3D Planning and Forearm Deformity Correction in Adolescents with Multiple Exostosis – Clinical Results

Abstract

Despite the 30% to 60% of patients with Multiple cartilaginous exostoses (MCE) showing forearm deformity, there is still no consensus regarding the preferred method and ideal timing of treatment, especially in teenage patients with multiple injuries in whom the treatment timing can have a strong psychological impact because disorder of endochondral bone growth can lead to joint instability and severe deformities of the involved extremity. Ulna lengthening, radius osteotomy, Distal radio ulnar joint (DRUJ) stabilization, and radial head reduction may be a good strategy to correct upper limb deformity. This study was to show reproducible planning and procedure to correct radius deformity, subluxation of the radio capitellar joint, ulna minus, carpal balance, and DRUJ incongruence in adolescents treated with ABC protocol (hybrid external fixation and volar radius plate using 3D model and software planning system methods) in Five adolescents with MCE and forearm deformity. After 1 year of the surgery, patients showed a DASH score was 8 and a VAS score was 1. On X-ray examination, Radial articular angle (RAA) = 21.55°, Palmar tilt =10°, ulnar variance (UV) = 1.2 mm, carpal slip (CS) = 64%, center of rotation of angulation (CORA) = 1.1° to ulna / 21.95° to radius and radial bowing (RB) = 11.45mm. The complication rate was 20% (one patient) and submitted ulna re-lengthening for improving DRUJ congruence. ABC protocol (hybrid external fixation and volar radius plate using a 3D model and software planning system) was found to be a safe and reliable treatment method for forearm deformity in adolescents with MCE.

Keywords

3D planning - bone lengthening - congenital - deformity correction - deformity planning - elbow - osteochondromaity - relative ulnar shortening - wrist deformity

Introduction

Despite 60% of patients with Multiple cartilaginous exostoses (MCE) showing forearm deformity choosing the best time and method of treatment in teenagers, can evaluate psychological problems because disorder of endochondral bone growth can lead to static complications with stiffness, joint incongruence, joint instability and severe deformities of the involved extremity.[1] [2] [3]

Ulna lengthening, distal radius osteotomy, distal radio ulnar joint (DRUJ) stabilization and radial head reduction as an “ABC protocol” to treat adolescents within the MCE option be good to correct upper limb deformity.

This approach is convenient, safe, and avoids complications.[4] [5]

The primary objective was to show reproducible planning and procedure to correct stiffness, distal and proximal radius deformity, radio capitellar joint dislocation, ulna minus, carpal balance, DRUJ deformity, and incongruence in adolescents treated with ABC protocol (hybrid external fixation and volar radius plate using 3D model and software planning system). Other goals were to show radiographic and clinic-functional results. (see [Table 1])

Table 1

ID	1	2	3	4	5	6	MEAN
Idade	10	15	16	10	15		12.5
Follow up years	10	2	2	2	3		4.25
Side	R	R	R	L	R		—
ROM pre (%)	52	45	63	50	46.5		49
ROM post (%)	93	88	95	79	92		88
RAA normal °	23	23	23	23	23		23
RAA pre °	12.5	42	38	24.35	29.15		27
RAA post °	20	23	23	22	20		21.313
UV normal (mm)	15	15	15	15	15		15
UV pre (mm)	17.3	20.7	10	18	20		19
UV post (mm)	1	1	1	2	1		1.35
Carpal slip normal (%)	50	50	50	50	50		50
Carpal Slip pre (%)	50	40	40	45	45		45
Carpal Slip post (%)	40	88	70	72	56		64
Tilt palmar normal°	11	11	11	11	11		11
Tilt palmar pre°	10	1	1	8	4		5.5
Tilt palmar post°	10	10	10	10	10		10
CORA normal ulna°	0	0	0	0	0		0
CORA pre ulna°	10	15	14	14	12		12.5
CORA post ulna°	0	2	1	1	1		1.1
CORA normal radius °	23	23	23	23	23		23
CORA pre radius °	20	15	32	17	18		17.5
CORA post radius °	21.9	22	23	22	22		21.925
RB normal (mm)	12	12	12	12	12		12
RB pre (mm)	10.11	23	26	18	16		16.603
RB post (mm)	13	10	11	12	11		11.475
DASH	5	11	12	16	1		8.25
VAS	1	1	2	2	1		1.25
Multiplier (mm)	4 (over)	1	1	1	2 (OVER)		1
Complications (%)	Re length	—	—	—	—		20
Consolidation time	92	120	63	100	112		106
Distraction time	67	93	—	82	78		80
Total time	159	213	63	182	200		188.5
Implants ulna	LRS/DCP	LRS	DCP	LRS	LRS
Implants radio	ndn	Volar plate	Volar plate	—-	—-
Classification	IIb	IIb	III	IIb	III

