Fig. 23.1
Increase in calcaneal inclination (X-ray) angle
Fig. 23.2
Increase in calcaneal inclination angle (clinical)
Fig. 23.3
Calcaneal varus (X-ray)
Fig. 23.4
Bilateral calcaneal varus (clinical)
Fig. 23.5
Metatarsus adductus
Numerous means of classifying the cavovarus deformity have been devised throughout the years. These classification schemes have been based on the apex of the deformity, the reducibility of the deformity, the associated conditions with the deformity, and the etiology of the deformity [4–6]. All of these considerations have their merit in the optimal surgical management of the cavovarus foot.
A critical component to the management of the cavovarus foot deformity is understanding the neuromuscular imbalances that are present. This deformity has long been thought to stem from underlying neurological disorder and be a primary cause in the development of the cavus foot. Identifying the specific pattern of muscular imbalance is essential in the surgical management of patients with a cavovarus foot as osseous correction alone is often insufficient in preventing recurrence of the deformity. In some neuromuscular diseases, muscle strength progressively worsens, and not realizing the etiological factor at the time of surgery dooms the patient to ultimate failure and recurrence of the cavovarus foot deformity.
Surgical Decision Making
The determination of the ideal approach for surgical intervention is dependent upon several important considerations that should be identified during the preoperative evaluation: Where is the apex of the deformity? What type of cavovarus deformity is identified (i.e., forefoot cavus, midfoot cavus, global cavus)? What is the first ray position? Is this deformity fixed or non-fixed? Finally, and most importantly, it is imperative to identify all forces causing imbalance in the foot. A careful examination of all muscles acting on the foot will provide invaluable information on how to dynamically balance the cavovarus foot. Commonly, muscle testing will demonstrate overpowering of the tibialis anterior muscle by the peroneus longus muscle with a plantarflexed first ray and overpowering of the peroneus brevis muscle by the posterior tibial muscle in the varus foot deformity [4, 7, 8].
Once this information has been ascertained, surgical correction is largely based on the utilization of both osseous and soft tissue procedures. The ideal combination of osseous and soft tissue procedures has not been identified for each pathological condition. It would be impossible to formulate such an algorithm due to the variation in severity of deformity, difference in patient anatomy, etiology of the deformity, and other varying factors. There is no single procedure or combination of procedures that has been found to offer reliably good long-term results across the cavovarus landscape. However, there are some basic concepts which much be considered.
Generally, in the milder or non-fixed cavovarus deformity, lesser metatarsophalangeal joint releases with digital arthrodesis are indicated along with soft tissue procedures such as the Jones tenosuspension and Hibbs tendon transfer. Osteotomies such as a dorsiflexory wedge osteotomy of the first metatarsal are indicated to reduce the plantarflexion deformity of the first ray [9–12].
In the more severe, fixed deformities demonstrating hindfoot involvement, calcaneal and midfoot osteotomies in conjunction with soft tissue procedures such as tendon transfers are often utilized. Commonly performed osseous surgical procedures within the rearfoot and midfoot include the Dwyer calcaneal osteotomy and Cole midfoot osteotomy. In the severe, fixed cavovarus deformity, calcaneal and midfoot osteotomies as well as midfoot and hindfoot arthrodesis are indicated [4, 13–16].
The question of when arthrodesis is indicated is a difficult one to answer. Preserving the viability of hindfoot and midfoot joints is important for sustained symptomatic relief and avoidance of additional surgical procedures (Figs. 23.6 and 23.7). It is accepted that triple arthrodesis ought to be avoided as long-term follow-up on the triple arthrodesis in several studies has demonstrated ankle pain and the development of premature arthritis in more than half of operated feet [17]. Therefore, triple arthrodesis is felt to serve better as a salvage procedure for cases with severe arthritis or in cases of recurrence following failed corrective osteotomies [18–21]. The pantalar arthrodesis is also reserved as a salvage procedure when no other options exist for these patients.
