Difficulties experienced by proactive players

Non-union of femoral shaft fractures is a cause of significant morbidity. It is when a fracture has ceased to show any clinical or radiographic evidence of healing and differs from delayed union which is when a fracture heals more slowly than clinically expected for the site or type of fracture. Prolongation of the healing time of fractures has adverse somatic, psychological and socioeconomic effects on patients. A nonunion that occurs despite the formation of a large volume of callus around the fracture site is commonly referred to as a hypertrophic nonunion, in contrast to an atrophic nonunion where little or no callus forms and bone resorption occurs at the fracture site. Occasionally, delayed unions or non unions occur without apparent cause, but in many instances some injury, patient and treatment variables may adversely influence fracture healing leading to delayed union or non union. These variables include: severe soft tissue damage associated with open and high energy closed fractures, infection, segmental fractures, pathologic fractures, poor local blood supply, systemic diseases, malnutrition, corticosteroid use and iatrogenic interference with healing.² Other variables reported to retard bone healing like distraction of a fracture site or interposition of soft tissues in a fracture site have not been examined systematically in experimental studies, but clinical experience shows that they can impair fracture healing.²

Non union is uncommon among femoral diaphyseal fractures treated with interlocking IM nailings.²¹Taitsman et al in their study reported some of the predisposing factors to include open fractures, comminuted fractures with segmental bones loss (Winquist type 4), delay to weight bearing, tobacco use and unreamed nail.^5,21,44,47Ricci et al had no statistically significant

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difference in the non union rate in both groups of retrograde and antegrade IM nailing of femoral fracture³¹ similarly, Wiss et al in their study reported a remarkably low incidence of non union.¹³Giannoudis et al in the study of non union of femoral diaphysis, reported reaming and non steroidal anti-inflammatory drugs (NSAID) as factors which may have inhibited union in 32 patients with non union of fracture of the femoral diaphysis and 67 comparable patients whose fracture had united. Other factors reported include; gender, age, smoking habit, type of fracture, soft-tissue injury (open or closed), type of nail, mode of locking, reaming versus non-reaming, infection, failure of the implant, distraction at the fracture site, and the time to full weight-bearing. They concluded that there was no relationship between the rate of union and the type of implant, mode of locking, reaming, distraction or smoking. However, there was a marked association between non union and the use of NSAIDs after injury and delayed healing was noted in patients who took NSAIDs and whose fractures had united.⁴⁸In situations where unreamed nails were used and there is poor callus formation by twelve week post operative period, treatment will include reaming and exchange nailing using a larger sized interlocking nail.

The use of plate augmentation method has been proposed, Chen et al reported its use as an alternative in their series when the distal fragment of the nail was too difficult to remove.⁴⁹ Twelve patients were treated with exchange nailing and bone grafting and 2 patients received plating and bone grafting.⁴⁹Two of 3 rebroken nails were treated with secondary exchange nailing and bone grafting. Overall, a success rate of 86% was reported.⁴⁹

In cases of non union with distraction at the site of fracture, removal of the proximal or distal screw(s) to enable dynamization may suffice however, rotational stability must be maintained.²¹ 3.20 Implant failure

IM nails without interlocking screws rarely fail as the result of fatigue stress, whereas the design

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of the interlocking nails introduces potential high-stress concentrations at the proximal and distal ends.⁴⁹Many biomechanical factors of nail breakage and the strength of different nails have been studied and improvement in the composition and design of IM nails has markedly reduced the frequency of nail breakage.^2,49Some factors determine the period of nail failure, and they include:

type of metal composition, size of implant, location of non union, pattern of fracture, patients activity and weight.^2,50The common location for fatigue failure is at the site of the non-union, where movement at the fractures sites results in implant deformation, hence nail failure is indicative of non-union of femoral fracture.²The incidence of nail breakage has been estimated to range from 0.5% to 3.3%.^50,51

Nail design is an important factor in relation to the frequency of nail breakage.^50,51 The specific types of nails used probably reflect a local bias. Franklin et al reported 8 broken AO/ASIF or Grosse-Kempf nails and found the most frequent site of breakage was at the junction of the top insertion portion and the proximal slot of the nail.⁵⁰This welded area has been documented previously to be weak.^{51, 52} Mechanical properties of the nail also play an important role in nail breakage. Wilkey and Mehserle tested mechanical characteristics of 8 femoral IM nailing systems and found strength and rigidity increased with increasing nail diameter in some but not all systems.⁵³Flexibility of the nail is important to prevent further comminution during insertion and to promote healing of the fracture by creating a load-sharing device.⁵⁰ Bucholz et al suggested the risk of fatigue failure of the nail for the distal part of the femoral shaft might be minimized by using nails that have a larger diameter and avoiding early weight bearing.⁵⁴However, more rigid and larger nails may result in increased comminution on insertion and are much more difficult to remove when they are broken, even with a custom-made hook.⁵⁴

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Sojbjerg et al measured nail strength and stiffness and found no difference between 12mm and 14mm nails.³⁷Chen et al in reported that all the broken nails were 12 or 13 mm in diameter.

Therefore, we are unsure whether a larger nail would decrease the chance of nail breakage .⁴⁹Fractures in the distal part of femur tend to be associated with breakage of nail more often than fractures located elsewhere.²⁰In their finite-element study, Bucholz et al found maximum stress occurred at the more proximal edge of the two distal holes.⁵⁴Their results indicated that fractures located less than 5cm from the more proximal edge of the 2 distal screw holes produced stress in the nail that was greater than its fatigue endurance limit.⁵⁴However, they were unable to validate this finding because only 1 distal-third fracture was included in their study. Chen et al in their study of the management of nonunion associated with broken IM nail of the femur reported 16 out of 17 nails broke at the upper and middle third, indicating that abnormal stress associated with nonunion or delayed union of the fracture may play a critical role in nail breakage.⁴⁹

Surgical technique is considered a critical factor in nail breakage. Technical errors during nail insertion may weaken the nail and impose stress-risers. Metal corrosion or cracks on the nail may occur with repeated drilling during nail insertion and predispose the nail to breakage.⁴⁹

Furthermore, improper choice of nail size or under-reaming of the medullary canal may result in the weakening of the nail by excessive impaction during insertion of the nail resulting in failure.

49Defects in the fabrication of the nail may be contributory. Premature weight bearing and lack of adequate bone support in a severely comminuted fracture have a higher risk for implant failure in the early postoperative stage.⁴⁹Delayed union and nonunion may play a critical role in the fatigue fracture of IM nails in the late stages of bone healing.⁴⁹

The complications of nail breakage can be minimized by using a nail long enough to be driven down to the subchondral area of the distal femur, especially in distal-third fractures of the femur.

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This increases the distance from the fracture site to the nail holes and decreases the stress-risers.^49,50In patients with comminuted fractures, protected weight bearing should be extended until callus formation is visible radiographically.⁴⁹In addition, changes to the basic design of the nail, such as a thicker nail wall, a wider proximal nail diameter, and reinforced screw holes, may be useful to reduce the incidence of nail breakage.^49,50The SIGN nail is a solid nail and has less breakage rates,⁵However this study aims to evaluate this in our environment. Finally, refinement of manufacturing techniques and the use of newly developed materials are other possibilities for decreasing nail breakage.^49,50

CHAPTER FOUR METHODOLOGY

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