Anterior vertebral body tethering for idiopathic scoliosis in growing children: A systematic review

Table 1 Study, design, inclusion criteria, study groups feature, follow-up, outcome measures and results of the included trials

Ref.	Design (level of evidence)	Study quality according to AAOS methodology	Inclusion criteria for AVBT	Study group	Control group	AVBT surgical approach	Follow-up	Outcomes at the final FU	Preoperative main features	Results at the final FU
Miyanji et al[14], 2020	Retrospective study (level IV)	High-quality study	Major main T or L curves ≥ 40°. Risser score ≤ 3. Sanders score < 5	AVBTs (n = 57). Female: 54 (94.74%). Mean age: 12.7 yr (8-16). Curves: Lenke 1: 48; Lenke 2: 6; Lenke 3: 1; Lenke 4: 0; Lenke 5: 1; Lenke 6: 1. Tether location: Thoracic (n = 55); lumbar (n = 2)	None	VATS plus mini-open for TL/L curves	Minimum 24 mo	Clinical and radiological assessment (success: Residual curve < 35° at maturity)	Tethered curve mean Cobb: 51°. Tethered curve flexibility: 41.8%. Untethered minor curve Cobb: 31.5°. TK (T5-T12): 18°. LL (L1-S1): -55.4°. Rib hump: 14.9 mm. Lumbar prominence: 3.9 mm	Tethered curve Cobb: 23°a. Tethered curve correction: 42.9%. Untethered minor curve Cobb: 22.3°a. TK (T5-T12): 22°a. LL (L1-S1): -56.5°. Rib hump: 10.3 mma. Lumbar prominence: 2.3 mma. Successful AVBT: 44 (77.19%)
Baker et al[17], 2021	Retrospective study (level IV)	Moderate quality study	N/A	AVBTs (n = 19 in 17 pts). Female: 12 (70.6%). Mean age: 12.9 yr. Curves: Lenke 1: 9 pts; Lenke 2: 3 pts; Lenke 3: 1 pts; Lenke 4: 0; Lenke 5: 4 pts; Lenke 6: 0. Tether location: Thoracic (n = 13); lumbar (n = 6)	None	VATS plus mini-open for TL/L curves	Minimum 24 mo (2 to 4 yr)	Radiological assessment (success: Residual curve < 35° at maturity)	Tethered curve Cobb: 45°. Tethered curve flexibility: 63%. Untethered minor curve Cobb: 28°. TK (T5-T12): 20°. LL (L1-S1): -59°. Rib hump: N/A. Lumbar prominence: N/A	Tethered curve Cobb: 20°a. Tethered curve correction: 73%. Untethered minor curve Cobb: 26°. TK (T5-T12): N/A. LL (L1-S1): -52°. Rib hump: N/A. Lumbar prominence: N/A. Successful AVBT: 9 (52.94%)
Hoernschemeyer et al[20], 2020	Retrospective study (level IV)	High-quality study	N/A	AVBTs (n = 29). Female: 26 (89.65%). Mean age: 12.7 yr (10-16). Curves: Lenke 1: 23; Lenke 2: 1; Lenke 3: 1; Lenke 4: 0; Lenke 5: 4; Lenke 6: 0. Tether location: Thoracic (n = 22); TL (n = 3); lumbar (n = 4)	None	VATS plus mini-open for TL/L curves	Minimum 24 mo (2 to 5 yr)	Radiological assessment (success: Residual curve ≤ 30° at maturity)	Tethered curve Cobb: MT: 40°. Long thoracic: MT = 56°; L = 22°; Left TL: L = 49°. Tether top, brace bottom: MT = 48°; L=38°. Tether top & bottom: MT = 48°; L = 42°; TK: 36.2°; LL: -60.83°. Rib hump: N/A. Lumbar prominence: N/A	Tethered curve Cobb: MT: 9°b. Long thoracic: MT = 21°; L = -1°. Left TL: L = 21°b. Tether top, brace bottom: MT = 23°a; L = 24°a. Tether top & bottom: MT = 24°a; L = 15°a; TK: 34.48°; LL: -57°. Rib hump: N/A. Lumbar prominence: N/A. Successful AVBT: 20 (74%)
