MPFL Reconstruction with Allograft: Surgical Guide

What Is MPFL Reconstruction?

Medial patellofemoral ligament (MPFL) reconstruction is a surgical procedure that replaces the torn MPFL with a tendon graft. The MPFL is the primary soft-tissue restraint preventing the kneecap from dislocating laterally, and once it is torn, it rarely heals with sufficient strength to prevent recurrent instability.

MPFL reconstruction is the gold standard surgical treatment for recurrent patellar instability and has become one of the most commonly performed procedures for patellar dislocation, with success rates exceeding 90% in preventing further dislocation.

Allograft vs. Autograft: Why Allograft?

A tendon graft is used to recreate the MPFL. Surgeons choose between two graft sources:

Autograft (patient's own tissue):

Gracilis or semitendinosus hamstring tendon (most common autograft)
Quadriceps tendon strip
Advantage: No disease transmission risk; biologically the patient's own tissue
Disadvantage: Donor site morbidity — pain, weakness, or complications at the harvest site

Allograft (donor tissue):

Processed tendon from a tissue bank (typically semitendinosus, tibialis anterior, or gracilis)
Advantages:
- No donor site morbidity — no additional incision or tendon sacrifice from the patient
- Shorter operative time
- Less post-operative pain (no harvest site)
- Excellent option for patients who have already had hamstring harvest (e.g., prior ACL reconstruction)
- Available in consistent size and quality
Disadvantages:
- Theoretical (extremely low) risk of disease transmission
- Slightly slower biological incorporation compared to autograft
- Higher cost

Unlike ACL reconstruction — where allograft has higher failure rates in young athletes — MPFL reconstruction places significantly less mechanical load on the graft, making allograft an excellent and widely accepted choice for this procedure.

Who Is a Candidate?

MPFL reconstruction with allograft is recommended for:

Recurrent patellar dislocations (two or more episodes) with confirmed MPFL insufficiency
First-time dislocation with significant anatomic risk factors (trochlear dysplasia, patella alta, increased TT-TG distance) predicting high recurrence risk
Failed non-surgical management — continued instability despite bracing and physical therapy
Patients who prefer to avoid autograft harvest — those who wish to minimize surgical morbidity
Revision cases — prior MPFL surgery that has failed, or patients without available autograft (prior hamstring harvest)

Additional procedures may be performed simultaneously depending on anatomy:

Tibial tubercle osteotomy (TTO): Realigns the patellar tendon insertion if the TT-TG distance is excessively large (>20 mm)
Lateral release or lengthening: Relieves excessive lateral tightness
Trochleoplasty: Deepens a severely dysplastic trochlear groove (reserved for severe cases)
Osteochondral repair: Addresses cartilage damage from prior dislocations

Pre-Operative Preparation

MRI review: Surgeon confirms MPFL tear pattern, evaluates trochlear morphology, patellar height, and cartilage status
CT scan: May be obtained to measure TT-TG distance and plan any bony procedures
Physical therapy (prehabilitation): Optimize quadriceps strength and range of motion before surgery — patients who enter surgery stronger recover faster
Medical clearance: Standard pre-operative labs and evaluation
Medications: Stop anti-inflammatory medications (ibuprofen, naproxen) 7–10 days before surgery; discuss blood thinners with your surgeon
Home preparation: Arrange for transportation, stock easy meals, set up a recovery area with the leg elevated

Day of Surgery

Anesthesia

MPFL reconstruction is typically performed under general anesthesia combined with a regional nerve block:

Adductor canal block or femoral nerve block for post-operative pain control
Periarticular local anesthetic injection around the knee for additional pain management

Surgical Steps (45–75 minutes)

Examination under anesthesia: Patellar tracking, mobility, and stability are assessed with the patient fully relaxed — confirms the degree of instability
Diagnostic arthroscopy: A camera is inserted through small incisions to inspect the joint surface, look for loose bodies or cartilage damage, and assess trochlear morphology from inside
Allograft preparation: The donor tendon (typically semitendinosus or tibialis anterior allograft) is thawed, sized, and prepared on a back table — sutures are placed in each end
Patellar tunnel or anchor placement: Two small bone tunnels are drilled into the medial border of the patella (or suture anchors are placed) to accept the graft — tunnel placement is critical to recreate the anatomic MPFL footprint
Femoral tunnel placement: A guide pin is placed at the anatomic MPFL femoral origin (between the medial epicondyle and adductor tubercle) using fluoroscopic guidance — this is the most critical step of the surgery, as malposition causes graft failure or abnormal patellar tracking
Graft passage: The allograft tendon is passed from the patellar attachment through the soft tissues along the anatomic MPFL path to the femoral tunnel
Graft tensioning and fixation: The graft is tensioned with the knee at 30–45 degrees of flexion, ensuring the patella tracks centrally without being overtightened — fixation at the femoral tunnel is with an interference screw or cortical button
Patellar tracking confirmation: The knee is taken through a full range of motion to confirm smooth, centered patellar tracking without excessive tension
Wound closure: Incisions are closed and a sterile dressing is applied
Brace application: A hinged knee brace locked in extension is placed

Fluoroscopy

Intra-operative fluoroscopy (live X-ray) is used to verify accurate femoral tunnel placement. The MPFL femoral origin is a precise anatomic point — even a few millimeters of error can cause graft failure or restrict motion.

Risks and Complications

Graft failure or re-dislocation: 5–10% — most commonly related to femoral tunnel malposition or a traumatic re-injury
Patellar fracture: Rare — risk associated with large patellar tunnels; technique-dependent
Over-constraint (overtightening): Causes medial patellar tilt, increased patellofemoral contact pressure, and anterior knee pain — avoided with careful intra-operative tensioning
Stiffness (arthrofibrosis): Loss of knee flexion — prevented by early range of motion in rehabilitation
Infection: <1% — standard surgical infection risk
Nerve injury: Infrapatellar branch of the saphenous nerve may be irritated, causing numbness on the front of the shin — usually temporary
DVT/PE: Low risk; chemical prophylaxis may be prescribed

What to Expect After Surgery

Outpatient procedure: Most patients go home the same day
Weight bearing: Partial weight bearing with crutches for 2–4 weeks, then progressive to full weight bearing
Brace: Hinged knee brace worn for 4–6 weeks
Physical therapy: Begins within the first week
Return to desk work: 1–2 weeks
Return to sports: 5–7 months depending on sport and recovery progress