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APPENDIX A. TRADITIONAL SURGICAL TREATMENTS FOR MENISCAL LINJURY

Traditional treatment for meniscal injury is surgery. The most aggressive surgical treatment is meniscectomy, which involves either complete or partial removal of the meniscus depending on the horizontal extent of the tear. Guided by arthroscopy, the damaged portion of the meniscus is surgically debrided and removed. In either operation, a peripheral rim of the meniscus must be kept to preserve any form of normal function within the knee. The decision as to whether to remove all or part of the meniscus is based on the severity of the tear, the restriction of activity caused by the tear, and the age of the tear. Total meniscectomy is generally performed on the most severe and avascular tears which cannot be otherwise repaired.^38,39

Current surgical techniques for meniscal injuries accelerate menisci and joint degeneration. Perhaps Lohmander et al, in their comprehensive review of surgical procedures for meniscal pathology, said it best: “there is a lack of evidence to support a protective role of repair or reconstructive surgery of the anterior cruciate ligament or meniscus against osteoarthritis development… Osteoarthritis developed in the injured joints is caused by intra-articular pathogenic processes initiated at the time of injury, combined with long-term changes in dynamic joint loading.”⁴⁰

To see what effect the absence of the meniscus has on degeneration within the knee, researchers from the UK, at the Institute of Medical and Biological Engineering, conducted an in vitro study by mounting dissected bovine knee joints in a pendulum friction simulator and monitoring wear on knee cartilage both with and without a meniscus. Their results showed no change in surface integrity or loss of cartilage with an intact meniscus, but removal of the meniscus resulted in immediate surface wear and cartilage deterioration.⁴¹ A similar study found that 10 years after undergoing meniscectomy, 65% of patients had radiographic evidence of joint space narrowing greater that 50%.⁴²

The results of total meniscectomy have led to a more cautious approach to meniscal excision, particularly with surgical techniques removing only the damaged portion of the meniscus. ^43-46 The thought is that if a portion of the meniscus is preserved, then meniscal function will be more normal as well. Studies have confirmed that removing only the torn portion of a meniscus lowers the severity of postoperative complications, shortens the length of hospital recovery and therapy, and reduces overall pain levels—but the nature of postoperative complications remains the same. These risks include degenerative osteoarthritis, joint instability, femoral and tibial surface damage, and risk of re-injury requiring re-operation.^45,46 Partial meniscectomy, like total meniscectomy, was found—via MRI volume measurement—to cause cartilage loss at a rate of 4.1% per year; a rate that is 78% faster than controls.⁴⁷ Other researchers noted that when meniscal integrity is compromised, such as with partial meniscectomy, the likelihood of developing degenerative arthritis is much increased.^48,49 One of the main reasons for this is that partial meniscectomy, by definition, puts additional strains on the ligamentous support of the knee to provide stability. Follow-up studies show that ligament laxity in the medial and lateral collateral ligaments and anterior cruciate ligaments is increased with meniscectomies.^50-53 In his study of post surgical function, McGinity et al documented that athletes who have undergone partial meniscectomy and total meniscectomy were equally likely to give up sports altogether as a direct result of the operation.⁵⁴

ADDITIONAL CONSEQUENCES OF SURGERY

Meniscectomy can provide temporary pain relief in the early stages following the operation, especially when an acute tear had caused excessive pain or popping preoperatively. Another immediate result may be a greater feeling of stability if the tear had previously been a source of instability. On long-term followup, however, these initial improvements have rarely been shown to last.^4,39,55 Complete pain relief from meniscectomy is nearly unheard of after more than 10 years and, at that point, more complex issues including limited range of motion, radiographic degeneration, crepitation, and severe functional impairment have usually begun to surface. In many cases, a simple meniscus tear, if operated on, can become a career-ending injury.^4,5,39,55 In long-term follow-up studies, four to 14 years after a meniscectomy, nearly 50% of patients had to decrease or stop their typical sporting activities.^39,55 This included adolescents who underwent total meniscectomy. The X-ray progression of the degenerative change paralleled the reduction in activity. Some 17 years after follow-up after total meniscectomy, the incidence of degenerative arthritis as documented by X-ray was 300% more likely in the knee that had the meniscectomy versus the nonoperated knee.⁵⁵

