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Sagittal Plane Malalignment in Paediatric Supracondylar Fractures of the Distal Humerus: A Review of the Literature

Abbas Rashid, Hani B Abdul-Jabar, Christopher P Bretherton, Addie Majed, Tony Corner

Abbas Rashid, Christopher P Bretherton, Addie Majed, Tony Corner, West Herts Shoulder and Elbow Unit, Department of Trauma & Orthopaedics, West Hertfordshire NHS Hospitals Trust, Vicarage Road, Watford, Hertfordshire, WD18 OHB, the United Kingdom
Hani B Abdul-Jabar, Department of Trauma & Orthopaedics, London Northwest Healthcare NHS Trust, Watford Road, Harrow, Middlesex HA1 3UJ, the United Kingdom

Correspondence to: Hani B Abdul-Jabar, Department of Trauma & Orthopaedics, London Northwest Healthcare NHS Trust, Watford Road, Harrow, Middlesex HA1 3UJ, the United Kingdom.
Email: hba999@gmail.com
Telephone: +44 208 9957231
Received: June 1, 2016
Revised: June 22, 2016
Accepted: June 23, 2016
Published online: August 23, 2016

ABSTRACT

AIM: Sagittal plane malalignment in supracondylar fractures of the humerus is thought to remodel well and be of doubtful functional significance. Consequently it has been given little attention. Our aim was to review the contemporary literature for consensus about the optimal radiographic method to assess sagittal plane alignment, define acceptable limits of reduction in this plane and assess the functional consequences of the ensuing hyperextension deformity.

METHODS: A search of MEDLINE(Ovid), PubMed, EMBASE, CINAHL and the Cochrane & DARE databases for “supracondylar fracture*” AND “sagittal” OR “anterior humeral line” OR “humerocapitellar angle” was conducted in October 2013.

RESULTS: The search identified 42 articles. Of these, 13 papers evaluated optimal radiological parameters or patient outcomes in supracondylar fractures with reference to sagittal plane deformity.

CONCLUSIONS: Inadequate reduction of supracondylar fractures in the sagittal plane results in loss of elbow flexion, although it may not be significantly disabling. The humerocapitellar angle has better reliability and prognostic value than any other radiographic measurement, but should not be used in isolation. In children under the age of 6 a humerocapitellar angle of 42 degrees +/- 18 degrees is acceptable. In older children who have limited remodelling potential, variability of +/- 6 degrees is acceptable.

Key words: Sagittal; Supracondylar fractures; Humerus; Range of motion; Remodelling; Radiographic measurement

© 2016 The Authors. Published by ACT Publishing Group Ltd.

Rashid A, Abdul-Jabar HB, Bretherton CP, Majed A, Corner T. Sagittal Plane Malalignment in Paediatric Supracondylar Fractures of the Distal Humerus: A Review of the Literature. International Journal of Orthopaedics 2016; 3(4): 609-615 Available from: URL: http: //www.ghrnet.org/index.php/ijo/article/view/1744

Introduction

Supracondylar fractures of the distal humerus constitute 3.3-17.9%[1,2] of all paediatric fractures and 58% of elbow fractures in children[3]. Skagg and Flynn’s review of 8361 supracondylar fractures revealed a male predominance of 60%, 60% were left sided and 98% were extension type. Unlike most paediatric fractures, which increase in incidence up to the age of 12, the average age at time of fracture is 6.7 years[1,2,4]. They are classified according to Wilkins’ modification of the Gartland classification[5]: Type I (undisplaced) accounting for 52%, Type IIa (displaced but with an intact posterior cortex and no rotational displacement) and Type IIb (same as Type IIa but with rotational displacement) accounting for 24% and Type III (displaced with no cortical continuity) accounting for 24%[3,6] (Figure 1). A type IV pattern has been proposed[7], which in addition to complete loss of cortical contact, describes instability in flexion and extension as assessed intra-operatively or under image guidance and may prove useful for operative decision making. Although this classification system has better reliability than other commonly used classification systems[8], several studies have highlighted its poor inter-observer reproducibility and therefore advocate examining the absolute degree of radiographic displacement when deciding how to manage these injuries[9,10]. As a consequence there has been an increase in the number of articles assessing the validity of various radiographic parameters to ensure adequate fracture reduction. This can help avoid elbow deformity, which may have functional consequences[11,12,13].

