Cubitus Varus—It’s More Than Just a Crooked Arm!

Abstract

Although cubitus varus has been regarded as a purely cosmetic problem in the pediatric population, symptomatic elbow instability, and ulnar neuropathy from the mechanical axis malalignment have been reported in adults. This overview discusses the biomechanical axis disruption that leads to soft tissue and morphologic bony alterations in the elbow and offers a compelling argument for corrective osteotomy to treat pediatric cubitus varus.

Cubitus varus deformity may occur after both pediatric supracondylar and lateral condyle fractures.¹ Although simply termed “cubitus varus,” the deformity is a combination of varus, extension, and internal rotation.² Indications for corrective osteotomy and timing of surgery have not been well established in the pediatric population.³ Pediatric cubitus varus has traditionally been considered a cosmetic problems with very few, if any, functional deficits or pain.^2,4,5 Although it is well reported in the adult orthopaedic literature that cubitus varus following a pediatric distal humerus fracture or congenital deformity can lead to posterolateral rotatory instability (PLRI),⁶ ulnar neuropathy,⁷ snapping triceps,⁸ progressive varus of the ulna,² and elbow joint malalignment as an adult.⁴ Children with cubitus varus typically have minimal loss motion although the arc of motion may be altered to increased hyperextension and decreased elbow flexion. Increased susceptibility to lateral condyle fractures has been suggested with cubitus varus deformity.⁹ Remodeling of the very young, skeletally immature elbow may restore loss of elbow flexion.¹⁰ In contrast to children, adults with cubitus varus typically present with symptomatic complaints of lateral elbow pain and recurrent instability that do not become apparent until decades after the development of the cubitus varus.⁶

BIOMECHANICAL AXIS DISRUPTION

O’Driscoll et al⁶ reported 25 adult elbows with cubitus varus who developed symptomatic PLRI decades after their initial injury. Surgical treatment consisted of lateral ulnar collateral ligament (LUCL) reconstruction, distal humeral osteotomy, or a combined LUCL reconstruction with distal humeral osteotomy. He posited that distal humeral varus leads to 2 distinct biomechanical disturbances.

• Varus malalignment of the upper extremity leads to medial displacement of the mechanical axis of the upper extremity. With repetitive varus forces on the elbow from activities of daily living, such as pushing up from a sitting position, the lateral collateral ligament complex experiences increased tensile forces and becomes attenuated, leading to further medial displacement of the mechanical axis (Fig. 1). A biomechanical cadaver study by Beuerlain et al¹¹ demonstrated that increased cubitus varus deformity does indeed lead to increased LUCL strain and increased ulnohumeral widening even in the presence of an intact LUCL.
• The triceps is displaced medially in cubitus varus, and this displaced triceps force vector leads to an external rotation (supination) moment arm on the ulna. Chronic medial triceps forces on the olecranon lead to medial elongation of the olecranon and external rotation of the ulna, which is the first stage of PLRI (Fig. 2).

FIGURE 1: Repeated tensile stress on the lateral elbow from varus malalignment leads to increased varus malalignment and further medial displacement of the mechanical axis. Reproduced with permission from O’Driscoll et al.⁶

FIGURE 2: A, Normal distal humerus with valgus carrying angle. The triceps force vector (F_T) is almost perpendicular to the joint line and can be resolved by two force vectors, F₁ and F_2val. F_2val is a slight valgus force. B, Distal humerus with cubitus varus. The triceps force vector (F_T1) is now resolved by F₁, which is perpendicular to the joint surface, and F_2var, which is now a varus force. F_2var leads to external rotation of the ulna (M_roll) along its long axis. Offset between F₁ and the axis of rotation causes a moment arm (MA) with triceps contraction that is subject to both external rotation and varus dddtorques. Reproduced with permission from O’Driscoll et al.⁶

Because of both of these biomechanical alterations, continued LUCL attenuation and olecranon external rotation eventually leads to radial head subluxation and eventually dislocation with frank PLRI¹² (Fig. 3).

FIGURE 3: With time, increased attenuation of the lateral elbow ligament complex combined with increased external rotation of the ulna leads to PLRI and radial head subluxation. Reproduced with permission from O’Driscoll et al.⁶

MORPHOLOGIC BONY AND SOFT TISSUE ALTERATIONS

Three-dimensional computed tomography scans have verified that morphologic changes in the elbow joint do occur in elbows with cubitus varus.⁴ When compared with the contralateral, uninjured elbow, elbows with cubitus varus show trochlear overgrowth posteriorly, leading to increased internal rotation of the posterior joint line of the distal humerus. The proximal ulna accommodates the trochlear overgrowth, with a lateral shift of the convex part of the trochlear notch and a longer articular surface from anterior to posterior. The ulna shifts to a more distal and medial position accompanied by increased external rotation and flexion when compared with the contralateral ulna. In addition, the lateral aspect of the capitellum overgrows distally and diameter of the radial head enlarges, although not enough to lead to increased cubitus varus. It is hypothesized that the medial overpull of the triceps leads to these bony morphologic changes, although it is possible that this may also be a sequel of physeal trauma to the elbow.

