J Shoulder Elbow Surg (2015) 24, 1197-1205
www.elsevier.com/locate/ymse
A new autocentering hinged external fixator of the elbow: a device that stabilizes the elbow axis without use of the articular pin Prospero Bigazzi, MDa,*, Marco Biondi, MDa, Andrea Corvi, MSc Engb, Sandra Pfanner, MDa, Giuseppe Checcucci, MDa, Massimo Ceruso, MDa a b
Department of Hand Surgery and Reconstructive Microsurgery, Azienda Ospedaliero Universitaria Careggi, Florence, Italy Department of Engineering, Universit a degli Studi di Firenze, Florence, Italy Background: Hinged external fixation of the elbow is an important tool for the orthopedic surgeon. It enables early postoperative mobilization that may result in better outcomes. All models require correct alignment with the elbow axis of rotation. There is a long learning curve to this procedure, it may be time-consuming, and it can be associated with a high dose of x-ray exposure. An axial pin can interfere with bone-ligament suture anchors and bone reconstruction plates. Materials and methods: A new external fixator has been designed and mechanically tested. The hinge has a special gear able to freely align itself with the center of elbow rotation during passive flexion-extension movements. It has been clinically tested on 7 patients affected by traumatic and post-traumatic elbow disorders. The maintenance of the correct position has been tested clinically with computed tomography scans and radiographs. Results: All patients had correct alignment of the axis of rotation of the external fixator with the axis of elbow rotation. No cases of misalignment, loss of fixation, pin loosening, or instability were found. Conclusion: A new self-centering hinged external fixator correctly aligns itself with the axis of elbow rotation. It does not interfere with ligamentous reconstruction anchors, distal plates, or screw fixation. The surgical technique is easy to learn and relatively quick. It can also be positioned without performing an arthrotomy to maintain reduction of simple dislocations of the elbow. Level of evidence: Level IV, Case Series, Treatment Study. Ó 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: External fixator of the elbow; elbow instability; elbow collateral ligament injury; elbow trauma; elbow fracture; elbow dislocation
Hinged external fixation of the elbow has been developed8 to maintain congruency and stability of both the humeroulnar and humeroradial joints. In 1975, Volkov and Oganesian were the first authors to report, in an English-language journal, an elbow hinged distraction *Reprint requests: Prospero Bigazzi, MD, Via del Palmerino n 11, I-50137 Florence, Italy. E-mail address: [email protected] (P. Bigazzi).
apparatus designed to eliminate ‘‘excessive friction between the surfaces, prevent abnormal joint kinematics and allow the newly formed joint surfaces to develop correctly.’’20 Hinged external fixation of the elbow allows active and passive range of motion, taking stress off the ligaments and maintaining articular stability. It enables early and secure postoperative rehabilitation that may reduce stiffness and result in a better final range of motion.13,18
1058-2746/$ - see front matter Ó 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. http://dx.doi.org/10.1016/j.jse.2015.05.036
1198
P. Bigazzi et al.
Figure 1 Elbow hinge configurations studied on a 3-dimensional anatomic model created with SolidWorks (Dassault Systemes, VelizyVillacoublay, France) and tested with the physiologic kinematic with visualNastran 4D (MSC Software Corp., Newport Beach, CA, USA).
The clinical indications for elbow external fixation vary from acute instability of ‘‘simple’’ elbow dislocations to complex post-traumatic fracture-dislocations.4,17 It may be used after complex arthrolysis and interposition arthroplasty of a stiff elbow, in which an extensive release of periarticular soft tissues or excision of heterotopic bone may cause instability.22 For a distraction purpose, with or without soft tissue interposition, it neutralizes contact forces across the joint, preventing ligamentous contraction.8 Furthermore, when it is applied in noncompliant patients, it protects ligamentous and bone reconstruction procedures with concentric reduction, allowing early postoperative physical therapy.1 Many devices are available with different features and a common surgical step: the positioning of a temporary pin in the center of elbow rotation. This surgical step is technically demanding,9 as the hinge axis must coincide exactly with the flexion-extension axis of elbow rotation,16 which passes through the center of the arcs formed by the trochlear sulcus and the capitellum. This axis is internally rotated 3 to 8 with regard to the plane of the epicondyles and forms an angle of 82 to 86 with the axis of the humerus. The axis pin should therefore pass parallel to the trochlea on the anteroposterior x-ray view and appear as a dot through the center of the trochlea from the lateral view. Madey et al15 reported that a misalignment of 5 caused a 3.7-fold increase in energy expenditure, whereas a 10 mismatch yielded a 7.1-fold increase. Proper placement often requires multiple drilling attempts and fluoroscopic localization, which can be time-consuming and is associated with a steep surgical learning curve. When an external fixator is first positioned, the hardware can impede ligament reconstruction, making it
Figure 2
The final design of the hinged elbow external fixator.
