Volume VII, Number 1 | April 2023

Should the Medial Pin in Pediatric Supracondylar Humerus Fracture Fixation be Abandoned? A Retrospective Review and Discussion of Ulnar Nerve Neuropraxia Rates and Surgical Technique

Authors

1. Jonathan Schneider DO – Larkin Community Hospital
2. Gregory Galvin DO – Larkin Community Hospital
3. Phong Truong DO – Larkin Community Hospital
4. Diego Galindo DO – Sunrise Health GME Consortium
5. James Seymour DO – MountainView Regional Medical Center
6. Jonathan Phillips MD – Orlando Health Arnold Palmer Hospital for Children Center for Orthopedics

OBJECTIVES:

The percutaneous medial pin in a crossed-pin construct is now rarely used for fixation of operatively treated pediatric supracondylar humerus fractures (SCH) likely due to older reports of high rates of ulnar neuropraxia. The objectives of this paper are to report the rate of ulnar nerve neuropraxia documented in a large case series at our institution over a ten-year period and to describe the surgical technique employed in this case series.

METHODS:

We retrospectively reviewed operative records over a ten-year period from June 2010 to June 1, 2020 at our institution of a single surgeon who routinely uses the medial pin in a crossed-pin construct. Of the records reviewed, 138 patients underwent a cross-pin construct with a medial pin. Data collected was age of patient, documented ulnar nerve neuropraxia (pre-operative & post-operative), and any documentation of re-operation or failure of fixation.

RESULTS:

Of the 138 patients reviewed, 1 patient (0.72%) had documented both pre-operative and postoperative ulnar nerve neuropraxia. The patient had both sensory and motor deficits that were still present at the 4-week post-operative visit and had complete resolution of ulnar nerve motor and sensory deficit at the 3-month post-operative visit. Ulnar nerve neuropraxia symptoms occurred in 1 patient (0.72%) after placement of a medial pin to achieve a crossed pin construct. The rate of new post-operative ulnar nerve neuropraxia symptoms in this data set was found to be at most 0.72%. The total rate of ulnar nerve neuropraxia symptoms, including symptoms at the time of injury, is 1.45%. There were no cases of failure of fixation or re-operation.

CONCLUSIONS:

Our results show a low rate of iatrogenic ulnar nerve neuropraxia with the medial pin. We believe that ulnar nerve neuropraxia can be largely minimized or avoided altogether with the utilization of good surgical technique. There are advantages to a crossed-pin construct using a medial pin and we believe this surgical technique should not be abandoned and is important in orthopedic surgery residency education.

KEYWORDS: CRPP, Closed Reduction Percuteanous Pinning, Pediatric Supracondylar Humerus Fractures, Pediatric, Supracondylar, Humerus, Fracture, Pediatric Trauma, Trauma, Ulnar Nerve Neuropraxia, Ulnar Nerve, Neuropraxia, Medial pin, Crossed pin, Crossed pin fixation

OBJECTIVES:

The most common pediatric elbow fracture requiring surgery is the supracondylar humerus fracture (1).  Although lateral pin placement remains the preferred method among many orthopedic surgeons treating these injuries, one surgical treatment option for children with a supracondylar humerus fracture is a medial-sided pin (i.e., cross-pin) construct (2).  

There is, however, some controversy regarding using routine medial-sided percutaneous pin placement for these fractures mostly due to previous published literature documenting higher risk of ulnar nerve injury and neuropraxia compared to lateral-only based constructs. Early case series documenting neuropraxia rates upwards of 15% (3).  Although it has been shown that there were no significant clinical differences in patient outcomes, specifically healing or elbow functional differences between a cross pin and lateral-only based pin construct (4), it has also been proven to be more biomechanically robust fixation in the lab (5).  The medial pin also has been shown to have several unique adjunct benefits versus the lateral pin such as fractures with medial-sided comminution and those with a high medial oblique fracture pattern. Nevertheless, some surgeons have opted to abandon the medial-sided pin altogether in their practice due to the earlier reported higher rates of complications associated with this pin. We believe that with good surgical technique, ulnar nerve neuropraxia can be largely minimized or avoided altogether. The objectives of this paper are to report the rate of ulnar nerve neuropraxia documented in a large case series at our institution over a ten-year period, to describe the surgical technique employed in this case series, and to add to the current body of literature.

METHODS:

After obtaining institutional review board approval, a query of the operative records was performed for a single surgeon who routinely uses a medial-based cross-pin construct for his supracondylar humerus fracture fixation. This yielded a total of 153 pediatric patients who were treated surgically with closed reduction and percutaneous pinning between June 1st, 2010 and June 1st, 2020. Approved senior orthopedic surgery residents confirmed the documentation of the medial pin the medical chart and radiographs of each patient reviewed. Data collected was age of patient, documented ulnar nerve neuropraxia (pre-operative or post-operative), or any documentation of re-operation or failure of fixation.

