Abstract
Background:
Patellofemoral arthroplasty (PFA) is a salvage procedure for patients presenting with bone-on-bone isolated patellofemoral osteoarthritis. Previous studies comparing PFA with total knee arthroplasties found that patients recover more quickly and have better average knee function following PFA, as care is taken to spare healthy cartilage, bone, and ligaments during the procedure. This allows preservation of native knee kinematics, resulting in better patient-reported outcomes, as well as mid-term and long-term results.
Indication:
PFA is indicated in patients with isolated primary or post-traumatic patellofemoral osteoarthritis. In some cases, the procedure may be indicated in patients suffering from patellar instability or trochlear dysplasia with associated arthritis. Contraindications for PFA include multicompartmental arthritis in the medial or lateral tibiofemoral compartments, inflammatory joint disease, tibiofemoral instability, malalignment, or lesions of 6 mm or more in diameter.
Technique Description:
After the initial lateral patellofemoral approach, degenerative changes in the patellofemoral joint were observed. Following preparation of the patella and femur, the trochlear implant is impacted on the prepared femoral surface. Cement is digitally impacted into the reamed patella, followed by placement of the final patellar implant and compression until the cement is dried.
Results:
Within 2 years postoperatively, patients are expected to have improved overall knee-specific quality of life, reduced pain, and a successful return to activities.
Discussion/Conclusion:
New PFA techniques have yielded significant improvement in patient-reported outcomes and high rates of survivorship following surgery.
This is a visual representation of the abstract.
Video Transcript
Patellofemoral arthritis is defined as isolated articular cartilage degradation along the trochlear groove and undersurface of the patella, with preservation of the medial and lateral compartment cartilage. Its prevalence can be as high as 11% to 24% in patients >55 years old. 3 Patients often present with pain and swelling in the affected knee, and isolated patellofemoral replacement may be of benefit in carefully selected patients.
Risk factors for patellofemoral osteoarthritis include patients >40 years old, female gender, high body mass index (≥30), and prior anterior cruciate ligament injury.
Our patient is a 48-year-old woman presenting with isolated left anterior knee pain for >3 years. The patient describes her pain as being sharp, stabbing, and consistent, though worse with stairs. The patient has failed an extensive course of conservative management in the form of physical therapy, activity modification, and cortisone injections.
On physical examination, the patient has a nonantalgic gait with normal strength and range of motion. The patient has a positive patellar grind test with more tenderness over the lateral patellar facet than the medial patellar facet. Standing radiographs reveal well-preserved joint space in the tibiofemoral compartment. Full-length x-rays reveal a neutral mechanical alignment without any mechanical axis deformity. Magnetic resonance imaging reconfirms a well-preserved joint space in the tibiofemoral compartments, with significant wear in the patellofemoral compartment. There is also concern for a posterolateral meniscus tear.
Our plan for this patient was to start with a diagnostic arthroscopy and partial lateral meniscectomy. This would be followed by an open patellofemoral arthroplasty.
The patient was positioned supine and a thigh torniquet was placed. After the operative leg was prepped and draped in the usual sterile manner, we began with a diagnostic arthroscopy, which confirmed patellofemoral wear. Inspection of the medial compartment revealed preserved cartilage surfaces and an intact meniscus. Inspection of the lateral compartment revealed preserved cartilage and fraying of the lateral meniscus in the body and posterior horn. This was debrided with the use of a shaver.
Following completion of the arthroscopy, we then proceeded to the open patellofemoral replacement. A lateral parapatellar arthrotomy was performed. Care was taken to release the lateral retinaculum and underlying joint capsule as separate layers. The infrapatellar and suprapatellar fat pads were then resected for further exposure.
With the knee in 90° of flexion and the patella everted, a drill guide is utilized in an anterior position to develop a working axis normal to the patient’s native trochlear articular surface. A guide pin is then advanced through the drill guide into the bone. A sizing guide and trial implant are then used to confirm the correct implant size. The appropriate femoral reamer is chosen based on the implant size determined in the prior step. The depth of resection is determined by a laser line visible on the reamer, which corresponds to a strong subchondral bone stock.
A guide block is then pinned into the femur with half pins, and the initial guide pin is removed. A secondary femoral reamer is utilized to prepare the femur from an inferior to superior fashion. The drill has a positive endpoint to ensure appropriate resection. During the reaming, the femur is copiously irrigated to prevent thermal necrosis.
A sharp awl is used to clean the reamed surface and ensure sharp margins with the surrounding cartilage.
A guide for the central screw is then pinned into the femur. The central screw is placed in a stepwise fashion with a pinned, followed by a reamer, and lastly by the final central screw implant. Copious irrigation is used to clear the reamed byproduct.
The implanted screw is then inspected to ensure a clean taper, and a final look of the prepared femoral surface confirms there is good bone stock, clear articular margins, and proper fit with the native trochlear surface. The final trochlear implant is then impacted onto the central screw. We then proceed to prepare the patella.
Osteophytes are first resected from the patella to restore the patient’s native anatomy. Following selection of an appropriately sized anatomy, a central pin is then inserted into the patella. The patella is then reamed and irrigated using pulsatile lavage.
On the back table, the cement is prepared. The cement is then digitally impacted into the reamed patella, followed by placement of the final patellar implant. The patella is then compressed into the reamed patella, and extruded cement is cleaned using curretes and pickups. The patella is compressed until the cement is dry.
A lateral lengthening procedure is then performed, where the cut edges of the superior oblique and deep transverse fibers are sutured together. Excess tension in the lateral structures is removed, while maintaining lateral soft-tissue integrity. This is followed by routine closure of the subcutaneous and skin layer.
Patients are weightbearing as tolerated immediately postoperative, with range of motion limited to 0 to 90° in the initial postoperative period. Patients are immediately started on formal physical therapy, focusing on strengthening and range of motion and should expect a return to sports by 6 to 9 months.
Potential complications associated with this procedure include persistent pain, patellar maltracking or instability, failure of either the patellar or trochlear implants secondary to septic or aseptic loosening, and extensor mechanism rupture. 2
Outcomes following patellofemoral arthroplasty are generally good, with improved patient-reported outcomes and 73% return to previous preferred activity at 2-year follow-up. 4
In a 4-year mean follow-up study, 76% of patients report good to excellent outcomes, with an overall implant survivorship of 92%. 1
We’d like to thank you for watching this video on our preferred technique for patellofemoral replacement.
Enclosed are selected references utilized in this video, thank you for your time.
Footnotes
Submitted October 19, 2021; accepted January 12, 2022.
One or more of the authors has declared the following potential conflict of interest or source of funding: N.N.V. is on the board or committee for American Orthopaedic Society for Sports Medicine, American Shoulder and Elbow Surgeons, and Arthroscopy Association of North America; is a paid consultant for Arthrex, Inc, and Stryker; received research support from Arthrex, Inc, Breg, Ossur, Smith & Nephew, and Wright Medical Technology, Inc.; received stock or stock options from Cymedica, and Omeros; is on the Editorial or governing board for SLACK Incorporated; received IP royalties from Smith & Nephew; and received publishing royalties, financial or material support from Vindico Medical-Orthopedics Hyperguide. J.C. is on the board or committee for American Orthopaedic Society for Sports Medicine, Arthroscopy Association of North America, and International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine; is a paid consultant for Arthrex, Inc., CONMED Linvatec, Ossur, and Smith & Nephew. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
