As the elderly population increases, the number of arthroplasty cases has been growing in recent years ^[1]. Along with that, the number of periprosthetic fractures is increasing. Periprosthetic fractures are often more difficult to treat than normal fractures, and we often encounter non-unions and re-fractures after surgery ^[2]. That are difficult to treat. We report a rare case of nonunion in which the humeral bone exhibited severe ballooning deformity after nonunion around the hemiarthroplasty stem.

A 79-year-old woman presented with right upper arm pain and instability. She underwent a cementless hemiarthroplasty at another hospital for her proximal humerus fracture, when she had a motorcycle accident 19 years ago. Ten years later, she had a motorcycle accident again and suffered a fracture around her right humerus stem distal end, and revision surgery with a cementless long stem hemiarthroplasty was performed at the former hospital. Regular follow-up for 8 years, but bone union was not obtained, and she was referred to our hospital for further treatment because of her right arm pain and dysfunction. She has a history of diabetes mellitus (HgbA1c 6.7%). Physical findings at the first visit to our hospital were swelling and pain in the right humerus. Active movement of her shoulder joint was 10° of flexion, 5° of extension, and 10° of abduction. Her nonunion site was unstable and had minimal function. X-ray at the time of referral showed a nonunion at the fracture and a severe ballooning deformity in the distal bone fragment (Fig. 1a).Computed tomography showed similar findings, and a thinned bone cortex was found at the same site (Fig. 1b). When we observed the images from the previous hospital for confirmation, we found that the ballooning deformation was gradually progressive (Fig. 2). We decided that nonunion surgery was difficult and chose total humerus replacement (Stryker Howmedica Modular Resection System) (Fig. 3). Surgical findings confirmed the nonunion and ballooning deformity of the distal humeral bone fragment and the cavity inside it (Fig. 4). No malignancy was found histopathologically in the deformed part of the ballooning. Three years after the total humeral replacement surgery, the patient has a stable upper arm and no pain. There was a slight improvement in active movement of her shoulder joint, but elbow joint function is maintained (Fig. 5). She is happy with her stable and painless upper arm.

There are some reports on the treatment of non-unions for periprosthetic humerus fracture. If there is no looseness in the prosthesis, performing internal fixation by using a locking plate is recommended. If there is looseness, revision with a longer stem by using a plate and/or bone graft is recommended ^[3]. There are some reports recommending revision using strut bone allograft and internal fixation using a plate or cable system when the bone is fragile due to loosening [4, 5, 6]. In this case, as well, we examined options including osteosynthesis using bone grafts such as autograft and allograft. However, we decided that osteosynthesis was difficult due to the severe ballooning deformity and the patient’s age and activities of daily living, and we performed total humeral replacement instead. The number of cases of total humeral replacement for tumor patients is increasing [7, 8]. In addition, case reports of total humeral replacement are also found in treatments for conditions other than tumors, such as periprosthetic fractures in patients with rheumatism ^[9]. In this case, total humeral replacement was performed on humeral nonunion with severe ballooning deformity. There are few reports of aseptic loosening around elbow replacement ^[10], but to the best of our knowledge, there has not been a report of severe ballooning deformity as in this case. It is presumed that the stem continued to move in the distal bone fragment as a result of the lack of fixation around the stem and the continued instability caused by the nonunion.

A total humeral replacement was performed on a nonunion around the periprosthetic humeral fracture that had ballooning deformity. Total humeral replacement can be a treatment option for some non-unions such as in this case.

Total humeral replacement can be one of the treatment options in cases where nonunion surgery is extremely difficult, considering the patient’s age and activities of daily living.