The Outcome of Supramalleolar Osteotomy for Correction of Ankle and Hindfoot Deformity
January 1st, 2003
Emmanouil D. Stamatis*
Paul S. Cooper**
Mark S. Myerson*
Abstract
In a five year period (1996-2001), we performed a supramalleolar osteotomy for the correction of distal tibial mechanical malalignment of at least 10°, with concomitant pain and with or without radiographic evidence of arthritic changes. We also applied the method, as an alternative to other common procedures, for the treatment of a small group of patients with degenerative changes of the ankle joint without previous traumatic event and without or moderately altered alignment. Of interest was the application of the method in order to correct a previous mal-united ankle arthrodesis and as a staged procedure prior to a total ankle replacement. There were 14 patients (15 feet) with an average follow up of 31.1 months. All osteotomies healed at an average time of 13.6 weeks. The average AOFAS score improved from 53.8 to 87 points, the average Takakura score from 56.7 to 82 and the average pain score from 13.5 to 31.4. In the presence of deformity the average values of TAS and TLS angles were significantly improved. The radiographic degenerative changes in the ankle joint showed no evidence of progression. The choice of technique did not influence the clinical- radiographic outcome and the healing time of the osteotomy.
Introduction
The supramalleolar osteotomy has been commonly reported as a surgical technique to correct congenital or acquired foot and ankle disorders in the pediatric population. The indications for its use include deformities secondary to residual equinovarus after poliomyelitis or correction of clubfoot deformity (11, 14, 21), growth disturbances after physeal injury (20), and paralytic conditions such as myelomeningocele (1,15). In contrast, supramalleolar osteotomy is an often recommended (2, 3, 5, 9, 16-18) but rarely reported procedure to correct pathologic entities of the adult foot and ankle. The indications for its use in the adult population have included the treatment of foot and ankle pain and deformity secondary to various forms of systemic illness (6, 19), the correction of significant malunion of the distal two- thirds of the tibia with or without concomitant arthritic changes in the tibiotalar joint (4, 23) and the treatment of idiopathic ankle arthritis (22).
The purposes of the current retrospective study were to evaluate the outcome of a consecutive series of supramalleolar osteotomies performed at our institutions and to identify the influence of the technique on the outcome and the union rate. We were particularly interested in the overall outcome of supramalleolar osteotomy regarding pain relief, the correction of any mechanical malalignment, alteration of the progression of ankle arthritis, whether the type of osteotomy (opening versus closing wedge) influences the final outcome, and whether the type of osteotomy has an influence on the time of osseous healing.
Materials and Methods
In a five year period (1996-2001), 23 consecutive supramalleolar osteotomies were performed by the senior authors (PSC, MSM) in 22 adults and adolescents. Of the 22 patients (23 feet), 6 patients (6 feet) were lost to the final follow-up: one patient (one foot) was conducted but declined to participate, three patients (three feet) had moved from the area and could not participate, and two patients (two feet) could not be located. Two patients (two feet) had a non-union of the osteotomy requiring further operative treatment, and their follow-up after the last reconstructive procedures is still in progress. All the remaining 14 patients (15 feet) were successfully conducted and evaluated both clinically and radiographicaly. All of the patients’ medical records, including preoperative and postoperative chart notes and radiographs, and operative reports, were reviewed. There were 7 male and 7 female who had an average age of 50 years (range, 16 to 67 years) at the time of the procedure. There were 13 right and 2 left feet.
The pathological findings leading to supramalleolar osteotomy included: (a) Three feet (two adolescent patients) with distal tibial valgus deformity either due to physeal disturbance from adjacent osteochondromata or from physeal dysplasia with concomitant severe flatfoot deformity, with no degenerative changes in the ankle joint; (b) two feet (two patients) with varus malunion of a distal tibial fracture in varus with or without degenerative changes in the ankle joint; (c) four feet (four patients) with valgus malunion of a distal tibial fracture in valgus with or without degenerative changes in the ankle joint. In one of these patients, the osteotomy was performed in order to restore the limb alignment prior to a planned staged total ankle replacement; (d) one foot with a malunited ankle arthrodesis in equinus; (e) five feet (five patients) with degenerative changes of the ankle joint and without or moderately altered limb alignment. Four feet had varus ankle deformity and one valgus (Tables I, II).
