In 1937, Blount described a group of patients with the onset of varus deformity in later childhood or early adolescence, a condition that he called adolescent tibia vara1. Thompson et al. clarified this classification by including children in whom varus developed at the age of four years or older and called it late-onset tibia vara2,3. The disorder was subclassified as juvenile if the onset of varus was between the ages of four and ten years and as adolescent if the onset of varus was at the age of eleven years or older. The deformity is thought to result from increased stress on the medial aspect of the knee due to the “fat-thigh gait”4 combined with the effect of obesity on the physes about the knee3-9. Particularly in older children, the genu varum deformity often includes distal femoral varus in addition to the deformity in the proximal part of the tibia10. The long-term effect of the varus is to potentiate the development of degenerative arthritis of the knee11-14.
Nonoperative treatment is ineffective for late-onset tibia vara15. Proximal tibial valgus osteotomy is the mainstay of treatment2,8,16-25, but a number of other procedures have also been performed, including hemiepiphysiodesis, physeal distraction, and distraction osteogenesis with use of a circular external fixator8,26-35. Although proximal tibial valgus osteotomy is commonly recommended, it is not a benign procedure and it is technically difficult. It is associated with a high rate of complications, including wound problems, neurovascular injury, malalignment, and loss of correction8,11,17,23,36-40. Distraction osteogenesis with a circular external fixator provides consistent correction of the tibial deformity and limb-length discrepancy associated with late-onset tibia vara, but it has the potential disadvantages of poor patient compliance, a high complication rate, and the need for a second anesthetic for device removal29,41,42.
Although we have utilized distraction osteogenesis for patients with pain, deformity, and knee instability but minimal or no remaining physeal growth, we have used hemiepiphyseal stapling for selected patients with sufficient remaining growth to allow correction of the deformity. Hemiepiphyseal stapling is technically simpler than the other procedures, and it requires only a small lateral incision over the proximal tibial physis and, if needed, the distal femoral physis. Although hemiepiphyseal stapling has been previously described in patients with late-onset tibia vara30,43, we are not aware of any reports dealing solely with the results of hemiepiphyseal stapling in patients with late-onset tibia vara. The purpose of this study was to report the outcome and complications of hemiepiphyseal stapling in a series of patients with late-onset tibia vara.
Materials and Methods
A review of records identified thirty-four children who had undergone hemiepiphyseal stapling for late-onset tibia vara at two institutions between January 1, 1992, and December 31, 1999. Eight of them (with nine involved extremities) with relatively mild deformities had been lost to follow-up less than two years after the index procedure, but, when last seen, they had either closed or closing physes in good alignment. Attempts to contact these patients were unsuccessful. The remaining twenty-six patients, with forty-two involved extremities, were followed for a minimum of two years after the surgery. In nine extremities, an osteotomy of the tibia had been performed concomitantly with a distal femoral hemiepiphyseal stapling, and those limbs were excluded from the study. Twenty-six patients (thirty-three extremities) were included in the study group.
The medical records of the twenty-six patients were reviewed for demographic information, surgical details, and complications. The result was considered to be final at either skeletal maturity or just prior to definitive corrective osteotomy for a residual deformity. All pertinent radiographs of the lower extremities, including those made preoperatively and at the most recent follow-up visit, were reviewed. We used standardized standing long-cassette anteroposterior radiographs of the lower extremity made with the knee facing directly anteriorly44,45 to measure the mechanical axis deviation, the mechanical medial proximal tibial angle, the mechanical lateral distal femoral angle, and limb-length discrepancy44,45. The knee joint was divided into zones for classification with a modification of the method described by Mielke and Stevens31 (Fig. 1). Medial (varus) zones were labeled -1, -2, -3, and -4 depending on the severity of varus angulation. The zone through which the mechanical axis passed was recorded.
The result was graded as normal alignment, varus undercorrection, or valgus overcorrection on the basis of the zone through which the mechanical axis passed on either the final radiograph or the radiograph made prior to osteotomy. Normal alignment indicated that the mechanical axis passed through zone 1 or -1. Mild varus undercorrection was defined as the mechanical axis passing through zone -2, and moderate varus undercorrection was defined as the mechanical axis passing through zone -3. Valgus overcorrection indicated that the mechanical axis passed through zone 2, 3, or 4.
The final result was classified as successful, partially successful, or unsuccessful. A successful result indicated that neither a proximal tibial nor a distal femoral valgus osteotomy was necessary, either because alignment was normal or because there was only mild residual varus deformity that was not a concern to the patient or family. A partially successful result indicated that a corrective osteotomy was necessary but hemiepiphyseal stapling obviated the need to perform an osteotomy on either the tibia or the femur that would have otherwise been necessary. An unsuccessful result indicated that an osteotomy was required to correct the residual varus or valgus deformity.