difficult to use suture anchors. However, the external fixator may also be difficult to apply after ligament reconstruction. In fact, the axial pin should pass exactly through the axis of elbow rotation where the suture anchor or transosseous sutures need to be placed. For these reasons, the application of an external fixator is a crucial step in the surgical treatment of the elbow and must be planned correctly. We present a new external fixator design with a special hinge that autocenters the axis of elbow rotation, avoiding
Demographic data and preoperative status of the patients, indications for hinged external fixator application, and postoperative passive and active arc of motion
Case Sex N
Age Injured side
1
Male
27
2
Male
46
3
Male
30
4
Male
29
5
Male
41
First diagnosis
Former surgical treatment
Time from Preoperative diagnosis injury/ previous treatment
Final surgical treatment with external fixator
Arthrolysis, radial head replacement, LCL reconstruction with triceps fascia, and external dynamic elbow fixation Arthrolysis, LCL 9 months Stiff elbow in Nondominant Terrible triad Elbow reduction, reconstruction an ulnarradial head with palmaris radialreplacement, longus, and humeral bone LCL external dynamic synostosis reconstruction elbow fixation Arthrolysis, radial 55 days Stiff elbow in Dominant Terrible triad Radial head ORIF, head replacement, chronic elbow reduction LCL reconstruction posterior and stabilization with triceps fascia, dislocation with ulnohumeral and external K-wire dynamic elbow fixation Arthrolysis, Dominant Complex distal ORIF 6 months Stiff elbow interposition humeral with humeral arthroplasty fracture articular with fascia lata, cartilage and external reabsorption dynamic elbow fixation Arthrolysis, radial 45 days Stiff elbow in Radial head Non Terrible triad head replacement, chronic resection, dominant and LCL reinsertion posterior proximal row homolateral with anchor, and elbow carpectomy transexternal dynamic dislocation scapholunate elbow fixation wrist dislocation
Dominant
Terrible triad
Elbow reduction and radial head resection
107 days
Stiff elbow in chronic posterior elbow dislocation
Indication for external fixator application
Postoperative active and passive flexionextension arc of motion with external fixator
Postoperative active and passive pronationsupination arc of motion with external fixator
90 ; 110
90 ; 120
LCL reconstruction 100 ; 110 protection and early postoperative rehabilitation
90 ; 110
45 ; 90
95 ; 110
Elbow distraction, 110 ; 130 medial and lateral collateral ligaments protection
175 ; 175
50 ; 90
0 ; 20
Ligamentous reconstruction protection and early postoperative rehabilitation
LCL reconstruction protection and early postoperative rehabilitation
LCL reconstruction protection and early postoperative rehabilitation
1199
(continued on next page)
Autocentering hinged external fixator of elbow
Table I
1200
Table I
(continued )
Case Sex N
Age Injured side
First diagnosis
Former surgical treatment
Time from Preoperative diagnosis injury/ previous treatment
6
Male
75
Dominant
Upper arm subamputation below the elbow and elbow dislocation
None
0
7
Female 67
Dominant
Chronic elbow dislocation in obese patient
None
10 days
Final surgical treatment with external fixator
Upper arm reimplantation, closed elbow reduction, and external dynamic elbow fixation Closed elbow joint Chronic elbow reduction and dislocation in external dynamic obese patient elbow fixation Upper arm subamputation below the elbow and elbow dislocation
Indication for external fixator application
Postoperative active and passive flexionextension arc of motion with external fixator
Postoperative active and passive pronationsupination arc of motion with external fixator
Redislocation prevention in unstable elbow and early postoperative rehabilitation
60 ; 90
80 ; 100
Redislocation prevention in unstable elbow and early postoperative rehabilitation
70 ; 80
170 ; 170
ORIF, open reduction and internal fixation; LCL, lateral collateral ligament.
P. Bigazzi et al.
Autocentering hinged external fixator of elbow
1201
the use of a provisional axial pin. This device may expand the indications for elbow external fixation.
Materials and methods In collaboration with the Department of Engineering, University of Florence, we developed a new external fixator based on the following parameters: - The device must be equipped with a self-centering system able to align its axis of rotation with the axis of elbow rotation, without an articular pin. - Once centered on the axis, it must be able to lock. - It must be unilateral. - It must be able to work as an articular distractor. - It must allow placement on either arm. To create this device, we first designed a 3-dimensional anatomic elbow model using SolidWorks software (Dassault Systemes, Velizy-Villacoublay, France). Second, we designed many dynamic simulated mechanisms with the Adams/Machinery software (MSC Software Corp., Newport Beach, CA, USA). Through Adams and SolidWorks, we studied and virtually tested several different hinge configurations (Fig. 1) until we arrived at the final autocentering mechanism design (Fig. 2). A model of this design was created in the university’s engineering department. The model was mechanically tested using varusvalgus stress and compression cycle loads for resistance. Between 2008 and 2014, we clinically tested the new external fixator on 7 patients (Table I). Five patients presented with a posttraumatic stiff elbow. Two patients had sustained an acute elbow injury: a subamputation of the proximal third of the forearm with fracture-dislocation of the elbow, and a subacute irreducible simple elbow dislocation observed in a morbidly obese patient. At the time of surgery, the mean age of the 7 patients was 40 years (6 men, 1 woman). Two patients were affected on the dominant arm and 5 on the nondominant arm. The same surgeon performed all the surgeries. The patients were positioned supine under general anesthesia. A brachial plexus block was performed in addition to obtain better control of postoperative pain. Every patient was treated with the application of the hinged external fixator as the final step of the surgery. In 6 cases, this served to protect the ligamentous reconstruction; 1 patient needed additional distraction after an interposition arthroplasty (case 4, Table I). In 1 case, application of the external fixator was the only procedure performed to maintain elbow reduction (case 7, Table I).