Eight patients (eight feet) had had no previous operative treatment, while three patients (three feet) had had previous ORIF of a distal tibia fracture; one patient (one foot) had had previous ORIF of a distal tibia fracture, subsequent arthrodesis of the ankle joint and surgical debridement for osteomyelitis; one patient (one foot) previous ORIF of a distal tibia fracture and two subsequent attempts with corrective osteotomies; and one patient (one of the two feet) had had previous osteochondroma excision. The average time between the previous or last procedure and the osteotomy was 19.5 months (range, 6 to 38 months). All previous procedures had been performed at other institutions except the osteochondroma excision.
All five patients (five feet) with degenerative arthritis of the ankle joint and without or moderately altered mechanical alignment had had a failure of previous conservative treatment including activity modifications, use of nonsteroidal anti-inflammatory medication and brace, and physiotherapy. The average time of conservative treatment prior to the osteotomy was 9.4 months (range, 6 to 14 months). Two patients (two feet) with a previous non-operatively treated and malunited distal tibial fracture had had a time interval from fracture healing to osteotomy 7 and 10 months. The adolescent patient (one foot) with the valgus malalignment and concomitant flatfoot deformity was treated operatively without any previous conservative treatment, to avoid further aggravation of the deformities.
All patients had preoperatively reported significant levels of pain and/or ankle deformity interfering with their activities.
Preoperative assessment
A standard preoperative clinical assessment was performed and scores were assigned with the use of the ankle-hindfoot scale of the American Orthopaedic Foot and Ankle Society (AOFAS) (7). (A preoperative score according to the ankle scale of Takakura (23) was retrospectively assigned to all patients. The scores were assigned based on the charts notes and patients’ responses during the last follow-up. The purpose for that retrospective use was the fact that the Takakura scale assigns more points to the range of motion of the ankle). Modified AOFAS and Takakura scores were assigned to the patient with the malunited ankle arthrodesis since the ankle motion was eliminated.
All patients had had bilateral, full length weight bearing radiographs of tibia including the knee and ankle joints, and the following lines were drawn: A line representing the tibial mechanical axis (which in the case of the tibia coincides with the anatomic axis) and a line representing the distal tibial articular surface were drawn. On the AP view the angle formed by these lines is the tibioplafond angle (TAS). On the lateral view these lines form the lateral tibial articular angle (TLS). According to the literature normal TAS and TLS average 91°- 93° and 80°-81° respectively (5, 9). Ideally the appropriate TAS and TLS angles can be determined using radiographs of the healthy contralateral limb.
The degree of the arthritic changes in the ankle joint preoperatively, was classified with the retrospective use of Takakura’s scale (23), based on the preoperative radiographs. According to this scale the arthritic changes were classified, stage 1 (no narrowing of the joint space but evidence of subchondral bone sclerosis and formation of osteophytes; stage 2 (narrowing of the joint space medially or laterally); stage 3 (obliteration of the medial or lateral joint space and contact between adjacent subchondral bone); and stage 4 (complete obliteration of the joint space with bone to bone contact).
In the presence of ankle deformity with or without altered TAS and TLS angles the center of rotation and angulation (CORA) was determined (17, 18). The CORA is located at the intersection of two lines which represent the mechanical axes of the proximal and distal segments. In cases with isolated angular deformity, the CORA is at the apex of the deformity (Fig 1-2). When translation deformity is also present the CORA is located above the level of the deformity. In cases of very distal tibial deformities or ankle deformities with minor to moderate alterations of the TAS angle, the CORA is at the level of ankle joint line (Fig 3-4). Finally in cases of equinus deformity (malunion) after an ankle fusion, the CORA is at the intersection of the mechanical axis of the tibia and the line through the ankle center of rotation. In such a case the CORA is the level of the lateral process of the talus (17).
The purpose of such a radiographic preoperative planning was the fact that a closing or opening wedge osteotomy at the level of the CORA would lead to complete realignment of the foot and ankle (Fig 1-2). If the osteotomy was made proximal or distal to the CORA, the center of the ankle would translate relative to the mechanical axis of the tibia, creating an unnecessary shift of loads and a clinical obvious “zig-zag” deformity. To avoid creating a secondary translational deformity when the osteotomy is intentionally made at a different level than the CORA, the osteotomy line should be translated as well as angulated (Fig 3-4). These osteotomy rules apply irrespective of the method of fixation chosen (16, 17, 18). All osteotomies were closing or opening wedge which are the most commonly described techniques (5, 6, 16, 17, 19, 22, 23). The size of the wedge was determined by drawing the desired correction angle on the preoperative radiographs and measuring the wedge size on a template, taking magnification into account. If the deformity was both in sagital and coronal planes a wedge modification was necessary to correct the deformity.
