Osteopetrosis and fracture: planning and management

Introduction

Osteopetrosis (OP), or marble bone disease, is a rare inherited genetic disorder characterized by increased bone density.¹ This is due to defects in the development and function of osteoclasts.¹ Osteopetrosis occurs in approximately 1 in 300.000 births.²

To date, there has been no definitive cure for OP.³ For most patients, the treatment involves complications, such as fractures, which are observed in 75% of patients.³ Treatment of these fractures is difficult and associated with a high rate of complications.⁴

We aimed to describe the fracture profile, possible complications, and difficulty of management in patients with osteopetrosis.

Methods

This was a retrospective, descriptive study including patients followed for OP and managed for fractures at our institute over a 27-year period between 1996 and 2022, with a minimum 2-year follow-up. We excluded patients with a follow-up of less than 2 years and those with missing data.

The diagnosis of OP was either already known and for which patients were regularly followed up or made following multiple fracture consultations and confirmed by radiological assessment. Patient data included age, sex, history of surgery, and fracture characteristics (type, site, and number).

Indications for the management of patients with osteopetrosis and intraoperative challenges have been reported. We also recorded all the complications encountered.

Clinical and radiological follow-up was carried out systematically in all patients at the second, sixth, and twelfth weeks postoperatively and at the final follow-up.

Data were analyzed using SPSS software version 26.0.

Patient anonymity was maintained during data collection. Written informed consent was obtained from all the participants.

The various parties involved in this work declare that they have no conflict of interest.

Results

Based on these criteria, 21 fractures in eight patients with OP were included in our study. All patients were young adults in their second to fourth decade of life, with a mean age of 28.4 years, 17–42 years). They were predominantly male with an M/F ratio of 3:1. Four patients had a history of orthopaedic treatment for childhood fractures.

A kinship was present in our series. Two patients had brothers. For the others, we found no family ties, but on questioning, four patients reported a fairly high rate of fractures in certain members of their families and were not followed up at our institute.

The majority of fractures involved the femur (17 fractures), followed by both leg bones (3 fractures). Upper-limb involvement is rare. We report a single case of supra- and intercondylar fracture of the left elbow.

The management of these fractures is surgical. Initial plate osteosynthesis was the most common indication (16 fractures), with a Dynamic Compression Plate (DCP) of 4.5 mm for diaphyseal fractures and a Dynamic Hip Screw (DHS) for subtrochanteric fractures ( Figure 1 and Figure 2).

Figure 1. 5 surgically treated femur fractures (over a 16-year period).

Figure 2. Subtrochanteric fracture, right and left, 7 years apart.

Only one patient was treated with an external fixator for an open fracture of the two leg bones, and another patient was treated with intramedullary pinning with a poor radiological result, necessitating repeat surgery ( Figure 3). Three fractures (one femoral and two 2-leg fractures) were initially treated orthopaedically.

Figure 3. Subtrochanteric fracture treated with intramedullary pinning; canal narrowness required revision with plate osteosynthesis.

Owing to the hardness of the bone, there was a high rate of intraoperative incidents involving broken instruments and implants, especially drill bits. However, tapping is difficult. The tap broke twice. We also reported breakage of intraosseous screws ( Figure 4).

Figure 4. Intraosseous fracture of proximal screws.

Given the hardness of the bone, we used certain devices to perforate the bone, such as tungsten drill bits, square points, burs, and taps.

Intraoperative bleeding was significant in most patients. Surgery in one patient was complicated by hemorrhagic shock, requiring transfusion of 6 packed red blood cells and a stay in the surgical intensive care unit.

Post-operative complications were mainly represented by:

Figure 5. Plate fracture treated with removal and replacement with a longer plate, complicated by pseudarthrosis.

A summary of the management of each patient is given in Table 1.