Surgical technique The first surgical step in the procedure involves holding the elbow in reduction (with or without arthrotomy) and then placing the hinged external fixator using 4 half-pins with small stab wounds. Two humeral pins are placed from lateral to medial with bicortical purchase and are connected to the fixator humeral rod. One pin should be placed close to the deltoid tuberosity and the other in the lower humeral shaft. Another 2 half-pins are placed anteromedially from the posterolateral aspect of the ulna and connected to the fixator’s ulnar rod. The second step consists of visually aligning the hinge of the external fixator to the axis of the elbow (lateral epicondyle) and securing clamps to the ulnar and
Figure 3 Elbow external fixator set in position at the end of the surgery. The device aligns the elbow axis of rotation during several cyclic flexion-extension movements. Once it is aligned, the central gear is locked, allowing early postoperative mobilization.
Figure 4 Patient during early postoperative mobilization. The hinged external fixator is aligned, the central gear is locked, and the patient can begin rehabilitation. humeral rods. After ensuring that all the connections are secure, the elbow must be anatomically reduced, and by performing several repeated cyclic motions, the central hinge mechanism selfcenters along the axis of elbow rotation (Fig. 3). When the mechanism is centered (about 2-3 cycles), it must be locked to the central gear, maintaining freedom of flexion-extension (Fig. 4). If necessary, distraction can be added after self-centering of the device.
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Figure 5
P. Bigazzi et al.
Postoperative CT scan shows correct alignment of the axis of rotation of the external fixator with the axis of elbow rotation.
Clinical examination The day after surgery, the patients started a program of active and passive mobilization carried out by an experienced occupational therapist. At night, the patients locked the external fixator, alternating flexion and extension positions. The external fixator was removed after a mean time of 45 days (range, 34-58 days), when the soft tissue healing process was expected to maintain stability. Clinical follow-ups were carried out at 2 weeks, 4 weeks, and 3, 6, and 12 months after surgery. To verify the correct alignment of the axis of rotation of the hinged external fixator, a computed tomography (CT) scan was performed at 2 weeks postoperatively. The aim of the CT scan was to compare the axis of elbow rotation with the axis of rotation of the hinged external fixator (Fig. 5). Radiographs were obtained at 4 weeks postoperatively to monitor elbow reduction.
Results The patients at baseline presented with heterogeneous traumatic and post-traumatic disabilities. For this reason, clinical outcomes were considered only in terms of
surgical complications and range of motion with the device. Clinical outcome measurements and the patient’s satisfaction or pain score were not taken into account. The patients achieved a mean active arc of motion of 75 (range, 45 -110 ) and a mean passive arc of motion of 100 (range, 80 -130 ) in flexion-extension. In pronationsupination, the mean active arc of motion was 100 (range, 0 -175 ), and the mean passive arc of motion was 115 (range, 20 -175 ). The hinged external fixator found and maintained the axis of elbow rotation in every patient. CT scans and radiographic imaging confirmed the correct alignment of the hinged axis of rotation to the elbow’s axis of rotation. No misalignment occurred postoperatively. Concentric reduction of the ulnohumeral and radiocapitellar joints was stable over time, with no subluxations or dislocations. The hinged external fixator did not interfere with suture anchors, distal plates, or screw fixation (Fig. 6). No complications, such as recurrent elbow instability, pin track infection or deep infection, pin loosening, or nerve injury, occurred postoperatively. No secondary procedures were necessary. The surgical technique was quick and easy, with a mean time of 22 minutes. The time needed
Autocentering hinged external fixator of elbow
1203 to set in place the humeral and ulnar pins with the rods connected to the central frame took only 18 minutes in the patient affected by a simple dislocation of the elbow (Fig. 7).
Discussion
Figure 6 (A) Intraoperative images of post-traumatic elbow osteoarthritis treated with a fascia lata interposition arthroplasty and collateral ligament reinsertion with bone suture anchors that would prevent the positioning of a traditional external fixator. (B) Clinical control at 45 days postoperatively before external fixator removal and radiographic control at 7-year follow-up.
