Ultra Short Osteotomy With Mortise‐Tenon Diaphyseal Prosthesis Reconstruction for Forearm Metastases: A Retrospective Study

ABSTRACT Objective Forearm diaphyseal metastases are rarely encountered and are predisposed to pathological fracture because torsional stress is repeatedly generated during pronation–supination. In addition, relatively long osteotomy is often required by conventional intercalary prostheses, and limited bone stock in the radius and ulna may be sacrificed. In this study, the feasibility and short‐ to mid‐term outcomes of an intercalary mortise–tenon diaphyseal prosthesis designed to enable ultra‐short osteotomy were evaluated in patients undergoing reconstruction after en bloc resection of forearm metastases. Methods Five consecutive patients with diaphyseal metastases of the forearm (radius, n = 3; ulna, n = 2) who were treated with en bloc resection and implantation of a custom mortise–tenon diaphyseal prosthesis between June 2019 and November 2023 were retrospectively reviewed. Pain and limb function were assessed using the visual analogue scale (VAS) and Musculoskeletal Tumor Society (MSTS) score, respectively. Osteotomy length, perioperative findings, complications, local recurrence, implant‐related events, and survival were recorded. Pre‐ and postoperative VAS and MSTS scores were compared using the Wilcoxon signed‐rank test. Results A mean follow‐up of 40.2 months (range, 19–72) was achieved. A mean osteotomy length of 3.6 cm (range, 3.0–4.0) was recorded, and reconstruction was completed with limited bone resection. Pathological fractures were observed in three patients, whereas Mirel's scores of 10 were documented in the remaining two patients. At final follow‐up, the mean VAS score was reduced to 0.4 (range, 0–1), and the mean MSTS score was increased to 26.2 (range, 25–27); statistical significance was reached for both comparisons. The 12‐ and 24‐month survival rates were estimated at 100% and 80%, respectively. No local recurrence, implant failure, or major postoperative complications were observed during follow‐up. Conclusion In this small retrospective case series, intercalary reconstruction using a mortise–tenon diaphyseal prosthesis after en bloc resection was shown to be feasible for forearm diaphyseal metastases, and substantial pain relief together with satisfactory functional recovery was achieved. Long‐term durability and oncologic outcomes should be confirmed in larger studies.