PubMed · 13564894
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W MOL. 1958. [Congenital hip dislocation].. https://pubmed.ncbi.nlm.nih.gov/13564894/
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PURPOSE OF THE STUDY: Hip dislocation after revision total hip arthroplasty (RTHA) is a frequent post-operative complication. Certain risk factors are well identified (nonunion of the greater trochanter, history of recurrent dislocation or infection, multiple procedures), the role of spine morphological remains to be fully examined. The purpose of this prospective analysis was to assess the role of spine morphology in post-operative dislocations. MATERIAL AND METHODS: Forty-nine patients who underwent RTHA between September 2002 and March 2002 were evaluated prospectively. A complete pre- and postoperative spinal work-up was available for all patients to evaluate the lumbopelvic static using the Legaye and Duval Beaupère morphology criteria and the pelvic-femoral angle to assess hip joint extension. Pre-, per- and post-operative data including the usual risk factors for dislocation related to the clinical situation and the technique used were recorded on a digital datasheet. Five patients developed postoperative dislocation despite the absence of defective implant position. There was no relation with access (p=0.832) or pelvic-femoral angle (p=0.515). RESULTS: The mean value of the sacral slope was significantly different (p=0.006) in patients who developed dislocation in comparison with the other patients. This difference remained significant (p=0.017) for the cohort of 33 patients who had no associated risk factor for postoperative dislocation (history of recurrent dislocation or infection, multiple procedures, tight nonunion of the greater trochanter). DISCUSSION: Our results suggest that the morphology of the lumbar spine can be involved in the risk of postoperative dislocation. The morphology of the lumbar spine affects the pelvic static and thus the landmarks usually used for implantation, but it can also limit the amplitude of pelvic movement when changing from the sitting to the standing position, which would be compensated for by greater hip movement, particularly extension. The method we used did not fully take into account the consequences of changes in spinal balance due to thoracic deformations nor to analgesic (or not) hip flexion and subsequent deformation of the lumbar spine.
We studied the reproducibility of ultrasonographic screening examination of the hip when read by diagnostic radiographers. In order to determine interobserver variability, 200 ultrasonograms were classified according to Graf's method by five observers (four radiographers and one radiologist). The kappa values for interobserver variability indicated moderate agreement (kappa 0.47) for the exact Graf classification and substantial agreement (kappa 0.65) for the classification of normal (type I) versus abnormal (type IIa-IV). Agreement was significantly different for normal, immature and abnormal hips. Comparison of the findings in our interobserver study with existing information based on other examinations and treatment revealed that only a small number of infants with mildly dysplastic hips would have been typed as normal by some observers as a result of observer variability. In conclusion, the interobserver agreement on the ultrasound assessment of the hip was good enough for screening purposes. Observer variability did not result in any severe cases being missed.
A mathematical model was developed to study the effect of the Chiari osteotomy on the distribution of contact hip stress over the weight-bearing area. It was shown that Chiari osteotomy can increase the weight-bearing area directly (on the lateral side), owing to the additional area formed by the ala ossis ilii segment, and indirectly (on the medial side), owing to the shift of the stress pole in the medial direction. As a consequence, the contact hip stress is reduced after Chiari osteotomy. The indirect effect is important and often larger than the direct one. Using the proposed mathematical model and standard anteroposterior roentgenographs from archives, the average peak stress on the weight-bearing area, normalised with respect to the body weight (pmax/ W(B)), was determined before and after Chiari osteotomy (8,310m(-2) and 4,480 m(-2), respectively) on a population of 29 dysplastic hips. The difference was statistically significant (p < 0.005). Based on the results presented, it can be concluded that the hip joint contact stress in dysplastic hips considerably decreases after Chiari osteotomy, indicating a favourable biomechanical effect of this operation.