Ankle fractures and post-traumatic osteoarthritis

              Ankle fractures and post-traumatic osteoarthritis

                                 Dr KS Dhillon FRCS, LLM

Introduction

There are several classifications for ankle fractures but the two commonly used are that by Danis-Weber and that by Lauge-Hansen. Familiarity with these two classifications is essential because published studies on ankle fractures use one or both these classification. The functional outcome of ankle fractures is good though there is a tendency to believe otherwise because the ankle is a small joint and is frequently injured. Despite the fact that the ankle is subjected to very high forces per square centimeter the incidence of post-traumatic osteoarthritis (OA) is low and the incidence of endstage OA is lower. The need for reconstructive surgery for endstage OA is very low. Although ankle replacement has been touted as a viable option for endstage OA, credible evidence for it is lacking. Ankle arthrodesis remains the gold standard.

Classification

Ankle fractures are usually classified according to a classification by Danis-Weber or that by Lange-Hansen.

Danis-Weber classification (1)

This classification is easy to use and is based on the level of the distal fibular fracture in relation to the tibio-fibular syndesmosis.

Type A – Infra-syndesmotic. The fibular fracture is below the level of the syndesmosis. The fracture is transverse and is due to an avulsion (stage 1- stable). The fracture may be associated with a vertical or oblique fracture of the medial malleolus (stage 2- usually unstable). About 20 to 25% of ankle fractures belong to this group.

Type B – Trans-syndesmotic. The fibular fracture is at the joint level and extends proximally in an oblique manner. Further force will produce a posterior malleolar fracture and if the force continues a tear of the deltoid ligament or an avulsion fracture of the medial malleolus will result (unstable fracture). This is the most common ankle fracture and constitutes about 60% of ankle fractures.

Type C – Supra-syndesmotic. The fibular fracture is above the joint line. Disruption of the syndesmosis occurs and there is an associated tear of the deltoid or an avulsion of the medial malleolus. These fractures are unstable and may be associated with a posterior malleolar fracture. External rotation of a pronated foot causes such fractures. The Type C fractures are not so common and constitute about 20% of all ankle fractures.

Lauge-Hansen (L-H) classification (2)

The L-H classification is based on the mechanism of the injury and is divided into 4 types depending on the directional force applied to the ankle.

Supination- External Rotation (S-ER) – This the most common type of ankle fracture comprising 40 to 75% of the fractures. There are 4 sequential phases of the injury.

1. Failure of the anterior-inferior tibio-fibular ligament (AITFL)
2. A spiral oblique fracture of the fibula at or above the ankle mortise
3. Failure of the posterior-inferior tibio-fibular ligament (PITFL) or fracture of the posterior malleolus
4. Tension failure of the Deltoid ligament or avulsion fracture of the medial malleolus

Supination-Adduction (S-AD) – These comprise about 10-20% of the fractures. There are 2 sequential phases of this injury.

1. Low avulsion fracture of the lateral malleolus or lateral ligament injury
2. Vertical shear fracture of the medial malleolus

Pronation – Abduction (P-AB) – These comprise about 5-20% of the fractures and usually there is a failure of the syndesmosis. There are 3 sequential phases of injury.

1. Failure of the deltoid or a transverse avulsion fracture of the medial malleolus
2. Failure of the AITFL and the PITFL
3. Transverse fibular fracture at or above the ankle mortise with comminution of the lateral cortex of the fibular 

Pronation – External rotation (P-ER). These fractures constitute about 7-19% of the ankle fractures and syndesmosis failure is common. There are 4 phases of the injury.

