Anatomic Investigation of Commonly Used Landmarks for Evaluating Rotation During Forearm Fracture Reduction

Complex Fractures of the Radial and Ulnar Shaft

SUMMARY

Successful management of radial and ulnar shaft fractures is an essential skill for all orthopaedic surgeons. The frequent presentation of these injuries coupled with the nuanced anatomic considerations that must be observed for successful outcomes dictate that these injuries require a thorough understanding by the treating surgeon. Intraoperative care to restore the anatomic radial bow and rotation is essential for the resumption of functional forearm rotation postinjury. Often, problems arising during the operative treatment of radial and ulnar shaft fractures come in predictable patterns that can be mitigated with preoperative planning and sound technique. Cases of increased complexity with segmental bone defects and soft tissue defects require a variety of advanced reconstructive techniques.

Developmental Anatomy of the Radial Bow in Pediatric Patients Using 3D Imaging

BACKGROUND

While radial bow shape is well characterized in adults, its development in children is not well understood. Previous studies on the radial bow use radiographs, thus, rotational positioning of the forearm could alter bowing measurements. This study used 3D imaging to better assess the pediatric radial bow.

METHODS

Computed tomography scans from the New Mexico Decedent Image Database were obtained for ages 2 to 16 (females) and 18 (males) (n=152). 3D models were generated using Slicer and Rhino software. Length of the entire radial bow (bicipital tuberosity to sigmoid notch), maximum radial bow, location of the maximum radial bow (bicipital tuberosity to the point of maximum bowing), and distal, middle, and proximal third radial bows were measured.

RESULTS

The length of the entire bow increased with age, with a strong correlation with age ( r =0.90, P <0.01). The maximum bow increased with age, with a strong correlation with age ( r =0.78, P <0.01). The maximum bow normalized to the length of the entire bow increased mildly with age, mean 0.059 ± 0.012 ( r =0.24, P =0.0024), but seems to plateau around age 8. The location of the maximum bow increased with age ( r =0.85, P <0.01). The normalized location of the maximum bow remained constant between ages, with a mean of 0.41 ± 0.10 ( r =0.12, P =0.14). The normalized distal third bow mildly increased with age ( r =0.34, P <0.01), the normalized middle third bow mildly increased with age ( r =0.25, P <0.01), and the normalized proximal third bow remained constant between ages ( r =0.096, P =0.24).

CONCLUSIONS

Normalized values for maximum, distal third, and middle third radial bow increase with age, while normalized values for location and proximal third radial bow remain relatively constant, suggesting the proportional shape of the radius changes during development, although qualitatively plateaus after age 8.

LEVEL OF EVIDENCE

Retrospective comparative study, Level-III.

Accuracy of the Lesser Trochanter Profile as a Marker of Femoral Rotation: Computed Tomography-Based Study of 1,722 Femora

BACKGROUND

The lesser trochanter (LT) profile is an often-used marker for proximal femoral rotation, particularly during the operative fixation of femoral fractures. Previous studies have come to conflicting conclusions about its reliability for this purpose.

METHODS

The SOMA (Stryker Orthopaedic Modeling and Analytics) database (Stryker) was used to identify 1,722 computed tomographic (CT) scans of whole femora. Each femur was taken through an 80° rotational arc in 2.5° increments, and the LT profile was constructed for each position. These 56,826 LT profile measurements were then correlated with the femoral rotation.

RESULTS

Across the arc of motion studied, the LT correlated weakly with proximal femoral rotation (R 2 = 0.32). There was a 35° arc, between 10° and 45° relative external rotation of the proximal femur, within which the LT profile only changed by 1 mm. The mean overall femoral anteversion was 21.2°, and women tended to have more femoral anteversion (23.9°) than men (19.2°). On average, men had a 1.6-mm more prominent LT than women. Side-to-side differences in femoral anteversion as well as LT position and size were not significant or were clinically unimportant.

