In slipped capital femoral epiphysis (SCFE ), shearing forces surpass the stability of the proximal femoral physis, causing the metaphysis to rotate on the epiphyseal tubercle as a fulcrum, resulting in an extension and a retroversion deformity.1,2 SCFE (>60 degrees).3 hip scores in the long term.4,5 SCFE deformity is directly related to the development of symptoms and early hip osteoarthritis.6 SCFE deformity leads to femoroacetabular impingement (FAI), resulting in articular cartilage damage and posing a risk for long-term osteoarthritis.7–11 SCFE have expanded from the short-term perspective, focusing on stabilizing the physis and preventing further slip, towards a long-term goal to prevent secondary FAI and further osteoarthritis.12
Hip arthroscopy is the mainstay of surgical treatment of cam-type FAI, and the role of arthroscopic cam resection of the femoral head-neck junction has been expanded to the treatment of symptomatic residual deformity associated with SCFE .13–16 SCFE .17 SCFE , including the Imhauser flexion-derotational intertrochanteric osteotomy,18 3 19,20 21 22 23 hip dislocation approach has gained popularity because of the possible complete restoration of the proximal femoral anatomy and improved outcomes.24–27 SCFE is challenging due to its 3-dimensional complexity.1,28–31 SCFE , the head-neck angle measurement, and SCFE classification are affected by the patient’s position, and radiographs do not allow for a comprehensive deformity analysis.32 33
This study investigates the improvement of impingement-free motion following a simulated osteochondroplasty, a derotation-osteotomy, and a combined flexion-derotation osteotomy in hips with untreated severe SCFE using 3D-CT and collision detection software.
METHODS
Study Population
After obtaining institutional review board approval, we identified 123 patients treated for SCFE who underwent a pelvic CT between 1998 and 2016. Out of 123 patients with CT scans, we excluded 105 patients due to a mild or moderate SCFE , postoperative CT, and those with CT that did not involve the femoral condyles. The study cohort comprised 18 patients with severe SCFE (slip angle >60 degrees), and preoperative CT was used to generate patient-specific 3D models. Of the 18 patients, no previous treatment was noted. Three patients (15%) had bilateral SCFE yielding a total of 21 hips evaluated. The contralateral hips of the 15 patients with unilateral SCFE were used as a control group. The mean age was 13 years (SD, ±2 y, Table 1 ). There were 14 male hips, and the mean body mass index (BMI) was 28±5. Seventeen (81%) hips were further classified as chronic (>3 wk of symptoms), while the remaining were considered acute on chronic (>3 wk of prodrome symptoms but with acute exacerbation in the last 3 wk). Eighteen out of the 21 hips (86%) were stable, and 3 hips were unstable slips, according to the Loder et al34 Table 1 ).
TABLE 1 -
Demographic Information of the Patient Series is Shown
Parameter
Value
Total hips (patients)
36 (18)
Total hips with severe SCFE (patients)
21 (18)
Total hips of asymptomatic controls (patients)
15 (15)
Age (years)
13±2 (10–16)
Sex (% male of all hips)
10 hips, 48
Side (% left of all hips)
12 hips, 57
Height (cm)
166±9 (152–179)
Weight (kg)
80±12 (53–97)
Body mass index (kg/m2 )
28±5 (22–36)
BMI percentile
93
Unstable hips according to Loder classification (% unstable of all hips)34
3 hips, 14
Severity based on slip Angle3 (% of all hips)
Mild <30 (deg)
0
Moderate 30–60 (deg)
0
Severe >60 (deg)
21 hips, 100
Classification based on the duration of symptoms (% of all hips), 52
Acute
0
Acute on chronic
4 hips, 19
Chronic
17 hips, 81
Continuous values are expressed as mean±SD, and range in parenthesis
Imaging, Bone Segmentation, and 3D Modeling
All patients underwent standardized AP, lateral radiographs, and CT scans, including the bilateral hip joint and the distal femoral condyles. CT scan was performed to assess SCFE severity, to measure the femoral version, and for surgical planning. Following the segmentation of CT images, we built a 3D virtual bone model (Fig. 1 ) of the pelvis and the femur for each hip using the Amira Visualization Toolkit (Visage Imaging Inc, Carlsbad, CA). Computer-assisted bone segmentation was performed by 2 independent observers not involved in the surgical care of the patients (TL and AB).. All 3D models were available from a previous study.35 Hip Flexion and Internal Rotation Resulting From Early Hip Impingement Conflict on Anterior Metaphysis of Patients With Untreated Severe SCFE Using 3D Modelling (TL and AB). The reference coordinate system for the acetabulum was the anterior pelvic plane (APP), defined by both anteroinferior iliac spines and the pubic tubercles, and for the femur, it was defined by the center of the femoral head, the knee center, and both femoral condyles as previously described.36
FIGURE 1: A virtual CT-based 3D model of a severe slipped capital femoral epiphysis patient is shown.
