The sacroiliac joint is an important source of low back pain and may be influenced by pathologies in adjoining structures such as the hip or the spine. This study aimed to investigate the influence of hip osteoarthritis on sacroiliac joint degeneration by examining the sacroiliac joints of hip osteoarthritis patients, focusing on the localization and quantity of vacuum phenomena. The preoperative computed tomography (CT) of 31 female hip replacement candidates (mean age 69.1) and pelvic CT of 34 age-matched controls (mean age 67.9) were used to reconstruct the sacroiliac joints three-dimensionally. The degeneration score of the sacroiliac joints on axial view, as well as the location and volume of vacuum phenomena in the three-dimensionally reconstructed sacroiliac joints, were analyzed. The total sacroiliac joint degeneration scores were similar in hip osteoarthritis patients and controls but the breakdown of the score revealed that joint space narrowing and vacuum phenomena in the sacroiliac joint increase in hip osteoarthritis, while osteophytes decrease. Three-dimensional reconstruction revealed that the volume of vacuum phenomena in the sacroiliac joint was significantly larger in the hip osteoarthritis group and the vacuum areas were localized in the antero-superior region of the sacroiliac joint. Our results suggest that hip osteoarthritis and sacroiliac joint degeneration are related, and that with further investigation, the sacroiliac joint may become a new treatment target in hip osteoarthritis.

Background: It is important to evaluate dynamic changes in the joint space width of the ankle mortise in detail in order to better understand the pathology of foot and ankle disorders. However, there are few reports on changes in the joint space width of the foot and ankle assessed using 3D images. The purpose of this study was to determine the changes in the joint space width of the ankle (tibiotalar joint) in association with dorsiflexion and plantar flexion of the ankle joint in healthy feet.Methods: Computed tomography (CT) images of 10 healthy feet were obtained in the neutral, plantarflexed and dorsiflexed positions of the ankle joint, from which 3D virtual models were fabricated of the tibia, fibula and talus. The 3D joint space width in these models was calculated using a custom made software program.Results: The joint space width increased in the order of dorsiflexion, neutral position and plantar flexion. Regarding the amount of change in dorsiflexion and plantar flexion relative to the neutral position, there were no significant differences in the middle‐middle position. On the other hand, there were highly significant differences in the medial‐anterior, medial‐middle and medial‐posterior positions.Conclusions: The joint space width of the ankle joint can be calculated accurately using 3D reconstruction images. Our findings should assist in clarifying pathology associated with movement of the ankle during the gait cycle based on changes in the joint space width in feet exhibiting disorders.

Spontaneous flexor tendon rupture is usually caused by trauma, systemic diseases, or carpal bone and joint disorders. Here we report a case of spontaneous flexor tendon rupture occurring in a systemic lupus erythematosus (SLE) patient following nonunion of the hamate hook after an insufficiency fracture, and which was also associated with tendon degeneration caused by SLE. A 57-year-old woman was diagnosed with SLE 22 years ago and being treated with oral prednisolone. She became unable to flex her left little finger without any history of trauma or sporting activity. CT showed nonunion of the hamate hook. MRI showed rupture of the flexor digitorum profundus tendon of the little finger. We performed tendon transfer and excision of the hamate hook. She recovered active flexion of the little finger at 4 months postoperatively with full satisfaction. There was no history of trauma that could have caused nonunion of the hamate hook. We considered that the insufficiency fracture of the hamate hook occurred as a result of osteoporosis caused by SLE and long-term steroid use. Nonunion of the hamate hook caused mechanical attrition of the tendons, and in combination with the tendon degeneration caused by SLE, further resulted in rupture of the flexor tendon. When we encounter a case of spontaneous flexor tendon rupture in a patient with systemic disease such as SLE or long-term steroid use, attention should be paid to the state of the carpal bones and joints as they sometimes accompany unexpected causes.