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Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study
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Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study ✩ Philip B. Kaiser, MD a,∗, Matthew D. Riedel, MD a, Rameez Qudsi, MD a, Ian T. Watkins, BS b, Mohammad Ghorbanhoseini, MD b, Ara Nazarian, PhD b, John Y. Kwon, MD b a b
Harvard Combined Orthopaedic Surgery Residency Program, Boston, MA, USA Beth Israel Deaconess Medical Center, Boston, MA, USA
a r t i c l e
i n f o
Article history: Accepted 3 October 2019 Available online xxx Keywords: Syndesmotic fixation Suture button Saphenous neurovascular bundle Posterior tibialis tendon
a b s t r a c t Background: Surgical fixation of syndesmotic instability using quadricortical fixation, whether screws or suture-button devices, places structures on the medial side of the tibia at iatrogenic risk. This study aims to radiographically map the anatomic course of structures on the medial aspect of the distal tibia to be able to at-risk zones (ARZs) for syndesmotic fixation. Methods: Eighteen fresh-frozen cadaveric ankle specimens were dissected. The saphenous neurovascular bundle (SNVB) and the posterior tibial tendon (PTT) were identified and marked with copper wiring. Standardized and calibrated lateral radiographs of the distal tibia and fibula were analyzed using a grid system consisting of 3 columnar zones from anterior to posterior and five 1-cm rows to chart the anatomic course of the SNVB and the PTT. Results: The SNVB was located in the more anterior zones (1, 2, or anterior to Zone 1) in 97.3% of specimens. The SNVB traversed from posterior to anterior as it descended proximal to distal. The PTT was found in Zone 3 (most posterior zone) for all specimens. The PTT was noted to pass behind (radiographically overlap) the tibia in 83.3% (15 of 18) of specimens between 1 and 3 cm above the tibiotalar joint. Conclusions: Placement of quadricortical syndesmotic fixation places structures on the medial ankle at risk. The SNVB is at considerable risk along the anterior course of the distal tibial while the PTT is only at risk in zone 3 at the distal extent of the tibia. © 2019 Published by Elsevier Ltd.
Introduction Ankle fractures with syndesmotic instability and isolated cases of syndesmotic injury require stabilization to maximize clinical outcomes and maintain mortise congruency. The benefits of tricortical versus quadricortical fixation are debated in the literature without clear consensus [2,5,7,16]. There is evidence to suggest quadricortical fixation with one or multiple screws is more rigid which may be beneficial in over-weight and diabetic patients with syndesmotic injury [16]. Additionally, syndesmotic suture buttons require quadricortical drilling and securing of a suture button on the medial side of the tibia. Both devices require unprotected ✩
Research performed at BIDMC, Harvard Medical School, Boston, MA. Correspondence to: Massachusetts General Hospital, Department of Orthopaedic Surgery, Harvard Orthopaedics Residency Program, 55 Fruit Street, Boston, MA 02114, USA. E-mail addresses: [email protected] (P.B. Kaiser), [email protected] (M.D. Riedel), [email protected] (J.Y. Kwon). ∗
drilling of the medial tibial and placement of hardware near important neurovascular and tendinous structures. Although prior studies have shown the potential for injury to the SNVB and PTT when placing quadricortical syndesmotic fixation, the rates of iatrogenic injury to medial structures during syndesmotic fixation remains unknown [10,19]. Furthermore, previous studies have demonstrated that removing hardware in cases of healed ankle fractures results in pain relief in only about half of patients which may indicate that a different source of pain, potentially iatrogenic injury to local tendinous or neurovascular structures, may be the etiology [1,10]. While prior studies have analyzed safe zones for medial malleolar screws with regards to PTT tendon abutment and irritation, there is a paucity of research analyzing the course of the SNVB and the PTT with respect to the risk of iatrogenic injury when placing quadricortical syndesmotic fixation [3]. The purpose of this study was to radiographically map the anatomic course of the SNVB and PTT on a lateral radiograph to be
https://doi.org/10.1016/j.injury.2019.10.009 0020-1383/© 2019 Published by Elsevier Ltd.
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
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[m5G;November 8, 2019;8:45]
P.B. Kaiser, M.D. Riedel and R. Qudsi et al. / Injury xxx (xxxx) xxx
Fig. 1. Cannulation of the saphenous vein and anterior aspect of the posterior tibial tendon with small gauge copper wire.
