Permanent patellar subluxation is treated with surgeries such as proximal realignment and distal realignment, however, it is difficult to cure this condition by using any methods. We performed mobile-bearing total knee arthroplasty (TKA) in a case of severe knee osteoarthritis complicated with permanent patellar subluxation since childhood, and obtained good results without performing any additional procedures.

The patient was an 82-year-old woman with severe pain in the left knee. During the initial examination, the range of motion of the left knee joint was -10°of extension to 140°of flexion, and the Japanese Orthopaedic Association (JOA) score for knee osteoarthritis was 40 points (maximum score: 100). Preoperative radiographs showed a varus deformity in the left lower extremity with a femorotibial angle (FTA) of 188°, the axial view showed luxation of the patella.

We performed TKA using a mobile-bearing implant. Intraoperative findings revealed that the central articular surface of the distal femur had disappeared, and that the patellar articular surface was concave and dome-shaped. The lateral patellofemoral ligament was released; this procedure was identical to that performed in conventional TKA.

Postoperative radiographs showed good alignment, with an FTA of 173°. In the axial view, the patella was located in a reduced position at any angle of knee joint flexion.

The postoperative range of motion of the left knee joint was 0°of extension to 130°of flexion. The patient was able to walk without the support of a T-shaped cane.

There are many surgical treatments for permanent patellar subluxation. The appropriate treatment is selected according to the type and seriousness of the dislocation and the age of the patient.

From the findings of the present case, we believe that in a case of knee osteoarthritis complicated with permanent patellar subluxation, surgery performed using a mobile-bearing implant would eliminate the necessity of performing additional proximal realignment and distal realignment.

Background

The bearing surface is one of the important factors that affect the longevity of total hip replacement (THR). The ceramic on ceramic bearing decreases the rate of dislocation event and the amount of wear debris. We encountered cases of incomplete seating of the liner with the TriAD acetabular system.

Objective: The number of hip prostheses replacement surgeries particularly in elder people with osteoporosis, has been increasing every year; given this scenario, treatment of postoperative periprosthetic femoral fracture has become a critical problem. Osteosynthesis is generally selected as the procedure of choice for the surgical treatment of fractures, provided the stem prostheses do not show loosening. Stable fixation of periprosthetic femoral fracture is difficult in the elderly because they have osteoporotic bone and most of the intramedullary space is occupied by the metal stem implanted in the proximal femoral shaft. With a view to solving this problem, we developed a new surgical treatment for postoperative periprosthetic femoral fracture; this procedure use a trimming intramedullary nail, which we have termed “docking nail.” [Materials] The subjects were 3 patients (81, 75 and 76 years old) who had suffered a femoral shaft fracture around the femoral prosthesis after total hip replacement; in all 3 patients, there was no apparent sign of loosening of the stem prosthesis. The implanted stem was cemented in one patient and uncemented in the other two.

Method: Using information on the size and shape of the stem prosthesis as well as information from the pre-operative radiographs, we cut the docking nail till the proper length was achieved and trimmed it to suit the cutting site in order to ensure that it was compatible with tip of the stem. We then performed osteosynthesis using instruments of an ordinary supracondylar type intramedullary nail. In cases where it was difficult to reposition or where it was necessary to remove excessive cement and bone from around the tip of stem and graft a free bone in the bony defect, we exposed the fracture site as minimally as possible. The major difference between our procedure and the conventional procedure is that in our procedure, the docking nail is connected to the tip of the implanted stem to ensure proper alignment. Postoperative immobilization was not used in any of the patients except for the 81-year-old patient, for whom partial weight-bearing was allowed at 4 weeks, and full weight bearing at 12 weeks. The mean follow up period was 22 months (range, 6–48 months).

Result: Within 3 months, bony union with good alignment was achieved in all 3 patients without malunion or infection. The clinical and radiographic examinations conducted during the follow-up period showed good results.

Conclusion: The advantages of this method are that it is less invasive and simple compared to the conventional methods. Its only disadvantage is that it requires considerable, preoperative planning and minor trimming of the nail. Although this series is small, we think that this new treatment can be recommended and will be beneficial for treating periprosthetic femoral fractures without a loose stem. However, these preliminary findings need to be confirmed by further investigations.