Fig. 23.6
Long-term follow-up: triple arthrodesis with severe adjacent-joint arthritis
Fig. 23.7
Long-term follow-up: triple arthrodesis with ankle varus and recurrence of the varus deformity
Steindler Stripping
Indications and Planning
Contracture of the plantar fascia and plantar intrinsic muscular is invariably present in the moderate to severe cavovarus foot. First described in 1920, Steindler stripping is complete release of the plantar fascia, flexor digitorum brevis muscle, and abductor halluces [22, 23]. This procedure is unlikely to be performed as an isolated procedure, as it is usually followed by bony correction of structural deformity. Release of the plantar fascia is a pivotal part of the correction of the cavus foot. It is this reason that a Steindler stripping is the first procedure performed on a cavus reconstruction. Mobilization of the rearfoot and reduction of the deformity after osteotomy are much easier if this release is performed.
Contraindications/Limitations
A Steindler stripping is almost always never performed alone, but in combination of one or more osseous procedures. It should be performed only on the severe cavovarus deformity, but not on the mild one. In less severe cases, release of the plantar soft tissue structures would not be necessary to allow for lowering of the longitudinal arch.
Technique, Pearls and Pitfalls
Incision placement for the Steindler stripping should be based on the other procedures required to correct the cavus deformity. When performed in combination with the Dwyer calcaneal osteotomy, the procedure can be performed by minimally elongating the lateral incision to meet the inferior border of the calcaneus. A curved mayo scissor is preferred with the curvature faced proximally to avoid the neurovascular structures as the muscle and ligament are transected (Fig. 23.8). Care must be taken to avoid cutting the skin on the medial side of the foot. Otherwise a painful scar may result. This modification of the original Steindler procedure is technically easy to perform as well as reproducible results.
Fig. 23.8
Plantar fascia visualized through extended Dwyer incision
If a calcaneal osteotomy is not indicated, the procedure is performed through a medial longitudinal incision adjacent to the calcaneus and along the glabrous junction.
One of the most common pitfalls of the procedure is incomplete release of the fascia. If performed through the lateral approach, it is imperative that the medial band and the abductor hallucis be completely transected. Injury to any neurovascular structure is unlikely with this procedure, but care must be taken. Modifications have been reported to help avoid damaging the plantar neurovascular [24, 25]. Regardless of the technique performed, a complete release must be performed to help mobilize the rearfoot in severe cavovarus feet.
Achilles Tendon Lengthening
Indications
Lengthening of the Achilles tendon is performed when there is a gastroc-soleus equinus diagnosed on examination. The Achilles tendon is not necessarily strong but contracted in patients with cavovarus deformity. Muscle testing and charger lateral ankle (forced maximum dorsiflexion view) radiographs should be obtained to confirm a contracted Achilles tendon and adequate talar excursion if the tendon is to be lengthened. If the talus is already maximally dorsiflexed within the ankle joint, no type of posterior soft tissue release or lengthening will allow additional dorsiflexion of the talus in the ankle.
A cavovarus deformity normally does not benefit from an Achilles tendon lengthening. Performing an Achilles tendon lengthening, thus resulting in its weakening, can in fact make the cavus foot more severe. The heel cord is resisting further contracture to the high-arched foot. Patient presenting with a presumed tight heel cord most often has a pseudoequinus deformity, which makes your physical exam that more important [26]. The fixed plantarflexed position of the forefoot upon the rearfoot causes the talus to dorsiflex within the ankle joint in order to get the forefoot on the same plane as the rearfoot (Fig. 23.9). Azmaipairashvili et al. noted the heel cord may appear tight but the os calcis is in calcaneus and should never be part of the corrective procedure [27] (Fig. 23.10).
Fig. 23.9
Fixed forefoot deformity causing pseudoequinus with weight bearing
Fig. 23.10
TAL open technique
Contraindications/Limitations
As mentioned, adequate motion about the ankle joint must be present when lengthening the Achilles tendon. Pseudoequinus should be corrected prior to attempting the Achilles lengthening or overlengthening can result. Specifically, dorsiflexion of the forefoot/midfoot will functionally plantarflex the talus within the ankle joint and thus improve ankle joint range of motion. This may prevent the need to lengthen the heel cord. It is also important to evaluate for a bony block equinus. Talar neck abutment dorsally against the tibia will prevent any improvement to the dorsiflexion range of motion about the ankle with lengthening of the Achilles tendon. This would potentially create a calcaneus gait and worsen the already cavus foot [28, 29].
