| Background:The incidence of DDH is between 0.15% and 2%, and there are reports that in the disease spectrum of the pediatric orthopaedic diseases in China, DDH is the most common disease causing limb deformity. If the nonsurgical methods are not effective enough, surgical treatment is required immediately. Harris et al. believed that the upper age at which hip reduction would achieve satisfactory acetabular development was 4 years.PPO is a kind of incomplete osteotomy which was proposed by Pemberton in 1965 and is one of the most popular methods used in the surgical treatment of DDH. Previous studies have confirmed PPO as an effective and safe treatment both in terms of clinical and radiographic outcomes in children. However, there are reports of residual gait abnormalities in patients previously treated with PPO for DDH that reduced lower limb function and made surgical revision challenging.Previous gait researches following PPO and other surgical procedures for DDH have primarily focused on the kinetics and kinematics parameters of the main joints of the lower extremity. The results of these studies indicate that during level walking, both the affected and unaffected hips of the unilateral DDH patients were subject to higher loading and loading rates when compared with the healthy controls. The increased loading and loading rates were associated with higher risk of AVN of the femoral head and degenerative hip OA. Comparing with the preoperative parameters, increased walking velocity, decreased total daily steps and an improvement in stride length were noted by some researchers. In addition, a decreased hip flexor moment of the affected limb was observed in the patients with unilateral DDH. Some researchers also reported that the patients with DDH showed significantly more anterior tilt at the affected side and rotation towards the healthy side of the pelvis. As we all known, the changes in gait probably affect the plantar pressure distribution of the foot. However, to our knowledge, there is no study to date has investigated the plantar pressures of patients with unilateral DDH following PPO.Objective:1. To compare and analyze the plantar pressure differences between the patients with unilateral DDH following PPO and healthy control, so as to provide objective evidences for evaluating the effect of surgery and rehabilitation.2. To sum up and summarize the plantar pressure parameters of the patients with unilateral DDH after PPO, finding the dangerous area of the foot injury and pain and providing valuable biomechanical information for the further protection and treatment measures.Methods:1. Twenty patients who underwent surgical procedure with combined open reduction and PPO for unilateral DDH before the age of 4 years participated in the study. Twenty age-matched healthy children were recruited as control group. All the participants performed dynamic plantar pressure tests using the Footscan? pressure plate.2. The radiographic results were evaluated using the modified Severin criteria and the clinical manifestations were graded according to the modified Mc Kay criteria.3. The parameters of CT%, PP and FTI of each masked zone in the 4 subphases in the DDH group and healthy controls were compared to evaluate changes of the plantar pressures during level walking.Results:1. The plantar pressure of patients with unilateral DDH after PPO did not restore to normal level.2. The mean total CT in the affected limb of DDH patients(576.2±102.8 ms) was significant smaller than in the unaffected side(634.8±116.0 ms, p=0.03) and control group(649.7±118.1 ms, p=0.04). The mean values of CT% were significantly increased during the FFPOP in the affected limb(45.7±5.8) compared to that of the control group(41.4±6.3, p=0.03) and the unaffected side(40.9±6.1, p=0.03). The affected limb showed a higher PP in the M4 zones(132.7±38.5 k Pa) than was seen in the control group(109.8±28.4, p=0.04) and the unaffected limb(116.7±33.2, p=0.002). The affected limb also showed a greater PP in the M5 zones(91.4±24.3 k Pa) than those in the control group(70.7±17.2, p=0.003) and the unaffected limb(75.4±15.8, p<0.001). In addition, the affected limb also manifested a significantly lower total FTI(120.0±27.4 Ns) than values of the unaffected limb(145.6±39.7 Ns, p<0.001) and control group(138.3±28.3 Ns, p=0.05).3. There were no significant plantar pressure differences between patients classified as ‘‘excellent or good’’ and those rated as ‘‘fair’’ according to the radiographic evaluation. The subgroups showed a similar trend when comparing with the control group.Conclusions:Although the clinical and radiographic results after PPO for unilateral DDH are encouraging, there exist residual deviations of plantar pressure during walking. A longer period of intensive rehabilitation is required to restore the symmetric distribution of the plantar pressure in the unilateral DDH patients. The affected limb also showed a greater PP in the M4 and M5 zones, which suggests a higher risk of injury and pain in those areas. The clinicians should pay enough attention to this in the postoperative rehabilitation of PPO. |
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