Technique Tip: Percutaneous Endoscopically-Assisted Calcaneal Slide Osteotomy

Introduction

Calcaneal slide osteotomy is a commonly performed surgical hindfoot procedure typically associated with mechanical weight-bearing axis realignment with medial or lateral displacement of the posterior calcaneus⁸. An oblique lateral heel incision, in line with the planned osteotomy, is the standard open approach to the calcaneus for the procedure. The oblique incision crosses directly over the arborization of the sural nerve on the lateral hindfoot, even if the main branch of the nerve may be avoided by careful dissection. The medial neurovascular structures in the tarsal tunnel are also at risk using a saw blade directed from lateral to medial, as over-penetration of the medial cortex with the saw could cause unintentional injury.

We describe a three incision, percutaneous endoscop- ically-assisted calcaneal osteotomy (PECO) technique that minimizes potential injury to both the sural nerve laterally and the plantar and medial neurovascular structures.

Materials and Methods

The patient is positioned supine on the operating table with the feet at the end of the bed, with a bump placed behind the ipsilateral hip so that the foot rolls to a slightly internally rotated position (Figure 1). A thigh tourniquet is placed, and standard sterile prep and draping proximal to the knee is performed. The PECO technique may be done in addition to other procedures for planovalgus or cavovarus deformity reconstruction as a part of the planned surgical treatment.

Figure 1. The patient is positioned supine on the operating table with a bump under the ipsilateral hip.

The proximal-posterior aspect of the osteotomy should start at approximately midway between the posterior aspect of the calcaneal tuberosity and the posterior aspect of the lateral malleolus, and aimed approximately 45 degrees anterior toward the plantar cortex (Figures 2A and B). Fluoroscopy may be used to identify these landmarks on the skin.

Figure 2. Lateral (Figure 2A) and medial (Figure 2B) portal site incisions are marked.

Two small (five millimeter) lateral heel skin-only incisions are made with a 15 blade, one at the proximal- posterior aspect and the other and the distal-plantar aspect of the planned 45 degree calcaneal osteotomy, with the incisions made parallel to the orientation of osteotomy. A blunt curved hemostat is used to dissect percutaneously down to the lateral wall of the calcaneus through each incision. The hemostat is then used to create a tunnel along and directly over the lateral calcaneal cortex between the two incisions, deep to the plane of the sural nerve.

Through the lateral proximal-posterior incision, the same curved hemostat is used to dissect directly medially, anterior to the distal Achilles tendon, and posterior to the medial neurovascular bundle, until it is prominent under the medial skin. A 15 blade is used to make a longitudinal five millimeter skin incision, exposing the tip of the hemostat. Through this single medial incision, the medial and plantar medial subcutaneous tunnel is developed with the hemostat, in a similar fashion to the lateral tunnel, in line with the planned osteotomy and directly adjacent to the medial periosteum. The hemostat, directed laterally, is passed deep to the medial head of the quadratus plantae and the neurovascular structures. Through the lateral distal-plantar incision, the plantar tunnel directly against the plantar calcaneal cortex is developed with the hemostat, completing the deep circumferential tunnel around the calcaneal tuberosity.

Suture shuttling begins with passing a No. 2 suture from medial to lateral using a hemostat passed through the lateral proximal-posterior incision into the medial incision. This suture is left in place (Figure 3). Next, an empty, closed right-angled clamp is passed through the medial incision plantarward and distalward along the medial calcaneal periosteum until the plantar medial curvature of the calcaneus is palpable with the tip of the instrument (Figure 4). To avoid an injury to the neurovascular structures, the suture previously placed in the medial incision can be used to guide the tip of the clamp down towards the calcaneus. This is performed by capturing the suture with the tip of the clamp, pulling the suture from the lateral incision allowing the clamp to make contact with the bone, and partially opening the clamp to release the suture, and redirecting the clamp towards the medial and plantar cortices respectively. A 4 millimeter dry scope cannula with an inserted blunt trochar and a No. 2 suture threaded through its distal eyelet (Figure 5) is passed into the lateral distal-plantar incision along the plantar calcaneal cortex until the tip of the right angle clamp is palpated with the cannula at the medial plantar curvature of the calcaneus. The blunt trochar is removed, and the tip of the right angle clamp is maneuvered so that it rests within the bore of the cannula (Figure 6). Position is confirmed with a gentle toggle of either instrument, resulting in movement of the other instrument. The arthroscopic camera is placed in the cannula to either assist the engagement of the instruments or to confirm the intra-cannula position of the clamp, and the grasping of the suture loop by the clamp is directly visualized (Figure 7). The loop is pulled by the clamp medially, out of the medial incision. The initially shuttled suture (from the lateral proximal- posterior incision to medial) is then placed in the suture loop. The suture is pulled around the medial and plantar cortex, out through the lateral distal-plantar incision. The result is a single suture touching the periosteum of the dorsal, medial, and plantar calcaneus, with each end exiting through the two small lateral incisions.

