Ankle instability is common and occurs approximately 20% of the time after one of the 27,000 daily ankle sprains. It occurs secondary to torn lateral ankle ligaments and/or insufficient treatment of the initial sprain. There are two types of instability: Mechanical and Functional. Mechanical instability is abnormal, excess motion of the ankle and/or subtalar joint. Functional instability is the subjective complaint of the ankle giving way despite normal ligament stability. This can be much more difficult to treat as the causes can be many: synovitis, cartilage lesion, inadequate rehab with resultant tendon weakness or abnormal proprioception, and others. The ligaments involved are the anterior talofibular ligament(ATFL), and the calcaneal fibular ligament(CFL) to varying degrees.
Patients will complain of pain over the anterior and lateral ankle joint and have intermittent recurrent sprains or give-way episodes. Swelling can come and go, but is often present after prolonged standing or walking. Patients will have positive ligamentous laxity on stress testing with anterior drawer and talar tilt tests. X-rays are needed to rule out fractures. Stress x-rays are of limited usefulness. MRI is usually required to determine the extent of the ligament injury, assess for any intra-articular injuries(talar osteochondral defect), and to evaluate the peroneal tendons.
The key to minimizing the risk of ankle instability is proper initial treatment of the patient’s ankle sprain. This includes the typical PRICE regimen: Protection(boot or ASO style brace), Rest(relative with occasional brief use of crutches), Ice, Compression(ACE bandage or sleeve), Elevation. Formal physical therapy is mandatory and should start within one week of the injury. This must include ROM, strength, and proprioception(balance) exercises. Once the initial swelling and pain have subsided a careful stability exam must be performed and an MRI obtained if the exam reveals ligament instability. Torn ligaments are a surgical indication especially for workers with physical job requirements. Intact ligaments do not guarantee that surgery won’t be required.
Surgical intervention is associated with an overall 90+ % success. Worker’s compensation patients as expected show somewhat lower success rates. The surgery should be performed by a fellowship trained orthopedic surgeon. The surgery is performed as an outpatient with regional nerve block anesthesia. This provides an average of 12-16 hours of pain relief post-operatively. An ankle scope is done to address any intra-articular lesions. The peroneal tendons should be checked even if intact on MRI as there can be split tears up to 25-30% of the time. They should be repaired as needed. The lateral ligaments are reattached to the fibula typically with some type of suture anchor(s). Usually the ligament tissue is adequate, but other local tissue may be incorporated into the repair.
Post-operatively the ankle is immobilized with a partial cast, followed by a bootwalker. Patient’s are non-weight bearing approximately 3 weeks and then can gradually progress to full weight-bearing in their boot. The boot is replaced by an ASO style brace at 6 weeks and physical therapy is started. Therapy will last 8-12 weeks and may include work conditioning. Patients will have swelling for 4-6 months and take approximately 6-9 months to reach MMI. Some degree of PPI is common and related to loss of side-to-side motion.
Patients can return to seated work only at 3 weeks post-op and gradual standing/walking at 6 weeks. Gradual progression of time on feet and lifting occurs after 6 weeks and full duty will typically take 4-6 months for workers with physical jobs. Long term restrictions are rare and usually limited in scope. This injury can be successfully treated by a fellowship trained orthopedic surgeon with early diagnosis and aggressive treatment.
Douglas A. Flory, MD
Board Certified Orthopedic Surgeon
Dual Fellowship trained in Sports Medicine(Knee/Shoulder) and Foot/Ankle
AthELITE ORTHOpedics and Sports Medicine
365 S. Park Ridge Road, Suite 102
Bloomington, IN 47401-8362
812-822-2675 // 812-822-2679 Fax