The most common applications for a hinged external fixator are for an unstable elbow, which can be caused by a simple dislocation or complex fracture-dislocation of the elbow, and after arthrolysis of a stiff elbow. Hinged elbow external fixation allows early postoperative mobilization of the joint, maintaining ligamentous and articular stability.10,19 In a case of fracture-dislocation with acute instability, it permits the injured soft tissues to heal relative to the axis of elbow rotation.11 Moreover, if internal fixation is not sufficient to maintain stability during early motion of the joint, external fixation helps by protecting the open reduction and internal fixation and preventing joint subluxation or dislocation until the soft tissues have healed. In addition, it can help reduce postoperative stiffness, which often follows a period of postoperative immobilization.5 After arthrolysis of a post-traumatic stiff elbow, the external fixator can be applied in distraction.2,21 The device can distract an unstable ulnohumeral joint after excision of heterotopic ossification, capsular release, and ligament reconstruction, with or without interposition arthroplasty.12 In cases of arthrolysis, joint distraction can gradually stretch the contracted capsule and collateral ligaments, allowing stability with maintenance of range of motion.20,21 Several clinical studies have shown favorable outcomes after hinged external fixation of the elbow,7,14 and many of these emphasize the importance of correct hinge placement, accurately aligned with the axis of elbow rotation. Misalignment of the hinge can generate abnormal joint kinematics, incongruous articulation, and elbow instability with increased stress transferred to the pin-bone interface, potentially resulting in pin loosening, pin breakage, or joint subluxation. It can also interfere with the healing of the ligaments, leading to soft tissue imbalance. Several devices are available on the market, and each one has a distinctive feature. The common procedure to correctly align the hinge to the center of elbow rotation is by freehand or navigated insertion of a provisional pin into the distal humerus.6 However, accurate pin positioning is challenging, has a long learning curve, is time-consuming, and increases radiation exposure.3 Multiple drilling attempts may leave a bone tunnel that could potentially affect ligamentous reconstructions or complex distal humerus fracture reduction. Furthermore, implantation of screws, plates, or anchors can impede pin insertion on the distal humerus.5
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P. Bigazzi et al.
Figure 7 (A) Top, Preoperative radiograph in a morbidly obese patient shows a simple posterior dislocation of the left elbow. Bottom, Early postoperative mobilization with the external fixator positioned without performing an arthrotomy. (B) Radiographic and clinical follow-up showed anatomic right elbow alignment and full range of motion regained.
Autocentering hinged external fixator of elbow To address these complications, we have developed a new noninvasive self-centering hinged external fixator that aligns itself with the axis of elbow rotation without the need of a temporary axial pin, which does not interfere with suture anchors, distal plates, or screws (Fig. 6). Ultimately, it can be positioned without performing an invasive procedure or arthrotomy to maintain reduction of the elbow (Fig. 7). Relatively minimal surgical time is needed to position the external fixator, which reduces anesthesia time, lowers patient morbidity, and potentially lowers the risk of infection and radiation exposure.
Conclusion A new hinged elbow external fixator has been designed for autoaligns itself to the elbow’s axis of rotation without the use of an axial pin and minimizes fluoroscopic exposure. This device can also be used in conjunction with distal humerus implants or ligament suture anchors. Its application can be carried out at the end of the reconstruction procedure to protect the reconstruction, and it may be used in a distraction mode.
Disclaimer The authors, their immediate families, and any research foundation with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
References 1. Berendes S, Zilkens C, Anastasiadis A, Graf M, Muhr G, Kalicke T. Additional external hinged fixator after open repositioning and internal fixation of acute elbow instability in non-compliant patients. Orthop Rev (Pavia) 2010;2:e21. http://dx.doi.org/10.4081/or.2010.e21 2. Cheng SL, Morrey BF. Treatment of the mobile, painful arthritic elbow by distraction interposition arthroplasty. J Bone Joint Surg Br 2000;82:233-8. 3. Cheung EV, O’Driscoll SW, Morrey BF. Complications of hinged external fixators of the elbow. J Shoulder Elbow Surg 2008;17:447-53. http://dx.doi.org/10.1016/j.jse.2007.10.006 4. Cobb TK, Morrey BF. Use of distraction arthroplasty in unstable fracture dislocation of the elbow. Clin Orthop Relat Res 1995;312: 201-10.