Technique
All varus deformities were corrected utilizing a medial opening wedge osteotomy, while the valgus and one equinus deformities were corrected with the use of a medial and an anterior closing wedge osteotomy, respectively. If the osteotomy was performed to correct deformity, it was located at the level of the CORA (Fig1-2) (18). In cases of distal tibial deformities where the CORA was at the ankle joint level or in cases without substantial angular deformity of the tibia (degenerative ankle arthritis), the osteotomy was performed 4-5 cm proximal to the medial malleolar tip (Fig 3-4). The fibular osteotomy was performed first utilizing a small lateral incision. The osteotomy was oblique, located at the same level with the planned tibial cut. No fixation was applied to the fibular osteotomy, except in one case where it was felt that additional stability to the osteotomy was required.
For a medial opening wedge osteotomy, after a medial skin incision was made, minimal periosteal stripping was performed, and sufficient only to complete the osteotomy. Then a horizontal cut was made to the tibia utilizing a broad oscillating saw, preserving the opposite cortex and periosteal sleeve to act as a fulcrum for the opening wedge and to enhance stability. Then, and under fluoroscopy, the tibial osteotomy was gently distracted using a lamina spreader until correction of the deformity, and the created space was filled with an appropriate shaped bone graft. If translation of the distal segment was necessary in addition to the angular correction then the opposite cortex was completely cut.
For a medial closing wedge osteotomy a K-wire was inserted to the tibia perpendicular to the mechanical axis and a second k-wire was inserted parallel to the ankle joint line intersecting the first K-wire ideally at the apex of the deformity. Once the pins were in place their position was checked with fluoroscopy and if it was satisfactory, they were used as a guide to make the tibial cuts. All but one osteotomies were fixed with a periarticular titanium plate (Ace DePuy, Warsaw, IN), which provided excellent stability permitting the insertion of at least three screws in the distal segment. One osteotomy was fixed utilizing a cervical spine plate.
Bone graft was utilized in all opening wedge osteotomies (In one case only allograft was utilized and in five a combination of autograft from the tibial tubercle and allograft), while no graft was used for the 9 closing wedge osteotomies.
Concomitant procedures
Eight patients (eight feet) underwent concomitant procedures. Four patients with ankle arthritis had had an ankle joint arthroscopy for evaluation of the extent of pathology and they subsequently underwent arthroscopic debridement of the involved cartilage. They additionally underwent Achilles tendon lengthening. One patient underwent a biplanar calcaneal osteotomy for the correction of a fixed varus hindfoot deformity. One patient had had extra articular lateral column lengthening, dorsal opening wedge osteotomy of the medial cuneiform and Achilles tendon lengthening for the correction of severe but flexible flatfoot deformity and one patient had had an Achilles tendon lengthening.
Post-operative management
The procedure was performed on an inpatient basis and all patients were observed overnight for pain control. All patients were discharged with the postoperative splint. After adequate wound healing and suture removal, the foot was placed in a removable, prefabricated fracture boot. All patients, depending on the stability of fixation, were kept non- or partial-weight bearing until there was evidence of radiographic healing. Early range of motion exercises without resistance were initiated early, in the cases where there was no concomitant procedure which differentiated the rehabilitation protocol.
Last follow-up assessment
The current study had received approval by the internal review board (IRB), and informed consent form was obtained from all patients. The first author (EDS), who was not directly involved in the procedures, conducted the review. All patients had standard clinical assessment and responded to questions regarding their pain level, limitations of activities, and walking ability. Scores were assigned with the use of the AOFAS and Takakura ankle-hindfoot scales. All radiographs, including those of the last follow-up were reviewed and the magnitude of preoperative and postoperative TAS and TLS angles was determined. Additionally preoperative and postoperative radiographs were reviewed to evaluate the degree of the arthritic changes in the ankle joint. The findings were classified with the use of Takakura’s scale (23). The time to osseous union was determined by reviewing all sequential postoperative radiographs and chart notes.
Data collection and analysis were performed with Microsoft Excel (Microsoft Corp, Bellevue, WA). Statistical analysis was performed to compare the preoperative and postoperative AOFAS and Takakura scores of the 12 patients (13 osteotomies), using the Student t-test for paired samples. The patient who in the meantime underwent a total ankle replacement and the patient with the modified scores were excluded. The significance was set at p< 0.05. The same test was utilized to compare the preoperative and postoperative pain scores of the 13 patients (14 osteotomies), excluding the patient with the ankle replacement. Preoperative and postoperative average values of TAS and TLS angles were also compared.