Technique, Pearls and Pitfalls
The Achilles tendon lengthening can be performed either open or percutaneous. The advantage to the open “Z” technique allows for a more precise degree of lengthening. The lengthening is obtained by bisecting the tendon anterior to posterior and exiting proximally posteriorly and anteriorly distally. The bisection must be long enough to allow for overlap of the tendon after released and held to the correct length. The Achilles is repaired with a lateral trap suture technique with nonabsorbable 2-0 suture. This open technique can result in overlengthening and rupture, but both are rare complications. Care must be taken to not perform this procedure until after the osseous work has been completed within the foot to prevent excessive lengthening or undercorrection.
Percutaneous TAL or triple hemisection is another option with the tendon being cut three times, two finger breaths apart with the tendon being cut from the center medialward then lateralward, and finally a medial hemisection through the tendon. Care must be made to cut this correctly or an overlengthening/calcaneal gait is a distinct possibility. If too little is cut, then undercorrection is very probable.
Management of Complication
The most common complication of an open TAL is wound complications. Care must be taken to perform this procedure in an atraumatic technique. Wound care and other conservative measure are often times enough to solve this problem.
Overcorrection of the Achilles tendon lengthening is a potentially devastating problem for the patient with cavovarus or most any foot structure. Once conservative care including extensive physical therapy fails to resolve or strengthen this tendon adequately, surgical intervention is required. An open technique to structurally shorten this tendon alone or in combination with an FHL tendon or peroneal tendon transfer should be considered [28, 29]. Unfortunately, a heel ulcer (Figs. 23.11 and 23.12) may result from overlengthening, ultimately requiring an ankle joint arthrodesis to resolve this problem.
Fig. 23.11
Calcaneal gait following Achilles tendon lengthening
Fig. 23.12
Calcaneal gait with plantar heel ulcer
Tibialis Anterior Tendon Transfer
Indications
The tibialis anterior tendon creates a dynamic supination force to the forefoot with an unopposed pull from the weakened evertors. The indication of the tibialis anterior transfer is to balance the inversion/eversion pull of the forefoot and/or remove the deforming force of the inverted foot.
Transfer of the tibialis anterior in whole or part (split tibialis anterior tendon transfer or STATT ) can be part of the treatment for the varus component in the cavovarus foot deformity. It is imperative to determine the underlying etiology of the cavovarus foot structure since specific conditions result in ultimate weakness of the tibialis anterior muscle [30, 31]. Relying on this tendon in the long term may result in minimal improvement or recurrence of the varus deformity. Shapiro and Bresnan noted that weakness over time makes transfer of this tendon inadvisable [32].
Contraindications/Limitations
The tibialis anterior tendon transfer has few contraindications. This procedure, as discussed earlier, should be rarely performed in isolation or with disease processes that result in weakening of the tendon. An in-depth physical examination of the tendon should be performed before any procedure takes place. The strength of the tibialis anterior must be accurately quantified to retain functionality. It is important to remember that one grade of muscle strength is typically lost during a tendon transfer [34].
Technique, Pearls and Pitfalls
The tibialis anterior tendon transfer is performed through a three-incision approach. The first incision is made over the insertion of the tibialis anterior (Fig. 23.13). A dorsal medial incision is made at the navicular-cuneiform joint and extending to the base of the metatarsal. The tendon is fully released from its insertion.
Fig. 23.13
Medial incision for tibialis anterior transfer; umbilical tape used to split the tendon
A second incision is made to the anterior-medial aspect of the leg directly over the palpated tibialis anterior tendon (Fig. 23.14). It is important that the incision is made proximal to the extensor retinaculum to prevent bowstringing of the tendon. Other techniques have been described where the tendon is passed superficial to the retinaculum [35]. If strength is to be optimized, the tendon is placed above the retinaculum. If the tendon excursion is more important, then the tendon is passed under the retinaculum within the sheath of the common extensor. Once the tendon is visualized, it is pulled proximal through the anterior-medial leg incision.
