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Establishing Normal Variances and Expectations for Quadriceps Limb Symmetry Index Benchmarks Based on Time from Surgery After Anterior Cruciate Ligament Reconstruction

Hazzard, S., Connolly, S., Wiater, A., Sprague, I., Doolan-Roy, E., Lampros, R. and Asnis, P.D., 2024. Establishing Normal Variances and Expectations for Quadriceps Limb Symmetry Index Benchmarks Based on Time from Surgery After Anterior Cruciate Ligament Reconstruction. International Journal of Sports Physical Therapy, 19(4), p.410.

In today’s letter

• Overview of the expected quad strength month by month post bone-tendon-bone graft from ACL reconstruction patients

• Rapid Results = Rapid Results = Patients undergoing bone-tendon-bone autograft are estimated to have 80% quadriceps symmetry at an average of 5.7 months for males and 7.1 months for females

• 3 Reads to check out to further you knowledge about ACL’s

• Meme of the week: I guess you’re never sitting down 😄 

Aim of study

• The study aimed to assess the variations in quadriceps strength percentages and functional benchmarks at different stages after anterior cruciate ligament (ACL) reconstruction surgery, considering factors such as sex, age, and graft type.

• The authors hypothesised that the majority of patients, particularly those with autograft ACL reconstructions, would not achieve 80% quadriceps symmetry until 4-6 months after surgery

Did you know?

• Post-operative rehabilitation after ACL reconstruction, with an emphasis on achieving quadriceps strength symmetry, has been having significant attention, especially for athletes returning to sports that involve pivoting movements.

• Various return-to-sport assessments and protocols have been proposed, with numerous studies showing that meeting specific criteria, such as quadriceps strength symmetry, can reduce the risk of reinjury.

Why?

Because it helps neuromuscular control and joint stability (especially during un-predictive scenarios) which in turn lowers the risk of re-injury during sport

• Limb symmetry index testing is now widely used to measure strength differences side to side, allowing clinicians to develop exercise progressions effectively.

 Methods

• A handheld dynamometer was used to measure quadriceps strength.

• The device was stabilised against an open-chain knee extension machine arm, locked at 60 degrees of knee flexion.

• Athletes performed 3 trials of maximum effort knee extensions against the hand held dynamometer, each lasting 5 seconds (the average of these trials was recorded)

• The timing of this strength testing varied depending on the patient's physical comfort and ability to perform single-leg exercises, such as:

1. Step-downs

2. Split squats

3. Single-leg deadlifts

Without significant pain.

• Typically, patients began these exercises 8-12 weeks after surgery.

Patients were cleared to begin a walk-to-run progression when:

1. They had minimal or no knee effusion (as assessed by the Sweep test)

2. No pain with loading the knee during walking or light impact activities

3. Adequate stationary hop mechanics (as judged by a physical therapist)

4. A quadriceps index of at least 80%.

Full clearance for returning to activity and agility sports was granted when:

1. Patients passed a standardised functional movement assessment (FMA) with no pain

2. No effusion

3. A quadriceps index over 90%

4. Could tolerate jogging.

• Additionally, Their hop testing (single-leg, triple-leg, and crossover hop) had to be greater than 90% compared to the uninvolved limb, with proper mechanics as assessed by a physical therapist.

• The physical therapist evaluated “proper” mechanics based on the absence of significant dynamic knee valgus, no hip drop, appropriate knee excursion, and the ability to land and maintain balance during hop testing.

• Estimates of time to reach 70%, 80%, and 90% quadriceps symmetry were derived from a fitted model that included fixed effects for graft type and sex.

• To assess the impact of age, the model was expanded to compare patients younger than 25 with those 25 or older.

Results

• A total of 164 patients were evaluated (98 female, 66 male) who underwent ACL reconstruction.

• Patients either received bone-tendon-bone (BTB) autograft (n=118) or BTB allograft (n=46) for their ACL graft

• Average estimated time to quad symmetry and activity based on either bone-tendon-bone autograft & allograft 👇

Autograft = The tissue is harvested from the patient's own body

Allograft = Obtained from a donor, typically from a cadaver, rather than the persons own body

• A group age of under 25 years was added to the model to better reflect high school and collegiate athletes 👇

Discussion

• Quadriceps strength is a major factor that significantly impacts not only patient-reported outcomes but also the rates of ACL re-injury.

• With only 55-80% of athletes returning to competitive sports after ACL surgery, there is an opportunity for physios & strength & conditioning coaches to optimise patient recovery, aiming to increase the percentage of athletes who return to their pre-injury level of competition.

• Quadriceps strength symmetry can help reduce complications for athletes when they return to sports.

• It’s important to provide a more reliable programme & guideline to achieve for patients to follow during the recovery process, rather than relying solely on chronological timelines.

• The study's results indicate that patients who underwent bone-patellar tendon-bone autografts experienced a slower progression in regaining quadriceps strength compared to those who received bone-patellar tendon-bone allografts, regardless of age or sex.

• Specifically, males and females under 25 who had a bone-patellar tendon-bone autograft took over 2 months longer, on average, to reach quadriceps strength milestones (70%, 80%, 90%) compared to those who had allografts, likely due to the increased trauma associated with graft harvesting in autograft procedures.

• When counseling patients, particularly younger ones and their parents, it is important to set evidence-based expectations, especially given the notably high risk of re-injury or ACL re-tear in individuals under 20 years of age

3 resources to check out

To further your knowledge about ACL’s

1. Muscle activation - LINK

2. Aspetars ACL rehab guideline - Infographic - LINK

3. ACL rehab exercises, from start to finish - LINK

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