|Year : 2019 | Volume
| Issue : 1 | Page : 11-16
Use of hexapod frame to gradually correct congenital and acquired forearm deformity
Lauren Elisabeth Wessel1, Hayley A Sacks2, Duretti Teferi Fufa1, Austin T Fragomen1, S Robert Rozbruch1
1 Department of Orthopedic Surgery, Hospital for Special Surgery, NY, USA
2 Department of Orthopaedic Surgery, School of Medicine, Weill Cornell Medical College, NY, USA
|Date of Web Publication||23-Aug-2019|
Dr. Lauren Elisabeth Wessel
Department of Orthopedic Surgery, Hospital for Special Surgery, 535 East 7th Street, NY 10021
Source of Support: None, Conflict of Interest: None
Introduction: Forearm deformity affects patients with Multiple Hereditary Exostosis (MHE), Ollier's disease, and other various congenital deformities as well as those with physeal growth arrest secondary to trauma. Acute correction of such deformities is complicated by risk of neurovascular compromise and as such, techniques that allow for gradual deformity correction are of great interest in this clinical setting. We hypothesized that the use of hexapod frame would allow for reliable correction without neurovascular compromise. Methods: This retrospective, case series reviewed all patients who underwent osteoplasty of the radius and ulna between January 1, 2008, and December 31, 2017, among two surgeons. Patient demographics, comorbidities, radiographic parameters, external fixation index (EFI), and complications were recorded from chart review. Six patients presented with a diagnosis of MHE, two patients with a diagnosis of Ollier's disease, one with short stature homeobox (SHOX) deletion, and one with physeal growth arrest. Results: Of the ten patients identified, the rate of lengthening proceeded between 0.5 and 1 mm/day with an average EFI of 3.7 months/cm for the radius and 7.4 months/cm for the ulna. Average radius and ulna lengthening were 1.5 cm and 2.7 cm, respectively. Average radial bow preoperatively was 1.7 cm with a location of the maximal radial bow at an average of 61% from the radial tuberosity. Radial bow was corrected to 0.6 cm on average with a location of the maximal radial bow at an average of 64%. Neither patients exhibited nerve deficit nor neurapraxia at the conclusion of treatment. One fracture occurred after frame removal, which was treated with open reduction and internal fixation. Conclusion: Hexapod frames can be used to safely correct forearm deformities without neurovascular compromise.
Keywords: Congenital, forearm, hexapod frame, limb lengthening, multiple hereditary exostosis
|How to cite this article:|
Wessel LE, Sacks HA, Fufa DT, Fragomen AT, Rozbruch S R. Use of hexapod frame to gradually correct congenital and acquired forearm deformity. J Limb Lengthen Reconstr 2019;5:11-6
|How to cite this URL:|
Wessel LE, Sacks HA, Fufa DT, Fragomen AT, Rozbruch S R. Use of hexapod frame to gradually correct congenital and acquired forearm deformity. J Limb Lengthen Reconstr [serial online] 2019 [cited 2019 Sep 15];5:11-6. Available from: http://www.jlimblengthrecon.org/text.asp?2019/5/1/11/265358
| Introduction|| |
Forearm deformity is a common problem affecting patients with Multiple Hereditary Exostosis (MHE) and Ollier's disease and those who sustain physeal growth arrests of various etiologies. Congenital and acquired forearm deformities can cause significant functional disability. Forearm lengthening with deformity correction may improve the appearance of the affected extremity, which also carries significant social benefit, particularly in a young patient population.
The correction of such deformities is complicated by the involvement of multiple extremities, which may preclude the availability of a normal contralateral limb for comparison,, and the degree of deformity present on initial consultation is often severe and multiplanar. As the presenting deformity may be more severe in cases associated with a syndromic presentation or upper extremity aplasia, the risk of neurovascular compromise when making large, acute deformity corrections in multiple planes also increases. In cases of forearm deformity with MHE, subluxation or dislocation of the radial head may occur in between 22% and 33% of the patients.,, This often leads to a loss of pronation, enhanced ulnar variance, and functional impairment.
While bone-lengthening techniques have long been described in the lower extremity, these techniques are less frequently described in the upper extremity due to its tolerance for greater disparity in limb length.,, When extreme disparities exist necessitating such correction, particular consideration should account for means in which to improve alignment while still minimizing risk to neurovascular structures. As with the lower extremity, a modular ring fixator and tensioned wires can provide a safe mechanism in which to correct even severe, complex deformities.