Fig. 23.14
Anterior central incision (second incision) for TA transfer
The third incision is made on the anterior-lateral of the foot. The incision can be made overlying the lateral cuneiform or the cuboid depending on the surgeon preference and correction desired. The more eversion required, then placement of the tendon should be within the cuboid; this provides a better mechanical advantage for the tendon. In our institution, the tendon is routed to the lateral cuneiform if mild to moderate correction is needed (Fig. 23.15). A more lateral incision over the cuboid is performed if a greater correction is needed. When performing a STATT, the split tendon is transferred to the lateral cuneiform or cuboid; thus, a lateral incision is needed.
Fig. 23.15
Incision site for placement of TA tendon into the third cuneiform or cuboid
An interference screw or anchor is then placed into the lateral cuneiform or cuboid with the tendon properly tensioned. The foot should be in a neutral position. Before the interference screw is inserted, it is important you check the positioning to make sure you have the correction needed. Once the interference screw is inserted, the author uses a suture button to augment the transferred tendon.
Management of Complications
Complications are rare when performing the tibialis anterior tendon transfer. Transient tendonitis as well as the prominence of the tendon along the anterior leg is the most common complication if one fails to transfer the tendon under the extensor retinaculum. The patient most often will do well with physical therapy and conservative treatment [36]. This is considered an in-phase transfer, and education is not usually necessary for muscle function.
Failure of the tendon attachment is the most common significant complication requiring surgical repair [34]. Failure of the fixation technique used is often to blame, which would include poor bone stock quality (Figs. 23.16 and 23.17). A suture button is often added to secure the interference screw used due to this complication. A corkscrew-type anchor is another viable option for repair of tendon insertional rupture. It is imperative that the patient is immobilized a minimum of 4–6 weeks postoperatively to prevent recurrent failure at the attachment site (Figs. 23.18 and 23.19).
Fig. 23.16
Insertion of TA into lateral cuneiform
Fig. 23.17
Failure of TA tendon transfer at insertion site
Fig. 23.18
Tendon preparation for Hibbs
Fig. 23.19
Anchor attachment and suturing for Hibbs
Overcorrection, although rare, is also a complication that can be very detrimental if not addressed. This results from tightening the tendon too much as the tendon is fixed to the bone. Excessive tightening creates a significant spasm to the tendon resulting in minimal eversion/inversion motion. If this is encountered, correction is required with lengthening of the tendon or removing the interference screw to decrease the tension on the tendon. Another option is for the tendon to be transferred medially to restore the inversion-to-eversion balance relationship [36].
Undercorrection can occur if the tendon is not placed under proper tension when attached to the bone. Everting the foot past neutral with attachment should permit some inversion. Inadequate tension will lose the function of this tendon transfer and further loss of dorsiflexion of the foot.
Hibbs Tenosuspension
Indications
In the flexible cavus foot with the presence of claw toes, the Hibbs tenosuspension can be employed to reduce the deforming force or dorsal contracture of the lesser digits at the MTPJs. This transfer of the four slips of the extensor digitorum longus into the middle or lateral cuneiform allows continued dorsiflexion strength at the ankle without the contracture to the lesser toes. The advantages of this procedure like the tibialis anterior, STATT, and Jones tendon transfer are that they are all in-phase tendon transfers and relatively easy to perform.
Contraindications/Limitations
Transfer of any tendon that is already weak will only weaken and not perform as intended [34, 36]. Therefore, the long common extensor must be strong enough to allow for an effective transfer. The goal of this procedure is not to dorsiflex the metatarsals if transferred into each individual metatarsal but only aid in dorsiflexion at the ankle joint. The goal is to remove the deforming force of dorsiflexion at the metatarsophalangeal joints and aid in dorsiflexion at the ankle joint.
Technique, Pearls and Pitfalls
The Hibbs tenosuspension is often not performed alone but in combination with other procedures including hammertoe repair, lesser metatarsal osteotomies, Lisfranc, or midfoot fusions/osteotomies. Either using Smith’s lines or fluoroscopy as an aid, the incision is centered over the lateral cuneiform (Fig. 23.20). The key is to be on the lateral aspect of the longitudinal midtarsal joint axis. This will allow the transfer to aid pronation of the forefoot with active dorsiflexion postoperatively. Care must be given as to the location if a posterior tibial tendon is being transferred as well. There is only so much anatomic area to attach tendons into the bone.
