Tibial tubercle avulsions are perhaps the most common extensor mechanism disruptions encountered during total knee arthro-plasty. Insall has previously described avulsions of the tibial tubercle as "an intraoperative complication that should be avoided rather than treated."1 This point is reinforced by the paucity of documented successes in managing tibial tubercle avulsions once they do occur.2-5 Therefore, great care should be taken intraoperatively to protect the attachment of the patella tendon to the tibial tubercle.
Three specific preventive measures to avoid this pitfall include:1
1. Protect the tubercle at its insertion site. Tension from the quadriceps mechanism above can cause the tendon to avulse by tearing across the periosteum, making adequate repair tenuous at best. This can be avoided by bringing the arthrotomy incision for initial exposure medial to the tibial tubercle and then raising a cuff of periosteum up to the tubercle. In tight knees in which exposure is difficult, the reflection of periosteum can be extended laterally with sharp vertical dissection to include up to 40% of the tubercle without significant loss of structural integrity of the extensor mechanism. This creates a "peel" of disection rather than a problematic transverse tear. If the tubercle does begin to avulse, a soft tissue sleeve is preserved that can be later repaired to the medial soft tissue envelope.
2. Extend proximal exposure when needed. Several means of enhancing exposure proximally have been described and are reviewed elsewhere in this text. These measures will help to protect the patella tendon attachment distally. The original quadriceps turndown as described by Coonse and Adams5 has been subsequently modified to become an expansion of a standard medial parapatellar arthrotomy. The proximal apex of the arthro-tomy is extended in "inverted-V" fashion by releasing the vastas lat-eralis distally and laterally until the patella can be adequately everted. The limitation of this exposure approach is the prolonged postoperative rehabilitation that must be observed. The "quadriceps snip" as described by Insall1 is a more versatile modification that simply extends the quadriceps tendon incision proximally and laterally at an oblique angle. This simple technique is sufficient the majority of the time to allow for adequate exposure. In those instances when the patellar tendon insertion is still under considerable tension, the quadriceps snip can be combined with a lateral retinacular release to afford an even greater exposure. The quadriceps snip release is repaired with the arthrotomy at wound closure. The major advantage of the quadriceps snip is that it allows for immediate motion postoperatively and avoids the problems of extensor lag often seen with the Coonse-Adams release.1
3. Osteotomize the tibial tubercle if necessary. If all previous measures to enhance exposure still do not afford adequate exposure, traumatic avulsion can still be avoided. It is far better to raise the tibial tubercle with a large wedge of tibial bone to allow for reattachment with wires or screws. Although some authors have reported excellent results with this method,6,7 others have reported complications at a disappointingly high frequency.8 Familiarity with the proper technique avoids complication.
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