Cubitus varus has recently been associated with ulnar nerve dislocation1-3, ulnar neuropathy4-9, snapping of the medial
head of the triceps10-12, secondary
distal humeral13 or lateral condylar
fracture14, avascular necrosis
of the distal humeral epiphysis15,
joint ganglia16, and even osteoarthritis5,17. Recently, one report has linked
cubitus varus and posterior dislocation of the radial head18, and several isolated cases in the
literature suggest an association between cubitus varus and posterolateral
rotatory instability19-22.
Posterolateral rotatory instability23-26 is
a three-dimensional kinematic disturbance of elbow motion
in which the radius and ulna subluxate with respect to the distal
part of the humerus, such that the forearm bones displace into external
rotation and valgus during flexion of the elbow. This instability
pattern is secondary to deficiency of the ulnar part of the lateral
collateral ligament. The majority of cases of posterolateral rotatory
instability are posttraumatic (following elbow dislocation, sprain,
or fracture) or iatrogenic (following radial head resection or tennis
elbow release), although posterolateral rotatory instability may
result from chronic overuse (such as crutch-walking or in patients
with poliomyelitis) or generalized ligamentous laxity27.
The purpose of this multicenter, international report is to describe
an association between long-standing cubitus varus deformity and
posterolateral rotatory instability of the elbow. We provide a biomechanical
explanation that supports a causal relationship between cubitus
varus and tardy posterolateral rotatory instability, and we then
test our hypothesis. These findings suggest that a normal valgus
carrying angle provides an inherent structural stability and a ligamentous balance
across the articulation. Understanding the biomechanical principles
will help to explain the clinical presentations, to guide treatment,
and to predict surgical failures.
This series included twenty-one operatively treated patients, eighteen
male patients (nineteen limbs) and four female patients (average
age, thirty-four years; range, thirteen to seventy years),
with long-standing cubitus varus deformity. At presentation,
all patients reported lateral elbow pain and symptoms of recurrent
instability. Some also had symptomatic medial snapping. The duration
of symptoms averaged two years (range, one day to nine years; median,
one year). Ten patients identified a specific traumatic event (such
as a fall on an outstretched arm [eight patients])
that had preceded the symptoms; in two others, new symptoms of instability
developed following surgery (following radial head resection in one [Case
16] and following tennis elbow release in the other [Case
17]). Two patients presented with new symptoms of less
than one week’s duration; four others had had symptoms for
less than two months. Two patients (Cases 10 and 17) also had ulnar
nerve symptoms.
Examination with the patient under anesthesia, typically aided by
fluoroscopy, was performed initially. Treatment varied according
to the surgeon (Table I). Combined reconstruction of the
lateral collateral ligament and osteotomy was performed in seven
limbs; ligament reconstruction alone, in ten; and osteotomy alone,
in four. One of these elbows (Case 7) was reconstructed by reattachment
of an avulsed fracture fragment along with the lateral collateral ligament
complex as well as a reconstruction of the medial collateral ligament.
Anterior capsular release was performed at the time of surgery in
one patient (Case 17). The ulnar nerve was transposed because of
ulnar nerve symptoms or dislocation in five patients (Cases 10,
13, 16, 17, and 21), and the dislocating portion of the triceps
was transposed laterally in three (Cases 16, 17, and 21). A total
elbow prosthesis (Coonrad-Morrey; Zimmer, Warsaw, Indiana)
was implanted in one seventy-year-old patient (Case 21) who had
advanced osteoarthritic changes.
