Functional Outcome Following Concurrent Medial Meniscus Posterior Horn Root Repair during High Tibial Osteotomy in Early Medial Compartment Osteoarthritis

Background: Meniscal root tears cause biomechanical changes comparable to a total meniscectomy. The resultant compromise in hoop stress, leads to decreased tibiofemoral contact area and increased contact pressure. This will lead to early arthritis. The meniscus root tear causes more detrimental changes in people with varus alignment of the lower limb. This increases the chances of progression to arthritis, causing joint pain and functional limitation, eventually necessitating early replacement surgery. Surgical management with repair of the meniscus, with corrective osteotomy restoring the normal anatomy, has been reported to improve clinical and functional outcomes and delay the replacement surgery. This study aimed to evaluate the functional outcome following concurrent Medial meniscus posterior horn root (MMPHRTs) repair during open medial wedge high tibial osteotomy (HTO) with medial osteoarthritis. Methods: We performed posterior horn root repair with open medial wedge HTO in 9 patients, between 2016 and 2021. The mean follow-up of patients was 2 years. The mean Lysholm and IKDC scores showed significant improvement (7 had excellent and 2 had satisfactory scores). Patients returned to their expected activity of daily living. Conclusion: Concurrent MMPHRT repair along with medial open wedge HTO for medial compartmental osteoarthritis with varus alignment gives good results and has shown good clinical and radiological outcome on short term follow-up.


Introduction
The meniscus is a crescent-shaped fibro cartilaginous tissue that is necessary for joint stability, congruity, and proprioception [1,2].The medial and lateral meniscus maintain 90 and 70% of the hoop tension, respectively [3].The meniscus circumferential collagen fibres translate axial forces into tensile forces.As a result, any radial tear in the meniscus will result in the loss of circumferential tension.Loss of circumferential hoop tension raises joint contact pressure, leading to osteoarthritis development [4][5][6][7].Medial Meniscus Posterior Horn Root Tears (MMPHRTs) cause a reduction of meniscal hoop tension, which can progress to medial compartment osteoarthritis [4][5][6][7].Arthroscopic MMPHRT repair is a well-established procedure and known to decelerate articular cartilage degeneration.The varus deformity of the lower extremities, which is frequent in medial knee osteoarthritis(OA), is a significant predictor of meniscal healing and long-term results after MMPHHRT repair [8][9][10][11][12][13].Hence, MMPHRT, in combination with deformity reduction, is also required to decompress unicompartmental overload.For medial compartment OA with varus malalignment, medial open-wedge high tibial osteotomy (OWHTO) is a joint preservation procedure [14][15][16][17].HTO transfers the weightbearing axis which is deviated.The medial open wedge osteotomy improves the medial proximal tibial angle while lowering the medial compartmental pressure.MMPHRT is a typical finding in osteoarthritic knees during OWHTO.The prevalence of root tear of medial meniscus has been widely recorded, accounting for 80 percent of osteoarthritis patients [18][19].
Joint preservation procedures aim to prolong the time to total knee arthroplasty, with reported 10-year survival rate of around 56% to 79% [20][21][22][23].By restoring medial meniscal hoop tension and the tibiofemoral contact surface during HTO, concurrent MMPHRT repair may be a viable method to avoid OA progression.Studies have shown that after HTO, denuded articular cartilage will be covered, and OA progression will be prevented [20][21][22][23].However, the quality of the resultant fibrous cartilage is not as good as the original hyaline cartilage [24].Our study hypothesized that medial open wedge HTO with concurrent medial meniscus root repair, is an ideal joint preserving procedure for patients with varus malalignment along with medial meniscus root tear.The above procedure would give long term benefit to patient and slowdown the progression of osteo arthritis in the involved extremity.

