Age over 65, higher BMI, and higher ASA comorbidity score were associated with longer operating and cutting times, ICU stay, and hospital length of stay. Those over 65 also had higher rates of transfusion. However, complication rates were generally similar between groups. Higher ASA score was associated with more minor and moderate systemic complications, but occurrence of local complications was similar between groups.

1. MAST/MISS TLIF
effect of Age, BMI & Comorbidity in 200 patients
Petrus Stone, Neurosurgeon, Private Practice
Bloemfontein, South Africa
2013-04-06

2. Disclosures
 MAST/MISS
Teaching on behalf
of Medtronic
 Sponsored
attendance/travel
 Study at my own
expense
 No animals were
harmed

3. Literature
 OPEN surgery
 Age – more
complicated
 BMI – more
complicated
 Comorbidity - more
complicated
 MI/MAST
 Age – some studies
 BMI – some studies
 Co-morbidity – no
comparisons

4. Family debate– MISS Pros & Cons
 Advantages (theoretical)
 Cosmesis,
 Pain,
 Hospital Stay,
 Blood Loss,
 Infection
 Disadvantages (theoretical)
 Fusion Rate,
 Steep Learning Curve,
 Irradiation exposure

5. Objective
 To what degree does
co-morbidity affect
(short term) outcome
 Use of Information
 Patient/procedure
selection
 Resource allocation
(length of stay, High
Care nights,
transfusion,
Physicians)

6. Patients / Materials And
Methods
 200 consecutive degenerative TLIF
cases since 2009-08-31
 Review case notes, hospital notes
(myself; senior nurse)
 Excluded 6 cases
 1x conversion to open
 1x aborted procedure (revision of
open TLIF; screw holes too big)
 1x cancellation on table (medical
aid interference)
 3 trauma thoraco-lumbar cases
 Stat analysis by UFS statistician

8. Descriptive Stats – The Procedures
 Surgical Time
 Median 3 hours (1h25-9h30) (case
no 9; 3 levels)
 Levels operated / Orange River TLIF
Class
 1: 56.5%
 A: 39%
 B-F: 15%
 2: 40%
 A: 24.5%
TLIF sub-classes to accommodate for extra
 B-F: 15.5%
work
 3: 3.5% • a – no extra work
 A: 2.5% • b – 30 minutes
• c – 60 minutes
 B-F: 1.0% • Etc
 Medtronic : n = 181 (90.5%) Examples
• Vertebroplasty;
 Navigation: n = 8 (4%) • adjacent level discectomy;
 Radiation exposure: median 3.1 • Same level wide decompression/lami;
minutes • Remove instrumentation

9. Descriptive Stats – Short term Outcome
Major  Duration follow up: 30-880
• threatening to life or limb days
function
• Early revision surgery  Length of ICU/High Care
Moderate stay
• prolonged hospital stay or  0 nights: 14,5%
outpatient treatment required
Minor  1 night: 75.5%
• inconvenient  2 nights: 9.5%
 Length of postoperative
hospital stay
 Median 3.9 days (0.9 to
17.9)
 Need for transfusion
 3.5%

10. Significant Complications
Moderate local complications %
Moderate systemic complications %
durotomies 7.5%
superficial sepsis 1.0% respiratory (chest infection, atelectasis,
sleep apnoea) 4.5%
iatrogenic end plate damage --> extra screws 0.5%
partial L5 weakness 1 (0.5%) 0.5%
arrhythmia 0.5%
persisting dysesthetic leg pain 0.5%
plunge with PAK needle (uncomplicated) 0.5% quadriceps hematoma 0.5%
screw too deep, Hb drop 0.5%
11.0% 5.5%
Major local complications % Major systemic complications %
decompression same stay 1.0% Pulmonary embolism 1.5%
fusion extension same stay 0.5% Unexpected epileptic fit 0.5%
severe L4 nerve root damage 0.5% tachy-arythmia -> cardioversion 0.5%
2.0% 2.5%

11. Age effect
Group name Age Group 2
Subgroup names <65 >65
Fisher’s Exact Test % % p-value Sig? Worse
Transfusion required 2.41 8.82 0.0969 - • Transfusion if >70:
Durotomy/CSF leak
Local (major)
6.63
1.81
11.76 0.2918 -
2.94 0.5284 -
15.8%
Local (moderate) 9.64 17.65 0.2241 - • LOS if >70: 3.8 vs
Local (minor) 0.60 0.00 1.0000 - 3.9 vs 5.7 days
• ICU stay (hours not
Local (All: M, M, M) 12.05 20.59 0.4077 -
Systemic (major) 2.41 2.94 1.0000 -
Systemic (moderate) 4.82 8.82 0.4028 - nights) if >65
Systemic (minor) 18.07 29.41 0.1577 -
Systemic (all) 25.30 41.17 0.1415 -
Local or Systemic (major) 4.22 5.88 0.6515 - Similar
Local or Systemic (moderate) 14.46 26.47 0.1914 - • Complications
Local or Systemic (minor) 18.67 29.41 0.1577 -
• Theater, Cutting,
Significant blood loss
1 night: 75.9%; 2
1 night: 75.76%; 2
Radiation time
nights: 6.63%
ICU nights nights 24.24% 0.0005 Yes
Kruskal-Wallis Test Median Median p-value Sig?
LOS postop (days) 3.80 4.90 0.0451 Yes
Theater Time (hours) 4.10 4.30 0.4115 -
Cutting Time (hours) 3.00 3.10 0.5770 -
ICU stay (hours) 20.50 21.70 0.0020 Yes
Radiation Exposure (mins) 3.10 3.10 0.6888 -