Simulation of Hip Impingement and Surgery
The virtual 3D bone models (Fig. 1 ) were exported to specific software for collision detection and quantification of impingement-free hip range of motion. This software was previously validated and allowed to simulate human hip motion using CT scans of plastic and cadaveric hips.36 hip simulation algorithm that accounts for a dynamic hip joint center and allows to calculate the hip range of motion with a higher linear and angular accuracy compared with other methods.37
Hip flexion and internal rotation (IR) in 90 degrees of flexion were simulated using the CT-based 3D models, and the impingement-free flexion and impingement-free IR in 90 degrees of flexion were recorded for the untreated severe SCFE hips. Impingement-free motion was assessed by the patient-specific initial point of impingement, defined as the amount of flexion and internal rotation recorded at initial detection of collision between the acetabular rim and the proximal femur. The effect of each specific surgical intervention on the impingement-free flexion and IR in 90 degrees of flexion was calculated and compared with the impingement hip motion before the intervention for the hips with severe SCFE and to the contralateral uninvolved hips as a control group.
The femoral 3D models were used to simulate osteochondroplasty of the femoral head-neck junction (cam resection, Fig. 2 and figures in supplementary material, Supplemental Digital Content 1, https://links.lww.com/BPO/A583 38 Fig. 2 ) using a virtual burr (surgical reaming device, similar to the electric pen drive of Synthes AG, Switzerland). The virtual sphere of the burr was used in a stepwise fashion while the extent and depth of the resection was visualized (red transparent in Fig. 2 and in figures in supplementary material, Supplemental Digital Content 1, https://links.lww.com/BPO/A583 hip impingement simulation and 5 y of experience in musculoskeletal imaging.
FIGURE 2: A femoral 3D model of a severe slipped capital femoral epiphysis patient after virtual cam resection is shown above. Below the resected bone volume is shown red transparent.
For the simulation of a derotation osteotomy (Fig. 3A ), a virtual intertrochanteric osteotomy was performed using the software (figures in supplementary material, Supplemental Digital Content 1, https://links.lww.com/BPO/A583 https://links.lww.com/BPO/A583 23 hip motion and to the control group (Fig. 4 ).
FIGURE 3: A-C, Schematic views of femoral derotation (A) and flexion-derotation-osteotomy (B and C) are shown.
FIGURE 4: Simulation of femoral derotation osteotomy to increase femoral version is shown for a severe slipped capital femoral epiphysis patient. The red zone represents the impingement zone. No impingement was noted after 30 degrees of derotation.
Finally, we used the software to simulate a flexion derotation osteotomy as described by Imhauser.18 SCFE hips, the flexion derotation intertrochanteric osteotomy (Fig. 3 ) was simulated with 10 degrees of derotation correction and 10 degrees of flexion correction. A second and a third simulation was performed with 20 degrees of derotation and 20 degrees of flexion and with 30 degrees of derotation and 30 degrees of flexion, respectively. The flexion component of the osteotomy was created by manipulating the distal femoral segment in an anterior direction according to the desired flexion correction, simulating an anterior wedge resection (Fig. 3 ). We then compared the impingement-free range of motion to the baseline measurements for each patient and to the contralateral uninvolved hip (Fig. 5 ).
FIGURE 5: Simulation of combined flexion and derotation osteotomy is shown for internal rotation in 90 degrees of flexion.