Varus malalignment of the distal part of the humerus was the result
of a fracture malunion in nineteen patients (following a supracondylar
fracture in seventeen and a lateral condylar fracture in two) and
was a congenital varus deformity in three limbs of two patients
(Cases 3 and 19), both of whom were Japanese. One of the two patients
underwent surgery (bilaterally) at the age of fourteen years, and
the other was operated on at the age of sixty years. The initial
pediatric fractures occurred at an average age of seven years (range,
two to eleven years), and the patients presented with the symptoms described
above at an average of twenty-seven years (range, five
to sixty-five years) later. These data are somewhat skewed by
the fact that one of the patients did not present until the long-standing
instability had caused severe arthritis at the age of seventy years
(sixty-five years after the fracture). With the exception of that
case, the patients presented at an average of twenty-five
years (range, five to fifty-one years) following the initial childhood
fracture. Except for two, these fractures were all initially treated
nonoperatively. The varus deformities averaged 15° (range, 0° to
35°). One patient (Case 15) had had a previous unsuccessful valgus
osteotomy that left persistent varus deformity. Rotational malalignment
was specifically recorded in only five limbs, which had an average
of 22° of internal rotation deformity. A secondary fracture developed in
six patients: a lateral epicondylar avulsion fracture developed
in five (Cases 3, 4, 7, 10, and 11) and a radial head fracture,
in one (Case 16). Symptoms began when the avulsion fractures occurred,
and surgery was performed within one week after the injury in two
of these patients (Cases 3 and 4). In the patient with the radial
head fracture, the symptoms of instability developed immediately
after a radial head resection, which was done two years after the
fracture.
All patients had tenderness over the lateral collateral ligament complex
and the common extensor tendon. A positive lateral pivot-shift
test or apprehension sign for posterolateral rotatory instability
and/or a posterolateral rotatory drawer sign was documented
in all limbs24. Laxity to varus
testing was present in fifteen limbs (Cases 1 through 4, 7, 8, 10,
14 through 18, 19R, 19L, and 21), and laxity to valgus testing was
present in two (Cases 7 and 8). The two patients with ulnar nerve
symptoms (Cases 10 and 17) had mild sensory abnormalities and percussion
tenderness. Three patients (Cases 16, 17, and 21) were noted to
have dislocation of the ulnar nerve and snapping of a portion of
the medial head of the triceps with elbow flexion. Two additional patients
(Cases 9 and 13) were found postoperatively to have snapping of
the medial head of the triceps over the medial epicondyle, although
the status of the ulnar nerve and the triceps with respect to dislocation
had not been clearly recorded preoperatively for these patients
or for the majority of patients. The mean preoperative Mayo Elbow
Performance Score28 (MEPS) was
59 points (range, 30 to 85 points).
Confirmation of the biomechanical disturbance was attempted and
established intraoperatively in three patients by stimulating the
triceps (predominantly the medial head) with use of a transcutaneous
electrical neural stimulation unit (Fas Tens 2220S; Rehabilicare,
New Brighton, Minnesota). While preventing the elbow from extending,
the combination of varus articular malalignment and medial elongation
of the olecranon permitted the triceps to roll the ulna into external
rotation and to subluxate the elbow posterolaterally (Fig. 1). However, stimulation
of the lateral portion of the triceps did not cause subluxation.
After surgical correction of the pathology, which included supracondylar
valgus osteotomy and transposition of a portion of the medial head
of the triceps to the lateral aspect of the olecranon, posterolateral
rotatory subluxation did not occur with triceps stimulation. Instead,
the elbow was more tightly reduced.
We performed the same test in a patient who had recurrent posterolateral
rotatory instability of the elbow but normal ulnohumeral alignment
and osseous anatomy of the distal part of the humerus. In that patient,
stimulation of the triceps with the elbow at 90° of flexion actually
reduced the elbow from a minimally subluxated position and never
caused subluxation. This active reduction by triceps contraction
did not require integrity of the lateral collateral ligament complex
nor of any of the lateral soft tissues, as the response was the
same with the lateral side completely open as it was with the tissues intact.
The duration of follow-up averaged three years (range,
one to eight years). The result was excellent in thirteen limbs,
good in six, fair in one, and poor in two. The postoperative Mayo Elbow
Performance Score improved to a mean of 87 points (range, 50 to
100 points). All patients had some degree of improvement in this
score and some relief of pain. Posterolateral rotatory instability
persisted in three patients (Cases 16, 17, and 20) postoperatively,
but all three had fewer symptoms and less marked physical findings
than they had had preoperatively. The reasons for the failure of
treatment in these three patients were not clear. Two patients had
marked secondary changes in the osseous architecture of the elbow,
and one patient had persistent varus angulation after the osteotomy. Motion
was maintained or improved in all patients. The two patients (Cases
16 and 17) with a poor result had arthritis with severe pain, instability,
and debility despite two attempts at ligament reconstruction and
correction of the carrying angle; both had had several previous
operations before the corrective osteotomy. The two patients with
neurologic symptoms preoperatively had persistent symptoms postoperatively
despite undergoing ulnar nerve transposition. One patient (Case
8) who had coexisting laxity of the medial collateral ligament that
was not addressed surgically had instability to valgus stress testing
but a good result overall.