Methods and Material
Approval from ethics committee of the institution was obtained for this longitudinal observational study.Between 2016 and 2021, 9 patients who underwent concurrent posterior horn root repair with open medial wedge high tibial osteotomy were included in the study.Patients with grade 4 Kellgren & Lawrence osteoarthritic changes, and those who did not meet the standard criteria for HTO were excluded.Patients reported hearing a pop noise while climbing the stairs or getting up from the low chair.The main symptom was pain, difficulty to sit cross legged and/or disturbed sleep at night due to pain.Clinical evaluation showed postero-medial joint line tenderness, positive standard tests for the meniscus and varus deformity of the involved limb.
Imaging included standard weight bearing radiographs (Fig. 1a-1d): anteroposterior (AP), lateral (LAT), standing AP with 45° of knee flexion (Rosenberg view), merchant views.Long leg alignment films with patella central was taken for the assessment of the mechanical axis and to look for the malalignment.Standard 3-Tesla MRI of the involved knee showed the root tear, with highest accuracy in coronal T2 weighted image."Ghost sign" in T1 sagittal image which typically shows increased signal or absence of dark signal found near the posterior root.Cartilage mapping also was done to look for the status of the cartilage.The patients were initially treated conservatively with analgesics, lifestyle modification and physiotherapy to relieve pain.Failure to respond to conservative management was considered for intervention.Preoperative planning was done for the corrective osteotomy by the Picture Archiving and Communication System (PACS) method and with printed radiographs of the long leg X-ray.Mechanical joint angles especially the lateral proximal femur angle (LPFA), lateral distal femur angle (LDFA), medial proximal tibial angle (MPTA), lateral distal tibial angle (LDTA) and proximal posterior tibial angle (PPTA) were measured and analyzed to choose the bone for deformity correction.Miniaci method [15,16,[20][21][22][23][24] was used in order to select the correction angle and gap required in OWHTO.Those with varus angle more than 4 degrees were considered for OWHTO.Surgery was done under tourniquet control and image intensifier guidance.Our preferred surgical technique for the repair of MMPHRT is arthroscopic transosseous transtibial single tunnel pullout repair technique as described by Laprade     Meniscus was probed to identify the tear and to determine repairability of root.It was followed by a biplanar medial open wedge HTO through a vertical incision of about 6-8 cm on the anteromedial border of the tibia medial to the tibial tuberosity (Fig. 2a).Sartorius fascia was dissected and upper border of PES anserinus was identified, a reverse L shaped incision was placed with the horizontal limb of the incision 1cm below the joint line and vertical limb of the incision close to the tibial tuberosity.Sub-periosteal mobilisation of the superficial MCL was done.A 2.5 mm drill bit (2.5-3.2) was passed from medial to lateral direction towards the hinge point.Hinge point is at the level of Gerdy's tubercle 10mm medial to the lateral cortex.Care was taken to prevent hinge fracture (Fig. 2b).The K-wires were placed under fluoroscopic guidance for the cut, which was directed towards the hinge point.Once the placement was satisfactory, the posterior dissection was carried out and radioopaque retractors were placed to protect the neuro-vascular structure.Osteotomy cut was taken with the help of an rd oscillating saw, which was advanced upto 2/3 the width of the tibial plateau.Separate ascending cut of the biplanar osteotomy was done at an angle of 110 degrees, 1-2 cm behind the tibial tuberosity parallel to anterior tibial margin in the frontal plane.
The osteotomy was opened gradually using the chisel to achieve desired gap by using specially calibrated spreading device (Fig. 2c).Intraoperatively alignment rod was placed from the center of the hip joint to the center of the ankle joint passing along the center of the knee joint to check alignment (Fig. 3a-3d).Once the alignment was confirmed a Puddu plate (fig 2d) (Arthrex, Naples, FL, USA) was positioned in the osteotomy site.Arthroscopically two bites were taken at 5-7 mm medial to the torn edge of the meniscus and the second 1 cm from the 1st stitch using the shuttle relay method with No. 2 nonabsorbable suture (Healthium Pvt ltd, Peenya, BLR) which was passed through the meniscus root by using Knee Scorpion (Arthrex, Naples, FL) (Fig. 4a, 4b).Various stitch configurations have been described, but we prefer a modifed Mason-Allen suture technique pattern.Sutures were thereafter retrieved from the lateral portal.An anatomical side specific root repair guide (Smith & Nephew Endoscopy, Andover, MA), was introduced from the medial portal, and it was centered on the footprint of root.A guide pin was advanced from the proximal medial tibia to the guide tip.A 5 mm tunnel is drilled over the protected guide pin, carefully breaching the tibial surface (Fig. 4c).Sutures were then retrieved through the tunnel with the help of inverted beath pin and shuttled exteriorly where they were secured with the suture disc and sometimes sutures were tied to plate (Fig. 4d).Wound was closed in layers and post operatively patient was put on a hinged knee locking brace.Rehabilitation was started the next post-operative day with quadriceps strengthening, ankle pump and protected straight leg raise, nonweight bearing walking and restricted range of movement from 0-60 degrees for 4 weeks.At 5 weeks postoperatively X-rays were done, healing at the osteotomy site was assessed and then