As the elbow functions as a hinge joint, deformities that lie outside its plane of motion may not correct[14]. Accordingly the importance of avoiding coronal plane malalignment, assessed using Baumann’s angle, has been established[4]. If allowed to occur it may contribute to cubitus varus, which has both cosmetic consequences of an undesirable gunstock deformity and functional sequela including limitation of range of motion, tardy ulnar nerve palsy and an increase risk of lateral epicondyle fractures[15,16,17,18]. Conversely, sagittal plane malalignment, assessed using anterior humeral line (AHL) and humerocapitellar angle (HCA), is thought to remodel well and any malalignment that persists as a hyperextension deformity is thought to be of doubtful functional significance[19]. As a consequence it has been given relatively little attention.

Our aim was to review the contemporary literature for consensus as to the optimal radiographic method to assess sagittal plane alignment, define acceptable limits of reduction in this plane with relation to age and time for potential remodelling and assess the functional consequences of the ensuing hyperextension deformity.

MATERIALS AND METHODS

A search of MEDLINE (Ovid), PubMed, EMBASE, CINAHL and the Cochrane & DARE databases for “supracondylar fracture*” AND “sagittal” OR “anterior humeral line” OR “humerocapitellar angle” was conducted in October 2013, which identified 85 articles. After removal of duplicates, 42 articles remained. Each of the 42 abstracts was screened using our exclusion / inclusion criteria specified in Table 1. Of these, 13 papers evaluated optimal radiological parameters or patient outcomes in supracondylar fractures with reference to sagittal plane deformity. The excluded papers were:

• Not related to the humerus (6)

• Not available in English Language (4)

• Conference abstracts (4)

• No long-term follow up (3)

• Patient outcome not primary focus of study (2)

• Surgical technique or protocol comparison (4)

• Not related to sagittal deformity (2)

• Anatomical studies (3)

• Biomechanical studies (1)

RESULTS

Table 2: Table 2 lists the articles included in the literature review and discusses their study design, parameters and outcomes.

DISCUSSION

Rogers et al[30] first described the AHL in 1978 as a line drawn on the lateral radiograph along the anterior humeral cortex which distally bisects the middle third of the capitellar ossification centre (Figure 2). Passage of the AHL anterior to the middle third of the capitellar ossification centre indicates the presence of posterior displacement of the distal fragment. However as the capitellar ossification centre, which normally appears between six months and two years, progressively increases in size until it reaches its adult configuration between ten and twelve years, the AHL may bisect it at different points depending on the age of the child making its use somewhat difficult. Herman et al[20] performed a radiographic study of inter and intra-observer variability of the AHL in different age groups and found that the capitellar bisection was more variable in children under the age of four years, passing almost equally through either the middle third or the anterior third of the capitellum. Although the AHL is useful for diagnosis of minimally displaced fractures, it is a poor predictor of functional outcome as it cannot differentiate between translation, which remodels well, and angulation, which does not[13].

The HCA quantifies the compliment of the angular relationship between the humeral shaft and the capitellum on the lateral radiograph (Figure 3). Unlike the AHL, it can differentiate between angular and translational deformity, which is of prognostic value[13]. Simanovsky et al[22] measured the HCA in 142 normal children, finding a mean of 41.6 ± 5.6 degrees with no statistically significant variation with age, sex, or side. This angle decreases with posterior angulation of the distal fragment and increases with anterior angulation of the distal fragment. Difficulty determining the capitellar ossification centre in younger children sometimes makes measurements difficult. Moraleda et al[24] assessed the intra-observer reliability of the HCA in 10 patients. The intraclass correlation coefficient at the time of fracture, at time of last follow up and for the uninjured elbow was 0.95, 0.84 and 0.76 respectively.

The lateral capitellohumerangle (LCHA) is a complement of the HCA. It measures the angle between the AHL and the capitellar physis and is perpendicular to the axis of HCA (Figure 4). Shank et al[29] measured the LCHA in 71 normal children, finding an mean value of 50.8 ± 6.2 degrees. They found good intra-observer (0.67) but only fair inter-observer reliability (0.37) for LCHA measurements. However intra-observer reliability is more relevant to the clinical utility of this measurement, as the surgeon will likely make treatment decisions based on his or her own measurements rather than those of others. Interestingly, LCHA intra-observer reliability was only moderate in 0-2 year age group and improved to excellent in the 8-10 and 10-12 year age groups. Thus, the measurement may be more reliable in patients approaching maturity, when remodelling of angular deformity is least predictable. The LCHA has not yet been studied in patients with supracondylar fractures of the humerus.