CONCLUSIONS

A large-scale, CT-based study shows that the LT profile is a less reliable marker of proximal femoral rotation than previously thought. This is true particularly if there is relative external rotation of the proximal femur, where the proximal femur can undergo up to 35° of rotation before 1 mm of change in the LT profile occurs. Care must be taken to check other markers of rotation such as by clinical examination during fixation of femoral fractures and not rely solely on the LT profile.

CLINICAL RELEVANCE

In the largest study of its kind, this CT-based study of 56,826 LT profile measurements found that when the proximal femur is externally rotated, the LT profile becomes an unreliable marker of rotation, which can lead to excessive internal rotation of the distal fracture fragment. The LT profile should be used with caution, and confirmation of rotation by other means is recommended.

Pediatric Forearm Malunions

The aim of this article is to review the evaluation and management of pediatric forearm malunions. Acceptable parameters for nonoperative management of pediatric forearm fractures are reviewed, followed by clinical and imaging workups of malunions and decision-making points for treatment. The landscape of available technology for planning and execution of corrective osteotomy is discussed. Several cases of pediatric forearm malunion are presented, along with surgical and functional outcomes. Recommendations are given regarding the authors' preferred approach for management of pediatric forearm malunions.

Increase in gap index over time after reduction of unstable paediatric both-bone forearm fracture does not cause displacement

This study investigated the effects of changes in the gap index on fracture displacement during follow-up. Patients who underwent closed reduction and casting with a diagnosis of unstable paediatric both-bone forearm fractures and a cast index < 0.8 were retrospectively evaluated. Patients were divided into Groups 1 and 2 based on their gap index (<0.15 and >0.15, respectively). Anteroposterior and lateral displacements of the radius and ulna and the gap index of the cast were measured on the X-ray after the first reduction and on the last X-ray before plaster removal. The mean patient age (n = 94, 74 boys and 20 girls; 51 in Group 1 and 43 in Group 2) was 7.09 ± 2.66 years. Fracture union times (plaster removal) were 38.8 ± 7.1 days. The mean cast index was 0.76 ± 0.05 (0.59-0.8). Both groups had similar distributions in terms of age, sex, fracture side, anatomic location and plaster removal time (p > 0.05). No significant differences were observed in either group in any radial or ulnar angulation values at any time point or the difference between the first and last values (all p > 0.05). Moreover, the gap index difference between the first and last measurements was significantly different in both groups (p = 0.002). If the cast index remains <0.8, despite the increase in the gap index in both groups, the amount of fracture displacement was small and acceptable.

3D analysis of the distal ulna with regard to the design of a new ulnar head prosthesis

STUDY DESIGN

A retrospective, single center, data analysis.

OBJECTIVE

Persistent pain and instability are common complications after distal ulnar head arthroplasty. One main reason may be the insufficient representation of the anatomical structures with the prosthesis. Some anatomical structures are neglected such as the ulnar head offset and the ulnar torsion which consequently influences the wrist biomechanics.

METHODS

CT scans of the ulnae of forty healthy and asymptomatic patients were analyzed in a three-dimensional surface calculation program. In the best fit principle, cylinders were fitted into the medullary canal of the distal ulna and the ulnar head to determine their size. The distance between the central axes of the two cylinders was measured, which corresponds to the ulnar offset, and also their rotational orientation was measured, which corresponds to the ulnar torsion.

RESULTS

The mean medullary canal diameter was 5.8 mm (±0.8), and the ulnar head diameter was 15.8 mm (±1.5). The distance between the two cylinder axes was 3.89 mm (±0.78). The orientation of this offset was at an average of 8.63° (±15.28) of supination, reaching from 23° pronation to 32° supination.

CONCLUSION

With these findings, a novel ulnar head prosthesis should have different available stem and head sizes but also have an existing but variable offset between these two elements. A preoperative three-dimensional analysis is due to the high variation of offset orientation highly recommended. These findings might help to better represent the patients natural wrist anatomy in the case of an ulnar head arthroplasty.

LEVEL OF EVIDENCE

III.

Radius Shaft Fractures-What Alignment is Acceptable at What Age? Plates or Flexible Nails?

INTRODUCTION

The transition from pediatric to adolescent fractures can lead to uncertainty on what level of surgical correction is warranted as remodeling is limited in these older patients.

