Courtesy Dr Sachin Tapasvi, Dr Ashok Shyam, Ortho TV

ACL Reconstruction: Surgical Planning, Technique and Key Principles

Introduction

Anterior Cruciate Ligament (ACL) reconstruction is one of the most commonly performed procedures in sports orthopaedics. Successful outcomes depend not only on surgical skill, but also on appropriate patient selection, graft choice, accurate tunnel placement, biological preservation, and secure fixation.

Modern ACL surgery has evolved considerably with improved understanding of ACL anatomy and biomechanics, leading to more anatomical and individualized reconstruction techniques.

Patient Selection for ACL Reconstruction

Clinical Diagnosis First

ACL injury is primarily a clinical diagnosis. The decision to proceed with surgery depends on several factors, including:

Symptomatic instability
Functional limitations
Failure of conservative treatment
Activity demands of the patient

Patients with recurrent instability during sports or daily activities are more likely to benefit from reconstruction.

Preoperative Evaluation and Planning

Patient-Specific Factors

Preoperative planning must be individualized. Important considerations include:

Activity Level

Sedentary individual versus athlete
Participation in pivoting sports versus non-pivoting activities

Occupational Requirements

Certain occupations may require:

Frequent kneeling
Climbing
Heavy manual activity

Cultural and Religious Needs

Activities involving kneeling or squatting may influence graft selection and rehabilitation goals.

Cosmetic Concerns

Incision placement and donor-site appearance may be important, especially in young patients.

Patient Expectations

Discussion should include:

Return to sports
Timing of return
Desired activity level
Daily functional goals

Previous ACL Surgery

Importance of Surgical History

If the patient previously underwent ACL reconstruction on the opposite knee, important questions include:

Which graft was used?
Was the patient satisfied with the outcome?

If prior results were satisfactory, using the same graft type may be advantageous.

Assessment of Associated Injuries

ACL tears are frequently associated with additional injuries that must be identified before surgery.

Common Associated Injuries

Meniscal tears
Collateral ligament injuries
Posterolateral corner injuries

These may require:

Combined procedures
Staged reconstruction

Failure to address associated pathology may compromise surgical outcomes.

Graft Selection Strategy

ACL Footprint-Based Graft Selection

The size of the native ACL footprint influences graft choice.

Small Footprint (<16 mm)

Preferred grafts:

Hamstring graft
Five- or six-strand hamstring constructs

Large Footprint (>16 mm)

Preferred grafts:

Bone–Patellar Tendon–Bone (BTB) graft
Quadriceps tendon graft

Importance of Graft Size

Minimum Recommended Diameter

A graft diameter of at least 8–8.5 mm is generally recommended.

Smaller grafts are associated with:

Higher re-rupture rates
Increased graft failure risk

Adequate graft diameter is therefore critical for long-term success.

Graft Healing Considerations

Different graft types incorporate and mature at different rates.

This influences:

Rehabilitation progression
Return-to-sport timelines

Biological healing should always be considered when designing postoperative rehabilitation protocols.

Operating Room Setup and Surgical Principles

Equipment

ACL reconstruction is highly dependent on arthroscopic technology.

Essential requirements include:

High-quality arthroscopy camera systems
Reliable instrumentation
Accurate drilling systems

Improved equipment contributes to greater surgical precision.

Patient Positioning

Positioning Techniques

Common methods include:

Side post
Leg holder systems

Proper positioning allows:

Full knee manipulation
Hyperflexion during femoral tunnel drilling
Improved arthroscopic access

Sterility and Surgical Preparation

Preparation Sequence

Sequential preparation should proceed from:

Foot
Knee
Entire limb

Modern sterility principles include:

Impervious drapes
Plasma sterilization
Autoclave systems

Older toxic sterilization agents such as formalin chambers and glutaraldehyde should be avoided.

Arthroscopic Portal Placement

Three-Portal Technique

A three-portal technique is commonly recommended.