1205 5. Deuel CR, Wolinsky P, Shepherd E, Hazelwood SJ. The use of hinged external fixation to provide additional stabilization for fractures of the distal humerus. J Orthop Trauma 2007;21:323-9. http://dx.doi.org/10. 1097/BOT.0b013e31804ea479 6. Egidy CC, Fufa D, Kendoff D, Daluiski A. Hinged external fixator placement at the elbow: navigated versus conventional technique. Comput Aided Surg 2012;17:294-9. http://dx.doi.org/10.3109/10929088.2012. 722683 7. Iordens GI, Den Hartog D, Van Lieshout EM, Tuinebreijer WE, De Haan J, Patka P, et al. Good functional recovery of complex elbow dislocations treated with hinged external fixation: a multicenter prospective study. Clin Orthop Relat Res 2015;473:1451-61. http://dx.doi. org/10.1007/s11999-014-3959-1 8. Judet R, Judet T. The use of a hinge distraction apparatus after arthrolysis and arthroplasty. Rev Chir Orthop Reparatrice Appar Mot 1978;64:353-65. 9. Jupiter JB, Ring D. Treatment of unreduced elbow dislocations with hinged external fixation. J Bone Joint Surg Am 2002;84:1630-5. 10. Kamineni S, Hirahara H, Neale P, O’Driscoll SW, An KN, Morrey BF. Effectiveness of the lateral unilateral dynamic external fixator after elbow ligament injury. J Bone Joint Surg Am 2007;89:1802-9. http:// dx.doi.org/10.2106/JBJS.E.00165 11. Kolb W, Guhlmann H, Windisch C, Marx F, Markgraf E, Koller H, et al. Complex osteoligamentary injuries of the elbow. Treatment with a hinged external fixator. Unfallchirurg 2008;111:584-91. http://dx. doi.org/10.1007/s00113-008-1444-6 12. Kulkarni GS, Kulkarni VS, Shyam AK, Kulkarni RM, Kulkarni MG, Nayak P. Management of severe extra-articular contracture of the elbow by open arthrolysis and a monolateral hinged external fixator. J Bone Joint Surg Br 2010;92:92-7. http://dx.doi.org/10.1302/0301-620X.92B1.22241 13. Lee DH. Treatment options for complex elbow fracture dislocations. Injury 2001;32(Suppl. 4):SD41-69. 14. McKee MD, Bowden SH, King GJ, Patterson SD, Jupiter JB, Bamberger HB, et al. Management of recurrent, complex instability of the elbow with a hinged external fixator. J Bone Joint Surg Br 1998;80: 1031-6. 15. Madey SM, Bottlang M, Steyers CM, Marsh JL, Brown TD. Hinged external fixation of the elbow: optimal axis alignment to minimize motion resistance. J Orthop Trauma 2000;14:41-7. 16. Morrey BF, Askew LJ, Chao EY. A biomechanical study of normal functional elbow motion. J Bone Joint Surg Am 1981;63: 872-7. 17. O’Driscoll SW, Jupiter JB, King GJ, Hotchkiss RN, Morrey BF. The unstable elbow. Instr Course Lect 2001;50:89-102. 18. Stavlas P, Jensen SL, Søjbjerg JO. Kinematics of the ligamentous unstable elbow joint after application of a hinged external fixation device: a cadaveric study. J Shoulder Elbow Surg 2007;16:491-6. http://dx.doi.org/10.1016/j.jse.2006.07.012 19. Tan V, Daluiski A, Capo J, Hotchkiss R. Hinged elbow external fixators: indications and uses. J Am Acad Orthop Surg 2005;13:503-14. 20. Volkov MV, Oganesian OV. Restoration of function in the knee and elbow with a hinge-distractor apparatus. J Bone Joint Surg Am 1975; 57:591-600. 21. Wang J, Li H, Zheng Q, Feng G, Li J, Pan Z. Distraction arthrolysis of posttraumatic elbow stiffness with a hinged external fixator. Orthopedics 2012;35:e1625-30. http://dx.doi.org/10.3928/0147744720121023-20 22. Zilkens C, Graf M. Treatment of acute and chronic elbow instability with a hinged external fixator after fracture dislocation. Acta Orthop Belg 2009;75:167-74.
www.elsevier.com/locate/ymse
A new autocentering hinged external fixator of the elbow: a device that stabilizes the elbow axis without use of the articular pin Prospero Bigazzi, MDa,*, Marco Biondi, MDa, Andrea Corvi, MSc Engb, Sandra Pfanner, MDa, Giuseppe Checcucci, MDa, Massimo Ceruso, MDa a b
Department of Hand Surgery and Reconstructive Microsurgery, Azienda Ospedaliero Universitaria Careggi, Florence, Italy Department of Engineering, Universit a degli Studi di Firenze, Florence, Italy Background: Hinged external fixation of the elbow is an important tool for the orthopedic surgeon. It enables early postoperative mobilization that may result in better outcomes. All models require correct alignment with the elbow axis of rotation. There is a long learning curve to this procedure, it may be time-consuming, and it can be associated with a high dose of x-ray exposure. An axial pin can interfere with bone-ligament suture anchors and bone reconstruction plates. Materials and methods: A new external fixator has been designed and mechanically tested. The hinge has a special gear able to freely align itself with the center of elbow rotation during passive flexion-extension movements. It has been clinically tested on 7 patients affected by traumatic and post-traumatic elbow disorders. The maintenance of the correct position has been tested clinically with computed tomography scans and radiographs. Results: All patients had correct alignment of the axis of rotation of the external fixator with the axis of elbow rotation. No cases of misalignment, loss of fixation, pin loosening, or instability were found. Conclusion: A new self-centering hinged external fixator correctly aligns itself with the axis of elbow rotation. It does not interfere with ligamentous reconstruction anchors, distal plates, or screw fixation. The surgical technique is easy to learn and relatively quick. It can also be positioned without performing an arthrotomy to maintain reduction of simple dislocations of the elbow. Level of evidence: Level IV, Case Series, Treatment Study. Ó 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: External fixator of the elbow; elbow instability; elbow collateral ligament injury; elbow trauma; elbow fracture; elbow dislocation
Hinged external fixation of the elbow has been developed8 to maintain congruency and stability of both the humeroulnar and humeroradial joints. In 1975, Volkov and Oganesian were the first authors to report, in an English-language journal, an elbow hinged distraction *Reprint requests: Prospero Bigazzi, MD, Via del Palmerino n 11, I-50137 Florence, Italy. E-mail address: [email protected] (P. Bigazzi).
