Tibial hemimelia: new classification and reconstructive options
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Tibial hemimelia is a rare congenital lower limb deficiency presenting with a wide spectrum of associated congenital anomalies, deficiencies and duplications. Reconstructive options have been limited, and the gold standard for treatment has remained amputation with prosthetic fitting. There is now a better understanding of the genetics, etiology and pathoanatomy of tibial hemimelia. Armed with this knowledge, I present here a new classification to guide treatment and prognosis and then discuss new treatment strategies and techniques for limb reconstruction based on this new classification scheme.
KeywordsTibial hemimelia Weber patelloplasty Paley classification Clubfoot Tibial aplasia Brown centralization of fibula
Tibial hemimelia presents with a wide range of pathology, ranging from a hypoplastic tibia to complete absence of the tibia. The fibula is always present and may be normally formed or dysplastic and, in some cases, duplicate. The quadriceps muscle may be normally formed, distally deficient or absent, and the patella may be normally formed, dysplastic or absent. Similarly, the cruciate and collateral ligaments may be present or absent. The knee may fully extend or have a flexion contracture or dislocation. The foot may be normally formed, deficient or duplicated. The ankle may range from normal motion to fixed equino-varus. Tibial hemimelia can be unilateral or bilateral, with an estimated 30% of cases being bilateral . Spiegel noted that 72% of unilateral cases reported in the literature affected the right side . The degree of dysplasia and type may vary significantly between sides. Unilateral cases have a leg length discrepancy.
The spectrum of pathology in tibial hemimelia is much wider than that seen with congenital femoral deficiency or fibular hemimelia. In fibular hemimelia, deficiency of rays of the foot is common but duplication is never seen. In contrast, in tibial hemimelia there can be foot ray deficiency or, more commonly, foot ray duplication. Duplication of skeletal elements is a hallmark of many cases of tibial hemimelia. This duplication can affect the toes, metatarsals, tarsals, fibula, femur and femoral condyle. At the same time partial or complete deficiency can also affect these same bones in association with tibial hemimelia.
Tibial hemimelia is associated with congenital anomalies affecting the ipsilateral limb either as suppressive or duplicated [3, 4, 5, 6, 7]. Associated anomalies include radial dysplasia, lobster claw deformity, hand syndactyly, polydactyly, triphalagism, missing fingers or toes, hip dysplasia, hip dislocation, coxa valga, hemivertebrae and myelomeningocele [8, 9, 10, 11]. Other associated congenital anomalies include deafness, cleft palate, pseudo-hermaphroditism, cryptorchidism and hypospadias . Schoenecker et al. reported on 57 patients with tibial hemimelia of whom 34 (60%) had other associated congenital anomalies . Launois and Kuss found that 24 of 41 (59%) patients with tibial hemimelia had other congenital associated anomalies .
The incidence of tibial hemimelia is reported to be one per million live births [13, 14]. Parent to child transmission [15, 16] as well as families with multiple siblings affected  have been described. Clark , and Lenz [19, 20] suggested that tibial hemimelia was an autosomal dominant disorder, while autosomal recessive inheritance was described by Fried , Mahjlondji  and McKay . In a breeding trial of Galloway cattle with tibial hemimelia, Ojo et al. implicated homozygosity of a single autosomal recessive gene with variable expressivity and pleiotropic effects on various body systems .
Tibial hemimelia is associated with several syndromes. Werner’s syndrome  is an autosomal dominant disorder that is currently thought to be a variant of triphalangeal thumb-polysyndactyly syndrome (TPTPS). Both diseases have been mapped to chromosome 7q . A deletion on chromosome 8q, contiguous with Langer–Giedion syndrome, or type II tricho–rhino–phalangeal syndrome (TRPS II) may also be responsible for tibial hemimelia . CHARGE syndrome, which is a pattern of congenital anomalies, including eye, nose, ear, heart, and genital defects, as well as tibial hemimelia [28, 29] is a mutation of the CHD7 gene (chromodomain helicase DNA-binding protein 7), located on chromosome 8q. CHD7 is known to be expressed by the developing limb bud mesenchyme [30, 31]. Tibial hemimelia is also linked to tibial hemimelia–diplopodia syndrome , tibial hemimelia–split hand and foot syndrome  and tibial hemimelia–micromelia–trigonal brachycephaly syndrome . The Gollop–Wolfgang complex is a very rare malformation characterized by ectrodactyly of the hand, ipsilateral bifurcation of the femur and tibial hemimelia ; both autosomal dominant and recessive inheritance have been reported for this malformation .