1. Failure of the Deltoid ligament or a transverse avulsion fracture of the medial malleolus
2. Failure of the AITFL
3. Spiral oblique fracture of the fibula above the ankle mortise
4. Failure of the PITFL or fracture of the posterior malleolus

Functional outcome and post-traumatic osteoarthritis

Functional Outcome

The outcome of treatment of ankle fractures is good. Egol et al (3) studied 232 patients who had surgical treatment of ankle fractures. At 1 year complete follow-up data was available in 198 patients (85%). Eighty eight percent of the patients at one year follow-up had no pain or mild ankle pain and 90% of the patients had no limitation or some limitation only in recreational activities. Young age, male sex, absences of diabetes mellitus, and a lower ASA class were predictive factors of good functional recovery after surgical treatment of ankle fractures at 1 year follow-up.

Lindsjö U (4) in a prospective study of 321 patients, with fracture dislocations of the ankle who were treated surgically, found excellent to good results in 82%, acceptable in 8% and poor results in 10% of the patients at 2 to 6 years follow-up. He found that the decisive factors that influenced the clinical outcome were the type of fracture, the accuracy of the reduction, and the sex of the patient. The outcome was good when the reduction was exact, fixation rigid and joint exercises were started early with early weight bearing with a below knee walking support. Men generally tend to do better than females.

Bauer et al (5) studied the natural history of ankle fractures in 143 patients who were treated conservatively by the closed method. The average follow-up was 29 years. Twenty patients had a Weber A, 103 Weber B and 20 patients Weber C fracture of the ankle. According the L-H classification 100 patients had S-ER, 15 S-AD, 14 P-AB and 14 P-ER fracture of the ankle. Eight three percent of the patients were symptom free at follow-up after an average of 29 years and 16% had occasional ache in the ankle. Eight two percentage of the patients had no OA and six patients (4%) had moderate OA and 2 patients (1.3%) had severe OA. The two patients with severe OA had a severe form of ankle fracture (S-ER type IV). The authors concluded that it is not necessary to have a perfect reduction of the fractures to have a good functional outcome in the treatment of ankle fractures.

Donken et al (6) in a study of 276 patients with S-ER type II – IV fractures who were followed-up for 21 years showed excellent or good results in 92% of the patients.
Complications associated open reduction and internal fixation are low. Nelson et al (7) studied the California (USA) discharge database of patients who had internal fixation of ankle fracture between 1995 and 2005. They found low short term complication rates which included a pulmonary embolism (0.34%), mortality (1.07%), wound infection (1.44%), amputation (0.16%) and reoperation for internal fixation (0.8%). Open fractures, older age, diabetes mellitus and peripheral vascular disease were predictors of short term complications.

Medium term complications in patients who were followed-up for five years included a 0.96% of patients who needed an ankle fusion or an arthroplasty. The medium term complications were more common in patients who had trimalleolar and open fractures of the ankle.

Post-traumatic Osteoarthritis

The primary cause of OA of the hip and the knee is idiopathic but the primary cause of OA of the ankle is trauma. Saltzman et al (8)) studied 639 patients with grade 3 and grade 4 (K-L) OA of the ankle who presented to a tertiary medical centre. They found that 70% of the ankle OA was post-traumatic while 12% was due rheumatoid arthritis and 7% was idiopathic. They also found that 8% of the hip OA was post-traumatic and for the knee the post-traumatic OA was seen in 12.5% of the patients.

Valderrabano et al (9)) found that 78% of the endstage OA of the ankle was post-traumatic in patients presenting at a tertiary medical centre. In 13% it was secondary and in 9% it was idiopathic. The cause of the post-traumatic OA was malleolar fractures (39%), ligament lesions (16%), pilon tibial fractures (14%), tibial fractures AO type 42 (5%), talus fractures AO type 43 (2%) and combined severe fractures (2%).

 The authors of the study did admit that there were two drawbacks in study. The first being the fact that the study was retrospective in nature it cannot provide the true prevalence rate of post-traumatic OA. The second important drawback is the fact that the study does not provide the exact pathomechanism of the OA in each etiological subgroup. It is easy to fathom that fractures of the distal tibia extending into the ankle joint can lead to secondary OA but how the fracture of the tibial shaft lead to OA remains unclear. One possible mechanism is that the fractures of the tibial shaft that lead to OA of the ankle have associated concomitant injury to the ankle which is not recognised.