Although O’Driscoll’s series did not find a relationship between degree of varus deformity and age of presentation,⁶ another series found that increased cubitus varus correlated to increased proximal ulna varus as well as younger age of injury, suggesting that earlier correction of cubitus varus in the growing child may prevent other morphologic changes in the elbow.²

Tardy ulnar nerve palsy with anterior dislocation of the nerve has also been reported in conjunction with cubitus varus.^7,13,14 It is thought that the internal rotation deformity of the distal humerus in conjunction with distal fibrosis and entrapment of the nerve affects the position and stability of the nerve; in these cases, ulnar nerve transposition is recommended in conjunction with corrective osteotomy. Similarly, snapping of the medial portion of the triceps may occur from the medial displacement of the triceps as well as the internal rotation of the distal humerus.⁸

SURGICAL CORRECTION

There are multiple reported techniques for the correction of cubitus varus, including the lateral closing wedge osteotomy,¹⁵ step-cut osteotomy,¹ dome osteotomy,¹⁶ external fixation with distraction osteogenesis,¹⁷ and computer aided multiplanar osteotomy.^18,19 Two recent reviews did not find that any 1 technique was safer or more effective than the others,^3,5 although the lateral closing wedge using a lateral approach seems to be less technically demanding and to have a decreased risk of nerve injuries compared with other surgical approaches.^3,20,21 The indications for which technique to select are unclear, and it is even uncertain whether correction of the internal rotation deformity is necessary for a successful result.²² Complications from distal humeral osteotomies have been well reported and include nerve injury, residual deformity, infection, unsightly scarring, and loss of fixation; the 14.5% complication rate reported in a recent meta-analysis should alert surgeons to the technical demands of this surgery.⁵

Corrective osteotomy in the distal humerus is a less technically demanding surgery in the pediatric population when compared with adolescents and adults (Table 1). In the author’s experience, anatomic distal humeral plates rarely fit well on the adolescent, skeletally mature patient with cubitus varus, as the anatomy is not normal and the deformity is multiplanar. Bending the plate and trialing different plates for “best fit” is much more time consuming than pin fixation, especially if the surgeon places anticipatory fixation pins in the lateral condyle before the osteotomy. The distal humeral plate is generally prominent, and the patient may desire removal, necessitating a second surgery. In addition, the radial nerve must be identified and protected when a longer lateral plate is needed for fixation; the author has not found this dissection to be necessary in skeletally immature patients in whom pin fixation is sufficient. Additional LUCL reconstruction has also been described in conjunction with distal humeral osteotomy to completely correct PLRI and cubitus varus in adults; there have also been reports of unplanned secondary surgery when PLRI was uncovered after distal humeral osteotomy.^6,23,24 As the pediatric patient has not had cubitus varus long enough to lead to PLRI, LUCL reconstruction is thankfully virtually unheard of in this population. Finally, O’Driscoll et al⁶ reported that even after bony and soft tissue reconstruction, some of their adult patients’ symptoms did not resolve.

TABLE 1: Comparison of Pediatric and Adult Distal Humeral Osteotomies

AUTHOR’S PREFERRED TECHNIQUE OF DISTAL HUMERAL OSTEOTOMY FOR PEDIATRIC CUBITUS VARUS

A closing wedge osteotomy is planned using the anteroposterior radiographs of the uninjured contralateral elbow as a template. The osteotomy is designed as 2 oblique osteotomies to minimize the amount of lateral prominence that will occur with the traditional osteotomy. The apex of the osteotomy is planned just proximal to the medial epicondyle. The degree of the planned osteotomy and the size of the wedge of bone taken laterally are noted. On the lateral radiograph, any planned correction of hyperextension deformity is also measured and noted.

A nonsterile tourniquet is placed proximally on the upper arm. A straight lateral incision is placed over the site of the planned osteotomy and the periosteum incised. A periosteal elevator or a freer is used to elevate the periosteum circumferentially and distally to the level of the medial epicondyle. Two smooth 0.062″ wires are placed as guide wires along the sites of the planned osteotomy (Fig. 4). A goniometer and ruler are used intraoperatively to confirm that the wedge is the correct planned size and angulation. Two 0.062 smooth wires are then placed retrograde from the lateral column up to the level of the distal guide wire (Fig. 5). With Hohman retractors placed circumferentially around the humerus and directed distally, the osteotomy is then performed along the inside the guidewires with either an osteotome or oscillating saw with irrigation to prevent thermal necrosis (Fig. 6). The osteotomies should be parallel in the lateral plane if sagittal plane deformity correction is not planned. Care should be taken to leave a small medial bridge, which will prevent the osteotomy from becoming completely destabilized (Fig. 7). If correction of hyperextension deformity is also planned, one of the osteotomies should incorporate the planned amount of flexion on the lateral plane. The author prefers adjust for planned flexion in the proximal cut, as it is easier to judge the long axis of the humerus.

FIGURE 4: Smooth guide wires along the planned osteotomy cuts.

FIGURE 5: Two smooth wires placed for planned fixation up to the level of the distal planned osteotomy cut.

FIGURE 6: Osteotome along planned proximal cut.

FIGURE 7: Complete osteotomy wedge removed with medial bridge remaining.

Once the osteotomy is complete, the 2 guidewires are removed. The surgeon flexes and pronates the elbow through the osteotomy. A satisfying crack is usually heard as the maneuver fractures the intact bridge. With the elbow flexed and pronated, the correction is confirmed under anteroposterior and lateral fluoroscopy. The 2 wires are then driven across the osteotomy site into the proximal cortex (Fig. 8). If needed, a third lateral wire can be placed for added stability.

FIGURE 8: Closing wedge osteotomy completed with placement of smooth wires affixing osteotomy site.

A long arm splint with a sidewall is placed, and the child is admitted for 23 hours of observation for swelling and pain. Postoperatively, repeat radiographs in the splint are taken at 7 to 10 days to confirm maintenance of the correction, and the splint is overwrapped to a cast. Typically, there is enough callus at 4 weeks to pull the pins in clinic and start early motion.

CONCLUSIONS

In short, correction of cubitus varus in the pediatric population is technically easier than in adolescents and adults, and can prevent long-term sequelae such as PLRI, ulnar neuritis, and chronic elbow pain. Pediatric orthopaedists should reconsider the long-held belief that cubitus varus is merely a cosmetic deformity.