Tendon split lengthening technique for flexor hallucis longus tendon rupture

The effect of hallux valgus on the anatomy of the nerves around the first metatarsal bone

OBJECTIVE

To identify the variations in the location of the nerves that may be at risk in hallux valgus (HV) surgery, and to reveal whether these nerves are affected by the anatomical changes associated with HV.

METHOD

In the formalin fixed, 46 lower extremities (19 female, 27 male) (9 normal, 14 mild HV, 21 moderate/severe HV), extensor hallucis longus tendon (EHL), deep plantar artery, medial dorsal cutaneous (MDCN), deep fibular (DFN), common plantar digital (CPDN) and proper plantar digital (PPDN) nerves were examined. The branches of MDCN extending to the medial side of foot were recorded in three segments. The positional topography of nerves according to EHL were analyzed on 360° circle and clock models.

RESULTS

Sex-related differences observed in some parameters in direct measurements were not found in the clock model comparisons. In advanced HV angles (> 20°), DFN was closer to EHL in the distal part of the metatarsal bone, while there was no difference in the proximal. The intersection of the medial branch of the MDCN with the EHL was more proximal in HV cases than in normal feet. The location of the nerves in the clock pattern did not change in HV. Of the nerve branches reaching the medial side of the foot, 65.2% were in Part I, 71.7% in Part II, and 4.3% in Part III.

CONCLUSION

Sex differences in the distance of the nerves to the EHL disappeared when the size effect of the cross-section of the first metatarsal bone region was eliminated with the clock model. Only in advanced HVA (>20°) (not in mild HV), the DFN being closer to the EHL distally and the intersection of the medial branch of the MDCN with the EHL in HV being more proximal than in normal can be interpreted as specific reflections of HV progress. The variations we revealed in the number of branches reaching the inside of the foot may explain the diversity of neuromas or nerve injuries associated with HV surgery.

Retro-Malleolar Z-Plasty of Flexor Hallucis Longus Tendon in Post-Traumatic Checkrein Deformity: A Case Series and Literature Review

Checkrein deformity (CD) is a dynamic deformity of the hallux characterized by flexion contracture of the interphalangeal (IF) joint and extension contracture of the metatarsophalangeal (MTP) joint, worsened by ankle dorsiflexion. It is due to post-traumatic or ischemic retraction of the long hallux flexor tendon (FHL) following soft tissue trauma, leg fractures, ankle fractures and, more rarely, calcaneal or talar fractures. Diagnosis is essentially clinical, associated with imaging, to rule out unrecognized causes and evaluate fracture healing process. Few cases are reported in literature without univocal treatment. Background and Objectives: To analyze clinical and functional outcomes in patients with CD treated with release and retro-malleolar Z-plasty lengthening of FHL tendon. Materials and Methods: Patients diagnosed with CD treated with retro-malleolar (at tarsal tunnel) Z-plasty lengthening of the FHL tendon between January 2016 and August 2020 were included. Clinical and functional outcomes were collected on admission and post-surgery and analysed retrospectively. Patients with a minimum follow-up of 18 months were included. Results: A total of 14 patients, with mean age of 37.4 years old, with CD diagnosis were included in the study. All patients were suffering from post-traumatic CD and the mean time from trauma to onset of deformity was of 7 months (range 1−12). At a mean follow-up of 31.8 months (range 18−48) we found a significant improvement (p < 0.05) in terms of pain relief (VAS), function (AOFAS score) and ROM of the IP and MTP hallux joints. No recurrence, loss of strength, nerve injury or tarsal tunnel syndrome were observed. No patient required revision surgery. Conclusions: In this case series the retro-malleolar FHL tendon Z-plasty proved to be a suitable option for CD correction, allowing a good clinical and functional recovery.