Radiographic Results
Osseous union was eventually achieved in all of the patients who
had an osteotomy, although a nonunion initially developed in one.
The postoperative humeroulnar angle of nine of the eleven limbs
treated with osteotomy was within 5° of the angle of the contralateral
limb. The average humeroulnar angle (and standard deviation) was +4° ±
5° (range, -7° to +10°), with two patients having a residual
varus deformity (Fig. 2-A and 2-B). Of the two patients with persistent
varus angulation, one (Case 20) had an unacceptable result.
Complications
Complications included one wound infection, which was treated
with oral antibiotics; one nonunion, which was treated successfully
with bone-grafting and revision internal fixation; and one forearm
compartment syndrome, which was treated with emergent decompression
without long-term sequelae. One patient had a transient sensory
ulnar neuropathy, which resolved completely within several months.
Two patients (Cases 9 and 13) in whom triceps mobility was not assessed preoperatively,
but who were noted to have snapping of the medial head of the triceps
postoperatively, continued to have intermittent mildly painful snapping
on the medial aspect of the elbow.
Work and Recreation
All patients, including one professional hockey player (Case 11),
who had a good or excellent result returned to their original work
or athletic level. The young patient with a fair result (Case 20)
was unable to participate in athletics; he was considering revision
osteotomy along with a reconstruction of the lateral collateral
ligament. The two patients with a poor result were receiving Workers’ Compensation.
We believe that this study demonstrated
a causal relationship between long-standing cubitus varus deformity and
delayed-onset (tardy) posterolateral rotatory instability of the
elbow. The instability developed at an average of two to three decades
after the osseous deformity occurred. While the degree of varus
deformity varied, there was no apparent direct relationship between
the degree of deformity and the age at presentation. Lateral elbow
pain typically predated symptoms of instability. Physical findings
included obvious cubitus varus, tenderness over the lateral collateral
ligament complex and the common extensor tendon, a prominent tendon
of the medial head of the triceps, and signs of posterolateral rotatory instability.
These signs included a positive posterolateral rotatory apprehension
test and positive lateral pivot-shift and posterolateral rotatory
drawer signs, although in several patients the lateral pivot shift
could be demonstrated only when the patient was under anesthesia.
The spectrum of cubitus varus and posterolateral rotatory instability
may also include dislocation (snapping) of a portion of the medial
head of the triceps and the ulnar nerve as well as ulnar neuropathy12, as were present in several of our
patients.
Cubitus varus malalignment secondary to a varus deformity of the
distal part of the humerus produces two biomechanical disturbances
that appear to act together to stretch out the lateral collateral
ligament complex. First, with varus malalignment the mechanical
axis (wrist to shoulder) displaces medial to the elbow. The repetitive
varus torque caused by this malalignment increases tensile stress
on the lateral collateral ligament, especially when an axial force
is applied to the limb, such as occurs when a person rises from
a chair (Fig. 3).
This can further alter the mechanical axis.
Second, varus malalignment also displaces the triceps force vector
medially to create repetitive external rotatory torque on the ulna.
With the elbow flexed to 90° and viewed from the posterior aspect,
it is readily apparent that varus deformity of the distal part of
the humerus causes medial displacement and external rotation of
the ulna along its long axis (Figs. 4-A and Fig. 4-B). As a result of this, the triceps
force vector, when resolved into two force vectors parallel and
perpendicular to the joint surface, causes medial displacement (F2var
in Fig. 4-B).