The purpose of this paper is to report on the technique and radiographic outcomes of application of the Ilizarov technique for the correction of forearm deformity. The secondary outcome was the neurovascular status after deformity correction. We hypothesized that the use of hexapod frame would allow for reliable correction of forearm deformity without neurovascular compromise.
| Methods|| |
This retrospective, case series was approved by the (blinded for review) Institutional Review Board.
We reviewed all patients who underwent operative procedure designated by the current procedural terminology definition of osteoplasty of the radius and ulna between January 1, 2008, and December 31, 2017, by two surgeons by gradual lengthening techniques. Such procedures included but were not limited to osteotomy, corticotomy, lengthening, and deformity correction. Patient demographics, comorbidities, and complications were recorded from the medical record. Operative records were reviewed for details related to operative technique, method of fixation, and rate of deformity correction.
Presenting radiographs were reviewed to characterize prefixation deformity, and radiographs at the final follow-up were reviewed to characterize overall deformity correction. All the measurements were performed along the anatomic axes of the radius and ulna. Pre- and postoperative anteroposterior (AP) imaging was utilized to measure the frontal plane length and angular measurements as well as radial bow [Figure 1]a, [Figure 1]b, [Figure 1]d and [Figure 1]e. To measure the radial bow, an initial line is drawn from the midpoint of the bicipital tuberosity to the subchondral bone at the most ulnar aspect of the radius at the wrist. A perpendicular line is then drawn from the point of the maximum radial bow to this line. The height of this perpendicular line is defined as the maximum radial bow. The distance from the bicipital tuberosity to the previously measured perpendicular line at the point of the maximum radial bow is then divided by the total length of the radius (the initial line drawn) to calculate the location of the maximum radial bow. Pre- and postoperative lateral imaging was utilized to measure the lateral plane length and angular measurements [Figure 1]c and [Figure 1]f.
|Figure 1: Pre- and post-distraction radiographs: Depiction of pre- and post-fixation radiographic parameters with relevant measurements in the anteroposterior and lateral views. (a/d) Pre- /Post-fixation anteroposterior X-ray of the forearm, respectively. Frontal plane angular deformity of the radius and ulna is depicted in noted measurements; (b/e) Pre-/Post-fixation anteroposterior X-ray of the forearm, respectively. Measurements of radial bow and bow location are depicted; (c/f) Pre- / Post-fixation lateral X-ray of the forearm, respectively. Lateral plane angular deformity of radius and ulna is depicted in noted measurements [Figures 1, 3, and 4 demonstrate the same patient]|
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External fixation indices (EFI) were calculated from the collected metrics. EFI was defined as the duration of external fixation in months divided by the total amount of bone transported and/or the amount of lengthening in centimeters.
Pearls and pitfalls
Preoperative planning is critical to the success of deformity surgery. When available, normal contralateral films should be used to establish target data for deformity correction. Templating is performed along the anatomic axes of the radius and ulna with the measurement of frontal and lateral plane length and angle parameters as well as the measurement of the radial bow for both the operative and contralateral arms. The center of rotation of angulation (CORA), which is the intersection of the proximal axis and distal axis of a deformed bone, is identified on the operative extremity.
Osteotomies are planned about the CORA of the radius and ulna, respectively, using trigonometric relationships to calculate target angular correction. If there is no significant angular deformity, osteotomies should be planned in the radial shaft to avoid the distal radial ulnar joint and proximal radial ulnar joint. The proximal ulna provides an ideal site for ulnar osteotomy, as it provides a wide surface of the bone with robust healing potential for distraction osteogenesis.
The proximal ring is placed orthogonal to the proximal segment, and the distal ring is placed orthogonal to the distal segment so that the frame matches the forearm deformity. Half-pin diameter should not exceed 1/3 of the bone diameter, and half-pins should be bicortical to prevent fracture. Osteotomies are made using a multiple drill-hole technique at the apex of deformity.
