- Discussion:
- w/ ankle fractures that occur above the syndesmosis, the lateral and/or
medial malleolus,
should be fixed first;
- subsequently, look for
objective evidence of syndesmotic widening;
- stabilization of syndesmosis may be achieved by placing one or two screws between tibia &
fibula to hold syndesmosis in position until syndesmotic ligament healing can occur;
- syndesmotic screw is a positioning screw that is used to hold but not compress the syndesmosis;
- it is sometimes necessary to position the screw thru the fibular plate;
- in these cases, place the plate along the posterolateral fibular border, inorder to facilitate entry of
the syndesmotic screw into the tibia;
- Preoperative Planning:
- flouroscopy is required inorder to ensure that the screws are inserted at the proper level and are placed parallel to the joint line;
- if a lateral incision is require to fix a concomitant lateral malleolar frx, then place the incision more posteriorly
inorder to facilitate screw insertion;
- patients need to be warned that hardware failure (screw breakage) is a common complication and does not imply that there was a surgical error;
- Proper Level for Syndesmotic Screw:
- place the first screw approximately 1 cm proximal to syndesmosis or 4 cm proximal to the ankle joint;
- if it is too low, it may pass thru the distal tibio-fibular articulation (or may pass thru the interosseous
ligament) which can localized calcification and/or pain;
- if the screw insertion is too high, it may cause the tip of the fibula to toe outward;
- it is also important to direct the screws parallel to the joint line inorder to avoid tilting the distal fibula;
- following insertion, get films to r/o malreduction of the fibula in notch of tibia, with inferior and anterior subluxation of talus;
- in the following examples the syndesmotic screws have been placed too low which may lead to chronic
syndesmotic pain (especially if the screw breaks within the tibial-fibular joint);
- Hardware:
-
number of screws and number of cortices:
- as noted by Mulligan and Hopkinson (1995), repair with 2 screws inserted thru 3 cortices each, proveded significantly
more stability than 1 screw;
- if screw engages only 3 cortices, normal external rotation of fibula during dorsiflexion of the ankle will not be affected;
- if adequate purchase is not achieved with 3 cortices, then far cortex should be fixed (4 cortices);
- if movement occurs, this screw will loosen in lateral cortex of tibia rather than break;
- screw engagement in the far cortex risks screw breakage;
- references:
-
Tricortical Versus Quadricortical Syndesmosis Fixation in Ankle Fractures: A Prospective, Randomized Study Comparing Two Methods of Syndesmosis Fixation.
-
Syndesmosis fixation: a comparison of three and four cortices of screw fixation without hardware removal.
-
size of screws:
-
3.5 mm: these should only be used in smaller patients;
-
4.5 mm screw (3.2 mm drill bit) usually 45 mm in length;
- in the abstract by MC Thompson et al, the authors examined syndesmotic fixation with either 3.5 or
4.5 mm tricortical screws;
- the authors noted that both the 3.5 and 4.5 mm screws demonstrated similar biomechanical characteristics and
did not find a biomechanical advantage of a 4.5-mm screw over a 3.5-mm in fixation of the syndesmosis;
- Biomechanical comparison of syndesmosis fixation with 3.5- and 4.5-millimeter stainless steel screws.