Hemiepiphyseal stapling (Figs. 2-A, 2-B, and 2-C) was performed at our institution when genu varum due to late-onset tibia vara was present in a patient who was skeletally immature and who, in the surgeon's judgment, had adequate growth remaining to allow full correction of the deformity. The surgeon based the decision regarding adequate remaining growth on the patient's chronological age, the widths of the physes, and the magnitude of the deformity. Skeletal age was not routinely assessed with the use of the Greulich and Pyle atlas46. Patients with a lower-extremity length discrepancy of >3 cm, laxity of the lateral collateral ligament, closing physes with a large deformity, or substantial pain when walking were not considered for hemiepiphyseal stapling alone.
There were twenty-one boys and five girls, with a mean age of 11.8 years (range, 8.1 to 14.9 years) at the time of the hemiepiphyseal stapling. Fifteen patients were white, and eleven were black. The mean body weight at the time of the surgery was 84 kg (range, 40 to 154 kg), with the weight of twenty-three of the twenty-six patients in excess of the 95th percentile for their age. The patients were followed postoperatively for a mean of 3.8 years (range, two to 6.8 years). Seven of the twenty-six patients were treated bilaterally with the index procedure. Lateral hemiepiphyseal stapling of the proximal part of the tibia was performed on all extremities, and concomitant lateral hemiepiphyseal stapling of the distal part of the femur was performed on fourteen extremities. Distal femoral stapling was indicated when >5° of distal femoral varus (a lateral distal femoral angle of ≥93°) was noted. All but three patients (three extremities) were skeletally mature at the time of final follow-up. The results in these three patients were considered to be final for the purpose of this study, as an osteotomy was ultimately required to complete the correction of the deformity.
The patient was placed in a supine position on a radiolucent table (Orthopedic Systems, Hayward, California) with adequate elevation of the ipsilateral hip to allow access to the lateral aspect of the knee. A 3 to 5-cm incision was made over the lateral aspect of the proximal tibial physis, just anterior to the fibula, and extraperiosteal dissection was performed. The physis was located with a Keith needle with the aid of fluoroscopy. Two or three cobalt-chromium-alloy Vitallium Blount staples (Zimmer, Warsaw, Indiana) were placed extraperiosteally across the lateral aspect of the proximal tibial physis. Distal femoral hemiepiphyseal stapling, when indicated, was performed through a second 3 to 5-cm incision over the lateral aspect of the distal femoral physis. These staples were also placed after an extraperiosteal dissection. Staple position was confirmed intraoperatively with use of anteroposterior and lateral fluoroscopy.
Postoperatively, patients were allowed to bear weight as tolerated without immobilization. The strategy for staple removal varied, depending on both the correction that had been obtained and the patient's age. Ideally, anatomic correction occurs concomitant with spontaneous physeal closure at skeletal maturity and staple removal is optional. For patients who are nearly but not yet skeletally mature, have minimal lower-extremity length discrepancy, and have a mechanical axis passing through the center of the knee, percutaneous drilling epiphysiodesis47-49 through the lateral incision can be performed concomitant with staple removal. In patients with substantial remaining growth, as determined by chronological age and the width of the physis on radiographs, overcorrection well into valgus zone 1 was allowed with the anticipation that rebound growth would result in the mechanical axis of the lower extremity passing through the center of the knee at skeletal maturity.
Preoperatively, the mechanical axis passed a mean of 58 mm (range, 27 to 157 mm) medial to the center of the knee. The mean mechanical axis deviation improved to 22 mm (range, -33 to 117 mm) at the time of the last follow-up. The mean medial proximal tibial angle (normal, 87° with a range of 85° to 89°) improved from 77° (range, 50° to 85°) preoperatively to 85° (range, 48° to 95°) at the time of the last follow-up. Preoperatively, the mean lateral distal femoral angle (normal, 88° with a range of 86° to 89°) was 92° (range, 87° to 100°) in the series as a whole and 96° (range, 92° to 100°) in the fourteen lower extremities that were treated with supplemental lateral distal femoral hemiepiphyseal stapling. The mean lateral distal femoral angle in these fourteen limbs improved to 86° (range, 79° to 97°).
Preoperatively, the mechanical axis passed through zone -2 in twelve knees, zone -3 in seventeen, and zone -4 in four. At the time of the last follow-up, the mechanical axis passed through the central portion of the knee (zone -1 or 1) in twenty (61%) of the thirty-three lower extremities. Of these twenty extremities, which were classified as having normal alignment, eleven had had a preoperative mechanical axis that passed through zone -2; eight, zone -3; and only one, zone -4 (Table I). In eleven extremities (33%), the final mechanical axis was medial to the central zones of the knee, which was considered to be varus undercorrection. Of these eleven extremities, four had mild varus and seven had moderate varus. One had been corrected so that the axis passed through zone -1, but rebound varus occurred after staple removal and the extremity ultimately was classified as having mild varus, with the mechanical axis passing through zone -2. A repeat hemiepiphyseal stapling was performed, and ultimately the alignment was in zone 1, but the result was considered to be a varus undercorrection because of the repeat stapling. The patient and his or her family were satisfied with the alignment of all of the four extremities that were classified as being in mild varus, and they declined additional surgery although a tibial osteotomy to correct the remaining deformity was offered.