There are various approaches to order of deformity correction depending on whether the radius and ulna have matched deformities:
- When the radius and ulna have matched deformity, both the bones will require osteotomy and should be stabilized to the chosen fixation apparatus prior to osteotomy to avoid gross loss of alignment
- When the radius and ulna do not have matching deformities and one bone requires only minor correction, the correction can be done in a staged fashion. In this instance, one bone is corrected, and then, the patient returns to the operating room for a frame modification and osteotomy of the second bone. This is particularly useful in the setting of extreme discrepancies in radial and ulnar deformities. In this way, the surgeon may uncouple the rate of deformity correction of the radius and ulna to reestablish anatomic relationships
- When the radius and ulna do not have matching deformities but both require significant correction, deformities can be addressed without a staged approach by utilizing uncoupled fixation. For example, a radius deformity can be corrected with a hexapod frame and the ulna can be simultaneously lengthened with a monolateral fixator, frame-within-a-frame concept [Figure 2]. A frame-in-frame construct allows differential lengthening rates by providing for the primary fixation device (hexapod frame) to be programmed to a different angular and length correction goal than that of the secondary fixation device (monolateral frame)
- Tensioned wires may be used as an augment for construct stability. The surgeon should pay particular attention to the cross-sectional anatomy at each level of the forearm when utilizing this technique.
|Figure 2: Operative technique, frame-within-a-frame: Clinical picture demonstrating uncoupling of distraction of the radius and ulna, utilizing the frame-within-a-frame technique. Distraction of the radius is achieved with a hexapod frame and distraction of the ulna is achieved with a monolateral frame|
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Depending on the extent of deformity correction, the surgeon may request a short-acting peripheral nerve block to aid postoperative neurovascular examination. Patients typically remain inpatient for at least one night for postoperative monitoring as well as pin care and strut adjustment education. Strut adjustments typically begin on the postoperative day 3.
Mounting parameters are measurements made relative to one ring designated the reference ring, which determines the location of the virtual hinge within the frame [Figure 3]. It is critical to obtain good intraoperative AP and lateral X-rays of the reference ring, as this will guide the programming of deformity correction. Care to ensure that each ring is orthogonal to its respective segment is critical in this regard. Deformity correction is done gradually in all cases, and the speed is typically no more than 1 mm per day in the upper extremity to protect any structures at risk, typically identified in the concavity of the deformity.
|Figure 3: Distraction osteogenesis: X-ray demonstrates placement of hexapod frame during lengthening. The sites of ulnar and radial osteotomies are marked [Figures 1, 3, and 4 demonstrate the same patient]|
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| Results|| |
Ten patients were identified as having undergone osteoplasty of the radius or ulna with hexapod frame. Demographics are reported in [Table 1]. Six patients presented with a diagnosis of MHE, two patients with a diagnosis of Ollier's disease, one with SHOX deletion, and one with physeal growth arrest. The average duration of lengthening was 5 months and average postoperative follow-up from the initial surgery was 15.3 months.
Frontal and lateral plane correction of the radius and ulna was achievable with hexapod frame [Table 2]. The rate of lengthening proceeded between 0.5 and 1 mm/day in all cases with an average EFI of 3.7 months/cm for the radius and 7.4 months/cm for the ulna. Average radius lengthening was 1.7 cm, and average ulnar lengthening was 3.5 cm. Two patients presented with dislocations of the radial head, which spontaneously reduced with length correction [Figure 4].
|Figure 4: Clinical photographs, not referenced in the text: Clinical photographs of pre- and postoperative arm alignment. Preoperative position depicted in top panels. Postoperative position depicted in bottom panels [Figures 1, 3, and 4 demonstrate the same patient]|
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With regard to angular deformity, average radial bow preoperatively was 1.7 cm with a location of the maximal radial bow at an average of 61% distance from the bicipital tuberosity. Postoperative radial bow was corrected to 0.6 cm on an average with a location of the maximal radial bow at an average of 64% distance from the bicipital tuberosity.
No patients exhibited nerve deficit, neurapraxia, infection nor complex regional pain syndrome at the conclusion of treatment. One fracture at the osteotomy site occurred after frame removal, which was treated with open reduction and internal fixation.
| Discussion|| |
Severe deformities of the forearm are associated with various genetic abnormalities as well as post-traumatic growth arrest and represent complex clinical problems. Symmetric or asymmetric lengthening of a short or deviated forearm may be indicated to realign the radius and ulna to improve function, improve motion, or reduce pain. Farr et al. reported a review of published data on gradual forearm deformity correction with the hexapod frame, citing an average rate of 0.5–1 mm lengthening per day. Average lengthening reported among the reviewed studies was 26 mm, with the maximum reported lengthening being 15 cm. Our 10 patient series resulted in similar average lengthening results to those reported in the literature.