apparatus designed to eliminate ‘‘excessive friction between the surfaces, prevent abnormal joint kinematics and allow the newly formed joint surfaces to develop correctly.’’20 Hinged external fixation of the elbow allows active and passive range of motion, taking stress off the ligaments and maintaining articular stability. It enables early and secure postoperative rehabilitation that may reduce stiffness and result in a better final range of motion.13,18
1058-2746/$ - see front matter Ó 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. http://dx.doi.org/10.1016/j.jse.2015.05.036
1198
P. Bigazzi et al.
Figure 1 Elbow hinge configurations studied on a 3-dimensional anatomic model created with SolidWorks (Dassault Systemes, VelizyVillacoublay, France) and tested with the physiologic kinematic with visualNastran 4D (MSC Software Corp., Newport Beach, CA, USA).
The clinical indications for elbow external fixation vary from acute instability of ‘‘simple’’ elbow dislocations to complex post-traumatic fracture-dislocations.4,17 It may be used after complex arthrolysis and interposition arthroplasty of a stiff elbow, in which an extensive release of periarticular soft tissues or excision of heterotopic bone may cause instability.22 For a distraction purpose, with or without soft tissue interposition, it neutralizes contact forces across the joint, preventing ligamentous contraction.8 Furthermore, when it is applied in noncompliant patients, it protects ligamentous and bone reconstruction procedures with concentric reduction, allowing early postoperative physical therapy.1 Many devices are available with different features and a common surgical step: the positioning of a temporary pin in the center of elbow rotation. This surgical step is technically demanding,9 as the hinge axis must coincide exactly with the flexion-extension axis of elbow rotation,16 which passes through the center of the arcs formed by the trochlear sulcus and the capitellum. This axis is internally rotated 3 to 8 with regard to the plane of the epicondyles and forms an angle of 82 to 86 with the axis of the humerus. The axis pin should therefore pass parallel to the trochlea on the anteroposterior x-ray view and appear as a dot through the center of the trochlea from the lateral view. Madey et al15 reported that a misalignment of 5 caused a 3.7-fold increase in energy expenditure, whereas a 10 mismatch yielded a 7.1-fold increase. Proper placement often requires multiple drilling attempts and fluoroscopic localization, which can be time-consuming and is associated with a steep surgical learning curve. When an external fixator is first positioned, the hardware can impede ligament reconstruction, making it
Figure 2
The final design of the hinged elbow external fixator.
difficult to use suture anchors. However, the external fixator may also be difficult to apply after ligament reconstruction. In fact, the axial pin should pass exactly through the axis of elbow rotation where the suture anchor or transosseous sutures need to be placed. For these reasons, the application of an external fixator is a crucial step in the surgical treatment of the elbow and must be planned correctly. We present a new external fixator design with a special hinge that autocenters the axis of elbow rotation, avoiding
Demographic data and preoperative status of the patients, indications for hinged external fixator application, and postoperative passive and active arc of motion
Case Sex N
Age Injured side
1
Male
27
2
Male
46
3
Male
30
4
Male
29
5
Male
41
First diagnosis
Former surgical treatment
Time from Preoperative diagnosis injury/ previous treatment
Final surgical treatment with external fixator
Arthrolysis, radial head replacement, LCL reconstruction with triceps fascia, and external dynamic elbow fixation Arthrolysis, LCL 9 months Stiff elbow in Nondominant Terrible triad Elbow reduction, reconstruction an ulnarradial head with palmaris radialreplacement, longus, and humeral bone LCL external dynamic synostosis reconstruction elbow fixation Arthrolysis, radial 55 days Stiff elbow in Dominant Terrible triad Radial head ORIF, head replacement, chronic elbow reduction LCL reconstruction posterior and stabilization with triceps fascia, dislocation with ulnohumeral and external K-wire dynamic elbow fixation Arthrolysis, Dominant Complex distal ORIF 6 months Stiff elbow interposition humeral with humeral arthroplasty fracture articular with fascia lata, cartilage and external reabsorption dynamic elbow fixation Arthrolysis, radial 45 days Stiff elbow in Radial head Non Terrible triad head replacement, chronic resection, dominant and LCL reinsertion posterior proximal row homolateral with anchor, and elbow carpectomy transexternal dynamic dislocation scapholunate elbow fixation wrist dislocation
Dominant
Terrible triad
Elbow reduction and radial head resection
107 days
Stiff elbow in chronic posterior elbow dislocation
Indication for external fixator application
Postoperative active and passive flexionextension arc of motion with external fixator
Postoperative active and passive pronationsupination arc of motion with external fixator
90 ; 110
90 ; 120
LCL reconstruction 100 ; 110 protection and early postoperative rehabilitation
90 ; 110
45 ; 90
95 ; 110
Elbow distraction, 110 ; 130 medial and lateral collateral ligaments protection
175 ; 175
50 ; 90
0 ; 20
Ligamentous reconstruction protection and early postoperative rehabilitation
LCL reconstruction protection and early postoperative rehabilitation
LCL reconstruction protection and early postoperative rehabilitation
1199
(continued on next page)
Autocentering hinged external fixator of elbow
Table I
1200
Table I
(continued )
Case Sex N
Age Injured side
First diagnosis
Former surgical treatment
Time from Preoperative diagnosis injury/ previous treatment
6
Male
75
Dominant
Upper arm subamputation below the elbow and elbow dislocation
None
0
7
Female 67
Dominant
Chronic elbow dislocation in obese patient
None
10 days
Final surgical treatment with external fixator
Upper arm reimplantation, closed elbow reduction, and external dynamic elbow fixation Closed elbow joint Chronic elbow reduction and dislocation in external dynamic obese patient elbow fixation Upper arm subamputation below the elbow and elbow dislocation
Indication for external fixator application
Postoperative active and passive flexionextension arc of motion with external fixator
Postoperative active and passive pronationsupination arc of motion with external fixator
Redislocation prevention in unstable elbow and early postoperative rehabilitation
60 ; 90
80 ; 100
Redislocation prevention in unstable elbow and early postoperative rehabilitation
70 ; 80
170 ; 170
ORIF, open reduction and internal fixation; LCL, lateral collateral ligament.