DISCUSSION

Adolescent diaphyseal radial shaft fractures present several unique challenges; the radial bow must be restored to preserve forearm rotation and there are several clinical scenarios where plating, even in the skeletally immature child, is strongly recommended and will have more reliable results over flexible intramedullary nails. In addition, judging how much angulation, rotation, and displacement will remodel in the older child can be a challenging decision, even for experienced pediatric orthopaedists.

CONCLUSION

This overview discusses parameters for acceptable alignment in these fractures, when surgical fixation should be considered, and circumstances where plating should be considered over flexible nails.

Rotational Anatomy of the Radius and Ulna: Surgical Implications

PURPOSE

The rotational anatomy of the forearm bones is not well defined. This study aims to further the understanding of the torsion of the radius and ulna to better guide treatment.

METHODS

Computed tomography images of 98 cadaveric forearms were obtained and 3-dimensional models of the radius and ulna were generated and analyzed. The rotation of the radius was evaluated by comparing the orientation of the distal radius central axis (DRCA) with the volar cortex of the distal radius (DR) and biceps tuberosity (BT). The rotation of the ulna was evaluated by assessing the orientation of the ulnar head with respect to the proximal ulna.

RESULTS

The DR volar cortex pronates from distal to proximal. The BT was 43.8° ± 16.9° supinated from the DRCA (range, 2.7°-86.5°). The mean difference in rotation between contralateral biceps tuberosities was 7.0° ± 7.1°. The volar cortex of the DR was 12.6° ± 5.4° supinated compared with the DRCA. The ulnar head was pronated 8.4° ± 14.9° with respect to the greater sigmoid notch (range, 50.3° pronation-22.0° supination).

CONCLUSIONS

The BT has a variable orientation relative to the DR, but it is generally located anteromedially in a supinated arm or 136° opposite the radial styloid. Understanding the rotational anatomy of the radius and ulna can play an important role in surgical planning and implant design. The rotational anatomy of the radius and ulna varies significantly between individuals, but is similar in contralateral limbs.

CLINICAL RELEVANCE

Distal radius volar cortex rotational anatomy can help guide treatment of DR fractures and malunions as well as assist in positioning of wrist arthroplasty implants, particularly in the presence of bone loss. The side-to-side similarities demonstrated in this study should be helpful in managing patients with segmental bone loss or fracture malunion and those requiring joint reconstruction.

Assessing distal radius malrotation following fracture using computed tomography

HYPOTHESIS

When the distal fracture fragment in distal radius fractures displaces, it commonly rotates as well as shortens and angulates.

AIM

The aim of this study was to assess the frequency and magnitude of malrotation of the distal fracture fragment using computed tomography (CT).

METHODS

A retrospective radiological assessment of 85 CT scans of the distal radius, 35 following fracture and 50 normal radii, was carried out. We developed and applied a simple method for measuring rotation of the distal radius relative to the diaphysis using routine CT scans of the wrist. A Mann-Whitney analysis was used to identify differences in radial rotation between fractures and controls. Intra- and inter-observer reliability were analyzed using intra-class correlation coefficients (ICCs) and Bland-Altman plots.

RESULTS

The articular surface of the distal radius is normally rotated in the long axis of the forearm relative to the diaphysis, either into pronation or into supination. The median radial rotation angle of controls was 1° pronation (range -15° to 4°) compared to 3° pronation (range -24° to 31°) in the fracture group. The absolute rotation angle was significantly greater in the fracture group (median 10°, range 0-31° vs. 3°, range 0-15°; p < 0.001) and outside the "normal range" of controls in 26 cases indicating that 75% had rotated appreciably following injury. Intra- and inter-observer reliability of measurements were good with ICCs of 0.99 and 0.98, respectively.

CONCLUSIONS

Malrotation of the distal radius appears common following distal radius fracture. Malrotation of the distal fracture fragment has been shown to affect distal radio-ulnar joint function. Despite this, rotational deformity is rarely addressed in clinical practice as it is difficult to appreciate on simple radiographs. The simplified method described here is easy to use in routine clinical practice and also appears reliable. Measuring radial rotation may be an important consideration when planning both primary treatment and corrective osteotomy for patients with distal radial malunion.

