A new technique of percutaneous minimally invasive surgery assisted by magnetic resonance neurography

Abstract

Aims: In order to release the contracture band completely without damaging normal tissues (such as the sciatic nerve) in the surgical treatment of gluteal muscle contracture (GMC), we tried to display the relationship between normal tissue and contracture bands by magnetic resonance neurography (MRN) images, and to predesign a minimally invasive surgery based on the MRN images in advance.

Methods: A total of 30 patients (60 hips) were included in this study. MRN scans of the pelvis were performed before surgery. The contracture band shape and external rotation angle (ERA) of the proximal femur were also analyzed. Then, the minimally invasive GMC releasing surgery was performed based on the images and measurements, and during the operation, incision lengths, surgery duration, intraoperative bleeding, and complications were recorded; the time of the first postoperative off-bed activity was also recorded. Furthermore, the patients' clinical functions were evaluated by means of Hip Outcome Score (HOS) and Ye et al's objective assessments, respectively.

Results: The contracture bands exhibited three typical types of shape - feather-like, striped, and mixed shapes - in MR images. Guided by MRN images, we designed minimally invasive approaches directed to each hip. These approaches resulted in a shortened incision length in each hip (0.3 cm (SD 0.1)), shorter surgery duration (25.3 minutes (SD 5.8)), less intraoperative bleeding (8.0 ml (SD 3.6)), and shorter time between the end of the operation and the patient's first off-bed activity (17.2 hours (SD 2.0)) in each patient. Meanwhile, no serious postoperative complications occurred in all patients. The mean HOS-Sports subscale of patients increased from 71.0 (SD 5.3) to 94.83 (SD 4.24) at six months postoperatively (p < 0.001). The follow-up outcomes from all patients were "good" and "excellent", based on objective assessments.

Conclusion: Preoperative MRN analysis can be used to facilitate the determination of the relationship between contracture band and normal tissues. The minimally invasive surgical design via MRN can avoid nerve damage and improve the release effect.

Fig. 1

Photograph showing confirmation of points A1 and A2 for skin markers. ASIS, anterior superior iliac spine; GT, greater trochanter; PSIS, posterior superior iliac spine; SN, sciatic nerve.

Fig. 2

a) Contracture release surgery was performed with a special scalpel though the preoperative designed incision (first at point A2, then at point A1 if required). b) The incision was wiped dry and sealed by a beauty pull tape.

Fig. 3

Contracture bands mostly displayed three types of MR morphology: a) feather shapes, b) strip shapes, and c) mixed shapes. d) In some cases, the thicker fibrotic contracture caused medial retraction of the affected muscles, resulting in the external rotation of proximal femur. Arrow indicates contracture bands.

Fig. 4

a) In the strong T2-Weighting axial image, the distance from oily capsules to fibrotic contractures was measured. R: oily capsule; arrow: fibrotic contracture. b) The distance from the oily capsule to the sciatic nerve was measured in the 3D images. Arrow: sciatic nerve.

Fig. 5

An example of patient-reported cosmetic satisfaction at six months postoperatively.