Keys To Addressing Peroneal Weakness With Lateral Ankle Instability

Although weakness in the peroneal tendon can be a factor in lateral ankle instability, physicians can overlook the peroneal tendon. Accordingly, this author discusses what to look for in the diagnostic workup, offers salient surgical pearls and presents a pertinent case study.

Ankle instability is commonly associated with peroneal pathology and oftentimes, the two are related and misunderstood. Clinicians often overlook peroneal weakness during the rehabilitation program. Peroneal tendons are the workhorse of the lateral ankle. These tendons are commonly torn and exhibit symptoms in a patient with concomitant ankle instability or functional instability. Traditionally these tendons, the peroneus longus and brevis, have gone overlooked and heal uneventfully.

We should make all efforts to treat the peroneal tendons nonoperatively and focus on rehabilitation of the lateral ligament complex. If patients still have ongoing pain, swelling and weakness, this leaves us no choice but to repair the lateral ankle complex. Multiple studies have demonstrated that when less than 50 percent of a tendon is torn, there may be good to excellent outcomes with few to no complications after surgical repair.^1–3

With this in mind, let us take a closer look at cases in which there are concomitant tears, revision cases or difficult cases in which there may not be any remaining tendon structures.

A Pertinent Guide To The Patient Workup

An important part of the clinical algorithm is the patient workup as it relates to peroneal pathology. The workup presents with a host of differentials, which we need to rule in or out.

Ankle stability is an important part of the patient workup. It is beyond the scope of this article to go into detail about each specific test although it is important to be aware of the tests and how they may relate to the patient sitting in front of you. The workup should include ankle stability as it pertains to peroneal pathology.

During the physical examination, confirm a clear distinction of the anterior talofibular ligament and calcaneofibular ligament. An anterior drawer test guides the clinician to grade the anterior talofibular ligament and a talar tilt test will help grade a calcaneofibular ligament injury. This is often difficult to ascertain clearly and a stress test may be more applicable. I will perform this in the office by comparing the unaffected limb to the affected limb without an ankle hematoma block. As we know, the dynamic stabilizers to the lateral ankle are the peroneals and the static stabilizers are the lateral ankle ligamentous structures. This knowledge will allow the clinician to include this in the surgical treatment plan when necessary.

Another key pathology to include in the workup is a cavus foot type. As we know, this foot type will place undue stress under the lateral hindfoot, exacerbate lateral ankle pain and concomitant metatarsal stress fractures, and cause various other problems. The pertinent clinical evaluation here is to include a Coleman block test and rule out a rigid hindfoot varus and/or plantarflexed medial column/first ray.⁴ This is a very simple comparison to the contralateral limb in stance phase and the test will confirm the inclusion of the hindfoot in the pathology. It is too easy to put on blinders and only look at a magnetic resonance image (MRI) of the peroneals, but it is of utmost importance to include the driving forces from proximal malalignment.

Also assess for subluxation of the peroneal tendons with force or resisted eversion with the knee bent. Subluxing or dislocating peroneals can be the driving force behind the peroneal pathology, and one should address this. The simple or subtle cavus foot that is driven by a varus hindfoot would typically need a lateral hindfoot osteotomy. A plantarflexed forefoot would typically need a dorsiflexion first metatarsal osteotomy. With a cavus foot type, manual muscle testing is prudent because the practitioner needs to determine the strength of the peroneals and dynamic foot stabilizers. It is also important to consider if a tendon transfer is necessary. A transferred tendon in the lower extremity will typically lose a grade of muscle power after the transfer. If one does not include this factor in the workup, the pathology will most likely recur when it could have been corrected in a single or staged fashion. Assessing these factors will also allow for more thorough surgical planning and operating room efficiency.

Additionally, rule out a neuromuscular disorder and work this up as necessary. Neuromuscular disorders include post-polio syndrome, Charcot-Marie-Tooth disease, cerebral palsy and peroneal neuropathies, just to name a few. These could lead to a potential foot drop and an inability to control the foot and ankle in the coronal plane, which may lead to instability and deformity. In these circumstances, a neurology consult is appropriate. If necessary, order an electromyogram (EMG) and/or nerve conduction velocity (NCV) to help discern the proximal pathology.

