Keywords
meniscus allograft transplantation - weight-bearing - patient-reported outcomes
Meniscus allograft transplantation (MAT) is a proven treatment option for patients
with symptomatic irreparable meniscus deficiency.[1]
[2] MAT has been associated with mid-term success rates between 75 and 90%, with longer
term functional survival rates reported to be between 50 and 70%.[1]
[2]
[3]
[4] Treatment failures are most often attributable to allograft tears, shrinkage, extrusion,
fixation failure, and progression of degenerative joint disease with 10 to 40% of
cases requiring reoperation.[5]
[6]
[7]
[8] MAT is typically reserved for patients ≤ 55 years of age with limited or correctable
articular cartilage pathology, normal or correctable lower extremity alignment, and
normal or correctable knee ligament stability.[4]
[9]
[10]
[11] In addition, patients must be willing and able to commit to prolonged and restrictive
postoperative management protocols.[9]
[12] When patients are adherent to prescribed protocols, return-to-work, return-to-sport,
and patient satisfaction levels after MAT are considered good to excellent.[5]
[13]
[14]
[15]
[16]
[17]
[18] However, nonadherence is common and can be associated with undesirable outcomes
and patient dissatisfaction.[12]
[19]
[20]
[21]
While no evidence for an optimal management protocol following MAT has been established,
the majority of those outlined in the peer-reviewed literature advocate for limited
weight-bearing and restricted knee range of motion (ROM) for 4 to 6 weeks, followed
by a progressive return to full weight-bearing and full ROM by 6 to 12 weeks postoperatively.[9]
[11]
[13]
[22] Recommended timing for return to athletic activities varies widely, but is typically
not prior to 9 months after MAT.[5]
[13]
[22] In light of demonstrated safety for early weight-bearing following MAT in conjunction
with significant advances in graft preservation and surgical techniques, consideration
for an accelerated rehabilitation protocol following MAT is appropriate.[7]
[23]
[24]
[25] As such, our joint preservation center implemented a shift in practice toward accelerated
weight-bearing following MAT. The objective of this study was to compare outcomes
for patients prescribed accelerated versus standard rehabilitation after MAT. The
study was designed to test the hypothesis that accelerated rehabilitation would be
associated with superior adherence, patient-reported outcomes, and patient satisfaction,
without diminishing patient safety, when compared with standard rehabilitation.
Methods
Study Patients
With Institutional Review Board approval (IRB 2003053, IRB 2008288), electronic medical
record (EMR) data were searched to identify all patients who had undergone fresh or
fresh-frozen MAT using a double bone plug technique for treatment of medial or lateral
meniscus deficiency at the authors' institution between January 1, 2015, and December
1, 2022. MAT surgeries were performed on patients with symptomatic meniscus deficiency
who chose this treatment option over other nonsurgical or surgical options as indicated
and were approved for coverage by their insurance provider. Patient demographics,
prior surgeries, MAT surgery data, and rehabilitation protocol assignment were documented.
Patients were included for analyses when they had a primary meniscus transplant with
or without concurrent procedures in the affected knee, and at least 1-year treatment
outcomes recorded in the EMR. Exclusion criteria included revision MAT, or insufficient
outcomes data available ([Fig. 1]).
Fig. 1 CONSORT flow diagram for study subjects.
MAT Surgeries
Radiographically size-matched meniscus allografts were obtained from American Association
of Tissue Banks (AATB)-accredited tissue banks and used in conformance of the tissue
to the Food and Drug Administration classification of a Human Cell and Tissue Product
under Section 361 of the Public Health Services Act. Fresh-frozen meniscus allografts
were obtained from one of three AATB-accredited tissue banks and used prior to labeled
expiration date. Fresh meniscus allografts preserved using the Missouri Osteochondral
Preservation System (MOPS) were obtained from one AATB-accredited tissue bank and
used within 56 days after recovery. All MAT procedures were performed by one of five
fellowship-trained orthopaedic surgeons using a double bone plug technique with suspensory
fixation of donor bone plugs in recipient sockets for root fixation as previously
described.[7]
[26] If indicated, concomitant procedures including ligament reconstruction or chondroplasty
were performed concurrently according to standard of care.
Rehabilitation Cohorts
Based on an evidence-based shift in practice toward use of fresh (viable) meniscus
allografts with meniscotibial ligament reconstruction and documented safety for early
weight-bearing following MAT, our joint preservation center instituted an accelerated
rehabilitation protocol for patients undergoing primary MAT ([Fig. 2]).[7]
[26]
[27]
[28]
[29] This shift in practice allowed for comparison of two patient cohorts, as follows:
Fig. 2 Comparison of standard versus accelerated post-MAT rehabilitation protocols. MAT,
meniscus allograft transplantation.
