VOL. 79-B, NO. 6, NOVEMBER 1997 969

M. R. Baumgaertner, MD, Associate ProfessorB. D. Solberg, MD, Clinical InstructorDepartment of Orthopaedics and Rehabilitation, Yale University School ofMedicine, Yale Physicians Building, 800 Harvard Avenue, New Haven,Connecticut 06510, USA.

Correspondence should be sent to Dr M. R. Baumgaertner.

©1997 British Editorial Society of Bone and Joint Surgery0301-620X/97/67949 $2.00

AWARENESS OF TIP-APEX DISTANCE REDUCES FAILURE OFFIXATION OF TROCHANTERIC FRACTURES OF THE HIP

MICHAEL R. BAUMGAERTNER, BRIAN D. SOLBERG

From Yale University, New Haven, USA

We compared the results of the surgical treatment oftrochanteric hip fractures before and after surgeonshad been introduced to the tip-apex distance (TAD) as amethod of evaluating screw position. There were 198fractures evaluated retrospectively and 118 afterinstruction.

The TAD is the sum of the distance from the tip of thescrew to the apex of the femoral head on antero-posterior and lateral views. This decreased from a meanof 25 mm in the control group to 20 mm in the studygroup (p = 0.0001). The number of mechanical failuresby cut-out of the screw from the head decreased from 16(8%) in the control group at a mean of 13 months tonone in the study group at a mean of eight months(p = 0.0015). There were significantly fewer poorreductions in the study group.

Our study confirms the importance of good surgicaltechnique in the treatment of trochanteric fractures andsupports the concept of the TAD as a clinically usefulway of describing the position of the screw.

J Bone Joint Surg [Br] 1997;79-B:969-71.Received 9 May 1997; Accepted 8 July 1997

A sliding hip screw with a fixed angle is commonly used tofix trochanteric fractures of the hip, but has a reportedfailure rate of 8% to 13%.1,2 Mechanical failure is usuallydue to cut-out through the femoral head when the fracturecollapses into varus. There is known to be an increased riskof cut-out in older or osteoporotic patients, those withunstable fractures, and after poor reduction or fixation.3-9

Accurate placement of the screw in the femoral head is

essential, but there is no simple method of describing anddocumenting this position.

We have devised the use of the tip-apex distance (TAD)from anteroposterior (AP) and lateral radiographs todescribe the position of the screw within the femoral headand have shown it to be highly predictive of failure by cut-out.10 We now report a prospective study to assess theeffect of the introduction of this concept on the manage-ment of trochanteric fractures of the hip in one hospital.

PATIENTS AND METHODS

We included all patients with trochanteric hip fracturestreated by a fixed-angle sliding hip screw and either asideplate or an intramedullary nail who had complete radio-logical and clinical records and a minimum follow-up ofthree months. Of 146 consecutive patients treated after theTAD concept had been introduced, 118 (118 fractures) metthese criteria. Our retrospective control group was a seriesof 198 fractures (193 patients) treated over the previousfour years.

For both groups, we recorded the patients’ age, genderand medical condition on the rating of the American Soci-ety of Anaesthesiologists.11 Fracture patterns were classi-fied according to the systems of Muller et al12 and ofEvans13 as modified by Kyle, Gustilo and Premer,14 andconsidered as stable (types I and II) or unstable (types IIIand IV). Reduction was assessed on the amount of dis-placement and neck-shaft alignment on immediate post-operative AP and lateral radiographs, being categorised asgood, acceptable or poor. A good reduction had normal orslightly valgus neck-shaft alignment on the AP radiograph,under 20° of angulation on the lateral and displacement ofless than 4 mm on either view. Acceptable reductions metthe requirements as regards alignment or displacement, butnot both. Poor reductions met neither criteria. Implant typeand angle were recorded for both prospective and retro-spective groups.Tip-apex distance. The calculation of TAD (Fig. 1) haspreviously been reported in detail.10 It is the sum of thedistances from the tip of the lag screw to the apex of thefemoral head on AP and lateral radiographs. For researchpurposes we adjusted for radiological magnification using

the known diameter of the hip screw, but for intraoperativeuse the TAD can easily be estimated from the fluoroscopicimages after guide-pin insertion (Fig. 1). It does not differ-entiate between peripheral or shallow placement, but thesmaller values confirm that the implant is more central anddeeply located.