At the time of the final follow-up, normal alignment was noted in fourteen (61%) of the twenty-three extremities with juvenile tibia vara and six of the ten with adolescent tibia vara. With the numbers available, there was no significant difference between these two groups with regard to final alignment (Table II).
Of the seven patients (seven extremities) with moderate varus undercorrection, one was later found to have a medial proximal tibial physeal bar that had not been apparent at the time of stapling. Two patients had early staple migration or breakage, which was not revised. Early in the series, one patient had distal femoral varus that had not been appreciated at the time of the proximal tibial stapling. The proximal tibial deformity was fully corrected, but the patient was left with residual femoral varus, which was later corrected with a distal femoral osteotomy. One patient was fifteen years of age at the time of the hemiepiphyseal stapling and had insufficient remaining growth to correct the deformity. The two remaining extremities with moderate undercorrection had had severe varus preoperatively, with the mechanical axis passing through zone -4 in both and a mechanical axis deviation of 118 mm in one and 157 mm in the other. Although the patients were young when the hemiepiphyseal stapling was performed, the deformities corrected very slowly, and an osteotomy was later performed because of increasing knee pain.
The mechanical axis of two extremities passed lateral to the central zones of the knee (through zone 2) at the time of follow-up, and these limbs were considered to have valgus overcorrection. Both of these patients had failed to return for follow-up at the requested time; they returned only after the valgus overcorrection had developed.
The results were also examined with regard to whether the procedure was successful in correcting the limb adequately to obviate the need for additional surgery. Of the twelve extremities (eleven patients) with a mild preoperative deformity (zone -2), eleven had normal final alignment and one had worsening of the varus in spite of the hemiepiphyseal stapling (Table III).
Of the seventeen extremities (sixteen patients) with a moderate preoperative deformity (zone -3), fourteen had alignment that was satisfactory to the patient at the time of follow-up. Of these fourteen extremities, eight (eight patients) had normal alignment at the time of follow-up, four (four patients) had residual mild varus undercorrection, and two (two patients) had valgus overcorrection. The hemiepiphyseal stapling in these fourteen extremities was considered to be successful in obviating the need for additional surgery. The remaining three extremities with moderate preoperative deformity had moderate varus undercorrection. In one of them, the distal part of the femur was adequately corrected and, although a tibial osteotomy was ultimately required, a femoral osteotomy was not. In the second extremity with moderate varus undercorrection, the tibia was corrected but there was residual varus of the distal part of the femur that required a distal femoral osteotomy. The hemiepiphyseal stapling in these two extremities was considered to be partially successful because, although an osteotomy was required in either the femur or the tibia, it was not needed in both, as would have been necessary without stapling. The final patient with residual moderate varus required a tibial osteotomy despite hemiepiphyseal stapling and was considered to have an unsuccessful result.
Of the four patients (four extremities) with a severe preoperative deformity (zone -4), one obtained complete correction and was considered to have a successful result. The other three patients subsequently required both femoral and tibial osteotomies for correction of the deformity and were considered to have an unsuccessful result. Thus, according to our criteria for outcome assessment, hemiepiphyseal stapling was successful in twenty-six extremities, partially successful in two, and unsuccessful in five. Of the twenty-nine extremities with mild or moderate preoperative varus, twenty-five had a successful result; two, a partially successful result; and two, an unsuccessful result.
Four patients (four extremities) had a lower-extremity length discrepancy of >2 cm (mean, 2.7 cm; range, 2.5 to 3.0 cm) at the time of the final follow-up. The result was classified as unsuccessful for three of these four extremities, and the residual discrepancy was corrected at the time of a definitive osteotomy. The remaining patient was asymptomatic with a 3.0-cm discrepancy and declined further treatment. No patient was found to have limited knee motion or to have knee hyperextension suggestive of recurvatum at the time of the final follow-up.
The staples were ultimately removed from ten extremities. Four of these extremities were considered failures and had the staples removed near or after skeletal maturity or at the time of an osteotomy. Another extremity had recurrence of the deformity after staple removal, as discussed previously, and was treated with repeat stapling. Three other extremities (two with a mechanical axis passing through zone -1 and one with a mechanical axis passing through zone -2) had the staples removed, after skeletal maturity, at the family's request. The final two extremities had the staples removed prior to skeletal maturity. At the time of the final follow-up (two and three years after the staple removal), which was after skeletal maturity, those two extremities had a mechanical axis passing through either zone 1 or zone -1.