able to define at-risk zones (ARZs) for quadricortical syndesmotic fixation. Materials and methods Eighteen thawed fresh-frozen transtibial cadaver specimens, with an average age of 54 years, were utilized for this study. Cadaver preparation and dissection was overseen by an experienced, fellowship-trained, orthopaedic foot and ankle surgeon. The skin was carefully removed from the medial tibia starting 10 cm proximal to the plafond. The SNVB along with its communicating branches were identified [13]. The SNVB was isolated as it was the most posterior of any anterior ankle anatomic structure at risk. The PTT was identified at the posteromedial aspect of the tibia and dissected distally until it passed under the colliculi. The PTT was isolated as it was the most anterior of any postero-medial anatomic structure at risk. All fascial and tendinous sheath attachments were preserved as to not distort the normal anatomy. Furthermore, no anatomic structure could be translated in space as only their respective medial aspects had been exposed. Once the medial structures were exposed, the saphenous vein, which lies anatomically in the middle of the SNVB, was cannulated with a small gauge copper wire. Similarly, the most anterior aspect of the PTT was threaded with copper wire, within its sheath when possible (Fig. 1). The most anterior aspect of the PTT was chosen since this would represent the border of the tendon to avoid when inserting syndesmotic fixation under lateral fluoroscopy. Next a calibrated 6 cm wire was constructed to be used in all radiographic images to be used to calibrate measurements (Fig. 2). The eighteen specimens, each with anatomic wires overlying the SNVB and the PTT along with the calibration wire, were imaged using a c-arm. Ankle specimens were held in neutral ankle dorsiflexion and the lateral ankle was placed on the image inten-
Fig. 2. A calibrated 6 cm wire was used in all radiographic images to calculate measurements.
sifier centered at the medial malleolus. Specimens were adjusted to obtain a perfect lateral ankle radiographs based on superimposition of the medial and lateral talar domes which usually corresponded with superimposition of the posterior distal tibia and posterior distal fibula [6]. Radiographs were analyzed using a grid system comprised of 1 cm row-increments moving cranially from the tibiotalar joint up to 5 cm and by three evenly distributed parallel columnar zones from anterior to posterior (Fig. 3). The anterior boundary of the columnar zone was placed at the anterior tibial shaft and the posterior boundary was placed at the posterior malleolus of the tibia. The position of respective metal wires placed within the SNVB and the PTT were charted according to this grid system and results compiled. The SNVB and PTT were counted twice in a row if it crossed over a columnar zone, once in each respective column in the same row. Results The SNVB was located in zone 1 or 2 (or anterior to Zone 1) in 97.3% of specimens (107 of 110 grid data points - Fig. 4). The SNVB traversed from proximal-posterior to distal-anterior. For the 16 specimens in which the SNVB crossed a columnar zone, the most common crossover was from zone 2 to zone 1 at 3–4 cm above the tibiotalar joint which occurred in 43.8% of specimens (7 of 16). Additionally, the SNVB was located anterior to zone 1 in 3 specimens at 1–2 cm above the tibiotalar joint and in 5 specimens 0–1 cm above the tibiotalar joint, which is reflected in the percentage values listed in those rows (Fig. 4).
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
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Fig. 3. A grid system comprised of 1 cm row-increments moving cranially from the tibiotalar joint up to 5 cm was divided by three evenly distributed parallel columnar zones from anterior to posterior.
3
Fig. 5. Data points demonstrating where posterior tibial tendon was located within the grid. The location was counted twice in a row if the tendon crossed over a columnar zone, once in each respective column in the same row.
The PTT was found in zone 3 in all specimens (18) with only one specimen demonstrating crossover of a columnar zone into zone 2 at its most distal extent (0–1 cm) (Fig. 5). The PTT was noted to pass behind (radiographically overlap) with the tibia in 83.3% (15 of 18) of specimens between 1 and 3 cm above the tibiotalar joint. The anterior tibialis tendon and posterior tibial neurovascular bundle were exposed in similar fashion but when checked radiographically consistently fell outside the grid system and hence were not included in the compiled analysis due to negligible risk during quadricortical syndesmotic fixation (Fig. 6). Discussion
Fig. 4. Data points demonstrating where saphenous vein was located with the grid. The location was counted twice in a row if the saphenous vein crossed over a columnar zone, once in each respective column in the same row.
The most common anatomic structures of the medial ankle at risk with quadricortical syndesmotic fixation are the SNVB and PTT. Our study found that the SNVB is at risk along the anterior course of the distal tibial in zones 1 and 2 (or anterior to Zone 1) in 97.3% of specimens as it traverses from proximal-posterior to distal-anterior. The PTT was found in zone 3 in all specimens and radiographically overlaps with the tibia on a true lateral radiograph of the ankle between 1 and 3 cm above the tibiotalar joint in 83.3% (15 of 18) of specimens. The anterior tibialis tendon and posterior tibial neurovascular bundle fell outside the grid system and hence should only be injured by errant drilling or misplaced syndesmotic fixation, especially when utilizing the proposed zone system to guide quadricortical syndesmotic fixation. The SNVB consists of a single vein and adjacent nerve that branches approximately 3 cm proximal to the tibiotalar joint and courses anteromedially along the distal tibia [13]. In a study by Pirozzi et al., suture buttons were placed in 20 cadaver specimens in standard fashion 2 cm proximal to the tibiotalar joint and angled 30° anterior in the coronal plane [19]. There was entrapment
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
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Fig. 6. The anterior tibialis tendon and posterior tibial neurovascular bundle fell outside the grid system on a lateral ankle radiograph.