Patients and Method

Five adolescents with MCE and forearm deformity were classified by Masada's[6] (see [Fig. 1]) and treated with “ABC protocol” in a single University Hospital, FMABC (Faculdade de Medicina do ABC), Santo André, Brazil.

Fig. 1 Masada et al. Classification for forearm deformity caused by multiple osteochodromas.

The implants used for ulna length, distal radius correction, and DRUJ stabilization were tested: LRS, Limb Rail System external fixator, Orthofix, Verona, Italy or Fixus 33, Amsterdam, Netherlands, 3D forearm deformity model developed by CT SCAN exam, software correction system (Orthopediatrics®, USA) and volar large locking plate (Hexagon®, SP Brazil, Techimport®, Rio Claro, Brazil).

Institutional protocol no. ETIK 1750176 was approved. Inclusion criteria were adolescent patients (immaturity skeletal) with a diagnosis of MCE associated with forearm deformity who were treated within ABC protocol. The exclusion criteria were patients who didn't complete treatment, in chemotherapy or radiotherapy treatment, or patients with mental illnesses.

ABC Treatment Protocol

Pre-operative Planning

Before surgery, clinical and complementary exams were analyzed and forearm radiographs and CT SCAN images were used to formulate and prepare 3D piece with reproducible variables: Radial articular angle (RAA) = 23°, tilt palmar =11°, ulnar variance (UV) = 0 mm, carpal slip (CS) = 50%, center of rotation of angulation (CORA) = 0° to ulna / 23° to radius and radial bowing (RB) = 12mm were suggested with standard parameters to forearm deformity correction.[6] [7] (see [Fig. 2])

Fig. 2 Radiographic parameters to plan and to treat forearm deformity.

Now, to perform a digital plan with Orthopediatrics® software: choose the forearm topic and change the final parameters of radius correction (Anterior posterior plan was 0° and now to change 23°, to lateral direction. In sagittal view was 0° and modified to 11°, in a palmar direction. Other planning was performed for ulna lengthening bone, with regular parameters and a Multiplier app system. The rotation aspect was 0° for both. Finally, the software creates two Guide Tables for ulna and radius deformity correction. (see [Fig. 3])

Fig. 3 Guide table and 3D digital planning forearm deformity correction.

The next step was to introduce pins and ex-fix in the 3D model (in ulna used LRS®, by Orthofix®, Verona, Italy or Fixus 33, Amsterdam, Netherlands) and in radius to perform hexapod Orthex®, Orthopediatrics®, Florida, USA). Now, surgeons calibrate all six struts according to the final line that radius table and ulna lengthening according to the table too. Another method (volar locking plate with 3D guide osteotomy procedure) was performed in radius acute correction. Both methods correct forearm deformity and show 3D models for patients and parents. (see [Figure 4])

Fig. 4 Comparative 3D forearm model to planning deformity correction methods.

Surgical Procedure

Patients were submitted to general anesthesia, and small incisions were performed with Fluoroscopy assisted was used to mark points to pin insertion and ulna osteotomy level.