Statistical Analysis
Statistical analysis was performed using Winstat software (R. Fitch software, Bad Krozingen, Germany). Normal distribution was tested using the Kolmogorov-Smirnov test. Because the data were not normally distributed, we only used nonparametric tests. Continuous variables were compared using the Friedman test and the Wilcoxon test because the data were not normally distributed. For the range of motion testing, the baseline (preoperative) range of motion was compared with (1) cam resection, (2) derotation osteotomy for 10 degrees correction, (3) 20 degrees correction, (4) derotation 30 degrees correction, (5) derotation, and flexion 10 degrees, 6) derotation and flexion 20 degrees, and (7) derotation and flexion 30 degrees. Because of the 7 subgroups, the level of significance was adjusted with the Bonferroni correction after counselling a statistician. This is a simple method for adjustment. The level of significance was 0.05/7=0.0071. This means a P value below 0.0071 was considered significant.
RESULTS
The impingement-free motion was limited in the hips with severe SCFE at baseline (Table 2 ). The mean impingement-free flexion (46±32 degrees vs. 122±9 degrees, P <0.001) and mean impingement-free IR in 90 degrees of flexion (−17±18 degrees vs. 36±11 degrees, P <0.001) were significantly decreased in the severe SCFE hips compared with the contralateral control hips (Table 2 ).
TABLE 2 -
Virtual Treatment Simulation of 21 Hips with Untreated Severe
SCFE Using Preoperative 3D-CT
Parameter
No treatment
Derotation 10 (deg)
Derotation 20 (deg)
Derotation 30 (deg)
Flexion
46±32 (0 to 113)
79±44 (10 to 130)*
103±43 (14 to 150)*
113±42 (19 to 160)*
Internal rotation in 90 degrees of flexion (deg)
−17±18 (−60 to 10)
−7±15 (−53 to 15)
3±15 (−43 to 25)*
13±15 (−33 to 35)*
* signifies significant difference compared with no treatment, P values below 0.0071 were considered significant.
level of significance was adjusted with the Bonferroni correction to 0.05/7=0.0071.
Derotation osteotomy was simulated to increase femoral version.
Simulation of motion after osteochondroplasty compared with the baseline motion of the severe SCFE hips showed improvement in impingement-free flexion (59±32 degrees, range 0 to 121 degrees vs. 46±32 degrees; P <0.001) and impingement-free IR in 90 degrees of flexion (–5±14 degrees, range −50 to 19 degrees vs. −17±18 degrees, P =0.002). However, when compared with the contralateral control group, the hip motion of severe SCFE hips after osteochondroplasty (Fig. 2 ) was significantly decreased (mean flexion 59±32 degrees vs. 122±9 degrees, P <0.001 and mean IR in 90 degrees of flexion (−5±14 degrees vs. 36±11 degrees, P <0.001).
After derotation-osteotomy (Fig. 4 ), mean impingement-free flexion increased significantly with 10, 20 and 30 degrees of correction (P <0.001, Table 2 ). However, mean impingement-free IRF-90 degrees was not improved after 10 degrees correction but significantly (P <0.001) improved to 3±15 degrees and 13±15 degrees (Table 2 ) with 20 and 30 degrees of simulated derotation (P <0.001), respectively. The mean impingement-free flexion after a 30 degrees derotation was not different compared with the control group (113 ± 42 degrees vs. 122±9 degrees; P =0.052). However, after the 30 degrees derotation, the impingement-free IRF-90 degrees persisted lower compared with the control group (13±15 degrees vs. 36±11 degrees, P <0.001).
Following the simulation of the flexion-derotation osteotomy (Fig. 5 ), mean impingement-free flexion increased significantly (P <0.001) for the 10, 20, and 30 degrees of combined correction (eg, to 138±47 degrees for the 30 degrees combined correction, Table 3 ). Mean impingement-free IR in 90 degrees of flexion did not improve significantly (P <0.001) with the 10 degrees combined correction but improved after the 20 and 30 degrees combined correction. (Table 3 ) When compared with the contralateral uninvolved control hips, mean flexion was no different for the 20 degrees combined correction (119± 45 degrees vs. 122±9 degrees; P =0.052). However, the mean impingement-free IR in 90 degrees of flexion persisted decreased after the 30 degrees combined flexion-derotation when compared with the contralateral uninvolved control hips (22±22 degrees vs. 36 degrees±11, P =0.009).
