This is Kurt Vandenberg and I'll be presenting on lateral meniscus allograft transplantation. We will discuss lateral meniscus deficiency in young patients and indications for lateral meniscus transplantation. For this all arthroscopic surgical procedure, we'll focus on identification and drilling of meniscus root tunnels in a minimally disruptive transficial technique. We'll also discuss potential complications and how to avoid them in post-operative protocols and results. While indications for lateral meniscus allograft transplantation in skeletally immature patients remains controversial, the procedure is indicated for patients with or without current knee pain or mechanical symptoms who have previously undergone total or subtotal lateral meniscectomy resulting from an irreparable lateral meniscus tear, in most cases for a discoid lateral meniscus. The goal of surgery is to re-establish the chondroprotective effects of the meniscus in the lateral compartment of the knee with the meniscus allograft. This can ideally be performed prior to the development of significant cartilage degenerative changes. The patient can be positioned in a standard knee arthroscopy setup and the majority of the lateral compartment work can be done with the knee in the figure 4 position. Using x-ray and MRI measurement criteria, a patient-specific right knee lateral meniscus allograft was obtained. The graft is prepared so that small bone plugs in the anterior and posterior roots can pass through six to seven millimeter diameter tunnels with number two non-absorbable braided suture placed in a crack-out fashion at the edge of each graft with an OPDS suture placed in the body for graft passage. In this right knee, a displaced bucket handle tear of this discoid lateral meniscus is demonstrated once again and the meniscus is debrided until a stable rim of meniscus approximately two millimeters in size is achieved throughout the periphery. There are no lateral compartment cartilage changes noted in this case. Identification of the anatomic meniscus root locations is critical, noting the proximity to the posterior lateral bundle of the ACL posteriorly and the tibial ACL footprint anteriorly demonstrated in further detail in our illustration. Placement of a 12 millimeter cannula in the medial portal is particularly helpful for graft passage. The posterior root tunnel is created first using this tibial ACL drill guide with a 3.5 millimeter barrel of this retrograde reamer which is then deployed to its seven millimeter diameter and using a retrograde reaming technique reamed to a depth of seven millimeters. As we look into this reamed tunnel we can see that we're above the proximal tibial physis without violation and a passing suture is retrieved. Here is an external view of this step of creating our posterior lateral meniscus root tunnel. AP and lateral x-rays were obtained in this case for demonstration purposes to show the position of the posterior lateral meniscus root tunnel on x-ray. Using the tibial ACL drill guide these steps are repeated for the anterior lateral meniscus root tunnel. Our anterior tunnel is reamed once again to a depth of seven millimeters with bone debris removed. We will intentionally wait to place the passing suture until after the posterior horn and body region have been secured. When drilling the posterior and anterior root tunnels it is important to leave at least a one centimeter bone bridge in the location of the anterior medial tibia in a location just above the PES tendons. X-ray views of the anterior and posterior lateral meniscus root tunnels together are demonstrated here. Through outside in spinal needle localization a suture passing device is passed just anterior to the popliteus tendon and out of the medial portal for facilitation of graft passage. Just prior to meniscal allograft passage arthroscopically we have retrieved the suture from the posterior root as well as the passing device that was placed near the popliteus tendon. Initial graft passage involves slight traction on the posterior root suture along with the PDS suture in the body of the lateral meniscus and traction of these sutures is done in careful combination with a large arthroscopic grasper held in the posterior horn of the lateral meniscal allograft through the medial portal. After initial graft passage the meniscal allograft is now secured within the posterior root and the PDS suture in the body region has been slightly tensioned. After the posterior root and body sutures are slightly tensioned and secured we then place a passing suture through the anterior root tunnel so that the anterior root suture can be secured and the small bone block brought into the anterior root tunnel and after graft passage of the graft seeding of the bone plugs from the anterior and posterior roots of the meniscal allograft are confirmed. The graft is then secured by tying the posterior and anterior root sutures over an approximately one centimeter bone bridge that we ensured to create when drilling the posterior and anterior roots. Suture anchor or button fixation can be used if desired for additional fixation. With the posterior and anterior roots of this lateral meniscal allograft now secured we can proceed with meniscus repair. We prefer an outside-in technique for this using an 18 gauge spinal needle and an outside-in meniscus suture passing device. We use number two braided non-absorbable sutures for this in combination of both vertical and horizontal mattress sutures. After initial meniscal repair sutures are placed a two centimeter transverse incision is placed just inferior and anterior to these sutures and they are gently tied over the capsule. After these sutures are tied arthroscopic evaluation of the meniscus stability is performed to determine if additional meniscal repair sutures are needed. Final arthroscopic inspection confirms that the anterior and posterior roots are stable with the bone plugs fully seated in the ream tunnels and coverage from the lateral meniscus in the lateral compartment has been restored. Post-operatively we recommend that the patient wear a hinged knee brace locked in full extension at all times. The range of motion, weight bearing, and return to sport protocol is outlined here. We would like to highlight some of the technical complications that can occur and how to avoid them. Inappropriate graft sizing can occur but can be avoided through detailed pre-operative measurements. Meniscal root tunnel drilling can be optimized through careful attention to the anatomic root locations. Enphyseal damage can be mitigated by keeping the reaming depth to less than approximately seven to eight millimeters and not exiting too proximally aiming for a location just above the pes. Graft passage can be complicated with suture management issues but this can be minimized by only passing the posterior root and body suture first. Also during meniscus repair take care not to over constrain the lateral meniscus posteriorly and allow for the natural lateral meniscus excursion.

lateral meniscus allograft transplantation

identification and drilling of meniscus root tunnels

minimally disruptive transficial technique

lateral meniscus deficiency

surgical steps and post-operative protocols