MINIMALLY INVASIVE PLATE OSTEOSYNTHESIS [MIPO] IN THE TREATMENT OF TIBIAL SHAFT FRACTURE WHERE INTRAMEDULLARY NAILING IS NOT INDICATED................

B Tudu*, M M Sahoo**, M R Mallik**,B S Sahoo***,P K Merly***,Partha Das**** **************************************************************************

ABSTRACT-: The aim of study was to examine the results of MIPO in tibial shaft fracture where intramedullary nailing is not indicated and proper number of screws for stable fixation. It was a prospective study of 24 closed tibial shaft fracture treated with LCP[8 to 14 hole] and screws.19 cases had bony union in an average of 21 weeks .3 cases had delayed union that required bone grafting and union in 36 to 40 weeks.36 fragments were fixed with 3 screws ,24 in cluster and 12 in separate positions.12 fragments were fixed with 4 screws ,9 in cluster and 3 in separated positions. Broken screws were found in 3 cases, all were in cluster variety. Malalignment was the common complication. we recommend at least 3 screws in separate position in each fragment to reduce the risk of screw breakage.

INTRODUCTION-: Closed intramedullary interlocking nailing of tibia is now considered to be the standard treatment for tibial shaft fracture. Over past decade there has been evolution in the technique used for plating of long bones. Plate osteosynthesis is particularly advantageous where intramedullary nailing is not indicated. These may include

1-grossly communited fracture shaft of tibia.

2-fracture proximal and distal shaft where locking is difficult

3 wound at nail entry site

4 fracture in children with growth physis

As a result of technical advancement MIPO has gained popularity in recent years and has achieved satisfactory clinical outcome. The plate is inserted by percutaneous approach by separate proximal and distal incision. This method require less soft tissue dissection ,preserves fracture hematoma ,periosteal blood supply ,decreases contact between bone and implant which results in undisturbed rapid callus and bone healing.

MATERIALS AND METHOD-: A prospective study was performed on all tibial shaft fracture patient treated with the MIPO technique at VSS MEDICAL COLLEGE AND HOSPITAL between 2008 June to 2010 august. The inclusion criteria are communited shaft fracture, open growth plate, nail entry site injury. All fractures were closed fractures and classified according to AO42 a,b,c. The operative time, fluoroscopy time, intraoperative complication, plate length, no and position of screw used in proximal and distal fragment, post operative complication, secondary procedure all noted.

SURGICAL TECHNIQUE:- Under anaesthesia both the lower limbs were prepared for better comparison of rotation and alignment. Indirect reduction by traction was achieved with sanchz pin distracter or external fixator. in distal tibial fracture, associated fibula fracture fixed with one third tubular plate first to achieve better reduction. once fracture reduction confirmed in C-arm LCP introduced away from fracture site over the medial aspect of tibia for better surface contact through extra periosteal approach.LCP has tapered end which helps in easy passage. once plate introduced

completely correct positioning and axial alignment checked in C-arm. Then plate was fixed with proximal and distal locking screws. Patient without any other associated injury were allowed hip and knee movements. Partial wt bearing started with crutches [10 to 15kg] from 4 th postop week onward. The progressive wt bearing was gradually increased as fracture union progress. Radiographic evaluation carried out every 6 weeks till complete healing

RESULTS -: 24 patients with closed tibial shaft fracture were treated with MIPO technique. there were 19 male and 5 female with avg age 34 years. All cases were followed up to 1 year minimum. The avg operative time was 2hours,avg C arm exposure were 17 times. The avg time to full wt bearing was 16 weeks and avg time to fracture unite was 21 weeks. there was no varus or valgus malalignment of more than 10°. 2 cases had shortening of 1.1cm and 0.8 cm. 3 cases got infected , 2 in immediate post operative period which improved with culture sensitivity and suitable antibiotic. One case developed infection after 6 months. In that case bone has already united so plate removed. 2 cases had delayed union with gap that required bone graft as secondary procedure. 3 cases had broken screw, one of them had two broken screws with loosened plate that needed revision. Other 2 cases bone already united , so broken screw removed. all broken screws were in the cluster group.

DISCUSSION:- closed intra medullary nailing is the standard treatment for closed tibial haft fracture. but in certain situation im nailing may not be indicated. in our series out of 24 cases 14 cases had communited fracture,7 cases had proximal and distal metaphyseal fracture where locking is difficult,2 had open growth plate and one patient has previous knee prosthesis.

Biological plating is the concept that is particularly useful in communited articular or metaphyseal or diaphyseal fracture that cannot be nailed. The technique described by Mast et al uses indirect reduction which minimises direct exposure and muscle stripping, reducing the fracture by distraction. In 1997 WENDA and KRETTEK introduced MIPO. Since then MIPO has gained popularity. FAROUK et al studied vascular supply to femur in cadaver and effect of two surgical plating technique MIPO and conventional plating on femoral vascularity. The results showed that MIPO maintained the integrity of the perforators and nutrient arteries and associated with superior periosteal and medullary perfusion.

In our series tibial shaft fracture were treated with MIPO by using LCP. The healing rate was 91.66% and in 2 cases bone graft was needed. The union rate was acceptable as compared to intramedullary nailing. MIPO does not make bone graft unnecessary but surely reduce the requirement of bone graft as compare to conventional plating. MIPO technique allows biological fracture healing by preserving the vascularity of all bone graft thus serving as a living bone graft. therefore primary bone graft is not necessary. However we recommend bone grafting in cases with no signs of callus at 3 month post operative period. In our cases delayed bone grafting done in 2 cases because of large bone gap.

The previous AO\ASIF guideline for a specific no of screws or cortices in each fragment should no longer be used in MIPO as the only information concerning anchoring a plate in the main fragment to achieve good fixation stability. Field et al found that deleting 40% of screws from plate bone construction did not have a deleterious effect on structural stiffness. Tornkvist et al also reported that the wider of bone screws increased the bending strength of screw-plate fixation and can be more effective than increasing the no of screws. from our data we recommend that three cluster screws in each major fragment has chance of screw breakage, so at least 3 separate screws

are preferable. However in our series avg age was 34 years with maximum 65 years. Most of the patient had good quality of bone. So we cannot deduce whether screw fixation in this manner would be effective in osteoporotic bones.

Since fracture is usually reduced closely by indirect technique malalignment is more common as compared to conventional technique. Care should be taken to maintain axial alignment and prevent rotation. In our series varus or valgus deformity was less than 10 degree which was acceptable in 3 cases. Shortening was also seen in two cases which was acceptable.

CONCLUSION:- Our results in this study are comparable to intramedullary nailing. Although the biomechanics of plate fixation is different and less stable as compared to nailing, the mechanical stability is enough for healing. Two major complications are malalignment and screw breakage. We recommend using at least 3 separate screws in each fragment to prevent stress on screws and breakage. Intraoperative limb length, axial alignment and rotation must be carefully assessed to prevent malalignment.

pre op x ray Immediate post op

6 month 12 month

REFERENCES:-

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2. Christopher M. Bono, Richard J. Levine, Juluru P. Rao, Fred F,Beherens- Non articular proximal tibial fracture: treatment option and decision making, Journal of American Academy of Orthopaedic surgeons 2001,9:176-186

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* prof,** asso prof,***asst prof,****junior resident