As I mentioned above, appropriate radiologic studies and advanced imaging are critical. Foot, ankle, long leg and calcaneal axial views are all typical to assess the lower limb. If proximal deformity exists, an orthopedic consult would be helpful to rule out any genu valgum or varum. For preoperative planning or for a suspected tendon or ligament pathology, order an MRI. The key here would be to assess the peroneal tendons for fatty infiltration.⁵ The shoulder literature has been extrapolated to the foot and ankle to be a guide for tendon integrity and possible transfers. If fatty infiltration is present within the muscle belly, one can presume it is deteriorated with a significant loss in muscle strength. In a recent article, authors developed a Goutallier classification based on the degree of fatty infiltration of the peroneal muscle fibers, which has been associated with peroneal tendon tears (see “A Closer Look At Goutallier Fatty Degeneration Staging” at right”).^6,7

Keeping all of these factors in mind as well as the patient’s activity and functional goals, one can map and execute a predictable surgical algorithm. The operative goals for restoring peroneal strength and lateral ankle stability are as follows: restore eversion power, prevent recurrent instability episodes, restore osseous alignment, and create a painless, plantigrade foot.

What You Should Know About The Operative Treatment Algorithm

After discussing an appropriate treatment algorithm with the patient, evaluate the risks, benefits and alternatives in detail, and plan the postoperative course. Discuss and implement a single or staged approach.

I perform surgery in a staged fashion if using multiple incisions. The staged surgery allows for osseous realignment first and subsequent tendon reconstruction four to six weeks later. There is some controversy over the timing of the second staged surgery. Most of this will depend on each patient’s situation.

In certain circumstances with a varus malalignment of the tibiotalar joint or a structural cavus foot deformity, one would typically correct this first with extra-articular osteotomies of the ankle or foot. The most common procedures would include an opening wedge osteotomy of the tibia, lateralizing calcaneal osteotomy and dorsiflexion first metatarsal osteotomy.

Redfern and Myerson have developed an intraoperative plan based on the peroneal tendon pathology, which would have been predetermined on MRI.⁸ Their article from 2004 illustrates a treatment plan. More specifically, a case involving pathology to both peroneal tendons or unusable, unstable tendon function would be a type III tendon tear. Type IIIA would elicit no muscle excursion and a type IIIB would have excursion of the proximal muscle belly. Utilizing this treatment algorithm has enabled me to work through many challenging cases and appropriately stage procedures.

Operative techniques for a type IIIA or B tendon tear of both peroneal tendons are challenging. Multiple authors have described allograft reconstruction utilizing various techniques with most of this literature being Level IV or V retrospective case series and studies.⁹ Pellegrini and colleagues describe a case involving a 41-year-old woman with bilateral congenital clubfoot and a history of previous surgery including peroneus brevis tenodesis to peroneus longus. A preoperative MRI showed a significantly diseased and striated peroneal brevis and longus. Intraoperative assessment revealed similar findings to the MRI and 2 cm of muscle excursion was present, which confirmed the potential function of allograft. The retrofibular groove was also deepened, which is an important component of peroneal pathoanatomy. Surgeons utilized a semitendinosus graft to recreate each peroneal tendon and at approximately 17 months, the patient had resumed normal activities with significantly less pain.

The key with the peroneal tendon assessment is to do a muscle excursion test and confirm that at least 1 to 2 cm of excursion is possible with no fatty infiltrates on preoperative MRI. This is rare but most commonly there is significant fatty infiltration within the peroneal muscle bellies, which leaves little to no room for allograft use. In addition to semitendinosus grafts, I have used Achilles, gracilis and peroneus longus allografts.

More often, there is little to no excursion, especially in a revision case, and there is little to no tendon to work with. During these instances, the potential of performing a tendon transfer is high. There appears to be two schools of thought when it comes to tendon transfers in the foot and ankle, more specifically with peroneal tendon pathology. When the surgeon encounters a nonfunctional peroneus brevis and debrides nonviable tendon, consider a tendon transfer into the fifth metatarsal base. Studies support both a single and a two-stage approach.^10-12  

A single-stage approach is an option when one is performing no or few osseous procedures. Authors have described harvest of the flexor digitorum longus and flexor hallucis longus with no significant functional differences in objective power and balance.¹³

I have had more success and experience with flexor hallucis longus single-stage transfers, typically with the patient in a supine position with a bump under the ipsilateral hip. Incise the plantar medial aspect of the midfoot, directly inferior to the master knot of Henry and the navicular. One may also make an incision at the great toe plantarly at the interphalangeal joint but this is more difficult to harvest and the harvest takes more time than necessary. After harvesting the flexor hallucis longus tendon, place a whip stitch in the distal margin of the tendon.

Proceed to make a 3 cm incision just posterior to the medial malleolus, centered between the malleolus and Achilles tendon. Carefully take dissection down to the posterior aspect of the tibiotalar joint capsule. The tendon is typically visible here adjacent to the posterior aspect of the tibia. Bring the Achilles tendon into this incision and keep it in a moistened gauze. Then make an incision from the posterior aspect of the fibula to the fifth metatarsal base and deepen it to the peroneal tendon sheath.

