ABSTRACT
PURPOSE: To examine the condition and triggers of stress fractures of the lateral tibial plateau (LTP) similar to type III lateral hinge fractures (LHFs) after open wedge high tibial osteotomy (OWHTO). METHODS: OWHTO was performed in 118 knees. They were examined for LHFs by computed tomography (CT). Patients were divided into the stress fracture group (Group SF) if they showed fracture lines on CT performed after starting weight-bearing walking and the normal group (Group N) for others. RESULTS: The mean age was significantly older in Group SF (Pâ¯=â¯0.022). Preoperatively, Group SF showed a significantly higher tibio-femoral angle (TFA, Pâ¯=â¯0.014). No significant differences were observed in TFA and weight-bearing line ratio after surgery. Correction angle was significantly higher in the SF group. And all of the SF were more than 13 degrees. There was no significant difference in LHF incidence between groups, whereas stress fracture incidence differed significantly for each type of LHF (chi-squared test, Pâ¯=â¯0.0001): 14.6% of type I cases, 100% of type II cases, 0% of type III cases, and 6.1% of those without LHF. DISCUSSION: The load on the LTP is assumed to act as a shearing force in type II fractures, which may contribute greatly to stress fractures. In type III, stress fractures may not occur because of the load dispersed at the fracture part. The stress fracture site is similar to type III LHF, and this kind of fracture is thought to be a delayed type III because it occurs after patients start weight-bearing walking. Moreover, they are observed in type I cases with a stable hinge and in 6% of cases without LHF. This study showed that high varus knees corrected with a large correction angle may develop stress fractures. OWHTO requires attention to stress fractures of the LTP, which can be regarded as delayed type III, in those developing LHFs postoperatively or having a high varus knee preoperatively. CONCLUSION: These results indicated the possibility of stress fracture in LTP during weight-bearing exercise after OWHTO, which was regarded as a delayed type III fracture. The results showed that Correction angle was more than 13 degrees, and lateral hinge fracture type II of the Takeuchi classification was an inducement of this stress fracture. LEVEL OF EVIDENCE: Level IV.
ABSTRACT
BACKGROUND/OBJECTIVE: Unicompartmental knee arthroplasty (UKA) is a low-invasive knee surgery that enables early recovery. Stress fracture of the medial tibial plateau (MTP) is a complication of UKA that prolongs treatment once it has occurred. We investigated factors affecting its occurrence. METHODS: The study subjects were 167 patients who underwent fixed-bearing UKA between 2009 and 2016 (45 men and 122 women of mean age 77 years, including 134 with osteoarthritis of the knee and 33 with spontaneous osteonecrosis). We measured bone mineral density, installation angle of the tibial component, and leg alignment in those patients who developed stress fracture within 3 months after UKA. RESULTS: Stress fracture did not occur in 155 patients (N group, 45 men and 110 women) and did occur in 12 (SF group, 12 women). The bone mineral density (BMD) of the proximal femur was significantly lower in the SF group, indicating that bone fragility may have contributed to stress fractures at this site. There was no significant difference in the preoperative tibio-femoral angle (TFA), however, postoperative TFA was larger and the magnitude of the change in the valgus direction (ΔTFA) was smaller in the SF group. DISCUSSION: In usual UKA for medial compartment, the leg is more extroverted postoperatively than preoperatively, and leaving the knee in the genu varus position, which places a greater load on the tibial component, may raise the risk of stress fracture. Although there was no difference between the two groups in the varus angle of the tibial component, in a scatter plot of postoperative TFA and the installation angle of the tibial component members of the SF group were concentrated in the region of high TFA and low varus angle. Varus of the leg and a low varus angle of the tibial component may thus be factors in the occurrence of stress fracture. CONCLUSION: Our results suggested that low BMD in the affected femur, large postoperative TFA, and a combination of large postoperative TFA and small varus angle of the tibial component may contribute to stress fracture of the MTP following UKA.
ABSTRACT
High tibial osteotomy (HTO) is a general procedure for the treatment of degenerative gonarthrosis. In recent years, it has been reported that opening wedge high tibial osteotomy (OWHTO) has become widespread with good results. Despite these facts, HTOs tend to be avoided due to the need for long-term postoperative treatment. To investigate the treatment period for total recovery (healing period) after OWHTO and the factors affecting it. There were 47 cases of medial type degenerative gonarthrosis who underwent OWHTO from 2008 through 2011. The definition of the healing period was based on the time-dependent changes of the Japanese Orthopaedic Association score, focusing especially on pain on walking and pain on ascending/descending stairs. This score was defined as the Ability score. In this study, the healing period ended when the Ability score reached its maximum or when it showed a perfect score. Patients' characteristics were examined to determine their effect on the healing period. The Ability score was 36.7 ± 10.1 (mean ± SD) before surgery and 51.6 ± 5.4 12 months after OWHTO. The healing period was 6.3 ± 3.9 months. Factors correlated with a longer healing period included female sex (correlation coefficient -0.35) and high BMI (correlation coefficient 0.33). Our study suggested that the healing period after OWHTO is approximately 6 months, and patients' BMI and sex appear to be related to this period. This information is expected to be helpful for counseling patients undergoing treatment for gonarthrosis. Level of evidence Therapeutic study, Level IV.