A cadaveric study of radial and ulnar bowing in the sagittal and coronal planes

BACKGROUND

This study provides a comprehensive, full-length assessment of radial and ulnar bowing in anteroposterior (AP) and sagittal planes.

METHODS

Radial and ulnar AP and lateral bowing were assessed using orthogonal digital photographs of 211 randomly selected cadaveric bilateral forearms (422 radius, 422 ulna bones) from a well-preserved osteologic collection.

RESULTS

In the radial AP plane, an apex-radial bow was present at a mean of 58% of bone length (slightly distal to midpoint), with a mean depth of 1.3 cm. In the radial lateral plane, an apex-dorsal bow occurred at a mean of 45% of bone length, with a mean depth of 0.8 cm. In the ulnar AP plane, apex-radial bow occurred at a mean of 32% of bone length with a mean depth of 1.0 cm. In the ulnar lateral plane, the majority of specimens (81%) had an apex-dorsal bow, whereas 19% had a reverse (apex-volar) bow. Lateral ulnar bow was located at a mean of 33% of bone length with a mean depth of 2.0 cm, with 36% of specimens possessing a lateral bow located at 35% or more distal along the ulna. Side-to-side differences for bow location and depth were less than 2% of bone length.

CONCLUSIONS

Ulnar lateral bow was found to be more distal than in previously published works, which analyzed only the proximal ulna, and this study describes a reverse ulnar bow in 19% of specimens. This demonstrates lateral ulnar morphology to be more variable than previously defined with minimal side-to-side variability, which are important considerations for fracture fixation and elbow arthroplasty.

[Posttraumatic torsional deformities of the forearm : Methods of measurement and decision guidelines for correction]

Forearm fractures are common in all age groups. Even if the adjacent joints are not directly involved, these fractures have an intra-articular character. One of the most common complications of these injuries is a painful limitation of the range of motion and especially of pronation and supination. This is often due to an underdiagnosed torsional deformity; however, in recent years new methods have been developed to make these torsional differences visible and quantifiable through the use of sectional imaging. The principle of measurement corresponds to that of the torsion measurement of the lower limbs. Computed tomography (CT) or magnetic resonance imaging (MRI) scans are created at defined heights. By searching for certain landmarks, torsional angles are measured in relation to a defined reference line. A new alternative is the use of 3D reformation models. The presence of a torsional deformity, especial of the radius, leads to an impairment of the pronation and supination of the forearm. In the presence of torsional deformities, radiological measurements can help to decide if an operation is needed or not. Unlike the lower limbs, there are still no uniform cut-off values as to when a correction is indicated. Decisions must be made together with the patient by taking the clinical and radiological results into account.

An Anatomic Investigation Into the Relationship Between Posterior Condylar Offset and Posterior Tibial Slope of One Thousand One Hundred Thirty-Eight Cadaveric Knees

BACKGROUND

Posterior condylar offset (PCO) and posterior tibial slope (PTS) have critical consequences in total knee arthroplasty, especially with regards to sagittal plane balancing. However, there has only been limited investigation into the functional consequences of each, and there have only been anecdotal observations regarding any associations between PCO and PTS.

METHODS

In a large osteological study of 1138 knees, standardized measurements of PCO and PTS were taken using previously described techniques on specimens of different age, race, and gender. Multiple linear regression was performed to determine the independent predictors of medial and lateral PTS.

RESULTS

Mean standardized medial PCO was greater than lateral PCO (1.22 ± 0.16 vs 1.15 ± 0.19 mm, P < .001) and medial PTS was greater than lateral PTS (7.3 ± 3.8° vs 5.7 ± 3.7°, P < .001). Decreasing PCO, female gender, and African-American race were associated with both increased medial and lateral PTS. Neither age nor femoral length correlated with medial or lateral PTS.

CONCLUSION

These data are the first to quantify that an inverse correlation between PCO and PTS exists. This relationship represents an important area for future biomechanical and clinical studies.