1. Anterolateral Portal

Primary viewing portal
Positioned high

2. Anteromedial Portal

Viewing and working portal
Positioned high and close to the medial patellar tendon border

3. Accessory Anteromedial Portal

Main working portal
Positioned low and medially

Principles of Portal Placement

Proper portal positioning improves:

Instrument maneuverability
Femoral tunnel orientation
Tunnel length
Arthroscopic visualization

A high anteromedial portal reduces crowding, while a low accessory portal improves access to the femoral footprint.

Femoral Tunnel Considerations

Influence of Portal Position

Portal placement affects femoral tunnel geometry.

More Lateral Anteromedial Portal

Produces longer tunnels

More Medial Portal

Creates shorter and more oblique tunnels

Ideal Femoral Tunnel

Desired Characteristics

An ideal femoral tunnel should:

Measure approximately 35–40 mm in length
Be anatomically positioned
Preserve surrounding structures

Tunnel drilling is commonly performed with the knee hyperflexed beyond 120°.

Importance of Femoral Tunnel Position

Femoral tunnel malposition is one of the leading causes of ACL reconstruction failure, accounting for more than 40% of failed cases in some series.

Accurate tunnel positioning is therefore one of the most important technical aspects of surgery.

Visualization Principles

Viewing the femoral footprint from the anteromedial portal provides superior visualization and improves understanding of native ACL anatomy.

Switching viewing portals during surgery may further improve anatomical orientation.

Step-by-Step Surgical Technique

1. Diagnostic Arthroscopy

Initial arthroscopy is used to:

Confirm ACL tear
Evaluate remnant tissue
Identify associated injuries

Useful remnant tissue should be preserved whenever possible.

2. Femoral Side Preparation

The femoral footprint is identified using:

ACL stump remnants
Anatomical landmarks

A radiofrequency probe may be used for marking the footprint. Tunnel size is matched to graft diameter.

3. Femoral Tunnel Creation

Steps include:

Insert guide pin
Drill tunnel in hyperflexion
Overdrill according to graft size
Remove tunnel debris
Measure tunnel length
Pass shuttle suture

4. Tibial Tunnel Creation

Tunnel Placement

The tibial tunnel is generally positioned:

Slightly medial to center
Approximately at the medial two-fifths of the footprint

Technical Considerations

Use serial drilling
Avoid cartilage injury

Graft Passage

The graft is passed through the tibial and femoral tunnels while ensuring:

Proper seating
Correct orientation
Smooth passage without twisting

Graft Fixation

Graft Cycling

The knee is cycled approximately 20 times between:

0° and 90° flexion

Purpose:

Remove collagen creep
Precondition the graft

Femoral Fixation Methods

Fixation method depends on graft type.

Soft Tissue Grafts

Options include:

Interference screws
Suspensory fixation devices

Bone–Patellar Tendon–Bone Grafts

Metal interference screws are often preferred for bone plug fixation.

Tibial Fixation

Knee Position During Fixation

Fixation is generally performed with the knee at:

Approximately 20° flexion

In patients with significant hyperextension:

Fixation in full extension may be preferred

A posterior drawer force is applied before final fixation.

Screw Size Selection

General guidelines include:

If the screwdriver fits snugly: use screw size +1 mm
In soft bone: use +2 mm screw
In very tight tunnels: use same-sized screw

Proper screw sizing improves fixation stability.

Key Surgical Principles

Important principles include:

Minimum graft diameter of at least 8–8.5 mm
Coverage of at least 80% of the native ACL footprint
Use of a three-portal technique
Visualization of the femoral footprint through the anteromedial portal
Anatomical tunnel placement
Preference for transportal or outside-in drilling techniques

Post-Fixation Rehabilitation

Following stable fixation of an isolated ACL reconstruction:

Accelerated rehabilitation protocols may be initiated

Rehabilitation should still respect graft biology and healing timelines.

Key Takeaways

Successful ACL reconstruction requires a patient-specific approach.

Critical factors include:

Appropriate graft choice
Accurate tunnel placement
Adequate graft size
Secure fixation
Recognition and treatment of associated injuries

The most common technical cause of failure remains femoral tunnel malposition. Careful surgical planning and precise execution are therefore essential for optimal outcomes.

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