Makhsous et al. 2007b
USA
Downs & Black score=18
Case Control
N=60

Population: Mean age = 37 yrs; Gender: males = 45, females = 15; Level of injury: paraplegia = 20, tetraplegia = 20, and able-bodied = 20.
Treatment: Two one hour protocols. 1) Alternative – sitting position was altered every 10 minutes between normal and WO-BPS (partially removed ischial support and lumbar support). 2) Normal – normal posture and pushups every 20 minutes.
Outcome Measures: Interface pressure on backrest and seat.

1. Those with tetraplegia had a larger contact area at the anterior portion of the cushion, as compared to the other groups.
2. The mean pressure over the whole cushion was significantly different for each group (p<0.001).
3. Tetraplegics had the highest mean pressure during the WO-BPS posture, as compared to the other groups (p<0.001).
4. The contact area of the posterior portion of the cushion and the peak interface pressure decreased in all groups, with the largest decrease in tetraplegics for the latter. The mean pressure on the anterior and middle portions of the cushion increased in all groups.
5. At the posterior portion of the seat where ischial tuberosities are usually positioned, average pressure was higher for those with paraplegia (88.9 mmHg).
6. Average push up time was 49 sec for those with paraplegia.

Burns & Betz 1999
USA
Downs & Black score=17
Prospective controlled trial
N=16

Population: Mean age = 46 yrs; Gender: males = 16; Level of injury: tetraplegic; Severity of injury: AIS: A = 7, B = 9.
Treatment: Two static wheelchair cushions (dry flotation and gel) upright and at 45° tilt, compared to a dynamic cushion that was composed of two air bladders (H & IT) that alternated between inflation and deflation.
Outcome Measures: Interface pressure at ischial tuberosities (IT) was assessed with Clinseat seating interface pressure sensor.

1. When compared in the high pressure condition, all cushions were significant (p<0.001), with means of 111 mmHg (dry flotation), 128 mmHg (gel), and 157 mmHg (dynamic).
2. When compared in the low pressure condition, only gel flotation (86 mmHg), and the dynamic cushion (71 mmHg), were significant (p<0.05).
3. The IT had a significantly higher mean during IT bladder inflation of the dynamic cushion than the high pressure position in the static cushions (p<0.01), with the dry flotation having significantly lower pressure than the gel cushion (p<0.01).
4. The IT had significantly lower mean in the lower pressure position only for the dynamic cushion as compared to the gel cushion (p<0.01).

Gilsdorf et al. 1991
USA
Downs & Black score=14
Case Series
N=17

Population: Paraplegics (N=6): Mean weight = 83 kg; Tetraplegics (N=5): Mean weight = 66 kg; Able-bodied controls (N=6): Mean weight = 76 kg.
Treatment: 30 minute sitting intervals, on different surfaces [Jay cushion; ROHO cushion; hard surface (controls only)] in a wheelchair that had a forceplate attached to it.
Outcome Measures: Normal & shear seating forces; Armrest forces; Centre of mass location.

1. On Jay cushion, tetraplegics had higher amplitude lateral movements and paraplegics had more lateral zero-crossings, when compared to ROHO cushion.
2. Larger arm force variation was found in paraplegics.
3. On the ROHO cushion, all subjects had larger normal and shear forces and an anterior centre of mass.
4. Paraplegics had more variation, while tetraplegics had less, on static force factors between cushion types.
5. SCI groups had higher force measurements than control group.
6. Armrest forces applied by paraplegics were larger than those applied by tetraplegics (8-9% vs. 5%, p<0.11).

Brienza & Karg 1998 USA
Downs & Black score=14
Case Series
N=12

Population: SCI: Age: 21-52 yrs; BMI = 17-32.3 kg/m2.
Treatment: Assessed forces for 3 different surfaces (flat foam, initial contour and final optimized contour) with the force sensing array (FAS) pad between the cushion and buttocks. Compared SCI to elderly subjects (No SCI).
Outcome Measures: Pressure mapping, BMI.

1. Depth values for the SCI group↑ from 37.9 mm to 52.5 mm (p<0.001).
2. A significant increase was also noted for the elderly group.
3. The mean max depth of the final contour was deeper for the SCI group (p=0.016).
4. Mean pressure values for initial and final cushions were significantly less than for flat cushions (p=0.006, p=0.003 respectively).
5. In general, mean and peak pressure were greater for the SCI subjects than for elderly subjects.
6. BMI was significantly related to peak and mean pressure values.

Seymour & Lacefield 1985
USA
Downs & Black score=13
Case Control
N=20

Population: Age = 16-35 yrs; Weight = 40.6-72.5 kg; 10 cases, 10 controls.
Treatment: 7 commercially available cushions and 1 experimental cushion were evaluated for each subject.
Outcome Measures: Temperature and pressure effects for each cushion. Subjects were asked to rate each cushion as to cosmesis, handling and suitability for purchase.

1. Greatest pressure was seen under the soft tissue areas of most subjects; no significant differences between the cases and controls.
2. Temperatures were lowest for gel, water and air cushions and highest for alternating pressure and foam cushions.
3. SCI group - Greatest pressure under a bony area occurred most often with the Spenco cushion (90.10 mmHg); controls - it occurred most often with the Tri-pad (89.20 mmHg) indicating that these cushions did not compare favorably to others.
4. There was wide variability in pressure measurements in individual subjects (SD=12.21 mmHg).  However, air filled (Bye Bye Decubiti) had the best pressure readings.
5. Cosmesis (83%) and handling (73%) were related to purchase decisions.

Garber 1985
USA
Downs & Black score=8
Case Series
N=251

Population: SCI: Gender: males = 207, females = 44.
Treatment: Assessment of pressure distribution for 7 cushions.
Outcome Measures: Seated pressure distribution.

No statistical results reported.

1. The air filled cushion (ROHO which was 1 of 2 used) produced the greatest pressure reduction in 51% of the subjects.
2. A foam cushion (the stainless comfy hard cushion) was effective for only 18% of the subjects even though it was the second most frequently prescribed cushion.
3. More subjects with tetraplegia received the ROHOs than subjects with paraplegia (55% vs. 45%) while more paraplegic subjects were prescribed the Jay cushion (a combination of foam and flotation materials (19% vs. 7%).

Takechi & Tokuhiro 1998
Japan
Downs & Black score=6
N=6
Case Series

Population: Age = 18-48 yrs; Gender: males = 6; Level of injury: paraplegia = 6; Severity of injury: complete = 6.
Treatment: Five different cushions (air cushion, contour cushion, polyurethane foam cushion, Cubicushion, silicone gel cushion).
Outcome Measures: Tekscan BigMat pressure mapping system measuring peak pressures and area of total contact.

1. If the area of contact was more widespread, the peak pressure was found to be lower.
2. The air cushion had the largest area of pressure distribution and the lowest peak pressure (257-87g/cm2). The silicone cushion hadthe second lowest (292-129g/cm2) peak pressure.