1. Effect of BMI on Patients with Multiligament Knee Injuries
TJ Ridley, MS4
Shane Cook, MD
Matthew Bollier, MD
Mark McCarthy, MD
Brian Wolf, MD
Ned Amendola, MD

2. Disclosures
Neither I, TJ Ridley, nor any family member(s), author(s), have any relevant financial relationships to be discussed, directly or indirectly, referred to or illustrated with or without recognition within the presentation

3. Multiligament Knee Injuries
Disruption of at least two major knee ligaments

4. Our Study Purpose
Evaluate impact of BMI on complications, associated injuries and mechanism of injury in surgically treated MLKI
Our goal was to evaluate the impact of body mass index (BMI) on complications and associated injuries in patients undergoing surgical treatment for multiligamentous knee injuries (MLKI).

5. Hypothesis
Post-operative complications as well as NV injuries and lower mechanisms of injury would occur more frequently in obese and morbidly obese patients.

6. 10 year Retrospective Review 126 MLKI (123 pts)
Inclusion Criteria
Injury to 2 or more knee ligaments
Multiligament repair and/or reconstruction performed by 1 of 3 sports medicine orthopaedic surgeons at our institution
One year minimum follow-up.

7. 10 year Retrospective Review 126 MLKI (123 pts)
BMI divided into
non-obese
obese
morbidly obese
BMI
# Pts
<30 87 29
>40 10

8. Number of ligaments injured in each group%
Additionally, we investigated knee dislocations, defined as an MLKI that involved both cruciates as well as one or more collateral ligaments
*defined as an MLKI that involved both cruciates as well as one or more collateral ligaments

9. %Revisions/Failed Graphs
Results
BMI
%Complications
%MUA
%Revisions/Failed Graphs
<30
8.05
13.79
10.34
>40 30 10 20
Surgical complications rates for non-obese, obese and morbidly obese patients were 8.05%, 10.34%, and 30%, respectively (P = 0.10). Complications included failed grafts, need for revision surgery, wound infections, and one DVT/PE (BMI 51). Manipulations under anesthesia (MUA) in these groups were 13.79%, 13.79%, and 10%, respectively. Revisions were needed in 8.05%, 0% and 20% of patients in these groups. Three wound complications were found in the obese group only

10. BMI vs Complication Rate

11. Results Cont. BMI Vasc. Inj (%) Nerve Inj (%) <30 2.3 11.49
10.34
20.69
>40 20
P = 0.13
P = 0.34
Images from Mark’s presentation, need help interpreting…
Vasc Inj: P = 0.129
Nerve Inj: P = 0.34

12. Mechanism of Injury BMI % Sports Injury % Low Energy % High Energy
<30
35.63
22.99
41.38
17.24
48.28
34.48
>40 10 60 30

13. BMI vs Mechanism of Injury

14. BMI as Continuous Variable
One unit increase in BMI increased OR of complications by 9.2%
p =
Lastly, we analyzed BMI versus complications with BMI as a continuous variable. Using odds ratio estimates and Wald confidence intervals, it was found that one unit increase in BMI increases the odds ratio of complications by 9.2%, with statistical significance (P = ).

15. Discussion

16. Increased Prevalence in Increased BMI
Peltola et al., Knee dislocation in overweight patients AJR AM J Roentgenol. 2009
Retrospective study: 24 patients with dislocation
11 BMI (45.8%) >25
2/11 BMI >40
Our study
86/126 (68.3%) BMI >25
BMI
# Pts
<30 89 29
>40 10
Increased body mass of patients remains a risk factor for low-energy knee dislocations, neurovascular injuries and postoperative complications. Current literature suggests that obesity is a risk factor for dislocation, and dislocation with low-energy mechanisms6-9,11
Several case reports have described low-velocity or ‘‘spontaneous’’ knee dislocations in obese patients4-9. Peltola et al.18, in a retrospective study of knee dislocations, evaluated the prevalence and cause of knee dislocations in patients with normal or increased body-mass indices. Of twenty-four patients, eleven had BMIs that were >25, and two of those eleven patients had BMI >40. Nine of the eleven overweight patients had sustained a knee dislocation due to low-energy trauma
Our study also found that MLKI undergoing surgical treatment were more prevalent in overweight and obese patients, with 86 out of the 126 total MLKI having a BMI >25.

