Medial Femoral Trochlea Osteochondral Flap

Vascularized osteochondral flaps are a new technique described for the reconstruction of challenging articular defects of the carpus. The medial femoral trochlea osteochondral flap is supplied by the descending geniculate artery. This osteochondral flap has shown promise in the treatment of recalcitrant scaphoid proximal pole nonunions and advanced avascular necrosis of the lunate. The anatomy, surgical technique, and results are discussed, with clinical cases provided.

Key points

  • Vascularized osteochondral flaps are a new technique described for the reconstruction of challenging articular defects of the carpus.

  • The medial femoral trochlea (MFT) osteochondral flap is supplied by the descending geniculate artery (DGA). This osteochondral flap has shown promise in the treatment of recalcitrant scaphoid proximal pole nonunions and advanced avascular necrosis of the lunate.

  • The anatomy, surgical technique, and results are discussed, with clinical cases provided.

Introduction

The DGA has become a versatile pedicle in reconstructive microsurgery. The DGA vessels supply the corticoperiosteal or corticocancellous medial femoral condyle (MFC) flap used in cases of nonunion of long bones, tubular bones of the hand, carpal and tarsal bones, and the craniofacial skeleton. In addition to providing bone from the apex of the condyle, the vessel branches have demonstrated the capability of providing cutaneous, osteocutaneous, or osteotendinous combinations and even served as a useful recipient vessel in extremity reconstruction.

The vascular distribution of this pedicle also includes periosteal vessels supplying the cartilage-bearing trochlea of the medial patellofemoral joint. The utility of harvesting this convex cartilaginous surface as a vascularized flap was described in a case report of scaphoid reconstruction of a recalcitrant proximal pole nonunion in 2008. Cadaveric studies have described the pertinent vascular arcade supplying this bone and cartilage, and an anatomic study elucidated the similarities between the convex curvature of the MFT and the proximal convex surfaces of the scaphoid, lunate, and capitate. The authors have used this segment of bone and cartilage as a free osteochondral flap for various articular defects. The most common applications have been reconstruction of recalcitrant scaphoid proximal pole nonunions and advanced avascular necrosis of the lunate (Kienböck disease).

Introduction

The DGA has become a versatile pedicle in reconstructive microsurgery. The DGA vessels supply the corticoperiosteal or corticocancellous medial femoral condyle (MFC) flap used in cases of nonunion of long bones, tubular bones of the hand, carpal and tarsal bones, and the craniofacial skeleton. In addition to providing bone from the apex of the condyle, the vessel branches have demonstrated the capability of providing cutaneous, osteocutaneous, or osteotendinous combinations and even served as a useful recipient vessel in extremity reconstruction.

The vascular distribution of this pedicle also includes periosteal vessels supplying the cartilage-bearing trochlea of the medial patellofemoral joint. The utility of harvesting this convex cartilaginous surface as a vascularized flap was described in a case report of scaphoid reconstruction of a recalcitrant proximal pole nonunion in 2008. Cadaveric studies have described the pertinent vascular arcade supplying this bone and cartilage, and an anatomic study elucidated the similarities between the convex curvature of the MFT and the proximal convex surfaces of the scaphoid, lunate, and capitate. The authors have used this segment of bone and cartilage as a free osteochondral flap for various articular defects. The most common applications have been reconstruction of recalcitrant scaphoid proximal pole nonunions and advanced avascular necrosis of the lunate (Kienböck disease).

Anatomy

The MFT flap shares the same vascular source vessel as the MFC corticoperiosteal flap. Both are supplied by periosteal vessels that are intimately adherent to the medial aspect of the distal femur. This filigree of vessels represents the terminal branches of the DGA. The DGA originates from the superficial femoral artery (SFA) within the adductor hiatus of the distal thigh and travels distally. At the level of the adductor insertion on the medial condyle, the DGA divides into smaller caliber longitudinal and transverse periosteal branches. The longitudinal branch is used to harvest the MFC corticoperiosteal flap. The transverse branch courses anteriorly to the region of the cartilage-bearing medial trochlea. The convex osteochondral segment of the proximal-most aspect of trochlea is harvested as the MFT flap for articular reconstruction ( Fig. 1 ).

Fig. 1
Representation of MFT flap vascular pedicle. A, DGA. B, transverse branch. C, longitudinal branch. D, SGA. Area of desired osteochondral harvest shaded in green. Inset demonstrates orientation of harvested segment as it relates to area of scaphoid reconstruction.
(Copyright 2013, The Curtis National Hand Center.)

Flap design

The osteochondral segment typically harvested for scaphoid and lunate reconstruction is approximately 2 cm × 1 cm × 1 cm, with the longest dimension measuring from proximal to distal. The segment is harvested from the proximal margin of the cartilage-bearing convex trochlea. This segment normally articulates with the medial patella and does not articulate with the tibia. The flap carries cartilage on one surface only ( Fig. 2 ). This is positioned during inset to articulate with the scaphoid fossa or lunate fossa of the radius (to recreate the greater curvature of the scaphoid or lunate, respectively).

Fig. 2
Typical size and appearance of harvested MFT osteochondral flap. Note that the flap provides convex cartilage on one surface only. ( Top : oblique view; Middle : posterior view; Bottom : anterior view.)

The osteochondral segment is harvested in continuity with the transverse periosteal branch of the DGA. The DGA is harvested proximally to gain pedicle length and caliber as it approaches its origin from the SFA in the adductor canal. The maximal length of the pedicle is approximately 13 cm with an arterial caliber of approximately 1.5 mm at its takeoff from the SFA.

Harvest technique

When used for small articular defects, the MFT is usually harvested without a skin island to avoid excess bulk. The following description is the technique of harvest without skin. The authors have described the skin harvest on the DGA pedicle previously.

An incision is created starting at the adductor hiatus, moving distally and anteriorly to the midpoint between the medial border of the patella and the MFC. This skin incision is continued to the subfascial plane as the vastus medialis muscle is retracted anteriorly. The DGA can then be identified as the medial column of the femur is exposed. The DGA may be dissected as proximally as its origin from the SFA in the adductor canal. Branches coursing anteriorly to the vastus medialis and posteriorly to the medial thigh skin may be ligated. The skin branches (which include the saphenous artery) provide options for skin paddle harvest if desired.

Ligation and elevation of the pedicle from proximal to distal facilitate subsequent bone harvest. As the pedicle elevation reaches the region of the adductor tendon insertion, the vessels become intimately invested in the periosteum of the medial condyle. Three large branches are encountered: the transverse branch, the longitudinal branch, and the superomedial geniculate artery (SGA).

The SGA courses deep into the popliteal fossa in the retrocondylar sulcus of the femur. In approximately 10% of patients the DGA may be absent and the SGA may serve as the pedicle, requiring dissection of this vessel from its origin off the popliteal artery.

The longitudinal branch serves as the pedicle for the (non–cartilage-bearing) MFC flap and is ligated when harvesting the MFT.

The transverse branch typically traverses the metaphyseal region and densely supplies the periosteum surrounding the MFT both on its medial aspect and proximal aspect ( Fig. 3 ). This branch is preserved and elevated with its attachments to the trochlea. As the dissection approaches the trochlea, it is performed subperiosteally to protect the small vessels.

Nov 21, 2017 | Posted by in Dental Materials | Comments Off on Medial Femoral Trochlea Osteochondral Flap
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