Test muscle excursion prior to tendon harvesting and debride the necrotic and nonviable tendon. It is important to release the deep crural fascia and periosteum posterior to the fibula. Then utilize a tendon passer or hemostat to bring the tendon from medial to lateral. At this point, bring the flexor hallucis longus down to the fifth metatarsal base and insert the flexor hallucis longus with a small anchor utilizing fluoroscopy. Alternatively, to avoid idiopathic metatarsal fractures, pass a drill from dorsal to plantar to facilitate tendon passing. Sew the tendon back on itself in this instance.  

Intraoperative pearls include confirming the retromalleolar groove in the fibula is deep enough and releasing the crural fascia appropriately. Hold the foot in a neutral position during tendon insertion into the fifth metatarsal base. Then meticulously close the tendon sheath. Splint the foot with a sugar tong and posterior splint to help control the postoperative stability.

Looking at the use of lateral transfer of the flexor hallucis longus or flexor digitorum longus  to address peroneal tendon tears, Seybold and colleagues looked at five-year outcomes for eight patients.¹⁰ They found that American Orthopaedic Foot and Ankle (AOFAS) scores improved from 64 to 86 with no subsequent bracing and all patients were able to return to normal preoperative activity.

Alternatively, during a staged fashion in which surgeons would perform osseous procedures first, several authors promote the utility of a silicone rod placement.11,12 This approach involves a Hunter silicone rod as a bridge allograft between muscle and the tendon insertion point. The rationale of utilizing this is to promote a pseudo-tendon sheath, which would potentially allow for a near normal tendon sheath for later tendon transfer. Wapner and Raikin and their respective colleagues report a six-week time difference between the first and second stages with success.^11,12 Wapner also reported that seven patients, more than eight years after surgery, would repeat the surgery with only minor complications noted.¹¹

Treating An Active Patient With A Long-Neglected Ankle Sprain

A 65-year-old active man presented to the orthopedic clinic for evaluation of ankle instability and pain. He relates a history of an ankle sprain almost 12 to 15 years ago, recalling that he felt a bad “pop” that he never had treated. The patient notes that his pain is typically worse on the golf course and during heavy activity. When asked where his pain is, he points to his fifth metatarsal base and lateral hindfoot. Pain levels reach an 8 out of 10 on the Visual Analogue Scale (VAS). The patient has tried an over-the-counter brace and orthotics prescribed by an outside consultant. He wears tennis shoes on a daily basis. The patient also has no pain or deformity in his contralateral limb.

After reviewing his medical history, he has no known hereditary neuromuscular disorders, no congenital lower limb deformities and no history of knee surgery or related surgical procedures to his foot or ankle. He is generally healthy with actively treated hypertension and hypercholesterolemia. The patient plays golf and hikes three or four times per week.

A gait examination reveals an antalgic gait and evident limb deformity. In stance, he has an obvious hindfoot varus from posterior and calf atrophy. Most notably, there is a full indentation about the lateral calf and lower leg with mild tenderness closer to the ankle and hindfoot. Range of motion exhibits decreased range in the ankle and subtalar joints specifically in the subtalar with a complete loss of eversion. The forefoot and midfoot are rigid with a loss in range of motion. He also exhibits a loss in passive ankle dorsiflexion and a positive Silfverskiold test. Manual muscle testing of both limbs in comparison reveals a loss of eversion (0 out of 5) and normal strength of the posterior tibial, anterior tibial and peroneus longus tendons. Specifically, the patient had a positive modified Romberg test and a positive anterior drawer and talar tilt in comparison to the contralateral limb. A Coleman block test revealed a fixed hindfoot varus when taking the first ray out of the equation.

Radiographically, his ankle is neutral on mortise and anteroposterior (AP) views, but his talus extrudes anteriorly approximately 5 mm on a lateral view. His Meary’s angle is elevated on a lateral view, showing clear incongruencies in the midfoot and subtalar joints. The calcaneal axial view shows a clear increase in varus attitude in relation to the patient’s tibia and his contralateral limb. His AP foot radiograph reveals a supinated forefoot and locked Chopart joint. Subsequent ankle MRIs reveal a loss of peroneus brevis and a striated peroneus longus about the lateral calcaneal wall. The lateral ankle complex also demonstrates incongruent anterior talofibular and calcaneofibular ligaments. There are no tibiotalar osteochondral defects or bone marrow edema, and a mild decrease in joint space within the posterior subtalar joint.

