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Methods (cont’d) Discussion

ISOMETRIC STRENGTH AND FUNCTIONAL TESTING AFTER MPFL RECONSTRUCTION IN ADOLESCENT ATHLETES

Michael Saper, DO, ATC, CSCS; Peter Fantozzi; Viviana Bompadre, PhD; Mimi Racicot, PT, DPT, SCS; Greg Schmale, MD Seattle Children’s, Department of Orthopaedics and Sports Medicine, Seattle, WA

Background Results Return to sport (RTS) after patella stabilization surgery involves the return of strength and dynamic knee stability, which can be assessed using isometric strength and performance testing. Despite reports of objective strength recovery and performance-based outcome measures after ACL reconstruction in the adolescent population, such reports in patients after medial patellofemoral ligament (MPFL) reconstruction are limited.1-3

•  To compare isometric strength and functional tests in the reconstructed limb with the non-injured limb.

•  An IRB-approved retrospective study. •  21 athletes (15 girls, 6 boys) underwent

MPFL reconstruction between May 2014 and June 2017 and underwent isometric and functional RTS testing.

•  Single pediatric fellowship-trained orthopedic surgeon.

•  Patients with bilateral surgery/complaints were excluded.

•  Indwelling femoral nerve catheters (94.7%) or a single shot femoral nerve block (5.3%).

•  Tourniquets were not utilized.

•  Peak torques during isometric strength testing were performed with a handheld digital dynamometer (Fig. 1).

•  Functional tests included: Lower Quarter Y-Balance Test (LQYBT) (Fig. 2) and single-leg hop testing (Fig. 3).

•  Limb Symmetry Indices (LSI) were

calculated using the following: LSI = (involved/uninvolved) x 100%.

•  Recovery of muscle strength was defined by an LSI ≥ 90%.

•  Passing the functional dynamic testing was defined as LSI ≥ 90% on all 4 components of the hop test.

•  Differences in peak torque between the involved and uninvolved limbs were compared using paired t-tests.

•  Correlations were examined among dependent and independent variables

•  Adolescent athletes undergoing patella stabilization surgery do not consistently recover satisfactory strength and dynamic knee stability by 7.9 months postoperatively.

•  There was a significant deficit in isometric strength in the involved limb after surgery, with deficits more pronounced in the quadriceps.

•  Limitations included small sample size, no control group, single surgeon, lack of patient-reported outcome measures.

•  After MPFL reconstruction, adolescents

may need prolonged rehabilitation programs beyond 8 months to allow for adequate recovery of muscle strength for safe RTS.

Purpose

Table 1. Patient Demographics Characteristic Value Age (y), mean (range) 15 (12-17) Graft Type (% auto) 66.6 Time to test (mo), mean (range) 7.8 (5.5-11.9) Concomitant TTO (%) 38.1

•  LQYBT composite scores positively correlated to hip abduction strength (r = 0.515, P = 0.035).

•  Only 46% of patients were able to achieve satisfactory performance on all 4 hop tests.

References 1.  Greenberg EM, Greenberg ET, Ganley T, Lawrence JT. Strength and

functional performance recovery after anterior cruciate ligament reconstruction in preadolescent athletes. Sports Health. 2014;6(4)309-312.

2.  Menetry J, Putnam S, Gard S. Return to sport after patellar dislocation or following surgery for patellofemoral instability. Knee Surg Sports Traumatol Arthosc. 2014;22(10):2320-2326.

3.  Krych A, O’Malley M, Johnson N, Mohan R, Hewett T, Stuart M, Dahm D. Functional testing and return to sport following stabilization surgery for recurrent lateral patellar instability in competitive athletes. Knee Surg Sports Traumatol Arthrosc (2016) doi:10.1007/s00167-016-4409-2.

Author Contact : Michael.saper@seattlechildrens.org

Methods Table 3. LSI of Involved Leg (%) Functional Test Data* LQYBT-composite 97.8 ± 3.7 Single hop for distance 89.8 ± 16.2 Triple hop for distance 94.0 ± 5.7 Crossover hop for distance 96.3 ± 12.1 Timed hop 100.5 ± 11.1 *Data reported as mean ± SD

Figure 2. LQYBT

Figure 1. Hip abduction Isometric strength testing

Figure 3. Diagram of single-leg hop tests

Conclusions

Table 2. Peak Torque (lbs)* and LSI (%) Test Involved Uninvolved LSI P Knee

Extension 69.8 ± 22.3 77.3 ± 19.7 84.4 0.043

Knee Flexion 41.1 ± 9.2 45.3 ± 9.5 93.5 0.083

Hip Abduction 23.4 ± 6.6 24.8 ± 21.8 97.8 0.045

*Data reported as mean ± SD