of at least a portion of the SNVB in 55.0% of specimens and the average distance of the suture button to the SNVB was 4.9 mm. The results of the current investigation corroborate their findings that the SNVB is at considerable risk during quadricortical syndesmotic fixation. Damage to the SNVB may result in sensory deficits, the development of painful saphenous neuromas as well as thrombosis and/or thrombophlebitis [19]. Particularly with suture button fixation, surgeons may consider a small medial incision to assure the SNVB is not entrapped and the button is positioned flush against the medial tibial cortex. The PTT is at risk along the posteromedial distal tibia before coursing between the superficial and deep deltoid ligaments under the medial malleolar colliculi. Additionally, this region of the PTT has been recognized as an area of relative hypovascularity potentially affecting natural healing capacity if iatrogenically injured during syndesmotic fixation [11]. While a case report described a posterior tibial tendon tear from errant quadricortical syndesmotic screw necessitating removal of hardware and repair of the tendon, the incidence of iatrogenic injury to the PTT is unknown [10]. This may be an under-recognized problem especially in cases where screws are placed too posteriorly and/or when fixation enters the posterior medial blind spot of the distal tibia as described by Wusu, et al. [10,22] This triangularly-shaped area results from the contour of the distal posterior medial tibia and measures approximately 5 mm wide with sides measuring approximately 12 mm x 12 mm. Protuberant screws in this area correspond to Zone 3 at 0–2 cm above the tibiotalar joint in our model. Because the PTT was consistently found in this zone in all 18 specimens examined, careful hardware placement is necessary and the use of a 45° external rotation oblique view may be helpful to iden-
tify potentially prominent screw fixation not well visualized on standard AP, mortise, and lateral radiographs in this area. The current investigation demonstrates that placement of quadricortical fixation in the more anterior zones (1 and 2) may help mitigate risk to the PTT. In the present study, the region from tibiotalar joint extending 5 cm cephalad was investigated as this encompasses the most common area for syndesmotic fixation. A biomechanical study by McBryde, et al. demonstrated less syndesmotic widening with a screw placed 2 cm proximal to the tibiotalar joint as compared to a screw placed at 3.5 cm. [12] However, a subsequent study by Kukreti, et al. demonstrated no difference in clinical outcomes between a syndesmotic screw placed 2 cm proximal to the tibiotalar joint compared to 3–5 cm above the joint [9]. Despite uncommon use of fixation close to the plafond, we included the results for the area 0–2 cm proximal to the tibiotalar joint as it helped to define the trajectory of the SNVB and the PTT. With regards to the SNVB and the most common placement of syndesmotic fixation, proximally at 4–5 cm above the tibiotalar joint it was found in zone 2 or 3 in 85% of specimens (17 of 20 grid data points), where as distally, 2–3 cm above the tibiotalar joint, it was found in Zone 1 in 63.6% of specimens (14 of 22 grid data points), reflecting its relative proximal-posterior to distal-anterior course. The PTT course was less variable and was found in zone 3 in all specimens, radiographically overlapping with the tibia in 83.3% (15 of 18) of specimens between 1 and 3 cm above the tibiotalar joint. Whether quadricortical screw fixation is even necessary is debated in the literature and has been compared to tricortical fixation in syndesmotic injuries. Wikerøy et al. compared syndesmotic fixation using a single quadricortical screw to two tricortical screws and found no difference in overall functional or osteoarthritis over a 8 year follow up period [21]. Notably, subgroup analysis demonstrated poorer overall result in obese patients, those with a posterior malleolus fracture, or in fractures with a syndesmotic width equal to or greater than 1.5 mm independent of the number of cortices used in fixation. Other studies have corroborated these findings demonstrating similar clinical outcomes when comparing tricortical to quadricortical screws for syndesmotic fixation [7,8,15]. Despite this, quadricortical syndesmotic fixation is commonly utilized in practice today. Furthermore, most syndesmotic suture button devices require drilling through the medial tibial cortex. While tricortical screw placement eliminates iatrogenic risk to medial structures, broken screw removal can be much more problematic then when a quadricortical screw is used. There are several limitations of this study. While this study focused on anatomic structures found on the medial aspect of the ankle, the anterior neurovascular bundle and peroneal vessels may be at risk at the anterior distal tibia and in the interval between the tibia and fibula respectively. Also, precise utilization of the grid system in the operating room may be challenging and consistent use of this system has not been studied. Clinically, in our own practice, we have applied these findings intra-operatively to assure a perfect lateral radiograph is obtained to avoid placement of syndesmotic fixation into zone 3 which may abut or injure the PTT. Furthermore, in conjunction with a goal of syndesmotic reduction and hardware placement along the trans-syndesmotic axis (TSA) to avoid fibular malreduction, the likely optimal position for quadricortical syndesmotic hardware is approximately at the junction of zone 1 and zone 2. [4,14,17,18,20] We do not routinely obtain a post-operative CT after ankle syndesmotic fixation to evaluate hardware placement or syndesmotic reduction. Unfortunately, there is not a completely ‘safe zone’ that avoids the SNVB and surgeons should consider a small medial incision when placing suture button syndesmotic fixation. Despite this, we feel that understanding of the ARZs on an intraoperative lateral radiograph helps to guide the placement of quadricortical syndesmotic fixation.
