Table 2 Characteristics, data, results and conclusions of the included studies

Agashe et al., Indian J Orthop, 2021 [38] (Retrospective)

30

13.0 y

19/11

6/6/18

0/20/10

2.1 y

Average HHS: 81.8

6.6%

Hip subluxation: 3.3%

Procedure safe, reliable and reproducible; first choice for treatment of moderate and severe SCFE.

Passaplan et al., Bone Joint Open, 2020 [37] (Retrospective)

18

12.9 y

14/4

1/3/14

8/8/2

9.4 y

Average HHS: 88.7; HOOS: 87.4; MdA: 16.5; UCLA: 8.4; CAM deformity: 22%

5.5%

Hip subluxation: 5.5%; Implant failure: 5.5%; Heterotopic ossification: 16.7%; Implant removal: 22.2%

Good long-term results with low incidence of AVN and osteoarthritis but frequent revision surgery (FAI and implant removal). Procedure technically demanding.

Zuo et al., J Orthop Surg Res, 2020 [36](Retrospective)

21

13.2 y

20/1

1/20/0

0/0/21

2.6 y

Average HHS: 96.7; WOMAC: 95.4

0%

Implant failure: 4.8%;

Procedure technically demanding but safe and extremely valuable for restoring hip anatomy and preserving function in severe SCFE.

Ebert et al., J Orthop Surg Res, 2019 [35] (Retrospective)

15

12.9 y

15/0

0/8/7

0/0/15

3.8 y

Average HHS: 85.7; NHP: 0.91; VAS: 1.6; SDC: 27.8

26.7%

Hip subluxation: 13.3%; implant failure caused by AVN: 13.3%

Satisfactory results in most patients but, considering the risk of complications, the procedure is only indicated in severe chronic or acute on chronic SCFE.

Davis et al., JPO, 2019 [34] (Retrospective)

48

13.8 y (stable) 12.5 y (unstable)

17/31

31/17/0

N/A

2.9 y (stable), 2.3 y (unstable)

No data are reported regarding the final results except complications

29.4% (stable), 6.4% (unstable)

Hip subluxation: 17.6% (stable); Heterotopic ossification: 9.7% (unstable), 5.9% (stable); Hardware removal: 12.9% (unstable), 29.4% (stable)

Effective procedure in stable and unstable hips. Complication rate higher in stable hips. Caution in chronic stable SCFE

Sikora-Klak et al., JPO, 2019 [33] (Retrospective Comparative)

14

13.1 y

14/0

0/9/5

0/?/?

2.4 y

No data are reported regarding the final results except complications

28.6%

Significant limb length inequality: 7.1%

In consideration to the high incidence of AVN observed, the authors are against the procedure in stable, moderate or severe SCFE, preferring Imhauser osteotomy (AVN: 0%).

Lerch et al., Bone Joint J, 2019 [32] (Retrospective)

46

13 y

32/14

9/12/27

0/0/46

9 y

Average HHS: 94; HOOS: 91; MdA: 17; UCLA: 8; WOMAC: 4; CAM deformity: 7.5%

5%

Heterotopic ossification: 5%; Implant failure: 7.5%; Implant removal: 17.5%

High functional score at long-term follow-up with low rate of AVN observed only in unstable, acute on chronic slip. Secondary impingement deformities can develop and require further surgery.

Novais al, Int Orthop, 2019 [31] (Retrospective Comparative)

27

12.6 y

0/27

14/0/13

0/0/27

2.4 y

Heyman and Herdon outcomes: excellent or good: 67%

26%

Trochanteric screw breakage: 3.7%

The theoretical advantage of preserving blood supply reducing AVN rate was not observed. However, the authors observed better results in comparison to closed reduction and percutaneous pinning.

Masquijo et al., JPO, 2019 [30] (Retrospective Multicentric)

21

12 y

6/15

4/4/13

Mean preoperative value of slip angle: 59.1°

3.4 y

Average HHS: 76.3

28.6%

Superficial infection: 4.8%; Implant removal: 28.6%

Procedure technically demanding with a high rate of complications probably related to the learning curve. AVN more frequent in unstable hip

Persinger et al., JPO, 2019 [29](Retrospective)

31

12.4 y

0/31

31/0/0

N/A

2.4 y

Satisfactory results: 94%

6.4%

Mild heterotopic ossification: 6.7%; Implant failure: 3.2%; Implant removal: 6.4%

Procedure safe and effective for unstable SCFE. Low incidence of AVN and other complications. No cases of AVN in patients treated < 24 h.

Trisolino et al., JPO, 2018 [28] (Retrospective Comparative)

15

13.9 y

15/0

0/0/15

0/0/15

3.7 y

NAHS (total): 85.4

20%

Mild heterotopic ossification: 6.7%

Procedure restored the proximal femoral anatomy but there is a potential risk of AVN in comparison to SCFE treated by in situ fixation.