We recommended that the aim should be a TAD of under25 mm, since we had no screw cut-out in our retrospectiveseries when this had been achieved, regardless of any otherfracture or patient variables. For purposes of comparisonwe also recorded the location of the tip of the screw asdefined by Kyle et al14 and Cleveland et al.15 In thismethod the femoral head is divided into superior, centraland inferior thirds on the AP view, and into anterior, centraland posterior thirds on the lateral view, giving a total ofnine separate zones.

A total of 41 attending surgeons operated during both

study periods. Seven were active only during the controlperiod, 28 (68%) during both periods, and six operated onlyduring the study period. At the end of the study, all wereasked to complete a questionnaire about their perceptionsof the fixation of trochanteric hip fractures.

We used Student’s t-test for analysis of interval data, achi-squared test for dichotomous variable data and con-tingency table analysis for multiple categorical data.

RESULTS

The two groups were similar with respect to gender andASA medical rating, but the mean age of the study groupwas 81 years as against 77 years for the control group(p = 0.001). There were more stable fractures in the studygroup (56%) than in the control group (45%) (p > 0.005).

There were 169 (85%) good or acceptable reductions and29 (15%) poor reductions in the control group, as against111 (94%) good or acceptable and 7 (6%) poor reductionsin the study group (p = 0.0002). Intramedullary implantswere used in 28% of the control group and 39% of thestudy group (p = 0.05); the use of 135° sideplates hadincreased, with significantly fewer 145° and 150° devicesbeing used in the study group (p = 0.001).

There were no cut-out failures in the 118 fractures of thestudy group at a mean follow-up of eight months (3 to 19),compared with 16 of 198 (8%) in the control group at amean follow-up of 13 months (3 to 48) (p = 0.0015). In thestudy group, one patient had delayed union in a varusposition after fractures of the sideplate screws and anotherhad deep infection which required removal of the implant.There were three non-cut-out failures in the controlgroup.

For the study group the mean TAD was 20 mm (6 to 40),significantly less than the mean of 25 mm (9 to 63) for thecontrol group (p = 0.0001). The TAD was less than the

970 M. R. BAUMGAERTNER, B. D. SOLBERG

THE JOURNAL OF BONE AND JOINT SURGERY

Fig. 1

The TAD can be estimated during operation by measuring the distancefrom the tip of the guide-pin to the apex of the femoral head on both theAP and lateral fluoroscopic images.

Fig. 2

The distribution of TAD for the study group of 118 fractures (white) and for the retrospective control group of182 fractures, showing those which did not cut out (grey) and those which did (black). The shift to smaller TADvalues, implying more central and deep screw placement, is well shown.

recommended maximum of 25 mm in 87% of the studygroup and in 75% of the control group (p = 0.006; Fig. 2),and the proportion of screws in the central zone in bothplanes was 64% and 43%, respectively (p = 0.0002).

To reduce bias due to changes in surgeons and their skillwe specifically reviewed the results for the 28 attendingsurgeons working throughout both periods. For this groupthe average TAD fell from 26 to 20 mm and cut-out failuresfrom 7% to zero.

Only 62% of the questionnaires were returned. Theperception was that improved technique was responsiblefor the decrease in the rate of cut-out. Of those who felt thatbetter technique was the cause for improvement, 80%highlighted the importance of better screw position, oftenusing the term “central and deep”, but only 20% used theterm TAD in their answer, and only 25% mentionedimproved quality of reduction.