P. Bigazzi et al.
Autocentering hinged external fixator of elbow
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the use of a provisional axial pin. This device may expand the indications for elbow external fixation.
Materials and methods In collaboration with the Department of Engineering, University of Florence, we developed a new external fixator based on the following parameters: - The device must be equipped with a self-centering system able to align its axis of rotation with the axis of elbow rotation, without an articular pin. - Once centered on the axis, it must be able to lock. - It must be unilateral. - It must be able to work as an articular distractor. - It must allow placement on either arm. To create this device, we first designed a 3-dimensional anatomic elbow model using SolidWorks software (Dassault Systemes, Velizy-Villacoublay, France). Second, we designed many dynamic simulated mechanisms with the Adams/Machinery software (MSC Software Corp., Newport Beach, CA, USA). Through Adams and SolidWorks, we studied and virtually tested several different hinge configurations (Fig. 1) until we arrived at the final autocentering mechanism design (Fig. 2). A model of this design was created in the university’s engineering department. The model was mechanically tested using varusvalgus stress and compression cycle loads for resistance. Between 2008 and 2014, we clinically tested the new external fixator on 7 patients (Table I). Five patients presented with a posttraumatic stiff elbow. Two patients had sustained an acute elbow injury: a subamputation of the proximal third of the forearm with fracture-dislocation of the elbow, and a subacute irreducible simple elbow dislocation observed in a morbidly obese patient. At the time of surgery, the mean age of the 7 patients was 40 years (6 men, 1 woman). Two patients were affected on the dominant arm and 5 on the nondominant arm. The same surgeon performed all the surgeries. The patients were positioned supine under general anesthesia. A brachial plexus block was performed in addition to obtain better control of postoperative pain. Every patient was treated with the application of the hinged external fixator as the final step of the surgery. In 6 cases, this served to protect the ligamentous reconstruction; 1 patient needed additional distraction after an interposition arthroplasty (case 4, Table I). In 1 case, application of the external fixator was the only procedure performed to maintain elbow reduction (case 7, Table I).
Surgical technique The first surgical step in the procedure involves holding the elbow in reduction (with or without arthrotomy) and then placing the hinged external fixator using 4 half-pins with small stab wounds. Two humeral pins are placed from lateral to medial with bicortical purchase and are connected to the fixator humeral rod. One pin should be placed close to the deltoid tuberosity and the other in the lower humeral shaft. Another 2 half-pins are placed anteromedially from the posterolateral aspect of the ulna and connected to the fixator’s ulnar rod. The second step consists of visually aligning the hinge of the external fixator to the axis of the elbow (lateral epicondyle) and securing clamps to the ulnar and
Figure 3 Elbow external fixator set in position at the end of the surgery. The device aligns the elbow axis of rotation during several cyclic flexion-extension movements. Once it is aligned, the central gear is locked, allowing early postoperative mobilization.
Figure 4 Patient during early postoperative mobilization. The hinged external fixator is aligned, the central gear is locked, and the patient can begin rehabilitation. humeral rods. After ensuring that all the connections are secure, the elbow must be anatomically reduced, and by performing several repeated cyclic motions, the central hinge mechanism selfcenters along the axis of elbow rotation (Fig. 3). When the mechanism is centered (about 2-3 cycles), it must be locked to the central gear, maintaining freedom of flexion-extension (Fig. 4). If necessary, distraction can be added after self-centering of the device.
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Figure 5
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Postoperative CT scan shows correct alignment of the axis of rotation of the external fixator with the axis of elbow rotation.
Clinical examination The day after surgery, the patients started a program of active and passive mobilization carried out by an experienced occupational therapist. At night, the patients locked the external fixator, alternating flexion and extension positions. The external fixator was removed after a mean time of 45 days (range, 34-58 days), when the soft tissue healing process was expected to maintain stability. Clinical follow-ups were carried out at 2 weeks, 4 weeks, and 3, 6, and 12 months after surgery. To verify the correct alignment of the axis of rotation of the hinged external fixator, a computed tomography (CT) scan was performed at 2 weeks postoperatively. The aim of the CT scan was to compare the axis of elbow rotation with the axis of rotation of the hinged external fixator (Fig. 5). Radiographs were obtained at 4 weeks postoperatively to monitor elbow reduction.
