Table 1 Characteristics of the selected studies that used pressure reduction as the primary outcome measure
Author, date | Location | Study design | Follow up period | Sample size | Sample characteristics | Intervention & Comparison | Outcome measures | Result |
|---|---|---|---|---|---|---|---|---|
Arts et al. 2012 [38] | Netherlands | Repeated measures | Same day | 171 (336 ft) | Diabetic neuropathy Previous plantar ulcer | Custom-made footwear Semi-customised footwear Barefoot | Peak plantar pressure (PPP) of < 200 kPa considered successful | Custom-made footwear is least effective in pressure reduction (< 200 KPa) at forefoot compared to midfoot and known ulcer locations (29% vs 81 and 62%) |
Arts et al. 2015 [39] | Netherlands | Repeated measures | Same day | 85 | Diabetic neuropathy Previous plantar foot ulcer | Various footwear modifications to custom or semi-custom footwear Footwear before modification | % plantar pressure reduction | MP, local cushion and plastazote top cover reduce PP respectively by15.9, 15, 14.2% and combinedly 24 and 22% at the forefoot. |
Bus et al. 2011 [30] | Netherlands | Repeated measures | Not reported | 23 | Diabetic Neuropathy, Foot deformity Foot ulcer | Fully custom-made footwear and insoles | In-shoe plantar pressure reduction by more than 25% (Criteria A) or below the absolute value of 200 kPa (Criteria B) | MB or MP, replacing the top cover, early rocker can reduce pressure at hallux and metatarsal area ranging from 10.1 to18.6% as an individual modification. |
Bus et al. 2004 [40] | Netherlands | Repeated measure | Not reported | 20 | Diabetic Neuropathy, History of healed plantar foot ulcers Foot deformity | Insoles; 9.5 mm thick flat PPT insole and custom-made insoles out of open-cell urethane foams of hardness 60–80. Custom-made insoles were made by CADCAM process. | Plantar pressure reduction FTI | Custom-made insoles reduce plantar pressure and FTI significantly at medial and lateral heal, MTH1 and FTI at lateral MTHs when compared with flat PPT insoles. |
Charanya et al. 2004 [41] | India | Case-control study | 6 months | 25 | Diabetic Neuropathy History of active and healed plantar ulcers Non-diabetic (Control) | Footwear with an insole made of 12 mm MCR, shore value 200, Toughened rocker profile rubber outsole | Foot sole hardness reduced close to normal, shore value 200 | Plantar ulcers healed in three-four weeks, foot sole skin hardness reduced to 25–30 from 45 to 50 shore values. |
Netherlands | Repeated measures | Not reported | 17 | Diabetic Neuropathy Higher barefoot plantar pressure (≥700 kPa) | Insole with various height arch supports and with and without a metatarsal dome | In-shoe plantar pressure reduction (36% & 39%), Walking convenience on a 10-point rating scale | Extra arch support and MD are respectively effective in 39% & 36% pressure reduction in central and medial regions of the forefoot | |
Hastings et al. 2007 [44] | USA | Repeated measure | 22 months | 20 | Diabetic Neuropathy History of plantar foot ulcers No active foot ulcers No Charcot neuropathy | Three footwear conditions; extra depth footwear with 1) Total Contact Insoles (TCI), 2) TCI with proximal Metatarsal Pad (MP), 3) TCI with distal MP, CT Scan | PPP CT Scan for positioning of MP against MTHs | Highest (57%) PPP reduction occurred at 2nd MTH when MP placed at 10.6 mm proximal to MTH line. Variable PPP under the 2nd MTH varied between 32 ± 16% when positioning of MP varies between 6.1 mm to 10.6 mm proximal to MTH line. |
Lin et al. 2013 [45] | China | Repeated measure | Not reported | 26 | Diabetic Neuropathy | Insole with pre-plug removal, post-plug removal, and post-plug removal + arch support | Mean peak pressure (MPP), maximum force, contact area | Removing insole plug is effective in offloading MPP by 32.3% and adding arch support reduces further 9.5% at the forefoot |