Our technique, however, expands on previously reported approaches to deformity correction in its uncoupling of radial and ulnar lengthening schedules. The use of a monolateral component for differential lengthening of the radius and ulna is advantageous specifically with regard to patients who suffer from impairment secondary to MHE, which exhibits a disproportionate involvement of the radius and ulna but with significant correction required for both. Utilization of uncoupled correction of the radius and ulna allows for the re-establishment of normal anatomic relationships.
The importance of restoration of the normal anatomic radial bow is additionally a critical consideration in the maintenance of forearm rotation and function., The correction of angular deformity is a critical consideration in distraction osteogenesis as it has implications with regard to union after consolidation. With regard to forearm fracture fixation, Schemitsch and Richards have reported on the effects of malunion after open reduction and internal fixation and demonstrated an important relation between the restoration of the normal magnitude and location of the maximal radial bow and functional outcome. Our outcomes demonstrate that deformity correction utilizing a hexapod frame technique can appropriately maintain radial bow, with the final location and magnitude of the maximum radial bow of our cohort being in line with population norms at 64% distance from the bicipital tuberosity and 0.6 cm, respectively.
In cases when simple osteochondroma excision would be insufficient, additional operative treatments for forearm deformity exist, although most have mixed to poor functional outcomes. The most common of the operative techniques available to address severe forearm deformity includes hemiepiphyseal stapling of the distal radius in children, immediate ulnar lengthening (Z-lengthening) with or without a concurrent corrective radial osteotomy, Sauve-Kapandji procedure, or creation of a one-bone forearm technique. While hemiepiphyseal stapling of the distal radius has demonstrated efficacy in improving increased radiocarpal angulation with low morbidity, this technique relies on remaining growth and would have been ineffective in our cohort. Immediate ulnar lengthening (Z-lengthening) with internal fixation and bone grafting has been studied in small series.,, However, relative ulnar shortening commonly recurs and often requires further lengthening. This technique may be combined with corrective radial osteotomy with improvement in radiographic appearance and forearm rotation in some studies.,
More invasive procedures include the Suave-Kapanji procedure as well as the creation of a one-bone forearm. The Sauve-Kapandji procedure involves fusion of the distal radioulnar joint combined with intentional formation of a distal ulnar pseudoarthrosis to allow pronation and supination of the forearm. It effectively mimics the outcome of ulnar lengthening by reducing the tethering effect of the distal ulna on the radial physis. Studies have shown postoperative improvement in forearm rotation, radial articular angle, and carpal slip,, but a second procedure is often necessary because the rotation gap in the ulna can fill in with bone. Finally, the creation of a one-bone forearm may be used to treat forearm deformity, but it is reserved for salvage procedure when other treatments have failed. Studies have demonstrated high postoperative complication rates and low functional outcome scores.,
Our study has a number of limitations. As a small cohort, we were limited by cohort size; however, as the severity of deformity requiring intervention for forearm lengthening procedures is extreme, this cohort nonetheless reports one of the largest yet to be reported on. In addition, given the nature of this retrospective review, we were limited by the data available in the patient medical record. Finally, given that, patients had varied presenting diagnoses and prior operative procedures, standardized questionnaires of hand and upper extremity function were of minimal value given different limitations inherent in each of these individual conditions. In contrast to characteristics such as range of motion, which may dependent of preoperative diagnosis or prior procedure, we focused our investigation to radiographic lengthening to quantify outcomes. The purpose of this study was to describe a technique for gradual correction of forearm deformity, uncoupling the rate of deformity correction in the radius and ulna, and to provide data demonstrating the efficacy of this technique (radiographic data) as well as safety of the technique (neurovascular compromise). As we cannot provide functional outcomes with these retrospective data, we suggest that the study of functional outcomes would be ideally suited for a future prospective study.
| Conclusion|| |
This retrospective review demonstrated that complex forearm deformities could be safely and reliably corrected by utilizing external fixation techniques to gradually restore normal anatomic length and relationships between the radius and ulna. Such cases require meticulous planning to account for frontal and lateral plane correction as well as accounting for any rotational deformity. Frame fixation is particularly well suited for such applications, as this technique allows for the correction of deformity in multiple planes concomitantly. In summary, hexapod frames can be used to gradually correct forearm deformities without neurovascular compromise.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]