This is logical when considering knee anatomy. A knee joint becomes unstable when ligaments, cartilages, or bone structures are weakened and unable to carry out the level of function of a healthy knee. Such is the case when the meniscus is removed from the knee and unable to perform the usual weightbearing and tracking functions, placing additional stress on the rest of the knee.^42,56 Common physical symptoms of instability after meniscectomy are crepitation, such as cracking or popping, and locking in the joint. One study following over 1,000 meniscectomy patients found that 10 to 20 years after the surgery, 27% had more crepitus in the knees having undergone meniscectomy than they had in the untreated knees.⁵ In this same group of patients, degenerative changes ranging from flattened tibial and femoral bone surfaces to significant joint space narrowing were found in 62.5% of the patients with X-ray evaluation of their knees.⁴

The greatest risk of partial and total meniscectomy is in the development of long term degenerative osteoarthritis. Numerous studies have confirmed that a large percentage of the meniscectomy population experience joint osteoarthritis later in life.^57-63 One study found that 15 to 22 years after having a meniscectomy, the odds ratio of knee degenerative arthritis was 2.6 after medial meniscectomy and 5.3 after later meniscectomy, using the non-operated knee as the control.⁵⁸ In one study, 20 to 29 years after meniscectomy, X-rays showed 53% had significant progression of degenerative arthritis compared to 13% of the non-operated knees.⁵⁹ Another group of researchers found that 21 years after meniscectomy, 71% of operated knees showed signs of at least mild degeneration and 48% showed signs of moderate or severe joint degeneration.⁶¹ Another study found that 40% of meniscectomies resulted in degenerative osteoarthritis, and many were accompanied by other injuries, including a large number of ligament tears.⁷⁵ One study noted that “although risk factors for post-traumatic osteoarthritis are multifactorial, the primary risk factor that stood out in this study was if a meniscectomy had been performed.” In this study the risk of developing osteoarthritis in the knee after meniscectomy was 100%.⁶³

Biomechanically, the development of osteoarthritis can be explained, in part, by the increased stress placed on the tibia and femur post meniscectomy. It is a fact that reducing the size of contact area on a surface increases pressure in the remaining area. Therefore, by removing all or part of the meniscus from the knee, the area through which weight is transmitted in the joint is reduced, thus increasing the pressure on both the tibia and the femur, and their articular cartilage. The amount of contact stress on the tibiofemoral joint can increase by 65% with only a 10% reduction in contact area, and this percentage increases in proportion to the amount of meniscus removed. Complete removal of the meniscus can increase contact stress by as much as 700%^61-64 (see Figure A1). What this means for any knee without a meniscus is that it now bears the pressure proportional to carrying seven extra people on one knee.

Figure A1. Increase in joint contact stress versus percent of meniscus removed. As the percentage of meniscus removed during surgery increases, joint contract stress increases exponentially. Thus arthroscopic meniscectomy dramatically increases the incidence of future degenerative knee arthritis. Source: 1. Baratz ME, et al. Meniscal tears: the effect of meniscectomy and of repair on intraarticular contact areas and stress in the human knee. A preliminary report. Am J Sports Med. 1986;14:270-275. 2. Lee SJ, et al. Tibiofemoral contact mechanics after serial medial meniscectomies in the human cadaveric knee. Am J Sports Med. 2006;34(8):1334-1344.

An additional aspect contributing to the acceleration of the osteoarthritic process is through structural wear of the articular cartilage (see Figure A2). By depriving the joint of the ability to lubricate the articular cartilage, the motion of the femur against the tibia will begin to break down the cartilage. When these articular cartilage cells, which are metabolically active, degenerate faster than they can regenerate, the result is the accelerated breakdown (degeneration) within the joint.⁶³ One study, which followed rabbits in three-month intervals after varying levels of injury, found that the amount of cartilage damage sustained was greatest in the meniscectomy subjects, proving this treatment to be even more damaging than non-treatment.⁶⁴ Although osteoarthritis (OA) may have a reputation as a slowlydeveloping disease only prevalent in the elderly, this is clearly not the case. Cartilage loss can develop from adolescent injuries and appear as early as a few years after a meniscectomy.^65-68 Precursors to OA, such as evidence of biological cartilage alterations, can appear in as little as three months post meniscectomy.^69,70 Because OA develops steadily with time, this can have devastating effects just five to 10 years after the procedure. The articular cartilage in a knee deteriorates at an average rate of 4.1% per year after meniscectomy.⁷¹ This rate is about twice the rate of normal cartilage loss with aging. After OA forms, the articular cartilage continues to deteriorate in the knee joint at a rate of about four to five percent per year.^44,45

