| BackgroundShortening subtrochanteric osteotomy (SSTO) is an attractive technique widely used by experienced doctors for safe reduction of the hip in treating patients with Crowe IV DDH by using THA. SSTO is complicated and with high complication rates for no experience doctors. According to our clinical experience, safe reduction can be done sometimes without SSTO usage for Crowe IV DDH. However, SSTO is a must when safe reduction is really difficult to achieve. It is still controversial that when the SSTO should be used and when it should not be used. The aim of this study was to analyze factors that can predict the usage of SSTO in a series of patients with Crowe IV DDH who underwent THA.PurposesIn this retrospective study, we determined the presence of key factors that can predict the use of SSTO by analyzing a series of patients with Crowe IV DDH who underwent THA. Secondly, we determined the factors that govern the use of SSTO in Crowe IV DDH patients with higher dislocation. Therefore, we determined a critical value of the height of dislocation to determine the use of SSTO. Additionally, as secondary acetabulum formation is founded an important factor, we furtherly discussed the necessity of Crowe IV DDH divided into two subtypes on base of secondary acetabulum formation or not.MethodsA consecutive of 112 cases Crowe IV patients with complete follow-up data, who underwent THA, and used SROM with 28 COC bearing surface were included from 2007 to 2015. Medical records were checked and radiographic reviews were performed to collect the patients data:sex, age, height, weight, BMI, the proximal femoral deformity or not, presence or absence of secondary acetabulum, if the proximal part of femoral component was Cone type sleeve type or triangle type sleeve, the dislocation height, rotation center hight, SSTO usage or not, complication rates. Digimizer software was used to measure the dislocation height and rotation center height. Then the hips were divided into two groups on base of secondary acetabulum formation or not. The anatomy morphology, selections of surgical techniques (SSTO usage or not), and complication rates were compared between the two groups.ResultsThe average dislocation height for Crowe IV DDH was 4.32± 1.63cm. SSTO was used in 87 patients, while the use was ignored in the remaining 58 patients. Harris scores were totally improved from 58.18±15.67 preoperatively to 91.20±3.79 post-operatively and the difference was significant. No nerve pulsy and vascular injury were reported in this study.In our samples, proximal femur deformity was observed in 13 hips; SSTO was used as mandatory technique in 12 hips. SSTO was used in 75 hips in the rest 132 hips with no proximal femur deformity. Significant difference was observed between proximal femur deformity patients and no proximal femur deformity patients.Secondary acetabulum formation was observed in 37 hips; SSTO was used in only 3 hips, which accounted for 8.1%. SSTO was used in 84 out of 108 hips, with no secondary acetabulum, which accounted for 77.8%. Significant difference was observed between secondary acetabulum formation patients and patients without secondary acetabulum.Cone type sleeve was used in 41 hips; 18 of them with SSTO, which accounted for 43.9%; while 104 hips were triangle type sleeve, of which SSTO was used in 69 hips, which accounted for 66.3%. Significant difference was observed in SSTO usage between cone type sleeve and triangle type sleeve.Logistic analysis showed that present proximal femur deformity, higher dislocation increased the risk associated with SSTO usage. Use of cone type sleeve using instead of regular triangle sleeve, especially secondary acetabulum formation, decreased the possibility of SSTO usage.According to the ROC curve, when dislocation height was adopted as an indicator, the critical value should be defined at 4.30 cm, and Youden index was maximal, when rotation center height was adopted as an indicator, the critical value should be defined at 6.03 cm, and Youden index was maximal.Additionally, The dislocation height for secondary acetabulum formation group was 4.74±1.57cm, while the dislocation height for no secondary acetabulum group was 3.12±1.15cm. Significantly difference was detected between two groups. The canal flare index for A group was 2.69±0.68, while the average canal flare index for B group was 3.42±0.79, significantly difference was detected between two groups. Pre-operative Harris scores was 58.13±15.33 in group A,58.32±16.85 in group B. Post-operative Harris scores was 90.76±4.14 in group A,90.97±5.11 in group B. No significant difference was found on Harris scores between A and B preoperatively and post-operatively. Complications of 4 cases peri-prosthesis fracture,4 cases dislocation and 4 cases nerve injury occur in group A; While only one case dislocation and one case nerve injury occur in group B. The complication rates of peri-prosthesis fracture, dislocation, nerve injury is higher in group A than that in group B. But no statistical significance was detected.ConclusionsWe found key factors that can predict SSTO usage in Crowe IV DDH patients. Proximal femur deformity and no secondary acetabulum formation were the key factors governing the use of SSTO. Cone type sleeve instead of sleeve could decrease the risk of SSTO. Higher dislocation height meant higher risk for SSTO usage in Crowe IV DDH patients. Dislocation height should be over 4.30cm or rotation center height be 6.03cm, especially with the use of SSTO.Furtherly study shows, Crowe IV DDH with secondary acetabulum formation is significantly different from Crowe IV DDH without secondary acetabulum formation on pathology, which cause the different selections of surgical techniques(SSTO usage or not). These important differences in fundamental parameters indicate the necessity to furtherly divide Crowe IV DDH into IVA and IVB two subtypes. It is beneficial to the evaluation of surgical difficulty in high dislocation patients, decision-making of SSTO usage or not and comparison of surgical effect between different authors. |
PDF Full Text Request