Additional statistical analysis was performed in order to identify the influence of the type of osteotomy on the postoperative AOFAS, Takakura and pain scores. The Student t-test for independent samples was utilized and the significance was set at p< 0.05. The same test was utilized to compare the influence of the osteotomy type on the time of osseous healing and the significance was again set at p< 0.05.
Results
All the data from the 14 patients (15 osteotomies) is included in tables I and II.
The average follow-up after the 15 osteotomies was 31.1 months (range, 12 to 59 months). The average time to healing was 13.6 weeks (range, 6 to 36 weeks, STD± 7.78). There were 9 closing wedge osteotomies (8 medial closing wedge and 1 anterior closing wedge) with an average time to healing of 10.6 weeks (range, 6 to 22 weeks, STD± 4.55) and 6 medial opening wedge with an average time to healing of 18.1 weeks (range, 10 to 36 weeks, STD±9.8). Comparing the healing time of these two groups of osteotomies, the difference was not statistically significant (p=0.06).
Excluding the patient who had already had a total ankle replacement before the time of the last follow up and the patient with the modified scores due to ankle arthrodesis, the remaining 12 patients (13 osteotomies) had an average preoperative AOFAS score of 53.8 (range, 18 to 80, STD±19.26). The average Takakura preoperative score was 56.7 (range, 22-85, STD±18.39).
The postoperative average AOFAS and Takakura scores were 87 (range, 68 to 100, STD±10.14) and 82 (range, 60 to 100, STD±13.6). The difference between the preoperative and postoperative scores was statistically significant with p<0.001. The patient with the mal-united ankle arthrodesis had preoperative and postoperative modified AOFAS scores of 8/92 and 51/92 respectively. The same values for the Takakura score were 5/80 and 45/80 respectively.
Excluding the patient who had already had a total ankle replacement at the time of the last follow up, the remaining patients reported that 5 feet had severe, 8 feet moderate, and one foot mild preoperative pain. The same patients reported that 4 feet were pain free postoperatively, while 8 had mild, and 2 moderate pain. From the two feet with moderate postoperative pain, one was that with the ankle fusion where significant degenerative arthritis was evident in the subtalar joint. The preoperative average pain score (as it was assigned from the AOFAS scale) was 13.5 (range, 0 to 30, STD±10.8) while the average postoperative score was 31.4 (range, 20 to 40, STD±6.6) and the difference was statistically significant (p<0.001).
The postoperative average AOFAS and Takakura scores, for the group of patients with opening wedge osteotomies, were 82 (range, 68 to 90) and 76.8 (range, 60 to 90), respectively. The same values, for the group of patients with closing wedge osteotomies (excluding the patient with the modified scores and the patient with the ankle replacement), were 91.2 (range, 72 to 100) and 86.4 (range, 60 to 100), respectively. The difference was not statistically significant (p=0.09).
The postoperative average level of pain was 28.3 (range, 20 to 30) and 33.75 (range, 20 to 40) for the opening wedge and closing wedge group respectively. The difference was not statistically significant (p=0.1).
Preoperatively, 9 out of 14 feet had evidence of arthritis in the ankle joint. One foot had stage 4 and 8 feet had stage 2 arthritic changes, according to Takakura scale (29). The patient with the stage 4 changes underwent the osteotomy in order to correct the mechanical axis and as a prelude for a staged total ankle replacement. The remaining 8 feet had no evidence of progression of the arthritic changes in the last follow-up radiographs.
The preoperative average TAS angle in the 7 feet with significant valgus malalignment (>5° beyond normal) was 106.2° (range, 100° to 116°, STD±5.21) and the postoperative average value was 92.1° (range, 89° to 98°, STD± 3), with the difference statistically significant (p<0.001). The preoperative average TAS angle in the 3 feet with significant varus malalignment (>5° below normal) was 72° (range, 68° to 78°) and the postoperative average value was 86.6° (range 84° to 90°), with the difference statistically significant (p=0.008).
The remaining 4 feet had no significant alterations of the TAS angle preoperatively. The preoperative average TLS angle was 82.4° (range, 78° to 89°, STD±3.3) and the postoperative average value was 84° (range, 80°-86°, STD±1.5), with no statistically significant difference (p=0.1).