Results The patients at baseline presented with heterogeneous traumatic and post-traumatic disabilities. For this reason, clinical outcomes were considered only in terms of
surgical complications and range of motion with the device. Clinical outcome measurements and the patient’s satisfaction or pain score were not taken into account. The patients achieved a mean active arc of motion of 75 (range, 45 -110 ) and a mean passive arc of motion of 100 (range, 80 -130 ) in flexion-extension. In pronationsupination, the mean active arc of motion was 100 (range, 0 -175 ), and the mean passive arc of motion was 115 (range, 20 -175 ). The hinged external fixator found and maintained the axis of elbow rotation in every patient. CT scans and radiographic imaging confirmed the correct alignment of the hinged axis of rotation to the elbow’s axis of rotation. No misalignment occurred postoperatively. Concentric reduction of the ulnohumeral and radiocapitellar joints was stable over time, with no subluxations or dislocations. The hinged external fixator did not interfere with suture anchors, distal plates, or screw fixation (Fig. 6). No complications, such as recurrent elbow instability, pin track infection or deep infection, pin loosening, or nerve injury, occurred postoperatively. No secondary procedures were necessary. The surgical technique was quick and easy, with a mean time of 22 minutes. The time needed
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Discussion
Figure 6 (A) Intraoperative images of post-traumatic elbow osteoarthritis treated with a fascia lata interposition arthroplasty and collateral ligament reinsertion with bone suture anchors that would prevent the positioning of a traditional external fixator. (B) Clinical control at 45 days postoperatively before external fixator removal and radiographic control at 7-year follow-up.
The most common applications for a hinged external fixator are for an unstable elbow, which can be caused by a simple dislocation or complex fracture-dislocation of the elbow, and after arthrolysis of a stiff elbow. Hinged elbow external fixation allows early postoperative mobilization of the joint, maintaining ligamentous and articular stability.10,19 In a case of fracture-dislocation with acute instability, it permits the injured soft tissues to heal relative to the axis of elbow rotation.11 Moreover, if internal fixation is not sufficient to maintain stability during early motion of the joint, external fixation helps by protecting the open reduction and internal fixation and preventing joint subluxation or dislocation until the soft tissues have healed. In addition, it can help reduce postoperative stiffness, which often follows a period of postoperative immobilization.5 After arthrolysis of a post-traumatic stiff elbow, the external fixator can be applied in distraction.2,21 The device can distract an unstable ulnohumeral joint after excision of heterotopic ossification, capsular release, and ligament reconstruction, with or without interposition arthroplasty.12 In cases of arthrolysis, joint distraction can gradually stretch the contracted capsule and collateral ligaments, allowing stability with maintenance of range of motion.20,21 Several clinical studies have shown favorable outcomes after hinged external fixation of the elbow,7,14 and many of these emphasize the importance of correct hinge placement, accurately aligned with the axis of elbow rotation. Misalignment of the hinge can generate abnormal joint kinematics, incongruous articulation, and elbow instability with increased stress transferred to the pin-bone interface, potentially resulting in pin loosening, pin breakage, or joint subluxation. It can also interfere with the healing of the ligaments, leading to soft tissue imbalance. Several devices are available on the market, and each one has a distinctive feature. The common procedure to correctly align the hinge to the center of elbow rotation is by freehand or navigated insertion of a provisional pin into the distal humerus.6 However, accurate pin positioning is challenging, has a long learning curve, is time-consuming, and increases radiation exposure.3 Multiple drilling attempts may leave a bone tunnel that could potentially affect ligamentous reconstructions or complex distal humerus fracture reduction. Furthermore, implantation of screws, plates, or anchors can impede pin insertion on the distal humerus.5
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Figure 7 (A) Top, Preoperative radiograph in a morbidly obese patient shows a simple posterior dislocation of the left elbow. Bottom, Early postoperative mobilization with the external fixator positioned without performing an arthrotomy. (B) Radiographic and clinical follow-up showed anatomic right elbow alignment and full range of motion regained.
Autocentering hinged external fixator of elbow To address these complications, we have developed a new noninvasive self-centering hinged external fixator that aligns itself with the axis of elbow rotation without the need of a temporary axial pin, which does not interfere with suture anchors, distal plates, or screws (Fig. 6). Ultimately, it can be positioned without performing an invasive procedure or arthrotomy to maintain reduction of the elbow (Fig. 7). Relatively minimal surgical time is needed to position the external fixator, which reduces anesthesia time, lowers patient morbidity, and potentially lowers the risk of infection and radiation exposure.
Conclusion A new hinged elbow external fixator has been designed for autoaligns itself to the elbow’s axis of rotation without the use of an axial pin and minimizes fluoroscopic exposure. This device can also be used in conjunction with distal humerus implants or ligament suture anchors. Its application can be carried out at the end of the reconstruction procedure to protect the reconstruction, and it may be used in a distraction mode.
Disclaimer The authors, their immediate families, and any research foundation with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
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