Presentation on theme: "SLIDING HIP SCREW FIXATION FOR PROXIMAL FEMUR FRACTURES: AN ANALYSIS OF THE PREDICTIVE FACTORS OF FAILURE Dr Tao Shan Lim MBBS Grad Dip Surg Anat Mr."— Presentation transcript:
1 SLIDING HIP SCREW FIXATION FOR PROXIMAL FEMUR FRACTURES: AN ANALYSIS OF THE PREDICTIVE FACTORS OF FAILUREDr Tao Shan Lim MBBS Grad Dip Surg AnatMr Karl Stoffel MDDr Rochelle Nicholls PhDDr Bianca Billik MBBSFremantle Orthopaedic UnitFremantle HospitalWestern AustraliaMr Chairman, ladies and gentlemen, this paper is a radiological analysis of failures of sliding hip screw fixation from a series of 731 proximal femur fractures.
2 The Sliding Hip Screw Trochanteric region #’s Maximises healing potentialElderly / co-morbiditiesThe sliding hip screw is designed for fractures of the neck and trochanteric region of the proximal femur. The patients are often elderly with multiple co-morbidities and are not a good candidates for re-operation.
3 Failure 8 – 23% Bone quality Fragment geometry Reduction Implant placementThus it’s concerning that the literature reports failure rates of between 8 and 23 percent, which is quite a high figure. Several predictive factors have been proposed however there is no clear consensus as to which is most important.Kaufer, Clinical Orthopaedics 1980, Jan-Feb:53–61.Dodds & Baumgaertner, Current Opinion in Orthopedics 2004, Feb:12-17
4 Baumgaertner, 1995 Tip – Apex Distance > 25mm 19 failures in 198 fractures (9.6%)16 cut outBaumgaertner’s landmark paper published in 1995 introduced a new measurement, the Tip Apex distance. When over 25mm it is strongly associated with hip screw cut out.Baumgaertner et al, J Bone Joint Surg Am Jul;77(7):
5 Baumgaertner, 1995 Tip – Apex Distance > 25mm 19 failures in 198 fractures (9.6%)16 cut out5 different devices142 sliding hip screw (3 manufacturers)56 intramedullary nail (2 manufacturers)What is often overlooked is that the results were derived from five different implants.Baumgaertner et al, J Bone Joint Surg Am Jul;77(7):
6 Study Aims Local experience of use Identify failures Dynamic Hip ScrewExclusive use since March 2001Identify failuresIdentify predictive factorsThe aim of our study was to describe the local experience of the Dynamic Hip Screw, and to identify failures and predictive factors. This implant is the only sliding hip screw in use at the three Western Australian Tertiary Hospitals.
7 Study Design Retrospective radiological audit 731 cases 701 patients 2002 – 2004We performed a retrospective radiological audit of 731 consecutive cases in 701 patients, over a three year period from 2002 to 2004.
8 Inclusion Criteria New adult proximal femur fracture Adequate imaging PreoperativeImplantInclusion criteria was a new adult proximal femur fracture with adequate imaging.
9 Methods Theatre database Ortho techs PACS Revision Cause A case listing from the theatre database was accompanied by implant data from the orthopaedic technicians’ files. All radiographs were assessed on the PACS system. Revision procedure was the recognized end point, and its’ cause identified as failure.
10 PACS Picture Archiving Computer System Fremantle Hospital 2001Sir Charles Gairdner Hospital2004Royal Perth HospitalFor consistency we included cases with imaging on the statewide Picture Archiving Computer System. This had been in place at Fremantle Hospital since 2001, and at Sir Charles Gairdner and Royal Perth Hospitals since 2004.
11 Fracture Classification AO / MullerEvan’sAll fractures were classified according to the AO / Muller classification,Müller et al; Manual of internal fixation: techniques recommended by the AO-ASIF group, ed 3, Berlin, 1991, Springer-Verlag
12 Fracture Classification AO / MullerEvan’sAs well as Evan’s method, which assesses position after fixation as stable or unstable.Evan E. J Bone Joint Surg 1949;31B:190–203
13 X-rays 1. Reduction Alignment AP Normal or slight valgus Alignment LateralLess than 20 degrees tilt of femoral headWe assessed implant imaging in three ways in a similar manner to Baumgaertner’s paper. Reduction consisted of two items: alignment and displacement. The former requires avoidance of valgus and excessive head fragment tilt.