Stuermer and Stuermer (10) in a prospective study of 214 patients with tibial fractures found that 20.1% of the patients had associated injury of the ankle. Of the 214 patients with tibial fractures, 45 ankles in 43 patients were found to have associated ankle injury. There was distal fibular fractures in 14, Maisonneuve fractures in 13, isolated rupture of the syndesmosis in 3, fracture of the posterior malleolus in 8 and fractures of the medial malleolus in 7 of the cases. In 38 of the 43 patients the syndesmosis was ruptured and 88.4% of the tibial injuries were spiral fractures located in the distal third of the tibia. Tibial fractures which have a potential for ankle injuries are those caused by pronation-eversion trauma, spiral fractures of the distal tibia, and those that are associated with proximal fibula fractures and fractures of fractures of the tibia with an intact fibula.

The studies by Saltzman and Valderrabano however do not provide the true prevalence rate of post-traumatic OA of the ankle. Lindsjö U (4) did a prospective study involving 321 patients with fracture dislocation of the ankle who were treated surgically and followed up for 2 to 6 years. He found a posttraumatic OA in 14% of the patients.

Bauer et al (5) who followed-up, 143 patients with conservative treated fractures of the ankle, for an average of 29 years showed a very low incidence of post-traumatic OA. Despite imperfect reduction of the fractures the incidence of moderate OA was 6% and severe OA 1.3%. The most common ankle fracture (30% of all ankle fractures) is the S-EV stage II and in this group of fractures only 1 patient out of 48 patients (2%) had a probable grade 1 OA. Kristensen and Hansen (11) found no OA in 94 patients with S-EV stage II fractures treated conservatively and followed-up for 16 to 25 years.
The latency period for development of endstage OA of the ankle after a fracture is rather long.

 Horisberger et al (12) in a study of 141 patients with ankle fractures who presented with endstage OA of the ankle found that the latency period between a fracture and endstage OA was 20.9 years (1-52 years). In 52.2% of the patients the endstage OA was due to malleolar fractures.

The number of patients who require reconstructive procedure after treatment of ankle fractures with open reduction and internal fixation is very low. SooHoo et al in population based study of 57,183 patients who had an open reduction and internal fixation of malleolar fractures found that 0.96% of patients required an ankle arthrodesis or ankle replacement on intermediate term follow-up (5 years). The mortality rate was 1.07%, infection rate 1.44 and amputation rate was 0.16% (13).

According to Daniels and Thomas (14) the ankle joint which is small and commonly injured is subjected to the highest forces per square centimeter. Despite these high forces the incidence of symptomatic ankle arthritis is much lower than larger joint such as the knee and hip due to various mechanical, biochemical and anatomic peculiarities of the ankle. These peculiarities make the ankle resilient to the process of aging and trauma.

Treatment of ankle post-traumatic OA

Non-surgical treatment

The pain in patients with ankle OA as in other joints is episodic in the early stages and such patients can be treated with analgesic or NSAIDs. In the later stages shoe wear medication can be useful. Shoes with cushioned heel or a rocker bottom sole modification can help reduce stresses across the ankle joint during heel strike. Braces and ankle orthosis can be useful but are often poorly tolerated. Corticosteroid injections can be useful in selected patients (15).