Figure 3. Non-absorbable suture is passed from the proximal lateral to proximal medial incisions.

Figure 4. Large right angle clamp is placed under the plantar medial calcaneus through a subcutaneous tunnel.

Figure 5. Suture is passed through eyelet in arthroscopic cannula.

Figure 6. View of plantar foot, heel at bottom of picture, forefoot at top. Docking of right angle clamp tip into cannula end is performed based on tactile feedback (clamp is medial, cannula is lateral).

Figure 7. View from plantar lateral to plantar medial: passage of the non-absorbable suture is confirmed endoscopically by grasping it within the cannula using the large right angle clamp previously placed in the medial subcutaneous tunnel.

A Gigli saw is shuttled using the suture into the same position (Figure 8). Soft tissue-protecting retractors are placed over the Gigli saw to protect the skin incisions during sawing (Figure 9). Gigli saw osteotomy is performed with care to avoid injury to the lateral soft tissue and the sural nerve. When the osteotomy is nearly complete, the sawing is performed carefully as it is held at almost a straight line by the surgeon’s fingers. Completion of the osteotomy is confirmed by an easily mobile posterior calcaneus. A ¼ inch osteotome is inserted through the distal-plantar incision and is gently rotated within the osteotomized calcaneus to distract and translate the tuberosity medially or laterally (Figure 10). Fluoroscopy is used to check displacement and alignment.

Figure 8. After successful passage of suture, the Gigli saw is shuttled around the calcaneus, deep to neurovascular structures.

Figure 9. Gigli saw cut with skin protecting retractors is performed.

Figure 10. The completed osteotomy is mobilized percutaneously with a ¼ inch ostotome.

Two percutaneous cannulated 6.5 millimeter screws are placed under fluoroscopic guidance across the osteotomy site from posterior to anterior, with start points proximal to the weight-bearing portion of the calcaneus and distal to the Achilles tendon insertion (Figures 11A-D).

Figure 11. Cannulated screw guidewires placed. Final fluoro views: lateral (Figure 11B) and axial (Figure 11C) of guidewires, and axial view of final screw placement (Figure 11D).

A single nylon skin suture is used to close each of the five small incisions, three for the osteotomy (two lateral and one medial), and two posteriorly for the two screws.

Results

Twenty-five patients have undergone PECO by a single surgeon at our institution, in all cases with additional procedures performed at the same setting for hindfoot alignment reconstruction. Institutional review board approval through practice surveillance was obtained. Preoperative and postoperative radiographic hindfoot alignment was assessed, as well as displacement of the osteotomy achieved intraoperatively. Clinical postoperative neurovascular complications were assessed in follow-up. Twenty-five patients underwent twenty-five displacement osteotomies (20 lateral displacement, 5 medial displacement; 13 men, 12 women; 14 left, 11 right) by the PECO technique. Average follow-up was 8 months. Mean correction based on intraoperative axial heel view was 7.3 +/- 2.0 mm of displacement. Mean correction on comparison of preoperative and postoperative hindfoot alignment radiographs relative to the axis of the tibial shaft was 13.9 +/- 7.5 mm⁶. No patients had vascular or wound complications. One patient (1/25, 4%) had persistent post-operative numbness in the sural nerve distribution.

Discussion

Despite an early learning curve, the lead author has found this technique to be both safe and efficient, particularly for soft tissue management about the hindfoot. Although arthroscopy about the calcaneus has been described previously³, few similar descriptions to our PECO technique exist. A four-incision percutaneous technique without endoscopic assistance has been noted previously⁴, but the technique description raises concerns for potential injury to medial plantar neurovascular structures by the Gigli saw. The previous technique included a plantar medial incision, did not use suture as an initial shuttling tool (instead primary passage of the Gigli saw), and did not use an endoscope to confirm position of the saw’s path as it went under the plantar calcaneus. Moreover, the Gigli saw was pulled through the plantar lateral and plantar medial incisions, which would place the plantar structures and medial neurovascular bundle at greater risk. In contrast, we recommend passing a non-absorbable suture initially and shuttling the Gigli saw thereafter to improve the procedure’s safety. The endoscope confirms the location of the suture’s path under the plantar medial heel, obviating the need for a fourth, plantar medial incision. Lastly, our preference is to have the Gigli saw exit from the proximal lateral and plantar lateral incisions to minimize injury potential to more critical plantar and medial structures, while protecting the skin with percutaneous skin retractors.

The perils of the open technique for calcaneal osteotomy have been noted in the literature. Previous reports and studies have shown risk to neurovascular structures, particularly on the medial side of the hindfoot, during calcaneal osteotomy procedures using a power saw^1,5,7. Branches of the lateral calcaneal nerve are directly in the path of the oblique incision commonly used in open techniques². The presently described PECO technique is clinically effective, minimally invasive, and maximally protective of neurovascular structures about the calcaneus during osteotomy.