14 X-rays 1. Reduction Displacement Less than 5mm displacement of any bone fragmentThe latter required less than 5mm displacement of any fracture fragment. Combining the two gives a good, acceptable or poor reduction.
15 X-rays 1. Reduction 2. Tip – Apex Distance In addition, The Tip-Apex distance as per Baumgaertner…Baumgaertner et al, J Bone Joint Surg Am Jul;77(7):
16 X-rays 1. Reduction 2. Tip – Apex Distance 3. Position of screw in femoral headAnd the position of the screw in the femoral head, by Cleveland’s method, were also recorded.Cleveland et al, J Bone Joint Surg Am Dec;41-A:
17 Exclusion Criteria Not a fracture Inadequate imaging 1 case (myeloma) 11 cases12 patients were excluded from the study, one without a fracture and 11 with inadequate imaging.
18 Demographics 387 Females, 120 Males Mean age 80.9 years Female : Male : 1Mean age 80.9 yearsRange 15.0 – 106.2SD 13.0The eligible study population consisted of 538 females and 193 males, with a mean age was 82 years.
19 AgeOver 90 percent of the patients were aged over 70…
20 ASA ScoreAnd the mean American Society of Anaesthesiologists score was 2.78.
21 Radiological Follow Up Intraoperative only25.3%Postoperative X-ray within 2 weeks33.8%X-ray between 2 weeks and 3 months17.9%X-ray after 3 months23.0%Current practice is to do follow up imaging on clinical grounds only, thus only 23% of cases had imaging after 3 months.
22 Surgeon Consultant 10.7% 41 min Fellow 1.8% 43 min Training registrar 50.6%39 minService registrar36.9%50 minTraining and service registrars performed the bulk of the cases, 51 and 36 percent respectively.
23 Surgeon Consultant 10.7% 41 min Fellow 1.8% 43 min Training registrar 50.6%39 minService registrar36.9%50 minP < 0.001The mean operating time was 43 minutes, with service registrars taking significantly longer than more senior staff.
24 Fracture Region 22.4% 76.3% 1.2% N = 164 N = 407 N = 9 Looking at fracture classification, about 22 percent occurred in the femoral neck and the remainder in the trochanteric region. We will discuss results of trochanteric group in this presentation.22.4% % %N = N = N = 9
25 Trochanter vs Neck Age (years) ASA Contralateral #NOF 82.7 2.85 11.5% 75.12.526.7%Patients with trochanteric fracture were of older age and poorer medical status than patients with femoral neck fracture, and were more likely to have had a previous contralateral fracture.
26 AO / Muller Classification 26646.9%23541.4%5710.1%N = 9Using the AO classification, pertrochanteric fractures accounted for nearly 90 percent of cases. Half of these were simple and half were multi-fragmentary.
27 AO / Muller Classification 26646.9%23541.4%5710.1%N = 9True intertrochanteric fractures made up the remainder.
28 AO / Muller Classification 26646.9%23541.4%5710.1%N = 9There were very few subtrochanteric and reverse oblique cases.
29 Evan’s Classification According to Evan’s classification, only 26% of fractures in this series were unstable.73.7%N = 41826.3%N = 149
30 Reduction Good 336 59.3% Acceptable 125 22.0% Poor 106 18.7% Here is an example of a poor reduction, with varus alignment and fragment displacement. This occurred in 18 percent of cases.
31 Cleveland ZoneThis diagram indicates the hip screw locations in the femoral head. about two thirds of hip screws were placed in the desired central central location. The remainder were three times more likely to be posterior than anterior.
32 Tip – Apex Distance Mean 20mm Stable ≈ unstable Range 5 to 44 SD 6.1 20 vs 22 mmThe mean tip-apex distance was 21 millimetres, with a range of 5 to 44 millimetres. In both stable and unstable fractures a similar mean distance was achieved.
33 Tip – Apex DistanceMore than three quarters of cases had a Tip – Apex distance of less than 25mm.
34 Failures 14 revisions - 2.5% 10 cut out 4 failures of plate screws In 567 cases!10 cut outSuperior breach of femoral head4 failures of plate screws“Reverse cut out”We found only 11 failures requiring revision in this group of 414 trochanteric region fractures, a failure rate of 2.7%.
