Spijkerman et al. 1995
Netherlands
D&B=18
Pre-Post
N=18

Population: Mean age=37.7yrs; Gender: males=15, females=3; Level of injury: C2-L2; Severity of injury: complete
Treatment: Interface pressure was assessed on SCI patients using various seat inclinations.
Outcome Measures: Mean pressure

1. Body tilt had a significant effect on the mean pressure, p=0.003.
2. At seat inclination of 5, 15 and 25 overall mean pressure was 86.79, 86.90 and 82.91.

Makhsous et al. 2007a
USA
Downs & Black score=14
Case Control/Repeated Measures
N=60

Population: SCI: Paraplegics (n=20): Mean age = 35.1 yrs; Gender: males =20; Mean weight = 87.2 kg; Mean time since injury = 8.4 yrs. Tetraplegics (n=20): Mean age = 36.5 yrs; Gender: males = 15, females = 5; Mean weight = 81.8 kg; Mean time since injury = 9.2 yrs; Controls (n=20): Mean age: 39.3 yrs; Gender: males = 10, females = 10; Mean weight = 71.3 kg.
Treatment: 2-1 hour sitting protocols: 1) Dynamic protocol: alternating every 10 minutes between normal sitting (sitting upright with full seat support and no added lumbar support) and an off-loading sitting (sitting upright with position in seat section tilted down 20 degrees with pressure to IT and coccyx) configuration; 2) Wheelchair pushup protocol: one wheelchair pushup every 20 minutes, while in normal sitting configuration.
Outcome Measures:  Transcutaneous partial pressure of oxygen (tcPO2) and carbon dioxide (tcPCO2).

1. In normal sitting, mean tcPO2 at IT was < 10mmHg and mean tcPCO2 was >60mmHg, for all groups. During off loading sitting configuration, IT tcPCO2 was maintained > 50mm Hg and tcPCO2 at <45 mm Hg for all groups. During pushup protocol (avg 49 sec), IT tcPO2 increased and tcPCO2 reduced only slightly.
2. With pressure release (off loading configuration) average perfusion recovery time for tcPO2 was 200-250 seconds for all groups.
3. tcPO2 perfusion recovery time was significantly shorter for control group than SCI groups, p<0.001.

Coggrave & Rose 2003 UK
Downs & Black score=14
Case Series
N=50

Population: SCI: Age = 20-83 yrs; Gender: males = 33, females = 13; Time since injury = 5 wks-50 yrs.
SCI, Frankel grade A-D
Treatment: Retrospective chart review.
Outcome Measures: Effect of pressure relief on transcutaneous oxygen tension (TCPO2).

1. Mean duration of pressure relief required to raise tissue oxygen to unloaded levels was 1 min 51 sec (range 42 secs-3½ mins).
2. Leaning forward with elbows or chest on knees, leaning from side to side or tilting back in wheelchair to > 65o were all effective for pressure relief (raising TCPO2 to unloaded levels) and more easily sustained for most individuals than a pressure relief lift.
3. Resulted in a change in practice at the seating clinic.

Henderson et al. 1994 USA
Downs & Black score=12
Case Series
N=10

Population: SCI: Age = 22-67 yrs; Gender: males = 9, females = 1; Time since injury = 1 mnth to 7 yrs.
Treatment: Subjects sat upright in wheelchair in neutral position; tipped backward at 35o & 65o; assisted to lean forward (>45o from wheelchair backrest). Pressures were measured at ischial tuberosity (IT) (point pressure) and circumscribed area around IT.
Outcome Measures: Pressure levels.

1. Average pressure in the resting seated position was 189 mmHg for point pressure area and 114 mmHg for the circumscribed area.
2. When patients were in the 65o backward tip position there was a 47% reduction in maximum point pressure and 36% reduction for the circumscribed area pressure. (p<0.05).
3. In the leaning forward position there was a 78% reduction in maximum point pressure and a 70% reduction in circumscribed area (p<0.05).

Hobson 1992
USA
Downs & Black score=10
Case Control
N=22

Population: SCI: Mean Age = 40.9 yrs; Gender: males = 10, females = 2; Mean weight = 59.8 kg; Level of injury: paraplegia = 7, tetraplegia = 5; Severity of injury: complete; Mean time since injury = 19.5 yrs; Chronicity = chronic. Able-Bodied: Mean age = 39.3 yrs; Gender: males = 6, females = 4.
Treatment: Nine typical wheelchair sitting postures.
Outcome Measures: Tangentially induced surface shear (TIS); Interface pressure.

1. Mean maximum pressure was on average 26% higher in the SCI group versus the able-bodied group.
2. Forward trunk flexion of 50° reduced the average pressure for both groups; however, SCI group encountered a 10% increase in pressure at the initial 30° of forward flexion before a reduction occurred.
3. SCI subjects had a mean peak pressure gradient that was 1.5-2.5 higher than able-bodied subjects. Maximum decrease of peak pressure gradient from a neutral position happened after the backrest reclined to 120° (18%).
4. When a sitting position change occurred, a similar shift to the anterior/posterior midline location of maximum pressure was experienced in both groups. From neutral, a forward trunk flexion at 30° and 50° produced a 2.4 and 2.7cm posterior shift. When the backrest reclined to 120°, the greatest posterior shift occurred at 6cm.
5. Maximum reduction of TIS occurred with forward trunk flexion of 50° (-133%) and full body tilt of 20° (-85%). Backward recline to 120° caused increase in TIS of 25%.