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
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Conclusions Drilling, protuberant screws, passing of a large-bore needle and potential entrapping fixation (suture buttons) can cause iatrogenic injury that may delay recovery and/or lead to worse clinical outcomes. Placement of quadricortical syndesmotic fixation places structures on the medial ankle at risk. The SNVB is at considerable risk along the anterior course of the distal tibial in zones 1 and 2 while the PTT is only at risk in zone 3 at the distal extent of the tibia. Despite the mutually exclusive AZRs of the SNVB and PTT, the grid system elucidates which structure may be more at risk during placement of quadricortical syndesmotic fixation. Declaration of Competing Interest The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding The author(s) received no financial support for the research, authorship, and/or publication of this article. References [1] Brown OL, Dirschl DR, Obremskey WT. Incidence of hardware-related pain and its effect on functional outcomes after open reduction and internal fixation of ankle fractures. J Orthop Trauma 2001;15(4):271–4. [2] Chapter 57 Davidovitch R, Egol K. Rockwood and green’s fractures in adults. Ankle fractures. Tornetta P, rockwood CA, Bucholz RW, Court-Brown CM, Heckman JD, editors. Chapter 57 Lippincott Williams & Wilkins; 2010. [3] DeMill SL, Bussewitz BW, Philbin TM. Injury to the posterior tibial tendon after open reduction internal fixation of the medial malleolus. Foot Ankle Spec 2015;8(5):360–3. doi:10.1177/107110 07920130 0204. [4] Gardner MJ, Demetrakopoulos D, Briggs SM, Helfet DL, Lorich DG. Malreduction of the tibiofibular syndesmosis in ankle fractures. Foot Ankle Int 2006;27(10):788–92. doi:10.1177/107110070602701005. [5] Heim D, Heim U, Regazzoni P. Malleolar fractures with ankle joint instability – experience with the positioning screw. Unfallchirurgie 1993;19(5):307–12. [6] Helms CA. Fundamentals of skeletal radiology. Elsevier Health Sciences; 2013.
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[7] Høiness P, Strømsøe K. Tricortical versus quadricortical syndesmosis fixation in ankle fractures: a prospective, randomized study comparing two methods of syndesmosis fixation. J Orthop Trauma 2004;18(6):331–7. [8] Karapinar H, Kalenderer O, Karapinar L, Altay T, Manisali M, Gunal I. Effects of three- or four-cortex syndesmotic fixation in ankle fractures. J Am Podiatr Med Assoc 2007;97(6):457–9. [9] Kukreti S, Faraj A, Miles JNV. Does position of syndesmotic screw affect functional and radiological outcome in ankle fractures? Injury 2005;36(9):1121–4. doi:10.1016/j.injury.2005.01.014. [10] Kwon JY, Campbell JT, Myerson MS. Posterior tibial tendon tear after 4-cortex syndesmotic screw fixation: a case report and literature review. J Orthop 2012(April):1–4. [11] Manske MC, McKeon KE, Johnson JE, McCormick JJ, Klein SE. Arterial anatomy of the tibialis posterior tendon. Foot Ankle Int 2014;36(4):436–43. doi:10.2106/ JBJS.L.00258. [12] McBryde A, Chiasson B, Wilhelm A, Donovan F, Ray T, Bacilla P. Syndesmotic screw placement: a biomechanical analysis. Foot Ankle Int 1997;18(5):262–6. doi:10.1177/107110 07970180 0503. [13] Mercer D, Morrell NT, Fitzpatrick J, et al. The course of the distal saphenous nerve: a cadaveric investigation and clinical implications. Iowa Orthop J 2011;31:231–5. [14] Miller AN, Barei DP, Iaquinto JM, Ledoux WR, Beingessner DM. Iatrogenic syndesmosis malreduction via clamp and screw placement. J Orthop Trauma 2013;27(2):100–6. doi:10.1097/BOT.0b013e31825197cb. [15] Moore JA, Shank JR, Morgan SJ, Smith WR. Syndesmosis fixation: a comparison of three and four cortices of screw