TABLE 3 -
Virtual Treatment Simulation of 21 Hips with Untreated Severe
SCFE Using Preoperative 3D-CT
Parameter
No treatment
Derotation 10 and Flexion 10 (deg)
Derotation 20 and Flexion 20 (deg)
Derotation 30 and Flexion 30 (deg)
Flexion
46±32 (0 to 113)
86±45 (10 to 139)*
119±45 (14 to 160)*
138±47 (39 to 180)*
Internal rotation in 90 degrees of flexion (deg)
−17±18 (−60 to 10)
-5±15 (−50 to 29)
11±21 (−47 to 37)*
22±22 (−40 to 49)*
* signifies significant difference compared with no treatment, P values below 0.0071 were considered significant.
level of significance was adjusted with the Bonferroni correction to 0.05/7=0.0071.
Flexion and derotation osteotomy was simulated to increase femoral version.
DISCUSSION
We compared the improvement of impingement-free flexion and IR in 90 degrees of flexion following simulated osteochondroplasty of the femoral head-neck junction, femoral derotation-osteotomy, and combined flexion-derotation-osteotomy in hips with severe SCFE (Fig. 3 ) to the contralateral uninvolved hips using specific software for collision detection. Although osteochondroplasty improved the limited hip motion, the achieved range of impingement-free motion was far from the normal hip motion simulated for the contralateral uninvolved hips. Similar findings were noted for improving impingement-free motion following a derotation osteotomy of 10 and 20 degrees and even after a flexion-derotation osteotomy with 10 degrees combined correction. A 30 degrees derotation osteotomy (Fig. 4 ) improved hip flexion to no difference compared with the contralateral uninvolved hip , but with persistent limited IR in 90 degrees of flexion (Table 2 ).
We found that simulated osteochondroplasty of the femoral head and neck junction did not normalize impingement-free motion as compared with the contralateral uninvolved control hips. Along the same lines, Wylie et al17 hip dislocation with or without a femoral osteotomy. They suggested arthroscopic osteochondroplasty to treat hips with mild SCFE deformity and only slightly limited hip IR in 90 degrees of flexion. Patients with severe SCFE deformity with obligatory external rotation in flexion benefit from a flexion-derotation osteotomy to improve the range of impingement-free motion. Besomi et al14 hip arthroscopy treatment, including osteochondroplasty in 17 patients with residual SCFE deformity, and found only 6 degrees of hip flexion and 14 degrees of IR improvement. Balakumar et al37 hip IR for patients with severe and moderate SCFE deformity treated with arthroscopic osteochondroplasty (mean improvement 20 degrees, range 0 to 20 degrees) compared with open femoral neck osteotomy (mean improvement 50 degrees, range 30 to 70 degrees). Based on our findings and previous studies, isolated osteochondroplasty improves hip motion in hips with severe SCFE ; the improvement, however, is modest and insufficient to restore impingement-free motion.
In this study, we observed significant improvement in impingement-free flexion and IR in 90 degrees of flexion following an isolated derotation osteotomy of the femur when we simulated a 30 degrees correction. Although correcting femoral retroversion is a component of most femoral osteotomies independent of the correction level, applying a pure derotation osteotomy to the treatment of FAI secondary to SCFE is relatively novel. Stevens et al23 SCFE deformity. They reported significant improvement in hip flexion, IR, and gait analysis. However, 2 patients required secondary arthroscopic osteochondroplasty to alleviate residual FAI, and 1 patient underwent a total hip replacement 62 months after the osteotomy. In addition, 2 patients had delayed union and some loss of correction, secondary to broken interlocking screws, and required revision surgery with reaming and nail exchange. Although our study confirms that a 30 degrees simple derotation osteotomy may normalize hip flexion, future studies are necessary to determine the clinical and functional outcomes of a pure derotation osteotomy and to define the specific preoperative criteria for the indication of this procedure. Applying collision detection software may enhance the ability of the treating surgeon to determine the amount of retroversion correction during surgery. Further steps are needed to apply this software in clinical practice; so far the software has been used for research purposes only (figures in supplementary material, Supplemental Digital Content 1, https://links.lww.com/BPO/A583
Simulation of hip range of motion and evaluation of different techniques of femoral osteotomy to assess the improvement in range of hip motion and the hip -joint geometry is not a novel concept, but the literature is scarce.31,40,41 SCFE and reported lower values for flexion and IR compared with the current study.31 41 3 SCFE and reported lower values for hip flexion and IR (61 and 66 degrees) after the simulation of a multiplanar femoral intertrochanteric osteotomy and the simulation of uniplanar flexion osteotomy (63 and 54 degrees). Interestingly, they found similar improvements in hip motion (apart from abduction) for both multiplanar and uniplanar femoral osteotomy. One advantage of the collision detection software used in the current study is the ability to determine the patient-specific impingement-free range of motion of the hip joint.