The next step was to perform ex-fix fixation in the ulna. Linear and angular pin placement and ulna variance and deformities were planned and corrected. After, to perform ulna lengthening bone, with software Guide Table parameters and Multiplier app system calculated length versus bone versus age versus sex.

Now, after 80 days (mean ulna length time), new general anesthesia was performed, and resecting the ulna exostosis, distal radius deformity correction, and DRUJ (distal radio ulnar joint) stabilization. The braquiorradialis tendon graft was dissected and prepared with Krakow suture until your insertion at the distal radius placement. The bone tunnels (∼30° oblique direction) of the distal radius (entrance point) to the distal one-fifth of the ulna (exit point) were made with the forearm in supination, using cannulated drill/guide (Axis® system, by Techimport, Rio Claro, SP), avoid joint articular surface. The BR graft passed through the bone tunnel with the Axis® guide system. Now, Tendon graft fixation with one specific Knotless anchor system (Poplock® 2.8mm, CONMED®, Tampa, USA) was performed in a 10mm proximal ulna tunnel, and the best tension was obtained with the forearm in a neutral position to stabilize the DRUJ. At that moment, transverse K-wire 2.0mm was passed through the ulna/radius and maintained for 6 weeks. After, distal radius osteotomy was performed with a volar large locking plate (acute correction) or hexapod ex-fix (standard correction).

After 106 days (mean healing time) and adequate or over-lengthening of the ulna, according to the Multiplier® app, with satisfactory bone formation, all implants were removed, in a surgical room setting, with general anesthesia.

The distraction distance, distraction period, consolidation period, and time to ulna lengthening were noted. The distraction speed was 1.0 mm/2 days, and the radius was acute with plate. After 1 year of the surgery, patients obtained an ideal ROM in the upper extremity.

Clinical-functional parameters with VAS = 1, DASH was 8, VAS of 1, and grip strength = 88% (opposite side). Radiograph parameters indicated DRUJ and elbow congruence after 12 months. Radial articular angle (RAA), ulnar variance (UV), carpal slip (CS), center of rotation of angulation (CORA) to ulna/radius, radial bowing (RB), and radiocapitellar congruence were measured using PA view and Palmar tilt was measured on the lateral view. Other additional procedures were performed with implant removal, reattachment of the ex-fix, and new acute ulna lengthening in one patient with plate and bone graft (first patient) because of DRUJ incongruence.[7] (see [Fig. 5])

Fig. 5 Comparative radiographic parameters aspects after new ulna lengthening correction.

Rehabilitation Protocol

After two weeks of the procedure, standard mobilization was employed to the upper limb (complete). Dressing change after one week postoperatively was done. After two weeks patients started rehabilitation sessions for ∼2 months and if possible, to start physical activities.

Statistical Methods

Data are presented as mean or median according to the type of variable and distribution. Parametric variables were assessed using the Mann–Whitney U test, and p < 0.05 was considered indicative of a statistically significant difference. The Statistical Package for the Social Sciences (SPSS) version 24.0 (SPSS Inc.) was used for data analyses.

Results

[Table 1] is presented data: patients' demographic characteristics, at the 12-month follow-up, the objective and clinical-functional outcomes. Clinic-functional mean results were ROM = 90.5% (non-affected side), DASH score = 8 [5–12], and VAS =1. On X-ray examination, Radial articular angle (RAA) = 21.55°, Palmar tilt =10°, ulnar variance (UV) = 1.2 mm, carpal slip (CS) = 64%, center of rotation of angulation (CORA) = 1.1° to ulna / 21.95° to radius and radial bowing (RB) = 11.45mm. The complication rate was 20% (one patient) and submitted ulna re-lengthening for improving DRUJ congruence.