Surgical Treatment

Ankle (Tibiotalar) fusion remains the gold standard for treatment of symptomatic endstage OA of the ankle (15). It gives excellent pain relief but the drawback of the procedure is the loss of motion and it can lead to accelerated development of OA of other joints of the foot including the talonavicular, calcaneocuboid, naviculocuneiform, 1st Tarsometatarsal and the 1st metatarsophalangeal joints. The ideal position for fusion of the ankle is (16):

1. 5% degree of valgus
2. Neutral ankle position (no plantar or dorsiflexion)
3. 5%-7 degrees of external rotation
4. Slightly posterior positioning of talus in relation to the tibial plafond

Complications can be frequent with open ankle arthrodesis. Morrey and Wiedeman (17) did a review of 60 patients who had ankle fusion for post-traumatic OA. They found that 58% of the patients had a fusion within the first year of the injury. The infection rate was 23%, non-union rate 23%, and poor alignment and early loss of position was seen in 15% of the patients’ with 7% developing a delayed union. Forty one of the 60 patients were followed up for an average of 7.5 years and 83% were satisfied with the procedure. Thirty of the 41 patients had no motion at the subtalar joint but there was a13 degrees of motion at the Chopart's joint at an average follow up of 7.5 years. With shoes the gait of the patients was nearly normal.

Morgan et al (18) followed up 101 patients with ankle arthrodesis for an average of 10 years (from 2 to 25 years). There was a much lower rate of pseudoarthrosis of 5% and it was only seen in patients with sensory loss. Good to excellent clinical results was seen in 90% of the patients.

Ankle joint replacement

Ankle joint replacement has been touted as a viable option for treatment of end stage ankle arthritis. However the earlier reports showed failure rates as high as 72% (19).More recent studies have reported an 89% survivorship at 10 years but the quality of evidence in support of ankle replacement is weak and fraught with bias. High quality randomised control trials comparing ankle replacement with other forms of treatment for ankle arthritis is lacking (20).

It well established that the long term outcome of hip and knee replacements is excellent. However the clinical outcome of ankle joint replacement is not better that arthrodesis of the ankle as many would expect. Daniels et al (21) published a level II therapeutic study in which they studied the patient reported clinical outcomes in patients with ankle reconstruction. The data was obtained from the Canadian Foot and Ankle Society (COFAS) Prospective Ankle Reconstruction Database. The surgery was carried out by subspecialty trained orthopaedic surgeons.

The minimal follow-up was at least 4 years. There were 388 ankle reconstructions with 281 ankle replacements and 108 ankle arthrodesis. There was minimal difference between the Ankle Osteoarthritis Scale (AOS) and Short Form-36 scores between the two groups.

Seven percent of the arthrodesis and 17% of the ankle replacements underwent revisions. The major complication rate was 7% for arthrodesis and 19% for ankle replacements. The authors concluded that the intermediate term clinical outcomes of ankle replacement and ankle arthrodesis are comparable while the rates of revision and major complication were higher for ankle replacement.

Conclusion

Although the ankle is a small joint which is exposed to very high forces per square centimeter and is frequently injured the functional outcome of ankle fractures is good to excellent in 80 to 90% of the patients. Even with imperfect reduction of ankle fractures the incidence of post-traumatic OA is low and it ranges between 7 to 14% while the incidence of endstage OA is about 1.3%. In patients with S-EV stage II fractures (most common fractures) no OA develops even after 20 years. The latency period for endstage OA is about 20 years. The number of surgically treated patients with malleolar fractures who require ankle arthrodesis or fusion is low at about 0.96%.

Ankle replacement for treatment of endstage OA has not lived up to its expectation and credible evidence to support it as viable option for treatment of endstage ankle OA is lacking, unlike knee and hip replacements. Ankle arthrodesis remains the gold standard.