DISCUSSION

We have shown a significant improvement in surgicaltechnique and results after surgeons had been made awareof the current local failure rate and were introduced tointraoperative estimation of the TAD. Many previousreports on the treatment of hip fracture have focused onvariables associated with the patient or the implants, butour study has shown that continuing education andincreased interest in technique can improve results. Johans-son et al16 showed significant improvement in reductionand position of implants when fixation was performed by asmall number of interested surgeons. They did not reportoutcomes, and it was not clear whether the smaller group ofsurgeons had improved, or had been selected because theywere better technicians.

Our questionnaire showed that surgeons had not specifi-cally measured the TAD during operation, but that theincreased emphasis on central and deep placement had ledto improved screw positions.

Other factors not related to improved surgical techniquecould have influenced the results. Although not significantlydifferent, there were more stable fractures in the studygroup, and this would be expected to decrease the rate ofcut-out. There was a shift away from the use of high-angleplate fixation, possibly because the initial study had identi-fied the use of a 150° device as an independent predictor ofcut-out, but the study group was older. An increase inintramedullary fixation did occur, but such devices have notbeen shown to influence the rate of cut-out.17

As this was a prospective study, the surgeons were awareof data collection, and the so-called Hawthorne effect mustapply: the outcome will have been influenced by the studyitself.18,19 During the duration of both treatment periods

there was no change in imaging technology or implantavailability.

We believe that our results confirm that surgical tech-nique is an important factor in the outcome of treatment forintertrochanteric hip fracture, and that it can be influencedby education and improved methods of assessment.

Although none of the authors have received or will receive benefits forpersonal or professional use from a commercial party related directly orindirectly to the subject of this article, benefits have been or will bereceived but are directed solely to a research fund, educational institution,or other non-profit institution with which one or more of the authors isassociated.

REFERENCES

1. Bannister GC, Gibson AG, Ackroyd CE, Newman JH. The fixationand prognosis of trochanteric fractures: a randomised prospectivecontrolled trial. Clin Orthop 1990;254:242-6.

2. Simpson AHRW, Varty K, Dodd CAF. Sliding hip screws: modes offailure. Injury 1989;20:227-31.

3. Larsson S, Friberg S, Hansson LI. Trochanteric fractures: influence ofreduction and implant position on impaction and complications. ClinOrthop 1990;259:130-9.

4. Mainds CC, Newman RJ. Implant failures in patients with proximalfractures of the femur treated with a sliding screw device. Injury1989;20:98-100.

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9. Davis TRC, Sher JL, Horsman A, et al. Intertrochanteric femoralfractures: mechanical failure after internal fixation. J Bone Joint Surg[Br] 1990;72-B:26-31.

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12. Muller ME, Nazarian S, Koch P, Schatzker J. The comprehensiveclassification of fractures of long bones. Berlin, etc; Springer-Verlag,1990.

13. Evans EM. Trochanteric fractures: a review of 110 cases treated bynail-plate fixation. J Bone Joint Surg [Br] 1951;33-B:192-204.

14. Kyle RF, Gustilo RB, Premer RF. Analysis of six hundred andtwenty-two intertrochanteric hip fractures: a retrospective and pro-spective study. J Bone Joint Surg [Am] 1979;61-A:216-21.

15. Cleveland M, Bosworth DM, Thompson FR, Wilson HJ Jr, Ishizu-ka T. A ten-year analysis of intertrochanteric fractures of the femur. JBone Joint Surg [Am] 1959;41-A:1399-1408.

16. Johansson A, Stromqvist B, Bauer G, Hansson LI, Pettersson H.Improved operations for femoral neck fracture: a radiographic evalu-ation. Acta Orthop Scand 1986;57:505-9.

17. Bridle SH, Patel AD, Bircher M, Calvert PT. Fixation of inter-trochanteric fractures of the femur: a randomised prospective compar-ison of the Gamma nail and the dynamic hip screw. J Bone Joint Surg[Br] 1991;73-B:330-4.

18. Bouchet C, Guillemin F, Briancon S. Nonspecific effects in longitud-inal studies: impact on quality of life measures. J Clin Epidemiol1996;49:15-20.

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