Thompson MC, Gesink DS. Foot Ankle Int 2000 Sep;21(9):736-41
-
bioabsorable screw fixation:
- in the report by Thordarson et al, 32 patients who had pronation-lateral rotation (PLR) fractures occurring 4 centimeters or more proximal to the ankle joint
or lower if the talus was displaced greater than one centimeter laterally were enrolled in this study;
- 17 patients were randomized to fibular plate fixation with a 4.5 ml polylactic acid (PLA) bioabsorbable syndesmotic screw, and 15
patients randomized to fibular plate fixation with a 4.5 mm stainless steel syndesmotic screw;
- all 32 patients had uncomplicated healing of their fibular fracture without loss of reduction;
- there was neither evidence of osteolysis nor sterile effusion in the patients who were treated with the PLA screw;
- no difference in range of motion or subjective complaints was noted in either group;
- use of the PLA syndesmotic screw at short-term follow-up was well tolerated and avoided the need for subsequent screw removal;
- in the report by W. David Hovis, MD et al (JBJS-A 2002) the authors assessed the efficacy of screws made of polylevolactic acid (PLLA) in the
treatment of syndesmotic disruptions associated with ankle fractures and fracture-dislocations;
- 33 consecutive patients with a syndesmotic disruption were managed with standard metallic plate-and-screw fixation of the malleolar
fracture and with 4.5-mm polylevolactic acid screws, with purchase in four cortices, for fixation of the syndesmosis;
- intraoperative radiographs confirmed reduction of the syndesmosis, and all of the patients were managed with a non-weight-bearing
plaster splint or brace for six weeks;
- all of the malleolar fractures healed in an anatomical position at an average of three months, and no postoperative displacement
of the syndesmosis or widening of the medial clear space was detectable on radiographs;
- no episodes of osteolysis or late inflammation secondary to the hydrolyzed polylactide occurred;
- 19 patients (83%) had an excellent result, and four patients (17%) had a good result;
- all twenty-three patients returned to their preinjury level of work and activities of daily living;
- no patient had malunion, nonunion, loss of reduction, or complications attributable to the biomechanical or biochemical properties of the implants;
- the authors conclude that polylevolactic acid screws are effective in stabilizing disruption of the syndesmosis during healing of unstable ankle fractures;
-
technical considerations:
- the authors inserted one 4.5 mm polylevolactic acid screw across the syndesmosis with purchase obtained in 4 cortices approximately
1-2 cm proximal to the plafond;
- w/ Maisonneuve fractures, 2 screws were inserted;
- references:
- Bioabsorbable versus stainless steel screw fixation of the syndesmosis in pronation-lateral rotation ankle fractures: a prospective randomized trial.
Thordarson DB. Foot Ankle Int 2001 Apr;22(4):335-8
- Treatment of Syndesmotic Disruptions of the Ankle with Bioabsorbable Screw Fixation
W. David Hovis, MD. Journal of Bone and Joint Surgery (American) 84:26-31 (2002)
-
K wire Fixation:
- two 1.5 mm K wires can be inserted obliquely across the distal tibio-fibular syndesmosis;
- is a less rigid form of fixation, which allows more physiologic ankle function, and does not require early hardware removal;
- Reduction of Frx:
- note that the main displacement of the fibula is posterior (not lateral);
- reduction is achieved w/ internal rotation of the ankle and manual translation of the fibula
in an anterior direction until it reaches the anterior tubercle of the tibia;
- fibular fracture is reduced & provisionally transfixed to the tibia w/ horizontal 1.6 mm K wire;
- Screw Insertion:
- prior to screw insertion, one assistant must firmly hold the fibula and the tibia together, so that the drill holes will not shift;
-
screw direction:
- because fibula is posterior to tibia, syndesmotic screw must be angled from posterolateral to
anteromedial in order to engage the tibia;
- if the drill is directed straight medially, it will skive off the posterior tibial surface;
- screw is inserted obliquely from back to front at angle 25 deg to 30 deg;
- it is directed from lateral to the medial cortex of the fibula, and into lateral cortex of the tibia
at right angles to the long axis;
- it is essential that the screw also be directed parallel to the joint line;
- if the screw is directed proximally or distally there may be shortening or lengthening at the frx site;
- screw should be parallel to joint to avoid displacement of fibula in an inferior or superior direction (use flouroscopy);
-
hardware:
- using the 2.5 mm drill bit in the double drill sleeve end, 2.5 mm both cortices of the fibula and at least one of the tibia;
- 3.5 mm tap is applied across the lateral tibial surface, while the fibula is held in firm reduction;
- this screw is placed either thru fibula or thru one of holes in fibular plate;
- fixation w/ lag screw is not performed since this could result in overtightening of screw and narrowing of syndesmosis;
- if this happens, dorsiflexion of ankle will be diminished;
-
syndesmotic reduction:
- dorsiflexion of the foot:
- conventional teaching mandates that during screw insertion foot is placed in dorsiflexion to bring the widest portion of talus into mortise;
- generally 5 deg of dorsiflexion is sufficient (more dorsiflexion might cause excessive widening of the mortise
which would then permanently remain in the widened position, leading to instability;
- other authors recommend full dorsiflexion;
- if screw is too tight it will restrict dorsiflexion (this is avoided by placing ankle in dorsiflexion during insertion);
- in contrast, the report by Paul Tornetta el at examinee whether overtightening of the syndesmosis limits maximal ankle dorsiflexion;
- using a cadaveric model, the authors found no difference before and after syndesmotic fixation (w/ maximal tightening);
- 19 cadaveric ankles were used for the study;
- angle between the reference wires with the ankle maximally dorsiflexed was measured before and after syndesmotic compression;
- syndesmotic compression was achieved with a 4.5-mm lag screw with the ankle in plantar flexion;
- there was no difference between the values for maximal dorsiflexion before and after syndesmotic compression;
- the authors concluded that the position of the ankle was not important during syndesmotic fixation;
- the authors caution that dorsiflexion of the ankle causes heel valgus and external rotation, which may cause an unstable
syndesmosis to be subluxated during dorsiflexion (leading to malreduction);
- ref: Overtightening of the Ankle Syndesmosis: Is It Really Possible?
