A Closer Look At The Distal Tibial Osteotomy For Ankle Varus

These authors discuss the distal tibial osteotomy and present a case study of a 23-year-old female with concomitant ankle varus and post-traumatic ankle pain.

Distal tibial osteotomies are powerful corrective procedures surgeons often use for realignment of various ankle deformities. A 23-year-old healthy female presented with a posteromedial talar dome lesion following a fall. The lesion was 11 mm x 17 mm x 5 mm. The patient had no significant past medical or surgical history. She was taking no medications, did not use tobacco and drank alcohol on occasion at the time of surgery.

   We sought to correct her medial talar dome lesion, stabilize her cartilage and give her support with a lateral soft tissue correction. Then if she did well, we would revisit the operative limb with a corrective tibial osteotomy.

   In August 2011, the patient underwent an ankle arthroscopy with extensive debridement, a medial malleolar osteotomy and debridement of the talar dome lesion with application of a juvenile hyaline cartilage implant. During this same operation, she also had an open modified lateral ankle stabilization procedure. After doing well through her recovery process from the primary procedure, she was ready for her secondary corrective procedure: a distal tibial osteotomy.

   In May 2012, we performed an ankle arthroscopy to debride any synovitis and subsequently performed an opening wedge tibial osteotomy. From the tibiotalar angle on an AP ankle radiograph, we determined the preoperative angular correction to be approximately 9 degrees. After an extensive debridement of her ankle joint through the standard anteromedial and anterolateral portals, we made an 8 cm longitudinal skin incision proximally from the medial malleolus. When deepening the dissection, one should carefully avoid the great saphenous vein and saphenous nerve, which usually lie in the anterior portion of the incision.

   We created full-thickness flaps to the level of the periosteum at the site of the proposed osteotomy. Using a Cobb elevator, we made a periosteal flap parallel to the skin incision. Since the deformity’s center of rotation and angulation (CORA) is at the level of the ankle joint, we normally perform our osteotomy about 4 cm proximal to the medial malleolar tip. Then we inserted a Steinmann pin under fluoroscopy proximal and distal to the proposed osteotomy. Before creating the osteotomy, we used Hohmann retractors to carefully avoid cutting the posterior tibial tendon and the posterior neurovascular bundle.

   Using a wide saw blade, we created an osteotomy, aiming slightly proximal to distal while extending the cut from medial to lateral under fluoroscopy. The lateral tibial cortex was intact so as to not destabilize the distal fragment. Using the wide Hintermann distractor, we were able to open the medially based wedge to our desired length while visualizing it directly under fluoroscopy. Once the ankle joint was congruent, we cut our allograft femoral neck just above the desired width, accounting for resorption and the width of the saw blade. After inserting the bone graft with a tamp and mallet, we removed the pins and applied a medial locking plate.

   We closed the periosteum and subcutaneous tissues in standard fashion with absorbable sutures and the skin with interrupted nonabsorbable sutures. We then placed the operative limb in a well-padded posterior splint.

   The patient remained non-weightbearing for six weeks in a cast and subsequently wore a weightbearing fracture boot for a month. She then transitioned to supportive shoes with custom-molded orthoses. Her follow-up consisted of serial radiographs until radiographic healing of at least two cortices was visible.

   The correction of her ankle varus and staged lateral collateral ligament stabilization decreased her varus moment upon heel strike, improved her ankle range of motion and decreased her talar tilt. All of these in combination act to neutralize her gait, prevent recurrent ankle sprains and decrease the contact forces acting on the medial talar dome. This will also decrease the likelihood of an ankle fusion in a young, active patient.

A Guide To Indications And Surgical Planning For Distal Tibial Osteotomies

Distal tibial osteotomies, or supramalleolar osteotomies, have been an orthopedic mainstay for the treatment of tibiotalar varus and valgus. Indications for these corrective osteotomies include post-traumatic deformities, ankle deformity secondary to systemic illnesses and idiopathic ankle arthritis.1,2 Distal tibial osteotomies are also indicated in the pediatric population for congenital tibial deformities including physeal growth arrest with concomitant growth disturbances.3

   Preoperative surgical planning for tibiotalar deformities and other angular deformities of the lower extremity involves assessing the patient’s gait, and mechanical and anatomic lower extremity axes, as well as obtaining proper radiographs. For the purpose of this case study, the focus remains on the coronal plane deformity.

   Assess the tibial mechanical axis on AP and lateral full-length weightbearing radiographs of the operative limb. Then draw the distal tibial articular surface with the angle formed between the tibial mechanical axis, resulting in the tibial-ankle surface angle on an AP view and the tibial-lateral surface angle on a lateral view. The normal tibial-ankle surface angle is approximately 91 to 93 degrees and the normal tibial-lateral surface angle is 80 to 81 degrees.4

   Using the standard Ilizarov principles of deformity correction, determine the center of rotation and angulation with the mechanical axes of the tibia and talus. To prevent the need for translation, make the tibial osteotomy at the center of rotation and angulation.5,6 When the center of rotation and angulation is at the level of the joint and with minimal deformity, one can create the osteotomy about 3 to 4 cm proximal to the joint line. One can determine the amount of correction needed, in terms of bone graft width, by the desired tibial-ankle surface angle correction to normal ankle alignment with the following formula:7

tan θ = height of wedge in millimeters / tibial width

What The Literature Reveals On Osteotomies

   Medial opening wedge osteotomies are the most common procedures for ankle varus but the literature is scarce regarding long-term outcomes.