Any sagittal plane deformity that fails to remodel usually results in a hyperextension deformity, which may or may not be clinically apparent. Until now these deformities have been deemed to be functionally inconsequential and have therefore been largely ignored. However there are several studies correlating sagittal plane deformity to loss of function[11,13]. In their retrospective review of 84 patients treated with a variety of methods over a 9-year period, France and Strong[11] found that HCA strongly correlated with a loss of flexion after supracondylar fracture and did not remodel reliably with growth. This resulted in unsatisfactory motion by the Flynn criteria (whereby 10 degrees or more of restricted motion is defined as an unsatisfactory result) in 22% of their patients although this was not considered functionally disabling. Likewise, Simanovsky et al[13] in their retrospective review of 223 patients treated over a 4 year period found the HCA at reduction strongly correlated with loss of flexion at skeletal maturity. They deemed that this occurred secondary to inconsistent remodelling, resulting in unsatisfactory motion by Flynn criteria in 45% of their patients. In fact 22/223 patients had a persistent sagittal plane deformity at skeletal maturity, 17 patients did not achieve radiographic remodelling at the last follow-up and 10 had limited elbow flexion of 10 degrees or more, although the majority were not subjectively aware of this and therefore did not consider it functionally disabling.

In their critical analysis of bone remodelling in malunited fractures in children, Gasco and De Pablos[31] reported poor remodelling capacity around the elbow, especially compared to the proximal humerus and distal radius. Theoretically any remodelling that does take place is generally better in the plane of motion of the joint[19] meaning that sagittal plane deformities remodel better than coronal plane deformities[32]. However 65% of the length of humerus is achieved by the age of 6 years and only 7% of the remainder of the growth of the humerus occurs at the distal humeral physis[4], meaning that even remodelling of sagittal plane deformities is unpredictable in children over the age of 6 years. France and Strong[11] in their series of supracondylar fractures treated by closed reduction and splinting, traction, and percutaneous pinning reported an average of 2 degrees of remodelling in the sagittal plane and no remodelling in the frontal plane[11]. However this group of fractures were heterogenous and treated in a variety of different ways. Moraleda et al[24] in their series of Gartland type II fractures all treated with splint immobilisation reported that the mean HCA at time of fracture was 12.8 degrees and at final follow-up was 30.5 degrees implying that the mean degree remodelling in the sagittal plane was 17.7 degrees. Although there are no studies quantifying the degree of sagittal plane deformity that can be accepted before ensuing functional limitation, Shank suggested that sagittal plane deformity beyond 3 Standard Deviations (18 degrees) of normal should not be accepted, particularly in older patients in whom the remodelling is less predictable[29].

As HCA measures angular deformity in one plane only, it is conceivable that the HCA may be normal with a coronal plane deformity. These measurements should therefore not be used in isolation. Another radiographic parameters that is less frequently used is the anterior coronoid line (ACL), although there are no validated studies looking at its prognostic value, variation with age or sex and reproducibility. The ACL is a curved line drawn on the lateral radiograph along the superior aspect of the ulna, through the coronoid and onto the anterior aspect of distal humeral shaft (Figure 5). Its passage through anterior part of the capitellum signifies normal anatomy. Although it provides information on anterior-posterior translation of the distal fragment, it does not allude to distal fragment rotation[33]. The accuracy of radiographic measurements depends, in part, on the reliability with which they can be obtained. If they cannot be measured reproducibly, changes may represent measurement error rather than clinical reality. High quality radiographs are therefore crucial in obtaining accurate and reproducible measurements of these angles.

This review has the typical limitations of most review articles. Notably that only 2 of these studies included were prospective in nature and that some of the anatomic studies which did not meet the inclusion criteria and were therefore excluded, may have contained some important information about inter- and intra- observer reliability.

CONCLUSION

Inadequate reduction of supracondylar fractures in the sagittal plane results in hyperextension deformity. Although the deformity is in the plane of motion of the joint, the remodelling capacity of the distal humerus is generally limited and is especially unpredictable after the age of 6 years. The consequent loss of flexion may lead to prolonged utilization of physical therapy or repeated clinic visits, although it may not be significantly disabling.

Special care should therefore be taken when assessing sagittal plane alignment. Although the HCA has better reliability and prognostic value than any other radiographic measurement, there may be significant individual variations due to the size of the capitellar ossification centre and arm position during radiographs. Based on this systematic review we suggest a combination of two radiographic parameters, including the HCA. In children under the age of 6 years who have the capacity to achieve some remodelling an HCA of 42 degrees +/- 18 degrees (3 standard deviations) is acceptable whereas in children over the age of 6 years with limited and unpredictable remodelling capacity an HCA of 42 degrees +/- 6 degrees (1 standard deviation) is acceptable.

CONFLICT OF INTEREST

The Authors declare that there is no conflict of interest.

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Peer reviewer: Yogesh Sharad Salphale, Shushrusha Hospital, Opp.Z.P, Chandrapur, 442401 (MS) India.

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