-
Standard: Patients were instructed to remain toe-touch weight-bearing through 4 weeks after
surgery, moving to partial weight-bearing between 4 and 6 weeks after surgery, and
released to weight-bearing as tolerated (WBAT) between 6 and 8 weeks. Treated knee
ROM was limited to 90 degrees for the first 2 weeks and then 120 degrees until 4 weeks
post-MAT. Limited stationary bike and closed chain strengthening exercises were initiated
by the physical therapist between 8 and 12 weeks postoperatively. Straight line jogging
was initiated followed by release to full plyometric, cutting, and jumping activities
at 9 months or more post-MAT based on assessments of strength, balance, and knee joint
health and the surgeon's discretion.
-
Accelerated: Patients were instructed to remain toe-touch weight-bearing through 2 weeks after
surgery and released to WBAT after the 2-week follow-up appointment. Treated knee
ROM was limited to 90 degrees for 6 weeks. Limited stationary bike, leg press, and
closed chain strengthening exercises were initiated between 10 and 12 weeks postoperatively.
At 5 months after MAT, straight line jogging was initiated followed by release to
full plyometric, cutting, and jumping activities at 8 months or more post-MAT based
on assessments of strength, balance, and knee joint health and the surgeon's discretion.
If necessary, each protocol was adjusted based on concomitant surgeries and assessment
of patient progress by the physician and physical therapist.
Patient adherence with the rehabilitation protocol was monitored and documented based
on patient communication and outpatient physical therapy reports. Patients were categorized
as nonadherent when definitive deviations from the prescribed protocol were documented
to occur during the first year after surgery.[12]
[30] Follow-up appointments were scheduled for 2 weeks, 6 weeks, 3 months, 6 months,
1 year, and then annually with standardized radiographic imaging ordered for each
appointment except for the 2-week follow-up appointment.
Outcome Measures
Patients were evaluated preoperatively and then at 6 months and yearly after MAT.
Demographic and operative data including age, sex, body mass index (BMI), and tobacco
use were collected from the EMR. Patient-reported outcome measures (PROMs), including
Patient-Reported Outcomes Measurement Information System Physical Function,[31] International Knee Documentation Committee (IKDC) form,[32] Single Assessment Numeric Evaluation (SANE),[33] and visual analog scale for pain[34] were collected at each time point. All reported complications and reoperations were
recorded in the EMR. For the purposes of the present study, treatment failure was
defined as need for revision surgery or conversion to knee arthroplasty (total [TKA]
or unicompartmental [UKA]) for any reason. Revision was defined as a second operation
to revise the meniscal allograft specifically. The decision to pursue revision surgery
or arthroplasty was based on the attending surgeon's discussion of joint pathology,
treatment options, and related prognosis in conjunction with patient preference and
informed consent. Patient satisfaction was measured using a single question from the
Surgical Satisfaction Questionnaire-8, “How satisfied are you with the results for
your surgery?” at final follow-up.[19]
[35] Final follow-up was defined as the longest time point post-MAT for which treatment
success/failure as defined a priori was available for each included patient. Treatment was categorized as successful
when patients returned to functional activities without need for revision or arthroplasty
surgery. Initial success rate was calculated using the formula: 100% − (revision% + failure%).
Statistical Analysis
Cases were included for statistical analyses when treatment success/failure data were
available for patients undergoing MAT for the first time (primary transplant) with
at least 1-year follow-up. Descriptive statistics were calculated to report means,
ranges, standard deviations, and percentages. Outcomes were compared based on patient
sex, BMI, age, concomitant procedures, history of ligament reconstruction, and reported
adherence to the treatment protocol. Chi-square or Fisher's exact tests were used
to assess for significant differences in proportions. Odds ratios were calculated
when significant differences were identified. Normality tests were performed, and
unpaired t-tests were used to assess differences between cohorts. Paired t-tests were performed to calculate differences between pre- and postoperative PROMs.
Statistical significance was set a priori at p < 0.05. Differences in PROMs were also assessed for minimum clinically important
differences.[36]
[37]
[38]
[39]
[40]
[41]
Results
From a total of 61 potentially eligible patients, 59 patients (accelerated: n = 35; standard: n = 24) with mean final follow-up times of 43 (range, 12–89) and 52 (range, 12–102)
months, respectively, were included. There were no statistically significant differences
between rehabilitation cohorts with respect to patient demographics, history of prior
ligament reconstruction, MAT surgical variables assessed, or follow-up duration. However,
nonadherence to the prescribed rehabilitation protocol was significantly different
between cohorts, with patients in the standard rehabilitation cohort 2.3x more likely to be nonadherent (p = 0.02) ([Table 1]).
