Aims. The aim of this study was to evaluate the clinical and radiological outcome of using an anatomical short-stem shoulder prosthesis to treat primary osteoarthritis of the glenohumeral joint. Patients and Methods. A total of 66 patients (67 shoulders) with a mean age of 76 years (63 to 92) were available for clinical and radiological follow-up at two different timepoints (T1, mean 2.6 years, . sd. 0.5; T2, mean 5.3 years,. sd. 0.7). Postoperative radiographs were analyzed for stem angle, cortical contact, and filling ratio of the stem. Follow-up radiographs were analyzed for timing and location of bone adaptation (cortical bone narrowing, osteopenia, spot welds, and condensation lines). The bone adaptation was classified as low (between zero and three features of bone remodelling around the humeral stem) or high (four or more features). Results. The mean Constant score improved significantly from 28.5 (. sd. 11.6) preoperatively to 75.5 (. sd. 8.5) at T1 (p < 0.001) and remained stable over time (T2: 76.6, . sd. 10.2). No stem loosening was seen. High bone adaptation was present in 42% of shoulders at T1, with a slight decrease to 37% at T2. Cortical bone narrowing and osteopenia in the region of the calcar decreased from 76% to 66% between T1 and T2. Patients with high bone adaptation had a significantly higher mean filling ratio of the stem at the metaphysis (0.60, . sd. 0.05 vs 0.55, . sd. 0.06; p = 0.003) and at the diaphysis (0.65 . sd. 0.05 vs 0.60 . sd. 0.05; p = 0.007). Cortical contact of the stem was also associated with high bone adaptation (14/25 shoulders, p = 0.001). The clinical outcome was not influenced by the radiological changes. Conclusion. Total shoulder arthroplasty using a short-stem humeral component resulted in good clinical outcomes with no evidence of loosening. However, approximately 40% of the shoulders developed substantial bone loss in the proximal humerus at between four and seven years of follow-up. Cite this article: Bone Joint J 2018;100-B:603–9

Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm sd 0.13).

CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (< 2 mm) or deficient (< 1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (sd 0.6) and only 6.2% of deficient and 26.4% of thin cement. In over 90% of these areas, the cement was directly supported by cortical bone or cortical bone with less than 1 mm of cancellous bone interposed.

When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.