Fig. 23.20
Smith’s lines to aid in incision placement
The four slips of the common extensor tendon are then sutured together for the transfer. A drill hole will then be made either into the lateral cuneiform or the cuboid. The same technique as the tibialis anterior tendon transfer is then performed. The foot is placed in a neutral position, then the tendon is tensioned and passed through the drill hole, and an interference screw is then placed. A suture button is attached to the plantar foot again to aid and augment the transfer.
Poor tensioning of the tendon at the attachment to the bone will significantly weaken the tendon and result in an ineffective dorsiflexion. Tendinitis or spasm may result if the attachment is overtightened to the bone. It is critical not to use a cutting needle when suturing the tendon ends together for transfer and attachment. This may result in rupture of the long extensor tendon due to weakening by the needle weaving through the tendon repeatedly.
Consideration must also be given to reattachment of the distal ends of the tendon slips into the short extensor tendons. If the transfer is being made to increase dorsiflexion at the ankle and not for the severe contracture of the lesser toes, it is possible for the flexor tendons to overpower the short extensors resulting in significant plantarflexion of the toes. This has resulted in a dragging and/or tripping on these toes.
Management of Complications
Complications are fortunately rare but can occur when performing the Hibbs tenosuspension. Failure of tendon-to-bone attachment is the most common obstacle (Figs. 23.21 and 23.22). Failure of either an interference screw or screw anchor can occur. The patient must be cast immobilized for 4 weeks postoperatively and careful weight bearing afterward to prevent rupture of the attachment.
Fig. 23.21
Rupture of EDL after Hibbs tenosuspension
Fig. 23.22
Failure of tendon-to-bone attachment
If rupture occurs, then early diagnosis and treatment are required. Based on the location of the initial attachment, either the reattachment with a larger interference screw with augmentation of a surgical button through the plantar aspect of the foot or use of a corkscrew-type anchor can be utilized.
Bone quality should be assessed when using any bone-type anchor, and augmentation should be done on initial attachment. Augmenting the attachment with suture to periosteum is also beneficial in securing the tendon and treating or preventing rupture.
If flexor digital contracture results from failure to reattach the distal slips to the long extensor tendon to the brevis tendons, then surgery is required. Digital flexor tendon release may be necessary if attachment of the distal extensor slips is not enough to stabilize the toes.
Insufficient length of the tendon for transfer and lack of physiologic tension on the tendon after transfer are two other complications. Typically the tendons are transected at the midshaft region of the lesser metatarsals to allow for more than enough length for transfer. If there is too little tendon available to attach into the lateral cuneiform, then attachment into the talar neck may be required. The foot should be held at 90° to the leg during transfer to ensure proper tension of the tendon complex. If performed correctly in the appropriate patient, this procedure will both correct claw toe deformity and aid in correction of flexible forefoot cavus deformity.
Posterior Tibial Tendon Transfer
Introduction
When correcting the cavovarus foot, proper balancing of muscles is just as important as correction of structural bony deformity. In the cavovarus, the foot posterior tibial tendon (PTT) is commonly a main source for the varus component of the deformity as a result of overpowering the weak peroneus brevis tendon.
Transferring the tendon accomplishes two important goals. First, the removal of the deforming inverted or varus force on the foot structure [2, 4, 7, 27]. There is some question as to the potential complications to the foot structure on PTT transfer; however, the release of the tendon does not cause a subsequent planovalgus deformity [37]. The potential to augment dorsiflexion at the ankle joint is also a major benefit. In severe cases of cavovarus deformity, there is weakness of the extensor tendons and drop foot results. Transfer of the PTT to the dorsum of the foot neutralizes the weakness of the extensor tendons [36, 38, 39].
Indications
When transferring the PTT from the medial foot to the dorsal midfoot, one must remember that this tendon will be out of phase with the rest of the anterior extrinsic muscles. Therefore, extensive neuromuscular re-education must be performed if possible prior to surgery as well as postoperatively, or the tendon must be used for static correction of the varus deformity [39–41]. Transfer of the PTT is performed on patients with significant varus deformity of the foot as well as weakness of dorsiflexors of the foot causing drop foot. The goal is to restore a more normal heel-to-toe gait.