This study has several limitations. First, the software for collision detection calculates the osseous range of motion without considering soft tissue (labrum, ligaments, or cartilage). Therefore, we believe the clinical hip motion may be even lower in these hips. Assessment of the soft tissues limiting motion may be unavoidable using pelvic CT imaging, although it could be integrated using magnetic resonance imaging in the future. However, previous collision detection studies used the same specific software to analyze hips with complex morphology, including post-Perthes disease, underlining the software’s validity for collision detection in hips with severe deformity. Second, we only tested 3 types of surgical intervention (osteochondroplasty, femoral derotation osteotomy , and flexion-derotation osteotomy, figures in supplementary material, Supplemental Digital Content 1, https://links.lww.com/BPO/A583 SCFE and the fact that femoral derotation osteotomy is a universally available and relatively low-demanding technique. Similarly, the flexion-derotation osteotomy is a well-accepted procedure for treating SCFE deformity that is technically less demanding than some of the procedures we did not test (eg, the modified Dunn procedure). Third, our study focused on the simulated surgical procedure without assessing the actual results of such procedures. No postoperative alpha angles after cam resection were calculated because of the severe displacement of the epiphysis and the femoral head center. Therefore, we lack information about those procedures’ complications and clinical improvement. Although comparing patient-specific interventions and outcomes was not the goal of our study, all patients were symptomatic at the time of image acquisition, and most of them underwent surgical treatment. Therefore, future studies should investigate the simulation of additional isolated or combined hip preservation procedures to investigate clinical and functional improvements of such procedures to establish the clinical application of the software in the clinical setting. A combination of femoral osteotomy and cam resection was not studied and could be an additional treatment approach for severe SCFE patients. Finally, our study was limited to hips with severe SCFE , and we cannot make any inference about the effects of the investigated procedures on the improvement of hip motion for hips with mild and moderate SCFE .
Preoperative planning is crucial before surgical corrections in patients with severe SCFE . The severity of the femoral deformity and the morphology of the acetabulum vary between patients resulting in complex FAI. Although femoral derotation osteotomy (30 degrees correction) or combined flexion and derotation osteotomy (20 degrees correction) enabled the restoration of impingement-free flexion, similar to the hip flexion of the control group, IR in 90 degrees of flexion remained lower than the control group, despite significant improvement. Furthermore, not all severe SCFE hips achieved normal motion after the simulation of derotational and flexion-derotation osteotomy (Figs. 3 and 4 ). Patient-specific 3D models and virtual surgical simulation provide a unique opportunity to understand the deformity better and determine the personalized bony correction needed to optimize impingement-free motion in patients with severe SCFE , but future studies should determine whether preoperative simulation and planning impact patient-specific symptoms and hip function.
CONCLUSION
Simulation of derotation-osteotomy (30 degrees correction) and flexion-derotation-osteotomy (20 degrees combined 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 hip motion.
REFERENCES
1. Novais EN, Hosseinzadeh S, Emami SA, et al. What is the association among epiphyseal rotation, translation, and the morphology of the epiphysis and metaphysis in
slipped capital femoral epiphysis ? Clin Orthop Relat Res. 2021;479:935–944.
2. Maranho DA, Bixby S, Miller PE, et al. A novel classification system for
slipped capital femoral epiphysis based on the radiographic relationship of the epiphyseal tubercle and the metaphyseal socket. JB JS Open Access. 2019;4:e0033.
3. Southwick WO. Osteotomy through the lesser trochanter for
slipped capital femoral epiphysis . J Bone Joint Surg Am. 1967;49:807–835.
