RESULTS
Patient Demographics & Clinical Outcomes
Of the patients eligible for study inclusion 145 of 176 (82.4%) patients completed all
surveys. 35 patients did not report engagement in sports prior to surgery, leaving 44 patients who
underwent isolated MPFLR and 66 patients who underwent concomitant MPFLR and TTO
available for matching. Prior to propensity score matching, iMPFLR and TTO patients had
significantly different clinical follow-up (46.4 ± 20.8 vs 56.0 ± 27.9 months, p = 0.043) and BMI
(25.2 ± 5.3 vs 27.9 ± 6.7, p = 0.041), while age (24.3 ± 9.1 vs 26.1 ± 9.3 years, p = 0.191) and
sex distribution (p = 0.338) were not significantly different.
After propensity score matching based on age, sex, BMI, and length of follow-up time,
the final cohort was consisted of 37 patients who underwent MPFLR and concomitant TTO
matched to 37 patients who underwent isolated MPFLR. Post-matching balance diagnostics
demonstrated an 87.0% reduction in the standardized mean difference (SMD) of the logit
propensity score between the two groups and a variance ratio of 0.949 with a 62.3% balance
improvement.
Demographics and clinical outcomes of the matched cohorts are shown in Table 1. The
mean follow-up of the group was 52.5 months (range: 24-117). A majority of the cohort was
female (70.2%). Patients who underwent TTO were found have been experiencing symptoms of
instability for a mean of 69 months, which was significantly longer compared to 44.6 months for
the iMPFLR group (p = 0.011). Even so, there were no significant differences with respect to
clinical outcomes between groups with respect to VAS pain, surgery satisfaction, Kujala, Tegner
scores, or MPFL-RSI (Table 1).
Preoperative Risk Factors
When comparing the two groups, patients who underwent TTO had significantly greater
TT-TG distances compared to the iMPFLR group (19.5 vs 14.4, p <.001). While all included
patients had preoperative MRI, only 27 patients in the iMPFLR group and 28 patients in the TTO
group additionally had preoperative lateral radiographs. Among these patients, the TTO group
had nearly double the rate of patella alta (35.7% vs 18.5%, p = 0.102), though this difference was
not significant. With respect to the Dejour classification, there was also nearly double the rate of
patients with Dejour B or C in the TTO group (42.8% vs 22.2%) compared to the iMPFLR
group. There were no patients who were classified as Dejour D (Table 2).
Rate of Return to Sport & Time to Return
The rate of return to sport for the iMPFLR cohort (67.6%) was similar to that the TTO
cohort (73.0%), p = 0.611. There was also no significant difference with respect to the rate of
return to pre-injury sport level (46.0% vs 40.5%, p = 0.826). Isolated MPFLR patients returned
significantly more quickly at a mean of 8.4 ± 4.5 months, while TTO patients returned at a mean
of 12.4 ± 6.6 months (p = 0.019). This was also true when only comparing those who returned to
their pre-injury sport level, with iMPFLR patients returning at 7.3 ± 4.3 months postoperatively
and TTO patients at 12.6 ± 5.5 months (p = 0.008).
When examining return to sport based on the Dejour classification in the entire cohort, it
was found that patients with Dejour B or C (no patients were class D) took significantly more
time to return to sport than those with no or mild trochlear pathology (59.9 ± 26.7 vs 34.3 ± 18.9
weeks, p = 0.003). However, their respective rates of return to sport (77.8% vs 69.4%, p = 0.519)
or return to pre-injury level of sport (41.7% vs 44.4%, p = 0.846) did not significantly differ in
this comparison.
Reasons for Lack of Return & Psychological Readiness
Overall, the MPFL-RSI passing rate (score greater than 56) was similar between iMPFLR
and TTO groups (48.6% vs 54.1%, p = 0.555). Mean MPFL-RSI scores were not significantly
between groups (53.9 ± 30.1 vs 62.4 ± 26.5, p = 0.184).
Regarding reasons patients provided for not returning to sport or to a lower level, fear of
re-injury was the most cited reason in both the iMPFLR (n = 7, 33.3%) and TTO groups (n = 9,
42.9%). These reasons are further detailed in Table 3.