At the molecular level, mutations of an enhancer of Sonic Hedge Hog (SHH) have been implicated in syndromic tibial hemimelia cases [36–38]. Diemling et al  recently described a deletion within the SHH repressor GLI3 in two patients with bilateral tibial hemimelia. They postulated that this leads to failure to restrict SHH signaling in the posterior aspect of the limb bud, which may cause failure of the tibia to form .
The pathoanatomy of limbs affected by tibial hemimelia has been examined. Evans and Smith  found either an absence or duplication of some muscles, with some muscles being functionless and attached to only one bone. Based on their results, these authors postulated a mesoblast disorder. Hovelacque and Noel suggested the same in their study of mouse embryos in 1909 . Turker et al.  dissected limbs with complete tibial aplasia and consistently observed that the affected leg had a dimple where the skin was tethered over fibula. The saphenous and lesser saphenous veins and sural and superficial and deep peroneal nerves were all intact. The posterior tibial neurovascular bundle was found to be short and acting as a tether. The lateral and superficial posterior compartment muscles were intact with normal insertions. The anterior and deep posterior compartments did not have a discrete boundary and their tendons had anomalous courses and sometimes split. There were no identifiable posterior tibial or anterior tibial muscle bellies, but all specimens had a tendon inserting medially on the midfoot that tethered the foot in supination while three specimens had an anomalous tendon inserting onto the neck of the talus. All specimens had a flat tendon-like structure on the anterior border of the fibula that wrapped around and inserted on the posterior capsule of the ankle. The abductor hallucis muscle was always present, even in feet without medial rays. No discrete plantar fascia was found. All specimens had subtalar coalitions, and some had midfoot coalitions and the talus articulated with the distal medial fibula on its posterolateral side.
Kalamchi and Dawe modified the Jones classification eliminating Jones type III and moving Jones type Ib into type II . Kalamchi type I is characterized by a total absence of the tibia, with knee flexion contracture of >45° and no active quadriceps function. The fibular head is proximally migrated with hypoplasia of the distal femur. Kalamchi type II is defined as the presence of distal tibial aplasia, with a proximal tibia present. There is active quadriceps function, with knee flexion contracture of between 25° and 45° present. There is less proximal migration of the fibula. Kalamchi type III has distal tibia aplasia with diastasis of the distal tibio-fibular syndesmosis. A normal knee joint is present and there is good quadriceps function. The talus is subluxated proximally with a prominent distal fibula.
Paley proposed a new classification in 2003  and modified it in 2015 . This classification is being reordered one last time in this review to ensure that the level of deficiency is accurately from the least to most deficient and as such is different than that published in 2015. The Paley classification is unique in that it was developed in direct relationship to treatment and prognosis (Fig. 3). There are five types and 11 subtypes in the Paley classification, as follows.
Paley type 1: Hypoplastic nondeficient tibia: valgus proximal tibia (genu valgum), relative overgrowth of proximal fibula, plafond present and normal
Paley type 2: Proximal and distal tibial epiphysis present with dysplastic ankle
Type 2A: Well-formed distal tibial physis and separate from proximal tibial physis; tibial plafond present but dysplastic; relative overgrowth of proximal fibula.
Type 2B: Delta tibia, proximal and distal growth plates connected through bracket epiphysis, malorientation of ankle and knee joints, ankle joint dysplastic, relative overgrowth of fibula.
Type 2C: Delayed ossification (cartilagenous anlage) of part, or all, of the tibia, dysplastic ankle joint, distal tibial physis absent, relative overgrowth of fibula.
Paley type 3: Proximal tibia and knee joint present, medial malleolus present, distal tibial plafond absent, tibio-fibular diastasis present
Type 3A: Tibial plafond missing, medial and lateral malleolus present, varus diaphyseal bowing tibia, distal fibula (lateral malleolus) with foot internally rotated around tibia, talus may be positioned between the tibia and fibula due to absence of tibial plafond, relative fibular overgrowth
Type 3B: Same as 3A with skin cleft separating tibia and fibula, foot always follows the fibula
Paley type 4: Distal tibial aplasia
Type 4A: knee joint present, complete absence of distal tibia from level of diaphysis, pointed bone end often covered by separate skin pouch, relative overgrowth of fibula
Type 4B: Epiphysis of proximal tibia present but absent proximal physis, knee joint present, delayed ossification of epiphysis, relative overgrowth of fibula
Paley type 5: Complete tibial aplasia
Type 5A: Complete absence of tibia, patella present; flexion contracture of knee, equino-varus contracture of dislocated foot and ankle
Type 5B: Complete absence of tibia, no patella present; flexion contracture of knee, auto-centralized fibula, quadriceps present, knee capsule present
Type 5C: Complete absence of tibia, no patella present; flexion contracture of knee, dislocated fibula, quadriceps absent, no knee capsule present.