4. Boyer DW, Mickelson MR. Ponseti IV.
Slipped capital femoral epiphysis . Long-term follow-up study of one hundred and twenty-one patients. J Bone Joint Surg Am. 1981;63:85–95.
5. Carney BT, Weinstein SL, Noble J. Long-term follow-up of
slipped capital femoral epiphysis . J Bone Joint Surg Am. 1991;73:667–674.
6. Castaneda P, Ponce C, Villareal G, et al. The natural history of osteoarthritis after a
slipped capital femoral epiphysis /the pistol grip deformity. J Pediatr Orthop. 2013;33(Suppl 1):S76–S82.
7. Fraitzl CR, Kafer W, Nelitz M, et al. Radiological evidence of
femoroacetabular impingement in mild
slipped capital femoral epiphysis : a mean follow-up of 14.4 years after pinning in situ. J Bone Joint Surg Br. 2007;89:1592–1596.
8. Leunig M, Casillas MM, Hamlet M, et al.
Slipped capital femoral epiphysis : early mechanical damage to the acetabular cartilage by a prominent femoral metaphysis. Acta Orthop Scand. 2000;71:370–375.
9. Sink EL, Zaltz I, Heare T, et al. Acetabular cartilage and labral damage observed during surgical
hip dislocation for stable
slipped capital femoral epiphysis . J Pediatr Orthop. 2010;30:26–30.
10. Ziebarth K, Leunig M, Slongo T, et al.
Slipped capital femoral epiphysis : relevant pathophysiological findings with open surgery. Clin Orthop Relat Res. 2013;471:2156–2162.
11. Lieberman EG, Pascual-Garrido C, Abu-Amer W, et al. Patients with symptomatic sequelae of
slipped capital femoral epiphysis have advanced cartilage wear at the time of surgical intervention. J Pediatr Orthop. 2021;41:e398–e403.
12. Millis MB, Novais EN. In situ fixation for
slipped capital femoral epiphysis : perspectives in 2011. J Bone Joint Surg Am. 2011;93(Suppl 2):46–51.
13. Saito M, Kuroda Y, Sunil Kumar KH, et al. Outcomes after arthroscopic osteochondroplasty for
femoroacetabular impingement secondary to
slipped capital femoral epiphysis : A systematic review. Arthroscopy. 2021;37:1973–1982.
14. Besomi J, Escobar V, Alvarez S, et al.
Hip arthroscopy following
slipped capital femoral epiphysis fixation: chondral damage and labral tears findings. J Child Orthop. 2021;15:24–34.
15. Basheer SZ, Cooper AP, Maheshwari R, et al. Arthroscopic treatment of
femoroacetabular impingement following
slipped capital femoral epiphysis .. Bone Joint J. 2016;98-B:21–27.
16. Wylie JD, Beckmann JT, Maak TG, et al. Arthroscopic treatment of mild to moderate deformity after
slipped capital femoral epiphysis : intra-operative findings and functional outcomes. Arthroscopy. 2015;31:247–253.
17. Wylie JD, McClincy MP, Uppal N, et al. Surgical treatment of symptomatic post-
slipped capital femoral epiphysis deformity: a comparative study between
hip arthroscopy and surgical
hip dislocation with or without intertrochanteric osteotomy. J Child Orthop. 2020;14:98–105.
18. Imhauser G. [Late results of Imhauser’s osteotomy for
slipped capital femoral epiphysis (author’s transl)]. Z Orthop Ihre Grenzgeb. 1977;115:716–725.
19. Barmada R, Bruch RF, Gimbel JS, et al. Base of the neck extracapsular osteotomy for correction of deformity in
slipped capital femoral epiphysis . Clin Orthop Relat Res. 1978;132:98–101.
20. Kramer WG, Craig WA, Noel S. Compensating osteotomy at the base of the femoral neck for
slipped capital femoral epiphysis . J Bone Joint Surg Am. 1976;58:796–800.
21. Dunn DM. The treatment of adolescent slipping of the upper femoral epiphysis. J Bone Joint Surg Br. 1964;46:621–629.
22. Fish JB. Cuneiform osteotomy of the femoral neck in the treatment of
slipped capital femoral epiphysis . J Bone Joint Surg Am. 1984;66:1153–1168.