fixation without hardware removal. Foot Ankle Int 2006;27(8):567–72. doi:10.1177/107110070602700801. [16] Needleman RL, Skrade DA, Stiehl JB. Effect of the syndesmotic screw on ankle motion. Foot Ankle 1989;10(1):17–24. doi:10.1177/107110078901000104. [17] Nimick CJ, Collman DR, Lagaay P. Fixation orientation in ankle fractures with syndesmosis injury. J Foot Ankle Surg 2013;52(3):315–18. doi:10.1053/j.jfas. 2013.02.005. [18] Phisitkul P, Ebinger T, Goetz J, Vaseenon T, Marsh JL. Forceps reduction of the syndesmosis in rotational ankle fractures: a cadaveric study. J Bone Jt Surg Am 2012;94(24):2256–61. doi:10.2106/JBJS.K.01726. [19] Pirozzi KM, Creech CL, Meyr AJ. Assessment of anatomic risk during syndesmotic stabilization with the suture button technique. J Foot Ankle Surg 2015;54(5):917–19. doi:10.1053/j.jfas.2015.04.005. [20] Putnam SM, Linn MS, Spraggs-Hughes A, McAndrew CM, Ricci WM, Gardner MJ. Simulating clamp placement across the trans-syndesmotic angle of the ankle to minimize malreduction: a radiological study. Injury 2017;48(3):770–5. doi:10.1016/j.injury.2017.01.029. [21] Wikerøy AKB, Høiness PR, Andreassen GS, Hellund JC, Madsen JE. No difference in functional and radiographic results 8.4 years after quadricortical compared with tricortical syndesmosis fixation in ankle fractures. J Orthop Trauma 2010;24(1):17–23. doi:10.1097/BOT.0b013e3181bedca1. [22] Wusu TO, Toussaint RJ, Ellington JK, Kwon JY. The posterior medial blind spot of the distal tibia. Foot Ankle Spec 2014;8(1):46–9. doi:10.1177/ 1938640014565051.
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
JID: JINJ
[m5G;November 8, 2019;8:45]
Injury xxx (xxxx) xxx
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study ✩ Philip B. Kaiser, MD a,∗, Matthew D. Riedel, MD a, Rameez Qudsi, MD a, Ian T. Watkins, BS b, Mohammad Ghorbanhoseini, MD b, Ara Nazarian, PhD b, John Y. Kwon, MD b a b
Harvard Combined Orthopaedic Surgery Residency Program, Boston, MA, USA Beth Israel Deaconess Medical Center, Boston, MA, USA
a r t i c l e
i n f o
Article history: Accepted 3 October 2019 Available online xxx Keywords: Syndesmotic fixation Suture button Saphenous neurovascular bundle Posterior tibialis tendon
a b s t r a c t Background: Surgical fixation of syndesmotic instability using quadricortical fixation, whether screws or suture-button devices, places structures on the medial side of the tibia at iatrogenic risk. This study aims to radiographically map the anatomic course of structures on the medial aspect of the distal tibia to be able to at-risk zones (ARZs) for syndesmotic fixation. Methods: Eighteen fresh-frozen cadaveric ankle specimens were dissected. The saphenous neurovascular bundle (SNVB) and the posterior tibial tendon (PTT) were identified and marked with copper wiring. Standardized and calibrated lateral radiographs of the distal tibia and fibula were analyzed using a grid system consisting of 3 columnar zones from anterior to posterior and five 1-cm rows to chart the anatomic course of the SNVB and the PTT. Results: The SNVB was located in the more anterior zones (1, 2, or anterior to Zone 1) in 97.3% of specimens. The SNVB traversed from posterior to anterior as it descended proximal to distal. The PTT was found in Zone 3 (most posterior zone) for all specimens. The PTT was noted to pass behind (radiographically overlap) the tibia in 83.3% (15 of 18) of specimens between 1 and 3 cm above the tibiotalar joint. Conclusions: Placement of quadricortical syndesmotic fixation places structures on the medial ankle at risk. The SNVB is at considerable risk along the anterior course of the distal tibial while the PTT is only at risk in zone 3 at the distal extent of the tibia. © 2019 Published by Elsevier Ltd.