Discussion

It's not clear how to choose the best time and Surgery method, especially in teenagers, to correct forearm deformity by MCE. Recurrency problems with psychological impact or over-treatment can be avoided. Of note, CORA is a stronger predictor of good results among lower limbs only. The natural length and angle of the upper limbs maintained unclear in the forearm and CORA parameter is insufficient to promote functional forearm correction. It's necessary to plan guidelines correction independents for radius and ulna. Ulna lengthening is the standard method to obtain the best relationship with DRUJ. Radius bone standard parameters into Orthopediatrics® software were necessary changing to obtain curve bone correction (lateral change 0° to 23° and palmar 0° to 11° angulation, respectively). Another important step is to start distal radius deformity correction after the ulna lengthening is complete.

In this study, different parameters and radiographic aspects were suggested to promote forearm correction: Ulnar variance (0 mm), carpal balance, CORA, radial bowling, Radial inclination (23°), tilt palmar (11°), with new standard parameters and patients showing excellent clinical and patient-reported and radiographic outcomes.

Nowadays, is very common to use 3D models and guides (performed by CT SCAN images) to improve the diagnosis, pre-op planning, and treatment of bone deformities. In addition, is possible to use the same 3D deformity model to plan into a digital-specific software system. All patients in our study were treated with ABC protocol.[8] [9]

The best time is unclear to correct forearm deformities and is limited to a certain range and tends to remain stable with age, bone site deformity, and sex. Chunxing Wu et al. reported a stronger relationship between the age versus length and epiphyseal ossification of the radius and ulna and impacted the best time to indicate the surgery treatment for deformity correction. In our study, four patients were submitted over treatment (ulna length) assisted by the Multiplier® app and Orthopediatrics® software planning correction to avoid other additional procedures.[10]

Forearm correction in MCE teenage' patients are a challenge. Other studies reported that the simple resection of exostosis doesn't prevent further deformity progression and is necessary lengthening of the ulna, distal Radius osteotomy, and Ligament reconstruction to restore DRUJ congruence and stabilization.

The present study reported ulnar lengthening with exostosis resection, DRUJ stabilization with distal interosseous membrane reconstruction, k-wire provisory fixation, and distal radius osteotomy correction too. Clinical results were obtained without any complications at this moment and all patients showed elbow and wrist stables and congruences.[4]

Traditional implants (volar locking plate) versus external fixator to distal radius correction is a critical point in literature: frontal and sagittal plane (volar tilt) and articular inclination. The study by Ross et al and this study demonstrates that if to change standard parameters of radius correction can achieve an acceptable reduction. All patients showed adequate radiographic, and patient-reported outcome parameters.[11]

This paper was a retrospective clinical analysis, and some limitations need to be acknowledged. The inclusion criterion was all MCEs subtypes, and the sample size was small for DASH and VAS analysis; however, it was sufficient for the statistical evaluation and reproducible to promote radiographic aspects with new standard parameters to forearm correction.

Conclusion

The standard forearm parameters with Radial Inclination, tilt palmar, Radial articular angle (RAA), ulnar variance (UV), carpal slip (CS), the center of rotation of angulation (CORA), radial bowing (RB), and distal radio ulnar joint (DRUJ) and elbow congruence are reproducible and significance parameters to planning and ABC protocol (hybrid external fixation, volar large radius plate using 3D model and software planning system) were safe and reproducible treatment method for forearm MCE deformity in teenagers.

Conflicto de los intereses

Los autores Marcio Aurelio Aita, Victor Bignatto Carvalho, Fabio Lucas Rodrigues, Kleber Oliveira Barbosa, Renato Tadeu S. Moretto y Ricardo Kaempf de Oliveira declaran que no tienen conflictos de intereses que revelar.

Informed Consent

An informed consent document was provided to all research participants, who read and signed it according to their will. The research presented here was approved by and was in accordance with the ethical standards of the Faculdade de Medicina do ABC Ethics Committee on human experimentation by n° 1750176. An informed consent document was provided to the patient, who read and signed it according to his will.

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Publication History

Received: 13 March 2024

Accepted: 11 October 2024

Article published online:
23 December 2024