Table 1 Generalities, patient characteristics, and main results of the included studies

[57]

Int Orthop

B

21

40.3

28.6

Single-incision flexor hallucis longus transfer for chronic Achilles tendon ruptures is a simple method with minimal morbidity and complications. The technique resulted in great patient satisfaction as well as excellent functional and clinical outcomes

[61]

Ann Transl Med

C

8

55.0

25.0

Autologous quadriceps tendon graft (in bone-tendon configuration) has proved as a simple technique that offers good results to patients with tissue defects in the Achilles tendon

[70]

Foot Ankle Surg

D

13

52.8

69.0

FDL tendon transfer represents an operative alternative in treating chronic Achilles tendon disorders. Good clinical outcomes with low complications and donor site morbidity were reported

[33]

BMC Musculoskelet Disord

C

24

50

29.0

Percutaneous repair of neglected Achilles rupture using the index technique proved a satisfactory patient-reported and objective measurement at a one-year follow-up. With only minor transient complications

[58]

J Clin Med

C

17

42.8

17.6

When an extensive defect is present, the reconstruction with an Achilles tendon allograft can be considered a proper treatment option, as it does not show a higher rate of complications than autologous techniques achieving similar functional outcomes

[67]

Bone Joint J

D

20

60.0

20.0

Transtendinous FHL transfer for neglected tendon Achilles ruptures, with a long harvest to allow reattachment of the triceps surae, provides reliable long-term function and good ankle plantarflexion strength. Despite the loss of strength in hallux plantar flexion, there is little comorbidity from the FHL harvest

[62]

Biomed Res Int

C

29

40.3

20.7

Surgical options can be determined by evaluating the presence of the Achilles tendon stumps and the gap length, which can avoid using the nearby tendon and yield satisfactory functional results

[60]

J Foot Ankle Surg

C

50

42

Using the modified spoon-shaped medial incision in the surgical repair of a chronic Achilles tendon rupture seems to be a safe and effective method that may reduce risk of incision skin necrosis and offers better function in patients with a chronic Achilles tendon rupture

[69]

Clin Sports Med

D

32

Peroneus brevis tendon transfer is an effective surgical technique for neglected Achilles tendon rupture. If the tendon gap is greater than 6 cm, a free gracilis autograft is indicated

[56]

Foot Ankle Surg

A

62

44.8

37.1

Free semitendinosus transfer, peroneus brevis transfer, and FHL tendon graft all resulted in significant functional improvement, and most patients were able to return to sports. No clear advantage of one technique over the others was shown

[68]

J Bone Joint Surg Am

D

Local tissue, local tendons, and allografts can be used to reconstruct the tendon, and end-to-end repair is possible if the gap is < 2.5 cm. Compared with acute injuries, chronic injuries are associated with a higher rate of postoperative infection and more prolonged recovery

[63]

Indian J Orthop

D

12

47.0

33.3

Combined surgical technique of gastrosoleus turndown flap augmentation with V–Y plasty for repairing complex defects in chronic Achilles tendon tears is a fair option with satisfactory functional outcome and fewer complications

[64]

Foot Ankle Orthop

D

10

51.7

40.0

The SLLS technique accompanied by autologous semitendinosus tendon grafting provided successful operative outcomes for patients with chronic Achilles tendon rupture regardless of the size of the defect, and thus long-term orthotic use was not needed after surgery

[66]

Foot Ankle Int

D

22

69.0

27.3

Chronic Achilles tendon ruptures were successfully treated by an all-endoscopic procedure. The endoscopically assisted FHL transfer provided excellent results while benefiting from the minimally invasive procedure advantages. However, it entailed some technical challenges and may not be suitable for less experienced surgeons

[59, 106]

Knee Surg Sports Traumatol Arthrosc

C

29

39.0

0.0

Endoscopy allowed scar tissue and adhesions to be removed, allowing the tendon ends to be mobilized out of the small proximal and distal incisions. Minimally invasive technique may result in a lower wound complication incidence and provide better early functional recovery and return to moderate-intensity exercise time than the conventional open procedure in treating chronic Achilles tendon ruptures

[65]

Orthop J Sports Med

D

19

46.7

10.5

Chronic Achilles tendon ruptures were successfully treated via minimally invasive reconstruction using a double-bundle FHL, which provided excellent functional improvement. It is best suited for patients with complex requirements who are at high risk for wound complications