Lott et al. 2006 [46] | USA | Repeated measure | Not reported | 20 | Diabetic Neuropathy History of midfoot or forefoot plantar ulcers | Four different conditions; 1) Barefoot, 2) Footwear, 3) Footwear + TCI, 4) Footwear + TCI + MP | Plantar pressure reduction Soft tissue thickness (STT) | PP & ST strain under 2nd MTH are highest at the barefoot condition and lowest at footwear + TCI + MP condition. Mean PP for all four conditions under 2nd MTH is 272 kPa, 173 kPa, 140 kPa and 98 kPa. |
Martinez-Santos et al. 2019 [47] | UK | Repeated measure | Not reported | 60 | Diabetic Neuropathy No previous ulcers | Insole with three different metatarsal bar (MB) positioning, two different types of materials | PPP | Maximum pressure reduction can be achieved by positioning metatarsal bar at 72% length of insole, irrespective of material type |
Mueller et al. 2006 [48] | USA | Repeated measure | Not reported | 20 | Diabetic Neuropathy history of plantar ulcers | Three footwear conditions: 1) Footwear, 2) Footwear with TCI, and 3) Footwear with TCI + MP | PPP PTI STT | TCI and metatarsal pad caused reductions of pressure under the metatarsal heads |
Owings et al. 2008 [49] | USA | Repeated measure | Not reported | 20 | Diabetic Neuropathy Higher (> 750 kPa) barefoot plantar pressure at MTH region | Three different type custom-made insoles (X, Y from shape-based and Z combined foot shape with plantar pressure data). Footwear with rigid rocker sole and flexible sole | Peak pressure FTI | Shape and pressure-based insoles (Z) showed improved offloading by 32 and 21%, PTI reduction 40 and 34% when compared to shape-only-based insoles (X-Polypropylene base, Y- EVA base). A similar trend was observed in flexible and rocker bottom shoes for the same insoles. |
Paton et al. 2012 [50] | UK | RCT | 18 months | 119 | Neuropathic diabetic foot ulceration | Prefabricated and custom-made insole | In-shoe pressure reduction, PTI, forefoot rate of load, total contact area | Prefab versus custom insoles, PPP ≥ 6%, |
Praet et al. 2003 [51] | Netherlands | Repeated measure | Not reported | 10 | Diabetic Neuropathy No active ulcer, No major foot deformities | Three different types of footwear designs | Peak pressure reduction at multiple areas under the foot | Rocker sole can offload the forefoot area by 65% |
Preece et al. 2017 [52] | UK | Case-control | Not reported | 168 | Diabetic Neuropathy (n = 17) Healthy control (N = 66) | Eight types of rocker sole design | Pressure reduction threshold of ≤200 kPa | Rocker apex position at 52%, 200 rocker angle, 950 apex angle yields effective offloading at most |
Tang et al. 2014 [53] | Sweden | RCT | Two years | 114 | Diabetic neuropathy Angiopathy Foot deformities Previous ulcers or amputation | Three types of insoles, custom made (35 & 55° shore hardness EVA) vs prefab insoles with hardcore EVA + soft microfiber top cover (Control) | PPP PTI | The overall PPP for the insoles was between 180 kPa to 211 kPa, PTI differences 14 kPa/sec & 20 kPa/sec with Control. |
Teffler et al. 2017 [54] | UK | Randomised crossover | Not reported | 20 | Diabetic neuropathy Increased forefoot plantar pressure No Charcot foot or partial amputation | Three types of insoles 1) Standard (Shape-based), milled insoles, 2) Milled, virtually optimised insoles and 3) 3D printed virtually optimised insoles | PPP | Virtually optimised insole reduced PPP by a mean of 41.3 kPa for milled and 40.5 kPa for 3D printed insoles in the same participants’ group. |
Tsung et al. 2004 [55] | China | Case-control | Not reported | 14 | Diabetic neuropathy No Charcot foot or partial amputation Control: no foot deformity | Five support conditions including footwear-only, flat insoles; and three custom-made insoles with three weight-bearing conditions; 1) Full weight-bearing (FWB), 2) Semi-weight-bearing (SWB) and 3) Non-weight-bearing (NWB) | MPP PTI Mean contact area | For 2–3 MTH regions, SWB insoles yield maximum offloading comparing to two other insoles type. For MTH1, NWB insoles provide maximum offloading. FWB insoles show maximum PTI comparing to NWB & SWB conditions. NWB insoles provide maximum arch support and contoured shaped insoles. |