Intraoperative assessment showed very little to no muscle excursion of the peroneals, which necessitated a tendon transfer. The patient had osseous procedures including a lateralizing calcaneal osteotomy, first metatarsal proximal closing wedge osteotomy and posterior tibial tendon transfer during the first stage, and return six weeks later for a flexor hallucis longus tendon transfer to the fifth metatarsal base. The postoperative course included 10 weeks of strict non-weightbearing from the initial surgery and then physical therapy began with initial passive range of motion. The patient was fully weightbearing by week 12 and had returned to near normal activity by five months.

The most important aspect of the rehabilitation phase of recovery is restoring near normal eversion power. Once the foot is plantigrade to the leg, balance the appropriate tendons and repair the ligaments. Understanding these aspects of the pathology will allow the treating physician to treat the underlying ankle instability, the structural varus deformity and therefore peroneal tendinopathy, which lends to recurrent instability episodes.

In Conclusion

Here are some take-home points to remember:

• A thorough preoperative assessment should include a neurology workup, proximal limb assessment and gait analysis. Take care to assess appropriate myotendinous strength and power.

• Radiographs should include a weightbearing proximal limb assessment and a calcaneal alignment view. Advanced imaging is prudent in determining the degree of muscle belly fatty infiltration, which may guide the treatment plan.

• Type III peroneal tendon tears consist of two types: tears exhibiting no muscle excursion and tears with proximal muscle excursion.

• When neither peroneal tendon is salvageable, surgeons may utilize an allograft or autograft. A semitendinosus tendon allograft is most commonly in use as a bridge graft and a flexor hallucis longus tendon harvest as an autograft transfer.

• Consider a staged approach to maintain skin bridges and creating a pseudo-sheath with a Hunter silicone rod.

Dr. McAlister is in private practice at Arcadia Orthopedics and Sports Medicine in Phoenix. He is a Fellow of the American College of Foot and Ankle Surgeons.

References

1.     Saxena A, Cassidy A. Peroneal tendon injuries: an evaluation of 49 tears in 41 patients. J Foot Ankle Surg. 2003;42(4):215-20.
2.     Demetracopoulos CA, Vineyard JC, Kiesau CD, Nunley JA 2nd. Long-term results of debridement and primary repair of peroneal tendon tears. Foot Ankle Int. 2014;35(3):252-7.
3.     Steginsky B, Riley A, Lucas DE, Philbin TM, Berlet GC. Patient-reported outcomes and return to activity after peroneus brevis repair. Foot Ankle Int. 2016;37(2):178-85.
4.     Coleman S, Chesnut W. A simple test for hindfoot flexibility in the cavovarus foot. Clin Orthop Relat Res. 1977; 123:60-2.
5.     Goutallier D, Postel JM, Gleyze P, et al. Influence of cuff muscle fatty degeneration on anatomic and functional outcomes after simple suture of full-thickness tears. J Shoulder Elbow Surg. 2003;12(6):550-4.
6.     Res LCS, Dixon T, Lubberts B, et al. Peroneal tendon tears: we should consider looking at the muscle instead. J Am Acad Orthop Surg. 2018;26(22):809-815.
7.     Goutallier D, Postel JM, Bernageau J, Lavau L, Voisin MC. Fatty muscle degeneration in cuff ruptures. Pre- and postoperative evaluation by CT scan. Clin Orthop Relat Res. 1994 (304):78-83.
8.     Redfern D and Myerson M. The management of concomitant tears of the peroneus longus and brevis tendons. Foot Ankle Int. 2004;25(10):695-707.
9.     Pellegrini MJ, Adams SB, Parekh SG. Reversal of peroneal tenodesis with allograft reconstruction of the peroneus brevis and longus: case report and surgical technique. Foot Ankle Spec. 2014;7(4):327-331.
10.     Seybold JD, Campbell JT, Jeng CL, Myerson MS. Outcome of lateral transfer of the FHL or FDL for concomitant peroneal tendon tears. Foot Ankle Int. 2016;37(6):576-81.
11.     Wapner KL, Taras JS, Lin SS, Chao W. Staged reconstruction for chronic rupture of both peroneal tendons using Hunter rod and flexor hallucis longus tendon transfer: a long-term followup study. Foot Ankle Int. 2006;27(8):591-7.
12.     Raikin SM, Schick FA, Karanjia HN. Use of a hunter rod for staged reconstruction of peroneal tendons. J Foot Ankle Surg. 2016;55(1):198-200.
13.     Jockel JR, Brodsky JW. Single-stage flexor tendon transfer for the treatment of severe concomitant peroneus longus and brevis tendon tears. Foot Ankle Int. 2013;34(5):666-72.