Peracetic acid sterilized tendon and ligament allografts for knee reconstruction

Autografts are the graft of choice for primary reconstruction of the anterior cruciate ligament (ACL); however, the availability of autografts is limited, and sizes may be unpredictable or insufficient depending on the surgical requirements. Over the years, allografts have provided a safe alternative due to improved processing methods and an abundant supply of grafts. The advantages of such grafts include attenuated donor site morbidity [13], shorter duration of surgery [13, 18, 22], smaller incisions, and a wider selection of graft sizes [4]. Some disadvantages may include slower biological remodelling and a theoretical risk of disease transmission [4] that can be minimized by using chemically sterilized allografts. Both allografts and autografts have reported similar functional outcomes in 10-year follow-up studies [15] and in reports with shorter follow-up [1, 6‐8, 10, 16‐19]. Allograft use is well reported for both anterior (ACL) [1, 2, 9, 10, 15, 19] and posterior cruciate ligament (PCL) reconstruction [16].

The aim of this study is to investigate whether tendons sterilized with peracetic acid used in knee surgery display similar rerupture and complication rates to values reported in the literature for other allografts and autografts.

Mean time to surgery was 10–83 months, depending on the group investigated (Table 2). Primary surgery was performed in 34% of the patients. The remaining 66% were revisions. The mean duration of surgery was 89–142 min (Table 2). Patients who underwent complex surgery stayed significantly (p = 0.01658) longer in the hospital than patients with ACL reconstruction.

Follow-up was at least 2 years for each surgical treatment and mean time was between 48 and 66 months and not significant different between groups (Table 3). The complication rate was 7.9%, none of these complications were related to the allograft (Table 3).

We recorded 3 reruptures (7.9%), of which 2 grafts were reruptured in one patient, due to the noncompliance of a multiple revision patient. Reruptures only occurred in the ACL patient group.

In ACL patients, presurgical Lachman test was positive with 2+ or higher in 80% of the patients and pivot shift test was positive in 100% of the patients, when data were available (Table 3). Postsurgery all patients had a negative pivot shift test and a Lachman test of < 2+. Due to insufficient data, KOOS and IKDC could not be analyzed.

Donor age, patient age and BMI did not differ for patients with and without rerupture (p = 0.84804; p = 0.70058 and p = 0.0659, respectively, Table 3).

Flexion angles (ROM) of 16 healthy knees were obtained from the contralateral side. These values were used as the reference. The ACL and PCL patients recorded flexion angles in the normal range with 138° and 130° of flexion, respectively, 6 months after reconstruction (Fig. 1). The COMPLEX and OTHER surgery groups showed lower flexion angles after 6 months due to longer restriction of movements for these patient groups (Fig. 1). At the final follow-up (Table 3, Fig. 1) patients in the ACL, PCL and OTHER surgery groups had similar values to the healthy knee with 132°, 130° and 134° flexion, respectively. Patients in the COMPLEX group showed a lower flexion angle (121°) compared to the healthy knee reference (p = 0.00072) and to the OTHER surgery group (p = 0.04553).

For the 38 patients the allografts used were 32 semitendinosus tendons, 1 gracilis tendon, 1 tibialis posterior tendon, 3 ligamentum patella with bone block and 1 ligamentum patella tendon, preshaped. The allograft tendons were used for a variety of procedures including, e.g., the reconstruction of the ACL, PCL, ACL + PCL, Larson plastic surgery and the medial patellofemoral ligament (MPFL). No correlation was found between rerupture and donor age (Table 3).