Introduction Ankle fractures with syndesmotic instability and isolated cases of syndesmotic injury require stabilization to maximize clinical outcomes and maintain mortise congruency. The benefits of tricortical versus quadricortical fixation are debated in the literature without clear consensus [2,5,7,16]. There is evidence to suggest quadricortical fixation with one or multiple screws is more rigid which may be beneficial in over-weight and diabetic patients with syndesmotic injury [16]. Additionally, syndesmotic suture buttons require quadricortical drilling and securing of a suture button on the medial side of the tibia. Both devices require unprotected ✩
Research performed at BIDMC, Harvard Medical School, Boston, MA. Correspondence to: Massachusetts General Hospital, Department of Orthopaedic Surgery, Harvard Orthopaedics Residency Program, 55 Fruit Street, Boston, MA 02114, USA. E-mail addresses: [email protected] (P.B. Kaiser), [email protected] (M.D. Riedel), [email protected] (J.Y. Kwon). ∗
drilling of the medial tibial and placement of hardware near important neurovascular and tendinous structures. Although prior studies have shown the potential for injury to the SNVB and PTT when placing quadricortical syndesmotic fixation, the rates of iatrogenic injury to medial structures during syndesmotic fixation remains unknown [10,19]. Furthermore, previous studies have demonstrated that removing hardware in cases of healed ankle fractures results in pain relief in only about half of patients which may indicate that a different source of pain, potentially iatrogenic injury to local tendinous or neurovascular structures, may be the etiology [1,10]. While prior studies have analyzed safe zones for medial malleolar screws with regards to PTT tendon abutment and irritation, there is a paucity of research analyzing the course of the SNVB and the PTT with respect to the risk of iatrogenic injury when placing quadricortical syndesmotic fixation [3]. The purpose of this study was to radiographically map the anatomic course of the SNVB and PTT on a lateral radiograph to be
https://doi.org/10.1016/j.injury.2019.10.009 0020-1383/© 2019 Published by Elsevier Ltd.
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
JID: JINJ 2
ARTICLE IN PRESS
[m5G;November 8, 2019;8:45]
P.B. Kaiser, M.D. Riedel and R. Qudsi et al. / Injury xxx (xxxx) xxx
Fig. 1. Cannulation of the saphenous vein and anterior aspect of the posterior tibial tendon with small gauge copper wire.
able to define at-risk zones (ARZs) for quadricortical syndesmotic fixation. Materials and methods Eighteen thawed fresh-frozen transtibial cadaver specimens, with an average age of 54 years, were utilized for this study. Cadaver preparation and dissection was overseen by an experienced, fellowship-trained, orthopaedic foot and ankle surgeon. The skin was carefully removed from the medial tibia starting 10 cm proximal to the plafond. The SNVB along with its communicating branches were identified [13]. The SNVB was isolated as it was the most posterior of any anterior ankle anatomic structure at risk. The PTT was identified at the posteromedial aspect of the tibia and dissected distally until it passed under the colliculi. The PTT was isolated as it was the most anterior of any postero-medial anatomic structure at risk. All fascial and tendinous sheath attachments were preserved as to not distort the normal anatomy. Furthermore, no anatomic structure could be translated in space as only their respective medial aspects had been exposed. Once the medial structures were exposed, the saphenous vein, which lies anatomically in the middle of the SNVB, was cannulated with a small gauge copper wire. Similarly, the most anterior aspect of the PTT was threaded with copper wire, within its sheath when possible (Fig. 1). The most anterior aspect of the PTT was chosen since this would represent the border of the tendon to avoid when inserting syndesmotic fixation under lateral fluoroscopy. Next a calibrated 6 cm wire was constructed to be used in all radiographic images to be used to calibrate measurements (Fig. 2). The eighteen specimens, each with anatomic wires overlying the SNVB and the PTT along with the calibration wire, were imaged using a c-arm. Ankle specimens were held in neutral ankle dorsiflexion and the lateral ankle was placed on the image inten-
Fig. 2. A calibrated 6 cm wire was used in all radiographic images to calculate measurements.
sifier centered at the medial malleolus. Specimens were adjusted to obtain a perfect lateral ankle radiographs based on superimposition of the medial and lateral talar domes which usually corresponded with superimposition of the posterior distal tibia and posterior distal fibula [6]. Radiographs were analyzed using a grid system comprised of 1 cm row-increments moving cranially from the tibiotalar joint up to 5 cm and by three evenly distributed parallel columnar zones from anterior to posterior (Fig. 3). The anterior boundary of the columnar zone was placed at the anterior tibial shaft and the posterior boundary was placed at the posterior malleolus of the tibia. The position of respective metal wires placed within the SNVB and the PTT were charted according to this grid system and results compiled. The SNVB and PTT were counted twice in a row if it crossed over a columnar zone, once in each respective column in the same row. Results The SNVB was located in zone 1 or 2 (or anterior to Zone 1) in 97.3% of specimens (107 of 110 grid data points - Fig. 4). The SNVB traversed from proximal-posterior to distal-anterior. For the 16 specimens in which the SNVB crossed a columnar zone, the most common crossover was from zone 2 to zone 1 at 3–4 cm above the tibiotalar joint which occurred in 43.8% of specimens (7 of 16). Additionally, the SNVB was located anterior to zone 1 in 3 specimens at 1–2 cm above the tibiotalar joint and in 5 specimens 0–1 cm above the tibiotalar joint, which is reflected in the percentage values listed in those rows (Fig. 4).
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
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Fig. 3. A grid system comprised of 1 cm row-increments moving cranially from the tibiotalar joint up to 5 cm was divided by three evenly distributed parallel columnar zones from anterior to posterior.
