Fig. 9.1
Anteroposterior radiograph (a) and MRI (b) demonstrating an osteochondral defect in the tibial plafond (OLTP) with a large overlying periarticular cyst
Diagnosis is usually made on a CT scan or magnetic resonance imaging (MRI) [2, 6]. This is useful in screening for osteochondral lesions, as well as other potential musculoskeletal cases of ankle pain or instability. The MRI is used to diagnose the lesion, as well as access the biological activity of the lesion. This is seen as signal change consistent with bone marrow edema within the subchondral bone adjacent to the lesion (Fig. 9.2). Absence of bone marrow edema may suggest that a lesion seen within the distal tibia may be inactive and an incidental finding not responsible for the patients pain. This may additionally be evaluated on a 3-phase technetium-labeled bone scan.
Fig. 9.2
Sagittal T2 and T2 MRI images demonstrating a posterior OLTP with active bone marrow edema
The MRI is not however very accurate in determining the true size and depth of the lesion, nor the presence of subtle associated subchondral cysts, which are all better evaluated on CT scans (Fig. 9.3). For preoperative planning CT scan is the preferred option [21].
Fig. 9.3
Sagittal cut CT scan demonstrating a small anterior periarticular cyst associated with an OLTP. White arrow indicates the intra-articular extension of the cyst demonstrating osteochondral involvement
9.5 Nonoperative Treatment
Initial nonoperative treatment follows the same protocol as for all OLTs. This includes initial rest, immobilization, and unloading protocol, in either a fracture boot or cast. The duration of nonoperative treatment is not well defined and should include input from the patient.
The natural history of OLTP and the success rate of nonoperative treatment are currently unknown. Shearer described 54 % good and excellent results with nonoperative treatment of OLT [16], while the author of this chapter reviewed sequential MRI studies of patients with diagnosed OLTs and showed that 45 % had MRI evidence of improvement (although 55 % did get worse or stayed the same) [8]. It is unclear whether these results translate to lesions in the tibial plafond.
Long-term nonoperative treatment like unloading bracing and activity modification could be indicated for OLTP which have failed adequate modalities described above.
9.6 Operative Treatment
Surgical treatment is indicated for patients with recalcitrant pain and functional limitations despite adequate nonoperative interventions described above.
Most OLTP can be surgically managed arthroscopically. Utilizing standard anteromedial and anterolateral portals, a diagnostic evaluation should be performed as described by Ferkel to evaluate for associated pathologies [9]. Very posterior lesions can be addressed via a posterior arthroscopic approach described by Van Dijk with the patient positioned prone [19].
Once identified (Fig. 9.4), the OLTP is managed by debriding nonviable or damaged cartilage and bone, curetting the rim and base of the lesion to ensure a stable cartilaginous rim and a vascularized bone base (Fig. 9.5).
Fig. 9.4
Arthroscopic view of OLTP in the central plafond
Fig. 9.5
OLTP post debridement of unstable cartilage
Associated cysts should be curetted or shaved, while larger cysts should be packed with bone graft. Bone grafting is usually performed in an antegrade manner. The debrided lesion is located arthroscopically with the ball tip of a microvector guide. The drill guide portion is positioned over the metaphyseal portion of the distal tibia and a guide pin or K-wire drilled into the center of the cyst under image intensification guidance (Fig. 9.6). Sequential cannulated drill bits are drilled over the wire creating an access channel to the cyst large enough to insert a curette (Fig. 9.7). The curette is used to scrape and remove the membranous cystic lining of the cyst (Fig. 9.8) and any sclerotic bone bordering the cyst, leaving bleeding cancellous bone at the cyst’s borders. Following irrigation, the arthroscope can be inserted down the bone tunnel to confirm the cyst has been adequately debrided and prepared under direct visualization. Bone graft (autologous, allograft, or synthetic) is then inserted down the bone tunnel and impacted into the cyst utilizing a bone tamp. Complete fill of the cyst can usually be seen under image intensification (Fig. 9.9). Adequate packing of the cyst is important to prevent synovial fluid entering through the joint into the cyst which may result in resorption of the graft or reformation of the cyst. This is assessed arthroscopically through the ankle joint while probing the communicating OLTP.
Fig. 9.6
Intraoperative image intensification image demonstrating placement of guide pin within the center of the distal tibial cyst
Fig. 9.7
Intraoperative image intensification image demonstrating reamer drilling into the cyst to enlarge the access channel
Fig. 9.8
Intraoperative image intensification image demonstrating curette debriding the walls of the cyst prior to grafting
Fig. 9.9
Intraoperative image intensification image demonstrating antegrade packing of bone graft material filling the cyst and access channel
Once the lesion base has been debrided to a stable construct, marrow stimulation can be performed, via either the ankle joint utilizing arthroscopic picks (Fig. 9.10) {author’s preference} or antegrade utilizing a drill bit or K-wire through the microvector guide. Once the “microfracture” holes have been created, the tourniquet is deflated and/or the arthroscopic pump is turned off and the area is monitored for aggressive bleeding or extravasation of bone marrow cells from the lesion base (Fig. 9.11).