References

1. Bugler KE, White TO, Thordarson DB. Focus On Ankle Fractures. The Journal of Bone and Joint Surgery. 2012; 1- 4.
2. Clare MP. A Rational Approach to Ankle Fractures. Foot Ankle Clin N Am 13 (2008) 593–610.
3. Egol KA, Tejwani NC, Walsh MG, Capla EL, Koval KJ. Predictors of short-term functional outcome following ankle fracture surgery. J Bone Joint Surg [Am] 2006; 88-A: 974-9.
4. Lindsjö U. Operative treatment of ankle fracture-dislocations. A follow-up study of 306/321 consecutive cases. Clin Orthop Relat Res. 1985 Oct;(199):28-38.
5. Bauer M, Jonsson K, Nilsson B. Thirty-year follow-up of ankle fractures. Acta Orthop Scand. 1985;56:103–106.
6. Donken CC, Verhofstad MH, Edwards MJ, van Laarhoven CJ. Twenty-one-year follow-up of supination-external rotation type II-IV (OTA type B) ankle fractures: a retrospective cohort study. J Orthop Trauma. 2012 Aug;26(8):e108-14.
7. Nelson F. SooHoo, Krenek L, Eagan MJ, Gurbani B, Ko CY, Zingmond DS. Complication Rates Following Open Reduction and Internal Fixation of Ankle Fractures. J Bone Joint Surg Am, 2009 May 01; 91(5):1042-1049.
8.  Saltzman CL, MD, Salamon ML, Blanchard GM, Thomas Huff T, Haye A, Buckwalter JA and Amendola A. Epidemiology of Ankle Arthritis: Report of a Consecutive Series of 639 Patients from a Tertiary Orthopaedic Center. Iowa Orthop J. 2005; 25: 44–46.
9. Valderrabano V, Horisberger M, Russell I, Dougall H, Hintermann B. Etiology of Ankle Osteoarthritis. Clin Orthop Relat Res. Jul 2009; 467(7): 1800–1806.
10. Stuermer EK, Stuermer KM. Tibial shaft fracture and ankle joint injury. J Orthop Trauma. 2008 Feb;22(2):107-12
11. Kristensen KD, Hansen T. Closed treatment of ankle fractures: stage II supination-eversion fractures followed for 20 years. Acta Orthop Scand. 1985; 56:107–109.
12. Horisberger M1, Valderrabano V, Hintermann B. Posttraumatic ankle osteoarthritis after ankle-related fractures. J Orthop Trauma. 2009 Jan; 23(1):60-7.
13. SooHoo NF, Krenek L, Eagan MJ, Gurbani B, Ko CY, Zingmond DS. Complication rates following open reduction and internal fixation of ankle fractures. J Bone Joint Surg Am. 2009 May;91(5):1042-9. doi: 10.2106/JBJS.H.00653.
14. Daniels T and Thomas R. Etiology and biomechanics of ankle arthritis. Foot Ankle Clin. 2008 Sep; 13(3):341-52.
15. Ankle arthritis; OrthopaedicsOne Articles at http://www.aofas.org/education/orthopaedicarticles/ankle-arthritis.pdf.
16. Buck P, Morrey BF, Chao EY. The optimum position of arthrodesis of the ankle. A gait study of the knee and ankle. J Bone Joint Surg Am 1987;69(7):1052-62.
17. Morrey BF, Wiedeman GP. Complications and long-term results of ankle arthrodeses following trauma. J Bone Joint Surg Am. 1980 Jul;62(5):777-84.
18. Morgan CD, Henke JA, Bailey RW, Kaufer H. Long-term results of tibiotalar arthrodesis. J Bone Joint Surg Am. 1985 Apr;67(4):546-50.
19. Gougoulias, N., A. Khanna, and N. Maffulli.  How successful are current ankle  replacements?: a systematic review of the  literature. Clin Orthop Relat Res 2010; 468(1):199-208.
20. Zaidi R, Cro S, Gurusamy K, Siva N, Macgregor A, Henricon A, Goldberg A. The outcome of total ankle replacement: A systemic review and meta-analysis. Bone Joint J 2013;95-B:1500–7.
21. Daniels TR, Younger ASE, Penner M, Wing K, Dryden PJ, Wong H, Glazebrook M. Intermediate-Term Results of Total Ankle Replacement and Ankle Arthrodesis. J Bone Joint Surg Am, 2014 Jan 15;96(2):135-142