Single and double hamstring tendon anterior cruciate ligament reconstruction – A prospective, comparative cohort study

INTRODUCTION

A good reconstruction outcome of the anterior cruciate ligament (ACL) is achievable using various grafts and surgical techniques.^[1,2] Due to their characteristics, hamstring tendons are commonly used.^[3] What surgical technique or graft type to choose depends on the individual case and is molded based on concomitant factors such as knee and limb injuries and the surgeon’s expertise and preference.^[4]

The use of hamstring tendons offers advantages over the bone-patellar tendon-bone graft, such as reduced inferior patellar contracture, quadriceps weakness, and donor site morbidity.^[5,6]

Semitendinosus and Gracilis quadrupled grafting (STGR) evidenced sufficient mechanical strength and satisfying outcomes in terms of joint stability, becoming a suitable alternative for ACL reconstruction. However, studies proved that STGR grafting impacts knee performance-limiting active knee flexion, accentuating muscle weakness^[7] up to 9 months after surgery, and lowering internal tibial torque and joint stability, thus negatively affecting athletic performance.^[8]

Over the past two decades, neurophysiological^[9] and biomechanical^[10] discoveries such as all-inside techniques^[11] led surgeons to opt for a onetendon approach.^[10] We found little evidence in the literature referring to Gracilis tendon (GR) grafting.^[12-14]

We were intrigued to examine ACL reconstruction using different autografts to provide standardized indications when choosing tendon grafts for ACL reconstruction. Thus, we compared the performance of ACL reconstruction using different autografts: ripled GR autograft, STGR, and tripled or quadrupled ST autografts.

We conducted a prospective, comparative cohort study to provide standardized indications that evaluate the pros and cons when choosing tendon grafts for ACL reconstruction to clinically and functionally inquire different outcomes between the mentioned groups.

MATERIALS AND METHODS

Design

We conducted a prospective, comparative cohort study including 311 patients who underwent ACL reconstruction using hamstring tendon autografts over 24 months (2009– 2010). We diagnosed the ACL injury based on our center’s standard protocol that includes accurate medical history, physical examination, and the use of a KT-1000 arthrometer. The diagnosis was confirmed using magnetic resonance imaging for all cases. In our center’s policy, all ACL ruptures are operated on. additionally addition, the ligaments status, and concomitant injuries were assessed and confirmed intraoperatively.

The atients were randomly grouped using a selection algorithm into quadrupled STGR and tripled or quadrupled ST grating. Consequently, one out of four patients was randomly selected for tripled GR grafting using the algorithm. This method was cautiously chosen because the GR autograft use alone has not been described in the literature and presented as an initial approach.

We considered a previous or concomitant ligamentous injury, significant trauma, significant meniscal damage, contralateral knee injury, concurrent fracture, severe osteoarthritis, and loss in follow-up as exclusion criteria due to possible confounders interfering with the study outcome. Intermediate clinical evaluations were performed without data collection.

Out of 311 candidates who presented with ACL injury included in the study, 21 were excluded for concomitant major meniscal lesions, other pathological findings, and bilateral injuries to avoid confounders. A total of 42 were lost during follow-up. At the end of the 5-year follow-up, 248 patients concluded the study; 44 were women (17.8%) and 204 were men (82.2%).

We divided the patients into three groups based on the team’s evaluation and treatment choice; we included 98 patients in the STGR group (Group 1), 63 in the GR group (Group 2), and 87 in the ST group (Group 3) [Figure 1]. The candidates were homogenously distributed between groups to avoid confounders. We conducted the follow-up and observation consequently.

Close

Figure 1:

Flowchart illustrating the exclusion and distribution of patients. STGR: Gracilis and semitendinosus, ST: Semitendinosus, GR: Gracilis.

Export to PPT

The same investigators evaluated all groups postoperatively at 5 years. The primary outcome was to evaluate knee stability using a KT-1000 knee arthrometer. Secondary evaluated outcomes were post-operative knee specific symptoms by Lysholm score, sports activity, and knee function outcomes using International Knee Documentation Committee (IKDC), and comparison between pre-operative and postoperative work and sports activities using Tegner ctivity cale was made.

RESULTS

After surgery, the STGR, GR, and ST groups averaged 91.52, 96.94, and 92.79 on IKDC, respectively, and Lysholm score averages were 95.88, 97.42, and 95.87, respectively. The Tegner score changed preoperatively to postoperatively by –0.53, –0.63, and –0.89 on the STGR, GR, and ST groups, respectively. KT-1000 side-to-side difference in postoperative scored 2.06, 2.55, and 2.22 on the STGR, GR, and ST groups, respectively.

