Primary stability of short stem prostheses for the shoulder—a biomechanical comparative study of two short stem designs

IF 2.1 3区医学 Q2 ORTHOPEDICS

Archives of Orthopaedic and Trauma Surgery Pub Date : 2025-08-20 DOI:10.1007/s00402-025-06041-1

Anna-Katharina Nolte, Maxime Marie Seifert, Sebastian Jäger, J. Philippe Kretzer, Mareike Schonhoff, Felix Zeifang, Raphael Trefzer, Benjamin Panzram, Tobias Renkawitz, Matthias Bülhoff

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Abstract

Introduction

The use of short stems has been a trend in shoulder arthroplasty within the last 15 years with excellent short- to mid-term clinical outcomes. Short stems anchor in the cancellous metaphysis and a high level of postoperative stability with absence of micro-movements at the bone-implant interface can be crucial for the following healing. The study aimed to assess the primary rotational stability of two uncemented short stems. The hypothesis was that the rotational stability is independent of implant design.

Materials and methods

A biomechanical in-vitro study was conducted on 12 fresh-frozen (six matched pairs) human cadaveric shoulders. Two short stems, one with a cylindrical and one with a rectangular stem shape design, were implanted in a cement-free technique. A sinusoidal torque force was applied, starting from 0.5 Nm (load level one) to 3.0 Nm (load level six) with increasing load levels (0.5 Nm per 500 cycles). The relative rotation between stem and bone was assessed with an optical measurement system.

Results

Mean donor age was 80 years (range 67–89 years), mean bone density was 0.41 g/cm² (range 0.21–0.64 g/cm²) with no significant difference between stem design groups (p = 0.155). The cylindrical stem design demonstrated a significantly higher relative rotation than the rectangular stem design at 2.0 Nm (p = 0.047), 2.5 Nm (p = 0.034) and 3.0 Nm (p = 0.016). The metaphyseal and diaphyseal filling ratio was significantly higher in the rectangular stem design group (p = 0.002, p = 0.001).

Conclusions

The cylindrical stem design shows a higher relative rotation in vitro imitating the immediate postoperative situation, indicating that rotational stability might depend on the implant design. However, the mid- to first long-term rates of aseptic stem loosening for the cylindrical stem design are generally low. It is important to consider the sensible postoperative healing phase during postoperative rehabilitation, especially for cylindrical stem designs, to promote secondary osseointegration.

Level of evidence

Experimental study.

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肩部短柄假体的初步稳定性——两种短柄设计的生物力学比较研究

在过去的15年中，短柄在肩关节置换术中的应用已成为一种趋势，具有良好的中短期临床效果。短柄锚定在松质干骺端，术后高度稳定且在骨-种植体界面无微运动，对后续愈合至关重要。该研究旨在评估两个未胶结短柄的主要旋转稳定性。假设旋转稳定性与种植体设计无关。材料与方法对12对新鲜冷冻（6对配对）人尸体肩部进行体外生物力学研究。两根短茎，一根是圆柱形的，另一根是矩形的，采用无水泥技术植入。施加正弦扭矩力，从0.5 Nm（负载级别1）到3.0 Nm（负载级别6），随着负载级别的增加（每500个周期0.5 Nm）。用光学测量系统评估骨与骨之间的相对旋转。结果供体平均年龄为80岁（67 ~ 89岁），平均骨密度为0.41 g/cm2 (0.21 ~ 0.64 g/cm2)，两组间差异无统计学意义（p = 0.155）。柱状茎在2.0 Nm （p = 0.047）、2.5 Nm （p = 0.034）和3.0 Nm （p = 0.016）处的相对旋转显著高于矩形茎。矩形干设计组干骺端和干骺端填充率显著较高（p = 0.002, p = 0.001）。结论圆柱形假体设计在体外模拟术后即时情况下具有较高的相对旋转，表明旋转稳定性可能取决于假体设计。然而，对于圆柱形阀杆设计，中长期无菌阀杆松动率通常较低。在术后康复中，考虑合理的术后愈合阶段是很重要的，特别是对于圆柱形茎设计，以促进继发性骨整合。证据水平：实验研究。

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来源期刊

Archives of Orthopaedic and Trauma Surgery 医学-外科

CiteScore

4.30

自引率

13.00%

发文量

424

审稿时长

2 months

期刊介绍： "Archives of Orthopaedic and Trauma Surgery" is a rich source of instruction and information for physicians in clinical practice and research in the extensive field of orthopaedics and traumatology. The journal publishes papers that deal with diseases and injuries of the musculoskeletal system from all fields and aspects of medicine. The journal is particularly interested in papers that satisfy the information needs of orthopaedic clinicians and practitioners. The journal places special emphasis on clinical relevance. "Archives of Orthopaedic and Trauma Surgery" is the official journal of the German Speaking Arthroscopy Association (AGA).