Clinton and Birch  tried to classify 125 tibial hemimelia limbs in 95 patients treated at their institution using the Jones classification. These authors reported 73 Jones type Ia, six Jones type Ib, 18 Jones type II, zero Jones type III and 12 Jones type IV cases; there were also 16 ‘unclassifiable’ cases (12.8%). Based on these results, Clinton and Birch  proposed adding a Jones type 5 to represent the miscellaneous ‘unclassifiable’ cases.
Paley, Packer and Burghardt (unpublished study, presented at LLRS meeting, Charleston, SC, July 2016) recently classified 113 tibial hemimelia limbs treated earlier by the author. These authors reported 47 Jones type Ia, five Jones type 1b, 18 Jones type II, two Jones type III and 10 Jones type IV cases; 31 cases in this series were ‘unclassifiable’ (27.4%). The same series was classified by the Weber classification. There were 18 Weber type I, 11 Weber type II, three Weber type IVa, 17 Weber type IIIb, zero Weber type IVa, two Weber type IVb, five Weber type Va, zero Weber type Vb, zero Weber type VIa, zero Weber type VIb, four Weber type VIIa and 47 Weber type VIIb cases; there were also six ‘unclassifiable’ cases using the Weber classification (5.3%).
When this same group of 113 tibial hemimelia limbs was classified using the Paley classification, there were no ‘unclassifiable’ cases and no Paley types without cases. There were five Paley type 1, 11 Paley type 2A, eight Paley type 2B, four Paley type 2C, 12 Paley type 3A, six Paley type 3B, 16 Paley type 4A, four Paley type 4B, 19 Paley type 5A, five Paley type 5B, and 23 Paley type 5C cases. When the various classifications were compared, the Jones classification was by far the quickest and easiest to learn, use and memorize. In comparison, the Weber classification was very difficult to learn, use and memorize and was by far the most confusing and time consuming. The Paley classification, despite having more subtypes than the Jones classification, was still relatively easy to use, learn and memorize, as well as being relatively quick for classifying tibial hemimelia. Its + or − modifier was very helpful in conveying the picture of the associated deficiencies or duplications that were present. The ease of use of the Paley classification of tibial hemimelia, combined with its efficiency and comprehensiveness, suggest that it be proposed as the new standard.
The wide variety of pathoanatomy in tibial hemimelia does not fit perfectly into any classification scheme. One example is the case report by Shrivastava et al. of an intercalary deficiency where the central portion of the tibia is missing but the proximal and distal tibia is intact .
Amputation is the recommended treatment for Jones type I tibial hemimelia [10, 11, 51, 52], although some authors do recommend reconstruction if the deformity is less severe [53, 54, 55], especially if there is a tibial anlage and an active quadriceps mechanism . The presence of a quadriceps is inferred by the presence of a patella. Physical examination and ultrasound and magnetic resonance imaging (MRI) examinations are useful methods to determine the presence of a patella, tibial anlage and quadriceps .
Brown published a surgical procedure for the treatment of Jones type I by fibular centralization in 1965 . This was usually combined with a Syme’s amputation. In his 15-year follow-up study (1972), in which 40 of 56 patients were available for review , 18 required secondary surgery due to a knee flexion deformity, 21/22 were ambulatory, and all but two were wearing braces while ambulatory. Based on the results of the follow-up study, Brown recommended attachment of the patellar ligament to the fibula, pre-operative traction, as well as femoral shortening and soft tissue releases as needed to gain extension. He also recommended surgery before age 1 year for maximal ambulatory and fibular articulation potential. Inferior results were noted with an absent quadriceps muscle.
Most authors have not reported good outcomes with the Brown procedure and have recommended knee disarticulation rather than reconstruction as the best option for total absence of the tibia [51, 52]. Many of the poor outcomes were due to progressive knee flexion contractures, knee instability and poor range of motion. For some patients in whom amputation was not an option, a limb that is weight bearing though less functional was considered a success .
Knee disarticulation has been described for treatment and also remains a salvage option for failed Brown procedures. Kalamachi  treated three children with the Brown procedure, and all went on to subsequent knee disarticulations. The failure was attributed to knee flexion contractures and the absence of active quadriceps function, leading the authors to recommend early disarticulation of the knee without any attempt of reconstruction. Alternatively, if the femur was severely hypoplastic, a femoro-fibular arthrodesis was performed to effectively lengthen the femur, creating a longer lever arm for improved prosthetic fitting. Similar results and conclusions were drawn by Schoenecker et al.  and Fernandez et al. .
