Femoral and Tibial Derotational Osteotomies With MPFL Reconstruction and Lateral Retinacular Lengthening

Abstract

Background:

Many anatomic factors contribute to patellar instability, including excessive femoral anteversion and external tibial torsion. Derotational osteotomies may be performed concomitantly with medial patellofemoral ligament (MPFL) reconstruction to address multiple factors and improve patellofemoral engagement.

Indications:

Proper identification of axial plane abnormalities is important as recurrence of instability may be higher in patients when these factors are not addressed. Femoral anteversion or tibial torsion of >20° can generate abnormal lateral forces in the patellofemoral joint, although an angle of up to 30° may be considered normal. Patients with bony rotational malalignment between 30° and 40° may be suitable for surgery, but this should be considered in the context of all patellofemoral pathology that is present. In patients with >40° of bony rotational malalignment, surgical intervention is nearly always warranted.

Technique Description:

The femur is derotated over a trochanteric entry nail. The distal portion of the isthmus is identified and vented with a drill bit. Overreaming of the intramedullary canal by 1.5 to 2 mm is performed. Two Schanz pins are placed proximal and distal to the osteotomy site, and they are oriented to produce external rotation of the distal femur to the degree desired. The osteotomy is then completed and the femur derotated to the desired correction with the Schanz pins aligned. The nail is placed and the proximal guide is used to place 1 proximal screw in dynamic position. With the Schanz pins still aligned, a perfect circle technique is used to place a distal screw in a static hole to maintain the correction. For the tibial osteotomy, the same process is repeated, only the venting of the tibia at the isthmus and the completion of the osteotomy are performed using an oscillating saw. In addition, Steinmann pins are used instead of Schanz pins.

Results:

Expected outcomes for this bilevel derotational osteotomy and MPFL reconstruction are very good. Patients have significant improvement in pain and patellofemoral stability.

Discussion/Conclusion:

Derotational osteotomies should be performed when long bone rotational deformity is identified as a primary risk factor contributing to instability during dynamic motion.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

This presentation and associated video describe a technique for femoral and tibial derotational osteotomies. The authors have nothing to disclose.

Background

By way of background, patellar instability is a common condition that primarily affects active, young patients. ³ Many anatomic risk factors contribute to this condition. ⁶ Derotational osteotomy is aimed at correcting rotational malalignment of the femur or tibia that contributes to patellofemoral instability and stabilizes the patella within the trochlear groove. It may be combined with other procedures, such as medial patellofemoral ligament (MPFL) reconstruction to address both rotational and soft tissue components of instability.

Indications

The patient is a 16-year-old girl with recurrent patellar instability with multiple episodes in both knees that have been occurring for years and now happening about 2 to 3 times per month. She is able to self-reduce and can play volleyball but has instability. The episodes also occur with daily activities such as walking down stairs. Conservative treatment with physical therapy, bracing, and taping was not able to adequately address the instability in her case.

Physical examination demonstrated 3 quadrants of lateral patellar translation with a soft endpoint, positive patellar apprehension, tight lateral retinaculum, and mild J sign bilaterally. The thigh-foot angle (TFA) was 25 degrees bilaterally. Prone hip internal rotation was 75°, and external rotation was 20° bilaterally.

Axial plan imaging showed femoral anteversion of 42° and external tibial torsion of 38°.

In patients with idiopathic tibial torsion, anterior knee pain and patellar instability are common indications for surgery. Standardized TFA thresholds (>30°) and computed tomography measurements help further establish objective indications.^5,7 For both femoral and tibial rotation, >40° nearly always leads to surgical correction, and 30° to 40° increases the likelihood. ¹

Various constructs have been described for derotational osteotomies, each with pros and cons.

Technique Description

The patient is positioned supine on a radiolucent operating room table to allow for intraoperative imaging. Feet are placed at the end of the bed, and the patient is on the edge of the table on the operative side. The operative side arm is well padded and placed across the chest.

Venting during a derotational osteotomy, before intramedullary reaming, allows marrow elements to escape and reduces intramedullary pressure while reaming. High-speed, low-pressure reaming also reduces intramedullary pressure while reaming.

When placing the pin, ensure it is at the tip of the greater trochanter. Due to the bow of the femur, aim anterior to ensure that the nail goes into the center of the canal.

Overreaming of the intramedullary canal by 1.5 to 2 mm is performed.

The starting reamer is reinserted at the time of Schanz pin placement to set the degree of correction because it is bigger than the nail. If the Schanz pin can be placed without hitting the entry reamer, then the nail can pass without impinging on the Schanz pin.