The most important finding of this retrospective data analysis is that allografts sterilized with peracetic acid can be used for different kinds of knee reconstructions with a success rate of 92%. A 100% survival rate of the allograft was recorded for PCL reconstruction, complex surgeries like simultaneous ACL + PCL, PCL and collateral ligaments, Larson plastic surgery, medial ligament plastic and MPFL reconstruction. The meta-analysis of Migliorini et al. [16] summarized that allografts can be considered a suitable alternative to autografts for PCL reconstruction. For ACL reconstruction the minimum follow-up was 32 months, survival of 86% after a median time of 66 months (5.5 years) was recorded with low complication rates not related to the allograft. Knees treated with allografts sterilized with peracetic acid showed good flexion angles with a negative Pivot shift test and Lachman test values below 2. We could confirm the findings of Ashton et al. [2] that there is no correlation between the donor age and rerupture rate. Allografts provide an acceptable alternative to autografts for reconstructive surgery [16]. Allografts aid in reducing graft harvest site morbidity and provide surgeons with an abundant supply of grafts [13], where the type of graft can be selected according to the patient requirements (diameter, length); however, the literature varies regarding rupture rates and on the use of allografts and autografts with no apparent differences between allografts or autograft use (1–12% for allograft and 1–13% for autograft [1, 10, 11, 18, 19, 26]) and some reports displaying higher rerupture rates for allografts (7–26% [6, 8]); however, in this retrospective analysis the use of chemically sterilized allografts displayed results similar to previous reports (6.6–13% for autografts and 6.5–12% for allografts, regardless of the sterilization method [7, 17, 18, 25]).

The mean follow-up (Table 3) was between 48–66 months and the range was between 24–95 months. All complications resolved and did not lead to ruptures. The mean time to failure of allografts used in this study was 54 months and is higher compared to other reports (18–22 months [23]), but lower than reported by Macchiarola et al. (6.8 ± 5.4 years [15]).

For most of the cases presented here (84%), semitendinosus tendon allografts were used. Semitendinosus graft use alone was only described in autografts [25] or in combination with gracilis grafts for allografts and autografts [9, 11, 20, 22, 24]. Interestingly, in this cohort semitendinosus tendons were also used for reconstruction of the MPFL or the collateral ligament. This displays the wide usability of chemically sterilized allografts; however, complications arise in both allografts and autografts and the complication rate in this cohort was 7.9% (not related to the allograft) with previous literature reporting rates ranging between 1.7–13% [11]. Previous biomechanical and other studies have supported that donor age is not correlated to the rerupture rate [2]. This follows our observations with no correlation between donor age and the rerupture rate.

This retrospective study also included secondary outcomes such as knee stability, range of motion (ROM) and did not focus on a specific group of patients such as athletes. The mean age of all patients was 34 years (range 14–55 years) and was within the range of published data, literature displaying lower age (27–33 years) [20]. The average BMI of all patients was 28 kg/m² (range 20.1–37.2 kg/m²) and was higher than in other studies [14, 20]. This must be considered when evaluating rerupture rates as it correlates with the BMI. Physical activity (i.e., sports) was the main reason for injury (50%) similar to other reports [7, 8, 18]. Investigations on knee stability and ROM within this cohort displayed a reduction in Lachman grading postsurgery as shown in previous reports using both autografts and allografts [12]. The number of patients with Lachman grading 2 or more prior to surgery (80% of patients) and postsurgery (0%) was within the reported ranges for presurgery (43–100% [7, 9, 14, 18, 24, 26]) and postsurgery (0–22%) for allografts and autografts [7, 9, 14, 18, 20, 24, 26]. A long-term follow-up reported autografts to display a lower negative Lachman grading at 10 years postoperation (31% [17]).

Positive Pivot shift was recorded in all patients before surgery and in none of the patients after surgery, which follows previous reports [22] while several groups reported a positive pivot shift postsurgery (5–15% [11, 18, 21]).

The ACL reconstruction only cohort (Fig. 1) displayed a flexion angle (138° after 6 months) similar to the healthy knees as described in previous reports [25]. Flexion in the PCL group was 130° which was confirmed by Migliorini et al. [16] with 131.7°. Flexion in the COMPLEX and OTHER-surgery groups reached a normal range later due to movement restrictions in these groups after surgery. Interestingly, Bach et al. [3] reported a similar outcome of 140° 51 months postoperation while Barret et al. [5] reported an average flexion of 121.1° after 2 years. The data presented here on stability and ROM of the knee are well within the range when compared to previous reports for allografts and autografts [3, 5, 25] irrespective of the allograft used and the procedure performed. In the literature, both non-irradiated and chemically sterilized allografts showed similar results to autografts with respect to activity scores and stability [21].

Chemically sterilized allografts are a promising alternative to autografts for ACL, PCL reconstruction as well as complex knee surgery. Further studies have to be carried out to underline these findings. All evaluated data were in the range reported in the literature (for allografts) and do not differ greatly from reports on autografts.