Do Osteochondroplasty Alone, Intertrochanteric Derotation Osteotomy, and Flexion-Derotation Osteotomy Improve Hip Flexion and Internal Rotation to Normal Range in Hips With Severe SCFE? - A 3D-CT Simulation Study

BACKGROUND

Severe slipped capital femoral epiphysis (SCFE) leads to femoroacetabular impingement and restricted hip motion. We investigated the improvement of impingement-free flexion and internal rotation (IR) in 90 degrees of flexion following a simulated osteochondroplasty, a derotation osteotomy, and a combined flexion-derotation osteotomy in severe SCFE patients using 3D-CT-based collision detection software.

METHODS

Preoperative pelvic CT of 18 untreated patients (21 hips) with severe SCFE (slip-angle>60 degrees) was used to generate patient-specific 3D models. The contralateral hips of the 15 patients with unilateral SCFE served as the control group. There were 14 male hips (mean age 13±2 y). No treatment was performed before CT. Specific collision detection software was used for the calculation of impingement-free flexion and IR in 90 degrees of flexion and simulation of osteochondroplasty, derotation osteotomy, and combined flexion-derotation osteotomy.

RESULTS

Osteochondroplasty alone improved impingement-free motion but compared with the uninvolved contralateral control group, severe SCFE hips had persistently significantly decreased motion (mean flexion 59±32 degrees vs. 122±9 degrees, P <0.001; mean IR in 90 degrees of flexion -5±14 degrees vs. 36±11 degrees, P <0.001). Similarly, the impingement-free motion was improved after derotation osteotomy, and impingement-free flexion after a 30 degrees derotation was equivalent to the control group (113± 42 degrees vs. 122±9 degrees, P =0.052). However, even after the 30 degrees derotation, the impingement-free IR in 90 degrees of flexion persisted lower (13±15 degrees vs. 36±11 degrees, P <0.001). Following the simulation of flexion-derotation osteotomy, mean impingement-free flexion and IR in 90 degrees of flexion increased for combined correction of 20 degrees (20 degrees flexion and 20 degrees derotation) and 30 degrees (30 degrees flexion and 30 degrees derotation). Although mean flexion was equivalent to the control group for both (20 degrees and 30 degrees) combined correction, the mean IR in 90 degrees of flexion persisted decreased, even after the 30 degrees combined flexion-derotation (22±22 degrees vs. 36 degrees±11, P =0.009).

CONCLUSIONS

Simulation of derotation-osteotomy (30 degrees correction) and flexion-derotation-osteotomy (20 degrees correction) normalized hip flexion for severe SCFE patients, but IR in 90 degrees of flexion persisted slightly lower despite significant improvement. Not all SCFE patients had improved hip motion with the performed simulations; therefore, some patients may need a higher degree of correction or combined treatment with osteotomy and cam-resection, although not directly investigated in this study. Patient-specific 3D-models could help individual preoperative planning for severe SCFE patients to normalize the hip motion.

LEVEL OF EVIDENCE

III, case-control study.

Prone vs Supine Positioning for Femoral Derotation Osteotomy: Kinematic and Physical Examination Outcomes Suggest Both Can Achieve Desired Results

Background: Femoral derotation osteotomy (FDO) for correction of internal rotation gait resulting from cerebral palsy (CP) can be performed with the patient in the prone or supine position. It is not known whether patient positioning during FDO affects the change in hip rotation. Purpose/Questions: We sought to compare the change in hip rotation following FDO performed on patients with CP in the prone or supine position through kinematic analysis. Methods: We conducted a consecutive retrospective cohort study of children with CP, ages 3 to 18 years and with Gross Motor Function Classification System (GMFCS) levels I to III, who underwent prone or supine FDO and pre- and postoperative motion analysis. The prone group included 37 patients (68 limbs) between 1990 and 1995. The supine group included 26 patients (47 limbs) between 2005 and 2015. The groups were matched for gender, age, and GMFCS level. The primary outcome was hip rotation in degrees during stance phase. Secondary outcomes included temporal-spatial parameters, hip abduction, hip and knee extension, and hip and knee passive range of motion (ROM). Results: The prone group had more bilateral patients (100%) than the supine group (81%). The supine group underwent more concomitant procedures. There was no difference between the prone and supine groups in postoperative stance hip rotation; both groups had significantly improved stance hip rotation, step width, and hip rotation passive ROM, pre- to postoperatively. Prone patients had improved postoperative hip extension, pelvic tilt, velocity, and cadence. Conclusions: There was no significant different in stance hip rotation between supine and prone FDO groups. Advocates of prone positioning for FDO suggest it allows more accurate assessment of rotation. Supine positioning may be more convenient when additional procedures are required. Based on our findings, either approach can achieve the desired result.