Predictors of Return to Sport
Multivariable logistic regression was utilized to assess the association of the
aforementioned candidate variables with the rate of return to sport at any level, as well as the rate
of return to pre-injury level. There were no preoperative characteristics found to be significantly
associated with respect to return to sport at any level (Table 4). However, when examining
patients who return to pre-injury sport level, both decreasing age (OR 1.25, 95% CI [1.04 –
1.50], p = 0.020) and male sex (OR 87.73, 95% CI [3.45 – 2230.34], p = 0.007) were
characteristics that were associated with significantly increased odds of return to a pre-injury
level of sport.
With respect to the time taken to return to sports postoperatively, it was found that
patients with Dejour B or C were significantly more likely to take a longer time than those with
mild or no trochlear pathology (β 28.69, [0.97 – 56.42], p = 0.043).
The association between MPFL-RSI and the rate of return to sports was examined in a
logistic regression controlling for age, sex, BMI, concomitant TTO, and duration of symptoms, it
was found that increasing MPFL-RSI score was significantly predictive of return to sport (OR
1.08, 95% CI [1.03, 1.13], p<.001), as well as return to pre-injury level of sport (OR OR 1.08,
95% CI [1.04, 1.13], p<.001).
Return to Work
Among the 37 patients who underwent isolated MPFLR, 23 had been employed prior to
surgery, while there were 26 patients in the TTO group that worked prior to surgery. Isolated
MPFLR patients returned to work at a rate of 95.2% at 3.1 ± 4.2 months, while TTO patients
returned to work at a rate of 88.4% at 4.9 ± 4.5 months. Neither the rate of return (p = 0.617) nor
time (p = 0.063) were found to be significantly different between cohorts. There was also no
significant difference found with respect to their ability to return to their subjective pre-injury
work level with 76.2% of the iMPFLR group and 65.4% of the TTO group endorsing this
statement (p = 0.421).
When examining return to work based on the Dejour classification in the entire cohort, it
was found that patients with Dejour B or C (no patients were class D) took more time to return to
work than those with no or mild trochlear pathology (20.3 ± 17.9 vs 11.0 ± 13.8 weeks, p =
0.058). However, their respective rates of return to work (100% vs 90.9%, p = 0.529) or return to
pre-injury level of work (90.0% vs 87.5%, p = 1.000) did not significantly differ in this
comparison.
Complications
There were 6 patients (16.2%) in the iMPFLR group that required subsequent
manipulation under anesthesia (MUA) for arthrofibrosis, while 3 patients (8.1%) in the TTO
group required MUA. The rate of any secondary procedure following MPFLR was 7 patients in
both iMPFLR (18.9%) and TTO groups (18.9%). There was a single instance of recurrent
instability in the iMPFLR group after a patient suffered persistent instability and subluxation
episodes, requiring revision MPFL reconstruction 12 months later. In the TTO group, there were
3 patients who required subsequent removal of hardware. One patient fractured the anteriorized
tip of the tibial osteotomy due to a fall from standing height, requiring removal of the femoral
tenodesis screw, though the patella was stable and aligned. The other two patients had prominent
and painful hardware with evidence of non-union on imaging. These patients underwent removal
of deep screws and the areas of non-union were augmented with a combination of demineralized
bone matrix and autologous bone marrow aspirate from the iliac crest.
