Deformed Tibial Nails: A Case Report and Biomechanical analysis

Mohan Pullagura*, Paul Banaszkiewicz

*Department of Trauma and Orthopaedic Surgery
  Queen Elizabeth Hospital Sheriff Hill,   Gateshead,   UK

Address for Correspondence
Paul Banaszkiewicz, Dept of Orthopaedics, 
Queen Elizabeth Hospital, 
Sheriff Hill, Gateshead, Newcastle. UK. NE9 6SX
E-mail: mohanpk73@yahoo.co.in
            pbanaszkiewicz@hotmail.com 
Tel:      00447766832733, 00441914453214

J.Orthopaedics 2007;4(2)e4

Introduction:

Intramedullary nailing (IM) is regarded as the procedure of choice for stabilization of displaced diaphyseal fractures of the tibia[3]. This is a load-sharing device, which allows early weight bearing through bone.

There are several reported reasons to remove IM nails. These include sepsis, pain and irritation at the point of insertion, the difficulty of treating a new fracture if a nail is in place because the nail can be deformed or the fracture can occur around or at the end of the nail (new fractures are much more difficult to manage when a nail is in place) and breakage of nails following fracture healing.

Excessive loading or repetitive cyclic loading can cause fatigue fracture of a nail especially if the fracture has not fully healed[2]. A high-energy injury can lead to deformation and angulation of the nail. Biomechanically the weakest point is at the site of fracture healing, hence the most common site of angulation[1].

Although it is uncommon to sustain a second high-energy injury after a recent nailing, some patients are eager to return to sports as quickly as possible, which increases the risk of subsequent trauma[11]. The deformation depends on the tensile strength of the nail (diameter), weight of the patient, time of original injury (fracture healing status) and the forces going through the nail and tissue envelope[6].

Case Report :

A 32-year-old man involved in a road traffic accident sustained a closed fracture of the middle thirds of his right tibia. The patient was treated with primary IM nailing on the same day. The medullary canal was reamed to 11mm and a 10mm Î 380mm cannulated ST-Pro tibial nail (Grosse-Kempf model) inserted with 2 locking screws proximally and distally. Postoperative radiographs demonstrated that normal tibial length was restored and the alignment of the fractured bone was normal in all planes. Post-operatively he made an uneventful recovery and was allowed to bear full weight within 4 weeks. After seven months the locking screws were removed under local anaesthesia because they were backing out. The fracture had radiographically united at this stage with callus formation seen on all four-bone cortices in AP and lateral radiographs. Eight months following IM nailing he sustained a second injury when two 15 stone players fell on him whilst playing football. The plain radiographs showed an angulation at the original fracture site and a deformed nail at the same level. The angulation was 11 degree valgus and 26 degree posterior. He was taken back to the theatre and attempted closed in-situ straightening of the nail performed using the three-point fixation principle. The bent nail could only be partially straightened but despite this the nail was successfully removed. Unfortunately it was reluctantly accepted that unavoidable fracture extension would occur with nail removal. The canal was over reamed to 12mm with particular attention to remove fibrous tissue around the fracture site and a 11mm Î 380mm IM nail inserted. The postoperative recovery was uneventful and solid radiological union was noted at 2 months.  

Fig.1 Antero-posterior view plain radiograph showing deformed nail

Fig 2 Antero-posterior view plain radiograph showing healing after re-nailing

Discussion :

There is good evidence that fracture stiffness is a reliable predictor of healing[10], to allow safe return to independent weight bearing and sedentary activities[8]. IM nails have no function after fracture healing[5]. Nails and interlocking screws tend to fail by plastic deformation or fatigue fractures and the failure rate is reported to be about 5-10%[4]. However routine removal of nails is not mandatory because the refracture can be as high as 21% depending on the implant design[9]. There are a few authors who advocate removal of nails 1-2 years after the injury in young and vigorous patients[5].