Ziebarth et al., CORR, 2017 [27] (Retrospective)

43

13 y

38/5

10/18/15

10/27/6

12 y

Average MdA: 17; Prevalence of limp: 0%; Positive Drehaman sign: 0%. Cumulative survivorship: 93%; Secondary impingement: 13%

0%

Refixation of the epiphysis: 9.3%; Reosteosyntesis of the greater trochanter: 2.3%; Implant removal: 20.9%

Procedure, when performed correctly, restored hip anatomy and hip function in stable, moderate or severe SCFE. No hips showed AVN or conversion to THA. Secondary impingement may persist in some hips that need further surgery.

Elmarghany et al., SICOT J, 2017 [26] (Prospective)

32

14 y

32/0

0/32/0

0/11/21

1.2 y

Average HHS: 96.2; MdA: 16.8; WOMAC: 3.3; Heyman and Herndon outcome: excellent or good 93.7%

9.3%

Postoperative deep infection: 3.1%; Revision for bad reduction: 3.1%

Procedure restored the normal proximal femoral anatomy, reducing the probability of secondary osteoarthritis and FAI.

Abdelazeem et al., Bone Joint J, 2016 [25] (Prospective)

32

14.3 y

32/0

0/32/0

0/10/22

2 y

Average HHS: 96.3; MdA: 16.8; WOMAC: 97

3.1%

Postoperative deep infection: 3.1%

Procedure safe and effective for stable SCCFE with high degree of slip.

Novais et al., CORR, 2015 [24] (Retrospective Comparative)

15

14 y

15/0

N/A

0/0/15

2.4 y

Heyman and Herdon outcomes: excellent/good: 60%

6.7%

Implant failure: 6.7%; Intraarticular pin penetration: 6.7%

Higher rate of excellent and results, with similar occurrence of complications when compared to SCFE treated by in situ pinning.

Upasani et al., JPO, 2014 [23] (Retrospective)

43

11.9 y

17/26

17/11/15

0/6/37

2.6 y

No data are reported regarding the final results but high complication rates are reported (>  40%)

23.2%

Femoral neck nonunion: 9.3%; Postoperative hip dislocation: 4.6%; Heterotopic ossification: 2.3%; Implant failure: 2.3%

Complication rate high. Presence of an expert surgeon during the procedure. AVN more frequent in unstable acute and acute on chronic SCFE (90%).

Souder et al., JPO, 2014 [22] (Retrospective Comparative)

17

12.2 y

10/7

N/A

N/A

1.3 y

AVN in 2/10 stable and in 2/7 unstable (Dunn); AVN in 0/64 stable and in 3/7 unstable (in situ pinning)

23.5%

Condrolysis: 5.9%; Implant failure: 5.9%

Attempts to anatomically reduce stable slips led to severe AVN in 20% of cases. Treatment of unstable slips remains problematic with high AVN rates whether treated by Dunn or in situ pinning.

Sankar et al., JBJS Am, 2013 [21] (Retrospective Multicentric)

27

12.6 y

0/27

27/0/0

0/6/37

1.8 y

Average HHS: 88 (no AVN), 60 (AVN); Satisfaction: 97.1% (no AVN), 65.8% (AVN); UCLA: 9.3 (no AVN), 5.9 (AVN)

25.9%

Implant failure: 14.8%

Procedure is able to restore anatomy and preserve hip function but AVN and implant complications may occur.

Madan et al., JBJS Br, 2013 [20] (Prospective)

28

12.9 y

11/17

9/11/8

0/0/28

3.2 y

Average HHS: 89.1; NAHS: 91.3

7.1%

Condrolysis: 3.6%

Procedure safe and reliable in patients with SCFE. ROM at final follow-up was nearly normal.

Massé et al., Hip Int, 2012 [19] (Retrospective)

20

14.3 y

18/2

N/A

8/4/8

2.0 y

Average HHS: 98.2; WOMAC: 0.6 (pain), 2.2 (function)

0%

Wire penetration in the hip joint: 5%; painful implant (removal): 5%;

The small number of technical complications appears favorable considering the surgical complexity of the procedure.

Huber et al., JBJS Br, 2011 [18] (Retrospective Multicentric)

30

12.2 y

27/3

3/?/?

3/17/10

3.8 y

Average HHS: 97.8; WOMAC: 5.9 (pain), 10.4 (stiffness), 5.7 function)

3.3%

Implant failure: 13.3%

Anatomical reduction can be achieved using this procedure with low risk of AVN. Implant failures may occur.

Slongo et al., JBJS Am, 2010 [17] (Retrospective)

23

11.9 y

20/3

0/9/14

N/A

2.4 y

Average HHS: 99; MdA: 17

8.7%

Wire penetration in the hip joint: 4.3%

Procedure minimizes secondary femoroacetabular Cam impingement and osteoarthritis. Complication rate low even in unstable SCFE.

Ziebarth et al., CORR, 2009 [16] (Retrospective Multicentric)

40

11.9 y

27/13

11/29/?

0/16/19 (no information on 5 hips)

2.6 y

Average HHS: 99.6; MdA: 17.8; WOMAC: 1.2 (pain), 3 (function)

0%

Heterotopic ossification: 2.5%; Residual impingement: 2.5%; Delayed union: 7.5%; Implant failure: 7.5%;

Acceptable complication rate. Procedure reproducible for full correction of moderate to severe SCFE with open physis.