Table 1
Variables assessed for patients undergoing meniscal allograft transplantation in accelerated
versus standard rehabilitation cohorts
|
Variables
|
Accelerated, n = 35
|
Standard, n = 24
|
p-Value
|
|
Age (y), Avg (SD)
|
30.7 (13.2)
|
26.0 (9.0)
|
0.07
|
|
Sex: female, n (%)
|
13 (37.1)
|
8 (33.3)
|
1
|
|
BMI, Avg (SD)
|
29.8 (7.1)
|
27.6 (4.5)
|
0.09
|
|
Tobacco use status, n (%)
|
3 (8.6)
|
2 (8.3)
|
1
|
|
Concurrent ligament reconstruction, n (%)
|
18 (51.4)
|
16 (66.7)
|
0.29
|
|
Previous ligament reconstruction, n (%)
|
11 (31.4)
|
14 (58.3)
|
0.06
|
|
Medial:lateral, n
|
25:12[a]
|
16:8
|
1
|
|
Nonadherence, n (%)
|
6 (17.1)
|
11 (45.8)
|
0.02
|
|
Follow-up (mo), Avg (SD)
|
43 (22.8)
|
52 (25.4)
|
0.15
|
Abbreviations: Avg, average; BMI, body mass index; SD, standard deviation.
Note: The p-value in bold italics indicates statistically significant differences.
a Two patients underwent concurrent medial and lateral meniscus allograft transplantations.
Treatment success rate for all patients combined was 81.4% with four treatment failures
(11.4%) in the accelerated cohort and seven treatment failures (29.2%) in the standard
cohort. Treatment failure occurred at a mean of 23 months (range, 1–60 months) for
patients in this study. For the 11 patients who experienced treatment failure, 6 patients
(55%) reported an acute injury during activity that was associated with a meniscus
allograft tear. Four patients (36%) reported an insidious onset of knee pain and/or
dysfunction without a clear mechanism for MAT failure. One patient (9%) did not provide
information related to treatment failure. Seven patients (64%) underwent revision
MAT, with none reporting need for further surgical intervention during the study period
(3–97 months after revision). One patient (9%) underwent repair of the meniscus allograft
with no need for further surgical intervention at 26months after repair. Three patients
(27%) who experienced treatment failure declined further surgical intervention of
any type and opted for nonsurgical management of their meniscus deficiency. No patients
opted for conversion to TKA or UKA during the study period. History of prior ligament
reconstruction was significantly associated with treatment failure (p = 0.04, OR=4.73). Patient age (p = 0.18), sex (p = 1), BMI (p = 0.87), tobacco use (p = 0.23), concurrent ligament reconstruction (p = 0.74), graft type (fresh vs. frozen, p = 0.31), laterality (medial vs. lateral, p = 0.48), and nonadherence (p = 0.71) were not significantly associated with treatment failure.
There were statistically significant and clinically meaningful improvements for all
measured PROMs for patients in the accelerated rehabilitation cohort. Patients in
the standard rehabilitation cohort did not report significant or clinically meaningful
improvements for any of the measured PROMs ([Table 2]).
Table 2
Patient-reported outcome measures prior to and after meniscus allograft transplantation
in accelerated versus standard rehabilitation cohorts
|
Group (n)
|
Preoperative
|
Final follow-up
|
p-Value
|
|
VAS pain
|
Accelerated (24)
|
5.0 (1.8)
|
2.4 (2.3)
|
<0.001
|
|
Standard (19)
|
4.3 (2.2)
|
3.3 (2.3)
|
0.19
|
|
PROMIS physical function
|
Accelerated (23)
|
39.5 (7.4)
|
46.0 (8.6)
|
0.003
|
|
Standard (15)
|
42.2 (8.6)
|
43.4 (7.4)
|
0.59
|
|
IKDC
|
Accelerated (15)
|
43.4 (8.7)
|
60.5 (20.5)
|
0.01
|
|
Standard (8)
|
52.2 (15.8)
|
50.4 (20.2)
|
0.78
|
|
SANE
|
Accelerated (11)
|
49.5 (15.9)
|
74 (22.8)
|
0.003
|
|
Standard (11)
|
52.1 (27.5)
|
57.3 (23.9)
|
0.66
|
Abbreviations: IKDC, International Knee Documentation Committee; PROMIS, Patient-Reported
Outcomes Measurement Information System; SANE, Single Assessment Numeric Evaluation;
VAS, visual analog scale.
Note: The p-values in bold italics indicate statistically significant improvements from preoperative
to final follow-up.