Pehlivanoglu et al[21], 2020	Prospective cohort study (level IV)	High-quality study	Age: 9-14 yr. Risser ≤ 2. Sanders ≤ 4). Curve progression after at least 6 mo of brace (> 40°). MT curve > 35°. Curve flexibility > 30%	AVBTs (n = 21). Female: 15 (71.43%). Mean age: 11.1 yr (9-14). Curves: Lenke 1: 21. Tether location: Thoracic (n = 21)	None	VATS	Minimum 24 mo	Radiological assessment	Tethered curve Cobb: 48.2°. Tethered curve flexibility: N/A. Untethered minor curve Cobb: 24.8°. TK (T5-T12): 26.8°; LL (L1-S1): -51.3°. Rib hump: N/A. Lumbar prominence: N/A	Tethered curve Cobb: 10.1°a. Tethered curve flexibility: N/A. Untethered minor curve Cobb: 9.6°a. TK (T5-T12): 26°; LL (L1-S1): -51.8°. Rib hump: N/A. Lumbar prominence: N/A. Successful AVBT: 20 (95.24%)
Newton et al[22], 2020	Retrospective case-control study (level III)	High-quality study	Age: 9-15 yr. Primary thoracic idiopathic scoliosis. Cobb angle: 40°-67°. Risser ≤ 1. No prior spine surgery	AVBTs (n = 23). Female: 16 (69.56%). Mean age: 12 yr (9-15). Curves: Lenke 1: 23. Tether location: Thoracic (n = 23)	PSF (n = 26). Female: 23 (88.46%). Mean age: 13 yr (10-14). Curves: Lenke 1: 26. Tether location: Thoracic (n = 26)	VATS	Minimum 24 mo (2 to 5 yr)	Clinical and radiological assessment (success: Residual curve < 35° at maturity)	AVBT group: Tethered curve Cobb: 53°. Untethered curve Cobb: 34°. TK (T2-T12): 25°. LL (L1-S1): N/A. Rib hump: N/A. Lumbar prominence: N/A. PSF group: MT: 54°; LT: 34°; TK (T2-T12): 25°	AVBT group: Tethered curve Cobb: 33°a. Untethered minor curve Cobb: 29°. TK (T2-T12): 12°; LL (L1-S1): N/A. Rib hump: N/A. Lumbar prominence: N/A. Successful AVBT: 12 (52%). PSF group: MT: 16°a; LT: 12°a; TK (T2-T12): 29°
Wong et al[23], 2019	Prospective cohort study; a single-centre, Phase-2A pilot study (level IV)	High-quality study	Juvenile or adolescent IS. Age: ≥ 8 and < 15 yr. Risser stage = 0. Bone age of ≤ 13 yr (hand/wrist X-ray). Major right thoracic scoliosis with a Cobb angle of 35°-55° and Lenke-1 curve pattern. TK (T5-T12) < 40°. Instrumentation to be applied no more cephalad than T4 and no more caudal than L2 (inclusive). Menses < 4 mo	AVBTs (n = 5). Female: All. Mean age: 11 yr (9-12). Curves: Lenke 1: All. Tether location: Thoracic (all)	None	VATS	Minimum 4 yr	Clinical and radiological assessment	Tethered curve mean Cobb: 40°. Tethered curve flexibility: 63.7%. Untethered curve Cobb: 20.6°. TK (T5-T12): N/A; LL (L1-S1): N/A; Rib hump: N/A. Lumbar prominence: N/A	Tethered curve Cobb: 18.9°a. Tethered curve correction: 53.8%. Untethered minor curve Cobb: 5°. Successful AVBT: 3 (60%)
Samdani et al[24], 2014	Retrospective study (level IV)	Moderate quality study	N/A	AVBTs (n = 11). Female: 8 (73%). Mean age: 12.3 yr. Curves: Lenke 1: All. Tether location: Thoracic (all)	None	VATS	Minimum 24 mo	Clinical and radiological assessment	Tethered curve Cobb: 44°. Tethered curve flexibility: 57%. Untethered curve Cobb: 25.1°. TK (T5-T12): 20.8°; LL (L1-S1): -47.5°. Rib hump: N/A. Lumbar prominence: N/A	Tethered curve Cobb: 13.5°a. Tethered curve correction: 70%. Untethered curve Cobb: 7.2°. TK (T5-T12): 21.6°; LL (L1-S1): -54.9°. Successful AVBT: 9 (81.8%)

^aP < 0.001.

