Department of Anatomical, Histological, Forensic Medicine and Orthopedics Sciences, Sapienza University of Rome, Rome, Italy.
Shoulder and Elbow Unit, Centro Ortopedico Traumatologico A. Alesini, Rome, Italy.
Bone Joint J. 2021 Mar;103-B(3):530-535. doi: 10.1302/0301-620X.103B3.BJJ-2020-1421.R1.
It has been hypothesized that proximal radial neck resorption (PRNR) following press-fit radial head arthroplasty (RHA) is due to stress-shielding. We compared two different press-fit stems by means of radiographs to investigate whether the shape and size of the stems are correlated with the degree of PRNR.
The radiographs of 52 RHAs were analyzed both at 14 days postoperatively and after two years. A cylindrical stem and a conical stem were implanted in 22 patients (group 1) and 30 patients (group 2), respectively. The PRNR was measured in the four quadrants of the radial neck and the degree of stem filling was calculated by analyzing the ratio between the prosthetic stem diameter (PSD) and the medullary canal diameter (MCD) at the proximal portion of the stem (level A), halfway along the stem length (level B), and distally at the stem tip (level C).
Overall, 50 of the 52 patients displayed PRNR. The mean PRNR observed was 3.9 mm (0 to 7.4). The degree of endomedullary stem filling at levels A, B, and C was 96%, 90%, and 68% in group 1, and 96%, 72%, and 57%, in group 2, with differences being significant at levels B (p < 0.001) and C (p < 0.001). No significant correlations emerged between the severity of PRNR and the three stem/canal ratios either within each group or between the groups.
PRNR in press-fit RHA appears to be independent of the shape and size of the stems. Other causes besides stem design should be investigated to explain completely this phenomenon. Cite this article: 2021;103-B(3):530-535.
有假说认为压配式桡骨头置换术后近段桡骨颈吸收（PRNR）是由于应力遮挡所致。我们通过 X 线片比较了两种不同的压配式柄，以研究柄的形状和尺寸是否与 PRNR 程度相关。
对 52 例 RHA 的 X 线片分别在术后 14 天和 2 年时进行分析。22 例患者（组 1）植入圆柱形柄，30 例患者（组 2）植入圆锥形柄。在桡骨颈的四个象限测量 PRNR，并通过分析近端柄（A 水平）、柄长一半处（B 水平）和远端柄尖端处（C 水平）的假体柄直径（PSD）与髓腔直径（MCD）之间的比值来计算柄的髓内填充程度。
总体而言，52 例患者中有 50 例出现 PRNR。观察到的平均 PRNR 为 3.9mm（0 至 7.4）。组 1 在 A、B 和 C 水平的髓内柄填充程度分别为 96%、90%和 68%，组 2 分别为 96%、72%和 57%，B 水平（p<0.001）和 C 水平（p<0.001）差异有统计学意义。无论是在每组内还是在组间，PRNR 的严重程度与三个柄/管比值之间均无显著相关性。
压配式 RHA 中的 PRNR 似乎与柄的形状和尺寸无关。应该研究除柄设计之外的其他原因，以完全解释这种现象。