Discussion

Osteopetrosis is a rare disease characterized by increased bone deposition in unresorbed calcified cartilage or primary spongiosis.⁵ Its incidence is approximately 1 in 300.000 births.² The condition is diagnosed based on radiographic findings of generalized osteosclerosis, mainly affecting the axial skeleton and long bones without involvement of the medullary canal.⁵ Brittle sclerotic bones are susceptible to severe fractures following relatively minor trauma, which would not result in fractures in healthy individuals.⁵

Few studies have focused on this subject. Indeed, the majority of publications were case reports.⁶

A personal history of fractures, as well as a family history, must be carefully considered. The diagnosis is often not made during the first consultation.⁷ Standard X-rays can guide the diagnosis, showing sclerosis in the long bones, skull, pelvis, and spine, associated with a characteristic “Erlenmeyer flask” appearance of the distal femur, or a “bone-in-bone” appearance in the spine and phalanges.⁸

Orthopaedic treatment is part of the therapeutic arsenal for these fractures. Indeed, cases of femoral fractures treated with casts and traction have been reported in the literature.⁹ However, longer recovery periods are required, with immobilization averaging three months and reduction difficult to maintain.⁵ This treatment can only be considered for diaphyseal fractures of long bones that are only slightly displaced, particularly in children.⁹

Osteosynthesis is the recommended treatment, despite the risk of failure; however, good preoperative planning and great care during surgery are required to avoid intraoperative incidents.⁶

Conventional plate fixation has shown limited success.^5,6 This could be explained by two factors.

Screw holes and plate ends create stress zones, increasing the risk of fractures.

Plates are prone to fracture because of the high stress they are subjected to during consolidation, which is generally delayed.

Locked titanium plates are a good alternative, as they are less rigid implant systems and therefore less susceptible to damage.⁵

With regard to drilling, some studies have recommended the use of a high-density metal drill bit, a diamond drill bit or a tungsten carbide drill bit considered to be reliable high-density drill.¹⁰ Dawar et al.¹¹ reported the use of multiple drill bits of progressive sizes and introduced the use of powerful high-speed motors to avoid back-and-forth drilling with continuous saline irrigation, thus preventing the problem of thermal necrosis. In addition, self-tapping screws minimize the risk of instrument breakage, eliminating the need for an additional tapping step.⁵

Plate fractures are generally caused by a short plate applied to the proximal femur.^6,12 Because stresses through the proximal femur are very high, any implant that terminates in this region creates stresses at the end of the plate.¹² Most authors recommend the use of longer plates to cover the entire bone.⁶ Table 2 summarizes the difficulties encountered in managing patients with OP and their solutions.

Few authors have described the results of intramedullary pinning in the literature, but they are associated with a high rate of revision surgery.⁷ Ding et al.⁴ recommended predrilling the pin under fluoroscopic control.

Intramedullary nailing is recommended to achieve long-term strength. However, it is very difficult to locate the medullary canal in long osteopetrotic bone.¹³ The procedure is laborious and involves opening the canal using drills and reamers adapted to this bone.¹³

Bone consolidation takes longer in patients with OP; therefore, the ban on weight-bearing must be prolonged. The time required for bone consolidation on the femoral shaft in these patients is approximately one year.⁷

Complications associated with fixation in patients with osteopetrosis should be considered when managing these fractures. Early complications consist mainly of significant blood loss, which can lead to hemorrhagic shock due to laborious synthesis and early sepsis of the material due to prolonged operating time.¹⁴ Late complications are fairly frequent, mainly delayed consolidation or pseudarthrosis due to the nature of the bone,¹⁵ fracture above or below the plate due to the biomechanical constraints imposed by the implant,⁵ and plate fracture due mainly to pseudarthrosis.¹² A less frequent complication is chronic sepsis, explained by some authors as a result of frequent haematological disorders in these patients, leading to disruption of the local vascularization of the bone and, hence, to poor resistance to infection.⁷ The reoperation rate reported in the literature is 29%.^5,16

The limitations of our study lie in its retrospective nature and small sample size; however, this is a rare pathology, with a small series in the literature. A multicenter study would enable better generalization of the results and could potentially lead to a consensus regarding fracture management in patients with OP.

Currently, there is no specific curative treatment for fractures in OP.¹ However, a better understanding of the pathology could eventually lead to the development of less invasive treatments with fewer complications.

Conclusion

OP fractures are a challenge for orthopaedic surgeons. Long-term follow-up is essential for the early detection of possible complications.

Orthopaedic treatment may be indicated for fractures of the long bones that are only slightly displaced, particularly in children. In all other cases, surgical treatment with plates remains the gold standard treatment. However, this surgery is lengthy and difficult. The prolonged duration of the operation and risk of infection must be clearly explained to the patient.

Good preoperative planning is essential to anticipate intraoperative technical difficulties. The risks and benefits of each fixation modality must be considered during planning.

Consent to publish

Written informed consent was obtained from all participants (or their legal guardians) for publication of this study, including relevant clinical details and accompanying images.