A young girl presenting bowing of the lower legs

The X-ray of the left lower leg showed anterior bending of the diaphysis of the tibia with signs of microfractures and an old fracture. The fracture could have caused the more pronounced bending of the left leg. Besides the old fracture and the anterior bending, no other abnormalities were observed.

Setting

The Haydom Lutheran Hospital is located in the North of Tanzania, around 300 km southwest of Arusha. It is the largest hospital in the Mbulu area, with more than 400 beds, serving around 300,000 people directly and 2 million as referral hospital. There are 700 staff members including 10-15 doctors. The nearest referral hospitals are in Arusha, six hours away by car. The hospital provides a limited number of laboratory tests, X-rays and a CT-scan (which is often not functioning). There are four major operating theatres with basic facilities. Trauma surgery is performed almost on a daily basis by an orthopaedic clinical officer or by visiting doctors from abroad. Screws, plates and nails are available.

Advice from the specialists

Differential diagnosis

Four specialists replied within two days. The e-mail was also sent to a travelling orthopaedic specialist who would visit Tanzania shortly. One of the specialists had treated a patient with similar malformations and suggested it might derive from congenital syphilis. Others thought that fluorosis or rickets may cause these malformations. Concluding, congenital syphilis and fluorosis were added to the differential diagnosis. The probability of these diagnoses will be discussed shortly.

Congenital syphilis is syphilis which is present in utero or at birth. One of the many possible clinical features is bone malformation. The stages of bone involvement vary considerably [1]. It may involve isolated syphilitic periostitis; however, metaphysitis and osteitis often occur concomitantly. Late effects are most commonly observed on the tibia. Rarely, the “sabre” tibia, also known as “sabre” shin, may be seen as the result of thickening of the anterior aspect of the tibia. Radiographically this appears as cortical sclerosis [1].

Fluorosis is an acquired disorder caused by high-level exposure to fluoride, resulting in dental malformations, skeletal symptoms and gastrointestinal complaints. Normally the dental manifestations precede the skeletal symptoms. Skeletal fluorosis most often manifests as stiffness, pain in the joints and bone changes including osteomalacia, osteoporosis, exostoses and osteoarthritis [2]. Since the presented patient had bone malformations which were present at birth without the described dental deviations and/or stiffness and pain in the joints, fluorosis seems to be unlikely.

Osteogenesis imperfecta is a group of autosomal dominant inherited collagen disorders which mainly affects the bones, but shows a wide spectrum of clinical manifestations. The most severe form of osteogenesis imperfecta is characterized by bone deformations resulting from multiple fractures. One of the possible malformations is bowing of the tibia. Bowing without preceding fractures is unlikely [3].

Osteitis deformans, also known as Paget’s disease, is a chronic condition of the bone characterized by a disorder of the normal bone remodelling process. It normally starts after the 5th decade of life. Symptoms are local pain, easy fractures and asymmetrical bone deformations. Patches of bone thickening are sometimes observed radiographically [4]. As our patient was only seven years old and her condition started with symmetrical isolated tibia bowing, Paget’s disease seems unlikely.

Rickets is a condition of the bone caused by vitamin D and calcium deficiency. The primary defect is inadequate mineralization of the osteoid. Rickets is often seen in young children including neonates. The first symptoms are craniotabes, ankle and wrist swelling, and leg deformities. The most typical leg deformity is acquired and manifests as leg bowing (genu varum). However, genu valgum, windswept deformities and bowing of the long bones occur as well. Sometimes isolated tibia bowing is observed [5]. The absence of other manifestations makes neonatal rickets unlikely.

Our literature research revealed Weismann-Netter syndrome as another cause of isolated “sabre” tibia. Since it was described in 1954, more that 100 case reports have been published. The Weismann-Netter syndrome is characterized by short stature, anterior bowing of the tibia and fibula, increased mass of the fibula, and posterior cortical thickening of both bones in the lower leg [7]. In several case reports the Weismann-Netter syndrome was accompanied by mental retardation. The aetiology of the syndrome is unknown, but the incidence of familial cases suggests a genetic component [7].

In summary, it is not easy to determine which underlying cause is responsible for the bone malformation in the presented patient; especially since not all diagnostic tools were present. In our opinion the Weismann-Netter syndrome is probably the most likely diagnosis because of the presence since birth and the short stature.