Fourteen patients were excluded because documentation was unavailable post-operatively to the point of pin removal mostly due to these patients having their initial fracture while on vacation or and not living permanently in the region and electing to follow up with a local provider in their respective state. This left a total of 139 patients, of which 138 underwent cross-pin fixation with a medial pin, and 1 patient who had a lateral-only based fixation for their supracondylar humerus fracture.

Our surgical technique and intraoperative reduction technique in approaching these pediatric supracondylar fractures starts first with traction once the patient is fully sedated under general anesthesia. Instead of “hyper-flexion” of the elbow or rather flexing it to about 140 degree for reduction which is commonly taught in many surgical textbooks, our reduction maneuver is performed while the elbow remains in about 30 degrees of elbow flexion. We pull traction on the upper extremity while in 30 degrees of flexion while simultaneously pushing anteriorly on the olecranon to maintain the reduction. We avoid flexion of the elbow of more than about 30 degrees as we find it unnecessary. Our goal is to place the medial pin first in our crossed pin construct and therefore we think it’s vital to drive the medial pin through the bone while the elbow remains in this relatively extended position. Maintaining the elbow in this 30 degree flexed position allows less tension on the ulnar nerve and keeps it relatively further away from the easily palpable medial epicondyle used as a landmark. The ulnar nerve is palpable posterior to the medial epicondyle and we always feel for this before placing our pin. We place our medial pin with a percutaneous approach while holding the reduction with our contralateral hand using anterior thumb pressure on the olecranon. Once the medial pin is driven past both the medial and lateral columns, we judiciously confirm under fluoroscopy for adequate pin placement crossing the fracture site. After satisfactory medial pin placement we then proceed placing the lateral pin with the elbow placed in 90 degrees of elbow flexion. We percutaneously place the lateral pin capturing both the lateral and medial columns while aiming for maximal pin spread across the fracture site that a crossed pin configuration allows. Throughout the entire reduction and surgical approach we avoid “hyperflexion” of the elbow.

RESULTS:

A total of 138 patients with a medial-based pin construct for their surgery also had adequate follow-up to the point of pin removal at our institution. This set was composed of 68 females and 71 males, with age ranging from approximately 1 year, 9 months to 13 years, 3 months for the oldest. The mean and median ages were 6.14 years and 6 years respectively, with a standard deviation of 2.32 years.

Figure 1: Distribution of patients by age in years. 17 patients between 1.75 and 3.35 years, 26 patients between 3.35 and 4.95 years, 40 patients between ages 4.95 and 6.55 years, 32 patients between ages 6.55 and 8.15 years, 16 patients between 8.15 and 9.75 years, 5 patients between 9.75 and 11.35 years, 2 patients between 11.35 and 12.95 years, and 1 patient between 12.95 and 14.55 years of age.

The time to pin removal ranged from 12 to 40 days post-operatively, with a mean and median time of 24.09 and 23 days respectively, and a standard deviation of 5.07 days. 116 children were followed to the point of observed union. Time to union ranged from 31 to 122 days, with a mean and median time of 57.14 and 55 days respectively, and a standard deviation of 17.80 days.

Of the 138 cases, only two cases documented ulnar nerve neuropraxia symptoms. In the two patients that reported ulnar neuropraxia symptoms, no malunion was reported. In one of these two patients, ulnar nerve neuropraxia symptoms was present at the time of injury. In this patient, the pin was removed at 17 days and radiographic union was documented at 34 days post-operatively. In the other patient, the pin was removed at 26 days and radiographic union was documented at 69 days post-operatively. Ulnar nerve neuropraxia symptoms occurred in 1 patient after placement of a medial pin to achieve a crossed pin construct. The rate of new post-operative ulnar nerve neuropraxia symptoms in this data set was found to be at most 0.72%. The total rate of ulnar nerve neuropraxia symptoms, including symptoms at the time of injury, is 1.45%.

Figure 2: Rates of ulnar nerve neuropraxia with cross-pin closed reduction percutaneous pinning (CRPP). 1) Neuropraxia document at time of injury in 1 patient (0.72%). 2) Neuropraxia first documented after cross-pin CRPP in 1 patient (0.72%). 3) No neuropraxia.

DISCUSSION:

Lyons et al. (1998) reported 19 cases of postoperative ulnar nerve palsies in 375 supracondylar fractures that underwent percutaneous pinning using a crossed pin construct (5%). 17 of the 19 patients were followed up, and all had spontaneous resolution of the nerve palsy. This is compared to our case series, which shows a 0.72% post-operative ulnar nerve palsy after using a crossed pin construct (6).

Green et al. (2005) presented a case series of 65 supracondylar humerus fractures treated with a crossed pin technique; they reported one case of iatrogenic ulnar nerve injury (1.5%). However, their technique involved using a mini-open medial incision as opposed to percutaneous pinning (7).

