Effects of heel apex position, apex angle and rocker radius on plantar pressure in the heel region.

Introduction Rocker shoes and insoles are used to prevent diabetic foot ulcers in persons with diabetes mellitus and loss of protective sensation, by reducing the plantar pressure in regions with high pressure values (>200 kPa) (e.g., hallux, metatarsal heads and heel). However, forefoot rocker shoes that reduce pressure in the forefoot inadvertently increase pressure in the heel. No studies focused on mitigating the negative effects on heel pressure by optimizing the heel rocker midsole, yet. Therefore, we analyze the effect of different heel rocker parameters on the heel plantar pressure. Methods In-shoe pressure was measured, while 10 healthy participants walked with control shoe and 10 different heel rocker settings. Peak pressure was determined in 7 heel masks, for all shoes. Generalized estimating equation was performed to test the effect of the different shoes on the peak pressure in the different heel masks. Results In the proximal heel, a rocker shoe with distal apex position, small rocker radius and large apex angle (100°), shows the largest significant decrease in peak pressure compared to rocker shoes with more proximally located apex positions. In the midheel and distal heel, the same rocker shoes or any other rocker shoes, analyzed in this study, do not reduce the PP more than 2% compared to the control shoe. For the midheel and distal heel region with high pressure values (>200 kPa), rocker shoes alone are not the correct options to reduce the pressure to below 200 kPa. Conclusion When using rocker shoes to reduce the pressure in the forefoot, a heel rocker midsole with a distal apex position, small rocker radius and apex angle of 100°, mitigates the negative effects on proximal heel pressure. For the midheel and distal heel, other footwear options as an addition or instead of rocker shoes are needed to reduce the pressure.引言 摇椅鞋与鞋垫（rocker shoes and insoles）可通过降低压力值高于200 kPa的区域（如拇趾（hallux）、跖骨头（metatarsal heads）及足跟）的足底压力（plantar pressure），用于预防罹患糖尿病（diabetes mellitus）且存在保护性感觉丧失（protective sensation）人群的糖尿病足溃疡（diabetic foot ulcers）。然而，可降低前掌压力的前掌摇椅鞋（forefoot rocker shoes），却会无意间升高足跟部位的压力。目前尚无研究通过优化足跟摇椅中底（heel rocker midsole），来缓解这类鞋款对足跟压力产生的负面影响。因此，本研究分析不同足跟摇椅参数对足跟足底压力的影响。 方法 本研究测量了10名健康受试者穿着对照鞋与10种不同足跟摇椅配置参数时的鞋内压力（in-shoe pressure）。针对所有鞋款，在7个足跟压力分区中测定峰值压力（peak pressure）。采用广义估计方程（Generalized estimating equation）检验不同鞋款对各足跟压力分区峰值压力的影响。 结果 在足跟近端区域，相较于顶点位置更靠近近端的摇椅鞋，采用顶点远端位置、较小摇椅曲率半径（rocker radius）以及100°顶点角度（apex angle）的摇椅鞋，其峰值压力降幅最为显著。而在足跟中段与足跟远端区域，本研究中所测试的上述摇椅鞋或其他摇椅鞋，其峰值压力降幅均未超过对照鞋的2%。对于压力值高于200 kPa的足跟中段与足跟远端高压区域，仅依靠摇椅鞋无法将压力降至200 kPa以下。 结论 当使用摇椅鞋降低前掌压力时，采用顶点远端位置、较小摇椅曲率半径以及100°顶点角度的足跟摇椅中底，可有效缓解其对足跟近端压力的负面影响。针对足跟中段与足跟远端区域，则需采用其他鞋类方案替代或搭配摇椅鞋，以达成降低压力的目标。