TABLE 1
Patient Demographics & Clinical Outcomes
Demographics
iMPFLR
TTO
p
N (patients)
37
37
Sex (female)
27 (70.2%)
27 (70.2%)
1
Age (years)
25.8 ± 10.4
26.1 ± 8.6
0.402
BMI
26.0 ± 6.1
26.2 ± 5.3
0.534
Symptom duration (months)
44.6 ± 70.3
69.3 ± 69.2
0.011
Follow-up (months)
50.6 ± 23.2
54.3 ± 26.9
0.717
VAS Pain
1.5 ± 2.3
1.1 ± 2.0
0.447
VAS Pain During Sport
2.4 ± 2.9
2.6 ± 2.8
0.717
Mean Satisfaction (%)
83.3 ± 26.3
85.0 ± 23.9
0.743
Kujala
84.9 ± 15.3
85.0 ± 15.3
0.505
Tegner - Pre-Injury
6.7 ± 2.1
5.7 ± 2.8
0.159
Tegner - Post-Injury
3.2 ± 1.9
2.8 ± 2.3
0.419
Tegner - Current
5.0 ± 2.0
5.0 ± 2.3
0.843
53.9 ± 30.1
48.6 (18)
62.4 ± 26.5
54.1 (20)
0.184
0.555
Clinical Outcomes
MPFL-RSI
MPFL-RSI Passing Rate, % (n)
*Concomitant tibial tubercle osteotomy during medial patellofemoral ligament reconstruction (MPFLR)
†Visual Analog Score
‡Difference in Tegner score was calculated as the difference between the score at latest follow-up and preinjury score
Abbreviations: TTO tibial tubercle osteotomy, VAS Visual Analog Scale, MPFL-RSI Medial Patellofemoral
Ligament Return to Sport Index
TABLE 2
Preoperative Risk Factors
Characteristic
TT-TG (mm)
Preoperative lateral x-ray
Caton-Deschamps Index
Patella alta, n (%)
Dejour class, n (%)
None
A
B
iMPFLR
(n=37)
TTO
(n=37)
14.4 ± 2.9
n=27
1.11 ± 0.13
5 (18.5)
19.5 ± 3.2
n=28
1.12 ± 0.22
10 (35.7)
19 (70.4)
2 (7.4)
6 (22.2)
12 (42.9)
3 (10.7)
10 (35.7)
p
<.001
0.695
0.102
0.189
-
C
D
-
2 (7.1)
-
-
TABLE 3
Reasons for Lack of Return to Sport at the Same or Higher Pre-Injury Level
Cohort
Reason for Lack of Return
iMPFLR
No Return, n (%)
Lower Level, n (%)
Overall, n (%)
Physical Symptoms
5 (41.7)
-
5 (23.8)
Pain
2 (16.7)
1 (11.1)
3 (14.3)
Fear of Re-Injury
Lack of Confidence
3 (25.0)
2 (16.7)
4 (44.4)
-
7 (33.3)
2 (16.7)
-
4 (44.4)
4 (19.0)
Physical Symptoms
3 (30.0)
-
3 (14.3)
Pain
3 (30.0)
2 (13.6)
5 (23.8)
Fear of Re-Injury
2 (20.0)
7 (63.6)
9 (42.9)
Lack of Confidence
1 (10.0)
-
1 (4.8)
Lifestyle Factors
1 (10.0)
2 (13.6)
3 (14.3)
Lifestyle Factors
TTO
TABLE 4
Multivariate Regression for Predictors of Return to Sport & Time to
Return Based on Preoperative Characteristics
Odds Ratio or
95% Confidence
Beta Coefficient
Interval
Logistic regression for Return to Sport at Any Level
Age
1.08
0.94 – 1.24
Sex
>999
<0.01 – >999
BMI
1.02
0.88 – 1.19
TTO
0.61
0.09 – 4.40
Symptom duration
0.99
0.97 – 1.01
TT-TG
1.31
0.91 – 1.89
Dejour classification
1.02
0.14 – 7.56
Patella alta
5.89
0.44 – 78.87
Logistic regression for Return to Pre-Injury Sport Level
Age
1.25
1.04 – 1.50
Sex
87.73
3.45 – 2230.34
BMI
1.08
0.92 – 1.28
TTO
2.15
0.19 – 24.33
Variable
p
0.278
0.999
0.782
0.627
0.281
0.146
0.984
0.181
0.020
0.007
0.335
0.536
Symptom duration
0.99
TT-TG
1.06
Dejour classification
2.11
Patella alta
15.88
Linear regression for Time Taken to Return to Sport
Age
0.32
Sex
-11.92
BMI
0.18
TTO
19.54
Symptom duration
-0.16
TT-TG
-0.27
Dejour classification
28.69
Patella alta
-9.09
0.97 – 1.01
0.73 – 1.52
0.11 – 39.19
0.80 – 316.06
0.493
0.772
0.617
0.070
-1.02 – 1.67
-35.94 – 12.10
-1.55 – 1.90
-5.87 – 44.94
-0.38 – 0.06
-3.99 – 3.45
0.97 – 56.42
-33.72 – 15.53
0.617
0.308
0.831
0.123
0.148
0.880
0.043
0.445