Objective This study aims to investigate compensatory rotational movements of the wrist joint in patients with proximal congenital radioulnar synostosis (CRUS), using a valid and reliable three-dimensional (3D) motion analysis technique. Methods A total of 26 patients (6 females, 14 males; mean age=15.3 years; and age range=6–32 years) who were diagnosed with unilateral proximal CRUS but were not operated were enrolled in this study. Patients were then categorized into 2 groups: Group I included 5 patients younger than 10 years, and Group II included 15 patients older than 10 years. Eighteen light-reflective skin markers were placed on the bony landmarks of both upper limbs, and both distal forearms were fixed using a U-shaped device to minimize forearm rotation. Each patient grasped the handle of an instrument that used a goniometer to measure wrist rotation; maximal passive pronation and supination angles of the wrist were measured in this manner and also using 3D motion analysis. Results There was a significant correlation between measurements by the goniometer and 3D motion analysis (r=0.985, p<0.001). The test-retest reliability of the 3D motion analysis was acceptable for both the affected side (ICC=0.992) and the contralateral normal side (ICC=0.997) with low standard measurement errors (1.3° and 0.8°, respectively). Although no significant difference was observed in the range of the wrist rotation between the affected and contralateral sides in Group I (p=0.686), there was a significant difference in the wrist rotation between the affected and contralateral sides in Group II (p=0.001). Further, the pronation angle of the wrist joint was significantly larger in the affected side than that in the contralateral normal side in Group II (p=0.001). Conclusion The 3D motion analysis technique seems to be a valid and reliable method to measure the rotation of the wrist joint. Unilateral proximal CRUS patients older than 10 years of age may develop rotational hypermobility of the wrist joint compared to the contralateral normal side as a compensatory phenomenon. Level of Evidence Level III, Diagnostic Study

Trapeziectomy is performed for trapeziometacarpal (TMC) arthritis but decreased lateral pinch strength is a major source of discomfort after the surgery. The magnitude of the decrease is unclear, however, and how the pressure changes in the TMC joint is unknown. To investigate this relationship, we designed a cadaveric study to measure TMC joint pressure using a lateral pinch model, and quantitatively evaluated the effect of trapeziectomy on the pressure measurements. For 10 cadaveric forearms, physiologic forces were applied across the thumb TMC joint by loading five tendons, thereby simulating lateral pinch. Using pressure sensors, we measured the lateral pinch pressure and TMC joint pressure, which averaged 10.1 (range, 4.2–16.2) kg/cm2 and 2.0 (range, 0.8–4.4) kg/cm2, respectively. A significant correlation between the measurements was found, with an average ratio of 19% (range, 10%–27%). After trapeziectomy and interposition of the tendon ball using flexor carpi radialis, the pressure measurements were repeated under the same conditions. Significant changes were found, which averaged 5.1 (range, 1.7–10.7) kg/cm2 for lateral pinch pressure and 15.0 (range, 5.6–25.6) kg/cm2 for TMC joint pressure. In conclusion, TMC joint pressure could be measured as the ratio relative to lateral pinch pressure using a cadaveric model. After trapeziectomy, the lateral pinch strength decreased, whereas the TMC joint pressure increased.

Purpose The aims of this study were to evaluate the degree of cortical thinning and the tumor area in simple radiographs in patients with enchondroma of the hand combined with pathologic fracture and to determine the surgical outcome of simultaneous tumor curettage and internal fixation of fracture. Methods We enrolled 23 bone lesions of 21 patients diagnosed with enchondroma of the hand. Of them, 9 bone lesions of 8 patients had pathologic fracture. We evaluated the degree of cortical thinning and tumor area in simple radiographs and compared them between patients with and without pathologic fracture. For patients with pathologic fracture, we performed curettage of the tumor through the fracture site and fixed the fracture using K-wires. We then evaluated the clinical outcome of these patients using the visual analog scale to measure pain intensity and Takigawa's criteria 1 year after surgery. Results There was a significant difference in the degree of cortical thinning between the 2 groups (P < 0.001); however, there was no significant difference in the percentage of tumor area (P = 0.259). The average time from surgery to bony union was 8.5 weeks in patients with pathologic fracture. The patients reported that they could return to their previous activities of daily living within 12 weeks of surgery. The average visual analog scale score was 0.6 at 1 year after surgery, and 6 patients were graded as excellent and 2 as good according to Takigawa's criteria. Conclusions Cortical thinning seems to be related to pathologic fracture. Our scoring system for cortical thinning may be helpful in evaluating the risk for pathologic fracture. Early 1-stage surgical treatment for pathologic hand fracture with enchondroma is a very useful method with satisfactory outcomes that could shorten the treatment period.