Weber  described an innovative surgical procedure in which the patella was converted into a tibial plateau by chondrodesis to the fibula at the time of centralization. The procedure was performed in the face of the severe knee flexion contracture requiring extensive surgical release of the knee contracture. After the patellar arthroplasty was performed, the residual knee contracture together with the foot contracture were gradually distracted with an external fixator to avoid the need to shorten the femur or fibula. This was followed by a chondrodesis of the fibula to the talus. Recurrent deformity due to failure of fusion at the chondrodesis sites were common complications.
In the presence of a tibial anlage (Jones type Ib) or a proximal tibia (Jones type II), some authors report good results with tibio-fibular synostosis [44, 45]. The use of an external fixator prior to reconstruction was reported as helpful to overcome soft tissue contractures . Schoenecker  recommended tibiofibular synostosis for Jones types Ib and II cases, combined with a Syme’s amputation. These patients were functional as below-knee amputees. Spiegel et al.  described some potential complications of amputation in patients with Jones type II treated with distal amputation (Chopart or Syme) due to prosthetic irritation from the overgrowth and prominence of the fibular head.
For Jones type IV deficiencies the options reported are stabilization of the ankle, arthrodesis or amputation [10, 11, 61]. Tokmakova et al.  felt that the treatment of choice was reconstruction of the ankle mortise as their patients were independent ambulators with stable ankles and plantigrade feet.
The author’s approach to surgical reconstruction for tibial hemimelia
Since Brown  introduced centralization of the fibula, many attempts to reconstruct the knee in the most severe types (Jones I) have met with poor results, as previously discussed. Similarly, poor results of reconstruction for Jones types I, II and IV have led most surgeons to conclude that through-knee amputation for Jones type I, through- or below-knee amputation for Jones type II and Syme’s amputation for Jones type IV are the best treatment for each type of tibial hemimelia. In light of the advances in modern prosthetics, the amputation option remains the gold standard and should be considered as the most tried and proven method of treatment. However, advances in the treatment of all types of tibial hemimelia offer new surgical options with excellent functional results as an alternative to amputation. Since the Paley classification was designed as a guide to treatment and prognosis, my discussion of surgical management is presented according to Paley type and subtype.
Paley type 1 tibial hemimelia (Fig. 4)
Paley type 2 tibial hemimelia
Patients with type 2 tibial hemimelia have a proximal and distal tibial epiphysis articulating as the knee and ankle. The knee is mobile but often unstable due to absence of cruciate ligaments and depression or deficiency of part of the tibial plateau. The ankle plafond is present but often dysplastic, and thus does not have much motion despite its presence. The presence of a plafond differentiates it from Paley type 3 tibial hemimelia which is more deficient due to the lack of a tibial plafond. Ankle diastasis is not typical, but some degree may be present depending on the severity of dysplastic changes of the tibial plafond. The foot is usually in equino-varus.
Paley type 2A tibial hemimelia (Fig. 5)
Paley type 2B tibial hemimelia (Fig. 6)
Paley type 2C tibial hemimelia (Fig. 7)
The unossified portion of the tibia will eventually ossify after many years. To accelerate this process, bone morphogenic protein (BMP2) can be inserted into the cartilage. This is an off-label use of INFUSE (Medtronic, Memphis, TN). The basis of its use in tibial hemimelia is the author’s experience using BMP2 in delayed ossification of the femoral neck to promote ossification in congenital femoral deficiency . Ossification of the tibia facilitates lengthening and deformity correction of the tibia through bone. If sufficient parts of the tibia are bony, an osteotomy can be made through the bony portion and pins placed in the bony portion. If an insufficient portion of the tibia is ossified to allow for external fixation, then open surgery is performed to acutely realign the foot with a tibial osteotomy, combined with resection of part of the fibular diaphysis. To ossify the tibial anlage (non-ossified portion of the tibia), BMP2 is inserted into drill holes in the cartilage. Stabilization of the osteotomy is achieved with retrograde axial Kirschner wires through the foot and up the tibia. In most cases, ossification of the anlage is already seen by 3 months after BMP2 implantation surgery. Lengthening is usually done 1 year later, after ossification of the unossified segment of tibia.
Paley type 3A tibial hemimelia (Fig. 8)
One ring is applied to the proximal tibia with one wire and two half pins. The second ring is applied to the foot with three calcaneal and one talar wire (refer to Fig. 12d). The equino-varus deformity is corrected by gradual distraction, then by repositioning the talus under the distal tibial epiphysis. Since the fibula is overgrown relative to the tibia, it does not need to be fixed to the distal ring. Its association with the talus and calcaneus causes it to follow the foot distally. This moves the fibula from its relatively overgrown proximal position down to the normal station.