35 Failures 14 revisions - 2.5% 10 cut out 4 failures of plate screws In 567 cases!10 cut outSuperior breach of femoral head4 failures of plate screws“Reverse cut out”There were 10 cases of cut out, requiring revision to total or hemi arthroplasty
36 Failures 14 revisions - 2.5% 10 cut out 4 failures of plate screws In 567 cases!10 cut outSuperior breach of femoral head4 failures of plate screws“Reverse cut out”And 4 failures of plate screws, requiring redo fixation.
37 Cut Out - TADP < 0.001Cases of cut out had a mean Tip Apex Distance which was significantly higher, 32mm compared to 20 millimetres.
38 Cut Out - TAD Cut Out TAD < 25 TAD ≥ 25 Yes 10 No 437 120 Total 0% 10No437120Total0%7.7%A tip apex distance of 25mm or more had a 7.7% chance of cut out, compared to zero for those under 25mm.
39 Cut Out Evan’s Unstable Displacement > 4mm Varus reduction 10 of 10 All ten cases of cut out occurred in unstable fractures in which there was unacceptable displacement; and eight of ten had a varus reduction.
40 Cut Out – Cleveland Zone This diagram shows cases of cut out by screw position in the femoral head. I will draw attention to a few crucial locations; here in the superior anterior zone 3 screws were placed and one cut out…
41 Cut Out – Cleveland Zone In the posterior zones there were four cases of cut out. While the posterior direction are advocated by some authors these screws were quite a long way off from the central cylinder of the head here. To the right we can see some of the consequences of such positioning.
44 Bivariate Regression Rank Variable P value 1 Tip-Apex Distance 2Evan’s Unstable9.10 x 10 -83Poor Reduction5.25 x 10 -74Inferior Posterior Hip Screw9.85 x 10 -65Superior Anterior Hip Screw3.11 x 10 -5Bivariate regression revealed Tip Apex distance as having the strongest relationship to cut out. This was followed by Evan’s unstable fracture, poor reduction, inferior posterior hip screw position and superior anterior hip screw position, Variables with no relationship included age, gender, medical status, surgeon level and plate angle.
45 Multivariate Regression RankVariableP value1Tip-Apex Distance1.58 x 10 -62Evan’s Unstable4.30 x 10 -33Poor Reduction6.21 x 10 -1A three variable model found tip-apex distance of over 25mm to be the most significantly associated with cut out.
46 Failure Rate of 2.5%? Choice of implant Quality of results Less unstableQuality of resultsMean TAD 20mm (Baumgaertner 25mm)Computerised PACSStatewide tertiary catchmentOne might wonder, why is the failure rate so low, less than three percent? Firstly some positive explanations. There is growing awareness that not all trochanteric region fractures are the same. 74% of fractures in this series were stable, compared to 45% in Baumgaertner’s series from a decade ago. The remainder may be getting an intramedullary device instead.
47 Failure Rate of 2.5%?To illustrate, here is a sample of usage of the Synthes Proximal Femoral Nail at Fremantle Hospital, during the same period.
48 Failure Rate of 2.5%? Choice of implant Quality of results Less unstableQuality of resultsMean TAD 20mm (Baumgaertner 25mm)Computerised PACSStatewide tertiary catchmentWith a mean Tip Apex Distance of 21mm, this series was more “on target” than Baumgaertner’s. The benefits of a single model of implant include better staff performance and validity of results.
49 Failure Rate of 2.5%? Choice of implant Quality of results Less unstableQuality of resultsMean TAD 20mm (Baumgaertner 25mm)Computerised PACSStatewide tertiary catchmentThe computerised PACS system provided high quality images and a state wide catchment; this may explain why the exclusion rate in this series is far lower than many others.
50 Study Weaknesses Level IV evidence Observer bias Loss of failures to the private sector? X-rays on clinical needNow for the negatives. Our study has a number of weaknesses. It is level IV evidence and we cannot control for observer bias at this stage. 15% of patients were insured, and failures in this group may have been lost to the private sector. By not routinely imaging patients after three months we may be missing further failures.
51 Summary Accurate reflection of experience Captures all complications and revisions in Western Australian tertiary centresTo conclude, we feel that this study is an accurate reflection of the local clinical experience with the Dynamic Hip Screw. It shows a low failure rate and captures all the complications and revisions at tertiary centres in the state of Western Australia.