The overall instability recurrence rate (defined as new onset of instability using KT-1000 after surgery) was relatively low. However, the study suggests a higher – yet not statistically significant – instability recurrence rate in the GR autograft group compared to other groups. The overall instability recurrence rate averaged 8.06% (nine patients, of which eight were male and one was female). Instability recurred in 9.2% of the STGR group, 4.6% in the ST group, and 11.1% in the GR group [Table 1].

On the subjective evaluation using IKDC, Lysholm, and pre-to-post-operative Tegner scores, the following data were obtained [Table 2]. IKDC scored lowest in the STGR group and highest in the GR group, reaching statistical significance only when comparing STGR with GR (P = 0.0018) and ST with the GR groups (P = 0.0034). The GR group had the highest IKDC and Lysholm scores, but Lysholm score significantly differed only between the ST and GR groups (P = 0.022).

Instability recurrence analysis (as above defined) using KT-1000 showed a significant difference between the STGR and GR groups; the STGR group had more stability than the GR group.

Although the delta in Tegner scores (∆ Tegner) from before to after surgery decreased for all groups, none of the differences were statistically significant.

DISCUSSION

A noteworthy finding of this study is that when using STGR autograft compared to the GR group, KT-1000 side-to-side presents lesser laxity and the difference reached statistical significance. This correlates to higher knee stability (as STGR is thicker) and is associated with inferior subjective outcomes. Considering both IKDC and Lysholm scores, pain and functional knee impairment peak in both the ST and STGR groups compared to the GR autograft group.

Many studies examined ACL reconstruction with different surgical procedures, illustrating different standards and indications. However, this led to conflicting results concerning some aspects, such as muscular atrophy in STGR autografting.^[17] Graft choice and single versus double tendon reconstructions,^[18,19] most surgeons favor STGR reconstruction with a quadrupled hamstring tendon.^[20-24] Our findings indicate that the use of GR graft reduces knee symptoms, yet that STGR and ST graft offer better knee stability.

We acknowledge that accepting a high error level (0.1) limits the power of our study yet considering the period in which we performed our observation, we expected that the average number of patients with ACL reconstruction would not allow a higher statistical power. In addition, we found limited evidence in the literature regarding ACL reconstruction using GR tendon only to compare our results with. This led us to consider GR autograft performance in our patient pool.

We would like to add that although a part of our evaluation assessed subjective (Tegner, IKDC, and Lysholm) patient scores, we believe in their validity and consider the post-operative experience of our patients as the ultimate target.

We believe that the treatment should never overlook a personalized approach that should be molded on the individual case and is necessary to obtain the best feasible outcome. Therefore, we encourage further studies aimed at considering treatment costs of early and late complications in ACL reconstruction.

Studies demonstrated that pain and hamstring muscle atrophy limit STGR autograft use in ACL reconstruction.^[19] We presume that GR autograft – although it leads to lower knee stability compared to STGR – is a reasonable substitute for ACL reconstruction, particularly in certain cases. Knees requiring a lesser functional demand or presenting with hyperlaxity may benefit from GR autograft ACL reconstruction.

We aspire to restore knee function while maintaining knee stability after ACL reconstruction with autografts and believe that more studies on the best autograft choice will get us one step closer to reaching this goal.

CONCLUSION

We conclude that choosing one tendon autograft in ACL reconstruction is a valid approach. However, using GR autograft offers less knee stability, and should be considered when operating knees that present hyperlaxity or require limited functional demand. GR alone autograft is correlated with better subjective outcomes. In addition, the KT-1000 side to side indicates that STGR autograft guarantees higher structural knee stability but is associated with less controlled pain compared to GR tendon autografting.

AUTHORS’ CONTRIBUTIONS

CM, TMM, and CG conducted the study, participated in the operations, and evaluated patients postoperatively. PV and BM selected, collected, and analyzed the patient’s database before and at follow-up. The coordination and the drafting were made by PG and final revision, rewriting, and editing was made by AA. All authors have critically reviewed and approved the final draft and are responsible for the manuscript’s content and similarity index.

ETHICAL APPROVAL

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the I.r.t.a.l. Ethics Committee. The approval was obtained in May 2014.