Once the foot is located under the distal tibial epiphysis, a planned second stage surgery can be carried out. The distal ring and wires are removed. The pin sites are covered by an occlusive dressing and the leg is prepped and draped free. A transverse incision is made on the medial side at the level of the tip of the medial malleolus. The tibio-talar joint is opened, and the distal tibia and proximal talus are exposed. The tibialis posterior tendon is located between the tibia and fibula, where the plafond should have been. It is moved out of this location to allow the fibula and tibia to come together. The tibio-fibular diastasis is treated next. This is fixed by using a syndesmotic suture system such as the TightRope® (Arthrex, Naples, FL), or the Ziptite™ Fixation System (Biomet Sports Medicine, LLC, Warsaw, IN). The syndesmotic suture with its two washers is used to reduce and compress across the diastasis.
The distal end of the tibial epiphyseal cartilage is carved with a knife to the concavity of the tibial plafond, matching the convexity of the dome of the talus, creating a biologic arthroplasty. A retrograde axial wire, perpendicular to the sole of the foot, is passed through the dome of the talus, through the epiphysis of the distal tibia, and continues proximally into the tibial intramedullary canal. If the tibia has a varus diaphyseal bow to it, a percutaneous osteotomy should be made at the apex of this bow with an acute valgus angular correction, thereby straightening the tibia. The wire is advanced up the tibia to stabilize this osteotomy.
The incision is then closed, and the foot ring is reapplied with three new wires. This helps ensure that the foot remains in a plantigrade position. The external fixator is left in place for 3 more months. The fibular wire as well as the transarticular tibial wire should be left in place even after fixator removal. The transarticular wire can be advanced into the calcaneus to allow for weight bearing. I prefer to leave both of these in place for 6 more months. This serves several purposes: prevention of fracture of the now osteoporotic tibia and fibula, stabilization of the ankle joint to prevent recurrence of equinus and retardation of the faster-growing fibula to prevent recurrent relative overgrowth. Six months later, both wires should be surgically removed. A solid Ankle-foot orthosis (AFO) is used until the wires are removed, after which the patient is placed into an articulated AFO with a plantarflexion stop. Physical therapy to regain ankle range of motion is initiated after the transarticular ankle wire is removed.
Paley type 3B tibial hemimelia (Fig. 9)
Paley type 4 tibial hemimelia
In this type of tibial hemimelia, there is a knee joint present. The degree of deficiency of the proximal tibia varies, but the knee is present and functional. To re-establish the integrity of the tibia, the fibula is transferred to the tibia at the level of agenesis of the tibia. The foot is in very severe equino-varus. The lack of a distal tibia precludes a successful functional ankle joint. Previous attempts by the author to perform a biologic arthroplasty by various means, including by transferring the proximal fibula on its vascular pedicle, distally to the level of the ankle joint so as to create a tibial plafond, has met with recurrent deformity and failure. Fusion of the talus to the distal fibular epiphysis remains the best option.
Paley type 4A tibial hemimelia (Fig. 10)
Once the foot is plantigrade and the talus is under the fibula, a second surgery to fuse the ankle and transfer the fibula to the tibia is performed. A few days before this surgery, the only tibial wire is removed to allow its pin site to heal prior to surgery. The foot ring and wires are removed (similar to Fig. 12d (i)). The pin sites are covered with an occlusive dressing (Tegaderm; 3M, Maplewood, MN) to minimize contamination during surgery. After the leg is prepped and draped free, a transverse lateral incision is made over the distal tip of the fibula (similar to Fig. 12f (i)). The distal epiphysis of the fibula and the dome of the talus are exposed. The capsular connections between them are cut to mobilize both bones relative to each other. A small incision is made proximally over the fibular wire. The fibular epiphysiodesis wires are cut proximally and pulled out distally. Two new wires are immediately inserted in the same track to protect the fibula from fracture. The fibula is osteoporotic at this stage, and without an intramedullary wire it could easily fracture due to manipulation that can occur during surgery. These two wires are brought out proximally through the small incision made over the head of the fibula. The distal fibular epiphysis is cut across its ossific nucleus. The talar ossific nucleus is exposed by cutting across the dome of the talus parallel to the sole of the foot (similar to Fig. 12f (i,ii)). The two ossific nuclei are then aligned, and the proximal wires are advanced through the talus and out the sole of the foot to hold the foot plantigrade to the fibula (similar to Fig. 12f(iii,iv)).
