Propensity score matching.

Background
Biomechanical studies showed that increasing number of anchors could improve the repair strength of the repaired cuff at time zero.
Purpose
The aim of this study was to determine if utilizing only a single anchor for a cuff tear repair is sufficient or otherwise to give a similar retear rate and clinical outcome as multiple anchors in a matched group of patients.
Study design
Cohort study; Level of evidence, 3.
Methods
Retrospective analysis of 346 matched consecutive patients (single anchor group, n = 173; multiple anchors group, n = 173) who had cuff tears ≤ 3*3 cm² (mediolateral * anteroposterior diameters) repaired by a single senior surgeon. Ultrasound was used to evaluate the integrity of repair 6 months post-surgery. Patient and surgeon reported outcomes were used to evaluate the clinical outcome of the method used for repair.
Results
6 months post-surgery; the retear rate for cuff tears ≤ 1*1 cm², tears ≤ 1 cm in mediolateral diameter and > 1 cm in anteroposterior diameter and tears > 1 cm in mediolateral diameter and ≤ 1 cm in anteroposterior diameter was similar in single and multiple anchors groups (4.8%) (3.3%) (P = 1.00), (10.8%) (7.9%) (P = 0.71) and (0%) (0%) respectively. Retear rate for cuff tears > 1*1 cm² was significantly higher in single anchor group (25.4%) compared to multiple anchors groups (10.9%) (P < 0.05). Operative time was significantly lower in single anchor group (14 minutes) compared to multiple anchors group (20 minutes) (P < 0.05) only for cuff tears ≤ 1*1 cm².
Conclusion
6-months post-surgery; there was no significant difference in retear rate or clinical outcome between patients with tears ≤ 3*3 cm² (mediolateral * anteroposterior diameters) who had their cuff tears repaired using a single anchor compared to those who had their cuff tears repaired using multiple anchors unless both the mediolateral and anteroposterior diameters of the tear were > 1 cm, for which the utilization of multiple anchors showed a significantly lower retear rate at 6 months post-surgery. Operative time was significantly shorter only when a single anchor was used for repair of tears ≤ 1*1 cm².

研究背景
生物力学研究证实，锚钉（anchor）植入数量的增加可提升肩袖修复完成即刻的修复强度。

研究目的
本研究旨在通过匹配患者队列，明确肩袖撕裂修复术中仅使用单枚锚钉，是否可达到与多枚锚钉相当的再撕裂率及临床预后。

研究设计
队列研究；证据等级：3级。

研究方法
回顾性分析346例连续匹配的肩袖撕裂患者，其中单锚钉组173例，多锚钉组173例。所有患者的肩袖撕裂尺寸（内外侧径×前后侧径）均≤3cm×3cm，且均由同一位高年资外科医师完成修复。术后6个月采用超声评估修复结构的完整性，并通过患者与术者报告的结局指标，评估该修复方式的临床疗效。

研究结果
术后6个月随访时，针对不同尺寸亚组的肩袖撕裂，单锚钉组与多锚钉组的再撕裂率如下：①撕裂尺寸≤1cm×1cm者：单锚钉组4.8%，多锚钉组4.8%（P=1.00）；②内外侧径≤1cm且前后侧径>1cm者：单锚钉组10.8%，多锚钉组7.9%（P=0.71）；③内外侧径>1cm且前后侧径≤1cm者：单锚钉组0%，多锚钉组0%。针对撕裂尺寸>1cm×1cm的患者，单锚钉组再撕裂率（25.4%）显著高于多锚钉组（10.9%，P<0.05）。仅针对撕裂尺寸≤1cm×1cm的患者，单锚钉组手术时间（14分钟）显著短于多锚钉组（20分钟，P<0.05）。

研究结论
术后6个月随访时，对于撕裂尺寸（内外侧径×前后侧径）≤3cm×3cm的肩袖撕裂患者，单锚钉修复与多锚钉修复的再撕裂率及临床预后无显著差异；仅当撕裂的内外侧径与前后侧径均>1cm时，多锚钉修复的术后6个月再撕裂率显著更低。此外，仅针对撕裂尺寸≤1cm×1cm的肩袖撕裂，单锚钉修复的手术时间显著更短。