17. Mechanism of Injury
Werner et al., Ultra-Low Velocity Knee Dislocations: Patient Characteristics, Complications, and Outcomes. AJSM 2013
12 year Case Series: 215 patients, 23 with “Ultra-low Velocity” dislocations
BMI significantly higher in ULV cohort
49.1 vs 34.1
Peltola et al. 9/11 Low-Energy Injury
Furthermore, in agreement with current literature, our study found that obese and morbidly obese individuals are more likely to have a MLKI caused by low-energy mechanisms (Table 1). Werner et al.11 also found that the average BMI was significantly higher in their ultra-low velocity (ULV) cohort (49.1 kg/m2 vs 34.1 kg/m2). Increasing number of reported cases may suggest that low-energy knee dislocations, although infrequent, may becoming more common. It is well known that obesity is widespread in the adult population, and we are continuing to see the effect of this epidemic on orthopaedic surgeons.
BMI
% Sports Injury
% Low Energy
% High Energy
<30
35.63
22.99
41.38
17.24
48.28
34.48
>40 10 60 30

18. Vascular Injury Case Series: 17 patients, avg BMI 48 Werner et al.
Azar et al. Ultra-low-velocity knee dislocations. AJSM 2011
Case Series: 17 patients, avg BMI 48
Vascular Injuries average BMI 54 (range 47-60)
Werner et al.
28.1% vascular injury in heavy ULV cohort, vs 4.7% in healthy ULV cohort
Current literature has shown that the risks of associated neurovascular injury are also higher in patients with increased BMI8-11, Azar et al.19 concluded that neurovascular injuries are frequent with knee dislocations in severely obese patients, and the likelihood of combined neurovascular injury tends to increase as BMI increases. Vascular injury is reported to occur in 25% to 30% of all knee dislocations3,9,13-15,17,
In a case series of ultra-low velocity knee dislocations by Azar et al.19, patients with vascular injuries had an average BMI of 54 (range, 47-60). Werner et al.11 also found that peroneal nerve injuries tended to occur more commonly in their heavier ULV cohort (39.1%) compared with all other patients with MLKI (8.4%), as well as vascular injuries (28.1% vs 4.7%). The rates of vascular injuries in our patients as it relates to BMI were less conclusive.
BMI
Vasc. Inj (%)
<30
2.3
10.34
>40

19. Nerve Injury
Azar et al. Ultra-low-velocity knee dislocations. AJSM 2011
Patients with nerve injury had average BMI 47 (range 42-67)
Combined nerve and vascular injury
Average BMI 60 (range 51-68)
BMI
Nerve Inj (%)
<30
11.49
20.69
>40 20
The reported frequency of neurologic injury with knee dislocation varies greatly in the literature, with reports of 9% to 49% (average, 22%)19.
Azar et al.19 found that patients with nerve injuries had an average BMI of 47 (range, 42-67); and those with both nerve and vascular injuries had an average BMI of 60 (range, 51-68).
our study found increased rates of nerve injuries in the obese and morbidly obese patients, although this was not a statically significant finding (P = 0.34).

20. Complications BMI significantly higher in ULV cohort (49.1 vs 34.1)
Werner et al., Ultra-Low Velocity Knee Dislocations: Patient Characteristics, Complications, and Outcomes. AJSM 2013
BMI significantly higher in ULV cohort (49.1 vs 34.1)
Significantly higher complication rate among ULV cohort compared with all other MLKI
73.9% vs 21.4%
Werner et al.11 in their retrospective review of 215 patients with MLKI found a significantly higher overall complication rate among the “heavier” ULV-MLKI (73.9%) compared with the entire MLKI cohort (21.4%). Additionally, Werner et al.11 reported the ULV-MLKI cohort had a higher reoperation rate, wound infection rate, and DVT rate.
While the increasing rate of complications in the three BMI groups was not statistically significant (8.05%, 10.34%, and 30%, P = 0.10), we were able to conclude with statistical significance that one unit increase in BMI increases the odds ratio of complications by 9.2%(P = ).
Complication Rate (%)
BMI

21. Complication Prevention
Azar et al. Ultra-low-velocity knee dislocations. AJSM 2011
Bilateral LE Ultrasound to rule out DVT
Provisional Joint Spanning Ex-Fix
Minimize Tourniquet Use
Obese Patients Kept NWB Longer Post-op
Complications may be decreased with a careful attention to details (Azar). Bilateral lower extremity ultrasounds have been suggested due to the high risk of DVT and PE in these patients. Provisional joint-spanning external fixation for several weeks may be also beneficial in certain cases. Tourniquet use should be minimized when possible. Lastly, obese patients should be kept non-weightbearing for a longer period of time post-operatively.

22. Study Limitations Large tertiary care center, difficult follow-up
Operative database
3 surgeons, varying techniques
Relative rarity of MLKI*
Our retrospective study has several limitations that very similarly echo those of previous studies11. Our tertiary care center has a large referral area with economically disadvantaged patients making it difficult for patient follow-up. Our study was also based on an operative database of patients leading to the inability to draw conclusions about non-operative treatment in MLKI. Lastly, the rarity of MLKI and small cohort of patients decreases the power and increases the difficulty in finding statistical significance. However, our cohort is among the largest in current literature.
Arciero, AJSM 2010
LaPrade, JBJS 2011

23. Conclusions
Surgical complications tended to occur more frequently in morbidly obese patients
Likelihood of neurovascular injuries tends to increase in obese patients
Obese and Morbidly obese more likely to have MLKI due to low-energy mechanisms
For every one unit increase in BMI, complication rates increased by 9.2%

24. Thank You