12. BMI effect
Group name BMI BMI Group 3
Subgroup names <35 >35 <35 35-40 >40
Fisher’s Exact Test % % p-value % % % p-value
Transfusion required 3.45 3.64 1.0000 3.45 0.00 7.69 0.2114
Durotomy/CSF leak 8.28 5.45 0.7642 8.28 6.90 3.85 0.9088
Local (major) 1.38 3.64 0.3038 1.38 6.90 0.00 0.1821 Worse
• ICU nights
Local (moderate) 12.41 7.27 0.4478 12.41 10.34 3.85 0.5757
Local (minor) 0.00 1.82 0.2750 0.00 0.00 3.85 0.1300
• Theater, Cutting, RE
Local (All: M, M, M) 13.79 12.73 0.1729 13.79 17.24 7.70 0.1149
Systemic (major) 2.76 1.82 1.0000 2.76 0.00 3.85 0.6015
Systemic (moderate)
Systemic (minor)
4.83
18.62
7.27
23.64
0.4985 4.83 6.90 7.69 0.6770
0.4338 18.62 24.14 23.08 0.6583
time
Systemic (all) 26.21 32.73 0.8746 26.21 31.04 34.62 0.9190
Local or Systemic (major) 4.14 5.46 0.7084 4.14 6.90 3.85 0.8519
Local or Systemic
(moderate) 17.24 14.54 0.6623 17.24 17.24 11.54 0.9036
Similar
Local or Systemic (minor)
ICU - zero nights
18.62
17.36
25.46
7.27
0.4338 18.62 24.14 26.93 0.6583
17.36 13.79 0.00
• Complications
ICU - one night 75.69 76.36 0.0381 75.69 68.97 84.62 0.0312
6.94 17.24 15.38
• Hospital LOS
ICU - two night 6.94 16.36
ICU nights
Kruskal-Wallis Test median median p-value p-value
LOS postop (days) 3.90 4.00 0.1588 3.90 3.90 4.40 0.3392
Theater Time (hours) 4.00 4.70 0.0209 4.00 4.60 5.20 0.0245
Cutting Time (hours) 2.80 3.50 0.0163 2.80 3.20 3.80 0.0216
ICU stay (hours) 21.00 22.00 0.1765 21.00 20.40 23.00 0.1687
Radiation Exposure (mins) 3.00 3.70 0.0153 3.00 3.00 5.30 0.0012

13. Comorbidity (ASA) effect
Group name ASA score ASA_Ex_BMI
Subgroup names ASA 1 ASA 2 ASA 3 ASA 1 ASA 2 ASA 3
Fisher’s Exact Test % % % p-value % % % p-value
Transfusion required 1.89 4.55 3.39 0.8867 1.59 4.69 0.00 0.5883
Durotomy/CSF leak 9.43 7.95 5.08 0.6999 7.94 7.81 0.00 1.0000
Local (major) 0.00 2.27 3.39 0.5810 0.00 3.13 0.00 0.4221 Summary
Local (moderate) 15.09 11.36 6.78 0.3714 14.29 10.16 0.00 0.5071
Local (minor) 0.00 0.00 1.69 0.5600 0.00 0.78 0.00 1.0000
More likely
Local (All: M, M, M) 15.09 13.63 11.86 0.4548 14.29 14.07 0.00 0.6124
Systemic (major) 3.77 2.27 1.69 0.7278 3.17 2.34 0.00 0.7349 • Minor & Moderate
Systemic (moderate) 1.89 6.82 6.78 0.4513 1.59 6.25 22.22 0.0491 systemic Cx
Systemic (minor) 13.21 21.59 23.73 0.3462 11.11 22.66 44.44 0.0255 • Theater & Cutting
Systemic (all) 18.87 30.68 32.20 0.6372 15.87 31.25 66.66 0.0358
time
Local or Systemic (major) 3.77 4.54 5.08 1.0000 3.17 5.47 0.00 0.8168
Local or Systemic (moderate) 16.98 18.18 13.56 0.6589 15.88 16.41 22.22 0.7344
• ICU stay? (integar
Local or Systemic (minor) 13.21 21.59 25.42 0.3462 11.11 23.44 44.44 0.0255 nights; not hours)
ICU - zero nights 26.42 12.64 6.78 26.98 9.45 0.00
ICU - one night 66.04 81.61 76.27 0.0115 66.67 81.10 66.67 0.0034
Similar occurrence
• Local Cx
ICU - two night 7.55 5.75 16.95 6.35 9.45 33.33
Kruskal-Wallis Test median median median p-value p-value
LOS postop (days) 3.80 3.90 4.00 0.2550 3.60 4.00 4.00 0.0857 • Major Systemic Cx
Theater Time (hours) 3.60 4.20 4.70 0.0063 3.50 4.50 4.10 0.0008 • Transfusion
Cutting Time (hours) 2.60 2.90 3.50 0.0153 2.40 3.30 2.90 0.0045 • ICU nights (hours
not nights)
ICU stay (hours) 20.20 21.10 22.00 0.1933 20.20 21.10 25.20 0.0362
Radiation Exposure (mins) 2.90 3.00 3.70 0.0509 2.90 3.30 2.90 0.1182
• LOS

14. Summary
 Age
 >70: longer LOS (4 vs 6 days)
 >70: transfusion more likely
(15 vs 2%)
 >65: ICU stay (hours not
nights)
 ISQ complications
 BMI
 Longer procedure, theater
time, irradiation time
 More ICU nights
 ISQ complications & LOS
 Comorbidity (ASA score)
 Longer procedure
 ISQ complications & LOS