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Fig. 5. Data points demonstrating where posterior tibial tendon was located within the grid. The location was counted twice in a row if the tendon crossed over a columnar zone, once in each respective column in the same row.
The PTT was found in zone 3 in all specimens (18) with only one specimen demonstrating crossover of a columnar zone into zone 2 at its most distal extent (0–1 cm) (Fig. 5). The PTT was noted to pass behind (radiographically overlap) with the tibia in 83.3% (15 of 18) of specimens between 1 and 3 cm above the tibiotalar joint. The anterior tibialis tendon and posterior tibial neurovascular bundle were exposed in similar fashion but when checked radiographically consistently fell outside the grid system and hence were not included in the compiled analysis due to negligible risk during quadricortical syndesmotic fixation (Fig. 6). Discussion
Fig. 4. Data points demonstrating where saphenous vein was located with the grid. The location was counted twice in a row if the saphenous vein crossed over a columnar zone, once in each respective column in the same row.
The most common anatomic structures of the medial ankle at risk with quadricortical syndesmotic fixation are the SNVB and PTT. Our study found that the SNVB is at risk along the anterior course of the distal tibial in zones 1 and 2 (or anterior to Zone 1) in 97.3% of specimens as it traverses from proximal-posterior to distal-anterior. The PTT was found in zone 3 in all specimens and radiographically overlaps with the tibia on a true lateral radiograph of the ankle between 1 and 3 cm above the tibiotalar joint in 83.3% (15 of 18) of specimens. The anterior tibialis tendon and posterior tibial neurovascular bundle fell outside the grid system and hence should only be injured by errant drilling or misplaced syndesmotic fixation, especially when utilizing the proposed zone system to guide quadricortical syndesmotic fixation. The SNVB consists of a single vein and adjacent nerve that branches approximately 3 cm proximal to the tibiotalar joint and courses anteromedially along the distal tibia [13]. In a study by Pirozzi et al., suture buttons were placed in 20 cadaver specimens in standard fashion 2 cm proximal to the tibiotalar joint and angled 30° anterior in the coronal plane [19]. There was entrapment
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
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Fig. 6. The anterior tibialis tendon and posterior tibial neurovascular bundle fell outside the grid system on a lateral ankle radiograph.
of at least a portion of the SNVB in 55.0% of specimens and the average distance of the suture button to the SNVB was 4.9 mm. The results of the current investigation corroborate their findings that the SNVB is at considerable risk during quadricortical syndesmotic fixation. Damage to the SNVB may result in sensory deficits, the development of painful saphenous neuromas as well as thrombosis and/or thrombophlebitis [19]. Particularly with suture button fixation, surgeons may consider a small medial incision to assure the SNVB is not entrapped and the button is positioned flush against the medial tibial cortex. The PTT is at risk along the posteromedial distal tibia before coursing between the superficial and deep deltoid ligaments under the medial malleolar colliculi. Additionally, this region of the PTT has been recognized as an area of relative hypovascularity potentially affecting natural healing capacity if iatrogenically injured during syndesmotic fixation [11]. While a case report described a posterior tibial tendon tear from errant quadricortical syndesmotic screw necessitating removal of hardware and repair of the tendon, the incidence of iatrogenic injury to the PTT is unknown [10]. This may be an under-recognized problem especially in cases where screws are placed too posteriorly and/or when fixation enters the posterior medial blind spot of the distal tibia as described by Wusu, et al. [10,22] This triangularly-shaped area results from the contour of the distal posterior medial tibia and measures approximately 5 mm wide with sides measuring approximately 12 mm x 12 mm. Protuberant screws in this area correspond to Zone 3 at 0–2 cm above the tibiotalar joint in our model. Because the PTT was consistently found in this zone in all 18 specimens examined, careful hardware placement is necessary and the use of a 45° external rotation oblique view may be helpful to iden-
tify potentially prominent screw fixation not well visualized on standard AP, mortise, and lateral radiographs in this area. The current investigation demonstrates that placement of quadricortical fixation in the more anterior zones (1 and 2) may help mitigate risk to the PTT. In the present study, the region from tibiotalar joint extending 5 cm cephalad was investigated as this encompasses the most common area for syndesmotic fixation. A biomechanical study by McBryde, et al. demonstrated less syndesmotic widening with a screw placed 2 cm proximal to the tibiotalar joint as compared to a screw placed at 3.5 cm. [12] However, a subsequent study by Kukreti, et al. demonstrated no difference in clinical outcomes between a syndesmotic screw placed 2 cm proximal to the tibiotalar joint compared to 3–5 cm above the joint [9]. Despite uncommon use of fixation close to the plafond, we included the results for the area 0–2 cm proximal to the tibiotalar joint as it helped to define the trajectory of the SNVB and the PTT. With