Poster 225: Acetabular Labral Blood Flow Using Laser Doppler Flowmetry Before & After All- Arthroscopic Capsular Autograft Labral Reconstruction

Abstract

Objectives:

All-arthroscopic capsular autograft labral reconstruction has been proposed to repair complex or irreparable tears without the downside of autograft related donor-site morbidity. Cadaveric studies have suggested that the acetabular labrum receives its blood supply from radial branches of the periacetabular periosteal vascular ring that penetrate the hip capsule, with perfusion remaining intact in most hips exhibiting labral tears. Despite this, little is known about the exact course of blood flow to labral tissue or how surgical reconstruction of this region affects microvasculature during hip arthroscopy. The purpose of this study was to examine the effects of all-arthroscopic capsular autograft labral reconstruction on labral blood flow in vivo using laser doppler flowmetry (LDF) to measure microvascular perfusion.

Methods:

After obtaining institutional review board approval, patients ≥18 years old undergoing arthroscopic repair of the acetabular labrum by a single surgeon were consented between 2018-2022. Labral repair was performed via a previously published capsular autograft labral reconstruction technique. An LDF probe (Moor Instruments) continuously measured microvascular blood flow flux (perfusion units [PU]) within 1mm³ of surrounding labral tissue (Figure 1). LDF measurements were taken medial and lateral to the region of the tear before/after labral reconstruction and before/after labral elevation from the acetabular rim. The mean of flux measurements was expressed as a percent change from each patient’s baseline measurements. The percent change in labral perfusion was analyzed using student t-tests and one-way ANOVA using Tukey’s method for multiple comparisons. Associations between preoperative demographics and labral perfusion were analyzed using multiple regression analyses. Lending from previous literature, flux decreases ≥50% were considered clinically significant.

Results:

This study included 41 patients [24 males (58.5%) and 17 females (41.5%)] undergoing arthroscopic labral repair with capsular autograft reconstruction with mean [SD] age 31.3 [8.4] years, BMI 24.8 [3.3] kg/m², lateral center edge angle (LCEA) 35.3 [4.9] degrees, Tönnis angle 5.8 [5.8] degrees, and mean arterial pressure 96.0 [10.9] mmHg. The mean [95% CI] percent change in blood flow following labral elevation was -9.24% [(-0.04) to (-18.1)]. Following labral reconstruction, the mean [95% CI] percent change in blood flow medially was -22.3% [(-11.9) to (-32.7)] and laterally -32.5% [(-23.6) to (-41.5)]. There was no significant difference between the changes in medial versus lateral perfusion (p=0.136) following repair. Unadjusted analyses stratifying for age, BMI, sex, type of impingement, Tönnis/Outerbridge class, amount of capsule used for augmentation, and suture technique revealed that none of these factors were correlated with significant differences in labral perfusion medially or laterally (p>0.05; Table 1). Multiple regression analyses controlling for demographic and intra-operative variables demonstrated that BMI, LCEA, suture technique, age, mean arterial pressure were not significantly associated with changes in medial or lateral labral perfusion (p>0.05; Table 2). Finally, all changes in flux were found to be significantly less than the 50% threshold, when comparing decreases following labral elevation (p<0.001) and labral reconstruction medially (p<0.001) and laterally (p<0.001).

Conclusions:

While the vascular nature of the acetabular labrum has been described in literature, preservation of labral blood flow following arthroscopic labral repair has not yet been objectively reported. This study found that techniques to preserve native hip anatomy and vascular supply may adequately maintain perfusion to labral tissue and promote healing. While laser doppler flowmetry may be affected by secondary operative factors, careful measures were taken to standardize the in vivo environment during each measurement. Additionally, blood flow measurements are only limited time assessments with no ability to speculate if observed changes are permanent or temporary. Although this study cannot be generalized to all variations of labral repair/reconstruction, these results suggest that surgeons can employ techniques that preserve microvascular tissue perfusion. The use of capsular augmentation enables preservation of the donor-tissue blood supply with local tissue transfer, suggesting that current labral repair techniques can preserve labral perfusion.