A Z-shaped incision is made around accessory skin pouch at the end of the tibia. The proximal longitudinal limb of the Z is medial to the tip of the tibia, the transverse part is in the crease below the tip and the longitudinal distal limb is lateral to the tibia. Fasciotomy of the anterior compartment is carried out. The tip of the tibial bone is uncovered. The anterior compartment muscles are elevated off of the lateral aspect of the tibia, and an extra-periosteal path is dissected to the fibula along the interosseous membrane. The fibula is exposed subperiosteally. The tibia is osteotomized near its tip to create a fresh surface for union to the transferred fibula. The wires in the fibula are pulled back to the level of the planned osteotomy. The fibula osteotomy is made at the level of the tibial cut. The fibula is then shifted over to the tibia under the muscles. The fibula is fixed to the tibia by first advancing the intramedullary wires. The fibula is then plated to the tibia using a mini locking plate and screws. All of the incisions are now closed in layers. External fixation wires are reinserted in the foot. These wires are fixed and tensioned to a ring. Six struts are connected between the femoral ring to the foot ring. The external fixator maintains the alignment of the foot and knee to achieve fusion of the tibia and fibula proximally and of the fibula and talus distally. A transverse fibular wire is added to compress the ankle fusion site. Ankle fusion takes approximately 3 months. After that, the external fixator is removed, leaving one wire buried in the foot and fibula to protect the fibula from fracture. The knee motion is restored with physical therapy. In the future, lengthening of the one bone leg can be carried out without crossing the knee joint. If symptomatic instability of the knee joint arises from the congenital absence of cruciate ligaments, the knee joint ligaments can be reconstructed.
Paley type 4b tibial hemimelia (Fig. 10)
In this type of tibial hemimelia, there is only a proximal tibial epiphysis present and no proximal tibial physis. The proximal tibial epiphysis is often unossified at an early age. The foot is in severe equinovarus, and the fibula is relatively overgrown and proximally migrated at the knee. The treatment preferred is also a two-stage surgery similar to that described for Paley type 4a tibial hemimelia. Since the tibial epiphysis is so small it needs to be fixed to the proximal femoral ring with an axial wire and/or a transverse tibial epiphysis wire to prevent the tibial epiphysis from being transported distally during the distal transport of the proximal fibula. There are two options for the fibular transport. The first option is to bring it down to station and then osteotomize as described for type 4a. The second option is to distract the fibular head below the level of the proximal tibial epiphysis. In this case the proximal tibial epiphysis is fused to the proximal fibular epiphysis (Fig. 10left leg). This has the advantage of preserving and transferring the proximal fibular physis to become the proximal tibial physis, thus reducing leg length discrepancy from the absence of a proximal tibial physis.
Since the proximal tibial epiphysis is too small for plating, intramedullary hooked wires as shown for Paley type 5a tibial hemimelia can be used instead (similar to Fig. 12h, i). If the proximal tibial epiphysis is unossified, then BMP2 is inserted into drill holes in the epiphyseal cartilage. The fixator (similar to Fig. 12i (i,ii)) remains in place for approximately 3–4 months until the proximal fibula fuses to the tibial epiphysis proximally and the distal fibular epiphysis fuses to the talus distally. After fixator removal, a cast is used for 1 month, followed by a knee–ankle–foot orthotic (KAFO). Knee range of motion is restored with physical therapy, including active and passive range-of-motion exercises.
Paley type 5 tibial hemimelia
Complete absence of the tibia presents the biggest challenge for reconstruction because there is no knee joint. While ankle fusion gives good function with little disability, knee fusion leads to significant disability for sitting and climbing stairs. It is preferable to avoid a knee fusion. Even if active knee motion cannot be achieved, a mobile knee joint supported by a brace is preferable to a knee fusion. This is not dissimilar to a paralytic knee from polio. Therefore, the following methods have been developed to reconstruct the knee.
Paley type 5A tibial hemimelia (Fig. 11)
Weber recommended performing the patellar arthroplasty as the index procedure combined with gradual correction of the remaining knee flexion contracture and foot equino-varus, using a circular external fixator (Ilizarov; Smith&Nephew, London, UK). Weber performed the patellar arthroplasty procedure through a longitudinal anterior incision. Fusion of the patella to the fibula was achieved using chondroplasty by suturing perichondral flaps of the patella and fibula together. A biologic arthroplasty of the ankle was carried out to stabilize the foot.
