Modified Insall's Anterior approach for Primary Total Knee Arthroplasty Dr (Prof) Raju Vaishya (MBBS, MS, MCh, FRCS) Sr Consultant Dept of Orthopaedics & Joint Replacement Surgery Indraprastha Apollo Hospitals, New Delhi, INDIA

Approaches for TKA Total Knee Arthroplasty (TKA) is traditionally done by anterior approaches of the knee joint. The most common anterior approach used is medial parapatellar approach (MPP). This approach gives good exposure of the joint with patellar eversion while extensor mechanism integrity is kept intact

Advantages of MPP Simplicity Gives good exposure of the joint with patellar eversion Extensor mechanism integrity is kept intact Disadvantages of MPP Violation of the medial retinaculum, including medial patellofemoral ligament. Occasional unpredictable soft tissue to soft tissue healing in some cases may pose problem in the form of patellar maltracking.

Insall’s approach (J Bone Joint Surg. 53A, 1971, 1584-86) The medial half of the quadriceps expansion is separated from the patella. A lateral parapatellar skin incision is used While early weight-bearing is encouraged, quadriceps exercises and knee motion are not stressed and the patient is allowed to recover these abilities at his own speed.

Insall’s approach Advantages: The midline incision does not weaken the medial retinaculum and vastus medialis insertion as is the case with comparable medial parapatellar incisions It also allows better exposure of the entire anterior compartment The incisional closure has inherent stability so that motion may be commenced without fear of separation and no immobilization is required.

Our modified Insall’s Approach Instead to stripping the quadriceps tendon from middle third of the patella, we stripped it from medial 1/4th of the patella. (due to concern of excessive dissection of the patellar tendon & possible healing problems later on)

Modified Insall’s Anterior Apporach We describe our experience of a novel approach for primary TKA, its results, merits and comparison with standard medial parapatellar approach (MPP) in 498 patients. The knee was opened by anterior mid line incision by stripping the quadriceps tendon from medial 1/4th of the patella.  

AIMS AND OBJECTIVE Compare the standard medial parapatellar approach (MPP) with modified Insall approach Its Merits and Demerits Complications

Materials and methods This study was conducted in Indraprastha Apollo hospital new Delhi during the period from 2000 to 2006. A total of 498 of either sex were selected ,out of which 272 patients between 46-88 yrs (average70 yrs) were operated by Modified Insall’s approach and 226 patients between 46-93 yrs (average 68 yrs) were selected for Medial parapatellar approach

Demographic data MPP MODIFIED INSALL N 226 272 Age in years Range(average) 46-93(68) 46-88(70) Sex Men Female 98 128 116 156 Weight 122-283(186) 131-275(182) Diagnosis OA RA Posttraumatic 188 38 236 34 02

Modified Insall’s Approach An anterior midline skin incision was preferred because of better healing with a less objectionable scar; it also results in a slightly smaller area of sensory denervation over the knee. The skin and subcutaneous tissues were dissected medially to expose the quadriceps mechanism. The quadriceps tendon is split starting about 2” above the superior pole of patella and the incision is extended distally over the medial 1/4 of the patella and through the ligamentum patellae to the tibial tubercle. The longitudinal fibres of the quadriceps expansion are then carefully separated from the medial ¼ of the patella; with care a substantial layer can be obtained

For the control group, a medial parapatellar approach was used. The surgical approach consisted of a straight anterior midline skin incision extending from the superior aspect of the tibial tubercle to the superior border of the patella. A limited medial parapatellar arthrotomy was used with 2 cm division of the quadriceps tendon above the superior pole of the patella, and extended around the medial border of the patella and distally to the tibial tubercle level. In both groups exposure was obtained with the eversion of patella.

Surgical steps Cutting of quadriceps Skin incision marking tendon Midline skin incision

Surgical steps Arthrotomy completed Stripping of quadriceps tendon from medial 1/4th of patella Complete exposure of the joint

Surgical steps Knee implantation completed 3 stiches over patella 3 stitch test in flexion

Deep closure in flexion Surgical steps Skin closure Deep closure in flexion

MPP MODIFIED INSALL Tourniquet time (mins) 68.4 56.2 Estimated Blood loss(ml) 200 129.6 Straight leg raising (days) Knee society score(12 weeks) 86 84 Time to achieve 90degree knee flexion 12.2 5.6 Time to discharge 7.2 6.2

Results The operative time in our modified approach was less (56.2 minutes) as compared to the standard MPP approach (68.4 minutes). The modified approach group had an earlier return to function in straight leg raising (3.5-2.6) as compared to the median parapatellar approach(8.2-3.6 days). Using the two tailed t-test the confidence interval was 95%. We found a difference in the two approaches by knee society scoring system with modified approach having better scores in first six weeks postoperatively but the results were similar after 12 weeks follow up. The knee scores averaged 86 and 84 for modified and standard approach at last follow up.

Results The time required to achieve knee flexion was earlier in modified approach (5.6 days) as compared to the standard approach(12.2 days). Average time to discharge was 6.2 days in modified approach and it was 13.2 days in standard approach. One case in standard approach had superficial infection which healed by prolonged antibiotics for one week. No other complications were noticed during hospital stay in both groups. In follow up none of the patients in this series has had patella fracture and patellar malalignment problem with quadriceps mechanism problems. Till last follow up no loosening of implants has been seen radiologically

Insall v/s our approach FEATURES INSALL’S APPROACH OUR APPROACH SKIN INCISION LATERAL PARA PATELLAR ANTERIOR MID LINE STRIPPING OF QUADS TENDON FROM MIDDLE 1/2 FROM MEDIAL 1/4 REPAIR OF QUADS TENDON NON SPECIFIC 3 STITCH TEST REHABILIATION CAUTIOUS AND SLOW AGGRESIVE

Conclusions Modified Insall’s anterior midline approach is safe and a versatile approach for primary TKA Our modifications in original Insall’s approach provide advantages in surgical exposure & better clinical outcomes Clinical outcomes are better than conventional MPP approach Does not carry any significant complications Bone to tendon healing in this approach seems to be better than tendon to tendon healing in MPP approach

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