International Orthopaedics (SICOT) (1995) 19:265-268 International Orthopaedics

© Springer-Verlag 1995

Critical steps in total knee arthroplasty

A method of analyzing operative procedures

M. J. Dunbar and M. Gross

Division of Orthopaedics Department of Surgery, Dalhousie University, Halifax, Nova Scotia, Canada B3H 2Y9

Accepted: 1 March 1994

Summary. We have analyzed the operation o f knee arthroplasty using the Whiteside Mark H prosthe- sis, and found that it could be broken down into 42 steps, some of which are more important than others and can be considered as critical. We have identified 4 criteria to evaluate a critical step: 1) it must be necessary to complete the procedure, 2) it must take a significantly longer time to perform than other steps, 3) it must be revised significantly more frequently than other steps and 4) it must take significantly longer to revise than other steps. Two steps have been found to which all 4 criteria ap- plied, namely placement o f the femoral cutting j ig and the first femoral saw cuts.

R~sum(L Nous avons trouvi it l'analyse de la technique opdratoire de l'arthroplastie du genou par la proth@se Whiteside Mark H que cette in- tervention consiste en une succession de 42 dtapes distinctes. Certaines de ces dtapes sont plus im- portantes que d'autres et jouent un r6le cl~. II n'existe pas dans la litt~rature de m6thode per- mettant d ' i tablir qu'une ~tape donnde d'une in- tervention joue un r6le cld dans cette intervention. Notre analyse a identifid quatre caractiristiques d'une dtape cl~: 1) l'opdration ne peut Ytre pour- suivie sans cette dtape; 2) la durde de l'~tape cl i est nettement plus longue que celle des autres dtapes; 3) l'dtape requiert des corrections nette- ment plus souvent que les autres dtapes; et 4) ces corrections prennent nettement plus de temps que pour les autres ~tapes. Grg~ce it cette mithodologie rigoureuse, deux dtapes ont montrd les quatre ca-

Reprint requests to: M. Gross

ract~ristiques requises et peuvent donc 6tre appe- lies dtapes cld. Ce sont le positionnement du guide de coupe f imorale et les coupes f imorales initia- les. Nous croyons que cette mdthodologie analy- tique peut s'appliquer it d'autres interventions chirurgicales afin de mieux comprendre le ddtail de leur complexitE

Introduction

An operation may be thought of as a single inter- vention, similar to the prescribing of a medicine, but on closer analysis it is seen to be a series of linked events or steps. Not all steps are of equal importance [1, 2, 3] but so far no method has been described to assess which are more significant than others. We have attempted to identify the critical steps in arthroplasty of the knee using the White- side Ortholoc II prosthesis.

Materials and methods Five third year residents and 2 fourth year residents of the Dalhousie Orthopaedic Programme, Halifax, N.S. Canada were observed performing the Whiteside Ortholoc II replace- ment arthroplasty of the knee under the direct supervision of 7 staff surgeons at the Victoria General and the Halifax Infirmary Hospitals over a 3 year period from 1989 to 1992. Thirty eight operations were assessed with the resident as the primary op- erator assisted by the staff surgeon. Each step in the procedure was identified and the length of time required to complete it recorded. Timing for each step began when the surgeon picked up the required instrument and stopped when it was discarded. Revision of a step, defined as a repetition or modification of the step after it had been initiated, was timed separately.

266 M.J. Dunbar and M. Gross: Critical steps in total knee arthroplasty

Table 1. Composite of steps for whiteside TKA obtained by pooling all surgeons techniques

Step description

1 Positioning, prep, and drape 23 Tibial cuts 2 Skin incision 24 Bone removal 3 Fascial capsule Incision 25 Tibial cleaning 4 Retractor placement 26 Tibial planer 5 Femoral preparation 27 Trial components 6 Femoral drilling 28 Lavage 7 Irrigation 29 Bone graft 8 Femoral reaming 30 Tibial real components 9 Femoral jig placement 31 Drilling and screw insett 10 Saw cut checks 32 Real femoral component 11 1st femoral saw cuts 33 Patellar thickness measure 12 Distal gauge attachment 34 Patellar surface prep. 13 2nd femoral saw cuts 35 Irrigation 14 Jig removal 36 Patellar comp. Place and fix 15 Bone removal 37 Irrigation 16 Meniscectomy 38 Post operative thickness measure 17 Tibial preparation 39 No thumb tracking test 18 Condylar notch removal 40 Soft tissue release 19 Template sizing 41 Drain insertion 20 Tibial drilling 42 Closure 21 Tibial reaming 22 Tibial jig placement

The data was stored in a Lotus 123 (TM) spreadsheet and transferred to a Minitab (TM) for statistical analysis. One-way analysis of variance tests were performed on the data sets using Tukey's procedure to delineate which steps were statistically different.

Results

Forty two steps were identified for the Whiteside TKA procedure (Table 1), but not all were used in each operation. On average, each of the 7 staff surgeons, who dictated the conduct of the opera- tion, used 30 of the identified steps to complete the procedure (Table 2), and there was no statistically significant difference (p > .05) in the number of steps used. Each surgeon used a different combi- nation of 30 steps out of the 42. The average time spent in the operating theatre is represented by steps 1-42, and the time from skin incision to closure by steps 2-42. However, there was a sig- nificant difference in the time taken by individual surgeons. On average, 2 steps were revised in each operation, taking 2.2% of the total operating time.

Of the 42 composite steps only 23 were always utilised by all surgeons (Fig. 1).

The average times required to complete each step as a percentage of the total operating time were significantly different (p < .001). Eight were identified as significantly different from the other 34 steps using the T-method, and these are marked with an asterisk in Fig. 2. They are described in Table 3 with the average length of time taken to perform them, and illustrated in Figure 3.