The goniometer is set at 22° of correction as the femur originally had 42° of anteversion. The goniometer is placed on the opposite side of the holder to help the person placing the other pin line up properly. The placement of the distal Schanz pin is distal to the distal portion of the nail so that it is out of the way of the nail.

The osteotomy is further created with a drill bit. Continue to weaken the bone with the drill bit and bring the drill across at the same level. Put the intramedullary guide pin back down before the osteotomy is completed manually.

The proximal interlocking screw is placed in a dynamic position, and the nail is sunk beneath the greater trochanter to allow for proximal movement of the nail without it becoming prominent at the tip of the greater trochanter. The external guide attached to the nail should be horizontal during placement of the proximal screw. This allows visualization of perfect circles distally with the C-arm in a full lateral position for the distal screw placement, and it means that only the rotation of the distal fragment needs to be controlled during placement of the distal screw.

The distal interlocking screw is placed with the hip and knee in a flexed position. Note that perfect circles can be obtained with minimal manipulation of the proximal femur because the external guide was oriented horizontally during proximal interlocking screw placement.

Typical screw placement is lateral to medial.

On the tibia, the guide pin is placed at the anterior corner of the plateau, and a starting reamer is introduced.

At the midshaft osteotomy site, find the lateral aspect of the crest, come to the anterior compartment just off the side of the crest, and incise right where there is a change from the periosteum to the anterior compartment. This allows for protection of the periosteum and later closure of the periosteum over the osteotomy, especially anteriorly. Incise the periosteum at the anterolateral edge of the crest, and protect the periosteum and anterior compartment musculature on the lateral side. Carefully elevate the periosteum over the ridge and continue the elevation to the medial aspect of the tibia.

Use a dropper to minimize heat necrosis from the oscillating saw.

Orient the Steinmann pin, for setting the degree of correction, perpendicular to the long axis of the tibia. Place the external guide (without the nail) on the proximal tibia when placing the proximal correction pin, so the pin is placed proximal to the dynamic hole. Internally rotate the proximal correction pin as much as possible without contacting the guide, which allows for placement of the distal correction pin in an anterior-to-posterior direction and avoids a cut-out at the medial malleolus.

The goniometer is set at 18° of correction for the tibia. The goniometer is on the opposite side of the pin, so the surgeon holding the goniometer can see both the pin and the goniometer. If the tibia does not easily rotate into the corrected position or the desired correction is > 20°, consider osteotomy of the fibula.

Place the C-arm as far from the medial side as possible to allow easier drill passage and screw placement. The proximal interlocking screw is placed medial to lateral. Note that the nail is sunk to a point where the dynamic hole is distal to the Steinmann pin.

At the time of distal screw drilling, ensure that the Steinmann pins are aligned, and both the proximal and distal tibia are controlled. Place the distal interlocking screw also in a medial-to-lateral direction such that the screw tip, if too long, will be in the anterior compartment and not prominent.

An MPFL reconstruction and lateral retinacular lengthening were also completed for this case. Final arthroscopy demonstrated the lateral edge of the patella lined up with the lateral edge of the trochlea, and the center of the patella was sitting in the center of the groove.

There are many tips to avoid complications. This includes venting the osteotomy sites before reaming to reduce the intramedullary pressure. Use high-speed, low-pressure reaming to reduce the intramedullary pressure. On the femur, reinsert the starting reamer at the time of correction pin placement to ensure that the nail can slide past the pin during insertion. Keep the femoral nail guide horizontal at the time of proximal screw placement.

On the tibia, place the guide on the proximal tibia when placing the proximal correction pin to ensure that the pin remains proximal to the dynamic hole. Internally rotate the proximal correction pin as much as possible without contacting the guide. If the tibia does not easily rotate into the corrected position or the desired correction is >20°, consider fibular osteotomy. Place screws from medial to lateral to avoid prominent screw tips.

Results

The osteotomy fixation level may influence postoperative healing time and weightbearing. The advantage of diaphyseal-level corrections is that they allow for early weightbearing as tolerated with crutches. A timeline of rehabilitation is shown here.

Patients undergo a formal functional test with physical therapy before returning to their desired sport, which can be as early as 6 months. The process averages 8 to 9 months. Physical therapy is a crucial portion of the recovery process.

Discussion/Conclusion

Previous studies have shown significant improvement in knee function and stability with high patient satisfaction.^2,4,8,9

In addition, the rate of redislocation is low. Patients younger than 25 years have the most favorable outcomes.

Thank you very much for the opportunity to present on this technique for femoral and tibial derotational osteotomies.