Paul Tornetta, III, MD et al.
The Journal of Bone and Joint Surgery 83-A: 489 (2001)
- Complications: Anterior & Posterior Subluxation of Fibula:
- this problem may be seen w/ improperly fixed syndesmotic injuries;
- this occurs when fibula is screwed to the tibia w/o visualization of the notch to ensure it is properly reduced;
- recognition that there is a problem is easy because the talus is subluxated in the same direction as the fibula is displaced;
- removing the bolt, repositioning the fibula in the notch under direct vision, and reinserting the bolt corrects the problem;
- PostOp Care:
- Wt Bearing:
- whether to allow wt bearing is controversial;
- concern is that screw will break w/ wt bearing;
- many advocate removal of syndesmotic screw before wt-bearing;
- if screw engages only 3 cortices, normal external rotation of fibula during dorsiflexion of the ankle will not be affected;
- radiolucency has been noted around such screws after pts have started to bear weight, suggesting that
loosening of the screw permits normal motion of the fibula;
- Screw Removal:
- many authors recommend removing the screw prior to full wt bearing, since the syndesmosis screw tends to limit
ankle motion (which would then transfer wt bearing forces against the screw - leading to breakage);
- generally syndesmotic screws are removed at 9-12 weeks, but there has been some recent
interest in waiting up to 4 months (to avoid late syndesmotic widening);
-
bioabsorbable screw:
- at the time of screw removal, consider insertion of a bioabsorbable screw which will provide continued syndesmotic fixation,
and screw breakage is not an issue;
The tibiofibular syndesmosis. Evaluation of the ligamentous structures, methods of fixation, and radiographic assessment.
J.S. Xenos MD, W.J. Hopkinson MD, M.E. Mulligan MD, and E.J. Olson MD.
JBJS Vol 77-A No 6. June 1995, p847.
Biomechanical Effects of Internal Fixation of the Distal Tibiofibular Syndesmotic Joint: Comparison of Two Fixation Techniques:
RE Peter, RM Harrington, MB Henley, and AF Tencer.
J. Orthop Trauma. 1994. Vol 8. No 3. p 215-219.
Mechanical considerations for the syndesmosis screw. A cadaver study.
The effect of the syndesmotic screw on the extension capacity of the ankle joint.
C Olerud. Arch Orthop Trauma Surg. Vol 104, 1985. p 299-302.
Operative treatment of syndesmotic disruptions without the use of a syndesmotic screw:
A prospective clinical study.
K Yamaguchi et al.
Foot Ankle Int.
Vol 15. 1994. p 407-414.
Mechanical considerations for the syndesmosis screw. A cadaver study.
Instability of the distal tibiofibular syndesmosis after bimalleolar and trimalleolar ankle fractures.
The tibiofibular syndesmosis. Evaluation of the ligamentous structures, methods of fixation, and radiographic assessment.
Operative treatment of syndesmotic disruptions without use of a syndesmotic screw: a prospective clinical study.
Clinical use of a syndesmosis screw in stage IV pronation-external rotation ankle fractures.
TA Parfenchuck, JM Frix, SL Bertrand.
Orthop Rev. Vol 23, 1994. p 23-28.
Ankle mortise stability in Weber C fractures.
Indications for syndesmotic fixation.
J Solari, J Benjamin, and J Wilson.
J. Orthop. Trauma. Vol 5, 1991. p 190-195.
The influence of a diastasis screw on the outcome of Weber type C ankle fractures.
HR Chissell, J Jones.
JBJS 77-B, 1995. p 435-438.
Stablization of ankle syndesmosis injuries with a syndesmosis screw.
RA Kaye.
Foot Ankle. Vol 9. 1989.
p 290-293.
- Anterior Syndesmosis;
- lag screw fixation if avulsed from bone (tubercle of Tillaux-Chaput), otherwise possible suture of ligament;
- if instability persists,
3.5 mm cortex screw is inserted as
fibulo-tibial transfixation (positioning) screw about 2-3 cm above the ankle;
- screw is inserted obliquely 25-30 deg starting posterolaterally & aiming anteromedially;
- this screw is fully threaded, not a lag screw;
