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Purpose: This study looked at postoperative malunion with restricted function after elastic stable intramedullary nailing (ESIN) in pediatric patients in their childhood or adolescence. The primary objective was to compare the magnitude of the osseous malposition to the healthy opposite side. Second, these individuals were treated with patient-specific surgical instrumentation, and functional outcomes were documented. Methods: Patients under the age of 18 at the time of a corrective osteotomy due to a forearm malunion after initial ESIN treatment were included in this study. The healthy contralateral side was used as a reference for preoperative analysis and planning of the osteotomy. Osteotomies were performed using patient-specific guides and the direction and extent of the malunion were compared to the change in range of motion (ROM) after the operation. Results: Fifteen patients met the inclusion criteria at three years after initial ESIN placement, with the most pronounced malposition in the rotational axis. The postoperative function significantly improved by 12° (pre-op: 60° ± 17; post-op: 72° ± 10) of pronation and 33° (pre-op: 43° ± 26; post-op: 76° ± 13) of supination. There was no correlation between the amount and direction of malformation and the change in ROM. Conclusions: The most noticeable malunion after forearm fractures treated with the ESIN technique is in the rotational direction. Patient-specific corrective osteotomy of pediatric forearm malunion following forearm fracture fixation with ESIN achieves significant improvement in forearm range of motion. Clinical relevance: The findings are clinically relevant since forearm fractures are the most common pediatric fracture, affecting a large number of patients who can benefit from the findings of this study. It has the potential to raise awareness of the significance of the accurate rotational component of intraoperative bone alignment in the ESIN procedure.
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STUDY DESIGN: A retrospective, single center, case-control study was performed. OBJECTIVE: The present study employed patient-specific biomechanical modeling to find potential biomechanical differences after spinal fusion at L4/5 in patients with and without subsequent development of adjacent segment disease (ASD). METHODS: The study population comprised patients who underwent primary spinal fusion at L4/5 and were either asymptomatic during > 4 years of follow-up (CTRL; n = 18) or underwent revision surgery for ASD at L3/4 (n = 20). Landmarks were annotated on preoperative and follow-up lateral radiographs, and specific musculoskeletal models were created using a custom-built modeling pipeline. Simulated spinal muscle activation and lumbar intervertebral shear loads in unfused segments were analyzed in upright standing and forward flexion. Differences between the pre- and postoperative conditions were computed for each patient. RESULTS: The average postoperative muscle activity in the upright standing posture was 88.4% of the preoperative activity in the CTRL group (p < 0.0001), but did not significantly change from pre- to postoperatively in the ASD group (98.0%). The average shear load magnitude at the epifusional joint L3/4 during upright standing increased from pre- to postoperatively in the ASD group (+ 3.9 N, +/- 17.4 (n = 18)), but decreased in the CTRL group (- 4.6 N, +/- 23.3 (n = 20); p < 0.001). CONCLUSION: Patient-specific biomechanical simulation revealed that spinal fusion surgery resulted in greater shear load magnitude and muscle activation and therefore greater forces at the epifusional segment in those with ASD compared with those without ASD. This is a first report of patient-specific disc load and muscle force calculation with predictive merits for ASD.