterolateral VBR surgery on the corresponding lower spine region over a nine-year period. Only patients were examined with X-rays and complete follow-up records. Exclusion criteria were changes due to degeneration and pathological fractures. Patients were divided into two groups, the thoracotomy group (Th10-L1) and the lumbotomy group (L2-5), respectively. Minimum one year after surgery, patients were asked about their well-being using a precasted questionnaire. RESULTS: No significant differences with respect to the subjective impression of the patients concerning their back pain, spinal functional impairment, their general functional status and their quality of life impairment. Unfortunately, however, only a rather modest but significant increase of the post-surgical life quality was reported. CONCLUSIONS: Patients who underwent VBR in the lower thoracic or lumbar spine show modest long-term well-being. The results suggest that injuries to the lower thoracic or lumbar spine requiring vertebral body replacement should be classified as severe injuries since they adversely affect the patients' long-term well-being. TRIAL REGISTRATION: Study of clinical outcome of patients after vertebral body replacement of the ventral thoracal and lumbal spine, DRKS00031452. Registered 10th March 2023 - Prospectively registered. Trial registration number DRKS00031452.

Validation of functional motor and language MRI with direct cortical stimulation.

BACKGROUND: Functional magnetic resonance imaging (fMRI) is a widely available method and is therefore progressively utilized in neurosurgical practice. This study was carried out to determine fMRI sensitivity and specificity and to emphasize the threshold dependence of fMRI data. METHODS: A total of 17 consecutive patients, scheduled for surgery on intracerebral lesions near eloquent brain areas, underwent preoperative motor (N = 12) and language (N = 5) fMRI. Functional data were analyzed with SPM software and displayed on a neuronavigation system for intraoperative guidance. High-risk maps for motor and language deficits obtained from direct electric cortical stimulation (DECS) were used for validation of functional activated areas. In a first analysis step, sensitivity and specificity were calculated in terms of a side-by-side correlation. The next step, the threshold dependence of fMRI data sensitivity and specificity, was estimated according to four statistical thresholds (p1 < 0.05, p2 < 0.0005, p3 < 0.00001, p4 < 0.0000001). RESULTS: Both functional imaging and DECS revealed definite results for the investigated areas in all patients. Calculation of sensitivity and specificity resulted in 100 % and 68 % for the motor group and a sensitivity of 75 % and specificity of 68 % for the language group at the fixed threshold analysis. Threshold-dependent analysis of the obtained data revealed a sensitivity/specificity relationship from 100 %/0 % at threshold (p1), 100 %/5 % at (p2), 74 %/9 % at (p3), and 37 %/36 % at (p4) for the motor group. Evaluation of threshold-dependent sensitivity and specificity for the language group resulted in 78 %/51 % at threshold (p1), 67 %/75 % at (p2), 50 %/78 % at (p3), and 33 %/89 % at (p4). CONCLUSIONS: The present findings on the threshold dependence of fMRI data demonstrate why individualized thresholds should be obtained in case of fMRI evaluation. Although the results are satisfying in most cases, fMRI is apparently not sufficient for critical intraoperative decision-making.

Fiber transformations in multifidus muscle of young patients with idiopathic scoliosis.

STUDY DESIGN: In this study, the authors investigated the superficial multifidus muscle in patients with idiopathic scoliosis. During spinal fusion, biopsies were taken bilaterally at the apex of the curve, and at the upper and lower end vertebrae. OBJECTIVES: To analyze the muscular reactions in response to bracing in patients with idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: The extent to which intervertebral mobility is restricted by an orthosis is still controversial. In addition, the effect of bracing on the erector spinae has not been investigated. METHODS: Of a total 30 patients, 11 had been treated with a corset for a year or more before surgery. Biopsies were investigated histochemically and the muscle fibers classified as Type I, IIA, IIB, or IIC (transitional fibers). The relative distribution of the fibers was calculated and their diameter was measured. RESULTS: In unbraced patients, a shift in the fiber distribution (from "slow" to "fast") was observed exclusively at the concave side of the apex. This shift was paralleled by an increased percentage of the intermediate Type IIC fiber (indicative of fiber transformation). In patients who always wore a corset, the relative amount of Type IIC fibers was increased, without preference for a specific location. CONCLUSIONS: Corset treatment elicits muscle fiber transformation processes at different levels along the scoliosis. This general reaction of the paraspinal muscles provides strong evidence against the existence of muscular disorders that are restricted to the area of the apex and are thus causing the scoliosis. As such, it must be assumed that the muscular changes in the apical region are secondary.