^bP > 0.05.

AVBT: Anterior vertebral body tethering; PSF: Posterior spinal fusion; pts: Patients; VATS: Video-Assisted Thoracoscopic Surgery; N/A: Not available; TL: Thoracolumbar; L: Lumbar; FU: Follow-up; IS: Idiopathic scoliosis; AAOS: American Academy of Orthopedic Surgeons.

Table 2 Perioperative complications, number of tether revisions and conversion to posterior spinal fusion and instrumentation of anterior vertebral body tethering procedures in the included studies

Ref.	Patients (n)	Perioperative complications		Tether revision			Conversion to PSF
		Type of complication	n of cases (%)	Causes	n of cases (%)	n of revisions (%)	Causes	n of cases (%)
Miyanji et al[14], 2020	57	Pulmonary. Atelectasis. Pneumonia. Superficial wound infection. Hip and shoulder pain. Numbness in the arm and breast	3 (5.26). 1 (1.75). 1 (1.75). 1 (1.75). 1 (1.75)	Overcorrection (loosening tether). Tether breakage (replaced). Adding on (extension of tether)	1 (1.75). 1 (1.75). 1 (1.75)	1 (1.75). 1 (1.75). 1 (1.75)	Insufficient correction of tethered curve and progression of the deformity. Adding on	5 (8.77). 1 (1.75)
Baker et al[17], 2020	17	N/A	N/A	Broken tether. Other complications	9 (52.94). 3 (17.7)	1 (5.88). 3 (17.7)	Overcorrection. Progression of the untethered thoracic curve in a patient with lumbar AVBT	1 (5.88). 1 (5.88)
Hoernschemeyer et al[20], 2020	29	Recurrent pneumothorax. Syncopal episodes (decompression of a Chiari 1 malformation, diagnosed after AVBT)	1 (3.45). 1 (3.45)	Broken tether. Overcorrection. Adding on	14 (48.275). 2 (6.9). 1 (3.45)	3 (10.3): 1 revisio. 2 PSF. 2 (6.9). 1 (3.45)	Progression of the tethered curve after broken tether	2 (6.9)
Pehlivanoglu et al[21], 2020	21	Chylothorax (conservatively managed)	1 (4.76)	Broken tether	1 (4.76)	1 (4.76)	-	-
Newton et al[22], 2020	23	Atelectasis with pulmonary oedema (treated with positive airway pressure that resolved by postoperative day 6). Pain radiating down the leg (3 yr postop resolved with physical therapy). Horner syndrome (withasymmetric pupils remaining)	1 (4.35). 1 (4.35). 1 (4.35)	Broken tether (revision for curve progression). Overcorrection (tether removal, tether replaced with less tension). Progression of the untethered curve. Second revision (broken tether with progression, progression)	12. 3. 2. 2	2 (8.7). 2 (8.7). 1 (4.35). 2 (8.7). 1 (4.35). 1 (4.35)	Curve progression (converted to PSF, indication to PSF, but not yet undergone)	3 (13). 3 (13)
Wong et al[23], 2019	5	Fever. Postop. Nausea. Postop. Vomiting. Postop. Haematuria. Reactive airways. Right pneumothorax. Left/dependent lung pleural effusion. Pneumonia. Conjunctivitis. Trunk listing	5 (100). 1 (20). 1 (20). 1 (20). 1 (20). 2 (40). 1 (20). 1 (20). 1 (20). 1 (20)	-	-	-	Overcorrection. Curve progression/distal decompensation	1 (20). 1 (20)
Samdani et al[24], 2014	11	Persistent atelectasis (bronchoscopy)	1 (9.1)	Overcorrection	2 (18.2)	2 (18.2)	-	-

AVBT: Anterior vertebral body tethering; PSF: Posterior spinal fusion.