Ozcelik et al. (2006) correlated iatrogenic ulnar nerve injury with sagittal angular insertion of the medial pin when cross-pinning. Specifically, they reported that anteroposterior insertion of the medial pin in the sagittal plane, with the elbow in hyperflexion, has higher rates of iatrogenic ulnar nerve injury (8).

Larson et al. (2006) performed a biomechanical study comparing different supracondylar humerus pinning constructs. In a humerus with an intact medial column, their results show that cross pinning with two lateral pins and one medial pin conferred the most torsional stability. Three lateral pins provided the second most stability, followed by standard cross pinning with one medial and lateral pin. Lastly, two lateral pin construct had the least torsional stability. In a supracondylar humerus fracture with medial column comminution, the two lateral and one medial cross pinned construct also conferred the most torsional stability. Compared to the three lateral pin construct, the standard crossed pin constructs showed no statistical difference in torsional stability.

Again, the two lateral pin construct had the least stability (9). Because of this, we think it’s beneficial for orthopedic residents taking call and rotating at pediatric trauma centers covering these fractures to be exposed and get trained on the medial pin technique. There has been a trend over the last 15 years with fewer surgeons utilizing the medial pin technique at all in their practice to the point where now some orthopedic residents doing a pediatric rotation may very well not even see a medial pin placed in the elbow during their entire rotation. We believe training ought to include a variety of construct exposures and techniques in the fixation of pediatric supracondylar humerus fractures in order to expose our future orthopedic surgeons to more surgical techniques especially when they encounter the more unstable fracture patterns such as those with medial comminution or those Gartland type IV patterns with instability in flexion and extension. Because of the low rate of ulnar nerve neuropraxia with good surgical technique and the reason stated above, we believe the medial pin construct and surgical technique in orthopedic surgery residency training should not be abandoned.

CONCLUSIONS:

Based on our data, the medial-sided pin in a CRPP construct should not be abandoned altogether. In fact, a medial-based pin provides many advantages over a lateral-only based construct. Our case series review in addition to several other recent papers in the literature suggest ulnar nerve neuropraxia rates to be much lower than initially reported.  We believe the medial-based pin construct should be still be a viable surgical option for any orthopedic surgeon treating pediatric elbow fractures in their practice. Although the trend over the years show fewer surgeons using medial-based pin constructs, we believe teaching this technique to residents in their surgical education is a worthwhile endeavor and should not be abandoned.

REFERENCES:

  1. Dimeglio A. Growth in pediatric orthopaedics. In: Morrissy RT, Weinstein SL, eds. Lovell and Winters’s Pediatric Orthopaedics. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006:35–65.
  2. Carter CT, Bertrand SL, Cearley DM. Management of pediatric type III Supracondylar humerus fractures in the United States: results of a national survey of pediatric orthopaedic surgeons. J Pediatr Orthopaed. 2013;33(7):750–754.
  3. Skaggs DL, Hale JM, Bassett J, Kaminsky C, Kay RM, Tolo VT. Operative treatment of supracondylar fractures of the humerus in children: the consequences of pin placement. J Bone Joint Surg Am. 2001;83A:735–740.
  4. Chen TLW, He CQ, Zheng TQ, Gan YQ, Huang MX, Zheng YD, Zhao JT: Stiffness of various pin configurations for paediatric supracondylar humeral fracture: a systematic review on biomechanical studies. J Ped Orthop B. 24:389-399. 10.1097/BPB.0000000000000196.
  5. Skaggs DL, Hale JM, Bassett J, Kaminsky C, Kay RM, Tolo VT. Operative treatment of supracondylar fractures of the humerus in children. The consequences of pin placement. J Bone Joint Surg Am. 2001 May;83(5):735-40. PMID: 11379744.
  6. Lyons JP, Ashley E, Hoffer MM. Ulnar nerve palsies after percutaneous cross-pinning of supracondylar fractures in children’s elbows. J Pediatr Orthop 1998;18:43–5. doi:10.1097/00004694-199801000-00009.
  7. Green DW, Widmann RF, Frank JS, Gardner MJ. Low incidence of ulnar nerve injury with crossed pin placement for pediatric supracondylar humerus fractures using a mini-open technique. J Orthop Trauma 2005;19:158–63. doi:10.1097/00005131-200503000-00002.
  8. Özçelik A, Tekcan A, Ömeroǧlu H. Correlation between iatrogenic ulnar nerve injury and angular insertion of the medial pin in supracondylar humerus fractures. J Pediatr Orthop Part B 2006;15:58–61. doi:10.1097/01202412-200601000-00012.
  9. Larson L, Firoozbakhsh K, Passarelli R, Bosch P. Biomechanical analysis of pinning techniques for pediatric supracondylar humerus fractures. J Pediatr Orthop 2006;26:573–8. doi:10.1097/01.bpo.0000230336.26652.1c.
The Journal of the American Osteopathic Academy of Orthopedics

Steven J. Heithoff, DO, FAOAO
Editor-in-Chief

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