Electromagnetic tracking for femoral derotation osteotomy-an in vivo study

Femoral derotation osteotomy delivers good to excellent results in the treatment of rotational gait abnormalities and especially in internal rotation gait. The outcome of the procedure has been evaluated in numerous short- and long-term studies. Although reasons for recurrence and over-/under-correction have been unveiled in earlier studies the mechanisms are still not fully understood. False intra-operative assessment of the derotation angle may contribute to imprecise outcomes. In a recent saw-bone study we evaluated an electromagnetic tracking system in comparison to conventional goniometer measurement and a CT reference measurement and found it to be extremely accurate, whereas the use of a conventional goniometer for derotation measurement showed a high inter- and intra-rater variability. The current study evaluates the electromagnetic tracking system for continuous intra-operative derotation control under real OR conditions. Adults (age: 18-40 years) with the diagnosis of internal rotation gait, independent of the underling pathology, undergoing a supracondylar deroation osteotomy were included. A rotational CT scan was conducted before and in close proximity after surgery and the difference served as reference for the electromagnetic tracking results. The results showed a mean deviation of 2.6° (1.2-5.5°) in comparison to the reference measurement of the pre- and post-operative CT scans. The system proved to be stable under OR conditions with a good usability and a small technical footprint. Electromagnetic tracking delivers a precise, reliable, and independent assessment of intra-operative derotation angles in femoral derotation osteotomies. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2652-2657, 2017.

Application of 3D technology and printing for femoral derotation osteotomy: case and technical report

In some surgical techniques like femoral derotation osteotomy, accuracy is a key factor that often is not optimal because of the lack of appropriate technology. 3D printing is emerging in many professional areas and its use in the medical field may enhance the results of certain surgeries. This case describes a patient who underwent an intramedullary nail fixation to treat a femoral shaft fracture. After nine months, the patient presented hip pain and "in toe" walking caused by a malrotation produced during the surgery. To address the consequent femoral derotation osteotomy, 3D technology was used throughout the whole process. A 3D model of the patient's femur was created to conduct a real and accuracy assessment of femoral anteversion. Then, a customized surgical guide was designed and printed to ensure the proper alignment during surgery. Given the success of this surgery, 3D printing can be considered a quick and inexpensive tool to improve surgical results.

Electromagnetic bone segment tracking to control femoral derotation osteotomy-A saw bone study

Correction of rotational gait abnormalities is common practice in pediatric orthopaedics such as in children with cerebral palsy. Femoral derotation osteotomy is established as a standard treatment, however, different authors reported substantial variability in outcomes following surgery with patients showing over- or under-correction. Only 60% of the applied correction is observed postoperatively, which strongly suggests intraoperative measurement error or loss of correction during surgery. This study was conducted to verify the impact of error sources in the derotation procedure and assess the utility of a newly developed, instrumented measurement system based on electromagnetic tracking aiming to improve the accuracy of rotational correction. A supracondylar derotation osteotomy was performed in 21 artificial femur sawbones and the amount of derotation was quantified during the procedure by the tracking system and by nine raters using a conventional goniometer. Accuracy of both measurement devices was determined by repeated computer tomography scans. Average derotation measured by the tracking system differed by 0.1° ± 1.6° from the defined reference measurement . In contrast, a high inter-rater variability was found in goniometric measurements (range: 10.8° ± 6.9°, mean interquartile distance: 6.6°). During fixation of the osteosynthesis, the tracking system reliably detected unintentional manipulation of the correction angle with a mean absolute change of 4.0° ± 3.2°. Our findings show that conventional control of femoral derotation is subject to relevant observer bias whereas instrumental tracking yields accuracy better than ±2°. The tracking system is a step towards more reliable and safe implementation of femoral correction, promising substantial improvements of patient safety in the future. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1106-1112, 2017.