Patient satisfaction data were provided by 69% of patients in the accelerated cohort
(n = 24) and 21% of patients in the standard cohort (n = 5). In the accelerated cohort, 88% of respondents (n = 21) reported they were satisfied or very satisfied with the results of their surgery,
and 40% of respondents (n = 2) in the standard cohort reported they were satisfied or very satisfied with the
results of their surgery.
Discussion
The results of this study allow for acceptance of the hypothesis in that accelerated
rehabilitation after MAT was associated with superior adherence, patient-reported
outcomes, and patient satisfaction, without diminishing patient safety, when compared
with standard rehabilitation. Patients who were prescribed accelerated rehabilitation
after MAT were significantly more adherent than patients who were prescribed standard
rehabilitation and reported statistically significant and clinically meaningful improvements
in knee pain and function for at least 1-year following MAT, whereas those in the
standard cohort did not. While not statistically different, treatment failure rate
was lower in the accelerated rehabilitation cohort when compared with the standard
rehabilitation cohort (11 vs. 29%). Importantly, initial outcomes for revision MAT
were associated with short-term success in all the patients who opted for this option
in the study population.
The overall treatment failure rate documented in the present study falls within the
range reported in previous studies.[1]
[3]
[4]
[9] Similarly, mechanisms for treatment failure and time to failure in our patient population
were similar to prior reports.[42]
[43]
[44] In previous studies, obesity, laterality, and articular cartilage pathology have
been associated with increased risk for treatment failure following MAT.[42]
[43]
[45] In our patient population, we did not note any statistically significant associations
for obesity or laterality with treatment failure. In our study population, only history
of prior ligament reconstruction was significantly associated with treatment failure,
suggesting that more complex indications for MAT may have higher risk for treatment
failure. In conjunction with previous studies, the data from the present study highlight
the importance of discussing potential risk factors for treatment failure during a
patient–health care team shared decision-making process when considering MAT for treatment
of symptomatic meniscus deficiency.
In previous studies, prescribed rehabilitation after MAT has typically included limited
weight-bearing and restricted knee ROM for a minimum of 4 to 6 weeks, progressive
return to full weight-bearing and ROM by 6 to 12 weeks postoperatively, and return
to athletic activities no sooner than 9 months after MAT.[5]
[13]
[14]
[15]
[16]
[22] The key differences for the accelerated rehabilitation protocol used in the present
study included:
-
Earlier initiation and faster progression of weight-bearing.
-
Knee flexion limitation (≤90 degrees) extended by 1 month.
-
Earlier return to straight line jogging and release to full plyometric, cutting, and
jumping activities.
These protocol differences were implemented based on previously reported results associated
with early weight-bearing after MAT[7] in conjunction with evidence-based advances in allograft preservation methods,[7]
[21]
[28] MAT fixation techniques,[7]
[24]
[25]
[26]
[28] and patient management strategies[7]
[12]
[21]
[30] that directly or indirectly mitigate known mechanisms of MAT failure. In the present
study, these differences were associated with patient safety based on a lower treatment
failure rate, better patient adherence to the prescribed postoperative rehabilitation
protocol, and greater improvement in PROMs after MAT when compared with the standard
rehabilitation cohort. Patient satisfaction was also high in the accelerated cohort.
These benefits associated with the accelerated weight-bearing rehabilitation protocol
may be related to better patient adherence, focus on return to normal activities of
daily living before progression to strengthening, and/or improved healing and joint
health. However, the benefits may also be associated with differences in graft types,
transplantation techniques, and/or other unaccounted for variables such that further
study is required before conclusive recommendations can be made.
Limitations for this study include that it was a single-center, nonrandomized design,
which did not control for patient variables, graft types, or transplantation techniques.
While this design is subject to confounding variables, it represents a “real-world”
scenario in terms of the spectrum of patients indicated for MAT, as well as the influences
of surgeon preferences. Further, we were only able to provide mid-term outcomes. However,
mean follow-up period exceeded 42 months for both cohorts, mean time to failure was
23 months, and only 3% of patients were lost to follow-up, such that treatment outcome
results are considered valid. Similarly, while outcome measures did not include diagnostic
imaging assessments, the criteria used to define treatment failure were conservative
and strict such that it is unlikely that success was overstated. This is further supported
by the robust PROMs data provided by all patients included in the study. Unfortunately,
patient satisfaction data were not provided at the same levels such that comparisons
between groups for this outcome measure could not be considered valid. Ongoing studies
at our center are expanding the patient population to provide sufficient data for
multivariate analyses and long-term outcome measures including patient satisfaction
data and diagnostic imaging assessments for more conclusive and generalizable results.
Conclusion
The results of this study demonstrate that accelerated weight-bearing after MAT is
safe, promotes patient adherence, and is associated with statistically significant
and clinically meaningful improvements in patient-reported knee pain and function
at early and mid-term follow-up.