One patient had a common peroneal nerve neurapraxia, probably due to excessive retraction at surgery. It resolved spontaneously three months postoperatively. No wound infections or other early complications developed. The staple backed out of the bone in five extremities. A reoperation was performed to reinsert staples in three of these extremities and ultimately led to a successful result. The other two patients with staple migration did not return for follow-up until after skeletal maturity. Both had residual moderate varus at that time.
The goal of surgical treatment of late-onset tibia vara is restoration of normal knee and limb alignment as well as normal joint orientation in order to minimize the risk of degenerative arthritis of the knee. Historically, the mainstay of treatment of late-onset tibia vara has been valgus osteotomy of the proximal part of the tibia. Alternatives to osteotomy include hemiepiphysiodesis8,50 and hemiepiphyseal stapling. Hemiepiphysiodesis, however, has the disadvantage of being permanent, as it irreversibly stops growth capacity, and thus requires accurate estimation of remaining growth, which is difficult51-53. Hemiepiphyseal stapling, as introduced by Blount30,43, is relatively easy to perform, perioperative morbidity is minimal, correction occurs at the site of the deformity, and longitudinal growth can resume following staple removal.
The primary criterion that we used to evaluate the preoperative severity of the deformity and the outcome of treatment was the mechanical alignment of the lower extremity. Once hemiepiphyseal stapling is performed, it is critical to follow the patient closely both clinically and radiographically to monitor correction. Patients and their families often note improvement—indeed, full correction of the deformity—and tend not to return for follow-up, despite preoperative warnings about the potential for overcorrection. Two of our patients had valgus overcorrection requiring operative treatment. We recommend achieving slight overcorrection of the varus deformity in patients with substantial remaining growth and allowing the mechanical axis to pass 1 to 2 cm lateral to the center of the knee prior to staple removal. Following staple removal, rebound varus will occur, usually bringing the mechanical axis back to the center of the knee. Again, clinical and radiographic follow-up is essential. Varus did recur in one of our patients. In some older adolescent patients with a minimal limb-length discrepancy, we have removed the staples when the mechanical axis passed through the center of the knee and have performed a proximal tibial epiphysiodesis to prevent rebound varus.
In retrospect, it was realized that three patients who were treated with hemiepiphyseal stapling in our series had had insufficient remaining growth to allow full correction of the deformity. Nevertheless, two of these patients, who did not obtain full correction of the deformity, did obtain complete correction of the femoral portion of the deformity, which otherwise would have required a corrective osteotomy. Three patients with a severe preoperative deformity obtained little correction despite the stapling and the seemingly adequate growth remaining; these patients were morbidly obese, and the medial aspect of the physis did not grow sufficiently to correct the deformity following the lateral hemiepiphyseal stapling. It is difficult to determine the amount of remaining growth of a pathologically altered medial-proximal aspect of a tibia, and determining bone age preoperatively may help one to ascertain which patients may not obtain full correction. We have not utilized this approach because we believe that the growth in this area does not follow age-dependent norms.
It is of crucial importance to adequately assess the deformity preoperatively, as distal femoral varus is frequently a major component of the overall varus deformity10. One of our patients ultimately required a distal femoral osteotomy after hemiepiphyseal stapling of the proximal part of the tibia had completely corrected the tibial deformity. Because of the relative abduction of the hip associated with the genu varum deformity, in spite of distal femoral varus the knee joint can appear parallel to the floor on a standing anteroposterior radiograph of the lower extremity, leading to the impression that the deformity is completely within the proximal part of the tibia. Careful preoperative planning and assessment of the deformities are essential to the success of operative intervention.
Historically, hemiepiphyseal stapling has been reserved for adolescents. More recently, Mielke and Stevens showed that hemiepiphyseal stapling, with careful insertion and removal of the staples without injury to the periosteum, is a safe and effective treatment for younger children who have an angular deformity of the knee31. In our series, stapling proved to be safe and effective for patients who were ten years of age or younger. We obtained complete correction in all five patients of that age.
In conclusion, hemiepiphyseal stapling is indicated in patients with late-onset tibia vara if the proximal tibial physis is still open and the varus deformity is mild or moderate. When distal femoral varus is present, lateral hemiepiphyseal stapling of the distal part of the femur should be performed concomitantly. Hemiepiphyseal stapling can be effective in selected patients with severe varus deformity, although osteotomy may be indicated in the majority of those patients. Frequent clinical and radiographic follow-up is mandatory to monitor the correction. ▪
The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at Washington University School of Medicine, St. Louis Shriners Hospital for Children, and St. Louis Children's Hospital, St. Louis, Missouri
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