In addition, the triceps force vector is offset from the center of
rotation of the deformity of the distal part of the humerus such
that the moment arm creates external rotation torque on the ulna
(that is, supination). These repetitive abnormal torques cause chronic
medial overpull of the triceps, which, during childhood growth,
can cause medial elongation of the olecranon (Fig. 5). Repetitive
stress to such a malaligned elbow, as would occur when the person
rises from a chair, can exacerbate and precipitate the biomechanical
alterations. In addition, the cubitus varus deformity may predispose
the elbow to injury during a fall (Fig. 6).
Whether the elbow sustains acute trauma or not, these abnormal
repetitive varus and external rotation torques combine to cause
attenuation of the lateral collateral ligament complex. Such attenuation
permits excessive external rotation (supination) of the forearm
with respect to the humerus. This represents the first stage of
the pattern of posterolateral rotatory instability26.
This biomechanical explanation for posterolateral rotatory instability
is consistent with and complementary to the previously proposed
mechanism (Fig. 7)24,26. The current description emphasizes
the effect of cubitus varus on the triceps in providing an external
rotation moment arm on the ulna. During a fall, the arm is extended
at the elbow and, upon impact with the ground, the elbow starts
to flex26. During flexion, the
triceps experiences an eccentric load to resist flexion and, in
the setting of chronic cubitus varus and attenuation of the lateral
collateral ligament complex, the eccentric triceps contraction causes
hypersupination of the forearm at the elbow (excessive external
rotation), which is the initial component of posterolateral rotatory
subluxation. Thus, we believe that contraction of the displaced
medial head of the triceps is important both in the activation of
the posterolateral rotatory instability and in the development of
the injury (such as during a fall).
Internal rotation is also a component of the clinical deformity of
posttraumatic supracondylar humeral varus malunion. It is possible
that such internal rotation deformity contributes to the instability.
Because rotational malalignment was recorded in only five of the
patients in this series, it is not possible to know its effect on
posterolateral rotatory instability. However, preliminary studies
of cadavera and with a mathematical model suggest that the important
factors in displacement of the triceps are the varus deformity and
the location of the triceps insertion on the olecranon, rather than
the internal rotation or flexion-extension deformity29.
Ligament reconstruction alone may provide an excellent result
in some patients, including those with a small (perhaps <15°)
varus angulation, those with elbow instability due to a discrete
injury (as opposed to chronic stretching of the ligament), or low-demand,
older, or nonathletic individuals. However, ligament reconstruction
without osteotomy places greater stress on the repair. All patients
in our series who had a varus deformity of >15° underwent
osteotomy. It appears that corrective osteotomy, which restores
a normal valgus alignment, helps to stabilize the ligamentous laxity.
Osteotomy alone may be adequate if there is only subtle instability or
if the patient places only limited demands on the elbow. For a large
deformity, we recommend that the osteotomy be combined with ligament
reconstruction because we have found that either osteotomy alone
or ligament reconstruction alone has a high likelihood of failure
in the presence of a large (>15°) osseous deformity and
high postoperative functional demands. Osteotomies, which do not
restore a valgus carrying angle, seem destined for failure on the
basis of biomechanical principles. Additional study and experience
with more patients with this problem is required before more definitive surgical
recommendations can be made.
In conclusion, varus malunion does not just alter the biomechanical
axis and the triceps force vector; it sets in motion a cycle of
changes, including chronic medial overpull (leading to medial elongation
of the olecranon) and increased stress on the lateral collateral
ligament, which further alter the biomechanical axis and triceps
force vectors in a positive feedback loop (Fig. 8) and may result
in varus and posterolateral rotatory elbow instability. This consequence
usually occurs in a tardy fashion, over several decades, but it
may be precipitated by a traumatic event that accelerates the process.
We believe that posterolateral rotatory instability is an important
cause of chronic elbow pain, instability, disability, and mechanical symptoms
in patients with cubitus varus deformity.
Note: The authors acknowledge G.K. Bal, MD, Fayetteville, North
Carolina; C. Basmania, MD, Durham, North Carolina; G.T. Gabel, MD,
Houston, Texas; and P. Hoffmeyer, MD, Geneva, Switzerland, for their
input regarding their experiences with this condition and its management.