regards to the SNVB and the most common placement of syndesmotic fixation, proximally at 4–5 cm above the tibiotalar joint it was found in zone 2 or 3 in 85% of specimens (17 of 20 grid data points), where as distally, 2–3 cm above the tibiotalar joint, it was found in Zone 1 in 63.6% of specimens (14 of 22 grid data points), reflecting its relative proximal-posterior to distal-anterior course. The PTT course was less variable and was found in zone 3 in all specimens, radiographically overlapping with the tibia in 83.3% (15 of 18) of specimens between 1 and 3 cm above the tibiotalar joint. Whether quadricortical screw fixation is even necessary is debated in the literature and has been compared to tricortical fixation in syndesmotic injuries. Wikerøy et al. compared syndesmotic fixation using a single quadricortical screw to two tricortical screws and found no difference in overall functional or osteoarthritis over a 8 year follow up period [21]. Notably, subgroup analysis demonstrated poorer overall result in obese patients, those with a posterior malleolus fracture, or in fractures with a syndesmotic width equal to or greater than 1.5 mm independent of the number of cortices used in fixation. Other studies have corroborated these findings demonstrating similar clinical outcomes when comparing tricortical to quadricortical screws for syndesmotic fixation [7,8,15]. Despite this, quadricortical syndesmotic fixation is commonly utilized in practice today. Furthermore, most syndesmotic suture button devices require drilling through the medial tibial cortex. While tricortical screw placement eliminates iatrogenic risk to medial structures, broken screw removal can be much more problematic then when a quadricortical screw is used. There are several limitations of this study. While this study focused on anatomic structures found on the medial aspect of the ankle, the anterior neurovascular bundle and peroneal vessels may be at risk at the anterior distal tibia and in the interval between the tibia and fibula respectively. Also, precise utilization of the grid system in the operating room may be challenging and consistent use of this system has not been studied. Clinically, in our own practice, we have applied these findings intra-operatively to assure a perfect lateral radiograph is obtained to avoid placement of syndesmotic fixation into zone 3 which may abut or injure the PTT. Furthermore, in conjunction with a goal of syndesmotic reduction and hardware placement along the trans-syndesmotic axis (TSA) to avoid fibular malreduction, the likely optimal position for quadricortical syndesmotic hardware is approximately at the junction of zone 1 and zone 2. [4,14,17,18,20] We do not routinely obtain a post-operative CT after ankle syndesmotic fixation to evaluate hardware placement or syndesmotic reduction. Unfortunately, there is not a completely ‘safe zone’ that avoids the SNVB and surgeons should consider a small medial incision when placing suture button syndesmotic fixation. Despite this, we feel that understanding of the ARZs on an intraoperative lateral radiograph helps to guide the placement of quadricortical syndesmotic fixation.
Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009
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Conclusions Drilling, protuberant screws, passing of a large-bore needle and potential entrapping fixation (suture buttons) can cause iatrogenic injury that may delay recovery and/or lead to worse clinical outcomes. Placement of quadricortical syndesmotic fixation places structures on the medial ankle at risk. The SNVB is at considerable risk along the anterior course of the distal tibial in zones 1 and 2 while the PTT is only at risk in zone 3 at the distal extent of the tibia. Despite the mutually exclusive AZRs of the SNVB and PTT, the grid system elucidates which structure may be more at risk during placement of quadricortical syndesmotic fixation. Declaration of Competing Interest The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding The author(s) received no financial support for the research, authorship, and/or publication of this article. References [1] Brown OL, Dirschl DR, Obremskey WT. Incidence of hardware-related pain and its effect on functional outcomes after open reduction and internal fixation of ankle fractures. J Orthop Trauma 2001;15(4):271–4. [2] Chapter 57 Davidovitch R, Egol K. Rockwood and green’s fractures in adults. Ankle fractures. Tornetta P, rockwood CA, Bucholz RW, Court-Brown CM, Heckman JD, editors. Chapter 57 Lippincott Williams & Wilkins; 2010. [3] DeMill SL, Bussewitz BW, Philbin TM. Injury to the posterior tibial tendon after open reduction internal fixation of the medial malleolus. Foot Ankle Spec 2015;8(5):360–3. doi:10.1177/107110 07920130 0204. [4] Gardner MJ, Demetrakopoulos D, Briggs SM, Helfet DL, Lorich DG. Malreduction of the tibiofibular syndesmosis in ankle fractures. Foot Ankle Int 2006;27(10):788–92. doi:10.1177/107110070602701005. [5] Heim D, Heim U, Regazzoni P. Malleolar fractures with ankle joint instability – experience with the positioning screw. Unfallchirurgie 1993;19(5):307–12. [6] Helms CA. Fundamentals of skeletal radiology. Elsevier Health Sciences; 2013.
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Please cite this article as: P.B. Kaiser, M.D. Riedel and R. Qudsi et al., Consideration of medial anatomical structures at risk when placing quadricortical syndesmotic fixation: A cadaveric study, Injury, https://doi.org/10.1016/j.injury.2019.10.009