Contraindications/Limitations
The transfer of the PTT to the dorsum of the foot is only performed when there is a significant varus/adducted deformity of the foot, typically with weakness or absent function of the peroneus brevis tendon. The tendon must be strong enough to give enough function once transferred knowing one grade of muscle strength will be lost after transfer [35, 41, 42].
Fixed deformity must be corrected prior to transfer of the PTT. If ignored, tendon transfer will be for naught since no increased motion will result. This correction would either be done by osteotomy or in severe cases, triple arthrodesis. Adequate motion at the ankle is required, and pseudoequinus must also be addressed with either midfoot fusion or osteotomy to lower the arch and place the talus into a functional position within the ankle joint. If equinus is still present, then an Achilles lengthening or gastrocnemius recession is required to allow the PTT transfer to function properly.
Technique
The technique most often performed is through a four-incision technique popularized by Hsu and Hoffer [42]. A medial incision is placed over the PTT insertion onto the navicular. Dissection to the distal tendon and navicular is followed by release of the tendon distal to the navicular tuberosity over the medial cuneiform to ensure maximum length of the harvested tendon (Fig. 23.23).
Fig. 23.23
Detachment of the PT tendon from the navicular tuberosity
A second incision is then placed along the posterior/medial border of the tibia at the myotendinous junction of the tibialis posterior approximately 15–20 cm proximal to the ankle joint. Dissection to the posterior tendons is performed, and the PTT is usually located deep to the flexor digitorum longus tendon directly on the posterior/medial tibia. It is beneficial if you pull on the distal end of the tendon to help find the tendon in this medial incision (Fig. 23.24).
Fig. 23.24
Identification of PT tendon proximal-medial, lower leg
The third incision is placed slightly distal to the second incision just anterior/medial to the fibula. Dissection is performed through the subcutaneous tissue, lateral to the extensor digitorum longus and interosseous membrane. The anterior muscles are retracted and pushed aside to visualize the interosseous membrane. A 4 cm opening is made through the interosseous membrane carefully. The neurovascular structures are just deep to the membrane at this point. A portion of at least 2 cm of the membrane should be removed to allow for adequate movement of the transferred tendon through this hole as the tendon is transferred (Fig. 23.25).
Fig. 23.25
Lateral incision for PT tendon transfer
The fourth incision is made directly over the lateral cuneiform. With the foot held at 90° to the leg, the PTT is then inserted into the lateral cuneiform through a trephine hole with a suture button, utilizing an interference screw, or with the surgeons’ anchoring system of choice (Fig. 23.26).
Fig. 23.26
PT tendon ready for insertion to cuneiform or cuboid
Pearls and Pitfalls
Maximal length must be obtained of the tendon at the medial navicular harvest site. Without proper length, the tendon may not reach the lateral cuneiform or cuboid for insertion. Harvesting a small section of the navicular tuberosity and then careful dissection of the tendon off of that bone can ensure maximal length. Proper mobilization of the tendon as it passes through the interosseous membrane can be another source of difficulty during the procedure. If the window in the membrane is not large enough, there can be stenosis of the tendon causing inability to gain proper length as well as lack of excursion when contracted.
There are two options for routing of the tendon once passed through the interosseous membrane. Transfer of the PTT deep to the extensor retinaculum allows for enhanced tendon excursion but gives up strength of the tendon since it is closer to the axis of motion (the ankle joint). If the tendon is not passed deep to the extensor retinaculum, but within the subcutaneous tissue, then the tendon will lose the pulley mechanism and gain strength in transfer. Unfortunately, there will be an obvious bowstring effect to the tendon when it is above the extensor retinaculum [43, 44]. This phenomenon is represented by the Blix curve, which describes the relationship of muscle length and contractile force [8].
Finally, the foot must be held in the correct position to allow for proper tensioning of the tendon during tendon attachment. The tendon should be secured with the foot in the resting neutral position with adequate tension to place the muscle at its resting length [42]. Excessive tension on the transferred tendon will cause the tendon not to function properly and result in more of a tenodesis [8, 36, 42–45].
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