Even in the presence of osseous bridging across the fracture fragments and with the nail sharing the load of the weight an excessive stress applied has lead to deformation of the nail and refracture through the bone. It has been shown that it takes eighteen months for bone to regain its tensile strength to 80% of the original. Good patient compliance is needed for the osseous healing process of the extremity and conscious exertion of stress (weight bearing) is just as important for healing as an implant material, which should withstand the unexpected excessive stress in the early phases of healing[7].

The implant diameter has been definitely shown to influence the bending strength by a factor of 4. However a 10mm or 11mm nail or a healed fracture cannot achieve the stiffness of the intact tibia.

The biomechanical analysis of the nail showed no corrosion or wear in the metal. The 10mm cannulated nail had a stiffness of 64.3 ± 6.1 Nm² and a yield bending moment of 86.2 ± 3.7 Nm[8]. The force required to permanently bend a nail of this diameter without any contribution from the bone-to-bone contact or from the foot contact with the floor was 718 N (body weight of a 73 kg person). Assuming the bone is healed with the foot on ground covered with the whole soft tissue envelope it would require 10 times the force to cause the same deformation. Therefore to cause re-fracture and nail deformation a force of between 718N(body weight of a 73 kg person) to 7180N(body weight of 730 kg) was required.

Conclusion:

In our case the patient went back to active sports after eight months with good clinical and radiological signs of union. The tensile strength of bone was not fully re –established. We would like to conclude that it might be better to wait till eighteen months before allowing patients to get back to active contact sports or high speed motor diving. This will avoid the complications of refracture, more soft tissue injury or nail fracture while attempting to straighten out the nail or extraction of the nail.

Reference :

1. Apivatthakakul T, Chiewchantanakit S: Percutaneous removal of a bent intramedullary nail. Injury. Nov; 2001; 32(9): 725-6

2. Burzyski N, Scheid DK: A modified technique for removing a bent intramedullary nail minimizing bone and soft tissue dissection. Journal of Orthopaedic Trauma 1994; 8:181-182

3. Court-Brown CM, Will E, Christie J, McQueen MM. Reamed or Unreamed nailing for closed tibial fractures. J Bone and Joint Surgery 1996; 78B: 580-583,

4. Cunnigham J. The Biomechanics of Fracture Fixation. Current Orthopaedics 2002; 457-464

5. David Seligson, Howard P A, Martin R. Difficulty in Removal of Certain Intramedullary Nails. Clinical Orthopaedics and Related Research 1997; 340,p202-206

6. Kelsch G, Kelsch R, Ulrich C. Unreamed tibial nail (UTN) bending: case report and problem solution. Arch Orthop Trauma Surg 2000; 123:558-562, 2003

7. Reeves EA. Testing of ST-Pro tibial nails to ASTM F1264-96b. Biomet Merck Ltd. R&D 2005; Test Report 72

8. Richardson J B, Cinningham J L, Goodship A E, O’Connor B T, Kenwright J. Measuring stiffness can define healing of tibial fractures. Journal of Bone and Joint Surgery (Br); 1994; 76:389-394

9. Takakuwa M, Funakoshi M, Ishizaki K, Aono T, Hamaguchi H. Fracture on Removal of the ACE Tibial Nail. Journal of Bone and Joint Surgery (Br) 1997, 79,3, p444-445

10. Wade R H, Moorcroft C I, Thomas P B M. Fracture stiffness as a guide to the management of tibial fractures. Journal of Bone and Joint Surgery (Br); 2001, 83,4:533-535

11. Yip KMH, Leung KS. Treatment of Deformed Tibial Intramedullary nail: Report of Two Cases. J Orthop Trauma 1996; 10:580-583

This is a peer reviewed paper 

Please cite as :Mohan Pullagura :Deformed Tibial Nails - A Case Report and Biomechanical analysis

J.Orthopaedics 2007;4(2)e4

URL: http://www.jortho.org/2007/4/2/e4

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