Paley–Weber patellar arthroplasty (Fig. 12)
A transverse concave proximal incision is made over the distal femur and proximal fibula. The fibula, patella and distal femur are exposed. Three lines outlining two visor flaps (like the visor on a motor cycle helmet) are marked. At the medial and lateral ends, the pedicle for each visor is kept as wide as possible. The proximal visor flap contains the patella. The distal visor flap is all capsular. In the Paley modification, the quadriceps muscle remains attached to the superior pole of the patella and no Z lengthening is done to the quadriceps tendon. This allows a new patella to form anterior to the femur. The proximal two visor incisions are made. The most inferior one is made after first detaching the biceps tendon laterally and the semitendinosis tendon medially. The medial head of the gastrocnemius muscle is identified. Dissection is carried out along the lateral border of this muscle to identify and protect the popliteal vessels. Once the vessels are protected, the inferior visor capsular incision is made. The perichondrium on the anterior surface of the patella is incised like the capital letter H, creating two flaps of perichondrium. The superior visor flap is brought under the inferior one to move it distally. If the patella is unossified, it is drilled in a T-shaped fashion to insert BMP2. Bone wax is used to seal the anterior and posterior aspect of the drill hole in the patella after the BMP2 is inserted in order to prevent leakage. The proximal fibular wires are exposed. The distal fibular wires are then exposed through a transverse incision at the tip of the distal fibular epiphysis. The dome of the talus and the distal fibula are exposed with the wires in place. The wires from the fibula are unbent and removed. New wires are immediately inserted. It is important to keep intramedullary wires in the fibula to prevent inadvertent fracture of the now osteoporotic fibula. The wires are retracted distally and the proximal epiphysis is cut across with a knife and then retracted proximally so that the distal epiphysis can be cut across. The fibular epiphyseal cuts expose the ossific nuclei of the proximal and distal fibula. The talus is cut across parallel to the sole of the foot exposing the talar ossific nucleus. The two wires are withdrawn proximally to align the distal epiphysis of the fibula with the ossific nucleus of the talus. The wires are then drilled antegrade through the talus and out the plantar aspect of the foot with the foot held 90° to the fibula. These wires are then withdrawn into the fibula. The upper end of the fibula can be slightly drilled to allow for insertion of the BMP2 with the patella apposed to the fibula anterior drill hole in the patella opposed to the hole in the fibular epiphysis. The two wires exiting the foot are now advanced in a retrograde fashion through the patella, and the wires protruding on the patellar articular surface are bent 180° into a hook. The hook is advanced into the substance of the patella to pull the patella down to the fibula. These two wires need to be pulled below the articular surface to prevent their protrusion into the knee joint. The medial and lateral perichondral flaps are sutured to the side of the fibula. The visor flaps can now be sewn across to each other. At the junction of the quadriceps muscle the remnant of the patella and the muscle are sutured to the inferior visor flap, that was flipped upwards. The remnant of the patella is also sutured to this capsular flap. The inferior aspect of this capsular flap is sutured to the superior edge of the patella in its new position. The inferior aspect of the patella, which is now posterior, is sutured to the posterior capsule. The biceps and semitendinosis tendons are sutured to the lateral and medial aspects of the fibula respectively. The skin is closed in layers over a drain. The wires in the foot can be reinserted. The distal ring is fixed and tensioned to these three wires. The proximal and distal rings are connected with struts. A transverse wire is drilled into the distal fibula and then arced and tensioned to the foot ring, which compresses the ankle fusion site. The two hook wires exiting the plantar aspect of the foot are secured to the foot ring under slight tension.
The external fixator remains on for 3–4 more months. After the external fixator is removed, the patient goes into a cast for a month; when the cast is removed they are fitted for a hip–knee–ankle–foot–orthotic (HKAFO). The brace is reduced from an HKAFO to a KAFO, after a couple years. The KAFO is needed for many years until the knee is sufficiently stable to allow walking without the brace. This is usually after age 10 years, when adequate hypertrophy of the joint surface and fibula has occurred.
Paley type 5B tibial hemimelia (Fig. 13)
Type 5C tibial hemimelia (Fig. 14)
It may take up to 5–6 months to centralize the knee and ankle such that the contractures at the knee and ankle are eliminated, the proximal fibula is centered under the femur and the talus is centered under the fibula. Once this is accomplished, the patient returns to the operating room where the distal ring and wires are removed and the leg is prepped and draped free. Tegaderm dressing is placed over the wire sites at the foot and the upper femoral ring after the patient is prepped and covered with a towel to prevent contact with the more sterile operative field. A transverse concave proximal incision is made at the level of the knee. The peroneal nerve is liberated and decompressed from the fibula. The biceps tendon is detached from the fibula laterally and the semitendinosis muscle is dissected free medially. The tensor fascia lata and its iliotibial band are also detached and mobilized. These three muscles are later connected to the remnant of the quadriceps muscle (usually ends in the mid thigh and does not continue to the knee) if present and then prepared to be transferred to the fibula to act as quadriceps muscle. The transferred muscles are all connected together with the lateral and medial muscles balancing each other and centralizing themselves to the iliotibial band, which acts as a central rib for the connection of all of these muscles. It is eventually attached to the front of the fibula to act as the patellar tendon.