Finally 6 patients (4 closing wedge and 2 opening wedge osteotomies) had side to side, postoperative, leg length discrepancy of at least 5mm, with an average of 8.8 mm (range, 5 to 12 mm, STD±2.3).
Complications occurred in 5 patients, except the two non-unions who required further procedures. One had delayed union of the osteotomy requiring bone graft from the iliac crest, one patient had a superficial infection which was addressed with local wound care and antibiotics, and three patients had decreased postoperative range of motion of the ankle joint comparing to that preoperatively. One of them, who underwent a medial closing wedge osteotomy below the level of CORA, had had increased lateral translation of the distal segment of the osteotomy with subsequent shift of the mechanical axis over the medial aspect of the ankle joint.
Discussion
There does not appear to be a consensus in the reported literature regarding the acceptable limits of angular deformity of the tibia and the potential for development of pain in the ankle joint or radiographic evidence of arthritis. Merchant et al (12) reported on the radiographic appearance and the clinical function of the knee and the ipsilateral ankle joints. They found that neither were statistically different in patients who had a combination of 5° angulation in the frontal plane and 10° or more in the sagittal plane when compared with patients who had less angulation. Kristensen et al (8), reported on angulations exceeding 10° compatible with normal function and absence of pain.
On the other hand, biomechanical studies on cadavers have showed that in the presence of malalignment, there is a decrease of the contact surface area in the ankle joint up to 40% (24, 25). Tarr et al (24) found that distal tibial deformities significantly alter total tibiotalar contact area, contact shape and contact location. Interestingly the greater changes were observed with deformities in the sagittal plane (as much as 42% for anterior bow of 15° and 40% for posterior bow of 15°). Ting et al (25), confirmed these findings and also found that the subtalar joint (acting as a torque transmitter and compensating coronal plane tibial deformities) plays a significant role in maintaining the talus in normal position relatively to the tibia. Thus, the presence of hindfoot stiffness severely affects tibiotalar contact pressure changes from angular deformities of the tibia.
Significant mechanical malalignment with subsequent displacement of the axis of motion of the ankle joint and altered load distribution and joint mechanics leads to increased stress, pain, articular cartilage damage and subsequent degenerative disease. The fact that previous studies have demonstrated the increased incidence of hindfoot disability (10, 13) after tibial fractures, dictates that in cases of concomitant tibial malunion and hindfoot stiffness realignment is imperative.
Previous clinical studies (4, 23) have demonstrated that supramalleolar osteotomy affords a satisfactory method of reducing or eliminating symptoms referable to the ankle and hindfoot following a significant malalignment of the distal tibia. Additionally, the mechanical correction was beneficial when there was evidence of arthritic changes in the ankle joint, since there was significant reduction of the progression of the disease. In another interesting clinical study (22), Takakura et al demonstrated that a supramalleolar osteotomy was an excellent alternative method of treatment in the presence of idiopathic arthritis of the ankle joint. The philosophy in that group of patients was to shift the loads and redistribute stresses to a part of the ankle joint which was not involved in the degenerative process.
In our series we performed a supramalleolar osteotomy for the correction of distal tibial mechanical malalignment of at least 10°, with concomitant pain and with or without radiographic evidence of arthritic changes. We also applied the method, as an alternative to other common procedures, for the treatment of a small group of patients with degenerative changes of the ankle joint without previous traumatic event and without or moderately altered alignment. Of interest was the application of the method in order to correct a previous mal-united ankle arthrodesis and as a staged procedure prior to a total ankle replacement.
Our results confirmed our hypotheses that (a) the overall outcome of supramalleolar osteotomy regarding pain relief, correction of any existent mechanical malalignment and the lack of progression of arthritic changes in the ankle joint, is very good, (b) the type of osteotomy (opening versus closing wedge) does not influence the final outcome, despite the issue that a closing wedge osteotomy may lead to leg length discrepancy or decreased strength and (c) ) the type of osteotomy (opening versus closing wedge) has no influence on the time of osseous healing. In fact this later comparison should probably have different result, if the two non-unions, which occurred after medial opening wedge osteotomies, had been taken into account.
Conclusions
The supramalleolar osteotomy for the treatment of pathologic entities of the adult distal tibia and foot and ankle, has received limited attention in the literature. It is technically demanding, and requires an extensive and careful preoperative planning. To our hands has been proved a useful procedure to: a. reconstruct the normal mechanical environment in malunion preventing or decelerating any long term deleterious effects and improving pain and function levels, and b. to shift and redistribute loads in the ankle joint in an effort to protect the articular cartilage from further degenerative process.
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