In Table 3 the average time was calculated from the number of times the step was actually per- formed. The mean total operating time was mea- sured from all the 38 procedures undertaken, and the average % of this time for an individual step was calculated whether or not the step was actually undertaken.

The 8 steps identified as significantly different in Fig. 2 constitute slightly more than half of the total operating time (Fig. 3).

Step 1 (positioning, preparation and draping) and step 42 (closure) account for roughly one quarter of the operating time. "Unaccounted time"

Table 2. Average values for the performance of steps and revisions (n = 38)

Average STD Maximum Minimum

Number of steps 29.54 2.63 35 25 Total OR time (min) 81.36 15.94 118.48 49.60 Skin-skin time (min) 72.63 15.70 108.87 43.48 Number of revisions 2.11 0.89 6 0 % of total OR 2.20 2.35 11.65 0

M. J. Dunbar and M. Gross: Critical steps in total knee arthroplasty 267

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Fig. 2. The average percentage of total operation time (n = 38) required for each of the forty-two identified steps (*p <0.001). Total operation time refers to time elapsed from the beginning of positioning the patient to the end of skin closure Fig. 5. The average percentage of total operation time (n = 38)

required for revision of an identified step (*p < 0.001). Total operation time refers to time elapsed from the beginning of positioning the patient to the end of skin closure

Fig. 3. Schematic representation of the average percentage of total operation time (n = 38) required for steps which took statistically significantly longer to perform as identified in Fig. 2

in Fig. 3 is the time taken between steps and is accounted for by unwrapping prosthetic compo- nents, changing saw and scalpel blades, etc. This comprises 21% of the total operating time.

The frequencies of revisions of individual steps are significantly different (p < .001). Again, using the Tukey's procedure, 5 steps are identified as being revised with a frequency significantly greater than the other 37. These are marked with an asterisk in Fig. 4 and also appear in Table 4.

The average percentage of total operating time required to revise each step is significantly dif- ferent (p < .001). The T-method identifies 3 steps

268 M.J. Dunbar and M. Gross: Critical steps in total knee arthroplasty

Table 3. Steps requiring a significantly greater % of total O.R. time for completion

No. Description Average time Average % of total time

1 Position, prep, and drape 9.23 rain. 11.53 3 Fascial capsule incision 3.37 rain. 4.16 9 Femoral jig place 3.01 min. 3.79

11 1st saw cuts 2.79 rain. 3.44 27 Trial components 4.07 min. 5.01 30 Tibial real comp. 3.09 rain. 3.79 36 Patellar comp. placement 7.53 rain. 2.93 42 Closure 13.03 min. 16.62

Table 4. Steps revised with a significantly greater frequency than the majority of steps

No. Description Frequency Average % of total OR time

3 Fascia1 capsule incision 18.42% 0.16% 9 Femoral jig placement 18.42% 0.43%

11 1st femoral saw cuts 36.84% 0.44% 13 2nd femoral saw cuts 21.05% 0.16% 23 Tibial cuts 47.37% 0.41%

as significantly different from the other 39, and these are marked with an asterisk in Fig. 5.

(ii)

(iii)

and (iv)

Discussion

An objective statistical method can be used to identify important steps in the Whiteside TKA. Four types of data were collected, namely the frequency of performance of a step, the length of time required to perform it, the frequency of re- vision of a step, and the length of time required to make the revision. When simple statistical meth- ods, such as one-way ANOVA and Tukey's pro- cedure, are used significant differences between the surgical steps can be identified. From this in- formation we have identified 4 criteria for defining the "critical steps" of the operation. They are: (i) The step must be performed by every surgeon

in each operation, It must require significantly longer time to complete than other steps, It must be revised with a frequency sig- nificantly greater than other steps,

It must require a significantly greater per- centage of total operating time to revise than the other steps.

Two steps fulfilled all 4 criteria. These were step 9 (femoral jig placement), and step 11 (1st femoral saw cuts). Step 3 (fascial capsule incision) and step 23 (tibial saw cuts) met 3 criteria. The remainder of thes teps satisfied 2 criteria or less.

Both of the critical steps involved the use of the femoral cutting jig, which is of vital importance considering the need for accurate bone cuts in the positioning of the femoral component [1, 4, 5], particularly in relation to femoral tracking [2]. This method of analysis can be applied to any surgical operation or other procedure which is a series of linked events. Critical steps in a surgical operation can be identified and measures taken to ensure that they are performed properly. Analysis of the step identified will indicate the optimum circumstances for its satisfactory fulfilment, and its influence on the clinical outcome.

References

1. Figgie HE, III, Goldberg VM, Heiple KG, Moller HS, lII, Gordon NH (1986) The influence of tibial-patellofemoral location on function of the knee in patients with the pos- terior stabilized condylar knee prosthesis. J Bone Joint Surg [Am] 68:1035-1040

2. Hoffmann AA, Bachus KN, Wyatt RWB (1991) Effect of the tibial cut on subsidence following total knee ar- throplasty. Clin Orthop 269:63-69

3. Hsu H-PG, Garg A, Walker PS, Spector M, Ewald FC (1989) Effect of knee component alignment on tibial load distribution with clinical correlation. Clin Orthop 248: 135-144

4. Jiang C, Insall JN (1989) Effect of rotation on the axial alignment of the femur Pitfall in the use of femoral in- tramedullary guides in total knee arthroplast. Clin Orthop 248:50-56

5. Tew W, Waugh W, Forster IW (1985) Comparing the results of different types of knee replacement: a method proposed and applied. J Bone Joint Surg [Br] 67:775-779