   Stamatis and colleagues retrospectively reviewed 13 cases of either distal tibial medial closing wedge osteotomies or medial opening wedge osteotomies for angular deformity with an average follow up of 33 months.8 There were six males and six females with a mean age of 46. Preoperative diagnoses included degenerative arthritis, post-traumatic malunion and congenital deformities. Surgeons performed seven medial closing and five medial opening wedge osteotomies. Outcome measures included American Orthopedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scores, Takakura ankle arthritis scores and pain levels.9

   Average AOFAS scores improved from 53.8 to 87 points and the Takakura score improved from 14.6 to 32.3 points.8 Pain levels also improved for this small subset of patients over their follow-up period. Researchers saw no significant difference in leg length discrepancy or the time to osseous healing between a medial closing and opening wedge osteotomy. There were two nonunions and one delayed union in this study.

   Harstall and colleagues used a lateral closing wedge osteotomy in the treatment of nine patients with ankle varus.10 The average follow-up for this group was 56 months and the average time to osseous union was 10 weeks. The AOFAS and pain scales both significantly improved postoperatively to 74 and 30 respectively. Despite the angular correction, one patient required subsequent arthrodesis at 16 months postoperatively. Researchers found that anecdotally with a laterally based wedge, the incidence of hardware removal due to irritation was minimal and there was decreased leg length discrepancy and medial soft tissue contracture.

   In a prospective study, Knupp and co-workers performed supramalleolar osteotomies on 94 ankles and followed them for 43 months.11 The aim of this study was to assess the progression of ankle arthritis and develop a classification algorithm using these findings. Preoperatively, researchers subdivided patients into categories based on the amount of ankle tilting (greater or less than 4 degrees) and the degree of joint space narrowing. Balancing procedures occurred as necessary to obtain a congruent joint. This happened for varus and valgus deformities of the ankle. The AOFAS scores for the varus and valgus ankles improved and total visual analogue scores improved as well. Of note, 10 ankles failed and went on to either total ankle replacement or arthrodesis. This low failure rate for supramalleolar osteotomies is similar to other studies.1,7,8

In Conclusion

Distal tibial osteotomies can decrease the progression of ankle joint arthritis. They are powerful corrective procedures that require careful preoperative planning in all planes. Here are some further take-home pearls.

• Use long leg and foot full weightbearing films from the unaffected limb as normal comparisons.
• When performing a medial opening wedge osteotomy, maintain the lateral cortical hinge.
• Use a wide angle Hintermann distractor to obtain the correction under fluoroscopy for easy osteotomy access.
• We suggest the femoral neck allograft for its thick tricortical strut.
• Slightly overcorrect the deformity to allow for some settling.

   Dr. McAlister is a current fellow at the Advanced Foot and Ankle Fellowship at the Orthopedic Foot and Ankle Center in Westerville, Ohio.

   Dr. Philbin is a fellowship-trained foot and ankle surgeon who is currently in private practice in Westerville, Ohio.

References

1. Takakura Y, Takaoka T, Tanaka Y, et al. Results of opening-wedge osteotomy for the treatment of a post-traumatic varus deformity of the ankle. J Bone Joint Surg Am. 1998; 80(2):213–218.
2. Pearce MS, Smith MA, Savidge GF. Supramalleolar tibial osteotomy for haemophilic arthropathy of the ankle. J Bone Joint Surg Br. 1994; 76(6):947–950.
3. Scheffer MM and Peterson HA. Opening-wedge osteotomy for angular deformities of long bones in children. J Bone Joint Surg Am. 1994; 76(3):325–334.
4. Mangone PG. Distal tibial osteotomies for the treatment of foot and ankle disorders. Foot Ankle Clin. 2001; 6(3):583–597.
5. Paley D and Herzenberg JE. Applications of external fixation to foot and ankle reconstruction. In: Myerson MS (ed.) Foot and Ankle Disorders, WB Saunders, Philadelphia, 2000, pp. 1135–1188.
6. Paley D, Herzenberg JE, Tetsworth K, et al. Deformity planning for frontal and sagittal plane corrective osteotomies. Orthop Clin North Am. 1994; 25(3):425–465.
7. Knupp M, Stufkens SAS, Pagenstert GI, et al. Supramalleolar osteotomy for tibiotalar varus malalignment. Tech Foot Ankle Surg. 2009; 8:17-23.
8. Stamatis ED, Cooper PS, Myerson MS. Supramalleolar osteotomy for the treatment of distal tibial angular deformities and arthritis of the ankle joint. Foot Ankle Int. 2003; 24(10):754–764.
9. Takakura Y, Tanaka Y, Kumai T, Tamai S. Low tibial osteotomy for osteoarthritis of the ankle. Results of a new operation in 18 patients. J Bone Joint Surg Br. 1995; 77(1):50–54.
10. Harstall R, Lehmann MD, Krause F, et al. Supramalleolar lateral closing wedge osteotomy of the treatment of varus ankle arthrosis. Foot Ankle Int. 2007; 28(5):542-548.
11. Knupp M, Stufkens SAS, Bolliger L, et al. Classification and treatment of supramalleolar deformities. Foot Ankle Int. 2011; 32(11):1023-1031.