MENISCAL REPAIR

As the importance of maintaining complete intact menisci has become more widely recognized, the desire for a less invasive and more curative treatment has been sought out for meniscal injuries. For this reason, many have turned to meniscal repair as their treatment of choice. Meniscal repair utilizes one of several suturing techniques to reattach a torn flap of the meniscus, rather than removing it. In preparation for meniscal repair, the meniscus is generally debrided to remove any tissue that is rendered too loose or “contaminated” to heal, and then the procedure is performed either open or through incision under arthroscopy.⁷² Meniscal repair is generally reserved for peripheral tears that extend into the red zone, because the likelihood of healing is greater in that region.^72,73

The short-term results of meniscal repair have varied significantly, with a range of both promising and disappointing outcomes.^74,75 Another concern associated with meniscal repair is, not surprisingly, long-term degenerative osteoarthritis.^76-79 And as the ability to track long-term results has become possible, repair failures and associated symptoms have been observed in large numbers, proving that the effectiveness of this treatment is questionable at best. Preoperative symptoms have been shown to reoccur as early as six months following meniscal repair and can lead to long-term joint damage decades later.^80,81 Specifically, as documented by CT arthrogram, completely healing from meniscal repair was found in only 58% of the menisci.⁸⁰ After a 13 year follow-up the failure rate in one Swedish study was 29%.⁸¹ In this same study, knee function showed a statistically significant decline in the meniscal-repaired knee compared to the non-operated knee. The authors noted, “We conclude that 13 years after repair, knee function is good but not better than after meniscectomy and not as good as in an uninjured knee.” Six independently performed studies, conducted an average of eight years after a repair, found that 10% to 38% of all meniscal repairs were considered failures.^82-87 And in 25% of all patients undergoing meniscal repair, the surgery will either not relieve their symptoms or the repair will fail and their symptoms will again return and need another operation or some other form of therapy.⁷⁶

MENISCAL ALLOGRAFT

The most recent contribution to surgical treatment of meniscus injuries has been the advent of the meniscal transplant. Transplantation can be performed either with human allograft or artificial collagen implants, with the majority utilizing cryopreserved (deep-frozen) allografts extracted from human cadaver knees. Before a transplant can be conducted, the patient must undergo arthroscopic removal of any remaining meniscal tissue to prepare for the new implant. Using one of two techniques—a bone plug or a bridge—the implant is placed inside the knee in alignment with the femur and tibia, and then sutured into place. This procedure requires careful measurement of the meniscus and precision in matching the size and placement of a new meniscus, as even the slightest error in measurement could cause improper tracking and damage to the knee.⁸⁸

This method has been monitored closely for short-term results but, because it is a relatively new treatment and methods between studies have varied, long-term results are difficult to assess. Based on what information we do have, however, the hope of long-term relief remains questionable. In a number of studies spanning from two to seven years after allograft transplantation, failure rates ranged from 28% to 58%, where symptoms such as allograft deterioration, new tears, and unresolved pain symptoms resulted in premature removal of allografts or additional arthroscopic surgeries.^88-90 As one study states, “[patients] should be advised that the procedure is not curative in the long term, and additional surgery will most likely be required”⁸⁸ (see Figure A2). Recovery time is another important issue in assessing any treatment, and transplants have a longer rehabilitation time than other meniscal operations. In documented transplantation cases, patients did not begin physical rehabilitation until eight weeks post operation, at which time they were started on non-strenuous activities such as cycling and followed, between nine and 12 weeks post operation, by swimming and walking. Even in the most successful knees, patients were informed that they should never return to arduous physical activity, including athletics.⁸⁹ Meniscal transplantation, having such a high failure rate, diminishes the hope that anyone, especially athletes, would have for maintaining an active lifestyle.

Figure A2. Healthy knee joint with intact meniscus and degenerated knee joint without meniscus. The removal of part or all of the meniscus during arthroscopic surgery accelerates the degeneration of the articular cartilage.