Results
There were 7 female and 2 male patients with an average BMI of 2 24.56 kg/m2 (Range 22-27.12kg/m ) with mean age of 45±5.1 years (40-50 yrs).The right leg was predominantly involved (Rt: Lt:: 8:1).The average varus was 8 degrees (Range 7-10).Intraoperatively 8 patients had type 2 meniscus tear and 1 had type 4 according to Laprade's classification.According to Outerbridge 5 patients had tibial side type 1 lesions, 2 patients had type 2 on the medial tibial condyle, 2 patients had type 3 in both medial femoral and tibial condyles.Preoperatively all patients had poor Lysholm and IKDC Scores.The mean followup of patients was 2 years with shortest being 6 months and longest 4 years.The mean Lysholm and IKDC scores showed significant improvement, with 7 excellent and 2 satisfactory scores.All patients had good clinical and radiological outcome.All attained good knee range of movement and showed satisfactory union at osteotomy site along with normal alignment at end of 3 months (Fig. 5a-5b), (Fig. 6a-6d).Patients returned to their expected activity of daily living.Three out of 9 (33.33%)showed progression by at least one grade on Xray KL grading and six out of Nine (66.66%) showed no progression.None desired to have arthroplasty at latest follow-up.One patient had superficial skin necrosis.He was managed with medial gastrocnemius flap (Fig. 7a-7c) and went on to heal with no further complications.

Discussion
Lower medial proximal tibial angle or varus malalignment predispose to joint degeneration in the affected compartment [4][5][6][7][8].Clinical improvement can be achieved by correcting the deformity and by reducing the tibiofemoral contact area.For medial compartment arthritis of the knee, open wedge high tibial osteotomy (OWHTO) is a well-known therapeutic option.This procedure provides the favourable mechanical environment for better healing of the articular cartilage by reducing the load on the involved compartment [14][15].Therefore, the transfer of the weight-bearing axis into the lateral compartment leads to adequate unloading in the affected compartment and contribute to significant clinical improvement [16].The long-term survival of HTO for medial OA has been reported to be between 56 and 79 percent [25][26].
Studies have shown that MMPHRT causes meniscal displacement, which weakens the properties of meniscus, worsening osteoarthritis [4,5].Various modalities of treatment have been tried for MMPHRT.At a 5-year follow-up, Krych et al found poor clinical outcome and increased risk of arthroplasty secondary to osteoarthritis following nonoperative treatment [27].Studies have shown that the arthroscopic partial meniscectomy is associated with worsening of osteoarthritis [28].dependent on cartilage recovery and subsequent healing of MMPHRT.Few factors like low healing potential of degenerative tissues and meniscal extrusion are biomechanical factors impeding healing of the repaired MMPHRT.There are several studies which suggest futility of MMPHRT along with HTO.Currently, there is no consensus whether MMPHRT should be repaired or not along with HTO.Our consensus is to have advantage of repaired meniscus along with HTO for near normal biomechanics of knee to last for a longer time.
Our study has several limitations.The number of cases is limited, probably due to ongoing covid pandemic.Second look arthroscopy was not done to assess the cartilage status.
Postoperative MRI could have been done to look for meniscal status post repair.Long term follow up is required to further assess for progression of osteoarthritis.

Conclusion
Concurrent MMPHRT Repair along with medial open wedge osteotomy for medial compartmental osteoarthritis with varus alignment, gives good results and has shown good clinical and radiological outcome at short term.However, long term studies are required to further assess the benefits of joint preservation surgery and its effects on articular cartilage.
Pilar A et al www.jkoaonline.com

Figure 2c :
Figure 2c: Distractor to open up the osteotomy site.
Fig 1a: B/L Standing AP view which shows reduced medial joint space and varus of knee Fig 1b: Rosenberg view which shows marked reduction of medial joint space left side.

Fig 3d :
Fig 3d: Guide wire passing through centre of tibial spine Fig 3c: Guide wire passing through centre of ankle

Fig 4d :
Fig 4d: MMPHRT which is anchored back to its attachment