23. Stevens PM, Anderson L, MacWilliams BA. Femoral shaft osteotomy for obligate outward rotation due to
SCFE . Strategies Trauma Limb Reconstr. 2017;12:27–33.
24. Ganz R, Gill TJ, Gautier E, et al. Surgical dislocation of the adult
hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br. 2001;83:1119–1124.
25. Ganz R, Huff TW, Leunig M. Extended retinacular soft-tissue flap for intra-articular
hip surgery: surgical technique, indications, and results of application. Instr Course Lect. 2009;58:241–255.
26. Leunig M, Slongo T, Kleinschmidt M, et al. Subcapital correction osteotomy in
slipped capital femoral epiphysis by means of surgical
hip dislocation. Oper Orthop Traumatol. 2007;19:389–410.
27. Novais EN, Hill MK, Carry PM, et al. Modified Dunn Procedure is superior to in situ pinning for short-term clinical and radiographic improvement in severe stable
SCFE . Clin Orthop Relat Res. 2015;473:2108–2117.
28. Allen MM, Rosenfeld SB. Treatment for post-
slipped capital femoral epiphysis deformity. Orthop Clin North Am. 2020;51:37–53.
29. Bland DC, Valdovino AG, Jeffords ME, et al. Evaluation of the three-dimensional translational and angular deformity in
slipped capital femoral epiphysis . J Orthop Res. 2020;38:1081–1088.
30. Kordelle J, Millis M, Jolesz FA, et al. Three-dimensional analysis of the proximal femur in patients with
slipped capital femoral epiphysis based on computed tomography. J Pediatr Orthop. 2001;21:179–182.
31. Mamisch TC, Kim YJ, Richolt JA, et al. Femoral morphology due to impingement influences the range of motion in
slipped capital femoral epiphysis . Clin Orthop Relat Res. 2009;467:692–698.
32. Jones CE, Cooper AP, Doucette J, et al. Southwick angle measurements and
SCFE slip severity classifications are affected by frog-lateral positioning. Skeletal Radiol. 2018;47:79–84.
33. Cherkasskiy L, Caffrey JP, Szewczyk AF, et al. Patient-specific 3D models aid planning for triplane proximal femoral osteotomy in
slipped capital femoral epiphysis . J Child Orthop. 2017;11:147–153.
34. Loder RT, Richards BS, Shapiro PS, et al. Acute
slipped capital femoral epiphysis : the importance of physeal stability. J Bone Joint Surg Am. 1993;75:1134–1140.
35. Lerch TD, Kim YJ, Kiapour AM, et al. Limited
Hip Flexion and Internal Rotation Resulting From Early
Hip Impingement Conflict on Anterior Metaphysis of Patients With Untreated Severe
SCFE Using 3D Modelling. J Pediatr Orthop. 2022;42:e963–e970.
36. Tannast M, Kubiak-Langer M, Langlotz F, et al. Noninvasive three-dimensional assessment of
femoroacetabular impingement . J Orthop Res. 2007;25:122–131.
37. Puls M, Ecker TM, Tannast M, et al. The Equidistant Method - a novel
hip joint simulation algorithm for detection of
femoroacetabular impingement . Comput Aided Surg. 2010;15:75–82.
38. Ecker TM, Puls M, Steppacher SD, et al. Computer-assisted femoral head-neck osteochondroplasty using a surgical milling device an in vitro accuracy study. J Arthroplasty. 2012;27:310–6.
39. Balakumar B, Flatt E, Madan S. Moderate and severe
SCFE (
Slipped Capital Femoral Epiphysis ) arthroscopic osteoplasty vs open neck osteotomy-a retrospective analysis of results. Int Orthop. 2019;43:2375–2382.
40. Kordelle J, Mamisch C, Kikinis R, et al. Anatomical analysis and preoperative planning of correctional osteotomies:
slipped capital femoral epiphysis (
SCFE ). Minim Invasive Ther Allied Technol. 2000;9:269–276.
41. Mamisch TC, Kim YJ, Richolt J, et al. Range of motion after computed tomography-based simulation of intertrochanteric corrective osteotomy in cases of
slipped capital femoral epiphysis : comparison of uniplanar flexion osteotomy and multiplanar flexion, valgisation, and rotational osteotomies. J Pediatr Orthop. 2009;29:336–340.