Suggestions for management

As the malformations seemed to be isolated and not progressive, the need for an exact diagnosis was not considered as the first priority. All specialists shared the opinion that an operation would be difficult but inevitable. On the X-ray no contraindications for orthopaedic surgery were seen.

Because of the disabling curvature all specialists agreed that the left lower leg should be operated (first). Concerning the right leg, they agreed on an expectative management at that moment. One specialist suggested that the curvature of the right leg might even decrease during growth. Depending on the available materials and the surgical skills of the local doctors different treatment options were suggested.

To correct the curvature of the left leg, the only option would be a wedge osteotomy of both the tibia and the fibula. Two big challenges must be faced: the condition of the soft tissue and the stabilization of the bone structures after surgery.

Concerning the soft tissue, two options were discussed: performing the wedge osteotomy with or without shortening of the lower leg. If one does not shorten the lower leg the traction on the soft tissue on the dorsal side of the lower leg may lead to high tension and necrosis. Incisions could reduce the tissue tension, but it was highly doubted this tension reduction would be sufficient. The safer option would be the combination of the wedge osteotomy with a shortening procedure. The biggest disadvantage of this technique would be the possible function loss of the extension muscles of the foot, as the soft tissue on the ventral side would be too long. If function loss would appear, one could try to treat this with a plaster cast or splint.

The second problem is the stabilization after surgery. One could choose to use a plaster cast which does not inflict any soft tissue damage, but often results in insufficient stability. The second option is external fixation. This leaves the wound in sight and can be used in combination with a leg splint to increase stability. Moreover, it offers the opportunity to adjust the bone position postoperatively. The third option would be internal fixation using osteosynthesis material (e.g. a plate, large bore K-wire, Rush pin or Steinmann pin). This would result in good osseal stability but could cause more soft tissue damage.

The osteotomy with or without shortening of the leg is a difficult procedure and the postoperative complications can be severe. If there is no doctor with sufficient surgical skills, no adequate postoperative care and/or no possibility to refer the patient, an amputation of the left lower leg under the knee joint is a worst-case option. This is only acceptable if it is believed to improve the patient’s condition, there are no better alternatives, and adequate prostheses are available. The operation itself is less complicated and the postoperative recovery and revalidation are less difficult compared to the options mentioned above.

Case report – follow up

A visiting tropical doctor from the Netherlands discussed the treatment options with the father of the young girl. He concluded that in order to improve the patient’s condition and to prevent new fractures, the patient should be operated on by a surgeon with experience in this kind of malformations.

The preferred method would be multiple osteotomies and intramedullary fixation (the “shish kebab technique”). A Dutch orthopaedic surgeon which was contacted by the specialists of Consult Online would be able to do such an operation in Arusha a couple of weeks later. The costs would be taken care of.

After the treatment options had been discussed, the father explained that they did not come for an operation. They only required a written letter from a doctor that explained the condition of the child. Without this letter the girl was not allowed to go to school. According to the father it would not be a big problem if his daughter was not able to walk in the future: ‘We are happy with her the way she is and she is happy too.’
Both the requested letter for the school and a referral letter containing all the clinical information were written and given to the father. If the family ever changed their mind, they would possess the information on the treatment options. After the final consultation father and daughter returned to the small village where they lived.

References

1. Palmer and Reeder, The Imaging of Tropical Diseases, with Epidemiological, Pathological and Clinical Correlation, 2nd edition, ISBN 3540662197, Springer 2001.
2. Gilber, A Small Dose of Toxicology, 2nd Edition, ebook 2011Castriota-Scanderbeg, Abnormal Skeletal Phenotypes: From Simple Signs to Complex Diagnoses, 1st edition, ISBN 3540679979, Springer 2005.
3. Van der Meer, Interne geneeskunde, 13th edition, ISBN 9031341789, Springer 2008.
4. Van der Brand, Kindergeneeskunde, 3de druk, ISBN 9035227115, Elsevier/Bunge 1998.
5. Weismann-Netter and Stuhl. Congenital osteopathy eventually familial defined especially by antero-posterior incurvation and thickening of both bones of the leg; diaphyseal tibio-peroneal toxopachyostosis. Presse Med. 1954;62:1618-1622.
6. Peippo et al., Weismann-Netter syndrome and mental retardation: a new patient and review of the literature. Am J Med Genet A. 2009;149A (11):2593-601