Before connecting the transferred muscle, it is important to release the fibula from the tethering posterior capsule. To avoid injury to the popliteal vessels, the medial head of the gastrocnemius muscle is identified. The vessels can easily be found just lateral to this muscle belly. The posterior capsule can now be safely cut. The next step is to stabilize the fibular head by creating new ligaments to the femur. This is done by creating an interosseous ligament between the femur and the fibula and two collateral ligaments. An allograft anterior or posterior tibial tendon is used. A drill hole is made transversely across the femoral epiphysis. A distal to proximal partial thickness hole is drilled to intersect the transverse drill hole at a T junction. The allograft tendon is split in half for half of its length. Both limbs of the split allograft tendon are inserted retrograde through the distal femoral hole exiting out the medial and lateral sides of the femoral epiphysis. The unsplit portion of the tendon is sutured to the tip of the fibular epiphysis. The lateral and medial halves are then pulled tight and advanced distally to be sutured to the medial and lateral aspects of the fibula. These form the medial and lateral collateral ligaments with a central cruciate-like ligament inside the joint. The fibula is now stabilized and tethered to the femur but is free to flex and extend 90°. Dislocation and recurrent flexion deformity were the main reason for failure of the original Brown procedure. The interosseous ligaments prevent subluxation from occurring while permitting hinge flexion of the two bones. These ligaments help load transfer between the femur and fibula in order to promote hypertrophy of the joint. The muscle transfers can now be sutured to the fibula to substitute for the absent quadriceps muscle. The ankle is fused as previously described. A wire is inserted from the foot through the fibula. The retrograde fibular wires stop at the knee. After the incision is closed, the foot ring, which was removed at the start of the procedure, is reapplied with the circular fixator struts. The foot is immobilized in a plantigrade position and the knee in full extension. One transverse fibular wire is inserted to compress the ankle fusion and to slightly distract the knee. Hinges are placed at the knee to allow the knee to be ranged passively in therapy and at home. The knee is always locked in extension during walking and at rest so as to allow the transferred muscles to heal. An alternative and older method was to advance the fibular wire across the knee to allow the ligaments, capsule and transferred muscles to heal before moving the knee. This wire would be removed 6 months later. The external fixator is left in situ for 3 months and then removed. At the time of removal it is sometimes necessary to cut the fascia lata at the level of the greater trochanter if an abduction contracture has developed. A cast is used for 1 month and then an HKAFO is prepared. While amputation remains the gold standard for treatment of Paley type 5c cases, this type of reconstruction should be considered on one side of bilateral type 5c cases or when amputation is not an acceptable option for the patient. Knee fusion is the other alternative to amputation. To save length, knee fusion could be done instead of the Paley knee reconstruction technique described above. The proximal fibular epiphysis should be fused to the distal femoral epiphysis in a way so as not to damage the adjacent physes of these two bones. This is achieved by minimizing dissection of the epiphyses so as not to devascularize them and by cutting across to the ossific nuclei of both bones. The ossific nuclei can be held in apposition to each other using the external fixator and an intramedullary wire until the knee is fused.
Tibial hemimelia can be best classified with the Paley classification. This classification is based on progressive deficiency and pathoanatomy and as such serves to guide reconstructive options. Combining this better understanding of the patho-anatomy of tibial hemimelia subtypes with improved distraction/surgical techniques offers new improved reconstructive options for all types of tibial hemimelia.
Through-knee amputation remains the most commonly used procedure for complete tibial aplasia (Paley type 5 tibial hemimelia). Amputations are reliable options that can be carried out by most orthopedic surgeons. The presence of a patella has now been shown to greatly improve the prognosis of treatment even for complete tibial aplasia [48, 60, 63]. Staged reconstruction using distraction by the Paley technique should also be considered, at least on one side, in bilateral cases of Paley types 5b and 5c.
Amputation is likely overused in Paley types 2, 3, and 4 tibial hemimelia. Reconstructive results for these types using the newer techniques described herein are reliable and successful in achieving a functional lower extremity. It is important to remember that a stable, painless plantigrade stiff ankle or ankle fusion is very functional and has sensation and proprioception. No prosthetic foot provides sensation or proprioception.
The reconstructive options for tibial hemimelia have improved greatly over the past three decades. With continued success and improvements, they may one day overtake the amputation option.
The author would like to thank Pamela Boullier Ross who illustrated all of the figures in this manuscript. The author would also like to thank the Paley Foundation for funding the cost of making these illustrations and giving permission for their reproduction in the Journal of Children’s Orthopedics.
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